某亚临界锅炉低氮燃烧器改造后高温腐蚀控制

The Control of High-temperature Corrosion after Low NO_x Combustion Retrofit for a Subcritical Boiler

某电厂600 MW亚临界锅炉低氮燃烧器改造后一直存在高温腐蚀现象严重、再热汽温偏差较大的问题,对改造后的锅炉进行了数值模拟计算。结果表明,改造后炉膛出口烟温偏差较小,炉内整体温度上升,但水冷壁贴壁区域温度反而有所降低,炉膛整体CO体积分数随着燃尽风率的增大而大幅上升,高温腐蚀风险增大。实际运行中再热汽温偏差较大与风箱结构引起的二次风实际不均匀程度有关。针对数值模拟结果进行燃烧调整后,炉内强还原性气氛区域CO体积分数有了明显下降,两侧再热汽温偏差从40℃下降至10℃以下,加减负荷时的再热汽温稳定程度亦有所提高。

The problems of serious high-temperature corrosion and reheat steam temperature deviation have been after low NOx combustion retrofit for a 600 MW subcritical boiler.The numerical simulation is employed for retrofit boiler.The results indicate that flue gas temperature deviation is small at furnace exit after retrofit.The temperature of furnace rises,on the contrary,the temperature of near the water wall reduces.The volume fraction of CO rises with over-fire air increases.The risk of high-temperature corrosion is increasing.In actual running,the large of flue gas temperature deviation is relevant to the degree of irregularity of secondary air.After combustion adjustment,the volume fraction of CO at the area of strong reducibility reduces significantly.The deviation of reheat steam temperature is from 40 ℃ to 10 ℃.The stability of reheat steam temperature improves at increasing and decreasing load.