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00582 Secondary effects in sampling ammonia during measurements in a circulating fluidized-bed combustor
09
higher laser input has the same effect. It is also shown that the sustained combustion temperature rises and the combustion period decreases with a higher oxygen content. Optimization of staged combustion minimizing NO, 98/00572 yield in pulverized coal flame Zhong, B. and Fu, W.-B. Ranshao Kexrre Yu Jishu, 1997, 3, (2), 169-174. (In Chinese) In this paper, optimization of staged combustion of pulverized coal is carried out and four-staged combustion of pulverized coal is determined through numerical modelling for low level of NO, yield. P.f. combustion behavior of Canadian coals in 98100573 relation to their petrographic characteristics Borrego, A. C. et al. DGMK Tagrrngsher., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 1019-1022. Selected Canadian coals’ combustion behaviour was studied in the light of their chemical and petrographical compositions. Despite the differences in their maceral composition, good relationships between petrographical and chemical rank parameters were found. Characteristic temperatures such as those of maximum reaction rate and maximum volatile release correlate well with coal rank, whereas reactivity and burnout temperatures appear to be affected by maceral composition. Pore structure evolution of low rank coals during 98100574 rapid and slow pyrolysis Albiniak, A. er al. DGMK Tugungsher., 1997, 9703, (Proceedings ICCS ‘97, Volume 2), 785-788. Varying in rank, seven coals were pyrolysed with the heating rates I4 Kimin and ltls K/s. During these procedures, the micro-, mesa-, and macroporosity changes occurring could be observed through benzene and carbon dioxide sorption measurements. and evaluations of the real and apparent densities. Mild conditions of pyrolysis lead to a greater overall porosity development, however rapid pyrolysis promoted the greater extent the micro-and mesopore development than slow pyrolysis. Coal rank very strongly influences the course of porosity development of the chars. 98100575 Process and apparatus for coal pyrolysis involving desulfurization Ikeda. Y. et al. Jpn. Kokai Tokkyo Koho JP 09,202,888 [97,202,888] (Cl. ClOJ3146) 5 Aug 1997, Appl. 96111,466, 26 Jan 1996, 4 pp. (In Japanese) A high-temperature gas is obtained by combustion of a part of char in a gasification furnace and used in the process for coal pyrolysis. The process involves the removal of HzS from the gases produced in the gasification furnace and the pyrolysis furnace by adding CaO or calcined dolomite to coal. It is preferable to separate by-product char and H&absorbing CaO from coal gas and classify the char and char-containing CaO, and fire charcontaining CaO to give CaS04. The apparatus consists of a pyrolysis furnace, a dust collector, a classifier for char and CaO, a combustion furnace for S-containing CaO, and a char-gasification furnace connected to the classifier via a char-recovery duct. CaO, added to coal, removes HIS from coal gas without an expensive desulfurization apparatus and CaS04 can be used for a cement material. 98100576 Relationship between combustion properties and formation of volatile matter of coal and biomass Li, W. DGMK Tagungsber., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 967-970. A study of nine hard coals and five biomasses was performed with pyrolysis and combustion tests under non-isothermal conditions in a TGA equipment. The results indicated limited correlations between pyrolysis results and combustion properties in some aspects. For CO and CH4 formation, a correlation was observed including hard coals and biomasses. Release of alkali vapor during coal combustion in a 98100577 semi-technical entrained flow reactor Reichelt, T. cf al. DGMK Tagungsher., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 1051-1054. The vapour release of one hard coal (Ruhr District) and one Rhenish brown coal during combustion was investigated in a semi-technical entrained flow reactor at 900-1300°C. Two independent methods-Excimer laser-induced fragmentation fluorescence (ELIF) and an extractive wetchemical method-were used to measure absolute gas-phase concentrations of Na and K compounds. Results of both methods are compared and discussed. 9atoo57a The release of NO during char combustion Zhu. Q. et al. DGMK Tagungsher., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 1123-1126. NO production from coal char combustion was compared with that from combustion of various carbons prepared as models for coal chars. The results show similar trends for both the carbons and the coal chars. The conversion of char nitrogen to NO during combustion is related to char structure and reactivity. NO is the primary product of char nitrogen oxidation and this is partly reduced on the surface and in the pores of the char to NZO and Nz.
