燃煤电厂石灰石-石膏湿法脱硫系统中痕量元素的迁移分布规律

燃煤电厂是煤炭消耗的主力军，煤炭在燃烧过程中，大量痕量元素随烟气排出.随着我国环保要求的不断提高，燃煤电厂的痕量元素排放受到广泛关注.石灰石-石膏湿法烟气脱硫(WFGD)系统不仅能高效吸收烟气中的SO₂，同时影响痕量元素的迁移分布.本研究对安徽省3个超低排放燃煤电厂的WFGD系统中进/出口烟尘、石灰石、工业水、污泥、石膏和脱硫废水等环境样品进行了采集，研究了Cr、As、Cd、Pb和Hg等痕量元素的迁移分布特征.结果表明：(1)WFGD系统对烟尘中痕量元素的去除率在95%以上，脱硫污泥中Cr、As和Hg浓度分别为29.9～52.2、12.5～36.7和2.2～6.5 mg/kg，约为石膏中Cr、As和Hg浓度的7～9倍.(2)元素质量平衡分析表明，痕量元素主要来源于烟气和石灰石，主要输出为污泥和石膏，废水中仅富集少量Cd.研究显示，脱硫石膏和污泥的处置及再利用过程中需着重关注痕量元素的环境影响.

Migration and Distribution Patterns of Trace Elements in Limestone-Gypsum Wet Flue Gas Gesulfurization System of Coal-Fired Power Plants

Coal-fired power plants are the primary coal consumers. During the combustion process of coal, many trace elements are discharged with flue gas. With the continuous improvement of China's environmental protection requirements, the emissions of trace elements from coal-fired power plants have received extensive attention. The limestone-gypsum wet flue gas desulfurization (WFGD) system can not only efficiently absorb SO₂ in flue gas, but also affect the migration and distribution of trace elements. This study collected environmental samples, including inlet/outlet dusts, limestone, industrial water, sludge, gypsum, and desulfurization wastewater in WFGD system of three typical ultra-low emission power plants in Anhui Province. The migration and distribution characteristics of trace elements, including Cr, As, Cd, Pb and Hg, were analyzed. The results showed that the removal rate of trace elements in the dust by WFGD system was over 95%. The concentrations of Cr, As, and Hg in desulfurized sludge were 29.9-52.2, 12.5-36.7, and 2.2-6.5 mg/kg, respectively, which are 7-9 times the concentration of Cr, As and Hg in gypsum. Elemental mass balance analysis showed that trace elements mainly came from dust and limestone, and were mainly trapped in sludge and gypsum. Only a small amount of Cd was accumulated in wastewater. This study indicated that the desulfurization gypsum and sludge disposal and reuse should focus on the environmental effects of the trace elements.