Improved membrane bundle for vacuum membrane distillation and method for manufacturing the same

Abstract

The vacuum membrane distillation module comprises a central core, a plurality of hollow fiber membranes, a shell that cylindrically houses the bundle of hollow fiber membranes and the central core, at least one circumferential holding structure that holds the ends of the plurality of hollow fiber membranes, at least one end cap that houses at least one circumferential holding structure, at least one support rod that extends in the longitudinal direction, and a potting material held between (i) an inner boundary formed by the outer circumferential surface of the central core and (ii) an outer boundary formed by the inner circumferential surface of at least one circumferential holding structure. Furthermore, at least one of (i) the outer circumferential surface of at least one end of the central core and (ii) the inner circumferential surface of at least one circumferential holding structure is provided with a structure for strengthening the bond with the potting material.

Description

Technical Field

[0001] The present disclosure relates to the field of membrane-based systems for separating dissolved substances from water.

[0002] <Cross-reference to Related Applications> This application claims priority to U.S. Provisional Patent Application No. 63 / 466,561, filed May 15, 2023, and U.S. Patent Application No. 18 / 662,224, filed May 13, 2024, the disclosures of which are hereby incorporated by reference in their entirety.

Background Art

[0003] A related application (PCT / US2022 / 051634) pending with the applicant describes a vacuum membrane distillation module comprising a housing and a removable hollow fiber membrane. In use, feed water enters from the bottom of the module, is directed through a central core to the top of the module, where the water is dispersed and enters the lumen at the upper end of the hollow fiber membrane. During vacuum membrane distillation, water vapor passes through the membrane to the permeate side, where it is withdrawn from the module under vacuum, condensed, and collected. Salts present in the feed water are retained in the liquid within the lumen side of the hollow fiber membrane, forming a concentrate stream that is discharged from the bottom of the module.

[0004] The hollow fiber membrane bundle is composed of a plurality of hollow fiber membranes arranged generally parallel longitudinally around a central core. The hollow fiber membranes and the central core are fixed at each end by membrane boots filled with potting material. The ends of the fiber membrane bundle and the central core extend across the potting material contained in their respective membrane boots such that the open ends of the hollow fiber membranes are exposed on the surface of the potting material. The lumen of the central core is also exposed at the upper surface of the potting material of the top membrane boot and fluidly connects to the space defined by the feed water inlet and the module top cap.

[0005] The potting material of the membrane boot is held laterally within the space between the inner circumference defined by the central core and the outer circumference defined by the membrane boot.

[0006] In vacuum membrane distillation processes, it is crucial to prevent raw water from leaking from the membrane's supply side to the permeate side. Leakage contaminates the purified water on the permeate side, rendering the module inoperable and requiring the removal, repair, or replacement of the hollow fiber membrane bundle.

[0007] The membrane boot separates the water supply side from the water permeable side of the system, particularly by the potting material. To perform this function, a robust waterproof seal must be formed between the potting material and the fibers, as well as between the potting material and the component that holds it (i.e., the membrane boot) and the central core. The inventors have previously confirmed that forming a chemical bond between the potting material and the fibers (achievable, for example, with epoxy-based potting materials) provides a more durable seal than mechanical bonding, such as gripping the fibers by compression of the potting material.

[0008] In the use of prior art embodiments, under certain conditions, the seal between the potting material and the central core, or between the potting material and the membrane boot, may fail. As shown in Figures 1 and 2, failure of the seal between the potting material and the central core results in water leakage to the permeate side, rendering the module inoperable.

[0009] Figure 1 is a photograph taken from above of a conventional VMD membrane bundle 1. There is a gap of several millimeters 2 between the central core 3 and the potting material 4, which is causing leakage from the central core. As is clear from this photograph, the central core 3 is set back several millimeters from the potting material 4, causing a large amount of water to leak from the central core to the permeable side of the hollow fiber membrane 5, which was causing module failure.

[0010] Figure 2 is a photograph taken from the bottom of the VMD membrane bundle 1, which was mounted on a VMD module, using a conventional design. It is clear that the water inlet 6 (connected to the central core 3, which is not visible in Figure 2 but is shown in Figure 1) is shifted outwards. It can be seen that an excessive amount of adhesive 7 has been applied around the water inlet 6 and the central core 3 (Figure 1). This indicates that an attempt was made to prevent the water inlet 6 and the central core 3 from rotating relative to the sealed hollow fiber membrane 5, but this attempt failed. The photograph in Figure 2 shows the water inlet 6 shifted outwards. The adhesive 7 visible around the central core was applied in an attempt to fix the rotation of the central core relative to the sealed fibers. However, this attempt was unsuccessful.

[0011] The inventors discovered that the seal between the potting material and the central core, or between the potting material and the membrane boot, can still be damaged, potentially leading to water leakage to the permeate side and module failure.

[0012] Therefore, it is necessary to improve the robustness and durability of the seal between the potting material and the member that holds the potting material.

[0013] This background information is provided to disclose information that the applicant believes may be relevant. It is not intended, nor should it be interpreted, to be considered prior art or well-known technology in the relevant field. [Overview of the project]

[0014] The following is a simplified overview of the general concept of the invention relating to this disclosure, providing a basic understanding of some aspects of the disclosure. This overview is not intended to provide a comprehensive overview of the disclosure. Nor is it intended to limit any important elements of the embodiments of the disclosure or to define a scope beyond what is explicitly or implicitly described in the following description and claims.

[0015] It has been found that the sealing performance between the potting material and the central core, or between the potting material and the membrane boot, can be significantly improved by designing the edges of the central core to enhance adhesion with the epoxy potting material.

