DETERMINATION OF VARIOUS HYDRAULIC RESISTANCES DURING CROSS-FLOW FILTRATION OF A STARCH GRAIN SUSPENSION THROUGH INORGANIC MEMBRANES

摘要

A model for the functioning of inorganic membranes and for the fouling mechanism hindering mass transfer during crossflow filtration is proposed. A four-step experimental method inspired by this model allows the main hydraulic resistances (deposit, internal fouling, polarization layer, membrane) and their relative importance to be measured. The influence on experimental performance and selectivity is studied for the following parameters: (i) membrane pore diameters (0.1, 0.2, 0.5 and 0.8 mu m) and (ii) tangential velocity, transmembrane pressure and starch suspension concentration for a 0.2-mu m-pore diameter membrane. The related values and resistance variations are calculated. Membrane resistance is proven to be negligible with regard to fouling resistance. The deposit resistance constitutes the main part of fouling. Its reduction as a result of increasing pore size is balanced by an increase of internal fouling and polarization layer resistances. The total resistance of fouling decreases with velocity and increases with pressure and concentration. Test results are consistent with predictions deduced from crossflow filtration laws. This confirms the validity of the model and the experimental method proposed. [References: 36]