0．3MW煤粉炉MILD燃烧的数值计算

Numerical Calculation of MILD Combustion for Pulverized Coal on 0.3 MW Furnace

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 impacts of air preheating temperature, nozzle injecting velocity and distance, and arrangements on MILD combustion for pulverized coal were numerically studied. It indicates that high temperature air is not an essen- tial condition for coal MILD combustion. Increasing injecting velocity and nozzle distance can enhance the recircula- tion of flue gas inside the furnace, but it is more effective to increase the nozzle distance than injecting velocity. The more concentrated the injecting flow is, the farther the recirculation flow reaches. Compared to conventional combus- tion, the coal particle ignites earlier, the peak temperature decreases by 200 K, the overall oxygen concentration is below 10%, CO distributes in a broader space, and NOx emission decreases by 1/2 under MILD combustion.