Characteristics of denitrification and mercury removal of Ce-W/TiO2 catalysts in SCR atmosphere
GENG Xin-ze, DUAN Yu-feng, HU Peng, LIU Shuai, LIANG Cai
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, China
The effects of reaction temperature and flue gas composition on the denitrification and mercury removal efficiency of Ce-W/TiO2 (Ce: W=2:1) catalysts were investigated in a fixed bed reactor. The results showed that the reaction temperature had a significant effect on the denitrification and mercury removal efficiency of Ce-W/TiO2. In the temperature range of 280~400℃, the denitration efficiency increased as temperature increased, while the mercury removal efficiency was higher at temperature 280℃ and 360℃, with the best denitrification and mercury removal efficiency at 360℃. In the SCR atmosphere, HCl had a great effect on the oxidative removal of Hg0. Low concentration of HCl was also beneficial to the improvement of denitration efficiency, but excessive HCl concentration had an inhibitory effect on NO removal. The presence of SO2 could promote the denitrification process and inhibit the oxidation of Hg0. The catalysts before and after the reaction were characterized by BET, XRD, SEM, TPD, XRF, NH3-TPD and other analytical methods. The results showed that Ce-W/TiO2 had no microporous structure, and the active components CeO2 and WO3 were distributed on the surface of the carrier in a highly dispersed form. At 280℃, part of Hg was adsorbed on the surface of the catalyst in the form of HgCl2. As the reaction temperature increased, the adsorption of mercury on the surface of the catalyst decreased sharply. HCl and SO2 in SCR atmosphere could affect the acidity of catalyst surface and increase the content of Cl and S, thus, affect the denitration and mercury removal efficiency of the catalyst.
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