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Title: Confounding effects of aqueous-phase impinger chemistry on apparent oxidation of mercury in flue gases

Gas-phase reactions between elemental mercury and chlorine are a possible pathway to producing oxidized mercury species such as mercuric chloride in combustion systems. This study examines the effect of the chemistry of a commonly used sample conditioning system on apparent and actual levels of mercury oxidation in a methane-fired, 0.3 kW, quartz-lined reactor in which gas composition (HCl, Cl{sub 2}, NOx, SO{sub 2}) and quench rate were varied. The sample conditioning system included two impingers in parallel: one containing an aqueous solution of KCl to trap HgCl{sub 2}, and one containing an aqueous solution of SnCl{sub 2} to reduce HgCl{sub 2} to elemental mercury (Hg{sup 0}). Gas-phase concentrations of Cl{sub 2} as low as 1.5 ppmv were sufficient to oxidize a significant fraction of the elemental mercury in the KCl impinger via the hypochlorite ion. Furthermore, these low, but interfering levels of Cl{sub 2} appeared to persist in flue gases from several doped rapidly mixed flames with varied post flame temperature quench rates. The addition of 0.5 wt% sodium thiosulfate to the KCl solution completely prevented the oxidation from occurring in the impinger. The addition of thiosulfate did not inhibit the KCl impinger's ability to capture HgCl{sub 2}. The effectivenessmore » of the thiosulfate was unchanged by NO or SO{sub 2}. These results bring into question laboratory scale experimental data on mercury oxidation where wet chemistry was used to partition metallic and oxidized mercury without the presence of sufficient levels of SO{sub 2}. 23 refs., 5 figs., 1 tab.« less
Authors:
; ; ; ; ;  [1]
  1. University of Utah, Salt Lake City, UT (United States). Department of Chemical Engineering
Publication Date:
OSTI Identifier:
21049831
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 42; Journal Issue: 7; Other Information: brydgercauch@yahoo.com
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; MERCURY; FLUE GAS; OXIDATION; BENCH-SCALE EXPERIMENTS; CHLORINE; SIMULATION; NITRIC OXIDE; CONCENTRATION RATIO; SULFUR DIOXIDE; THIOSULFATES; CHEMICAL STATE; AQUEOUS SOLUTIONS; MERCURY CHLORIDES; POTASSIUM CHLORIDES; TIME DEPENDENCE; IMPINGEMENT; CHEMICAL REACTIONS