Simplified Mechanisms of Nitrogen Migration Paths for Ammonia-Coal Co-Combustion Reactions

Ammonia–coal co-combustion has emerged as a promising strategy for reducing carbon emissions from coal utilization, although its underlying reaction mechanisms remain insufficiently understood. The Chemkin simulation of zero-dimensional homogeneous reaction model and entrained flow reaction model was employed here, and the ROP (rate of production) and sensitivity analysis was performed for analyzing in-depth reaction mechanisms. The nitrogen conversion pathways were revealed, and the mechanisms were simplified. Based on simplified mechanisms, molecular-level reaction pathways and thermochemical conversion networks of nitrogen-containing precursors were established. The results indicate that NO emissions peak at a 30% co-firing ratio, while N 2 O formation increases steadily. The NH radical facilitates NO reduction to N 2 O, with NH + NO → N 2 O + H identified as the dominant pathway. Enhancing NNH formation and suppressing NCO intermediates are key to improving nitrogen conversion to N 2 . This paper quantifies the correlation between NO x precursors such as HCN and NH 3 and intermediates such as NCO and NNH during ammonia–coal co-firing and emphasizes the important role of N 2 O. These insights offer a molecular-level foundation for designing advanced ammonia–coal co-combustion systems aimed at minimizing NO x emissions.