600MW超临界锅炉防止高温腐蚀技术改造和运行调整

The Retrofit of High-Temperature Corrosion Prevention and Operation Adjustment for 600-MWSupercritical Boiler

某发电公司600 MW超临界锅炉燃烧器区域两侧墙水冷壁管向火侧存在大面积高温腐蚀现象,为了消除水冷壁运行的安全隐患,对锅炉燃烧系统进行改造,对水冷壁侧墙影响较大的两侧主燃烧器进行优化设计,同时前后墙各加装3层贴壁风,降低了水冷壁侧墙还原性气体浓度。通过调整炉内横纵向空气的分布,使贴壁风改造后产生的高温受热面管壁超温、尾部烟道CO浓度升高和NOx排放浓度分布不均等负面影响得到有效控制。改造后锅炉总体性能良好,引起锅炉水冷壁大面积高温腐蚀的因素得到控制,水冷壁侧墙壁面CO体积分数平均为0.02%,H2S体积分数平均在60×10-6以下;改造前后锅炉效率和NOx排放浓度基本持平。

The high-temperature corrosion was discovered in large area of the fire-side water-walls at the burner zones in one 600-MW supercritical boiler. In order to mitigate the possible risk to the water-wall operation, the retrofit of the boiler combustion system and the optimal design on the main burners with great impacts on both sidewalls are carried out. Meanwhile, three layers of close-to-wall air are installed along the front and back water-walls to reduce the concentration of de-oxidation atmosphere near the water-walls. Through the adjustment of the horizontal and vertical air distribution in the furnace, the negative effects of tube wall overheat in high-temperature heating areas, the increase of CO concentration in the rear pass and the uneven distribution of NOx emission concentration caused by the installation of the three layers of close-to-wall air are effectively harnessed. After the retrofit, the factors causing high-temperature corrosion of boiler water walls are constrained, the average volume fraction of CO near the sidewalls is about 0.02%, and that of H2S is less than 60× 10-6. Additionally, the boiler efficiency and the NOx emission concentration are almost kept at the same level as those before the retrofit, which shows the good overall performance of the boiler.