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04851 Coal copyrolysis with coke-oven gas. II. Combustion reactivity of chars from coal copyrolysis with coke-oven gas
09
Combustion
(burners, combustion
systems)
Advanced Goal-Fired low Emission Boiler System.‘. The LEBS (Low emission Boiler System) programme aims to develop an advanced pulverized coal (PC)-fired power generation system for commercial application by the year 2000. Environmental concerns are expected to tighten regulations for new coal-fired plants, so the system must achieve very low emissions and high cycle efficiency at a life cycle east equivalent to a conventional PC plant meeting new US Source Performance Standards (NSPS). B&W has coupled advanced environmental control technologies capable of achieving emissions of NO,, SO,, and particulate far below current NPS with an advanced boiler equipped with improved combustion and heat-transfer subsystems to meet this objective. The plant used conventional state-of-the-art equipment along with developing new technologies to meet the goals of the programme. This combination of new and proven technologies allows B&W to meet the current demands in the marketplace. The design of the advanced generating plant and its relevance to hoth the foreign and domestic markets is presented in this paper.
Catalytic influence of ash elements on NO. forma97194848 tion in char combustion under fluidired bed conditions Kopsel, R. F. W. and Halang, S. Fuel, 1997, 76, (4) 34.5-351. Coal nitrogen is the only source for the formation of nitrogen oxides under fluid bed combustion conditions. Most of the reactions in which nitrogen oxides are formed or reduced are catalytic ones. To investigate the influence of coal ash, comparative experiments were carried out with original, de-ashed and impregnated lignite and hard coal. Pyrolytic experiments and elementary analysis showed that the organic coal structure is not changed by de-ashing. Char combustion was carried out in a thermobalance in the temperature range between 500 and 900°C. The NO, formation and reduction reactions are strongly influenced hy the catalytic efficiency of the ash. The influence is more marked for lignite than for hard coal. The emissions of NO, are diminished by ash over wide temperature ranges. Both decreases and increases in NO, emissions can arise from the influence of individual ash components.
97194849 combustion
09
Li, H. ef al. J. Therm. Analysis, 1997, 49, (3). 1417-1422. In order to examine the possible formation of chlorinated organic compounds during the combustion of blends of refuse derived fuels and coal under conditions similar to those of an atmospheric fluidized bed combustion (AFBC) system, a series of experiments were conducted using a TG interfaced to FTIR. Additional experiments using a tube furnace preheated to AFBC operating temperatures were also conducted. The combustion products were cryogenically trapped and analysed with a GCI MS system. The chlorination of phenols and the condensation reactions of chlorophenols were investigated in this study. A possible mechanism for the formation of chlorinated organic compounds, such as dibenzodioxins and dibenzofurans, by chlorination and condensation reactions involving phenols, was proposed.
COMBUSTION Burners,
97194844 design
Combustion
An approach
Systems
to multivariable
combustion
control
Kocijan, J. J. Proc. Cont., 7, (4), 291-301. This paper presents an approach to multivariable combustion control design within the Individual Channel Design (ICD) framework for analysis and control design. ICD is a framework which involves an interplay between customer specification, uncertain plant characteristics, and the multivariable feed-back design itself. The ICD framework can incorporate established multivariable methods and process engineering knowledge can he incorporated. The combustion control has been designed and evaluated with a computer simulation of both a linearized model and a non-linear model of the closed-loop system. The ICD multivariable framework clearly shows what the main possibilities and difficulties posed by a combustion process for multivariable control are, and how much trade-off between control specifications is possible, by way of simple graphical frequency response indicators. Solutions are also presented for problems such as integrity of closed-loop control, balance of input-output channels, simple and transparent controller structure, and robustness.
Behavior of heavy metals in different 97194845 systems with and without co-combustion
coal firing
Blumel, W. and Wilgeroth, U. VGB Tech. Ver. Gmsskraftwerksbetr., [Tagttngsber.] VGB-TB., 1997, 114, 1-18. The paper presents the technical problems concerning the chemical and physical behaviour of heavy metals in coal combustion, especially in cocombustion with wastes such as paint sludges, old tyres and old oils. Discussed, among other topics, are: phase distribution of metals in the combustion gases and ashes, metal recovery in the ashes and dust, metals in boiler and flue gas deposits and dust, and arsenic distribution in the ashes and deposits.
