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

International Nuclear Information System (INIS)

Ginsberg, T.; Chen, J.C.

1984-01-01

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

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

International Nuclear Information System (INIS)

Loboiko, A.I.

2000-03-01

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

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

International Nuclear Information System (INIS)

Ginsberg, T.; Chen, J.C.

1984-01-01

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

Simulant - water experiments to characterize the debris bed formed in severe core melt accidents

International Nuclear Information System (INIS)

Mathai, Amala M.; Anandan, J.; Sharma, Anil Kumar; Murthy, S.S.; Malarvizhi, B.; Lydia, G.; Das, Sanjay Kumar; Nashine, B.K.; Selvaraj, P.

2015-01-01

Molten Fuel Coolant Interaction (WO) and debris bed configuration on the core catcher plate assumes importance in assessing the Post Accident Heat Removal (PARR) of a heat generating debris bed. The key factors affecting the coolability of the debris bed are the bed porosity, morphology of the fragmented particles, degree of spreading/heaping of the debris on the core catcher and the fraction of lump formed. Experiments are conducted to understand the fragmentation kinetics and subsequent debris bed formation of molten woods metal in water at interface temperatures near the spontaneous nucleation temperature of water. Morphology of the debris particles is investigated to understand the fragmentation mechanisms involved. The spreading behavior of the debris on the catcher plate and the particle size distribution are presented for 5 kg and 10 kg melt inventories. Porosity of the undisturbed bed on the catcher plate is evaluated using a LASER sensor technique. (author)

Effect of particle stratification on debris-bed dryout

International Nuclear Information System (INIS)

Gabor, J.D.; Cassulo, J.C.; Pederson, D.R.

1982-01-01

Significant work has been performed on debris-bed dryout on beds of either uniformly sized particles or particles of a wide size range which are well mixed. This work has provided an understanding of the mechanisms of dryout and an empirical basis for containment analysis. However, the debris bed resulting from a HCDA would not consist of uniformly sized particles and for certain scenarios the bed could be stratified rather than well mixed. Tests have been conducted on the effect of particle size distribution on dryout and concluded that not only is the mean particle size an important parameter but also the standard deviation of the distribution and change in porosity. The D6 in-pile test at Sandia with a 114-mm deep stratified bed resulted in a reduced dryout heat flux compared to a uniformly mixed bed. Because of the many questions concerning the dryout behavior of stratified beds of wide size distribution out-of-pile experiments in which metal particles in water pools are inductively heated were initiated at Argonne

Dryout heat flux and flooding phenomena in debris beds consisting of homogeneous diameter particles

International Nuclear Information System (INIS)

Maruyama, Yu; Abe, Yutaka; Yamano, Norihiro; Soda, Kunihisa

1988-08-01

Since the TMI-2 accident, which occurred in 1979, necessity of understanding phenomena associated with a severe accident have been recognized and researches have been conducted in many countries. During a severe accident of a light water reactor, a debris bed consisting of the degraded core materials would be formed. Because the debris bed continues to release decay heat, the debris bed would remelt when the coolable geometry is not maintained. Thus the degraded core coolability experiments to investigate the influence of the debris particle diameter and coolant flow conditions on the coolability of the debris bed and the flooding experiments to investigate the dependence of flooding phenomena on the configuration of the debris bed have been conducted in JAERI. From the degraded core coolability experiments, the following conclusions were derived; the coolability of debris beds would be improved by coolant supply into the beds, Lipinski's 1-dimensional model shows good agreement with the measured dryout heat flux for the beds under stagnant and forced flow conditions from the bottom of the beds, and the analytical model used for the case that coolant is fed by natural circulation through the downcomer reproduces the experimental results. And the following conclusions were given from the flooding experiments ; no dependence between bed height and the flooding constant exists for the beds lower than the critical bed height, flooding phenomena of the stratified beds would be dominated by the layer consisting of smaller particles, and the predicted dryout heat flux by the analytical model based on the flooding theory gives underestimation under stagnant condition. (author)

Transient core-debris bed heat-removal experiments and analysis

International Nuclear Information System (INIS)

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

1982-08-01

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

An experimental simulation study of debris quenching in a radially stratified porous bed

International Nuclear Information System (INIS)

Sehgal, B.R.; Nayak, A.K.; Stepanyan, A.

2004-01-01

During a severe accident condition in a nuclear power plant, the core melt can fail the reactor vessel and relocate into the containment basement. In some accident management schemes, the vessel cavity is flooded with water. For these a particulate debris bed is likely to form on the cavity floor due to melt break-up in water. . In this situation, the coolability of debris bed on the containment floor is a crucial issue. This is because the debris bed still generates the decay heat and if it is uncoolable, it can eventually remelt and react with concrete basement generating a lot of noncondensable gases and pressurising the containment. Hence, it is important to cool the debris bed as an accident management programme. The main parameters affecting the coolability of the debris bed are its porosity which is a function of the size and shape of the particles which constitute the debris bed, the operating condition such as water flooding from the top or bottom of debris bed, water temperature and non-condensable gas generated during bed-concrete interactions. It is found from previous studies that the debris bed has a non-uniform particle distribution or a porosity stratification. This can happen both in radial and axial plane. For example, the bed can have a lower porosity at the centre and higher porosity at the periphery. It is of interest to investigate the quenching phenomena in such configurations so as to find an effective means of quenching the heat generating bed. While most of the previous investigations mainly concentrate on quenching of a homogenous or axially stratified particulate bed with volumetric heat generation, there are almost no studies on the above phenomena in a radially stratified porous bed. So the objective of this paper is to investigate the quenching phenomena in a radially stratified bed. To simulate the phenomena, we conducted experiments in an experimental facility named as POMECO (POrous MEdia COolability). The facility has a square

Experimental results on the coolability of a debris bed with multidimensional cooling effects

International Nuclear Information System (INIS)

Rashid, M.; Kulenovic, R.; Laurien, E.; Nayak, A.K.

2011-01-01

Research highlights: ► Performing of dryout experiments with a polydispersed bed for top- and bottom-flooding. ► Study of influence of different down comer configurations on the coolability of debris bed. ► Measurement of temperature profiles, pressure drops and determination of dryout heat flux. ► Observation of noticeable increase in coolability of debris bed with the use of down comer is observed. - Abstract: Within the reactor safety research, the removal of decay heat from a debris bed (formed from corium and residual water) is of great importance. In order to investigate experimentally the long term coolability of debris beds, the scaled test facility “DEBRIS” (Fig. 1) has been built at IKE. A large number of experiments had been carried out to investigate the coolability limits for different bed configurations (). Analyses based on one-dimensional configurations underestimate the coolability in realistic multidimensional configurations, where lateral water access and water inflow via bottom regions are favoured. Following the experiments with top- and bottom-flooding flow conditions this paper presents experimental results of boiling and dryout tests at different system pressures based on top- and bottom-flooding via a down comer configuration. A down comer with an internal diameter of 10 mm has been installed at the centre of the debris bed. The debris bed is built up in a cylindrical crucible with an inner diameter of 125 mm. The bed of height 640 mm is composed of polydispersed particles with particle diameters 2, 3 and 6 mm. Since the long term coolability of such particle bed is limited by the availability of coolant inside the bed and not by heat transfer limitations from the particles to the coolant, the bottom inflow of water improves the coolability of the debris bed and an increase of the dryout heat flux can be observed. With increasing system pressure, the coolability limits are enhanced (increased dryout heat flux).

Two-Phase Flow Effect on the Ex-Vessel Corium Debris Bed Formation in Severe Accident

International Nuclear Information System (INIS)

Kim, Eunho; Park, Jin Ho; Kim, Moo Hwan; Park, Hyun Sun; Ma, Weimin; Bechta, Sevostian V.

2014-01-01

In Korean IVR-ERVC(In-Vessel Retention of molten corium through External Reactor Vessel Cooling) strategy, if the situation degenerates into insufficient external vessel cooling, the molten core mixture can directly erupt into the flooded cavity pool from the weakest point of the vessel. Then, FCI (molten Fuel Coolant Interaction) will fragment the corium jet into small particulates settling down to make porous debris bed on the cavity basemat. To secure the containment integrity against the MCCI (Molten Core - Concrete Interaction), cooling of the heat generating porous corium debris bed is essential and it depends on the characteristics of the bed itself. For the characteristics of corium debris bed, many previous experimental studies with simulant melts reported the heap-like shape mostly. There were also following experiments to develop the correlation for the heap-like shaped debris bed. However, recent studies started to consider the effect of the decay heat and reported some noticeable results with the two-phase flow effect on the debris bed formation. The Kyushu University and JAEA group reported the experimental studies on the 'self-leveling' effect which is the flattening effect of the particulate bed by the inside gas generation. The DECOSIM simulation study of RIT (Royal Institute of Technology, Sweden) with Russian researchers showed the 'large cavity pool convection' effect, which is driven by the up-rising gas bubble flow from the pre-settled debris bed, on the particle settling trajectories and ultimately final bed shape. The objective of this study is verification of the two-phase flow effect on the ex-vessel corium debris bed formation in the severe accident. From the analysis on the test movie and resultant particle beds, the two-phase flow effect on the debris bed formation, which has been reported in the previous studies, was verified and the additional findings were also suggested. For the first, in quiescent pool the

Internal structure of an ex-vessel corium debris bed during severe accidents of LWRs

Energy Technology Data Exchange (ETDEWEB)

Kim, Eunho; Park, Jin Ho; Moriyama, Kiyofumi; Park, Hyun Sun [POSTECH, Daejeon (Korea, Republic of)

2015-10-15

In the aspect of the coolability assessment the configuration of the debris bed, including internal and external characteristics, has significant importance as boundary conditions for simulations, however, relatively little investigation of the sedimentation process. For the development of a debris bed, recently there have been several studies that focused on thermal characteristics of corium particles. Yakush et al. performed simulation studies and showed that two phase natural convection affects the particle settling trajectory and changes the final arrival location of particles to result more flattened bed. Those simulation results have been supported by the experimental studies of Kim et al. using simulant particles and air bubble injection. For the internal structure of a debris bed, there have been several simulation and experimental studies, which investigated the effect of internal structure on debris bed coolability. Magallon has reported the particle size distribution at three elevations of the debris bed of FARO L-31 case, where the mean particle size was bigger for the lower elevation. However, there is a lack of detailed information on the characteristics of the debris bed, including the local structure and porosity. In this study, we investigated the internal structure of the debris bed using a mixture of stainless steel particles and air bubble injection. Local particle sedimentation quantity, particle size distribution change in radial direction and axial direction, and bed porosity was measured to investigate a relationship between the internal structure and the accident condition. An experimental investigation was carried out for the internal structure of ex-vessel corium debris bed in the flooded cavity during sever accident. Moderate corium discharge in high flooding level was assumed for full fragmentation of melt jet. The test particle mixture was prepared by following an empirical correlation, which reflects the particle size distribution of

Internal structure of an ex-vessel corium debris bed during severe accidents of LWRs

International Nuclear Information System (INIS)

Kim, Eunho; Park, Jin Ho; Moriyama, Kiyofumi; Park, Hyun Sun

2015-01-01

In the aspect of the coolability assessment the configuration of the debris bed, including internal and external characteristics, has significant importance as boundary conditions for simulations, however, relatively little investigation of the sedimentation process. For the development of a debris bed, recently there have been several studies that focused on thermal characteristics of corium particles. Yakush et al. performed simulation studies and showed that two phase natural convection affects the particle settling trajectory and changes the final arrival location of particles to result more flattened bed. Those simulation results have been supported by the experimental studies of Kim et al. using simulant particles and air bubble injection. For the internal structure of a debris bed, there have been several simulation and experimental studies, which investigated the effect of internal structure on debris bed coolability. Magallon has reported the particle size distribution at three elevations of the debris bed of FARO L-31 case, where the mean particle size was bigger for the lower elevation. However, there is a lack of detailed information on the characteristics of the debris bed, including the local structure and porosity. In this study, we investigated the internal structure of the debris bed using a mixture of stainless steel particles and air bubble injection. Local particle sedimentation quantity, particle size distribution change in radial direction and axial direction, and bed porosity was measured to investigate a relationship between the internal structure and the accident condition. An experimental investigation was carried out for the internal structure of ex-vessel corium debris bed in the flooded cavity during sever accident. Moderate corium discharge in high flooding level was assumed for full fragmentation of melt jet. The test particle mixture was prepared by following an empirical correlation, which reflects the particle size distribution of

Experimental investigation of coolability behaviour of irregularly shaped particulate debris bed

International Nuclear Information System (INIS)

Kulkarni, P.P.; Rashid, M.; Kulenovic, R.; Nayak, A.K.

2010-01-01

In case of a severe nuclear reactor accident, the core can melt and form a particulate debris bed in the lower plenum of the reactor pressure vessel (RPV). Due to the decay heat, the particle bed, if not cooled properly, can cause failure of the RPV. In order to avoid further propagation of the accident, complete coolability of the debris bed is necessary. For that, understanding of various phenomena taking place during the quenching is important. In the frame of the reactor safety research, fundamental experiments on the coolability of debris beds are carried out at IKE with the test facility 'DEBRIS'. In the present paper, the boiling and dry-out experimental results on a particle bed with irregularly shaped particles mixed with stainless steel balls have been reported. The pressure drops and dry-out heat fluxes of the irregular-particle bed are very similar to those for the single-sized 3 mm spheres bed, despite the fact that the irregular-particle bed is composed of particles with equivalent diameters ranging from 2 to 10 mm. Under top-flooding conditions, the pressure gradients are all smaller than the hydrostatic pressure gradient of water, indicating an important role of the counter-current interfacial drag force. For bottom-flooding with a liquid inflow velocity higher than about 2.7 mm/s, the pressure gradient generally increases consistently with the vapour velocity and the fluid-particle drag becomes important. The system pressures (1 and 3 bar) have negligible effects on qualitative behaviour of the pressure gradients. The coolability of debris beds is mainly limited by the counter-current flooding limit (CCFL) even under bottom-flooding conditions with low flow rates. The system pressure and the flow rate are found to have a distinct effect on the dry-out heat flux. Different classical models have been used to predict the pressure drop characteristics and the dry-out heat flux (DHF). Comparisons are made among the models and experimental results for

PIV Visualization of Bubble Induced Flow Circulation in 2-D Rectangular Pool for Ex-Vessel Debris Bed Coolability

Energy Technology Data Exchange (ETDEWEB)

Han, Teayang; Kim, Eunho; Park, Hyun Sun; Moriyama, Kiyofumi [POSTECH, Pohang (Korea, Republic of)

2015-10-15

The previous research works demonstrated the debris bed formation on the flooded cavity floor in experiments. Even in the cases the core melt is once solidified, the debris bed can be re-melted due to the decay heat. If the debris bed is not cooled enough by the coolant, the re-melted debris bed will react with the concrete base mat. This situation is called the molten core-concrete interaction (MCCI) which threatens the integrity of the containment by generated gases which pressurize the containment. Therefore securing the long term coolability of the debris bed in the cavity is crucial. According to the previous research works, the natural convection driven by the rising bubbles affects the coolability and the formation of the debris bed. Therefore, clarification of the natural convection characteristics in and around the debris bed is important for evaluation of the coolability of the debris bed. In this study, two-phase flow around the debris bed in a 2D slice geometry is visualized by PIV method to obtain the velocity map of the flow. The DAVINCI-PIV was developed to investigate the flow around the debris bed. In order to simulate the boiling phenomena induced by the decay heat of the debris bed, the air was injected separately by the air chamber system which consists of the 14 air-flowmeters. The circulation flow developed by the rising bubbles was visualized by PIV method.

Experimental investigation of multidimensional cooling effects on the coolability of a debris bed

International Nuclear Information System (INIS)

Rashidi, M.; Kulenovici, R.; Laurieni, E.

2011-01-01

During a severe accident in a light water reactor, the core can melt and be relocated to the lower plenum of the reactor pressure vessel. There it can form a particulate debris bed due to the possible presence of water. Within the reactor safety research, the removal of decay heat from a debris bed (formed from corium and residual water) is of great importance. In order to investigate experimentally the long-term coolability of debris beds, the down-scaled non nuclear test facility DEBRIS has been established at IKE. The major objectives of the experimental investigations at this test facility are the determination of local pressure drops for steady state boiling to check friction laws, the determination of dryout heat fluxes under various conditions for validation of numerical models, and the analysis of quenching processes of dry hot debris beds. A large number of 1D-experiments were carried out to investigate the coolability limits for different bed configurations at various thermohydraulic conditions, and to validate numerical models which can be used in reactor safety studies. Analyses based on one-dimensional configurations underestimate the coolability in realistic multidimensional configurations, where lateral water access and water inflow via bottom regions are favored. This paper presents 2D experimental results, based on various kinds of water inflow conditions into the bed, boiling and dryout tests with different bed configurations and different system pressures. Preliminary results show that the system pressure has no significant effect on the fundamental shape of the pressure gradient inside the bed, whereas with increasing system pressure the coolability limits are increased

Experimental and theoretical study of large scale debris bed reflood in the PEARL facility

Energy Technology Data Exchange (ETDEWEB)

Chikhi, Nourdine, E-mail: nourdine.chikhi@irsn.fr; Fichot, F.

2017-02-15

Highlights: • Five reflooding tests have been carried out with an experimental bed, 500 mm in height and 500 mm in diameter, made of 4 mm stainless steel balls. • For the first time, such a large bed was heated practically homogenously. • The quench front velocity was determined according to thermocouple measurements inside the bed. • An analytical model, assuming a quasi-steady progression of the quench front, allows to predict the conversion ratio in most cases. • It appears that the efficiency of cooling can be increased only up to a certain limit when increasing the inlet water flow rate. - Abstract: During a severe accident in a nuclear power plant, the degradation of fuel rods and melting of materials lead to the accumulation of core materials, which are commonly, called “debris beds”. To stop core degradation and avoid the reactor vessel rupture, the main accident management procedure consists in injecting water. In the case of debris bed, the reflooding models used for Loss of Coolant Accident are not applicable. The IRSN has launched an experimental program on debris bed reflooding to develop new models and to validate severe accident codes. The PEARL facility has been designed to perform, for the first time, the reflooding of large scale debris bed (Ø540 mm, h = 500 mm and 500 kg of steel debris) in a pressurized containment. The bed is heated by means of an induction system. A specific instrumentation has been developed to measure the debris bed temperature, pressure drop inside the bed and the steam flow rate during the reflooding. In this paper, the results of the first integral reflooding tests performed in the PEARL facility at atmospheric pressure up to 700 °C are presented. Focus is made on the quench front propagation and on the steam flow rate during reflooding. The effect of water injection flow rate, debris initial temperature and residual power are also discussed. Finally, an analytical model providing the steam flow rate and

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.

Review of the Technical Status on the Debris Bed Cooling Model

International Nuclear Information System (INIS)

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

2007-09-01

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 debris

Development of an ex-vessel corium debris bed with two-phase natural convection in a flooded cavity

International Nuclear Information System (INIS)

Kim, Eunho; Lee, Mooneon; Park, Hyun Sun; Moriyama, Kiyofumi; Park, Jin Ho

2016-01-01

Highlights: • For ex-vessel severe accidents in LWRs with wet-cavity strategy, development of debris bed with two-phase natural convection flow due to thermal characteristics of prototypic corium particles was investigated experimentally by using simulant particles and local air bubble control system. • Based on the experimental results of this study, an analytical model was established to describe the spreading of the debris bed in terms of two-phase flow and the debris injection parameters. • This model was then used to analyze the formation of debris beds at the reactor scale, and a sensitivity analysis was carried out based on key accident parameters. - Abstract: During severe accidents of light water reactors (LWRs), the coolability of relocated corium from the reactor vessel is a significant safety issue and a threat to the integrity of containment. With a flooded cavity, a porous debris bed is expected to develop on the bottom of the pool due to breakup and fragmentation of the melt jet. As part of the coolability assessment under accident conditions, the geometrical configuration of the debris bed is important. The Debris Bed Research Apparatus for Validation of the Bubble-Induced Natural Convection Effect Issue (DAVINCI) experimental apparatus facility was constructed to investigate the formation of debris beds under the influence of a two-phase flow induced by steam generation due to the decay heat of the debris bed. Using this system, five kilograms of stainless steel simulant debris were injected from the top of the water level, while air bubbles simulating the vapor flow were injected from the bottom of the particle catcher plate. The airflow rate was determined based on the quantity of settled debris, which will form a heat source due to the decay of corium. The radial distribution of the settled debris was examined using a ‘gap–tooth’ approach. Based on the experimental results of this study, an analytical model was established to

Development of an ex-vessel corium debris bed with two-phase natural convection in a flooded cavity

Energy Technology Data Exchange (ETDEWEB)

Kim, Eunho; Lee, Mooneon; Park, Hyun Sun, E-mail: hejsunny@postech.ac.kr; Moriyama, Kiyofumi; Park, Jin Ho

2016-03-15

Highlights: • For ex-vessel severe accidents in LWRs with wet-cavity strategy, development of debris bed with two-phase natural convection flow due to thermal characteristics of prototypic corium particles was investigated experimentally by using simulant particles and local air bubble control system. • Based on the experimental results of this study, an analytical model was established to describe the spreading of the debris bed in terms of two-phase flow and the debris injection parameters. • This model was then used to analyze the formation of debris beds at the reactor scale, and a sensitivity analysis was carried out based on key accident parameters. - Abstract: During severe accidents of light water reactors (LWRs), the coolability of relocated corium from the reactor vessel is a significant safety issue and a threat to the integrity of containment. With a flooded cavity, a porous debris bed is expected to develop on the bottom of the pool due to breakup and fragmentation of the melt jet. As part of the coolability assessment under accident conditions, the geometrical configuration of the debris bed is important. The Debris Bed Research Apparatus for Validation of the Bubble-Induced Natural Convection Effect Issue (DAVINCI) experimental apparatus facility was constructed to investigate the formation of debris beds under the influence of a two-phase flow induced by steam generation due to the decay heat of the debris bed. Using this system, five kilograms of stainless steel simulant debris were injected from the top of the water level, while air bubbles simulating the vapor flow were injected from the bottom of the particle catcher plate. The airflow rate was determined based on the quantity of settled debris, which will form a heat source due to the decay of corium. The radial distribution of the settled debris was examined using a ‘gap–tooth’ approach. Based on the experimental results of this study, an analytical model was established to

Modes of heat removal from a heat-generating debris bed

International Nuclear Information System (INIS)

Squarer, D.; Hochreiter, L.E.; Piecznski, A.T.

1984-01-01

In the worst hypothetical accident in a light water reactor, when all protection systems fail, the core could be converted into a deep particulate bed either in-vessel or ex-vessel. The containment of such an accident depends on the coolability of a heat-generating debris bed. Some recent experimental and analytical studies that are concerned with heat removal from such a particulate bed are reviewed. Studies have indicated that bed dryout flux and, therefore, the heat removal rate from the particulate bed increases with the particle diameter (i.e., the permeability) for pool boiling conditions and can exceed the critical heat flux of a flat plate. Bed dryout in a large particle bed (i.e., a few millimetres) was found to be closely related to the ''flooding'' limit of the bed. Dryout under forced flow conditions was found to be affected by both forced and natural convection for mass flow rate smaller than m /SUB cr/ , whereas above this mass flow rate, bed dryout is proportional to the mass flow rate. Recent analyses were found to be in agreement with experimental data; however, additional research is needed to assess factors not accounted for in previous studies (e.g., effect of pressure, multidimensionality, stratification, etc.). Based on the expected pressure and particle sizes in a postulated severe accident sequence, a debris bed should be coolable, given a sufficient water supply

Coarse-grained debris flow dynamics on erodible beds

Science.gov (United States)

Lanzoni, Stefano; Gregoretti, Carlo; Stancanelli, Laura Maria

2017-03-01

A systematic set of flume experiments is used to investigate the features of velocity profiles within the body of coarse-grained debris flows and the dependence of the transport sediment concentration on the relevant parameters (runoff discharge, bed slope, grain size, and form). The flows are generated in a 10 m long laboratory flume, initially filled with a layer consisting of loose debris. After saturation, a prescribed water discharge is suddenly supplied over the granular bed, and the runoff triggers a debris flow wave that reaches nearly steady conditions. Three types of material have been used in the tests: gravel with mean grain size of 3 and 5 mm, and 3 mm glass spheres. Measured parameters included: triggering water discharge, volumetric sediment discharge, sediment concentration, flow depth, and velocity profiles. The dynamic similarity with full-sized debris flows is discussed on the basis of the relevant dimensionless parameters. Concentration data highlight the dependence on the slope angle and the importance of the quasi-static friction angle. The effects of flow rheology on the shape of velocity profiles are analyzed with attention to the role of different stress-generating mechanisms. A remarkable collapse of the dimensionless profiles is obtained by scaling the debris flow velocity with the runoff velocity, and a power law characterization is proposed following a heuristic approach. The shape of the profiles suggests a smooth transition between the different rheological regimes (collisional and frictional) that establish in the upper and lower regions of the flow and is compatible with the presence of multiple length scales dictated by the type of contacts (instantaneous or long lasting) between grains.

Development and application of surrogate model for assessment of ex-vessel debris bed dryout probability - 15157

International Nuclear Information System (INIS)

Yakush, S.E.; Lubchenko, N.T.; Kudinov, P.

2015-01-01

In this work we consider a water-cooled power reactor severe accident scenario with pressure vessel failure and subsequent release of molten corium. A surrogate model for prediction of dryout heat flux for ex-vessels debris beds of different shapes is developed. Functional form of dryout heat flux dependence on problem parameters is developed by the analysis of coolability problem in non-dimensional variables. It is shown that for a flat debris bed the dryout heat flux can be represented in terms of three 1-dimensional functions for which approximating formulas are found. For two-dimensional debris beds (cylindrical, conical, Gaussian heap, mound-shaped), an additional function taking into account the bed shape geometry is obtained from numerical simulations using DECOSIM code as a full model. With the surrogate model in hand, risk analysis of debris bed coolability is carried out by Monte Carlo sampling of the input parameters within selected ranges, with assumed distribution functions

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

International Nuclear Information System (INIS)

Atkhen, K.; Berthoud, G.

2001-01-01

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

Experimental study and modelling of pressure losses during reflooding of a debris beds

International Nuclear Information System (INIS)

Clavier, Remi

2015-01-01

This work deals with single and two-phase flow pressure losses in porous media. The aim is to improve understanding and modeling of momentum transfer inside particle beds, in relation with nuclear safety issues concerning the reflooding of debris beds during severe nuclear accidents. Indeed, the degradation of the core during such accidents can lead to the collapse of the fuel assemblies, and to the formation of a debris bed, which can be described as a hot porous medium. This thesis is included in a nuclear safety research project on coolability of debris beds during reflooding sequences. An experimental study of single and two-phase cold-flow pressure losses in particle beds is proposed. The geometrical characteristics of the debris and the hydrodynamic conditions are representative of the real case, in terms of granulometry, particle shapes, and flow velocities. The new data constitute an important contribution. In particular, they contain pressure losses and void fraction measurements in two-phase air-water flows with non-zero liquid Reynolds numbers, which did not exist before. Predictive models for pressure losses in single and two-phase flow through particle beds have been established from experimental data. Their structures are based on macroscopic equations obtained from the volume averaging of local conservation equations. Single-phase flow pressure losses can be described by a Darcy-Forchheimer law with a quadratic correction, in terms of filtration velocity, with a better-than-10 % precision. Numerical study of single-phase flows through porous media shows that this correlation is valid for disordered smooth particle beds. Two-phase flow pressure losses are described using a generalized Darcy-Forchheimer structure, involving inertial and cross flow terms. A new model is proposed and compared to the experimental data and to the usual models used in severe accident simulation codes. (author)

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-02-15

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

Experimental investigation on single-phase pressure losses in nuclear debris beds: Identification of flow regimes and effective diameter

Energy Technology Data Exchange (ETDEWEB)

Clavier, R., E-mail: remi.clavier@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire (IRSN) – PSN-RES/SEREX/LE2M, Cadarache bât. 327, 13115 St Paul-lez-Durance (France); Chikhi, N., E-mail: nourdine.chikhi@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire (IRSN) – PSN-RES/SEREX/LE2M, Cadarache bât. 327, 13115 St Paul-lez-Durance (France); Fichot, F. [Institut de Radioprotection et de Sûreté Nucléaire (IRSN) – PSN-RES/SAG/LEPC, Cadarache bât. 700, 13115 St Paul-lez-Durance (France); Quintard, M. [Université de Toulouse – INPT – UPS – Institut de Mécanique des Fluides de Toulouse (IMFT), Allée Camille Soula, F-31400 Toulouse (France); CNRS – IMFT, F-31400 Toulouse (France)

2015-10-15

Highlights: • Single-phase pressure drops versus flow rates in particle beds are measured. • Conditions are representative of the reflooding of a nuclear fuel debris bed. • Darcy, weak inertial, strong inertial and weak turbulent regimes are observed. • A Darcy–Forchheimer law is found to be a good approximation in this domain. • A predictive correlation is derived from new experimental data. - Abstract: During a severe nuclear power plant accident, the degradation of the reactor core can lead to the formation of debris beds. The main accident management procedure consists in injecting water inside the reactor vessel. Nevertheless, large uncertainties remain regarding the coolability of such debris beds. Motivated by the reduction of these uncertainties, experiments have been conducted on the CALIDE facility in order to investigate single-phase pressure losses in representative debris beds. In this paper, these results are presented and analyzed in order to identify a simple single-phase flow pressure loss correlation for debris-bed-like particle beds in reflooding conditions, which cover Darcean to Weakly Turbulent flow regimes. The first part of this work is dedicated to study macro-scale pressure losses generated by debris-bed-like particle beds, i.e., high sphericity (>80%) particle beds with relatively small size dispersion (from 1 mm to 10 mm). A Darcy–Forchheimer law, involving the sum of a linear term and a quadratic deviation, with respect to filtration velocity, has been found to be relevant to describe this behavior in Darcy, Strong Inertial and Weak Turbulent regimes. It has also been observed that, in a restricted domain (Re = 15 to Re = 30) between Darcy and Weak Inertial regimes, deviation is better described by a cubic term, which corresponds to the so-called Weak Inertial regime. The second part of this work aims at identifying expressions for coefficients of linear and quadratic terms in Darcy–Forchheimer law, in order to obtain a

CHARACTERISTICS OF SELF-LEVELING BEHAVIOR OF DEBRIS BEDS IN A SERIES OF EXPERIMENTS

Directory of Open Access Journals (Sweden)

SONGBAI CHENG

2013-06-01

Full Text Available During a hypothetical core-disruptive accident (CDA in a sodium-cooled fast reactor (SFR, degraded core materials can form roughly conically-shaped debris beds over the core-support structure and/or in the lower inlet plenum of the reactor vessel from rapid quenching and fragmentation of the core material pool. However, coolant boiling may ultimately lead to leveling of the debris bed, which is crucial to the relocation of the molten core and heat-removal capability of the debris bed. To clarify the mechanisms underlying this self-leveling behavior, a large number of experiments were performed within a variety of conditions in recent years, under the constructive collaboration between the Japan Atomic Energy Agency (JAEA and Kyushu University (Japan. The present contribution synthesizes and gives detailed comparative analyses of those experiments. Effects of various experimental parameters that may have potential influence on the leveling process, such as boiling mode, particle size, particle density, particle shape, bubbling rate, water depth and column geometry, were investigated, thus giving a large palette of favorable data for the better understanding of CDAs, and improved verifications of computer models developed in advanced fast reactor safety analysis codes.

Characteristics of Self-Leveling Behavior of Debris Beds in A Series of Experiments

Energy Technology Data Exchange (ETDEWEB)

Cheng, Songbai; Yamano, Hidemasa; Suzuki, Tohru; Tobita, Yoshiharu [Japan Atomic Energy Agency, Ibaraki (Japan); Yuya, Nakamura; Bin, Zhang; Tatsuya, Matsumoto; Koji, Morita [Kyushu Univ., Fukuoka (Japan)

2013-06-15

During a hypothetical core-disruptive accident (CDA) in a sodium-cooled fast reactor (SFR), degraded core materials can form roughly conically-shaped debris beds over the core-support structure and/or in the lower inlet plenum of the reactor vessel from rapid quenching and fragmentation of the core material pool. However, coolant boiling may ultimately lead to leveling of the debris bed, which is crucial to the relocation of the molten core and heat-removal capability of the debris bed. To clarify the mechanisms underlying this self-leveling behavior, a large number of experiments were performed within a variety of conditions in recent years, under the constructive collaboration between the Japan Atomic Energy Agency (JAEA) and Kyushu University (Japan). The present contribution synthesizes and gives detailed comparative analyses of those experiments. Effects of various experimental parameters that may have potential influence on the leveling process, such as boiling mode, particle size, particle density, particle shape, bubbling rate, water depth and column geometry, were investigated, thus giving a large palette of favorable data for the better understanding of CDAs, and improved verifications of computer models developed in advanced fast reactor safety analysis codes.

Characteristics of Self-Leveling Behavior of Debris Beds in A Series of Experiments

International Nuclear Information System (INIS)

Cheng, Songbai; Yamano, Hidemasa; Suzuki, Tohru; Tobita, Yoshiharu; Yuya, Nakamura; Bin, Zhang; Tatsuya, Matsumoto; Koji, Morita

2013-01-01

During a hypothetical core-disruptive accident (CDA) in a sodium-cooled fast reactor (SFR), degraded core materials can form roughly conically-shaped debris beds over the core-support structure and/or in the lower inlet plenum of the reactor vessel from rapid quenching and fragmentation of the core material pool. However, coolant boiling may ultimately lead to leveling of the debris bed, which is crucial to the relocation of the molten core and heat-removal capability of the debris bed. To clarify the mechanisms underlying this self-leveling behavior, a large number of experiments were performed within a variety of conditions in recent years, under the constructive collaboration between the Japan Atomic Energy Agency (JAEA) and Kyushu University (Japan). The present contribution synthesizes and gives detailed comparative analyses of those experiments. Effects of various experimental parameters that may have potential influence on the leveling process, such as boiling mode, particle size, particle density, particle shape, bubbling rate, water depth and column geometry, were investigated, thus giving a large palette of favorable data for the better understanding of CDAs, and improved verifications of computer models developed in advanced fast reactor safety analysis codes

Summary of Disposable Debris Shields (DDS) Analysis for Development of Solid Debris Collection at NIF

International Nuclear Information System (INIS)

Shaughnessy, D.A.; Moody, K.J.; Grant, P.M.; Lewis, L.A.; Hutcheon, I.D.; Lindvall, R.; Gostic, J.M.

2011-01-01

Collection of solid debris from the National Ignition Facility (NIF) is being developed both as a diagnostic tool and as a means for measuring nuclear reaction cross sections relevant to the Stockpile Stewardship Program and nuclear astrophysics. The concept is straightforward; following a NIF shot, the debris that is produced as a result of the capsule and hohlraum explosion would be collected and subsequently extracted from the chamber. The number of nuclear activations that occurred in the capsule would then be measured through a combination of radiation detection and radiochemical processing followed by mass spectrometry. Development of the catcher is challenging due to the complex environment of the NIF target chamber. The collector surface is first exposed to a large photon flux, followed by the debris wind that is produced. The material used in the catcher must be mechanically strong in order to withstand the large amount of energy it is exposed to, as well as be chemically compatible with the form and composition of the debris. In addition, the location of the catcher is equally important. If it is positioned too close to the center of the target chamber, it will be significantly ablated, which could interfere with the ability of the debris to reach the surface and stick. If it is too far away, the fraction of the debris cloud collected will be too small to result in a statistically significant measurement. Material, geometric configuration, and location must all be tested in order to design the optimal debris collection system for NIF. One of the first ideas regarding solid debris collection at NIF was to use the disposable debris shields (DDS), which are fielded over the final optics assemblies (FOA) 7 m away from the center of the target chamber. The DDS are meant to be replaced after a certain number of shots, and if the shields could be subsequently analyzed after removal, it would serve as a mechanism for fielding a relatively large collection area

Analysis of dryout behaviour in laterally non-homogeneous debris beds using the MEWA-2D code

International Nuclear Information System (INIS)

Rahman, Saidur; Buerger, Manfred; Buck, Michael; Pohlner, Georg; Kulenovic, Rudi; Nayak, Arun Kumar; Sehgal, Bal Raj

2009-01-01

The present study analyses the impact of lateral non-homogeneities on the coolability of heated, initially water filled debris beds. Debris beds which may be formed in a postulated severe accident in light water reactors can not be expected to have a homogeneous structure. Lateral non-homogeneities are given e.g. already by a variation in height as in a heap of debris. Internally, less porous or more porous region may occur, the latter even as downcomer-like structures are considered to favour supply of water to the bed and thus coolability. In previous work it has been shown that such non-homogeneities are often strongly enhancing coolability, as compared to earlier investigations on laterally homogeneous beds. The present contribution aims at extending the view by analysing further cases of non-homogeneities with the MEWA-2D code. Especially, effects of capillary forces are considered in contrast to earlier analysis. Part of the paper deals with specific experiments performed in the POMECO facility at KTH in which a laterally stratified debris bed has been considered, whereby especially a strong jump of porosity, from 0.26 to 0.38, has been established. Astonishingly, under top as well as bottom flooding, dryout in these experiments occurred first in the lateral layer with higher porosity. Understanding is now provided by the effect of capillary forces: water is drawn from this layer to the less porous one. This effect improves the cooling in the less porous layer while it reduces coolability of the more porous layer. No real loop behaviour of inflow via the higher porosities with subsequent upflow in the less porous layer establishes here, in contrast to expectations. Other cases (different lateral heating in an otherwise homogeneous bed, closed downcomer in a homogeneous bed and heap-like debris) show, on the other hand, strongly improved coolability by such loops establishing due to the lateral differences in void and the corresponding pressure differences

Elementary theory of bed-sediment entrainment by debris flows and avalanches

Science.gov (United States)

Iverson, Richard M.

2012-01-01

Analyses of mass and momentum exchange between a debris flow or avalanche and an underlying sediment layer aid interpretations and predictions of bed-sediment entrainment rates. A preliminary analysis assesses the behavior of a Coulomb slide block that entrains bed material as it descends a uniform slope. The analysis demonstrates that the block's momentum can grow unstably, even in the presence of limited entrainment efficiency. A more-detailed, depth-integrated continuum analysis of interacting, deformable bodies identifies mechanical controls on entrainment efficiency, and shows that entrainment rates satisfy a jump condition that involves shear-traction and velocity discontinuities at the flow-bed boundary. Explicit predictions of the entrainment rateEresult from making reasonable assumptions about flow velocity profiles and boundary shear tractions. For Coulomb-friction tractions, predicted entrainment rates are sensitive to pore fluid pressures that develop in bed sediment as it is overridden. In the simplest scenario the bed sediment liquefies completely, and the entrainment-rate equation reduces toE = 2μ1gh1 cos θ(1 − λ1)/ , where θ is the slope angle, μ1 is the flow's Coulomb friction coefficient, h1 is its thickness, λ1 is its degree of liquefaction, and is its depth-averaged velocity. For values ofλ1ranging from 0.5 to 0.8, this equation predicts entrainment rates consistent with rates of 0.05 to 0.1 m/s measured in large-scale debris-flow experiments in which wet sediment beds liquefied almost completely. The propensity for bed liquefaction depends on several factors, including sediment porosity, permeability, and thickness, and rates of compression and shear deformation that occur when beds are overridden.

Fluidized Bed Reactor as Solid State Fermenter

Directory of Open Access Journals (Sweden)

Krishnaiah, K.

2005-01-01

Full Text Available Various reactors such as tray, packed bed, rotating drum can be used for solid-state fermentation. In this paper the possibility of fluidized bed reactor as solid-state fermenter is considered. The design parameters, which affect the performances are identified and discussed. This information, in general can be used in the design and the development of an efficient fluidized bed solid-state fermenter. However, the objective here is to develop fluidized bed solid-state fermenter for palm kernel cake conversion into enriched animal and poultry feed.

Experiments and procedures for bottom-heating heat-transfer experiments through UO2 debris beds in sodium

International Nuclear Information System (INIS)

Sowa, E.S.; Pedersen, D.R.; Pavlik, J.; Purviance, R.

1982-01-01

Real materials experiments in heat transfer through beds of UO 2 in sodium have been performed at Argonne National Laboratory over a period of years. The most recent method utilizes the resistive heating in a sheet tungsten filament located at the base of the debris container. A schematic diagram of the apparatus is shown. The tungsten is clamped between two water cooled copper electrodes. The filament is a sheet of tungsten 0.15 mm thick, 5 cm wide and 18 cm long. Two 6.5 mm thick sheets of boron nitride sandwich the filament. The upper face of the upper boron nitride sheet is in intimate contact with the bottom of the debris container. Temperatures are measured at various levels in the bed as well as in the boron nitride plate. In addition, the sodium pool temperature is measured by the thermocouple. The heat transferral through the bed is measured by the temperature difference and mass flowrate in a NaK condenser located above the debris bed. The NaK inlet and outlet temperatures are recorded individually, as well as, differentially

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

International Nuclear Information System (INIS)

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

Enhanced stability of steep channel beds to mass failure and debris flow initiation

Science.gov (United States)

Prancevic, J.; Lamb, M. P.; Ayoub, F.; Venditti, J. G.

2015-12-01

Debris flows dominate bedrock erosion and sediment transport in very steep mountain channels, and are often initiated from failure of channel-bed alluvium during storms. While several theoretical models exist to predict mass failures, few have been tested because observations of in-channel bed failures are extremely limited. To fill this gap in our understanding, we performed laboratory flume experiments to identify the conditions necessary to initiate bed failures in non-cohesive sediment of different sizes (D = 0.7 mm to 15 mm) on steep channel-bed slopes (S = 0.45 to 0.93) and in the presence of water flow. In beds composed of sand, failures occurred under sub-saturated conditions on steep bed slopes (S > 0.5) and under super-saturated conditions at lower slopes. In beds of gravel, however, failures occurred only under super-saturated conditions at all tested slopes, even those approaching the dry angle of repose. Consistent with theoretical models, mass failures under super-saturated conditions initiated along a failure plane approximately one grain-diameter below the bed surface, whereas the failure plane was located near the base of the bed under sub-saturated conditions. However, all experimental beds were more stable than predicted by 1-D infinite-slope stability models. In partially saturated sand, enhanced stability appears to result from suction stress. Enhanced stability in gravel may result from turbulent energy losses in pores or increased granular friction for failures that are shallow with respect to grain size. These grain-size dependent effects are not currently included in stability models for non-cohesive sediment, and they may help to explain better the timing and location of debris flow occurrence.

COOLOCE debris bed experiments and simulations investigating the coolability of cylindrical beds with different materials and flow modes

Energy Technology Data Exchange (ETDEWEB)

Takasuo, E.; Kinnunen, T.; Holmstroem, S.; Lehtikuusi, T. [VTT Technical Research Centre of Finland (Finland)

2013-07-15

The COOLOCE experiments aim at investigating the coolability of debris beds of different geometries, flow modes and materials. A debris bed may be formed of solidified corium as a result of a severe accident in a nuclear power reactor. The COOLOCE-8 test series consisted of experiments with a top-flooded test bed with irregular gravel as the simulant material. The objective was to produce comparison data useful in estimating the effects of different particle materials and the possible effect of the test arrangement on the results. It was found that the dryout heat flux (DHF) measured for the gravel was lower compared to previous experiments with spherical beads, and somewhat lower compared to the early STYX experiments. The difference between the beads and gravel is at least partially explained by the smaller average size of the gravel particles. The COOLOCE-9 test series included scoping experiments examining the effect of subcooling of the water pool in which the debris bed is immersed. The experiments with initially subcooled pool suggest that the subcooling may increase DHF and increase coolability. The aim of the COOLOCE-10 experiments was to investigate the effect of lateral flooding on the DHF a cylindrical test bed. The top of the test cylinder and its sidewall were open to water infiltration. It was found that the DHF is increased compared to a top-flooded cylinder by more than 50%. This suggests that coolability is notably improved. 2D simulations of the top-flooded test beds have been run with the MEWA code. Prior to the simulations, the effective particle diameter for the spherical beads and the irregular gravel was estimated by single-phase pressure loss measurements performed at KTH in Sweden. Parameter variations were done for particle size and porosity used as input in the models. It was found that with the measured effective particle diameter and porosity, the simulation models predict DHF with a relatively good accuracy in the case of spherical

Cooling of particulate debris beds: analysis of the initial D-series experiments

International Nuclear Information System (INIS)

Rivard, J.B.

1978-01-01

In an effort to provide basic data on the cooling of fast reactor debris, three in-pile experiments employing oxide fuel particulate in liquid sodium were completed in late 1977. Preliminary results from these experiments were reported shortly after their completion at the Third Post-Accident Heat Removal Information Exchange, at Argonne National Laboratory. In these experiments, a distribution of 100 μm to 1000 μm-sized particles of enriched UO 2 was fission-heated to simulate decay-heated debris. In each experiment, the UO 2 particles were contained in a closed, flat-bottomed vessel 012 mm in diameter which was insulated on the diameter and bottom. Sufficient sodium was included to saturate the bed of particles and to provide a volume of bulk sodium above the bed at a controlled temperature. Parameters of interest in the experiments are given

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)

Modelling debris flows down general channels

Directory of Open Access Journals (Sweden)

S. P. Pudasaini

2005-01-01

Full Text Available This paper is an extension of the single-phase cohesionless dry granular avalanche model over curved and twisted channels proposed by Pudasaini and Hutter (2003. It is a generalisation of the Savage and Hutter (1989, 1991 equations based on simple channel topography to a two-phase fluid-solid mixture of debris material. Important terms emerging from the correct treatment of the kinematic and dynamic boundary condition, and the variable basal topography are systematically taken into account. For vanishing fluid contribution and torsion-free channel topography our new model equations exactly degenerate to the previous Savage-Hutter model equations while such a degeneration was not possible by the Iverson and Denlinger (2001 model, which, in fact, also aimed to extend the Savage and Hutter model. The model equations of this paper have been rigorously derived; they include the effects of the curvature and torsion of the topography, generally for arbitrarily curved and twisted channels of variable channel width. The equations are put into a standard conservative form of partial differential equations. From these one can easily infer the importance and influence of the pore-fluid-pressure distribution in debris flow dynamics. The solid-phase is modelled by applying a Coulomb dry friction law whereas the fluid phase is assumed to be an incompressible Newtonian fluid. Input parameters of the equations are the internal and bed friction angles of the solid particles, the viscosity and volume fraction of the fluid, the total mixture density and the pore pressure distribution of the fluid at the bed. Given the bed topography and initial geometry and the initial velocity profile of the debris mixture, the model equations are able to describe the dynamics of the depth profile and bed parallel depth-averaged velocity distribution from the initial position to the final deposit. A shock capturing, total variation diminishing numerical scheme is implemented to

Enviromental and Social Impact of the Pouring of Solid Waste and Debris About the Quality of the Medellin River and Some of its Affluents

OpenAIRE

Carvajal Flórez, Elizabeth; Ingeniera Ambiental Universidad Nacional de Colombia. Magíster en Ingeniería Universidad de Antioquia. Docente Institución Universitaria

2009-01-01

This research aims at evaluating the influence of the pouring of home solid waste and debris about the quality of the Medellin River and some of its main tributaries such as the La Hueso, La Iguaná and La García streams, under sanitary, environmental, and social criteria. A theoretical-practical method was used, which deals the issue of the inadequate disposal of home waste and debris on the hillsides and beds of streams being the object of the study, establishing in the social reality a trut...

Experimental Investigation of the Effect of Particle Shape on Frictional Pressure drop in Particulate Debris Bed

International Nuclear Information System (INIS)

Park, Jin Ho; Kim, Eun Ho; Park, Hyun Sun

2014-01-01

To ensure the long-term cooling of corium in the reactor cavity, it is important to ensure the coolant ingression into the internally heat generated corium debris bed which is governed by pressure drop in porous media. For this reason, it is necessary to understand pressure drop mechanisms in porous bed to verify the feasibility of water penetration into particulate debris bed. According to the previous investigations on molten fuel-coolant interaction (FCI) experiments, it was found that quenched particulate debris bed was composed of irregular shape particles. Therefore, empirical or semiempirical models based on the Ergun equation (Ergun, 1952) for single-phase flow in porous media composed of single sized spherical particle were developed to consider the effect of particle shape on frictional pressure drop by means of adding a shape factor or modifying the Ergun constants etc. (Leva, 1959, Handley and Heggs, 1968, Macdonald, 1979, Foumeny et al., 1996). An experimental investigate on single-phase frictional pressure drop of water in packed bed was conducted in the transparent cylindrical test section with the inner diameter of 100 mm and the height of 700 mm to study the effect of particle shape on frictional pressure drop in porous media. This paper reports the experimental data for spherical particles with the diameter of 2 mm and 5 mm and cylindrical particles with ED of 2 mm and 5 mm. And also, the experimental data compared with the models to predict frictional pressure drop in particulate bed. The conclusions are summarized as follows. As a result of the experiment to measure frictional pressure drop in particulate bed composed of cylindrical particles the models predict the experimental data well within 22.11 % except the Handley and Heggs model when ED is applied to the models

Experimental Investigation of the Effect of Particle Shape on Frictional Pressure drop in Particulate Debris Bed

Energy Technology Data Exchange (ETDEWEB)

Park, Jin Ho; Kim, Eun Ho; Park, Hyun Sun [POSTECH, Pohang (Korea, Republic of)

2014-10-15

To ensure the long-term cooling of corium in the reactor cavity, it is important to ensure the coolant ingression into the internally heat generated corium debris bed which is governed by pressure drop in porous media. For this reason, it is necessary to understand pressure drop mechanisms in porous bed to verify the feasibility of water penetration into particulate debris bed. According to the previous investigations on molten fuel-coolant interaction (FCI) experiments, it was found that quenched particulate debris bed was composed of irregular shape particles. Therefore, empirical or semiempirical models based on the Ergun equation (Ergun, 1952) for single-phase flow in porous media composed of single sized spherical particle were developed to consider the effect of particle shape on frictional pressure drop by means of adding a shape factor or modifying the Ergun constants etc. (Leva, 1959, Handley and Heggs, 1968, Macdonald, 1979, Foumeny et al., 1996). An experimental investigate on single-phase frictional pressure drop of water in packed bed was conducted in the transparent cylindrical test section with the inner diameter of 100 mm and the height of 700 mm to study the effect of particle shape on frictional pressure drop in porous media. This paper reports the experimental data for spherical particles with the diameter of 2 mm and 5 mm and cylindrical particles with ED of 2 mm and 5 mm. And also, the experimental data compared with the models to predict frictional pressure drop in particulate bed. The conclusions are summarized as follows. As a result of the experiment to measure frictional pressure drop in particulate bed composed of cylindrical particles the models predict the experimental data well within 22.11 % except the Handley and Heggs model when ED is applied to the models.

