Water vapor permeable membrane module

Abstract

The present invention makes it possible to provide a water vapor permeable membrane module in which water vapor permeability and durability can be enhanced.　The water vapor permeable membrane module according to the present invention is provided with a hollow fiber membrane bundle comprising a plurality of hollow fiber membranes that extend in an axial direction. Each of the plurality of hollow fiber membranes is covered by a covering portion obtained by braiding a plurality of filaments. The filaments are monofilaments.

Description

Water vapor permeable membrane module

[0001] The present invention relates to a water vapor permeable membrane module.

[0002] Gas separation membrane modules that separate moisture contained in gas using hollow fiber membranes are known. In a gas separation membrane module, a hollow fiber bundle consisting of multiple hollow fiber membranes is packed into a cylindrical casing, and both ends of the hollow fiber bundle are airtightly fixed to the casing with the end faces of each hollow fiber membrane open. When using a gas separation membrane module for dehumidification, a wet gas is passed through each hollow fiber membrane and a dry purge gas is passed outside each hollow fiber membrane in the casing, causing the moisture contained in the wet gas to permeate each hollow fiber membrane. This separates the moisture from the wet gas, yielding a dry gas. For example, Patent Document 1 below describes a gas separation membrane module in which the ends of a hollow fiber bundle consisting of multiple hollow fiber membranes are fixed to a resin tube sheet, and the hollow fiber bundle and tube sheet are disposed inside a casing.

[0003] JP 2013-86000 A

[0004] In the gas separation membrane module described above, the arrangement of the hollow fiber membranes is prone to become uneven during the process of fixing the hollow fiber bundle to the tube sheet during the manufacturing process of the gas separation membrane module. This often results in a small gap between the hollow fiber membranes or causes the hollow fiber membranes to be placed in direct contact with each other. This makes it difficult for gas to flow between the hollow fiber membranes. This makes it difficult for moisture that has permeated through the hollow fiber membranes to move between the gas to be dehumidified and the gas to be humidified flowing inside and outside the hollow fiber membranes, respectively, which could result in a decrease in the water vapor permeability of the gas separation membrane module. Furthermore, when compressed gas at high pressure flows through the hollow fiber membranes, an outward pressure is applied to the inner circumferential surface of each hollow fiber membrane, causing the hollow fiber membranes to expand. If the diameter of each hollow fiber membrane becomes too large, the pressure resistance of each hollow fiber membrane decreases, which could result in a decrease in the durability of the water vapor permeable membrane module.

[0005] In view of the above circumstances, an object of the present invention is to provide a water vapor permeable membrane module that can improve water vapor permeability and durability.

[0006] The present invention has the following aspects. [1] A water vapor permeable membrane module comprising a hollow fiber membrane bundle consisting of a plurality of hollow fiber membranes extending along an axial direction, each of the plurality of hollow fiber membranes being covered with a covering portion formed by braiding a plurality of filaments, and the ratio of the area of ​​the portion of the outer circumferential surface of the hollow fiber membrane covered with the covering portion to the area of ​​the outer circumferential surface of the hollow fiber membrane is in the range of 5% to 65%. That is, in the water vapor permeable membrane module of the present invention, because each hollow fiber membrane is covered with a covering portion, when used for dehumidification, a dry purge gas can be stably flowed along the outer circumferential surface of each hollow fiber membrane. This allows moisture contained in the moist compressed gas flowing inside each hollow fiber membrane to be efficiently permeated to the outside of each hollow fiber membrane, thereby improving water vapor permeability.

[0007] [2] The water vapor-permeable membrane module according to [1], wherein the filament is a monofilament. [3] The water vapor-permeable membrane module according to [1] or [2], wherein the outer diameter of the filament is in the range of 0.01 to 0.25 times the outer diameter of the hollow fiber membrane. [4] The water vapor-permeable membrane module according to any one of [1] to [3], wherein the filament is composed of one or more resins selected from the group consisting of polyphenylene sulfide, polyacrylonitrile, polypropylene, polyvinylidene fluoride, polyarylate, perfluoroalkoxyalkane, polytetrafluoroethylene, polyether ether ketone, polybenzimidazole, polysulfone, polyphenylsulfone, polyethersulfone, polyimide, polyetherimide, polyamide, and polyamideimide. [5] A water vapor permeable membrane module according to any one of [1] to [4], comprising a cylindrical case extending along the axial direction and open on both sides in the axial direction, and a resin sealant, the hollow fiber membrane bundle being filled inside the case, and the sealant sealing between the plurality of hollow fiber membranes and between the hollow fiber membrane bundle and the case. [6] A water vapor permeable membrane module according to [5], wherein a purge gas flows inside the case, and the purge gas is part of the gas discharged from the hollow fiber membrane bundle.

[0008] According to the present invention, it is possible to provide a water vapor permeable membrane module that can improve water vapor permeability and durability.

[0009] FIG. 1 is a cross-sectional view showing a water vapor permeable membrane module according to one embodiment of the present invention, taken along the axial direction. FIG. 2 is a view of a water vapor permeable membrane module according to one embodiment of the present invention, seen from the upstream side. FIG. 3 is an external view showing hollow fiber membranes and a covering portion according to one embodiment of the present invention. FIG. 4 is a first cross-sectional view showing a sealant molding step for a water vapor permeable membrane module according to one embodiment of the present invention. FIG. 5 is a second cross-sectional view showing a sealant molding step for a water vapor permeable membrane module according to one embodiment of the present invention. FIG. 6 is a third cross-sectional view showing a sealant molding step for a water vapor permeable membrane module according to one embodiment of the present invention.

[0010] The following terms used in this specification and claims have the following meanings. A numerical range expressed by the term "to" means a numerical range with the numbers before and after the term "to" as the lower and upper limits. "Filling rate of hollow fiber membranes in the case" means the ratio of the total cross-sectional area of ​​each hollow fiber membrane, based on the outer edge, to the cross-sectional area of ​​the interior of the case in a cross section of the case cut perpendicular to the axial direction. "Effective length of the case" means the length of the hollow fiber membranes that contribute to water vapor separation in the case, and is typically the length between the sealing materials in the case. "Coverage rate" means the ratio of the area of ​​the portion of the outer surface of the hollow fiber membrane that is covered by the covering portion to the area of ​​the outer surface of the hollow fiber membrane.

[0011] The water vapor permeable membrane module of the present invention transfers moisture that has permeated through the hollow fiber membrane between the gas to be dehumidified and the gas to be humidified that flow inside and outside the hollow fiber membrane. An example of a water vapor permeable membrane module of the present invention will now be described with reference to the drawings. Note that the dimensions and other details of the drawings shown in the following description are merely examples, and the present invention is not necessarily limited thereto. Appropriate modifications can be made within the scope of the present invention.

[0012] In the following description, arrow Df is shown in each figure as appropriate. Arrow Df indicates the direction in which compressed gas flows in the water vapor permeable membrane module. In the following description, the side in which the arrow Df points (+Df side) in the direction in which compressed gas flows is referred to as the "downstream side," and the side opposite to the side in which the arrow Df points (-Df side) in the direction in which compressed gas flows is referred to as the "upstream side."

