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Sample records for bed high temperature

  1. Experimental investigation of thermal de-stratification in rock bed TES systems for high temperature applications

    International Nuclear Information System (INIS)

    Okello, Denis; Nydal, Ole J.; Banda, Eldad J.K.

    2014-01-01

    Highlights: • High thermal stratifications exists rock bed TES when charge with high temperature heat. • Faster thermal degradation occurs in highly stratified bed irrespective of the bed length. • Average rate of heat loss as a function of storage time increases with increasing average bed temperature. - Abstract: Solar energy fluctuates so much that it cannot promote continuous use. Integration of Thermal Energy Storage (TES) with solar energy collection devices has the potential of making solar energy available on demand. Thermal energy can be stored in a bed of rocks at temperatures suitable for applications like cooking, boiling space heating, etc. During charging, temperature stratification is observed in the bed. In a stratified system, if the heat is used immediately, then it is possible to extract heat at reasonably high temperature from the top. For cases where the system is to be used after sometime (later at night or the following morning), the high temperature heat at the top is observed to degrade as the system tries to establish thermal equilibrium irrespective of the bed height. The average rate of heat loss from the TES unit to the ambient is found to increase with increasing average bed temperatures

  2. Discussion on Design Transients of Pebble-bed High Temperature Gas-cooled Reactor

    International Nuclear Information System (INIS)

    Wang Yan; Li Fu; Zheng Yanhua

    2014-01-01

    In order to assure high quality for the components and their supports in the reactor coolant system, etc., some thermal-hydraulic transient conditions will be selected and researched for equipment design evaluation to satisfy the requirements ASME code, which are based on the conservative estimates of the magnitude and frequency of the temperature and pressure transients resulting from various operating conditions in the plant. In the mature design on pressurized water reactor, five conditions are considered. For the developing advanced pebble-bed high temperature gas-cooled reactor(HTGR), its design and operation has much difference with other reactors, so the transients of the pebble-bed high temperature gas-cooled reactor have distinctive characteristics. In this paper, the possible design transients of the pebble-bed HTGR will be discussed, and the frequency of design transients for equipment fatigue analysis and stress analysis due to cyclic stresses is also studied. The results will provide support for the design and construct of the pebble-bed HTGR. (author)

  3. Predicting freeboard heat transfer by using empirical correlations in high temperature fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Biyikli, Suleyman [Okan University Tuzla Kampusu, Faculty of Engineering and Architecture (Turkey)], email: suleyman.biyikli@okan.edu.tr

    2011-07-01

    This article investigates the heat transfer characteristics for horizontal tubes in a freeboard region of high temperature fluidized beds. The freeboard entrainment heights are calculated by using empirical correlations described in detail and used in estimating the heat transfer coefficients from a horizontal tube occurring by radiation, gas convection, and particle contact mechanisms in high temperature a fluidized bed combustor. The total average of these coefficients around a horizontal tube carrying water in high temperature fluidized beds can be written as the sum of convective, radiative, and fluidized-particle contact heat transfer coefficients and these correlations are tested against certain published experimental measurements. In full agreement with this data, it was observed that the calculated heat transfer coefficients increased with increasing gas velocity at a given tube elevation and they decreased and approached the values of single-phase gas convection and radiation with increasing tube elevation in the freeboard region while the relative contribution of radiation increases and approaches a constant fraction of total heat transfer.

  4. High temperature degradation by erosion-corrosion in bubbling fluidized bed combustors

    Directory of Open Access Journals (Sweden)

    Hou Peggy

    2004-01-01

    Full Text Available Heat-exchanger tubes in fluidized bed combustors (FBCs often suffer material loss due to combined corrosion and erosion. Most severe damage is believed to be caused by the impact of dense packets of bed material on the lower parts of the tubes. In order to understand this phenomenon, a unique laboratory test rig at Berkeley was designed to simulate the particle hammering interactions between in-bed particles and tubes in bubbling fluidized bed combustors. In this design, a rod shaped specimen is actuated a short distance within a partially fluidized bed. The downward specimen motion is controlled to produce similar frequencies, velocities and impact forces as those experienced by the impacting particle aggregates in practical systems. Room temperature studies have shown that the degradation mechanism is a three-body abrasion process. This paper describes the characteristics of this test rig, reviews results at elevated temperatures and compares them to field experience. At higher temperatures, deposits of the bed material on tube surfaces can act as a protective layer. The deposition depended strongly on the type of bed material, the degree of tube surface oxidation and the tube and bed temperatures. With HCl present in the bed, wastage was increased due to enhanced oxidation and reduced oxide scale adherence.

  5. INTENSIFICATION OF HEAT TRANSFER IN A HIGH-TEMPERATURED FLUIDIZED BED

    Directory of Open Access Journals (Sweden)

    А. O. Redko

    2017-10-01

    Full Text Available Purpose. This paper highlights experimental research of heat exchange in coarse particles to ensure the performance of ecological characteristics of Heat supply system. Methodology. The test stand has been developed to solve the defined task. It helps to do the research at the temperature of fluidizing bed and pulsating fluidizing bed at the range 800–1000°С. The temperature of the fluidized bed was provided by burning natural gas and wood waste. Sand and chamotte with a particle size of 1.0 to 5.0 mm were used as the layer material. The heat-transfer coefficient from the layer to the surface, immersed in the layer, and the density of the heat flux were measured by a calorimetric method under steady-state conditions. Smooth tubes and transversely finned with different height and rib spacing were investigated. Experiments in a high-temperature pulsating fluidized bed were carried out with pulsating combustion of natural gas in a layer or in a sublattice chamber into which natural gas and air were separately supplied. The frequency of combustion pulsations was provided by the automation system. The flash frequency was regulated in the range from 0.14 to 5 Hz. Findings. It is presented the results of physical modeling to find out the heat-transfer coefficients of smooth and finned tubes in fluidizing bed of coarse particles in the process of wood waste and gaseous fuel combusting. It is proved that the coefficient of heat transfer increases with increasing temperature by 2–2,5 times in the bed which contains particles diameter of 2.5–5 mm is 300–350Vt/(m2 К that is much higher than for layer furnaces. The results of the experiments are presented in the form of a generalized relationship that takes into account the diameter of the particles and the value of the finning coefficient. Heat transfer of finned tubes is 15–20% less then smooth tubes but the density of heat flow referred to the area of a finned tube is 0,12–0,20 МVt/m2 that

  6. Graphite beds for coolant filtration at high temperature

    International Nuclear Information System (INIS)

    Heathcock, R.E.; Lacy, C.S.

    1978-01-01

    High temperature filtration will be provided for new Ontario Hydro CANDU heat transport systems. Filtration has been shown to effectively reduce the concentration of circulating corrosion products in our heat transport systems, hence, minimizing the processes of activity transport. This paper will present one option we have for this application; Deep Bed Granular Graphite Filters. The filter system is described by discussing pertinent aspects of its development programme. The compatibility of the filter and the heat transport coolant are demonstrated by results from loop tests, both out- and in-reactor, and by subsequent results from a large filter installation in the NPD NGS heat transport system. (author)

  7. Temperature distribution in spouted bed and heat transfer

    International Nuclear Information System (INIS)

    Takeda, Hiroshi; Yamamoto, Yutaka

    1976-01-01

    Temperature distribution in spouted bed was measured by using brass and graphite spouted beds so as to investigate heat transfer characteristic of spouted bed applied to an apparatus of PyC coating. These spouted beds are batch type and are spouted by air or nitrogen gas of room temperature, and the outer wall of beds are heated by nichrome or graphite heater. Particles used for experiments are alumina spherical particles and the diameter is 0.80 -- 1.12 mm. Temperature condition is in the range of 400 -- 1,400 0 C. In the neighborhood of 400 0 C, the spouting condition is stable, while the spouting condition becomes unstable in the case of above 1,000 0 C. This is caused by abrupt temperature increase of spouting gas. It was found that heat transfer coefficient h sub(w) of our low temperature experiments was closer to the calculated from Malek et al.'s equation, h sub(p) of our experiments was several times greater than the calculated from Uemaki et al.'s equation. On the other hand, h sub(p) of high temperature experiments was compared with an experimental relation for convective heat transfer of fluidized bed, it was found that Nu sub(p) of our experiments was nearly equal to or greater than the calculated from the relation, this would be caused by radiant heat transfer. (auth.)

  8. Analysis of impact of mixing flow on the pebble bed high temperature reactor

    International Nuclear Information System (INIS)

    Hao Chen; Li Fu; Guo Jiong

    2014-01-01

    The impact of the mixing flow in the pebble flow on pebble bed high temperature gas cooled reactor (HTR) was analyzed in the paper. New code package MFVSOP which can simulate the mixing flow was developed. The equilibrium core of HTR-PM was selected as reference case, the impact of the mixing flow on the core parameters such as core power peak factor, power distribution was analyzed with different degree of mixing flow, and uncertainty analysis was carried out. Numerical results showed that the mixing flow had little impact on key parameters of pebble bed HTR, and the multiple-pass-operation-mode in pebble bed HTR can reduce the uncertainty arouse from the mixing flow. (authors)

  9. Stability analysis of the high temperature thermal pebble bed nuclear reactor concept

    International Nuclear Information System (INIS)

    Vondy, D.R.

    1981-02-01

    A study was made of the stability of the high temperature gas-cooled pebble bed core against xenon-driven oscillation. This generic study indicated that a core as large as 3000 MW(t) could be stable. Several aspects present a challenge to analysis including the void space above the pebble bed, the effects of possible control rod configurations, and the temperature feedback contribution. Special methods of analysis were developed in this effort. Of considerable utility was the scheme of including an azimuthal buckling loss term in the neturon balance equations admitting direct solution of the first azimuthal harmonic for a core having azimuthal symmetry. This technique allows the linear stability analysis to be done solving two-dimensional (RZ) problems instead of three-dimensional problems. A scheme for removing the fundamental source contribution was also implemented to allow direct iteration toward the dominant harmonic solution, treating up to three dimensions with diffusion theory

  10. Preliminary Safeguards Assessment for the Pebble-Bed Fluoride High-Temperature Reactor (PB-FHR) Concept

    Energy Technology Data Exchange (ETDEWEB)

    Disser, Jay; Arthur, Edward; Lambert, Janine

    2016-09-01

    This report examines a preliminary design for a pebble bed fluoride salt-cooled high temperature reactor (PB-FHR) concept, assessing it from an international safeguards perspective. Safeguards features are defined, in a preliminary fashion, and suggestions are made for addressing further nuclear materials accountancy needs.

  11. 3D DEM simulation and analysis of void fraction distribution in a pebble bed high temperature reactor

    International Nuclear Information System (INIS)

    Yang, Xingtuan; Gui, Nan; Tu, Jiyuan; Jiang, Shengyao

    2014-01-01

    Highlights: • We show a detailed analysis of void fraction (VF) in HTR-10 of China using DEM. • Radial distribution (RD) of VF is uniform in the core and oscillated near the wall. • Axial distribution (AD) is linearly varied along height due to effect of gravity. • Steady RD of VF in the conical base is Gaussian-like, larger than packing bed. • Joint linear and normal distribution of VF is analyzed and explained. - Abstract: The current work analyzes the radial and axial distributions of void fraction of a pebble bed high temperature reactor. A three-dimensional pebble bed corresponding to our test facility of pebble bed type gas-cooled high temperature reactor (HTR-10) in Tsinghua University is simulated via discrete element method, and the radial and axial void fraction profiles are calculated. It validates the oscillating characteristics of radial void fraction near the wall. Detailed calculations show the differences of void fraction profiles between the stationary packing bed and the dynamically discharging bed. Based on the vertically and circumferentially averaged radial distribution and horizontally averaged axial distribution of void fraction, a fully three-dimensional analytical distribution of void fraction throughout the bed is established. The results show the combined effects of gravity and void variation in the pebble bed caused by the pebble discharging. It indicates the linearly increased packing effect caused by gravity in the vertical (axial) direction and the normal distribution of void in the horizontal (radial) direction by pebble drainage. These two effects coexist in the conical base of the bed whereas only the former effect exists in the cylindrical volume of the bed

  12. Analytical calculation of the fuel temperature reactivity coefficient for pebble bed and prismatic high temperature reactors for plutonium and uranium-thorium fuels

    International Nuclear Information System (INIS)

    Talamo, Alberto

    2007-01-01

    We analytically evaluated the fuel coefficient of temperature both for pebble bed and prismatic high temperature reactors when they utilize as fuel plutonium and minor actinides from light water reactors spent fuel or a mixture of 50% uranium, enriched 20% in 235 U, and 50% thorium. In both cores the calculation involves the evaluation of the resonances integrals of the high absorbers fuel nuclides 240 Pu, 238 U and 232 Th and it requires the esteem of the Dancoff-Ginsburg factor for a pebble bed or prismatic core. The Dancoff-Ginsburg factor represents the only discriminating parameter in the results for the two different reactors types; in fact, both the pebble bed and the prismatic reactors share the same the pseudo-cross-section describing an infinite medium made of graphite filled by TRISO particles. We considered only the resolved resonances with a statistical spin factor equal to one and we took into account 267, 72, 212 resonances in the range 1.057-5692, 6.674-14485, 21.78-3472 eV for 240 Pu, 238 U and 232 Th, respectively, for investigating the influence on the fuel temperature reactivity coefficient of the variation of the TRISO kernel radius and TRISO particles packing fraction from 100, 200 to 300 μm and from 10% to 50%, respectively. Finally, in the pebble bed core, we varied the radius of the pebble for setting a fuel temperature reactivity coefficient similar to the one of a prismatic core

  13. Transmutation of plutonium in pebble bed type high temperature reactors

    International Nuclear Information System (INIS)

    Bende, E.E.

    1997-01-01

    The pebble bed type High Temperature Reactor (HTR) has been studied as a uranium-free burner of reactor grade plutonium. In a parametric study, the plutonium loading per pebble as well as the type and size of the coated particles (CPs) have been varied to determine the plutonium consumption, the final plutonium burnup, the k ∞ and the temperature coefficients as a function of burnup. The plutonium loading per pebble is bounded between 1 and 3 gr Pu per pebble. The upper limit is imposed by the maximal allowable fast fluence for the CPs. A higher plutonium loading requires a longer irradiation time to reach a desired burnup, so that the CPs are exposed to a higher fast fluence. The lower limit is determined by the temperature coefficients, which become less negative with increasing moderator-actinide ratio. A burnup of about 600 MWd/kgHM can be reached. With the HTR's high efficiency of 40%, a plutonium supply of 1520 kg/GW e a is achieved. The discharges of plutonium and minor actinides are then 450 and 110 kg/GW e a, respectively. (author)

  14. Plutonium burning in a pebble-bed type high temperature nuclear reactor

    Energy Technology Data Exchange (ETDEWEB)

    Bende, E.E

    2000-01-24

    This thesis deals with the pebble-bed High Temperature Reactor that is fuelled with pure reactor-grade plutonium. It is stressed that neither burnable poisons nor fertile materials like 238U and 212Th are present in the calculational models throughout this thesis. Chapter 2 discusses the general properties of the pebble-bed HTR: the passive safety features of this reactor; different fuel scenarios according to which the pebble-bed HTR can be operated; properties of the pebbles and the coated particles (CPs), including a concise overview of the mechanisms that can lead to coated particle failure. Special attention is paid to the effect of Pu as fuel inside these CPs thereby aiming to indicate which mechanisms are of concern when such CPs are considered as fuel in future reactors. In the last part of this chapter constraints are listed that were imposed to the models considered in the framework of this thesis. Chapter 3 presents the results of unit-cell calculations performed with three code systems. The main objective of this chapter is to compare the calculational results of one particular code system, which is a candidate for the generation of cross sections for a full-core calculation, to those of the other two code systems. Also some reactor physics interpretations of the calculational results are presented. The unit-cell calculations embrace the computation of a number of reactor physics parameters for pebbles with a varying plutonium mass per pebble and with different types of coated particles. For one pebble configuration, these parameters have been calculated for various fuel temperatures and over-all (uniform) temperatures. For that particular pebble configuration, also the results of a two burnup calculations were compared. Chapter 4 reports the results of a parameter study in which the number of coated particles per pebble as well as the type and size of the CPs have been varied. The effect of different pebble configurations on several reactor physics

  15. Consideration of emergency source terms for pebble-bed high temperature gas-cooled reactor

    International Nuclear Information System (INIS)

    Tao, Liu; Jun, Zhao; Jiejuan, Tong; Jianzhu, Cao

    2009-01-01

    Being the last barrier in the nuclear power plant defense-in-depth strategy, emergency planning (EP) is an integrated project. One of the key elements in this process is emergency source terms selection. Emergency Source terms for light water reactor (LWR) nuclear power plant (NPP) have been introduced in many technical documents, and advanced NPP emergency planning is attracting attention recently. Commercial practices of advanced NPP are undergoing in the world, pebble-bed high-temperature gas-cooled reactor (HTGR) power plant is under construction in China which is considered as a representative of advanced NPP. The paper tries to find some pieces of suggestion from our investigation. The discussion of advanced NPP EP will be summarized first, and then the characteristics of pebble-bed HTGR relating to EP will be described. Finally, PSA insights on emergency source terms selection and current pebble-bed HTGR emergency source terms suggestions are proposed

  16. Pebble Bed Reactors Design Optimization Methods and their Application to the Pebble Bed Fluoride Salt Cooled High Temperature Reactor (PB-FHR)

    Science.gov (United States)

    Cisneros, Anselmo Tomas, Jr.

    The Fluoride salt cooled High temperature Reactor (FHR) is a class of advanced nuclear reactors that combine the robust coated particle fuel form from high temperature gas cooled reactors, direct reactor auxillary cooling system (DRACS) passive decay removal of liquid metal fast reactors, and the transparent, high volumetric heat capacitance liquid fluoride salt working fluids---flibe (33%7Li2F-67%BeF)---from molten salt reactors. This combination of fuel and coolant enables FHRs to operate in a high-temperature low-pressure design space that has beneficial safety and economic implications. In 2012, UC Berkeley was charged with developing a pre-conceptual design of a commercial prototype FHR---the Pebble Bed- Fluoride Salt Cooled High Temperature Reactor (PB-FHR)---as part of the Nuclear Energy University Programs' (NEUP) integrated research project. The Mark 1 design of the PB-FHR (Mk1 PB-FHR) is 236 MWt flibe cooled pebble bed nuclear heat source that drives an open-air Brayton combine-cycle power conversion system. The PB-FHR's pebble bed consists of a 19.8% enriched uranium fuel core surrounded by an inert graphite pebble reflector that shields the outer solid graphite reflector, core barrel and reactor vessel. The fuel reaches an average burnup of 178000 MWt-d/MT. The Mk1 PB-FHR exhibits strong negative temperature reactivity feedback from the fuel, graphite moderator and the flibe coolant but a small positive temperature reactivity feedback of the inner reflector and from the outer graphite pebble reflector. A novel neutronics and depletion methodology---the multiple burnup state methodology was developed for an accurate and efficient search for the equilibrium composition of an arbitrary continuously refueled pebble bed reactor core. The Burnup Equilibrium Analysis Utility (BEAU) computer program was developed to implement this methodology. BEAU was successfully benchmarked against published results generated with existing equilibrium depletion codes VSOP

  17. Renewable side reflector structure for a pebble bed high temperature reactor

    International Nuclear Information System (INIS)

    Martin, Roger.

    1977-01-01

    The description is given of a renewable side reflector structure for a pebble bed high temperature reactor of the kind comprising a cylindrical graphite vessel constituting the neutron reflector, this vessel being filled with graphite pebbles containing the nuclear fuel and enclosed in a concrete protective containment. The internal peripheral area of the vessel is constituted by a line of adjacent graphite rods mounted so that they can rotate about their longitudinal axis and manoeuvrable from outside the concrete containment by means of a shaft passing into it [fr

  18. Analytical calculation of the fuel temperature reactivity coefficient for pebble bed and prismatic high temperature reactors for plutonium and uranium-thorium fuels

    Energy Technology Data Exchange (ETDEWEB)

    Talamo, Alberto [Department of Nuclear and Reactor Physics, Royal Institute of Technology - KTH, Roslagstullsbacken 21, S-10691 Stockholm (Sweden)]. E-mail: alby@anl.gov

    2007-01-15

    We analytically evaluated the fuel coefficient of temperature both for pebble bed and prismatic high temperature reactors when they utilize as fuel plutonium and minor actinides from light water reactors spent fuel or a mixture of 50% uranium, enriched 20% in {sup 235}U, and 50% thorium. In both cores the calculation involves the evaluation of the resonances integrals of the high absorbers fuel nuclides {sup 240}Pu, {sup 238}U and {sup 232}Th and it requires the esteem of the Dancoff-Ginsburg factor for a pebble bed or prismatic core. The Dancoff-Ginsburg factor represents the only discriminating parameter in the results for the two different reactors types; in fact, both the pebble bed and the prismatic reactors share the same the pseudo-cross-section describing an infinite medium made of graphite filled by TRISO particles. We considered only the resolved resonances with a statistical spin factor equal to one and we took into account 267, 72, 212 resonances in the range 1.057-5692, 6.674-14485, 21.78-3472 eV for {sup 240}Pu, {sup 238}U and {sup 232}Th, respectively, for investigating the influence on the fuel temperature reactivity coefficient of the variation of the TRISO kernel radius and TRISO particles packing fraction from 100, 200 to 300 {mu}m and from 10% to 50%, respectively. Finally, in the pebble bed core, we varied the radius of the pebble for setting a fuel temperature reactivity coefficient similar to the one of a prismatic core.

  19. Porous structure analysis of large-scale randomly packed pebble bed in high temperature gas-cooled reactor

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Cheng; Yang, Xingtuan; Liu, Zhiyong; Sun, Yanfei; Jiang, Shengyao [Tsinghua Univ., Beijing (China). Key Laboratory of Advanced Reactor Engineering and Safety; Li, Congxin [Ministry of Environmental Protection of the People' s Republic of China, Beijing (China). Nuclear and Radiation Safety Center

    2015-02-15

    A three-dimensional pebble bed corresponding to the randomly packed bed in the heat transfer test facility built for the High Temperature Reactor Pebble bed Modules (HTR-PM) in Shandong Shidaowan is simulated via discrete element method. Based on the simulation, we make a detailed analysis on the packing structure of the pebble bed from several aspects, such as transverse section image, longitudinal section image, radial and axial porosity distributions, two-dimensional porosity distribution and coordination number distribution. The calculation results show that radial distribution of porosity is uniform in the center and oscillates near the wall; axial distribution of porosity oscillates near the bottom and linearly varies along height due to effect of gravity; the average coordination number is about seven and equals to the maximum coordination number frequency. The fully established three-dimensional packing structure analysis of the pebble bed in this work is of fundamental significance to understand the flow and heat transfer characteristics throughout the pebble-bed type structure.

  20. High temperature CO2 capture using calcium oxide sorbent in a fixed-bed reactor

    International Nuclear Information System (INIS)

    Dou Binlin; Song Yongchen; Liu Yingguang; Feng Cong

    2010-01-01

    The gas-solid reaction and breakthrough curve of CO 2 capture using calcium oxide sorbent at high temperature in a fixed-bed reactor are of great importance, and being influenced by a number of factors makes the characterization and prediction of these a difficult problem. In this study, the operating parameters on reaction between solid sorbent and CO 2 gas at high temperature were investigated. The results of the breakthrough curves showed that calcium oxide sorbent in the fixed-bed reactor was capable of reducing the CO 2 level to near zero level with the steam of 10 vol%, and the sorbent in CaO mixed with MgO of 40 wt% had extremely low capacity for CO 2 capture at 550 deg. C. Calcium oxide sorbent after reaction can be easily regenerated at 900 deg. C by pure N 2 flow. The experimental data were analyzed by shrinking core model, and the results showed reaction rates of both fresh and regeneration sorbents with CO 2 were controlled by a combination of the surface chemical reaction and diffusion of product layer.

  1. Probabilistic safety assessment framework of pebble-bed modular high-temperature gas-cooled reactor

    International Nuclear Information System (INIS)

    Liu Tao; Tong Jiejuan; Zhao Jun; Cao Jianzhu; Zhang Liguo

    2009-01-01

    After an investigation of similar reactor type probabilistic safety assessment (PSA) framework, Pebble-bed Modular High-Temperature Gas-cooled Reactor (HTR-PM) PSA framework was presented in correlate with its own design characteristics. That is an integral framework which spreads through event sequence structure with initiating events at the beginning and source term categories in the end. The analysis shows that it is HTR-PM design feature that determines its PSA framework. (authors)

  2. Modeling and Application of Pneumatic Conveying for Spherical Fuel Element in Pebble-Bed Modular High-Temperature Gas-Cooled Reactor

    International Nuclear Information System (INIS)

    Zhou Shuyong; Wang Junsan; Wang Yuding; Cai Ruizhong; Zhang Xuan; Cao Jianting

    2014-01-01

    The fuel handling system is an important system for on-load refueling in pebble-bed modular high-temperature gas-cooled reactor. A dynamic model of pneumatic conveying for spherical fuel element in fuel handling system was established to describe the pneumatically conveying process. The motion characteristics of fuel elements in pipeline and the effect of fuel elements on gas velocity were studied using the model. The results show that the theoretical analyses are consistent with the experimental. The research has been used in developing full scope simulator for pebble-bed modular high-temperature gas-cooled reactor, also provides references for the design and optimization of the fuel handling system. (author)

  3. Feasibility study - Lowered bed temperature in Fluidised Bed boilers for waste; Foerstudie - Saenkt baeddtemperatur i FB-pannor foer avfallsfoerbraenning

    Energy Technology Data Exchange (ETDEWEB)

    Niklasson, Fredrik

    2009-01-15

    Waste incineration generally serves two purposes; 1) dispose of waste and 2) generation of heat and power. In the process of power production from waste fuels, the steam temperatures in super heaters are generally limited by the severe fouling and corrosion that occurs at elevated material temperatures, caused by high concentrations of alkali metals and chloride in the flue gas and fly ash. The overall aim of a continuation of present project is to determine if a reduced temperature of the bed zone in a fluidized bed waste incinerator reduces the amount of alkali chlorides in the flue gas. If so, a reduced bed temperature might enable increased steam temperature in super heaters, or, at unchanged steam temperature, improve the lifespan of the super heaters. The results from the project are of interest for plant owners wishing to improve performance of existing plants. The results may also be used to modify the design of future plants by boiler manufacturers. The aim of present pre-study was to determine how far the bed temperature can be reduced in a waste fired fluidized bed boiler in Boraas while maintaining a stable operation with sufficient combustion temperature in the freeboard to fulfil the directives of waste incineration. A continuation of the project will be based on the results from present study. The work is based on experiments at the test boiler. During the present study, no other measurements were performed apart from some sampling of bed material and ashes at different modes of operation. The experiments show that it is possible to alter the air and recycled flue gas in such a manner that the bed temperature is reduced from about 870 deg C to 700 deg C at 100% load and normal fuel mixture, while fulfilling the directive of 850 deg C at 2 seconds. Within normal variations of the fuel properties, however, the bed temperature increases to somewhat above 700 deg C if the fuel turns dry, while it falls below 650 deg C when the fuel turns wet. With

  4. Theoretical and experimental research of natural convection in the core of the high temperature pebble bed reactor

    International Nuclear Information System (INIS)

    Schuerenkraemer, M.

    1984-04-01

    The physical model of the developed THERMIX-2D-code for computing thermohydraulic behaviour of the core of high temperature pebble bed reactors is verified by experiments with natural convection flow. Such fluid flow behaviour can be of very high importance for the real reactor in the case of natural heat removal decay. The experiments are performed in a special set up testing-stand with pressures up to 30 bars and temperatures up to 300 0 C by using air and helium as fluid. In comparison with the experimental data the numerical results show that a good and useful simulation is given by the program. Pure natural convection flow in packed pebble beds is calculated with a very high degree of reliability. The investigation of flow stability demonstrate that radial-symmetric relations are not given temporarily when national convection is overlayed by forced convection flow. In the discussion it is explained when and to what extent the program leds to useful results in such situations. The test of the effective heat conductivity lambdasub(eff) results in an improvement of the lambdasub(eff)-data used so far for temperatures below 1300 0 C. (orig.) [de

  5. Ash behavior and de-fluidization in low temperature circulating fluidized bed biomass gasifier

    DEFF Research Database (Denmark)

    Narayan, Vikas

    ensures that high-alkali biomass fuels can be used without risks of bed de-fluidization. This thesis aims to understand the behavior of alkali metals and ash in the LTCFB system. The thesis work involved measurements made on bed material and product gas dust samples on a 100kW LTCFB gasifier placed......Biomass is increasingly used as a fuel for power generation. Herbaceous fuels however, contain high amounts of alkali metals which get volatilized at high temperatures and forms salts with low melting points and thus condense on pipelines, reactor surfaces and may cause de-fluidization. A Low......-Temperature Circulating Fluidized Bed System (LTCFB) gasifier allows pyrolysis and gasification of biomass to occur at low temperatures thereby improving the retention of alkali and other ash species within the system and minimizing the amount of ash species in the product gas. In addition, the low reactor temperature...

  6. Global scaling analysis for the pebble bed advanced high temperature reactor

    International Nuclear Information System (INIS)

    Blandford, E.D.; Peterson, P.F.

    2009-01-01

    Scaled Integral Effects Test (IET) facilities play a critical role in the design certification process of innovative reactor designs. Best-estimate system analysis codes, which minimize deliberate conservatism, require confirmatory data during the validation process to ensure an acceptable level of accuracy as defined by the regulator. The modular Pebble Bed Advanced High Temperature Reactor (PB-AHTR), with a nominal power output of 900 MWth, is the most recent UC Berkeley design for a liquid fluoride salt cooled, solid fuel reactor. The PB-AHTR takes advantage of technologies developed for gas-cooled high temperature thermal and fast reactors, sodium fast reactors, and molten salt reactors. In this paper, non-dimensional scaling groups and similarity criteria are presented at the global system level for a loss of forced circulation transient, where single-phase natural circulation is the primary mechanism for decay heat removal following a primary pump trip. Due to very large margin to fuel damage temperatures, the peak metal temperature of primary-loop components was identified as the key safety parameter of interest. Fractional Scaling Analysis (FSA) methods were used to quantify the intensity of each transfer process during the transient and subsequently rank them by their relative importance while identifying key sources of distortion between the prototype and model. The results show that the development of a scaling hierarchy at the global system level informs the bottom-up scaling analysis. (author)

  7. The effects of temperatures on the pebble flow in a pebble bed high temperature reactor

    International Nuclear Information System (INIS)

    Sen, R. S.; Cogliati, J. J.; Gougar, H. D.

    2012-01-01

    The core of a pebble bed high temperature reactor (PBHTR) moves during operation, a feature which leads to better fuel economy (online refueling with no burnable poisons) and lower fuel stress. The pebbles are loaded at the top and trickle to the bottom of the core after which the burnup of each is measured. The pebbles that are not fully burned are recirculated through the core until the target burnup is achieved. The flow pattern of the pebbles through the core is of importance for core simulations because it couples the burnup distribution to the core temperature and power profiles, especially in cores with two or more radial burnup 'zones '. The pebble velocity profile is a strong function of the core geometry and the friction between the pebbles and the surrounding structures (other pebbles or graphite reflector blocks). The friction coefficient for graphite in a helium environment is inversely related to the temperature. The Thorium High Temperature Reactor (THTR) operated in Germany between 1983 and 1989. It featured a two-zone core, an inner core (IC) and outer core (OC), with different fuel mixtures loaded in each zone. The rate at which the IC was refueled relative to the OC in THTR was designed to be 0.56. During its operation, however, this ratio was measured to be 0.76, suggesting the pebbles in the inner core traveled faster than expected. It has been postulated that the positive feedback effect between inner core temperature, burnup, and pebble flow was underestimated in THTR. Because of the power shape, the center of the core in a typical cylindrical PBHTR operates at a higher temperature than the region next to the side reflector. The friction between pebbles in the IC is lower than that in the OC, perhaps causing a higher relative flow rate and lower average burnup, which in turn yield a higher local power density. Furthermore, the pebbles in the center region have higher velocities than the pebbles next to the side reflector due to the

  8. The effects of temperatures on the pebble flow in a pebble bed high temperature reactor

    Energy Technology Data Exchange (ETDEWEB)

    Sen, R. S.; Cogliati, J. J.; Gougar, H. D. [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415 (United States)

    2012-07-01

    The core of a pebble bed high temperature reactor (PBHTR) moves during operation, a feature which leads to better fuel economy (online refueling with no burnable poisons) and lower fuel stress. The pebbles are loaded at the top and trickle to the bottom of the core after which the burnup of each is measured. The pebbles that are not fully burned are recirculated through the core until the target burnup is achieved. The flow pattern of the pebbles through the core is of importance for core simulations because it couples the burnup distribution to the core temperature and power profiles, especially in cores with two or more radial burnup 'zones '. The pebble velocity profile is a strong function of the core geometry and the friction between the pebbles and the surrounding structures (other pebbles or graphite reflector blocks). The friction coefficient for graphite in a helium environment is inversely related to the temperature. The Thorium High Temperature Reactor (THTR) operated in Germany between 1983 and 1989. It featured a two-zone core, an inner core (IC) and outer core (OC), with different fuel mixtures loaded in each zone. The rate at which the IC was refueled relative to the OC in THTR was designed to be 0.56. During its operation, however, this ratio was measured to be 0.76, suggesting the pebbles in the inner core traveled faster than expected. It has been postulated that the positive feedback effect between inner core temperature, burnup, and pebble flow was underestimated in THTR. Because of the power shape, the center of the core in a typical cylindrical PBHTR operates at a higher temperature than the region next to the side reflector. The friction between pebbles in the IC is lower than that in the OC, perhaps causing a higher relative flow rate and lower average burnup, which in turn yield a higher local power density. Furthermore, the pebbles in the center region have higher velocities than the pebbles next to the side reflector due to the

  9. Measurement of flow field in the pebble bed type high temperature gas-cooled reactor

    International Nuclear Information System (INIS)

    Lee, Sa Ya; Lee, Jae Young

    2008-01-01

    In this study, flow field measurement of the Pebble Bed Reactor(PBR) for the High Temperature Gascooled Reactor(HTGR) was performed. Large number of pebbles in the core of PBR provides complicated flow channel. Due to the complicated geometries, numerical analysis has been intensively made rather than experimental observation. However, the justification of computational simulation by the experimental study is crucial to develop solid analysis of design method. In the present study, a wind tunnel installed with pebbles stacked was constructed and equipped with the Particle Image Velocimetry(PIV). We designed the system scaled up to realize the room temperature condition according to the similarity. The PIV observation gave us stagnation points, low speed region so that the suspected high temperature region can be identified. With the further supplementary experimental works, the present system may produce valuable data to justify the Computational Fluid Dynamics(CFD) simulation method

  10. High power density reactors based on direct cooled particle beds

    Science.gov (United States)

    Powell, J. R.; Horn, F. L.

    Reactors based on direct cooled High Temperature Gas Cooled Reactor (HTGR) type particle fuel are described. The small diameter particle fuel is packed between concentric porous cylinders to make annular fuel elements, with the inlet coolant gas flowing inwards. Hot exit gas flows out along the central channel of each element. Because of the very large heat transfer area in the packed beds, power densities in particle bed reactors (PBRs) are extremely high resulting in compact, lightweight systems. Coolant exit temperatures are high, because of the ceramic fuel temperature capabilities, and the reactors can be ramped to full power and temperature very rapidly. PBR systems can generate very high burst power levels using open cycle hydrogen coolant, or high continuous powers using closed cycle helium coolant. PBR technology is described and development requirements assessed.

  11. Fusion energy for alternate applications: the design of a high temperature falling bed as a long-lived blanket

    International Nuclear Information System (INIS)

    Harkness, S.D.; Stevens, H.C.; Hall, M.M.; Gohar, M.Y.A.; de Paz, J.F.

    1979-01-01

    The high temperature falling bed conceptual design work has consisted of a coordinated effort in neutronics, materials science, thermal hydraulics and mechanical design. The neutronics work has been based on a one-dimensional transport analysis and has been used to scope the implication of blanket dimensions, breeding materials, ceramic pebble material and coolant choice on both tritium breeding capabilities and energy deposition into the high temperature region of the blanket. The materials science effort has concentrated on defining the selection of a particular ceramic material. The thermal hydraulic analysis has been concerned with sizing the heat transfer system and defining the temperature gradients in the high temperature blanket. The mechanical design work has evaluated how such a system might be constructed from the point of view of maintainability and structural support

  12. Control of the Bed Temperature of a Circulating Fluidized Bed Boiler by using Particle Swarm Optimization

    Directory of Open Access Journals (Sweden)

    AYGUN, H.

    2012-05-01

    Full Text Available Circulating fluidized bed boilers are increasingly used in the power generation due to their higher combustion efficiency and lower pollutant emissions. Such boilers require an effective control of the bed temperature, because it influences the boiler combustion efficiency and the rate of harmful emissions. A Particle-Swarm-Optimization-Proportional-Integrative-Derivative (PSO-PID controller for the bed temperature of a circulating fluidized bed boiler is presented. In order to prove the capability of the proposed controller, its performances are compared at different boiler loads with those of a Fuzzy Logic (FL controller. The simulation results demonstrate some advantages of the proposed controller.

  13. High power density reactors based on direct cooled particle beds

    International Nuclear Information System (INIS)

    Powell, J.R.; Horn, F.L.

    1985-01-01

    Reactors based on direct cooled HTGR type particle fuel are described. The small diameter particle fuel is packed between concentric porous cylinders to make annular fuel elements, with the inlet coolant gas flowing inwards. Hot exit gas flows out long the central channel of each element. Because of the very large heat transfer area in the packed beds, power densities in particle bed reactors (PBR's) are extremely high resulting in compact, lightweight systems. Coolant exit temperatures are high, because of the ceramic fuel temperature capabilities, and the reactors can be ramped to full power and temperature very rapidly. PBR systems can generate very high burst power levels using open cycle hydrogen coolant, or high continuous powers using closed cycle helium coolant. PBR technology is described and development requirements assessed. 12 figs

  14. SHOVAV-JUEL. A one dimensional space-time kinetic code for pebble-bed high-temperature reactors with temperature and Xenon feedback

    International Nuclear Information System (INIS)

    Nabbi, R.; Meister, G.; Finken, R.; Haben, M.

    1982-09-01

    The present report describes the modelling basis and the structure of the neutron kinetics-code SHOVAV-Juel. Information for users is given regarding the application of the code and the generation of the input data. SHOVAV-Juel is a one-dimensional space-time-code based on a multigroup diffusion approach for four energy groups and six groups of delayed neutrons. It has been developed for the analysis of the transient behaviour of high temperature reactors with pebble-bed core. The reactor core is modelled by horizontal segments to which different materials compositions can be assigned. The temperature dependence of the reactivity is taken into account by using temperature dependent neutron cross sections. For the simulation of transients in an extended time range the time dependence of the reactivity absorption by Xenon-135 is taken into account. (orig./RW)

  15. Studies on high-performance ceramic heat exchanger for ultra high temperature. 2nd Report. Heat transfer of finned tube bundle immersed in fluidized bed; Chokoon`yo koseino ceramic netsu kokanki ni kansuru kenkyu. 2. Ryudo sonai no rin kangun no netsudentatsu tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Himeji, Y; Kumada, M [Gifu University, Gifu (Japan). Faculty of Engineering

    1998-03-25

    Studies were carried out to develop a high-performance ceramic heat exchanger for ultra high temperatures using a fluidized bed. In the former study, Heat transfer coefficient had been improved by applying fluidized bed to the heat exchanger for high temperature with smooth ceramic tubes. In this study, finned ceramic tubes were applied instead of smooth tubes for more improvement of heat transfer and experiments were performed on condition that the maximum bed temperature was 1100degC. Fluidization remained stable and the bed temperature uniform in the bed similarly as the case of smooth tube. A heat transfer coefficient of finned tube was evaluated and it was improved about 3 times as large as that of smooth tube. The performance of the heat exchanger was also evaluated using temperature efficiency and exergy efficiency. 4 refs., 11 figs., 1 tab.

  16. Temperature and pressure distributions in a 400 kW{sub t} fluidized bed straw gasifier

    Energy Technology Data Exchange (ETDEWEB)

    Erguedenler, A.; Ghaly, A.E.; Hamdullahpur, F. [Technical Univ. of Nova Scotia, Halifax (Canada)

    1993-12-31

    The temperature and pressure distribution characteristics of a 400 kW (thermal) dual-distributor type fluidized bed straw gasifier were investigated. The effects of the bed height, equivalence ratio (actual air-fuel ratio:stoichiometric air-fuel ratio) and fluidization velocity on the temperature and pressure variations in the gasifier were studied. Generally, the bed temperature reached the steady state condition within 15--20 minutes. The average temperature of the dense bed ranged from 649{degrees}C to 875{degrees}C depending on the levels of operating parameters used. The bed temperature increased linearly with increases in the equivalence ratio, higher bed temperatures were observed with lower bed height and no clear trend for the bed temperature with respect to variations in fluidization velocity was observed. The bed height, equivalence ratio and fluidization velocity affected the pressure drop in the fluidized bed gasifier. Increasing the fluidization velocity and/or decreasing the equivalence ratio resulted in higher pressure drops in the dense bed and the freeboard regions whereas increasing the bed height increased the pressure drop only in the dense bed.

  17. Development and testing of nuclear graphite for the German pebble-bed high temperature reactor

    International Nuclear Information System (INIS)

    Haag, G.; Delle, W.; Nickel, H.; Theymann, W.; Wilhelmi, G.

    1987-01-01

    Several types of high temperature reactors have been developed in the Federal Republic of Germany. They are all based on spherical fuel elements being surrounded by graphite as reflector material. As an example, HTR-500 developed by the Hochtemperatur Reaktorbau GmbH is shown. The core consists of the top reflector, the side reflector with inner and outer parts, the bottom reflector and the core support columns. The most serious problem with respect to fast neutron radiation damage had to be solved for the materials of those parts near the pebble bed. Regarding the temperature profile in the core, the top reflector is at 300 deg C, and as cooling gas flows from the top downward, the temperature of the inner side reflector rises to about 700 deg C at the bottom. Fortunately, the highest fast neutron load accumulated during the life time of a reactor corresponds to the lowest temperature. This makes graphite components easier to survive neutron exposure without being mechanically damaged, although the maximum fast neutron fluence is as high as 4 x 10 22 /cm 2 at about 400 deg C. HTR graphite components are divided into four classes according to loading. The raw materials for nuclear graphite, the development of pitch coke nuclear graphite, the irradiation behavior of ATR-2E and ASR-IRS and others are reported. (Kako, I.)

  18. Flow distribution of pebble bed high temperature gas cooled reactors using large eddy simulation

    International Nuclear Information System (INIS)

    Gokhan Yesilyurt; Hassan, Y.A.

    2003-01-01

    A High Temperature Gas-cooled Reactor (HTGR) is one of the renewed reactor designs to play a role in nuclear power generation. This reactor design concepts is currently under consideration and development worldwide. Since the HTGR concept offers inherent safety, has a very flexible fuel cycle with capability to achieve high burnup levels, and provides good thermal efficiency of power plant, it can be considered for further development and improvement as a reactor concept of generation IV. The combination of coated particle fuel, inert helium gas as coolant and graphite moderated reactor makes it possible to operate at high temperature yielding a high efficiency. In this study the simulation of turbulent transport for the gas through the gaps of the spherical fuel elements (fuel pebbles) will be performed. This will help in understanding the highly three-dimensional, complex flow phenomena in pebble bed caused by flow curvature. Under these conditions, heat transfer in both laminar and turbulent flows varies noticeably around curved surfaces. Curved flows would be present in the presence of contiguous curved surfaces. In the case of a laminar flow and of an appreciable effect of thermogravitional forces, the Nusselt (Nu) number depends significantly on the curvature shape of the surface. It changes with order of 10 times. The flow passages through the gap between the fuel balls have concave and convex configurations. Here the action of the centrifugal forces manifests itself differently on convex and concave parts of the flow path (suppression or stimulation of turbulence). The flow of this type has distinctive features. In such flow there is a pressure gradient, which strongly affects the boundary layer behavior. The transition from a laminar to turbulent flow around this curved flow occurs at deferent Reynolds (Re) numbers. Consequently, noncircular curved flows as in the pebble-bed situation, in detailed local sense, is interesting to be investigated. To the

  19. Water-ingress analysis for the 200 MWe pebble-bed modular high temperature gas-cooled reactor

    International Nuclear Information System (INIS)

    Zheng Yanhua; Shi Lei; Wang Yan

    2010-01-01

    Water ingress into the primary circuit is generally recognized as one of the severe accidents with potential hazard to the modular high temperature gas-cooled reactor adopting steam-turbine cycle, which will cause a positive reactivity introduction, as well as the chemical corrosion of graphite fuel elements and reflector structure material. Besides, increase of the primary pressure may result in the opening of the safety valves, consequently leading the release of radioactive isotopes and flammable water gas. The analysis of such a kind of important and particular accident is significant to verify the inherent safety characteristics of the modular HTR plants. Based on the preliminary design of the 200 MWe high temperature gas-cooled reactor pebble-bed modular (HTR-PM), the design basis accident of a double-ended guillotine break of one heating tube and the beyond design basis accident of a large break of the main steam collection plate have been analyzed by using TINTE code, which is a special transient analysis program for high temperature gas-cooled reactors. Some safety relevant concerns, such as the fuel temperature, the primary loop pressure, the graphite corrosion, the water gas releasing amount, as well as the natural convection influence on the condition of failing to close the blower flaps, have been studied in detail. The calculation results indicate that even under some severe hypothetical postulates, the HTR-PM is able to keep the inherent safeties of the modular high temperature gas-cooled reactor and has a relatively good natural plant response, which will not result in environmental radiation hazard.

  20. Feasibility of Thorium Fuel Cycles in a Very High Temperature Pebble-Bed Hybrid System

    Directory of Open Access Journals (Sweden)

    L.P. Rodriguez

    2015-08-01

    Full Text Available Nuclear energy presents key challenges to be successful as a sustainable energy source. Currently, the viability of the use thorium-based fuel cycles in an innovative nuclear energy generation system is being investigated in order to solve these key challenges. In this work, the feasibility of three thorium-based fuel cycles (232Th-233U, 232Th-239Pu, and 232Th-U in a hybrid system formed by a Very High Temperature Pebble-Bed Reactor (VHTR and two Pebble-Bed Accelerator Driven Systems (ADSs was evaluated using parameters related to the neutronic behavior such as nuclear fuel breeding, minor actinide stockpile, the energetic contribution of each fissile isotope, and the radiotoxicity of the long lived wastes. These parameters were used to compare the fuel cycles using the well-known MCNPX ver. 2.6e computational code. The results obtained confirm that the 232Th-233U fuel cycle is the best cycle for minimizing the production of plutonium isotopes and minor actinides. Moreover, the inclusion of the second stage in the ADSs demonstrated the possibility of extending the burnup cycle duration and reducing the radiotoxicity of the discharged fuel from the VHTR.

  1. A kinetic study of gaseous potassium capture by coal minerals in a high temperature fixed-bed reactor

    DEFF Research Database (Denmark)

    Zheng, Yuanjing; Jensen, Peter Arendt; Jensen, Anker Degn

    2008-01-01

    The reactions between gaseous potassium chloride and coal minerals were investigated in a lab-scale high temperature fixed-bed reactor using single sorbent pellets. The applied coal minerals included kaolin, mullite, silica, alumina, bituminous coal ash, and lignite coal ash that were formed...... into long cylindrical pellets. Kaolin and bituminous coal ash that both have significant amounts of Si and Al show superior potassium capture characteristics. Experimental results show that capture of potassium by kaolin is independent of the gas oxygen content. Kaolin releases water and forms metakaolin...... when heated at temperatures above 450°C. The amounts of potassium captured by metakaolin pellet decreases with increasing reaction temperature in the range of 900-1300°C and increases again with further increasing the temperature up to 1500°C. There is no reaction of pre-made mullite with KCl...

  2. FY 1974 Report on results of Sunshine Project. Feasibility study on digging high-temperature beds; 1974 nendo koon chiso kussaku ni kansuru feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1975-03-31

    The desired target geothermal conditions for which the digging equipment is to be developed are 3,000 to 5,000 m as depth, 400 degrees C as temperature and 500 kg/cm{sup 2} as pressure. As the first phase, the study is conducted on feasibility of development of techniques for digging high-temperature beds under a temperature condition of 250 degrees C, where the rotary table type digger is mainly studied. It is most widely used for digging oil wells as well as geothermal wells. The current rotary table B type digger is studied as the equipment serviceable at 250 degrees C as the target temperature level for the moment for digging high-temperature beds. The studied items include the problems involved in the digger body, pipes, bits and other members, and also measures to expand its possibility. Also studied/surveyed are applicability of the new digging techniques now under development to geothermal wells, and techniques for fracturing high-temperature rocks. This report summarizes to help select the methods desired to be developed in the future, and plan development of the digging systems. (NEDO)

  3. Bed agglomeration characteristics of palm shell and corncob combustion in fluidized bed

    International Nuclear Information System (INIS)

    Chaivatamaset, Pawin; Sricharoon, Panchan; Tia, Suvit

    2011-01-01

    Bed particle agglomeration was studied experimentally in an atmospheric laboratory scale fluidized bed combustor using quartz sand as bed material. Palm shell and corncob were tested. The objectives of the study were (i) to describe the contributions of the biomass ash properties and the operating conditions on the bed agglomeration tendency in term of the bed defluidization time (t def ) and the extent of potassium accumulation in the bed (K/Bed) and (ii) to further elucidate the ash inorganic behaviors and the governing bed agglomeration mechanisms. Defluidization caused by the bed agglomeration was experienced in all experiments during combustion of these biomasses, as a consequence of the presence of potassium in biomass. The experimental results indicated that biomass ash characteristics were the significant influence on the bed agglomeration. The increasing bed temperature, bed particle size and static bed height and the decreasing fluidizing air velocity enhanced the bed agglomeration tendency. The SEM/EDS analyses on the agglomerates confirmed that the agglomeration was attributed to the formation of potassium silicate liquid enriched on the surface of quartz sand particles in conjunction with the high surface temperature of the burning biomass char particles. Thermodynamic examination based on the phase diagram analysis confirmed that the molten phase formation was responsible for the agglomeration. In this study, the high molten ash fraction resulting from the high potassium content in biomass promoted the agglomeration and thus defluidization. - Highlights: → Palm shell and corncob of Thailand are tested their bed agglomeration behaviors during fluidized bed combustion. → The increase of bed temperature, bed particle size and static bed height and the decrease of air velocity enhance bed agglomeration. → The formation of ash derived potassium silicate melts enriched on sand surface is the key process. → The collision between char and sand

  4. Finite difference program for calculating hydride bed wall temperature profiles

    International Nuclear Information System (INIS)

    Klein, J.E.

    1992-01-01

    A QuickBASIC finite difference program was written for calculating one dimensional temperature profiles in up to two media with flat, cylindrical, or spherical geometries. The development of the program was motivated by the need to calculate maximum temperature differences across the walls of the Tritium metal hydrides beds for thermal fatigue analysis. The purpose of this report is to document the equations and the computer program used to calculate transient wall temperatures in stainless steel hydride vessels. The development of the computer code was motivated by the need to calculate maximum temperature differences across the walls of the hydrides beds in the Tritium Facility for thermal fatigue analysis

  5. Experimental investigation on feasibility of two-region-designed pebble-bed high-temperature gas-cooled reactor

    International Nuclear Information System (INIS)

    Yang Xingtuan; Hu Wenping; Jiang Shengyao

    2009-01-01

    Phenomenological experiments were performed on a 2-dimensional scaled model of the two-region designed pebble-bed high-temperature gas-cooled reactor core consisting of the distinct fuel pebble region and graphite pebble region. Issues with respect to the feasibility of the two-region design, including the establishment of the two-region arrangement, the mixing zone between the two regions, and the stagnant zone existence, were investigated. Three equilibrium conditions were proposed to evaluate the stable two-region arrangement formation. The general characteristics of the flow of the pebble bed were analyzed on basis of the observed phenomenon. It was found that a stable two-region arrangement was formed under the experimental conditions: the pebbles' motion was to some extent random but also confined by the neighbors of pebbles so that the mixing zone is constrained to a reasonable size. Guide plates utilized to improve mixing are proved to be effective without noticeable effect on the two-region arrangement features. Stagnant zones were observed under the experimental conditions and they were expected to be avoided by improving the design of the experimental setup. (author)

  6. Ultra-high temperature direct propulsion

    International Nuclear Information System (INIS)

    Araj, K.J.; Slovik, G.; Powell, J.R.; Ludewig, H.

    1987-01-01

    Potential advantages of ultra-high exhaust temperature (3000 K - 4000 K) direct propulsion nuclear rockets are explored. Modifications to the Particle Bed Reactor (PBR) to achieve these temperatures are described. Benefits of ultra-high temperature propulsion are discussed for two missions - orbit transfer (ΔV = 5546 m/s) and interplanetary exploration (ΔV = 20000 m/s). For such missions ultra-high temperatures appear to be worth the additional complexity. Thrust levels are reduced substantially for a given power level, due to the higher enthalpy caused by partial disassociation of the hydrogen propellant. Though technically challenging, it appears potentially feasible to achieve such ultra high temperatures using the PBR

  7. Pore Scale Thermal Hydraulics Investigations of Molten Salt Cooled Pebble Bed High Temperature Reactor with BCC and FCC Configurations

    Directory of Open Access Journals (Sweden)

    Shixiong Song

    2014-01-01

    CFD results and empirical correlations’ predictions of pressure drop and local Nusselt numbers. Local pebble surface temperature distributions in several default conditions are investigated. Thermal removal capacities of molten salt are confirmed in the case of nominal condition; the pebble surface temperature under the condition of local power distortion shows the tolerance of pebble in extreme neutron dose exposure. The numerical experiments of local pebble insufficient cooling indicate that in the molten salt cooled pebble bed reactor, the pebble surface temperature is not very sensitive to loss of partial coolant. The methods and results of this paper would be useful for optimum designs and safety analysis of molten salt cooled pebble bed reactors.

  8. Numerical investigation of the 3-dimensional steady-state temperature- and flow distribution in the core of a pebble bed high temperature reactor

    International Nuclear Information System (INIS)

    Verfondern, K.

    1983-01-01

    This work presents a computer model determining the steady-state temperature- and flow field in 3 dimensions in the core of a pebble bed high temperature reactor. The numerical sprinkler method, basind on the Thermix-model, allows to describe the thermo-hydraulics of a non-rotational-symmetric core-geometry. The AVR-reactor in Juelich, in operation since 1967, represents a suitable investigation-object for the computer model of Thermix-3D. It is in a 3D-mesh-structure to reproduce very precisely the so called ''graphite noses'', in which the shut-down rods are conducted as well as the filling cones in the inner and outer area. The results of the final calculation of the normal operation condition for the AVR-reactor unambiguously show, that within the core reproduced in 3 dimensions there are evident deviations in the flow profile and in the temperatures of the cooling gas in contrast to a 2D-handling. (orig.) [de

  9. Localization of the Hot Spot in the Gap of Pebble Bed of Very High Temperature Gas Cooled Reactor(VHTGR)

    International Nuclear Information System (INIS)

    Lee, Sa Ya; Hong, Sung Je; Lee, Jae Young

    2010-01-01

    Pebble Bed Reactor(PBR) has been investigated intensively due to its benefits in management, but its complicated flow geometry requests reliable analytical methods. Hassan and Lee et al. have been made three dimensional computational methods. Hassan also measured local velocity fields with Particle Tracking Velocimetry(PTV), in small sized packed bed using liquid coolant, and Lee et al. measured flow field in the 2-dimensional wind tunnel with a hot wire system. In the present study, we develop the scaled up wind tunnel of pebble bed to use air as coolant in the same Reynolds number condition, as 21614, of the PBMR-250MWth. In order to measure the local surface temperature, the heating system and temperature measurement system were installed and heat transfer analogy was performed. The local surface temperature data shows that the predicted hot spots by Lee et al. at the top and bottom of the pebble by the velocity field measurement are reasonable, but the heat conduction is prior than contact effect at contact points

  10. Development and application of a high-temperature sampling probe for burning chamber conditions in fluidized-bed combustion; Korkean laempoetilan naeytteenottosondin kehittaeminen ja soveltaminen leijukerrospolton tulipesaeolosuhteisiin

    Energy Technology Data Exchange (ETDEWEB)

    Larjava, K.; Paerkkae, M. [VTT Chemical Technology, Espoo (Finland); Linna, V. [VTT Energy, Jyvaeskylae (Finland). Environmental Technology

    1997-10-01

    Determination of heavy and alkali metals and other condensing compounds (e.g. chlorides) in combustion chamber conditions is limited by the poor suitability of traditional methods for sampling at high temperatures. IFRF has developed a high-temperature sampling probe for sampling HCN and NH{sub 3}, which has been tested for sampling of NH{sub 3} by Chalmers University of Technology in Sweden. VTT Chemical Technology and Chalmers University of Technology have in their preliminary experiments determined contents of vaporous heavy metals in the combustion chamber of a 12 MW circulating fluidized-bed boiler using this probe. According to the results, the modified probe is suitable for heavy metal determination in combustion chamber. Based on this series of experiments, modification of the probe has been started on the own financing of VTT Chemical Technology and a field measurement was performed in November 1994 to test the present version of the probe. Based on the results of that measurement, the probe has been modified further on as a part of this LIEKKI 2 project. Similar kind of a principle has been applied in the probe which has been developed by VTT Energy during 1994. The probe is built for determination of gas composition of fluidized bed in full-scale boilers. The purpose of this project is to develop and test a sampling probe for fluidized bed combustion. The main advantage of the probe is that condensation losses in sampling due to high temperature gradients can be avoided. Thus, the probe is very suitable for sampling vaporous heavy and alkali metals and other condensing species as well as burning gases and alternatively also solids at high temperatures

  11. Gasification of high ash, high ash fusion temperature bituminous coals

    Science.gov (United States)

    Liu, Guohai; Vimalchand, Pannalal; Peng, WanWang

    2015-11-13

    This invention relates to gasification of high ash bituminous coals that have high ash fusion temperatures. The ash content can be in 15 to 45 weight percent range and ash fusion temperatures can be in 1150.degree. C. to 1500.degree. C. range as well as in excess of 1500.degree. C. In a preferred embodiment, such coals are dealt with a two stage gasification process--a relatively low temperature primary gasification step in a circulating fluidized bed transport gasifier followed by a high temperature partial oxidation step of residual char carbon and small quantities of tar. The system to process such coals further includes an internally circulating fluidized bed to effectively cool the high temperature syngas with the aid of an inert media and without the syngas contacting the heat transfer surfaces. A cyclone downstream of the syngas cooler, operating at relatively low temperatures, effectively reduces loading to a dust filtration unit. Nearly dust- and tar-free syngas for chemicals production or power generation and with over 90%, and preferably over about 98%, overall carbon conversion can be achieved with the preferred process, apparatus and methods outlined in this invention.

  12. Numerical investigation of the flow at the pebble bed of the high temperature gas cooled reactors

    International Nuclear Information System (INIS)

    Costa, Franklin C.; Navarro, Moyses A.; Santos, Andre A.C.

    2011-01-01

    This paper presents a numerical investigation of the thermal and fluid dynamics among the fuel spheres and the cooling fluid, appearing in the core of pebble bed reactor (PBR-Peeble Bed Reactor) using the CFD-Computational Fluid Dynamics CFX 13.0. The paper presents the two analysis results. In the first phase it was considered two heat transfer models for the fuel spheres. In a model it was established volumetric load generation, with thermal conduction for both the fuel and coating. The other model prescribes a heat flux at the sphere surfaces. In this analysis, it was proceed two simulation in the two sphere arrangements, one considering the spheres in contact, and the other with 2 mm spacing between them. At the second analysis it was evaluated the sphere arrangement influence on the thermal and fluid dynamic behavior of the bed. The four simulations present differences in the flow and in the surface and maximum temperature profiles of the coating.(author)

  13. Fusion blanket high-temperature heat transfer

    International Nuclear Information System (INIS)

    Fillo, J.A.

    1983-01-01

    Deep penetration of 14 MeV neutrons makes two-temperature region blankets feasible. A relatively low-temperature (approx. 300 0 C) metallic structure is the vacuum/coolant pressure boundary, while the interior of the blanket, which is a simple packed bed of nonstructural material, operates at very high temperatures (>1000 0 C). The water-cooled shell structure is thermally insulated from the steam-cooled interior. High-temperature steam can dramatically increase the efficiency of electric power generation, as well as produce hydrogen and oxygen-based synthetic fuels at high-efficiency

  14. Preliminary Neutronic Design of High Burnup OTTO Cycle Pebble Bed Reactor

    OpenAIRE

    Setiadipura, T; Irwanto, D; Zuhair, Zuhair

    2015-01-01

    The pebble bed type High Temperature Gas-cooled Reactor (HTGR) is among the interesting nuclear reactor designs in terms of safety and flexibility for co-generation applications. In addition, the strong inherent safety characteristics of the pebble bed reactor (PBR) which is based on natural mechanisms improve the simplicity of the PBR design, in particular for the Once-Through-Then-Out (OTTO) cycle PBR design. One of the important challenges of the OTTO cycle PBR design, and nuclear reactor ...

  15. Calcium oxide/carbon dioxide reactivity in a packed bed reactor of a chemical heat pump for high-temperature gas reactors

    International Nuclear Information System (INIS)

    Kato, Yukitaka; Yamada, Mitsuteru; Kanie, Toshihiro; Yoshizawa, Yoshio

    2001-01-01

    The thermal performance of a chemical heat pump that uses a calcium oxide/carbon dioxide reaction system was discussed as a heat storage system for utilizing heat output from high temperature gas reactors (HTGR). Calcium oxide/carbon dioxide reactivity for the heat pump was measured using a packed bed reactor containing 1.0 kg of reactant. The reactor was capable of storing heat at 900 deg. C by decarbonation of calcium carbonate and generating up to 997 deg. C by carbonation of calcium oxide. The amount of stored heat in the reactor was 800-900 kJ kg -1 . The output temperature of the reactor could be controlled by regulating the carbonation pressure. The thermal storage performance of the reactor was superior to that of conventional sensible heat storage systems. A heat pump using this CaO/CO 2 reactor is expected to contribute to thermal load leveling and to realize highly efficient utilization of HTGR output due to the high heat storage density and high-quality temperature output of the heat pump

  16. Pressure drop in packed beds of spherical particles at ambient and elevated air temperatures

    Directory of Open Access Journals (Sweden)

    Pešić Radojica

    2015-01-01

    Full Text Available The aim of this work was the experimental investigation of the particle friction factor for air flow through packed bed of particles at ambient and elevated temperatures. The experiments were performed by measuring the pressure drop across the packed bed, heated to the desired temperature by hot air. Glass spherical particles of seven different diameters were used. The temperature range of the air flowing through the packed bed was from 20ºC to 350ºC and the bed voidages were from 0.3574 to 0.4303. The obtained results were correlated using a number of available literature correlations. The overall best fit of all of the experimental data was obtained using Ergun [1] equation, with mean absolute deviation of 10.90%. Ergun`s equation gave somewhat better results in correlating the data at ambient temperature with mean absolute deviation of 9.77%, while correlation of the data at elevated temperatures gave mean absolute deviation of 12.38%. The vast majority of the correlations used gave better results when applied to ambient temperature data than to the data at elevated temperatures. Based on the results obtained, Ergun [1] equation is proposed for friction factor calculation both at ambient and at elevated temperatures. [Projekat Ministarstva nauke Republike Srbije, br. ON172022

  17. Study on Characteristic of Temperature Coefficient of Reactivity for Plutonium Core of Pebbled Bed Reactor

    Science.gov (United States)

    Zuhair; Suwoto; Setiadipura, T.; Bakhri, S.; Sunaryo, G. R.

    2018-02-01

    As a part of the solution searching for possibility to control the plutonium, a current effort is focused on mechanisms to maximize consumption of plutonium. Plutonium core solution is a unique case in the high temperature reactor which is intended to reduce the accumulation of plutonium. However, the safety performance of the plutonium core which tends to produce a positive temperature coefficient of reactivity should be examined. The pebble bed inherent safety features which are characterized by a negative temperature coefficient of reactivity must be maintained under any circumstances. The purpose of this study is to investigate the characteristic of temperature coefficient of reactivity for plutonium core of pebble bed reactor. A series of calculations with plutonium loading varied from 0.5 g to 1.5 g per fuel pebble were performed by the MCNPX code and ENDF/B-VII library. The calculation results show that the k eff curve of 0.5 g Pu/pebble declines sharply with the increase in fuel burnup while the greater Pu loading per pebble yields k eff curve declines slighter. The fuel with high Pu content per pebble may reach long burnup cycle. From the temperature coefficient point of view, it is concluded that the reactor containing 0.5 g-1.25 g Pu/pebble at high burnup has less favorable safety features if it is operated at high temperature. The use of fuel with Pu content of 1.5 g/pebble at high burnup should be considered carefully from core safety aspect because it could affect transient behavior into a fatal accident situation.

  18. Use of a fluidized bed combustor and thermogravimetric analyzer for the study of coal ignition temperature

    International Nuclear Information System (INIS)

    Ávila, Ivonete; Crnkovic, Paula M.; Luna, Carlos M.R.; Milioli, Fernando E.

    2017-01-01

    Highlights: • Coal ignition tests were conducted in a fluidized bed and thermogravimetric conditions. • The use of two different ignition criteria showed a similar coal ignition temperature. • Coal ignition temperature was obtained by the changes of gas concentrations in FBC. • Ignition temperatures were associated with the activation energy of coal combustion. - Abstract: Ignition experiments with two bituminous coals were carried out in an atmospheric bubbling fluidized bed combustor (FBC) and a thermogravimetric analyzer (TGA). In the FBC tests, the rapid increase in O_2, CO_2, and SO_2 concentrations is an indication of the coal ignition. In the TGA technique, the ignition temperature was determined by the evaluation of the TGA curves in both combustion and pyrolysis processes. Model-Free Kinetics was applied and the coal ignition temperatures were associated with changes in the activation energy values during the combustion process. The results show the coal with the lowest activation energy also showed the lowest ignition temperature, highest values of volatile content and a higher heating value. The application of two different ignition criteria (TGA and FBC) resulted in similar ignition temperatures. The FBC curves indicated the high volatile coal ignites in the freeboard, i.e. during the feeding in the reactor, whereas the low volatile coal ignites in the bed. Finally, the physicochemical characteristics of the investigated coal types were correlated with their reactivities for the prediction of the ignition temperatures behaviors under different operating conditions as those in FBC.

  19. Sustainability of thorium-uranium in pebble-bed fluoride salt-cooled high temperature reactor

    International Nuclear Information System (INIS)

    Zhu, G.; Zou, Y.; Xu, H.

    2016-01-01

    Sustainability of thorium fuel in a Pebble-Bed Fluoride salt-cooled High temperature Reactor (PBFHR) is investigated to find the feasible region of high discharge burnup and negative Flibe (2LiF-BeF_2) salt Temperature Reactivity Coefficient (TRC). Dispersion fuel or pellet fuel with SiC cladding and SiC matrix is used to replace the tri-structural-isotropic (TRISO) coated particle system for increasing fuel loading and decreasing excessive moderation. To analyze the neutronic characteristics, an equilibrium calculation method of thorium fuel self-sustainability is developed. We have compared two refueling schemes (mixing flow pattern and directional flow pattern) and two kinds of reflector materials (SiC and graphite). This method found that the feasible region of breeding and negative Flibe TRC is between 20 vol% and 62 vol% fuel loading in the fuel. A discharge burnup could be achieved up to about 200 MWd/kgHM. The case with directional flow pattern and SiC reflector showed superior burnup characteristics but the worst radial power peak factor, while the case with mixing flow pattern and SiC reflector, which was the best tradeoff between discharge burnup and radial power peak factor, could provide burnup of 140 MWd/kgHM and about 1.4 radial power peak factor with 50 vol% dispersion fuel. In addition, Flibe salt displays good neutron properties as a coolant of quasi-fast reactors due to the strong "9Be(n,2n) reaction and low neutron absorption of "6Li (even at 1000 ppm) in fast spectrum. Preliminary thermal hydraulic calculation shows a good safety margin. The greatest challenge of this reactor may be the decades irradiation time of the pebble fuel. (A.C)

  20. Comparative evaluation of pebble-bed and prismatic fueled high-temperature gas-cooled reactors

    Energy Technology Data Exchange (ETDEWEB)

    Kasten, P.R.; Bartine, D.E.

    1981-01-01

    A comparative evaluation has been performed of the HTGR and the Federal Republic of Germany's Pebble Bed Reactor (PBR) for potential commercial applications in the US. The evaluation considered two reactor sizes (1000 and 3000 MW(t)) and three process applications (steam cycle, direct cycle, and process heat, with outlet coolant temperatures of 750, 850, and 950/sup 0/C, respectively). The primary criterion for the comparison was the levelized (15-year) cost of producing electricity or process heat. Emphasis was placed on the cost impact of differences between the prismatic-type HTGR core, which requires periodic refuelings during reactor shutdowns, and the pebble bed PBR core, which is refueled continuously during reactor operations. Detailed studies of key technical issues using reference HTGR and PBR designs revealed that two cost components contributing to the levelized power costs are higher for the PBR: capital costs and operation and maintenance costs. A third cost component, associated with nonavailability penalties, tended to be higher for the PBR except for the process heat application, for which there is a large uncertainty in the HTGR nonavailability penalty at the 950/sup 0/C outlet coolant temperature. A fourth cost component, fuel cycle costs, is lower for the PBR, but not sufficiently lower to offset the capital cost component. Thus the HTGR appears to be slightly superior to the PBR in economic performance. Because of the advanced development of the HTGR concept, large HTGRs could also be commercialized in the US with lower R and D costs and shorter lead times than could large PBRs. It is recommended that the US gas-cooled thermal reactor program continue giving primary support to the HTGR, while also maintaining its cooperative PBR program with FRG.

  1. Comparative evaluation of pebble-bed and prismatic fueled high-temperature gas-cooled reactors

    International Nuclear Information System (INIS)

    Kasten, P.R.; Bartine, D.E.

    1981-01-01

    A comparative evaluation has been performed of the HTGR and the Federal Republic of Germany's Pebble Bed Reactor (PBR) for potential commercial applications in the US. The evaluation considered two reactor sizes [1000 and 3000 MW(t)] and three process applications (steam cycle, direct cycle, and process heat, with outlet coolant temperatures of 750, 850, and 950 0 C, respectively). The primary criterion for the comparison was the levelized (15-year) cost of producing electricity or process heat. Emphasis was placed on the cost impact of differences between the prismatic-type HTGR core, which requires periodic refuelings during reactor shutdowns, and the pebble bed PBR core, which is refueled continuously during reactor operations. Detailed studies of key technical issues using reference HTGR and PBR designs revealed that two cost components contributing to the levelized power costs are higher for the PBR: capital costs and operation and maintenance costs. A third cost component, associated with nonavailability penalties, tended to be higher for the PBR except for the process heat application, for which there is a large uncertainty in the HTGR nonavailability penalty at the 950 0 C outlet coolant temperature. A fourth cost component, fuel cycle costs, is lower for the PBR, but not sufficiently lower to offset the capital cost component. Thus the HTGR appears to be slightly superior to the PBR in economic performance. Because of the advanced development of the HTGR concept, large HTGRs could also be commercialized in the US with lower R and D costs and shorter lead times than could large PBRs. It is recommended that the US gas-cooled thermal reactor program continue giving primary support to the HTGR, while also maintaining its cooperative PBR program with FRG

  2. Influence of various chlorine additives on the partitioning of heavy metals during low-temperature two-stage fluidized bed incineration.

    Science.gov (United States)

    Peng, Tzu-Huan; Lin, Chiou-Liang

    2014-12-15

    In this study, a pilot-scale low-temperature two-stage fluidized bed incinerator was evaluated for the control of heavy metal emissions using various chlorine (Cl) additives. Artificial waste containing heavy metals was selected to simulate municipal solid waste (MSW). Operating parameters considered included the first-stage combustion temperature, gas velocity, and different kinds of Cl additives. Results showed that the low-temperature two-stage fluidized bed reactor can be an effective system for the treatment of MSW because of its low NO(x), CO, HCl, and heavy metal emissions. The NO(x) and HCl emissions could be decreased by 42% and 70%, respectively. Further, the results showed that heavy metal emissions were reduced by bed material adsorption and filtration in the second stage. Regarding the Cl addition, although the Cl addition would reduce the metal capture in the first-stage sand bed, but those emitted metals could be effectively captured by the filtration of second stage. No matter choose what kind of additive, metal emissions in the low-temperature two-stage system are still lower than in a traditional high-temperature one-stage system. The results also showed that metal emissions depend not only on the combustion temperature but also on the physicochemical properties of the different metal species. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Fluidised bed heat exchangers

    International Nuclear Information System (INIS)

    Elliott, D.E.; Healey, E.M.; Roberts, A.G.

    1974-01-01

    Problems that have arisen during the initial stages of development of fluidised bed boilers in which heat transfer surfaces are immersed in fluidised solids are discussed. The very high heat transfer coefficients that are obtained under these conditions can be exploited to reduce the total heat transfer surface to a fraction of that in normal boilers. However, with the high heat flux levels involved, tube stressing becomes more important and it is advantageous to use smaller diameter tubes. One of the initial problems was that the pumping power absorbed by the fluidised bed appeared to be high. The relative influence of the fluidising velocity (and the corresponding bed area), tube diameter, tube spacing, heat transfer coefficient and bed temperature on pumping power and overall cost was determined. This showed the importance of close tube packing and research was undertaken to see if this would adversely affect the heat transfer coefficient. Pressure operation also reduces the pumping power. Fouling and corrosion tests in beds burning coal suggest that higher temperatures could be reached reliably and cost studies show that, provided the better refractory metals are used, the cost of achieving higher temperatures is not unduly high. It now remains to demonstrate at large scale that the proposed systems are viable and that the methods incorporated to overcome start up and part lead running problems are satisfactory. The promising role of these heat transfer techniques in other applications is briefly discussed

  4. On natural circulation in High Temperature Gas-Cooled Reactors and pebble bed reactors for different flow regimes and various coolant gases

    International Nuclear Information System (INIS)

    Melesed'Hospital, G.

    1983-01-01

    The use of CO 2 or N 2 (heavy gas) instead of helium during natural circulation leads to improved performance in both High Temperature Gas-Cooled Reactors (HTGR) and in Pebble Bed Reactors (PBR). For instance, the coolant temperature rise corresponding to a coolant pressure level and a rate of afterheat removal could be only 18% with CO 2 as compared to He, for laminar flow in HTGR; this value would be 40% in PBR. There is less difference between HTGR and PBR for turbulent flows; CO 2 is found to be always better than N 2 . These types of results derived from relationships between coolant properties, coolant flow, temperature rise, pressure, afterheat levels and core geometry, are obtained for HTGR and PBR for various flow regimes, both within the core and in the primary loop

  5. Sustainability of thorium-uranium in pebble-bed fluoride salt-cooled High Temperature Reactor - 15171

    International Nuclear Information System (INIS)

    Zhu, G.; Zou, Y.; Xu, Hongjie

    2015-01-01

    Sustainability of thorium fuel in a pebble-bed fluoride salt-cooled high temperature reactor (PB-FHR) is investigated to find the feasible region of high discharge burnup and negative FLiBe (2LiF-BeF 2 ) salt temperature reactivity coefficient (TRC). Dispersion fuel or pellet fuel with SiC cladding and SiC matrix is used to replace the tri-structural-isotropic (TRISO) coated particle system for increasing heavy metal loading and decreasing excessive moderation. In order to analyze the neutronic characteristics, an equilibrium calculation method of thorium fuel self-sustainability is developed. We have compared 2 refueling schemes (mixing flow pattern and directional flow pattern) and 2 kinds of reflector materials (SiC and graphite). This method has found that the feasible regions of breeding and negative FLiBe TRC is between 20 vol% and 62 vol% heavy metal loading in the fuel. A discharge burnup could be achieved up to about 200 MWd/kgHM. The case with directional flow pattern and SiC reflector showed superior burnup characteristics but the worst radial power peak factor, while the case with mixing flow pattern and SiC reflector, which was the best tradeoff between discharge burnup and radial power peak factor, could provide burnup of 140 MWd/kgHM and about 1.4 radial power peak factor with 50 vol% dispersion fuel. In addition, FLiBe salt displays good neutron properties as a coolant of quasi-fast reactors due to the strong 9 Be(n,2n) reaction and low neutron absorption of 6 Li (even at 1000 ppm) in fast spectrum. Preliminary thermal hydraulic calculation shows good safety margins. The greatest challenge of this reactor may be the very long irradiation time of the pebble fuel. (authors)

  6. Quasi-direct numerical simulation of a pebble bed configuration, Part-II: Temperature field analysis

    International Nuclear Information System (INIS)

    Shams, A.; Roelofs, F.; Komen, E.M.J.; Baglietto, E.

