U.S. patent application number 10/424327 was filed with the patent office on 2003-10-16 for hollow fiber membrane contactor.
Invention is credited to Cho, Kwantai, Delozier, Clifton J., Holstein, Linus I., Pittman, R. Allen, Runkle, Charles J., Sengupta, Amitava.
Application Number | 20030192820 10/424327 |
Document ID | / |
Family ID | 25389467 |
Filed Date | 2003-10-16 |
United States Patent
Application |
20030192820 |
Kind Code |
A1 |
Cho, Kwantai ; et
al. |
October 16, 2003 |
Hollow fiber membrane contactor
Abstract
The present invention is directed to a contactor for degassing a
liquid. The contactor includes a perforated core and a microporous
membrane fabric wrapped around the core. The fabric includes a
polymethyl pentene hollow fiber as a weft fiber and a warp yarn. A
tube sheet secures the ends of the wound fiber and a shell encases
the tube sheet and fabric. The shell has at least one opening to
permit fluid flow through the shell and an end cap. In a further
embodiment the invention is directed to a contactor for degassing a
liquid wherein the contactor is adapted to withstand pressures
greater than 0.4 MPa and temperatures greater than 50.degree.
C.
Inventors: |
Cho, Kwantai; (Charlotte,
NC) ; Delozier, Clifton J.; (Fort Mill, SC) ;
Holstein, Linus I.; (Pineville, NC) ; Pittman, R.
Allen; (Charlotte, NC) ; Runkle, Charles J.;
(Charlotte, NC) ; Sengupta, Amitava; (Charlotte,
NC) |
Correspondence
Address: |
ROBERT H. HAMMER III, P.C.
3121 SPRINGBANK LANE
SUITE I
CHARLOTTE
NC
28226
US
|
Family ID: |
25389467 |
Appl. No.: |
10/424327 |
Filed: |
April 28, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10424327 |
Apr 28, 2003 |
|
|
|
09886653 |
Jun 21, 2001 |
|
|
|
Current U.S.
Class: |
210/321.83 ;
210/321.74; 210/498 |
Current CPC
Class: |
B01D 71/26 20130101;
B01D 63/02 20130101; B01D 19/0031 20130101; B01D 63/026 20130101;
B01D 2313/23 20130101; B01D 61/00 20130101; B01D 63/024
20130101 |
Class at
Publication: |
210/321.83 ;
210/321.74; 210/498 |
International
Class: |
B01D 063/00 |
Claims
That which is claimed:
1. A contactor for degassing a liquid comprising: a perforated
core; a pre-shrunk microporous membrane fabric wrapped around said
core, said fabric comprising a polymethyl pentene hollow fiber weft
and a polyolefin warp yarn wherein the weft count is between 50 and
70 fibers per inch, the warp count is between 3 and 12 yarns per
inch, and the warp yarn is finer than an 80 denier 40 filament
yarn; a tube sheet securing the ends of said fiber; a shell
encasing said tube sheet and fabric; at least one opening in said
shell to permit fluid flow through said shell; and an end cap
affixed to the shell.
2. A contactor according to claim 1 wherein said polyolefin yarn is
a 40 denier/20 filament polypropylene yarn.
3. A contactor according to claim 1 wherein said fabric is
pre-shrunk by heating said fabric to a temperature between about
55.degree. C. and about 65.degree. C. for about 2 to 8 hours.
4. A contactor according to claim 1 wherein said polymethyl pentene
hollow fiber is a skinned fiber.
5. A contactor according to claim 1 wherein said weft fiber count
is between 60 and 65 fibers per inch.
6. A contactor according to claim 1 wherein the aspect ratio of
said fabric is between 0.10 to 6.0 inches.sup.-1.
7. A contactor according to claim 1 wherein a liquid passes through
the shell side of the contactor.
8. A contactor according to claim 1 wherein said polymethyl pentene
hollow fiber fabric equates to an active membrane area greater than
0.05 m.sup.2.
