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Thermal analysis of a fluidized bed drying process for crops. Part II: experimental results and model verification
11 00100528
Polyaromatic environmental impact in coal-tire blend atmospheric fluidized bed (AFB) combustion
Mastral, A. M.-e! al. Energy Fuels, 2006, 14,-(l), 164-168. This paper describes how for the first time the use of a waste material can be combined with trying to get cheaper power with a lower consumption of fossil fuel. A coal-tire blend (I:1 in organic matter) was burned in an atmosoheric fluidized bed (AFB) combustion olant with an airflow of 860 ‘L/h and 20% excess oxygen at three’ different combustion temperatures. (750, 850, and 950°C). The combustion conditions were-the same as those used in AFB coal combustion in order to compare the organic emissions obtained with both fuels. As the inorganic components in tires are less and in lower amounts than in coal, the work was focused on organic emissions. Organic emissions from each run were trapped and from each sample, after extraction by sonication with DMF (DMF), the content in polycyclic aromatic hydrocarbons (PAH) was detected by fluorescence-spectroscopy in the synchronous mode (FS). It is concluded that the introduction of tyres in the feeder increases the total PAH amount emitted with respect to coal emissions, with minimal variations at the combustion temperature studied in this work: thus, the higher the temperature, the lower the amount of emitted polycyclic aromatic hydrocarbons.
00100529 Pressurized drop tube furnace test of global coal aasification characteristics chin, Y. et al. Inr. J. Energy Res., 2000, 24, (9) 749-758. Pressurized drop tube furnace (PDTF) tests were performed with an Indonesian sub-bituminous coal while .temperature; oxygen/coal ratio, steam/coal ratio and pressure were systematically varied. The tests were desiened to investieate the effects of these exoerimental parameter; on the pulvehzed coal gasification characteristics at elevated pressure. The results showed that the gasification at elevated pressure -is more productive than that at atmospheric pressure, considering the carbon conversion and cold gas efficiency. The oxygen/coal ratio at the maximum cold gas efficiency ranged between 0.5 and 0.7 g/g. Only when the temperature was sufficiently high, did the increase of steam/coal ratio result in the improvement of cold gas efficiency. As the pressure increased, the contribution of carbon conversion by heterogeneous reactions increased while the conversion by pyrolysis decreased. 00/00530 Reactors with circulating fluldized bed Hartman, M. et al. Chem. Listy, 1999, 93, (12), 788-793. (In Czech) In circulating fluidized beds, a gas stream is used to transport the fine particles upwards and then they are recycled to the bottom of the column. The flow structure is complex and varies widely depending mainly on the vessel geometry, _gas velocity and particle size distribution. Unlike the bubbled bed, the entrv. exit and wall configurations have a strong effect on the flow and mixing patterns of both phases in the column. The tendency is for small particles to form larger, irregular aggregates, which disintegrate and form again at appreciable frequencies. Simple core-annulus models for circulating fluidized beds assume the up-flow of gas and entrained solids in a diluted central core and the down-flow of dense clusters in a relatively thin annular zone near the walls. Rapid heat and mass transfer between gas and particulate solids, uniform temperature in the whole CFB, virtually a plug flow of gas and possible stepwise addition of one or more gaseous components at different levels are among the main features of the CFB reactors. The most rapidly expanding field of CFB application is the efficient combustion and pressure gasification of carbon containing residues, in particular fossil fuels. 00100531
Solid circulation and as bypassing in spoutfluidized bed with draft tube at e9evated pressure
Xiao, R. et al. Ranliao Huaxue Xuebao. 1999. 27, (4). 370-376. (In Chinese) An experimental study on solid circulation and gas bypassing of spoutfluidized bed with draft tube at elevated pressure was performed in a 20 cm diameter cylindrical column with a 600 conical distributor. For bed material, glass beads with a mean diameter of 2.0 mm were used. A new method was develooed for measurine solid circulation under pressure and a gas (CO; tracers) were employed to investigate the characteristics of the gas bypassing. The solid circulation and gas bypassing were strongly dependent bn each other and influenced-by geometric parameters and operation conditions. For predicting solid circulation in a spout-fluidized bed with draft tube at elevated pressure an experimental correlation was proposed.
