Spiral membrane element

Abstract

The present invention provides a spiral membrane element that improves the durability of the bonding portion between the membrane leaf and the central tube and makes the separation and recovery of the central tube easier during recirculation. The spiral membrane element (E) of the present invention comprises: a plurality of membrane leaves (L) having a permeate-side flow path between opposing separation membranes; and a perforated central tube (5) having the membrane leaves (L) wound around it while the supply-side flow path is provided between the membrane leaves (L), wherein the spiral membrane element (E) has a bonding portion (13) formed by bonding the two ends of the inner peripheral side end of the membrane leaves (L) in the axial direction (A1) to the central tube (5), and in at least a portion of the bonding portion (13), there is a tapered portion (5b) of the outer peripheral side of the central tube (5) with an enlarged diameter towards the center side in the axial direction (A1).

Description

Technical Field

[0001] The present invention relates to a spiral membrane element (hereinafter, sometimes simply referred to as "membrane element") having a structure that facilitates recirculation. Background Technology

[0002] Spiral membrane elements are manufactured, for example, by winding multiple membrane blades and a feed water separator around a central tube, sandwiching a permeate separator between opposing separation membranes, and then fabricating FRP (fiber reinforced plastic) around its periphery. Anti-telescoping devices (ATDs) installed at both ends are integrated during FRP fabrication. U-shaped seals are installed on the ATDs to prevent bypass flow in the gap between the element and the inner surface of the container. The membrane blades are liquid-tight by being sealed on three sides, and a permeate flow path is provided between opposing separation membranes.

[0003] Spiral membrane elements inevitably degrade over time due to years of use and membrane fouling. Regarding membrane fouling, some degree of recovery can be achieved through physical flushing (increasing the flow rate on the supply water side) or chemical cleaning, but this will eventually reach its limit, necessitating replacement of the element itself. Replaced, used membrane elements are sometimes reused for other applications that do not require high performance, but most are disposed of through methods such as landfill or incineration.

[0004] The disposal of used membrane elements is a major challenge. Landfill disposal is not sustainable because landfill capacity is limited, and membrane elements, which are mostly made of plastic, do not decompose underground and thus remain semi-permanently underground. On the other hand, incineration releases CO2, a greenhouse gas, posing a problem from an environmental perspective.

[0005] Therefore, it is desirable to recycle as much of the membrane element as possible after it has been used. For example, in Patent Document 1, as a method for reusing a conventional spiral membrane element after it has been used, a method is proposed to remove the separation functional layer of the RO membrane element with an acidic aqueous solution or the like and regenerate it into a UF membrane that serves as a porous support.

[0006] Furthermore, methods for recycling a portion of used membrane elements have been proposed. For example, as a technique for reusing the central tube (material recycling), Patent Document 2 discloses a fluid separation element in which a membrane unit comprising a separation membrane, a permeate flow path material, and a source flow path material is formed around the central tube, and an outer casing is formed on the outside of the membrane unit. A separator is sandwiched between the central tube and the membrane unit. This separator is bonded to the membrane unit and installed relative to the central tube in a manner that it is only in close contact with its outer peripheral surface, thereby allowing the central tube to be easily pulled out and disassembled from the membrane unit and the separator.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 11-156169

[0010] Patent Document 2: Japanese Patent Application Publication No. 11-267467 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, in the membrane element described in Patent Document 2, since the separator is located between the membrane leaf and the central tube, it is difficult to ensure sufficient durability relative to the force applied in the axial direction. Deformation of the membrane leaf due to positional offset may become the cause of seal failure.

[0013] Furthermore, Patent Document 2 discloses a method to prevent positional displacement caused by forces in the direction of the original fluid flow. This method involves providing a tapered section in the central tube with an outer diameter that increases from the upstream to the downstream side. However, the sealing portion on the downstream side of the membrane blade generates forces in the opposite direction to those at the adhesive portion of the central tube. Therefore, this tapered section can promote positional displacement of the separator. Specifically, the operating membrane blade experiences high external pressure due to the operating pressure, while the internal pressure on the permeation side is low. Consequently, the force caused by this pressure difference acts on the adhesive portion, and this force acts towards the central side in the axial direction of the central tube, thus creating opposing forces on the upstream and downstream sides.

[0014] However, membrane elements are made from plastic materials derived from crude oil, a valuable fossil resource. Once the membrane elements are used up, they can also be considered valuable carbon resources, requiring the recycling (chemical recycling) of the plastic materials.

