Performance of CuOx-neutral Al2O3 sorbents on mercury removal from simulated coal combustion flue gas

Copper based sorbents are used to control mercury emissions in coal-fired flue gas. CuOx impregnated on neutral Al2O3 (CuOx-Al2O3) sorbents were found to enhance catalytic oxidation of elemental mercury in the presence of hydrogen chloride (HCl). The Hg-0 oxidation rates increased along with the increasing HCl concentration and temperature. The mercury oxidation rates were over 65% in the presence of 50 ppm HCl and the mercury adsorption amounts were over 75% in the early stage of the mercury removal process. CuOx-Al2O3 sorbents demonstrated good mercury removal capacity. The effect of HCl is due to the formation of active chlorine. CuOx-Al2O3 sorbents also have excellent sulfur resistance in the presence of HCl. A mixture of CuOx-Al2O3 and activated carbon can remove more than 90% Hg-0 with a lower mercury removal cost for industrial applications. The characterizations of the CuOx-Al2O3 sorbents were measured suggesting CuOx species work as catalysts via the redox shift between Cu2+ and Cu+. The mercury oxidation mechanism of the sorbents is proposed to follow the Mars-Maessen mechanism. (C) 2014 Elsevier B.V. All rights reserved.