Experimental investigation of particulate debris spreading in a pool

Energy Technology Data Exchange (ETDEWEB)

Konovalenko, A., E-mail: kono@kth.se [Division of Nuclear Power Safety, Royal Institute of Technology (KTH) , Roslagstullsbacken 21, Stockholm 106 91 (Sweden); Basso, S., E-mail: simoneb@kth.se [Division of Nuclear Power Safety, Royal Institute of Technology (KTH) , Roslagstullsbacken 21, Stockholm 106 91 (Sweden); Kudinov, P., E-mail: pkudinov@kth.se [Division of Nuclear Power Safety, Royal Institute of Technology (KTH) , Roslagstullsbacken 21, Stockholm 106 91 (Sweden); Yakush, S.E., E-mail: yakush@ipmnet.ru [Institute for Problems in Mechanics of the Russian Academy of Sciences, Ave. Vernadskogo 101 Bldg 1, Moscow 119526 (Russian Federation)

2016-02-15

Termination of severe accident progression by core debris cooling in a deep pool of water under reactor vessel is considered in several designs of light water reactors. However, success of this accident mitigation strategy is contingent upon the effectiveness of heat removal by natural circulation from the debris bed. It is assumed that a porous bed will be formed in the pool in the process of core melt fragmentation and quenching. Debris bed coolability depends on its properties and system conditions. The properties of the bed, including its geometry are the outcomes of the debris bed formation process. Spreading of the debris particles in the pool by two-phase turbulent flows induced by the heat generated in the bed can affect the shape of the bed and thus influence its coolability. The goal of this work is to provide experimental data on spreading of solid particles in the pool by large-scale two-phase flow. The aim is to provide data necessary for understanding of separate effects and for development and validation of models and codes. Validated codes can be then used for prediction of debris bed formation under prototypic severe accident conditions. In PDS-P (Particulate Debris Spreading in the Pool) experiments, air injection at the bottom of the test section is employed as a means to create large-scale flow in the pool in isothermal conditions. The test section is a rectangular tank with a 2D slice geometry, it has fixed width (72 mm), adjustable length (up to 1.5 m) and allows water filling to the depth of up to 1 m. Variable pool length and depth allows studying two-phase circulating flows of different characteristic sizes and patterns. The average void fraction in the pool is determined by video recording and subsequent image processing. Particles are supplied from the top of the facility above the water surface. Results of several series of PDS-P experiments are reported in this paper. The influence of the gas flow rate, pool dimensions, particle density

Assessment of capability of models for prediction of pressure drop and dryout heat flux in a heat generating particulate debris bed

International Nuclear Information System (INIS)

Kulkarni, P.P.; Nayak, A.K.; Rashid, M.; Kulenovic, R.

2009-01-01

During a severe accident in a light water reactor, the core can melt and be relocated to the lower plenum of the reactor pressure vessel. There it can form a particulate debris bed due to the possible presence of water. This bed, if not quenched in time, can lead to the failure of the pressure vessel because of the insufficient heat removal of decay heat in the debris bed. Therefore, addressing the issue of coolability behaviour of heat generating particulate debris bed is of prime importance in the framework of severe accident management strategies, particularly in case of above mentioned late phase scenario of an accident. In order to investigate the coolability behaviour of particulate debris bed, experiments were carried out at IKE test facility 'DEBRIS' on particle beds of irregularly shaped particles mixed with spheres under top- and bottom-flooding condition. The pressure drop and dryout heat flux (DHF) were measured for top- and bottom-flooding conditions. For top-flooding conditions, it was found that the pressure gradients are all smaller than the hydrostatic pressure gradient of water, indicating an important role of the counter-current interfacial shear stress of the two-phase flow. For bottom-flooding with a relatively high liquid inflow velocity, the pressure gradient increases consistently with the vapour velocity and the fluid-particle drags become important. Also, with additional forced liquid inflow from the bottom, the DHF increases dramatically. In all the cases, it was found that the DHF is significantly larger with bottom-flooding condition compared to top-flooding condition. Different models such as Lipinski, Reed, Tung and Dhir, Hu and Theophanous, and Schulenberg and Mueller have been used to predict the pressure drop characteristics and the DHF of heat generating particulate debris beds. Comparison is made among above mentioned models and experimental results for DHF and pressure drop characteristics. Considering the overall trend in

Idealized debris flow in flume with bed driven by a conveyor belt

Science.gov (United States)

Ling, Chi-Hai; Chen, Cheng-lung

1989-01-01

The generalized viscoplastic fluid (GVF) model is used to derive the theoretical expressions of two-dimensional velocities and surface profile for debris flow established in a flume with bed driven by a conveyor belt. The rheological parameters of the GVF model are evaluated through the comparison of theoretical results with measured data. A slip velocity of the established (steady) nonuniform flow on the moving bed (i.e., the conveyor belt) is observed, and a relation between the slip velocity and the velocity gradient at the bed is derived. Two belts, one rough and the other smooth, were tested. The flow profile in the flume is found to be linear and dependent on the roughness of the belt, but not much on its speed.

Debris bed cooling following an HCDA in a fast reactor. Final report

International Nuclear Information System (INIS)

Abdel-Khalik, S.I.

1983-01-01

Natural convection within simulated core debris beds has been experimentally and theoretically investigated. The effect of heating method on bed behavior has been found to be important. For directly-heated beds, variations of the downward and upward power fraction and Nusselt numbers with bed loading, power density, particle size, overlying fluid layer height and top surface boundary condition have been determined. Generalized correlations for the upward and downward Nusselt numbers as functions of the internal Rayleigh number have been obtained. Particle tracing techniques have been used to visualize the flow patterns within the bed and overlying fluid layer. The temperature distributions within the bed and overlying fluid layer have also been measured. The experimental data have been compared with COMMIX-lA predictions. Poor agreement has been obtained for both the integral quantities, i.e. downward and upward power fractions and Nusselt numbers, as well as the steady state velocity and temperature distributions. The code does not correctly predict either the magnitude or even the trend of the data

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

Energy Technology Data Exchange (ETDEWEB)

Bechaud, C.; Duval, F.; Fichot, F. [CEA Cadarache, Inst. de Protection et de Surete Nucleaire13 - Saint-Paul-lez-Durance (France); Quintard, M. [Institut de Mecanique des Fluides de Toulouse, 31 (France); Parent, M. [CEA Grenoble, Dept. de Thermohydraulique et de Physique, 38 (France)

2001-07-01

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

Dryout heat flux in a debris bed with forced coolant flow from below

International Nuclear Information System (INIS)

Bang, Kwang-Hyun; Kim, Jong-Myung

2004-01-01

The objective of the present study is to experimentally investigate the enhancement of dryout heat flux in debris beds with coolant flow from below. The experimental facility consists mainly of an induction heater (40 kW, 35 kHz), a double-wall quartz-tube test section containing steel-particle bed and coolant injection and recovery condensing loop. A fairly uniform heating of particle bed was achieved by induction heating. This paper reports the experimental data for 5 mm particle bed and 300 mm bed height. The dryout heat rate data were obtained of both top-flooding case and forced coolant injection from below with the injection mass flux up to 1.5 kg/m 2 s. For the top-flooded case, the volumetric dryout heat rate was about 4 MW/m 3 and it increased as the rate of coolant injection from below was increased. At the coolant injection mass flux of 1.5 kg/m 2 s, the volumetric dryout heat rate was about 10 MW/m 3 , the enhancement factor was more than two. (author)

Investigation of flow regime in debris bed formation behavior with nonspherical particles

Directory of Open Access Journals (Sweden)

Songbai Cheng

2018-02-01

Full Text Available It is important to clarify the characteristics of flow regimes underlying the debris bed formation behavior that might be encountered in core disruptive accidents of sodium-cooled fast reactors. Although in our previous publications, by applying dimensional analysis technique, an empirical model, with its reasonability confirmed over a variety of parametric conditions, has been successfully developed to predict the regime transition and final bed geometry formed, so far this model is restricted to predictions of debris mixtures composed of spherical particles. Focusing on this aspect, in this study a new series of experiments using nonspherical particles have been conducted. Based on the knowledge and data obtained, an extension scheme is suggested with the purpose of extending the base model to cover the particle-shape influence. Through detailed analyses and given our current range of experimental conditions, it is found that, by coupling the base model with this scheme, respectable agreement between experiments and model predictions for the regime transition can be achieved for both spherical and nonspherical particles. Knowledge and evidence from our work might be utilized for the future improvement of design of an in-vessel core catcher as well as the development and verification of sodium-cooled fast reactor severe accident analysis codes in China.

Comparison of Two Phase Pressure Drop Models in 1-D Top Flooded Debris Bed

International Nuclear Information System (INIS)

Lee, Moon Eon; Park, Jin Ho; Kim, Eun ho; Park, Hyun Sun

2016-01-01

The dry out of coolant inside debris bed can be considered as the limitation of cooling in the conservative point of view and the heat flux through whole bed at the situation is named as Dryout Heat Flux (DHF). The modeling of DHF for debris bed started from early 1980s by several researchers. It is known that DHF mainly occurs by hydrodynamic limitation inside porous media. Therefore, there have been following attempts to capture flow resistance in porous media, precisely. Up to date, although there are about seven pressure drop models available in literatures, it is hard to find comparison of those models with a wide range of DHF experimental data. The one attempt[9] was conducted in 2013, but due to lack of consideration of the capillary pressure in his work, the DHF values that he calculated seem to be underestimated, especially in the range of the small particle diameter cases. In this research, the importance of capillary pressure in the comparison of pressure drop model with experimental data was checked and model selection among pressure drop models for the DHF calculation was also conducted. The model comparison with 108 experimental data from various conditions has been conducted and the Schmidt model shows the best agreement to the experimental data although Reed, Rahman model also show similar results.

Comparison of Two Phase Pressure Drop Models in 1-D Top Flooded Debris Bed

Energy Technology Data Exchange (ETDEWEB)

Lee, Moon Eon; Park, Jin Ho; Kim, Eun ho; Park, Hyun Sun [POSTECH, Pohang (Korea, Republic of)

2016-05-15

The dry out of coolant inside debris bed can be considered as the limitation of cooling in the conservative point of view and the heat flux through whole bed at the situation is named as Dryout Heat Flux (DHF). The modeling of DHF for debris bed started from early 1980s by several researchers. It is known that DHF mainly occurs by hydrodynamic limitation inside porous media. Therefore, there have been following attempts to capture flow resistance in porous media, precisely. Up to date, although there are about seven pressure drop models available in literatures, it is hard to find comparison of those models with a wide range of DHF experimental data. The one attempt[9] was conducted in 2013, but due to lack of consideration of the capillary pressure in his work, the DHF values that he calculated seem to be underestimated, especially in the range of the small particle diameter cases. In this research, the importance of capillary pressure in the comparison of pressure drop model with experimental data was checked and model selection among pressure drop models for the DHF calculation was also conducted. The model comparison with 108 experimental data from various conditions has been conducted and the Schmidt model shows the best agreement to the experimental data although Reed, Rahman model also show similar results.

Simulation of the arrival and evolution of debris in a PWR lower head with the SFD ICARE2 code

International Nuclear Information System (INIS)

Fichot, F.; Babik, F.; Zabiego, M.; Barrachin, M.; Chatelard, P.; Lefevre, B.

1999-01-01

In a severe accident scenario, the prediction of vessel failure is related to the prediction of the behaviour of solid and liquid debris which have fallen into the lower plenum. One of the difficulties is to define the initial debris bed conditions. They will depend on the presence of water or not in the lower plenum. They will also depend on the rate and composition of the falling debris. In this context, IPSN performs calculations using the ICARE2 code in order to predict the core degradation in a scenario similar to TMI-2, and to estimate the so-called initial conditions of the debris bed, i.e. the history of the debris falling into the lower plenum and the evolution of this debris bed. The latest version of ICARE2 (V3mod0) which deals with molten pools and debris bed allows to follow the materials from their early melting in the core region to their later relocation into the lower plenum. A description of the modeling of the debris bed and molten pool formation is provided in this paper. The debris bed modeling is based on a porous medium approach. Mass and energy conservation equations for each of the three phases and momentum conservation equations for the liquid and gas phases are solved. Up to now, due to the lack of knowledge, no model has been developed to estimate the debris size distribution. It is chosen by the user at the beginning of the calculation. As the temperature increases in the debris bed, a molten pool appears and starts to grow. Thermal effects of the natural convection movements in the pool are taken into account using classical correlations. The present study corresponds to a first application of the new capabilities of ICARE2. However it shows the interest of such an approach for a problem where the behaviour in the vessel is closely related to the previous events that occurred in the core region. Improvements are foreseen, especially for the natural convection, crust formation and interaction with water. (authors)

Models for dryout in debris beds. Review and application to the analysis of PAHR

International Nuclear Information System (INIS)

Yamakoshi, Yoshinori

2000-03-01

There are many models for dryout in debiris beds and various conditions under which these models are applicable. For a reliable analysis of post-accident heat removal (PAHR), it is important that characteristics and applicability of each model should be made clear. In this report, formulation of the models for dryout and applicability of them are studied through comparing with experimental data. A new model for dryout prediction is also discussed here. It is difficult to predict the dryout power especially for a relatively shallow bed using a conventional model for channeled beds. The new model, which is based on the one-dimensional model derived by Lipinski, has permeability of channels in the governing equation, and enables us to predict the dryout power for relatively shallow beds. The following conclusions are derived from comparing the predicted dryout power with experimental data. The model for series heat removal is applicable to a packed bed while the DEBRIS-MD underestimates the dryout power for it. Either the original model assuming channel formation on the top of the bed or the modified model is applicable to a relatively deep bed with channels. For a relatively shallow bed with channels, the dryout power predicted by the modified model agrees with the experimental data in comparison with other models. (author)

Critical comparison of hydrodynamic models for gas-solid fluidized beds - Part II: freely bubbling gas-solid fluidized beds

NARCIS (Netherlands)

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

2005-01-01

Correct prediction of spontaneous bubble formation in freely bubbling gas¿solid fluidized beds using Eulerian models, strongly depends on the description of the internal momentum transfer in the particulate phase. In this part, the comparison of the simple classical model, describing the solid phase

2D model for melt progression through rods and debris

International Nuclear Information System (INIS)

Fichot, F.

2001-01-01

During the degradation of a nuclear core in a severe accident scenario, the high temperatures reached lead to the melting of materials. The formation of liquid mixtures at various elevations is followed by the flow of molten materials through the core. Liquid mixture may flow under several configurations: axial relocation along the rods, horizontal motion over a plane surface such as the core support plate or a blockage of material, 2D relocation through a debris bed, etc.. The two-dimensional relocation of molten material through a porous debris bed, implemented for the simulation of late degradation phases, has opened a new way to the elaboration of the relocation model for the flow of liquid mixture along the rods. It is based on a volume averaging method, where wall friction and capillary effects are taken into account by introducing effective coefficients to characterize the solid matrix (rods, grids, debris, etc.). A local description of the liquid flow is necessary to derive the effective coefficients. Heat transfers are modelled in a similar way. The derivation of the conservation equations for the liquid mixture falling flow (momentum) in two directions (axial and radial-horizontal) and for the heat exchanges (energy) are the main points of this new model for simulating melt progression. In this presentation, the full model for the relocation and solidification of liquid materials through a rod bundle or a debris bed is described. It is implemented in the ICARE/CATHARE code, developed by IPSN in Cadarache. The main improvements and advantages of the new model are: A single formulation for liquid mixture relocation, in 2D, either through a rod bundle or a porous debris bed, Extensions to complex structures (grids, by-pass, etc..), The modeling of relocation of a liquid mixture over plane surfaces. (author)

SCDAP/RELAP5 Modeling of Movement of Melted Material Through Porous Debris in Lower Head

International Nuclear Information System (INIS)

Siefken, L. J.

1998-01-01

Designs are described for implementing models for calculating the movement of melted material through the interstices in a matrix of porous debris in the lower head of a reactor vessel. The COUPLE model in SCDAP/RELAP5 represents both the porous and nonporous debris that results from core material slumping into the lower head during a severe accident in a Light Water Reactor. Currently, the COUPLE model has no capability to model the movement of material that melts within a matrix of porous material. The COUPLE model also does not have the capability to model the movement of liquefied core plate material that slumps onto a porous debris bed in the lower head. In order to advance beyond the assumption the liquefied material always remains stationary, designs are developed for calculations of the movement of liquefied material through the interstices in a matrix of porous material. Correlations are identified for calculating the permeability of the porous debris and for calculating the rate of flow of liquefied material through the interstices in the debris bed. Correlations are also identified for calculating the relocation of solid debris that has a large amount of cavities due to the flowing away of melted material. Equations are defined for calculating the effect on the temperature distribution in the debris bed of heat transported by moving material and for changes in effective thermal conductivity and heat capacity due to the movement of material. The implementation of these models is expected to improve the calculation of the material distribution and temperature distribution of debris in the lower head for cases in which the debris is porous and liquefied material is present within the porous debris

Solid phase transport in series fluidised bed reactors

International Nuclear Information System (INIS)

Hayes, M.R.

1980-01-01

In a multistage counter-current fluidised bed column, fluidised bed material is recycled within each stage and a fraction is continuously withdrawn to the next lower stage at a rate dependent only on the rate of removal of the fluidised bed material from the base of the column. It has a particular application to the ion exchange treatment of liquids containing suspended solids, for example leach solutions from uranium ores. (author)

On the solid stress in a fluidized bed

International Nuclear Information System (INIS)

Qassim, R.Y.; Souza, R. de.

1980-09-01

The existence of solid stress in an incipiently gas-fluidized bed is shown by experimental measurement. This stress is shown to have two components: an isotropic pressure and an extra stress which depends on the relative velocity between fluid and solid. Both the solid pressure and the solid extra stress component are found to be of the same order of magnitude as the fluid pressure. (Author) [pt

Management and characteristics of recycled manure solids used for bedding in Midwest freestall dairy herds.

Science.gov (United States)

Husfeldt, A W; Endres, M I; Salfer, J A; Janni, K A

2012-04-01

Interest in using recycled manure solids (RMS) as a bedding material for dairy cows has grown in the US Midwest. Cost of common bedding materials has increased in recent years and availability has decreased. Information regarding the composition of RMS and its use as a bedding material for dairy cows in the Midwest is very limited. The objectives of this study were to characterize RMS as a bedding material, observe bedding management practices, document methods of obtaining RMS, and describe housing facilities. We visited 38 Midwest dairy operations bedding freestalls with RMS to collect data. Methods of obtaining RMS for bedding included separation of anaerobic digested manure, separation of raw manure, and separation of raw manure followed by mechanical drum-composting for 18 to 24 h. Average bedding moisture of unused RMS was 72.4% with a pH of 9.16. Unused samples contained (on a dry basis) 1.4% N, 44.9% C, 32.7C:N ratio, 0.44% P, 0.70% K, 76.5% neutral detergent fiber, 9.4% ash, 4.4% nonfiber carbohydrates, and 1.1% fat. Moisture was lowest for drum-composted solids before and after use as freestall bedding. After use in the stalls, digested solids had lower neutral detergent fiber content (70.5%) than drum-composted (75.0%) and separated raw (73.1%) solids. Total N content was greater in digested solids (2.0%) than in separated raw (1.7%) solids. Total bacterial populations in unused bedding were greatest in separated raw manure solids but were similar between digested and drum-composted manure solids. Drum-composted manure solids had no coliform bacteria before use as freestall bedding. After use as bedding, digested manure solids had lower total bacteria counts compared with drum-composted and separated raw manure solids, which had similar counts. Used bedding samples of digested solids contained fewer environmental streptococci than drum-composted and separated raw solids and had reduced Bacillus counts compared with separated raw solids. Coliform counts

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

NARCIS (Netherlands)

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

2006-01-01

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

Experimental study of head loss and filtration for LOCA debris

International Nuclear Information System (INIS)

Rao, D.V.; Souto, F.J.

1996-02-01

A series of controlled experiments were conducted to obtain head loss and filtration characteristics of debris beds formed of NUKON trademark fibrous fragments, and obtain data to validate the semi-theoretical head loss model developed in NUREG/CR-6224. A thermally insulated closed-loop test set-up was used to conduct experiments using beds formed of fibers only and fibers intermixed with particulate debris. A total of three particulate mixes were used to simulate the particulate debris. The head loss data were obtained for theoretical fiber bed thicknesses of 0.125 inches to 4.0 inches; approach velocities of 0.15 to 1.5 ft/s; temperatures of 75 F and 125 F; and sludge-to-fiber nominal concentration ratios of 0 to 60. Concentration measurements obtained during the first flushing cycle were used to estimate the filtration efficiencies of the debris beds. For test conditions where the beds are fairly uniform, the head loss data were predictable within an acceptable accuracy range by the semi-theoretical model. The model was equally applicable for both pure fiber beds and the mixed beds. Typically the model over-predicted the head losses for very thin beds and for thin beds at high sludge-to-fiber mass ratios. This is attributable to the non-uniformity of such debris beds. In this range the correlation can be interpreted to provide upper bound estimates of head loss. This is pertinent for loss of coolant accidents in boiling water reactors

Interaction of debris with a solid obstacle: Numerical analysis

International Nuclear Information System (INIS)

Kosinska, Anna

2010-01-01

The subject of this research is the propagation of a cloud of solid particles formed from an explosion-damaged construction. The main objective is the interaction of the cloud (debris) with a solid beam located at some distance from the explosion. The mathematical model involves the flow of the gas using standard conservation equations, and this part of the model is solved numerically. The solid particles are treated as a system of solid points (so-called Lagrangian approach), whose motion is the result of the flowing gas as well as collisions with obstacles. These two issues are described respectively by Newton's second law and the hard-sphere model. The model is used to simulate various cases where the influence of different parameters like the value of the pressure of the explosion, the particle size, the number of particles and the obstacle location are investigated. The results are presented as snapshots of particle location, and also as the particle total momentum during collision with the beam.

Apparatus for controlling molten core debris

International Nuclear Information System (INIS)

Golden, M.P.; Tilbrook, R.W.; Heylmun, N.F.

1972-01-01

Disclosed is an apparatus for containing, cooling, diluting, dispersing and maintaining subcritical the molten core debris assumed to melt through the bottom of a nuclear reactor pressure vessel in the unlikely event of a core meltdown. The apparatus is basically a sacrificial bed system which includes an inverted conical funnel, a core debris receptacle including a spherical dome, a spherically layered bed of primarily magnesia bricks, a cooling system of zig-zag piping in graphite blocks about and below the bed and a cylindrical liner surrounding the graphite blocks including a steel shell surrounded by firebrick. Tantalum absorber rods are used in the receptacle and bed. 9 claims, 22 figures

Dynamic behavior of a solid particle bed in a liquid pool

International Nuclear Information System (INIS)

Liu Ping; Yasunaka, Satoshi; Matsumoto, Tatsuya; Morita, Koji; Fukuda, Kenji; Yamano, Hidemasa; Tobita, Yoshiharu

2007-01-01

Dynamic behavior of solid particle beds in a liquid pool against pressure transients was investigated to model the mobility of core materials in a postulated disrupted core of a liquid metal fast reactor. A series of experiments was performed with a particle bed of different bed heights, comprising different monotype solid particles, where variable initial pressures of the originally pressurized nitrogen gas were adopted as the pressure sources. Computational simulations of the experiments were performed using SIMMER-III, a fast reactor safety analysis code. Comparisons between simulated and experimental results show that the physical model for multiphase flows used in the SIMMER-III code can reasonably represent the transient behaviors of pool multiphase flows with rich solid phases, as observed in the current experiments. This demonstrates the basic validity of the SIMMER-III code on simulating the dynamic behaviors induced by pressure transients in a low-energy disrupted core of a liquid metal fast reactor with rich solid phases

Interaction of debris with a solid obstacle: numerical analysis.

Science.gov (United States)

Kosinska, Anna

2010-05-15

The subject of this research is the propagation of a cloud of solid particles formed from an explosion-damaged construction. The main objective is the interaction of the cloud (debris) with a solid beam located at some distance from the explosion. The mathematical model involves the flow of the gas using standard conservation equations, and this part of the model is solved numerically. The solid particles are treated as a system of solid points (so-called Lagrangian approach), whose motion is the result of the flowing gas as well as collisions with obstacles. These two issues are described respectively by Newton's second law and the hard-sphere model. The model is used to simulate various cases where the influence of different parameters like the value of the pressure of the explosion, the particle size, the number of particles and the obstacle location are investigated. The results are presented as snapshots of particle location, and also as the particle total momentum during collision with the beam. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Analyses on ex-vessel debris formation and coolability in SARNET frame

International Nuclear Information System (INIS)

Pohlner, G.; Buck, M.; Meignen, R.; Kudinov, P.; Ma, W.; Polidoro, F.; Takasuo, E.

2014-01-01

Highlights: • Melt outflow varies from dripping melt outflow to molten corium jets of variable size. • Experiments show clear trend of producing particles in size range 2-4 mm. • Code calculations show complete solidification of particles, yielding formation of fragmented debris beds. • Limits of debris bed cooling and coolability margins are analysed. - Abstract: The major aim of work in the SARNET2 European project on ex-vessel debris formation and coolability was to get an overall perspective on coolability of melt released from a failed reactor pressure vessel and falling into a water-filled cavity. Especially, accident management concepts for BWRs, dealing with deep water pools below the reactor vessel, are addressed, but also shallower pools in existing PWRs, with questions about partial cooling and time delay of molten corium concrete interaction. The subject can be divided into three main topics: (i) Debris bed formation by breakup of melt, (ii) Coolability of debris and (iii) Coupled treatment of the processes. Accompanied by joint collaborations of the partners, the performed work comprises theoretical, experimental and modelling activities. Theoretical work was done by KTH on the melt outflow conditions from a RPV and on the quantification of the probability of yielding a non-coolable ex-vessel bed by use of probabilistic assessment. IKE introduced a theoretical concept to improve debris bed coolability. A large amount of experimental work was done by partners (KTH, VTT, IKE) on the coolability of debris beds using different bed geometries, particles, heating methods and water feeds, yielding a valuable base for code validation. Modelling work was mainly done by IKE, IRSN, RSE and VTT concerning jet breakup and/or debris bed formation and cooling in 2D and 3D geometries. A benchmark for the DEFOR-A experiment of KTH was performed. Important progress was reached for several tasks and aspects and important insights are given, enabling to focus the

Fluid bed solids heater. Final technical report

Energy Technology Data Exchange (ETDEWEB)

Preuit, L. C.

1980-01-01

A solids heater which operates at up to 2000 F was designed, fabricated, installed and operated through checkout at the Morgantown Energy Technology Center at Morgantown, West Virginia. The system, designated the 2000 F Fluid Bed Solids Heater (FBSH) uses a fluidized bed to heat limestone to 600 F and aluminium oxide or silicon carbide to 2000 F and discharges heated solids upon demand. The FBSH with added valve handling and pressurization equipment is known as the Valve Hot Solids Test Unit and is intended for use by the US Department of Energy for testing of valves for severe service applications in coal conversion and utilization processes. The FBSH as designed and supplied by Combustion Power Company includes process equipment, controls, the enclosing building and other associated equipment. In the 600 F range of operation it can circulate limestone through two valve test trains simultaneously on a continuous basis. Only one valve test train is used for 2000 F solids and operation in that range is also continuous. Limestone, crushed to minus 5/16 size, is heated, discharged, and recycled at a maximum average rate of 250 lb/min while aluminum oxide or silicon carbide, No. 8 grit, is circulated at rates up to 167 lb/min. The FBSH control system is designed for automatic operation, and capability is included for external computerized data acquisition and/or supervisory control. An operating and maintenance manual and as-built drawings have been submitted. This report describes the FBSH equipment, its design basis, and its operation. It has been prepared and submitted in fulfillment of Contract Number DIAC05-77ET10499.

Investigation of Gas Solid Fluidized Bed Dynamics with Non-Spherical Particles

Energy Technology Data Exchange (ETDEWEB)

Choudhuri, Ahsan [Univ. of Texas, El Paso, TX (United States). Dept. of Mechanical Engineering

2013-06-30

One of the largest challenges for 21st century is to fulfill global energy demand while also reducing detrimental impacts of energy generation and use on the environment. Gasification is a promising technology to meet the requirement of reduced emissions without compromising performance. Coal gasification is not an incinerating process; rather than burning coal completely a partial combustion takes place in the presence of steam and limited amounts of oxygen. In this controlled environment, a chemical reaction takes place to produce a mixture of clean synthetic gas. Gas-solid fluidized bed is one such type of gasification technology. During gasification, the mixing behavior of solid (coal) and gas and their flow patterns can be very complicated to understand. Many attempts have taken place in laboratory scale to understand bed hydrodynamics with spherical particles though in actual applications with coal, the particles are non-spherical. This issue drove the documented attempt presented here to investigate fluidized bed behavior using different ranges of non-spherical particles, as well as spherical. For this investigation, various parameters are controlled that included particle size, bed height, bed diameter and particle shape. Particles ranged from 355 µm to 1180 µm, bed diameter varied from 2 cm to 7 cm, two fluidized beds with diameters of 3.4 cm and 12.4 cm, for the spherical and non-spherical shaped particles that were taken into consideration. Pressure drop was measured with increasing superficial gas velocity. The velocity required in order to start to fluidize the particle is called the minimum fluidization velocity, which is one of the most important parameters to design and optimize within a gas-solid fluidized bed. This minimum fluidization velocity was monitored during investigation while observing variables factors and their effect on this velocity. From our investigation, it has been found that minimum fluidization velocity is independent of bed

Short communication: Environmental mastitis pathogen counts in freestalls bedded with composted and fresh recycled manure solids.

Science.gov (United States)

Cole, K J; Hogan, J S

2016-02-01

An experiment was conducted to compare bacterial counts of environmental mastitis pathogens in composted recycled manure solids bedding with those in fresh recycled manure solids. Eighteen Holstein cows were housed in 1 pen with 18 stalls. One row of 9 freestalls included mattresses and was bedded weekly with composted recycled manure solids. The second row of 9 freestalls included mattresses and was bedded weekly with fresh recycled manure solids. The back one-third of stalls toward the alleyway was covered in 25 to 50 mm of bedding. Samples were taken from the back one-third of 4 stalls for both treatments on d 0, 1, 2, and 6 of each week. After 3 wk, bedding treatments were switched between rows, making the total duration 6 wk. Mean total gram-negative bacterial counts were approximately 0.5 log10 cfu/g of dry matter lower in the composted recycled manure solids on d 0 compared with fresh recycled manure solids. Klebsiella species, coliform, and Streptococcus species counts were at least 1.0 log10 cfu/g of dry matter lower in composted compared with fresh recycled manure solids on d 0. Only gram-negative bacterial counts on d 1 were reduced in composted recycled manure solids compared with fresh recycled manure solids. Differences were not observed between treatments in gram-negative bacterial, coliform, Klebsiella species, or Streptococcus species counts on d 2 and 6. Ash content was higher in composted recycled manure solids compared with fresh recycled manure solids on d 0, 1, 2, and 6. Despite the increase in ash after composting, bacterial counts of mastitis pathogens in composted recycled manure solids were comparable with those in fresh recycled manure when used as freestall bedding. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Product removal and solids transport from fluidized-bed calciners

International Nuclear Information System (INIS)

Grimmett, E.S.; Munger, D.H.

1978-09-01

Methods of removing the solid product from pilot-plant and production fluidized-bed calciners, and transporting product to underground storage vaults are reported here. Testing of dense-phase solids transport systems in test loops during development of a 15-cm-diam. and 30-cm-diam. calciner are described. A lean-phase solid transport system is used with the Waste Calcining Facility. The results of some recent tests done in a lean-phase transport system connected to the 30-cm-diam. calciner are included in this report

Numerical investigation of solid mixing in a fluidized bed coating process

Science.gov (United States)

Kenche, Venkatakrishna; Feng, Yuqing; Ying, Danyang; Solnordal, Chris; Lim, Seng; Witt, Peter J.

2013-06-01

Fluidized beds are widely used in many process industries including the food and pharmaceutical sectors. Despite being an intensive research area, there are no design rules or correlations that can be used to quantitatively predict the solid mixing in a specific system for a given set of operating conditions. This paper presents a numerical study of the gas and solid dynamics in a laboratory scale fluidized bed coating process used for food and pharmaceutical industries. An Eulerian-Eulerian model (EEM) with kinetic theory of granular flow is selected as the modeling technique, with the commercial computational fluid dynamics (CFD) software package ANSYS/Fluent being the numerical platform. The flow structure is investigated in terms of the spatial distribution of gas and solid flow. The solid mixing has been evaluated under different operating conditions. It was found that the solid mixing rate in the horizontal direction is similar to that in the vertical direction under the current design and operating conditions. It takes about 5 s to achieve good mixing.

Non-intrusive measurement and hydrodynamics characterization of gas–solid fluidized beds: a review

OpenAIRE

Sun, Jingyuan; Yan, Yong

2016-01-01

Gas-solid fluidization is a well-established technique to suspend or transport particles and has been applied in a variety of industrial processes. Nevertheless, our knowledge of fluidization hydrodynamics is still limited for the design, scale-up and operation optimization of fluidized bed reactors. It is therefore essential to characterize the two-phase flow behaviours in gas-solid fluidized beds and monitor the fluidization processes for control and optimization. A range of non-intrusive t...

TMI-2 core debris analysis

International Nuclear Information System (INIS)

Cook, B.A.; Carlson, E.R.

1985-01-01

One of the ongoing examination tasks for the damaged TMI-2 reactor is analysis of samples of debris obtained from the debris bed presently at the top of the core. This paper summarizes the results reported in the TMI-2 Core Debris Grab Sample Examination and Analysis Report, which will be available early in 1986. The sampling and analysis procedures are presented, and information is provided on the key results as they relate to the present core condition, peak temperatures during the transient, temperature history, chemical interactions, and core relocation. The results are then summarized

Mathematical model for solid fuel combustion in fluidized bed

International Nuclear Information System (INIS)

Kostikj, Zvonimir; Noshpal, Aleksandar

1994-01-01

A mathematical model for computation of the combustion process of solid fuel in fluidized bed is presented in this work. Only the combustor part of the plant (the fluidized bed and the free board) is treated with this model. In that manner, all principal, physical presumption and improvements (upon which this model is based) are given. Finally, the results of the numerical realisation of the mathematical model for combustion of minced straw as well as the results of the experimental investigation of a concrete physical model are presented. (author)

On the influence of water subcooling and melt jet parameters on debris formation

Energy Technology Data Exchange (ETDEWEB)

Manickam, Louis, E-mail: louis@safety.sci.kth.se; Kudinov, Pavel; Ma, Weimin; Bechta, Sevostian; Grishchenko, Dmitry

2016-12-01

Highlights: • Melt and water configuration effects on debris formation is studied experimentally. • Melt superheat and water subcooling are most influential compared to jet size. • Melt-water configuration and material properties influence particle fracture rate. • Results are compared with large scale experiments to study effect of spatial scales. - Abstract: Breakup of melt jet and formation of a porous debris bed at the base-mat of a flooded reactor cavity is expected during the late stages of a severe accident in light water reactors. Debris bed coolability is determined by the bed properties including particle size, morphology, bed height and shape as well as decay heat. Therefore understanding of the debris formation phenomena is important for assessment of debris bed coolability. A series of experiments was conducted in MISTEE-Jet facility by discharging binary-oxide mixtures of WO{sub 3}–Bi{sub 2}O{sub 3} and WO{sub 3}–ZrO{sub 2} into water in order to investigate properties of resulting debris. The effect of water subcooling, nozzle diameter and melt superheat was addressed in the tests. Experimental results reveal significant influence of water subcooling and melt superheat on debris size and morphology. Significant differences in size and morphology of the debris at different melt release conditions is attributed to the competition between hydrodynamic fragmentation of liquid melt and thermal fracture of the solidifying melt droplets. The particle fracture rate increases with increased subcooling. Further the results are compared with the data from larger scale experiments to discern the effects of spatial scales. The present work provides data that can be useful for validation of the codes used for the prediction of debris formation phenomena.

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

DEFF Research Database (Denmark)

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

2013-01-01

-chemical processes are divided in two successive sections: drying and conversion (which includes pyrolysis, gasification and combustion). The second model is an empirical 1D approach. The two models need input data such as composition, temperature and feeding rate of biomass and primary air. Temperature, species...... to describe the thermo-chemical conversion process of a solid fuel bed in a grate-fired boiler is presented. In this work both models consider the incoming solid fuel as subjected to drying, pyrolysis, gasification and combustion. In the first approach the biomass bed is treated as a 0D system, but the thermo...... concentrations and velocity of the producer gas leaving the fuel bed provided by the two models are compared. A sensitivity analysis with respect to mass flow rate of the primary air is also performed, as well as a further comparison regarding the dependence of the producer gas properties on the initial moisture...

Controlling thermal properties of dense gas fluidized beds for concentrated solar power by internal and external solids circulation

Science.gov (United States)

Ammendola, Paola; Bareschino, Piero; Chirone, Riccardo; Salatino, Piero; Solimene, Roberto

2017-06-01

Fluidization technology displays a long record of success stories, mostly related to applications to thermal and thermochemical processes, which are fostering extension to novel and relatively unexplored fields. Application of fluidized beds to collection and thermal storage of solar radiation in Concentrated Solar Power (CSP) is one of the most promising, a field which poses challenging issues and great opportunities to fluidization scientists and technologists. The potential of this growing field calls for reconsideration of some of the typical design and operation guidelines and criteria, with the goal of exploiting the inherently good thermal performances of gas-fluidized beds at their best. "Creative" and non-conventional design and operation of fluidized beds, like those based on internal and external solids circulation, may be beneficial to the enhancement of thermal diffusivity and surface-to-bed heat transfer, improving the potential for application in the very demanding context of CSP with thermal energy storage. This paper investigated: i) a fluidized bed configuration with an uneven distribution of the fluidizing gas to promote vortices in the scale of bed height (internal solids circulation); ii) a dual fluidized bed configuration characterized by an external solids circulation achieved by the operation of a riser and a bubbling fluidized bed. CFD simulations showed the hydrodynamics conditions under which the internal solids circulation was established. The hydrodynamic characterization of the external solids circulation was achieved by an experimental study carried out with different cold models. The dual fluidized bed system was optimized in terms of operating conditions and geometrical features of the connections between two fluidized beds.

Nonlinear thermal interaction between a heat-generating particulate bed and a solid

International Nuclear Information System (INIS)

Cheung, F.B.; Stein, R.P.; Epstein, M.; Gabor, J.D.; Bingle, J.D.

1980-01-01

The process of combined conduction and radiation in a large, heat-generating, dry particulate bed in sudden contact with a semi-infinite solid is studied analytically by a successive approximation method and numerically by a finite difference method. The transient behavior of the system, in particular, the behavior of the temperature at the particulate bed-solid interface, is obtained as a function of two dimensionless controlling parameters. Also obtained are the conditions leading to incipient melting of the system. Based upon the finite difference solution, the present approximate method, which is shown to be rather simple and convenient to use, is found to yield rapidly converging and sufficiently accurate results

Refined model for the coolability of core debris with flow entry from the bottom

International Nuclear Information System (INIS)

Schulenberg, T.; Mueller, U.

1986-01-01

Within the context of a hypothetical severe accident in light water reactors also heat generating debris beds of a coarse particle size are discussed. A refined model for two-phase flow in particle beds is presented. Compared to previous models this model takes into account the effect of interfacial drag forces between liquid and vapor. These effects are important in coarse debris beds. The model is based on the momentum equations for separated flow, which are closed by empirical relations for the wall shear stress and the interfacial drag. When the refined model is applied to LWR severe accident scenarios an increased dryout heat flux is predicted for debris beds with flow entry from the bottom driven by a moderate downcomer head

Non-local rheology of stony debris flow propagating over a cohesionless sediment bed

Science.gov (United States)

Lanzoni, Stefano; Gregoretti, Carlo

2016-04-01

normal to the flow, with particular attention to the role played by frictional stresses near to the movable bed over which the debris flow propagates.

SCDAP/RELAP5 modeling of movement of melted material through porous debris in lower head

International Nuclear Information System (INIS)

Siefken, L. J.; Harvego, E. A.

2000-01-01

A model is described for the movement of melted metallic material through a ceramic porous debris bed. The model is designed for the analysis of severe accidents in LWRs, wherein melted core plate material may slump onto the top of a porous bed of relocated core material supported by the lower head. The permeation of the melted core plate material into the porous debris bed influences the heatup of the debris bed and the heatup of the lower head supporting the debris. A model for mass transport of melted metallic material is applied that includes terms for viscosity and turbulence but neglects inertial and capillary terms because of their small value relative to gravity and viscous terms in the momentum equation. The relative permeability and passability of the porous debris are calculated as functions of debris porosity, particle size, and effective saturation. An iterative numerical solution is used to solve the set of nonlinear equations for mass transport. The effective thermal conductivity of the debris is calculated as a function of porosity, particle size, and saturation. The model integrates the equations for mass transport with a model for the two-dimensional conduction of heat through porous debris. The integrated model has been implemented into the SCDAP/RELAP5 code for the analysis of the integrity of LWR lower heads during severe accidents. The results of the model indicate that melted core plate material may permeate to near the bottom of a 1m deep hot porous debris bed supported by the lower head. The presence of the relocated core plate material was calculated to cause a 12% increase in the heat flux on the external surface of the lower head

The physics of debris flows

Science.gov (United States)

Iverson, Richard M.

1997-08-01

Recent advances in theory and experimentation motivate a thorough reassessment of the physics of debris flows. Analyses of flows of dry, granular solids and solid-fluid mixtures provide a foundation for a comprehensive debris flow theory, and experiments provide data that reveal the strengths and limitations of theoretical models. Both debris flow materials and dry granular materials can sustain shear stresses while remaining static; both can deform in a slow, tranquil mode characterized by enduring, frictional grain contacts; and both can flow in a more rapid, agitated mode characterized by brief, inelastic grain collisions. In debris flows, however, pore fluid that is highly viscous and nearly incompressible, composed of water with suspended silt and clay, can strongly mediate intergranular friction and collisions. Grain friction, grain collisions, and viscous fluid flow may transfer significant momentum simultaneously. Both the vibrational kinetic energy of solid grains (measured by a quantity termed the granular temperature) and the pressure of the intervening pore fluid facilitate motion of grains past one another, thereby enhancing debris flow mobility. Granular temperature arises from conversion of flow translational energy to grain vibrational energy, a process that depends on shear rates, grain properties, boundary conditions, and the ambient fluid viscosity and pressure. Pore fluid pressures that exceed static equilibrium pressures result from local or global debris contraction. Like larger, natural debris flows, experimental debris flows of ˜10 m³ of poorly sorted, water-saturated sediment invariably move as an unsteady surge or series of surges. Measurements at the base of experimental flows show that coarse-grained surge fronts have little or no pore fluid pressure. In contrast, finer-grained, thoroughly saturated debris behind surge fronts is nearly liquefied by high pore pressure, which persists owing to the great compressibility and moderate

The physics of debris flows

Science.gov (United States)

Iverson, R.M.

1997-01-01

Recent advances in theory and experimentation motivate a thorough reassessment of the physics of debris flows. Analyses of flows of dry, granular solids and solid-fluid mixtures provide a foundation for a comprehensive debris flow theory, and experiments provide data that reveal the strengths and limitations of theoretical models. Both debris flow materials and dry granular materials can sustain shear stresses while remaining static; both can deform in a slow, tranquil mode characterized by enduring, frictional grain contacts; and both can flow in a more rapid, agitated mode characterized by brief, inelastic grain collisions. In debris flows, however, pore fluid that is highly viscous and nearly incompressible, composed of water with suspended silt and clay, can strongly mediate intergranular friction and collisions. Grain friction, grain collisions, and viscous fluid flow may transfer significant momentum simultaneously. Both the vibrational kinetic energy of solid grains (measured by a quantity termed the granular temperature) and the pressure of the intervening pore fluid facilitate motion of grains past one another, thereby enhancing debris flow mobility. Granular temperature arises from conversion of flow translational energy to grain vibrational energy, a process that depends on shear rates, grain properties, boundary conditions, and the ambient fluid viscosity and pressure. Pore fluid pressures that exceed static equilibrium pressures result from local or global debris contraction. Like larger, natural debris flows, experimental debris flows of ???10 m3 of poorly sorted, water-saturated sediment invariably move as an unsteady surge or series of surges. Measurements at the base of experimental flows show that coarse-grained surge fronts have little or no pore fluid pressure. In contrast, finer-grained, thoroughly saturated debris behind surge fronts is nearly liquefied by high pore pressure, which persists owing to the great compressibility and moderate

Characteristics of debris in the lower head of a BWR in different severe accident scenarios

International Nuclear Information System (INIS)

Phung, Viet-Anh; Galushin, Sergey; Raub, Sebastian; Goronovski, Andrei; Villanueva, Walter; Kööp, Kaspar; Grishchenko, Dmitry; Kudinov, Pavel

2016-01-01

Highlights: • Station blackout scenario with delayed recovery of safety systems in a Nordic BWR is considered. • Genetic algorithm and random sampling methods are used to explore accident scenario domain. • Main groups of scenarios are identified. • Ranges and distributions of characteristics of debris bed in the lower head are determined. - Abstract: Nordic boiling water reactors (BWRs) adopt ex-vessel debris cooling to terminate severe accident progression. Core melt released from the vessel into a deep pool of water is expected to fragment and form a coolable debris bed. Characteristics of corium melt ejection from the vessel determine conditions for molten fuel–coolant interactions (FCI) and debris bed formation. Non-coolable debris bed or steam explosion can threaten containment integrity. Vessel failure and melt ejection mode are determined by the in-vessel accident progression. Characteristics (such as mass, composition, thermal properties, timing of relocation, and decay heat) of the debris bed formed in the process of core relocation into the vessel lower plenum define conditions for the debris reheating, remelting, melt-vessel structure interactions, vessel failure and melt release. Thus core degradation and relocation are important sources of uncertainty for the success of the ex-vessel accident mitigation strategy. The goal of this work is improve understanding how accident scenario parameters, such as timing of failure and recovery of different safety systems can affect characteristics of the debris in the lower plenum. Station blackout scenario with delayed power recovery in a Nordic BWR is considered using MELCOR code. The recovery timing and capacity of safety systems were varied using genetic algorithm (GA) and random sampling methods to identify two main groups of scenarios: with relatively small ( 100 tons) amount of relocated debris. The domains are separated by the transition regions, in which relatively small variations of the input

Characteristics of debris in the lower head of a BWR in different severe accident scenarios

Energy Technology Data Exchange (ETDEWEB)

Phung, Viet-Anh, E-mail: vaphung@kth.se; Galushin, Sergey, E-mail: galushin@kth.se; Raub, Sebastian, E-mail: raub@kth.se; Goronovski, Andrei, E-mail: andreig@kth.se; Villanueva, Walter, E-mail: walterv@kth.se; Kööp, Kaspar, E-mail: kaspar@safety.sci.kth.se; Grishchenko, Dmitry, E-mail: dmitry@safety.sci.kth.se; Kudinov, Pavel, E-mail: pavel@safety.sci.kth.se

2016-08-15

Highlights: • Station blackout scenario with delayed recovery of safety systems in a Nordic BWR is considered. • Genetic algorithm and random sampling methods are used to explore accident scenario domain. • Main groups of scenarios are identified. • Ranges and distributions of characteristics of debris bed in the lower head are determined. - Abstract: Nordic boiling water reactors (BWRs) adopt ex-vessel debris cooling to terminate severe accident progression. Core melt released from the vessel into a deep pool of water is expected to fragment and form a coolable debris bed. Characteristics of corium melt ejection from the vessel determine conditions for molten fuel–coolant interactions (FCI) and debris bed formation. Non-coolable debris bed or steam explosion can threaten containment integrity. Vessel failure and melt ejection mode are determined by the in-vessel accident progression. Characteristics (such as mass, composition, thermal properties, timing of relocation, and decay heat) of the debris bed formed in the process of core relocation into the vessel lower plenum define conditions for the debris reheating, remelting, melt-vessel structure interactions, vessel failure and melt release. Thus core degradation and relocation are important sources of uncertainty for the success of the ex-vessel accident mitigation strategy. The goal of this work is improve understanding how accident scenario parameters, such as timing of failure and recovery of different safety systems can affect characteristics of the debris in the lower plenum. Station blackout scenario with delayed power recovery in a Nordic BWR is considered using MELCOR code. The recovery timing and capacity of safety systems were varied using genetic algorithm (GA) and random sampling methods to identify two main groups of scenarios: with relatively small (<20 tons) and large (>100 tons) amount of relocated debris. The domains are separated by the transition regions, in which relatively small

Experimental investigation on the hydrodynamics of a gas–liquid–solid fluidized bed using vibration signature and pressure fluctuation analyses

International Nuclear Information System (INIS)

Sheikhi, Amir; Sotudeh-Gharebagh, Rahmat; Mostoufi, Navid; Zarghami, Reza

2013-01-01

Highlights: • Bed shell vibration fluctuation is introduced as a novel non-invasive monitoring method in three-phase fluidized beds. • Analyses of vibration signatures and pressure fluctuations were performed to characterize gas–liquid–solid fluidized beds. • These enabled further investigation on the dual effect of solid particles on the local and global bed hydrodynamics. -- Abstract: Simultaneous analyses of vibration signatures and pressure fluctuations were performed to investigate the hydrodynamics of a conventional three-phase gas–liquid–solid fluidized bed over a wide range of operating conditions. Non-intrusive vibration signature and pressure fluctuation signals were acquired by means of accelerometers and a piezoresistive pressure transducer, respectively. Comprehensive study on the standard deviation of pressure fluctuations was conducted simultaneously with two new statistical analyses on the pressure fluctuations, namely signal energy and average cycle frequency, which presented a new method of determining minimum liquid-fluidization velocity. This enabled further investigation on the dual effect of solid particles on the local hydrodynamics in the three-phase beds. The vibration analysis of the bed was introduced as a novel and non-invasive tool, which proved to be a robust representative of the global governing regimes suggesting a new approach on the dual effect of solid particles on the bed global hydrodynamics. These methods can pave the way towards the non-invasive hydrodynamic characterization of industrial three-phase reactors

Non-intrusive measurement and hydrodynamics characterization of gas-solid fluidized beds: a review

Science.gov (United States)

Sun, Jingyuan; Yan, Yong

2016-11-01

Gas-solid fluidization is a well-established technique to suspend or transport particles and has been applied in a variety of industrial processes. Nevertheless, our knowledge of fluidization hydrodynamics is still limited for the design, scale-up and operation optimization of fluidized bed reactors. It is, therefore, essential to characterize the two-phase flow behaviours in gas-solid fluidized beds and monitor the fluidization processes for control and optimization. A range of non-intrusive techniques have been developed or proposed for measuring the fluidization dynamic parameters and monitoring the flow status without disturbing or distorting the flow fields. This paper presents a comprehensive review of the non-intrusive measurement techniques and the current state of knowledge and experience in the characterization and monitoring of gas-solid fluidized beds. These techniques are classified into six main categories as per sensing principles, electrostatic, acoustic emission and vibration, visualization, particle tracking, laser Doppler anemometry and phase Doppler anemometry as well as pressure-fluctuation methods. Trends and future developments in this field are also discussed.