Stackable heat exchanger for processing carbonaceous material
00/00532
Koppelman, E. PCT Int. Appl. WO 99 50,609 (Cl. F28F9/26), 7 Ott 1999, US Appl. 50,393, 30 Mar 1998. 23. The present invention relates to a heat exchanger apparatus including a plurality of selectively detachable cells to accommodate the treatment of carbonaceous material, such as wood, peat or subbituminous coal, in
Process
heating,
power
and
incineration
(energy
applications
in industry)
varying amounts. The invention also relates to systems and processes for mineral removal from the carbonaceous materials and thereafter upgrading the carbonaceous material for use as fuel. 00100533
Study of the adsorption of CdClz vapor on various minerals using a drop tube furnace
Masseron. R. et al. Environ. Sci. Technol.. 1999. 33. (201. 3634-3640. Fixed bed’or thermogravimetric apparatus were’used’to’perform most of these studies and it is often difficult to correlate the results of these experiments with incineration flue gas conditions. To analyse the reaction between heavy metal vapour and suspended particles more accuratelv. the GRE laboratorv has develooed a droo tube furnace. With this’ experimental set-up, it was possible d quantify the adsorption of cadmium chloride on different sorbents in conditions representative of incinerators; a dilution stream of particles was in contact with a counter current flow of metal vaoours at hieh temperature during a few seconds. Leaching was done&to quantify tYhe physical sorbed and chemisorbed fractions of the metal. Silica, alumina, alumina-silica, and calcium oxide were utilized and the influence of sorbent surface area, gas temperature and metal vapour concentration was investigated. Alumina and calcium oxide were found to be more effective for cadmium capture. The leachable fraction of cadmium on each sorbent appears to be very low. This is in favour of a chemisorption mechanism. In order to obtain characteristic values of vapour chemisorption on these sorbents, the results of the study were correlated with Freundlich isotherms.
Thermal analysis of a fluidized bed drying process for crops. Part I: mathematical modeling
00100534
Hajidavalloo, E. and Hamdullahpur, F. Inr. J Energy Res., 2000, 24, (9), 791-807. Development of a comprehensive mathematical model to simulate the simultaneous heat and mass transfer processes in a bubbling fluidized bed is described. Although the model is applicable to a wide range of particles, wheat is chosen as an example. In the development of the model, the commonly used two-phase theory is not used because of its insensitivity to the particle group used in the bed. Instead, a new hydrodynamic model is developed for each specific particle group. The behaviour of bubbles in a bed of group D particles (wheat) is modelled with the consideration that they grow in size as they rise in the bed, but are of the same size at any height in the bed. The voidage of bubbles, particles and interstitial gas is modelled separately. A newly developed expression to determine the minimum fluidization velocity of wet particles is used. The model considers the presence of different phases inside the bed and their physical variation along the bed. The interstitial gas phase, the bubble phase and the solid phase are modelled separately. The drying mechanism for the solid phase is considered in two stages: the falling rate and the constant rate, with appropriate temperature and moisture diffusion coefficients and wall effects. The simultaneous heat and mass transfer processes during the drying process including the internal and external effects are modelled for each phase. A set of coupled non-linear partial differential equations is employed to accurately model the drying process without using any adjustable parameters. A numerical code is developed to solve the governing partial differential equations using a control volume-based discretization approach. Piecewise profiles expressing the variation of dependent variables between the grid points are used to evaluate the required integrals. 00/00535
Thermal analysis of a fluidized bed drying process for crops. Part II: experimental results and model verification
Hajidavalloo, E. and Hamdullahpur, F. Inr. J. Energy Res., 2000, 24, (9) 809-820. An experimental investigation was undertaken to provide key data for the drying of wheat, and to assess the validity of the mathematical model described in Part I, and test its accuracy. The results of numerical solutions are compared with experimental data for wheat grains. Wheat is one of the main agricultural products and has extensive application in drying systems and therefore the accuracy of results for this product is of primary concern. Furthermore, as the desorption isotherms of wheat material are well documented, it is possible to accurately simulate the drying processes. Wheat belongs to the hygroscopic materials group and has a very low-mass diffusivity. Usually, no constant rate period is observed in the course of drying of wheat in the moderate range of initial moisture content, and drying takes place in the falling rate mode. In this study, it was confirmed that immediately after the particles are exposed to the drying medium, the surface moisture of material transfers rapidly due to low external resistance to heat and mass transfer. However, later on the moisture removal rate decreases noticeably with time because of the high internal resistance to diffusion. In the experiments, temperature at different elevations, humidity of the exit air, bed pressure drop, fluidization velocity and moisture content of particles at different times are measured. Each experiment is repeated at three inlet air Fuel and Energy Abstracts
January 2001
55
12 Refractories/ceramics (properties, production, applications) temperatures: 40, 49.5, and 60°C. Results of the model predictions show very good agreement with a large number of experimental data obtained in drying wheat. The agreement of model prediction and experimental data indicates that the model is fully predictable for drying of other materials in the fluidized bed with no restriction in the range of operational conditions such as the air temperature and the relative humidity. The model can be applied to the other type of processes such as spouted bed and fixed-bed drying with slight modification. It is found that the drying of grain materials is usually controlled by internal mass transfer parameters. The inlet air temperature has an important effect on the magnitude of drying rate while the gas velocity and bed hold-up do not show significant contribution to the drying rate. The initial moisture content of the bed materials can have an important effect on the drying rate depending on the physical properties of bed materials.
