Reburning mechanisms in A pulverized coal combustor

Abstract

Mechanisms governing the inter-conversion and destruction of nitrogenous species in the fuel rich reburning zone of a laboratory coal combustor were explored. Emphasis was on a configuration in which the primary flame was of pulverized coal and the reburning fuel was natural gas, although other fuels were also considered. The objective was to extract models to be used in estimating reburning effectiveness in practical combustors. Reburning mechanism occur in two regimes; one in which fast reactions between NO and hydrocarbons are usually limited by mixing; the other in which reactions have slowed and in which known gas phase chemistry controls. For the latter regime, a simplified model based on detailed gas phase chemical kinetic mechanisms and known rate coefficients was able to predict temepral profiles of NO, NH3 and HCN. Reactions with hydrocarbons played important roles in both regimes and the Fenimore N2 fixation reactions limited reburning effectiveness at low primary NO values.