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00614 Ash sintering and deposit formation in PFBC
09
Analyzing peat pyrolysis by in-situ FTIR Feng, J. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (7), 16-20. In this study the objective is to analyse peat pyrolysis using in-situ pyrolysisFTIR and to establish the pyrolysis model.
QQlOO612
Ash characteristics and minerals behavior during 99/00613 coal blend combustion Qiu, J. el at. Proc. Annu. Int. Pimburgh Coal Conf., 1997, 14, (12), 3-8. The mineral behaviours and ash characteristics of several individual coals and a series of two-component coal blends were studied. The ash fusibility and viscosity were measured and analysed. Some samples were heated progressively from 800°C to Tl (initial deformation temperature) at 100°C intervals in reducing atmosphere. Mineral composition and types at each temperature interval were determined by x-ray diffraction analysis. Proposed were the prediction methods for slagging tendency. Ash sintering and deposit formation in PFBC QQiQQ614 Steenari, B.-M. et al. Fuel, 1998, 77, (5). 407-417. Using chemical and X-ray diffraction methods agglomerated bed material and deposits from various surfaces in the bed area and in the flue gas duct of pressurized fluidized bed combustion (PFBC) plants were examined. Crystalline compounds present in the deposits were identified and possible mechanisms leading to the formation of bed material agglomerates, deposits and fouling on surfaces in the flue gas duct are discussed. In the sintering and fouling process all of the chemical systems CaS-CaSOd-alkali and silicate systems containing iron-rich species, silicate-alkali-chlorine oxides are important.
Assessment of PAH emissions as a function of QQIOO615 coal combustion variables in fluidised bed. 2. Air excess percentage Mastral, A. M. ef al. Fuel, 1998, 77, (13). 1513-1516. With the aim of studying the influence of the air excess percentage on the PAH formation and emission, a low rank coal combustion was carried out in a fluidized bed combustion pilot plant at laboratory scale. The experiments were performed at 850°C with a constant air total flow of 860 L h-l, varying the coal feeding rate and therefore the air excess percentages. In each experiment, five samples have been collected from two cyclones, nylon filter, bubbling system and adsorption system. FS (fluorescence spectroscopy in mode synchronous) has been used to analyse the PAH contained in these five samples after extraction by sonication with dimethyl-formamide (DMF). The analyses show that the total PAH amount keeps a close relationship with the air excess percentage: the higher the air excess. the lower the total PAH amount emitted.
QQlOO616 Fehrs, J. E. Mater.,
Biomass
assessments
for co-firing
Making Bus. Biomass Energy, Environ., Chemical, Fibers Edited by Proc. Biomass Conf. Am. 3rd, 1997, (2), 1463-1472.
Overend, R. P. and Chornet, E. The co-combustion of biomass materials with fossil fuels has been carried out by the pulp and paper industry for many years, primarily as a method to dispose of large quantities of waste biomass. However, co-firing at utility power plants is relatively new and is gaining popularity. Co-firing refers to substitution of biomass fuels or other alternative, non-fossil fuels for coal in boilers designed for coal combustion. Co-firing of biomass is typically limited to no more than about 20% of the fuel input due primarily to concerns about derating of the boiler. The benefits of co-firing biomass are varied. Biomass fuels may be available at a price below this cost, resulting in lower fuel procurement expenditures. Utilities that co-fire may be able to provide a disposal service to waste biomass generators within the utility’s service area. Biomass contains low levels of sulfur, and the formation of SO2 when co-firing will be reduced by an amount proportional to the cofiring rate. Formation of NO, may also be reduced, due to the combustion process when co-firing, however the reduction is not proportional to co-fire rate, but may actually be greater than the co-fire rate.
