进料方式对超细分级机分级性能的影响

采用数值模拟方法对两种不同进料方式的分级机进行了气固两相流研究,分析了内部压降、气相速度、固相浓度分布等特性;对两种进料方式的分级机进行了应用研究,对比分析了上下进料方式下的特征粒径和细粉粒径分布特点。结果表明:采用上进料方式由于增加了机械撒料盘,进出口压差更大,同时转子外沿圆柱面上的切向和径向速度分布更为均匀,有利于减小分级粒径的波动,得到粒径分布窄的细粉;采用上进料方式有利于提高颗粒浓度分布的均匀性,但受转速的影响较大;采用上进料和下进料两种方式均能取得较好的分级效果,分级后细粉粒径小且分布窄,主要集中在1~30 μm,30 μm以下的颗粒含量达到90%以上。研究结果对分级机进料方式的设计和结构优化有一定指导作用。

Effect of feeding type on classification performance of superfine classifier

The gas-solids two-phase flow in the superfine classifier with two different feeding types was studied by numerical simulation.The pressure difference,air velocity and solids concentration distribution were analyzed.The performance superfine classifier with two feeding types was studied by experiments,and the characteristic particle size and size distribution of fine powder of under and upper feeding type were compared and analyzed.The results showed that compared with the under feeding type,the pressure drop between inlet and outlet of the superfine classifier of the upper feeding type was bigger due to adding the mechanical spreading plate.For the upper feeding type,the tangential and radial velocities of cylindrical surface along the rotor were distributed more uniformly,which helped to reduce the fluctuation of classification size and obtain fine powder with narrow particle size distribution.Particle concentration was distributed uniformly with the upper feeding type,but was affected heavily by rotor speed.According to the experiment,both under feeding and upper feeding types could obtain good classification performance.After classification,the size of fine powder was small,with narrow distribution,mainly in the range of 1-30 μm.The percentage of particle less than 30 μm of fine powder was above 90%.The study results could provide guidance to designing the feeding type and optimizing the geometry of the superfine classifier.