WorldWideScience

Sample records for bed model development

  1. Fluidized bed incinerator development

    International Nuclear Information System (INIS)

    A fluidized bed incinerator is being developed for burning rad contaminated solid and liquid waste materials. In situ neutralization of acid gases by the bed material, catalytic afterburning, and gas filtration are used to produce a clean flue gas without the use of aqueous scrubbing

  2. Development and testing of analytical models for the pebble bed type HTRs

    International Nuclear Information System (INIS)

    The pebble bed type gas cooled high temperature reactor (HTR) appears to be a good candidate for the next generation nuclear reactor technology. These reactors have unique characteristics in terms of the randomness in geometry, and require special techniques to analyze their systems. This study includes activities concerning the testing of computational tools and the qualification of models. Indeed, it is essential that the validated analytical tools be available to the research community. From this viewpoint codes like MCNP, ORIGEN and RELAP5, which have been used in nuclear industry for many years, are selected to identify and develop new capabilities needed to support HTR analysis. The geometrical model of the full reactor is obtained by using lattice and universe facilities provided by MCNP. The coupled MCNP-ORIGEN code is used to estimate the burnup and the refuelling scheme. Results obtained from Monte Carlo analysis are interfaced with RELAP5 to analyze the thermal hydraulics and safety characteristics of the reactor. New models and methodologies are developed for several past and present experimental and prototypical facilities that were based on HTR pebble bed concepts. The calculated results are compared with available experimental data and theoretical evaluations showing very good agreement. The ultimate goal of the validation of the computer codes for pebble bed HTR applications is to acquire and reinforce the capability of these general purpose computer codes for performing HTR core design and optimization studies

  3. Process development and modeling of fluidized-bed reactor with coimmobilized biocatalyst for fuel ethanol production

    Science.gov (United States)

    Sun, May Yongmei

    This research focuses on two steps of commercial fuel ethanol production processes: the hydrolysis starch process and the fermentation process. The goal of this research is to evaluate the performance of co-immobilized biocatalysts in a fluidized bed reactor with emphasis on economic and engineering aspects and to develop a predictive mathematical model for this system. The productivity of an FBR is higher than productivity of a traditional batch reactor or CSTR. Fluidized beds offer great advantages over packed beds for immobilized cells when small particles are used or when the reactant feed contains suspended solids. Plugging problems, excessive pressure drops (and thus attrition), or crushing risks may be avoided. No mechanical stirring is required as mixing occurs due to the natural turbulence in the fluidized process. Both enzyme and microorganism are immobilized in one catalyst bead which is called co-immobilization. Inside this biocatalyst matrix, starch is hydrolyzed by the enzyme glucoamylase to form glucose and then converted to ethanol and carbon dioxide by microorganisms. Two biocatalysts were evaluated: (1) co-immobilized yeast strain Saccharomyces cerevisiae and glucoamylase. (2) co-immobilized Zymomonas mobilis and glucoamylase. A co-immobilized biocatalyst accomplishes the simultaneous saccharification and fermentation (SSF process). When compared to a two-step process involving separate saccharification and fermentation stages, the SSF process has productivity values twice that given by the pre-saccharified process when the time required for pre-saccharification (15--25 h) was taken into account. The SSF process should also save capital cost. The information about productivity, fermentation yield, concentration profiles along the bed, ethanol inhibition, et al., was obtained from the experimental data. For the yeast system, experimental results showed that: no apparent decrease of productivity occurred after two and half months, the productivity

  4. Dynamic model development and validation for a nitrifying moving bed biofilter: Effect of temperature and influent load on the performance

    DEFF Research Database (Denmark)

    Sin, Gürkan; Weijma, Jan; Spanjers, Henri;

    2008-01-01

    A mathematical model with adequate complexity integrating hydraulics, biofilm and microbial conversion processes is successfully developed for a continuously moving bed biofilter performing tertiary nitrification. The model was calibrated and validated using data from Nether Stowey pilot plant in...... hydraulic loading had relatively negligible impact. Overall, the calibrated model can now reliably be used for design and process optimization purposes....

  5. Biomass Torrefaction Process Review and Moving Bed Torrefaction System Model Development

    Energy Technology Data Exchange (ETDEWEB)

    Jaya Shakar Tumuluru; Shahab Sokhansanj; Christopher T. Wright; Richard D. Boardman

    2010-08-01

    Torrefaction is currently developing as an important preprocessing step to improve the quality of biomass in terms of physical properties, and proximate and ultimate composition. Torrefaction is a slow heating of biomass in an inert or reduced environment to a maximum temperature of 300 C. Torrefaction can also be defined as a group of products resulting from the partially controlled and isothermal pyrolysis of biomass occurring in a temperature range of 200-230 C and 270-280 C. Thus, the process can also be called a mild pyrolysis as it occurs at the lower temperature range of the pyrolysis process. At the end of the torrefaction process, a solid uniform product with lower moisture content and higher energy content than raw biomass is produced. Most of the smoke-producing compounds and other volatiles are removed during torrefaction, producing a final product that will have a lower mass but a higher heating value. An important aspect of research is to establish a degree of torrefaction where gains in heating value offset the loss of mass. There is a lack of literature on torrefaction reactor designs and a design sheet for estimating the dimensions of the torrefier based on capacity. This study includes (a) conducting a detailed review on the torrefaction of biomass in terms of understanding the process, product properties, off-gas compositions, and methods used, and (b) to design a moving bed torrefier, taking into account the basic fundamental heat and mass transfer calculations. Specific objectives include calculating the dimensions like diameter and height of the moving packed bed for different capacities, designing the heat loads and gas flow rates, and developing an interactive excel sheet where the user can define design specifications. In this report, 25-1000 kg/hr are used in equations for the design of the torrefier, examples of calculations, and specifications for the torrefier.

  6. Biomass Torrefaction Process Review and Moving Bed Torrefaction System Model Development

    Energy Technology Data Exchange (ETDEWEB)

    Jaya Shakar Tumuluru; Shahab Sokhansanj; Christopher T. Wright

    2010-08-01

    Torrefaction is currently developing as an important preprocessing step to improve the quality of biomass in terms of physical properties, and proximate and ultimate composition. Torrefaction is a slow heating of biomass in an inert or reduced environment to a maximum temperature of 300°C. Torrefaction can also be defined as a group of products resulting from the partially controlled and isothermal pyrolysis of biomass occurring in a temperature range of 200–230ºC and 270–280ºC. Thus, the process can also be called a mild pyrolysis as it occurs at the lower temperature range of the pyrolysis process. At the end of the torrefaction process, a solid uniform product with lower moisture content and higher energy content than raw biomass is produced. Most of the smoke-producing compounds and other volatiles are removed during torrefaction, producing a final product that will have a lower mass but a higher heating value. An important aspect of research is to establish a degree of torrefaction where gains in heating value offset the loss of mass. There is a lack of literature on torrefaction reactor designs and a design sheet for estimating the dimensions of the torrefier based on capacity. This study includes a) conducting a detailed review on the torrefaction of biomass in terms of understanding the process, product properties, off-gas compositions, and methods used, and b) to design a moving bed torrefier, taking into account the basic fundamental heat and mass transfer calculations. Specific objectives include calculating the dimensions like diameter and height of the moving packed bed for different capacities, designing the heat loads and gas flow rates, and developing an interactive excel sheet where the user can define design specifications. In this report, 25–1000 kg/hr are used in equations for the design of the torrefier, examples of calculations, and specifications for the torrefier.

  7. Modelling of Devolatilization in Fluidized Bed Combustion

    DEFF Research Database (Denmark)

    Stenseng, Mette; Lin, Weigang; Johnsson, Jan Erik;

    1997-01-01

    A mathematical model is developed to describe the devolatilization process in a circulating fluidized bed combustor. The model is a combination of two submodels: single particle devolatilization and fluid dynamics. The single particle model includes the influence of both chemical kinetics and hea...

  8. Development of a simulation tool based on a segregated model to optimize the design and the scale up of animal cell culture in fixed-bed bioreactor [abstract

    OpenAIRE

    Gelbgras, V.; Drugmand, JC.; Haut, B

    2010-01-01

    The fixed-bed bioreactor is a promising system for the process intensification of the adherent animal cell culture. Nevertheless the fixed-bed bioreactor presents heterogeneity of the cell and the species concentrations which can complicate its optimization and its scale-up. The aim of this work is to develop a mathematical model of the evolution of the cell concentration and the species concentrations to study the process optimization and the bioreactor scale-up. The developed model is used ...

  9. Energy recovery by gasification of agricultural and forestry wastes in fluidized bed reactors and in moving bed reactors with internal recycle of pyrolysis gas; process development and reactor modelling. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Aarsen, F.G. van den; Susanto, H.; Beenackers, A.A.C.M.; Swaaij, W.P.M. van

    1986-01-01

    A modified co-current moving gasifier bed has been developed which substantially reduces product gas tar content compared to conventional down draft gasifiers and allows for a better scale-up of the reactor. These improvements have been realized by installing an ejector in the air inlet which sucks the pyrolysis gases into the gasifying air stream and allows for subsequent combustion of the pyrolysis products in a separate combustor. In relation to the modelling of a fluidized bed biomass gasifier, we studied the fast pyrolysis of beech wood particles and the char-carbondioxide gasification kinetics in a bench scale fluidized bed reactor. A 30 cm diameter fluidized bed biomass gasifier has been constructed and the reactor performance on wood and rice husks has been studied. Those experiments (at 50 kg biomass/hr) revealed that a good gas quality is produced if the reactor is operated above 800/sup 0/ C, in the co-current mode (bottomfeed). Ongoing research is on mass transfer and flow behaviour in the fluidized bed reactor; a mathematical model of the fluidized bed gasifier is under development.

  10. Modeling biomass gasification in circulating fluidized beds

    Science.gov (United States)

    Miao, Qi

    In this thesis, the modeling of biomass gasification in circulating fluidized beds was studied. The hydrodynamics of a circulating fluidized bed operating on biomass particles were first investigated, both experimentally and numerically. Then a comprehensive mathematical model was presented to predict the overall performance of a 1.2 MWe biomass gasification and power generation plant. A sensitivity analysis was conducted to test its response to several gasifier operating conditions. The model was validated using the experimental results obtained from the plant and two other circulating fluidized bed biomass gasifiers (CFBBGs). Finally, an ASPEN PLUS simulation model of biomass gasification was presented based on minimization of the Gibbs free energy of the reaction system at chemical equilibrium. Hydrodynamics plays a crucial role in defining the performance of gas-solid circulating fluidized beds (CFBs). A 2-dimensional mathematical model was developed considering the hydrodynamic behavior of CFB gasifiers. In the modeling, the CFB riser was divided into two regions: a dense region at the bottom and a dilute region at the top of the riser. Kunii and Levenspiel (1991)'s model was adopted to express the vertical solids distribution with some other assumptions. Radial distributions of bed voidage were taken into account in the upper zone by using Zhang et al. (1991)'s correlation. For model validation purposes, a cold model CFB was employed, in which sawdust was transported with air as the fluidizing agent. A comprehensive mathematical model was developed to predict the overall performance of a 1.2 MWe biomass gasification and power generation demonstration plant in China. Hydrodynamics as well as chemical reaction kinetics were considered. The fluidized bed riser was divided into two distinct sections: (a) a dense region at the bottom of the bed where biomass undergoes mainly heterogeneous reactions and (b) a dilute region at the top where most of homogeneous

  11. Rotary Bed Reactor for Chemical-Looping Combustion with Carbon Capture. Part 1: Reactor Design and Model Development

    KAUST Repository

    Zhao, Zhenlong

    2013-01-17

    Chemical-looping combustion (CLC) is a novel and promising technology for power generation with inherent CO2 capture. Currently, almost all of the research has been focused on developing CLC-based interconnected fluidized-bed reactors. In this two-part series, a new rotary reactor concept for gas-fueled CLC is proposed and analyzed. In part 1, the detailed configuration of the rotary reactor is described. In the reactor, a solid wheel rotates between the fuel and air streams at the reactor inlet and exit. Two purging sectors are used to avoid the mixing between the fuel stream and the air stream. The rotary wheel consists of a large number of channels with copper oxide coated on the inner surface of the channels. The support material is boron nitride, which has high specific heat and thermal conductivity. Gas flows through the reactor at elevated pressure, and it is heated to a high temperature by fuel combustion. Typical design parameters for a thermal capacity of 1 MW have been proposed, and a simplified model is developed to predict the performances of the reactor. The potential drawbacks of the rotary reactor are also discussed. © 2012 American Chemical Society.

  12. DEVELOPMENT OF AN EXPERIMENTAL TEST BED DESIGNATED FOR MODEL STUDIES OF AERODYNAMICS OF PREMISES USING METHOD OF DIGITAL FLOW VISUALIZATION

    Directory of Open Access Journals (Sweden)

    Varapaev Vladimir Nikolaevich

    2012-12-01

    Full Text Available In the article, the authors present their findings generated at the laboratory of aerodynamic and aero-acoustic testing of structural units of MGSU. The authors provide information about the principle of operation and a brief description of the experimental test bed designated for the physical research of patterns of air flows arising inside building premises of various geometric shapes. The authors also demonstrate the basic parameters of the test bed, the principle of operation of its recording devices and some of its characteristics. The test bed is designated for the identification of characteristics of three-dimensional flows of models under research and for the verification of results of numerical studies. The measurement bed has advanced measurement and registration units. The management principle is based on the method of digital flow visualization, PIV method and Doppler flow meter implemented in the LDA anemometer. The test stand generates two or three component vector fields of turbulent gas flow velocities. It may be applicable to the study of liquids in case of research of hydraulics-related problems. Some results of the flow study are provided in the article, as well.

  13. Modeling Changes in Bed Surface Texture and Aquatic Habitat Caused by Run-of-River Hydropower Development

    Science.gov (United States)

    Fuller, T. K.; Venditti, J. G.; Nelson, P. A.; Popescu, V.; Palen, W.

    2014-12-01

    Run-of-river (RoR) hydropower has emerged as an important alternative to large reservoir-based dams in the renewable energy portfolios of China, India, Canada, and other areas around the globe. RoR projects generate electricity by diverting a portion of the channel discharge through a large pipe for several kilometers downhill where it is used to drive turbines before being returned to the channel. Individual RoR projects are thought to be less disruptive to local ecosystems than large hydropower because they involve minimal water storage, more closely match the natural hydrograph downstream of the project, and are capable of bypassing trapped sediment. However, there is concern that temporary sediment supply disruption may degrade the productivity of salmon spawning habitat downstream of the dam by causing changes in the grain size distribution of bed surface sediment. We hypothesize that salmon populations will be most susceptible to disruptions in sediment supply in channels where; 1) sediment supply is high relative to transport capacity prior to RoR development, and 2) project design creates substantial sediment storage volume. Determining the geomorphic effect of RoR development on aquatic habitat requires many years of field data collection, and even then it can be difficult to link geomorphic change to RoR development alone. As an alternative, we used a one-dimensional morphodynamic model to test our hypothesis across a range of pre-development sediment supply conditions and sediment storage volumes. Our results confirm that coarsening of the median surface grain-size is greatest in cases where pre-development sediment supply was highest and sediment storage volumes were large enough to disrupt supply over the course of the annual hydrograph or longer. In cases where the pre-development sediment supply is low, coarsening of the median surface grain-size is less than 2 mm over a multiple-year disruption period. When sediment supply is restored, our results

  14. Hydrodynamic modeling of a circulating fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Afsin Gungor; Nurdil Eskin [Istanbul Technical University, Istanbul (Turkey). Mechanical Engineering Faculty

    2007-03-15

    Hydrodynamics plays a crucial role in defining the performance of circulating fluidized beds (CFB). The numerical simulation of CFBs is very important in the prediction of its flow behavior. From this point of view, in the present study a dynamic two dimensional model is developed considering the hydrodynamic behavior of CFB. In the modeling, the CFB riser is analyzed in two regions: The bottom zone in turbulent fluidization regime is modeled in detail as two-phase flow which is subdivided into a solid-free bubble phase and a solid-laden emulsion phase. In the upper zone core-annulus solids flow structure is established. Simulation model takes into account the axial and radial distribution of voidage, velocity and pressure drop for gas and solid phase, and solids volume fraction and particle size distribution for solid phase. The model results are compared with and validated against atmospheric cold bed CFB units' experimental data given in the literature for axial and radial distribution of void fraction, solids volume fraction and particle velocity, total pressure drop along the bed height and radial solids flux.

  15. Development of a simulation tool based on a segregated model to optimize the design and the scale up of animal cell culture in fixed-bed bioreactor [abstract

    Directory of Open Access Journals (Sweden)

    Gelbgras, V.

    2010-01-01

    Full Text Available The fixed-bed bioreactor is a promising system for the process intensification of the adherent animal cell culture. Nevertheless the fixed-bed bioreactor presents heterogeneity of the cell and the species concentrations which can complicate its optimization and its scale-up. The aim of this work is to develop a mathematical model of the evolution of the cell concentration and the species concentrations to study the process optimization and the bioreactor scale-up. The developed model is used as a simulation tool to study the influence of different phenomena on the cell heterogeneity. In this work, the importance of the adherent phase is investigated. This phase takes place in the beginning of the process. To realize a good implementation of the process, it is important to control the adherent cell concentration and to minimize the heterogeneity during this phase. If cell concentration heterogeneity appears, it will have repercussions during the whole process. In the model, four cell populations are considered: the viable cells in suspension in the medium, the captured cells by the fixed-bed in suspension in the medium, the adherent cells on the fixed-bed and the dead cells in suspension in the medium. Five extracellular species are considered: glucose, glutamine, oxygen, ammonia and lactate. Five phenomena are modeled: the culture medium flow through the fixed-bed (with axial convection, radial dispersion and axial dispersion, the cell capture by the fixed-bed, the cell adherence on the fixed-bed, the cell growth with a maximal cell concentration imposed by the specific area of the fixed-bed and the cell death. The interaction between cells and species is modeled by a Monod equation for the specific growth rate. The model equations are solved with a routine developed with Matlab 6.5. This routine used the Finite Volume Method coupled with a Newton-Raphson algorithm. The model parameters are experimentally identified by cell cultures in a pilot

  16. Pebble Bed Reactor Dust Production Model

    International Nuclear Information System (INIS)

    The operation of pebble bed reactors, including fuel circulation, can generate graphite dust, which in turn could be a concern for internal components; and to the near field in the remote event of a break in the coolant circuits. The design of the reactor system must, therefore, take the dust into account and the operation must include contingencies for dust removal and for mitigation of potential releases. Such planning requires a proper assessment of the dust inventory. This paper presents a predictive model of dust generation in an operating pebble bed with recirculating fuel. In this preliminary work the production model is based on the use of the assumption of proportionality between the dust production and the normal force and distance traveled. The model developed in this work uses the slip distances and the inter-pebble forces computed by the authors PEBBLES. The code, based on the discrete element method, simulates the relevant static and kinetic friction interactions between the pebbles as well as the recirculation of the pebbles through the reactor vessel. The interaction between pebbles and walls of the reactor vat is treated using the same approach. The amount of dust produced is proportional to the wear coefficient for adhesive wear (taken from literature) and to the slip volume, the product of the contact area and the slip distance. The paper will compare the predicted volume with the measured production rates. The simulation tallies the dust production based on the location of creation. Two peak production zones from intra pebble forces are predicted within the bed. The first zone is located near the pebble inlet chute due to the speed of the dropping pebbles. The second peak zone occurs lower in the reactor with increased pebble contact force due to the weight of supported pebbles. This paper presents the first use of a Discrete Element Method simulation of pebble bed dust production

  17. Fluid bed porosity mathematical model for an inverse fluidized bed bioreactor with particles growing biofilm.

    Science.gov (United States)

    Campos-Díaz, K E; Bandala-González, E R; Limas-Ballesteros, R

    2012-08-15

    A new mathematic model to estimate bed porosity as a function of Reynolds and Archimedes numbers was developed based in experimental data. Experiments were performed using an inverse fluidized bed bioreactor filled with polypropylene particles, Lactobacillus acidophillus as the immobilized strain and fluidized with a Man-Rogosa-Sharpe culture medium under controlled temperature and pH conditions. Bed porosity was measured at different flow rates, starting from 0.95 to 9.5 LPM. The new model has several advantages when compared with previously reported. Among them, advantages such as standard deviation values ≤ 1% between experimental and calculated bed porosity, its applicability in traditional and inverse fluidization, wall effects do not take account, it gives excellent agreement with spherical particles with or without biofilm, and inertial drag coefficient allow extend the new model a non-spherical particles. PMID:22484706

  18. Review on Biomass Torrefaction Process and Product Properties and Design of Moving Bed Torrefaction System Model Development

    Energy Technology Data Exchange (ETDEWEB)

    Jaya Shankar Tumuluru; Christopher T. Wright; Shahab Sokhansanj

    2011-08-01

    A Review on Torrefaction Process and Design of Moving Bed Torrefaction System for Biomass Processing Jaya Shankar Tumuluru1, Shahab Sokhansanj2 and Christopher T. Wright1 Idaho National Laboratory Biofuels and Renewable Energy Technologies Department Idaho Falls, Idaho 83415 Oak Ridge National Laboratory Bioenergy Resource and Engineering Systems Group Oak Ridge, TN 37831 Abstract Torrefaction is currently developing as an important preprocessing step to improve the quality of biomass in terms of physical properties, and proximate and ultimate composition. Torrefaction is a slow heating of biomass in an inert or reduced environment to a maximum temperature of 300 C. Torrefaction can also be defined as a group of products resulting from the partially controlled and isothermal pyrolysis of biomass occurring in a temperature range of 200-230 C and 270-280 C. Thus, the process can also be called a mild pyrolysis as it occurs at the lower temperature range of the pyrolysis process. At the end of the torrefaction process, a solid uniform product with lower moisture content and higher energy content than raw biomass is produced. Most of the smoke-producing compounds and other volatiles are removed during torrefaction, which produces a final product that will have a lower mass but a higher heating value. There is a lack of literature on the design aspects of torrefaction reactor and a design sheet for estimating the dimensions of the torrefier based on capacity. This study includes (a) conducting a detailed review on the torrefaction of biomass in terms of understanding the process, product properties, off-gas compositions, and methods used, and (b) to design a moving bed torrefier, taking into account the basic fundamental heat and mass transfer calculations. Specific objectives include calculating the dimensions like diameter and height of the moving packed bed torrefier for different capacities ranging from 25-1000 kg/hr, designing the heat loads and gas flow rates, and

  19. Improved computational model (AQUIFAS) for activated sludge, integrated fixed-film activated sludge, and moving-bed biofilm reactor systems, Part I: Semi-empirical model development.

    Science.gov (United States)

    Sen, Dipankar; Randall, Clifford W

    2008-05-01

    Research was undertaken to develop a model for activated sludge, integrated fixed-film activated sludge (IFAS), and moving-bed biofilm reactor (MBBR) systems. The model can operate with up to 12 cells (reactors) in series, with biofilm media incorporated to one or more cells, except the anaerobic cells. The process configuration can be any combination of anaerobic, anoxic, aerobic, post-anoxic with or without supplemental carbon, and reaeration; it can also include any combination of step feed and recycles, including recycles for mixed liquor, return activated sludge, nitrates, and membrane bioreactors. This paper presents the structure of the model. The model embeds a biofilm model into a multicell activated sludge model. The biofilm flux rates for organics, nutrients, and biomass can be computed by two methods--a semi-empirical model of the biofilm that is relatively simpler, or a diffusional model that is computationally intensive. The values of the kinetic parameters for the model were measured using pilot-scale activated sludge, IFAS, and MBBR systems. For the semiempirical version, a series of Monod equations were developed for chemical oxygen demand, ammonium-nitrogen, and oxidized-nitrogen fluxes to the biofilm. Within the equations, a second Monod expression is used to simulate the effect of changes in biofilm thickness and fraction nitrifiers in the biofilm. The biofilm flux model is then linked to the activated sludge model. The diffusional model and the verification of the models are presented in subsequent papers (Sen and Randall, 2008a, 2008b). The model can be used to quantify the amount of media and surface area required to achieve nitrification, identify the best locations for the media, and optimize the dissolved oxygen levels and nitrate recycle rates. Some of the advanced features include the ability to apply different media types and fill fractions in cells; quantify nitrification, denitrification, and biomass production in the biofilm and

  20. Moving granular-bed filter development program. Topical report

    Energy Technology Data Exchange (ETDEWEB)

    Newby, R.A.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1994-04-01

    Advanced, coal-based, power plants, such as IGCC and Advanced-PFBC, are currently nearing commercial demonstration. These power plant technologies require hot gas filtration as part of their gas cleaning trains. Ceramic barrier filters are the major filter candidates being developed for these hot gas cleaning applications. While ceramic barrier filters achieve high levels of particle removal, concerns exist for their reliability and operability in these applications. An alternative hot gas filtration technology is the moving granular bed filter. An advanced, moving granular bed filter has been conceived, and early development activities performed by the Westinghouse Electric Corporation, Science and Technology Center. This document reports on the Base Contract tasks performed to resolve the barrier technical issues for this technology. The concept, the Standleg Moving Granular Bed Filter (SMGBF) has a concurrent downward, gas and bed media flow configuration that results in simplified features and improved scaleup feasibility compared to alternative designs. Two modes of bed media operation were assessed in the program: once-through using pelletized power plant waste as bed media, and recycle of bed media via standleg and pneumatic transport techniques. Cold Model testing; high-temperature, high-pressure testing; and pelletization testing using advanced power plant wastes, have been conducted in the program. A commercial, economic assessment of the SMGBF technology was performed for IGCC and Advanced-PFBC applications. The evaluation shows that the barrier technical issues can be resolved, and that the technology is potentially competitive with ceramic barrier filters.

  1. Modeling downstream fining in sand-bed rivers. I: Formulation

    Science.gov (United States)

    Wright, S.; Parker, G.

    2005-01-01

    In this paper a numerical modeling formulation is presented for simulation of the development of the longitudinal profile and bed sediment distribution in sand-bed rivers. The objective of the model application, which is presented in the companion paper (Wright and Parker, 2005), is to study the development of two characteristics of large, low-slope, sand-bed rivers: (1) a downstream decrease in bed slope (i.e. concave upward longitudinal profile) and (2) a downstream decrease in characteristic bed sediment diameter (e.g. the median bed surface size D50). Three mechanisms that lead to an upward concave profile and downstream fining are included in the modeling formulation: (1) a delta prograding into standing water at the downstream boundary, (2) sea-level rise, and (3) tectonic subsidence. In the companion paper (Wright and Parker, 2005) the model is applied to simulate the development of the longitudinal profile and downstream fining in sand-bed rivers flowing into the ocean during the past 5000 years of relatively slow sea-level rise. ?? 2005 International Association of Hydraulic Engineering and Research.

  2. Model of Fluidized Bed Containing Reacting Solids and Gases

    Science.gov (United States)

    Bellan, Josette; Lathouwers, Danny

    2003-01-01

    A mathematical model has been developed for describing the thermofluid dynamics of a dense, chemically reacting mixture of solid particles and gases. As used here, "dense" signifies having a large volume fraction of particles, as for example in a bubbling fluidized bed. The model is intended especially for application to fluidized beds that contain mixtures of carrier gases, biomass undergoing pyrolysis, and sand. So far, the design of fluidized beds and other gas/solid industrial processing equipment has been based on empirical correlations derived from laboratory- and pilot-scale units. The present mathematical model is a product of continuing efforts to develop a computational capability for optimizing the designs of fluidized beds and related equipment on the basis of first principles. Such a capability could eliminate the need for expensive, time-consuming predesign testing.

  3. Development of standardized air-blown coal gasifier/gas turbine concepts for future electric power systems. Volume 2, Appendix A: Fixed bed gasifier and sulfur sorbent regeneration subsystem computer model development: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Blough, E.; Russell, W.; Leach, J.W.

    1990-08-01

    Computer models have been developed for evaluating conceptual designs of integrated coal gasification combined cycle power plants. An overall system model was developed for performing thermodynamic cycle analyses, and detailed models were developed for predicting performance characteristics of fixed bed coal gasifiers and hot gas clean up subsystem components. The overall system model performs mass and energy balances and does chemical equilibrium analyses to determine the effects of changes in operating conditions, or to evaluate proposed design changes. An existing plug flow model for fixed bed gasifiers known as the Wen II model was revised and updated. Also, a spread sheet model of zinc ferrite sulfur sorbent regeneration subsystem was developed. Parametric analyses were performed to determine how performance depends on variables in the system design. The work was done to support CRS Sirrine Incorporated in their study of standardized air blown coal gasifier gas turbine concepts.

  4. DEVELOPMENT OF AN EXPERIMENTAL TEST BED DESIGNATED FOR MODEL STUDIES OF AERODYNAMICS OF PREMISES USING METHOD OF DIGITAL FLOW VISUALIZATION

    OpenAIRE

    Varapaev Vladimir Nikolaevich; Doroshenko Sergey Aleksandrovich; Kapustin Sergey Aleksandrovich; Orekhov Genrikh Vasil'evich; Churin Pavel Sergeevich

    2012-01-01

    In the article, the authors present their findings generated at the laboratory of aerodynamic and aero-acoustic testing of structural units of MGSU. The authors provide information about the principle of operation and a brief description of the experimental test bed designated for the physical research of patterns of air flows arising inside building premises of various geometric shapes. The authors also demonstrate the basic parameters of the test bed, the principle of operation of its recor...

  5. Analysis of Operation Parameters in a Dual Fluidized Bed Biomass Gasifier Integrated with a Biomass Rotary Dryer: Development and Application of a System Model

    Directory of Open Access Journals (Sweden)

    Nargess Puadian

    2014-07-01

    Full Text Available An integrated system model was developed in UniSim Design for a dual fluidized bed (DFB biomass gasifier and a rotary biomass dryer using a combination of user-defined and built-in unit operations. A quasi-equilibrium model was used for modelling biomass steam gasification in the DFB gasifier. The biomass drying was simulated with consideration of mass and energy balances, heat transfer, and dryer’s configuration. After validation using experimental data, the developed system model was applied to investigate: (1 the effects of gasification temperature and steam to biomass (S/B ratio on the gasification performance; (2 the effect of air supplied to the fast fluidized bed (FFB reactor and feed biomass moisture content on the integrated system performance, energy and exergy efficiencies. It was found that gasification temperature and S/B ratio have positive effects on the gasification yields; a H2/CO ratio of 1.9 can be achieved at the gasification temperature of 850 °C with a S/B ratio of 1.2. Consumption of excessive fuel in the system at higher biomass feed moisture content can be compensated by the heat recovery such as steam generation while it has adverse impact on exergy efficiency of the system.

  6. Pulse Detonation Engine Test Bed Developed

    Science.gov (United States)

    Breisacher, Kevin J.

    2002-01-01

    A detonation is a supersonic combustion wave. A Pulse Detonation Engine (PDE) repetitively creates a series of detonation waves to take advantage of rapid burning and high peak pressures to efficiently produce thrust. NASA Glenn Research Center's Combustion Branch has developed a PDE test bed that can reproduce the operating conditions that might be encountered in an actual engine. It allows the rapid and cost-efficient evaluation of the technical issues and technologies associated with these engines. The test bed is modular in design. It consists of various length sections of both 2- and 2.6- in. internal-diameter combustor tubes. These tubes can be bolted together to create a variety of combustor configurations. A series of bosses allow instrumentation to be inserted on the tubes. Dynamic pressure sensors and heat flux gauges have been used to characterize the performance of the test bed. The PDE test bed is designed to utilize an existing calorimeter (for heat load measurement) and windowed (for optical access) combustor sections. It uses hydrogen as the fuel, and oxygen and nitrogen are mixed to simulate air. An electronic controller is used to open the hydrogen and air valves (or a continuous flow of air is used) and to fire the spark at the appropriate times. Scheduled tests on the test bed include an evaluation of the pumping ability of the train of detonation waves for use in an ejector and an evaluation of the pollutants formed in a PDE combustor. Glenn's Combustion Branch uses the National Combustor Code (NCC) to perform numerical analyses of PDE's as well as to evaluate alternative detonative combustion devices. Pulse Detonation Engine testbed.

  7. Computational fluid dynamic modeling of fluidized-bed polymerization reactors

    Energy Technology Data Exchange (ETDEWEB)

    Rokkam, Ram [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    Polyethylene is one of the most widely used plastics, and over 60 million tons are produced worldwide every year. Polyethylene is obtained by the catalytic polymerization of ethylene in gas and liquid phase reactors. The gas phase processes are more advantageous, and use fluidized-bed reactors for production of polyethylene. Since they operate so close to the melting point of the polymer, agglomeration is an operational concern in all slurry and gas polymerization processes. Electrostatics and hot spot formation are the main factors that contribute to agglomeration in gas-phase processes. Electrostatic charges in gas phase polymerization fluidized bed reactors are known to influence the bed hydrodynamics, particle elutriation, bubble size, bubble shape etc. Accumulation of electrostatic charges in the fluidized-bed can lead to operational issues. In this work a first-principles electrostatic model is developed and coupled with a multi-fluid computational fluid dynamic (CFD) model to understand the effect of electrostatics on the dynamics of a fluidized-bed. The multi-fluid CFD model for gas-particle flow is based on the kinetic theory of granular flows closures. The electrostatic model is developed based on a fixed, size-dependent charge for each type of particle (catalyst, polymer, polymer fines) phase. The combined CFD model is first verified using simple test cases, validated with experiments and applied to a pilot-scale polymerization fluidized-bed reactor. The CFD model reproduced qualitative trends in particle segregation and entrainment due to electrostatic charges observed in experiments. For the scale up of fluidized bed reactor, filtered models are developed and implemented on pilot scale reactor.

  8. Stochastic modeling in sediment dynamics: Exner equation for planar bed incipient bed load transport conditions

    Science.gov (United States)

    Ancey, Christophe

    2010-06-01

    Even under flow equilibrium conditions, river bed topography continuously evolves with time, producing trains of irregular bed forms. The idea has recently emerged that the variability in the bed form geometry results from some randomness in sediment flux. In this paper, we address this issue by using the Exner equation and a population exchange model derived in an earlier paper. In this model, particle entrainment and deposition are idealized as population exchanges between the stream and the bed, which makes it possible to use birth-death Markov process theory to track the number of moving grains. The paper focuses on nascent bed forms on initially planar beds, a situation in which the coupling between the stream and bed is weak. In a steady state, the number of moving particles follows a negative binomial distribution. Although this probability distribution does not enter the family of heavy-tailed distributions, it may give rise to large and frequent fluctuations because the standard deviation can be much larger than the mean, a feature that is not accounted for with classic probability laws (e.g., Hamamori's law) used so far for describing bed load fluctuations. In the large-system limit, the master equation of the birth-death Markov process can be transformed into a Fokker-Planck equation. This transformation is used here to show that the number of moving particles can be described as an Ornstein-Uhlenbeck process. An important consequence is that in the long term, the number of moving particles follows a Gaussian distribution. Laboratory experiments show that this approximation is correct when the mean number per unit length of stream, ?/L, is sufficiently large (typically two particles per centimeter in our experiments). The particle number fluctuations give rise to bed elevation fluctuations, whose spectrum falls off like ω-2 in the high-frequency regime (with ω the angular frequency) and variance grows linearly with time. These features are in agreement

  9. A numerical model of gas-fluidized beds

    NARCIS (Netherlands)

    Kuipers, J.A.M.; Duin, van K.J.; Beckum, van F.P.H.; Swaaij, van W.P.M.

    1992-01-01

    A first-principles model for gas-fluidized bed based on the so-called "two-fluid model" (TFM) has been developed. In the TFM approach, both phases are considered to be continuous and fully interpenetrating. The equations of mass, momentum and thermal energy conservation, supplemented with the necess

  10. Modeling particle population balances in fluidized-bed wood gasifiers

    International Nuclear Information System (INIS)

    An unsteady model is developed for the particle size distribution in fluidized-bed reactors including fragmentation, abrasion, elutriation and the chemical reactions of wood gasification. Based on the assumption of constant conditions (gas composition, temperature, velocity) of the surrounding atmosphere, an analytical solution is developed for the distribution of sizes belonging to the classes of mother and fine particles. It is found that for the typical feed sizes (minimum above 3 × 10−2 mm) and the usual maximum size of fine particles (2.4 × 10−3 mm), the behavior of fine particles is quasi-steady with respect to mother particles. The numerical solution of the quasi-steady formulation of particle population balances is also coupled with a two-phase (bubble and emulsion), three-zone (bed, splash zone and freeboard) model for a bubbling fluidized-bed reactor, giving predictions of the producer gas composition in agreement with measurements for air gasification of wood. - Highlights: • Particle size distribution in fluidized-bed gasifiers is modeled. • Fragmentation, abrasion, elutriation and the chemical reactions of wood gasification are described. • A quasi-steady behavior of the fine particles with respect to mother particles is found. • The particle size distribution model is coupled with a transport model for a bubbling fluidized bed. • Good agreement is obtained between measurements and predictions for highly variable operating conditions

  11. Modeling and field observations of char bed processes in black liquor recovery boilers

    Energy Technology Data Exchange (ETDEWEB)

    Engblom, M.

    2010-07-01

    The char bed plays an important role in kraft black liquor combustion. Stable operation of the char bed promotes efficient and safe operation of the black liquor recovery boiler. It also plays a crucial role in the recovery of the pulping chemicals. Char bed operation involves controlling the char bed size and shape. Mathematical modeling based on computational fluid dynamics (CFD) haas been applied to recovery boilers for increased insights into the recovery furnace processes and to aid in the design of new boilers. So far, all CED-based char bed models reported in literature have used a fixed bed shape. This imposes restrictions on simulation of char bed burning by not considering inherently occurring changes in bed shape. In this thesis, a CED -based recovery furnace model is further developed to predict changes in bed shape. The new model is used in simulation of existing recovery boilers. The predictions of bed shape are compared with observations from real boilers. The furnace model is capable of correctly simulating the overall response of the char bed size to operational changes. This confirms the current quantitative overall understanding of char bed burning. In addition to modeling, visual observations of the char bed processes were made in this work. The observations provide validation data concerning the physical behavior of the char bed, and the findings from the observations can be used in further development of char bed models. Modeling and simulations of fundamental laboratory scale char bed experiments reported in literature are also carried out. The simulations complement the experimental data by providing detailed insights into gas phase reactions that can occur inside the gas boundary layer above a char bed. (orig.)

  12. Development of the Packed Bed Reactor ISS Flight Experiment

    Science.gov (United States)

    Patton, Martin O.; Bruzas, Anthony E.; Rame, Enrique; Motil, Brian J.

    2012-01-01

    Packed bed reactors are compact, require minimum power and maintenance to operate, and are highly reliable. These features make this technology a leading candidate as a potential unit operation in support of long duration human space exploration. On earth, this type of reactor accounts for approximately 80% of all the reactors used in the chemical process industry today. Development of this technology for space exploration is truly crosscutting with many other potential applications (e.g., in-situ chemical processing of planetary materials and transport of nutrients through soil). NASA is developing an ISS experiment to address this technology with particular focus on water reclamation and air revitalization. Earlier research and development efforts funded by NASA have resulted in two hydrodynamic models which require validation with appropriate instrumentation in an extended microgravity environment. The first model developed by Motil et al., (2003) is based on a modified Ergun equation. This model was demonstrated at moderate gas and liquid flow rates, but extension to the lower flow rates expected in many advanced life support systems must be validated. The other model, developed by Guo et al., (2004) is based on Darcy s (1856) law for two-phase flow. This model has been validated for a narrow range of flow parameters indirectly (without full instrumentation) and included test points where the flow was not fully developed. The flight experiment presented will be designed with removable test sections to test the hydrodynamic models. The experiment will provide flexibility to test additional beds with different types of packing in the future. One initial test bed is based on the VRA (Volatile Removal Assembly), a packed bed reactor currently on ISS whose behavior in micro-gravity is not fully understood. Improving the performance of this system through an accurate model will increase our ability to purify water in the space environment.

  13. Bed form dynamics in distorted lightweight scale models

    Science.gov (United States)

    Aberle, Jochen; Henning, Martin; Ettmer, Bernd

    2016-04-01

    The adequate prediction of flow and sediment transport over bed forms presents a major obstacle for the solution of sedimentation problems in alluvial channels because bed forms affect hydraulic resistance, sediment transport, and channel morphodynamics. Moreover, bed forms can affect hydraulic habitat for biota, may introduce severe restrictions to navigation, and present a major problem for engineering structures such as water intakes and groynes. The main body of knowledge on the geometry and dynamics of bed forms such as dunes originates from laboratory and field investigations focusing on bed forms in sand bed rivers. Such investigations enable insight into the physics of the transport processes, but do not allow for the long term simulation of morphodynamic development as required to assess, for example, the effects of climate change on river morphology. On the other hand, this can be achieved through studies with distorted lightweight scale models allowing for the modification of the time scale. However, our understanding of how well bed form geometry and dynamics, and hence sediment transport mechanics, are reproduced in such models is limited. Within this contribution we explore this issue using data from investigations carried out at the Federal Waterways and Research Institute in Karlsruhe, Germany in a distorted lightweight scale model of the river Oder. The model had a vertical scale of 1:40 and a horizontal scale of 1:100, the bed material consisted of polystyrene particles, and the resulting dune geometry and dynamics were measured with a high spatial and temporal resolution using photogrammetric methods. Parameters describing both the directly measured and up-scaled dune geometry were determined using the random field approach. These parameters (e.g., standard deviation, skewness, kurtosis) will be compared to prototype observations as well as to results from the literature. Similarly, parameters describing the lightweight bed form dynamics, which

  14. Numerical modeling of fluidized-bed combustor

    Energy Technology Data Exchange (ETDEWEB)

    Sha, W T; Soo, S L

    1977-11-01

    Optimum design of fluidized-bed combustor requires high carbon burn-up, good sulfur retention, minimized sorbent (Ca) utilization, efficient feed distribution and mechanical layout. These parameters are strongly affected by the dynamics of the fluidized bed. The dynamic behavior of fluidized combustor is formulated in terms of multidomain - multiphase mechanics. Fluidization, bubble mechanics, coal combustion, sorbent sulfation, oxidation, solids movement and elutriation, and heat transfer are explicitly taken into account in the proposed numerical model. The model solves conservation equations of mass, momentum and energy coupled with chemical reactions as boundary value problem in space and initial value problem in time. Multi-fluid model and modified implicit multi-field numerical scheme are employed. The objective of this numerical model is for use in engineering design and scaling. Progress to date shows that all necessary relations can be incorporated within the framework of an overall multidomain - multiphase model for deterministic computation. Provisions are made for subsequent refinements of submodels of individual mechanism and improvements of the existing numerical model. These refinements and improvements can be achieved as better understanding of physical phenomena and more experimental data become available. The numerical model outlined in this report is specifically designed for the fluidized-bed combustor; however, it can readily be extended to various coal gasification systems.

  15. Development of a new method for improving load turndown in fluidized bed combustors: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Brown, R.C.

    1988-12-01

    The objective of this research was to investigate a new concept in fluidized bed design that improves load turndown capability. This improvement is accomplished by independently controlling heat transfer and combustion in the combustor. The design consists of two fluidized beds, one central and one annular. The central bed serves as the combustion bed. The annular bed is fluidized separately from the combustion bed and its level of fluidization determine the overall heat transfer rate from the combustion bed to the surrounding water jacket. Early theoretical considerations suggested a load turndown exceeding ten was possible for this design. This research consisted of three major phases: development of a computational model to predict heat transfer in the two-bed combustor, heat transfer measurements in hot-and-cold flow models of the combustor, and combustion tests in an optimally designed combustor. The computation model was useful in selecting the design of the combustor. Annular bed width and particle sizes were chosen with the aid of the model. The heat transfer tests were performed to determine if the existing correlations for fluidized bed heat transfer coefficients were sufficiently accurate for high aspect ratio fluidized beds (such as the annular bed in the combustor). Combustion tests were performed in an optimally designed combustor. Three fuel forms were used: double screened, crushed coal, coal-water-limestone mixtures (CWLM), and coal-limestone briquettes. 18 refs., 30 figs., 8 tabs.

  16. Determination of true bed thickness using folded bed model and borehole data

    Energy Technology Data Exchange (ETDEWEB)

    Xu, S.S.; Velasquillo-Martinez, L.G.; Grajales-Nishimura, J.M.; Murillo-Muneton, G. [Inst. Mexicano del Petroleo, Mexico City (Mexico); Garcia-Hernandez, J. [Petroleos Mexicanos Exploracion y Produccion, Tamaulipas (Mexico); Nieto-Samaniego, A.F. [Nacional Autonoma de Mexico Univ., Veracruz (Mexico). Centro de Geociencias

    2007-11-15

    The actual thickness of a given formation perpendicular to the bedding plane is known as the true bed thickness. Petroleum engineers rely on information regarding true bed thickness, particularly in dipping beds and in deviated holes because reservoir volume and isochore maps depend on these properties and not on the measured thickness. True bed thickness can be estimated from information gathered from well logs such as the dipmeter and borehole images. However, when deviations and dips exceed 10 degrees, corrections are needed. In this paper, a folded bed model was proposed to calculate the true bed thickness in the subsurface utilizing well log data. The value of true bed thickness (t) was shown to depend on the angle and the direction of the dip of the measured formation, as well as the drift angle and azimuth of the borehole. A case study from the Cantarell oil field in the southern Gulf of Mexico, offshore Campeche, was used to test the folded bed method. The model was shown to yield more uniform spatial change of the values of t, compared to the monoclinal bed model that often overestimates the average value of t. The maximum relative deviation of t from the monoclinal bed model reached 22.3 per cent and the maximum absolute deviation of t reached 34.5 m. The key factors that influence the values of t were found to be the bed dip, the dip difference between the top and base of the bed and the deviated angle of the well. The folded bed model yielded fewer changed values of the true bed thickness. 10 refs., 2 tabs., 9 figs.

  17. Modeling of Sulfur Retention in Circulating Fluidized Bed Coal Combustors

    Institute of Scientific and Technical Information of China (English)

    乔锐; 吕俊复; 刘青; 吴学安; 岳光溪

    2001-01-01

    A comprehensive model for predicting the sulfur retention performance in circulating fluidized bedcombustors was developed which involves the different residence times, the wide particle size distribution andthe different forms of sulfur in the coal. In addition, the reductive decomposition of CaSO4 is highlighted. Thesimulation results from the model show that the sulfur contents, the bed temperature, the sorbent particle sizedistribution and the sorbent activity or the maximum conversion rate can significantly influence the sulfuretention performance in circulating fluidized bed (CFB) combustors.``

  18. Hydrodynamic Reaction Model of a Spouted Bed Electrolytic Reactor

    Science.gov (United States)

    Alireza Shirvanian, Pezhman; Calo, Joseph

    2002-08-01

    An Eulerian model is presented that has been developed to describe the hydrodynamics, mass transfer, and metal ion reduction mass transfer in a cylindrical, spouted bed electrolytic reactor. Appropriate boundary conditions are derived from kinetic theory and reaction kinetics for the hydrodynamics and mass transfer and reaction on the cathodic conical bottom of the reactor, respectively. This study was undertaken as a part of a project focused on the development of a Spouted Bed Electrolytic Reactor (SBER) for metals recovery. The results presented here include the effect of particle loading, inlet jet velocity, Solution pH, and temperature on void fraction distribution, pressure drop, particles recirculation rate, and metal recovery rate.

  19. Key technologies for tritium storage bed development

    Energy Technology Data Exchange (ETDEWEB)

    Yu, S.H.; Chang, M.H.; Kang, H.G.; Chung, D.Y.; Oh, Y.H.; Jung, K.J. [National Fusion Research Institute, Yusung-gu, Daejeon (Korea, Republic of); Chung, H.; Koo, D. [Korea Atomic Energy Research Institute, Yusung-gu, Daejeon (Korea, Republic of); Sohn, S.H.; Song, K.M. [Korea Hydro and Nuclear Power Co, Yusung-daero, Yusung-gu, Daejeon (Korea, Republic of)

    2015-03-15

    ITER Storage and Delivery System (SDS) is a complex system involving tens of storage beds. The most important SDS getter bed will be used for the absorption and desorption of hydrogen isotopes in accordance with the fusion fuel cycle scenario. In this paper the current status concerning research/development activities for the optimal approach to the final SDS design is introduced. A thermal analysis is performed and discussed on the aspect of heat losses considering whether the reflector and/or the feed-through is present or not. A thermal hydraulic simulation shows that the presence of 3 or 4 reflectors minimize the heat loss. Another important point is to introduce the real-time gas analysis in the He{sup 3} collection system. In this study 2 independent strength methods based on gas chromatography and quadruple mass spectrometer for one and on a modified self-assaying quadruple mass spectrometer for the second are applied to separate the hydrogen isotopes in helium gas. Another issue is the possibility of using depleted uranium getter material for the storage of hydrogen isotopes, especially of tritium.

  20. Key technologies for tritium storage bed development

    International Nuclear Information System (INIS)

    ITER Storage and Delivery System (SDS) is a complex system involving tens of storage beds. The most important SDS getter bed will be used for the absorption and desorption of hydrogen isotopes in accordance with the fusion fuel cycle scenario. In this paper the current status concerning research/development activities for the optimal approach to the final SDS design is introduced. A thermal analysis is performed and discussed on the aspect of heat losses considering whether the reflector and/or the feed-through is present or not. A thermal hydraulic simulation shows that the presence of 3 or 4 reflectors minimize the heat loss. Another important point is to introduce the real-time gas analysis in the He3 collection system. In this study 2 independent strength methods based on gas chromatography and quadruple mass spectrometer for one and on a modified self-assaying quadruple mass spectrometer for the second are applied to separate the hydrogen isotopes in helium gas. Another issue is the possibility of using depleted uranium getter material for the storage of hydrogen isotopes, especially of tritium

  1. A multistage model of hospital bed requirements.

    OpenAIRE

    Pendergast, J F; Vogel, W B

    1988-01-01

    This article presents a model for projecting future hospital bed requirements, based on clinical judgment and basic probability theory. Clinical judgment is used to define various categories of care, including a category for patients who are inappropriately hospitalized, for a large teaching hospital with a heavy indigent and psychiatric workload. Survey results and discharge abstract data are then used to calculate expected discharges and patient days for each clinical category. These expect...

  2. In-Bed Accountability Development for a Passively Cooled, Electrically Heated Hydride (PACE) Bed

    International Nuclear Information System (INIS)

    A nominal 1500 STP-L PAssively Cooled, Electrically heated hydride (PACE) Bed has been developed for implementation into a new Savannah River Site tritium project. The 1.2 meter (four-foot) long process vessel contains on internal 'U-tube' for tritium In-Bed Accountability (IBA) measurements. IBA will be performed on six, 12.6 kg production metal hydride storage beds.IBA tests were done on a prototype bed using electric heaters to simulate the radiolytic decay of tritium. Tests had gas flows from 10 to 100 SLPM through the U-tube or 100 SLPM through the bed's vacuum jacket. IBA inventory measurement errors at the 95% confidence level were calculated using the correlation of IBA gas temperature rise, or (hydride) bed temperature rise above ambient temperature, versus simulated tritium inventory.Prototype bed IBA inventory errors at 100 SLPM were the largest for gas flows through the vacuum jacket: 15.2 grams for the bed temperature rise and 11.5 grams for the gas temperature rise. For a 100 SLPM U-tube flow, the inventory error was 2.5 grams using bed temperature rise and 1.6 grams using gas temperature rise. For 50 to 100 SLPM U-tube flows, the IBA gas temperature rise inventory errors were nominally one to two grams that increased above four grams for flows less than 50 SLPM. For 50 to 100 SLPM U-tube flows, the IBA bed temperature rise inventory errors were greater than the gas temperature rise errors, but similar errors were found for both methods at gas flows of 20, 30, and 40 SLPM.Electric heater IBA tests were done for six production hydride beds using a 45 SLPM U-tube gas flow. Of the duplicate runs performed on these beds, five of the six beds produced IBA inventory errors of approximately three grams: consistent with results obtained in the laboratory prototype tests

  3. Experimental modelling of outburst flood - bed interactions

    Science.gov (United States)

    Carrivick, J. L.; Xie, Z.; Sleigh, A.; Hubbard, M.

    2009-04-01

    Outburst floods are a sudden release and advancing wave of water and sediment, with a peak discharge that is often several orders of magnitude greater than perennial flows. Common outburst floods from natural sources include those from glacial and moraine-impounded lakes, freshwater dyke and levee bursts, volcanic debris dams, landslides, avalanches, coastal bay-bars, and those from tree or vegetation dams. Outburst flood hazards are regularly incorporated into risk assessments for urban, coastal and mountainous areas, for example. Outburst flood hazards are primarily due to direct impacts, caused by a frontal surge wave, from debris within a flow body, and from the mass and consistency of the flows. A number of secondary impacts also pose hazards, including widespread deposition of sediment and blocked tributary streams. It is rapid landscape change, which is achieved the mobilization and redistribution of sediment that causes one of the greatest hazards due to outburst floods. The aim of this project is therefore to parameterise hydrodynamic - sedimentary interactions in experimental outburst floods. Specifically, this project applies laboratory flume modelling, which offers a hitherto untapped opportunity for examining complex interactions between water and sediment within outburst floods. The experimental set-up is of a tradition lock-gate design with a straight 4 m long tank. Hydraulics are scaled at 1:20 froude scale and the following controls on frontal wave flow-bed interactions and hence on rapid landscape change are being investigated: 1. Pre-existing mobile sediment effects, fixed bed roughness effects, sediment concentration effects, mobile bed effects. An emphasis is being maintained on examining the downstream temporal and spatial change in physical character of the water / sediment frontal wave. Facilities are state-of-the-art with a fully-automated laser bed-profiler to measure bed elevation after a run, Seatek arrays to measure transient flow

  4. Steam gasification of char from wood chips fast pyrolysis: Development of a semi-empirical model for a fluidized bed reactor application

    International Nuclear Information System (INIS)

    This study, performed in the context of GAYA project, focuses on the development of a simple predictive model about steam gasification of char from woodchips fast pyrolysis. A semi-empirical model was developed through experiments in a macro thermogravimetric analyzer which owns the peculiar ability of fast heating, as well as to deal with macro-size particles and higher mass loads compared to conventional TGA. The experimental results show that gasification is controlled by chemical kinetics and internal transfer phenomena. During gasification, char particles can be considered as isothermal in a given range of temperatures and particle sizes, more likely for low values. The gasification model was based on the effectiveness factor, which involves the chemical kinetics and diffusion rate. The chemical kinetics were expressed by a classical Arrhenius law, whereas empirical expressions from mathematical fitting of the experimental data were established for the diffusion coefficient and surface function. The diffusion coefficient from this work is suspected to probably include supplementary rate limiting phenomena, apart from steam porous diffusion, such as H2 inhibition and/or the decrease of temperature within char particles because of the endothermic character of gasification. The model globally predicts with accuracy the gasification rate in typical operating conditions of a fluidized bed reactor. For its simplicity and reliability, this approach can be used for the modelling of char gasification in the conditions of interest. - Highlights: • Char gasification is controlled by chemical kinetics and internal transfers. • Char particles are isothermal during gasification only at certain conditions. • The temperature decrease within char particles may affect gasification rate. • Gasification within the particle could be inhibited by the produced H2. • The developed semi-empirical model predicts with accuracy gasification rate

  5. MATHEMATICAL MODEL OF RIVER BED CHANGE DOWNSTREAM OF XIAOLANGDI RESERVOIR

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A mathematical model of river bed change downstream of the Xiaolangdi Reservoir was developed based on the most recent achievement of sediment theory in the Yellow River. The model was verified by the comparison of computed results and measured data from 1986 to 1996. Numerical prediction of the erosion and deposition downstream of the Xiaolangdi Reservoir in its first operation year was carried out, and a series of suggestions were given for reservoir operation mode in its early operation period.

  6. Model for boiling and dryout in particle beds

    International Nuclear Information System (INIS)

    Over the last ten years experiments and modeling of dryout in particle beds have produced over fifty papers. Considering only volume-heated beds, over 250 dryout measurements have been made, and are listed in this work. In addition, fifteen models to predict dryout have been produced and are discussed. A model is developed in this report for one-dimensional boiling and dryout in a porous medium. It is based on conservation laws for mass, momentum, and energy. The initial coupled differential equations are reduced to a single first-order differential equation with an algebraic equation for the upper boundary condition. The model includes the effects of both laminar and turbulent flow, two-phase friction, and capillary force. The boundary condition at the bed bottom includes the possibility of inflowing liquid and either an adiabatic or a bottom-cooled support structure. The top of the bed may be either channeled or subcooled. In the first case the channel length and the saturation at the base of the channels are predicted. In the latter case, a criterion for penetration of the subcooled zone by channels is obtained

  7. Modelling of thermal and mechanical behaviour of pebble beds

    International Nuclear Information System (INIS)

    FZK (Forshungzentrum Karlsruhe) is developing a Helium Cooled Pebble Bed (HCPB) Blanket Concept for fusion power reactors based on the use of ceramic breeder materials and beryllium multiplier in the form of pebble beds. The design of such a blanket requires models and computer codes describing the thermal-mechanical behavior of pebble beds to evaluate the temperatures, stresses, deformations and mechanical interactions between pebble beds and the structure with required accuracy and reliability. The objective to describe the beginning of life condition for the HCPB blanket seems near to be reached. Mechanical models that describe the thermo-mechanical behavior of granular materials used in form of pebble beds are implemented in a commercial structure code. These models have been calibrated using the results of a large series of dedicated experiments. The modeling work is practically concluded for ceramic breeder; it will be carried on in the next year for beryllium to obtain the required correlations for creep and the thermal conductivity. The difficulties for application in large components (such as the HCPB blanket) are the limitations of the present commercial codes to manage such a set of constitutive equations under complex load conditions and large mesh number. The further objective is to model the thermal cycles during operation; the present correlations have to be adapted for the release phase. A complete description of the blanket behavior during irradiation is at the present out of our capability; this objective requires an extensive R and D program that at the present is only at the beginning. (Y.Tanaka)

  8. Integrated design approach of the pebble bed modular using models

    International Nuclear Information System (INIS)

    The Pebble Bed Modular Reactor (PBMR) is the first pebble bed reactor that will be utilised in a high temperature direct Brayton cycle configuration. This implies that there are a number of unique features in the PBMR that extend from the German experience base. One of the challenges in the design of the PBMR is managing the integrated design process between the designers, the physicists and the analysts. This integrated design process is managed through model-based development work. Three-dimensional CAD models are constructed of the components and parts in the reactor. From the CAD models, CFD models, neutronic models, shielding models, FEM models and other thermodynamic models are derived. These models range from very simple models to extremely detailed and complex models. The models are used in legacy software as well as commercial off-the-shelf software. The different models are also used in code-to-code comparisons to verify the results. This paper will briefly discuss the different models and the interaction between the models, showing the iterative design process that is used in the development of the reactor at PBMR. (author)

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

    International Nuclear Information System (INIS)

    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

  10. ADVANCED SORBENT DEVELOPMENT PROGRAM; DEVELOPMENT OF SORBENTS FOR MOVING-BED AND FLUIDIZED-BED APPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    AYALA, R E; VENKATARAMANI, V S

    1998-09-30

    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 (900-1000 °F) 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

  11. ADVANCED SORBENT DEVELOPMENT PROGRAM DEVELOPMENT OF SORBENTS FOR MOVING-BED AND FLUIDIZED-BED APPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    R.E Ayala; V.S. Venkataramani; Javad Abbasian; Rachid B. Slimane; Brett E. Williams; Minoo K. Zarnegar; James R. Wangerow; Andy H. Hill

    2000-03-31

    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 (900-1000 F) 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

  12. Numerical Modeling and Prediction of Bubbling Fluidized Beds

    OpenAIRE

    England, Jonas Andrew

    2011-01-01

    Numerical modeling and prediction techniques are used to determine pressure drop, minimum fluidization velocity and segregation for bubbling fluidized beds. The computational fluid dynamics (CFD) code Multiphase Flow with Interphase eXchange (MFIX) is used to study a two-stage reactor geometry with a binary mixture. MFIX is demonstrated to accurately predict pressure drop versus inlet gas velocity for binary mixtures. A new method is developed to predict the pressure drop versus inlet gas v...

  13. Mathematical model of processes of reactor with gasified fluidized bed

    International Nuclear Information System (INIS)

    An original scheme of steam generator with gasifying fluidized bed has been presented as a possible solution for reconstruction of furnace with pulverized burning of coal. The method is effective when applied in combination with desulfurization for the purpose of reducing the CO2 emissions level. A mathematical model has been developed, which determines the correlation primary (fluidizing) and (burning out) secondary air with sufficient for the practice accuracy

  14. Applicability of annular flow model to countercurrent flow in debris beds consisting of large particles

    International Nuclear Information System (INIS)

    Countercurrent flow limitation (CCFL) is the dominant dryout phenomenon in a debris bed that may be formed during a severe accident such as that observed at Three Mile Island unit 2. The actual CCFL situation in a debris bed is very complex, and it is difficult to treat. An annular flow model was developed to predict CCFL in a pipe. If a hypothetical flow channel were assumed, CCFL in a debris bed could be treated in the same manner as CCFL in a pipe. The purpose of this study is to investigate whether the annular flow model developed for CCFL in a pipe is applicable for CCFL in a debris bed

  15. Waste tyre pyrolysis: modelling of a moving bed reactor.

    Science.gov (United States)

    Aylón, E; Fernández-Colino, A; Murillo, R; Grasa, G; Navarro, M V; García, T; Mastral, A M

    2010-12-01

    This paper describes the development of a new model for waste tyre pyrolysis in a moving bed reactor. This model comprises three different sub-models: a kinetic sub-model that predicts solid conversion in terms of reaction time and temperature, a heat transfer sub-model that calculates the temperature profile inside the particle and the energy flux from the surroundings to the tyre particles and, finally, a hydrodynamic model that predicts the solid flow pattern inside the reactor. These three sub-models have been integrated in order to develop a comprehensive reactor model. Experimental results were obtained in a continuous moving bed reactor and used to validate model predictions, with good approximation achieved between the experimental and simulated results. In addition, a parametric study of the model was carried out, which showed that tyre particle heating is clearly faster than average particle residence time inside the reactor. Therefore, this fast particle heating together with fast reaction kinetics enables total solid conversion to be achieved in this system in accordance with the predictive model. PMID:20510597

  16. Modeling of fluidized-bed combustion of coal: Phase II, final reports. Volume VI. FBC-Data Base-Management-System (FBC-DBMS) development

    Energy Technology Data Exchange (ETDEWEB)

    Louis, J.F.; Tung, S.E.

    1980-10-01

    The primary goal of the Fluidized Bed Combustor Data Base, (FBCDB), situated in MIT's Energy laboratory, is to establish a data repository for the express use of designers and research personnel involved in FBC development. DBMS is a software that provides an efficient way of storing, retrieving, updating and manipulating data using an English-like query language. It is anticipated that the FBCDB would play an active and a direct role in the development of FBC technology as well as in the FBC commercial application. After some in-house experience and after a careful and extensive review of commercially available database systems, it was determined that the Model 204 DBMS by Computer Corporation of America was the most suitable to our needs. The setup of a prototype in-house database also allowed us to investigate and understand fully the particular problems involved in coordinating FBC development with a DBMS. Various difficult aspects were encountered and solutions had been sought. For instance, we found that it was necessary to rename the variables to avoid repetition as well as to increase usefulness of our database and, hence, we had designed a classification system for which variables were classified under category to achieve standardization of variable names. The primary content of FBCDB is a collection of data points defined by the value of a number of specific FBC variables. A user may interactively access the database from a computer terminal at any location, retrieve, examine, and manipulate the data as well as produce tables or graphs of the results.

  17. Pulsed atmospheric fluidized-bed combustor development

    International Nuclear Information System (INIS)

    Pulsed atmospheric fluidized-bed combustion (PAFBC) is a unique and innovative coal-fueled technology that has the potential to meet these conditions and provide heat and/or process steam to small industrial, commercial, institutional and residential complexes. The potential of Pulse Atmospheric Fluidized Bed Combustion (PAFBC) technology has been amply demonstrated under the sponsorship of a previous DOE/METC contract (DE-AC21-88MC25069). The environmental performance of a coal-fired laboratory-scale system (1.5 million British Thermal Units per hour) (MMBtu/hr) significantly surpassed that of conventional bubbling and circulating fluidized-bed combustion units (see Table 1 for performance comparison). Prompted by these encouraging results in combustion, sulfur capture, emissions control, and enhanced heat transfer, Island Creek Coal Company (ICC) and Baltimore Thermal Energy Corporation expressed interest in the technology and offered to participate by providing host sites for field testing. EA's have been submitted independently for each of these field test sites. This submission addresses the preliminary testing of the PAFBC unit at Manufacturing and Technology Conversion International's (MTCI) Baltimore, MD facility

  18. COMPUTATIONAL MODELING OF CIRCULATING FLUIDIZED BED REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Ibrahim, Essam A

    2013-01-09

    Details of numerical simulations of two-phase gas-solid turbulent flow in the riser section of Circulating Fluidized Bed Reactor (CFBR) using Computational Fluid Dynamics (CFD) technique are reported. Two CFBR riser configurations are considered and modeled. Each of these two riser models consist of inlet, exit, connecting elbows and a main pipe. Both riser configurations are cylindrical and have the same diameter but differ in their inlet lengths and main pipe height to enable investigation of riser geometrical scaling effects. In addition, two types of solid particles are exploited in the solid phase of the two-phase gas-solid riser flow simulations to study the influence of solid loading ratio on flow patterns. The gaseous phase in the two-phase flow is represented by standard atmospheric air. The CFD-based FLUENT software is employed to obtain steady state and transient solutions for flow modulations in the riser. The physical dimensions, types and numbers of computation meshes, and solution methodology utilized in the present work are stated. Flow parameters, such as static and dynamic pressure, species velocity, and volume fractions are monitored and analyzed. The differences in the computational results between the two models, under steady and transient conditions, are compared, contrasted, and discussed.

