Simultaneous NO and mercury removal over MnOx/TiO2 catalyst in different atmospheres

Abstract

In this study, manganese oxides supported on titania was prepared by sol-gel method and employed as SCR catalyst for simultaneous NO and mercury removal from coal combustion flue gas. The simultaneous NO and Hg0 conversion rate on MnOx/TiO2 was evaluated in different atmospheres, and the interaction between denitration and demercuration was investigated. The results indicated that MnOx/TiO2 had good activity in simultaneously removing NO and Hg0 in SCR atmosphere (NH3+NO+O2+N2). However, both NO conversion and Hg0 removal efficiency were inhibited in simulated coal combustion flue gas compared to that in SCR atmosphere because of the presence of SO2 leading to the generation of sulfite and sulfate on the catalyst. H2O in simulated coal combustion flue gas had negative effect on the catalytic performance as well. NO conversion in oxy-fuel combustion flue gas was lower than that in air combustion flue gas, while Hg0 removal efficiency in oxy-fuel combustion flue gas was higher than that in air combustion flue gas. Hg0 displayed no obvious influence on NO conversion and N2 selectivity over SCR process. And SCR atmosphere showed almost no inhibition to Hg0 removal when the temperature was below 300°C. At the optimal temperature for NO conversion (250°C), the inhibition of SCR atmosphere on Hg0 removal became stronger as the space velocity (GHSV) increased, but the inhibitive effect could be ignored when GHSV slowed down to 50,000h−1 or less.