- Email: [email protected]
00318 Numerical investigation of oxy-coal combustion to evaluate burner and combustor design concepts
09 Combustion (bumers, combustion systems) CO in the stack gas was 8 mg/MJ, the average concentration of NOx was 59 mg/MJ and the average total hydrocarbon concentration was below 1 ppm, at an average O2-concentration of 4.6%. The low contents of potassium and sodium in the hydrolysis residue make the material attractive as a gas turbine fuel and the conclusion of this test is that direct combustion may be a feasible approach for gas turbine applications.
05100313 Combustion optimization of biomass residue pellets for domestic heating with a mural boiler Gonz~ilez, J. F. J. et al. Biomass and Bioenergy, 2004, 27, (2), 145-154. The purpose of this study was to optimize the combustion process of different residues in a 11.6 kW mural boiler for domestic heating. The fuels used were pellets from three biomass residues (tomato, olive stone and cardoon (Cynara cardunculus L.)) and the forest pellet recommended by the boiler manufacturer. Previously, the fuels were characterized by means of the higher heating value, proximate and ultimate analyses. The influence of the residue type, fuel mass flow, draught and residue mixture on the combustion parameters was studied. A TESTO 300 M-I analyser was used to determine the principal parameters of the combustion process (CO2, CO and 02 contents, fumes temperature, not-burnt gaseous and sensitive heat losses in the fumes, volumetric flow rate and velocity of the fumes, air excess coefficient, efficiency). The behaviour of the three residues is similar to that of the forest pellet. The boiler efficiencies obtained with the maximum fuel mass flow (100%) and minimum draught (0%) were 90%, 90.5%, 89.7% and 9t.6% for tomato, forest, olive stone and cardoon pellets, respectively. The optimum residue mixture was tomato (75%) and forest (25%) with a boiler efficiency of 92.4% for a mass flow and draught of 75% and 0%, respectively.
05100314 Comparative study of flame structures and NOx emission characteristics in fuel injection recirculation and fuel gas recirculation combustion system Park, J. et al. International Journal of Energy Research, 2004, 28, (10), 861-885. A numerical study with momentum-balanced boundary conditions has been conducted to grasp the chemical effects of added CO2 to fuel- and oxidizer-sides on flame structure and NO emission behaviour in H2-O2 diffusion flames with varying flame location. A reaction mechanism is proposed to show better agreements with experimental results in CO2added hydrogen flames. Oxidizer-side dilution results in significantly higher flame temperatures and NO emission. Flame location is dramatically changed due to high diffusivity of hydrogen according to variation of the composition of fuel- and oxidizer-sides. This affects flame structure and NO emission considerably especially the chemical effects of added CO2. The present work also displays separately thermal contribution and prompt NO emission due to the chemical effects caused by thermal dissociation of added CO2 in NO emission behaviour. It is found that flame temperature and the flame location affect the contribution of thermal and prompt NO due to chemical effects considerably in NO emission behaviour.
05/00315 Improved solid fuels from co-pyrolysis of a highsulphur content coal and different lignocellulosic wastes Cordero, T. et al. Fuel, 2004, 83, (11-12), 1585-1590. Co-pyrolysis of blends of a high-sulphur coal with different biomass wastes has been investigated as a way to obtain improved solid fuels. Experiments have been performed in a thermogravimetric laboratory system and in a pilot-scale mobile bed furnace, this last operating at 600°C. The presence of biomass enhances coal desulphurization upon thermal treatment in significant relative amounts, giving rise about as much as twice percent sulphur loss at high biomass-to-coal ratios in the starting blend in comparison with the S loss occurring upon pyrolysis of coal alone. Combustion experiments with chars resulting from copyrolysis of these coal-biomass blends confirm this significantly improved desulphurization. Thus, co-pyrolysis of blends of highsulphur coals with biomass wastes provides a potential way to obtain improved solid fuels combining good heating values with environmentally acceptable S contents. The chars resulting from co-pyrolysis show heating values within the range of high-quality solid fuels whereas the ash contents remain in the vicinity of that of the starting coal except in the case of the coal-straw blend where the relatively high ash content of this biomass waste leads to co-pyrolysis chars with substantially higher ash contents and lower heating values.
