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Model comparisons with drop tube combustion data for various devolatilization submodels
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96/02971 Mathematical modeling of thermal processing of single particles of solid fuels Patskov, V. P. et al., Inzh.-Fiz. Zh., 1995, 68, (1), 96-109. (In Russian) Describes the development of a mathematical model, an algorithm and a computer program for thermal processing of single particles of solid fuel which take into account the moisture evaporation stage, volatiles yield and combustion of coking residue. The calculations of the effect of conditions on gasification-combustion of single particles of a brown coal (Chelabinsk) were performed. 96/02972 Measurements of particle flame temperatures using three-color optical pyrometry Panagiotou, T. et 01., Combustion & Flame, Feb. 1996, 104, (3), 272-287. A three-colour near-infrared optical pyrometer, with wavelengths centered at 998, 810, and 640 nm, was used to monitor the combustion of polymer particles. 96/02973 A microscopic study of ash deposits In a two-stage entrained-bed coal gasifier Koyama, S. et al., Fuel, Mar. 1996, 75, f4), 459-465. Deposits adhering to the wall of a 50td' two-stage entrained-bed coal gasifier were analysed for morphology, structure, composition and sintering strength. Deposits were classified into three types: powder, lump, and fused slag. Of these, the powdery deposit consisted of melted ash particles, soot and char. Char considered as unmelted particles was produced at a lower oxygen/coal ratio. It served as a dispersive material in the deposit and prevented complete sintering even at high temperature. Because the two-stage gasifier operates with a lower oxygen/coal ratio at the gas exit zone and a higher oxygen/coal ratio at the molten slag exit zone, the slagging problem at the gas exit zone was decreased by the production of an adequate amount of char during gasification. 96/02974 Milliken clean coal project - Update Janik, G. S. et al., Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem., 1995, 40, (4), 1029-1033. The paper describes the Milliken Clean Coal Demonstration Project, which uses forced-oxidation formic acid-enhancedwet limestone scrubbing technology to reduce S02 and NO, emissions in coal combustion processes. Also discusses the background, a description of the SHU (SaarbergHoelter-Umwelttechnik) contactor, start-up results, parametric test plan, retrofittingwith low-NO, concentric firing system burners, parametric test results, and long-term test results. 96/02975 Model comparisons with drop tube combustion data for various devolatilizatlon submodels Brewster, B. S. et al., Energy Fuels, 1995, 9, (5), 870-879, Predictions of a two-dimensional, axisymetric combustion model, using various devolatilization submodel options, are compared with new experimental data from a nearlaminar, drop-tube furnace. Included in the devolatilization submodelsthat were tested are the commonlyused empiricaloneand two-step models and a chemical, coal network model with parameters based on coal structure. The aim of this work was to evaluate the latter approach as compared with the simple, empirical approach usually used in such calculations and to assess the role of turbulence in a near-laminar reacting flow. 96/02976 Modeling flows with curved detonation waves Menikoff, R. et al., Combustion & Flame, Feb. 1996, 104, (3), 219-240. The nonzero width of a curved detonation front has a significant effect on its propagation. Physically, the curvature effect is a small but important correction. In numerical simulations, the curvature effect tends to be greately exaggerated due to an artificially large width of an underresolved wave. In the context of reactive fluid flow, a detonationwave consists of a lead shock followed by a thin reaction zone. The curvature effect is determined by the dynamics within the reaction zone; in particular, the competition between a source term for the rate of chemical energy release and a geometric source term due to front curvature. 96/02977
Modeling of fluidized-bed combustors
Prom. Energ., 1995, (4), 21-27. (In Russian)
Presents a modelling study of fluidized-bed combustion of high-ash coal. The results of testing of an industrial fluidized-bed reactor in combustion of brown coal are also described. 96/02978 Modeling of the flow structure in circulating fluidized beds De Diego, L. F. et al., Powder Technol., 1995,85, (1), 19-27. Radial solids flux profiles, at different axial positions, gas velocities, particle sizes and solids circulating fluxes, in a cold circulating fluidized bed were measured with two solids (sand and coal). These profiles showed a core-annulusflow structure with upward solids flux in the core in a diluted suspension and downward solids flux in the annulus in a denser suspension. The upward and downward solids fluxes decreased with the height of the diluted region. This demonstrated there was a net solid transfer from the core in the annulus. A mathematical model was developed for prediction of the solids flow structure in the circulating fluidized bed.
