US 6,569,341 B2Granted

Osmotic distillation process

AssigneeCMS Technology Holdings, Inc.

InventorJohn J. Bowser

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Abstract

A method of raising the concentration of a liquid mixture utilizes osmotic distillation to transfer a volatile liquid component from the mixture in contact with one side of a nonporous, preferably high free volume, gas permeable membrane to a strip solution in contact with the other side of the membrane. Due to its nonporous nature the gas permeable membrane resists penetration and wetting by oily components that may be present in the feed mixture. Similarly, occlusion of the membrane by solids is resisted. Preferably, an amorphous copolymer of perfluoro-2,2-dimethyl-1,3-dioxole is useful for the gas permeable membrane. Osmotic distillation utilizing such high free volume, nonporous gas permeable membranes can concentrate difficult liquid mixtures such as pulpy fruit juices and especially, limonene-containing juices, for example, orange juice. The process can be operated at high flux for long durations between membrane cleanings. Additionally, less contamination of the strip solution into the feed mixture occurs to provide a high quality concentrate.

Claims13

Dependent claims

A process for concentrating a liquid feed mixture comprising the steps of

providing a feed mixture of components present in initial concentration, the mixture comprising a volatile liquid component in which mixture said volatile liquid component is soluble and over which mixture said volatile liquid component has a first vapor pressure, and a strip solution over which the volatile liquid component has a second vapor pressure different from the first vapor pressure;
providing a two sided membrane structure comprising a nonporous membrane on one side and coextensive with a microporous substrate on the second side, the nonporous membrane comprising a polymer composition having a free volume of at least about 15% and being of a composition which is permeable to the volatile liquid component and not wettable by either the feed mixture or the strip solution;
contacting the feed mixture with the nonporous membrane while contacting the strip solution with the microporous substrate;
maintaining the second vapor pressure below the first vapor pressure, thereby causing the volatile liquid component to permeate the membrane from the feed mixture to the strip solution and thus producing a concentrated liquid mixture comprising components other than the volatile liquid component present at concentration greater than the initial concentration;
and
removing the concentrated liquid mixture
in which the volatile liquid component permeates the membrane at a steady rate of at least 0.1 L/(m2·h) continuously for at least 1 hour.

4 more elements

Dependencies are inferred from the claim text.