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01497 Influence of slit width on pulverized coal ignition and combustion with slitted blunt body
09 Combustion (burners, combustion systems) the behaviour of a pilot-scale fluidized-bed combustor, followed by comparison of its predictions with measurements and also with the results predicted by the previous code. The computer code replaces the conventional numerical integration of the analytical solution of population balance with direct integration in ODE form, by using a powerful integrator LSODE. This results in a reduction of CPU time by two orders of magnitude. For the prediction of physically expected variation of char holdup with excess air, an energy balance on char particles must be incorporated into the system model. When the predicted and measured temperature and concentration profiles were compared they proved that the present code produces better agreement than the previous one in bed-concentration profiles.
Experimental investigation of the laser diagnostics for fuel combustion in power-generating equipment
98Jo1494 bustion
The IEA model for circulating fluidized bed com-
Hannes, J. et al. Proc. Int. Conf. Fluid. Bed Cornbust., 1995, 13, (l), 287296. The paper presents a mathematical model IEA (International Energy Agency) to describe the fluid-dynamics and the combustion processes in a circulating fluidized bed combustor. The hydrodynamic model for the riser is kept one-dimensional in a vertical direction. The lateral dimension is considered by distinction between bubble and emulsion phases in the dense bottom region and a core-annulus approach in the transition region. The elements of the particle recycle system are modelled individually to get their partial flows and hold-ups. The gas phase is balanced with respect to the chemical reactions and the link to the particle phase. The thermal behaviour of the system can be described with the heat transfer model.
gal01 487
Mikhelyaev, S. V. el al. Avtometriya, 1996, (2), 3-12. (In Russian) An evaluation of the suitability of diagnostic methods for monitoring of fuel combustion in power plants using laser probes. Experiments were done in the power plants, and laboratory modelling was done by using water jets, gasoline burners, and coal dust-fired burners. The methods were efficient and suitable.
Filtration combustion 98101488 Aldushin, A. P. Prog. Astronaut. Aeronaut., 1997, 173, 95-115. The numerical results for filtration combustion (FC) systems are presented. FC refers to the propagation of exothermic reaction waves in a porous medium through which there is gas filtration. Filtration combustion covers a wide range of combustion processes in porous media having a common mechanism of reaction front propagation, which is mainly the delivery of gaseous reactant to the combustion front from the environment by the filtration process. Applications include natural, technological, and industrial processes, such as underground fires, coal gasification, self-propagating high-temperature synthesis (SHS), ore calcination, oil extraction, and waste incineration, among others. Topics which are discussed include classification of FC processes, the governing equations, FC waves in closed systems, FC waves in open systems (natural filtration), FC waves with forced gas filtration, and stability of FC waves. Formation and dispersion of toxic combustion by 98lO1489 products from small-scale combustion systems Ozdogan, S. et al. Energy, 1997, 22, (7), 681-692. The work focuses on the pollutants SO,, CO, NO,, methane and other volatile organics, and particulate matter. First- and second-law efficiencies have been evaluated. Next, the turbulent flows of exhaust gases through the stack have been modelled for both natural draft stacks and stacks equipped with forced draft fans. Velocity and temperature profiles in the stacks and for the plumes have been obtained from the numerical model for specified meteorological conditions. 98lo1490
Fractal analysis of combustion generated inorganic
ash aerosols Liu, B. 8. and Helble, J. J. Chemical Physical Processes Corndust., 1997, 273-276. The oxidization of inorganic compounds contained within coal particles forms inorganic aerosols during pulverized coal combustion. The fundamental relationship between ash particle fractal structure and ash particle size and composition (coalescence rate) is explored in this study.
Gas analysers for monitoring and adjustment of 98101491 fuel combustion units Beskov, V. S. Energetik, 1997, (5), 36. (In Russian) Gas analysers of the MRU series used for adjustment of fuel combustors and for reference measurements of the composition and parameters of flue gases from power plants, waste incinerators and industrial facilities are presented.
Group combustion model and calculation analysis of semicoal particles
98io1492
Liu, X. and Shen, S. Ranshao Kerue Yu Jishu, 1997, 3, (3), 303-308. (In Chinese) The combustion state of a cloud of semi-coal particles is introduced and a QS model for group combustion of a spherical cloud of semi-coal particles has been developed. The results on the burning rate and particle temperature of a cloud of semi-coal particles are presented and the results from a group combustion theory are used to provide the comparison between a cloud of big radius particles and one of small radius particles.
