Investigation on mercury removal method from flue gas in the presence of sulfur dioxide.

A new integrated process was developed for the removal and reclamation of mercury from the flue gas in the presence of SO2, typically derived from nonferrous metal smelting. The new process contains a pre-desulfurization unit (Stage I) and a co-absorption unit (Stage II). In Stage I, 90% of the SO2 from flue gas can be efficiently absorbed by ferric sulfate and reclaimed sulfuric acid. Meanwhile, the proportion of Hg(2+) and Hg(0) in the flue gas can be redistributed in this stage. Then, over 95% of the Hg(0) and the residual SO2 can be removed simultaneously with a composite absorption solution from the flue gas in Stage II, which is much more efficient for the Hg(0) reclaiming than the traditional method. The composite absorption solution in Stage II, which is composed of 0.1g/L HgSO4, 1.0% H2O2 and H2SO4, could effectively remove and reclaim Hg(0) overcoming the negative effect of SO2 on Hg(0) absorption. Moreover, the concentrations of HgSO4 and H2O2 were adjusted with the changes in of the concentrations of Hg(0) and SO2 in the flue gas. It is a potential and promising technology for the mercury removal and reclaim from the flue gas in the presence of SO2.