  19. New Developments in Spinning Fluidised Bed Incineration Technology

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    At the present time, the sewage treatment plants in the UK produce about 25 million tons of sewage sludge each year at a concentration of 4% solids. New regulations forbid sea dumping and in the near future new incinerators will be required to dispose of about 5 million tons per year. Bubbling fluidised bed incinerators are widely used to burn sewage sludge at a typical consumption rate of about 0.02kg(dry)·s-1·m2, and it follows that over 300 conventional fluidised bed incinerators of 3m diameter could be required to cope with the increased demand.At Sheffield University Waste Incineration Centre (SUWIC) research work is being carried out to develop a novel spinning fluidised bed incinerator. The key factor to note is that when air flows up through a bed of near mono-sized particles, it fluidises when the pressure drop across the bed is equal to the weight of the bed. Normally, the weight of the bed is determined by gravity. However, if the bed is contained by a cylindrical air distributor 'plate' that is rotating rapidly about its axis, then the effective weight of the bed can be increased dramatically. The airflow passing through the bed can be increased proportionally to the "g" level produced by the rotation and it follows that the process has been intensified. In exploratory tests with a spinning fluidised bed we have achieved combustion intensities with coal combustion as high as 100MW/m3. A problem with burning coal is that it was difficult to remove the heat and rotating water seals had to be used to transfer cooling water into the bed. In the case of sewage and other sludges, this problem does not exist since the flue gases can remove the small amount of heat released. The rotating fluidised bed sludge incinerator is a novel device, which is very compact. It is able to solve the turndown problem encountered with conventional fluidised beds by simply changing the rotation speed. Bearing in mind that a centrifugal sludge de-watering unit is already used

  20. Numerical modeling of straw combustion in a fixed bed

    DEFF Research Database (Denmark)

    Zhou, Haosheng; Jensen, Anker; Glarborg, Peter;

    2005-01-01

    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 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 packing condition, and heat capacity of the straw have considerable effects on the model predictions of straw combustion in the fixed bed....

  1. An Improved Model Describing Mass Transfer In Three-Phase Fluidized Beds

    OpenAIRE

    Asfour, Abdel Fattah A.

    1990-01-01

    A model for describing mass transfer in three-phase fluidized beds has been developed and tested using experimental data. The presence of two distinguishable mass transfer zones in three-phase fluidized beds led to the idea of interfacing a plug flow model (PFM) with an axial dispersion model (ADM) at the separation boundary between these zones to yield the proposed model. The model reported here has been valildated at a wide range of operating conditions and proved to perform better th...

  2. CFD modeling of a prismatic spouted bed with two adjustable gas inlets

    NARCIS (Netherlands)

    Gryczka, Oliver; Heinrich, Stefan; Deen, Niels G.; Sint Annaland, van Martin; Kuipers, Johannes A.M.; Mörl, Lothar

    2009-01-01

    Since the invention of the spouted bed technology by Mathur and Gishler (1955), different kinds of apparatus design were developed and a huge number of applications in nearly all branches of industry have emerged. Modeling of spouted beds by means of modern simulation tools, like discrete particle m

  3. Mechanistic modelling of fluidized bed drying processes of wet porous granules

    DEFF Research Database (Denmark)

    Mortier, Séverine Thérèse F.C.; De Beer, Thomas; Gernaey, Krist;

    2011-01-01

    Fluidized bed dryers are frequently used in industrial applications and also in the pharmaceutical industry. The general incentives to develop mechanistic models for pharmaceutical processes are listed, and our vision on how this can particularly be done for fluidized bed drying processes of wet...

  4. Bed composition generation for morphodynamic modeling: Case study of San Pablo Bay in California, USA

    Science.gov (United States)

    van der Wegen, M.; Dastgheib, A.; Jaffe, B.E.; Roelvink, D.

    2011-01-01

    Applications of process-based morphodynamic models are often constrained by limited availability of data on bed composition, which may have a considerable impact on the modeled morphodynamic development. One may even distinguish a period of "morphodynamic spin-up" in which the model generates the bed level according to some ill-defined initial bed composition rather than describing the realistic behavior of the system. The present paper proposes a methodology to generate bed composition of multiple sand and/or mud fractions that can act as the initial condition for the process-based numerical model Delft3D. The bed composition generation (BCG) run does not include bed level changes, but does permit the redistribution of multiple sediment fractions over the modeled domain. The model applies the concept of an active layer that may differ in sediment composition above an underlayer with fixed composition. In the case of a BCG run, the bed level is kept constant, whereas the bed composition can change. The approach is applied to San Pablo Bay in California, USA. Model results show that the BCG run reallocates sand and mud fractions over the model domain. Initially, a major sediment reallocation takes place, but development rates decrease in the longer term. Runs that take the outcome of a BCG run as a starting point lead to more gradual morphodynamic development. Sensitivity analysis shows the impact of variations in the morphological factor, the active layer thickness, and wind waves. An important but difficult to characterize criterion for a successful application of a BCG run is that it should not lead to a bed composition that fixes the bed so that it dominates the "natural" morphodynamic development of the system. Future research will focus on a decadal morphodynamic hindcast and comparison with measured bathymetries in San Pablo Bay so that the proposed methodology can be tested and optimized. ?? 2010 The Author(s).

  5. BWR lower plenum debris bed models for MELCOR

    International Nuclear Information System (INIS)

    Work is underway at Oak Ridge National Laboratory (ORNL) to incorporate certain models of the Boiling Water Reactor Severe Accident Response (BWRSAR) code into a local version of MELCOR. Specifically, the BWR lower plenum debris bed and bottom head response models taken from BWRSAR are being tested within the local MELCOR code structure. Upon successful completion of testing, recommendations for formal adoption of these models will be made to the Nuclear Regulatory Commission (NRC) and to the MELCOR code development staff at Sandia National Laboratories (SNL). The SNL code development staff retain exclusive responsibility for maintaining the configuration control for the official version of MELCOR. The BWR lower plenum debris bed and bottom head response models permit the calculation of heatup, melting, and relocation of the debris after dryout. They predict the response of the lower plenum internal structures and the bottom head as well as the composition and timing of material release from the vessel. They have been previously applied in severe accident analyses for the Containment Performance Improvement (CPI) Program and the Mark I shell survivability study (NUREG/CR-5423), and in recent assessments of candidate accident management strategies. This paper provides a brief description of the purpose and operation of these models. 11 refs., 15 figs., 5 tabs

  6. A CFD model for biomass combustion in a packed bed furnace

    Science.gov (United States)

    Karim, Md. Rezwanul; Ovi, Ifat Rabbil Qudrat; Naser, Jamal

    2016-07-01

    Climate change has now become an important issue which is affecting environment and people around the world. Global warming is the main reason of climate change which is increasing day by day due to the growing demand of energy in developed countries. Use of renewable energy is now an established technique to decrease the adverse effect of global warming. Biomass is a widely accessible renewable energy source which reduces CO2 emissions for producing thermal energy or electricity. But the combustion of biomass is complex due its large variations and physical structures. Packed bed or fixed bed combustion is the most common method for the energy conversion of biomass. Experimental investigation of packed bed biomass combustion is difficult as the data collection inside the bed is challenging. CFD simulation of these combustion systems can be helpful to investigate different operational conditions and to evaluate the local values inside the investigation area. Available CFD codes can model the gas phase combustion but it can't model the solid phase of biomass conversion. In this work, a complete three-dimensional CFD model is presented for numerical investigation of packed bed biomass combustion. The model describes the solid phase along with the interface between solid and gas phase. It also includes the bed shrinkage due to the continuous movement of the bed during solid fuel combustion. Several variables are employed to represent different parameters of solid mass. Packed bed is considered as a porous bed and User Defined Functions (UDFs) platform is used to introduce solid phase user defined variables in the CFD. Modified standard discrete transfer radiation method (DTRM) is applied to model the radiation heat transfer. Preliminary results of gas phase velocity and pressure drop over packed bed have been shown. The model can be useful for investigation of movement of the packed bed during solid fuel combustion.

  7. Modeling on Flash Flood Disaster Induced by Bed Load

    Institute of Scientific and Technical Information of China (English)

    CAO Shuyou; LIU Xingnian; HUANG Er; YANG Keiun

    2008-01-01

    Flash floods result from a complex interaction among hydro-meteorological, hydrologi-cal, and hydraulic processes across various spatial and temporal scales. Sichuan Province suffers flash floods frequently owing to mountain weather and topography. A flash flood and gravel bed load transport are two key relative problems in mountain river engineering. Bed materials are often encountered in alternate scouring and deposition in mountain fluvial processes during a flash flood.In this circumstance, CRS-1 bed load numerical model jointly with scale physical model is em-ployed to predict water level and gravel bed scour and deposition for design of flood control dykes and flash flood disaster mitigation. A case study on the mechanism of a flash flood disaster in-duced by bed load transport for a hydropower station in Sichuan Province is conducted. Finally,suggestions to protect the hydropower station are proposed.

  8. Equilibrium modeling of gasification: Gibbs free energy minimization approach and its application to spouted bed and spout-fluid bed gasifiers

    Energy Technology Data Exchange (ETDEWEB)

    Jarungthammachote, S.; Dutta, A. [Energy Field of Study, School of Environment, Resources and Development, Asian Institute of Technology, P.O. Box 4, Klongluang, Pathumthani 12120 (Thailand)

    2008-06-15

    Spouted beds have been found in many applications, one of which is gasification. In this paper, the gasification processes of conventional and modified spouted bed gasifiers were considered. The conventional spouted bed is a central jet spouted bed, while the modified spouted beds are circular split spouted bed and spout-fluid bed. The Gibbs free energy minimization method was used to predict the composition of the producer gas. The major six components, CO, CO{sub 2}, CH{sub 4}, H{sub 2}O, H{sub 2} and N{sub 2}, were determined in the mixture of the producer gas. The results showed that the carbon conversion in the gasification process plays an important role in the model. A modified model was developed by considering the carbon conversion in the constraint equations and in the energy balance calculation. The results from the modified model showed improvements. The higher heating values (HHV) were also calculated and compared with the ones from experiments. The agreements of the calculated and experimental values of HHV, especially in the case of the circular split spouted bed and the spout-fluid bed were observed. (author)

  9. Reactor modeling and physicochemical properties characterization for a polyethylene fluidized bed reactor

    OpenAIRE

    F. A. N. Fernandes; L. M. F. LONA BATISTA

    1999-01-01

    A new steady state model for the fluidized bed reactor and a physicochemical characterization model were developed for the simulation of polyethylene production using gas-phase technology. The association of these models was done in order to predict the characteristics of the polymer produced in the fluidized bed reactor (molecular weight, polydispersity, melt index, and other characteristics) throughout the reactor and also to predict the growth of the polymer particle.

  10. Reactor modeling and physicochemical properties characterization for a polyethylene fluidized bed reactor

    Directory of Open Access Journals (Sweden)

    FERNANDES F. A. N.

    1999-01-01

    Full Text Available A new steady state model for the fluidized bed reactor and a physicochemical characterization model were developed for the simulation of polyethylene production using gas-phase technology. The association of these models was done in order to predict the characteristics of the polymer produced in the fluidized bed reactor (molecular weight, polydispersity, melt index, and other characteristics throughout the reactor and also to predict the growth of the polymer particle.

  11. Modeling nitrate removal in a denitrification bed

    Science.gov (United States)

    Denitrification beds are being promoted to reduce nitrate concentrations in agricultural drainage water to alleviate the adverse environmental effects associated with nitrate pollution in surface water. In this system, water flows through a trench filled with a carbon media where nitrate is transfor...

  12. Modelling of seed drying in fluidised and spouted bed dryers

    OpenAIRE

    Jittanit, W.; Srzednicki, G.; Driscoll, R

    2010-01-01

    Drying experiments were conducted in the fluidised bed dryer (FBD) and spouted bed dryer (SBD) at temperature 40-80°C using maize, rice and wheat seed samples. The experimental data were fitted into four thin-layer drying models by least square method. As a result, Page’s model and two-compartment model were the best-fitted models. Due to the limitation of these models, Page’s model and the twocompartment model were modified by adding the drying temperature term. Subsequently, these models co...

  13. Investigations for a model experiment on quenching of debris bed

    International Nuclear Information System (INIS)

    Within the frame of a severe nuclear accident research project funded by the Federal Ministry for Education, Science, Research and Technology (BMBF) the problem of heat and mass transfer in a debris bed is investigated theoretically and experimentally. Model-oriented single-effect experiments, both steady state but especially quenching experiments shall be carried out. First exploratory quenching tests were performed with small-scale (300 cm3) inductively heated beds composed of carbon steel balls and contained in various types of crucibles. Initial bed temperatures ranged from 300 to 800 degree C, in particular cases the bed temperatures were raised up to 1300 degree C. Test results obtained so far demonstrate the complexity of the phenomena and the many influencing parameters, among others size of particles, bed temperature, and type of crucible. The integrity of an appropriate test vessel, both diamagnetic and of sufficiently high resistance against thermal stress, is a major problem

  14. Computer-aided modeling framework – a generic modeling template for catalytic membrane fixed bed reactors

    DEFF Research Database (Denmark)

    Fedorova, Marina; Sin, Gürkan; Gani, Rafiqul

    2013-01-01

    This work focuses on development of computer-aided modeling framework. The framework is a knowledge-based system that is built on a generic modeling language and structured based on workflows for different general modeling tasks. The overall objective of this work is to support the model develope...... catalytic membrane fixed bed models is developed. The application of the modeling template is highlighted with a case study related to the modeling of a catalytic membrane reactor coupling dehydrogenation of ethylbenzene with hydrogenation of nitrobenzene....

  15. Representation of Thwaites Glacier Bed Uncertainty for Modeling Experiments

    Science.gov (United States)

    Jackson, C. S.; Goff, J. A.; Waibel, S.; Greene, C. A.; Johnson, J. V.; Young, D. A.; Blankenship, D. D.

    2013-12-01

    Thwaites catchment includes a landward sloping bed and a marine ice sheet. The sensitivity of this glacier to a warming ocean is likely dependent on specific details of its bed. Goff et al., (submitted to JGR Earth Surface) has created a conditional simulation of Thwaites Glacier bed that includes inhomogeneous statistics and channelized morphology that takes advantage of the high resolution inferences of bed geometry taken from flight paths of aerogeophysical surveys to make inferences of the type of features that are likely to exist between flight paths. This effort is now being extended to represent the uncertainties due to 1) off-nadir radar energy being interpreted inappropriately as being from bed features at nadir, 2) mischaracterization of roughness, 3) flight track spacing density, and 4) the failure to identify individual glacier carved channels. Estimates of the high-resolution bed (at 250 meter resolution) and its uncertainty will be compared against a so-called 'mass conserving' bed. The point of this effort is to capture the elements of the way ice-penetrating radar data is used to estimate ice thickness for use in modeling experiments where bed uncertainties are likely to play an important role. This exercise is interesting from an uncertainty quantification point of view insofar as while the actual uncertainties are high dimensional (i.e. every grid point that has not been observed directly), what matters to sea level rise experiments is some low-dimensional summary of what is important to glacier dynamics.

  16. Atmospheric fluidized bed coal combustion research, development and application

    CERN Document Server

    Valk, M

    1994-01-01

    The use of fluidized bed coal combustion technology has been developed in the past decade in The Netherlands with a view to expanding the industrial use of coal as an energy supply. Various research groups from universities, institutes for applied science and from boiler industries participated and contributed to this research area. Comprehensive results of such recent experimentation and development work on atmospheric fluidized bed combustion of coal are covered in this volume. Each chapter, written by an expert, treats one specific subject and gives both the theoretical background as well a

  17. ITER Tritium Storage and Delivery Bed Development and Test

    International Nuclear Information System (INIS)

    The ITER fuel cycle plant is composed of various subsystems such as a fuel storage and delivery system (SDS), a tokamak exhaust processing system (TEP), and a hydrogen isotope separation system (ISS). The main purpose of the SDS is to store and supply the D-T gas needed for the DT plasma operation. Korea shares in the construction of the ITER fuel cycle plant with the EU, Japan and US, and is responsible for the development and supply of the SDS. We have developed an SDS bed and tested not only its performance for a hydrogen delivery and recovery but also its in-bed calorimetric performance

  18. Modeling downstream fining in sand-bed rivers. II: Application

    Science.gov (United States)

    Wright, S.; Parker, G.

    2005-01-01

    In this paper the model presented in the companion paper, Wright and Parker (2005) is applied to a generic river reach typical of a large, sand-bed river flowing into the ocean in order to investigate the mechanisms controlling longitudinal profile development and downstream fining. Three mechanisms which drive downstream fining are studied: a delta prograding into standing water, sea-level rise, and tectonic subsidence. Various rates of sea-level rise (typical of the late Holocene) and tectonic subsidence are modeled in order to quantify their effects on the degree of profile concavity and downstream fining. Also, several other physical mechanisms which may affect fining are studied, including the relative importance of the suspended versus bed load, the effect of the loss of sediment overbank, and the influence of the delta bottom slope. Finally, sensitivity analysis is used to show that the grain-size distribution at the interface between the active layer and substrate has a significant effect on downstream fining. ?? 2005 International Association of Hydraulic Engineering and Research.

  19. Analytical model for freeboard and in-bed limestone sulfation in fluidized-bed coal combustors

    Energy Technology Data Exchange (ETDEWEB)

    Fee, D.C.; Myles, K.M.; Marroquin, G.; Fan, L.S.

    1984-01-01

    A new model, which combines in-bed and freeboard sulfation, significantly improves the ability to predict sulfur capture by limestone sorbents in fluidized-bed coal combustors. In this model, the in-bed hydrodynamics are described in terms of a bubble phase and an emulsion phase while the freeboard region has only a diluted emulsion phase. The solids, which are in the emulsion phases, are considered to be completely back-mixed; the gaseous bubble phase travels in plug-flow but exchanges with the emulsion phase. The sulfation reaction occurs principally in the emulsion phase and the reaction rate is a direct function of the sulfur dioxide concentration, the extent of the calcium oxide conversion (as measured by a thermogravimetric analyzer), and the amount of limestone present in the bed and in the freeboard. The amount present, or holdup, in the free-board is calculated from empirical correlations for elutriation and from particle-time trajectories as predicted from equations of motion. 19 references, 4 figures.

  20. Feasibility Study of a Lunar Analog Bed Rest Model

    Science.gov (United States)

    Cromwell, Ronita L.; Platts, Steven H.; Yarbough, Patrice; Buccello-Stout, Regina

    2010-01-01

    The purpose of this study was to determine the feasibility of using a 9.5deg head-up tilt bed rest model to simulate the effects of the 1/6 g load to the human body that exists on the lunar surface. The lunar analog bed rest model utilized a modified hospital bed. The modifications included mounting the mattress on a sled that rolled on bearings to provide freedom of movement. The weight of the sled was off-loaded using a counterweight system to insure that 1/6 body weight was applied along the long axis (z-axis) of the body. Force was verified through use of a force plate mounted at the foot of the bed. A seating assembly was added to the bed to permit periods of sitting. Subjects alternated between standing and sitting positions throughout the day. A total of 35% of the day was spent in the standing position and 65% was spent sitting. In an effort to achieve physiologic fluid shifts expected for a 1/6 G environment, subjects wore compression stockings and performed unloaded foot and ankle exercises. Eight subjects (3 females and 5 males) participated in this study. Subjects spent 13 days in the pre-bed rest phase, 6 days in bed rest and 3 days post bed rest. Subjects consumed a standardized diet throughout the study. To determine feasibility, measures of subject comfort, force and plasma volume were collected. Subject comfort was assessed using a Likert scale. Subjects were asked to assess level of comfort (0-100) for 11 body regions and provide an overall rating. Results indicated minimal to no discomfort as most subjects reported scores of zero. Force measures were performed for each standing position and were validated against subject s calculated 1/6 body weight (r(sup 2) = 0.993). The carbon monoxide rebreathing technique was used to assess plasma volume during pre-bed rest and on the last day of bed rest. Plasma volume results indicated a significant decrease (p = 0.001) from pre to post bed rest values. Subjects lost on average 8.3% (sd = 6.1%) during the

  1. Neutronic modeling of pebble bed reactors in APOLLO2

    International Nuclear Information System (INIS)

    In this thesis we develop a new iterative homogenization technique for pebble bed reactors, based on a 'macro-stochastic' transport approximation in the collision probability method. A model has been developed to deal with the stochastic distribution of pebbles with different burnup in the core, considering spectral differences in homogenization and depletion calculations. This is generally not done in the codes presently used for pebble bed analyses, where a pebble with average isotopic composition is considered to perform the cell calculation. Also an iterative core calculation scheme has been set up, where the low-order RZ SN full-core calculation computes the entering currents in the spectrum zones subdividing the core. These currents, together with the core keff, are then used as surface source in the fine-group heterogeneous calculation of the multi-pebble geometries. The developed method has been verified using reference Monte Carlo simulations of a simplified PBMR- 400 model. The pebbles in this model are individually positioned and have different randomly assigned burnup values. The APOLLO2 developed method matches the reference core keff within ± 100 pcm, with relative differences on the production shape factors within ± 4%, and maximum discrepancy of 3% at the hotspot. Moreover, the first criticality experiment of the HTR-10 reactor was used to perform a first validation of the developed model. The computed critical number of pebbles to be loaded in the core is very close to the experimental value of 16890, only 77 pebbles less. A method to calculate the equilibrium reactor state was also developed and applied to analyze the simplified PBMR-400 model loaded with different fuel types (UO2, Pu, Pu + MA). The potential of the APOLLO2 method to compute different fluxes for the different pebble types of a multi-pebble geometry was used to evaluate the bias committed by the average composition pebble approximation. Thanks to a 'compensation of error', this

  2. Preliminary Investigation of Momentary Bed Failure Using a Multi-dimensional Eulerian Two-phase Model

    Science.gov (United States)

    Cheng, Z.; Hsu, T. J.; Calantoni, J.

    2014-12-01

    In the past decade, researchers have clearly been making progress in predicting coastal erosion/recovery; however, evidences are also clear that existing coastal evolution models cannot predict coastal responses subject to extreme storm events. In this study, we investigate the dynamics of momentary bed failure driven by large horizontal pressure gradients, which may be the dominant sediment transport mechanism under intense storm condition. Recently, a multi-dimensional two-phase Eulerian sediment transport model has been developed and disseminated to the research community as an open-source code. The numerical model is based on extending an open-source CFD library of solvers, OpenFOAM. Model results were validated with published sediment concentration and velocity data measured in steady and oscillatory flow. The 2DV Reynolds-averaged model showed wave-like bed instabilities when the criteria of momentary bed failure was exceeded. These bed instabilities were responsible for the large transport rate observed during plug flow and the onset of the instabilities was associated with a large erosion depth. To better resolve the onset of bed instabilities, subsequent energy cascade and the resulting large sediment transport rate and sediment pickup flux, 3D turbulence-resolving simulations were also carried out. Detailed validation of the 3D turbulence-resolving Eulerian two-phase model will be presented along with the expanded investigation on the dynamics of momentary bed failure.

  3. Dispersed plug flow model for upflow anaerobic sludge bed reactors with focus on granular sludge dynamics

    NARCIS (Netherlands)

    Kalyuzhnyi, S.V.; Fedorovich, V.V.; Lens, P.N.L.

    2006-01-01

    A new approach to model upflow anaerobic sludge bed (UASB)-reactors, referred to as a one-dimensional dispersed plug flow model, was developed. This model focusses on the granular sludge dynamics along the reactor height, based on the balance between dispersion, sedimentation and convection using on

  4. 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.

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

    International Nuclear Information System (INIS)

    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

  6. Simulation of seagrass bed mapping by satellite images based on the radiative transfer model

    Science.gov (United States)

    Sagawa, Tatsuyuki; Komatsu, Teruhisa

    2015-06-01

    Seagrass and seaweed beds play important roles in coastal marine ecosystems. They are food sources and habitats for many marine organisms, and influence the physical, chemical, and biological environment. They are sensitive to human impacts such as reclamation and pollution. Therefore, their management and preservation are necessary for a healthy coastal environment. Satellite remote sensing is a useful tool for mapping and monitoring seagrass beds. The efficiency of seagrass mapping, seagrass bed classification in particular, has been evaluated by mapping accuracy using an error matrix. However, mapping accuracies are influenced by coastal environments such as seawater transparency, bathymetry, and substrate type. Coastal management requires sufficient accuracy and an understanding of mapping limitations for monitoring coastal habitats including seagrass beds. Previous studies are mainly based on case studies in specific regions and seasons. Extensive data are required to generalise assessments of classification accuracy from case studies, which has proven difficult. This study aims to build a simulator based on a radiative transfer model to produce modelled satellite images and assess the visual detectability of seagrass beds under different transparencies and seagrass coverages, as well as to examine mapping limitations and classification accuracy. Our simulations led to the development of a model of water transparency and the mapping of depth limits and indicated the possibility for seagrass density mapping under certain ideal conditions. The results show that modelling satellite images is useful in evaluating the accuracy of classification and that establishing seagrass bed monitoring by remote sensing is a reliable tool.

  7. Packed bed heat storage: Continuum mechanics model and validation

    Science.gov (United States)

    Knödler, Philipp; Dreißigacker, Volker; Zunft, Stefan

    2016-05-01

    Thermal energy storage (TES) systems are key elements for various types of new power plant concepts. As possible cost-effective storage inventory option, packed beds of miscellaneous material come into consideration. However, high technical risks arise due to thermal expansion and shrinking of the packed bed's particles during cyclic thermal operation, possibly leading to material failure. Therefore, suitable tools for designing the heat storage system are mandatory. While particle discrete models offer detailed simulation results, the computing time for large scale applications is inefficient. In contrast, continuous models offer time-efficient simulation results but are in need of effective packed bed parameters. This work focuses on providing insight into some basic methods and tools on how to obtain such parameters and on how they are implemented into a continuum model. In this context, a particle discrete model as well as a test rig for carrying out uniaxial compression tests (UCT) is introduced. Performing of experimental validation tests indicate good agreement with simulated UCT results. In this process, effective parameters required for a continuous packed bed model were identified and used for continuum simulation. This approach is validated by comparing the simulated results with experimental data from another test rig. The presented method significantly simplifies subsequent design studies.

  8. Circulating fluidized bed combustion in the turbulent regime: Modeling of carbon combustion efficiency and sulfur retention

    Energy Technology Data Exchange (ETDEWEB)

    Adanez, J.; Gayan, P.; Grasa, G.; Diego, L.F. de; Armesto, L.; Cabanillas, A.

    1999-07-01

    In this work carbon combustion efficiencies and sulfur retentions in CFBC under the turbulent regime were studied. Experimental results were obtained from the combustion of a lignite and an anthracite with a limestone in a CBF pilot plant with 20 cm internal diameter and 6.5 m height. The effect of operating conditions such as coal and limestone particle size distributions, temperature, excess air, air velocity and Ca/S molar ratio on carbon combustion efficiency and sulfur retention was studied. On the other hand, a mathematical model for the carbon combustion efficiencies and sulfur retentions in circulating fluidized bed combustors operating under the turbulent regime was developed. The model has been developed considering the hydrodynamics behavior of a turbulent bed, the kinetics of carbon combustion and sulfur retention in the riser. The hydrodynamics characteristics of the turbulent regime were previously studied in a cold pilot plant and equations to determine the axial and radial voidage in the bed were proposed. A core-annulus structure in the dilute region of the bed was found in this regime. Carbon combustion and sulfur retention were modeled by modifying a model developed for fast beds and taking into account turbulent regime characteristics. The experimental results of carbon combustion efficiencies and sulfur retentions were compared with those predicted by the model and a good correlation was found for all the conditions used.

  9. Discrete element modelling of fluidised bed spray granulation

    OpenAIRE

    Goldschmidt, MJV; Weijers, GGC; Boerefijn, R; Kuipers, JAM Hans

    2002-01-01

    A novel discrete element spray granulation model capturing the key features of fluidised bed hydrodynamics, liquid-solid contacting and agglomeration is presented. The model computes the motion of every individual particle and droplet in the system, considering the gas phase as a continuum. Micro scale processes such as particle-particle collisions, droplet-particle coalescence and agglomeration are directly taken into account by simple closure models. Simulations of the hydrodynamic behaviou...

  10. STUDY ON SIMILARITY LAWS OF A DISTORTED RIVER MODEL WITH A MOVABLE BED

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this study, by considering the scale ratio related to thespecific gravity of the submerged bed material,and introducing a degree of distortion, n the similarity laws for a distorted river model with a movable bed were derived under the conditions that the values of dual dimensionless parameters in a regime-criterion diagram for the bars are the same in a model as they are in a prototype, and that a resistance law such as the Manning-Strickler-type formula is to be valid for a model and a prototype. The usefulness of the similarity laws derived in this study was verified by comparing the bed forms from the distroted model experiments with the bed forms from the 1/50-scale undistorted model experiments, which were performed by the Hokkaido Development Bureau (H. D.B. ), Japan, to examine the tentative plan for the improvement of a low-flow channel in the Chubetsu River, which is a tributary of the Ishikari River. It is considered that the distorted model experiments to be valid with either sand or lightweight bed material.

  11. Modeling and Simulation of Fixed Bed Adsorption Column using Integrated CFD Approach

    Directory of Open Access Journals (Sweden)

    A.M. Shariff

    2010-01-01

    Full Text Available The understanding of detailed fluid flow in the fixed bed adsorption column is substantially crucial since the mass and heat transfer in the bed is influenced by the column hydrodynamics. In this study, an integrated CFD model was developed to model and simulate the adsorption dynamics and hydrodynamics of gaseous fluid (CH4 and CO2 mixture in the fixed bed adsorption column. The developed integrated model was used to determine the CO2 concentration factor at the column (which indicating the CO2 adsorption capacity as a function of time, based on different operating conditions. The simulated results were compared with experimental data and found to give a good agreement with error less than 2.5%. The effect of various influencing parameters such as feed velocity, bed porosity and feed concentration were studied to investigate their influences on the CO2 adsorption capacity. Besides, the effect of inlet CO2 concentration on the bed temperature profile was also studied in the present study.

  12. A comparative analysis of two solid mixing models suitable for coal fluidized bed combustors and gasifiers

    Energy Technology Data Exchange (ETDEWEB)

    Abanades, J.C.; Atares, S.; Grasa, G.

    1999-07-01

    Rapid solid mixing is important to avoid undesirable temperature profiles in fluidized beds combustors and gasifiers. In this work, two alternative mathematical models for solid axial mixing are compared and their suitability for coal based fluidized beds is discussed. The two models: the Dispersion Model (May (1959)) and the Countercurrent Backmixing Model (van Deemter (1967)) were postulated early in the development of fluidized beds and both have been applied successfully despite their fundamental differences in conception. A numerical analysis investigating the convergence in the predictions of both models under practical conditions has been carried out. There is a wide area of practical interest in which both models are close (relative to typical experimental errors). Reasonable values for the bubble/slug parameters in the CCBM model are able to fit data where the dispersion model has been previously successful. This result has been confirmed with both their experimental data and other published works. The conclusion from this analysis is that the CCBM model is more reliable idealization in describing and scaling up solid mixing in coal based fluidized beds.

  13. Development of second-generation pressurized fluidized bed combustion process

    Energy Technology Data Exchange (ETDEWEB)

    Wolowodiuk, W.; Robertson, A. [Foster Wheeler Development Corp., Livingston, NJ (United States); Bonk, D. [Dept. of Energy, Morgantown, WV (United States)

    1995-12-01

    Under the sponsorship of the United States Department of Energy, Foster Wheeler Development Corporation, and its team members, Westinghouse, Gilbert/Commonwealth, and the Institute of Gas Technology are developing second-generation pressurized fluidized bed combustion technology capable of achieving net plant efficiency in excess of 45 percent based on the higher heating value of the coal. A three-phase program entails design and costing of a 500 MWe power plant and identification of developments needed to commercialize this technology (Phase 1), testing of individual components (Phase 2), and finally testing these components in an integrated mode (Phase 3). This paper briefly describes the results of the first two phases as well as the progress on the third phase. Since other projects which use the same technology are in construction or in negotiation stages-namely, the Power System Development Facility and the Four Rivers Energy Modernization Projects-brief descriptions of these are also included.

  14. Thermal enhancement cartridge heater modified (TECH Mod) tritium hydride bed development, Part 1 - Design and fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Klein, J.E.; Estochen, E.G. [Savannah River National Laboratory, Aiken, SC (United States)

    2015-03-15

    The Savannah River Site (SRS) tritium facilities have used first generation (Gen1) LaNi{sub 4.25}Al{sub 0.75} (LANA0.75) metal hydride storage beds for tritium absorption, storage, and desorption. The Gen1 design utilizes hot and cold nitrogen supplies to thermally cycle these beds. Second and third generation (Gen2 and Gen3) storage bed designs include heat conducting foam and divider plates to spatially fix the hydride within the bed. For thermal cycling, the Gen2 and Gen3 beds utilize internal electric heaters and glovebox atmosphere flow over the bed inside the bed external jacket for cooling. The currently installed Gen1 beds require replacement due to tritium aging effects on the LANA0.75 material, and cannot be replaced with Gen2 or Gen3 beds due to different designs of these beds. At the end of service life, Gen1 bed desorption efficiencies are limited by the upper temperature of hot nitrogen supply. To increase end-of-life desorption efficiency, the Gen1 bed design was modified, and a Thermal Enhancement Cartridge Heater Modified (TECH Mod) bed was developed. Internal electric cartridge heaters in the new design to improve end-of-life desorption, and also permit in-bed tritium accountability (IBA) calibration measurements to be made without the use of process tritium. Additional enhancements implemented into the TECH Mod design are also discussed. (authors)

  15. Thermal enhancement cartridge heater modified (TECH Mod) tritium hydride bed development, Part 1 - Design and fabrication

    International Nuclear Information System (INIS)

    The Savannah River Site (SRS) tritium facilities have used first generation (Gen1) LaNi4.25Al0.75 (LANA0.75) metal hydride storage beds for tritium absorption, storage, and desorption. The Gen1 design utilizes hot and cold nitrogen supplies to thermally cycle these beds. Second and third generation (Gen2 and Gen3) storage bed designs include heat conducting foam and divider plates to spatially fix the hydride within the bed. For thermal cycling, the Gen2 and Gen3 beds utilize internal electric heaters and glovebox atmosphere flow over the bed inside the bed external jacket for cooling. The currently installed Gen1 beds require replacement due to tritium aging effects on the LANA0.75 material, and cannot be replaced with Gen2 or Gen3 beds due to different designs of these beds. At the end of service life, Gen1 bed desorption efficiencies are limited by the upper temperature of hot nitrogen supply. To increase end-of-life desorption efficiency, the Gen1 bed design was modified, and a Thermal Enhancement Cartridge Heater Modified (TECH Mod) bed was developed. Internal electric cartridge heaters in the new design to improve end-of-life desorption, and also permit in-bed tritium accountability (IBA) calibration measurements to be made without the use of process tritium. Additional enhancements implemented into the TECH Mod design are also discussed. (authors)

  16. THERMAL ENHANCEMENT CARTRIDGE HEATER MODIFIED TECH MOD TRITIUM HYDRIDE BED DEVELOPMENT PART I DESIGN AND FABRICATION

    Energy Technology Data Exchange (ETDEWEB)

    Klein, J.; Estochen, E.

    2014-03-06

    The Savannah River Site (SRS) tritium facilities have used 1{sup st} generation (Gen1) LaNi{sub 4.25}Al{sub 0.75} (LANA0.75) metal hydride storage beds for tritium absorption, storage, and desorption. The Gen1 design utilizes hot and cold nitrogen supplies to thermally cycle these beds. Second and 3{sup rd} generation (Gen2 and Gen3) storage bed designs include heat conducting foam and divider plates to spatially fix the hydride within the bed. For thermal cycling, the Gen2 and Gen 3 beds utilize internal electric heaters and glovebox atmosphere flow over the bed inside the bed external jacket for cooling. The currently installed Gen1 beds require replacement due to tritium aging effects on the LANA0.75 material, and cannot be replaced with Gen2 or Gen3 beds due to different designs of these beds. At the end of service life, Gen1 bed desorption efficiencies are limited by the upper temperature of hot nitrogen supply. To increase end-of-life desorption efficiency, the Gen1 bed design was modified, and a Thermal Enhancement Cartridge Heater Modified (TECH Mod) bed was developed. Internal electric cartridge heaters in the new design to improve end-of-life desorption, and also permit in-bed tritium accountability (IBA) calibration measurements to be made without the use of process tritium. Additional enhancements implemented into the TECH Mod design are also discussed.

  17. Modeling of a fluidized bed reactor for the ethylene-propylene copolymerization

    Directory of Open Access Journals (Sweden)

    Juan Guillermo Cadavid Estrada

    2010-04-01

    Full Text Available A mathematical model for the ethylene - propylene copolymerization with a Ziegler - Natta catalyst in a gas phase fludized bed reactor is presented. The model includes a two active site kinetic model with spontaneous transfer reactions and site deactivation. Also, it is studied and simulated the growth of a polymeric particle which is exposed to an outside atmosphere (monomers concentrations and temperature that represent the emulsion phase conditions of the reactor. Particle growth model is the basis for the study of the sizes distribution into the reactor. Two phase model of Kunii-Levenspiel is the basis for the modelling and simulation of the fluid bed reactor, the models developed consider two extreme cases for the gas mixed grade in emulsion phase (perfectly mixed and plug flow. The solution of the models includes mass (for the two monomers and energy balances, coupled with the particle growth and residence time distribution models.

  18. Experiments and Modelling of Coal Pyrolysis under Fluidized Bed Conditions

    Institute of Scientific and Technical Information of China (English)

    ZhangYongzhe; XuXiangdong; 等

    1999-01-01

    The pyrolysis behavior of two Chinese coals has been investigated in a laboratory-scale bubbling fluidized bed system in Siegen University,Germany,Experimental equipment and procedure are introduced.The amounts of pyrolysis species of each coal were measured,calcuated and compared.A new method was presented to determine the needed parameters in FG-DVC model with the experimental results instead of other much more complicated experiments.

  19. Atmospheric fluidized bed combustor development program. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Ashworth, R.A.; Melick, T.A.; Plessinger, D.A.; Sommer, T.M. [Energy and Environmental Research Corp., Orville, OH (United States); Keener, H.M. [Ohio State Univ., Columbus, OH (United States). Ohio Agricultural Research and Development Center; Webner, R.L. [Will-Burt, Orrville, OH (United States)

    1995-12-01

    The objective of this project was to demonstrate and promote the commercialization of a coal-fired atmospheric fluidized bed combustion (AFBC) system, with limestone addition for SO{sub 2} emissions control and a baghouse for particulate emissions control. This AFBC system was targeted for small scale industrial-commercial-institutional space and process heat applications in the 1 x 10{sup 6} to 10 x 10{sup 6} Btu/hr capacity range. A cost effective and environmentally acceptable AFBC technology in this size range would displace a considerable amount of gas/oil with coal while resulting in significant total cost savings to the owner/operators. The project itself was separated into three levels: (1) feasibility, (2--3) subsystem development and integration, and (4) proof-of-concept. In Level (1), the technical and economic feasibility of a 1 million Btu/hr coal-fired AFBC air heater was evaluated. In Level (2--3), the complete EER fluidized bed combustor (1.5 million Btu/hr) system was developed and tested. The goal or reducing SO{sub 2} emissions to 1.2 lb/10{sup 6} Btu, from high sulfur Ohio coal, was achieved by adding limestone with a Ca/S (coal) ratio of {approximately} 3.0. Finally, in Level (4), the proof-of-concept system, a 2.2 million Btu/hr unit was installed and successfully operated at Cedar Lane Farms, a commercial nursery in Ohio.

  20. Batch top-spray fluid bed coating: Scale-up insight using dynamic heat- and mass-transfer modelling

    DEFF Research Database (Denmark)

    Hede, Peter Dybdahl; Bach, P.; Jensen, Anker Degn

    2009-01-01

    A mathematical model was developed for batch top-spray fluid bed coating processes based on Ronsse et al. [2007a.b. Combined population balance and thermodynamic modelling of the batch top-spray fluidised bed coating process. Part I-model development and validation. journal of Food Engineering 78......, 296-307; Combined population balance and thermodynamic modelling of the batch top-spray fluidised bed coating process. Part II-model and process analysis. journal of Food Engineering 78, 308-322]. The model is based on one-dimensional discretisation of the fluid bed into a number of well-mixed control......-TEC Anhydro) production-scale, the gradients become too large to use the simple combined drying force/relative droplet size scale-up approach without also increasing the inlet fluidisation air temperature significantly. Instead, scale-up in terms of combinations of the viscous Stokes theory with simulated...

  1. A phenomenological energy model of biomass pyrolysis under autothermal fluidized bed conditions

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, J.; Beaton, P. [University of the Orient, Santiago de Cuba (Cuba). Faculty of Mechanical Engineering; Zanzi, R. [Royal Inst. of Technology, Stockholm (Sweden). Dept. of Chemical Engineering and Technology

    2006-06-15

    In Cuba a variety of types of biomass is being investigated for energy conversion through thermochemical processes into solid, liquid, and gas products. A continuous bench fluidized bed pyrolysis has been designed and is currently under testing. In this article, a transport model has been developed to simulate the axial temperature fields in a bench. The model and experimental results indicated that (1) two zones exist inside of the fluidization column, the dense bed where the exothermic and endothermic reactions are active, and the freeboard zone where the temperature of the pyrolysis product decreases continuously; (2) the bed temperature increases with an increase in the air factor. The predicted temperature is in quantitative agreement with experimental measurements. (Author)

  2. Development and stability of bed forms: a numerical analysis of dune pattern coarsening and giant dunes

    Science.gov (United States)

    Gao, Xin; Narteau, Clement; Rozier, Olivier

    2015-04-01

    We investigate the development and stability of transverse dunes for ranges of flow depths and velocities using a cellular automaton dune model. Subsequent to the initial bed instability, dune pattern coarsening is driven by bed form interactions. Collisions lead to two types of coalescence associated with upstream or downstream dominant dunes. In addition, a single collision-ejection mechanism enhances the exchange of mass between two consecutive bed forms (through-passing dunes). The power-law increases in wavelength and amplitude exhibit the same exponents, which are independent of flow properties. Contrary to the wavelength, dune height is not only limited by flow depth but also by the strength of the flow. Superimposed bedforms may propagate and continuously destabilize the largest dunes. Then, we identify three classes of steady-state transverse dune fields according to the periodicity in crest-to-crest spacing and the mechanism of size limitation. In all cases, the steady state is reached when the bed shear stress in the dune trough regions is close to its critical value for motion inception. Such a critical shear stress value is reached and maintained through the dynamic equilibrium between flow strength and dune aspect ratio. Comparisons with natural dune fields show that many of them may have reached such a steady state. Finally, we infer that the sedimentary patterns in the model may be used to bring new constraints on the stability of modern and ancient dune fields.

  3. Multiple model identification of a cold flow circulating fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Panday, Rupen; Famouri, P.; Woerner, B.D.; Turton, R.; •Ludlow, J.C.; Shadle, L.J.; Boyle, E.J.

    2008-05-13

    Solids circulation rate is an important parameter that is essential to the control and improved performance of a circulating fluidized bed system. The present work focuses on the identification of a cold flow circulating fluidized bed using a multiple model identification technique that considers the given set-up as a nonlinear dynamic system and predicts the solids circulation rate as a function of riser aeration, move air flow rate, and total riser pressure drop. The predictor model obtained from this technique is trained on glass beads data sets in which riser aeration and move air flow are varied randomly one at a time. The global linear state space model obtained from the N4SID algorithm is trained on the same data set and the prediction results of solids circulation rate from both these algorithms are tested against data obtained at operating conditions different from the training data. The comparison between the two methods shows that the prediction results obtained from the multiple model technique are better than those obtained from the global linear model. The number of local models is increased from two to five and two third order state space models are sufficient for the present sets of data.

  4. Modeling results for mass production layering in a fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Boehm, K.J., E-mail: kuboehm@gmail.com [Center for Energy Research, M/C 0438 460D EBU II, University of California, San Diego, CA 92093-0438 (United States); Raffray, A.R. [Center for Energy Research, M/C 0438 460D EBU II, University of California, San Diego, CA 92093-0438 (United States); Alexander, N.B.; Goodin, D.T. [General Atomics, P.O. Box 85608, San Diego, CA 92186-5608 (United States)

    2011-06-15

    A fluidized bed has been proposed as a layering device for the mass production of inertial fusion energy fuel pellets. During this layering process, the frozen deuterium or deuterium-tritium mixture filled into a hollow capsule (about 2-4 mm in diameter) is redistributed leading to a fuel layer of uniform thickness on the inside of the fuel capsule. Several physical processes have been identified to interact with each other to influence the outcome of the layering process in a fluidized bed, which needs to fulfill symmetry requirements of the fuel layer thickness, smoothness and surface damage requirements of the outside target surface and must be able to produce a large number of targets (500 000 per day). This work describes the development and use of numerical tools to conduct a trade-off study focusing on the influence of different flow conditions of the fluidizing gas on the total layering time, final layer uniformity and outer surface damage.

  5. Experimental modelling of flow - bed interactions in Jökulhlaups

    Science.gov (United States)

    Carrivick, J. L.; Xie, Z.; Sleigh, A.; Hubbard, M.

    2009-04-01

    Jökulhlaups (glacial outburst floods) are a sudden release and advancing wave of water and sediment from a glacier, with a peak discharge that is often several orders of magnitude greater than perennial flows. Jökulhlaup hazards are regularly incorporated into risk assessments for glaciated areas because the associated flood hazards are numerous. Jökulhlaup hazards are primarily due to direct impacts, caused by a frontal surge wave, from debris within a flow body, and from the mass and consistency of the flows. A number of secondary impacts also pose hazards, including widespread deposition of sediment and blocked tributary streams. It is rapid landscape change, which is achieved the mobilization and redistribution of sediment that causes one of the greatest hazards due to jökulhlaups. However, direct measurement of such phenomena is virtually impossible. The aim of this project is therefore to parameterise hydrodynamic - sedimentary interactions in experimental jökulhlaups. Specifically, this project applies laboratory flume modelling, which offers a hitherto untapped opportunity for examining complex interactions between water and sediment within outburst floods. The experimental set-up is of a tradition lock-gate design with a straight 4 m long tank. Hydraulics are scaled at 1:20 froude scale and the following controls on frontal wave flow-bed interactions and hence on rapid landscape change are being investigated: 1. Pre-existing mobile sediment effects, fixed bed roughness effects, sediment concentration effects, mobile bed effects. An emphasis is being maintained on examining the downstream temporal and spatial change in physical character of the water / sediment frontal wave. Facilities are state-of-the-art with a fully-automated laser bed-profiler to measure bed elevation after a run, Seatek arrays to measure transient flow depths, 0.5 Hz Ultrasonic Velocimeter Profiling to measure within-flow velocities, and Ultrasonic High-Concentration Meter (UHCM

  6. Model of rough bed for numerical simulation of saltation

    Czech Academy of Sciences Publication Activity Database

    Kharlamova, Irina; Vlasák, Pavel

    19, 3 (2015), s. 366-385. ISSN 1964-8189 R&D Projects: GA ČR GA103/09/1718; GA ČR GAP105/10/1574 Institutional support: RVO:67985874 Keywords : saltation * bed load transport * rough bed * armoured bed * bed roughness Subject RIV: BK - Fluid Dynamics Impact factor: 0.514, year: 2014

  7. Local CFD kinetic model of cadmium vaporization during fluid bed incineration of municipal solid waste

    Energy Technology Data Exchange (ETDEWEB)

    Soria, J. [Instituto Multidisciplinario de Investigación y Desarrollo de la Patagonia Norte (IDEPA, CONICET-UNCo) y Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquén (Argentina); Laboratoire Procédés, Matériaux et Energie Solaire (CNRS-PROMES), 7 Rue du Four Solaire, Odeillo, 66120 Font-Romeu (France); Gauthier, D., E-mail: Daniel.Gauthier@promes.cnrs.fr [Laboratoire Procédés, Matériaux et Energie Solaire (CNRS-PROMES), 7 Rue du Four Solaire, Odeillo, 66120 Font-Romeu (France); Falcoz, Q.; Flamant, G. [Laboratoire Procédés, Matériaux et Energie Solaire (CNRS-PROMES), 7 Rue du Four Solaire, Odeillo, 66120 Font-Romeu (France); Mazza, G. [Instituto Multidisciplinario de Investigación y Desarrollo de la Patagonia Norte (IDEPA, CONICET-UNCo) y Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquén (Argentina)

    2013-03-15

    Highlights: ► A 2-D local CFD model for simulating the Cd vaporization process is presented. ► It includes a kinetic expression of Cd vaporization into the incineration process. ► Pyrolysis, volatiles’ combustion and residual carbon combustion are also taken into account. ► It fits very well the experimental results obtained on a lab-scale fluidized bed reported in literature. ► It also compares favorably with a model developed previously by the group. -- Abstract: The emissions of heavy metals during incineration of Municipal Solid Waste (MSW) are a major issue to health and the environment. It is then necessary to well quantify these emissions in order to accomplish an adequate control and prevent the heavy metals from leaving the stacks. In this study the kinetic behavior of Cadmium during Fluidized Bed Incineration (FBI) of artificial MSW pellets, for bed temperatures ranging from 923 to 1073 K, was modeled. FLUENT 12.1.4 was used as the modeling framework for the simulations and implemented together with a complete set of user-defined functions (UDFs). The CFD model combines the combustion of a single solid waste particle with heavy metal (HM) vaporization from the burning particle, and it takes also into account both pyrolysis and volatiles’ combustion. A kinetic rate law for the Cd release, derived from the CFD thermal analysis of the combusting particle, is proposed. The simulation results are compared with experimental data obtained in a lab-scale fluidized bed incinerator reported in literature, and with the predicted values from a particulate non-isothermal model, formerly developed by the authors. The comparison shows that the proposed CFD model represents very well the evolution of the HM release for the considered range of bed temperature.

  8. Local CFD kinetic model of cadmium vaporization during fluid bed incineration of municipal solid waste

    International Nuclear Information System (INIS)

    Highlights: ► A 2-D local CFD model for simulating the Cd vaporization process is presented. ► It includes a kinetic expression of Cd vaporization into the incineration process. ► Pyrolysis, volatiles’ combustion and residual carbon combustion are also taken into account. ► It fits very well the experimental results obtained on a lab-scale fluidized bed reported in literature. ► It also compares favorably with a model developed previously by the group. -- Abstract: The emissions of heavy metals during incineration of Municipal Solid Waste (MSW) are a major issue to health and the environment. It is then necessary to well quantify these emissions in order to accomplish an adequate control and prevent the heavy metals from leaving the stacks. In this study the kinetic behavior of Cadmium during Fluidized Bed Incineration (FBI) of artificial MSW pellets, for bed temperatures ranging from 923 to 1073 K, was modeled. FLUENT 12.1.4 was used as the modeling framework for the simulations and implemented together with a complete set of user-defined functions (UDFs). The CFD model combines the combustion of a single solid waste particle with heavy metal (HM) vaporization from the burning particle, and it takes also into account both pyrolysis and volatiles’ combustion. A kinetic rate law for the Cd release, derived from the CFD thermal analysis of the combusting particle, is proposed. The simulation results are compared with experimental data obtained in a lab-scale fluidized bed incinerator reported in literature, and with the predicted values from a particulate non-isothermal model, formerly developed by the authors. The comparison shows that the proposed CFD model represents very well the evolution of the HM release for the considered range of bed temperature

  9. Development and Application of a Process Window for Achieving High-Quality Coating in a Fluidized Bed Coating Process

    OpenAIRE

    Laksmana, F. L.; Hartman Kok, P. J. A.; Vromans, H; Frijlink, H. W.; Van der Voort Maarschalk, K.

    2009-01-01

    Next to the coating formulation, process conditions play important roles in determining coating quality. This study aims to develop an operational window that separates layering from agglomeration regimes and, furthermore, the one that leads to the best coating quality in a fluidized bed coater. The bed relative humidity and the droplet size of the coating aerosol were predicted using a set of engineering models. The coating quality was characterized using a quantitative image analysis method...

  10. Modeling of laminar forced convection in spherical- pebble packed beds

    International Nuclear Information System (INIS)

    There are many parameters that have significant effects on forced convection heat transfer in packed beds, including Reynolds and Prandtl numbers of flow, porosity, pebble geometry, local flow conditions, wall and end effects. In addition, there have been many experimental investigations on forced convection heat transfer in packed beds and each have studied the effect of some of these parameters. Yet, there is not a reliable correlation that includes the effect of main parameters: at the same time, the prediction of precise correct limits for very low and high Reynolds numbers is off hand. In this article a general well-known model of convection heat transfer from isothermal bodies, next to some previous reliable experimental data has been used as a basis for a more comprehensive and accurate correlation to calculate the laminar constant temperature pebble-fluid forced convection heat transfer in a homogeneous saturated bed with spherical pebbles. Finally, for corroboration, the present results are compared with previous works and show a very good agreement for laminar flows at any Prandtl number and all porosities

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

    Energy Technology Data Exchange (ETDEWEB)

    Unknown

    2002-03-29

    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 2800 F) 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

  12. Modeling-based optimization of a fixed-bed industrial reactor for oxidative dehydrogenation of propane

    Institute of Scientific and Technical Information of China (English)

    Ali Darvishi; Razieh Davand; Farhad Khorasheh; Moslem Fattahi

    2016-01-01

    An industrial scale propylene production via oxidative dehydrogenation of propane (ODHP) in multi-tubular re-actors was modeled. Multi-tubular fixed-bed reactor used for ODHP process, employing 10000 of smal diameter tubes immersed in a shel through a proper coolant flows. Herein, a theory-based pseudo-homogeneous model to describe the operation of a fixed bed reactor for the ODHP to correspondence olefin over V2O5/γ-Al2O3 catalyst was presented. Steady state one dimensional model has been developed to identify the operation parameters and to describe the propane and oxygen conversions, gas process and coolant temperatures, as well as other pa-rameters affecting the reactor performance such as pressure. Furthermore, the applied model showed that a double-bed multitubular reactor with intermediate air injection scheme was superior to a single-bed design due to the increasing of propylene selectivity while operating under lower oxygen partial pressures resulting in propane conversion of about 37.3%. The optimized length of the reactor needed to reach 100%conversion of the oxygen was theoretically determined. For the single-bed reactor the optimized length of 11.96 m including 0.5 m of inert section at the entrance region and for the double-bed reactor design the optimized lengths of 5.72 m for the first and 7.32 m for the second reactor were calculated. Ultimately, the use of a distributed oxygen feed with limited number of injection points indicated a significant improvement on the reactor performance in terms of propane conversion and propylene selectivity. Besides, this concept could overcome the reactor run-away temperature problem and enabled operations at the wider range of conditions to obtain enhanced propyl-ene production in an industrial scale reactor.

  13. Local CFD kinetic model of cadmium vaporization during fluid bed incineration of municipal solid waste.

    Science.gov (United States)

    Soria, J; Gauthier, D; Falcoz, Q; Flamant, G; Mazza, G

    2013-03-15

    The emissions of heavy metals during incineration of Municipal Solid Waste (MSW) are a major issue to health and the environment. It is then necessary to well quantify these emissions in order to accomplish an adequate control and prevent the heavy metals from leaving the stacks. In this study the kinetic behavior of Cadmium during Fluidized Bed Incineration (FBI) of artificial MSW pellets, for bed temperatures ranging from 923 to 1073 K, was modeled. FLUENT 12.1.4 was used as the modeling framework for the simulations and implemented together with a complete set of user-defined functions (UDFs). The CFD model combines the combustion of a single solid waste particle with heavy metal (HM) vaporization from the burning particle, and it takes also into account both pyrolysis and volatiles' combustion. A kinetic rate law for the Cd release, derived from the CFD thermal analysis of the combusting particle, is proposed. The simulation results are compared with experimental data obtained in a lab-scale fluidized bed incinerator reported in literature, and with the predicted values from a particulate non-isothermal model, formerly developed by the authors. The comparison shows that the proposed CFD model represents very well the evolution of the HM release for the considered range of bed temperature. PMID:23410804

  14. Evaluation of drying models of apple (var. Ligol) dried in a fluidized bed dryer

    International Nuclear Information System (INIS)

    Highlights: ► Three new drying models are formulated. ► The developed models are various modifications of the Page model. ► Nineteen models are used to describe the fluidized bed drying of apple. ► The Page model and formulated model is considered as the most appropriate. - Abstract: Three new drying models were formulated. The developed models are various modifications of the Page model. The models were used to describe the drying behaviour of apple (var. Ligol) dried in a fluidized bed dryer. The suitability of new models to describe the drying characteristics were compared to the accuracy of sixteen models available from the literature. The accuracies of the models were measured using the correlation coefficient (R), root mean square error (RMSE), and reduced chi-square (χ2). Three new developed models described the drying characteristics of apple cubes satisfactorily (R > 0.997). The Page model and one of the empirical models formulated by the authors of this study can be considered as the most appropriate (R > 0.9977, RMSE = 0.0094–0.0167, χ2 = 0.0001–0.0002). The effect of drying air temperature on the drying models parameters were also determined. The shrinkage of apple cubes during drying was measured to assess the changes in quality of dried apples

  15. Modeling of fluidized-bed combustion of coal: Phase II, final reports. Volume V. Appendix: stability and instability in fluidized-bed combustion

    Energy Technology Data Exchange (ETDEWEB)

    Louis, J.F.; Tung, S.E.

    1980-10-01

    This document is the fifth of the seven volumes series of our Phase II Final Report. The material developed in this volume has not been incorporated into the system model. It will be used as a precursor of a transient model to be developed in the next phase of our model work. There have been various fluidized combustor models of differing complexity and scope published in the literature. Most of these models have identified and predicted - often in satisfactory agreement with results from pilot units - the key steady state combustor characteristics such as the mass of carbon in the bed (carbon loading), the combustion efficiency, the sulfur retention by the solid sorbent and the pollutant (mainly NO/sub x/) emissions. These models, however, cannot be in most instances successfully used to study the extinction and ignition characteristics of the combustor because they are isothermal in structure in the sense that the bed temperature is not an output variable but rather an input one and must be a priori specified. In order to remedy these inadequacies of the previous models, we here present a comprehensive account of the formulation and some typical results of a new nonisothermal model which has been developed in order to study, among other things, the ignition and extinction characteristics of the AFBC units. This model is able to predict the temperature patterns in the bed, the carbon loading, the combustion efficiency and the O/sub 2/ and CO concentration profiles in the combustor for the different design or operational characteristics.

  16. A One-Dimensional (1-D) Three-Region Model for a Bubbling Fluidized-Bed Adsorber

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Andrew; Miller, David C.

    2012-01-01

    A general one-dimensional (1-D), three-region model for a bubbling fluidized-bed adsorber with internal heat exchangers has been developed. The model can predict the hydrodynamics of the bed and provides axial profiles for all temperatures, concentrations, and velocities. The model is computationally fast and flexible and allows for any system of adsorption and desorption reactions to be modeled, making the model applicable to any adsorption process. The model has been implemented in both gPROMS and Aspen Custom Modeler, and the behavior of the model has been verified.

  17. Mathematical modeling of municipal solid waste plasma gasification in a fixed-bed melting reactor

    OpenAIRE

    Zhang, Qinglin

    2011-01-01

    The increasing yield of municipal solid waste (MSW) is one of the main by-products of modern society. Among various MSW treatment methods, plasma gasification in a fixed-bed melting reactor (PGM) is a new technology, which may provide an efficient and environmental friendly solution for problems related to MSW disposals. General objectives of this work are to develop mathematical models for the PGM process, and using these models to analyze the characteristics of this new technology. In this ...

  18. Modeling and simulation of biomass air-steam gasification in a fluidized bed

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    By considering the features of fluidized-bed reactors and the kinetic mechanism of biomass gasification,a steady-state,isothermal,one-dimensional and twophase mathematical model of biomass gasification kinetics in bubbling fluidized beds was developed.The model assumes the existence of two phases - a bubble and an emulsion phase - with chemical reactions occurring in both phases.The axial gas dispersion in the two phases is accounted for and the pyrolysis of biomass is taken to be instantaneous.The char and gas species CO,CO2,H2,H2O,CH4 and 8 chemical reactions are included in the model.The mathematical model belongs to a typical boundary value problem of ordinary differential equations and its solution is obtained by a Matlab program.Utilizing wood powder as the feedstock,the calculated data show satisfactory agreement with experimental results and proves the effectiveness and reliability of the model.

  19. Mathematical Modeling of a Simulated Fixed Bed for Desalting Operation

    OpenAIRE

    M.A. OLUTOYE; Mohamed ALHASSAN

    2006-01-01

    Continue survival of the petrochemical industry in the face of advancement in processing technology must change for better performance. In doing so, the pre-treatment stage of crude, which include desalting will go a long way at improving the overall quality of the product obtained. It is in view of this that a mathematical modeling of adsorption of a fixed simulated bed for desalting operation was carried out to determine the variation of the concentration of adsorbate (mol/l) and the amount...

  20. Validation of new empirical model for self-leveling behavior of cylindrical particle beds based on experimental database

    International Nuclear Information System (INIS)

    During a material relocation phase of core disruptive accidents (CDAs) in sodium cooled fast reactors (SFRs), debris beds can be formed in the lower plenum region due to rapid quenching and fragmentation of molten core materials. Heat removal from debris beds is crucial to achieve so called in-vessel retention (IVR) of degraded core materials. Coolant boiling in the beds may lead to leveling of their mound shape, and then changes coolability of the beds with decay heat as well as neutronic characteristics. To clarify the mechanisms underlying this self-leveling behavior, several series of experiments using simulant materials has been performed in collaboration between Japan Atomic Energy Agency (JAEA) and Kyushu University in Japan. In the present study, experiments in a cylindrical system were employed to develop experimental data on self-leveling process of particle beds. In the experiments, to simulate the coolant boiling due to the decay heat in fuel, nitrogen gas was percolated uniformly through the bottom of the particle bed with a conical shape mound using a gas injection method. Time variations in bed height during the self-leveling process were measured for key experimental parameters on particle size, density and sphericity, and gas flow rate. Using a dimensional analysis approach, a new model was proposed to correlate the experimental data on transient bed height with an empirical equation using a characteristic time of self-leveling development and a terminal equilibrium height of the bed. It was demonstrated that the proposed model predicts self-leveling development of particle beds with reasonable accuracy in the present ranges of experimental conditions. (author)

  1. Numerical Modeling of Seismoelectric Fields through Thin-Beds

    Science.gov (United States)

    Grobbe, N.; Slob, E. C.

    2014-12-01

    The seismoelectric effect might help improving our knowledge of the subsurface. This complex physical phenomenon can be described by Biot's poroelasticity equations coupled to Maxwell's electromagnetic equations. Besides simultaneously offering seismic resolution and electromagnetic sensitivity, the coefficient coupling these two types of fields can in principal provide us with direct information on important medium parameters like porosity and permeability. Two types of seismoelectric coupling can be distinguished: 1) localized coupling generating an electromagnetic field that is present inside the seismic wave and travels with its velocity, referred to as the coseismic field 2) An independent electromagnetic field diffusing with electromagnetic velocity, referred to as the seismoelectric conversion, providing us with information at depth. One of the major challenges of seismoelectrics is the very weak signal-to-noise ratio of especially the seismoelectric conversion. In order to make seismoelectrics applicable in the field, we need to find ways to improve the signal-to-noise ratio of this second order effect. Can nature help us? It is well-known that a seismic wave travelling through a package of thin-beds, can experience amplitude-tuning effects that result in anomalously high amplitudes for the seismic signal. Can similar enhancing signal effects occur for seismoelectric phenomena? Using our analytically based, numerical modeling code ESSEMOD (ElectroSeismic and Seismoelectric Modeling), we investigate what effects thin-beds can have on the seismoelectric signal, thereby focusing especially on the seismoelectric conversion. We will highlight the factors that play a role in the possible enhancement of the seismoelectric signal-to-noise ratio by thin-beds. We show that the seismoelectric method is sensitive to changes in medium parameters on a spatial scale that is much smaller than the seismic resolution. Acknowledgements: This research was funded as a Shell

  2. 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. PMID:26050934

  3. Reduced Order Model of a Spouted Fluidized Bed Utilizing Proper Orthogonal Decomposition

    Science.gov (United States)

    Beck-Roth, Stephanie R.

    2011-07-01

    A reduced order model utilizing proper orthogonal decomposition for approximation of gas and solids velocities as well as pressure, solids granular temperature and gas void fraction for use in multiphase incompressible fluidized beds is developed and presented. The methodology is then tested on data representing a flat-bottom spouted fluidized bed and comparative results against the software Multiphase Flow with Interphase eXchanges (MFIX) are provided. The governing equations for the model development are based upon those implemented in the (MFIX) software. The three reduced order models explored are projective, extrapolative and interpolative. The first is an extension of the system solution beyond an original time sequence. The second is a numerical approximation to a new solution based on a small selected parameter deviation from an existing CFD data set. Finally an interpolative methodology approximates a solution between two existing CFD data sets both which vary a single parameter.

  4. Modeling of chip bed packing in a continuous kraft cooking digester

    OpenAIRE

    Laakso, Sampsa

    2008-01-01

    This work focused on modeling of the chip bed packing phenomena in a continuous kraft cooking digester. A better understanding of chip bed packing would make it possible to optimize chip flow conditions in the digester, thereby ensuring uniform fiber quality and production efficiency. Chips are fed continuously into the digester, with the chip flow forming a solid bed. As the solid chip bed moves slowly downwards, cooking reactions proceed, which leads to softening of the chips. The soft...

  5. Report on the development of equipment and techniques for drilling and machining bedded salt

    International Nuclear Information System (INIS)

    Equipment and techniques are being developed in the evaluation of bedded salt as a storage media for nuclear waste. Beginning with the Conceptual Design Report for the Waste Isolation Pilot Plant and continuing with field and laboratory experiments indicate the need for a more complete understanding of bedded salt as an engineering material. This report discusses various aspects of bedded salt in its comparison to other materials, machining methods in the laboratory and equipment development to support experiments in mines

  6. Artificial neural network modeling of fixed bed biosorption using radial basis approach

    Science.gov (United States)

    Saha, Dipendu; Bhowal, Avijit; Datta, Siddhartha

    2010-04-01

    In modern day scenario, biosorption is a cost effective separation technology for the removal of various pollutants from wastewater and waste streams from various process industries. The difficulties associated in rigorous mathematical modeling of a fixed bed bio-adsorbing systems due to the complexities of the process often makes the development of pure black-box artificial neural network (ANN) models particularly useful in this field. In this work, radial basis function network has been employed as ANN to model the breakthrough curves in fixed bed biosorption. The prediction has been compared to the experimental breakthrough curves of Cadmium, Lanthanum and a dye available in the literature. Results show that this network gives fairly accurate representation of the actual breakthrough curves. The results obtained from ANN modeling approach shows the better agreement between experimental and predicted breakthrough curves as the error for all these situations are within 6%.

  7. Computational fluid dynamics modeling of coal gasification in a pressurized spout-fluid bed

    Energy Technology Data Exchange (ETDEWEB)

    Zhongyi Deng; Rui Xiao; Baosheng Jin; He Huang; Laihong Shen; Qilei Song; Qianjun Li [Southeast University, Nanjing (China). Key Laboratory of Clean Coal Power Generation and Combustion Technology of Ministry of Education

    2008-05-15

    Computational fluid dynamics (CFD) modeling, which has recently proven to be an effective means of analysis and optimization of energy-conversion processes, has been extended to coal gasification in this paper. A 3D mathematical model has been developed to simulate the coal gasification process in a pressurized spout-fluid bed. This CFD model is composed of gas-solid hydrodynamics, coal pyrolysis, char gasification, and gas phase reaction submodels. The rates of heterogeneous reactions are determined by combining Arrhenius rate and diffusion rate. The homogeneous reactions of gas phase can be treated as secondary reactions. A comparison of the calculated and experimental data shows that most gasification performance parameters can be predicted accurately. This good agreement indicates that CFD modeling can be used for complex fluidized beds coal gasification processes. 37 refs., 7 figs., 5 tabs.

