多变量煤质特性对循环流化床锅炉效率的影响

Effect of multivariable coal quality characteristics on efficiency of CFB boilers

循环流化床燃烧技术是一种比较成熟的洁净煤技术,具有煤种适应性广、燃烧效率高、高效炉内脱硫脱氮及负荷变化范围大等优点,在我国洁净煤发电领域处于优先地位。在目前煤炭市场紧张的形势下,一些燃煤电厂为降低成本、提升自身经济效益,不得不掺烧燃用偏离设计值较多的劣质煤,导致全厂热效率下降,煤耗增加,运行经济性下降。为了研究煤质发生变化时其对锅炉效率的影响,通过锅炉热平衡计算方法,建立多变量煤质特性变化的数学模型,研究煤质特性对锅炉各项热损失的综合影响,获得相应的定量关系。以某超临界循环流化床锅炉燃用不同煤种的燃烧试验为依据,验证了模型的准确性。并以此为基础,探讨了燃用燃料变更为一种矸石、煤泥和末原煤的混煤(BC煤)后锅炉效率的变化。结果表明:随着煤质特性变差,锅炉各项损失增加,变化幅度各不相同,锅炉效率降低。模型计算结果能够为电厂锅炉设计及劣质燃料(矸石、煤泥等)的掺烧提供一定的理论支撑。

Circulating fluidized bed combustion is an advanced and widely used clean coal technology,with fuel flexibility,high combustion efficiency and low emissions etc.In order to lower the fuel cost of the power plant regarding current situation of coal market,low-grade coal is commonly adopted as the blending fuel,which deviates from the designed coal characteristics.However,variations of coal quality result in lower boiler efficiency and higher coal consumption.In the present study,a mathematic model is presented based on the heat balance calculation of the boiler,to investigate the effects of the coal characteristics with multivariable parameters on the heat losses quantitatively.The accuracy of the model is verified by the test results with various coal types in a supercritical CFB boiler.Further research and estimation on the boiler efficiency with a blend fuel(BC coal)consisting of coal gangue,coal slime,etc.is carried out.The results show that the principal heat losses increase and the boiler efficioncy decreases with lower coal quality,providing the fundamental and theoretical support for the boiler design and the blending of low-grade fuel,especially for coal gangue and coal slime.