[0016] According to a first aspect of the present disclosure, a vacuum membrane distillation module includes a hollow fiber membrane, the ends of which are fixed to a potting material, the potting material being held between an inner boundary formed by the outer circumferential surface of a central core and an outer boundary formed by the inner circumferential surface of at least one circumferential retaining structure, and at least one of the outer circumferential surface of the ends of the central core and the inner circumferential surface of at least one circumferential retaining structure being configured to enhance the bond with the potting material. Preferably, the potting material is an epoxy material.

[0017] At least one circumferential retaining structure may be the shell or vessel of the vacuum membrane distillation module. Alternatively, the vacuum membrane distillation module may include a membrane bundle assembly removable from the vacuum membrane distillation module, where at least one circumferential retaining structure is a membrane boot.

[0018] According to a second aspect of the present disclosure, a membrane bundle for a vacuum membrane distillation module is provided, wherein at least one of the outer circumferential surfaces of the ends of a central core or the inner circumferential surfaces of a membrane boot is configured to enhance the bond with a potting material. Preferably, the potting material is an epoxy material.

[0019] Preferably, both ends of the central core are configured to enhance the bond with the epoxy potting material. More preferably, the ends of the central core and the membrane boot are configured to enhance the bond with the epoxy potting material.

[0020] In one embodiment, the shape of the ends of the central core and / or the membrane boot is configured to increase the effective surface area of ​​the central core that contacts the potting material.

[0021] In one embodiment, the ends of the central core are formed with threaded outer surfaces that engage with the potting material, thereby increasing the contact area with the potting material compared to a smooth cylindrical surface. Furthermore, the peak-and-valley shape enhances the engagement between the central core and the potting material, resisting movement of the central core relative to the potting material. Similarly, the membrane boot may be formed with threaded inner surfaces.

[0022] In another embodiment, the end surfaces of the central core are formed with openings that allow the potting material to penetrate, thus providing a non-smooth shape that increases the contact area with the potting material and strengthens the engagement between the central core and the potting material. This resists the central core moving relative to the potting material. Similarly, the inner circumferential surface of the membrane boot may be formed with openings.

[0023] In another embodiment, the end surfaces of the central core may be provided with a coating containing a porous material that facilitates the penetration or absorption of the potting material. Similarly, the inner circumferential surface of the membrane boot may be formed with a coating containing a porous material.

[0024] Two or more methods described herein may be combined to obtain additional effects. For example, an opening may be provided on the threaded surface.

[0025] This disclosure further provides a vacuum membrane distillation module including the membrane bundle disclosed herein.

[0026] In another embodiment, the disclosure provides a method for manufacturing a bundle of hollow fiber membranes for use in a vacuum membrane distillation module. The bundle comprises a plurality of hollow fiber membranes having first and second ends, each end of which is secured by a membrane boot containing a potting material radially sealed within a space defined by the inner surface of the membrane boot and the outer surface of a central core. The method includes the step of shaping at least one of the inner surface of the membrane boot or the outer surface of the central core to enhance engagement with the potting material.

[0027] The surface may include one or more of a threaded portion, an opening, or a coating including a porous material.

[0028] In one aspect of the present disclosure, a vacuum membrane distillation module includes an extending central core having a first longitudinal axis, a plurality of extending hollow fiber membranes having a second longitudinal axis substantially coaxial or substantially parallel to the first longitudinal axis of the extending central core, and at least one circumferential retaining structure that holds a potting material and at least one end of the plurality of extending hollow fiber membranes. At least one end of the plurality of extending hollow fiber membranes is fixed with the potting material. At least one end cap for holding at least one circumferential retaining structure is also provided. The potting material is held between (i) an inner boundary formed by an outer peripheral surface of the extending central core and (ii) an outer boundary formed by an inner peripheral surface of at least one circumferential retaining structure. An extending shell that cylindrically houses the extending hollow fiber membrane bundle and the extending central core has a third longitudinal axis substantially coaxial or substantially parallel to the first longitudinal axis of the extending central core. Further, at least one of (i) an outer peripheral surface of at least one end of the extending central core and (ii) an inner peripheral surface of at least one circumferential retaining structure includes a structure for strengthening the bond with the potting material.

[0029] According to still other aspects of the present disclosure, a vacuum membrane distillation module includes an extending central core having a first longitudinal axis, a plurality of extending hollow fiber membranes having a second longitudinal axis substantially coaxial or substantially parallel to the first longitudinal axis of the extending central core, a shell extending having a third longitudinal axis substantially coaxial or substantially parallel to the first longitudinal axis of the extending central core that cylindrically houses the extending hollow fiber membrane bundle and the extending central core, at least one circumferential retaining structure that holds at least one end of the plurality of extending hollow fiber membranes, at least one end cap that holds the at least one circumferential retaining structure, at least one support rod extending longitudinally, a potting material held between (i) an inner boundary formed by an outer peripheral surface of the extending central core and (ii) an outer boundary formed by an inner peripheral surface of the at least one circumferential retaining structure, and a plurality of hollow fiber membranes extending generally longitudinally and having ends fixed to the potting material. Further, at least one of (i) an outer peripheral surface of at least one end of the extending central core and (ii) an inner peripheral surface of the at least one circumferential retaining structure includes a structure for strengthening the bond with the potting material.

[0030] According to still other aspects of the present disclosure, a vacuum membrane distillation module includes an extending central core having at least one end, at least one circumferential retaining structure, at least one end cap, at least one support rod that engages with the at least one end cap to impart longitudinal mechanical rigidity, a potting material held between (i) an inner boundary formed by an outer peripheral surface of the central core and (ii) an outer boundary formed by an inner peripheral surface of the at least one circumferential retaining structure, and a plurality of hollow fiber membranes extending generally longitudinally. The ends of the plurality of hollow fiber membranes are fixed to the potting material, and at least one of (i) an outer peripheral surface of at least one end of the central core and (ii) an inner peripheral surface of the at least one circumferential retaining structure includes a structure for strengthening the bond with the potting material.

