1
09 Combustion (burners, combustion systems) 99100644 The effecting factors of sulfur evolution during coal combustion Liu, Z. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (3). 1-7. In this paper, in order to investigate the effect factors of sulfur evolution during coal combustion by means of improved automatic sulfur analyser three kinds of bituminous coal and one kind of anthracite have been used. The results show that the rate and quantity of sulfur evolution is affected by the temperature, retention time, different coal, sulfur forms, calcium-based content in coal, oxygen concentration and flow velocity of air. 99loo645 An eigenvalue method for computing the burning rates of HMX propellants Prasad, K. et al. Combustion and Flame, 1998, 115, (3) 406-416. In order to study the combustion of HMX propellants, a mathematical model for a three-tiered system consisting of solid, liquid, and gas is derived. In this study the burning rate is computed as an eigenvalue, which removes the uncertainty associated with employing evaporation and condensation rate laws in its evaluation. Results are presented for laser- assisted and self-deflagration of HMX monopropellants and are compared with experimental results. The burning rates are computed over a wide range of ambient pressures and compare well with experimental results from 1 to 90 atmospheres. The burning rate is found to be proportional to the pressure raised to the 0.82 power. Sensitivity of the burning rate to initial propellant temperature was calculated and was found to be extremely low, in agreement with past theoretical predictions and experimental data. Results for laser-assisted combustion show a distinct primary and secondary flame separated by a dark zone, the length of which is dependent upon the incident laser flux intensity. 99100646 Evolution of pore fractal dimensions for burning porous chars He, R. et al. Fuel, 1998, 77, (12), 1291-1295. For three Chinese chars the’ evolution of pore fractal dimensions was investigated. The pores of porous chars can be classified into macro-, micro- and transition-pores based on their fractal dimensions and the radius ranges of the macro-, micro- and transition-pores may be different for various chars. For different conversions in the char combustion process, the fractal dimensions of the micro-pores for different chars are almost the same and the fractal dimensions of macro-pores for the same kind of chars are roughly unchanged. The effects of fractal structure on combustion rate are also discussed. 99KKf647 Experlmental measurements In the BYU controlled profile reactor Tree, D. R. et al. Progress in Energy and Combustion Science, 24, (5), 355- 383. An issue of continuing international importance is the energy conversion of fossil fuels or waste products to electricity and heat through clean and efficient combustion processes. The Controlled Profile Reactor (CPR) is a small scale (0.2-0.4 MW) combustion facility that has been used to obtain data for model validation, the testing of new combustion concepts, and the development of new combustion instrumentation, The CPR has a cylindrical, down-fired combustion chamber, 240 cm long and 80 cm in diameter. This review of the past ten years of research completed in the CPR includes a description of the reactor and instrumentation used, a summary of three experimental data sets which have been obtained in the reactor, and a description of novel tests and instrumentation. Measure- ments obtained include gas species, gas temperature, particle velocity, particle size, particle number density, particle-cloud temperature profiles, radiation and total heat flux to the wall, and wall temperatures. Species data include the measurement of CO, COz, NO, NO,, 02, NH3 and HCN. The three combustion studies included one with natural gas combustion in a swirling flow, and two pulverized-coal combustion studies involving Utah Blind Canyon and Pittsburgh #8 coals. Most, but not all of the above measurements were obtained in each study. The second coal study involving the Pittsburgh #8 coal contained the most complete set of data and is described in detail in Section 3 of the paper. Novel combustion instrumentation includes the use of Coherent Anti-Stokes Raman Spectro- scopy (CARS) to measure gas temperature. Novel combustion experiments include the measurement of NO, and burnout with coal-char blends. The measurements have led to an improved understanding of the combustion process and an understanding of the strengths and weaknesses associated with different aspects of comprehensive combustion models. 99l99646 The experimental study of combustion rate of coal blend Zhou, J. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (2), 83-89. Using single-particle coal combustion experimental equipment, an experi- mental study of combustion rate of coal blends has been performed. Two parameters, an ignition characteristic index and a burnout characteristic index of coal blends, are introduced. The predicted values fit to the experimental results of coal blend. 99199649 Experimental study on self-desulfurization characteristics of biobrlquette In combustion Lu, G. et al. Energy Fuels, 1998, 12, (4). 