Mercury chemistry of brominated activated carbons – Packed-bed breakthrough experiments

Abstract

Coal-fired power plants provided between 45% and 50% of the United States net energy generation in the years between 1999 and 2010 and will continue to be a primary source of electricity into the future. Among the major environmental concerns of coal utilization is the release of mercury (Hg), which was recently regulated by the US EPA in the Mercury and Air Toxics Standards (MATS) ruling in December 2011. Among the variety of potential methods for Hg capture, activated carbon injection (ACI) is viewed by the EPA as a viable, ready technology available to energy utilities to comply with MATS. However, there remain significant questions regarding the complicated interaction between the carbon sorbent, Hg, and contaminants present in combustion flue gas, such as SO2 and NOx (NO and NO2). In this study, bromine-impregnated carbon fiber (Br-ACF) was tested for Hg capture and oxidation in a controlled flue gas environment to elucidate trends in the interaction of the flue gas components. These results are compared with prior surface analysis results from this group to provide additional support to prior conclusions. Compared to baseline capture rates in a clean environment, results indicate that NOx promotes the oxidation of Hg, while SO2 prevents the adsorption or oxidation of Hg on the Br-ACF.