[0031] According to yet another aspect of the present disclosure, a vacuum membrane distillation module includes an extending central core, an extending hollow fiber membrane bundle, and a module top cap positioned longitudinally spaced from the module bottom cap, these being housed in a substantially cylindrical shell. The extending central core, the extending hollow fiber membrane bundle, the module top cap, the module bottom cap, and the substantially cylindrical shell have substantially coaxial or substantially parallel longitudinal axes.

[0032] In this embodiment or other embodiments, the vacuum membrane distillation module includes at least two, at least three, at least four, at least five, at least six, or at least seven support rods that engage with at least one end cap. In this embodiment or other embodiments, the potting material is an epoxy material. In this embodiment or other embodiments, the structure includes at least one of a threaded portion and an opening. In this embodiment or other embodiments, the structure includes a threaded portion and an opening. In this embodiment or other embodiments, the opening penetrates the threaded portion. In this embodiment or other embodiments, the opening is generally perpendicular to the threaded portion. In this embodiment or other embodiments, the outer boundary formed by the inner surface of at least one circumferential retaining structure includes a membrane boot. In this embodiment or other embodiments, the at least one circumferential retaining structure is the shell or vessel of the vacuum membrane distillation module. In this embodiment or other embodiments, the hollow fiber membrane is housed in a membrane bundle assembly removable from the vacuum membrane distillation module, and the at least one circumferential retaining structure is a membrane boot.

[0033] According to yet another aspect of the present disclosure, a membrane bundle of a vacuum membrane distillation module is provided, wherein at least one of the outer circumferential surfaces of the ends of the central core or the inner circumferential surfaces of the membrane boots has a structure for enhancing the bond with the potting material.

[0034] In this embodiment or other embodiments, the structure is at least one of an opening and a threaded portion. In this embodiment or other embodiments, the structure is an opening and a threaded portion. In this embodiment or other embodiments, the potting material is an epoxy material. In this embodiment or other embodiments, the inner circumferential surface of the membrane boot has an opening within the surface on which the threaded portion is provided.

[0035] A further aspect of this disclosure provides a method for manufacturing a hollow fiber membrane bundle for use in a vacuum membrane distillation module. The hollow fiber membrane bundle comprises a plurality of hollow fiber membranes having first and second ends, the hollow fiber membranes being fixed at the first end in a first membrane boot and the second end in a second membrane boot. The first membrane boot and the second membrane boot each contain a potting material between their respective inner surfaces and the outer surface of a central core. The method includes (a) preparing a plurality of hollow fiber membranes; (b) stretching the plurality of hollow fiber membranes longitudinally; (c) preparing a first membrane boot and a second membrane boot; (d) preparing a potting material; (e) arranging the first membrane boot, the second membrane boot, and the plurality of hollow fiber membranes so that the first and second membrane boots include the first and second ends of the plurality of hollow fiber membranes; and (f) filling the first and second membrane boots at least partially with the potting material to fix the plurality of hollow fiber membranes within the first and second membrane boots.

[0036] In this embodiment or other embodiments, the method further includes the step of forming at least one of the inner surface of the membrane boot or the outer surface of the central core into a shape that enhances engagement with the potting material. In this embodiment or other embodiments, the shape is selected from an opening and a threaded portion. In this embodiment or other embodiments, the shape is a coating comprising a porous material.

[0037] In this embodiment or other embodiments, the potting material engages with at least one of the openings, threads, and membrane pores, forming a potting material bonded through these openings, threads, and pores.

[0038] Other aspects, features, and / or advantages will become further apparent by reading the non-limiting description of specific embodiments given below for illustrative purposes only with reference to the accompanying drawings. [Brief explanation of the drawing]

[0039] Some embodiments of this disclosure are shown for illustrative purposes only, with reference to the accompanying drawings. [Figure 1] This is a top perspective view of a conventional vacuum membrane distillation (VMD) membrane bundle with the module top cap removed. [Figure 2] This is a perspective view of the bottom surface of a conventional VMD membrane bundle. [Figure 3] This is a longitudinal cross-sectional view of a fiber membrane distillation module showing the module shell, the fiber membrane bundle with the module top cap, and the module bottom cap. [Figure 3A] Figure 3 is a detailed view of the module top cap and threaded section. [Figure 3B] Figure 3 is a detailed view of the module bottom cap and threaded section. [Figure 4] Figure 3 is an exploded view of a membrane bundle for VMD. [Figure 5A] This is a perspective view of the central core related to this disclosure. [Figure 5B] This is a plan view of the central core related to this disclosure. [Figure 5B-1] This is an end view of the central core related to this disclosure. [Figure 5C] This is a cross-sectional view along line 5C-5C in Figure 5B. [Figure 5D] This is an enlarged view of the detailed 5D section of Figure 5C. [Figure 5E] This is an enlarged view of the detailed 5E section of Figure 5C. [Figure 6A] This is a perspective view of the retaining ring related to this disclosure. [Figure 6B] This is a plan view of the retaining ring related to this disclosure. [Figure 6C] This is a side view of the retaining ring related to this disclosure. [Figure 6D] This is a bottom view of the retaining ring related to this disclosure. [Figure 6E] This is an enlarged view of the detailed section E in Figure 6B. [Figure 6F] This is a cross-sectional view along line 6F-6F in Figure 6C. [Figure 6G] This is an enlarged view of the detailed 6G section of Figure 6F. [Figure 6H] This is an enlarged view of the detailed 6H section of Figure 6F. [Figure 7A] This is a perspective view of the central core related to this disclosure. [Figure 7B] This is a plan view of the central core related to this disclosure. [Figure 7B-1] This is an end view of the central core related to this disclosure. [Figure 7C] This is a cross-sectional view along line 7C-7C in Figure 7B. [Figure 7D] This is an enlarged view of the detailed 7D section of Figure 7C. [Figure 7E] This is an enlarged view of the detailed 7E section of Figure 7C. [Figure 7F] This is a detailed, enlarged view of the 7th floor section of Figure 7B-1. [Figure 8A] This is a perspective view of the retaining ring related to this disclosure. [Figure 8B] This is a plan view of the retaining ring related to this disclosure. [Figure 8C] This is a side view of the retaining ring related to this disclosure. [Figure 8D] This is a bottom view of the retaining ring related to this disclosure. [Figure 8E] This is an enlarged view of the detailed 8E section of Figure 8B. [Figure 8F] Figure 8D is a detailed enlarged view of section 8F. [Figure 8G] This is an enlarged view of the detailed 8C section of Figure 8G. [Figure 8H] Figure 8G is a magnified view of the detailed 8H section. [Figure 8I] This is an enlarged view of the detailed 8I section of Figure 8G. [Figure 9] This is a partial cross-sectional perspective view of the membrane bundle related to this disclosure. [Figure 10A] This is a plan view of a central core coated with a porous thermoplastic material relating to this disclosure. [Figure 10A-1] Figure 10A is an end view of the central core. [Figure 10B] This is a cross-sectional view along line 10B-10B in Figure 10A. [Figure 10C] This is an enlarged view of the detailed 10C section of Figure 10B. [Figure 11A] This is a side view of the membrane module related to this disclosure. [Figure 11B] This is a cross-sectional view along line 11B-11B in Figure 11A. [Figure 11C] This is an enlarged view of the detailed 11C section of Figure 11B.

