Investigation of membrane filtration in a rotating disk geometry: Use of computational fluid dynamics and laboratory evaluation

The feasibility, fluid dynamics and particle transport mechanics of rotary membrane filtration were investigated. The hypothesis tested was that, by rotating a disk membrane filter, a significant back-transport of suspended particles from the membrane could be accomplished due to centrifugal force and high shear rates. This hypothesis was tested by investigating in computational simulations and laboratory experiments the fluid dynamics of rotary membrane filtration, developing a better understanding of particle transport and fouling and evaluating the feasibility of treating feed streams with high solids loading. A commercial prototype rotary membrane disk filtration pilot and a laboratory pilot, which was designed and constructed as part of this research, were evaluated with respect to permeate flux performance as a function of feed solids concentration. The laboratory pilot was further evaluated to investigate particle transport and fouling behavior as a function of the operating parameters of rotation rate and transmembrane pressure drop. A high-fidelity computational fluids dynamics model of the laboratory pilot was developed. Results from simulations carried out with this model were used in concert with results from laboratory experiments to analyze particle transport and to draw general conclusions. Permeate flux in rotary membrane disk filtration was found to be very insensitive to particle loading in the feed stream. The correlation between rotation rate and permeate flux was very strong. Permeate flux performance was linked to high centrifugal force and radial drag near the membrane surface. A performance trade-off existed between the generation of high shear rates and centrifugal accelerations via high rotation rates and the radial distribution of the transmembrane pressure drop across the membrane. Permeate interior to the disk was under the influence of centrifugal force and therefore imparted a back pressure opposing filtration which increased with rotation rate.