Calculation of average volatile flame temperature 97194646 oil shale particle during fluidized bed combustion
of
Wang, G. et al. Ranshao Kexue Yu Jishu., 1995, 1, (4), 354-359. (In Chinese) The temperature of the flame from combustion of volatile matter substantially affects the fluidized-bed combustion of oil shale. When oil shale is fed to a fluidized-bed combustor, devolatilization occurs, and a diffusion flame sheet forms. The energy feedback from the flame, at a higher temperature than that of air, enhances the rate of subsequent devolatilization. By taking the chemical reaction in the flame sheet into account, and coupling heat transfer with mass transfer between the flame sheet and the particle surface, and adopting the Schwab-Zeldovich transformation approach, an analysis solution for the average flame temperature was obtained. The calculated result found good agreement with experimental data.
Calculation of the temperature 97104847 and gasification products in an exit duct
of coal combustion
Yanchenko, G. A. lzu. Vyssh. Uchebn. Zaved., Gem. Zh., 1997, (l-2), (In Russian) A method is developed for this calculation.
420
Fuel and Energy Abstracts
November
1997
Chlorinated organic compounds evolved during the of blends of refuse-derived fuels and coals
l-4.
97/94856 Co-combustion in power plants
of sewage sludge and other wastes
Hoffmann, V. Mater. - Landesunweltamt Nordrher,l-M/ePtfalert.. 1997, 42, (Kreislaufwirtschaft und Abfallverwertung in Thermischen Prozessen). hl70. (In German) Sewage sludge disposal by co-combustion with coal in clecrical power plants is addressed in this article. The composition and heating value of the sewage sludge, and emissions and ash resulting from the co-combustion process are discussed.
97104851 Coal copyrolysis with coke-oven gas. II. Combustion reactivity of chars from coal copyrolysis with coke-oven gas Liao, H. et al. Ranliao Huaxrre Xuebao, 1997, 25, (3). 207-212. (In Chinese) Xianfeng lignite chars obtained from co-pyrolysis with coke-oven gas under various operation conditions, were investigated for their combustion reactivities of. TGiDTG and its resultant combustion characteristic parameters and R-f curves were implemented. The results indicated that the combustion reactivities of the chars are related to pyrolysis processing conditions. With the increase of pyrolysis pressure, the chars reactivity gradually decreases, however, the effect of pressure on chars reactivity becomes less remarkable at a higher heating rate. At a given pressure the reactivity of chars increases with the rise of heating rate, and this effect was more notable under a higher pressure. The reactivities of chars from coal co-pyrolysis with coke-oven gas are similar to those from hydropyrolysis, but lower than those from pyrolysis under N1.
97194852 Coal pulsating combustion model Xu, W. Ranshuo Kexue Yu Jishu., 1996, 2. (3), 260-269.
(In Chinese) Pulsed combustion of coal in an advanced Rijke-type comhustor, characterized by high combustion and heat-transfer efficiency and low environmental pollution, was researched and the results are reported. It is possible that the thermal efficiency of industrial boilers can be increased by 5% to -10% with essentially smoke-free operation. An analysis model of pulsed coal combustion was developed and can be used to explain many experimental phenomena of pulsed combustion of coal. When the coal bed is located in lower half of the Rijke tube, it is probable that this arrangement induces oscillation. An excited pulsed combustion is caused by coupling of the combustion process with gas flow velocity.