9. A contactor according to claim 1 wherein the packing fraction of
the wound fabric is between about 35% and 45%.
10. A contactor according to claim 1 wherein the said warp fiber
count is between 6 and 7 fibers per inch.
11. A contactor for degassing a liquid: wherein said contactor is
adapted to withstand pressures greater than 0.4 MPa and
temperatures greater than 50.degree. C. and further comprises; a
shell; a pre-shrunk microporous membrane fabric comprising a
polymethyl pentene hollow fiber weft and a warp yarn wherein said
weft count is between 50 and 70 fibers per inch and said warp count
is between 3 and 12 yarns per inch; and at least one opening in
said shell to permit the fluid flow through said shell.
12. A contactor according to claim 11 wherein said warp yarn is a
polyolefin yarn finer than an 80 denier 40 filament yarn.
13. A contactor according to claim 12 wherein said polyolefin yarn
is a 40 denier/20 filament polypropylene yarn.
14. A contactor according to claim 11 wherein said polymethyl
pentene hollow fiber is a skinned fiber.
15. A contactor according to claim 11 wherein said fabric has a
weft fiber count of between 60 and 65 fibers per inch.
16. A contactor according to claim 11 wherein the aspect ratio of
said fabric is between 0.10 to 6.0 inches.sup.-1.
17. A contactor according to claim 11 wherein a liquid passes
through the shell side of the contactor.
18. A contactor according to claim 11 wherein said polymethyl
pentene hollow fiber fabric equates to an active membrane area
greater than 0.05 m.sup.2.
19. A contactor according to claim 11 wherein packing fraction of
the wound fabric is between about 35% and 45%.
20. A contactor according to claim 11 wherein said warp yarn count
is between 6 and 7 yarns per inch.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation application from
co-pending U.S. patent application Ser. No. 09/886,653 filed Jun.
21, 2001.
FIELD OF THE INVENTION
[0002] This invention is directed to a hollow fiber membrane
contactor.
BACKGROUND OF THE INVENTION
[0003] Hollow fiber membrane contactors are known. For example, see
U.S. Pat. Nos. 3,288,877; 3,755,034; 4,220,535; 4,664,681;
4,940,617; 5,186,832; 5,264,171; 5,284,584; and 5,449,457, each is
incorporated herein by reference. In general, such contactors
utilize a thin walled membrane to separate, via diffusion, gaseous,
solid or liquid components from a solution or colloidal mixture.
Hollow fiber membrane diffusion contactors are commercially
available under the name of LIQUI-CEL.RTM. from Celgard, Inc. of
Charlotte, N.C. and under the name of SEPAREL.RTM. from Dianippon
Ink and Chemicals of Tokyo, Japan (DIC). Such contactors have
numerous uses, one being the degassing of fluids.
[0004] The SEPAREL.RTM. contactor comprises a shell surrounding a
hollow fiber fabric that is wound around a perforated core. The
SEPAREL.RTM. contactor uses a fabric made of polymethyl pentene
(PMP) hollow fibers and polyester yarn. Hollow fibers made from PMP
exhibits unique diffusion properties. See Japanese Kokai 2-102714
(published Apr. 16, 1990). Additionally, the SEPAREL.RTM. contactor
operating parameters are limited to a maximum temperature of
50.degree. C. and a maximum feed water pressure of 0.4 Mpa. See,
Hollow Fiber Membrane Degassing Module--SEPAREL.RTM.,
www.dic.co.jp.
[0005] Commercial PMP fabrics used in the manufacture of contactors
utilize the PMP hollow fibers as the fill or weft and polyester
yarns as the warp yarn. This fabric has a tendency to break if the
fabric is wound under tension. One possible explanation for this
weakness is the use of polyester warp yarn in the production of the
fabric. Polyester is a relatively stiff material that does not bend
and flex well. When a PMP fabric is wound around a mandrel the warp
yarns absorb most of the applied load, thus fabrics using polyester
warp yarns break and tear. Fabrics similar to those described in
Japanese Kokai 2-102714 have been shown to break at essentially
zero tension during winding. Some degree of winding tension is
desirable to create a well-formed fiber bundle that fits properly
within a contactor shell.
