Mercury removal over the vanadia-titania catalyst in CO2-enriched conditions

The removal of gas-phase elemental mercury was investigated in CO2-enriched flue gas (oxy-fuel combustion) using selective catalytic reduction (SCR) catalysts (V2O5-WO3/TiO2). Experiments were carried out using various concentrations of CO2,O-2, NH3, NO and temperatures. The removal of NO and Hg-0 in the CO2-enriched flue gas condition increased with the temperature and decreased again, the maximum Hg-0 and NO removal was observed at approximately 65% and 85%, respectively at 250-350 degrees C, which indicated that Hg-0 and NO could be simultaneously removed over V2O5-WO3/TiO2. The presence of enriched CO2 (80 vol.%) assisted the Hg-0 removal and inhibited the NO removal, whereas the effect of NO on the Hg-0 removal varied according to the NO concentrations. The presence of Hg-0 promoted NO removal in CO2-enriched flue gas at low temperature 200-300 degrees C whereas inhibited NO removal greatly at high temperature (>300 degrees C). In the SCR system, the presence of NH3 inhibited the Fig removal greatly. The mercury species analysis and catalyst characterization results showed that the removal of Hg-0 over V2O5-WO3/TiO2 at 250-350 degrees C was mainly attributed to the oxidation of Hg-0. Mechanisms of the oxidation of Hg-0 at 250-350 degrees C in the CO2-enriched flue gas condition over the V2O5-WO3/TiO2 catalysts were: (1) the reaction between vanadia oxide and Hg-0 to form adsorbed mercuric oxide (HgO(ad)-V2O4); (2) the oxidation of Hg-0 by chemisorbed oxygen on the surface of catalyst; (3) the oxidation of Hg-0 by function group of C=O to form Hg-0 and C-O-C. (C) 2014 Elsevier B.V. All rights reserved.