Temperature-programmed decomposition desorption of mercury species over activated arbon sorbents for mercury removal from coal-derived fuel gas†

The mercury (Hg⁰) removal process for coal-derived fuel gas in the integrated gasification combined cycle (IGCC) process will be one of the important issues for the development of a clean and highly efficient coal power generation system. Recently, iron-based sorbents, such as iron oxide (Fe ₂O₃), supported iron oxides on TiO₂, and iron sulfides, were proposed as active mercury sorbents. TheH₂S is one of the main impurity compounds in coal-derived fuel gas; therefore, H₂S injection is not necessary in this system. HCl is also another impurity in coal-derived fuel gas. In this study, the contribution of HCl to the mercury removal from coal-derived fuel gas by a commercial activated carbon (AC) was studied using a emperatureprogrammed decomposition desorption (TPDD) technique. The TPDD technique was applied to understand the decomposition characteristics of the mercury species on the sorbents. The Hg⁰-removal experiments were carried out in a laboratory-scale fixed-bed reactor at 80-300 ⁰C using simulated fuel gas and a commercial AC, and the TPDD experiments were carried out in a U-tube reactor in an inert carrier gas (He orN2) after mercury removal. The following results were obtained from this study: (1) HCl contributed to the mercury removal from the coal-derived fuel gas by the AC. (2) The mercury species captured on the AC in the HCl- and H₂S-presence system was more stable than that of the H₂S-presence system. (3) The stability of the mercury surface species formed on the AC in the H ₂S-absence and HClpresence system was similar to that of mercury chloride (HgCl_x) species. copyright