Dynamic microfiltration with a vibrating hollow fiber membrane module: Filtration of yeast suspensions

A novel dynamic microfiltration system consisting of a vibrating hollow fiber membrane module is presented. The vibrations induce the shear rate at the membrane surface which makes it possible to filtrate at low feed cross-flow velocity and thus at a low transmembrane pressure. Results from test filtrations of bakers yeast suspensions are presented and the critical flux concept is used to evaluate the filtration data. The critical flux at the maximum degree of vibration is improved 325% compared to the critical flux at the minimum degree of vibration. An equation to calculate the membrane surface shear rate from the vibration frequency and amplitude is presented. The correlation between the critical flux and average surface shear rate is Jp,crit=8.22(γ¯s)0.26. It is further shown that when operating below the critical flux in a 4.5 h test filtration the permeability is kept constant. Above the critical flux, the transmembrane pressure increases resulting in a decrease in membrane permeability.