褐煤预干燥对锅炉传热特性及运行经济性的影响

Influence of Lignite Dryness on Heat Transfer and Operation Economy of Power Boilers

以某300MW褐煤燃烧机组为研究对象,计算和分析褐煤干燥程度(即水分质量分数分别为34.1%、30.0%、25.0%、20.0%和18.0%)对锅炉运行中炉膛燃烧及各受热面传热特性的影响,研究了褐煤干燥前后锅炉热经济性的变化.结果表明:随着褐煤干燥程度的加深,理论燃烧温度比水分质量分数为34.1%的原褐煤分别提高了50.19K、101.51K、134.82K和148.13K,最大升高幅度达8.18%,炉膛内燃烧加剧,辐射放热量增加,烟气流速降低,各受热面的对流传热系数和辐射传热系数减小,但单位燃料的对流传热量却有所增加,锅炉排烟温度下降,锅炉热效率和运行经济性提高.

Taking a 300 MW lignite-fired unit as an object of study, the influence of lignite dryness on fur nace combustion and heat-transfer characteristics of the boiler was analyzed through calculation respective ly with lignite moisture content of 34.1%, 30.0%, 25.0%, 20.0% and 18.0%, so as to study the varia tion of boiler thermal economy before and after lignite drying. Results show that with the rise of dryness, the theoretical combustion temperature of lignite has been respectively increased by 50.19 K, 101.51 K, 134.82 K and 148.13 K, compared with the original lignite with moisture content of 34.1%, and the high est temperature rise reaches 8. 18%, resulting in enhanced in-furnace combustion, increased heat radia tion, lowered flue gas velocity, reduced convective and radiant heat-transfer coefficient of heating surface, increased convective heat transfer per unit of fuel, lowered exhaust gas temperature, and finally increased boiler efficiency and operation economy.