    2013-01-01

    Highlights: ► Quasi direct numerical simulations (q-DNSs) of a pebble bed configuration have been performed. ► This q-DNS database may serve as a reference for the validation of different turbulence modeling approaches. ► A wide range of qualitative and quantitative data throughout the computational domain has been generated. ► Results for mean, RMS of temperature and respective turbulent heat fluxes are extensively reported in this paper. -- Abstract: Good prediction of the flow and heat transfer phenomena in the pebble bed core of a high temperature reactor (HTR) is a challenge for available turbulence models, which still require to be validated. While experimental data are generally desirable in this validation process, due to the complex geometric configuration and measurement difficulties, a very limited amount of data is currently available. On the other hand, direct numerical simulation (DNS) is considered an accurate simulation technique, which may serve as an alternative for validating turbulence models. In the framework of the present study, quasi-direct numerical simulation (q-DNS) of a single face cubic centered pebble bed is performed, which will serve as a reference for the validation of different turbulence modeling approaches in order to perform calculations for a randomly arranged pebble bed. These simulations were performed at a Reynolds number of 3088, based on pebble diameter, with a porosity level of 0.42. Results related to flow field (mean, RMS and covariance of velocity) have been presented in Part-I, whereas, in the present article, we focus our attention to the analysis of the temperature field. A wide range of qualitative and quantitative data for the thermal field (mean, RMS and turbulent heat flux) has been generated

  7. Hybrid Molten Bed Gasifier for High Hydrogen Syngas Production

    Energy Technology Data Exchange (ETDEWEB)

    Rue, David [Gas Technology Institute, Des Plaines, IL (United States)

    2017-05-23

    was stable over the full oxygen to fuel firing range (0.8 to 1.05 of fuel gas stoichiometry) and with all fuel gases (natural gas and two syngas compositions), with steam, and without steam. The lower Btu content of the syngases presented no combustion difficulties. The molten bed was stable throughout testing. The molten bed was easily established as a bed of molten glass. As the composition changed from glass cullet to cullet with slag, no instabilities were encountered. The bed temperature and product syngas temperature remained stable throughout testing, demonstrating that the bed serves as a good heat sink for the gasification process. Product syngas temperature measured above the bed was stable at ~1600ºF. Testing found that syngas quality measured as H2/CO ratio increased with decreasing oxygen to fuel gas stoichiometric ratio, higher steam to inlet carbon ratio, higher temperature, and syngas compared with natural gas. The highest H2/CO ratios achieved were in the range of 0.70 to 0.78. These values are well below the targets of 1.5 to 2.0 that were expected and were predicted by modeling. The team, however, is encouraged that the HMB process can and will achieve H2/CO ratios up to 2.0. Changes needed include direct injection of coal into the molten bed of slag to prevent coal particle bypass into the product gas stream, elevation of the molten bed temperature to approximately 2500ºF, and further decrease of the oxygen to fuel gas ratio to well below the 0.85 minimum ratio used in the testing in this project.

  8. FY 1975 Report on results of Sunshine Project. Development of techniques of digging high-temperature beds (Feasibility study on digging high-temperature beds); 1975 nendo koon chiso kussaku gijutsu no kaihatsu seika hokokusho. Koon chiso kussaku ni kansuru feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1976-03-31

    The environmental conditions for which the digging techniques are to be developed have been set at 3,000 to 5,000 m as depth, 400 degrees C as temperature and 500 kg/cm{sup 2} as pressure. The environmental temperature was set at 250 degrees C as the first phase in the previous year. In this year, the temperature level is increased to 400 degrees C for the feasibility study on technological development. For development of the high-temperature bed digging apparatuses, masts, sub-structures, drawworks, slurry pumps, and pipe addition handling are studied as the problems involved in the rotary table method. Also studied are the related themes, e.g., drill pipes, drill collars, casing pipes, slurry, cementing and instruments to be installed in geothermal wells. For development of the bits, various problems to be solved are studied, including slurry circulation systems, bit diameter and speed of rotation, and bit configurations as those involved in the digging systems; heat-resistant materials, bit tooth forms, hardening of the edges, bearing configurations and cooling mechanisms as those involved in the bit structures; and optimum service conditions and selective use standards for roller cutter and solid bits. Other items studied include structures of the apparatuses for geothermal well mouth, and wear of digging tools for the air drilling method. (NEDO)

  9. Temperature Measurements to Characterize Dispersion Within Pressure Swing Adsorption (PSA) Beds

    National Research Council Canada - National Science Library

    Buettner, L

    1997-01-01

    ...) as the feed contaminant and air as the carrier. In-bed, vapor-phase concentrations at each axial position were measured and correlated to the magnitude of the temperature swings during a cycle...

  10. Experimental measurement of variation of heat transfer coefficient and temperature gradients in 16'' deep fluidised beds

    International Nuclear Information System (INIS)

    Blacker, P.T.; McLain, D.R.

    1962-04-01

    The object of the experiments was to choose suitable particulate materials for a fluidised bed cooler, to test a deep fluidised bed for uniformity of heat transfer coefficient, and to explore the temperature distribution in a centrally heated annular fluidised bed. This memorandum records the techniques used and some of the practical aspects involved, together with the performance results obtained, for the assistance of other experimenters who may wish to use fluidised beds as a laboratory technique. Mathematical correlation of the results has not been attempted since some of the properties of the bed material were not known and to determine them was beyond the scope of the work programme. Rather, we have compared our results with those of other experimenters. Graphite tubes, for use in steady state thermal stress experiments, are to be heated by a graphite radiant heater situated in the bore and cooled on the outer surface. The tubes are 2 cm. bore, 8 cm. outside diameter and 48 cm. long. The outside temperature of the tubes is to be between 500 deg. C. and 1500 deg. C. It is estimated that the heat transfer rate required for fracture at the outer surface is 30 watts/cm 2 . This could readily be achieved by cooling with liquid metals, water or high velocity gas. However, serious problems of either materials compatibility or mechanical complexity make these undesirable. A water-cooled fluidised bed of compatible solids fluidised with nitrogen gas can overcome most of these problems and give heat transfer coefficients close to that required, vis. about 0.1 w/cm C . A coolant bed about 20'' long would be required and an annulus of about 2'' radial width round the specimen was considered to be practicable

  11. Experimental measurement of variation of heat transfer coefficient and temperature gradients in 16'' deep fluidised beds

    Energy Technology Data Exchange (ETDEWEB)

    Blacker, P T; McLain, D R [Reactor Development Division, Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)

    1962-04-15

    The object of the experiments was to choose suitable particulate materials for a fluidised bed cooler, to test a deep fluidised bed for uniformity of heat transfer coefficient, and to explore the temperature distribution in a centrally heated annular fluidised bed. This memorandum records the techniques used and some of the practical aspects involved, together with the performance results obtained, for the assistance of other experimenters who may wish to use fluidised beds as a laboratory technique. Mathematical correlation of the results has not been attempted since some of the properties of the bed material were not known and to determine them was beyond the scope of the work programme. Rather, we have compared our results with those of other experimenters. Graphite tubes, for use in steady state thermal stress experiments, are to be heated by a graphite radiant heater situated in the bore and cooled on the outer surface. The tubes are 2 cm. bore, 8 cm. outside diameter and 48 cm. long. The outside temperature of the tubes is to be between 500 deg. C. and 1500 deg. C. It is estimated that the heat transfer rate required for fracture at the outer surface is 30 watts/cm{sup 2}. This could readily be achieved by cooling with liquid metals, water or high velocity gas. However, serious problems of either materials compatibility or mechanical complexity make these undesirable. A water-cooled fluidised bed of compatible solids fluidised with nitrogen gas can overcome most of these problems and give heat transfer coefficients close to that required, vis. about 0.1 w/cm C . A coolant bed about 20'' long would be required and an annulus of about 2'' radial width round the specimen was considered to be practicable.

  12. Infant's bed climate and bedding in the Japanese home.

    Science.gov (United States)

    Nakamura Ikeda, Rie; Fukai, Kiyoko; Okamoto Mizuno, Kazue

    2012-06-01

    to assess the bed climate of infants in their homes in Japan. descriptive, exploratory, non-experimental research design. the data were collected at the participants' homes under normal circumstances. nineteen healthy infants between the ages of two and five months. Their mothers, who joined a parenting class organised by a maternity clinic in Okayama, Japan, consented to participate in this study. we visited the infants' homes and interviewed their mothers concerning the types and use of bedding. The temperature and relative humidity of the bed climate at the back and foot of the bedding, and in the room were measured every minute for four consecutive days. Differences among the bed climates measured during three seasons (spring, summer, and autumn) were assessed by one-way analysis of variance. The bed temperature was higher for infants than for adults. No significant difference in temperature was noted among the three seasons. The bed temperature was about 36.0°C when waterproof sheets and futon mattresses for children or adult were used. The average relative humidity of the bed climate at the back was highest in summer, followed by that in spring and autumn; the differences were significant. The use of waterproof sheets and futon mattresses for children in summer increased the relative humidity to 80% or more. The use of infant beds, sunoko drainboards, and cotton futon mattresses in summer was effective in reducing the bed humidity. these results suggest that nurse-midwives should advise the parents on comfortable bed climates for their infants, as well as how to select and use bedding for them. Copyright © 2010 Elsevier Ltd. All rights reserved.

  13. Low-temperature nitriding of austenitic steel in a vibrofluidized bed

    Science.gov (United States)

    Baraz, V. R.; Grachev, S. V.

    1999-11-01

    The prospects for use of a vibrofluidized bed (VFB) for low-temperature nitrogen saturation of high-strength austenitic steel based on Cr-Ni-Mn (12Kh17N8G2S2MF) are considered. The positive effect of preliminary plastic deformation on the intensity of nitriding is described. The temperature and time parameters of nitriding in a VFB for strain-aging austenitic steel 12Kh17N8G2S2MF are shown to be adequate for the regimes of the final heat-treatment operation of aging. This creates the possibility of combining the operations of surface alloying and strain aging into a single cycle. This combined treatment increases substantially the resistance of the steel to cyclic loads while preserving the strength parameters. It is shown that the presented method of low-temperature nitriding in a VFB is expedient for improving the service characteristics of austenitic steel 12Kh17N8G2S2MF used for production of force springs of automobile brake systems.

  14. Numerical study on influences of bed resettling, breeding zone orientation, and purge gas on temperatures in solid breeders

    Energy Technology Data Exchange (ETDEWEB)

    Van Lew, Jon T., E-mail: jtvanlew@fusion.ucla.edu; Ying, Alice; Abdou, Mohamed

    2016-11-01

    Highlights: • Volume-conserving pebble fragmentation model in DEM to study thermomechanical responses to crushed pebbles in ensembles. • Parametric studies of ITER-relevant pebble beds with coupled CFD-DEM models. • Finding breeder temperatures are complex functions of orientation, fragmentation size, and packing fraction. • Recommendations of breeder unit orientation are given in terms of material selection. - Abstract: We apply coupled computational fluid dynamics and discrete element method (CFD-DEM) modeling tools with new numerical implementations of pebble fragmentation to study the combined effects of granular crushing and ensemble restructuring, granular fragment size, and initial packing for different breeder volume configurations. In typical solid breeder modules, heat removal from beds relies on maintaining pebble–pebble and pebble–wall contact integrity. However, contact is disrupted when an ensemble responds to individually crushed pebbles. Furthermore, restructuring of metastable packings after crushing events are, in part, dependent on gravity forces acting upon the pebbles. We investigate two representative pebble bed configurations under constant volumetric heat sources; modeling heat removed from beds via inter-particle conduction, purge gas convection, and contact between pebble beds and containers. In one configuration, heat is removed from at walls oriented parallel to the gravity vector (no gap formation possible); in the second, heat is removed at walls perpendicular to gravity, allowing for the possibility of gap formation between bed and wall. Judging beds on increase in maximum temperatures as a function of crushed pebble amount, we find that both pebble bed configurations to have advantageous features that manifest at different stages of pebble crushing. However, all configurations benefit from achieving high initial packing fractions.

  15. Advanced sorbent development progam; development of sorbents for moving-bed and fluidized-bed applications

    International Nuclear Information System (INIS)

    Ayala, R.E.; Venkataramani, V.S.

    1998-01-01

    The integrated gasification combined cycle (IGCC) power system using high-temperature coal gas cleanup is one of the most promising advanced technologies for the production of electric power from coal in an environmentally acceptable manner. Unlike conventional low-temperature cleanup systems that require costly heat exchangers, high-temperature coal gas cleanup systems can be operated near 482-538 C (900-1000F) or higher, conditions that are a closer match with the gasifier and turbine components in the IGCC system, thus resulting is a more efficient overall system. GE is developing a moving-bed, high-temperature desulfurization system for the IGCC power cycle in which zinc-based regenerable sorbents are currently being used as desulfurization sorbents. Zinc titanate and other proprietary zinc-based oxides are being considered as sorbents for use in the Clean Coal Technology Demonstration Program at Tampa Electric Co.s (TECo) Polk Power Station. Under cold startup conditions at TECo, desulfurization and regeneration may be carried out at temperatures as low as 343 C (650 F), hence a versatile sorbent is desirable to perform over this wide temperature range. A key to success in the development of high-temperature desulfurization systems is the matching of sorbent properties for the selected process operating conditions, namely, sustainable desulfurization kinetics, high sulfur capacity, and mechanical durability over multiple cycles. Additionally, the sulfur species produced during regeneration of the sorbent must be in a form compatible with sulfur recovery systems, such as sulfuric acid or elemental sulfur processes. The overall objective of this program is to develop regenerable sorbents for hydrogen sulfide removal from coal-derived fuel gases in the temperature range 343-538 C (650-1000 F). Two categories of reactor configurations are being considered: moving-bed reactors and fluidized-bed (bubbling and circulating) reactors. In addition, a cost assessment and

  16. Neutron physical investigations on the shutdown effect of small boronated absorbing spheres for pebble-bed high-temperature gas-cooled reactors

    International Nuclear Information System (INIS)

    Sgouridis, S.; Schurrer, F.; Muller, H.; Ninaus, W.; Oswald, K.; Neef, R.D.; Schaal, H.

    1987-01-01

    An emergency shutdown system for high-temperature gas-cooled pebble-bed reactors is proposed in addition to the common absorber rod shutdown system. This system is based on the strongly absorbing effect of small boronated graphite spheres (called KLAK), which trickle in case of emergency by gravity from the top reflector into the reactor core. The inner reflector of the Siemens-Argonaut reactor was substituted by an assembly of spherical Arbeitsgemeinschaft Versuchsreaktor fuel elements, and the shutdown effect was examined by installing well-defined KLAK nests inside this assembly. The purpose was to develop and prove a calculational procedure for determining criticality values for assemblies of large fuel spheres and small absorbing spheres

  17. Development and application of a high-temperature sampling probe for burning chamber conditions of fluidized-bed combustion; Korkean laempoetilan naeytteenottosondin kehittaeminen ja soveltaminen leijukerrospolton tulipesaeolosuhteisiin

    Energy Technology Data Exchange (ETDEWEB)

    Larjava, K.; Paerkkae, M.; Jormanainen, P.; Roine, J.; Paakkinen, K. [VTT Chemistry, Espoo (Finland); Linna, V. [VTT Energy, Jyvaeskylae (Finland)

    1996-12-01

    A sampling probe for the burning chamber conditions of fluidized-bed combustion will be developed in this project. The probe will be suitable for sampling vaporous heavy and alkali metals and other condensing compounds (e.g. chlorides) as well combustion gases and alternatively also flue gas particles at high temperatures. The knowledge gained with the probe will help understanding, developing and modeling combustion processes and will thus aid the manufacturers of the boilers. (author)

  18. Tracking channel bed resiliency in forested mountain catchments using high temporal resolution channel bed movement

    Science.gov (United States)

    Martin, Sarah E.; Conklin, Martha H.

    2018-01-01

    This study uses continuous-recording load cell pressure sensors in four, high-elevation (1500-1800 m), Sierra Nevada headwater streams to collect high-temporal-resolution, bedload-movement data for investigating the channel bed movement patterns within these streams for water years 2012-2014. Data show an annual pattern where channel bed material in the thalweg starts to build up in early fall, peaks around peak snow melt, and scours back to baseline levels during hydrograph drawdown and base flow. This pattern is punctuated by disturbance and recovery of channel bed material associated with short-term storm events. A conceptual model, linking sediment sources at the channel margins to patterns of channel bed fill and scour in the thalweg, is proposed building on the results of Martin et al. (2014). The material in the thalweg represents a balance between sediment supply from the channel margins and sporadic, conveyor-belt-like downstream transport in the thalweg. The conceptual model highlights not only the importance of production and transport rates but also that seasonal connectedness between the margins and thalweg is a key sediment control, determining the accumulation rate of sediment stores at the margins and the redistribution of sediment from margins to thalweg that feeds the conveyor belt. Disturbance and recovery cycles are observed at multiple temporal scales; but long term, the channel beds are stable, suggesting that the beds act as short-term storage for sediment but are in equilibrium interannually. The feasibility of use for these sensors in forested mountain stream environments is tested. Despite a high failure rate (50%), load cell pressure sensors show potential for high-temporal-resolution bedload measurements, allowing for the collection of channel bed movement data to move beyond time-integrated change measurements - where many of the subtleties of bedload movement patterns may be missed - to continuous and/or real-time measurements. This

  19. FBR and RBR particle bed space reactors

    International Nuclear Information System (INIS)

    Powell, J.R.; Botts, T.E.

    1983-01-01

    Compact, high-performance nuclear reactor designs based on High-Temperature Gas Reactors (HTGRs) particulate fuel are investigated. The large surface area available with the small-diameter (approx. 500 microns) particulate fuel allows very high power densities (MW's/liter), small temperature differences between fuel and coolant (approx. 10 0 K), high coolant-outlet temperatures (1500 to 3000 0 K, depending on design), and fast reactor startup (approx. 2 to 3 seconds). Two reactor concepts are developed - the Fixed Bed Reactor (FBR), where the fuel particles are packed into a thin annular bed between two porous cylindrical drums, and the Rotating Bed Reactor (RBR), where the fuel particles are held inside a cold rotating (typically approx. 500 rpm) porous cylindrical drum. The FBR can operate steady-state in the closed-cycle He-cooled mode or in the open-cycle H 2 -cooled mode. The RBR will operate only in the open-cycle H 2 -cooled mode

  20. High temperature fusion reactor design

    International Nuclear Information System (INIS)

    Harkness, S.D.; dePaz, J.F.; Gohar, M.Y.; Stevens, H.C.

    1979-01-01

    Fusion energy may have unique advantages over other systems as a source for high temperature process heat. A conceptual design of a blanket for a 7 m tokamak reactor has been developed that is capable of producing 1100 0 C process heat at a pressure of approximately 10 atmospheres. The design is based on the use of a falling bed of MgO spheres as the high temperature heat transfer system. By preheating the spheres with energy taken from the low temperature tritium breeding part of the blanket, 1086 MW of energy can be generated at 1100 0 C from a system that produces 3000 MW of total energy while sustaining a tritium breeding ratio of 1.07. The tritium breeding is accomplished using Li 2 O modules both in front of (6 cm thick) and behind (50 cm thick) the high temperature ducts. Steam is used as the first wall and front tritium breeding module coolant while helium is used in the rear tritium breeding region. The system produces 600 MW of net electricity for use on the grid

  1. US/FRG joint report on the pebble bed high temperature reactor resource conservation potential and associated fuel cycle costs

    International Nuclear Information System (INIS)

    Teuchert, E.; Ruetten, H.J.; Worley, B.A.; Vondy, D.R.

    1979-11-01

    Independent analyses at ORNL and KFA have led to the general conclusion that the flexibility in design and operation of a high-temperature gas-cooled pebble-bed reactor (PBR) can result in favorable ore utilization and fuel costs in comparison with other reactor types, in particular, with light-water reactors (LWRs). Fuel reprocessign and recycle show considerable promise for reducing ore consumption, and even the PBR throwaway cycle is competitive with fuel recycle in an LWR. The best performance results from the use of highly enriched fuel. Proliferation-resistant measures can be taken using medium-enriched fuel at a modest ore penalty, while use of low-enriched fuel would incur further ore penalty. Breeding is possible but net generation of fuel at a significant rate would be expensive, becoming more feasible as ore costs increase substantially. The 233 U inventory for a breeder could be produced by prebreeders using 235 U fuel

  2. High Temperature Fluoride Salt Test Loop

    Energy Technology Data Exchange (ETDEWEB)

    Aaron, Adam M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cunningham, Richard Burns [Univ. of Tennessee, Knoxville, TN (United States); Fugate, David L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Holcomb, David Eugene [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Kisner, Roger A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Peretz, Fred J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Robb, Kevin R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wilson, Dane F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Yoder, Jr, Graydon L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-12-01

    Effective high-temperature thermal energy exchange and delivery at temperatures over 600°C has the potential of significant impact by reducing both the capital and operating cost of energy conversion and transport systems. It is one of the key technologies necessary for efficient hydrogen production and could potentially enhance efficiencies of high-temperature solar systems. Today, there are no standard commercially available high-performance heat transfer fluids above 600°C. High pressures associated with water and gaseous coolants (such as helium) at elevated temperatures impose limiting design conditions for the materials in most energy systems. Liquid salts offer high-temperature capabilities at low vapor pressures, good heat transport properties, and reasonable costs and are therefore leading candidate fluids for next-generation energy production. Liquid-fluoride-salt-cooled, graphite-moderated reactors, referred to as Fluoride Salt Reactors (FHRs), are specifically designed to exploit the excellent heat transfer properties of liquid fluoride salts while maximizing their thermal efficiency and minimizing cost. The FHR s outstanding heat transfer properties, combined with its fully passive safety, make this reactor the most technologically desirable nuclear power reactor class for next-generation energy production. Multiple FHR designs are presently being considered. These range from the Pebble Bed Advanced High Temperature Reactor (PB-AHTR) [1] design originally developed by UC-Berkeley to the Small Advanced High-Temperature Reactor (SmAHTR) and the large scale FHR both being developed at ORNL [2]. The value of high-temperature, molten-salt-cooled reactors is also recognized internationally, and Czechoslovakia, France, India, and China all have salt-cooled reactor development under way. The liquid salt experiment presently being developed uses the PB-AHTR as its focus. One core design of the PB-AHTR features multiple 20 cm diameter, 3.2 m long fuel channels

  3. Simulation of a high efficiency multi-bed adsorption heat pump

    International Nuclear Information System (INIS)

    TeGrotenhuis, W.E.; Humble, P.H.; Sweeney, J.B.

    2012-01-01

    Attaining high energy efficiency with adsorption heat pumps is challenging due to thermodynamic losses that occur when the sorbent beds are thermally cycled without effective heat recuperation. The multi-bed concept described here enables high efficiency by effectively transferring heat from beds being cooled to beds being heated. A simplified lumped-parameter model and detailed finite element analysis are used to simulate a sorption compressor, which is used to project the overall heat pump coefficient of performance. Results are presented for ammonia refrigerant and a nano-structured monolithic carbon sorbent specifically modified for the application. The effects of bed geometry and number of beds on system performance are explored, and the majority of the performance benefit is obtained with four beds. Results indicate that a COP of 1.24 based on heat input is feasible at AHRI standard test conditions for residential HVAC equipment. When compared on a basis of primary energy input, performance equivalent to SEER 13 or 14 are theoretically attainable with this system. - Highlights: ► A multi-bed concept for adsorption heat pumps is capable of high efficiency. ► Modeling is used to simulate sorption compressor and overall heat pump performance. ► Results are presented for ammonia refrigerant and a nano-structured monolithic carbon sorbent. ► The majority of the efficiency benefit is obtained with four beds. ► Predicted COP as high as 1.24 for cooling is comparable to SEER 13 or 14 for electric heat pumps.

  4. Development of a low-temperature two-stage fluidized bed incinerator for controlling heavy-metal emission in flue gases

    International Nuclear Information System (INIS)

    Peng, Tzu-Huan; Lin, Chiou-Liang; Wey, Ming-Yen

    2014-01-01

    This study develops a low-temperature two-stage fluidized bed system for treating municipal solid waste. This new system can decrease the emission of heavy metals, has low construction costs, and can save energy owing to its lower operating temperature. To confirm the treatment efficiency of this system, the combustion efficiency and heavy-metal emission were determined. An artificial waste containing heavy metals (chromium, lead, and cadmium) was used in this study. The tested parameters included first-stage temperature and system gas velocity. Results obtained using a thermogravimetric analyzer with a differential scanning calorimeter indicated that the first-stage temperature should be controlled to at least 400 °C. Although, a large amount of carbon monoxide was emitted after the first stage, it was efficiently consumed in the second. Loss of the ignition values of ash residues were between 0.005% and 0.166%, and they exhibited a negative correlation with temperature and gas velocity. Furthermore, the emission concentration of heavy metals in the two-stage system was lower than that of the traditional one-stage fluidized bed system. The heavy-metal emissions can be decreased by between 16% and 82% using the low-temperature operating process, silica sand adsorption, and the filtration of the secondary stage. -- Graphical abstract: Heavy-metal emission concentrations in flue gases under different temperatures and gas velocities (dashed line: average of the heavy-metal emission in flue gases in the one-stage fluidized-bed incinerator). Highlights: • Low temperature two-stage system is developed to control heavy metal. • The different first-stage temperatures affect the combustion efficiency. • Surplus CO was destroyed efficiently by the secondary fluidized bed combustor. • Metal emission in two-stage system is lower than in the traditional system. • Temperature, bed adsorption, and filtration are the main control mechanisms

  5. Computational and experimental prediction of dust production in pebble bed reactors, Part II

    Energy Technology Data Exchange (ETDEWEB)

    Hiruta, Mie; Johnson, Gannon [Department of Mechanical Engineering, University of Idaho, 1776 Science Center Drive, Idaho Falls, ID 83401 (United States); Rostamian, Maziar, E-mail: mrostamian@asme.org [Department of Mechanical Engineering, University of Idaho, 1776 Science Center Drive, Idaho Falls, ID 83401 (United States); Potirniche, Gabriel P. [Department of Mechanical Engineering, University of Idaho, 1776 Science Center Drive, Idaho Falls, ID 83401 (United States); Ougouag, Abderrafi M. [Idaho National Laboratory, 2525 N Fremont Avenue, Idaho Falls, ID 83401 (United States); Bertino, Massimo; Franzel, Louis [Department of Physics, Virginia Commonwealth University, Richmond, VA 23284 (United States); Tokuhiro, Akira [Department of Mechanical Engineering, University of Idaho, 1776 Science Center Drive, Idaho Falls, ID 83401 (United States)

    2013-10-15

    Highlights: • Custom-built high temperature, high pressure tribometer is designed. • Two different wear phenomena at high temperatures are observed. • Experimental wear results for graphite are presented. • The graphite wear dust production in a typical Pebble Bed Reactor is predicted. -- Abstract: This paper is the continuation of Part I, which describes the high temperature and high pressure helium environment wear tests of graphite–graphite in frictional contact. In the present work, it has been attempted to simulate a Pebble Bed Reactor core environment as compared to Part I. The experimental apparatus, which is a custom-designed tribometer, is capable of performing wear tests at PBR relevant higher temperatures and pressures under a helium environment. This environment facilitates prediction of wear mass loss of graphite as dust particulates from the pebble bed. The experimental results of high temperature helium environment are used to anticipate the amount of wear mass produced in a pebble bed nuclear reactor.

  6. Experimental Simulation of Methane Hydrate Extraction at High Pressure Conditions: Influence of the Sediment Bed

    Science.gov (United States)

    Agudo, J. R.; Park, J.; Luzi, G.; Williams, M.; Rauh, C.; Wierschem, A.; Delgado, A.

    2017-10-01

    Being a clean alternative to other fossil fuels, Methane Hydrate (MH) is currently considered as one of the most important potential sources for hydrocarbon fuels [1]. In addition, the high energy density of MH and its stability at higher temperatures as compared to LNG (Liquefied Natural Gas) makes MH a potential greener method for energy transportation. At the same time, the low thermodynamic stability of MH strongly questions the future exploitation of gas hydrate deposits, turning its extraction into a possible geohazard [2]. Fluctuations in pressure, temperature, salinity, degree of saturation or sediment bed properties may cause methane gas release from the water lattice. We experimentally study the influence of the sediment bed geometry during formation-dissociation of MH. For this purpose, MH is synthesized within regular substrates in a 93 cm3 high pressure vessel. The regular substrates are triangular and quadratic arrangements of identical glass spheres with a diameter of 2 and 5 mm, respectively. MH formation within regular substrate reduces the possibility of spontaneous nucleation to a unique geometrical configuration. This fact permits us to characterize the kinetics of MH formation-dissociation as a function of the sediment bed geometry. Preliminary experimental results reveal a strong dependence of MH formation on the geometry of the regular substrate. For instance, under the same pressure and temperature, the kinetics of MH production is found to change by a factor 3 solely depending on the substrate symmetry, i.e. triangular or quadratic.

  7. Modular high-temperature reactor launched (and wallchart)

    International Nuclear Information System (INIS)

    Steinwarz, W.

    1987-01-01

    In view of the need for a technically unsophisticated, safe and economic reactor system, the KWU group has integrated the experience gained from German light-water reactor engineering and from successful operation of the German AVR experimental high-temperature reactor into the development of the High-Temperature Reactor (HTR)-module. The main components are illustrated and explained and technical data for the HTR-module is given. Safety is also considered. This includes graphs of core heat-up temperature for pebble-bed HTR and a graph of the temperature load of the fuel elements. The operation, control and applications are considered. The latter includes use in combined heat and power generation and community heating. Feasibility studies have shown that the HTR-module is cheaper, comparatively, than coal-fired power stations. (U.K.)

  8. The characteristics of bed agglomeration during fluidized bed combustion of eucalyptus bark

    International Nuclear Information System (INIS)

    Chaivatamaset, Pawin; Tia, Suvit

    2015-01-01

    The bed agglomeration behaviors were investigated experimentally when eucalyptus bark was burning tested in a laboratory scale fluidized bed reactor. The focuses of this work were the influences of operating conditions and bed materials on the bed agglomeration tendency and the elucidation in the behaviors of fuel inorganic elements and the governing mode of the agglomeration. It was found that the defluidization caused by the bed agglomeration was clearly detectable from the decrease in measured bed pressure. The growth of bed particle and accumulation of agglomerates during combustion provided the partial to complete defluidization. The defluidization was promoted by the increase of bed temperature and bed particle size, and the decrease of fluidizing air velocity. The SEM-EDS analyses revealed that the bed agglomeration was mainly attributed to the formation of potassium silicate compounds as liquid phase during the combustion. This was initiated by the chemical reaction between the bed particle and the released ash constituents. In this study, the inorganic migration from fuel particle to bed particle was likely dominated by the condensation/reaction. The thermodynamic examination by ternary phase diagram analysis corroborated that the liquid phase formation of the ash derived materials controlled the agglomeration. The alumina sand prevented the bed agglomeration since it was inactive in the formation of viscous molten substances during combustion at the observed temperatures. - Highlights: • The behaviors of bed agglomeration were studied during the fluidized bed combustion of eucalyptus bark. • The increase in bed temperature and sand size, and the decrease of air velocity promoted bed defluidization. • The formation of molten potassium silicate compounds conduced to the bed agglomeration. • Condensation/reaction was the dominant inorganic migration mechanism from fuel particle to bed particle. • The alumina sand prevented effectively the bed

  9. Establishing Bedding Requirements during Transport and Monitoring Skin Temperature during Cold and Mild Seasons after Transport for Finishing Pigs

    Directory of Open Access Journals (Sweden)

    John McGlone

    2014-05-01

    Full Text Available The broad aim of this study was to determine whether bedding level in the transport trailer influenced pig performance and welfare. Specifically, the objective was to define the bedding requirements of pigs during transportation in commercial settings during cold and mild weather. Animals (n = 112,078 pigs on 572 trailers used were raised in commercial finishing sites and transported in trailers to commercial processing plants. Dead on arrival (DOA, non-ambulatory (NA, and total dead and down (D&D data were collected and skin surface temperatures of the pigs were measured by infrared thermography. Data were collected during winter (Experiment 1 and fall/spring (Experiment 2. Total D&D percent showed no interaction between bedding level and outside air temperature in any experiments. Average skin surface temperature during unloading increased with outside air temperature linearly in both experiments (P < 0.01. In conclusion, over-use of bedding may be economically inefficient. Pig skin surface temperature could be a useful measure of pig welfare during or after transport.

  10. Reduced bed temperature at thermo-chemical conversion of difficult fuels; Saenkt baeddtemperatur vid termokemisk omvandling av svaara braenslen

    Energy Technology Data Exchange (ETDEWEB)

    Niklasson, Fredrik; Haraldsson, Conny; Johansson, Andreas; Claesson, Frida; Baefver, Linda; Ryde, Daniel

    2010-05-15

    This work investigates the prospect of reducing the concentrations of alkali chlorides in the flue gas by lowering the temperature in the bottom zone of a fluidized bed (FB) furnace below the often used 850 deg C. The directive of a retention time of at least two seconds above 850 deg C is fulfilled by the raise of the flue gas temperature that follows the combustion of unburned gases at the point of injection of secondary and tertiary air, above the bottom bed zone. The aim of the present experiments is to determine the dependency between the temperature and the amount of alkali metals leaving the bottom bed for some selected waste and biomass fuels. The results are intended for plant owners as well as boiler manufacturers. The experiments were performed in an FB-reactor, which was externally heated to specific temperatures between 550 and 850 deg C. The reactor is made of a quartz glass tube with an inner diameter of 60 mm and a length of 1.2 m. The fluidized bed rests upon a porous plate of sintered quartz. The bed material used was 180 gram purified sea sand with particle sizes between 0.1 and 0.3 mm. The fluidizing gas was a mixture of nitrogen and air, introduced in the bottom of the reactor by mass flow controllers. At the outlet of the reactor, the flue gas was divided between conventional gas analyzers and an ICP-MS instrument. The gas flow to the ICP-MS instrument was cooled before a slip stream was sucked out via a capillary to a nebulizer from which the sample gas was led to the ICP-MS instrument. The function of the nebulizer is normally to form an aerosol of liquids, but here it was used solely as a pump. In addition, a known flow of krypton was added into the nebulizer to be used as an internal standard. The novel technique to measure the amount of alkali metals on-line from a batch fired FB-reactor has been shown to work in practice and to provide interesting results, which so far is qualitative only. Further development and calibration work is

  11. Transient quenching of superheated debris beds during bottom reflood

    International Nuclear Information System (INIS)

    Tutu, N.K.; Ginsberg, T.; Klein, J.; Schwarz, C.E.; Klages, J.

    1984-01-01

    The experimental data suggest that for small liquid supply rate and low initial particle temperature, the bed quench process is a one-dimensional frontal phenomenon. The bed heat flux is constant during most of the duration of the quench period. The range of conditions which display one-dimensional frontal cooling characteristics is identified as the deep bed regime of bed quenching, and a limiting mathematical model was developed to describe the observed behavior. For large liquid supply rate and high initial bed temperature, the bed quench process is a complex phenomenon. Under these conditions, the bed heat flux displays a nonuniform time dependence. In order to characterize this shallow bed regime, it was necessary to develop a detailed transient model of the coolant-debris interaction. This model, while developed for the shallow bed regime, also applies to the deep bed regime. Numerical computations clearly demonstrate the importance of developing a general reliable model for the solid-fluid heat transfer coefficients

  12. Fluid-bed process for SYNROC production

    International Nuclear Information System (INIS)

    Ackerman, F.J.; Grens, J.Z.; Ryerson, F.J.; Hoenig, C.L.; Bazan, F.; Peters, P.E.; Smith, R.; Campbell, J.H.

    1983-01-01

    SYNROC is a titanate-based ceramic waste developed for the immobilization of high-level nuclear reactor waste. Lawrence Livermore National Laboratory (LLNL) has investigated a fluid-bed technique for the large-scale production of SYNROC precursor powders. Making SYNROC in a fluid bed permits slurry drying, calcination and reduction-oxidation reactions to be carried out in a single unit. We present the results of SYNROC fluid-bed studies from two fluid-bed units 10 cm in diameter: an internally heated fluid-bed unit developed by Exxon Idaho and an externally heated unit constructed at LLNL. Bed operation over a range of temperatures, feed rates, fluidizing rates, and redox conditions indicate that SYNROC powders of a high density and a uniform particle size can be produced. These powders facilitate the densification step and yield dense ceramics (greater than 95% theoretical density) with well-developed phases and low leaching rates

  13. Fluidized-bed calciner with combustion nozzle and shroud

    International Nuclear Information System (INIS)

    Wielang, J.A.; Palmer, W.B.; Kerr, W.B.

    1977-01-01

    A nozzle employed as a burner within a fluidized bed is coaxially enclosed within a tubular shroud that extends beyond the nozzle length into the fluidized bed. The open-ended shroud portion beyond the nozzle end provides an antechamber for mixture and combustion of atomized fuel with an oxygen-containing gas. The arrangement provides improved combustion efficiency and excludes bed particles from the high-velocity, high-temperature portions of the flame to reduce particle attrition. 4 claims, 2 figures

  14. Advanced control system for temperature control in the pressurized fluid bed of Escatron Thermal Plant Power; Sistema de Control Avanzado para Control de la Temperatura del Lecho Fluido a Presion de la Central Termica de Escatron

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-07-01

    In the P. F-B. C a small problem appears, particularly in Escatron the bed temperature gradient is very high. Such gradient very occasionally reaches 50 degree centigree in a same plane. With the reduction of bed difference of temperature, the average bed temperature could be increased with the result steam cycle benefit, at the same time combustion gases would go at a higher temperature to the gas turbine, increasing therefore its performance. The SCAP system will allow to face the resolution of the injection of combustible problem and in this manner achieve the homogenization of bed temperature in Escatron PFBC Thermal Power Station. (Author)

  15. Random detailed model for probabilistic neutronic calculation in pebble bed Very High Temperature Reactors

    International Nuclear Information System (INIS)

    Perez Curbelo, J.; Rosales, J.; Garcia, L.; Garcia, C.; Brayner, C.

    2013-01-01

    The pebble bed nuclear reactor is one of the main candidates for the next generation of nuclear power plants. In pebble bed type HTRs, the fuel is contained within graphite pebbles in the form of TRISO particles, which form a randomly packed bed inside a graphite-walled cylindrical cavity. Pebble bed reactors (PBR) offer the opportunity to meet the sustainability requirements, such as nuclear safety, economic competitiveness, proliferation resistance and a minimal production of radioactive waste. In order to simulate PBRs correctly, the double heterogeneity of the system must be considered. It consists on randomly located pebbles into the core and TRISO particles into the fuel pebbles. These features are often neglected due to the difficulty to model with MCPN code. The main reason is that there is a limited number of cells and surfaces to be defined. In this study, a computational tool which allows getting a new geometrical model of fuel pebbles for neutronic calculations with MCNPX code, was developed. The heterogeneity of system is considered, and also the randomly located TRISO particles inside the pebble. Four proposed fuel pebble models were compared regarding their effective multiplication factor and energy liberation profiles. Such models are: Homogeneous Pebble, Five Zone Homogeneous Pebble, Detailed Geometry, and Randomly Detailed Geometry. (Author)

  16. Endurance and failure of an alumina-based monopropellant microthruster with integrated heater, catalytic bed and temperature sensors

    Science.gov (United States)

    Khaji, Zahra; Klintberg, Lena; Barbade, Dhananjay; Palmer, Kristoffer; Thornell, Greger

    2017-05-01

    Monopropellant ceramic microthrusters with an integrated heater, catalytic bed and two temperature sensors, but of various designs, were manufactured by milling a fluidic channel and chamber, and a nozzle, and screen printing platinum patterns on green tapes of alumina that were stacked and laminated before sintering. In order to increase the surface area of the catalytic bed, the platinum paste was mixed with a sacrificial paste that disappeared during sintering, to leave behind a porous and rough layer. As an early development level in manufacturing robust and high-temperature tolerant microthrusters, the influence of design on the temperature gradients and dry temperature tolerance of the devices was studied. On average, the small reaction chambers showed a more than 1.5 times higher dry temperature tolerance (in centigrade) compared to devices with larger chambers, independent of the heater and device size. However, for a given temperature, big devices consumed on average 2.9 times more power than the small ones. It was also found that over the same area and under the same heating conditions, devices with small chambers were subjected to approximately 40% smaller temperature differences. A pressure test done on two small devices with small chambers revealed that pressures of at least 26.3 bar could be tolerated. Above this pressure, the interfaces failed but the devices were not damaged. To investigate the cooling effect of the micropropellant, the endurance of a full thruster was also studied under wet testing where it was fed with 31 wt.% hydrogen peroxide. The thruster demonstrated complete evaporation and/or full decomposition at a power above 3.7 W for a propellant flow of 50 µl min-1. At this power, the catalytic bed locally reached a temperature of 147 °C. The component was successfully heated to an operating temperature of 307 °C, where it cracked. Under these firing conditions, and assuming complete decomposition, calculations give a thrust and

  17. Effect of bed configuration on pebble flow uniformity and stagnation in the pebble bed reactor

    International Nuclear Information System (INIS)

    Gui, Nan; Yang, Xingtuan; Tu, Jiyuan; Jiang, Shengyao

    2014-01-01

    Highlights: • Pebble flow uniformity and stagnation characteristics are very important for HTR-PM. • Arc- and brachistochrone-shaped configuration effects are studied by DEM simulation. • Best bed configurations with uniform flow and no stagnated pebbles are suggested. • Detailed quantified characteristics of bed configuration effects are shown for explanation. - Abstract: Pebble flow uniformity and stagnation characteristics are very important for the design of pebble bed high temperature gas-cooled reactor. Pebble flows inside some specifically designed contraction configurations of pebble bed are studied by discrete element method. The results show the characteristics of stagnation rates, recycling rates, radial distribution of pebble velocity and residence time. It is demonstrated clearly that the bed with a brachistochrone-shaped configuration achieves optimum levels of flow uniformity and recycling rate concentration, and almost no pebbles are stagnated in the bed. Moreover, the optimum choice among the arc-shaped bed configurations is demonstrated too. Detailed information shows the quantified characteristics of bed configuration effects on flow uniformity. In addition, a good design of the pebble bed configuration is suggested

  18. Carbon Bed Mercury Emissions Control For Mixed Waste Treatment

    International Nuclear Information System (INIS)

    Soelberg, Nick; Enneking, Joe

    2010-01-01

    Mercury has had various uses in nuclear fuel reprocessing and other nuclear processes, and so is often present in radioactive and mixed (both radioactive and hazardous according to the Resource Conservation and Recovery Act) wastes. Depending on regulatory requirements, the mercury in the off-gas must be controlled with sometimes very high efficiencies. Compliance to the Hazardous Waste Combustor (HWC) Maximum Achievable Control Technology (MACT) standards can require off-gas mercury removal efficiencies up to 99.999% for thermally treating some mixed waste streams. Several test programs have demonstrated this level of off-gas mercury control using fixed beds of granular sulfur-impregnated activated carbon. Other results of these tests include: (a) The depth of the mercury control mass transfer zone was less than 15-30 cm for the operating conditions of these tests, (b) MERSORB(reg s ign) carbon can sorb Hg up to 19 wt% of the carbon mass, and (c) the spent carbon retained almost all (98-99.99%) of the Hg; but when even a small fraction of the total Hg dissolves, the spent carbon can fail the TCLP test when the spent carbon contains high Hg concentrations. Localized areas in a carbon bed that become heated through heat of adsorption, to temperatures where oxidation occurs, are referred to as 'bed hot spots.' Carbon bed hot spots must be avoided in processes that treat radioactive and mixed waste. Key to carbon bed hot spot mitigation are (a) designing for sufficient gas velocity, for avoiding gas flow maldistribution, and for sufficient but not excessive bed depth, (b) monitoring and control of inlet gas flowrate, temperature, and composition, (c) monitoring and control of in-bed and bed outlet gas temperatures, and (d) most important, monitoring of bed outlet CO concentrations. An increase of CO levels in the off-gas downstream of the carbon bed to levels about 50-100 ppm higher than the inlet CO concentration indicate CO formation in the bed, caused by carbon bed

  19. High-Temperature Thermal Energy Storage for electrification and district heating

    DEFF Research Database (Denmark)

    Pedersen, A. Schrøder; Engelbrecht, K.; Soprani, S.

    stability upon thermal cycling. The most promising material consists of basalt, diabase, and magnetite, whereas the less suited rocks contain larger proportions of quartz and mica. An HT-TES system, containing 1.5 m3 of rock pieces, was constructed. The rock bed was heated to 600 ˚C using an electric heater......The present work describes development of a High Temperature Thermal Energy Storage (HT-TES) system based on rock bed technology. A selection of rocks was investigated by thermal analysis in the range 20-800 ˚C. Subsequently, a shortlist was defined primarily based on mechanical and chemical...... to simulate thermal charging from wind energy. After complete heating of the rock bed it was left fully charged for hours to simulate actual storage conditions. Subsequently the bed discharging was performed by leading cold air through the rock bed whereby the air was heated and led to an exhaust. The results...

  20. Experimental studies on the coolability of packed beds. Flooding of hot dry packed beds

    International Nuclear Information System (INIS)

    Leininger, S.; Kulenovic, R.; Laurien, E.

    2013-01-01

    In case of a severe accident in a nuclear power plant meltdown of the reactor core can occur and form a packed bed in the lower plenum of the reactor pressure vessel (RPV) after solidification due to contact with water. The removal of after-heat and the long-term coolability is of essential interest. The efficient injection of cooling water into the packed bed has to be assured without endangering the structural integrity of the reactor pressure vessel. The experiments performed aimed to study the dry-out and the quenching (flooding) of hot dry packed beds. Two different inflow variants, bottom- and top-flooding including the variation of the starting temperature of the packed bed and the injection rate were studied. In case of bottom flooding the quenching time increases with increasing packed bed temperature and decreasing injection rate. In case of top flooding the flow pattern is more complex, in a first phase the water flows preferentially toward the RPV wall, the flow paths conduct the water downwards. The flow resistance of the packed bed increases with increasing bed temperatures. The quenching temperatures increase significantly above average.

  1. Low-temperature gasification of waste tire in a fluidized bed

    International Nuclear Information System (INIS)

    Xiao Gang; Ni Mingjiang; Chi Yong; Cen Kefa

    2008-01-01

    In order to recovery energy and materials from waste tire efficiently, low-temperature gasification is proposed. Experiments are carried out in a lab-scale fluidized bed at 400-800 deg. C when equivalence ratio (ER) is 0.2-0.6. Low heat value (LHV) of syngas increases with increasing temperature or decreasing ER, and the yield is in proportion to ER linearly. The yield of carbon black decreases with increasing temperature or ER lightly. When temperature is over 600 deg. C, characteristics of carbon black is similar. When temperature is over 700 deg. C, LHV of syngas rises up lightly with increasing temperature, which indicates that it hardly facilitates gasification any more. It is suitable for tire gasification when temperature is 650-700 deg. C and ER is 0.2-0.4. Under this condition, LHV and yield of syngas are about 4000-9000 kJ/Nm 3 and 1.8-3.7 Nm 3 /kg, respectively; surface area and yield of carbon black lie in range of 20-30 m 3 /g and 550-650 g/kg, respectively. The carbon balance of these experiments achieves 85-95% when temperature is over 600 deg. C

  2. High Temperature Particle Filtration Technology; TOPICAL

    International Nuclear Information System (INIS)

    Besmann, T.M.

    2001-01-01

    High temperature filtration can serve to improve the economic, environmental, and energy performance of chemical processes. This project was designed to evaluate the stability of filtration materials in the environments of the production of dimethyldichlorosilane (DDS). In cooperation with Dow Corning, chemical environments for the fluidized bed reactor where silicon is converted to DDS and the incinerator where vents are cornbusted were characterized. At Oak Ridge National Laboratory (ORNL) an exposure system was developed that could simulate these two environments. Filter samples obtained from third parties were exposed to the environments for periods up to 1000 hours. Mechanical properties before and after exposure were determined by burst-testing rings of filter material. The results indicated that several types of filter materials would likely perform well in the fluid bed environment, and two materials would be good candidates for the incinerator environment

  3. Tests of Bed Agglomeration Tendency Using a Rotating Furnace; Roterugn foer bedoemning av sintringsbenaegenhet

    Energy Technology Data Exchange (ETDEWEB)

    Larfeldt, Jenny; Zintl, Frank [TPS Termiska Processer AB, Nykoeping (Sweden)

    2003-08-01

    Bed sintering is a well known problem in fluidised bed boilers. In order to avoid bed sintering the bed material turn over ratio is high which leads a high consumption of bed material. This work aims at developing and evaluating a method for testing the bed agglomeration tendency of a FB bed material by using a rotating furnace. A rotating furnace has been designed and tests have shown that three temperatures describing the increasing agglomeration tendency can be evaluated; TA when several particles stick to each other and to the crucible wall, TB when half of the material sticks to the wall and TC when almost all the material forms a ball in the crucible. Comparison with bed agglomeration tests has shown that TA is between 80 deg C to 130 deg C lower than the bed agglomeration temperature from fluid bed tests. It is shown that TB is closer to the bed agglomeration temperature and finally that the temperature TC is higher than the bed agglomeration temperature. It is concluded that in the rotating furnace sticking of particles is visualised early, and that this sticking will not cause defluidisation of the bed until more than half of the material in the crucible is sticky. Repeated tests has been performed at a heating rate of 5 deg/minute and a rotating speed of 12 rpm and a furnace inclination of 20 deg was found to give distinct results in the evaluation. The evaluation has shown to be reproducible at lower temperatures. At higher temperatures, around 1,000 deg C, the evaluation was complicated by a poor picture quality which probably can be improved by proper cooling of the camera. It has also been shown that sticking of material in the rotating furnace could be detected at relatively low temperatures of 750 deg C that disappeared at higher temperatures. This is likely to be explained by melting salts that evaporates as temperature increase. At even higher temperatures the sticking reappeared until a ball was formed in the crucible. The latter sticking is

  4. Method of Heating a Foam-Based Catalyst Bed

    Science.gov (United States)

    Fortini, Arthur J.; Williams, Brian E.; McNeal, Shawn R.

    2009-01-01

    A method of heating a foam-based catalyst bed has been developed using silicon carbide as the catalyst support due to its readily accessible, high surface area that is oxidation-resistant and is electrically conductive. The foam support may be resistively heated by passing an electric current through it. This allows the catalyst bed to be heated directly, requiring less power to reach the desired temperature more quickly. Designed for heterogeneous catalysis, the method can be used by the petrochemical, chemical processing, and power-generating industries, as well as automotive catalytic converters. Catalyst beds must be heated to a light-off temperature before they catalyze the desired reactions. This typically is done by heating the assembly that contains the catalyst bed, which results in much of the power being wasted and/or lost to the surrounding environment. The catalyst bed is heated indirectly, thus requiring excessive power. With the electrically heated catalyst bed, virtually all of the power is used to heat the support, and only a small fraction is lost to the surroundings. Although the light-off temperature of most catalysts is only a few hundred degrees Celsius, the electrically heated foam is able to achieve temperatures of 1,200 C. Lower temperatures are achievable by supplying less electrical power to the foam. Furthermore, because of the foam s open-cell structure, the catalyst can be applied either directly to the foam ligaments or in the form of a catalyst- containing washcoat. This innovation would be very useful for heterogeneous catalysis where elevated temperatures are needed to drive the reaction.

  5. High flux Particle Bed Reactor systems for rapid transmutation of actinides and long lived fission products

    International Nuclear Information System (INIS)

    Powell, J.; Ludewig, H.; Maise, G.; Steinberg, M.; Todosow, M.

    1993-01-01

    An initial assessment of several actinide/LLFP burner concepts based on the Particle Bed Reactor (PBR) is described. The high power density/flux level achievable with the PBR make it an attractive candidate for this application. The PBR based actinide burner concept also possesses a number of safety and economic benefits relative to other reactor based transmutation approaches including a low inventory of radionuclides, and high integrity, coated fuel particles which can withstand extremely high in temperatures while retaining virtually all fission products. In addition the reactor also posesses a number of ''engineered safety features,'' which, along with the use of high temperature capable materials further enhance its safety characteristics

  6. Gas distributor for fluidized bed coal gasifier

    Science.gov (United States)

    Worley, Arthur C.; Zboray, James A.

    1980-01-01

    A gas distributor for distributing high temperature reaction gases to a fluidized bed of coal particles in a coal gasification process. The distributor includes a pipe with a refractory reinforced lining and a plurality of openings in the lining through which gas is fed into the bed. These feed openings have an expanding tapered shape in the downstream or exhaust direction which aids in reducing the velocity of the gas jets as they enter the bed.

  7. Addition of Bacillus sp. inoculums in bedding for swine on a pilot scale: effect on microbial population and bedding temperature.

    Science.gov (United States)

    Corrêa, E K; Ulguim, R R; Corrêa, L B; Castilhos, D D; Bianchi, I; Gil-Turnes, C; Lucia, T

    2012-10-01

    Thermal and microbiological characteristics of beddings for swine were compared according to their depth and of addition of inoculums. Bedding was added to boxes at 0.25 (25D) and 0.50 m (50D), with three treatments: control (no inoculums); T1, with 250 g of Bacillus cereus var. toyoii at 8.4 × 10(7) CFU; and T2, with 250 g of a pool of B. subtilis, Bacillus licheniformis and Bacillus polymyxa at 8.4 × 10(7) CFU (250 g for 25D and 500 g for 50D). Mean temperatures were 28.5 ± 3.9 at the surface and 35.2 ± 8.9 inside the beddings. The most probable number (MPN) of thermophilic bacteria was higher for T1 and T2 than for the control (P<0.05). The MPN of thermophilic bacteria and fungi was greater for D50 than for D25 (P<0.05). The use of 25D without inoculums is recommended due to the reduction of thermophilic microbiota. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Synthesis and crystal structure of lithium beryllium deuteride Li2BeD4.

    Science.gov (United States)

    Bulychev, Boris M; Shpanchenko, Roman V; Antipov, Evgeny V; Sheptyakov, Denis V; Bushmeleva, Svetlana N; Balagurov, Anatoly M

    2004-10-04

    Single-phase ternary deuteride Li(2)BeD(4) was synthesized by a high-pressure high-temperature technique from LiD and BeD(2). The crystal structure of Li(2)BeD(4) was solved from X-ray and neutron powder diffraction data. The compound crystallizes in the monoclinic space group P2(1)/c with lattice parameters a = 7.06228(9) A, b = 8.3378(1) A, c = 8.3465(1) A, beta =93.577(1) degrees, and Z = 8. Its structure contains isolated BeD(4) tetrahedra and Li atoms that are located in the structure interstices. Li(2)BeD(4) does not undergo any structural phase transitions at temperatures down to 8 K.

  9. Bed-To-Wall Heat Transfer in a Supercritical Circulating Fluidised Bed Boiler

    Directory of Open Access Journals (Sweden)

    Błaszczuk Artur

    2014-06-01

    Full Text Available The purpose of this work is to find a correlation for heat transfer to walls in a 1296 t/h supercritical circulating fluidised bed (CFB boiler. The effect of bed-to-wall heat transfer coefficient in a long active heat transfer surface was discussed, excluding the radiation component. Experiments for four different unit loads (i.e. 100% MCR, 80% MCR, 60% MCR and 40% MCR were conducted at a constant excess air ratio and high level of bed pressure (ca. 6 kPa in each test run. The empirical correlation of the heat transfer coefficient in a large-scale CFB boiler was mainly determined by two key operating parameters, suspension density and bed temperature. Furthermore, data processing was used in order to develop empirical correlation ranges between 3.05 to 5.35 m·s-1 for gas superficial velocity, 0.25 to 0.51 for the ratio of the secondary to the primary air, 1028 to 1137K for bed temperature inside the furnace chamber of a commercial CFB boiler, and 1.20 to 553 kg·m-3 for suspension density. The suspension density was specified on the base of pressure measurements inside the boiler’s combustion chamber using pressure sensors. Pressure measurements were collected at the measuring ports situated on the front wall of the combustion chamber. The obtained correlation of the heat transfer coefficient is in agreement with the data obtained from typical industrial CFB boilers.

  10. Characteristic behaviour of Pebble Bed High Temperature Gas-cooled Reactors during water ingress events

    International Nuclear Information System (INIS)

    Khoza, Samukelisiwe N.; Serfontein, Dawid E.; Reitsma, Frederik

    2014-01-01

    The presence of water on the tube-side of the steam generators in high temperature gas-cooled reactors (HTGRs) with indirect cycle layouts presents a possibility for a penetration of neutron moderating steam into the core, which may cause a power excursion. This article presents results on the effect of water ingress into the core of the two South African Pebble Bed Modular Reactor design concepts, i.e. the PBMR-200 MW th and the PBMR-400 MW th developed by PBMR SOC Ltd. The VSOP 99/05 suite of codes was used for the simulation of this event. Partial steam vapour pressures were added in stages into the primary circuit in order to investigate the effect of water ingress on reactivity, power profiles and thermal neutron flux profiles. The effects of water ingress into the core are explained by increased neutron moderation, due to the addition of 1 H, which leads to a decrease in resonance capture by 238 U and therefore an increase in the multiplication factor. The more effective moderation of neutrons by definition reduces the fast neutron flux and increases the thermal flux in the core, i.e. leads to a softer spectrum. The more effective moderation also increases the average increase in lethargy between collisions of a neutron with successive fuel kernels, which reduces the probability for neutron capture in the radiative capture resonances of 238 U. The resulting higher resonance escape probability also increases the thermal flux in the core. The softening of the neutron spectrum leads to an increased effective microscopic fission cross section in the fissile isotopes and thus to increased neutron absorption for fission, which reduces the remaining number of neutrons that can diffuse into the reflectors. Therefore water ingress into the core leads to a reduced thermal neutron flux in the reflectors. The power density spatial distribution behaved similarly to the thermal neutron flux in the core. Analysis of possible mechanisms was conducted. The results show that

  11. METHOD OF CALCULATION OF THE NON-STATIONARY TEMPERATURE FIELD INSIDE OF THERMAL PACKED BED ENERGY STORAGE

    Directory of Open Access Journals (Sweden)

    Ermuratschii V.V.

    2014-04-01

    Full Text Available e paper presents a method of the approximate calculation of the non-stationary temperature field inside of thermal packed bed energy storages with feasible and latent heat. Applying thermoelectric models and computational methods in electrical engineering, the task of computing non-stationary heat transfer is resolved with respect to third type boundary conditions without applying differential equations of the heat transfer. For sub-volumes of the energy storage the method is executed iteratively in spatiotemporal domain. Single-body heating is modeled for each sub-volume, and modeling conditions are assumed to be identical for remained bod-ies, located in the same sub-volume. For each iteration step the boundary conditions will be represented by re-sults at the previous step. The fulfillment of the first law of thermodynamics for system “energy storage - body” is obtained by the iterative search of the mean temperature of the energy storage. Under variable boundary con-ditions the proposed method maybe applied to calculating temperature field inside of energy storages with packed beds consisted of solid material, liquid and phase-change material. The method may also be employed to compute transient, power and performance characteristics of packed bed energy storages.

  12. Computational and experimental prediction of dust production in pebble bed reactors, Part II

    Energy Technology Data Exchange (ETDEWEB)

    Mie Hiruta; Gannon Johnson; Maziar Rostamian; Gabriel P. Potirniche; Abderrafi M. Ougouag; Massimo Bertino; Louis Franzel; Akira Tokuhiro

    2013-10-01

    This paper is the continuation of Part I, which describes the high temperature and high pressure helium environment wear tests of graphite–graphite in frictional contact. In the present work, it has been attempted to simulate a Pebble Bed Reactor core environment as compared to Part I. The experimental apparatus, which is a custom-designed tribometer, is capable of performing wear tests at PBR relevant higher temperatures and pressures under a helium environment. This environment facilitates prediction of wear mass loss of graphite as dust particulates from the pebble bed. The experimental results of high temperature helium environment are used to anticipate the amount of wear mass produced in a pebble bed nuclear reactor.

  13. Modeling of river bed deformation composed of frozen sediments with increasing environmental temperature

    Directory of Open Access Journals (Sweden)

    E. I. Debolskaya

    2013-01-01

    Full Text Available This paper is devoted to investigation of the influence of river flow and of the temperature rise on the deformation of the coastal slopes composed of permafrost with the inclusion of ice layer. The method of investigation is the laboratory and mathematical modeling. The laboratory experiments have shown that an increase in water and air temperature changes in a laboratory analogue of permafrost causes deformation of the channel even without wave action, i.e. at steady-state flow and non-erosive water flow velocity. The previously developed model of the bed deformation was improved to account for long-term changes of soil structure with increasing temperature. The three-dimensional mathematical model of coastal slopes thermoerosion of the rivers flowing in permafrost regions, and its verification was based on the results of laboratory experiments conducted in the hydraulic tray. Analysis of the results of mathematical and laboratory modeling showed that bed deformation of the rivers flowing in the permafrost zone, significantly different from the deformation of channels composed of soils not susceptible to the influence of the phase transition «water-ice», and can occur even under the non-erosive velocity of the water flow.

  14. Fluidized-bed nuclear reactor

    International Nuclear Information System (INIS)

    Grimmett, E.S.; Kunze, J.F.

    1975-01-01

    A reactor vessel containing a fluidized-bed region of particulate material including both a neutron-moderating and a fertile substance is described. A gas flow including fissile material passes through the vessel at a sufficient rate to fluidize the particulate material and at a sufficient density to support a thermal fission reaction within the fluidized-bed region. The high-temperature portion of a heat transfer system is located within the fluidized-bed region of the reactor vessel in direct contact with the fluidized particles. Heat released by fission is thereby transferred at an enhanced rate to a coolant circulating within the heat transfer system. Fission products are continuously removed from the gas flow and supplemental fissile material added during the reactor operation. (U.S.)

  15. SYNROC production using a fluid bed calciner

    International Nuclear Information System (INIS)

    Ackerman, F.J.; Grens, J.Z.; Ryerson, F.J.; Hoenig, C.L.; Bazan, F.; Campbell, J.H.

    1982-01-01

    SYNROC is a titanate-based ceramic developed for immobilization of high-level nuclear reactor wastes in solid form. Fluid-bed SYNROC production permits slurry drying, calcining and redox to be carried out in a single unit. We present results of studies from two fluid beds; the Idaho Exxon internally-heated unit and the externally-heated unit constructed at Lawrence Livermore National laboratory. Bed operation over a range of temperature, feed rate, fluidizing rate and redox conditions indicate that high density, uniform particle-size SYNROC powders are produced which facilitate the densification step and give HUP parts with dense, well-developed phases and good leaching characteristics. 3 figures, 3 tables

  16. Fluidized-bed calcination of simulated commercial high-level radioactive wastes

    International Nuclear Information System (INIS)

    Freeby, W.A.

    1975-11-01

    Work is in progress at the Idaho Chemical Processing Plant to verify process flowsheets for converting simulated commercial high-level liquid wastes to granular solids using the fluidized-bed calcination process. Primary emphasis in the series of runs reported was to define flowsheets for calcining simulated Allied-General Nuclear Services (AGNS) waste and to evaluate product properties significant to calcination, solids storage, or post treatment. Pilot-plant studies using simulated high-level acid wastes representative of those to be produced by Nuclear Fuel Services, Inc. (NFS) are also included. Combined AGNS high-level and intermediate-level waste (0.26 M Na in blend) was successfully calcined when powdered iron was added (to result in a Na/Fe mole ratio of 1.0) to the feed to prevent particle agglomeration due to sodium nitrate. Long-term runs (approximately 100 hours) showed that calcination of the combined waste is practical. Concentrated AGNS waste containing sodium at concentrations less than 0.2 M were calcined successfully; concentrated waste containing 1.13 M Na calcined successfully when powdered iron was added to the feed to suppress sodium nitrate formation. Calcination of dilute AGNS waste by conventional fluid-bed techniques was unsuccessful due to the inability to control bed particle size--both particle size and bed level decreased. Fluid-bed solidification of AGNS dilute waste at conditions in which most of the calcined solids left the calciner vessel with the off-gas was successful. In such a concept, the steady-state composition of the bed material would be approximately 22 wt percent calcined solids deposited on inert particles. Calcination of simulated NFS acid waste indicated that solidification by the fluid-bed process is feasible

  17. A scaled experimental study of control blade insertion dynamics in Pebble-Bed Fluoride-Salt-Cooled High-Temperature Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Buster, Grant C., E-mail: grant.buster@gmail.com; Laufer, Michael R.; Peterson, Per F.

    2016-07-15

    Highlights: • A granular dynamics scaling methodology is discussed. • Control blade insertion in a representative pebble-bed core is experimentally studied. • Control blade insertion forces and pebble displacements are experimentally measured. • X-ray tomography techniques are used to observe pebble displacement distributions. - Abstract: Direct control element insertion into a pebble-bed reactor core is proposed as a viable control system in molten-salt-cooled pebble-bed reactors. Unlike helium-cooled pebble-bed reactors, this reactor type uses spherical fuel elements with near-neutral buoyancy in the molten-salt coolant, thus reducing contact forces on the fuel elements. This study uses the X-ray Pebble Bed Recirculation Experiment facility to measure the force required to insert a control element directly into a scaled pebble-bed. The required control element insertion force, and therefore the contact force on fuel elements, is measured to be well below recommended limits. Additionally, X-ray tomography is used to observe how the direct insertion of a control element physically displaces spherical fuel elements. The tomography results further support the viability of direct control element insertion into molten-salt-cooled pebble-bed reactor cores.

  18. Evaluation of a clay-based acidic bedding conditioner for dairy cattle bedding.

    Science.gov (United States)

    Proietto, R L; Hinckley, L S; Fox, L K; Andrew, S M

    2013-02-01

    This study investigated the effects of a clay-based acidic bedding conditioner on sawdust bedding pH, dry matter (DM), environmental pathogen counts, and environmental bacterial counts on teat ends of lactating dairy cows. Sixteen lactating Holstein cows were paired based on parity, days in milk, milk yield, and milk somatic cell count, and were negative for the presence of an intramammary pathogen. Within each pair, cows were randomly assigned to 1 of 2 treatments with 3-wk periods in a crossover design. Treatment groups consisted of 9 freestalls per group bedded with either untreated sawdust or sawdust with a clay-based acidic bedding conditioner, added at 3- to 4-d intervals over each 21-d period. Bedding and teat ends were aseptically sampled on d 0, 1, 2, 7, 14, and 21 for determination of environmental bacterial counts. At the same time points, bedding was sampled for DM and pH determination. The bacteria identified in the bedding material were total gram-negative bacteria, Streptococcus spp., and coliform bacteria. The bacteria identified on the teat ends were Streptococcus spp., coliform bacteria, and Klebsiella spp. Teat end score, milk somatic cell count, and intramammary pathogen presence were measured weekly. Bedding and teat cleanliness, environmental high and low temperatures, and dew point data were collected daily. The bedding conditioner reduced the pH, but not the DM, of the sawdust bedding compared with untreated sawdust. Overall environmental bacterial counts in bedding were lower for treated sawdust. Total bacterial counts in bedding and on teat ends increased with time over both periods. Compared with untreated sawdust, the treated bedding had lower counts of total gram-negative bacteria and streptococci, but not coliform counts. Teat end bacterial counts were lower for cows bedded on treated sawdust for streptococci, coliforms, and Klebsiella spp. compared with cows bedded on untreated sawdust. The clay-based acidic bedding conditioner

  19. High temperature thermal energy storage in moving sand

    Science.gov (United States)

    Turner, R. H.; Awaya, H. I.

    1978-01-01

    Several high-temperature (to 500 C) heat-storage systems using sand as the storage medium are described. The advantages of sand as a storage medium include low cost for sand, widespread availability, non-toxicity, non-degradation characteristics, easy containment, and safety. The systems considered include: stationary sand with closely spaced tubes throughout the volume, the use of a fluidized bed, use of conveyor belt transporter, and the use of a blower rapid transport system. For a stationary sand bed, very close spacing of heat transfer tubes throughout the volume is required, manifesting as high power related system cost. The suggestion of moving sand past or around pipes is intended to reduce the power related costs at the penalty of added system complexity. Preliminary system cost estimates are offered. These rough calculations indicate that mobile sand heat storage systems cost less than the stationary sand approach.

  20. The influence of thorium on the temperature reactivity coefficient in a 400 MWth pebble bed high temperature plutonium incinerating reactor

    International Nuclear Information System (INIS)

    Richards, Guy A.; Serfontein, Dawid E.

    2014-01-01

    This article investigates advanced fuel cycles containing thorium and reactor grade plutonium (Pu(PWR)) in a 400 MW th Pebble Bed Modular Reactor (PBMR) Demonstration Power Plant. Results presented were determined from coupled neutronics and thermo-hydraulic simulations of the VSOP 99/05 diffusion codes. In a previous study impressive burn-ups (601 MWd/kg heavy metal (HM)) and thus plutonium destruction rates (69.2 %) were obtained with pure plutonium fuel with mass loadings of 3 g Pu(PWR)/fuel sphere or less. However the safety performance was poor in that the limit on the maximum fuel temperature during equilibrium operation was exceeded and positive Uniform Temperature Reactivity Coefficients (UTCs) were obtained. In the present study fuel cycles containing mixtures of thorium and plutonium achieved negative maximum UTCs. Plutonium only fuel cycles also achieved negative maximum UTCs, provided that much higher mass loadings are used. It is proposed that the lower thermal neutron flux was responsible for this effect. The plutonium only fuel cycle with 12 g Pu(PWR)/fuel sphere also achieved the adopted safety limits for the PBMR DPP-400 in that the maximum fuel temperature and the maximum power density did not exceed 1130°C or 4.5 kW/sphere respectively. This design would thus be licensable and could potentially be economically feasible. However the burn-up was much lower at 181 MWd/kgHM and thus the plutonium destruction fraction was also much lower at 24.5%, which may be sub-optimal with respect to proliferation and waste disposal objectives and therefore further optimisation studies are proposed. (author)

  1. Tritium measurement technique using ''in-bed'' calorimetry

    International Nuclear Information System (INIS)

    Klein, J.E.; Mallory, M.K.; Nobile, A. Jr.

    1991-01-01

    One of the new technologies that has been introduced to the Savannah River Site (SRS) is the production scale use of metal hydride technology to store, pump, and compress hydrogen isotopes. For tritium stored in metal hydride storage beds, a unique relationship does not exist between the amount of tritium in the bed and the pressure-volume-temperature properties of the hydride material. Determining the amount of tritium in a hydride bed after desorbing the contents of the bed to a tank and performing pressure, volume, temperature, and composition (PVTC) measurements is not practical due to long desorption/absorption times and the inability to remove tritium ''heels'' from the metal hydride materials under normal processing conditions. To eliminate the need to remove tritium from hydride storage beds for measurement purposes, and ''in-bed'' tritium calorimetric measurement technique has been developed. The steady-state temperature rise of a gas stream flowing through a jacketed metal hydride storage bed is measured and correlated with power input to electric heaters used to simulate the radiolytic power generated by the decay of tritium to 3 He. Temperature rise results for prototype metal hydride storage beds and the effects of using different gases in the bed are shown. Linear regression results shows that for 95% confidence intervals, temperature rise measurements can be obtained in 14 hours and have an accuracy of ±1.6% of a tritium filled hydride storage bed

  2. Rock bed heat accumulators. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Riaz, M.

    1977-12-01

    The principal objectives of the research program on rock bed heat accumulators (or RBHA) are: (1) to investigate the technical and economic feasibility of storing large amounts of thermal energy (in the tens of MWt range) at high temperature (up to 500/sup 0/C) over extended periods of time (up to 6 months) using native earth or rock materials; (2) to conduct studies to establish the performance characteristics of large rock bed heat accumulators at various power and temperature levels compatible with thermal conversion systems; and (3) to assess the materials and environmental problems associated with the operation of such large heat accumulators. Results of the study indicate that rock bed heat accumulators for seasonal storage are both technically and economically feasible, and hence could be exploited in various applications in which storage plays an essential role such as solar power and total energy systems, district and cogeneration heating systems.

  3. Methodology of the On-Iine FoIIow Simulation of Pebble-bed High-temperature Reactors

    International Nuclear Information System (INIS)

    Xia Bing; Li Fu; Wei Chunlin; Zheng Yanhua; Chen Fubing; Zhang Jian; Guo Jiong

    2014-01-01

    The on-line fuel management is an essential feature of the pebble-bed high-temperature reactors (PB-HTRs), which is strongly coupled with the normal operation of the reactor. For the purpose of on-line analysis of the continuous shuffling scheme of numerous fuel pebbles, the follow simulation upon the real operation is necessary for the PB-HTRs. In this work, the on-line follow simulation methodology of the PB-HTRs’ operation is described, featured by the parallel treatments of both neutronics analysis and fuel cycling simulation. During the simulation, the operation history of the reactor is divided into a series of burn-up cycles according to the behavior of operation data, in which the steady-state neutron transport equations are solved and the diffusion theory is utilized to determine the physical features of the reactor core. The burn-up equations of heavy metals, fission products and neutron poisons including B-10, decoupled from the pebble flow term, are solved to analyze the burn-up process within a single burn-up cycle. The effect of pebble flow is simulated separately through a discrete fuel shuffling pattern confined by curved pebble flow channels, and the effect of multiple pass of the fuel is represented by logical batches within each spatial region of the core. The on-line thermal-hydraulics feedback is implemented for each bur-up cycle by using the real thermal-hydraulics data of the core operation. The treatment of control rods and absorber balls is carried out by utilizing a coupled neutron transport-diffusion calculation along with discontinuity factors. The physical models mentioned above are established mainly by using a revised version of the V.S.O.P program system. The real operation data of HTR-10 is utilized to verify the methodology presented in this work, which gives good agreement between simulation results and operation data. (author)

  4. Fluidized bed gasification of high tonnage sorghum, cotton gin trash and beef cattle manure: Evaluation of synthesis gas production

    International Nuclear Information System (INIS)

    Maglinao, Amado L.; Capareda, Sergio C.; Nam, Hyungseok

    2015-01-01

    Highlights: • High tonnage sorghum, cotton gin trash and beef cattle manure were characterized and gasified in a fluidized bed reactor. • Biomass gasification at 730 °C and ER = 0.35 produced synthesis gas with an average energy content of 4.19 MJ Nm −3 . • Synthesis gas heating value and yield were relatively constant at reaction temperatures from 730 °C to 800 °C. • Optimum hydrogen production on HTS gasification was achieved at 780 °C temperature and ER of 0.4. - Abstract: Fluidized bed gasification using high-tonnage sorghum, cotton gin trash and beef cattle manure was performed in a pilot scale bubbling fluidized bed reactor equipped with the necessary feedback control system. Characterization of biomass showed that the high-tonnage sorghum had the highest energy and carbon content of 19.58 MJ kg −1 and 42.29% wt , respectively among the three feed stocks. At 730 °C reaction temperature and equivalence ratio of 0.35, comparable yields of methane, nitrogen and carbon dioxide (within ± 1.4% vol ) were observed in all three feed stocks. The gasification system produced synthesis gas with an average heating value of 4.19 ± 0.09 MJ Nm −3 and an average yield of 1.98 ± 0.1 Nm 3 kg −1 of biomass. Carbon conversion and gasification efficiencies indicated that most of the carbon was converted to gaseous products (85% average ) while 48% average of the energy from the biomass was converted into combustible gas. The production of hydrogen was significantly affected by the biomass used during gasification. The synthesis gas heating value and yield were relatively constant at reaction temperatures from 730 °C to 800 °C. Utilizing high-tonnage sorghum, the optimum hydrogen production during gasification was achieved at a reaction temperature of 780 °C and an equivalence ratio of 0.40.