Combined combustion of biomass, 97104853 age sludge and coal in an atmospheric fluidized
municipal sewbed installation
van Doom, J. et al. Biomass Energy Environ., Proc. Eur. Biornergy Conf.. 9th., 1996, 2, 1007-1012. Edited by Chartier, P., Elsevier, Oxford, UK. Combustion hehaviour and flue gas emissions are affected by the cocombustion of biomass or municipal sewage sludge with coal in a fluidized bed installation. In the case of coal-wood and coal-straw co-combustion, the concentrations of NOz, SOz and CO in the flue gas decreased with increasing biomass contribution in the fuel mixture. Co-combustion of coal and sewage sludge resulted in a substantial increase in SOa concentration in the flue gas upon increasing the sludge ratio. Compared with coal-firing, the concentration of chlorine in the flue gas increased when increasing the amount of straw or sewage sludge. No operational problems were observed with co-firing wood and coal. In the case of straw and sewage sludge agglomeration of the bed material occurred; for commercial applications
Combustion
(burners, combustion
systems)
Advanced Goal-Fired low Emission Boiler System.‘. The LEBS (Low emission Boiler System) programme aims to develop an advanced pulverized coal (PC)-fired power generation system for commercial application by the year 2000. Environmental concerns are expected to tighten regulations for new coal-fired plants, so the system must achieve very low emissions and high cycle efficiency at a life cycle east equivalent to a conventional PC plant meeting new US Source Performance Standards (NSPS). B&W has coupled advanced environmental control technologies capable of achieving emissions of NO,, SO,, and particulate far below current NPS with an advanced boiler equipped with improved combustion and heat-transfer subsystems to meet this objective. The plant used conventional state-of-the-art equipment along with developing new technologies to meet the goals of the programme. This combination of new and proven technologies allows B&W to meet the current demands in the marketplace. The design of the advanced generating plant and its relevance to hoth the foreign and domestic markets is presented in this paper.
Catalytic influence of ash elements on NO. forma97194848 tion in char combustion under fluidired bed conditions Kopsel, R. F. W. and Halang, S. Fuel, 1997, 76, (4) 34.5-351. Coal nitrogen is the only source for the formation of nitrogen oxides under fluid bed combustion conditions. Most of the reactions in which nitrogen oxides are formed or reduced are catalytic ones. To investigate the influence of coal ash, comparative experiments were carried out with original, de-ashed and impregnated lignite and hard coal. Pyrolytic experiments and elementary analysis showed that the organic coal structure is not changed by de-ashing. Char combustion was carried out in a thermobalance in the temperature range between 500 and 900°C. The NO, formation and reduction reactions are strongly influenced hy the catalytic efficiency of the ash. The influence is more marked for lignite than for hard coal. The emissions of NO, are diminished by ash over wide temperature ranges. Both decreases and increases in NO, emissions can arise from the influence of individual ash components.
97194849 combustion
09
Li, H. ef al. J. Therm. Analysis, 1997, 49, (3). 1417-1422. In order to examine the possible formation of chlorinated organic compounds during the combustion of blends of refuse derived fuels and coal under conditions similar to those of an atmospheric fluidized bed combustion (AFBC) system, a series of experiments were conducted using a TG interfaced to FTIR. Additional experiments using a tube furnace preheated to AFBC operating temperatures were also conducted. The combustion products were cryogenically trapped and analysed with a GCI MS system. The chlorination of phenols and the condensation reactions of chlorophenols were investigated in this study. A possible mechanism for the formation of chlorinated organic compounds, such as dibenzodioxins and dibenzofurans, by chlorination and condensation reactions involving phenols, was proposed.
COMBUSTION Burners,
97194844 design
Combustion
An approach
Systems
to multivariable
combustion
control
Kocijan, J. J. Proc. Cont., 7, (4), 291-301. This paper presents an approach to multivariable combustion control design within the Individual Channel Design (ICD) framework for analysis and control design. ICD is a framework which involves an interplay between customer specification, uncertain plant characteristics, and the multivariable feed-back design itself. The ICD framework can incorporate established multivariable methods and process engineering knowledge can he incorporated. The combustion control has been designed and evaluated with a computer simulation of both a linearized model and a non-linear model of the closed-loop system. The ICD multivariable framework clearly shows what the main possibilities and difficulties posed by a combustion process for multivariable control are, and how much trade-off between control specifications is possible, by way of simple graphical frequency response indicators. Solutions are also presented for problems such as integrity of closed-loop control, balance of input-output channels, simple and transparent controller structure, and robustness.
Behavior of heavy metals in different 97194845 systems with and without co-combustion
coal firing
Blumel, W. and Wilgeroth, U. VGB Tech. Ver. Gmsskraftwerksbetr., [Tagttngsber.] VGB-TB., 1997, 114, 1-18. The paper presents the technical problems concerning the chemical and physical behaviour of heavy metals in coal combustion, especially in cocombustion with wastes such as paint sludges, old tyres and old oils. Discussed, among other topics, are: phase distribution of metals in the combustion gases and ashes, metal recovery in the ashes and dust, metals in boiler and flue gas deposits and dust, and arsenic distribution in the ashes and deposits.