Combustion (burners, combustion systems)
96/02979 Modelling of sulfur retention In circulating fluidized bed combustors Adanez, J. et al., Fuel, Feb. 1996, 75, (3), 262-270. The effects of operating conditions (linear gas velocity, Ca/S molar ratio, type of coal and limestone, etc.) on sulphur retention efficiency in a circulating fluidized bed combustor were studied. The operating conditions affect the sulphur retention differently. To explain this, a mathematical model was developed. To determine axial voidage profiles, the model uses a modified exponential decay hydrodynamic model, which divides the bed into a dense region at the bottom of the bed and a dilute region above. In the dilute region a core-annulusstructurewith solid dispersion from core to annulus is considered. 96/02980 Model/ing of turbulent reacting flows with gasesous fuels in a combustion chamber Celik, C. et al., Fuel, Mar. 1996, 75, (4), 431-436. The object of this study was to develop an efficient mathematical model of turbulent, chemically reacting gas-phase flows under two-dimensional steady-stateconditions.The solution of the Navier-Stokes equations incorporating physical modelling for turbulence, combustion and thermal radiation was obtained by combining several computer codes previously developed. Numerical results for quantities such as temperature, stream function and species mole number distributions within the flow field were obtained.The performanceof the model was tested with experimental data from the M-2 trial and the IFRF (International Flame Research Foundation). The model assumes a perfectly stirred reactor, so it does not describe the mixing pattern of the reactants. 96/02981 A new heterogeneous burning velocity formula for the propagation of a laminar flame front through a polydlsperse spray of droplets Greenberg, J, B. er al., Combustion & Flame, Feb. 1996, 104, (3), 358-368. Describes a new burning velocity formula for the heterogeneous mode of laminar combustion of a premixed polydisperse spray of droplets which has been derived, using activation energy asymptotics and the method of multiple scales. 96/02982 New process to avoid emissions: Constant pressure in coke ovens Giertz, J. et al., Proc. Ironmaking Conference, 1995,54,439-444. The paper describes a chamber pressure regulator (PROven), effective in emission control from coke ovens. 96/02983 NO and N2 formation during char combustion: Is it HCN or surface attached nitrogen? (Brief Communication) Goel, S. et al., Combustion & Flame, Jan. 1996,104, (1), 213-217. 96/02984 Numerical modeling of a deep, fixed bed combustor Bryden, K. M. and Ragland, K. W. Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem., 1995, 40, (3), 666-670. Describes a computational model for the WTE combustor which has been developed and adjusted to within 6% of heat output of 10.1 MW/m2 of the Aurora, MN test run. The dee!?, fixed-bed combustor obtains high energy release rates due to the high air velocity and extended reaction zone. 96/02985 Numerical modeling of chemistry and gas dynamics during shock-induced ethylene combustion Clifford, L. 1. et aI., Combustion & Flame, Feb. 1996, 104, (3), 311-327. Presents the results of a numerical study of shock-induced ethylene combustion. An in other reactive flow problems the computational time increases significantly when finite rate chemistry is included. Compares the accuracy and efficiency of a variety of methods when applied to this combustion problem. 96/02986 Numerical predictions of the carbon burnout performance of coal-fired non-slagging vertical cyclone combustors Moghiman, M. et aI., J. Inst. of Energy, Mar. 1996,69, (478), 31-38. The paper describes the modifications and evolution of a finite-difference solution procedure for predicting the aero and particle dynamics of a 500 kW coal-fired non-slagging vertical cyclone combustor incorporating a fragmentation model and modified volatile burning law. Validation of the procedure was carried out from experimental data from a prototype firing natural gas, where an algebraic stress model of turbulence was needed to model cyclonic flows. The fragmentation model was based on experimental work indicatingthat fragmentation occurred early in the unit and at 80% of the coal diameter.
