- Email: [email protected]
Study on combustion kinetics of coal powder
10 Engines (power generation and propulsion, electrical vehicles) that of tar decomposition by Weibull distribution formation and development of anisotropic textures is the reaction between the mesophase from the pyrolysis and the char from sawdust, in contrast, it is promoted by PVC.
function. The obstructed by of caking coal waste tyre and
02/01646 Study on combustion kinetics of coal powder Zhang, W. and Jian, M. Nanjing Huagong Daxue Xuebao. Ziran Kexueban, 2001, 23, (2), 20-23. (In Chinese) The main techniques adopted in the measurement of combustion kinetic parameters consist of thermogravimetry, DTFS and pyro-test. A new unit for the test of gas-solid reaction was developed in which coal powder can be steadily kept in suspension. The unit can better stimulate industrial fluidized bed reactor and detect the burnout of coal powder, combustion reaction rate and surface temperature of the particles. Based on test results and the mathematics model, the kinetic parameters, such as reaction rate, activation energy, constant in Arrhenius equation, were derived. Except for anthracite, soft coal was tested and researched. The test results will supply more reliable kinetic data for the design of industrial fluidized bed reactors.
02/01646 systems
Suifation phenomena in fiuidized bed combustion
Anthony, E.J. and Granatstein, D.L. Progress in Energy and Combustion Science, 2001, 27, (2), 215-236. Fiuidized bed combustors (FBCs) are noted for their ability to capture SO* in situ via direct reaction with Ca-based sorbents. However, despite more than 30 years of intensive study of suifation processes in atmospheric FBC boilers and numerous laboratory studies, there are still many uncertainties and disagreements on the subject. In particular, the mechanisms of the suifation reaction are still not properly understood, and there is dispute over the explanation of the weiiknown temperature maximum for optimum sulfur capture found in FBC boilers. This paper discusses these points of contention and suggests the most probable mechanisms and explanations for the various phenomena seen with sulfur capture, based on current literature and personal experimentation. 02iOl647 The effect of pressure on coal char combustion Liakos, H.H. er al. Appl. Therm. Eng., 2001, 21, (9), 917-928. A two-dimensional, two-phase combustion model of pulverized coal char at elevated pressures is presented in this paper. This is often encountered in furnaces used for power generation, industrial heating and steam production, and for conversion of solids to gas and liquid products. In pressurized circulating fluidized bed boilers, the effect of pressure on char combustion is significant. Of particular importance is to reveal the relative significance of the diffusion and chemical reaction, as controlling mechanisms, and to evaluate the effect of total pressure on the performance of the combustion chamber. The partial differential equations of conservation of mass, momentum and energy are solved taking into consideration turbulent flow, interphase massand heat-transfer, radiation and varying operational conditions (e.g. feed of coal and primary and secondary air). The equations are integrated with the finite volume method and are solved for the flow field, temperature field in the gaseous and solid phases and the concentration of reactants and products. The results show that both chemical reaction and diffusion mechanisms control the combustion at elevated pressure. Moreover, the effect of pressure on the reaction kinetics proves to be significant.
02iO1646 The effect of volume change of coal during carbonization in the direction of coke oven width on the internal gas pressure in the plastic layer Nomura, S. and Arima, T. Fuel, 2001, 80, (9), 1307-1315. The coking pressure in a coke oven, which is caused by the internal gas pressure in the coal plastic layer, is determined by the gas permeability of the layer. The gas permeability of the plastic layer depends on its density as well as the physical property of the plastic coal itself. The plastic layer is sandwiched between the coke and the resolidifying layers and the coal layer and the effect of the volume change of these outer layers in the direction of coke oven width, i.e. contraction and compression, on the density of the plastic layer and the internal gas pressure was studied. A sandwich carbonization test, where different kinds of coals were charged in the test coke oven, showed that the internal gas pressure depends not only on the kind of coal in the plastic phase but also on the kind of coal in the resolidifying and the coke phases near the oven wails. The relative volume of coke transformed from the unit volume of coal was measured using an X-ray CT scanner and it varied greatly across the coke oven width depending on the kinds of coals. The volume change of coal during carbonization in the direction of coke oven width affects the density of the plastic layer and the internal gas pressure. The relative volume of semicoke and coke transformed from the unit volume of coal near the oven wails is higher
for a high coking pressure coal than that for a low coking pressure coal. This causes the plastic layer to have a high density and the generation of dangerously high internal gas pressure in the oven centre.
