300MW循环流化床锅炉空气预热器热风再循环研究

Study on Air Preheater Hot Air Recirculation of 300MW Circulating Fluidized-bed Boiler

针对循环流化床锅炉空预器运行过程中常见的低温腐蚀问题,建立了一种应用热风再循环后空预器性能的计算模型,并以某典型300 MW亚临界CFB机组为例,分别对其在冬季运行工况和不同环境温度下应用热风再循环时空预器的热力特性和阻力特性进行了详细的计算分析。结果表明:以案例机组为例,当环境温度为-10℃时,可将空预器入口风温提高到20℃,此时热风再循环率为11.19%,冷端平均壁温为75.32℃,风机电耗增加32.05%,机组的低温腐蚀现象可得到有效抑制;但随着环境温度的不断降低,空预器所需的热风再循环率不断提高,风机电耗将大幅增加,当环境温度低于-15℃时,一般不宜采用热风再循环技术。

In order to solve the air preheater＇s low-temperature corrosion during operation of the circulating fluidized-bed boiler, a calculation model was established to evaluate the performance of air preheater after employing the hot air recirculation. Taking a typical 300 MW subcritical CFB unit as a case, a detailed analysis of the unit＇s thermodynamic and resistance performance in winter operating conditions and different ambient temperatures was carried out.. The results show that： for the reference unit, when the ambient temperature is-10℃, the air preheater＇s inlet air temperature can be heated to 20℃ and the hot air recirculation rate is 11.19%. Thus, the average wall temperature could increase to 75.32 ℃ and the electricity consumption of the draft fan would increase by 32.05%.In this case the low-temperature corrosion of the unit can be effectively suppressed. However, with the decrease of the ambient temperature, the hot air recirculation rate become larger, and the electricity consumption of the draft fan would increase accordingly. When the temperature reduces to less than-15℃,generally the hot air recirculation technology is no longer applicable for the air preheater.