Non-intrusive measurement and hydrodynamics characterization of gas–solid fluidized beds: a review

International Nuclear Information System (INIS)

Sun, Jingyuan; Yan, Yong

2016-01-01

Gas–solid fluidization is a well-established technique to suspend or transport particles and has been applied in a variety of industrial processes. Nevertheless, our knowledge of fluidization hydrodynamics is still limited for the design, scale-up and operation optimization of fluidized bed reactors. It is, therefore, essential to characterize the two-phase flow behaviours in gas–solid fluidized beds and monitor the fluidization processes for control and optimization. A range of non-intrusive techniques have been developed or proposed for measuring the fluidization dynamic parameters and monitoring the flow status without disturbing or distorting the flow fields. This paper presents a comprehensive review of the non-intrusive measurement techniques and the current state of knowledge and experience in the characterization and monitoring of gas–solid fluidized beds. These techniques are classified into six main categories as per sensing principles, electrostatic, acoustic emission and vibration, visualization, particle tracking, laser Doppler anemometry and phase Doppler anemometry as well as pressure-fluctuation methods. Trends and future developments in this field are also discussed. (topical review)

Exchange between the stagnant and flowing zone in gas-flowing solids-fixed bed contactors

Directory of Open Access Journals (Sweden)

ALEKSANDAR P. DUDUKOVIC

2005-02-01

Full Text Available In countercurrent gas – flowing solids – fixed bed contactors, a fraction of the flowing solids is in motion (dynamic holdup, while the other fraction is resting on the fixed bed elements. In this study it was experimentally proved that the stagnant zone should not be considered as a dead part of the column, but that there is a dynamic exchange between these two portions of flowing solids particles. Combining a mathematical model with tracer experiments, the rate of exchange was determined and it was shown that only a small part (ca. 20 % of the stagnant region should be considered as a dead one.

Prediction of mass fraction of agglomerated debris in a LWR severe accident

International Nuclear Information System (INIS)

Kudinov, P.; Davydov, M.

2011-01-01

Ex-vessel termination of accident progression in Swedish type Boiling Water Reactors (BWRs) is contingent upon efficacy of melt fragmentation and solidification in a deep pool of water below reactor vessel. When liquid melt reaches the bottom of the pool it can create agglomerated debris and “cake” regions that increase hydraulic resistance of the bed and affect coolability of the bed. This paper discusses development and application of a conservative-mechanistic approach to quantify mass fractions of agglomerated debris. Experimental data from the DEFOR-A (Debris Bed Formation and Agglomeration) tests with high superheat of binary oxidic simulant material melt is used for validation of the methods. Application of the approach to plant accident analysis suggests that melt superheat has less significant influence on agglomeration of the debris than jet penetration depth. The paper also discusses the impact of the uncertainty in the jet disintegration and penetration behavior on the agglomeration mode map. (author)

Hydrodynamic Modelling of Municipal Solid Waste Residues in a Pilot Scale Fluidized Bed Reactor

Directory of Open Access Journals (Sweden)

João Cardoso

2017-11-01

Full Text Available The present study investigates the hydrodynamics and heat transfer behavior of municipal solid waste (MSW gasification in a pilot scale bubbling fluidized bed reactor. A multiphase 2-D numerical model following an Eulerian-Eulerian approach within the FLUENT framework was implemented. User defined functions (UDFs were coupled to improve hydrodynamics and heat transfer phenomena, and to minimize deviations between the experimental and numerical results. A grid independence study was accomplished through comparison of the bed volume fraction profiles and by reasoning the grid accuracy and computational cost. The standard deviation concept was used to determine the mixing quality indexes. Simulated results showed that UDFs improvements increased the accuracy of the mathematical model. Smaller size ratio of the MSW-dolomite mixture revealed a more uniform mixing, and larger ratios enhanced segregation. Also, increased superficial gas velocity promoted the solid particles mixing. Heat transfer within the fluidized bed showed strong dependence on the MSW solid particles sizes, with smaller particles revealing a more effective process.

DEM-CFD simulation of purge gas flow in a solid breeder pebble bed

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hao [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230027 (China); Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Li, Zhenghong [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); University of Science and Technology of China, Hefei 230027 (China); Guo, Haibing [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Ye, Minyou [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230027 (China); Huang, Hongwen, E-mail: inpclane@sina.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

2016-12-15

Solid tritium breeding blanket applying pebble bed concept is promising for fusion reactors. Tritium bred in the pebble bed is purged out by inert gas. The flow characteristics of the purge gas are important for the tritium transport from the solid breeder materials. In this study, a randomly packed pebble bed was generated by Discrete Element Method (DEM) and verified by radial porosity distribution. The flow parameters of the purge gas in channels were solved by Computational Fluid Dynamics (CFD) method. The results show that the normalized velocity magnitudes have the same damped oscillating patterns with radial porosity distribution. Besides, the bypass flow near the wall cannot be ignored in this model, and it has a slight increase with inlet velocity. Furthermore, higher purging efficiency becomes with higher inlet velocity and especially higher in near wall region.

Models and correlations of the DEBRIS Late-Phase Melt Progression Model

International Nuclear Information System (INIS)

Schmidt, R.C.; Gasser, R.D.

1997-09-01

The DEBRIS Late Phase Melt Progression Model is an assembly of models, embodied in a computer code, which is designed to treat late-phase melt progression in dry rubble (or debris) regions that can form as a consequence of a severe core uncover accident in a commercial light water nuclear reactor. The approach is fully two-dimensional, and incorporates a porous medium modeling framework together with conservation and constitutive relationships to simulate the time-dependent evolution of such regions as various physical processes act upon the materials. The objective of the code is to accurately model these processes so that the late-phase melt progression that would occur in different hypothetical severe nuclear reactor accidents can be better understood and characterized. In this report the models and correlations incorporated and used within the current version of DEBRIS are described. These include the global conservation equations solved, heat transfer and fission heating models, melting and refreezing models (including material interactions), liquid and solid relocation models, gas flow and pressure field models, and the temperature and compositionally dependent material properties employed. The specific models described here have been used in the experiment design analysis of the Phebus FPT-4 debris-bed fission-product release experiment. An earlier DEBRIS code version was used to analyze the MP-1 and MP-2 late-phase melt progression experiments conducted at Sandia National Laboratories for the US Nuclear Regulatory Commission

Solid Waste Transportation through Ocean Currents: Marine Debris Sightings and their Waste Quantification at Port Dickson Beaches, Peninsular Malaysia

Directory of Open Access Journals (Sweden)

Chong Jing Yi

2016-07-01

Full Text Available Four beaches at Port Dickson, Peninsular Malaysia, namely Saujana Beach, Nelayan Beach, Bagan Pinang Beach and Cermin beach have been sampled for marine debris from 7th June 2014 until 26th July 2014, on every Saturday. These beaches face the Strait of Malacca with a coastline stretching 18 km each. Our observations revealed a total debris items of 13193 in those beaches. The top three items of highest frequency were cigarette butts, foamed fragments and food wrappers. Plastic debris scaled high upto 41% of the total debris. Compared to the ocean conservancy�s 2013 report of marine debris in Malaysian beaches, which was 27,005 items with in 6.44 km, the current count is slightly low. However, Malaysia was ranked 14th place among the top 20 countries in International Marine Debris Watch program. Nelayan Beach is the dirtiest beach in Port Dickson. Around 50% of the total plastic items collected are found on those beaches. The marine debris items indicated that they arrived there by land-based and ocean-based activities. High energy conditions such as wind and waves in the beaches correlated well with less debris deposition on the beaches. With debris equivalent of 4193 items/km, Malaysia harvests less solid wastes compared to Croatia, USA, Singapore and Turkey. However, a nation wide survey is needed to assess the seriousness of marine debris problem in Malaysia.

Numerical simulation of gas-solid flow in an interconnected fluidized bed

Directory of Open Access Journals (Sweden)

Canneto Giuseppe

2015-01-01

Full Text Available The gas-particles flow in an interconnected bubbling fluidized cold model is simulated using a commercial CFD package by Ansys. Conservation equations of mass and momentum are solved using the Eulerian granular multiphase model. Bubbles formation and their paths are analyzed to investigate the behaviour of the bed at different gas velocities. Experimental tests, carried out by the cold model, are compared with simulation runs to study the fluidization quality and to estimate the circulation of solid particles in the bed.

Short communication: Bacterial counts in recycled manure solids bedding replaced daily or deep packed in freestalls.

Science.gov (United States)

Sorter, D E; Kester, H J; Hogan, J S

2014-05-01

An experiment was conducted to compare bacterial counts of mastitis pathogens in deep-packed manure solids bedding with those in manure solids bedding replaced daily from mattresses. Eighteen Holstein cows were housed in 1 pen with 18 stalls. One row of 9 stalls was equipped with mattresses topped with bedding. The back one-third of these stalls toward the alleyway was covered in 25 mm of recycled manure solids, which was removed daily for the next 6 d and replaced with bedding from the brisket board and lunge space areas of stalls. The second row of 9 stalls was bedded for 3 wk with 100 to 150 mm of deep-pack recycled manure bedding from which only fecal matter was removed daily. After 3 wk, bedding treatments were changed between rows in a switchback design. Mean total gram-negative bacterial counts did not differ between treatments throughout the experiment. Coliform and Klebsiella spp. bacterial counts were lower in daily replaced bedding compared with deep pack across the experiment and on each of d 0, 1, 2, and 6. Streptococcal counts were reduced in daily replacement stalls compared with deep-pack stalls on d 0 and greater in daily replacement stalls compared with deep-pack stalls on d 1, 2, and 6. Daily replacement of recycled manure bedding from the back one-third of the stalls appeared to be an effective approach to reducing exposure to coliforms, specifically Klebsiella, but not streptococci. However, bacterial counts in bedding from both treatments were elevated throughout the trial and resulted in considerable risk for exposure to teats and development of intramammary infections. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Solid-State Anaerobic Digestion of Dairy Manure from a Sawdust-Bedded Pack Barn: Moisture Responses

Directory of Open Access Journals (Sweden)

Eunjong Kim

2018-02-01

Full Text Available Bedded pack manure has long been considered an unsuitable feedstock for conventional anaerobic digestion systems due to its high solids content. However, solid-state anaerobic digestion (SS-AD provides an opportunity to generate methane from such high-solids feedstocks. This study was conducted to determine the influence of moisture content on the digestion of bedded pack dairy manure using SS-AD. Mixtures of sawdust bedding and dairy manure were prepared with moisture contents (MCs of 70, 76, and 83% and digested at 37 °C for 85 days. The performance of digesters containing manure at 83% MC was 1.3 to 1.4-fold higher than that of digesters containing 70% MC manure in terms of volatile solids (VS reduction and biogas production. VS reduction rates were 55 to 75% and cumulative methane yield ranged from 64 to 90 NmL (gVS−1. These values are lower than those from SS-AD of fresh manure and this is likely due to the partial decomposition of biodegradable materials during the two to three-month period before the manure was removed from the barn. However, in terms of efficient management of farm odors and providing a renewable energy source for heating, SS-AD of bedded pack manure offers a potential alternative to the conventional composting systems currently in use.

Debris Flows and Related Phenomena

Science.gov (United States)

Ancey, C.

Torrential floods are a major natural hazard, claiming thousands of lives and millions of dollars in lost property each year in almost all mountain areas on the Earth. After a catastrophic eruption of Mount St. Helen in the USA in May 1980, water from melting snow, torrential rains from the eruption cloud, and water displaced from Spirit Lake mixed with deposited ash and debris to produce very large debris flows and cause extensive damage and loss of life [1]. During the 1985 eruption of Nevado del Ruiz in Colombia, more than 20,000 people perished when a large debris flow triggered by the rapid melting of snow and ice at the volcano summit, swept through the town of Armero [2]. In 1991, the eruption of Pinatubo volcano in the Philippines disperses more than 5 cubic kilometres of volcanic ash into surrounding valleys. Much of that sediment has subsequently been mobilised as debris flows by typhoon rains and has devastated more than 300 square kilometres of agricultural land. Even, in Eur opean countries, recent events that torrential floods may have very destructive effects (Sarno and Quindici in southern Italy in May 1998, where approximately 200 people were killed). The catastrophic character of these floods in mountainous watersheds is a consequence of significant transport of materials associated with water flows. Two limiting flow regimes can be distinguished. Bed load and suspension refer to dilute transport of sediments within water. This means that water is the main agent in the flow dynamics and that the particle concentration does not exceed a few percent. Such flows are typically two-phase flows. In contrast, debris flows are mas s movements of concentrated slurries of water, fine solids, rocks and boulders. As a first approximation, debris flows can be treated as one-phase flows and their flow properties can be studied using classical rheological methods. The study of debris flows is a very exciting albeit immature science, made up of disparate elements

On the entrainment of solid particles from a fluidized bed

Energy Technology Data Exchange (ETDEWEB)

Sciazko, M. (Institute of Chemical Processing of Coal, Zabrze (Poland)); Bandrowski, J.; Raczek, J. (Politechnika Slaska, Gliwice (Poland). Inst. of Chemical Engineering and Apparatus Construction)

1991-04-01

This paper presents a generalized approach to the phenomenon of entrainment of solids from a fluidized bed. Starting with the discussion of the transport disengaging height (TDH) and of the elutriation of particles above the TDH, one arrives finally at the relationship between the elutriation rate constant, saturation carrying capacity and choking parameters of pneumatic transport. (orig.).

Experiments and simulation of a net closing mechanism for tether-net capture of space debris

Science.gov (United States)

Sharf, Inna; Thomsen, Benjamin; Botta, Eleonora M.; Misra, Arun K.

2017-10-01

This research addresses the design and testing of a debris containment system for use in a tether-net approach to space debris removal. The tether-net active debris removal involves the ejection of a net from a spacecraft by applying impulses to masses on the net, subsequent expansion of the net, the envelopment and capture of the debris target, and the de-orbiting of the debris via a tether to the chaser spacecraft. To ensure a debris removal mission's success, it is important that the debris be successfully captured and then, secured within the net. To this end, we present a concept for a net closing mechanism, which we believe will permit consistently successful debris capture via a simple and unobtrusive design. This net closing system functions by extending the main tether connecting the chaser spacecraft and the net vertex to the perimeter and around the perimeter of the net, allowing the tether to actuate closure of the net in a manner similar to a cinch cord. A particular embodiment of the design in a laboratory test-bed is described: the test-bed itself is comprised of a scaled-down tether-net, a supporting frame and a mock-up debris. Experiments conducted with the facility demonstrate the practicality of the net closing system. A model of the net closure concept has been integrated into the previously developed dynamics simulator of the chaser/tether-net/debris system. Simulations under tether tensioning conditions demonstrate the effectiveness of the closure concept for debris containment, in the gravity-free environment of space, for a realistic debris target. The on-ground experimental test-bed is also used to showcase its utility for validating the dynamics simulation of the net deployment, and a full-scale automated setup would make possible a range of validation studies of other aspects of a tether-net debris capture mission.

Numerical investigation of debris materials prior to debris flow hazards using satellite images

Science.gov (United States)

Zhang, N.; Matsushima, T.

2018-05-01

The volume of debris flows occurred in mountainous areas is mainly affected by the volume of debris materials deposited at the valley bottom. Quantitative evaluation of debris materials prior to debris flow hazards is important to predict and prevent hazards. At midnight on 7th August 2010, two catastrophic debris flows were triggered by the torrential rain from two valleys in the northern part of Zhouqu City, NW China, resulting in 1765 fatalities and huge economic losses. In the present study, a depth-integrated particle method is adopted to simulate the debris materials, based on 2.5 m resolution satellite images. In the simulation scheme, the materials are modeled as dry granular solids, and they travel down from the slopes and are deposited at the valley bottom. The spatial distributions of the debris materials are investigated in terms of location, volume and thickness. Simulation results show good agreement with post-disaster satellite images and field observation data. Additionally, the effect of the spatial distributions of the debris materials on subsequent debris flows is also evaluated. It is found that the spatial distributions of the debris materials strongly influence affected area, runout distance and flow discharge. This study might be useful in hazard assessments prior to debris flow hazards by investigating diverse scenarios in which the debris materials are unknown.

Numerical modelling of biomass combustion: Solid conversion processes in a fixed bed furnace

Science.gov (United States)

Karim, Md. Rezwanul; Naser, Jamal

2017-06-01

Increasing demand for energy and rising concerns over global warming has urged the use of renewable energy sources to carry a sustainable development of the world. Bio mass is a renewable energy which has become an important fuel to produce thermal energy or electricity. It is an eco-friendly source of energy as it reduces carbon dioxide emissions. Combustion of solid biomass is a complex phenomenon due to its large varieties and physical structures. Among various systems, fixed bed combustion is the most commonly used technique for thermal conversion of solid biomass. But inadequate knowledge on complex solid conversion processes has limited the development of such combustion system. Numerical modelling of this combustion system has some advantages over experimental analysis. Many important system parameters (e.g. temperature, density, solid fraction) can be estimated inside the entire domain under different working conditions. In this work, a complete numerical model is used for solid conversion processes of biomass combustion in a fixed bed furnace. The combustion system is divided in to solid and gas phase. This model includes several sub models to characterize the solid phase of the combustion with several variables. User defined subroutines are used to introduce solid phase variables in commercial CFD code. Gas phase of combustion is resolved using built-in module of CFD code. Heat transfer model is modified to predict the temperature of solid and gas phases with special radiation heat transfer solution for considering the high absorptivity of the medium. Considering all solid conversion processes the solid phase variables are evaluated. Results obtained are discussed with reference from an experimental burner.

Effect of fluidization number on the combustion of simulated municipal solid waste in a fluidized bed

International Nuclear Information System (INIS)

Anwar Johari; Mutahharah, M.M.; Abdul, A.; Salema, A.; Kalantarifard, A.; Rozainee, M.

2010-01-01

The effect of fluidization number on the combustion of simulated municipal solid was in a fluidized bed was investigated. Simulated municipal solid waste was used a sample and it was formulated from major waste composition found in Malaysia which comprised of food waste, paper, plastic and vegetable waste. Proximate and ultimate analyses of the simulated were conducted and results showed its composition was similar to the actual Malaysian municipal solid waste composition. Combustion study was carried out in a rectangular fluidized bed with sand of mean particle size of 0.34 mm as a fluidising medium. The range of fluidization numbers investigated was 3 to 11 U mf . The combustion was carried out at stoichiometric condition (Air Factor = 1). Results showed that the best fluidization number was in the range of 5 to 7 U mf with 5 U mf being the most optimum in which the bed temperature was sustained in a much longer period. (author)

Numerical simulation of the gas-solid flow in a square circulating fluidized bed with secondary air injection

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhengyang [Harbin Institute of Technology, Harbin (China). Post-doctor Station of Civil Engineering; Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.; Sun, Shaozeng; Zhao, Ningbo; Wu, Shaohua [Harbin Institute of Technology, Harbin (China). Combustion Engineering Research Inst.; Tan, Yufei [Harbin Institute of Technology, Harbin (China). School of Municipal and Environmental Engineering

2013-07-01

The dynamic behavior of gas-solid flow in an experimental square circulating fluidized bed setup (0.25 m x 0.25 m x 6.07 m) is predicted with numerical simulation based on the theory of Euler-Euler gas-solid two-phase flow and the kinetic theory of granular flows. The simulation includes the operation cases with secondary injection and without air-staging. The pressure drop profile, local solids concentration and particle velocity was compared with experimental results. Both simulation and experimental results show that solids concentration increases significantly below the secondary air injection ports when air-staging is adopted. Furthermore, the flow asymmetry in the solid entrance region of the bed was investigated based on the particle concentration/velocity profile. The simulation results are in agreement with the experimental results qualitatively.

Identification of defluidization region in a gas-solid fluidized bed using a method based on pressure fluctuation measurements

Directory of Open Access Journals (Sweden)

M. R. Parise

2009-09-01

Full Text Available Industrial applications that involve fluidized bed operations must prevent the undesirable phenomenon of partial or complete bed defluidization. Defluidization can be avoided by increasing the gas velocity and/or, in some cases, changing the solid feed conditions in the system, provided that the changes in the hydrodynamics of the flow are detected early enough. The use of a technique that can perform an early detection of the defluidization condition in industrial applications is important, in order to avoid the loss of efficiency or even an undesirable shutting down of the process. The objective of this work is to show the application of a method for early detection of the condition where the bed is tending to the defluidization, in a gas-solid fluidized bed flow. The method is based on pressure fluctuation measurements. Experimental tests are carried out using two solid particles: microcrystalline cellulose and sand. Results show that the proposed method is efficient in detecting the fluidization condition in a conventional bubbling bed regime. The potential of application of the technique is also shown for the control of the defluidization phenomenon in industry.

Numerical Simulation of Dense Gas-Solid Fluidized Beds: A Multiscale Modeling Strategy

NARCIS (Netherlands)

van der Hoef, Martin Anton; van Sint Annaland, M.; Deen, N.G.; Kuipers, J.A.M.

2008-01-01

Gas-solid fluidized beds are widely applied in many chemical processes involving physical and/or chemical transformations, and for this reason they are the subject of intense research in chemical engineering science. Over the years, researchers have developed a large number of numerical models of

Numerical simulation of dense gas-solid fluidized beds : a multiscale modeling strategy

NARCIS (Netherlands)

Hoef, van der M.A.; Sint Annaland, van M.; Deen, N.G.; Kuipers, J.A.M.

2008-01-01

Gas-solid fluidized beds are widely applied in many chemical processes involving physical and/or chemical transformations, and for this reason they are the subject of intense research in chemical engineering science. Over the years, researchers have developed a large number of numerical models of

Coupled Eulerian-Lagrangian transport of large debris by tsunamis

Science.gov (United States)

Conde, Daniel A. S.; Ferreira, Rui M. L.; Sousa Oliveira, Carlos

2016-04-01

Tsunamis are notorious for the large disruption they can cause on coastal environments, not only due to the imparted momentum of the incoming wave but also due to its capacity to transport large quantities of solid debris, either from natural or human-made sources, over great distances. A 2DH numerical model under development at CERIS-IST (Ferreira et al., 2009; Conde, 2013) - STAV2D - capable of simulating solid transport in both Eulerian and Lagrangian paradigms will be used to assess the relevance of Lagrangian-Eulerian coupling when modelling the transport of solid debris by tsunamis. The model has been previously validated and applied to tsunami scenarios (Conde, 2013), being well-suited for overland tsunami propagation and capable of handling morphodynamic changes in estuaries and seashores. The discretization scheme is an explicit Finite Volume technique employing flux-vector splitting and a reviewed Roe-Riemann solver. Source term formulations are employed in a semi-implicit way, including the two-way coupling of the Lagrangian and Eulerian solvers by means of conservative mass and momentum transfers between fluid and solid phases. The model was applied to Sines Port, a major commercial port in Portugal, where two tsunamigenic scenarios are considered: an 8.5 Mw scenario, consistent with the Great Lisbon Earthquake and Tsunami of the 1st November 1755 (Baptista, 2009), and an hypothetical 9.5 Mw worst-case scenario based on the same historical event. Open-ocean propagation of these scenarios were simulated with GeoClaw model from ClawPack (Leveque, 2011). Following previous efforts on the modelling of debris transport by tsunamis in seaports (Conde, 2015), this work discusses the sensitivity of the obtained results with respect to the phenomenological detail of the employed Eulerian-Lagrangian formulation and the resolution of the mesh used in the Eulerian solver. The results have shown that the fluid to debris mass ratio is the key parameter regarding the

Integral analysis of debris material and heat transport in reactor vessel lower plenum

International Nuclear Information System (INIS)

Suh, K.Y.; Henry, R.E.

1994-01-01

An integral, fast-running, two-region model has been developed to characterize the debris material and heat transport in the reactor lower plenum under severe accident conditions. The debris bed is segregated into the oxidic pool and an overlying metallic layer. Debris crusts can develop on three surfaces: the top of the molten pool, the RPV wall, and the internal structures. To account for the decay heat generation, the crust temperature profile is assumed to be parabolic. The oxidic debris pool is homogeneously mixed and has the same material composition, and hence the same thermophysical properties, as the crusts, while the metallic constituents are assumed to rise to the top of the debris pool. Steady-state relationships are used to describe the heat transfer rates, with the assessment of solid or liquid state, and the liquid superheat in the pool being based on the average debris temperature. Natural convection heat transfer from the molten debris pool to the upper, lower and embedded crusts is calculated based on the pool Rayleigh number with the conduction heat transfer from the crusts being determined by the crust temperature profile. The downward heat flux is transferred to the lowest part of the RPV lower head through a crust-to-RPV contact resistance. The sideward heat flux is transferred to the upper regions of the RPV lower head as well as to the internal structures. The upward heat flux goes to the metal layer, water, or available heat sink structures above. Quenching due to water ingression is modeled separately from the energy transfer through the crust. The RPV wall temperature distribution and the primary system pressure are utilized to estimate challenges to the RPV integrity. ((orig.))

Orbital Debris and NASA's Measurement Program

Science.gov (United States)

Africano, J. L.; Stansbery, E. G.

2002-05-01

Since the launch of Sputnik in 1957, the number of manmade objects in orbit around the Earth has dramatically increased. The United States Space Surveillance Network (SSN) tracks and maintains orbits on over nine thousand objects down to a limiting diameter of about ten centimeters. Unfortunately, active spacecraft are only a small percentage ( ~ 7%) of this population. The rest of the population is orbital debris or ``space junk" consisting of expended rocket bodies, dead payloads, bits and pieces from satellite launches, and fragments from satellite breakups. The number of these smaller orbital debris objects increases rapidly with decreasing size. It is estimated that there are at least 130,000 orbital debris objects between one and ten centimeters in diameter. Most objects smaller than 10 centimeters go untracked! As the orbital debris population grows, the risk to other orbiting objects, most importantly manned space vehicles, of a collision with a piece of debris also grows. The kinetic energy of a solid 1 cm aluminum sphere traveling at an orbital velocity of 10 km/sec is equivalent to a 400 lb. safe traveling at 60 mph. Fortunately, the volume of space in which the orbiting population resides is large, collisions are infrequent, but they do occur. The Space Shuttle often returns to earth with its windshield pocked with small pits or craters caused by collisions with very small, sub-millimeter-size pieces of debris (paint flakes, particles from solid rocket exhaust, etc.), and micrometeoroids. To get a more complete picture of the orbital-debris environment, NASA has been using both radar and optical techniques to monitor the orbital debris environment. This paper gives an overview of the orbital debris environment and NASA's measurement program.

Simulation and uncertainties of the heat transfer from a heat-generating DEBRIS bed in the lower plenum

International Nuclear Information System (INIS)

Schaaf, K.; Trambauer, K.

1999-01-01

The findings of the TMI-2 post-accident analyses indicated that internal cooling mechanisms may have a considerable potential to sustain the vessel integrity after a relocation of core material to the lower plenum, provided that water is continuously available in the RPV. Numerous analytical and experimental research activities are currently underway in this respect. This paper illustrates some major findings of the experimental work on internal cooling mechanisms and describes the limitations and the uncertainties in the simulation of the heat transfer processes. Reference is made especially to the joint German DEBRIS/ RPV research program, which encompasses the experimental investigation of the thermal-hydraulics in gaps, of the heat transfer within a particulate debris bed, and of the high temperature performance of vessel steel, as well as the development of simulation models for the heat transfer in the lower head and the structural response of the RPV. In particular, the results of uncertainty and sensitivity analyses are presented, which have been carried out at GRS using an integral model that describes the major phenomena governing the long-term integrity of the reactor vessel. The investigation of a large-scale relocation indicated that the verification of a gap cooling mechanism as an inherent mechanism is questionable in terms of a stringent probabilistic uncertainty criterion, as long as the formation of a large molten pool cannot be excluded. (author)

Gas-solid hydroxyethylation of potato starch in a stirred vibrating fluidized bed reactor

NARCIS (Netherlands)

Kuipers, N.J M; Stamhuis, Eize; Beenackers, A.A C M

A novel reactor for modifying cohesive C-powders such as in the gas-solid hydroxyethylation of semidry potato starch is characterized, the so-called stirred vibrating fluidized bed reactor. Good fluidization characteristics are obtained in this reactor for certain combinations of stirring and

Coupled prediction of flash flood response and debris flow occurrence: Application on an alpine extreme flood event

Science.gov (United States)

Destro, Elisa; Amponsah, William; Nikolopoulos, Efthymios I.; Marchi, Lorenzo; Marra, Francesco; Zoccatelli, Davide; Borga, Marco

2018-03-01

The concurrence of flash floods and debris flows is of particular concern, because it may amplify the hazard corresponding to the individual generative processes. This paper presents a coupled modelling framework for the predictions of flash flood response and of the occurrence of debris flows initiated by channel bed mobilization. The framework combines a spatially distributed flash flood response model and a debris flow initiation model to define a threshold value for the peak flow which permits identification of channelized debris flow initiation. The threshold is defined over the channel network as a function of the upslope area and of the local channel bed slope, and it is based on assumptions concerning the properties of the channel bed material and of the morphology of the channel network. The model is validated using data from an extreme rainstorm that impacted the 140 km2 Vizze basin in the Eastern Italian Alps on August 4-5, 2012. The results show that the proposed methodology has improved skill in identifying the catchments where debris-flows are triggered, compared to the use of simpler thresholds based on rainfall properties.

Fixed bed gasification of solid biomass fuels

Energy Technology Data Exchange (ETDEWEB)

Haavisto, I [Condens Oy, Haemeenlinna (Finland)

1997-12-31

Fixed bed biomass gasifiers are feasible in the effect range of 100 kW -10 MW. Co-current gasification is available only up to 1 MW for technical reasons. Counter-current gasifiers have been used in Finland and Sweden for 10 years in gasification heating plants, which are a combination of a gasifier and an oil boiler. The plants have proved to have a wide control range, flexible and uncomplicated unmanned operation and an excellent reliability. Counter-current gasifiers can be applied for new heating plants or for converting existing oil and natural gas boilers into using solid fuels. There is a new process development underway, aiming at motor use of the producer gas. The development work involves a new, more flexible cocurrent gasifier and a cleaning step for the counter-current producer gas. (orig.)

Fixed bed gasification of solid biomass fuels

Energy Technology Data Exchange (ETDEWEB)

Haavisto, I. [Condens Oy, Haemeenlinna (Finland)

1996-12-31

Fixed bed biomass gasifiers are feasible in the effect range of 100 kW -10 MW. Co-current gasification is available only up to 1 MW for technical reasons. Counter-current gasifiers have been used in Finland and Sweden for 10 years in gasification heating plants, which are a combination of a gasifier and an oil boiler. The plants have proved to have a wide control range, flexible and uncomplicated unmanned operation and an excellent reliability. Counter-current gasifiers can be applied for new heating plants or for converting existing oil and natural gas boilers into using solid fuels. There is a new process development underway, aiming at motor use of the producer gas. The development work involves a new, more flexible cocurrent gasifier and a cleaning step for the counter-current producer gas. (orig.)

Debris flows: behavior and hazard assessment

Science.gov (United States)

Iverson, Richard M.

2014-01-01

Debris flows are water-laden masses of soil and fragmented rock that rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form lobate deposits when they spill onto valley floors. Because they have volumetric sediment concentrations that exceed 40 percent, maximum speeds that surpass 10 m/s, and sizes that can range up to ~109 m3, debris flows can denude slopes, bury floodplains, and devastate people and property. Computational models can accurately represent the physics of debris-flow initiation, motion and deposition by simulating evolution of flow mass and momentum while accounting for interactions of debris' solid and fluid constituents. The use of physically based models for hazard forecasting can be limited by imprecise knowledge of initial and boundary conditions and material properties, however. Therefore, empirical methods continue to play an important role in debris-flow hazard assessment.

A novel mechanical model for phase-separation in debris flows

Science.gov (United States)

Pudasaini, Shiva P.

2015-04-01

Understanding the physics of phase-separation between solid and fluid phases as a two-phase mass moves down slope is a long-standing challenge. Here, I propose a fundamentally new mechanism, called 'separation-flux', that leads to strong phase-separation in avalanche and debris flows. This new model extends the general two-phase debris flow model (Pudasaini, 2012) to include a separation-flux mechanism. The new flux separation mechanism is capable of describing and controlling the dynamically evolving phase-separation, segregation, and/or levee formation in a real two-phase, geometrically three-dimensional debris flow motion and deposition. These are often observed phenomena in natural debris flows and industrial processes that involve the transportation of particulate solid-fluid mixture material. The novel separation-flux model includes several dominant physical and mechanical aspects that result in strong phase-separation (segregation). These include pressure gradients, volume fractions of solid and fluid phases and their gradients, shear-rates, flow depth, material friction, viscosity, material densities, boundary structures, gravity and topographic constraints, grain shape, size, etc. Due to the inherent separation mechanism, as the mass moves down slope, more and more solid particles are brought to the front, resulting in a solid-rich and mechanically strong frontal surge head followed by a weak tail largely consisting of the viscous fluid. The primary frontal surge head followed by secondary surge is the consequence of the phase-separation. Such typical and dominant phase-separation phenomena are revealed here for the first time in real two-phase debris flow modeling and simulations. However, these phenomena may depend on the bulk material composition and the applied forces. Reference: Pudasaini, Shiva P. (2012): A general two-phase debris flow model. J. Geophys. Res., 117, F03010, doi: 10.1029/2011JF002186.

Study of the obtainment of Mo_2C by gas-solid reaction in a fixed and rotary bed reactor

International Nuclear Information System (INIS)

Araujo, C.P.B. de; Souza, C.P. de; Souto, M.V.M.; Barbosa, C.M.; Frota, A.V.V.M.

2016-01-01

Carbides' synthesis via gas-solid reaction overcomes many of the difficulties found in other processes, requiring lower temperatures and reaction times than traditional metallurgic routes, for example. In carbides' synthesis in fixed bed reactors (FB) the solid precursor is permeated by the reducing/carburizing gas stream forming a packed bed without mobility. The use of a rotary kiln reactor (RK) adds a mixing character to this process, changing its fluid-particle dynamics. In this work ammonium molybdate was subjected to carbo-reduction reaction (CH4 / H2) in both reactors under the same gas flow (15L / h) and temperature (660 ° C) for 180 minutes. Complete conversion was observed Mo2C (dp = 18.9nm modal particles sizes' distribution) in the fixed bed reactor. In the RK reactor this conversion was only partial (∼ 40%) and Mo2C and MoO3 (34nm dp = bimodal) could be observed on the produced XRD pattern. Partial conversion was attributed to the need to use higher solids loading in the reactor CR (50% higher) to avoid solids to centrifuge. (author)

The effect of bed non-uniformities and porosity of particles on dryout in boiling particle beds

International Nuclear Information System (INIS)

Macbeth, R.V.; Mogford, D.J.; Willshire, S.J.

1988-03-01

This report relates to an on-going experimental programme concerned with the coolability of beds of reactor core debris or rubble immersed in a liquid coolant, as might occur in an accident situation. The objectives are to develop experimental techniques, improve the understanding of bed cooling mechanisms, determine dry-out limitations of various bed configurations and particle shapes and sizes and devise ways of improving bed coolability. The report concentrates on a recently discovered effect on bed coolability of particle porosity, such as exists in fragmented UO 2 fuel pellets. It is shown that porosity can lower bed dry-out powers by a factor of 4 or 5. A mechanism which explains the effect is presented. The report also gives results of bed non-uniformities obtained by mixing glass particles with the dielectrically heated 'ferrite' particles used in the experiments. (author)

Studies for determining drain solid flow in bed silt, using radioisotope techniques

International Nuclear Information System (INIS)

Sanchez, W.

1976-01-01

A process for measuring solid flow in silt bed using isotopic technique is studied. Comparative studies for initial movement of grinded glass grains and sand grains is done. The development for determining the minimum mass of radioative grains of sand, used for flow evaluation is also studied. Further experiments in the field of reference confirm technological conditions for the method [pt

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.

Investigation of the suspected presence of solid hydrocarbon in bedded salt samples from the Palo Duro Basin, Texas

International Nuclear Information System (INIS)

1985-10-01

This report contains laboratory test results for two bedded salt samples from the Grabbe No. 1 (PD-2) Well of the Palo Duro Basin, Texas. This study was commissioned to determine whether or not solid hydrocarbons exist in bedded salt samples in the Palo Duro Basin. Laboratory investigations include electron microprobe examinations on polished thin sections and optical examinations and chemical tests on insoluble residues of the salt samples. No direct evidence was found that identifiable solid hydrocarbons are present in either sample of the bedded salt core. The total carbon content of the two salt samples was measured yielding 0.016 and 0.022 weight percent carbon. Detailed microscopic analyses showed that the carbon in the samples was associated with calcite, clays, and the epoxy resin used in sample preparation

Influence of Bubble-Bubble interactions on the macroscale circulation patterns in a bubbling gas-solid fluidized bed

NARCIS (Netherlands)

Laverman, J.A.; van Sint Annaland, M.; Kuipers, J.A.M.

2007-01-01

The macro-scale circulation patterns in the emulsion phase of a gas-solid fluidized bed in the bubbling regime have been studied with a 3D Discrete Bubble Model. It has been shown that bubble-bubble interactions strongly influence the extent of the solids circulation and the bubble size

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. Copyright © 2013 Elsevier B.V. All rights reserved.

Gasification of solid waste — potential and application of co-current moving bed gasifiers

NARCIS (Netherlands)

Groeneveld, M.J.; van Swaaij, Willibrordus Petrus Maria

1979-01-01

A review is given of gasification processes for solid fuels with special emphasis on waste gasification. Although the co-current moving bed gasifier has not been under consideration for a long time, it offers interesting possibilities for waste gasification. Some operational data are given. Two

Erosion and deposition on a debris-flow fan

Science.gov (United States)

Densmore, A. L.; Schuerch, P.; Rosser, N. J.; McArdell, B. W.

2011-12-01

The ability of a debris flow to entrain or deposit sediment controls the downstream evolution of flow volume, and ultimately dictates both the geomorphic impact of the flow and the potential hazard that it represents. Our understanding of the patterns of, and controls on, such flow volume changes remains extremely limited, however, partly due to a poor mechanistic grasp of the interactions between debris flows and their bed and banks. In addition, we lack a good understanding of the cumulative long-term effects of sequences of flows in a single catchment-fan system. Here we begin to address these issues by using repeated terrestrial laser scanning (TLS) to characterize the detailed surface change associated with the passage of multiple debris flows on the Illgraben fan, Switzerland. We calculate surface elevation change along a 300 m study reach, and from this derive the downfan rate of flow volume change, or lag rate; for comparison, we also derive the spatially-averaged lag rate over the entire ~2 km length of the fan. Lag rates are broadly comparable over both length scales, indicating that flow behavior does not vary significantly across the fan for most flows, but importantly we find that flow volume at the fan head is a poor predictor of volume at the fan toe. The sign and magnitude of bed elevation change scale with local flow depth; at flow depths 2 m. On the Illgraben fan, this depth corresponds to a basal shear stress of 3-4 kPa. Because flow depth is in part a function of channel cross-sectional topography, which varies strongly both within and between flows, this result indicates that erosion and deposition are likely to be highly dynamic. The dependence of flow volume change on both the channel topography and the flow history may thus complicate efforts to predict debris-flow inundation areas by simple flow routing. We then apply a 2d numerical model of debris-flow fan evolution to explore the key controls on debris-flow routing and topographic

The reactive solid-gas flow of a fluidized bed for UO2 conversion

International Nuclear Information System (INIS)

Juanico, L.E.

1991-01-01

The reactive solid-gas flow of a fluidized bed for UO 2 conversion was modeled. The sedimentation-reaction process was treated using the drift-flux equations. Also, the associated pressure transient due to the reaction gas release was analyzed. An experiment was carried out to compare the results, and pressure transient was numerically simulated, reaching interesting conclusions. (Author) [es

Runoff-generated debris flows: observations and modeling of surge initiation, magnitude, and frequency

Science.gov (United States)

Kean, Jason W.; McCoy, Scott W.; Tucker, Gregory E.; Staley, Dennis M.; Coe, Jeffrey A.

2013-01-01

Runoff during intense rainstorms plays a major role in generating debris flows in many alpine areas and burned steeplands. Yet compared to debris flow initiation from shallow landslides, the mechanics by which runoff generates a debris flow are less understood. To better understand debris flow initiation by surface water runoff, we monitored flow stage and rainfall associated with debris flows in the headwaters of two small catchments: a bedrock-dominated alpine basin in central Colorado (0.06 km2) and a recently burned area in southern California (0.01 km2). We also obtained video footage of debris flow initiation and flow dynamics from three cameras at the Colorado site. Stage observations at both sites display distinct patterns in debris flow surge characteristics relative to rainfall intensity (I). We observe small, quasiperiodic surges at low I; large, quasiperiodic surges at intermediate I; and a single large surge followed by small-amplitude fluctuations about a more steady high flow at high I. Video observations of surge formation lead us to the hypothesis that these flow patterns are controlled by upstream variations in channel slope, in which low-gradient sections act as “sediment capacitors,” temporarily storing incoming bed load transported by water flow and periodically releasing the accumulated sediment as a debris flow surge. To explore this hypothesis, we develop a simple one-dimensional morphodynamic model of a sediment capacitor that consists of a system of coupled equations for water flow, bed load transport, slope stability, and mass flow. This model reproduces the essential patterns in surge magnitude and frequency with rainfall intensity observed at the two field sites and provides a new framework for predicting the runoff threshold for debris flow initiation in a burned or alpine setting.

Estimating construction and demolition debris generation using a materials flow analysis approach.

Science.gov (United States)

Cochran, K M; Townsend, T G

2010-11-01

The magnitude and composition of a region's construction and demolition (C&D) debris should be understood when developing rules, policies and strategies for managing this segment of the solid waste stream. In the US, several national estimates have been conducted using a weight-per-construction-area approximation; national estimates using alternative procedures such as those used for other segments of the solid waste stream have not been reported for C&D debris. This paper presents an evaluation of a materials flow analysis (MFA) approach for estimating C&D debris generation and composition for a large region (the US). The consumption of construction materials in the US and typical waste factors used for construction materials purchasing were used to estimate the mass of solid waste generated as a result of construction activities. Debris from demolition activities was predicted from various historical construction materials consumption data and estimates of average service lives of the materials. The MFA approach estimated that approximately 610-78 × 10(6)Mg of C&D debris was generated in 2002. This predicted mass exceeds previous estimates using other C&D debris predictive methodologies and reflects the large waste stream that exists. Copyright © 2010 Elsevier Ltd. All rights reserved.

Two stage fluid bed-plasma gasification process for solid waste valorisation: Technical review and preliminary thermodynamic modelling of sulphur emissions

International Nuclear Information System (INIS)

Morrin, Shane; Lettieri, Paola; Chapman, Chris; Mazzei, Luca

2012-01-01

Highlights: ► We investigate sulphur during MSW gasification within a fluid bed-plasma process. ► We review the literature on the feed, sulphur and process principles therein. ► The need for research in this area was identified. ► We perform thermodynamic modelling of the fluid bed stage. ► Initial findings indicate the prominence of solid phase sulphur. - Abstract: Gasification of solid waste for energy has significant potential given an abundant feed supply and strong policy drivers. Nonetheless, significant ambiguities in the knowledge base are apparent. Consequently this study investigates sulphur mechanisms within a novel two stage fluid bed-plasma gasification process. This paper includes a detailed review of gasification and plasma fundamentals in relation to the specific process, along with insight on MSW based feedstock properties and sulphur pollutant therein. As a first step to understanding sulphur partitioning and speciation within the process, thermodynamic modelling of the fluid bed stage has been performed. Preliminary findings, supported by plant experience, indicate the prominence of solid phase sulphur species (as opposed to H 2 S) – Na and K based species in particular. Work is underway to further investigate and validate this.

Basal interstitial water pressure in laboratory debris flows over a rigid bed in an open channel

Directory of Open Access Journals (Sweden)

N. Hotta

2012-08-01

Full Text Available Measuring the interstitial water pressure of debris flows under various conditions gives essential information on the flow stress structure. This study measured the basal interstitial water pressure during debris flow routing experiments in a laboratory flume. Because a sensitive pressure gauge is required to measure the interstitial water pressure in shallow laboratory debris flows, a differential gas pressure gauge with an attached diaphragm was used. Although this system required calibration before and after each experiment, it showed a linear behavior and a sufficiently high temporal resolution for measuring the interstitial water pressure of debris flows. The values of the interstitial water pressure were low. However, an excess of pressure beyond the hydrostatic pressure was observed with increasing sediment particle size. The measured excess pressure corresponded to the theoretical excess interstitial water pressure, derived as a Reynolds stress in the interstitial water of boulder debris flows. Turbulence was thought to induce a strong shear in the interstitial space of sediment particles. The interstitial water pressure in boulder debris flows should be affected by the fine sediment concentration and the phase transition from laminar to turbulent debris flow; this should be the subject of future studies.

Extensions to SCDAP/RELAP5/MOD2 debris analysis models for the severe accident analysis of Savannah River Site (SRS) reactors preliminary design report

International Nuclear Information System (INIS)

Siefken, L.J.; Moore, R.L.

1989-06-01

Proposed extensions to the debris analysis model in the SCDAP/RELAP5 code to perform severe accident analyses of Savannah River Plant reactors are described. Designs are presented for the following areas of development: (a) calculating convective and radiative heat transfer at the surfaces of a debris region; (b) calculating heatup of a structure and supported debris that interfaces with several fluid control volumes; (c) modeling the addition of transported material to the surfaces of any structure represented by the debris analysis model; (d) calculating the two-dimensional heatup of an arbitrary number of structures in the reactor system; (e) modeling the effect of natural convection of liquefied material on heat transfer in a debris bed; and (f) modeling fission product release and aerosol generation in a debris bed. 11 refs., 12 figs., 7 tabs

ASTM standards for fire debris analysis: a review.

Science.gov (United States)

Stauffer, Eric; Lentini, John J

2003-03-12

The American Society for Testing and Materials (ASTM) recently updated its standards E 1387 and E 1618 for the analysis of fire debris. The changes in the classification of ignitable liquids are presented in this review. Furthermore, a new standard on extraction of fire debris with solid phase microextraction (SPME) was released. Advantages and drawbacks of this technique are presented and discussed. Also, the standard on cleanup by acid stripping has not been reapproved. Fire debris analysts that use the standards should be aware of these changes.

Characteristics of immobilized lactobacillus delbrueckii in a liquid-solid fluidized bed bioreactor for lactic acid production

Energy Technology Data Exchange (ETDEWEB)

Wang, Henian; Seki, M.; Furusaki, S. [The Univ. of Tokyo (Japan). Faculty of Engineering

1995-04-20

A fluidized bed bioreactor was employed for lactic acid production using immobilized cells. First, the cell release rate was discussed. A liquid-solid fluidized bed reactor with immobilized cells was used to perform continuous lactic acid fermentation without any operational problems. The performance of the reactor was investigated under different conditions. Cell release rate and contribution of free cells to lactic acid production were studied quantitatively. The results showed that under low gel holdup and low dilution rate conditions, free cells played a significant role in lactic acid production. However, increasing solid holdup decreased the free cell concentration in the broth due to high lactic acid concentration and also decreased the contribution of the free cells to lactic acid production. The effects of growth nutrients on reactor performance were investigated. 16 refs., 12 figs.

In situ measurements of post-fire debris flows in southern California: Comparisons of the timing and magnitude of 24 debris-flow events with rainfall and soil moisture conditions

Science.gov (United States)

Kean, J.W.; Staley, D.M.; Cannon, S.H.

2011-01-01

Debris flows often occur in burned steeplands of southern California, sometimes causing property damage and loss of life. In an effort to better understand the hydrologic controls on post-fire debris-flow initiation, timing and magnitude, we measured the flow stage, rainfall, channel bed pore fluid pressure and hillslope soil-moisture accompanying 24 debris flows recorded in five different watersheds burned in the 2009 Station and Jesusita Fires (San Gabriel and Santa Ynez Mountains). The measurements show substantial differences in debris-flow dynamics between sites and between sequential events at the same site. Despite these differences, the timing and magnitude of all events were consistently associated with local peaks in short duration (landslides. By identifying the storm characteristics most closely associated with post-fire debris flows, these measurements provide valuable guidance for warning operations and important constraints for developing and testing models of post-fire debris flows. copyright. 2011 by the American Geophysical Union.

Prediction of corium debris characteristics in lower plenum of a nordic BWR in different accident scenarios using MELCOR code - 15367

International Nuclear Information System (INIS)

Phung, V.A.; Galushin, S.; Raub, S.; Goronovski, A.; Villanueva, W.; Koeoep, K; Grishchenko, D.; Kudinov, P.