02lO1649 The stron -jet/weak-jet problem: new experiments and CF 8
Yimer, I. er al. Combusrion and Flame, 2001, 124, (3) 481-502. The strong-jet/weak-jet coupling is basic to a new generation of uitralow-NOx burners that are diffusion type and rely on lower flame temperatures through controlled mixing of the air, the fuel, and recirculated combustion products. Further, to developing a theory on the isolated jet pair in a previous publication, where the jet trajectories were predicted and compared with experimental data with good agreement, new experimental results of cold modeiiing by using flow visualization and laser Doppler veiocimetry (LDV) are reported in this paper. Mathematical modeiiing by using a commercial computational fluid dynamics code (CFD) was employed to predict the flow field. CFD is also used to predict a mixing progress variable, Rlz for the three stream mixing of air, fuel, and combustion products for the first time. Flow visualization reveals very interesting behaviour of large-scale structures and engulfment as the fuel and combustion air interact and mix. The measured mean and root-mean-squared velocities on the plane of bilateral symmetry are compared with the CFD predictions. The profiles across the jet cross-sections and the behaviour along the air jet axis closely follow the experimental results, however, the fuel jet trajectory is poorly predicted. Constraints in the model due to the assumption of normal or well-developed turbulence spectrum in concentration fluctuations are highlighted. 02/01660 Thermal analysis in combustion research Stenseng, M. er a/. J. Therm. Anal. Calorim., 2001, 64, (3), 1325-i 334. Thermal analysis is widely used in combustion research for both fundamental and practical investigations. Efficient combustion of solid fuels in power plants requires understanding of properties and behaviour of fuel and ash under a wide range of conditions. At the Department of Chemical Engineering, Technical University of Denmark, thermogravimetric analysis and differential scanning calorimetry are applied in order to investigate various aspects of combustion and char reactivity and ash melting gasification processes: pyrolysis, behaviour. This paper shows examples of the application of simuitaneous thermal analysis in these three research areas, and it demonstrates the flexibility of this technique in combustion research.
Thermal degradation of a solid fuel in a drum-type ovroivtic reactor
02/01661
G&asiov, G.Y. and Ter-Oganesyan, G.K. Fir. Goreniya Vzryva, 2001, 37, (3), 70-75. (In Russian) Kinetic parameters of high temperature pyrolysis of oil shale were detected. A simple mathematical model of process dynamics of thermal destruction of solid fuel was developed. A design example of drum-type pyrolysis reactor was given.
