“双U形燃烧”对炉内燃烧特性影响的数值模拟

Effects of Double-U Combustion Mode on the Characteristics of Furnace Combustion

通过数值模拟方法研究了某2 045t/h对冲燃烧锅炉在典型优化燃烧方式下的炉内贴壁区域平均烟气温度、还原性气氛以及折焰角出口截面平均NO体积分数、煤粉燃尽率、烟气温度偏差和炉膛底渣量。结果表明:通过优化同层燃烧器叶片角度和煤量分布的"双U形燃烧"模式相对传统燃烧模式可降低贴壁区域平均烟气温度约100K,同时折焰角出口烟气温度偏差系数变化较小;侧墙水冷壁贴壁区域高CO体积分数的区域面积占比由约40%降至仅约10%,使得该区域的高温腐蚀有望得到显著改善;折焰角出口煤粉燃尽率有所下降,底渣量略有增加;实际应用中,高还原性气氛区域的CO体积分数较摸底试验的下降幅度约为40%。

Numerical simulations were conducted to study the combustion characteristics in the furnace of a 2 045 t/h opposed firing boiler adopting double-U combustion mode, such as the average flue gas temperature and the reductive atmosphere near water wall, the average NO concentration, the burnout rate and the flue gas temperature deviation at furnace arch exit, as well as the amount of bottom ash, etc. Results show that compared with traditional combustion modes, the double-U mode, realized through optimizing the angle of same layer burner blades and the distribution of coal flows, could help to reduce the flue gas temperature near water wall by about 100 K, while the deviation factor of flue gas temperature at furnace arch exit remains unchanged. Under the mode of double-U combustion, the area containing high concentration of CO reduces from 40% to 10%, resulting in lower risk of high-temperature corrosion in that area; the burnout rate reduces at arch exit, while the amount of bottom ash increases slightly. In actual practice, comparing with baseline test, the volume fraction of CO in high reduction atmosphere reduces by about 40 %.