2015-01-01

Severe accident management strategy in Nordic boiling water reactors (BWRs) relies on ex-vessel core debris coolability. The mode of corium melt release from the vessel determines conditions for ex-vessel accident progression and threats to containment integrity, e.g., formation of a non-coolable debris bed and possibility of energetic steam explosion. In-vessel core degradation and relocation is an important stage which determines characteristics of corium debris in the vessel lower plenum, such as mass, composition, thermal properties, timing of relocation, and decay heat. These properties affect debris reheating and remelting, melt interactions with the vessel structures, and possibly vessel failure and melt ejection mode. Core degradation and relocation is contingent upon the accident scenario parameters such as recovery time and capacity of safety systems. The goal of this work is to obtain a better understanding of the impact of the accident scenarios and timing of the events on core relocation phenomena and resulting properties of the debris bed in the vessel lower plenum of Nordic BWRs. In this study, severe accidents in a Nordic BWR reference plant are initiated by a station black out event, which is the main contributor to core damage frequency of the reactor. The work focuses on identifying ranges of debris bed characteristics in the lower plenum as functions of the accident scenario with different recovery timing and capacity of safety systems. The severe accident analysis code MELCOR coupled with GA-IDPSA is used in this work. GA-IDPSA is a Genetic Algorithm-based Integrated Deterministic Probabilistic Safety Analysis tool, which has been developed to search uncertain input parameter space. The search is guided by different target functions. Scenario grouping and clustering approach is applied in order to estimate the ranges of debris characteristics and identify scenario regions of core relocation that can lead to significantly different debris bed

An experimental study on quenching of a radially stratified heated porous bed

International Nuclear Information System (INIS)

Nayak, Arun K.; Sehgal, Bal Raj; Stepanyan, Armen V.

2006-01-01

The quenching characteristics of a volumetrically-heated particulate bed composed of radially stratified sand layers were investigated experimentally in the POMECO facility. The sand bed simulates the corium particulate debris bed which is formed when the molten corium released from the vessel fragments in water and deposits on the cavity floor during a postulated severe accident in a light water reactor (LWR). The electrically-heated bed was quenched by water from a water column established over top of it, and later also with water coming from its bottom, which was circulating from the water overlayer through downcomers. A series of experiments were conducted to reveal the effects of the size of downcomers, and their locations in the bed, on the quenching characteristics of the radially stratified debris beds. The downcomers were found to significantly increase the bed quenching rate. To simulate the non-condensable gases generated during the MCCI, air and argon were injected from the bottom of the bed at different flow rates. The effects of gas flow rate and its properties on the quenching behaviour were observed. The results indicate that the non-condensable gas flows reduce the quenching rate significantly. The gas properties also affect the quenching characteristics

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.

Advanced circulating fluidised bed technology (CFB) for large-scale solid biomass fuel firing power plants

Energy Technology Data Exchange (ETDEWEB)

Jaentti, Timo; Zabetta, Edgardo Coda; Nuortimo, Kalle [Foster Wheeler Energia Oy, Varkaus (Finland)

2013-04-01

Worldwide the nations are taking initiatives to counteract global warming by reducing their greenhouse gas emissions. Efforts to increase boiler efficiency and the use of biomass and other solid renewable fuels are well in line with these objectives. Circulating fluidised bed boilers (CFB) are ideal for efficient power generation, capable to fire a broad variety of solid biomass fuels from small CHP plants to large utility power plants. Relevant boiler references in commercial operation are made for Finland and Poland.

Method for the combustion of a gas, in fixed bed, with an oxidized solid and associated installation

OpenAIRE

Abanades García, Juan Carlos; Fernández García, José Ramón

2014-01-01

[EN] The present invention pertains to the field of the generation of energy from combustible gases, incorporating the capture of carbon dioxide for use or permanent storage and, specifically relates to cyclical methods of gas combustion with oxidized solids (chemical looping processes), in fixed bed, for solving the problem of controlling temperature in the combustion of gaseous fuels in fixed beds of metal oxides operating at high pressures, and also the associated installation.

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

of the syngas predicted by the two models is equal to about 7%. The application to different types of biomass shows that the difference in the predictions increases as the carbon content grows. The phenomenological model, in fact, generally considers higher conversion rates of this element to volatiles......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 treated as a 0D system, where the thermo-chemical processes are divided in two successive sections: drying and conversion. Phenomenological laws are written to characterize the syngas release as a function of the main governing parameters. The second model is an empirical 1D approach. Temperature, species...

Solid fuel feed system for a fluidized bed

Science.gov (United States)

Jones, Brian C.

1982-01-01

A fluidized bed for the combustion of coal, with limestone, is replenished with crushed coal from a system discharging the coal laterally from a station below the surface level of the bed. A compartment, or feed box, is mounted at one side of the bed and its interior separated from the bed by a weir plate beneath which the coal flows laterally into the bed while bed material is received into the compartment above the plate to maintain a predetermined minimum level of material in the compartment.

Experimental observations of granular debris flows

Science.gov (United States)

Ghilardi, P.

2003-04-01

Various tests are run using two different laboratory flumes with rectangular cross section and transparent walls. The grains used in a single experiment have an almost constant grain sizes; mean diameter ranges from 5 mm to 20 mm. In each test various measurements are taken: hydrograms, velocity distribution near the transparent walls and on the free surface, average flow concentration. Concentration values are measured taking samples. Velocity distributions are obtained from movies recorded by high speed video cameras capable of 350 frames per second; flow rates and depth hydrograms are computed from the same velocity distributions. A gate is installed at the beginning of one of the flumes; this gate slides normally to the bed and opens very quickly, reproducing a dam-break. Several tests are run using this device, varying channel slope, sediment concentration, initial mixture thickness before the gate. Velocity distribution in the flume is almost constant from left to right, except for the flow sections near the front. The observed discharges and velocities are less than those given by a classic dam break formula, and depend on sediment concentration. The other flume is fed by a mixture with constant discharge and concentration, and is mainly used for measuring velocity distributions when the flow is uniform, with both rigid and granular bed, and to study erosion/deposition processes near debris flow dams or other mitigation devices. The equilibrium slope of the granular bed is very close to that given by the classical equilibrium formulas for debris flow. Different deposition processes are observed depending on mixture concentration and channel geometry.

A real two-phase submarine debris flow and tsunami

International Nuclear Information System (INIS)

Pudasaini, Shiva P.; Miller, Stephen A.

2012-01-01

The general two-phase debris flow model proposed by Pudasaini is employed to study subaerial and submarine debris flows, and the tsunami generated by the debris impact at lakes and oceans. The model, which includes three fundamentally new and dominant physical aspects such as enhanced viscous stress, virtual mass, and generalized drag (in addition to buoyancy), constitutes the most generalized two-phase flow model to date. The advantage of this two-phase debris flow model over classical single-phase, or quasi-two-phase models, is that the initial mass can be divided into several parts by appropriately considering the solid volume fraction. These parts include a dry (landslide or rock slide), a fluid (water or muddy water; e.g., dams, rivers), and a general debris mixture material as needed in real flow simulations. This innovative formulation provides an opportunity, within a single framework, to simultaneously simulate the sliding debris (or landslide), the water lake or ocean, the debris impact at the lake or ocean, the tsunami generation and propagation, the mixing and separation between the solid and fluid phases, and the sediment transport and deposition process in the bathymetric surface. Applications of this model include (a) sediment transport on hill slopes, river streams, hydraulic channels (e.g., hydropower dams and plants); lakes, fjords, coastal lines, and aquatic ecology; and (b) submarine debris impact and the rupture of fiber optic, submarine cables and pipelines along the ocean floor, and damage to offshore drilling platforms. Numerical simulations reveal that the dynamics of debris impact induced tsunamis in mountain lakes or oceans are fundamentally different than the tsunami generated by pure rock avalanches and landslides. The analysis includes the generation, amplification and propagation of super tsunami waves and run-ups along coastlines, debris slide and deposition at the bottom floor, and debris shock waves. It is observed that the

A real two-phase submarine debris flow and tsunami

Energy Technology Data Exchange (ETDEWEB)

Pudasaini, Shiva P.; Miller, Stephen A. [Department of Geodynamics and Geophysics, Steinmann Institute, University of Bonn Nussallee 8, D-53115, Bonn (Germany)

2012-09-26

The general two-phase debris flow model proposed by Pudasaini is employed to study subaerial and submarine debris flows, and the tsunami generated by the debris impact at lakes and oceans. The model, which includes three fundamentally new and dominant physical aspects such as enhanced viscous stress, virtual mass, and generalized drag (in addition to buoyancy), constitutes the most generalized two-phase flow model to date. The advantage of this two-phase debris flow model over classical single-phase, or quasi-two-phase models, is that the initial mass can be divided into several parts by appropriately considering the solid volume fraction. These parts include a dry (landslide or rock slide), a fluid (water or muddy water; e.g., dams, rivers), and a general debris mixture material as needed in real flow simulations. This innovative formulation provides an opportunity, within a single framework, to simultaneously simulate the sliding debris (or landslide), the water lake or ocean, the debris impact at the lake or ocean, the tsunami generation and propagation, the mixing and separation between the solid and fluid phases, and the sediment transport and deposition process in the bathymetric surface. Applications of this model include (a) sediment transport on hill slopes, river streams, hydraulic channels (e.g., hydropower dams and plants); lakes, fjords, coastal lines, and aquatic ecology; and (b) submarine debris impact and the rupture of fiber optic, submarine cables and pipelines along the ocean floor, and damage to offshore drilling platforms. Numerical simulations reveal that the dynamics of debris impact induced tsunamis in mountain lakes or oceans are fundamentally different than the tsunami generated by pure rock avalanches and landslides. The analysis includes the generation, amplification and propagation of super tsunami waves and run-ups along coastlines, debris slide and deposition at the bottom floor, and debris shock waves. It is observed that the

Systems and Sensors for Debris-flow Monitoring and Warning

Directory of Open Access Journals (Sweden)

Lorenzo Marchi

2008-04-01

Full Text Available Debris flows are a type of mass movement that occurs in mountain torrents. They consist of a high concentration of solid material in water that flows as a wave with a steep front. Debris flows can be considered a phenomenon intermediate between landslides and water floods. They are amongst the most hazardous natural processes in mountainous regions and may occur under different climatic conditions. Their destructiveness is due to different factors: their capability of transporting and depositing huge amounts of solid materials, which may also reach large sizes (boulders of several cubic meters are commonly transported by debris flows, their steep fronts, which may reach several meters of height and also their high velocities. The implementation of both structural and nonstructural control measures is often required when debris flows endanger routes, urban areas and other infrastructures. Sensor networks for debris-flow monitoring and warning play an important role amongst non-structural measures intended to reduce debris-flow risk. In particular, debris flow warning systems can be subdivided into two main classes: advance warning and event warning systems. These two classes employ different types of sensors. Advance warning systems are based on monitoring causative hydrometeorological processes (typically rainfall and aim to issue a warning before a possible debris flow is triggered. Event warning systems are based on detecting debris flows when these processes are in progress. They have a much smaller lead time than advance warning ones but are also less prone to false alarms. Advance warning for debris flows employs sensors and techniques typical of meteorology and hydrology, including measuring rainfall by means of rain gauges and weather radar and monitoring water discharge in headwater streams. Event warning systems use different types of sensors, encompassing ultrasonic or radar gauges, ground vibration sensors, videocameras, avalanche

The study of solid circulation rate in a compartmented fluidized bed gasifier (CFBG)

Science.gov (United States)

Wee, S. K.; Pok, Y. W.; Law, M. C.; Lee, V. C. C.

2016-06-01

Biomass waste has been abundantly available in Malaysia since the booming of palm oil industry. In order to tackle this issue, gasification is seen a promising technology to convert waste into energy. In view of the heat requirement for endothermic gasification reaction as well as the complex design and operation of multiple fluidized beds, compartmented fluidized bed gasifier (CFBG) with the combustor and the gasifier as separate compartments is proposed. As such, solid circulation rate (SCR) is one of the essential parameters for steady gasification and combustion to be realized in their respective compartments. Experimental and numerical studies (CFD) on the effect of static bed height, main bed aeration, riser aeration and v-valve aeration on SCR have been conducted in a cold- flow CFBG model with only river sand as the fluidizing medium. At lower operating range, the numerical simulations under-predict the SCR as compared to that of the experimental results. Also, it predicts slightly different trends over the range. On the other hand, at higher operating range, the numerical simulations are able to capture those trends as observed in the experimental results at the lower operating range. Overall, the numerical results compare reasonably well with that of the experimental works.

Debris thickness patterns on debris-covered glaciers

Science.gov (United States)

Anderson, Leif S.; Anderson, Robert S.

2018-06-01

Many debris-covered glaciers have broadly similar debris thickness patterns: surface debris thickens and tends to transition from convex- to concave-up-down glacier. We explain this pattern using theory (analytical and numerical models) paired with empirical observations. Down glacier debris thickening results from the conveyor-belt-like nature of the glacier surface in the ablation zone (debris can typically only be added but not removed) and from the inevitable decline in ice surface velocity toward the terminus. Down-glacier thickening of debris leads to the reduction of sub-debris melt and debris emergence toward the terminus. Convex-up debris thickness patterns occur near the up-glacier end of debris covers where debris emergence dominates (ablation controlled). Concave-up debris thickness patterns occur toward glacier termini where declining surface velocities dominate (velocity controlled). A convex-concave debris thickness profile inevitably results from the transition between ablation-control and velocity-control down-glacier. Debris thickness patterns deviating from this longitudinal shape are most likely caused by changes in hillslope debris supply through time. By establishing this expected debris thickness pattern, the effects of climate change on debris cover can be better identified.

The use of dielectric heating in particulate bed dryout experiments

International Nuclear Information System (INIS)

Stevens, G.F.; Willshire, S.J.

1984-09-01

Decay-heated, liquid-saturated debris beds arise in hypothetical severe accidents with LMFBR and PWR, and a large international effort is currently engaged in experimental studies of the cooling limitations of such beds. Dryout is one of the important cooling limitations. Dielectric heating offers a means of closely simulating decay heating in beds of irregular particles, and is under development at AEE Winfrith for application to experimental studies of dryout. This report describes progress to date. (author)

Solid diffusion control of the adsorption of basic dyes onto granular activated carbon and natural zeolite in fixed bed columns

Directory of Open Access Journals (Sweden)

M. MARINKOVSKI

2001-07-01

Full Text Available The adsorption of basic dyes from aqueous solutions onto granular activated carbon and natural zeolite was studied using a fixed bed column. The design procedures for fixed bed adsorption columns were investigated for two basic dyes Maxilon Goldgelb GL EC 400 % (MG-400 and Maxilon Schwarz FBL-01 300 % (MS-300. A computer program based on the solid diffusion control model has been developed. The model parameters: solid diffusion coefficient, DS, axial dispersion coefficient, DL and external mass transfer coefficient, kf for all the investigated systems were estimated by means of a best fit approach.

Method of burning sulfur-containing fuels in a fluidized bed boiler

Science.gov (United States)

Jones, Brian C.

1982-01-01

A method of burning a sulfur-containing fuel in a fluidized bed of sulfur oxide sorbent wherein the overall utilization of sulfur oxide sorbent is increased by comminuting the bed drain solids to a smaller average particle size, preferably on the order of 50 microns, and reinjecting the comminuted bed drain solids into the bed. In comminuting the bed drain solids, particles of spent sulfur sorbent contained therein are fractured thereby exposing unreacted sorbent surface. Upon reinjecting the comminuted bed drain solids into the bed, the newly-exposed unreacted sorbent surface is available for sulfur oxide sorption, thereby increasing overall sorbent utilization.

Hydrodynamics of circulating and bubbling fluidized beds

International Nuclear Information System (INIS)

Gidaspow, D.P.; Tsuo, Y.P.; Ding, J.

1991-01-01

This paper reports that a review of modeling of the hydrodynamics of fluidization of bubbling beds showed that inviscid two-fluid models were able to predict a great deal of the behavior of bubbling beds because the dominant mechanism of energy dissipation is the drag between the particles and the fluid. The formation, the growth and the bursting of bubbles were predicted. Predicted wall-to-bed heat transfer coefficients and velocity profiles of jets agreed with measurements. Time average porosity distributions agreed with measurements done using gamma-ray densitometers without the use of any adjustable parameters. However, inviscid models could not correctly predict rates of erosion around tubes immersed into fluidized beds. To correctly model such behavior, granular stresses involving solids viscosity were added into the computer model. This viscosity arises due to random collision of particles. Several models fro this viscosity were investigated and the results compared to measurements of solids distributions in two-dimensional beds and to particle velocities reported in the literature. While in the case of bubbling beds the solids viscosity plays the role of a correction, modeling of a circulating fluidized bed (CFB) without a viscosity is not possible. Recent experimental data obtained at IIT and at IGT show that in CFB the solids viscous dissipation is responsible for as much as half of the pressure drop. From such measurement, solids viscosities were computed. These were used in the two fluid hydrodynamic model, to predict radial solids distributions and solids velocities which matched the experimental distributions. Most important, the model predicted cluster formation and transient internal circulation which is responsible for the favorable characteristics of CFBs, such as good wall-to-bed heat transfer. Video tape movies of computations compared favorably with high speed movies of the experiments

Investigation of Orbital Debris: Mitigation, Removal, and Modeling the Debris Population

Science.gov (United States)

Slotten, Joel

The population of objects in orbit around Earth has grown since the late 1950s. Today there are over 21,000 objects over 10 cm in length in orbit, and an estimated 500,000 more between 1 and 10 cm. Only a small fraction of these objects are operational satellites. The rest are debris: old derelict spacecraft or rocket bodies, fragments created as the result of explosions or collisions, discarded objects, slag from solid rockets, or even flaked off paint. Traveling at up to 7 km/s, a collision with even a 1 cm piece of debris could severely damage or destroy a satellite. This dissertation examines three aspects of orbital debris. First, the concept of a self-consuming satellite is explored. This nanosatellite would use its own external structure as propellant to execute a deorbit maneuver at the end of its operational life, thus allowing it to meet current debris mitigation standards. Results from lab experiments examining potential materials for this concept have shown favorable results. Second, Particle in Cell techniques are modified and used to model the plasma plume from a micro-cathode arc thruster. This model is then applied to the concept of an ion beam shepherd satellite. This satellite would use its plasma plume to deorbit another derelict satellite. Results from these simulations indicate the micro-cathode arc thruster could potentially deorbit a derelict CubeSat in a matter of a few weeks. Finally, the orbital debris population at geosynchronous orbit is examined, focusing on variations in the density of the population as a function of longitude. New insights are revealed demonstrating that the variation in population density is slightly less than previously reported.

Combustion of municipal solid wastes with oil shale in a circulating fluidized bed. Final report

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-06-30

The problem addressed by our invention is that of municipal solid waste utilization. The dimensions of the problem can be visualized by the common comparison that the average individual in America creates in five years time an amount of solid waste equivalent in weight to the Statue of Liberty. The combustible portion of the more than 11 billion tons of solid waste (including municipal solid waste) produced in the United States each year, if converted into useful energy, could provide 32 quads per year of badly needed domestic energy, or more than one-third of our annual energy consumption. Conversion efficiency and many other factors make such a production level unrealistic, but it is clear that we are dealing with a very significant potential resource. This report describes research pertaining to the co-combustion of oil shale with solid municipal wastes in a circulating fluidized bed. The oil shale adds significant fuel content and also constituents that can possible produce a useful cementitious ash.

Response of a Brook Trout Population and Instream Habitat to a Catastrophic Flood and Debris Flow

Science.gov (United States)

Criag N. Roghair; C. Andrew Dolloff; Martin K. Underwood

2002-01-01

In June 1995, a massive flood and debris flow impacted fish and habitat along the lower 1.9 km of the Staunton River, a headwater stream located in Shenandoah National Park, Virginia. In the area affected by debris flow, the stream bed was scoured and new substrate materials were deposited, trees were removed from a 30-m-wide band in the riparian area, and all fish...

Debris filtering efficiency and its effect on long term cooling capability

International Nuclear Information System (INIS)

Jung, Min-Su; Kim, Kyu-Tae

2013-01-01

Highlights: • Debris filtering efficiencies for two debris filter designs used in PWRs are provided. • Various debris used in the tests are selected to simulate actual debris found in PWRs. • Debris filter efficiency is explained by flow-hole size and grid strap height. • The effect of debris filters on flow blockage during LTC after a LOCA is described. -- Abstract: A cutting-edge debris-filter designs, Protective Grid (P-grid) and Guardian Grid (G-grid) attached to the upper part of bottom nozzle, have been employed for the PWRs in Korea since 2000s to protect the fuel from debris-induced fuel failures. The debris-filter efficiency of the P-grid and G-grid designs is improved by relatively smaller flow areas formed by the grid straps and dimples. The debris-filter efficiency of the P-grid design is further improved by the relatively smaller flow-hole bottom nozzle. The debris-filter flow tests employing eighteen debris types showed that the debris-filter efficiencies of the P-grid and G-grid designs are 91 and 96%, respectively, while that of the SYS80 fuel design having only the standard flow-hole bottom nozzle is 26%. The slightly better debris-filter efficiency of the G-grid design against the P-grid design may be explained by relatively smaller flow areas at the G-grid dimple region as well as by the relatively longer solid end plug and the higher G-grid strap. The P-grid design may capture circular shapes of debris larger than 3.44 mm in diameter at the flow holes formed by the P-grid dimples, whereas the G-grid design may capture circular shapes of debris larger than 2.54 mm in diameter at the flow holes formed by the G-grid dimples. The aforementioned difference in the debris-filter efficiency between the P-grid and G-grid designs may be predicted by the solid modeling technique generating three-dimensional flow paths. Using the minimum flow-hole areas generated by the P-grid and G-grid designs, on the other hand, the effect of debris injected from

Method and apparatus for a combination moving bed thermal treatment reactor and moving bed filter

Energy Technology Data Exchange (ETDEWEB)

Badger, Phillip C.; Dunn, Jr., Kenneth J.

2015-09-01

A moving bed gasification/thermal treatment reactor includes a geometry in which moving bed reactor particles serve as both a moving bed filter and a heat carrier to provide thermal energy for thermal treatment reactions, such that the moving bed filter and the heat carrier are one and the same to remove solid particulates or droplets generated by thermal treatment processes or injected into the moving bed filter from other sources.

Numerical and experimental studies on effects of moisture content on combustion characteristics of simulated municipal solid wastes in a fixed bed

International Nuclear Information System (INIS)

Sun, Rui; Ismail, Tamer M.; Ren, Xiaohan; Abd El-Salam, M.

2015-01-01

Highlights: • The effects of moisture content on the burning process of MSW are investigated. • A two-dimensional mathematical model was built to simulate the combustion process. • Temperature distributions, process rates, gas species were measured and simulated. • The The conversion ratio of C/CO and N/NO in MSW are inverse to moisture content. - Abstract: In order to reveal the features of the combustion process in the porous bed of a waste incinerator, a two-dimensional unsteady state model and experimental study were employed to investigate the combustion process in a fixed bed of municipal solid waste (MSW) on the combustion process in a fixed bed reactor. Conservation equations of the waste bed were implemented to describe the incineration process. The gas phase turbulence was modeled using the k–ε turbulent model and the particle phase was modeled using the kinetic theory of granular flow. The rate of moisture evaporation, devolatilization rate, and char burnout was calculated according to the waste property characters. The simulation results were then compared with experimental data for different moisture content of MSW, which shows that the incineration process of waste in the fixed bed is reasonably simulated. The simulation results of solid temperature, gas species and process rate in the bed are accordant with experimental data. Due to the high moisture content of fuel, moisture evaporation consumes a vast amount of heat, and the evaporation takes up most of the combustion time (about 2/3 of the whole combustion process). The whole bed combustion process reduces greatly as MSW moisture content increases. The experimental and simulation results provide direction for design and optimization of the fixed bed of MSW

Numerical and experimental studies on effects of moisture content on combustion characteristics of simulated municipal solid wastes in a fixed bed

Energy Technology Data Exchange (ETDEWEB)

Sun, Rui, E-mail: Sunsr@hit.edu.cn [School of Energy Science and Engineering, Harbin Institute of Technology, 92, West Dazhi Street, Harbin 150001 (China); Ismail, Tamer M., E-mail: temoil@aucegypt.edu [Department of Mechanical Engineering, Suez Canal University, Ismailia (Egypt); Ren, Xiaohan [School of Energy Science and Engineering, Harbin Institute of Technology, 92, West Dazhi Street, Harbin 150001 (China); Abd El-Salam, M. [Department of Basic Science, Cairo University, Giza (Egypt)

2015-05-15

Highlights: • The effects of moisture content on the burning process of MSW are investigated. • A two-dimensional mathematical model was built to simulate the combustion process. • Temperature distributions, process rates, gas species were measured and simulated. • The The conversion ratio of C/CO and N/NO in MSW are inverse to moisture content. - Abstract: In order to reveal the features of the combustion process in the porous bed of a waste incinerator, a two-dimensional unsteady state model and experimental study were employed to investigate the combustion process in a fixed bed of municipal solid waste (MSW) on the combustion process in a fixed bed reactor. Conservation equations of the waste bed were implemented to describe the incineration process. The gas phase turbulence was modeled using the k–ε turbulent model and the particle phase was modeled using the kinetic theory of granular flow. The rate of moisture evaporation, devolatilization rate, and char burnout was calculated according to the waste property characters. The simulation results were then compared with experimental data for different moisture content of MSW, which shows that the incineration process of waste in the fixed bed is reasonably simulated. The simulation results of solid temperature, gas species and process rate in the bed are accordant with experimental data. Due to the high moisture content of fuel, moisture evaporation consumes a vast amount of heat, and the evaporation takes up most of the combustion time (about 2/3 of the whole combustion process). The whole bed combustion process reduces greatly as MSW moisture content increases. The experimental and simulation results provide direction for design and optimization of the fixed bed of MSW.

TMI-2 core debris analytical methods and results

International Nuclear Information System (INIS)

Akers, D.W.; Cook, B.A.

1984-01-01

A series of six grab samples was taken from the debris bed of the TMI-2 core in early September 1983. Five of these samples were sent to the Idaho National Engineering Laboratory for analysis. Presented is the analysis strategy for the samples and some of the data obtained from the early stages of examination of the samples (i.e., particle size-analysis, gamma spectrometry results, and fissile/fertile material analysis)

Mechanics of debris flows and rock avalanches: Chapter 43

Science.gov (United States)

Iverson, Richard M.; Fernando, Harindra Joseph

2012-01-01

Debris flows are geophysical phenomena intermediate in character between rock avalanches and flash floods. They commonly originate as water-laden landslides on steep slopes and transform into liquefied masses of fragmented rock, muddy water, and entrained organic matter that disgorge from canyons onto valley floors. Typically including 50%–70% solid grains by volume, attaining speeds >10 m/s, and ranging in size up to ∼109 m3, debris flows can denude mountainsides, inundate floodplains, and devastate people and property (Figure 43.1). Notable recent debris-flow disasters resulted in more than 20,000 fatalities in Armero, Colombia, in 1985 and in Vargas state, Venezuela, in 1999.

Leaching behavior of harmful components from cement solidities of fluidized-bed coal ash

Energy Technology Data Exchange (ETDEWEB)

Baba, T.; Fukuoka, H.; Shigemoto, N. [Fuji Clean Co., Kagawa (Japan)

2008-07-15

Solidifies of fluidized-bed fly ash with slag cement were prepared by hydrothermal treatment after adding gypsum, Na3PO{sub 4}, or Al2(SO{sub 4}){sub 3}. XRD analysis of the solidifies was performed and leaching behavior of Pb and F from the solidities was investigated. The fly ash-cement and fly ash-cement-gypsum solidifies showed rather high leaching concentration of F and Pb. The F leaching was explained by solubility products of a Ca(OH){sub 2} CaF2 system. The Pb leaching concentrations roughly agreed with the theoretical curve for hydroxo complexes of Pb, showing a strong dependence on pH. Addition of Na3PO{sub 4} and Al2(SO{sub 4}){sub 3}, to cement solidities gave katoite and aluminium phosphate, and ettringite, respectively, and these solidities showed lower leaching concentrations of F and Pb than the fly ash-cement and fly ash-cement-gypsum solidifies. Capture of F and Pb in crystalline components such as ettringite probably accounts for such leaching suppression.

Evolution of Fine-Grained Channel Margin Deposits behind Large Woody Debris in an Experimental Gravel-Bed Flume

Science.gov (United States)

ONeill, B.; Marks, S.; Skalak, K.; Puleo, J. A.; Wilcock, P. R.; Pizzuto, J. E.

2014-12-01

Fine grained channel margin (FGCM) deposits of the South River, Virginia sequester a substantial volume of fine-grained sediment behind large woody debris (LWD). FGCM deposits were created in a laboratory setting meant to simulate the South River environment using a recirculating flume (15m long by 0.6m wide) with a fixed gravel bed and adjustable slope (set to 0.0067) to determine how fine sediment is transported and deposited behind LWD. Two model LWD structures were placed 3.7 m apart on opposite sides of the flume. A wire mesh screen with attached wooden dowels simulated LWD with an upstream facing rootwad. Six experiments with three different discharge rates, each with low and high sediment concentrations, were run. Suspended sediment was very fine grained (median grain size of 3 phi) and well sorted (0.45 phi) sand. Upstream of the wood, water depths averaged about 0.08m, velocities averaged about 0.3 m/s, and Froude numbers averaged around 0.3. Downstream of the first LWD structure, velocities were reduced tenfold. Small amounts of sediment passed through the rootwad and fell out of suspension in the area of reduced flow behind LWD, but most of the sediment was carried around the LWD by the main flow and then behind the LWD by a recirculating eddy current. Upstream migrating dunes formed behind LWD due to recirculating flow, similar to reattachment bars documented in bedrock canyon rivers partially obstructed by debouching debris fans. These upstream migrating dunes began at the reattachment point and merged with deposits formed from sediment transported through the rootwad. Downstream migrating dunes formed along the channel margin behind the LWD, downstream of the reattachment point. FGCM deposits were about 3 m long, with average widths of about 0.8 m. Greater sediment concentration created thicker FGCM deposits, and higher flows eroded the sides of the deposits, reducing their widths.

Inulinase production in a packed bed reactor by solid state fermentation.

Science.gov (United States)

Dilipkumar, M; Rajamohan, N; Rajasimman, M

2013-07-01

In this work, production of inulinase was carried out in a packed bed reactor (PBR) under solid state fermentation. Kluyveromyces marxianus var. marxianus was used to produce the inulinase using pressmud as substrate. The parameters like air flow rate, packing density and particle size were optimized using response surface methodology (RSM) to maximize the inulinase production. The optimum conditions for the maximum inulinase production were: air flow rate - 0.82 L/min, packing density - 40 g/L and particle size - 0.0044 mm (mesh - 14/20). At these optimized conditions, the production of inulinase was found to be 300.5 unit/gram of dry substrate (U/gds). Copyright © 2013 Elsevier Ltd. All rights reserved.

Fluidized bed incinerator development

International Nuclear Information System (INIS)

Ziegler, D.L.; Johnson, A.J.

1976-01-01

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

Apparatus for controlling fluidized beds

Science.gov (United States)

Rehmat, A.G.; Patel, J.G.

1987-05-12

An apparatus and process are disclosed for control and maintenance of fluidized beds under non-steady state conditions. An ash removal conduit is provided for removing solid particulates from a fluidized bed separate from an ash discharge conduit in the lower portion of the grate supporting such a bed. The apparatus and process of this invention is particularly suitable for use in ash agglomerating fluidized beds and provides control of the fluidized bed before ash agglomeration is initiated and during upset conditions resulting in stable, sinter-free fluidized bed maintenance. 2 figs.

Occurrence of bromine in fluidised bed combustion of solid recovered fuel

Energy Technology Data Exchange (ETDEWEB)

Vainikka, P.

2011-12-15

Corrosive ash species are the single most important factor limiting the electric efficiency of steam boiler plants fired with waste or biomass. Chlorine has been found to have a central role in the chemistry involved as it reduces the melting temperature of ash, forms corrosive vapour and gas species in the furnace and halogenated deposits on boiler heat transfer surfaces. In this context chlorine has been extensively researched. At the time of writing this thesis there was hardly any published data available on the occurrence of bromine (Br) in the aforementioned context. The objective of this work was to review the occurrence of bromine in solid fuels and characterise the behaviour of bromine in full-scale fluidised bed combustion. The review on the occurrence of bromine in solid fuels revealed that in anthropogenic wastes bromine is mainly found in connection to flame retarded substances. Several weight percentages of bromine can be found in plastics treated with brominated flame retardants (BFRs). Bromine is typically found some 100-200 mg kg-1 in mixed municipal solid wastes (MSW). Bromine may be enriched in fuels with high share of plastics, such as solid recovered fuel (SRF) or refuse derived fuel (RDF). Up to 2000 mg kg-1 was found as a monthly average in SRF, typical levels being 20-200 mg kg-1. Wastewater sludge from paper mills may contain bromine 20-100 mg kg-1 due the use of bromine based biocides. In other fuels bromine may be found in significant amounts in marine influenced coal deposits and peat as well as in biomass treated with brominated pesticides. In the experimental part SRF, spruce bark and wastewater sludge from a paper mill were co-fired in a full- scale bubbling fluidised bed (BFB) boiler, and the collected fuels, aerosols and waterwall deposits were analysed with the focus on the fate of bromine. Bromine was mainly found to form water soluble high vapour pressure alkali metal halides in the furnace - in the form of KBr(g) and NaBr(g) as

Chaotic hydrodynamics of fluidized beds

Energy Technology Data Exchange (ETDEWEB)

Van der Stappen, M.L.M. [Unit Process and Systems Engineering, Advanced Manufacturing Technology Group, Unilever Research Laboratorium, Vlaardingen (Netherlands)

1996-12-31

The major goals of this thesis are: (1) to develop and evaluate an analysis method based on techniques from non-linear chaos theory to characterize the nonlinear hydrodynamics of gas-solids fluidized beds quantitatively; and (2) to determine the dependence of the chaotic invariants on the operating conditions and investigate how the chaos analysis method can be profitably applied to improve scale-up and design of gas-solids fluidized bed reactors. Chaos theory is introduced in chapter 2 with emphasis on analysis techniques for (experimental) time series, known from literature at the start of this work (1990-1991). In chapter 3, the testing of existing and newly developed techniques on both model and fluidized bed data is described. This leads to the development of the chaos analysis method to analyze measured pressure fluctuations time series of a fluidized bed. Following, in chapter 4, this method is tested and all choices for the parameters are evaluated. The influence of the experimental parameters and external disturbances on the measurements and analysis results is discussed and quantified. The result is a chaos measurement and analysis protocol, which is further used in this work. In chapter 5, the applications to fluidized beds are discussed. It is shown that the entropy is a good measure for the characterization of the dynamical behavior of gas-solids bubbling/slugging fluidized beds. Entropy is applied to characterize the influence of the operating conditions, to assess regime transitions and to analyze dimensionless similar beds of different scale. Quantitative design correlations that relate entropy to the operating parameters (including the bed diameter) are described. Finally, it is discussed how the results of this work might be used in scaling up the chaotic dynamics of fluidized beds. The overall conclusions and outlook from this work are presented in chapter 6. 182 refs.

Porous debris behavior modeling of QUENCH-02, QUENCH-03 and QUENCH-09 experiments

International Nuclear Information System (INIS)

Kisselev, A.E.; Kobelev, G.V.; Strizhov, V.F.; Vasiliev, A.D.

2006-01-01

The heat-up, melting, relocation, hydrogen generation phenomena, relevant for high-temperature stages both in a reactor case and small-scale integral tests like QUENCH, are governed in particular by heat and mass transfer in porous debris and molten pools which are formed in the core region. Porous debris formation and behavior in QUENCH experiments (QUENCH-02, QUENCH-03, QUENCH-09) plays a considerable role and its adequate modeling is important for thermal analysis. In particular, the analysis of QUENCH experiments shows that the major hydrogen release takes place in debris and melt regions formed in the upper part of the fuel assembly. The porous debris model was implemented in the Russian best estimate numerical code RATEG/SVECHA/HEFEST developed for modelling thermal hydraulics and severe accident phenomena in a reactor. The original approach for debris evolution is developed in the model from classical principles using a set of parameters including debris porosity; average particle diameter; temperatures and mass fractions of solid, liquid and gas phases; specific interface areas between different phases; effective thermal conductivity of each phase, including radiative heat conductivity; mass and energy fluxes through the interfaces. The debris model is based on the system of continuity, momentum and energy conservation equations, which consider the dynamics of volume-averaged velocities and temperatures of fluid, solid and gaseous phases of porous debris. The model is used for calculation of QUENCH experiments. The results obtained by the model are compared to experimental data concerning different aspects of thermal behavior: thermal hydraulics of porous debris, radiative heat transfer in a porous medium, the generalized melting and refreezing behavior of materials, hydrogen production. (author)

A CFD model for biomass combustion in a packed bed furnace

Energy Technology Data Exchange (ETDEWEB)

Karim, Md. Rezwanul [Faculty of Science, Engineering and Technology, Swinburne University of Technology, VIC 3122 (Australia); Department of Mechanical & Chemical Engineering, Islamic University of Technology, Gazipur 1704 (Bangladesh); Ovi, Ifat Rabbil Qudrat [Department of Mechanical & Chemical Engineering, Islamic University of Technology, Gazipur 1704 (Bangladesh); Naser, Jamal, E-mail: jnaser@swin.edu.au [Faculty of Science, Engineering and Technology, Swinburne University of Technology, VIC 3122 (Australia)

2016-07-12

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 CO{sub 2} 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.

The influence of process parameters in production of lipopeptide iturin A using aerated packed bed bioreactors in solid-state fermentation.

Science.gov (United States)

Piedrahíta-Aguirre, C A; Bastos, R G; Carvalho, A L; Monte Alegre, R

2014-08-01

The strain Bacillus iso 1 co-produces the lipopeptide iturin A and biopolymer poly-γ-glutamic acid (γ-PGA) in solid-state fermentation of substrate consisting of soybean meal, wheat bran with rice husks as an inert support. The effects of pressure drop, oxygen consumption, medium permeability and temperature profile were studied in an aerated packed bed bioreactor to produce iturin A, diameter of which was 50 mm and bed height 300 mm. The highest concentrations of iturin A and γ-PGA were 5.58 and 3.58 g/kg-dry substrate, respectively, at 0.4 L/min after 96 h of fermentation. The low oxygen uptake rates, being 23.34 and 22.56 mg O2/kg-dry solid substrate for each air flow rate tested generated 5.75 W/kg-dry substrate that increased the fermentation temperature at 3.7 °C. The highest pressure drop was 561 Pa/m at 0.8 L/min in 24 h. This is the highest concentration of iturin A produced to date in an aerated packed bed bioreactor in solid-state fermentation. The results can be useful to design strategies to scale-up process of iturin A in aerated packed bed bioreactors. Low concentration of γ-PGA affected seriously pressure drop, decreasing the viability of the process due to generation of huge pressure gradients with volumetric air flow rates. Also, the low oxygenation favored the iturin A production due to the reduction of free void by γ-PGA production, and finally, the low oxygen consumption generated low metabolic heat. The results show that it must control the pressure gradients to scale-up the process of iturin A production.

Experimental study on the rheological behaviour of debris flow

Directory of Open Access Journals (Sweden)

A. Scotto di Santolo

2010-12-01

Full Text Available A model able to describe all the processes involved in a debris flow can be very complex owing to the sudden changing of the material that turns from solid into liquid state. The two phases of the phenomenon are analysed separately referring to soil mechanics procedures with regard to the trigger phase, and to an equivalent fluid for the post-failure phase. The present paper is devoted to show the experimental results carried out to evaluate the behaviour assumed by a pyroclastic-derived soil during the flow. A traditional fluid tool has been utilized: a standard rotational rheometer equipped with two different geometries. The soils tested belong to deposits that cover the slopes of the Campania region, Italy, often affected by debris flows. The influence of solid concentration C_v and grain size distribution was tested: the soils were destructurated, sieved and mixed with water starting from the in situ porosity. All material mixtures showed a non-Newtonian fluid behaviour with a yield stress τ_y that increases with a solid volumetric concentration and decreases for an increase of sand fraction. The experimental data were fitted with standard model for fluids. A simple relation between C_v and τ_y was obtained. The yield stress seems to be a key parameter for describing and predicting the post-failure behaviour of debris flows. These results suggest that in the field a small change in solid fraction, due to rainfall, will cause a slight decrease of the static yield stress, readily inducing a rapid flow which will stop only when the dynamic yield stress is reached, namely on a much smoother slope. This can explain the in situ observed post-failure behaviour of debris flows, which are able to flow over very long distances even on smooth slopes.

Debris and pool formation/heat transfer in FARO-LWR: experiments and analyses

International Nuclear Information System (INIS)

Magallon, D.; Annunziato, A.; Corradini, M.

1999-01-01

The FARO-LWR experiments examine the debris and pool formation from a pour of core melt materials (UO 2 /ZrO 2 and UO 2 /ZrO 2 /Zr) into a pool of water at prototypic accident conditions. The experiments give unique data on the debris bed initial conditions, morphology and heat transfer after the core melt has slump and (partly) quenched into the water of the lower head. Quantities of up to 170 kg of corium melt are poured by gravity into water of depth between 1 and 2 m through a nozzle of diameter 0.1 m at different system pressures. The debris is collected in a flat bottom catcher of diameter 0.66 m. It reaches heights up to 0.2 m depending on the melt quantity. In general, the melt reaches the bottom only partially fragmented. The debris which forms consists of a conglomerate ('cake') in contact with the collecting structure and overlaying fragments (loose debris). The mean particle size of the loose debris is in the range 3.5 - 4.8 mm. The upper surface of the debris is flat. A gap is present between the cake and the bottom plate. The paper reviews the debris formation and heat transfer to the bottom steel structure from these tests and describes the development of a model to predict the debris and pool formation process. Sensitivity analyses have been performed by the COMETA code to study the behaviour of the ratio between the cake mass and the total mass. (authors)

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

Science.gov (United States)

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

2015-09-01

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

Study on the leaching behavior of actinides from nuclear fuel debris

Science.gov (United States)

Kirishima, Akira; Hirano, Masahiko; Akiyama, Daisuke; Sasaki, Takayuki; Sato, Nobuaki

2018-04-01

For the prediction of the leaching behavior of actinides contained in the nuclear fuel debris generated by the Fukushima Daiichi nuclear power plant accident in Japan, simulated fuel debris consisting of a UO2-ZrO2 solid solution doped with 137Cs, 237Np, 236Pu, and 241Am tracers was synthesized and investigated. The synthesis of the debris was carried out by heat treatment at 1200 °C at different oxygen partial pressures, and the samples were subsequently used for leaching tests with Milli-Q water and seawater. The results of the leaching tests indicate that the leaching of actinides depends on the redox conditions under which the debris was generated; for example, debris generated under oxidative conditions releases more actinide nuclides to water than that generated under reductive conditions. Furthermore, we found that, as Zr(IV) increasingly substituted U(IV) in the fluorite crystal structure of the debris, the actinide leaching from the debris decreased. In addition, we found that seawater leached more actinides from the debris than pure water, which seems to be caused by the complexation of actinides by carbonate ions in seawater.

Coefficient of solid-gas heat transfer in particle fixed bed; Coeficiente de transferencia de calor gas-solido em leito fixo de particulas

Energy Technology Data Exchange (ETDEWEB)

Fernandes Filho, Francisco

1991-03-01

The work presents a study on heat transfer between gas and solid phases for fixed beds in the absence of mass transfer and chemical reactions. Mathematical models presented in the literature were analyzed concerning to the assumptions made on axial dispersion in the fluid phase and interparticle thermal conductivity. Heat transfer coefficients and their dependency on flow conditions, particles and packed bed characteristics were experimentally determined through the solution of the previous mathematical models. Pressure drop behaviour for the packed beds used for the heat transfer study was also included. (author) 32 refs., 12 figs.

Staged fluidized-bed combustion and filter system

International Nuclear Information System (INIS)

Mei, J.S.; Halow, J.S.

1994-01-01

A staged fluidized-bed combustion and filter system are described for substantially reducing the quantity of waste through the complete combustion into ash-type solids and gaseous products. The device has two fluidized-bed portions, the first primarily as a combustor/pyrolyzer bed, and the second as a combustor/filter bed. The two portions each have internal baffles to define stages so that material moving therein as fluidized beds travel in an extended route through those stages. Fluidization and movement is achieved by the introduction of gases into each stage through a directional nozzle. Gases produced in the combustor/pyrolyzer bed are permitted to travel into corresponding stages of the combustor/filter bed through screen filters that permit gas flow but inhibit solids flow. Any catalyst used in the combustor/filter bed is recycled. The two beds share a common wall to minimize total volume of the system. A slightly modified embodiment can be used for hot gas desulfurization and sorbent regeneration. Either side-by-side rectangular beds or concentric beds can be used. The system is particularly suited to the processing of radioactive and chemically hazardous waste. 10 figures

Fluidized bed volume reduction of diverse radwastes

International Nuclear Information System (INIS)

McFee, J.N.; McConnell, J.W.; Waddoups, D.A.; Gray, M.F.; Harwood, L.E.; Clayton, N.J.; Drown, D.C.

1981-01-01

Method and apparatus for a fluidized bed radwaste volume reduction system are claimed. Low level radioactive wastes, combustible solids, ion exchange resins and filter sludges, and liquids, emanating from a reactor facility are introduced separately through an integrated waste influent system into a common fluidized bed vessel where volume reduction either through incineration or calcination occurs. Addition of a substance to the ion exchange resin before incineration inhibits the formation of low-melting point materials which tend to form clinkers in the bed. Solid particles are scrubbed or otherwise removed from the gaseous effluent of the vessel in an off-gas system, before the cooled and cleaned off-gas is released to the atmosphere. Iodine is chemically or physically removed from the off-gas. Otherwise, the only egress materials from the volume reduction system are containerized dry solids and tramp material. The bed material used during each mode may be circulated, cleaned, stored and exchanged from within the bed vessel by use of a bed material handling system. An instrumentation and control system provides operator information, monitors performance characteristics, implements start up and shut down procedures, and initiates alarms and emergency procedures during abnormal conditions

Mathematical modelling of the transport of a poorly sorted granular mixture as a debris-flow. The case of Madeira Island torrential floods in 2010

Science.gov (United States)

Ferreira, Rui M. L.; Oliveira, Rodrigo P.; Conde, Daniel

2016-04-01

On the 20th February 2010, heavy rainfall was registered at Madeira Island, North Atlantic. Stony debris flows, mudflows and mudslides ensued causing severe property loss, 1.5 m thick sediment deposits at downtown Funchal including 16th century monuments, and a death toll of 47 lives. Debris-flow fronts propagated downstream while carrying very high concentrations of solid material. These two-phase solid-fluid flows were responsible for most of the infrastructural damage across the island, due to their significantly increased mass and momentum. The objective of the present modelling work is to validate a 2DH model for torrential flows featuring the transport and interaction of several size fractions of a poorly-sorted granular mixture typical of stony debris flow in Madeira. The module for the transport of poorly-sorted material was included in STAV-2D (CERIS-IST), a shallow-water and morphology solver 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. STAV-2D also includes formulations of flow resistance and bedload transport adequate for debris-flows with natural mobile beds (Ferreira et al., 2009) and has been validated with both theoretical solutions and laboratory data (Soares-Frazão et al., 2012; Canelas et al., 2013). The modelling of the existing natural and built environment is fully explicit. All buildings, streets and channels are accurately represented within the mesh geometry. Such detail is relevant for the reliability of the validation using field data, since the major sedimentary deposits within the urban meshwork of Funchal were identified and characterized in terms of volume and grain size distribution during the aftermath of the 20th February of 2010 event. Indeed, the measure of the quality of the numerical results is the agreement between simulated and estimated volume of deposited sediment and between estimated and

Permeability and compression of fibrous porous media generated from dilute suspensions of fiberglass debris during a loss of coolant accident

International Nuclear Information System (INIS)

Lee, Saya; Abdulsattar, Suhaeb S.; Vaghetto, Rodolfo; Hassan, Yassin A.

2015-01-01

Highlights: • Experimental investigation on fibrous debris buildup was conducted. • Head loss through fibrous media was recorded at different approach velocities. • A head loss model through fibrous media was proposed for high porosity (>0.99). • A compression model of fibrous media was developed. - Abstract: Permeability of fibrous porous media has been studied for decades in various engineering applications, including liquid purifications, air filters, and textiles. In nuclear engineering, fiberglass has been found to be a hazard during a Loss-of-Coolant Accident. The high energy steam jet from a break impinges on surrounding fiberglass insulation materials, producing a large amount of fibrous debris. The fibrous debris is then transported through the reactor containment and reaches the sump strainers. Accumulation of such debris on the surface of the strainers produces a fibrous bed, which is a fibrous porous medium that can undermine reactor core cooling. The present study investigated the buildup of fibrous porous media on two types of perforated plate and the pressure drop through the fibrous porous media without chemical effect. The development of the fibrous bed was visually recorded in order to correlate the pressure drop, the approach velocity, and the thickness of the fibrous porous media. The experimental results were compared to semi-theoretical models and theoretical models proposed by other researchers. Additionally, a compression model was developed to predict the thickness and the local porosity of a fibrous bed as a function of pressure

Volatile organic compound adsorption in a gas-solid fluidized bed.

