Efficient removal of Hg0 from cement kiln flue gas using CexFeyOz composite catalyst.

ABSTRACT

In this study, a kind of CexFeyOz composite with oxygen vacancy structure and strong oxygen storage capacity was prepared by coprecipitation method. Under the condition of no HCl of flue gas, the Hg0 in the flue gas of cement kiln was efficiently and economically removed by using 6-8% oxygen. The results showed that the optimum preparation conditions of the catalyst were Ce-Fe molar ratio of 1-11 and calcination temperature of 550 °C. In addition, the reaction temperature, space velocity, the concentration of O2, SO2, and NO had significant effects on the removal efficiency of Hg0 at different rates. More precisely, at the reaction temperature of 350 °C, low airspeed, high concentration of O2, and low concentration of SO2 and NO, the efficiency reached the highest value. According to XPS results, the elemental valence of the CexFeyOz composite changed after the reaction. The redox pairs of Ce3+-Ce4+ and Fe3+-Fe2+ had the ability to transfer electrons, which enabled more oxygen adsorbed on the catalyst surface to be converted into O2-, leading to the improvement of the oxidation efficiency of Hg0.