[0040] Throughout the drawing, the same number indicates the same part.

[0041] In some of the drawings, the elements are illustrated for the sake of brevity and clarity and are not necessarily drawn to scale. For example, the dimensions of some elements in the drawings may be exaggerated relative to others in order to facilitate understanding of each embodiment disclosed. Also, common elements that are useful or necessary in commercially viable embodiments but are well known to those skilled in the art may not be shown in order not to impede the visibility of the embodiments of this disclosure. [Modes for carrying out the invention]

[0042] To achieve the above and related objectives, several exemplary embodiments are described herein in connection with the following description and drawings. These embodiments represent various ways of implementing the principles disclosed herein. Other advantages and features will become apparent by referring to the following detailed description in conjunction with the drawings.

[0043] Figure 3 is a longitudinal section view of a membrane distillation module 10 (HFDM, hollow fiber membrane distillation module, or simply module), showing a module shell 12, a fiber membrane bundle 22 with a module top cap 18, and a module bottom cap 20. The module 10 is suitable for housing the fiber membrane bundle 22 of the present disclosure. The module includes a housing comprising a module shell 12 ("container body"). The upper end of the module shell 12 is provided with a module top flange 14, and the lower end with a module bottom flange 16. Each flange may be manufactured from engineering plastic and is joined to the container body by a chemical welding, welding, or bonding process. Figure 3A is a magnified view of the part indicated as detail 3A in Figure 3 (module top cap 18 and threaded portion). Figure 3B is a magnified view of the part indicated as detail 3B in Figure 3 (module bottom cap 20 and threaded portion 33).

[0044] Figure 3A is an enlarged view of detail 3A of Figure 3, showing the shell 12, flange 14, the threaded portion 33 on the outer diameter of the central core 32, and the threaded portion 35 on the inner diameter of the module top cap 18. The central core 32 can have various cross-sectional shapes, such as triangular, square, pentagonal, elliptical, or circular. The central core 32 preferably has a circular cross-sectional shape, in which case the central core 32 is cylindrical. The upper boot flange 48 supports the module top cap 18, which is screw-connected to the boot flange 48. The spacer ring 54a surrounds the upper membrane boot 44.

[0045] Figure 3B is an enlarged view of the detailed 3B portion of Figure 3, showing the module bottom flange 16, the threaded portion 33 on the outer diameter of the central core 32, and the threaded portion 35 on the inner diameter of the bottom boot 46. The threaded portions 33 and 35 increase the surface area of ​​the outer diameter of the central core 32 and the inner diameter of the receiving portion 36, thereby improving engagement with the potting material 23 (in one embodiment, epoxy or other thermoplastic material) and providing a vacuum seal to prevent leakage.

[0046] Referring to Figures 3, 3A, and 3B, in one embodiment, the shell 12 is a single cylindrical tube made of a thermoplastic material capable of withstanding operating temperatures of 5°C to 100°C. The shell 12 may consist of multiple components (not shown). The module top flange 14 has a structure for connecting to a corresponding flange provided on a vapor collector header (not shown). The flanges are connected by interconnecting bolts 58, as shown in Figure 4. One or more sealing members (not shown), such as gaskets, are provided between the flanges to provide a seal under vacuum.

[0047] Referring to Figure 3B, the module bottom flange 16 is similarly structured to connect to the module bottom cap 20. The module bottom cap 20 functions as the bottom cap of the membrane module to accommodate the fiber membrane bundle 22.

[0048] In one embodiment, the module bottom cap 20 may be manufactured from a single thermoplastic resin. In one embodiment, the module bottom cap 20 includes an industry-standard 12-inch flange 24 having the same bolt pattern as the module bottom flange 16. In one embodiment, the lower end incorporates a hydraulic connection to the cap, which includes a water inlet 26, a concentrated water outlet 28, and a leak outlet 30. The water inlet 26 is fluidly connected to the central core 32 of the fiber membrane bundle 22.