Science.gov (United States)

Ng, Y L; Yan, R; Tsen, L T S; Yong, L C; Liu, M; Liang, D T

2004-01-01

Fluidization finds many process applications in the areas of catalytic reactions, drying, coating, combustion, gasification and microbial culturing. This work aims to compare the dynamic adsorption characteristics and adsorption rates in a bubbling fluidized bed and a fixed bed at the same gas flow-rate, gas residence time and bed height. Adsorption with 520 ppm methanol and 489 ppm isobutane by the ZSM-5 zeolite of different particle size in the two beds enabled the differentiation of the adsorption characteristics and rates due to bed type, intraparticle mass transfer and adsorbate-adsorbent interaction. Adsorption of isobutane by the more commonly used activated carbon provided the comparison of adsorption between the two adsorbent types. With the same gas residence time of 0.79 seconds in both the bubbling bed and fixed bed of the same bed size of 40 mm diameter and 48 mm height, the experimental results showed a higher rate of adsorption in the bubbling bed as compared to the fixed bed. Intraparticle mass transfer and adsorbent-adsorbate interaction played significant roles in affecting the rate of adsorption, with intraparticle mass transfer being more dominant. The bubbling bed was observed to have a steeper decline in adsorption rate with respect to increasing outlet concentration compared to the fixed bed. The adsorption capacities of zeolite for the adsorbates studied were comparatively similar in both beds; fluidizing, and using smaller particles in the bubbling bed did not increase the adsorption capacity of the ZSM-5 zeolite. The adsorption capacity of activated carbon for isobutane was much higher than the ZSM-5 zeolite for isobutane, although at a lower adsorption rate. Fourier transform infra-red (FTIR) spectroscopy was used as an analytical tool for the quantification of gas concentration. Calibration was done using a series of standards prepared by in situ dilution with nitrogen gas, based on the ideal gas law and relating partial pressure to gas

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.

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Fluidised-bed combustion of gasification residue

Energy Technology Data Exchange (ETDEWEB)

Korpela, T.; Kudjoi, A.; Hippinen, I.; Heinolainen, A.; Suominen, M.; Lu Yong [Helsinki Univ. of Technology (Finland). Lab of Energy Economics and Power Plant Engineering

1996-12-01

Partial gasification processes have been presented as possibilities for future power production. In the processes, the solid materials removed from a gasifier (i.e. fly ash and bed material) contain unburnt fuel and the fuel conversion is increased by burning this gasification residue either in an atmospheric or a pressurised fluidised-bed. In this project, which is a part of European JOULE 2 EXTENSION research programme, the main research objectives are the behaviour of calcium and sulphur compounds in solids and the emissions of sulphur dioxide and nitrogen oxides (NO{sub x} and N{sub 2}O) in pressurised fluidised-bed combustion of gasification residues. (author)

RELATION BETWEEN PRECIPITATION AND INITIATION OF DEBRIS FLOWS IN THE JIANGJIA RAVINE,YUNNAN PROVINCE, SOUTHWEST CHINA

Institute of Scientific and Technical Information of China (English)

Zili FENG; Peng CUI; Xiaoqing CHEN; Jie CHEN

2006-01-01

In the Jiangjia Ravine, debris flows are often triggered by short-duration rainstorms frequently. To reveal the unique initiation process of debris flows, rainfall and debris flow initiation in an upstream area was continually observed. It is concluded that flash floods resulting from short-duration rainstorms play a key role in the initiation of debris flows. Surface runoff forms flash floods due to special topographic conditions. The flash floods mobilize the sediment deposits in the upper section of the branch gullies,hence, high density viscous debris flows initiate. The initiation of debris flows in the Jiangjia Ravine has a close relation with precipitation. Applying the Takahashi model of debris flow initiation, it is concluded that: to mobilize cohesive deposits in the gully bed the depth of flash floods must exceed a critical depth. This critical depth of floods makes the definition of thresholds of rainfall intensity possible. Considering the change in the initial infiltration rate at different initial water content of bank slopes, and the influence of antecedent precipitation on the initial water content, the relation between the thresholds of rainfall intensity and the antecedent precipitation show good agreement with the empirical relation established by previous research.

The flooding phenomenon and its connection with dry-out in boiling particle beds

International Nuclear Information System (INIS)

Macbeth, R.V.; Anderson, A.R.

1986-03-01

Experimental studies of boiling in particle beds representing reactor core debris have been restricted to very small beds compared with those that may be found in a reactor. The use of air and water to simulate some of the many features of boiling in a particle bed has given results that were inconclusive. The work reported here is that carried out at Winfrith to extend the dryout data to larger particle diameters, and to provide new experimental data which removes earlier doubts, and makes the air-water analogue position much clearer. (U.K.)

Dynamic transition between fixed- and mobile-bed: mathematical and numerical aspects

Science.gov (United States)

Zugliani, Daniel; Pasqualini, Matteo; Rosatti, Giorgio

2017-04-01

Free-surface flows with high sediment transport (as debris flow or hyper-concentrated flow) are composed by a mixture of fluid and solid phase, usually water and sediment. When these flows propagate over loose beds, particles constituting the mixture of water and sediments strongly interact with the ones forming the bed, leading to erosion or deposition. However, there are lots of other situations when the mixture flows over rigid bedrocks or over artificially paved transects, so there is no mass exchange between bed and mixture. The two situations are usually referred to as, respectively, mobile- and fixed-bed conditions. From a mathematical point of view, the systems of Partial Differential Equations (PDEs) that describe these flows derive from mass and momentum balance of both phases, but, the two resulting PDEs systems are different. The main difference concerns the concentration: in the mobile-bed condition, the concentration is linked to the local flow conditions by means of a suitable rheological relation, while in the fixed-bed case, the concentration is an unknown of the problem. It is quite common that a free surface flow with high sediment transport, in its path, encounters both conditions. In the recent work of Rosatti & Zugliani 2015, the mathematical and numerical description of the transition between fixed- and mobile-bed was successfully resolved, for the case of low sediment transport phenomena, by the introduction of a suitable erodibility variable and satisfactory results were obtained. The main disadvantage of the approach is related to the erodibility variable, that changes in space, based on bed characteristics, but remains constant in time. However, the nature of the bed can change dynamically as result of deposition over fixed bed or high erosion over mobile bed. With this work, we extend the applicability of the mentioned approach to the more complex PDEs describing the hyper-concentrated flow. Moreover, we introduce a strategy that allows

Debris disc constraints on planetesimal formation

Science.gov (United States)

Krivov, Alexander V.; Ide, Aljoscha; Löhne, Torsten; Johansen, Anders; Blum, Jürgen

2018-02-01

Two basic routes for planetesimal formation have been proposed over the last decades. One is a classical `slow-growth' scenario. Another one is particle concentration models, in which small pebbles are concentrated locally and then collapse gravitationally to form planetesimals. Both types of models make certain predictions for the size spectrum and internal structure of newly born planetesimals. We use these predictions as input to simulate collisional evolution of debris discs left after the gas dispersal. The debris disc emission as a function of a system's age computed in these simulations is compared with several Spitzer and Herschel debris disc surveys around A-type stars. We confirm that the observed brightness evolution for the majority of discs can be reproduced by classical models. Further, we find that it is equally consistent with the size distribution of planetesimals predicted by particle concentration models - provided the objects are loosely bound `pebble piles' as these models also predict. Regardless of the assumed planetesimal formation mechanism, explaining the brightest debris discs in the samples uncovers a `disc mass problem'. To reproduce such discs by collisional simulations, a total mass of planetesimals of up to ˜1000 Earth masses is required, which exceeds the total mass of solids available in the protoplanetary progenitors of debris discs. This may indicate that stirring was delayed in some of the bright discs, that giant impacts occurred recently in some of them, that some systems may be younger than previously thought or that non-collisional processes contribute significantly to the dust production.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-11-01

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

Occurrence and persistence of fungicides in bed sediments and suspended solids from three targeted use areas in the United States.

Science.gov (United States)

Smalling, Kelly L; Reilly, Timothy J; Sandstrom, Mark W; Kuivila, Kathryn M

2013-03-01

To document the environmental occurrence and persistence of fungicides, a robust and sensitive analytical method was used to measure 34 fungicides and an additional 57 current-use pesticides in bed sediments and suspended solids collected from areas of intense fungicide use within three geographic areas across the United States. Sampling sites were selected near or within agricultural research farms using prophylactic fungicides at rates and types typical of their geographic location. At least two fungicides were detected in 55% of the bed and 83% of the suspended solid samples and were detected in conjunction with herbicides and insecticides. Six fungicides were detected in all samples including pyraclostrobin (75%), boscalid (53%), chlorothalonil (41%) and zoxamide (22%). Pyraclostrobin, a strobilurin fungicide, used frequently in the United States on a variety of crops, was detected more frequently than p,p'-DDE, the primary degradate of p,p'-DDT, which is typically one of the most frequently occurring pesticides in sediments collected within highly agricultural areas. Maximum fungicide concentrations in bed sediments and suspended solids were 198 and 56.7 μg/kg dry weight, respectively. There is limited information on the occurrence, fate, and persistence of many fungicides in sediment and the environmental impacts are largely unknown. The results of this study indicate the importance of documenting the persistence of fungicides in the environment and the need for a better understanding of off-site transport mechanisms, particularly in areas where crops are grown that require frequent treatments to prevent fungal diseases. Published by Elsevier B.V.

An integrated study to evaluate debris flow hazard in alpine environment

Science.gov (United States)

Tiranti, Davide; Crema, Stefano; Cavalli, Marco; Deangeli, Chiara

2018-05-01

Debris flows are among the most dangerous natural processes affecting the alpine environment due to their magnitude (volume of transported material) and the long runout. The presence of structures and infrastructures on alluvial fans can lead to severe problems in terms of interactions between debris flows and human activities. Risk mitigation in these areas requires identifying the magnitude, triggers, and propagation of debris flows. Here, we propose an integrated methodology to characterize these phenomena. The methodology consists of three complementary procedures. Firstly, we adopt a classification method based on the propensity of the catchment bedrocks to produce clayey-grained material. The classification allows us to identify the most likely rheology of the process. Secondly, we calculate a sediment connectivity index to estimate the topographic control on the possible coupling between the sediment source areas and the catchment channel network. This step allows for the assessment of the debris supply, which is most likely available for the channelized processes. Finally, with the data obtained in the previous steps, we modelled the propagation and depositional pattern of debris flows with a 3D code based on Cellular Automata. The results of the numerical runs allow us to identify the depositional patterns and the areas potentially involved in the flow processes. This integrated methodology is applied to a test-bed catchment located in Northwestern Alps. The results indicate that this approach can be regarded as a useful tool to estimate debris flow related potential hazard scenarios in an alpine environment in an expeditious way without possessing an exhaustive knowledge of the investigated catchment, including data on historical debris flow events.

An Integrated Study to Evaluate Debris Flow Hazard in Alpine Environment

Directory of Open Access Journals (Sweden)

Davide Tiranti

2018-05-01

Full Text Available Debris flows are among the most dangerous natural processes affecting the alpine environment due to their magnitude (volume of transported material and the long runout. The presence of structures and infrastructures on alluvial fans can lead to severe problems in terms of interactions between debris flows and human activities. Risk mitigation in these areas requires identifying the magnitude, triggers, and propagation of debris flows. Here, we propose an integrated methodology to characterize these phenomena. The methodology consists of three complementary procedures. Firstly, we adopt a classification method based on the propensity of the catchment bedrocks to produce clayey-grained material. The classification allows us to identify the most likely rheology of the process. Secondly, we calculate a sediment connectivity index to estimate the topographic control on the possible coupling between the sediment source areas and the catchment channel network. This step allows for the assessment of the debris supply, which is most likely available for the channelized processes. Finally, with the data obtained in the previous steps, we modeled the propagation and depositional pattern of debris flows with a 3D code based on Cellular Automata. The results of the numerical runs allow us to identify the depositional patterns and the areas potentially involved in the flow processes. This integrated methodology is applied to a test-bed catchment located in Northwestern Alps. The results indicate that this approach can be regarded as a useful tool to estimate debris flow related potential hazard scenarios in an alpine environment in an expeditious way without possessing an exhaustive knowledge of the investigated catchment, including data on historical debris flow events.

The effect of moisture content on solid-state anaerobic digestion of dairy manure from a sawdust-bedded pack barn

Science.gov (United States)

The effect of moisture content on solid-state anaerobic digestion of dairy manure from a Korean sawdust-bedded pack barn was determined using laboratory-scale digesters operated at three moisture levels (70, 76, and 83% on a wet basis) at 37 C for 85 days. Results showed that digesters containing m...

Time series analysis of pressure fluctuation in gas-solid fluidized beds

Directory of Open Access Journals (Sweden)

C. Alberto S. Felipe

2004-09-01

Full Text Available The purpose of the present work was to study the differentiation of states of typical fluidization (single bubble, multiple bubble and slugging in a gas-solid fluidized bed, using spectral analysis of pressure fluctuation time series. The effects of the method of measuring (differential and absolute pressure fluctuations and the axial position of the probes in the fluidization column on the identification of each of the regimes studied were evaluated. Fast Fourier Transform (FFT was the mathematic tool used to analysing the data of pressure fluctuations, which expresses the behavior of a time series in the frequency domain. Results indicated that the plenum chamber was a place for reliable measurement and that care should be taken in measurement in the dense phase. The method allowed fluid dynamic regimes to be differentiated by their dominant frequency characteristics.

Experimental study on evolution of bed structures of natural mountain rivers

Directory of Open Access Journals (Sweden)

Huai-xiang Liu

2011-06-01

Full Text Available Bed structures in many mountain rivers provide additional resistance to the flow. A field experiment was conducted on debris flow deposits in the valley of the Jiangjiagou Ravine, a tributary of the Yangtze River in southwestern China, to study the evolution and distribution of bed structures and their relationship with environmental conditions. Water and sediment from the Jiangjiagou main stream were diverted into the experimental channel. Several hydrological schemes were adopted to scour the channel until equilibrium was reached. During this process the evolutions of bed structures and channel configuration were investigated. The results indicate that stronger bed structures mean greater stream power consumption, greater resistance, and greater slope in a certain section when rivers are in dynamic equilibrium. Thus, to some extent the longitudinal profiles of channels can be determined by the distribution of bed structures. In natural cases, the strength and evolution of bed structures are under the influence of environmental conditions such as discharge and bed-load transportation rate. That is, given the same conditions, the same bed structure distribution and longitudinal profile can be predicted.

Vision-based Ground Test for Active Debris Removal

Directory of Open Access Journals (Sweden)

Seong-Min Lim

2013-12-01

Full Text Available Due to the continuous space development by mankind, the number of space objects including space debris in orbits around the Earth has increased, and accordingly, difficulties of space development and activities are expected in the near future. In this study, among the stages for space debris removal, the implementation of a vision-based approach technique for approaching space debris from a far-range rendezvous state to a proximity state, and the ground test performance results were described. For the vision-based object tracking, the CAM-shift algorithm with high speed and strong performance, and the Kalman filter were combined and utilized. For measuring the distance to a tracking object, a stereo camera was used. For the construction of a low-cost space environment simulation test bed, a sun simulator was used, and in the case of the platform for approaching, a two-dimensional mobile robot was used. The tracking status was examined while changing the position of the sun simulator, and the results indicated that the CAM-shift showed a tracking rate of about 87% and the relative distance could be measured down to 0.9 m. In addition, considerations for future space environment simulation tests were proposed.

The testing of the in situ fire extinction system of the Trawsfynydd splitter debris storage package

International Nuclear Information System (INIS)

Newman, R.N.

1987-01-01

The proposed design of a Magnox splitter debris storage drum for Trawsfynydd incorporates an in situ solid fire extinguishant Graphex CK23 on the debris surface. This is an interlamellar graphite residue compound that intumesces when heated to provide an air-restricting layer. Two series of fire tests with the extinguishant in place have been carried out on full sized drums containing unirradiated splitter debris, to demonstrate the effectiveness of the system. (author)

Bacterial counts on teat skin and in new sand, recycled sand, and recycled manure solids used as bedding in freestalls.

Science.gov (United States)

Rowbotham, R F; Ruegg, P L

2016-08-01

On modern dairy farms, environmental mastitis pathogens are usually the predominant cause of mastitis, and bedding often serves as a point of exposure to these organisms. The objective of this longitudinal study was to determine bacterial populations of 4 different bedding types [deep-bedded new sand (NES), deep-bedded recycled sand (RS), deep-bedded manure solids (DBMS), and shallow-bedded manure solids over foam core mattresses (SBMS)] and of teat skin swabs of primarily primiparous cows housed in a single facility over all 4 seasons. Samples of bedding were collected weekly (n=49wk) from pens that each contained 32 lactating dairy cows. Throughout the length of the same period, composite swabs of teat skin were collected weekly from all cows before and after premilking teat sanitation. Median numbers of streptococci and streptococci-like organisms (SSLO) were >8.6×10(6) cfu/g and >6.9×10(3) cfu/teat swab for all bedding types and teat swabs, respectively. Numbers of SSLO were greatest in samples of SBMS (2.1×10(8) cfu/g) and least in samples of NES (8.6×10(6) cfu/g), RS (1.3×10(7) cfu/g), and DBMS (1.7×10(7) cfu/g). Numbers of gram-negative bacteria in bedding (5.5×10(4) to 1.2×10(7) cfu/g) were fewer than numbers of SSLO (8.6×10(6) to 2.1×10(8) cfu/g). Numbers of coliform bacteria were greatest in samples of DBMS (2.2×10(6) cfu/g) and least in samples of NES (3.6×10(3) cfu/g). In general, the relative number of bacteria on teat skin corresponded to exposure in bedding. Numbers of gram-negative bacteria recovered from prepreparation teat swabs were greatest for cows bedded with DBMS (1.0×10(4) cfu/swab) and RS (2.5×10(3) cfu/swab) and least for cows bedded with NES (5.8×10(2) cfu/swab). Median numbers of coliform and Klebsiella spp. recovered from prepreparation teat swabs were below the limit of detection for all cows except those bedded with DBMS. Numbers of SSLO recovered from prepreparation teat swabs were least for cows bedded with DBMS (6.9�

Safe disposal and recycling of water disaster debris in pakistan

International Nuclear Information System (INIS)

Latif, A.

2014-01-01

Depending upon the nature, the disaster may produce large masses of debris. Waste masses from single disaster integrate to larger magnitude annually. This will ultimately causes the extra work load on personnel and reflects the poor existing debris management facilities. Besides, it will take longer time to rehabilitate the debris exaggerated regions. The study focuses on 2 main cases of disaster i.e. earthquake of 2005 and flood of 2010 in Pakistan. Complete analysis involve two stages: the first stage involve development of disaster and disaster debris effects guidance whereas the second stage involves the development of set of criteria to make efficient environment and positive impacts of successful debris managing scheme. Such principles were employed to evaluate efficiency of debris managing scheme for detailed analysis. The discussion of the detailed analysis depicts methodology which assists the disaster managers, planners and researcher to simply multitude of work. Moreover, the disaster and disaster debris influence direction, the effect evaluation criterion and managing criteria have been established having the effect they can be virtually put into service for prospect debris managing scheme, planning and retort. With respect to character and strictness, calamity may make high magnitude of waste. By keeping in view the precedent calamities in the United States (US), concluded that in few situations produced waste masses approximately five to fifteen times more than yearly waste production rate from a single occasion. Same results were revealed by subsequent tsunami of Indian Ocean. Such kind of large masses may effects the existing solid debris management system and human resources. Major disaster yields large masses of debris in few hours or sometimes even in minutes. The volume of disaster debris depends upon the magnitude of trees ball up, indemnity to houses, business, services etc. The disaster remaining may be equally large in metropolitan and non

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-02-15

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

Apparatus and process for controlling fluidized beds

Science.gov (United States)

Rehmat, Amirali G.; Patel, Jitendra G.

1985-10-01

An apparatus and process for control and maintenance of fluidized beds under non-steady state conditions. An ash removal conduit is provided for removing solid particulates from a fluidized bed separate from an ash discharge conduit in the lower portion of the grate supporting such a bed. The apparatus and process of this invention is particularly suitable for use in ash agglomerating fluidized beds and provides control of the fluidized bed before ash agglomeration is initiated and during upset conditions resulting in stable, sinter-free fluidized bed maintenance.

Summary of Blast Shield and Material Testing for Development of Solid Debris Collection at the National Ignition Facility (NIF)

International Nuclear Information System (INIS)

Shaughnessy, D.A.; Gostic, J.M.; Moody, K.J.; Grant, P.M.; Lewis, L.A.; Hutcheon, I.D.

2011-01-01

The ability to collect solid debris from the target chamber following a NIF shot has application for both capsule diagnostics, particularly for fuel-ablator mix, and measuring cross sections relevant to the Stockpile Stewardship program and nuclear astrophysics. Simulations have shown that doping the capsule with up to 10 15 atoms of an impurity not otherwise found in the capsule does not affect its performance. The dopant is an element that will undergo nuclear activations during the NIF implosion, forming radioactive species that can be collected and measured after extraction from the target chamber. For diagnostics, deuteron or alpha induced reactions can be used to probe the fuel-ablator mix. For measuring neutron cross sections, the dopant should be something that is sensitive to the 14 MeV neutrons produced through the fusion of deuterium and tritium. Developing the collector is a challenge due to the extreme environment of the NIF chamber. The collector surface is exposed to a large photon flux from x-rays and unconverted laser light before it is exposed to a debris wind that is formed from vaporized material from the target chamber center. The photons will ablate the collector surface to some extent, possibly impeding the debris from reaching the collector and sticking. In addition, the collector itself must be mechanically strong enough to withstand the large amount of energy it will be exposed to, and it should be something that will be easy to count and chemically process. In order to select the best material for the collector, a variety of different metals have been tested in the NIF chamber. They were exposed to high-energy laser shots in order to evaluate their postshot surface characterization, morphology, degree of melt, and their ability to retain debris from the chamber center. The first set of samples consisted of 1 mm thick pieces of aluminum that had been fielded in the chamber as blast shields protecting the neutron activation diagnostic. Ten

The thermal conductivity of beds of spheres

International Nuclear Information System (INIS)

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

1987-01-01

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

Experimental study of single-phase pressure drops in coarse particle beds

Energy Technology Data Exchange (ETDEWEB)

Clavier, R., E-mail: remi.clavier@irsn.fr [IRSN Cadarache, Saint Paul-lez-Durance (France); Chikhi, N., E-mail: nourdine.chikhi@irsn.fr [IRSN Cadarache, Saint Paul-lez-Durance (France); Fichot, F., E-mail: florian.fichot@irsn.fr [IRSN Cadarache, Saint Paul-lez-Durance (France); Quintard, M., E-mail: Michel.Quintard@imft.fr [Université de Toulouse, Allée Camille Soula, F-31400 Toulouse (France); INPT, UPS, Allée Camille Soula, F-31400 Toulouse (France); IMFT (Institut de Mécanique des Fluides de Toulouse), Allée Camille Soula, F-31400 Toulouse (France); CNRS, F-31400 Toulouse (France)

2017-02-15

Motivated by uncertainty reduction in nuclear debris beds coolability, experiments have been conducted on the CALIDE facility in order to investigate single-phase pressure losses in representative debris beds, i.e., high sphericity (>80%) particle beds with small size dispersion (from 1 mm to 10 mm), for which no validated model exists. In this paper, experimental results are presented and analyzed in order to identify a simple correlation for single-phase flow pressure losses generated in this kind of porous media in reflooding flowing conditions, which cover Darcy to weakly turbulent regimes. In the literature, it has been observed that their behavior can be accurately described by a Darcy–Forchheimer law, involving the sum of a linear term and a quadratic non-linear deviation, with respect to the filtration velocity. Expressions for the coefficients of the linear and quadratic terms are determined by assessing the possibility to evaluate equivalent diameters, i.e., characteristic lengths allowing correct predictions of the linear and quadratic terms by the Ergun equation. It has been observed that the Sauter diameter of particles allows a very precise prediction of the linear term, while the quadratic term can be predicted using the product of the Sauter diameter and a sphericity coefficient as an equivalent diameter.

Effects of episodic sediment supply on bedload transport rate in mountain rivers. Detecting debris flow activity using continuous monitoring

Science.gov (United States)

Uchida, Taro; Sakurai, Wataru; Iuchi, Takuma; Izumiyama, Hiroaki; Borgatti, Lisa; Marcato, Gianluca; Pasuto, Alessandro

2018-04-01

Monitoring of sediment transport from hillslopes to channel networks as a consequence of floods with suspended and bedload transport, hyperconcentrated flows, debris and mud flows is essential not only for scientific issues, but also for prevention and mitigation of natural disasters, i.e. for hazard assessment, land use planning and design of torrent control interventions. In steep, potentially unstable terrains, ground-based continuous monitoring of hillslope and hydrological processes is still highly localized and expensive, especially in terms of manpower. In recent years, new seismic and acoustic methods have been developed for continuous bedload monitoring in mountain rivers. Since downstream bedload transport rate is controlled by upstream sediment supply from tributary channels and bed-external sources, continuous bedload monitoring might be an effective tool for detecting the sediments mobilized by debris flow processes in the upper catchment and thus represent an indirect method to monitor slope instability processes at the catchment scale. However, there is poor information about the effects of episodic sediment supply from upstream bed-external sources on downstream bedload transport rate at a single flood time scale. We have examined the effects of sediment supply due to upstream debris flow events on downstream bedload transport rate along the Yotagiri River, central Japan. To do this, we have conducted continuous bedload observations using a hydrophone (Japanese pipe microphone) located 6.4 km downstream the lower end of a tributary affected by debris flows. Two debris flows occurred during the two-years-long observation period. As expected, bedload transport rate for a given flow depth showed to be larger after storms triggering debris flows. That is, although the magnitude of sediment supply from debris flows is not large, their effect on bedload is propagating >6 km downstream at a single flood time scale. This indicates that continuous bedload

Dynamic interaction of two-phase debris flow with pyramidal defense structures: An optimal strategy to efficiently protecting the desired area

Science.gov (United States)

Kattel, Parameshwari; Kafle, Jeevan; Fischer, Jan-Thomas; Mergili, Martin; Tuladhar, Bhadra Man; Pudasaini, Shiva P.

2017-04-01

In this work we analyze the dynamic interaction of two phase debris flows with pyramidal obstacles. To simulate the dynamic interaction of two-phase debris flow (a mixture of solid particles and viscous fluid) with obstacles of different dimensions and orientations, we employ the general two-phase mass flow model (Pudasaini, 2012). The model consists of highly non-linear partial differential equations representing the mass and momentum conservations for both solid and fluid. Besides buoyancy, the model includes some dominant physical aspects of the debris flows such as generalized drag, virtual mass and non-Newtonian viscous stress as induced by the gradient of solid-volume-fraction. Simulations are performed with high-resolution numerical schemes to capture essential dynamics, including the strongly re-directed flow with multiple stream lines, mass arrest and debris-vacuum generation when the rapidly cascading debris mass suddenly encounters the obstacle. The solid and fluid phases show fundamentally different interactions with obstacles, flow spreading and dispersions, run-out dynamics, and deposition morphology. A forward-facing pyramid deflects the mass wider, and a rearward-facing pyramid arrests a portion of solid-mass at its front. Our basic study reveals that appropriately installed obstacles, their dimensions and orientations have a significant influence on the flow dynamics, material redistribution and redirection. The precise knowledge of the change in dynamics is of great importance for the optimal and effective protection of designated areas along the mountain slopes and the runout zones. Further important results are, that specific installations lead to redirect either solid, or fluid, or both, in the desired amounts and directions. The present method of the complex interactions of real two-phase mass flows with the obstacles may help us to construct defense structures and to design advanced and physics-based engineering solutions for the prevention

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.

Operating Characteristics of a Continuous Two-Stage Bubbling Fluidized-Bed Process

International Nuclear Information System (INIS)

Youn, Pil-Sang; Choi, Jeong-Hoo

2014-01-01

Flow characteristics and the operating range of gas velocity was investigated for a two-stage bubbling fluidized-bed (0.1 m-i.d., 1.2 m-high) that had continuous solids feed and discharge. Solids were fed in to the upper fluidized-bed and overflowed into the bed section of the lower fluidized-bed through a standpipe (0.025 m-i.d.). The standpipe was simply a dense solids bed with no mechanical or non-mechanical valves. The solids overflowed the lower bed for discharge. The fluidizing gas was fed to the lower fluidized-bed and the exit gas was also used to fluidize the upper bed. Air was used as fluidizing gas and mixture of coarse (<1000 μm in diameter and 3090 kg/m 3 in apparent density) and fine (<100 μm in diameter and 4400 kg/m 3 in apparent density) particles were used as bed materials. The proportion of fine particles was employed as the experimental variable. The gas velocity of the lower fluidized-bed was defined as collapse velocity in the condition that the standpipe was emptied by upflow gas bypassing from the lower fluidized-bed. It could be used as the maximum operating velocity of the present process. The collapse velocity decreased after an initial increase as the proportion of fine particles increased. The maximum took place at the proportion of fine particles 30%. The trend of the collapse velocity was similar with that of standpipe pressure drop. The collapse velocity was expressed as a function of bulk density of particles and voidage of static bed. It increased with an increase of bulk density, however, decreased with an increase of voidage of static bed

TMI-2 core debris grab samples: Examination and analysis: Part 1

International Nuclear Information System (INIS)

Akers, D.W.; Carlson, E.R.; Cook, B.A.; Ploger, S.A.; Carlson, J.O.

1986-09-01

Six samples of particulate debris were removed from the TMI-2 core rubble bed during September and October 1983, and five more samples were obtained in March 1984. The samples (up to 174 g each) were obtained at two locations in the core: H8 (center) and E9 (mid-radius). Ten of the eleven samples were examined at the Idaho National Engineering Laboratory to obtain data on the physical and chemical nature of the debris and the postaccident condition of the core. Portions of the samples also were subjected to differential thermal analysis at Rockwell Hanford Operations and metallurgical and chemical examinations at Argonne National Laboratories. This report presents results of the examination of the core debris grab samples, including physical, metallurgical, chemical, and radiochemical analyses. The results indicate that temperatures in the core reached at least 3100 K during the TMI-2 accident, fuel melting and significant mixing of core structural material occurred, and large fractions of some radionuclides (e.g., 90 Sr and 144 Ce) were retained in the core

Effects of debris generated by chemical reactions on head loss through emergency-core cooling-system strainers

International Nuclear Information System (INIS)

Howe, K.; Ghosh, A.; Maji, A.K.; Letellier, B.C.; Johns, R.; Chang, T.Y.

2004-01-01

The effect of debris generated during a loss of coolant accident (LOCA) on the emergency core cooling system (ECCS) strainers has been studied via numerous avenues over the last several years. The research described in this manuscript examines the generation and effect of secondary materials -- not debris generated in the LOCA itself, but materials created by chemical reactions between exposed surfaces/debris and cooling system water. The secondary materials studied in the research were corrosion products from exposed metallic surfaces and paint chips that may precipitate out of solution, with a focus on the corrosion products of aluminium, iron, and zinc. The processes of corrosion and leaching of metals with subsequent precipitation is important because: (1) the surface area of exposed metal inside containment represents a large potential source term, even for slow chemical reactions; the chemical composition of the cooling system water (boric acid, lithium, etc.) may affect corrosion or precipitation in ways that have not been studied thoroughly in the past; and (3) an eyewitness report of the presence of gelatinous material in the Three Mile Island containment pool after the 1979 accident suggests the formation of a secondary material that has not been examined under the generic safety issue (GSI)-191 research program. This research was limited in scope and consisted only of small-scale tests. Several key questions were investigated: (1) do credible corrosion mechanisms exist for leaching metal ions from bulk solid surfaces or from zinc-based paint chips, and if so, what are the typical rate constants? (2) can corrosion products accumulate in the containment pool water to the extent that they might precipitate as new chemical species at pH and temperatures levels that are relevant to the LOCA accident sequence? and (3) how do chemical precipitants affect the head loss across an existing fibrous debris bed? A full report of the research is available. (authors)

Tracing the contribution of debris flow-dominated channels to gravel-bed torrential river channel: implementing pit-tags in the upper Guil River (French Alps)

Science.gov (United States)

Arnaud-Fassetta, Gilles; Lissak, Candide; Fort, Monique; Bétard, François; Carlier, Benoit; Cossart, Etienne; Madelin, Malika; Viel, Vincent; Charnay, Bérengère; Bletterie, Xavier

2014-05-01

In the upper, wider reaches of Alpine valleys, shaping of active channels is usually subject to rapid change. It mostly depends upon hydro-climatic variability, runoff concentration and sediment supply, and may result in alternating sequences of fluvial and debris-flow pulses, as recorded in alluvial fans and terraces. Our study, carried in the frame of SAMCO (ANR) project, focuses on the upper Guil River Valley (Queyras, Southern French Alps) cut into the slaty shale "schistes lustrés". Steep, lower order drains carry a contrasted solid discharge, including predominantly sandy-loam particles mixed with gravels and boulders (sandstone schists, ophiolites). Abundant sediment supply by frost shattering, snow avalanche and landslides is then reworked during snowmelt or summer storm runoff events, and may result in catastrophic, very destructive floods along the main channel, as shown by historical records. Following the RI-30 year 2000 flood, our investigations included sediment budgets, i.e. balance of erosion and deposition, and the mapping of the source, transport and storage of various sediments (talus, colluvium, torrential fans, terraces). To better assess sediment fluxes and sediment delivery into the main channel network, we implemented tracers (pit-tags) in selected sub-catchments, significantly contributing to the sediment yield of the valley bottoms during the floods and/or avalanches: Maloqueste, Combe Morel, Bouchouse and Peyronnelle catchments. The first three are direct tributaries of the Guil River whereas the Peyronnelle is a left bank tributary of the Peynin River, which joins the Guil River via an alluvial cone with high human and material stakes. The Maloqueste and the Combe Morel are two tributaries facing each other in the Guil valley, representing a double lateral constraint for the road during flood events of the Guil River. After pit-tag initialisation in laboratory, we set them up along the four tributaries: Maloqueste (20 pit-tags), Combe

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

International Nuclear Information System (INIS)

Morita, Koji; Matsumoto, Tatsuya; Taketa, Shohei; Nishi, Shinpei; Cheng, Songbai; Suzuki, Tohru; Tobita, Yoshiharu

2014-01-01

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)

Enhanced Productivity of Chemical Processes Using Dense Fluidized Beds

Energy Technology Data Exchange (ETDEWEB)

Sibashis Banerjee; Alvin Chen; Rutton Patel; Dale Snider; Ken Williams; Timothy O' Hern; Paul Tortora

2008-02-29

The work detailed in this report addresses Enabling Technologies within Computational Technology by integrating a “breakthrough” particle-fluid computational technology into traditional Process Science and Engineering Technology. The work completed under this DOE project addresses five major development areas 1) gas chemistry in dense fluidized beds 2) thermal cracking of liquid film on solids producing gas products 3) liquid injection in a fluidized bed with particle-to-particle liquid film transport 4) solid-gas chemistry and 5) first level validation of models. Because of the nature of the research using tightly coupled solids and fluid phases with a Lagrangian description of the solids and continuum description of fluid, the work provides ground-breaking advances in reactor prediction capability. This capability has been tested against experimental data where available. The commercial product arising out of this work is called Barracuda and is suitable for a wide (dense-to-dilute) range of industrial scale gas-solid flows with and without reactions. Commercial applications include dense gas-solid beds, gasifiers, riser reactors and cyclones.

Simultaneous measurement of local particle movement, solids concentrations and bubble properties in fluidized bed reactors using a novel fiber optical technique

Energy Technology Data Exchange (ETDEWEB)

Tayebi, Davoud

1999-12-31

This thesis develops a new method for simultaneous measurements of local flow properties in highly concentrated multiphase flow systems such as gas-solid fluidized bed reactors. The method is based on fiber optical technique and tracer particles. A particle present in the measuring volume in front of the probe is marked with a fluorescent dye. A light source illuminates the particles and the detecting fibres receive reflected light from uncoated particles and fluorescent light from the tracer particle. Using optical filters, the fluorescent light can be distinguished and together with a small fraction of background light from uncoated particles can be used for determination of local flow properties. Using this method, one can simultaneously measure the local movement of a single tracer particle, local bubble properties and the local solids volume fractions in different positions in the bed. The method is independent of the physical properties of the tracer particles. It is also independent of the local solids concentrations in the range of 0 to 60 vol.-%, but is mainly designed for highly concentrated flow systems. A computer programme that uses good signals from at least three sensors simultaneously to calculate the tracer particle velocity in two dimensions have been developed. It also calculates the bubble properties and local solids volume fractions from the same time series. 251 refs., 150 figs., 5 tabs.

Simultaneous measurement of local particle movement, solids concentrations and bubble properties in fluidized bed reactors using a novel fiber optical technique

Energy Technology Data Exchange (ETDEWEB)

Tayebi, Davoud

1998-12-31

This thesis develops a new method for simultaneous measurements of local flow properties in highly concentrated multiphase flow systems such as gas-solid fluidized bed reactors. The method is based on fiber optical technique and tracer particles. A particle present in the measuring volume in front of the probe is marked with a fluorescent dye. A light source illuminates the particles and the detecting fibres receive reflected light from uncoated particles and fluorescent light from the tracer particle. Using optical filters, the fluorescent light can be distinguished and together with a small fraction of background light from uncoated particles can be used for determination of local flow properties. Using this method, one can simultaneously measure the local movement of a single tracer particle, local bubble properties and the local solids volume fractions in different positions in the bed. The method is independent of the physical properties of the tracer particles. It is also independent of the local solids concentrations in the range of 0 to 60 vol.-%, but is mainly designed for highly concentrated flow systems. A computer programme that uses good signals from at least three sensors simultaneously to calculate the tracer particle velocity in two dimensions have been developed. It also calculates the bubble properties and local solids volume fractions from the same time series. 251 refs., 150 figs., 5 tabs.

Integration of two-phase solid fluid equations in a catchment model for flashfloods, debris flows and shallow slope failures

KAUST Repository

Bout, B.

2018-04-09

An integrated, modeling method for shallow landslides, debris flows and catchment hydrology is developed and presented in this paper. Existing two-phase debris flow equations and an adaptation on the infinite slope method are coupled with a full hydrological catchment model. We test the approach on the 4 km2 Scaletta catchment, North-Eastern Sicily, where the 1-10-2009 convective storm caused debris flooding after 395 shallow landslides. Validation is done based on the landslide inventory and photographic evidence from the days after the event. Results show that the model can recreate the impact of both shallow landslides, debris flow runout, and debris floods with acceptable accuracy (91 percent inventory overlap with a 0.22 Cohens Kappa). General patterns in slope failure and runout are well-predicted, leading to a fully physically based prediction of rainfall induced debris flood behavior in the downstream areas, such as the creation of a debris fan at the coastal outlet.

UTILIZATION OF PINE NEEDLES AS BED MATERIAL IN SOLID STATE FERMENTATION FOR PRODUCTION OF LACTIC ACID BY LACTOBACILLUS STRAINS

Directory of Open Access Journals (Sweden)

Manoj Kumar Ghosh

Full Text Available Pine needles, which are abundantly found as underexploited biomass in coniferous forests, are responsible for fire hazards and air pollution. Utilization of pine needles as bed material in lactic acid production with solid state fermentation (SSF has been studied here. This investigation compared lactic acid production by pure strains of Lactobacilli, (1 L. delbrueckii (NCIM2025; (2 L. pentosus (NCIM 2912; (3 Lactobacillus sp. (NCIM 2734; (4 Lactobacillus sp. (NCIM2084; and a co-culture of the first two strains. The studies required 6 g per flask powdered dry pine needles as bed material, 2 g/L (inoculum, liquid production media based on pure glucose or whey substituted glucose, at 60, 80, and 120 g/L sugar levels, 37 oC, and an initial pH of 6.5. Co-culture attained a maximum lactic acid concentration of 45.10 g/L, followed by that of strain-1, 43.87 g/L and strain-4, 26.15 g/L, in 80 g/L pure glucose media. With 120g/L total sugar in whey-substituted media, the co-culture attained maximum lactic acid production of 44.88 g/L followed by that of strain-1, 43.67 g/L. The present experimental studies indicated better compatibility of pine needle bed with co-culture in solid state fermentation of lactic acid, which may prove to be an eco-friendly technology for utilization of biomass as well as minimizing fires in coniferous forests.

Hydrodynamics of a hybrid circulating fluidized bed reactor with a partitioned loop seal system

Energy Technology Data Exchange (ETDEWEB)

Bae, Dal-Hee; Moon, Jong-Ho; Jin, Gyoung Tae; Shun, Dowon [Korea Institute of Energy Research, Daejeon (Korea, Republic of); Yun, Minyoung; Park, Chan Seung; Norbeck, Joseph M. [University of California, Riverside (United States)

2015-07-15

A circulating fluidized bed (CFB) with a hybrid design has been developed and optimized for steam hydrogasification. The hybrid CFB is composed of a bubbling fluidized bed (BFB) type combustor and a fast fluidized bed (FB) type gasifier. Char is burnt in the combustor and the generated heat is supplied to the gasifier along with the bed materials. Two different types of fluidized beds are connected to each other with a newly developed partitioned loop seal to avoid direct contact between two separate gas streams flowing in each fluidized bed. Gas mixing tests were carried out with Air and Argon in a cold model hybrid CFB to test the loop seal efficiency. Increase in solid inventory in the loop seal can improve the gas separation efficiency. It can be realized at higher gas velocity in fast bed and with higher solid inventory in the loop seal system. In addition, bed hydrodynamics was investigated with varying gas flow conditions and particle sizes in order to obtain a full understanding of changes of solid holdup in the FB. The solid holdup in the FB increased with increasing gas velocity in the BFB. Conversely, increase in gas velocity in the FB contributed to reducing the solid holdup in the FB. It was observed that changing the particle size of bed material does not have a big impact on hydrodynamic parameters.

Hydrodynamics of a hybrid circulating fluidized bed reactor with a partitioned loop seal system

International Nuclear Information System (INIS)

Bae, Dal-Hee; Moon, Jong-Ho; Jin, Gyoung Tae; Shun, Dowon; Yun, Minyoung; Park, Chan Seung; Norbeck, Joseph M.

2015-01-01

A circulating fluidized bed (CFB) with a hybrid design has been developed and optimized for steam hydrogasification. The hybrid CFB is composed of a bubbling fluidized bed (BFB) type combustor and a fast fluidized bed (FB) type gasifier. Char is burnt in the combustor and the generated heat is supplied to the gasifier along with the bed materials. Two different types of fluidized beds are connected to each other with a newly developed partitioned loop seal to avoid direct contact between two separate gas streams flowing in each fluidized bed. Gas mixing tests were carried out with Air and Argon in a cold model hybrid CFB to test the loop seal efficiency. Increase in solid inventory in the loop seal can improve the gas separation efficiency. It can be realized at higher gas velocity in fast bed and with higher solid inventory in the loop seal system. In addition, bed hydrodynamics was investigated with varying gas flow conditions and particle sizes in order to obtain a full understanding of changes of solid holdup in the FB. The solid holdup in the FB increased with increasing gas velocity in the BFB. Conversely, increase in gas velocity in the FB contributed to reducing the solid holdup in the FB. It was observed that changing the particle size of bed material does not have a big impact on hydrodynamic parameters

A review of dryout heat fluxes and coolability of particle beds. APRI 4, Stage 2 Report

International Nuclear Information System (INIS)

Lindholm, Ilona

2002-04-01

Dryout heat flux experiments on particle beds have been reviewed. The observed dryout heat flux varies from some tens of kW/m 2 to well over 1 MW/m 2 . The variation can be qualitatively and to some extent also quantitatively explained. The effect of particle diameter has been clearly demonstrated. For particles having diameter less than about 1 mm, the dryout heat flux on the order of 100-200 kW/m 2 , and increases on square of the particle diameter. For larger than 1 mm particles the dryout heat flux increases on square root of the particle diameter. Typical values for ∼ 5 mm particles is 500 kW/m 2 to 1 MW/m 2 . An effect of bed thickness can be seen for small particles and medium range (50-500 mm) beds. For thick beds, > 500 mm, the dryout heat flux does not any more change as the bed height increases. The dryout heat flux increases with increasing coolant pressure. This can be explained by the increasing vapour density, which can remove more latent heat from the bed. Debris bed stratification, with small particles on top, clearly decreases the dryout heat flux. The dryout heat flux in a stratified bed can even be smaller than a heat flux of an equivalent debris bed consisting of the smaller particles alone. This is due to the capillary force, which draws liquid towards the smaller particles and causes the dryout to occur at the interface of the particle layers. A model has been developed by Lipinski to estimate dryout heat fluxes in a particle bed. The model has been derived based on solution of momentum, energy and mass conservation equations for two phases. The 1-D model can take into account variable particle sizes (stratification) along the bed and different coolant entry positions. It has been shown that the model can quite well predict the observed dryout characteristics in most experiments. The simpler 0-D model can give reasonable estimates for non-stratified beds. Results and observations of several tests on melt jet fragmentation in a water pool

Application of process tomography in gas-solid fluidised beds in different scales and structures

Science.gov (United States)

Wang, H. G.; Che, H. Q.; Ye, J. M.; Tu, Q. Y.; Wu, Z. P.; Yang, W. Q.; Ocone, R.

2018-04-01

Gas-solid fluidised beds are commonly used in particle-related processes, e.g. for coal combustion and gasification in the power industry, and the coating and granulation process in the pharmaceutical industry. Because the operation efficiency depends on the gas-solid flow characteristics, it is necessary to investigate the flow behaviour. This paper is about the application of process tomography, including electrical capacitance tomography (ECT) and microwave tomography (MWT), in multi-scale gas-solid fluidisation processes in the pharmaceutical and power industries. This is the first time that both ECT and MWT have been applied for this purpose in multi-scale and complex structure. To evaluate the sensor design and image reconstruction and to investigate the effects of sensor structure and dimension on the image quality, a normalised sensitivity coefficient is introduced. In the meantime, computational fluid dynamic (CFD) analysis based on a computational particle fluid dynamic (CPFD) model and a two-phase fluid model (TFM) is used. Part of the CPFD-TFM simulation results are compared and validated by experimental results from ECT and/or MWT. By both simulation and experiment, the complex flow hydrodynamic behaviour in different scales is analysed. Time-series capacitance data are analysed both in time and frequency domains to reveal the flow characteristics.

Numerical simulation of coupled binary gas-solid interaction during carbon dioxide sequestration in a coal bed

International Nuclear Information System (INIS)

Feng Qiyan; Zhou Lai; Chen Zhongwei; Liu Jishan

2008-01-01

Complicated coupled binary gas-solid interaction arises during carbon dioxide sequestration in a coal seam, which combines effects of CO 2 -CH 4 counter adsorption, CO 2 -CH 4 counter diffusion, binary gas flow and coal bed deformation. Through solving a set of coupled field governing equations, a novel full coupled Finite Element (FE) model was established by COMSOL Multiphysics. The new FE model was applied to the quantification of coal porous pressure, coal permeability, gas composition fraction and coal displacement when CO 2 was injected in a CH 4 saturated coal bed. Numerical results demonstrate that CH 4 is swept by the injected CO 2 accompanied by coal volumetric deformation. Compared to the single CH 4 in situ, CH 4 -CO 2 counter-diffusion induced coal swelling can make more compensation for coal shrinkage due to effective stress. Competing influences between the effective stress and the CH 4 -CO 2 counter-diffusion induced volume change governs the evolution of porous pressure and permeability, which is controlled by the porous pressure correspondingly. This achievement extends our ability to understand the coupled multi-physics of the CO 2 geological sequestration and CO 2 enhanced coal bed methane recovery under field conditions. (authors)

Wildfire impacts on the processes that generate debris flows in burned watersheds

Science.gov (United States)

Parise, M.; Cannon, S.H.

2012-01-01

Every year, and in many countries worldwide, wildfires cause significant damage and economic losses due to both the direct effects of the fires and the subsequent accelerated runoff, erosion, and debris flow. Wildfires can have profound effects on the hydrologic response of watersheds by changing the infiltration characteristics and erodibility of the soil, which leads to decreased rainfall infiltration, significantly increased overland flow and runoff in channels, and movement of soil. Debris-flow activity is among the most destructive consequences of these changes, often causing extensive damage to human infrastructure. Data from the Mediterranean area and Western United States of America help identify the primary processes that result in debris flows in recently burned areas. Two primary processes for the initiation of fire-related debris flows have been so far identified: (1) runoff-dominated erosion by surface overland flow; and (2) infiltration-triggered failure and mobilization of a discrete landslide mass. The first process is frequently documented immediately post-fire and leads to the generation of debris flows through progressive bulking of storm runoff with sediment eroded from the hillslopes and channels. As sediment is incorporated into water, runoff can convert to debris flow. The conversion to debris flow may be observed at a position within a drainage network that appears to be controlled by threshold values of upslope contributing area and its gradient. At these locations, sufficient eroded material has been incorporated, relative to the volume of contributing surface runoff, to generate debris flows. Debris flows have also been generated from burned basins in response to increased runoff by water cascading over a steep, bedrock cliff, and incorporating material from readily erodible colluvium or channel bed. Post-fire debris flows have also been generated by infiltration-triggered landslide failures which then mobilize into debris flows. However

Solid-state Fermentation of Xylanase from Penicillium canescens 10-10c in a Multi-layer-packed Bed Reactor

Science.gov (United States)

Assamoi, Antoine A.; Destain, Jacqueline; Delvigne, Frank; Lognay, Georges; Thonart, Philippe

Xylanase is produced by Penicillium canescens 10-10c from soya oil cake in static conditions using solid-state fermentation. The impact of several parameters such as the nature and the size of inoculum, bed-loading, and aeration is evaluated during the fermentation process. Mycelial inoculum gives more production than conidial inoculum. Increasing the quantity of inoculum enhances slightly xylanase production. Forced aeration induces more sporulation of strain and reduces xylanase production. However, forced moistened air improves the production compared to production obtained with forced dry air. In addition, increasing bed-loading reduces the specific xylanase production likely due to the incapacity of the Penicillium strain to grow deeply in the fermented soya oil cake mass. Thus, the best cultivation conditions involve mycelial inoculum form, a bed loading of 1-cm height and passive aeration. The maximum xylanase activity is obtained after 7 days of fermentation and attains 10,200 U/g of soya oil cake. These levels are higher than those presented in the literature and, therefore, show all the potentialities of this stock and this technique for the production of xylanase.

Numerical module for debris behavior under severe accident conditions

International Nuclear Information System (INIS)

Kisselev, A.E.; Kobelev, G.V.; Strizhov, V.F.; Vasiliev, A.D.

