Efficient Removal of Elemental Mercury from Coal-Fired Flue Gas over Sulfur-Containing Sorbent at Low Temperatures.

In the work, sulfur-containing sorbents were employed to remove elemental mercury (Hg) from coal-fired flue gas. The work used the thermogravimetric analysis, Brunauer-Emmett-Teller method, scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy to characterize the physicochemical properties of the sorbents. The Hg removal performance of these used sorbents from the simulated coal-fired flue gas was evaluated by a bench-scale fixed-bed reactor. The results indicated that a generous amount of elemental sulfur covered the surface and pore structure of the used sorbent. With the rise of HS selective oxidation temperature, both the sulfur content and specific surface area decreased rapidly. Used-Fe/SC120 could achieve the mercury removal efficiency of above 90% at 90 °C. The high temperature was not conducive to the mercury capture due to the release of surface elemental sulfur. The presence of O and SO inhibited Hg removal in different degrees because of the decreased active sulfur sites and competitive adsorption. Meanwhile, NO promoted the Hg removal efficiency by enhancing the Hg oxidation. The further analysis showed that the surface elemental sulfur was vital to capture the Hg from coal-fired flue gas, which reacted with Hg to form HgS.