调节同层二次风以缓解双切圆锅炉高温腐蚀的数值模拟

Numerical simulation on regulating secondary air in same layer to alleviate high temperature corrosion of dual tangential boiler

针对某双切圆锅炉热角区域高温腐蚀问题,本文提出调节同层二次风流量的方法来改善热角上游的还原性氛围。基于Fluent软件模拟了不同冷角二次风流量工况下的炉内燃烧情况,结果表明:增加冷角二次风量可以基本消除双切圆锅炉水冷壁附近CO体积分数过高(>8%)的区域,大大缓解水冷壁高温腐蚀的问题。5%工况和10%工况下,炉膛近壁面安全区域面积占比分别上升了1.20%和1.35%,出口NO_(x)平均质量浓度分别升高2.99%和8.89%;而15%工况的炉膛防腐效果最佳,近壁面安全区域面积占比上升了3.60%,同时腐蚀严重区域占比下降了4.99%,出口NO_(x)平均质量浓度升高较明显,上升18.91%。在一般电厂实际调整过程中,冷角二次风增量应设置在5%~10%,对于燃用高硫煤且NO_(x)排放较低的电厂,建议将冷角二次风增量设置为15%左右,以最大限度缓解高温腐蚀。

In view of the high temperature corrosion phenomenon in the hot corner area of a dual tangential boiler,in this paper,a method of adjusting the secondary air flow in the same layer to improve the reducing atmosphere in the upstream of the hot corner was adopted.Based on Fluent software,the combustion conditions in the furnace under different cold angle secondary air flow conditions were simulated and compared with the original conditions.The high temperature corrosion severity of water wall was reflected by the distribution of CO concentration near the wall.The results showed that the area with high CO concentration(>8%)near the water wall of dual tangential circular boiler could be basically eliminated by increasing the secondary air volume at the cold angle,and the problem of high temperature corrosion of the water wall could be greatly alleviated.Under 5%and 10%working conditions,the proportion of safe area near the furnace wall increased by 1.20%and 1.35%,respectively,while the proportion of seriously corroded area decreased by 0.013%and 1.02%,respectively.The screen bottom temperature,pulverized coal burnout rate,average furnace outlet temperature and oxygen volume fraction almost remained unchanged,and the average NO_(x)mass concentration at the outlet increased by 2.99%and 8.89%,respectively.15%working condition had the best anti-corrosion effect,and the proportion of safe area near the wall increased by 3.60%.Meanwhile,the proportion of serious corrosion area decreased by 4.99%,and the temperature at the bottom of the screen and the burnout rate of pulverized coal increased slightly.The average temperature and oxygen volume fraction at the furnace outlet almost hardly changed.The average mass concentration of NO_(x)at the outlet increased by 18.91%.In the actual adjustment process of general power plants,the increment of cold angle secondary air should be set between 5%and 10%.For power plants burning high sulfur coal with low NO_(x)emission,the increment of cold angle secondary air can be set at about 15%to minimize high temperature corrosion.