Thermal design of contraflow exchangers incorporting entropy
00/00536
Smith, E. M. ImechE Cons. Trans., 1999, 33-38. Two-stream plate-fin contraflow exchangers have been previously optimized for minimum frontal area and minimum volume. Working with the information provided, which includes, mass flow rates, exchanger duty, allowable pressure losses and inlet temperatures, the search involved altering the local geometry of the compact surface until the optimum design was achieved. This paper takes the design process further, exploring how pressure losses and temperature profiles might also be selected for an acceptable rate of entropy production using fixed surface geometries.
Type performance of Fischer-Tropsch liquids in modified off-highway diesel engine test cycle
12
REFRACTORIES/ CERAMICS Properties, production,
applications
00100540 In-situ carbon content adjustment in polymerderived WC/N ceramics by reactive heat treatment. Calculations of the pyrolysis product composition Galusek, D. er al. Silic. Ind., 1999, 64, (l-2), 3-7. A simplified mechanistic approach has been developed to estimate the range of compositional changes during the reactive heat treatment of different preceramic organosilicon precursors resulting in their conversion to amorphous Si/C/N ceramics. The calculation uses the composition of cross-linked polysilazane as a starting value and combines the conversion degrees of them. reactions with the highest thermodynamical probability which take part during the precursor thermal decomposition This approach allows to estimate a stoichiometry of the Si/C/N ceramics, provided the reactions yield thermodynamically stable, equilibrium products. Calculated data are consistent with experimental values and indicate that the stoichiometry of the product is detected by the structure and chemical composition of the polymer, rather than the conditions applied during pyrolysis. However, in certain limits given by the chemistry of the polymer, the stoichiometry of the product can be affected by a proper adjustment of the experimental conditions.
00/00537
Suppes, G. J. et al. Sec. Automat. Eng.. [Spec. Publ.] SP, 1999, SP1461, 41-53. Fischer-Tropsch (FT) conversion of gasification products to liquid hydrocarbon fuel, generally involves FT synthesis followed by mild refining of the FT synthetic oil into diesel, kerosene, and naphtha. These FT products are derived typically by mixing condensable gaseous reactor effluent (=Cs-Cza) with hydrocracked liquid reactor effluent (=Czo+). This mixture of FI liquids (FTL), then undergoes hydrotreatment and distillation to yield the desired products. This paper evaluates compression-ignition engine performance during preliminary tests of the condensable gaseous reactor effluent (&s-C& portion of the (FTL) from a Syntroleurn Corporation plant. Engine operability, fuel economy, maximum torque and emissions were evaluated for both FIL and mixtures of FTL with gasoline, di-ethyl ether, hexanes and ethanol. It was the nitric oxide and particulate emissions that the emphasis was placed upon. However, hydrocarbon, carbon dioxide, and oxygen concentrations were also analysed. Engine tests were performed with neat FIL, as well as with FTL formulations containing (1) 25% gasoline; (2) 25% hexanes; (3) 20%, 25%, and 33% of a equal volume mixtures of ethanol and di-Et ether and (4) 20% and 25% ethanol. Comparisons were made of these performances with US 1D and US 2D diesels. A three-mode test sequence was performed consistent with heavy duty diesel engine applications and each of the fuels met or exceeded goals on reduced emissions and operability of the unmodified engine. With several of these formulations, significant emission performance advantages were observed.
