中空纤维超滤膜错流过滤膜污染的CFD模拟

摘要

利用有限元分析软件Comsol Multiphsics中的自由流动、达西定律以及物质传递耦合膜阻力公式,建立中空纤维膜的膜污染计算流体力学(CFD)模型,并通过实验室小试对模型参数进行了修正.结果表明,过滤初期,膜通量的快速下降是由于污染物质吸附作用在膜表面快速累积而引起的,随后,由于污染物质吸附达到动态饱和,同时滤饼层尚未形成,总阻力系数增长缓慢,因而通量下降亦较缓慢;最后,随着过滤的进行,已累积的污染物质在膜表面分布趋于均匀,滤饼层基本形成,此阶段通量下降较为明显.模型可准确地预测中空纤维超滤膜膜通量的变化,解析膜内污染物质浓度分布及其浓差极化层厚度动态变化,为研究膜内物质浓度分布可视化提供手段.%Acomputational fluid dynamics(CFD)model was established to describe membrane fouling in hollow fiber membrane,by coupling free flow equation,Darcy law and membrane resistance-coupled mass transfer formula in the finite element analysis software Comsol Multiphsics.The model parameters were calibrated with data from lab scale experiments.Thc rcsults showed that in the initial stage of filtration,the rapid decline of filtration flux was due tO the adsorption and rapid accumulation of pollutants on the membrane surface.Subsequently,the adsorption of pollutants reached equilibrium,while the cake layer had not yet formed.Therefore,the total resistance increased slowly,and the decline of filtration flux slowed down.Finally,with the progress of filtration,the distribution of the accumulated contaminants on the membrane tended to be uniform and the cake layer was formed,resulting significant decrease of filtration flux decreases at this stage.Themodelcan accurately predictand analyze the change of the permeate flux,the concentration distribution of the contaminants in the membrane and the change of the thickness of the polarized layer,thus providingamethodtovisualize the distribution of substances' concentration in the membrane.