10
ENGINES Power generation and propulsion, electrical vehicles
02/01662 An experimental study on the effect of pressure and stmin rate on CH chemiiuminescence of premixed fueilean methanelair flames Higgins, B. er a/. Fuel, 2001, 80, (1 I), 1583-1591. This article reports systematic measurements of CH chemiiuminescene from a premixed, iaminar flame and a premixed, strained, counter-flow flame at ambient pressures ranging from 0.5 to 2.5 MPa and equivalence from 0.66 to 0.86. The objective of this study was to investigate the possibility of using chemiiuminescence as an active feedback control parameter to deduce the equivalence ratio, and therefore NO, production and combustion stability, for premixed flames at high pressure. The chemiluminescence signal from the first electronically excited state of CH to ground (at 431.5 nm) was detected through a band-pass, optical filter in combination with a photomultiplier tube. CH chemiluminescence at high pressure was found to have a power law dependence with equivalence ratio and pressure, and was proportional to mass flowrate. Using the premixed counter-flow flame, strain was shown not to influence chemiiuminescence. Further, a comparison of these findings with previous results of OH chemilumiFuel and Energy Abstracts
May 2662
209
function. The obstructed by of caking coal waste tyre and
02/01646 Study on combustion kinetics of coal powder Zhang, W. and Jian, M. Nanjing Huagong Daxue Xuebao. Ziran Kexueban, 2001, 23, (2), 20-23. (In Chinese) The main techniques adopted in the measurement of combustion kinetic parameters consist of thermogravimetry, DTFS and pyro-test. A new unit for the test of gas-solid reaction was developed in which coal powder can be steadily kept in suspension. The unit can better stimulate industrial fluidized bed reactor and detect the burnout of coal powder, combustion reaction rate and surface temperature of the particles. Based on test results and the mathematics model, the kinetic parameters, such as reaction rate, activation energy, constant in Arrhenius equation, were derived. Except for anthracite, soft coal was tested and researched. The test results will supply more reliable kinetic data for the design of industrial fluidized bed reactors.
02/01646 systems
Suifation phenomena in fiuidized bed combustion
Anthony, E.J. and Granatstein, D.L. Progress in Energy and Combustion Science, 2001, 27, (2), 215-236. Fiuidized bed combustors (FBCs) are noted for their ability to capture SO* in situ via direct reaction with Ca-based sorbents. However, despite more than 30 years of intensive study of suifation processes in atmospheric FBC boilers and numerous laboratory studies, there are still many uncertainties and disagreements on the subject. In particular, the mechanisms of the suifation reaction are still not properly understood, and there is dispute over the explanation of the weiiknown temperature maximum for optimum sulfur capture found in FBC boilers. This paper discusses these points of contention and suggests the most probable mechanisms and explanations for the various phenomena seen with sulfur capture, based on current literature and personal experimentation. 02iOl647 The effect of pressure on coal char combustion Liakos, H.H. er al. Appl. Therm. Eng., 2001, 21, (9), 917-928. A two-dimensional, two-phase combustion model of pulverized coal char at elevated pressures is presented in this paper. This is often encountered in furnaces used for power generation, industrial heating and steam production, and for conversion of solids to gas and liquid products. In pressurized circulating fluidized bed boilers, the effect of pressure on char combustion is significant. Of particular importance is to reveal the relative significance of the diffusion and chemical reaction, as controlling mechanisms, and to evaluate the effect of total pressure on the performance of the combustion chamber. The partial differential equations of conservation of mass, momentum and energy are solved taking into consideration turbulent flow, interphase massand heat-transfer, radiation and varying operational conditions (e.g. feed of coal and primary and secondary air). The equations are integrated with the finite volume method and are solved for the flow field, temperature field in the gaseous and solid phases and the concentration of reactants and products. The results show that both chemical reaction and diffusion mechanisms control the combustion at elevated pressure. Moreover, the effect of pressure on the reaction kinetics proves to be significant.
02iO1646 The effect of volume change of coal during carbonization in the direction of coke oven width on the internal gas pressure in the plastic layer Nomura, S. and Arima, T. Fuel, 2001, 80, (9), 1307-1315. The coking pressure in a coke oven, which is caused by the internal gas pressure in the coal plastic layer, is determined by the gas permeability of the layer. The gas permeability of the plastic layer depends on its density as well as the physical property of the plastic coal itself. The plastic layer is sandwiched between the coke and the resolidifying layers and the coal layer and the effect of the volume change of these outer layers in the direction of coke oven width, i.e. contraction and compression, on the density of the plastic layer and the internal gas pressure was studied. A sandwich carbonization test, where different kinds of coals were charged in the test coke oven, showed that the internal gas pressure depends not only on the kind of coal in the plastic phase but also on the kind of coal in the resolidifying and the coke phases near the oven wails. The relative volume of coke transformed from the unit volume of coal was measured using an X-ray CT scanner and it varied greatly across the coke oven width depending on the kinds of coals. The volume change of coal during carbonization in the direction of coke oven width affects the density of the plastic layer and the internal gas pressure. The relative volume of semicoke and coke transformed from the unit volume of coal near the oven wails is higher
for a high coking pressure coal than that for a low coking pressure coal. This causes the plastic layer to have a high density and the generation of dangerously high internal gas pressure in the oven centre.
