Significance of RuO_2 Modified SCR Catalyst for Elemental Mercury Oxidation in Coal-fired Flue Gas

摘要

Catalytic conversion of elemental mercury (Hg°) to its oxidized form has been considered as an effective way to enhance mercury removal from coal-fired power plants. In order to make good use of the existing selective catalytic reduction of NO_x (SCR) catalysts as a cobenefit of Hg° conversion at lower level HC1 in flue gas, various catalysts supported on titanium dioxide (TiO_2) and commercial SCR catalysts were investigated at various cases. Among the tested catalysts, ruthenium oxides (RuO_2) not only showed rather high catalytic activity on Hg° oxidation by itself, but also appeared to be well cooperative with the commercial SCR catalyst for Hg° conversion. In addition, the modified SCR catalyst with RuO_2 displayed an excellent tolerance to SO_2 and ammonia without any distinct negative effects on NO_x reduction and SO_2 conversion. The demanded HC1 concentration for Hg° oxidation can be reduced dramatically, and Hg° oxidation efficiency over RuO_2 doped SCR catalyst was over 90% even at about 5 ppm HC1 in the simulated gases. Ru modified SCR catalyst shows a promising prospect for the cobenefit of mercury emission control.