- Email: [email protected]
01463 combustion of sludge in coal power plants
09 Combustion (bumers, combustion systems) compositions of the fuel (sludge/coal ratio, moisture content). As a result of the analysis, the parameters limiting the amount of sludge in a mixture with coal are identified.
04/01463
Cocombustion of sludge in coal power plants
Buck, P. WLB, Wasser, Luft und Boden, 2003, 47, (3), 52-54. (In German) Both thermally dried and mechanically dewatered sewage sludge are burnt together with hard coal in a power plant. The officially approved amount of municipal sewage sludge amounts to _<40000 tons dry matter/year and a maximum mass flow of 4% of the amount of coal. The dried sewage sludge is conveyed pneumatically. The mechanical dewatered sewage sludge is ground and dried together with the coal in the coal mills. The co-combustion of sewage sludge did not cause any substantial change of gaseous releases. The byproducts fly ash and gypsum are completely utilized.
04/01464 Combustion behaviour of ultra clean coal obtained by chemical demineralisation Rubiera, F. et al. Fuel, 2003, 82, (15 17), 2145-2151. The increasing environmental concern caused by the use of fossil fuels and the concomitant need for improved combustion efficiency is leading to the development of new coal cleaning and utilization processes. However, the benefits achieved by the removal of most mineral matter from coal either by physical or chemical methods can be annulled if poor coal combustibility characteristics are attained. In this work a high volatile bituminous coal with 6% ash content was subjected to chemical demineralization via hydrofluoric and nitric acid leaching, the ash content of the clean coal was reduced to 0.3%. The original and treated coals were devolatilized in a drop tube furnace and the structure and morphology of the resultant chars was analysed by optical and scanning electron microscopies. The reactivity characteristics of the chars were studied by isothermal combustion tests in air at different temperatures in a thermogravimetric system. Comparison of the combustion behaviour and pollutant emissions of both coals was conducted in a drop tube furnace operating at 1000°C. The results of this work indicate that the char obtained from the chemically treated coal presents very different structure, morphology and reactivity behaviour than the char from the original coal. The changes induced by the chemical treatment increased the combustion efficiency determined in the drop tube furnace, in fact higher burnout levels were obtained for the demineralized coal.
04/01465 Combustion process for the synthesis of fullerenes and fuilerenic soot from liquid hydrocarbon Diener, M e t al. PCT Int. Appl. WO 03 50040 (CI. C01B31/00), 19 Jun 2003, US Appl. PV337 750. A combustion apparatus for the production of carbon nanomaterials including fullerenes and fullerenic soot has multiple inlets for introducing an oxygen-containing gas and a hydrocarbon fuel gas in the combustion system such that a flame can be established from the mixed gases, a droplet delivery apparatus for introducing droplets of a liquid hydrocarbon feedstock into the flame, and a collector apparatus for collecting condensable products containing carbon nanomaterials that are generated in the combustion system. The droplet delivery apparatus has multiple spray nozzles arranged radially around the burner for mixing the hydrocarbon feedstock with oxygen and generating a spray of liquid droplets, which are injected into the flame or the reaction zone. The droplets have a Sauter mean diameter of _<40 ~t. The pressure in the combustion system downstream of the burner surface is maintained between 20-200 Torr. The burner surface consists of a porous refractory plate. The burner has a plenum, which is in thermal contact with a liquid to provide temperature control of the plenum. The reaction zone upstream of the flame is thermally insulated to retain heat from the flame to expose the liquid hydrocarbon feedstock or products at or above 1000°C for at least I ms. The liquid hydrocarbon feedstock is a coal tar distillate or a petroleum distillate which contains >30 wt.% of poly-nuclear aromatic hydrocarbons. The fuel gas is methane or natural gas.