  8. Mechanistic model for cuttings removal from solid bed in inclined channels

    Energy Technology Data Exchange (ETDEWEB)

    Ramadan, A.; Skalle, P. [Department of Petroleum Engineering and Applied Geophysics, NTNU, S.P. Andersens vei 15 A, N-7491 Trondheim (Norway); Johansen, S.T. [SINTEF Material Technology, Trondheim (Norway); Svein, J. [SINTEF Industrial Management, Trondheim (Norway); Saasen, A. [Statoil Drilling and Well Fluids, N-4035 Stavanger (Norway)

    2001-09-01

    This paper presents the results and analysis of a set of erosion rate experiments, designed to investigate the removal rate of stationary sand bed particles in an inclined channel. The erosion rate tests of three beds with different bed particle-size ranges show that beds with intermediate average particle size have the maximum erosion rate. The theoretical analysis using a mechanistic model supports this observation. The instantaneous acceleration of bed particles at the beginning of transportation is correlated with particle removal rate. It is shown that the mechanistic model can predict optimum operating parameters to improve the efficiency of hole cleaning.

  9. Artificial neural network models for biomass gasification in fluidized bed gasifiers

    DEFF Research Database (Denmark)

    Puig Arnavat, Maria; Hernández, J. Alfredo; Bruno, Joan Carles;

    2013-01-01

    Artificial neural networks (ANNs) have been applied for modeling biomass gasification process in fluidized bed reactors. Two architectures of ANNs models are presented; one for circulating fluidized bed gasifiers (CFB) and the other for bubbling fluidized bed gasifiers (BFB). Both models determin...... experimental data used R2 > 0.98. Furthermore a sensitivity analysis has been applied in each ANN model showing that all studied input variables are important....

  10. Development of XZ-1200 ripple-bed iodine adsorber

    International Nuclear Information System (INIS)

    The structure and specifications of XZ-1200 ripple-bed iodine adsorbers are described in detail. The performance of the adsorbers in use in Daya Bay NPP are presented and compared with that of the French ones

  11. Development of an Internally Circulating Fluidized Bed Membrane Reactor for Hydrogen Production from Natural Gas

    Institute of Scientific and Technical Information of China (English)

    XIE Dong-lai; GRACE John R; LIM C Jim

    2006-01-01

    An innovative Internally Circulating Fluidized Bed Membrane Reactor (ICFBMR) was designed and operated for ultra-pure hydrogen production from natural gas. The reactor includes internal catalyst solids circulation for conveying heat between a reforming zone and an oxidation zone. In the reforming zone, catalyst particles are transported upwards by reactant gas where steam reforming reactions are taking place and hydrogen is permeating through the membrane surfaces. Air is injected into the oxidation zone to generate heat which is carried by catalyst particles to the reforming zone supporting the endothermic steam reforming reaction. The technology development process is introduced: cold model test,pilot plant and industrial demonstration unit. The process flow diagram and key components of each unit are described.The ICFBMR process has the potential to provide improved performance relative to conventional SMR fixed-bed tubular reactors.

  12. Modeling the axial and lateral mixing of solids in fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Abanades, J.C.; Grasa, G.S. [CSIC, Inst. Carboquim, Zaragoza (Spain). Dept. of Energy & Environment

    2001-11-14

    The solid flow patterns in fluidized beds are often depicted as a number of convective currents induced by rising bubbles. This description is revisited in this work to develop a mathematical model for both the axial and the lateral mixing of solids in fluidized beds. The model uses concepts similar to those used in the countercurrent backmixing model, which is widely used for axial mixing only. Mixing experiments using coal and PVC (as a white tracer) were carried out to obtain experimental concentration maps for model validation. The model reproduces well the general features observed during the mixing experiments, as well as the effects of gas velocity, particle size, and the presence of internals. The selection of most model parameters can be justified with observations of bed and bubble properties. The choice of the exchange rate of solids between countercurrent phases is discussed in light of the new data derived in this work, previously published data, and a sensitivity analysis of the model predictions for this parameter.

  13. Intense transport of bed load - modeling based on experimentally observed flow structure

    Science.gov (United States)

    Matoušek, Václav

    2016-04-01

    A modeling approach is discussed which enables to predict characteristics of steady uniform open-channel flow carrying a large amount of sediment (bed load). The approach considers a layered structure of the sediment-laden flow and employs conditions at layer interfaces to evaluate the flow slope, depth, the thickness of the layers and flow rates of both the sediment and sediment-water mixture. It is based on experimental observations obtained for lightweight granular materials in a laboratory tilting flume. Besides visual observations of a development of the layered structure of the flow, detailed profiles of the longitudinal velocity were collected together with integral characteristics of the flow (depths and slopes, flow rates) in the flume. Values of the grain velocity and concentration at the interfaces were determined from the measurements and observations. In the upper plane bed regime of bed load transport, the flow structure appears to be composed of up to three distinct layers (water layer, linear collisional layer and dense sliding layer). Depending on a value of the bed Shields parameter (and associated flow conditions) the number of layers may change and the thicknesses of the particular layers vary. It appears that collisional layers in flows in which they dominate the flow depth (typically Shields bigger than 1) exhibit a virtually constant value of the collisional-layer Richardson number. Velocity and concentration profiles across the collisional layer can be considered linear. At the bottom of the flow, the Coulomb yield criterion with the assumption of the zero fluid contribution balances the bed shear stress applied by the flowing mixture of water and sediment. These features are employed in the discussed modeling approach and lead to a depth-averaged flow model composed of a set of balance and constitutive equations. A kinetic-theory based formula for granular shear stress at the bottom of the collisional layer is added to close the set of

  14. Radionuclide transport in running waters, sensitivity analysis of bed-load, channel geometry and model discretisation

    International Nuclear Information System (INIS)

    In this report, further investigations of the model concept for radionuclide transport in stream, developed in the SKB report TR-05-03 is presented. Especially three issues have been the focus of the model investigations. The first issue was to investigate the influence of assumed channel geometry on the simulation results. The second issue was to reconsider the applicability of the equation for the bed-load transport in the stream model, and finally the last issue was to investigate how the model discretisation will influence the simulation results. The simulations showed that there were relatively small differences in results when applying different cross-sections in the model. The inclusion of the exact shape of the cross-section in the model is therefore not crucial, however, if cross-sectional data exist, the overall shape of the cross-section should be used in the model formulation. This could e.g. be accomplished by using measured values of the stream width and depth in the middle of the stream and by assuming a triangular shape. The bed-load transport was in this study determined for different sediment characteristics which can be used as an order of magnitude estimation if no exact determinations of the bed-load are available. The difference in the calculated bed-load transport for the different materials was, however, found to be limited. The investigation of model discretisation showed that a fine model discretisation to account for numerical effects is probably not important for the performed simulations. However, it can be necessary for being able to account for different conditions along a stream. For example, the application of mean slopes instead of individual values in the different stream reaches can result in very different predicted concentrations

  15. A convolution model of rock bed thermal storage units

    Science.gov (United States)

    Sowell, E. F.; Curry, R. L.

    1980-01-01

    A method is presented whereby a packed-bed thermal storage unit is dynamically modeled for bi-directional flow and arbitrary input flow stream temperature variations. The method is based on the principle of calculating the output temperature as the sum of earlier input temperatures, each multiplied by a predetermined 'response factor', i.e., discrete convolution. A computer implementation of the scheme, in the form of a subroutine for a widely used solar simulation program (TRNSYS) is described and numerical results compared with other models. Also, a method for efficient computation of the required response factors is described; this solution is for a triangular input pulse, previously unreported, although the solution method is also applicable for other input functions. This solution requires a single integration of a known function which is easily carried out numerically to the required precision.

  16. Modeling river total bed material load discharge using artificial intelligence approaches (based on conceptual inputs)

    Science.gov (United States)

    Roushangar, Kiyoumars; Mehrabani, Fatemeh Vojoudi; Shiri, Jalal

    2014-06-01

    This study presents Artificial Intelligence (AI)-based modeling of total bed material load through developing the accuracy level of the predictions of traditional models. Gene expression programming (GEP) and adaptive neuro-fuzzy inference system (ANFIS)-based models were developed and validated for estimations. Sediment data from Qotur River (Northwestern Iran) were used for developing and validation of the applied techniques. In order to assess the applied techniques in relation to traditional models, stream power-based and shear stress-based physical models were also applied in the studied case. The obtained results reveal that developed AI-based models using minimum number of dominant factors, give more accurate results than the other applied models. Nonetheless, it was revealed that k-fold test is a practical but high-cost technique for complete scanning of applied data and avoiding the over-fitting.

  17. A model for the thermodynamic analysis in a batch type fluidized bed dryer

    International Nuclear Information System (INIS)

    An original model for thermodynamic analysis of a batch type fluidized bed dryer is proposed herein considering two separate systems comprised of drying air medium as a control volume and particles to be dried as a control mass. By means of the proposed model, energetic and exergetic analyses of a drying column of a batch type fluidized bed dryer are carried out as an original contribution to literature since there is no such like model in which the analyses are performed considering two separate systems. The energetic efficiencies evaluated by means of the proposed model using the data in literature are compared with those in literature and a good conformity is satisfied with an acceptable error margin of ±9%. A new correlation is also developed with a mean deviation of ±10% in order to evaluate the energetic efficiency for not only corn drying process but also drying processes of other particles at inlet air temperature of 50 °C. Effects of air mass flow rate, mass of particle and ambient temperature on energetic and exergetic efficiencies are analyzed and some concluding remarks are highlighted for further studies. - Highlights: • Energetic and exergetic analyses of a batch type fluidized bed dryer are developed. • An original model is proposed for thermodynamic analyses in a fluidized bed dryer. • The proposed model is compared with the data in literature with an accuracy of ±9%. • Effect of air mass flow rate is more significant than that of ambient temperature. • Effect of mass of particle is more significant than that of ambient temperature

  18. CFD modeling of space-time evolution of fast pyrolysis products in a bench-scale fluidized-bed reactor

    Science.gov (United States)

    A model for the evolution of pyrolysis products in a fluidized bed has been developed. In this study the unsteady constitutive transport equations for inert gas flow and decomposition kinetics were modeled using the commercial computational fluid dynamics (CFD) software FLUENT-12. The model system d...

  19. Modeling of waste/near field interactions for a waste repository in bedded salt: the Dynamic Network (DNET) model

    International Nuclear Information System (INIS)

    The Fuel Cycle Risk Analysis Division of Sandia National Laboratories has been funded by the US Nuclear Regulatory Commission to develop a methodology for use in assessing the long-term risk from the disposal of radioactive wastes in deep geologic formations. As part of this program, the Dynamic Network (DNET) model was developed to investigate waste/near field interactions associated with the disposal of radioactive wastes in bedded salt formations. The model is a quasi-multi-dimensional network model with capabilities for simulating processes such as fluid flow, heat transport, salt dissolution, salt creep, and the effects of thermal expansion and subsedence on the rock units surrounding the repository. The use of DNET has been demonstrated in the analysis of a hypothetical disposal site containing a bedded salt formation as the host medium for the repository. An example of this demonstration analysis is discussed. Furthermore, the outcome of sensitivity analyses performed on the DNET model are presented

  20. CFD Model of Dense Gas-solid Systems in Jetting Fl uidized Beds

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A CFD code has been developed based on the conservation principles describing gas and solid flow in fluidized beds. This code is employed to simulate not only the spatiotemporal gas- and solid-phase velocities and voidage profiles in a two-dimensional bed but also fluid dynamics in the jet region. The computational results show that gas flow direction is upward in the entire bed accompanied with random local circulations, whilst solid flow direction is upward at the center and downward near the wall. The radical reason of strong back-mixing of solid particles and good transfer behavior between two phases is that the jet entrains solid particles. Numerical calculation indicates that gas velocity, solid velocity and pressure profile have a significant change when the voidage is 0. 8. The simulated time-averaged voidage profiles agree with the experimental results and simulated data reported by Gidaspow and Ettehadieh(1983). Therefore, CFD model can be regarded as a useful tool to study the jet characteristics in dense gas-solid fluidized beds.

  1. Mathematical simulation of radial heat transfer in packed beds by pseudohomogeneous modeling

    Institute of Scientific and Technical Information of China (English)

    Rodrigo Béttega; Marcos Flávio Pinto Moreira; Ronaldo Guimar(a)es Corrêa; José Teixeira Freire

    2011-01-01

    Uniform flow regime and constant effective thermal conductivity inside packed beds are commonly accepted in the evaluation of the fluid dynamics and heat transfer in such systems. However, several authors have confirmed the presence of an oscillatory velocity profile caused by the effective contribution of porosity profile in the fluid dynamic behavior of packed beds, which directly influences the heat transfer inside the beds. This paper describes the application of a pseudo-homogeneous mathematical model for describing heat transfer in packed beds with oscillatory profiles of velocity and porosity, using a radius-dependent model for effective thermal conductivity kr. Several temperature profiles were obtained in a packed bed system with thermal source located on the wall. The simulated temperature and effective thermal conductivity obtained from simulations were compared with experimental data and calculation from a model based on uniform kr fitting. The results indicate that the proposed mathematical modeling was capable of better representing the heat transfer in the packed bed.

  2. The development of an integrated multistaged fluid bed retorting process. Annual report, October 1991--September 1992

    Energy Technology Data Exchange (ETDEWEB)

    Carter, S.; Vego, A.; Stehn, J.; Taulbee, D.; Robl, T.; Hower, J.; Mahboub, K.; Robertson, R.; Hornsberger, P.; Oduroh, P.; Simpson, A.

    1992-12-01

    This report summarizes the progress made on the development of an integrated multistage fluidized bed retorting process (KENTORT II) during the period of October 1, 1991 through September 30, 1992. The KENTORT II process includes integral fluidized bed zones for pyrolysis (shale oil production), gasification (synthesis gas production), and combustion of the spent oil shale for process heat. The purpose of this program is to design and test the KENTORT II process at the 50-lb/hr scale. The work completed this year involved several different areas. Basic studies of the cracking and coking kinetics of shale oil vapors were carried out in fluidized and fixed bed reactors using both freshly generated shale oil vapors and model compounds. The design and fabrication of the 50-lb/hr KENTORT II reactor was completed and installation of the process components was initiated. The raw oil shale sample (Cleveland Member from Montgomery County, Kentucky) for the program was mined, prepared, characterized and stored. A preliminary study of KENTORT II-derived oil for possible paving applications was completed, and it was concluded that the shale exhibits acceptable properties as an asphalt recycling agent.

  3. Bioleaching model of a copper-sulfide ore bed in heap and dump configurations

    Science.gov (United States)

    Casas, J. M.; Vargas, T.; Martinez, J.; Moreno, L.

    1998-08-01

    A two-dimensional (2-D) model for a heap or dump bioleaching of a copper ore containing mainly chalcocite and pyrite has been developed. The rate of the mineral sulfide dissolution was related to the rate of oxidation by bacteria attached onto the ore surface. The latter was calculated using the model of Michaelis-Menten, where both temperature and dissolved oxygen in the leach solution were taken into account by the kinetic equation. Oxygen transport through the ore bed was associated with natural air convection originating from the decrease in gas density inside the ore bed, which was attributable not only to heating, but also to humidification and decrease in the oxygen concentration. The model was used to estimate air-velocity fields and profiles of temperature and oxygen concentrations as well as mineral conversions during the bioleaching operation for ore beds with different pyrite contents, bacterial populations, widths, heights, and permeabilities. The model provides a useful tool for the design, improvement, and optimization of industrial operating conditions.

  4. Analysis of fluidized bed granulation process using conventional and novel modeling techniques.

    Science.gov (United States)

    Petrović, Jelena; Chansanroj, Krisanin; Meier, Brigitte; Ibrić, Svetlana; Betz, Gabriele

    2011-10-01

    Various modeling techniques have been applied to analyze fluidized-bed granulation process. Influence of various input parameters (product, inlet and outlet air temperature, consumption of liquid-binder, granulation liquid-binder spray rate, spray pressure, drying time) on granulation output properties (granule flow rate, granule size determined using light scattering method and sieve analysis, granules Hausner ratio, porosity and residual moisture) has been assessed. Both conventional and novel modeling techniques were used, such as screening test, multiple regression analysis, self-organizing maps, artificial neural networks, decision trees and rule induction. Diverse testing of developed models (internal and external validation) has been discussed. Good correlation has been obtained between the predicted and the experimental data. It has been shown that nonlinear methods based on artificial intelligence, such as neural networks, are far better in generalization and prediction in comparison to conventional methods. Possibility of usage of SOMs, decision trees and rule induction technique to monitor and optimize fluidized-bed granulation process has also been demonstrated. Obtained findings can serve as guidance to implementation of modeling techniques in fluidized-bed granulation process understanding and control. PMID:21839830

  5. Acidification of calf bedding reduces fly development and bacterial abundance

    Science.gov (United States)

    Environmental stressors, such as high fly density, can impact calf well-being. Sodium bisulfate (SBS) is an acidifier that reduces the pH of flooring and bedding, creating a medium that neither bacteria nor immature flies (also known as larvae or maggots) can thrive in. Two experiments were conducte...

  6. Development and Implementation of a Hardware In-the-Loop Test Bed for Unmanned Aerial Vehicle Control Algorithms

    Science.gov (United States)

    Nyangweso, Emmanuel; Bole, Brian

    2014-01-01

    Successful prediction and management of battery life using prognostic algorithms through ground and flight tests is important for performance evaluation of electrical systems. This paper details the design of test beds suitable for replicating loading profiles that would be encountered in deployed electrical systems. The test bed data will be used to develop and validate prognostic algorithms for predicting battery discharge time and battery failure time. Online battery prognostic algorithms will enable health management strategies. The platform used for algorithm demonstration is the EDGE 540T electric unmanned aerial vehicle (UAV). The fully designed test beds developed and detailed in this paper can be used to conduct battery life tests by controlling current and recording voltage and temperature to develop a model that makes a prediction of end-of-charge and end-of-life of the system based on rapid state of health (SOH) assessment.

  7. Some Challenges Posed by Coal Bed Methane Regional Assessment Modeling.

    Science.gov (United States)

    Moore, Catherine R; Doherty, John; Howell, Stephen; Erriah, Leon

    2015-01-01

    Coal measures (coal bearing rock strata) can contain large reserves of methane. These reserves are being exploited at a rapidly increasing rate in many parts of the world. To extract coal seam gas, thousands of wells are drilled at relatively small spacing to depressurize coal seams to induce desorption and allow subsequent capture of the gas. To manage this process effectively, the effect of coal bed methane (CBM) extraction on regional aquifer systems must be properly understood and managed. Groundwater modeling is an integral part of this management process. However, modeling of CBM impacts presents some unique challenges, as processes that are operative at two very different scales must be adequately represented in the models. The impacts of large-scale gas extraction may be felt over a large area, yet despite the significant upscaling that accompanies construction of a regional model, near-well conditions and processes cannot be ignored. These include the highly heterogeneous nature of many coal measures, and the dual-phase flow of water and gas that is induced by coal seam depressurization. To understand these challenges, a fine-scale model was constructed incorporating a detailed representation of lithological heterogeneity to ensure that near-well processes and conditions could be examined. The detail of this heterogeneity was at a level not previously employed in models built to assess groundwater impacts arising from CBM extraction. A dual-phase reservoir simulator was used to examine depressurization and water desaturation processes in the vicinity of an extractive wellfield within this fine-scale model. A single-phase simulator was then employed so that depressurization errors incurred by neglecting near-well, dual-phase flow could be explored. Two models with fewer lithological details were then constructed in order to examine the nature of depressurization errors incurred by upscaling and to assess the interaction of the upscaling process with the

  8. Development of the Dynamic Test Bed of JRTR Based on MARS

    International Nuclear Information System (INIS)

    The JRTR simulator is also used as a dynamic test bed (DTB) to validate the control logics in RRS (reactor regulating system), which is under development. In the previous study, we have developed the PCS (primary coolant system) model of JRTR in batch mode. In this study, the MARS code has been integrated into simulator environment. To be used as a DTB for validating the RRS, a reactor kinetics model is an essential part. Although the MARS code has a point kinetics model, it lacks the xenon reactivity model. Therefore, we have also developed the iodine xenon transient model for the DTB test. A point kinetics model for the DTB of JRTR has been developed and merged into the simulator environment. Through several verification tests, it is found that the iodine-xenon transient model has been incorporated into the MARS successfully and the CAR worth model also works in proper way. In addition, the capability of real-time calculation was also verified in these tests. Consequently, it is concluded that the developed PCS model with modified point kinetics can be used in the full-scope simulator for the JRTR if all the interfaces are connected to 3 KeyMaster

  9. Development of an In-Situ Decommissioning Sensor Network Test Bed for Structural Condition Monitoring - 12156

    International Nuclear Information System (INIS)

    The Savannah River National Laboratory (SRNL) has established an In Situ Decommissioning (ISD) Sensor Network Test Bed, a unique, small scale, configurable environment, for the assessment of prospective sensors on actual ISD system material, at minimal cost. The Department of Energy (DOE) is presently implementing permanent entombment of contaminated, large nuclear structures via ISD. The ISD end state consists of a grout-filled concrete civil structure within the concrete frame of the original building. Validation of ISD system performance models and verification of actual system conditions can be achieved through the development a system of sensors to monitor the materials and condition of the structure. The ISD Sensor Network Test Bed has been designed and deployed to addresses the DOE-Environmental Management Technology Need to develop a remote monitoring system to determine and verify ISD system performance. Commercial off-the-shelf sensors have been installed on concrete blocks taken from walls of the P Reactor Building at the Savannah River Site. Deployment of this low-cost structural monitoring system provides hands-on experience with sensor networks. The initial sensor system consists of groutable thermistors for temperature and moisture monitoring, strain gauges for crack growth monitoring, tilt-meters for settlement monitoring, and a communication system for data collection. Baseline data and lessons learned from system design and installation and initial field testing will be utilized for future ISD sensor network development and deployment. The Sensor Network Test Bed at SRNL uses COTS sensors on concrete blocks from the outer wall of the P Reactor Building to measure conditions expected to occur in ISD structures. Knowledge and lessons learned gained from installation, testing, and monitoring of the equipment will be applied to sensor installation in a meso-scale test bed at FIU and in future ISD structures. The initial data collected from the sensors

  10. Modeling of carbon sequestration in coal-beds: A variable saturated simulation

    International Nuclear Information System (INIS)

    Storage of carbon dioxide in deep coal seams is a profitable method to reduce the concentration of green house gases in the atmosphere while the methane as a byproduct can be extracted during carbon dioxide injection into the coal seam. In this procedure, the key element is to keep carbon dioxide in the coal seam without escaping for a long term. It is depended on many factors such as properties of coal basin, fracture state, phase equilibrium, etc., especially the porosity, permeability and saturation of the coal seam. In this paper, a variable saturation model was developed to predict the capacity of carbon dioxide sequestration and coal-bed methane recovery. This variable saturation model can be used to track the saturation variability with the partial pressures change caused by carbon dioxide injection. Saturation variability is a key factor to predict the capacity of carbon dioxide storage and methane recovery. Based on this variable saturation model, a set of related variables including capillary pressure, relative permeability, porosity, coupled adsorption model, concentration and temperature equations were solved. From results of the simulation, historical data agree with the variable saturation model as well as the adsorption model constructed by Langmuir equations. The Appalachian basin, as an example, modeled the carbon dioxide sequestration in this paper. The results of the study and the developed models can provide the projections for the CO2 sequestration and methane recovery in coal-beds within different regional specifics

  11. Development of Research Reactor Simulator and Its Application to Dynamic Test-bed

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Kee Choon; Park, Jae Chang; Lee, Seung Wook; Bang, Dane; Bae, Sung Won [KAERI, Daejeon (Korea, Republic of)

    2014-08-15

    We developed HANARO and the Jordan Research and Training Reactor (JRTR) real-time simulator for operating staff training. The main purpose of this simulator is operator training, but we modified this simulator as a dynamic test-bed to test the reactor regulating system in HANARO or JRTR before installation. The simulator configuration is divided into hardware and software. The simulator hardware consists of a host computer, 6 operator stations, a network switch, and a large display panel. The simulator software is divided into three major parts: a mathematical modeling module, which executes the plant dynamic modeling program in real-time, an instructor station module that manages user instructions, and a human machine interface (HMI) module. The developed research reactors are installed in the Korea Atomic Energy Research Institute nuclear training center for reactor operator training. To use the simulator as a dynamic test-bed, the reactor regulating system modeling software of the simulator was replaced by a hardware controller and the simulator and target controller were interfaced with a hard-wired and network-based interface.

  12. Development of Research Reactor Simulator and Its Application to Dynamic Test-bed

    International Nuclear Information System (INIS)

    We developed HANARO and the Jordan Research and Training Reactor (JRTR) real-time simulator for operating staff training. The main purpose of this simulator is operator training, but we modified this simulator as a dynamic test-bed to test the reactor regulating system in HANARO or JRTR before installation. The simulator configuration is divided into hardware and software. The simulator hardware consists of a host computer, 6 operator stations, a network switch, and a large display panel. The simulator software is divided into three major parts: a mathematical modeling module, which executes the plant dynamic modeling program in real-time, an instructor station module that manages user instructions, and a human machine interface (HMI) module. The developed research reactors are installed in the Korea Atomic Energy Research Institute nuclear training center for reactor operator training. To use the simulator as a dynamic test-bed, the reactor regulating system modeling software of the simulator was replaced by a hardware controller and the simulator and target controller were interfaced with a hard-wired and network-based interface

  13. Development of research reactor simulator and its application to dynamic test-bed

    International Nuclear Information System (INIS)

    We developed a real-time simulator for 'High-flux Advanced Neutron Application ReactOr (HANARO), and the Jordan Research and Training Reactor (JRTR). The main purpose of this simulator is operator training, but we modified this simulator into a dynamic test-bed (DTB) to test the functions and dynamic control performance of reactor regulating system (RRS) in HANARO or JRTR before installation. The simulator hardware consists of a host computer, 6 operator stations, a network switch, and a large display panel. The software includes a mathematical model that implements plant dynamics in real-time, an instructor station module that manages user instructions, and a human machine interface module. The developed research reactor simulators are installed in the Korea Atomic Energy Research Institute nuclear training center for reactor operator training. To use the simulator as a dynamic test-bed, the reactor regulating system modeling software of the simulator was replaced by actual RRS cabinet, and was interfaced using a hard-wired and network-based interface. RRS cabinet generates control signals for reactor power control based on the various feedback signals from DTB, and the DTB runs plant dynamics based on the RRS control signals. Thus the Hardware-In-the-Loop Simulation between RRS and the emulated plant (DTB) has been implemented and tested in this configuration. The test result shows that the developed DTB and actual RRS cabinet works together simultaneously resulting in quite good dynamic control performances. (author)

  14. Engineering bed models for solid fuel conversion process in grate-fired boilers

    DEFF Research Database (Denmark)

    Costa, M.; Massarotti, N.; Indrizzi, V.;

    2014-01-01

    A comparison between two numerical models describing the thermo-chemical conversion process of a solid fuel bed in a grate-fired boiler is presented. Both models consider the incoming biomass as subjected to drying, pyrolysis, gasification and combustion. In the first approach the biomass bed is ...

  15. DSNP models used in the pebble-bed HTGR dynamic simulation. V.2

    International Nuclear Information System (INIS)

    A detailed description is given of the components that were used in the DSNP simulation of the PNP-500 high temperature gas-cooled pebble-bed reactor. Each component presented in this report describes in detail the mathematical model that was used, and the assumptions that were made in developing the model. Most of the models were developed using basic physical principles with the simplication that could be justified on the basis of the requested accuracy. Most of the models were developed as either one dimensional or lumped parameter models. The heat transfer and flow correlations, which are mostly based on semiempirical correlations were either provided by KFA or were adapted from the available literature. A short description of DSNP is also given, with a comprehensive list of all the statements available in Rev. 4.1 of DSNP. (H.K.)

  16. Code development for debris bed coolability problem. Final report for the period 1997-05-01 - 1999-08-14

    International Nuclear Information System (INIS)

    The study was devoted to the problem of debris bed coolability arising from severe accident at nuclear power reactor. After reactor core melting occurs and subsequent debris bed is formed in the lower plenum of reactor pressure vessel (RPV) it is important to confine this debris bed inside RPV boundary. One of the possible accident scenarios assumes the interaction between coolant and molten core materials resulting from rapid melt quenching, freezing and fragmentation. Particulated fuel and steel may subsequently settle on available surfaces within the reactor vessel, forming debris porous beds which produce radioactive decay heating. In case of severe core degradation, such heat transfer mechanisms as radiation, conduction and natural single-phase convection may appear to be insufficient and coolant boiling may happen on the surface or inside the bed. Depending on rate of heat generation there may be sufficient debris cool down or its 'dryout' which pose a danger for RPV integrity. The study considers development of 2D numerical code capable to predict coolant saturation as a function of different parameters. Analysis of previous activities on one-dimensional and multi-dimensional models was done. On the basis of the analysis it was concluded that the correct prediction of the debris saturation on dryant power requires two-dimensional numerical simulation considering the processes like two-phase convection, capillary effects, different models of permeability, different models of heat transfer between solid debris and coolant, non-homogeneity of parameters porous medium, heat and mass transfer between debris bed and a highly porous gap along the inner RPV surface. Particular attention was given to consideration of boundary conditions for debris bed. Introduction of the analytical model for dependence of gap properties on heat flux from debris bed allowed to create an algorithm for use in numerical calculations and finally to develop a code which allowed for stable

  17. Real time test bed development for power system operation, control and cyber security

    Science.gov (United States)

    Reddi, Ram Mohan

    The operation and control of the power system in an efficient way is important in order to keep the system secure, reliable and economical. With advancements in smart grid, several new algorithms have been developed for improved operation and control. These algorithms need to be extensively tested and validated in real time before applying to the real electric power grid. This work focuses on the development of a real time test bed for testing and validating power system control algorithms, hardware devices and cyber security vulnerability. The test bed developed utilizes several hardware components including relays, phasor measurement units, phasor data concentrator, programmable logic controllers and several software tools. Current work also integrates historian for power system monitoring and data archiving. Finally, two different power system test cases are simulated to demonstrate the applications of developed test bed. The developed test bed can also be used for power system education.

  18. Process modeling and thermodynamic analysis of Lurgi fixed-bed coal gasifier in an SNG plant

    International Nuclear Information System (INIS)

    Highlights: • A comprehensive model is proposed for the Lurgi fixed-bed gasifier. • A strategy is proposed to accelerate the convergence of the model solutions. • Satisfactory agreement between model predictions and industrial data is obtained. • An exergy analysis is applied to both the Lurgi gasifier and the gasification system. - Abstract: This paper presents a comprehensive steady state kinetic model of a commercial-scale pressurized Lurgi fixed-bed dry bottom coal gasifier. The model is developed using the simulator Aspen Plus. Five sequential modules: drying zone, pyrolysis zone, gasification zone, combustion zone and overall heat recovery unit, are considered in the main process model. A non-linear programming (NLP) model is employed to estimate the pyrolysis products, which include char, coal gas and high-weight hydrocarbons/distillable liquids (tar, phenol, naphtha and oil). To accelerate solution convergence, an external FORTRAN subroutine is used to simulate the kinetics of the combustion and gasification processes which are formulated in terms of a series of continuous stirred-tank reactors. The model is validated with industrial data. The effects of two key operating parameters, namely oxygen/coal mass ratio and steam/coal mass ratio, on the thermodynamic efficiencies of the Lurgi gasifier and the gasification system as a whole are investigated via extensive simulation studies

  19. Numerical model of saltation in open channel with rough bed

    Czech Academy of Sciences Publication Activity Database

    Kharlamova, Irina; Vlasák, Pavel

    Praha : Ústav termomechaniky AV ČR, v. v. i., 2012 - (Jonáš, P.; Uruba, V.), s. 13 ISBN 978-80-87012-42-0. [Colloquium FLUID DYNAMICS 2012. Praha (CZ), 24.10.2012-26.10.2012] R&D Projects: GA ČR GA103/09/1718 Institutional support: RVO:67985874 Keywords : saltation length * saltation height * bed roughness * bed shear stress * shear velocity Subject RIV: BK - Fluid Dynamics

  20. Modeling for Anaerobic Fixed-Bed Biofilm Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Liu, B. Y. M.; Pfeffer, J. T.

    1989-06-01

    The specific objectives of this research were: 1. to develop an equilibrium model for chemical aspects of anaerobic reactors; 2. to modify the equilibrium model for non-equilibrium conditions; 3. to incorporate the existing biofilm models into the models above to study the biological and chemical behavior of the fixed-film anaerobic reactors; 4. to experimentally verify the validity of these models; 5. to investigate the biomass-holding ability of difference packing materials for establishing reactor design criteria.

  1. Rigging Test Bed Development for Validation of Multi-Stage Decelerator Extractions

    Science.gov (United States)

    Kenig, Sivan J.; Gallon, John C.; Adams, Douglas S.; Rivellini, Tommaso P.

    2013-01-01

    The Low Density Supersonic Decelerator project is developing new decelerator systems for Mars entry which would include testing with a Supersonic Flight Dynamics Test Vehicle. One of the decelerator systems being developed is a large supersonic ringsail parachute. Due to the configuration of the vehicle it is not possible to deploy the parachute with a mortar which would be the preferred method for a spacecraft in a supersonic flow. Alternatively, a multi-stage extraction process using a ballute as a pilot is being developed for the test vehicle. The Rigging Test Bed is a test venue being constructed to perform verification and validation of this extraction process. The test bed consists of a long pneumatic piston device capable of providing a constant force simulating the ballute drag force during the extraction events. The extraction tests will take place both inside a high-bay for frequent tests of individual extraction stages and outdoors using a mobile hydraulic crane for complete deployment tests from initial pack pull out to canopy extraction. These tests will measure line tensions and use photogrammetry to track motion of the elements involved. The resulting data will be used to verify packing and rigging as well, as validate models and identify potential failure modes in order to finalize the design of the extraction system.

  2. CFD based combustion model for sewage sludge gasification in a fluidized bed

    Institute of Scientific and Technical Information of China (English)

    Yiqun WANG; Lifeng YAN

    2009-01-01

    Gasification is one potential way to use sewage sludge as renewable energy and solve the environmental problems caused by the huge amount of sewage sludge. In this paper, a three-dimensional Computational Fluid Dynamics (CFD) model has been developed to simulate the sewage sludge gasification process in a fluidized bed. The model describes the complex physical and chemical phenomena in the gasifier including turbulent flow, heat and mass transfer, and chemical reactions. The model is based on the Eulerian-Lagrangian concept using the non-premixed combustion modeling approach. In terms of the CFD software FLUENT, which represents a powerful tool for gasifIer analysis, the simulations provide detailed information on the gas products and temperature distribution in the gasifier. The model sensitivity is analyzed by performing the model in a laboratory-scale fluidized bed in the literature, and the model validation is carried out by comparing with experimental data from the literature. Results show that reasonably good agreement was achieved. Effects of temperature and Equivalence Ratio (ER) on the quality of product syngas (H2 + CO) are also studied.

  3. Hydraulic fracturing model featuring initiation beyond the wellbore wall for directional well in coal bed

    Science.gov (United States)

    Li, Yuwei; Jia, Dan; Wang, Meng; Liu, Jia; Fu, Chunkai; Yang, Xinliang; Ai, Chi

    2016-08-01

    In developing internal fracture systems in coal beds, the initiation mechanism differs greatly from that of conventional ones and initiations may be produced beyond the wellbore wall. This paper describes the features of the internal structure of coal beds and RFPA2D simulation is used to attest the possible occurrence of initiation beyond the wellbore wall in coal bed hydraulic fracturing. Using the theory of elasticity and fracture mechanics, we analyse the stress distribution in the vicinal coal rock. Then by taking into consideration the effects of the spatial relationship between coal bed cleats and the wellbore, we establish a model for calculating both tensile and shear initiation pressure that occur along cleats beyond the wellbore wall. The simulation in this paper indicates that for shear initiations that happen along coal cleats, the pressure required to initiate fracture for cleats beyond the wellbore wall is evidently lower than that on the wellbore wall, thus it is easier to initiate shear fractures for cleats beyond the wellbore wall. For tensile failure, the pressure required to initiate tensile fracture for cleats beyond the wellbore wall is obviously higher than that for cleats at the wellbore wall, thus it is easier to initiate tensile fractures for cleats at the wellbore wall. On the one hand, this paper has proved the possible occurrence of initiations beyond the wellbore wall and has changed the current assumption that hydraulic fractures can only occur at the wellbore wall. On the other hand, the established theoretical model provides a new approach to calculating the initiation pressure in hydraulic fracturing.

  4. Development of a fluidized bed system for adsorption of phenol from aqueous solutions with commercial macroporous resins

    Directory of Open Access Journals (Sweden)

    R. A. Corrêa

    2007-03-01

    Full Text Available This work is related to removal of phenol from wastewaters by adsorption onto polymeric resins, a current alternative to activated carbon. A closed circuit, bench-scale liquid fluidized bed system was developed for this purpose. Phenol aqueous solutions with initial concentrations in the range of 0.084 to 0.451 kg/m³ were used to fluidize small permeable capsules of stainless steel screen containing a commercial resin at 308 K. Experiments were carried out using a fluidizing velocity 20% above that of the minimum fluidization of the capsules. Typically, 30 passages of the liquid volume circulating through the bed were required to reach a quasi-equilibrium concentration of phenol in the treated effluent. A simple batch adsorption model using the Freundlich isotherm successfully predicted final phenol concentrations. Suspended solids, often present in residual waters and a common cause of fixed bed clogging, were simulated with wood sawdust.

  5. DEVELOPMENT OF COAL DRY BENEFICIATION WITH AIR-DENSE MEDIUM FLUIDIZED BED IN CHINA

    Institute of Scientific and Technical Information of China (English)

    Qingru Chen; Lubin Wei

    2005-01-01

    In China more than two-thirds of available coal reserves are in arid areas, where, to beneficiate the run-of-mine coal,there is not enough water resource required by conventional processing. Developing efficient dry beneficiation technology is of great significance for efficient coal utilization in China, notably the clean coal technology (CCT). The dry coal beneficiation technology with air-dense medium fluidized bed utilizes air-solid suspension as beneficiating medium whose density is consistent for beneficiation, similar in principle to the wet dense medium beneficiation using liquid-solid suspension as separating medium. The heavy portion in feedstock whose density is higher than the density of the fluidized bed will sink, whereas the lighter portion will float, thus stratifying the feed materials according to their density.In order to obtain efficient dry separation in air-dense medium fluidized bed, stable fluidization with well dispersed micro-bubbles must be achieved to ensure low viscosity and high fluidity. The pure buoyancy of beneficiation materials plays a main role in fluidized bed, and the displaced distribution effect should be restrained. The displaced distribution effects include viscosity displaced distribution effect and movement displaced distribution effect. The former is caused by viscosity of the fluidized bed. It decreases with increasing air flow velocity. Movement displaced distribution effect will be large when air flow rate is too low or too high. If medium particle size distribution and air flow are well controlled, both displaced distribution effects could be controlled effectively. A beneficiation displaced distribution model may be used to optimize beneficiation of feedstock with a wide particle size distribution and multiple components in the fluidized bed. The rheological characteristics of fluidized beds were studied using the falling sphere method. Experimental results indicated that the fluidized bed behaves as a Bingham fluid

  6. Numerical Modeling of Bifurcation Evolution in a Sand-bed Braided River

    Science.gov (United States)

    De Haas, T.; Schuurman, F.; Kleinhans, M. G.

    2012-12-01

    River bifurcations are key units in a braided river. Although simple bifurcations are well understood and can be analyzed by 1D models (e.g. Bolla Pittaluga et al., 2003 and Kleinhans et al., 2008), predicting the stability and dynamics of multiple interacting bifurcations in a braided river with migrating bars requires understanding of the interaction between braid bars, channel network and bifurcations, in particular the upstream curvature and downstream backwater effects. Our objective is to understand the evolution of bifurcations at migrating bars in a braided river and the effects on bar evolution. We used the 3D numerical morphodynamic model Delft3D to produce a dynamically braiding sand bed river. This model solves the 3D-flow and computes sediment transport and bed level change accounting for effects of transverse bed slope. It includes a simple bank erosion model to reactivate emerged areas. The morphology of mid-channel bars produced by the model was analyzed and the partitioning of water and sediment over the bifurcating channels are compared with a 1D model concept. Next, the evolution of bars is linked to that of the bifurcations, in order to infer relations between bar morphology and bifurcation evolution. We find that upstream bar dynamics have a major effect on the stability of bifurcations. Migration and elongation of bars can close the upstream entrance of a bifurcation channel, independent of the stability of the bifurcation. Moreover, bifurcation angle and upstream curvature can be affected by upstream bar migration and elongation, which steers flow and sediment partitioning at the bifurcation. At the same time, the partitioning of water and sediment over a bifurcation affects bar shape. Sediment eroded at one of the bar sides just downstream of the bifurcation deposits downstream of the braid bar in the form of tail bars. Hence bar shape as observable on imagery contains useful information about the evolution of the upstream bifurcation and

  7. Modeling of realistic pebble bed reactor geometries using the Serpent Monte Carlo code

    International Nuclear Information System (INIS)

    Highlights: • The explicit stochastic geometry model in Serpent is documented. • A pebble bed criticality benchmark was calculated demonstrating the geometry model. • Stochastic pebble configurations were obtained from discrete element simulations. • Results deviate from experiments but are in line with example calculations. - Abstract: This paper documents the models available in Serpent for high temperature reactor (HTR) calculations. It is supplemented by a calculation example of ASTRA critical pebble bed experiments. In the pebble bed reactor modeling, different methods have been used to model the double heterogeneity problem occurring in pebble bed reactor calculations. A solution was sought to avoid unphysical simplifications in the pebble bed modeling and the stochastic geometry modeling features available in the Monte Carlo code Serpent were applied for exact placement of pebbles and fuel particles. Randomly packed pebble beds were produced in discrete element method (DEM) simulations and fuel particles were positioned randomly inside the pebbles. Pebbles and particles are located using a Cartesian search mesh, which provides necessary computational efficiency. Serpent uses Woodcock delta-tracking which provides efficient neutron tracking in the complicated geometries. This detailed pebble bed modeling approach was tested by calculating the ASTRA criticality benchmark experiment done at the Kurchatov Institute in 2004. The calculation results are in line with the sample calculations provided with the benchmark documentation. The material library selected for the calculations has a major effect on the results. The difference in graphite absorption cross section is considered the cause of this result. The model added in Serpent is very efficient with a calculation time slightly higher than with a regular lattice approximation. It is demonstrated that Serpent can be used for pebble bed reactor calculations with minimal geometric approximations as it

  8. A mathematical model of particles entrainment in the freeboard of bubbling fluidized bed

    International Nuclear Information System (INIS)

    A two-component flow with a low concentration occurs in the freeboard after the eruption of the bubbles at the free surface of the bubbling fluidized beds. A three-dimensional mathematical model of gas-particle mixture turbulent flow is developed in this work. The gas turbulence is modeled using standard k-ε turbulence model. The dispersed phase is treated by the Lagrangian approach. Coupling between the gas phase and the dispersed particles is modeled by adding, source term in the momentum equation for gas phase. By using the equation for determining the drag coefficient, the particle's shape is involved in the model, as well. Experimental investigations for determining the conditions at the bed surface, the origin of erupting bubbles and their erupting mechanism and for selecting dominant influencing parameters are done. Comparisons of the experimentally obtained results with the results of other authors, which are in reasonable agreement, are used for determining the dominant influencing parameter related to the phenomena of bursting bubbles. On a base of observation, the dynamic eruption mechanism of single bursting bubble is proposed. This bubble eruption mechanism is used like a boundary condition in the numerical experimentation for investigation of the entrainment of particles and its separation along the freeboard height. The numerical solving of the developed mathematical model is accomplished by using the CFD technology. For graphical design and mesh generation of the flow domain and for numerical solving of the equations of the developed mathematical model, the software packages Gambit and FLUENT are used, respectively. The testing and verification of the proposed erupting bubble mechanism and the developed mathematical model for two-component flow in the freeboard, is made by numerical experimentation in 3D cylindrical flow domain, in the following conditions: eruption of isolated central bursting bubble; determining of particles terminal velocity

  9. Development of Monte Carlo-based pebble bed reactor fuel management code

    International Nuclear Information System (INIS)

    Highlights: • A new Monte Carlo-based fuel management code for OTTO cycle pebble bed reactor was developed. • The double-heterogeneity was modeled using statistical method in MVP-BURN code. • The code can perform analysis of equilibrium and non-equilibrium phase. • Code-to-code comparisons for Once-Through-Then-Out case were investigated. • Ability of the code to accommodate the void cavity was confirmed. - Abstract: A fuel management code for pebble bed reactors (PBRs) based on the Monte Carlo method has been developed in this study. The code, named Monte Carlo burnup analysis code for PBR (MCPBR), enables a simulation of the Once-Through-Then-Out (OTTO) cycle of a PBR from the running-in phase to the equilibrium condition. In MCPBR, a burnup calculation based on a continuous-energy Monte Carlo code, MVP-BURN, is coupled with an additional utility code to be able to simulate the OTTO cycle of PBR. MCPBR has several advantages in modeling PBRs, namely its Monte Carlo neutron transport modeling, its capability of explicitly modeling the double heterogeneity of the PBR core, and its ability to model different axial fuel speeds in the PBR core. Analysis at the equilibrium condition of the simplified PBR was used as the validation test of MCPBR. The calculation results of the code were compared with the results of diffusion-based fuel management PBR codes, namely the VSOP and PEBBED codes. Using JENDL-4.0 nuclide library, MCPBR gave a 4.15% and 3.32% lower keff value compared to VSOP and PEBBED, respectively. While using JENDL-3.3, MCPBR gave a 2.22% and 3.11% higher keff value compared to VSOP and PEBBED, respectively. The ability of MCPBR to analyze neutron transport in the top void of the PBR core and its effects was also confirmed

  10. Artificial neural network modelling approach for a biomass gasification process in fixed bed gasifiers

    International Nuclear Information System (INIS)

    Highlights: • 2 Different equilibrium models are developed and their performance is analysed. • Neural network prediction models for 2 different fixed bed gasifier types are developed. • The influence of different input parameters on neural network model performance is analysed. • Methodology for neural network model development for different gasifier types is described. • Neural network models are verified for various operating conditions based on measured data. - Abstract: The number of the small and middle-scale biomass gasification combined heat and power plants as well as syngas production plants has been significantly increased in the last decade mostly due to extensive incentives. However, existing issues regarding syngas quality, process efficiency, emissions and environmental standards are preventing biomass gasification technology to become more economically viable. To encounter these issues, special attention is given to the development of mathematical models which can be used for a process analysis or plant control purposes. The presented paper analyses possibilities of neural networks to predict process parameters with high speed and accuracy. After a related literature review and measurement data analysis, different modelling approaches for the process parameter prediction that can be used for an on-line process control were developed and their performance were analysed. Neural network models showed good capability to predict biomass gasification process parameters with reasonable accuracy and speed. Measurement data for the model development, verification and performance analysis were derived from biomass gasification plant operated by Technical University Dresden

  11. Mathematical Modeling and Simulation of the Dehydrogenation of Ethyl Benzene to Form Styrene Using Steady-State Fixed Bed Reactor

    Directory of Open Access Journals (Sweden)

    Zaidon M. Shakoor

    2013-05-01

    Full Text Available In this research, two models are developed to simulate the steady state fixed bed reactor used for styrene production by ethylbenzene dehydrogenation. The first is one-dimensional model, considered axial gradient only while the second is two-dimensional model considered axial and radial gradients for same variables.The developed mathematical models consisted of nonlinear simultaneous equations in multiple dependent variables. A complete description of the reactor bed involves partial, ordinary differential and algebraic equations (PDEs, ODEs and AEs describing the temperatures, concentrations and pressure drop across the reactor was given. The model equations are solved by finite differences method. The reactor models were coded with Mat lab 6.5 program and various numerical techniques were used to obtain the desired solution.The simulation data for both models were validated with industrial reactor results with a very good concordance.

  12. A CFD Model for Fluid Dynamics in a Gas-fluidised Bed

    Institute of Scientific and Technical Information of China (English)

    ZHANG Kai; Stefano Brandani

    2004-01-01

    A modified particle bed model derived from the two-fluid momentum balance equations was employed to predict the gas-fluidised bed behaviour. Additional terms are included in both the fluid and the particle momentum balance equations to take into account the effect of the dispersed solid phase. This model has been extended to two-dimensional formulations and has been implemented in the commercial code CFX 4.3. The model correctly simulates the homogeneous fluidisation of Geldart Group A and the bubbling fluidisation of Geldart Group B in gas-solid fluidised beds.

  13. StratBAM: A Discrete-Event Simulation Model to Support Strategic Hospital Bed Capacity Decisions.

    Science.gov (United States)

    Devapriya, Priyantha; Strömblad, Christopher T B; Bailey, Matthew D; Frazier, Seth; Bulger, John; Kemberling, Sharon T; Wood, Kenneth E

    2015-10-01

    The ability to accurately measure and assess current and potential health care system capacities is an issue of local and national significance. Recent joint statements by the Institute of Medicine and the Agency for Healthcare Research and Quality have emphasized the need to apply industrial and systems engineering principles to improving health care quality and patient safety outcomes. To address this need, a decision support tool was developed for planning and budgeting of current and future bed capacity, and evaluating potential process improvement efforts. The Strategic Bed Analysis Model (StratBAM) is a discrete-event simulation model created after a thorough analysis of patient flow and data from Geisinger Health System's (GHS) electronic health records. Key inputs include: timing, quantity and category of patient arrivals and discharges; unit-level length of care; patient paths; and projected patient volume and length of stay. Key outputs include: admission wait time by arrival source and receiving unit, and occupancy rates. Electronic health records were used to estimate parameters for probability distributions and to build empirical distributions for unit-level length of care and for patient paths. Validation of the simulation model against GHS operational data confirmed its ability to model real-world data consistently and accurately. StratBAM was successfully used to evaluate the system impact of forecasted patient volumes and length of stay in terms of patient wait times, occupancy rates, and cost. The model is generalizable and can be appropriately scaled for larger and smaller health care settings. PMID:26310949

  14. Performance Analysis of an Integrated Fixed Bed Gasifier Model for Different Biomass Feedstocks

    Directory of Open Access Journals (Sweden)

    Sharmina Begum

    2013-12-01

    Full Text Available Energy recovery from biomass by gasification technology has attracted significant interest because it satisfies a key requirement of environmental sustainability by producing near zero emissions. Though it is not a new technology, studies on its integrated process simulation and analysis are limited, in particular for municipal solid waste (MSW gasification. This paper develops an integrated fixed bed gasifier model of biomass gasification using the Advanced System for Process ENngineering (Aspen Plus software for its performance analysis. A computational model was developed on the basis of Gibbs free energy minimization. The model is validated with experimental data of MSW and food waste gasification available in the literature. A reasonable agreement between measured and predicted syngas composition was found. Using the validated model, the effects of operating conditions, namely air-fuel ratio and gasifier temperature, on syngas production are studied. Performance analyses have been done for four different feedstocks, namely wood, coffee bean husks, green wastes and MSWs. The ultimate and proximate analysis data for each feedstock was used for model development. It was found that operating parameters have a significant influence on syngas composition. An air-fuel ratio of 0.3 and gasifier temperature of 700 °C provides optimum performance for a fixed bed gasifier for MSWs, wood wastes, green wastes and coffee bean husks. The developed model can be useful for gasification of other biomasses (e.g., food wastes, rice husks, poultry wastes and sugarcane bagasse to predict the syngas composition. Therefore, the study provides an integrated gasification model which can be used for different biomass feedstocks.

  15. Modeling of reaction kinetics in bubbling fluidized bed biomass gasification reactor

    Energy Technology Data Exchange (ETDEWEB)

    Thapa, R.K.; Halvorsen, B.M. [Telemark University College, Kjolnes ring 56, P.O. Box 203, 3901 Porsgrunn (Norway); Pfeifer, C. [University of Natural Resources and Life Sciences, Vienna (Austria)

    2013-07-01

    Bubbling fluidized beds are widely used as biomass gasification reactors as at the biomass gasification plant in Gussing, Austria. The reactor in the plant is a dual circulating bubbling fluidized bed gasification reactor. The plant produces 2MW electricity and 4.5MW heat from the gasification of biomass. Wood chips as biomass and olivine particles as hot bed materials are fluidized with high temperature steam in the reactor. As a result, biomass undergoes endothermic chemical reaction to produce a mixture of combustible gases in addition to some carbon-dioxide (CO2). The combustible gases are mainly hydrogen (H2), carbon monoxide (CO) and methane (CH4). The gas is used to produce electricity and heat via utilization in a gas engine. Alternatively, the gas is further processed for gaseous or liquid fuels, but still on the process of development level. Composition and quality of the gas determine the efficiency of the reactor. A computational model has been developed for the study of reaction kinetics in the gasification rector. The simulation is performed using commercial software Barracuda virtual reactor, VR15. Eulerian-Lagrangian approach in coupling of gas-solid flow has been implemented. Fluid phase is treated with an Eulerian formulation. Discrete phase is treated with a Lagrangian formulation. Particle-particle and particle-wall interactions and inter-phase heat and mass transfer have been taken into account. Series of simulations have been performed to study model prediction of the gas composition. The composition is compared with data from the gasifier at the CHP plant in Güssing, Austria. The model prediction of the composition of gases has good agreements with the result of the operating plant.

  16. Numerical models for the analysis of thermal behavior and coolability of a particulate debris bed in reactor lower head

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Kwang Il; Kim, Sang Baik; Kim, Byung Seok [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2002-04-01

    This report provides three distinctive, but closely related numerical models developed for the analysis of thermal behavior and coolability of a particulate debris bed that is may be formed inside the reactor lower head during severe accident late phases. The first numerical module presented in the report, MELTPRO-DRY, is used to analyze numerically heat-up and melting process of the dry particle bed, downward- and sideward-relocation of the liquid melt under gravity force and capillary force acting among porous particles, and solidification of the liquid melt relocated into colder region. The second module, MELTPROG-WET, is used to simulate numerically the cooling process of the particulate debris bed under the existence of water, which is subjected to two types of numerical models. The first type of WET module utilizes distinctive models that parametrically simulate the water cooling process, that is, quenching region, dryout region, and transition region. The choice of each parametric model depends on temperature gradient between the cooling water and the debris particles. The second type of WET module utilizes two-phase flow model that mechanically simulates the cooling process of the debris bed. For a consistent simulation from the water cooling to the dryout debris bed, on the other hand, the aforementioned two modules, MELTPROG-DRY and MELTPROG-WET, were integrated into a single computer program DBCOOL. Each of computational models was verified through limited applications to a heat-generating particulate bed contained in the rectangular cavity. 22 refs., 5 figs., 2 tabs. (Author)

  17. Investigation of the capability of a Numerical model to simulate a Mining Pit in River Bed

    Directory of Open Access Journals (Sweden)

    Mona Ghafouri Azar

    2014-02-01

    Full Text Available Rivers are the most essential source of aggregates for civil works such as construction of roads, canals, concrete buildings and many other construction purposes. However, the improper mining of sand and gravel from bed rivers may cause significant damage to them in terms of mass bank failure, channel bed erosion. In this research, because of the widespread use of numerical models in different types of hydraulic problems, the variation of the packed bed river profile due to digging a trapezoidal pit in the bed river is analyzed by a leading numerical model. the simulation data is compared with the measured value and the result is discussed and the reason why the numerical model was almost unsuccessful to simulate this phenomenon is discussed. The objective of this research is to investigate limitation of a particular CFD model by comparison of its results with the experimental data. finally other related numerical models is introduced and.

  18. Model for high rate gas flows in deformable and reactive porous beds

    Energy Technology Data Exchange (ETDEWEB)

    Weston, A M

    1985-01-08

    This report presents the development of a one dimensional planar Lagrange hydrodynamic computer model which describes the processes preceding detonation. The model treats gas flow, deflagration, and compaction in a porous bed of reactive material. The early part of deflagration to detonation experiment with porous HMX is simulated. Sensitivity of the simulation calculation to ignition and burn rate parameters is illustrated and discussed. The effects of changing the mean particle size of the porous material are investigated. There is widespread interest in runaway reaction hazards that may be associated with porosity in propellant and explosive materials. Experimentally, such reactions are initiated and observed in long, thick walled hollow tubes, filled with a granular porous bed of reactive material. We will present comparisons with an experiment on porous HMX to illustrate details of the model and to point out what we believe are important features of the observed phenomenon. A geometric finite element cell is devised that allows gas to flow through a compacting matrix. The experimental simulation considers the DDT process from initial squib burn through the onset of general matrix deflagration (convective burning), to the development of a fully dense compaction wave. While this simulation did not calculate turnover to detonation, it did illustrate that the transition occurred as soon as the compaction wave became fully dense. It is shown that deflagration and gas permeation lags compaction at the time of transition. This suggests that the actual transition involves an additional compaction dependent process. 18 references, 20 figures, 3 tables.

  19. MODELING LARGE WOOD STRUCTURES IN SAND BED STREAMS

    Science.gov (United States)

    In-stream large wood structures (LWS) are becoming increasingly popular throughout the world. The LWS improve aquatic habitat quality and protect banks from erosion. While most reports describe the LWS in the Northwest as successful, LWS in one Mississippi sand-bed stream had an unacceptable failure...

  20. 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.

  1. Development of a composite UAV wing test-bed for structural health monitoring research

    Science.gov (United States)

    Oliver, J. A.; Kosmatka, J. B.; Farrar, Charles R.; Park, Gyuhae

    2007-04-01

    In order to facilitate damage detection and structural health monitoring (SHM) research for composite unmanned aerial vehicles (UAV) a specialized test-bed has been developed. This test-bed consists of four 2.61 m all-composite test-pieces emulating composite UAV wings, a series of detailed finite element models of the test-pieces and their components, and a dynamic testing setup including a mount for simulating the cantilevered operation configuration of real wings. Two of the wings will have bondline damage built in; one undamaged and one damaged wing will also be fitted with a range of embedded and attached sensors-piezoelectric patches, fiber-optics, and accelerometers. These sensors will allow collection of realistic data; combined with further modal testing they will allow comparison of the physical impact of the sensors on the structure compared to the damage-induced variation, evaluation of the sensors for implementation in an operational structure, and damage detection algorithm validation. At the present time the pieces for four wings have been fabricated and modally tested and one wing has been fully assembled and re-tested in a cantilever configuration. The component part and assembled wing finite element models, created for MSC.Nastran, have been correlated to their respective structures using the modal information. This paper details the design and manufacturing of the test-pieces, the finite element model construction, and the dynamic testing setup. Measured natural frequencies and mode shapes for the assembled cantilevered wing are reported, along with finite element model undamaged modal response, and response with a small disbond at the root of the top main spar-skin bondline.

  2. Bed models for solid fuel conversion process in grate-fired boilers

    DEFF Research Database (Denmark)

    Costa, M.; Massarotti, N.; Indrizzi, V.;

    2013-01-01

    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......Because of the complexity to describe and solve thermo-chemical processes occurring in a fuel bed in grate-fired boiler, it is often necessary to simplify the process and use modeling techniques based on overall mass, energy and species conservation. A comparison between two numerical models 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...

  3. TIN Dataset Model of Overburden Above the Mahogany Bed in the Uinta Basin, Utah and Colorado

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — An ESRI TIN data model of the overburden material above the Mahogany bed was needed to perform calculations in the Uinta Basin, Utah and Colorado as part of a 2009...

  4. TIN Dataset Model of the Mahogany Bed Structure in the Uinta Basin, Utah and Colorado

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — An ESRI TIN data model of the Mahogany bed structure was needed to perform overburden calculations in the Uinta Basin, Utah and Colorado as part of a 2009 National...

  5. Raster Dataset Model of the Mahogany Bed Structure in the Uinta Basin, Utah and Colorado

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — An ESRI GRID raster data model of the Mahogany bed structure was needed to perform overburden calculations in the Uinta Basin, Utah and Colorado as part of a 2009...

  6. Raster Dataset Model of Overburden Above the Mahogany Bed in the Uinta Basin, Utah and Colorado

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — An ESRI GRID raster data model of the overburden material above the Mahogany bed was needed to perform calculations in the Uinta Basin, Utah and Colorado as part of...

  7. Modeling phosphorus removal and recovery from anaerobic digester supernatant through struvite crystallization in a fluidized bed reactor.

    Science.gov (United States)

    Rahaman, Md Saifur; Mavinic, Donald S; Meikleham, Alexandra; Ellis, Naoko

    2014-03-15

    The cost associated with the disposal of phosphate-rich sludge, the stringent regulations to limit phosphate discharge into aquatic environments, and resource shortages resulting from limited phosphorus rock reserves, have diverted attention to phosphorus recovery in the form of struvite (MAP: MgNH4PO4·6H2O) crystals, which can essentially be used as a slow release fertilizer. Fluidized-bed crystallization is one of the most efficient unit processes used in struvite crystallization from wastewater. In this study, a comprehensive mathematical model, incorporating solution thermodynamics, struvite precipitation kinetics and reactor hydrodynamics, was developed to illustrate phosphorus depletion through struvite crystal growth in a continuous, fluidized-bed crystallizer. A thermodynamic equilibrium model for struvite precipitation was linked to the fluidized-bed reactor model. While the equilibrium model provided information on supersaturation generation, the reactor model captured the dynamic behavior of the crystal growth processes, as well as the effect of the reactor hydrodynamics on the overall process performance. The model was then used for performance evaluation of the reactor, in terms of removal efficiencies of struvite constituent species (Mg, NH4 and PO4), and the average product crystal sizes. The model also determined the variation of species concentration of struvite within the crystal bed height. The species concentrations at two extreme ends (inlet and outlet) were used to evaluate the reactor performance. The model predictions provided a reasonably good fit with the experimental results for PO4-P, NH4-N and Mg removals. Predicated average crystal sizes also matched fairly well with the experimental observations. Therefore, this model can be used as a tool for performance evaluation and process optimization of struvite crystallization in a fluidized-bed reactor. PMID:24384559

  8. The Physical Models of Cyclone Diplegs in Fluidized Beds

    Institute of Scientific and Technical Information of China (English)

    K.Smolders; D.Geldart; J.Baeyens

    2001-01-01

    In most industrial fluidization units, two- or three-stage cyclone systems are used to clean the product gases. To return the solids to the bed, these cyclones are fitted with diplegs. By pass of gas from the bed through the dipleg is partially overcome by the back pressure build-up in the dipleg and by adding a trickle valve at the bottom of the dipleg. Diplegs of primary cyclones, operating at a high solid loading behave differently from diplegs of secondary and tertiary cyclones which operate at low solid loading. Both types have been investigated by pressure drop measurements, visual observation and by measurements of the air flow rate flowing up the riser. The primary dipleg was also studied using electrical capacitance tomography. The results are reported hereafter and will give a first indication towards the right design of the dipleg and the selection of the trickle valve. The influence of gas flow in the dipleg on the conversion in a catalytic fluidized bed reactor is found to be negligible.

  9. Mathematical modeling of salt-gradient ion-exchange simulated moving bed chromatography for protein separations

    Institute of Scientific and Technical Information of China (English)

    卢建刚

    2004-01-01

    The salt-gradient operation mode used in ion-exchange simulated moving bed chromatography (SMBC) can improve the efficiency of protein separations. A detailed model that takes into account any kind of adsorption/ion-exchange equilibrium, salt gradient, size exclusion, mass transfer resistance, and port periodic switching mechanism, was developed to simulate the complex dynamics. The model predictions were verified by the experimental data on upward and downward gradients for protein separations reported in the literature. All design and operating parameters (number, configuration, length and diameter of columns, particle size, switching period, flow rates of feed, raffinate, desorbent and extract, protein concentrations in feed, different salt concentrations in desorbent and feed) can be chosen correctly by numerical simulation. This model can facilitate the design, operation, optimization, control and scale-up of salt-gradient ion-exchange SMBC for protein separations.

  10. Drucker-Prager-Cap creep modelling of pebble beds in fusion blankets

    International Nuclear Information System (INIS)

    Modelling of thermal and mechanical behaviour of pebble beds for fusion blankets is an important issue to understand the interaction of solid breeder and beryllium pebble beds with the surrounding structural material. Especially the differing coefficients of thermal expansion of these materials cause high stresses and strains during irradiation induced volumetric heating. To describe this process, the coupled thermomechanical behaviour of both pebble bed materials has to be modelled. Additionally, creep has to be considered contributing to bed deformations and stress relaxation. Motivated by experiments, we use a continuum mechanical approach called Drucker-Prager/Cap theory to model the macroscopic pebble bed behaviour. The model accounts for pressure dependent shear failure, inelastic hardening, and volumetric creep. The elastic part is described by a nonlinear elasticity law. The model has been implemented by user-defined routines in the commercial finite-element code ABAQUS. To check the numerics, the implementation is compared to an analytical solution. Furthermore, the Drucker-Prager/Cap tool is applied to a single ceramic breeder bed subject to creep under volumetric heating

  11. Experimental and modelling study of drinking water hydrogenotrophic denitrification in packed-bed reactors

    International Nuclear Information System (INIS)

    The aim of this work was to study hydrogenotrophic denitrification in packed-bed reactors under draw-fill and continuous operation. Three bench-scale packed-bed reactors with gravel in different sizes (mean diameter 1.75, 2.41 and 4.03 mm) as support media were used, in order to study the effect of particle size on reactors performance. The maximum denitrification rate achieved under draw-fill operation was 4.4 g NO3--N/ld for the filter with gravel of 2.41 mm. This gravel size was chosen to perform experiments under continuous operation. Feed NO3--N concentrations and hydraulic loadings (HL) ranged between 20-200 mg/l and 5.7-22.8 m3/m2 d, respectively. A comparison between the two operating modes showed that, for low HL the draw-fill operation achieved higher denitrification rates, while for high HL and intermediate feed concentrations (40-60 mg NO3--N/l) the continuous operation achieved higher denitrification rates (4.67-5.65 g/ld). Finally, experiments with three filters in series (with gravels of 4.03, 2.41 and 1.75 mm mean diameter) were also performed under continuous operation. The maximum denitrification rate achieved was 6.2 g NO3--N/ld for feed concentration of 340 mg/l and HL of 11.5 m3/m2 d. A model, which describes denitrification in packed-bed reactors, was also developed. The model predicts the concentration profiles of NO3--N along filter height, in draw-fill as well as in continuous operation, satisfactorily.

