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06376 Mathematical modelling of fluidized bed combustion. 1. Combustion of carbon in bubbling beds
09
Combustion (burners, combustion systems)
96lo6360
The fate of Buifur, chlorlnr and trace elements durIng the flash pyrolyala of coal Sciazko,M. et al., Coal Sci. Technol., 1995, 24, 909-912. A bituminous coal and brown coal is pyrolyzed in a circulating fluidized bed in the presence or absence of dolomite. In both cases, the sulphur and Cl concentrations in the gas product increase in runs without dolomite.
96lQ6369 A heurlrtlc model of turbulent mixing applled to blowout of turbulent Jet dlffuslon flames Tieszen, S. R. et al., Combustion & Flame, Sep. 1996, 106, (4), 442-466. Describes a phenomenological study which has been conducted on jet flames near blowout for the purpose of determining the blowout mechanism.
96D6361 The fearlblllty deelgn of preaaurlzed circulating fluldlzed bed combuatlon system Ishihara, I. et al., Sekiran Riyo Gijutsu Kaigi Koenshy 1995, 48-59. (In Japanese) Gives the progress of pressurized circulating fluidized bed combustion systems for coal duringthe period 1991-1994. The system is highly effrcient and low in pollutant emission. A boiler was designed using the system and the feature includes an external heat exchanger and re-heater, low corrosion, and low NO, and SO, emission.
96106370 The Identification of dangerously coking coals Barriocanal, C. et al., Coal Sci. Technol., 1995, 24, 989-992. The paper confirms the view that internal gas pressures generated within the plastic layers of carbonizing coal is associated with volatiles trapped therein. The methods used appear useful in identifying potentially dangerously coking coals, but precisely what property of such coals which differentiate them from others, with similar chemical properties at room temperature, has yet to be established.
96lO6362
Fire praventatlon durlng use of alternatlva fuels Gol’dberg, A. S. Elekfr. SW., 1995, (ll), 60-64. (In Russian) The paper discusses the possibility of ignition and explosion of fuel dust during switching to new types of fue!, particularly from high-sulphur to low-sulphur coal and safety measures in thermal power plants. 96lo6363 Flash co-pyrolysis of coal retaining depolymerlzad polyethylene as radical donor Tomita, H. et al., Coal Sci. Technol., 1995, 24, 1511-1514. In the present study, brown and bituminous coals were swollen with THF. The swollen coals were then physically incorporated with depolymerized polyethylene and subjected to flash pyrolysis in a Curie-point pyrolyzer and an entrained-flow pyrolyzer. Flash hydropyrolyala of northern Chlneaa coal 96106364 Zhu, Z. er al., Fuel, Oct. 1996, 75, (12), 1429-1433. Two kinds of northern Chinese coals, Dongshen bituminous coal and Zalannoer lignite, were flash-hydropyrolysed in a small entrainment reactor with volatiles residence time varying from approximately 2 to approximately 70s. Yields of products were determined for a series of temperatures from 550 to 850°C, with a range of hydrogen pressure from 0.1 to 6.0 MPa. Flash pyrolyala of coal. Formatlon of volatllea at 96106365 different temoeraturea Christiansen, J.‘V. er al., Coal Sci. Technol., 1995, 24, 905-908. Describes how pyrolyzes of coals at different temperature lead to significant variations -in product distribution although qualitatively the overall product composition is maintained. In general the yields of all the single comwunds increase with increasinn temuerature or increase UDto a certain temperature above which they level oui, whereby the quant’atitive variations develop. A general tendency of decreasing yields of aikylated compounds relative to their nonalkylated counterparts is demonstrated to develop at higher temperatures possibly due to thermal dealkylations. However, alternative mechanisms lead to the nonalkylated products directly from the coal matrix upon pyrolysis appear to play a major role. Fundamantala on combuatlon and gaalflcatlon 96106366 bahavlour of coal particle trapped on molten slag layer Noda, R. er al., J. Chem. Eng. Jpn., 1996, 29, (2), 235-241. In order to develop a slagging coal gasifier and an integral gasification combined cycle process, the fundamental behaviour of combustion/gasification of a coal particle trapped on the molten slag layer was studied with a laboratory-scale batch reactor. The experimental set-up consisted of dropping a single coal particle onto the molten slag layer, and using air and COr reactants to burn and gasify the coal particle, respectively. The product gas concentrations and the surface temperatures of coal particle and slag layer were continuously measured by gas analyzers and a two-dimensional two-colour pyrometer, respectively. 96106367 Gas evolution In the programmed-temperature pyrolysla of coal Huann. H. et al.. Coal Sci. Technol.. 1995. 24. 845-848. In thii’study, a novel programmed-temperature pyrolysis system was used to investigate gas evolution from coal pyrolysis at a slow heating rate. The characteristic parameters of the gas-evolution, such as production of selected gases, and total gas and liquid yields, are correlated with coal and data including proximate analysis, ultimate analysis and C structural data from “C NMR. 96106366 Heat transfer between a vertical tube bundle and fine partlclaa In a CFB downcomer wlth and without circulation of solids C$y,ng, S. et al., Chemical Engineering&Processing, Jan. 1996, 35, (l), The paper reports experimental data on the heat transfer between an electrically heated vertical finned tube bundle and cracking catalyst, fluidized with air in the downcomer of a circulating fluidized bed system. The effects of the air fluidizing velocity, bed temperature and external recirculation of solids were investigated.
