Patent Application
20060081524
This application discloses a hollow fiber membrane contactor, and method of making the same.
The use of hollow fiber membrane contactors to produce ultrapure liquids, which are essential to some industries, is generally known. Ultrapure liquids are free or substantially free from: minerals, ions, and gases. The most common dissolved or entrained gas is air, which has as its major components nitrogen, oxygen, and carbon dioxide.
Such hollow fiber membrane contactors are commercially available under the name of LIQUI-CEL® from Membrana a division of Polypore Inc. of Charlotte, N.C. and under the name of SEPAREL® from Dainippon Ink and Chemicals of Tokyo, Japan.
To facilitate manufacture of hollow fiber membrane contactors, the hollow fiber membranes are typically formed into a fabric (e.g., woven or knitted). The fabric is wound around a mandrel (e.g., a perforated center tube) and fixed into place by potting the fabric edges, with either thermosetting or thermoplastic materials, to form a unitized structure. This unit can then be inserted within a shell (housing) and sealed, i.e., with or without O-rings, to make a membrane contactor.
U.S. Pat. No. 3,827,562 discloses a blood filter device. The blood filter device utilizes a plurality of filter cloth layers disposed generally parallel to the path of blood flow and being supported in spaced relation and against collapse by a relatively coarse mesh arranged in layers and disposed between adjacent filter cloth layers.
U.S. Pat. No. 4,572,724 discloses a blood filter including a housing having upper and lower chambers with a cylindrical filter element disposed in the lower chamber.
U.S. Pat. No. 4,784,768 discloses a capillary filter arrangement for the sterilization of liquid media comprising two semipermeable capillary fiber bundles which are arranged adjacent each other in a single housing. The opposite openings of the housing are each sealed by end caps. The housing comprises at its ends cast layers in which the ends of the capillary fiber bundles are received. The ends of the first capillary fiber bundle are sealed with respect to the first distributing chamber and the ends of the second capillary fiber bundle are sealed with respect to the second distributing chamber so that the entire internal lumen of the first and second capillary fiber bundles respectively are in flow connection only with the second and first distributing chambers.
U.S. Pat. No. 5,362,406 discloses a leucocyte depletion filter assembly including a cylindrical housing having first and second chambers and an inlet into the first chamber and an outlet from the second chamber and a vent. A porous degassing element is positioned between the first and second chambers to remove gas from the liquid. The degassing element communicates with a vent covered with a liquophobic membrane, which allows gas but not the liquid to flow through the vent. A hollow, cylindrical filter element is positioned in the second chamber, and comprises a fibrous mass of microfibers capable of decreasing the leucocyte content of the liquid.
U.S. Pat. No. 5,468,388 discloses a pressurizable filter module for aqueous media having a degassing feature, the improvement comprising the use of a hydrophobic membrane between the inlet plenum of the filter module and the pressure relief valve.
U.S. Pat. No. 5,919,357 discloses a filter cartridge assembly comprising at least one filter cartridge, a first end cap, a second end cap, and a liquid transfer tube. The filter cartridge includes a housing with two ends, which contains a filter media. The first end cap is disposed on one end of the housing, and it includes a fluid inlet port, a fluid outlet port, a first fluid distributor and a vent including at least one hydrophobic membrane positioned in a channel formed in the first end cap that allows entrapped air to be removed from the cartridge. The second end cap is disposed on the second end of the housing, and it includes a product collection plenum, and a second fluid distributor that separates the filter media from the product collection plenum. The liquid transfer tube is disposed within the housing and extends from the product collection plenum to the fluid outlet port.
U.S. Pat. No. 6,623,631 discloses a vacuum filtration device for aqueous media that includes a hydrophilic tubular filter element in a cylindrical housing, and at least one hydrophobic gas-permeable membrane coupled with a gas bleed-off valve to allow the escape of air entrained in the filtration medium.
U.S. Pat. No. 6,635,179 discloses a filtration assembly, which is constructed so that two separate filtration compartments exist, resulting in redundant filtration of the fluid prior to infusion. Each compartment holds a filter, which preferably consists of a longitudinal bundle of semipermeable hollow fibers.