Fuel and Energy Abstracts May 1996 207
96/02971 Mathematical modeling of thermal processing of single particles of solid fuels Patskov, V. P. et al., Inzh.-Fiz. Zh., 1995, 68, (1), 96-109. (In Russian) Describes the development of a mathematical model, an algorithm and a computer program for thermal processing of single particles of solid fuel which take into account the moisture evaporation stage, volatiles yield and combustion of coking residue. The calculations of the effect of conditions on gasification-combustion of single particles of a brown coal (Chelabinsk) were performed. 96/02972 Measurements of particle flame temperatures using three-color optical pyrometry Panagiotou, T. et 01., Combustion & Flame, Feb. 1996, 104, (3), 272-287. A three-colour near-infrared optical pyrometer, with wavelengths centered at 998, 810, and 640 nm, was used to monitor the combustion of polymer particles. 96/02973 A microscopic study of ash deposits In a two-stage entrained-bed coal gasifier Koyama, S. et al., Fuel, Mar. 1996, 75, f4), 459-465. Deposits adhering to the wall of a 50td' two-stage entrained-bed coal gasifier were analysed for morphology, structure, composition and sintering strength. Deposits were classified into three types: powder, lump, and fused slag. Of these, the powdery deposit consisted of melted ash particles, soot and char. Char considered as unmelted particles was produced at a lower oxygen/coal ratio. It served as a dispersive material in the deposit and prevented complete sintering even at high temperature. Because the two-stage gasifier operates with a lower oxygen/coal ratio at the gas exit zone and a higher oxygen/coal ratio at the molten slag exit zone, the slagging problem at the gas exit zone was decreased by the production of an adequate amount of char during gasification. 96/02974 Milliken clean coal project - Update Janik, G. S. et al., Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem., 1995, 40, (4), 1029-1033. The paper describes the Milliken Clean Coal Demonstration Project, which uses forced-oxidation formic acid-enhancedwet limestone scrubbing technology to reduce S02 and NO, emissions in coal combustion processes. Also discusses the background, a description of the SHU (SaarbergHoelter-Umwelttechnik) contactor, start-up results, parametric test plan, retrofittingwith low-NO, concentric firing system burners, parametric test results, and long-term test results. 96/02975 Model comparisons with drop tube combustion data for various devolatilizatlon submodels Brewster, B. S. et al., Energy Fuels, 1995, 9, (5), 870-879, Predictions of a two-dimensional, axisymetric combustion model, using various devolatilization submodel options, are compared with new experimental data from a nearlaminar, drop-tube furnace. Included in the devolatilization submodelsthat were tested are the commonlyused empiricaloneand two-step models and a chemical, coal network model with parameters based on coal structure. The aim of this work was to evaluate the latter approach as compared with the simple, empirical approach usually used in such calculations and to assess the role of turbulence in a near-laminar reacting flow. 96/02976 Modeling flows with curved detonation waves Menikoff, R. et al., Combustion & Flame, Feb. 1996, 104, (3), 219-240. The nonzero width of a curved detonation front has a significant effect on its propagation. Physically, the curvature effect is a small but important correction. In numerical simulations, the curvature effect tends to be greately exaggerated due to an artificially large width of an underresolved wave. In the context of reactive fluid flow, a detonationwave consists of a lead shock followed by a thin reaction zone. The curvature effect is determined by the dynamics within the reaction zone; in particular, the competition between a source term for the rate of chemical energy release and a geometric source term due to front curvature. 96/02977
Modeling of fluidized-bed combustors
Prom. Energ., 1995, (4), 21-27. (In Russian)
Presents a modelling study of fluidized-bed combustion of high-ash coal. The results of testing of an industrial fluidized-bed reactor in combustion of brown coal are also described. 96/02978 Modeling of the flow structure in circulating fluidized beds De Diego, L. F. et al., Powder Technol., 1995,85, (1), 19-27. Radial solids flux profiles, at different axial positions, gas velocities, particle sizes and solids circulating fluxes, in a cold circulating fluidized bed were measured with two solids (sand and coal). These profiles showed a core-annulusflow structure with upward solids flux in the core in a diluted suspension and downward solids flux in the annulus in a denser suspension. The upward and downward solids fluxes decreased with the height of the diluted region. This demonstrated there was a net solid transfer from the core in the annulus. A mathematical model was developed for prediction of the solids flow structure in the circulating fluidized bed.
