An integrative process for Hg0 removal using vaporized H2O2/Na2S2O8

• An innovative liquid-phase multi-component absorbent (LMA) for Hg0 removal was prepared.
• A novel flue gas purification integrative process of preoxidation by vaporized LMA and Ca(OH)2 absorption was proposed.
• The simultaneous removal efficiencies of SO2, NO and Hg0 were 100%, 83.2% and 91.5%, respectively.
• The reaction mechanism of simultaneous removal of SO2, NO and Hg0 was proposed.

In this paper, a novel integrative process of preoxidation of Hg0 to Hg2+ by a vaporized liquid-phase multi-component oxidant (LMO) made up of H2O2 and Na2S2O8 and then Ca(OH)2 absorption for removing Hg0 from coal-fired flue gas is proposed. For the establishment of optimal reaction conditions, the effects of various key factors such as concentration ratio of Na2S2O8 to H2O2, pH of LMO, addition rate of LMO, reaction temperature and concentrations of CO2, O2, SO2 and NO on Hg0 removal were investigated systematically. The results indicated that the Hg0 removal efficiency was significantly affected by the pH of LMO, the reaction temperature and the addition rate of LMO. The influences of other gases, such as O2, CO2 and SO2, could be neglected; however, the effect of NO was either promotion or inhibitory, depending on its concentration. Under the optimal reaction conditions, the simultaneous removal efficiencies of 100% for SO2, 83.2% for NO and 91.5% for Hg0 were obtained. Based on the references and the characterizations of removal products by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and cold vapor atom fluorescence spectrometry (CVAFS), the reaction mechanism of removing SO2, NO and Hg0 and the kinetics of Hg0 removal were put forward.

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