SG2080/25.4-M969型锅炉末级过热器壁温超限原因分析及处理

CAUSE ANALYSIS OF TUBE-WALL TEMPERATURE OVERRUN IN THE FINAL-STAGE SUPERHEATER OF SG2080/25.4-M969 TYPE BOILER AND DISPOSAL THEREOF

国华沧东发电有限责任公司3、4号超临界机组的SG2080/25.4-M969锅炉运行过程中,由于末级过热器管壁温度频繁超限,导致2台锅炉的过热汽温达不到设计值。以4号锅炉为研究对象,对末级过热器管壁温度频繁超限的原因进行的试验表明,水平烟道左侧的温度场不均匀是导致锅炉末级过热器左侧管壁金属温度超限的主要原因。通过配风方式的调整,降低了左侧过热蒸汽温度与最高管壁金属温度的差值,提高了左侧过热蒸汽温度的运行值。另外,建议取消炉膛-风箱差压控制方式,在一定负荷区间保持二次风门开度的相对稳定,以获取稳定的烟气温度场和速度场分布。经调整后,3、4号锅炉末级过热器温度可接近或达到设计值运行。

In the operation process of SG2080/25.4-M969 type boilers for ultra-supercritical units no.3 and no.4 in Guohua Cangdong Power Generation Co Ltd,owing to frequent overrun of the tube-wall temperature in final-stage superheater,the temperature of superheated steam in said two boilers can＇t reach the designed values.Taking boiler no.4 as the object of study,the causes leading to frequent overrun of tube-wall temperature in final-stage superheater have been tesed,it shows that the main cause resulting in frequent overrun of the left-side tube-wall metall＇s temperature is the non-uniform temperature field at the left-side in the horizontal flue duct.Through adjustment of the air distribution mode,the difference value between the left-side superheated steam temperature and the highest tube-wall metall temperature has been reduced,enhancing the operation value of the left-side superheated steam temperature.Moreover,cacellation of differential pressure control mode for boiler-windbox has been recommended,the open-degree of secondary air gate being maintained at a relative stable level in a certain load range,so as to obtain a stable flue gas temperture field and stable speed field distribution.After the said adjustment,the temperature of fianl-stage superheater in boiler no.3 and no.4 can close to or reach the designed value in operation.