Mercury research at the University of Utah has focused on gas-phase oxidation by chlorine and bromine under air-fired and oxygen-fired (27% O2 in CO2) conditions. The experimental work has been performed in a bench-scale, laminar, methane-fired, 300 W, quartz-lined reactor. Mercury concentrations and species have been measured using a wet conditioning system and a Tekran 2537A mercury analyzer.
The results of Preciado et al. (2014) show that oxy-firing produces modest increases in mercury oxidation. With chlorine concentrations of 100 to 500 ppmv (as HCl) the extents of oxidation range from 6 to 21% for oxy-firing and from 4 to 15% for air-firing. With bromine concentrations of 10 to 50 ppmv (as HBr) extents of oxidation range from 43 to 69% for oxygen-firing and from 15 to 46% for air-firing. Higher extents of oxidation under oxy-firing conditions are understandable given that the CO2 molecule is a more effective third body than N2; carbon dioxide is more effective than N2 at stablizing the HgCl and HgBr transition state complexes.
Preciado, I., T. Young, and G.D. Silcox, “Mercury Oxidation by Halogens under Air- and Oxygen-Fired Conditions,” Energy and Fuels, 28, 1255-1261, 2014