- Email: [email protected]
Calculation of solid fuel combustion rate in circulating systems
09 Combustion (burners, combustion systems) 00100447 Experimental research on boiler combustion performance of the 300 MW unit Xiang, J. et al. Huazhong Ligong Dame Xuebao, 1999.27, (8), 107-109. (In Chinese) Experimental studies have been carried out to analyse the effect of coal quality on NO, emission and unburned carbon in ash concentrations. Chinese lean coals (fixed carbon content varied from 60% to 75%) have been fired in a tangentially full-scale power plant (300 MW power unit, 1024 t/h boiler). In furnace NO, emission and unburned carbon in flying ash concentrations have been measured synchronously with different combustion condition. Identical trends in NO. emission as a function of coal content and excessive oxygen content have been obtained. The nitrogen content of coals has been found to be proportional to NO,. Finally, it is evident that there is a relationship between operation condition and unburned carbon in flying ash content.
00100448 Modelling of the combustion process and NO, emission in a utility boiler Xu, M. er al. Fuel, 2000, 79, (13) 1611-1619. This paper presents numerical simulation of the flow and combustion process in the furnace of a pulverized coal fired utility boiler of 350 MWe with 24 swirl burners installed at the furnace front wall. Five different cases with 100, 95, 85, 70 and 50% boiler full load are simulated. The comparison between the simulation and the plant data is stressed in this study. The heat flux to furnace walls between the measured values and the calculation results is compared. It is found that increasing the load leads to consistent variations in the properties presented and the exception is observed for the full load case where the predicted exit gas temperature is lower than the 95% one and the total heat to the boiler walls is smaller. This might be due to the fact of considering a linear scaling of the input parameters between the 70% and 100% load. The increase of the air flow rate led as expected to a reduction of the furnace outlet temperature and to a small decrease in NO, emissions. It shows that the NO, model used shows a higher sensitivity to temperature than to oxygen level in the furnace. The model used considered the De Soete mechanism for the nitrogen from volatiles and the contribution of char was considered in a similar way. The agreement for all cases except the one of 50% boiler load between the calculation results with the plant data validates the models and algorithm employed in the computation. The furnace performance under different boiler loads is predicted and compared in order to meet the requirements of NO, abatement and avoiding some negative side effects on the furnace.
;:;;:I49
Novel fuel regulator for coal-dust concurrent
Litovkin, V. V. and Grechanyi, A. N. Energ. Elekrrif. (Kiev), 1999, 3, 44-46. (In Russian) A novel fuel regulator is described for controlling coal-dust fired concurrent boilers. The control system uses pressure signals of the medium in the steam-water channel instead of temperature signals. The efficiency and reliability of the boiler is improved by the control scheme, owing to the improvement of the control quality by reducing time lag in the control loop.
09
00/00451 Application of plastic clad silica fibers to multiple zone flame measurements in industrial power burners Wojcik, W. Opt. Appl., 1999, 29, (l-2). 201-212. The paper presents information covering a period of 7 years on the application of fibre optic technology in monitoring, protection and start-up systems for industrial burners. A brief description of the phenomena under investigation as well as theoretical assumptions are provided. In addition, information is provided on the design of a measuring device and examples of test results with the use of this device.
Calculation of solid fuel combustion rate in circulating systems
00100452
Shraiber, A. A. Prom. Tepforekh., 1998, 20, (4), 3842. (In Russian) Solutions suitable for the analysis of distribution functions of burning particles by sizes and carbon mass concentrations in circulating systems have been obtained. This paper considers various schemes of the ash behaviour during particle combustion. The solutions are represented in the form of series in terms of the number of particles that pass through the circulating contour.
Chemistry and kinetics of chemical vapor infiltration of pyrocarbon VII: infiltration of caplllaries of equal size Hu, Z.J. et al. Carbon, 2000, 38, (7). 1059-1065. 00100453
Capillaries, 1 mm in diameter and 17 mm in depth, were infiltrated at a temperature of 1100°C and pressures of 20 kPa (Pure methane) and 30 kPa (methane-hydrogen mixture (7:l)). The residence time of the gas in the deposition reactor was 0.5 seconds, at the lower pressure of 20 kPa, residence times of 1 and 2 seconds were studied additionally. The thickness of the deposited carbon layers was determined using an X-ray microscope, i.e. without cutting the samples. In the experiments with 0.5 and 1 second residence times, an increase of the deposition rate from the mouth to the depth of the pores was obtained. The gradient of the deposition rate decreases with increasing residence time of the gas and becomes negative at 2 seconds. Hydrogen, either formed by decomposition of methane or added to the feed gas, leads to an increase in the gradient. The homogeneous-heterogeneous model of carbon deposition from methane is used to interpret the results with special consideration of deposition chemistry and diffusivity of the relevant hydrocarbon species.