  5. Biomass oxygen/steam gasification in a pressurized bubbling fluidized bed: Agglomeration behavior

    International Nuclear Information System (INIS)

    Zhou, Chunguang; Rosén, Christer; Engvall, Klas

    2016-01-01

    Highlights: • Dolomite is a superior material in preventing bed agglomeration. • Small molten ash particles deposited on magnesite at bed temperatures above 1000 °C. • The performance, when using magnesite, is sensitive to temperature disturbances. • The anti-agglomeration mechanisms of Ca- and Mg-bearing materials were discussed. - Abstract: In this study, the anti-agglomeration abilities of Ca- and Mg-containing bed materials, including dolomite and magnesite, in a pressurized bubbling fluidized bed gasifier using pine pellets and birch chips as feedstock, is investigated. The most typical bed material—silica sand—was also included as a reference for comparison. The sustainability of the operation was evaluated via analyzing the temperatures at different levels along the bed height. During the performances, the aim was to keep the temperature at the bottom zone of the reactor at around 870 °C. However, the success highly depends on the bed materials used in the bed and the temperature can vary significantly in case of agglomeration or bad mixing of bed materials and char particles. Both Glanshammar and Sala dolomites performed well with no observed agglomeration tendencies. In case of magnesite, the bed exhibited a high agglomeration tendency. Silica sand displayed the most severe agglomeration among all bed materials, even when birch chips with a low silica content was fed at a relatively low temperature. The solid samples of all the bed materials were inspected by light microscopy and Scanning Electron Microscopy (SEM). The Energy Dispersive Spectroscopy (EDS) detector was used to detect the elemental distribution in the surface. The crystal chemical structure was analyzed using X-ray Diffraction (XRD). Magnesite agglomerates glued together by big molten ash particles. There was no coating layer detected on magnesite particles at bed temperatures – below 870 °C. But when the temperature was above 1000 °C, a significant amount of small molten

  6. Development of high temperature gas cooled reactor in China

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Wentao [Paul Scherrer Institute, Villigen (Switzerland). Dept. of Nuclear Energy and Safety; Schorer, Michael [Swiss Nuclear Forum, Olten (Switzerland)

    2018-02-15

    High temperature gas cooled reactor (HTGR) is one of the six Generation IV reactor types put forward by Generation IV International Forum (GIF) in 2002. This type of reactor has high outlet temperature. It uses Helium as coolant and graphite as moderator. Pebble fuel and ceramic reactor core are adopted. Inherit safety, good economy, high generating efficiency are the advantages of HTGR. According to the comprehensive evaluation from the international nuclear community, HTGR has already been given the priority to the research and development for commercial use. A demonstration project of the High Temperature Reactor-Pebble-�bed Modules (HTR-PM) in Shidao Bay nuclear power plant in China is under construction. In this paper, the development history of HTGR in China and the current situation of HTR-PM will be introduced. The experiences from China may be taken as a reference by the international nuclear community.

  7. Thermohydraulic modeling of very high temperature reactors in regimes with loss of coolant using CFD

    Energy Technology Data Exchange (ETDEWEB)

    Moreira, Uebert G.; Dominguez, Dany S. [Universidade Estadual de Santa Cruz (UESC), Ilh´eus, BA (Brazil). Programa de P´os-Graduacao em Modelagem Computacional em Ciencia e Tecnologia; Mazaira, Leorlen Y.R.; Lira, Carlos A.B.O. [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear; Hernandez, Carlos R.G., E-mail: uebert.gmoreira@gmail.com, E-mail: dsdominguez@gmail.com, E-mail: leored1984@gmail.com, E-mail: cabol@ufpe.br, E-mail: cgh@instec.cu [Instituto Superior de Tecnologas y Ciencias Aplicadas (InSTEC), La Habana (Cuba)

    2017-07-01

    The nuclear energy is a good alternative to meet the continuous increase in world energy demand. In this perspective, VHTRs (Very High Temperature Reactors) are serious candidates for energy generation due to its inherently safe performance, low power density and high conversion efficiency. However, the viability of these reactors depends on an efficient safety system in the operation of nuclear plants. The HTR (High Temperature Reactor)-10 model, an experimental reactor of the pebble bed type, is used as a case study in this work to perform the thermohydraulic simulation. Due to the complex patterns flow that appear in the pebble bed reactor core, and advances in computational capacity, CFD (Computational Fluid Dynamics) techniques are used to simulate these reactors. A realistic approach is adopted to simulate the central annular column of the reactor core, which each pebble bed element is modeled in detail. As geometrical model of the fuel elements was selected the BCC (Body Centered Cubic) arrangement. Previous works indicate this arrangement as the configuration that obtain higher fuel temperatures inside the core. Parameters considered for reactor design are available in the technical report of benchmark issues by IAEA (TECDOC-1694). Among the results obtained, we obtained the temperature profiles with different mass flow rates for the coolant. In general, the temperature distributions calculated are consistent with phenomenological behaviour. Even without consider the reactivity changes to reduce the reactor power or other safety procedures, the maximum temperatures do not exceed the recommended limits for fuel elements. (author)

  8. Thermohydraulic modeling of very high temperature reactors in regimes with loss of coolant using CFD

    International Nuclear Information System (INIS)

    Moreira, Uebert G.; Dominguez, Dany S.

    2017-01-01

    The nuclear energy is a good alternative to meet the continuous increase in world energy demand. In this perspective, VHTRs (Very High Temperature Reactors) are serious candidates for energy generation due to its inherently safe performance, low power density and high conversion efficiency. However, the viability of these reactors depends on an efficient safety system in the operation of nuclear plants. The HTR (High Temperature Reactor)-10 model, an experimental reactor of the pebble bed type, is used as a case study in this work to perform the thermohydraulic simulation. Due to the complex patterns flow that appear in the pebble bed reactor core, and advances in computational capacity, CFD (Computational Fluid Dynamics) techniques are used to simulate these reactors. A realistic approach is adopted to simulate the central annular column of the reactor core, which each pebble bed element is modeled in detail. As geometrical model of the fuel elements was selected the BCC (Body Centered Cubic) arrangement. Previous works indicate this arrangement as the configuration that obtain higher fuel temperatures inside the core. Parameters considered for reactor design are available in the technical report of benchmark issues by IAEA (TECDOC-1694). Among the results obtained, we obtained the temperature profiles with different mass flow rates for the coolant. In general, the temperature distributions calculated are consistent with phenomenological behaviour. Even without consider the reactivity changes to reduce the reactor power or other safety procedures, the maximum temperatures do not exceed the recommended limits for fuel elements. (author)

  9. Experimental study of flow field characteristics on bed configurations in the pebble bed reactor

    International Nuclear Information System (INIS)

    Jia, Xinlong; Gui, Nan; Yang, Xingtuan; Tu, Jiyuan; Jia, Haijun; Jiang, Shengyao

    2017-01-01

    Highlights: • PTV study of flow fields of pebble bed reactor with different configurations are carried out. • Some criteria are proposed to quantify vertical velocity field and flow uniformity. • The effect of different pebble bed configurations is also compared by the proposed criteria. • The displacement thickness is used analogically to analyze flow field characteristics. • The effect of mass flow variation in the stagnated region of the funnel flow is measured. - Abstract: The flow field characteristics are of fundamental importance in the design work of the pebble bed high temperature gas cooled reactor (HTGR). The different effects of bed configurations on the flow characteristics of pebble bed are studied through the PTV (Particle Tracking Velocimetry) experiment. Some criteria, e.g. flow uniformity (σ) and mass flow level (α), are proposed to estimate vertical velocity field and compare the bed configurations. The distribution of the Δθ (angle difference between the individual particle velocity and the velocity vector sum of all particles) is also used to estimate the resultant motion consistency level. Moreover, for each bed configuration, the thickness of displacement is analyzed to measure the effect of the funnel flow zone based on the boundary layer theory. Detailed information shows the quantified characteristics of bed configuration effects on flow uniformity and other characteristics; and the sequence of levels of each estimation criterion is obtained for all bed configurations. In addition, a good design of the pebble bed configuration is suggested and these estimation criteria can be also applied and adopted in testing other geometry designs of pebble bed.

  10. Semi-dry flue gas desulfurization using Ca(OH)2 in a fluidized bed reactor with bed materials

    International Nuclear Information System (INIS)

    Park, Young Oak; Roh, Hak Jae; Oh, Chang Sup; Kim, Yong Ha

    2010-01-01

    The main objective of present work is to reduce sulfur dioxide emission from power plant for the environment protection. The fluidized bed (FB) was used as the reactor with bed materials in a new semi-dry flue gas desulfurization (FGD) process to achieve high desulfurization efficiency (>98%). Fine powder of Ca(OH) 2 as sorbent and water were continuously fed separately to the bed reactor where bed materials (2 mm glass beads) were fluidized vigorously with flue gas (flow 720 Nm 3 / hr) using bench scale plant of stainless steel column. We have investigated different effects of water injection flow rate, Ca/ S molar ratio and weight of bed materials on SO 2 removal. The increments in the Ca/ S molar ratio and water injection flow rate have been resulted higher desulfurization efficiency with certain disadvantages such as higher sorbent cost and lower temperature of the treated flue gas, respectively. (author)

  11. Parametric study for high conversion pebble bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Teuchert, E.; Ruetten, H. J.

    1975-06-15

    Tables are presented of fuel cycle costs, conversion ratios and accompanying variations in fuel element designs for a 3,00 MWth high conversion pebble bed reactor with initial high enriched uranium/thorium cycle and subsequent recycling of U-233, Pu-239 and Pu-241.

  12. Fluidised bed cereal cooking

    International Nuclear Information System (INIS)

    Jenkins, Simon Anthony

    2002-01-01

    Man has been cooking food for thousands of years for a number of reasons: to improve flavour and palatability, sterilise, increase digestibility, improve texture and colour. Increasingly more advanced techniques are employed today in food production plants to engineer foods with many different properties. With this in mind manufacturers are constantly seeking to improve processing techniques and apply new or different technologies (such as microwaves, RF and extrusion) to develop foods with new properties (like puffed texture starches) and to increase process efficiencies (energy efficiency, water reduction). This thesis reports on work undertaken to demonstrate the potential to achieve high temperature starch conversion of whole wheat grains in a fluidised bed, thereby reducing the amount of water required and processing time. Specifically, wheat from the farm at 14% water content is cooked in a fluidised bed. The fluidised bed heats the wheat quickly by convective heating. In addition, energy can be delivered directly to the grain by microwave heating during fluidisation. Degree of starch conversion is determined by measuring the reduction in size of endotherm of reaction as observed by Differential Scanning Calorimetry. The fluidising gas, processing temperature and starting moisture content were varied in order to investigate their effect on the cooking process. A mathematical model based on energy and species concentration equations was developed to help understand the internal grain processes. The model coupled the thermal energy equation with water diffusion. The effect of water evaporation was represented as a thermal sink in the energy equation. Popular kinetic models from literature were adapted to predict the degree of starch conversion. The model gives solutions consistent with experimental data and physical intuition. A commercial computational fluid dynamics package was used to study simple airflow and particle tracks in the fluidisation column. A

  13. Gas cleaning with hot char beds studied by stable isotopes

    DEFF Research Database (Denmark)

    Egsgaard, Helge; Ahrenfeldt, Jesper; Ambus, Per

    2014-01-01

    The chemistry taking place in a high temperature char bed used for binding aromatic tar compounds has been studied in detail. 13C labelled tar compounds were used to trace the incorporation into the char bed using isotope ratio mass spectrometry (IRMS) and GC-MS. Furthermore, compounds labelled...

  14. Temperature prediction in a coal fired boiler with a fixed bed by fuzzy logic based on numerical solution

    International Nuclear Information System (INIS)

    Biyikoglu, A.; Akcayol, M.A.; Oezdemir, V.; Sivrioglu, M.

    2005-01-01

    In this study, steady state combustion in boilers with a fixed bed has been investigated. Temperature distributions in the combustion chamber of a coal fired boiler with a fixed bed are predicted using fuzzy logic based on data obtained from the numerical solution method for various coal and air feeding rates. The numerical solution method and the discretization of the governing equations of two dimensional turbulent flow in the combustion chamber and one dimensional coal combustion in the fixed bed are explained. Control Volume and Finite Difference Methods are used in the discretization of the equations in the combustion chamber and in the fixed bed, respectively. Results are presented as contours within the solution domain and compared with numerical ones. Comparison of the results shows that the difference between the numerical solution and fuzzy logic prediction throughout the computational domain is less than 1.5%. The statistical coefficient of multiple determinations for the investigated cases is about 0.9993 to 0.9998. This accuracy degree is acceptable in predicting the temperature values. So, it can be concluded that fuzzy logic provides a feasible method for defining the system properties

  15. An SEM/EDX study of bed agglomerates formed during fluidized bed combustion of three biomass fuels

    International Nuclear Information System (INIS)

    Scala, Fabrizio; Chirone, Riccardo

    2008-01-01

    The agglomeration behaviour of three biomass fuels (exhausted and virgin olive husk and pine seed shells) during fluidized bed combustion in a lab-scale reactor was studied by means of SEM/EDX analysis of bed agglomerate samples. The effect of the fuel ash composition, bed temperature and sand particle size on agglomeration was investigated. The study was focused on the main fuel ash components and on their interaction with the bed sand particles. Agglomeration was favoured by high temperature, small sand size, a high fraction of K and Na and a low fraction of Ca and Mg in the fuel ash. An initial fuel ash composition close to the low-melting point eutectic composition appears to enhance agglomeration. The agglomerates examined by SEM showed a hollow structure, with an internal region enriched in K and Na where extensive melting is evident and an external one where sand particles are only attached by a limited number of fused necks. Non-molten or partially molten ash structures deposited on the sand surface and enriched in Ca and Mg were also observed. These results support an ash deposition-melting mechanism: the ash released by burning char particles inside the agglomerates is quantitatively deposited on the sand surface and then gradually embedded in the melt. The low-melting point compounds in the ash migrate towards the sand surface enriching the outermost layer, while the ash structure is progressively depleted of these compounds

  16. User's manual for ASTERIX-2: A two-dimensional modular code system for the steady state and xenon transient analysis of a pebble bed high temperature reactor

    International Nuclear Information System (INIS)

    Wu, T.; Cowan, C.L.; Lauer, A.; Schwiegk, H.J.

    1982-03-01

    The ASTERIX modular code package was developed at KFA Laboratory-Juelich for the steady state and xenon transient analysis of a pebble bed high temperature reactor. The code package was implemented on the Stanford Linear Accelerator Center Computer in August, 1980, and a user's manual for the current version of the code, identified as ASTERIX-2, was prepared as a cooperative effort by KFA Laboratory and GE-ARSD. The material in the manual includes the requirements for accessing the program, a description of the major subroutines, a listing of the input options, and a listing of the input data for a sample problem. The material is provided in sufficient detail for the user to carry out a wide range of analysis from steady state operations to the xenon induced power transients in which the local xenon, temperature, buckling and control feedback effects have been incorporated in the problem solution. (orig.)

  17. User's manual for ASTERIX-2: a two-dimensional modular-code system for the steady-state and xenon-transient analysis of a pebble-bed high-temperature reactor

    International Nuclear Information System (INIS)

    Lauer, A.; Schwiegk, H.J.; Wu, T.; Cowan, C.L.

    1982-03-01

    The ASTERIX modular code package was developed at KFA Laboratory-Juelich for the steady state and xenon transient analysis of a pebble bed high temperature reactor. The code package was implemented on the Stanford Linear Accelerator Center Computer in August, 1980, and a user's manual for the current version of the code, identified as ASTERIX-2, was prepared as a cooperative effort by KFA Laboratory and GE-ARSD. The material in the manual includes the requirements for accessing the program, a description of the major subroutines, a listing of the input options, and a listing of the input data for a sample problem. The material is provided in sufficient detail for the user to carry out a wide range of analyses from steady state operations to the xenon induced power transients in which the local xenon, temperature, buckling and control feedback effects have been incorporated in the problem solution

  18. Bed agglomeration in fluidized combustor fueled by wood and rice straw blends

    DEFF Research Database (Denmark)

    Thy, Peter; Jenkins, Brian; Williams, R.B.

    2010-01-01

    Abstract Petrographic techniques have been used to examine bed materials from fluidized bed combustion experiments that utilized wood and rice straw fuel blends. The experiments were conducted using a laboratory-scale combustor with mullite sand beds, firing temperatures of 840 to 1030 °C, and run...... areas between bed particles, ultimately led to bed agglomeration. The interfaces and the presence of gas bubbles in the cement suggest a bonding material with a high surface tension and a liquid state. The cement films originate by filling of irregularities on individual and partially agglomerated bed...

  19. Material Control and Accounting Design Considerations for High-Temperature Gas Reactors

    International Nuclear Information System (INIS)

    Bjornard, Trond; Hockert, John

    2011-01-01

    The subject of this report is domestic safeguards and security by design (2SBD) for high-temperature gas reactors, focusing on material control and accountability (MC and A). The motivation for the report is to provide 2SBD support to the Next Generation Nuclear Plant (NGNP) project, which was launched by Congress in 2005. This introductory section will provide some background on the NGNP project and an overview of the 2SBD concept. The remaining chapters focus specifically on design aspects of the candidate high-temperature gas reactors (HTGRs) relevant to MC and A, Nuclear Regulatory Commission (NRC) requirements, and proposed MC and A approaches for the two major HTGR reactor types: pebble bed and prismatic. Of the prismatic type, two candidates are under consideration: (1) GA's GT-MHR (Gas Turbine-Modular Helium Reactor), and (2) the Modular High-Temperature Reactor (M-HTR), a derivative of Areva's Antares reactor. The future of the pebble-bed modular reactor (PBMR) for NGNP is uncertain, as the PBMR consortium partners (Westinghouse, PBMR (Pty) and The Shaw Group) were unable to agree on the path forward for NGNP during 2010. However, during the technology assessment of the conceptual design phase (Phase 1) of the NGNP project, AREVA provided design information and technology assessment of their pebble bed fueled plant design called the HTR-Module concept. AREVA does not intend to pursue this design for NGNP, preferring instead a modular reactor based on the prismatic Antares concept. Since MC and A relevant design information is available for both pebble concepts, the pebble-bed HTGRs considered in this report are: (1) Westinghouse PBMR; and (2) AREVA HTR-Module. The DOE Office of Nuclear Energy (DOE-NE) sponsors the Fuel Cycle Research and Development program (FCR and D), which contains an element specifically focused on the domestic (or state) aspects of SBD. This Material Protection, Control and Accountancy Technology (MPACT) program supports the present

  20. Two stage, low temperature, catalyzed fluidized bed incineration with in situ neutralization for radioactive mixed wastes

    International Nuclear Information System (INIS)

    Wade, J.F.; Williams, P.M.

    1995-01-01

    A two stage, low temperature, catalyzed fluidized bed incineration process is proving successful at incinerating hazardous wastes containing nuclear material. The process operates at 550 degrees C and 650 degrees C in its two stages. Acid gas neutralization takes place in situ using sodium carbonate as a sorbent in the first stage bed. The feed material to the incinerator is hazardous waste-as defined by the Resource Conservation and Recovery Act-mixed with radioactive materials. The radioactive materials are plutonium, uranium, and americium that are byproducts of nuclear weapons production. Despite its low temperature operation, this system successfully destroyed poly-chlorinated biphenyls at a 99.99992% destruction and removal efficiency. Radionuclides and volatile heavy metals leave the fluidized beds and enter the air pollution control system in minimal amounts. Recently collected modeling and experimental data show the process minimizes dioxin and furan production. The report also discusses air pollution, ash solidification, and other data collected from pilot- and demonstration-scale testing. The testing took place at Rocky Flats Environmental Technology Site, a US Department of Energy facility, in the 1970s, 1980s, and 1990s

  1. HTR-2002: Proceedings of the conference on high temperature reactors

    International Nuclear Information System (INIS)

    2002-01-01

    High temperature reactors are considered as future inherently safe and efficient energy sources. The presentations covered all the relevant aspects of the existing HTGRs and/or helium cooled pebble bed reactors. They were sorted into 7 sessions: HTR Projects and Programmes; Fuel and Fuel Cycle; Physics and Neutronics; Thermohydraulic Calculation; Engineering, Design and Applications; Materials and Components; Safety and Licensing

  2. Effect of heat bed temperature of 3D bioprinter to hardness and compressive strength of scaffold bovine hydroxyapatite

    Science.gov (United States)

    Triyono, Joko; Pratama, Aditya; Sukanto, Heru; Nugroho, Yohanes; Wijayanta, Agung Tri

    2018-02-01

    This study aimed to investigate the effect of heat bed temperature of 3D bioprinter toward compressive strength and hardness bovine bone hydroxyapatite scaffold for bone filler applications. BHA-glycerin mixed with a ratio of 1:1, and keep it for 24 hours. After the homogenization process acquired, bio-Ink with shaped slurry will be used as a material for a 3D printer. The printing process with a temperature variation have performed by setting up heat bed temperature. After printing process was completed, the 3D scaffold was detained on the heat bed for 10 minutes before being picked up. The test results in this study had the lowest hardness value of 9.82±0.62 VHN and the highest number of 24.32±0.99 VHN. The compressive strength testing had the lowest value of 1.62±0.16 MPa with the highest number of 5.67±0.39 MPa. Pore observation using a scanning electron microscope. The result shows that the size of the pores were not much different, that was ±100-200 µm. This observation also indicated that the pore form was square pores.

  3. DEVELOPMENT OF DISPOSABLE SORBENTS FOR CHLORIDE REMOVAL FROM HIGH TEMPERATURE COAL-DERIVED GASES

    Energy Technology Data Exchange (ETDEWEB)

    Gopala Krishnan; Raghubir Gupta

    1999-09-01

    Advanced integrated-gasification combined-cycle (IGCC) and integrated-gasification fuel cell (IGFC) systems require the development of high temperature sorbents for the removal of hydrogen chloride (HCl) vapor to less than 1 parts-per-million (ppm) levels. HCl is a highly reactive, corrosive, and toxic gas which must be removed to meet environmental regulations, to protect power generation equipment, and to minimize deterioration of hot gas desulfurization sorbents. The objective of this program was to develop disposable, alkali-based sorbents capable of reducing HCl vapor levels to less than 1 ppm in the temperature range from 400 to 750 C and pressures in the range from 1 to 20 atm. The primary areas of focus of this program were to investigate different methods of sorbent fabrication, testing their suitability for different reactor configurations, obtaining reaction kinetics data, and conducting a preliminary economic feasibility assessment. This program was a joint effort between SRI International (SRI), Research Triangle Institute (RTI), and General Electric Corporate Research and Development (GE-CRD). SRI, the prime contractor and RTI, a major subcontractor, performed most of the work in this program. Thermochemical calculations indicated that sodium-based sorbents were capable of reducing HCl vapor levels to less than 1 ppm at temperatures up to 650 C, but the regeneration of spent sorbents would require complex process steps. Nahcolite (NaHCO{sub 3}), a naturally-occurring mineral, could be used as an inexpensive sorbent to remove HCl vapor in hot coal gas streams. In the current program, nahcolite powder was used to fabricate pellets suitable for fixed-bed reactors and granules suitable for fluidized-bed reactors. Pilot-scale equipment were used to prepare sorbents in large batches: pellets by disk pelletization and extrusion techniques, and granules by granulation and spray-drying techniques. Bench-scale fixed- and fluidized-bed reactors were assembled at

  4. Water and sediment temperatures at mussel beds in the upper Mississippi River basin

    Science.gov (United States)

    Newton, Teresa J.; Sauer, Jennifer; Karns, Byron

    2013-01-01

    Native freshwater mussels are in global decline and urgently need protection and conservation. Declines in the abundance and diversity of North American mussels have been attributed to human activities that cause pollution, waterquality degradation, and habitat destruction. Recent studies suggest that effects of climate change may also endanger native mussel assemblages, as many mussel species are living close to their upper thermal tolerances. Adult and juvenile mussels spend a large fraction of their lives burrowed into sediments of rivers and lakes. Our objective was to measure surface water and sediment temperatures at known mussel beds in the Upper Mississippi (UMR) and St. Croix (SCR) rivers to estimate the potential for sediments to serve as thermal refugia. Across four mussel beds in the UMR and SCR, surface waters were generally warmer than sediments in summer, and were cooler than sediments in winter. This suggests that sediments may act as a thermal buffer for mussels in these large rivers. Although the magnitude of this effect was usually cause mortality in laboratory studies. These data suggest that elevated water temperatures resulting from global warming, thermal discharges, water extraction, and/or droughts have the potential to adversely affect native mussel assemblages.

  5. Heat exchangers for high-temperature thermodynamic cycles

    International Nuclear Information System (INIS)

    Fraas, A.P.

    1975-01-01

    The special requirements of heat exchangers for high temperature thermodynamic cycles are outlined and discussed with particular emphasis on cost and thermal stress problems. Typical approaches that have been taken to a comprehensive solution intended to meet all of the many boundary conditions are then considered by examining seven typical designs including liquid-to-liquid heat exchangers for nuclear plants, a heater for a closed cycle gas turbine coupled to a fluidized bed coal combustion chamber, steam generators for nuclear plants, a fossil fuel-fired potassium boiler, and a potassium condenser-steam generator. (auth)

  6. Gas Turbine High Temperature Gas (Helium) Reactor Using Pebble Bed Fuel Derived from Spent Fuel

    International Nuclear Information System (INIS)

    Cole, Quentin

    2013-01-01

    Project goals: Build on the $1B investment spent during the NGNP Project for the only true Inherently Safe Small Modular Reactor Design – the only SMR design that can make this claim due to negative temperature coefficient of reactivity - no containment required – less construction cost. NPMC in Partnership with Pebble Bed Modular Group, a fully owned subsidiary of Eskom, RSA to Factory Build Complete Plant in Modular Sections at Factory Site in Oswego, NY for transport to site by rail or shipping for world wide export. NPMC will provide Project and Construction Management of all new builds from plant sites through construction, commissioning and startup using local labor. License and Construct ion of spent fuel processing facility in both NY and South Africa using Proven Technology. Ultimate goals of project: 1. Award of the 2013 US DOE Innovative SMR $452M cost share grant for US NRC License Certification 2.Build Full Scale Demonstration Plant at Koeburg, RSA with World Bank Funding managed by NPMC in collaboration with our legal firm, Haynes and Boone LLP 3. Take Plant Orders Immediately (10% Down Payment) 4. Form Strategic Alliance with Domestic and/or International Utility

  7. The influence of temperature on limestone sulfation and attrition under fluidized bed combustion conditions

    Energy Technology Data Exchange (ETDEWEB)

    Montagnaro, Fabio [Dipartimento di Chimica - Universita degli Studi di Napoli Federico II, Complesso Universitario del Monte di Sant' Angelo, 80126 Napoli (Italy); Salatino, Piero [Istituto di Ricerche sulla Combustione - CNR, Piazzale Vincenzo Tecchio 80, 80125 Napoli (Italy); Dipartimento di Ingegneria Chimica - Universita degli Studi di Napoli Federico II, Piazzale Vincenzo Tecchio 80, 80125 Napoli (Italy); Scala, Fabrizio [Istituto di Ricerche sulla Combustione - CNR, Piazzale Vincenzo Tecchio 80, 80125 Napoli (Italy)

    2010-04-15

    The influence of temperature on attrition of two limestones during desulfurization in a fluidized bed reactor was investigated. Differences in the microstructure of the two limestones were reflected by a different thickness of the sulfate shell formed upon sulfation and by a different value of the ultimate calcium conversion degree. Particle attrition and fragmentation were fairly small under moderately bubbling fluidization conditions for both limestones. An increase of temperature from 850 C to 900 C led to an increase of the attrition rate, most likely because of a particle weakening effect caused by a faster CO{sub 2} evolution during calcination. This weakening effect, however, was not sufficiently strong to enhance particle fragmentation in the bed. The progress of sulfation, associated to the build-up of a hard sulfate shell around the particles, led in any case to a decrease of the extent of attrition. Sulfation at 900 C was less effective than at 850 C, and this was shown to be related to the porosimetric features of the different samples. (author)

  8. Experimental study of gas combustion fluidized bed and radiation contribution to heat transfer inside the bed. Gas nensho ryudoso to sono sonai netsudentatsu ni okeru fukusha no kiyo ni tsuite no jikkenteki kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Y; Takahashi, S [Mechanical Engineering Lab., Tsukuba, Ibaraki (Japan); Maki, H [Science Univ. of Tokyo, Noda, Chiba (Japan). Faculty of Science and Technology

    1992-11-25

    Fluidized bed as a coal combustion boiler has a practical application, but, there is not an example of which gas like helium as a cooling medium flow in a thin tube with diameter of 6 mm like a stirling engine and necessary data for selecting the medium of fluidized bed and estimating the heat transfer coefficient. Specially, it is difficult to correctly estimate the radiation effect concerned with the heat transfer coefficient in case of interposing the heat transfer tube at 800 [degree]C in the high-temperature fluidized bed at more than 900 [degree]C. Therefore, for investigating the thermal characteristics when the temperature of pipe itself is at high temperature, in the gas combustion fluidized bed in which alumina particle as fluidized medium is filled, the cooling tubes by using carbonic acid gas as a cooling medium was interposed, heat transfer coefficient was measured, radiation effect was clarified by experiment, and characteristics of the gas combustion and of the exhaust gas of fluidized bed when gas is used for a fuel was investigated. 13 refs., 12 figs., 1 tab.

  9. Thermal conductivity and diffusivity of Permian Basin bedded salt at elevated pressure and temperature

    International Nuclear Information System (INIS)

    Durham, W.B.; Boro, C.O.; Beiriger, J.M.; Montan, D.N.

    1983-10-01

    Measurements of thermal conductivity and diffusivity were made on five core samples of bedded rock salt from the Permian Basin in Texas to determine its suitability as an underground nuclear waste repository. The sample size was 100 mm in diameter by 250 mm in length. Measurements were conducted under confining pressures ranging from 3.8 to 31.0 MPa and temperatures from room temperature to 473 K. Conductivity showed no dependence on confining pressure but evidenced a monotonic, negative temperature dependence. Four of the five samples showed conductivities clustered in a range of 5.6 +- 0.5 W/m.K at room temperature, falling to 3.6 +- 0.3 W/m.K at 473 K. These values are approximately 20% below those for pure halite, reflecting perhaps the 5 to 20%-nonhalite component of the samples. Diffusivity also showed a monotonic, negative temperature dependence, with four of the five samples clustered in a range of 2.7 +- 0.4 x 10 -6 m 2 /s at room temperature, and 1.5 +- 0.3 x 10 -6 m 2 /s at 473 K, all roughly 33% below the values for pure halite. One sample showed an unusually high conductivity (it also had the highest diffusivity), about 20% higher than the others; and one sample showed an unusually low diffusivity (it also had the lowest conductivity), roughly a factor of 2 lower than the others. 27 references, 8 figures, 4 tables

  10. Bed retained products in swept fixed bed (SFB) coal hydropyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Mastral, A.M.; Perez-Surio, M.J. [CSIC, Zaragosa (Spain). Inst. de Carboquimica

    1997-12-31

    The hydropyrolysis of a low rank coal in a swept fixed bed (SFB) reactor is carried out by fixing the hydrogen pressure (40 kg/cm{sup 2}), the hydrogen flow (2 l/min) and the residence time (10 min) at increasing temperatures (400 C, 500 C and 600 C) and coal bed heights (h, 1.5h, 2h, 2.5h and 3h). It is shown that the percentages of tars and char directly depend on the coal bed height and that there is not only a quantitative dependence, but also the height of the coal bed is very important and plays a relevant role on the nature of the conversion products. (orig.)

  11. Experimental study on coolability of particulate core-metal debris bed with oxidization, (2). Fragmentation and enhanced heat transfer in zircaloy debris bed

    International Nuclear Information System (INIS)

    Su, Guanghui; Sugiyama, Ken-ichiro; Aoki, Hiroomi; Kimura, Iichi

    2006-01-01

    The oxidization and coolability characteristics of the particulate Zircaloy debris bed, which is deposited under the hard debris and through which first vapor penetrates and then water penetrates, are studied in the present paper. In the vapor penetration experiments, it is found that Zircaloy debris particles are effectively broken into small pieces after making thick oxidized layer with deep clacks by rapid oxidization under the condition that vapor with 20 cm/s penetrates for 30 to 70 min at an initial debris bed temperature of 1,030degC. It is also confirmed in the water penetration experiments that the oxidized particle debris bed has potentially of high coolability when water penetrates through the fully oxidized particle bed because of a high capillary force originating from those particles with deep cracks on their surfaces. Based on the present study, a new scenario for the appearance and disappearance of the hot spot in the TMI-2 accident is possible. The particulate core-metal core-metal debris bed is first heated up by rapid oxidization with heat generation when vapor can penetrate through the debris bed with porosities. This corresponds to the appearance of the hot spot. The resultant oxidized particulate debris bed causes a high coolability due to its high capillary force when the water can touch the debris bed at wet condition. This corresponds to the disappearance of the hot spot. (author)

  12. Evolution of Particle Bed Reactor Fuel

    Science.gov (United States)

    Jensen, Russell R.; Evans, Robert S.; Husser, Dewayne L.; Kerr, John M.

    1994-07-01

    To realize the potential performance advantages inherent in a particle bed reactor (PBR) for nuclear thermal propulsion (NTP) applications, high performance particle fuel is required. This fuel must operate safely and without failure at high temperature in high pressure, flowing hydrogen propellant. The mixed mean outlet temperature of the propellant is an important characteristic of PBR performance. This temperature is also a critical parameter for fuel particle design because it dictates the required maximum fuel operating temperature. In this paper, the evolution in PBR fuel form to achieve higher operating temperatures is discussed and the potential thermal performance of the different fuel types is evaluated. It is shown that the optimum fuel type for operation under the demanding conditions in a PBR is a coated, solid carbide particle.

  13. CFD Analysis of the Fuel Temperature in High Temperature Gas-Cooled Reactors

    International Nuclear Information System (INIS)

    In, W. K.; Chun, T. H.; Lee, W. J.; Chang, J. H.

    2005-01-01

    High temperature gas-cooled reactors (HTGR) have received a renewed interest as potential sources for future energy needs, particularly for a hydrogen production. Among the HTGRs, the pebble bed reactor (PBR) and a prismatic modular reactor (PMR) are considered as the nuclear heat source in Korea's nuclear hydrogen development and demonstration project. PBR uses coated fuel particles embedded in spherical graphite fuel pebbles. The fuel pebbles flow down through the core during an operation. PMR uses graphite fuel blocks which contain cylindrical fuel compacts consisting of the fuel particles. The fuel blocks also contain coolant passages and locations for absorber and control material. The maximum fuel temperature in the core hot spot is one of the important design parameters for both PBR and PMR. The objective of this study is to predict the fuel temperature distributions in PBR and PMR using a computational fluid dynamics(CFD) code, CFX-5. The reference reactor designs used in this analysis are PBMR400 and GT-MHR600

  14. The high-temperature reactor

    International Nuclear Information System (INIS)

    Kirchner, U.

    1991-01-01

    The book deals with the development of the German high-temperature reactor (pebble-bed), the design of a prototype plant and its (at least provisional) shut-down in 1989. While there is a lot of material on the HTR's competitor, the fast breeder, literature is very incomplete on HTRs. The author describes HTR's history as a development which was characterised by structural divergencies but not effectively steered and monitored. There was no project-oriented 'community' such as there was for the fast breeder. Also, the new technology was difficult to control there were situations where no one quite knew what was going on. The technical conditions however were not taken as facts but as a basis for interpretation, wishes and reservations. The HTR gives an opportunity to consider the conditions under which large technical projects can be carried out today. (orig.) [de

  15. The importance of the AVR pebble-bed reactor for the future of nuclear power

    International Nuclear Information System (INIS)

    Pohl, P.

    2006-01-01

    The AVR pebble-bed high temperature gas-cooled reactor (HTGR) at Juelich (Germany)) operated from 1967 to 1988 and was certainly the most important HTGR project of the past. The reactor was the mass test bed for all development steps of HTGR pebble fuel. Some early fuel charges failed under high temperature conditions and contaminated the reactor. An accurate pebble measurement (Cs 137) allowed to clean the core from unwanted pebbles after 1981. The coolant activity went down and remained very low for the remaining reactor operation. A melt-wire experiment in 1986 revealed max. coolant temperatures of >1280 deg. C and fuel temperatures of >1350 deg. C, explained by under-estimated bypasses. The fuel still in the core achieved high burn-ups and showed under the extreme temperature conditions excellent fission product retention. Thus, the AVR operation qualified the HTGR fuel, and an average discharge burn-up of 112% fifa revealed an excellent fuel economy of the pebble-bed reactor. Furthermore, the AVR operation offers many meaningful data for code-to-experiment comparisons. (authors)

  16. The thermal denigration in fluid-bed to make uranyl product

    International Nuclear Information System (INIS)

    Ma Zhenrong; Cui Yulin; Zhu Changbing; Fan Chuanyong; Liu Yanfeng

    2010-01-01

    Nuclear fuel reprocessing plant used the thermal denigration to high concentration of uranyl nitrate solution in fluid-bed to make uranyl product. First the uranyl nitrate solution were concentrated in evaporator, into 300 gU/L, 600 gU/L, 750 gU/L and 1000 gU/L.When the fluid-bed was in good fluidity state at 320 degree C, the solution was sprayed all over the surface of the fine crystal seeds through the dual-channel air-blast nozzles to make new crystal seed and to make them grow up. The denigration reaction occurred when the internal temperature of the fluid-bed was kept at about 300 degree C by the outside and inside heat apparatus. The product were transported crossing the valve and spiral transfer to pack. The tail gas was purified and discharged. Through the fluid-bed's running, the variation discipline of temperature and the pressure, the effect curve of the quality of product accumulated to pressure drop were determined. At the same time, the gentrification temperature, the distributed heat and the transfer mode were tested. (authors)

  17. Development of the fluidized bed thermal treatment process for treating mixed waste

    International Nuclear Information System (INIS)

    Semones, G.B.; Williams, P.M.; Stiefvater, S.P.; Mitchell, D.L.; Roecker, B.D.

    1993-01-01

    A fluidized bed system is being developed at Rocky Flats for the treatment of mixed waste (a mixture of radioactive and chemically hazardous waste). The current program builds on experience gained in the 1970's and 1980's in tests with bench-scale, pilot-scale, and demonstration-scale fluidized bed systems. The system operates at low temperatures (∼ 525--600 degree C) which eliminates many of the disadvantages associated with high temperature thermal treatment processes. The process has shown the ability to destroy polychlorinated biphenyls (PCB's) with 99.9999% (''six-nines'') destruction efficiency in tests monitored by the Environmental Protection Agency (EPA). The bed makes use of in situ neutralization of acidic off-gases by incorporating sodium carbonate (Na 2 CO 3 ) in the bed media. This eliminates using wet scrubbers to treat the off-gas; these produce a high volume of secondary waste. Once in operation, it is expected that the fluidized bed process will yield up to a 40:1 reduction in the volume of the waste

  18. Development of Chinese HTR-PM pebble bed equivalent conductivity test facility

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Cheng; Yang, Xingtuan; Jiang, Shengyao [Tsinghua Univ., Beijing (China). Inst. of Nuclear and New Energy Technology

    2016-01-15

    The first two 250-MWt high-temperature reactor pebble bed modules (HTR-PM) have been installing at the Shidaowan plant in Shandong Province, China. The values of the effective thermal conductivity of the pebble bed core are essential parameters for the design. For their determination, Tsinghua University in China has proposed a full-scale heat transfer experiment to conduct comprehensive thermal transfer tests in packed pebble bed and to determine the effective thermal conductivity.

  19. Application of Distributed Temperature Sensing for coupled mapping of sedimentation processes and spatio-temporal variability of groundwater discharge in soft-bedded streams

    DEFF Research Database (Denmark)

    Sebok, Eva; Duque, C; Engesgaard, Peter

    2015-01-01

    , maximum and mean streambed temperatures as well as the daily amplitude and standard deviation of temperatures. The identified potential high-discharge areas were mostly located near the channel banks, also showing temporal variability because of the scouring and redistribution of streambed sediments......The delineation of groundwater discharge areas based on Distributed Temperature Sensing (DTS) data of the streambed can be difficult in soft-bedded streams where sedimentation and scouring processes constantly change the position of the fibre optic cable relative to the streambed. Deposition...... variability in streambed temperatures between October 2011 and January 2012. Detailed monthly streambed elevation surveys were carried out to monitor the position of the fibre optic cable relative to the streambed and to quantify the effect of sedimentation processes on streambed temperatures. Based...

  20. Hydrogen production from water gas shift reaction in a high gravity (Higee) environment using a rotating packed bed

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei-Hsin; Syu, Yu-Jhih [Department of Greenergy, National University of Tainan, Tainan 700 (China)

    2010-10-15

    Hydrogen production via the water gas shift reaction (WGSR) was investigated in a high gravity environment. A rotating packed bed (RPB) reactor containing a Cu-Zn catalyst and spinning in the range of 0-1800 rpm was used to create high centrifugal force. The reaction temperature and the steam/CO ratio ranged from 250 to 350 C and 2 to 8, respectively. A dimensionless parameter, the G number, was derived to account for the effect of centrifugal force on the enhancement of the WGSR. With the rotor speed of 1800 rpm, the induced centrifugal force acting on the reactants was as high as 234 g on average in the RPB. As a result, the CO conversion from the WGSR was increased up to 70% compared to that without rotation. This clearly revealed that the centrifugal force was conducive to hydrogen production, resulting from intensifying mass transfer and elongating the path of the reactants in the catalyst bed. From Le Chatelier's principle, a higher reaction temperature or a lower steam/CO ratio disfavors CO conversion; however, under such a situation the enhancement of the centrifugal force on hydrogen production from the WGSR tended to become more significant. Accordingly, a correlation between the enhancement of CO conversion and the G number was established. As a whole, the higher the reaction temperature and the lower the steam/CO ratio, the higher the exponent of the G number function and the better the centrifugal force on the WGSR. (author)

  1. Preparation and characterization of thin-film Pd–Ag supported membranes for high-temperature applications

    NARCIS (Netherlands)

    Fernandez Gesalaga, Ekain; Coenen, Kai; Helmi Siasi Farimani, Arash; Melendez, J.; Zuniga, Jon; Pacheco Tanaka, David Alfredo; van Sint Annaland, Martin; Gallucci, Fausto

    2015-01-01

    This paper reports the preparation, characterization and stability tests of thin-film Pd–Ag supported membranes for high-temperature fluidized bed membrane reactor applications. Various thin-film supported membranes have been prepared by simultaneous Pd–Ag electroless plating and have been initially

  2. High-temperature turbopump assembly for space nuclear thermal propulsion

    Science.gov (United States)

    Overholt, David M.

    1993-01-01

    The development of a practical, high-performance nuclear rocket by the U.S. Air Force Space Nuclear Thermal Propulsion (SNTP) program places high priority on maximizing specific impulse (ISP) and thrust-to-weight ratio. The operating parameters arising from these goals drive the propellant-pump design. The liquid hydrogen propellant is pressurized and pumped to the reactor inlet by the turbopump assembly (TPA). Rocket propulsion is effected by rapid heating of the propellant from 100 K to thousands of degrees in the particle-bed reactor (PBR). The exhausted propellant is then expanded through a high-temperature nozzle. One approach to achieve high performance is to use an uncooled carbon-carbon nozzle and duct turbine inlet. The high-temperature capability is obtained by using carbon-carbon throughout the TPA hot section. Carbon-carbon components in development include structural parts, turbine nozzles/stators, and turbine rotors. The technology spinoff is applicable to conventional liquid propulsion engines plus a wide variety of other turbomachinery applications.

  3. High-temperature turbopump assembly for space nuclear thermal propulsion

    International Nuclear Information System (INIS)

    Overholt, D.M.

    1993-01-01

    The development of a practical, high-performance nuclear rocket by the U.S. Air Force Space Nuclear Thermal Propulsion (SNTP) program places high priority on maximizing specific impulse (ISP) and thrust-to-weight ratio. The operating parameters arising from these goals drive the propellant-pump design. The liquid hydrogen propellant is pressurized and pumped to the reactor inlet by the turbopump assembly (TPA). Rocket propulsion is effected by rapid heating of the propellant from 100 K to thousands of degrees in the particle-bed reactor (PBR). The exhausted propellant is then expanded through a high-temperature nozzle. One approach to achieve high performance is to use an uncooled carbon-carbon nozzle and duct turbine inlet. The high-temperature capability is obtained by using carbon-carbon throughout the TPA hot section. Carbon-carbon components in development include structural parts, turbine nozzles/stators, and turbine rotors. The technology spinoff is applicable to conventional liquid propulsion engines plus a wide variety of other turbomachinery applications

  4. Three-Dimensional Analysis of the Hot-Spot Fuel Temperature in Pebble Bed and Prismatic Modular Reactors

    International Nuclear Information System (INIS)

    In, W. K.; Lee, S. W.; Lim, H. S.; Lee, W. J.

    2006-01-01

    High temperature gas-cooled reactors(HTGR) have been reviewed as potential sources for future energy needs, particularly for a hydrogen production. Among the HTGRs, the pebble bed reactor(PBR) and a prismatic modular reactor(PMR) are considered as the nuclear heat source in Korea's nuclear hydrogen development and demonstration project. PBR uses coated fuel particles embedded in spherical graphite fuel pebbles. The fuel pebbles flow down through the core during an operation. PMR uses graphite fuel blocks which contain cylindrical fuel compacts consisting of the fuel particles. The fuel blocks also contain coolant passages and locations for absorber and control material. The maximum fuel temperature in the core hot spot is one of the important design parameters for both a PBR and a PMR. The objective of this study is to predict the hot-spot fuel temperature distributions in a PBR and a PMR at a steady state. The computational fluid dynamics(CFD) code, CFX-10 is used to perform the three-dimensional analysis. The latest design data was used here based on the reference reactor designs, PBMR400 and GTMHR60

  5. Performance of Sandy Dry Beds for sludge dewatering

    International Nuclear Information System (INIS)

    Al-Muzaini, S.

    2003-01-01

    Sludge produced by the Jahra treatment plant was assessed. The assessment was directed at determining the performance of sand drying beds. The assessment of quality of the sludge produced was based on the standards for land application of sewage sludge. Analyses were carried out for trace heavy metals and bacteria. The results of analyses showed that the sludge produced was high in organic matter and sand content but low in heavy metals. The collected data indicated that the sand drying beds at the Jahra treatment plant are at present inadequate to handle the projected sludge production. The investigation showed that the sand drying beds are fully used and the plant will require 3-4 times the capacity of the existing drying beds when the plant becomes fully operational. In addition, these sand drying beds are subjected to uncontrollable conditions such as temperature, rainfall and sludge drainage rate. Thus, sand drying beds have become less popular as a dewatering system. This paper evaluates the performance of the existing sand drying beds and suggests the most appropriate technology to alleviate the above mentioned problems. (author)

  6. Thermomechanical interactions of particle bed-structural wall in a layered configuration. Pt. 1. Effect of particle bed thermal expansions

    International Nuclear Information System (INIS)

    Tehranian, F.

    1995-01-01

    Materials in the form of particle beds have been considered for shielding and tritium breeding as well as neutron multiplication in many of the conceptual reactor design studies. As the level of effort of the fusion blanket community in the area of out-of-pile and in-pile (ITER) testing of integrated test modules increases, so does the need for modelling capability for predicting the thermomechanical responses of the test modules under reactor environment.In this study, the thermomechanical responses of a particle bed-structural wall system in a layered configuration, subjected to bed temperature rise and/or external coolant pressure, were considered. Equations were derived which represent the dependence of the particle-to-particle and particle-to-wall contact forces and areas on the structural wall deformations and in turn on the thermomechanical loads. Using the derived equations, parametric analyses were performed to study the variations in the thermomechanical response quantities of a beryllium particle bed-stainless steel structural wall when subjected to thermomechanical loads. The results are presented in two parts. In Part I, presented in this paper, the derivation of the analytical equations and the effects of bed temperature rise are discussed. In Part II of this study, also presented in this symposium, the effects of external coolant pressure as well as the combined effects of bed temperature rise and coolant pressure on the thermomechanical responses are given.It is shown that, depending on the stiffness of the structural walls, uniform bed temperature rises in the range 100-400 C result in non-uniform effective thermal properties through the prticle bed and could increase the bed effective thermal conductivity by a factor of 2-5 and the bed-wall interface thermal conductance by even a larger factor. (orig.)

  7. Chemical-looping combustion in a reverse-flow fixed bed reactor

    International Nuclear Information System (INIS)

    Han, Lu; Bollas, George M.

    2016-01-01

    A reverse-flow fixed bed reactor concept for CLC (chemical-looping combustion) is explored. The limitations of conventional fixed bed reactors, as applied to CLC, are overcome by reversing the gas flow direction periodically to enhance the mixing characteristics of the bed, thus improving oxygen carrier utilization and energy efficiency with respect to power generation. The reverse-flow reactor is simulated by a dusty-gas model and compared with an equivalent fixed bed reactor without flow reversal. Dynamic optimization is used to calculate conditions at which each reactor operates at maximum energy efficiency. Several cases studies illustrate the benefits of reverse-flow operation for the CLC with CuO and NiO oxygen carriers and methane and syngas fuels. The results show that periodic reversal of the flow during reduction improves the contact between the fuel and unconverted oxygen carrier, enabling the system to suppress unwanted catalytic reactions and axial temperature and conversion gradients. The operational scheme presented reduces the fluctuations of temperature during oxidation and increases the high-temperature heat produced by the process. CLC in a reverse-flow reactor has the potential to achieve higher energy efficiency than conventional fixed bed CLC reactors, when integrated with a downstream gas turbine of a combined cycle power plant. - Highlights: • Reverse-flow fixed bed CLC reactors for combined cycle power systems. • Dynamic optimization tunes operation of batch and transient CLC systems. • The reverse-flow CLC system provides stable turbine-ready gas stream. • Reverse-flow CLC fixed bed reactor has superior CO 2 capture and thermal efficiency.

  8. Real time thermal hydraulic model for high temperature gas-cooled reactor core

    International Nuclear Information System (INIS)

    Sui Zhe; Sun Jun; Ma Yuanle; Zhang Ruipeng

    2013-01-01

    A real-time thermal hydraulic model of the reactor core was described and integrated into the simulation system for the high temperature gas-cooled pebble bed reactor nuclear power plant, which was developed in the vPower platform, a new simulation environment for nuclear and fossil power plants. In the thermal hydraulic model, the helium flow paths were established by the flow network tools in order to obtain the flow rates and pressure distributions. Meanwhile, the heat structures, representing all the solid heat transfer elements in the pebble bed, graphite reflectors and carbon bricks, were connected by the heat transfer network in order to solve the temperature distributions in the reactor core. The flow network and heat transfer network were coupled and calculated in real time. Two steady states (100% and 50% full power) and two transients (inlet temperature step and flow step) were tested that the quantitative comparisons of the steady results with design data and qualitative analysis of the transients showed the good applicability of the present thermal hydraulic model. (authors)

  9. Thermal treatment of soil co-contaminated with lube oil and heavy metals in a low-temperature two-stage fluidized bed incinerator

    International Nuclear Information System (INIS)

    Samaksaman, Ukrit; Peng, Tzu-Huan; Kuo, Jia-Hong; Lu, Chien-Hsing; Wey, Ming-Yen

    2016-01-01

    Highlights: • Low-temperature two-stage fluidized bed incineration was applied for soil remediation. • Co-firing of polyethylene with co-contaminated soil was studied. • Co-firing of polyethylene in soil remediation can promote residue quality. • The leachability of heavy metals passed the regulatory threshold values. - Abstract: This study presents the application of a low-temperature two-stage fluidized bed incinerator to remediate contaminants in the soil. The system was designed to control emissions of both gaseous pollutants and heavy metals during combustion. Soil co-contaminated with lube oil and heavy metals such as cadmium, chromium, copper, and lead was examined. Experiments were conducted by estimating various parameters such as operating temperature in the first-stage reactor (500–700 °C), ratio of sand bed height/diameter in the second-stage reactor (H/D: 3, 4, 6), and gas velocity (0.21–0.29 m/s). Heavy metal and gaseous pollutant emissions were also investigated during contaminated soil co-firing with polyethylene. The experimental results indicated that the destruction and removal efficiency of lube oil in treated soil products ranged from 98.27 to 99.93%. On the other hand, leaching tests of bottom ashes illustrated that heavy metals such as chromium, copper, and lead in leachates were complied with the regulations. For gaseous emissions, carbon monoxide concentrations decreased apparently with increasing ratio of sand bed height/diameter in the second-stage reactor. The increase of gas velocity had significant potential to generate the lowest carbon monoxide and particulate matter emissions. Nevertheless, during co-firing with polyethylene, emissions of organic pollutants such as benzene, toluene, ethylbenzene, and xylene and polycyclic aromatic hydrocarbons decrease by using the low-temperature two-stage fluidized bed incineration system.

  10. New deployment of high temperature gas-cooled reactor

    International Nuclear Information System (INIS)

    Sekimoto, Hiroshi; Tsuchie, Yasuo; Kunitomi, Kazuhiko; Shiozawa, Shusaku; Konuki, Kaoru; Inagaki, Yoshiyuki; Hayakawa, Hitoshi

    2002-01-01

    The high temperature gas-cooled reactor (HTGR) is now under a condition difficult to know it well, because of considering not only power generation, but also diverse applications of its nuclear heat, of having extremely different safe principle from that of conventional reactors, of having two types of pebble-bed and block which are extremely different types, of promoting its construction plan in South Africa, of including its application to disposition of Russian surplus weapons plutonium of less reporting HTTR in Japan in spite of its full operation, and so on. However, HTGR is expected for an extremely important nuclear reactor aiming at the next coming one of LWR. HTGR which is late started and developed under complete private leading, is strongly conscious at environmental problem since its beginning. Before 30 years when large scale HTGR was expected to operate, it advertised a merit to reduce wasted heat because of its high temperature. As ratio occupied by electricity expands among application of energies, ratio occupied by the other energies are larger. When considering applications except electric power, high temperature thermal energy from HTGR can be thought wider applications than that from LWR and so on. (G.K.)

  11. Bed rest from the perspective of the high-risk pregnant woman.

    Science.gov (United States)

    Gupton, A; Heaman, M; Ashcroft, T

    1997-01-01

    To describe the experience of prolonged bed rest from the perspective of women during high-risk pregnancies. A focused ethnographic study that used interviews, participant diaries, and field notes as data sources. Participants were obtained from an acute-care hospital antepartum unit and an antepartum home care program. Twenty-four women with complications of pregnancy requiring prolonged bed rest (range, 7-50 days). A model of the stress process in pregnant women on bed rest emerged from the data analysis. Stressors were grouped into situational (sick role, lack of control, uncertainty, concerns regarding fetus's well-being, and being tired of waiting), environmental (feeling like a prisoner, being bored, and having a sense of missing out), and family (role reversal and worry about older children) categories. Two main mediators of stress were social support and coping. Families, friends, and professionals were perceived as sources of support. Women used coping strategies, such as keeping a positive attitude, taking it 1 day at a time, doing it for the baby, getting used to it, setting goals, and keeping busy. Manifestations of stress were evidenced by adverse physical symptoms, emotional reactions, and altered social relationships. Prolonged bed rest is a stressful experience for pregnant women at high risk. Understanding the stress process in pregnant women confined to bed rest may assist nurses in developing interventions to reduce stressors and enhance mediators.

  12. Performance and metallography of a uranium tritide bed operated at elevated temperatures and tritium pressures

    International Nuclear Information System (INIS)

    Mote, M.W. Jr.; Mintz, J.M.

    1986-12-01

    A uranium gettering bed was cycled between room temperature/zero pressure and 600C/275 psi (D 2 ) for 210 cycles over a period of 8 months. Metallographic examination of the hardware revealed an acceptable amount of reaction between the uranium and the stainless steel container. This exposure is estimated to represent about ten years of normal use

  13. Coolability of oxidized particulate debris bed accumulated in horizontal narrow gaps

    International Nuclear Information System (INIS)

    Arai, Y.; Sugiyama, K.; Narabayashi, T.

    2007-01-01

    When LOCA occurs in a nuclear reactor system, the coolability of the core would be kept as reported at a series of presentations in ICONE14. Therefore the probability of the core meltdown is negligible small. However, from the view point of defense in depth, it is necessary to be sure that the coolability of the bottom of reactor pressure vessel (RPV) is maintained even if a part of the core should melt and a substantial amount of debris should be deposited on the lower plenum. We carried out an experimental study in order to observe the coolability of particulate core-metal debris bed with 12 mm thickness accompanied with rapid heat generation because of oxidization, which was reported at ICONE14. The coolability was assured by a small amount of coolant supply because of high capillary force of oxidized fine particulate debris produced. In the present study, we examined the coolability of particulate debris bed deposited in narrower gap of 1 mm or 5 mm that coolant supply is hard. The particulate debris beds were piled up on the stainless steel sheet with 0.1 mm thickness, which was used to measure the bottom temperatures of particulate debris bed by using a thermo-video camera. We set up a heat supply section with heat input of 2.1 kW, which simulates the hard debris bed deposited on the particulate debris bed as reported for the TMI-2 accident. We measured the temperatures of the bottom surface of the heat supply section and the heat fluxes released into debris bed as well as the temperatures at the bottom of debris bed on the stainless steel sheet. It is found that when only the upper surface of particulate debris bed is in the film boiling, capillary force causes coolant supply to the particulate debris bed. Therefore, in the condition of thicker gap with small particulate debris, coolability of debris bed is improved. We find out that smaller particulate debris is moved by vapor movement. As a result, the area that high capillary force is caused because of

  14. Report on research and development achievements in fiscal 1980 in Sunshine Project. Development of a high-temperature bed drilling technology (Feasibility study on high-temperature bed drilling); 1980 nendo koon chiso kusaku gijutsu no kaihatsu seika hokokusho. Koon chiso kussaku ni kansuru feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1981-03-01

    Discussions were given on feasibility of a technology to drill efficiently a high-temperature bed (350 degrees C and 400 kg/cm{sup 2}) to 3 to 5 km. This paper summarizes the bit items for development (bearings, cutters, blade tips, sealing materials, a tip retaining method and structures). The roller cutter bit had the retaining power of the mother cutter material strengthened by using improved carbonized steel and heat treatment. A bit bearing using heat resistant material showed a life of 40 hours or longer at 350 degrees C. The solid bit using a two-layered ultra hard blade tip achieved a drilling rate of 0.84 m/h without any breakage. Studies were also advanced on the air friction drilling method. This paper also dwelled on heat and corrosion resistant blade tips, materials, enhancement of heat resistance in powder sintered cutters, and studies on the bit sealing. In addition to discussions on the percussion drilling as a new drilling method, discussions were given on slanted drilling, air drilling and multi-leg drilling. The paper summarizes these discussions together with development problems to be solved in the future. Research and development works were carried out also on an explosion preventing device, a roll packer, and a rotating head prevent device. (NEDO)

  15. High Levels Of Bed Occupancy Associated With Increased Inpatient And Thirty-Day Hospital Mortality In Denmark

    DEFF Research Database (Denmark)

    Madsen, Flemming; Ladelund, Steen; Linneberg, Allan

    2014-01-01

    to low bed occupancy rates. Being admitted to a hospital outside of normal working hours or on a weekend or holiday was also significantly associated with increased mortality. The health risks of bed shortages, including mortality, could be better documented as a priority health issue. Resources should......High bed occupancy rates have been considered a matter of reduced patient comfort and privacy and an indicator of high productivity for hospitals. Hospitals with bed occupancy rates of above 85 percent are generally considered to have bed shortages. Little attention has been paid to the impact...... be allocated to researching the causes and effects of bed shortages, with the aim of creating greater interest in exploring new methods to avoid or reduce bed shortages....

  16. Effects of Temperature and Residence Time on the Emissions of PIC and Fine Particles during Fixed Bed Combustion of Conifer Stemwood Pellets

    Energy Technology Data Exchange (ETDEWEB)

    Boman, Christoffer; Lindmark, Fredrik; Oehman, Marcus; Nordin, Anders [Umeaa Univ. (Sweden). Energy Technology and Thermal Process Chemistry; Pettersson, Esbjoern [Energy Technology Centre, Piteaa (Sweden); Westerholm, Roger [Stockholm Univ., Arrhenius Laboratory (Sweden). Dept. of Analytical Chemistry

    2006-07-15

    The use of wood fuel Pellets has proved to be well suited for the small-scale market enabling controlled and efficient combustion with low emission of products of incomplete combustion (PIC). Still a potential for further emission reduction exists and a thorough understanding of the influence of combustion conditions on the emission characteristics of air pollutants like PAH and particulate matter (PM) is important. The objective was to determine the effects of temperature and residence time on the emission performance and characteristics with focus on hydrocarbons and PM during combustion of conifer stemwood Pellets in a laboratory fixed bed reactor (<5 kW). Temperature and residence time after the bed section were varied according to statistical experimental designs (650-970 deg C and 0.5-3.5 s) with the emission responses; CO, organic gaseous carbon, NO, 20 VOC compounds, 43 PAH compounds, PM{sub tot}, fine particle mass/count median diameter (MMD and CMD) and number concentration. Temperature was negatively correlated with the emissions of all studied PIC with limited effects of residence time. The PM{sub tot} emissions of 15-20 mg/MJ was in all cases dominated by fine (<1 {mu}m) particles of K, Na, S, Cl, C, O and Zn. Increased residence time resulted in increased fine particle sizes (i.e. MMD and CMD) and decreased number concentrations. The importance of high temperature (>850 deg C) in the bed zone with intensive, air rich and well mixed isothermal conditions for 0.5-1.0 s in the post combustion zone was illustrated for wood Pellets combustion with almost a total depletion of all studied PIC. The results emphasize the need for further verification studies and technology development work.

  17. Preliminary neutronic design of high burnup OTTO cycle pebble bed reactor

    International Nuclear Information System (INIS)

    Setiadipura, T.; Zuhair; Irwanto, D.

    2015-01-01

    The pebble bed type High Temperature Gas-cooled Reactor (HTGR) is among the interesting nuclear reactor designs in terms of safety and flexibility for co-generation applications. In addition, the strong inherent safety characteristics of the pebble bed reactor (PBR) which is based on natural mechanisms improve the simplicity of the PBR design, in particular for the Once-Through-Then-Out (OTTO) cycle PBR design. One of the important challenges of the OTTO cycle PBR design, and nuclear reactor design in general, is improving the nuclear fuel utilization which is shown by attaining a higher burnup value. This study performed a preliminary neutronic design study of a 200 MWt OTTO cycle PBR with high burnup while fulfilling the safety criteria of the PBR design.The safety criteria of the design was represented by the per-fuel-pebble maximum power generation of 4.5 kW/pebble. The maximum burnup value was also limited by the tested maximum burnup value which maintained the integrity of the pebble fuel. Parametric surveys were performed to obtain the optimized parameters used in this study, which are the fuel enrichment, per-pebble heavy metal (HM) loading, and the average axial speed of the fuel. An optimum design with burnup value of 131.1 MWd/Kg-HM was achieved in this study which is much higher compare to the burnup of the reference design HTR-MODUL and a previously proposed OTTO-cycle PBR design. This optimum design uses 17% U-235 enrichment with 4 g HM-loading per fuel pebble. (author)

  18. Preliminary Neutronic Design of High Burnup OTTO Cycle Pebble Bed Reactor

    Directory of Open Access Journals (Sweden)

    T. Setiadipura

    2015-04-01

    Full Text Available The pebble bed type High Temperature Gas-cooled Reactor (HTGR is among the interesting nuclear reactor designs in terms of safety and flexibility for co-generation applications. In addition, the strong inherent safety characteristics of the pebble bed reactor (PBR which is based on natural mechanisms improve the simplicity of the PBR design, in particular for the Once-Through-Then-Out (OTTO cycle PBR design. One of the important challenges of the OTTO cycle PBR design, and nuclear reactor design in general, is improving the nuclear fuel utilization which is shown by attaining a higher burnup value. This study performed a preliminary neutronic design study of a 200 MWt OTTO cycle PBR with high burnup while fulfilling the safety criteria of the PBR design.The safety criteria of the design was represented by the per-fuel-pebble maximum power generation of 4.5 kW/pebble. The maximum burnup value was also limited by the tested maximum burnup value which maintained the integrity of the pebble fuel. Parametric surveys were performed to obtain the optimized parameters used in this study, which are the fuel enrichment, per-pebble heavy metal (HM loading, and the average axial speed of the fuel. An optimum design with burnup value of 131.1 MWd/Kg-HM was achieved in this study which is much higher compare to the burnup of the reference design HTR-MODUL and a previously proposed OTTO-cycle PBR design. This optimum design uses 17% U-235 enrichment with 4 g HM-loading per fuel pebble

  19. Temperature effects on biohydrogen production in a granular sludge bed induced by activated carbon carriers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kuo-Shing [Department of Safety Health and Environmental Engineering, Chung tai Institute of Health Sciences and Technology, Taichung (China); Lin, Ping-Jei [Department of Chemical Engineering, Feng Chia University, Taichung (China); Chang, Jo-Shu [Department of Chemical Engineering, National Cheng Kung University, Tainan (China)

    2006-03-15

    Temperature effects on H{sub 2} production performance of a novel carrier-induced granular sludge bed (CIGSB) reactor were investigated. Using sucrose-based synthetic wastewater as the feed, the CIGSB system was operated at 30-45 {sup 0}C to identify the optimal working temperature. It was found that H{sub 2} production was the most efficient at 40 {sup 0}C, especially when it was operated at a low hydraulic retention time (HRT) of 0.5h. The overall maximal hydrogen production rate and yield were 7.66l/h/l and 3.88mol H{sub 2}/mol sucrose, respectively, both of them occurred at 40 {sup 0}C. The biomass content tended to decrease as the temperature was increased, suggesting that granular sludge formation may be inhibited at high temperatures. However, increasing temperature gave better specific H{sub 2} production rate, signifying that the average cellular activity for H{sub 2} production may be enhanced as the temperature was increased. The H{sub 2} yield and gas phase H{sub 2} content did not vary considerably regardless of changes in temperature and HRT. This reflects that the CIGSB was a relatively stable H{sub 2}-producing system. The major soluble products from hydrogen fermentation were butyric acid and acetic acid, accounting for 46+-3% and 28+-2% of total soluble microbial products (SMP), respectively. Thus, the dominant H{sub 2} producers in the mixed culture belonged to acidogenic bacteria that underwent butyrate-type fermentation. (author)

  20. Investigation of heat transfer in bed and freeboard of fluidized bed combustors

    International Nuclear Information System (INIS)

    Mitor, V.V.; Matsnev, V.V.; Sorokin, A.P.

    1986-01-01

    Experimental results for heat transfer between immersed bundles of bare tubes and fluidized beds are reported. The experimental results are obtained on industrial boilers with a bed area from 2,5 to 4 m/sup 2/ under conditions of long term operation. The bed temperature range has been 1073 0 K-1233 0 K, gas velocity between 1,8-4,5 m/s, mean particle size from 1,5 mm to 6,0 mm, freeboard furnace height of 2,3 and 5 m. The obtained data are compared with experimental results from literature

  1. Coal-fired power plants and the causes of high temperature corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Oakey, J E; Simms, N J [British Coal Corporation, Coal Technology Development Div., Cheltenham, Glos (United Kingdom); Tomkings, A B [ERA Technology Ltd., Leatherhead, Surrey (United Kingdom)

    1996-12-01

    The heat exchangers in all types of coal-fired power plant operate in aggressive, high temperature environments where high temperature corrosion can severely limit their service lives. The extent of this corrosion is governed by the combined effects of the operating conditions of the heat exchanger and the presence of corrosive species released from the coal during operation. This paper reviews the coal-related factors, such as ash deposition, which influence the operating environments of heat exchangers in three types of coal-fired power plant - conventional pulverized coal boilers, fluidized bed boilers and coal gasification systems. The effects on the performance of the materials used for these heat exchangers are then compared. (au) 35 refs.

  2. Burnup performance of OTTO cycle pebble bed reactors with ROX fuel

    International Nuclear Information System (INIS)

    Ho, Hai Quan; Obara, Toru

    2015-01-01

    Highlights: • A 300 MW t Small Pebble Bed Reactor with Rock-like oxide fuel is proposed. • Using ROX fuel can achieve high discharged burnup of spent fuel. • High geological stability can be expected in direct disposal of the spent ROX fuel. • The Pebble Bed Reactor with ROX fuel can be critical at steady state operation. • All the reactor designs have a negative temperature coefficient. - Abstract: A pebble bed high-temperature gas-cooled reactor (PBR) with rock-like oxide (ROX) fuel was designed to achieve high discharged burnup and improve the integrity of the spent fuel in geological disposal. The MCPBR code with a JENDL-4.0 library, which developed the analysis of the Once-Through-Then-Out (OTTO) cycle in PBR, was used to perform the criticality and burnup analysis. Burnup calculations for eight cases were carried out for both ROX fuel and a UO 2 fuel reactor with different heavy-metal loading conditions. The effective multiplication factor of all cases approximately equalled unity in the equilibrium condition. The ROX fuel reactor showed lower FIFA than the UO 2 fuel reactor at the same heavy-metal loading, about 5–15%. However, the power peaking factor and maximum power per fuel ball in the ROX fuel core were lower than that of UO 2 fuel core. This effect makes it possible to compensate for the lower-FIFA disadvantage in a ROX fuel core. All reactor designs had a negative temperature coefficient that is needed for the passive safety features of a pebble bed reactor

  3. Combustion of peanut shells in a cone-shaped bubbling fluidized-bed combustor using alumina as the bed material

    International Nuclear Information System (INIS)

    Arromdee, Porametr; Kuprianov, Vladimir I.

    2012-01-01

    Highlights: ► We propose burning of peanut shells in a conical fluidized bed using alumina sand. ► We examine hydrodynamic, combustion and emission characteristics of the reactor. ► High, over 99%, combustion efficiency is achievable. ► Emissions of CO and NO from the combustor meet the national emission limits. ► Composition of the bed material undergoes significant changes during the combustion. -- Abstract: This paper reports experimental studies on burning peanut shells in the conical fluidized-bed combustor using alumina sand as the fluidizing agent. Prior to combustion tests, hydrodynamic regimes and characteristics of a conical alumina–biomass bed were investigated under cold-state conditions for variable percentage of peanut shells in the mixture and static bed height. With selected particle sizes (300–500 μm) and static bed height (30 cm), alumina ensured bubbling fluidization regime of the bed at operating conditions specified for firing biomass. Combustion tests were performed at 60 kg/h and 45 kg/h fuel feed rates, while ranging excess air from 20% to 80% at a fixed combustor load. Temperature and gas concentrations (O 2 , CO, C x H y as CH 4 , and NO) were measured along radial and axial directions inside the reactor as well as at stack in order to characterize combustion and emission performance of the combustor for the ranges of operating conditions. For firing 60 kg/h peanut shells, excess air of 40% can be selected as an appropriate value ensuring high, about 99%, combustion efficiency and rather low emissions of CO and NO: 520 ppm and 125 ppm, respectively (both on a dry basis and at 6% O 2 ). With reducing combustor load, the combustion efficiency and emission characteristics were improved to a little extent. No evidence of bed agglomeration was found during 30-h combustion tests on this conical fluidized-bed combustor using alumina sand as the bed material. However, the timescale effect on the composition of the bed material was

  4. Effect of Different Operating Temperatures on the Biological Hydrogen Methanation in Trickle Bed Reactors

    Directory of Open Access Journals (Sweden)

    Andreas Lemmer

    2018-05-01

    Full Text Available To improve the reactor efficiency, this study investigated the influence of temperature on the biological hydrogen methanation (BHM in trickle-bed reactors (TBR. Rising temperatures increase the metabolic activity of methanogenic microorganisms, thus leading to higher reactor specific methane formation rates (MFR. In order to quantify the potential for improved performance, experiments with four different operating temperatures ranging from 40 to 55 °C were carried out. Methane content increased from 88.29 ± 2.12 vol % at 40 °C to 94.99 ± 0.81 vol % at 55 °C with a stable biological process. Furthermore, a reactor specific methane formation rate (MFR of up to 8.85 ± 0.45 m3 m−3 d−1 was achieved. It could be shown that the microorganisms were able to adapt to higher temperatures within hours. The tests showed that TBR performance with regard to BHM can be significantly increased by increasing the operating temperature.

  5. An experimental test facility to support development of the fluoride-salt-cooled high-temperature reactor

    International Nuclear Information System (INIS)

    Yoder, Graydon L.; Aaron, Adam; Cunningham, Burns; Fugate, David; Holcomb, David; Kisner, Roger; Peretz, Fred; Robb, Kevin; Wilgen, John; Wilson, Dane

    2014-01-01

    Highlights: • • A forced convection test loop using FLiNaK salt was constructed to support development of the FHR. • The loop is built of alloy 600, and operating conditions are prototypic of expected FHR operation. • The initial test article is designed to study pebble bed heat transfer cooled by FLiNaK salt. • The test facility includes silicon carbide test components as salt boundaries. • Salt testing with silicon carbide and alloy 600 confirmed acceptable loop component lifetime. - Abstract: The need for high-temperature (greater than 600 °C) energy transport systems is significantly increasing as the world strives to improve energy efficiency and develop alternatives to petroleum-based fuels. Liquid fluoride salts are one of the few energy transport fluids that have the capability of operating at high temperatures in combination with low system pressures. The fluoride-salt-cooled high-temperature reactor design uses fluoride salt to remove core heat and interface with a power conversion system. Although a significant amount of experimentation has been performed with these salts, specific aspects of this reactor concept will require experimental confirmation during the development process. The experimental facility described here has been constructed to support the development of the fluoride-salt-cooled high-temperature reactor concept. The facility is capable of operating at up to 700 °C and incorporates a centrifugal pump to circulate FLiNaK salt through a removable test section. A unique inductive heating technique is used to apply heat to the test section, allowing heat transfer testing to be performed. An air-cooled heat exchanger removes added heat. Supporting loop infrastructure includes a pressure control system, a trace heating system, and a complement of instrumentation to measure salt flow, temperatures, and pressures around the loop. The initial experiment is aimed at measuring fluoride-salt heat transfer inside a heated pebble bed

  6. Similitude study of a moving bed granular filter

    Energy Technology Data Exchange (ETDEWEB)

    Robert C. Brown; Huawei Shi; Gerald Colver; Saw-Choon Soo [Iowa State University, IA (United States)

    2003-12-10

    The goal of this study was to evaluate the performance of a moving bed granular filter designed for hot gas clean up. This study used similitude theory to devise experiments that were conducted at near-ambient conditions while simulating the performance of filters operated at elevated temperatures and pressures (850{sup o}C and 1000 kPa). These experiments revealed that the proposed moving bed granular filter can operate at high collection efficiencies, typically exceeding 99%, and low pressure drops without the need for periodic regeneration through the use of a continuous flow of fresh granular filter media in the filter. In addition, important design constraints were discovered for the successful operation of the proposed moving bed granular filter.