05/00316 Mesoscale combustion: a first step towards liquid fueled batteries Kyritsis, D. C. et al. Experimental Thermal and Fluid Science, 2004, 28, (7), 763-770. The development of a liquid-fuelled mesoscale catalytic combustor is presented, based on the coupling of multiplexed electrosprays for liquid fuel dispersion and a stack of catalytic grids. The grids act as a compact catalytic reactor for combustion initiation, stabilization and enhanced conversion, as well as ground electrodes for the electrospray.
The combustor has a volume on the order of few cm 3 and operates on various fuels, including JP8 jet fuel, which is electrosprayed at a flow rate on the order of 10 g/h and equivalence ratios varying from 0.35 to 0.70. Temperatures in the range 900-1300 K are achieved with a +5% uniformity over the top circular surface of the burner. Using gas chromatographic analysis of the exhaust gases, a combustion efficiency in excess of 97% is estimated. This estimate was confirmed by exhaust gas composition measurements by photoionization mass spectrometry for operation with dodecane, the most abundant component of JP8. These measurements showed that alkenes and aldehydes are the major hydrocarbon products and that there is no significant molecular growth chemistry. The capability of the system to burn cleanly and efficiently even notoriously polluting fuels was demonstrated.
05/00317
Mild combustion
Cavaliere, A. and de Joannon, M. Progress in Energy and Combustion Science, 2004, 30, (3), 329 366. Mild combustion is characterized by both an elevated temperature of reactants and a low temperature increase in the combustion process. These features are the results of several technological demands coming from different application fields. This review paper aims to collect information that could be useful in understanding the fundamentals and applications of mild combustion. The information in this field are still sparse, because of the recent identification of the process, so that many speculative considerations have been presented in order to make the whole framework more consistent and rich with potential new applications. A rigorous definition of mild combustion is preliminarily given in order to fix the input variables of the process. Under these constraints the influence of the physical, thermodynamic and chemical variables on the most relevant outlet parameters are analysed. The physical aspects taken into account are atomization, evaporation, mixing and radiative heat transfer. In particular, the evolution of the mixing layer for high temperature diluted oxidant is analysed. It is shown that mass fluxes through the stoichiometric isosurfaces are lower than those in not diluted conditions and that the annihilation of these isosurfaces is enhanced in the mild combustion conditions. Both effects infer low rates of heat release according to the experimental results reported in the literature. The thermodynamic aspects are dealt through .the comparative analysis of the minimum, maximum and equilibrium temperature profiles versus the mixture fraction in the whole allowable range for the diluted and not-diluted cases. The chemical aspects have been analysed in relation to the chemical kinetics rates for different oxidative routes and the temporal evolution of the self-ignition process. The molecular oxygen addition, the hydroperoxide dissociation and atomic hydrogen oxidation are evaluated in wide pressure and temperature ranges. In such a way self-ignition regimes that rely on different preferential chemical kinetics routes are identified and comparison between diluted/not diluted conditions are performed for a fixed evolution time. In this case it is shown that mild combustion conditions extend the pressure temperature range, in which the oxidation is depressed, at relatively low pressure, whereas the 'ceiling temperature' is shifted to lower temperature for mild combustion condition at higher pressure. The second part of the review shows the potentialities of the diluted high temperature air combustion in applications related both to efficiency and pollution of thermal generation as well as to abatement of the pollutants along the flue gas stream of a primary combustion system. Some selected examples in these fields as land-base gas-turbines, boiler combustion chamber and domestic heating systems are presented. In these, the emphasis, is put preliminarily on aspects related more to efficiency than to pollution reduction, even though this target is implicitly taken into consideration. Then environmental benefits are dealt in relation to the major and minor species, either organic or inorganic, which can be produced in gas/liquid combustion. They include carbonaceous material, unburned hydrocarbons, nitrogen oxides and sulphur oxides. Finally, a classification of the possible processes relevant along the whole fuel transformation in mild combustion is given. In particular 'clean', 'cleaning', 'clearing' combustion processes are identified as a convenient categorization in relation to the incorporation of pre-combustion or post-combustion units in the main combustion systems.