689-696. In this study a new kind of biobriquette, with scallop shell as desulfurizer, was developed, and using combustion experiments its self-desulfurization behaviour was studied. The biobriquettes with Tsukumi limestone and calcium hydroxide as desulfurizers were also investigated experimentally for comparison and further understanding on the self-desulfurization char- acteristics. The influence of the furnace temperature, types of coal and desulfurizer, and structure of added desulfurizer on the behaviour of desulfurization was elucidated by measuring the time concentration history of SO2 emission in combustion flue gas and calculating the desulfurization efficiency. The desulfurization efficiency was not sensitive to the tempera- ture in the range 973-1173 K. However, the efficiency was strongly affected by coal type, and it changed from about 25 to 67% for the eight tested types of coals under the same experiment conditions. The desulfurization efficiency has been found to also be a function of the calcination temperature of the desulfurizer. On the basis of experimental results, a shrinking-core reaction model was used to simulate the desulfurization process during the char combustion of biobriquette by a finite volume numerical method. The calculated results generally agreed with the experimental results. Finally, in order to improve the desulfurization efficiency, an improvement on the biobriquette structure, namely dual layered biobriquette, was proposed and tested. 99100650 Extent of coal combustion in the blast furnace at different coal injection rates and different blast furnace parameters Bachhofen, H.-J. et al. Ironmaking Conf. Proc., 1998, 57, 667-674. An inclined horizontal probe (inclination 35”) was used at blast furnace 1, Schwelgern to provide nine measuring points above the furnace radius at the top, and 15 gas sampling points were installed along the furnace height, at which gas can be simultaneously sampled and analysed. At the same time dust can be removed from the gas, which can then be analysed for Ccoke and &,,I. This made it possible to measure the extent of coal conversion in the blast furnace in relation to different influencing factors such as coal injection rates, coal properties, oxygen enrichment and the radial flow of gas and other blast furnace parameters. The tests were carried out with coal injection rates between 130 and 190 kg/t HM, oxygen contents between 22.5 and 24.1%. and volatile components in the injected coal between 18 and 42%, and under different radial gas flow conditions at the top. The amounts of dust caught with the aid of the inclined probe are highest in the centre of the furnace and at the periphery of the blast furnace. The iron oxide content is at a maximum at the furnace periphery on account of the greater degree of burden degradation there, and the alkali content in the furnace centre on account of the high temperatures prevailing there. The C,,,;,, content is also highest in the centre of the furnace. Observations of the course of ETA CO and %Hz values above the furnace radius at the top show that gas conversion generally accords with the water shift reaction, but that the composition of the gas in the furnace centre often does not agree with this correlation, and is heavily determined by the coal rising in the blast furnace and still emitting its volatile parts in the upper shaft. Accordingly, it is not surprising that the Hz contents measured in the furnace centre are correlated with the C,,,,, contents in the dust. Rising coal injection rates lead to increasing C,,,, contents in the dust. This can be counteracted by increasing the added oxygen. In the blast furnace, no influence of volatile matter on the extent of coal conversion was detected. 99lOO651 Fast pyrolysis with circulating heat carriers Schmalfeld, J. et al. DGMK Tagungsber., 1998, 9802, 287-294. (In German) Described is the process design, operating characteristics, and fields of application of fast heat pyrolysis with circulating heat carriers (coke, ash, or sand). Conversion of refinery vacuum residues, gas generation from dried sewage sludges, and pyrolysis of plastic mixtures are given as examples. 99100652 Flow characteristics of circulating gas-solid fluldlzed bed heat exchanger with multiple vertical pipes Park, S. I. et al. International Journal of Energy Research, 1998, 22, (lo), 911-921. Studied were the flow characteristics of a circulating gas-solid fluidized-bed heat exchanger with multiple vertical pipes. The glass beads were circulated inside the vertical pipes of the heat exchanger with fluidizing air and the pressure drop and circulation rate of solid particles were measured. In addition, the one-dimensional velocity distribution of solid particles and the pressure distribution inside the vertical pipe were analysed. The prediction on the pressure drop with the circulation of solid particles was proved to be reasonably accurate by comparing with the measured results. 99100653 Fluidization, combustion and emission behavior of biomass in fluldlzed bed combustion units Kaferstein, P. et al. Proc. Int. Conf. Fluid. Bed Combust., 1997, 14, (l), IS- 27. Over the height and the cross-section inside a circulating fluidized bed riser with a thermal power of 60 kW gaseous components were measured. The combustion behaviour of lignite (German brown coal), hard coal, biomass (China reed), and sewage sludge was investigated. The burn-out behaviour was investigated by in-situ and real time measurement of the oxygen consumption using solid electrolyte sensor probes within a bubbling fluidized bed combustor with 15 kW thermal power. Over the small riser cross-section which differed for the various fuels non-uniform oxygen concentration profiles were found. The feed location and the fuel distribution also influenced the horizontal oxygen profile. The reasons for the non-uniformity of the horizontal oxygen concentration profile are the 64 Fuel and Energy Abstracts January 1999