  12. A numerical model of the deep-bed drying of extruded fish feed and its experimental validation

    DEFF Research Database (Denmark)

    Haubjerg, Anders Fjeldbo; Veje, Christian; Jørgensen, Bo Nørregaard; Simonsen, Benny

    A deep bed drying model for the description of moisture and temperature on an individual pellet level has been developed. Experimental validation is carried out in a special designed lab batch dryer, based on recordings of average moisture content and pellet surface temperature, on the air exhaust...... side. The model comprise empirical recording of moisture desorption isotherms and semi-empirical relations for moisture diffusivity and heat and mass transfer coefficients, in particular including the effect of air temperature on moisture diffusivity....

  13. Development of a trickle bed reactor of electro-Fenton process for wastewater treatment

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Yangming [Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 401122 (China); School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Liu, Hong, E-mail: liuhong@cigit.ac.cn [Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 401122 (China); Shen, Zhemin, E-mail: zmshen@sjtu.edu.cn [School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang, Wenhua [School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2013-10-15

    Highlights: • An electrochemical trickle bed reactor was composed of C-PTFE-coated graphite chips. • The trickle bed reactor had a high H{sub 2}O{sub 2} production rate in a dilute electrolyte. • An azo dye was effectively decomposed by the electro-Fenton process in the reactor. -- Abstract: To avoid electrolyte leakage and gas bubbles in the electro-Fenton (E-Fenton) reactors using a gas diffusion cathode, we developed a trickle bed cathode by coating a layer composed of carbon black and polytetrafluoroethylene (C-PTFE) onto graphite chips instead of carbon cloth. The trickle bed cathode was optimized by single-factor and orthogonal experiments, in which carbon black, PTFE, and a surfactant were considered as the determinant of the performance of graphite chips. In the reactor assembled by the trickle bed cathode, H{sub 2}O{sub 2} was generated with a current of 0.3 A and a current efficiency of 60%. This performance was attributed to the fine distribution of electrolyte and air, as well as the effective oxygen transfer from the gas phase to the electrolyte–cathode interface. In terms of H{sub 2}O{sub 2} generation and current efficiency, the developed trickle bed reactor had a performance comparable to that of the conventional E-Fenton reactor using a gas diffusion cathode. Further, 123 mg L{sup −1} of reactive brilliant red X-3B in aqueous solution was decomposed in the optimized trickle bed reactor as E-Fenton reactor. The decolorization ratio reached 97% within 20 min, and the mineralization reached 87% within 3 h.

  14. A coupled transport and solid mechanics formulation with improved reaction kinetics parameters for modeling oxidation and decomposition in a uranium hydride bed.

    Energy Technology Data Exchange (ETDEWEB)

    Salloum, Maher N.; Shugard, Andrew D.; Kanouff, Michael P.; Gharagozloo, Patricia E.

    2013-03-01

    Modeling of reacting flows in porous media has become particularly important with the increased interest in hydrogen solid-storage beds. An advanced type of storage bed has been proposed that utilizes oxidation of uranium hydride to heat and decompose the hydride, releasing the hydrogen. To reduce the cost and time required to develop these systems experimentally, a valid computational model is required that simulates the reaction of uranium hydride and oxygen gas in a hydrogen storage bed using multiphysics finite element modeling. This SAND report discusses the advancements made in FY12 (since our last SAND report SAND2011-6939) to the model developed as a part of an ASC-P&EM project to address the shortcomings of the previous model. The model considers chemical reactions, heat transport, and mass transport within a hydride bed. Previously, the time-varying permeability and porosity were considered uniform. This led to discrepancies between the simulated results and experimental measurements. In this work, the effects of non-uniform changes in permeability and porosity due to phase and thermal expansion are accounted for. These expansions result in mechanical stresses that lead to bed deformation. To describe this, a simplified solid mechanics model for the local variation of permeability and porosity as a function of the local bed deformation is developed. By using this solid mechanics model, the agreement between our reacting bed model and the experimental data is improved. Additionally, more accurate uranium hydride oxidation kinetics parameters are obtained by fitting the experimental results from a pure uranium hydride oxidation measurement to the ones obtained from the coupled transport-solid mechanics model. Finally, the coupled transport-solid mechanics model governing equations and boundary conditions are summarized and recommendations are made for further development of ARIA and other Sandia codes in order for them to sufficiently implement the model.

  15. Mathematical Modeling of the Impact of Hospital Occupancy: When Do Dwindling Hospital Beds Cause ED Gridlock?

    Directory of Open Access Journals (Sweden)

    Lori Whelan

    2014-01-01

    Full Text Available Objectives. The time emergency department (ED patients spend from presentation to admittance is known as their length of stay (LOS. This study aimed to quantify the inpatient occupancy rate (InptOcc/ED LOS relationship and develop a methodology for identifying resource-allocation triggers using InptOcc-LOS association-curve inflection points. Methods. This study was conducted over 200 consecutive days at a 700-bed hospital with an annual ED census of approximately 50,000 using multivariate spline (piecewise regression to model the InptOcc/LOS relationship while adjusting for confounding covariates. Nonlinear modeling was used to assess for InptOcc/LOS associations and determine the inflection point where InptOcc profoundly impacted LOS. Results. At lower InptOcc, there was no association. Once InptOcc reached ≥88%, there was a strong InptOcc/LOS association; each 1% InptOcc increase predicted a 16-minute (95% CI, 12–20 minutes LOS prolongation, while the confounder-adjusted analysis showed each 1% InptOcc increase >89% precipitating a 13-minute (95% CI, 10–16 minutes LOS prolongation. Conclusions. The study hospital’s InptOcc was a significant predictor of prolonged ED LOS beyond the identified inflection point. Spline regression analysis identified a clear inflection point in the InptOcc-LOS curve that potentially identified a point at which to optimize inpatient bed availability to prevent increased costs of prolonged LOS.

  16. Design report on SCDAP/RELAP5 model improvements - debris bed and molten pool behavior

    International Nuclear Information System (INIS)

    The SCDAP/RELAP5/MOD3 computer code is designed to describe the overall reactor coolant system thermal-hydraulic response, core damage progression, and in combination with VICTORIA, fission product release and transport during severe accidents. Improvements for existing debris bed and molten pool models in the SCDAP/RELAP5/MOD3.1 code are described in this report. Model improvements to address (a) debris bed formation, heating, and melting; (b) molten pool formation and growth; and (c) molten pool crust failure are discussed. Relevant data, existing models, proposed modeling changes, and the anticipated impact of the changes are discussed. Recommendations for the assessment of improved models are provided

  17. Design report on SCDAP/RELAP5 model improvements - debris bed and molten pool behavior

    Energy Technology Data Exchange (ETDEWEB)

    Allison, C.M.; Rempe, J.L.; Chavez, S.A.

    1994-11-01

    the SCDAP/RELAP5/MOD3 computer code is designed to describe the overall reactor coolant system thermal-hydraulic response, core damage progression, and in combination with VICTORIA, fission product release and transport during severe accidents. Improvements for existing debris bed and molten pool models in the SCDAP/RELAP5/MOD3.1 code are described in this report. Model improvements to address (a) debris bed formation, heating, and melting; (b) molten pool formation and growth; and (c) molten pool crust failure are discussed. Relevant data, existing models, proposed modeling changes, and the anticipated impact of the changes are discussed. Recommendations for the assessment of improved models are provided.

  18. Heat Transfer in a Fixed Biomass Char Bed

    DEFF Research Database (Denmark)

    Fjellerup, Jan Søren; Henriksen, Ulrik Birk; Glarborg, P.; Jensen, A.; Arendt, P.

    2002-01-01

    A thermal conductivity model based on the Yagi and Kunii model together with a bed model was developed to describe the thermal conductivity of a straw char bed. The bed model describes the relationship between the distance between particles and the external porosity. To verify the model, thermal ...

  19. Experimental, kinetic and numerical modeling of hydrogen production by catalytic reforming of crude ethanol over a commercial catalyst in packed bed tubular reactor and packed bed membrane reactor

    International Nuclear Information System (INIS)

    The demand for hydrogen energy has increased tremendously in recent years essentially because of the increase in the word energy consumption as well as recent developments in fuel cell technologies. The energy information administration has projected that world energy consumption will increase by 59% over the next two decades, from 1999 to 2020, in which the largest share is still dominated by fossil fuels (oil, natural gas and coal). Carbon dioxide (CO2) emissions resulting from the combustion of these fossil fuels currently are estimated to account for three-fourth of human-caused CO2 emissions worldwide. Greenhouse gas emission, including CO2, should be limited, as recommended at the Kyoto Conference, Japan, in December 1997. In this regard, hydrogen (H2) has a significant future potential as an alternative fuel that can solve the problems of CO2 emissions as well as the emissions of other air contaminants. One of the techniques to produce hydrogen is by reforming of hydrocarbons or biomass. Crude ethanol (a form of biomass, which essentially is fermentation broth) is easy to produce, is free of sulphur, has low toxicity, and is also safe to handle, transport and store. In addition, crude ethanol consists of oxygenated hydrocarbons, such as ethanol, lactic acid, glycerol, and maltose. These oxygenated hydrocarbons can be reformed completely to H2 and CO2, the latter of which could be separated from H2 by membrane technology. This provides for CO2 capture for eventual storage or destruction. In the case of using crude ethanol, this will result in negative CO2, emissions. In this paper, we conducted experimental work on production of hydrogen by the catalytic reforming of crude ethanol over a commercial promoted Ni-based catalyst in a packed bed tubular reactor as well as a packed bed membrane reactor. As well, a rigorous numerical model was developed to simulate this process in both the catalytic packed bed tubular reactor and packed bed membrane reactor. The

  20. Artificial neural network (ANN) modeling of adsorption of methylene blue by NaOH-modified rice husk in a fixed-bed column system.

    Science.gov (United States)

    Chowdhury, Shamik; Saha, Papita Das

    2013-02-01

    In this study, rice husk was modified with NaOH and used as adsorbent for dynamic adsorption of methylene blue (MB) from aqueous solutions. Continuous removal of MB from aqueous solutions was studied in a laboratory scale fixed-bed column packed with NaOH-modified rice husk (NMRH). Effect of different flow rates and bed heights on the column breakthrough performance was investigated. In order to determine the most suitable model for describing the adsorption kinetics of MB in the fixed-bed column system, the bed depth service time (BDST) model as well as the Thomas model was fitted to the experimental data. An artificial neural network (ANN)-based model was also developed for describing the dynamic dye adsorption process. An extensive error analysis was carried out between experimental data and data predicted by the models by using the following error functions: correlation coefficient (R(2)), average relative error, sum of the absolute error and Chi-square statistic test (χ(2)). Results show that with increasing bed height and decreasing flow rate, the breakthrough time was delayed. All the error functions yielded minimum values for the ANN model than the traditional models (BDST and Thomas), suggesting that the ANN model is the most suitable model to describe the fixed-bed adsorption of MB by NMRH. It is also more rational and reliable to interpret dynamic dye adsorption data through a process of ANN architecture. PMID:22562342

  1. Measurement and modeling of bed shear stress under solitary waves

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, S.; Guard, P.A.; Baldock, T.E.

    ) of the water particles, and kinematic viscosity (ν ): ν Au R e = (2) In order to estimate R e , the semi-excursion length of the water particles needs to be estimated properly for the solitary waves. This semi-excursion of the water particle... ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ =νν (8) where, z 0 is roughness height, z is depth, ν is kinematic viscosity. It was also shown that to leading order bed shear stress, τ , can be expressed as convolution integral of the depth integrated averaged horizontal velocity, u , Eq...

  2. CO2 Absorption in a Lab-Scale Fixed Solid Bed Reactor: Modelling and Experimental Tests

    Directory of Open Access Journals (Sweden)

    Roberto Gabbrielli

    2004-09-01

    Full Text Available The CO2 absorption in a lab-scale fixed solid bed reactor filled with different solid sorbents has been studied under different operative conditions regarding temperature (20-200°C and input gas composition (N2, O2, CO2, H2O at 1bar pressure. The gas leaving the reactor has been analysed to measure the CO2 and O2 concentrations and, consequently, to evaluate the overall CO2 removal efficiency. In order to study the influence of solid sorbent type (i.e. CaO, coal bottom ash, limestone and blast furnace slag and of mass and heat transfer processes on CO2 removal efficiency, a one-dimensional time dependent mathematical model of the reactor, which may be considered a Plug Flow Reactor, has been developed. The quality of the model has been confirmed using the experimental results.

  3. Circulating fluidized bed combustion in the turbulent regime: modelling of carbon combustion efficiency and sulphur retention

    Energy Technology Data Exchange (ETDEWEB)

    Adanez, J.; Gayan, P.; Grasa, G.; de Diego, L.F.; Armesto, L.; Cabanillas, A. [Instituto de Carboquimica (CSIC), Zaragoza (Spain). Dept. of Energy and Environment

    2001-08-10

    A model has been developed considering the hydrodynamic behaviour of a turbulent circulating fluidized bed, the kinetics of coal combustion and sulphur retention in the riser. The hydrodynamic characteristics of the turbulent fluidization regime were integrated together with the kinetic submodels of char combustion and sulphur retention by limestone. From the combustion of a lignite and an anthracite with limestone addition in a hot CBF pilot plant of 20 cm internal diameter and 6.5 m high, the effect of operating conditions such as temperature, excess air, air velocity, Ca/S molar ratio, coal and limestone particle size distributions on carbon combustion efficiency and sulphur retention were studied. The experimental results were compared with those predicted by the model and a good correlation was found for all the conditions used. 56 refs., 10 figs., 1 tab.

  4. A New Mathematical Model for Description of the Liquid Discrete Flow Within a Packed Bed

    Institute of Scientific and Technical Information of China (English)

    WANG Cheng-shan; MU Xiao-jing; ZHENG Shao-bo; JIANG Guo-chang; XIAO Xing-guo; WANG Wen-zhong

    2008-01-01

    The molten liquid discrete flow inside a packed bed is a typical transport phenomenon in the blast furnace.As for the reportcd mathematieal models presenting the liquid discrete flow within the packed bed,there are some barriers for their application to an engineering scale-up,or some imperfections in model descriptions. To overcome these deficieneies,the effects of the packed bed on the liquid discrete flow have been divided into reststance action and dispcrsal action,and appropriate descriptions have been given for thc two actions,respectively.Consequently,a new mathematical model has been built to present the liquid discrete flow inside a coke bed in the blast furnace. The mathcmatical model can predict the distribution of liquid flux and the liquid flowing range inside the packed bed at any time.The prediction of this model accords well with the experimental data.The model will be much better for the simulation of the ironmaking process,compared with the existent model.

  5. Water temperatures within spawning beds in two chalk streams and implications for salmonid egg development

    Science.gov (United States)

    Acornley, R. M.

    1999-02-01

    Water temperatures within brown trout (Salmo trutta L.) spawning gravels were measured in two Hampshire chalk streams from October 1995 to April 1996 inclusive. During the winter, mean intra-gravel water temperatures were higher than those in the stream, and increased with depth in the gravel bed. The amplitude of diel fluctuations in water temperature decreased with depth in the gravel bed, although diel fluctuations were still evident at a depth of 30 cm. Differences in intra-gravel temperature gradients between the two study sites were attributed to differences in the amplitude of stream water temperature fluctuations and there was no evidence that either of the study sites were located in zones of upwelling groundwater. Published equations are used to predict, from temperature, the timing of important stages in the development of brown trout embryos (eyeing, hatching and emergence) for eggs spawned in the autumn and winter and buried at different depths in the gravel bed.

  6. Development of a fluid bed weak base ion exchange process for the recovery of uranium

    International Nuclear Information System (INIS)

    The ability to recover uranium from leach solutions containing suspended solids using continuous counter-current fluid bed ion exchange is the key to reducing post leach recovery costs. Weak base resins offer the advantage of higher product purity over strong base resins and details of a laboratory programme are given in which the fluidisation, extraction and elution properties of a series of weak base resins were examined for their usefulness in the fluid bed contactor. A macroporous polystyrene resin selected from the laboratory tests has been tested on the pilot plant scale and it was concluded that resins of this type are suitable for use in the fluid bed contactor. These resins may therefore be considered for use in low cost recovery operations. During the pilot plant programme a simple method of predicting column operation based on laboratory scale stir tests was developed. (author)

  7. Modeling of Sediment Bed Behavior for Critical Velocity in Horizontal Piping

    International Nuclear Information System (INIS)

    This paper compares results from a predictive tool for modeling transport of a multiphase mixture (solids in a liquid) in a pipeline, (up to and including plugging) with experiments performed to support the Hanford site's Waste Treatment and Immobilization Plant (WTP). The treatment of high-level waste at the DOE Office of River Protection's WTP will involve the transfer of high solid content suspensions through pipelines. Pipeline plugging was identified as a significant potential issue by a panel of external experts. In response to their concerns an experimental effort was initiated at PNNL to determine the critical velocities for a variety of operating conditions. A computational method has been developed to predict the dynamic behavior of a sediment bed in response to the surrounding suspension flow. The flow field is modeled using a lattice kinetics method, similar to the lattice Boltzmann method, which scales very well on highly parallel computers. Turbulent quantities are calculated using a k-epsilon RANS model. This work is part of a larger effort to develop a process simulation capability for a wide range of applications. Solids are represented using two different continuum fields. The suspended solids are treated as passive scalars in the flow field, including terms for hindered settling and Brownian diffusion. Normal stresses created by the irreversible collisions of particles during shearing are added to the pressure tensor. The sediment bed interface is represented using a continuum phase field with a diffuse interface. The bed may change with time due to settling, erosion and deposition through convection. The erosion rates are calculated using the local shear stress obtained from the turbulence model. The method is compared with data from the PNNL pipeline experiments conducted at PNNL (Poloski et al. 2008). The experimental flow loop consists of 3-inch schedule 40 piping with instrumentation for determining flow rate and pressure gradient. The

  8. Fluidized-bed reactor modeling for production of silicon by silane pyrolysis

    Science.gov (United States)

    Dudukovic, M. P.; Ramachandran, P. A.; Lai, S.

    1986-01-01

    An ideal backmixed reactor model (CSTR) and a fluidized bed bubbling reactor model (FBBR) were developed for silane pyrolysis. Silane decomposition is assumed to occur via two pathways: homogeneous decomposition and heterogeneous chemical vapor deposition (CVD). Both models account for homogeneous and heterogeneous silane decomposition, homogeneous nucleation, coagulation and growth by diffusion of fines, scavenging of fines by large particles, elutriation of fines and CVD growth of large seed particles. At present the models do not account for attrition. The preliminary comparison of the model predictions with experimental results shows reasonable agreement. The CSTR model with no adjustable parameter yields a lower bound on fines formed and upper estimate on production rates. The FBBR model overpredicts the formation of fines but could be matched to experimental data by adjusting the unkown jet emulsion exchange efficients. The models clearly indicate that in order to suppress the formation of fines (smoke) good gas-solid contacting in the grid region must be achieved and the formation of the bubbles suppressed.

  9. Plans of a test bed for ionospheric modelling based on Fennoscandian ground-based instrumentation

    Science.gov (United States)

    Kauristie, Kirsti; Kero, Antti; Verronen, Pekka T.; Aikio, Anita; Vierinen, Juha; Lehtinen, Markku; Turunen, Esa; Pulkkinen, Tuija; Virtanen, Ilkka; Norberg, Johannes; Vanhamäki, Heikki; Kallio, Esa; Kestilä, Antti; Partamies, Noora; Syrjäsuo, Mikko

    2016-07-01

    One of the recommendations for teaming among research groups in the COSPAR/ILWS roadmap is about building test beds in which coordinated observing supports model development. In the presentation we will describe a test bed initiative supporting research on ionosphere-thermosphere-magnetosphere interactions. The EISCAT incoherent scatter radars with their future extension, EISCAT3D, form the backbone of the proposed system. The EISCAT radars are surrounded by versatile and dense arrays of ground-based instrumentation: magnetometers and auroral cameras (the MIRACLE and IMAGE networks), ionospheric tomography receivers (the TomoScand network) and other novel technology for upper atmospheric probing with radio waves (e.g. the KAIRA facility, riometers and the ionosonde maintained by the Sodankylä Geophysical Observatory). As a new opening, close coordination with the Finnish national cubesat program is planned. We will investigate opportunities to establish a cost efficient nanosatellite program which would support the ground-based observations in a systematic and persistent manner. First experiences will be gathered with the Aalto-1 and Aalto-2 satellites, latter of which will be the Finnish contribution to the international QB50 mission. We envisage close collaboration also in the development of data analysis tools with the goal to integrate routines and models from different research groups to one system, where the different elements support each other. In the longer run we are aiming for a modelling framework with observational guidance which gives a holistic description on ionosphere-thermosphere processes and this way enables reliable forecasts on upper atmospheric space weather activity.

  10. CFD modeling of a spouted bed with a porous draft tube

    Institute of Scientific and Technical Information of China (English)

    Salar Azizi; Seyyed Hossein Hosseini; M. Moraveji; Goodarz Ahmadi

    2010-01-01

    Spouted bed with a porous draft tube is used for drying of grains and chemical products and thermal disinfestations process. This work provides a computational fluid dynamics (CFD) simulation of binary mixtures of glass particles in a spouted bed with a porous draft tube. The simulation used the multi-fluid Eulerian-Eulerian approach based on kinetic theory of granular flows, incorporating a kinetic-frictional constitutive model for dense assemblies of particulate solids and Gidaspow's drag model for the inter-action between gas and particles. Influences of solids mass fraction and inlet gas flow rate on pressure distribution, gas and particle velocities were studied. The modeling results were compared with the exper-imental work of Ishikura, Nagashima, and lde (2003) for the flow condition along the axis of the spouted bed. Good agreement between the modeling results and experimental data was observed.

  11. Debris bed coolability using a 3-D two phase model in a porous medium

    International Nuclear Information System (INIS)

    During a severe nuclear accident, a part of the molten corium resulting from the core degradation may relocate in the lower plenum of the reactor vessel. In order to predict the safety margin of the reactor under such conditions, the coolability of this porous heat-generating medium is evaluated in this study and compared with other investigations. In this work, conservation equations derived for debris beds are implemented in the three dimensional thermal-hydraulic module of the CATHARE code. The coolant flow is a two phase flow with phase change. The momentum balance equation for each fluid phase is an extension of Darcy's law. This extension takes into account the capillary effects between the two phases, the relative permeabilities and passabilities of each phase, the interfacial drag force between liquid and gas, and the porous bed configuration (porosity, particle diameter,... ). The model developed is three-dimensional which is important to better predict the flow in configuration such as counter-current flow or to emphasize preferential ways induced by porous geometry. The energy balance equations of the three phases (liquid, gas and solid phase) are obtained by a volume averaging process of the local conservation equations. In this method, the local thermal non-equilibrium between the three phases is considered and the heat exchanges, the phase change rate as well as the thermal dispersion coefficients are calculated as a function of the local geometry of the porous medium. Such a method allows the numerical estimation of these thermal properties which are very difficult to determine experimentally. This feature is a great advantage of this approach. After a brief description of the thermal-hydraulic model, one-dimensional predictions of critical dryout fluxes are presented and compared with results from the literature. Reasonable agreement is obtained. Then a two-dimensional calculation is presented and shows the influence of the porous medium

  12. The Silurian Reservoir Bed-Differentiated Asphalts in Tarim Basin and Modeling Experiments on Their Origin

    Institute of Scientific and Technical Information of China (English)

    刘洛夫; 刘宏江; 王洪玉; 曾溅辉

    2002-01-01

    There is a type of asphalt that originated from differentiation from reservoir bed (named reservoir bed-differentiated asphalt) in the Silurian asphaltic sandstones of the Tarim Basin. These asphalts are the result of second-time charging of hydrocarbons into the Silurian reservoir, which were derived from Lower Paleozoic source rocks. Asphalt was differentiated from the reservoir bed in the hydrocarbon gathering area of secondary migration. The differen tiation is caused by changes in reservoir physical properties when pearl or chain hydrocarbons migrating through and gathering in the reservoir bed, and light components are lost and heavy ones are involved in the formation of asphalt or heavy oil. There are two kinds of occurrence of these asphalts in the Silurian system of the Tarim Basin. One is the poor heavy oil layer with lower oil saturation in trap and the other is scattered hydrocarbon distributed along the transport layer and unconformity surface. Reservoir bed-differentiated asphalts have two characteristics: total hydrocarbon content is high in extractable organic matter and the ratio of saturated to aromatic hydrocarbon is usually greater than unity. The physically modeling experiment has confirmed these characteristics and the genesis of the reservoir bed-differentiated asphalts.

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

    Energy Technology Data Exchange (ETDEWEB)

    Archie Robertson

    2003-07-23

    Foster Wheeler Power Group, Inc. is working under US Department of Energy 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% and produce 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 amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the April 1--June 30, 2003 time period.

  14. DEVELOPMENT OF PRESSURIZED CIRCULATING FLUDIZED BED PARTIAL GASIFICATION MODULE (PGM)

    Energy Technology Data Exchange (ETDEWEB)

    Archie Robertson

    2002-07-10

    Foster Wheeler Power Group, Inc. is working under US Department of Energy 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% and produce 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 amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the April 1--June 30, 2002 time period.

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

    Energy Technology Data Exchange (ETDEWEB)

    Archie Robertson

    2003-10-29

    Foster Wheeler Power Group, Inc. is working under US Department of Energy 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% and produce 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 amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the July 1--September 30, 2003 time period.

  16. Development of Pressurized Circulating Fluidized Bed Partial Gasification Module (PGM)

    Energy Technology Data Exchange (ETDEWEB)

    A. Robertson

    2002-09-30

    Foster Wheeler Power Group, Inc. is working under US Department of Energy 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% and produce 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 amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the July 1-September 30, 2002 time period.

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

    Energy Technology Data Exchange (ETDEWEB)

    Unknown

    2003-01-30

    Foster Wheeler Power Group, Inc. is working under US Department of Energy 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% and produce 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 amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building bock that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the October 1--December 31, 2002 time period.

  18. Space Suit Portable Life Support System Test Bed (PLSS 1.0) Development and Testing

    Science.gov (United States)

    Watts, Carly; Campbell, Colin; Vogel, Matthew; Conger, Bruce

    2012-01-01

    A multi-year effort has been carried out at NASA-JSC to develop an advanced extra-vehicular activity Portable Life Support System (PLSS) design intended to further the current state of the art by increasing operational flexibility, reducing consumables, and increasing robustness. Previous efforts have focused on modeling and analyzing the advanced PLSS architecture, as well as developing key enabling technologies. Like the current International Space Station Extra-vehicular Mobility Unit PLSS, the advanced PLSS comprises three subsystems required to sustain the crew during extra-vehicular activity including the Thermal, Ventilation, and Oxygen Subsystems. This multi-year effort has culminated in the construction and operation of PLSS 1.0, a test bed that simulates full functionality of the advanced PLSS design. PLSS 1.0 integrates commercial off the shelf hardware with prototype technology development components, including the primary and secondary oxygen regulators, Ventilation Subsystem fan, Rapid Cycle Amine swingbed carbon dioxide and water vapor removal device, and Spacesuit Water Membrane Evaporator heat rejection device. The overall PLSS 1.0 test objective was to demonstrate the capability of the Advanced PLSS to provide key life support functions including suit pressure regulation, carbon dioxide and water vapor removal, thermal control and contingency purge operations. Supplying oxygen was not one of the specific life support functions because the PLSS 1.0 test was not oxygen rated. Nitrogen was used for the working gas. Additional test objectives were to confirm PLSS technology development components performance within an integrated test bed, identify unexpected system level interactions, and map the PLSS 1.0 performance with respect to key variables such as crewmember metabolic rate and suit pressure. Successful PLSS 1.0 testing completed 168 test points over 44 days of testing and produced a large database of test results that characterize system level

  19. Model description and kinetic parameter analysis of MTBE biodegradation in a packed bed reactor

    DEFF Research Database (Denmark)

    Waul, Christopher Kevin; Arvin, Erik; Schmidt, Jens Ejbye

    2008-01-01

    A dynamic modeling approach was used to estimate in-situ model parameters, which describe the degradation of methyl tert-butyl ether (MTBE) in a laboratory packed bed reactor. The measured dynamic response of MTBE pulses injected at the reactor's inlet was analyzed by least squares and parameter ...

  20. Three-Dimensional Computational Fluid Dynamics Modeling of a Prismatic Spouted Bed

    NARCIS (Netherlands)

    Gryczka, O.; Heinrich, S.; Deen, N.G.; Kuipers, J.A.M.; Mörl, L.

    2009-01-01

    Modern simulation tools like discrete particle models or continuum models have been established as precious methods to gain insight into the complex processes in fluidized and spouted beds. Valuable information on parameters influencing the hydrodynamics can be obtained directly from computer simula

  1. Modeling of reaction-induced flow maldistributions in packed beds

    Energy Technology Data Exchange (ETDEWEB)

    Stroh, F.; Balakotaiah, V. (Dept. of Chemical Engineering, Univ. of Houston, Houston, TX (United States))

    1991-07-01

    This paper examines reaction-induced flow maldistributions in adiabatic, down-flow packed beds. Using linear stability analysis it is shown that for the case of a constant heat source, the uniform flow loses stability when a certain dimensionless group, the Darcy buoyancy number, exceeds a critical value. Center manifold theory is used to analyze the local bifurcation picture for the case of a simple and double zero eigenvalue. it is found that for large Peclet numbers, all the bifurcations from the uniform solution are subcritical in nature and are unstable locally. Orthogonal collocation and continuation techniques are combined with the local theory to determine the various branches of bifurcating solutions. The temperature and flow distributions of stable and unstable solution branches are presented for several aspect ratios and Peclet numbers. Numerical simulations predict direct transitions from uniform flow to periodic or chaotic flows. It is also found that there is a wide range of the Darcy buoyancy number in which the uniform and maldistributed flows are stable and coexist.

  2. Modeling of reaction-induced flow maldistributions in packed beds

    International Nuclear Information System (INIS)

    This paper examines reaction-induced flow maldistributions in adiabatic, down-flow packed beds. Using linear stability analysis it is shown that for the case of a constant heat source, the uniform flow loses stability when a certain dimensionless group, the Darcy buoyancy number, exceeds a critical value. Center manifold theory is used to analyze the local bifurcation picture for the case of a simple and double zero eigenvalue. it is found that for large Peclet numbers, all the bifurcations from the uniform solution are subcritical in nature and are unstable locally. Orthogonal collocation and continuation techniques are combined with the local theory to determine the various branches of bifurcating solutions. The temperature and flow distributions of stable and unstable solution branches are presented for several aspect ratios and Peclet numbers. Numerical simulations predict direct transitions from uniform flow to periodic or chaotic flows. It is also found that there is a wide range of the Darcy buoyancy number in which the uniform and maldistributed flows are stable and coexist

  3. Test-bed development & measurement plan for evaluating transmit diversity in DVB networks

    OpenAIRE

    H Shirazi; Di Bari, R; Cosmas, J; Nilavalan, R; Y. Zhang; Bard, M.; Loo, J.

    2007-01-01

    This paper presents a test-bed development and measurement plan for evaluating transmit diversity in the DVB network. Transmit diversity reduces the complexity and improves the power consumption of the personal receiving devices by improving the transmission of signals in NLOS cluttered environments. Also, it is more practical than receive diversity due to the difficulty of locating two receive antennas far enough apart in a small mobile device. Test service scenarios were developed to illust...

  4. Development program on pressurized fluidized-bed combustion. Annual report, July 1, 1974--June 30, 1975

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, G.J.; Cunningham, P.; Fischer, J.

    1975-07-01

    The feasibility of using fluidized-bed combustors in power and steam plants is being evaluated. The concept involves burning fuels such as coal in a fluidized bed of either a naturally occurring, calcium-containing limestone or dolomite or in a synthetically prepared calcium-containing stone. The calcium oxide in the stone reacts with the sulfur released during combustion to form calcium sulfate, which remains in the bed, thus decreasing the level of SO/sub 2/ in the flue gas. Levels of NO/sub x/ in the flue gas are also low. The effect of operating variables and type of stone on the levels of SO/sub 2/ and NO/sub x/ is being determined. Behavior of trace elements during combustion has been preliminarily evaluated. The properties of a fluidized bed at minimum fluidization at different temperatures and pressures have been determined. The CaSO/sub 4/ produced in the combustion process is regenerated to CaO for reuse in the combustor by reductive decomposition at 1095/sup 0/C (2000/sup 0/F). The effects of operating variables on sulfur release during regeneration are being evaluated. Another regeneration process, solid-solid reaction of CaSO/sub 4/ with CaS, is also being investigated. Fundamental investigations of the kinetics of sulfation and regeneration reactions for the natural and synthetic stones are continuing. A model for the sulfation reaction is presented. The status of the new combustor andancillary regenerator equipment is discussed. (auth)

  5. CFD simulation on hydrodynamics in fluidized beds: assessment of gradient approximations and turbulence models

    Science.gov (United States)

    Guo, Yuan; Deng, Baoqing; Ge, Daqiang; Shen, Xiuzhong

    2015-08-01

    CFD simulations of gas-solid fluidized beds have been performed in Euler-Euler framework. Green-Gauss Cell Based gradient approximation can predict the solid velocity well among gradient approximations. The dispersed choice in the turbulence model can reproduce the solid velocity correctly while the mixture and per phase choices cannot. The standard k-ɛ model, RNG k-ɛ model and SST k-ω model with the dispersed choice can predict the solid velocity well.

  6. Anomalous diffusion for bed load transport with a physically-based model

    Science.gov (United States)

    Fan, N.; Singh, A.; Foufoula-Georgiou, E.; Wu, B.

    2013-12-01

    Diffusion of bed load particles shows both normal and anomalous behavior for different spatial-temporal scales. Understanding and quantifying these different types of diffusion is important not only for the development of theoretical models of particle transport but also for practical purposes, e.g., river management. Here we extend a recently proposed physically-based model of particle transport by Fan et al. [2013] to further develop an Episodic Langevin equation (ELE) for individual particle motion which reproduces the episodic movement (start and stop) of sediment particles. Using the proposed ELE we simulate particle movements for a large number of uniform size particles, incorporating different probability distribution functions (PDFs) of particle waiting time. For exponential PDFs of waiting times, particles reveal ballistic motion in short time scales and turn to normal diffusion at long time scales. The PDF of simulated particle travel distances also shows a change in its shape from exponential to Gamma to Gaussian with a change in timescale implying different diffusion scaling regimes. For power-law PDF (with power - μ) of waiting times, the asymptotic behavior of particles at long time scales reveals both super-diffusion and sub-diffusion, however, only very heavy tailed waiting times (i.e. 1.0 < μ < 1.5) could result in sub-diffusion. We suggest that the contrast between our results and previous studies (for e.g., studies based on fractional advection-diffusion models of thin/heavy tailed particle hops and waiting times) results could be due the assumption in those studies that the hops are achieved instantaneously, but in reality, particles achieve their hops within finite times (as we simulate here) instead of instantaneously, even if the hop times are much shorter than waiting times. In summary, this study stresses on the need to rethink the alternative models to the previous models, such as, fractional advection-diffusion equations, for studying

  7. Magnetic fabric of sheared till: A strain indicator for evaluating the bed deformation model of glacier flow

    Science.gov (United States)

    Hooyer, T.S.; Iverson, N.R.; Lagroix, F.; Thomason, J.F.

    2008-01-01

    Wet-based portions of ice sheets may move primarily by shearing their till beds, resting in high sediment fluxes and the development of subglacial landforms. This model of glacier movement, which requires high bed shear strains, can be tested using till microstructural characteristics that evolve during till deformation. Here we examine the development of magnetic fabric using a ring shear device to defom two Wisconsin-age basal tills to shear strains as high as 70. Hysteresis experiments and the dependence of magnetic susceptibility of these tills on temperature demonstrate that anisotropy of magnetic susceptibility (AMS) develops during shear due to the rotation of primarily magnetite particles that are silt sized or smaller. At moderate shear strains (???6-25), principal axes of maximum magnetic susceptibility develop a strong fabric (S1 eignevalues of 0.83-0.96), without further strengthening at higher strains, During deformation, directions of maximum susceptibility cluster strongly in the direction of shear and plunge 'up-glacier,' consistent with the behavior of pebbles and sand particles studied in earlier experiments. In contrast, the magnitude of AMS does not vary systematically with strain and is small relative to its variability among samples; this is because most magnetite grains are contained as inclusions in larger particles and hence do not align during shear. Although processes other than pervasive bed deformation may result in strong flow parallel fabrics, AMS fabrics provide a rapid and objective means of identifying basal tills that have not been sheared sufficiently to be compatible with the bed deformation model. Copyright 2008 by the American Geophysical Union.

  8. Moving granular-bed filter development program, Option III: Development of moving granular-bed filter technology for multi-contaminant control. Task 14: Test plan; Topical report

    Energy Technology Data Exchange (ETDEWEB)

    Haas, J.C.; Olivo, C.A.; Wilson, K.B.

    1994-04-01

    An experimental test plan has been prepared for DOE/METC review and approval to develop a filter media suitable for multi-contaminant control in granular-bed filter (GBF) applications. The plan includes identification, development, and demonstration of methods for enhanced media morphology, chemical reactivity, and mechanical strength. The test plan includes media preparation methods, physical and chemical characterization methods for fresh and reacted media, media evaluation criteria, details of test and analytical equipment, and test matrix of the proposed media testing. A filter media composed of agglomerated limestone and clay was determined to be the best candidate for multi-contaminate control in GBF operation. The combined limestone/clay agglomerate has the potential to remove sulfur and alkali species, in addition to particulate, and possibly halogens and trace heavy metals from coal process streams.

  9. Hyporheic Exchange in Gravel-Bed Rivers with Pool-Riffle Morphology: A 3D Model

    Science.gov (United States)

    Tonina, D.; Buffington, J. M.

    2004-12-01

    The hyporheic zone is a saturated band of sediment that surrounds river flow and forms a linkage between the river and the aquifer. It is a rich ecotone where benthic, hyporheic, and groundwater species temporarily or permanently reside. Head gradients along the streambed draw river water into the hyporheic zone and expel pore water into the stream. This process, known as hyporheic exchange, is important for delivering nutrients, oxygen and other solutes to the sediment, and for washing away waste products to support this ecotone. It is an essential component of the carbon and nitrogen cycles, and it controls in-stream contaminant transport. Although hyporheic exchange has been studied in sand-bed rivers with two-dimensional dune morphology, few studies have been conducted for gravel-bed rivers with three-dimensional pool-riffle geometry. The hyporheic zone of gravel-bed rivers is particularly important for salmonids, many of which are currently at risk world wide. Salmon and trout lay their eggs within the hyporheic zone for incubation. After hatching, the alevins live in the gravel before emerging into the stream. The upwelling and downwelling hyporheic fluxes are intense in these streams due to the highly permeable sediment and strong head variations forced by shallow flow over high-amplitude bed forms. Moreover, gravel-bed rivers show a wide range of flow regimes that change seasonally and have strong effects on hyporheic exchange. To study this exchange, we used four sets of pool-riffle geometries in twelve recirculating flume experiments. We kept a constant bed-form wavelength, but changed the bed-form amplitude and imposed three discharges, covering a wide range of hydraulic and geometric characteristics. Hyporheic exchange was predicted from a three-dimensional model based on bedform-induced pumping transport, where the boundary head profile is the pressure head distribution at the sediment interface, measured with an array of mini-piezometers buried within

  10. RSMASS system model development

    International Nuclear Information System (INIS)

    RSMASS system mass models have been used for more than a decade to make rapid estimates of space reactor power system masses. This paper reviews the evolution of the RSMASS models and summarizes present capabilities. RSMASS has evolved from a simple model used to make rough estimates of space reactor and shield masses to a versatile space reactor power system model. RSMASS uses unique reactor and shield models that permit rapid mass optimization calculations for a variety of space reactor power and propulsion systems. The RSMASS-D upgrade of the original model includes algorithms for the balance of the power system, a number of reactor and shield modeling improvements, and an automatic mass optimization scheme. The RSMASS-D suite of codes cover a very broad range of reactor and power conversion system options as well as propulsion and bimodal reactor systems. Reactor choices include in-core and ex-core thermionic reactors, liquid metal cooled reactors, particle bed reactors, and prismatic configuration reactors. Power conversion options include thermoelectric, thermionic, Stirling, Brayton, and Rankine approaches. Program output includes all major component masses and dimensions, efficiencies, and a description of the design parameters for a mass optimized system. In the past, RSMASS has been used as an aid to identify and select promising concepts for space power applications. The RSMASS modeling approach has been demonstrated to be a valuable tool for guiding optimization of the power system design; consequently, the model is useful during system design and development as well as during the selection process. An improved in-core thermionic reactor system model RSMASS-T is now under development. The current development of the RSMASS-T code represents the next evolutionary stage of the RSMASS models. RSMASS-T includes many modeling improvements and is planned to be more user-friendly. RSMASS-T will be released as a fully documented, certified code at the end of

  11. Evaporation and Flow of Coolant at the Bottom of a Particle-Bed modelling Relocated Debris

    International Nuclear Information System (INIS)

    Subject of the presented work is the experimental investigation of cooling-mechanisms which set in after the relocation of molten debris to the lower plenum during a nuclear accident with core melt. Emphasis is put on the influence of the bottom area of the porous debris. Experiments are carried out with a bed of steel balls (Diam = 2 and 4 mm), heated with an induction coil. The particle-bed is located inside a glass trough with inclining bottom. The particle-bed represents a section from the lower plenum of the RPV. At present, the model-fluid R134a is used and heating rates of up to 560 kW/m2 per unit horizontal cross-sectional area of the article-bed are realized. With these experiments, the evaporation inside the particle-bed and the resulting flow of liquid and gaseous coolant and the influence of an inclining bottom are investigated in detail. The results obtained in the first steady-state experiments and transient experiments are presented and discussed. (authors)

  12. The microelectronics and photonics test bed (MPTB) space, ground test and modeling experiments

    International Nuclear Information System (INIS)

    This paper is an overview of the MPTB (microelectronics and photonics test bed) experiment, a combination of a space experiment, ground test and modeling programs looking at the response of advanced electronic and photonic technologies to the natural radiation environment of space. (author)

  13. Flow near a model spur dike with a fixed scoured bed

    Science.gov (United States)

    Three-dimensional flow velocities were measured using an acoustic Doppler velocimeter at a closely spaced grid over a fixed scoured bed with a submerged spur dike. Three-dimensional flow velocities were measured at 3484 positions around the trapezoidal shaped submerged model spur dike over a fixed ...

  14. Modeling of structural effects in biomedical elements after titanium oxidation in fluidized bed

    Science.gov (United States)

    Jasiński, J.; Szota, M.; Mendzik, K.

    2010-06-01

    Oxidation is one of the most employed methods to improve titanium and its alloys properties especially due to medical application. This process like most of the thermochemical treatment processes substantially influences on the characteristic of surface layers and the same on its mechanical and useful properties. Oxide coatings produced during titanium oxidation were examined due to their composition identification. Titanium was oxidized in fluidized bed in temperature range between 500÷700°C. Microstructures of titanium with a visible oxide coating on its surface after thermochemical treatment and changes of grain size in core of titanium samples are described. Moreover Xray phase analysis of obtained oxides coatings was made as well as microhardness measurements of titanium surface layers after oxidation process. Finally, the surfaces of titanium after oxidation in fluidized bed were measured by Auger electron spectroscopy. All research results are used to built numerical model of oxidation process in fluidized. Titanium oxidation process in fluidized bed is very complicated, because changes of parameters are non linear characteristics. This fact and lack of mathematical algorithms describing this process makes modeling properties of titanium elements by traditional numerical methods difficult or even impossible. In this case it is possible to try using artificial neural network. Using neural networks for modeling oxidizing in fluidized bed is caused by several nets' features: non linear character, ability to generalize the results of calculations for data out of training set, no need for mathematical algorithms describing influence changes input parameters on modeling materials properties.

  15. A Strategy for Coal Bed Methane and Coal Mine Methane Development and Utilization in China

    OpenAIRE

    Energy Sector Management Assistance Program

    2007-01-01

    China is short of clean energy, particularly conventional natural gas. The proven per capital natural gas reserve is only 1/12th of the world average. However, China has large coal bed methane (CBM) resources with development potential which can be recovered from surface boreholes independent of mining and in advance of mining, and also captured as a part of underground coal mining operati...

  16. Numerical and experimental modelling of dam break interaction with a sediment bed

    OpenAIRE

    McMullin, Nicholas

    2015-01-01

    A dam break event is considered, taking place over a uniform sediment bed. Understanding and modelling the erosion that occurs when the fluid behind the dam collapses at release has important applications in coastline morphodynamics / beach erosion modelling. A new coupled two dimensional Navier-Stokes solver and sediment transport model is presented with novel methods for dealing with non-converging solutions to the Navier-Stokes equations and a new adaptation to the Youngs [1982] volume...

  17. Processes and parameters involved in modeling radionuclide transport from bedded salt repositories. Final report. Technical memorandum

    International Nuclear Information System (INIS)

    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

  18. A new model for two-dimensional numerical simulation of pseudo-2D gas-solids fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tingwen; Zhang, Yongmin

    2013-10-11

    Pseudo-two dimensional (pseudo-2D) fluidized beds, for which the thickness of the system is much smaller than the other two dimensions, is widely used to perform fundamental studies on bubble behavior, solids mixing, or clustering phenomenon in different gas-solids fluidization systems. The abundant data from such experimental systems are very useful for numerical model development and validation. However, it has been reported that two-dimensional (2D) computational fluid dynamic (CFD) simulations of pseudo-2D gas-solids fluidized beds usually predict poor quantitative agreement with the experimental data, especially for the solids velocity field. In this paper, a new model is proposed to improve the 2D numerical simulations of pseudo-2D gas-solids fluidized beds by properly accounting for the frictional effect of the front and back walls. Two previously reported pseudo-2D experimental systems were simulated with this model. Compared to the traditional 2D simulations, significant improvements in the numerical predictions have been observed and the predicted results are in better agreement with the available experimental data.

  19. Research on the pyrolysis of hardwood in an entrained bed process development unit

    Energy Technology Data Exchange (ETDEWEB)

    Kovac, R.J.; Gorton, C.W.; Knight, J.A.; Newman, C.J.; O' Neil, D.J. (Georgia Inst. of Tech., Atlanta, GA (United States). Research Inst.)

    1991-08-01

    An atmospheric flash pyrolysis process, the Georgia Tech Entrained Flow Pyrolysis Process, for the production of liquid biofuels from oak hardwood is described. The development of the process began with bench-scale studies and a conceptual design in the 1978--1981 timeframe. Its development and successful demonstration through research on the pyrolysis of hardwood in an entrained bed process development unit (PDU), in the period of 1982--1989, is presented. Oil yields (dry basis) up to 60% were achieved in the 1.5 ton-per-day PDU, far exceeding the initial target/forecast of 40% oil yields. Experimental data, based on over forty runs under steady-state conditions, supported by material and energy balances of near-100% closures, have been used to establish a process model which indicates that oil yields well in excess of 60% (dry basis) can be achieved in a commercial reactor. Experimental results demonstrate a gross product thermal efficiency of 94% and a net product thermal efficiency of 72% or more; the highest values yet achieved with a large-scale biomass liquefaction process. A conceptual manufacturing process and an economic analysis for liquid biofuel production at 60% oil yield from a 200-TPD commercial plant is reported. The plant appears to be profitable at contemporary fuel costs of $21/barrel oil-equivalent. Total capital investment is estimated at under $2.5 million. A rate-of-return on investment of 39.4% and a pay-out period of 2.1 years has been estimated. The manufacturing cost of the combustible pyrolysis oil is $2.70 per gigajoule. 20 figs., 87 tabs.

  20. Model investigations 3D of gas-powder two phase flow in descending bed with consideration radial distribution of flow

    Directory of Open Access Journals (Sweden)

    B. Panic

    2013-04-01

    Full Text Available The results of experimental investigations concerning radial distribution of powder accumulation in bed and static pressure were presented in this paper. To realize this research physical model of gas-powder two phase flow with descending bed was projected and constructed. Amounts of “dynamic” and “static” powder accumulated in bed, in dependence on gas velocity and of bed particles were investigated. In 3D model “static” powder (with its radial distribution at the tuyere level and in the higher part of bed was measured. The influence of bed particles, powder and gas radial distribution on values of interaction forces between flow phases in investigated system was defined.

  1. Comparison of waste water treatment between completely mixed and fluidised bed reactor; development and structure of biomass

    Energy Technology Data Exchange (ETDEWEB)

    Toman, M.; Mejac, B.

    1988-08-01

    The aerobic biological treatment of waste water from production of semisynthetic antibiotics in a completely mixed reactor and in a fluidised bed reactor was studied. The formation and development of new biomass on the sand of a fluidised bed was observed, so that differences in the structure of organisms of the concomitant biocenosis could be detected. In a fluidised bed reactor the same quality of treatednwater was gained on account of a 4-5 times higher volumetric and hydraulic loading as it was the case with a conventional activated sludge plant. The biocenosis of the fluidised bed was abundant in individua and species. The biofilm of the sand depended on substrate degradation rate as well as on rubbing among the sand particles. An optimal biofilm developed on the sand of a fluidised bed reactor 10 to 15 days after the experiment had began, and that condition remained unchanged as the experiment continued.

  2. Design and Development of a High Efficiency CarbonGranular Bed Filter in Industrial Scale

    Institute of Scientific and Technical Information of China (English)

    张济宇; 旷戈; 林诚

    2004-01-01

    The new dust removal technical route using the carbon-granular bed filter, packed of carbon particles with appropriate grade derive from an online-process vibration sieve, to replace the traditional baggy filter had been developed successfully for capturing the micro-carbon dusts produced from pulverization of petroleum coke,and the green close loop of carbon materials is thus completed in the combined pulverizing and classifying system and pulverized carbon dust removal process. The high dust removal efficiency greater than 99%, low outlet dust concentration less than 100 mg-m-S, low pressure drop through dust filtration chamber less than 980 Pa, simple and easy design, and flexible and stable operation were achieved also with the carbon-granular bed filter in both bench and industrial scale operations.

  3. Modelling glacier-bed overdeepenings and possible future lakes for the glaciers in the Himalaya-Karakoram region

    DEFF Research Database (Denmark)

    Linsbauer, A.; Frey, H.; Haeberli, W.;

    2016-01-01

    Surface digital elevation models (DEMs) and slope-related estimates of glacier thickness enable modelling of glacier-bed topographies over large ice-covered areas. Due to the erosive power of glaciers, such bed topographies can contain numerous overdeepenings, which when exposed following glacier...... retreat may fill with water and form new lakes. In this study, the bed overdeepenings for ∼28000 glaciers (40 775km2) of the Himalaya-Karakoram region are modelled using GlabTop2 (Glacier Bed Topography model version 2), in which ice thickness is inferred from surface slope by parameterizing basal shear...... stress as a function of elevation range for each glacier. The modelled ice thicknesses are uncertain (±30%), but spatial patterns of ice thickness and bed elevation primarily depend on surface slopes as derived from the DEM and, hence, are more robust. About 16 000 overdeepenings larger than 104m2 were...

  4. Development of fluidized-bed furnace for thermal treatment of ammonium uranyl carbonate

    International Nuclear Information System (INIS)

    At present the ammonium uranyl carbonate (AUC) route is developed at a scale of 10 kg/day of UO2. This UO2 is directly compactible and sinterable to densities of 10.55-10.65 gm/cc. The equipment developed include precipitation tank with filtration and methanol washing and fluidized bed furnaces for thermal treatment of AUC and U3O8. During the design and development of these furnaces many experiments were conducted to study fluidization of AUC powder. In this paper the findings of these studies are presented. (author)

  5. Three phase Eulerian-granular model applied on numerical simulation of non-conventional liquid fuels combustion in a bubbling fluidized bed

    Directory of Open Access Journals (Sweden)

    Nemoda Stevan Đ.

    2016-01-01

    Full Text Available The paper presents a two-dimensional CFD model of liquid fuel combustion in bubbling fluidized bed. The numerical procedure is based on the two-fluid Euler-Euler approach, where the velocity field of the gas and particles are modeled in analogy to the kinetic gas theory. The model is taking into account also the third - liquid phase, as well as its interaction with the solid and gas phase. The proposed numerical model comprise energy equations for all three phases, as well as the transport equations of chemical components with source terms originated from the component conversion. In the frame of the proposed model, user sub-models were developed for heterogenic fluidized bed combustion of liquid fuels, with or without water. The results of the calculation were compared with experiments on a pilot-facility (power up to 100 kW, combusting, among other fuels, oil. The temperature profiles along the combustion chamber were compared for the two basic cases: combustion with or without water. On the basis of numerical experiments, influence of the fluid-dynamic characteristics of the fluidized bed on the combustion efficiency was analyzed, as well as the influence of the fuel characteristics (reactivity, water content on the intensive combustion zone. [Projekat Ministarstva nauke Republike Srbije, br. TR33042: Improvement of the industrial fluidized bed facility, in scope of technology for energy efficient and environmentally feasible combustion of various waste materials in fluidized bed

  6. Ash related bed agglomeration during fluidized bed combustion, further development of the classification method based on CCSEM; CCSEM-luokitusmenetelmaen jatkokehittaeminen tuhkan aiheuttaman agglomeroitumisen tutkimisessa leiju- ja kiertopetipoltossa

    Energy Technology Data Exchange (ETDEWEB)

    Laitinen, R.; Patrikainen, T.; Heikkinen, R.; Tiainen, M.; Virtanen, M. [Oulu Univ. (Finland). Inst. of Chemistry

    1997-10-01

    The scope of this project is to use the information and experience gained from the development of classification method to predict ash related problems like bed agglomeration during fluidised combustion. If boilers have to be shut down due to slagging or agglomeration of the bed material may cause significant economic losses for the entire energy production chain. Mineral classification methods based on the scanning electron microscopy are commonly used for coal ash investigation. In this work different biomass, peat, and peat-wood ash, fluidised-bed materials, and bed agglomerates were analysed with SEM-EDS combined with automatic image analysis software. The properties of ash particles are different depending on the fuel type. If biomass like wood or bark are added to peat the resulting ash has different properties. Due to the low mineral content in the original peat and to the fact that the majority of inorganic material is bound to the organic matrix, the classification has turned out to be less informative than was hoped. However, good results are obtained the by use of quasiternary diagrams. With these diagrams the distribution of particle composition is easily illustrated and thus meaningful prediction can be made of the slagging and agglomerating properties of ash. The content of ten different elements are determined for each particle by SEM-EDS combined with Link AIA software. The composition of the diagram corners can be varied Freely within these ten elements. (orig.)

  7. Transient modelling of sulphur-iodine cycle thermochemical hydrogen generation coupled to pebble bed modular reactor

    International Nuclear Information System (INIS)

    A transient control volume model of the sulphur iodine (S-I) and Westinghouse hybrid sulphur (HyS) cycles is presented. These cycles are some of the leading candidates for hydrogen generation using a high temperature heat source. The control volume models presented here are based on a heat and mass balance in each reaction chamber coupled to the relevant reaction kinetics. The chemical kinetics expressions are extracted from a relevant literature review. Two assumptions regarding reaction chamber pressure are identified, namely a constant pressure condition and a differential form of ideal gas law. The HyS model is based on an application of the Nernst equation. This application of the Nernst equation suggests that in the HyS cycle the hydrogen generation rate is directly proportional to the SO2 production rate. The observed chemical kinetic response time of the sulphuric acid decomposition section is on the order of 30 seconds, whereas the response time of the hydrogen iodide decomposition section is on the order of 500 seconds. It is concluded that the decomposition of hydrogen iodide (HI) is the rate limiting step of the entire S-I cycle. High temperature nuclear reactors are ideal candidates for use as a driving heat source for both the S-I and HyS cycle. The pebble bed modular reactor is a type of very high temperature reactor (VHTR ) suitable for nuclear hydrogen generation. A methodology for coupling of the S-I or HyS cycle to a pebble bed modular reactor (PBMR) via an intermediate heat exchanger (IHX) is developed. A 2-D THERMIX heat transfer model of a PBMR-268 is presented, and this model is coupled to a point kinetics model. The point kinetics model was developed to meet the same specifications as the RELAP5 point kinetics module. A steady-state integration of the S-I and HyS cycle models to the PBMR 268 heat transfer model is performed. The integration assumes that 100% of the heat energy from the PBMR-268 is deposited into the chemical plant via the

  8. Predictive models for hospital bed management using data mining techniques

    OpenAIRE

    Oliveira, Sérgio Manuel Costa; Portela, Filipe; Santos, Manuel Filipe; Machado, José Manuel; Abelha, António

    2014-01-01

    Series : Advances in intelligent systems and computing, vol. 276 It is clear that the failures found in hospital management are usually related to the lack of information and insufficient resources management. The use of Data Mining (DM) can contribute to overcome these limitations in order to identify relevant data on patient’s management and providing important information for managers to support their decisions. Throughout this study, were induced DM models capable to ma...

  9. 3D Geological Modeling of CoalBed Methane (CBM) Resources in the Taldykuduk Block Karaganda Coal Basin, Kazakhstan

    Science.gov (United States)

    Sadykov, Raman; Kiponievich Ogay, Evgeniy; Royer, Jean-Jacques; Zhapbasbayev, Uzak; Panfilova, Irina

    2015-04-01

    Coal Bed Methane (CBM) is gas stored in coal layers. It can be extracted from wells after hydraulic fracturing and/or solvent injection, and secondary recovery techniques such as CO2 injection. Karaganda Basin is a very favorable candidate region to develop CBM production for the following reasons: (i) Huge gas potential; (ii) Available technologies for extracting and commercializing the gas produced by CBM methods; (iii) Experience in degassing during underground mining operations for safety reasons; (iv) Local needs in energy for producing electricity for the industrial and domestic market. The objectives of this work are to model the Taldykuduk block coal layers and their properties focusing on Coal Bed Methane production. It is motivated by the availability of large coal bed methane resources in Karaganda coal basin which includes 4 300 Bm3 equivalent 2 billion tons of coal (B = billion = 109) with gas content 15-25 m3/t of coal (for comparison San Juan basin (USA) has matrix (m) and the fracture (f) for which the initial and boundary conditions are different. The resulting comprehensive 3D models had helped in better understanding the tectonic structures of the region, especially the relationships between the fault systems.

  10. Modeling the methanolysis of triglyceride catalyzed by immobilized lipase in a continuous-flow packed-bed reactor

    International Nuclear Information System (INIS)

    Highlights: • A Burkholderia lipase was immobilized on alkyl-grafted celite carriers. • Celite-alkyl-lipase catalyzed the methanolysis of triglyceride in packed-bed reactor. • The kinetics of the enzymatic transesterification follows Ping Pong Bi Bi mechanism. • Models were developed to discuss the mass transfer and enzyme kinetics in the PBR. - Abstract: A Burkholderia lipase was immobilized on celite grafted with long alkyl groups. The immobilized lipase-catalyzed methanolysis of sunflower oil in a packed-bed reactor (PBR) follows the Ping Pong Bi Bi mechanism. The external mass transfer and enzymatic reaction that simultaneously occurred in the PBR were investigated via the mathematical models. The overall biodiesel production in the PBR was verified to work in an enzymatic reaction-limited regime. Triglyceride conversion and biodiesel yield were higher under a lower reactant feeding rate, while a larger amount of biocatalyst would be required to achieve the designated conversion rate if a higher reactant feeding rate was employed. The PBR can achieve nearly complete conversion of triglyceride at a biocatalyst bed height of 60 cm (ca. 29 g biocatalyst) and a flow rate of 0.1 ml min−1, whereas the biodiesel yield was lower than 67%, probably due to the positional specificity of Burkholderia lipase and the accumulation of glycerol

  11. CFD Model of HDS Catalyst Tests in Trickle-Bed Reactor

    Czech Academy of Sciences Publication Activity Database

    Tukač, V.; Prokešová, A.; Hanika, Jiří; Zbuzek, M.; Kubička, D.

    Prague : Orgit, 2014, s. 85. ISBN 978-80-02-02555-9. [International Congress of Chemical and Process Engineering /21./ - CHISA 2014 and Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction /17./ - PRES 2014. Prague (CZ), 23.08.2014-27.08.2014] Grant ostatní: GA MPO FR-TI3/084 Institutional support: RVO:67985858 Keywords : CFD model solution * reactor bed * catalyst activity tests Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  12. Size exclusion deep bed filtration: Experimental and modelling uncertainties

    International Nuclear Information System (INIS)

    A detailed uncertainty analysis associated with carboxyl-modified latex particle capture in glass bead-formed porous media enabled verification of the two theoretical stochastic models for prediction of particle retention due to size exclusion. At the beginning of this analysis it is established that size exclusion is a dominant particle capture mechanism in the present study: calculated significant repulsive Derjaguin-Landau-Verwey-Overbeek potential between latex particles and glass beads is an indication of their mutual repulsion, thus, fulfilling the necessary condition for size exclusion. Applying linear uncertainty propagation method in the form of truncated Taylor's series expansion, combined standard uncertainties (CSUs) in normalised suspended particle concentrations are calculated using CSUs in experimentally determined parameters such as: an inlet volumetric flowrate of suspension, particle number in suspensions, particle concentrations in inlet and outlet streams, particle and pore throat size distributions. Weathering of glass beads in high alkaline solutions does not appreciably change particle size distribution, and, therefore, is not considered as an additional contributor to the weighted mean particle radius and corresponded weighted mean standard deviation. Weighted mean particle radius and LogNormal mean pore throat radius are characterised by the highest CSUs among all experimental parameters translating to high CSU in the jamming ratio factor (dimensionless particle size). Normalised suspended particle concentrations calculated via two theoretical models are characterised by higher CSUs than those for experimental data. The model accounting the fraction of inaccessible flow as a function of latex particle radius excellently predicts normalised suspended particle concentrations for the whole range of jamming ratios. The presented uncertainty analysis can be also used for comparison of intra- and inter-laboratory particle size exclusion data

  13. Pilot development of polygeneration process of circulating fluidized bed combustion combined with coal pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Qu, X. [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan (China); Graduate School, Chinese Academy of Sciences, Beijing (China); Liang, P. [College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao (China); Wang, Z. [Ningbo Branch of Academy of Ordnace Science, Ningbo (China); Zhang, R.; Sun, D.; Bi, J. [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan (China); Gong, X. [Hengyuan Coal Electrochemical Co., Ltd, Fugu (China); Gan, Z. [State Key Laboratory of Low Carbon Energy, ENN Science and Technology Ltd, Langfang (China)

    2011-01-15

    A pilot polygeneration process of a 75 t h{sup -1} circulating fluidized bed (CFB) boiler combined with a moving bed coal pyrolyzer was developed based on laboratory-scale experimental results. The process operation showed good consistency and integration between boiler and pyrolyzer. Some critical operating parameters such as hot ash split flow from the CFB boiler to the pyrolyzer, mixing of hot ash and coal particles, control of pyrolysis temperature and solid inventory in the pyrolyzer, and pyrolysis gas clean-up were investigated. Yields of 6.0 wt-% tar and 8.0 wt-% gas with a heating value of about 26 MJ m{sup -3} at 600 C were obtained. Particulate content in tar was restrained less than 4.0 wt-% by using a granular filter of the moving bed. Operation results showed that this pilot polygeneration process was successfully scaled up. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Modelling of a circulating fluidized bed using computational fluid dynamic software

    Energy Technology Data Exchange (ETDEWEB)

    Torres, E.C.; Steward, F. [New Brunswick Univ., Centre for Nuclear Research, Fredericton, NB (Canada); Pugsley, T. [New Brunswick Univ., Dept. of Chemical Engineering, Fredericton, NB (Canada)

    1998-09-01

    A computational fluid dynamics (CFD) software called `FLUENT` was used to model the hydrodynamics of the riser of a laboratory scale circulating fluidized bed. A circulating fluidized bed is a type of fluidized bed that operates at high gas velocities. Its two most important applications are for combustion purposes and for fluid catalytic cracking. Results from the simulated cold model were compared with experimental data. Predictions of the model were in good agreement with trends observed experimentally.The two main considerations when applying CFD to the experimental set-up are granular multiphase models and the turbulence conditions for the gas and solid phases. The time dependent model provides outputs that predict the radial and axial distribution of the gas and solids in the riser which correspond to different operating conditions of riser solids mass flux and gas velocity. By introducing more accurate particle flow data at the entrance and at the walls into the boundary conditions the CFD model could be significantly improved.9 refs., 1 tab., 10 figs.

  15. Using autoregressive integrated moving average (ARIMA models to predict and monitor the number of beds occupied during a SARS outbreak in a tertiary hospital in Singapore

    Directory of Open Access Journals (Sweden)

    Earnest Arul

    2005-05-01

    Full Text Available Abstract Background The main objective of this study is to apply autoregressive integrated moving average (ARIMA models to make real-time predictions on the number of beds occupied in Tan Tock Seng Hospital, during the recent SARS outbreak. Methods This is a retrospective study design. Hospital admission and occupancy data for isolation beds was collected from Tan Tock Seng hospital for the period 14th March 2003 to 31st May 2003. The main outcome measure was daily number of isolation beds occupied by SARS patients. Among the covariates considered were daily number of people screened, daily number of people admitted (including observation, suspect and probable cases and days from the most recent significant event discovery. We utilized the following strategy for the analysis. Firstly, we split the outbreak data into two. Data from 14th March to 21st April 2003 was used for model development. We used structural ARIMA models in an attempt to model the number of beds occupied. Estimation is via the maximum likelihood method using the Kalman filter. For the ARIMA model parameters, we considered the simplest parsimonious lowest order model. Results We found that the ARIMA (1,0,3 model was able to describe and predict the number of beds occupied during the SARS outbreak well. The mean absolute percentage error (MAPE for the training set and validation set were 5.7% and 8.6% respectively, which we found was reasonable for use in the hospital setting. Furthermore, the model also provided three-day forecasts of the number of beds required. Total number of admissions and probable cases admitted on the previous day were also found to be independent prognostic factors of bed occupancy. Conclusion ARIMA models provide useful tools for administrators and clinicians in planning for real-time bed capacity during an outbreak of an infectious disease such as SARS. The model could well be used in planning for bed-capacity during outbreaks of other infectious

  16. Anaerobic tapered fluidized bed reactor for starch wastewater treatment and modeling using multilayer perceptron neural network

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Anaerobic treatability of synthetic sago wastewater was investigated in a laboratory anaerobic tapered fluidized bed reactor (ATFBR) with a mesoporous granular activated carbon (GAC) as a support material. The experimental protocol was defined to examine the effect of the maximum organic loading rate (OLR), hydraulic retention time (HRT), the efficiency of the reactor and to report on its steady-state performance. The reactor was subjected to a steady-state operation over a range of OLR up to 85.44 kg COD/(m3·d). The COD removal efficiency was found to be 92% in the reactor while the biogas produced in the digester reached 25.38 m3/(m3·d) of the reactor. With the increase of OLR from 83.7 kg COD/(m3·d), the COD removal efficiency decreases. Also an artificial neural network (ANN) model using multilayer perceptron (MLP) has been developed for a system of two input variable and five output dependent variables. For the training of the input-output data, the experimental values obtained have been used. The output parameters predicted have been found to be much closer to the corresponding experimental ones and the model was validated for 30% of the untrained data. The mean square error (MSE) was found to be only 0.0146.

