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04056 Pyrometric measurement of the temperature and size of individual combusting fuel particles
09 Combustion (burners, combustion systems) considerable differences between coal types, but even coals of similar properties can display large variations in combustion performance. Advanced low-NO, combustion conditions can reduce the differences between coals. Confidence in the NRTF results is enhanced by comparison with large plant data; the NRTF gave good agreement with a large utility boiler in both absolute emission and coal effects for NO,.
signals. A discrimination method was developed to confirm that the detected particle was valid for particle sizing. Several series of measurements were made at a PEFR at different process conditions and some typical results are shown. 9alO4057
A quasi-steady shrinking core analysis of wood
combustion
Pol cyclic aromatic hydrocarbon opposed flow dix usion flames of ethane
90io4051
formatlon
in
Vincitore, A. M. and Senkan, S. M. Combustion and Flame, 1998, 114, (l/2), 259-266. Heated micro-probe sampling and gas chromatography/mass spectrometry (GC/MS) has been used to study the effect of fuel-side carbon density on the levels of polycyclic aromatic hydrocarbon (PAH) formation in atmospheric pressure, opposed flow, ethane diffusion flames. Mole fraction profiles of about 30 major and minor species, as well as trace aromatic and substituted aromatic hydrocarbons and PAHs were quantified by direct gas analysis of the samples withdrawn from within the flame without any preconcentration. Results indicate that fuel-side carbon density and changes in flame temperature markedly influence the levels of benzene and PAH formed within opposed flow diffusion flames.
Porphyrin- and metalloporphyrin-derived as models for coal char combustion and pyrolysis
98io4052
Ouedraogo, A. et al. Combustion and Flame, 1998, 114, (l/2), 1-12. The combustion of individual chunkwood and particle wood elements is simulated in a shrinking core model which has been developed and validated by comparison with literature data. The model is formulated on the physical evidence that large wood specimens inserted into a hot convective environment lose weight mostly over a relatively thin outside layer, while the interior (core) remains relatively undisturbed. The modelling of the complete process requires a correlation of the turbulent heat and mass transfer coefficients which include explicitly the effects of transpiration of volatilized organic compounds and moisture, along with geometry, and equivalent radius. Fuel properties, moisture content and size are found to be determining factors in the fuel element burn-out time. Combustion is more rapid with drier and smaller elements, the shrinking rate slows down with moisture, due to the cooling effects of transpiration and the latent heat of evaporation.
carbons
Jones, J. M. er al. Fuel, 1997, 76, (13) 1235-1240. The paper reports on the pyrolysis and combustion characteristics of carbons prepared by carbonization of porphyrinand metalloporphyrincontaining precursors. Regardless of heat-treatment temperature, all the metals studied-vanadium, iron, cobalt and copper-catalysed the combustion of the carbons. In general, the reactivities of all the carbons decreased with increasing heat-treatment temperature and a compensation effect on the rate was observed, with both the activation energies and the preexponential factors decreasing. A marked influence was witnessed by the metals on the release of nitrogen species during pyrolysis. Less HCN and CHsCN were released in the volatiles for metalloporphyrin-derived carbons than for porphyrin-derived carbons. Also studied was the vanadyl system for nitrogen release during combustion. Less fuel-nitrogen is converted to NO and more is converted to nitrogen and HCN during combustion of this carbon.
Pressurized combustion of biomass-derived low calorific value, fuel gas
9aio4053
Andries, J. et al. Biomass Gasif. Pyrolysis, [Conf.], 1997, 282-290. Edited by Kaltschmitt, M. and Bridgwater, A. V., CPL Press, Newbury, UK. The pressurized combustion of low-calorific value fuel gas was studied Laboratory for Thermal Power Engineering of the Delft University of Technology, which is operating a 1.5 MWth pressurized bubbling fluidized bed gasifier.
Primary and secondary measures for the reduction gal04054 of nitric oxide emissions from biomass combustion
Nussbaumer, T. Dev. Thermochem. Biomass Convers., 1997, 2, 1447-1461. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. The fuel-bound nitrogen is mainly responsible for the nitric oxide emissions from biomass combustion; thermal NO, are only of minor importance. Since biomass combustion leads to higher NO, emissions than gas or light fuel oil combustion, primary or secondary measures for NO, reduction are necessary for future combustion plants. In order to minimize NO, emissions by primary measures, the fuel nitrogen must be reduced to molecular nitrogen in zones with an excess air ratio ~1. Investigations into the following techniques for the reduction of fuel NO, are presented: air staging with and without separate reduction chamber, fuel staging and flue gas recirculation.