446
Fuel and Energy Abstracts November 1996
96lQ6371 lgnltlon of a granular propellant bed Wildegger-Gaissmaier, A. E. and Johnston, I. R. Combustion & Flame, Aug. 1996, 106, (3), 219-230. An experimental and theoretical study is reported on the ignition process of a low vulnerability ammunition (LOVA) propellant bed in a 127-mm (5-in) bore gun charge. The theoretical investigation was with a two-phase flow interior ballistics code and the model oredictions showed the marked influence the igniter system can have on pressure wave development, flame spreading, and the overall interior ballistics performance. A number of different igniter systems were investigated in an empty and propellantfilled gun simulator. Pressure, flame spreading, and high-speed film records were used to analyze the ignition/combustion event. 96106372 Kinetics of coal pyrolysis: A comparlaon between the Isothermal and the non-Isothermal methods Lazaro, M. J. et al., Coal Sci. Technol., 1995, 24, 849-852. Compares the kinetic parameters calculated for the pyrolysis of coal by using both methods, isothermal and non-isothermal, assuming the same reaction model and applying the same data treatment. Klnetlca of poroalty evolution durlng feat heatlng 96106373 of coal Tomeczek. J. and Gil. S. Coal Sci. Technol.. 1995. 24. 925-928. The aim of the study was to measure the kinetics of the pore structure variation during coal pyrolysis, useful for mathematical modelling. The process proceeded in two stages; the first was associated with volatile release followed by slow but large porosity evolution. 96106374 Laser diagnostlca for droplet characterlxatlon: Application of morphology dependent resonances Chen? G. er al., Pro . Energy Combusr. Sci., 1996, 22, (2), 163-188. A mtcron-sized liqul,d droplet acts as a very high-quality factor optical cavity. The cavity modes are referred to as morphology-dependent resonances (MDRS), which are sensitive to the droplet size, shape, and inclusions. The MDRs greatly lower the input intensity needed to generate detectable amounts of linear and nonlinear optical radiation and exhibit sharp peaks in the spectra of elastic scattering, fluorescence, lasing, and simulated Raman scattering. Novel spectroscopic-based techniques are now available for droplet diagnostics of its physical, chemical, and thermal properties. In particular, the authors review how viscosity, near-surface temperature, species, and species concentration in multicomponent droplets. 96106375 Local extinction Karlovltz number for pramlxed flames Chung, S. H. et al., Combustion & Flame, Sep. 1996, 106, (4), 515-520. The extinction of laminar premixed flames under the influence of stretch is studied experimentally and numerically. Experiment involves measuring the velocity field of methane/air and propane/air flames in an opposed jet with a laser Doppler velocimeter and computations are made using several chemical kinetic mechanisms. The major result is that, in contrast to the various orevious claims of extinction Karovitz number beinn anvwhere between’0.03 and 20, it is found to be constant around unity 6r the mixtures tested. That is, premixed flames are extinguished when the physical flow time approximately equals the chemical reaction time. 96196376 Mathematical modallln of fluldlzed bad combuahon. 1. Combustion of carbon In bu%bling beds Sriramulu, S. et al., Fuel, Oct. 1996, 75, (12), 1351-1362. A three-phase model for carbon combustion in fluidized beds has been developed to take into account the effects of gas backmixing and solids circulation. Inclusion of these phenomena is expected ultimately to be important in extending the fluidized bed combustion model to predict N,O emissions. Transient mass and energy balance equations are presented in this paper for the fast bubble regime, these equations can be easily modified for the slow bubble operating regime. The system of nine first-order semilinear hyperbolic partial differential equations has been solved numerically. The transient solution permits comparison of the predictive capability of the model with published data on combustion rates, burnout times and particle temperatures obtained from batch experiments.