98io1493
Heat transfer in dilute gas-particle suspensions
Wang, X. S. et al. Chemical Ertg. Sci., 1997, 52, (20), 3617-3621. A thermal entrance region exists at both the upper and lower end of a vertical heat transfer surface in circulation fluidized-bed (CFB 7 coal combustors . The so-called ‘length effect’ of heat transfer in CFB risers is due to the thermal entrance regions. The effects of bed temperature and superficial gas velocity on the thermal entrance are not significantsand the proposed model can be applied to suspension densities ~20 kg/m .
gal01 495 Influence of pressure on the hetero eneous formation and destruction of nitrogen oxides during cflar combustion Croiset, E. et al. Combustion and Flame, 1997, 112, (l/2), 33-44. The paper focuses on the influence of pressure on the heterogeneous formation and destruction of NO and NzO during the burning of char in a pressurized fixed-bed reactor. The cotnbustion experiments were performed at 0.2, 0.6, and 1.0 MPa for temperatures between 850 and 1200 K with a char from a high volatile bituminous coal. It was assumed that the nitrogen oxides originating from the fuel-nitrogen were formed solely in surface reactions. A mechanism with eight reactions describing the heterogeneous formation and destruction of nitrogen oxides was then considered. In this mechanism, NO is formed from nitrogen bound at active sites (-CNO), and NzO is formed by reactions between NO and (-CNO). The rate of each of the eight reactions was determined at different pressures. Total pressure was found to have no effect on the formation rates of NO and NzO. NzO production was characterized by a high activation energy of 120 kJ mol-i. A pressure increase accelerates the decomposition of NO and NzO on the char, it was confirmed and NzO is more readily reduced on the char than NO. Rates of reactions requiring only active sites were independent of pressure, whereas, except for NzO formation, rates of reactions involving gaseous species decrease with increases in pressure.
98/01498 Influence of process parameters on nitrogen oxide formation in pulverized coal burners van der Lam, R. P. et al. Prog.‘Energy Combust. Sci., 1997, 23, (4), 349377. The influence of burner operating conditions, burner geometry and fuel parameters on the formation of nitrogen oxide during combustion of pulverized coal is described. Particular attention has been paid to combustion test facilities with self-sustaining flames, while extensions have been made to full-scale boilers and furnace-modelling. Since coal combustion and flame aerodynamics have been reviewed previously, these phenomena are only treated briefly.
Influence of slit width on pulverized coal ignition and combustion with slitted blunt body
9Blo1497
Shi, X. et al. Ranshao Kexue Yu Jishu, 1997, 3, (3), 322-326. (In Chinese) Hot experimental results with different slit width of slitted blunt body were analysed. In consequence the authors concluded the slit width has great influence on the pulverized coal ignition and flame stability and the optimal value of slit width is about 10% of blunt body width under condition of experiments. This is very useful for the slitted blunt body used in power plant.
98lO1498 Lamellar carbon structure evolution in combustion by quantitative digital analysis of HRTEM fringe Images. Shim, H.-S. et al. Chemical Physical Processes Combust. 1997, 163-166. Information on the nature and degree of crystallinity of carbon materials such as coal and char can be obtained using high resolution transmission electron microscopy (HRTEM) fringe image coupled with semi-quantitative digital analysis. Large differences in crystal structure as a function of parent coal type and to a lesser degree of combustion residence time were revealed after HRTM analysis of high temperature combustion chars.
98lo1499 A mathematical model of SOa emission in fluidizedbed 011shale combustion Li, S. Y. DGMK Tagungsber., 1997, 9703 (Proceedings ICCS ‘97, Volume I 2), 1135-1138. SOz emission characteristics in fluidized bed oil shale combustion was experimentally and mathematically investigated. A mathematical model for predicting transient SOz release from oil shale particle was developed, which includes heat transfer, mass transfer, chemical reaction, and selfdesulfurization by alkali oxides contained in oil shale. Reasonable agreement between the model and the experimental data was found. The numerical calculation indicated that the flame temperature is about 80°C higher than the bed temperature, promoting the release process of SOz. The CaO contained in shale ash acts as a adsorbent for SOz capture.