Blast furnace models to analyse raceway zone 99/00617 formation and to predict lining life Gordon, Y. et al. Ironmaking Conf. Proc., 1998, 57, 351-361. Developed was a two-dimensional mathematical model of material and gas movement, heat and mass transfer in the blast furnace. Semi-empirical equations were used to calculate the raceway dimensions. The regularities of raceway formation and its influence on material and gas velocities, temperature and concentration of the furnace were studied. The possibility of the formation of two circulation zones in the raceway region was illustrated. In addition, a mathematical model of coke and coal combustion was developed. The optimal tuyere parameters for coal injection system were determined. The computer based system was developed to verify the temperature of gas, burden and melt inside the furnace and to estimate the heat transfer coefficient from the process gas to lining. This system utilizes measurements of temperature in several refractory elements with different thermophysical properties installed in the furnace walls and the direct and inverse problems of conductivity. The same system was applied to carry out the inspection of lining thickness, heat load on shaft plate coolers and lining in a blast furnace and other metallurgical furnaces.
Combustion
(burners,
combustion
systems)
QQlOO616 Burning characteristics gaseous/solid and emissions of blends of pulverized coal with waste tirederived fuel Levendis, Y. A. et al. Combusr. Sci. Technol., 1998, 131, (l-6), 147-185. From blends of a pulverized bituminous coal and ground waste automobile tyres the combustion behaviour and the emissions were studied. Coal and tyre particles were in the size ranges of 63-75 and 180-212 ,Lm, respectively. Combustion of cylindrical streams of particles took place under steady flow conditions, in an electric-heated drop-tube furnace in air, at a gas temperature of 1150” and a particle heating rate of 10 s. The bulk equivalence ratio, 4, in the furnace was varied in the range of 0.5 to 2, by varying the particle mass loading. Volatile flame interactions were apparent at a lower 4 for tyre crumb particles than for coal particles and became progressively more intense with increasing 4, until, at sufficiently high 4s large group flames formed for tyre particles. As particle flame interactions increased, average maximum temperatures in the flame decreased. Coal particles resisted the formation of group flames, even at high 4s. Such observations correlated with the trends observed for the PAH emissions of the two fuels, those of tyre crumb being much higher than those of coal and commencing at a lower 4. A certain degree of stratification in the combustion of blends of particles of the two fuels was observed. This kept the PAH emissions at levels much lower than those expected based on the weighted average emissions of the two fuels. NO, emissions from tires were much lower than those of coal, while those of the blends were close to the weighted average emissions. Combustion of fuel blends in the two aforementioned particle size cuts, generated the lowest NO, emissions when the small coal particles were combined with either the small or the large tyre particles. SOI emissions from the blends were found to be close to the weighted average emissions of the two fuels. Blending coal with tyre reduced the CO2 emissions of coal but increased the CO emissions. CO emissions were significant only in the fuel-rich region. tyre ash was of similar size and shape as the parent tyre particles themselves. Particulate emissions (soot and ash), increased with @. Generally, tyre produced more mass of submicron particulates than coal. Based on weighted average of the two fuels, particulate emissions of blends of the two fuels were close to those expected. QQlOO619 Catalytic effects on the ignition temperature of coal Wu, Z. er al. Fuel, 1998, 77, (S), 891-893. Investigated for various catalysts are the effects on the ignition temperature of coal including alkali salts, alkaline earth salts, and transition metal salts. The catalytic activity of alkali salts and alkaline earth salts is determined by the first ionization energy of the metal: the lower the first ionization energy, the higher the catalytic activity. In general, the salts with the water of crystalization are more effective catalysts. Transition metal salts show excellent catalytic activities: they reduce the ignition temperature, raise the volume of volatile, and strengthen the homogeneous combustion. For certain catalyst series in which each member has the same cation, but different anions, With the decrease of the anion acidity, catalytic activities increase. 