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04029 Fluidized bed combustion of low grade coals and biomass
09
An experimental study of the fate of char nitrogen in pulverized coal flames
98lo4027
Spinti, J. P. 1997, 390 pp. Avail. UMI, Order No. DA9812372. Absrr. Inr., B, 1998, 58, (lo), 5521.
From Diss.
Experimental study on visualization of the ignition of pulverized-coal and air stream in a laboratory-scale singleburner furnace
9alO4028
Zhou, H. and Cheng, H. Ranshao Kexue Yu Jishu, 1997, 3, (4), 349-354. (In Chinese) The ignition front of the pulverized-coal and air stream in a laboratoryscale single-burner furnace is separated from its background by an image processing system. The ignition distance is defined as the shortest distance of the flame front to the outlet of the burner and the experiments show that the average ignition distance is shortened obviously as the coal concentration increases for a kind of bituminous coal. For a normal bluff-body burner with a higher combustion stability, its ignition of pulverized-coal and air stream tends to occur firstly at the stress layer in the outer side of the separated stream behind the burner.
Fluidized bed combustion of low grade coals and :Y%::: Armesto, L. et al. Dev. Thermochem. Biomass Cowers., 1997, 2, 13991407. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. One of the most promising methods for combustion is fluidized bed. Its application to boilers is recognized primarily for its low sensitivity to fuel quality and its capacity to limits air pollution. Despite being used all over the world for biomass, as well as coal combustion, there are no results available on the joint utilization of these fuels. The utilization of biomass in blends with low grade coal is expected to improve the conversion of the fossil fuels due to the high volatile content of the biomass. The renewable origin of the biomass means the emissions of SOz and NO. as well as those of CO1 are reduced. The main objective of the proposed paper is to demonstrate the technical feasibility of the circulating fluidized bed as a clean technology for the combustion of low grade coal/biomass blends. The paper collects and analyses combustion test data. The tests aim to achieve high efficiency and low emission, and to this end, studies the influence of biomass content in blends, bed temperature and fluidization velocity. 98lo4030
Fluidized bed combustion: mixing and pollutant
limitation Leckner, B. Prog. Energy Combusr. Sci., 1998, 24, (1) 31-61. The paper discusses fluidized bed combustion applications and the principal criteria determining the form and size of a combustion chamber are explained. The presentation concentrates on processes in large combustors, especially mixing between fuel and air. Large concentration differences may be present in the combustion chamber, but the concentration cannot be properly predicted. Mixing is important not only for combustion but also for sulphur capture through the formation of reducing zones. This and other factors influencing sulphur capture are discussed. The nitrogen chemistry and the influence of particle surfaces on the path of reactions are described briefly. Efforts are made to apply basic knowledge regarding fluid dynamics and chemical reactions to combustors by mathematical models, but also qualitative judgements are useful, as is seen from methods proposed to reduce the emission of NzO. In general, more measurements are needed from large combustion chambers to describe the processes in such chambers and to verify how the large amount of results available from laboratory-scale investigations can be applied for qualitative design and optimization studies. 98lo4031
Formation of nitrogen oxides in combustion of
solid fuels Munts, V. A. er al. Teploenergerika, 1997, (12), 26-30. (In Russian) For coals and shales with different yields of volatile nitrogen-containing compounds, the paper presents experimental data on the determination of kinetic constants of burning for fluidized-bed conditions and NO, formation. The results suggest that the NO, formation occurs at both the volatiles burning stage and the coke residue burning stage. The general equations are given for calculating the degree of fuel nitrogen conversion into nitrogen oxides in coke and volatiles burning. The calculation data was compared with available experimental data for the combustion conditions in a fluidized bed and a pulverized coal flame.
Fundamental study on NzO formation/decomposi90104032 tion characteristics by means of low-temperature pulverized coal combustton Naruse, I. et al. Symp. (lnr.) Combusr., [Proc.], 1996, 26, (2), 3213-3221. By means of a one-dimensional electric heated laminar drop furnace for various coal types, NzO formation/decomposition characteristics and its mechanisms in pulverized coal combustion, especially at low temperature, are investigated. The behaviour of nitrogen compounds along the furnace axis is studied by analysing both the sampled burning particles and combustion gas and by calculating the mass balance of nitrogen. Furthermore, the effects of the combustion efficiency and the ratio of fixed carbon to volatile matter content (fuel ratio) on NzO formation/ decomposition characteristics were experimentally elucidated. Data from testing nine different types of coal show that the exit NzO concentration has a good correlation with the combustion efficiency and the fuel ratio.