[0013] The water vapor permeable membrane module 10 of this embodiment is a dehumidification device that dehumidifies compressed gas PA1 and discharges dried compressed gas PA2. The compressed gas PA2 discharged from the water vapor permeable membrane module 10 is supplied to equipment (not shown). The equipment uses the compressed gas PA2 to move itself or a part of the equipment. Examples of equipment include a robot whose moving parts are moved by the compressed gas PA2 and a train pantograph. As will be described later, the water vapor permeable membrane module 10 of this embodiment can also be used as a humidification device that humidifies compressed gas PA1 and discharges moist compressed gas PA2.

[0014] For example, when an atmosphere Am at atmospheric pressure (0.1 MPaA), a temperature of 20° C., and a relative humidity of 25% is compressed to 0.8 MPaA to generate compressed gas PA1, the relative humidity of the compressed gas PA1 becomes 100% at a temperature of 20° C. Therefore, the compressed gas PA1 is prone to condensation.

[0015] If compressed gas PA1 is supplied to equipment (not shown) without being dehumidified at all, the moisture contained in compressed gas PA1 is likely to condense due to a drop in temperature inside the equipment, and drainage is likely to occur inside the equipment. If drainage occurs inside the equipment, problems such as rusting of components constituting the equipment will occur. Therefore, the water vapor permeable membrane module 10 of this embodiment dehumidifies compressed gas PA1 and supplies dried compressed gas PA2 to the equipment.

[0016] As described above, the water vapor permeable membrane module 10 dehumidifies the compressed gas PA1 and discharges the dried compressed gas PA2. As shown in Figure 1, the water vapor permeable membrane module 10 includes a case 20, a first flange 31, a second flange 32, a hollow fiber membrane bundle 40, a sealant 38, and a branch pipe 35.

[0017] 1 is a virtual axis that indicates the central axis of the case 20. In this embodiment, the central axis J extends in a direction parallel to the direction Df of flow of compressed gas. In the following description, the direction in which the central axis J extends may be referred to as the "axial direction."

[0018] The case 20 extends along the axial direction and has a cylindrical shape that is open on both sides in the axial direction. In this embodiment, the case 20 is cylindrical. A hollow fiber membrane bundle 40 and a sealing material 38 are housed inside the case 20. An air intake port 20a is provided in a downstream side (+Df side) portion of the case 20. An air exhaust port 20b is provided in an upstream side (-Df side) portion of the case 20. The air intake port 20a and the air exhaust port 20b each connect the inside of the case 20 to the outside of the case 20.

[0019] The material of the case 20 is not particularly limited and may be metal such as aluminum or stainless steel, or resin such as acrylic resin or polycarbonate resin. The shape of the case 20 is not limited to a cylindrical shape and may be other shapes such as a rectangular or hexagonal cylindrical shape. The axial length of the case 20 is not particularly limited, and the effective length can be set within a range of 10 mm to 1000 mm. The outer diameter of the case 20 is preferably 4 mm to 225 mm. The inner diameter of the case 20 is preferably 2 mm to 220 mm.

[0020] The first flange 31 is attached to the upstream end (-Df side) of the case 20. Although not shown, a gasket is disposed between the first flange 31 and the case 20, and the first flange 31 is airtightly attached to the case 20. The first flange 31 is provided with a supply portion 31a. The supply portion 31a is provided with a hole that penetrates the supply portion 31a in the axial direction. The compressed gas PA1 flows into the inside of the first flange 31 through this through hole.

[0021] The second flange 32 is attached to the downstream end (+Df side) of the case 20. Although not shown, a gasket is disposed between the second flange 32 and the case 20, and the second flange 32 is airtightly attached to the case 20. The second flange 32 is provided with a discharge section 32a. The discharge section 32a is provided with a through-hole 32c and a branch hole 32d. The through-hole 32c is a hole that penetrates the discharge section 32a in the axial direction. The compressed gas PA2 dehumidified by the hollow fiber membrane bundle 40 is discharged via the through-hole 32c and supplied to equipment not shown.

[0022] The branch hole 32d is a hole that penetrates the discharge portion 32a in a direction substantially perpendicular to the axial direction. One end of the branch hole 32d is connected to the inner circumferential surface of the through hole 32c, and the other end of the branch hole 32d is connected to the outer circumferential surface of the discharge portion 32a. The inside of the branch hole 32d is connected to the inside of the through hole 32c.

[0023] The material of the first flange 31 and the second flange 32 is not particularly limited, and examples thereof include acrylic, polycarbonate, polysulfone, polyolefin, polyvinyl chloride, etc. The first flange 31 and the second flange 32 may be made of one type of material or two or more types of material. The first flange 31 and the second flange 32 may also be made of a metal such as aluminum.

[0024] The hollow fiber membrane bundle 40 is made up of a plurality of hollow fiber membranes 42 extending along the axial direction. In this embodiment, the hollow fiber membrane bundle 40 has a plurality of covering portions 43. The hollow fiber membrane bundle 40 extends from the upstream end (-Df side) of the case 20 to the downstream end (+Df side). The hollow fiber membrane bundle 40 is packed inside the case 20. Inside the case 20, both end portions of the hollow fiber membrane bundle 40 are airtightly fixed to the inner peripheral surface of the case 20 by sealing materials 38.

[0025] The end faces of each hollow fiber membrane 42 are open at the upstream (-Df side) end and downstream (+Df side) end of the case 20. This allows the interior of each hollow fiber membrane 42 to communicate with the internal spaces of the first flange 31 and the second flange 32. Thus, compressed gas PA1 supplied from the supply unit 31a is dehumidified while flowing downstream through the interior of each hollow fiber membrane 42 via the internal space of the first flange 31, and the dehumidified compressed gas PA2 is discharged via the internal space of the second flange 32 and the through-hole 32c of the discharge unit 32a.

[0026] The shape of the hollow fiber membranes 42 is not particularly limited, but is typically cylindrical. The outer diameter of the hollow fiber membranes 42 is preferably 0.2 mm to 6.0 mm, and more preferably 0.4 mm to 2.0 mm. The inner diameter of the hollow fiber membranes 42 is preferably 0.1 mm to 5.5 mm, and more preferably 0.5 mm to 1.5 mm. The membrane thickness of the hollow fiber membranes 42 is preferably 0.05 mm to 1.5 mm. The filling rate of the hollow fiber membranes 42 relative to the case 20 is preferably 1% to 70%, and more preferably 50% or less. The number of hollow fiber membranes 42 constituting the hollow fiber membrane bundle 40 is preferably 1 to 100,000.

[0027] The material of the hollow fiber membrane 42 is not particularly limited, and examples thereof include polysulfone, polyethersulfone, polyimide, polyetherimide, silicone, cellulose acetate, fluorine-based ion exchange resin, polyvinylidene fluoride, and polytetrafluoroethylene. Among these, polysulfone, polyethersulfone, polyimide, polyetherimide, and fluorine-based ion exchange resin are preferred because of their excellent water vapor permeability. The hollow fiber membrane 42 may be made of one type of material or two or more types of material.