04/01466 Combustion rates of graphite rods in the forward stagnation field with high-temperature airflow Makino, A. et al. Combustion and Flame, 2003, 132, (4), 743-753. An experiment has been conducted to measure combustion rates of graphite rods in the forward stagnation field with high-temperature airflow of 1280 K, to elucidate its combustion behaviour. It is found that the combustion rate in the high-temperature airflow is enhanced, because of the elevated transport property due to an increase in the airflow temperature, when the mass flow rate of air is kept constant, and that it is reduced, because of a reduced mass transfer rate of oxygen through the thickened boundary layer, due to reduced density in the gas phase, when the velocity gradient is the same. It is also confirmed that even in the high-temperature air combustion, there occurs an abrupt decrease in the combustion rate when the velocity gradient is lower than about 1000 s 1, because of the establishment of
200
Fuel and Energy Abstracts
May 2004
the CO flame. Theoretical works have also been conducted and it is found that the combustion rate can fairly be obtained numerically, as far as the trend and the approximate magnitude are concerned. It has turned out that the combustion rate in the high-temperature oxidizerflow has nearly the same value as that in the room-temperature airflow even when the oxygen mass fraction is reduced to be about 0.15. It is also found that the oxygen mass fraction can be reduced to be about 0.07, when there exists enough CO2 in the oxidizer and the surface temperature is enough high, say, more than 2000 K.
04/01467 Effects of initial temperature on the structure of laminar CH4-air premixed flames Mishra, D. P. Fuel, 2003, 82, (12), 1471-1475. The growing popularity of natural gas as a eco-friendly fuel, is of paramount motivation of present investigation. In the present paper, the effect of initial temperature on the flame structure have been investigated in which laminar one-dimensional planar propagating flames of CH4/air mixtures is simulated numerically using detailed chemical kinetic scheme and realistic transport models. The burning velocities are fundamentally important in developing models to predict progress of combustion. Hence, the burning velocities as a function of initial temperature of un-burnt gas have been computed for stoichiometric mixture. The present predictions of burning velocities are compared with reported experimental data. The present prediction lies within the scatter of experimental data. A correlation in the form of Su/ Su.0 = (Su/Su,o)l.575 has been developed to describe the dependence of initial temperature on the burning velocity for stoichiometric mixture. The structures of flame are investigated in details for initial temperature of 300 and 600 K which clearly indicate that detailed chemical kinetics are essential for prediction of the effects of initial temperature on the burning velocities. The present study will help in designing and developing the regenerative combustion systems.
04/01468 Elutriation and entrainment from a pilot-scale ash agglomerating combustor/gasifier Yang, W.-C Journal of the Chinese Institute of Chemical Engineers, 2003, 34, (1), 1-5. Elutriation and entrainment phenomena of an earlier Westinghouse ash agglomerating combustor/gasifier process development unit is discussed. The reactor was 0.508 m in inside diameter and 11.6 m in height and was operated at 1580 kPa and 955-1065 ° during tests using coke breeze and char derived from different coals. Data from the process development unit were compared with an entrainment model.
04/01469 Energy analysis of the thermal operation of coke oven batteries Afanas'ev, A. S. et al. Khimiya Tverdogo Topliva (Moscow, Russian Federation), 2003, 1, 69-76. (In Russian) Analysis of thermal operation of coke oven batteries is presented in this paper.
04/01470 Fuel combustion in the fluidized bed of an inert material equipped with an unmovable catalytic small-volume package Yazykov, N. A. et aL Khimiya v Interesakh Ustoichivogo Razvitiya, 2003, 11, (1), 321-326. The capability of combustion of solid fuels (such as the brown coal of the Kansk-Achinsk coal deposit) in the fluidized bed of an inert material in the presence of unmovable catalytic packages is investigated. This arrangement of the catalytic process is shown to allow the achievement of the same parameters of the fuel burn off and the content of toxic substances in the flue gas as in the case of fuel combustion in the fluidized bed of catalyst grains. The new arrangement of catalytic processes can be recommended for the accomplishing of some other exothermic catalytic reactions which require the maintenance of isothermal conditions.
04/01471 Kinetics and products of pyrolysis of hard and brown coal Nedel'ko, V. V. et al. Khimiya Tverdogo Topliva (Moscow, Russian Federation), 2003, 1, 58-68. (In Russian) Pyrolysis of hard coal (Kuznetsk Basin) and brown coal (Moscow Basin) in a wide temperature range was studied. The study included the kinetics of separate stages of coal pyrolysis and product composition of pyrolytic reactions. The non-isothermal pyrolysis of hard coal under anaerobic conditions involves three basic stages: (1) desorption of moisture and gases; (2) sublimation of difficult-to-volatilize components of coal (predominantly tar compounds); and (3) formation of volatile products by thermal decomposition of condensed components of coal as well as through interaction between organic and mineral components of coal. A relationship between the kinetics of moisture desorption and coal particle size was observed. The pyrolysis of brown coal was a staged process.
