超超临界锅炉低NO_x燃烧优化对高温腐蚀的影响

Influence of Low NO_x Combustion Optimization on the High-temperature Corrosion for an Ultra-supercritical Boiler

为了评估低NO_x燃烧器升级后水冷壁高温腐蚀的可能性,对某超超临界锅炉炉内燃烧进行了数值模拟,并对SOFA(燃烬风)上摆的燃烧优化工况做了水冷壁贴壁气氛测试。结果表明:主燃烧区的上部和COFA、SOFA(分离式燃烬风喷嘴)之间的还原区发生高温腐蚀的可能性较大;SOFA上摆扩大了还原区,增加了高温腐蚀的可能性,还原区贴壁H_2S平均浓度沿着炉膛高度的增加而升高,为180~400μl/L;SOFA摆角的偏差使得局部H_2S浓度达到了800μl/L,进一步加剧了局部区域高温腐蚀的风险;强氧化强还原交替变动,使得SOFA以上区域(43.3~46.1 m)的高温腐蚀风险较典型还原区更为严重。在锅炉实际运行中,应尽可能权衡降低NO_x排放和控制高温腐蚀风险。

In order to estimate the possibility of high-temperature corrosion of water-wall after upgrading the low NOxburner,the numerical simulation is carried out for an ultra-supercritical boiler combustion and the pinning atmosphere of water-wall is measured after increasing the angle of SOFA. The results show that the upper part of the main combustion zone and the reductive zone between OFA and SOFA are more likely to have the high-temperature corrosion.The reductive zone is increased due to the enlarged angle of over-fire air,resulting in a higher possibility of hightemperature corrosion near the water-wall. The average concentration of H2S near the water-wall increases along with the height of furnace,about 180 ~ 400 μl/L. The risk of high-temperature corrosion is increased because of the deviation in SOFA. The largest concentration of H2S is 800 μl/L. Further the risk of high-temperature corrosion in the zone of 43. 3 ~ 46. 1 m is more serious than that in the typical reduction zone due to the alternation of the pinning atmospheres between strong oxidation atmosphere and strong reductive atmosphere. In the actual operation of boiler,reducing NOxemission and controlling the risk of high-temperature corrosion should be balanced.