[0006] Another possible explanation for the tearing exhibited by
such PMP fabrics is a failure to utilize properly spaced or sized
warp yarn. For example, fabrics similar to those described in
Japanese Kokai 2-102714 (which tear during winding) exhibit a
maximum warp yarn count of approximately 5 lines (yarns) per inch.
See JP 2-102714, Embodiment 3.
[0007] U.S. Pat. No. 4,911,846 discloses an artificial lung made
with a hollow fiber cord fabric. Note, U.S. Pat. No. 4,911,846,
FIGS. 11 and 12. The cord fabric comprises polyolefin hollow fibers
(including PMP hollow fibers), as weft fibers and warp fibers
(including polyesters, polyamides, polyimides, polyacrylonitriles,
polypropylenes, polyarylates, polyvinyl alcohols, etc.). The warp
yarns are preferably multifilament yarns of polyesters or
polyamides having a yarn fineness of 10 to 150 deniers, more
preferably 25 to 75 deniers. See U.S. Pat. No. 4,911,846 col. 6,
lines 3-14. No information is provided regarding the spacing of the
warp yarn or the makeup of non-polyester, non-polyamide warp
yarns.
[0008] Accordingly, a need exists for an improved contactor
preferably employing a fabric that is not susceptible to breakage
and operable at higher temperatures and pressures than known PMP
hollow fiber contactors.
SUMMARY OF THE INVENTION
[0009] The present invention is directed to a contactor for
degassing a liquid comprising a perforated core and a microporous
membrane fabric wrapped around the core. The fabric comprises a
polymethyl pentene hollow fiber, as a weft fiber, and a polyolefin
warp yarn. In preferred embodiments the fabric has a weft fiber
count between 50 and 70 fibers per inch and a warp yarn count
between 3 and 12 yarns per inch. A tube sheet secures the ends of
the wound fabric and a shell encases the tube sheet and wound
fabric. The shell has at least one opening to permit liquid flow
through the shell and an end cap.
[0010] In a further embodiment, the invention is directed to a
contactor for degassing a liquid wherein the contactor is adapted
to withstand pressures greater than 0.4 MPa and temperatures
greater than 50.degree. C. The contactor according to this
embodiment further comprises a shell and a microporous membrane
fabric comprising a polymethyl pentene hollow fiber, as a weft
fiber, and a warp yarn with fiber and yarn counts similar to those
mentioned above. The fabric is preferably wrapped around a
perforated core and situated inside the shell. The shell has at
least one opening to permit the liquid flow through the shell.
DESCRIPTION OF THE DRAWINGS
[0011] For the purpose of illustrating the invention, there is
shown in the drawings a form which is presently preferred; it being
understood, however, that this invention is not limited to the
precise arrangements and instrumentalities shown.
[0012] FIG. 1 is a schematic illustration of a hollow fiber
membrane contactor.
[0013] FIG. 2 is an illustration of the fabric according to the
invention.
[0014] FIG. 3 is a schematic illustration of a second embodiment of
the membrane contactor.
[0015] FIG. 4 is a schematic illustration of a third embodiment of
the membrane contactor.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Referring to the drawings wherein like numerals indicate
like elements, there is shown in FIG. 1 an embodiment of a hollow
fiber membrane contactor 10 according to the invention. The
contactor 10 includes a core tube 12. The core tube 12 has a
plurality of perforations 14. Hollow fibers 16 surround the core
tube 12. A shell 13 surrounds the fibers and the core tube 12. Tube
sheets 26 secure the lateral ends of fibers 16 to tube 12. The
lateral ends of shell 13 are closed with end caps 15.
