96lQO703 The lnterpla of transport, kinetics, and thermal interactions In the stab1-Yity of premixed hydrogen/air flames near surfaces Vlachos, D. G. Combusrion & Flame, Oct. 1995, 103, (I), 59-75. The stability of premixed hydrogen/air flames near surfaces is studied using numerical bifurcation theory and detailed kinetics. Two-parameter continuation diagrams are constructed to determine the effects of inlet composition and pressure in flame stability. Sensitivity analysis is used to elucidate the roles of transport mechanisms, chemical heat, and chainbranching in ignition and extinction. The author has found that flame instabilities can be caused by chemical autocatalysis (kinetic runaway) or thermal autocatalysis (thermal runaway) when three multiple solutions coexist, and by both mechanisms when five multiple solutions coexist. Low pressures favour the kinetic feedback mechanism and high pressures the thermal one. 96100704 Laboratorv studv of the corrosion behavlour of alloys exposed In a nbnequlilbrated coal gaslflcatlon atmosphere at 600” Norton, J. F. and Levi, T. P. Mafer. Corros., 1995, 46, (5), 286-296. Discusses the corrosion behaviour of three candidate heat exchanger alloys (HR 3C, MA 956, HR 160) exposed at 600” to a non-equilibrated reducing atmosphere containing 64% CO and 0.2% H S. The kinetics and mechanisms of corrosive degradation are describe d for test durations of up to 2000 hours. Significant differences in the corrosion rate and in the depths of metal loss were observed. 96iOO705 Lar e Ilgnlte-flred steam generators wlth clrculatIng fluldlred-be 8 combustion. lnltlal operatlng experience from the 400 metric tons/h Goldenberg power plant of the RWE Energle AG (Germany) Wohlsein, J. et al., VGB Kraffwerksrech., 1995, 75, (31, 215-219. (In German) The paper describes the plant concept of a 400 tons/h lignite-fired steam generator (Goldenberg, Germany) with circulating fluidized-bed furnace, including concept improvements because of initial operating problems such as discharge of ashes from the furnace, wear of evaporator coils, and wear of the flue dust cyclone system. Lateral mlxlng of coarse particles In fluldlzed beds 96lQO706 of flne particles Bi, J. et al., Chem. Eng. Res. Des., 1995, 73, (2), 162-167. A study was made of the lateral mixing of coarse particles in three rectangular fluidized beds, connected respectively with fine particle circulating bed crossflowing the rectangular beds. Residence time distribution and dispersion coefficients of the coarse particles along the lateral direction was experimentally investigated. 96lOQ707 Low NO, burner and burner management system controls retrofit at Pennsylvanla Electric Company’s Shawvllle Statlon Unlts 3 and 4 Dirkse, R. D. et al., Proc. Am. Power Conf, 1995, 57, (l), 247-251. Discusses the implementation of the new controls in a power plant with pulverized coal as the primary fuel. 96/00708 Low-NO, burners and coflrlng coal water slurry at Pennsvlvanla Electric’s Seward Station Melick,*T. et al., Proc. Am. Power Conf, 1995, 57, (2), 1601-1606. Describes the installation by Pennsylvania Electric Company of new lowNO, burners and a coal water slurry firing system, designed and supplied by EER Corooration. on Boiler 14 at the Seward eeneratine station. Pkesents data -summarizing the combustion and emissioi control-performance of the new burners firing pulverized coal and coal-water slurry over a range of boiler operating conditions. 96lOO709 Low-temperature oxldatlon and spontaneous combustlon of coal Li, W. and Li, B. Meitan Zhuanhua, 1995, 18, (l), 10-18. (In Chinese) Discusses the low-temperature oxidation of coal associated with spontaneous combustion. Mathematical modellng of combustion of pulver96/00710 lzed coal In steam boiler furnaces Bebenchikov, A. M. er al., Fiz. Goreniya Vzryva, 1995,31, (2), 23-31. (In Russian) Describes a model which has been developed of pulverized coal combustion in a boiler, and it is used to calculate aerodynamics, combustion, and heat transfer in coal-fired boilers. Means of preventlon of nltrogen oxide emlsslons 96lQO711 by technological methods of combustion of solld fuels Yoworskii, I. A. Teploenergetika (Moscow), 1995, (2), 17-23. (In Russian) The paper discusses the formation of NO, formation in coal combustion, including conversion of coal N to N7 and NO,. Also discussed is the catalytic action of CaO and NO reduction on char particle surface.