Combustion (burners, combustion systems)
96lo6360
The fate of Buifur, chlorlnr and trace elements durIng the flash pyrolyala of coal Sciazko,M. et al., Coal Sci. Technol., 1995, 24, 909-912. A bituminous coal and brown coal is pyrolyzed in a circulating fluidized bed in the presence or absence of dolomite. In both cases, the sulphur and Cl concentrations in the gas product increase in runs without dolomite.
96lQ6369 A heurlrtlc model of turbulent mixing applled to blowout of turbulent Jet dlffuslon flames Tieszen, S. R. et al., Combustion & Flame, Sep. 1996, 106, (4), 442-466. Describes a phenomenological study which has been conducted on jet flames near blowout for the purpose of determining the blowout mechanism.
96D6361 The fearlblllty deelgn of preaaurlzed circulating fluldlzed bed combuatlon system Ishihara, I. et al., Sekiran Riyo Gijutsu Kaigi Koenshy 1995, 48-59. (In Japanese) Gives the progress of pressurized circulating fluidized bed combustion systems for coal duringthe period 1991-1994. The system is highly effrcient and low in pollutant emission. A boiler was designed using the system and the feature includes an external heat exchanger and re-heater, low corrosion, and low NO, and SO, emission.
96106370 The Identification of dangerously coking coals Barriocanal, C. et al., Coal Sci. Technol., 1995, 24, 989-992. The paper confirms the view that internal gas pressures generated within the plastic layers of carbonizing coal is associated with volatiles trapped therein. The methods used appear useful in identifying potentially dangerously coking coals, but precisely what property of such coals which differentiate them from others, with similar chemical properties at room temperature, has yet to be established.
96lO6362
Fire praventatlon durlng use of alternatlva fuels Gol’dberg, A. S. Elekfr. SW., 1995, (ll), 60-64. (In Russian) The paper discusses the possibility of ignition and explosion of fuel dust during switching to new types of fue!, particularly from high-sulphur to low-sulphur coal and safety measures in thermal power plants. 96lo6363 Flash co-pyrolysis of coal retaining depolymerlzad polyethylene as radical donor Tomita, H. et al., Coal Sci. Technol., 1995, 24, 1511-1514. In the present study, brown and bituminous coals were swollen with THF. The swollen coals were then physically incorporated with depolymerized polyethylene and subjected to flash pyrolysis in a Curie-point pyrolyzer and an entrained-flow pyrolyzer. Flash hydropyrolyala of northern Chlneaa coal 96106364 Zhu, Z. er al., Fuel, Oct. 1996, 75, (12), 1429-1433. Two kinds of northern Chinese coals, Dongshen bituminous coal and Zalannoer lignite, were flash-hydropyrolysed in a small entrainment reactor with volatiles residence time varying from approximately 2 to approximately 70s. Yields of products were determined for a series of temperatures from 550 to 850°C, with a range of hydrogen pressure from 0.1 to 6.0 MPa. Flash pyrolyala of coal. Formatlon of volatllea at 96106365 different temoeraturea Christiansen, J.‘V. er al., Coal Sci. Technol., 1995, 24, 905-908. Describes how pyrolyzes of coals at different temperature lead to significant variations -in product distribution although qualitatively the overall product composition is maintained. In general the yields of all the single comwunds increase with increasinn temuerature or increase UDto a certain temperature above which they level oui, whereby the quant’atitive variations develop. A general tendency of decreasing yields of aikylated compounds relative to their nonalkylated counterparts is demonstrated to develop at higher temperatures possibly due to thermal dealkylations. However, alternative mechanisms lead to the nonalkylated products directly from the coal matrix upon pyrolysis appear to play a major role. Fundamantala on combuatlon and gaalflcatlon 96106366 bahavlour of coal particle trapped on molten slag layer Noda, R. er al., J. Chem. Eng. Jpn., 1996, 29, (2), 235-241. In order to develop a slagging coal gasifier and an integral gasification combined cycle process, the fundamental behaviour of combustion/gasification of a coal particle trapped on the molten slag layer was studied with a laboratory-scale batch reactor. The experimental set-up consisted of dropping a single coal particle onto the molten slag layer, and using air and COr reactants to burn and gasify the coal particle, respectively. The product gas concentrations and the surface temperatures of coal particle and slag layer were continuously measured by gas analyzers and a two-dimensional two-colour pyrometer, respectively. 96106367 Gas evolution In the programmed-temperature pyrolysla of coal Huann. H. et al.. Coal Sci. Technol.. 1995. 24. 845-848. In thii’study, a novel programmed-temperature pyrolysis system was used to investigate gas evolution from coal pyrolysis at a slow heating rate. The characteristic parameters of the gas-evolution, such as production of selected gases, and total gas and liquid yields, are correlated with coal and data including proximate analysis, ultimate analysis and C structural data from “C NMR. 96106366 Heat transfer between a vertical tube bundle and fine partlclaa In a CFB downcomer wlth and without circulation of solids C$y,ng, S. et al., Chemical Engineering&Processing, Jan. 1996, 35, (l), The paper reports experimental data on the heat transfer between an electrically heated vertical finned tube bundle and cracking catalyst, fluidized with air in the downcomer of a circulating fluidized bed system. The effects of the air fluidizing velocity, bed temperature and external recirculation of solids were investigated.