[0017] Referring to FIG. 1, a liquid 18 preferably enters the
contactor 10 via a liquid inlet 20 of the core tube 12. The liquid
18 travels through the inlet 20 of the core tube 12 and exits the
core tube 12 via perforations 14 when a block 22 diverts the
liquid. The liquid 18 then travels over the exterior surfaces of
the hollow fibers 16. The liquid 18 re-enters the core tube 12 via
perforations 14 on the other side of the block 22 and exits the
core tube 12 via a liquid outlet 24. The hollow fibers 16 surround
the core tube 12 and are maintained generally parallel to core
tube's 12 axis via tube sheets 26. The hollow fibers 16 extend
through the tube sheet 26 and are in communication with headspaces
28 on either end of contactor 10, so that a vacuum 30 drawn at
ports 32 and 34 is in communication with the lumen side of hollow
fibers 16 via headspaces 28. Port 34, for example, may also be used
to introduce a sweep gas, which facilitates entrained gas
removal.
[0018] The membrane contactor 10 is preferably an external flow,
hollow fiber membrane module. The membrane contactor 10 has a lumen
side and a shell side. The lumen side, also known as the internal
side, is defined, in large part, by the lumen of the hollow fiber.
The shell side, also known as the external side, is defined, in
part, by the external surface of the hollow fiber. The liquid
travels through the shell (or external) side, while the vacuum (or
vacuum and sweep gas) is applied to the lumen (or internal) side.
Thereby, entrained gases from the liquid pass, via diffusion, from
the shell side through the membrane to the lumen side.
[0019] Preferably, the hollow fibers 16 are semi-permeable, gas
selective, heterogeneous, integrally asymmetric, and liquid
impermeable membranes. The membrane is, preferably, a single layer
membrane (e.g., not a composite or multi-layered membrane) and is
made from a homopolymer of PMP. The membrane is, preferably, a
skinned membrane and the skin is on the shell side. The membrane
has a permeability of less than 100 Barrers (10.sup.-8 standard
cm.sup.3.cm/sec.cm.sup.2.cm(Hg)). For example, see U.S. Pat. No.
4,664,681, incorporated herein by reference. The total membrane in
the contactor preferably has an active surface area greater than
0.05 m.sup.2 and most preferably between 0.1 m.sup.2 to 350
m.sup.2.
[0020] Referring now to FIG. 2, the hollow fibers 16 are preferably
made into a fabric 36 having a fill or weft yarn 38 and a warp yarn
40. Preferably the fabric is a weft insertion knitted fabric where
the warp yarn is the knitting yarn. The weft yarn 38 is the hollow
fiber 16. The fabric 36 preferably has a weft fiber count between
50 and 70 fibers per inch and most preferably between 60 and 65
fibers per inch.
[0021] The warp yarn 40 should be flexible, yet strong, and inert
to the liquid flowing through the contactor. The warp yarns 40 are
preferably multifilament polyolefin yarns. Most preferably the
yarns are selected from the group consisting of polypropylene and
polyethylene. Those skilled in the art recognize that the term
filament is sometimes used synonymously with cut filament which is
also called staple fiber. Accordingly, as used herein the term yarn
should be interpreted to include yarns made from filament and
staple fiber. Preferably, the yarn possesses a fineness sufficient
to resist tearing but not too large as to cause noticeable gaps
between fabric layers. Preferably the warp yarn should be between
80 denier/40 filament (i.e., a 80/40 yarn) and 20 denier/10
filament (a 20/10 yarn), most preferably around 40 denier/20
filament (a 40/20 yarn). Optionally, the warp yarn may include a
surface finish, e.g. a silicon oil surface finish.
