A NUMERICAL INVESTIGATION OF ASPECTS OF COAL POWDER COMBUSTION IN A COUNTERFLOW COMBUSTOR

Favourable aerodynamic conditions for controlled, stabilized pulverized coal combustion can be achieved by the use of a counterflow combustor. In response to initial experimental testing, predictions of the behaviour of coal particles in such combustors are presented, based on a theoretical numerical model. Two counterflow configurations are considered: a relatively small horizontal chamber, and a vertical chamber with a volume eight times as large. Attention is focused on particle trajectories, and the effects of initial particle size and temperature, angle of injection, wall impingement and gravity are examined. Qualitatively the behaviour of both the gas and particle phases is found to be similar in both configurations. Overall qualitative validation of the predictive capability of the model is provided by comparison with experimental data for both configurations. In general, the results indicate the possibility of achieving optimal conditions for combustion through appropriate adjustment of the flow and thermal conditions in the primary and secondary jets of this countercurrent set-up.