00/00538 Use of pulverized coal fuel in Ukrainian blast furnaces; Part 1 Piskanovsky, S. T. er a/. Mefall. Gornorudn. Prom-~., 1998, 2, 8-l 1. (In Russian) In the ironmaking industry of the Ukrain, the possibility of using pulverized non-coking coals to partially replace coke has been suggested. Its impact on the technological parameters of blast furnace operation are discussed in this paper.
00100539 Influences of coal type on the performance of a pressurised fluidised bed combustion power plant Huang, Y. et al. Fuel, 2000, 79, (13), 1595-1601. The performance of a combined cycle pressurized fluidized bed combustion (PFBC) plant has been calculated, using the ECLIPSE process simulator, for a wide range of coal properties. The overall efficiency varies between 40.8 and 43.4% on a higher heating value basis according to the changing coal properties. A mathematical equation has been developed, using the least-squares algorithm, which can be used to predict the efficiency of a PFBC plant for a given coal. The prediction indicates that the parameters, such as ash content, moisture content, sulfur content and calorific value of the coals, affect the overall efficiency. However, the ash content is found to be the most significant factor influencing plant performance. 56
Fuel and Energy Abstracts
January 2001
An investigation into the crystallization of Dicer glass-ceramic
00100541
Wood, D. J. et al. J. Mater. Sci. Lett., 1999, 18, (13), 1001-1002. The aim of the present investigation is to study the crystallization of DicorTM glass-ceramic, with a particular emphasis on the role of fluorine and silicon tetrafluoride loss on the crystallization mechanism. The results obtained have implications for the use of DicorTM, since one of the advantages cited for this material is that its hardness is similar to human enamel, but the cerammed surface has been shown to be much harder and much more abrasive toward enamel than the bulk material. The formation of an enstatite phase at the surface of the glass-ceramic is clearly undesirable and has implications for the wear of opposing teeth and for the determination of fracture toughness using indentation methods.
Aqueous sol-gel method for the synthesis of nano-sized ceramic powders
00100542
Pramanik, P. Ghosh, N. N. Ceram. Trans., 1999, 94, 195-203. The aqueous sol-gel method was used to synthesize a series of nanosized multicomponent ceramic powders. Metal formates and precipitated silica were used as precursor compounds instead of metal alkoxides and water was used as reaction medium instead of the commonly used solvent alcohol. Precipitated silica and aqueous solutions of metal formates were mixed together in order to prepare the gels. The gels prepared using this method were calcined at different temperatures and characterized by X-ray powder diffraction, IR spectroscopy, DTA, TEM and TG. This aqueous sol-gel method is shown to provide homogeneous and nanosized ceramic powders at effectively low temperatures and offers the potential of technically simpler and cost effective route than other reported sol-gel methods.
Ceramic surfacing method for repair of coke oven refractories
00100543
Balanov, V. G. and Krupoder, L. V. Koks Khim., 1999, 5, 16-17. (In Russian) If a ceramic surfacing method is used to replace the damaged coating of the coke ovens with a similar refractory material, the surface life of coke ovens can be increased. Also outlined are the economic advantages of ceramic as compared to gunite.