[0022] The count of the warp yarn is also an important factor in
the design of the fabric. Too few warp yarns and the fabric will be
susceptible to tearing. Too many will diminish the efficiency of
the contactor by blocking surface area of the hollow fibers. In
preferred embodiments the warp yarn count is between about 3 and 12
yarns per inch of fabric; most preferably around 6 to 7 yarns per
inch.
[0023] When wound, the fabric 36 and the core tube 12 form a hollow
membrane unit 42. Unit 42 is preferably cylindrical. In use, it is
expected that the unit 42 will have a diameter ranging between
about 2 in. and 16 in. and a length ranging between about 8 in. and
72 in. Larger sizes are possible. The aspect ratio of the unit 42
is defined as L/D.sup.2 where L is the nominal length of the unit
and D is the nominal diameter of the unit. Preferably, the aspect
ratio will range between 0.1 to 6.0 in..sup.-1.
[0024] Furthermore, the fabric 36 is preferably wound under tension
to create a unit 42 having a packing fraction of between about 35%
to 45%. Packing fraction (PF) is defined as the number of fibers
(n) multiplied by the cross-sectional area of each fiber (A.sub.f)
divided by the cross-sectional area of the fiber bundle (A.sub.b)
where the cross-sectional area of the fiber bundle excludes the
area occupied by the core tube 12. Stated symbolically, 1 PF = n *
A f A b
[0025] Additionally, PMP hollow fibers have a natural tendency to
shrink which increases with temperature. Accordingly, in preferred
embodiments of the invention, the PMP fabric 36 is preshrunk prior
to winding. A preferred method of preshrinking and stabilizing the
fabric is to heat the fabric to about 15.degree. C. above the
expected operating temperature for approximately 2 to 8 hours,
preferably 4 hours. Heating the fabric between about 55.degree. C.
and about 65.degree. C. for about 2 to 8 hours, preferably 4 hours,
should provide adequate fiber stabilization for most anticipated
applications. Preshrinking the fabric and winding the fabric under
tension aids in achieving a well-formed bundle that contributes to
the higher operating parameters (e.g., temperature and pressure)
achieved by the invention.
[0026] Hollow fiber membrane units 42 formed according to the
invention may be combined with other structural elements to create
a contactor. Such structural elements are well known in the art and
generally consist of an outer shell with at least one opening in
the shell to permit fluid flow through the shell. Commonly assigned
U.S. patent application Ser. No. 09/816,730, filed Mar. 22, 2001,
incorporated herein by reference, discloses several possible
structures for contactors, all of which are applicable to the
present invention.
[0027] Referring to FIG. 3, contactor 10' is the same as shown in
FIG. 2 but for a flow diverting baffle 50 located within the shell
side, and port 34 has been moved. The baffle 50 is added to promote
distribution of liquid over all exterior surfaces of the hollow
fibers 16. Port 34 is moved to illustrate the non-criticality of
port location.
[0028] Referring to FIG. 4, contactor 10" differs from contactors
10 and 10' by moving liquid outlet 24 from the terminal end of core
tube 12 to the contactor shell, as illustrated. Vacuum 30 is in
communication with headspace 28 which, in turn, is in communication
with the lumens of hollow fibers 16. The second headspace
illustrated in the previous embodiments has been eliminated. Liquid
18 enters the liquid inlet 20 of the core tube 12. Liquid 18 exits
the tube 12 via perforations 14, travels over the exterior surfaces
of the hollow fibers 16, and exits the shell side via an outlet 24.
The outlet designated 24 may be placed at other locations on the
exterior of the contactor so that it maintains communication with
the shell side.
[0029] The contactor according to the invention may be formed using
any of the methods known by those skilled in the art. One such
method is set forth in commonly assigned U.S. patent application
Ser. No. 09/851,242, filed May 8, 2001.
[0030] The present invention may be embodied in other specific
forms without departing from the spirit or essential attributes
thereof, and, accordingly, reference should be made to the appended
claims, rather than to the foregoing specification, as indicating
the scope of the invention.
* * * * *
References