Integrated removal of NO and mercury from coal combustion flue gas using manganese oxides supported on TiO2

A catalyst composed of manganese oxides supported on titania(MnO/TiO) synthesized by a sol–gel method was selected to remove nitric oxide and mercury jointly at a relatively low temperature in simulated flue gas from coal-fired power plants. The physico-chemical characteristics of catalysts were investigated by X-ray fluorescence(XRF), X-ray diffraction(XRD), and X-ray photoelectron spectroscopy(XPS) analyses, etc. The effects of Mn loading,reaction temperature and individual flue gas components on denitration and Hg~0 removal were examined. The results indicated that the optimal Mn/Ti molar ratio was 0.8 and the best working temperature was 240°C for NO conversion. Oand a proper ratio of [NH]/[NO]are essential for the denitration reaction. Both NO conversion and Hg~0 removal efficiency could reach more than 80% when NO and Hg~0 were removed simultaneously using Mn0.8 Tiat 240°C.Hg~0 removal efficiency slightly declined as the Mn content increased in the catalysts. The reaction temperature had no significant effect on Hg~0 removal efficiency. Oand HCl had a promotional effect on Hg~0 removal. SO2 and NHwere observed to weaken Hg~0 removal because of competitive adsorption. NO first facilitated Hg~0 removal and then had an inhibiting effect as NO concentration increased without O, and it exhibited weak inhibition of Hg~0 removal efficiency in the presence of O. The oxidation of Hg~0 on Mn O x/TiOfollows the Mars–Maessen and Langmuir–Hinshelwood mechanisms.