  17. Experiments and Modeling of the Preparation of Ultrafine Calcium Carbonate in Spouted Beds with Inert Particles

    Institute of Scientific and Technical Information of China (English)

    林诚; 朱涛; 朱跃姿; 张济宇

    2003-01-01

    A novel reaction-drying process was carried out in a spouted bed reactor with inert particles and used to prepare ultrafine CaCO3 particles. Effects of concentrations of CO2 and Ca(OH)2, and reaction temperature on Ca(OH)2 conversion were experimentally investigated. The particle sizes and composition of CaCO3 produced were characterized with transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results indicated that ultrafine CaCO3 particles with mean size of 80 nm could be obtained with this novel process.By modifying the Arrhenius Equation and considering the Ca(OH)2 state, a kinetic model was established to describe the process in the spouted bed. The model parameters estimated from the reaction-drying experiments were found to fit well the experimental data, indicating the applicability of the proposed kinetic model.

  18. Progress in the Development of the Modular Pebble-Bed Advanced High Temperature Reactor

    International Nuclear Information System (INIS)

    This review article summarizes recent progress by students and faculty at U.C. Berkeley working on the development of the Pebble-Bed Advanced High Temperature Reactor (PB-AHTR). The 410-MWe PBAHTR is a liquid salt cooled reactor that operates at near atmospheric pressure and high power density (20 to 30 MW/m3, compared to 4.8 MW/m3 for helium cooled reactors). Operating with a core inlet temperature of 600 deg. C and outlet temperature of 704 deg. C, the PB-AHTR uses well understood materials of construction including Alloy 800H with Hastelloy N cladding for the reactor vessel and primary loop components, and graphite for core and reflector structures. Recent work by the NE 170 senior design class has developed physical arrangements for the major reactor and power conversion components, along with the structural design for the reactor building and turbine hall featuring seismic base isolation, design for aircraft crash protection, shielding analysis, and design of a multiple-zone ventilation and containment system to provide effective control of radioactive and chemical contamination. The resulting total building volume is 260 m3/MWe, compared to 343 m3/MWe to 486 m3/MWe for current large (1150 to 1600 MWe) LWR designs. These results suggest the potential for significant reductions in construction time and cost. Neutronics studies have verified the capability to design the PB-AHTR with negative fuel and coolant temperature reactivity coefficients, for both LEU and deep-burn TRU fuels. Depletion analysis was also performed to identify optimal core designs to maximize fuel utilization. The additional moderation provided by the coolant simplifies design to achieve optimal moderation, and the spent fuel volume is approximately half that of helium cooled reactors. In collaboration with the Czech Nuclear Research Institute, initial zero-power critical tests were performed to validate PB-AHTR neutronics models. Liquid salts are unique among candidate reactor coolants due

  19. Development of a fluidized-bed method for on-line evaluation of radiotracers in vitro

    International Nuclear Information System (INIS)

    This study presents the development of a continuously operating fluidized-bed bioreactor for on-line evaluation of radiotracers in vitro, which combines tissue-like three-dimensional cell cultivation in open porous microcarriers with a technique for on-line radioactivity detection. The long time stability of steady-state permits a large number of experiments using the same culture. All relevant parameters (O2, pH, T, etc.) can be adjusted according to the experimental requirements. The flux of the circulating medium can be adapted to the blood flow of the corresponding organism, while the input function of the radiotracer is freely adjustable for simulation of in vivo conditions. Sampling and examination of the immobilized cells care possible at any time. Using this system, the kinetics of 2-[18F]fluoro-2-deoxyglucose (FDG) in human glioma cells (86HG39) were studied and it was shown that the dependence of the lumped constant (LC) for FDG on the medium glucose concentration is similar to that obtained in the rat brain. For normoglycemic concentrations the LC was determined to be in the range of 0.7, while in hypoglycemia it increased progressively up to a value of 1.22 at a glucose concentration of 3 mM. The rate constants in the three compartment model were found to be similar to those obtained in vivo using PET; indicating the validity of the system for tracer evaluation. Furthermore the kinetics of both diastereomeric forms of 4-[18F]fluoro-proline was investigated and found that both diastereomeres were not metabolized and reached an identical intracellular steady state concentration. The trans-form was transported three times faster than the cis-diastereomere, indicated by the rate constants. (orig.)

  20. Breakdown development in cover beds, and landscape features induced by intrastratal gypsum karst

    Directory of Open Access Journals (Sweden)

    Andrejchuk V.

    1996-01-01

    Full Text Available Intrastratal karst is by far the predominant gypsum karst type. Its development may begin in deep-seated settings within rocks already buried by younger strata, and it proceeds increasingly rapidly as uplift brings gypsum sequences into progressively shallower positions. Such development commonly occurs under confined (artesian hydrogeological conditions, that subsequently change to open conditions (phreatic-water table-vadose. The general evolutionary line of intrastratal karst is typified by progressive emergence of a sequence into a shallower position, activation of groundwater circulation and development of cave systems within karst units, commencement of gravitational breakdown and its upward propagation through overlying beds, and development of a karst landscape. These processes and phenomena progress through the directed evolution of karst types as follows: deep-seated intrastratal karst (1K to subjacent 1K to entrenched 1K to denuded karst. One of the main characteristics of intrastratal karst is that it induces gravitational breakdown in cover beds. With the aid of processes other then simple breakdown, such effects may propagate upwards and may, or may not, reach the surface, depending upon the thickness and structure of the overburden. A karst landscape evolves when such features reach the surface. This paper considers the conditions and mechanisms of such development.

  1. A mass transfer model for the fixed-bed adsorption of ferulic acid onto a polymeric resin: axial dispersion and intraparticle diffusion.

    Science.gov (United States)

    Davila-Guzman, Nancy E; Cerino-Córdova, Felipe J; Soto-Regalado, Eduardo; Loredo-Cancino, Margarita; Loredo-Medrano, José A; García-Reyes, Refugio B

    2016-08-01

    In this study, amberlite XAD-16 (XAD-16) bed column system was used to remove ferulic acid (FA) from aqueous solutions. Laboratory-scale column experiments were conducted in downflow fixed bed at initial FA concentration of 1 g/L, initial pH 3, and 25°C. The performance of the adsorbent bed under different flow rates (1.3-7.7 mL/min) was studied. The bed utilization efficiency was in the range of 64.64-72.21% at the studied flow rates. A mass transfer model considering both axial dispersion and intraparticle diffusion was developed to predict the breakthrough curves of FA adsorption on XAD-16. This model predicted the experimental data better than Bohart-Adams model and Thomas model, based on the low deviation between predicted and experimental data. The axial dispersion coefficient value varied from 6.45 × 10(-6) to 1.10 × 10(-6) m(2)/s at flow rate from 1.3 to 7.7 mL/min, whereas the intraparticle diffusion coefficient was 1.04 × 10(-10) m(2)/s, being this last resistance the rate-limiting step. In conclusion, axial dispersion and intraparticle diffusion phenomena play the major role in predicting the adsorption of FA onto XAD-16 in fixed-bed columns. PMID:26789835

  2. Comparative analysis of CFD models for jetting fluidized beds: Effect of particle-phase viscosity

    Institute of Scientific and Technical Information of China (English)

    Pei Pei; Kai Zhang; Gang Xu; Yongping Yang; Dongsheng Wen

    2012-01-01

    Under the Eulerian-Eulerian framework of simulating gas-solid two-phase flow,the accuracy of the hydrodynamic prediction is strongly affected by the selection of rheology of the particulate phase,for which a detailed assessment is still absent.Using a jetting fluidized bed as an example,this work investigates the influence of solid theology on the hydrodynamic behavior by employing different particle-phase viscosity models.Both constant particle-phase viscosity model (CVM) with different viscosity values and a simple two-fluid model without particle-phase viscosity (NVM) are incorporated into the classical twofluid model and compared with the experimental measurements.Qualitative and quantitative results show that the jet penetration depth,jet frequency and averaged bed pressure drop are not a strong function of the particle-phase viscosity.Compared to CVM,the NVM exhibits better predictions on the jet behaviors,which is more suitable for investigating the hydrodynamics of gas-solid fluidized bed with a central jet.

  3. Development and Validation of a Lifecycle-based Prognostics Architecture with Test Bed Validation

    Energy Technology Data Exchange (ETDEWEB)

    Hines, J. Wesley [Univ. of Tennessee, Knoxville, TN (United States); Upadhyaya, Belle [Univ. of Tennessee, Knoxville, TN (United States); Sharp, Michael [Univ. of Tennessee, Knoxville, TN (United States); Ramuhalli, Pradeep [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jeffries, Brien [Univ. of Tennessee, Knoxville, TN (United States); Nam, Alan [Univ. of Tennessee, Knoxville, TN (United States); Strong, Eric [Univ. of Tennessee, Knoxville, TN (United States); Tong, Matthew [Univ. of Tennessee, Knoxville, TN (United States); Welz, Zachary [Univ. of Tennessee, Knoxville, TN (United States); Barbieri, Federico [Univ. of Tennessee, Knoxville, TN (United States); Langford, Seth [Univ. of Tennessee, Knoxville, TN (United States); Meinweiser, Gregory [Univ. of Tennessee, Knoxville, TN (United States); Weeks, Matthew [Univ. of Tennessee, Knoxville, TN (United States)

    2014-11-06

    On-line monitoring and tracking of nuclear plant system and component degradation is being investigated as a method for improving the safety, reliability, and maintainability of aging nuclear power plants. Accurate prediction of the current degradation state of system components and structures is important for accurate estimates of their remaining useful life (RUL). The correct quantification and propagation of both the measurement uncertainty and model uncertainty is necessary for quantifying the uncertainty of the RUL prediction. This research project developed and validated methods to perform RUL estimation throughout the lifecycle of plant components. Prognostic methods should seamlessly operate from beginning of component life (BOL) to end of component life (EOL). We term this "Lifecycle Prognostics." When a component is put into use, the only information available may be past failure times of similar components used in similar conditions, and the predicted failure distribution can be estimated with reliability methods such as Weibull Analysis (Type I Prognostics). As the component operates, it begins to degrade and consume its available life. This life consumption may be a function of system stresses, and the failure distribution should be updated to account for the system operational stress levels (Type II Prognostics). When degradation becomes apparent, this information can be used to again improve the RUL estimate (Type III Prognostics). This research focused on developing prognostics algorithms for the three types of prognostics, developing uncertainty quantification methods for each of the algorithms, and, most importantly, developing a framework using Bayesian methods to transition between prognostic model types and update failure distribution estimates as new information becomes available. The developed methods were then validated on a range of accelerated degradation test beds. The ultimate goal of prognostics is to provide an accurate assessment for

  4. MODELING MOISTURE DIFFUSIVITY AND ENERGY CONSUMPTION OF CANTALOUPE SEEDS IN FIXED AND FLUIDIZED BED CONDITIONS

    Directory of Open Access Journals (Sweden)

    Reza Amiri Chayjan

    2012-12-01

    Full Text Available   Background.The main goal in cantaloupe seed drying is the reduction of its moisture content to a safe level, allowing storage in a long period of time. Fluidized bed dryer is a drying process with better heat and mass transfer and shorter drying time. This method is a gentle and uniform drying procedure. Fluidized bed is suitable for sensitive and high moisture materials. Drying parameters of moisture diffusivity and energy are vitally important in modelling and optimizing of the seed dryer system. Material and methods. This study investigated thin layer characteristics of cantaloupe seeds under fixed, semi fluidized and fluidized bed drying with initial moisture content about 61.99% (d.b.. A laboratory fluid- ized bed dryer was utilized in this research. Air temperature levels of 45, 55, 65 and 75°C were applied in drying experiments. Effective moisture diffusivity (Deff of cantaloupe seeds was computed by Fick’s second law in diffusion. Activation energy and specific energy consumption of cantaloupe seeds under different drying conditions were calculated. Results.Calculated values of Deff for drying experiments were in the range of 2.23·10-10and 8.61·10-10m2/s. Values of Deff increased as the input air temperature increased. Activation energy values were computed be- tween 39.21 and 37.55 kJ/mol for 45°C to 75°C, respectively. Specific energy consumption for cantaloupe seeds was calculated at the boundary of 1.58·105and 6.18·105kJ/kg. Conclusion.Results indicated that applying the fluidized bed condition is more effective for convective drying of cantaloupe seeds. Increasing air velocity tends to decrease in activation energy. Decreasing in drying air temperature in different bed conditions caused increase in the energy value. The aforesaid drying parameters are necessary to optimize the operational condition of fluidized bed dryer and to perfect design of the system.  

  5. Application of noncatalytic gas-solid reactions for a single pellet of changing size to the modeling of fluidized-bed combustion of coal char containing sulfur

    Energy Technology Data Exchange (ETDEWEB)

    Rehmat, A.; Saxena, S.C.; Land, R.H.

    1980-09-01

    A mechanistic model is developed for coal char combustion, with sulfur retention by limestone or dolomite sorbent, in a gas fluidized bed employing noncatalytic single pellet gas-solid reactions. The shrinking core model is employed to describe the kinetics of chemical reactions taking place on a single pellet; changes in pellet size as the reaction proceeds are considered. The solids are assumed to be in back-mix condition whereas the gas flow is regarded to be in plug flow. Most char combustion occurs near the gas distributor plate (at the bottom of the bed), where the bubbles are small and consequently the mass transfer rate is high. For such a case, the analysis is considerably simplified by ignoring the bubble phase since it plays an insignificant role in the overall rate of carbon conversion. Bubble-free operation is also encounterd in the turbulent regime, where the gas flow is quite high and classical bubbles do not exist. Formulation of the model includes setting up heat and mass balance equations pertaining to a single particle (1) exposed to a varying reactant concentration along the height of the bed and (2) whose size changes during reaction. These equations are then solved numerically to account for particles of all sizes in the bed in obtaining the overall carbon conversion efficiency and resultant sulfur retention. In particular, the influence on sorbent requirement of several fluid-bed variables such as oxygen concentration profile, particle size, reaction rate for sulfation reaction, and suflur adsorption efficiency are examined.

  6. Development of high voltage and high current test bed for transmission line components

    International Nuclear Information System (INIS)

    India is responsible for delivery of 8+1(prototype) RF sources to ITER project. Each RF source will provide 2.5 MW of RF power at VSWR 2:1 in the frequency range of 35 to 65 MHz. Eight such RF sources will generate total 20 MW of RF power. A large number of high power transmission line components are required for connecting various stages of RF source. To test these passive transmission line components at high voltage and current level, similar to the level expected during operation, a test facility is required. A test bed based on the concept of standing wave resonator is being developed at ITER-India RFPS lab, which can be configured and operated for various lengths of the resonator for optimum requirement, for example, it may be quarter wave (λ/4), half wave (λ/2) and three quarter wave (3λ/4). RF power is fed to the resonator through a 12 inch coaxial Tee. Input impedance of the resonator is matched with external RF source (50 ohm) using a tunable matching capacitor, which provides impedance matching for different operating conditions at resonance frequency. Peak voltage and current level of ∼ 32 kV and ∼ 900 A can be achieved inside the resonator during operation with an estimated input power of ∼ 20 kW. The Device Under Test (i.e. transmission line components for testing) needs to be connected in-line during operation. In this paper, detailed design and simulation results are presented for the test bed. A brief description of future development and test plan for the test bed is described. (author)

  7. Modeling of methanol decomposition on Pt/CeO2/ZrO2 catalyst in a packed bed microreactor

    Science.gov (United States)

    Pohar, Andrej; Belavič, Darko; Dolanc, Gregor; Hočevar, Stanko

    2014-06-01

    Methanol decomposition on Pt/CeO2/ZrO2 catalyst is studied inside a packed bed microreactor in the temperature range of 300-380 °C. The microreactor is fabricated using low-temperature co-fired ceramic (LTCC) technology, which is well suited for the production of relatively complex three-dimensional structures. It is packed with 2 wt% Pt-CeO2 catalyst, which is deposited onto ZrO2 spherical particles. A 1D mathematical model, which incorporates diffusion, convection and mass transfer through the boundary layer to the catalyst particles, as well as a 3D computational fluid dynamics model, are developed to describe the methanol decomposition process inside the packed bed. The microreactor exhibits reliable operation and no catalyst deactivation was observed during three months of experimentation. A comparison between the 1D mathematical model and the 3D model, considering the full 3D geometry of the microreactor is made and the differences between the models are identified and evaluated.

  8. Modeling the transition between upper plane bed regime and sheet flow without an active layer formulation. Preliminary results.

    Science.gov (United States)

    Viparelli, E.; Hernandez Moreira, R. R.; Blom, A.

    2015-12-01

    A perusal of the literature on bedload transport revealed that, notwithstanding the large number of studies on bedform morphology performed in the past decades, the upper plane bed regime has not been thoroughly investigated and the distinction between the upper plane bed and sheet flow transport regimes is still poorly defined. Previous experimental work demonstrated that the upper plane bed regime is characterized by long wavelength and small amplitude bedforms that migrate downstream. These bedforms, however, were not observed in experiments on sheet flow transport suggesting that the upper plane bed and the sheet flow are two different regimes. We thus designed and performed experiments in a sediment feed flume in the hydraulic laboratory of the Department of Civil and Environmental Engineering at the University of South Carolina at Columbia to study the transition from upper plane bed to sheet flow regime. Periodic measurements of water surface and bed elevation, bedform geometry and thicknesses of the bedload layer were performed by eyes, and with cameras, movies and a system of six ultrasonic probes that record the variations of bed elevation at a point over time. We used the time series of bed elevations to determine the probability functions of bed elevation. These probability functions are implemented in a continuous model of river morphodynamics, i.e. a model that does not use the active layer approximation to describe the sediment fluxes between the bedload and the deposit and that should thus be able to capture the details of the vertical and streamwise variation of the deposit grain size distribution. This model is validated against the experimental results for the case of uniform material. We then use the validated model in the attempt to study if and how the spatial distribution of grain sizes in the deposit changes from upper plane bed regime to sheet flow and if these results are influenced by the imposed rates of base level rise.

  9. 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)

  10. METHODS FOR MODELING THE PACKING OF FUEL ELEMENTS IN PEBBLE BED REACTORS

    Energy Technology Data Exchange (ETDEWEB)

    Abderrafi M. Ougouag; Joshua J. Cogliati; Jan-Leen Kloosterman

    2005-09-01

    Two methods for the modeling of the packing of pebbles in the pebble bed reactors are presented and compared. The first method is based on random generation of potential centers for the pebbles, followed by rejection of points that are not compatible with the geometric constraint of no (or limited) pebbles overlap. The second method models the actual physical packing process, accounting for the dynamic of pebbles as they are dropped onto the pebble bed and as they settle therein. A simplification in the latter model is the assumption of a starting point with very dilute packing followed by settling. The results from the two models are compared and the properties of the second model and the dependence of its results on many of the modeling parameters are presented. The first model (with no overlap allowed) has been implemented into a code to compute Dancoff factors. The second model will soon be implemented into that same code and will also be used to model flow of pebbles in a reactor and core densification in the simulation of earthquakes. Both methods reproduce experimental values well, with the latter displaying a high level of fidelity.

  11. CFD Modelling of Heat Supply in Fluidized Bed Fast Pyrolysis of Biomass

    OpenAIRE

    Mellin, Pelle; Wu, Yueshi; Kantarelis, Efthymios; Yang, Weihong

    2014-01-01

    This paper investigates the heat supply to the fast pyrolysis process, by addition of oxygen in the fluidizing gas. Since the technology will be further developed, a solution for the heat supply in a large-scale reactor must be conceived, which is one option to achieve the primary target: to operate with as little extra heat as possible. Corrections for the granular bed material and the biomass particles are implemented in the simulation. User Defined Functions (UDF) is extensively used to de...

  12. Generic Investigations on Transport Theory Modelling of High Temperature Reactors of Pebble Bed Type

    OpenAIRE

    Sureda Sureda, Antonio Jaime

    2008-01-01

    The GRS (Gesellschaft fuer Anlagen und Reaktorsicherheit = Company for Plant and Reactor Safety) maintains and further develops the code system DORT-TD/HERMIX-DIREKT, which is a complex tool for the simulation of coupled neutronics/thermal-hydraulics transients and accident scenarios of high-temperature gas cooled reactors of pebble bed type. With this tool, GRS takes part in the international benchmark activity "OECD/NEA PBMR400 Transient Benchmark”, which aims at the simulation of transient...

  13. Modelling of NOx emissions from pressurized fluidized bed combustion - A parameter study

    DEFF Research Database (Denmark)

    Jensen, Anker; Johnsson, Jan Erik

    1997-01-01

    Simulations with a mathematical model of a pressurized bubbling fluidized-bed combustor (PFBC) combined with a kinetic model for NO formation and reduction are reported. The kinetic model for NO formation and reduction considers NO and NH3 as the fixed nitrogen species, and includes homogeneous r...... velocity, the bubble size, the bubble rise velocity and the gas interchange coefficient between bubble and dense phase. The most important combustion parameters are the rates of CO and CH4 combustion and the CO/(CO + CO2) ratio from char combustion. (C) 1997 Elsevier Science Ltd....

  14. Development program on pressurized fluidized-bed combustion. Annual report, July 1975--June 1976

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, G.J.; Johnson, I.; Cunningham, P.T.

    1976-07-01

    The feasibility of using fluidized-bed combustors in power and steam plants is being evaluated. The concept involves burning fuels such as coal in a fluidized bed of either a limestone (CaCO/sub 3/) or a synthetically prepared calcium-containing stone. The calcium reacts with the sulfur to form CaSO/sub 4/, which remains in the bed, thus decreasing the level of SO/sub 2/ in the flue gas. Levels of NO/sub x/ in the flue gas are low. In a separate step, the CaSO/sub 4/ is regenerated to CaO by reductive decomposition at Ca/sub solar/ 1100/sup 0/C for reuse in the combustor. Progress is reported on the following: the effect of regeneration operating variables on extent of regeneration and SO/sub 2/ concentration in the off-gas using coal as the source of reducing agent and of heat; the alternate combustion and regeneration behavior of stone; the rate and extent of sulfation of agents impregnated on Al/sub 2/O/sub 3/; the effect of variables on sorption and release of sulfur for CaO-impregnated stone; attrition resistance of stone; the kinetic and structural changes occurring during half-calcination of dolomite; the CaS-CaSO/sub 4/ regeneration reaction; and the volatility of trace elements when heating coal ash. Procurement and disposal of regenerated stone, minimum fluidization studies, modeling of a gas-solid combustion reaction and of the regeneration process, combustion studies using different sizes of coal and additive and also using lignite are reported.

  15. Modular Pebble-Bed Reactor Project: Laboratory-Directed Research and Development Program FY 2002 Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Petti, David Andrew; Dolan, Thomas James; Miller, Gregory Kent; Moore, Richard Leroy; Terry, William Knox; Ougouag, Abderrafi Mohammed-El-Ami; Oh, Chang H; Gougar, Hans D

    2002-11-01

    This report documents the results of our research in FY-02 on pebble-bed reactor technology under our Laboratory Directed Research and Development (LDRD) project entitled the Modular Pebble-Bed Reactor. The MPBR is an advanced reactor concept that can meet the energy and environmental needs of future generations under DOE’s Generation IV initiative. Our work is focused in three areas: neutronics, core design and fuel cycle; reactor safety and thermal hydraulics; and fuel performance.

  16. DEVELOPMENT OF A SENSOR NETWORK TEST BED FOR ISD MATERIALS AND STRUCUTRAL CONDITION MONITORING

    Energy Technology Data Exchange (ETDEWEB)

    Zeigler, K.; Ferguson, B.; Karapatakis, D.; Herbst, C.; Stripling, C.

    2011-07-06

    The P Reactor at the Savannah River Site is one of the first reactor facilities in the US DOE complex that has been placed in its end state through in situ decommissioning (ISD). The ISD end state consists of a grout-filled concrete civil structure within the concrete frame of the original building. To evaluate the feasibility and utility of remote sensors to provide verification of ISD system conditions and performance characteristics, an ISD Sensor Network Test Bed has been designed and deployed at the Savannah River National Laboratory. The test bed addresses the DOE-EM Technology Need to develop a remote monitoring system to determine and verify ISD system performance. Commercial off-the-shelf sensors have been installed on concrete blocks taken from walls of the P Reactor Building. Deployment of this low-cost structural monitoring system provides hands-on experience with sensor networks. The initial sensor system consists of: (1) Groutable thermistors for temperature and moisture monitoring; (2) Strain gauges for crack growth monitoring; (3) Tiltmeters for settlement monitoring; and (4) A communication system for data collection. Preliminary baseline data and lessons learned from system design and installation and initial field testing will be utilized for future ISD sensor network development and deployment.

  17. Development of the reed bed in Matsalu wetland, Estonia: responses to neotectonic land uplift, sea level changes and human influences

    Directory of Open Access Journals (Sweden)

    Mats Meriste

    2015-05-01

    Full Text Available We studied reed bed development in Matsalu wetland and the Kasari River delta, Estonia, since the late 18th century using historical schemes, topographical maps and aerial photographs. Our aim was to understand the mechanisms controlling reed distribution in Matsalu wetland, the largest coastal wetland of the eastern Baltic Sea occupying an area of about 25 km2. Natural development of the reed bed in Matsalu Bay and the Kasari delta is mainly controlled by shoreline displacement due to post-glacial neotectonic land uplift. The dredging of the Kasari delta in the 1920s–1930s caused a rapid seaward migration of reed bed communities due to the dispersal of fragmented rhizomes on the shallow sea bottom and along the canal banks reaching Matsalu Bay, while the landward parts of the former wetland were occupied by meadow communities. The expansion of the reed bed started in between the 1951s and 1970s and a maximum extent of 27 km2 was gained by the late 1970s at the peak of eutrophication. In the last decades the reed bed development has been influenced by sea level rise and increased intensity of cyclonic activity in the Baltic Sea, which has caused the deterioration of the reed bed that was weakened by eutrophication due to nutrient inflow from agricultural landscapes mainly in the 1960s–1980s.

  18. New developments in measurements technology relevant to the studies of deep geological repositories in bedded salt

    International Nuclear Information System (INIS)

    This report presents new developments in measurement technology relevant to the studies of deep geological repositories for nuclear waste disposal during all phases of development, i.e., site selection, site characterization, construction, operation, and decommission. Emphasis has been placed on geophysics and geotechnics with special attention to those techniques applicable to bedded salt. The techniques are grouped into sections as follows: tectonic environment, state of stress, subsurface structures, fractures, stress changes, deformation, thermal properties, fluid transport properties, and other approaches. Several areas that merit further research and developments are identified. These areas are: in situ thermal measurement techniques, fracture detection and characterization, in situ stress measurements, and creep behavior. The available instrumentations should generally be improved to have better resolution and accuracy, enhanced instrument survivability, and reliability for extended time periods in a hostile environment

  19. New developments in measurements technology relevant to the studies of deep geological repositories in bedded salt

    Energy Technology Data Exchange (ETDEWEB)

    Mao, N.; Ramirez, A.L.

    1980-10-22

    This report presents new developments in measurement technology relevant to the studies of deep geological repositories for nuclear waste disposal during all phases of development, i.e., site selection, site characterization, construction, operation, and decommission. Emphasis has been placed on geophysics and geotechnics with special attention to those techniques applicable to bedded salt. The techniques are grouped into sections as follows: tectonic environment, state of stress, subsurface structures, fractures, stress changes, deformation, thermal properties, fluid transport properties, and other approaches. Several areas that merit further research and developments are identified. These areas are: in situ thermal measurement techniques, fracture detection and characterization, in situ stress measurements, and creep behavior. The available instrumentations should generally be improved to have better resolution and accuracy, enhanced instrument survivability, and reliability for extended time periods in a hostile environment.

  20. Creepy landscapes : river sediment entrainment develops granular flow rheology on creeping bed.

    Science.gov (United States)

    Prancevic, J.; Chatanantavet, P.; Ortiz, C. P.; Houssais, M.; Durian, D. J.; Jerolmack, D. J.

    2015-12-01

    To predict rates of river sediment transport, one must first address the zeroth-order question: when does sediment move? The concept and determination of the critical fluid shear stress remains hazy, as observing particle motion and determining sediment flux becomes increasingly hard in its vicinity. To tackle this problem, we designed a novel annular flume experiment - reproducing an infinite river channel - where the refractive index of particles and the fluid are matched. The fluid is dyed with a fluorescent powder and a green laser sheet illuminates the fluid only, allowing us to observe particle displacements in a vertical plane. Experiments are designed to highlight the basic granular interactions of sediment transport while suppressing the complicating effects of turbulence; accordingly, particles are uniform spheres and Reynolds numbers are of order 1. We have performed sediment transport measurements close to the onset of particle motion, at steady state, and over long enough time to record averaged rheological behavior of particles. We find that particles entrained by a fluid exhibit successively from top to bottom: a suspension regime, a dense granular flow regime, and - instead of a static bed - a creeping regime. Data from experiments at a range of fluid stresses can be collapsed onto one universal rheologic curve that indicates the effective friction is a monotonic function of a dimensionless number called the viscous number. These data are in remarkable agreement with the local rheology model proposed by Boyer et al., which means that dense granular flows, suspensions and bed-load transport are unified under a common frictional flow law. Importantly, we observe slow creeping of the granular bed even in the absence of bed load, at fluid stresses that are below the apparent critical value. This last observation challenges the classical definition of the onset of sediment transport, and points to a continuous transition from quasi-static deformation to

  1. Surviving Bed Rest

    Science.gov (United States)

    ... doctor will give you specific information about the duration of your bed rest. continue How Does Bed ... reading about high-risk pregnancy issues, learn about breastfeeding or how to encourage your child's development instead. ...

  2. Modeling glacier beds in the Austrian Alps: How many lakes will form in future?

    Science.gov (United States)

    Koehler, Dominik; Geilhausen, Martin; Linsbauer, Andreas

    2014-05-01

    Glacial retreat exposes landscapes with relief characteristics greatly differing from the former ice covered surfaces. If glacial retreat exposes natural basins capable of forming proglacial lakes, then the downstream hydrologic and geomorphic systems in such catchments will be significantly altered due to discharge modifications, sediment trapping, decoupling effects and long term sediment storage (e.g. Geilhausen et al. 2013). Further implications are related to hydropower management, tourism and natural hazards. Consequently, sound knowledge of present day glacier beds ("proglacial zones of tomorrow") and in particular the total number, locations and characteristics of overdeepenings are of importance. For Austria, however, this important information about significant future changes of high alpine regions is yet missing. An interdisciplinary research project is currently in preparation to close this gap. This paper presents results of a pilot study. We used a novel GIS-based approach (GlabTop, cf. Linsbauer et al. 2012) to compute approximate glacier beds in the Austrian Alps. GlabTop ('Glacier bed Topography') is based on an empirical relation between average basal shear stress and elevation range of individual glaciers and makes use of digital elevation models (DEM), glacier outlines and branch lines (i.e. a set of lines covering all important glacier branches). DEMs and glacier outlines were derived from the Austrian glacier inventory (1998) and branch lines were manually digitized. The inventory includes 911 glaciers of which 876 (96%) were considered and 35 were excluded due to size restrictions ( 0.01 km²) with the potential of forming proglacial lakes when glacier retreat reveals the bed. The total area and volume of all overdeepenings is approx. 10 km² and 236 Mio m³ respectively and 33 lakes will be larger than 1 km³. A total glacier volume of 16 ± 5 km³ with an average ice thickness of 36 ± 11 m was calculated for 1998. Comparisons with

  3. Mathematical Modelling of Catalytic Fixed-Bed Reactor for Carbon Dioxide Reforming of Methane over Rh/Al2O3 Catalyst

    OpenAIRE

    Nor Aishah Saidina Amin; Istadi Istadi; New Pei Yee

    2010-01-01

    A one-dimensional mathematical model was developed to simulate the performance of catalytic fixed bed reactor for carbon dioxide reforming of methane over Rh/Al2O3 catalyst at atmospheric pressure. The reactions involved in the system are carbon dioxide reforming of methane (CORM) and reverse water gas shift reaction (RWGS). The profiles of CH4 and CO2 conversions, CO and H2 yields, molar flow rate and mole raction of all species as well as reactor temperature along the axial bed...

  4. The development of an integrated multistaged fluid-bed retorting process. Final report, September 1990--August 1994

    Energy Technology Data Exchange (ETDEWEB)

    Carter, S.D.; Taulbee, D.N.; Stehn, J.L.; Vego, A.; Robl, T.L.

    1995-02-01

    This summarizes the development of the KENTORT II retorting process, which includes integral fluidized bed zones for pyrolysis, gasification, and combustion of oil shale. Purpose was to design and test the process at the 50-lb/hr scale. The program included bench- scale studies of coking and cracking reactions of shale oil vapors over processed shale particles to address issues of scaleup associated with solid-recycle retorting. The bench-scale studies showed that higher amounts of carbon coverage reduce the rate of subsequent carbon deposition by shale oil vapors onto processed shale particles; however carbon-covered materials were also active in terms of cracking and coking. Main focus was the 50-lb/hr KENTORT II PDU. Cold-flow modeling and shakedown were done before the PDU was made ready for operation. Seven mass-balanced, steady-state runs were completed within the window of design operating conditions. Goals were achieved: shale feedrate, run duration (10 hr), shale recirculation rates (4:1 to pyrolyzer and 10:1 to combustor), bed temperatures (pyrolyzer 530{degree}C, gasifier 750{degree}C, combustor 830{degree}C), and general operating stability. Highest oil yields (up to 109% of Fischer assay) were achieved for runs lasting {ge} 10 hours. High C content of the solids used for heat transfer to the pyrolysis zone contributed to the enhanced oil yield achieved.

  5. GRID Raster Dataset Model of the LaClede Bed Structure in the Green River and Washakie Basins, southwestern Wyoming

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — An ESRI GRID raster data model of the LaClede bed of the Laney Member of the Eocene Green River Formation structure was needed to perform overburden calculations in...

  6. TIN Model of the LaClede Bed Structure in the Green River and Washakie Basins, southwestern Wyoming

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — An ESRI TIN raster data model of the LaClede bed of the Laney Member of the Eocene Green River Formation structure was needed to perform overburden calculations in...

  7. The emergence of nonuniform spatiotemporal fractionation schemes within the standard BED model

    International Nuclear Information System (INIS)

    Purpose: Nonuniform spatiotemporal radiotherapy fractionation schemes, i.e., delivering distinct dose distributions in different fractions can potentially improve the therapeutic ratio. This is possible if the dose distributions are designed such that similar doses are delivered to normal tissues (exploit the fractionation effect) while hypofractionating subregions of the tumor. In this paper, the authors develop methodology for treatment planning with nonuniform fractions and demonstrate this concept in the context of intensity-modulated proton therapy (IMPT). Methods: Treatment planning is performed by simultaneously optimizing (possibly distinct) IMPT dose distributions for multiple fractions. This is achieved using objective and constraint functions evaluated for the cumulative biologically equivalent dose (BED) delivered at the end of treatment. BED based treatment planning formulations lead to nonconvex optimization problems, such that local gradient based algorithms require adequate starting positions to find good local optima. To that end, the authors develop a combinatorial algorithm to initialize the pencil beam intensities. Results: The concept of nonuniform spatiotemporal fractionation schemes is demonstrated for a spinal metastasis patient treated in two fractions using stereotactic body radiation therapy. The patient is treated with posterior oblique beams with the kidneys being located in the entrance region of the beam. It is shown that a nonuniform fractionation scheme that hypofractionates the central part of the tumor allows for a skin and kidney BED reduction of approximately 10%–20%. Conclusions: Nonuniform spatiotemporal fractionation schemes represent a novel approach to exploit fractionation effects that deserves further exploration for selected disease sites

  8. The emergence of nonuniform spatiotemporal fractionation schemes within the standard BED model

    Energy Technology Data Exchange (ETDEWEB)

    Unkelbach, Jan, E-mail: junkelbach@mgh.harvard.edu; Papp, Dávid [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States)

    2015-05-15

    Purpose: Nonuniform spatiotemporal radiotherapy fractionation schemes, i.e., delivering distinct dose distributions in different fractions can potentially improve the therapeutic ratio. This is possible if the dose distributions are designed such that similar doses are delivered to normal tissues (exploit the fractionation effect) while hypofractionating subregions of the tumor. In this paper, the authors develop methodology for treatment planning with nonuniform fractions and demonstrate this concept in the context of intensity-modulated proton therapy (IMPT). Methods: Treatment planning is performed by simultaneously optimizing (possibly distinct) IMPT dose distributions for multiple fractions. This is achieved using objective and constraint functions evaluated for the cumulative biologically equivalent dose (BED) delivered at the end of treatment. BED based treatment planning formulations lead to nonconvex optimization problems, such that local gradient based algorithms require adequate starting positions to find good local optima. To that end, the authors develop a combinatorial algorithm to initialize the pencil beam intensities. Results: The concept of nonuniform spatiotemporal fractionation schemes is demonstrated for a spinal metastasis patient treated in two fractions using stereotactic body radiation therapy. The patient is treated with posterior oblique beams with the kidneys being located in the entrance region of the beam. It is shown that a nonuniform fractionation scheme that hypofractionates the central part of the tumor allows for a skin and kidney BED reduction of approximately 10%–20%. Conclusions: Nonuniform spatiotemporal fractionation schemes represent a novel approach to exploit fractionation effects that deserves further exploration for selected disease sites.

  9. Pressurized Fluidized Bed Combustion Second-Generation System Research and Development

    Energy Technology Data Exchange (ETDEWEB)

    A. Robertson; D. Horazak; R. Newby; H. Goldstein

    2002-11-01

    Research is being conducted under United States Department of Energy (DOE) Contract DE-AC21-86MC21023 to develop a new type of coal-fired plant for electric power generation. This new type of plant--called a Second-Generation or Advanced Pressurized Circulating Fluidized Bed Combustion (APCFB) plant--offers the promise of efficiencies greater than 45% (HHV), with both emissions and a cost of electricity that are significantly lower than conventional pulverized-coal-fired plants with scrubbers. The APCFB plant incorporates the partial gasification of coal in a carbonizer, the combustion of carbonizer char in a pressurized circulating fluidized bed boiler (PCFB), and the combustion of carbonizer syngas in a topping combustor to achieve gas turbine inlet temperatures of 2300 F and higher. A conceptual design was previously prepared for this new type of plant and an economic analysis presented, all based on the use of a Siemens Westinghouse W501F gas turbine with projected carbonizer, PCFB, and topping combustor performance data. Having tested these components at the pilot plant stage, the referenced conceptual design is being updated to reflect more accurate performance predictions together with the use of the more advanced Siemens Westinghouse W501G gas turbine and a conventional 2400 psig/1050 F/1050 F/2-1/2 in. steam turbine. This report describes the updated plant which is projected to have an HHV efficiency of 48% and identifies work completed for the October 2001 through September 2002 time period.

  10. Modeling the supercritical desorption of orange essential oil from a silica-gel bed

    Directory of Open Access Journals (Sweden)

    Silva E.A.

    2000-01-01

    Full Text Available One of the most important byproducts of the orange juice industry is the oil phase. This is a mixture of terpenes, alcohols, and aldehydes, dissolved in approximately 96% limonene. To satisfactorily use oil phase as an ingredient in the food and cosmetics industries separation of the limonene is required. One possibility is to use a fixed bed of silica gel to remove the light or aroma compounds from the limonene. The aroma substances are then extracted from the bed of silica gel using supercritical carbon dioxide. This work deals with the modeling of the desorption step of the process using mass balance equations coupled with the Langmuir equilibrium isotherm. Data taken from the literature for the overall extraction curves were used together with empirical correlations to calculate the concentration profile of solute in the supercritical phase at the bed outlet. The system of equations was solved by the finite volume technique. The overall extraction curves calculated were in good agreement with the experimental ones.

  11. Mathematical modelling of slow pyrolysis of segregated solid wastes in a packed-bed pyrolyser

    Energy Technology Data Exchange (ETDEWEB)

    Yao Bin Yang; Anh N. Phan; Changkook Ryu; Vida Sharifi; Jim Swithenbank [Sheffield University Waste Incineration Centre (SUWIC), Sheffield (United Kingdom). Department of Chemical and Process Engineering

    2007-01-15

    Waste segregation is being explored as one of the potential effective ways for waste management, where wastes are separated for either recycling or energy recovery. In this paper, three segregated wastes, contaminated waste wood, cardboard and waste textile are pyrolysed in a slow-heating packed-bed reactor for the purpose of solid, liquid and gas recovery. The effect of final temperature was investigated and product yields and compositions were measured. Mathematical modelling was employed to simulate the heat, mass transfer and kinetic processes inside the reactor. Both a parallel reaction model and a function group model were used to predict the product yields as well as their compositions. Char yield of 21-34%, tar 34-46% and gas 23-43% were obtained. It is found that packed-bed pyrolysis produces 30-100% more char compared to standard TGA tests and the local heating rate across the packed-bed reactor differs remarkably from the programmed wall-heating rate and varies greatly in both time and space. Mathematical modelling suggests that wood has higher tar cracking ability than cardboard and textile wastes during pyrolysis, and the effects of mineral contents in the fuel need to be explored. CO{sub 2}, CO, tar and water are the main released species during the major stage of the pyrolysis processes which occurs between 250 and 450{sup o}C, whereas noticeable quantity of hydrogen and light hydrocarbons is observed only at higher temperature levels and at the final stage. 39 refs., 10 figs. 4 tabs.

  12. A mechanistic model linking insect (Hydropsychidae) silk nets to incipient sediment motion in gravel-bedded streams

    Science.gov (United States)

    Albertson, Lindsey K.; Sklar, Leonard S.; Pontau, Patricia; Dow, Michelle; Cardinale, Bradley J.

    2014-09-01

    Plants and animals affect stream morphodynamics across a range of scales, yet including biological traits of organisms in geomorphic process models remains a fundamental challenge. For example, laboratory experiments have shown that silk nets built by caddisfly larvae (Trichoptera: Hydropsychidae) can increase the shear stress required to initiate bed motion by more than a factor of 2. The contributions of specific biological traits are not well understood, however. Here we develop a theoretical model for the effects of insect nets on the threshold of sediment motion, τ*crit, that accounts for the mechanical properties, geometry, and vertical distribution of insect silk, as well as interactions between insect species. To parameterize the model, we measure the tensile strength, diameter, and number of silk threads in nets built by two common species of caddisfly, Arctopsyche californica and Ceratopsyche oslari. We compare model predictions with new measurements of τ*crit in experiments where we varied grain size and caddisfly species composition. The model is consistent with experimental results for single species, which show that the increase in τ*crit above the abiotic control peaks at 40-70% for 10-22 mm sediments and declines with increasing grain size. For the polyculture experiments, however, the model underpredicts the measured increase in τ*crit when two caddisfly species are present in sediments of larger grain sizes. Overall, the model helps explain why the presence of caddisfly silk can substantially increase the forces needed to initiate sediment motion in gravel-bedded streams and also illustrates the challenge of parameterizing the behavior of multiple interacting species in a physical model.

  13. Surface-particle-emulsion heat transfer model between fluidized bed and horizontal immersed tube

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A mathematical model, surface-particle-emulsion heat transfer model, is presented by considering voidage variance in emulsion in the vicinity of an immersed surface. Heat transfer near the surface is treated by dispersed particles touching the surface and through the emulsion when the distance from the surface is greater than the diameter of a particle. A film with an adjustable thickness which separates particles from the surface is not introduced in this model. The coverage ratio of particles on the surface is calculated by a stochastic model of particle packing density on a surface. By comparison of theoretical solutions with experimental data from some references, the mathematical model shows better qualitative and quantitative prediction for local heat transfer coefficients around a horizontal immersed tube in a fluidized bed.

  14. A simple process modelling for a dry-feeding entrained bed coal gasifier

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.; Choi, S.; Paek, M. [Korean Advanced Institute of Science & Technology, Taejon (Republic of Korea). Dept. of Mechanical Engineering

    2011-07-01

    A dry-feeding entrained bed coal gasifier was numerically modelled by simultaneously solving the rate equations for chemical reactions of the solid and gas phases. This model describes simplified physical and chemical processes in the entrained bed coal gasifier. Chemical reaction processes for coal gasification and combustion are considered along with the simplified gas flow passage in the reactor, so that progress of reactions at the designated spatial location is represented. Gasification phenomena of coal particles were separated into devolatilization, gas-phase, and solid-phase reactions. Coal gasifier geometry was simplified to a pseudo-two-dimensional (pseudo-2D) reactor model based on the 1D plug flow concept. The dimension in the pseudo-2D model was conceptually divided by considering the recirculation effect. As a result, carbon conversion, cold gas efficiency, and temperature distribution were obtained at variable oxygen to coal mass ratio, steam to coal mass ratio, and operating pressure. Operating conditions could be appropriately controlled by knowing the degree of reaction in the reactor.

  15. Model of fragmentation of limestone particles during thermal shock and calcination in fluidised beds

    Energy Technology Data Exchange (ETDEWEB)

    Saastamoinen, J.; Pikkarainen, T.; Tourunen, A.; Rasanen, M.; Jantti, T. [VTT Technical Research Center, Jyvaskyla (Finland)

    2008-11-15

    Fragmentation of limestone due to thermal shock and calcination in a fluidised bed was studied through experiments and modelling. The time for heating was estimated by model calculations and the time for calcination by measurements. Fragmentation due to thermal shock was carried out by experiments in a CO{sub 2} atmosphere in order to prevent the effect of calcination. It was found to be much less than fragmentation due to calcination. Average particle sizes before and after fragmentation are presented for several types of limestone. The effects of particle size and gas composition on the primary fragmentation were studied through experiments. Increasing the fluidisation velocity increased the tendency to fragment. The evolution of the particle size distribution (PSD) of limestone particles due to thermal shock and during calcination (or simultaneous calcination and sulphation) were calculated using a population balance model. Fragmentation due to thermal shock is treated as an instantaneous process. The fragmentation frequency during calcination is presented as exponentially decaying over time. In addition to the final PSD, this model also predicts the PSD during the calcination process. The fragmentation was practically found to end after 10 min. Furthermore. a population balance method to calculate the particle size distribution and amount of limestone in fluidised beds in dynamic and steady state, when feeding history is known, is presented.

  16. Development of fluidized bed combustion of biomass; Leijupolttoprosessin kehittaeminen vaikeille biopolttoaineille soveltuvaksi

    Energy Technology Data Exchange (ETDEWEB)

    Hiltunen, M.; Vaehaenen-Koivuluoma, T. [Foster Wheeler Energia Oy, Karhula (Finland)

    1997-10-01

    Some commercial BFB boilers burning biofuels, or biofuels and industrial wood wastes have suffered serious problems in bed material sintering. In worst cases the cumulation of reactive alkali compounds has caused total sintering of bed material even during a few days` operation. This presentation reports the results obtained from three separate cases, where sintering problems occurred. Boiler A burned biofuel with quartz sand and limestone addition. Boiler B burned softwood bark and industrial wood waste with sand addition. Boiler C burned softwood bark and sludge with sand addition. Due to the fuel used, bed sintering occurred in all boilers. Obviously, sintering was also influenced by some technical problems. Bed material samples have been analyzed with XRF and SEM-EDS techniques. According to these analyses, the main reason for sintering in boiler A is the cumulation of reactive potassium in bed material. In boiler B, the main reason is the fuel change from a mixture of softwood bark and industrial wood waste to pure industrial wood waste. The extra load of reactive sodium exceeded the critical concentration of alkali compounds in bed material. Also in boiler C, the fuel change from a mixture of softwood bark and sludge to pure softwood bark seems to be one of the reasons for bed sintering. After the fuel change the bed saturated with reactive potassium and the bed sintered. (orig.)

  17. Development Of A Mobile Robot As A Test Bed For Tele-Presentation

    Directory of Open Access Journals (Sweden)

    Diogenes Armando D. Pascua

    2016-01-01

    Full Text Available In this paper a human-sized tracked wheel robot with a large payload capacity for tele-presentation is presented. The robot is equipped with different sensors for obstacle avoidance and localization. A high definition web camera installed atop a pan and tilt assembly was in place as a remote environment feedback for users. An LCD monitor provides the visual display of the operator in the remote environment using the standard Skype teleconferencing software. Remote control was done via the internet through the free Teamviewer VNC remote desktop software. Moreover, this paper presents the design details, fabrication and evaluation of individual components. Core mobile robot movement and navigational controls were developed and tested. The effectiveness of the mobile robot as a test bed for tele-presentation were evaluated and analyzed by way of its real time response and time delay effects of the network.

  18. CLC in packed beds using syngas and CuO/Al2O3: Model description and experimental validation

    International Nuclear Information System (INIS)

    Highlights: • CLC with CuO/Al2O3 and syngas and air has been demonstrated experimentally. • Model predicts accurately only if kinetics describe the complete solid reduction. • CuO/Al2O3 is proven to catalyze the reversed water gas shift reaction. • H2O is more effective to suppress carbon deposition on CuO/Al2O3 than CO2. • The OC reaction rate is not permanently affected by exposure to H2S. - Abstract: The objective of this work is to study the performance of the oxygen carrier in a packed bed with periodic switching between oxidizing and reducing conditions. In this paper the performance of CuO/Al2O3 as the oxygen carrier in a packed bed reactor with syngas as the fuel are investigated, while also studying the (possible) carbon deposition and the effect of sulphur impurities on the stability of the carrier. Both experiments and simulations are used in this work. Cyclic experiments (oxidation with air and reduction with syngas) have been carried out in a lab scale packed bed reactor with 13 wt% CuO/Al2O3. The experimental results were well described by a 1D reactor model, provided that critical attention was given to the reaction rate for the complete reduction reaction, including a dramatic decrease in reaction rate at high solid conversions. Feeding syngas (pH2 = pCO = 0.1 bar) resulted in 1.1% carbon deposition of the feed. Steam was proven to be more effective in reducing carbon deposition than CO2. Moreover, it has been found that CuO/Al2O3 catalyzed the water gas shift reaction and the reaction rate was not permanently affected by exposure to H2S, two key factors for CLC operation. The results of this work imply that CuO/Al2O3 is an effective oxygen carrier as the first packed bed reactor in a TSCLC process and that the developed model is able to describe the performance at larger scales accurately

  19. Modeling of sorption enhanced steam methane reforming in an adiabatic fixed bed reactor

    OpenAIRE

    Fernández García, José Ramón; Abanades García, Juan Carlos; Murillo Villuendas, Ramón

    2012-01-01

    Sorption enhanced methane reforming (SER), employing a CaO-based solid as a high temperature CO2 sorbent, is generally considered to be a promising route for H2 production. In this paper we present a dynamic pseudo-homogeneous model to describe the operation of a packed bed reactor in which the SER reaction is carried out under adiabatic conditions. This reactor can be implemented according to several process schemes, including a novel Ca/Cu looping process for hydrogen generation with inhere...

  20. Improving fuel quality by whole crude oil hydrotreating: A kinetic model for hydrodeasphaltenization in a trickle bed reactor

    International Nuclear Information System (INIS)

    Highlights: ► Asphaltene contaminant must be removed to a large extent from the fuel to meet the regulatory demand. ► Kinetics for hydrodeasphaltenization are estimated via experimentation and modeling. ► Using the kinetic parameters, a full process model for the trickle bed reactor (TBR) is developed. ► The model is used for simulating the behavior of the TBR to get further insight of the process. ► The influences of operating conditions in the hydrodeasphaltenization process are reported. -- Abstract: Fossil fuel is still a predominant source of the global energy requirement. Hydrotreating of whole crude oil has the ability to increase the productivity of middle distillate fractions and improve the fuel quality by simultaneously reducing contaminants such as sulfur, nitrogen, vanadium, nickel and asphaltene to the levels required by the regulatory bodies. Hydrotreating is usually carried out in a trickle bed reactor (TBR) where hydrodesulfurization (HDS), hydrodenitrogenation (HDN), hydrodemetallization (HDM) and hydrodeasphaltenization (HDAs) reactions take place simultaneously. To develop a detailed and a validated TBR process model which can be used for design and optimization of the hydrotreating process, it is essential to develop kinetic models for each of these reactions. Most recently, the authors have developed kinetic models for all of these chemical reactions except that of HDAs. In this work, a kinetic model (in terms of kinetic parameters) for the HDAs reaction in the TBR is developed. A three phase TBR process model incorporating the HDAs reactions with unknown kinetic parameters is developed. Also, a series of experiments has been conducted in an isothermal TBR under different operating conditions affecting the removal of asphaltene. The unknown kinetic parameters are then obtained by applying a parameter estimation technique based on minimization of the sum of square errors (SSEs) between the experimental and predicted concentrations of

  1. Modified graphical autocatalytic set model of combustion process in circulating fluidized bed boiler

    Science.gov (United States)

    Yusof, Nurul Syazwani; Bakar, Sumarni Abu; Ismail, Razidah

    2014-07-01

    Circulating Fluidized Bed Boiler (CFB) is a device for generating steam by burning fossil fuels in a furnace operating under a special hydrodynamic condition. Autocatalytic Set has provided a graphical model of chemical reactions that occurred during combustion process in CFB. Eight important chemical substances known as species were represented as nodes and catalytic relationships between nodes are represented by the edges in the graph. In this paper, the model is extended and modified by considering other relevant chemical reactions that also exist during the process. Catalytic relationship among the species in the model is discussed. The result reveals that the modified model is able to gives more explanation of the relationship among the species during the process at initial time t.

  2. 3D numerical model of the spherical particle saltation in a channel with a rough fixed bed

    Czech Academy of Sciences Publication Activity Database

    Lukerchenko, Nikolay; Piatsevich, Siarhei; Chára, Zdeněk; Vlasák, Pavel

    2009-01-01

    Roč. 57, č. 2 (2009), s. 100-112. ISSN 0042-790X R&D Projects: GA ČR GA103/06/1487 Institutional research plan: CEZ:AV0Z20600510 Keywords : 3D Saltation Model * Bed-Load Transport * Particle-Bed Collision * Particle Rotation * Particle Lateral Dispersion Subject RIV: BK - Fluid Dynamics Impact factor: 1.000, year: 2009

  3. Experimental and modeling study of sulfur dioxide oxidation in packed-bed tubular reactor

    Directory of Open Access Journals (Sweden)

    Hanen NOURI

    2013-08-01

    Full Text Available The conversion of sulfur dioxide into sulfur trioxide is a reaction which interests not only the industry of sulfuric acid production but also the processes of pollution control of certain gas effluents containing SO2. This exothermic reaction needs a very good control of temperature, that's why it is led in the industry in a multistage converter with intermediate heat exchangers. Microreactors represent a good alternative for such reaction due to their intensification of mass and heat transfer and enhancement of temperature control. In this study, this reaction was conducted in a stainless steel tubular (4mm ID packed bed reactor using particles of vanadium pentoxide as catalyst at atmospheric pressure. Experiments were performed with different inlet SO2 concentration in 3-9% range and reaction temperature between 685-833K. We noticed that the conversion decreases with the amount of SO2 and increases with the temperature until an optimum, above this value the conversion drop according to the shape of the equilibrium curve. Controlling rate mechanism is studied by varying temperature. Pseudohomogeneous perfect plug flow is used to describe this small tubular reactor. Numerical simulations with MATLAB were performed to validate the experimental results. Good agreement between the model predictions and the experimental results is achieved. Fluid flow description inside the packed bed reactor was performed by using the free fluid and porous media flow model. This model was solved by the commercial software COMSOL Multiphysics. Velocity profile inside the reactor is theoretically obtained.

  4. Soil-plant system development 9 to 136 years after marly gully beds rehabilitation (French Southern Alps)

    Science.gov (United States)

    Erktan, Amandine; Cohen, Marianne; Zerouali, Laila; Poulenard, Jérôme; Cécillon, Lauric; Rey, Freddy

    2013-04-01

    gully beds restored in 2002 (8.3±4 mg.kg-1; ANOVA test, ptrap fine sediment, thus increasing sand content. In parallel, we observed that plant cover and litter accumulation in gully beds were highest in gully beds rehabilitated 136 years ago (ANOVA test, p<0.001), contrary to plant richness which did not show any significant change in gully beds rehabilitated 9 or 136 years ago (around 4 species.m-2). This suggests that plant establishment occurs in the first decade after bed stabilization while the spread of the cover requires more time. We conclude that within the first ten years after gully beds rehabilitation, a real soil-plant system has already developed with early signs of pedogenesis, which could be somehow nutrient limited.

  5. Physiological Observations and Omics to Develop Personalized Sensormotor Adaptability Countermeasures Using Bed Rest and Space Flight Data

    Science.gov (United States)

    Mulavara, A. P.; Seidler, R. D.; Feiveson, A.; Oddsson, L.; Zanello, S.; Oman, C. M.; Ploutz-Snyder, L.; Peters, B.; Cohen, H. S.; Reschke, M.; Wood, S.; Bloomberg, J. J.

    2014-01-01

    Astronauts experience sensorimotor disturbances during the initial exposure to microgravity and during the re-adapation phase following a return to an earth-gravitational environment. These alterations may disrupt the ability to perform mission critical functional tasks requiring ambulation, manual control and gaze stability. Interestingly, astronauts who return from space flight show substantial differences in their abilities to readapt to a gravitational environment. The ability to predict the manner and degree to which individual astronauts would be affected would improve the effectiveness of countermeasure training programs designed to enhance sensorimotor adaptability. For such an approach to succeed, we must develop predictive measures of sensorimotor adaptability that will allow us to foresee, before actual space flight, which crewmembers are likely to experience the greatest challenges to their adaptive capacities. The goals of this project are to identify and characterize this set of predictive measures that include: 1) behavioral tests to assess sensory bias and adaptability quantified using both strategic and plastic-adaptive responses; 2) imaging to determine individual brain morphological and functional features using structural magnetic resonance imaging (MRI), diffusion tensor imaging, resting state functional connectivity MRI, and sensorimotor adaptation task-related functional brain activation; 3) genotype markers for genetic polymorphisms in Catechol-O-Methyl Transferase, Dopamine Receptor D2, Brain-derived neurotrophic factor and genetic polymorphism of alpha2-adrenergic receptor that play a role in the neural pathways underlying sensorimotor adaptation. We anticipate these predictive measures will be significantly correlated with individual differences in sensorimotor adaptability after long-duration space flight and an analog bed rest environment. We will be conducting a retrospective study leveraging data already collected from relevant

  6. Development of a thermal–hydraulic analysis code for the Pebble Bed Water-cooled Reactor

    International Nuclear Information System (INIS)

    Highlights: ► Main design features of the PBWR were put forward. ► Thermal–hydraullics analysis code for the PBWR was developed and verified. ► Key thermal–hydraullics parameters were calculated in normal operation. ► The PBWR has a great pressure loss but an excellent heat transfer characteristic. ► Maximum fuel temperature and MDNBR are in conformity with safety criterion. - Abstract: The Pebble Bed Water-cooled Reactor (PBWR) is a water-moderated water-cooled pebble bed reactor in which millions of tristructural-isotropic (TRISO) coated micro-fuel elements (MFE) pile in each assembly. Light water is used as coolant that flows from bottom to top in the assembly while the moderator water flows in the reverse direction out of the assembly. Steady-state thermal–hydraullic analysis code for the PBWR will provide a set of thermal hydraulic parameters of the primary loop so that heat transported out of the core can match with the heat generated by the core for a safe operation of the reactor. The key parameters of the core including the void fraction, pressure drop, heat transfer coefficients, the temperature distribution and the Departure from Nucleate Boiling Ratio (DNBR) is calculated for the core in normal operation. The code can calculate for liquid region, water-steam two phase region and superheated steam region. The results show that the maximum fuel temperature is much lower than the design limitation and the flow distribution can meet the cooling requirement in the reactor core. As a new type of nuclear reactor, the main design features with a sufficient safety margin were also put forward in this paper.

  7. One-dimensional modeling of radial heat removal during depressurized heatup transients in modular pebble-bed and prismatic high temperature gas-cooled reactors

    International Nuclear Information System (INIS)

    A one-dimensional computational model was developed to evaluate the heat removal capabilities of both prismatic-core and pebble-bed modular HTGRs during depressurized heatup transients. A correlation was incorporated to calculate the temperature- and neutron-fluence-dependent thermal conductivity of graphite. The modified Zehner-Schluender model was used to determine the effective thermal conductivity of a pebble bed, accounting for both conduction and radiation. Studies were performed for prismatic-core and pebble-bed modular HTGRs, and the results were compared to analyses performed by GA and GR, respectively. For the particular modular reactor design studied, the prismatic HTGR peak temperature was 2152.20C at 38 hours following the transient initiation, and the pebble-bed peak temperature was 1647.80C at 26 hours. These results compared favorably with those of GA and GE, with only slight differences caused by neglecting axial heat transfer in a one-dimensional radial model. This study found that the magnitude of the initial power density had a greater effect on the temperature excursion than did the initial temperature

  8. Kinetic modelling of tyre pyrolysis in a conical spouted bed reactor

    Energy Technology Data Exchange (ETDEWEB)

    Olazar, Martin; Lopez, Gartzen; Arabiourrutia, Miriam; Elordi, Gorka; Aguado, Roberto; Bilbao, Javier [University of the Basque Country, Faculty of Science and Technology, Department of Chemical Engineering, P.O. Box 644, E48080 Bilbao (Spain)

    2008-01-15

    A novel kinetic model has been proposed for the thermal pyrolysis of tyres. The model is based on a reaction scheme that considers an intermediate lump and parallel reactions for the formation of the different product lumps. Seven lumps have been taken, which are gas (C{sub 4}), non-aromatic liquid (C{sub 5}-C), aromatics (C), tar (C{sub 11+}), char (low grade carbon black), intermediate and the original tyre. The kinetic data have been obtained in a pilot plant provided with a conical spouted bed reactor. The inert gas used is nitrogen and the temperature has been varied from 425 to 610 C. Discontinuous runs have been carried out for obtaining the kinetic data, and the product stream has been analysed on-line at different reaction times, thereby monitoring the evolution with time of mass fraction of the different components. The kinetic model gives reasonable predictions for lump yields. (author)

  9. An extended version of the countercurrent backmixing model suitable for solid mixing in two-dimensional fluidised beds

    Energy Technology Data Exchange (ETDEWEB)

    Abanades, J.C.; Grasa, G. [CSIC, Inst. Carboquimica, Zaragoza (Spain). Dept. of Energy & Environment

    2001-10-08

    A new mathematical model to describe axial and lateral mixing in fluidised beds is presented. The model is an extension of previous versions of the countercurrent backmixing model (CCBM) that were restricted to axial mixing only. The fluidised bed is divided into parallel 'mixing columns', which are convective currents induced by the bubbles. Each mixing column has a central upflowing stream of solids and two adjacent moving downwards. The practical application of the model requires a minimum knowledge of the bubble properties and the definition of one empirical parameter: the exchange coefficient between countercurrent phases, K. The model can be rapidly solved with the proposed algorithm and reproduces semi-quantitatively the main features observed in mixing experiments carried out in a bidimensional fluidised bed of coal and PVC as tracer.

  10. Three dimensional model for particle saltation close to stream beds, including a detailed description of the particle interaction with turbulence and inter-particle collisions

    KAUST Repository

    Moreno, Pablo M.

    2011-05-19

    We present in this paper a new three-dimensional (3-D) model for bed-load sediment transport, based on a Lagrangian description. We analyze generalized sub-models for the velocities after collision and the representation of the bed-roughness. The free-flight sub-model includes the effect of several forces, such as buoyancy, drag, virtual mass, lift, Basset and Magnus, and also addresses the particle rotation. A recent methodology for saving computational time in the Basset force is also employed. The sub-models for the post-collision velocity and rotation are based on the conservation of linear and angular momentum during the collision with the bed. We develop a new 3-D representation for the bed roughness by using geometric considerations. In order to address the interaction of particles with the turbulent flow, we tracked the particles through a computed turbulent velocity field for a smooth flat plate. This velocity field was used as a surrogate of the 3-D turbulent conditions close to the bed in streams. We first checked that the basic turbulence statistics for this velocity field could be used to approximate those in an open-channel flow. We then analyzed the interaction of the sediment and the turbulence for a single and multiple particles. We compared numerical results with experimental data obtained by Niño and García (1998b). We show that model predictions are in good agreement with existing data, in the sand size range. © 2011 ASCE.

  11. Neural networks for the generation of sea bed models using airborne lidar bathymetry data

    Directory of Open Access Journals (Sweden)

    Kogut Tomasz

    2016-06-01

    Full Text Available Various sectors of the economy such as transport and renewable energy have shown great interest in sea bed models. The required measurements are usually carried out by ship-based echo sounding, but this method is quite expensive. A relatively new alternative is data obtained by airborne lidar bathymetry. This study investigates the accuracy of these data, which was obtained in the context of the project ‘Investigation on the use of airborne laser bathymetry in hydrographic surveying’. A comparison to multi-beam echo sounding data shows only small differences in the depths values of the data sets. The IHO requirements of the total horizontal and vertical uncertainty for laser data are met. The second goal of this paper is to compare three spatial interpolation methods, namely Inverse Distance Weighting (IDW, Delaunay Triangulation (TIN, and supervised Artificial Neural Networks (ANN, for the generation of sea bed models. The focus of our investigation is on the amount of required sampling points. This is analyzed by manually reducing the data sets. We found that the three techniques have a similar performance almost independently of the amount of sampling data in our test area. However, ANN are more stable when using a very small subset of points.

