Kinetic insights into the effects of coal quality and operating parameters on the NO and N2O formation behaviors in fluidized bed coal/ammonia co-combustion

• A new heterogeneous reaction model for coal/ammonia co-firing was developed. • Effects of coal quality on nitrogen oxide behaviors were studied. • The nitrogen content in coal has a more pronounced effect on NO x formation. • N 2 O production mainly occurs under high NH 3 ratios and low temperature conditions. • The N 2 O production is constrained by the availability of HCN with the NH 3 injected. High-percentage ammonia co-firing in coal-fired fluidized bed boilers represents an effective and promising carbon reduction strategy. The scalability of ammonia co-combustion, nevertheless, could be compromised by uncontrolled nitrogen oxide generation through fuel-N conversion pathways. Crucially, coal quality characteristics—notably nitrogen and volatile matter content—dictate the abundance and speciation of fuel-nitrogen, directly governing nitrogen oxide generation patterns. In this work, a new heterogeneous reaction model for fluidized bed coal/ammonia co-firing was developed by integrating coal pyrolysis modeling (quantifying coal quality parameters) with a chemical reaction kinetics method. A comparative analysis of nitrogen oxide emission disparities was conducted across coals with divergent quality characteristics. Furthermore, the effects of combustion temperature, oxygen concentration, and ammonia distribution strategy on the nitrogen migration path were investigated. The specific results are as follows: the influences of the co-firing ratio and temperature on the formation behaviors of nitrogen oxide are asynchronous. Low co-firing ratios (10 %∼30 %) combined with high temperatures (900 ℃∼950 ℃) conditions favor NO x generation, whereas N 2 O production predominantly occurs under high co-firing ratios (40 %∼100 %) and low-temperature (750 ℃∼800 ℃) conditions. The elevated nitrogen content in coal enhances both NO x and N 2 O generation during coal/ammonia co-firing, with a more pronounced effect on NO x formation. Reaction pathway analysis reveals that N 2 O is primarily generated through reactions between NO/NO 2 and NCO/NH radicals. The N 2 O production is constrained by the availability of HCN, which serves as the precursor to NCO intermediates. The introduction of ammonia exerts negligible mechanistic effects on NO x and N 2 O formation characteristics under anthracite combustion conditions. In contrast, in bituminous coal scenarios, N 2 O concentrations exhibit a distinct increase to a peak followed by a decline with the ammonia increased. For lignite conditions, ammonia demonstrates pronounced suppression of NO x emissions, with NO x levels decreasing progressively with larger co-firing ratios. These findings can provide technical support and actionable guidance for controlling nitrogen oxide emissions in practical coal-fired fluidized bed boilers integrated with ammonia co-combustion systems.