Pulverized coal combustion. Concept for the lowest 96iO4065 NO, emissions Greul, U. et al. Chem. Eng. Technol., 1998, 21, (l), 51-55. Various NO, reduction techniques using pulverized coal were investigated in a combustion reactor of the fuel separated staging pilot plant consisting of an electric oven with a build-in ceramic tube (2.5 m long, 250 mm diameter). The metering scale, the reactor, the flue gas filter and the suction stack are designed for a coal mass flow of l-5 kg/h. The coal was burned in the main combustion zone under varying oxygen/coal ratio. Advanced air and fuel staging measures were studied in the combustion of various coals. The paper compares the advantages and disadvantages of reduction measures, the selection of suitable parameters for various coal types are determined and new developments and improvements are progressed.
Pyrometric measurement of the temperature and 98/04056 size of individual combustlng fuel pSrtiClSS
Joutsenoja, T. et al. Appl. Opt., 1997, 36, (7), 1525-1535. The development of a two-colour pyrometric technique for the in situ simultaneous measurement of individual fuel-particle temperatures and sizes in a pressurized entrained flow reactor (PEFR) is reported. A method that requires only a single optical port was developed and a specially designed optical probe was manufactured for the measurements at the PEFR. The fuel-particle temperature was obtained by applying two-colour pyrometry. The particle size was determined from the same pyrometric
Relationship between combustion properties and formation of volatile matter of coal and biomass
98/04058
Li, W. et al. DGMK Tagungsber., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 967-970. Under non-isothermal conditions in TGA apparatus, nine hard coals and five biomasses were studied by pyrolysis and combustion tests. Only in some aspects did the results indicate limited correlations between pyrolysis results and combustion properties. For CO and CH4 formation, a correlation was observed including hard coals and biomasses. A review of NO, formation and reduction mechanisms in combustion systems with particular reference to coal
98/04059
Williams, A. et al. Combust. Emiss. Control III, 1997, l-26. Edited by Adams, M., Institute of Energy, London, UK. In recent years, considerable reductions have been witnessed in the level of NO, emitted by burners fired by natural gas, oil, or pulverized coal. This has been brought about by a number of approaches, such as reducing the temperature or by fuel staging, both of which minimize the NO,-forming reactions in fuel-rich zones. In gaseous or light fuel flames reductions of -8O-90% are currently possible, but the level is only about 50-60% for pulverized coal combustion. Thus there is considerable interest in reducing NO, further and this is the subject of a number of collaborative research projects, such as the current UK DTI-NO, project. In this review, the NO,forming reactions are discussed, giving an indication of the way that they can be used for computational fluid dynamic (CFD) modelling of flames. Natural gas burners and staged oil spray flames are among the applications considered, where in both cases prompt NO, becomes dominant at low NO, levels. However, particular attention is devoted to pulverized coal combustion using some of the DTI-NO, project results from laboratory experiments. An ‘advanced coal model’ detailing some aspects of the work is outlined. The effect of coal composition, rank, and the nature of the nitrogen functionalities on NO, formation, and on residual carbon burn-out are discussed and NO, improving methods are considered.
9alO4060 Scale-up effect for emission characteristics of NO. and unburned carbon in fly ash on pulverized coal combustion Makino, H. and Kimoto, M. FACT, 1996, 21, (Proceedings of the International Joint Power Generation Conference, Volume 1: Environmental Control/Fuels and Combustion Technologies, 1996), 95-100. Test furnaces and power plants display differing NO, and unburned carbon emission characteristics in fly ash on pulverized coal combustion. As burner and furnace sizes influence these characteristics. If a new combustion technology would be developed at small-scale test facility, it is necessary to clear the scaling-up influences on the emission characteristics and to evaluate the effects of applying the new technology to utility boilers. The emissions of NO, and unburned carbon in fly ash from 0.1 t/h test furnace was compared with that from 1.5 t/h large test furnace and some utility boilers. We obtained the correlation among the emissions of these furnaces, It is possible to estimate the NO, and unburned carbon emissions for furnaces with various capacities from the emissions for the 0.1 t/h smallscale test furnace.