05•00318 Numerical investigation of oxy-coal combustion to evaluate burner and combustor design concepts Chui, E. H. et al. Energy, 2004, 29, (9-10), 1285 1296. Significant progress has been made in both experimental investigations and numerical modelling of oxy-fuel combustion for CO2 capture purposes at the CANMET Vertical Combustor Research Facility. Detailed in-flame measurements have revealed insights into flow field development and pollutant formation characteristics over a wide range of operating conditions using natural gas and coals. A numerical modelling capability has also been developed in parallel and validated by in-flame data. This study marks the first use by CANMET of this numerical modelling expertise to develop design ideas before expensive and time-consuming experimental work is done. Its focus is on evaluating burner and combustor design concepts for oxy-coal
Fuel and Energy Abstracts
January 2005
43
10 Engines (power generation and propulsion, electrical vehicles) combustion when air is substituted with oxygen in the recycled flue gas mode. Model results indicate that a new burner design approach can potentially reduce NOx at furnace exit by over 70% with respect to the existing design, while providing significant improvements in overall flame characteristics. Also, the numerical study produces quantitative evidence in support of enlarging the present combustor to an inner diameter of 1 m in order to minimize wall effects, which become important when trying to expand the flame volume so as to improve oxygen management within the flame. The first set of experimental results collected from the new burner~ombustor combination validates the predicted improvements in NOx reduction and combustion performance.
05•00319 N20 and NO emissions from co-firing MSW with coals in pilot scale CFBC Li, Z. et al. Fuel Processing Technology, 2004, 85, (14), 1539 1549. Co-firing municipal solid waste (MSW) with bituminous coal and anthracite was conducted using pilot scale circulating fluidized-bed combustion. Both N20 and NO emissions from co-firing MSW with bituminous coal are higher than those obtained from co-firing with anthracite. N20 decreases significantly, whereas NO rises with the increase of Ca/(S+0.5C1) molar ratios. Increasing the co-firing rates leads to the reduction of N20 emission, but an increase of NO emission. Raising furnace temperature is an effective way to control N20 emission, but NO emission is scarcely affected.
05/00320 Optimization of hydrogen production by filtration combustion of methane by oxygen enrichment and depletion Bingue, J. P. et al. International Journal eft'Hydrogen Energy, 2004, 29, (13), 1365-1370. Transient filtration combustion waves formed in a porous matrix of randomly arranged alumina pellets are studied experimentally for rich and ultra-rich methane/air waves with oxygen enrichment and depletion. A single filtration velocity (12 cm/s) was used and the mixture equivalence ratio was varied from 1 to 3.5. The air and oxidizer content were adjusted to retain the filtration velocity constant for each equivalence ratio. Six oxidizer compositions (10%, 15%, 21%, 25%, 30%, and 35% Oz) were comparatively analysed focusing on combustion temperatures, combustion wave velocities, major and minor products of combustion. The studied range of equivalence ratios covered the underadiabatic (upstream) and superadiabatic (downstream) regimes of transient filtration waves where combustion temperatures are less than and greater than adiabatic temperatures, respectively.
05/00321 Pyrolysis and combustion of PVC, PVC-wood and PVC-coal mixtures in a two-stage fluidized bed process Saeed, L. et al. Fuel Processing Technology, 2004, 85, (14), 1565-1583. Several tests using pure bottle-grade polyvinyl chlorine (PVC), with wood (pine) and with Polish coal have been performed in a two-stage combustion test facility which contains two reactors. The first reactor is a bubbling fluidized bed (BFB) where the fuel is pyrolysed in the temperature range 200-400°C. The second reactor is a circulating fluidized bed (CFB) operated at a temperature of around 800°C. The pyrolysed gases from the BFB reactor or the circulating fluidized bed combustor (CFBC) are analysed with a Fourier transform infrared (FT-IR) spectrometer. The main part of this work concentrates on the first stage of decomposition of PVC in the first reactor, which mainly yields volatiles (mainly HC1) and solid residue. The results show that there is an interaction in PVC/wood pine mixtures, which affects the degradation of PVC. The same interaction also occurred with the PVC/ Polish coal mixture. For the two-stage combustion test, the chemical analysis of char samples taken from the bed of the first reactor, when 100% PVC is used, shows that the chlorine content is below 0.1 wt% at chlorine to carbon mass ratio <0.001 kg Cl/kg C.