Combustion
(burners, combustion
systems)
gal00579 Researches on SOP removal in desulphurized CWS combustion Fan, H. et al. Proc. Int. Tech. Conf Coal Util. Fuel Syst., 1996, 21, 799-808. Desulfurized coal-water slurry (CWS) combustion was studied to investigate the SO? removal. The limestone sorbent is mixed in CWS prior to combustion. Limestone calcines react with a portion of the SO? in the furnace. Unreacted lime becomes active and reacts with the SO? in flue pass and bag-filter. The sorbent utilization and SO1 removal efficiency increase because SOz-removal occurs in three zones: in the furnace, flue pass and bag-filter. The paper describes how SO? removal is affected by the flame temperature and CaiS ratio. The effects of humidification and bag-filter were also studied. A test was done in a CWS combustion facility consisting of a combustor, a flue gas pass, and a filter; flue gas concentrations and flame temperature were measured. The flame temperature was controlled between 1100 and 1500°C. The furnace temperature and CaiS ratio are two important factors. The optimum flame temperature is related to the residence time in the furnace. SOz removal is also affected by humidification and the bag-filter; removal efficiency can be influenced by up to 20%. A 70% removal efficiency is achieved at Ca/S ratio of I.5 and 1200°C of flame temperature. Therefore, SOz removal in CWS combustion is a good method of its control in coal based fuel combustion. X-ray diffraction instrument was used to study the mechanism. 98100580 Results from sampling full-scale coal combustion systems for air toxic emissions Wesnor, J. D. Proc. Inr. Tech. Conf. Coal Util. Fuel Sysr., 1995, 20, I-I 0. ABB has been actively developing a knowledge base on the Title III hazardous air pollutants, more commonly called air toxics. In addition to design experience and database acquired in Europe. ABB has conducted source sampling and analysis at commercial installations for hazardous air pollutants to determine the emission rates and removal performance of various types of equipment. Several different plants hosted these activities, allowing for variation in fuel type and composition, boiler configuration, and air pollution control equipment. This paper discusses the results of these investigations. 98/005at On the role of limestone in the conversion of fuel-N in fluidized-bed combustion (FBC) of coal Schafer, S. et al. DGMK Tugungsber., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 1091-1094. An established SOz control technique is limestone addition in FBC of coal. However, CaO interferes with fuel-N conversion by enhancing the NO emission while strongly reducing NzO release. In laboratory experiments, the role of Ca-compounds on combustion of HCN was studied. CaCN? is an intermediate product that directs the fuel-N conversion towards the formation of NH? which is subsequently quickly oxidized to NO. Gaseous SO:, the concentration of which is controlled in FBC by limestone, interacts as well with fuel-N intermediates and suppresses the formation of NO while favouring NzO formation. 9aioo582 Secondary effects in sampling ammonia during measurements in a circulating fluidized-bed combustor Kassman, H. et al. J. Inst. Energy, 1997, 70, (484), 95-103. Two sampling techniques were used in previous work to measure the ammonia concentration in the combustion chamber of a circulating fluidized-bed (CFB) boiler: a gas-quenching (GQ) probe where the sample is quenched directly in the probe tip by a circulating trapper solution. and a gas-sampling probe connected to a Fourier-transform infra-red (FTIR) instrument. This paper attempts to estimate the influence of potential secondary reactions with NH3 in the GQ probe tip by means of a plug-flow model. The calculations showed that heterogeneous and homogeneous reactions could be of importance to the accuracy of the measurement. This contradicts the almost identical results relative to the parallel FTIR measurement, and the conversion of NH? is probably overestimated by the model. In addition, transients obtained during the FTIR measurement were used to study the accuracy of the gas-sampling probe. 9aioo583 Spontaneous ignition delays as a diagnostic of the propensity of alkanes to cause engine knock Griffiths, J. F. er al. Combustion and Flame, 1997, 111 1 (4), 327-337. An investigation has been carried out into the spontaneous ignition of a range of alkanes (C&k) and of mixtures of the primary reference fuels (PRF), n-heptane + i-octane (2.2.4 trimethylpentane). Autoignition delays were measured over a wide range of compressed gas temperatures (T,) at gas densities of 131 mol mm3 in a rapid compression machine. A reference temperature, typical of that reached in the end gas of spark ignition engines under violent knocking conditions was used as a basis of comparison of ignition delay of the single fuels with the comparable PRF mixtures with respect to the research octane number (RON). The results are presented, 9aioo584 Status and prospects of research in the International Flame Research Foundation (IFRF). I Daimon, J. Kogyo Kanetsu, 1997, 34, (3) 25-32. (In Japanese). Research activities in IFRF are reviewed. Cement kiln burners, pulverized coal burners for power generation, combined combustion of biomass, sewage sludge and pulverized coal, combustion behaviour of solid fuels, combustion of natural gas with pure oxygen, combustion of pulverized coal with recycle exhaust gas, modelling, and flame measurements are among the activities reported.
