Experimental Study On The Vibrate Shear Dynamic Filtration System

A major obstacle in applying filtration is the permeate flux decline due to filtering media contamination and cake layer thickening.Selecting the right membrane and filtration technique is an important consideration to ensure a successful system development and long term performance.The use of high membrane shear rates has long been recognized as one of the most efficient factors for increasing permeate flux as it reduces both concentration polarization and cake build-up in microfiltration(MF).In classical cross-flow filtration,high shear rates at the membrane surface are obtained by increasing the tangential fluid velocity.Therefore it requires much energy to drive the pumps.Vibratory-Shear-Enhanced-Processing(VSEP) is a new technologies developed in recent years.The maximum shear rate produced by VSEP is between 3 and 10 times than in the conventional cross-flow systems.The performance of a VSEP vibrating laboratory module was investigated in filtration of Al₂O₃ suspensions and in microfiltration(MF) of CaCO₃ suspensions.This paper study on operation parameters such as concentration of suspension,displacement and frequency of oscillation to filtration flux.Based on the experimental results,we choose the optimal scheme. The results of experiments show that with the increase of concentration,filtration flux decreases sharply and static filtration flux also decreases,the increase of displacement and frequency of oscillation can enhance static filtration flux.The variation of permeate flux with shear rate was investigated.In the case of CaCO₃ MF the permeate flux was found to be proportional to r_m^0.2522 at a shear rate below 0.7×106 S^-1 and to r_m^0.165 at higher shear rate.The results also verify that the shear rate has an effect on reducing the concentration polarization and membrane fouling.As to experimental model analysis,a mathematical models of filtration flux is built.An empirical equation for static filtration flux is presented and verified by experimental data.The influence factors are summed up into the displacement and frequency of oscillation and some important dimensionless numbers like Re and Eu to obtain a feasible formula that provides basis for scale-up of the module.