99100620 Chemical limits to flame inhibition Babushok, V. et a/. Combustion and Flame, 1998, 115, (4), 551-560. Dealt with in this paper are the ultimate limits of chemical contributions to flame inhibition. Particular attention is focused on the inhibition cycles which regenerate the inhibitor. This leads to the definition of an idealized ‘perfect’ inhibition cycle. It is shown that for such an inhibitor in a stoichiometric methane/air flame additive levels in the 0.001-0.01 mole percent range will lead to a decrease in flame velocity of approximately 30%. This efficiency corresponds roughly to the observed behaviour of metallic inhibitors such as iron pentacarbonyl which is known to be as much as two orders of magnitude more effective than currently used suppressants. This correspondence between the behaviour of a ‘perfect inhibitor’ and iron carbonyl leads to the conclusion that only gas-phase processes can account for its inhibitive power. 99100621 Classification of volatile products evolved during temperature-programmed co-pyrolysis of Turkish oil shales with low density polyethylene Ballice, L. er a/. Fuel, 1998, 77, (l3), 1341-1441. This paper investigates the temperature programmed co-pyrolysis of Turkish oil shales with LDPE. The aim of this research was to determine the volatile product distribution and product evolution rate of coprocessing of oil shale with LDPE. A series co-pyrolysis operation was performed with oil shale and LDPE using a 1:3, l:l, 3:l total carbon ratio of oil shale to plastic. A fixed bed reactor was used to pyrolyse small sample of oil shale and LDPE mixture under an inert gas flow (Argon). A special sampling technique was used for collecting organic products eluted from the reactor at different temperature and time intervals. The co-pyrolysis products were analysed by capillary gas chromatography and the total product evolution rate was investigated as a function of temperature and time. The recovery of total organic carbon as a organic volatile products was also determined. The assessments were based on incorporating the results on temperatureprogrammed pyrolysis of oil shale 1.2 and LDPE. The effect of coprocessing of oil shale with LDPE was determined by calculating the difference between the experimental and the hypothetical mean value of conversion of total organic carbon into volatile products. The effect of kerogen type of oil shale on co-pyrolysis operation was also investigated. Conversion into
Fuel and Energy Abstracts
January 1999
61
Analyzing peat pyrolysis by in-situ FTIR Feng, J. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (7), 16-20. In this study the objective is to analyse peat pyrolysis using in-situ pyrolysisFTIR and to establish the pyrolysis model.
QQlOO612
Ash characteristics and minerals behavior during 99/00613 coal blend combustion Qiu, J. el at. Proc. Annu. Int. Pimburgh Coal Conf., 1997, 14, (12), 3-8. The mineral behaviours and ash characteristics of several individual coals and a series of two-component coal blends were studied. The ash fusibility and viscosity were measured and analysed. Some samples were heated progressively from 800°C to Tl (initial deformation temperature) at 100°C intervals in reducing atmosphere. Mineral composition and types at each temperature interval were determined by x-ray diffraction analysis. Proposed were the prediction methods for slagging tendency. Ash sintering and deposit formation in PFBC QQiQQ614 Steenari, B.-M. et al. Fuel, 1998, 77, (5). 407-417. Using chemical and X-ray diffraction methods agglomerated bed material and deposits from various surfaces in the bed area and in the flue gas duct of pressurized fluidized bed combustion (PFBC) plants were examined. Crystalline compounds present in the deposits were identified and possible mechanisms leading to the formation of bed material agglomerates, deposits and fouling on surfaces in the flue gas duct are discussed. In the sintering and fouling process all of the chemical systems CaS-CaSOd-alkali and silicate systems containing iron-rich species, silicate-alkali-chlorine oxides are important.
