Microfiltration of Deforming Droplets

Abstract

Control of permeate flux is important in microfiltration processes as it influences trans-membrane pressure and fouling of a membrane. Particles of vegetable oil ranging from 1 to 15 μm were passed through a 4 μm slotted pore membrane at various flux rates. Various intensities of shear were applied parallel to the membrane by vibrating the membrane at different frequencies. At the lowest permeate flux rate (200 l m⁻² hr⁻¹) the membrane fouled because the drag force was too low to squeeze the deformable oil droplets through the membrane. At higher flux rates the drag force over the oil droplets increased and deformation, and passage, of oil droplets into the permeate was possible. Without any applied shear highest trans-membrane pressure was observed due to fouling, which could be modelled by a pore blocking model. A positive displacement pump was used in experiments which maintained nearly constant flow of permeate. Flux rates varied from 200 up to 1200 l m⁻² hr⁻¹, and the highest shear rate used was 8,000 s⁻¹. The experimental system provided a simple technique for assessing the behaviour of the microfilter during the filtration of these deforming particles.