  7. Performance of a pilot-scale, steam-blown, pressurized fluidized bed biomass gasifier

    Science.gov (United States)

    Sweeney, Daniel Joseph

    With the discovery of vast fossil resources, and the subsequent development of the fossil fuel and petrochemical industry, the role of biomass-based products has declined. However, concerns about the finite and decreasing amount of fossil and mineral resources, in addition to health and climate impacts of fossil resource use, have elevated interest in innovative methods for converting renewable biomass resources into products that fit our modern lifestyle. Thermal conversion through gasification is an appealing method for utilizing biomass due to its operability using a wide variety of feedstocks at a wide range of scales, the product has a variety of uses (e.g., transportation fuel production, electricity production, chemicals synthesis), and in many cases, results in significantly lower greenhouse gas emissions. In spite of the advantages of gasification, several technical hurdles have hindered its commercial development. A number of studies have focused on laboratory-scale and atmospheric biomass gasification. However, few studies have reported on pilot-scale, woody biomass gasification under pressurized conditions. The purpose of this research is an assessment of the performance of a pilot-scale, steam-blown, pressurized fluidized bed biomass gasifier. The 200 kWth fluidized bed gasifier is capable of operation using solid feedstocks at feedrates up to 65 lb/hr, bed temperatures up to 1600°F, and pressures up to 8 atm. Gasifier performance was assessed under various temperatures, pressure, and feedstock (untreated woody biomass, dark and medium torrefied biomass) conditions by measuring product gas yield and composition, residue (e.g., tar and char) production, and mass and energy conversion efficiencies. Elevated temperature and pressure, and feedstock pretreatment were shown to have a significant influence on gasifier operability, tar production, carbon conversion, and process efficiency. High-pressure and temperature gasification of dark torrefied biomass

  8. The effect of bed particle size and deposit morphology on the filtration of magnetite through granular graphite beds

    International Nuclear Information System (INIS)

    Barbieri, R.R.; Bercovich, E.J.; Liberman, S.J.

    1980-01-01

    Graphite filters are of great interest for water purification in nuclear power reactors' primary systems due to their possible operation at high temperature. The influence of the bed particle size on the retention of magnetite from aqueous suspensions at room temperature was studied. The filtration coefficient changes from 0.0 to 0.18 as the mean graphite particle diameter decreases from 1.2 to 0. mm. As the retention increases, there is also an increase in the differential pressure across the bed, so both effects must be considered in order to optimize filter's operation. The specific effective volume of the deposit was calculated with the Blake-Kozeny equation and the experimental specific volumes. These are much larger than the specific volume of solid magnetite. From the results, information regarding the morphology of the deposit in the filter is obtained. (M.E.L) [es

  9. A safety re-evaluation of the AVR pebble bed reactor operation and its consequences for future HTR concepts

    Energy Technology Data Exchange (ETDEWEB)

    Moormann, R.

    2008-06-15

    The AVR pebble bed reactor (46 MW{sub th}) was operated 1967-88 at coolant outlet temperatures up to 990 C. A principle difference of pebble bed HTRs as AVR to conventional reactors is the continuous movement of fuel element pebbles through the core which complicates thermohydraulic, nuclear and safety estimations. Also because of a lack of other experience AVR operation is still a relevant basis for future pebble bed HTRs and thus requires careful examination. This paper deals mainly with some insufficiently published unresolved safety problems of AVR operation and of pebble bed HTRs but skips the widely known advantageous features of pebble bed HTRs. The AVR primary circuit is heavily contaminated with metallic fission products (Sr-90, Cs-137) which create problems in current dismantling. The amount of this contamination is not exactly known, but the evaluation of fission product deposition experiments indicates that the end of life contamination reached several percent of a single core inventory, which is some orders of magnitude more than precalculated and far more than in large LWRs. A major fraction of this contamination is bound on graphitic dust and thus partly mobile in depressurization accidents, which has to be considered in safety analyses of future reactors. A re-evaluation of the AVR contamination is performed here in order to quantify consequences for future HTRs (400 MW{sub th}). It leads to the conclusion that the AVR contamination was mainly caused by inadmissible high core temperatures, increasing fission product release rates, and not - as presumed in the past - by inadequate fuel quality only. The high AVR core temperatures were detected not earlier than one year before final AVR shut-down, because a pebble bed core cannot yet be equipped with instruments. The maximum core temperatures are still unknown but were more than 200 K higher than calculated. Further, azimuthal temperature differences at the active core margin of up to 200 K were

  10. A safety re-evaluation of the AVR pebble bed reactor operation and its consequences for future HTR concepts

    International Nuclear Information System (INIS)

    Moormann, R.

    2008-06-01

    The AVR pebble bed reactor (46 MW th ) was operated 1967-88 at coolant outlet temperatures up to 990 C. A principle difference of pebble bed HTRs as AVR to conventional reactors is the continuous movement of fuel element pebbles through the core which complicates thermohydraulic, nuclear and safety estimations. Also because of a lack of other experience AVR operation is still a relevant basis for future pebble bed HTRs and thus requires careful examination. This paper deals mainly with some insufficiently published unresolved safety problems of AVR operation and of pebble bed HTRs but skips the widely known advantageous features of pebble bed HTRs. The AVR primary circuit is heavily contaminated with metallic fission products (Sr-90, Cs-137) which create problems in current dismantling. The amount of this contamination is not exactly known, but the evaluation of fission product deposition experiments indicates that the end of life contamination reached several percent of a single core inventory, which is some orders of magnitude more than precalculated and far more than in large LWRs. A major fraction of this contamination is bound on graphitic dust and thus partly mobile in depressurization accidents, which has to be considered in safety analyses of future reactors. A re-evaluation of the AVR contamination is performed here in order to quantify consequences for future HTRs (400 MW th ). It leads to the conclusion that the AVR contamination was mainly caused by inadmissible high core temperatures, increasing fission product release rates, and not - as presumed in the past - by inadequate fuel quality only. The high AVR core temperatures were detected not earlier than one year before final AVR shut-down, because a pebble bed core cannot yet be equipped with instruments. The maximum core temperatures are still unknown but were more than 200 K higher than calculated. Further, azimuthal temperature differences at the active core margin of up to 200 K were observed

  11. Prevention of Bed Agglomeration Problems in a Fluidized Bed Boiler by Finding the Trigging Value of Sewage Sludge Dosage Added to Combustion of Biofuels

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Kajsa; Gervind, Pernilla

    2009-07-01

    Agglomeration of bed sand is a common problem during combustion of biofuels with high ash content in fluidized bed boilers. Former studies have shown that co-combustion of biofuels with sewage sludge increases the agglomeration temperature. Sewage sludge has a low heating value and high ash content. It would therefore be better to use sludge as an additive to the combustion than as a co-combusted biofuel. In this study the trigging value of sludge addition to the combustion of some biofuel was investigated. The effect of adding sludge with different precipitation chemicals, iron sulphate and aluminium sulphate, was investigated. The biofuels used for the experiments were bark, refused derived fuel (RDF) and a mixture of wood and straw, 75/25 % on energy basis. All experiments were carried out in a laboratory scale fluidized bed reactor. Analyses of chemical composition of bed sand and SEM/EDX analyses were performed after the combustion. Eventually agglomeration tests were performed in order to find the agglomeration temperature of the samples. Some of the samples sintered during the combustion and were not tested for the agglomeration temperature. SEM/EDX showed that all samples of bed sand contained sand particles with more or less coatings. In some cases the coatings seemed to consist of one dense inner layer and one more porous outer layer. From SEM/EDX and chemical composition analyses it was found that the total amount of phosphorous in the bed sand samples was increased with an increased addition of sludge in all experiments. The concentration of phosphorous was especially higher in the outer layers/coatings. It was also found that elements from the sludge seem to get caught by a sticky layer at the bed sand surface and form a non-sticky or less sticky layer that prevents agglomeration. The total amount of aluminium was increased with an increased addition of sludge for the wood/straw samples, while it increased with an increased amount of combusted fuel for

  12. A uranium bed with ceramic body for tritium storage

    Energy Technology Data Exchange (ETDEWEB)

    Khapov, A.S.; Grishechkin, S.K.; Kiselev, V.G. [' All Russia Research Institute of Automatics' - FSUE VNIIA, Moscow (Russian Federation)

    2015-03-15

    It is widely recognized that ceramic coatings provide an attractive solution to lower tritium permeation in structural materials. Alumina based ceramic coatings have the highest permeation reduction factor for hydrogen. For this reason an attempt was made to apply crack-free low porous ceramics as a structural material of a bed body for tritium storage in a setup used for hydrogenating neutron tube targets at VNIIA. The present article introduces the design of the bed. This bed possesses essentially a lower hydrogen permeation factor than traditionally beds with stainless steel body. Bed heating in order to recover hydrogen from the bed is suggested to be implemented by high frequency induction means. Inductive heating allows decreasing the time necessary for tritium release from the bed as well as power consumption. Both of these factors mean less thermal power release into glove box where a setup for tritium handling is installed and thus causes fewer problems with pressure regulations inside the glove box. Inductive heating allows raising tritium sorbent material temperature up to melting point. The latter allows achieving nearly full tritium recovery.

  13. CIRCULATING MOVING BED COMBUSTION PROOF OF CONCEPT

    Energy Technology Data Exchange (ETDEWEB)

    Jukkola, Glen

    2010-06-30

    Circulating Moving Bed (CMB) combustion technology has its roots in traditional circulating fluidized bed technology and involves a novel method of solid fuel combustion and heat transfer. CMB technology represents a step change in improved performance and cost relative to conventional PC and FBC boilers. The CMB heat exchanger preheats the energy cycle working fluid, steam or air, to the high temperature levels required in systems for advanced power generation. Unique features of the CMB are the reduction of the heat transfer surfaces by about 60% as a result of the enhanced heat transfer rates, flexibility of operation, and about 30% lower cost over existing technology. The CMB Phase I project ran from July 2001 through March 2003. Its objective was to continue development of the CMB technology with a series of proof of concept tests. The tests were conducted at a scale that provided design data for scale up to a demonstration plant. These objectives were met by conducting a series of experiments in ALSTOM Power’s Multi-use Test Facility (MTF). The MTF was modified to operate under CMB conditions of commercial interest. The objective of the tests were to evaluate gas-to-solids heat transfer in the upper furnace, assess agglomeration in the high temperature CMB bubbling bed, and evaluate solids-to-tube heat transfer in the moving bed heat exchanger. The Phase I program results showed that there are still some significant technical uncertainties that needed to be resolved before the technology can be confidently scaled up for a successful demonstration plant design. Work remained in three primary areas: • scale up of gas to solid heat transfer • high temperature finned surface design • the overall requirements of mechanical and process design. The CMB Phase II workscope built upon the results of Phase I and specifically addressed the remaining technical uncertainties. It included a scaled MTF heat transfer test to provide the necessary data to scale up gas

  14. Improvement of Combustion Characteristics in Fluidized Bed

    International Nuclear Information System (INIS)

    Mohamed, H.S.; El Sourougy, M.R.; Faik, M.

    2009-01-01

    The present investigation is directed towards the experimental study of the effect of a new design of the bed temperature on the overall thermal efficiency and heat transfer by conduction, convection and radiation in gaseous fuel-fluidized bed combustion system. The experiments are performed on a water-cooled fluidized bed model furnace with cylindrical cross-section of 0.25 m diameter and its height is 0.60 m. the fluidising medium used is sand particles with average diameter 1.5 mm. The bed temperature is varied between 700 degree C and 1100 degree C. Measurements f carbon dioxide, carbon monoxide and oxygen concentrations are carried out by using water-cooled sampling probe, and infrared and paramagnetic analyzers. The results obtained show that the bed temperature, the total heat transfer to the wall and the bed combustion efficiency increase with the decrease of the air-fuel ratio. It is also found that 91% of the total heat transfer is in the fluidising part of the bed and most of this heat is transferred by convection from hot sand particles to the wall. Two empirical formulae for the calculation of the wall heat transfer coefficient and the particle convective heat transfer coefficient are proposed. A verification of the proposed empirical formulae is made by comparing the calculated values with the experimental results.

  15. Sustainability and Efficiency Improvements of Gas-Cooled High Temperature Reactors

    International Nuclear Information System (INIS)

    Marmier, Alain

    2012-01-01

    This thesis covers 3 fundamental aspects of High Temperature Reactor (HTR) performance: fuel testing under irradiation for maximized safety and sustainability, fuel architecture for improved economy and sustainability, and a novel Balance of Plant concept to enable future high-tech process heat applications with minimized R and D. The HTR concept features important inherent and passive safety characteristics: high thermal inertia and good thermal conductivity of the core; a negative Doppler coefficient; high quality of fuel elements and low power density. These features keep the core temperature within safe boundaries and minimise fission product release, even in case of severe accidents. The Very High Temperature reactor (VHTR) is based on the same safety concept as the initial HTR, but it aims at offering better economy with a higher reactor outlet temperature (and thus efficiency) and a high fuel discharge burn-up (and thus better sustainability). The inherent safety features of HTR have been demonstrated in small pebble-bed reactors in practice, but have to be replicated for reactors with industrially relevant size and power. An increase of the power density (in order to increase the helium coolant outlet temperature) leads to higher fuel temperatures and therefore higher fuel failure probability. The core of a pebble-bed reactor consists of 6 cm diameter spheres (pebbles) that form a randomly packed porous bed, which is cooled by high pressure helium. These pebbles contain thousands of 1 mm diameter fuel particles baked into a graphite matrix. These fuel particles, in turn, consist of a fuel kernel with successive coatings of pyrocarbon and silicon carbide layers. The coating layers are designed to contain the fission products that build up during operation of the reactor. The feasibility and performance of the fuel requires experimental verification in view of fuel qualification and licensing. For HTR fuel, the required test string comprises amongst others

  16. Effect of temperature in fluidized bed fast pyrolysis of biomass: oil quality assessment in test units

    NARCIS (Netherlands)

    Westerhof, Roel Johannes Maria; Brilman, Derk Willem Frederik; van Swaaij, Willibrordus Petrus Maria; Kersten, Sascha R.A.

    2010-01-01

    Pine wood was pyrolyzed in a 1 kg/h fluidized bed fast pyrolysis reactor that allows a residence time of pine wood particles up to 25 min. The reactor temperature was varied between 330 and 580 °C to study the effect on product yields and oil composition. Apart from the physical−chemical analysis, a

  17. FY 1975 Report on results of Sunshine Project. Development of techniques of digging high-temperature beds (Conceptual designs of automatic digging systems); 1975 nendo koon chiso kussaku gijutsu no kaihatsu seika hokokusho. Jido kussaku system no gainen sekkei

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1976-03-31

    This project is aimed at development of automatic rotary table type digging apparatus capable of digging high-temperature beds of 3,000 to 5,000 m in depth, 400 degrees C and 500 kg/cm{sup 2}. The automatic excavation apparatus is designed based on the concept that the driller is separated from the running drawworks side for other works. However, it is operated manually in a traditional manner, when the bed for which it is to be used is under complex conditions, or when the bed properties require frequent changes in digging conditions with respect to bit load and speed of rotation. The apparatus works, when the bed is considered to be under essentially constant conditions at a fairly high depth, in such a way that a combination of bit load and speed of rotation is set by the driller, and the work line wound on the drawworks drum is let out to keep the bit load constant. It is equipped with, e.g., a controller, converter and brake operating device, detecting suspension load by the controller, when it increases, increasing speed of air motor after comparing the load with the reference level, and relaxing the brake, to keep the suspension load at the set level. When the suspension load decreases, on the other hand, the air motor is decelerated to tighten the brake. (NEDO)

  18. Researchers solve big mysteries of pebble bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Shams, Afaque; Roelofs, Ferry; Komen, E.M.J. [Nuclear Research and Consultancy Group (NRG), Petten (Netherlands); Baglietto, Emilio [Massachusetts Institute of Technology, Cambridge, MA (United States). Dept. of Nuclear Science and Engineering; Sgro, Titus [CD-adapco, London (United Kingdom). Technical Marketing

    2014-03-15

    The PBR is one type of High Temperature Reactors, which allows high temperature work while preventing the fuel from melting (bringing huge safety margins to the reactor) and high electricity efficiency. The design is also highly scalable; a plant could be designed to be as large or small as needed, and can even be made mobile, allowing it to be used onboard a ship. In a PBR, small particles of nuclear fuel, embedded in a moderating graphite pebble, are dropped into the reactor as needed. At the bottom, the pebbles can be removed simply by opening a small hatch and letting gravity pull them down. To cool the reactor and create electricity, helium gas is pumped through the reactor to pull heat out which is then run through generators. One of the most difficult problems to deal with has been the possible appearance of local temperature hotspots within the pebble bed heating to the point of melting the graphite moderators surrounding the fuel. Obviously, constructing a reactor and experimenting to investigate this possibility is out of the question. Instead, nuclear engineers have been attempting to simulate a PBR with various CFD codes. The thermo-dynamic analysis to simulate realistic conditions in a pebble bed are described and the results are shown. (orig.)

  19. Combustion of gases released from peat or biomass in fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Raiko, R. [Tampere Univ. of Technology (Finland). Energy and Process Engineering

    1996-12-01

    Temperature and gas concentration experiments have been conducted to determine at what temperature carbon monoxide, methane and propane begin to react within the particulate phase of a bubbling fluidized bed. The fluidized bed reactor used in these experiments was a stainless-steel tube with an internal diameter of 50 mm surrounded by an electric heater. Two different natural quartz sands were used (d{sub p} =0.35 mm and 0.6 mm). The bed height used varied between 100 and 260 mm (in unfluidized state). A porous plate distributor, made of kaowool, was used to avoid jets appearing at the distributor. The bed was operated at incipient fluidization (u = 5.9-9 cm/s). The bed temperatures used ranged from 600 deg C to 850 deg C. It was found that carbon monoxide, methane and propane react inside a fluidized bed, but often other conditions than temperature have a considerable effect on the rate of the reaction. The critical temperature was found to be 650 deg C for propane and carbon monoxide and 700 deg C for methane. With under-stoichiometric mixture of carbon monoxide and air the heat release can be over 2.5 MW/m{sup 3} when bed temperature is 650 deg C. According to these experiments it is obvious that the reaction mechanism for carbon monoxide oxidation inside a fluidized bed differs greatly from that of gas phase only. The results of our more than 1300 test runs show clearly the varying effects of the different bed materials. Even with the same bed material totally different results can be obtained. In order to elucidate the possible changes of particle surface, microscopic and porosimetric studies was conducted with both fresh bed particles and used bed particles. Also the effect of commonly used ingredients, like limestone and dolomite, was tested. A global model for carbon monoxide oxidation inside a fluidized bed was introduced. The model was tested against measured data from the laboratory-scale fluidized bed test rig. (Abstract Truncated)

  20. Hostile environments and high temperature measurements; Proceedings of the Conference, Kansas City, MO, Nov. 6-8, 1989

    Science.gov (United States)

    Topics presented include the identification of stagnant region in a fluidized bed combustor, high sensitivity objective grating speckle, an X-ray beam method for displacement and strain distributions using the moire method, and high-temperature deformation of a Ti-alloy composite under complex loading. Also addressed are a hybrid procedure for dynamic characterization of ceramics at elevated temperature, thermo-structural measurements in a SiC coated carbon-carbon hypersonic glide vehicle, and recent experience with elevated-temperature foil strain gages with application to thin-gage materials.

  1. Corn Drying with Zeolite in The Fluidized Bed Dryer under Medium Temperature

    Directory of Open Access Journals (Sweden)

    Mohamad Djaeni

    2013-08-01

    Full Text Available Drying is an important step to find high quality of corn. Based on Standard of National Industry, populer as SNI, number 01-3920-1995, the corn was well stored at moisture content 14% or below (wet basis. However, conventional corn drying dealed with in-efficient energy process and corn quality degradation. This research evaluated the performance of corn drying assisted by zeolite as moisture adsorbent. In this process, the zeolite and corn were placed in the dryer fluidized by warm air as drying medium under 40 - 50oC. The air evaporated water product from corn, and at same time the zeolite adsorbed moisture in air. So, the relative humidity of air in dryer can be kept low in which enhanced the driving force for drying. Beside that, the moisture adsoprtion by zeolite was exothermic process that can supply the energy for drying or keep the dryer temperature. Thus, the drying rate can be faster. This work foccussed to observe the effect of drying temperature, air velocity, and corn to zeolite ratio on drying time as well as corn quality. As indicators, the drying rate was estimated and the proxymates content such as protein, fat, and carbohydrate content were analyzed. The results showed that compared with conventional fluidised bed dryer, corn drying with zeolite, can speed up drying time as well as improving the constant of drying rate. In addition, the corn proximate nutrition content can be well retained. At operating temperature 40oC, air velocity 9 m.s-1, and zeolite to corn ratio 1:2, the drying time can be 60 minutes shorter compared to that without zeolite.

  2. Effect of bed particles to combustion of gases in fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Raiko, R.; Wallen, V.; Etelaeaho, R.; Correia, S. [Tampere Univ. of Technology (Finland). Energy and Process Engineering

    1997-10-01

    The objective of this project was to obtain experimental data on effects of sand particles to the combustion of gases. The effect of the surface area of the particles was tested using different sized particles. The fluidized bed reactor used in these experiments was a stainless-steel tube with an internal diameter of 42 mm surrounded by an electric heater. The test rig was built in the Laboratory of Energy and Process Engineering at Tampere University of Technology. In order to elucidate the possible changes of particle surface, microscopic and porosimetric studies were conducted with both fresh bed particles and used bed particles. These measurements indicate that carbon monoxide significantly reacts with oxygen in the particulate or emulsion phase of a fluidized bed, if the residence time is long enough. The reaction rate depends mainly on temperature, air coefficient, residence time and particle size of the solids. It seems that the combustion enhances if the average particle size increases. Whether this is caused by increased free path length or reduced specific surface area of the bed is yet unknown. The first might be more probable cause because the majority of reactions often took place in the freeboard right above the bed. It was clear that the bed hindered proper combustion in several cases. (orig.)

  3. Direct contact condensation in packed beds

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yi; Klausner, James F.; Mei, Renwei; Knight, Jessica [Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611 (United States)

    2006-12-15

    A diffusion driven desalination process was recently described where a very effective direct contact condenser with a packed bed is used to condense water vapor out of an air/vapor mixture. A laboratory scale direct contact condenser has been fabricated as a twin tower structure with two stages, co-current and countercurrent. Experiments have been operated in each stage with respective saturated air inlet temperatures of 36, 40 and 43{sup o}C. The temperature and humidity data have been collected at the inlet and exit of the packed bed for different water to air mass flow ratios that vary between 0 and 2.5. A one-dimensional model based on conservation principles has been developed, which predicts the variation of temperature, humidity, and condensation rate through the condenser stages. Agreement between the model and experiments is very good. It is observed that the countercurrent flow stage condensation effectiveness is significantly higher than that for the co-current stage. The condensation heat and mass transfer rates were found to decrease when water blockages occur within the packed bed. Using high-speed digital cinematography, it was observed that this problem can occur at any operating condition, and is dependent on the packing surface wetting characteristics. This observation is used to explain the requirement for two different empirical constants, depending on packing diameter, suggested by Onda for the air side mass transfer coefficient correlation. (author)

  4. The R&D of HTGR high temperature helium sampling loop: From HTR-10 to HTR-PM

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Chao, E-mail: fangchao@tsinghua.edu.cn [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center of Advanced Nuclear Energy Technology, Tsinghua University, Beijing 100084 (China); The Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Beijing 100084 (China); Bao, Xuyin; Yang, Chen; Yang, Yanran; Cao, Jianzhu [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Collaborative Innovation Center of Advanced Nuclear Energy Technology, Tsinghua University, Beijing 100084 (China); The Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Beijing 100084 (China)

    2016-09-15

    A High Temperature Helium Sampling Loop (HTHSL) for studying the transportation (deposition) behavior and total amount of solid fission products in high-temperature helium coming from the steam generator (SG) in the 10 MW High Temperature Gas-cooled Test Reactor (HTR-10) and High Temperature Reactor-Pebble bed Modules (HTR-PM) are researched and designed, respectively. Through the optimal design and simulation based on thermohydraulics analysis, the three-sleeve structure of deposition sampling device (DSD) could realize full-length temperature control evenly so that it could be used to study fission products in the primary circuit of HTR-10. On the other hand, an improved DSD is also designed for HTR-PM based on corresponding simulations, which could be used to sample the important nuclei in the high temperature helium from SG. These schemes offer two different methods to obtain the original source term in the high temperature helium, which will provide deeper understanding for the analysis of source terms of HTGR.

  5. Validation of SCALE for High Temperature Gas-Cooled Reactors Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ilas, Germina [ORNL; Ilas, Dan [ORNL; Kelly, Ryan P [ORNL; Sunny, Eva E [ORNL

    2012-08-01

    This report documents verification and validation studies carried out to assess the performance of the SCALE code system methods and nuclear data for modeling and analysis of High Temperature Gas-Cooled Reactor (HTGR) configurations. Validation data were available from the International Handbook of Evaluated Reactor Physics Benchmark Experiments (IRPhE Handbook), prepared by the International Reactor Physics Experiment Evaluation Project, for two different HTGR designs: prismatic and pebble bed. SCALE models have been developed for HTTR, a prismatic fuel design reactor operated in Japan and HTR-10, a pebble bed reactor operated in China. The models were based on benchmark specifications included in the 2009, 2010, and 2011 releases of the IRPhE Handbook. SCALE models for the HTR-PROTEUS pebble bed configuration at the PROTEUS critical facility in Switzerland have also been developed, based on benchmark specifications included in a 2009 IRPhE draft benchmark. The development of the SCALE models has involved a series of investigations to identify particular issues associated with modeling the physics of HTGRs and to understand and quantify the effect of particular modeling assumptions on calculation-to-experiment comparisons.

  6. RESEARCH ON THE INFLUENCE OF TEMPERATURE ON THE ACTIVATION OF SELECTED POROUS MNO2 BEDS

    Directory of Open Access Journals (Sweden)

    Iwona Skoczko

    2016-09-01

    Full Text Available Rising demands concerning water treatment and conservation make it necessary to search for more effective as well as cheap and ecologically safe solutions. During the filtration process quartz sand is replaced by filter materials which also have a strong effect on account of reactions taking place on a bed’s surface. Today’s technologies for groundwater and seepage water treatment in rapid filters make use of oxidation beds. They are able to effectively remove manganese (II and iron (II compounds based on heterogeneous oxidation catalysis. The main catalyst of the manganese removal process in terms of its catalytic oxidation in filtration beds is manganese dioxide. This compound is used as an oxidizing agent in many processes. The research conducted as part of this paper was aimed at creating a product with the qualities similar to a popular Greensand bed protected by patent. The authors tested washed quartz sand varying in granulation which was subject to activation in 10% KMnO4 solution. Grains of quartz sand after covering them with a permanent coat of manganese oxide developed the superficial oxidation layer. While performing the tests, a temperature of the process served as a variable. The beds produced as a result of the experiment enable the removal of iron and manganese from water without prior alkylation. Furthermore, they are an effective method of purifying water of organic pollutants and ammoniacal nitrogen. They function as oxidizing and filtering masses.

  7. Simulation in CFD of a Pebble Bed: Advanced high temperature reactor core using OpenFOAM

    International Nuclear Information System (INIS)

    Dahl, Pamela M.; Su, Jian

    2017-01-01

    Numerical simulations of a Pebble Bed nuclear reactor core are presented using the multi-physics tool-kit OpenFOAM. The HTR-PM is modeled using the porous media approach, accounting both for viscous and inertial effects through the Darcy and Forchheimer model. Initially, cylindrical 2D and 3D simulations are compared, in order to evaluate their differences and decide if the 2D simulations carry enough of the sought information, considering the savings in computational costs. The porous medium is considered to be isotropic, with the whole length of the packed bed occupied homogeneously with the spherical fuel elements. Steady-state simulations for normal equilibrium operation are performed, using a semi sine function of the power density along the vertical axis as the source term for the energy balance equation.Total pressure drop is calculated and compared with that obtained from literature for a similar case. At a second stage, transient simulations are performed, where relevant parameters are calculated and compared to those of the literature. (author)

  8. Simulation in CFD of a Pebble Bed: Advanced high temperature reactor core using OpenFOAM

    Energy Technology Data Exchange (ETDEWEB)

    Dahl, Pamela M.; Su, Jian, E-mail: sujian@nuclear.ufrj.br [Coordenacao de Pos-Graduacao e Pesquisa de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear

    2017-07-01

    Numerical simulations of a Pebble Bed nuclear reactor core are presented using the multi-physics tool-kit OpenFOAM. The HTR-PM is modeled using the porous media approach, accounting both for viscous and inertial effects through the Darcy and Forchheimer model. Initially, cylindrical 2D and 3D simulations are compared, in order to evaluate their differences and decide if the 2D simulations carry enough of the sought information, considering the savings in computational costs. The porous medium is considered to be isotropic, with the whole length of the packed bed occupied homogeneously with the spherical fuel elements. Steady-state simulations for normal equilibrium operation are performed, using a semi sine function of the power density along the vertical axis as the source term for the energy balance equation.Total pressure drop is calculated and compared with that obtained from literature for a similar case. At a second stage, transient simulations are performed, where relevant parameters are calculated and compared to those of the literature. (author)

  9. SPOUTED BED DESIGN CONSIDERATIONS FOR COATED NUCLEAR FUEL PARTICLES

    Energy Technology Data Exchange (ETDEWEB)

    Marshall, Douglas W.

    2017-07-01

    High Temperature Gas Cooled Reactors (HTGRs) are fueled with tristructural isotropic (TRISO) coated nuclear fuel particles embedded in a carbon-graphite fuel body. TRISO coatings consist of four layers of pyrolytic carbon and silicon carbide that are deposited on uranium ceramic fuel kernels (350µm – 500µm diameters) in a concatenated series of batch depositions. Each layer has dedicated functions such that the finished fuel particle has its own integral containment to minimize and control the release of fission products into the fuel body and reactor core. The TRISO coatings are the primary containment structure in the HTGR reactor and must have very high uniformity and integrity. To ensure high quality TRISO coatings, the four layers are deposited by chemical vapor deposition (CVD) using high purity precursors and are applied in a concatenated succession of batch operations before the finished product is unloaded from the coating furnace. These depositions take place at temperatures ranging from 1230°C to 1550°C and use three different gas compositions, while the fuel particle diameters double, their density drops from 11.1 g/cm3 to 3.0 g/cm3, and the bed volume increases more than 8-fold. All this is accomplished without the aid of sight ports or internal instrumentation that could cause chemical contamination within the layers or mechanical damage to thin layers in the early stages of each layer deposition. The converging section of the furnace retort was specifically designed to prevent bed stagnation that would lead to unacceptably high defect fractions and facilitate bed circulation to avoid large variability in coating layer dimensions and properties. The gas injection nozzle was designed to protect precursor gases from becoming overheated prior to injection, to induce bed spouting and preclude bed stagnation in the bottom of the retort. Furthermore, the retort and injection nozzle designs minimize buildup of pyrocarbon and silicon carbide on the

  10. Simulation of petcoke gasification in slagging moving bed reactors

    Energy Technology Data Exchange (ETDEWEB)

    Nagpal, Soumitro; Sarkar, T.K.; Sen, P.K. [Research and Development Center, Engineers India Limited, Gurgaon 122001 (India)

    2005-03-25

    A mathematical model for simulation of moving bed petcoke gasifiers was developed. The model introduces a new feed characterization method, gas-phase resistance and volatilization models. The model is validated using reported data for a slagging gasifier. Effect of feed oxygen-to-coke and steam-to-coke ratios and feed coke rates on gasification performance was examined. Slagging zone moving bed gasifier operation with very high petcoke fluxes of over 4000 kg/m{sup 2}/h was possible with high petcoke conversion. Peak gas temperatures exceeded 1500 {sup o}C. Fluxes higher than 5000 kg/m{sup 2}/h are limited by an approach to fluidization of small particles in the combustion zone. The moving bed gasifier performance was found superior to performance of an entrained flow gasifier (EFG) with respect to energy efficiency and oxygen consumption.

  11. Wall-to-bed heat transfer in gas-solid fluidized beds: a computational and experimental study

    NARCIS (Netherlands)

    Patil, D.J.; Smit, J.; van Sint Annaland, M.; Kuipers, J.A.M.

    2006-01-01

    The wall-to-bed heat transfer in gas-solid fluidized beds is mainly determined by phenomena prevailing in a thermal boundary layer with a thickness in the order of magnitude of the size of a single particle. In this thermal boundary layer the temperature gradients are very steep and the local

  12. Determination of electrical resistivity of dry coke beds

    Energy Technology Data Exchange (ETDEWEB)

    Eidem, P.A.; Tangstad, M.; Bakken, J.A. [NTNU, Trondheim (Norway)

    2008-02-15

    The electrical resistivity of the coke bed is of great importance when producing FeMn, SiMn, and FeCr in a submerged arc furnace. In these processes, a coke bed is situated below and around the electrode tip and consists of metallurgical coke, slag, gas, and metal droplets. Since the basic mechanisms determining the electrical resistivity of a coke bed is not yet fully understood, this investigation is focused on the resistivity of dry coke beds consisting of different carbonaceous materials, i.e., coke beds containing no slag or metal. A method that reliably compares the electrical bulk resistivity of different metallurgical cokes at 1500{sup o} C to 1600{sup o}C is developed. The apparatus is dimensioned for industrial sized materials, and the electrical resistivity of anthracite, charcoal, petroleum coke, and metallurgical coke has been measured. The resistivity at high temperatures of the Magnitogorsk coke, which has the highest resistivity of the metallurgical cokes investigated, is twice the resistivity of the Corus coke, which has the lowest electrical resistivity. Zdzieszowice and SSAB coke sort in between with decreasing resistivities in the respective order. The electrical resistivity of anthracite, charcoal, and petroleum coke is generally higher than the resistivity of the metallurgical cokes, ranging from about two to about eight times the resistivity of the Corus coke at 1450{sup o}C. The general trend is that the bulk resistivity of carbon materials decreases with increasing temperature and increasing particle size.

  13. Women's experience of hospitalized bed rest during high-risk pregnancy.

    Science.gov (United States)

    Rubarth, Lori Baas; Schoening, Anne M; Cosimano, Amy; Sandhurst, Holly

    2012-01-01

    To describe the lived experience of the hospitalized pregnant woman on bed rest. A qualitative, phenomenological design. Three high-risk antepartum units in the midwestern United States. A self-selected, convenience sample of 11 high-risk pregnant women. Phenomenological study using thematic analysis of completed handwritten journals and/or online blogs. Women described the battles that they fought each day for the lives of their unborn children. Using an imagery of war, three categories emerged: (a) the war within, (b) fighting each battle, and (c) bringing in reinforcements. Women experience many different emotions and stressors during restricted bed rest. A nurse's understanding of this experience is essential to provide adequate care and coping strategies for women at this time. © 2012 AWHONN, the Association of Women's Health, Obstetric and Neonatal Nurses.

  14. High Temperature Calcination - MACT Upgrade Equipment Pilot Plant Test

    Energy Technology Data Exchange (ETDEWEB)

    Richard D. Boardman; B. H. O& #39; Brien; N. R. Soelberg; S. O. Bates; R. A. Wood; C. St. Michel

    2004-02-01

    About one million gallons of acidic, hazardous, and radioactive sodium-bearing waste are stored in stainless steel tanks at the Idaho Nuclear Technology and Engineering Center (INTEC), which is a major operating facility of the Idaho National Engineering and Environmental Laboratory. Calcination at high-temperature conditions (600 C, with alumina nitrate and calcium nitrate chemical addition to the feed) is one of four options currently being considered by the Department of Energy for treatment of the remaining tank wastes. If calcination is selected for future processing of the sodium-bearing waste, it will be necessary to install new off-gas control equipment in the New Waste Calcining Facility (NWCF) to comply with the Maximum Achievable Control Technology (MACT) standards for hazardous waste combustors and incinerators. This will require, as a minimum, installing a carbon bed to reduce mercury emissions from their current level of up to 7,500 to <45 {micro}g/dscm, and a staged combustor to reduce unburned kerosene fuel in the off-gas discharge to <100 ppm CO and <10 ppm hydrocarbons. The staged combustor will also reduce NOx concentrations of about 35,000 ppm by 90-95%. A pilot-plant calcination test was completed in a newly constructed 15-cm diameter calciner vessel. The pilot-plant facility was equipped with a prototype MACT off-gas control system, including a highly efficient cyclone separator and off-gas quench/venturi scrubber for particulate removal, a staged combustor for unburned hydrocarbon and NOx destruction, and a packed activated carbon bed for mercury removal and residual chloride capture. Pilot-plant testing was performed during a 50-hour system operability test January 14-16, followed by a 100-hour high-temperature calcination pilot-plant calcination run January 19-23. Two flowsheet blends were tested: a 50-hour test with an aluminum-to-alkali metal molar ratio (AAR) of 2.25, and a 50-hour test with an AAR of 1.75. Results of the testing

  15. Fluidized-bed firing of washery wastes

    Energy Technology Data Exchange (ETDEWEB)

    Rubin, Yu M; Gavrik, M V

    1978-01-01

    Tailings containing SiO2 (56.76%), A12O3 (25.63%), Fe2O3 (10.22%) plus CaO, MgO and SOat3 were fluidized at 1.7-2.0 m/s. This gives a uniform pressure of 6 kg-f/m2 at bed heights of 100 mm, though this is higher in the upper layers where the fine material tends to concentrate. The resistance of the bed is directly proportional to its height. Minimum oxygen, maximum carbon dioxide and maximum temperature are found in the section 250-300 mm above the grid (bed height 500 mm); in the upper zone of the bed, some decrease in temperature and carbon dioxide, and increase in oxygen are associated with the ingress of air through the discharge chute. Waste heat should be utilised to help to cover costs of desulphurising stack gases.

  16. Fluidized bed combustion of single coal char particles at high CO{sub 2} concentration

    Energy Technology Data Exchange (ETDEWEB)

    Scala, F.; Chirone, R. [CNR, Naples (Italy)

    2010-12-15

    Combustion of single coal char particles was studied at 850{sup o}C in a lab-scale fluidized bed at high CO{sub 2} concentration, typical of oxyfiring conditions. The burning rate of the particles was followed as a function of time by continuously measuring the outlet CO and O{sub 2} concentrations. Some preliminary evaluations on the significance of homogeneous CO oxidation in the reactor and of carbon gasification by CO{sub 2} in the char were also carried out. Results showed that the carbon burning rate increases with oxygen concentration and char particle size. The particle temperature is approximately equal to that of the bed up to an oxygen concentration of 2%, but it is considerably higher for larger oxygen concentrations. Both CO{sub 2} gasification of char and homogeneous CO oxidation are not negligible. The gasification reaction rate is slow and it is likely to be controlled by intrinsic kinetics. During purely gasification conditions the extent of carbon loss due to particle attrition by abrasion (estimated from the carbon mass balance) appears to be much more important than under combustion conditions.

  17. Coolability of a 3D homogeneous debris bed, experimental and numerical investigations

    International Nuclear Information System (INIS)

    Atkhen, K.; Berthoud, G.

    2001-01-01

    Within the framework of nuclear safety analysis, we present here experimental and numerical results in the field of debris bed coolability. Experimental data are provided by the SILFIDE 3D experimental facility in which the debris bed is heated by induction, at Electricite de France (EDF). Numerical computations are obtained with MC3D-REPO which is a 3-phase and 3D code developed by the Commissariat a l'Energie Atomique (CEA). The uniform debris bed consists of 2 and 3,17 mm diameter steel beads contained in a 50 cm x 60 cm x 10 cm vessel. Water is used as a coolant and can be introduced either by the top or the bottom of the bed at a determined temperature. Due to heterogeneous power distribution within the bed, two definitions for the critical heat flux are proposed: the classical mean value and the local flux (much higher). Even in the first case, the measured dryout heat flux is higher than the Lipinsky 1-D flux. Temperature curve analyses show that the dryout phenomenon is very local, therefore one should be careful about the right flux definition to use. As the injected power is being increased stepwise, steady temperature stages above saturation temperature before dryout can be observed. A discussion is proposed. For some very high values of the induction power, some spheres melted together, leading to a bigger non-porous region. Even if the local temperature went over 1300 C, the bed was still coolable and the critical heat flux value was not impacted. Some parametric studies led to the following conclusions: bottom coolant injection leads to a twice time higher critical flux than by top injection, the influence of the height of the water pool above debris bed is negligible, a sub-cooled liquid injection has no influence on the coolability. Fluidization of surface particles is also discussed. The MC3D-REPO model assumes a thermal equilibrium between the three phases, which gives results in agreement with experiments until dryout occurs. (author)

  18. Neutronic design of a Liquid Salt-cooled Pebble Bed Reactor (LSPBR)

    International Nuclear Information System (INIS)

    De Zwaan, S. J.; Boer, B.; Lathouwers, D.; Kloosterman, J. L.

    2006-01-01

    A renewed interest has been raised for liquid salt cooled nuclear reactors. The excellent heat transfer properties of liquid salt coolants provide several benefits, like lower fuel temperatures, higher coolant outlet temperatures, increased core power density and better decay heat removal. In order to benefit from the online refueling capability of a pebble bed reactor, the Liquid Salt Pebble Bed Reactor (LSPBR) is proposed. This is a high temperature pebble-bed reactor with a fuel design similar to existing HTRs, but using a liquid salt as a coolant. In this paper, the selection criteria for the liquid salt coolant are described. Based on its neutronic properties, LiF-BeF 2 (FLIBE) was selected for the LSPBR. Two designs of the LSPBR were considered: a cylindrical core and an annular core with a graphite inner reflector. Coupled neutronic-thermal hydraulic calculations were performed to obtain the steady state power distribution and the corresponding fuel temperatures. Finally, calculations were performed to investigate the decay heat removal capability in a protected loss-of-forced cooling accident. The maximum allowable power that can be produced with the LSPBR is hereby determined. (authors)

  19. Programmes and projects for high-temperature reactor development

    International Nuclear Information System (INIS)

    Bogusch, Edgar; Hittner, Dominique

    2009-01-01

    An increasing attention has to be recognised worldwide on the development of High-Temperature Reactors (HTR) which has started in Germany and other countries in the 1970ies. While pebble bed reactors with spherical fuel elements have been developed and constructed in Germany, countries such as France, the US and Russia investigated HTR concepts with prismatic block-type fuel elements. The concept of a modular HTR formerly developed by Areva NP was an essential basis for the HTR-10 in China. A pebble bed HTR for electricity production is developed in South Africa. The construction is planned after the completion of the licensing procedure. Also the US is planning an HTR under the NGNP (Next Generation Nuclear Plant) Project. Due to the high temperature level of the helium coolant, the HTR can be used not only for electricity production but also for supply of process heat. Including its inherent safety features the HTR is an attractive candidate for heat supply to various types of plants e.g. for hydrogen production or coal liquefactions. The conceptual design of an HTR with prismatic fuel elements for the cogeneration of electricity and process heat has been developed by Areva NP. On the European scale the HTR development is promoted by the RAPHAEL (ReActor for Process heat, Hydrogen And ELectricity generation) project. RAPHAEL is an Integrated Project of the Euratom 6th Framework Programme for the development of technologies towards a Very High-Temperature Reactor (VHTR) for the production of electricity and heat. It is financed jointly by the European Commission and the partners of the HTR Technology Network (HTR-TN) and coordinated by Areva NP. The RAPHAEL project not only promotes HTR development but also the cooperation with other European projects such as the material programme EXTREMAT. Furthermore HTR technology is investigated in the frame of Generation IV International Forum (GIF). The development of a VHTR with helium temperatures above 900 C for the

  20. Thermal fatigue and creep evaluation for the bed in tritium SDS

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Woo-seok, E-mail: wschoi@kaeri.re.kr [Korea Atomic Energy Research Institute, Yuseong, Daejeon (Korea, Republic of); Park, Chang-gyu [Korea Atomic Energy Research Institute, Yuseong, Daejeon (Korea, Republic of); Ju, Yong-sun [KOASIS, Yuseong, Daejeon (Korea, Republic of); Kang, Hyun-goo; Jang, Min-ho; Yun, Sei-hun [National Fusion Research Institute, Yuseong, Daejeon (Korea, Republic of)

    2016-11-01

    Highlights: • To evaluate the integrity of the ITER tritium SDS bed, three kinds of assessments were conducted. • The structural analysis showed that the stress induced from the thermal load and the internal pressure is within the design stress intensity. • The combined fatigue and creep assessment was also performed according to the procedure of ASME code Subsection NH. • A new operation procedure to obtain more integrity margin was recommended. • The other operation procedure could be considered which makes the rapid operation possible giving up the marginal integrity. - Abstract: The primary vessel of ITER tritium SDS bed is made of stainless steel. It is heated beyond 500 °C to desorb tritium. During this process the primary vessel is subject to thermal stress. And it is also subject to thermal fatigue by the iterative process of absorption and desorption. In addition, its operation temperature range is in the thermal creep temperature region. Therefore, the tritium SDS bed should have sufficient design stress intensity under the high temperature operating conditions. It should also be free of damage due to fatigue during the design life. Thermal analysis and structural analysis was performed using a finite element method to calculate the temperature and the stress distribution of the ITER tritium SDS bed due to the internal pressure and thermal loads. The thermal fatigue and creep effects were also evaluated since the tritium SDS bed was heated to hot temperature region where creep occurs. Based on the distribution of the primary stress and secondary stress results, two evaluation cross-sections were selected. The evaluation showed that the calculated value on the cross-sections satisfied all of the limits of the design code requirements.

  1. High-temperature reactor developments in the Netherlands

    International Nuclear Information System (INIS)

    Schram, R.P.C.; Cordfunke, E.H.P.; Heek, A.I. van

    1996-01-01

    The high-temperature reactor development in the Netherlands is embedded in the WHITE reactor program, in which several Dutch research institutes and engineering companies participate. The activities within the WHITE program are focused on the development of a small scale HTR for combined heat and power generation. In 1995, design choices for a pebble bed reactor were made at ECN. The first concept HTR will have a closed cycle helium turbine and a power level of 40 MWth. It is intended to make the market introduction of a commercially competitive HTR feasible. As a part of the HTR program at ECN, chemical aspects of HTR fuel and coated particles are studied. Experimental work on the oxidation resistance of coating materials and fission product attack on coating materials as well as thermochemical calculations of the fuel particles are done at ECN. The concept-HTR of ECN is fuelled with UO 2 , but the use of thorium is considered. The composition of the fuel determines the oxygen potential, which plays a key role in chemical safety of the fuel. Thermochemical calculations of the chemical form of cesium inside the HTR fuel particles were performed for a wide oxygen potential range. The chemical form of cesium determines the cesium pressure inside the fuel particle, which in turn determines the release behavior of Cs from defective particles. At normal operating temperatures and low oxygen potentials, the chemical form of cesium is C 60 Cs. It is known that cesium carbon compounds decompose above 650degC in vacuum. The stability of these compounds in the fuel particles at high temperatures(1000-1600degC) is questioned. Decomposition of these compounds may result in high cesium pressures even at normal operating conditions. Experimental work on the thermodynamic properties of cesium compounds at high temperatures is currently performed. (J.P.N.)

  2. Dry out of a fluidized particle bed with internal heat generation

    International Nuclear Information System (INIS)

    Keowen, R.S.; Catton, I.

    1975-03-01

    An apparatus was designed to adequately simulate the characteristics of a particle bed formed by nuclear reactor fuel after the reactor has been operable for some length of time at high power. This was accomplished by using a 10 KW, 453 Kc induction heater, coupled through a multi-turn work coil to particle beds of cast steel shot and lead shot in water. The temperature response and dryout condition was determined for various bed levels, particle diameters, and heat fluxes. Analysis of the data retrieved from the bed was used to generate a family of curves to predict the necessary conditions for dryout to occur within a fluidized particle bed with internal heat generation. The results presented here, with internal heat generation, show that previous results with bottom heating and volume heating are conservative. (U.S.)

  3. Fluidized bed selective pyrolysis of coal

    Science.gov (United States)

    Shang, Jer Y.; Cha, Chang Y.; Merriam, Norman W.

    1992-01-01

    The present invention discloses a process for the pyrolysis of coal which comprises the effective utilization of two zonal inclined fluidized beds, where said zones can be selectively controlled as to temperature and heating rate. The first zonal inclined fluidized bed serves as a dryer for crushed coal and additionally is controlled to selectively pyrolyze said coal producing substantially carbon dioxide for recycle use. The second zonal inclined fluidized bed further pyrolyzes the coal to gaseous, liquid and char products under controlled temperature and heating rate zones designed to economically integrate the product mix. The gas and liquid products are recovered from the gaseous effluent stream while the char which remains can be further treated or utilized in a subsequent process step.

  4. Local total and radiative heat-transfer coefficients during the heat treatment of a workpiece in a fluidised bed

    International Nuclear Information System (INIS)

    Gao, W.M.; Kong, L.X.; Hodgson, P.D.

    2006-01-01

    The heat-transfer coefficients around a workpiece immersed in an electrically heated heat treatment fluidised bed were studied. A suspension probe designed to simulate a workpiece of complex geometry was developed to measure local total and radiative heat-transfer coefficients at a high bed temperature. The probe consisted of an energy-storage region separated by insulation from the fluidised bed, except for the measuring surface, and a multi-thermocouple measurement system. Experiments in the fluidised bed were performed for a fluidising medium of 120-mesh alumina, a wide temperature range of 110-1050 deg. C and a fluidising number range of 1.18-4.24. It was found that the workpiece surface temperature has a more significant effect on heat transfer than the bed temperature. The total heat-transfer coefficient at the upper surface of the workpiece sharply decreased at the start of heating, and then steadily increased as heating progressed, while a sharp decrease became a rapid increase and then a slow increase for the radiative heat-transfer coefficient. A great difference in the heat-transfer coefficients around the workpiece was observed

  5. Modelling of Effects of Operating Conditions and Coal Reactivity on Temperature of Burning Particles in Fluidized Bed Combustion

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Karel; Hartman, Miloslav; Pohořelý, Michael; Trnka, Otakar

    2004-01-01

    Roč. 1, č. 2 (2004), s. 261-274 ISSN 1211-1910 R&D Projects: GA AV ČR IAA4072201; GA AV ČR IAA4072001 Institutional research plan: CEZ:AV0Z4072921 Keywords : fluidized bed combustion * char temperature * modelling Subject RIV: DI - Air Pollution ; Quality

  6. Bed mixing dryer for high moisture content fuels

    Energy Technology Data Exchange (ETDEWEB)

    Hulkkonen, S; Heinonen, O. [Imatran Voima Oy, Vantaa (Finland)

    1998-12-31

    Bed mixing dryer is a new type of fuel drying technology for fluidized bed combustion. The idea is to extract hot bed material from the fluidized bed and use it as a heat source for drying the fuel. Drying occurs at steam atmosphere which makes it possible to recover the latent heat of evaporation to process. This improves the thermal efficiency of the power plant process considerably, especially in combined heat and power applications. Imatran Voima Oy (IVO) has developed the Bed Mixing Dryer technology since early 1990s. The first pilot plant was built in 1994 to IVO`s Kuusamo peat and wood fired power plant. The capacity of the plant is 6 MW{sub e} and 20 MW of district heat. In Kuusamo the dryer is connected to a bubbling fluidized bed. Since it`s commissioning the dryer has been used successfully for about 3000 hours during the heating season in wintertime. The second application of the technology will be a demonstration project in Oerebro (S). IVO Power Engineering Ltd will supply in 1997 a dryer to Oerebro Energi`s peat, wood and coal fired CHP plant equipped with circulating fluidized bed boiler. The fuel to be dried is sawdust with fuel input of about 60 MW. In Kuusamo the dryer produces 3 MW of additional district heat and in Oerebro 6 MW. The fuels in Kuusamo are peat, saw dust and bark. In addition to the municipal heat production this type of drying technology has its benefits in pulp and paper industry processes. Disposal of paper mill sludges is becoming more difficult and costly which has resulted in need of alternative treatment. Drying of the sludge before combustion in a boiler for power production is an attractive option. At the moment IVO is carrying out several studies to apply the Bed Mixing Dryer in pulp and paper industry processes. Economy of drying the sludge looks promising

  7. Bed mixing dryer for high moisture content fuels

    Energy Technology Data Exchange (ETDEWEB)

    Hulkkonen, S.; Heinonen, O. [Imatran Voima Oy, Vantaa (Finland)

    1997-12-31

    Bed mixing dryer is a new type of fuel drying technology for fluidized bed combustion. The idea is to extract hot bed material from the fluidized bed and use it as a heat source for drying the fuel. Drying occurs at steam atmosphere which makes it possible to recover the latent heat of evaporation to process. This improves the thermal efficiency of the power plant process considerably, especially in combined heat and power applications. Imatran Voima Oy (IVO) has developed the Bed Mixing Dryer technology since early 1990s. The first pilot plant was built in 1994 to IVO`s Kuusamo peat and wood fired power plant. The capacity of the plant is 6 MW{sub e} and 20 MW of district heat. In Kuusamo the dryer is connected to a bubbling fluidized bed. Since it`s commissioning the dryer has been used successfully for about 3000 hours during the heating season in wintertime. The second application of the technology will be a demonstration project in Oerebro (S). IVO Power Engineering Ltd will supply in 1997 a dryer to Oerebro Energi`s peat, wood and coal fired CHP plant equipped with circulating fluidized bed boiler. The fuel to be dried is sawdust with fuel input of about 60 MW. In Kuusamo the dryer produces 3 MW of additional district heat and in Oerebro 6 MW. The fuels in Kuusamo are peat, saw dust and bark. In addition to the municipal heat production this type of drying technology has its benefits in pulp and paper industry processes. Disposal of paper mill sludges is becoming more difficult and costly which has resulted in need of alternative treatment. Drying of the sludge before combustion in a boiler for power production is an attractive option. At the moment IVO is carrying out several studies to apply the Bed Mixing Dryer in pulp and paper industry processes. Economy of drying the sludge looks promising

  8. Transient core-debris bed heat-removal experiments and analysis

    International Nuclear Information System (INIS)

    Ginsberg, T.; Klein, J.; Klages, J.; Schwarz, C.E.; Chen, J.C.

    1982-08-01

    An experimental investigation is reported of the thermal interaction between superheated core debris and water during postulated light-water reactor degraded core accidents. Data are presented for the heat transfer characteristics of packed beds of 3 mm spheres which are cooled by overlying pools of water. Results of transient bed temperature and steam flow rate measurements are presented for bed heights in the range 218 mm-433 mm and initial particle bed temperatures between 530K and 972K. Results display a two-part sequential quench process. Initial frontal cooling leaves pockets or channels of unquenched spheres. Data suggest that heat transfer process is limited by a mechanism of countercurrent two-phase flow. An analytical model which combines a bed energy equation with either a quasisteady version of the Lipinski debris bed model or a critical heat flux model reasonably well predicts the characteristic features of the bed quench process. Implications with respect to reactor safety are discussed

  9. Photocatalytic Degradation of Chlorobenzene by TiO2 in High-Temperature and High-Pressure Water

    Directory of Open Access Journals (Sweden)

    N. Kometani

    2008-01-01

    Full Text Available A fluidized-bed-type flow reactor available for the photocatalytic treatment of the suspension of model soil under high-temperature, high-pressure conditions was designed. An aqueous suspension containing hydrogen peroxide (H2O2 as an oxidizer and inorganic oxides as a model soil, titania (TiO2, silica (SiO2, or kaoline (Al2Si2O5(OH4 was continuously fed into the reactor with the temperature and the pressure controlled to be T=20–400∘C and P = 30 MPa, respectively. The degradation of chlorobenzene (CB in water was chosen as a model oxidation reaction. It appeared that most of the model soils are not so harmful to the SCWO treatment of CB in solutions. When the TiO2 suspension containing H2O2 was irradiated with near-UV light, the promotion of the degradation caused by photocatalytic actions of TiO2 was observed at all temperatures. Persistence of the photocatalytic activity in the oxidation reaction in high-temperature, high-pressure water would open up a possibility of the development of the hybrid process based on the combination of SCWO process and TiO2 photocatalysis for the treatment of environmental pollutants in soil and water, which are difficult to handle by conventional SCWO process or catalytic SCWO process alone.

  10. Investigation on catalytic gasification of high-ash coal with mixing-gas in a small-scale fluidised bed

    Energy Technology Data Exchange (ETDEWEB)

    Chen, X.; Zhang, J.; Lin, J. [Fuzhou University, Fuzhou (China)

    2005-10-15

    The experimental study on the Yangquan high-ash coal catalytic gasification with mixing gas by using solid alkali or waste liquid of viscose fiber as the catalyst in a small-scale fluidized bed with 28 mm i.d. was carried out. The loading saturation levels of two catalysts in Yangquan high-ash coal are about 6%. Under the gasification temperature ranging from 830 to 900{sup o}C and from 900 to 920{sup o}C, the apparent reaction order of Yangquan high-ash coal with respect to the unreacted carbon fraction approximates to 2.3 and 1/3 for the non-catalyst case, respectively. Also, the different values of apparent reaction order in the two temperature ranges are presented for the case with 3% solid alkali catalyst loaded. At the low temperature ranging from 830 to 860{sup o}C, the apparent reaction order of catalytic gasification is 1 since enough active carbon sites on the coal surface are formed during the catalytic gasification by solid alkali. But at the high temperature ranging from 860 to 920{sup o}C, the sodium carbonate produced by the reaction of solid alkali with carbon dioxide can be easily fused, transferred and re-distributed, which affects the gasification reaction rate, and the apparent reaction order of catalytic gasification is reduced to 1.3. 10 refs., 9 figs., 4 tab s.

  11. The thermal conductivity of beds of spheres

    International Nuclear Information System (INIS)

    McElroy, D.L.; Weaver, F.J.; Shapiro, M.; Longest, A.W.; Yarbrough, D.W.

    1987-01-01

    The thermal conductivities (k) of beds of solid and hollow microspheres were measured using two radial heat flow techniques. One technique provided k-data at 300 K for beds with the void spaces between particles filled with argon, nitrogen, or helium from 5 kPa to 30 MPa. The other technique provided k-data with air at atmospheric pressure from 300 to 1000 K. The 300 K technique was used to study bed systems with high k-values that can be varied by changing the gas type and gas pressure. Such systems can be used to control the operating temperature of an irradiation capsule. The systems studied included beds of 500 μm dia solid Al 2 O 3 , the same Al 2 O 3 spheres mixed with spheres of silica--alumina or with SiC shards, carbon spheres, and nickel spheres. Both techniques were used to determine the k-value of beds of hollow spheres with solid shells of Al 2 O 3 , Al 2 O 3 /center dot/7 w/o Cr 2 O 3 , and partially stabilized ZrO 2 . The hollow microspheres had diameters from 2100 to 3500 μm and wall thicknesses from 80 to 160 μm. 12 refs., 7 figs., 4 tabs

  12. Improved lignin pyrolysis for phenolics production in a bubbling bed reactor--Effect of bed materials.

    Science.gov (United States)

    Li, Dongbing; Briens, Cedric; Berruti, Franco

    2015-01-01

    Lignin pyrolysis was studied in a bubbling fluidized bed reactor equipped with a fractional condensation train, using nitrogen as the fluidization gas. The effect of different bed materials (silica sand, lignin char, activated lignin char, birch bark char, and foamed glass beads) on bio-oil yield and quality was investigated for a pyrolysis temperature of 550 °C. Results how that a bed of activated lignin char is preferable to the commonly used silica sand: pyrolysis of Kraft lignin with a bed of activated lignin char not only provides a pure char product, but also a higher dry bio-oil yield (with a relative increase of 43%), lower pyrolytic water production, and better bio-oil quality. The bio-oil obtained from Kraft lignin pyrolysis with a bed of activated lignin char has a lower average molecular weight, less tar, more phenolics, and less acidity than when sand is used as bed material. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Effects of high salinity wastewater on methanogenic sludge bed systems

    NARCIS (Netherlands)

    Ismail, S.; Gonzalez-Contreras, P.A.; Jeison, D.A.; Lier, van J.B.

    2008-01-01

    The attainable loading potentials of anaerobic sludge bed systems are strongly dependent on the growth of granular biomass with a particular wastewater. Experiments were conducted to determine the effects of high salinity wastewater on the biological and physical properties of methanogenic sludge.

  14. The Safety of Hospital Beds: Ingress, Egress, and In-Bed Mobility.

    Science.gov (United States)

    Morse, Janice M; Gervais, Pierre; Pooler, Charlotte; Merryweather, Andrew; Doig, Alexa K; Bloswick, Donald

    2015-01-01

    To explore the safety of the standard and the low hospital bed, we report on a microanalysis of 15 patients' ability to ingress, move about the bed, and egress. The 15 participants were purposefully selected with various disabilities. Bed conditions were randomized with side rails up or down and one low bed with side rails down. We explored the patients' use of the side rails, bed height, ability to lift their legs onto the mattress, and ability to turn, egress, and walk back to the chair. The standard bed was too high for some participants, both for ingress and egress. Side rails were used by most participants when entering, turning in bed, and exiting. We recommend that side rails be reconsidered as a means to facilitate in-bed movement, ingress, and egress. Furthermore, single deck height settings for all patients are not optimal. Low beds as a safety measure must be re-evaluated.

  15. Investigation on the Permeability Evolution of Gypsum Interlayer Under High Temperature and Triaxial Pressure

    Science.gov (United States)

    Tao, Meng; Yechao, You; Jie, Chen; Yaoqing, Hu

    2017-08-01

    The permeability of the surrounding rock is a critical parameter for the designing and assessment of radioactive waste disposal repositories in the rock salt. Generally, in the locations that are chosen for radioactive waste storage, the bedded rock salt is a sedimentary rock that contains NaCl and Na2SO4. Most likely, there are also layers of gypsum ( {CaSO}_{ 4} \\cdot 2 {H}_{ 2} {O)} present in the salt deposit. Radioactive wastes emit a large amount of heat and hydrogen during the process of disposal, which may result in thermal damage of the surrounding rocks and cause a great change in their permeability and tightness. Therefore, it is necessary to investigate the permeability evolution of the gypsum interlayer under high temperature and high pressure in order to evaluate the tightness and security of the nuclear waste repositories in bedded rock salt. In this study, a self-designed rock triaxial testing system by which high temperature and pressure can be applied is used; the μCT225kVFCB micro-CT system is also employed to investigate the permeability and microstructure of gypsum specimens under a constant hydrostatic pressure of 25 MPa, an increasing temperature (ranging from 20 to 650 °C), and a variable inlet gas pressure (1, 2, 4, 6 MPa). The experimental results show: (a) the maximum permeability measured during the whole experiment is less than 10-17 m2, which indicates that the gypsum interlayer has low permeability under high temperature and pressure that meet the requirements for radioactive waste repository. (b) Under the same temperature, the permeability of the gypsum specimen decreases at the beginning and then increases as the pore pressure elevates. When the inlet gas pressure is between 0 and 2 MPa, the Klinkenberg effect is very pronounced. Then, as the pore pressure increases, the movement behavior of gas molecules gradually changes from free motion to forced directional motion. So the role of free movement of gas molecules gradually

  16. Use of soft hydrothermal processing to improve and recycle bedding for laboratory animals.

    Science.gov (United States)

    Miyamoto, T; Li, Z; Kibushi, T; Yamasaki, N; Kasai, N

    2008-10-01

    Cage bedding for laboratory rodents can influence animal wellbeing and thus the experimental data. In addition, a large amount of used bedding containing excrement is discharged as medical waste from life science institutes and breeding companies. We developed a ground-breaking system to improve fresh bedding and recycle used bedding by applying a soft hydrothermal process with high-temperature and high-pressure dry steam. The system removes both harmful organic components and aromatic hydrocarbons that can affect animals' metabolism. The purpose of the present study was to evaluate the chemical and physical properties of the improved fresh bedding and the recycled used bedding treated by the system. The results showed that 68-99% of the predominant aromatic hydrocarbons were removed from fresh bedding treated at 0.35 MPa and 140 degrees C for 120 min ('improved bedding'). In addition, 59.4-99.0% of predominant harmful organic compounds derived from excrement were removed from used bedding treated at 0.45 MPa and 150 degrees C for 60 min ('recycled bedding'). The soft hydrothermal treatment increased the number of acidic functional groups on the bedding surface and gave it the high adsorptive efficiency of ammonia gas. Harmful substances such as microorganisms, heavy metals and pesticides decreased below the detection limit. The results clearly showed that the improved and recycled bedding is safer for laboratory rodents and has the potential to ameliorate conditions in primary and secondary enclosures (e.g. cages and animal rooms) used for maintaining laboratory animals. This process may be one of the most advanced techniques in providing an alternative to softwood and other bedding, economizing through the recycling of used bedding and reducing bedding waste from animal facilities.

  17. Production of polycrystalline silicon by fluidized-bed-problems and recent progress of study

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, Toshinori

    1988-10-01

    Concerning the production of polycrystalline silicon from SiH/sub 4/ by applying fluidized bed reaction, recent progress of study, problems involved, and countermeasures to them were reported. For the experiment, stainless tube with 50mm inside diameter attached with electric heater on the wall as auxillary heat source was used to measure the temperature distribution in the bed. As the diluting gas, hydrogen and argon were used to investigate the effect of diluent gas and it was understood that sort of diluent gas affected on the crogging and reaction rate. It was indicated that, in the fluidized bed reaction which gave large depositing area and high productivity, contamination was easily occurred. Observation of fine powder by electronic-microscope revealed that different diluent caused the difference of fine powder shape and that the higher the reaction temperature the more fine powder was produced. Crogging condition was affected by tower diameter, together with temperature and fluidizing conditions. In addition, two recent patents were introduced. 11 references, 10 figures.

  18. Thermodynamic evaluation of supercritical oxy-type power plant with high-temperature three-end membrane for air separation

    Directory of Open Access Journals (Sweden)

    Kotowicz Janusz

    2014-09-01

    Full Text Available Among the technologies which allow to reduce greenhouse gas emissions, mainly of carbon dioxide, special attention deserves the idea of ‘zero-emission’ technology based on boilers working in oxy-combustion technology. In the paper a thermodynamic analysis of supercritical power plant fed by lignite was made. Power plant consists of: 600 MW steam power unit with live steam parameters of 650 °C/30 MPa and reheated steam parameters of 670 °C/6 MPa; circulating fluidized bed boiler working in oxy-combustion technology; air separation unit and installation of the carbon dioxide compression. Air separation unit is based on high temperature membrane working in three-end technology. Models of steam cycle, circulation fluidized bed boiler, air separation unit and carbon capture installation were made using commercial software. After integration of these models the net electricity generation efficiency as a function of the degree of oxygen recovery in high temperature membrane was analyzed.

  19. Multicell fluidized bed boiler design construction and test program. Quarterly progress status report, January--March 1979

    Energy Technology Data Exchange (ETDEWEB)

    None

    1979-07-01

    The objective of this program is to design, construct, and test a multicell fluidized-bed boiler as a pollution-free method of burning high-sulfur or highly corrosive coals without excessive maintenance problems. The fluidized-bed boiler will provide approximately 300,000 pounds of steam per hour. Steam pressure and temperature conditions were selected to meet requirements of the site at which the boiler was installed.

  20. Performances of continuous dryer with inert medium fluidized bed

    Directory of Open Access Journals (Sweden)

    Arsenijević Zorana Lj.

    2008-01-01

    Full Text Available A fluid bed dryer with inert particles represents a very attractive alternative to other drying technologies according to the main efficiency criteria, i.e. specific water evaporation rate, specific heat consumption and speci­fic air consumption. A high drying efficiency results from the large con­tact area and from the large temperature difference between the inlet and outlet air. A rapid mixing of the particles leads to nearly isothermal conditions throughout the bed. A fluid bed dryer with inert particles was used for drying of slurries. Experiments were performed in a cylindrical column 215 mm in diameter with glass spheres as inert particles. In this paper, results of drying experi­ments with slurries of Zineb fungicide, copper hydroxide, calcium carbo­nate and pure water used as the feed material are presented. In our fluidized bed we successfully dried a number of other materials such as: fungicides and pesticides (Ziram, Propineb, Mangozeb, copper oxy-chloride, copper oxy-sulphate, Bordeaux mixture, other inorganic compounds (calcium sulphate, cobalt carbonate, electrolytic copper, sodium chloride, and a complex compound (organo-bentonite. The effects of operating conditions on dryer throughput and product quality were investigated. Main performance criteria, i.e. specific water evaporation rate, specific heat consumption and specific air consumption, were quantified. Temperature profile along the bed was mapped, and nearly isothermal conditions were found due to thorough mixing of the particles. Analysis of drying and energy efficiencies as a function of inlet and outlet air temperature difference was performed for deeper insight in dryer behavior and for optimizing dryer design and operation from an energy point of view. A simple mathematical model based on an overall heat balance predicts the dryer performance quite well. The industrial prototype with fluid bed of 0.8 m in diameter and capacity 650 kg of evaporated moisture per

  1. SUPPORTED LIQUID CATALYSTS FOR REMOVAL OF HIGH TEMPERATURE FUEL CELL CONTAMINANTS

    Energy Technology Data Exchange (ETDEWEB)

    Alan W. Weimer (PI); Peter Czerpak; Patrick Hilbert

    2000-01-01

    A novel catalytic synthesis gas oxidation process using molten carbonate salts supported on compatible fluidized iron oxide particles (supported-liquid-phase-catalyst (SLPC) fluidized bed process) was investigated. This process combines the advantages of large scale fluidized bed processing with molten salt bath oxidation. Molten salt catalysts can be supported within porous fluidized particles in order to improve mass transfer rates between the liquid catalysts and the reactant gases. Synthesis gas can be oxidized at reduced temperatures resulting in low NO{sub x} formation while trace sulfides and halides are captured in-situ. Hence, catalytic oxidation of synthesis gas can be carried out simultaneously with hot gas cleanup. Such SLPC fluidized bed processes are affected by inter-particle liquid capillary forces that may lead to agglomeration and de-fluidization of the bed. An understanding of the origin and strength of these forces is needed so that they can be overcome in practice. Process design is based on thermodynamic free energy minimization calculations that indicate the suitability of eutectic Na{sub 2}CO{sub 3}/K{sub 2}CO{sub 3} mixtures for capturing trace impurities in-situ (< 1 ppm SO{sub x} released) while minimizing the formation of NO{sub x}(< 10 ppm). Iron oxide has been identified as a preferred support material since it is non-reactive with sodium, is inexpensive, has high density (i.e. inertia), and can be obtained in various particle sizes and porosities. Force balance modeling has been used to design a surrogate ambient temperature system that is hydrodynamically similar to the real system, thus allowing complementary investigation of the governing fluidization hydrodynamics. The primary objective of this research was to understand the origin of and to quantify the liquid capillary interparticle forces affecting the molten carbonate SLPC fluidized bed process. Substantial theoretical and experimental exploratory results indicate process

  2. Airflow attenuation and bed net utilization: observations from Africa and Asia

    DEFF Research Database (Denmark)

    von Seidlein, Lorenz; Ikonomidis, Konstantin; Bruun, Rasmus

    2012-01-01

    Background/Methods Qualitative studies suggest that bed nets affect the thermal comfort of users. To understand and reduce this discomfort the effect of bed nets on temperature, humidity, and airflow was measured in rural homes in Asia and Africa, as well as in an experimental wind tunnel. Two...... discomfort is a factor limiting bed net use and open a range of architectural possibilities to overcome this limitation. Keywords: Malaria; Bed nets; Africa; Tanzania; The Gambia; Asia; Thailand; Philippines; Airflow; Temperature; Humidity; Climate...... investigators with architectural training selected 60 houses in The Gambia, Tanzania, Philippines, and Thailand. Data-loggers were used to measure indoor temperatures in hourly intervals over a 12 months period. In a subgroup of 20 houses airflow, temperature and humidity were measured at five-minute intervals...

  3. Effect of heat source shape on the thermal field in the pebble bed core of High Temperature Gas-cooled Reactor (HTGR)

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Leisheng; Lee, Jaeyoung [Handong Global University, Pohang (Korea, Republic of)

    2015-10-15

    In this study, in order to minimize the error brought by non-uniform heat flux, the spherical heaters are employed as heat source; subsequently, thermal field and heat transfer characteristics of the pebbles are investigated. The thermal field of the pebble surface in PBR is measured with heat source in different shapes. The HTGR design concept exhibits excellent safety features due to the low power density and the large amount of graphite present in the core which gives a large thermal inertia in an accident such as loss of coolant. However, the possible appearance of hot spots in the pebble bed cores of HTGR may affect the integrity of the pebbles, which has drawn the attention of many scientists to investigate the thermal field and to predict the maximum temperature locations in the pebbles using CFD method, Lee et.al has also done some experimental work on measuring the surface temperature of the pebbles as well as visualizing flow patterns of the coolant gas, and it was found that the temperature near the contacting points between pebbles was not higher than the flow stagnation points due to the higher thermal conductivity of the pebble. Certain error of temperature measurement might occur because of not very uniform heat flux in the pebbles since heater in cylindrical shape was utilized as heat source in previous experiment. More uniform heat flux and more complicated thermal profile are found in the result obtained using spherical heaters. The result shows that the temperature in contact point is higher than that in the top point, which is different from the previous results. The complex thermal phenomena observed in the lower-half side-sphere can be explained by the flow pattern near the surface.

  4. Optimized core design and fuel management of a pebble-bed type nuclear reactor

    NARCIS (Netherlands)

    Boer, B.

    2009-01-01

    The core design of a pebble-bed type Very High Temperature Reactor (VHTR) is optimized, aiming for an increase of the coolant outlet temperature to 1000 C, while retaining its inherent safety features. The VHTR has been selected by the international Generation IV research initiative as one of the

  5. Development and high temperature sealing performance study of double sealing flange

    International Nuclear Information System (INIS)

    Zhang Qinhua; Fu Yuan; Xie Leidong; Li Zhong; Tang Zhongfeng

    2013-01-01

    Background: Flange is an important component used in the connection between pipes or between pipe and equipment. It is widely used in mechanical industry, petrochemical industry and nuclear industry. Ordinary flange could be oxidized oi corroded under high temperature and strong corrosion condition, which leads to flange's failure. Purpose: The aim is to design and validate the double sealing flange which could be used in high temperature and strong corrosion condition stably and supplied as a reliable detachable connection for petrochemical industry and nuclear industry under high temperature and strong corrosion environment. Methods: New flange is designed using flexible graphite spiral wound gaskets and C style metal ring double sealing structure. The unique protection gas design ensures the graphite spiral wound gasket used in high temperature reliably. Test bed is built to verify the stability of the flange. Results: Pressure reducing of graphite spiral wound gasket is only 0.01 MPa at 750℃, 0.7 MPa for 43 h, there is not obvious oxidation phenomenon at the same time. The leakage rate of metal C sealing ring is 11.51×10 -4 atm cc/s, and the metal C ring sealing's performance meets the engineering requirements. Conclusion: The leakage rate of double sealing flange is almost zero under 0.7 MPa at 750℃, which meets the engineering requirements. It avoids oxidizing at high temperature and corroding under strong corrosion condition. (authors)

  6. A new method to quantify fluidized bed agglomeration in the combustion of biomass fuels

    Energy Technology Data Exchange (ETDEWEB)

    Oehman, M. [Umeaa Univ. (Sweden). Dept. of Chemistry

    1997-12-31

    The present licentiate thesis is a summary and discussion of four papers, dealing with the development, evaluation and use of a new method to quantify bed agglomeration tendencies for biomass fuels. An increased utilization of biomass related fuels has many environmental benefits, but also requires careful studies of potential new problems associated with these fuels such as bed agglomeration/defluidization during combustion and gasification in fluidized beds. From a thorough literature survey, no suitable methods to determine bed agglomeration tendencies of different fuels, fuel combinations or fuels with additives appeared to be available. It therefore seemed of considerable interest to develop a new method for the quantification of fluidized bed agglomeration tendencies for different fuels. A bench scale fluidized bed reactor (5 kW), specially designed to obtain a homogeneous isothermal bed temperature, is used. The method is based on controlled increase of the bed temperature by applying external heat to the primary air and to the bed section walls. The initial agglomeration temperature is determined by on- or off-line principal component analysis of the variations in measured bed temperatures and differential pressures. Samples of ash and bed material for evaluation of agglomeration mechanisms may also be collected throughout the operation. To determine potential effects of all the process related variables on the determined fuel specific bed agglomeration temperature, an extensive sensitivity analysis was performed according to a statistical experimental design. The results showed that the process variables had only relatively small effects on the agglomeration temperature, which could be determined to 899 deg C with a reproducibility of {+-} 5 deg C (STD). The inaccuracy was determined to be {+-} 30 deg C (STD). The method was also used to study the mechanism of both bed agglomeration using two biomass fuels and prevention of bed agglomeration by co

  7. An Experimental Study on Axial Temperature Distribution of Combustion of Dewatered Poultry Sludge in Fluidized bed combustor

    Directory of Open Access Journals (Sweden)

    Abbas A.H.

