N2O formation pathways in swirl-stabilised NH3/CH4 and NH3/Biogas combustion

Abstract

This study examines the effects of inlet temperature and CO₂ dilution on the N₂O formation mechanisms in NH₃/CH₄ and NH₃/biogas swirl combustion. Key reactions governing N₂O kinetics include the formation pathways NH + NO ⇌ N₂O + H and NNH + O ⇌ N₂O + H, as well as the primary consumption pathway N₂O + H ⇌ N₂ + OH. At a global equivalence ratio (φ_G) of 0.8, the introduction of CO₂ effectively suppresses N₂O formation in NH₃ flames by reducing the concentrations of H, O, and OH radicals. In contrast, increasing the inlet temperature accelerates the N₂O formation rate, enhancing its retention in the flame. Under fuel-rich conditions (φ_G = 1.1), CO₂ dilution generally reduces N₂O emissions and exhibits a trend dependent on NH₃ blending levels and temperature, with elevated inlet temperatures consistently suppressing N₂O formation. The findings indicate that effective control of N₂O emissions can be achieved by optimizing the CO₂ dilution ratio and inlet temperature based on the ammonia blending ratio. The results contribute to the advancement of clean energy technologies by informing the design of low-emission fuel strategies involving ammonia and renewable fuel mixtures.