Role of SO ₂ for Elemental Mercury Removal from Coal Combustion Flue Gas by Activated Carbon

Abstract

In order to clarify the role of SO 2 in the removal of mercury from coal combustion flue gas by activated carbon, the removal of Hg 0 vapor from simulated coal combustion flue gas containing SO 2 by a commercial activated carbon (AC) was studied. The Hg 0 removal experiments were carried out in a conventional flow type packed bed reactor system with simulated flue gases having a composition of Hg 0 (4.9 ppb), SO 2 (0 or 500 ppm), CO 2 (10%), H 2O (0 or 15%), O 2 (0 or 5%), and N 2 (balance gas) at a space velocity (SV) of 6.0 × 10 4 h −1 in a temperature rang 60−100 °C. It was found that, for SO 2 containing flue gas, the presence of both O 2 and H 2O was necessary for the removal of Hg 0 and the Hg 0 removal was favored by lowering the reaction temperature in the order of 60 > 80 > 100 °C. The presence of SO 2 in the flue was essential for the removal of Hg 0 by untreated activated carbon. The activated carbons pretreated with SO 2 or H 2SO 4 prior to the Hg 0 removal also showed Hg 0 removal activities even in the absence of SO 2; however, the presence of SO 2 also suppressed the Hg 0 removal of the SO 2-pretreated AC or H 2SO 4 preadded AC.