05/00322 Pyrolysis of a Victorian brown coal and gasification of nascent char in CO2 atmosphere in a wiremesh reactor Jamil, K. et al. Fuel, 2004, 83, (7-8), 833-843. Temperature-programmed pyrolysis of a Victorian brown coal was performed under flow of atmospheric He or CO2 in a wire-mesh reactor, in which extent of the secondary reactions of volatiles was minimized. Over the ranges of heating rate, holding temperature and holding time of 0.5-1000°C s a, 500_900oc, and 0-120 s, respectively, changing the atmosphere from He to CO2 influenced neither the yield nor composition of tar. Even under heating at 1000°C s -1, the tar evolution was completed before temperature reached 600°C. Below this temperature, CO2 behaved as an inert gas in the pore systems of pyrolysing particles. After completion of the tar evolution (above 600°C), CO2 participated in the formation of light gases from the nascent char. Initial CO2 gasification of the nascent char occurred at a considerably high rate simultaneously with its thermal cracking. The char yield decreased by 11 wt%-daf in the course of heating the char in CO2 from 700 to 900°C at 1000°C s -1. It was estimated that about a
44
Fuel and Energy Abstracts January 2005
half of the decrease was caused by the C O 2 gasification at an average rate over 20 wt%-daf-coal s -1. Rate of such rapid CO2 gasification seemed to strongly depend on the rate of thermal cracking, i.e. concentration of radicals formed by the thermal cracking. This hypothesis was consistent with the observed heating rate effects on the rates of the thermal cracking and CO2 gasification of the char.
05/00323 Reference components of jet fuels: kinetic modeling and experimental results Agosta, A. et al. Experimental Thermal and Fluid Science, 2004, 28, (7), 701-708. The goal of this work is to give some kinetic insight on the autoignition and combustion behaviour of full boiling range hydrocarbon fuels. The initial attention is devoted to the selection of possible components of a surrogate that reproduces the reaction behaviour of typical real fuels. n-Oodecane and iso-cetane are the reference components for the different alkane classes, while methylcyclohexane and decalin represented naphthenes and alphamethylnaphthalene represented aromatics. Several oxidation results have been obtained in a pressurized flow reactor both for neat components and selected mixtures. The reactivity maps of the different experiments are reported in terms of CO production. The experimental results clearly confirm that autoignition properties of the mixture cannot be simply reproduced by linear blending rules. Semi-detailed or lumped kinetic models for the oxidation and combustion of pure components are briefly discussed and model predictions are compared with the overall set of experimental measurements. The general agreement with the experimental data, including the mixtures, indicates the viability and interest of the proposed approach.
05/00324 The combustion of oil sand beds containing an axial fracture Mehta, S. and Karim, G. A. International Journal oj~ Global Energy Issues, 2003, 20, (3), 277 289. The processes within simplified laboratory cylindrical beds of specially reconstituted oil sand during oil recovery are described. The beds contained a small diameter cylindrical axial passage of high permeability representing a fracture where hot vitiated air of known composition was fed steadily. The fuel sand cores tested contained either pure hydrocarbon or extracted oil off naturally occurring oil sands. It was shown that combustion appeared to have been sustained mainly by the oxidation of the light fuel fractions rather than by the coke deposits produced by the cracking reactions. Most of the burning took place, for the conditions examined, within the fracture rather than the main granular bed.
05/00325 The influence of elevated pressure on the kinetics of evolution of selected gaseous products during coal pyrolysis Porada, S. Fuel, 2004, 83, (7 8), 1071 1078. The paper discusses the influence of the pressure of pyrolysis on the formation kinetics of C1-C3 hydrocarbons, hydrogen, CO and CO2 during pyrolysis of three selected coals of different rank. The examinations were carried out within the pressure range of 0.1-10 MPa under the conditions of constant residence time of primary products in the reaction zone. It was found that the pressure of pyrolysis exerts a significant influence on the formation rate of CH4, H2, CO and CO2. Also, the formal kinetic parameters of formation reactions of major gaseous products during pressure pyrolysis of the examined coals were calculated.
