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Effects of Multi-component Flue Gases on Hg0 Removal over HNO3-Modified Activated Carbon

Tong, Li, Xu, Wenqing, Zhou, Xuan, Liu, Ruihui, Zhu, Tingyu
Energy & Fuels 2015 v.29 no.8 pp. 5231-5236
adsorption, binding capacity, carbon, flue gas, hydrochloric acid, mercuric chloride, mercury, nitric oxide, nitrogen dioxide, sulfur dioxide
The impact of the coexistence of SO₂ and NO in flue gas on Hg⁰ removal over HNO₃-modified activated carbon (HNO₃-AC) was evaluated. In addition, the effect of adding HCl on Hg⁰ removal was also investigated. Hg⁰ removal strongly depends upon the composition of the acidic gas. The results indicated that physically adsorbed SO₂ inhibited Hg⁰ removal because of competitive adsorption, while chemically adsorbed SO₂ slightly promoted Hg⁰ removal by generating HgSO₄. The formation of N-containing active species, such as NO₂, facilitates the removal of Hg⁰ in the presence of NO to primarily produce Hg(NO₃)₂ or HgO. In comparison to the study performed under NO, SO₂ suppressed Hg⁰ removal by weakening the amount of active NO₂ species that were generated over the samples. The presence of HCl strongly affected Hg⁰ removal, and HgCl₂ and Hg₂Cl₂ were produced in all of the flue gases containing HCl. In addition, the binding abilities between mercury and the different groups that formed on the samples follow the order: Cl- > S- > N-containing groups.