Characterization of ceramic glass in hydroxyapatite containing glass coated titanium composites 00100544
Yang, X. et aLProcess. Fabr. Adv. Mater. VI, Proc. Symp., 6th, 1998, 2, 1693-1701. Edited by Khor K.A., Srivatsan T.S., Moore J.J. Hydroxyapatite (HA)-glass (G) ceramics were prepared using HA with different degrees of crystallinity and characteristics. For two hours, the HA was synthesized chemically and fired at various temperatures (2001200”). The properties of these HA-G ceramics as well as the reaction of glass with HA, were investigated by differential scanning calorimetry, X-ray diffraction and Fourier transform infrared spectroscopy. HA slightly reacted with glass and formed a small amount of boron containing apatite. The pull-out strength study of the HA-G-Ti
Polyaromatic environmental impact in coal-tire blend atmospheric fluidized bed (AFB) combustion
Mastral, A. M.-e! al. Energy Fuels, 2006, 14,-(l), 164-168. This paper describes how for the first time the use of a waste material can be combined with trying to get cheaper power with a lower consumption of fossil fuel. A coal-tire blend (I:1 in organic matter) was burned in an atmosoheric fluidized bed (AFB) combustion olant with an airflow of 860 ‘L/h and 20% excess oxygen at three’ different combustion temperatures. (750, 850, and 950°C). The combustion conditions were-the same as those used in AFB coal combustion in order to compare the organic emissions obtained with both fuels. As the inorganic components in tires are less and in lower amounts than in coal, the work was focused on organic emissions. Organic emissions from each run were trapped and from each sample, after extraction by sonication with DMF (DMF), the content in polycyclic aromatic hydrocarbons (PAH) was detected by fluorescence-spectroscopy in the synchronous mode (FS). It is concluded that the introduction of tyres in the feeder increases the total PAH amount emitted with respect to coal emissions, with minimal variations at the combustion temperature studied in this work: thus, the higher the temperature, the lower the amount of emitted polycyclic aromatic hydrocarbons.
00100529 Pressurized drop tube furnace test of global coal aasification characteristics chin, Y. et al. Inr. J. Energy Res., 2000, 24, (9) 749-758. Pressurized drop tube furnace (PDTF) tests were performed with an Indonesian sub-bituminous coal while .temperature; oxygen/coal ratio, steam/coal ratio and pressure were systematically varied. The tests were desiened to investieate the effects of these exoerimental parameter; on the pulvehzed coal gasification characteristics at elevated pressure. The results showed that the gasification at elevated pressure -is more productive than that at atmospheric pressure, considering the carbon conversion and cold gas efficiency. The oxygen/coal ratio at the maximum cold gas efficiency ranged between 0.5 and 0.7 g/g. Only when the temperature was sufficiently high, did the increase of steam/coal ratio result in the improvement of cold gas efficiency. As the pressure increased, the contribution of carbon conversion by heterogeneous reactions increased while the conversion by pyrolysis decreased. 00/00530 Reactors with circulating fluldized bed Hartman, M. et al. Chem. Listy, 1999, 93, (12), 788-793. (In Czech) In circulating fluidized beds, a gas stream is used to transport the fine particles upwards and then they are recycled to the bottom of the column. The flow structure is complex and varies widely depending mainly on the vessel geometry, _gas velocity and particle size distribution. Unlike the bubbled bed, the entrv. exit and wall configurations have a strong effect on the flow and mixing patterns of both phases in the column. The tendency is for small particles to form larger, irregular aggregates, which disintegrate and form again at appreciable frequencies. Simple core-annulus models for circulating fluidized beds assume the up-flow of gas and entrained solids in a diluted central core and the down-flow of dense clusters in a relatively thin annular zone near the walls. Rapid heat and mass transfer between gas and particulate solids, uniform temperature in the whole CFB, virtually a plug flow of gas and possible stepwise addition of one or more gaseous components at different levels are among the main features of the CFB reactors. The most rapidly expanding field of CFB application is the efficient combustion and pressure gasification of carbon containing residues, in particular fossil fuels. 00100531
Solid circulation and as bypassing in spoutfluidized bed with draft tube at e9evated pressure
Xiao, R. et al. Ranliao Huaxue Xuebao. 1999. 27, (4). 370-376. (In Chinese) An experimental study on solid circulation and gas bypassing of spoutfluidized bed with draft tube at elevated pressure was performed in a 20 cm diameter cylindrical column with a 600 conical distributor. For bed material, glass beads with a mean diameter of 2.0 mm were used. A new method was develooed for measurine solid circulation under pressure and a gas (CO; tracers) were employed to investigate the characteristics of the gas bypassing. The solid circulation and gas bypassing were strongly dependent bn each other and influenced-by geometric parameters and operation conditions. For predicting solid circulation in a spout-fluidized bed with draft tube at elevated pressure an experimental correlation was proposed.
