Experimental study on combustion characteristics of volatiles and residual solids in ammonia co-firing with biomass pellets

Co-firing ammonia (NH₃) with biomass is a promising approach for clean boiler applications. Biomass has low-energy density, and NH₃ exhibits weak combustion efficiency and stability. However, biomass pelletization pre-treatment can improve fuel properties, and increased volatile release during combustion stabilize NH₃ burning. To investigate effect of NH₃ on biomass pellet combustion, biomass pellet co-firing with NH₃ experimental system was built. The study examined the influence of ammonia content (AC = 0–100 mL/min) on flame characteristics and analyzed residue morphology and elemental composition. The results showed that NH₃ addition extended volatile combustion duration (1.8–8.0 s). For rice husk pellets (RHP), corn straw pellets (CSP), and poplar wood pellets (PWP), the longest durations were at AC = 75, 50, and 50 mL/min, reaching 48.4 s, 50.9 s, and 51.5 s, respectively. NH₃ delayed ignition by 0–4.6 s. Flame height increased for RHP, while it decreased by 38 % for PWP. Increasing AC reduced soot formation in RHP and CSP, but showed stage-dependent effects on PWP. At AC = 50 mL/min, PWP exhibited a higher mass loss rate, and residues had different elemental compositions. This study provides insights for optimizing ammonia-biomass co-firing and advancing decarbonization in the power industry.