The role of iodine monochloride for the oxidation of elemental mercury.

The removal of Hg(0) by the homogenous gas-phase reaction and particle-induced reaction was investigated under various conditions. Iodine monochloride was found to be efficient for Hg(0) oxidation, with the apparent 2nd-order rate constant of about 10.5(±0.3)×10(-17) cm(3) molecules(-1) s(-1) and 5.7(±0.3)×10(-17) cm(3) molecules(-1) s(-1) at 273 K and 373 K, respectively. The pilot-scale tests showed that the removal of Hg(0) by ICl increased significantly in presence of flyash. It was predicted that over 90% of Hg(0) removal efficiency can be obtained with 0.2 ppmv ICl and 20 g/m(3) flyash in flue gas. Though the reaction between Hg(0) and ICl was by far faster than that of Hg(0)/Cl(2), the major product was found to be HgCl(2) rather than HgI(2), which implicated that iodine might partly act as the accelerant in Hg(0) oxidation by facilitating the formation of certain intermediates. The results indicated that using ICl to oxidize elemental mercury in coal-fired flue gas can save the consumption of iodine, and it appeared to be a promising oxidant to enhance the removal of Hg(0).