Stackable heat exchanger for processing carbonaceous material
00/00532
Koppelman, E. PCT Int. Appl. WO 99 50,609 (Cl. F28F9/26), 7 Ott 1999, US Appl. 50,393, 30 Mar 1998. 23. The present invention relates to a heat exchanger apparatus including a plurality of selectively detachable cells to accommodate the treatment of carbonaceous material, such as wood, peat or subbituminous coal, in
Process
heating,
power
and
incineration
(energy
applications
in industry)
varying amounts. The invention also relates to systems and processes for mineral removal from the carbonaceous materials and thereafter upgrading the carbonaceous material for use as fuel. 00100533
Study of the adsorption of CdClz vapor on various minerals using a drop tube furnace
Masseron. R. et al. Environ. Sci. Technol.. 1999. 33. (201. 3634-3640. Fixed bed’or thermogravimetric apparatus were’used’to’perform most of these studies and it is often difficult to correlate the results of these experiments with incineration flue gas conditions. To analyse the reaction between heavy metal vapour and suspended particles more accuratelv. the GRE laboratorv has develooed a droo tube furnace. With this’ experimental set-up, it was possible d quantify the adsorption of cadmium chloride on different sorbents in conditions representative of incinerators; a dilution stream of particles was in contact with a counter current flow of metal vaoours at hieh temperature during a few seconds. Leaching was done&to quantify tYhe physical sorbed and chemisorbed fractions of the metal. Silica, alumina, alumina-silica, and calcium oxide were utilized and the influence of sorbent surface area, gas temperature and metal vapour concentration was investigated. Alumina and calcium oxide were found to be more effective for cadmium capture. The leachable fraction of cadmium on each sorbent appears to be very low. This is in favour of a chemisorption mechanism. In order to obtain characteristic values of vapour chemisorption on these sorbents, the results of the study were correlated with Freundlich isotherms.
Thermal analysis of a fluidized bed drying process for crops. Part I: mathematical modeling
00100534
Hajidavalloo, E. and Hamdullahpur, F. Inr. J Energy Res., 2000, 24, (9), 791-807. Development of a comprehensive mathematical model to simulate the simultaneous heat and mass transfer processes in a bubbling fluidized bed is described. Although the model is applicable to a wide range of particles, wheat is chosen as an example. In the development of the model, the commonly used two-phase theory is not used because of its insensitivity to the particle group used in the bed. Instead, a new hydrodynamic model is developed for each specific particle group. The behaviour of bubbles in a bed of group D particles (wheat) is modelled with the consideration that they grow in size as they rise in the bed, but are of the same size at any height in the bed. The voidage of bubbles, particles and interstitial gas is modelled separately. A newly developed expression to determine the minimum fluidization velocity of wet particles is used. The model considers the presence of different phases inside the bed and their physical variation along the bed. The interstitial gas phase, the bubble phase and the solid phase are modelled separately. The drying mechanism for the solid phase is considered in two stages: the falling rate and the constant rate, with appropriate temperature and moisture diffusion coefficients and wall effects. The simultaneous heat and mass transfer processes during the drying process including the internal and external effects are modelled for each phase. A set of coupled non-linear partial differential equations is employed to accurately model the drying process without using any adjustable parameters. A numerical code is developed to solve the governing partial differential equations using a control volume-based discretization approach. Piecewise profiles expressing the variation of dependent variables between the grid points are used to evaluate the required integrals. 00/00535
Thermal analysis of a fluidized bed drying process for crops. Part II: experimental results and model verification
Hajidavalloo, E. and Hamdullahpur, F. Inr. J. Energy Res., 2000, 24, (9) 809-820. An experimental investigation was undertaken to provide key data for the drying of wheat, and to assess the validity of the mathematical model described in Part I, and test its accuracy. The results of numerical solutions are compared with experimental data for wheat grains. Wheat is one of the main agricultural products and has extensive application in drying systems and therefore the accuracy of results for this product is of primary concern. Furthermore, as the desorption isotherms of wheat material are well documented, it is possible to accurately simulate the drying processes. Wheat belongs to the hygroscopic materials group and has a very low-mass diffusivity. Usually, no constant rate period is observed in the course of drying of wheat in the moderate range of initial moisture content, and drying takes place in the falling rate mode. In this study, it was confirmed that immediately after the particles are exposed to the drying medium, the surface moisture of material transfers rapidly due to low external resistance to heat and mass transfer. However, later on the moisture removal rate decreases noticeably with time because of the high internal resistance to diffusion. In the experiments, temperature at different elevations, humidity of the exit air, bed pressure drop, fluidization velocity and moisture content of particles at different times are measured. Each experiment is repeated at three inlet air Fuel and Energy Abstracts
January 2001
55
12 Refractories/ceramics (properties, production, applications) temperatures: 40, 49.5, and 60°C. Results of the model predictions show very good agreement with a large number of experimental data obtained in drying wheat. The agreement of model prediction and experimental data indicates that the model is fully predictable for drying of other materials in the fluidized bed with no restriction in the range of operational conditions such as the air temperature and the relative humidity. The model can be applied to the other type of processes such as spouted bed and fixed-bed drying with slight modification. It is found that the drying of grain materials is usually controlled by internal mass transfer parameters. The inlet air temperature has an important effect on the magnitude of drying rate while the gas velocity and bed hold-up do not show significant contribution to the drying rate. The initial moisture content of the bed materials can have an important effect on the drying rate depending on the physical properties of bed materials.
