Abstract: Full-scale numerical investigation was conducted to characterize NOX emission behavior in an industrial cement precalciner under staged combustion and biomass co-firing conditions. An Euler-Lagrange framework was employed to develop a three-dimensional model that resolves gas-phase combustion, pyrolysis of pulverized coal and biomass, as well as the formation and reduction pathways of NO. The model was validated through grid-independence analysis and comparison with on-site industrial measurements, with prediction deviations of temperature and NO concentration within 10%, demonstrating satisfactory accuracy for industrial-scale simulation.The simulation results reveal that NO formation and reduction along the precalciner height exhibit a distinct evolution pattern, characterized by an initial low-rate conversion region, an intermediate strong reduction zone, and a downstream region dominated by NO formation. Based on this understanding, the effects of staged combustion optimization, including extension of the reduction zone and redistribution of fuel injection and oxygen concentration, were systematically evaluated. In addition, the NOX mitigation performance of biomass co-firing with pulverized coal (corn straw) was investigated.The results indicate that staged combustion effectively suppresses NO formation by enhancing the reducing atmosphere within the precalciner. Moreover, biomass co-firing provides an efficient alternative for NOX reduction without additional structural modification: when the biomass co-firing ratio is increased to 30%, the NO concentration at the precalciner outlet can be maintained at approximately 300ppm, while the raw meal decomposition rate remains above 92%. The present study provides quantitative insights into NOX emission characteristics and offers practical guidance for low-NOX operation of industrial cement precalciners.
