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03873 Effect of MnO2 on the combustion-supporting efficiency of pulverized coal and its mechanism
09 99103870
Development of ash formation and deposition model during coal combustion and gasification
Ando, T. et al. Sekitan Riyo Gijutsu Kaigi Koenshu, 1998, 8, 71-89. (In Japanese) the composition and particle size During combustion and gasification, variation of inorganic particles were monitored in order to study the mechanisms of ash formation and factors that affect the ash deposition and growth. CCSEM (computer-controlled SEM) with EDX (energy dispersive X-ray detector) was used for the analysis. For use in coal gasification simulation, modelling of the ash formation behaviour is studied and a program is made to predict the composition and particle size distribution of coal ash in combustion from the CCSEM data of the original coal. 99103871
Development of methods for combustion and gasification of low-grade coal taking into account modern ecological requirements
Maistrenko, 0. Y. Energ. Elektrif., 1997, (5), 1-5. (In Ukrainian) Changes are considered for the modernization of coal-based power plants in the Ukraine. Potential modifications include low-NO,-emission swirl burners, high-load pulverized coal supply system, separation into low- and high-ash coal streams and their combustion without gas and heavy fuel oil. 99103872
Effect of coal particle size distribution on agglomerate formation in a fiuidized bed combustor (FBC)
Reddy, G. V. and Mahapatra, S. K. Energy Convers. Manage., 1999 (Pub. 1998), 40, (4). 447-458. To determine the reasons for agglomeration in a fluidized bed combustion (FBC) power plant, an investigation was conducted. Two typical coal samples were collected for investigation, the first when the plant was operating smoothly and the second immediately after agglomeration. These two samples were subjected to analysis. Agglomeration of the bed material in FBC plants was found to take place when the coal sample contains either too many very fine particles or too many very coarse particles or both in very large proportion. The very fine particles present in the coal have considerable plastic properties (caking and swelling tendency), which cause agglomeration. The coarser particles are denser because of their higher ash content and their higher density causes an increase in minimum fluidization velocity; this leads to agglomeration and defluidization. Medium size coal particles are most suitable for combustion in a FBC.
Effect of MnOa on the combustion-supporting 99103873 efficiency of pulverized coal and its mechanism Shen, F. et al. Gangtie, 1998, 33, (9), 1-3, 8. (In Chinese) The paper studied the effect of MnOz on the combustion efficiency of different kind of pulverized coal and the mechanism for the increasing of the combustion efficiency by MnOZ. The combustion efficiency was greatly increased with the increasing of MnOz amount, 18% for anthracite coal (volatile material content 8%) and 8% for bituminous coal (volatile matter content 33%) with the addition of 5% MnOZ. The mechanism for the increase in the combustion efficiency involves the release of active oxygen during the thermal decomposition of MnOz, which promotes the flame propagation during the initial stage of the combustion. The combustion efficiency can be further increased by the addition of MnOZ in combination with oxygen enrichment. 99103874
Effects of pressure and oxygen concentration on the combustion of different coals
Joutsenoja, T. et al. Energy Fuels, 1999, 13, (l), 130-145. For simultaneous in-situ measurement of the temperature and size of individual coal particles in a pressurized entrained flow reactor, a pyrometric method was used. Several series of measurements were made in the gas temperature range 1150-1270 K to study the effects of pressure (0.2-1.0 MPa) and oxygen volume fraction (3-30 ~01%) on the particle temperature and size distributions and on the mean degree of burn-off at well-defined residence times. The fuels used were lignite from France, highvolatile bituminous (hvb) coals from Germany and Poland (mixture) and anthracite from Germany; reactivity varied greatly between the coals. Milled fuel was sieved into nominal-size fractions in the range from 75 to including size and 180 pm. Results from in-situ particle measurements, temperature recording, have not been presented previously at elevated pressures for such a wide range of coals. Measurements on combustion rates, particle temperatures and particle sizes were analysed with a singleparticle combustion model. Compared to the oxygen content and temperature, the effect of pressure on the surface reaction kinetics for an anthracite was found to be small. 99103875
Estimation of the composition change in products of under round coal combustion due to the formation of combust Bbie gases
Yanchenko, G. A. Izv. Vyssh. Uchebn. Zaved., Gorn. Zh., 1998, (5/6), l-4. (In Russian) From the existing data of full-scale experiments on the in-situ combustion of coal, it is indicated that the products include both the gases from the complete combustion of coal in air and the combustible gases generated by incomplete combustion of coal, its gasification and thermal decomposition. Correlations used in the calculation of the effect of CO, H2 and CH4 on the composition of the product gas are discussed here.