[0015] As the central tube of the collection pipe is mainly in contact with the permeate water, even after the membrane element has been used, there is relatively little fouling, making it suitable for recirculation. However, because it is bonded and fixed to the membrane leaf near both ends, there are issues with the time and cost involved in removing it. Therefore, there is a need for a method that allows for easy removal of the central tube from the used membrane element, and a structure for using this method.

[0016] Therefore, the object of the present invention is to provide a spiral membrane element that improves the durability of the bonding portion between the membrane leaf and the central tube, and makes the separation and recycling of the central tube easier during recirculation.

[0017] Methods for solving problems

[0018] The above objectives can be achieved through the following invention.

[0019] [1] A spiral membrane element comprising: a plurality of membrane blades having a permeation-side flow path between opposing separation membranes; and a perforated central tube having the membrane blades wound around it while the supply-side flow path is disposed between the membrane blades, wherein the spiral membrane element has an adhesive portion formed by bonding the two axially oriented ends of the inner peripheral side ends of the membrane blades to the central tube, and having a tapered portion in at least a portion of the adhesive portion having a centrally oriented diameter-expanded outer peripheral side of the central tube.

[0020] According to the spiral membrane element of the present invention, in at least a portion of the adhesive portion, there is a tapered portion with an expanded diameter on the central side facing the outer periphery of the central tube in the axial direction. Therefore, the force caused by the differential pressure between the operating pressure and the permeation pressure, i.e., the force applied to the central side of the central tube, becomes a force pressing towards the tapered surface, thus reducing the risk of the adhesive portion peeling off due to the differential pressure. Furthermore, by having the tapered portion, the adhesive portion can be easily peeled off by applying an impact force or the like from the end opposite to the central side of the central tube, making the separation and recovery of the central tube easier during recirculation. As a result, a spiral membrane element that improves the durability of the adhesive portion between the membrane leaf and the central tube, and makes the separation and recovery of the central tube easier during recirculation, can be provided.

[0021] [2] According to the spiral membrane element of [1], there is a tapered portion with a central diameter expansion facing the outer periphery of the central tube in the axial direction throughout the entire region of the adhesive portion.

[0022] Throughout the entire area of ​​the adhesive portion, there is a tapered portion with a centrally enlarged diameter facing the outer periphery of the central tube in the axial direction, thereby improving the durability of the adhesive portion between the membrane leaf and the central tube in the entirety of the adhesive portion on the upstream and downstream sides, and making the separation and recycling of the central tube easier during recirculation.

[0023] [3] According to the spiral membrane element described in [1] or [2], wherein the inclination angle θ of the cone satisfies tanθ = 0.005~0.1.

[0024] When the inclination angle θ of the cone satisfies tanθ = 0.005~0.1, there is no need to make special changes to the shape of the membrane blades. The effective membrane area of ​​the filled separation membrane can be fully maintained while giving full play to the effect of the cone.

[0025] [4] The spiral membrane element according to any one of [1] to [3], wherein the central tube has a divisible structure at a position closer to the center than the adhesive portion.

[0026] When the central tube has a severable structure located closer to the center than the adhesive portion, for example, when the sealing portions at both ends of the membrane leaf are cut off during a recycling process, the membrane leaf surrounding the central tube can be cut off without cutting the central tube, allowing the end portion to be separated from the central part of the central tube and recovered. Therefore, by reconnecting it to the central part of the central tube, the end portion of the central tube can be reused.

[0027] Invention Effects

[0028] The spiral membrane element according to the present invention provides a spiral membrane element that improves the durability of the adhesion between the membrane leaf and the central tube, and makes the separation and recycling of the central tube easier during circulation. Attached Figure Description

[0029] Figure 1A This is a perspective view showing an exploded view of a portion of an example of the membrane element of the present invention.

[0030] Figure 1B This is a perspective view showing the main part after a portion of an example of the membrane element of the present invention has been removed.

[0031] Figure 2 This is a side sectional view showing an example of the membrane element of the present invention.

[0032] Figure 3A This is a perspective view illustrating an example of the manufacturing process of the membrane element of the present invention.

[0033] Figure 3B This is a perspective view illustrating an example of the manufacturing process of the membrane element of the present invention.

[0034] Figure 4A This is a top view illustrating an example of the process of cutting off the sealing portions on both sides.

[0035] Figure 4B This is an unfolded diagram showing an example of the process of cutting off the sealing portions on both sides; it is a diagram showing one of the membrane leaves unfolded.

[0036] Figure 5 This is a longitudinal sectional view illustrating an example of the process of separating the central tube from the sealed portions on both sides after the cut-off.

[0037] Figure 6A This is a side sectional view showing another example of the membrane element of the present invention.