U.S. Pat. No. 6,719,907 discloses a dual-stage filtration cartridge, which includes a housing having a first end and an opposing second end. The housing has a primary fluid inlet and outlet at the first end of the cartridge. The housing also defines first and second filtration stages with the first filtration stage including first filtering elements disposed between the first and second ends of the housing. Each stage has a separate inter-lumen fiber space, but shares a common extra-lumen space. The primary fluid inlet communicates with the first filtering elements at the first end so that fluid flows through the first filtering elements toward the second end. The second filtration stage includes second filtering elements disposed between the first and second ends of the housing with the fluid outlet communicating with the second filtering elements at the first end.
U.S. Pat. No. 6,746,513 discloses a gas separation module, which includes an adsorbent filter medium inside the case that holds the active gas separation membrane. The adsorbent filter is positioned upstream of the membrane and is operative to extract from the feed gas contaminants which adversely affect membrane separation performance and which if not removed, would cause the membrane separation performance to deteriorate.
However, the above-mentioned prior art references fail to provide multiple separation capabilities in a single device; therefore, there is still a need for a multi-functional, high-purity membrane contactor, which provides multiple separation capabilities in a single device.
A hollow fiber membrane contactor includes a perforated center tube, a first mat comprising a first hollow fiber membrane, a second mat comprising a second hollow fiber membrane, a first tube sheet, a second tube sheet, a shell, and end caps. The first and second hollow fiber membranes are dissimilar. The first and second mats surround the center tube, and the first and second tube sheets affix the first and second mats to the center tube. The first hollow fiber membrane has a first lumen, and the second hollow fiber membrane has a second lumen. The first lumen may be open at the first tube sheet and closed at the second tube sheet while the second lumen may be open at the second tube sheet and closed at the first tube sheet. The shell surrounds the first and second mats, and it is sealed to the tube sheets. The end caps are affixed to the shell thereby defining headspaces therebetween the tube sheets and the end caps.
For the purpose of illustrating the invention, there is shown in the drawings a form that is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.
a, and 5b are cross longitudinal sectional views of end caps from the embodiment of
Referring to the drawings wherein like numerals indicate like elements, there is shown, in
Referring to
The perforated center tube 22 may be made of any material, which possesses sufficient mechanical strength to provide the desired support for the mats 30 and 32, and the first and second tube sheets 26 and 28. The center tube may be made of a polymeric material, a metal, or a composite material. The center tube 22 may be made of any polyolefin, for example polyethylene. The center tube 22 includes a plurality of perforations 34. The center tube 22 possesses a channel, and the first center tube end 36 and the second center tube end 38. The second center tube end 38 may be closed via a plug 20. Plug 20 may, for example, be a permanent plug or a removable plug. Additionally, the second center tube end 38 may contain circumferential helical grooves (e.g. screw threads for the removable plug).
The first and second membrane mats 30 and 32 are dissimilar hollow fiber membrane mats. The first and second membrane mats 30 and 32 are each adapted to facilitate a different separation goal, examples of which include, but are not limited to, gas separation or particulate filtration. First and second mat 30 and 32, as discussed below in further detail, may be dissimilar with respect to their materials of construction, porosity ranges, Gurley number ranges, pore size ranges, and the like. The instant specification describes the instant invention with reference to only two dissimilar membrane mats for convenience only; however, the instant claimed invention is not so limited, and other configurations, for example three or more dissimilar membrane mats, are also included.
The first membrane mat 30 may comprise a plurality of first hollow fiber membranes 31. The first membrane mat 30 may have any thickness, i.e. a single layer of first hollow fiber membranes 31 or multiple layers of first hollow fiber membranes 31 arranged atop each other. For example, the first membrane mat 30 has a thickness, i.e. a single layer of first hollow fiber membranes 31 or multiple layers of first hollow fiber membranes 31 arranged atop each other, in the range of about 1 to about 25 cm. The first membrane mat 30 may be hydrophobic or hydrophilic. Furthermore, the first membrane mat 30 may be adapted to facilitate the degassing of a fluid; in the alternative, first membrane mat 30 may be adapted to facilitate microfiltration or ultrafiltration of a fluid. The first membrane mat 30 may also be adapted to facilitate the addition of a gas, a liquid, or particles to a fluid. The first membrane mat 30 may be constructed using processes well known in the art. Generally, in hollow fiber mat construction, hollow fiber membranes are knitted or woven into a mat.