446
Fuel and Energy Abstracts November 1996
96lQ6371 lgnltlon of a granular propellant bed Wildegger-Gaissmaier, A. E. and Johnston, I. R. Combustion & Flame, Aug. 1996, 106, (3), 219-230. An experimental and theoretical study is reported on the ignition process of a low vulnerability ammunition (LOVA) propellant bed in a 127-mm (5-in) bore gun charge. The theoretical investigation was with a two-phase flow interior ballistics code and the model oredictions showed the marked influence the igniter system can have on pressure wave development, flame spreading, and the overall interior ballistics performance. A number of different igniter systems were investigated in an empty and propellantfilled gun simulator. Pressure, flame spreading, and high-speed film records were used to analyze the ignition/combustion event. 96106372 Kinetics of coal pyrolysis: A comparlaon between the Isothermal and the non-Isothermal methods Lazaro, M. J. et al., Coal Sci. Technol., 1995, 24, 849-852. Compares the kinetic parameters calculated for the pyrolysis of coal by using both methods, isothermal and non-isothermal, assuming the same reaction model and applying the same data treatment. Klnetlca of poroalty evolution durlng feat heatlng 96106373 of coal Tomeczek. J. and Gil. S. Coal Sci. Technol.. 1995. 24. 925-928. The aim of the study was to measure the kinetics of the pore structure variation during coal pyrolysis, useful for mathematical modelling. The process proceeded in two stages; the first was associated with volatile release followed by slow but large porosity evolution. 96106374 Laser diagnostlca for droplet characterlxatlon: Application of morphology dependent resonances Chen? G. er al., Pro . Energy Combusr. Sci., 1996, 22, (2), 163-188. A mtcron-sized liqul,d droplet acts as a very high-quality factor optical cavity. The cavity modes are referred to as morphology-dependent resonances (MDRS), which are sensitive to the droplet size, shape, and inclusions. The MDRs greatly lower the input intensity needed to generate detectable amounts of linear and nonlinear optical radiation and exhibit sharp peaks in the spectra of elastic scattering, fluorescence, lasing, and simulated Raman scattering. Novel spectroscopic-based techniques are now available for droplet diagnostics of its physical, chemical, and thermal properties. In particular, the authors review how viscosity, near-surface temperature, species, and species concentration in multicomponent droplets. 96106375 Local extinction Karlovltz number for pramlxed flames Chung, S. H. et al., Combustion & Flame, Sep. 1996, 106, (4), 515-520. The extinction of laminar premixed flames under the influence of stretch is studied experimentally and numerically. Experiment involves measuring the velocity field of methane/air and propane/air flames in an opposed jet with a laser Doppler velocimeter and computations are made using several chemical kinetic mechanisms. The major result is that, in contrast to the various orevious claims of extinction Karovitz number beinn anvwhere between’0.03 and 20, it is found to be constant around unity 6r the mixtures tested. That is, premixed flames are extinguished when the physical flow time approximately equals the chemical reaction time. 96196376 Mathematical modallln of fluldlzed bad combuahon. 1. Combustion of carbon In bu%bling beds Sriramulu, S. et al., Fuel, Oct. 1996, 75, (12), 1351-1362. A three-phase model for carbon combustion in fluidized beds has been developed to take into account the effects of gas backmixing and solids circulation. Inclusion of these phenomena is expected ultimately to be important in extending the fluidized bed combustion model to predict N,O emissions. Transient mass and energy balance equations are presented in this paper for the fast bubble regime, these equations can be easily modified for the slow bubble operating regime. The system of nine first-order semilinear hyperbolic partial differential equations has been solved numerically. The transient solution permits comparison of the predictive capability of the model with published data on combustion rates, burnout times and particle temperatures obtained from batch experiments.