Combustion
(burners, combustion
systems)
High efficiency power generation from coal and wastes utilizing high temperature air combustion technology. (Part ii: Thermal performance of compact high temperature air preheater and MEET boiler)
99103878
Iwahaski, T. et al. FACT (Am. Sot. Mech. Eng.), 1998, 22, (l), 489-494. As critical components of the MEET system, the compact high temperature air preheater and the MEET boiler are the direct evolutions of the high temperature air combustion technology. An innovative hardware concept for a compact high-temperature air preheater has been proposed and preliminary experimentation using the MEET-I high temperature air preheater, based on this concept, successfully demonstrated continuous high-temperature air generation with almost no temperature fluctuation. The heat transfer characteristics in the MEET boiler were experimentally measured and the heat transfer promotion effect and the uniform heat transfer field were confirmed. Excellent combustion was also achieved with the low BTU gas of about 3000 kcal/m7.
99103877
ignition of fuel mixtures by standing acoustic
waves
Vainshtein, P. et al. Combustion and Flame, 1999, 118, (3), 370-380. A stationary problem of ignition of a fuel mixture enclosed between two parallel walls which are kept at a constant temperature, is examined. A onestep, Arrhenius reaction of large activation energy with negligible reactant depletion represents the chemistry. The Frank-Kamenetskii parameter is assumed to be very small, so that a thermal explosion does not occur without the action of some external source. A standing plane sonic wave is imposed in the longitudinal direction. The distance between the walls is much smaller than the sound wavelength. Rayleigh’s type vertical acoustic streaming that appears in the region leads to forced heat convection. The effect of that forced convection on heat transfer in the presence of heat release due to the chemical reaction is analysed theoretically. The analysis demonstrates that acoustic streaming at large streaming Reynolds numbers results in ignition of the mixture.
influence of process conditions on the pyrolysis of Pakistani oil shales
99103878
Williams, P. T. and Ahmad, N. Fuel, 1999, 78, (6), 653-662. A thermogravimetric analyser (TGA) and a fixed bed reactor were used to pyrolyse oil shale samples of two geological ages, Infracambrian and Focene from two regions of Pakistan to determine the influence of temperature and heating rate on thermal degradation. The heating rates investigated in the TGA were, 5-4o”C min-’ to a final temperature of 950°C. For the oil shale samples analysed in the TGA, increasing the heating rate shifted the reaction to higher temperatures. The main region of weight loss corresponding to hydrocarbon oil and gas release was between 2OO’C and 620°C and at higher temperatures, significant weight loss was attributed to carbonate decomposition. Two of the oil shale samples were also investigated in a fixed bed reactor to determine the influence of heating rate and temperature of pyrolysis on the yield of products and composition of the gases evolved. The pyrolysis reactor was 200 cm’ volume, constructed of stainless steel and externally electrically heated. The samples were heated to 520°C at heating rates similar to those of the TGA; in addition, the influence of pyrolysis temperature between 400 and 650°C was also investigated. The maximum oil yield was optimized in terms of heating rate and in terms of temperature at 500°C. Maximum oil yields at 20°C min-’ were between 12.0 and 16.5 wt% for the two oil shales used representing a considerable potential source of liquid hydrocarbons for Pakistan. Gaseous yield increased linearly with both increasing heating rate and increased pyrolysis temperature. There was a corresponding decrease in spent shale. Alkene/alkane gas ratios were determined and were linked to secondary reactions, which were discussed in relation to the formation of oil.
A laboratory study of spontaneous combustion of coal: the influence of inorganic matter and reactor size
99103879
Sujanti, W. and Zhang, D.-k. Fuel, 1999, 78, (5), 549-556. The effect of inorganic matter on the spontaneous combustion behaviour of a Victorian brown coal was the subject of a laboratory investigation. Fourteen samples were prepared, namely, the raw coal, water-washed coal, acid-washed coal and acid-washed coal doped with 11 additives. Each of the samples was then tested in an isothermal reactor to obtain its critical ambient temperature, above which spontaneous combustion occurs. The relative effectiveness of the additives was determined by comparing their critical ambient temperatures with those of the raw coal and the acidwashed coal. Potassium chloride, Montan powder and sodium chloride were found to be the most effective inhibitors, followed by magnesium acetate and calcium chloride. The presence of sodium nitrate and ammonium chloride in the coal samples did not show any significant influence on the spontaneous combustion. However, calcium carbonate, sodium acetate, potassium acetate and pyrite promoted the spontaneous combustion. The effect of additive loading was also investigated for an inhibition agent (KCI) and a promotion agent (NaAc). It was revealed that the effectiveness of these promotion and inhibition agents was enhanced with an increase in the additive loading. Low-temperature oxidation kinetics were also estimated by an energy balance approach and compared with the self-heating potential of these samples. The effects of reactor size and reactor specific surface area on the critical ambient temperatures are also discussed.