10
ENGINES Power generation and propulsion, electrical vehicles
05/00326
A new parallel-type hybrid electric-vehicle
Huang, K. D. and Tzeng, S.-C. Applied Energy, 2004, 79, (1), 51 64. This new system promises an internal-combustion engine that always maintains optimal operating conditions. The system comprises two parts: (1) an internal-combustion power-distribution device and (2) an integrated design involving the engine and electronic motor. The internal-combustion power-distribution device provides an engine capable of constantly operating in an optimal fashion, minimizing emissions and maximizing thermal-efficiency. The electric motor can generate extra power. Notably, the integrated torque design comprises
05100313 Combustion optimization of biomass residue pellets for domestic heating with a mural boiler Gonz~ilez, J. F. J. et al. Biomass and Bioenergy, 2004, 27, (2), 145-154. The purpose of this study was to optimize the combustion process of different residues in a 11.6 kW mural boiler for domestic heating. The fuels used were pellets from three biomass residues (tomato, olive stone and cardoon (Cynara cardunculus L.)) and the forest pellet recommended by the boiler manufacturer. Previously, the fuels were characterized by means of the higher heating value, proximate and ultimate analyses. The influence of the residue type, fuel mass flow, draught and residue mixture on the combustion parameters was studied. A TESTO 300 M-I analyser was used to determine the principal parameters of the combustion process (CO2, CO and 02 contents, fumes temperature, not-burnt gaseous and sensitive heat losses in the fumes, volumetric flow rate and velocity of the fumes, air excess coefficient, efficiency). The behaviour of the three residues is similar to that of the forest pellet. The boiler efficiencies obtained with the maximum fuel mass flow (100%) and minimum draught (0%) were 90%, 90.5%, 89.7% and 9t.6% for tomato, forest, olive stone and cardoon pellets, respectively. The optimum residue mixture was tomato (75%) and forest (25%) with a boiler efficiency of 92.4% for a mass flow and draught of 75% and 0%, respectively.
05100314 Comparative study of flame structures and NOx emission characteristics in fuel injection recirculation and fuel gas recirculation combustion system Park, J. et al. International Journal of Energy Research, 2004, 28, (10), 861-885. A numerical study with momentum-balanced boundary conditions has been conducted to grasp the chemical effects of added CO2 to fuel- and oxidizer-sides on flame structure and NO emission behaviour in H2-O2 diffusion flames with varying flame location. A reaction mechanism is proposed to show better agreements with experimental results in CO2added hydrogen flames. Oxidizer-side dilution results in significantly higher flame temperatures and NO emission. Flame location is dramatically changed due to high diffusivity of hydrogen according to variation of the composition of fuel- and oxidizer-sides. This affects flame structure and NO emission considerably especially the chemical effects of added CO2. The present work also displays separately thermal contribution and prompt NO emission due to the chemical effects caused by thermal dissociation of added CO2 in NO emission behaviour. It is found that flame temperature and the flame location affect the contribution of thermal and prompt NO due to chemical effects considerably in NO emission behaviour.
05/00315 Improved solid fuels from co-pyrolysis of a highsulphur content coal and different lignocellulosic wastes Cordero, T. et al. Fuel, 2004, 83, (11-12), 1585-1590. Co-pyrolysis of blends of a high-sulphur coal with different biomass wastes has been investigated as a way to obtain improved solid fuels. Experiments have been performed in a thermogravimetric laboratory system and in a pilot-scale mobile bed furnace, this last operating at 600°C. The presence of biomass enhances coal desulphurization upon thermal treatment in significant relative amounts, giving rise about as much as twice percent sulphur loss at high biomass-to-coal ratios in the starting blend in comparison with the S loss occurring upon pyrolysis of coal alone. Combustion experiments with chars resulting from copyrolysis of these coal-biomass blends confirm this significantly improved desulphurization. Thus, co-pyrolysis of blends of highsulphur coals with biomass wastes provides a potential way to obtain improved solid fuels combining good heating values with environmentally acceptable S contents. The chars resulting from co-pyrolysis show heating values within the range of high-quality solid fuels whereas the ash contents remain in the vicinity of that of the starting coal except in the case of the coal-straw blend where the relatively high ash content of this biomass waste leads to co-pyrolysis chars with substantially higher ash contents and lower heating values.
05/00316 Mesoscale combustion: a first step towards liquid fueled batteries Kyritsis, D. C. et al. Experimental Thermal and Fluid Science, 2004, 28, (7), 763-770. The development of a liquid-fuelled mesoscale catalytic combustor is presented, based on the coupling of multiplexed electrosprays for liquid fuel dispersion and a stack of catalytic grids. The grids act as a compact catalytic reactor for combustion initiation, stabilization and enhanced conversion, as well as ground electrodes for the electrospray.
