Thermal Stability and Adsorption of Mercury Compounds in Fly Ash

Fly ashes were collected from five power plants under two loads in China. The ashes were heated at four different temperatures, and mercury speciation was determined based on the release regular pattern of mercury with temperature. The mercury concentration, unburned carbon content and mean ash particle sizes were measured. The correlation of mercury capture and unburned carbon content, mean ash particle sizes were analyzed. Results indicate that the amount of unburned carbon and mercury adsorb is significantly positively correlated in fly ash; the smaller the mean ash particle size, the more mercury particles are captured. There was little HgO and HgSO4, and the main form of mercury compounds in fly ash were HgCl2 and HgS. The high element Cl content can result in high HgCl2 ratio in particular mercury and element S play an important role in adsorbing mercury.