Mercury in Chinese Coals: Modes of Occurrence and its Removal Statistical Laws during Coal Separation
2017
Pan, Jin-He | Zhou, Chang-Chun | Cong, Long-Fei | Zhang, Ning-Ning | Liu, Cheng | Peng, Chang-Bin | Ouyang, Chang-Heng
As one of the dangerous trace elements in coal, mercury has become an advanced research hotspot in coal purification. The content of ash, sulfur, and mercury of raw coals from four high-Hg coal preparation plants located in the main production areas of China was tested. To distinguish the connection between mercury content and the content of ash or sulfur, person correlation analysis and regression correlation analysis were performed by SPSS. The modes of occurrence of mercury in coal samples of these four plants were studied by sequential chemical extraction procedure (SCEP). The laws of mercury removal during coal preparation were researched by analyzing the mercury contents of feedings and products from the four plants. Results showed that mercury in coal was significantly associated with inorganic constituents or sulfur or both of them. The sulfide associated form is the dominant mode of occurrence of mercury in coals. Removal statistical laws of mercury during the process of preparation can be summarized as follows: (1) mercury in coal tends to concentrate in the fine fraction; (2) dense medium separation has a more obvious effect on mercury removal than flotation; (3) qualified clean coal products with up to standard mercury content are difficult to obtain by a conventional gravity separation or flotation process. This work facilitates understanding of the modes of mercury occurrence in other Chinese coals, and provides a foundation for removal of mercury in clean coal technology.
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