Combustion
(burners, combustion
systems)
Gas property effects on droplet atomization and combustion in an air-assist atomizer
98lo4033
Aftel, R. et al. Symp. (Inr.) Cornbust., [Proc.], 1996, 26, (l), 1645-1651. To determine the effect of these gases on droplet size, density, and velocity in kerosene spray flames using a two-dimensional phase Doppler interferometer, nitrogen, argon and CO2 were used as the atomizing gas in an ‘air-assist’ fuel nozzle. Data were obtained with these atomizing gases and compared to the reference, air-assist case, since air is the most commonly used atomizing fluid. Comparisons were made between the gases on a mass and momentum flux basis. Both burning and non-burning sprays were investigated. The presence of 02 in the atomizing gas and gas density have significant effect on the atomization, mixing and combustion processes, which, in turn, influence droplet lifetimes, flame structure, and emission levels. gal04034 Gas-phase combustion synthesis of particles Wooldridge, M. S. Prog. Energy Combusr. Sci., 1998, 24, (l), 63-87. A summary is presented of recent experimental and theoretical investigations of the fundamental processes governing gas-phase combustion synthesis of particles. For the production of non-oxide, single-oxide, and mixed-oxide powders, various experimental methods and results are reviewed. Parameters influencing particle morphology and composition including electric field effects are also discussed. For the different growth regimes, including homogenous nucleation, agglomeration, and coalescence, the paper presents nucleation and growth models. 98/04035 Get more knowledge about burning coal Anon. Power, 1998, 142, (2), 25-26, 28-29. Techniques to help balance emission reduction and increased efficiency coal combustion are reviewed. 98104036 Ignition and burnout time of coal particle fluidized bed combustor
in
in
Liu, B. et al. Ranshao Kexue Yu Jishu, 1997, 3, (4), 412-416. (In Chinese) In order to calculate the ignition and burnout times and/or the temperature of coal particles in a fluidized-bed combustor, a thermodynamic model was developed and tested in a bench-scale combustor. The ignition temperature was a function of the surrounding conditions and the particles themselves, and not necessarily a function of the particle size distribution. Under defined environment conditions, the ignition and burnout time had a smooth shift with bed temperature. With the development of combustion process, the ash layer had a stronger and stronger effect on combustion. The model is particularly applicable for large particles under industrial combustion conditions in which the residual carbon content in the coal particles tends toward a certain level. gal04037
Industrial combustion control using UV emission
tomography
Leipertz, A. et al. Symp. (Inr.) Cornbust., (Proc.], 1996, 26, (2), 2869-2875. Based on UV emission spectroscopy measurements in combination with tomographic evaluation procedures, a new strategy for industrial combustion monitoring and control is presented. This new strategy prevents the production of combustion NO, by an early detection of NO, generating flame radicals in a two-dimensional plane of the combustion system. Preliminary results for the usability of this new control strategy are presented. Testing has been carried out in various combustion systems for the tomographic sensor system for the control loop. A strong correlation of high temperature and high NO, flue gas emission with the appearance of NH and CN radiative emission bands were found in an incineration station. In a tomographic test with two single UV sensors under brown coal firing conditions, the radial intensity distribution was calculated. Along a line perpendicular to the connecting line of the two sensors, the determination of the temperature found by comparing the spectra with Planck’s function was in good agreement with suction thermocouple measurements. Using the same burner with propane fuel, the two-dimensional CH distribution in the longitudinal cross section was detected. These measurements indicate the principal usability of the new sensor and a strategy to prevent NO, generation in industrial combustion systems in the early stage of development.
Inorganic chemistry of biomass combustion: problems and solutions
98lo4030
Blander, M. Dev. Thermochem. Biomass Comers., 1997, 2, 1293-1302. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. Fouling and corrosion problems are presented by high temperature molten products of biomass combustion. The total inorganic chemistry of biomass combustion has been calculated with a free energy minimization computer program with a large database for solids, liquids and gases. Theories and models which predict the properties of multicomponent molten salts and silicates from the properties of the subsidiary binaries are also included in the model. Two different types of low melting liquids are indicated by the calculations: (1) a very low melting (<500-700°C) silicate containing aluminium, .potassium, sodium and other oxides and (22 a low melting potassium rtch reciprocal salt solution of K+, Caz-, Na /COs2-, S04’-, Cl-. It is possible, via the computer program and knowledge of the combustion chemistry, to determine additives which will minimize fouling and corrosion.
