Sodium ascorbate as additive in red mud slurry for simultaneous desulfurization and denitrification: Insights into the multiple influence factors and reaction mechanism

Abstract

Based on the ultra-low emission demand of SO2 and NOx in flue gas, a new absorption method was proposed to improve the desulfurization and denitrification efficiency and reduce the amount of ozone by using sodium ascorbate as an additive in red mud slurry. Compared with pure red mud slurry, the red mud (RM) + sodium ascorbate (SA) slurry significantly improved the denitrification efficiency from 24% to 84% and the desulfurization efficiency to 98%. Meanwhile, the effects of RM, SA concentration, reaction time and O3/NO molar ratio on desulfurization and denitrification efficiencies were studied. The results showed that the RM + SA composite slurry maintained high efficiencies of desulfurization and denitrification for 240 min under the optimized conditions. As an antioxidant, the introduction of SA inhibited the excessive oxidation of sulfite, and itself could easily react with NO2 through the redox reaction, greatly promoting the absorption of NO2. In addition, the reaction mechanism of the simultaneous removal of SO2 and NO2 by red mud and sodium ascorbic mixed slurry combined was proposed.