Different Design Strategies for Metal Sulfide Sorbents to Capture Low Concentrations of Gaseous Hg in Coal-Fired Flue Gas and High Concentrations of Gaseous Hg in Smelting Flue Gas.

Capturing gaseous Hg using regenerable metal sulfides is a promising technology to recover gaseous Hg from both coal-fired flue gas (CFG) and smelting flue gas (SFG) for the centralized control. Gaseous Hg concentration in SFG is 2-3 orders of magnitude higher than that in CFG; therefore, the design strategy of metal sulfides for capturing gaseous Hg from CFG is quite different from that from SGF. In this work, the structure-activity relationship of metal sulfides to capture Hg was investigated according to the remarkable difference in MoO loading on sulfureted FeTiO to capture low/high concentrations of gaseous Hg. The rate of Hg adsorption onto metal sulfides was mainly related to the amounts of adsorption sites and S on the surface, the affinity of adsorption sites to gaseous Hg, and the gaseous Hg concentration. Meanwhile, the capacity for Hg adsorption was approximately equal to the less of the amount of adsorption sites and S on the surface. Furthermore, capturing low concentrations of gaseous Hg from CFG required the metal sulfide sorbents having more adsorption sites with strong affinity to gaseous Hg, while capturing high concentrations of gaseous Hg from SFG required the sorbents with enough adsorption sites.