Catalytic Oxidation and Stabilized Adsorption of Elemental Mercury from Coal-Derived Fuel Gas

Abstract

The aim of this study is to develop an efficient process for the stabilized removal of elemental mercury (Hg0) from coal-derived fuel gas by the aid of the catalytic oxidation of Hg0 over activated carbon (AC). The experiments were performed in the temperature range of 120–240 °C with simulated coal-derived gases containing varying concentrations of CO, H2, CO2, H2O, and H2S. O2 was introduced to promote the oxidation reaction between H2S and Hg0 over the AC sorbent to form mercury sulfide (HgS). The results indicated that the Hg0 removal capacity of AC could be dramatically improved in the presence of both H2S and O2. The presence of O2 was indispensable for the efficient and stable removal of Hg0 from H2S-containing fuel gas. The high temperature and high content of reducing gases, such as CO and H2, may inhibit the oxidation reaction and decrease the Hg0 removal efficiency, whereas the high content of H2O can promote Hg0 removal. On the basis of thermodynamic analysis, as well as the temperature-programmed decomposition (TPD) and X-ray photoelectron spectroscopy (XPS) characterization of the sorbents, it is suggested that the partial oxidation of H2S with O2 to active sulfur may contribute to the stabilized removal of Hg0 by the reaction of active sulfur with Hg0 to form HgS.