Fluidized beds as turbulence promoters in the concentration of food liquids by reverse osmosis

Fluidized beds offer a potential improvement of reverse osmosis processes for food liquids, less fouling of the membrane, and reduced energy consumption. Our experiments were concerned with tubular systems in which fluidized beds of glass, steel, and lead beads were used. Glass beads appeared to be preferable, since they caused little damage to the membrane. Only with the larger glass beads (3 mm) did the membrane skin become corrugated, so that the rejection decreased. The permeate flux for Gouda cheese whey was almost equal to that of an empty tube for which the velocity was about thirty times higher. The erosive action of the glass beads on the fouling layer was partially responsible for this effect. For reverse osmosis of skim milk and potato fruit water the bed did not reduce the fouling layer to a sufficient extent and, therefore, had a lower permeate flux than an empty tube.