99/00648 The experimental study of combustion rate of coal blend

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09 Combustion (burners, combustion systems)

99100644 The effecting factors of sulfur evolution during coal combustion Liu, Z. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (3). 1-7. In this paper, in order to investigate the effect factors of sulfur evolution during coal combustion by means of improved automatic sulfur analyser three kinds of bituminous coal and one kind of anthracite have been used. The results show that the rate and quantity of sulfur evolution is affected by the temperature, retention time, different coal, sulfur forms, calcium-based content in coal, oxygen concentration and flow velocity of air.

99loo645 An eigenvalue method for computing the burning rates of HMX propellants Prasad, K. et al. Combustion and Flame, 1998, 115, (3) 406-416. In order to study the combustion of HMX propellants, a mathematical model for a three-tiered system consisting of solid, liquid, and gas is derived. In this study the burning rate is computed as an eigenvalue, which removes the uncertainty associated with employing evaporation and condensation rate laws in its evaluation. Results are presented for laser- assisted and self-deflagration of HMX monopropellants and are compared with experimental results. The burning rates are computed over a wide range of ambient pressures and compare well with experimental results from 1 to 90 atmospheres. The burning rate is found to be proportional to the pressure raised to the 0.82 power. Sensitivity of the burning rate to initial propellant temperature was calculated and was found to be extremely low, in agreement with past theoretical predictions and experimental data. Results for laser-assisted combustion show a distinct primary and secondary flame separated by a dark zone, the length of which is dependent upon the incident laser flux intensity.

99100646 Evolution of pore fractal dimensions for burning porous chars He, R. et al. Fuel, 1998, 77, (12), 1291-1295. For three Chinese chars the’ evolution of pore fractal dimensions was investigated. The pores of porous chars can be classified into macro-, micro- and transition-pores based on their fractal dimensions and the radius ranges of the macro-, micro- and transition-pores may be different for various chars. For different conversions in the char combustion process, the fractal dimensions of the micro-pores for different chars are almost the same and the fractal dimensions of macro-pores for the same kind of chars are roughly unchanged. The effects of fractal structure on combustion rate are also discussed.

99KKf647 Experlmental measurements In the BYU controlled profile reactor Tree, D. R. et al. Progress in Energy and Combustion Science, 24, (5), 355- 383. An issue of continuing international importance is the energy conversion of fossil fuels or waste products to electricity and heat through clean and efficient combustion processes. The Controlled Profile Reactor (CPR) is a small scale (0.2-0.4 MW) combustion facility that has been used to obtain data for model validation, the testing of new combustion concepts, and the development of new combustion instrumentation, The CPR has a cylindrical, down-fired combustion chamber, 240 cm long and 80 cm in diameter. This review of the past ten years of research completed in the CPR includes a description of the reactor and instrumentation used, a summary of three experimental data sets which have been obtained in the reactor, and a description of novel tests and instrumentation. Measure- ments obtained include gas species, gas temperature, particle velocity, particle size, particle number density, particle-cloud temperature profiles, radiation and total heat flux to the wall, and wall temperatures. Species data include the measurement of CO, COz, NO, NO,, 02, NH3 and HCN. The three combustion studies included one with natural gas combustion in a swirling flow, and two pulverized-coal combustion studies involving Utah Blind Canyon and Pittsburgh #8 coals. Most, but not all of the above measurements were obtained in each study. The second coal study involving the Pittsburgh #8 coal contained the most complete set of data and is described in detail in Section 3 of the paper. Novel combustion instrumentation includes the use of Coherent Anti-Stokes Raman Spectro- scopy (CARS) to measure gas temperature. Novel combustion experiments include the measurement of NO, and burnout with coal-char blends. The measurements have led to an improved understanding of the combustion process and an understanding of the strengths and weaknesses associated with different aspects of comprehensive combustion models.

99l99646 The experimental study of combustion rate of coal blend Zhou, J. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1997, 14, (2), 83-89. Using single-particle coal combustion experimental equipment, an experi- mental study of combustion rate of coal blends has been performed. Two parameters, an ignition characteristic index and a burnout characteristic index of coal blends, are introduced. The predicted values fit to the experimental results of coal blend.