[0038] Figure 6BThis is a longitudinal sectional view showing another example of the process of separating the central tube from the sealed portions on both sides after the cut-off.

[0039] Figure 7A This is a perspective view showing another example of the central tube of a membrane element.

[0040] Figure 7B This is a perspective view showing another example of the central tube of a membrane element.

[0041] Figure 7C This is a perspective view showing another example of the central tube of a membrane element.

[0042] Figure 8 This is a side sectional view showing another example of the membrane element of the present invention.

[0043] Explanation of reference numerals in the attached figures

[0044] 1: Separation membrane

[0045] 2: Supply-side spacers

[0046] 3: Through the side spacer

[0047] 5: Central tube

[0048] 5b: Conical part

[0049] 11: Sealing parts on both sides

[0050] 12: Outer peripheral sealing part

[0051] 13: Adhesive part

[0052] 15: Exterior components

[0053] A1: Axial direction

[0054] E: Membrane element

[0055] R: Wrapped body

[0056] L: Membranous leaf. Detailed Implementation

[0057] (Helical membrane element)

[0058] like Figures 1A-1B As shown, the spiral membrane element E of the present invention comprises: a plurality of membrane blades L having a permeate-side flow path between opposing separation membranes 1; and a perforated central tube 5, which allows a supply-side flow path to be located between the membrane blades L and wound around the membrane blades L. Typically, the permeate-side flow path is formed by the permeate-side spacer 3, and the supply-side flow path is formed by the supply-side spacer 2. In addition, the membrane blades L are generally structured such that their three sides are sealed together with the permeate-side spacer 3.

[0059] Therefore, in this embodiment, an example of a used membrane element E is shown, which includes: a plurality of membrane blades L, a permeation-side spacer 3 sandwiched between opposing separation membranes 1, and having a two-sided sealing portion 11 and an outer peripheral sealing portion 12 that seal the two-sided ends and the outer peripheral end in the axial direction A1; a supply-side spacer 2 sandwiched between the membrane blades L; and a perforated central tube 5 wound with the membrane blades L and the supply-side spacer 2.

[0060] When the membrane element E of the present invention becomes a used membrane element E, it has a structure that facilitates the recycling of the central tube 5, and during operation, it can improve the durability of the bonding portion 13 between the membrane leaf L and the central tube 5.

[0061] Therefore, examples of the envisioned recycling method will also be described. In the examples of the recycling method described later, a method is shown that can recycle not only the central tube 5, but also the permeate-side spacers 3 and the like contained in the membrane leaf L. However, the present invention is not limited to membrane element E that can only be used in such a recycling method.

[0062] Furthermore, the spiral membrane element E of the present invention is sometimes described as a membrane element E that has been used up; both are the same. A membrane element E that has been used up can be exemplified as one that, even if cleaned with chemicals, cannot be expected to restore its function as a membrane element E.

[0063] In this specification, the membrane leaf L wound around the central tube 5 and the supply-side spacer 2 are referred to as the winding body R, such as Figure 1A As shown, the membrane element E is typically a structure with an outer fitting 15 on the outer periphery of the wound body R.

[0064] In the membrane element E of this embodiment, a two-sided sealing portion 11 and an outer peripheral sealing portion 12 are provided as a sealing portion to prevent mixing between the supply-side flow path and the permeation-side flow path, but as... Figure 1B As shown, the two-sided sealing portions 11 in the sealing section are formed by sealing the two ends of both sides of the membrane leaf L in the axial direction A1 using an adhesive. The outer peripheral sealing portion 12 is formed by sealing the top end of the outer peripheral side of the membrane leaf L using an adhesive. The area surrounded by the opposing separation membrane 1, the two-sided sealing portions 11 and the outer peripheral sealing portion 12 forms a permeate flow path, which is a structure that communicates with the opening 5a of the central tube 5.

[0065] like Figures 1B-2As shown, the membrane element E of the present invention has an adhesive portion 13 formed by bonding the two ends of the inner peripheral side end (base end) of the membrane leaf L in the axial direction A1 to the central tube 5, thereby sealing the central tube 5 and the base end of the membrane leaf L. In this example, a wound body R is formed by winding the membrane leaf L and the supply side spacer 2 around the central tube 5 via such adhesive portion 13. It should be noted that there is no particular limitation on the adhesive used for sealing; for example, any conventionally known adhesive such as urethane adhesive or epoxy adhesive can be used.