02lO1649 The stron -jet/weak-jet problem: new experiments and CF 8
Yimer, I. er al. Combusrion and Flame, 2001, 124, (3) 481-502. The strong-jet/weak-jet coupling is basic to a new generation of uitralow-NOx burners that are diffusion type and rely on lower flame temperatures through controlled mixing of the air, the fuel, and recirculated combustion products. Further, to developing a theory on the isolated jet pair in a previous publication, where the jet trajectories were predicted and compared with experimental data with good agreement, new experimental results of cold modeiiing by using flow visualization and laser Doppler veiocimetry (LDV) are reported in this paper. Mathematical modeiiing by using a commercial computational fluid dynamics code (CFD) was employed to predict the flow field. CFD is also used to predict a mixing progress variable, Rlz for the three stream mixing of air, fuel, and combustion products for the first time. Flow visualization reveals very interesting behaviour of large-scale structures and engulfment as the fuel and combustion air interact and mix. The measured mean and root-mean-squared velocities on the plane of bilateral symmetry are compared with the CFD predictions. The profiles across the jet cross-sections and the behaviour along the air jet axis closely follow the experimental results, however, the fuel jet trajectory is poorly predicted. Constraints in the model due to the assumption of normal or well-developed turbulence spectrum in concentration fluctuations are highlighted. 02/01660 Thermal analysis in combustion research Stenseng, M. er a/. J. Therm. Anal. Calorim., 2001, 64, (3), 1325-i 334. Thermal analysis is widely used in combustion research for both fundamental and practical investigations. Efficient combustion of solid fuels in power plants requires understanding of properties and behaviour of fuel and ash under a wide range of conditions. At the Department of Chemical Engineering, Technical University of Denmark, thermogravimetric analysis and differential scanning calorimetry are applied in order to investigate various aspects of combustion and char reactivity and ash melting gasification processes: pyrolysis, behaviour. This paper shows examples of the application of simuitaneous thermal analysis in these three research areas, and it demonstrates the flexibility of this technique in combustion research.
Thermal degradation of a solid fuel in a drum-type ovroivtic reactor
02/01661
G&asiov, G.Y. and Ter-Oganesyan, G.K. Fir. Goreniya Vzryva, 2001, 37, (3), 70-75. (In Russian) Kinetic parameters of high temperature pyrolysis of oil shale were detected. A simple mathematical model of process dynamics of thermal destruction of solid fuel was developed. A design example of drum-type pyrolysis reactor was given.
10
ENGINES Power generation and propulsion, electrical vehicles
02/01662 An experimental study on the effect of pressure and stmin rate on CH chemiiuminescence of premixed fueilean methanelair flames Higgins, B. er a/. Fuel, 2001, 80, (1 I), 1583-1591. This article reports systematic measurements of CH chemiiuminescene from a premixed, iaminar flame and a premixed, strained, counter-flow flame at ambient pressures ranging from 0.5 to 2.5 MPa and equivalence from 0.66 to 0.86. The objective of this study was to investigate the possibility of using chemiiuminescence as an active feedback control parameter to deduce the equivalence ratio, and therefore NO, production and combustion stability, for premixed flames at high pressure. The chemiluminescence signal from the first electronically excited state of CH to ground (at 431.5 nm) was detected through a band-pass, optical filter in combination with a photomultiplier tube. CH chemiluminescence at high pressure was found to have a power law dependence with equivalence ratio and pressure, and was proportional to mass flowrate. Using the premixed counter-flow flame, strain was shown not to influence chemiiuminescence. Further, a comparison of these findings with previous results of OH chemilumiFuel and Energy Abstracts
May 2662
209