N2O Formation from Combustion of Char Particles with NO

Abstract

Devolatilized coal particles were combusted with NO as the only oxidizing agent. The effect of different NO concentrations in the inlet gas, as well as the effect of changing gas residence time within and after the fixed bed, on the emission of N2O from the char particles burning at single particle conditions is reported. The experiments were carried out in a fixed bed reactor containing quartz sand (SiO2) to support the coal particles. The bituminous coal particles were devolatilized in situ prior to the actual combustion in an argon flow. The inlet gas mixture contained NO and Ar. The NO concentration was varied between 5 and 50% and the inlet gas flow was varied between 395 and 1200 mL(NTP)/min (NTP = 273 K, 1 atm). The bed temperature was 1073 K. The off-gases were analyzed for N2O, CO, and CO2. Extremely high yields of N2O (150−430% of the char nitrogen content) were obtained in all cases when the devolatilized coal particles were combusted with NO. The N2O formation increased with increasing NO concentration in the inlet gas for low NO concentrations (5−20%) and reached a plateau for higher NO concentrations. The N2O formation increased with increasing gas residence time within and after the fixed bed.