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02824 Unmixed combustion: an alternative to fire
10 Engines (power generation
and propulsion,
electrical vehicles)
anular flow, simulating a coal transport flow, into much larger turbulent flow structures, causing increased residence times in the pre-ignition region. Particle-imaging techniques in a non-reacting flow show that, in the pre-ignition region, the motion of the smaller particles (~30 pm) are affected by the large flow structures and form clusters with long residence times. Flame stability improvements are attributed to increased particle heating rates in the clusters by radiation due to increased absorptivity and increased residence time in the near burner zone. The NO, reduction can be explained by the generation of large-scale particle clusters that provide local instantaneous fuel-rich combustion environments. This work demonstrates that the production of large-scale clustering effects has the potential to provide an alternative means of simultaneously controlling NO, and improving flame stability relative to existing staging techniques.
enhanced delivery of heat to surfaces, rapidly supplying heat for cold starting engines and direct generation of dry inert gases are also possible. Unmixed combustion also allows the delivery of heat uniformly throughout a volume. This method of heat delivery is potentially useful for supplying heat to endothermic reactions carried out in packed beds of catalyst. Experimental evaluation of this technique for steam reforming shows that while conventional steam reforming is a strongly endothermic reaction with an unfavourable equilibrium, the use of unmixed combustion allows a redefinition of the system’s thermodynamics, making the reaction weakly exothermic with a more favourable equilibrium.
Thermodynamic evaluation for combined combustion of wastes in coal-fired furnaces
10 ENGINES
00102821
Born, M. and Arnold, T. &i/r. Abfalhvirrsch, 1999, 9, 141-158. (In German) The focus of this report is on the problems encountered during the use of alternative fuels affecting the combustion process, thermodynamic calculations are used to form the basis of this investigation. It is shown that using the calculations, predictions can be made regarding the expected corrosion problems by the use of alternative fuels instead of brown coal.
Thermogravimetric study about the accelerating effect of coal-burning additive on combustibility of coal and gangue
00/02822
Tan, 2. ef cl. Cuihua Xuehao, 1999, 20, (3). 263-266. (In Chinese) The combustibility of Nanpiao coal and Fuxin gangue was studied with particular attention given to the accelerating effect of a coal-burning additive, using TG and DTG with linearly increasing temperature in an air atmosphere. The addition of 5% BJ, a coal-burning additive, made the temperature of the maximum combustion rate for Nanpiao bituminous coal decrease a80 K, and made the combustion rate at 773 K increase by 20%. Similar results were obtained for the low rank Fuxin gangue, but the accelerating effect on it was not so good as that on Nanpiao coal. In addition, the catalytic effect of the coal-burning additive on the combustion of graphite was observed and the kinetic study was carried out. The activation energy, the reaction order and the frequency factor for the combustion of graphite were determined to be 241-O kJ/mol, 4.8, and 8.9 x 10” min. i, respectively. The activation energy, the reaction order and the frequency factor for the catalytic oxidation of graphite doped with 5% coalburning additive were found to be 174.3 kJ/mol, 2.6 and 5.4 x 10” min-‘, respectively.
Two-dimensional combustion modeling of heterogeneous solid propellants with finite Peclet number
00/02823
Knott, G. M. and Brewster, M. Q. Comhus/ion and Flame, 2000, 121, (l/22), 91-106. A combustion model has been formulated to solve the burning rate eigenvalue problem for a model heterogeneous solid propellant (twodimensional sandwich) with Peclet number of O(l), similar to what has been done previously for homogeneous energetic solids. A two-step reaction sequence (high-activation-energy, condensed-phase decomposition followed by low-activation-energy, gas-phase heat release) has been extended from one to two dimensions for non-premixed (heterogeneous fuel/oxidizer) composite solids. Gas-phase stream-wise diffusion, the primary driving force for solid pyrolysis, has been accounted for by including a finite value of the Peclet number. The results show that the value of the Peclet number, a non-dimensional burning rate, is constrained to a reasonably small interval by the eigenvalue expression obtained from activation energy asymptotic analysis of the condensed-phase thermal decomposition zone. These results demonstrate the feasibility of and general approach for solving the two-dimensional composite propellant burning rate as an eigenvalue problem. 00/02824 Unmixed combustion: an alternative to fire Lyon, R. K. and Cole, J. A. Comhus~ion and Flame, 2000, 121, (l/2). 249261. A new form of combustion has been studied with properties that are greatly different from combustion via fire. Called unmixed combustion, it occurs when fuel and air alternately pass over a catalyst that undergoes oxidation and reduction, storing oxygen from the air and delivering it to the fuel. Examples of catalysts include finely divided Cu/CuO or FeO/FezOs supported on y-alumina. The full heat of combustion of the fuel is released, the fuel is converted to COz and water and the air is depleted of oxygen, all without any need for the fuel and air to mix. Thus unmixed combustion is an alternative to fire, another way of using fuel and air to generate heat. The properties and characteristics of unmixed combustion are different from those of combustion by fire in a number of ways, some obvious, some subtle, suggesting a number of applications where conventional combustion is not or cannot be used. One example are situations in which it is difficult to provide complete mixing but in which complete combustion is required; e.g. rotary kiln incinerators. These incinerators have a failure mode called ‘puffing’ to which unmixed combustion may be relevant. In the area of pollution control unmtxed combustion is capable of burning natural gas and pyridine with zero NO, production; of burning sulfur-containing fuels in a manner that facilitates subsequent removal of the SO,; and of burning coal in a manner that directly provides sequestration ready COz. Greatly