[0049] Referring to Figures 3 and 3B, the water inlet 26 is, in one embodiment, a standard 2-inch male "camlock" connection type. A series of seals (not shown) ensure hydraulic integrity at the interface between the module bottom cap 20 and the ends 32a and 32b of the central core 32 of the fiber membrane bundle 22.

[0050] The liquid flowing from the membrane fibers 42 is collected at the module bottom cap 20 and, in one embodiment, is sent to the concentrated water outlet 28 of a 2-inch male "camlock" type connector. A series of seals 40b, 40c, and 40d ensure hydraulic integrity at the interface between the fiber membrane bundle 22 and the module bottom cap 20 and the concentrated water outlet 28.

[0051] The leak outlet 30 is provided on the module bottom cap 20 of the fiber membrane bundle 22. All liquid passing through the membrane is collected through a 1-inch male "camlock" type leak outlet 30 in one embodiment and returned to a process leak tank (not shown).

[0052] For water supply, concentrates, and leaks, the male "Camlock" connector corresponds to the female "Camlock" connector, which is typically connected with braided or rubber hoses, but may also be connected with hard pipes.

[0053] The module bottom cap 20 is equipped with a receiving section 36 for a fiber bundle 22, the diameter of which is approximately 8 inches in one embodiment. The receiving section 36 is configured to provide a complete vacuum. The receiving section 36 is located in the center of the module bottom cap 20 and, in one embodiment, is a female connector for a fiber bundle 20 with a diameter of approximately 150 mm. In the center of the receiving section for the fiber bundle is an end core receiving section 38 for receiving a central core end connector 34 of the fiber bundle 22.

[0054] As shown in Figure 3B, the inner circumference of the receiving portion 36 is provided with two O-ring seals 40c and 40d. In other words, the O-rings 40c and 40d fit into the chamfered portion provided on the outer diameter of the central core connector 34. These O-rings are configured to maintain vacuum and hydraulic integrity and to ensure that the fiber membrane bundle 22 is securely fixed. A gasket 37 is provided to form a vacuum seal between the module bottom cap 20 and the module bottom flange 16.

[0055] Figure 4 is an exploded view of the hollow fiber membrane bundle in Figure 3, showing how multiple hollow fiber membranes 42 (collectively shown as fiber membrane bundle 22) are arranged between upper and lower membrane boots 44, 46 (also called "membrane boots"). The ends 42a, 42b of the hollow fiber membranes 42 are fixed to the membrane boots 44, 46 by chemical bonding with a potting material 23. The potting material 23 used to fix the ends of the multiple hollow fiber membranes 42 to the membrane boots may be a thermoplastic polymer. The membrane boots 44 and 46 each have a bundle flange 48 (top) and 50 (bottom), respectively. The bundle flanges 48 and 50 fit "inside" the membrane boots 44, 46. That is, the upper bundle flange 48 fits into the lower end of the upper membrane boot 44, and the lower bundle flange 50 fits into the upper end of the lower membrane boot 46. As described above, the support rods 52 (one or more, four in Figure 4) are fixed at their respective ends to the corresponding bundle flanges 48 and 50, structurally supporting the fiber membrane bundles 22 (i.e., providing longitudinal tension to the fiber membrane bundles). In one embodiment, each bundle flange 48 and 50 is composed of two halves for ease of assembly. The bundle flanges 48 and 50 are provided with two rows of concentric openings 48a and 50a to accommodate two sets of bolts (generally 58) used for different purposes. For example, the inner row of openings 48a formed in the bundle flange 48 accommodates bolts 58a for attaching the bundle flange 48 to the upper membrane boot 44 "upward". The outer row of openings 48b formed in the bundle flange 48 accommodates another bolt 58b for attaching the bundle flange 50 to the support rods 52 "downward".

[0056] The central core 32, best shown in Figures 3 and 3B, extends through the center of the fiber membrane bundle 22. Referring to Figure 4, the central core connector 34 provides a fluid connection for the supply water to flow into the central core 32 from the supply water inlet 26 of the module bottom cap 20. The module top cap 18 is sealed and mounted to the top membrane boot 44. The central core 32 transports the supply water from the inlet 26 of the module bottom cap 20 to the module top cap 18. There, the supply water is distributed to the hollow fiber membrane 42 and flows downward through the lumen (tube) (not shown) of the hollow fiber membrane 42. In some embodiments, the supply water may be supplied to the outside of the hollow fiber membrane 42. A spacer ring 54a, positioned between the top bundle flange 48 and the module top cap 18, assists in the fitting and sealing of the module top cap 18. The inner surface of the spacer ring has a chamfered portion 39 at one end for accommodating an O-ring 40a. As shown in Figure 4, another spacer ring 54b assists in the fitting and sealing of the bottom membrane boot 46 and the module bottom cap 20. The projections 56 radiating from the module top cap 18 are sized to approach or contact the inner circumference of the module shell 12, thereby positioning and supporting the membrane elements in the correct axial direction and protecting the fiber membrane bundle 22 from malfunctions and damage caused by lateral movement within the shell 12.

[0057] The vapor flow around the fiber membrane 42 is affected by the fiber packing density. The packing density of the fiber membrane bundle 22 is set to provide optimal performance for a given application. Water vapor that has passed through the hollow fiber membrane 42 is discharged from the fiber membrane bundle 22 and enters the space S formed between the outer circumference of the fiber membrane bundle 22 and the inner surface of the module shell 12, where it is extracted under vacuum through a vapor header (not shown).

