Elemental mercury removal from simulated coal-fired flue gas by modified tonstein in coal seam

•Modified tonstein (CuBr2-TCS) effectively removed Hg0 from simulated flue gas.•O2 significantly facilitated Hg0 removal by the spent adsorbent after the cycle.•The adding order of NO and SO2 had a large effect on the performance of CuBr2-TCS.•Both Cu2+ and Br played key roles in the process of Hg0 removal. Tonstein in coal seam (TCS) is a kind of mining solid waste, which was developed to a novel adsorbent (CuBr2-TCS) by using copper bromide modification. In this paper, CuBr2-TCS was subjected to elemental mercury (Hg0) removal experiment in simulated coal-fired flue gas (SFG). Several characterization methods were used to determine the mineralogical characteristics of TCS and reaction mechanisms. In-depth, the Hg0 removal performances of CuBr2-TCS under different flue gas components were explored. The results revealed that CuBr2-TCS exhibited 92.1% and 78.3% Hg0 removal efficiency in dry and wet SFG, respectively. HCl and O2 facilitated Hg0 removal performance of CuBr2-TCS by supplementing oxygen atoms and halogens, respectively, accompanying some intermediate transition products such as Cu2OBr2. SO2 played a serious suppressive role. SO2 acting alone or NO and SO2 acting simultaneously caused irreversible changes in the surface functional groups that formed active sites with NO. However, the thermal stability of the adsorbed mercury on the adsorbent which was spent in N2 + SO2 + O2 atmosphere became better. In addition, the spent adsorbent that first went through the Hg0 removal process in N2 + NO atmosphere, exhibited higher Hg0 removal efficiency in N2 + SO2 + NO atmosphere than that first reacted in N2 + SO2 atmosphere. CuBr2-TCS is a cost-effective adsorbent for the Hg0 abatement from the coal-fired flue gas (CFG).