98lo1500
Method for combustion in fluidited incinerator
Takada, T. Jpn. Kokai Tokkyo Koho JP 09,273,734 [97,273,734] (Cl. F23G7/00), 21 Ott 1997, Appl. 96/108,556, 3 Apr 1996, 3 pp. (In Japanese) Powdered coal is supplied continuously into the fluidized bed with oxide of alkali and/or alkali earth metals as a medium to promote the conversion of incineration products into Hz0 and easy-to-solidify dust. The incinerator
Fuel and Energy Abstracts
March 1998
131
Experimental investigation of the laser diagnostics for fuel combustion in power-generating equipment
98Jo1494 bustion
The IEA model for circulating fluidized bed com-
Hannes, J. et al. Proc. Int. Conf. Fluid. Bed Cornbust., 1995, 13, (l), 287296. The paper presents a mathematical model IEA (International Energy Agency) to describe the fluid-dynamics and the combustion processes in a circulating fluidized bed combustor. The hydrodynamic model for the riser is kept one-dimensional in a vertical direction. The lateral dimension is considered by distinction between bubble and emulsion phases in the dense bottom region and a core-annulus approach in the transition region. The elements of the particle recycle system are modelled individually to get their partial flows and hold-ups. The gas phase is balanced with respect to the chemical reactions and the link to the particle phase. The thermal behaviour of the system can be described with the heat transfer model.
gal01 487
Mikhelyaev, S. V. el al. Avtometriya, 1996, (2), 3-12. (In Russian) An evaluation of the suitability of diagnostic methods for monitoring of fuel combustion in power plants using laser probes. Experiments were done in the power plants, and laboratory modelling was done by using water jets, gasoline burners, and coal dust-fired burners. The methods were efficient and suitable.
Filtration combustion 98101488 Aldushin, A. P. Prog. Astronaut. Aeronaut., 1997, 173, 95-115. The numerical results for filtration combustion (FC) systems are presented. FC refers to the propagation of exothermic reaction waves in a porous medium through which there is gas filtration. Filtration combustion covers a wide range of combustion processes in porous media having a common mechanism of reaction front propagation, which is mainly the delivery of gaseous reactant to the combustion front from the environment by the filtration process. Applications include natural, technological, and industrial processes, such as underground fires, coal gasification, self-propagating high-temperature synthesis (SHS), ore calcination, oil extraction, and waste incineration, among others. Topics which are discussed include classification of FC processes, the governing equations, FC waves in closed systems, FC waves in open systems (natural filtration), FC waves with forced gas filtration, and stability of FC waves. Formation and dispersion of toxic combustion by 98lO1489 products from small-scale combustion systems Ozdogan, S. et al. Energy, 1997, 22, (7), 681-692. The work focuses on the pollutants SO,, CO, NO,, methane and other volatile organics, and particulate matter. First- and second-law efficiencies have been evaluated. Next, the turbulent flows of exhaust gases through the stack have been modelled for both natural draft stacks and stacks equipped with forced draft fans. Velocity and temperature profiles in the stacks and for the plumes have been obtained from the numerical model for specified meteorological conditions. 98lo1490
Fractal analysis of combustion generated inorganic
ash aerosols Liu, B. 8. and Helble, J. J. Chemical Physical Processes Corndust., 1997, 273-276. The oxidization of inorganic compounds contained within coal particles forms inorganic aerosols during pulverized coal combustion. The fundamental relationship between ash particle fractal structure and ash particle size and composition (coalescence rate) is explored in this study.
Gas analysers for monitoring and adjustment of 98101491 fuel combustion units Beskov, V. S. Energetik, 1997, (5), 36. (In Russian) Gas analysers of the MRU series used for adjustment of fuel combustors and for reference measurements of the composition and parameters of flue gases from power plants, waste incinerators and industrial facilities are presented.
Group combustion model and calculation analysis of semicoal particles
98io1492
Liu, X. and Shen, S. Ranshao Kerue Yu Jishu, 1997, 3, (3), 303-308. (In Chinese) The combustion state of a cloud of semi-coal particles is introduced and a QS model for group combustion of a spherical cloud of semi-coal particles has been developed. The results on the burning rate and particle temperature of a cloud of semi-coal particles are presented and the results from a group combustion theory are used to provide the comparison between a cloud of big radius particles and one of small radius particles.
