Research On Skim Milk Ultrafiltration With A Recip-rocating Rotating Hollow Fiber Membrane Module

The membrane separation so far is developed rapidly,but fouling and concentration po-larization are main disadvantages in the membrane filtration process whenever long-term op-eration with proper efficiency is considered. Enhanced the shear rate on membrane surface isa common way to delay the permeate flux decline.Shear-enhanced or dynamic filtration con-sists in creating the shear rate at the membrane by a relative motion between the membraneand a moving part such as a rotating membrane, or a disk rotating near a fixed circular mem-brane or by vibrating the membrane either longitudinally or torsionally around a perpendicu-lar axis.It can reduce the fouling and concentration polarization and delay the permeate fluxdecline.This paper has design a novel dynamic filtration system called reciprocating rotatinghollow fiber membrane plant, which take advantage of the reciprocating rotation of membrane,make vectors superposition of the flow field and the membrane rotating velocity produced theenhancement of shear rate on membrane.It investigated the performance of the plant fromboth experiment research and theory calculation.As to experiment research,the effects of different kinds of parameters fixed one or fewbundles membrane in the plants on the decline of membrane permeate flux were investigated.When the plants mounted on one bundles, the effects of the module’s geometry parametersand rotating parameters as well as the characteristics of tested fluid on the decline of mem-brane permeate flux were considered. The results indicated that a better shear enhancing effi-ciency could be obtained while the angular velocity and/or the radial distance of membranesfrom the central hollow shaft were increased. The greater vectors superposition of the flowfield and the membrane rotating velocity，which was reflected on a relative greater velocitygradient，would be obtained once the reciprocating rotation cycle was optimized. Otherwise，simply increasing or decreasing the rotation cycle would weaken the efficiency of shear en-hancement. With the same operating parameters，the reciprocating rotation filtration was morefavorable in slowing the decline of membrane permeate flux than the dead end filtration or theuni-directional rotation filtration.When the plant mounted on more than one bundles mem-brane, only rotation parameters on the decline of permeate flux was demonstrated.When re- searched on the energy consume of module in the same conditions, the more bundles ofmembrane fixed, the less energy of module consumed.As to theory analysis, our research used the test result of PIV to reflect on the flow fieldand the shear rate on the membrane surface, the equation of the shear rate on membrane wasdeduced,and combined with the experiment, the experience model of the permeate declinewith time was built.The results of above study demonstrate that the novel dynamice filtration separator withenhanced shear rate might has great value for its remarkable advantages such as high shearrate,low transmembrane pressure, simplified structure and high enhancement performance infiltration which might supply a reference on the pratical engineering.