Intensified membrane filtration with corrugated membranes

Crossflow membrane microfiltration of 30% (w/w) water-in-oil emulsions is reported using hydrophobic PVDF and PTFE membranes. The flux performance of corrugated membranes is compared with that of flat membranes. The influence of crossflow velocity (CFV), flow channel height and transmembrane pressure (TMP) were investigated. The effect of varying the angle of corrugation (between the flow direction and the corrugation) on the overall flux performance was also examined. Experiments on flat and corrugated membranes have shown that increases in CFV and/or decreases in flow channel height result in an improved permeate flux caused by increased shear effects on the membrane surface. The use of corrugated membranes, however, enhanced the flux in a more efficient way by preferentially promoting turbulence near the membrane wall region, repeatedly mixing the boundary layer and hence reducing the concentration polarization. The angle of corrugation was also found to have a marked effect on the flux. Flux increases of about 30, 100 and 160% in comparison with flat membranes was achieved for parallel, 45 and 90° angle of corrugation, respectively. It was illustrated that corrugations with angles of 45 and 90° can lead to a reduction in energy consumption of up to 80 and 88%, respectively. The TMP affected both the flux and the flux decline. The `breakthrough pressure' at which both phases permeate through the membrane was found to be 1.5 bar. Membrane fouling behaviour is analyzed and the applicability of filtration models to the experimental results identified. The fouling analysis revealed that the filtration process occurs in two distinct stages; initial pore blocking for 20 min followed by cake layer formation. The two stages can be best explained by a `cake filtration' model.