Thermochemical analysis of premixed ammonia/biogas flames in a model gas turbine swirl combustion system

This study examined the premixed NH3/biogas combustion at near stoichiometric using an experimentally validated numerical method. Raising the NH3 wt.% in NH3/CH4 combustion at φ = 0.8 brought up the average reaction temperature (Tavg) due to heat retention. Intensified by CO2 addition, Tavg in NH3/biogas increased by a factor of 1.2 compared to NH3/CH4. At φ = 1.1, higher NH3 and CO2 wt.% reduced Tavg. The local Damköhler number (Da) was reduced marginally in the absence of CO2 as φ increased from 0.8 to 1.1. Conversely, local Da grew considerably in the presence of CO2 and was particularly sensitive to variations in the excess air ratio. Increased NH3 wt.% promoted NO emission, primarily via N + OH → NO + H and H + HCNO → CH2 + NO pathways. NH3/biogas produced more NO than NH3/CH4 from φ = 0.9 to 1.1, but as φ approached 1.1, NO is generally lowered. N2O is produced mainly by NH + NO → N2O + H. Fuel-lean operation generally results in a higher N2O than fuel-rich operation. The NH3/biogas combustion at φ = 0.8 is a potential clean fuel solution in lowering NO emissions, as compared to NH3/CH4 combustion.