COMPOSITE ION CONDUCTING MEMBRANE TUBING AND PROCESS OF MAKING SAME

Abstract

A composite ion conducting tube is made by wrapping a support material or ion conducting sheet to from a tube having overlaps of layers that are bonded. The ion conducting sheet or tape used to make the tube may be very thin and the tube may be formed in situ by wrapping the support material and then coating with ion conducting polymer. The ion conducting tubes may be used in a pervaporation module or desalination system. The ion conducting tubes may be spirally wrapped or longitudinally wrapped and may be very thin having a tube wall thickness of no more than 25 microns.

Claims

1. An ion conducting tube comprising: a) a composite ion conducting sheet comprising: i) a permeable support material; and ii) an ion conducting polymer that is coupled to the support material; b) an overlap area formed by an outer layer of the composite ion conducting sheet over an inner layer of the composite ion conducting sheet; wherein the outer layer of the composite ion conducting sheet is attached to the inner layer of the composite ion conducting sheet in the overlap area to form said ion conducting tube; c) a length from a first end to a second end; and d) a tube conduit extending along said length.

2. The ion conducting tube of claim 1, wherein the thickness of the composite ion conducting sheet is no more than 25 microns.

3. The ion conducting tube of claim 1, wherein the thickness of the composite ion conducting sheet is no more than 15 microns.

4. The ion conducting tube of claim 1, wherein the tube has a tube surface area that is the product of an outer circumference of the tube and a length of the tube, and wherein the overlap area is no more than 40% of a tube surface area.

5. The ion conducting tube of claim 1, wherein the tube has a tube surface area that is the product of an outer circumference of the tube and a length of the tube, and wherein the overlap area is no more than 20% of a tube surface area.

6. The ion conducting tube of claim 4, wherein the ion conducting tube is a longitudinally wrapped tube, wherein the overlap area extends longitudinally along the length of the tube.

7. The ion conducting tube of claim 4, wherein the ion conducting tube is a spirally wrapped tube having a wrap angle of the composite ion conducting sheet around the ion conducting tube.

8. The ion conducting tube of claim 1, wherein the ion conducting polymer is a cation conducting polymer.

9. The ion conducting tube of claim 1, wherein the ion conducting polymer is an anion conducting polymer.

10. The ion conducting tube of claim 1, wherein the support material is a porous fluoropolymer having pores.

11. The ion conducting tube of claim 10, wherein the porous fluoropolymer is expanded polytetrafluorethylene.

12. The ion conducting tube of claim 1, further comprising a mandrel configured within the tube conduit.

13. The ion conducting tube of claim 1, further comprising a mandrel, and wherein the ion conducting tube is configured within the mandrel.

14. A process for making an ion conducting tube as described in claim 1 comprising: a) wrapping the support material around a mandrel to form a wrapped mandrel; b) coating the wrapped mandrel with the ion conducting to form the composite ion conducting sheet; c) bonding the overlap areas to form the ion conducting tube.

15. The process of claim 14, further comprising bonding the support material together before coating the wrapped mandrel with ion conducting polymer.

16. The process of claim 14, wherein bonding the overlap areas includes heating the composite ion conducting sheet.

17. The process of claim 14, further comprising swelling the ion conducting polymer and removing the ion conducting tube from the mandrel.

18. A process for making an ion conducting tube as described in claim 1 comprising: a) wrapping the composite ion conducting sheet around a mandrel to form a wrapped mandrel; b) then, bonding the composite ion conducting sheet together to form the ion conducting tube.

19. The process of claim 18, further comprising removing the ion conducting tube from the mandrel.

20. The process of claim 18, further comprising swelling the ion conducting polymer and removing the ion conducting tube from the mandrel.

Description

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0033] The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention.

[0034] FIG. 1 is a diagram of a pervaporation unit.

[0035] FIG. 2 shows a perspective view of an exemplary ion conducting tube comprising a spirally wrapped ion conducting membrane sheet to form a spiral wrapped ion conducting tube.

[0036] FIG. 3 shows a perspective view of an exemplary ion conducting tube comprising a longitudinally wrapped, or cigarette wrapped ion conducting membrane sheet to form a longitudinally wrapped ion conducting tube.

[0037] FIG. 4 shows a side view of an ion conducting tube configured over a support mandrel having apertures to allow fluid contact with the ion conducting tube.

[0038] FIG. 5 shows a cross sectional view of an exemplary ion conducting sheet comprising an ion conducting polymer and a support material.

[0039] FIG. 6 shows a cross sectional view of an exemplary ion conducting sheet comprising an ion conducting polymer and a support material.

[0040] FIG. 7 shows a cross sectional view of an exemplary spiral wrapped tube comprising ion conducting tape that is bonded together in an overlap area.

[0041] FIG. 8 shows an exemplary module comprising a plurality of ion conducting tubes, as described herein.

[0042] Corresponding reference characters indicate corresponding parts throughout the several views of the figures. The figures represent an illustration of some of the embodiments of the present invention and are not to be construed as limiting the scope of the invention in any manner. Further, the figures are not necessarily to scale, some features may be exaggerated to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0043] As used herein, the terms comprises, comprising, includes, including, has, having or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Also, use of a or an are employed to describe elements and components described herein. This is done merely for convenience and to give a general sense of the scope of the invention. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

[0044] Certain exemplary embodiments of the present invention are described herein and are illustrated in the accompanying figures. The embodiments described are only for purposes of illustrating the present invention and should not be interpreted as limiting the scope of the invention. Other embodiments of the invention, and certain modifications, combinations and improvements of the described embodiments, will occur to those skilled in the art and all such alternate embodiments, combinations, modifications, improvements are within the scope of the present invention.

