Numerical predictions of burner performance during pulverized coal combustion

The performance of four burners in terms of temperature and velocity profiles, residence time and NO_x emissions was predicted using numerical simulations and a two-dimensional model for pulverized coal combustion. Numerical predictions for two burners used in a pilot-scale 0.5 MM Btu/hr (146.5 kW) Down-fired combustor (DFC) are presented. Two other burner configurations were evaluated and compared with the ones used with the DFC for attaining lower NO_x levels. Simulations were conducted for both coal and coal-water slurry as primary fuels. A sensitivity analysis of predictions with respect to variations of the model parameters was performed. The results suggest that the higher NO_x reduction with one of the burners used in the DFC is due to the improved near-burner aerodynamics and to better flame attachment. These improved conditions are influenced by a combination of geometric and flow parameters, such as burner dimensions, quarl diameter, inlet velocity, inlet temperature and swirl number.