Power generation and propulsiofi, electrical vehicles 00102825
Alkali metal vapor removal from coal gasification flue
gases
Inai, M. el a/. Kagaku Kogaku Ronhunshu, 1999, 25, (3), 400-405. (In Japanese) With the aim of reducing the corrosion on gas turbine blades with alkali vapour in direct coal fired turbines (DCFT) systems using a pressurized coal partial combustor (PCPC), a study on a dry type alkali sorbent has been conducted. Kaolinite and zeolite were found to be very effective for capturing the NaCl vapour. It was also found that coexistent gases such as Hz0 and HzS promoted the NaCl vapour capture on kaolinite whereas HCI gas suppressed it. The amount of sodium captured on kaolinite was estimated to be around 30 mass% of kaolinite. From the instrumental analysis of kaolinite using XPS (XPS) and X-ray diffraction (XRD), it was found that chemical adsorption and chemical reaction was mostly responsible for the capture of sodium on kaolinite.
Analysis of auxiliary power systems with conventional synchronous generators
00/02826
Lyshevski, S. E. Energy Convers. Manage., 2000, 41, (13), 1379-1387. Auxiliary power systems are widely use and new, challenging problems in analysis, design and deployment of high performance power generation systems call for comprehensive analysis of the energy conversion. The main aim presented in the paper is to develop a complete mathematicJ model to perform non-linear analysis of auxiliary power systems that integrate diesels and synchronous generators. This permits study of the energy conversion needed to perform thorough analysis and to design energy management systems. In this paper, the full spectrum of the physical phenomena of interconnected energy conversion processes in diesels and synchronous generators is studied. The fundamental research reported allows the engineering enterprise in the development of high performance generation systems to be promoted.
Comparison between two gas turbine solutions to increase combined power plant efficiency
00/02827
Carcasci, C. and Facchini, B. Energy Conversion & Managemenr. 2000, 41, (8), 757-713. Significant research efforts are currently centred on developing advanced gas turbine systems for electric power generation applications. Gas-steam combined cycles are often used to obtain a high efficiency power plant. Two innovative gas turbine technologies have recently been proposed for combined cycle applications. Two gas-steam combined cycles using thermodynamic analysis are presented: a combined cycle with three pressure levels with reheat heat recovery boiler is used with two different gas turbine technologies (high pressure ratio and reheat against “H” technology). This analysis constitutes a comparison not only between two different constructive solutions but also between two different gas turbine (GT) techniques (reheat and GT steam cooling) and technologies (a consolidated and an advanced gas turbine technology) applied to a combined cycle.
Comparison of the fractionation of a coal tar pitch by solvent solubility and by planar chromatography
OOlO2828
Lazaro, M. J. er al. Fuel, 1999, 78. (7). 795-801. Two methods of fractionation of a coal tar pitch, one based on solvent solution separation and the other on preparative thin layer chromatography were compared for effectiveness of the separation. The fractions were characterized using size exclusion chromatography (SEC) and UVfluorescence spectroscopy (UV-F). Fractionation by planar chromatography was found to give a better separation and to use less solvent than the solvent separation method. Both SEC and UV-F clearly showed less overlap in fractions separated by planar chromatography, compared to solvent fractionation. The cleaner separation of the heaviest fraction is particularly relevant for the mass spectroscopic investigation of large molecule mass materials, where the presence of lighter materials was
Fuel and Energy Abstracts
September 2000 313
and propulsion,
electrical vehicles)
anular flow, simulating a coal transport flow, into much larger turbulent flow structures, causing increased residence times in the pre-ignition region. Particle-imaging techniques in a non-reacting flow show that, in the pre-ignition region, the motion of the smaller particles (~30 pm) are affected by the large flow structures and form clusters with long residence times. Flame stability improvements are attributed to increased particle heating rates in the clusters by radiation due to increased absorptivity and increased residence time in the near burner zone. The NO, reduction can be explained by the generation of large-scale particle clusters that provide local instantaneous fuel-rich combustion environments. This work demonstrates that the production of large-scale clustering effects has the potential to provide an alternative means of simultaneously controlling NO, and improving flame stability relative to existing staging techniques.
