Mercury Removal from Coal Combustion Flue Gas by Fly Ash

The effect of physicochemical properties on the mercury adsorption performance of three fly ash samples has been investigated. The samples were tested for mercury adsorption using a fixed-bed with a simulated gas. X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy and other methods were used to characterize the samples. The results indicate that mercury adsorption on fly ash is mainly physisorption and chemisorption. Uncompleted burned carbon is an important factor for the improvement of mercury removal efficiency, especially, the C-M bond may improve the oxidation of mercury, which formed via the reaction of C and Ti, Si and other elements. The higher specific surface areas and smaller pore diameter are all beneficial for the high mercury removal efficiency. The presence of O₂ plays a positive role on Hg adsorption of modified fly ash, while SO₂ has double role of inhibition because of competitive adsorption and promotion to chemisorption. In addition, sample modified with FeCl₃ has a great performance in Hg removal.