Fuel and Energy Abstracts
96100712 Measuring the lamlnar burning velocity of methane/diluent/alr mlxtures within a constant-volume combustion bomb In a micro-gravity environment Clarke, A. er al., J. Inst. of Energy, Sep. 1995, 68, (476), 130-136. The laminar burning velocity of methane and air has been determined for a range of equivalence ratios, with various levels of carbon dioxide and nitrogen as diluents. Carbon dioxide and nitrogen are both present in natural gas, and in biogas there can be as much as 40% carbon dioxide. Furthermore, mixtures of carbon dioxide and nitrogen can be used to simulate the products of combustion, thus enabling measurements of the burning velocity to be made that correspond to conditions of exhaust-gas recirculation. The data presented in this paper covers higher levels of diluents than previously reported, with up to 60% of either nitrogen or carbon dioxide as part of the fuel. Because of the effects of buoyancy during the combustion process within a constant-volume bomb, the centre of the flame kernai rises, the flame-front deviates from that of an ideal sphere at low values of burning velocity.
96100713 Methodology for the selectlon of low NO, flrlng alternatlves Herzau, J. el al., Proc. Am. Power Conr, 1995, 57, (2), 1182-1187. Discusses Combustion Modification (CM) which is often used as a technique for reducing NO,,formation frdm uiility boilers. CM can be implemented by changing bmler operation parameters using the existing firing equipment, or through the hardware modifications. Achievable potential NO, reduction levels and long term operational effects of either approach is boiler specific. Implementation of either methodology can lead to changes in boiler operating efficiency, reliability, availability, and maintenance costs. An economic analysis of alternatives must accurately reflect associated costs.
96100714 Mlcroscales of turbulent combustion Arpaci, V. S. Prog. Energy Cornbust. Sci., 1995, 21, (2), 153-171. A novel approach leading t&the microscales of compIex‘t&bulent flows is reviewed. The approach is illustrated in terms of the classical microscales proposed by Taylor, Kolmogorov, Oboukhov-Corrsin and Batchelor. A thermal mesomicroscale between the Kolmogorov and Batchelor scales is introducted. The foundations of a well-known correla;ion for forced convection over a flat plate is interpreted. A model for heat transfer in pulse combustor tailpipes is proposed. The model correlates well with the existing experimental data.
96lOQ715 Mlxlng layer lgnltlon of hydrogen Combustion & Flame, Oct. 1995, 103, (l), X-&Y~ C. and Linan, A. A theoretical analysis is given for the high-temperature ignition in a laminar mixing layer between hydrogen and air at the high temperatures characteristic of supersonic combustion. The authors analyze the most important practical case where the temperature of the air stream is higher than that of the hydrogen stream. In this case, the chemical reactions responsible for ignition occur in the air side of the mixing layer, where the mixture is lean. A simplified reduced mechanism is found to describe the ignition process. The radicals of OH and H follow the steady-state approximation while the radical 0 is the chain branching species following an autocatalytic reaction with moderately large activation energy. Numerical results of the governing equations for large values of the activation energy are presented.
Modellng sulfur retentlon In clrculatlng fluldlzed 96100716 bed combustors Li, X. er al., Chem. Enn. Sci., 1995, 50, (14). 2235-2242. Describes the development of a mathem&al’model to evaluate the performance of sulphur retention by limestone in circulating fluidized beds. The model considers particle movement and attrition, calcination and initial pore size distribution, pore plugging and cyclone performance.
96100717 Molecular orbltal study on the N,O formatlon mechanism durlng coal char combustion Ninomiya, Y. and Koketsu, J. Nippon Enerugi Gakkaishi, 1995, 74, (6), 359-364. (In Japanese) A review of sources and mechanism of formation of NO,, especially the formation of N,O in combustion of coal semicoke. Describes recent results on the formation of Nz!, in low-temperature combustion at -8OO”, including a MO study of formation mechanism of N,O. 9610071 a New burners for space heatlng and domestlc hot water appliances Pernaud, A. B. GAZ d’aujourd’hui, Oct. 1995, 119, (lo), 427-433. (In French) For several years now, the Research and Development Division of Gaz de France has been engaged in R&D activities with industrial partners involved in the manufacturing of gas equipment and appliances. The article presents the experimental methods used as well as some recent results concerning burners in residential and commercial appliances used for space heating and the production of domestic hot water.