[0058] As shown in Figure 4, the effective membrane length LE is the length of the fiber bundle between the top membrane boot 44 and the bottom membrane boot 46, and contributes to vapor generation. The total membrane bundle length LT, which is the total length of the membrane bundle, includes LE, the length of the module bottom cap 20 (including the bundle inlet cam lock connector 26 in one embodiment), and the lengths of the two membrane boots 44, 46 (LP). In one embodiment, the membrane length LE is about 70 cm, but may be about 80 cm, about 90 cm, about 100 cm, about 110 cm, 120 cm, or other values ​​in between. In one embodiment, the length LP is about 5 cm, about 10 cm, about 15 cm, about 20 cm, about 25 cm, or other values ​​in between.

[0059] It has been found that the sealing performance between the potting material 23 and the central core 32, or between the potting material 23 and the membrane boots 54a and 54b, can be significantly improved by designing the ends of the central core 32 to enhance adhesion with the potting material 23.

[0060] Figures 5A to 5E show a central core 60 according to the present disclosure, which has threaded outer surfaces 60a and 60b at each end. Figure 5A is a perspective view of the threaded central core 60 according to the present disclosure. Figure 5B is a plan view of the central core according to the present disclosure. Figure 5B-1 is an end view of the central core of Figure 5B. Figure 5C is a cross-sectional view along line CC of the plan view. Figure 5D is a detail D portion of Figure 5C, showing a cross-section of the threaded end. Figure 5D includes a component 60d with a threaded portion 64a formed on the outer diameter of the central core 60.

[0061] Figure 5E is a detailed 5E portion of Figure 5C, showing an enlarged view of the threaded portion 64 and its associated parts. Figure 5E shows the individual threads of the threaded portion 64 in terms of pitch angle 64a, thread width 64b, and thread depth 64c. In one embodiment, these dimensions are in the range of approximately 0.1 to 3 mm.

[0062] In one embodiment, a central core 60 may be used instead of the central core 32 shown in Figure 3. The threaded portions 60a and 60b serve to secure the potting material 23.

[0063] Figures 6A to 6H show modified membrane boots. In particular, Figure 6A shows a membrane boot 70 in which a threaded portion 70a is formed on the inner diameter of the ring 70. The ring 70 forms the outer circumference of the membrane boots (44, 46, etc.) and holds the potting material 23. The threaded portion 70a forms a raised shape to enhance engagement with the potting material 23 and increases the surface area for the potting material 23 to adhere to the ring 70 (corresponding to rings 54a and 54b).

[0064] Figure 6B is a top view of the ring 70b, showing detail E, which is the opening 70e that penetrates the threaded portion 70a. Figure 6C is a side view of the ring 70 showing the cross section line 6F-6F. Figure 6D is a bottom view of the ring 70. Figure 6E is an enlarged view of detail E in Figure 6B, showing the opening 70e. Figure 6F is a cross-sectional view along the line 6F-6F in Figure 6C. Figure 6G is an enlarged view of detail G in Figure 6F, showing the threaded portion 70a that strengthens the engagement between the potting material 23 and the inner circumference of the bottom membrane boot 46. Figure 6H is an exploded view of detail H in Figure 6F, showing how the threaded portion penetrating the ring is formed vertically or longitudinally.

[0065] Figures 7A to 7F illustrate further disclosed embodiments in which the threaded portions 80a and 80b of the central core 80 are provided with openings 88 formed in the threads 84 (Figure 7F), thereby promoting the penetration of the potting material 23 and increasing the contact area, thereby further enhancing the engagement between the potting material 23 and the central core 80. In this embodiment, as shown in Figure 7F, the openings 88 are spaced apart along the entire length of the threaded portion 84. This allows the threaded portion 84 to be formed with openings 88 so that the potting material 23 and the thermoplastic material of the central core 80 interlock and engage with each other. Other arrangements of the openings may be considered to achieve the desired engagement effect.

[0066] More specifically, Figure 7A is a perspective view of the threaded central core 80 according to this disclosure. Figure 7B is a side view of the central core 80, including a cross section 82 showing the detail 7F portion which is Figure 7F. Figure 7C is a cross section along line 7C-7C of the side view of Figure 7B. Figure 7D is the detail 7D portion of Figure 7C, showing a threaded end 80a having a threaded portion 84. Figure 7E is the detail 7E portion of Figure 7C, an enlarged cross-section of the threaded portion, showing the individual threads of the threaded portion 84 in terms of pitch angle 84a, thread width 84b, and thread depth 84c. The pitch angle dimension 84a is approximately in the range of 45 to 135 degrees, 60 to 120 degrees, or 75 to 105 degrees, or about 90 degrees. These dimensions may be in the range of approximately 0.1 to 3 mm for the thread width 86b and thread depth 84c. Figure 7F shows an opening 88 that penetrates the threaded portion 84 (Figure 7D) in the longitudinal direction. In one embodiment, the opening 88 has an angular spacing dimension of approximately 2 to 4 degrees, and the radius 88b is approximately 1.5 to 2 inches in one embodiment.

[0067] In one embodiment, a central core 80 (Figure 7A) may be used instead of the central core 32 shown in Figure 3. The threaded portion 84 serves to lock the potting material 23.

[0068] Figures 8A to 8I show modified membrane boots 90. In particular, Figure 8A shows a membrane boot 90 in which a threaded portion 90a is formed on the inner diameter of the ring 90. The ring 90 forms the outer circumference of the membrane boots 44 and 46 and holds the potting material 23. The threaded portion 90a forms a raised shape to enhance engagement with the potting material 23 and increases the surface area for the potting material 23 to adhere to the ring 90. Figure 8B is a top view of the ring 80, showing detail 8E, which is the opening 90e through the threaded portion 90a. Figure 8C is a side view of the ring 90 having a cross section 8G. Figure 8D is a bottom view of the ring 90. Figure 8E is an enlarged view of detail 8E in Figure 8B, showing the opening 90b. Figure 8F is an enlarged view of detail 8F in Figure 8D, which is the opening 90d-1. Figure 8G is an exploded view of detail 8G in Figure 8C, showing the threaded portion formed on the inner diameter of the ring 90. Figure 8H is an exploded view of the detailed 8H section of Figure 8G, showing the threaded portion that penetrates the ring 90.