Scaling characteristics of aerodynamics, 96104061 transfer, and pollutant emissions In industrial flames
heat
Weber, R. Symp. (Int.) Combust., [Proc.], 1996, 26, (2), 3343-3354. A review of the necessary knowledge for successful scaling of small-scale flames into industrial ones has been carried out from the viewpoint of fluid flow, heat transfer and pollutant emissions. Constant velocity and constant residence time scaling criteria have been scrutinized for their applicability in engineering of gaseous, spray-oil, and pulverized coal flames. Specific considerations are given to scaling natural gas flames spanning the thermal input range of 7 kW to 14 MW. A methodology derived for scaling of the emission data with heat extraction has been used to quantify the spread in the NO, correlation of Rokke et al. It has been concluded that to make the derived correlations applicable to industrial situations, the important effects of flue gas entrainment through the external (in-furnace) recircula-
Fuel and Energy Abstracts
September 1996 379
signals. A discrimination method was developed to confirm that the detected particle was valid for particle sizing. Several series of measurements were made at a PEFR at different process conditions and some typical results are shown. 9alO4057
A quasi-steady shrinking core analysis of wood
combustion
Pol cyclic aromatic hydrocarbon opposed flow dix usion flames of ethane
90io4051
formatlon
in
Vincitore, A. M. and Senkan, S. M. Combustion and Flame, 1998, 114, (l/2), 259-266. Heated micro-probe sampling and gas chromatography/mass spectrometry (GC/MS) has been used to study the effect of fuel-side carbon density on the levels of polycyclic aromatic hydrocarbon (PAH) formation in atmospheric pressure, opposed flow, ethane diffusion flames. Mole fraction profiles of about 30 major and minor species, as well as trace aromatic and substituted aromatic hydrocarbons and PAHs were quantified by direct gas analysis of the samples withdrawn from within the flame without any preconcentration. Results indicate that fuel-side carbon density and changes in flame temperature markedly influence the levels of benzene and PAH formed within opposed flow diffusion flames.
Porphyrin- and metalloporphyrin-derived as models for coal char combustion and pyrolysis
98io4052
Ouedraogo, A. et al. Combustion and Flame, 1998, 114, (l/2), 1-12. The combustion of individual chunkwood and particle wood elements is simulated in a shrinking core model which has been developed and validated by comparison with literature data. The model is formulated on the physical evidence that large wood specimens inserted into a hot convective environment lose weight mostly over a relatively thin outside layer, while the interior (core) remains relatively undisturbed. The modelling of the complete process requires a correlation of the turbulent heat and mass transfer coefficients which include explicitly the effects of transpiration of volatilized organic compounds and moisture, along with geometry, and equivalent radius. Fuel properties, moisture content and size are found to be determining factors in the fuel element burn-out time. Combustion is more rapid with drier and smaller elements, the shrinking rate slows down with moisture, due to the cooling effects of transpiration and the latent heat of evaporation.
carbons
Jones, J. M. er al. Fuel, 1997, 76, (13) 1235-1240. The paper reports on the pyrolysis and combustion characteristics of carbons prepared by carbonization of porphyrinand metalloporphyrincontaining precursors. Regardless of heat-treatment temperature, all the metals studied-vanadium, iron, cobalt and copper-catalysed the combustion of the carbons. In general, the reactivities of all the carbons decreased with increasing heat-treatment temperature and a compensation effect on the rate was observed, with both the activation energies and the preexponential factors decreasing. A marked influence was witnessed by the metals on the release of nitrogen species during pyrolysis. Less HCN and CHsCN were released in the volatiles for metalloporphyrin-derived carbons than for porphyrin-derived carbons. Also studied was the vanadyl system for nitrogen release during combustion. Less fuel-nitrogen is converted to NO and more is converted to nitrogen and HCN during combustion of this carbon.
Pressurized combustion of biomass-derived low calorific value, fuel gas
9aio4053
Andries, J. et al. Biomass Gasif. Pyrolysis, [Conf.], 1997, 282-290. Edited by Kaltschmitt, M. and Bridgwater, A. V., CPL Press, Newbury, UK. The pressurized combustion of low-calorific value fuel gas was studied Laboratory for Thermal Power Engineering of the Delft University of Technology, which is operating a 1.5 MWth pressurized bubbling fluidized bed gasifier.
Primary and secondary measures for the reduction gal04054 of nitric oxide emissions from biomass combustion
Nussbaumer, T. Dev. Thermochem. Biomass Convers., 1997, 2, 1447-1461. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. The fuel-bound nitrogen is mainly responsible for the nitric oxide emissions from biomass combustion; thermal NO, are only of minor importance. Since biomass combustion leads to higher NO, emissions than gas or light fuel oil combustion, primary or secondary measures for NO, reduction are necessary for future combustion plants. In order to minimize NO, emissions by primary measures, the fuel nitrogen must be reduced to molecular nitrogen in zones with an excess air ratio ~1. Investigations into the following techniques for the reduction of fuel NO, are presented: air staging with and without separate reduction chamber, fuel staging and flue gas recirculation.