[0028] As shown in FIG. 1 , each of the multiple hollow fiber membranes 42 is coated with a coating portion 43. Each coating portion 43 is substantially cylindrical and extends in the axial direction. Each coating portion 43 covers the outside of a different hollow fiber membrane 42. The upstream end (-Df side) of the coating portion 43 is positioned substantially at the same position as the upstream end of the hollow fiber membrane 42. The downstream end (+Df side) of the coating portion 43 is positioned substantially at the same position as the downstream end of the hollow fiber membrane 42. The axial length of the coating portion 43 is substantially the same as the axial length of the hollow fiber membrane 42. At least a portion of the inner circumferential surface of each coating portion 43 contacts the outer circumferential surface of the hollow fiber membrane 42. The entire inner circumferential surface of each coating portion 43 may contact the outer circumferential surface of the hollow fiber membrane 42. As shown in FIG. 2 , at least some of the coating portions 43 among the multiple coating portions 43 contact other coating portions 43. In this embodiment, each hollow fiber membrane 42 is covered with the covering portion 43, so that the hollow fiber membranes 42 can be prevented from coming into contact with each other.

[0029] As shown in FIG. 3 , the covering portion 43 is formed by braiding a plurality of filaments 43 a. In this embodiment, "braided" means that a plurality of filaments 43 a are woven together. The plurality of braided filaments 43 a constitute the covering portion 43. In this embodiment, the covering portion 43 is formed by 24 filaments 43 a. The number of filaments 43 a forming the covering portion 43 may be 23 or less, or may be 25 or more. In this embodiment, 12 filaments 43 a extend in a direction inclined toward one side in the circumferential direction of the hollow fiber membrane 42 from the axial direction. The other 12 filaments 43 a extend in a direction inclined toward the other side in the circumferential direction of the hollow fiber membrane 42 from the axial direction.

[0030] In this embodiment, the filaments 43a extending in a direction inclined from the axial direction toward one side of the circumferential direction of the hollow fiber membrane 42 are spaced apart in the axial direction. Similarly, the filaments 43a extending in a direction inclined from the axial direction toward the other side of the circumferential direction of the hollow fiber membrane 42 are spaced apart in the axial direction. As a result, gaps 43c are formed between the filaments 43a. In this embodiment, when viewed from the outside of the coating portion 43, each gap 43c is approximately diamond-shaped. The interior and exterior of the coating portion 43 are connected via each gap 43c. As a result, a portion of the outer peripheral surface of the hollow fiber membrane 42 is exposed to the outside of the coating portion 43 via each gap 43c. In this embodiment, the coverage rate is preferably in the range of 5% to 65%. Because air outside the coating portion 43 can flow into the interior of the coating portion 43 through the gaps 43c, the air outside the coating portion 43 can come into contact with the outer peripheral surface of the hollow fiber membrane 42. Furthermore, air inside the coating portion 43 is discharged to the outside of the coating portion 43 through the gaps 43c. This allows air to circulate around the hollow fiber membrane 42. In this embodiment, the coverage rate was calculated by performing image processing on a photograph of the appearance of the hollow fiber membrane 42 coated with the coating portion 43, and then calculating the coverage rate as the ratio of the area of ​​the coating portion 43 to the sum of the area of ​​the hollow fiber membrane 42 exposed outside the coating portion 43 through the gaps 43c and the area of ​​the coating portion 43.

[0031] In this embodiment, the filament 43a is a monofilament composed of a single fiber. The filament 43a may be a multifilament composed of multiple fibers. In this embodiment, since the filament 43a is a monofilament, the outer diameter of the filament 43a is the same as the outer diameter of a single fiber. In this embodiment, the outer diameter of the filament 43a is preferably in the range of 0.01 to 0.25 times the outer diameter of the hollow fiber membrane 42.

[0032] In the present embodiment, the filament 43 a is made of a resin. The material of the filament 43 a is not particularly limited, and is preferably one or more resins selected from the group consisting of polyphenylene sulfide, polyacrylonitrile, polypropylene, polyvinylidene fluoride, polyarylate, perfluoroalkoxyalkane, polytetrafluoroethylene, polyether ether ketone, polybenzimidazole, polysulfone, polyphenylsulfone, polyethersulfone, polyimide, polyetherimide, polyamide, and polyamideimide.

[0033] As shown in FIG. 1 , the sealant 38 holds both end portions of the hollow fiber membrane bundle 40 in the axial direction. The sealant 38 is fixed to the inner peripheral surface of the case 20 by adhesive. In this embodiment, the sealant 38 is made of resin. The material of the sealant 38 is not particularly limited, and examples include epoxy, polyurethane, silicone, and acrylic. Among these, from the viewpoints of adhesion durability and moldability, epoxy and polyurethane are more preferable as the material of the sealant 38. The sealant 38 may be made of one type of material, or two or more types of material. In this embodiment, two sealants 38 are provided. The sealant 38 has a first sealant 38a and a second sealant 38b.

[0034] The first sealing material 38a is disposed inside the case 20. In the axial direction, the first sealing material 38a is disposed between the upstream end (-Df side) of the case 20 and the exhaust port 20b. The first sealing material 38a is fixed to the inner peripheral surface of the case 20 by adhesive. The first sealing material 38a holds the upstream end of the hollow fiber membrane bundle 40. As shown in FIG. 2, the first sealing material 38a seals the spaces between the multiple hollow fiber membranes 42 and also seals the space between the hollow fiber membrane bundle 40 and the case 20. As shown in FIG. 1, the first sealing material 38a airtightly seals the space inside the first flange 31 and the space inside the case 20.

[0035] The second sealing material 38b is disposed inside the case 20. In the axial direction, the second sealing material 38b is disposed between the downstream end (+Df side) of the case 20 and the intake port 20a. The second sealing material 38b is fixed to the inner peripheral surface of the case 20 by adhesive. The second sealing material 38b holds the downstream end of the hollow fiber membrane bundle 40. Although not shown, similar to the first sealing material 38a, the second sealing material 38b seals the spaces between the multiple hollow fiber membranes 42 and also seals the space between the hollow fiber membrane bundle 40 and the case 20. The second sealing material 38b airtightly seals the space inside the second flange 32 and the space inside the case 20.

[0036] The axial dimension of the first sealing material 38 a and the axial dimension of the second sealing material 38 b are preferably 5 mm or more, respectively. By setting the axial dimension of the first sealing material 38 a and the axial dimension of the second sealing material 38 b within this range, the adhesion between the first sealing material 38 a and the second sealing material 38 b and the case 20 can be improved.

[0037] The branch pipe 35 is an air passage that connects the branch hole 32d of the exhaust portion 32a and the intake port 20a of the case 20. One end of the branch pipe 35 is connected to the branch hole 32d. The other end of the branch pipe 35 is connected to the intake port 20a. This connects the inside of the through hole 32c of the exhaust portion 32a to the inside of the case 20 via the branch pipe 35.

