DYNAMIC TURBULENCE PROMOTION IN REVERSE OSMOSIS PROCESSING OF LIQUID FOODS

SUMMARY– The phenomenon of concentration polarization operates to reduce the efficiency of solvent-solute separation in the processing of foods by reverse osmosis. The viscous nature of most food concentrates aggravates the problem. Disrupting the boundary layer by mechanically inducing turbulence in the fluid stream improves the permeation efficiency. Flux improvement of up to 3-fold is possible with dynamic turbulence promotion involving plastic spheres moving randomly with the orange juice concentrate. Concentrate (and sphere) movement is pulsed alternately from one end of the membrane flow channel to the other. The spheres are confined within the flow channel to avoid the problem of moving them through the recycling pumps. A net movement of concentrate results when the pump volume is greater in one direction than the other. The permeation rate with dynamic turbulence promotion does not drop off significantly with time. The long-term effects of sphere movement on the membrane surface are not known but are believed not to be serious.