Study on the effect and its mechanism of H2O, O2 and CO2 on NTP combined with CH4-SCR

Abstract

AbstractIn this paper, the influence mechanism of O2/H2O/CO2on the removal of CH4and NOxby non-thermal plasma (NTP) combined with selective catalytic reduction of NOxby CH4(NTP-CH4-SCR) were investigated. The results show that the increase of NTP energy density (0 J/L-491 J/L) promoted the CH4removal but inhibited the NOxremoval in NTP-CH4-SCR. In CH4-SCR, H2O could significantly reduce catalyst activity, adding 0.5% H2O decreased the removal efficiency of CH4and NOxfrom 30–2.9% and 58.4–1.8% respectively. In NTP-CH4-SCR, the increase of H2O content (0.5%-10.4%) contributed to formation of oxidizing free radicals such as OH and HO2, thus the CH4removal efficiency increased from 24.1–37.4%. The increase of O2content (0%-10%) promoted the adsorption of NO and the reaction of adsorption products with CH4oxidation products, causing the CH4removal efficiency increased from 1.3–32.3% and NOxremoval efficiency increased from 1.5–61.6% in CH4-SCR. Increasing O2(0–10%) produced more O and HO2radicals in NTP-CH4-SCR, resulting in the increase of CH4removal efficiency from 18.6–44.9%. However, these O and HO2radicals would react with N radicals to form NO2, NO3et al., thus decreasing NOxremoval efficiency from 68–40.8%. The change of CO2concentration has little effect on CH4and NOxremoval efficiency.