[0066] In a typical membrane element E, such as Figure 1A As shown, an upstream end component 10, such as a sealing carrier, is provided on the upstream side of the wound body R, and a downstream end component 20, such as an anti-expansion component, is provided on the downstream side. These upstream end components 10 and downstream end components 20 can also be integrated with the wound body R by winding the FRP into an outer component 15 around the outer periphery of the wound body R.

[0067] In a typical 8-inch diameter spiral membrane element E, the membrane blades L are wound in approximately 15 to 30 sets. When using the membrane element E, it is housed in a pressure vessel, and the supply fluid 7 is supplied from one end face of the membrane element E.

[0068] like Figure 1A As shown, the supplied supply liquid 7 flows along the supply-side spacer 2 in a direction parallel to the axial direction A1 of the central tube 5, and is discharged as concentrate 9 from the other end face of the membrane element E. In addition, during the flow of the supply liquid 7 along the supply-side spacer 2, the permeate 8 that permeates through the separation membrane 1 flows along the permeate-side spacer 3, flows into the interior of the central tube 5 through the opening 5a, and is discharged from the end of the central tube 5.

[0069] like Figure 2 As shown, the central tube 5 of the present invention has an opening 5a, and in at least a portion of the adhesive portion 13, it has a tapered portion 5b whose outer circumference faces the central side of the central tube 5 and is enlarged in the axial direction A1. In the illustrated example, the adhesive portion 13 exists on both the upstream and downstream sides, but it may also be provided on at least one of the upstream and downstream sides. In either case, the total area of ​​the tapered portion 5b relative to the total area of ​​the adhesive portion 13 is preferably 10-200%, more preferably 50-150%, and even more preferably 80-120%.

[0070] In this embodiment, an example is shown where the tapered portion 5b, with its outer periphery of the central tube 5 expanding towards the central side in the axial direction A1, is shown throughout the entire region of the adhesive portion 13. That is, an example is shown where the total area of ​​the tapered portion 5b is more than 100% of the total area of ​​the upstream and downstream sides of the adhesive portion 13.

[0071] The inclination angle θ of the cone 5b preferably satisfies tanθ=0.005~0.1, and more preferably satisfies tanθ=0.01~0.035. It should be noted that the inclination angle θ refers to the angle θ between the surface of the cone 5b and the axial direction A1 in a cross-section transverse to the axial direction A1.

[0072] The outer peripheral surface of the cone 5b is not limited to having a straight cross-sectional shape; it can also be a broken line or a curve composed of multiple line segments. However, from the viewpoint of improving the durability of the adhesive portion 13 on an average basis and the recyclability of the central tube 5 during recycling, a straight cross-sectional shape is preferred.

[0073] It should be noted that when the cross-sectional shape of the outer peripheral surface of the cone 5b is a broken line or a curve, it is preferable that the inclination angle increases monotonically in the direction of diameter expansion. Furthermore, when the cross-sectional shape of the outer peripheral surface of the cone 5b is a broken line or a curve, the inclination angle θ of the straight line connecting the starting and ending points of the cone 5b preferably satisfies tanθ = 0.005~0.1, and more preferably tanθ = 0.01~0.035.

[0074] To adjust the peel force with the adhesive portion 13, the outer peripheral surface of the cone portion 5b can also be surface-treated. For example, to reduce the peel force, the surface of the cone portion 5b can be modified, or a coating with a higher release property than the material constituting the central tube 5 can be formed. Such adjustment of the peel force can be performed at least on a portion of the cone portion 5b, on the entire cone portion 5b, or on the entire length of the central tube 5.

[0075] The supply-side spacer 2 typically serves to ensure a gap for uniformly supplying fluid to the membrane surface. Such a supply-side spacer 2 can be made of materials such as mesh, woven fabric, or textured sheets, and a maximum thickness of approximately 0.1 to 3 mm can be used as needed. Furthermore, spacers are provided on both sides of the separation membrane 1, but typically different flow paths are used on the supply liquid side as the supply-side spacer 2, and different flow paths are used on the permeate side as the permeate side spacer 3. Preferably, a coarse and thick mesh flow path is used in the supply-side spacer 2, while a fine mesh fabric or woven fabric flow path is used in the permeate side spacer 3.

[0076] In applications such as seawater desalination and wastewater treatment, when using RO membranes and NF membranes, such as Figure 1A As shown, the permeate-side spacer 3 is positioned between the opposing separation membranes 1 in the membrane leaf L. It is required that the permeate-side spacer 3 support the pressure applied to the separation membrane 1 from the back of the membrane and ensure the flow path of the permeate.

