燃煤电厂汞排放特性实验研究

Mercury emission characteristics from coal-fired power plants

选取了我国6个比较有代表性的燃煤电厂,采用美国EPA推荐使用的OH方法,对其入炉煤、底渣、飞灰、脱硫产物及烟气进行了取样分析,并针对系统汞的排放进行了平衡计算.测量了不同电厂的除尘器灰的含碳量,以分析其对飞灰中汞富集因子的影响.实验结果表明:在所测的6个燃煤电厂中,底渣排汞量不到总汞的1%,煤中的汞在燃烧区域以后绝大部分以气态和飞灰吸附态的形式排放,并随着机组容量的增大,气态汞的排放比例也有所增大.飞灰中的残碳对气态汞向飞灰的富集有促进作用,飞灰的含碳量与飞灰中汞的富集因子呈正相关关系.烟气中的氯元素可以提高可溶性二价汞的含量.实验研究表明,循环流化床燃烧方式可以极大地减少气态汞的排放量,其机理还有待于进一步研究.

To evaluate the mercury emissions, and to comprehend and compare the speciation characteristics of mercury in different power plants, six representative coal-fired power plants were selected, of which there were five pulverized coal boilers and one circulating fluidized bed boiler, whose capacities ranged from 50 MW to 600 MW with different flue gas cleaning up devices such as electrostatic precipitator （ESP）, fabric filter （FF） and flue gas desulfurization （FGD）. Samples of feeding coal, bottom ash, fly ash, desulfurization sorbent and flue gas were taken at the inlet and outlet of pollution control devices from the six different coal-fired power plants. The results of mercury emission and mercury balance show that the mercury speciation distribution changes greatly depending on coal types, combustion boilers and different air pollution control devices （APCD）. The fly ash exerts dif- ferent influences on mercury adsorption, and the chlorine content in flue gas can convert more oxidized mercury. It is shown that circulating fluidized bed combustion （CFBC） can decrease the total gaseous mercury emission, however the mechanism needs to be further investigated.