[0069] Figure 9 is a partial cross-sectional view of a membrane bundle, showing a central core 60 having a threaded portion 60a on its outer circumference and a membrane boot 70 having a threaded portion 70a on its inner circumference. The hollow fiber membrane 42 is sealed with a potting material 23. The threaded portions 60a and 70a are formed to interlock and engage with each other, the potting material 23 and the membrane boot 70 (made of CPVC or a similar thermoplastic material) and the central core 60 (made of a similar material). The potting material 23 is filled into the threaded portions 60a and 70a. Any central core (e.g., 80 in Figure 7A) or membrane boot (e.g., 90 in Figure 8A) disclosed herein, for example, having an opening and a threaded portion, can be used as a substitute for the central core 60 or membrane boot 70.

[0070] In another embodiment, an opening 88 (most clearly shown in Figure 7F or 8G) on the surface of the membrane boot 44 and threaded portions and openings (70, 70a or 90, 90a) on the surface of the central core 32 form a strong bond between the potting material 23, the central core 32, and the membrane boot 44, thereby providing a robust and durable seal between the components.

[0071] Figures 10A to 10C illustrate further embodiments of the present invention. Figure 10A shows the ends 100a and 100b of the central core 100 coated with a porous thermoplastic material 102 (also shown in stippling). This configuration further strengthens the engagement between the central core 100 and the potting material 23 by promoting the penetration of the potting material 23 (not shown in Figure 10) and increasing the contact area. In this embodiment, as shown in Figures 10B and 10C, the porous thermoplastic material 102 is positioned on the outer surface of the ends of the central core 100 (see detail in part 10C of Figure 10B). This creates a structure in which the potting material 23 and the porous thermoplastic material 102 interlock and engage with each other at the ends 100a and 100b of the central core 100. The effect of the porous material 102 forming a strong bond with the potting material 23 can be obtained without providing threads or openings. In this embodiment, the porous material 102 can serve as a substitute for threads or openings and perform similar functions. Figure 10C also shows that the end portion 100c of the central core 100 may be formed of a porous thermoplastic material 102 that is bonded to the body 100c of the central core 100.

[0072] In one embodiment, a central core 100 may be used instead of the central core 32 shown in Figure 3. The porous thermoplastic material 102 plays a role in locking the potting material 23. In one embodiment, threads and openings are not required to obtain good sealing performance.

[0073] Referring to Figures 5, 6, 7, 8, 9, and 10, it can be seen that the central cores in Figures 5A-5E, 7A-7F, and 10A-10C are interchangeable with each other, and also interchangeable with central core 32. Furthermore, it can be seen that the membrane boots in Figures 6A-6H and 8A-81 are interchangeable with each other, and also interchangeable with membrane boots 44 and 46.

[0074] Figure 11 shows one embodiment in which the central core 132, central core end connector 134, and lower membrane boot 144 are formed from a porous thermoplastic material. That is, the components are formed from a porous thermoplastic material, rather than being coated with it as shown in Figure 10C. Figure 11 and detail 11C show the inner surface of the bottom membrane boot 144 and the outer surfaces of the central core 133 and central core end connector 134 formed from the porous thermoplastic material (shown as stippling in Figure 11C). The potting material 123 penetrates the porous thermoplastic material, forming a strong bond between the potting material 123, the central core 132, and the retaining ring 144. As a result, a robust and durable seal is provided between the components.

[0075] In one embodiment, a central core 132 made of a porous thermoplastic material can be used instead of the central core 32 shown in Figure 3. The central core 132 made of a porous thermoplastic material serves to secure the potting material 23. Leakage Test Procedure

[0076] As described above, the boot and central core components are threaded as explained above. The fiber membrane 42 is sealed with potting material 23 between the membrane boots 44 and 46 and the central core 32. Threaded portions 35 are formed on the inside of the membrane boots 44 and 46. Both ends 32a and 32b of the central core 32 have threaded portions that penetrate the potting material (Figure 9, central core 60, threaded portion 60a, potting material 23). The membrane bundle 22 was tested using a test apparatus in which the bundle was mounted in a completely sealed state. Water was then introduced outside the fibers at a pressure of 100 kPa. Leakage from damaged fibers or poor sealing between fibers or around the boots and central core could be observed from both sides of the bundle. This represents the maximum water and vacuum pressure to which the system is exposed. Test results

[0077] Leakage test results [Table 1]

[0078] No leaks were confirmed in any of the bundles.

[0079] While various embodiments are described in this disclosure for illustrative purposes, such descriptions are not intended to limit the scope to these embodiments. Conversely, the applicant's teachings described and illustrated herein encompass various alternatives, modifications, and equivalents, and their general scope is defined by the appended claims without departing from the embodiments. The scope of this disclosure fully encompasses other embodiments that would be apparent to those skilled in the art and is not limited by anything other than the appended claims. Where an element is referred to in the singular, it means "one or more" unless it explicitly means "unique." All structural and functional equivalents to the elements of the embodiments described above and any additional embodiments recognizable to those skilled in the art are intended to be encompassed by the appended claims. Furthermore, not all problems addressed by this disclosure require a corresponding system or method, but are instead encompassed by the appended claims. Moreover, no elements, components, or method steps in this disclosure, whether expressly described in the claims or not, are intended to be made available to the public. However, any changes or modifications made to the shape, material, workpiece and manufacturing material details are also included in this disclosure, as long as they do not deviate from the spirit and scope of this specification as set forth in the appended claims and are obvious to those skilled in the art.

