The role of iodine monochloride for the oxidation of elemental mercury

The removal of Hg0 by the homogenous gas-phase reaction and particle-induced reaction was investigated under various conditions. Iodine monochloride was found to be efficient for Hg0 oxidation, with the apparent 2nd-order rate constant of about 10.5(±0.3) × 10−17 cm3 molecules−1 s−1 and 5.7(±0.3) × 10−17 cm3 molecules−1 s−1 at 273 K and 373 K, respectively. The pilot-scale tests showed that the removal of Hg0 by ICl increased significantly in presence of flyash. It was predicted that over 90% of Hg0 removal efficiency can be obtained with 0.2 ppmv ICl and 20 g/m3 flyash in flue gas. Though the reaction between Hg0 and ICl was by far faster than that of Hg0/Cl2, the major product was found to be HgCl2 rather than HgI2, which implicated that iodine might partly act as the accelerant in Hg0 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 Hg0.