Experimental study of CO2/H2/NH3 influence on CH4 flameless combustion process in semi-industrial furnace

A flameless combustion mode was employed in a semi-industrial furnace to investigate the effect of NH3 on CH4, which was diluted by CO2/H2 combustible mixtures, serving as the primary fuel. Emission characteristics, as well as toxic compounds and temperature distribution maps, were presented for selected fuels. The combustion system was tested at a constant firing rate of 150 kWth and a constant fuel bulk velocity of 85 m/s. We investigated the effects of equivalence ratio, fuel composition and volume share of NH3 in the fuel. It was found that the equivalence ratio and NH3 amount have the most significant impact on the emission of fuel nitric oxide in the flameless combustion process. The dilution of CH4 with CO2 affects the stretch rate, resulting in an increase in CO levels as well as promoting NO level growth. The calculated dimensionless Conversion Factor (CF) shows that the dilution gas, CO2, significantly impacts the reduction of NH3 to NO, but only for low-content fuel-bound nitrogen (up to 1%). The lowest values of CF were measured for a high equivalence ratio, corresponding to the typical oxygen content for flameless combustion process.