  12. Modeling and simulation of an activated carbon–CO2 four bed based adsorption cooling system

    International Nuclear Information System (INIS)

    Highlights: • A transient mathematical model of a 4-bed adsorption chiller is proposed. • The performances of the cyclic-steady-state system are presented for different heating and cooling water inlet temperatures. • The desorption pressure has a big influence in the performances. • With 80 kg of Maxsorb III, the CO2 based adsorption chiller produces 2 kW of cooling power and presents a COP of 0.1. - Abstract: In this study, a transient mathematical model of a 4-bed adsorption chiller using Maxsorb III as the adsorbent and CO2 as the refrigerant has been analyzed. The performances of the cyclic-steady-state system are presented for different heating and cooling water inlet temperatures. It is found that the desorption pressure has a big influence in the performances due to the low critical point of CO2 (Tc = 31 °C). With 80 kg of Maxsorb III, the CO2 based adsorption chiller produces 2 kW of cooling power and presents a COP of 0.1, at driving heat source temperature of 95 °C along with a cooling temperature of 27 °C and at optimum desorption pressure of 79 bar. The present thermal compression air-conditioning system could be driven with solar energy or waste heat from internal combustion engines and therefore is suitable for both residential and mobile air-conditioning applications

  13. Neural networks for the generation of sea bed models using airborne lidar bathymetry data

    Science.gov (United States)

    Kogut, Tomasz; Niemeyer, Joachim; Bujakiewicz, Aleksandra

    2016-06-01

    Various sectors of the economy such as transport and renewable energy have shown great interest in sea bed models. The required measurements are usually carried out by ship-based echo sounding, but this method is quite expensive. A relatively new alternative is data obtained by airborne lidar bathymetry. This study investigates the accuracy of these data, which was obtained in the context of the project `Investigation on the use of airborne laser bathymetry in hydrographic surveying'. A comparison to multi-beam echo sounding data shows only small differences in the depths values of the data sets. The IHO requirements of the total horizontal and vertical uncertainty for laser data are met. The second goal of this paper is to compare three spatial interpolation methods, namely Inverse Distance Weighting (IDW), Delaunay Triangulation (TIN), and supervised Artificial Neural Networks (ANN), for the generation of sea bed models. The focus of our investigation is on the amount of required sampling points. This is analyzed by manually reducing the data sets. We found that the three techniques have a similar performance almost independently of the amount of sampling data in our test area. However, ANN are more stable when using a very small subset of points.

  14. Development of a 3D multigroup program for Dancoff factor calculation in pebble bed reactors

    International Nuclear Information System (INIS)

    Highlights: • Development of a 3D Monte Carlo based code for pebble bed reactors. • Dancoff sensitivity to clad, moderator and fuel cross sections is considered. • Sensitivity of Dancoff to number of energy groups is considered. • Sensitivity of Dancoff to number of fuel and their arrangement is considered. • Excellent agreements vs. MCNP code. - Abstract: The evaluation of multigroup constants in reactor calculations depends on several parameters. One of these parameters is the Dancoff factor which is used for calculating the resonance integral and flux depression in the resonance region in heterogeneous systems. In the current paper, a computer program (MCDAN-3D) is developed for calculating three dimensional black and gray Dancoff coefficients, based on Monte Carlo, escape probability and neutron free flight methods. The developed program is capable to calculate the Dancoff factor for an arbitrary arrangement of fuel and moderator pebbles. Moreover this program can simulate fuels with homogeneous and heterogeneous compositions. It might generate the position of Triso particles in fuel pebbles randomly as well. It could calculate the black and gray Dancoff coefficients since fuel region might have different cross sections. Finally, the effects of clad and moderator are considered and the sensitivity of Dancoff factor with fuels arrangement variation, number of TRISO particles and neutron energy has been studied

  15. Development of a moving bed pilot plant for thermochemical energy storage with CaO/Ca(OH)2

    Science.gov (United States)

    Schmidt, Matthias; Gollsch, Marie; Giger, Franz; Grün, Manfred; Linder, Marc

    2016-05-01

    Thermochemical energy storage, for instance with Ca(OH)2, offers high energy densities at low material costs and could therefore be a promising storage alternative for CSP-plants. Yet, due to the low thermal conductivity of the Ca(OH)2 material large storage capacities operated in an indirectly heated fixed bed also require large heat exchangers. In other words the fixed bed concept somehow opposes one of the main advantages of Ca(OH)2, its low material costs. One approach to overcome this issue is to detach the costly reactor with the heat exchanger (power) from the storage material (capacity). This can be accomplished by a moving bed concept where the material moves through the reactor. Therefore a novel moving bed pilot plant was developed within the consortium of the European project TCS Power. The pilot plant was set into operation and revealed important information about the material flow through the reactor and the operation strategy of a moving bed concept.

  16. Characteristics modeling for supercritical circulating fluidized bed boiler working in oxy-combustion technology

    Science.gov (United States)

    Balicki, Adrian; Bartela, Łukasz

    2014-06-01

    Among the technologies which allow to reduce greenhouse gas emission, mainly carbon dioxide, special attention deserves the idea of `zeroemission' technology based on boilers working in oxy-combustion technology. In the paper the results of analyses of the influence of changing two quantities, namely oxygen share in oxidant produced in the air separation unit, and oxygen share in oxidant supplied to the furnace chamber on the selected characteristics of a steam boiler including the degree of exhaust gas recirculation, boiler efficiency and adiabatic flame temperature, was examined. Due to the possibility of the integration of boiler model with carbon dioxide capture, separation and storage installation, the subject of the analysis was also to determine composition of the flue gas at the outlet of a moisture condensation installation. Required calculations were made using a model of a supercritical circulating fluidized bed boiler working in oxy-combustion technology, which was built in a commercial software and in-house codes.

  17. Power law persistence in the atmosphere An ideal test bed for climate models

    CERN Document Server

    Bunde, A; Govindan, R B; Havlin, S; Koscielny-Bunde, E; Rybski, D; Vjushin, D; Bunde, Armin; Eichner, Jan; Govindan, Rathinaswamy; Havlin, Shlomo; Koscielny-Bunde, Eva; Rybski, Diego; Vjushin, Dmitry

    2002-01-01

    We review recent results on the appearance of long-term persistence in climatic records and how they can be used to evaluate climate models. The persistence can be characterized, for example, by the correlation C(s) of temperature variations separated by s days. We show that, contrary to previous expectations, C(s) decays for large s as a power law, C(s) ~ s^(-gamma). For continental stations, the exponent gamma is always close to 0.7, while for stations on islands gamma ~ 0.4. In contrast to the temperature fluctuations, the fluctuations of the rainfall usually cannot be characterized by long term power law correlations but rather by pronounced short term correlations. The universal persistence law for the temperature fluctuations on continental stations represents an ideal (and uncomfortable) test bed for the state of the art global climate models and allows to evaluate their performance.

  18. Development and application of a process window for achieving high-quality coating in a fluidized bed coating process

    NARCIS (Netherlands)

    Laksmana, F.L.; Hartman Kok, P.J.A.; Vromans, H.; Frijlink, H.W.; Van Der Voort Maarschalk, K.

    2009-01-01

    Next to the coating formulation, process conditions play important roles in determining coating quality. This study aims to develop an operational window that separates layering from agglomeration regimes and, furthermore, the one that leads to the best coating quality in a fluidized bed coater. The

  19. Review of the Technical Status on the Debris Bed Cooling Model

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eui Kwang; Cho, Chung Ho; Lee, Yong Bum

    2007-09-15

    Preliminary safety analyses of the KALIMER-600 design have shown that the design has inherent safety characteristics and is capable of accommodating double-fault initiators such as ATWS events without coolant boiling or fuel melting. However, for the future design of sodium cooled fast reactor, the evaluation of the safety performance and the determination of containment requirements may be worth due consideration of triple-fault accident sequences of extremely low probability of occurrence that leads to core melting. For any postulated accident sequence which leads to core melting, in-vessel retention of the core debris will be required as a design requirement for the future design of sodium cooled fast reactor. Also, proof of the capacity of the debris bed cooling is an essential condition to solve the problem of in-vessel retention of the core debris. In this study, review of the technical status on the debris bed cooling model was carried out for in-vessel retention of the core debris0.

  20. Stochastic-deterministic modeling of bed load transport in shallow water flow over erodible slope: Linear stability analysis and numerical simulation

    Science.gov (United States)

    Bohorquez, Patricio; Ancey, Christophe

    2015-09-01

    In this article we propose a stochastic bed load transport formulation within the framework of the frictional shallow-water equations in which the sediment transport rate results from the difference between the entrainment and deposition of particles. First we show that the Saint-Venant-Exner equations are linearly unstable in most cases for a uniform base flow down an inclined erodible bed for Shields numbers in excess of the threshold for incipient sediment motion allowing us to compute noise-induced pattern formation for Froude numbers below 2. The wavelength of the bed forms are selected naturally due to the absolute character of the bed instability and the existence of a maximum growth rate at a finite wavelength when the particle diffusivity coefficient and the water eddy viscosity are present as for Turing-like instability. A numerical method is subsequently developed to analyze the performance of the model and theoretical results through three examples: the simulation of the fluctuations of the particle concentration using a stochastic Langevin equation, the deterministic simulation of anti-dunes formation over an erodible slope in full sediment-mobility conditions, and the computation of noise-induced pattern formation in hybrid stochastic-deterministic flows down a periodic flume. The full non-linear numerical simulations are in excellent agreement with the theoretical solutions. We conclude highlighting that the proposed depth-averaged formulation explains the developments of upstream migrating anti-dunes in straight flumes since the seminar experiments by Gilbert (1914).

  1. Pebble bed modular reactor safeguards: developing new approaches and implementing safeguards by design

    Energy Technology Data Exchange (ETDEWEB)

    Beyer, Brian David [Los Alamos National Laboratory; Beddingfield, David H [Los Alamos National Laboratory; Durst, Philip [INL; Bean, Robert [INL

    2010-01-01

    The design of the Pebble Bed Modular Reactor (PBMR) does not fit or seem appropriate to the IAEA safeguards approach under the categories of light water reactor (LWR), on-load refueled reactor (OLR, i.e. CANDU), or Other (prismatic HTGR) because the fuel is in a bulk form, rather than discrete items. Because the nuclear fuel is a collection of nuclear material inserted in tennis-ball sized spheres containing structural and moderating material and a PBMR core will contain a bulk load on the order of 500,000 spheres, it could be classified as a 'Bulk-Fuel Reactor.' Hence, the IAEA should develop unique safeguards criteria. In a multi-lab DOE study, it was found that an optimized blend of: (i) developing techniques to verify the plutonium content in spent fuel pebbles, (ii) improving burn-up computer codes for PBMR spent fuel to provide better understanding of the core and spent fuel makeup, and (iii) utilizing bulk verification techniques for PBMR spent fuel storage bins should be combined with the historic IAEA and South African approaches of containment and surveillance to verify and maintain continuity of knowledge of PBMR fuel. For all of these techniques to work the design of the reactor will need to accommodate safeguards and material accountancy measures to a far greater extent than has thus far been the case. The implementation of Safeguards-by-Design as the PBMR design progresses provides an approach to meets these safeguards and accountancy needs.

  2. Exploring a semimechanistic episodic Langevin model for bed load transport: Emergence of normal and anomalous advection and diffusion regimes

    Science.gov (United States)

    Fan, Niannian; Singh, Arvind; Guala, Michele; Foufoula-Georgiou, Efi; Wu, Baosheng

    2016-04-01

    Bed load transport is a highly stochastic, multiscale process, where particle advection and diffusion regimes are governed by the dynamics of each sediment grain during its motion and resting states. Having a quantitative understanding of the macroscale behavior emerging from the microscale interactions is important for proper model selection in the absence of individual grain-scale observations. Here we develop a semimechanistic sediment transport model based on individual particle dynamics, which incorporates the episodic movement (steps separated by rests) of sediment particles and study their macroscale behavior. By incorporating different types of probability distribution functions (PDFs) of particle resting times Tr, under the assumption of thin-tailed PDF of particle velocities, we study the emergent behavior of particle advection and diffusion regimes across a wide range of spatial and temporal scales. For exponential PDFs of resting times Tr, we observe normal advection and diffusion at long time scales. For a power-law PDF of resting times (i.e., f>(Tr>)˜Tr-ν), the tail thickness parameter ν is observed to affect the advection regimes (both sub and normal advective), and the diffusion regimes (both subdiffusive and superdiffusive). By comparing our semimechanistic model with two random walk models in the literature, we further suggest that in order to reproduce accurately the emerging diffusive regimes, the resting time model has to be coupled with a particle motion model able to produce finite particle velocities during steps, as the episodic model discussed here.

  3. NUMERICAL SOLUTION OF STEADY STATE DISPERSION FLOW MODEL FOR LACTOSE-LACTASE HYDROLYSIS WITH DIFFERENT KINETICS IN FIXED BED

    Directory of Open Access Journals (Sweden)

    OLAOSEBIKAN ABIDOYE OLAFADEHAN

    2010-06-01

    Full Text Available A detailed computational procedure for evaluating lactose hydrolysis with immobilized enzyme in a packed bed tubular reactor under dispersion flow conditions is presented. The dispersion flow model for lactose hydrolysis using different kinetics, taking cognizance of external mass transfer resistances, was solved by the method of orthogonal collocation. The reliability of model simulations was tested using experimental data from a laboratory packed bed column, where the -galactosidase of Kluyveromyces fragilis was immobilized on spherical chitosan beads. Comparison of the simulated results with experimental exit conversion shows that the dispersion flow model and using Michaelis-Menten kinetics with competitive product (galactose inhibition are appropriate to interpret the experimental results and simulate the process of lactose hydrolysis in a fixed bed.

  4. Model Behavior and Sensitivity in an Application of the Cohesive Bed Component of the Community Sediment Transport Modeling System for the York River Estuary, VA, USA

    Directory of Open Access Journals (Sweden)

    Kelsey A. Fall

    2014-05-01

    Full Text Available The Community Sediment Transport Modeling System (CSTMS cohesive bed sub-model that accounts for erosion, deposition, consolidation, and swelling was implemented in a three-dimensional domain to represent the York River estuary, Virginia. The objectives of this paper are to (1 describe the application of the three-dimensional hydrodynamic York Cohesive Bed Model, (2 compare calculations to observations, and (3 investigate sensitivities of the cohesive bed sub-model to user-defined parameters. Model results for summer 2007 showed good agreement with tidal-phase averaged estimates of sediment concentration, bed stress, and current velocity derived from Acoustic Doppler Velocimeter (ADV field measurements. An important step in implementing the cohesive bed model was specification of both the initial and equilibrium critical shear stress profiles, in addition to choosing other parameters like the consolidation and swelling timescales. This model promises to be a useful tool for investigating the fundamental controls on bed erodibility and settling velocity in the York River, a classical muddy estuary, provided that appropriate data exists to inform the choice of model parameters.

  5. Invasive species and coal bed methane development in the Powder River Basin, Wyoming

    Science.gov (United States)

    Bergquist, E.; Evangelista, P.; Stohlgren, T.J.; Alley, N.

    2007-01-01

    One of the fastest growing areas of natural gas production is coal bed methane (CBM) due to the large monetary returns and increased demand for energy from consumers. The Powder River Basin, Wyoming is one of the most rapidly expanding areas of CBM development with projections of the establishment of up to 50,000 wells. CBM disturbances may make the native ecosystem more susceptible to invasion by non-native species, but there are few studies that have been conducted on the environmental impacts of this type of resource extraction. To evaluate the potential effects of CBM development on native plant species distribution and patterns of non-native plant invasion, 36 modified Forest Inventory and Analysis plots (each comprised of four 168-m2 subplots) were established in the Powder River Basin, Wyoming. There were 73 168-m2 subplots on control sites; 42 subplots on secondary disturbances; 14 on major surface disturbances; eight on well pads; and seven on sites downslope of CBM wells water discharge points. Native plant species cover ranged from 39.5 ?? 2.7% (mean ?? 1 SE) in the secondary disturbance subplots to 17.7 ?? 7.5% in the pad subplots. Non-native plant species cover ranged from 31.0 ?? 8.4% in the discharge areas to 14.7 ?? 8.9% in the pad subplots. The control subplots had significantly less non-native species richness than the combined disturbance types. The combined disturbance subplots had significantly greater soil salinity than the control sites. These results suggest that CBM development and associated disturbances may facilitate the establishment of non-native plants. Future research and management decisions should consider the accumulative landscape-scale effects of CBM development on preserving native plant diversity. ?? Springer Science+Business Media B.V. 2006.

  6. Numerical modelling of the formation of fibrous bedding-parallel veins

    Science.gov (United States)

    Torremans, Koen; Muchez, Philippe; Sintubin, Manuel

    2014-05-01

    Bedding-parallel veins with a fibrous infill oriented orthogonal to the vein wall, are often observed in fine-grained metasedimentary sequences. Several mechanisms have been proposed for their formation, mostly with respect to effects of fluid overpressures and anisotropy of the host-rock fabric in order to explain the inferred extensional failure with sub-vertical opening. Abundant pre-folding, bedding-parallel fibrous dolomite veins are found associated with the Nkana-Mindola stratiform Cu-Co deposit in Zambia. The goal of this study is to better understand the formation mechanisms of these veins and to explain their particular spatial and thickness distribution, with respect to failure of transversely isotropic rocks. The spatial distribution and thickness variation of these veins was quantified during a field campaign in thirteen line transects perpendicular to undeformed veins in underground crosscuts. The fibrous dolomite veins studied are not related to lithological contrasts, but to a strong bedding-parallel shaly fabric, typical for the black shale facies of the Copperbelt Orebody Member. The host rock can hence be considered as transversely isotropic. Growth morphologies vary from antitaxial with a pronounced median surface to asymmetric syntaxial, always with small but quantifiable growth competition. A microstructural fabric study reveals that the undeformed dolomite veins show low-tortuosity vein walls and quantifiable growth competition. Here, we use a Discrete Element Method numerical modelling approach with ESyS-Particle (http://launchpad.net/esys-particle) to simulate the observed properties of the veins. Calibrated numerical specimens with a transversely isotropic matrix are repeatedly brought to failure under constant strain rates by changing the effective strain rates at model boundaries. After each fracture event, fractures in the numerical model are filled with cohesive vein material and the experiment is repeated. By systematically varying

  7. The Development of Ni/Dolomite Catalyst in Simultaneous Biomass Gasification and Reforming in Fluidized Bed

    Directory of Open Access Journals (Sweden)

    Anawat Ketcong

    2009-01-01

    Full Text Available Simultaneous gasification and steam reforming of the biomass on Ni/dolomite catalyst in fluidized bed reactor were studied in the gaseous production in the one stage reactor. Problem statement: The parameters such as temperature, steam flow rate, biomass feed rate, gas flow rate for fluidization, oxygen flow rate and catalyst types were studied to produce the high gaseous products including tar elimination. Approach: The temperature at 780°C, steam flow rate of 222 mmoL h-1, gas flow rate for fluidization 450 mL min-1 and oxygen input 50 mL min-1 were found to be the suitable conditions. The Ni/Dolomite and the developed Ni/Dolomite were studied about their performance. Results: It was confirmed that Ni/Dolomite and newly developed Ni-WO3/Dolomite show high performance in biomass gasification. Conclusion/Recommendations: It was claimed that Ni/Dolomite catalyst was the effective and give best performance for tar cracking. Newly developed Ni-WO3/Dolomite catalyst was investigated to resist sulfur nd coking. Three types of catalyst were used in the biomass gasification, which are Ni/Dolomite, Ni/Dolomite+Silica binder and Ni-WO3/Dolomite. From the XRD analysis, structures of type 1 (Ni/dolomite and type 2 (Ni/Dolomite+Silica binder were similar which were in CaCO3, MgNiO2, NiO and MgO forms. Type 3 (Ni-WO3/Dolomite was CaWO4, MgNiO2, NiO and MgO forms. When the catalytic gasification was operated, newly Ni- WO3/Dolomite catalyst was the best catalyst for bamboo and palm shell biomasses, which could produce the high carbon monoxide and hydrogen but low methane and carbon dioxide were found. Carbon deposition on catalyst was around 0.37 mg according to the TG analysis.

  8. Particle pressures in fluidized beds. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, C.S.; Rahman, K.; Jin, C.

    1996-09-01

    This project studies the particle pressure, which may be thought of as the force exerted by the particulate phase of a multiphase mixture, independently of that exerted by other phases. The project is divided into two parts, one concerning gas and the other liquid fluidized beds. Previous work on gas fluidized beds had suggested that the particle pressures are generated by bubbling action. Thus, for these gas fluidized bed studies, the particle pressure is measured around single bubbles generated in 2-D fluidized beds, using special probes developed especially for this purpose. Liquid beds are immune from bubbling and the particle pressures proved too small to measure directly. However, the major interest in particle pressures in liquid beds lies in their stabilizing effect that arises from the effective elasticity (the derivative of the particle pressure with respect to the void fraction), they impart to the bed. So rather than directly measure the particle pressure, the authors inferred the values of the elasticity from measurements of instability growth in liquid beds; the inference was made by first developing a generic stability model (one with all the normally modeled coefficients left undetermined) and then working backwards to determine the unknown coefficients, including the elasticity.

  9. Particle Pressures in Fluidized Beds. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, C.S.; Rahman, K.; Jin, C.

    1996-09-01

    This project studies the particle pressure, which may be thought of as the force exerted by the particulate phase of a multiphase mixture, independently of that exerted by other phases. The project is divided into two parts, one concerning gas and the other liquid fluidized beds. Previous work on gas fluidized beds had suggested that the particle pressures are generated by bubbling action. Thus, for these gas fluidized bed studies, the particle pressure is measured around single bubbles generated in 2-D fluidized beds, using special probes developed especially for this purpose. Liquid beds are immune from bubbling and the particle pressures proved too small to measure directly. However, the major interest in particle pressures in liquid beds lies in their stabilizing effect that arises from the effective elasticity (the derivative of the particle pressure with respect to the void fraction): they impart to the bed. So rather than directly measure the particle pressure, we inferred the values of the elasticity from measurements of instability growth in liquid beds the inference was made by first developing a generic stability model (one with all the normally modeled coefficients left undetermined)and then working backwards to determine the unknown coefficients, including the elasticity.

  10. Discrete element modeling and fibre optical measurements for fluidized bed spray granulation

    OpenAIRE

    Link, J. M.; Godlieb, W.; Deen, N. G.; Heinrich, S.; Tripp, P.; M. Peglow; Kuipers, J.A.M.; Schönherr, M.; Mörl, L.

    2006-01-01

    Spout fluidized beds are frequently used for the production of granules or particles through granulation. The products find application in a large variety of applications, for example detergents, fertilizers, pharmaceuticals and food. Spout fluidized beds have a number of advantageous properties, such as a high mobility of the particles, which prevents undesired agglomeration and yields excellent heat transfer properties. The particle growth mechanism in a spout fluidized bed as function of p...

  11. Bed slope effects on turbulent wave boundary layers: 1. Model validation and quantification of rough-turbulent results

    DEFF Research Database (Denmark)

    Fuhrman, David R.; Fredsøe, Jørgen; Sumer, B. Mutlu

    2009-01-01

    streaming is conceptually explained using analogies from steady converging and diffuser flows. A parametric study is undertaken to assess both the peak and time-averaged bed shear stresses in converging and diverging half periods under rough-turbulent conditions. The results are presented as friction factor......A numerical model solving incompressible Reynolds-averaged Navier-Stokes equations, combined with a two-equation k-omega turbulence closure, is used to study converging-diverging effects from a sloping bed on turbulent (oscillatory) wave boundary layers. Bed shear stresses from the numerical model...... diagrams. A local similarity condition is derived for relating oscillatory flow in a convergent-divergent tunnel, as considered herein, to shoaling shallow-water waves by matching spatial gradients in the free stream orbital length....

  12. Modeling of fixed-bed column studies for the adsorption of cadmium onto novel polymer-clay composite adsorbent

    International Nuclear Information System (INIS)

    Kaolinite clay was treated with polyvinyl alcohol to produce a novel water-stable composite called polymer-clay composite adsorbent. The modified adsorbent was found to have a maximum adsorption capacity of 20,400 ± 13 mg/L (1236 mg/g) and a maximum adsorption rate constant of ∼7.45 x 10-3 ± 0.0002 L/(min mg) at 50% breakthrough. Increase in bed height increased both the breakpoint and exhaustion point of the polymer-clay composite adsorbent. The time for the movement of the Mass Transfer Zone (δ) down the column was found to increase with increasing bed height. The presence of preadsorbed electrolyte and regeneration were found to reduce this time. Increased initial Cd2+ concentration, presence of preadsorbed electrolyte, and regeneration of polymer-clay composite adsorbent reduced the volume of effluent treated. Premodification of polymer-clay composite adsorbent with Ca- and Na-electrolytes reduced the rate of adsorption of Cd2+ onto polymer-clay composite and lowered the breakthrough time of the adsorbent. Regeneration and re-adsorption studies on the polymer-clay composite adsorbent presented a decrease in the bed volume treated at both the breakpoint and exhaustion points of the regenerated bed. Experimental data were observed to show stronger fits to the Bed Depth Service Time (BDST) model than the Thomas model.

  13. Dynamic Modeling and Control Studies of a Two-Stage Bubbling Fluidized Bed Adsorber-Reactor for Solid-Sorbent CO{sub 2} Capture

    Energy Technology Data Exchange (ETDEWEB)

    Modekurti, Srinivasarao; Bhattacharyya, Debangsu; Zitney, Stephen E.

    2013-07-31

    A one-dimensional, non-isothermal, pressure-driven dynamic model has been developed for a two-stage bubbling fluidized bed (BFB) adsorber-reactor for solid-sorbent carbon dioxide (CO{sub 2}) capture using Aspen Custom Modeler® (ACM). The BFB model for the flow of gas through a continuous phase of downward moving solids considers three regions: emulsion, bubble, and cloud-wake. Both the upper and lower reactor stages are of overflow-type configuration, i.e., the solids leave from the top of each stage. In addition, dynamic models have been developed for the downcomer that transfers solids between the stages and the exit hopper that removes solids from the bottom of the bed. The models of all auxiliary equipment such as valves and gas distributor have been integrated with the main model of the two-stage adsorber reactor. Using the developed dynamic model, the transient responses of various process variables such as CO{sub 2} capture rate and flue gas outlet temperatures have been studied by simulating typical disturbances such as change in the temperature, flowrate, and composition of the incoming flue gas from pulverized coal-fired power plants. In control studies, the performance of a proportional-integral-derivative (PID) controller, feedback-augmented feedforward controller, and linear model predictive controller (LMPC) are evaluated for maintaining the overall CO{sub 2} capture rate at a desired level in the face of typical disturbances.

  14. Mathematical Modelling of Catalytic Fixed-Bed Reactor for Carbon Dioxide Reforming of Methane over Rh/Al2O3 Catalyst

    Directory of Open Access Journals (Sweden)

    Nor Aishah Saidina Amin

    2010-10-01

    Full Text Available A one-dimensional mathematical model was developed to simulate the performance of catalytic fixed bed reactor for carbon dioxide reforming of methane over Rh/Al2O3 catalyst at atmospheric pressure. The reactions involved in the system are carbon dioxide reforming of methane (CORM and reverse water gas shift reaction (RWGS. The profiles of CH4 and CO2 conversions, CO and H2 yields, molar flow rate and mole raction of all species as well as reactor temperature along the axial bed of catalyst were simulated. In addition, the effects of different reactor temperature on the reactor performance were also studied. The models can also be applied to analyze the performances of lab-scale micro reactor as well as pilot-plant scale reactor with certain modifications and model verification with experimental data. © 2008 BCREC UNDIP. All rights reserved.[Received: 20 August 2008; Accepted: 25 September 2008][How to Cite: N.A.S. Amin, I. Istadi, N.P. Yee. (2008. Mathematical Modelling of Catalytic Fixed-Bed Reactor for Carbon Dioxide Reforming of Methane over Rh/Al2O3 Catalyst. Bulletin of Chemical Reaction Engineering and Catalysis, 3 (1-3: 21-29.  doi:10.9767/bcrec.3.1-3.7120.21-29][How to Link/DOI: http://dx.doi.org/10.9767/bcrec.3.1-3.7120.21-29 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/7120

  15. Modeling cesium ion exchange on fixed-bed columns of crystalline silicotitanate granules

    International Nuclear Information System (INIS)

    A mathematical model is presented to simulate Cs exchange in fixed-bed columns of a novel crystalline silicotitanate (CST) material, UOP IONSIV IE-911. A local equilibrium is assumed between the macropores and the solid crystals for the particle material balance. Axial dispersed flow and film mass-transfer resistance are incorporated into the column model. Cs equilibrium isotherms and diffusion coefficients were measured experimentally, and dispersion and film mass-transfer coefficients were estimated from correlations. Cs exchange column experiments were conducted in 5--5.7 M Na solutions and simulated using the proposed model. Best-fit diffusion coefficients from column simulations were compared with previously reported batch values of Gu et al. and Huckman. Cs diffusion coefficients for the column were between 2.5 and 5.0 x 10-11 m2/s for 5--5.7 M Na solutions. The effect of the isotherm shape on the Cs diffusion coefficient was investigated. The proposed model provides good fits to experimental data and may be utilized in designing commercial-scale units

  16. Modeling of convective drying kinetics of Pistachio kernels in a fixed bed drying system

    Directory of Open Access Journals (Sweden)

    Balbay Asım

    2013-01-01

    Full Text Available Drying kinetics of Pistachio kernels (PKs with initial moisture content of 32.4% (w.b was investigated as a function of drying conditions in a fixed bed drying system. The drying experiments were carried out at different temperatures of drying air (40, 60 and 80°C and air velocities (0.05, 0.075 and 0.1 m/s. Several experiments were performed in terms of mass of PKs (15g and 30g using a constant air velocity of 0.075 m/s. The fit quality of models was evaluated using the determination coefficient (R2, sum square error (SSE and root mean square error (RMSE. Among the selected models, the Midilli et al model was found to be the best models for describing the drying behavior of PKs. The activation energies were calculated as 29.2 kJ/mol and effective diffusivity values were calculated between 1.38 and 4.94x10-10 m2/s depending on air temperatures.

  17. Performance of fluidized bed steam gasification of biomass - Modeling and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Loha, Chanchal; Chatterjee, Pradip K. [Thermal Engineering Group, Central Mechanical Engineering Research Institute, CSIR, Durgapur 713 209 (India); Chattopadhyay, Himadri [Dept. of Mechanical Engineering, Jadavpur University, Kolkata 700 032 (India)

    2011-03-15

    This paper presents the investigation of the performance from different biomasses in a fluidized bed gasifier where steam has been used as gasifying as well as fluidizing agent. An experimental setup is fabricated to study the gasification performance of rice husk, which is of special relevance to rice-producing countries like China and India. An equilibrium modeling approach is deployed to predict the gas composition which has been compared with the experimental results. Calibration of the model with appropriate modeling coefficients was necessary to achieve close resemblance with the experimental values. Further, the model is used to predict the gas compositions from other biomass and benchmarked with the performance of coal. In this study, the gasification temperature is varied from 650 C to 800 C, whereas the steam-to-biomass ratio (S/B) is varied from 0.75 to 2.00. As the gasification temperature increases, the production of H{sub 2} and CO increases but the generation of CH{sub 4} and CO{sub 2} reduces. The steam-to-biomass ratio was again found to influence the production rates. With increasing steam input, H{sub 2}, CO{sub 2} and CH{sub 4} were found to increase while CO reduces. (author)

  18. A study on evaluation of pebble flow velocity with modification of the kinematic model for pebble bed reactor

    International Nuclear Information System (INIS)

    Highlights: ► A modified kinematic method is proposed for analysis of pebble flow velocity. ► Experiments are performed to derive the coefficients and to verify the results. ► The method and result can be used for the advanced analysis of pebble bed reactor. - Abstract: A pebble bed reactor is filled by a large number of pebbles, which are randomly piled up in the core region. During the process of fuel loading and extraction, the pebbles flow downward through the core. The basic physics of the dense granular flow such as pebble flow is not fully understood; hence, the dynamic core of the pebble bed reactor has been a subject of concern among designers and regulators. The kinematic model is one of the representative models for the reconstruction of the granular flow velocity, however, it is noted that there are some limitations in the reconstruction ability. In this study, a modified kinematic model was proposed to enhance the reconstruction ability of the pebble velocity profile. Pebble flow experiments were performed to derive the coefficients needed for the modified kinematic model and to verify the reconstruction ability and the applicability of the proposed method in the annular core. The modified kinematic model can contribute to accurate velocity evaluation as well as large applicability for the specific core types such as an annular core. Also, the results can be used for reference data in the design of a pebble bed reactor

  19. Development of Bed Ridges in Open Channels and their Effects on Secondary Currents and Wall Shear

    Directory of Open Access Journals (Sweden)

    Kamran Ansari

    2012-07-01

    Full Text Available A numerical analysis of the ridges on the bed of wide, open channels and their effects on the distribution of secondary currents and wall shear is undertaken using CFD (Computational Fluid Dynamics. The presence of the lines of boil, consisting of low speed streaks, periodically in the transverse direction, is reported in the literature due to the presence of the ridges. In the present work, simulations are run on channel sections with varying the number of ridges on the bed and the size of these ridges. The effect of these variations on the flow structures and shear stress distribution in wide open channels is reported. The results offer an interesting insight into the 3D (Three-Dimensional flow structures involved and the link between flow structures and bed morpho-dynamics in prismatic channels.

  20. Design modeling of fuel particles for high-burnup in pebble-bed fast reactors

    International Nuclear Information System (INIS)

    The thermomechanical and neutron lifetime of different fuel particle designs is assessed by applying a new performance modeling platform comprised of an analytical stress code and finite element engineering hydrocode. Our investigation is based on fuel for fast reactors with the goal of high-burnup to provide minimal waste disposal. Fuel designs are considered based on variations of the standard Modular Pebble-Bed Reactor (MPBR) design in which the spherical fuel kernel contained by a three-layer coating system comprised of inner Pyrolytic Carbon (IPyC), Silicon Carbide (SiC), and outer PyC (OPyC). The neutronics calculations used in our investigation are based on a new fusion-fission engine concept called LIFE (Laser Inertial Confinement Fusion-Fission Energy). Particle stresses are calculated accounting for the interplay between mechanisms such as irradiation-induced swelling and creep, thermal expansion, anisotropic elastic effects, and layer a sphericity. In addition, mechanisms such as corrosion and void coalescence are considered in order to avoid failure of the particles by way of layer cracking and leakage of the fission products, or other pathways. Our design investigation involves a parametric study of layer materials with respect to their thermal conductivity, irradiation resistance, constitutive and other properties and layer thickness to develop a fuel particle design with optimized resistance to failure mechanisms for the desired operating conditions. A key component of the modeling platform is the capability to examine the time and space evolution of all mechanisms affecting performance which are often neglected for the conditions at low burn-up levels. Specifically, temperature variation as a function of depth into the layers generates stresses and also affects the amount of swelling, particularly at high fluence. Moreover, irradiation temperature cycling has been identified as a source of additional time-varying stresses that can lead to cracking

  1. Numerical model of spherical particle saltation in a channel with a transversely tilted rough bed

    Czech Academy of Sciences Publication Activity Database

    Lukerchenko, Nikolay; Piatsevich, Siarhei; Chára, Zdeněk; Vlasák, Pavel

    2009-01-01

    Roč. 57, č. 3 (2009), s. 182-190. ISSN 0042-790X R&D Projects: GA ČR GA103/06/1487 Institutional research plan: CEZ:AV0Z20600510 Keywords : saltation * transversely tilted bed * particle-bed collision * particle sorting Subject RIV: BK - Fluid Dynamics Impact factor: 1.000, year: 2009

  2. Modelling of a fluidized bed carbonator reactor to capture CO{sub 2} from a combustion flue gas

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, M.; Rodriguez, N.; Grasa, G.; Abanades, J.C. [CSIC, Oviedo (Spain)

    2009-03-15

    In recent years several processes incorporating a carbonation-calcination loop in an interconnected fluidized bed reactor have been proposed as a way to capture CO{sub 2} from flue gases. This paper is a first approximation to the modelling of a fluidized bed carbonator reactor. In this reactor the flue gas comes into contact with an active bed composed of particles with very different activities, depending on their residence time in the bed and in the carbonation-calcination loop. The model combines the residence time distribution functions with existing knowledge about sorbent deactivation rates and sorbent reactivity. The fluid dynamics of the solids (CSTR) and gases (PF) in the carbonator are based on simple assumptions. The carbonation rates are modelled defining a characteristic time for the transition between a fast reaction regime to a regime with a zero reaction rate. On the basis of these assumptions the model is able to predict the CO{sub 2} capture efficiency for the flue gas depending on the operating and design conditions. Operating windows with high capture efficiencies are discussed, as well as those conditions where only modest capture efficiencies are possible.

  3. The diffusion model of fractal heat and mass transfer in fluidized bed a local fractional arbitrary Euler-Lagrange formula

    Directory of Open Access Journals (Sweden)

    Cheng Xu

    2015-01-01

    Full Text Available In this manuscript, the local fractional arbitrary Euler-Lagrange formula are utilized to address the diffusion model of fractal heat and mass transfer in a fluidized bed based on the Fick's law with local fractional vector calculus. This article has been corrected. Link to the correction 10.2298/TSCI150923149E

  4. The diffusion model of fractal heat and mass transfer in fluidized bed a local fractional arbitrary Euler-Lagrange formula

    OpenAIRE

    Cheng Xu; Wang Lin

    2015-01-01

    In this manuscript, the local fractional arbitrary Euler-Lagrange formula are utilized to address the diffusion model of fractal heat and mass transfer in a fluidized bed based on the Fick's law with local fractional vector calculus. This article has been corrected. Link to the correction 10.2298/TSCI150923149E

  5. Rise time of inverted triangular prism intruder in vibrating granular bed: Experiments and model

    Science.gov (United States)

    Nuraini, N.; Adriani, I. K.; Baladram, M. S.; Viridi, S.

    2012-05-01

    Experiment results and a qualitative model of the phenomenon called Brazil nut effect (BNE) with inverted triangular prism are reported in this work. The model is constructed by considering some forces (earth gravitational force, buoyant force, and fluid viscous force) and using Newton's second law of motion. The rise time of BNE T is defined as time needed for the intruder to be on granular surface with all of his parts (no part is still immersed in the granular bed). One side of the triangular base of the intruder l is varied from 1.5 to 5 cm with other two sides are kept in constant values (1 and 3 cm). It has been observed in experiment that l with value 3-4 cm gives the smaller rise time. Plot of T versus l has the form of concave up parabolic curve with minimum lies at l between 3-4 cm. This observation has been confirmed by the proposed model with the same order of magnitude and similar curve trend.

  6. Recent Developments in the Design, Capabilities and Autonomous Operations of a Lightweight Surface Manipulation System and Test-bed

    Science.gov (United States)

    Dorsey, John T.; Jones, Thomas C.; Doggett, W. R.; Brady, Jeffrey S.; Berry, Felecia C.; Ganoe, George G.; Anderson, Eric; King, Bruce D.; Mercer, David C.

    2011-01-01

    The first generation of a versatile high performance device for performing payload handling and assembly operations on planetary surfaces, the Lightweight Surface Manipulation System (LSMS), has been designed and built. Over the course of its development, conventional crane type payload handling configurations and operations have been successfully demonstrated and the range of motion, types of operations and the versatility greatly expanded. This enhanced set of 1st generation LSMS hardware is now serving as a laboratory test-bed allowing the continuing development of end effectors, operational techniques and remotely controlled and automated operations. This paper describes the most recent LSMS and test-bed development activities, that have focused on two major efforts. The first effort was to complete a preliminary design of the 2nd generation LSMS that has the capability for limited mobility and can reposition itself between lander decks, mobility chassis, and fixed base locations. A major portion of this effort involved conducting a study to establish the feasibility of, and define, the specifications for a lightweight cable-drive waist joint. The second effort was to continue expanding the versatility and autonomy of large planetary surface manipulators using the 1st generation LSMS as a test-bed. This has been accomplished by increasing manipulator capabilities and efficiencies through both design changes and tool and end effector development. A software development effort has expanded the operational capabilities of the LSMS test-bed to include; autonomous operations based on stored paths, use of a vision system for target acquisition and tracking, and remote command and control over a communications bridge.

  7. Improved computational model (AQUIFAS) for activated sludge, integrated fixed-film activated sludge, and moving-bed biofilm reactor systems, part II: multilayer biofilm diffusional model.

    Science.gov (United States)

    Sen, Dipankar; Randall, Clifford W

    2008-07-01

    Research was undertaken to develop a diffusional model of the biofilm that can be applied in lieu of a semi-empirical model to upgrade an activated sludge system to an integrated fixed-film activated sludge (IFAS) or moving-bed biofilm reactor (MBBR) system. The model has been developed to operate with up to 12 cells (reactors) in series, with biofilm media incorporated to one or more of the zone cells, except the anaerobic zone cells. The values of the kinetic parameters for the model were measured using pilot-scale activated sludge, IFAS, and MBBR systems. The biofilm is divided into 12 layers and has a stagnant liquid layer. Diffusion and substrate utilization are calculated for each layer. The equations are solved simultaneously using a finite difference technique. The biofilm flux model is then linked to the activated sludge model. Advanced features include the ability to compute the biofilm thickness and the effect of biofilm thickness on performance. The biofilm diffusional model is also used to provide information and create a table of biofilm yields at different substrate concentrations that can be used in the semi-empirical model. PMID:18710146

  8. Developing mathematical modelling competence

    DEFF Research Database (Denmark)

    Blomhøj, Morten; Jensen, Tomas Højgaard

    2003-01-01

    In this paper we introduce the concept of mathematical modelling competence, by which we mean being able to carry through a whole mathematical modelling process in a certain context. Analysing the structure of this process, six sub-competences are identified. Mathematical modelling competence...... cannot be reduced to these six sub-competences, but they are necessary elements in the development of mathematical modelling competence. Experience from the development of a modelling course is used to illustrate how the different nature of the sub-competences can be used as a tool for finding the...... balance between different kinds of activities in a particular educational setting. Obstacles of social, cognitive and affective nature for the students' development of mathematical modelling competence are reported and discussed in relation to the sub-competences....

  9. Evolution of bed form height and length during a discharge wave

    OpenAIRE

    Warmink, J.J.; Schielen, R.M.J.; Dohmen-Janssen, C.M.; Lancker, van, V.; Garlan, T.

    2013-01-01

    This research focusses on modeling the evolution of bed form during a discharge wave for application in operational flood forecasting. The objective of this research was to analyze and predict the bed form evolution during a discharge wave in a flume experiment. We analyzed the data of a flume experiment and show that dune length is determined by development of secondary bed forms during the receding limb of the discharge wave. Secondly, three models were compared to predict the bed form evol...

  10. Numerical Modeling of Reactive Multiphase Flow for FCC and Hot Gas Desulfurization Circulating Fluidized Beds

    Energy Technology Data Exchange (ETDEWEB)

    None

    2005-07-01

    This work was carried out to understand the behavior of the solid and gas phases in a CFB riser. Only the riser is modeled as a straight pipe. A model with linear algebraic approximation to solids viscosity of the form, {musubs} = 5.34{epsisubs}, ({espisubs} is the solids volume fraction) with an appropriate boundary condition at the wall obtained by approximate momentum balance solution at the wall to acount for the solids recirculation is tested against experimental results. The work done was to predict the flow patterns in the CFB risers from available experimental data, including data from a 7.5-cm-ID CFB riser at the Illinois Institute of Technology and data from a 20.0-cm-ID CFB riser at the Particulate Solid Research, Inc., facility. This research aims at modeling the removal of hydrogen sulfide from hot coal gas using zinc oxide as the sorbent in a circulating fluidized bed and in the process indentifying the parameters that affect the performance of the sulfidation reactor. Two different gas-solid reaction models, the unreacted shrinking core (USC) and the grain model were applied to take into account chemical reaction resistances. Also two different approaches were used to affect the hydrodynamics of the process streams. The first model takes into account the effect of micro-scale particle clustering by adjusting the gas-particle drag law and the second one assumes a turbulent core with pseudo-steady state boundary condition at the wall. A comparison is made with experimental results.

  11. A review of correlations to model the packing structure and effective thermal conductivity in packed beds of mono-sized spherical particles

    International Nuclear Information System (INIS)

    This paper presents a review of the literature describing the packing structure and effective thermal conductivity of randomly packed beds consisting of mono-sized particles. In this study particular attention was given to the packing structure (porosity, coordination number, and contact angles) and heat transfer by solid conduction, gas conduction, contact area, surface roughness, as well as thermal radiation. New methods to analyse the models were developed giving new insights into the shortcomings of the correlations to predict and define the packing structure, as well as to simulate the effective thermal conductivity in the near-wall region. This information is of particular importance in the design and operation of high temperature packed bed nuclear reactors.

  12. Bed inventory overturn in a circulating fluid bed riser with pant-leg structure

    Energy Technology Data Exchange (ETDEWEB)

    Jinjing Li; Wei Wang; Hairui Yang; Junfu Lv; Guangxi Yue [Tsinghua University, Beijing (China). Key Laboratory for Thermal Science and Power Engineering of Ministry of Education

    2009-05-15

    The special phenomenon, nominated as bed inventory overturn, in circulating fluid bed (CFB) riser with pant-leg structure was studied with model calculation and experimental work. A compounded pressure drop mathematic model was developed and validated with the experimental data in a cold experimental test rig. The model calculation results agree well with the measured data. In addition, the intensity of bed inventory overturn is directly proportional to the fluidizing velocity and is inversely proportional to the branch point height. The results in the present study provide significant information for the design and operation of a CFB boiler with pant-leg structure. 15 refs., 10 figs., 1 tab.

  13. Studies on Pyrolysis Kinetic of Newspaper Wastes in a Packed Bed Reactor: Experiments, Modeling, and Product Characterization

    Directory of Open Access Journals (Sweden)

    Aparna Sarkar

    2015-01-01

    Full Text Available Newspaper waste was pyrolysed in a 50 mm diameter and 640 mm long reactor placed in a packed bed pyrolyser from 573 K to 1173 K in nitrogen atmosphere to obtain char and pyro-oil. The newspaper sample was also pyrolysed in a thermogravimetric analyser (TGA under the same experimental conditions. The pyrolysis rate of newspaper was observed to decelerate above 673 K. A deactivation model has been attempted to explain this behaviour. The parameters of kinetic model of the reactions have been determined in the temperature range under study. The kinetic rate constants of volatile and char have been determined in the temperature range under study. The activation energies 25.69 KJ/mol, 27.73 KJ/mol, 20.73 KJ/mol and preexponential factors 7.69 min−1, 8.09 min−1, 0.853 min−1 of all products (solid reactant, volatile, and char have been determined, respectively. A deactivation model for pyrolysis of newspaper has been developed under the present study. The char and pyro-oil obtained at different pyrolysis temperatures have been characterized. The FT-IR analyses of pyro-oil have been done. The higher heating values of both pyro-products have been determined.

  14. Numerical modeling of the vertical hydrofluorination zone in the moving bed furnace for the production of UF{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Jourde, J.; Patisson, F.; Ablitzer, D. [Ecole des Mines, Nancy (France). Lab. de Science et Genie des Materiaux Metalliques; Houzelot, J.L. [Ecole des Mines, Nancy (France). Lab. des Sciences du Genie Chimique

    1996-12-31

    Uranium tetrafluoride UF{sub 4} is produced in the moving bed furnace, a reactor in which solid- and gas counterflow. Due to the highly exothermic nature of the chemical reactions involved, the-reactor operation requires a careful temperature control. To provide operators with an appropriate tool for the predictive simulation, optimization and control of the process an overall numerical model of the furnace has been developed. This article describes the part of the model concerning the vertical hydrofluorination zone. The differential equations representing the mass, energy and momentum balances are solved using the finite volume method. The physicochemical parameters necessary for the calculation are detailed. The rate of the main reaction, the hydrofluorination of UO{sub 2}, has been determined with the aid of a specific kinetic model. The computed parameters, namely the temperature and solid and gas compositions, are visualized in the form of isovalue maps. The initial results reveal the influence of a thermodynamic limitation of the reaction at temperatures higher than 650 K. (author)

  15. A shallow-flow model for the propagation of tsunamis over complex geometries and mobile beds

    Directory of Open Access Journals (Sweden)

    D. A. S. Conde

    2013-10-01

    Full Text Available A distinguishable feature of overland tsunami propagation is the incorporation of solids within the flow column, either sediment from the natural environment or remains from built infrastructure. This article describes a 2DH (two-dimensional horizontal mathematical model particularly suited for tsunami propagation over complex and dynamic geometries, such as river and estuarine mobile beds. The discretization scheme is based on a finite-volume method using a flux-splitting technique featuring a reviewed Roe–Riemann solver, with appropriate source-term formulations to ensure full conservativeness. The model is validated with laboratory data and paleo-tsunami evidence. As a forecasting application, it is applied to a tsunami scenario in the Tagus estuary, an effort justified by the numerous catastrophic tsunamis that are known to have struck this location over the past two millennia. The obtained results show that, despite the significant differences in Lisbon's layout and morphology, a 1755-like tsunami would still inflict a devastating impact on this major city.

  16. Characteristics modeling for supercritical circulating fluidized bed boiler working in oxy-combustion technology

    Directory of Open Access Journals (Sweden)

    Balicki Adrian

    2014-06-01

    Full Text Available Among the technologies which allow to reduce greenhouse gas emission, mainly carbon dioxide, special attention deserves the idea of ‘zeroemission’ technology based on boilers working in oxy-combustion technology. In the paper the results of analyses of the influence of changing two quantities, namely oxygen share in oxidant produced in the air separation unit, and oxygen share in oxidant supplied to the furnace chamber on the selected characteristics of a steam boiler including the degree of exhaust gas recirculation, boiler efficiency and adiabatic flame temperature, was examined. Due to the possibility of the integration of boiler model with carbon dioxide capture, separation and storage installation, the subject of the analysis was also to determine composition of the flue gas at the outlet of a moisture condensation installation. Required calculations were made using a model of a supercritical circulating fluidized bed boiler working in oxy-combustion technology, which was built in a commercial software and in-house codes.

  17. RISK ANALYSIS DEVELOPED MODEL

    Directory of Open Access Journals (Sweden)

    Georgiana Cristina NUKINA

    2012-07-01

    Full Text Available Through Risk analysis developed model deciding whether control measures suitable for implementation. However, the analysis determines whether the benefits of a data control options cost more than the implementation.

  18. Numerical modeling of oxygen mass transfer from PbO spheres packed bed to liquid lead bismuth eutectic: A venturi-type PbO mass exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Marino, A., E-mail: amarino@sckcen.be [SCK-CEN, Boeretang 200, B-2400 Mol (Belgium); Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene (Belgium); Lim, J.; Keijers, S.; Van den Bosch, J. [SCK-CEN, Boeretang 200, B-2400 Mol (Belgium); Deconinck, J. [Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene (Belgium)

    2013-12-15

    Highlights: • A CFD model of oxygen mass transfer in LBE is developed. • The model is used to design a venturi type PbO mass exchanger. • The effect of re-circulation flow on the oxygen concentration is simulated. • Recirculation of 6% the total flow rate can prevent poisoning of the PbO spheres. - Abstract: A numerical model of oxygen mass transfer from a PbO spheres packed bed into liquid lead bismuth eutectic (LBE) has been developed and implemented in the commercial CFD code CFX. Based on the model, a venturi-type PbO mass exchanger (PbO MX) has been designed. The venturi-type has been selected to create a re-circulation flow from the outlet to the inlet of PbO spheres packed bed in order to avoid the poisoning of PbO surface by dissolved metallic impurities in the LBE circuit. The oxygen concentration at the inlet can be kept high enough by the re-circulation flow to prevent the poisoning of the PbO surface. This is expected to improve the reliability and stability of the PbO MX. The oxygen mass transfer in LBE through the PbO MX and the effect of re-circulation flow on the oxygen concentration are simulated and discussed. The developed CFD model gives a robust design of an oxygen control system, based on PbO MX technology.

  19. Reference Model Development

    Energy Technology Data Exchange (ETDEWEB)

    Jepsen, Richard [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2011-11-02

    Presentation from the 2011 Water Peer Review in which principal investigator discusses project progress to develop a representative set of Reference Models (RM) for the MHK industry to develop baseline cost of energy (COE) and evaluate key cost component/system reduction pathways.

  20. Simplified models for pebble-bed HTR core burn-up calculations with Monteburns2.0©

    International Nuclear Information System (INIS)

    Highlights: ► PBMR-400 annular core is very difficult to simulate in a reliable way. ► Nuclide evolutions given by different lattice models can differ significantly. ► To split fixed lattice models into two axial zones does not affect results significantly. ► We can choose a (simplified) core model on the basis of the analysis aim. ► Monteburns gives by survey burn-up calculations reasonable nuclide evolution trends. - Abstract: This paper aims at comparing some simplified models to simulate irradiation cycles of Pu fuelled pebble-bed reactors with Monteburns2.0© code. As a reference core, the PBMR-400 (proposed in the framework of the EU PUMA project, where this kind of core fuelled by a Pu and Pu–Np fuel has been studied) was taken into account. Pebble-bed High Temperature Reactor (HTR) cores consist of hundreds of thousands pebbles arranged stochastically in a cylindrical or annular space and each pebble is a single fuel element, and it is able to reach ultra-high burn-ups, i.e. up to 750 GWd/tHM (for Pu-based fuels). Additionally, pebble-bed cores are characterised by a continuous recirculation of pebbles from the top to the bottom of the core. Modelling accurately with current computer codes such an arrangement, in order to predict the behaviour of the core itself, is a very difficult task and any depletion code specifically devoted to pebble-bed burn-up calculation is not available at the moment. Because of limitations of the most common current MCNP-based depletion codes as well as huge calculation times, simplified models have to be implemented. After an analysis of the literature available on pebble-bed models for criticality and burn-up calculations, a preliminary assessment of the impact of different kind of simplified models for a Pu-Np fuelled Pebble-Bed Modular Reactor (PBMR), proposed in the framework of the EU PUMA project, is shown, particularly as far as burn-up prediction with Monteburns2.0© code is concerned.

  1. Operating experience and development of fluidized-bed denitrators for UNH at Tokai Reprocessing Plant

    International Nuclear Information System (INIS)

    The fluidized bed denitrator for uranyl nitrate hexahydrate (UNH) at Tokai reprocessing plant has been operated since 1976. About 170 tons of spent fuel have been reprocessed, and the denitrator has encountered numerous operational problems during the period. This report deals with these technical problems and the associated countermeasures taken, including the dismantling and reconstruction of equipment and the improvement of operating method. The major problems encountered were as follows: (1) the crystallization of UNH on the UNH feeding line, (2) spray nozzle clogging and candle filter clogging, (3) particle growth, (4) plugging of the drawing-out line by nozzle caking, and (5) slugging in fluidized-bed denitration. The total quantity and quality of UO3 products obtained so far at the plant are also briefly described together with some future R and D programs such as the improvement of UO3 reactivity and the automation of denitrators. (Aoki, K.)

  2. Modeling moisture diffusivity, activation energy and specific energy consumption of squash seeds in a semi fluidized and fluidized bed drying.

    Science.gov (United States)

    Chayjan, Reza Amiri; Salari, Kamran; Abedi, Qasem; Sabziparvar, Ali Akbar

    2013-08-01

    This study investigated thin layer drying of squash seeds under semi fluidized and fluidized bed conditions with initial moisture content about 83.99% (d.b.). An experimental fluidized bed dryer was also used in this study. Air temperature levels of 50, 60, 70 and 80 °C were applied in drying samples. To estimate the drying kinetic of squash seed, seven mathematical models were used to fit the experimental data of thin layer drying. Among the applied models, Two-term model has the best performance to estimate the thin layer drying behavior of the squash seeds. Fick's second law in diffusion was used to determine the effective moisture diffusivity of squash seeds. The range of calculated values of effective moisture diffusivity for drying experiments were between 0.160 × 10(-9) and 0.551 × 10(-10) m(2)/s. Moisture diffusivity values decreased as the input air temperature decreased. Activation energy values were found to be between 31.94 and 34.49 kJ/mol for 50 °C to 80 °C, respectively. The specific energy consumption for squash seeds was calculated at the boundary of 0.783 × 10(6) and 2.303 × 10(6) kJ/kg. Increasing in drying air temperature in different bed conditions led to decrease in specific energy value. Results showed that applying the semi fluidized bed condition is more effective for convective drying of squash seeds. The aforesaid drying characteristics are useful to select the best operational point of fluidized bed dryer and to precise design of system. PMID:24425968

  3. EFFECTIVENESS OF THE BANGALORE UNIVERSITY B.ED CURRICULUM IN DEVELOPING PROPER ATTITUDE TOWARDS TEACHING PROFESSION

    OpenAIRE

    N.N.Prahallada

    2016-01-01

    The present study explored the variables that contribute to the effectiveness of teachers training program in Bangalore University for the education sector. A sample of 52 students were selected which included both male and female teacher trainees of B.E.S B.Ed. College; with the help of a research questionnaire their response was recorded. This study determined that their effectiveness could have been increased if rigorous training need analysis had been done. The study also finds that facto...

  4. Modeling and simulation of a solar powered two bed adsorption air conditioning system

    International Nuclear Information System (INIS)

    A simple lumped parameter model is established to investigate the performance of a solar powered adsorption air conditioning system driven by flat-type solar collectors with three different configurations of glazes: (i) single glazed cover; (ii) double glazed cover and (iii) transparent insulation material (TIM) cover. The dynamic performance of a continuous adsorption cycle using a double adsorber along with heat recovery is measured in terms of the temperature histories, gross solar coefficient of performance and specific cooling power. Also, the influences of some important design and operational parameters on the performance of the system are studied. It is found that the chosen three types of collector configurations make no big difference on the performance, but the adsorbent mass and lumped capacitance have significant effects on the system performance as well as on the system size. Simulation results indicate that the effect of overall heat transfer coefficient is not predominant if the cycle duration is longer. Also, there exists an optimum time to initiate the heating of the adsorbent bed in a day's operation

  5. Multi-fluid modeling of density segregation in a dense binary fluidized bed

    Institute of Scientific and Technical Information of China (English)

    Zhongxi Chao; Yuefa Wang; Jana P.Jakobsen; Maria Fernandino; Hugo A.Jakobsen

    2012-01-01

    This paper presents simulation results of the density segregation in a dense binary gas fluidized bed using a multi-fluid model from Chao et al.(2011).The segregation behavior of two types of particles with approximately same particle diameters and different particle densities was studied and validated using the experimental data from Formisani et al.(2008),Some detailed information regarding the gas,particle velocity profiles,the distributions of the particle volume fractions and the flotsam-to-total particle volume fraction ratios is presented.The simulation results show that the simulated axial average flotsam-to-total particle volume fraction ratio distribution agrees reasonably with the experimental data of Formisani et al.(2008).The binary particle velocities are closely coupled though the segregation exists.The segregation behavior and the particle velocity profiles are superficial gas velocity dependent.The number and distribution of particle velocity vortices change dramatically with superficial gas velocity:at a comparatively low superficial gas velocity,the particles mainly segregate axially,and at a comparatively high superficial gas velocity,the particles segregate both axially and radially.

  6. Treatment of wastewater from coffee bean processing in anaerobic fixed bed reactors with different support materials: performance and kinetic modeling.

    Science.gov (United States)

    Fia, Fátima R L; Matos, Antonio T; Borges, Alisson C; Fia, Ronaldo; Cecon, Paulo R

    2012-10-15

    An evaluation was performed of three upflow anaerobic fixed bed reactors for the treatment of wastewater from coffee bean processing (WCP). The supports used were: blast furnace cinders, polyurethane foam and crushed stone with porosities of 53, 95 and 48%, respectively. The testing of these 139.5 L reactors consisted of increasing the COD of the influent (978; 2401 and 4545 mg L(-1)), while maintaining the retention time of 1.3 days. For the maximum COD applied, the reactor filled with foam presented removals of 80% (non-filtered samples) and 83% (filtered samples). The greater performance of the reactor filled with foam is attributed to its porosity, which promoted greater collection of biomass. From the results, it could be concluded that the reactors presented satisfactory performance, especially when using the foam as a support. Furthermore, the modified Stover-Kincannon and second order for multicomponent substrate degradation models were successfully used to develop a model of the experimental data. PMID:22609965

  7. Investigation of coalescence kinetics of microcristalline cellulose in fluidised bed spray agglomeration: experimental studies and modelling approach

    Directory of Open Access Journals (Sweden)

    M. Peglow

    2005-06-01

    Full Text Available In this paper a model for fluidized bed spray agglomeration is presented. To describe the processes of heat and mass transfer, a physical based model is derived. The model takes evaporation process from the wetted particles as well as the effects of transfer phenomena between suspension gas and bypass gas into account. The change of particle size distribution during agglomeration, modeled by population balances, is linked to the heat and mass transfer model. A new technique is derived to extract agglomeration and nucleation rates from experimental data. Comparisons of experiments and simulations are presented.

  8. A Physical Protection Systems Test Bed for International Counter-Trafficking System Development

    International Nuclear Information System (INIS)

    Physical protection systems have a widespread impact on the nuclear industry in areas such as nuclear safeguards, arms control, and trafficking of illicit goods (e.g., nuclear materials) across international borders around the world. Many challenges must be overcome in design and deployment of foreign border security systems such as lack of infrastructure, extreme environmental conditions, limited knowledge of terrain, insider threats, and occasional cultural resistance. Successful security systems, whether it be a system designed to secure a single facility or a whole border security system, rely on the entire integrated system composed of multiple subsystems. This test bed is composed of many unique sensors and subsystems, including wireless unattended ground sensors, a buried fiber-optic acoustic sensor, a lossy coaxial distributed sensor, wireless links, pan-tilt-zoom cameras, mobile power generation systems, unmanned aerial vehicles, and fiber-optic-fence intrusion detection systems. A Common Operating Picture software architecture is utilized to integrate a number of these subsystems. We are currently performance testing each system for border security and perimeter security applications by examining metrics such as probability of sense and a qualitative understanding of the sensors vulnerability of defeat. The testing process includes different soil conditions for buried sensors (e.g., dry, wet, and frozen) and an array of different tests including walking, running, stealth detection, and vehicle detection. Also, long term sustainability of systems is tested including performance differences due to seasonal variations (e.g. summer versus winter, while raining, in foggy conditions). The capabilities of the test bed are discussed. Performance testing results, both at the individual component level and integrated into a larger system for a specific deployment (in situ), help illustrate the usefulness and need for integrated testing facilities to carry out this

  9. Development of Ex-Vessel Corium Debris Bed under Two-Phase Natural Convection Flows in Flooded Cavity Pool during Severe Accident

    International Nuclear Information System (INIS)

    The objective of this study is experimental verification of the two-phase flow effect on the ex-vessel corium debris bed formation. Especially, dynamic growth trend of debris bed was observed by utilizing 'Gap-Tooth' approach for reflecting the heat generation change of developing debris bed. For massive discharge of melt during very short time, there must be corium melt pool which is harder to be cooled. However, for the condition of deep enough cavity flooding and long enough melt release time, the development of corium fragments debris bed can be expected, which is more advantageous for cooling due to its porous characteristics. Though the 'Dripping mode' of melt release in deep cavity pool for long term cooling could not be the most conservative condition, but it might be one of the most probable ones and worthy of consideration. On the assessment of the porous corium debris bed coolability, most studies have used various arbitrary assumptions on the debris bed like flat, cylinder and mound shape. However it is also known that the coolability largely depends on the debris bed shape, especially the bed height and overall distribution state. The process of debris bed development includes a series of complex physical phenomena and still there is little study which covers all of those. From the time sequential comparative studies with quiescent pool condition test and air bubble driven natural convection condition test, it was observed that the two-phase natural convection induces the slower bed mound top growth rate and the flatter configuration of debris bed, which are known as to guarantee the higher coolability and the delay of dryout occurrence. Development of ex-vessel corium debris bed in the flooded cavity pool during severe accident was experimentally studied. Dripping mode of corium discharge with deep cavity pool depth and long melt release time was assumed for full fragmentation of melt jet. The two-phase natural convection flows was

  10. Six-Degree Head-Down Tilt Bed Rest: Forty Years of Development as a Physiological Analog for Weightlessness

    Science.gov (United States)

    Smith, Jeffrey D.; Cromwell, Ronita L.; Kundrot, Craig E.; Charles, John B.

    2011-01-01

    Early on, bed rest was recognized as a method for inducing many of the physiological changes experienced by spaceflight. Head-down tilt (HDT) bed rest was first introduced as an analog for spaceflight by a Soviet team led by Genin and Kakurin. Their study was performed in 1970 (at -4 degrees) and lasted for 30 days; results were reported in the Russian Journal of Space Biology (Kosmicheskaya Biol. 1972; 6(4): 26-28 & 45-109). The goal was to test physiological countermeasures for cosmonauts who would soon begin month-long missions to the Salyut space station. HDT was chosen to produce a similar sensation of blood flow to the head reported by Soyuz cosmonauts. Over the next decade, other tilt angles were studied and comparisons with spaceflight were made, showing that HDT greater than 4 degrees was superior to horizontal bed rest for modeling acute physiological changes observed in space; but, at higher angles, subjects experienced greater discomfort without clearly improving the physiological comparison to spaceflight. A joint study performed by US and Soviet investigators, in 1979, set the goal of standardization of baseline conditions and chose 6-degrees HDT. This effectively established 6-degree HDT bed rest as the internationally-preferred analog for weightlessness and, since 1990, nearly all further studies have been conducted at 6-degrees HDT. A thorough literature review (1970-2010) revealed 534 primary scientific journal articles which reported results from using HDT as a physiological analog for spaceflight. These studies have ranged from as little as 10 minutes to the longest duration of 370 days. Long-term studies lasting four weeks or more have resulted in over 170 primary research articles. Today, the 6-degree HDT model provides a consistent, thoroughly-tested, ground-based analog for spaceflight and allows the proper scientific controls for rigorous testing of physiological countermeasures; however, all models have their strengths and limits. The 6

  11. Coupling of a radiative heat transfer model and a three-dimensional combustion model for a circulating fluidized bed furnace

    International Nuclear Information System (INIS)

    A 3D semi-empirical model for reactive two-phase flow in a circulating fluidized bed furnace (CFB3D) is modified by implementing the radiative zone method to solve the radiation heat transfer. The radiative properties of the gas and particle phase have been calculated using detailed information of gas and particle distribution obtained from the CFB3D model. A recently published WSGGM for oxygen-fired combustion has been used to calculate the absorption coefficient of gaseous combustion products. The results of implementing the radiative zonal approach have been compared with those obtained using empirical radiative correlations. The temperature field obtained by using the radiative zone method is more uniform than the one obtained by empirical correlation, and the total heat flux to the wall is slightly higher. The long distance effect of radiation has been found more important in the upper furnace where the gas is the dominant phase. Detailed discussion concerning the obtained results is presented.- Highlights: • Radiative zone model is used to analyze a large scale CFB furnace. • A semi-empirical model for CFB processes is presented. • The radiative effect of long distance is taken into account. • The geometric optic is used for radiative properties of particles. • The WSGGM is used for radiative properties of combustion gases

  12. Low cost test bed tool development for validation of mission control events

    Science.gov (United States)

    Montanez, L.; Cervantes, D.; Tatge, L.

