基于FLOW-3D的10μm微孔滤膜堵塞机理数值模拟

Simulation on the Fouling Mechanism of Micro-pore Filter Membrane in Size of 10μm with FLOW-3D

目前对微孔滤膜堵塞机理的研究主要是基于对滤膜堵塞试验数据分析所得的堵塞指数,而从虚拟仿真角度使滤膜堵塞过程可视化则有利于人们对滤膜堵塞机理的深刻认识。以10μm微孔滤膜为分析对象,基于FLOW-3D对膜孔尺寸附近的颗粒相对于微孔滤膜的摆放位置及倾斜角度与膜孔堵塞的关系,以及颗粒与膜孔间的架桥截留等进行了仿真分析。研究结果表明,短径大于膜孔尺寸的颗粒一定会被膜孔截留,短径小于膜孔尺寸的颗粒通常情况下均会通过膜孔,除非该颗粒恰好位于膜孔上方、短径与膜孔尺寸相近且长径与膜孔平行。堵孔后的颗粒表面会承受较大的液体压力。小颗粒与大颗粒的组合会形成稳定的架桥,架桥是长短径均小于膜孔尺寸颗粒的主要沉积形式。呈一定尺寸分布的颗粒在通过滤膜微孔时,大颗粒拦截首先发生,然后才是小颗粒之间的架桥,这两个机理联合作用导致膜孔堵塞。实际污染样液对滤膜微孔的堵塞结果验证了仿真分析的正确性。仿真结果可为基于滤膜堵塞法的油液污染颗粒定量检测模型研究提供参考。

The mechanism of membrane pore fouling has mainly been determined by fouling index which is obtained by analyzing the filtrate flux data based on the filter classical fouling models so far.However,it is better to understand the filter fouling mechanism by visualizing the membrane plugging process with a simulation model.Taken a 10μm micro-pore filter membrane as an example,the relationship between membrane fouling and the position and the inclination angle of particles with size close to membrane pore size relative to filter membrane are studied by using FLOW-3 D software.Furthermore,the principles of the bridge interception of the particles by the membrane pores are also discussed.The results show that a single particle can be intercepted when its short diameter is larger than the pore size.Usually,a particle whose short diameter is smaller than the pore size will pass through the membrane only when it is located just above the membrane pore and its short diameter is close to the pore size,and meanwhile the direction of its long diameter is parallel to the membrane pore.The surface of a particle trapped in a pore suffers from a big dragging force.The combination of small particles and large particles can cause a stable bridge.Bridging interception is the main way for the deposition of particles that both the long and short diameters are smaller than the membrane pore size.When the particles with a certain size distribution pass through the microporous membrane,the interception of large particles occurs first,and then the bridging between small particles,and the combination of these two mechanisms leads to membrane pore plugging.The simulation model are validated through plugging test of actual polluted oil sample on micro-pore filter membrane.The simulation results can provide a reference for studying the quantitative detection model of contaminated oil samples based on filter fouling.