The combustor has a volume on the order of few cm 3 and operates on various fuels, including JP8 jet fuel, which is electrosprayed at a flow rate on the order of 10 g/h and equivalence ratios varying from 0.35 to 0.70. Temperatures in the range 900-1300 K are achieved with a +5% uniformity over the top circular surface of the burner. Using gas chromatographic analysis of the exhaust gases, a combustion efficiency in excess of 97% is estimated. This estimate was confirmed by exhaust gas composition measurements by photoionization mass spectrometry for operation with dodecane, the most abundant component of JP8. These measurements showed that alkenes and aldehydes are the major hydrocarbon products and that there is no significant molecular growth chemistry. The capability of the system to burn cleanly and efficiently even notoriously polluting fuels was demonstrated.
05/00317
Mild combustion
Cavaliere, A. and de Joannon, M. Progress in Energy and Combustion Science, 2004, 30, (3), 329 366. Mild combustion is characterized by both an elevated temperature of reactants and a low temperature increase in the combustion process. These features are the results of several technological demands coming from different application fields. This review paper aims to collect information that could be useful in understanding the fundamentals and applications of mild combustion. The information in this field are still sparse, because of the recent identification of the process, so that many speculative considerations have been presented in order to make the whole framework more consistent and rich with potential new applications. A rigorous definition of mild combustion is preliminarily given in order to fix the input variables of the process. Under these constraints the influence of the physical, thermodynamic and chemical variables on the most relevant outlet parameters are analysed. The physical aspects taken into account are atomization, evaporation, mixing and radiative heat transfer. In particular, the evolution of the mixing layer for high temperature diluted oxidant is analysed. It is shown that mass fluxes through the stoichiometric isosurfaces are lower than those in not diluted conditions and that the annihilation of these isosurfaces is enhanced in the mild combustion conditions. Both effects infer low rates of heat release according to the experimental results reported in the literature. The thermodynamic aspects are dealt through .the comparative analysis of the minimum, maximum and equilibrium temperature profiles versus the mixture fraction in the whole allowable range for the diluted and not-diluted cases. The chemical aspects have been analysed in relation to the chemical kinetics rates for different oxidative routes and the temporal evolution of the self-ignition process. The molecular oxygen addition, the hydroperoxide dissociation and atomic hydrogen oxidation are evaluated in wide pressure and temperature ranges. In such a way self-ignition regimes that rely on different preferential chemical kinetics routes are identified and comparison between diluted/not diluted conditions are performed for a fixed evolution time. In this case it is shown that mild combustion conditions extend the pressure temperature range, in which the oxidation is depressed, at relatively low pressure, whereas the 'ceiling temperature' is shifted to lower temperature for mild combustion condition at higher pressure. The second part of the review shows the potentialities of the diluted high temperature air combustion in applications related both to efficiency and pollution of thermal generation as well as to abatement of the pollutants along the flue gas stream of a primary combustion system. Some selected examples in these fields as land-base gas-turbines, boiler combustion chamber and domestic heating systems are presented. In these, the emphasis, is put preliminarily on aspects related more to efficiency than to pollution reduction, even though this target is implicitly taken into consideration. Then environmental benefits are dealt in relation to the major and minor species, either organic or inorganic, which can be produced in gas/liquid combustion. They include carbonaceous material, unburned hydrocarbons, nitrogen oxides and sulphur oxides. Finally, a classification of the possible processes relevant along the whole fuel transformation in mild combustion is given. In particular 'clean', 'cleaning', 'clearing' combustion processes are identified as a convenient categorization in relation to the incorporation of pre-combustion or post-combustion units in the main combustion systems.
