The Use of Flux Enhancement Methods for High Flux Cross-flow Membrane Microfiltration Systems

P. Mikulášek, J. Cakl, P. Pospíšil and P. Doleček

Abstract
The influence of the two techniques (membrane backflushing and two-phase gas-liquid flow) on permeate flux during the microfiltration of model dispersions on ceramic membrane has been studied. The experiments were carried out with aqueous titania dispersions filtered through a ceramic tubular membrane. The influence of various transmembrane pressures, feed concentrations, backflushing duration and frequencies, liquid and gas flow velocities, and the influence of periodic gas flow is also presented. Based on the results of experiments presented in this work, it appears that constant gas-liquid flow has a positive influence on permeate flux. The level of flux enhancement depends both on the gas flow rate and flow pattern. From analysis of experimental results it may be concluded that two-phase flow seems to expand the particle cake as it increases, both, cake porosity and thickness, thus allowing higher fluxes. The enhancement of flux was better observed during the microfiltration of more concentrated dispersions. Periodic gas flow is not so significant for the flux enhancement and strongly depends on the periodic gas flow mode and on the concentration of the dispersion. This experimental study demonstrated that in cross-flow microfiltration of dispersions, the membrane backflushing could maintain permeate flux at a constant and high level over the duration of an experiment. It was observed that the effect of back-flushing on flux enhancement was more pronounced when the backpulse duration was shorter, the transmembrane pressure difference was higher, and the retentate velocity was lower in forward filtration.

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Keywords
Microfiltration, ceramic membrane, backflushing, two-phase gas-liquid flow