Thermal design of contraflow exchangers incorporting entropy
00/00536
Smith, E. M. ImechE Cons. Trans., 1999, 33-38. Two-stream plate-fin contraflow exchangers have been previously optimized for minimum frontal area and minimum volume. Working with the information provided, which includes, mass flow rates, exchanger duty, allowable pressure losses and inlet temperatures, the search involved altering the local geometry of the compact surface until the optimum design was achieved. This paper takes the design process further, exploring how pressure losses and temperature profiles might also be selected for an acceptable rate of entropy production using fixed surface geometries.
Type performance of Fischer-Tropsch liquids in modified off-highway diesel engine test cycle
12
REFRACTORIES/ CERAMICS Properties, production,
applications
00100540 In-situ carbon content adjustment in polymerderived WC/N ceramics by reactive heat treatment. Calculations of the pyrolysis product composition Galusek, D. er al. Silic. Ind., 1999, 64, (l-2), 3-7. A simplified mechanistic approach has been developed to estimate the range of compositional changes during the reactive heat treatment of different preceramic organosilicon precursors resulting in their conversion to amorphous Si/C/N ceramics. The calculation uses the composition of cross-linked polysilazane as a starting value and combines the conversion degrees of them. reactions with the highest thermodynamical probability which take part during the precursor thermal decomposition This approach allows to estimate a stoichiometry of the Si/C/N ceramics, provided the reactions yield thermodynamically stable, equilibrium products. Calculated data are consistent with experimental values and indicate that the stoichiometry of the product is detected by the structure and chemical composition of the polymer, rather than the conditions applied during pyrolysis. However, in certain limits given by the chemistry of the polymer, the stoichiometry of the product can be affected by a proper adjustment of the experimental conditions.
00/00537
Suppes, G. J. et al. Sec. Automat. Eng.. [Spec. Publ.] SP, 1999, SP1461, 41-53. Fischer-Tropsch (FT) conversion of gasification products to liquid hydrocarbon fuel, generally involves FT synthesis followed by mild refining of the FT synthetic oil into diesel, kerosene, and naphtha. These FT products are derived typically by mixing condensable gaseous reactor effluent (=Cs-Cza) with hydrocracked liquid reactor effluent (=Czo+). This mixture of FI liquids (FTL), then undergoes hydrotreatment and distillation to yield the desired products. This paper evaluates compression-ignition engine performance during preliminary tests of the condensable gaseous reactor effluent (&s-C& portion of the (FTL) from a Syntroleurn Corporation plant. Engine operability, fuel economy, maximum torque and emissions were evaluated for both FIL and mixtures of FTL with gasoline, di-ethyl ether, hexanes and ethanol. It was the nitric oxide and particulate emissions that the emphasis was placed upon. However, hydrocarbon, carbon dioxide, and oxygen concentrations were also analysed. Engine tests were performed with neat FIL, as well as with FTL formulations containing (1) 25% gasoline; (2) 25% hexanes; (3) 20%, 25%, and 33% of a equal volume mixtures of ethanol and di-Et ether and (4) 20% and 25% ethanol. Comparisons were made of these performances with US 1D and US 2D diesels. A three-mode test sequence was performed consistent with heavy duty diesel engine applications and each of the fuels met or exceeded goals on reduced emissions and operability of the unmodified engine. With several of these formulations, significant emission performance advantages were observed.
