Coal-fired power plants is the emission sources of the mercury in the atmosphere, and measures for the mitigation of mercury emission are needed. In fact, at present coal-fired power plants, the mercury in the flue gas is removed with fly ash and desulfurization gypsum at electrostatic precipitator and wet flue gas desulfurization system, respectively. The by-products produced by coal-fired power plants such as fly ash and desulfurization gypsum are used as cement materials or gypsum boards. However, the presence of mercury in the by-products is a concern of re-release. The potential re-emission of mercury from a by-products depends on the chemical form of the mercury in it. In order to control the re-emission of mercury, to clarify of mercury forms in by-products is very important.<br/>In this study, an analysis of the chemical form of mercury in the desulfurization gypsum from a coal-fired power plant was performed by combining temperature programmed desorption (TPD) method and cold vapor atomic absorption. The TPD curve of the model sample for each mercury compound showed a unique peak temperature, and the chemical form of mercury was identified by comparing the peak temperature with that of the desulfurization gypsum. A linear combination of the TPD curve of each model sample was curve-fitted to that of the desulfurization gypsum. The ratio of each form of mercury present in the desulfurization gypsum was calculated from the area ratio of the TPD curve of the model sample used in the analysis. The results indicated that mercury in the desulfurization gypsum was mainly adsorbed mercury by unburned carbon.

Mercury forms in FGD gypsum produced from different FGD systems

2019 Fall National Meeting

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