Flux Enhancement in Crossflow Membrane Filtration: Fouling and It's Minimization by Flow Reversal
Fouling problems are perhaps the single most important reason for relatively slow acceptance of ultrafiltration in many areas of chemical and biological processing. To overcome the losses in permeate flux associated with concentration polarization and fouling in cross flow membrane filtration, we investigated the concept of flow reversal as a method to enhance membrane flux in ultrafiltration. Conceptually, flow reversal prevents the formation of stable hydrodynamic and concentration boundary layers at or near the membrane surface. Further more, periodic reversal of the flow direction of the feed stream at the membrane surface results in prevention and mitigation of membrane fouling. Consequently, these advantages are expected to enhance membrane flux significantly. A crossflow membrane filtration unit was designed and built to test the concept of periodic flow reversal for flux enhancement. The essential elements of the system include a crossflow hollow fiber membrane module integrated with a two-way valve to direct the feed flow directions. The two-way valve is controlled by a controller-timer for periodic reversal of flow of feed stream. Another important feature of the system is that with changing feed flow direction, the permeate flow direction is also changed to maintain countercurrent feed and permeate flows for enhanced mass transfer driving force (concentration difference). Three feed solutions (Bovine serum albumin (BSA), apple juice and citrus fruit pectin) were studied in crossflow membrane filtration. These solutes are well-known in membrane filtration for their fouling and concentration polarization potentials. Laboratory-scale tests on a hollow-fiber ultrafiltration membrane module using each of the feed solutes show that under flow reversal conditions, the permeate flux is significantly enhanced when compared with the conventional unidirectional flow. The flux enhancement is dramatic (by an order of magnitude) with increased feed concentration and operating transmembrane pressure. Thus, flow reversal technology seems an attractive alternative to mitigate fouling problem in crossflow membrane filtration.
- Research Organization:
- North Carolina A & T State Univ., Greensboro, NC (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG26-00NT40834
- OSTI ID:
- 859173
- Country of Publication:
- United States
- Language:
- English
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FLUX ENHANCEMENT IN CROSSFLOW MEMBRANE FILTRATION: FOULING AND IT'S MINIMIZATION BY FLOW REVERSAL
FLUX ENHANCEMENT IN CROSSFLOW MEMBRANE FILTRATION: FOULING AND IT'S MINIMIZATION BY FLOW REVERSAL