Distribution of Mercury in FGD Byproducts

摘要

Recent reports on the partitioning of mercury (Hg) in flue gas desulfurization (FGD)rnsludge have differed on the distribution of Hg between the aqueous and solid phases. Inrnone case, the Hg was accounted exclusively to the fine, rather than crystalline, portionrnof the solid gypsum.In another, Hg was found to be about evenly distributed betweenrnthe gypsum and the recycle water.More effective Hg control strategies can berndeveloped if the Hg is limited to, or more concentrated in, a particular fraction. Forrnexample, handling of the fines as a separate process stream might be beneficial if thernHg was present in that phase preferentially. To investigate the extent of partitioning ofrnHg among the different fractions of the sludge, a size separation based onrnsedimentation was applied to FGD product slurries. Those results showed that Hgrnreported preferentially to the top layer containing the more slowly settling solid. Furtherrnexperiments resulted in the isolation of a mercury-binding phase present in at leastrnsome FGD gypsums.