[0045] As shown in FIG. 1, an exemplary heat exchanger module which exchanges heat between the incoming cold membrane circulating stream and the steam obtained from the membrane contactor.

[0046] Referring to FIGS. 2 and 7, an exemplary ion conducting tube 10 comprises a spirally wrapped ion conducting membrane sheet 40, or ion conducting tape 44 to form a spiral wrapped ion conducting tube 32. The ion conducting tube 10 is has a tube wall 20 formed by the spirally wrapped ion conducting tape 44 that is wrapped at a wrap angle 33 with respect to the longitudinal axis 27 of the tube, or length axis of the tube, a line extending along the center of the tube conduit 22. An exemplary wrap angle may be 80 degrees or less, 75 degrees or less, 60 degrees or less, 45 degrees or less, 30 degrees or less and any range between and including the wrap angles provided. A smaller wrap angle may provide less overlap area and therefore better performance. The tube has an outside surface 12 and an inside surface 14, and a tube conduit 22 extending along the length 29 of the tube. The ion conducting tape 44 comprises an ion conducting polymer 42 and a support material 50, and has a width 45. The spiral wrap forms an overlap area 24 between adjacent tape wraps and this overlap area has an overlap with 25 as shown in FIG. 7. As shown in FIG. 7, the ion conducting polymer 42 of a first layer of the ion conducting tape 44 is bonded to the ion conducting polymer 42 of a second layer of the ion conducting tape 44 to form the bonded area 26. As described herein the overlap width may be fraction of the tape width, such as no more than about 30% of the tape width, no more than about 25% of the tape width, no more than about 20% of the tape width, no more than about 10% of the tape width, or even no more than about 5% of the tape width to provide a high percentage of the spiral wrapped tube 32 that is only a single layer, thereby increase the rate of transfer of ions through the tube. The tube wall thickness 21 is the thickness of the bonded area or both layers in the overlap area and the tube wall thickness is the thickness of a single ion conducting tape 44 otherwise.

[0047] As shown in FIG. 3, an exemplary ion conducting tube 10 comprises a longitudinally wrapped, or cigarette wrapped ion conducting membrane sheet 40 to form a longitudinal wrapped ion conducting tube 34. The ion conducting sheet 40 is wrapped around the longitudinal axis 27 of the tube. In this embodiment, the length of the tube 29 is the width of the ion conducting sheet and the wrap angle is perpendicular to the longitudinal axix 27. The longitudinal wrapped ion conducting tube 34 has an overlap are 25 having an overlap width 25. Again, the overlap width may be no more than about 30% of the tape width, no more than about 25% of the tape width, no more than about 20% of the tape width, no more than about 10% of the tape width, or even no more than about 5% of the tape width to provide a high percentage of the spiral wrapped tube 32 that is only a single layer, thereby increase the rate of transfer of ions through the tube.

[0048] As shown in FIG. 4, an ion conducting tube 10 is configured over a support mandrel 54 having apertures 56 to allow fluid contact with the ion conducting tube. A support mandrel may be rigid, such as a metal or plastic tube, or may be pliable and able to bend and flex. The apertures may form a substantial part of the mandrel and may be at least 50% of the area, at least 75% of the area, at least 80% of the area, at least 90% of the area, whereby the higher the aperture area percentage the higher the contact of fluid with the ion conducting tube, and therefore more ion transfer. The exemplary mandrel has adapter ends 55, 55 that may comprise a fitting for attachment to a module frame.

[0049] Referring now to FIGS. 5 and 6, an exemplary ion conducting sheet 40, such as an ion conducting tape 44, comprises an ion conducting polymer 42 and a support material 50 and has a single sheet thickness 41. A tape is simple a sheet that is narrow and conducive for spiral wrapping. The support material may be a porous material and the ion conducting polymer, such as an ionomer, may fill a substantial portion of the pores in the support material, such as by being imbibed into the support material. The ion conducting polymer may extends along one or both of the opposing surfaces of the composite ion conducting sheet as a surface layer 48 and has a surface layer thickness 49. In FIG. 5, the ion conducting polymer fills the pores of the support material and extends along both opposing surfaces. As shown in FIG. 6 the ion conducting polymer is imbibed into the support material and extends along one surface of the support material.

[0050] As shown in FIG. 7, the ion conducting layers extending along the opposing surfaces are bonded together in the overlap area 24 to form a bonded area 26 between the surface layer 48 and surface layer 48. Note that the surface layer may extend into the support 50 to bond layers of ion conducting sheets or tapes together. A fluid tight seal may be formed by the overlap and bonded area.

[0051] As shown in FIG. 8, an exemplary module 70 comprises a plurality of ion conducting tubes 10 that extend from a tube inlet 72 to a tube outlet 74. A flow of fluid flows through the tubes and a cross flow of fluid flow around the outside surface of the tubes from a cross-flow inlet 76 to a cross-flow outlet 78. Moisture may be transferred from or to the cross-flow fluid depending on the desired arrangement. The ion conducting tubes may be potted with potting 75 or otherwise attached to the inlet frame 71 and outlet from 73. Each tube may be configured around a mandrel 54 and the mandrel may have ends that are conducive to potting or attachment to the frame. The mandrel may have an adapter end 55 which comprises a fitting on the ends that can be secured to the frame and the adapter may have threads or beveled ends for sealing. Also note that the mandrel may have apertures along the center portion but not proximal the ends where the mandrel is attached to the frame.

[0052] It will be apparent to those skilled in the art that various modifications, combinations and variations can be made in the present invention without departing from the scope of the invention. Specific embodiments, features and elements described herein may be modified, and/or combined in any suitable manner. Thus, it is intended that the present invention cover the modifications, combinations and variations of this invention provided they come within the scope of the appended claims and their equivalents