[0038] A switching unit 36 ​​is disposed in the discharge section 32a. In this embodiment, the switching unit 36 ​​is a three-way valve. The switching unit 36 ​​is capable of switching the air volume ratio, which is the ratio of the air volume of the compressed gas PA2 flowing through the branch pipe 35 to the air volume of the compressed gas PA2 discharged from the through hole 32c. In this embodiment, the switching unit 36 ​​is a mixing valve. In this embodiment, the air volume ratio is preferably in the range of 10% to 50%.

[0039] The compressed gas PA2 flowing through the branch pipe 35 flows into the interior of the case 20 via the intake port 20a. In this embodiment, the compressed gas PA2 flowing into the interior of the case 20 serves as a purge gas Gp that discharges moisture contained in the compressed gas PA1 flowing inside each hollow fiber membrane 42 to the outside of the water vapor permeable membrane module 10. In the following description, the compressed gas PA2 flowing through the branch pipe 35 and the interior of the case 20 is referred to as the purge gas Gp. The purge gas Gp is ​​a portion of the compressed gas PA2 discharged from the hollow fiber membrane bundle 40. In other words, the purge gas Gp is ​​a portion of the compressed gas PA2 dehumidified by the water vapor permeable membrane module 10. Therefore, the water vapor pressure of the purge gas Gp is ​​lower than the water vapor pressure of the compressed gas PA1 flowing inside the hollow fiber membranes 42. The purge gas Gp flows upstream (toward the -Df side) inside the case 20. The purge gas Gp passes through the gaps 43c of the covering portion 43, comes into contact with each hollow fiber membrane 42, and flows upstream between the hollow fiber membranes 42. The purge gas Gp is ​​exhausted to the outside of the case 20 through the exhaust port 20b of the case 20. Note that the purge gas Gp does not have to be part of the compressed gas PA2, and may be generated by a purge gas supply device (not shown) and supplied to the inside of the case 20.

[0040] Next, we will explain how the water vapor permeable membrane module 10 of this embodiment dehumidifies the humidified compressed gas PA1 and discharges the dried compressed gas PA2. When the compressed gas PA1 is supplied from the supply portion 31a of the first flange 31, the compressed gas PA1 flows downstream (toward +Df) through each hollow fiber membrane 42. Meanwhile, the purge gas Gp that flows into the case 20 from the intake port 20a of the case 20 flows between the hollow fiber membranes 42 from downstream to upstream (toward -Df). As described above, the purge gas Gp flows upstream while contacting each hollow fiber membrane 42 through the gaps 43c of the covering portion 43. Furthermore, as described above, the water vapor pressure of the purge gas Gp is ​​lower than the water vapor pressure of the compressed gas PA1 flowing through the hollow fiber membranes 42. As a result, moisture contained in the compressed gas PA1 flowing inside each hollow fiber membrane 42 permeates outside the hollow fiber membranes 42 and is discharged by the purge gas Gp to the outside of the water vapor permeable membrane module 10 via the exhaust port 20b. This removes moisture from the compressed gas PA1 flowing inside each hollow fiber membrane 42, dehumidifying the compressed gas PA1. Therefore, the water vapor permeable membrane module 10 generates compressed gas PA2, which has a lower water vapor pressure than compressed gas PA1. The compressed gas PA2 is discharged from each hollow fiber membrane 42 into the space inside the second flange 32. A portion of the compressed gas PA2 is discharged through the through-holes 32c, and another portion of the compressed gas PA2 is supplied to the inside of the case 20 as purge gas Gp.

[0041] As described above, the water vapor permeable membrane module 10 of this embodiment can also be used as a humidifier that humidifies dried compressed gas PA1 and discharges the moistened compressed gas PA2. The operation of humidifying dried compressed gas PA1 and discharging the moistened compressed gas PA2 is described below. When dried compressed gas PA1 is supplied from the supply portion 31a of the first flange 31, the compressed gas PA1 flows downstream (toward the +Df side) through each hollow fiber membrane 42. Meanwhile, moistened purge gas Gp that flows into the interior of the case 20 through the intake port 20a of the case 20 flows between the hollow fiber membranes 42 from the downstream side toward the upstream side (toward the -Df side). The moistened purge gas Gp is ​​generated by a purge gas supply device (not shown) and supplied to the interior of the case 20. Alternatively, a liquid such as water may be supplied to the interior of the case 20 instead of the purge gas Gp. The water vapor pressure of the purge gas Gp is ​​greater than the water vapor pressure of the compressed gas PA1 flowing through the interior of the hollow fiber membranes 42. As a result, moisture contained in the purge gas Gp flowing inside the case 20 permeates into each hollow fiber membrane 42 and transfers to the compressed gas PA1 flowing inside each hollow fiber membrane 42. This humidifies the compressed gas PA1 flowing inside each hollow fiber membrane 42. Therefore, the water vapor permeable membrane module 10 generates a humid compressed gas PA2 with a water vapor pressure higher than that of the compressed gas PA1. The compressed gas PA2 is discharged from each hollow fiber membrane 42 into the space inside the second flange 32. A portion of the compressed gas PA2 is discharged through the through-holes 32c.

[0042] Next, the sealing material forming process Ps for forming the sealing material 38 will be described. The sealing material forming process Ps is part of the manufacturing process for the water vapor permeable membrane module 10. The sealing material forming process Ps includes an application process P01, an injection process P02, a curing process P03, and a cutting process P04. In this specification, the term "workers, etc." includes workers and assembly equipment, etc., who perform each task. Each task may be performed by a worker alone, by an assembly device alone, or by a worker and an assembly device together.

[0043] As shown in FIG. 4 , in the application step P01, the hollow fiber membrane bundle 40, both ends of which have been coated with a sealing agent 83, is housed inside the case 20. In the application step P01, first, an operator applies the sealing agent 83 to both ends of the hollow fiber membrane bundle 40. The operator then seals each hollow fiber membrane 42 by injecting a portion of the sealing agent 83 into both ends of the interior of each hollow fiber membrane 42. Therefore, when injecting a liquid sealant 38d into the interior of the case 20 in the injection step P02, the liquid sealant 38d can be prevented from penetrating into the hollow fiber membranes 42. In this embodiment, the material of the sealing agent 83 is, for example, a silicone resin. The material of the sealing agent 83 is not limited to this.

[0044] Next, the worker places the hollow fiber membrane bundle 40 inside the case 20. At this time, the axial length of the hollow fiber membrane bundle 40 is longer than the axial length of the case 20, and both ends of the hollow fiber membrane bundle 40 extend beyond the case 20 on both sides in the axial direction. As described above, because each hollow fiber membrane 42 is covered with a covering portion 43, the hollow fiber membranes 42 are arranged at intervals. This prevents the hollow fiber membranes 42 from coming into direct contact with each other. Furthermore, because each hollow fiber membrane 42 is covered with a covering portion 43, it is easy to prevent the hollow fiber membranes 42 from being unevenly arranged in the internal space of the case 20 when viewed from the upstream side (-Df side) and downstream side (+Df side). As a result, the hollow fiber membranes 42 are arranged evenly at intervals. Once the hollow fiber membrane bundle 40 is placed inside the case 20, the coating process P01 is completed.

