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Mercury Speciation of Flue Gas Desulphurization By-Products in Coal-Fired Power Plants in China

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Document pages: 11 pages

Abstract: The aim of this study was to develop and examine the morphology anddistribution of mercury (Hg) in flue gas desulfurization (FGD) by-product. Mercuryin the coal of coal-fired power plants is concentrated in the by-products ofdesulfurization process, and it is widely used as an additive in cement,building materials and other industries. Due to the different stability ofvarious forms of mercury in the environment, subsequent use of productscontaining desulfurization by-product additives will continue to be releasedinto the environment, endangering human health. Therefore, it is very necessaryto study the form and distribution of mercury in the by-products ofdesulfurization in coal-fired power plants to provide a theoretical basis forsubsequent harmless treatment. Forcontent and morphology of mercury analysis, 1 sample of dry FGD ash and 6samples of wet FGD gypsum were analyzed. The total 7 samples were extractedusing a modification of sequential chemical extractions (SCE) method, which wasemployed for the partitioning Hg into four fractions: water soluble, acidsoluble, H2O2 soluble, andresidual. The Hg analysis was done with United States Environmental ProtectionAgency (USEPA) method 7471B. Comparing with the wet FGD gypsums of coal-fired boilers, thetotal Hg content in the dry FGD by-product was as high as 1.22mg kg, while the total Hg content in the FGD gypsum is 0.23 - 0.74mg kg, which was 2 times over the wet FGD gypsum. The concentration of watersoluble Hg in the dry FGD by-product was the highest amount (0.72 mg kg), accountingfor 59.02 of the total mercury. While residual Hg content was 0.16 mg kg, onlyabout 13.11 of the total mercury. Mercury content in FGD gypsum was expressedin the form of ρ (residual Hg) > ρ (H2O2 soluble Hg) > ρ (water soluble Hg) > ρ (acid soluble Hg). The morphology and distribution of mercury in FGDby-products is supposed to be analyzed before utilization, and the impact ofmercury on the environment should be considered.

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