    2016-01-01

    Full Text Available A laboratory scale bubbling fluidized bed combustor was designed and fabricated to study the combustion of dewatered poultry sludge at different operational parameters. This paper present a study on the influence of equivalent ratio, secondary to primary air ratio and the fuel feed rate on the temperature distribution along the combustor. The equivalent ratio has been changed between 0.8 to 1.4% under poultry sludge feed rate of 10 kg/h and from 0.8 to 1 under poultry sludge feed rate of 15 kg/h. The secondary to primary air ratio was varied from 0.1 to 0.5 at 0.65 m injection height and 1.25 equivalent ratio. The results showed that these factors had a significant influence on the combustion characteristics of poultry sludge. The temperature distribution along the combustor was found to be strongly dependent on the fuel feed rate and the equivalent ratio and it increased when these two factors increased. However, the secondary air ratio increased the temperature in the lower region of the combustor while no significant effect was observed at the upper region of the combustor. The results suggested that the poultry sludge can be used as a fuel with high thermal combustor efficiency.

  8. Neutronic behavior of thorium fuel cycles in a very high temperature hybrid system

    International Nuclear Information System (INIS)

    Rodriguez Garcia, Lorena; Milian Perez, Daniel; Garcia Hernandez, Carlos; Milian Lorenzo, Daniel; Velasco, Abanades

    2013-01-01

    Nuclear energy needs to guarantee four important issues to be successful as a sustainable energy source: nuclear safety, economic competitiveness, proliferation resistance and a minimal production of radioactive waste. Pebble bed reactors (PBR), which are very high temperature systems together with fuel cycles based in Thorium, they could offer the opportunity to meet the sustainability demands. Thorium is a potentially valuable energy source since it is about three to four times as abundant as Uranium. It is also a widely distributed natural resource readily accessible in many countries. This paper shows the main advantages of the use of a hybrid system formed by a Pebble Bed critical nuclear reactor and two Pebble Bed Accelerator Driven Systems (ADSs) using a variety of fuel cycles with Thorium (Th+U 233 , Th+Pu 239 and Th+U). The parameters related to the neutronic behavior like deep burn, nuclear fuel breeding, Minor Actinide stockpile, power density profiles and other are used to compare the fuel cycles using the well-known MCNPX computational code. (author)

  9. Neutronic behavior of thorium fuel cycles in a very high temperature hybrid system

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Garcia, Lorena; Milian Perez, Daniel; Garcia Hernandez, Carlos; Milian Lorenzo, Daniel, E-mail: dperez@instec.cu, E-mail: cgh@instec.cu, E-mail: dmilian@instec.cu [Higher Institute of Technologies and Applied Sciences, Havana (Cuba); Velasco, Abanades, E-mail: abanades@etsii.upm.es [Department of Simulation of Thermo Energy Systems, Polytechnic University of Madrid (Spain)

    2013-07-01

    Nuclear energy needs to guarantee four important issues to be successful as a sustainable energy source: nuclear safety, economic competitiveness, proliferation resistance and a minimal production of radioactive waste. Pebble bed reactors (PBR), which are very high temperature systems together with fuel cycles based in Thorium, they could offer the opportunity to meet the sustainability demands. Thorium is a potentially valuable energy source since it is about three to four times as abundant as Uranium. It is also a widely distributed natural resource readily accessible in many countries. This paper shows the main advantages of the use of a hybrid system formed by a Pebble Bed critical nuclear reactor and two Pebble Bed Accelerator Driven Systems (ADSs) using a variety of fuel cycles with Thorium (Th+U{sup 233}, Th+Pu{sup 239} and Th+U). The parameters related to the neutronic behavior like deep burn, nuclear fuel breeding, Minor Actinide stockpile, power density profiles and other are used to compare the fuel cycles using the well-known MCNPX computational code. (author)

  10. Temperature of loose coated particles in irradiation tests

    International Nuclear Information System (INIS)

    Conlin, J.A.

    1975-04-01

    An analysis is presented of the temperature of a monolayer bed of loose High-Temperature Gas-Cooled Reactor (HTGR) type fissioning fuel particles in an annular cavity. Both conduction and radiant heat transfer are taken into account, and the effect of particle contact with the annular cavity surfaces is evaluated. Charts are included for the determination of the maximum surface temperature of the particle coating for any size particle or power generation rate in a fuel bed of this type. The charts are intended for the design and evaluation of irradiation experiments on loose beds of coated fuel particles of the type used in HTGRs. Included in an Appendix is a method for estimating the temperature of a particle in circular hole. (U.S.)

  11. High temperature gas cleaning for pressurized gasification. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Alden, H.; Hagstroem, P.; Hallgren, A.; Waldheim, L. [TPS Termiska Processer AB, Nykoeping (Sweden)

    2000-04-01

    The purpose of the project was to build an apparatus to study pressurized, high temperature gas cleaning of raw gasification gas generated from biomass. A flexible and easy to operate pressurized apparatus was designed and installed for the investigations in high temperature gas cleaning by means of thermal, catalytic or chemical procedures. A semi continuos fuel feeding concept, at a maximum rate of 700 g/h, allowed a very constant formation of a gas product at 700 deg C. The gas product was subsequently introduced into a fixed bed secondary reactor where the actual gas cleanup or reformation was fulfilled. The installation work was divided into four work periods and apart from a few delays the work was carried out according to the time plan. During the first work period (January - June 1994) the technical design, drawings etc. of the reactor and additional parts were completed. All material for the construction was ordered and the installation work was started. The second work period (July - December 1994) was dedicated to the construction and the installation of the different components. Initial tests with the electrical heating elements, control system and gas supply were assigned to the third work period (January - June 1995). After the commissioning and the resulting modifications, initial pyrolysis and tar decomposition experiments were performed. During the fourth and final work period, (June - December 1995) encouraging results from first tests allowed the experimental part of the project work to commence, however in a slightly reduced program. The experimental part of the project work comparatively studied tar decomposition as a function of the process conditions as well as of the choice of catalyst. Two different catalysts, dolomite and a commercial Ni-based catalyst, were evaluated in the unit. Their tar cracking ability in the pressure interval 1 - 20 bar and at cracker bed temperatures between 800 - 900 deg C was compared. Long term tests to study

  12. Aerosol sampling of an experimental fluidized bed coal combustor

    International Nuclear Information System (INIS)

    Newton, G.J.; Peele, E.R.; Carpenter, R.L.; Yeh, H.C.

    1977-01-01

    Fluidized bed combustion of coal, lignite or other materials has a potential for widespread use in central electric generating stations in the near future. This technology may allow widespread use of low-grade and/or high sulfur fuels due to its high energy utilization at low combustion temperature and its ability to meet emission criteria by using limestone bed material. Particulate and gaseous products resulting from fuel combustion and fluidization of bed material are discharged and proceed out the exhaust clean-up system. Sampling philosophy, methodology and equipment used to obtain aerosol samples from the exhaust system of the 18-inch fluidized bed combustor (FBC) at the Morgantown Energy Research Center (MERC) are described. Identification of sampling sites led to design of an aerosol sampling train which allowed a known quantity of the effluent streams to be sampled. Depending on the position, a 15 to 25 l/min sample is extracted from the duct, immediately diluted and transferred to a sampling/aging chamber. Transmission and scanning electron microscope samples, two types of cascade impactor samples, vapor-phase and particulate-phase organic samples, spiral duct aerosol centrifuge samples, optical size measurements and filter samples were obtained. Samples are undergoing physical, chemical and biological tests to help establish human health risk estimates for fluidized bed coal combustion and to provide information for use in design and evaluation of control technologies

  13. Heat exchanger support apparatus in a fluidized bed

    Science.gov (United States)

    Lawton, Carl W.

    1982-01-01

    A heat exchanger is mounted in the upper portion of a fluidized combusting bed for the control of the temperature of the bed. A support, made up of tubes, is extended from the perforated plate of the fluidized bed up to the heat exchanger. The tubular support framework for the heat exchanger has liquid circulated therethrough to prevent deterioration of the support.

  14. Barriers to high conversion operations in an ebullated bed unit -- Relationship between sedimentation and operability

    Energy Technology Data Exchange (ETDEWEB)

    Sherwood, D. [Criterion Catalysts Company L.P., Houston, TX (United States)

    2000-07-01

    Ebullated-Bed (EB) catalytic processes are high temperature, high pressure residue hydrocrackers, which transform sour feeds into light, sweet products. EB processes typically involve one or more trains, with one, two, or three EB reactors in series. The key to operating any EB process is to control the 'sediment' which tends to increase with increasing level of conversion. Sediment problems are generally attributed to the catalyst. While this is true in some cases, there are certain problems that occur regardless of the catalyst used, whereas in some situations sediments from the EB process can actually be controlled by the catalyst. This paper describes two typical sedimentation patterns; one in which the sediment increases, and another in which sediment decreases as the EB products move through the recovery section. The benefits of sediment control are illustrated for the latter sedimentation pattern.

  15. The Metabolic Cost of a High Intensity Exercise Program During Bed Rest

    Science.gov (United States)

    Hackney, Kyle; Everett, Meghan; Guined, Jamie; Cunningham, Daid

    2012-01-01

    Background: Given that disuse-related skeletal muscle atrophy may be exacerbated by an imbalance between energy intake and output, the amount of energy required to complete exercise countermeasures is an important consideration in the well being of subject health during bed rest and spaceflight. Objective: To evaluate the energy cost of a high intensity exercise program performed during short duration bed rest. Methods: 9 subjects (8 male and 1 female; 34.5 +/- 8.2 years) underwent 14 days of bed rest and exercise countermeasures. Exercise energy expenditure and excess post exercise oxygen consumption (EPOC) were collected once in each of 5 different exercise protocols (30 second, 2 minute and 4 minute intervals, continuous aerobic and a variety of resistance exercises) during bed rest. Body mass, basal metabolic rate (BMR), upper and lower leg muscle, subcutaneous, and intramuscular adipose tissue (IMAT) volumes were assessed before and at the end of bed rest. Results: There were no significant differences in body mass (pre: 75.1 +/- 10.5 kg; post: 75.2 +/- 10.1 kg), BMR (pre: 1649 +/- 216 kcal; post: 1657 +/- 177 kcal), muscle subcutaneous, or IMAT volumes (Table 2) after 14 days of bed rest and exercise. Body mass was maintained with an average daily intake of 2710 +/- 262 kcal (36.2 +/- 2.1 kcal/kg/day), while average daily energy expenditure was 2579 +/-311 kcal (34.5 +/- 3.6 kcal/kg/day). Exercise energy expenditure was significantly greater as a result of continuous aerobic exercise than all other exercise protocols.

  16. Uranium-thorium fuel cycle in a very high temperature hybrid system

    International Nuclear Information System (INIS)

    Hernandez, C.R.G.; Oliva, A.M.; Fajardo, L.G.; Garcia, J.A.R.; Curbelo, J.P.; Abadanes, A.

    2011-01-01

    Thorium is a potentially valuable energy source since it is about three to four times as abundant as Uranium. It is also a widely distributed natural resource readily accessible in many countries. Therefore, Thorium fuels can complement Uranium fuels and ensure long term sustainability of nuclear power. The main advantages of the use of a hybrid system formed by a Pebble Bed critical nuclear reactor and two Pebble Bed Accelerator Driven Systems (ADSs) using a Uranium-Thorium (U + Th) fuel cycle are shown in this paper. Once-through and two step U + Th fuel cycle was evaluated. With this goal, a preliminary conceptual design of a hybrid system formed by a Graphite Moderated Gas-Cooled Very High Temperature Reactor and two ADSs is proposed. The main parameters related to the neutronic behavior of the system in a deep burn scheme are optimized. The parameters that describe the nuclear fuel breeding and Minor Actinide stockpile are compared with those of a simple Uranium fuel cycle. (author)

  17. Pellet bed reactor for multi-modal space power

    International Nuclear Information System (INIS)

    Buden, D.; Williams, K.; Mast, P.; Mims, J.

    1987-01-01

    A review of forthcoming space power needs for both civil and military missions indicates that power requirements will be in the tens of megawatts. The electrical power requirements are envisioned to be twofold: long-duration lower power levels will be needed for station keeping, communications, and/or surveillance; short-duration higher power levels will be required for pulsed power devices. These power characteristics led to the proposal of a multi-modal space power reactor using a pellet bed design. Characteristics desired for such a multimegawatt reactor power source are standby, alert, and pulsed power modes; high-thermal output heat source (approximately 1000 MWt peak power); long lifetime station keeping power (10 to 30 years); high temperature output (1500 K to 1800 K); rapid-burst power transition; high reliability (above 95 percent); and stringent safety standards compliance. The proposed pellet bed reactor is designed to satisfy these characteristics

  18. Thermal energy storage systems using fluidized bed heat exchangers

    Science.gov (United States)

    Weast, T.; Shannon, L.

    1980-06-01

    A rotary cement kiln and an electric arc furnace were chosen for evaluation to determine the applicability of a fluid bed heat exchanger (FBHX) for thermal energy storage (TES). Multistage shallow bed FBHX's operating with high temperature differences were identified as the most suitable for TES applications. Analysis of the two selected conceptual systems included establishing a plant process flow configuration, an operational scenario, a preliminary FBHX/TES design, and parametric analysis. A computer model was developed to determine the effects of the number of stages, gas temperatures, gas flows, bed materials, charge and discharge time, and parasitic power required for operation. The maximum national energy conservation potential of the cement plant application with TES is 15.4 million barrels of oil or 3.9 million tons of coal per year. For the electric arc furnance application the maximum national conservation potential with TES is 4.5 million barrels of oil or 1.1 million tons of coal per year. Present time of day utility rates are near the breakeven point required for the TES system. Escalation of on-peak energy due to critical fuel shortages could make the FBHX/TES applications economically attractive in the future.

  19. Avoiding Carbon Bed Hot Spots in Thermal Process Off-Gas Systems

    International Nuclear Information System (INIS)

    Soelberg, Nick; Enneking, Joe

    2011-01-01

    Mercury has had various uses in nuclear fuel reprocessing and other nuclear processes, and so is often present in radioactive and mixed (radioactive and hazardous) wastes. Test programs performed in recent years have shown that mercury in off-gas streams from processes that treat radioactive wastes can be controlled using fixed beds of activated sulfur-impregnated carbon, to levels low enough to comply with air emission regulations such as the Hazardous Waste Combustor (HWC) Maximum Achievable Control Technology (MACT) standards. Carbon bed hot spots or fires have occurred several times during these tests, and also during a remediation of tanks that contained mixed waste. Hot spots occur when localized areas in a carbon bed become heated to temperatures where oxidation occurs. This heating typically occurs due to heat of absorption of gas species onto the carbon, but it can also be caused through external means such as external heaters used to heat the carbon bed vessel. Hot spots, if not promptly mitigated, can grow into bed fires. Carbon bed hot spots and fires must be avoided in processes that treat radioactive and mixed waste. Hot spots are detected by (a) monitoring in-bed and bed outlet gas temperatures, and (b) more important, monitoring of bed outlet gas CO concentrations. Hot spots are mitigated by (a) designing for appropriate in-bed gas velocity, for avoiding gas flow maldistribution, and for sufficient but not excessive bed depth, (b) appropriate monitoring and control of gas and bed temperatures and compositions, and (c) prompt implementation of corrective actions if bed hot spots are detected. Corrective actions must be implemented quickly if bed hot spots are detected, using a graded approach and sequence starting with corrective actions that are simple, quick, cause the least impact to the process, and are easiest to recover from.

  20. Optimized Core Design and Fuel Management of a Pebble-Bed Type Nuclear Reactor

    International Nuclear Information System (INIS)

    Boer, Brian

    2007-01-01

    The Very High Temperature Reactor (VHTR) has been selected by the international Generation IV research initiative as one of the six most promising nuclear reactor concepts that are expected to enter service in the second half of the 21st century. The VHTR is characterized by a high plant efficiency and a high fuel discharge burnup level. More specifically, the (pebble-bed type) High Temperature Reactor (HTR) is known for its inherently safe characteristics, coming from a negative temperature reactivity feedback, a low power density and a large thermal inertia of the core. The core of a pebble-bed reactor consists of graphite spheres (pebbles) that form a randomly packed porous bed, which is cooled by high pressure helium. The pebbles contain thousands of fuel particles, which are coated with several pyrocarbon and silicon carbon layers that are designed to contain the fission products that are formed during operation of the reactor. The inherent safety concept has been demonstrated in small pebble-bed reactors in practice, but an increase in the reactor size and power is required for cost-effective power production. An increase of the power density in order to increase the helium coolant outlet temperature is attractive with regard to the efficiency and possible process heat applications. However, this increase leads in general to higher fuel temperatures, which could lead to a consequent increase of the fuel coating failure probability. This thesis deals with the pebble-bed type VHTR that aims at an increased coolant outlet temperature of 1000 degrees C and beyond. For the simulation of the neutronic and thermal-hydraulic behavior of the reactor the DALTON-THERMIX coupled code system has been developed and has been validated against experiments performed in the AVR and HTR-10 reactors. An analysis of the 400 MWth Pebble Bed Modular Reactor (PBMR) design shows that the inherent safety concept that has been demonstrated in practice in the smaller AVR and HTR-10

  1. Post-combustion CO2 capture with activated carbons using fixed bed adsorption

    Science.gov (United States)

    Al Mesfer, Mohammed K.; Danish, Mohd; Fahmy, Yasser M.; Rashid, Md. Mamoon

    2018-03-01

    In the current work, the capturing of carbon dioxide from flue gases of post combustion emission using fixed bed adsorption has been carried out. Two grades of commercial activated carbon (sorbent-1 and sorbent-2) were used as adsorbent. Feed consisting of CO2 and N2 mixture was used for carrying out the adsorption. The influence of bed temperature, feed rate, equilibrium partial pressure and initial % CO2 in feed were considered for analyzing adsorption-desorption process. It was found that the total adsorption-desorption cycle time decreases with increased column temperature and feed rates. The time required to achieve the condition of bed saturation decreases with increased bed temperature and feed rates. The amount of CO2 adsorbed/Kg of the adsorbent declines with increased bed temperature with in studied range for sorbent-1 and sorbent-2. It was suggested that the adsorption capacity of the both the sorbents increases with increased partial pressure of the gas.

  2. Characteristic Studies of Micron Zinc Particle Hydrolysis in a Fixed Bed Reactor

    Directory of Open Access Journals (Sweden)

    Lv Ming

    2015-09-01

    Full Text Available Zinc fuel is considered as a kind of promising energy sources for marine propeller. As one of the key steps for zinc marine energy power system, zinc hydrolysis process had been studied experimentally in a fixed bed reactor. In this study, we focus on the characteristics of micron zinc particle hydrolysis. The experimental results suggested that the steam inner diffusion is the controlling step of accumulative zinc particles hydrolysis reaction at a relative lower temperature and a relative higher water partial pressure. In other conditions, the chemical reaction kinetics was the controlling step. And two kinds of chemical reaction kinetics appeared in experiments: the surface reaction and the gas-gas reaction. The latter one occurs usually for larger zinc particles and high reaction temperature. Temperature seems to be one of the most important parameters for the dividing of different reaction mechanisms. Several parameters of the hydrolysis process including heating rate, water partial pressure, the particle size and temperature were also studied in this paper. Results show that the initial reaction temperature of zinc hydrolysis in fixed bed is about 410°C. And the initial reaction temperature increases as the heating rate increases and as the water partial pressure decreases. The total hydrogen yield increases as the heating rate decreases, as the water partial pressure increases, as the zinc particle size decreases, and as the reaction temperature increases. A hydrogen yield of more than 81.5% was obtained in the fixed bed experiments.

  3. Fluid-bed combustion

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, G.; Schoebotham, N.

    1981-02-01

    In Energy Equipment Company's two-stage fluidized bed system, partial combustion in a fluidized bed is followed by burn-off of the generated gases above the bed. The system can be retrofitted to existing boilers, and can burn small, high ash coal efficiently. It has advantages when used as a hot gas generator for process drying. Tests on a boiler at a Cadbury Schweppes plant are reported.

  4. Pebble Fuel Handling and Reactivity Control for Salt-Cooled High Temperature Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Per [Univ. of California, Berkeley, CA (United States). Dept. of Nuclear Engineering; Greenspan, Ehud [Univ. of California, Berkeley, CA (United States). Dept. of Nuclear Engineering

    2015-02-09

    This report documents the work completed on the X-PREX facility under NEUP Project 11- 3172. This project seeks to demonstrate the viability of pebble fuel handling and reactivity control for fluoride salt-cooled high-temperature reactors (FHRs). The research results also improve the understanding of pebble motion in helium-cooled reactors, as well as the general, fundamental understanding of low-velocity granular flows. Successful use of pebble fuels in with salt coolants would bring major benefits for high-temperature reactor technology. Pebble fuels enable on-line refueling and operation with low excess reactivity, and thus simpler reactivity control and improved fuel utilization. If fixed fuel designs are used, the power density of salt- cooled reactors is limited to 10 MW/m3 to obtain adequate duration between refueling, but pebble fuels allow power densities in the range of 20 to 30 MW/m3. This can be compared to the typical modular helium reactor power density of 5 MW/m3. Pebble fuels also permit radial zoning in annular cores and use of thorium or graphite pebble blankets to reduce neutron fluences to outer radial reflectors and increase total power production. Combined with high power conversion efficiency, compact low-pressure primary and containment systems, and unique safety characteristics including very large thermal margins (>500°C) to fuel damage during transients and accidents, salt-cooled pebble fuel cores offer the potential to meet the major goals of the Advanced Reactor Concepts Development program to provide electricity at lower cost than light water reactors with improved safety and system performance.This report presents the facility description, experimental results, and supporting simulation methods of the new X-Ray Pebble Recirculation Experiment (X-PREX), which is now operational and being used to collect data on the behavior of slow dense granular flows relevant to pebble bed reactor core designs. The X

  5. Pebble Fuel Handling and Reactivity Control for Salt-Cooled High Temperature Reactors

    International Nuclear Information System (INIS)

    Peterson, Per; Greenspan, Ehud

    2015-01-01

    This report documents the work completed on the X-PREX facility under NEUP Project 11- 3172. This project seeks to demonstrate the viability of pebble fuel handling and reactivity control for fluoride salt-cooled high-temperature reactors (FHRs). The research results also improve the understanding of pebble motion in helium-cooled reactors, as well as the general, fundamental understanding of low-velocity granular flows. Successful use of pebble fuels in with salt coolants would bring major benefits for high-temperature reactor technology. Pebble fuels enable on-line refueling and operation with low excess reactivity, and thus simpler reactivity control and improved fuel utilization. If fixed fuel designs are used, the power density of salt- cooled reactors is limited to 10 MW/m 3 to obtain adequate duration between refueling, but pebble fuels allow power densities in the range of 20 to 30 MW/m 3 . This can be compared to the typical modular helium reactor power density of 5 MW/m3. Pebble fuels also permit radial zoning in annular cores and use of thorium or graphite pebble blankets to reduce neutron fluences to outer radial reflectors and increase total power production. Combined with high power conversion efficiency, compact low-pressure primary and containment systems, and unique safety characteristics including very large thermal margins (>500°C) to fuel damage during transients and accidents, salt-cooled pebble fuel cores offer the potential to meet the major goals of the Advanced Reactor Concepts Development program to provide electricity at lower cost than light water reactors with improved safety and system performance.This report presents the facility description, experimental results, and supporting simulation methods of the new X-Ray Pebble Recirculation Experiment (X-PREX), which is now operational and being used to collect data on the behavior of slow dense granular flows relevant to pebble bed reactor core designs. The X-PREX facility uses novel

  6. Low temperature circulating fluidized bed gasification and co-gasification of municipal sewage sludge. Part 1: Process performance and gas product characterization

    DEFF Research Database (Denmark)

    Thomsen, Tobias Pape; Sárossy, Zsuzsa; Gøbel, Benny

    2017-01-01

    Results from five experimental campaigns with Low Temperature Circulating Fluidized Bed (LT-CFB) gasification of straw and/or municipal sewage sludge (MSS) from three different Danish municipal waste water treatment plants in pilot and demonstration scale are analyzed and compared. The gasification...... process is characterized with respect to process stability, process performance and gas product characteristics. All experimental campaigns were conducted at maximum temperatures below 750°C, with air equivalence ratios around 0.12 and with pure silica sand as start-up bed material. A total of 8600kg...... particles in the system. Co-gasification of MSS with sufficient amounts of cereal straw was found to be an effective way to mitigate these issues as well as eliminate thermal MSS drying requirements. Characterization of gas products and process performance showed that even though gas composition varied...

  7. Metaphysics methods development for high temperature gas cooled reactor analysis

    International Nuclear Information System (INIS)

    Seker, V.; Downar, T. J.

    2007-01-01

    Gas cooled reactors have been characterized as one of the most promising nuclear reactor concepts in the Generation-IV technology road map. Considerable research has been performed on the design and safety analysis of these reactors. However, the calculational tools being used to perform these analyses are not state-of-the-art and are not capable of performing detailed three-dimensional analyses. This paper presents the results of an effort to develop an improved thermal-hydraulic solver for the pebble bed type high temperature gas cooled reactors. The solution method is based on the porous medium approach and the momentum equation including the modified Ergun's resistance model for pebble bed is solved in three-dimensional geometry. The heat transfer in the pebble bed is modeled considering the local thermal non-equilibrium between the solid and gas, which results in two separate energy equations for each medium. The effective thermal conductivity of the pebble-bed can be calculated both from Zehner-Schluender and Robold correlations. Both the fluid flow and the heat transfer are modeled in three dimensional cylindrical coordinates and can be solved in steady-state and time dependent. The spatial discretization is performed using the finite volume method and the theta-method is used in the temporal discretization. A preliminary verification was performed by comparing the results with the experiments conducted at the SANA test facility. This facility is located at the Institute for Safety Research and Reactor Technology (ISR), Julich, Germany. Various experimental cases are modeled and good agreement in the gas and solid temperatures is observed. An on-going effort is to model the control rod ejection scenarios as described in the OECD/NEA/NSC PBMR-400 benchmark problem. In order to perform these analyses PARCS reactor simulator code will be coupled with the new thermal-hydraulic solver. Furthermore, some of the other anticipated accident scenarios in the benchmark

  8. The effects of fabric for sleepwear and bedding on sleep at ambient temperatures of 17°C and 22°C

    Directory of Open Access Journals (Sweden)

    Shin M

    2016-04-01

    Full Text Available Mirim Shin,1 Mark Halaki,1 Paul Swan,2 Angus Ireland,2 Chin Moi Chow1 1Exercise, Health and Performance Research Group, Faculty of Health Sciences, The University of Sydney, Lidcombe, 2Australian Wool Innovation Limited, The Woolmark Company, Sydney, NSW, Australia Abstract: The fibers used in clothing and bedding have different thermal properties. This study aimed to investigate the influences of textile fabrics on sleep under different ambient temperature (Ta conditions. Seventeen healthy young participants (ten males underwent nine nights of polysomnography testing including an adaptation night. Participants were randomized to each of the three binary factors: sleepwear (cotton vs wool, bedding (polyester vs wool, and Ta (17°C vs 22°C with relative humidity set at 60%. Skin temperature (Tsk and core temperature (Tc were monitored throughout the sleep period. Sleep onset latency (SOL was significantly shortened when sleeping in wool with trends of increased total sleep time and sleep efficiency compared to cotton sleepwear. At 17°C, the proportion of sleep stages 1 (%N1 and 3 (%N3 and rapid eye movement sleep was higher, but %N2 was lower than at 22°C. Interaction effects (sleepwear × Ta showed a significantly shorter SOL for wool than cotton at 17°C but lower %N3 for wool than cotton at 22°C. A significantly lower %N2 but higher %N3 was observed for wool at 17°C than at 22°C. There was no bedding effect on sleep. Several temperature variables predicted the sleep findings in a stepwise multiple regression analysis and explained 67.8% of the variance in SOL and to a lesser degree the %N2 and %N3. These findings suggest that sleepwear played a contributory role to sleep outcomes and participants slept better at 17°C than at 22°C.Keywords: cotton, polyester, wool, polysomnography, skin temperature, core body temperature

  9. Analysis of Precooling Injection Transient of Steam Generator for High Temperature Gas Cooled Reactor

    Directory of Open Access Journals (Sweden)

    Yan Wang

    2017-01-01

    Full Text Available After a postulated design basis accident leads high temperature gas cooled reactor to emergency shutdown, steam generator still remains with high temperature level and needs to be cooled down by a precooling before reactor restarts with clearing of fault. For the large difference of coolant temperature between inlet and outlet of steam generator in normal operation, the temperature distribution on the components of steam generator is very complicated. Therefore, the temperature descending rate of the components in steam generator needs to be limited to avoid the potential damage during the precooling stage. In this paper, a pebble-bed high temperature gas cooled reactor is modeled by thermal-hydraulic system analysis code and several postulated precooling injection transients are simulated and compared to evaluate their effects, which will provide support for the precooling design. The analysis results show that enough precooling injection is necessary to satisfy the precooling requirements, and larger mass flow rate of precooling water injection will accelerate the precooling process. The temperature decrease of steam generator is related to the precooling injection scenarios, and the maximal mass flow rate of the precooling injection should be limited to avoid the excessively quick temperature change of the structures in steam generator.

  10. Quench cooling of superheated debris beds in containment during LWR core meltdown accidents

    International Nuclear Information System (INIS)

    Ginsberg, T.; Chen, J.C.

    1984-01-01

    Light water reactor core meltdown accident sequence studies suggest that superheated debris beds may settle on the concrete floor beneath the reactor vessel. A model for the heat transfer processes during quench (removal of stored energy from initial temperature to saturation temperature) of superheated debris beds cooled by an overlying pool of water has been presented in a prior paper. This paper discusses the coolability of decay-heated debris beds from the standpoint of their transient quench characteristics. It is shown that even though a debris bed configuration may be coolable from the point of view of steady-state decay heat removal, the quench behavior from an initially elevated temperature may lead to bed melting prior to quench of the debris

  11. Quasi-direct numerical simulation of a pebble bed configuration. Part I: Flow (velocity) field analysis

    International Nuclear Information System (INIS)

    Shams, A.; Roelofs, F.; Komen, E.M.J.; Baglietto, E.

    2013-01-01

    Highlights: ► Quasi direct numerical simulations (q-DNS) of a pebble bed configuration has been performed. ► This q-DNS database may serve as a reference for the validation of different turbulence modeling approaches. ► A wide range of qualitative and quantitative data throughout the computational domain has been generated. ► Results for mean, RMS and covariance of velocity field are extensively reported in this paper. -- Abstract: High temperature reactors (HTR) are being considered for deployment around the world because of their excellent safety features. The fuel is embedded in a graphite moderator and can sustain very high temperatures. However, the appearance of hot spots in the pebble bed cores of HTR's may affect the integrity of the pebbles. A good prediction of the flow and heat transport in such a pebble bed core is a challenge for available turbulence models and such models need to be validated. In the present article, quasi direct numerical simulations (q-DNS) of a pebble bed configuration are reported, which may serve as a reference for the validation of different turbulence modeling approaches. Such approaches can be used in order to perform calculations for a randomly arranged pebble bed. Simulations are performed at a Reynolds number of 3088, based on pebble diameter, with a porosity level of 0.42. Detailed flow analyses have shown complex physics flow behavior and make this case challenging for turbulence model validation. Hence, a wide range of qualitative and quantitative data for velocity and temperature field have been extracted for this benchmark. In the present article (part I), results related to the flow field (mean, RMS and covariance of velocity) are documented and discussed in detail. Moreover, the discussion regarding the temperature field will be published in a separate article

  12. Geomechanics of bedded salt

    International Nuclear Information System (INIS)

    Serata, S.; Milnor, S.W.

    1979-01-01

    Creep data from the literature search is reinterpreted by SGI, resulting in a better understanding of the temperature and stress state dependence of the octahedral creep rate and the octahedral shear strength. The concept of a transition strength between the elastic and the plastic states is in agreement with the data. The elastic and rheological properties of salt are described, and a set of constitutive equations is presented. The dependence of material properties on parameters such as temperature is considered. Findings on the permeability of salt are summarized, and the in-situ behavior of openings in bedded salt is described based on extensive engineering experience. A stress measuring system utilizing a finite element computer code is discussed. Geological factors affecting the stability of salt openings are considered, and the Stress Control Technique for designing stable openings in bedded salt formations is explained

  13. Defluidization in fluidized bed gasifiers using high-alkali content fuels

    DEFF Research Database (Denmark)

    Narayan, Vikas; Jensen, Peter Arendt; Henriksen, Ulrik Birk

    2016-01-01

    samples,agglomeration could be attributed to viscous silicate melts formed from reaction of inorganic alkalineand alkali earth species with silica from the bed particles. A mathematical model that addresses the defluidization behavior of alkali-rich samples was developed based on the experiments performed...... and calcium, which may form viscous melts that adhere on the surface of the colliding bed particles and bind them to form agglomerates. In this paper, studies were made to understand the behavior of inorganic elements (mainly K, Si and Ca) on agglomeration and de-fluidization of alkali rich bed...... in the bench-scale fluidized bed reactor as well as on results from literature. The model was then used topredict the de-fluidization behavior of alkali-rich bed material in a large-scale LTCFB gasifier....

  14. Heat Transfer in a Fixed Bed of Straw Char

    DEFF Research Database (Denmark)

    Fjellerup, Jan Søren; Henriksen, Ulrik Birk; Jensen, Anker

    2003-01-01

    A model for the thermal conductivity of a straw char bed has been developed. The model extends the work of Yagi and Kunii to describe heat transfer in a bed of cylinders, using a relationship between the interparticle distance and the external porosity. To verify the model, thermal conductivity...... the experimental uncertainty over the range of conditions investigated. The heat transfer model was used in a parametric study to evaluate the effect of gas flow rate, particle diameter, porosity, and temperature on the thermal conductivity in a straw char bed....... experiments were performed on shredded and un-shredded straw char samples, varying particle size, bed packing (loose or dense), and temperature. Predictions with the model, using the measured external porosity and particle diameter as input parameters, are in agreement with measurements within...

  15. Devolatilization of oil sludge in a lab-scale bubbling fluidized bed.

    Science.gov (United States)

    Liu, Jianguo; Jiang, Xiumin; Han, Xiangxin

    2011-01-30

    Devolatilization of oil sludge pellets was investigated in nitrogen and air atmosphere in a lab-scale bubbling fluidized bed (BFB). Devolatilization times were measured by the degree of completion of the evolution of the volatiles for individual oil sludge pellets in the 5-15 mm diameter range. The influences of pellet size, bed temperature and superficial fluidization velocity on devolatilization time were evaluated. The variation of devolatilization time with particle diameter was expressed by the correlation, τ(d) = Ad(p)(N). The devolatilization time to pellet diameter curve shows nearly a linear increase in nitrogen, whereas an exponential increase in air. No noticeable effect of superficial fluidization velocity on devolatilization time in air atmosphere was observed. The behavior of the sludge pellets in the BFB was also focused during combustion experiments, primary fragmentation (a micro-explosive combustion phenomenon) was observed for bigger pellets (>10mm) at high bed temperatures (>700 °C), which occurred towards the end of combustion and remarkably reduce the devolatilization time of the oil sludge pellet. The size analysis of bed materials and fly ash showed that entire ash particle was entrained or elutriated out of the BFB furnace due to the fragile structure of oil sludge ash particles. Copyright © 2010 Elsevier B.V. All rights reserved.

  16. On-line temperature control of fluidized bed incinerator using fuzzy algorithm; Fuzzu seigyo donyu ni yoru ryudosogata shokyakuro unten no jidoka

    Energy Technology Data Exchange (ETDEWEB)

    Okayasu, S.; Kuratani, T.; Imai, H. [Ajinomoto Co. Inc., Tokyo (Japan)

    1995-03-15

    Automatic control of incinerators for their stable operation has been desired for the preservation of the environment in the factory. An on-line fuzzy control system has been successfully introduced for temperature control of the fluidized bed of incinerator for industrial wastes. In this case, manual control can be applied to the plant instead of a PID control system, because of the complexity of the waste materials and the large delay in detection of the temperature change in the fluidized bed sand. On the basis of analyzing the dynamic performance of the process and the know-how of skilled operators, membership functions and fuzzy control rules are selected, then determined carefully for the system. Introduction of the system resulted in almost the same performance as manual control. Subsequently the operators are freed from manual operation in the control room for an hour. 6 refs., 5 figs., 4 tabs.

  17. Fluidized combustion of beds of large, dense particles in reprocessing HTGR fuel

    International Nuclear Information System (INIS)

    Young, D.T.

    1977-03-01

    Fluidized bed combustion of graphite fuel elements and carbon external to fuel particles is required in reprocessing high-temperature gas-cooled reactor (HTGR) cores for recovery of uranium. This burning process requires combustion of beds containing both large particles and very dense particles as well as combustion of fine graphite particles which elutriate from the bed. Equipment must be designed for optimum simplicity and reliability as ultimate operation will occur in a limited access ''hot cell'' environment. Results reported in this paper indicate that successful long-term operation of fuel element burning with complete combustion of all graphite fines leading to a fuel particle product containing <1% external carbon can be performed on equipment developed in this program

  18. Experimental measurement of effective thermal conductivity of packed lithium-titanate pebble bed

    International Nuclear Information System (INIS)

    Mandal, D.; Sathiyamoorthy, D.; Vinjamur, M.

    2012-01-01

    Lithium titanate is a promising solid breeder material for the fusion reactor blanket. Packed lithium titanate pebble bed is considered for the blanket. The thermal energy; that will be produced in the bed during breeding and the radiated heat from the reactor core absorbed must be removed. So, the experimental thermal property data are important for the blanket design. In past, a significant amount of works were conducted to determine the effective thermal conductivity of packed solid breeder pebble bed, in helium atmosphere, but no flow of gas was considered. With increase in gas flow rate, effective thermal conductivity of pebble bed increases. Particle size and void fraction also affect the thermal properties of the bed significantly. An experimental facility with external heat source was designed and installed. Experiments were carried out with lithium-titanate pebbles of different sizes at variable gas flow rates and at different bed wall temperature. It was observed that effective thermal conductivity of pebble bed is a function of particle Reynolds number and temperature. From the experimental data two correlations have been developed to estimate the effective thermal conductivity of packed lithium-titanate pebble bed for different particle Reynolds number and at different temperatures. The experimental details and results are discussed in this paper.

  19. An Intelligent FPGA Based Anti-Sweating System for Bed Sore Prevention in a Clinical Environment

    Directory of Open Access Journals (Sweden)

    K. S. Jaichandar

    2011-01-01

    Full Text Available Bed sores, a common problem among immobile patients occur as a result of continuous sweating due to increase in skin to bed surface temperature in patients lying on same posture for prolonged period. If left untreated, the skin can break open and become infected. Currently adopted methods for bed sores prevention include: use of two hourly flip chat for repositioning patient or use of air fluidized beds. However, the setbacks of these preventive measures include either use of costly equipment or wastage of human resources. This paper introduces an intelligent low cost FPGA based anti-sweating system for bed sores prevention in a clinical environment. The developed system consists of bed surface implanted temperature sensors interfaced with an FPGA chip for sensing the temperature change in patient’s skin to bed surface. Based on the temperature change, the FPGA chip select the - mode (heater/cooler and speed of the fan module. Furthermore, an alarm module was implemented to alert the nurse to reposition the patient only if patient’s skin to bed surface temperature exceeds a predefined threshold thereby saving human resources. By integrating the whole system into a single FPGA chip, we were able to build a low cost compact system without sacrificing processing power and flexibility.

  20. Coupling scales for modelling heavy metal vaporization from municipal solid waste incineration in a fluid bed by CFD.

    Science.gov (United States)

    Soria, José; Gauthier, Daniel; Flamant, Gilles; Rodriguez, Rosa; Mazza, Germán

    2015-09-01

    Municipal Solid Waste Incineration (MSWI) in fluidized bed is a very interesting technology mainly due to high combustion efficiency, great flexibility for treating several types of waste fuels and reduction in pollutants emitted with the flue gas. However, there is a great concern with respect to the fate of heavy metals (HM) contained in MSW and their environmental impact. In this study, a coupled two-scale CFD model was developed for MSWI in a bubbling fluidized bed. It presents an original scheme that combines a single particle model and a global fluidized bed model in order to represent the HM vaporization during MSW combustion. Two of the most representative HM (Cd and Pb) with bed temperatures ranging between 923 and 1073K have been considered. This new approach uses ANSYS FLUENT 14.0 as the modelling platform for the simulations along with a complete set of self-developed user-defined functions (UDFs). The simulation results are compared to the experimental data obtained previously by the research group in a lab-scale fluid bed incinerator. The comparison indicates that the proposed CFD model predicts well the evolution of the HM release for the bed temperatures analyzed. It shows that both bed temperature and bed dynamics have influence on the HM vaporization rate. It can be concluded that CFD is a rigorous tool that provides valuable information about HM vaporization and that the original two-scale simulation scheme adopted allows to better represent the actual particle behavior in a fluid bed incinerator. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Stress Tolerance of Bed Bugs: A Review of Factors That Cause Trauma to Cimex lectularius and C. Hemipterus

    Directory of Open Access Journals (Sweden)

    Joshua B. Benoit

    2011-04-01

    Full Text Available Recent emergence of bed bugs (Cimex spp. has prompted a significant expansion of research devoted to this pest. The ability to survive and recover from stress has significant implications on the distribution and survival of insects, and bed bugs are no exception. Research on bed bug stress tolerance has shown considerable progress and necessitates a review on this topic. Bed bugs have an extraordinary ability to resist dehydration between bloodmeals, and this represents a critical factor allowing their prolonged survival when no host is available. High relative humidities are detrimental to bed bugs, leading to reduced survival in comparison to those held at lower relative humidities. Continual exposure of bed bugs, eggs and mobile stages, to temperatures below freezing and short term exposure (=1 h to temperatures below −16 to −18 °C results in mortality. The upper thermal limit for short term exposure of eggs, nymphs and adults is between 40–45 °C for the common (Cimex lectularius and tropical (C. hemipterus bed bugs. Long-term exposure to temperatures above 35 °C results in significant reduction in survival of mobile bed bugs. Eggs for C. lectularius and C. hemipterus are no longer viable when held below 10 °C or above 37 °C throughout embryogenesis. Blood feeding, although necessary for survival and reproduction, is discussed as a stress due to thermal and osmotic fluctuations that result from ingesting a warm bloodmeal from a vertebrate host. Cold, heat, water stress and blood feeding prompted the expression of heat shock proteins (Hsps. Pesticide application is a common human-induced stress for urban pests, and recent studies have documented pesticide resistance in many bed bug populations. High levels of traumatic insemination (mating of bed bugs has been linked to reduced survival and fecundity along with possibly exposing individuals to microbial infections after cuticular penetration by the paramere (=male reproductive organ

  2. An in situ spatially resolved analytical technique to simultaneously probe gas phase reactions and temperature within the packed bed of a plug flow reactor.

    Science.gov (United States)

    Touitou, Jamal; Burch, Robbie; Hardacre, Christopher; McManus, Colin; Morgan, Kevin; Sá, Jacinto; Goguet, Alexandre

    2013-05-21

    This paper reports the detailed description and validation of a fully automated, computer controlled analytical method to spatially probe the gas composition and thermal characteristics in packed bed systems. As an exemplar, we have examined a heterogeneously catalysed gas phase reaction within the bed of a powdered oxide supported metal catalyst. The design of the gas sampling and the temperature recording systems are disclosed. A stationary capillary with holes drilled in its wall and a moveable reactor coupled with a mass spectrometer are used to enable sampling and analysis. This method has been designed to limit the invasiveness of the probe on the reactor by using the smallest combination of thermocouple and capillary which can be employed practically. An 80 μm (O.D.) thermocouple has been inserted in a 250 μm (O.D.) capillary. The thermocouple is aligned with the sampling holes to enable both the gas composition and temperature profiles to be simultaneously measured at equivalent spatially resolved positions. This analysis technique has been validated by studying CO oxidation over a 1% Pt/Al2O3 catalyst and the spatial resolution profiles of chemical species concentrations and temperature as a function of the axial position within the catalyst bed are reported.

  3. Ceramic breeder pebble bed packing stability under cyclic loads

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chunbo, E-mail: chunbozhang@fusion.ucla.edu [Fusion Science and Technology Center, University of California, Los Angeles, CA 90095-1597 (United States); Ying, Alice; Abdou, Mohamed A. [Fusion Science and Technology Center, University of California, Los Angeles, CA 90095-1597 (United States); Park, Yi-Hyun [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2016-11-01

    Highlights: • The feasibility of obtaining packing stability for pebble beds is studied. • The responses of pebble bed to cyclic loads have been presented and analyzed in details. • Pebble bed packing saturation and its applications are discussed. • A suggestion is made regarding the improvement of pebbles filling technique. - Abstract: Considering the optimization of blanket performance, it is desired that the bed morphology and packing state during reactor operation are stable and predictable. Both experimental and numerical work are performed to explore the stability of pebble beds, in particular under pulsed loading conditions. Uniaxial compaction tests have been performed for both KIT’s Li{sub 4}SiO{sub 4} and NFRI’s Li{sub 2}TiO{sub 3} pebble beds at elevated temperatures (up to 750 °C) under cyclic loads (up to 6 MPa). The obtained data shows the stress-strain loop initially moves towards the larger strain and nearly saturates after a certain number of cyclic loading cycles. The characterized FEM CAP material models for a Li{sub 4}SiO{sub 4} pebble bed with an edge-on configuration are used to simulate the thermomechanical behavior of pebble bed under ITER pulsed operations. Simulation results have shown the cyclic variation of temperature/stress/strain/gap and also the same saturation trend with experiments under cyclic loads. Therefore, it is feasible for pebble bed to maintain its packing stability during operation when disregarding pebbles’ breakage and irradiation.

  4. Physics of the pebble-bed high temperature reactor in massive water ingress accidents

    International Nuclear Information System (INIS)

    Scherer, W.

    1989-10-01

    A point-kinetics model was developed to describe qualitatively hypothetical water ingress transients in the primary loop of High Temperature Reactors. Neutron kinetics, heat-flow balance and the chemical reaction of graphite corrosion together with their mutual influence are included. The qualitative behaviour of the transients is calculated and discussed for two fictitious examples, namely the long-term water ingress into a medium sized HTR (HTR-500) and the 'startup' of a small HTR after an intensive water flooding of the core. The model developed and the computer code KINKOR are thought to be tools for the general understanding of the water ingress phenomena and should be looked at as basis for more elaborated systems. (orig./HP) [de

  5. Calibration of an experimental model of tritium storage bed designed for 'in situ' accountability

    International Nuclear Information System (INIS)

    Bidica, Nicolae; Stefanescu, Ioan; Bucur, Ciprian; Bulubasa, Gheorghe; Deaconu, Mariea

    2009-01-01

    Full text: Objectives: Tritium accountancy of the storage beds in tritium facilities is an important issue for tritium inventory control. The purpose of our work was to perform calibration of an experimental model of tritium storage bed with a special design, using electric heaters to simulate tritium decay, and to evaluate the detection limit of the accountancy method. The objective of this paper is to present an experimental method used for calibration of the storage bed and the experimental results consisting of calibration curves and detection limit. Our method is based on a 'self-assaying' tritium storage bed. The basic characteristics of the design of our storage bed consists, in principle, of a uniform distribution of the storage material on several copper thin fins (in order to obtain a uniform temperature field inside the bed), an electrical heat source to simulate the tritium decay heat, a system of thermocouples for measuring the temperature field inside the bed, and good thermal isolation of the bed from the external environment. Within this design of the tritium storage bed, the tritium accounting method is based on determining the decay heat of tritium by measuring the temperature increase of the isolated storage bed. Experimental procedure consisted in measuring of temperature field inside the bed for few values of the power injected with the aid of electrical heat source. Data have been collected for few hours and the temperature increase rate was determined for each value of the power injected. Graphical representation of temperature rise versus injected powers was obtained. This accounting method of tritium inventory stored as metal tritide is a reliable solution for in-situ tritium accountability in a tritium handling facility. Several improvements can be done regarding the design of the storage bed in order to improve the measurement accuracy and to obtain a lower detection limit as for instance use of more accurate thermocouples or special

  6. WTP Pretreatment Facility Potential Design Deficiencies--Sliding Bed and Sliding Bed Erosion Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, E. K. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-05-06

    This assessment is based on readily available literature and discusses both Newtonian and non-Newtonian slurries with respect to sliding beds and erosion due to sliding beds. This report does not quantify the size of the sliding beds or erosion rates due to sliding beds, but only assesses if they could be present. This assessment addresses process pipelines in the Pretreatment (PT) facility and the high level waste (HLW) transfer lines leaving the PT facility to the HLW vitrification facility concentrate receipt vessel.

  7. WTP Pretreatment Facility Potential Design Deficiencies--Sliding Bed and Sliding Bed Erosion Assessment

    International Nuclear Information System (INIS)

    Hansen, E. K.

    2015-01-01

    This assessment is based on readily available literature and discusses both Newtonian and non-Newtonian slurries with respect to sliding beds and erosion due to sliding beds. This report does not quantify the size of the sliding beds or erosion rates due to sliding beds, but only assesses if they could be present. This assessment addresses process pipelines in the Pretreatment (PT) facility and the high level waste (HLW) transfer lines leaving the PT facility to the HLW vitrification facility concentrate receipt vessel.

  8. DEVELOPMENT OF PRESSURIZED CIRCULATING FLUIDIZED BED PARTIAL GASIFICATION MODULE (PGM)

    International Nuclear Information System (INIS)

    Unknown

    2001-01-01

    Foster Wheeler Development Corporation is working under DOE contract No. DE-FC26-00NT40972 to develop a partial gasification module (PGM) that represents a critical element of several potential coal-fired Vision 21 plants. When utilized for electrical power generation, these plants will operate with efficiencies greater than 60% while producing near zero emissions of traditional stack gas pollutants. The new process partially gasifies coal at elevated pressure producing a coal-derived syngas and a char residue. The syngas can be used to fuel the most advanced power producing equipment such as solid oxide fuel cells or gas turbines or processed to produce clean liquid fuels or chemicals for industrial users. The char residue is not wasted; it can also be used to generate electricity by fueling boilers that drive the most advanced ultra-supercritical pressure steam turbines. The unique aspect of the process is that it utilizes a pressurized circulating fluidized bed partial gasifier and does not attempt to consume the coal in a single step. To convert all the coal to syngas in a single step requires extremely high temperatures ((approx)2500 to 2800F) that melt and vaporize the coal and essentially drive all coal ash contaminants into the syngas. Since these contaminants can be corrosive to power generating equipment, the syngas must be cooled to near room temperature to enable a series of chemical processes to clean the syngas. Foster Wheeler's process operates at much lower temperatures that control/minimize the release of contaminants; this eliminates/minimizes the need for the expensive, complicated syngas heat exchangers and chemical cleanup systems typical of high temperature gasification. By performing the gasification in a circulating bed, a significant amount of syngas can still be produced despite the reduced temperature and the circulating bed allows easy scale up to large size plants. Rather than air, it can also operate with oxygen to facilitate

  9. Modelling of HTR (High Temperature Reactor Pebble-Bed 10 MW to Determine Criticality as A Variations of Enrichment and Radius of the Fuel (Kernel With the Monte Carlo Code MCNP4C

    Directory of Open Access Journals (Sweden)

    Hammam Oktajianto

    2014-12-01

    Full Text Available Gas-cooled nuclear reactor is a Generation IV reactor which has been receiving significant attention due to many desired characteristics such as inherent safety, modularity, relatively low cost, short construction period, and easy financing. High temperature reactor (HTR pebble-bed as one of type of gas-cooled reactor concept is getting attention. In HTR pebble-bed design, radius and enrichment of the fuel kernel are the key parameter that can be chosen freely to determine the desired value of criticality. This paper models HTR pebble-bed 10 MW and determines an effective of enrichment and radius of the fuel (Kernel to get criticality value of reactor. The TRISO particle coated fuel particle which was modelled explicitly and distributed in the fuelled region of the fuel pebbles using a Simple-Cubic (SC lattice. The pebble-bed balls and moderator balls distributed in the core zone using a Body-Centred Cubic lattice with assumption of a fresh fuel by the fuel enrichment was 7-17% at 1% range and the size of the fuel radius was 175-300 µm at 25 µm ranges. The geometrical model of the full reactor is obtained by using lattice and universe facilities provided by MCNP4C. The details of model are discussed with necessary simplifications. Criticality calculations were conducted by Monte Carlo transport code MCNP4C and continuous energy nuclear data library ENDF/B-VI. From calculation results can be concluded that an effective of enrichment and radius of fuel (Kernel to achieve a critical condition was the enrichment of 15-17% at a radius of 200 µm, the enrichment of 13-17% at a radius of 225 µm, the enrichments of 12-15% at radius of 250 µm, the enrichments of 11-14% at a radius of 275 µm and the enrichment of 10-13% at a radius of 300 µm, so that the effective of enrichments and radii of fuel (Kernel can be considered in the HTR 10 MW. Keywords—MCNP4C, HTR, enrichment, radius, criticality 

  10. A low tritium hydride bed inventory estimation technique

    Energy Technology Data Exchange (ETDEWEB)

    Klein, J.E.; Shanahan, K.L.; Baker, R.A. [Savannah River National Laboratory, Aiken, SC (United States); Foster, P.J. [Savannah River Nuclear Solutions, Aiken, SC (United States)

    2015-03-15

    Low tritium hydride beds were developed and deployed into tritium service in Savannah River Site. Process beds to be used for low concentration tritium gas were not fitted with instrumentation to perform the steady-state, flowing gas calorimetric inventory measurement method. Low tritium beds contain less than the detection limit of the IBA (In-Bed Accountability) technique used for tritium inventory. This paper describes two techniques for estimating tritium content and uncertainty for low tritium content beds to be used in the facility's physical inventory (PI). PI are performed periodically to assess the quantity of nuclear material used in a facility. The first approach (Mid-point approximation method - MPA) assumes the bed is half-full and uses a gas composition measurement to estimate the tritium inventory and uncertainty. The second approach utilizes the bed's hydride material pressure-composition-temperature (PCT) properties and a gas composition measurement to reduce the uncertainty in the calculated bed inventory.

  11. High-temperature reactor developments in the Netherlands

    International Nuclear Information System (INIS)

    Schram, R.P.C.; Cordfunke, E.H.P.; Heek, A.I. van.

    1996-01-01

    The high-temperature reactor development in the Netherland is embedded in the WHITE reactor program, in which several Dutch research institutes and engineering companies participate. The activities within the WHITE program are focused on the development of a small scale HTS for combined heat and power generation. In 1995, design choices for a pebble bed reactor were made at ECN. The first concept HTR will gave a closed cycle helium turbine and a power level of 40 MWth. It is intended to make the market introduction of a commercially competitive HTR feasible. The design will be an optimization of the Peu-a-Peu (PAP) concept of KFA Juelich. Computer codes necessary for the evaluation of reactor physics aspects of this reactor are developed in cooperation with international partners. An evaluation of a 20 MWth PAP concept showed that the maximum fuel termmperature after depressurization does not exceed 1300 C. (orig.)

  12. Predicted peak temperature-rises around a high-level radioactive waste canister emplaced in the deep ocean bed

    International Nuclear Information System (INIS)

    Kipp, K.L.

    1978-06-01

    A simple mathematical model of heat conduction was used to evaluate the peak temperature-rise along the wall of a canister of high-level radioactive waste buried in deep ocean sediment. Three different amounts of vitrified waste, corresponding to standard Harvest, large Harvest, and AVM canisters, and three different waste loadings were studied. Peak temperature-rise was computed for the nine cases as a function of canister geometry and storage time between reprocessing and burial. Lower waste loadings or longer storage times than initially envisaged are necessary to prevent the peak temperature-rise from exceeding 200 0 C. The use of longer, thinner cylinders only modestly reduces the storage time for a given peak temperature. Effects of stacking of waste canisters and of close-packing were also studied. (author)

  13. CFD-DEM simulation of a conceptual gas-cooled fluidized bed nuclear reactor

    International Nuclear Information System (INIS)

    Almeida, Lucilla C.; Su, Jian

    2015-01-01

    Several conceptual designs of the fluidized-bed nuclear reactor have been proposed due to its many advantages over conventional nuclear reactors such as PWRs and BWRs. Amongst their characteristics, the enhanced heat transfer and mixing enables a more uniform temperature distribution, reducing the risk of hot-spot and excessive fuel temperature, in addition to resulting in a higher burnup of the fuel. Furthermore, the relationship between the bed height and reactor neutronics turns the coolant flow rate control into a power production mechanism. Moreover, the possibility of removing the fuel by gravity from the movable core in case of a loss-of-cooling accident increases its safety. High-accuracy modeling of particles and coolant flow in fluidized bed reactors is needed to evaluate reliably the thermal-hydraulic efficiency and safety margin. The two-way coupling between solid and fluid can account for high-fidelity solid-solid interaction and reasonable accuracy in fluid calculation and fluid-solid interaction. In the CFD-DEM model, the particles are modeled as a discrete phase, following the DEM approach, whereas the fluid flow is treated as a continuous phase, described by the averaged Navier-Stokes equations on a computational cell scale. In this work, the coupling methodology between Fluent and Rocky is described. The numerical approach was applied to the simulation of a bubbling fluidized bed and the results were compared to experimental data and showed good agreement. (author)

  14. A Computational-Experimental Study of Plasma Processing of Carbides at High Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Bronson, Arturo [Univ. of Texas, El Paso, TX (United States); Kumar, Vinod [Univ. of Texas, El Paso, TX (United States)

    2016-02-01

    appears to grow with Ti ions migrating outward from the Ti3AlC/Ti2AlC/TiC core and oxygen ions diffusing inwardly toward the core. The transient temperature distribution of a cylindrical, carbide packed bed (i.e., B4C) was simulated with COMSOL software to determine the response of the bed to a sudden temperature spike exposed to the outer wall of the bed. The temperature distribution of B4C was similarly heated and compared with Hf and Zr metal. The thermal conductivity of Hf and Zr is higher than the B4C packed bed and hence they respond quicker than B4C. The packed bed still takes approximately 1200 s to plateau the temperature distribution between the cylinder surfaces to the centerline of the carbide packed bed of 5 cm diameter. Though the modeling of the distributions in the carbide packed bed gives an understanding of the transient heat response behavior driven by radiation, the effect of the plasma on the surface temperature of individual carbide particles needs further investigation to understand the plasma contribution to densification of a carbide packed bed.

  15. Gasification of palm empty fruit bunch in a bubbling fluidized bed: a performance and agglomeration study.

    Science.gov (United States)

    Lahijani, Pooya; Zainal, Zainal Alimuddin

    2011-01-01

    Gasification of palm empty fruit bunch (EFB) was investigated in a pilot-scale air-blown fluidized bed. The effect of bed temperature (650-1050 °C) on gasification performance was studied. To explore the potential of EFB, the gasification results were compared to that of sawdust. Results showed that maximum heating values (HHV) of 5.37 and 5.88 (MJ/Nm3), dry gas yield of 2.04 and 2.0 (Nm3/kg), carbon conversion of 93% and 85 % and cold gas efficiency of 72% and 71 % were obtained for EFB and sawdust at the temperature of 1050 °C and ER of 0.25. However, it was realized that agglomeration was the major issue in EFB gasification at high temperatures. To prevent the bed agglomeration, EFB gasification was performed at temperature of 770±20 °C while the ER was varied from 0.17 to 0.32. Maximum HHV of 4.53 was obtained at ER of 0.21 where no agglomeration was observed. Copyright © 2010 Elsevier Ltd. All rights reserved.

  16. Numerical modeling of pyrolysis of sawdust in a packed bed

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Qingmin; Chen, Xiaoping [Southeast Univ., Nanjing (China). School of Energy and Environment

    2013-07-01

    An unsteady, one-dimensional mathematical model has been developed to describe the pyrolysis of sawdust in a packed bed. The sawdust bed was pyrolyzed using the hot gas and an electric heater outside the bed as the source of energy. The developed model includes mass, momentum and energy conservations of gas and solid within the bed. The gas flow in the bed is modeled using Darcy's law for fluid through a porous medium. The heat transfer model includes heat conduction inside the bed and convection between the bed and the hot gas. The kinetic model consists of primary pyrolysis reaction. A finite volume fully implicit scheme is employed for solving the heat and mass transfer model equations. A Runge-Kutta fourth order method is used for the chemical kinetics model equations. The model predictions of mass loss history and temperature were validated with published experimental results, showing a good agreement. The effects of inlet temperature on the pyrolysis process have been analyzed with model simulation. A sensitivity analysis using the model suggests that the predictions could be improved by considering the second reaction which could generate volatile flowing in the void.

  17. Effect of process temperature on morphology of CNTs grown in a vertically fluidized bed reactor with Fe{sub 2}O{sub 3}/Al{sub 2}O{sub 3} catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Shukrullah, Shazia, E-mail: zshukrullah@gmail.com; Mohamed, Norani Muti, E-mail: noranimuti-mohamed@petronas.com.my; Shaharun, Maizatul Shima, E-mail: maizats@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak (Malaysia)

    2015-07-22

    Carbon nanotubes (CNTs) are one of the most researched materials due to their exceptional mechanical and electrical properties. Among the various techniques, catalytic chemical vapor deposition in a fluidized bed reactor is the most promising technique for bulk production of CNTs. To meet the demand of good quality along with the bulk production of CNTs, the effect of reaction temperature on the micro structures, morphology, diameter, quality and quantity of CNTs was investigated in these studies. CNTs were synthesized at process temperature ranging from 700-850°C by catalytic decomposition of C{sub 2}H{sub 4} on Fe{sub 2}O{sub 3}/Al{sub 2}O{sub 3} catalyst a vertical fluidized bed reactor. The microstructures of the grown CNTs at different reaction temperatures were investigated by using scanning electron microscope. The results of this study depicted a positive correlation between the average diameter of CNTs and reaction temperature. Narrow diameters (35∼40 nm) of CNTs with fewer defects were found at the low and mild temperatures, in particular 800°C. At this temperature, a dynamic equilibrium between the rate of C{sub 2}H{sub 4} decomposition and CNTs quantity was found due to maximum carbon diffusion over catalyst. The CNTs produced with Fe{sub 2}O{sub 3}/Al{sub 2}O{sub 3} catalyst wer e also exhibiting high quality with relatively small mean outer diameter and fewer surface defects.

  18. Report on research and development achievements in fiscal 1980 in Sunshine Project. Development of a high-temperature bed drilling technology (Research and development of bit materials); 1980 nendo koon chiso kussaku gijutsu no kaihatsu seika hokokusho. Bit zairyo no kenkyu kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1981-03-01

    Development is made on bit materials that can efficiently drill high-temperature ground bed to 3,000 to 5,000 m under geothermal conditions of 350 degrees C and 400 kg/cm{sup 2}. Alloy composition excellent in corrosion resistance, oxidation resistance, high-temperature hardness, and repulsion resistance without decreasing damage resistance lower than the existing products is Cr{sub 3}C{sub 2} amount of 1%, WC of 2.5 microns, and Co/(Co + Ni) of 50%. Dispersion strengthening is most suitable for a metallurgically sintered powder cutter. Adding carbide of 5% by volume or metal as dispersion strengthening particles enhances hardness almost without damaging tenacity. Compression yield has also increased. Good dispersion strengthened materials include W and WC. On cutter materials for rock drilling bits used under severe conditions of high temperatures, high pressures, and corrosion environment, natures nearly close to the target were provided, and prospect for shape provision was obtained. These natures include mechanical properties at elevated temperatures, corrosion and wear resistance, an inside strengthening method, and a surface hardening method. Dispersion strengthening by adding micro fine hard powder to the inside strengthening method was used to have obtained the intended achievement. Positioning of the metallurgically sintered powder was made clear. (NEDO)

  19. Effect of secondary air injection on the combustion efficiency of sawdust in a fluidized bed combustor

    Directory of Open Access Journals (Sweden)

    K. V. N. Srinivasa Rao

    2008-03-01

    Full Text Available Agricultural wastes like bagasse, paddy husks, sawdust and groundnut shells can be effectively used as fuels for fluidized bed combustion; otherwise these biomass fuels are difficult to handle due to high moisture and fines content. In the present work the possibility of using sawdust in the fluidized bed combustor, related combustion efficiencies and problems encountered in the combustion process are discussed. The temperature profiles for sawdust with an increase in fluidizing velocity along the vertical height above the distributor plate indicate that considerable burning of fuel particles is taking place in the freeboard zone rather than complete burning within the bed. Therefore, an enlarged disengagement section is provided to improve the combustion of fines. The temperature profiles along the bed height are observed at different feed rates. The feed rate of sawdust corresponding to the maximum possible temperature was observed to be 10.2 kg/h. It is observed that 50-60% excess air is optimal for reducing carbon loss during the burning of sawdust. The maximum possible combustion efficiency with sawdust is 99.2% and is observed with 65% excess air.

  20. Cooling of a polyethylene tunnel type greenhouse by means of a rock bed

    Energy Technology Data Exchange (ETDEWEB)

    Kurklu, Ahmet; Bilgin, Sefai [Akdeniz Univ., Dept. of Agricultural Mechanisation, Antalya (Turkey)

    2004-10-01

    An experiment was conducted to cool a 15 m{sup 2} ground area plastic-tunnel-type greenhouse by the use of a rock bed. An identical greenhouse with no rock bed was also erected for control purposes. Two rock-bed canals, each with the dimensions of 3 x l.25 x 0.75 m, were dug in the soil of the experimental greenhouse. After the canals were filled with the rocks and insulated, the top surface was covered by a soil layer of thickness enough for the root development depth of the plants. Air was pushed through the rock bed by a centrifugal fan with a 1100 m{sup 3}/h flow rate. Energy stored in the rock bed during the day was dumped outside the greenhouse at night using the cooler outside air. The results of the measurements showed that the rock-bed system maintained air temperature 14 deg C lower at maximum in the experimental greenhouse than the control one. The temperature difference seemed to increase with increasing solar radiation and outside air temperature. Relative humidity during the day remained at about 40% in the experimental greenhouse and was always higher than that in the control one. The coefficient of performance (COP) of the rock-bed system was higher than 3 in general, and it was observed that this value increased with decreasing rock-bed temperature. The average solar collection efficiency was 38%. The rock-bed system seems to have a significant potential for cooling applications in greenhouses. (Author)

  1. Characterization of ash melting behaviour at high temperatures under conditions simulating combustible solid waste gasification.

    Science.gov (United States)

    Niu, Miaomiao; Dong, Qing; Huang, Yaji; Jin, Baosheng; Wang, Hongyan; Gu, Haiming

    2018-05-01

    To achieve high-temperature gasification-melting of combustible solid waste, ash melting behaviour under conditions simulating high-temperature gasification were studied. Raw ash (RA) and gasified ash (GA) were prepared respectively by waste ashing and fluidized bed gasification. Results of microstructure and composition of the two-ash indicated that GA showed a more porous structure and higher content of alkali and alkali earth metals among metallic elements. Higher temperature promoted GA melting and could reach a complete flowing state at about 1250°C. The order of melting rate of GA under different atmospheres was reducing condition > inert condition > oxidizing condition, which might be related to different existing forms of iron during melting and different flux content with atmosphere. Compared to RA, GA showed lower melting activity at the same condition due to the existence of an unconverted carbon and hollow structure. The melting temperature for sufficient melting and separation of GA should be at least 1250°C in this work.

  2. Research and application of packing density for pebble bed in HTR

    International Nuclear Information System (INIS)

    Yu Fujiang; Xie Fei; Sun Ximing

    2015-01-01

    The pebble bed high temperature gas-cooled reactor is one of the major types of reactors developed by Chinese nuclear technology. The statistical analysis for packing density in the pebble bed is an important issue of physical-thermal calculation and safety analysis. Aimed to this problem, a new kind of method was set up to solve this problem. Compared with the traditional lattice-fill method and the experiment, its efficiency and accuracy were verified, while helping to find out the best length of unit in the traditional lattice-fill method. This method was used to analyze the boundary effects observed by experiments. (authors)

  3. Unsteady void measurements within debris beds using high speed X-ray tomography

    Energy Technology Data Exchange (ETDEWEB)

    Laurien, E., E-mail: Laurien@ike.uni-stuttgart.de; Stürzel, T., E-mail: thilo.stuerzel@stihl.de; Zhou, M., E-mail: mi.zhou@ike.uni-stuttgart.de

    2017-02-15

    Highlights: • A high speed X-ray tomography facility has been built for the investigation on two-phase flow. • The two-phase flow through beds of packed plastic spheres has been investigated in the facility. • 3D-reconstructions from the measurements show the fluxes in the two-phase flow. • The gas fraction has been calculated from the reconstruction and used for validation of the modeling. • A new bed with closest regular spheres arrangement has been manufactured by 3D-plotter and used in the measurement. - Abstract: Two-phase flow and boiling within debris beds representing a destroyed reactor core after a severe accident with core fragmentation can be simulated by using the porous media approach. In this approach, a local pressure drop and the heat transfer between the solid debris particles and the two-phase flow is modelled with the help flow-pattern maps, in which the boundaries between bubbly, slug, and annular flow are assumed. In order to support further understanding of these flows we have developed a very fast X-ray measurement device to visualize the 3D-void distribution within particle beds or porous media, which are otherwise un-accessible internally. The experimental setup uses a scanned electron beam directed in circles on a tungsten target to generate the X-rays. The particle bed, which has a diameter of 70 mm, is located between this target and a field of 256 X-ray detectors, which are arranged on a circle concentric to the target. The void distribution is reconstructed numerically from the attenuation of signals, which penetrates the particle bed and the two-phase flow inside. A 3D frame rate of up to 1000 Hz can be reached. The spatial resolution is such that bubbles with a diameter > 1.7 mm can be detected. We have investigated two-phase flows air/water through beds of packed plastic spheres (diameter between 3 and 15 mm) as well as through plastic beds, which were manufactured using a ‘3D-plotter’. Flow patterns can be

  4. Comparison of high temperature gas particulate collectors for low level radwaste incinerator volume reduction systems

    International Nuclear Information System (INIS)

    Moscardini, R.L.; Johnston, J.R.; Waters, R.M.; Zievers, J.F.

    1983-01-01

    Incinerator system off-gases must be treated to prevent the release of particulates, noxious gases and radioactive elements to the environment. Fabric filters, venturi scrubbers, cyclone separators, an ceramic or metal filter candles have been used for particulate removal. Dry high temperature particulate collectors have the advantage of not creating additional liquid wastes. This paper presents a graphical comparison of different methods for filtering particles from high temperature incineration system off-gases. Eight methods of off-gas handling are compared. A much larger group may be present, but some judicious selection of different, but related systems was done for this paper based on experience with the Combustion Engineering Waste Incineration System (CE/WIS) Prototype. The eight types are: Inertial Devices, Electrostatic Precipitators (ESP), Standard Fabric Bags, Woven Ceramic Bags, Granular Beds, Sintered Metal Tubes, Felted Ceramic Bags and Ceramic Filter Candles. For high temperature LLRW particulate collection in incinerator off-gas systems, ceramic filter candles are the best overall choice

  5. Use of plutonium and minor actinides as fuel in high temperature pebble bed reactors for waste minimization

    International Nuclear Information System (INIS)

    Meier, Astrid; Bernnat, Wolfgang; Lohnert, Guenther

    2009-01-01

    Energy production by nuclear fission gives rise to longlived radionuclides, such as plutonium and americium. The ''PuMA'' (Plutonium and Minor Actinides Waste Management) research project within the 6th Framework Program of the European Union serves to minimize waste arisings and transmute plutonium and minor actinides from spent LWR fuel elements by means of modular high-temperature reactors (HTR). Coating the fuel, which consists of kernels approx. 250 μm in radius and surrounded by graphite as the moderator material, allows very high operating and accident temperatures and very high burnups. One point examined is whether the inherent safety characteristics known for uranium oxide also exist for (PuO 2 + MAO 2 ) fuel. On the basis of a reference reactor similar to the South African PBMR-400, various loading strategies at maximum burnup are considered with a view to the inherent safety of the HTR. (orig.)

  6. Esterification of oleic acid in a three-phase, fixed-bed reactor packed with a cation exchange resin catalyst.

    Science.gov (United States)

    Son, Sung Mo; Kimura, Hiroko; Kusakabe, Katsuki

    2011-01-01

    Esterification of oleic acid was performed in a three-phase fixed-bed reactor with a cation exchange resin catalyst (Amberlyst-15) at high temperature, which was varied from 80 to 120 °C. The fatty acid methyl ester (FAME) yields in the fixed-bed reactor were increased with increases in the reaction temperature, methanol flow rate and bed height. Moreover, the FAME yields were higher than those obtained using a batch reactor due to an equilibrium shift toward the product that resulted from continuous evaporation of the produced water. In addition, there was no catalyst deactivation during the esterification of oleic acid. However, addition of sunflower oil to the oleic acid reduced the FAME yield obtained from simultaneous esterification and transesterification. The FAME yield was 97.5% at a reaction temperature of 100 °C in the fixed-bed with a height of 5 cm when the methanol and oleic acid feed rates were 8.6 and 9.0 mL/h, respectively. Copyright © 2010 Elsevier Ltd. All rights reserved.

  7. Tritium storage metal-bed pyrophoricity measurements

    International Nuclear Information System (INIS)

    Longhurst, G.R.; Neilson, R.M. Jr.; Porter, L.J.

    1987-01-01

    A safety concern for metal-bed tritium storage systems is the possibility of spontaneous combustion and/or explosion if the bed is accidentally exposed to air. This may result in the dispersion of tritium or tritiated compounds. Of several materials being considered for use in tritium storage beds, uranium (U), zirconium-cobalt (ZrCo), and lanthanum-nickel aluminide (LaNi 5-x Al x ) are of particular interest. It is well known that uranium that has been activated by cycles of hydriding and dehydriding is extremely pyrophoric when exposed to air or other oxidizers. Uranium hydride has also been found to be mildly pyrophoric, but less is known about the pyrophoric natures of the hydrides of the other materials. An experiment is in progress to evaluate the pyrophoric response of these materials and their hydrides and deuterides in air. Small (<100 mg) samples of depleted uranium were hydrided and then exposed to atmospheres of air, oxygen, or nitrogen using a thermogravimetric analyzer to monitor the sample weight and temperature. There was not an immediate pyrophoric response at room temperature, but ignition occured at moderately elevated temperatures for air and oxygen atmospheres. The experimental apparatus has been upgraded, and tests are continuing on these materials

  8. [Thermal energy utilization analysis and energy conservation measures of fluidized bed dryer].