05•00318 Numerical investigation of oxy-coal combustion to evaluate burner and combustor design concepts Chui, E. H. et al. Energy, 2004, 29, (9-10), 1285 1296. Significant progress has been made in both experimental investigations and numerical modelling of oxy-fuel combustion for CO2 capture purposes at the CANMET Vertical Combustor Research Facility. Detailed in-flame measurements have revealed insights into flow field development and pollutant formation characteristics over a wide range of operating conditions using natural gas and coals. A numerical modelling capability has also been developed in parallel and validated by in-flame data. This study marks the first use by CANMET of this numerical modelling expertise to develop design ideas before expensive and time-consuming experimental work is done. Its focus is on evaluating burner and combustor design concepts for oxy-coal
Fuel and Energy Abstracts
January 2005
43
10 Engines (power generation and propulsion, electrical vehicles) combustion when air is substituted with oxygen in the recycled flue gas mode. Model results indicate that a new burner design approach can potentially reduce NOx at furnace exit by over 70% with respect to the existing design, while providing significant improvements in overall flame characteristics. Also, the numerical study produces quantitative evidence in support of enlarging the present combustor to an inner diameter of 1 m in order to minimize wall effects, which become important when trying to expand the flame volume so as to improve oxygen management within the flame. The first set of experimental results collected from the new burner~ombustor combination validates the predicted improvements in NOx reduction and combustion performance.
05•00319 N20 and NO emissions from co-firing MSW with coals in pilot scale CFBC Li, Z. et al. Fuel Processing Technology, 2004, 85, (14), 1539 1549. Co-firing municipal solid waste (MSW) with bituminous coal and anthracite was conducted using pilot scale circulating fluidized-bed combustion. Both N20 and NO emissions from co-firing MSW with bituminous coal are higher than those obtained from co-firing with anthracite. N20 decreases significantly, whereas NO rises with the increase of Ca/(S+0.5C1) molar ratios. Increasing the co-firing rates leads to the reduction of N20 emission, but an increase of NO emission. Raising furnace temperature is an effective way to control N20 emission, but NO emission is scarcely affected.
05/00320 Optimization of hydrogen production by filtration combustion of methane by oxygen enrichment and depletion Bingue, J. P. et al. International Journal eft'Hydrogen Energy, 2004, 29, (13), 1365-1370. Transient filtration combustion waves formed in a porous matrix of randomly arranged alumina pellets are studied experimentally for rich and ultra-rich methane/air waves with oxygen enrichment and depletion. A single filtration velocity (12 cm/s) was used and the mixture equivalence ratio was varied from 1 to 3.5. The air and oxidizer content were adjusted to retain the filtration velocity constant for each equivalence ratio. Six oxidizer compositions (10%, 15%, 21%, 25%, 30%, and 35% Oz) were comparatively analysed focusing on combustion temperatures, combustion wave velocities, major and minor products of combustion. The studied range of equivalence ratios covered the underadiabatic (upstream) and superadiabatic (downstream) regimes of transient filtration waves where combustion temperatures are less than and greater than adiabatic temperatures, respectively.
05/00321 Pyrolysis and combustion of PVC, PVC-wood and PVC-coal mixtures in a two-stage fluidized bed process Saeed, L. et al. Fuel Processing Technology, 2004, 85, (14), 1565-1583. Several tests using pure bottle-grade polyvinyl chlorine (PVC), with wood (pine) and with Polish coal have been performed in a two-stage combustion test facility which contains two reactors. The first reactor is a bubbling fluidized bed (BFB) where the fuel is pyrolysed in the temperature range 200-400°C. The second reactor is a circulating fluidized bed (CFB) operated at a temperature of around 800°C. The pyrolysed gases from the BFB reactor or the circulating fluidized bed combustor (CFBC) are analysed with a Fourier transform infrared (FT-IR) spectrometer. The main part of this work concentrates on the first stage of decomposition of PVC in the first reactor, which mainly yields volatiles (mainly HC1) and solid residue. The results show that there is an interaction in PVC/wood pine mixtures, which affects the degradation of PVC. The same interaction also occurred with the PVC/ Polish coal mixture. For the two-stage combustion test, the chemical analysis of char samples taken from the bed of the first reactor, when 100% PVC is used, shows that the chlorine content is below 0.1 wt% at chlorine to carbon mass ratio <0.001 kg Cl/kg C.
