| Coal is the major source of power nowadays. Mercury emissions attributed to coal combustion caused great harm to the global ecological environment and human health. It has become a hot research topic that how to control mercury emissions from coal combustion. It is essential to analyze the mercury speciation distribution in the flue gas, because the physical and chemical properties are different in the different forms. Mercury in coal can be removed without heat value loss in the process of pyrolysis under low temperature by using mild thermal upgrading.Two coal samples with high mercury content from Guizhou province were selected in the study. Firstly, the releasing characteristics and speciation distribution of mercury during mild thermal upgrading process before coal combustion were studied. Then the software of chemical thermodynamic calculation was used to predict the speciation distribution of mercury in flue gases during combustion and pyrolysis.The mild thermal upgrading experiment was carried out by using a horizontal tube furnace. The releasing characteristics and speciation distribution of mercury were studied under different temperatures, atmospheres, residence times and heating rates. The mercury in coal was analyzed by DMA80. The gaseous mercury was collected by using Ontario hydro method and analyzed by QM201. It indicates that temperature is the primary factor affected on the mercury release. The mercury release efficiency is highly improved between 350 and 400℃under low-oxidizing atmosphere and the percentage of divalent mercury is higher.Finally, FactSage5.4, the software of chemical thermodynamic calculation was used to predict the speciation distribution of mercury in flue gases during combustion and pyrolysis. The result showed that the atmosphere, the ratio of S and Cl and pressure had significant influences on the speciation distribution of mercury in flue gases. |
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