00/00538 Use of pulverized coal fuel in Ukrainian blast furnaces; Part 1 Piskanovsky, S. T. er a/. Mefall. Gornorudn. Prom-~., 1998, 2, 8-l 1. (In Russian) In the ironmaking industry of the Ukrain, the possibility of using pulverized non-coking coals to partially replace coke has been suggested. Its impact on the technological parameters of blast furnace operation are discussed in this paper.
00100539 Influences of coal type on the performance of a pressurised fluidised bed combustion power plant Huang, Y. et al. Fuel, 2000, 79, (13), 1595-1601. The performance of a combined cycle pressurized fluidized bed combustion (PFBC) plant has been calculated, using the ECLIPSE process simulator, for a wide range of coal properties. The overall efficiency varies between 40.8 and 43.4% on a higher heating value basis according to the changing coal properties. A mathematical equation has been developed, using the least-squares algorithm, which can be used to predict the efficiency of a PFBC plant for a given coal. The prediction indicates that the parameters, such as ash content, moisture content, sulfur content and calorific value of the coals, affect the overall efficiency. However, the ash content is found to be the most significant factor influencing plant performance. 56
Fuel and Energy Abstracts
January 2001
An investigation into the crystallization of Dicer glass-ceramic
00100541
Wood, D. J. et al. J. Mater. Sci. Lett., 1999, 18, (13), 1001-1002. The aim of the present investigation is to study the crystallization of DicorTM glass-ceramic, with a particular emphasis on the role of fluorine and silicon tetrafluoride loss on the crystallization mechanism. The results obtained have implications for the use of DicorTM, since one of the advantages cited for this material is that its hardness is similar to human enamel, but the cerammed surface has been shown to be much harder and much more abrasive toward enamel than the bulk material. The formation of an enstatite phase at the surface of the glass-ceramic is clearly undesirable and has implications for the wear of opposing teeth and for the determination of fracture toughness using indentation methods.
Aqueous sol-gel method for the synthesis of nano-sized ceramic powders
00100542
Pramanik, P. Ghosh, N. N. Ceram. Trans., 1999, 94, 195-203. The aqueous sol-gel method was used to synthesize a series of nanosized multicomponent ceramic powders. Metal formates and precipitated silica were used as precursor compounds instead of metal alkoxides and water was used as reaction medium instead of the commonly used solvent alcohol. Precipitated silica and aqueous solutions of metal formates were mixed together in order to prepare the gels. The gels prepared using this method were calcined at different temperatures and characterized by X-ray powder diffraction, IR spectroscopy, DTA, TEM and TG. This aqueous sol-gel method is shown to provide homogeneous and nanosized ceramic powders at effectively low temperatures and offers the potential of technically simpler and cost effective route than other reported sol-gel methods.
Ceramic surfacing method for repair of coke oven refractories
00100543
Balanov, V. G. and Krupoder, L. V. Koks Khim., 1999, 5, 16-17. (In Russian) If a ceramic surfacing method is used to replace the damaged coating of the coke ovens with a similar refractory material, the surface life of coke ovens can be increased. Also outlined are the economic advantages of ceramic as compared to gunite.
Characterization of ceramic glass in hydroxyapatite containing glass coated titanium composites 00100544
Yang, X. et aLProcess. Fabr. Adv. Mater. VI, Proc. Symp., 6th, 1998, 2, 1693-1701. Edited by Khor K.A., Srivatsan T.S., Moore J.J. Hydroxyapatite (HA)-glass (G) ceramics were prepared using HA with different degrees of crystallinity and characteristics. For two hours, the HA was synthesized chemically and fired at various temperatures (2001200”). The properties of these HA-G ceramics as well as the reaction of glass with HA, were investigated by differential scanning calorimetry, X-ray diffraction and Fourier transform infrared spectroscopy. HA slightly reacted with glass and formed a small amount of boron containing apatite. The pull-out strength study of the HA-G-Ti