Enhanced elemental mercury removal from coal-fired flue gas by sulfur-chlorine compounds
- University of California, Berkeley, CA (United States). Environmental Energy Technology Division
Oxidation of Hg{sup 0} with any oxidant or converting it to a particle-bound form can facilitate its removal. Two sulfur-chlorine compounds, sulfur dichloride (SCl{sub 2}) and sulfur monochloride (S{sub 2}Cl{sub 2}), were investigated as oxidants for Hg{sup 0} by gas-phase reaction and by surface-involved reactions in the presence of flyash or activated carbon. The gas-phase reaction between Hg{sup 0} and SCl{sub 2} is shown to be more rapid than the gas-phase reaction with chlorine, and the second order rate constant was 9.1({+-}0.5) x 10{sup -18} mL-molecules{sup -1}.s{sup -1} at 373 K. The presence of flyash or powdered activated carbon in flue gas can substantially accelerate the reaction. The predicted Hg{sup 0} removal is about 90% with 5 ppm SCl {sub 2} or S{sub 2}Cl{sub 2} and 40 g/m{sup 3} of flyash in flue gas. The combination of activated carbon and sulfur-chlorine compounds is an effective alternative. We estimate that co-injection of 3-5 ppm of SCl{sub 2} (or S{sub 2}Cl{sub 2}) with 2-3 Lb/MMacf of untreated Darco-KB is comparable in efficiency to the injection of 2-3 Lb/MMacf Darco-Hg-LH. Extrapolation of kinetic results also indicates that 90% of Hg{sup 0} can be removed if 3 Lb/MMacf of Darco-KB pretreated with 3% of SCl{sub 2} or S{sub 2}Cl{sub 2} is used. Mercuric sulfide was identified as one of the principal products of the Hg{sup 0}/SCl{sub 2} or Hg{sup 0}/S{sub 2}Cl{sub 2} reactions. Additionally, about 8% of SCl{sub 2} or S{sub 2}Cl{sub 2} in aqueous solutions is converted to sulfide ions, which would precipitate mercuric ion from FGD solution. 14 refs., 5 figs., 1 tab.
- OSTI ID:
- 21222272
- Journal Information:
- Environmental Science and Technology, Vol. 43, Issue 14; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
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