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Show PAPER NO.7 DEVELOPMENT OF A THREE DIMENSIONAL COAL COMBUSTION MODEL H.Kaneda~(Kure Research Laboratory, Babcock-Hitachi KK); K.Yamazaki and K.Kiyama (Kure Works, Babcock-Hitachi KK); K.C.Karki and S.V.Patankar (Innovative Research, Inc., MN) A mathematical coal combustion model to predict NO concentration in a utility boiler furnace has been developed. The model solves the time averaged conservation equations for species that are important in NO formation and reduction in fossil boilers using the eddy-dissipation combustion model. The flow field is solved by the SIMPLER algorithm and the turbulence is calculated by the standard k-E model. The radiation is handled by the six-flux model of radiation. The model is verified using the data which is obtained during the trial operation of a lOOOMWe utility boiler. 1. INTRODUCTION We have been developing 10w-NOx combustion technology such as 10w-NOx burners and Two Stage Combustion (TSC) on account of the stringent environmental protection regulations in Japan. However, these technologies slow down the combustion efficiency and make it difficult to recover "trade-off" defects between NOx reduction and increasing unburned carbon in ash (UBC). TSC, increasing the residence time of combustion gas between sub-stoichiometric burner zone and After-Air injection point (NO port), can accelerate the post flame NOx decay and consequently augment NOx reduction. In general, UBC tends to increase, if the residence time of the combustion gas between NO port and furnace exit is too short. This also changes the heat release pattern in the furnace. Therefore, the recent newly designed boiler tends to have larger furnace volume. In this paper, outlines of the mathematical coal combustion model developed as a tool to study the optimum design conditions for efficient and smaller size furnaces and prediction results of the lOOOMW utility boiler furnace are described. e 2. MATHEMATICAL MODEL A mathematical model for pulverized-coal-fired furnaces involves simulation of many complex inter-dependent physical and chemical processes. These include turbulent fluid mechanics, gaseous turbulent combustion, particle transport, coal devolatilization, 1 |