Fuel and Energy Abstfacts
September 1998 377
An experimental study of the fate of char nitrogen in pulverized coal flames
98lo4027
Spinti, J. P. 1997, 390 pp. Avail. UMI, Order No. DA9812372. Absrr. Inr., B, 1998, 58, (lo), 5521.
From Diss.
Experimental study on visualization of the ignition of pulverized-coal and air stream in a laboratory-scale singleburner furnace
9alO4028
Zhou, H. and Cheng, H. Ranshao Kexue Yu Jishu, 1997, 3, (4), 349-354. (In Chinese) The ignition front of the pulverized-coal and air stream in a laboratoryscale single-burner furnace is separated from its background by an image processing system. The ignition distance is defined as the shortest distance of the flame front to the outlet of the burner and the experiments show that the average ignition distance is shortened obviously as the coal concentration increases for a kind of bituminous coal. For a normal bluff-body burner with a higher combustion stability, its ignition of pulverized-coal and air stream tends to occur firstly at the stress layer in the outer side of the separated stream behind the burner.
Fluidized bed combustion of low grade coals and :Y%::: Armesto, L. et al. Dev. Thermochem. Biomass Cowers., 1997, 2, 13991407. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. One of the most promising methods for combustion is fluidized bed. Its application to boilers is recognized primarily for its low sensitivity to fuel quality and its capacity to limits air pollution. Despite being used all over the world for biomass, as well as coal combustion, there are no results available on the joint utilization of these fuels. The utilization of biomass in blends with low grade coal is expected to improve the conversion of the fossil fuels due to the high volatile content of the biomass. The renewable origin of the biomass means the emissions of SOz and NO. as well as those of CO1 are reduced. The main objective of the proposed paper is to demonstrate the technical feasibility of the circulating fluidized bed as a clean technology for the combustion of low grade coal/biomass blends. The paper collects and analyses combustion test data. The tests aim to achieve high efficiency and low emission, and to this end, studies the influence of biomass content in blends, bed temperature and fluidization velocity. 98lo4030
Fluidized bed combustion: mixing and pollutant
limitation Leckner, B. Prog. Energy Combusr. Sci., 1998, 24, (1) 31-61. The paper discusses fluidized bed combustion applications and the principal criteria determining the form and size of a combustion chamber are explained. The presentation concentrates on processes in large combustors, especially mixing between fuel and air. Large concentration differences may be present in the combustion chamber, but the concentration cannot be properly predicted. Mixing is important not only for combustion but also for sulphur capture through the formation of reducing zones. This and other factors influencing sulphur capture are discussed. The nitrogen chemistry and the influence of particle surfaces on the path of reactions are described briefly. Efforts are made to apply basic knowledge regarding fluid dynamics and chemical reactions to combustors by mathematical models, but also qualitative judgements are useful, as is seen from methods proposed to reduce the emission of NzO. In general, more measurements are needed from large combustion chambers to describe the processes in such chambers and to verify how the large amount of results available from laboratory-scale investigations can be applied for qualitative design and optimization studies. 98lo4031
Formation of nitrogen oxides in combustion of
solid fuels Munts, V. A. er al. Teploenergerika, 1997, (12), 26-30. (In Russian) For coals and shales with different yields of volatile nitrogen-containing compounds, the paper presents experimental data on the determination of kinetic constants of burning for fluidized-bed conditions and NO, formation. The results suggest that the NO, formation occurs at both the volatiles burning stage and the coke residue burning stage. The general equations are given for calculating the degree of fuel nitrogen conversion into nitrogen oxides in coke and volatiles burning. The calculation data was compared with available experimental data for the combustion conditions in a fluidized bed and a pulverized coal flame.
Fundamental study on NzO formation/decomposi90104032 tion characteristics by means of low-temperature pulverized coal combustton Naruse, I. et al. Symp. (lnr.) Combusr., [Proc.], 1996, 26, (2), 3213-3221. By means of a one-dimensional electric heated laminar drop furnace for various coal types, NzO formation/decomposition characteristics and its mechanisms in pulverized coal combustion, especially at low temperature, are investigated. The behaviour of nitrogen compounds along the furnace axis is studied by analysing both the sampled burning particles and combustion gas and by calculating the mass balance of nitrogen. Furthermore, the effects of the combustion efficiency and the ratio of fixed carbon to volatile matter content (fuel ratio) on NzO formation/ decomposition characteristics were experimentally elucidated. Data from testing nine different types of coal show that the exit NzO concentration has a good correlation with the combustion efficiency and the fuel ratio.