    Science.gov (United States)

    Xing, Liming; Zhao, Zhengsheng

    2012-07-01

    To propose measures for enhancing thermal energy utilization by analyzing drying process and operation principle of fluidized bed dryers,in order to guide optimization and upgrade of fluidized bed drying equipment. Through a systematic analysis on drying process and operation principle of fluidized beds,the energy conservation law was adopted to calculate thermal energy of dryers. The thermal energy of fluidized bed dryers is mainly used to make up for thermal consumption of water evaporation (Qw), hot air from outlet equipment (Qe), thermal consumption for heating and drying wet materials (Qm) and heat dissipation to surroundings through hot air pipelines and cyclone separators. Effective measures and major approaches to enhance thermal energy utilization of fluidized bed dryers were to reduce exhaust gas out by the loss of heat Qe, recycle dryer export air quantity of heat, preserve heat for dry towers, hot air pipes and cyclone separators, dehumidify clean air in inlets and reasonably control drying time and air temperature. Such technical parameters such air supply rate, air inlet temperature and humidity, material temperature and outlet temperature and humidity are set and controlled to effectively save energy during the drying process and reduce the production cost.

  9. Hypothetical accident scenario analyses for a 250-MW(t) modular high temperature gas-cooled reactor

    International Nuclear Information System (INIS)

    Harrington, R.M.; Ball, S.J.; Cleveland, J.C.

    1985-11-01

    This paper describes calculations performed to characterize the inherent safety of a 250-MW(t), 100-MW(e), pebble bed modular high temperature gas-cooled reactor (HTGR) design with vertical in-line arrangement (i.e., upflow core with steam generators directly above the core). A variety of postulated accident sequences involving combinations of loss of forced primary coolant (helium) circulation, loss of primary coolant pressurization, and loss of heat sink were studied and were discussed

  10. Fluidized bed gasification of sugar cane bagasse. Influence on gas composition

    Energy Technology Data Exchange (ETDEWEB)

    Esperanza, E.; Aleman, Y. [Univ. of las Villas, Santa Clara (Cuba). Biomass Thermoconversion group/CETA; Arauzo, J.; Gea, G. [Univ. of Zaragoza (Spain). Chemical and Environmental Engineering Dept.

    1999-07-01

    Air and steam gasification of biomass has been studied at different temperatures. The experiments have been carried out in a bench scale plant. It consists of an atmospheric bubbling fluidized bed gasifier heated by an electric furnace. The gasification process have been carried out at high heating rates and low residence time of the gases. The biomass used has been Cuban sugar cane bagasse. Three operating parameters have been evaluated to improve the gas composition: Equivalence Ratio (E.R.) in the range of 0.15 to 0.55; the bed temperature from 780 to 920 deg C; and steam/biomass ratio (S/B) from 0.1 g/g to 0.5 g/g. The results obtained show the effect of these operating parameters in gas composition and the conditions to obtain higher yield to gas and else the maximum energy.

  11. Styrene biofiltration in a trickle-bed reactor

    Directory of Open Access Journals (Sweden)

    V. Novak

    2008-04-01

    Full Text Available The biological treatment of styrene waste gas in a trickle-bed filter (TBF was investigated. The bioreactor consisted of a two-part glass cylinder (ID 150 mm filled with 25 mm polypropylene Pall rings serving as packing material. The bed height was 1m. Although the laboratory temperature was maintained at 22 ºC, the water temperature in the trickle-bed filter was slightly lower (about 18 ºC.The main aim of our study was to observe the effect of empty-bed residence time (EBRT on bioreactor performance at a constant pollutant concentration over an extended time period. The bioreactor was inoculated with a mixed microbial consortium isolated from a styrene-degrading biofilter that had been running for the previous two years. After three weeks of acclimation period, the bioreactor was loaded with styrene (100 mg.m-3. EBRT was in the range of 53 s to 13 s. A maximum elimination capacity (EC of 11.3 gC.m-3.h-1 was reached at an organic loading (OL rate of 18.6 gC.m-3.h-1.

  12. Critical Issues for Particle-Bed Reactor Fuels

    Science.gov (United States)

    Evans, Robert S.; Husser, Dewayne L.; Jensen, Russell R.; Kerr, John M.

    1994-07-01

    Particle-Bed Reactors (PBRs) potentially offer performance advantages for nuclear thermal propulsion, including very high power densities, thrust-to-weight ratios, and specific impulses. A key factor in achieving all of these is the development of a very-high-temperature fuel. The critical issues for all such PBR fuels are uranium loading, thermomechanical and thermochemical stability, compatibility with contacting materials, fission product retention, manufacturability, and operational tolerance for particle failures. Each issue is discussed with respect to its importance to PBR operation, its status among current fuels, and additional development needs. Mixed-carbide-based fuels are recommended for further development to support high-performance PBRs.

  13. Continuous monitoring bed-level dynamics on an intertidal flat: Introducing novel, stand-alone high-resolution SED-sensors

    NARCIS (Netherlands)

    Hu, Z.; Lenting, W.; Van der Wal, D.; Bouma, T.J.

    2015-01-01

    Tidal flat morphology is continuously shaped by hydrodynamic forces, resulting in a highly dynamic bed surface. The knowledge of short-term bed-level changes is important both for assessing sediment transport processes as well as for understanding critical ecological processes, such as vegetation

  14. Lifetime evaluation of superheater tubes exposed to steam oxidation, high temperature corrosion and creep

    Energy Technology Data Exchange (ETDEWEB)

    Henriksen, N [Elsamprojekt A/S, Faelleskemikerne, Fredericia (Denmark); Hede Larsen, O; Blum, R [I/S Fynsvaerket, Faelleskemikerne, Odense (Denmark)

    1996-12-01

    Advanced fossil fired plants operating at high steam temperatures require careful design of the superheaters. The German TRD design code normally used in Denmark is not precise enough for the design of superheaters with long lifetimes. The authors have developed a computer program to be used in the evaluation of superheater tube lifetime based on input related to tube dimensions, material, pressure, steam temperature, mass flux, heat flux and estimated corrosion rates. The program is described in the paper. As far as practically feasible, the model seems to give a true picture of the reality. For superheaters exposed to high heat fluxes or low internal heat transfer coefficients as is the case for superheaters located in fluidized bed environments or radiant environments, the program has been extremely useful for evaluation of surface temperature, oxide formation and lifetime. The total uncertainty of the method is mainly influenced by the uncertainty of the determination of the corrosion rate. More precise models describing the corrosion rate as a function of tube surface temperature, fuel parameters and boiler parameters need to be developed. (au) 21 refs.

  15. High temperature energy storage performances of methane reforming with carbon dioxide in a tubular packed reactor

    International Nuclear Information System (INIS)

    Lu, Jianfeng; Chen, Yuan; Ding, Jing; Wang, Weilong

    2016-01-01

    Highlights: • Energy storage of methane reforming in a tubular packed reactor is investigated. • Thermochemical storage efficiency approaches maximum at optimal temperature. • Sensible heat and heat loss play important roles in the energy storage system. • The reaction and energy storage models of methane reforming reactor are established. • The simulated methane conversion and energy storage efficiency fit with experiments. - Abstract: High temperature heat transfer and energy storage performances of methane reforming with carbon dioxide in tubular packed reactor are investigated under different operating conditions. Experimental results show that the methane reforming in tubular packed reactor can efficiently store high temperature thermal energy, and the sensible heat and heat loss besides thermochemical energy storage play important role in the total energy storage process. When the operating temperature is increased, the thermochemical storage efficiency first increases for methane conversion rising and then decreases for heat loss rising. As the operating temperate is 800 °C, the methane conversion is 79.6%, and the thermochemical storage efficiency and total energy efficiency can be higher than 47% and 70%. According to the experimental system, the flow and reaction model of methane reforming is established using the laminar finite-rate model and Arrhenius expression, and the simulated methane conversion and energy storage efficiency fit with experimental data. Along the flow direction, the fluid temperature in the catalyst bed first decreases because of the endothermic reaction and then increases for the heat transfer from reactor wall. As a conclusion, the maximum thermochemical storage efficiency will be obtained under optimal operating temperature and optimal flow rate, and the total energy efficiency can be increased by the increase of bed conductivity and decrease of heat loss coefficient.

  16. High-Resolution Adaptive Optics Test-Bed for Vision Science

    International Nuclear Information System (INIS)

    Wilks, S.C.; Thomspon, C.A.; Olivier, S.S.; Bauman, B.J.; Barnes, T.; Werner, J.S.

    2001-01-01

    We discuss the design and implementation of a low-cost, high-resolution adaptive optics test-bed for vision research. It is well known that high-order aberrations in the human eye reduce optical resolution and limit visual acuity. However, the effects of aberration-free eyesight on vision are only now beginning to be studied using adaptive optics to sense and correct the aberrations in the eye. We are developing a high-resolution adaptive optics system for this purpose using a Hamamatsu Parallel Aligned Nematic Liquid Crystal Spatial Light Modulator. Phase-wrapping is used to extend the effective stroke of the device, and the wavefront sensing and wavefront correction are done at different wavelengths. Issues associated with these techniques will be discussed

  17. The Safety of Hospital Beds

    Science.gov (United States)

    Gervais, Pierre; Pooler, Charlotte; Merryweather, Andrew; Doig, Alexa K.; Bloswick, Donald

    2015-01-01

    To explore the safety of the standard and the low hospital bed, we report on a microanalysis of 15 patients’ ability to ingress, move about the bed, and egress. The 15 participants were purposefully selected with various disabilities. Bed conditions were randomized with side rails up or down and one low bed with side rails down. We explored the patients’ use of the side rails, bed height, ability to lift their legs onto the mattress, and ability to turn, egress, and walk back to the chair. The standard bed was too high for some participants, both for ingress and egress. Side rails were used by most participants when entering, turning in bed, and exiting. We recommend that side rails be reconsidered as a means to facilitate in-bed movement, ingress, and egress. Furthermore, single deck height settings for all patients are not optimal. Low beds as a safety measure must be re-evaluated. PMID:28462302

  18. Morphological characteristics of overdeepenings in high-mountain glacier beds

    Science.gov (United States)

    Haeberli, Wilfried; Cochachin, Alejo; Fischer, Urs; Giráldez, Claudia; Linsbauer, Andreas; Salazar, Cesar

    2014-05-01

    Overdeepenings, i.e. closed topographic depressions with adverse slopes in the flow direction, are characteristic for glacier beds and glacially sculpted landscapes. Besides their importance as geomorphological landforms, groundwater bodies and sedimentary archives, they are of increasing interest in relation to climate-induced lake formation in de-glaciating landscapes and to depth erosion under ice age conditions in connection with the long-term safety of radioactive waste repositories in some mid-latitude countries. Quantitative predictions of their shape, distribution and conditions of occurrence, however, remain difficult. One major problem thereby relates to the still unsatisfactory treatment in glacier erosion theory of sediment evacuation at glacier beds, especially by subglacial meltwater. An alternative way of searching for realistic/empirical quantitative estimates is, therefore, to analyse the geometry of well-documented overdeepenings. The present study attempts to do this by combining statistical analyses of (a) detailed bathymetries from recently exposed lakes in the Peruvian Andes, (b) numerous bed overdeepenigs below still existing glaciers of the Swiss Alps and the Himalaya-Karakoram region modelled with a robust shear stress approximation linking surface slope to ice thickness at high resolution, and (c, for comparison) reconstructed overdeepenings produced by ice age glaciers in the Swiss Plateau based on numerous drillings and geophysical soundings. The sample of (a) has the advantage that geometries are exactly measured and only subject to young/small sedimentation effects. Sample (b) allows for a comparison with a modern model calculation and with known glacier characteristics. Sample (c) may provide some insights into the question how safely results from high mountain topography can be transferred to sites with markedly different topographic, climatic and glaciological controls (cold-arid lowland). Where possible, mean and maximum values of

  19. Experiment and modeling of low-concentration methane catalytic combustion in a fluidized bed reactor

    International Nuclear Information System (INIS)

    Yang, Zhongqing; Yang, Peng; Zhang, Li; Guo, Mingnv; Ran, Jingyu

    2016-01-01

    Highlights: • The catalytic combustion of 0.15~3 vol. % low concentration methane in a fluidized bed was studied. • A mathematical model was proposed on the basis of gas–solid flow theory. • A comparative analysis of the established model with plug flow, mixed flow and K-L models was carried out. • The axial methane profile along fluidized bed was predicted by using the mathematical model. • The bed temperature has greater impact on methane conversion than fluidized velocity. - Abstract: This study undertakes a theoretical analysis and an experimental investigation into the characteristics of low-concentration methane catalytic combustion in a bubbling fluidized bed reactor using 0.5 wt.% Pd/Al_2O_3 as catalytic particles. A mathematical model is established based on gas–solid flow theory and is used to study the effects of bed temperature and fluidized velocity on methane catalytic combustion, and predict the dimensionless methane concentration axial profile in reactor. It is shown that methane conversion increases with bed temperature, but decreases with increasing fluidized velocity. These theoretical results are found to correlate well with the experimental measurement, with a deviation within 5%. A comparative analysis of the developed model with plug flow, mixed flow and K-L models is also carried out, and this further verifies that the established model better reflects the characteristics of low-concentration methane catalytic combustion in a bubbling fluidized bed. Using this reaction model, it was found that the difference in methane conversion between dense and freeboard zones gradually increases with bed temperature; the dense zone reaction levels off at 650 °C, thereby minimizing the difference between the dense and freeboard regions to around 15%. With an increase in bed temperature, the dimensionless methane concentration in the dense zone decreases exponentially, while in the splash zone, it varies from an exponential decay to a slow

  20. Hydrodynamics study on drying of pepper in swirling fluidized bed dryer (SFBD)

    Science.gov (United States)

    Syaif Haron, Nazrul; Hazri Zakaria, Jamal; Faizal Mohideen Batcha, Mohd

    2017-08-01

    Malaysia is one of the pepper producer with exports quantity reaching more than 90000 tonnes between 2010 until 2016. Drying of pepper is mandatory before their export and at present, pepper was dried by sun drying to reduce cost. This conventional drying method was time consuming and may take four days during rainy season, which retards the production of pepper. This paper proposes the swirling fluidized bed drying (SFBD) method, which was known to have high mixing ability and improved solid-gas contact to shorten the drying time of products. A lab scale SFBD system was constructed to carry out this study. Hydrodynamic study was conducted for three beds loadings of 1.0 kg, 1.4 kg at a drying temperature of 90°C. The SFBD has shown excellent potential to dry the pepper with a relatively short drying time compared to the conventional method. Batch drying for the bed loads studied only took 3 hours of drying time only. It was found that bed higher bed loading of wet pepper requires longer drying time due to higher amount of moisture content in the bed. Four distinct regimes of operation were found during drying in the SFBD and these regimes offer flexibility of operation. The total bed pressure drop was relatively low during drying.

  1. Experience in a 6.2 MW{sub e} pressurized fluidized bed gasifier with high ash Indian coals

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, G.; Rajasekaran, A.; Periyakaruppan, V.; Krishnamoorthy, S. [Bharat Heavy Electricals Ltd., Tiruchirappalli (India)

    2006-07-01

    Bharat Heavy Electrical Limited has installed a 165 tons/day air-blown pressurized fluidized bed gasifier (PFBG) as an add-on to their 6.2 MW IGCC demonstration plant and has operated it for more than 4000 hours. Improvements in the gasifier refractory lining, ash extraction and cooling devices, air distribution and temperature measuring devices were incorporated to improve the reliability and performance. Coal with 30-42% ash and high calorific value in the range of 15-20 MJ/kg was used during these operations with crushed coal of 1-4 mm as well as -6 mm coal with fines. Tests were conducted at gasifier pressure of 0.3-1.0 MPa, fluidized bed temperature of 980-1050{sup o}C and at various fluidized velocities and air to steam ratios. Once through carbon conversion efficiency of 90%, cold gas efficiency of 69% and dry gas calorific value of 4.4-4.6 MJ/Nm{sup 3} were obtained. About 15% char in fly ash (with 40% ash coal) was established by TGA. Seal pot system was added for recyling fly ash from the first cyclone to enhance carbon conversion, other parameters and to reduce the char in fly ash to acceptable level. Trends and correlations were established for constituents of gas, carbon conversion efficiency, cold gas efficiency, calorific value of gas and gas yield. BHEL is currently working with a partner to install a 125 MW IGCC plant. The paper elaborates the schematic and constructional details of the PFBG, operating experience and performance. 3 refs., 9 figs.

  2. Automated Design and Optimization of Pebble-bed Reactor Cores

    International Nuclear Information System (INIS)

    Gougar, Hans D.; Ougouag, Abderrafi M.; Terry, William K.

    2010-01-01

    We present a conceptual design approach for high-temperature gas-cooled reactors using recirculating pebble-bed cores. The design approach employs PEBBED, a reactor physics code specifically designed to solve for and analyze the asymptotic burnup state of pebble-bed reactors, in conjunction with a genetic algorithm to obtain a core that maximizes a fitness value that is a function of user-specified parameters. The uniqueness of the asymptotic core state and the small number of independent parameters that define it suggest that core geometry and fuel cycle can be efficiently optimized toward a specified objective. PEBBED exploits a novel representation of the distribution of pebbles that enables efficient coupling of the burnup and neutron diffusion solvers. With this method, even complex pebble recirculation schemes can be expressed in terms of a few parameters that are amenable to modern optimization techniques. With PEBBED, the user chooses the type and range of core physics parameters that represent the design space. A set of traits, each with acceptable and preferred values expressed by a simple fitness function, is used to evaluate the candidate reactor cores. The stochastic search algorithm automatically drives the generation of core parameters toward the optimal core as defined by the user. The optimized design can then be modeled and analyzed in greater detail using higher resolution and more computationally demanding tools to confirm the desired characteristics. For this study, the design of pebble-bed high temperature reactor concepts subjected to demanding physical constraints demonstrated the efficacy of the PEBBED algorithm.

  3. High performance biological methanation in a thermophilic anaerobic trickle bed reactor.

    Science.gov (United States)

    Strübing, Dietmar; Huber, Bettina; Lebuhn, Michael; Drewes, Jörg E; Koch, Konrad

    2017-12-01

    In order to enhance energy efficiency of biological methanation of CO 2 and H 2 , this study investigated the performance of a thermophilic (55°C) anaerobic trickle bed reactor (ATBR) (58.1L) at ambient pressure. With a methane production rate of up to 15.4m 3 CH4 /(m 3 trickle bed ·d) at methane concentrations above 98%, the ATBR can easily compete with the performance of other mixed culture methanation reactors. Control of pH and nutrient supply turned out to be crucial for stable operation and was affected significantly by dilution due to metabolic water production, especially during demand-orientated operation. Considering practical applications, inoculation with digested sludge, containing a diverse biocenosis, showed high adaptive capacity due to intrinsic biological diversity. However, no macroscopic biofilm formation was observed at thermophilic conditions even after 313days of operation. The applied approach illustrates the high potential of thermophilic ATBRs as a very efficient energy conversion and storage technology. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Control and experimental characterization of a methanol reformer for a 350 W high temperature polymer electrolyte membrane fuel cell system

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen; Sahlin, Simon Lennart

    2013-01-01

    is the water and methanol mixture fuel flow and the burner fuel/air ratio and combined flow. An experimental setup is presented capable of testing the methanol reformer used in the Serenergy H3 350 Mobile Battery Charger; a high temperature polymer electrolyte membrane (HTPEM) fuel cell system......This work presents a control strategy for controlling the methanol reformer temperature of a 350 W high temperature polymer electrolyte membrane fuel cell system, by using a cascade control structure for reliable system operation. The primary states affecting the methanol catalyst bed temperature....... The experimental system consists of a fuel evaporator utilizing the high temperature waste gas from the cathode air cooled 45 cell HTPEM fuel cell stack. The fuel cells used are BASF P1000 MEAs which use phosphoric acid doped polybenzimidazole membranes. The resulting reformate gas output of the reformer system...

  5. Optimisation of Experimental Conditions for Ex-Bed Desulfurization

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, J. M.; Ruiz, E.; Otero, J.

    2010-12-22

    This report compiles the results of the work conducted by CIEMAT for Task 6.3 Sulfur and Nitrogen Compounds Abatement of the FLEXGAS project Near Zero Emission Advanced Fluidized Bed Gasification, which has been carried out with financial support from the Research Fund for Coal and Steel, RFCR-CT-2007-00005. The assignment of CIEMAT in Task 6.3 has dealt with the experimental study of ex-bed desulfurization at high temperature and high pressure. Based on a review of the state of the art, a zinc oxide sorbent was chosen as a promising candidate for bulk sulfur removal in highly reducing gases such as those from coal and waste oxygen gasification or for a polishing stage in low sulfur content gases, which is typically the case in biomass gasification gases. The work accomplished has included the study of the sulfidation and regeneration stages in order to determine successful operating conditions and the assessment of the long term performance of the sorbent over subsequent sulfidation and regeneration cycles. (Author) 36 refs.

  6. Coupling scales for modelling heavy metal vaporization from municipal solid waste incineration in a fluid bed by CFD

    Energy Technology Data Exchange (ETDEWEB)

    Soria, José, E-mail: jose.soria@probien.gob.ar [Institute for Research and Development in Process Engineering, Biotechnology and Alternative Energies (PROBIEN, CONICET – UNCo), 1400 Buenos Aires St., 8300 Neuquén (Argentina); Gauthier, Daniel; Flamant, Gilles [Processes, Materials and Solar Energy Laboratory (PROMES-CNRS, UPR 8521), 7 Four Solaire Street, Odeillo, 66120 Font-Romeu (France); Rodriguez, Rosa [Chemical Engineering Institute, National University of San Juan, 1109 Libertador (O) Avenue, 5400 San Juan (Argentina); Mazza, Germán [Institute for Research and Development in Process Engineering, Biotechnology and Alternative Energies (PROBIEN, CONICET – UNCo), 1400 Buenos Aires St., 8300 Neuquén (Argentina)

    2015-09-15

    Highlights: • A CFD two-scale model is formulated to simulate heavy metal vaporization from waste incineration in fluidized beds. • MSW particle is modelled with the macroscopic particle model. • Influence of bed dynamics on HM vaporization is included. • CFD predicted results agree well with experimental data reported in literature. • This approach may be helpful for fluidized bed reactor modelling purposes. - Abstract: Municipal Solid Waste Incineration (MSWI) in fluidized bed is a very interesting technology mainly due to high combustion efficiency, great flexibility for treating several types of waste fuels and reduction in pollutants emitted with the flue gas. However, there is a great concern with respect to the fate of heavy metals (HM) contained in MSW and their environmental impact. In this study, a coupled two-scale CFD model was developed for MSWI in a bubbling fluidized bed. It presents an original scheme that combines a single particle model and a global fluidized bed model in order to represent the HM vaporization during MSW combustion. Two of the most representative HM (Cd and Pb) with bed temperatures ranging between 923 and 1073 K have been considered. This new approach uses ANSYS FLUENT 14.0 as the modelling platform for the simulations along with a complete set of self-developed user-defined functions (UDFs). The simulation results are compared to the experimental data obtained previously by the research group in a lab-scale fluid bed incinerator. The comparison indicates that the proposed CFD model predicts well the evolution of the HM release for the bed temperatures analyzed. It shows that both bed temperature and bed dynamics have influence on the HM vaporization rate. It can be concluded that CFD is a rigorous tool that provides valuable information about HM vaporization and that the original two-scale simulation scheme adopted allows to better represent the actual particle behavior in a fluid bed incinerator.

  7. Coupling scales for modelling heavy metal vaporization from municipal solid waste incineration in a fluid bed by CFD

    International Nuclear Information System (INIS)

    Soria, José; Gauthier, Daniel; Flamant, Gilles; Rodriguez, Rosa; Mazza, Germán

    2015-01-01

    Highlights: • A CFD two-scale model is formulated to simulate heavy metal vaporization from waste incineration in fluidized beds. • MSW particle is modelled with the macroscopic particle model. • Influence of bed dynamics on HM vaporization is included. • CFD predicted results agree well with experimental data reported in literature. • This approach may be helpful for fluidized bed reactor modelling purposes. - Abstract: Municipal Solid Waste Incineration (MSWI) in fluidized bed is a very interesting technology mainly due to high combustion efficiency, great flexibility for treating several types of waste fuels and reduction in pollutants emitted with the flue gas. However, there is a great concern with respect to the fate of heavy metals (HM) contained in MSW and their environmental impact. In this study, a coupled two-scale CFD model was developed for MSWI in a bubbling fluidized bed. It presents an original scheme that combines a single particle model and a global fluidized bed model in order to represent the HM vaporization during MSW combustion. Two of the most representative HM (Cd and Pb) with bed temperatures ranging between 923 and 1073 K have been considered. This new approach uses ANSYS FLUENT 14.0 as the modelling platform for the simulations along with a complete set of self-developed user-defined functions (UDFs). The simulation results are compared to the experimental data obtained previously by the research group in a lab-scale fluid bed incinerator. The comparison indicates that the proposed CFD model predicts well the evolution of the HM release for the bed temperatures analyzed. It shows that both bed temperature and bed dynamics have influence on the HM vaporization rate. It can be concluded that CFD is a rigorous tool that provides valuable information about HM vaporization and that the original two-scale simulation scheme adopted allows to better represent the actual particle behavior in a fluid bed incinerator

  8. Evaluation of proposed German safety criteria for high-temperature gas-cooled reactors

    International Nuclear Information System (INIS)

    Barsell, A.W.

    1980-05-01

    This work reviews proposed safety criteria prepared by the German Bundesministerium des Innern (BMI) for future licensing of gas-cooled high-temperature reactor (HTR) concepts in the Federal Republic of Germany. Comparison is made with US General Design Criteria (GDCs) in 10CFR50 Appendix A and with German light water reactor (LWR) criteria. Implications for the HTR design relative to the US design and safety approach are indicated. Both inherent characteristics and design features of the steam cycle, gas turbine, and process heat concepts are taken into account as well as generic design options such as a pebble bed or prismatic core

  9. Characterization of fluidization regime in circulating fluidized bed reactor with high solid particle concentration using computational fluid dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Chalermsinsuwan, Benjapon; Thummakul, Theeranan; Piumsomboon, Pornpote [Chulalongkorn University, Bangkok (Thailand); Gidaspow, Dimitri [Armour College of Engineering, Chicago (United States)

    2014-02-15

    The hydrodynamics inside a high solid particle concentration circulating fluidized bed reactor was investigated using computational fluid dynamics simulation. Compared to a low solid particle reactor, all the conventional fluidization regimes were observed. In addition, two unconventional fluidization regimes, circulating-turbulent and dense suspension bypassing regimes, were found with only primary gas injection. The circulating-turbulent fluidization regime showed uniformly dense solid particle distribution in all the system directions, while the dense suspension bypassing fluidization regime exhibited the flow of solid particles at only one side system wall. Then, comprehensive fluidization regime clarification and mapping were evaluated using in-depth system parameters. In the circulating-turbulent fluidization regime, the total granular temperature was low compared to the adjacent fluidization regimes. In the dense suspension bypassing fluidization regime, the highest total granular temperature was obtained. The circulating-turbulent and dense suspension bypassing fluidization regimes are suitable for sorption and transportation applications, respectively.

  10. High School Students’ Use of Sunscreen and Tanning Beds

    Centers for Disease Control (CDC) Podcasts

    This podcast is an interview with Corey Basch, EdD, MPH, assistant professor in the Department of Public Health at William Paterson University. Dr. Basch discusses her study on high school students’ use of sunscreen and tanning beds between 2001 and 2011.

  11. Coal-char combustion in a fluidised bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Mehrotra, S.P.; Pande, M. [Indian Institute of Technolgy, Kanpur (India)

    2001-12-01

    Combustion of bituminous coal chars ranging from 0.8 mm to 1.8 mm has been studied in a fluidised bed reactor at temperatures ranging from 500 to 850{sup o}C. The fluidised bed consists of inert sand particles of average size of 0.5 mm and reactive coal char particles. A heat balance has been worked out to calculate the rate of combustion of char from measured incremental changes in the bed temperature during combustion. Investigations on partially burnt particles suggest that the ash layer which builds up around the burning core of char particles is non-flaking and the particles burn in a shrinking core manner. Analysis of rate data indicates that the rate of combustion is controlled by chemical reaction kinetics, though diffusion of oxygen through the bundary layer begins to influence the overall reaction kinetics at higher temperatures. The burnt out time varies linearly with particle size. Activation energy for the chemical reaction control regime is found to be around 68 kJ/mole.

  12. Analysis of the delayed afterheat removal for a pebble-bed high temperature reactor concept as a contribution to the possibility for limitation of hypothetical accidents

    International Nuclear Information System (INIS)

    Rehm, W.

    1980-02-01

    The report presents the analysis of thermodynamic transients for a pebble-bed HTR concept which occur during the delayed after-heat removal of an overheated HTR-core. The consequences of the temperature behaviour are considered for the components of the circuit and the heat exchanger. The analysis is based on a core heatup following a depressurization of the primary circuit and a hypothetical loss of all the redundant cooling systems. By means of calculations it is demonstrated that a regular core structure and a coolable circuit geometry remain. In addition, it appears that the efficiency of the first fission product barrier is not impaired. The slow temperature transients of 2 0 C/min allow the possibility to restart failed afterheat loops to limit the temperature excursion. Provided that certain design and control features are incorporated, the afterheat removal systems can be restarted successfully even after long delay periods. During corresponding emergency procedures the heat exchangers are not demaged. The problems arising from failure limits for specific concepts must be solved. The consequences of total failure of afterheat removal systems are discussed. These consequences can be limited by taking into account the characteristic features of the HTR-system together with additional counter-measures. (orig.) [de

  13. Experimental investigation into a packed bed thermal storage solution for solar gas turbine systems

    CSIR Research Space (South Africa)

    Klein, P

    2013-09-01

    Full Text Available High temperature thermal storage in randomly packed beds of ceramic particles is proposed as an effective storage solution for Solar Gas Turbine (SGT) cycles in the near term. Numerical modelling of these systems allows for optimised thermal storage...

  14. High-Temperature Piezoelectric Sensing

    Directory of Open Access Journals (Sweden)

    Xiaoning Jiang

    2013-12-01

    Full Text Available Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented.

  15. Air gasification of rice husk in bubbling fluidized bed reactor with bed heating by conventional charcoal.

    Science.gov (United States)

    Makwana, J P; Joshi, Asim Kumar; Athawale, Gaurav; Singh, Dharminder; Mohanty, Pravakar

    2015-02-01

    An experimental study of air gasification of rice husk was conducted in a bench-scale fluidized bed gasifier (FBG) having 210 mm diameter and 1600 mm height. Heating of sand bed material was performed using conventional charcoal fuel. Different operating conditions like bed temperature, feeding rate and equivalence ratio (ER) varied in the range of 750-850 °C, 25-31.3 kg/h, and 0.3-0.38, respectively. Flow rate of air was kept constant (37 m(3)/h) during FBG experiments. The carbon conversion efficiencies (CCE), cold gas efficiency, and thermal efficiency were evaluated, where maximum CCE was found as 91%. By increasing ER, the carbon conversion efficiency was decreased. Drastic reduction in electric consumption for initial heating of gasifier bed with charcoal compared to ceramic heater was ∼45%. Hence rice husk is found as a potential candidate to use directly (without any processing) in FBG as an alternative renewable energy source from agricultural field. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. The Physiology of Bed Rest. Chapter 39

    Science.gov (United States)

    Fortney, Suzanne M.; Schneider, Victor S.; Greenleaf, John E.

    1996-01-01

    Prolonged rest in bed has been utilized by physicians and other health-care workers to immobilize and confine patients for rehabilitation and restoration of health since time immemorial. The sitting or horizontal position is sought by the body to relieve the strain of the upright or vertical postures, for example during syncopal situations, bone fractures, muscle injuries, fatigue, and probably also to reduce energy expenditure. Most health-care personnel are aware that adaptive responses occurring during bed rest proceed concomitantly with the healing process; signs and symptoms associated with the former should be differentiated from those of the latter. Not all illnesses and infirmities benefit from prolonged bed rest. Considerations in prescribing bed rest for patients-including duration, body position, mode and duration of exercise, light-dark cycles, temperature, and humidity-have not been investigated adequately. More recently, adaptive physiological responses have been measured in normal, healthy subjects in the horizontal or slightly head-down postures during prolonged bed rest as analogs for the adaptive responses of astronauts exposed to the microgravity environment of outer and bed-rest research.

  17. Effect of various drying bed on thermodynamic characteristics

    Directory of Open Access Journals (Sweden)

    Ali Motevali

    2017-09-01

    Full Text Available In this study thermodynamic parameter and energy consumption in drying of two plant dill and mint in three bed drying including fix, semi fix and fluid with using a hot air drying was investigated. Experimental was conducted in three bed drying including fix, semi fix and fluid and four levels temperature (30, 40, 50 and 60 °C. Maximum energy consumption in dill drying at 40 °C and fluid bed to be 16.41 MJ and minimum energy consumption at 30 °C and fix bed to be 2.77 MJ. Also minimum energy consumption in mint drying at 60 °C and fix bed to be 3.64 MJ and maximum energy consumption at 40 °C and fluid bed to be 28.65 MJ. The highest energy, drying and thermal efficiency for both mint and dill was achieved at 60 °C on the fixed bed, whereas the lowest efficiency was at 40 °C and on the fluidized bed. Also the highest power and specific heat consumption for both mint and dill was achieved at 40 °C on the fluid bed, whereas the lowest efficiency was at 30 °C and on the fluidized bed.

  18. Bed agglomeration in fluidized combustor fueled by wood and rice straw blends

    DEFF Research Database (Denmark)

    Thy, Peter; Jenkins, Brian; Williams, R.B.

    2010-01-01

    Abstract Petrographic techniques have been used to examine bed materials from fluidized bed combustion experiments that utilized wood and rice straw fuel blends. The experiments were conducted using a laboratory-scale combustor with mullite sand beds, firing temperatures of 840 to 1030 °C, and ru...

  19. Bed agglomeration in fluidized combustor fueled by wood and rice straw blends

    NARCIS (Netherlands)

    Thy, P.; Jenkins, B.M.; Williams, R.B.; Lesher, C.E.; Bakker, R.R.

    2010-01-01

    Petrographic techniques have been used to examine bed materials from fluidized bed combustion experiments that utilized wood and rice straw fuel blends. The experiments were conducted using a laboratory-scale combustor with mullite sand beds, firing temperatures of 840 to 1030 °C, and run durations

  20. The pebble-bed high-temperature reactor as a source of nuclear process heat. Vol. 3

    International Nuclear Information System (INIS)

    Kugeler, K.; Schulten, R.; Kugeler, M.; Niessen, H.F.; Roeth-Kamat, M.; Hohn, H.; Woike, O.; Germer, J.H.

    1974-08-01

    The characteristic questions concerning a process heat reactor with high helium outlet temperatures are dealt with in this volume like e.g. fuel element design, corrosion, and fission product release. Furthermore, some possibilities of the technical realization of the hot-gas ducting and intermediate heat exchangers are described. Important parameters for the design of the reactor such as core power density, helium inlet and outlet temperatures, helium pressure and fuel cycle burn-up and conversion and the effect of these on the primary circuit are investigated. The important question regarding which reactor vessel is to be chosen for nuclear process heat plants is discussed with the aid of the integrated and non-integrated concepts using prestressed concrete, cast iron and cast steel. Thereafter, considerations on the safety of the nuclear plant are given. Finally, mention is made of the availability of the nuclear plant and of the status of development of the HTR technology. (orig.) [de

  1. Operation of a steam hydro-gasifier in a fluidized bed reactor

    OpenAIRE

    Park, Chan Seung; Norbeck, Joseph N.

    2008-01-01

    Carbonaceous material, which can comprise municipal waste, biomass, wood, coal, or a natural or synthetic polymer, is converted to a stream of methane and carbon monoxide rich gas by heating the carbonaceous material in a fluidized bed reactor using hydrogen, as fluidizing medium, and using steam, under reducing conditions at a temperature and pressure sufficient to generate a stream of methane and carbon monoxide rich gas but at a temperature low enough and/or at a pressure high enough to en...

  2. Gas generation by co-gasification of biomass and coal in an autothermal fluidized bed gasifier

    International Nuclear Information System (INIS)

    Wang, Li-Qun; Chen, Zhao-Sheng

    2013-01-01

    In this study, thermochemical biomass and coal co-gasification were performed on an autothermal fluidized bed gasifier, with air and steam as oxidizing and gasifying media. The experiments were completed at reaction temperatures of 875 °C–975 °C, steam-to-biomass ratio of 1.2, and biomass-to-coal ratio of 4. This research aims to determine the effects of reaction temperature on gas composition, lower heating value (LHV), as well as energy and exergy efficiencies, of the product gas. Over the ranges of the test conditions used, the product gas LHV varies between 12 and 13.8 MJ/Nm 3 , and the exergy and energy efficiencies of the product gas are in the ranges of 50.7%–60.8% and 60.3%–85.1%, respectively. The results show that high reaction temperature leads to higher H 2 and CO contents, as well as higher exergy and energy efficiencies of the product gas. In addition, gas LHV decreases with temperature. The molar ratio of H 2 /CO is larger than 1 at temperatures above 925 °C. Our experimental analysis shows that co-gasification of biomass and coal in an autothermal fluidized bed gasifier for gas production is feasible and promising. -- Highlights: • An innovative steam co-gasification process for gas production was proposed. • Co-gasification of biomass and coal in an autothermal fluidized bed gasifier was tested. • High temperature favors H 2 production. • H 2 and CO contents increase, whereas CO 2 and CH 4 levels decrease with increase in T. • Exergy and energy efficiencies of gases increase with increase in T

  3. Wear oxidation of evaporator coils in fluidised bed captive power plants

    International Nuclear Information System (INIS)

    Ghosal, S.K.; De, P.K.

    2000-01-01

    Combustion of pulverised coal or gas to form steam in thermal power plants is a common practice. Corrosion of water-wall, superheater and reheater tubes is the typical problem faced in these power plants. Modification of process conditions, redesigning of equipment and selection of more corrosion resistant materials are few methods which have been tried to combat corrosion to a certain extent. Restricted heat transfer efficiency is another problem associated with these power plants. In order to bring upon improvements, fluidized bed combustors are being used in some advanced thermal power plants at present because of excellent combustion and heat transfer efficiencies. Even with low grade coals, higher combustion efficiency could be achieved in these combustors due to excellent gas/solid chemical reactivity at relatively low reaction temperatures. Further improvements in in-bed heat transfer and bed temperature uniformity have been possible with the use of sand in bed. However, erosion, corrosion and combined erosion/corrosion are some of the major modes of material degradation associated with these fluidized bed combustors using sand. Recently in a captive power unit using bubbling fluidized bed combustors containing sand, evaporator coils made of carbon steel were seen to be severely affected by erosion corrosion. The directional nature of metal removal from the studs, tube OD and ultimately the rupture of the thinned tube wall confirmed the above observation. Microstructural examinations showed loss of carbon at certain places including those near the leaked/punctured regions at the prevailing bed temperature of 850 deg C. This paper describes the detailed investigations carried out on wear oxidation phenomenon occurred in a captive thermal power plant using advanced bubbling fluidized bed combustors. (author)

  4. Heat-transfer characteristics of flowing and stationary particle-bed-type fusion-reactor blankets

    International Nuclear Information System (INIS)

    Nietert, R.E.

    1983-02-01

    The following five appendices are included: (1) physical properties of materials, (2) thermal entrance length Nusselt number variations, (3) stationary particle bed temperature variations, (4) falling bed experimental data and calculations, and (5) stationary bed experimental data and calculations

  5. Effects of water vapor pretreatment time and reaction temperature on CO(2) capture characteristics of a sodium-based solid sorbent in a bubbling fluidized-bed reactor.

    Science.gov (United States)

    Seo, Yongwon; Jo, Sung-Ho; Ryu, Chong Kul; Yi, Chang-Keun

    2007-10-01

    CO(2) capture from flue gas using a sodium-based solid sorbent was investigated in a bubbling fluidized-bed reactor. Carbonation and regeneration temperature on CO(2) removal was determined. The extent of the chemical reactivity after carbonation or regeneration was characterized via (13)C NMR. In addition, the physical properties of the sorbent such as pore size, pore volume, and surface area after carbonation or regeneration were measured by gas adsorption method (BET). With water vapor pretreatment, near complete CO(2) removal was initially achieved and maintained for about 1-2min at 50 degrees C with 2s gas residence time, while without proper water vapor pretreatment CO(2) removal abruptly decreased from the beginning. Carbonation was effective at the lower temperature over the 50-70 degrees C temperature range, while regeneration more effective at the higher temperature over the 135-300 degrees C temperature range. To maintain the initial 90% CO(2) removal, it would be necessary to keep the regeneration temperature higher than about 135 degrees C. The results obtained in this study can be used as basic data for designing and operating a large scale CO(2) capture process with two fluidized-bed reactors.

  6. High Temperature Air/Steam Gasification of Biomass Wastes - Stage 1. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Blasiak, Wlodzimierz; Szewczyk, Dariusz; Lucas, Carlos; Rafidi, Nabil; Abeyweera Ruchira; Jansson, Anna; Bjoerkman, Eva [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Materials Science and Engineering

    2003-05-01

    In Jan 2002 the Division of Energy and Furnace Technology started the project High Temperature Air an Steam Gasification (HTAG) of biomass wastes, following the approval made by Swedish Energy Agency. The research proved successful; with the fixed bed updraft gasifier coupled to the highly regenerative preheater equipment able to produce a fuel gas not only from wood pellets but also from wood chips, bark and charcoal with considerably reduced amount of tar. This report provides information on solid biomass conversion into fuel gas as a result of air and steam gasification process performed in a fixed bed updraft gasifier. The first chapter of the report presents the overall objectives and the specific objectives of the work. Chapter 2 summarizes state-of-the-art on the gasification field stating some technical differences between low and high temperature gasification processes. Description and schemes of the experimental test rig are provided in Chapter 3. The equipment used to perform measurements of different sort and that installed in the course of the work is described in Chapter 4. Chapter 5 describes the methodology of experiments conducted whose results were processed and evaluated with help of the scheme of equations presented in Chapter 6, called raw data evaluation. Results of relevant experiments are presented and discussed in Chapter 7. A summary discussion of the tar analysis is presented in Chapter 8. Chapter 9 summarizes the findings of the research work conducted and identifies future efforts to ensure the development of next stage. Final chapter provides a summary of conclusions and recommendations of the work. References are provided at the end of the report. Aimed to assist the understanding of the work done, tables and graphs of experiments conducted, irrespective to their quality, are presented in appendices.

  7. Recent improvements in the filtration of corrosion products in high temperature water and application to reactor circuits

    International Nuclear Information System (INIS)

    Darras, R.; Dolle, L.; Chenouard, J.; Laylavoix, F.

    1977-01-01

    The nature and physico-chemical behavior of corrosion products released by structural materials into high temperature water flowing in power reactor circuits have been investigated in test loops and different power plants. The results improve more particularly the knowledge of probable rate constants governing their disappearance through deposition of crud on the fuel cladding. It appears that a considerable limitation of radioactivity transportation in the primary circuit components of pressurized water reactors is in a general way only possible through extraction of the corrosion products by filtration at a rate adequate to minimize the amount of crud deposited in the core. This extraction rate has been estimated; its magnitude implicates a filtration operating on the high temperature water in the primary circuit which allows the necessary high flows. The application of magnetic and electromagnetic so as deep granular graphite bed filters has been studied. The results concerning efficiencies and limiting yields at high temperatures are given. Estimates concerning technological feasibility and corresponding investments are discussed

  8. Characteristics and utilisation of high-temperature (HTHP) filter dusts from pfb gasification of biomass

    Energy Technology Data Exchange (ETDEWEB)

    Ranta, J. [VTT Energy, Espoo (Finland)

    1996-12-31

    The aim of the study was to survey characteristics, utilisation and possible environmental impacts of solid wastes, i.e., in case of biomass, mainly high-temperature filter ash (HTHP) from pressurised fluidised-bed gasification (PFBG). The aim is to utilise solid wastes (slag, filter dust, additives) from biomass gasification instead of dumping. One alternative is recycling to the soil as liming material or fertiliser. It is expected that the ash recycled to forest soils changes the environment less than non-recycled ash. (orig.) 3 refs.

  9. Characteristics and utilisation of high-temperature (HTHP) filter dusts from pfb gasification of biomass

    Energy Technology Data Exchange (ETDEWEB)

    Ranta, J [VTT Energy, Espoo (Finland)

    1997-12-31

    The aim of the study was to survey characteristics, utilisation and possible environmental impacts of solid wastes, i.e., in case of biomass, mainly high-temperature filter ash (HTHP) from pressurised fluidised-bed gasification (PFBG). The aim is to utilise solid wastes (slag, filter dust, additives) from biomass gasification instead of dumping. One alternative is recycling to the soil as liming material or fertiliser. It is expected that the ash recycled to forest soils changes the environment less than non-recycled ash. (orig.) 3 refs.

  10. Accounting for porous structure in effective thermal conductivity calculations in a pebble bed reactor

    International Nuclear Information System (INIS)

    Antwerpen, W. van; Rousseau, P.G.; Toit, C.G. du

    2009-01-01

    A proper understanding of the mechanisms of heat transfer, flow and pressure drop through a packed bed of spheres is of utmost importance in the design of a high temperature pebble bed reactor. A thorough knowledge of the porous structure within the packed bed is important to any rigorous analysis of the transport phenomena, as all the heat and flow mechanisms are influenced by the porous structure. In this paper a new approach is proposed to simulate the effective thermal conductivity employing a combination of new and existing correlations for randomly packed beds. More attention is given to packing structure based on coordination number and contact angles, resulting in a more rigorous differentiation between the bulk and near-wall regions. The model accounts for solid conduction, gas conduction, contact area, surface roughness as well as radiation. (author)

  11. Optimization of MOX fuel cycles in pebble bed HTGR

    International Nuclear Information System (INIS)

    Wei Jinfeng; Li Fu; Sun Yuliang

    2013-01-01

    Compared with light water reactor (LWR), the pebble bed high temperature gas-cooled reactor (HTGR) is able to operate in a full mixed oxide (MOX) fuelled core without significant change to core structure design. Based on a reference design of 250 MW pebble bed HTGR, four MOX fuel cycles were designed and evaluated by VSOP program package, including the mixed Pu-U fuel pebbles and mixed loading of separate Pu-pebbles and U-pebbles. Some important physics features were investigated and compared for these four cycles, such as the effective multiplication factor of initial core, the pebble residence time, discharge burnup, and temperature coefficients. Preliminary results show that the overall performance of one case is superior to other equivalent MOX fuel cycles on condition that uranium fuel elements and plutonium fuel elements are separated as the different fuel pebbles and that the uranium fuel elements are irradiated longer in the core than the plutonium fuel elements, and the average discharge burnup of this case is also higher than others. (authors)

  12. In Developping a Bench-Scale Circulating Fluidized Bed Combustor to Burn High Ash Brazilian Coal-Dolomites Mixtures

    Science.gov (United States)

    Ramírez Behainne, Jhon Jairo; Hory, Rogério Ishikawa; Goldstein, Leonardo; Bernárdez Pécora, Araí Augusta

    This work considers some of the questions in burning high ash Brazilian coal-dolomite mixtures in a bench-scale circulating fluidized bed combustor (CFBC). Experimental tests were performed with the CE4500 coal from Santa Catarina State, in southern Brazil, with a Sauter mean diameter d p =43 μm. The coal particles were mixed with dolomite particles of d p = 111 μm and this fuel mixture was fed into the circulating fluidized reactor, previously loaded with quartz sand particles of d p =353 μm. This inert material was previously heated by the combustion of liquefied petroleum gas up to the ignition temperature of the fuel mixture. The CFBC unit has a 100mm internal diameter riser, 4.0m high, as well as a 62.8mm internal diameter downcomer. The loop has a cyclone, a sampling valve to collect particles and a 62.8mm internal diameter L-valve to recirculate the particles in the loop. A screw feeder with a rotation control system was used to feed the fuel mixture to the reactor. The operational conditions were monitored by pressure taps and thermocouples installed along the loop. A data acquisition system showed the main operational conditions to control. Experimental tests performed put in evidence the problems found during bed operation, with special attention to the solids feed device, to the L-valve operation, to particle size, solids inventory, fluidized gas velocity, fuel mixture and recirculated solids feeding positions.

  13. Bacillus cereus in free-stall bedding.

    Science.gov (United States)

    Magnusson, M; Svensson, B; Kolstrup, C; Christiansson, A

    2007-12-01

    To increase the understanding of how different factors affect the bacterial growth in deep sawdust beds for dairy cattle, the microbiological status of Bacillus cereus and coliforms in deep sawdust-bedded free stalls was investigated over two 14-d periods on one farm. High counts of B. cereus and coliforms were found in the entire beds. On average, 4.1 log(10) B. cereus spores, 5.5 log(10) B. cereus, and 6.7 log(10) coliforms per gram of bedding could be found in the upper layers of the sawdust likely to be in contact with the cows' udders. The highest counts of B. cereus spores, B. cereus, and coliforms were found in the bedding before fresh bedding was added, and the lowest immediately afterwards. Different factors of importance for the growth of B. cereus in the bedding material were explored in laboratory tests. These were found to be the type of bedding, pH, and the type and availability of nutrients. Alternative bedding material such as peat and mixtures of peat and sawdust inhibited the bacterial growth of B. cereus. The extent of growth of B. cereus in the sawdust was increased in a dose-dependent manner by the availability of feces. Urine added to different bedding material raised the pH and also led to bacterial growth of B. cereus in the peat. In sawdust, a dry matter content greater than 70% was needed to lower the water activity to 0.95, which is needed to inhibit the growth of B. cereus. In an attempt to reduce the bacterial growth of B. cereus and coliforms in deep sawdust beds on the farm, the effect of giving bedding daily or a full replacement of the beds was studied. The spore count of B. cereus in the back part of the free stalls before fresh bedding was added was 0.9 log units lower in stalls given daily bedding than in stalls given bedding twice weekly. No effect on coliform counts was found. Replacement of the entire sawdust bedding had an effect for a short period, but by 1 to 2 mo after replacement, the counts of B. cereus spores in the

  14. Highly efficient high temperature electrolysis

    DEFF Research Database (Denmark)

    Hauch, Anne; Ebbesen, Sune; Jensen, Søren Højgaard

    2008-01-01

    High temperature electrolysis of water and steam may provide an efficient, cost effective and environmentally friendly production of H-2 Using electricity produced from sustainable, non-fossil energy sources. To achieve cost competitive electrolysis cells that are both high performing i.e. minimum...... internal resistance of the cell, and long-term stable, it is critical to develop electrode materials that are optimal for steam electrolysis. In this article electrolysis cells for electrolysis of water or steam at temperatures above 200 degrees C for production of H-2 are reviewed. High temperature...... electrolysis is favourable from a thermodynamic point of view, because a part of the required energy can be supplied as thermal heat, and the activation barrier is lowered increasing the H-2 production rate. Only two types of cells operating at high temperature (above 200 degrees C) have been described...

  15. Reduction of SO sub 2 emission from a fluidized-bed under staged combustion by coarse limestone

    International Nuclear Information System (INIS)

    Khan, W.Z.; Gibbbs, B.M.

    1998-01-01

    A study was performed to investigate the effect of course limestone on the reduction of SO sub 2 emission from a fluidized-bed under staged combustion. The limestone of 1.2-2.5 mm size was premixed with fine coal of 1-3 mm size and fed under bed. The staging levels, bed height, and Ca/S ratio was fixed at 70:30, 30 cm and 3:1, respectively. A maximum of around 50% reduction in SO sub 2 emissions was achieved at both excess air of 20 and 40% and at 830 deg. C. bed temperature. The SO sub 2 emissions were very sensitive to bed temperature. The course limestone was found better in desulfurization efficiency at lower temperature than fine limestone. (author)

  16. Combustion of peanut and tamarind shells in a conical fluidized-bed combustor: a comparative study.

    Science.gov (United States)

    Kuprianov, Vladimir I; Arromdee, Porametr

    2013-07-01

    Combustion of peanut and tamarind shells was studied in the conical fluidized-bed combustor using alumina sand as the bed material to prevent bed agglomeration. Morphological, thermogravimetric and kinetic characteristics were investigated to compare thermal and combustion reactivity between the biomass fuels. The thermogravimetric kinetics of the biomasses was fitted using the Coats-Redfern method. Experimental tests on the combustor were performed at 60 and 45 kg/h fuel feed rates, with excess air within 20-80%. Temperature and gas concentrations were measured along radial and axial directions in the reactor and at stack. The axial temperature and gas concentration profiles inside the combustor exhibited sensible effects of fuel properties and operating conditions on combustion and emission performance. High (≈ 99%) combustion efficiency and acceptable levels of CO, CxHy, and NO emissions are achievable when firing peanut shells at excess air of about 40%, whereas 60% is more preferable for burning tamarind shells. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Parametric Investigation of Brayton Cycle for High Temperature Gas-Cooled Reactor

    International Nuclear Information System (INIS)

    Chang Oh

    2004-01-01

    The Idaho National Engineering and Environmental Laboratory (INEEL) is investigating a Brayton cycle efficiency improvement on a high temperature gas-cooled reactor (HTGR) as part of Generation-IV nuclear engineering research initiative. In this project, we are investigating helium Brayton cycles for the secondary side of an indirect energy conversion system. Ultimately we will investigate the improvement of the Brayton cycle using other fluids, such as supercritical carbon dioxide. Prior to the cycle improvement study, we established a number of baseline cases for the helium indirect Brayton cycle. These cases look at both single-shaft and multiple-shaft turbomachinery. The baseline cases are based on a 250 MW thermal pebble bed HTGR. The results from this study are applicable to other reactor concepts such as a very high temperature gas-cooled reactor (VHTR), fast gas-cooled reactor (FGR), supercritical water reactor (SWR), and others. In this study, we are using the HYSYS computer code for optimization of the helium Brayton cycle. Besides the HYSYS process optimization, we performed parametric study to see the effect of important parameters on the cycle efficiency. For these parametric calculations, we use a cycle efficiency model that was developed based on the Visual Basic computer language. As a part of this study we are currently investigated single-shaft vs. multiple shaft arrangement for cycle efficiency and comparison, which will be published in the next paper. The ultimate goal of this study is to use supercritical carbon dioxide for the HTGR power conversion loop in order to improve the cycle efficiency to values great than that of the helium Brayton cycle. This paper includes preliminary calculations of the steady state overall Brayton cycle efficiency based on the pebble bed reactor reference design (helium used as the working fluid) and compares those results with an initial calculation of a CO2 Brayton cycle

  18. Heat Transport upon River-Water Infiltration investigated by Fiber-Optic High-Resolution Temperature Profiling

    Science.gov (United States)

    Vogt, T.; Schirmer, M.; Cirpka, O. A.

    2010-12-01

    Infiltrating river water is of high relevance for drinking water supply by river bank filtration as well as for riparian groundwater ecology. Quantifying flow patterns and velocities, however, is hampered by temporal and spatial variations of exchange fluxes. In recent years, heat has become a popular natural tracer to estimate exchange rates between rivers and groundwater. Nevertheless, field investigations are often limited by insufficient sensors spacing or simplifying assumptions such as one-dimensional flow. Our interest lies in a detailed local survey of river water infiltration at a restored river section at the losing river Thur in northeast Switzerland. Here, we measured three high-resolution temperature profiles along an assumed flow path by means of distributed temperature sensing (DTS) using fiber optic cables wrapped around poles. Moreover, piezometers were equipped with standard temperature sensors for a comparison to the DTS data. Diurnal temperature oscillations were tracked in the river bed and the riparian groundwater and analyzed by means of dynamic harmonic regression and subsequent modeling of heat transport with sinusoidal boundary conditions to quantify seepage velocities and thermal diffusivities. Compared to the standard temperature sensors, the DTS data give a higher vertical resolution, facilitating the detection of process- and structure-dependent patterns of the spatiotemporal temperature field. This advantage overcompensates the scatter in the data due to instrument noise. In particular, we could demonstrate the impact of heat conduction through the unsaturated zone on the riparian groundwater by the high resolution temperature profiles.

  19. Energy extraction from wine dregs by self-sustained burning with fluidized-bed combustor

    Energy Technology Data Exchange (ETDEWEB)

    Leu, J.H. [Yu-Da Inst. of Business Technology, Taiwan (China). Dept. of Marketing and Logistics Management; Chung, Y.N.; Pan, T.S.; Chen, C.S. [Dayeh Univ., Taiwan (China). Dept. of Electrical Engineering

    2005-07-01

    Wine dregs typically have moisture contents of between 70 and 80 per cent, and the disposal of wine dregs in Taiwan is both costly and time-consuming. This paper described a method of extracting energy from wine dregs through the use of a pre-drying technique with a fluidized bed technology. A bubble-type fluidized bed combustor was used to combust high moisture Chinese Kaoliang wine lees. The system consisted of an incinerator, a feeding system, a heat recovery system, and an air pollution control system. Results of the experimental study showed that 92.3 per cent combustion was achieved for the wine lees at temperatures of 860 degrees C. Sulfur oxide (SO{sub x}) emissions and nitrogen oxide (NO{sub x}) emissions were negligible. Carbon monoxide (CO) emissions were suppressed to 92 ppm by modulating operating temperatures, axial temperature distributions, and primary and excess air. 3 refs., 3 tabs., 7 figs.

  20. Removal of hazardous gaseous pollutants from industrial flue gases by a novel multi-stage fluidized bed desulfurizer.

    Science.gov (United States)

    Mohanty, C R; Adapala, Sivaji; Meikap, B C

    2009-06-15

    Sulfur dioxide and other sulfur compounds are generated as primary pollutants from the major industries such as sulfuric acid plants, cupper smelters, catalytic cracking units, etc. and cause acid rain. To remove the SO(2) from waste flue gas a three-stage counter-current multi-stage fluidized bed adsorber was developed as desulfurization equipment and operated in continuous bubbling fluidization regime for the two-phase system. This paper represents the desulfurization of gas mixtures by chemical sorption of sulfur dioxide on porous granular calcium oxide particles in the reactor at ambient temperature. The advantages of the multi-stage fluidized bed reactor are of high mass transfer and high gas-solid residence time that can enhance the removal of acid gas at low temperature by dry method. Experiments were carried out in the bubbling fluidization regime supported by visual observation. The effects of the operating parameters such as sorbent (lime) flow rate, superficial gas velocity, and the weir height on SO(2) removal efficiency in the multistage fluidized bed are reported. The results have indicated that the removal efficiency of the sulfur dioxide was found to be 65% at high solid flow rate (2.0 kg/h) corresponding to lower gas velocity (0.265 m/s), wier height of 70 mm and SO(2) concentration of 500 ppm at room temperature.

  1. High temperature materials and mechanisms

    CERN Document Server

    2014-01-01

    The use of high-temperature materials in current and future applications, including silicone materials for handling hot foods and metal alloys for developing high-speed aircraft and spacecraft systems, has generated a growing interest in high-temperature technologies. High Temperature Materials and Mechanisms explores a broad range of issues related to high-temperature materials and mechanisms that operate in harsh conditions. While some applications involve the use of materials at high temperatures, others require materials processed at high temperatures for use at room temperature. High-temperature materials must also be resistant to related causes of damage, such as oxidation and corrosion, which are accelerated with increased temperatures. This book examines high-temperature materials and mechanisms from many angles. It covers the topics of processes, materials characterization methods, and the nondestructive evaluation and health monitoring of high-temperature materials and structures. It describes the ...

  2. Status of the in-pile test of HCPB pebble-bed assemblies in the HFR Petten

    Energy Technology Data Exchange (ETDEWEB)

    Laan, J.G. van der; Fokkens, J.H.; Hofmans, H.E.; Jong, M.; Magielsen, A.J.; Pijlgroms, B.J.; Stijkel, M.P. [NRG, Petten (Netherlands); Conrad, R. [JRC, Inst. for Energy, Petten (Netherlands); Malang, S.; Reimann, J. [FZK, Karlsruhe (Germany); Roux, N. [CEA Saclay (France)

    2002-06-01

    In the framework of developing the helium cooled pebble-bed (HCPB) blanket an irradiation test of pebble-bed assemblies is prepared at the HFR Petten. The test objective is to concentrate on the effect of neutron irradiation on the thermal-mechanical behaviour of the HCPB breeder pebble-bed at DEMO representative levels of temperature and defined thermal-mechanical loads. The basic test elements are EUROFER-97 cylinders with a horizontal bed of ceramic breeder pebbles sandwiched between two beryllium beds. The pebble beds are separated by EUROFER-97 steel plates. The heat flow is managed such as to have a radial temperature distribution in the ceramic breeder pebble-bed as flat as reasonably possible. The paper reports on the project status, and presents the results of pre-tests, material characteristics, the manufacturing of the pebble-bed assemblies, and the nuclear and thermo-mechanical loading parameters. (orig.)

  3. Dehydration/hydration of granular beds for thermal storage applications: a combined NMR and temperature study

    NARCIS (Netherlands)

    Donkers, P.A.J.; Pel, L.; Adan, O.C.G.

    For heat/cold storage systems a granular bed of salt hydrates is studied during dehydration/hydration. The water density in these beds are measured with help of NMR. Diffusion based dehydration of a granular bed of Na2SO4·10H2O is shown to be internally limited as larger grains dehydrate faster than

  4. High temperature refrigerator

    International Nuclear Information System (INIS)

    Steyert, W.A. Jr.

    1978-01-01

    A high temperature magnetic refrigerator is described which uses a Stirling-like cycle in which rotating magnetic working material is heated in zero field and adiabatically magnetized, cooled in high field, then adiabatically demagnetized. During this cycle the working material is in heat exchange with a pumped fluid which absorbs heat from a low temperature heat source and deposits heat in a high temperature reservoir. The magnetic refrigeration cycle operates at an efficiency 70% of Carnot

  5. Bioenergy originating from biomass combustion in a fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Crujeira, T.; Gulyurtlu, I.; Lopes, H.; Abelha, P.; Cabrita, I. [INETI/DEECA, Lisboa (Portugal)

    2008-07-01

    Bioenergy could significantly contribute to reducing and controlling greenhouse emissions (GHG) and to replace fossil fuels in large power plants. Although the use of biomass, originating from forests, could be beneficial, particularly in preventing fires, there are obstacles to achieve a sustainable supply chain of biomass in most European countries. In addition, there are also technical barriers as requirements of biomass combustion may differ from those of coal, which could mean significant retrofitting of existing installations. The combustion behaviour of different biomass materials were studied on a pilot fluidised bed combustor, equipped with two cyclones for particulate matter removal. The gaseous pollutants leaving the stack were sampled under isokinetic conditions for particulate matter, chlorine compounds, heavy metals and dioxins and furans (PCDD/F). The results obtained indicated that the combustion of these materials did not present any operational problem, although for temperatures above 800{sup o}C, bed agglomeration could be observed for all biomass materials studied. Most of the combustion of biomass, contrary to what is observed for coal, takes place in the riser where the temperature was as much as 150{sup o}C above that of the bed. Stable combustion conditions were achieved as well as high combustion efficiency. When compared with the emissions of bituminous coal, the most used fossil fuel, the emissions of CO and SO2 were found to be lower and NOx emissions were similar to those of coal. HCl and PCDD/F could be considerable with biomasses containing high chlorine levels, as in the case of straw. It was observed that the nature of ash could give rise serious operating problems.

  6. The pebble-bed high-temperature reactor as a source of nuclear process heat. Vol. 10

    International Nuclear Information System (INIS)

    Schulten, R.; Kugeler, K.; Kugeler, M.; Niessen, H.F.; Roeth-Kamat, M.; Woike, O.

    1974-08-01

    The necessary development steps, which have to be taken for the construction of a prototype plant for nuclear process heat, are enumerated. In particular, the work which is involved for the development of the nuclear steam-reforming technique, for the further development of the ball-shaped fuel elements at high gas outlet temperatures and for the reactor components, is described in detail. A brief survey of the needs of development of the IHX (intermediate heat exchanger) is given. An attempt is made to give overall time and cost estimates. (orig.) [de

  7. High temperature thermal storage for solar gas turbines using encapsulated phase change materials

    CSIR Research Space (South Africa)

    Klein, P

    2014-01-01

    Full Text Available in the near term. Sensible heat storage in packed beds involves a random packing of ceramic pebbles/particles in an insulated container. The temperature change of the solid during charging/discharging is used to store/release thermal energy. The primary... the packed bed due to vaporization and condensation effects. 2.3. Macro-encapsulation of PCM In the macro-encapsulation approach the PCM is retained within a hollow shell material. The shell can be preformed, filled with a molten PCM and sealed; or it can...

  8. Temperature uniformity mapping in a high pressure high temperature reactor using a temperature sensitive indicator

    NARCIS (Netherlands)

    Grauwet, T.; Plancken, van der I.; Vervoort, L.; Matser, A.M.; Hendrickx, M.; Loey, van A.

    2011-01-01

    Recently, the first prototype ovomucoid-based pressure–temperature–time indicator (pTTI) for high pressure high temperature (HPHT) processing was described. However, for temperature uniformity mapping of high pressure (HP) vessels under HPHT sterilization conditions, this prototype needs to be

  9. Evaluation of High-Temporal-Resolution Bedload Sensors for Tracking Channel Bed Movement and Transport Thresholds in Forested Mountain Headwater Catchments.

    Science.gov (United States)

    Martin, S.; Conklin, M. H.; Bales, R. C.

    2014-12-01

    High temporal resolution data is required to take channel bed movement data beyond time integrated changes between measurements where many of the subtleties of bedload movement patterns are often missed. This study used continuous bedload scour sensors (flexible, fluid-filled pans connected to a pressure transducer) to collect high temporal resolution, long term bedload movement data for 4 high elevation (1500-1800 m) Sierra Nevada headwater streams draining 1 km2 catchments and to investigate the physical channel characteristics under which they perform best. Data collected by the scour sensors were used to investigate the disturbance and recovery patterns of these streams, to relate the observed patterns to channel bed stability, and to evaluate whether the channel bed is acting as a sediment source, sink, or storage across various temporal scales. Finally, attempts are made to identify discharge thresholds for bed movement from scour sensor and discharge data and to compare these threshold values to observed changes in the channel bed. Bedload scour data, turbidity data, and stream discharge data were collected at 15 minute intervals for (WY 2011 to WY 2014), including both above average (2011) and below average (2012, 2013, 2014) water years. Bedload scour sensors were found to have a relatively high (60%) failure rate in these systems. In addition, they required in situ calibrations as the factory and laboratory calibrations did not translate well to the field deployments. Data from the working sensors, showed patterns of abrupt channel bed disturbance (scour and/or fill) on an hour to day temporal scale followed by gradual recovery on a day to month scale back to a stable equilibrium bed surface elevation. These observed patterns suggest the bed acts as a short term source or sink for sediment, but is roughly sediment neutral over longer time periods implying the changes in bed elevation are reflective of fluctuations in storage rather than a true source or

  10. Effect of temperature, hydraulic residence time and elevated PCO2 on acid neutralization within a pulsed limestone bed reactor

    Science.gov (United States)

    Watten, B.J.; Lee, P.C.; Sibrell, P.L.; Timmons, M.B.

    2007-01-01

    Limestone has potential for reducing reagent costs and sludge volume associated with treatment of acid mine drainage, but its use is restricted by slow dissolution rates and the deposition of Fe, Al and Mn-based hydrolysis products on reactive surfaces. We evaluated a pulsed limestone bed (PLB) reactor (15 L/min capacity) that uses a CO2 pretreatment step to accelerate dissolution and hydraulic shearing forces provided by intermittent fluidization to abrade and carry away surface scales. We established the effects of hydraulic residence time (HRT, 5.1-15.9 min), temperature (T, 12-22 ??C) and CO2 tension (PCO2, 34.5-206.8 kPa) on effluent quality when inlet acidity (Acy) was fixed at 440 mg/L (pH=2.48) with H2SO4. The PLB reactor neutralized all H+ acidity (N=80) while concurrently providing unusually high levels of effluent alkalinity (247-1028 mg/L as CaCO3) that allow for side-stream treatment with blending. Alkalinity (Alk) yields rose with increases in PCO2, HRT and settled bed height (BH, cm) and decreased with T following the relationship (R2=0.926; p<0.001): (Alk)non-filtered=-548.726+33.571??(PCO2)0.5+33.671??(HRT)+7.734??(BH)-5.197??(T). Numerical modeling showed CO2 feed requirements for a target Alk yield decrease with increases in HRT, T and the efficiency of off-gas (CO2) recycling. ?? 2007 Elsevier Ltd. All rights reserved.

  11. Lignite air-steam gasification in the fluidized bed of iron-containing slag catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, B.N.; Shchipko, M.L.; Golovin, Yu. [Inst. of Chemistry of Natural Organic Materials, Academgorodok, Krasnoyarsk (Russian Federation)

    1995-12-01

    The influence of fluidized bed of iron-containing slag particles on air-steam gasification of powdered Kansk-Achinsk lignite in entrained flow was studied in pilot installation with productivity about 60 kg per hour. Slag of Martin process and boiler slag were used as catalytic active materials until their complete mechanical attrition. Two following methods of catalytic gasification of lignite were compared: the partial gasification in stationary fluidized bed of slag particles with degree of fuel conversion 40-70% and complete gasification in circulating bed of slag particles. In the first case only the most reactive part of fuel is gasified with the simultaneously formation of porous carbon residue with good sorption ability. It was found the catalytic fluidized bed improves heat transfer from combustion to reduction zone of gas-generator and increases the rate of fuel conversion at the temperature range 900-1000{degrees}C. At these temperatures the degree of conversion is depended considerably on the duration time of fuel particles in the catalytic fluidized bed. The influence of catalytic fluidized bed height and velocity of reaction mixture on the temperature profiles in the gas-generator was studied. The optimal relationship was found between the fluidized bed height and velocity of flow which makes possible to produce the gas with higher calorific value at maximum degree of fuel conversion.

  12. Using multiple bed load measurements: Toward the identification of bed dilation and contraction in gravel-bed rivers

    Science.gov (United States)

    Marquis, G. A.; Roy, A. G.

    2012-02-01

    This study examines bed load transport processes in a small gravel-bed river (Béard Creek, Québec) using three complementary methods: bed elevation changes between successive floods, bed activity surveys using tags inserted into the bed, and bed load transport rates from bed load traps. The analysis of 20 flood events capable of mobilizing bed material led to the identification of divergent results among the methods. In particular, bed elevation changes were not consistent with the bed activity surveys. In many cases, bed elevation changes were significant (1 to 2 times the D50) even if the bed surface had not been activated during the flood, leading to the identification of processes of bed dilation and contraction that occurred over 10% to 40% of the bed surface. These dynamics of the river bed prevent accurate derivation of bed load transport rates from topographic changes, especially for low magnitude floods. This paper discusses the mechanisms that could explain the dilation and contraction of particles within the bed and their implications in fluvial dynamics. Bed contraction seems to be the result of the winnowing of the fine sediments under very low gravel transport. Bed dilation seems to occur on patches of the bed at the threshold of motion where various processes such as fine sediment infiltration lead to the maintenance of a larger sediment framework volume. Both processes are also influenced by flood history and the initial local bed state and in turn may have a significant impact on sediment transport and morphological changes in gravel-bed rivers.

  13. Method for the combustion of a gas, in fixed bed, with an oxidized solid and associated installation

    OpenAIRE

    Abanades García, Juan Carlos; Fernández García, José Ramón

    2014-01-01

    [EN] The present invention pertains to the field of the generation of energy from combustible gases, incorporating the capture of carbon dioxide for use or permanent storage and, specifically relates to cyclical methods of gas combustion with oxidized solids (chemical looping processes), in fixed bed, for solving the problem of controlling temperature in the combustion of gaseous fuels in fixed beds of metal oxides operating at high pressures, and also the associated installation.

  14. Tile Effect of P reconsolidation on the Thermal Conductivity of Particulate Beds

    International Nuclear Information System (INIS)

    Weidenfeld, G.

    2001-09-01

    The thermal conductivity of particulate beds is an important property for many industrial handling processes as well as storage of particulate materials. This property can be affected by a few conditions, such as, temperature and external axial pressure. In the first part of this work, a background for the thermal conductivity of particulate bed is given. This includes a review of experimental and theoretical studies on the thermal conductivity of particulate beds. It is also a reviewed parameters that influence the thermal conductivity of particulate beds, such as, temperature. This study presents a new experimental apparatus that enables to measure the thermal conductivity in steady-state while the particulate bed is under axial consolidation stresses. The experimental apparatus was analyzed and characterized experimentally and by numerical simulations. An analytical model, that predicts the thermal conductivity of particulate beds under axial consolidation stress was developed. The model results were compared to the experimental results for 0.5 and 1 mm steel spheres and showed a good agreement. The experimental results showed a significant effect of the compression state on the bed and its pre-consolidation for 0.5 and 1 mm steel spheres. The effect of the compression state on the bed and its pre-consolidation was even more significant for limestone powder

  15. Diesel NO{sub x} reduction by plasma-regenerated absorbent beds

    Science.gov (United States)

    Wallman, P.H.; Vogtlin, G.E.

    1998-02-10

    Reduction of NO{sub x} from diesel engine exhaust by use of plasma-regenerated absorbent beds is described. This involves a process for the reduction of NO{sub x} and particulates from diesel engines by first absorbing NO{sub x} onto a solid absorbent bed that simultaneously acts as a physical trap for the particulate matter, and second regenerating said solid absorbent by pulsed plasma decomposition of absorbed NO{sub x} followed by air oxidation of trapped particulate matter. The absorbent bed may utilize all metal oxides, but the capacity and the kinetics of absorption and desorption vary between different materials, and thus the composition of the absorbent bed is preferably a material which enables the combination of NO{sub x} absorption capability with catalytic activity for oxidation of hydrocarbons. Thus, naturally occurring or synthetically prepared materials may be utilized, particularly those having NO{sub x} absorption properties up to temperatures around 400 C which is in the area of diesel engine exhaust temperatures. 1 fig.

  16. Axial concentration profiles and N{sub 2}O flue gas in a pilot scale bubbling fluidised bed coal combustor

    Energy Technology Data Exchange (ETDEWEB)

    Tarelho, L.A.C.; Matos, M.A.A.; Pereira, F.J.M.A. [Environment and Planning Department, University of Aveiro, 3810-193 Aveiro (Portugal)

    2005-05-15

    Atmospheric Bubbling Fluidised Bed Coal Combustion (ABFBCC) of a bituminous coal and anthracite with particle diameters in the range 500-4000 {mu}m was investigated in a pilot-plant facility (circular section with 0.25 m internal diameter and 3 m height). The experiments were conducted at steady-state conditions using three excess air levels (10%, 25% and 50%) and bed temperatures in the 750-900 {sup o}C range. Combustion air was staged, with primary air accounting for 100%, 80% and 60% of total combustion air. For both types of coal, virtually no N{sub 2}O was found in significant amounts inside the bed. However, just above the bed-freeboard interface, the N{sub 2}O concentration increased monotonically along the freeboard and towards the exit flue. The N{sub 2}O concentrations in the reactor ranged between 0-90 ppm during bituminous coal combustion and 0-30 ppm for anthracite. For both coals, the lowest values occurred at the higher bed temperature (900 {sup o}C) with low excess air (10%) and high air staging (60% primary air), whereas the highest occurred at the lower bed temperature (750 {sup o}C for bituminous, 825 {sup o}C for anthracite) with high excess air (50%) and single stage combustion. Most of the observed results could be qualitatively interpreted in terms of a set of homogeneous and heterogeneous reactions, where catalytic surfaces (such as char, sand and coal ash) can play an important role in the formation and destruction of N{sub 2}O and its precursors (such as HCN, NH{sub 3} and HCNO) by free radicals (O, H, OH) and reducing species (H{sub 2}, CO, HCs)

  17. Debris bed cooling following an HCDA in a fast reactor. Final report

    International Nuclear Information System (INIS)

    Abdel-Khalik, S.I.