Assessment of PAH emissions as a function of QQIOO615 coal combustion variables in fluidised bed. 2. Air excess percentage Mastral, A. M. ef al. Fuel, 1998, 77, (13). 1513-1516. With the aim of studying the influence of the air excess percentage on the PAH formation and emission, a low rank coal combustion was carried out in a fluidized bed combustion pilot plant at laboratory scale. The experiments were performed at 850°C with a constant air total flow of 860 L h-l, varying the coal feeding rate and therefore the air excess percentages. In each experiment, five samples have been collected from two cyclones, nylon filter, bubbling system and adsorption system. FS (fluorescence spectroscopy in mode synchronous) has been used to analyse the PAH contained in these five samples after extraction by sonication with dimethyl-formamide (DMF). The analyses show that the total PAH amount keeps a close relationship with the air excess percentage: the higher the air excess. the lower the total PAH amount emitted.
QQlOO616 Fehrs, J. E. Mater.,
Biomass
assessments
for co-firing
Making Bus. Biomass Energy, Environ., Chemical, Fibers Edited by Proc. Biomass Conf. Am. 3rd, 1997, (2), 1463-1472.
Overend, R. P. and Chornet, E. The co-combustion of biomass materials with fossil fuels has been carried out by the pulp and paper industry for many years, primarily as a method to dispose of large quantities of waste biomass. However, co-firing at utility power plants is relatively new and is gaining popularity. Co-firing refers to substitution of biomass fuels or other alternative, non-fossil fuels for coal in boilers designed for coal combustion. Co-firing of biomass is typically limited to no more than about 20% of the fuel input due primarily to concerns about derating of the boiler. The benefits of co-firing biomass are varied. Biomass fuels may be available at a price below this cost, resulting in lower fuel procurement expenditures. Utilities that co-fire may be able to provide a disposal service to waste biomass generators within the utility’s service area. Biomass contains low levels of sulfur, and the formation of SO2 when co-firing will be reduced by an amount proportional to the cofiring rate. Formation of NO, may also be reduced, due to the combustion process when co-firing, however the reduction is not proportional to co-fire rate, but may actually be greater than the co-fire rate.
Blast furnace models to analyse raceway zone 99/00617 formation and to predict lining life Gordon, Y. et al. Ironmaking Conf. Proc., 1998, 57, 351-361. Developed was a two-dimensional mathematical model of material and gas movement, heat and mass transfer in the blast furnace. Semi-empirical equations were used to calculate the raceway dimensions. The regularities of raceway formation and its influence on material and gas velocities, temperature and concentration of the furnace were studied. The possibility of the formation of two circulation zones in the raceway region was illustrated. In addition, a mathematical model of coke and coal combustion was developed. The optimal tuyere parameters for coal injection system were determined. The computer based system was developed to verify the temperature of gas, burden and melt inside the furnace and to estimate the heat transfer coefficient from the process gas to lining. This system utilizes measurements of temperature in several refractory elements with different thermophysical properties installed in the furnace walls and the direct and inverse problems of conductivity. The same system was applied to carry out the inspection of lining thickness, heat load on shaft plate coolers and lining in a blast furnace and other metallurgical furnaces.
