The application of coal liquefaction residue raffinate slag-based sorbents for elemental mercury removal from coal-fired flue gas

Abstract

Capture of elemental mercury (Hg0) attracts global attention because of its toxicity and bioaccumulation. Carbon-based sorbents are extensively studied due to the high porosity that can increase Hg0 adsorption ability. In this study, the RS-based sorbents were prepared from sulfur-containing coal liquefaction residue raffinate slag (CLR-RS), an industrial waste, by CH3COOK activation. The N2 adsorption, XRD, SEM, XRF, Hg-TPD, and XPS techniques were used to study the physicochemical properties of sorbents. The sorbent that was prepared at 850 °C from the blend of CH3COOK/RS at 3:5 (by mass) exhibited excellent Hg0 removal performance under N2 + O2, and an improved performance was observed under N2 + O2 + SO2 + NO + H2O. The Hg-TPD and XPS analyses revealed that HgS and HgO were formed on used RS-based sorbents. O2 in flue gas could improve the ability in capturing Hg0 by promoting the formation of HgS and HgO. The findings have suggested that the prepared sorbents based on CLR-RS could be potentially applied for industrial Hg0 capture, and the sustainable utilization could be realized by recycling RS.