04/01463
Cocombustion of sludge in coal power plants
Buck, P. WLB, Wasser, Luft und Boden, 2003, 47, (3), 52-54. (In German) Both thermally dried and mechanically dewatered sewage sludge are burnt together with hard coal in a power plant. The officially approved amount of municipal sewage sludge amounts to _<40000 tons dry matter/year and a maximum mass flow of 4% of the amount of coal. The dried sewage sludge is conveyed pneumatically. The mechanical dewatered sewage sludge is ground and dried together with the coal in the coal mills. The co-combustion of sewage sludge did not cause any substantial change of gaseous releases. The byproducts fly ash and gypsum are completely utilized.
04/01464 Combustion behaviour of ultra clean coal obtained by chemical demineralisation Rubiera, F. et al. Fuel, 2003, 82, (15 17), 2145-2151. The increasing environmental concern caused by the use of fossil fuels and the concomitant need for improved combustion efficiency is leading to the development of new coal cleaning and utilization processes. However, the benefits achieved by the removal of most mineral matter from coal either by physical or chemical methods can be annulled if poor coal combustibility characteristics are attained. In this work a high volatile bituminous coal with 6% ash content was subjected to chemical demineralization via hydrofluoric and nitric acid leaching, the ash content of the clean coal was reduced to 0.3%. The original and treated coals were devolatilized in a drop tube furnace and the structure and morphology of the resultant chars was analysed by optical and scanning electron microscopies. The reactivity characteristics of the chars were studied by isothermal combustion tests in air at different temperatures in a thermogravimetric system. Comparison of the combustion behaviour and pollutant emissions of both coals was conducted in a drop tube furnace operating at 1000°C. The results of this work indicate that the char obtained from the chemically treated coal presents very different structure, morphology and reactivity behaviour than the char from the original coal. The changes induced by the chemical treatment increased the combustion efficiency determined in the drop tube furnace, in fact higher burnout levels were obtained for the demineralized coal.
04/01465 Combustion process for the synthesis of fullerenes and fuilerenic soot from liquid hydrocarbon Diener, M e t al. PCT Int. Appl. WO 03 50040 (CI. C01B31/00), 19 Jun 2003, US Appl. PV337 750. A combustion apparatus for the production of carbon nanomaterials including fullerenes and fullerenic soot has multiple inlets for introducing an oxygen-containing gas and a hydrocarbon fuel gas in the combustion system such that a flame can be established from the mixed gases, a droplet delivery apparatus for introducing droplets of a liquid hydrocarbon feedstock into the flame, and a collector apparatus for collecting condensable products containing carbon nanomaterials that are generated in the combustion system. The droplet delivery apparatus has multiple spray nozzles arranged radially around the burner for mixing the hydrocarbon feedstock with oxygen and generating a spray of liquid droplets, which are injected into the flame or the reaction zone. The droplets have a Sauter mean diameter of _<40 ~t. The pressure in the combustion system downstream of the burner surface is maintained between 20-200 Torr. The burner surface consists of a porous refractory plate. The burner has a plenum, which is in thermal contact with a liquid to provide temperature control of the plenum. The reaction zone upstream of the flame is thermally insulated to retain heat from the flame to expose the liquid hydrocarbon feedstock or products at or above 1000°C for at least I ms. The liquid hydrocarbon feedstock is a coal tar distillate or a petroleum distillate which contains >30 wt.% of poly-nuclear aromatic hydrocarbons. The fuel gas is methane or natural gas.
04/01466 Combustion rates of graphite rods in the forward stagnation field with high-temperature airflow Makino, A. et al. Combustion and Flame, 2003, 132, (4), 743-753. An experiment has been conducted to measure combustion rates of graphite rods in the forward stagnation field with high-temperature airflow of 1280 K, to elucidate its combustion behaviour. It is found that the combustion rate in the high-temperature airflow is enhanced, because of the elevated transport property due to an increase in the airflow temperature, when the mass flow rate of air is kept constant, and that it is reduced, because of a reduced mass transfer rate of oxygen through the thickened boundary layer, due to reduced density in the gas phase, when the velocity gradient is the same. It is also confirmed that even in the high-temperature air combustion, there occurs an abrupt decrease in the combustion rate when the velocity gradient is lower than about 1000 s 1, because of the establishment of
200
Fuel and Energy Abstracts
May 2004
the CO flame. Theoretical works have also been conducted and it is found that the combustion rate can fairly be obtained numerically, as far as the trend and the approximate magnitude are concerned. It has turned out that the combustion rate in the high-temperature oxidizerflow has nearly the same value as that in the room-temperature airflow even when the oxygen mass fraction is reduced to be about 0.15. It is also found that the oxygen mass fraction can be reduced to be about 0.07, when there exists enough CO2 in the oxidizer and the surface temperature is enough high, say, more than 2000 K.