Combustion
(burners,
combustion
systems)
QQlOO616 Burning characteristics gaseous/solid and emissions of blends of pulverized coal with waste tirederived fuel Levendis, Y. A. et al. Combusr. Sci. Technol., 1998, 131, (l-6), 147-185. From blends of a pulverized bituminous coal and ground waste automobile tyres the combustion behaviour and the emissions were studied. Coal and tyre particles were in the size ranges of 63-75 and 180-212 ,Lm, respectively. Combustion of cylindrical streams of particles took place under steady flow conditions, in an electric-heated drop-tube furnace in air, at a gas temperature of 1150” and a particle heating rate of 10 s. The bulk equivalence ratio, 4, in the furnace was varied in the range of 0.5 to 2, by varying the particle mass loading. Volatile flame interactions were apparent at a lower 4 for tyre crumb particles than for coal particles and became progressively more intense with increasing 4, until, at sufficiently high 4s large group flames formed for tyre particles. As particle flame interactions increased, average maximum temperatures in the flame decreased. Coal particles resisted the formation of group flames, even at high 4s. Such observations correlated with the trends observed for the PAH emissions of the two fuels, those of tyre crumb being much higher than those of coal and commencing at a lower 4. A certain degree of stratification in the combustion of blends of particles of the two fuels was observed. This kept the PAH emissions at levels much lower than those expected based on the weighted average emissions of the two fuels. NO, emissions from tires were much lower than those of coal, while those of the blends were close to the weighted average emissions. Combustion of fuel blends in the two aforementioned particle size cuts, generated the lowest NO, emissions when the small coal particles were combined with either the small or the large tyre particles. SOI emissions from the blends were found to be close to the weighted average emissions of the two fuels. Blending coal with tyre reduced the CO2 emissions of coal but increased the CO emissions. CO emissions were significant only in the fuel-rich region. tyre ash was of similar size and shape as the parent tyre particles themselves. Particulate emissions (soot and ash), increased with @. Generally, tyre produced more mass of submicron particulates than coal. Based on weighted average of the two fuels, particulate emissions of blends of the two fuels were close to those expected. QQlOO619 Catalytic effects on the ignition temperature of coal Wu, Z. er al. Fuel, 1998, 77, (S), 891-893. Investigated for various catalysts are the effects on the ignition temperature of coal including alkali salts, alkaline earth salts, and transition metal salts. The catalytic activity of alkali salts and alkaline earth salts is determined by the first ionization energy of the metal: the lower the first ionization energy, the higher the catalytic activity. In general, the salts with the water of crystalization are more effective catalysts. Transition metal salts show excellent catalytic activities: they reduce the ignition temperature, raise the volume of volatile, and strengthen the homogeneous combustion. For certain catalyst series in which each member has the same cation, but different anions, With the decrease of the anion acidity, catalytic activities increase. 99100620 Chemical limits to flame inhibition Babushok, V. et a/. Combustion and Flame, 1998, 115, (4), 551-560. Dealt with in this paper are the ultimate limits of chemical contributions to flame inhibition. Particular attention is focused on the inhibition cycles which regenerate the inhibitor. This leads to the definition of an idealized ‘perfect’ inhibition cycle. It is shown that for such an inhibitor in a stoichiometric methane/air flame additive levels in the 0.001-0.01 mole percent range will lead to a decrease in flame velocity of approximately 30%. This efficiency corresponds roughly to the observed behaviour of metallic inhibitors such as iron pentacarbonyl which is known to be as much as two orders of magnitude more effective than currently used suppressants. This correspondence between the behaviour of a ‘perfect inhibitor’ and iron carbonyl leads to the conclusion that only gas-phase processes can account for its inhibitive power. 99100621 Classification of volatile products evolved during temperature-programmed co-pyrolysis of Turkish oil shales with low density polyethylene Ballice, L. er a/. Fuel, 1998, 77, (l3), 1341-1441. This paper investigates the temperature programmed co-pyrolysis of Turkish oil shales with LDPE. The aim of this research was to determine the volatile product distribution and product evolution rate of coprocessing of oil shale with LDPE. A series co-pyrolysis operation was performed with oil shale and LDPE using a 1:3, l:l, 3:l total carbon ratio of oil shale to plastic. A fixed bed reactor was used to pyrolyse small sample of oil shale and LDPE mixture under an inert gas flow (Argon). A special sampling technique was used for collecting organic products eluted from the reactor at different temperature and time intervals. The co-pyrolysis products were analysed by capillary gas chromatography and the total product evolution rate was investigated as a function of temperature and time. The recovery of total organic carbon as a organic volatile products was also determined. The assessments were based on incorporating the results on temperatureprogrammed pyrolysis of oil shale 1.2 and LDPE. The effect of coprocessing of oil shale with LDPE was determined by calculating the difference between the experimental and the hypothetical mean value of conversion of total organic carbon into volatile products. The effect of kerogen type of oil shale on co-pyrolysis operation was also investigated. Conversion into
Fuel and Energy Abstracts
January 1999
61