2005-01-01

The late phase of a hypothetical severe accident in a nuclear reactor is characterized by the appearance of porous debris and liquid pools in core region and lower head of the reactor vessel. Thermal hydraulics and heat transfer in these regions are very important for adequate analysis of severe accident dynamics. The purpose of this work is to develop a universal module which is able to model above-mentioned phenomena on the basis of modern physical concepts. The original approach for debris evolution is developed from classical principles using a set of parameters including debris porosity; average particle diameter; temperatures and mass fractions of solid, liquid and gas phases; specific interface areas between different phases; effective thermal conductivity of each phase, including radiative heat conductivity; mass and energy fluxes through the interfaces. The calculation results of several tests on modeling of porous debris behavior, including the MP-1 experiment, are presented in comparison with experimental data. The results are obtained using this module implemented into the Russian best estimate code, RATEG/SVECHA/HEFEST, which was developed for modeling severe accident thermal hydraulics and late phase phenomena in VVER nuclear power plants. (author)

Estimation of Rheological Properties of Viscous Debris Flow Using a Belt Conveyor

Science.gov (United States)

Hübl, J.; Steinwendtner, H.

2000-09-01

Rheological parameters of viscous debris flows are influenced by a great amount of factors and are therefore extremely difficult to estimate. Because of this uncertainties a belt conveyor (conveyor channel) was constructed to measure flow behaviour and rheological properties of natural debris flow material. The upward movement of the smooth rubberised belt between fixed lateral plastic walls causes a stationary wave relative to these bends. This special experimental design enables to study behaviour of viscous ebris flow material with maximum grain diameters up to 20 mm within several minutes and to hold measuring equipment very simple. The conveyor channel was calibrated first with Xanthan, a natural polysaccharide used as thickener in food technology, whose rheological properties are similar to viscous debris flow material. In a second step natural debris flow material was investigated. Velocities and rheological parameters were measured with varying solid concentration and slope of the channel. In cases where concentration of coarse particles exceed around 15% by volume the conveyor channel obtains an alternative to expensive commercial viscometers for determination of rheological parameters of viscous debris flows.

Upper Pleistocene turbidite sand beds and chaotic silt beds in the channelized, distal, outer-fan lobes of the Mississippi fan

Science.gov (United States)

Nelson, C.H.; Twichell, D.C.; Schwab, W.C.; Lee, H.J.; Kenyon, Neil H.

1992-01-01

Cores from a Mississippi outer-fan depositional lobe demonstrate that sublobes at the distal edge contain a complex local network of channelized-turbidite beds of graded sand and debris-flow beds of chaotic silt. Off-lobe basin plains lack siliciclastic coarse-grained beds. The basin-plain mud facies exhibit low acoustic backscatter on SeaMARC IA sidescan sonar images, whereas high acoustic backscatter characteristic of the lobe sand and silt facies. The depth of the first sand-silt layer correlates with relative backscatter intensity and stratigraphic age of the distal sublobes (i.e., shallowest sand = highest backscatter and youngest sublobe). The high proportion (>50%) of chaotic silt compared to graded sand in the distal, outer-fan sublobes may be related to the unstable, muddy, canyon-wall source areas of the extensive Mississippi delta-fed basin slope. A predominace of chaotic silt in cores or outcrops from outer-fan lobes thus may predict similar settings for ancient fans.

Effect of bed particles to combustion of gases in fluidized bed

Energy Technology Data Exchange (ETDEWEB)

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

1997-10-01

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

Experimental investigations on friction laws and dryout heat flux of particulate beds packed with multi-size spheres and irregular particles

International Nuclear Information System (INIS)

Li, Liangxing; Ma, Weimin

2011-01-01

This paper is concerned with reducing uncertainty in quantification of debris bed coolability in a hypothetical severe accident of light water reactors (LWRs). A test facility named POMECO-FL is constructed to investigate the friction laws of adiabatic single and two-phase flow in a particulate bed packed with multi-size spheres or irregular particles. The same types of particles were then loaded in the test section of the POMECO-HT facility to obtain the dryout heat flux of the volumetrically heated particulate bed. The POMECO-HT facility features a high power capacity (up to 2.1 MW/m 2 ) which enables coolability study on particulate bed with broad variations in porosity and particle diameters under both top-flooding and bottom-injection conditions. The results show that given the effective particle diameter obtained from single-phase flow through the packed bed with multi-size spheres or irregular particles, both the pressure drop and the dryout heat flux of two-phase flow through the bed can be predicted by the Reed model. The bottom injection of coolant increases the dryout heat flux significantly. Meanwhile, the elevation of the dryout position is moving upwards with increasing bottom-injection flowrate. The experimental data provides insights for interpretation of debris bed coolability, as well as high-quality data for validation of the coolability analysis models and codes. (author)

The influence of basal-ice debris on patterns and rates of glacial erosion

Science.gov (United States)

Ugelvig, Sofie V.; Egholm, David L.

2018-05-01

Glaciers have played a key role for shaping much of Earth's high topography during the cold periods of the Late Cenozoic. However, despite of their distinct influence on landscapes, the mechanisms of glacial erosion, and the properties that determine their rate of operation, are still poorly understood. Theoretical models of subglacial erosion generally highlight the influence of basal sliding in setting the pace of erosion, but they also point to a strong influence of other subglacial properties, such as effective bed pressure and basal-ice debris concentration. The latter properties are, however, not easily measured in existing glaciers, and hence their influence cannot readily be confirmed by observations. In order to better connect theoretical models for erosion to measurable properties in glaciers, we used computational landscape evolution experiments to study the expected influence of basal-ice debris concentration for subglacial abrasion at the scale of glaciers. The computational experiments couple the two erosion processes of quarrying and abrasion, and furthermore integrate the flow of ice and transport of debris within the ice, thus allowing for the study of dynamic feedbacks between subglacial erosion and systematic glacier-scale variations in basal-ice debris concentration. The experiments explored several physics-based models for glacial erosion, in combination with different models for basal sliding to elucidate the relationship between sliding speed, erosion rate and basal-ice debris concentration. The results demonstrate how differences in debris concentration can explain large variations in measured rates. The experiments also provide a simple explanation for the observed dependence of glacier-averaged rate of erosion on glacier size: that large glacier uplands feed more debris into their lower-elevation parts, thereby strengthening their erosive power.

Investigation of gas–solids flow in a circulating fluidized bed using 3D electrical capacitance tomography

International Nuclear Information System (INIS)

Mao, Mingxu; Ye, Jiamin; Wang, Haigang; Yang, Wuqiang

2016-01-01

The hydrodynamics of gas–solids flow in the bottom of a circulating fluidized bed (CFB) are complicated. Three-dimensional (3D) electrical capacitance tomography (ECT) has been used to investigate the hydrodynamics in risers of different shapes. Four different ECT sensors with 12 electrodes each are designed according to the dimension of risers, including two circular ECT sensors, a square ECT sensor and a rectangular ECT sensor. The electrodes are evenly arranged in three planes to obtain capacitance in different heights and to reconstruct the 3D images by linear back projection (LBP) algorithm. Experiments were carried out on the four risers using sands as the solids material. The capacitance and differential pressure are measured under the gas superficial velocity from 0.6 m s −1 to 3.0 m s −1 with a step of 0.2 m s −1 . The flow regime is investigated according to the solids concentration and differential pressure. The dynamic property of bubbling flows is analyzed theoretically and the performance of the 3D ECT sensors is evaluated. The experimental results show that 3D ECT can be used in the CFB with different risers to predict the hydrodynamics of gas–solids bubbling flows. (paper)

Endoglucanase production with the newly isolated Myceliophtora sp. i-1d3b in a packed bed solid state fermentor

Directory of Open Access Journals (Sweden)

A. I. Zanelato

2012-12-01

Full Text Available This work is aimed to produce endoglucanase through solid state fermentation in a packed bed bioreactor with the use of the fungus Myceliophtora sp. I-1D3busing a mixture of wheat bran (WB and sugar cane bagasse (SCB as culture medium. Preliminary tests were performed in polypropylene plastic bags, controlling the variables temperature (40, 45, and 50ºC, initial moisture content (75, 80, and 85%, w.b., and weight proportion SCB/WB (1:1, 7:3, and 9:1. The highest enzyme activities in plastic bags were obtained using the substrate proportion of 7:3, 50ºC temperature, and 80% initial moisture content (878 U/grams of dry solid. High activities of filter-paper cellulase and xylanase were also obtained in plastic bags and some results are reported. For the packed bed experiments, the temperature (45 and 50ºC and the air flow rate (80, 100 and 120L/h were the controlled variables. Activity of endoglucanase was similar to plastic bag tests. A longitudinal gradient of moisture content, was observed increasing from the bottom to the top of the reactor, even though the longitudinal enzyme activity profile was flat for almost the whole bed. Air flow rate did not affect enzyme activity, while experiments carried out at 50ºC showed higher enzyme activities. The maximum temperature peak observed was at about 6ºC above the process temperature.

Proceedings of the Workshop on in-vessel core debris retention and coolability

International Nuclear Information System (INIS)

1999-01-01

This conference on in-vessel core debris retention and coolability is composed of 37 papers grouped in three sessions: session 1 (Keynote papers: Key phenomena of late phase core melt progression, accident management strategies and status quo of severe fuel damage codes, In-vessel retention as a severe accident management scheme, GAREC analyses in support of in-vessel retention concept, Latest findings of RASPLAV project); session 2 - Experiments and model development with five sub-sessions: sub-session 1 (Debris bed heat transfer: Debris and Pool Formation/Heat Transfer in FARO-LWR: Experiments and Analyses, Evaporation and Flow of Coolant at the Bottom of a Particle-Bed modelling Relocated Debris, Investigations on the Coolability of Debris in the Lower Head with WABE-2D and MESOCO-2D, Uncertainty and Sensitivity Analysis of the Heat Transfer Mechanisms in the Lower Head, Simulation of the Arrival and Evolution of Debris in a PWR Lower Head with the SFD ICARE2 code), sub-session 2 (Corium properties, molten pool natural convection, and crust formation: Physico-chemistry and corium properties for in-vessel retention, Experimental data on heat flux distribution from volumetrically heated pool with frozen boundaries, Thermal hydraulic phenomena in corium pools - numerical simulation with TOLBIAC and experimental validation with BALI, TOLBIAC code simulations of some molten salt RASPLAV experiments, SIMECO experiments on in-vessel melt pool formation and heat transfer with and without a metallic layer, Numerical investigation of turbulent natural convection heat transfer in an internally-heated melt pool and metallic layer, Current status and validation of CON2D and 3D code, Free convection of heat-generating fluid in a constrained during experimental simulation of heat transfer in slice geometry), sub-session 3 (Gap formation and gap cooling: Quench of molten aluminum oxide associated with in-vessel debris retention by RPV internal water, Experimental investigations

Response characteristics of probe-transducer systems for pressure measurements in gas-solid fluidized beds: how to prevent pitfalls in dynamic pressure measurements

NARCIS (Netherlands)

Ommen, van J.R.; Schouten, J.C.; Stappen, van der M.L.M.; Bleek, van den C.M.

1999-01-01

It is long known already that the pressure probe–transducer systems applied in gas–solid fluidized beds can distort the measured pressure fluctuations. Several rules of thumb have been proposed to determine probe length and internal diameter required to prevent this. Recently, Xie and Geldart [H.-Y.

Lower end fitting debris collector and end cap spacer grid

International Nuclear Information System (INIS)

Bryan, W.J.

1990-01-01

This patent describes a nuclear reactor having fuel assemblies including an upper end fitting and spaced nuclear fuel rod spacer grids for supporting and spacing a plurality of elongated nuclear fuel rods. Each includes a hollow active portion of nuclear fuel filled cladding intermediate the rod ends and tapering end cap of solid material with a circumferential groove on the rod end which first encounters reactor coolant flow, a lower end filtering debris collector and end cap spacer grid for capturing and retaining deleterious debris carried by reactor coolant before it enters the active region of a fuel assembly and creates fuel rod cladding damage

Flow regimes in vertical gas-solid contact systems

Energy Technology Data Exchange (ETDEWEB)

Yerushalmi, J.; Cankurt, N. T.; Geldart, D.; Liss, B.

1976-01-01

The flow characteristics in fluidized beds, i.e., gas-solid systems, was studied to determine the flow regimes, the interaction of gas and solid in the various flow regimes and the dependence of this interaction and of transition between flow regimes on the properties of the gas and solid, on the gas and solid flow rates, and on the containing vessel. Fluidized beds with both coarse and fine particles are considered. Test results using high speed photography to view the operation of a 2-dimensional bed are discussed. (LCL)

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

International Nuclear Information System (INIS)

Freeby, W.A.

1975-11-01

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

Field and flume investigations of the effects of logjams and woody debris on streambed morphology

Science.gov (United States)

Leung, V.; Montgomery, D. R.; McHenry, M. L.

2014-12-01

Interactions among wood debris, fluid flow and sediment transport in rivers are first-order controls on channel morphodynamics, affecting streambed morphology, sediment transport, sediment storage and aquatic habitat. Woody debris increases the hydraulic and topographic complexity in rivers, leading to a greater diversity of aquatic habitats and an increase in the number of large pools that are important fish habitat and breeding grounds. In the past decade, engineered logjams have become an increasingly used tool in river management for simultaneously decreasing the rate of riverbank migration and improving aquatic habitat. Sediment deposits around woody debris build up riverbanks and counteract bank migration caused by erosion. Previous experiments on flow visualization around model woody debris suggest the amount of sediment scour and deposition are primarily related to the presence of roots and the obstructional area of the woody debris. We present the results of fieldwork and sediment transport experiments of streambed morphology around stationary woody debris. Field surveys on the Hoh River and the Elwha River, WA, measure the local streambed morphology around logjams and individual pieces of woody debris. We quantified the amount of local scour and dam-removal related fine sediment deposition around natural and engineered logjams of varying sizes and construction styles, located in different geomorphic settings. We also quantified the amount of local scour around individual pieces of woody debris of varying sizes, geometries and orientations relative to flow. The flume experiments tested the effects of root geometry and log orientation of individual stationary trees on streambed morphology. The flume contained a deformable sediment bed of medium sand. We find that: 1) the presence of roots on woody debris leads to greater areas of both sediment scour and deposition; and 2) the amount of sediment scour and deposition are related to the wood debris cross

Fluidized-bed reactors processes and operating conditions

CERN Document Server

Yates, John G

2016-01-01

The fluidized-bed reactor is the centerpiece of industrial fluidization processes. This book focuses on the design and operation of fluidized beds in many different industrial processes, emphasizing the rationale for choosing fluidized beds for each particular process. The book starts with a brief history of fluidization from its inception in the 1940’s. The authors present both the fluid dynamics of gas-solid fluidized beds and the extensive experimental studies of operating systems and they set them in the context of operating processes that use fluid-bed reactors. Chemical engineering students and postdocs as well as practicing engineers will find great interest in this book.

Data summary of municipal solid waste management alternatives. Volume 5, Appendix C, Fluidized-bed combustion

Energy Technology Data Exchange (ETDEWEB)

None

1992-10-01

This appendix provides information on fluidized-bed combustion (FBC) technology as it has been applied to municipal waste combustion (MWC). A review of the literature was conducted to determine: (1) to what extent FBC technology has been applied to MWC, in terms of number and size of units was well as technology configuration; (2) the operating history of facilities employing FBC technology; and (3) the cost of these facilities as compared to conventional MSW installations. Where available in the literature, data on operating and performance characteristics are presented. Tabular comparisons of facility operating/cost data and emissions data have been complied and are presented. The literature review shows that FBC technology shows considerable promise in terms of providing improvements over conventional technology in areas such as NOx and acid gas control, and ash leachability. In addition, the most likely configuration to be applied to the first large scale FBC dedicated to municipal solid waste (MSW) will employ circulating bed (CFB) technology. Projected capital costs for the Robbins, Illinois 1600 ton per day CFB-based waste-to-energy facility are competitive with conventional systems, in the range of $125,000 per ton per day of MSW receiving capacity.

Effects of process parameters on solid self-microemulsifying particles in a laboratory scale fluid bed.

Science.gov (United States)

Mukherjee, Tusharmouli; Plakogiannis, Fotios M

2012-01-01

The purpose of this study was to select the critical process parameters of the fluid bed processes impacting the quality attribute of a solid self-microemulsifying (SME) system of albendazole (ABZ). A fractional factorial design (2(4-1)) with four parameters (spray rate, inlet air temperature, inlet air flow, and atomization air pressure) was created by MINITAB software. Batches were manufactured in a laboratory top-spray fluid bed at 625-g scale. Loss on drying (LOD) samples were taken throughout each batch to build the entire moisture profiles. All dried granulation were sieved using mesh 20 and analyzed for particle size distribution (PSD), morphology, density, and flow. It was found that as spray rate increased, sauter-mean diameter (D(s)) also increased. The effect of inlet air temperature on the peak moisture which is directly related to the mean particle size was found to be significant. There were two-way interactions between studied process parameters. The main effects of inlet air flow rate and atomization air pressure could not be found as the data were inconclusive. The partial least square (PLS) regression model was found significant (P SME manufacturing process.

Universal stability curve for pattern formation in pulsed gas-solid fluidized beds of sandlike particles

Science.gov (United States)

de Martín, Lilian; Ottevanger, Coen; van Ommen, J. Ruud; Coppens, Marc-Olivier

2018-03-01

A granular layer can form regular patterns, such as squares, stripes, and hexagons, when it is fluidized with a pulsating gas flow. These structures are reminiscent of the well-known patterns found in granular layers excited through vibration, but, contrarily to them, they have been hardly explored since they were first discovered. In this work, we investigate experimentally the conditions leading to pattern formation in pulsed fluidized beds and the dimensionless numbers governing the phenomenon. We show that the onset to the instability is universal for Geldart B (sandlike) particles and governed by the hydrodynamical parameters Γ =ua/(utϕ ¯) and f /fn , where ua and f are the amplitude and frequency of the gas velocity, respectively, ut is the terminal velocity of the particles, ϕ ¯ is the average solids fraction, and fn is the natural frequency of the bed. These findings suggest that patterns emerge as a result of a parametric resonance between the kinematic waves originating from the oscillating gas flow and the bulk dynamics. Particle friction plays virtually no role in the onset to pattern formation, but it is fundamental for pattern selection and stabilization.

Dryout heat flux experiments with deep heterogeneous particle bed

International Nuclear Information System (INIS)

Lindholm, I.; Holmstroem, S.; Miettinen, J.; Lestinen, V.; Hyvaerinen, J.; Pankakoski, P.; Sjoevall, H.

2006-01-01

A test facility has been constructed at Technical Research Centre of Finland (VTT) to simulate as accurately as possible the ex-vessel core particle bed in the conditions of Olkiluoto nuclear power plant. The STYX particle bed reproduces the anticipated depth of the bed and the size range of particles having irregular shape. The bed is immersed in water, creating top flooding conditions, and internally heated by an array of electrical resistance heating elements. Dryout tests have been successfully conducted at 0.1-0.7 MPa pressure for both uniformly mixed and stratified bed geometries. In all tests, including the stratified ones, the dry zone first formed near the bottom of the bed. The measured dryout heat fluxes increased with increasing pressure, from 232 kW/m 2 at near atmospheric pressure to 451 kW/m 2 at 0.7 MPa pressure. The data show some scatter even for the uniform bed. The tests with the stratified bed indicate a clear reduction of critical power due to the presence of a layer of small particles on top of the uniform bed. Comparison of data with various critical power (dryout heat flux) correlations for porous media shows that the most important parameter in the models is the effective particle diameter. Adiabatic debris bed flow resistance measurements were conducted to determine the most representative particle diameter. This diameter is close, but not equal, to the particle number-weighted average diameter of the bed material. With it, uniform bed data can be calculated to within an accuracy of 3-28% using Lipinski's 0-D model. In the stratified bed experiments, it appears that the top layer was partially fluidized, hence the measured critical power was significantly higher than calculated. Future experiments are being planned with denser top layer material to eliminate non-prototypic fluidization

Apically extruded dentin debris by reciprocating single-file and multi-file rotary system.

Science.gov (United States)

De-Deus, Gustavo; Neves, Aline; Silva, Emmanuel João; Mendonça, Thais Accorsi; Lourenço, Caroline; Calixto, Camila; Lima, Edson Jorge Moreira

2015-03-01

This study aims to evaluate the apical extrusion of debris by the two reciprocating single-file systems: WaveOne and Reciproc. Conventional multi-file rotary system was used as a reference for comparison. The hypotheses tested were (i) the reciprocating single-file systems extrude more than conventional multi-file rotary system and (ii) the reciprocating single-file systems extrude similar amounts of dentin debris. After solid selection criteria, 80 mesial roots of lower molars were included in the present study. The use of four different instrumentation techniques resulted in four groups (n = 20): G1 (hand-file technique), G2 (ProTaper), G3 (WaveOne), and G4 (Reciproc). The apparatus used to evaluate the collection of apically extruded debris was typical double-chamber collector. Statistical analysis was performed for multiple comparisons. No significant difference was found in the amount of the debris extruded between the two reciprocating systems. In contrast, conventional multi-file rotary system group extruded significantly more debris than both reciprocating groups. Hand instrumentation group extruded significantly more debris than all other groups. The present results yielded favorable input for both reciprocation single-file systems, inasmuch as they showed an improved control of apically extruded debris. Apical extrusion of debris has been studied extensively because of its clinical relevance, particularly since it may cause flare-ups, originated by the introduction of bacteria, pulpal tissue, and irrigating solutions into the periapical tissues.

Characterizing Dusty Debris Disks with the Gemini Planet Imager

Science.gov (United States)

Chen, Christine; Arriaga, Pauline; Bruzzone, Sebastian; Choquet, Elodie; Debes, John H.; Donaldson, Jessica; Draper, Zachary; Duchene, Gaspard; Esposito, Thomas; Fitzgerald, Michael P.; Golimowski, David A.; Hines, Dean C.; Hinkley, Sasha; Hughes, A. Meredith; Kalas, Paul; Kolokolova, Ludmilla; Lawler, Samantha; Matthews, Brenda C.; Mazoyer, Johan; Metchev, Stanimir A.; Millar-Blanchaer, Max; Moro-Martin, Amaya; Nesvold, Erika; Padgett, Deborah; Patience, Jenny; Perrin, Marshall D.; Pueyo, Laurent; Rantakyro, Fredrik; Rodigas, Timothy; Schneider, Glenn; Soummer, Remi; Song, Inseok; Stark, Chris; Weinberger, Alycia J.; Wilner, David J.

2017-01-01

We have been awarded 87 hours of Gemini Observatory time to obtain multi-wavelength observations of HST resolved debris disks using the Gemini Planet Imager. We have executed ~51 hours of telescope time during the 2015B-2016B semesters observing 12 nearby, young debris disks. We have been using the GPI Spec and Pol modes to better constrain the properties of the circumstellar dust, specifically, measuring the near-infrared total intensity and polarization fraction colors, and searching for solid-state spectral features of nearby beta Pic-like disks. We expect that our observations will allow us to break the degeneracy among the particle properties such as composition, size, porosity, and shape. We present some early results from our observations.

Optimization of lipase production by solid-state fermentation of olive pomace: from flask to laboratory-scale packed-bed bioreactor.

Science.gov (United States)

Oliveira, Felisbela; Salgado, José Manuel; Abrunhosa, Luís; Pérez-Rodríguez, Noelia; Domínguez, José M; Venâncio, Armando; Belo, Isabel

2017-07-01

Lipases are versatile catalysts with many applications and can be produced by solid-state fermentation (SSF) using agro-industrial wastes. The aim of this work was to maximize the production of Aspergillus ibericus lipase under SSF of olive pomace (OP) and wheat bran (WB), evaluating the effect on lipase production of C/N ratio, lipids, phenols, content of sugars of substrates and nitrogen source addition. Moreover, the implementation of the SSF process in a packed-bed bioreactor and the improvement of lipase extraction conditions were assessed. Low C/N ratios and high content of lipids led to maximum lipase production. Optimum SSF conditions were achieved with a C/N mass ratio of 25.2 and 10.2% (w/w) lipids in substrate, by the mixture of OP:WB (1:1) and supplemented with 1.33% (w/w) (NH 4 ) 2 SO 4 . Studies in a packed-bed bioreactor showed that the lower aeration rates tested prevented substrate dehydration, improving lipase production. In this work, the important role of Triton X-100 on lipase extraction from the fermented solid substrate has been shown. A final lipase activity of 223 ± 5 U g -1 (dry basis) was obtained after 7 days of fermentation.

LATE PLIOCENE-HOLOCENE DEBRIS FLOW DEPOSITS IN THE IONIAN SEA (EASTERN MEDITERRANEAN

Directory of Open Access Journals (Sweden)

GIOVANNI ALOISI DE LARDEREL

1997-11-01

Full Text Available Widespread coring of the Eastern Mediterranean Basin has outlined the existence of a systematic relation between lithology of debris flow deposits and physiographic setting. Whilst the topographic highs are characterized by pelagic sedimentation, the basin floors are alternatively subject to pelagic sedimentation and re-sedimentation pro cesses. Amongst the latters, turbidity flows and debris flows are the most common transport mechanisms.In this paper we present the study of the debris flow pro cess in the Ionian Sea using visual description of cores, grain size, carbonate content and smear slide analysis carried out on gravity and piston cores recovered over the past 20 years. A distinction has been made between debris flow deposits originating from the continental margins (North Africa and Malta Escarpment and those emplaced in the small basins amidst the Calabrian and Mediterranean ridges "Cobblestone Topography". As a result of the difference in setting, the former debris flow deposits include a great variety of lithologies and ages whilst the latter involve the pelagic sediments forming the typical Eastern Mediterranean Plio-Quaternary succession. A detailed study of clast and matrix structures makes it possible to describe the flows in terms of existing classifications of sediment gravity flows and to assume a clast support mechanism. Finally, biostratigraphy coupled with the presence of widespread marker beds enabled us to estimate the age of emplacement of the deposits and to hypothesize a triggering mechanism for flow initiation. Three flows are strictly related to the pelagic turbidite named homogenite, triggered by the explosive eruption of the Santorini volcano (Minoan eruption and therefore have an estimated age of 3,500 BP. The other deposits have ages ranging from 9,000 BP to about 70,000 BP and were originated by debris flows triggered by events such as earthquakes and glacial low sea level stands.    

Field measurement of basal forces generated by erosive debris flows

Science.gov (United States)

McCoy, S.W.; Tucker, G.E.; Kean, J.W.; Coe, J.A.

2013-01-01

It has been proposed that debris flows cut bedrock valleys in steeplands worldwide, but field measurements needed to constrain mechanistic models of this process remain sparse due to the difficulty of instrumenting natural flows. Here we present and analyze measurements made using an automated sensor network, erosion bolts, and a 15.24 cm by 15.24 cm force plate installed in the bedrock channel floor of a steep catchment. These measurements allow us to quantify the distribution of basal forces from natural debris‒flow events that incised bedrock. Over the 4 year monitoring period, 11 debris‒flow events scoured the bedrock channel floor. No clear water flows were observed. Measurements of erosion bolts at the beginning and end of the study indicated that the bedrock channel floor was lowered by 36 to 64 mm. The basal force during these erosive debris‒flow events had a large‒magnitude (up to 21 kN, which was approximately 50 times larger than the concurrent time‒averaged mean force), high‒frequency (greater than 1 Hz) fluctuating component. We interpret these fluctuations as flow particles impacting the bed. The resulting variability in force magnitude increased linearly with the time‒averaged mean basal force. Probability density functions of basal normal forces were consistent with a generalized Pareto distribution, rather than the exponential distribution that is commonly found in experimental and simulated monodispersed granular flows and which has a lower probability of large forces. When the bed sediment thickness covering the force plate was greater than ~ 20 times the median bed sediment grain size, no significant fluctuations about the time‒averaged mean force were measured, indicating that a thin layer of sediment (~ 5 cm in the monitored cases) can effectively shield the subjacent bed from erosive impacts. Coarse‒grained granular surges and water‒rich, intersurge flow had very similar basal force distributions despite

Resolved granular debris-flow simulations with a coupled SPH-DCDEM model

Science.gov (United States)

Birjukovs Canelas, Ricardo; Domínguez, José M.; Crespo, Alejandro J. C.; Gómez-Gesteira, Moncho; Ferreira, Rui M. L.

2016-04-01

Debris flows represent some of the most relevant phenomena in geomorphological events. Due to the potential destructiveness of such flows, they are the target of a vast amount of research (Takahashi, 2007 and references therein). A complete description of the internal processes of a debris-flow is however still an elusive achievement, explained by the difficulty of accurately measuring important quantities in these flows and developing a comprehensive, generalized theoretical framework capable of describing them. This work addresses the need for a numerical model applicable to granular-fluid mixtures featuring high spatial and temporal resolution, thus capable of resolving the motion of individual particles, including all interparticle contacts. This corresponds to a brute-force approach: by applying simple interaction laws at local scales the macro-scale properties of the flow should be recovered by upscaling. This methodology effectively bypasses the complexity of modelling the intermediate scales by resolving them directly. The only caveat is the need of high performance computing, a demanding but engaging research challenge. The DualSPHysics meshless numerical implementation, based on Smoothed Particle Hydrodynamics (SPH), is expanded with a Distributed Contact Discrete Element Method (DCDEM) in order to explicitly solve the fluid and the solid phase. The model numerically solves the Navier-Stokes and continuity equations for the liquid phase and Newton's motion equations for solid bodies. The interactions between solids are modelled with classical DEM approaches (Kruggel-Emden et al, 2007). Among other validation tests, an experimental set-up for stony debris flows in a slit check dam is reproduced numerically, where solid material is introduced trough a hopper assuring a constant solid discharge for the considered time interval. With each sediment particle undergoing tens of possible contacts, several thousand time-evolving contacts are efficiently treated

Particle flow of ceramic breeder pebble beds in bi-axial compression experiments

International Nuclear Information System (INIS)

Hermsmeyer, S.; Reimann, J.

2002-01-01

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

Indigenous microbial capability in solid manure residues to start-up solid-phase anaerobic digesters.

Science.gov (United States)

Yap, S D; Astals, S; Jensen, P D; Batstone, D J; Tait, S

2017-06-01

Batch solid-phase anaerobic digestion is a technology for sustainable on-farm treatment of solid residues, but is an emerging technology that is yet to be optimised with respect to start-up and inoculation. In the present study, spent bedding from two piggeries (site A and B) were batch digested at total solids (TS) concentration of 5, 10 and 20% at mesophilic (37°C) and thermophilic (55°C) temperatures, without adding an external inoculum. The results showed that the indigenous microbial community present in spent bedding was able to recover the full methane potential of the bedding (140±5 and 227±6L CH 4 kgVS fed -1 for site A and B, respectively), but longer treatment times were required than for digestion with an added external inoculum. Nonetheless, at high solid loadings (i.e. TS level>10%), the digestion performance was affected by chemical inhibition due to ammonia and/or humic acid. Thermophilic temperatures did not influence digestion performance but did increase start-up failure risk. Further, inoculation of residues from the batch digestion to subsequent batch enhanced start-up and achieved full methane potential recovery of the bedding. Inoculation with liquid residue (leachate) was preferred over a solid residue, to preserve treatment capacity for fresh substrate. Overall, the study highlighted that indigenous microbial community in the solid manure residue was capable of recovering full methane potential and that solid-phase digestion was ultimately limited by chemical inhibition rather than lack of suitable microbial community. Copyright © 2017 Elsevier Ltd. All rights reserved.

Process for producing volatile hydrocarbons from hydrocarbonaceous solids

Energy Technology Data Exchange (ETDEWEB)

1949-02-03

In a process for producing volatile hydrocarbons from hydrocarbonaceous solids, a hydrocarbonaceus solid is passed in subdivided state and in the form of a bed downwardly through an externally unheated distilling retort wherein the evolution of volatiles from the bed is effected while solid material comprising combustible heavy residue is discharged from the lower portion of the bed and retort, combustibles are burned from the discharged solid material. The admixture resultant combustion gases with the vapours evolved in the retort is prevented, and a stream of hydrocarbon fluid is heated by indirect heat exchange with hot combustion gases produced by burning to a high temperature and is introduced into the distilling retort and direct contact with bed, supplying heat to the latter for effecting the evolution of volatiles from the hydrocarbonaceous solid. The improvement consists of subjecting the volatile distillation products evolved and removed from the bed to a fractionation and separating selected relatively light and heavy hydrocarbon fractions from the distillation products, withdrawing at least one of the selected fractions from the prcess as a product heating at least one other of the selected fractions to high temperature by the indirect heat exchange with hot combustion gases, and introducing the thus heated hydrocarbon fraction into direct contact with the bed.

Update on status of fluidized-bed combustion technology

International Nuclear Information System (INIS)

Stallings, J.; Boyd, T.; Brown, R.

1992-01-01

During the 1980s, fluidized-bed combustion technology has become the dominant technology for solid-fuel-fired power generation systems in the United States. Atmospheric fluidized beds as large as 160 MWe in capacity are now in operation, while pressurized systems reaching 80 MWe have started up in the last year. The commercial status, boiler performance, emissions, and future developments for both atmospheric and pressurized fluidized-bed combustion systems are discussed

"State of the Art" of technical protection measures in Austria and the effectiveness documented during bedload and debris flow events

Science.gov (United States)

Moser, Markus; Mehlhorn, Susanne; Rudolf-Miklau, Florian; Suda, Jürgen

2017-04-01

Since the beginning of systematic torrent control in Austria 130 years ago, barriers are constructed for protection purposes. Until the end of the 1960s, solid barriers were built at the exits of depositional areas to prevent dangerous debris flows from reaching high consequence areas. The development of solid barriers with large slots or slits to regulate sediment transport began with the use of reinforced concrete during the 1970s (Rudolf-Miklau, Suda 2011). In order to dissipate the energy of debris flows debris flow breakers have been designed since the 1980s. By slowing and depositing the surge front of the debris flow, downstream reaches of the stream channel and settlement areas should be exposed to considerably lower dynamic impact. In the past, the technological development of these constructions was only steered by the experiences of the engineering practice while an institutionalized process of standardization comparable to other engineering branches was not existent. In future all structures have to be designed and dimensioned according to the EUROCODE standards. This was the reason to establish an interdisciplinary working group (ON-K 256) at the Austrian Standards Institute (ASI), which has managed to developed comprehensive new technical standards for torrent control engineering, including load models, design, dimensioning and life cycle assessment of torrent control works (technical standard ONR 24800 - series). Extreme torrential events comprise four definable displacement processes floods; fluvial solid transport; hyper-concentrated solid transport (debris floods) and debris flow (stony debris flow or mud-earth flow). As a rule, the design of the torrential barriers has to follow its function (Kettl, 1984). Modern protection concepts in torrent control are scenario-oriented and try to optimize different functions in a chain of protections structures (function chain). More or less the first step for the designing the optimal construction type is

Monte Carlo simulation on influence of cutting beds on density log in the horizontal wells

International Nuclear Information System (INIS)

Yu Huawei; Sun Jianmeng; Li Xiaopeng; Zhang Qiongyao; Li Na

2009-01-01

Cuttings debris may be deposited in the bottom of a horizontal hole because of gravity of the earth. It has lower density than the formation, so cuttings beds can have a significant effect on the density log responses. Monte Carlo method was used to study the effect of cuttings bed on the computed log density, with various formation densities and cuttings bed thicknesses of 0-5 cm in the horizontal borehole.In order to guarantee the reliability of results, simulation results were compared to the experimental data. MC simulations show that the density measurement can be corrected using the ridge-rib graph, if the thickness of the cutting bed is less than 2 cm. Otherwise, it is difficulty to correct the effect of the cutting bed on the formation density measurement. Finally, the cuttings beds correction charts and formulas for DSDL-8723 double-detector density logging tool which is in the horizontal borehole are made preliminarily. (authors)

Association between stall surface and some animal welfare measurements in freestall dairy herds using recycled manure solids for bedding.

Science.gov (United States)

Husfeldt, A W; Endres, M I

2012-10-01

The objective of this cross-sectional study was to investigate the association between stall surface and some animal welfare measurements in upper Midwest US dairy operations using recycled manure solids as bedding material. The study included 34 dairy operations with herd sizes ranging from 130 to 3,700 lactating cows. Forty-five percent of the herds had mattresses and 55% had deep-bedded stalls. Farms were visited once between July and October 2009. At the time of visit, at least 50% of the cows in each lactating pen were scored for locomotion, hygiene, and hock lesions. On-farm herd records were collected for the entire year and used to investigate mortality, culling, milk production, and mastitis incidence. Stall surface was associated with lameness and hock lesion prevalence. Lameness prevalence (locomotion score ≥ 3 on a 1 to 5 scale) was lower in deep-bedded freestalls (14.4%) than freestalls with mattresses (19.8%). Severe lameness prevalence (locomotion score ≥ 4) was also lower for cows housed in deep-bedded freestalls (3.6%) than for cows housed in freestalls with mattresses (5.9%). In addition, the prevalence of hock lesions (hock lesion scores ≥ 2 on a 1 to 3 scale, with 1=no lesion, 2=hair loss or mild lesion, and 3=swelling or severe lesion) and severe hock lesions (hock lesion score=3) was lower in herds with deep-bedded freestalls (49.4%; 6.4%) than in herds with mattresses (67.3%; 13.2%). Herd turnover rates were not associated with stall surface; however, the percentage of removals due to voluntary (low milk production, disposition, and dairy) and involuntary (death, illness, injury, and reproductive) reasons was different between deep-bedded and mattress-based freestalls. Voluntary removals averaged 16% of all herd removals in deep-bedded herds, whereas in mattress herds, these removals were 8%. Other welfare measurements such as cow hygiene, mortality rate, mastitis incidence, and milk production were not associated with stall surface

Mechanical properties of fuel debris for defueling toward decommissioning

International Nuclear Information System (INIS)

Hoshino, Takanori; Kitagaki, Toru; Yano, Kimihiko; Okamura, Nobuo; Koizumi, Kenji; Ohara, Hiroshi; Fukasawa, Tetsuo

2015-01-01

In the decommissioning of the Fukushima Daiichi Nuclear Power Plant (1F), safe and steady defueling work is required. Before defueling 1F, it is necessary to evaluate fuel debris for properties related to the defueling procedure and technology. While defueling after the Three Mile Island Nuclear Power Plant Unit 2 (TMI-2) accident, a core boring system played an important role. Considering the working principle of core boring, hardness, elastic modulus, and fracture toughness were found to be important fuel debris properties that had a profound effect on the performance of the boring machine. It is speculated that uranium and zirconium oxide solid solution ((U,Zr)O_2) is one of the major materials of fuel debris in 1F, according to the TMI-2 accident experience and the results of past severe accident studies. In addition, the Zr content of 1F fuel debris is expected to be higher than that of TMI-2 debris, because the 1F reactors were boiling-water reactor (BWR). In this report, the mechanical properties of (U,Zr)O_2 are evaluated in the ZrO_2 content range from 10% to 65%. The hardness, elastic modulus, and fracture toughness were measured by Vickers test, ultrasonic pulse echo method, and indentation fracture method, respectively. In the ZrO_2 content range under 50%, the Vickers hardness and fracture toughness of (U,Zr)O_2 increased, and the elastic modulus decreased slightly with ZrO_2 content. In the case of 55% and 65% ZrO_2, all of those measures increased slightly with ZrO_2 content. Summarizing those results, ZrO_2 content affects mechanical properties significantly in the case of low ZrO_2 content. Higher Zr content (exceeding 50%) has little effect on mechanical properties. In the future, nonradioactive surrogate debris will be necessary for small-scale functional and large-scale mockup tests of various defueling technologies. These results are useful to select the material for surrogate debris. (author)

Multi-gene genetic programming based predictive models for municipal solid waste gasification in a fluidized bed gasifier.

Science.gov (United States)

Pandey, Daya Shankar; Pan, Indranil; Das, Saptarshi; Leahy, James J; Kwapinski, Witold

2015-03-01

A multi-gene genetic programming technique is proposed as a new method to predict syngas yield production and the lower heating value for municipal solid waste gasification in a fluidized bed gasifier. The study shows that the predicted outputs of the municipal solid waste gasification process are in good agreement with the experimental dataset and also generalise well to validation (untrained) data. Published experimental datasets are used for model training and validation purposes. The results show the effectiveness of the genetic programming technique for solving complex nonlinear regression problems. The multi-gene genetic programming are also compared with a single-gene genetic programming model to show the relative merits and demerits of the technique. This study demonstrates that the genetic programming based data-driven modelling strategy can be a good candidate for developing models for other types of fuels as well. Copyright © 2014 Elsevier Ltd. All rights reserved.

Young Debris Disks With Newly Discovered Emission Features

Science.gov (United States)

Ballering, N.

2014-04-01

We analyzed the Spitzer/IRS spectra of young A and F stars that host debris disks with previously unidentified silicate emission features. Such features probe small, warm dust grains in the inner regions of these young systems where terrestrial planet formation may be proceeding (Lisse et al. 2009). For most systems, these regions are too near their host star to be directly seen with high-contrast imaging and too warm to be imaged with submillimeter interferometers. Mid-infrared excess spectra - originating from the thermal emission of the debris disk dust - remain the best data to constrain the properties of the debris in these regions. For each target, we fit physically-motivated model spectra to the data. Typical spectra of unresolved debris disks are featureless and suffer severe degeneracies between the dust location and the grain properties; however, spectra with solid-state emission features provide significantly more information, allowing for a more accurate determination of the dust size, composition, and location (e.g. Chen et al. 2006; Olofsson et al. 2012). Our results shed light on the dynamic properties occurring in the terrestrial regions of these systems. For instance, the sizes of the smallest grains and the nature of the grain size distribution reveal whether the dust originates from steady-state collisional cascades or from stochastic collisions. The properties of the dust grains - such as their crystalline or amorphous structure - can inform us of grain processing mechanisms in the disk. The location of this debris illuminates where terrestrial planet forming activity is occurring. We used results from the Beta Pictoris - which has a well-resolved debris disk with emission features (Li et al. 2012) - to place our results in context. References: Chen et al. 2006, ApJS, 166, 351 Li et al. 2012, ApJ, 759, 81 Lisse et al. 2009, ApJ, 701, 2019 Olofsson et al. 2012, A&A, 542, A90

Study of dryout heat fluxes in beds of inductively heated particles

International Nuclear Information System (INIS)

Dhir, V.K.; Catton, I.

1977-02-01

Experimental observations of the dryout heat fluxes for inductively heated particulate beds have been made. The data were obtained when steel and lead particles in the size distribution 295-787 microns were placed in a 4.7 cm diameter pyrex glass jar and inductively heated by passing radio frequency current through a 13.3 cm diameter multi-turn work coil encircling the jar. Distilled water, methanol and acetone were used as coolants in the experiments, while the bed height was varied from 1.0 to 8.9 cm. Different mechanisms for the dryout in deep and shallow beds have been identified. Dryout in shallow beds is believed to occur when the vapor velocity in the gas jets exceeds a certain critical velocity at which choking of the vapor occurs, leading to obstruction in the flow of the liquid toward the bed. However, deep beds dry out when gravitational force can no longer maintain a downward coolant flow rate necessary to dissipate the heat generated in the bed. The heat flux data of the investigation and that from two previous investigations made at Argonne Laboratory and at UCLA have been correlated with semi-theoretical correlations based on the proposed hydrodynamic models. The deep and shallow bed correlations are used to predict the bed height at which transition from deep to shallow bed would occur. An application of the study has been made to determine the maximum coolable depths of the core debris as a function of the particle size, bed porosity and decay heat

Flow-sediment-large woody debris interplay: Introducing an appropriately scaled laboratory experiment

Science.gov (United States)

Friedrich, H.; Spreitzer, G.; Tunnicliffe, J. F.

2017-12-01

The morphology of steep (>0.01 m/m) forested streams is governed not only by water-sediment interplay, but also by accumulations of coarse and fine organic debris. In this project we look at the jamming dynamics (formation, persistence and hydraulic feedbacks) of large woody debris with the help of scaled laboratory experiments. In New Zealand, the recruitment of wood from both natural tree-fall and forest harvesting has led to obstruction of culverts, bridges and other river constrictions. Understanding the dynamics of jam formation and persistence is important for harvest practice guidelines, management of sediment accumulation, as well as establishing impacts to habitat and infrastructure. In this study, we provide the context of our work, present our experimental setup for studying the complex flow-sediment-wood interactions and present some initial results. In our experimental setup, we varied feed rates of sediment and organic fine material in order to establish concentration thresholds for jam formation, and development of sediment retention capacity upstream of the jam. Large woody debris accumulation is studied for different blocking scenarios, and the effect on sediment transport is measured. Sediment quantities and changes in channel bed morphology upstream of the critical cross section are evaluated, together with resulting backwater effects, and associated energy losses. In the long term, our results will inform our understanding of the processes that take place from the mobilization of woody debris to accumulation.

Fluidized bed calciner

International Nuclear Information System (INIS)

Sheely, W.F.

1986-01-01

A unique way to convert radioactive scrap into useful nuclear fuel products was developed for the Department of Energy at Hanford. An advanced, fluidized bed calciner is used to convert metallic nitrate scrap or waste solutions into benign, solid and gaseous products. There are broad potential applications of this concept beyond those in the nuclear industry

Solid Waste Transportation through Ocean Currents: Marine Debris Sightings and their Waste Quantification at Port Dickson Beaches, Peninsular Malaysia

OpenAIRE

Chong Jing Yi; Narayanan Kannan

2016-01-01

Four beaches at Port Dickson, Peninsular Malaysia, namely Saujana Beach, Nelayan Beach, Bagan Pinang Beach and Cermin beach have been sampled for marine debris from 7th June 2014 until 26th July 2014, on every Saturday. These beaches face the Strait of Malacca with a coastline stretching 18 km each. Our observations revealed a total debris items of 13193 in those beaches. The top three items of highest frequency were cigarette butts, foamed fragments and food wrappers. Plastic debris scaled h...

Artificial neural network based modelling approach for municipal solid waste gasification in a fluidized bed reactor.

Science.gov (United States)

Pandey, Daya Shankar; Das, Saptarshi; Pan, Indranil; Leahy, James J; Kwapinski, Witold

2016-12-01

In this paper, multi-layer feed forward neural networks are used to predict the lower heating value of gas (LHV), lower heating value of gasification products including tars and entrained char (LHV p ) and syngas yield during gasification of municipal solid waste (MSW) during gasification in a fluidized bed reactor. These artificial neural networks (ANNs) with different architectures are trained using the Levenberg-Marquardt (LM) back-propagation algorithm and a cross validation is also performed to ensure that the results generalise to other unseen datasets. A rigorous study is carried out on optimally choosing the number of hidden layers, number of neurons in the hidden layer and activation function in a network using multiple Monte Carlo runs. Nine input and three output parameters are used to train and test various neural network architectures in both multiple output and single output prediction paradigms using the available experimental datasets. The model selection procedure is carried out to ascertain the best network architecture in terms of predictive accuracy. The simulation results show that the ANN based methodology is a viable alternative which can be used to predict the performance of a fluidized bed gasifier. Copyright © 2016 Elsevier Ltd. All rights reserved.

Rainfall threshold calculation for debris flow early warning in areas with scarcity of data

Science.gov (United States)

Pan, Hua-Li; Jiang, Yuan-Jun; Wang, Jun; Ou, Guo-Qiang

2018-05-01

Debris flows are natural disasters that frequently occur in mountainous areas, usually accompanied by serious loss of lives and properties. One of the most commonly used approaches to mitigate the risk associated with debris flows is the implementation of early warning systems based on well-calibrated rainfall thresholds. However, many mountainous areas have little data regarding rainfall and hazards, especially in debris-flow-forming regions. Therefore, the traditional statistical analysis method that determines the empirical relationship between rainstorms and debris flow events cannot be effectively used to calculate reliable rainfall thresholds in these areas. After the severe Wenchuan earthquake, there were plenty of deposits deposited in the gullies, which resulted in several debris flow events. The triggering rainfall threshold has decreased obviously. To get a reliable and accurate rainfall threshold and improve the accuracy of debris flow early warning, this paper developed a quantitative method, which is suitable for debris flow triggering mechanisms in meizoseismal areas, to identify rainfall threshold for debris flow early warning in areas with a scarcity of data based on the initiation mechanism of hydraulic-driven debris flow. First, we studied the characteristics of the study area, including meteorology, hydrology, topography and physical characteristics of the loose solid materials. Then, the rainfall threshold was calculated by the initiation mechanism of the hydraulic debris flow. The comparison with other models and with alternate configurations demonstrates that the proposed rainfall threshold curve is a function of the antecedent precipitation index (API) and 1 h rainfall. To test the proposed method, we selected the Guojuanyan gully, a typical debris flow valley that during the 2008-2013 period experienced several debris flow events, located in the meizoseismal areas of the Wenchuan earthquake, as a case study. The comparison with other

Scaling of permeabilities and friction factors of homogeneously expanding gas-solids fluidized beds: Geldart’s A powders and magnetically stabilized beds

Directory of Open Access Journals (Sweden)

Hristov Jordan Y.

2006-01-01

Full Text Available The concept of a variable friction factor of fluid-driven de form able powder beds undergoing fluidization is discussed. The special problem discussed addresses the friction factor and bed permeability relationships of Geldart’s A powders and magnetically stabilized beds in axial fields. Governing equations and scaling relation ships are developed through three approaches (1 Minimization of the pressure drop with respect to the fluid velocity employing the Darcy-Forchheimer equation together with the Richardson-Zaki scaling law, (2 Minimization of the pres sure drop across an equivalent-channel replacing the actual packed beds by a straight pipe with bed-equivalent obstacle of a simple geometry, and (3 Entropy minimization method applied in cases of the Darcy-Forchheimer equation and the equivalent-channel model. Bed-to-surface heat transfer coefficients are commented in the context of the porosity/length scale relationships developed. Both the pressure drop curves developments and phase diagram de signs are illustrated by applications of the intersection of asymptotes technique to beds exhibiting certain degree of cohesion.

Fluidized-bed design for ICF reactor blankets using solid-lithium compounds

International Nuclear Information System (INIS)

Sucov, E.W.; Malick, F.S.; Green, L.; Hall, B.O.

