固液混合物振动筛分机理研究

Screening Mechanism of the Solid-liquid Mixture Vibration Screen

振动筛分技术是固液混合物分离的一种手段,被广泛应用于钻井液固相控制、河道淤泥处理和煤矿脱水等领域。现有研究对固液混合物的振动筛分机理缺乏认识,限制了振动设备筛分效率的提升空间。针对这一问题,采用计算流体力学与离散单元耦合法(CFD DEM)研究了固液混合物振动筛分机理。首先,利用Hertz-Mindlin JKR Cohesion接触模型引入湿颗粒之间的碰撞行为;其次,应用多孔介质描述了筛网的细孔特征;然后,运用动网格模拟了筛网的直线振动轨迹;最后,分析了固相颗粒物料的动力学特性和液相流动特性,并对比研究了振动系统的振幅和振动频率对固液混合物筛分效率的影响。研究结果表明,增加振幅和振动频率可提高固液混合物筛分效率,但当振幅大于3.0 mm和频率大于22.3 Hz时,振动筛对固液混合物的筛分效率影响的敏感性减弱;振幅小于或等于3.0 mm和频率小于或等于22.3 Hz时,固液混合物振动筛分效率对振幅的变化最敏感,振动频率次之;固液混合物的透筛区域集中在筛网长度比小于20%的区域。

Vibration screening technology is a means for the separation of solid-liquid mixture,which is widely used in solid phase control of drilling fluid,river mud treatment and dehydration of coal mine.However,the existing research lacks sufficient comprehension for the vibration screening mechanism of solid-liquid mixture,which limits the improvement of screening efficiency of vibration equipment.In order to solve this problem,the CFD-DEM(Computational Fluid Dynamics-Discrete Element Method)coupling method is used to study the screening mechanism of solid-liquid mixture vibration screen.Firstly,Hertz-Mindlin with JKR Cohesion model is used to simulate the collision characteristics between wet particles.Secondly,porous media is used to describe the hole characteristics of screen.Then the linear vibration trajectory of the screen is simulated by using dynamic mesh.Finally,dynamic characteristics of granular materials and flow characteristics of liquid are analyzed,and the effect of vibration frequency and amplitude on the screening efficiency of solid-liquid mixture are compared.The results show that screening efficiency of solid-liquid mixture can be improved by increasing the amplitude and frequency appropriately,but when A>3.0 mm and f>22.3 Hz,the effect of vibration screen on screening efficiency of solid-liquid mixture is weakened;when A63.0 mm and f622.3 Hz,the screening efficiency of solid-liquid mixture is more sensitive to the change of amplitude,and that of the vibration frequency next to it.The passing area of solid-liquid mixture is mainly concentrated in the area where the length of the screen L<20%.