Surface compositions of carbon sorbents exposed to simulated low-rank coal flue gases
- Energy and Environmental Research Center, Grand Forks, ND (US)
Bench-scale testing of elemental mercury (Hg{sup 0}) sorption on selected activated carbon sorbents was conducted to develop a better understanding of the interaction among the sorbent, flue gas constituents, and Hg{sup 0}. The results of the fixed-bed testing under simulated lignite combustion flue gas composition for activated carbons showed some initial breakthrough followed by increased mercury (Hg) capture for up to {approximately}4.8 hr. After breakthrough, the Hg in the effluent stream was primarily in an oxidized form ({gt}90%). Aliquots of selected activated carbons were exposed to simulated flue gas containing Hg{sup 0} vapor for varying time intervals to explore surface chemistry changes as the initial breakthrough, Hg capture, and oxidation occurred. The samples were analyzed by X-ray photoelectron spectroscopy to determine changes in the abundance and forms of sulfur, chlorine, oxygen, and nitrogen moieties as a result of interactions of flue gas components on the activated carbon surface during the sorption process. The data are best explained by a competition between the bound hydrogen chloride (HCl) and increasing sulfur (S(VI)) for a basic carbon binding site. Because loss of HCl is also coincident with Hg breakthrough or loss of the divalent Hg ion (Hg{sup 2+}), the competition of Hg{sup 2+} with S(VI) on the basic carbon site is also implied. Thus, the role of the acid gases in Hg capture and release can be explained. 25 refs., 4 figs., 4 tabs.
- OSTI ID:
- 20638456
- Journal Information:
- Journal of the Air and Waste Management Association, Vol. 55, Issue 6; ISSN 1047-3289
- Country of Publication:
- United States
- Language:
- English
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