    1983-01-01

    Natural convection within simulated core debris beds has been experimentally and theoretically investigated. The effect of heating method on bed behavior has been found to be important. For directly-heated beds, variations of the downward and upward power fraction and Nusselt numbers with bed loading, power density, particle size, overlying fluid layer height and top surface boundary condition have been determined. Generalized correlations for the upward and downward Nusselt numbers as functions of the internal Rayleigh number have been obtained. Particle tracing techniques have been used to visualize the flow patterns within the bed and overlying fluid layer. The temperature distributions within the bed and overlying fluid layer have also been measured. The experimental data have been compared with COMMIX-lA predictions. Poor agreement has been obtained for both the integral quantities, i.e. downward and upward power fractions and Nusselt numbers, as well as the steady state velocity and temperature distributions. The code does not correctly predict either the magnitude or even the trend of the data

  18. Catalyzed deuterium-deuterium and deuterium-tritium fusion blankets for high temperature process heat production

    International Nuclear Information System (INIS)

    Ragheb, M.M.H.; Salimi, B.

    1982-01-01

    Tritiumless blanket designs, associated with a catalyzed deuterium-deuterium (D-D) fusion cycle and using a single high temperature solid pebble or falling bed zone, for process heat production, are proposed. Neutronics and photonics calculations, using the Monte Carlo method, show that an about 90% heat deposition fraction is possible in the high temperature zone, compared to a 30 to 40% fraction if a deuterium-tritium (D-T) fusion cycle is used with separate breeding and heat deposition zones. Such a design is intended primarily for synthetic fuels manufacture through hydrogen production using high temperature water electrolysis. A system analysis involving plant energy balances and accounting for the different fusion energy partitions into neutrons and charged particles showed that plasma amplification factors in the range of 2 are needed. In terms of maximization of process heat and electricity production, and the maximization of the ratio of high temperature process heat to electricity, the catalyzed D-D system outperforms the D-T one by about 20%. The concept is thought competitive to the lithium boiler concept for such applications, with the added potential advantages of lower tritium inventories in the plasma, reduced lithium pumping (in the case of magnetic confinement) and safety problems, less radiation damage at the first wall, and minimized risks of radioactive product contamination by tritium

  19. Is high-resolution inverse characterization of heterogeneous river bed hydraulic conductivities needed and possible?

    Directory of Open Access Journals (Sweden)

    W. Kurtz

    2013-10-01

    Full Text Available River–aquifer exchange fluxes influence local and regional water balances and affect groundwater and river water quality and quantity. Unfortunately, river–aquifer exchange fluxes tend to be strongly spatially variable, and it is an open research question to which degree river bed heterogeneity has to be represented in a model in order to achieve reliable estimates of river–aquifer exchange fluxes. This research question is addressed in this paper with the help of synthetic simulation experiments, which mimic the Limmat aquifer in Zurich (Switzerland, where river–aquifer exchange fluxes and groundwater management activities play an important role. The solution of the unsaturated–saturated subsurface hydrological flow problem including river–aquifer interaction is calculated for ten different synthetic realities where the strongly heterogeneous river bed hydraulic conductivities (L are perfectly known. Hydraulic head data (100 in the default scenario are sampled from the synthetic realities. In subsequent data assimilation experiments, where L is unknown now, the hydraulic head data are used as conditioning information, with the help of the ensemble Kalman filter (EnKF. For each of the ten synthetic realities, four different ensembles of L are tested in the experiments with EnKF; one ensemble estimates high-resolution L fields with different L values for each element, and the other three ensembles estimate effective L values for 5, 3 or 2 zones. The calibration of higher-resolution L fields (i.e. fully heterogeneous or 5 zones gives better results than the calibration of L for only 3 or 2 zones in terms of reproduction of states, stream–aquifer exchange fluxes and parameters. Effective L for a limited number of zones cannot always reproduce the true states and fluxes well and results in biased estimates of net exchange fluxes between aquifer and stream. Also in case only 10 head data are used for conditioning, the high

  20. USING A MICRO-UAV FOR ULTRA-HIGH RESOLUTION MULTI-SENSOR OBSERVATIONS OF ANTARCTIC MOSS BEDS

    Directory of Open Access Journals (Sweden)

    A. Lucieer

    2012-07-01

    Full Text Available This study is the first to use an Unmanned Aerial Vehicle (UAV for mapping moss beds in Antarctica. Mosses can be used as indicators for the regional effects of climate change. Mapping and monitoring their extent and health is therefore important. UAV aerial photography provides ultra-high resolution spatial data for this purpose. We developed a technique to extract an extremely dense 3D point cloud from overlapping UAV aerial photography based on structure from motion (SfM algorithms. The combination of SfM and patch-based multi-view stereo image vision algorithms resulted in a 2 cm resolution digital terrain model (DTM. This detailed topographic information combined with vegetation indices derived from a 6-band multispectral sensor enabled the assessment of moss bed health. This novel UAV system has allowed us to map different environmental characteristics of the moss beds at ultra-high resolution providing us with a better understanding of these fragile Antarctic ecosystems. The paper provides details on the different UAV instruments and the image processing framework resulting in DEMs, vegetation indices, and terrain derivatives.

  1. A mathematical model for supplying air-cooling for a building using a packed bed

    Energy Technology Data Exchange (ETDEWEB)

    Marewo, G.T. [Zimbabwe Univ., Mathematics Dept., Harare (Zimbabwe); Henwood, D.J. [School of Computing and Mathematical Sciences, Brighton (United Kingdom)

    2006-01-15

    The cooling system at the Harare International School uses a packed bed system for storing the coldness of the night-time to be used later for day-time air-conditioning. A two-phase mathematical model is described for the packed bed which includes heat dispersion in the fluid, and heat loss to the environment. This is in contrast to other studies, where at least one of these terms is neglected to simplify the mathematical model. A numerical method for obtaining a solution is proposed and implemented. Using measured inlet temperatures, the measured and predicted outlet temperatures of the bed show good trend agreement. The differences in detail are examined through sensitivity analyses for both the heat convection transfer and air velocity. It is apparent that adjusting these parameters can increase the agreement between the predicted and measured data. A parametric study for heat storage with various materials and bed sizes is given, which indicates how the code may be used as a tool for improving design and operational parameters. Practical application: A mathematical model of a packed bed is described; the bed is made up of fluid flowing over solid material with heat interchange between the two. The solid material is idealized as spheres and the fluid temperature is assumed uniform in a cross-section of the bed. The model includes heat interchange between the bed and its surrounding environment and allows for time varying fluid velocity. The input data is the inlet temperature to the bed, which may be measured. The comparison with measured data may be helpful to anyone attempting to develop and test a similar model. The sensitivity tests give an understanding of the significance of some of the parameters involved. The Appendix gives a mathematical statement of the problem and an outline of an approach to developing computer code for a numerical solution. (Author)

  2. Conceptual design of a fluidized bed nuclear reactor : Statics, dynamics and safety-related aspects

    NARCIS (Netherlands)

    Agung, A.

    2007-01-01

    In this thesis a conceptual design of an innovative high temperature reactor based on the fluidization principle (FLUBER) is proposed. The reactor should satisfy the following requirements: (a) modular and low power, (b)) large shutdown margin, (c) able to produce power when the bed of particles

  3. A comparative study on the effective thermal conductivity of a single size beryllium pebble bed

    International Nuclear Information System (INIS)

    Abou-Sena, A.; Ying, A.; Abdou, M.

    2004-01-01

    Solid breeder blankets generally use beryllium-helium pebble beds to ensure sufficient tritium breeding. The data of the effective thermal conductivity, k eff , of beryllium pebble beds is important to the design of fusion blankets. It serves as a database for benchmarking the models of pebble beds. The objective of this paper is to review and compare the available data (obtained by several studies) of the effective thermal conductivity of beryllium pebble beds in order to address the current status of these data. Two comparisons are presented: one for the data of k eff versus bed mean temperature and the second one for the data of k eff versus external applied pressures. The data (k eff versus bed temperature) reported by Enoeda et al., Dalle Donne et al., and UCLA, have a similar particle size and packing fraction. Despite their similarity, the standard deviation values of their data are around 32%. Also, the data of the effective thermal conductivity as a function of mechanical pressure have standard deviation values of ∼50%. From the presented comparisons, significant discrepancies among the available data of k eff of the beryllium pebble beds were observed. These discrepancies may be attributed to the apparent differences among available studies, such as experiment technique, packing fraction, particle characteristics, bed dimensions, and temperature range and gradient across the bed. (author)

  4. Nuclear graphite for high temperature reactors

    International Nuclear Information System (INIS)

    Marsden, B.J.

    2001-01-01

    The cores and reflectors in modern High Temperature Gas Cooled Reactors (HTRs) are constructed from graphite components. There are two main designs; the Pebble Bed design and the Prism design. In both of these designs the graphite not only acts as a moderator, but is also a major structural component that may provide channels for the fuel and coolant gas, channels for control and safety shut off devices and provide thermal and neutron shielding. In addition, graphite components may act as a heat sink or conduction path during reactor trips and transients. During reactor operation, many of the graphite component physical properties are significantly changed by irradiation. These changes lead to the generation of significant internal shrinkage stresses and thermal shut down stresses that could lead to component failure. In addition, if the graphite is irradiated to a very high irradiation dose, irradiation swelling can lead to a rapid reduction in modulus and strength, making the component friable.The irradiation behaviour of graphite is strongly dependent on its virgin microstructure, which is determined by the manufacturing route. Nevertheless, there are available, irradiation data on many obsolete graphites of known microstructures. There is also a well-developed physical understanding of the process of irradiation damage in graphite. This paper proposes a specification for graphite suitable for modern HTRs. (author)

  5. Oxidation of ethene in a wall-cooled packed-bed reactor

    NARCIS (Netherlands)

    Schouten, E.P.S.; Borman, P.C.; Westerterp, K.R.

    1994-01-01

    The selective oxidation of ethene over a silver on α-alumina catalyst was studied in a pilot plant with a wall-cooled tubular packed bed reactor. Gas and solid temperatures in the catalyst bed were measured at different axial and radial positions as well as concentrations at different axial

  6. Malaria in pregnant women in an area with sustained high coverage of insecticide-treated bed nets

    Directory of Open Access Journals (Sweden)

    Mshinda Hassan

    2008-07-01

    Full Text Available Abstract Background Since 2000, the World Health Organization has recommended a package of interventions to prevent malaria during pregnancy and its sequelae that includes the promotion of insecticide-treated bed nets (ITNs, intermittent preventive treatment in pregnancy (IPTp, and effective case management of malarial illness. It is recommended that pregnant women in malaria-endemic areas receive at least two doses of sulphadoxine-pyrimethamine in the second and third trimesters of pregnancy. This study assessed the prevalence of placental malaria at delivery in women during 1st or 2nd pregnancy, who did not receive intermittent preventive treatment for malaria (IPTp in a malaria-endemic area with high bed net coverage. Methods A hospital-based cross-sectional study was done in Ifakara, Tanzania, where bed net coverage is high. Primi- and secundigravid women, who presented to the labour ward and who reported not using IPTp were included in the study. Self-report data were collected by questionnaire; whereas neonatal birth weight and placenta parasitaemia were measured directly at the time of delivery. Results Overall, 413 pregnant women were enrolled of which 91% reported to have slept under a bed net at home the previous night, 43% reported history of fever and 62% were primigravid. Malaria parasites were detected in 8% of the placenta samples; the geometric mean (95%CI placental parasite density was 3,457 (1,060–11,271 parasites/μl in primigravid women and 2,178 (881–5,383 parasites/μl in secundigravid women. Fifteen percent of newborns weighed Conclusion The observed incidence of LBW and prevalence of placental parasitaemia at delivery suggests that malaria remains a problem in pregnancy in this area with high bed net coverage when eligible women do not receive IPTp. Delivery of IPTp should be emphasized at all levels of implementation to achieve maximum community coverage.

  7. Dynamics of a small direct cycle pebble bed HTR

    International Nuclear Information System (INIS)

    Verkerk, E.C.; Heek, A.I. van

    2001-01-01

    The Dutch market for combined generation of heat and power identifies a unit size of 40 MW thermal for the conceptual design of a nuclear cogeneration plant. The ACACIA system provides 14 MW(e) electricity combined with 17 t/h of high temperature steam (220 deg. C, 10 bar) with a pebble bed high temperature reactor directly coupled with a helium compressor and a helium turbine. To come to quantitative statements about the ACACIA transient behaviour, a calculational coupling between the high temperature reactor core analysis code package Panthermix (Panther-Thermix/Direkt) and the thermal hydraulic code RELAP5 for the energy conversion system has been made. This paper will present the analysis of safety related transients. The usual incident scenarios Loss of Coolant Incident (LOCI) and Loss of Flow Incident (LOFI) have been analysed. Besides, also a search for the real maximum fuel temperature (inside a fuel pebble anywhere in the core) has been made. It appears that the maximum fuel temperatures are not reached during a LOFI or LOCI with a halted mass flow rate, but for situations with a small mass flow rate, 1-0.5%. As such, a LOFI or LOCI does not represent the worst-case scenario in terms of maximal fuel temperature. (author)

  8. Application of CaO-Based Bed Material for Dual Fluidized Bed Steam Biomass Gasification

    Science.gov (United States)

    Koppatz, S.; Pfeifer, C.; Kreuzeder, A.; Soukup, G.; Hofbauer, H.

    Gasification of biomass is a suitable option for decentralized energy supply based on renewable sources in the range of up to 50 MW fuel input. The paper presents the dual fluidized bed (DFB) steam gasification process, which is applied to generate high quality and nitrogen-free product gas. Essential part of the DFB process is the bed material used in the fluidized reactors, which has significant impact on the product gas quality. By the use of catalytically active bed materials the performance of the overall process is increased, since the bed material favors reactions of the steam gasification. In particular, tar reforming reactions are favored. Within the paper, the pilot plant based on the DFB process with 100kW fuel input at Vienna University of Technology, Austria is presented. Actual investigations with focus on CaO-based bed materials (limestone) as well as with natural olivine as bed material were carried out at the pilot plant. The application of CaO-based bed material shows mainly decreased tar content in the product gas in contrast to experiments with olivine as bed material. The paper presents the results of steam gasification experiments with limestone and olivine, whereby the product gas composition as well as the tar content and the tar composition are outlined.

  9. Simulant - water experiments to characterize the debris bed formed in severe core melt accidents

    International Nuclear Information System (INIS)

    Mathai, Amala M.; Anandan, J.; Sharma, Anil Kumar; Murthy, S.S.; Malarvizhi, B.; Lydia, G.; Das, Sanjay Kumar; Nashine, B.K.; Selvaraj, P.

    2015-01-01

    Molten Fuel Coolant Interaction (WO) and debris bed configuration on the core catcher plate assumes importance in assessing the Post Accident Heat Removal (PARR) of a heat generating debris bed. The key factors affecting the coolability of the debris bed are the bed porosity, morphology of the fragmented particles, degree of spreading/heaping of the debris on the core catcher and the fraction of lump formed. Experiments are conducted to understand the fragmentation kinetics and subsequent debris bed formation of molten woods metal in water at interface temperatures near the spontaneous nucleation temperature of water. Morphology of the debris particles is investigated to understand the fragmentation mechanisms involved. The spreading behavior of the debris on the catcher plate and the particle size distribution are presented for 5 kg and 10 kg melt inventories. Porosity of the undisturbed bed on the catcher plate is evaluated using a LASER sensor technique. (author)

  10. Thermal-hydraulic and characteristic models for packed debris beds

    International Nuclear Information System (INIS)

    Mueller, G.E.; Sozer, A.

    1986-12-01

    APRIL is a mechanistic core-wide meltdown and debris relocation computer code for Boiling Water Reactor (BWR) severe accident analyses. The capabilities of the code continue to be increased by the improvement of existing models. This report contains information on theory and models for degraded core packed debris beds. The models, when incorporated into APRIL, will provide new and improved capabilities in predicting BWR debris bed coolability characteristics. These models will allow for a more mechanistic treatment in calculating temperatures in the fluid and solid phases in the debris bed, in determining debris bed dryout, debris bed quenching from either top-flooding or bottom-flooding, single and two-phase pressure drops across the debris bed, debris bed porosity, and in finding the minimum fluidization mass velocity. The inclusion of these models in a debris bed computer module will permit a more accurate prediction of the coolability characteristics of the debris bed and therefore reduce some of the uncertainties in assessing the severe accident characteristics for BWR application. Some of the debris bed theoretical models have been used to develop a FORTRAN 77 subroutine module called DEBRIS. DEBRIS is a driver program that calls other subroutines to analyze the thermal characteristics of a packed debris bed. Fortran 77 listings of each subroutine are provided in the appendix

  11. Particle fuel bed tests

    International Nuclear Information System (INIS)

    Horn, F.L.; Powell, J.R.; Savino, J.M.

    1985-01-01

    Gas-cooled reactors, using packed beds of small diameter coated fuel particles have been proposed for compact, high-power systems. The particulate fuel used in the tests was 800 microns in diameter, consisting of a thoria kernel coated with 200 microns of pyrocarbon. Typically, the bed of fuel particles was contained in a ceramic cylinder with porous metallic frits at each end. A dc voltage was applied to the metallic frits and the resulting electric current heated the bed. Heat was removed by passing coolant (helium or hydrogen) through the bed. Candidate frit materials, rhenium, nickel, zirconium carbide, and zirconium oxide were unaffected, while tungsten and tungsten-rhenium lost weight and strength. Zirconium-carbide particles were tested at 2000 K in H 2 for 12 hours with no visible reaction or weight loss

  12. Catalytic steam gasification of biomass in fluidized bed at low temperature: Conversion from livestock manure compost to hydrogen-rich syngas

    International Nuclear Information System (INIS)

    Xiao, Xianbin; Le, Duc Dung; Li, Liuyun; Meng, Xianliang; Cao, Jingpei; Morishita, Kayoko; Takarada, Takayuki

    2010-01-01

    Utilizing large amounts of animal waste as a source of renewable energy has the potential to reduce its disposal problems and associated pollution issues. Gasification characteristics of the manure compost make it possible for low temperature gasification. In this paper, an energy efficient approach to hydrogen-rich syngas from manure compost is represented at relatively low temperature, around 600 o C, in a continuous-feeding fluidized bed reactor. The effects of catalyst performance, reactor temperature, steam, and reaction type on gas yield, gas composition, and carbon conversion efficiency are discussed. The Ni-Al 2 O 3 catalyst simultaneously promotes tar cracking and steam reforming. Higher temperature contributes to higher gas yield and carbon conversion. The steam introduction increases hydrogen yield, by steam reforming and water-gas shift reaction. Two-stage gasification is also tried, showing the advantage of better catalyst utilization and enhancing the catalytic reactions to some extent.

  13. Effects of reduction temperature to Ni and Fe content and the morphology of agglomerate of reduced laterite limonitic nickel ore by coal-bed method

    Science.gov (United States)

    Abdul, Fakhreza; Pintowantoro, Sungging; Kawigraha, Adji; Nursidiq, Ahlidin

    2018-04-01

    As the current drop of nickel sulfide ore on earth, the attention to nickel laterite ore processing was inscreased in order to fulfill the future nickel demand needs. This research aims to optimized the process of nickel laterite ore extraction using coal bed method. This research was conducted by reducing low grade nickel laterite ore (limonitic) with nickel content of 1.25 %. The reduction process was carried out using CO gas which formed by the reaction of coal and dolomite. The Briquette of nickel ore, coal, Na2SO4 mixtures incorporated in the crucible with bed, then reduced for 6 hours at the temperature of 1200 °C. 1400 °C, and 1400 °C. The result of the research shown that the highest increase of Ni content and Ni recovery value was in the reduction temperature of 1400 °C with the increase of 3.44 %, and the recovery value of Ni equal to 86.75 %. While the highest increase of Fe content and Fe recovery value, respectively, was in the reduction temperature of 1300 °C with the increase of 22.67 % and 1200 °C with Fe recovery value of 89.41 %.

  14. Atmospheric Fluidized Bed Combustion testing of North Dakota lignite

    Energy Technology Data Exchange (ETDEWEB)

    Goblirsch, G; Vander Molen, R H; Wilson, K; Hajicek, D

    1980-05-01

    The sulfur retention by the inherent alkali, and added limestone sorbent, perform about the same and are reasonably predictable within a range of about +-10% retention by application of alkali to sulfur ratio. Temperature has a substantial effect on the retention of sulfur by the inherent alkali or limestone. The temperature effect is not yet fully understood but it appears to be different for different coals and operational conditions. The emission of SO/sub 2/ from the fluid bed burning the Beulah lignite sample used for these tests can be controlled to meet or better the current emission standards. The injection of limestone to an alkali-to-sulfur molar ratio of 1.5 to 1, should lower the SO/sub 2/ emissions below the current requirement of 0.6 lb SO/sub 2//10/sup 6/ Btu to 0.4 lb SO/sub 2//10/sup 6/ Btu, a safe 33% below the standard. Agglomeration of bed material, and consequent loss of fluidization quality can be a problem when burning high sodium lignite in a silica bed. There appears, however, to be several ways of controlling the problem including the injection of calcium compounds, and careful control of operating conditions. The heat transfer coefficients measured in the CPC and GFETC tests are comparable to data obtained by other researchers, and agree reasonably well with empirical conditions. The NO/sub x/ emissions measured in all of the tests on Beulah lignite are below the current New Source Performance Standard of 0.5 lb NO/sub 2//10/sup 6/ Btu input. Combustion efficiencies for the Beulah lignite are generally quite high when ash recycle is being used. Efficiencies in the range of 98% to 99%+ have been measured in all tests using this fuel.

  15. Long-term, high frequency in situ measurements of intertidal mussel bed temperatures using biomimetic sensors

    Science.gov (United States)

    Helmuth, Brian; Choi, Francis; Matzelle, Allison; Torossian, Jessica L.; Morello, Scott L.; Mislan, K.A.S.; Yamane, Lauren; Strickland, Denise; Szathmary, P. Lauren; Gilman, Sarah E.; Tockstein, Alyson; Hilbish, Thomas J.; Burrows, Michael T.; Power, Anne Marie; Gosling, Elizabeth; Mieszkowska, Nova; Harley, Christopher D.G.; Nishizaki, Michael; Carrington, Emily; Menge, Bruce; Petes, Laura; Foley, Melissa M.; Johnson, Angela; Poole, Megan; Noble, Mae M.; Richmond, Erin L.; Robart, Matt; Robinson, Jonathan; Sapp, Jerod; Sones, Jackie; Broitman, Bernardo R.; Denny, Mark W.; Mach, Katharine J.; Miller, Luke P.; O’Donnell, Michael; Ross, Philip; Hofmann, Gretchen E.; Zippay, Mackenzie; Blanchette, Carol; Macfarlan, J.A.; Carpizo-Ituarte, Eugenio; Ruttenberg, Benjamin; Peña Mejía, Carlos E.; McQuaid, Christopher D.; Lathlean, Justin; Monaco, Cristián J.; Nicastro, Katy R.; Zardi, Gerardo

    2016-01-01

    At a proximal level, the physiological impacts of global climate change on ectothermic organisms are manifest as changes in body temperatures. Especially for plants and animals exposed to direct solar radiation, body temperatures can be substantially different from air temperatures. We deployed biomimetic sensors that approximate the thermal characteristics of intertidal mussels at 71 sites worldwide, from 1998-present. Loggers recorded temperatures at 10–30 min intervals nearly continuously at multiple intertidal elevations. Comparisons against direct measurements of mussel tissue temperature indicated errors of ~2.0–2.5 °C, during daily fluctuations that often exceeded 15°–20 °C. Geographic patterns in thermal stress based on biomimetic logger measurements were generally far more complex than anticipated based only on ‘habitat-level’ measurements of air or sea surface temperature. This unique data set provides an opportunity to link physiological measurements with spatially- and temporally-explicit field observations of body temperature. PMID:27727238

  16. Release of nitrogen precursors from coal and biomass residues in a bubbling fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    P. Abelha; I. Gulyurtlu; I. Cabrita [Instituto Nacional de Engenharia, Lisbon (Portugal)

    2008-01-15

    This work was undertaken with the aim of quantifying the relative amounts of NH{sub 3} and HCN released from different residues during their devolatilization under fluidized bed conditions. The results were compared with data collected for bituminous coals of different origin. The relation between amounts of HCN and NH{sub 3} released and the levels of NOX and N{sub 2}O formed during cocombustion was also addressed. The partitioning of nitrogen between volatiles and char was also quantified. The pyrolysis studies were undertaken in a small fluidized bed reactor of 80 mm of ID and 500 mm high using an inert atmosphere (N{sub 2}). The HCN and NH{sub 3} were quantified by bubbling the pyrolysis gases in absorbing solutions which were subsequently analyzed with selective electrodes. The combustion studies were carried out on a pilot installation. The fluidized bed combustor is square in cross section with each side being 300 mm long. There is secondary air supply to the freeboard at different heights to deal with high volatile fuels as almost all waste materials are. The temperatures in the bed and in the freeboard and that of the flue gases leaving the reactor were continuously monitored. The results obtained suggest that, while coal releases nitrogen mostly as HCN, residues like RDF and sewage sludge give out fuel-N in greater quantities as NH{sub 3}. Residues at fluidized bed combustion (FBC) temperatures release more than 80% of the fuel-N with the volatiles. The NH{sub 3} evolved during pyrolysis acted as a reducing agent on NOX emissions. The presence of calcium significantly reduces the emission of N{sub 2}O probably by interfering with HCN chemistry. With high amounts of residues in the fuel mixture, the relative importance of char on the nitrogen chemistry substantially decreases. By using cocombustion, it is possible to reduce fuel-N conversion to NOX and N{sub 2}O, by tuning the amounts of coal and residue in the mixture. 29 refs., 18 figs., 3 tabs.

  17. Oxidation of tritium by hopcalite bed

    Energy Technology Data Exchange (ETDEWEB)

    Nishikawa, Masabumi; Shinnai, Kohsuke; Matsunaga, Sohichi; Kinoshita, Yoshihiko

    1984-08-01

    Oxidation by the catalyst bed with a metal oxide and subsequent adsorption to the porous dehydrative reagents is supposed to be effective process for scavenging tritium from an inert atmosphere. Use of spongy copper oxide or wires of copper oxide is not recommended to use as the metal oxide catalyst from the view point of mass transfer because of sintering and of limited effective surface area. Use of hopcalites and copper oxide-kieselguhr are examined in this study and it is concluded that hopcalites are more suitable as the metal oxide catalyst because they not only remain the oxidation power on hydrogen isotopes even at an ambient temperature, but also show a negligible drop in oxidation performances with repeated regeneration. The effective temperature is about 400/sup 0/C for hopcalites and 300-600/sup 0/C for copper oxide-kieselguhr to use as the oxidation bed of tritium.

  18. Oxidation of tritium by hopcalite bed

    International Nuclear Information System (INIS)

    Nishikawa, Masabumi; Shinnai, Kohsuke; Matsunaga, Sohichi; Kinoshita, Yoshihiko

    1984-01-01

    Oxidation by the catalyst bed with a metal oxide and subsequent adsorption to the porous dehydrative reagents is supposed to be effective process for scavenging tritium from an inert atmosphere. Use of spongy copper oxide or wires of copper oxide is not recommended to use as the metal oxide catalyst from the view point of mass transfer because of sintering and of limited effective surface area. Use of hopcalites and copper oxide-kieselguhr are examined in this study and it is concluded that hopcalites are more suitable as the metal oxide catalyst because they not only remain the oxidation power on hydrogen isotopes even at an ambient temperature, but also show a negligible drop in oxidation performances with repeated regeneration. The effective temperature is about 400 0 C for hopcalites and 300--600 0 C for copper oxide-kieselguhr to use as the oxidation bed of tritium. (author)

  19. Volatiles combustion in fluidized beds. Final technical report, 4 September 1992--4 June 1995

    Energy Technology Data Exchange (ETDEWEB)

    Pendergrass, R.A. II; Raffensperger, C.; Hesketh, R.P.

    1996-02-29

    The goal of this project is to investigate the conditions in which volatiles will burn within both the dense and freeboard regions of fluidized beds. Experiments using a fluidized bed operated at incipient fluidization are being conducted to characterize the effect of particle surface area, initial fuel concentration, and particle type on the inhibition of volatiles within a fluidized bed. A review of the work conducted under this grant is presented in this Final Technical Report. Both experimental and theoretical work have been conducted to examine the inhibition of the combustion by the fluidized bed material, sand. It has been shown that particulate phase at incipient fluidization inhibits the combustion of propane by free radical destruction at the surface of sand particles within the particulate phase. The implications of these findings is that at bed temperatures lower than the critical temperatures, gas combustion can only occur in the bubble phase or at the top surface of a bubbling fluidized bed. In modeling fluidized bed combustion this inhibition by the particulate phase should be included.

  20. Advanced Core Design And Fuel Management For Pebble-Bed Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Hans D. Gougar; Abderrafi M. Ougouag; William K. Terry

    2004-10-01

    A method for designing and optimizing recirculating pebble-bed reactor cores is presented. At the heart of the method is a new reactor physics computer code, PEBBED, which accurately and efficiently computes the neutronic and material properties of the asymptotic (equilibrium) fuel cycle. This core state is shown to be unique for a given core geometry, power level, discharge burnup, and fuel circulation policy. Fuel circulation in the pebble-bed can be described in terms of a few well?defined parameters and expressed as a recirculation matrix. The implementation of a few heat?transfer relations suitable for high-temperature gas-cooled reactors allows for the rapid estimation of thermal properties critical for safe operation. Thus, modeling and design optimization of a given pebble-bed core can be performed quickly and efficiently via the manipulation of a limited number key parameters. Automation of the optimization process is achieved by manipulation of these parameters using a genetic algorithm. The end result is an economical, passively safe, proliferation-resistant nuclear power plant.

  1. Conceptual design of a passively safe thorium breeder Pebble Bed Reactor

    International Nuclear Information System (INIS)

    Wols, F.J.; Kloosterman, J.L.; Lathouwers, D.; Hagen, T.H.J.J. van der

    2015-01-01

    Highlights: • This work proposes three possible designs for a thorium Pebble Bed Reactor. • A high-conversion PBR (CR > 0.96), passively safe and within practical constraints. • A thorium breeder PBR (220 cm core) in practical regime, but not passively safe. • A passively safe breeder, requiring higher fuel reprocessing and recycling rates. - Abstract: More sustainable nuclear power generation might be achieved by combining the passive safety and high temperature applications of the Pebble Bed Reactor (PBR) design with the resource availability and favourable waste characteristics of the thorium fuel cycle. It has already been known that breeding can be achieved with the thorium fuel cycle inside a Pebble Bed Reactor if reprocessing is performed. This is also demonstrated in this work for a cylindrical core with a central driver zone, with 3 g heavy metal pebbles for enhanced fission, surrounded by a breeder zone containing 30 g thorium pebbles, for enhanced conversion. The main question of the present work is whether it is also possible to combine passive safety and breeding, within a practical operating regime, inside a thorium Pebble Bed Reactor. Therefore, the influence of several fuel design, core design and operational parameters upon the conversion ratio and passive safety is evaluated. A Depressurized Loss of Forced Cooling (DLOFC) is considered the worst safety scenario that can occur within a PBR. So, the response to a DLOFC with and without scram is evaluated for several breeder PBR designs using a coupled DALTON/THERMIX code scheme. With scram it is purely a heat transfer problem (THERMIX) demonstrating the decay heat removal capability of the design. In case control rods cannot be inserted, the temperature feedback of the core should also be able to counterbalance the reactivity insertion by the decaying xenon without fuel temperatures exceeding 1600 °C. Results show that high conversion ratios (CR > 0.96) and passive safety can be combined in

  2. Final Report on Utilization of TRU TRISO Fuel as Applied to HTR Systems Part I: Pebble Bed Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Brian Boer; Abderrafi M. Ougouag

    2011-03-01

    The Deep-Burn (DB) concept [ ] focuses on the destruction of transuranic nuclides from used light water reactor (LWR) fuel. These transuranic nuclides are incorporated into tri-isotopic (TRISO) coated fuel particles and used in gas-cooled reactors with the aim of a fractional fuel burnup of 60 to 70% in fissions per initial metal atom (FIMA). This high performance is expected through the use of multiple recirculation passes of the fuel in pebble form without any physical or chemical changes between passes. In particular, the concept does not call for reprocessing of the fuel between passes. In principle, the DB pebble bed concept employs the same reactor designs as the presently envisioned low-enriched uranium core designs, such as the 400 MWth Pebble Bed Modular Reactor (PBMR-400) [ ]. Although it has been shown in the previous Fiscal Year (FY) (2009) that a PuO2 fueled pebble bed reactor concept is viable, achieving a high fuel burnup while remaining within safety-imposed prescribed operational limits for fuel temperature, power peaking, and temperature reactivity feedback coefficients for the entire temperature range, is challenging. The presence of the isotopes 239Pu, 240Pu, and 241Pu that have resonances in the thermal energy range significantly modifies the neutron thermal energy spectrum as compared to a standard, UO2-fueled core. Therefore, the DB pebble bed core exhibits a relatively hard neutron energy spectrum. However, regions within the pebble bed that are near the graphite reflectors experience a locally softer spectrum. This can lead to power and temperature peaking in these regions. Furthermore, a shift of the thermal energy spectrum with increasing temperature can lead to increased absorption in the resonances of the fissile Pu isotopes. This can lead to a positive temperature reactivity coefficient for the graphite moderator under certain operating conditions. Regarding the coated particle performance, the FY 2009 investigations showed that no

  3. Final Report on Utilization of TRU TRISO Fuel as Applied to HTR Systems Part I: Pebble Bed Reactors

    International Nuclear Information System (INIS)

    Boer, Brian; Ougouag, Abderrafi M.

    2011-01-01

    The Deep-Burn (DB) concept focuses on the destruction of transuranic nuclides from used light water reactor (LWR) fuel. These transuranic nuclides are incorporated into tri-isotopic (TRISO) coated fuel particles and used in gas-cooled reactors with the aim of a fractional fuel burnup of 60 to 70% in fissions per initial metal atom (FIMA). This high performance is expected through the use of multiple recirculation passes of the fuel in pebble form without any physical or chemical changes between passes. In particular, the concept does not call for reprocessing of the fuel between passes. In principle, the DB pebble bed concept employs the same reactor designs as the presently envisioned low-enriched uranium core designs, such as the 400 MWth Pebble Bed Modular Reactor (PBMR-400). Although it has been shown in the previous Fiscal Year (FY) (2009) that a PuO2 fueled pebble bed reactor concept is viable, achieving a high fuel burnup while remaining within safety-imposed prescribed operational limits for fuel temperature, power peaking, and temperature reactivity feedback coefficients for the entire temperature range, is challenging. The presence of the isotopes 239Pu, 240Pu, and 241Pu that have resonances in the thermal energy range significantly modifies the neutron thermal energy spectrum as compared to a standard, UO2-fueled core. Therefore, the DB pebble bed core exhibits a relatively hard neutron energy spectrum. However, regions within the pebble bed that are near the graphite reflectors experience a locally softer spectrum. This can lead to power and temperature peaking in these regions. Furthermore, a shift of the thermal energy spectrum with increasing temperature can lead to increased absorption in the resonances of the fissile Pu isotopes. This can lead to a positive temperature reactivity coefficient for the graphite moderator under certain operating conditions. Regarding the coated particle performance, the FY 2009 investigations showed that no significant

  4. Clinical physiology of bed rest

    Science.gov (United States)

    Greenleaf, John E.

    1993-01-01

    Maintenance of optimal health in humans requires the proper balance between exercise, rest, and sleep as well as time in the upright position. About one-third of a lifetime is spent sleeping; and it is no coincidence that sleeping is performed in the horizontal position, the position in which gravitational influence on the body is minimal. Although enforced bed rest is necessary for the treatment of some ailments, in some cases it has probably been used unwisely. In addition to the lower hydrostatic pressure with the normally dependent regions of the cardiovascular system, body fuid compartments during bed rest in the horizontal body position, and virtual elimination of compression on the long bones of the skeletal system during bed rest (hypogravia), there is often reduction in energy metabolism due to the relative confinement (hypodynamia) and alteration of ambulatory circadian variations in metabolism, body temperature, and many hormonal systems. If patients are also moved to unfamiliar surroundings, they probably experience some feelings of anxiety and some sociopsychological problems. Adaptive physiological responses during bed rest are normal for that environment. They are attempts by the body to reduce unnecessary energy expenditure, to optimize its function, and to enhance its survival potential. Many of the deconditioning responses begin within the first day or two of bed rest; these early responses have prompted physicians to insist upon early resumption of the upright posture and ambulation of bedridden patients.

  5. IRPhE-DRAGON-DPR, OECD High Temperature Reactor Dragon Project, Primary Documents

    International Nuclear Information System (INIS)

    2004-01-01

    Description: The DRAGON Reactor Experiment (DRE): The first demonstration High temperature gas reactor (HTGR) was built in the 1960's. Thirteen OECD countries began a project in 1959 to build an experimental reactor known as Dragon at Winfrith in the UK. The reactor - which operated successfully between 1966 and 1975 - had a thermal output of 20 MW and achieved a gas outlet temperature of 750 deg. C. The High Temperature Reactor concept, if it justified its expectations, was seen as having its place as an advanced thermal reactor between the current thermal reactor types such as the PWR, BWR, and AGR and the sodium cooled fast breeder reactor. It was expected that the HTR would offer better thermal efficiency, better uranium utilisation, either with low enriched uranium fuel or high enriched uranium thorium fuel, better inherent safety and lower unit power costs. In the event all these potential advantages were demonstrated to be in principle achievable. This view is still shared today. In fact Very High Temperature Reactors is one of the concepts retained for Generation IV. Projects on constructing Modular Pebble Bed Reactors are under way. Here all available Dragon Project Reports (DPR) - approximately 1000 - are collected in electronic form. An index points to the reports (PDF format); each table in the report is accessible in EXCEL format with the aim of facilitating access to the data. These reports describe the design, experiments and modelling carried out over a period of 17 years. 2 - Related or auxiliary information: IRPHE-HTR-ARCH-01, Archive of HTR Primary Documents NEA-1728/01. 3 - Software requirements: Acrobat Reader, Microsoft Word, HTML Browser required

  6. Inherent safe design of advanced high temperature reactors - concepts for future nuclear power plants

    International Nuclear Information System (INIS)

    Hodzic, A.; Kugeler, K.

    1997-01-01

    This paper discusses the applicable solutions for a commercial size High Temperature Reactor (HTR) with inherent safety features. It describes the possible realization using an advanced concept which combines newly proposed design characteristics with some well known and proven HTR inherent safety features. The use of the HTR technology offers the conceivably best solution to meet the legal criteria, recently stated in Germany, for the future reactor generation. Both systems, block and pebble bed ,reactor, could be under certain design conditions self regulating in terms of core nuclear heat, mechanical stability and the environmental transfer. 23 refs., 7 figs

  7. Anaerobic up flow fluidized bed reactor performance as a primary treatment unit in domestic wastewater treatment

    Directory of Open Access Journals (Sweden)

    M.A. Moharram

    2016-04-01

    The efficiencies of Total nitrogen removal ranged between 2.23 and 10.83% with an apparent decrease during the low temperature high rate stages. Nitrite removal was in the range of (23.08–77% with up to the 2 mg/L in the effluent water when obtaining high organic loading and warm temperature. These results demonstrated that the domestic wastewater could be anaerobically treated in a fluidized bed UASB reactor with very low HRT reaching 2.5 h.

  8. Effect of friction on pebble flow pattern in pebble bed reactor

    International Nuclear Information System (INIS)

    Li, Yu; Gui, Nan; Yang, Xingtuan; Tu, Jiyuan; Jiang, Shengyao

    2016-01-01

    Highlights: • A 3D DEM study on particle–wall/particle friction in pebble bed reactor is carried out. • Characteristic values are defined to evaluate features of pebble flow pattern quantitatively. • Particle–wall friction is dominant to determine flow pattern in a specific pebble bed. • Friction effect of hopper part on flow field is more critical than that of cylinder part. • Three cases of 1:1 full scale practical pebble beds are simulated for demonstration. - Abstract: Friction affects pebble flow pattern in pebble-bed high temperature gas-cooled reactor (HTGR) significantly. Through a series of three dimensional DEM (discrete element method) simulations it is shown that reducing friction can be beneficial and create a uniform and consistent flow field required by nuclear engineering. Particle–wall friction poses a decisive impact on flow pattern, and particle–particle friction usually plays a secondary role; relation between particle–wall friction and flow pattern transition is also concluded. Moreover, new criteria are created to describe flow patterns quantitatively according to crucial issues in HTGR like stagnant zone, radial uniformity and flow sequence. Last but not least, it is proved that friction control of hopper part is more important than that of cylinder part in practical pebble beds, so reducing friction between pebbles and hopper surface is the engineering priority.

  9. The effects of applying silicon carbide coating on core reactivity of pebble-bed HTR in water ingress accident

    Energy Technology Data Exchange (ETDEWEB)

    Zuhair, S.; Setiadipura, Topan [National Nuclear Energy Agency of Indonesia, Serpong Tagerang Selatan (Indonesia). Center for Nuclear Reactor Technology and Safety; Su' ud, Zaki [Bandung Institute of Technology (Indonesia). Dept. of Physics

    2017-03-15

    Graphite is used as the moderator, fuel barrier material, and core structure in High Temperature Reactors (HTRs). However, despite its good thermal and mechanical properties below the radiation and high temperatures, it cannot avoid corrosion as a consequence of an accident of water/air ingress. Degradation of graphite as a main HTR material and the formation of dangerous CO gas is a serious problem in HTR safety. One of the several steps that can be adopted to avoid or prevent the corrosion of graphite by the water/air ingress is the application of a thin layer of silicon carbide (SiC) on the surface of the fuel element. This study investigates the effect of applying SiC coating on the fuel surfaces of pebble-bed HTR in water ingress accident from the reactivity points of view. A series of reactivity calculations were done with the Monte Carlo transport code MCNPX and continuous energy nuclear data library ENDF/B-VII at temperature of 1200 K. Three options of UO{sub 2}, PuO{sub 2}, and ThO{sub 2}/UO{sub 2} fuel kernel were considered to obtain the inter comparison of the core reactivity of pebble-bed HTR in conditions of water/air ingress accident. The calculation results indicated that the UO{sub 2}-fueled pebble-bed HTR reactivity was slightly reduced and relatively more decreased when the thickness of the SiC coating increased. The reactivity characteristic of ThO{sub 2}/UO{sub 2}-fueled pebble-bed HTR showed a similar trend to that of UO{sub 2}, but did not show reactivity peak caused by water ingress. In contrast with UO{sub 2}- and ThO{sub 2}-fueled pebble-bed HTR, although the reactivity of PuO{sub 2}-fueled pebble-bed HTR was the lowest, its characteristics showed a very high reactivity peak (0.33 Δk/k) and this introduction of positive reactivity is difficult to control. SiC coating on the surface of the plutonium fuel pebble has no significant impact. From the comparison between reactivity characteristics of uranium, thorium and plutonium cores with 0

  10. A comparison between CFD simulation and experimental investigation of a packed-bed thermal energy storage system

    International Nuclear Information System (INIS)

    Cascetta, Mario; Cau, Giorgio; Puddu, Pierpaolo; Serra, Fabio

    2016-01-01

    Highlights: • Thermocline formation inside a sensible type packed bed during a complete cycle. • Thermal properties of both phases must be temperature-dependent in the simulation. • Bed porosity increases from the center to the container wall. • Thermal dispersion and solid conduction must be considered in the model. • The wall influences the radial temperature profile and the amount of energy stored. - Abstract: This work presents the comparison between CFD and experimental results obtained on a sensible thermal energy storage system based on alumina beads freely poured into a carbon steel tank. Experimental investigations of charging and discharging phases were carried out at a constant mass flow rate using air as heat transfer fluid. The experimental set-up was instrumented with several thermocouples to detect axial and radial temperature distribution as well as reservoir wall temperature. The experimental results were compared with those obtained from CFD simulations carried out with the FLUENT software. The computational domain consists of an axisymmetric tank of cylindrical shape filled with a porous bed coupled with the wall. The governing equations are solved for incompressible turbulent flow and fully developed forced convection, based on the two-phase transient model equation (LTNE-local thermal non-equilibrium) to calculate the temperature of fluid and solid phases. The porosity of the bed is considered variable in the radial direction, while the thermodynamic properties of both phases are temperature-dependent. The influence of the thermal dispersion within the porous bed, as well as the effective conductivity between the beads was considered. The heat transfer coefficient was calculated according to correlation for forced convection within porous media. Numerical results show a good agreement with experimental ones if thermal properties are considered temperature-dependent and the experimental temperature profile at the inlet of the bed is

  11. Numerical simulations of helium flow through prismatic fuel elements of very high temperature reactors

    International Nuclear Information System (INIS)

    Ribeiro, Felipe Lopes; Pinto, Joao Pedro C.T.A.

    2013-01-01

    The 4 th generation Very High Temperature Reactor (VHTR) most popular concept uses a graphite-moderated and helium cooled core with an outlet gas temperature of approximately 1000 deg C. The high output temperature allows the use of the process heat and the production of hydrogen through the thermochemical iodine-sulfur process as well as highly efficient electricity generation. There are two concepts of VHTR core: the prismatic block and the pebble bed core. The prismatic block core has two popular concepts for the fuel element: multihole and annular. In the multi-hole fuel element, prismatic graphite blocks contain cylindrical flow channels where the helium coolant flows removing heat from cylindrical fuel rods positioned in the graphite. In the other hand, the annular type fuel element has annular channels around the fuel. This paper shows the numerical evaluations of prismatic multi-hole and annular VHTR fuel elements and does a comparison between the results of these assembly reactors. In this study the analysis were performed using the CFD code ANSYS CFX 14.0. The simulations were made in 1/12 fuel element models. A numerical validation was performed through the energy balance, where the theoretical and the numerical generated heat were compared for each model. (author)

  12. Heat transfer to immersed horizontal tubes in gas fluidized bed dryers

    Energy Technology Data Exchange (ETDEWEB)

    Jonassen, Ola

    1999-10-01

    The main objective of this study was to construct heat pump fluidized bed dryers of the FHT type with improved dewatering capacity for a given size of the dryer. The use of heat exchangers immersed in the fluidized bed drying chambers is an important part of the FHT (Fluidized Bed High Temperature Heat Pump Dryer) concept. A pilot plant FHT dryer was built and successfully tested on fish meal raw material and seaweed. The plant included two fluidized bed drying chambers with immersed heat exchangers. The gain in water vapor of the drying air through the chambers was increased up to four times that of adiabatic drying. The energy saving concept was retained as a SMER ratio of 3.5 to 4.7 was measured in the same tests. Therefore optimization of the immersed heat exchangers was considered the most important single objective for this work. The optimization study of the heat exchangers was confined to the actual operating conditions for the dryers using: (1) Bubbling gas fluidized beds were used, (2) air as the only type of fluidising gas, (3) beds at atmospheric pressure, (4) bed temperatures below 100 {sup o}C, (5) fluidized particles of Geldart classes B and D, (6) horizontal tube banks for the immersed heat exchanger, and the influence of radiation heat transfer was ignored. The heat transfer study was confined to the fluidized bed side of the heat exchanger surface. It was concluded early in this work that the bubbles play a major role in generating the particle circulation inside the bed and hence also in heat transfer. Publications describing the most important bubble induced mechanisms contributing to high rates of heat transfer were found to be limited. Therefore the first part of this study was aimed at establishing a method for locating and measuring the size and rise velocity of bubbles inside the bed. The method established through this work using differential pressure measurements from two static pressure probes was used later in the study of heat transfer

  13. Numerical analysis of a heat-generating, truncated conical porous bed in a fluid-filled enclosure

    International Nuclear Information System (INIS)

    Chakravarty, Aranyak; Datta, Priyankan; Ghosh, Koushik; Sen, Swarnendu; Mukhopadhyay, Achintya

    2016-01-01

    Analysis of natural convection in enclosures containing heat generating porous medium has important applications related to geothermal, chemical, thermal and nuclear energy such as in-vessel cooling of debris beds in nuclear reactors, cooling of coal stockpiles etc. The objective of the present numerical study is to characterise the pattern of fluid flow and energy transfer during steady laminar natural convective flow in a cylindrical enclosure with a centrally placed heat generating porous bed. Flow through porous region is modelled using Darcy–Brinkmann–Forchheimer model and local thermal equilibrium is assumed for the porous region. Analysis is carried out for a wide range of Rayleigh number (Ra), Darcy number (Da) and thermal conductivity ratio, as well as for different bed geometries. It is observed that in addition to Ra and Da, the bed geometry also plays a very important role in determining flow field and temperature distribution within the enclosure. Interestingly, a significant change is observed in energy transfer mode from the porous bed corresponding to specific values of bed permeability and bed heat generation rate. This is characterised in terms of Ra and Da. Further, it is observed that this change in energy transfer mode is highly dependent on Ra. - Highlights: • Natural convection is analysed in an enclosure with a heat generating porous bed. • Effect of dimensionless parameters as well as bed geometry has been investigated. • Energy transfer mechanism from porous bed changes with dimensionless parameters. • Bed geometry significantly affects fluid flow and energy transfer in the enclosure.

  14. High temperature fluidized bed zero valent iron process for flue gas nitrogen monoxide removal

    International Nuclear Information System (INIS)

    Cheng, C.Y.; Chen, S.S.; Tang, C.H.; Chang, Y.M.; Cheng, H.H.; Liu, H.L.

    2008-01-01

    Nitrogen oxides (NO x ) are generated from a variety of sources, and are critical components of photochemical smog. Zero valent iron (ZVI) has been used to remove NO x in a number of studies. The ZVI process requires no extra chemicals or catalysts. In this study, a fluidized ZVI process for removing NO x from flue gases was proposed. The study examined the effects of temperature, ZVI dosage and influent NO concentrations, and observed the kinetic effects between the fluidized ZVI and NO x . A life cycle analysis of the process was also provided. The parametric analysis was conducted in a series of column studies using a continuous emissions monitoring system. Minimum fluidization velocity equations were provided, and the drag coefficient was determined. Capacities of ZVI for NO removal at different temperatures were calculated. Results of the study suggested that temperature, influent concentrations, and flow rates all influenced kinetic coefficients. Different temperatures resulted in different rates of NO removal. It was concluded that between 673 K and 773 K, almost complete NO removals were achieved. 14 refs., 2 tabs., 9 figs

  15. Advances in high temperature chemistry

    CERN Document Server

    Eyring, Leroy

    1969-01-01

    Advances in High Temperature Chemistry, Volume 2 covers the advances in the knowledge of the high temperature behavior of materials and the complex and unfamiliar characteristics of matter at high temperature. The book discusses the dissociation energies and free energy functions of gaseous monoxides; the matrix-isolation technique applied to high temperature molecules; and the main features, the techniques for the production, detection, and diagnosis, and the applications of molecular beams in high temperatures. The text also describes the chemical research in streaming thermal plasmas, as w

  16. FY 1975 Report on results of Sunshine Project. Development of techniques of digging high-temperature beds (Development of solid bits and air-friction bearings); 1975 nendo koon chiso kussaku gijutsu no kaihatsu. Solid bit oyobi air friction bearing no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1976-03-31

    A combination of superhard alloy and diamond powder has been widely used as the solid type edge. The solid type with only a superhard alloy edge is no better than the traditional metal bit. It is ironical to admit that one of the most important items in the development of solid bits for digging high-temperature beds is not related to high temperature itself but development of highly efficient, long serviceable bits, growing out of the inefficient digging mechanisms for the conventional solid bits. It is considered that use of a superhard alloy edge is disadvantageous for digging hard rocks in the so-called scratching manner, for the two major reasons: (1) a superhard alloy is certainly resistant to wear, but nothing to that of diamond, and (2) it is homogeneous and lacks directional properties, such as the cleavage plane of diamond, which is effective for cutting. This project is aimed at development, on a trial basis, and eventual commercialization of new types of solid bits serviceable for extended periods by drastically improving suerhard alloys to provide them with new structures, e.g., those corresponding to the crystal axes of diamond, and also introducing a concept of crushing. (NEDO)

  17. Core-adjacent instrumentation systems for pebble bed reactors for process heat application - state of planning

    International Nuclear Information System (INIS)

    Benninghofen, G.; Serafin, N.; Spillekothen, H.G.; Hecker, R.; Brixy, H.; Serpekian, T.

    1982-06-01

    Planning and theoretical/experimental development work for core surveillance instrumentation systems is being performed to meet requirements of pebble bed reactors for process heat application. Detailed and proved instrumentation concepts are now available for the core-adjacent instrumentation systems. The current work and the results of neutron flux measurements at high temperatures are described. Operation devices for long-term accurate gas outlet temperature measurements up to approximately 1423 deg. K will also be discussed. (author)

  18. Accelerated carbonation of steelmaking slags in a high-gravity rotating packed bed

    International Nuclear Information System (INIS)

    Chang, E-E; Pan, Shu-Yuan; Chen, Yi-Hung; Tan, Chung-Sung; Chiang, Pen-Chi

    2012-01-01

    Highlights: ► The carbonation conversion in a RPB was higher than that in traditional reactors. ► The optimum conditions were operated at 750 rpm and 65 °C for 30 min. ► The product on BOF slag was identified as crystallized calcite based on SEM and XRD. ► The diffusivity ranged from 10 −7 to 10 −6 cm 2 s −1 based on the shrinking core model. - Abstract: Carbon dioxide (CO 2 ) sequestration using the accelerated carbonation of basic oxygen furnace (BOF) slag in a high-gravity rotating packed bed (RPB) under various operational conditions was investigated. The effects of reaction time, reaction temperature, rotation speed and slurry flow rate on the CO 2 sequestration process were evaluated. The samples of reacted slurry were analyzed quantitatively using thermogravimetric analysis (TGA) and atomic absorption spectrometry (AAS) and qualitatively using X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and transmission electron microscopy (TEM). The sequestration experiments were performed at a liquid-to-solid ratio of 20:1 with a flow rate of 2.5 L min −1 of a pure CO 2 stream under atmospheric temperature and pressure. The results show that a maximum conversion of BOF slag was 93.5% at a reaction time of 30 min and a rotation speed of 750 rpm at 65 °C. The experimental data were utilized to determine the rate-limiting mechanism based on the shrinking core model (SCM), which was validated by the observations of SEM and TEM. Accelerated carbonation in a RPB was confirmed to be a viable method due to its higher mass-transfer rate.

  19. The Pebble Bed Modular Reactor: An obituary

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Steve, E-mail: stephen.thomas@gre.ac.u [Public Services International Research Unit (PSIRU), Business School, University of Greenwich, 30 Park Row, London SE10 9LS (United Kingdom)

    2011-05-15

    The High Temperature Gas-cooled Reactor (HTGR) has exerted a peculiar attraction over nuclear engineers. Despite many unsuccessful attempts over half a century to develop it as a commercial power reactor, there is still a strong belief amongst many nuclear advocates that a highly successful HTGR technology will emerge. The most recent attempt to commercialize an HTGR design, the Pebble Bed Modular Reactor (PBMR), was abandoned in 2010 after 12 years of effort and the expenditure of a large amount of South African public money. This article reviews this latest attempt to commercialize an HTGR design and attempts to identify which issues have led to its failure and what lessons can be learnt from this experience. It concludes that any further attempts to develop HTGRs using Pebble Bed technology should only be undertaken if there is a clear understanding of why earlier attempts have failed and a high level of confidence that earlier problems have been overcome. It argues that the PBMR project has exposed serious weaknesses in accountability mechanisms for the expenditure of South African public money. - Research highlights: {yields} In this study we examine the reasons behind the failure of the South African PBMR programme. {yields} The study reviews the technical issues that have arisen and lessons for future reactor developments. {yields} The study also identifies weaknesses in the accountability mechanisms for public spending.

  20. High-temperature superconductivity

    International Nuclear Information System (INIS)

    Lynn, J.W.

    1990-01-01

    This book discusses development in oxide materials with high superconducting transition temperature. Systems with Tc well above liquid nitrogen temperature are already a reality and higher Tc's are anticipated. The author discusses how the idea of a room-temperature superconductor appears to be a distinctly possible outcome of materials research

  1. Numerical modeling of straw combustion in a fixed bed

    DEFF Research Database (Denmark)

    Zhou, Haosheng; Jensen, Anker; Glarborg, Peter

    2005-01-01

    . The straw combustion processes include moisture evaporation, straw pyrolysis, gas combustion, and char combustion. The model provides detailed information of the structure of the ignition flame front. Simulated gas species concentrations at the bed surface, ignition flame front rate, and bed temperature......Straw is being used as main renewable energy source in grate boilers in Denmark. For optimizing operating conditions and design parameters, a one-dimensional unsteady heterogeneous mathematical model has been developed and experiments have been carried out for straw combustion in a fixed bed...... are in good agreement with measurements at different operating conditions such as primary air-flow rate, pre-heating of the primary air, oxygen concentration, moisture content in straw, and bulk density of the straw in the fixed bed. A parametric study indicates that the effective heat conductivity, straw...

  2. Non-slag co-gasification of biomass and coal in entrained-bed furnace

    Science.gov (United States)

    Itaya, Yoshinori; Suami, Akira; Kobayashi, Nobusuke

    2018-02-01

    Gasification is a promising candidate of processes to upgrade biomass and to yield clean gaseous fuel for utilization of renewable energy resources. However, a sufficient amount of biomass is not always available to operate a large scale of the plant. Co-gasification of biomass with coal is proposed as a solution of the problem. Tar emission is another subject during operation in shaft or kiln type of gasifiers employed conventionally for biomass. The present authors proposed co-gasification of biomass and coal in entrained-bed furnace, which is a representative process without tar emission under high temperature, but operated so to collect dust as flyash without molten slag formation. This paper presents the works performed on co-gasification performance of biomass and pulverized coal to apply to entrained-bed type of furnaces. At first, co-gasification of woody powder and pulverized coal examined using the lab-scale test furnace of the down-flow entrained bed showed that the maximum temperatures in the furnace was over 1500 K and the carbon conversion to gas achieved at higher efficiency than 80-90 percent although the residence time in the furnace was as short as a few seconds. Non-slag co-gasification was carried out successfully without slag formation in the furnace if coal containing ash with high fusion temperature was employed. The trend suggesting the effect of reaction rate enhancement of co-gasification was also observed. Secondary, an innovative sewage sludge upgrading system consisting of self-energy recovery processes was proposed to yield bio-dried sludge and to sequentially produce char without adding auxiliary fuel. Carbonization behavior of bio-dried sludge was evaluated through pyrolysis examination in a lab-scale quartz tube reactor. The thermal treatment of pyrolysis of sludge contributed to decomposition and removal of contaminant components such as nitrogen and sulfur. The gasification kinetics of sludge and coal was also determined by a

  3. Commissioning of the THTR-300-MWe prototype power plant - A milestone for further application of this high-temperature reactor line

    International Nuclear Information System (INIS)

    Simon, M.; Baust, E.; Schoening, J.

    1986-10-01

    With the completion of the THTR 300 and the development of the follow-on plant HTR 500, the BBC/HRB company group has taken the pebble bed high-temperature reactor to the threshold of the commercial stage. The HTR is an important innovation in the field of reactor technology which can play an important role in the intermediate and long-term supply of safe, environmental friendly and economic energy. The power level of 550 MW meets the requirements of the present energy market which shows a trend towards smaller power units as a result of grid size, investment effort, and the slower increase in electricity demand in industrial nations. The advantages of the high-temperature reactor, such as high thermal efficiency, low waste heat, low radiation exposure of operating and maintenance personnel, high inherent safety, simple mode of operation, flexible fuel cycle with the potential to extend fuel resources, high availability, are currently uncontested and will represent the future standards for the peaceful uses of nuclear energy. For special applications in industry (steam and electric power as a cogeneration product) and in case of special siting conditions (near industrial centers), BBC/HRB developed a small 100 MW HTR, which can also be constructed as a 200 MW twin plant at favorable cost conditions. For an economic use of domestic coal in a processed form, the HTR represents the optimum solution as to economic and environmental aspects as well as extension of resources, especially if combined with conventional gasification procedures and in direct application of nuclear process heat at high gas temperatures of about 950 deg. C. In this field the development of the heat-exchanging components remains to be completed, before commercial application will be possible. The HTR is particularly well suited for erection in developing countries and industrial threshold countries which turn to nuclear energy for the first time. On an international level the interest in the

  4. Theory and measurements of electrophoretic effects in monolith, fixed-bed, and fluidized-bed plasma reactors

    International Nuclear Information System (INIS)

    Morin, T.J.

    1989-01-01

    Pressure gradients and secondary flow fields generated by the passage of electrical current in a d.c. gas discharge or gas laser are topics of longstanding interest in the gaseous electronics literature. These hydrodynamic effects of space charge fields and charged particle density gradients have been principally exploited in the development of gas separation and purification processes. In recent characterization studies of fixed-bed and fluidized-bed plasma reactors several anomalous flow features have been observed. These reactors involve the contacting of a high-frequency, resonantly-sustained, disperse gas discharge with granular solids in a fixed or fluidized bed. Anomalies in the measured pressure drops and fluidization velocities have motivated the development of an appropriate theoretical approach to, and some additional experimental investigations of electrophoretic effects in disperse gas discharges. In this paper, a theory which includes the effects of space charge and diffusion is used to estimate the electric field and charged particle density profiles. These profiles are then used to calculate velocity fields and gas flow rates for monolith, fixed-bed, and fluidized-bed reactors. These results are used to rationalize measurements of gas flow rates and axial pressure gradients in high-frequency disperse gas discharges with and without an additional d.c. axial electric field

  5. Evaluation of ADCP apparent bed load velocity in a large sand-bed river: Moving versus stationary boat conditions

    Science.gov (United States)

    Jamieson, E.C.; Rennie, C.D.; Jacobson, R.B.; Townsend, R.D.

    2011-01-01

    Detailed mapping of bathymetry and apparent bed load velocity using a boat-mounted acoustic Doppler current profiler (ADCP) was carried out along a 388-m section of the lower Missouri River near Columbia, Missouri. Sampling transects (moving boat) were completed at 5- and 20-m spacing along the study section. Stationary (fixed-boat) measurements were made by maintaining constant boat position over a target point where the position of the boat did not deviate more than 3 m in any direction. For each transect and stationary measurement, apparent bed load velocity (vb) was estimated using ADCP bottom tracking data and high precision real-time kinematic (RTK) global positioning system (GPS). The principal objectives of this research are to (1) determine whether boat motion introduces a bias in apparent bed load velocity measurements; and (2) evaluate the reliability of ADCP bed velocity measurements for a range of sediment transport environments. Results indicate that both high transport (vb>0.6 m/s) and moving-boat conditions (for both high and low transport environments) increase the relative variability in estimates of mean bed velocity. Despite this, the spatially dense single-transect measurements were capable of producing detailed bed velocity maps that correspond closely with the expected pattern of sediment transport over large dunes. ?? 2011 American Society of Civil Engineers.

  6. EXPERIMENTAL STUDY OF HIGH LEVELS OF SO2 REMOVAL IN ATMOSPHERIC-PRESSURE FUIDIZED-BED COMBUSTORS

    Science.gov (United States)

    The report describes tests conducted in an atmospheric-pressure-fluidized-bed combustor (FBC) with a cross-section of 1 x 1.6 m) to demonstrate high levels of S02 removal when burning a high-sulfur coal and feeding limestone sorbent for S02 removal. The goal was to achieve 90-plu...

  7. Evaluation of cage micro-environment of mice housed on various types of bedding materials.

    Science.gov (United States)

    Smith, Ellen; Stockwell, Jason D; Schweitzer, Isabelle; Langley, Stephen H; Smith, Abigail L

    2004-07-01

    A variety of environmental factors can affect the outcomes of studies using laboratory rodents. One such factor is bedding. Several new bedding materials and processing methods have been introduced to the market in recent years, but there are few reports of their performance. In the studies reported here, we have assessed the cage micro-environment (in-cage ammonia levels, temperature, and humidity) of mice housed on various kinds of bedding and their combinations. We also compared results for bedding supplied as Nestpaks versus loose bedding. We studied C57BL/6J mice (commonly used) and NOD/LtJ mice (heavy soilers) that were maintained, except in one study, in static duplex cages. In general, we observed little effect of bedding type on in-cage temperature or humidity; however, there was considerable variation in ammonia concentrations. The lowest ammonia concentrations occurred in cages housing mice on hardwood bedding or a mixture of corncob and alpha cellulose. In one experiment comparing the micro-environments of NOD/LtJ male mice housed on woodpulp fiber bedding in static versus ventilated caging, we showed a statistically significant decrease in ammonia concentrations in ventilated cages. Therefore, our data show that bedding type affects the micro-environment in static cages and that effects may differ for ventilated cages, which are being used in vivaria with increasing frequency. Copyright 2004 American Association for Laboratory Animal Science

  8. Heat pump cycle by hydrogen-absorbing alloys to assist high-temperature gas-cooled reactor in producing hydrogen

    International Nuclear Information System (INIS)

    Satoshi, Fukada; Nobutaka, Hayashi

    2010-01-01

    A chemical heat pump system using two hydrogen-absorbing alloys is proposed to utilise heat exhausted from a high-temperature source such as a high-temperature gas-cooled reactor (HTGR), more efficiently. The heat pump system is designed to produce H 2 based on the S-I cycle more efficiently. The overall system proposed here consists of HTGR, He gas turbines, chemical heat pumps and reaction vessels corresponding to the three-step decomposition reactions comprised in the S-I process. A fundamental research is experimentally performed on heat generation in a single bed packed with a hydrogen-absorbing alloy that may work at the H 2 production temperature. The hydrogen-absorbing alloy of Zr(V 1-x Fe x ) 2 is selected as a material that has a proper plateau pressure for the heat pump system operated between the input and output temperatures of HTGR and reaction vessels of the S-I cycle. Temperature jump due to heat generated when the alloy absorbs H 2 proves that the alloy-H 2 system can heat up the exhaust gas even at 600 deg. C without any external mechanical force. (authors)

  9. Astronomical cycle origin of bedded chert: A middle Triassic bedded chert sequence, Inuyama, Japan

    Science.gov (United States)

    Ikeda, Masayuki; Tada, Ryuji; Sakuma, Hironobu

    2010-09-01

    Astronomical forcing is one of the main drivers of climate change, and astronomical cyclicity recorded in sediments provides a clue to understand the dynamics of the global climate system. Bedded cherts consist of rhythmic alternations of chert and shale beds. Although previous studies have hypothesized that the origin of bedded chert is related to astronomical cycles (e.g. Fischer, 1976; Hori et al., 1993), conclusive proof remains elusive. To explore this possibility, we established a continuous, high-resolution lithostratigraphy of middle Triassic bedded chert in Central Japan. The average duration of each chert-shale couplet is 20 kyr, similar to that of the precession cycle. Spectral analysis of a bed number series of thickness variations in chert beds was performed assuming that each chert-shale couplet represents a 20-kyr precession cycle. The results reveal cycles involving approximately 200, 20, 5, and 2-3 beds, corresponding to periodicities of approximately 4000, 400, 100, and 40-60 kyr, respectively. By further assuming that the 20-bed cycle represents a 405-kyr eccentricity cycle of constant and stable periodicity, we converted the bed number series to a time series. Spectral analysis of the time series revealed distinct periodicities of 3600, 117, 97, and 38 kyr, in addition to 405 kyr. Besides 3600 kyr, these periodicities agree well with the 120, 95, and 37 kyr periodicities for eccentricity cycles and the obliquity cycle during the Triassic. Moreover, we detected amplitude modulation of the approximately 100-kyr cycle of thickness variations in chert beds with a 405-kyr periodicity, which may correspond to amplitude modulation of 100-kyr climatic precession cycle with the 405-kyr periodicity. The approximately 3600-kyr periodicity described above and 1800-kyr periodicity manifested as the amplitude modulation of the 405-kyr cycle are correlated to present-day long-term eccentricity cycles of 2400 and 4800 kyr evolved by chaotic behavior of solar

  10. THR-TH: a high-temperature gas-cooled nuclear reactor core thermal hydraulics code

    International Nuclear Information System (INIS)

    Vondy, D.R.

    1984-07-01

    The ORNL version of PEBBLE, the (RZ) pebble bed thermal hydraulics code, has been extended for application to a prismatic gas cooled reactor core. The supplemental treatment is of one-dimensional coolant flow in up to a three-dimensional core description. Power density data from a neutronics and exposure calculation are used as the basic information for the thermal hydraulics calculation of heat removal. Two-dimensional neutronics results may be expanded for a three-dimensional hydraulics calculation. The geometric description for the hydraulics problem is the same as used by the neutronics code. A two-dimensional thermal cell model is used to predict temperatures in the fuel channel. The capability is available in the local BOLD VENTURE computation system for reactor core analysis with capability to account for the effect of temperature feedback by nuclear cross section correlation. Some enhancements have also been added to the original code to add pebble bed modeling flexibility and to generate useful auxiliary results. For example, an estimate is made of the distribution of fuel temperatures based on average and extreme conditions regularly calculated at a number of locations

  11. THR-TH: a high-temperature gas-cooled nuclear reactor core thermal hydraulics code

    Energy Technology Data Exchange (ETDEWEB)

    Vondy, D.R.

    1984-07-01

    The ORNL version of PEBBLE, the (RZ) pebble bed thermal hydraulics code, has been extended for application to a prismatic gas cooled reactor core. The supplemental treatment is of one-dimensional coolant flow in up to a three-dimensional core description. Power density data from a neutronics and exposure calculation are used as the basic information for the thermal hydraulics calculation of heat removal. Two-dimensional neutronics results may be expanded for a three-dimensional hydraulics calculation. The geometric description for the hydraulics problem is the same as used by the neutronics code. A two-dimensional thermal cell model is used to predict temperatures in the fuel channel. The capability is available in the local BOLD VENTURE computation system for reactor core analysis with capability to account for the effect of temperature feedback by nuclear cross section correlation. Some enhancements have also been added to the original code to add pebble bed modeling flexibility and to generate useful auxiliary results. For example, an estimate is made of the distribution of fuel temperatures based on average and extreme conditions regularly calculated at a number of locations.

  12. Multi-stage circulating fluidized bed syngas cooling

    Science.gov (United States)

    Liu, Guohai; Vimalchand, Pannalal; Guan, Xiaofeng; Peng, WanWang

    2016-10-11

    A method and apparatus for cooling hot gas streams in the temperature range 800.degree. C. to 1600.degree. C. using multi-stage circulating fluid bed (CFB) coolers is disclosed. The invention relates to cooling the hot syngas from coal gasifiers in which the hot syngas entrains substances that foul, erode and corrode heat transfer surfaces upon contact in conventional coolers. The hot syngas is cooled by extracting and indirectly transferring heat to heat transfer surfaces with circulating inert solid particles in CFB syngas coolers. The CFB syngas coolers are staged to facilitate generation of steam at multiple conditions and hot boiler feed water that are necessary for power generation in an IGCC process. The multi-stage syngas cooler can include internally circulating fluid bed coolers, externally circulating fluid bed coolers and hybrid coolers that incorporate features of both internally and externally circulating fluid bed coolers. Higher process efficiencies can be realized as the invention can handle hot syngas from various types of gasifiers without the need for a less efficient precooling step.

  13. The experimental investigation on the performance of a low temperature waste heat-driven multi-bed desiccant dehumidifier (MBDD) and minimization of entropy generation

    KAUST Repository

    Myat, Aung; Thu, Kyaw; Ng, K. C.

    2012-01-01

    We present the experimental investigation on the performance of multi-bed desiccant dehumidification system (MBDD) using a thermodynamic framework with an entropy generation analysis. The cyclic steady state performance of adsorption-desorption processes at the assorted heat source temperatures, and typical ambient humidity conditions was carried out. MBDD unit uses type-RD silica gel pore surface area with of 720 m 2/g. It has a nominal diameter range of 0.4 to 0. 7 mm. The key advantages of MBDD are: (i) it has no moving parts rendering less maintenance, (ii) energy-efficient means of dehumidification by adsorption process with low temperature heat source as compared to the conventional methods, (iii) although it is a pecked bed desiccant, a laminar chamber is employed by arranging the V-shaped configuration of heat exchangers and (iv) it is environmental friendly with the low-carbon footprint. Entropy generation analysis was performed at the assorted heat source temperatures to investigate the performance of MBDD. By conducting the entropy minimization, it is now able to locate the optimal operating conditions of the system while the specific entropy generation is found to be minimal. This analysis shows that the minimization of entropy generation in the dehumidification cycle leads to the maximization of COP in the MBDD and thus, higher delivery of useful effects at the same input resources. © 2011 Elsevier Ltd. All rights reserved.

  14. The experimental investigation on the performance of a low temperature waste heat-driven multi-bed desiccant dehumidifier (MBDD) and minimization of entropy generation

    KAUST Repository

    Myat, Aung

    2012-06-01

    We present the experimental investigation on the performance of multi-bed desiccant dehumidification system (MBDD) using a thermodynamic framework with an entropy generation analysis. The cyclic steady state performance of adsorption-desorption processes at the assorted heat source temperatures, and typical ambient humidity conditions was carried out. MBDD unit uses type-RD silica gel pore surface area with of 720 m 2/g. It has a nominal diameter range of 0.4 to 0. 7 mm. The key advantages of MBDD are: (i) it has no moving parts rendering less maintenance, (ii) energy-efficient means of dehumidification by adsorption process with low temperature heat source as compared to the conventional methods, (iii) although it is a pecked bed desiccant, a laminar chamber is employed by arranging the V-shaped configuration of heat exchangers and (iv) it is environmental friendly with the low-carbon footprint. Entropy generation analysis was performed at the assorted heat source temperatures to investigate the performance of MBDD. By conducting the entropy minimization, it is now able to locate the optimal operating conditions of the system while the specific entropy generation is found to be minimal. This analysis shows that the minimization of entropy generation in the dehumidification cycle leads to the maximization of COP in the MBDD and thus, higher delivery of useful effects at the same input resources. © 2011 Elsevier Ltd. All rights reserved.

