关键词: 超临界锅炉, 旋流燃烧器, 水冷壁, 高温腐蚀, 贴壁风

Abstract: 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 NO_x 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 NO_x emission concentration are almost kept at the same level as those before the retrofit, which shows the good overall performance of the boiler.

Key words: supercritical boiler, swirl burner, water-wall, high-temperature corrosion, close-to-wall air