Removal Of Gaseous Elemental Mercury By Cylindrical Activated Coke Loaded With CoO_x-CeO₂ From Simulated Coal Combustion Flue

Mercury（Hg） is known as hazardous substance and global polutant due to its high volatility, persistence, bioaccumulation and neurological toxicity. Mercury can cause global mercury pollution with its atmospheric diffusion,and do great harm to the environment and human health. The coal-fired power plant has been considered to be the largest anthropogenic source of mercury emission, and elemental mercury（Hg⁰） is the most difficult to be directly removed. As a result, development of adsorbent-catalyst and viable technology for effective remove of Hg⁰ from flue gas is the primary objective and task of mercury control.Co-Cemixed oxides supported on commercial cylindrical activated coke granular（CoCe/AC） were prepared by impregnation method, and its Hg⁰ removal performances were evaluated in a fixed-bed reactor system under simulated coal combustion flue gas conditions at 110²30°C.The effects of Co/Cemolar ratio in CoO_x-CeO₂ mixed oxides, CoO_x-CeO₂ loading value, reaction temperature and flue gas components（O₂, NO, SO₂, H2O） on Hg⁰ removal efficiency were investigated, respectively. BET, XRD, SEM, FTIR, TGA and XPS analysis were employed to analyze the characteristics of the sorbent-catalysts; The synergic effect between CoO_x and CeO₂ as well as the mechanism involved in Hg⁰ removal was investigated.The experimental results showed that the modified AC posessed higher Hg⁰ removal efficiency than virgin AC, moreover, CoCe/AC performed better than Co/AC and Ce/AC, which indicated that CoO_x and CeO₂ have a synergy on Hg⁰ removal. Up to 92.5% of Hg⁰ removal efficiency could be obtained over Co_4.5Ce₆/AC at 170°C. Additionally, different with pure N2 condition, the existence of O₂ and NO could increase Hg⁰ removal efficiency. SO₂ exhibited an inhibitive effect on Hg⁰ removal in the absence of O₂, however, SO₂ can promote Hg⁰ removal process with the aid of O₂. H2O（g） could slightly hinder Hg⁰ removal. The characterization results exhibited that addition of cobalt oxide led to the excellent dispersity of CeO₂ on AC. TGA and XPS analysis results revealed that the captured mercury species on the used Co_4.5Ce₆/AC mainly existed as Hg O, the results illustrated that Hg⁰ removal efficiency of Co_4.5Ce₆/AC resulted from the adsorption and catalytic oxidation of Hg⁰, both lattice oxygen and chemisorption oxygen contributed to Hg⁰ oxidation. Results indicated that within the temperature range of activated coke simultaneous removal of SO₂ and NOx, Co_4.5Ce₆/AC exhibited excellent performance on Hg⁰ removal, appeared to be promising in industrial application.