Using bromine gas to enhance mercury removal from flue gas of coal-fired power plants
- University of California, Berkeley, CA (United States). Environmental Energy Technology Division, Lawrence Berkeley National Laboratory
Bromine gas was evaluated for converting elemental mercury (Hg{sup 0} to oxidized mercury, a form that can readily be captured by the existing air pollution control device. The gas-phase oxidation rates of Hg{sup 0} by Br{sub 2} decreased with increasing temperatures. SO{sub 2}, CO, HCl, and H{sub 2}O had insignificant effect, while NO exhibited a reverse course of effect on the Hg{sup 0} oxidation: promotion at low NO concentrations and inhibition at high NO concentrations. A reaction mechanism involving the formation of van der Waals clusters is proposed to account for NO's reverse effect. The apparent gas-phase oxidation rate constant, obtained under conditions simulating a flue gas without flyash, was 3.61 x 10{sup -17} cm{sup 3}molecule{sup -1}s{sup -1} at 410 K corresponding to a 50% Hg{sup 0} oxidation using 52 ppm Br{sub 2} in a reaction time of 15 s. Flyash in flue gas significantly promoted the oxidation of Hg{sup 0} by Br{sub 2}, and the unburned carbon component played a major role in the promotion primarily through the rapid adsorption of Br{sub 2} which effectively removed Hg{sup 0} from the gas phase. At a typical flue gas temperature, SO{sub 2} slightly inhibited the flyash-induced Hg{sup 0} removal. Conversely, NO slightly promoted the flyash induced Hg{sup 0} removal by Br{sub 2}. Norit Darco-Hg-LH and Darco-Hg powder activated carbons, which have been demonstrated in field tests, were inferred for estimating the flyash induced Hg{sup 0} oxidation by Br{sub 2}. Approximately 60% of Hg{sup 0} is estimated to be oxidized with the addition of 0.4 ppm of gaseous Br{sub 2} into full scale power plant flue gas. 21 refs., 4 figs., 2 tabs.
- OSTI ID:
- 20862369
- Journal Information:
- Environmental Science and Technology, Vol. 41, Issue 4; Other Information: sgchang@lbl.gov; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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