Temperature-Programmed Decomposition Desorption of Mercury Species over Activated Carbon Sorbents for Mercury Removal from Coal-Derived Fuel Gas

摘要

The mercury (Hg~0) 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_2O_3), supported iron oxides on TiO_2, and iron sulfides, were proposed as active mercury sorbents. The H_2S is one of the main impurity compounds in coal-derived fuel gas; therefore, H_2S injection is not necessary in this system. HCl is also another impurity in coal-derived fuel gas. In this study, the contribution of HO to the mercury removal from coal-derived fuel gas by a commercial activated carbon (AC) was studied using a temperature-programmed decomposition desorption (TPDD) technique. The TPDD technique was applied to understand the decomposition characteristics of the mercury species on the sorbents. The Hg~0-removal experiments were carried out in a laboratory-scale fixed-bed reactor at 80-300 ℃ 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 or N_2) after mercury removal. The following results were obtained from this study: (1) HC1 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 H_2S-presence system was more stable than that of the H_2S-presence system. (3) The stability of the mercury surface species formed on the AC in the H_2S-absence and HC1-presence system was similar to that of mercury chloride (HgCl_x) species.