Pulverized coal combustion. Concept for the lowest 96iO4065 NO, emissions Greul, U. et al. Chem. Eng. Technol., 1998, 21, (l), 51-55. Various NO, reduction techniques using pulverized coal were investigated in a combustion reactor of the fuel separated staging pilot plant consisting of an electric oven with a build-in ceramic tube (2.5 m long, 250 mm diameter). The metering scale, the reactor, the flue gas filter and the suction stack are designed for a coal mass flow of l-5 kg/h. The coal was burned in the main combustion zone under varying oxygen/coal ratio. Advanced air and fuel staging measures were studied in the combustion of various coals. The paper compares the advantages and disadvantages of reduction measures, the selection of suitable parameters for various coal types are determined and new developments and improvements are progressed.
Pyrometric measurement of the temperature and 98/04056 size of individual combustlng fuel pSrtiClSS
Joutsenoja, T. et al. Appl. Opt., 1997, 36, (7), 1525-1535. The development of a two-colour pyrometric technique for the in situ simultaneous measurement of individual fuel-particle temperatures and sizes in a pressurized entrained flow reactor (PEFR) is reported. A method that requires only a single optical port was developed and a specially designed optical probe was manufactured for the measurements at the PEFR. The fuel-particle temperature was obtained by applying two-colour pyrometry. The particle size was determined from the same pyrometric
Relationship between combustion properties and formation of volatile matter of coal and biomass
98/04058
Li, W. et al. DGMK Tagungsber., 1997, 9703, (Proceedings ICCS ‘97, Volume 2) 967-970. Under non-isothermal conditions in TGA apparatus, nine hard coals and five biomasses were studied by pyrolysis and combustion tests. Only in some aspects did the results indicate limited correlations between pyrolysis results and combustion properties. For CO and CH4 formation, a correlation was observed including hard coals and biomasses. A review of NO, formation and reduction mechanisms in combustion systems with particular reference to coal
98/04059
Williams, A. et al. Combust. Emiss. Control III, 1997, l-26. Edited by Adams, M., Institute of Energy, London, UK. In recent years, considerable reductions have been witnessed in the level of NO, emitted by burners fired by natural gas, oil, or pulverized coal. This has been brought about by a number of approaches, such as reducing the temperature or by fuel staging, both of which minimize the NO,-forming reactions in fuel-rich zones. In gaseous or light fuel flames reductions of -8O-90% are currently possible, but the level is only about 50-60% for pulverized coal combustion. Thus there is considerable interest in reducing NO, further and this is the subject of a number of collaborative research projects, such as the current UK DTI-NO, project. In this review, the NO,forming reactions are discussed, giving an indication of the way that they can be used for computational fluid dynamic (CFD) modelling of flames. Natural gas burners and staged oil spray flames are among the applications considered, where in both cases prompt NO, becomes dominant at low NO, levels. However, particular attention is devoted to pulverized coal combustion using some of the DTI-NO, project results from laboratory experiments. An ‘advanced coal model’ detailing some aspects of the work is outlined. The effect of coal composition, rank, and the nature of the nitrogen functionalities on NO, formation, and on residual carbon burn-out are discussed and NO, improving methods are considered.
9alO4060 Scale-up effect for emission characteristics of NO. and unburned carbon in fly ash on pulverized coal combustion Makino, H. and Kimoto, M. FACT, 1996, 21, (Proceedings of the International Joint Power Generation Conference, Volume 1: Environmental Control/Fuels and Combustion Technologies, 1996), 95-100. Test furnaces and power plants display differing NO, and unburned carbon emission characteristics in fly ash on pulverized coal combustion. As burner and furnace sizes influence these characteristics. If a new combustion technology would be developed at small-scale test facility, it is necessary to clear the scaling-up influences on the emission characteristics and to evaluate the effects of applying the new technology to utility boilers. The emissions of NO, and unburned carbon in fly ash from 0.1 t/h test furnace was compared with that from 1.5 t/h large test furnace and some utility boilers. We obtained the correlation among the emissions of these furnaces, It is possible to estimate the NO, and unburned carbon emissions for furnaces with various capacities from the emissions for the 0.1 t/h smallscale test furnace.
Scaling characteristics of aerodynamics, 96104061 transfer, and pollutant emissions In industrial flames
heat
Weber, R. Symp. (Int.) Combust., [Proc.], 1996, 26, (2), 3343-3354. A review of the necessary knowledge for successful scaling of small-scale flames into industrial ones has been carried out from the viewpoint of fluid flow, heat transfer and pollutant emissions. Constant velocity and constant residence time scaling criteria have been scrutinized for their applicability in engineering of gaseous, spray-oil, and pulverized coal flames. Specific considerations are given to scaling natural gas flames spanning the thermal input range of 7 kW to 14 MW. A methodology derived for scaling of the emission data with heat extraction has been used to quantify the spread in the NO, correlation of Rokke et al. It has been concluded that to make the derived correlations applicable to industrial situations, the important effects of flue gas entrainment through the external (in-furnace) recircula-
Fuel and Energy Abstracts
September 1996 379