The pulverized coal mixer is one of the important equipments in the middle storage type boiler. Its normal operation is the key to ensure the stable combustion of the pulverized coal boiler. Combing with the positive pressure off powder occurred in pulverized coal mixer of a 300 MW unit boiler under full load conditions, this paper carried out numerical simulation to analyse the flow field and particle trajectories by using the Fluent software. The large on-way resistance and local resistance of the primary air pipe behind the coal mixer and the defects in structural design of the pulverized coal mixer are considered as the major reasons for off powder. To solve this problem, it suggests that the coal mixer tray should be moved vertically down by 60 mm, and the inner side of the powder inlet be longitudinally extended by 30 mm. Moreover, numerical simulation and experiments were performed to verify the optimized structure. The results show that, after structure optimization, under full load condition, the pulverized coal output of coal mixer for a single primary air pipe increased by 3 t/h, and the coal flow at the outlet was uniform and smooth, no off powder was observed.%煤粉混合器是中间储仓式锅炉输粉重要设备之一,其正常运行是保证煤粉锅炉稳定燃烧的关键所在.针对某电厂300 MW机组锅炉煤粉混合器在满负荷工况下出现正压脱粉现象,借助Fluent软件对该现象进行了流场、颗粒轨迹模拟,分析认为煤粉混合器后一次风管沿程阻力和局部阻力偏大,以及煤粉混合器结构设计缺陷是导致脱粉的主要原因,对此,提出了将煤粉混合器托盘纵向下移60 mm,下粉口内侧纵向延长30 mm的优化改造方案,并借助数值模拟及试验对优化改进后的结构进行验证.结果表明,优化改进后锅炉在满负荷工况下,每层平均多下粉3 t/h左右,下粉均匀流畅,未出现脱粉现象.
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