Simultaneous removal of Hg0 and NO from flue gas by Co0.3-Ce0.35-Zr0.35O2 impregnated with MnOx

Abstract

Hg0 removal with SCR system can result in co-benefits of the apparatus, but the simultaneous removal efficiencies of Hg0 and NO are not good enough and the mechanism of interaction between Hg0 and SCR atmosphere has not been well known. In our previous work, Co0.3-Ce0.35-Zr0.35O2 has been proved to have an excellent Hg0 oxidation efficiency. Therefore, in the present work, Co0.3-Ce0.35-Zr0.35O2 was used as a support to load SCR active component Mn and to obtain Mn0.1/Co0.3-Ce0.35-Zr0.35O2 catalyst. Mn0.1/Co0.3-Ce0.35-Zr0.35O2 showed excellent simultaneous efficiencies of Hg0 oxidation (83.6%) and NO conversion (89.4%) at 180°C under a high GHSV 180,000h−1. Furthermore, the interaction between Hg0 and SCR atmosphere lowered the simultaneous efficiencies when compared to the separated ones. The decrease of Hg0 oxidation efficiency in SCR+Hg0 atmosphere was mainly attributed to the competitive adsorption between NH3 and Hg0. Although NO and O2 were beneficial for Hg0 oxidation, it could not offset the inhibitive effect of NH3. Meanwhile, HgO accumulated on the catalyst surface resulted in occupation of active sites, which was responsible for the decrease of NO conversion in SCR+Hg0 atmosphere. The individual gas components (H2O and SO2) showed negative effects on the simultaneous efficiencies of Hg0 oxidation and NO conversion.