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

In this article, wheat straw (WS) char, a common agricultural waste and renewable biomass, was pyrolyzed and then modified by KFeO reagent to develop an efficient sorbent for removal of Hg 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 KFeO loading, reaction temperature, Hg inlet concentration and concentrations of gas mixtures O, NO and SO in flue gas on Hg removal were investigated in a fixed-bed reactor. The results show that KFeO-impregnation can improve pore structure of WS char and produce new active sites, which significantly enhance Hg removal. Increasing Hg inlet concentration significantly decreases Hg removal efficiency. O in flue gas promotes Hg oxidation by replenishing the oxygen groups on the surface of modified chars. The presence of NO obviously promotes Hg removal since it can oxidize Hg to Hg(NO). SO in flue gas significantly decreases Hg removal efficiency due to the competition adsorption between SO and Hg. The increase in reaction temperature has a dual impact on Hg removal.