(723p) Ultrafiltration in Turbular Membranes Inserted Concentrically with a Ring Rod of Varying Ring Distances

Raising fluid velocity or creating turbulent behavior in the cross-flow membrane modules has two conflicting effects on ultrafiltration: They are the desirable effect of decrease in concentration polarization resistance and the undesirable effect of increase in frictional pressure loss. Since, along the flow channel in an ultrafilter, transmembrane pressure decreases while concentration polarization resistance increases. It appears therefore that gradually increasing the turbulent strength along the flow channel might suitably suppress the increasing resistance to permeation due to concentration polarization while properly maintaining the decreasing tranemembrane pressure. It is the purpose of present study to investigate the effect of varying baffled-ring distance on ultrafiltration and to derive the prediction equation for estimating the permeate flux, in a tubular membrane of a ring-rod insert with decreasing buffled-ring distance. It was found that the concentration polarization resistance could be reduced in a ring-rod tubular membrane ultrafilter by the turbulent behavior. The performance will be further improved if the baffled-ring distances gradually and properly decrease along the cross-flow channel with fixed number of baffled rings. Theoretical analysis was based on the mass and momentum balances coupled with the application of resistance-in-series model. Correlation predictions are rather acceptable for higher feed concentration comparing with the experimental results for ultrafiltration of dextran T500 aqueous solution in a tubular ceramic membrane of a nine-ring rod insert with gradually decreasing the baffled-ring distances.