Fuel and Energy Abstracts
November 1999 407
Development of ash formation and deposition model during coal combustion and gasification
Ando, T. et al. Sekitan Riyo Gijutsu Kaigi Koenshu, 1998, 8, 71-89. (In Japanese) the composition and particle size During combustion and gasification, variation of inorganic particles were monitored in order to study the mechanisms of ash formation and factors that affect the ash deposition and growth. CCSEM (computer-controlled SEM) with EDX (energy dispersive X-ray detector) was used for the analysis. For use in coal gasification simulation, modelling of the ash formation behaviour is studied and a program is made to predict the composition and particle size distribution of coal ash in combustion from the CCSEM data of the original coal. 99103871
Development of methods for combustion and gasification of low-grade coal taking into account modern ecological requirements
Maistrenko, 0. Y. Energ. Elektrif., 1997, (5), 1-5. (In Ukrainian) Changes are considered for the modernization of coal-based power plants in the Ukraine. Potential modifications include low-NO,-emission swirl burners, high-load pulverized coal supply system, separation into low- and high-ash coal streams and their combustion without gas and heavy fuel oil. 99103872
Effect of coal particle size distribution on agglomerate formation in a fiuidized bed combustor (FBC)
Reddy, G. V. and Mahapatra, S. K. Energy Convers. Manage., 1999 (Pub. 1998), 40, (4). 447-458. To determine the reasons for agglomeration in a fluidized bed combustion (FBC) power plant, an investigation was conducted. Two typical coal samples were collected for investigation, the first when the plant was operating smoothly and the second immediately after agglomeration. These two samples were subjected to analysis. Agglomeration of the bed material in FBC plants was found to take place when the coal sample contains either too many very fine particles or too many very coarse particles or both in very large proportion. The very fine particles present in the coal have considerable plastic properties (caking and swelling tendency), which cause agglomeration. The coarser particles are denser because of their higher ash content and their higher density causes an increase in minimum fluidization velocity; this leads to agglomeration and defluidization. Medium size coal particles are most suitable for combustion in a FBC.
Effect of MnOa on the combustion-supporting 99103873 efficiency of pulverized coal and its mechanism Shen, F. et al. Gangtie, 1998, 33, (9), 1-3, 8. (In Chinese) The paper studied the effect of MnOz on the combustion efficiency of different kind of pulverized coal and the mechanism for the increasing of the combustion efficiency by MnOZ. The combustion efficiency was greatly increased with the increasing of MnOz amount, 18% for anthracite coal (volatile material content 8%) and 8% for bituminous coal (volatile matter content 33%) with the addition of 5% MnOZ. The mechanism for the increase in the combustion efficiency involves the release of active oxygen during the thermal decomposition of MnOz, which promotes the flame propagation during the initial stage of the combustion. The combustion efficiency can be further increased by the addition of MnOZ in combination with oxygen enrichment. 99103874
Effects of pressure and oxygen concentration on the combustion of different coals
Joutsenoja, T. et al. Energy Fuels, 1999, 13, (l), 130-145. For simultaneous in-situ measurement of the temperature and size of individual coal particles in a pressurized entrained flow reactor, a pyrometric method was used. Several series of measurements were made in the gas temperature range 1150-1270 K to study the effects of pressure (0.2-1.0 MPa) and oxygen volume fraction (3-30 ~01%) on the particle temperature and size distributions and on the mean degree of burn-off at well-defined residence times. The fuels used were lignite from France, highvolatile bituminous (hvb) coals from Germany and Poland (mixture) and anthracite from Germany; reactivity varied greatly between the coals. Milled fuel was sieved into nominal-size fractions in the range from 75 to including size and 180 pm. Results from in-situ particle measurements, temperature recording, have not been presented previously at elevated pressures for such a wide range of coals. Measurements on combustion rates, particle temperatures and particle sizes were analysed with a singleparticle combustion model. Compared to the oxygen content and temperature, the effect of pressure on the surface reaction kinetics for an anthracite was found to be small. 99103875
Estimation of the composition change in products of under round coal combustion due to the formation of combust Bbie gases
Yanchenko, G. A. Izv. Vyssh. Uchebn. Zaved., Gorn. Zh., 1998, (5/6), l-4. (In Russian) From the existing data of full-scale experiments on the in-situ combustion of coal, it is indicated that the products include both the gases from the complete combustion of coal in air and the combustible gases generated by incomplete combustion of coal, its gasification and thermal decomposition. Correlations used in the calculation of the effect of CO, H2 and CH4 on the composition of the product gas are discussed here.