[0045] In the injection step P02, a liquid sealing material 38d is injected into the case 20. In the injection step P02, an operator first fixes a first cover member 81 and a second cover member 82 to the upstream end (-Df side) and downstream end (+Df side) of the case 20, respectively. Next, the operator rotates the case 20 housing the hollow fiber membrane bundle 40 in the circumferential direction of the case 20, applying centrifugal force to the case 20, and injects a predetermined amount of liquid sealing material 38d through the injection port 81a of the first cover member 81 and the injection port 82a of the second cover member 82. As a result, as shown in FIG. 5 , a portion of the liquid sealing material 38d is injected into the case 20. Inside the case 20, the liquid sealing material 38d comes into contact with the inner circumferential surface of the case 20, each covering portion 43, and each hollow fiber membrane 42. When the injection of the liquid sealing material 38d is completed, the injection step P02 is completed.

[0046] In the curing step P03, the worker hardens the liquid sealant 38d. The hardened sealant 38d is fixed to the case 20. The hardened sealant 38d also fixes the hollow fiber membranes 42 to one another. As a result, the hollow fiber membrane bundle 40 is fixed to the case 20 via the hardened sealant 38d. When the liquid sealant 38d is hardened, the curing step P03 ends.

[0047] In the cutting process P04, the shapes of the first sealing material 38a, the second sealing material 38b, and the hollow fiber membrane bundle 40 are adjusted. In the cutting process P04, the worker first removes the first cover member 81 and the second cover member 82 from the case 20. Next, the worker cuts off the portions of the hardened sealing material 38d and the hollow fiber membrane bundle 40 that protrude beyond the case 20 on both sides in the axial direction. This adjusts the shapes of the hollow fiber membrane bundle 40, the first sealing material 38a, and the second sealing material 38b to the appropriate shapes, as shown in FIG. 6 . At this time, both ends of each hollow fiber membrane 42 to which the sealing agent 83 has been applied and injected are removed, leaving both ends of each hollow fiber membrane 42 open. When the cutting process P04 is completed, the sealing material forming process Ps is also completed. Note that the sealing material molding process Ps is not limited to the above-described process, as long as the first sealing material 38a and the second sealing material 38b can be molded into appropriate shapes and the first sealing material 38a and the second sealing material 38b can be fixed to the case 20.

[0048] According to this embodiment, the water vapor permeable membrane module 10 includes a hollow fiber membrane bundle 40 consisting of a plurality of hollow fiber membranes 42 extending along the axial direction. Each of the hollow fiber membranes 42 is covered with a covering 43 formed by braiding a plurality of filaments 43a. Therefore, because each hollow fiber membrane 42 is covered with the covering 43, the hollow fiber membranes 42 are arranged at intervals. This prevents the hollow fiber membranes 42 from coming into direct contact with each other. Furthermore, as described above, the hollow fiber membranes 42 can be evenly arranged in the internal space of the case 20 when viewed from the upstream side (-Df side) and the downstream side (+Df side). Furthermore, because the covering 43 is formed of a plurality of braided filaments 43a, as described above, a purge gas Gp can flow around the hollow fiber membranes 42 through the gaps 43c between the filaments 43a. This allows a stable flow of dry purge gas Gp around the outer circumferential surface of each hollow fiber membrane 42. This makes it possible to increase the amount of moisture contained in the moist compressed gas PA1 flowing inside each hollow fiber membrane 42 that permeates to the outside of each hollow fiber membrane 42. This therefore makes it possible to improve the water vapor permeability of the water vapor permeable membrane module 10.

[0049] Furthermore, in this embodiment, since each hollow fiber membrane 42 is covered with the covering portion 43, even if pressure spreading outward is applied to the inner circumferential surface of each hollow fiber membrane 42 when compressed gas PA1 is flowed inside each hollow fiber membrane 42, the covering portion 43 can prevent each hollow fiber membrane 42 from expanding. This prevents the diameter of each hollow fiber membrane 42 from becoming too large, thereby preventing a decrease in the pressure resistance of each hollow fiber membrane 42. This can improve the durability of the water vapor permeable membrane module 10. This can more stably improve the water vapor permeability performance of the water vapor permeable membrane module 10.

[0050] In this embodiment, the covering 43 prevents the hollow fiber membranes 42 from coming into direct contact with each other, thereby preventing the hollow fiber membranes 42 from rubbing against each other. This prevents the hollow fiber membranes 42 from being damaged, further improving the durability of the water vapor permeable membrane module 10. This allows the water vapor permeability of the water vapor permeable membrane module 10 to be improved more stably.

[0051] According to this embodiment, the filaments 43a are monofilaments. When the filaments 43a constituting the covering portion 43 are multifilaments, the filaments become flattened in both the circumferential and axial directions during braiding. When the filaments become flattened in both the circumferential and axial directions of the hollow fiber membrane 42, the area of ​​the gaps 43c in each covering portion 43 decreases, increasing the coverage rate. This reduces the effective membrane surface area of ​​each hollow fiber membrane 42, making it difficult to stably flow the dried purge gas Gp over the outer circumferential surface of each hollow fiber membrane 42. This may result in a decrease in the water vapor permeability of the water vapor permeable membrane module 10. In contrast, in this embodiment, the filaments 43a are monofilaments, preventing the filaments 43a from becoming flattened in both the circumferential and axial directions during braiding. This prevents an increase in the coverage rate, thereby stably improving the water vapor permeability of the water vapor permeable membrane module 10.

[0052] According to this embodiment, the coverage rate, i.e., the ratio of the area of ​​the portion of the outer surface of the hollow fiber membrane 42 that is covered by the covering portion to the area of ​​the outer surface of the hollow fiber membrane 42, is in the range of 5% to 65%. This prevents the coverage rate from becoming too high, thereby preventing a reduction in the effective membrane surface area of ​​each hollow fiber membrane 42 from causing an excessive decrease in the effective flow rate of the purge gas Gp flowing near the outer surface. This increases the amount of moisture contained in the compressed gas PA1 that permeates out of each hollow fiber membrane 42, thereby stably increasing the amount of moisture discharged to the outside of the water vapor permeable membrane module 10 via the purge gas Gp. This further improves the water vapor permeability of the water vapor permeable membrane module 10.

[0053] Furthermore, in this embodiment, the coverage rate can be prevented from becoming too small, and the area of ​​the gap 43c can be prevented from becoming too large. Therefore, the strength of the covering portion 43 can be prevented from becoming too small. This more effectively prevents the diameter of each hollow fiber membrane 42 from becoming too large due to the covering portion 43 when the compressed gas PA1 is flowed through the inside of each hollow fiber membrane 42. Therefore, the durability of the water vapor permeable membrane module 10 can be improved, and the water vapor permeability of the water vapor permeable membrane module 10 can be more stably improved.

