Simultaneous removal of SO2, NO and Hg0 through an integrative process utilizing a cost-effective complex oxidant

Abstract

A novel process of pre-oxidation combining with post-absorption to simultaneously remove SO2, NO and Hg0 from flue gas was proposed. A vaporized complex oxidant (CO) consisted of cost-effective H2O2 and NaClO2 was prepared to oxidize Hg0 and NO, then the oxidation products were absorbed by the Ca(OH)2 solution that was followed. For the establishment of the optimal reaction conditions, the influences of various reaction factors on the simultaneous removal of SO2, NO and Hg0 were investigated, i.e., the molar ratio of H2O2 to NaClO2 in CO, the adding rate of CO, the pH of CO, the reaction temperature, the flue gas residence time and the coexistence gases. The experimental results indicated that the desulfurization was constant in all tests, whereas the removal of NO and Hg0 was primarily affected by the NaClO2 addition, the adding rate of CO, the pH of CO, and the reaction temperature. Meanwhile, NO and SO2 were characterized as the promoters for the Hg0 removal. Under the optimal reaction conditions, the best simultaneous removal efficiencies were 100% for SO2, 87% for NO and 92% for Hg0. According to the characterizations of removal products by UV–vis, EDX, XRD, AFS and XPS, the reaction mechanism was speculated.