The Effect of CaBr2 on Mercury Speciation in Flue Gas: An Experimental and DFT Study

Abstract

Background: Additives affect the formation of different mercury speciation in coal-fired derived flue gas. Objective: In order to study the effect of the additive CaBr2 content, the Ontario Hydro Method (OHM) method has been applied to analyze the mercury speciation at the entrance and export of denitration (SCR). Method: Density Functional Theory (DFT) has been used to study the adsorption of mercury halide on unburned carbon surface. Result: The results show that along with the increasing amount of additive CaBr2, there is an increasing trend of the ratio of Hg2+ in flue gas. Conclusion: CaBr2 addition contributes to oxidize Hg 0 to Hg2+ and increase the mercury concentration through SCR. DFT results indicate that the adsorption of HgBr and HgBr2 on unburned carbon surface is chemisorption, and Br-C bond is stronger than Hg-C bond, both these bonds are covalent interaction.