Experimental and mechanistic study on the removal of elemental mercury in coal-fired flue gas by SO2-modified activated coke within a wide temperature range

• Modified activated coke exhibits excellent sulfur resistance performance. • In situ modified activated coke is a potential technical means. • The mechanism of SO 2 modified activated coke at low temperatures has been explained. The Cold Oxidation Adsorption Process (COAP) technology has effectively demonstrated the adsorption of SO 2 and NOx in flue gas during actual industrial applications, achieving emissions below 1 ppmv. This positions COAP as a promising flue gas treatment technology for the future. The original activated coke cannot effectively adsorb elemental mercury in flue gas, and its mercury removal performance needs to be improved. Therefore, this study proposes a low-cost and low-energy-consumption modification method for activated coke. This method conducts in-situ modification of activated coke through a regeneration tower and low-concentration SO 2 , so as to effectively remove elemental mercury within a wide temperature range. Through laboratory modification experiments and fixed-bed adsorption experiments, it has been found that under the condition of -20 °C, the adsorption efficiency of SO 2 -modified activated coke for mercury reaches 95 %. The results showed that the adsorption efficiency of SO 2 modified activated coke for mercury reached 95 % under COAP technology conditions. In addition, under the condition of 1500 ppm SO 2 , the lowest mercury removal efficiency is not less than 75 %, demonstrating excellent resistance to SO 2 .The oxidation mechanism of mercury on the surface of activated coke was characterized by XPS, and Hg-TPD, indicating that –COOH, O*, R-S-S-, and R-SO x (x=1,2) played key roles in the adsorption process of mercury. In summary, SO 2 modified activated coke exhibited excellent mercury removal performance over a wide temperature range.