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借助数值模拟的方法研究了空气预热温度、燃烧器喷嘴射流速度、喷嘴间距以及喷嘴布置形式等对煤粉MILD燃烧的影响规律.结果表明:高风温并非实现煤粉MILD燃烧的必要条件;增大射流速度和喷嘴间距均能提高炉膛内的烟气循环量,但喷嘴间距的影响比射流速度更为重要;射流动量越集中,烟气回流距离越远.相对于常规燃烧方式,MILD燃烧方式下煤粉着火提前,炉膛温度峰值降低200,K左右,炉膛内局部O2体积分数均低于10%,CO分布范围扩大,NOx排放降低为常规方式下的1/2.
The effect of air preheating temperature, jet velocity, nozzle spacing and nozzle layout on the MILD combustion of pulverized coal was studied by means of numerical simulation.The results show that high air temperature is not a necessary condition to achieve MILD combustion of pulverized coal. Increasing the jet velocity and nozzle spacing can increase the flue gas circulation in the furnace, but the effect of nozzle spacing is more important than the jet velocity; the more the jet momentum is concentrated, the farther the flue gas backflow distance.Compared with the conventional combustion mode, MILD In the combustion mode, the pulverized coal ignites ahead of time, the peak temperature of the furnace decreases about 200 K, the partial volume fraction of O2 in the furnace is lower than 10%, the distribution range of CO is expanded, and the NOx emission is reduced to 1/2 in the conventional mode.