98io1493
Heat transfer in dilute gas-particle suspensions
Wang, X. S. et al. Chemical Ertg. Sci., 1997, 52, (20), 3617-3621. A thermal entrance region exists at both the upper and lower end of a vertical heat transfer surface in circulation fluidized-bed (CFB 7 coal combustors . The so-called ‘length effect’ of heat transfer in CFB risers is due to the thermal entrance regions. The effects of bed temperature and superficial gas velocity on the thermal entrance are not significantsand the proposed model can be applied to suspension densities ~20 kg/m .
gal01 495 Influence of pressure on the hetero eneous formation and destruction of nitrogen oxides during cflar combustion Croiset, E. et al. Combustion and Flame, 1997, 112, (l/2), 33-44. The paper focuses on the influence of pressure on the heterogeneous formation and destruction of NO and NzO during the burning of char in a pressurized fixed-bed reactor. The cotnbustion experiments were performed at 0.2, 0.6, and 1.0 MPa for temperatures between 850 and 1200 K with a char from a high volatile bituminous coal. It was assumed that the nitrogen oxides originating from the fuel-nitrogen were formed solely in surface reactions. A mechanism with eight reactions describing the heterogeneous formation and destruction of nitrogen oxides was then considered. In this mechanism, NO is formed from nitrogen bound at active sites (-CNO), and NzO is formed by reactions between NO and (-CNO). The rate of each of the eight reactions was determined at different pressures. Total pressure was found to have no effect on the formation rates of NO and NzO. NzO production was characterized by a high activation energy of 120 kJ mol-i. A pressure increase accelerates the decomposition of NO and NzO on the char, it was confirmed and NzO is more readily reduced on the char than NO. Rates of reactions requiring only active sites were independent of pressure, whereas, except for NzO formation, rates of reactions involving gaseous species decrease with increases in pressure.
98/01498 Influence of process parameters on nitrogen oxide formation in pulverized coal burners van der Lam, R. P. et al. Prog.‘Energy Combust. Sci., 1997, 23, (4), 349377. The influence of burner operating conditions, burner geometry and fuel parameters on the formation of nitrogen oxide during combustion of pulverized coal is described. Particular attention has been paid to combustion test facilities with self-sustaining flames, while extensions have been made to full-scale boilers and furnace-modelling. Since coal combustion and flame aerodynamics have been reviewed previously, these phenomena are only treated briefly.
Influence of slit width on pulverized coal ignition and combustion with slitted blunt body
9Blo1497
Shi, X. et al. Ranshao Kexue Yu Jishu, 1997, 3, (3), 322-326. (In Chinese) Hot experimental results with different slit width of slitted blunt body were analysed. In consequence the authors concluded the slit width has great influence on the pulverized coal ignition and flame stability and the optimal value of slit width is about 10% of blunt body width under condition of experiments. This is very useful for the slitted blunt body used in power plant.
98lO1498 Lamellar carbon structure evolution in combustion by quantitative digital analysis of HRTEM fringe Images. Shim, H.-S. et al. Chemical Physical Processes Combust. 1997, 163-166. Information on the nature and degree of crystallinity of carbon materials such as coal and char can be obtained using high resolution transmission electron microscopy (HRTEM) fringe image coupled with semi-quantitative digital analysis. Large differences in crystal structure as a function of parent coal type and to a lesser degree of combustion residence time were revealed after HRTM analysis of high temperature combustion chars.
98lo1499 A mathematical model of SOa emission in fluidizedbed 011shale combustion Li, S. Y. DGMK Tagungsber., 1997, 9703 (Proceedings ICCS ‘97, Volume I 2), 1135-1138. SOz emission characteristics in fluidized bed oil shale combustion was experimentally and mathematically investigated. A mathematical model for predicting transient SOz release from oil shale particle was developed, which includes heat transfer, mass transfer, chemical reaction, and selfdesulfurization by alkali oxides contained in oil shale. Reasonable agreement between the model and the experimental data was found. The numerical calculation indicated that the flame temperature is about 80°C higher than the bed temperature, promoting the release process of SOz. The CaO contained in shale ash acts as a adsorbent for SOz capture.
98lo1500
Method for combustion in fluidited incinerator
Takada, T. Jpn. Kokai Tokkyo Koho JP 09,273,734 [97,273,734] (Cl. F23G7/00), 21 Ott 1997, Appl. 96/108,556, 3 Apr 1996, 3 pp. (In Japanese) Powdered coal is supplied continuously into the fluidized bed with oxide of alkali and/or alkali earth metals as a medium to promote the conversion of incineration products into Hz0 and easy-to-solidify dust. The incinerator
Fuel and Energy Abstracts
March 1998
131