Fuel and Energy Abstracts
January 1996
49
higher laser input has the same effect. It is also shown that the sustained combustion temperature rises and the combustion period decreases with a higher oxygen content. Optimization of staged combustion minimizing NO, 98/00572 yield in pulverized coal flame Zhong, B. and Fu, W.-B. Ranshao Kexrre Yu Jishu, 1997, 3, (2), 169-174. (In Chinese) In this paper, optimization of staged combustion of pulverized coal is carried out and four-staged combustion of pulverized coal is determined through numerical modelling for low level of NO, yield. P.f. combustion behavior of Canadian coals in 98100573 relation to their petrographic characteristics Borrego, A. C. et al. DGMK Tagrrngsher., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 1019-1022. Selected Canadian coals’ combustion behaviour was studied in the light of their chemical and petrographical compositions. Despite the differences in their maceral composition, good relationships between petrographical and chemical rank parameters were found. Characteristic temperatures such as those of maximum reaction rate and maximum volatile release correlate well with coal rank, whereas reactivity and burnout temperatures appear to be affected by maceral composition. Pore structure evolution of low rank coals during 98100574 rapid and slow pyrolysis Albiniak, A. er al. DGMK Tugungsher., 1997, 9703, (Proceedings ICCS ‘97, Volume 2), 785-788. Varying in rank, seven coals were pyrolysed with the heating rates I4 Kimin and ltls K/s. During these procedures, the micro-, mesa-, and macroporosity changes occurring could be observed through benzene and carbon dioxide sorption measurements. and evaluations of the real and apparent densities. Mild conditions of pyrolysis lead to a greater overall porosity development, however rapid pyrolysis promoted the greater extent the micro-and mesopore development than slow pyrolysis. Coal rank very strongly influences the course of porosity development of the chars. 98100575 Process and apparatus for coal pyrolysis involving desulfurization Ikeda. Y. et al. Jpn. Kokai Tokkyo Koho JP 09,202,888 [97,202,888] (Cl. ClOJ3146) 5 Aug 1997, Appl. 96111,466, 26 Jan 1996, 4 pp. (In Japanese) A high-temperature gas is obtained by combustion of a part of char in a gasification furnace and used in the process for coal pyrolysis. The process involves the removal of HzS from the gases produced in the gasification furnace and the pyrolysis furnace by adding CaO or calcined dolomite to coal. It is preferable to separate by-product char and H&absorbing CaO from coal gas and classify the char and char-containing CaO, and fire charcontaining CaO to give CaS04. The apparatus consists of a pyrolysis furnace, a dust collector, a classifier for char and CaO, a combustion furnace for S-containing CaO, and a char-gasification furnace connected to the classifier via a char-recovery duct. CaO, added to coal, removes HIS from coal gas without an expensive desulfurization apparatus and CaS04 can be used for a cement material. 98100576 Relationship between combustion properties and formation of volatile matter of coal and biomass Li, W. DGMK Tagungsber., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 967-970. A study of nine hard coals and five biomasses was performed with pyrolysis and combustion tests under non-isothermal conditions in a TGA equipment. The results indicated limited correlations between pyrolysis results and combustion properties in some aspects. For CO and CH4 formation, a correlation was observed including hard coals and biomasses. Release of alkali vapor during coal combustion in a 98100577 semi-technical entrained flow reactor Reichelt, T. cf al. DGMK Tagungsher., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 1051-1054. The vapour release of one hard coal (Ruhr District) and one Rhenish brown coal during combustion was investigated in a semi-technical entrained flow reactor at 900-1300°C. Two independent methods-Excimer laser-induced fragmentation fluorescence (ELIF) and an extractive wetchemical method-were used to measure absolute gas-phase concentrations of Na and K compounds. Results of both methods are compared and discussed. 9atoo57a The release of NO during char combustion Zhu. Q. et al. DGMK Tagungsher., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 1123-1126. NO production from coal char combustion was compared with that from combustion of various carbons prepared as models for coal chars. The results show similar trends for both the carbons and the coal chars. The conversion of char nitrogen to NO during combustion is related to char structure and reactivity. NO is the primary product of char nitrogen oxidation and this is partly reduced on the surface and in the pores of the char to NZO and Nz.
