N2O Formation/Destruction Characteristics and Mechanisms in High-Temperature Pulverized Coal Combustion.

Abstract

Characteristics and reaction mechanisms of N2O formation/destruction in high-temperature pulverized coal combustion are studied experimentally and theoretically. The experimental results show that N2O is mainly formed during the initial stage of volatile matter combustion, but that the N2O concentration at the exit of the furnace reaches a low value. The maximum N2O concentrations in different types of coal depend on the temperature gradient, the content of volatile matter and the flame structure around coal particles. N2O concentration at the exit increases with increasing air ratio. By numerical analysis of combustion behavior using a single-particle combustion model, it becomes clear that N2O is mainly produced by NH (formed by the decomposition of NH3) and N2 in the initial volatile matter combustion region, after which N2O is formed by NCO produced by the oxidation of HCN ; however, N2O is decomposed by H radicals.