[0054] Furthermore, in this embodiment, the coverage rate can be prevented from becoming too small, which more effectively prevents the hollow fiber membranes 42 from rubbing against each other. This further improves the durability of the water vapor permeable membrane module 10, thereby more stably improving the water vapor permeability of the water vapor permeable membrane module 10.

[0055] According to this embodiment, the outer diameter of the filaments 43a is in the range of 0.01 to 0.25 times the outer diameter of the hollow fiber membranes 42. This prevents the outer diameter of the filaments 43a from becoming too large, thereby preventing the coverage rate from becoming too large. This prevents the effective membrane surface area of ​​the outer peripheral surface of each hollow fiber membrane 42 from becoming too small, thereby preventing the flow rate of the purge gas Gp, which is effectively used for water vapor permeation and flows along the outer peripheral surface of each hollow fiber membrane 42, from becoming too small. This allows the water vapor permeation performance of the water vapor permeable membrane module 10 to be more suitably improved.

[0056] Furthermore, in this embodiment, the outer diameter of the filaments 43a can be prevented from becoming too small, and therefore the strength of the filaments 43a can be prevented from becoming too small. Therefore, the strength of the covering portion 43 can be prevented from becoming too small. This more effectively prevents the diameter of each hollow fiber membrane 42 from becoming too large when the compressed gas PA1 is flowed through the hollow fiber membranes 42. Therefore, the durability of the water vapor permeable membrane module 10 can be more effectively improved, and the water vapor permeability of the water vapor permeable membrane module 10 can be more stably improved.

[0057] According to this embodiment, the filaments 43a are made of one or more resins selected from the group consisting of polyphenylene sulfide, polyacrylonitrile, polypropylene, polyvinylidene fluoride, polyarylate, perfluoroalkoxyalkane, polytetrafluoroethylene, polyetheretherketone, polybenzimidazole, polysulfone, polyphenylsulfone, polyethersulfone, polyimide, polyetherimide, polyamide, and polyamideimide. This improves the heat resistance and strength of the filaments 43a compared to when the filaments 43a are made of polyester. This prevents thermal deformation and a decrease in pressure resistance of the covering 43 during use of the water vapor-permeable membrane module 10, thereby more effectively improving the durability of the water vapor-permeable membrane module 10. This more consistently improves the water vapor permeability of the water vapor-permeable membrane module 10.

[0058] According to this embodiment, purge gas Gp flows inside the case 20, and the purge gas Gp is ​​part of the gas discharged from the hollow fiber membrane bundle 40. Therefore, because part of the dry compressed gas PA2 discharged from the hollow fiber membrane bundle 40 is used as the purge gas Gp, the configuration for generating the dry compressed gas PA2 can be simplified compared to when a separate purge gas supply device for supplying the purge gas Gp to the inside of the case 20 is provided.

[0059] Furthermore, in this embodiment, the compressed gas PA2 dehumidified by the water vapor permeable membrane module 10 can be supplied to the above-mentioned equipment (not shown). This prevents the moisture contained in the compressed gas PA2 from condensing due to a temperature drop or the like within the equipment, thereby preventing rusting of the components that make up the equipment. This allows the equipment to operate stably.

[0060] [Examples] The present invention will be specifically described below using examples of the present embodiment, but the present invention is not limited by the following description. Example 1 shown in Table 1 is an example, and Examples 2 and 3 are comparative examples. Examples 4 to 8 shown in Table 2 are examples, and Examples 9 to 11 are comparative examples. Example 12 shown in Table 3 is a comparative example. Examples 13 to 15 shown in Table 4 are examples, and Example 16 is a comparative example. As described above, the outer diameter of a monofilament composed of a single fiber is the same as the outer diameter of the fiber. Furthermore, the outer diameter of a multifilament composed of multiple fibers is larger than the outer diameter of the fiber.

[0061] Example 1: A water vapor permeable membrane module similar to the water vapor permeable membrane module illustrated in Figures 1 and 2 was fabricated. An acrylic cylindrical case with an outer diameter of 55 mm, an inner diameter of 50 mm, and a length of 250 mm was used. A fluororesin hollow fiber membrane (Sunsep membrane, manufactured by AGC Engineering Co., Ltd.) with an outer diameter of 1.0 mm and an inner diameter of 0.78 mm was used as the hollow fiber membrane. The number of hollow fiber membranes was 500. The covering portion was a braided covering portion made of polyphenylene sulfide resin monofilaments with a filament diameter of 0.10 mm. The covering rate was 45%. Epoxy resin was used as the sealing material, and molding was performed using the sealing material molding process described above. Both ends of the hollow fiber membrane bundle were fixed to the case with sealing material, resulting in an effective length of 190 mm. Example 2: A braided covering portion made of multifilaments composed of 50 fibers with a fiber diameter of 0.06 mm was used. The covering rate was 100%. A water vapor permeable membrane module was fabricated in the same manner as in Example 1, except for the coating portion. [Example 3] A water vapor permeable membrane module was fabricated in the same manner as in Example 1, except that the hollow fiber membranes were not coated with a coating portion. [Example 4] A fluororesin hollow fiber membrane (Sunsep membrane, manufactured by AGC Engineering Co., Ltd.) with an outer diameter of 1.0 mm and an inner diameter of 0.78 mm was used as the hollow fiber membrane. The number of hollow fiber membranes was one. The coating portion was a braided monofilament with a filament diameter of 0.06 mm. The coating rate was 35%. A water vapor permeable membrane module was fabricated in the same manner as in Example 1, except for the number of hollow fiber membranes and the coating portion. [Example 5] A water vapor permeable membrane module was fabricated in the same manner as in Example 4, except that the filament diameter was 0.08 mm and the coating rate was 40%. [Example 6] A water vapor permeable membrane module was fabricated in the same manner as in Example 4, except that the filament diameter was 0.10 mm and the coating rate was 45%. [Example 7] A water vapor-permeable membrane module was produced in the same manner as in Example 4, except that the filament diameter was 0.17 mm and the coverage was 55%. [Example 8] A water vapor-permeable membrane module was produced in the same manner as in Example 4, except that the filament diameter was 0.25 mm and the coverage was 65%. [Example 9] A water vapor-permeable membrane module was produced in the same manner as in Example 4, except that the filament diameter was 0.30 mm and the coverage was 70%.[Example 10] A hollow fiber membrane made of fluororesin (Sunsep membrane, manufactured by AGC Engineering Co., Ltd.) with an outer diameter of 1.0 mm and an inner diameter of 0.78 mm was used. The number of hollow fiber membranes was one. A covering portion was used in which a multifilament consisting of three fibers with a fiber diameter of 0.06 mm was braided. The covering rate was 70%. A water vapor permeable membrane module was fabricated in the same manner as in Example 2, except for the number of hollow fiber membranes and the covering rate. [Example 11] A water vapor permeable membrane module was fabricated in the same manner as in Example 10, except that a multifilament consisting of 50 fibers was used and the covering rate was 100%. [Example 12] A water vapor permeable membrane module was fabricated in the same manner as in Example 4, except that the hollow fiber membrane was not covered with a covering rate. [Example 13] A hollow fiber membrane made of fluororesin (Sunsep membrane, manufactured by AGC Engineering Co., Ltd.) with an outer diameter of 1.0 mm and an inner diameter of 0.78 mm was used. The number of hollow fiber membranes was one. A coating made by braiding monofilaments made of polyphenylene sulfide resin was used as the coating portion. The coating rate was 45%. [Example 14] A hollow fiber membrane was produced in the same manner as in Example 13, except that the coating rate was 35%. [Example 15] A hollow fiber membrane was produced in the same manner as in Example 13, except that the coating rate was 5%. [Example 16] A hollow fiber membrane was produced in the same manner as in Example 13, except that the hollow fiber membrane was not coated with a coating portion.