  15. Coolability of volumetrically heated particle beds

    Energy Technology Data Exchange (ETDEWEB)

    Rashid, Muhammad

    2017-03-22

    In case of a severe nuclear reactor accident, with loss of coolant, a particle bed may be formed from the fragmentation of the molten core in the residual water at different stages of the accident. To avoid further propagation of the accident and maintain the integrity of the reactor pressure vessel, the decay heat of the particle bed must be removed. To better understand the various thermo-hydraulic processes within such heat-generating particle beds, the existing DEBRIS test facility at IKE has been modified to be able to perform novel boiling, dryout and quenching experiments. The essential experimental data includes the pressure gradients measured by 8 differential pressure transducers along the bed height as a function of liquid and vapour superficial velocities, the determination of local dryout heat fluxes for different system pressures as well as the local temperature distribution measured by a set of 51 thermocouples installed inside the particle bed. The experiments were carried out for two different particle beds: a polydispersed particle bed which consisted of stainless steel balls (2 mm, 3 mm and 6 mm diameters) and an irregular particle bed which consisted of a mixture of steel balls (3 mm and 6 mm) and irregularly shaped Al{sub 2}O{sub 3} particles. Additionally, all experiments were carried out for different flow conditions, such as the reference case of passive 1D top-flooding, 1D bottom flooding (driven by external pumps and different downcomer configurations) and 2D top-/bottom-/lateral flooding with a perforated downcomer. In this work, it has been observed that for both particle beds with downcomer configurations an open downcomer leads to the best coolability (dryout heat flux = 1560 kW/m{sup 2}, polydispersed particle bed, psys = 1 bar) of the particle bed, mainly due to bottom-flow with enhanced natural convection. It has also been shown that a potential lateral flow via a perforation of the downcomer does not bring any further improvements

  16. Coolability of volumetrically heated particle beds

    International Nuclear Information System (INIS)

    Rashid, Muhammad

    2017-01-01

    In case of a severe nuclear reactor accident, with loss of coolant, a particle bed may be formed from the fragmentation of the molten core in the residual water at different stages of the accident. To avoid further propagation of the accident and maintain the integrity of the reactor pressure vessel, the decay heat of the particle bed must be removed. To better understand the various thermo-hydraulic processes within such heat-generating particle beds, the existing DEBRIS test facility at IKE has been modified to be able to perform novel boiling, dryout and quenching experiments. The essential experimental data includes the pressure gradients measured by 8 differential pressure transducers along the bed height as a function of liquid and vapour superficial velocities, the determination of local dryout heat fluxes for different system pressures as well as the local temperature distribution measured by a set of 51 thermocouples installed inside the particle bed. The experiments were carried out for two different particle beds: a polydispersed particle bed which consisted of stainless steel balls (2 mm, 3 mm and 6 mm diameters) and an irregular particle bed which consisted of a mixture of steel balls (3 mm and 6 mm) and irregularly shaped Al 2 O 3 particles. Additionally, all experiments were carried out for different flow conditions, such as the reference case of passive 1D top-flooding, 1D bottom flooding (driven by external pumps and different downcomer configurations) and 2D top-/bottom-/lateral flooding with a perforated downcomer. In this work, it has been observed that for both particle beds with downcomer configurations an open downcomer leads to the best coolability (dryout heat flux = 1560 kW/m 2 , polydispersed particle bed, psys = 1 bar) of the particle bed, mainly due to bottom-flow with enhanced natural convection. It has also been shown that a potential lateral flow via a perforation of the downcomer does not bring any further improvements in

  17. Exercise countermeasures for bed-rest deconditioning

    Science.gov (United States)

    Greenleaf, John (Editor)

    1993-01-01

    The purpose for this 30-day bed rest study was to investigate the effects of short-term, high intensity isotonic and isokinetic exercise training on maintenance of working capacity (peak oxygen uptake), muscular strength and endurance, and on orthostatic tolerance, posture and gait. Other data were collected on muscle atrophy, bone mineralization and density, endocrine analyses concerning vasoactivity and fluid-electrolyte balance, muscle intermediary metabolism, and on performance and mood of the subjects. It was concluded that: The subjects maintained a relatively stable mood, high morale, and high esprit de corps throughout the study. Performance improved in nearly all tests in almost all the subjects. Isotonic training, as opposed to isokinetic exercise training, was associated more with decreasing levels of psychological tension, concentration, and motivation; and improvement in the quality of sleep. Working capacity (peak oxygen uptake) was maintained during bed rest with isotonic exercise training; it was not maintained with isokinetic or no exercise training. In general, there was no significant decrease in strength or endurance of arm or leg muscles during bed rest, in spite of some reduction in muscle size (atrophy) of some leg muscles. There was no effect of isotonic exercise training on orthostasis, since tilt-table tolerance was reduced similarly in all three groups following bed rest. Bed rest resulted in significant decreases of postural stability and self-selected step length, stride length, and walking velocity, which were not influenced by either exercise training regimen. Most pre-bed rest responses were restored by the fourth day of recovery.

  18. Bed Agglomeration During the Steam Gasification of a High Lignin Corn Stover Simultaneous Saccharification and Fermentation (SSF) Digester Residue

    Energy Technology Data Exchange (ETDEWEB)

    Howe, Daniel T.; Taasevigen, Danny J.; Gerber, Mark A.; Gray, Michel J.; Fernandez, Carlos A.; Saraf, Laxmikant; Garcia-Perez, Manuel; Wolcott, Michael P.

    2015-11-13

    This research investigates the bed agglomeration phenomena during the steam gasification of a high lignin residue produced from the simultaneous saccharification and fermentation (SSF) of corn stover in a bubbling fluidized bed. The studies were conducted at 895°C using alumina as bed material. Biomass was fed at 1.5 kg/hr, while steam was fed to give a velocity equal to 2.5 times the minimum fluidization velocity, with a steam/carbon ratio of 0.9. The pelletized feedstock was co-fed with a cooling nitrogen stream to mitigate feed line plugging issues. Tar production was high at 50.3 g/Nm3, and the fraction of C10+ compounds was greater than that seen in the gasification of traditional lignocellulosic feedstocks. Carbon closures over 94 % were achieved for all experiments. Bed agglomeration was found to be problematic, indicated by pressure drop increases observed below the bed and upstream of the feed line. Two size categories of solids were recovered from the reactor, +60 mesh and -60 mesh. After a 2.75-hour experiment, 61.7 wt % was recovered as -60 mesh particles and 38.2 wt% of the recovered reactor solids were +60 mesh. A sizeable percentage, 31.8 wt%, was +20 mesh. The -60 mesh particles were mainly formed by the initial bed material (Al2O3). Almost 50 wt. % of the + 20 mesh particles was found to be formed by organics. The unreacted carbon remaining in the reactor resulted in a low conversion rate to product gas. ICP-AES, SEM, SEM-EDS, and XRD confirmed that the large agglomerates (+ 20 mesh) were not encapsulated bed material but rather un-gasified feedstock pellets with sand particles attached to it.

  19. High throughput photo-oxidations in a packed bed reactor system.

    Science.gov (United States)

    Kong, Caleb J; Fisher, Daniel; Desai, Bimbisar K; Yang, Yuan; Ahmad, Saeed; Belecki, Katherine; Gupton, B Frank

    2017-12-01

    The efficiency gains produced by continuous-flow systems in conducting photochemical transformations have been extensively demonstrated. Recently, these systems have been used in developing safe and efficient methods for photo-oxidations using singlet oxygen generated by photosensitizers. Much of the previous work has focused on the use of homogeneous photocatalysts. The development of a unique, packed-bed photoreactor system using immobilized rose bengal expands these capabilities as this robust photocatalyst allows access to and elaboration from these highly useful building blocks without the need for further purification. With this platform we were able to demonstrate a wide scope of singlet oxygen ene, [4+2] cycloadditions and heteroatom oxidations. Furthermore, we applied this method as a strategic element in the synthesis of the high-volume antimalarial artemisinin. Copyright © 2017. Published by Elsevier Ltd.

  20. The Importance of Splat Events to the Spatiotemporal Structure of Near-Bed Fluid Velocity and Bed Load Motion Over Bed Forms: Laboratory Experiments Downstream of a Backward Facing Step

    Science.gov (United States)

    Leary, K. C. P.; Schmeeckle, M. W.

    2017-12-01

    Flow separation/reattachment on the lee side of alluvial bed forms is known to produce a complex turbulence field, but the spatiotemporal details of the associated patterns of bed load sediment transported remain largely unknown. Here we report turbulence-resolving, simultaneous measurements of bed load motion and near-bed fluid velocity downstream of a backward facing step in a laboratory flume. Two synchronized high-speed video cameras simultaneously observed bed load motion and the motion of neutrally buoyant particles in a laser light sheet 6 mm above the bed at 250 frames/s downstream of a 3.8 cm backward facing step. Particle Imaging Velocimetry (PIV) and Acoustic Doppler Velocimetry (ADV) were used to characterize fluid turbulent patterns, while manual particle tracking techniques were used to characterize bed load transport. Octant analysis, conducted using ADV data, coupled with Markovian sequence probability analysis highlights differences in the flow near reattachment versus farther downstream. Near reattachment, three distinct flow patterns are apparent. Farther downstream we see the development of a dominant flow sequence. Localized, intermittent, high-magnitude transport events are more apparent near flow reattachment. These events are composed of streamwise and cross-stream fluxes of comparable magnitudes. Transport pattern and fluid velocity data are consistent with the existence of permeable "splat events," wherein a volume of fluid moves toward and impinges on the bed (sweep) causing a radial movement of fluid in all directions around the point of impingement (outward interaction). This is congruent with flow patterns, identified with octant analysis, proximal to flow reattachment.

  1. Experimental study of fluidized bed agglomeration of acerola powder

    Directory of Open Access Journals (Sweden)

    G. C. Dacanal

    2008-03-01

    Full Text Available The aim of this work was to study the main effects of acerola powder on fluidized bed agglomeration. A 2(4-1 fractional factoring design was used to evaluate the main operating conditions (fluidizing air temperature, fluidizing air velocity, atomizing air flow and height of nozzle in the bed. The mechanical and physicochemical product changes were determined by analysis of particle diameter, moisture content, wetting time and bed porosity. The particle enlargement by agglomeration occurred when the relative humidity in the bed increased and, thus, the moisture of the product increased. However, the excessive increase in relative humidity resulted in a decrease in yield, caused by caking and product incrustation. The consolidation of small granules resulted in an increase in the instant properties, decreasing the wetting time and increasing the solubility in a short period of agitation.

  2. FEM Modeling of the Relationship between the High-Temperature Hardness and High-Temperature, Quasi-Static Compression Experiment.

    Science.gov (United States)

    Zhang, Tao; Jiang, Feng; Yan, Lan; Xu, Xipeng

    2017-12-26

    The high-temperature hardness test has a wide range of applications, but lacks test standards. The purpose of this study is to develop a finite element method (FEM) model of the relationship between the high-temperature hardness and high-temperature, quasi-static compression experiment, which is a mature test technology with test standards. A high-temperature, quasi-static compression test and a high-temperature hardness test were carried out. The relationship between the high-temperature, quasi-static compression test results and the high-temperature hardness test results was built by the development of a high-temperature indentation finite element (FE) simulation. The simulated and experimental results of high-temperature hardness have been compared, verifying the accuracy of the high-temperature indentation FE simulation.The simulated results show that the high temperature hardness basically does not change with the change of load when the pile-up of material during indentation is ignored. The simulated and experimental results show that the decrease in hardness and thermal softening are consistent. The strain and stress of indentation were analyzed from the simulated contour. It was found that the strain increases with the increase of the test temperature, and the stress decreases with the increase of the test temperature.

  3. FEM Modeling of the Relationship between the High-Temperature Hardness and High-Temperature, Quasi-Static Compression Experiment

    Directory of Open Access Journals (Sweden)

    Tao Zhang

    2017-12-01

    Full Text Available The high-temperature hardness test has a wide range of applications, but lacks test standards. The purpose of this study is to develop a finite element method (FEM model of the relationship between the high-temperature hardness and high-temperature, quasi-static compression experiment, which is a mature test technology with test standards. A high-temperature, quasi-static compression test and a high-temperature hardness test were carried out. The relationship between the high-temperature, quasi-static compression test results and the high-temperature hardness test results was built by the development of a high-temperature indentation finite element (FE simulation. The simulated and experimental results of high-temperature hardness have been compared, verifying the accuracy of the high-temperature indentation FE simulation.The simulated results show that the high temperature hardness basically does not change with the change of load when the pile-up of material during indentation is ignored. The simulated and experimental results show that the decrease in hardness and thermal softening are consistent. The strain and stress of indentation were analyzed from the simulated contour. It was found that the strain increases with the increase of the test temperature, and the stress decreases with the increase of the test temperature.

  4. Bed Bugs

    Science.gov (United States)

    Prevent, identify, and treat bed bug infestations using EPA’s step-by-step guides, based on IPM principles. Find pesticides approved for bed bug control, check out the information clearinghouse, and dispel bed bug myths.

  5. High Maturity Is Not a Procrustean Bed

    Science.gov (United States)

    2014-07-01

    for public release; distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT In Greek mythology , Procrustes was a rogue smith and bandit who...Institute of Technology Jo Ann Lane, University of Southern California Supannika Koolmanojwong, University of Southern California Abstract. In Greek ... mythology , Procrustes was a rogue smith and bandit who invited travellers to rest in his “perfectly sized bed.” When they accepted, he forcibly bound

  6. High School Students’ Use of Sunscreen and Tanning Beds

    Centers for Disease Control (CDC) Podcasts

    2014-08-20

    This podcast is an interview with Corey Basch, EdD, MPH, assistant professor in the Department of Public Health at William Paterson University. Dr. Basch discusses her study on high school students’ use of sunscreen and tanning beds between 2001 and 2011.  Created: 8/20/2014 by Preventing Chronic Disease (PCD), National Center for Chronic Disease Prevention and Health Promotion (NCCDPHP).   Date Released: 8/20/2014.

  7. Supersymmetry at high temperatures

    International Nuclear Information System (INIS)

    Das, A.; Kaku, M.

    1978-01-01

    We investigate the properties of Green's functions in a spontaneously broken supersymmetric model at high temperatures. We show that, even at high temperatures, we do not get restoration of supersymmetry, at least in the one-loop approximation

  8. Revision of Drucker-Prager cap creep modelling of pebble beds in fusion blankets

    International Nuclear Information System (INIS)

    Hofer, D.; Kamlah, M.; Hermsmeyer, S.

    2004-01-01

    A continuum model commonly used in soil mechanics analysis is compiled by use of a finite element software and has been used to simulate the thermomechanical behaviour of pebble beds. The Drucker-Prager Cap theory accounts for inelastic volume change, cap hardening, nonlinear elasticity and pressure dependent shear failure. The hardening mechanism allows for defining the hydrostatic pressure yield stress as a function of the volumetric inelastic strain. Volumetric creep is considered in order to simulate the pebble bed behaviour at high temperatures. Here, the strain hardening option has been used for the consolidation creep mechanism. The model has been calibrated using the fitting curves of the oedometric test given by Reimann et al. The fitted data has been used to calculate a pebble bed with simplified boundary conditions loaded by non-uniform volumetric heating. This calculation demonstrated that the model is capable of representing creep behaviour under volumetric heating conditions. (author)

  9. Experimental confirmation of the ITER cryopump high temperature regeneration scheme

    International Nuclear Information System (INIS)

    Day, C.; Haas, H.

    2007-01-01

    therefore essential for tritium inventory control. In the TIMO test bed at FZK, a half scale pump model of the torus exhaust cryopump with fully ITER relevant cryosorbent coating has been under detailed investigation over the last years, in order to determine the required high temperature regeneration conditions (times, pressures, temperatures). To replicate the ITER conditions most neatly, multi-cycle tests have been performed, aiming to identify any poisoning effects on cryopumping that may arise in the region of high accumulated gas loads of water-likes. Furthermore, the regeneration behaviour of representative water-likes has been investigated by high resolution gas analysis. The regeneration efficiency has been assessed by comparing pumping speeds before and after the contamination of the pump with the high molecular species. This paper summarizes the experimental results and draws conclusions with respect to ITER and the regeneration frequency to be considered for the ITER operational plan. (orig.)

  10. Quench cooling of superheated debris beds in containment during LWR core meltdown accidents

    International Nuclear Information System (INIS)

    Ginsberg, T.; Chen, J.C.

    1984-01-01

    Light water reactor core meltdown accident sequence studies suggest that superheated debris beds may settle on the concrete floor beneath the reactor vessel. A model for the heat transfer processes during quench of superheated debris beds cooled by an overlying pool of water has been presented in a prior paper. This paper discusses the coolability of decay-heated debris beds from the standpoint of their transient quench characteristics. It is shown that even though a debris bed configuration may be coolable from the point of view of steady-state decay heat removal, the quench behavior from an initially elevated temperature may lead to bed melting prior to quench of the debris

  11. High temperature high vacuum creep testing facilities

    International Nuclear Information System (INIS)

    Matta, M.K.

    1985-01-01

    Creep is the term used to describe time-dependent plastic flow of metals under conditions of constant load or stress at constant high temperature. Creep has an important considerations for materials operating under stresses at high temperatures for long time such as cladding materials, pressure vessels, steam turbines, boilers,...etc. These two creep machines measures the creep of materials and alloys at high temperature under high vacuum at constant stress. By the two chart recorders attached to the system one could register time and temperature versus strain during the test . This report consists of three chapters, chapter I is the introduction, chapter II is the technical description of the creep machines while chapter III discuss some experimental data on the creep behaviour. Of helium implanted stainless steel. 13 fig., 3 tab

  12. Gasification of biochar from empty fruit bunch in a fluidized bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Mohd Salleh, M. A.; Hussein Kisiki, N.; Yusuf, H. M.; Ghani, W. A. K. [Department of Chemical and Enviromental Engineering University Putra Malaysia, 43400, Serdang (Malaysia)

    2010-07-15

    A biochar produced from empty fruit bunches (EFB) was gasified in a fluidized bed using air to determine gas yield, overall carbon conversion, gas quality, and composition as a function of temperature. The experiment was conducted in the temperature range of 500-850 {sup o}C. It was observed that biochar has the potential to replace coal as a gasification agent in power plants. Hydrogen gas from biochar was also optimized during the experiment. High temperatures favor H{sub 2} and CO formation. There was an increase of H{sub 2} over the temperature range from 500-850 {sup o}C from 5.53% to 27.97% (v/v), with a heating value of 30 kJ/g. The C conversion in the same temperature range increased from 76% to 84%. Therefore, there are great prospects for the use of biochar from EFB as an alternative fuel in power plants, as a renewable energy providing an alternative path to biofuels. Results from this work enable us to better understand syn gas production under high treatment temperatures. (authors)

  13. Importance of spinel reaction kinetics in packed-bed chemical looping combustion using a CuO/Al2O3 oxygen carrier

    NARCIS (Netherlands)

    San Pio, M.A.; Sabatino, F.; Gallucci, F.; van Sint Annaland, M.

    2018-01-01

    Chemical looping combustion is especially competitive for electrical power generation with integrated CO2 capture when it is operated at high temperatures (1000–1200 °C) and high pressures (15 bar or higher). For these demanding conditions, dynamically operated packed bed reactors have been

  14. Seaweed beds support more juvenile reef fish than seagrass beds in a south-western Atlantic tropical seascape

    Science.gov (United States)

    Eggertsen, L.; Ferreira, C. E. L.; Fontoura, L.; Kautsky, N.; Gullström, M.; Berkström, C.

    2017-09-01

    Seascape connectivity is regarded essential for healthy reef fish communities in tropical shallow systems. A number of reef fish species use separate adult and nursery habitats, and hence contribute to nutrient and energy transfer between habitats. Seagrass beds and mangroves often constitute important nursery habitats, with high structural complexity and protection from predation. Here, we investigated if reef fish assemblages in the tropical south-western Atlantic demonstrate ontogenetic habitat connectivity and identify possible nurseries on three reef systems along the eastern Brazilian coast. Fish were surveyed in fore reef, back reef, Halodule wrightii seagrass beds and seaweed beds. Seagrass beds contained lower abundances and species richness of fish than expected, while Sargassum-dominated seaweed beds contained significantly more juveniles than all other habitats (average juvenile fish densities: 32.6 per 40 m2 in Sargassum beds, 11.2 per 40 m2 in back reef, 10.1 per 40 m2 in fore reef, and 5.04 per 40 m2 in seagrass beds), including several species that are found in the reef habitats as adults. Species that in other regions worldwide (e.g. the Caribbean) utilise seagrass beds as nursery habitats were here instead observed in Sargassum beds or back reef habitats. Coral cover was not correlated to adult fish distribution patterns; instead, type of turf was an important variable. Connectivity, and thus pathways of nutrient transfer, seems to function differently in east Brazil compared to many tropical regions. Sargassum-dominated beds might be more important as nurseries for a larger number of fish species than seagrass beds. Due to the low abundance of structurally complex seagrass beds we suggest that seaweed beds might influence adult reef fish abundances, being essential for several keystone species of reef fish in the tropical south-western Atlantic.

  15. The influence of fine char particles burnout on bed agglomeration during the fluidized bed combustion of a biomass fuel

    Energy Technology Data Exchange (ETDEWEB)

    Scala, Fabrizio; Chirone, Riccardo [Istituto di Ricerche sulla Combustione, CNR, P.le V. Tecchio, 80-80125 Naples (Italy); Salatino, Piero [Dipartimento di Ingegneria Chimica, Universita degli Studi di Napoli Federico II, P.le V. Tecchio, 80-80125 Naples (Italy)

    2003-11-15

    The combustion of biomass char in a bubbling fluidized bed is hereby addressed, with specific reference to the influence that the combustion of fine char particles may exert on ash deposition and bed agglomeration phenomena. Experiments of steady fluidized bed combustion (FBC) of powdered biomass were carried out with the aim of mimicking the postcombustion of attrited char fines generated in the fluidized bed combustion of coarse char. Experimental results showed that the char elutriation rate is much smaller than expected on the basis of the average size of the biomass powder and of the carbon loading in the combustor. Samples of bed material collected after prolonged operation of the combustor were characterized by scanning electron microscopy (SEM)-EDX analysis and revealed the formation of relatively coarse sand-ash-carbon aggregates. The phenomenology is consistent with the establishment of a char phase attached to the bed material as a consequence of adhesion of char fines onto the sand particles. Combustion under sound-assisted fluidization conditions was also tested. As expected, enhancement of fines adhesion on bed material and further reduction of the elutriation rate were observed. Experimental results are interpreted in the light of a simple model which accounts for elutriation of free fines, adhesion of free fines onto bed material and detachment of attached fines by attrition of char-sand aggregates. Combustion of both free and attached char fines is considered. The parameters of the model are assessed on the basis of the measured carbon loadings and elutriation rates. Model computations are directed to estimate the effective size and the peak temperature of char-sand aggregates. The theoretical estimates of the effective aggregate size match fairly well those observed in the experiments.

  16. Experiments and procedures for bottom-heating heat-transfer experiments through UO2 debris beds in sodium

    International Nuclear Information System (INIS)

    Sowa, E.S.; Pedersen, D.R.; Pavlik, J.; Purviance, R.

    1982-01-01

    Real materials experiments in heat transfer through beds of UO 2 in sodium have been performed at Argonne National Laboratory over a period of years. The most recent method utilizes the resistive heating in a sheet tungsten filament located at the base of the debris container. A schematic diagram of the apparatus is shown. The tungsten is clamped between two water cooled copper electrodes. The filament is a sheet of tungsten 0.15 mm thick, 5 cm wide and 18 cm long. Two 6.5 mm thick sheets of boron nitride sandwich the filament. The upper face of the upper boron nitride sheet is in intimate contact with the bottom of the debris container. Temperatures are measured at various levels in the bed as well as in the boron nitride plate. In addition, the sodium pool temperature is measured by the thermocouple. The heat transferral through the bed is measured by the temperature difference and mass flowrate in a NaK condenser located above the debris bed. The NaK inlet and outlet temperatures are recorded individually, as well as, differentially

  17. Evaluation of the mechanical performance of silicon carbide in TRISO fuel at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Rohbeck, Nadia, E-mail: nadia.rohbeck@manchester.ac.uk; Xiao, Ping, E-mail: p.xiao@manchester.ac.uk

    2016-09-15

    The HTR design envisions fuel operating temperatures of up to 1000 °C and in case of an accident even 1600 °C are conceivable. To ensure safety in all conditions a thorough understanding of the impact of an extreme temperature environment is necessary. This work assesses the high temperature mechanical performance of the silicon carbide (SiC) layer within the tristructural-isotropic (TRISO) fuel particle as it poses the main barrier against fission product release into the primary circuit. Therefore, simulated fuel was fabricated by fluidized bed chemical vapour deposition; varying the deposition conditions resulted in strongly differing SiC microstructures for the various samples. Subsequently the TRISO particles were annealed in inert atmosphere at temperatures ranging from 1600 °C up to 2200 °C. Scanning electron microscopy and Raman spectroscopy showed that strong disintegration of the SiC layer occurred from 2100 °C onwards, but initial signs of porosity formation were visible already at 1800 °C. Still, the elastic modulus and hardness as measured by nanoindentation were hardly impaired. After annealing stoichiometric SiC coatings showed a reduction in fracture strength as determined by a modified crush test, however the actual annealing temperature from 1600 °C to 2000 °C had no measureable effect. Furthermore, a technique was developed to measure the elastic modulus and hardness in situ up to 500 °C using a high temperature nanoindentation facility. This approach allows conducting tests while the specimen and indenter tip are heated to a specific measurement temperature, thus obtaining reliable values for the temperature dependent mechanical properties of the material. For the SiC layer in TRISO particles it was found that the elastic modulus decreased slightly from room temperature up to 500 °C, whereas the hardness was reduced more severely to approximately half of its ambient temperature value.

  18. Evaluation of the mechanical performance of silicon carbide in TRISO fuel at high temperatures

    International Nuclear Information System (INIS)

    Rohbeck, Nadia; Xiao, Ping

    2016-01-01

    The HTR design envisions fuel operating temperatures of up to 1000 °C and in case of an accident even 1600 °C are conceivable. To ensure safety in all conditions a thorough understanding of the impact of an extreme temperature environment is necessary. This work assesses the high temperature mechanical performance of the silicon carbide (SiC) layer within the tristructural-isotropic (TRISO) fuel particle as it poses the main barrier against fission product release into the primary circuit. Therefore, simulated fuel was fabricated by fluidized bed chemical vapour deposition; varying the deposition conditions resulted in strongly differing SiC microstructures for the various samples. Subsequently the TRISO particles were annealed in inert atmosphere at temperatures ranging from 1600 °C up to 2200 °C. Scanning electron microscopy and Raman spectroscopy showed that strong disintegration of the SiC layer occurred from 2100 °C onwards, but initial signs of porosity formation were visible already at 1800 °C. Still, the elastic modulus and hardness as measured by nanoindentation were hardly impaired. After annealing stoichiometric SiC coatings showed a reduction in fracture strength as determined by a modified crush test, however the actual annealing temperature from 1600 °C to 2000 °C had no measureable effect. Furthermore, a technique was developed to measure the elastic modulus and hardness in situ up to 500 °C using a high temperature nanoindentation facility. This approach allows conducting tests while the specimen and indenter tip are heated to a specific measurement temperature, thus obtaining reliable values for the temperature dependent mechanical properties of the material. For the SiC layer in TRISO particles it was found that the elastic modulus decreased slightly from room temperature up to 500 °C, whereas the hardness was reduced more severely to approximately half of its ambient temperature value.

  19. Modeling of a Large-Scale High Temperature Regenerative Sulfur Removal Process

    DEFF Research Database (Denmark)

    Konttinen, Jukka T.; Johnsson, Jan Erik

    1999-01-01

    model that does not account for bed hydrodynamics. The pilot-scale test run results, obtained in the test runs of the sulfur removal process with real coal gasifier gas, have been used for parameter estimation. The validity of the reactor model for commercial-scale design applications is discussed.......Regenerable mixed metal oxide sorbents are prime candidates for the removal of hydrogen sulfide from hot gasifier gas in the simplified integrated gasification combined cycle (IGCC) process. As part of the regenerative sulfur removal process development, reactor models are needed for scale......-up. Steady-state kinetic reactor models are needed for reactor sizing, and dynamic models can be used for process control design and operator training. The regenerative sulfur removal process to be studied in this paper consists of two side-by-side fluidized bed reactors operating at temperatures of 400...

  20. Hydrogen production methods efficiency coupled to an advanced high temperature accelerator driven system

    International Nuclear Information System (INIS)

    Rodríguez, Daniel González; Lira, Carlos Alberto Brayner de Oliveira

    2017-01-01

    The hydrogen economy is one of the most promising concepts for the energy future. In this scenario, oil is replaced by hydrogen as an energy carrier. This hydrogen, rather than oil, must be produced in volumes not provided by the currently employed methods. In this work two high temperature hydrogen production methods coupled to an advanced nuclear system are presented. A new design of a pebbled-bed accelerator nuclear driven system called TADSEA is chosen because of the advantages it has in matters of transmutation and safety. For the conceptual design of the high temperature electrolysis process a detailed computational fluid dynamics model was developed to analyze the solid oxide electrolytic cell that has a huge influence on the process efficiency. A detailed flowsheet of the high temperature electrolysis process coupled to TADSEA through a Brayton gas cycle was developed using chemical process simulation software: Aspen HYSYS®. The model with optimized operating conditions produces 0.1627 kg/s of hydrogen, resulting in an overall process efficiency of 34.51%, a value in the range of results reported by other authors. A conceptual design of the iodine-sulfur thermochemical water splitting cycle was also developed. The overall efficiency of the process was calculated performing an energy balance resulting in 22.56%. The values of efficiency, hydrogen production rate and energy consumption of the proposed models are in the values considered acceptable in the hydrogen economy concept, being also compatible with the TADSEA design parameters. (author)

  1. Hydrogen production methods efficiency coupled to an advanced high temperature accelerator driven system

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, Daniel González; Lira, Carlos Alberto Brayner de Oliveira [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear; Fernández, Carlos García, E-mail: danielgonro@gmail.com, E-mail: mmhamada@ipen.br [Instituto Superior de Tecnologías y Ciencias aplicadas (InSTEC), La Habana (Cuba)

    2017-07-01

    The hydrogen economy is one of the most promising concepts for the energy future. In this scenario, oil is replaced by hydrogen as an energy carrier. This hydrogen, rather than oil, must be produced in volumes not provided by the currently employed methods. In this work two high temperature hydrogen production methods coupled to an advanced nuclear system are presented. A new design of a pebbled-bed accelerator nuclear driven system called TADSEA is chosen because of the advantages it has in matters of transmutation and safety. For the conceptual design of the high temperature electrolysis process a detailed computational fluid dynamics model was developed to analyze the solid oxide electrolytic cell that has a huge influence on the process efficiency. A detailed flowsheet of the high temperature electrolysis process coupled to TADSEA through a Brayton gas cycle was developed using chemical process simulation software: Aspen HYSYS®. The model with optimized operating conditions produces 0.1627 kg/s of hydrogen, resulting in an overall process efficiency of 34.51%, a value in the range of results reported by other authors. A conceptual design of the iodine-sulfur thermochemical water splitting cycle was also developed. The overall efficiency of the process was calculated performing an energy balance resulting in 22.56%. The values of efficiency, hydrogen production rate and energy consumption of the proposed models are in the values considered acceptable in the hydrogen economy concept, being also compatible with the TADSEA design parameters. (author)

  2. Local heat transfer coefficient in a fluidized bed

    International Nuclear Information System (INIS)

    Al-Busoul, A. M.

    1999-01-01

    This paper presents an experimental study for the local heat transfer coefficient. The experiments was conducted inside a reactor with inner diameter (I D = 142mm) at atmospheric conditions (temperature mean value = 29 deg.) The bed was heated by means of a parochial electric heater with a diameter of (d h = 29 mm) and a constant power of 5W. The following factors varied: particles type and diameter, fluid velocity, bed height and heater position inside the reactor. The results were presented and discussed. (author). 15 refs., 7 figs

  3. Batch statistical process control of a fluid bed granulation process using in-line spatial filter velocimetry and product temperature measurements.

    Science.gov (United States)

    Burggraeve, A; Van den Kerkhof, T; Hellings, M; Remon, J P; Vervaet, C; De Beer, T

    2011-04-18

    Fluid bed granulation is a batch process, which is characterized by the processing of raw materials for a predefined period of time, consisting of a fixed spraying phase and a subsequent drying period. The present study shows the multivariate statistical modeling and control of a fluid bed granulation process based on in-line particle size distribution (PSD) measurements (using spatial filter velocimetry) combined with continuous product temperature registration using a partial least squares (PLS) approach. Via the continuous in-line monitoring of the PSD and product temperature during granulation of various reference batches, a statistical batch model was developed allowing the real-time evaluation and acceptance or rejection of future batches. Continuously monitored PSD and product temperature process data of 10 reference batches (X-data) were used to develop a reference batch PLS model, regressing the X-data versus the batch process time (Y-data). Two PLS components captured 98.8% of the variation in the X-data block. Score control charts in which the average batch trajectory and upper and lower control limits are displayed were developed. Next, these control charts were used to monitor 4 new test batches in real-time and to immediately detect any deviations from the expected batch trajectory. By real-time evaluation of new batches using the developed control charts and by computation of contribution plots of deviating process behavior at a certain time point, batch losses or reprocessing can be prevented. Immediately after batch completion, all PSD and product temperature information (i.e., a batch progress fingerprint) was used to estimate some granule properties (density and flowability) at an early stage, which can improve batch release time. Individual PLS models relating the computed scores (X) of the reference PLS model (based on the 10 reference batches) and the density, respectively, flowabililty as Y-matrix, were developed. The scores of the 4 test

  4. Simulation of energetic- and exergetic performance of microwave-assisted fluidized bed drying of soybeans

    International Nuclear Information System (INIS)

    Ranjbaran, M.; Zare, D.

    2013-01-01

    The performance of microwave-assisted fluidized bed drying of soybeans was simulated (using a previously validated mathematical model) and analyzed based on the first- and second law of thermodynamics. The energy and exergy analysis were carried out for several drying conditions. The effects of inlet air temperature, microwave power density, bed thickness and inlet air velocity on the efficiencies and inefficiencies of drying process have been simulated and discussed. Generally, application of microwave energy during fluidized bed drying enhanced the exergy efficiency of drying process. However, the results showed that it was more efficient not to apply microwave energy at the first stage of fluidized bed drying process. The application of higher levels of drying air temperature led in higher exergy efficiencies. The values of mean relative deviations for the predictions of efficiencies and inefficiencies of drying process were less than 14%, compared with those calculated using experimental data. - Highlights: • Introducing a mathematical model to predict the efficiency of microwave-assisted fluidized bed dryers. • Energy and exergy analysis in microwave-assisted fluidized bed drying of grains. • Providing practical recommendations for efficient use of microwave power during drying

  5. High temperature structural silicides

    International Nuclear Information System (INIS)

    Petrovic, J.J.

    1997-01-01

    Structural silicides have important high temperature applications in oxidizing and aggressive environments. Most prominent are MoSi 2 -based materials, which are borderline ceramic-intermetallic compounds. MoSi 2 single crystals exhibit macroscopic compressive ductility at temperatures below room temperature in some orientations. Polycrystalline MoSi 2 possesses elevated temperature creep behavior which is highly sensitive to grain size. MoSi 2 -Si 3 N 4 composites show an important combination of oxidation resistance, creep resistance, and low temperature fracture toughness. Current potential applications of MoSi 2 -based materials include furnace heating elements, molten metal lances, industrial gas burners, aerospace turbine engine components, diesel engine glow plugs, and materials for glass processing

  6. Human thermoregulatory function during exercise and immersion after 35 days of horizontal bed-rest and recovery.

    Science.gov (United States)

    Mekjavic, Igor B; Golja, Petra; Tipton, Michael J; Eiken, Ola

    2005-10-01

    The present study evaluated the effect of 35 days of experimental horizontal bed-rest on exercise and immersion thermoregulatory function. Fifteen healthy male volunteers were assigned to either a Control (n = 5) or Bed-rest (n = 10) group. Thermoregulatory function was evaluated during a 30-min bout of submaximal exercise on a cycle ergometer, followed immediately by a 100-min immersion in 28 degrees C water. For the Bed-rest group, exercise and immersion thermoregulatory responses observed post-bed-rest were compared with those after a 5 week supervised active recovery period. In both trials, the absolute work load during the exercise portion of the test was identical. During the exercise and immersion, we recorded skin temperature, rectal temperature, the difference in temperature between the forearm and third digit of the right hand (DeltaT(forearm-fingertip))--an index of skin blood flow, sweating rate from the forehead, oxygen uptake and heart rate at minute intervals. Subjects provided ratings of temperature perception and thermal comfort at 5-min intervals. Exercise thermoregulatory responses after bed-rest and recovery were similar. Subjective ratings of temperature perception and thermal comfort during immersion indicated that subjects perceived similar combinations of Tsk and Tre to be warmer and thermally less uncomfortable after bed-rest. The average (SD) exercise-induced increase in Tre relative to resting values was not significantly different between the Post-bed-rest (0.4 (0.2) degrees C) and Recovery (0.5 (0.2) degrees C) trials. During the post-exercise immersion, the decrease in Tre, relative to resting values, was significantly (P forearm-fingertip) was 5.2 (0.9) degrees C and 5.8 (1.0) degrees C at the end of the post-bed-rest and recovery immersions, respectively. The gain of the shivering response (increase in VO(2) relative to the decrease in Tre; VO(2)/Tre) was 1.19 l min(-1) degrees C(-1) in the Recovery trial, and was significantly

  7. High temperature resistive phase transition in A15 high temperature superconductors

    International Nuclear Information System (INIS)

    Chu, C.W.; Huang, C.Y.; Schmidt, P.H.; Sugawara, K.

    1976-01-01

    Resistive measurements were made on A15 high temperature superconductors. Anomalies indicative of a phase transition were observed at 433 0 K in a single crystal Nb 3 Sn and at 485 0 K in an unbacked Nb 3 Ge sputtered thin film. Results are compared with the high temperature transmission electron diffraction studies of Nb 3 Ge films by Schmidt et al. A possible instability in the electron energy spectrum is discussed

  8. Oxygen Carrier Aided Combustion (OCAC of Wood Chips in a Semi-Commercial Circulating Fluidized Bed Boiler Using Manganese Ore as Bed Material

    Directory of Open Access Journals (Sweden)

    Magnus Rydén

    2016-11-01

    Full Text Available Oxygen Carrier Aided Combustion (OCAC is realized by using an active oxygen-carrying bed material in fluidized bed boilers. The active material is reduced in fuel rich parts of the boiler and oxidized in air rich parts. Advantages could be achieved such as new mechanisms for oxygen transport in space and time. Here calcined manganese ore has been used as active bed material in a 12 MWth circulating fluidized bed boiler. The fuel was wood chips and the campaign lasted more than two weeks. From an operational point of view, manganese ore worked excellently. From the temperature profile of the boiler it can be concluded that fuel conversion was facilitated, especially in the dense bottom bed. The effect did not always translate to reduced emissions, which suggests that final combustion in the cyclone outlet was also influenced. Substituting 10% of the sand bed with manganese ore made it possible to reduce the air to fuel ratio without generating large amounts of CO. The use of 100% manganese ore resulted in higher emissions of CO than the sand reference, but, when combined sulphur feeding, dramatic reductions in CO emissions, up to 90% compared to sand reference, was achieved.

  9. Heat transfer to immersed horizontal tubes in gas fluidized bed dryers

    Energy Technology Data Exchange (ETDEWEB)

    Jonassen, Ola

    1999-07-01

    The main objective of this study was to construct heat pump fluidized bed dryers of the FHT type with improved dewatering capacity for a given size of the dryer. The use of heat exchangers immersed in the fluidized bed drying chambers is an important part of the FHT (Fluidized Bed High Temperature Heat Pump Dryer) concept. A pilot plant FHT dryer was built and successfully tested on fish meal raw material and seaweed. The plant included two fluidized bed drying chambers with immersed heat exchangers. The gain in water vapor of the drying air through the chambers was increased up to four times that of adiabatic drying. The energy saving concept was retained as a SMER ratio of 3.5 to 4.7 was measured in the same tests. Therefore optimization of the immersed heat exchangers was considered the most important single objective for this work. The optimization study of the heat exchangers was confined to the actual operating conditions for the dryers using: (1) Bubbling gas fluidized beds were used, (2) air as the only type of fluidizing gas,(3) beds at atmospheric pressure, (4) bed temperatures below 100 {sup o}C, (5) fluidized particles of Geldart classes B and D, (6) horizontal tube banks for the immersed heat exchanger and the influence of radiation heat transfer was ignored. The heat transfer study was confined to the fluidized bed side of the heat exchanger surface. It was concluded early in this work that the bubbles play a major role in generating the particle circulation inside the bed and hence also in heat transfer. Publications describing the most important bubble induced mechanisms contributing to high rates of heat transfer were found to be limited. Therefore the first part of this study was aimed at establishing a method for locating and measuring the size and rise velocity of bubbles inside the bed. The method established through this work using differential pressure measurements from two static pressure probes was used later in the study of heat transfer

  10. Study of the Apparent Kinetics of Biomass Gasification Using High-Temperature Steam

    Energy Technology Data Exchange (ETDEWEB)

    Alevanau, Aliaksandr

    2010-10-15

    Among the latest achievements in gasification technology, one may list the development of a method to preheat gasification agents using switched ceramic honey combs. The best output from this technology is achieved with use of water steam as a gasification agent, which is heated up to 1600 deg C. The application of these temperatures with steam as a gasification agent provides a cleaner syngas (no nitrogen from air, cracked tars) and the ash melts into easily utilised glass-like sludge. High hydrogen content in output gas is also favourable for end-user applications.Among the other advantages of this technology is the presumable application of fixed-bed-type reactors fed by separately produced and preheated steam. This construction assumes relatively high steam flow rates to deliver the heat needed for endothermic reactions involving biomass. The biomass is to be heated uniformly and evenly in the volume of the whole reactor, providing easier and simpler control and operation in comparison to other types of reactors. To provide potential constructors and exploiters of these reactors with the kinetic data needed for the calculations of vital parameters for both reactor construction and exploitation, basic experimental research of high-temperature steam gasification of four types of industrially produced biomass has been conducted.Kinetic data have been obtained for straw and wood pellets, wood-chip charcoal and compressed charcoal of mixed origin

  11. The ESKOM pebble bed modular reactor

    International Nuclear Information System (INIS)

    Gittus, J.H.

    1999-01-01

    An audit has been made of the design, construction, safety, economics and marketability of the ESKOM pebble bed modular reactor (PBMR). In this paper that audit is briefly summarized. The principal conclusions of the audit are as follows. The design is sound. It is a logical development of the designs proposed for other, modern, high-temperature gas-cooled reactors. More than 80% of the cost of constructing and commissioning a series of PBMRs would be spent in South Africa. The PBMR is much safer than existing nuclear power reactors and for many practical purposes it may be treated as a conventional chemical plant. The PBMR is economically competitive with thermal power stations. There is a substantial global market for the PBMR. (author)

  12. Performance of CVD and CVR coated carbon-carbon in high temperature hydrogen

    Science.gov (United States)

    Adams, J. W.; Barletta, R. E.; Svandrlik, J.; Vanier, P. E.

    As a part of the component development process for the particle bed reactor (PBR), it is necessary to develop coatings which will be time and temperature stable at extremely high temperatures in flowing hydrogen. These coatings must protect the underlying carbon structure from attack by the hydrogen coolant. Degradation which causes small changes in the reactor component, e.g. hole diameter in the hot frit, can have a profound effect on operation. The ability of a component to withstand repeated temperature cycles is also a coating development issue. Coatings which crack or spall under these conditions would be unacceptable. While refractory carbides appear to be the coating material of choice for carbon substrates being used in PBR components, the method of applying these coatings can have a large effect on their performance. Two deposition processes for these refractory carbides, chemical vapor deposition (CVD) and chemical vapor reaction (CVR), have been evaluated. Screening tests for these coatings consisted of testing of coated 2-D and 3-D weave carbon-carbon in flowing hot hydrogen at one atmosphere. Carbon loss from these samples was measured as a function of time. Exposure temperatures up to 3,000 K were used, and samples were exposed in a cyclical fashion cooling to room temperature between exposures. The results of these measurements are presented along with an evaluation of the relative merits of CVR and CVD coatings for this application.

  13. Design and development of fluidized bed reactor system for production of trichlorosilane as a precursor for high purity silicon

    International Nuclear Information System (INIS)

    Kumar, Rajesh; Mohan, Sadhana; Bhanja, K.; Nayak, S.; Bhattacharya, S.K.

    2009-01-01

    Trichlorosilane is widely used as precursor material for production of high purity silicon. It is mainly produced by reaction of metallurgical grade silicon with anhydrous HCl gas in a fluidized bed reactor. To develop this process on commercial scale a pilot size fluidized bed reactor system was designed and developed and successfully operated. This paper discusses the critical issues related to these activities. (author)

  14. Volatile Removal Assembly Flight Experiment and KC-135 Packed Bed Experiment: Results and Lessons Learned

    Science.gov (United States)

    Holder, Donald W.; Parker, David

    2000-01-01

    The Volatile Removal Assembly (VRA) is a high temperature catalytic oxidation process that will be used as the final treatment for recycled water aboard the International Space Station (ISS). The multiphase nature of the process had raised concerns as to the performance of the VRA in a microgravity environment. To address these concerns, two experiments were designed. The VRA Flight Experiment (VRAFE) was designed to test a full size VRA under controlled conditions in microgravity aboard the SPACEHAB module and in a 1 -g environment and compare the performance results. The second experiment relied on visualization of two-phase flow through small column packed beds and was designed to fly aboard NASA's microgravity test bed plane (KC-135). The objective of the KC-135 experiment was to understand the two-phase fluid flow distribution in a packed bed in microgravity. On Space Transportation System (STS) flight 96 (May 1999), the VRA FE was successfully operated and in June 1999 the KC-135 packed bed testing was completed. This paper provides an overview of the experiments and a summary of the results and findings.

  15. Model-free adaptive control of supercritical circulating fluidized-bed boilers

    Science.gov (United States)

    Cheng, George Shu-Xing; Mulkey, Steven L

    2014-12-16

    A novel 3-Input-3-Output (3.times.3) Fuel-Air Ratio Model-Free Adaptive (MFA) controller is introduced, which can effectively control key process variables including Bed Temperature, Excess O2, and Furnace Negative Pressure of combustion processes of advanced boilers. A novel 7-input-7-output (7.times.7) MFA control system is also described for controlling a combined 3-Input-3-Output (3.times.3) process of Boiler-Turbine-Generator (BTG) units and a 5.times.5 CFB combustion process of advanced boilers. Those boilers include Circulating Fluidized-Bed (CFB) Boilers and Once-Through Supercritical Circulating Fluidized-Bed (OTSC CFB) Boilers.

  16. High-entropy alloys as high-temperature thermoelectric materials

    Energy Technology Data Exchange (ETDEWEB)

    Shafeie, Samrand [Surface and Microstructure Engineering Group, Materials and Manufacturing Technology, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Guo, Sheng, E-mail: sheng.guo@chalmers.se [Surface and Microstructure Engineering Group, Materials and Manufacturing Technology, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Hu, Qiang [Institute of Applied Physics, Jiangxi Academy of Sciences, Nanchang 330029 (China); Fahlquist, Henrik [Bruker AXS Nordic AB, 17067 Solna (Sweden); Erhart, Paul [Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Palmqvist, Anders, E-mail: anders.palmqvist@chalmers.se [Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-41296 Gothenburg (Sweden)

    2015-11-14

    Thermoelectric (TE) generators that efficiently recycle a large portion of waste heat will be an important complementary energy technology in the future. While many efficient TE materials exist in the lower temperature region, few are efficient at high temperatures. Here, we present the high temperature properties of high-entropy alloys (HEAs), as a potential new class of high temperature TE materials. We show that their TE properties can be controlled significantly by changing the valence electron concentration (VEC) of the system with appropriate substitutional elements. Both the electrical and thermal transport properties in this system were found to decrease with a lower VEC number. Overall, the large microstructural complexity and lower average VEC in these types of alloys can potentially be used to lower both the total and the lattice thermal conductivity. These findings highlight the possibility to exploit HEAs as a new class of future high temperature TE materials.

  17. Thermal decomposition of selected chlorinated hydrocarbons during gas combustion in fluidized bed

    Directory of Open Access Journals (Sweden)

    Olek Malgorzata

    2013-01-01

    Full Text Available Abstract Background The process of thermal decomposition of dichloromethane (DCM and chlorobenzene (MCB during the combustion in an inert, bubbling fluidized bed, supported by LPG as auxiliary fuel, have been studied. The concentration profiles of C6H5CI, CH2Cl2, CO2, CO, NOx, COCl2, CHCl3, CH3Cl, C2H2, C6H6, CH4 in the flue gases were specified versus mean bed temperature. Results The role of preheating of gaseous mixture in fluidized bed prior to its ignition inside bubbles was identified as important factor for increase the degree of conversion of DCM and MCB in low bed temperature, in comparison to similar process in the tubular reactor. Conclusions Taking into account possible combustion mechanisms, it was identified that autoignition in bubbles rather than flame propagation between bubbles is needed to achieve complete destruction of DCM and MCB. These condition occurs above 900°C causing the degree of conversion of chlorine compounds of 92-100%.

  18. Considerations on valorization of biomass origin materials in co-combustion with coal in fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    I. Gulyurtlu; P. Abelha; H. Lopes; A. Crujeira; I. Cabrita [DEECA-INETI, Lisbon (Portugal)

    2007-07-01

    Co-combustion of biomass materials with coal is currently gaining increasing importance, in order to meet the targets on greenhouse gas emissions, defined in the Kyoto protocol. Co-firing of coal with biomass materials could be the short-term solution in reducing CO{sub 2} emissions from power stations. The work undertaken studied co-firing of meat and bone meal (MBM), olive cake and straw pellets with bituminous coals from Colombia (CC) and Poland (PC), which are commonly used in European power stations. The co-combustion studies were carried out on the pilot fluidized bed installation of INETI. Gaseous pollutants and solid concentration in flue gases and ashes from different locations were monitored. Results obtained indicate that the co-feeding of biomass materials did not present any problem and ensured stable combustion conditions and high efficiency. However, for temperatures above 800{sup o}C, bed agglomeration could be observed for all biomass species studied. Most of the combustion of biomass material, contrary to that of coal, was observed to take place in the riser where the temperature was as high as 150-250{sup o}C above that of the bed. SO{sub 2} and NOx levels were found to be lower. The emissions of dioxins could be considerable with fuels with high Cl as is the case with straw. However, mixing of fuels with high S content could lead to a strong reduction in dioxin emissions. Ashes produced from biomass combustion may be considered for further reutilization or landfilling. Other options depend on their characteristics, chemical composition and leaching behaviour. This was evaluated in this study.

  19. The behavior of xenon dynamic adsorption on granular activated carbon packed bed adsorber

    International Nuclear Information System (INIS)

    Chongyang Zhou; Shujuan Feng; Guoqing Zhou; Yuren Jin; Junfu Liang; Jingming Xu

    2011-01-01

    In order to retard radioxenon release into the atmosphere from nuclear power station or to sensitively monitor its concentration to ensure environmental and human safety, it is necessary to know the behavior of xenon dynamic adsorption on granular activated carbon pack bed adsorber. The quantities, including the dynamic adsorption coefficient (k d ), the amount of xenon adsorbed (q), the length of mass transfer zone (L MTZ ) and the length of the unused bed (LUB), used to describe the adsorption behavior, were sorted out and calculated. The factors, including xenon concentrations, pressures and temperatures, to affect these quantities were investigated. The results show that: (1) The values of k d and q decrease with increasing temperatures, but increase with increasing pressures, (2) The values of L MTZ and LUB increase with increasing temperatures or pressures, but are independent of concentrations. Knowledge of these quantities is very helpful for packed bed adsorber operation. (author)

  20. Tritium inventory measurements by 'in-bed' gas flowing calorimetry

    International Nuclear Information System (INIS)

    Hayashi, T.; Suzuki, T.; Yamada, M.; Okuno, K.

    1996-01-01

    In order to establish the 'in-bed' tritium accounting technology for the ITER scale tritium storage system, a gas flowing calorimetry has been studied using a scaled ZrCo bed (25 g tritium capacity). The basic calorimetric characteristics, steady state temperature raise of He gas stream flowing through a secondary coil line fixed in the ZrCo tritide, was measured and correlated with the stored tritium inventory. The results shows that about 4 degrees raise of He stream temperature can be detected for each gram of tritium storage. The sensitivity of this calorimetry is about 0.05 g of tritium, calculated by 0.2 degrees of temperature sensor error. The accuracy is better than 0.25 g of tritium on 25 g storage, evaluated by 2 times of standard deviation from the repeat measurements. This accuracy of < 1% on full storage capacity is satisfied the target accountability to measure ± 1 gram of tritium on 100 g storage for ITER. 13 refs., 7 figs

  1. Water infiltration and heat transfer in one dimensional unsaturated packed beds; Fuhowa ryushi sonai no ichijigen suibun nagare to dennetsu tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, K; Akahori, M; Hattori, M [Nagaoka University of Technology, Niigata (Japan); Shiraishi, N [Toshiba Corp., Tokyo (Japan)

    1998-05-25

    Water and heat transport in unsaturated packed beds due to supplying hot water have been investigated experimentally and theoretically. Using various sizes of glass beads, capillary pressure and permeability in packed beds were measured in unsaturated beds. The distributions in water saturation and temperature were predicted for one dimensional packed bed, based on a model assuming local thermal equilibrium among water, gas and particles at any specific space. The predicted temperature distributions were compared with the experimental results obtained using various glass sizes. In layered packed beds, water saturation becomes discontinuous at the interface of two layers because of the difference of the water characteristics between two beds. Water penetrates faster in coarse-over fine-textured profile compared with in fine-over coarse-textured profile. Similarly, the temperature rises faster in former profile under the same supplied heat quantity. 11 refs., 13 figs., 1 tab.

  2. High temperature vapors science and technology

    CERN Document Server

    Hastie, John

    2012-01-01

    High Temperature Vapors: Science and Technology focuses on the relationship of the basic science of high-temperature vapors to some areas of discernible practical importance in modern science and technology. The major high-temperature problem areas selected for discussion include chemical vapor transport and deposition; the vapor phase aspects of corrosion, combustion, and energy systems; and extraterrestrial high-temperature species. This book is comprised of seven chapters and begins with an introduction to the nature of the high-temperature vapor state, the scope and literature of high-temp

  3. Evaluation of high temperature pressure sensors

    International Nuclear Information System (INIS)

    Choi, In-Mook; Woo, Sam-Yong; Kim, Yong-Kyu

    2011-01-01

    It is becoming more important to measure the pressure in high temperature environments in many industrial fields. However, there is no appropriate evaluation system and compensation method for high temperature pressure sensors since most pressure standards have been established at room temperature. In order to evaluate the high temperature pressure sensors used in harsh environments, such as high temperatures above 250 deg. C, a specialized system has been constructed and evaluated in this study. The pressure standard established at room temperature is connected to a high temperature pressure sensor through a chiller. The sensor can be evaluated in conditions of changing standard pressures at constant temperatures and of changing temperatures at constant pressures. According to the evaluation conditions, two compensation methods are proposed to eliminate deviation due to sensitivity changes and nonlinear behaviors except thermal hysteresis.

  4. Status of the fluidized bed unit

    International Nuclear Information System (INIS)

    Williams, P.M.; Wade, J.F.

    1994-01-01

    Rocky Flats has a serious mixed waste problem. No technology or company has a license and available facilities to remedy this dilemma. One solution under study is to use a catalytic fluidized bed unit to destroy the combustible portion of the mixed waste. The fluidized bed thermal treatment program at Rocky Flats is building on knowledge gained over twenty years of successful development activity. The FBU has numerous technical advantages over other thermal technologies to treat Rocky Flats' mixed waste, the largest being the lower temperature (700 degrees C versus 1000 degrees C) which reduces acid corrosion and mechanical failures and obviates the need for ceramic lining. Successful demonstrations have taken place on bench, pilot, and full-scale tests using radioactive mixed wastes. The program is approaching implementation and licensing of a production-scale fluidized bed system for the safe treatment of mixed waste. The measure for success on this project is the ability to work closely with the community to jointly solve problems and respond to concerns of mixed waste treatment at Rocky Flats

  5. Sodium and steam leak simulation studies for fluidized bed steam generators

    International Nuclear Information System (INIS)

    Keeton, A.R.; Vaux, W.G.; Lee, P.K.; Witkowski, R.E.

    1976-01-01

    An experimental program is described which was conducted to study the effects of sodium or steam leaking into an operating fluidized bed of metal or ceramic particles at 680 to 800 0 K. This effort was part of the early development studies for a fluidized-bed steam generator concept using helium as the fluidizing gas. Test results indicated that steam and small sodium leaks had no effect on the quality of fluidization, heat transfer coefficient, temperature distribution, or fluidizing gas pressure drop across the bed. Large sodium leaks, however, immediately upset the operation of the fluidized bed. Both steam and sodium leaks were detected positively and rapidly at an early stage of a leak by instruments specifically selected to accomplish this

  6. Modeling of laser radiation transport in powder beds with high-dispersive metal particles

    Energy Technology Data Exchange (ETDEWEB)

    Kharanzhevskiy, Evgeny, E-mail: eh@udsu.ru [Udmurt State University, 426034 Universitetskaya St., 1, Izhevsk (Russian Federation); Kostenkov, Sergey [Udmurt State University, 426034 Universitetskaya St., 1, Izhevsk (Russian Federation)

    2014-02-15

    Highlights: ► Transport of laser energy in dispersive powder beds was numerically simulated. ► The results of simulating are compared with physicals experiments. ► We established the dependence of the extinction coefficient from powder properties. ► A confirmation of a geometric optic approach for monodisperse powders was proposed. -- Abstract: Two-dimensional transfer of laser radiation in a high-dispersive powder heterogeneous media is numerically calculated. The size of particles is comparable with the wave length of laser radiation so the model takes into account all known physical effects that are occurred on the vacuum–metal surface interface. It is shown that in case of small particles size both morphology of powder particles and porosity of beds influence on absorptance by the solid phase and laser radiation penetrate deep into the area of geometric shadow. Intensity of laser radiation may be described as a function corresponded to the Beer–Lambert–Bouguer law.

  7. Modeling of laser radiation transport in powder beds with high-dispersive metal particles

    International Nuclear Information System (INIS)

    Kharanzhevskiy, Evgeny; Kostenkov, Sergey

    2014-01-01

    Highlights: ► Transport of laser energy in dispersive powder beds was numerically simulated. ► The results of simulating are compared with physicals experiments. ► We established the dependence of the extinction coefficient from powder properties. ► A confirmation of a geometric optic approach for monodisperse powders was proposed. -- Abstract: Two-dimensional transfer of laser radiation in a high-dispersive powder heterogeneous media is numerically calculated. The size of particles is comparable with the wave length of laser radiation so the model takes into account all known physical effects that are occurred on the vacuum–metal surface interface. It is shown that in case of small particles size both morphology of powder particles and porosity of beds influence on absorptance by the solid phase and laser radiation penetrate deep into the area of geometric shadow. Intensity of laser radiation may be described as a function corresponded to the Beer–Lambert–Bouguer law

  8. Deep Bed Iodine Sorbent Testing FY 2011 Report

    International Nuclear Information System (INIS)

    Soelberg, Nick; Watson, Tony

    2011-01-01

    Nuclear fission results in the production of fission products (FPs) and activation products that increasingly interfere with the fission process as their concentrations increase. Some of these fission and activation products tend to evolve in gaseous species during used nuclear fuel reprocessing. Analyses have shown that I129, due to its radioactivity, high potential mobility in the environment, and high longevity (half life of 15.7 million years), can require control efficiencies of up to 1,000x or higher to meet regulatory emission limits. Deep-bed iodine sorption testing has been done to evaluate the performance of solid sorbents for capturing iodine in off-gas streams from nuclear fuel reprocessing plants. The objectives of the FY 2011 deep bed iodine sorbent testing are: (1) Evaluate sorbents for iodine capture under various conditions of gas compositions and operating temperature (determine sorption efficiencies, capacities, and mass transfer zone depths); and (2) Generate data for dynamic iodine sorption modeling. Three tests performed this fiscal year on silver zeolite light phase (AgZ-LP) sorbent are reported here. Additional tests are still in progress and can be reported in a revision of this report or a future report. Testing was somewhat delayed and limited this year due to initial activities to address some questions of prior testing, and due to a period of maintenance for the on-line GC. Each test consisted of (a) flowing a synthetic blend of gases designed to be similar to an aqueous dissolver off-gas stream over the sorbent contained in three separate bed segments in series, (b) measuring each bed inlet and outlet gas concentrations of iodine and methyl iodide (the two surrogates of iodine gas species considered most representative of iodine species expected in dissolver off-gas), (c) operating for a long enough time to achieve breakthrough of the iodine species from at least one (preferably the first two) bed segments, and (d) post-test purging

  9. Processes and parameters involved in modeling radionuclide transport from bedded salt repositories. Final report. Technical memorandum

    International Nuclear Information System (INIS)

    Evenson, D.E.; Prickett, T.A.; Showalter, P.A.

    1979-07-01

    The parameters necessary to model radionuclide transport in salt beds are identified and described. A proposed plan for disposal of the radioactive wastes generated by nuclear power plants is to store waste canisters in repository sites contained in stable salt formations approximately 600 meters below the ground surface. Among the principal radioactive wastes contained in these canisters will be radioactive isotopes of neptunium, americium, uranium, and plutonium along with many highly radioactive fission products. A concern with this form of waste disposal is the possibility of ground-water flow occurring in the salt beds and endangering water supplies and the public health. Specifically, the research investigated the processes involved in the movement of radioactive wastes from the repository site by groundwater flow. Since the radioactive waste canisters also generate heat, temperature is an important factor. Among the processes affecting movement of radioactive wastes from a repository site in a salt bed are thermal conduction, groundwater movement, ion exchange, radioactive decay, dissolution and precipitation of salt, dispersion and diffusion, adsorption, and thermomigration. In addition, structural changes in the salt beds as a result of temperature changes are important. Based upon the half-lives of the radioactive wastes, he period of concern is on the order of a million years. As a result, major geologic phenomena that could affect both the salt bed and groundwater flow in the salt beds was considered. These phenomena include items such as volcanism, faulting, erosion, glaciation, and the impact of meteorites. CDM reviewed all of the critical processes involved in regional groundwater movement of radioactive wastes and identified and described the parameters that must be included to mathematically model their behavior. In addition, CDM briefly reviewed available echniques to measure these parameters

  10. Comparison of Several Thermal Conductivity Constants for Thermal Hydraulic Calculation of Pebble Bed Reactor

    Science.gov (United States)

    Irwanto, Dwi; Setiadipura, Topan; Pramutadi, Asril

    2017-07-01

    There are two type of High Temperature Gas Reactor (HTGR), prismatic and pebble bed. Pebble Bed type has unique configuration because the fuels are randomly distributed inside the reactor core. In term of safety features, Pebble Bed Reactor (PBR) is one of the most promising reactor type in avoiding severe nuclear accidents. In order to analyze heat transfer and safety of this reactor type, a computer code is now under development. As a first step, calculation method proposed by Stroh [1] is adopted. An approach has been made to treat randomly distributed pebble balls contains fissile material inside the reactor core as a porous medium. Helium gas act as coolant on the reactor system are carrying heat flowing in the area between the pebble balls. Several parameters and constants are taken into account in the new developed code. Progress of the development of the code especially comparison of several thermal conductivity constants for a certain PBR-case are reported in the present study.

  11. Control room conceptual design of nuclear power plant with multiple modular high temperature gas-cooled reactors

    International Nuclear Information System (INIS)

    Jia Qianqian; Qu Ronghong; Zhang Liangju

    2014-01-01

    A conceptual design of the control room layout for the nuclear power plant with multiple modular high temperature gas-cooled reactors has been developed. The modular high temperature gas-cooled reactors may need to be grouped to produce as much energy as a utility demands to realize the economic efficiency. There are many differences between the multi-modular plant and the current NPPs in the control room. These differences may include the staffing level, the human-machine interface design, the operation mode, etc. The potential challenges of the human factor engineering (HFE) in the control room of the multi-modular plant are analyzed, including the operation workload of the multi-modular tasks, how to help the crew to keep situation awareness of all modules, and how to support team work, the control of shared system between modules, etc. A concept design of control room for the multi-modular plant is presented based on the design aspect of HTR-PM (High temperature gas-cooled reactor pebble bed module). HFE issues are considered in the conceptual design of control room for the multi-modular plant and some design strategies are presented. As a novel conceptual design, verifications and validations are needed, and focus of further work is sketch out. (author)

  12. An experimental simulation study of debris quenching in a radially stratified porous bed

    International Nuclear Information System (INIS)

    Sehgal, B.R.; Nayak, A.K.; Stepanyan, A.

    2004-01-01

    During a severe accident condition in a nuclear power plant, the core melt can fail the reactor vessel and relocate into the containment basement. In some accident management schemes, the vessel cavity is flooded with water. For these a particulate debris bed is likely to form on the cavity floor due to melt break-up in water. . In this situation, the coolability of debris bed on the containment floor is a crucial issue. This is because the debris bed still generates the decay heat and if it is uncoolable, it can eventually remelt and react with concrete basement generating a lot of noncondensable gases and pressurising the containment. Hence, it is important to cool the debris bed as an accident management programme. The main parameters affecting the coolability of the debris bed are its porosity which is a function of the size and shape of the particles which constitute the debris bed, the operating condition such as water flooding from the top or bottom of debris bed, water temperature and non-condensable gas generated during bed-concrete interactions. It is found from previous studies that the debris bed has a non-uniform particle distribution or a porosity stratification. This can happen both in radial and axial plane. For example, the bed can have a lower porosity at the centre and higher porosity at the periphery. It is of interest to investigate the quenching phenomena in such configurations so as to find an effective means of quenching the heat generating bed. While most of the previous investigations mainly concentrate on quenching of a homogenous or axially stratified particulate bed with volumetric heat generation, there are almost no studies on the above phenomena in a radially stratified porous bed. So the objective of this paper is to investigate the quenching phenomena in a radially stratified bed. To simulate the phenomena, we conducted experiments in an experimental facility named as POMECO (POrous MEdia COolability). The facility has a square

  13. First results of the post-irradiation examination of the Ceramic Breeder materials from the Pebble Bed Assemblies Irradiation for the HCPB Blanket concept

    International Nuclear Information System (INIS)

    Hegeman, J.; Magielsen, A.J.; Peeters, M.; Stijkel, M.P.; Fokkens, J.H.; Laan, J.G. van der

    2006-01-01

    In the framework of developing the European Helium Cooled Pebble-Bed (HCPB) blanket an irradiation test of pebble-bed assemblies is performed in the HFR Petten. The experiment is focused on the thermo-mechanical behavior of the HCPB type breeder pebble-bed at DEMO representative levels of temperature and defined thermal-mechanical loads. To achieve representative conditions a section of the HCPB is simulated by EUROFER-97 cylinders with a horizontal bed of ceramic breeder pebbles sandwiched between two beryllium beds. Floating Eurofer-97 steel plates separate the pebble-beds. The structural integrity of the ceramic breeder materials is an issue for the design of the Helium Cooled Pebble Bed concept. Therefore the objective of the post irradiation examination is to study deformation of pebbles and the pebble beds and to investigate the microstructure of the ceramic pebbles from the Pebble Bed Assemblies. This paper concentrates on the Post Irradiation Examination (PIE) of the four ceramic pebble beds that have been irradiated in the Pebble Bed Assembly experiment for the HCPB blanket concept. Two assemblies with Li 4 SiO 4 pebble-beds are operated at different maximum temperatures of approximately 600 o C and 800 o C. Post irradiation computational analysis has shown that both have different creep deformation. Two other assemblies have been loaded with a ceramic breeder bed of two types of Li 2 TiO 3 beds having different sintering temperatures and consequently different creep behavior. The irradiation maximum temperature of the Li 2 TiO 3 was 800 o C. To support the first PIE result, the post irradiation thermal analysis will be discussed because thermal gradients have influence on the pebble-bed thermo-mechanical behavior and as a result it may have impact on the structural integrity of the ceramic breeder materials. (author)

  14. Bedding material affects mechanical thresholds, heat thresholds and texture preference

    Science.gov (United States)

    Moehring, Francie; O’Hara, Crystal L.; Stucky, Cheryl L.

    2015-01-01

    It has long been known that the bedding type animals are housed on can affect breeding behavior and cage environment. Yet little is known about its effects on evoked behavior responses or non-reflexive behaviors. C57BL/6 mice were housed for two weeks on one of five bedding types: Aspen Sani Chips® (standard bedding for our institute), ALPHA-Dri®, Cellu-Dri™, Pure-o’Cel™ or TEK-Fresh. Mice housed on Aspen exhibited the lowest (most sensitive) mechanical thresholds while those on TEK-Fresh exhibited 3-fold higher thresholds. While bedding type had no effect on responses to punctate or dynamic light touch stimuli, TEK-Fresh housed animals exhibited greater responsiveness in a noxious needle assay, than those housed on the other bedding types. Heat sensitivity was also affected by bedding as animals housed on Aspen exhibited the shortest (most sensitive) latencies to withdrawal whereas those housed on TEK-Fresh had the longest (least sensitive) latencies to response. Slight differences between bedding types were also seen in a moderate cold temperature preference assay. A modified tactile conditioned place preference chamber assay revealed that animals preferred TEK-Fresh to Aspen bedding. Bedding type had no effect in a non-reflexive wheel running assay. In both acute (two day) and chronic (5 week) inflammation induced by injection of Complete Freund’s Adjuvant in the hindpaw, mechanical thresholds were reduced in all groups regardless of bedding type, but TEK-Fresh and Pure-o’Cel™ groups exhibited a greater dynamic range between controls and inflamed cohorts than Aspen housed mice. PMID:26456764

  15. Behavior of highly radioactive iodine on charcoal in moist air

    International Nuclear Information System (INIS)

    Lorenz, R.A.; Manning, S.R.; Martin, W.J.

    1976-01-01

    The behavior of highly radioactive iodine adsorbed on charcoal exposed to moist air (110 torr water vapor partial pressure) was investigated in a series of six experiments. The amount of radioactive 130 I on the well-insulated 28-cm 3 bed ranged from 50 to 570 Ci, and the relative humidity was 47 percent at the bed inlet temperature of 70 0 C. Radioactive iodine was released from the test beds at a continuous fractional release rate of approximately 7 x 10 -6 /hr for all types of charcoal tested. The chemical form of the released iodine was such that it was very highly penetrating with respect to the nine different types of commercial impregnated charcoals tested in backup collection beds. Two types of silver-nitrate-coated adsorption materials behaved similarly to the charcoals. Silver-exchanged type 13-X molecular sieve adsorbers were 20 to 50 times more efficient for adsorbing the highly penetrating iodine, but not as efficient as normally found for collecting methyl iodide. The chemical form of the highly penetrating iodine was not determined. When the moist air velocity was decreased from 28.5 fpm (25 0 C) to as low as 0.71 fpm (25 0 C), the charcoal bed temperature rose slowly and reached the ignition temperature in three of the experiments. At 0.71 fpm (25 0 C) the ignited charcoal beds reached maximum temperatures of 430 to 470 0 C because of the limited oxygen supply. The charcoal exposed for four years at Oak Ridge ignited at 283 0 C compared with 368 0 C for unused charcoal from the same batch. Two of the experiments used charcoal containing 1 or 2 percent TEDA (triethylene-diamine) and a proprietary flame retardant. The oxidation and ignition behavior of these charcoals did not appear to be affected adversely by the presence of the TEDA

  16. High-temperature hydrogen-air-steam detonation experiments in the BNL small-scale development apparatus

    International Nuclear Information System (INIS)

    Ciccarelli, G.; Ginsburg, T.; Boccio, J.; Economos, C.; Finfrock, C.; Gerlach, L.; Sato, K.; Kinoshita, M.

    1994-08-01

    The Small-Scale Development Apparatus (SSDA) was constructed to provide a preliminary set of experimental data to characterize the effect of temperature on the ability of hydrogen-air-steam mixtures to undergo detonations and, equally important, to support design of the larger scale High-Temperature Combustion Facility (HTCF) by providing a test bed for solution of a number of high-temperature design and operational problems. The SSDA, the central element of which is a 10-cm inside diameter, 6.1-m long tubular test vessel designed to permit detonation experiments at temperatures up to 700K, was employed to study self-sustained detonations in gaseous mixtures of hydrogen, air, and steam at temperatures between 300K and 650K at a fixed initial pressure of 0.1 MPa. Hydrogen-air mixtures with hydrogen composition from 9 to 60 percent by volume and steam fractions up to 35 percent by volume were studied for stoichiometric hydrogen-air-steam mixtures. Detonation cell size measurements provide clear evidence that the effect of hydrogen-air gas mixture temperature, in the range 300K-650K, is to decrease cell size and, hence, to increase the sensitivity of the mixture to undergo detonations. The effect of steam content, at any given temperature, is to increase the cell size and, thereby, to decrease the sensitivity of stoichiometric hydrogen-air mixtures. The hydrogen-air detonability limits for the 10-cm inside diameter SSDA test vessel, based upon the onset of single-head spin, decreased from 15 percent hydrogen at 300K down to between 9 and 10 percent hydrogen at 650K. The one-dimensional ZND model does a very good job at predicting the overall trends in the cell size data over the range of hydrogen-air-steam mixture compositions and temperature studied in the experiments

  17. Evaluation of the Mechanical Performance of Silicon Carbide in TRISO Fuel at High Temperatures

    International Nuclear Information System (INIS)

    Rohbeck, N.; Xiao, P.

    2014-01-01

    The HTR design envisions fuel operating temperatures of up to 1000°C and in case of an accident even 1600°C are conceivable. To ensure safety in all conditions a thorough understanding of the impact of an extreme temperature environment is necessary. This work assesses the high temperature mechanical performance of the silicon carbide (SiC) layer within the tristructural-isotropic (TRISO) fuel particle as it poses the main barrier against fission product release into the primary circuit. Therefore simulated fuel was fabricated by fluidized bed chemical vapour deposition; varying the deposition conditions resulted in strongly differing SiC microstructures for the various samples. Subsequently the TRISO particles were annealed in inert atmosphere at temperatures ranging from 1600°C up to 2200°C. Scanning electron microscopy and Raman spectroscopy showed that strong disintegration of the SiC layer occurred from 2100°C onwards, but initial signs of porosity formation were visible already at 1800°C. Still, the elastic modulus and hardness as measured by nanoindentation were hardly impaired. After annealing stoichiometric SiC coatings showed a reduction in fracture strength as determined by a modified crush test, however the actual annealing temperature from 1600°C to 2000°C had no measureable effect. Furthermore, a technique was developed to measure the elastic modulus and hardness in-situ up to 500°C using a high temperature nanoindentation facility. This approach allows conducting numerous tests on small sample volumes and thus promises to improve our knowledge of irradiation effects on the mechanical properties. For the SiC layer in TRISO particles it was found that the elastic modulus decreased slightly from room temperature up to 500°C, whereas the hardness was reduced more severely to approximately half of its ambient temperature value. (author)

  18. Study on the profitableness of electricity generation with high temperature reactors

    International Nuclear Information System (INIS)

    Kolb, G.

    1978-08-01

    The programme group 'Systemforschung und Technologische Entwicklung' (STE) of the Nuclear Research Centre Juelich in cooperation with the internal institutions 'Projekttraegerschaft Entwicklung von Hochtemperaturreaktoren' (PTH) and 'Institut fuer Reaktorentwicklung' (IRE) on the one hand, and the external partner 'Hochtemperatur-Reactorbau GmbH' (HRB) and 'Gesellschaft fuer Hochtemperaturreactor Technik' (GHT) on the other hand have set up a study on fuel cycle costs, electricity production cost and the economical use as well as uranium resource protection by introduction of high temperature reactors (HTR) with pebble bed core to generate electricity. The pressurized-water reactor (PWR) today on the market serves as comparison. The working results obtained sofar are compiled in the present report. It was particularly noted that - the HTR can economically fully compete with the PWR for electricity generation - the necessary supply of natural uranium for the HTR in open circuit is about one third lower and in the closed circuit, almost two thirds lower than in the corresponding PWR. A further reduction is possible on a long-term basis by highly converting HTW systems. (orig.) [de

  19. Bed models for solid fuel conversion process in grate-fired boilers

    DEFF Research Database (Denmark)

    Costa, M.; Massarotti, N.; Indrizzi, V.

    2013-01-01

    -chemical processes are divided in two successive sections: drying and conversion (which includes pyrolysis, gasification and combustion). The second model is an empirical 1D approach. The two models need input data such as composition, temperature and feeding rate of biomass and primary air. Temperature, species...... to describe the thermo-chemical conversion process of a solid fuel bed in a grate-fired boiler is presented. In this work both models consider the incoming solid fuel as subjected to drying, pyrolysis, gasification and combustion. In the first approach the biomass bed is treated as a 0D system, but the thermo...... concentrations and velocity of the producer gas leaving the fuel bed provided by the two models are compared. A sensitivity analysis with respect to mass flow rate of the primary air is also performed, as well as a further comparison regarding the dependence of the producer gas properties on the initial moisture...

  20. 7 CFR 2902.15 - Bedding, bed linens, and towels.

    Science.gov (United States)

    2010-01-01

    ... PROCUREMENT Designated Items § 2902.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that... minimum biobased content is 12 percent and shall be based on the amount of qualifying biobased carbon in..., and silk are not qualifying biobased feedstocks for the purpose of determining the biobased content of...