Removal of mercury from flue gas using coal gasification slag

Coal combustion often produces mercury emissions. Coal gasification fine slag (FS) was used to remove Hg 0 from flue gas. To increase the removal efficiency, two ionic liquids (IL-T and IL-B) were immobilized on the surface of FS. The mercury removal performance was evaluated in a fixed-bed reactor in the presence of SO 2 + O 2 . The experimental results showed that the mercury removal efficiency increased when the adsorbents were supported by ionic liquids (FS-T and FS-B). The effect of 0.6% SO 2 on the capture of Hg 0 was negligible for all three adsorbents. The total mercury removal efficiencies exceeded 90% for FS-T and FS-B in the atmosphere of 0.6% SO 2 + 6% O 2 . When the initial mercury concentration was 60 μg/m 3 , the effective adsorption time was about 80 min for FS and longer than 120 min for FS-T and FS-B. In the presence of 0.6% SO 2 + 6% O 2 , Hg 0 and Hg 2+ were detected in exhaust gas using FS and FS-B and in solid phase using the three adsorbents. According to XPS analysis, an oxidation reaction occurred on the surface of FS and FS-T. For FS-B, the Br − anion of IL-B was the active site and oxidized Hg 0 to Hg 2+ on the surface as well as in the gas phase. • 0.6% SO 2 was not affected the capture of Hg 0 . • The mercury removal exceeded 90% for FS-T and FS-B in 0.6% SO 2 + 6% O 2 . • A low concentration of SO 2 promoted the oxidation of Hg 0 to Hg 2+ . • Oxidation reaction occurred on the surface of the adsorbents of FS and FS-T. • Oxidation process happened both the surface and gas phase.