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Numerical simulations were conducted to study the combustion characteristics in a coaxial Twin Swirl Combustor (TSC) burning pulverized coal. Results under different stoichiometric ratios show that volatiles release in between two recirculation zones close to the secondary air inlet, and char burns mostly in the near-wall region due to the centrifugal force brought in by two swirling airflows. Intensive near-wall burning of pulverized coal favors a relatively high wall temperature, contributing to continuous molten slag discharge. An evenly distributed temperature profile with an average of about 1500 K in the chamber is obtained, which is beneficial for low NOx emissions. The case with stoichiometric ratios of 0.9 yielded lower NOx emission rates near exit while remains high volatile conversion rate and char burnout rate, as compared with the case with stoichiometric ratios of 0.8.

computation, modeling, simulation, numerical methods