Membrane-based removal of condensable vapors

• US 5,236,474 A
• Filed: 09/09/1992
• Issued: 08/17/1993
• Est. Priority Date: 09/13/1991
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: Bend Research Inc. (Lonza Group AG)
• Inventors: Schofield, Richard W., Friesen, Dwayne T., McCray, Scott B., Ray, Roderick J., Newbold, David D.
• Primary Examiner(s): SPITZER, ROBERT H
• Application Number:
  US07/942,679
• Time in Patent Office: 342 Days
• Field of Search: 55/16, 55/68, 55/158, 55/267-269, 55/23
• US Class Current: 95/47
• CPC Class Codes: B01D 2313/221 Heat exchangers
• CPC Class Codes: B01D 53/22 by diffusion manufacturing semi-permeable membranes B01D67/00; form, structure or properties of semi-permeable membranes B01D69/00; material for semi-permeable membranes B01D71/00
• CPC Class Codes: B01D 53/268 by diffusion
• CPC Class Codes: B01D 63/02 Hollow fibre modules

Abstract

A process for removing and recovering a condensable vapor from a gas stream by a membrane contactor is disclosed wherein a gas stream containing a condensable vapor is circulated on one side of hollow fiber membranes while cool extraction fluid is circulated on the other side under a total pressure differential, thereby condensing the condensable vapor in the gas stream, the condensed vapor permeating the membrane and becoming entrained in the cool extraction fluid.

Claims

1. A process for removing and recovering a condensable vapor from a gas stream comprising the steps:

(a) providing at least one hollow fiber membrane having a feed side and a permeate side;

(b) contacting the feed side of said membrane with a gas stream containing a condensable vapor;

(c) contacting the permeate side of said membrane with a cool extraction fluid, the total permeate side pressure being less than the total feed side pressure said total permeate side pressure being maintained by throttling said cool extraction fluid with a throttle valve after said fluid has been pressurized with a liquid circulation pump and prior to contact with said permeate side; and

(d) entraining in said cool extraction fluid on the permeate side condensed vapor from said gas stream.

2. The process of claim 1 including removing said condensed vapor from said cool extraction fluid.

3. The process of claim 2 including forming a recycle stream by recycling said cool extraction fluid to the permeate side of said membrane in step (c).

4. The process of claim 3 wherein the method for removing said condensed vapor from said cool extraction fluid comprises removing condensed vapor from said recycle stream at a rate equal to the rate at which condensed vapor is entrained in said cool extraction fluid.

5. The process of claim 2 wherein the method for removing said condensed vapor from said extraction fluid is selected from the group consisting of distillation, vacuum distillation, membrane distillation, evaporation, vacuum evaporation, liquid/liquid extraction, phase separation, crystallization, adsorption, reverse osmosis, nanofiltration, and pervaporation.

6. The process of claim 1 wherein said feed side is the outside of said hollow fiber and said permeate side is the lumen of said hollow fiber.

7. The process of claim 1 wherein said condensable vapor is selected from the vapors of the group consisting of chlorofluorocarbons, chlorinated hydrocarbons, non-chlorinated hydrophobic organics, non-chlorinated hydrophilic organics, and inorganic compounds.

8. The process of claim 7 wherein said chlorinated hydrocarbons are selected from the group consisting of methylene chloride, trichloroethylene, trichloroethane, carbon tetrachloride, and chlorobenzene.

9. The process of claim 7 wherein said non-chlorinated hydrophobic organics are selected from the group consisting of benzene, toluene, xylene, ethyl benzene, cyclohexane, propane, butane, hexane, and octane.

10. The process of claim 7 wherein said non-chlorinated hydrophilic organics are selected from the group consisting of ethanol, methanol, phenols, cresols, acetone, ethyl acetate, methyl ethyl ketone, methyl t-butyl ketone, nitrobenzene, triethyleamine, acetonitriles, dimethyl formamide, and dimethylacetamide.

11. The process of claim 7 wherein said inorganic compounds are selected from the group consisting of water and ammonia.

12. The process of claim 1 wherein said hollow fiber membrane is nonporous.

13. The process of claim 1 wherein said hollow fiber membrane is microporous.

14. The process of claim 1 wherein said hollow fiber membrane is hydrophilic.

15. The process of claim 14 said hollow fiber membrane is selected from the group consisting of cellulose acetate, regenerated cellulose, polyimide, polyamide, polymethacrylates, polyvinylalcohol, polyethylacetate, and polyacrylonitrile.

16. The process of claim 1 wherein said hollow fiber membrane is hydrophobic.

17. The process of claim 16 wherein said hollow fiber membrane is selected from a group consisting of polysulfone, polyethersulfone, silicone-rubber coated polysulfone, silicone rubber, natural rubber, butyl rubber, polyvinylchloride, tygon, polyarylene ethers, substituted polyacetylenes, polyurethane, hydrophobic polyimides, polyethylene, polypropylene, polybutylene, polyisoprene, polybutadiene, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidine chloride, polyhexafluoro propylene, polystyrene, and copolymers thereof.

18. The process of claim 1 wherein said cool extraction fluid is selected from the group consisting of hydrophilic and hydrophobic compounds.

19. The process of claim 18 wherein said cool extraction fluid is a hydrophilic compound and is selected from the group consisting of water, glycerol, ethylene glycol, polyethylene glycol, propylene carbonate, acetonitrile, dimethylacetamide, stearic acid, octanol, phenols, and cresols.

20. The process of claim 18 wherein said cool extraction fluid is a hydrophobic compound and is selected from the group consisting of dodecane, silicone oil, and petroleum naphtha.

21. The process of claim 1 wherein said cool extraction fluid comprises a mixture of compounds.

22. The process of claim 1 wherein said cool extraction fluid consists essentially of the liquid form of said condensable vapor.

23. The process of claim 1 wherein the difference in temperature between said cool extraction fluid and said feed gas is at least 1°

C.

24. The process of claim 1 wherein the difference in pressure between said permeate side and said feed side is from 0.001 to 1 atm.

25. The process of claim 1 wherein said feed gas and said cool extraction fluid flow in opposite directions.

26. The process of claim 1 wherein said feed gas is air, said condensable vapor is water vapor, and said cool extraction fluid is water.