00100454 Coal hydropyrolysis method Yabe, H. et al. Jpn. Kokai Tokkyo Koho JP 11 228,973 [99 228,973] (Cl. ClOGl/OO), 24 Aug 1999, Appl. 1998/27,921. 10 Feb 1998. 5. (In Japanese) A method for flash hydropyrolysis of coal is described. The procedure can be used for manufacturing gas, tar and char and comprises of fluidizing the coal by blowing a gas atmosphere containing a highconcentration of hydrogen (e.g., ~30%). The hydrogen gas is mixed with a high-temperature gas produced by a generator, in which the high-temperature gas is derived from gasification of at least a part of char after separation from a cyclone with oxygen gas. At least a part of gas produced from pyrolysis is used for refining hydrogen gas and the remaining H gas can be fed into the pyrolysis reactor for recycling.
00100455
COMBUSTION Burners, combustion systems
00/00450 Advanced low NO, burners with integrated reburn Hepburn, P. et al. Eur. Comm., [Rep.] EUR, 1999, , 1-41. Low- NO,-formation pulverized coal-fired staged burners were designed with integrated reburn zones. The reburning fuels used were natural gas or heavy fuel oil, taking into account the amount of reburn fuel fraction, the degree of reburn fuel mixing, the primary-reburn zone stoichiometry and the burnout zone stoichiometry. The NO. level can be reduced by up to 30% by the recirculation and combustion of natural gas the reburn fuel. The lowest NO. emissions was achieved with a high reburn gas injection velocity, a reburn zone temperature of 1400” and a reburn zone stoichiometry of 0.82-0.90. With reburn using heavy fuel oil, no reburn effect was achieved, this was believed to be caused by the poor quality of the pulverized coal for the tests.
Combustion behavior of Bowen Basin coals,
Australia Benfell, K. E. et al. Fuel Process. Technol., 1999, 60, (l), 1-14. Tightly constrained experimental thermogravimetry proves to be effective for characterizing the effects of rank and maceral variations on Bowen Basin coal combustion behaviour. These coals show an increase in char burnout temperature with rank for both dull, inertinite-rich and bright, vitrinite-rich coals. Dull coals in comparison to their bright rank equivalent have higher char burnouts and peak combustion temperatures. However, the maximum rates of combustion for dull coals are lower than their bright counterparts.
00100456 Combustion of low-grade coals in circulating fluidized bed
Yu, M. A. Ekotekhnol. Resursosberezhenie, 1997, 6, 3-8. (In Russian) Demonstrated in this paper is the necessity of boilers of circulating fluidized bed (CFB) for combustion of high-ash coals of low reactivity. The special features of the CFB combustion for the anthracite culm and Donets poor coal are investigated at the experimental and pilotscale facilities. The optimal combustion regimes for the coals have been determined. An investigation was also carried out into the influence of the temperature of the returned coke-ash residue on the efficiency of coal combustion. Fuel and Energy Abstracts
January 2001
47
00100448 Modelling of the combustion process and NO, emission in a utility boiler Xu, M. er al. Fuel, 2000, 79, (13) 1611-1619. This paper presents numerical simulation of the flow and combustion process in the furnace of a pulverized coal fired utility boiler of 350 MWe with 24 swirl burners installed at the furnace front wall. Five different cases with 100, 95, 85, 70 and 50% boiler full load are simulated. The comparison between the simulation and the plant data is stressed in this study. The heat flux to furnace walls between the measured values and the calculation results is compared. It is found that increasing the load leads to consistent variations in the properties presented and the exception is observed for the full load case where the predicted exit gas temperature is lower than the 95% one and the total heat to the boiler walls is smaller. This might be due to the fact of considering a linear scaling of the input parameters between the 70% and 100% load. The increase of the air flow rate led as expected to a reduction of the furnace outlet temperature and to a small decrease in NO, emissions. It shows that the NO, model used shows a higher sensitivity to temperature than to oxygen level in the furnace. The model used considered the De Soete mechanism for the nitrogen from volatiles and the contribution of char was considered in a similar way. The agreement for all cases except the one of 50% boiler load between the calculation results with the plant data validates the models and algorithm employed in the computation. The furnace performance under different boiler loads is predicted and compared in order to meet the requirements of NO, abatement and avoiding some negative side effects on the furnace.
;:;;:I49
Novel fuel regulator for coal-dust concurrent
Litovkin, V. V. and Grechanyi, A. N. Energ. Elekrrif. (Kiev), 1999, 3, 44-46. (In Russian) A novel fuel regulator is described for controlling coal-dust fired concurrent boilers. The control system uses pressure signals of the medium in the steam-water channel instead of temperature signals. The efficiency and reliability of the boiler is improved by the control scheme, owing to the improvement of the control quality by reducing time lag in the control loop.