enhanced delivery of heat to surfaces, rapidly supplying heat for cold starting engines and direct generation of dry inert gases are also possible. Unmixed combustion also allows the delivery of heat uniformly throughout a volume. This method of heat delivery is potentially useful for supplying heat to endothermic reactions carried out in packed beds of catalyst. Experimental evaluation of this technique for steam reforming shows that while conventional steam reforming is a strongly endothermic reaction with an unfavourable equilibrium, the use of unmixed combustion allows a redefinition of the system’s thermodynamics, making the reaction weakly exothermic with a more favourable equilibrium.
Thermodynamic evaluation for combined combustion of wastes in coal-fired furnaces
10 ENGINES
00102821
Born, M. and Arnold, T. &i/r. Abfalhvirrsch, 1999, 9, 141-158. (In German) The focus of this report is on the problems encountered during the use of alternative fuels affecting the combustion process, thermodynamic calculations are used to form the basis of this investigation. It is shown that using the calculations, predictions can be made regarding the expected corrosion problems by the use of alternative fuels instead of brown coal.
Thermogravimetric study about the accelerating effect of coal-burning additive on combustibility of coal and gangue
00/02822
Tan, 2. ef cl. Cuihua Xuehao, 1999, 20, (3). 263-266. (In Chinese) The combustibility of Nanpiao coal and Fuxin gangue was studied with particular attention given to the accelerating effect of a coal-burning additive, using TG and DTG with linearly increasing temperature in an air atmosphere. The addition of 5% BJ, a coal-burning additive, made the temperature of the maximum combustion rate for Nanpiao bituminous coal decrease a80 K, and made the combustion rate at 773 K increase by 20%. Similar results were obtained for the low rank Fuxin gangue, but the accelerating effect on it was not so good as that on Nanpiao coal. In addition, the catalytic effect of the coal-burning additive on the combustion of graphite was observed and the kinetic study was carried out. The activation energy, the reaction order and the frequency factor for the combustion of graphite were determined to be 241-O kJ/mol, 4.8, and 8.9 x 10” min. i, respectively. The activation energy, the reaction order and the frequency factor for the catalytic oxidation of graphite doped with 5% coalburning additive were found to be 174.3 kJ/mol, 2.6 and 5.4 x 10” min-‘, respectively.
Two-dimensional combustion modeling of heterogeneous solid propellants with finite Peclet number
00/02823
Knott, G. M. and Brewster, M. Q. Comhus/ion and Flame, 2000, 121, (l/22), 91-106. A combustion model has been formulated to solve the burning rate eigenvalue problem for a model heterogeneous solid propellant (twodimensional sandwich) with Peclet number of O(l), similar to what has been done previously for homogeneous energetic solids. A two-step reaction sequence (high-activation-energy, condensed-phase decomposition followed by low-activation-energy, gas-phase heat release) has been extended from one to two dimensions for non-premixed (heterogeneous fuel/oxidizer) composite solids. Gas-phase stream-wise diffusion, the primary driving force for solid pyrolysis, has been accounted for by including a finite value of the Peclet number. The results show that the value of the Peclet number, a non-dimensional burning rate, is constrained to a reasonably small interval by the eigenvalue expression obtained from activation energy asymptotic analysis of the condensed-phase thermal decomposition zone. These results demonstrate the feasibility of and general approach for solving the two-dimensional composite propellant burning rate as an eigenvalue problem. 00/02824 Unmixed combustion: an alternative to fire Lyon, R. K. and Cole, J. A. Comhus~ion and Flame, 2000, 121, (l/2). 249261. A new form of combustion has been studied with properties that are greatly different from combustion via fire. Called unmixed combustion, it occurs when fuel and air alternately pass over a catalyst that undergoes oxidation and reduction, storing oxygen from the air and delivering it to the fuel. Examples of catalysts include finely divided Cu/CuO or FeO/FezOs supported on y-alumina. The full heat of combustion of the fuel is released, the fuel is converted to COz and water and the air is depleted of oxygen, all without any need for the fuel and air to mix. Thus unmixed combustion is an alternative to fire, another way of using fuel and air to generate heat. The properties and characteristics of unmixed combustion are different from those of