Computational modeling of autothermal combustion of mechanically-activated micronized coal

Burdukov et al. [6] showed experimentally that enhancement of coal reactivity when micronized in a high-impact disintegrator mill makes it possible to attain self-igniting and self-sustaining (autothermal) compact-flame combustion in a cold environment, akin to that of heavy oil. We present computational modeling of autothermal combustion of mechanically-activated microground coal in a 5 MW pilot-scale combustor that complements the experiments of Burdukov et al. [7]. The aim was to verify the applicability of the comprehensive model of pulverized coal combustion to microground coal and to validate the submodel of the coal reactivity enhancement. The modeling follows the standard RANS approach to computing two-phase (reactive dispersed particles in gaseous medium) multi-component system, but with several new modifications related to particle heat transfer and their reactions. For reference, the study includes also the case with non-activated coal of the same granulation micronized in a vibrocentrifugal mill. The computations showed good agreement with the measurements and observations confirming that the model can reproduce the autothermal combustion of activated micronized coal and, thus, be employed with credible certainty to the computational design and optimization of new combustion (and gasification) devices fired with mechanically activated coal dust.