Combustion
(burners, combustion
systems)
High efficiency power generation from coal and wastes utilizing high temperature air combustion technology. (Part ii: Thermal performance of compact high temperature air preheater and MEET boiler)
99103878
Iwahaski, T. et al. FACT (Am. Sot. Mech. Eng.), 1998, 22, (l), 489-494. As critical components of the MEET system, the compact high temperature air preheater and the MEET boiler are the direct evolutions of the high temperature air combustion technology. An innovative hardware concept for a compact high-temperature air preheater has been proposed and preliminary experimentation using the MEET-I high temperature air preheater, based on this concept, successfully demonstrated continuous high-temperature air generation with almost no temperature fluctuation. The heat transfer characteristics in the MEET boiler were experimentally measured and the heat transfer promotion effect and the uniform heat transfer field were confirmed. Excellent combustion was also achieved with the low BTU gas of about 3000 kcal/m7.
99103877
ignition of fuel mixtures by standing acoustic
waves
Vainshtein, P. et al. Combustion and Flame, 1999, 118, (3), 370-380. A stationary problem of ignition of a fuel mixture enclosed between two parallel walls which are kept at a constant temperature, is examined. A onestep, Arrhenius reaction of large activation energy with negligible reactant depletion represents the chemistry. The Frank-Kamenetskii parameter is assumed to be very small, so that a thermal explosion does not occur without the action of some external source. A standing plane sonic wave is imposed in the longitudinal direction. The distance between the walls is much smaller than the sound wavelength. Rayleigh’s type vertical acoustic streaming that appears in the region leads to forced heat convection. The effect of that forced convection on heat transfer in the presence of heat release due to the chemical reaction is analysed theoretically. The analysis demonstrates that acoustic streaming at large streaming Reynolds numbers results in ignition of the mixture.
influence of process conditions on the pyrolysis of Pakistani oil shales
99103878
Williams, P. T. and Ahmad, N. Fuel, 1999, 78, (6), 653-662. A thermogravimetric analyser (TGA) and a fixed bed reactor were used to pyrolyse oil shale samples of two geological ages, Infracambrian and Focene from two regions of Pakistan to determine the influence of temperature and heating rate on thermal degradation. The heating rates investigated in the TGA were, 5-4o”C min-’ to a final temperature of 950°C. For the oil shale samples analysed in the TGA, increasing the heating rate shifted the reaction to higher temperatures. The main region of weight loss corresponding to hydrocarbon oil and gas release was between 2OO’C and 620°C and at higher temperatures, significant weight loss was attributed to carbonate decomposition. Two of the oil shale samples were also investigated in a fixed bed reactor to determine the influence of heating rate and temperature of pyrolysis on the yield of products and composition of the gases evolved. The pyrolysis reactor was 200 cm’ volume, constructed of stainless steel and externally electrically heated. The samples were heated to 520°C at heating rates similar to those of the TGA; in addition, the influence of pyrolysis temperature between 400 and 650°C was also investigated. The maximum oil yield was optimized in terms of heating rate and in terms of temperature at 500°C. Maximum oil yields at 20°C min-’ were between 12.0 and 16.5 wt% for the two oil shales used representing a considerable potential source of liquid hydrocarbons for Pakistan. Gaseous yield increased linearly with both increasing heating rate and increased pyrolysis temperature. There was a corresponding decrease in spent shale. Alkene/alkane gas ratios were determined and were linked to secondary reactions, which were discussed in relation to the formation of oil.
A laboratory study of spontaneous combustion of coal: the influence of inorganic matter and reactor size
99103879
Sujanti, W. and Zhang, D.-k. Fuel, 1999, 78, (5), 549-556. The effect of inorganic matter on the spontaneous combustion behaviour of a Victorian brown coal was the subject of a laboratory investigation. Fourteen samples were prepared, namely, the raw coal, water-washed coal, acid-washed coal and acid-washed coal doped with 11 additives. Each of the samples was then tested in an isothermal reactor to obtain its critical ambient temperature, above which spontaneous combustion occurs. The relative effectiveness of the additives was determined by comparing their critical ambient temperatures with those of the raw coal and the acidwashed coal. Potassium chloride, Montan powder and sodium chloride were found to be the most effective inhibitors, followed by magnesium acetate and calcium chloride. The presence of sodium nitrate and ammonium chloride in the coal samples did not show any significant influence on the spontaneous combustion. However, calcium carbonate, sodium acetate, potassium acetate and pyrite promoted the spontaneous combustion. The effect of additive loading was also investigated for an inhibition agent (KCI) and a promotion agent (NaAc). It was revealed that the effectiveness of these promotion and inhibition agents was enhanced with an increase in the additive loading. Low-temperature oxidation kinetics were also estimated by an energy balance approach and compared with the self-heating potential of these samples. The effects of reactor size and reactor specific surface area on the critical ambient temperatures are also discussed.
Fuel and Energy Abstracts
November 1999 407