Mercury Adsorption/Oxidation Mechanisms on Fly Ash Under N2 Atmosphere

Mercury adsorption/oxidation plays a crucial role in mercury transformation during coal combustion. To gain an intuitive understanding of the adsorption/oxidation mechanisms between mercury and fly ash, changes in mercury speciation of fly ash before and after Hg adsorption were investigated using temperature-programmed decomposition–atomic fluorescence spectroscopy (TPD-AFS). The results directly reveal that the primary adsorption/oxidation mechanism between mercury and fly ash is the heterogeneous oxidation reaction of Hg0 to HgCl2. The mercury adsorption capacity exhibits a strong positive correlation with both the unburned carbon (UBC) content and the specific surface area (SSA) of the fly ash, whereas the presence of metal oxides has a negligible effect on mercury adsorption. Higher inlet concentrations of Hg0 enhance mercury adsorption, while flue gas components such as N2, O2, and CO2 have minimal influence on mercury adsorption.