Integrative process of preoxidation and absorption for simultaneous removal of SO2, NO and Hg0

• An innovative aqueous complex oxidant (ACO) composed of NaClO2 and NaBr was prepared.
• A novel flue gas purification integrative process of preoxidation by vaporized ACO and Ca(OH)2 absorption was proposed.
• The simultaneous removal efficiencies of SO2, NO and Hg0 were 100%, 91% and 93%, respectively.
• The reaction mechanism of simultaneous removal of SO2, NO and Hg0 was proposed.

This paper proposes a novel semidry integrative process for simultaneous removal of SO2, NO and Hg0, in which, the insoluble NO and Hg0 are first pre-oxidized by a vaporized aqueous complex oxidant (ACO) composed of NaClO2 and NaBr, then NO2 and Hg2+ are absorbed by Ca(OH)2. The effects of various influencing factors such as the molar ratio of NaClO2 to NaBr in ACO, the injection rate of ACO, the ACO pH, the reaction temperature and the concentrations of O2, CO2, NO and SO2 on the simultaneous removal were systematically investigated, and the average simultaneous removal efficiencies were 100%, 91% and 93% for SO2, NO and Hg0, respectively under the optimal reaction conditions. The reaction mechanism was proposed based the characterizations of removal products by UV–Vis, SEM, XRD, EDS, XPS and AFS, and the literature references.