    2003-01-01

    The Cassini Program is one of the last large interplanetary spacecraft missions. It is a joint effort between the European Space Agency, the Italian Space Agency and NASA.The U.S. portion of the mission is managed for NASA by the Jet Propulsion Laboratory (JPL). The primary mission is to survey the complex Saturnian system and release the ESA-Huygens probe at Titan. The success of the Cassini Mission has been largely due its many simulation test beds and its rigorous test program.

  13. Erosion of heat exchanger tubes in fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, E.K.; Flemmer, R.L.C.

    1991-01-01

    This final report describes the activities of the 3-year project entitled Erosion of Heat Exchanger Tubes In Fluidized Beds.'' which was completed at the end of 1990. Project accomplishments include the collection of a substantial body of wear data In a 24in. [times] 24in. fluidized bed, comparative wear results In a 6in. [times] 6in. fluidized bed, the development of a dragometer and the collection of a comprehensive set of drag force data in the 24in. [times] 24in. bed, Fast Fourier Transform (FFT) analysis of bubble probe data to establish dominant bubble frequencies in the 24in. [times] 24in. bed, the use of a heat flux gauge for measurement of heat transfer coefficients in the 24in. [times] 24in. bed and the modeling of the tube wear in the 24in. [times] 24in. bed. Analysis of the wear data from the 24in. square bed indicates that tube wear increases with increase in superficial velocity, and with increase in tube height. The latter effect is a result of the tubes higher up in the bed seeing greater movement of dense phase than tubes lower down In the bed. In addition, tube wear was found to decrease with increase in particle size, for constant superficial velocity. Three models of tube wear were formulated and provided acceptable prediction of wear when compared with the experimental data.

  14. Modelling of N2O Reduction in a Circulating Fluidized Bed Boiler

    DEFF Research Database (Denmark)

    Johnsson, Jan Erik; Åmand, Lars Erik; Dam-Johansen, Kim;

    1996-01-01

    The addition of limestone for sulphur retention in Fluidized Bed Combustion (FBC) has been observed to influence the emission of N2O, and in many cases a lower emission was observed. The catalytic activity of a Danish limestone (Stevns Chalk) for decomposition of N2O in a laboratory fixed bed...... quartz reactor was measured. It was found that calcined Stevns Chalk is a very active catalyst for N2O decomposition in an inert atmosphere compared to bed material, i.e. a mixture of ash and sand. However, in FBC the limestone is exposed to a mixture of gases, including CO, CO2 and SO2, and sulphation...... uncalcined or recarbonated limestone had negligible activity. Sulphation of the calcined limestone under oxidizing conditions lowered the activity, however sulphidation under reducing conditions showed that CaS is an active catalyst for the reduction of N2O by CO. Without CO present a gas solid reaction...

  15. Fluidised bed cereal cooking

    International Nuclear Information System (INIS)

    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

  16. Analysis and Modeling of Wangqing Oil Shale Drying Characteristics in a Novel Fluidized Bed Dryer with Asynchronous Rotating Air Distributor

    Institute of Scientific and Technical Information of China (English)

    Yang Ning; Zhou Yunlong; Miao Yanan

    2016-01-01

    In order to replace the conventional distributor, a novel asynchronous rotating air distributor, which can optimize the drying ability of lfuidized bed and strengthen the drying performance of oil shale particles, is creatively designed in this study. The rotating speed of the asynchronous rotating air distributor with an embedded center disk and an encircling disk is regulated to achieve the different air supply conditions. The impacts of different drying conditions on the drying characteristic of Wangqing oil shale particles are studied with the help of electronic scales. The dynamics of experimental data is analyzed with 9 common drying models. The results indicate that the particles distribution in lfuidized bed can be improved and the drying time can be reduced by decreasing the rotating speed of the embedded center disk and increasing the rotating speed of the encircling disk. The drying process of oil shale particles involves a rising drying rate period, a constant drying rate period and a falling drying rate period. Regulating the air distributor rotating speed reasonably will accelerate the shift of particles from the rising drying rate period to the falling drying rate period directly. The two-term model ifts properly the oil shale particles drying simulation among 9 drying models at different air supply conditions. Yet the air absorbed in the particles’ pores is diffused along with the moisture evaporation, and a small amount of moisture remains on the wall of lfuidized bed in each experiment, thus, the values of drying simulation are less than the experimental values.

  17. Modeling N2O Reduction and Decomposition in a Circulating Fluidized bed Boiler

    DEFF Research Database (Denmark)

    Johnsson, Jan Erik; Åmand, Lars-Erik; Dam-Johansen, Kim;

    1996-01-01

    combustion chamber and the cyclone was calculated taking three mechanisms into account: Reduction by char, catalytic decomposition over bed material and thermal decomposition. The calculated destruction rate was in good agreement with the measured destruction of N2O injected at different levels in the boiler...... decomposition over bed material, and homogeneous thermal decomposition was negligible. However, at higher levels in the combustor the solids concentration is lower: at the top 60% of the N2O destruction was due to thermal decomposition and in the cyclone heterogeneous destruction of N2O was insignificant. It...

  18. Modeling the supercritical desorption of orange essential oil from a silica-gel bed

    OpenAIRE

    2000-01-01

    One of the most important byproducts of the orange juice industry is the oil phase. This is a mixture of terpenes, alcohols, and aldehydes, dissolved in approximately 96% limonene. To satisfactorily use oil phase as an ingredient in the food and cosmetics industries separation of the limonene is required. One possibility is to use a fixed bed of silica gel to remove the light or aroma compounds from the limonene. The aroma substances are then extracted from the bed of silica gel using supercr...

  19. Development of Methane and Nitrous Oxide Emission Factors for the Biomass Fired Circulating Fluidized Bed Combustion Power Plant

    OpenAIRE

    Chang-Sang Cho; Jae-Hwan Sa; Ki-Kyo Lim; Tae-Mi Youk; Seung-Jin Kim; Seul-Ki Lee; Eui-Chan Jeon

    2012-01-01

    This study makes use of this distinction to analyze the exhaust gas concentration and fuel of the circulating fluidized bed (CFB) boiler that mainly uses wood biomass, and to develop the emission factors of Methane (CH4), Nitrous oxide (N2O). The fuels used as energy sources in the subject working sites are Wood Chip Fuel (WCF), RDF and Refused Plastic Fuel (RPF) of which heating values are 11.9 TJ/Gg, 17.1 TJ/Gg, and 31.2 TJ/Gg, respectively. The average concentrations of CH4 and N2O were me...

  20. Product Development Process Modeling

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The use of Concurrent Engineering and other modern methods of product development and maintenance require that a large number of time-overlapped "processes" be performed by many people. However, successfully describing and optimizing these processes are becoming even more difficult to achieve. The perspective of industrial process theory (the definition of process) and the perspective of process implementation (process transition, accumulation, and inter-operations between processes) are used to survey the method used to build one base model (multi-view) process model.

  1. Multifluid modeling of the desulfurization process within a bubbling fluidized bed coal gasifier

    OpenAIRE

    Armstrong, L-M.; Gu, Sai; Luo, K. H.; P Mahanta

    2013-01-01

    The desulfurization process to a two-dimensional (2-D) and three-dimensional (3-D) Eulerian-Eulerian computational fluid dynamic (CFD) model of a coal bubbling fluidized gasifier is introduced. The desulfurization process is important for the reduction of harmful SOx emissions; therefore, the development of a CFD model capable of predicting chemical reactions involving desulfurization is key to the optimization of reactor designs and operating conditions. To model the process, one gaseous pha...

  2. Development of an Indoor Location Based Service Test Bed and Geographic Information System with a Wireless Sensor Network

    Directory of Open Access Journals (Sweden)

    Shau-Shiun Jan

    2010-03-01

    Full Text Available In order to provide the seamless navigation and positioning services for indoor environments, an indoor location based service (LBS test bed is developed to integrate the indoor positioning system and the indoor three-dimensional (3D geographic information system (GIS. A wireless sensor network (WSN is used in the developed indoor positioning system. Considering the power consumption, in this paper the ZigBee radio is used as the wireless protocol, and the received signal strength (RSS fingerprinting positioning method is applied as the primary indoor positioning algorithm. The matching processes of the user location include the nearest neighbor (NN algorithm, the K-weighted nearest neighbors (KWNN algorithm, and the probabilistic approach. To enhance the positioning accuracy for the dynamic user, the particle filter is used to improve the positioning performance. As part of this research, a 3D indoor GIS is developed to be used with the indoor positioning system. This involved using the computer-aided design (CAD software and the virtual reality markup language (VRML to implement a prototype indoor LBS test bed. Thus, a rapid and practical procedure for constructing a 3D indoor GIS is proposed, and this GIS is easy to update and maintenance for users. The building of the Department of Aeronautics and Astronautics at National Cheng Kung University in Taiwan is used as an example to assess the performance of various algorithms for the indoor positioning system.

  3. Characterization and CFD-modeling of the hydrodynamics of a prismatic spouted bed apparatus

    NARCIS (Netherlands)

    Gryczka, O.; Heinrich, S.; Deen, N.G.; Sint Annaland, van M.; Kuipers, J.A.M.; Jacob, M.; Mörl, L.

    2009-01-01

    Recently the importance of spouted bed technology has significantly increased in the context of drying processes as well as granulation, agglomeration or coating processes. However, the understanding of the complex interactions within and between the single phases is still low and needs further impr

  4. Development and linearization of generalized material balance equation for coal bed methane reservoirs

    International Nuclear Information System (INIS)

    A generalized material balance equation was presented at the Escuela de Petroleos de la Universidad Industrial de Santander for coal seam gas reservoirs based on Walsh's method, who worked in an analogous approach for oil and gas conventional reservoirs (Walsh, 1995). Our equation was based on twelve similar assumptions itemized by Walsh for his generalized expression for conventional reservoirs it was started from the same volume balance consideration and was finally reorganized like Walsh (1994) did. Because it is not expressed in terms of traditional (P/Z) plots, as proposed by King (1990), it allows to perform a lot of quantitative and qualitative analyses. It was also demonstrated that the existent equations are only particular cases of the generalized expression evaluated under certain restrictions. This equation is applicable to coal seam gas reservoirs in saturated, equilibrium and under saturated conditions, and to any type of coal beds without restriction on especial values of the constant diffusion

  5. Development of a Ventilation and Air-conditioning System using Fixed Bed Desiccant Units

    Science.gov (United States)

    Miyazaki, Takahiko; Akisawa, Atsushi; Shindoh, Shinji; Masazumi, Godo; Takeshi, Takatsuka; Hamamoto, Yoshinori; Mori, Hideo

    The study investigated fixed bed desiccant units for ventilation and air-conditioning. The system mainly dehumidifies the outdoor fresh air to be supplied to an air-conditioned room. Hence, the airconditioning load of the air-conditioner in the room can be mitigated. Several adsorbents were compared from the viewpoints of humidity ratio at the outlet of the desiccant unit, dehumidified quantity per unit volume, and dehumidified quantity per unit adsorbent mass. The performance of the desiccant unit was predicted by simulation which was validated by comparison with experiment. The results revealed the most suitable adsorbent to reduce the desiccant unit size. It was also found that the humidity ratio at the outlet of the desiccant unit could be lowered by shortening the dimensionless switching time.

  6. Development of Moving Bed Technology for Heat Treatment and Grinding of Dismantled Concrete

    International Nuclear Information System (INIS)

    The factors such as gas or fluid velocity, length, width and depth of each stage, number of Zig-Zag stage, angle of each stage, position of feed stage, size and amount of feed material, amount of treated concrete waste, method of fluid distribution, surface area of heat transfer, position of heater, method of heating, temperature difference between the heater and the material, amount of heat have been found to be important factors in the system. The capability of the system has been analyzed and evaluated by means of total efficiency and grade separation efficiency the experiments by using the simulated Zig-Zag type moving bed flow process with bench scale(3.2m high, Ifi-stage) have shown that the total efficiency has been in the range of 92% - 95% and the grade efficiency of 93% - 95%, respectively, elucidating that the system is quite good

  7. Development and Preparation of Controlled Release (CR Tablet Formulations of Procainamide Fluid-Bed Technique

    Directory of Open Access Journals (Sweden)

    Morteza Rafiee-Tehrani

    1995-08-01

    Full Text Available The need for controlled release (CR formulation of procainamide, an antiarrhythmic drug is well known. The aim of this investigation was an attempt to establish controlled release procainamide tablet formulations by fluid bed technique. The procainamide granules were prepared, using PVP as binder. A laboratory size fluidlzed bed drier (Uni-Glatt was used for coating the procainamide granules. As polymers, Eudragit RSPO, ethylcelluiose and Eudragit S 100 + ethylcelluiose (1:1 have been utilized. Triethylciirate (TECwas used as plasticizer in this investigation. The ratio of TEC to polymers was 1:9 in most experiments. However, in some formulations this ratio was increased to (1:4."nThe coated granules were compressed using an excentric tabletting machine. Drug release patterns of all formulations prepared were investigated. The dissolution media were consisted of hydrochloric acid buffer pH 1.5 for the first 2h and phosphate buffer pH 8.8 for remaining period of time in all experiments.For comparison, a commercially available brand of procainamide controlled release tablet was included in this study. Cross section scanning electron micrographs of coated and uncoated granules were taken. Granules coated with Eudragit RSPO, ethylcellulose and the combination of Eudragit S 100 and ethylcellulose (1:1 exhibited proper release behaviour. The release profiles were analyzed to check whether the release was diffusion-controlled or followed first-order kinetics. The release from most of the formulations prepared seems to correspond to the first-order kinetics. It was also concluded that, air suspension technique is a suitable method for the fabrication of controlled release formulations of procainamide tablets.

  8. A generalized theory for non-classical transport with angular-dependent path-length distributions 2: Anisotropic diffusion in model pebble bed reactor cores

    CERN Document Server

    Vasques, Richard

    2013-01-01

    We describe an analysis of neutron transport in the interior of model pebble bed reactor (PBR) cores, considering both crystal and random pebble arrangements. Monte Carlo codes were developed for (i) generating random realizations of the model PBR core, and (ii) performing neutron transport inside the crystal and random heterogeneous cores; numerical results are presented for two different choices of material parameters. These numerical results are used to investigate the anisotropic behavior of neutrons in each case and to assess the accuracy of estimates for the diffusion coefficients obtained with the diffusion approximations of different models: the atomic mix model, the Behrens correction, the Lieberoth correction, the generalized linear Boltzmann equation (GLBE), and the new GLBE with angular-dependent path-length distributions. This new theory utilizes a non-classical form of the Boltzmann equation in which the locations of the scattering centers in the system are correlated and the distance-to-collisi...

  9. Evaluation of photon migration using a two speed model for characterization of packed powder beds and dense particulate suspensions.

    Science.gov (United States)

    Pan, Tianshu; Dali, Sarabjyot; Sevick-Muraca, Eva

    2005-05-16

    A two-speed photon diffusion equation is developed for light propagation in a powder bed of high volume fraction or dense particulate suspension, whereby the light speed is impacted by the refractive index difference between particles and the suspending medium. The equation is validated using Monte Carlo simulation of light propagation coupled with dynamic simulation of particle sedimentation for the non-uniform arrangement of powder particles. Frequency domain experiments at 650 nm for a 77-microm-diameter resin-powder and 50-microm-diameter lactose-powder beds as well as resin-water and lactose-ethanol suspensions confirm the scattering and absorption coefficients derived from the two-speed diffusion equation. PMID:19495266

  10. GRID Raster Dataset Model of Overburden Above the LaClede Bed in the Green River and Washakie Basins, southwestern Wyoming

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — An ESRI GRID raster data model of the overburden material above the LaClede bed of the Laney Member of the Eocene Green River Formation was needed to perform...

  11. Simultaneous heat and mass transfer in packed bed brying of seeds having a mucilage coating

    Directory of Open Access Journals (Sweden)

    M. M. Prado

    2008-03-01

    Full Text Available The simultaneous heat and mass transfer between fluid phase and seeds having a mucilaginous coating was studied during packed bed drying. To describe the process, a two-phase model approach was employed, in which the effects of bed shrinkage and nonconstant physical properties were considered. The model took into account bed contraction by employing moving coordinates. Equations relating shrinkage and structural parameters of the packed bed with moisture content, required in the drying model, were developed from experimental results in thick-layer bed drying. The model verification was based on a comparison between experimental and predicted data on moisture content and temperature along the bed. Parametric studies showed that the application of correlations capable of incorporating changes in bed properties gives better data simulation. By experimental-theoretical analysis, the importance of shrinkage for a more accurate interpretation of heat and mass transfer phenomena in the drying of porous media composed of mucilaginous seeds is corroborated.

  12. Development of a test bed for operator aid and advanced control concepts in nuclear power plants

    International Nuclear Information System (INIS)

    A great amount of research and development is currently under way in the utilization of artificial intelligence (AI), expert system, and control theory advances in nuclear power plants as a basis for operator aids and automatic control systems. This activity requires access to the measured dynamic responses of the plant to malfunction, operator- or automatic-control-initiated actions. This can be achieved by either simulating plant behavior or by using an actual plant. The advantage of utilizing an actual plant versus a simulator is that the true behavior is assured of both the power generation system and instrumentation. Clearly, the disadvantages of using an actual plant are availability due to licensing, economic, and risk constraints and inability to address accident conditions. In this work the authors have decided to employ a functional one-ninth scale model of a pressurized water reactor (PWR). The scaled PWR (SPWR) facility is a two-loop representation of a Westinghouse PWR utilizing freon as the working fluid and electric heater rods for the core. The heater rods are driven by a neutron kinetics model accounting for measured thermal core conditions. A control valve in the main steam line takes the place of the turbine generator. A range of normal operating and accident situations can be addressed. The SPWR comes close to offering all the advantages of both a simulator and an actual physical plant in regard to research and development on AI, expert system, and control theory applications. The SPWR is being employed in the development of an expert-system-based operator aid system. The current status of this project is described

  13. Heat Transfer in a Fixed Bed of Straw Char

    DEFF Research Database (Denmark)

    Fjellerup, Jan Søren; Henriksen, Ulrik Birk; Jensen, Anker; Jensen, Peter Arendt; Glarborg, Peter

    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...... 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....

  14. Analysis of tire-road contact area in a control oriented test bed for dynamic friction models

    OpenAIRE

    J. Aguilar-Martínez; Alvarez-Icaza, L.

    2015-01-01

    The longitudinal and transversal forces distributed over the tire-road contact area are experimentally analyzed to validate the use of the lumped parameters LuGre dynamic friction model for traction-braking control purposes. To perform the analysis, a test bed based on a scaled quarter vehicle model that consists of a roller, a wheel and a servomotor was designed and built. In this device, the roller represents the road and the vehicle mass, and the tire is directly coupled to the shaft of th...

  15. Double-layer structure model of the uranium generating bed in the land basins of the northwestern China and its significance

    International Nuclear Information System (INIS)

    The paper puts forward a double layer structure model of uranium generating bed in the land basins of Northwestern China, i.e. uranium ganerating bed = source layer of uranium+gathering uranium layer. The mechanism of its formation: Feldspar was hydromicatized. Some feldspar, quarts detrital silicate minerals were replaced to redden by the authigenesis of hematite and goethite. In the course of the oxidation, a little uranium is released from the detrital minerals. Because of the oxidation environment, the released uranium wasn't able to be precipitated, only to diffuse to the adjacent grey bed which has low Eh value with uranium-bearing 'stagnant water' fixed in pores during the dewatering process of the diagenesis and form minable uranium deposit. The significance of the model for uranium prospecting are as follows: (1) Uranium source range is much expanded concerning ruanium prospecting in sandstone. (2) For the potential assessment of basin and the selection of potential area, the model is an important prospecting criterion. (3) By using the main criterion uranium-generating bed-arkosic red beds well, the buried ore bodies can be found provided that arkosic red beds were regarded as a significant criterion of uranium-generating bed

  16. DEPTH-INTEGRATED MODELING FOR AGGRADING/DEGRADING MOBILE CHANNELS I: MODEL DEVELOPMENT

    Institute of Scientific and Technical Information of China (English)

    En-Tian LIN; Chih-Tsung HSU; Keh-Chia YEH

    2006-01-01

    A depth-integrated model has been developed to simulate the alluvial process of channel bed under overloading and under-loading sediment discharge conditions. The hydrodynamic sub-model based on the explicit-finite-analytic method is used to obtain the flow field. Then the sediment transport modes, including the bed-load and suspended load, are modeled with the aid of the empirically auxiliary relations. In the depth-integrated model, the sediment exchange rate is treated as a source term specified at the reference level, rather than a boundary condition as usually adopted in vertical 2-D or 3-D models. The deposition or erosion rate of the bed is then determined by comparing the flow-laden suspended-sediment concentration profile against the equilibrium concentration profile, and their difference is used to compute the sediment exchange rate for a given time interval. Assessment of the good accuracy of the proposed model is demonstrated by using van Rijn's (1981) experiment for the case of clear water passing a movable bed. In the companion paper, the verification and the field application of the proposed model are presented.

  17. IMPACT fragmentation model developments

    Science.gov (United States)

    Sorge, Marlon E.; Mains, Deanna L.

    2016-09-01

    The IMPACT fragmentation model has been used by The Aerospace Corporation for more than 25 years to analyze orbital altitude explosions and hypervelocity collisions. The model is semi-empirical, combining mass, energy and momentum conservation laws with empirically derived relationships for fragment characteristics such as number, mass, area-to-mass ratio, and spreading velocity as well as event energy distribution. Model results are used for several types of analysis including assessment of short-term risks to satellites from orbital altitude fragmentations, prediction of the long-term evolution of the orbital debris environment and forensic assessments of breakup events. A new version of IMPACT, version 6, has been completed and incorporates a number of advancements enabled by a multi-year long effort to characterize more than 11,000 debris fragments from more than three dozen historical on-orbit breakup events. These events involved a wide range of causes, energies, and fragmenting objects. Special focus was placed on the explosion model, as the majority of events examined were explosions. Revisions were made to the mass distribution used for explosion events, increasing the number of smaller fragments generated. The algorithm for modeling upper stage large fragment generation was updated. A momentum conserving asymmetric spreading velocity distribution algorithm was implemented to better represent sub-catastrophic events. An approach was developed for modeling sub-catastrophic explosions, those where the majority of the parent object remains intact, based on estimated event energy. Finally, significant modifications were made to the area-to-mass ratio distribution to incorporate the tendencies of different materials to fragment into different shapes. This ability enabled better matches between the observed area-to-mass ratios and those generated by the model. It also opened up additional possibilities for post-event analysis of breakups. The paper will discuss

  18. Comparative simulation study of gas-phase propylene polymerization in fluidized bed reactors using aspen polymers and two phase models

    Directory of Open Access Journals (Sweden)

    Shamiria Ahmad

    2013-01-01

    Full Text Available A comparative study describing gas-phase propylene polymerization in fluidized-bed reactors using Ziegler-Natta catalyst is presented. The reactor behavior was explained using a two-phase model (which is based on principles of fluidization as well as simulation using the Aspen Polymers process simulator. The two-phase reactor model accounts for the emulsion and bubble phases which contain different portions of catalysts with the polymerization occurring in both phases. Both models predict production rate, molecular weight, polydispersity index (PDI and melt flow index (MFI of the polymer. We used both models to investigate the effect of important polymerization parameters, namely catalyst feed rate and hydrogen concentration, on the product polypropylene properties, such as production rate, molecular weight, PDI and MFI. Both the two-phase model and Aspen Polymers simulator showed good agreement in terms of production rate. However, the models differed in their predictions for weight-average molecular weight, PDI and MFI. Based on these results, we propose incorporating the missing hydrodynamic effects into Aspen Polymers to provide a more realistic understanding of the phenomena encountered in fluidized bed reactors for polyolefin production.

  19. A Continuous Lumping Model for Hydrocracking on a Zeolite Cata- lysts: Model Development and Parameter Identification

    OpenAIRE

    Becker, Per Julian; Celse, Benoit; Guillaume, Denis; Costa, Victor,; Bertier, Luc; Guillon, Emmanuelle; Pirngruber, Gerhard

    2016-01-01

    International audience Process models are a vital tool for the development of industrial hydrocracking units and to drive innovationof process design and novel catalysts. A hydrocracking model, based on the continuous lumpingapproach, is presented in this work. A zeolite catalyst was used for hydrocracking of pre-treated VGOfeeds. The model includes inhibition terms for organic nitrogen and NH3 gas. A total of 74 data points,from experimental runs in a fixed-bed pilot plant, have been used...

  20. Digital image analysis measurements of bed expansion and segregation dynamics in dense gas-fluidized beds

    NARCIS (Netherlands)

    Goldschmidt, M.J.V.; Link, J.M.; Mellema, S.; Kuipers, J.A.M.

    2003-01-01

    One of the most crucial steps in the development of fundamental hydrodynamic models is the validation of these models with accurate, detailed experimental data. Therefore a whole-field, non-intrusive digital image analysis technique has been developed which enables measurement of bed expansion and s

  1. Oxidative coupling of methane in a fixed bed reactor over perovskite catalyst: A simulation study using experimental kinetic model

    Institute of Scientific and Technical Information of China (English)

    Nakisa Yaghobi; Mir Hamid Reza Ghoreishy

    2008-01-01

    The oxidative coupling of methane (OCM) to ethylene over a perovskite titanate catalyst in a fixed bed reactor was studied experimentally and numerically. The two-dimensional steady state model accounted for separate energy equations for the gas and solid phases coupled with an experimental kinetic model. A lumped kinetic model containing four main species CH4, O2, COx (CO2, CO), and C2 (C2H4 and C2H6) was used with a plug flow reactor model as well. The results from the model agreed with the experimental data. The model was used to analyze the influence of temperature and feed gas composition on the conversion and selectivity of the reactor performance. The analytical results indicate that the conversion decreases, whereas, C2 selectivity increases by increasing gas hourly space velocity (GHSV) and the methane conversion also decreases by increasing the methane to oxygen ratio.

  2. Mathematical Modelling of Catalytic Fixed-Bed Reactor for Carbon Dioxide Reforming of Methane over Rh/Al2O3 Catalyst

    Directory of Open Access Journals (Sweden)

    New Pei Yee

    2008-04-01

    Full Text Available A one-dimensional mathematical model was developed to simulate the performance of catalytic fixed bedreactor for carbon dioxide reforming of methane over Rh/Al2O3 catalyst at atmospheric pressure. The reactionsinvolved in the system are carbon dioxide reforming of methane (CORM and reverse water gas shiftreaction (RWGS. The profiles of CH4 and CO2 conversions, CO and H2 yields, molar flow rate and molefraction of all species as well as reactor temperature along the axial bed of catalyst were simulated. In addition,the effects of different reactor temperature on the reactor performance were also studied. The modelscan also be applied to analyze the performances of lab-scale micro reactor as well as pilot-plant scale reactorwith certain modifications and model verification with experimental data. © 2008 BCREC UNDIP. All rights reserved.[Received: 20 August 2008; Accepted: 25 September 2008][How to Cite: N.A.S. Amin, I. Istadi, N.P. Yee. (2008. Mathematical Modelling of Catalytic Fixed-Bed Reactor for Carbon Dioxide Reforming of Methane over Rh/Al2O3 Catalyst. Bulletin of Chemical Reaction Engineering and Catalysis, 3 (1-3: 21-29. doi:10.9767/bcrec.3.1-3.19.21-29

  3. Two-dimensional numerical modelling of radiation transfer in powder beds at selective laser melting

    International Nuclear Information System (INIS)

    The radiation transfer equation is numerically solved in a layer of homogeneous absorbing scattering medium, which is equivalent to the powder bed, irradiated with a normally incident laser beam of an axially symmetric profile to estimate the spatial distribution of the deposited thermal energy. The scattering and lateral transport of laser radiation is shown to decrease the intensity of the heat source at the axis and to produce its weak tail around the laser spot. This decreases the maximum temperature in the powder bed. Narrowing the laser beam to increase the precision of selective laser melting becomes ineffective when the beam radius approaches the extinction length in the powder because it does not adequately narrow the zone of energy deposition

  4. Use of black oil simulator for coal bed methane reservoir model

    Energy Technology Data Exchange (ETDEWEB)

    Sonwa, R.; Enachescu, C.; Rohs, S. [Golder Associates GmbH, Celle (Germany)

    2013-08-01

    This paper starts from the work done by Seidle et al. (1990) and other authors on the topic of coal degasification and develops a more accurate representative naturally fractured CBM-reservoir by using a Discrete Fracture Network modeling approach. For this issue we firstly calibrate the reservoir simulator tNAVIGATOR by showing his ability to reproduce the work done by Seidle et al. and secondly generate a DFN model using FracMan in accordance with the distribution and orientation of the cleats. tNavigator was then used to simulate multiphase flow through the DFN- Model. (orig.)

  5. Coal gasification by indirect heating in a single moving bed reactor: Process development & simulation

    Directory of Open Access Journals (Sweden)

    Junaid Akhlas

    2015-10-01

    Full Text Available In this work, the development and simulation of a new coal gasification process with indirect heat supply is performed. In this way, the need of pure oxygen production as in a conventional gasification process is avoided. The feasibility and energetic self-sufficiency of the proposed processes are addressed. To avoid the need of Air Separation Unit, the heat required by gasification reactions is supplied by the combustion flue gases, and transferred to the reacting mixture through a bayonet heat exchanger installed inside the gasifier. Two alternatives for the flue gas generation have been investigated and compared. The proposed processes are modeled using chemical kinetics validated on experimental gasification data by means of a standard process simulator (Aspen PlusTM, integrated with a spreadsheet for the modeling of a special type of heat exchanger. Simulation results are presented and discussed for proposed integrated process schemes. It is shown that they do not need external energy supply and ensure overall efficiencies comparable to conventional processes while producing syngas with lower content of carbon dioxide.

  6. Hydrographic surveying and 3d modelling of river bed with Hypack

    OpenAIRE

    Krajnc, Urška

    2006-01-01

    In thesis Hydrographic surveying on river Drava is presented. Functions and characteristics of used instruments along with working methods are described. The final results are obtained from GPS, Echo sounder and Compass measurements. The practical part of the thesis is mainly focused on Hypack Max software. Necessary settings in program are summarized. All geodetic steps through software are presented and at the end the relief of the river bed is displayed.

  7. A model for complex flows of soft glassy materials with application to flows through fixed fiber beds

    KAUST Repository

    Sarkar, Arijit

    2015-11-01

    © 2015 The Society of Rheology. The soft glassy rheology (SGR) model has successfully described the time dependent simple shear rheology of a broad class of complex fluids including foams, concentrated emulsions, colloidal glasses, and solvent-free nanoparticle-organic hybrid materials (NOHMs). The model considers a distribution of mesoscopic fluid elements that hop from trap to trap at a rate which is enhanced by the work done to strain the fluid element. While an SGR fluid has a broad exponential distribution of trap energies, the rheology of NOHMs is better described by a narrower energy distribution and we consider both types of trap energy distributions in this study. We introduce a tensorial version of these models with a hopping rate that depends on the orientation of the element relative to the mean stress field, allowing a range of relative strengths of the extensional and simple shear responses of the fluid. As an application of these models we consider the flow of a soft glassy material through a dilute fixed bed of fibers. The dilute fixed bed exhibits a range of local linear flows which alternate in a chaotic manner with time in a Lagrangian reference frame. It is amenable to an analytical treatment and has been used to characterize the strong flow response of many complex fluids including fiber suspensions, dilute polymer solutions and emulsions. We show that the accumulated strain in the fluid elements has an abrupt nonlinear growth at a Deborah number of order one in a manner similar to that observed for polymer solutions. The exponential dependence of the hopping rate on strain leads to a fluid element deformation that grows logarithmically with Deborah number at high Deborah numbers. SGR fluids having a broad range of trap energies flowing through fixed beds can exhibit a range of rheological behaviors at small Deborah numbers ranging from a yield stress, to a power law response and finally to Newtonian behavior.

  8. Removal of Pb(II) ions from aqueous solution using water hyacinth root by fixed-bed column and ANN modeling.

    Science.gov (United States)

    Mitra, Tania; Singha, Biswajit; Bar, Nirjhar; Das, Sudip Kumar

    2014-05-30

    Hyacinth root was used as a biosorbent for generating adsorption data in fixed-bed glass column. The influence of different operating parameters like inlet Pb(II) ion concentration, liquid flow rate and bed height on the breakthrough curves and the performance of the column was studied. The result showed that the adsorption efficiency increased with increase in bed height and decreased with increase in inlet Pb(II) ion concentration and flow rate. Increasing the flow rate resulted in shorter time for bed saturation. The result showed that as the bed height increased the availability of more number of adsorption sites in the bed increased, hence the throughput volume of the aqueous solution also increased. The adsorption kinetics was analyzed using different models. It was observed that maximum adsorption capacity increased with increase in flow rate and initial Pb(II) ion concentration but decreased with increase in bed height. Applicability of artificial neural network (ANN) modeling for the prediction of Pb(II) ion removal was also reported by using multilayer perceptron with backpropagation, Levenberg-Marquardt and scaled conjugate algorithms and four different transfer functions in a hidden layer and a linear output transfer function. PMID:24727010

  9. Observation and simulation of heterogeneous 2D water and solute flow processes in ditch beds for subsequent catchment modelling

    Science.gov (United States)

    Dages, Cecile; Samouelian, Anatja; Lanoix, Marthe; Dollinger, Jeanne; Chakkour, Sara; Chovelon, Gabrielle; Trabelsi, Khouloud; Voltz, Marc

    2015-04-01

    Ditches are involved in the transfer of pesticide to surface and groundwaters (e.g. Louchart et al., 2001). Soil horizons underlying ditch beds may present specific soil characteristics compared to neighbouring field soils due to erosion/deposition processes, to the specific biological activities (rooting dynamic and animal habitat) in the ditches (e.g. Vaughan et al., 2008) and to management practices (burning, dredging, mowing,...). Moreover, in contrast to percolation processes in field soils that can be assumed to be mainly 1D vertical, those occurring in the ditch beds are by essence 2D or even 3D. Nevertheless, due to a lake of knowledge, these specific aspects of transfer within ditch beds are generally omitted for hydrological simulation at the catchment scale (Mottes et al., 2014). Accordingly, the aims of this study were i) to characterize subsurface solute transfer through ditch beds and ii) to determine equivalent hydraulic parameters of the ditch beds for use in catchment scale hydrological simulations. A complementary aim was to evaluate the error in predictions performed when percolation in ditches is assumed to be similar to that in the neighbouring field soil. First, bromide transfer experiments were performed on undisturbed soil column (15 cm long with a 15 cm inner-diameter), horizontally and vertically sampled within each soil horizon underlying a ditch bed and within the neighboring field. Columns were sampled at the Roujan catchment (Hérault, France), which belongs to the long term Mediterranean hydrological observatory OMERE (Voltz and Albergel, 2002). Second, for each column, a set of parameters was determined by inverse optimization with mobile-immobile or dual permeability models, with CXTFIT (Toride et al., 1999) or with HYDRUS (Simunek et al., 1998). Third, infiltration and percolation in the ditch was simulated by a 2D flow domain approach considering the 2D variation in hydraulic properties of the cross section of a ditch bed. Last

  10. An investigation of the reactivity of chars formed in fluidized-bed gasifiers: equipment development and initial tests

    Energy Technology Data Exchange (ETDEWEB)

    A. Cousins; N. Paterson; D.R. Dugwell; R. Kandiyoti [Imperial College London, London (United Kingdom). Department of Chemical Engineering

    2006-03-15

    Chars formed during air and oxygen blown gasification processes have a low reactivity. This is due to changes that occur in the structure and morphology of the original coal during heating. In part, the changes depend on conditions prevailing during the pyrolysis stage and partly on the length of time spent at peak temperature. Previous work in this laboratory has highlighted that the gasification reactivity of a char depends on the conditions of its formation. This means that chars must be prepared under realistic conditions when conducting laboratory scale reactivity studies that are intended to support a larger scale development. This is not easy to do and requires the development of dedicated methods for preparing the char. In this paper, the development of a laboratory-scale test, based on a laboratory-scale spouted bed gasifier, is described that is able to prepare chars under conditions that represent those in an air-blown gasifier. The reactivity of the prepared chars is then examined to identify how the reactivity of the char varies within the envisaged operating window of the process. A feature of this apparatus is that the char formation time is known accurately, which has required the development of novel feeding and draining mechanisms. These enable the coal particles to be injected quickly into the reactor and the sand/char bed drained and quenched rapidly after a known residence time. The extent of char deactivation can be measured with residence times between 2 and 3600 s. In this paper, the validation of the experiment is described and some preliminary results are reported. 7 refs., 10 figs., 2 tabs.

  11. Calculation of local bed to wall heat transfer in a fluidized-bed

    International Nuclear Information System (INIS)

    Surface to bed heat transfer in a fluidized-bed largely depends upon its local and global hydrodynamical behavior including particle velocity, particle trajectory, gas velocity, and void fraction. In this study, a computer program was developed in order to calculate the local bed to wall heat transfer, by accounting for the local and global instantaneous hydrodynamics of the bed. This is accomplished by utilizing the CHEMFLUB computer program. This information at a given location is interpreted so that the most appropriate heat transfer model is utilized for each time increment. These instantaneous heat transfer coefficient for the given location. Repeating the procedure for different locations, a space average heat transfer coefficient is also calculated. This report briefly summarizes the various heat transfer models employed and gives sample computer results reporting the case study for Mickley - Trilling's experimental set-up. Comparisons with available experimental data and correlations are also provided in order to compare and evaluate the computer results

  12. Recent advances in development of the fluidized bed and fixed bed in the anthraquinone route%蒽醌法流化床与固定床的发展趋势

    Institute of Scientific and Technical Information of China (English)

    王伟建; 潘智勇; 李文林; 郑博; 宗保宁

    2016-01-01

    In this paper, the research progress of the fixed bed catalyst and fluidized bed catalyst and their advantages and disadvantages are introduced. The influences of the factors during Ni-based catalyst and Pd-based catalyst preparation process on their catalytic performance are introduced. Researches on the catalysts with high catalytic activity and selectivity for the hydrogenation reaction are reviewed. The characteristics and research progress of hydrogenation reactors are also introduced and compared. Based on the detailed comparisons between the fluidized bed and fixed bed, it is concluded that the production with fluidized bed has many advantages of relative lower cost, less anthraquinone degradation, high catalyst utilization rate and high hydrogenation efficiency. From an application perspective, the differences between fluidized bed and fixed bed are introduced. The paper finally points out that the production with fluidized bed has become the developing tendency of the anthraquinone route and will replace the process with fixed bed. The practical research difficulties, developing trend and some suggestions for the development of the anthraquinone route are presented.%综述了国内外蒽醌法流化床与固定床催化剂的研究进展,并且重点介绍了它们的优点和缺点,总结出各种因素对镍催化剂和钯催化剂催化氢化性能的影响,同时单独介绍了蒽醌加氢催化剂在选择性、活性等方面的内容。还介绍了氢化反应器的特点和研究进展,并进行了比较。在详细比较了流化床与固定床生产技术优缺点的基础上,总结出流化床相比于固定床技术具有生产成本低、蒽醌降解少、催化剂利用率高、氢效高等优点。与此同时,简单介绍了蒽醌法流化床和固定床反应器应用方面相互比较的数据,得出流化床在大规模装置生产方面具有明显优势。最后指出蒽醌法流化床技术将取代固定床技术成为

  13. Characterizing the sediment bed in terms of resistance to motion: Toward an improved model of saltation thresholds for aeolian transport

    Science.gov (United States)

    Edwards, Brandon L.; Namikas, Steven L.

    2015-12-01

    Models of aeolian transport thresholds generate a wide range of predictions, and error in threshold modeling leads to uncertainty in predicting aeolian events. This paper proposes a new characterization of the representative grain size for use in prediction of transport thresholds. This characterization is based on the distribution of resistance to motion in the sediment bed. The traditional grain size distribution uses a mean diameter to represent the sediment bed. However, the distribution of inertial forces resisting motion is not linearly proportional to the distribution of grain diameters, so that an arithmetic mean does not adequately represent the distribution of the resisting forces. A simple relation of shear stress to weight force is used to represent the threshold condition. Based on comparison with threshold observations drawn from the literature, the model provides reliable predictions of threshold stress and shear velocity for dry quartz grains over a wide range of grain sizes. Given that the dataset was drawn from studies employing a variety of experimental conditions and techniques, and that these studies spanned a range of nearly eight decades, the model is considered to provide a robust approximation of threshold conditions.

  14. Modeling oxy-fuel combustion in a 3D circulating fluidized bed using the hybrid Euler–Lagrange approach

    International Nuclear Information System (INIS)

    Results of experiments and numerical simulations of the coal oxy-fuel combustion process in an experimental circulating fluidized bed (CFB) are presented in this paper. The simulations were carried out using the hybrid Euler–Lagrange approach to model the dense particle transport in the CFB pilot installation combined with a model of the combustion process. The main aim of presented work is to demonstrate the applicability of the hybrid Euler–Lagrange technique for modeling the particle transport process in the CFB, which also includes the coal combustion process modeling. To the best knowledge of the authors, there is no implementation of the hybrid Euler–Lagrange Dense Discrete Phase Model (DDPM) approach for modeling the CFB in the 3D domain with combustion process simulations, which is available in literature. Both the experiments and numerical simulations were carried out for three oxidizer compositions O2/CO2, i.e. 21, 30, and 35% of the oxygen volume fraction. In order to investigate the numerical model sensitivity when combustion conditions change, additional tests were evaluated for case with 35% of the oxygen for three excess oxygen ratios equal to 1.05, 1.15, and 1.25. The important aspect of modeling the radiative heat transfer during the fluidization process combined with oxy-fuel combustion was also investigated. The set of numerical simulations was performed for different radiation model configurations. The numerical results were compared with the temperature profile measured within the combustion chamber of the pilot test rig. - Highlights: • Hybrid Euler–Lagrange approach has been used for modelling particle transport. • Numerical results have been validated against experimental data. • New strategy for resolving particle transport in circulating fluidized bed has been shown

  15. Approach to development of high flux research reactor with pebble-bed core

    International Nuclear Information System (INIS)

    Full text: The research nuclear reactor of a basin-type IRT with the designed power of 1 MW was put into operation in 'Sosny' settlement not far from Minsk-city in the Republic of Belarus in 1962. In 1971 after its modernization the power was increased up to 4 MW and maximum density of neutron flux in the core was: Thermal 5·1013 neutr./cm2.s Fast (E>0.8 MeV) 2·1013 neutr./cm2.s The reactor has been used for carrying out investigations in the field of solid-state physics, radiation construction materials, radiobiology, gaseous chemically reacting coolants and others. After the Chernobyl NPP accident, in the former USSR the requirements on safety of nuclear reactors have become sufficiently stricter. As to some parameters these requirements became the same as for reactors of nuclear power plants. In this connection the reactor in 'Sosny' settlement did not answer these new requirements by a number of performances such as seismicity of building, efficiency of control and protection system, corrosion in the reactor vessel and others, and it was shutdown in 1987 and its decommissioning was performed during 1988-1999. At the Joint Institute of Power and Nuclear Research -'SOSNY' have been carried out investigations on feasibility of creation of the research reactor with pebble-bed core. The concept of such reactor supposes using the following technical approaches: - Using as fuel the brought sphere micro fuel elements with the diameter of 500-750 mkm to an industrial level; - Organization of reactor operation in the regime with minimum possible fueling with 235U; - Implementation of hydraulic loading - unloading of micro fuel elements with the frequency of one or several days. Physical calculations of the core were carried out with the help of MCU-RFFI program based on the Monte-Carlo method. Two configurations of the pebble-bed core in the high flux reactor have been considered. The first configuration is the core with a neutron trap and an annular fuel layer formed

  16. COMPUTATIONAL FLUID DYNAMICS FOR DENSE GAS-SOLID FLUIDIZED BEDS: A MULTI-SCALE MODELING STRATEGY

    Institute of Scientific and Technical Information of China (English)

    M. A. van der Hoef; M. van Sint Annaland; J. A. M. Kuipers

    2005-01-01

    Dense gas-particle flows are encountered in a variety of industrially important processes for large scale production of fuels, fertilizers and base chemicals. The scale-up of these processes is often problematic and is related to the intrinsic complexities of these flows which are unfortunately not yet fully understood despite significant efforts made in both academic and industrial research laboratories. In dense gas-particle flows both (effective) fluid-particle and (dissipative) particle-particle interactions need to be accounted for because these phenomena to a large extent govern the prevailing flow phenomena, i.e. the formation and evolution of heterogeneous structures. These structures have significant impact on the quality of the gas-solid contact and as a direct consequence thereof strongly affect the performance of the process. Due to the inherent complexity of dense gas-particles flows, we have adopted a multi-scale modeling approach in which both fluid-particle and particle-particle interactions can be properly accounted for. The idea is essentially that fundamental models, taking into account the relevant details of fluid-particle (lattice Boltzmann model) and particle-particle (discrete particle model) interactions, are used to develop closure laws to feed continuum models which can be used to compute the flow structures on a much larger (industrial) scale. Our multi-scale approach (see Fig. 1 ) involves the lattice Boltzmann model, the discrete particle model, the continuum model based on the kinetic theory of granular flow,and the discrete bubble model. In this paper we give an overview of the multi-scale modeling strategy, accompanied by illustrative computational results for bubble formation. In addition, areas which need substantial further attention will be highlighted.

  17. EXPERIMENTAL AND COMPUTATIONAL MODELLING OF 3-D FLOW AND BED SHEAR STRESSES DOWNSTREAM FROM A MULTIPLE DUCT TIDAL BARRAGE

    OpenAIRE

    Jeffcoate, Penelope

    2013-01-01

    The near-field depth-varying velocities and resulting bed stresses downstream from a tidal barrage have not previously been studied. The flow through and downstream of a row of seven open draft tubes in a barrage has been investigated through laboratory experiment in a wide flume, 3-D RANS CFD simulation and 2-D depth-averaged computation. When there is no turbine representation and hence negligible swirl in the draft tubes, agreement between the experiments and 3-D modelling is shown to be g...

  18. Criticality calculations on realistic modelling of pebble-bed HTR-PROTEUS as a validation for the woodcock tracking method implemented in the MORET 5 Monte Carlo code

    International Nuclear Information System (INIS)

    The MORET code is a three dimensional Monte Carlo criticality code. It is designed to calculate the effective multiplication factor (keff) of any geometrical configuration as well as the reaction rates in the various volumes and the neutron leakage out of the system. A recent development for the MORET code consists of the implementation of an alternate neutron tracking method known as the pseudo-scattering tracking method. This method has been successfully implemented in the MORET code and its performances have been tested by the means of an extensive parametric study on very simple geometrical configurations. In this context, the goal of the present work is to validate the pseudo-scattering method against realistic configurations. In this perspective, pebble-bed cores are particularly well-adapted cases to model as they exhibit large amount of volumes stochastically arranged on two different levels (the pebbles in the core and the TRISO particles inside each pebble). This paper will introduce the techniques and methods used to model pebble-bed cores in a realistic way. The results of the criticality calculations, as well as the pseudo-scattering tracking method performance in terms of computation time will be presented. (authors)

  19. Modeling of replenishment of sediments on a water-worked gravel bed channel

    Science.gov (United States)

    Juez, Carmelo; Battisacco, Elena; Schleiss, Anton J.; Franca, Mário J.

    2016-04-01

    The presence of dams causes a sediment deficit downstream. Hence, the surface structure of the riverbeds is altered by this interruption in the sediment continuity and The presence of dams causes a sediment deficit downstream. The surface structure of the riverbed is altered by this interruption in the sediment continuity and becoming water-worked. The main morphological effects verified in these cases are thus the generation of armored layers, bank instability, riverbed incision, changes in the channel width and coarsening of the bed particles. These results impact on the riverbed topographic variability and structure of the bedforms. Surface complexity is thus reduced with further ecological implications. The lack of fine material and surface complexity leads to the loss of aquatic and riparian habitats, limiting the possibilities for fish spawning. Nowadays, the revitalization of disturbed river reaches forms an integral part of river management. Sediment transport and associated channel morphology are understood as key processes for recreating and maintaining aquatic ecosystems. For this purpose several replenishment techniques have been considered in order to supply sediments lacking in the downstream reaches. The replenishment techniques can be seen as a pulse-like addition of sedimentary material that initially disturbs the channel. In this work, the response of the flow to the complementary material which is added in the channel is studied by means of the 2D shallow water equations in combination with the Exner equation. The numerical scheme is built by means of a weakly-coupled treatment between the hydrodynamic and morphodynamic equations leading to an efficient and robust solution. Computational outcomes are compared with experimental data obtained from several replenishment configurations studied in the laboratory. The results are analyzed by means of: (i) temporal evolution of the material spreading, (ii) occupational ratio along the channel which is

  20. Characterization of limestone reactivity with SO{sub 2} and sulfur capture modelling under fluidized bed combustion conditions; Bestaemning av kalkstensreaktivitet med avseende paa SO{sub 2} och modellering av avsvavling foer foerbraenning i fluidiserad baedd

    Energy Technology Data Exchange (ETDEWEB)

    Mattisson, T. [Chalmers Univ. of Technology and Univ. of Goeteborg, Goeteborg (Sweden). Dept. of Inorganic Chemistry; Lyngfelt, A. [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Energy Conversion

    1996-12-01

    During combustion of fossil fuels, SO{sub 2} is released to the atmosphere. Because of environmental concern with acid rain, the capture of SO{sub 2} is a very important process. Fluidized bed combustion (FBC) is a combustion method where limestone may be added to the furnace chamber to capture SO{sub 2} as the stable product CaSO{sub 4}. In the present work a relatively simple laboratory method has been developed for characterizing limestone reactivity with SO{sub 2}. The reactivity data from such investigations are used, together with residence time and particle size distribution, in a sulfur capture model for fluidized bed boilers that predicts the sulfur capture as a function of the Ca/S molar ratio. In addition, the model predicts the conversion of CaO to CaSO{sub 4} for all particle sizes present in a boiler. The model was developed and verified using data from two boilers, a 12 and a 40 MW circulating fluidized bed boiler, and showed reasonable agreement for both boilers. In addition to the development of a sulfur capture model, the effects of SO{sub 2} and CO{sub 2} concentrations, particle size, temperature variations, and reducing conditions on the sulfation reaction was studied using a fixed-bed quartz reactor. The sulfation reaction was also studied for long periods of time, up to 60 hours. This was done because of the long residence times of certain particle sizes that may exist in a fluidized bed boiler. From the parameter study it was found that particle size and variations between oxidizing and reducing conditions had a large effect on the sulfation behaviour. The investigation of long sulfation times showed that the reaction continued even at high degrees of conversion, although at a very slow rate. CO{sub 2} concentration had a moderate effect on the sulfation reaction while temperature variations showed no effect on the final conversion between CaO and CaSO{sub 4}. 29 refs, 25 figs, 4 tabs

  1. Application of CFD Modeling to Hydrodynamics of CycloBio Fluidized Sand Bed in Recirculating Aquaculture Systems

    Institute of Scientific and Technical Information of China (English)

    LIU Yao; SONG Xiefa; LIANG Zhenlin; PENG Lei

    2014-01-01

    To improve the efficiency of a CycloBio fluidized sand bed (CB FSB) in removal of dissolved wastes in recirculating aquaculture systems, the hydrodynamics of solid-liquid flow was investigated using computational fluid dynamics (CFD) modeling tools. The dynamic characteristics of silica sand within the CB FSB were determined using three-dimensional, unsteady-state simula-tions with the granular Eulerian multiphase approach and the RNG k-ε turbulence model, and the simulation results were validated using available lab-scale measurements. The bed expansion of CB FSB increased with the increase in water inflow rate in numerical simulations. Upon validation, the simulation involving 0.55 mm particles, the Gidaspow correlation for drag coefficient model and the Syamlal-O’Brien correlation for kinetic granular viscosity showed the closest match to the experimental results. The volume frac-tion of numerical simulations peaked as the wall was approached. The hydrodynamics of a pilot-scale CB FSB was simulated in or-der to predict the range of water flow to avoid the silica sand overflowing. The numerical simulations were in agreement with the experimental results qualitatively and quantitatively, and thus can be used to study the hydrodynamics of solid-liquid multiphase flow in CB FSB, which is of importance to the design, optimization, and amplification of CB FSBs.

  2. Batch and continuous fixed-bed column biosorption of thorium(IV) from aqueous solutions. Equilibrium and dynamic modeling

    International Nuclear Information System (INIS)

    Biosorption of thorium(IV) from aqueous solution by Cystoseira indica alga was investigated in batch and fixed-bed column experiments. In the batch study the effects of pH and initial concentration were investigated. The optimum pH for Th(IV) biosorption was found to be 3.5. The experimental isotherms obtained at different pH conditions were analyzed using three two-parameter models and three three-parameter models. Among the two-parameter models the Langmuir model and among the three-parameter models the Redlich-Peterson model vividly described the equilibrium data. The results showed that C. indica alga is a homogeneous biosorbent and Th(IV) biosorption is a favorable and physical process. The maximum biosorption capacity from the Langmuir model was 151.3, 195.7 and 120.6 mg/g at pH 2.5, 3.5 and 4.5, respectively. The continuous isotherm obtained from the column data was modeled by the Langmuir model and the maximum biosorption capacity was 283.8 mg/g. The experimental data were fitted by the use of an analytical and a numerical model, namely Clark and mass transfer models. The results showed that the mass transfer model adequately described the experimental data. Sensitivity analysis revealed that the value of kin has more effect than the axial dispersion coefficient (D z) on the shape of breakthrough curve. (author)

  3. 坐浴床的研制与临床应用%Development and Clinical Application of Sitz Bed Bath

    Institute of Scientific and Technical Information of China (English)

    颜峰; 卢克群

    2014-01-01

    Objective To explore the development and the effect of clinical application of sitz bath bed.Methods Patients were randomly divided into three groups , A, B and C.The patients in group A take a squatting bath directly , and patients in group B and C adopt the sitz bath chair and sitz bath bed respectively.Then the duration time , wound healing time , comfort and satisfaction level of the sitz bath in the three groups were compared.Results The duration time , wound healing time , comfort and satisfaction level of sitz bath in the group C and group A have a significant difference ( P<0.01 );Group C and group B have significant difference in wound healing time , comfort and satisfaction level ( P <0.05 ).Conclusion The sitz bath bed is convenient and comfortable and plays an active role in clinical treatment , and it is worth popularization and clinical application.%目的:探讨坐浴床的研制及临床应用效果。方法将患者随机分为A、B、C 3组,A组直接蹲在地上,B组坐在普通坐浴椅上,C组患者坐在坐浴床上,比较3组患者每次坐浴持续时间、切口愈合时间、舒适度和满意度的情况。结果 C组与A组患者坐浴持续时间、切口愈合时间、舒适度、满意度的比较差异有统计学意义( P<0.01);C组与B组患者在坐浴持续时间上无明显差异(P>0.05),在切口愈合时间、舒适度和满意度比较差异有统计学意义(P<0.05)。结论本坐浴床使用方便、舒适,坐浴效果好,值得临床推广应用。

  4. Life cycle Prognostic Model Development and Initial Application Results

    Energy Technology Data Exchange (ETDEWEB)

    Jeffries, Brien; Hines, Wesley; Nam, Alan; Sharp, Michael; Upadhyaya, Belle [The University of Tennessee, Knoxville (United States)

    2014-08-15

    In order to obtain more accurate Remaining Useful Life (RUL) estimates based on empirical modeling, a Lifecycle Prognostics algorithm was developed that integrates various prognostic models. These models can be categorized into three types based on the type of data they process. The application of multiple models takes advantage of the most useful information available as the system or component operates through its lifecycle. The Lifecycle Prognostics is applied to an impeller test bed, and the initial results serve as a proof of concept.

  5. Modeling the operation of a three-stage fluidized bed reactor for removing CO2 from flue gases.

    Science.gov (United States)

    Mohanty, C R; Meikap, B C

    2011-03-15

    A bubbling counter-current multistage fluidized bed reactor for the sorption of carbon dioxide (CO(2)) by hydrated lime particles was simulated employing a two-phase model, with the bubble phase assumed to be in plug flow, and the emulsion phase in plug flow and perfectly mixed flow conditions. To meet prescribed permissible limit to emit carbon dioxide from industrial flue gases, dry scrubbing of CO(2) was realized. For the evaluation, a pilot plant was built, on which also the removal efficiency of CO(2) was verified at different solids flow rates. The model results were compared with experimental data in terms of percentage removal efficiency of carbon dioxide. The comparison showed that the EGPF model agreed well with the experimental data satisfactorily. The removal efficiency was observed to be mainly influenced by flow rates of adsorbent and CO(2) concentration. PMID:21255918

  6. Full-Wave Algorithm to Model Effects of Bedding Slopes on the Response of Subsurface Electromagnetic Geophysical Sensors near Unconformities

    CERN Document Server

    Sainath, Kamalesh

    2015-01-01

    We propose a full-wave pseudo-analytical numerical electromagnetic (EM) algorithm to model subsurface induction sensors, traversing planar-layered geological formations of arbitrary EM material anisotropy and loss, which are used, for example, in the exploration of hydrocarbon reserves. Unlike past pseudo-analytical planar-layered modeling algorithms that impose parallelism between the formation's bed junctions however, our method involves judicious employment of Transformation Optics techniques to address challenges related to modeling arbitrarily-oriented, relative slope (i.e., tilting) between said junctions. The algorithm exhibits this flexibility, both with respect to anisotropy in the formation layers as well as junction tilting, via employing special planar slabs that coat each "flattened" (i.e., originally tilted) planar interface, locally redirecting the incident wave within the coating slabs to cause wave fronts to interact with the flattened interfaces as if they were still tilted with a specific, ...

  7. Bed rest and immunity

    Science.gov (United States)

    Sonnenfeld, Gerald; Aviles, Hernan; Butel, Janet S.; Shearer, William T.; Niesel, David; Pandya, Utpal; Allen, Christopher; Ochs, Hans D.; Blancher, Antoine; Abbal, Michel

    2007-02-01

    Space flight has been shown to result in altered immune responses. The current study was designed to investigate this possibility by using the bed rest model of some space flight conditions. A large number of women are included as subjects in the study. The hypothesis being tested is: 60 days head-down tilt bed rest of humans will affect the immune system and resistance to infection. Blood, urine and saliva samples will be obtained from bed rest subjects prior to, at intervals during, and after completion of 60 days of head-down tilt bed rest. Leukocyte blastogenesis, cytokine production and virus reactivation will be assessed. The ability of the subjects to respond appropriately to immunization with the neoantigen bacteriophage φX-174 will also be determined. Bed rest is being carried out at MEDES, Toulouse France, and the University of Texas Medical Branch, Galveston, TX. The studies to be carried out in France will also allow assessment of the effects of muscle/bone exercise and nutritional countermeasures on the immune system in addition to the effects of bed rest.

  8. Development and Implementation of 3-D, High Speed Capacitance Tomography for Imaging Large-Scale, Cold-Flow Circulating Fluidized Bed

    Energy Technology Data Exchange (ETDEWEB)

    Marashdeh, Qussai [Tech4imaging LLC, Columbus, OH (United States)

    2013-02-01

    A detailed understanding of multiphase flow behavior inside a Circulating Fluidized Bed (CFB) requires a 3-D technique capable of visualizing the flow field in real-time. Electrical Capacitance Volume Tomography (ECVT) is a newly developed technique that can provide such measurements. The attractiveness of the technique is in its low profile sensors, fast imaging speed and scalability to different section sizes, low operating cost, and safety. Moreover, the flexibility of ECVT sensors enable them to be designed around virtually any geometry, rendering them suitable to be used for measurement of solid flows in exit regions of the CFB. Tech4Imaging LLC has worked under contract with the U.S. Department of Energy's National Energy Technology Laboratory (DOE NETL) to develop an ECVT system for cold flow visualization and install it on a 12 inch ID circulating fluidized bed. The objective of this project was to help advance multi-phase flow science through implementation of an ECVT system on a cold flow model at DOE NETL. This project has responded to multi-phase community and industry needs of developing a tool that can be used to develop flow models, validate computational fluid dynamics simulations, provide detailed real-time feedback of process variables, and provide a comprehensive understating of multi-phase flow behavior. In this project, a complete ECVT system was successfully developed after considering different potential electronics and sensor designs. The system was tested at various flow conditions and with different materials, yielding real-time images of flow interaction in a gas-solid flow system. The system was installed on a 12 inch ID CFB of the US Department of Energy, Morgantown Labs. Technical and economic assessment of Scale-up and Commercialization of ECVT was also conducted. Experiments conducted with larger sensors in conditions similar to industrial settings are very promising. ECVT has also the potential to be developed for imaging multi

  9. Cretaceous oceanic red beds (CORBs): Different time scales and models of origin

    Science.gov (United States)

    Hu, Xiumian; Scott, Robert W.; Cai, Yuanfeng; Wang, Chengshan; Melinte-Dobrinescu, Mihaela C.

    2012-12-01

    The Cretaceous oceanic red bed (CORB) is a newly opened window on global oceanic and climate changes during the Cretaceous greenhouse world. As a result of the International Geoscience Programmes 463, 494 and 555 (2002-2010), CORBs have been documented in many places by numerous publications. The principle goal of this paper is to summarize scientific advances on CORBs including chronostratigraphy, sedimentology, mineralogy, elemental and isotopic geochemistry, and their relationship to oceanic anoxic events (OAEs), palaeoclimate and palaeoceanography. We propose a new geochemical classification of the CORBs using CaO, Al2O3 and SiO2 values, which lithologically refer to marly, clayey, and cherty CORBs respectively. Detailed mineralogical studies indicate that hematite, goethite and Mn2 +-bearing calcite are the minerals imparting the red color of CORBs. Hematite clusters of several to tens of nanometers in the calcite structure are the main cause of the red coloring of limestones, and the Mn2 +-bearing calcite gives additional red color. Goethite was thought to form originally with hematite, and was subsequently transformed to hematite during late diagenesis. Chronostratigraphic data allow the distinction of two groups of CORBs by their durations. Short-term CORBs are generally less than 1 myr in duration, and seem to be on the scale of Milankovitch cycles. During the deposition of Cretaceous reddish intervals from ODP cores 1049 and 1050, low primary productivity and relatively high surface temperature resulted in low organic carbon flux into the sediments which reduced oxygen demand and produced oxidizing early diagenetic conditions. In such an oxic environment, iron oxides formed imparting the reddish color. The long-term CORBs' depositional events lasted longer than 4 myr, and may be a possible consequence of the OAEs. Enhanced amounts of organic carbon and pyrite burial during and after the OAEs would have resulted in a large and abrupt fall in atmospheric CO

  10. A simple model for the dispersion of radioactive wastes dumped on the deep-sea bed

    International Nuclear Information System (INIS)

    A simple model has been developed for the dispersion of radioactive materials in a closed and finite ocean. It allows for the simultaneous action of both diffusion and horizontal (but not vertical) advection, and thus avoids the major limitations of previous models such as that of Webb and Morley. It is sufficiently versatile to handle non-Fickian diffusion and radioactive decay, but requires numerical integration using some semi-empirical form for the Green's function of diffusion from a point source. The model has been used to estimate equilibrium concentrations of radioactive materials in sea water arising from the continuous release of material from a dump on the bottom of the deep ocean, using parameters appropriate for the North Atlantic. It is found that except under rather extreme conditions the surface concentrations do not exceed the long-term average value which would be established in a perfectly mixed ocean. The concentrations are also rather insensitive to the values of the diffusion and advection parameters used, except for that for vertical diffusion, but depend strongly on the overall removal rate of material from the ocean, including processes other than radioactive decay. It is suggested that safety assessments of deep-sea dumping should utilize estimates of the environmental capacities of the oceans based on the long-term 'well-mixed' average concentrations (which are very easily calculated) using a safety factor of no more than ten to allow for the possible effects of pluming and upwelling. In so far as their results are comparable, the present model yields estimates which are close to those of the Webb-Morley model for overall half-lives between 30 and 3000 years, but which become increasingly more restrictive for longer-lived materials. (author)

  11. Breakdown development in cover beds, and landscape features induced by intrastratal gypsum karst

    OpenAIRE

    Andrejchuk V.; Klimchouk A.

    1996-01-01

    Intrastratal karst is by far the predominant gypsum karst type. Its development may begin in deep-seated settings within rocks already buried by younger strata, and it proceeds increasingly rapidly as uplift brings gypsum sequences into progressively shallower positions. Such development commonly occurs under confined (artesian) hydrogeological conditions, that subsequently change to open conditions (phreatic-water table-vadose). The general evolutionary line of intrastratal karst is typified...

  12. An integrated mathematical model for chemical oxygen demand (COD) removal in moving bed biofilm reactors (MBBR) including predation and hydrolysis.

    Science.gov (United States)

    Revilla, Marta; Galán, Berta; Viguri, Javier R

    2016-07-01

    An integrated mathematical model is proposed for modelling a moving bed biofilm reactor (MBBR) for removal of chemical oxygen demand (COD) under aerobic conditions. The composite model combines the following: (i) a one-dimensional biofilm model, (ii) a bulk liquid model, and (iii) biological processes in the bulk liquid and biofilm considering the interactions among autotrophic, heterotrophic and predator microorganisms. Depending on the values for the soluble biodegradable COD loading rate (SCLR), the model takes into account a) the hydrolysis of slowly biodegradable compounds in the bulk liquid, and b) the growth of predator microorganisms in the bulk liquid and in the biofilm. The integration of the model and the SCLR allows a general description of the behaviour of COD removal by the MBBR under various conditions. The model is applied for two in-series MBBR wastewater plant from an integrated cellulose and viscose production and accurately describes the experimental concentrations of COD, total suspended solids (TSS), nitrogen and phosphorous obtained during 14 months working at different SCLRs and nutrient dosages. The representation of the microorganism group distribution in the biofilm and in the bulk liquid allow for verification of the presence of predator microorganisms in the second reactor under some operational conditions. PMID:27085154

  13. Variability of bed drag on cohesive beds under wave action

    Science.gov (United States)

    Safak, Ilgar

    2016-01-01

    Drag force at the bed acting on water flow is a major control on water circulation and sediment transport. Bed drag has been thoroughly studied in sandy waters, but less so in muddy coastal waters. The variation of bed drag on a muddy shelf is investigated here using field observations of currents, waves, and sediment concentration collected during moderate wind and wave events. To estimate bottom shear stress and the bed drag coefficient, an indirect empirical method of logarithmic fitting to current velocity profiles (log-law), a bottom boundary layer model for combined wave-current flow, and a direct method that uses turbulent fluctuations of velocity are used. The overestimation by the log-law is significantly reduced by taking turbulence suppression due to sediment-induced stratification into account. The best agreement between the model and the direct estimates is obtained by using a hydraulic roughness of 10  m in the model. Direct estimate of bed drag on the muddy bed is found to have a decreasing trend with increasing current speed, and is estimated to be around 0.0025 in conditions where wave-induced flow is relatively weak. Bed drag shows an increase (up to fourfold) with increasing wave energy. These findings can be used to test the bed drag parameterizations in hydrodynamic and sediment transport models and the skills of these models in predicting flows in muddy environments.

