A mathematical model of simultaneous formation of volatile-NO and char-NO during the packed-bed combustion of coal-char particles under an NH 3O 2Ar gas stream

Abstract

A mathematical model for the simultaneous formation of volatile-NO and char-NO in coal combustion has been developed from the proposed kinetic mechanism involving 36 heterogeneous and homogeneous reactions, taking account of the effect of heat and mass transfer. The model can describe not only the rate process of NO formation but also those of the main reactions of combustion: C + 1 2 O 2 → CO , CO + OH → CO 2 + H, etc. To check the applicability of the model, the packed-bed combustion of coal-char particles was carried out in an NH 3O 2Ar gas stream. Sample coal-char particles were from Taisei coal (a Chinese anthracite) and an NH 3 gas simulated the volatile nitrogen compounds (volatile-N) evolved during coal combustion. The predictions of the present model compared favourably with the experimental data for the transient formation and reduction of CO 2, CO, N 2 and NH 3, as well as of NO. The relative contributions of volatile-NO and char-NO to the total fuel-NO emissions can be separated theoretically by the present model. In addition, char-N 2 from char-N and volatile-N 2 from volatile-N (NH 3) are distinguished both theoretically and experimentally.