1983-01-01

A fluidized-bed concept for blankets of dry or wetted first-wall ICF reactors using solid-lithium compounds is described. The reaction chamber is a right cylinder, 32 m high and 20 m in diameter; the blanket is composed of 36 steel tanks, 32 m high, which carry the sintered Li 2 O particles in the fluidizing helium gas. Each tank has a radial thickness of 2 m which generates a tritium breeding ration (TBR) of 1.27 and absorbs over 98% of the neutron energy; reducing the thickness to 1.2 m produces a TBR of 1.2 and energy absorption of 97% which satisfy the design goals. Calculations of tritium diffusion through the grains and heat removal from the grains showed that neither could be removed by the carrier gas; tritium and heat are therefore removed by removing the grains themselves by varying the helium flow rate. The particles are continuously fed into the bottom of the tanks at 300 0 C and removed at the top at 475 0 C. Tritium and heat extraction are easily and conveniently done outside the reactor

Integration of two-phase solid fluid equations in a catchment model for flashfloods, debris flows and shallow slope failures

KAUST Repository

Bout, B.; Lombardo, Luigi; van Westen, C.J.; Jetten, V.G.

2018-01-01

An integrated, modeling method for shallow landslides, debris flows and catchment hydrology is developed and presented in this paper. Existing two-phase debris flow equations and an adaptation on the infinite slope method are coupled with a full

Coolability of volumetrically heated particle beds

Energy Technology Data Exchange (ETDEWEB)

Rashid, Muhammad

2017-03-22

In case of a severe nuclear reactor accident, with loss of coolant, a particle bed may be formed from the fragmentation of the molten core in the residual water at different stages of the accident. To avoid further propagation of the accident and maintain the integrity of the reactor pressure vessel, the decay heat of the particle bed must be removed. To better understand the various thermo-hydraulic processes within such heat-generating particle beds, the existing DEBRIS test facility at IKE has been modified to be able to perform novel boiling, dryout and quenching experiments. The essential experimental data includes the pressure gradients measured by 8 differential pressure transducers along the bed height as a function of liquid and vapour superficial velocities, the determination of local dryout heat fluxes for different system pressures as well as the local temperature distribution measured by a set of 51 thermocouples installed inside the particle bed. The experiments were carried out for two different particle beds: a polydispersed particle bed which consisted of stainless steel balls (2 mm, 3 mm and 6 mm diameters) and an irregular particle bed which consisted of a mixture of steel balls (3 mm and 6 mm) and irregularly shaped Al{sub 2}O{sub 3} particles. Additionally, all experiments were carried out for different flow conditions, such as the reference case of passive 1D top-flooding, 1D bottom flooding (driven by external pumps and different downcomer configurations) and 2D top-/bottom-/lateral flooding with a perforated downcomer. In this work, it has been observed that for both particle beds with downcomer configurations an open downcomer leads to the best coolability (dryout heat flux = 1560 kW/m{sup 2}, polydispersed particle bed, psys = 1 bar) of the particle bed, mainly due to bottom-flow with enhanced natural convection. It has also been shown that a potential lateral flow via a perforation of the downcomer does not bring any further improvements

Coolability of volumetrically heated particle beds

International Nuclear Information System (INIS)

Rashid, Muhammad

2017-01-01

In case of a severe nuclear reactor accident, with loss of coolant, a particle bed may be formed from the fragmentation of the molten core in the residual water at different stages of the accident. To avoid further propagation of the accident and maintain the integrity of the reactor pressure vessel, the decay heat of the particle bed must be removed. To better understand the various thermo-hydraulic processes within such heat-generating particle beds, the existing DEBRIS test facility at IKE has been modified to be able to perform novel boiling, dryout and quenching experiments. The essential experimental data includes the pressure gradients measured by 8 differential pressure transducers along the bed height as a function of liquid and vapour superficial velocities, the determination of local dryout heat fluxes for different system pressures as well as the local temperature distribution measured by a set of 51 thermocouples installed inside the particle bed. The experiments were carried out for two different particle beds: a polydispersed particle bed which consisted of stainless steel balls (2 mm, 3 mm and 6 mm diameters) and an irregular particle bed which consisted of a mixture of steel balls (3 mm and 6 mm) and irregularly shaped Al 2 O 3 particles. Additionally, all experiments were carried out for different flow conditions, such as the reference case of passive 1D top-flooding, 1D bottom flooding (driven by external pumps and different downcomer configurations) and 2D top-/bottom-/lateral flooding with a perforated downcomer. In this work, it has been observed that for both particle beds with downcomer configurations an open downcomer leads to the best coolability (dryout heat flux = 1560 kW/m 2 , polydispersed particle bed, psys = 1 bar) of the particle bed, mainly due to bottom-flow with enhanced natural convection. It has also been shown that a potential lateral flow via a perforation of the downcomer does not bring any further improvements in

Orbital debris: a technical assessment

National Research Council Canada - National Science Library

Committee on Space Debris, National Research Council

..., and other debris created as a byproduct of space operations. Orbital Debris examines the methods we can use to characterize orbital debris, estimates the magnitude of the debris population, and assesses the hazard that this population poses to spacecraft...

Comparison of correlations for heat transfer in sphere-pac beds

International Nuclear Information System (INIS)

Fundamenski, W.R.; Gierszewski, P.J.

1991-08-01

The design of a tritium breeding blanket for a fusion reactor requires the knowledge of heat transfer within the blanket. In this paper three models for effective bed heat transfer are compared against the experimental database in order to choose a reference correlation to be used in blanket design. Two parameters are used to describe heat transfer in a packed bed: effective thermal conductivity of the bed, and a heat transfer coefficient at the bed-solid interface

Numerical simulation of the debris flow dynamics with an upwind scheme and specific friction treatment

Science.gov (United States)

Sánchez Burillo, Guillermo; Beguería, Santiago; Latorre, Borja; Burguete, Javier

2014-05-01

Debris flows, snow and rock avalanches, mud and earth flows are often modeled by means of a particular realization of the so called shallow water equations (SWE). Indeed, a number of simulation models have been already developed [1], [2], [3], [4], [5], [6], [7]. Debris flow equations differ from shallow water equations in two main aspects. These are (a) strong bed gradient and (b) rheology friction terms that differ from the traditional SWE. A systematic analysis of the numerical solution of the hyperbolic system of equations rising from the shallow water equations with different rheological laws has not been done. Despite great efforts have been done to deal with friction expressions common in hydraulics (such as Manning friction), landslide rheologies are characterized by more complicated expressions that may deal to unphysical solutions if not treated carefully. In this work, a software that solves the time evolution of sliding masses over complex bed configurations is presented. The set of non- linear equations is treated by means of a first order upwind explicit scheme, and the friction contribution to the dynamics is treated with a suited numerical scheme [8]. In addition, the software incorporates various rheological models to accommodate for different flow types, such as the Voellmy frictional model [9] for rock and debris avalanches, or the Herschley-Bulkley model for debris and mud flows. The aim of this contribution is to release this code as a free, open source tool for the simulation of mass movements, and to encourage the scientific community to make use of it. The code uses as input data the friction coefficients and two input files: the topography of the bed and the initial (pre-failure) position of the sliding mass. In addition, another file with the final (post-event) position of the sliding mass, if desired, can be introduced to be compared with the simulation obtained result. If the deposited mass is given, an error estimation is computed by

Drying of materials in fluidized bed: mathematical modeling

International Nuclear Information System (INIS)

Wildhagen, Gloria Regina S.; Silva, Eder F.; Calcada, Luis A.; Massarani, Giulio

2000-01-01

A three phase mathematical model for drying process in a fluidized bed was established. This model representing a bubble, interstitial gas and solid phase was based on principles of mass and energy conservation and on empirical relations for heat and mass transfer between phases. A fluidized bed dryer was built to test the results of proposed model with those obtained by experiments using alumina particles as a bed charge. A good agreement between the numerical and the experimental results were observed(author)

Modeling and Simulation of a lab-scale Fluidised Bed

Directory of Open Access Journals (Sweden)

Britt Halvorsen

2002-04-01

Full Text Available The flow behaviour of a lab-scale fluidised bed with a central jet has been simulated. The study has been performed with an in-house computational fluid dynamics (CFD model named FLOTRACS-MP-3D. The CFD model is based on a multi-fluid Eulerian description of the phases, where the kinetic theory for granular flow forms the basis for turbulence modelling of the solid phases. A two-dimensional Cartesian co-ordinate system is used to describe the geometry. This paper discusses whether bubble formation and bed height are influenced by coefficient of restitution, drag model and number of solid phases. Measurements of the same fluidised bed with a digital video camera are performed. Computational results are compared with the experimental results, and the discrepancies are discussed.

Biogasification of solid wastes by two-phase anaerobic fermentation

International Nuclear Information System (INIS)

Ghosh, S.; Vieitez, E.R.; Liu, T.; Kato, Y.

1997-01-01

Municipal, industrial and agricultural solid wastes, and biomass deposits, cause large-scale pollution of land and water. Gaseous products of waste decomposition pollute the air and contribute to global warming. This paper describes the development of a two-phase fermentation system that alleviates methanogenic inhibition encountered with high-solids feed, accelerates methane fermentation of the solid bed, and captures methane (renewable energy) for captive use to reduce global warming. The innovative system consisted of a solid bed reactor packed with simulated solid waste at a density of 160 kg/m 3 and operated with recirculation of the percolated culture (bioleachate) through the bed. A rapid onset of solids hydrolysis, acidification, denitrification and hydrogen gas formation was observed under these operating conditions. However, these fermentative reactions stopped at a total fatty acids concentration of 13,000 mg/l (as acetic) at pH 5, with a reactor head-gas composition of 75 percent carbon dioxide, 20 percent nitrogen, 2 percent hydrogen and 3 percent methane. Fermentation inhibition was alleviated by moving the bioleachate to a separate methane-phase fermenter, and recycling methanogenic effluents at pH 7 to the solid bed. Coupled operation of the two reactors promoted methanogenic conversion of the high-solids feed. (author)

Internal dust recirculation system for a fluidized bed heat exchanger

Science.gov (United States)

Gamble, Robert L.; Garcia-Mallol, Juan A.

1981-01-01

A fluidized bed heat exchanger in which air is passed through a bed of particulate material containing fuel disposed in a housing. A steam/water natural circulation system is provided in a heat exchange relation to the bed and includes a steam drum disposed adjacent the bed and a tube bank extending between the steam drum and a water drum. The tube bank is located in the path of the effluent gases exiting from the bed and a baffle system is provided to separate the solid particulate matter from the effluent gases. The particulate matter is collected and injected back into the fluidized bed.

Woody debris

Science.gov (United States)

Donna B. Scheungrab; Carl C. Trettin; Russ Lea; Martin F. Jurgensen

2000-01-01

Woody debris can be defined as any dead, woody plant material, including logs, branches, standing dead trees, and root wads. Woody debris is an important part of forest and stream ecosystems because it has a role in carbon budgets and nutrient cycling, is a source of energy for aquatic ecosystems, provides habitat for terrestrial and aquatic organisms, and contributes...

Wholesale debris removal from LEO

Science.gov (United States)

Levin, Eugene; Pearson, Jerome; Carroll, Joseph

2012-04-01

Recent advances in electrodynamic propulsion make it possible to seriously consider wholesale removal of large debris from LEO for the first time since the beginning of the space era. Cumulative ranking of large groups of the LEO debris population and general limitations of passive drag devices and rocket-based removal systems are analyzed. A candidate electrodynamic debris removal system is discussed that can affordably remove all debris objects over 2 kg from LEO in 7 years. That means removing more than 99% of the collision-generated debris potential in LEO. Removal is performed by a dozen 100-kg propellantless vehicles that react against the Earth's magnetic field. The debris objects are dragged down and released into short-lived orbits below ISS. As an alternative to deorbit, some of them can be collected for storage and possible in-orbit recycling. The estimated cost per kilogram of debris removed is a small fraction of typical launch costs per kilogram. These rates are low enough to open commercial opportunities and create a governing framework for wholesale removal of large debris objects from LEO.

Diesel NO{sub x} reduction by plasma-regenerated absorbent beds

Science.gov (United States)

Wallman, P.H.; Vogtlin, G.E.

1998-02-10

Reduction of NO{sub x} from diesel engine exhaust by use of plasma-regenerated absorbent beds is described. This involves a process for the reduction of NO{sub x} and particulates from diesel engines by first absorbing NO{sub x} onto a solid absorbent bed that simultaneously acts as a physical trap for the particulate matter, and second regenerating said solid absorbent by pulsed plasma decomposition of absorbed NO{sub x} followed by air oxidation of trapped particulate matter. The absorbent bed may utilize all metal oxides, but the capacity and the kinetics of absorption and desorption vary between different materials, and thus the composition of the absorbent bed is preferably a material which enables the combination of NO{sub x} absorption capability with catalytic activity for oxidation of hydrocarbons. Thus, naturally occurring or synthetically prepared materials may be utilized, particularly those having NO{sub x} absorption properties up to temperatures around 400 C which is in the area of diesel engine exhaust temperatures. 1 fig.

Expanded-bed chromatography in primary protein purification.

Science.gov (United States)

Anspach, F B; Curbelo, D; Hartmann, R; Garke, G; Deckwer, W D

1999-12-31

Chromatography in stable expanded beds enables proteins to be recovered directly from cultivations of microorganisms or cells and preparations of disrupted cells, without the need for prior removal of suspended solids. The general performance of an expanded bed is comparable to a packed bed owing to reduced mixing of the adsorbent particles in the column. However, optimal operating conditions are more restricted than in a packed bed due to the dependence of bed expansion on the size and density of the adsorbent particles as well as the viscosity and density of the feedstock. The feedstock composition may become the most limiting restriction owing to interactions of adsorbent particles with cell surfaces, DNA and other substances, leading to their aggregation and consequently to bed instabilities and channeling. Despite these difficulties, expanded-bed chromatography has found widespread applications in the large scale purification of proteins from mammalian cell and microbial feedstocks in industrial bioprocessing. The basics and implementation of expanded-bed chromatography, its advantages as well as problems encountered in the use of this technique for the direct extraction of proteins from unclarified feedstocks are addressed.

Oxidation of ethene in a wall-cooled packed-bed reactor

NARCIS (Netherlands)

Schouten, E.P.S.; Borman, P.C.; Westerterp, K.R.

1994-01-01

The selective oxidation of ethene over a silver on α-alumina catalyst was studied in a pilot plant with a wall-cooled tubular packed bed reactor. Gas and solid temperatures in the catalyst bed were measured at different axial and radial positions as well as concentrations at different axial

Fluidized bed combustion with the use of Greek solid fuels

Directory of Open Access Journals (Sweden)

Kakaras Emmanuel

2003-01-01

Full Text Available The paper is an overview of the results obtained up to date from the combustion and co-combustion activities with Greek brown coal in different installations, both in semi-industrial and laboratory scale. Combustion tests with Greek lignite were realized in three different Circulating Fluidized Bed Combustion (CFBC facilities. Low rank lignite was burned in a pilot scale facility of approx. 100kW thermal capacity, located in Athens (NTUA and a semi-industrial scale of 1.2 MW thermal capacity, located at RWE's power station Niederaussem in Germany. Co-combustion tests with Greek xylitic lignite and waste wood were carried out in the 1 MWth CFBC installation of AE&E, in Austria. Lab-scale co-combustion tests of Greek pre-dried lignite with biomass were accomplished in a bubbling fluidized bed in order to investigate ash melting problems. The obtained results of all aforementioned activities showed that fluidized bed is the appropriate combustion technology to efficiently exploit the low quality Greek brown coal either alone or in conjunction with biomass species.

Determination of viscosity in recirculating fluidized bed using radioactive tracer

International Nuclear Information System (INIS)

Silva, G.G. da.

1986-01-01

The use of radioactive tracer for measuring viscosity is proposed. The methodology relates the terminal velocity of a radioactive sphere in interior of fluid with the viscosity, which can be a fluidized bed or total flow of solids. The arrangement is composed by two γ detectors placed externally and along the bed. Both detectors are coupled by amplifier to electronic clock. The drop time of sphere between two detectors is measured. The bed viscosity two detectors is measured. The bed viscosity is calculated from mathematical correlations of terminal velocity of the sphere. (M.C.K.)

Disaster Characteristics and Mitigation Measures of Huge Glacial Debris Flows along the Sichuan-Tibet Railway

Science.gov (United States)

Liu, Jinfeng; You, Yong; Zhang, Guangze; Wang, Dong; Chen, Jiangang; Chen, Huayong

2017-04-01

accumulation length is 1.91 km and 1.75 km, and the accumulation width is 4.71 km and 3.68 km for the case of P=0.5% and P=1% respectively. The accumulation depth along the main flow direction is 40˜60m and 25˜35m. Consequently, four plans of railway alignment including passing through the down-stream by tunnel, passing through the gully outlet by tunnel and bridge, passing through the middle-lower part of the accumulation fan by railway bed and bridge, passing through the middle-lower part of the accumulation fan by tunnel were presented. The four plans were compared and related debris flow mitigation measures were provided.

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

International Nuclear Information System (INIS)

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

2012-01-01

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

SYNROC production using a fluid bed calciner

International Nuclear Information System (INIS)

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

1982-01-01

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

A two-phase debris-flow model that includes coupled evolution of volume fractions, granular dilatancy, and pore-fluid pressure

Science.gov (United States)

George, David L.; Iverson, Richard M.

2011-01-01

Pore-fluid pressure plays a crucial role in debris flows because it counteracts normal stresses at grain contacts and thereby reduces intergranular friction. Pore-pressure feedback accompanying debris deformation is particularly important during the onset of debrisflow motion, when it can dramatically influence the balance of forces governing downslope acceleration. We consider further effects of this feedback by formulating a new, depth-averaged mathematical model that simulates coupled evolution of granular dilatancy, solid and fluid volume fractions, pore-fluid pressure, and flow depth and velocity during all stages of debris-flow motion. To illustrate implications of the model, we use a finite-volume method to compute one-dimensional motion of a debris flow descending a rigid, uniformly inclined slope, and we compare model predictions with data obtained in large-scale experiments at the USGS debris-flow flume. Predictions for the first 1 s of motion show that increasing pore pressures (due to debris contraction) cause liquefaction that enhances flow acceleration. As acceleration continues, however, debris dilation causes dissipation of pore pressures, and this dissipation helps stabilize debris-flow motion. Our numerical predictions of this process match experimental data reasonably well, but predictions might be improved by accounting for the effects of grain-size segregation.

Space Debris & its Mitigation

Science.gov (United States)

Kaushal, Sourabh; Arora, Nishant

2012-07-01

Space debris has become a growing concern in recent years, since collisions at orbital velocities can be highly damaging to functioning satellites and can also produce even more space debris in the process. Some spacecraft, like the International Space Station, are now armored to deal with this hazard but armor and mitigation measures can be prohibitively costly when trying to protect satellites or human spaceflight vehicles like the shuttle. This paper describes the current orbital debris environment, outline its main sources, and identify mitigation measures to reduce orbital debris growth by controlling these sources. We studied the literature on the topic Space Debris. We have proposed some methods to solve this problem of space debris. We have also highlighted the shortcomings of already proposed methods by space experts and we have proposed some modification in those methods. Some of them can be very effective in the process of mitigation of space debris, but some of them need some modification. Recently proposed methods by space experts are maneuver, shielding of space elevator with the foil, vaporizing or redirecting of space debris back to earth with the help of laser, use of aerogel as a protective layer, construction of large junkyards around international space station, use of electrodynamics tether & the latest method proposed is the use of nano satellites in the clearing of the space debris. Limitations of the already proposed methods are as follows: - Maneuvering can't be the final solution to our problem as it is the act of self-defence. - Shielding can't be done on the parts like solar panels and optical devices. - Vaporizing or redirecting of space debris can affect the human life on earth if it is not done in proper manner. - Aerogel has a threshold limit up to which it can bear (resist) the impact of collision. - Large junkyards can be effective only for large sized debris. In this paper we propose: A. The Use of Nano Tubes by creating a mesh

DebriSat Hypervelocity Impact Test

Science.gov (United States)

2015-08-01

public release; distribution unlimited.  Targets: Scaled Multishock Shield, DebrisLV, and DebriSat  500-600 g hollow aluminum and nylon projectile... insulation . DebriSat’s internal components were structurally similar to real flight hardware but were nonfunctional. AEDC-TR-15-S-2 6...structures with an AL 5052 honeycomb core and M55J carbon fiber face sheets. The basic system characteristics of the DebriSat are given in Table 1

Particle flow of ceramic breeder pebble beds in bi-axial compression experiments

International Nuclear Information System (INIS)

Hermsmeyer, S.; Reimann, J.

2002-01-01

Pebble beds of ceramic material are investigated within the framework of developing solid breeder blankets for future fusion power plants. A thermo-mechanical characterisation of such pebble beds is mandatory for understanding the behaviour of pebble beds, and thus the overall blanket, under fusion environment conditions. The mechanical behaviour of pebble beds is typically explored with uni-axial, bi-axial and tri-axial compression experiments. The latter two types of experiment are particularly revealing since they contain explicitly, beyond a compression behaviour of the bed, information on the conditions for pebble flow, i.e. macroscopic relocation, in the pebble bed. (orig.)

JSC Orbital Debris Website Description

Science.gov (United States)

Johnson, Nicholas L.

2006-01-01

Purpose: The website provides information about the NASA Orbital Debris Program Office at JSC, which is the lead NASA center for orbital debris research. It is recognized world-wide for its leadership in addressing orbital debris issues. The NASA Orbital Debris Program Office has taken the international lead in conducting measurements of the environment and in developing the technical consensus for adopting mitigation measures to protect users of the orbital environment. Work at the center continues with developing an improved understanding of the orbital debris environment and measures that can be taken to control its growth. Major Contents: Orbital Debris research is divided into the following five broad efforts. Each area of research contains specific information as follows: 1) Modeling - NASA scientists continue to develop and upgrade orbital debris models to describe and characterize the current and future debris environment. Evolutionary and engineering models are described in detail. Downloadable items include a document in PDF format and executable software. 2) Measurements - Measurements of near-Earth orbital debris are accomplished by conducting ground-based and space-based observations of the orbital debris environment. The data from these sources provide validation of the environment models and identify the presence of new sources. Radar, optical and surface examinations are described. External links to related topics are provided. 3) Protection - Orbital debris protection involves conducting hypervelocity impact measurements to assess the risk presented by orbital debris to operating spacecraft and developing new materials and new designs to provide better protection from the environment with less weight penalty. The data from this work provides the link between the environment defined by the models and the risk presented by that environment to operating spacecraft and provides recommendations on design and operations procedures to reduce the risk as

Bi-objective optimization of a multiple-target active debris removal mission

Science.gov (United States)

Bérend, Nicolas; Olive, Xavier

2016-05-01

The increasing number of space debris in Low-Earth Orbit (LEO) raises the question of future Active Debris Removal (ADR) operations. Typical ADR scenarios rely on an Orbital Transfer Vehicle (OTV) using one of the two following disposal strategies: the first one consists in attaching a deorbiting kit, such as a solid rocket booster, to the debris after rendezvous; with the second one, the OTV captures the debris and moves it to a low-perigee disposal orbit. For multiple-target ADR scenarios, the design of such a mission is very complex, as it involves two optimization levels: one for the space debris sequence, and a second one for the "elementary" orbit transfer strategy from a released debris to the next one in the sequence. This problem can be seen as a Time-Dependant Traveling Salesman Problem (TDTSP) with two objective functions to minimize: the total mission duration and the total propellant consumption. In order to efficiently solve this problem, ONERA has designed, under CNES contract, TOPAS (Tool for Optimal Planning of ADR Sequence), a tool that implements a Branch & Bound method developed in previous work together with a dedicated algorithm for optimizing the "elementary" orbit transfer. A single run of this tool yields an estimation of the Pareto front of the problem, which exhibits the trade-off between mission duration and propellant consumption. We first detail our solution to cope with the combinatorial explosion of complex ADR scenarios with 10 debris. The key point of this approach is to define the orbit transfer strategy through a small set of parameters, allowing an acceptable compromise between the quality of the optimum solution and the calculation cost. Then we present optimization results obtained for various 10 debris removal scenarios involving a 15-ton OTV, using either the deorbiting kit or the disposal orbit strategy. We show that the advantage of one strategy upon the other depends on the propellant margin, the maximum duration allowed

Mass and heat transfer between a fluidized bed and a freely moving submerged sphere

NARCIS (Netherlands)

Prins, W.; Valk, M.

1995-01-01

For fluidized bed combustion and gasification of solid fuels, but also for various other fluidized bed processes such as drying, granulation and evaporation, mass and heat transport to (or from) a particle freely moving in the fluidized bed is of great importance. The combustion rate of a

The equivalent electrical permittivity of gas-solid mixtures at intermediate solid volume fractions.

Energy Technology Data Exchange (ETDEWEB)

Torczynski, John Robert; Ceccio, Steven Louis; Tortora, Paul Richard

2005-07-01

Several mixture models are evaluated for their suitability in predicting the equivalent permittivity of dielectric particles in a dielectric medium for intermediate solid volume fractions (0.4 to 0.6). Predictions of the Maxwell, Rayleigh, Bottcher and Bruggeman models are compared to computational simulations of several arrangements of solid particles in a gas and to the experimentally determined permittivity of a static particle bed. The experiment uses spherical glass beads in air, so air and glass permittivity values (1 and 7, respectively) are used with all of the models and simulations. The experimental system used to measure the permittivity of the static particle bed and its calibration are described. The Rayleigh model is found to be suitable for predicting permittivity over the entire range of solid volume fractions (0-0.6).

Scaling up debris-flow experiments on a centrifuge

Science.gov (United States)

Hung, C.; Capart, H.; Crone, T. J.; Grinspum, E.; Hsu, L.; Kaufman, D.; Li, L.; Ling, H.; Reitz, M. D.; Smith, B.; Stark, C. P.

2013-12-01

Boundary forces generated by debris flows can be powerful enough to erode bedrock and cause considerable damage to infrastructure during runout. Formulation of an erosion-rate law for debris flows is therefore a high priority, and it makes sense to build such a law around laboratory experiments. However, running experiments big enough to generate realistic boundary forces is a logistical challenge to say the least [1]. One alternative is to run table-top simulations with unnaturally weak but fast-eroding pseudo-bedrock, another is to extrapolate from micro-erosion of natural substrates driven by unnaturally weak impacts; hybrid-scale experiments have also been conducted [2]. Here we take a different approach in which we scale up granular impact forces by running our experiments under enhanced gravity in a geotechnical centrifuge [3]. Using a 40cm-diameter rotating drum [2] spun at up to 100g, we generate debris flows with an effective depth of over several meters. By varying effective gravity from 1g to 100g we explore the scaling of granular flow forces and the consequent bed and wall erosion rates. The velocity and density structure of these granular flows is monitored using laser sheets, high-speed video, and particle tracking [4], and the progressive erosion of the boundary surfaces is measured by laser scanning. The force structures and their fluctuations within the granular mass and at the boundaries are explored with contact dynamics numerical simulations that mimic the lab experimental conditions [5]. In this presentation we summarize these results and discuss how they can contribute to the formulation of debris-flow erosion law. [1] Major, J. J. (1997), Journal of Geology 105: 345-366, doi:10.1086/515930 [2] Hsu, L. (2010), Ph.D. thesis, University of California, Berkeley [3] Brucks, A., et al (2007), Physical Review E 75, 032301, doi:10.1103/PhysRevE.75.032301 [4] Spinewine, B., et al (2011), Experiments in Fluids 50: 1507-1525, doi: 10.1007/s00348

Debris flow-induced topographic changes: effects of recurrent debris flow initiation.

Science.gov (United States)

Chen, Chien-Yuan; Wang, Qun

2017-08-12

Chushui Creek in Shengmu Village, Nantou County, Taiwan, was analyzed for recurrent debris flow using numerical modeling and geographic information system (GIS) spatial analysis. The two-dimensional water flood and mudflow simulation program FLO-2D were used to simulate debris flow induced by rainfall during typhoon Herb in 1996 and Mindulle in 2004. Changes in topographic characteristics after the debris flows were simulated for the initiation of hydrological characteristics, magnitude, and affected area. Changes in topographic characteristics included those in elevation, slope, aspect, stream power index (SPI), topographic wetness index (TWI), and hypsometric curve integral (HI), all of which were analyzed using GIS spatial analysis. The results show that the SPI and peak discharge in the basin increased after a recurrence of debris flow. The TWI was higher in 2003 than in 2004 and indicated higher potential of landslide initiation when the slope of the basin was steeper. The HI revealed that the basin was in its mature stage and was shifting toward the old stage. Numerical simulation demonstrated that the parameters' mean depth, maximum depth, affected area, mean flow rate, maximum flow rate, and peak flow discharge were increased after recurrent debris flow, and peak discharge occurred quickly.

A globally complete map of supraglacial debris cover and a new toolkit for debris cover research

Science.gov (United States)

Herreid, Sam; Pellicciotti, Francesca

2017-04-01

A growing canon of literature is focused on resolving the processes and implications of debris cover on glaciers. However, this work is often confined to a handful of glaciers that were likely selected based on criteria optimizing their suitability to test a specific hypothesis or logistical ease. The role of debris cover in a glacier system is likely to not go overlooked in forthcoming research, yet the magnitude of this role at a global scale has not yet been fully described. Here, we present a map of debris cover for all glacierized regions on Earth including the Greenland Ice Sheet using 30 m Landsat data. This dataset will begin to open a wider context to the high quality, localized findings from the debris-covered glacier research community and help inform large-scale modeling efforts. A global map of debris cover also facilitates analysis attempting to isolate first order geomorphological and climate controls of supraglacial debris production. Furthering the objective of expanding the inclusion of debris cover in forthcoming research, we also present an under development suite of open-source, Python based tools. Requiring minimal and often freely available input data, we have automated the mapping of: i) debris cover, ii) ice cliffs, iii) debris cover evolution over the Landsat era and iv) glacier flow instabilities from altered debris structures. At the present time, debris extent is the only globally complete quantity but with the expanding repository of high quality global datasets and further tool development minimizing manual tasks and computational cost, we foresee all of these tools being applied globally in the near future.

Coarse grid simulation of bed expansion characteristics of industrial-scale gas–solid bubbling fluidized beds

NARCIS (Netherlands)

Wang, J.; van der Hoef, Martin Anton; Kuipers, J.A.M.

2010-01-01

Two-fluid modeling of the hydrodynamics of industrial-scale gas-fluidized beds proves a long-standing challenge for both engineers and scientists. In this study, we suggest a simple method to modify currently available drag correlations to allow for the effect of unresolved sub-grid scale

Spatial-temporal analysis of marine debris on beaches of Niterói, RJ, Brazil: Itaipu and Itacoatiara.

Science.gov (United States)

Silva, Melanie Lopes da; Araújo, Fábio Vieira de; Castro, Rebeca Oliveira; Sales, Alessandro Souza

2015-03-15

In many areas of the world, studies of marine debris are conducted with an emphasis on analyzing their composition, quantification and distribution on sandy beaches. However, in Brazil, studies are still restricted to some areas of the coast, and the quantities and the spatial and temporal patterns are unknown. To enhance the marine debris information in these areas, we selected the Itaipu and Itacoatiara beaches in Niterói, RJ, to collect, quantify and qualify the solid residues present in their sands. We collected 12 samples and recorded 118.39 kg of residues in Itaipu and 62.94 kg in Itacoatiara. At both beaches, the largest portion of debris was located on the upper part of the beach. Several debris items were related to food and drink consumption on the beaches, which indicated the contribution of beach users to pollution. Most of the debris was plastic. The greatest amount of debris was found at Itaipu in January and February and at Itacoatiara in January and March, months related to both the holiday season and abundant rainfall. The results demonstrated the necessity to implement an Environmental Education project for these areas to reduce its degradation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Exploiting Orbital Data and Observation Campaigns to Improve Space Debris Models

Science.gov (United States)

Braun, V.; Horstmann, A.; Reihs, B.; Lemmens, S.; Merz, K.; Krag, H.

The European Space Agency (ESA) has been developing the Meteoroid and Space Debris Terrestrial Environment Reference (MASTER) software as the European reference model for space debris for more than 25 years. It is an event-based simulation of all known individual debris-generating events since 1957, including breakups, solid rocket motor firings and nuclear reactor core ejections. In 2014, the upgraded Debris Risk Assessment and Mitigation Analysis (DRAMA) tool suite was released. In the same year an ESA instruction made the standard ISO 24113:2011 on space debris mitigation requirements, adopted via the European Cooperation for Space Standardization (ECSS), applicable to all ESA missions. In order to verify the compliance of a space mission with those requirements, the DRAMA software is used to assess collision avoidance statistics, estimate the remaining orbital lifetime and evaluate the on-ground risk for controlled and uncontrolled reentries. In this paper, the approach to validate the MASTER and DRAMA tools is outlined. For objects larger than 1 cm, thus potentially being observable from ground, the MASTER model has been validated through dedicated observation campaigns. Recent campaign results shall be discussed. Moreover, catalogue data from the Space Surveillance Network (SSN) has been used to correlate the larger objects. In DRAMA, the assessment of collision avoidance statistics is based on orbit uncertainty information derived from Conjunction Data Messages (CDM) provided by the Joint Space Operations Center (JSpOC). They were collected for more than 20 ESA spacecraft in the recent years. The way this information is going to be used in a future DRAMA version is outlined and the comparison of estimated manoeuvre rates with real manoeuvres from the operations of ESA spacecraft is shown.

Assessment of different bedding systems for lactating cows in freestall housing

Science.gov (United States)

The objective of this study was to compare different bedding systems for lactating cows in freestall housing. Bedding systems included new sand (NS), recycled byproducts of manure separation (organic solids [OS] and recycled sand [RS]), and foam-core mattresses with a shallow layer of OS (MS). The e...

Italian experience on the processing of solid radioactive wastes

International Nuclear Information System (INIS)

Costa, A.; De Angelis, G.

1989-12-01

Experimental work is under way in Italy for treatment and conditioning of different types of solid radioactive wastes. The following wastes are taken into account in this paper: Magnox fuel element debris, solid compactable wastes, radiation sources and contaminated carcasses. The metallic debris, consisting of Magnox splitters and braces, are conditioned, after drying and separation of corrosion products, by means of a two component epoxy system (base product + hardener). Solid compactable wastes are reduced in volume by using a press. The resulting pellets are transferred to a final container and conditioned with a cement mortar of a suitable consistency. As to the radiation sources, mainly contained in lightning-rods, gas detectors and radioactive thickness gauges, the encapsulation in a cementitious grout is a common practice for their incorporation. Early experiments, with satisfactory results, have also been conducted for the cementation of contaminated carcasses. (author)

Study on effective particle diameters and coolability of particulate beds packed with irregular multi-size particles

Energy Technology Data Exchange (ETDEWEB)

Thakre, S.; Ma, W.; Kudinov, P.; Bechta, S. [Royal Institute of Technology, KTH. Div. of Nuclear Power Safety, Stockholm (Sweden)

2013-08-15

One of the key questions in severe accident research is the coolability of the debris bed, i.e., whether decay heat can be completely removed by the coolant flow into the debris bed. Extensive experimental and analytical work has been done to substantiate the coolability research. Most of the available experimental data is related to the beds packed with single size (mostly spherical) particles, and less data is available for multi-size/irregular-shape particles. There are several analytical models available, which rely on the mean particle diameter and porosity of the bed in their predictions. Two different types of particles were used to investigate coolability of particulate beds at VTT, Finland. The first type is irregular-shape Aluminum Oxide gravel particles whose sizes vary from 0.25 mm to 10 mm, which were employed in the STYX experiment programme (2001-2008). The second type is spherical beads of Zirconium silicate whose sizes vary between 0.8 mm to 1 mm, which were used in the COOLOCE tests (Takasuo et al., 2012) to study the effect of multi-dimensional flooding on coolability. In the present work, the two types of particles are used in the POMECO-FL and POMECO-HT test facility to obtain their effective particle diameters and dryout heat flux of the beds, respectively. The main idea is to check how the heaters' orientations (vertical in COOLOCE vs. horizontal in POMECO-HT) and diameters (6 mm in COOLOCE vs. 3 mm in POMECO-HT) affect the coolability (dryout heat flux) of the test beds. The tests carried out on the POMECO-FL facility using a bed packed with aluminum oxide gravel particles show the effective particle diameter of the gravel particles is 0.65 mm, by which the frictional pressure gradient can be predicted by the Ergun equation. After the water superficial velocity is higher than 0.0025 m/s, the pressure gradient is underestimated. The effective particle diameter of the zirconium particles is found as 0.8 mm. The dryout heat flux is measured on

Study on effective particle diameters and coolability of particulate beds packed with irregular multi-size particles

International Nuclear Information System (INIS)

Thakre, S.; Ma, W.; Kudinov, P.; Bechta, S.

2013-08-01

One of the key questions in severe accident research is the coolability of the debris bed, i.e., whether decay heat can be completely removed by the coolant flow into the debris bed. Extensive experimental and analytical work has been done to substantiate the coolability research. Most of the available experimental data is related to the beds packed with single size (mostly spherical) particles, and less data is available for multi-size/irregular-shape particles. There are several analytical models available, which rely on the mean particle diameter and porosity of the bed in their predictions. Two different types of particles were used to investigate coolability of particulate beds at VTT, Finland. The first type is irregular-shape Aluminum Oxide gravel particles whose sizes vary from 0.25 mm to 10 mm, which were employed in the STYX experiment programme (2001-2008). The second type is spherical beads of Zirconium silicate whose sizes vary between 0.8 mm to 1 mm, which were used in the COOLOCE tests (Takasuo et al., 2012) to study the effect of multi-dimensional flooding on coolability. In the present work, the two types of particles are used in the POMECO-FL and POMECO-HT test facility to obtain their effective particle diameters and dryout heat flux of the beds, respectively. The main idea is to check how the heaters' orientations (vertical in COOLOCE vs. horizontal in POMECO-HT) and diameters (6 mm in COOLOCE vs. 3 mm in POMECO-HT) affect the coolability (dryout heat flux) of the test beds. The tests carried out on the POMECO-FL facility using a bed packed with aluminum oxide gravel particles show the effective particle diameter of the gravel particles is 0.65 mm, by which the frictional pressure gradient can be predicted by the Ergun equation. After the water superficial velocity is higher than 0.0025 m/s, the pressure gradient is underestimated. The effective particle diameter of the zirconium particles is found as 0.8 mm. The dryout heat flux is measured on

Contribution to the knowledge of spouted beds, including in particular an experimental study on the void fraction of the dense phase

International Nuclear Information System (INIS)

Eljas, Yves.

1975-10-01

The spouted bed is a gas-solid contact technique used to replace fluidisation when the solid particles are too large and too dense. Part one gives a bibliographical study on the aerodynamic aspect of spouted beds. Part two describes an experimental study of the void fraction distribution in a two-dimensional bed [fr

A finite volume solver for three dimensional debris flow simulations based on a single calibration parameter

Science.gov (United States)

von Boetticher, Albrecht; Turowski, Jens M.; McArdell, Brian; Rickenmann, Dieter

2016-04-01

Debris flows are frequent natural hazards that cause massive damage. A wide range of debris flow models try to cover the complex flow behavior that arises from the inhomogeneous material mixture of water with clay, silt, sand, and gravel. The energy dissipation between moving grains depends on grain collisions and tangential friction, and the viscosity of the interstitial fine material suspension depends on the shear gradient. Thus a rheology description needs to be sensitive to the local pressure and shear rate, making the three-dimensional flow structure a key issue for flows in complex terrain. Furthermore, the momentum exchange between the granular and fluid phases should account for the presence of larger particles. We model the fine material suspension with a Herschel-Bulkley rheology law, and represent the gravel with the Coulomb-viscoplastic rheology of Domnik & Pudasaini (Domnik et al. 2013). Both composites are described by two phases that can mix; a third phase accounting for the air is kept separate to account for the free surface. The fluid dynamics are solved in three dimensions using the finite volume open-source code OpenFOAM. Computational costs are kept reasonable by using the Volume of Fluid method to solve only one phase-averaged system of Navier-Stokes equations. The Herschel-Bulkley parameters are modeled as a function of water content, volumetric solid concentration of the mixture, clay content and its mineral composition (Coussot et al. 1989, Yu et al. 2013). The gravel phase properties needed for the Coulomb-viscoplastic rheology are defined by the angle of repose of the gravel. In addition to this basic setup, larger grains and the corresponding grain collisions can be introduced by a coupled Lagrangian particle simulation. Based on the local Savage number a diffusive term in the gravel phase can activate phase separation. The resulting model can reproduce the sensitivity of the debris flow to water content and channel bed roughness, as

Mathematical modeling of Kluyveromyces marxianus growth in solid-state fermentation using a packed-bed bioreactor.

Science.gov (United States)

Mazutti, Marcio A; Zabot, Giovani; Boni, Gabriela; Skovronski, Aline; de Oliveira, Débora; Di Luccio, Marco; Rodrigues, Maria Isabel; Maugeri, Francisco; Treichel, Helen

2010-04-01

This work investigated the growth of Kluyveromyces marxianus NRRL Y-7571 in solid-state fermentation in a medium composed of sugarcane bagasse, molasses, corn steep liquor and soybean meal within a packed-bed bioreactor. Seven experimental runs were carried out to evaluate the effects of flow rate and inlet air temperature on the following microbial rates: cell mass production, total reducing sugar and oxygen consumption, carbon dioxide and ethanol production, metabolic heat and water generation. A mathematical model based on an artificial neural network was developed to predict the above-mentioned microbial rates as a function of the fermentation time, initial total reducing sugar concentration, inlet and outlet air temperatures. The results showed that the microbial rates were temperature dependent for the range 27-50 degrees C. The proposed model efficiently predicted the microbial rates, indicating that the neural network approach could be used to simulate the microbial growth in SSF.

Analysis of the vertical penetration of a heated fluid layer in a solid, miscible bed

International Nuclear Information System (INIS)

Eck, G.

1982-03-01

The present study investigates the mass and heat transfer for the vertical penetration of a heated fluid layer in a solid, miscible bed using water-salt solutions (ZnBr 2 , NaBr) and polyethylenglycol 1500 (PEG) as simulation materials. The time depending spatial distribution of the molten material (PEG) has been measured for the first time with conductivity probes. The dependence of the downward heat flux on the density ratio rho*, i.e. the density of the fluid / the density of the molten solid, has been investigated with two different methods of heating, planar heating with a heat exchanger in a defined initial distance to the PEG-surface and electrolytical volume heating with a defined and timely constant power input. For 1 2 two layers have been observed in the fluid. This phenomenon is caused among other things by an anomality of the mixture density of the system salt solution-PEG. This process affects the downward heat flux so strongly, that it is impossible to transfer the results of such a system in this region of rho* to another system, for example to a corecatcher. The discrepancies between the measured heat fluxes and heat transfer coefficients of this study and that of other authors can be explained by the different construction of the planar heater, or by different boundary conditions in the case of volume heating. (orig.) [de

A comparative study of charcoal gasification in two types of spouted bed reactors

International Nuclear Information System (INIS)

Abdul Salam, P.; Bhattacharya, S.C.

2006-01-01

Gasification is considered to be a favourable method for converting a solid fuel into a more versatile gaseous fuel. Performance of a gasifier depends on the design of the gasifier, type of fuel used and air flow rate, etc. The applications of spouted bed for a variety of processes such as drying, coating, pyrolysis, gasification and combustion have been reported. Gasification of solid fuels in a spouted bed, which has certain potential advantages over other fluid bed configurations, appears to be an under-exploited technique so far. Central jet distributors are the most commonly used in the experimental studies that has been reported in the literature. Circular slit distributor is a new concept. This paper presents results of a comparative experimental study on air gasification of charcoal in central jet and circular slit inert sand spouted beds. The experiments were carried for an equivalence ratio of 0.25. The effect of spouting velocity and type of the distributor on the gasification performance were discussed. The steady state dense bed temperature varied between 979 and 1183 deg C for central jet spouted bed and between 964 and 1235 deg C for circular slit spouted bed. At higher spouting velocities, the gasification efficiency of the circular slit spouted bed was slightly more compared with that of central jet spouted bed

Temporal and spatial variability in thalweg profiles of a gravel-bed river

Science.gov (United States)

Madej, Mary Ann

1999-01-01

This study used successive longitudinal thalweg profiles in gravel-bed rivers to monitor changes in bed topography following floods and associated large sediment inputs. Variations in channel bed elevations, distributions of residual water depths, percentage of channel length occupied by riffles, and a spatial autocorrelation coefficient (Moran's I) were used to quantify changes in morphological diversity and spatial structure in Redwood Creek basin, northwestern California. Bed topography in Redwood Creek and its major tributaries consists primarily of a series of pools and riffles. The size, frequency and spatial distribution of the pools and riffles have changed significantly during the past 20 years. Following large floods and high sediment input in Redwood Creek and its tributaries in 1975, variation in channel bed elevations was low and the percentage of the channel length occupied by riffles was high. Over the next 20 years, variation in bed elevations increased while the length of channel occupied by riffles decreased. An index [(standard deviation of residual water depth/bankfull depth) × 100] was developed to compare variations in bed elevation over a range of stream sizes, with a higher index being indicative of greater morphological diversity. Spatial autocorrelation in the bed elevation data was apparent at both fine and coarse scales in many of the thalweg profiles and the observed spatial pattern of bed elevations was found to be related to the dominant channel material and the time since disturbance. River reaches in which forced pools dominated, and in which large woody debris and bed particles could not be easily mobilized, exhibited a random distribution of bed elevations. In contrast, in reaches where alternate bars dominated, and both wood and gravel were readily transported, regularly spaced bed topography developed at a spacing that increased with time since disturbance. This pattern of regularly spaced bed features was reversed

Measurement of Gas Velocities in the Presence of Solids in the Riser of a Cold Flow Circulating Fluidized Bed

International Nuclear Information System (INIS)

Spenik, J.; Ludlow, J.C.; Compston, R.; Breault, R.W.

2007-01-01

The local gas velocity and the intensity of the gas turbulence in a gas/solid flow are a required measurement in validating the gas and solids flow structure predicted by computational fluid dynamic (CFD) models in fluid bed and transport reactors. The high concentration and velocities of solids, however, make the use of traditional gas velocity measurement devices such as pitot tubes, hot wire anemometers and other such devices difficult. A method of determining these velocities has been devised at the National Energy Technology Laboratory employing tracer gas. The technique developed measures the time average local axial velocity gas component of a gas/solid flow using an injected tracer gas which induces changes in the heat transfer characteristics of the gas mixture. A small amount of helium is injected upstream a known distance from a self-heated thermistor. The thermistor, protected from the solids by means of a filter, is exposed to gases that are continuously extracted from the flow. Changes in the convective heat transfer characteristics of the gas are indicated by voltage variations across a Wheatstone bridge. When pulsed injections of helium are introduced to the riser flow the change in convective heat transfer coefficient of the gas can be rapidly and accurately determined with this instrument. By knowing the separation distance between the helium injection point and the thermistor extraction location as well as the time delay between injection and detection, the gas velocity can easily be calculated. Variations in the measured gas velocities also allow the turbulence intensity of the gas to be estimated

Autogenic dynamics of debris-flow fans

Science.gov (United States)

van den Berg, Wilco; de Haas, Tjalling; Braat, Lisanne; Kleinhans, Maarten

2015-04-01

Alluvial fans develop their semi-conical shape by cyclic avulsion of their geomorphologically active sector from a fixed fan apex. These cyclic avulsions have been attributed to both allogenic and autogenic forcings and processes. Autogenic dynamics have been extensively studied on fluvial fans through physical scale experiments, and are governed by cyclic alternations of aggradation by unconfined sheet flow, fanhead incision leading to channelized flow, channel backfilling and avulsion. On debris-flow fans, however, autogenic dynamics have not yet been directly observed. We experimentally created debris-flow fans under constant extrinsic forcings, and show that autogenic dynamics are a fundamental intrinsic process on debris-flow fans. We found that autogenic cycles on debris-flow fans are driven by sequences of backfilling, avulsion and channelization, similar to the cycles on fluvial fans. However, the processes that govern these sequences are unique for debris-flow fans, and differ fundamentally from the processes that govern autogenic dynamics on fluvial fans. We experimentally observed that backfilling commenced after the debris flows reached their maximum possible extent. The next debris flows then progressively became shorter, driven by feedbacks on fan morphology and flow-dynamics. The progressively decreasing debris-flow length caused in-channel sedimentation, which led to increasing channel overflow and wider debris flows. This reduced the impulse of the liquefied flow body to the flow front, which then further reduced flow velocity and runout length, and induced further in-channel sedimentation. This commenced a positive feedback wherein debris flows became increasingly short and wide, until the channel was completely filled and the apex cross-profile was plano-convex. At this point, there was no preferential transport direction by channelization, and the debris flows progressively avulsed towards the steepest, preferential, flow path. Simultaneously

Theory and measurements of electrophoretic effects in monolith, fixed-bed, and fluidized-bed plasma reactors

International Nuclear Information System (INIS)

Morin, T.J.

1989-01-01

Pressure gradients and secondary flow fields generated by the passage of electrical current in a d.c. gas discharge or gas laser are topics of longstanding interest in the gaseous electronics literature. These hydrodynamic effects of space charge fields and charged particle density gradients have been principally exploited in the development of gas separation and purification processes. In recent characterization studies of fixed-bed and fluidized-bed plasma reactors several anomalous flow features have been observed. These reactors involve the contacting of a high-frequency, resonantly-sustained, disperse gas discharge with granular solids in a fixed or fluidized bed. Anomalies in the measured pressure drops and fluidization velocities have motivated the development of an appropriate theoretical approach to, and some additional experimental investigations of electrophoretic effects in disperse gas discharges. In this paper, a theory which includes the effects of space charge and diffusion is used to estimate the electric field and charged particle density profiles. These profiles are then used to calculate velocity fields and gas flow rates for monolith, fixed-bed, and fluidized-bed reactors. These results are used to rationalize measurements of gas flow rates and axial pressure gradients in high-frequency disperse gas discharges with and without an additional d.c. axial electric field

Reducing beryllium content in mixed bed solid-type breeder blankets

Energy Technology Data Exchange (ETDEWEB)

Shimwell, J., E-mail: mail@jshimwell.com [Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Lilley, S.; Morgan, L.; Packer, L.; Kovari, M.; Zheng, S. [Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); McMillan, J. [Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

2016-11-01

Highlights: • The ratio of breeder ceramic to neutron multiplier of breeder blankets was varied linearly with depth. • Blankets with varying composition were found to perform better than uniform composition breeder blankets. • It was also possible to reduce the amount of beryllium required by the blanket. - Abstract: Beryllium (Be) is a precious resource with many high value uses, the low energy threshold (n,2n) reaction makes Be an excellent neutron multiplier for use in fusion breeder blankets. Estimates of Be requirements and available resources suggest that this could represent a major supply difficulty for solid-type blanket concepts. Reducing the quantity of Be required by breeder blankets would help to alleviate the problem to some extent. In addition, it is important that the reduction in the Be quantity does not diminish the blanket's performance in key aspects such as the tritium breeding ratio (TBR), energy multiplication and peak nuclear heating. Mixed pebble bed designs allow for the multiplier fraction to be varied throughout the blanket. This neutronics study used MCNP 6 to investigate linear variations of the multiplier fraction in relation to blanket depth, in order to better utilise the important multiplying Be(n,2n) and breeding reactions. Blankets with a uniform multiplier fraction showed little scope for reduction in Be mass. Blankets with varying multiplier fractions were able to simultaneously use 10% less Be, increase the energy amplification by 1%, reduce the peak heating by 7% and maintaining a sufficient TBR when compared to the performance achievable using a uniform composition.

