Experimental study on NOx emission characteristics under oxy-fuel combustion

Abstract

Abstract This study focuses on the emission characteristics of NOx under oxy-fuel combustion conditions. A comparative analysis with air combustion was performed. NOx emission, control measures and influence factors under different working conditions were studied. Experiments were carried out on a 3-MWth test platform and a laboratory platform. The ‘π’-type furnace was adopted, with the furnace width of 2.6 m, depth of 2.0 m and height of 10.5 m for the 3-MWth coal-fired boiler. NOx emissions at different oxygen concentrations and different air distribution were investigated; the effects of H2O and CO2 concentration on denitrification efficiency and SO2/SO3 conversion rate were explored. Experiment results suggest that, compared with air combustion, NO concentration (volume basis) at the furnace outlet under oxy-fuel combustion is higher than that of air combustion, but the amount of NOx emissions in the discharged gas significantly decrease compared to the air combustion conditions. In addition, the formation of NOx can be effectively controlled through staged combustion. Furthermore, the selective catalytic reduction (SCR) denitrification efficiency and the conversion rate of SO2 to SO3 decreases when the CO2 concentration and the H2O content increase, indicating that CO2 and H2O have an adverse effect on the performance of the catalyst. Additionally, compared with CO2 concentration, H2O content has a greater effect on catalyst performance.