05/00322 Pyrolysis of a Victorian brown coal and gasification of nascent char in CO2 atmosphere in a wiremesh reactor Jamil, K. et al. Fuel, 2004, 83, (7-8), 833-843. Temperature-programmed pyrolysis of a Victorian brown coal was performed under flow of atmospheric He or CO2 in a wire-mesh reactor, in which extent of the secondary reactions of volatiles was minimized. Over the ranges of heating rate, holding temperature and holding time of 0.5-1000°C s a, 500_900oc, and 0-120 s, respectively, changing the atmosphere from He to CO2 influenced neither the yield nor composition of tar. Even under heating at 1000°C s -1, the tar evolution was completed before temperature reached 600°C. Below this temperature, CO2 behaved as an inert gas in the pore systems of pyrolysing particles. After completion of the tar evolution (above 600°C), CO2 participated in the formation of light gases from the nascent char. Initial CO2 gasification of the nascent char occurred at a considerably high rate simultaneously with its thermal cracking. The char yield decreased by 11 wt%-daf in the course of heating the char in CO2 from 700 to 900°C at 1000°C s -1. It was estimated that about a
44
Fuel and Energy Abstracts January 2005
half of the decrease was caused by the C O 2 gasification at an average rate over 20 wt%-daf-coal s -1. Rate of such rapid CO2 gasification seemed to strongly depend on the rate of thermal cracking, i.e. concentration of radicals formed by the thermal cracking. This hypothesis was consistent with the observed heating rate effects on the rates of the thermal cracking and CO2 gasification of the char.
05/00323 Reference components of jet fuels: kinetic modeling and experimental results Agosta, A. et al. Experimental Thermal and Fluid Science, 2004, 28, (7), 701-708. The goal of this work is to give some kinetic insight on the autoignition and combustion behaviour of full boiling range hydrocarbon fuels. The initial attention is devoted to the selection of possible components of a surrogate that reproduces the reaction behaviour of typical real fuels. n-Oodecane and iso-cetane are the reference components for the different alkane classes, while methylcyclohexane and decalin represented naphthenes and alphamethylnaphthalene represented aromatics. Several oxidation results have been obtained in a pressurized flow reactor both for neat components and selected mixtures. The reactivity maps of the different experiments are reported in terms of CO production. The experimental results clearly confirm that autoignition properties of the mixture cannot be simply reproduced by linear blending rules. Semi-detailed or lumped kinetic models for the oxidation and combustion of pure components are briefly discussed and model predictions are compared with the overall set of experimental measurements. The general agreement with the experimental data, including the mixtures, indicates the viability and interest of the proposed approach.
05/00324 The combustion of oil sand beds containing an axial fracture Mehta, S. and Karim, G. A. International Journal oj~ Global Energy Issues, 2003, 20, (3), 277 289. The processes within simplified laboratory cylindrical beds of specially reconstituted oil sand during oil recovery are described. The beds contained a small diameter cylindrical axial passage of high permeability representing a fracture where hot vitiated air of known composition was fed steadily. The fuel sand cores tested contained either pure hydrocarbon or extracted oil off naturally occurring oil sands. It was shown that combustion appeared to have been sustained mainly by the oxidation of the light fuel fractions rather than by the coke deposits produced by the cracking reactions. Most of the burning took place, for the conditions examined, within the fracture rather than the main granular bed.
05/00325 The influence of elevated pressure on the kinetics of evolution of selected gaseous products during coal pyrolysis Porada, S. Fuel, 2004, 83, (7 8), 1071 1078. The paper discusses the influence of the pressure of pyrolysis on the formation kinetics of C1-C3 hydrocarbons, hydrogen, CO and CO2 during pyrolysis of three selected coals of different rank. The examinations were carried out within the pressure range of 0.1-10 MPa under the conditions of constant residence time of primary products in the reaction zone. It was found that the pressure of pyrolysis exerts a significant influence on the formation rate of CH4, H2, CO and CO2. Also, the formal kinetic parameters of formation reactions of major gaseous products during pressure pyrolysis of the examined coals were calculated.
10
ENGINES Power generation and propulsion, electrical vehicles
05/00326
A new parallel-type hybrid electric-vehicle
Huang, K. D. and Tzeng, S.-C. Applied Energy, 2004, 79, (1), 51 64. This new system promises an internal-combustion engine that always maintains optimal operating conditions. The system comprises two parts: (1) an internal-combustion power-distribution device and (2) an integrated design involving the engine and electronic motor. The internal-combustion power-distribution device provides an engine capable of constantly operating in an optimal fashion, minimizing emissions and maximizing thermal-efficiency. The electric motor can generate extra power. Notably, the integrated torque design comprises