Combustion
(burners, combustion
systems)
gal00579 Researches on SOP removal in desulphurized CWS combustion Fan, H. et al. Proc. Int. Tech. Conf Coal Util. Fuel Syst., 1996, 21, 799-808. Desulfurized coal-water slurry (CWS) combustion was studied to investigate the SO? removal. The limestone sorbent is mixed in CWS prior to combustion. Limestone calcines react with a portion of the SO? in the furnace. Unreacted lime becomes active and reacts with the SO? in flue pass and bag-filter. The sorbent utilization and SO1 removal efficiency increase because SOz-removal occurs in three zones: in the furnace, flue pass and bag-filter. The paper describes how SO? removal is affected by the flame temperature and CaiS ratio. The effects of humidification and bag-filter were also studied. A test was done in a CWS combustion facility consisting of a combustor, a flue gas pass, and a filter; flue gas concentrations and flame temperature were measured. The flame temperature was controlled between 1100 and 1500°C. The furnace temperature and CaiS ratio are two important factors. The optimum flame temperature is related to the residence time in the furnace. SOz removal is also affected by humidification and the bag-filter; removal efficiency can be influenced by up to 20%. A 70% removal efficiency is achieved at Ca/S ratio of I.5 and 1200°C of flame temperature. Therefore, SOz removal in CWS combustion is a good method of its control in coal based fuel combustion. X-ray diffraction instrument was used to study the mechanism. 98100580 Results from sampling full-scale coal combustion systems for air toxic emissions Wesnor, J. D. Proc. Inr. Tech. Conf. Coal Util. Fuel Sysr., 1995, 20, I-I 0. ABB has been actively developing a knowledge base on the Title III hazardous air pollutants, more commonly called air toxics. In addition to design experience and database acquired in Europe. ABB has conducted source sampling and analysis at commercial installations for hazardous air pollutants to determine the emission rates and removal performance of various types of equipment. Several different plants hosted these activities, allowing for variation in fuel type and composition, boiler configuration, and air pollution control equipment. This paper discusses the results of these investigations. 98/005at On the role of limestone in the conversion of fuel-N in fluidized-bed combustion (FBC) of coal Schafer, S. et al. DGMK Tugungsber., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 1091-1094. An established SOz control technique is limestone addition in FBC of coal. However, CaO interferes with fuel-N conversion by enhancing the NO emission while strongly reducing NzO release. In laboratory experiments, the role of Ca-compounds on combustion of HCN was studied. CaCN? is an intermediate product that directs the fuel-N conversion towards the formation of NH? which is subsequently quickly oxidized to NO. Gaseous SO:, the concentration of which is controlled in FBC by limestone, interacts as well with fuel-N intermediates and suppresses the formation of NO while favouring NzO formation. 9aioo582 Secondary effects in sampling ammonia during measurements in a circulating fluidized-bed combustor Kassman, H. et al. J. Inst. Energy, 1997, 70, (484), 95-103. Two sampling techniques were used in previous work to measure the ammonia concentration in the combustion chamber of a circulating fluidized-bed (CFB) boiler: a gas-quenching (GQ) probe where the sample is quenched directly in the probe tip by a circulating trapper solution. and a gas-sampling probe connected to a Fourier-transform infra-red (FTIR) instrument. This paper attempts to estimate the influence of potential secondary reactions with NH3 in the GQ probe tip by means of a plug-flow model. The calculations showed that heterogeneous and homogeneous reactions could be of importance to the accuracy of the measurement. This contradicts the almost identical results relative to the parallel FTIR measurement, and the conversion of NH? is probably overestimated by the model. In addition, transients obtained during the FTIR measurement were used to study the accuracy of the gas-sampling probe. 9aioo583 Spontaneous ignition delays as a diagnostic of the propensity of alkanes to cause engine knock Griffiths, J. F. er al. Combustion and Flame, 1997, 111 1 (4), 327-337. An investigation has been carried out into the spontaneous ignition of a range of alkanes (C&k) and of mixtures of the primary reference fuels (PRF), n-heptane + i-octane (2.2.4 trimethylpentane). Autoignition delays were measured over a wide range of compressed gas temperatures (T,) at gas densities of 131 mol mm3 in a rapid compression machine. A reference temperature, typical of that reached in the end gas of spark ignition engines under violent knocking conditions was used as a basis of comparison of ignition delay of the single fuels with the comparable PRF mixtures with respect to the research octane number (RON). The results are presented, 9aioo584 Status and prospects of research in the International Flame Research Foundation (IFRF). I Daimon, J. Kogyo Kanetsu, 1997, 34, (3) 25-32. (In Japanese). Research activities in IFRF are reviewed. Cement kiln burners, pulverized coal burners for power generation, combined combustion of biomass, sewage sludge and pulverized coal, combustion behaviour of solid fuels, combustion of natural gas with pure oxygen, combustion of pulverized coal with recycle exhaust gas, modelling, and flame measurements are among the activities reported.
Fuel and Energy Abstracts
January 1996
49