[0062] [Water vapor permeability evaluation] Compressed air containing saturated water vapor at an atmospheric pressure of 0.7 MPaG and at 20°C was supplied from the supply section to the water vapor permeable membrane modules of Examples 1 to 11, and the dew point of the compressed air discharged from the discharge section was measured. The air volume ratio was 25%. The dew point of the compressed gas was measured using a mirror-cooled dew point meter. The lower the dew point of the discharged compressed air, the better the water vapor permeability. The results of the water vapor permeability evaluation for each example are shown in Tables 1 and 2.

[0063]

[0064] As shown in Table 1, the water vapor permeable membrane module of Example 1, in which the covering portion made of braided monofilaments was covered, had superior water vapor permeability compared to the water vapor permeable membrane modules of Examples 2 and 3. In the water vapor permeable membrane module of Example 1, each hollow fiber membrane is covered with a covering portion, so the hollow fiber membranes are arranged at intervals and are evenly arranged in the internal space of the case. Furthermore, because the coverage rate is within the range of 5% to 65%, it is possible to prevent the coverage rate from becoming too high, i.e., the effective membrane surface area of ​​each hollow fiber membrane from becoming too small. As a result, as described above, it is possible to prevent the flow rate of the purge gas flowing near the outer surface of each hollow fiber membrane from becoming too small. This increases the amount of moisture permeating from the compressed air to the outside of each hollow fiber membrane. Therefore, the water vapor permeability of the water vapor permeable membrane module can be improved.

[0065] In Example 2, where the coverage is greater than 65%, the effective membrane surface area of ​​each hollow fiber membrane becomes too small, making it difficult to stably flow dry purge gas around the outer surface of each hollow fiber membrane. This reduces the amount of moisture that permeates from the compressed air to the outside of each hollow fiber membrane. This, in turn, reduces the water vapor permeability of the water vapor permeable membrane module.

[0066] In Example 3, in which the hollow fiber membranes are not covered by a covering, as described above, the hollow fiber membranes are unevenly arranged inside the case, which makes them prone to direct contact with each other. As a result, the flow rate of the purge gas flowing near the outer surface of each hollow fiber membrane becomes too small, reducing the amount of moisture that permeates from the compressed air to the outside of each hollow fiber membrane. This results in a decrease in the water vapor permeability of the water vapor permeable membrane module.

[0067]

[0068] As shown in Table 2, the water vapor permeable membrane modules of Examples 4 to 8, in which the outer diameter of the filaments was between 0.01 and 0.25 times the outer diameter (1.0 mm) of the hollow fiber membrane and the coverage was between 5% and 65%, had superior water vapor permeability compared to the water vapor permeable membrane modules of Examples 9 to 11. The water vapor permeability of the water vapor permeable membrane modules of Examples 4 to 8 was comparable. The water vapor permeable membrane modules of Examples 4 to 8 were able to prevent the outer diameter of the filaments 43a from becoming too large, thereby preventing the coverage from exceeding 65%. Therefore, the effective membrane surface area of ​​the hollow fiber membrane was prevented from becoming too small, allowing a stable flow of dry purge gas around the outer surface of the hollow fiber membrane. This increased the amount of moisture permeating from the compressed air to the outside of the hollow fiber membrane, thereby improving the water vapor permeability of the water vapor permeable membrane module.

[0069] In Example 9, where the outer diameter of the filament is greater than 0.25 times the outer diameter of the hollow fiber membrane, the coverage is greater than 65%, resulting in a too small effective membrane surface area of ​​the hollow fiber membrane. This makes it difficult to stably flow dry purge gas around the outer surface of the hollow fiber membrane, reducing the amount of moisture permeating from the compressed air to the outside of the hollow fiber membrane. This, in turn, reduces the water vapor permeability of the water vapor permeable membrane module.

[0070] In Examples 10 and 11, in which the multifilament is covered with a braided covering, the coverage is greater than 65%, resulting in a too small effective membrane surface area of ​​the hollow fiber membrane. This makes it difficult to stably flow dry purge gas around the outer surface of the hollow fiber membrane, reducing the amount of moisture that permeates from the compressed air to the outside of the hollow fiber membrane. This results in a decrease in the water vapor permeability of the water vapor permeable membrane module. In Example 11, in which the number of fibers constituting the filament is greater than in Example 10, the coverage is greater than in Example 10, resulting in a decrease in the water vapor permeability.

[0071] The water vapor permeable membrane modules of Examples 4 to 8, which are working examples, have a coverage rate of 65% or less, so they have equivalent water vapor permeability regardless of the coverage rate, demonstrating the maximum water vapor permeability inherent to the hollow fiber membrane, regardless of the coverage rate. In contrast, the water vapor permeable membrane modules of Examples 9 to 11, which are comparative examples, have a coverage rate greater than 65%, so their water vapor permeability decreases as the coverage rate increases. Therefore, by setting the coverage rate to 65%, it is possible to obtain a water vapor permeable membrane module that can effectively demonstrate the inherent water vapor permeability of the hollow fiber membrane.

[0072] [First durability performance evaluation] The water vapor permeable membrane modules of Examples 1, 4, 11, and 14 were immersed in hot water at 60°C and subjected to a pressure fluctuation test in which the pressure of the compressed gas supplied to the water vapor permeable membrane module was varied. The water vapor permeable membrane modules were then removed from the hot water and dried, after which a confirmation test was performed to check for damage to the hollow fiber membranes.

[0073] In the pressure fluctuation test, the pressure of the compressed gas supplied to the water vapor permeable membrane module was repeatedly increased from 0.00 MPaG to 0.85 MPaG and then reduced to 0.00 MPaG. In the pressure fluctuation test, one cycle consisted of increasing the pressure of the compressed gas from 0.00 MPaG to 0.85 MPaG and then reducing the pressure to 0.00 MPaG. The time required for one cycle of pressure fluctuation was 24 seconds, and the pressure of the compressed gas was gradually varied over 24 seconds. In the pressure fluctuation test, the pressure of the compressed gas flowing inside each hollow fiber membrane fluctuated, causing each hollow fiber membrane to repeatedly expand and contract with each cycle. As the expansion amount of the hollow fiber membrane increases, the hollow fiber membrane is more susceptible to damage. Furthermore, in the pressure fluctuation test, as described above, each hollow fiber membrane repeatedly expands and contracts with each cycle, and therefore the coating also repeatedly expands and contracts with each cycle.

