Removal of elemental Mercury from flue gas using wheat straw chars modified by K2FeO4 reagent

Abstract

ABSTRACTIn this article, wheat straw (WS) char, a common agricultural waste and renewable biomass, was pyrolyzed and then modified by K2FeO4 reagent to develop an efficient sorbent for removal of Hg0 from flue gas. Brunauer–Emmett–Teller, scanning electron microscopy with energy spectrum and X-ray diffraction (XRD) were employed to characterize the sorbents. The effects of K2FeO4 loading, reaction temperature, Hg0 inlet concentration and concentrations of gas mixtures O2, NO and SO2 in flue gas on Hg0 removal were investigated in a fixed-bed reactor. The results show that K2FeO4-impregnation can improve pore structure of WS char and produce new active sites, which significantly enhance Hg0 removal. Increasing Hg0 inlet concentration significantly decreases Hg0 removal efficiency. O2 in flue gas promotes Hg0 oxidation by replenishing the oxygen groups on the surface of modified chars. The presence of NO obviously promotes Hg0 removal since it can oxidize Hg0 to Hg(NO3)2. SO2 in flue gas significantly decreases Hg0 removal efficiency due to the competition adsorption between SO2 and Hg0. The increase in reaction temperature has a dual impact on Hg0 removal.