NO emission during the co-combustion of biomass and coal at high temperature: An experimental and numerical study.

Biomass/coal co-combustion presents a promising avenue for reducing carbon dioxide emissions. However, the mechanism of NO generation during co-combustion in pulverized coal-fired furnaces remains unclear. Herein, this study investigates NO emission characteristics at elevated temperatures, emphasizing mechanistic understanding. The experiments and simulations were conducted across temperatures ranging from 1000 °C to 1600 °C. In addition to exploring how fundamental conditions (temperature, oxygen concentration, and biomass blending ratio (BBR)) affect NO generation, the study also investigates the interactions between biomass and coal, as well as between fuel NO and thermal NO. The results indicate that the change in NO production with increasing temperature is non-monotonic, attributable to the combined contribution of fuel NO and thermal NO. Moreover, the interaction between biomass and coal manifests predominantly during the char combustion stage, owing to the disparate combustion characteristics and reactivity of biomass char and coal char. Numerical simulations were highly consistent with the experimental findings, underscoring a reduction in the rate of production (ROP) for major elementary reactions leading to NO formation as the BBR increased, consequently mitigating NO emissions. By integrating experimental insights with reaction kinetics calculations, this study proposes pathways for fuel NO and thermal NO generation during co-combustion at high temperatures, involving precursors such as NCO, HNO, and NH. These findings offer a deeper understanding of the mechanism of fuel NO and thermal NO emission during co-combustion at high temperatures. [Display omitted] • NO emission characteristics at 1000–1600 °C of co-combustion were investigated. • Biomass-coal interaction on NO emission was explored using PCA and deviation analysis. • Non-monotonic change in NO emission with temperature, due to thermal NO formation. • Temperature increase affected the conversion pathways of NH and HNO. • Proposed thermal NO and fuel NO generation paths at high temperatures. [ABSTRACT FROM AUTHOR]