99199649 Experimental study on self-desulfurization characteristics of biobrlquette In combustion Lu, G. et al. Energy Fuels, 1998, 12, (4). 689-696. In this study a new kind of biobriquette, with scallop shell as desulfurizer, was developed, and using combustion experiments its self-desulfurization behaviour was studied. The biobriquettes with Tsukumi limestone and

calcium hydroxide as desulfurizers were also investigated experimentally for comparison and further understanding on the self-desulfurization char- acteristics. The influence of the furnace temperature, types of coal and desulfurizer, and structure of added desulfurizer on the behaviour of desulfurization was elucidated by measuring the time concentration history of SO2 emission in combustion flue gas and calculating the desulfurization efficiency. The desulfurization efficiency was not sensitive to the tempera- ture in the range 973-1173 K. However, the efficiency was strongly affected by coal type, and it changed from about 25 to 67% for the eight tested types of coals under the same experiment conditions. The desulfurization efficiency has been found to also be a function of the calcination temperature of the desulfurizer. On the basis of experimental results, a shrinking-core reaction model was used to simulate the desulfurization process during the char combustion of biobriquette by a finite volume numerical method. The calculated results generally agreed with the experimental results. Finally, in order to improve the desulfurization efficiency, an improvement on the biobriquette structure, namely dual layered biobriquette, was proposed and tested.

99100650 Extent of coal combustion in the blast furnace at different coal injection rates and different blast furnace parameters Bachhofen, H.-J. et al. Ironmaking Conf. Proc., 1998, 57, 667-674. An inclined horizontal probe (inclination 35”) was used at blast furnace 1, Schwelgern to provide nine measuring points above the furnace radius at the top, and 15 gas sampling points were installed along the furnace height, at which gas can be simultaneously sampled and analysed. At the same time dust can be removed from the gas, which can then be analysed for Ccoke and &,,I. This made it possible to measure the extent of coal conversion in the blast furnace in relation to different influencing factors such as coal injection rates, coal properties, oxygen enrichment and the radial flow of gas and other blast furnace parameters. The tests were carried out with coal injection rates between 130 and 190 kg/t HM, oxygen contents between 22.5 and 24.1%. and volatile components in the injected coal between 18 and 42%, and under different radial gas flow conditions at the top. The amounts of dust caught with the aid of the inclined probe are highest in the centre of the furnace and at the periphery of the blast furnace. The iron oxide content is at a maximum at the furnace periphery on account of the greater degree of burden degradation there, and the alkali content in the furnace centre on account of the high temperatures prevailing there. The C,,,;,, content is also highest in the centre of the furnace. Observations of the course of ETA CO and %Hz values above the furnace radius at the top show that gas conversion generally accords with the water shift reaction, but that the composition of the gas in the furnace centre often does not agree with this correlation, and is heavily determined by the coal rising in the blast furnace and still emitting its volatile parts in the upper shaft. Accordingly, it is not surprising that the Hz contents measured in the furnace centre are correlated with the C,,,,, contents in the dust. Rising coal injection rates lead to increasing C,,,, contents in the dust. This can be counteracted by increasing the added oxygen. In the blast furnace, no influence of volatile matter on the extent of coal conversion was detected.

99lOO651 Fast pyrolysis with circulating heat carriers Schmalfeld, J. et al. DGMK Tagungsber., 1998, 9802, 287-294. (In German) Described is the process design, operating characteristics, and fields of application of fast heat pyrolysis with circulating heat carriers (coke, ash, or sand). Conversion of refinery vacuum residues, gas generation from dried sewage sludges, and pyrolysis of plastic mixtures are given as examples.

99100652 Flow characteristics of circulating gas-solid fluldlzed bed heat exchanger with multiple vertical pipes Park, S. I. et al. International Journal of Energy Research, 1998, 22, (lo), 911-921. Studied were the flow characteristics of a circulating gas-solid fluidized-bed heat exchanger with multiple vertical pipes. The glass beads were circulated inside the vertical pipes of the heat exchanger with fluidizing air and the pressure drop and circulation rate of solid particles were measured. In addition, the one-dimensional velocity distribution of solid particles and the pressure distribution inside the vertical pipe were analysed. The prediction on the pressure drop with the circulation of solid particles was proved to be reasonably accurate by comparing with the measured results.

99100653 Fluidization, combustion and emission behavior of biomass in fluldlzed bed combustion units Kaferstein, P. et al. Proc. Int. Conf. Fluid. Bed Combust., 1997, 14, (l), IS- 27. Over the height and the cross-section inside a circulating fluidized bed riser with a thermal power of 60 kW gaseous components were measured. The combustion behaviour of lignite (German brown coal), hard coal, biomass (China reed), and sewage sludge was investigated. The burn-out behaviour was investigated by in-situ and real time measurement of the oxygen consumption using solid electrolyte sensor probes within a bubbling fluidized bed combustor with 15 kW thermal power. Over the small riser cross-section which differed for the various fuels non-uniform oxygen concentration profiles were found. The feed location and the fuel distribution also influenced the horizontal oxygen profile. The reasons for the non-uniformity of the horizontal oxygen concentration profile are the

64 Fuel and Energy Abstracts January 1999