Comparing and interpreting laboratory results of Hg oxidation by a chlorine species

Several researchers have performed experimental work in attempts to explain the effects of various flue-gas components on the oxidation of elemental mercury (Hg-0). Some have concluded that water (H2O) inhibits Hg oxidation by chlorine (Cl-2). In recently published work, it was found that sulfur dioxide (SO2) and nitric oxide (NO) also have an inhibitory effect on Hg oxidation. This paper aims to serve three purposes. First, to present data obtained in a laboratory scale apparatus, designed to test the effects of Cl-2 on the oxidation of Hg-0 with respect to temperature. The results show that as temperature increases, Cl-2 is less effective as an Hg oxidizing agent. Second, this paper presents a consolidation of data taken from several sources, where the effects of various flue-gas components on the oxidation of Hg-0 is observed and discussed. The summary of these results shows the following general trends: at high temperatures, hydrogen chloride (HCl) is the primary chlorine species responsible for Hg-0 oxidation, while at lower temperatures, Cl-2 is the dominant species. Third, a simple two reaction model is suggested to predict the experimental data shown in this paper. The results show that the predicted percent Hg oxidation values correspond very well with the observed experimental values. (C) 2007 Elsevier B. V. All rights reserved.