CIRCULATING MOVING BED COMBUSTION PROOF OF CONCEPT

Energy Technology Data Exchange (ETDEWEB)

Jukkola, Glen

2010-06-30

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

Space debris: modeling and detectability

Science.gov (United States)

Wiedemann, C.; Lorenz, J.; Radtke, J.; Kebschull, C.; Horstmann, A.; Stoll, E.

2017-01-01

High precision orbit determination is required for the detection and removal of space debris. Knowledge of the distribution of debris objects in orbit is necessary for orbit determination by active or passive sensors. The results can be used to investigate the orbits on which objects of a certain size at a certain frequency can be found. The knowledge of the orbital distribution of the objects as well as their properties in accordance with sensor performance models provide the basis for estimating the expected detection rates. Comprehensive modeling of the space debris environment is required for this. This paper provides an overview of the current state of knowledge about the space debris environment. In particular non-cataloged small objects are evaluated. Furthermore, improvements concerning the update of the current space debris model are addressed. The model of the space debris environment is based on the simulation of historical events, such as fragmentations due to explosions and collisions that actually occurred in Earth orbits. The orbital distribution of debris is simulated by propagating the orbits considering all perturbing forces up to a reference epoch. The modeled object population is compared with measured data and validated. The model provides a statistical distribution of space objects, according to their size and number. This distribution is based on the correct consideration of orbital mechanics. This allows for a realistic description of the space debris environment. Subsequently, a realistic prediction can be provided concerning the question, how many pieces of debris can be expected on certain orbits. To validate the model, a software tool has been developed which allows the simulation of the observation behavior of ground-based or space-based sensors. Thus, it is possible to compare the results of published measurement data with simulated detections. This tool can also be used for the simulation of sensor measurement campaigns. It is

Detecting debris flows using ground vibrations

Science.gov (United States)

LaHusen, Richard G.

1998-01-01

Debris flows are rapidly flowing mixtures of rock debris, mud, and water that originate on steep slopes. During and following volcanic eruptions, debris flows are among the most destructive and persistent hazards. Debris flows threaten lives and property not only on volcanoes but far downstream in valleys that drain volcanoes where they arrive suddenly and inundate entire valley bottoms. Debris flows can destroy vegetation and structures in their path, including bridges and buildings. Their deposits can cover roads and railways, smother crops, and fill stream channels, thereby reducing their flood-carrying capacity and navigability.

Fluidised bed heat exchangers

International Nuclear Information System (INIS)

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

1974-01-01

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

Characterization of hydrodynamics and solids mixing in fluidized beds involving biomass

Science.gov (United States)

Fotovat, Farzam

This thesis focuses on the characterization of hydrodynamics and mixing phenomena in fluidized beds containing mixtures of sand and irregular biomass particles. The first objective of this study is understanding the effect of the large biomass particles on the bubbling characteristics and gas distribution pattern of sand fluidized beds. The second objective is the characterization of mixing/segregation of biomass and sand particles under fluidization conditions. A variety of experimental techniques are employed to study the behavior of two constituting phases of a fluidized bed, i.e., dilute (bubble) and dense (emulsion) phases. Exploring the characteristic fluidization velocities of sand-biomass mixtures unveils that the onset of bubbling in these systems occurs at a higher gas velocity compared to that of the initial fluidization velocity (Uif). The initial bubbling velocity (Uib), the final fluidization velocity ( Uff), and the transition gas velocity from bubbling to turbulent regime (Uc) rise by increasing the fraction of biomass in the mixture. Statistical analysis of the pressure signal at top of the bed reveals that increasing the biomass load hinders the evolution of bubbles at a low gas velocity (Uactive biomass particle is tracked for a long period of time and its instantaneous position is recorded. The acquired data is then processed to achieve the time-averaged concentration profile of biomass particles. This profile represents the segregation of biomass particles, which tend to accumulate in the upper levels of the bed. Changes in the fraction of biomass with increasing gas velocity are inferred from the local changes of the time-averaged pressure drop values at the top of the bed. To determine the parameters affecting the movement and segregation of biomass particles, their circulatory motion is also scrutinized using the RPT data. The circulation of biomass is impeded when the load of biomass rises at U=0.36 m/s, resulting in a more pronounced

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

International Nuclear Information System (INIS)

Almeida, Lucilla C.; Su, Jian

2015-01-01

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

Physical-Mathematical Model for Fixed-Bed Solid Fuel Gasification Process Simulation

Directory of Open Access Journals (Sweden)

Slyusarskiy Konstantin V.

2017-01-01

Full Text Available Phycial-mathmatical model for fixed-bed coal gasification process simulation is proposed. The heterogeneous carbon oxidation chemical reactions were simulated via Arrhenius equation while homogeneous reactions in gas phase were calculated using Gibbs free energy minimization procedure. The syngas component concentration field and fuel conversion distribution as well as syngas final temperature and composition were defined for fixed bed gasification of T-grade coal of Kuznetskiy deposit. The optimal fuel residence time and gasifyer specific productivity were defined. The prevail reactions in oxidizing and reduction zones together with its height were defined.

Numerical analysis of a heat-generating, truncated conical porous bed in a fluid-filled enclosure

International Nuclear Information System (INIS)

Chakravarty, Aranyak; Datta, Priyankan; Ghosh, Koushik; Sen, Swarnendu; Mukhopadhyay, Achintya

2016-01-01

Analysis of natural convection in enclosures containing heat generating porous medium has important applications related to geothermal, chemical, thermal and nuclear energy such as in-vessel cooling of debris beds in nuclear reactors, cooling of coal stockpiles etc. The objective of the present numerical study is to characterise the pattern of fluid flow and energy transfer during steady laminar natural convective flow in a cylindrical enclosure with a centrally placed heat generating porous bed. Flow through porous region is modelled using Darcy–Brinkmann–Forchheimer model and local thermal equilibrium is assumed for the porous region. Analysis is carried out for a wide range of Rayleigh number (Ra), Darcy number (Da) and thermal conductivity ratio, as well as for different bed geometries. It is observed that in addition to Ra and Da, the bed geometry also plays a very important role in determining flow field and temperature distribution within the enclosure. Interestingly, a significant change is observed in energy transfer mode from the porous bed corresponding to specific values of bed permeability and bed heat generation rate. This is characterised in terms of Ra and Da. Further, it is observed that this change in energy transfer mode is highly dependent on Ra. - Highlights: • Natural convection is analysed in an enclosure with a heat generating porous bed. • Effect of dimensionless parameters as well as bed geometry has been investigated. • Energy transfer mechanism from porous bed changes with dimensionless parameters. • Bed geometry significantly affects fluid flow and energy transfer in the enclosure.

Study of the obtainment of Mo{sub 2}C by gas-solid reaction in a fixed and rotary bed reactor; Estudo da obtencao de Mo{sub 2}C por reacao gas-solido em reator de leito fixo e rotativo

Energy Technology Data Exchange (ETDEWEB)

Araujo, C.P.B. de; Souza, C.P. de; Souto, M.V.M.; Barbosa, C.M.; Frota, A.V.V.M., E-mail: cpbaraujo@gmail.com [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

2016-07-01

Carbides' synthesis via gas-solid reaction overcomes many of the difficulties found in other processes, requiring lower temperatures and reaction times than traditional metallurgic routes, for example. In carbides' synthesis in fixed bed reactors (FB) the solid precursor is permeated by the reducing/carburizing gas stream forming a packed bed without mobility. The use of a rotary kiln reactor (RK) adds a mixing character to this process, changing its fluid-particle dynamics. In this work ammonium molybdate was subjected to carbo-reduction reaction (CH4 / H2) in both reactors under the same gas flow (15L / h) and temperature (660 ° C) for 180 minutes. Complete conversion was observed Mo2C (dp = 18.9nm modal particles sizes' distribution) in the fixed bed reactor. In the RK reactor this conversion was only partial (∼ 40%) and Mo2C and MoO3 (34nm dp = bimodal) could be observed on the produced XRD pattern. Partial conversion was attributed to the need to use higher solids loading in the reactor CR (50% higher) to avoid solids to centrifuge. (author)

[Research progress in post-fire debris flow].

Science.gov (United States)

Di, Xue-ying; Tao, Yu-zhu

2013-08-01

The occurrence of the secondary disasters of forest fire has significant impacts on the environment quality and human health and safety. Post-fire debris flow is one of the most hazardous secondary disasters of forest fire. To understand the occurrence conditions of post-fire debris flow and to master its occurrence situation are the critical elements in post-fire hazard assessment. From the viewpoints of vegetation, precipitation threshold and debris flow material sources, this paper elaborated the impacts of forest fire on the debris flow, analyzed the geologic and geomorphic conditions, precipitation and slope condition that caused the post-fire debris flow as well as the primary mechanisms of debris-flow initiation caused by shallow landslide or surface runoff, and reviewed the research progress in the prediction and forecast of post-fire debris flow and the related control measures. In the future research, four aspects to be focused on were proposed, i. e., the quantification of the relationships between the fire behaviors and environmental factors and the post-fire debris flow, the quantitative research on the post-fire debris flow initiation and movement processes, the mechanistic model of post-fire debris flow, and the rapid and efficient control countermeasures of post-fire debris flow.

Post-accident heat removal research: A state of the art review

International Nuclear Information System (INIS)

Mueller, U.; Schulenberg, T.

1983-11-01

For a realistic assessment of the consequence of extremely unlikely reactor accidents resulting in core degradation or core meltdown key questions are how to remove the decay heat from the reactor system and how to retain the radioactive core debris within the containment. Usually, this complex of questions is referred to as Post-Accident Heat Removal (PAHR). In this article the research work on PAHR performed by various institutions during the last decade has been reviewed. The main results have been summarized under the chapter headings ''Accident Scenarios,'' - ''Core Debris Accommodation Concepts,'' and ''PAHR Topics.'' Particular emphasis has been placed on the presentation of the following problems: characteristics and coolability of solid core debris in the vector vessel, heat removal from molten pools of core material, and core-melt interaction with structural materials. Some unresolved or insufficiently answered questions relating to special ''PAHR Topics'' have been mentioned or discussed at the end of the particular Chapter. Problem areas of major uncertainty have been identified and listed at the end of the review article. They include the following subjects: formation of debris beds and bed characteristics, post dryout behaviour of particle beds, long-term availability and proper location of heat sinks, creep rupture of structures under high thermal loads. (orig.) [de

The reductive decomposition of calcium sulphate I. Kinetics of the apparent solid-solid reaction

NARCIS (Netherlands)

Kamphuis, B.; Potma, A.W.; Prins, W.; van Swaaij, Willibrordus Petrus Maria

1992-01-01

The reductive decomposition of calcium sulphate by hydrogen is used for the regeneration of calcium-based atmospheric fluidized bed combustion (AFBC) SO2 sorbents. The apparent solid¿solid reaction between CaS and CaSO4, one of the steps involved in the reaction mechanism of the reductive

Thiokol Solid Rocket Motors

Science.gov (United States)

Graves, S. R.

2000-01-01

This paper presents viewgraphs on thiokol solid rocket motors. The topics include: 1) Communications; 2) Military and government intelligence; 3) Positioning satellites; 4) Remote sensing; 5) Space burial; 6) Science; 7) Space manufacturing; 8) Advertising; 9) Space rescue space debris management; 10) Space tourism; 11) Space settlements; 12) Hazardous waste disposal; 13) Extraterrestrial resources; 14) Fast package delivery; and 15) Space utilities.

An experimental study on coolability of a particulate bed with radial stratification or triangular shape

Energy Technology Data Exchange (ETDEWEB)

Thakre, Sachin; Li, Liangxing; Ma, Weimin, E-mail: ma@safety.sci.kth.se

2014-09-15

Highlights: • Dryout heat flux of a particulate bed with radial stratification is obtained. • It was found to be dominated by hydrodynamics in the bigger size of particle layer. • Coolability of a particulate bed with triangular shape is investigated. • The coolability is improved in the triangular bed due to lateral ingression of coolant. • Coolability of both beds is enhanced by a downcomer. - Abstract: This paper deals with the results of an experimental study on the coolability of particulate beds with radial stratification and triangular shape, respectively. The study is intended to get an idea on how the coolability is affected by the different features of a debris bed formed in a severe accident of light water reactors. The experiments were performed on the POMECO-HT facility which was constructed to investigate two-phase flow and heat transfer in particulate beds under either top-flooding or bottom-fed condition. A downcomer is designed to enable investigation of the effectiveness of natural circulation driven coolability. Two homogenous beds were also employed in the present study to compare their dryout power densities with those of the radially stratified bed and the triangular bed. The results show that the dryout heat fluxes of the homogeneous beds at top-flooding condition can be predicted by the Reed model. For the radially stratified bed, the dryout heat flux is dominated by two-phase flow in the columns packed with larger particles, and the dryout occurred initially near the boundary between the middle column and a side column. Given the same volume of particles under top-flooding condition, the dryout power density of the triangular bed is about 69% higher than that of the homogenous bed. The coolability of all the beds is enhanced by bottom-fed coolant driven by either forced injection or downcomer-induced natural circulation.

An experimental study on coolability of a particulate bed with radial stratification or triangular shape

International Nuclear Information System (INIS)

Thakre, Sachin; Li, Liangxing; Ma, Weimin

2014-01-01

Highlights: • Dryout heat flux of a particulate bed with radial stratification is obtained. • It was found to be dominated by hydrodynamics in the bigger size of particle layer. • Coolability of a particulate bed with triangular shape is investigated. • The coolability is improved in the triangular bed due to lateral ingression of coolant. • Coolability of both beds is enhanced by a downcomer. - Abstract: This paper deals with the results of an experimental study on the coolability of particulate beds with radial stratification and triangular shape, respectively. The study is intended to get an idea on how the coolability is affected by the different features of a debris bed formed in a severe accident of light water reactors. The experiments were performed on the POMECO-HT facility which was constructed to investigate two-phase flow and heat transfer in particulate beds under either top-flooding or bottom-fed condition. A downcomer is designed to enable investigation of the effectiveness of natural circulation driven coolability. Two homogenous beds were also employed in the present study to compare their dryout power densities with those of the radially stratified bed and the triangular bed. The results show that the dryout heat fluxes of the homogeneous beds at top-flooding condition can be predicted by the Reed model. For the radially stratified bed, the dryout heat flux is dominated by two-phase flow in the columns packed with larger particles, and the dryout occurred initially near the boundary between the middle column and a side column. Given the same volume of particles under top-flooding condition, the dryout power density of the triangular bed is about 69% higher than that of the homogenous bed. The coolability of all the beds is enhanced by bottom-fed coolant driven by either forced injection or downcomer-induced natural circulation

Debris flow analysis with a one dimensional dynamic run-out model that incorporates entrained material

Science.gov (United States)

Luna, Byron Quan; Remaître, Alexandre; van Asch, Theo; Malet, Jean-Philippe; van Westen, Cees

2010-05-01

Estimating the magnitude and the intensity of rapid landslides like debris flows is fundamental to evaluate quantitatively the hazard in a specific location. Intensity varies through the travelled course of the flow and can be described by physical features such as deposited volume, velocities, height of the flow, impact forces and pressures. Dynamic run-out models are able to characterize the distribution of the material, its intensity and define the zone where the elements will experience an impact. These models can provide valuable inputs for vulnerability and risk calculations. However, most dynamic run-out models assume a constant volume during the motion of the flow, ignoring the important role of material entrained along its path. Consequently, they neglect that the increase of volume enhances the mobility of the flow and can significantly influence the size of the potential impact area. An appropriate erosion mechanism needs to be established in the analyses of debris flows that will improve the results of dynamic modeling and consequently the quantitative evaluation of risk. The objective is to present and test a simple 1D debris flow model with a material entrainment concept based on limit equilibrium considerations and the generation of excess pore water pressure through undrained loading of the in situ bed material. The debris flow propagation model is based on a one dimensional finite difference solution of a depth-averaged form of the Navier-Stokes equations of fluid motions. The flow is treated as a laminar one phase material, which behavior is controlled by a visco-plastic Coulomb-Bingham rheology. The model parameters are evaluated and the model performance is tested on a debris flow event that occurred in 2003 in the Faucon torrent (Southern French Alps).

Comparison of an Inductance In-Line Oil Debris Sensor and Magnetic Plug Oil Debris Sensor

Science.gov (United States)

Dempsey, Paula J.; Tuck, Roger; Showalter, Stephen

2012-01-01

The objective of this research was to compare the performance of an inductance in-line oil debris sensor and magnetic plug oil debris sensor when detecting transmission component health in the same system under the same operating conditions. Both sensors were installed in series in the NASA Glenn Spiral Bevel Gear Fatigue Rig during tests performed on 5 gear sets (pinion/gear) when different levels of damage occurred on the gear teeth. Results of this analysis found both the inductance in-line oil debris sensor and magnetic plug oil debris sensor have benefits and limitations when detecting gearbox component damage.

Numerical simulation of a full-loop circulating fluidized bed under different operating conditions

Energy Technology Data Exchange (ETDEWEB)

Xu, Yupeng [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Musser, Jordan M. [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Li, Tingwen [National Energy Technology Lab. (NETL), Morgantown, WV (United States); AECOM, Morgantown, WV (United States); Rogers, William A. [National Energy Technology Lab. (NETL), Morgantown, WV (United States)

2017-10-17

Both experimental and computational studies of the fluidization of high-density polyethylene (HDPE) particles in a small-scale full-loop circulating fluidized bed are conducted. Experimental measurements of pressure drop are taken at different locations along the bed. The solids circulation rate is measured with an advanced Particle Image Velocimetry (PIV) technique. The bed height of the quasi-static region in the standpipe is also measured. Comparative numerical simulations are performed with a Computational Fluid Dynamics solver utilizing a Discrete Element Method (CFD-DEM). This paper reports a detailed and direct comparison between CFD-DEM results and experimental data for realistic gas-solid fluidization in a full-loop circulating fluidized bed system. The comparison reveals good agreement with respect to system component pressure drop and inventory height in the standpipe. In addition, the effect of different drag laws applied within the CFD simulation is examined and compared with experimental results.

Marine debris removal: one year of effort by the Georgia Sea Turtle-Center-Marine Debris Initiative.

Science.gov (United States)

Martin, Jeannie Miller

2013-09-15

Once in the marine environment, debris poses a significant threat to marine life that can be prevented through the help of citizen science. Marine debris is any manufactured item that enters the ocean regardless of source, commonly plastics, metal, wood, glass, foam, cloth, or rubber. Citizen science is an effective way to engage volunteers in conservation initiatives and provide education and skill development. The Georgia Sea Turtle Center Marine Debris Initiative (GSTC-MDI) is a grant funded program developed to engage citizens in the removal of marine debris from the beaches of Jekyll Island, GA, USA and the surrounding areas. During the first year of effort, more than 200 volunteers donated over 460 h of service to the removal of marine debris. Of the debris removed, approximately 89% were plastics, with a significant portion being cigarette materials. Given the successful first year, the GSTC-MDI was funded again for a second year. Copyright © 2013 Elsevier Ltd. All rights reserved.

An Ontological Architecture for Orbital Debris Data

OpenAIRE

Rovetto, Robert J.

2017-01-01

The orbital debris problem presents an opportunity for inter-agency and international cooperation toward the mutually beneficial goals of debris prevention, mitigation, remediation, and improved space situational awareness (SSA). Achieving these goals requires sharing orbital debris and other SSA data. Toward this, I present an ontological architecture for the orbital debris domain, taking steps in the creation of an orbital debris ontology (ODO). The purpose of this ontological system is to ...

Combustion of palm oil solid waste in fluidized bed combustor

International Nuclear Information System (INIS)

Abdullah, I.; Shamsuddin, A.H.; Sopian, K.

2000-01-01

Results of experimental investigations of fluidized bed combustion of palm oil wastes consisting of shell, fibre and empty fruit bunches high heating value of 17450 kJ/kg and low heating value of 14500 kJ/kg. The fluidized bed combuster used has a vessel size of 486 x 10 6 mm 3 , surface area of evaporation tubes and distribution air pipes of 500 mm 2 and 320 mm 2 respectively. It was found that a fuel feeding rate 160 kg/h is required to achieve a steam flow rate of 600 kg/h, with the combustion efficiency 96% and boiler efficiency of 72%, emission level of flue gas NO x at less than 180 ppm, SO 2 at less than 20 ppm are measured in the flue gas. (Author)

Colisional Cloud Debris and Propelled Evasive Maneuvers

Science.gov (United States)

Ferreira, L. S.; Jesus, A. D. C.; Carvalho, T. C. F.; Sousa, R. R.

2017-10-01

Space debris clouds exist at various altitudes in the environment outside the Earth. Fragmentation of debris and/or collision between the debris of a cloud increases the amount of debris, producing smaller debris. This event also increases significantly the chances of collision with operational vehicles in orbit. In this work we study clouds of debris that are close to a spacecraft in relation to its distance from the center of the Earth. The results show several layers of colliding debris depending on their size over time of evasive maneuvers of the vehicle. In addition, we have tested such maneuvers for propulsion systems with a linear and exponential mass variation model. The results show that the linear propulsion system is more efficient.

Sediment delivery in debris-flow torrents: two case studies in the Italian Alps

Science.gov (United States)

Bertoldi, Gabriele; Vincenzo, D'Agostino

2013-04-01

stream length of 1.4 km downstream of the source areas. Topographical survey of these cross sections have been repeated periodically regardless the occurrence of rainstorm events, so directly detecting morphological changes and tracks of new flow depths on the banks. To monitor the recharging rates from the hillslopes surrounding the channel, some sediment traps have been also installed in the Rio Rudan and in the Rio Gadria (8 and 6 sediment traps respectively). Thanks to the time comparison of the cross sections under observation a sediment budget was conducted both for successive flood events and/or for silent periods. This budget has been related to morphological, geometric and flow dependent variables in order to detect the forcing and, in case it exists, a trend of the phenomena. The debris recharge of the channels from the directly connected sediment source areas resulted lowly dependent on the rain storms causing debris flows, and more related with the year rainfall, local bank instabilities and failures, which might be amplified by the channel bed moisture before/after the debris-flow occurrence.

Mathematical modelling of fluidized bed reactors

Energy Technology Data Exchange (ETDEWEB)

Werther, J [BASF A.G., Ludwigshafen am Rhein (Germany, F.R.)

1978-11-01

Among the many fluidized bed models to be found in the literature, the two-phase model originally proposed by May has proved most suitable for accomodation of recent advances in flow mechanics: this model resolves the gas/solids fluidized bed into a bubble phase and a suspension phase surrounding the bubbles. Its limitation to slow reactions is a disadvantage. On the basis of the analogy between fluidized beds and gas/liquid systems, a general two-phase model that is valid for fast reactions has therefore been developed and its validity is confirmed by comparison with the experimental results obtained by others. The model describes mass transfer across the phase interface with the aid of the film theory known from gas/liquid reactor technology, and the reaction occurring in the suspension phase as a pseudo-homogeneous reaction. Since the dependence of the performance of fluidized bed reactors upon geometry is accounted for, the model can also be used for scale-up calculations. Its use is illustrated with the aid of design diagrams.

Debris Examination Using Ballistic and Radar Integrated Software

Science.gov (United States)

Griffith, Anthony; Schottel, Matthew; Lee, David; Scully, Robert; Hamilton, Joseph; Kent, Brian; Thomas, Christopher; Benson, Jonathan; Branch, Eric; Hardman, Paul;

Simulation of granular and gas-solid flows using discrete element method

Science.gov (United States)

Boyalakuntla, Dhanunjay S.

2003-10-01

In recent years there has been increased research activity in the experimental and numerical study of gas-solid flows. Flows of this type have numerous applications in the energy, pharmaceuticals, and chemicals process industries. Typical applications include pulverized coal combustion, flow and heat transfer in bubbling and circulating fluidized beds, hopper and chute flows, pneumatic transport of pharmaceutical powders and pellets, and many more. The present work addresses the study of gas-solid flows using computational fluid dynamics (CFD) techniques and discrete element simulation methods (DES) combined. Many previous studies of coupled gas-solid flows have been performed assuming the solid phase as a continuum with averaged properties and treating the gas-solid flow as constituting of interpenetrating continua. Instead, in the present work, the gas phase flow is simulated using continuum theory and the solid phase flow is simulated using DES. DES treats each solid particle individually, thus accounting for its dynamics due to particle-particle interactions, particle-wall interactions as well as fluid drag and buoyancy. The present work involves developing efficient DES methods for dense granular flow and coupling this simulation to continuum simulations of the gas phase flow. Simulations have been performed to observe pure granular behavior in vibrating beds. Benchmark cases have been simulated and the results obtained match the published literature. The dimensionless acceleration amplitude and the bed height are the parameters governing bed behavior. Various interesting behaviors such as heaping, round and cusp surface standing waves, as well as kinks, have been observed for different values of the acceleration amplitude for a given bed height. Furthermore, binary granular mixtures (granular mixtures with two particle sizes) in a vibrated bed have also been studied. Gas-solid flow simulations have been performed to study fluidized beds. Benchmark 2D

SCDAP/RELAP5 modeling of fluid heat transfer and flow losses through porous debris in a light water reactor

International Nuclear Information System (INIS)

Harvego, E. A.; Siefken, L. J.

2000-01-01

The SCDAP/RELAP5 code is being developed at the Idaho National Engineering and Environmental Laboratory under the primary sponsorship of the U.S. Nuclear Regulatory Commission (NRC) to provide best-estimate transient simulations of light water reactor coolant systems during severe accidents. This paper describes the modeling approach used in the SCDAP/RELAP5 code to calculate fluid heat transfer and flow losses through porous debris that has accumulated in the vessel lower head and core regions during the latter stages of a severe accident. The implementation of heat transfer and flow loss correlations into the code is discussed, and calculations performed to assess the validity of the modeling approach are described. The different modes of heat transfer in porous debris include: (1) forced convection to liquid, (2) forced convection to gas, (3) nucleate boiling, (4) transition boiling, (5) film boiling, and (6) transition from film boiling to convection to vapor. The correlations for flow losses in porous debris include frictional and form losses. The correlations for flow losses were integrated into the momentum equations in the RELAP5 part of the code. Since RELAP5 is a very general non-homogeneous non-equilibrium thermal-hydraulics code, the resulting modeling methodology is applicable to a wide range of debris thermal-hydraulic conditions. Assessment of the SCDAP/RELAP5 debris bed thermal-hydraulic models included comparisons with experimental measurements and other models available in the open literature. The assessment calculations, described in the paper, showed that SCDAP/RELAP5 is capable of calculating the heat transfer and flow losses occurring in porous debris regions that may develop in a light water reactor during a severe accident

Debris filtering effectiveness and pressure drop tests of debris resistance-bottom end piece

International Nuclear Information System (INIS)

Chung, Moon Ki; Song, Chul Hwa; Chung, Heung June; Won, Soon Yeun; Cho, Young Ro; Kim, Bok Deuk

1992-03-01

In this final report, described are the test conditions and test procedures for the debris filtering effectiveness and pressure drop tests for developing the Debris Resistance-Bottom End Piece (DR-BEP). And the test results are tabulated for later evaluation. (Author)

Active Space Debris Removal System

Directory of Open Access Journals (Sweden)

Gabriele GUERRA

2017-06-01

Full Text Available Since the start of the space era, more than 5000 launches have been carried out, each carrying satellites for many disparate uses, such as Earth observation or communication. Thus, the space environment has become congested and the problem of space debris is now generating some concerns in the space community due to our long-lived belief that “space is big”. In the last few years, solutions to this problem have been proposed, one of those is Active Space Debris Removal: this method will reduce the increasing debris growth and permit future sustainable space activities. The main idea of the method proposed below is a drag augmentation system: use a system capable of putting an expanded foam on a debris which will increase the area-to-mass ratio to increase the natural atmospheric drag and solar pressure. The drag augmentation system proposed here requires a docking system; the debris will be pushed to its release height and then, after un-docking, an uncontrolled re-entry takes place ending with a burn up of the object and the foam in the atmosphere within a given time frame. The method requires an efficient way to change the orbit between two debris. The present paper analyses such a system in combination with an Electric Propulsion system, and emphasizes the choice of using two satellites to remove five effective rockets bodies debris within a year.

Backwater development by woody debris

Science.gov (United States)

Geertsema, Tjitske; Torfs, Paul; Teuling, Ryan; Hoitink, Ton

2017-04-01

Placement of woody debris is a common method for increasing ecological values in river and stream restoration, and is thus widely used in natural environments. Water managers, however, are afraid to introduce wood in channels draining agricultural and urban areas. Upstream, it may create backwater, depending on hydrodynamic characteristics including the obstruction ratio, the Froude number and the surface level gradient. Patches of wood may trigger or counter morphological activity, both laterally, through bank erosion and protection, and vertically, with pool and riffle formation. Also, a permeable construction composed of wood will weather over time. Both morphodynamic activity and weathering cause backwater effects to change in time. The purpose of this study is to quantify the time development of backwater effects caused by woody debris. Hourly water levels gauged upstream and downstream of patches and discharge are collected for five streams in the Netherlands. The water level drop over the woody debris patch relates to discharge in the streams. This relation is characterized by an increasing water level difference for an increasing discharge, up to a maximum. If the discharge increases beyond this level, the water level difference reduces to the value that may represent the situation without woody debris. This reduction depends primarily on the obstruction ratio of the woody debris in the channel cross-section. Morphologic adjustments in the stream and reorientation of the woody material reduce the water level drop over the patches in time. Our results demonstrate that backwater effects can be reduced by optimizing the location where woody debris is placed and manipulating the obstruction ratio. Current efforts are focussed on representing woody debris in a one-dimensional numerical model, aiming to obtain a generic tool to achieve a stream design with woody debris that minimizes backwater.

NASA's New Orbital Debris Engineering Model, ORDEM2010

Science.gov (United States)

Krisko, Paula H.

2010-01-01

This paper describes the functionality and use of ORDEM2010, which replaces ORDEM2000, as the NASA Orbital Debris Program Office (ODPO) debris engineering model. Like its predecessor, ORDEM2010 serves the ODPO mission of providing spacecraft designers/operators and debris observers with a publicly available model to calculate orbital debris flux by current-state-of-knowledge methods. The key advance in ORDEM2010 is the input file structure of the yearly debris populations from 1995-2035 of sizes 10 micron - 1 m. These files include debris from low-Earth orbits (LEO) through geosynchronous orbits (GEO). Stable orbital elements (i.e., those that do not randomize on a sub-year timescale) are included in the files as are debris size, debris number, material density, random error and population error. Material density is implemented from ground-test data into the NASA breakup model and assigned to debris fragments accordingly. The random and population errors are due to machine error and uncertainties in debris sizes. These high-fidelity population files call for a much higher-level model analysis than what was possible with the populations of ORDEM2000. Population analysis in the ORDEM2010 model consists of mapping matrices that convert the debris population elements to debris fluxes. One output mode results in a spacecraft encompassing 3-D igloo of debris flux, compartmentalized by debris size, velocity, pitch, and yaw with respect to spacecraft ram direction. The second output mode provides debris flux through an Earth-based telescope/radar beam from LEO through GEO. This paper compares the new ORDEM2010 with ORDEM2000 in terms of processes and results with examples of specific orbits.

Improving hydrolysis of food waste in a leach bed reactor

Energy Technology Data Exchange (ETDEWEB)

Browne, James D.; Allen, Eoin; Murphy, Jerry D., E-mail: jerry.murphy@ucc.ie

2013-11-15

Highlights: • This paper assesses leaching of food waste in a two phase digestion system. • Leaching is assessed with and without an upflow anaerobic sludge blanket (UASB). • Without the UASB, low pH reduces hydrolysis, while increased flows increase leaching. • Inclusion of the UASB increases pH to optimal levels and greatly improves leaching. • The optimal conditions are suggested as low flow with connection to the UASB. - Abstract: This paper examines the rate of degradation of food waste in a leach bed reactor (LBR) under four different operating conditions. The effects of leachate recirculation at a low and high flow rate are examined with and without connection to an upflow anaerobic sludge blanket (UASB). Two dilution rates of the effective volume of the leach bed reactors were investigated: 1 and 6 dilutions per LBR per day. The increase in dilution rate from 1 to 6 improved the destruction of volatile solids without connection to the UASB. However connection to the UASB greatly improved the destruction of volatile solids (by almost 60%) at the low recirculation rate of 1 dilution per day. The increase in volatile solids destruction with connection to the UASB was attributed to an increase in leachate pH and buffering capacity provided by recirculated effluent from the UASB to the leach beds. The destruction of volatile solids for both the low and high dilution rates was similar with connection to the UASB, giving 82% and 88% volatile solids destruction respectively. This suggests that the most efficient leaching condition is 1 dilution per day with connection to the UASB.

Improving hydrolysis of food waste in a leach bed reactor

International Nuclear Information System (INIS)

Browne, James D.; Allen, Eoin; Murphy, Jerry D.

2013-01-01

Highlights: • This paper assesses leaching of food waste in a two phase digestion system. • Leaching is assessed with and without an upflow anaerobic sludge blanket (UASB). • Without the UASB, low pH reduces hydrolysis, while increased flows increase leaching. • Inclusion of the UASB increases pH to optimal levels and greatly improves leaching. • The optimal conditions are suggested as low flow with connection to the UASB. - Abstract: This paper examines the rate of degradation of food waste in a leach bed reactor (LBR) under four different operating conditions. The effects of leachate recirculation at a low and high flow rate are examined with and without connection to an upflow anaerobic sludge blanket (UASB). Two dilution rates of the effective volume of the leach bed reactors were investigated: 1 and 6 dilutions per LBR per day. The increase in dilution rate from 1 to 6 improved the destruction of volatile solids without connection to the UASB. However connection to the UASB greatly improved the destruction of volatile solids (by almost 60%) at the low recirculation rate of 1 dilution per day. The increase in volatile solids destruction with connection to the UASB was attributed to an increase in leachate pH and buffering capacity provided by recirculated effluent from the UASB to the leach beds. The destruction of volatile solids for both the low and high dilution rates was similar with connection to the UASB, giving 82% and 88% volatile solids destruction respectively. This suggests that the most efficient leaching condition is 1 dilution per day with connection to the UASB

Comparison of coal/solid recovered fuel (SRF) with coal/refuse derived fuel (RDF) in a fluidised bed reactor

International Nuclear Information System (INIS)

Wagland, S.T.; Kilgallon, P.; Coveney, R.; Garg, A.; Smith, R.; Longhurst, P.J.; Pollard, S.J.T.; Simms, N.

2011-01-01

An experimental study was undertaken to compare the differences between municipal solid waste (MSW) derived solid recovered fuel (SRF) (complying with CEN standards) and refuse derived fuel (RDF). Both fuels were co-combusted with coal in a 50 kW fluidised bed combustor and the metal emissions were compared. Synthetic SRF was prepared in the laboratory by grinding major constituents of MSW such as paper, plastic, textile and wood. RDF was obtained from a local mechanical treatment plant. Heavy metal emissions in flue gas and ash samples from the (coal + 10% SRF) fuel mixture were found to be within the acceptable range and were generally lower than that obtained for coal + 10% RDF fuel mixture. The relative distribution of heavy metals in ash components and the flue gas stream shows the presence of a large fraction (up to 98%) of most of the metals in the ash (except Hg and As). Thermo-gravimetric (TG) analysis of SRF constituents was performed to understand the behaviour of fuel mixtures in the absence and presence of air. The results obtained from the experimental study will enhance the confidence of fuel users towards using MSW-derived SRF as an alternative fuel.

Evaluation of materials for retention of sodium and core debris in reactor systems. Annual progress report, September 1977-December 1978

International Nuclear Information System (INIS)

Swanson, D.G.; Zehms, E.H.; McClelland, J.D.; Meyer, R.A.; van Paassen, H.L.L.

1978-12-01

This report considers some of the consequences of a hypothetical core disruptive accident in a nuclear reactor. The interactions expected between molten core debris, liquid sodium, and materials that might be employed in an ex-vessel sacrificial-bed or in the reactor building are discussed. Experimental work performed for NRC by Sandia Laboratories and Hanford Engineering Development Laboratory on the interactions between liquid sodium and basalt concrete is reviewed. Studies of molten steel interactions with concrete at Sandia Laboratories and molten UO 2 interactions with concrete at The Aerospace Corporation are also discussed. The potential of MgO for use in core containment is discussed and refractory materials other than MgO are reviewed. Finally, results from earlier experiments with molten core debris and various materials performed at The Aerospace Corporation are presented

Plastic Beaches: occurrence and accumulation of marine debris on barrier islands in the Gulf of Mexico

Science.gov (United States)

Wessel, C.; Albins, K.; Cebrian, J.

2016-02-01

Marine debris is any persistent solid material that is manufactured or processed and directly or indirectly, intentionally or unintentionally, disposed of or abandoned into the marine environment (33USC§1951). Marine debris is an economic, environmental, human health and aesthetic problem posing a complex challenge. Coastal communities are among the most seriously affected because of increased expenses for beach cleaning, public health and waste disposal, as well as a loss of income from decreased tourism. To better document this problem we are monitoring the occurrence and accumulation rate of marine debris on 6 barrier islands in the northern Gulf of Mexico (nGoM). Surveys are conducted at low tide and consist of 100m-long transects along the shoreline extending from the water edge to the upland shoreline limit. All debris larger than 5 mm is collected and recorded. Debris is then sorted by material, and dry mass is recorded. With this information we are investigating four specific questions: (1) what are the major types and possible sources (land or ocean based) of shoreline debris; (2) does the rate of debris deposition onto the shoreline show seasonal oscillations; (3) how does debris deposition change from east to west in the nGoM; and (4) what are the possible causes of the temporal and spatial trends found (e.g. rainfall and runoff, human population, boat traffic)? During the first year of sampling we are beginning to see trends emerge. More trash consistently washes up on the ocean side versus the sound side of the barrier islands, which suggests either large amounts of trash in the nGoM is ocean-based debris, or it is driven by beach goers, or both. In addition, we have found a significant increase in the amount of trash on the shoreline during tourist/boating season (May to September), although trash items tend to be smaller in size during that season. At the presentation we will discuss these and other trends that emerge with a more complete data set.

On the influence of debris in glacier melt modelling: a new temperature-index model accounting for the debris thickness feedback

Science.gov (United States)

Carenzo, Marco; Mabillard, Johan; Pellicciotti, Francesca; Reid, Tim; Brock, Ben; Burlando, Paolo

2013-04-01

The increase of rockfalls from the surrounding slopes and of englacial melt-out material has led to an increase of the debris cover extent on Alpine glaciers. In recent years, distributed debris energy-balance models have been developed to account for the melt rate enhancing/reduction due to a thin/thick debris layer, respectively. However, such models require a large amount of input data that are not often available, especially in remote mountain areas such as the Himalaya. Some of the input data such as wind or temperature are also of difficult extrapolation from station measurements. Due to their lower data requirement, empirical models have been used in glacier melt modelling. However, they generally simplify the debris effect by using a single melt-reduction factor which does not account for the influence of debris thickness on melt. In this paper, we present a new temperature-index model accounting for the debris thickness feedback in the computation of melt rates at the debris-ice interface. The empirical parameters (temperature factor, shortwave radiation factor, and lag factor accounting for the energy transfer through the debris layer) are optimized at the point scale for several debris thicknesses against melt rates simulated by a physically-based debris energy balance model. The latter has been validated against ablation stake readings and surface temperature measurements. Each parameter is then related to a plausible set of debris thickness values to provide a general and transferable parameterization. The new model is developed on Miage Glacier, Italy, a debris cover glacier in which the ablation area is mantled in near-continuous layer of rock. Subsequently, its transferability is tested on Haut Glacier d'Arolla, Switzerland, where debris is thinner and its extension has been seen to expand in the last decades. The results show that the performance of the new debris temperature-index model (DETI) in simulating the glacier melt rate at the point scale

Governing equations for heat and mass transfer in heat-generating porous beds

International Nuclear Information System (INIS)

Chawla, T.C.; Pedersen, D.R.; Minkowycz, W.J.

1985-01-01

Upon dryout of the bed, the dominant modes of heat transfer are conduction and radiation. Radiation is modeled through the Rosseland approximation. The melting of stainless-steel particulate imbedded in the fuel is modeled by assuming the bed to be a continuum with conduction and radiation as the dominant modes of heat transfer. The molten steel, after it drains to the bottom of the bed, is assumed to disappear into cracks and mortar joints of the MgO bricks. The melting of fuel in the interior of the bed is modeled identically to the steel particulate, except for the bed settling which is more pronounced in the case of fuel melting and is assumed to be instantaneous owing to the significant weight of overlying bed and sodium pool. The molten layer of fuel, as it collects at the bottom of the bed, causes the heatup of the MgO lining to the eutectic temperature (2280 0 C), and the MgO lining begins to dissolve. The density gradient caused by the dissolution of MgO leads to natural convection and mixing in the molten layer. The submerged fuel particulate also begins to dissolve in the molten solution and ultimately leads to the conversion of debris to a molten pool of fuel and MgO. The process of penetration of the MgO lining continues until the mixing process lowers the concentration of fuel in the volume of the pool to the level where the internal heat rate per unit volume is not enough to keep the body of the pool molten and leads to freezing in the cooler part of the pool. As the molten pool reaches a frozen or a quiescent state, the MgO brick lining thickness provided is deemed 'safe' for a given bed loading and the external rate of cooling. (author)

Comparison of ANN (MLP), ANFIS, SVM, and RF models for the online classification of heating value of burning municipal solid waste in circulating fluidized bed incinerators.

Science.gov (United States)

You, Haihui; Ma, Zengyi; Tang, Yijun; Wang, Yuelan; Yan, Jianhua; Ni, Mingjiang; Cen, Kefa; Huang, Qunxing

2017-10-01

The heating values, particularly lower heating values of burning municipal solid waste are critically important parameters in operating circulating fluidized bed incineration systems. However, the heating values change widely and frequently, while there is no reliable real-time instrument to measure heating values in the process of incinerating municipal solid waste. A rapid, cost-effective, and comparative methodology was proposed to evaluate the heating values of burning MSW online based on prior knowledge, expert experience, and data-mining techniques. First, selecting the input variables of the model by analyzing the operational mechanism of circulating fluidized bed incinerators, and the corresponding heating value was classified into one of nine fuzzy expressions according to expert advice. Development of prediction models by employing four different nonlinear models was undertaken, including a multilayer perceptron neural network, a support vector machine, an adaptive neuro-fuzzy inference system, and a random forest; a series of optimization schemes were implemented simultaneously in order to improve the performance of each model. Finally, a comprehensive comparison study was carried out to evaluate the performance of the models. Results indicate that the adaptive neuro-fuzzy inference system model outperforms the other three models, with the random forest model performing second-best, and the multilayer perceptron model performing at the worst level. A model with sufficient accuracy would contribute adequately to the control of circulating fluidized bed incinerator operation and provide reliable heating value signals for an automatic combustion control system. Copyright © 2017 Elsevier Ltd. All rights reserved.

Controlling the Growth of Future LEO Debris Populations with Active Debris Removal

Science.gov (United States)

Liou, J.-C.; Johnson, N. L.; Hill, N. M.

2008-01-01

Active debris removal (ADR) was suggested as a potential means to remediate the low Earth orbit (LEO) debris environment as early as the 1980s. The reasons ADR has not become practical are due to its technical difficulties and the high cost associated with the approach. However, as the LEO debris populations continue to increase, ADR may be the only option to preserve the near-Earth environment for future generations. An initial study was completed in 2007 to demonstrate that a simple ADR target selection criterion could be developed to reduce the future debris population growth. The present paper summarizes a comprehensive study based on more realistic simulation scenarios, including fragments generated from the 2007 Fengyun-1C event, mitigation measures, and other target selection options. The simulations were based on the NASA long-term orbital debris projection model, LEGEND. A scenario, where at the end of mission lifetimes, spacecraft and upper stages were moved to 25-year decay orbits, was adopted as the baseline environment for comparison. Different annual removal rates and different ADR target selection criteria were tested, and the resulting 200-year future environment projections were compared with the baseline scenario. Results of this parametric study indicate that (1) an effective removal strategy can be developed based on the mass and collision probability of each object as the selection criterion, and (2) the LEO environment can be stabilized in the next 200 years with an ADR removal rate of five objects per year.

Disaster Debris Recovery Database - Landfills

Data.gov (United States)

U.S. Environmental Protection Agency — The US EPA Disaster Debris Recovery Database (DDRD) promotes the proper recovery, recycling, and disposal of disaster debris for emergency responders at the federal,...

Disaster Debris Recovery Database - Recovery

Data.gov (United States)

U.S. Environmental Protection Agency — The US EPA Disaster Debris Recovery Database (DDRD) promotes the proper recovery, recycling, and disposal of disaster debris for emergency responders at the federal,...

Bubble Swarm Rise Velocity in Fluidized Beds.

Czech Academy of Sciences Publication Activity Database

Punčochář, Miroslav; Růžička, Marek; Šimčík, Miroslav

2016-01-01

Roč. 152, OCT 2 (2016), s. 84-94 ISSN 0009-2509 R&D Projects: GA ČR(CZ) GA15-05534S Institutional support: RVO:67985858 Keywords : bubbling fluidized bed * gas-solid * bubble swarm velocity Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.895, year: 2016

Circumstellar Gas in Young Planetary Debris Disks

Science.gov (United States)

Roberge, A.

Circumstellar (CS) disks orbiting young stars fall into two categories: primordial disks, composed of unprocessed interstellar dust and gas, and debris disks, produced by the destruction of solid planetary bodies. In the first class, the most abundant gas is H_2; in the second, it appears that the H_2 gas has disappeared, possibly through incorporation into gas giant planets. The lifetime of H_2 gas in a CS disk is therefore of great importance, as it dictates the timescale for the formation of giant planets. FUSE observations of H_2 in CS disk systems have shown that FUV absorption spectroscopy may sensitively probe for small amounts of gas along the line of sight to the star. Most importantly, the FUSE non-detection of H_2 gas in the Beta Pictoris disk suggests that the primordial gas lifetime is less than about 12 Myr, and that gas giant planets must form very quickly. However, this suggestion is based on one system, and needs to be tested in additional systems with a range of ages, especially since there are indications that age is not the only factor in the evolution of a CS disk. We propose for FUSE observations of 3 additional debris disk systems, Fomalhaut, HD3003, and HD2884. Fomalhaut is an intermediate age debris disk, one of the Fabulous Four CS disks first discovered in 1984. The other two disks are younger, with ages similar to that of Beta Pic. All three stars are brighter in the FUV than Beta Pic, permitting us to sensitively probe for traces of H_2 gas. We will also measure the amount of secondary atomic gas produced from planetary bodies in these disks, in an effort to understand the entire evolution of CS gas in young planetary systems.

Heat transfer and flow characteristics around a finned-tube bank heat exchanger in fluidized bed

International Nuclear Information System (INIS)

Honda, Ryosuke; Umekawa, Hisashi; Ozawa, Mamoru

2009-01-01

Principal heat transfer mechanisms in a fluidized bed have been classified into three categories, i.e. solid convection, gas convection and radiation. Among these mechanisms, the solid convection is a dominant mechanism in the bubbling fluidized bed. This solid convection is substantially caused by the bubble movement, thus the visualization of the void fraction distribution becomes a very useful method to understand the characteristics of the fluidized-bed heat exchanger. In this study, the heat transfer coefficient and the void fraction around the heat transfer tube with annuler fin were measured. For the quantitative measurement of the void fraction, neutron radiography and image processing technique were employed. Owing to the existence of the annuler fin, the restriction of the particle movements was put. This restriction suppressed the disturbance caused by tubes, and the influence of the tube arrangement on the flow and heat transfer characteristics could be clearly expressed.

Heat transfer and flow characteristics around a finned-tube bank heat exchanger in fluidized bed

Energy Technology Data Exchange (ETDEWEB)

Honda, Ryosuke [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Umekawa, Hisashi [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan)], E-mail: umekawa@kansai-uac.jp; Ozawa, Mamoru [Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan)

2009-06-21

Principal heat transfer mechanisms in a fluidized bed have been classified into three categories, i.e. solid convection, gas convection and radiation. Among these mechanisms, the solid convection is a dominant mechanism in the bubbling fluidized bed. This solid convection is substantially caused by the bubble movement, thus the visualization of the void fraction distribution becomes a very useful method to understand the characteristics of the fluidized-bed heat exchanger. In this study, the heat transfer coefficient and the void fraction around the heat transfer tube with annuler fin were measured. For the quantitative measurement of the void fraction, neutron radiography and image processing technique were employed. Owing to the existence of the annuler fin, the restriction of the particle movements was put. This restriction suppressed the disturbance caused by tubes, and the influence of the tube arrangement on the flow and heat transfer characteristics could be clearly expressed.

Small satellites and space debris issues

Science.gov (United States)

Yakovlev, M.; Kulik, S.; Agapov, V.

2001-10-01

The objective of this report is the analysis of the tendencies in designing of small satellites (SS) and the effect of small satellites on space debris population. It is shown that SS to include nano- and pico-satellites should be considered as a particularly dangerous source of space debris when elaborating international standards and legal documents concerning the space debris problem, in particular "International Space Debris Mitigation Standard". These issues are in accordance with the IADC goals in its main activity areas and should be carefully considered within the IADC framework.

Incidence of Debris Discs Around FGK Stars in the Solar Neighbourhood