09
00/00451 Application of plastic clad silica fibers to multiple zone flame measurements in industrial power burners Wojcik, W. Opt. Appl., 1999, 29, (l-2). 201-212. The paper presents information covering a period of 7 years on the application of fibre optic technology in monitoring, protection and start-up systems for industrial burners. A brief description of the phenomena under investigation as well as theoretical assumptions are provided. In addition, information is provided on the design of a measuring device and examples of test results with the use of this device.
Calculation of solid fuel combustion rate in circulating systems
00100452
Shraiber, A. A. Prom. Tepforekh., 1998, 20, (4), 3842. (In Russian) Solutions suitable for the analysis of distribution functions of burning particles by sizes and carbon mass concentrations in circulating systems have been obtained. This paper considers various schemes of the ash behaviour during particle combustion. The solutions are represented in the form of series in terms of the number of particles that pass through the circulating contour.
Chemistry and kinetics of chemical vapor infiltration of pyrocarbon VII: infiltration of caplllaries of equal size Hu, Z.J. et al. Carbon, 2000, 38, (7). 1059-1065. 00100453
Capillaries, 1 mm in diameter and 17 mm in depth, were infiltrated at a temperature of 1100°C and pressures of 20 kPa (Pure methane) and 30 kPa (methane-hydrogen mixture (7:l)). The residence time of the gas in the deposition reactor was 0.5 seconds, at the lower pressure of 20 kPa, residence times of 1 and 2 seconds were studied additionally. The thickness of the deposited carbon layers was determined using an X-ray microscope, i.e. without cutting the samples. In the experiments with 0.5 and 1 second residence times, an increase of the deposition rate from the mouth to the depth of the pores was obtained. The gradient of the deposition rate decreases with increasing residence time of the gas and becomes negative at 2 seconds. Hydrogen, either formed by decomposition of methane or added to the feed gas, leads to an increase in the gradient. The homogeneous-heterogeneous model of carbon deposition from methane is used to interpret the results with special consideration of deposition chemistry and diffusivity of the relevant hydrocarbon species.
00100454 Coal hydropyrolysis method Yabe, H. et al. Jpn. Kokai Tokkyo Koho JP 11 228,973 [99 228,973] (Cl. ClOGl/OO), 24 Aug 1999, Appl. 1998/27,921. 10 Feb 1998. 5. (In Japanese) A method for flash hydropyrolysis of coal is described. The procedure can be used for manufacturing gas, tar and char and comprises of fluidizing the coal by blowing a gas atmosphere containing a highconcentration of hydrogen (e.g., ~30%). The hydrogen gas is mixed with a high-temperature gas produced by a generator, in which the high-temperature gas is derived from gasification of at least a part of char after separation from a cyclone with oxygen gas. At least a part of gas produced from pyrolysis is used for refining hydrogen gas and the remaining H gas can be fed into the pyrolysis reactor for recycling.
00100455
COMBUSTION Burners, combustion systems
00/00450 Advanced low NO, burners with integrated reburn Hepburn, P. et al. Eur. Comm., [Rep.] EUR, 1999, , 1-41. Low- NO,-formation pulverized coal-fired staged burners were designed with integrated reburn zones. The reburning fuels used were natural gas or heavy fuel oil, taking into account the amount of reburn fuel fraction, the degree of reburn fuel mixing, the primary-reburn zone stoichiometry and the burnout zone stoichiometry. The NO. level can be reduced by up to 30% by the recirculation and combustion of natural gas the reburn fuel. The lowest NO. emissions was achieved with a high reburn gas injection velocity, a reburn zone temperature of 1400” and a reburn zone stoichiometry of 0.82-0.90. With reburn using heavy fuel oil, no reburn effect was achieved, this was believed to be caused by the poor quality of the pulverized coal for the tests.
Combustion behavior of Bowen Basin coals,
Australia Benfell, K. E. et al. Fuel Process. Technol., 1999, 60, (l), 1-14. Tightly constrained experimental thermogravimetry proves to be effective for characterizing the effects of rank and maceral variations on Bowen Basin coal combustion behaviour. These coals show an increase in char burnout temperature with rank for both dull, inertinite-rich and bright, vitrinite-rich coals. Dull coals in comparison to their bright rank equivalent have higher char burnouts and peak combustion temperatures. However, the maximum rates of combustion for dull coals are lower than their bright counterparts.
00100456 Combustion of low-grade coals in circulating fluidized bed
Yu, M. A. Ekotekhnol. Resursosberezhenie, 1997, 6, 3-8. (In Russian) Demonstrated in this paper is the necessity of boilers of circulating fluidized bed (CFB) for combustion of high-ash coals of low reactivity. The special features of the CFB combustion for the anthracite culm and Donets poor coal are investigated at the experimental and pilotscale facilities. The optimal combustion regimes for the coals have been determined. An investigation was also carried out into the influence of the temperature of the returned coke-ash residue on the efficiency of coal combustion. Fuel and Energy Abstracts
January 2001
47