초록 ▼

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 memb

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.

대표청구항 ▼

1. 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

1. 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. 2. The process of claim 1 in which the membrane structure is in the form selected from the group consisting of a flat sheet, a pleated sheet, a spiral rolled sheet, a tube, a tube ribbon and a hollow fiber. 3. The process of claim 2 in which the membrane structure is a hollow fiber. 4. The process of claim 1 in which the microporous substrate is selected from the group consisting of a perforated sheet; porous woven or nonwoven fabric; microporous polymer film and microporous, hollow fiber. 5. The process of claim 1 in which the volatile liquid component is water. 6. The process of claim 1 in which the volatile liquid component is alcohol. 7. The process of claim 1 in which the feed mixture comprises a temperature sensitive substance selected from the group consisting of sugars; polysaccharides; carboxylic salts; proteins; fruit juice other than orange juice, grape juice, pineapple juice, apple juice, pear juice, cranberry juice and mixtures thereof; vegetable juice; soup broth; tea; neutraceuticals; latices; biological substances and mixtures thereof. 8. The process of claim 7 in which the biological substance is selected from the group consisting of vaccine, peptide hormone, recombinant protein, enzyme, nucleic acid, fermentation product selected from the group consisting of antibiotic, fungicide and oligopeptide, animal body fluid, and mixtures thereof. 9. The process of claim 1 in which the polymer composition comprises a high free volume polymer selected from the group consisting of polytrimethylsilyipropyne and an amorphous copolymer of perflnoro-2,2-dimethyl-1,3-dioxole. 10. The process of claim 9 in which the amorphous copolymer is a copolymer of perfluoro-2,2-dimethyl-1,3-dioxole and a complementary amount of at least one monomer selected from the group consisting of tetrafluoroethylene, perfluoromethyl vinyl ether, vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene. 11. The process of claim 10 in which the amorphous copolymer is a dipolymer of perfluoro-2,2-dimethyl-1,3-dioxole and tetrafluoroethylene. 12. The process of claim 11 in which the dipolymer comprises 50-95 mole % polymerized perfluoro-2,2-dimethyl-1,3-dioxole. 13. The process of claim 9 in which the membrane has an oxygen/nitrogen selectivity of at least about 1.5.