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

In 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 Hg-0 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, Hg-0 inlet concentration and concentrations of gas mixtures O-2, NO and SO2 in flue gas on Hg-0 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 Hg-0 removal. Increasing Hg-0 inlet concentration significantly decreases Hg-0 removal efficiency. O-2 in flue gas promotes Hg-0 oxidation by replenishing the oxygen groups on the surface of modified chars. The presence of NO obviously promotes Hg-0 removal since it can oxidize Hg-0 to Hg(NO3)(2). SO2 in flue gas significantly decreases Hg-0 removal efficiency due to the competition adsorption between SO2 and Hg-0. The increase in reaction temperature has a dual impact on Hg-0 removal.