  14. Ash management in circulating fluidized bed combustors

    Energy Technology Data Exchange (ETDEWEB)

    K. Redemann; E.-U. Hartge; J. Werther [Hamburg University of Technology, Hamburg (Germany). Institute of Solids Process Engineering and Particle Technology

    2008-12-15

    Ash management in fluidized bed combustion systems means keeping the particle size distribution of the bed inventory in a given range. A dynamic particle population balancing model was developed for this purpose. It was successfully applied to a refuse-derived fuel fired combustor and a coal-fired circulating fluidized bed combustor. Both were large-scale commercial units. The model uses the concept of the attrited ash particle size distribution which represents the particle size distribution of the attrited ash including the generated fines and replaces the consideration of the particle attrition in the model calculations. The model offers the possibility to gain additional information about the particle size distributions and the solids mass flows at any location of the fluidized bed system. In addition, the model provides information about the dynamic behavior of the plant and about mean residence times of particle size classes in the plant. Uncertainties about the ash formation characteristics of fuels make the management of the bed inventory a very important issue. In this context the population balancing model is used to predict the plant behavior under various operating conditions. The results of the calculations carried out give useful information about the possibilities to manage the ash inventory of such a plant. It could be shown that the recirculation of a fine fraction of the bottom drain solids is a very effective method to manage the particle size distribution of the bed inventory. The calculation results further reveal that the mean residence time of particles is strongly dependent on their size. 21 refs., 19 figs., 4 tabs.

  15. Ground-penetrating imaging radar development for bridge deck and road bed inspection

    Energy Technology Data Exchange (ETDEWEB)

    Warhus, J.P.; Mast, J.E.; Nelson, S.D.; Johansson, E.M.

    1993-05-01

    Ground-penetrating imaging radar (GPIR) is proposed for large-area inspection of concrete and concrete/asphalt composite bridge decks and roadways. This technique combines ground-penetrating radar (GPR) with unique image reconstruction algorithms developed for identification and characterization of subsurface flaws and structural features. New data acquisition hardware and image reconstruction techniques, under development at LLNL, offer the possibility for reliable and efficient, high-resolution subsurface imaging through the use of improved ultra-wideband transmitters, antennas, and arrays, and enhanced image- and signal-processing software. A field test of a limited-capability prototype system is planned for FY-93, as is completion of a conceptual design for a practical inspection system. A follow-on program for FY-94 would focus on development and demonstration of an advanced bridge inspection system prototype based on the conceptual design completed during FY-93.

  16. Development of Ada language control software for the NASA power management and distribution test bed

    Science.gov (United States)

    Wright, Ted; Mackin, Michael; Gantose, Dave

    1989-01-01

    The Ada language software developed to control the NASA Lewis Research Center's Power Management and Distribution testbed is described. The testbed is a reduced-scale prototype of the electric power system to be used on space station Freedom. It is designed to develop and test hardware and software for a 20-kHz power distribution system. The distributed, multiprocessor, testbed control system has an easy-to-use operator interface with an understandable English-text format. A simple interface for algorithm writers that uses the same commands as the operator interface is provided, encouraging interactive exploration of the system.

  17. Numerical simulation of ceramic breeder pebble bed thermal creep behavior

    International Nuclear Information System (INIS)

    The evolution of ceramic breeder pebble bed thermal creep deformation subjected to an external load and a differential thermal stress was studied using a modified discrete numerical code previously developed for the pebble bed thermomechanical evaluation. The rate change of creep deformation was modeled at the particle contact based on a diffusion creep mechanism. Numerical results of strain histories have compared reasonably well with those of experimentally observed data at 740 C using activation energy of 180 KJ/mole. Calculations also show that, at this activation energy level, a particle bed at an elevated temperature of 800 C may cause undesired local sintering at a later time when it is subjected to an external load of 6.3 MPa. Thus, by tracking the stress histories inside a breeder pebble bed the numerical simulation provides an indication of whether the bed may encounter an undesired condition under a typical operating condition. (orig.)

  18. Bifurcation instability and chute cutoff development in meandering gravel-bed rivers

    NARCIS (Netherlands)

    Van Dijk, Wout M.; Schuurman, Filip; Van de Lageweg, Wietse I.; Kleinhans, Maarten G.

    2014-01-01

    Chute cutoffs reduce sinuosity of meandering rivers and potentially cause a transition from a single to a multiple channel river. The channel bifurcation of the main channel and the mouth of the incipient chute channel controls sediment and flow partitioning and development of the chute. Recent chan

  19. Experimental studies and CFD simulations of conical spouted bed hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z.

    2008-07-01

    This thesis involved both experimental research and mathematical modelling of the hydrodynamics of conical spouted beds. Although conical spouted beds are commonly used for drying suspensions, solutions and pasty materials, they can also be used for catalytic partial oxidation of methane to synthesis gas, coal gasification and liquefaction, and pyrolysis of sawdust. Pressure transducers and static pressure probes were used in the experimental studies to investigate the evolution of the internal spout and the local static pressure distribution. Optical fibre probes were used to measure axial particle velocity profiles and voidage profiles. The gas mixing behaviour inside a conical spouted bed was examined using a step trace injection technique in which helium was used as the tracer and thermal conductivity cells were used as the detectors. For the mathematical modelling, a stream-tube model based on the bed structure inside a conical spouted bed was proposed to simulate partial spouting states. An adjustable parameter was introduced into the model to enable total pressure drop prediction under different operating conditions, and to estimate axial superficial gas velocity profiles and gauge pressure profiles. A mathematical model based on characteristics of conical spouted beds and FLUENT software was also developed and validated using measured experimental data. The proposed CFD model can simulate both stable spouting and partial spouting states, with an adjustable solids-phase source term. The effect of all possible factors on simulation results were investigated, including the fluid inlet profile, solid bulk viscosity, frictional viscosity, restitution coefficient, exchange coefficient, and solid phase source term. In addition to simulating the gas mixing behaviours inside a conical spouted bed, the new CFD model simulated cylindrical packed beds and cylindrical fluidized beds in one code package.

  20. A stochastic model for early placental development.

    KAUST Repository

    Cotter, Simon L

    2014-08-01

    In the human, placental structure is closely related to placental function and consequent pregnancy outcome. Studies have noted abnormal placental shape in small-for-gestational-age infants which extends to increased lifetime risk of cardiovascular disease. The origins and determinants of placental shape are incompletely understood and are difficult to study in vivo. In this paper, we model the early development of the human placenta, based on the hypothesis that this is driven by a chemoattractant effect emanating from proximal spiral arteries in the decidua. We derive and explore a two-dimensional stochastic model, and investigate the effects of loss of spiral arteries in regions near to the cord insertion on the shape of the placenta. This model demonstrates that disruption of spiral arteries can exert profound effects on placental shape, particularly if this is close to the cord insertion. Thus, placental shape reflects the underlying maternal vascular bed. Abnormal placental shape may reflect an abnormal uterine environment, predisposing to pregnancy complications. Through statistical analysis of model placentas, we are able to characterize the probability that a given placenta grew in a disrupted environment, and even able to distinguish between different disruptions.

  1. Severe accident assessment: development of the gas flux dryout model for cooling of core debris

    International Nuclear Information System (INIS)

    A model for boiling and dryout in a particle debris bed with permeable boundary conditions is developed and compared with various dryout models, and incorporated into the modified MARCH/KAERI computer code to analyze for the combined mechanisms of thermal interactions. Comparative and parametric studies show that the particle sizes have an important effect on debris bed cooling but not apparent effect on the magnitude of peak pressure in the containment building. It is also shown that the gas flux model represents an improvement of the combined thermal interactions among core debris, water and gas over the previous models. (Author)

  2. Recharge-induced groundwater flow over a plane sloping bed: Solutions for steady and transient flow using physical and numerical models

    Science.gov (United States)

    Chapman, T. G.

    2005-07-01

    The free surface profile and outflow hydrograph for groundwater under conditions of steady uniform recharge followed by recession have been studied in viscous fluid model tests, using a sloping bed with a gradient of 0.2. The data have been compared with the nonlinear Boussinesq model and a modification of that model simulating the outflow seepage surface, obtained from a finite difference solution of the free boundary problem. It is shown that for a given bed slope, there is close to a linear relationship between outflow and storage raised to a power n, where n ranges from almost 2 for zero slopes to just above 1 at a gradient of 0.3. There is also a simple relationship between outflow and storage in the final stage of recession, when a drainage front occurs on the bed. These results lead to simple algorithms for prediction of the outflow under unsteady recharge conditions.

  3. Analysis of the fluid-bed stability of FCC catalysts at high temperature in terms of bed elasticity

    Institute of Scientific and Technical Information of China (English)

    Paola Lettieri; Luca Mazzer

    2008-01-01

    The effect of temperature on the fluid-bed stability of three FCC catalysts has been analyzed through considerations on fluid-bed elasticity. Experimental findings on the effect of temperature on the elasticity modulus at minimum bubbling conditions, (E)mb, were analyzed using the hydrodynamic fluid-bed stability model developed by Foscolo and Gibilaro (1984) and adopting the interparticle-forces-based stability criterion developed by Mutsers and Rietema (1977). For both models, the parameters which control changes in (E)mb with temperature are discussed, in order to establish the origin of the fluid-bed elasticity and analyze the ability of these models to discriminate between the relative importance of the hydrodynamic and interparticle forces on the stability of the fluidized catalysts.

  4. Cost and cost effectiveness of long-lasting insecticide-treated bed nets - a model-based analysis

    Directory of Open Access Journals (Sweden)

    Pulkki-Brännström Anni-Maria

    2012-04-01

    Full Text Available Abstract Background The World Health Organization recommends that national malaria programmes universally distribute long-lasting insecticide-treated bed nets (LLINs. LLINs provide effective insecticide protection for at least three years while conventional nets must be retreated every 6-12 months. LLINs may also promise longer physical durability (lifespan, but at a higher unit price. No prospective data currently available is sufficient to calculate the comparative cost effectiveness of different net types. We thus constructed a model to explore the cost effectiveness of LLINs, asking how a longer lifespan affects the relative cost effectiveness of nets, and if, when and why LLINs might be preferred to conventional insecticide-treated nets. An innovation of our model is that we also considered the replenishment need i.e. loss of nets over time. Methods We modelled the choice of net over a 10-year period to facilitate the comparison of nets with different lifespan (and/or price and replenishment need over time. Our base case represents a large-scale programme which achieves high coverage and usage throughout the population by distributing either LLINs or conventional nets through existing health services, and retreats a large proportion of conventional nets regularly at low cost. We identified the determinants of bed net programme cost effectiveness and parameter values for usage rate, delivery and retreatment cost from the literature. One-way sensitivity analysis was conducted to explicitly compare the differential effect of changing parameters such as price, lifespan, usage and replenishment need. Results If conventional and long-lasting bed nets have the same physical lifespan (3 years, LLINs are more cost effective unless they are priced at more than USD 1.5 above the price of conventional nets. Because a longer lifespan brings delivery cost savings, each one year increase in lifespan can be accompanied by a USD 1 or more increase in price

  5. NASA Electric Aircraft Test Bed (NEAT) Development Plan - Design, Fabrication, Installation

    Science.gov (United States)

    Dyson, Rodger W.

    2016-01-01

    As large airline companies compete to reduce emissions, fuel, noise, and maintenance costs, it is expected that more of their aircraft systems will shift from using turbofan propulsion, pneumatic bleed power, and hydraulic actuation, to instead using electrical motor propulsion, generator power, and electrical actuation. This requires new flight-weight and flight-efficient powertrain components, fault tolerant power management, and electromagnetic interference mitigation technologies. Moreover, initial studies indicate some combination of ambient and cryogenic thermal management and relatively high bus voltages when compared to state of practice will be required to achieve a net system benefit. Developing all these powertrain technologies within a realistic aircraft architectural geometry and under realistic operational conditions requires a unique electric aircraft testbed. This report will summarize existing testbed capabilities located in the U.S. and details the development of a unique complementary testbed that industry and government can utilize to further mature electric aircraft technologies.

  6. ACS air bearing test-bed design

    OpenAIRE

    Glitt, Sascha

    2010-01-01

    This thesis is about the construction and design of a new air bearing test-bed to verify the programmed ACS attitude control algorithm and to validate the ACS MATLAB/SimuLink¬ model of NPSAT1, the second small satellite currently under development at the Naval Postgraduate School Space Systems Academic Group. The software was already verified and validated using a comparable air bearing test-bed. But due to changes in hardware from commercial magnetic torque rods to custom, NPS-built, magneti...

  7. Experiment and modeling for the separation of guaifenesin enantiomers using simulated moving bed and Varicol units.

    Science.gov (United States)

    Gong, Rujin; Lin, Xiaojian; Li, Ping; Yu, Jianguo; Rodrigues, Alirio E

    2014-10-10

    The separation of guaifenesin enantiomers by both simulated moving bed (SMB) process and Varicol process was investigated experimentally and theoretically, where the columns were packed with cellulose tris 3,5-dimethylphenylcarbamate (Chiralcel OD) stationary phase and a mixture of n-hexane and ethanol was used as mobile phase. The operation conditions were designed based on the separation region with the consideration of mass transfer resistance and axial dispersion, and the experiments to separate guaifenesin enantiomers were carried out on VARICOL-Micro unit using SMB process with the column configuration of 1/2/2/1 and Varicol process with the column configuration of 1/1.5/1.5/1, respectively. Single enantiomer with more than 99.0% purity was obtained in both processes with the productivity of 0.42 genantiomer/dcm(3) CSP for SMB process and 054 genantiomer/dcm(3) CSP for Varicol process. These experimental results obtained from SMB and Varicol processes were compared with those reported from literatures. In addition, according to the numerical simulation, the effects of solid-film mass transfer resistance and axial dispersion on the internal profiles were discussed, and the effect of column configuration on the separation performance of SMB and Varicol processes was analyzed for a few columns system. The feasibility and efficiency for the separation of guaifenesin enantiomers by SMB and Varicol processes were evaluated. PMID:25047823

  8. Formal deduction of the Saint-Venant-Exner model including arbitrarily sloping sediment beds and associated energy

    CERN Document Server

    Fernández-Nieto, E D; Narbona-Reina, G; Zabsonré, J D

    2015-01-01

    In this work we present a deduction of the Saint-Venant-Exner model through an asymptotic analysis of the Navier-Stokes equations. A multi-scale analysis is performed in order to take into account that the velocity of the sediment layer is smaller than the one of the fluid layer. This leads us to consider a shallow water type system for the fluid layer and a lubrication Reynolds equation for the sediment one. This deduction provides some improvements with respect to the classical Saint-Venant-Exner model: (i) the deduced model has an associated energy. Moreover, it allows us to explain why classical models do not have an associated energy and how to modify them in order to recover a model with this property. (ii) The model incorporates naturally a necessary modification that must be taken into account in order to be applied to arbitrarily sloping beds. Furthermore, we show that this modification is different of the ones considered classically, and that it coincides with a classical one only if the solution ha...

  9. Tumour bed irradiation of human tumour xenografts in a nude rat model using a common X-ray tube

    International Nuclear Information System (INIS)

    Studies that investigate the radiation of human tumour xenografts require an appropriate radiation source and highly standardized conditions during radiation. This work reports on the design of standardized irradiation device using a commercially available X-ray tube with a custom constructed lead collimator with two circular apertures and an animal bed plate, permitting synchronous irradiation of two animals. Dosimetry and the corresponding methodology for radiotherapy of human non-small cell lung cancer xenograft tumours transplanted to and growing subcutaneously on the right lower limb in a nude rat model were investigated. Procedures and results described herein prove the feasibility of use of the device, which is applicable for any investigation involving irradiation of non-tumorous and tumorous lesions in small animals. (author)

  10. Tumour bed irradiation of human tumour xenografts in a nude rat model using a common X-ray tube

    Indian Academy of Sciences (India)

    S V Tokalov; W Enghardt; N Abolmaali

    2010-06-01

    Studies that investigate the radiation of human tumour xenografts require an appropriate radiation source and highly standardized conditions during radiation. This work reports on the design of a standardized irradiation device using a commercially available X-ray tube with a custom constructed lead collimator with two circular apertures and an animal bed plate, permitting synchronous irradiation of two animals. Dosimetry and the corresponding methodology for radiotherapy of human non-small cell lung cancer xenograft tumours transplanted to and growing subcutaneously on the right lower limb in a nude rat model were investigated. Procedures and results described herein prove the feasibility of use of the device, which is applicable for any investigation involving irradiation of non-tumorous and tumorous lesions in small animals.

  11. Physiological water model development

    Science.gov (United States)

    Doty, Susan

    1993-01-01

    The water of the human body can be categorized as existing in two main compartments: intracellular water and extracellular water. The intracellular water consists of all the water within the cells and constitutes over half of the total body water. Since red blood cells are surrounded by plasma, and all other cells are surrounded by interstitial fluid, the intracellular compartment has been subdivided to represent these two cell types. The extracellular water, which includes all of the fluid outside of the cells, can be further subdivided into compartments which represent the interstitial fluid, circulating blood plasma, lymph, and transcellular water. The interstitial fluid surrounds cells outside of the vascular system whereas plasma is contained within the blood vessels. Avascular tissues such as dense connective tissue and cartilage contain interstitial water which slowly equilibrates with tracers used to determine extracellular fluid volume. For this reason, additional compartments are sometimes used to represent these avascular tissues. The average size of each compartment, in terms of percent body weight, has been determined for adult males and females. These compartments and the forces which cause flow between them are presented. The kidneys, a main compartment, receive about 25 percent of the cardiac output and filters out a fluid similar to plasma. The composition of this filtered fluid changes as it flows through the kidney tubules since compounds are continually being secreted and reabsorbed. Through this mechanism, the kidneys eliminate wastes while conserving body water, electrolytes, and metabolites. Since sodium accounts for over 90 percent of the cations in the extracellular fluid, and the number of cations is balanced by the number of anions, considering the renal handling sodium and water only should sufficiently describe the relationship between the plasma compartment and kidneys. A kidney function model is presented which has been adapted from a

  12. DEVELOPMENT OF PRESSURIZED CIRCULATIONG FLUIDIZED BED PARTIAL GASIFICATION MODULE(PGM)

    Energy Technology Data Exchange (ETDEWEB)

    Archie Robertson

    2003-04-17

    Foster Wheeler Power Group, Inc. is working under US Department of Energy 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% and produce 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 amount of syngas and char produced by the PGM can be tailored to fit the production objectives of the overall plant, i.e., power generation, clean liquid fuel production, chemicals production, etc. Hence, PGM is a robust building block that offers all the advantages of coal gasification but in a more user-friendly form; it is also fuel flexible in that it can use alternative fuels such as biomass, sewerage sludge, etc. This report describes the work performed during the January 1--March 31, 2003 time period.

  13. Educational Game Development Models

    Directory of Open Access Journals (Sweden)

    Mehmet Emin Korkusuz

    2013-12-01

    Full Text Available Recent research on the subject shows that students spend more time on computer games than other activities such as reading book or watching TV. It is possible that this time-consuming activity can become much more effective by educator-game sector cooperation. Which type of game students prefer mostly; how the educational content can be articulated the games without diminishing the playability and enjoyableness of it; and the impact of the competition in the games on process and students are just several titles examined in the studies. This scope presents the types of computer game, qualities of educational games, and educational games designs which are recommended for developing educational games. It also presents a set of knowledge about the importance of educational games in mathematics and physic education, and some studies on this field. In the scope, some strategies, about educational game development process, are recommended educators and software developers in the sector who intend to develop educational games based on the literature.

  14. Development of methane and nitrous oxide emission factors for the biomass fired circulating fluidized bed combustion power plant.

    Science.gov (United States)

    Cho, Chang-Sang; Sa, Jae-Hwan; Lim, Ki-Kyo; Youk, Tae-Mi; Kim, Seung-Jin; Lee, Seul-Ki; Jeon, Eui-Chan

    2012-01-01

    This study makes use of this distinction to analyze the exhaust gas concentration and fuel of the circulating fluidized bed (CFB) boiler that mainly uses wood biomass, and to develop the emission factors of Methane (CH(4)), Nitrous oxide (N(2)O). The fuels used as energy sources in the subject working sites are Wood Chip Fuel (WCF), RDF and Refused Plastic Fuel (RPF) of which heating values are 11.9 TJ/Gg, 17.1 TJ/Gg, and 31.2 TJ/Gg, respectively. The average concentrations of CH(4) and N(2)O were measured to be 2.78 ppm and 7.68 ppm, respectively. The analyzed values and data collected from the field survey were used to calculate the emission factor of CH(4) and N(2)O exhausted from the CFB boiler. As a result, the emission factors of CH(4) and N(2)O are 1.4 kg/TJ (0.9-1.9 kg/TJ) and 4.0 kg/TJ (2.9-5.3 kg/TJ) within a 95% confidence interval. Biomass combined with the combustion technology for the CFB boiler proved to be more effective in reducing the N(2)O emission, compared to the emission factor of the CFB boiler using fossil fuel. PMID:23365540

  15. Development of Methane and Nitrous Oxide Emission Factors for the Biomass Fired Circulating Fluidized Bed Combustion Power Plant

    Directory of Open Access Journals (Sweden)

    Chang-Sang Cho

    2012-01-01

    Full Text Available This study makes use of this distinction to analyze the exhaust gas concentration and fuel of the circulating fluidized bed (CFB boiler that mainly uses wood biomass, and to develop the emission factors of Methane (CH4, Nitrous oxide (N2O. The fuels used as energy sources in the subject working sites are Wood Chip Fuel (WCF, RDF and Refused Plastic Fuel (RPF of which heating values are 11.9 TJ/Gg, 17.1 TJ/Gg, and 31.2 TJ/Gg, respectively. The average concentrations of CH4 and N2O were measured to be 2.78 ppm and 7.68 ppm, respectively. The analyzed values and data collected from the field survey were used to calculate the emission factor of CH4 and N2O exhausted from the CFB boiler. As a result, the emission factors of CH4 and N2O are 1.4 kg/TJ (0.9–1.9 kg/TJ and 4.0 kg/TJ (2.9–5.3 kg/TJ within a 95% confidence interval. Biomass combined with the combustion technology for the CFB boiler proved to be more effective in reducing the N2O emission, compared to the emission factor of the CFB boiler using fossil fuel.

  16. Modeling Auxin-regulated Development

    OpenAIRE

    Krupinski, Pawel; Jönsson, Henrik

    2010-01-01

    The phytohormone auxin plays an essential role in many aspects of plant growth and development. Its patterning, intercellular transport, and means of signaling have been extensively studied both in experiments and computational models. Here, we present a review of models of auxin-regulated development in different plant tissues. This includes models of organ initiation in the shoot apical meristem, development of vascular strands in leafs and stems, and auxin-related functioning in roots. The...

  17. Models for Sustainable Regional Development

    DEFF Research Database (Denmark)

    Rasmussen, Lauge Baungaard

    The chapter presents a model for integrated cross-cultural knowledge building and entrepreneurship. In addtion, narrative and numeric simulations methods are suggested to promote a further development and implementation of the model in China.......The chapter presents a model for integrated cross-cultural knowledge building and entrepreneurship. In addtion, narrative and numeric simulations methods are suggested to promote a further development and implementation of the model in China....

  18. Fluidised bed heat exchangers

    International Nuclear Information System (INIS)

    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

  19. Three phase Eulerian-granular model applied on numerical simulation of non-conventional liquid fuels combustion in a bubbling fluidized bed

    OpenAIRE

    Nemoda Stevan Đ.; Mladenović Milica R.; Paprika Milijana J.; Erić Aleksandar M.; Grubor Borislav D.

    2016-01-01

    The paper presents a two-dimensional CFD model of liquid fuel combustion in bubbling fluidized bed. The numerical procedure is based on the two-fluid Euler-Euler approach, where the velocity field of the gas and particles are modeled in analogy to the kinetic gas theory. The model is taking into account also the third - liquid phase, as well as its interaction with the solid and gas phase. The proposed numerical model comprise energy equations for all three...

  20. Mathematical simulation of working processes in the furnace of a circulating fluidized bed boiler

    Energy Technology Data Exchange (ETDEWEB)

    V.A. Dvoinishnikov; A.V. Larkov [Moscow Power Engineering Institute, Moscow (Russian Federation)

    2009-01-15

    A software system developed for simulating and calculating boiler furnaces with circulating fluidized beds is described. The main principles on which the system is constructed are outlined, and the physical and mathematical models of processes in circulating fluidized bed furnaces are described together with the calculation algorithm. Results from a study of analyzing the effect the grinding fineness of initial fuel particles has on the processes in a circulating fluidized bed furnace are presented.

  1. Use of an in vitro flat-bed biofilm model to measure biologically active anti-odour compounds.

    Science.gov (United States)

    Saad, S; Hewett, K; Greenman, J

    2013-09-01

    The objective of this study was to demonstrate the utility of a modified flat-bed perfusion biofilm matrix system for testing toothpaste formulations directly, without dilution, as a layer in direct contact with the biofilm matrix surface. Final biofilm yields and volatile sulphur compounds (VSC) biogenesis were measured to show the relative efficacy of toothpaste formulations. Diffusion characteristics of the flat-bed system to exposure with Meridol® tooth and tongue gel (TTG; 1,400 ppm F(-) from amine fluoride/stannous fluoride, 0.5 % zinc lactate, oral malodour counteractives) was assessed using a bioluminescent target species Escherichia coli Nissle 1917/pGLITE coupled with a low-light photon camera to visualise the kill kinetics. Tongue-flora derived, mixed culture biofilms (n = 4) received 5, 15 and 30 min treatment with TTG, respectively, to determine the optimum time of exposure. VSC biogenesis was measured from headspace samples by gas chromatography prior to and following treatment of two daily applications for 4 days of treatment (TTG), positive control (CHX gel) and negative controls (placebo and sham treatment). Viable counts were performed at the end of experiments by destructive sampling of the biofilms and plating onto selective and non-selective agar. Following a single treatment with TTG, the E. coli biofilm with lux target gave >50 % reduction of luminescence within 2 to 3 h before recovering to a steady state over 10 h, suggesting biofilm cidal activity rather biostasis. For mixed culture biofilms, 15- and 30-min treatment exposure with TTG gave almost identical reductions in final biofilm yields. For comparing efficacy of treatments, biofilms treated with TTG gave greatest reductions in both pre-post levels of H2S (P < 0.01) and CH3SH (P < 0.05) and population yields at the end of the experiments (P < 0.001) compared to placebo and positive control. The in vitro flat-bed perfusion model may be used to replicate many of

  2. Numerical simulation of nuclear pebble bed configurations

    Energy Technology Data Exchange (ETDEWEB)

    Shams, A., E-mail: shams@nrg.eu [Nuclear Research and Consultancy Group (NRG), Petten (Netherlands); Roelofs, F., E-mail: roelofs@nrg.eu [Nuclear Research and Consultancy Group (NRG), Petten (Netherlands); Komen, E.M.J., E-mail: komen@nrg.eu [Nuclear Research and Consultancy Group (NRG), Petten (Netherlands); Baglietto, E., E-mail: emiliob@MIT.EDU [Massachusetts Institute of Technology (MIT) (United States)

    2015-08-15

    the reference q-DNS. This paper reports a detailed comparison of LES, Hybrid (RANS/LES) and RANS models with the reference q-DNS. These simulations are performed for a well-defined single face cubic centred pebble configuration. The obtained flow and thermal fields are extensively analyzed to understand the flow physics in such complex flow regime. Furthermore, lessons learned from these simulations are summarized in the form of guidelines for such complex flow configurations. In addition, following these guidelines, a strategy has been developed to perform large eddy simulations of a realistic limited sized random pebble bed.

  3. Numerical simulation of nuclear pebble bed configurations

    International Nuclear Information System (INIS)

    the reference q-DNS. This paper reports a detailed comparison of LES, Hybrid (RANS/LES) and RANS models with the reference q-DNS. These simulations are performed for a well-defined single face cubic centred pebble configuration. The obtained flow and thermal fields are extensively analyzed to understand the flow physics in such complex flow regime. Furthermore, lessons learned from these simulations are summarized in the form of guidelines for such complex flow configurations. In addition, following these guidelines, a strategy has been developed to perform large eddy simulations of a realistic limited sized random pebble bed

  4. Hydrodynamic analysis of a three-fluidized bed reactor cold flow model for chemical looping hydrogen generation. Pressure characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Zhipeng; Xiang, Wenguo; Chen, Shiyi; Wang, Dong [Southeast Univ., Nanjing (China). School of Energy and Environment

    2013-07-01

    Chemical looping hydrogen generation (CLHG) can produce pure hydrogen with inherent separation of CO{sub 2} from fossils fuel. The process involves a metal oxide, as an oxygen carrier, such as iron oxide. The CLHG system consists of three reactors: a fuel reactor (FR), a steam reactor (SR) and an air reactor (AR). In the FR, the fuel gases react with iron oxides (hematite Fe{sub 2}O{sub 3}, magnetite Fe{sub 3}O{sub 4}, wuestite FeO), generating reduced iron oxides (FeO or even Fe), and with full conversion of gaseous fuels, pure CO{sub 2} can be obtained after cooling the flue gas from the fuel reactor; in the SR, FeO and Fe reacts with steam to generate magnetite (Fe{sub 3}O{sub 4}) and H{sub 2}, the latter representing the final target product of the process; in the AR, the magnetite is oxidized back to hematite which is used in another cycle. A cold flow model of three-fluidized bed for CLHG corresponding to 50 KW hot units has been built. A major novelty of this facility is the compact fuel reactor, which integrates a bubble and a fast fluidized bed to avoid the incomplete conversion of the fuel gas caused by the thermodynamics equilibrium. In order to study the pressure characteristics and the solids concentration of the system, especially in the fuel reactor, the gas velocity of three reactors, gas flow of L-type value, total solids inventory (TSI) and the secondary air of fuel reactor were varied. Results show that the pressure and the solids concentration are strongly influenced by the fluidizing-gas velocity of three reactors. Moreover, the entrainment of the upper part of fuel reactor increases as the total solids inventory increases, and the operating range of the FR can be changed by introducing secondary air or increasing the total solids inventory.

  5. Models of scientific software development

    OpenAIRE

    Segal, Judith

    2008-01-01

    Over the past decade, I have performed several field studies with scientists developing software either on their own or together with software engineers. Based on these field study data, I identify a model of scientific software development as practiced in many scientific laboratories and communities. This model does not fit the standard software engineering models. For example, the tasks of requirement elicitation and software evaluation are not clearly delineated. Nevertheless, it appears t...

  6. The adsorption of copper in a packed-bed of chitosan beads: modeling, multiple adsorption and regeneration.

    Science.gov (United States)

    Osifo, Peter O; Neomagus, Hein W J P; Everson, Raymond C; Webster, Athena; vd Gun, Marius A

    2009-08-15

    In this study, exoskeletons of Cape rock lobsters were used as raw material in the preparation of chitin that was successively deacetylated to chitosan flakes. The chitosan flakes were modified into chitosan beads and the beads were cross-linked with glutaraldehyde in order to study copper adsorption and regeneration in a packed-bed column. Five consecutive adsorption and desorption cycles were carried out and a chitosan mass loss of 25% was observed, after the last cycle. Despite the loss of chitosan material, an improved efficiency in the second and third cycles was observed with the adsorbent utilizing 97 and 74% of its adsorbent capacity in the second and third cycles, respectively. The fourth and fifth cycles, however, showed a decreased efficiency, and breakage of the beads was observed after the fifth cycle. In the desorption experiments, 91-99% of the adsorbed copper was regenerated in the first three cycles. It was also observed that the copper can be regenerated at a concentration of about a thousand fold the initial concentration. The first cycle of adsorption could be accurately described with a shrinking core particle model combined with a plug flow column model. The input parameters for this model were determined by batch characterization methods, with as only fitting parameter, the effective diffusion coefficient of copper in the bead. PMID:19321260

  7. The adsorption of copper in a packed-bed of chitosan beads: Modeling, multiple adsorption and regeneration

    International Nuclear Information System (INIS)

    In this study, exoskeletons of Cape rock lobsters were used as raw material in the preparation of chitin that was successively deacetylated to chitosan flakes. The chitosan flakes were modified into chitosan beads and the beads were cross-linked with glutaraldehyde in order to study copper adsorption and regeneration in a packed-bed column. Five consecutive adsorption and desorption cycles were carried out and a chitosan mass loss of 25% was observed, after the last cycle. Despite the loss of chitosan material, an improved efficiency in the second and third cycles was observed with the adsorbent utilizing 97 and 74% of its adsorbent capacity in the second and third cycles, respectively. The fourth and fifth cycles, however, showed a decreased efficiency, and breakage of the beads was observed after the fifth cycle. In the desorption experiments, 91-99% of the adsorbed copper was regenerated in the first three cycles. It was also observed that the copper can be regenerated at a concentration of about a thousand fold the initial concentration. The first cycle of adsorption could be accurately described with a shrinking core particle model combined with a plug flow column model. The input parameters for this model were determined by batch characterization methods, with as only fitting parameter, the effective diffusion coefficient of copper in the bead.

  8. The adsorption of copper in a packed-bed of chitosan beads: Modeling, multiple adsorption and regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Osifo, Peter O., E-mail: petero@vut.ac.za [Department of Chemical Engineering, Vaal University of Technology, P/Bag X021, Vanderbijlpark 1900 (South Africa); Neomagus, Hein W.J.P.; Everson, Raymond C. [School of Chemical and Minerals Engineering, North-West University, P/Bag X6001, Potchefstroom 2520 (South Africa); Webster, Athena [University of Utah, Chemistry Department, Salt Lake City, UT 84112 (United States); Gun, Marius A. vd [Sulzer Elbar B.V., Spikweien 36, NL-5943 AD Lomm (Netherlands)

    2009-08-15

    In this study, exoskeletons of Cape rock lobsters were used as raw material in the preparation of chitin that was successively deacetylated to chitosan flakes. The chitosan flakes were modified into chitosan beads and the beads were cross-linked with glutaraldehyde in order to study copper adsorption and regeneration in a packed-bed column. Five consecutive adsorption and desorption cycles were carried out and a chitosan mass loss of 25% was observed, after the last cycle. Despite the loss of chitosan material, an improved efficiency in the second and third cycles was observed with the adsorbent utilizing 97 and 74% of its adsorbent capacity in the second and third cycles, respectively. The fourth and fifth cycles, however, showed a decreased efficiency, and breakage of the beads was observed after the fifth cycle. In the desorption experiments, 91-99% of the adsorbed copper was regenerated in the first three cycles. It was also observed that the copper can be regenerated at a concentration of about a thousand fold the initial concentration. The first cycle of adsorption could be accurately described with a shrinking core particle model combined with a plug flow column model. The input parameters for this model were determined by batch characterization methods, with as only fitting parameter, the effective diffusion coefficient of copper in the bead.

  9. Particle flow of ceramic breeder pebble beds in bi-axial compression experiments

    International Nuclear Information System (INIS)

    Pebble beds of Tritium breeding ceramic material are investigated within the framework of developing solid breeder blankets for future nuclear fusion power plants. For the thermo-mechanical characterisation of such pebble beds, bed compression experiments are the standard tools. New bi-axial compression experiments on 20 and 30 mm high pebble beds show pebble flow effects much more pronounced than in previous 10 mm beds. Owing to the greater bed height, conditions are reached where the bed fails in cross direction and unhindered flow of the pebbles occurs. The paper presents measurements for the orthosilicate and metatitanate breeder materials that are envisaged to be used in a solid breeder blanket. The data are compared with calculations made with a Drucker-Prager soil model within the finite-element code ABAQUS, calibrated with data from other experiments. It is investigated empirically whether internal bed friction angles can be determined from pebble beds of the considered heights, which would simplify, and broaden the data base for, the calibration of the Drucker-Prager pebble bed models

  10. Erosion of heat exchanger tubes in fluidized beds. Annual report, 1990

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, E.K.; Flemmer, R.L.C.

    1991-01-01

    This final report describes the activities of the 3-year project entitled ``Erosion of Heat Exchanger Tubes In Fluidized Beds.`` which was completed at the end of 1990. Project accomplishments include the collection of a substantial body of wear data In a 24in. {times} 24in. fluidized bed, comparative wear results In a 6in. {times} 6in. fluidized bed, the development of a dragometer and the collection of a comprehensive set of drag force data in the 24in. {times} 24in. bed, Fast Fourier Transform (FFT) analysis of bubble probe data to establish dominant bubble frequencies in the 24in. {times} 24in. bed, the use of a heat flux gauge for measurement of heat transfer coefficients in the 24in. {times} 24in. bed and the modeling of the tube wear in the 24in. {times} 24in. bed. Analysis of the wear data from the 24in. square bed indicates that tube wear increases with increase in superficial velocity, and with increase in tube height. The latter effect is a result of the tubes higher up in the bed seeing greater movement of dense phase than tubes lower down In the bed. In addition, tube wear was found to decrease with increase in particle size, for constant superficial velocity. Three models of tube wear were formulated and provided acceptable prediction of wear when compared with the experimental data.

  11. Global- and local-scale characterisation of bed surface structure in coarse-grained alluvial rivers

    Science.gov (United States)

    Powell, Mark; Ockelford, Annie; Nguyen, Thao; Wood, Jo; Rice, Steve; Reid, Ian; Tate, Nick

    2013-04-01

    It is widely recognised that adjustments in bed surface grain size (texture) and grain arrangement (structure) exert significant controls on the stability of coarse-grained alluvial rivers. Modifications to bed surface texture and structure occur during active sediment transport and are mediated by the process of mobile armouring which concentrates coarser-than-average particles on the surface and organises them into a variety of grain- and bedform-scale configurations. Textural aspects of surface armouring are well understood to the extent that sediment transport models can be used to predict the size distribution of armours that develop under different sediment supply regimes and shear stresses. Research has also found that the adjustment of bed surface grain size is often patchy and that the development of finer-grained and coarser-grained areas of the bed has important implications for both the rate and grain size of transported sediment. The structural aspects of stream-bed armouring, however, are less well understood, largely because of the difficulty of recognising and characterising bedforms and bed-structures that have dimensions similar to their constituent particles. Moreover, bed structure is generally parameterised using global scale descriptors of the bed surface such that information on the spatial heterogeneity of the structure is lost. The aim of this poster is to characterise the structural characteristics of water-worked river gravels, paying particular attention to quantifying the spatial heterogeneity of those characteristics using local scale descriptors. Results reported from a number of flume experiments designed to simulate the spatio-temporal evolution of bed configurations (surface texture and structure) as the system adjusts to a condition of equilibrium transport are used to evaluate the spatial variability of bed surface structure and explore its significance for modelling sediment transport rates in gravel-bed rivers. Keywords: bed

  12. A Pilot-scale Demonstration of Reverse Osmosis Unit for Treatment of Coal-bed Methane Co-produced Water and Its Modeling

    Institute of Scientific and Technical Information of China (English)

    钱智; 刘新春; 余志晟; 张洪勋; 琚宜文

    2012-01-01

    This study presents the first demonstration project in China for treatment of coal-bed methane(CBM) co-produced water and recycling.The work aims to provide a research and innovation base for solving the pollution problem of CBM extraction water.The reverse osmosis(RO) unit is applied to the treatment of CBM co-produced water.The results indicate that system operation is stable,the removal efficiency of the total dissolved solids(TDS) is as high as 97.98%,and Fe,Mn,and F-are almost completely removed.There is no suspended solids(SS) detected in the treated water.Furthermore,a model for the RO membrane separation process is developed to describe the quantitative relationship between key physical quantities-membrane length,flow velocity,salt concentration,driving pressure and water recovery rate,and the water recovery restriction equation based on mass balance is developed.This model provides a theoretical support for the RO system design and optimization.The TDS in the CBM co-produced water are removed to meet the "drinking water standards" and "groundwater quality standards" of China and can be used as drinking water,irrigation water,and livestock watering.In addition,the cost for treatment of CBM co-produced water is assessed,and the RO technology is an efficient and cost-effective treatment method to remove pollutants.

  13. Biosorption of cadmium(II) ions by citrus peels in a packed bed column: effect of process parameters and comparison of different breakthrough curve models

    Energy Technology Data Exchange (ETDEWEB)

    Chatterjee, Abhijit; Schiewer, Silke [Department of Civil and Environmental Engineering, University of Alaska Fairbanks, Fairbanks, AK (United States)

    2011-09-15

    The efficiency of low cost citrus peels as biosorbents for removal of cadmium ions from aqueous solution was investigated in a fixed bed column, a process that could be applied to treat industrial wastewaters similar to commonly used ion exchange columns. Effluent concentration versus time profiles (i.e., breakthrough curves) were experimentally determined in a laboratory-scale packed bed column for varying operational parameters such as flow rate (2, 9, and 15.5 mL/min), influent cadmium concentration (5, 10, and 15 mg/L), and bed height (24, 48, and 72 cm) at pH 5.5. Column operation was most efficient for empty bed contact times of at least 10 min, which were apparently necessary for mass transfer. While the sorption capacity was largely unaffected by operational variables, the Thomas (Th) rate constant increased with the flow rate, and slightly decreased with increasing column length. Three widely used semi-mechanistic models (Th, Bohart-Adams, and Yoon-Nelson) were shown to be equivalent and the generalized model was compared with a two-parameter empirical model (dose-response). The latter was found to be able to better simulate the breakthrough curve in the region of breakthrough and saturation. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Using Natural Stable Calcium Isotopes to Rapidly Assess Changes in Bone Mineral Balance Using a Bed Rest Model to Induce Bone Loss

    Science.gov (United States)

    Morgan, J. L. L.; Skulan, J. L.; Gordon, G. E.; Smith, Scott M.; Romaniello, S. J.; Anbar, A. D.

    2012-01-01

    Metabolic bone diseases like osteoporosis result from the disruption of normal bone mineral balance (BMB) resulting in bone loss. During spaceflight astronauts lose substantial bone. Bed rest provides an analog to simulate some of the effects of spaceflight; including bone and calcium loss and provides the opportunity to evaluate new methods to monitor BMB in healthy individuals undergoing environmentally induced-bone loss. Previous research showed that natural variations in the Ca isotope ratio occur because bone formation depletes soft tissue of light Ca isotopes while bone resorption releases that isotopically light Ca back into soft tissue (Skulan et al, 2007). Using a bed rest model, we demonstrate that the Ca isotope ratio of urine shifts in a direction consistent with bone loss after just 7 days of bed rest, long before detectable changes in bone mineral density (BMD) occur. The Ca isotope variations tracks changes observed in urinary N-teleopeptide, a bone resorption biomarker. Bone specific alkaline phosphatase, a bone formation biomarker, is unchanged. The established relationship between Ca isotopes and BMB can be used to quantitatively translate the changes in the Ca isotope ratio to changes in BMD using a simple mathematical model. This model predicts that subjects lost 0.25 0.07% ( SD) of their bone mass from day 7 to day 30 of bed rest. Given the rapid signal observed using Ca isotope measurements and the potential to quantitatively assess bone loss; this technique is well suited to study the short-term dynamics of bone metabolism.

  15. Bed expansion crucible tests

    International Nuclear Information System (INIS)

    The Am/Cm program will vitrify the americium and curium currently stored in F-canyon. A batch flowsheet has been developed (with non-radioactive surrogate feed in place of the F-canyon solution) and tested full-scale in the 5-inch Cylindrical Induction Melter (CIM) facility at TNX. During a normal process run, a small bed expansion occurs when oxygen released from reduction of cerium (IV) oxide to cerium (III) oxide is trapped in highly viscous glass. The bed expansion is characterized by a foamy layer of glass that slowly expands as the oxygen is trapped and then dissipates when the viscosity of the foam becomes low enough to allow the oxygen to escape. Severe bed expansions were noted in the 5-inch CIM when re-heating after an interlock during the calcination phase of the heat cycle, escaping the confines of the melter vessel. In order to better understand the cause of the larger than normal bed expansion and to develop mitigating techniques, a series of three crucible tests were conducted

  16. Development of a numerical 2-dimensional beach evolution model

    DEFF Research Database (Denmark)

    Baykal, Cüneyt

    2014-01-01

    to compute the nearshore depth-averaged wave-induced current velocities and mean water level changes, a sediment transport model to compute the local total sediment transport rates occurring under the action of wind waves, and a bottom evolution model to compute the bed level changes in time based on......This paper presents the description of a 2-dimensional numerical model constructed for the simulation of beach evolution under the action of wind waves only over the arbitrary land and sea topographies around existing coastal structures and formations. The developed beach evolution numerical model...... is composed of 4 submodels: a nearshore spectral wave transformation model based on an energy balance equation including random wave breaking and diffraction terms to compute the nearshore wave characteristics, a nearshore wave-induced circulation model based on the nonlinear shallow water equations...

  17. The development and use of a laboratory scale reactor to study aspects of gasification in an air blown fluidised bed

    Energy Technology Data Exchange (ETDEWEB)

    Cousins, A.; Zhuo, Y.; Reed, G.P.; Paterson, N.; Dugwell, D.R.; Kandiyoti, R. [Imperial College London, London (United Kingdom). Dept of Chemical Engineering

    2006-07-01

    A laboratory scale reactor has been used to study aspects of air blown, spouted bed gasifiers. The effects of operating conditions on the release of fuel-N has been studied using both coal and sewage sludge. The work has clarified the reactions involved and shown that steam has an important effect on the formation of NH{sub 3} from both volatile-N and char-N. The HCN concentration depends strongly on the residence time at temperature and on the presence (and depth) of a char bed. Trace element results indicate that bed temperatures above 900{sup o}C enhanced depletion of Ba, Pb and Zn from the bed residue and their enrichment in the fines. Mercury and selenium were released and their subsequent capture required low temperature filters operating below 120{sup o}C. The reactor was modified to enable char samples to be prepared and collected under controlled conditions. Results show the decreasing reactivity of the char with increasing temperature, time, pressure and particle size. There appears to be an initial decrease in reactivity during pyrolysis and a further longer- term decrease caused by graphitisation. 10 refs., 8 figs., 6 tabs.

  18. Retrieval process development and enhancements: Hydraulic test bed integrated testing. Fiscal year 1995 technology development summary report

    International Nuclear Information System (INIS)

    The Retrieval Process Development and Enhancements Program is sponsored by the U.S. Department of Energy (DOE) Office of Science and Technology to investigate waste dislodging and conveyance processes suitable for the retrieval of high-level radioactive waste. This program, represented by industry, national laboratories, and academia, is testing the performance of a technology of high-pressure waterjet dislodging and pneumatic conveyance integrated as a scarifier as a means of retrieval of waste inside waste storage tanks. Waste stimulants have been designed to challenge this retrieval process, and this technology has been shown to mobilize and convey the waste stimulants, at target retrieval rates while operating within the space envelope and the dynamic loading constraints of postulated deployment systems. The approach has been demonstrated to be versatile in dislodging and conveying a broad range of waste forms, from hard wastes to soft sludge wastes, through the use of simple and reliable in-tank components

  19. Full-wave algorithm to model effects of bedding slopes on the response of subsurface electromagnetic geophysical sensors near unconformities

    Science.gov (United States)

    Sainath, Kamalesh; Teixeira, Fernando L.

    2016-05-01

    We propose a full-wave pseudo-analytical numerical electromagnetic (EM) algorithm to model subsurface induction sensors, traversing planar-layered geological formations of arbitrary EM material anisotropy and loss, which are used, for example, in the exploration of hydrocarbon reserves. Unlike past pseudo-analytical planar-layered modeling algorithms that impose parallelism between the formation's bed junctions, our method involves judicious employment of Transformation Optics techniques to address challenges related to modeling relative slope (i.e., tilting) between said junctions (including arbitrary azimuth orientation of each junction). The algorithm exhibits this flexibility, both with respect to loss and anisotropy in the formation layers as well as junction tilting, via employing special planar slabs that coat each "flattened" (i.e., originally tilted) planar interface, locally redirecting the incident wave within the coating slabs to cause wave fronts to interact with the flattened interfaces as if they were still tilted with a specific, user-defined orientation. Moreover, since the coating layers are homogeneous rather than exhibiting continuous material variation, a minimal number of these layers must be inserted and hence reduces added simulation time and computational expense. As said coating layers are not reflectionless however, they do induce artificial field scattering that corrupts legitimate field signatures due to the (effective) interface tilting. Numerical results, for two half-spaces separated by a tilted interface, quantify error trends versus effective interface tilting, material properties, transmitter/receiver spacing, sensor position, coating slab thickness, and transmitter and receiver orientation, helping understand the spurious scattering's effect on reliable (effective) tilting this algorithm can model. Under the effective tilting constraints suggested by the results of said error study, we finally exhibit responses of sensors

  20. Heat and Mass Transfer Enforcement of Vibrating Fluidized Bed

    Institute of Scientific and Technical Information of China (English)

    ChuZhide; YangJunhong; 等

    1994-01-01

    This paper briefly introduces the development of vibrating fluidized bed at home and abroad,elaborates the vibration properties of vibrating fluidized bed.the fluidizing velocity and pressure drop of the bed layer,it also deduces the non-steady state drying dynamic equations of vibrating fluidized bed,analyzes main factors which influence the drying rate and inquires into drying rules of fixed bed and vibrating fluidized bed.

  1. Parametric sensitivity of a CFD model concerning the hydrodynamics of trickle-bed reactor (TBR

    Directory of Open Access Journals (Sweden)

    Janecki Daniel

    2016-03-01

    Full Text Available The aim of the present study was to investigate the sensitivity of a multiphase Eulerian CFD model with respect to relations defining drag forces between phases. The mean relative error as well as standard deviation of experimental and computed values of pressure gradient and average liquid holdup were used as validation criteria of the model. Comparative basis for simulations was our own data-base obtained in experiments carried out in a TBR operating at a co-current downward gas and liquid flow. Estimated errors showed that the classical equations of Attou et al. (1999 defining the friction factors Fjk approximate experimental values of hydrodynamic parameters with the best agreement. Taking this into account one can recommend to apply chosen equations in the momentum balances of TBR.

  2. Implementation of a strainer model for calculating the pressure drop across beds of compressible, fibrous materials

    International Nuclear Information System (INIS)

    Mineral wool insulation debris, which is generated during a loss-of-coolant-accident (LOCA), has the potential to undermine the long-term recirculation capability of the emergency core coolant system (ECCS) in a nuclear power plant. Most importantly, ECCS pumps are faced with an increasing pressure drop while insulation debris accumulates at the pump suction strainers. The presented study aims at modelling the pressure drop of flows across growing cakes of compressible, fibrous materials and at the implementation of the model into a general-purpose three-dimensional (3D) computational fluid dynamics (CFD) code. Computed pressure drops are compared with experimentally found values. The ability of the CFD implementation to simulate 3D flows with a non-uniformly distributed particle phase is exemplified using a step-like channel geometry with a horizontally embedded strainer plate

  3. Flue gas desulfurization by a powder-particle spouted bed

    Energy Technology Data Exchange (ETDEWEB)

    Moeini, M.; Hatamipour, M.S. [Chemical Engineering Department, University of Isfahan, Isfahan (Iran)

    2008-01-15

    The powder-particle spouted bed process is one of the semi-dry processes that have been developed for flue gas desulfurization. In this study, which is designed for SO{sub 2} removal by a powder-particle spouted bed, the reaction term is included in one-dimensional and streamtube models that were presented previously for spouted beds. Hydrated lime is used as the sorbent in this process. The predictions of the models are compared with some published experimental data and it is found that the developed models are valid. The results of two models are compared with each other and their various properties are evaluated. The effects of different operating conditions on SO{sub 2} removal efficiency are also investigated and preferred operating conditions are discussed. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  4. A model of fluff layer erosion and subsequent bed erosion in the presence of the bioturbator, Hydrobia ulvae

    OpenAIRE

    Orvain, Francis; Le Hir, Pierre; Sauriau, Pierre-guy

    2003-01-01

    Previous studies have shown that the gastropod Hydrobia ulvae destabilizes the top layers of fine-grained sediments. This process is mediated by the formation of a "biogenic" fluff layer that includes tracks, faecal pellets and mucus. This fluff layer has been shown to be easily resuspended before general bed erosion. In order to examine how fluff layer and bed. erosion interact, flume experiments were performed with fluid sediments of varying water contents. Ten thousand snails were placed a...

  5. Long-duration bed rest as an analog to microgravity.

    Science.gov (United States)

    Hargens, Alan R; Vico, Laurence

    2016-04-15

    Long-duration bed rest is widely employed to simulate the effects of microgravity on various physiological systems, especially for studies of bone, muscle, and the cardiovascular system. This microgravity analog is also extensively used to develop and test countermeasures to microgravity-altered adaptations to Earth gravity. Initial investigations of bone loss used horizontal bed rest with the view that this model represented the closest approximation to inactivity and minimization of hydrostatic effects, but all Earth-based analogs must contend with the constant force of gravity by adjustment of the G vector. Later concerns about the lack of similarity between headward fluid shifts in space and those with horizontal bed rest encouraged the use of 6 degree head-down tilt (HDT) bed rest as pioneered by Russian investigators. Headward fluid shifts in space may redistribute bone from the legs to the head. At present, HDT bed rest with normal volunteers is the most common analog for microgravity simulation and to test countermeasures for bone loss, muscle and cardiac atrophy, orthostatic intolerance, and reduced muscle strength/exercise capacity. Also, current physiologic countermeasures are focused on long-duration missions such as Mars, so in this review we emphasize HDT bed rest studies with durations of 30 days and longer. However, recent results suggest that the HDT bed rest analog is less representative as an analog for other important physiological problems of long-duration space flight such as fluid shifts, spinal dysfunction and radiation hazards. PMID:26893033

  6. Modeling arsenite oxidation by chemoautotrophic Thiomonas arsenivorans strain b6 in a packed-bed bioreactor

    International Nuclear Information System (INIS)

    Arsenic is a major toxic pollutant of concern for the human health. Biological treatment of arsenic contaminated water is an alternative strategy to the prevalent conventional treatments. The biological treatment involves a pre-oxidation step transforming the most toxic form of arsenic, As (III), to the least toxic form, As (V), respectively. This intermediate process improves the overall efficiency of total arsenic removal from the contaminated water. As (III) oxidation by the chemoautotrophic bacterium Thiomonas arsenivorans strain b6 was investigated in a fixed-film reactor under variable influent As (III) concentrations (500–4000 mg/L) and hydraulic residence times (HRTs) (0.2–1 day) for a duration of 137 days. During the entire operation, seven steady-state conditions were obtained with As (III) oxidation efficiency ranging from 48.2% to 99.3%. The strong resilience of the culture was exhibited by the recovery of the bioreactor from an As (III) overloading of 5300 ± 400 mg As (III)/L day operated at a HRT of 0.2 day. An arsenic mass balance revealed that As (III) was mainly oxidized to As (V) with unaccounted arsenic (≤ 4%) well within the analytical error of measurement. A modified Monod flux expression was used to determine the biokinetic parameters by fitting the model against the observed steady-state flux data obtained from operating the bioreactor under a range of HRTs (0.2–1 day) and a constant influent As (III) concentration of 500 mg/L. Model parameters, k = 0.71 ± 0.1 mg As (III)/mg cells h, and Ks = 13.2 ± 2.8 mg As (III)/L were obtained using a non-linear estimation routine and employing the Marquardt–Levenberg algorithm. Sensitivity analysis revealed k to be more sensitive to model simulations of As (III) oxidation under steady-state conditions than parameter Ks. -- Highlights: ► As (III) oxidation. ► Biokinetic parameters. ► Model validation and sensitivity analysis.

  7. A model based on Hirano-Exner equations for two-dimensional transient flows over heterogeneous erodible beds

    Science.gov (United States)

    Juez, C.; Ferrer-Boix, C.; Murillo, J.; Hassan, M. A.; García-Navarro, P.

    2016-01-01

    In order to study the morphological evolution of river beds composed of heterogeneous material, the interaction among the different grain sizes must be taken into account. In this paper, these equations are combined with the two-dimensional shallow water equations to describe the flow field. The resulting system of equations can be solved in two ways: (i) in a coupled way, solving flow and sediment equations simultaneously at a given time-step or (ii) in an uncoupled manner by first solving the flow field and using the magnitudes obtained at each time-step to update the channel morphology (bed and surface composition). The coupled strategy is preferable when dealing with strong and quick interactions between the flow field, the bed evolution and the different particle sizes present on the bed surface. A number of numerical difficulties arise from solving the fully coupled system of equations. These problems are reduced by means of a weakly-coupled strategy to numerically estimate the wave celerities containing the information of the bed and the grain sizes present on the bed. Hence, a two-dimensional numerical scheme able to simulate in a self-stable way the unsteady morphological evolution of channels formed by cohesionless grain size mixtures is presented. The coupling technique is simplified without decreasing the number of waves involved in the numerical scheme but by simplifying their definitions. The numerical results are satisfactorily tested with synthetic cases and against experimental data.

  8. The GNEP Coupled End-to-End (CETE) Research, Development, and Demonstration Project: Overview of the CETE Test-bed Capabilities and Operations

    International Nuclear Information System (INIS)

    The U.S. Department of Energy is conducting a complete, coupled end-to-end demonstration of advanced nuclear fuel reprocessing at Oak Ridge National Laboratory (ORNL) in support of the Global Nuclear Energy Partnership (GNEP). The test-bed consists of a set of small-scale reprocessing operations that incorporate spent fuel receipt, characterization, head-end processing (fuel shearing and voloxidation), aqueous separations, conversion of fission product wastes to solid forms and conversion of actinides to solid forms for fuel fabrication. The test-bed is configured to process multi-kilogram quantities of light water reactor spent fuel. The processing equipment is located within two facilities that are specially designed to handle highly radioactive materials, the Irradiated Fuels Examination Laboratory (IFEL) and the Radiochemical Engineering Development Center (REDC). This paper provides descriptions of facility capabilities used to perform spent fuel reprocessing activities. (authors)

  9. Evaluation of the co-registration capabilities of a MRI/PET compatible bed in an Experimental autoimmune encephalomyelitis (EAE) model

    Energy Technology Data Exchange (ETDEWEB)

    Esposito, Giovanna, E-mail: giovanna.esposito@unito.it [Molecular and Preclinical Imaging Center, University of Torino (Italy); D' angeli, Luca; Bartoli, Antonietta [Molecular and Preclinical Imaging Center, University of Torino (Italy); Chaabane, Linda [INSPE-Division of Neuroscience, San Raffaele Scientific Institute, 20132 Milano (Italy); Terreno, Enzo [Molecular and Preclinical Imaging Center, University of Torino (Italy)

    2013-02-21

    Positron Emission Tomography (PET) with {sup 18}F-FDG is a promising tool for the detection and evaluation of active inflammation in animal models of neuroinflammation. MRI is a complementary imaging technique with high resolution and contrast suitable to obtain the anatomical data required to analyze PET data. To combine PET and MRI modalities, we developed a support bed system compatible for both scanners that allowed to perform imaging exams without animal repositioning. With this approach, MRI and PET data were acquired in mice with Experimental autoimmune encephalomyelitis (EAE). In this model, it was possible to measure a variation of {sup 18}F-FDG uptake proportional to the degree of disease severity which is mainly related to Central Nervous System (CNS) inflammation. Against the low resolved PET images, the co-registered MRI/PET images allowed to distinguish the different brain structures and to obtain a more accurate tracer evaluation. This is essential in particular for brain regions whose size is of the order of the spatial resolution of PET.

  10. An overview of CFD modelling of small-scale fixed-bed biomass pellet boilers with preliminary results from a simplified approach

    International Nuclear Information System (INIS)

    Highlights: ► Overview of the overall approach of modelling fixed-bed biomass boilers in CFD. ► Bed sub-models of moisture evaporation, devolatisation and char combustion reviewed. ► A method of embedding a combustion model in discrete fuel zones within the CFD is suggested. ► Includes sample of preliminary results for a 50 kW pellet boiler. ► Clear physical trends predicted. - Abstract: The increasing global energy demand and mounting pressures for CO2 mitigation call for increased efficient utilization of biomass, particularly for heating domestic and commercial buildings. The authors of the present paper are investigating the optimization of the combustion performance and NOx emissions of a 50 kW biomass pellet boiler fabricated by a UK manufacturer. The boiler has a number of adjustable parameters including the ratio of air flow split between the primary and secondary supplies, the orientation, height, direction and number of the secondary inlets. The optimization of these parameters provides opportunities to improve both the combustion efficiency and NOx emissions. When used carefully in conjunction with experiments, Computational Fluid Dynamics (CFD) modelling is a useful tool for rapidly and at minimum cost examining the combustion performance and emissions from a boiler with multiple variable parameters. However, modelling combustion and emissions of a small-scale biomass pellet boiler is not trivial and appropriate fixed-bed models that can be coupled with the CFD code are required. This paper reviews previous approaches specifically relevant to simulating fixed-bed biomass boilers. In the first part it considers approaches to modelling the heterogeneous solid phase and coupling this with the gas phase. The essential components of the sub-models are then overviewed. Importantly, for the optimization process a model is required that has a good balance between accuracy in predicting physical trends, with low computational run time. Finally, a

  11. Influence of Ordovician carbonate reservoir beds in Tarim Basin by faulting

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The quality of the Ordovician carbonate reservoir beds in the Tarim Basin is closely related to the development of secondary pores,fractures and cavities. Karstification is important in improving the properties of reservoir beds,and karstification related to unconformity has caught wide attention. Compared with the recent research on the unconformity karst reservoir bed improvement,this paper shows a new way of carbonate reservoir bed transformation. Based on field survey,core and slices observation,transformation of Ordovician carbonate reservoir beds by faulting can be classified into three types: (1) Secondary faults and fracturs generated by faulting improved carbonate reservoir bed properties,which were named the Lunnan or Tazhong82 model; (2) upflow of deep geothermal fluids caused by faulting,with some components metasomatizing with carbonate and forming some secon-dary deposit,such as fluorite. It can improve carbonate reservoir bed properties obviously and is named the Tazhong 82 model; and (3) the faulting extending up to the surface increased the depth of supergene karstification and the thickness of reservoir bed. It is named the Hetianhe model. Trans-formation effect of carbonate reservoir beds by faulting was very significant,mainly distributed on the slopes or on the edge or plunging end of the uplift.

  12. Modelling the effects of macrofauna on sediment transport and bed elevation: Application over a cross-shore mudflat profile and model validation

    Science.gov (United States)

    Orvain, Francis; Le Hir, Pierre; Sauriau, Pierre-Guy; Lefebvre, Sébastien

    2012-08-01

    The effects of 2 functional groups of bioturbators have been predicted in terms of long-term impact on erodability: (1) one superficial mobile deposit-feeder, the gastropod Hydrobia ulvae; and (2) one endobenthic deposit-feeder, the bivalve Scrobicularia plana. Different scenarios of morphodynamical cross-shore 1DH/1DV model were performed to simulate the equilibrium profile of an intertidal mudflat under tide and wave forcings. This process-based model for erosion is able to simulate multiphasic sequential resuspension, by discriminating various erosion behaviour like benthos-generated fluff-layer erosion (BGFL) and general bed loosening and burrowing activity in deep layers. The results were analysed and compared to examine the long-term effect of macrofauna after 14 years. It reveals that the impact of the bivalve S. plana is very significant after only 4 years of simulation while the effect of the gastropod H. ulvae is negligible in terms of sediment transport even after 14 years. More generally, this reveals the strong impact of stationary endobenthic bioturbators that induces a high downward shift of the upper shore while the effects of superficial motile bioturbators remain very low. This impact is mainly due to the effect of endobenthic species in deep layers associated to burrowing activities and their consequences on the bed erosion, but the production of a fluff layer by surface grazer like H. ulvae at the sediment surface can be neglected. The importance of macrofauna mediation of bed erodability is discussed in this study by comparing the activities of the two functional groups of bioturbation on the general functioning of intertidal mudflats. The model outcomes (transferred in a 1DV framework) were in close agreement with the measured results of flume data at 3 different bathymetric levels of the mudflat over the cross-shore profile. This validation step revealed that model of sediment transport under influence of biota effects does not need further

  13. Bed Scouring During the Release of an Ice Jam

    Directory of Open Access Journals (Sweden)

    Michail Manolidis

    2014-04-01

    Full Text Available A model is developed for simulating changes in river bed morphology as a result of bed scouring during the release of an ice jam. The model couples a non-hydrostatic hydrodynamic model with the processes of erosion and deposition through a grid expansion technique. The actual movement of bed load is implemented by reconstructing the river bed in piecewise linear elements in order to bypass the limitations of the step-like approximation that the hydrodynamic model uses to capture the bed bathymetry. Initially, an ice jam is modeled as a rigid body of water near the free surface that constricts the flow. The ice jam does not exchange mass or momentum with the stream, but the ice body can have a realistic shape and offer resistance to the flow of water through the constriction. An ice jam release is modeled by suddenly enabling the ice to flow and exchange mass and momentum with the water. The resulting release resembles a dam break wave accelerating and causing flow velocities to rise rapidly. The model is used to simulate the 1984 ice jam in the St. Clair River, which is part of the Huron-Erie Corridor. The jam had a duration of 24 days, and its release was accompanied by high flow velocities. It is speculated that high flow velocities during the release of the jam caused scouring of the river bed. This led to an increase in the river’s conveyance that is partly responsible for the persistence of low water levels in the upper Great Lakes. The simulations confirm that an event similar to the 1984 ice jam will indeed cause scouring of the St. Clair River bed.

  14. Developing A Holistic Wellness Model

    Directory of Open Access Journals (Sweden)

    D. A. Els

    2006-11-01

    Full Text Available The objective of the present study was the development of a holistic theoretical wellness model that served as frame of reference for the construction of a valid and reliable inventory that was considered suitable for the assessment of wellness of employees of a South African life insurance organisation. The 5 Factor Wellness Inventory was developed from existing proven wellness inventories. A non-random sample of 673 employees of the organisation concerned participated in a cross-sectional survey by completing the Inventory and a biographical questionnaire. Goodness of fit between the holistic wellness model and a data set derived from the application of the 5 Factor Wellness Inventory was determined empirically. The structural equation modelling statistics produced acceptable goodnessof- fit indices albeit with some scope for improvement. The Root Mean Square Error of Approximation indices supported acceptance of the holistic work-wellness model. The validity of the Inventory was also estimated.

  15. Development of NASA's Space Communications and Navigation Test Bed Aboard ISS to Investigate SDR, On-Board Networking and Navigation Technologies

    Science.gov (United States)

    Reinhart, Richard C.; Kacpura, Thomas J.; Johnson, Sandra K.; Lux, James P.

    2010-01-01

    NASA is developing an experimental flight payload (referred to as the Space Communication and Navigation (SCAN) Te