PREDICTION OF STAGED COAL COMBUSTION IN 3-DIMENSIONAL FURNACES

A 3-D numerical method was used for the study of staged coal combustio n in a semi-industrial-scale furnace experimentally investigated in th e International Flame Research Foundation (IFRF). Detailed evaluation of the 3-D code against experimental data for temperature, oxygen and nitrogen monoxide concentration is presented. In the numerical algorit hm is incorporated a higher-order finite-differencing scheme for ail e quations, along with a general devolatilisation model. in order to min imise time and memory requirements, the computational domain was limit ed to one quarter of the furnace with the aid of cyclic boundary condi tions. A reasonable degree of agreement is indicated by comparison of predicted and experimental results. The NO post-processor used employs a simplified reaction path for the formation and destruction of NO, a nd both fuel NO and thermal NO are accounted for. Predicted NO levels indicate that under staged combustion conditions the relative effect o f char nitrogen on the total NO formed is more important than in norma l combustion conditions, where most NO is formed from the nitrogen con tained in the volatile. The experimental observation that burner aerod ynamic changes affect mostly conversion of volatile nitrogen to NO is correctly predicted.