Claims

1. An extending central core having a first longitudinal axis, A plurality of extending hollow fiber membranes having a second longitudinal axis substantially coaxial with or substantially parallel to the first longitudinal axis of the extending central core, A circumferential holding structure for holding a potting material and at least one end of the plurality of extending hollow fiber membranes, wherein at least one end of the plurality of extending hollow fiber membranes is fixed to the potting material, An end cap holding the at least one circumferential holding structure, wherein the potting material is held between (i) an inner boundary formed by the outer circumferential surface of the extending central core and (ii) an outer boundary formed by the inner circumferential surface of the at least one circumferential holding structure, An extending shell that cylindrically houses an extending hollow fiber membrane bundle and the extending central core, the shell having a third longitudinal axis substantially coaxial with or substantially parallel to the first longitudinal axis of the extending central core, A vacuum membrane distillation module characterized in that at least one of the following is provided: (i) the outer circumferential surface of at least one end of the extending central core, and (ii) the inner circumferential surface of the at least one circumferential holding structure, which is provided with a structure for strengthening the bond with the potting material.

2. An extending central core having at least one end, At least one circumferential holding structure, At least one end cap, At least one support rod that engages with the at least one end cap to provide longitudinal mechanical rigidity, A potting material comprising: (i) an inner boundary formed by the outer circumferential surface of the extending central core; and (ii) an outer boundary formed by the inner circumferential surface of at least one circumferential holding structure; It has a plurality of hollow fiber membranes that extend generally in the longitudinal direction, The ends of the plurality of hollow fiber membranes are fixed to the potting material. A vacuum membrane distillation module characterized in that at least one of the following is provided: (i) the outer circumferential surface of at least one end of the extending central core, and (ii) the inner circumferential surface of the at least one circumferential holding structure, which is provided with a structure for strengthening the bond with the potting material.

3. The extending central core, An extended hollow fiber membrane bundle is housed within a module top cap, which is positioned at a longitudinal distance from the module bottom cap, It comprises a substantially cylindrical shell that houses the central core, the hollow fiber membrane bundle, the module top cap, and the module bottom cap, A vacuum membrane distillation module characterized in that the extending central core, the extending hollow fiber membrane bundle, the module top cap, the module bottom cap, and the substantially cylindrical shell have substantially coaxial or substantially parallel longitudinal axes.

4. A vacuum membrane distillation module according to claim 1 or 2, characterized in that the potting material is an epoxy material.

5. The vacuum membrane distillation module according to claim 1 or 2, characterized in that the structure comprises at least one of a threaded portion or an opening.

6. The vacuum membrane distillation module according to claim 1 or 2, characterized in that the structure comprises a threaded portion and an opening.

7. The vacuum membrane distillation module according to claim 6, characterized in that the structure comprises a threaded portion and an opening, the opening passing through the threaded portion.

8. The vacuum membrane distillation module according to claim 7, characterized in that the opening is substantially perpendicular to the threaded portion.

9. The vacuum membrane distillation module according to claim 8, characterized in that the outer boundary formed by the inner circumferential surface of the at least one circumferential holding structure includes a membrane boot.

10. The vacuum membrane distillation module according to claim 1 or 2, characterized in that the at least one circumferential holding structure is the shell or container of the vacuum membrane distillation module.

11. A vacuum membrane distillation module according to any one of claims 1, 2, and 4 to 10, characterized in that the plurality of hollow fiber membranes are housed in a membrane bundle assembly removable from the vacuum membrane distillation module, and the at least one circumferential holding structure is a membrane boot.

12. A membrane bundle for a vacuum membrane distillation module, characterized in that at least one of the outer circumferential surfaces of the end of an extending central core or the inner circumferential surface of a membrane boot has a structure for strengthening the bond with the potting material.

13. The membrane bundle of a vacuum membrane distillation module according to claim 12, characterized in that the structure comprises at least one of an opening or a threaded portion.

14. The membrane bundle of a vacuum membrane distillation module according to claim 12, characterized in that the structure comprises an opening and a threaded portion.

15. The film bundle according to claim 12, characterized in that the potting material is an epoxy material.

16. The membrane bundle according to claim 12, characterized in that the inner circumferential surface of the membrane boot has an opening within the surface on which the threaded portion is formed.

17. A vacuum membrane distillation module comprising the membrane bundle described in claim 12.

18. A method for manufacturing a hollow fiber membrane bundle used in a vacuum membrane distillation module, The hollow fiber membrane bundle includes a plurality of hollow fiber membranes having a first end and a second end, and the plurality of hollow fiber membranes are fixed at the first end in the first membrane boot and the second end in the second membrane boot. The first membrane boot and the second membrane boot each contain a potting material between their respective inner surfaces and the outer surface of the central core. The aforementioned method, a. The step of preparing the plurality of hollow fiber membranes, b. The step of extending the plurality of hollow fiber membranes in the longitudinal direction, c. The steps of preparing the first membrane boot and the second membrane boot, d. Steps to prepare potting materials, e. The steps of arranging the first membrane boot, the second membrane boot, and the plurality of hollow fiber membranes, such that the first membrane boot and the second membrane boot include the first and second ends of the plurality of hollow fiber membranes, f. A method comprising the step of at least partially filling the first membrane boot and the second membrane boot with the potting material and fixing the plurality of hollow fiber membranes inside the first membrane boot and the second membrane boot.

19. The method according to claim 18, further comprising the step of forming at least one of the inner circumferential surface of the membrane boot or the outer circumferential surface of the central core in a shape that enhances engagement with the potting material.

20. The method according to claim 19, characterized in that the shape is selected from an opening, a threaded portion, and a coating including a porous material.

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