Numerical study of NO_x reduction by reburning mechanically-activated micronized coal in a full-scale tangentially-fired boiler

摘要

The paper presents some results of numerical simulation of the effects of reburning of mechanicallyactivated micronized coal on NO_x reduction in a tangentially fired boiler of 500 t/h steam production. The conventional RANS approach was used to compute two-phase (reactive dispersed particles in gaseous medium) multi-component system, with some modifications of models of particle heat transfer and their reactions. The comprehensive model was earlier verified in simulation of an 5 MW experimental combustor as well as in a full-scale real boiler. The comparison with the standard firing with pulverized coal showed that reburning of non-activated fine coal leads to a NO_x reduction by about 20%, but increases the unburnt carbon residual by 23%. However, reburning of mechanically-activated coal of the same granulation reduces NO_x by 30% and also diminishes the unburnt residual by 35%, demonstrating that reburning in general, but especially of activated micronized coal, is a feasible option for achieving significant reduction in NO_x emission.