Calculation of average volatile flame temperature 97194646 oil shale particle during fluidized bed combustion
of
Wang, G. et al. Ranshao Kexue Yu Jishu., 1995, 1, (4), 354-359. (In Chinese) The temperature of the flame from combustion of volatile matter substantially affects the fluidized-bed combustion of oil shale. When oil shale is fed to a fluidized-bed combustor, devolatilization occurs, and a diffusion flame sheet forms. The energy feedback from the flame, at a higher temperature than that of air, enhances the rate of subsequent devolatilization. By taking the chemical reaction in the flame sheet into account, and coupling heat transfer with mass transfer between the flame sheet and the particle surface, and adopting the Schwab-Zeldovich transformation approach, an analysis solution for the average flame temperature was obtained. The calculated result found good agreement with experimental data.
Calculation of the temperature 97104847 and gasification products in an exit duct
of coal combustion
Yanchenko, G. A. lzu. Vyssh. Uchebn. Zaved., Gem. Zh., 1997, (l-2), (In Russian) A method is developed for this calculation.
420
Fuel and Energy Abstracts
November
1997
Chlorinated organic compounds evolved during the of blends of refuse-derived fuels and coals
l-4.
97/94856 Co-combustion in power plants
of sewage sludge and other wastes
Hoffmann, V. Mater. - Landesunweltamt Nordrher,l-M/ePtfalert.. 1997, 42, (Kreislaufwirtschaft und Abfallverwertung in Thermischen Prozessen). hl70. (In German) Sewage sludge disposal by co-combustion with coal in clecrical power plants is addressed in this article. The composition and heating value of the sewage sludge, and emissions and ash resulting from the co-combustion process are discussed.
97104851 Coal copyrolysis with coke-oven gas. II. Combustion reactivity of chars from coal copyrolysis with coke-oven gas Liao, H. et al. Ranliao Huaxrre Xuebao, 1997, 25, (3). 207-212. (In Chinese) Xianfeng lignite chars obtained from co-pyrolysis with coke-oven gas under various operation conditions, were investigated for their combustion reactivities of. TGiDTG and its resultant combustion characteristic parameters and R-f curves were implemented. The results indicated that the combustion reactivities of the chars are related to pyrolysis processing conditions. With the increase of pyrolysis pressure, the chars reactivity gradually decreases, however, the effect of pressure on chars reactivity becomes less remarkable at a higher heating rate. At a given pressure the reactivity of chars increases with the rise of heating rate, and this effect was more notable under a higher pressure. The reactivities of chars from coal co-pyrolysis with coke-oven gas are similar to those from hydropyrolysis, but lower than those from pyrolysis under N1.
97194852 Coal pulsating combustion model Xu, W. Ranshuo Kexue Yu Jishu., 1996, 2. (3), 260-269.
(In Chinese) Pulsed combustion of coal in an advanced Rijke-type comhustor, characterized by high combustion and heat-transfer efficiency and low environmental pollution, was researched and the results are reported. It is possible that the thermal efficiency of industrial boilers can be increased by 5% to -10% with essentially smoke-free operation. An analysis model of pulsed coal combustion was developed and can be used to explain many experimental phenomena of pulsed combustion of coal. When the coal bed is located in lower half of the Rijke tube, it is probable that this arrangement induces oscillation. An excited pulsed combustion is caused by coupling of the combustion process with gas flow velocity.
Combined combustion of biomass, 97104853 age sludge and coal in an atmospheric fluidized
municipal sewbed installation
van Doom, J. et al. Biomass Energy Environ., Proc. Eur. Biornergy Conf.. 9th., 1996, 2, 1007-1012. Edited by Chartier, P., Elsevier, Oxford, UK. Combustion hehaviour and flue gas emissions are affected by the cocombustion of biomass or municipal sewage sludge with coal in a fluidized bed installation. In the case of coal-wood and coal-straw co-combustion, the concentrations of NOz, SOz and CO in the flue gas decreased with increasing biomass contribution in the fuel mixture. Co-combustion of coal and sewage sludge resulted in a substantial increase in SOa concentration in the flue gas upon increasing the sludge ratio. Compared with coal-firing, the concentration of chlorine in the flue gas increased when increasing the amount of straw or sewage sludge. No operational problems were observed with co-firing wood and coal. In the case of straw and sewage sludge agglomeration of the bed material occurred; for commercial applications