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WHY DOES FLUE GAS ELEMENTAL MERCURY CONCENTRATION INCREASE ACROSS A WET SCRUBBER?
Citation:
Chang*, J.C S. AND S. B. Ghorishi. WHY DOES FLUE GAS ELEMENTAL MERCURY CONCENTRATION INCREASE ACROSS A WET SCRUBBER? Presented at A&WMA Mega Symposium on Power Plant Air Pollution Control, Washington, DC, 19-22 May 2003.
Description:
The paper describes the results of research investigating the potential reduction of oxidized mercury (Hg2+) to elemental mercury (Hg0) and subsequent emission of Hg0 from wet scrubbers. Experiments were performed in a bench-scale, wet scrubber simulator containing solutions used as a typical scrubbing liquor. HgCI2-laden gases were continuously introduced into the simulator, and emissions of Hg0 were monitored. It was found that emissions of Hg0 were obtained when S(IV), in the form of sulfite and bisulfite compounds, were added to the scrubbing liquor. Literature data suggests that the absorbed Hg2+ readily forms complexes with S(IV) ions. Apparently, the Hg*S(IV) complexes are unstable and the Hg2+ is rapidly reduced and emitted as Hg0. The experimental data were analyzed by a first-order reaction model which assumes that the rate of the reduction of Hg2+ is controlled by the concentration of Hg*S(IV) complexes in the scrubbing liquor. The experimental data and model predictions indicated that the flue gas Hg0 concentration increase across wet scrubbers can result from emissions of reduced Hg2+ in the presence of S(IV) in the scrubbing liquor.