The first hollow fiber membrane 31 may have a wall thickness in the range of about 5 to about 1000 μm, a porosity in the range of about 10 to about 80%, and a Gurley number in the range of about 1 to about 2000 seconds/10 cc. Gurley number refers to the time in seconds required to pass 10 cc of air through one square inch of product under a pressure of 12.2 inches of water. Additionally, the first hollow fiber membranes 31 may have any average pore size, for example the first hollow fiber membranes 31 may have an average pore size in the range of about 10 to about 2000 nanometer. The first hollow fiber membrane 31 may be any material, for example a polymer. The polymer, for example, may be any synthetic polymer, cellulose, or synthetically modified cellulose. Synthetic polymers include, but are not limited to, polyethylene, polypropylene, polybutylene, poly (isobutylene), poly (methyl pentene), polysulfone, polyethersulfone, polyester, polyetherimide, polyacrylnitril, polyamide, polymethylmethacrylate (PMMA), ethylenevinyl alcohol, fluorinated polyolefins, copolymers thereof, and blends thereof. Preferably, the first hollow fiber membranes 31 are made of polyolefins. The first hollow fiber membrane 31 may be a hydrophobic hollow fiber membrane suitable for gas transfer; in the alternative, the first hollow fiber membrane 31 may be a hydrophilic membrane suitable for particulate microfiltration or ultrafiltration. The first hollow fiber membrane 31 may include a porous or non-porous skin or a coating. Skinned hydrophobic hollow fiber membranes are commercially available, for example, under the trademark OXYPLUS® from Membrana GmbH of Wuppertal, Germany.
The second membrane mat 32 may comprise a plurality of second hollow fiber membranes 33. The second membrane mat 32 may have any thickness, i.e. a single layer of second hollow fiber membranes 33 or multiple layers of second hollow fiber membranes 33 arranged atop each other. For example, the second membrane mat 32 has a thickness, i.e. a single layer of second hollow fiber membranes 33 or multiple layers of second hollow fiber membranes 33 arranged atop each other, in the range of about 1 to about 25 cm. The second membrane mat 32 may be hydrophobic or hydrophilic. Furthermore, the second membrane mat 32 may be adapted to facilitate microfiltration or ultrafiltration; in the alternative, the second membrane mat 32 may be adapted to facilitate the degassing of a liquid. The second membrane mat 32 may also be adapted to facilitate the addition of a gas, a liquid, or particles to a fluid. The second membrane mat 32 may be constructed using processes well known in the art. Generally, in hollow fiber mat construction, hollow fiber membranes are knitted or weaved into a mat.
The second hollow fiber membrane 33 may have a wall thickness in the range of about 5 to about 1000 μm, a porosity in the range of about 10 to about 80%, and a Gurley number in the range of about 1 to about 2000 seconds/10 cc. Additionally, the second hollow fiber membranes 33 may have any average pore size, for example the second hollow fiber membranes 33 may have an average pore size in the range of about 10 to about 2000 nanometer. The second hollow fiber membrane 33 may be any material, for example a polymer, as described hereinabove. Preferably, the second hollow fiber membranes 33 are made of polyolefins. The second hollow fiber membrane 33 may be a hydrophilic hollow fiber membrane suitable for particulate microfiltration or ultrafiltration; in the alternative, the second hollow fiber membrane 33 may be a hydrophobic hollow fiber membrane suitable for gas transfer. The second hollow fiber membrane 33 may include a porous or non-porous skin or a coating. Hydrophilic hollow fiber membranes are commercially available, for example, under the trademark MicroPES® and UltraPES® from Membrana GmbH of Wuppertal, Germany.
Generally, the first hollow fiber membrane 31 has a first lumen and the second hollow fiber membrane 33 has a second lumen. The first lumen may be open at the first tube sheet 26 while the second lumen may be sealed at the first tube sheet 26, and the first lumen may be sealed at the second tube sheet 28 while the second lumen may be open at the second tube sheet 28. However, in the alternative, the first lumen may be sealed at the first tube sheet 26 while the second lumen may be open at the first tube sheet 26, and the first lumen may be open at the second tube sheet 28 while the second lumen may be sealed at the second tube sheet 28.
The first and second membrane mats 30 and 32 may be selected from the group consisting of a leaf mat, a looped mat, a tape mat, and combinations thereof. As used herein, leaf mat refers to a sheet of hollow fiber membranes arranged perpendicular to the length of the leaf mat. A looped mat, as used herein, refers to a folded sheet of hollow fiber membranes arranged perpendicular to the length of the looped mat. In the alternative, a looped mat may be a repeatedly folded single strand of a very long fiber membrane. A tape mat, as used herein, refers to a sheet of hollow fiber membranes arranged parallel to the length of the mat.