Combustion
(burners, combustion
systems)
Gas property effects on droplet atomization and combustion in an air-assist atomizer
98lo4033
Aftel, R. et al. Symp. (Inr.) Cornbust., [Proc.], 1996, 26, (l), 1645-1651. To determine the effect of these gases on droplet size, density, and velocity in kerosene spray flames using a two-dimensional phase Doppler interferometer, nitrogen, argon and CO2 were used as the atomizing gas in an ‘air-assist’ fuel nozzle. Data were obtained with these atomizing gases and compared to the reference, air-assist case, since air is the most commonly used atomizing fluid. Comparisons were made between the gases on a mass and momentum flux basis. Both burning and non-burning sprays were investigated. The presence of 02 in the atomizing gas and gas density have significant effect on the atomization, mixing and combustion processes, which, in turn, influence droplet lifetimes, flame structure, and emission levels. gal04034 Gas-phase combustion synthesis of particles Wooldridge, M. S. Prog. Energy Combusr. Sci., 1998, 24, (l), 63-87. A summary is presented of recent experimental and theoretical investigations of the fundamental processes governing gas-phase combustion synthesis of particles. For the production of non-oxide, single-oxide, and mixed-oxide powders, various experimental methods and results are reviewed. Parameters influencing particle morphology and composition including electric field effects are also discussed. For the different growth regimes, including homogenous nucleation, agglomeration, and coalescence, the paper presents nucleation and growth models. 98/04035 Get more knowledge about burning coal Anon. Power, 1998, 142, (2), 25-26, 28-29. Techniques to help balance emission reduction and increased efficiency coal combustion are reviewed. 98104036 Ignition and burnout time of coal particle fluidized bed combustor
in
in
Liu, B. et al. Ranshao Kexue Yu Jishu, 1997, 3, (4), 412-416. (In Chinese) In order to calculate the ignition and burnout times and/or the temperature of coal particles in a fluidized-bed combustor, a thermodynamic model was developed and tested in a bench-scale combustor. The ignition temperature was a function of the surrounding conditions and the particles themselves, and not necessarily a function of the particle size distribution. Under defined environment conditions, the ignition and burnout time had a smooth shift with bed temperature. With the development of combustion process, the ash layer had a stronger and stronger effect on combustion. The model is particularly applicable for large particles under industrial combustion conditions in which the residual carbon content in the coal particles tends toward a certain level. gal04037
Industrial combustion control using UV emission
tomography
Leipertz, A. et al. Symp. (Inr.) Cornbust., (Proc.], 1996, 26, (2), 2869-2875. Based on UV emission spectroscopy measurements in combination with tomographic evaluation procedures, a new strategy for industrial combustion monitoring and control is presented. This new strategy prevents the production of combustion NO, by an early detection of NO, generating flame radicals in a two-dimensional plane of the combustion system. Preliminary results for the usability of this new control strategy are presented. Testing has been carried out in various combustion systems for the tomographic sensor system for the control loop. A strong correlation of high temperature and high NO, flue gas emission with the appearance of NH and CN radiative emission bands were found in an incineration station. In a tomographic test with two single UV sensors under brown coal firing conditions, the radial intensity distribution was calculated. Along a line perpendicular to the connecting line of the two sensors, the determination of the temperature found by comparing the spectra with Planck’s function was in good agreement with suction thermocouple measurements. Using the same burner with propane fuel, the two-dimensional CH distribution in the longitudinal cross section was detected. These measurements indicate the principal usability of the new sensor and a strategy to prevent NO, generation in industrial combustion systems in the early stage of development.
Inorganic chemistry of biomass combustion: problems and solutions
98lo4030
Blander, M. Dev. Thermochem. Biomass Comers., 1997, 2, 1293-1302. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. Fouling and corrosion problems are presented by high temperature molten products of biomass combustion. The total inorganic chemistry of biomass combustion has been calculated with a free energy minimization computer program with a large database for solids, liquids and gases. Theories and models which predict the properties of multicomponent molten salts and silicates from the properties of the subsidiary binaries are also included in the model. Two different types of low melting liquids are indicated by the calculations: (1) a very low melting (<500-700°C) silicate containing aluminium, .potassium, sodium and other oxides and (22 a low melting potassium rtch reciprocal salt solution of K+, Caz-, Na /COs2-, S04’-, Cl-. It is possible, via the computer program and knowledge of the combustion chemistry, to determine additives which will minimize fouling and corrosion.
Fuel and Energy Abstfacts
September 1998 377