The role of iodine monochloride for the oxidation of elemental mercury

Abstract

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.