Combustion (burners, combustion systems)
96/02979 Modelling of sulfur retention In circulating fluidized bed combustors Adanez, J. et al., Fuel, Feb. 1996, 75, (3), 262-270. The effects of operating conditions (linear gas velocity, Ca/S molar ratio, type of coal and limestone, etc.) on sulphur retention efficiency in a circulating fluidized bed combustor were studied. The operating conditions affect the sulphur retention differently. To explain this, a mathematical model was developed. To determine axial voidage profiles, the model uses a modified exponential decay hydrodynamic model, which divides the bed into a dense region at the bottom of the bed and a dilute region above. In the dilute region a core-annulusstructurewith solid dispersion from core to annulus is considered. 96/02980 Model/ing of turbulent reacting flows with gasesous fuels in a combustion chamber Celik, C. et al., Fuel, Mar. 1996, 75, (4), 431-436. The object of this study was to develop an efficient mathematical model of turbulent, chemically reacting gas-phase flows under two-dimensional steady-stateconditions.The solution of the Navier-Stokes equations incorporating physical modelling for turbulence, combustion and thermal radiation was obtained by combining several computer codes previously developed. Numerical results for quantities such as temperature, stream function and species mole number distributions within the flow field were obtained.The performanceof the model was tested with experimental data from the M-2 trial and the IFRF (International Flame Research Foundation). The model assumes a perfectly stirred reactor, so it does not describe the mixing pattern of the reactants. 96/02981 A new heterogeneous burning velocity formula for the propagation of a laminar flame front through a polydlsperse spray of droplets Greenberg, J, B. er al., Combustion & Flame, Feb. 1996, 104, (3), 358-368. Describes a new burning velocity formula for the heterogeneous mode of laminar combustion of a premixed polydisperse spray of droplets which has been derived, using activation energy asymptotics and the method of multiple scales. 96/02982 New process to avoid emissions: Constant pressure in coke ovens Giertz, J. et al., Proc. Ironmaking Conference, 1995,54,439-444. The paper describes a chamber pressure regulator (PROven), effective in emission control from coke ovens. 96/02983 NO and N2 formation during char combustion: Is it HCN or surface attached nitrogen? (Brief Communication) Goel, S. et al., Combustion & Flame, Jan. 1996,104, (1), 213-217. 96/02984 Numerical modeling of a deep, fixed bed combustor Bryden, K. M. and Ragland, K. W. Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem., 1995, 40, (3), 666-670. Describes a computational model for the WTE combustor which has been developed and adjusted to within 6% of heat output of 10.1 MW/m2 of the Aurora, MN test run. The dee!?, fixed-bed combustor obtains high energy release rates due to the high air velocity and extended reaction zone. 96/02985 Numerical modeling of chemistry and gas dynamics during shock-induced ethylene combustion Clifford, L. 1. et aI., Combustion & Flame, Feb. 1996, 104, (3), 311-327. Presents the results of a numerical study of shock-induced ethylene combustion. An in other reactive flow problems the computational time increases significantly when finite rate chemistry is included. Compares the accuracy and efficiency of a variety of methods when applied to this combustion problem. 96/02986 Numerical predictions of the carbon burnout performance of coal-fired non-slagging vertical cyclone combustors Moghiman, M. et aI., J. Inst. of Energy, Mar. 1996,69, (478), 31-38. The paper describes the modifications and evolution of a finite-difference solution procedure for predicting the aero and particle dynamics of a 500 kW coal-fired non-slagging vertical cyclone combustor incorporating a fragmentation model and modified volatile burning law. Validation of the procedure was carried out from experimental data from a prototype firing natural gas, where an algebraic stress model of turbulence was needed to model cyclonic flows. The fragmentation model was based on experimental work indicatingthat fragmentation occurred early in the unit and at 80% of the coal diameter.
Fuel and Energy Abstracts May 1996 207