[0074] After the pressure fluctuation test was completed, the water vapor permeable membrane module was removed from the hot water and dry air at atmospheric pressure and a temperature of approximately 20°C was supplied to dry the water vapor permeable membrane module. A confirmation test was conducted every 7,200 cycles of the pressure fluctuation test. In the confirmation test, the hollow fiber membranes were visually inspected for damage. The results of the first durability performance evaluation for each example are shown in Table 3.

[0075]

[0076] As shown in Table 3, the water vapor permeable membrane modules of Examples 1 and 4 had superior durability to the water vapor permeable membrane modules of Comparative Examples 11 and 12. The hollow fiber membranes of Examples 1 and 4 were covered with a covering portion with a coverage rate of 5% or more and 65% or less, which prevented the hollow fiber membranes from expanding significantly during pressure fluctuation tests. This improved durability of the water vapor permeable membrane modules. Furthermore, the water vapor permeable membrane module of Example 1, which had 500 hollow fiber membranes, and the water vapor permeable membrane module of Example 4, which had one hollow fiber membrane, both had high durability. Therefore, the water vapor permeable membrane modules of the Examples had high durability regardless of the number of hollow fiber membranes.

[0077] When the hollow fiber membrane repeatedly expands and contracts during a pressure fluctuation test, the fibers constituting the coating may rub against each other, resulting in fiber breakage. Furthermore, the greater the coverage, the more likely the fibers are to rub against each other, and therefore, if the coverage is too high, the fibers are more likely to break. Therefore, in Example 11, which is covered with a coating having a coverage of more than 65%, fiber breakage is likely to occur during the pressure fluctuation test, resulting in a decrease in the strength of the coating. As a result, the hollow fiber membrane is more likely to expand during the pressure fluctuation test, resulting in a greater degree of breakage. This, in turn, reduces the durability of the water vapor permeable membrane module.

[0078] In Example 12, in which the hollow fiber membranes were not covered with a covering portion, the hollow fiber membranes were prone to large expansion amounts in the pressure fluctuation test, which made them prone to breakage, thereby reducing the durability of the water vapor permeable membrane module.

[0079] [Second durability performance evaluation] The hollow fiber membranes of Examples 13 to 16 were immersed in warm water at 90°C, and the water pressure of the water supplied to the inside of the hollow fiber membrane was increased to measure the burst water pressure, which is the water pressure at which the hollow fiber membrane bursts. In the second durability performance evaluation, the water pressure of the water supplied to the inside of the hollow fiber membrane was increased to 5.0 MPaG. In the second durability performance evaluation, the smaller the strength of the coating, the greater the amount of expansion of the hollow fiber membrane due to the water pressure, and therefore the smaller the burst water pressure. The results of the second durability performance evaluation for each example are shown in Table 4.

[0080]

[0081] As shown in Table 4, the hollow fiber membranes of Examples 13 to 15, which had a coverage rate of 5% or more, had superior durability compared to the hollow fiber membrane of Example 16. The hollow fiber membranes of Examples 13 to 14 did not burst even when the water pressure was increased to 5.0 MPaG. The hollow fiber membrane of Example 15 burst when the water pressure was increased to 5.0 MPaG. As described above, the hollow fiber membranes of Examples 13 to 15 can prevent the coverage rate from becoming too small, thereby preventing the gap area from becoming too large. This prevents the strength of the coating from becoming too small. Therefore, the expansion amount of the hollow fiber membrane due to water pressure can be prevented from increasing, preventing the hollow fiber membrane from bursting. This improves the durability of the hollow fiber membrane.

[0082] In Example 16, in which the hollow fiber membranes are not covered with a covering, the hollow fiber membranes are prone to large expansion due to water pressure, which makes them prone to breakage, further reducing the durability of the water vapor permeable membrane module.

[0083] Although the embodiments of the present invention have been described above, the configurations and combinations thereof in the embodiments are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments.

[0084] The water vapor permeable membrane module does not need to have a branch pipe. This simplifies the configuration of the water vapor permeable membrane module and increases the flow rate of gas supplied to the equipment. In this case, a purge gas supply device that supplies purge gas to the inside of the case may be provided, and the purge gas generated by the purge gas supply device may be supplied to the inside of the case.

[0085] In a water vapor permeable membrane module, moist gas may be discharged by supplying moisture to the dry gas flowing inside the hollow fiber membranes. In this case, by supplying moist purge gas to the inside of the case, the moisture contained in the purge gas permeates into the membranes of each hollow fiber membrane and is supplied to the gas. The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2023-136424, filed on August 24, 2023, are hereby incorporated by reference as part of the disclosure of the present specification.

[0086] 10...water vapor permeable membrane module, 20...case, 38...sealing material, 40...hollow fiber membrane bundle, 42...hollow fiber membrane, 43...covering portion, 43a...filament, Gp...purge gas, PA1, PA2...compressed gas

Claims

1. A water vapor permeable membrane module comprising a hollow fiber membrane bundle consisting of a plurality of hollow fiber membranes extending along an axial direction, each of the plurality of hollow fiber membranes being covered with a covering portion in which a plurality of filaments are braided, and the ratio of the area of ​​the portion of the outer circumferential surface of the hollow fiber membrane that is covered with the covering portion to the area of ​​the outer circumferential surface of the hollow fiber membrane is in the range of 5% to 65%.

2. The water vapor permeable membrane module according to claim 1, wherein said filaments are monofilaments.

3. The water vapor permeable membrane module according to claim 1, wherein the outer diameter of the filament is in the range of 0.01 to 0.25 times the outer diameter of the hollow fiber membrane.

4. A water vapor permeable membrane module according to any one of claims 1 to 3, wherein the filaments are composed of one or more resins selected from the group consisting of polyphenylene sulfide, polyacrylonitrile, polypropylene, polyvinylidene fluoride, polyarylate, perfluoroalkoxyalkane, polytetrafluoroethylene, polyether ether ketone, polybenzimidazole, polysulfone, polyphenylsulfone, polyethersulfone, polyimide, polyetherimide, polyamide, and polyamideimide.

5. A water vapor permeable membrane module as described in any one of claims 1 to 3, comprising: a cylindrical case extending along the axial direction and opening on both sides in the axial direction; and a resin sealing material, wherein the hollow fiber membrane bundle is filled inside the case, and the sealing material seals between the multiple hollow fiber membranes and between the hollow fiber membrane bundle and the case.

6. The water vapor permeable membrane module according to claim 5, wherein a purge gas flows inside said case, said purge gas being a part of the gas discharged from said hollow fiber membrane bundle.

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