combustion by fire in a number of ways, some obvious, some subtle, suggesting a number of applications where conventional combustion is not or cannot be used. One example are situations in which it is difficult to provide complete mixing but in which complete combustion is required; e.g. rotary kiln incinerators. These incinerators have a failure mode called ‘puffing’ to which unmixed combustion may be relevant. In the area of pollution control unmtxed combustion is capable of burning natural gas and pyridine with zero NO, production; of burning sulfur-containing fuels in a manner that facilitates subsequent removal of the SO,; and of burning coal in a manner that directly provides sequestration ready COz. Greatly
Power generation and propulsiofi, electrical vehicles 00102825
Alkali metal vapor removal from coal gasification flue
gases
Inai, M. el a/. Kagaku Kogaku Ronhunshu, 1999, 25, (3), 400-405. (In Japanese) With the aim of reducing the corrosion on gas turbine blades with alkali vapour in direct coal fired turbines (DCFT) systems using a pressurized coal partial combustor (PCPC), a study on a dry type alkali sorbent has been conducted. Kaolinite and zeolite were found to be very effective for capturing the NaCl vapour. It was also found that coexistent gases such as Hz0 and HzS promoted the NaCl vapour capture on kaolinite whereas HCI gas suppressed it. The amount of sodium captured on kaolinite was estimated to be around 30 mass% of kaolinite. From the instrumental analysis of kaolinite using XPS (XPS) and X-ray diffraction (XRD), it was found that chemical adsorption and chemical reaction was mostly responsible for the capture of sodium on kaolinite.
Analysis of auxiliary power systems with conventional synchronous generators
00/02826
Lyshevski, S. E. Energy Convers. Manage., 2000, 41, (13), 1379-1387. Auxiliary power systems are widely use and new, challenging problems in analysis, design and deployment of high performance power generation systems call for comprehensive analysis of the energy conversion. The main aim presented in the paper is to develop a complete mathematicJ model to perform non-linear analysis of auxiliary power systems that integrate diesels and synchronous generators. This permits study of the energy conversion needed to perform thorough analysis and to design energy management systems. In this paper, the full spectrum of the physical phenomena of interconnected energy conversion processes in diesels and synchronous generators is studied. The fundamental research reported allows the engineering enterprise in the development of high performance generation systems to be promoted.
Comparison between two gas turbine solutions to increase combined power plant efficiency
00/02827
Carcasci, C. and Facchini, B. Energy Conversion & Managemenr. 2000, 41, (8), 757-713. Significant research efforts are currently centred on developing advanced gas turbine systems for electric power generation applications. Gas-steam combined cycles are often used to obtain a high efficiency power plant. Two innovative gas turbine technologies have recently been proposed for combined cycle applications. Two gas-steam combined cycles using thermodynamic analysis are presented: a combined cycle with three pressure levels with reheat heat recovery boiler is used with two different gas turbine technologies (high pressure ratio and reheat against “H” technology). This analysis constitutes a comparison not only between two different constructive solutions but also between two different gas turbine (GT) techniques (reheat and GT steam cooling) and technologies (a consolidated and an advanced gas turbine technology) applied to a combined cycle.
Comparison of the fractionation of a coal tar pitch by solvent solubility and by planar chromatography
OOlO2828
Lazaro, M. J. er al. Fuel, 1999, 78. (7). 795-801. Two methods of fractionation of a coal tar pitch, one based on solvent solution separation and the other on preparative thin layer chromatography were compared for effectiveness of the separation. The fractions were characterized using size exclusion chromatography (SEC) and UVfluorescence spectroscopy (UV-F). Fractionation by planar chromatography was found to give a better separation and to use less solvent than the solvent separation method. Both SEC and UV-F clearly showed less overlap in fractions separated by planar chromatography, compared to solvent fractionation. The cleaner separation of the heaviest fraction is particularly relevant for the mass spectroscopic investigation of large molecule mass materials, where the presence of lighter materials was
Fuel and Energy Abstracts
September 2000 313