The first tube sheet 26 may be located near the first center tube end 36 while the second tube sheet 28 may be located near the second center tube end 38. The first and second tube sheets 26 and 28 may be cylindrical in cross section with sufficient thickness to provide support for membrane mats 30 and 32 and to withstand the pressure exerted on them during operation. The first and second tube sheets 26 and 28 function to hold membrane mats 30 and 32 in place, and to partition the contactor 10, into a shell side passageway, a first lumen side passageway, and a second lumen side passage way. The first and second tube sheets 26 and 28 may be comprised of any material, for example a potting material, which may be a thermoplastic or a thermoset. An exemplary thermoplastic potting material includes, but is not limited to, polyethylene. An exemplary thermoset potting material includes, but is not limited to, an epoxy.
Plug 20 functions to seal off the center tube 22 at the second center tube end 38. Plug 20 may be made of any material, for example polyethylene. Plug 20 may be any shape, for example plug 20 may be cylindrical in cross section with sufficient thickness to withstand the pressure exerted on it during operation. Plug 20 may have circumferential helical grooves, which are complimentary to the circumferential helical grooves of the second center tube end 38, to secure plug 20 to center tube 22. In the alternative, plug 20 may be an integral component of center tube 22, or it may be an integral component of second tube sheet 28. Plug 20 may be a permanent plug or a removable plug.
Spacers may be used to maintain the space between the wound layers of the membrane mats 30 and 32 to promote uniform distribution of fluid over their entire surfaces.
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The vacuum port 54 is a permeate outlet means for removing gases, which permeate through the walls of the first hollow fiber membranes 31 into the first lumens. The vacuum port 54 is generally a port, nozzle, fitting, or other opening adapted for withdrawing the permeated gas.
The filtrate port 50 is a permeate outlet means adapted for removing fluids, which permeate through the walls of the second hollow fiber membrane 33 into the second lumens. The filtrate port 50 is generally a port, nozzle, fitting, or other opening, which allows the removal of the permeated fluid from the hollow fiber membrane contactor 10.
The auxiliary port 52 is generally a port, nozzle, fitting, or other opening adapted for back flushing contactor 10. Port 52 may be connected to center tube 22 via a second connecting tube 60. Second connecting tube 60 may be a cylindrical tube which fits into the center tube 22; in the alternative, the second connecting tube 60 is an extension of the center tube 22.
As will be readily apparent to those of ordinary skill, placement of ports may vary, so long as the integrity of the shell side passageway, first lumen side passageway, and second lumen side passageway according to instant invention is maintained as shown in
In construction, the first and second dissimilar membrane mats 30 and 32 are wrapped around center tube 22 in sequence offset from each other in a length-wise alignment relationship; in the alternative, mats 30 and 32 are wrapped around center tube 22 in alternate layers offset from each other in a length-wise alignment relationship. Next, the respective ends of the first and second mats 30 and 32 are affixed to center tube 22 via potting thereby forming first and second tube sheets 26 and 28. In the alternative, the winding and potting steps may be performed simultaneously. The first and second tube sheets 26 and 28 may then be cut thereby forming alternate open and sealed lumen ends, i.e. the first lumens may be open at the first tube sheet 26 while the second lumens may be sealed at the first tube sheet 26, and the first lumens may be sealed at the second tube sheet 28 while the second lumens may be open at the second tube sheet 28. This structure is, then, disposed within shell 14, and first and second tube sheets 26 and 28 are sealed to the shell 14, for example via O-rings or potting material. End caps 16 and 18 are adjoined to first and second shell ends 40 and 42, respectively; thereby, forming first headspace 62 and second headspace 64 therebetween first and second tube sheets 26 and 28 and end caps 16 and 18, respectively.
In alternative construction, first and second tape mats may be wound perpendicular to the center tube 22. The ends of the first and second tape mats may then be collected in a circular bunch, and connected to a side port, i.e. a vacuum port or a filtrate port, on the shell side.
In operation as shown in
In the alternative operation, as shown in
The present invention may be embodied in other forms without departing from the spirit and the essential attributes thereof, and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicated the scope of the invention.