04/01467 Effects of initial temperature on the structure of laminar CH4-air premixed flames Mishra, D. P. Fuel, 2003, 82, (12), 1471-1475. The growing popularity of natural gas as a eco-friendly fuel, is of paramount motivation of present investigation. In the present paper, the effect of initial temperature on the flame structure have been investigated in which laminar one-dimensional planar propagating flames of CH4/air mixtures is simulated numerically using detailed chemical kinetic scheme and realistic transport models. The burning velocities are fundamentally important in developing models to predict progress of combustion. Hence, the burning velocities as a function of initial temperature of un-burnt gas have been computed for stoichiometric mixture. The present predictions of burning velocities are compared with reported experimental data. The present prediction lies within the scatter of experimental data. A correlation in the form of Su/ Su.0 = (Su/Su,o)l.575 has been developed to describe the dependence of initial temperature on the burning velocity for stoichiometric mixture. The structures of flame are investigated in details for initial temperature of 300 and 600 K which clearly indicate that detailed chemical kinetics are essential for prediction of the effects of initial temperature on the burning velocities. The present study will help in designing and developing the regenerative combustion systems.
04/01468 Elutriation and entrainment from a pilot-scale ash agglomerating combustor/gasifier Yang, W.-C Journal of the Chinese Institute of Chemical Engineers, 2003, 34, (1), 1-5. Elutriation and entrainment phenomena of an earlier Westinghouse ash agglomerating combustor/gasifier process development unit is discussed. The reactor was 0.508 m in inside diameter and 11.6 m in height and was operated at 1580 kPa and 955-1065 ° during tests using coke breeze and char derived from different coals. Data from the process development unit were compared with an entrainment model.
04/01469 Energy analysis of the thermal operation of coke oven batteries Afanas'ev, A. S. et al. Khimiya Tverdogo Topliva (Moscow, Russian Federation), 2003, 1, 69-76. (In Russian) Analysis of thermal operation of coke oven batteries is presented in this paper.
04/01470 Fuel combustion in the fluidized bed of an inert material equipped with an unmovable catalytic small-volume package Yazykov, N. A. et aL Khimiya v Interesakh Ustoichivogo Razvitiya, 2003, 11, (1), 321-326. The capability of combustion of solid fuels (such as the brown coal of the Kansk-Achinsk coal deposit) in the fluidized bed of an inert material in the presence of unmovable catalytic packages is investigated. This arrangement of the catalytic process is shown to allow the achievement of the same parameters of the fuel burn off and the content of toxic substances in the flue gas as in the case of fuel combustion in the fluidized bed of catalyst grains. The new arrangement of catalytic processes can be recommended for the accomplishing of some other exothermic catalytic reactions which require the maintenance of isothermal conditions.
04/01471 Kinetics and products of pyrolysis of hard and brown coal Nedel'ko, V. V. et al. Khimiya Tverdogo Topliva (Moscow, Russian Federation), 2003, 1, 58-68. (In Russian) Pyrolysis of hard coal (Kuznetsk Basin) and brown coal (Moscow Basin) in a wide temperature range was studied. The study included the kinetics of separate stages of coal pyrolysis and product composition of pyrolytic reactions. The non-isothermal pyrolysis of hard coal under anaerobic conditions involves three basic stages: (1) desorption of moisture and gases; (2) sublimation of difficult-to-volatilize components of coal (predominantly tar compounds); and (3) formation of volatile products by thermal decomposition of condensed components of coal as well as through interaction between organic and mineral components of coal. A relationship between the kinetics of moisture desorption and coal particle size was observed. The pyrolysis of brown coal was a staged process.