[0077] Furthermore, the external pressure acting on the operating membrane leaf L is high due to the operating pressure, while the internal pressure on the permeation side is low. Therefore, the force caused by this pressure difference acts on the adhesive portion 13, and this force acts towards the central side of the central tube 5 in the axial direction A1. In this invention, regarding the adhesive portion 13 on the downstream side, it also has a tapered portion 5b in its region that expands in diameter towards the central side of the central tube 5 in the axial direction A1. Therefore, the force caused by the pressure difference between the operating pressure and the permeation pressure, that is, the force applied to the central side of the central tube 5, becomes a force in the direction of pressing towards the tapered surface, thus reducing the risk of the adhesive portion 13 peeling off due to the pressure difference.

[0078] For the through-side spacer 3, in order to ensure the function described above, it is preferable to form the through-side spacer 3 from a warp-knitted fabric, and more preferably from a warp-knitted fabric that has undergone resin impregnation reinforcement or welding treatment after the fabric is formed.

[0079] Various porous membranes can be used as the separation membrane 1, but a composite semi-permeable membrane having a separation functional layer on the surface of the porous support is preferred. As the porous support, a porous support having a polymer porous layer on one side of the nonwoven fabric layer is preferred.

[0080] Such composite semi-permeable membranes are called RO (reverse osmosis) membranes, NF (nanofiltration) membranes, and FO (forward osmosis) membranes according to their filtration performance and treatment methods. They can be used for ultrapure water production, seawater desalination, desalination of alkaline water, and wastewater reuse treatment.

[0081] Various sheets, films, tapes, etc., can be used as outer components 15, and fiber-reinforced resin (FRP) may be used for reinforcement as needed. In a structure in which the upstream side component 10 and the downstream side component 20 are firmly integrated by the outer FRP, it is difficult to disassemble and recycle the upstream side component 10 and the downstream side component 20. However, by cutting off the sealing portions 11 on both sides during recycling, their separation and recycling become easy.

[0082] (Preparation method of spiral membrane element)

[0083] The membrane element described above can be manufactured using the same methods as before. That is, for example, as... Figure 3A As shown, a plurality of membrane units U are prepared as follows: a supply-side spacer 2 is sandwiched between separation membranes 1 folded in a manner with the supply-side surface (separation functional layer side) facing each other, and a permeation-side spacer 3 is placed on the separation membrane 1. An adhesive 4 for forming the two-sided sealing portions 11 and an adhesive 6 for forming the outer peripheral sealing portion 12 are coated on the permeation-side spacer 3.

[0084] Next, for example, Figure 3BAs shown, membrane units U are stacked according to the number of membrane leaves L to form a laminate LB, which is extended at one end and fixed to the permeate side spacer 3 of the central tube 5. The laminate LB is then wound around the central tube 5. At this time, only the uppermost membrane unit U is not supported by the permeate side spacer 3, and the adhesive 4 for forming the two side sealing portions 11 and the adhesive 6 for forming the outer peripheral side sealing portion 12 are applied to the separation membrane 1.

[0085] In addition, adhesive 4a is applied continuously to the inner peripheral ends of adhesive 4 of each membrane unit U, and adhesive 4b is applied continuously to the two ends of the permeation side spacer 3 disposed at the lowermost side, in a manner that is fixed near the central tube 5 and continuous with adhesive 4a.

[0086] After winding, the shape of the wound body R is maintained, and the adhesive 4 is cured, thereby forming the two-sided sealing portion 11, the outer peripheral sealing portion 12, and the adhesive portion 13 that seals the outer periphery of the central tube 5. In particular, the adhesive portion 13 is mainly formed by adhesive 4a and adhesive 4b. As a result, a membrane element E is manufactured having a plurality of membrane leaves L having permeation side flow paths between opposing separation membranes 1 and a perforated central tube 5 wound with the membrane leaves L while the supply side flow path is provided between the membrane leaves L.

[0087] In this invention, the central tube 5 has a conical portion 5b, which differs from conventional structures. However, as long as the inclination angle θ of the conical portion 5b is not particularly large, there is no need to modify the membrane unit U, and conventional membrane units U can be used directly. In this case, some deformation of the membrane unit U may sometimes occur near the conical portion 5b, but it is unlikely to cause deformation to the extent that it impairs the separation function of the separation membrane 1. In this way, conventional membrane units U can be wound around the central tube 5 having the conical portion 5b, and the adhesive 4, etc., can be cured.

[0088] Next, as needed, upstream end components 10, such as sealing carriers, can be installed on the upstream side of the wound body R, and downstream end components 20, such as anti-expansion components, can be installed on the downstream side at the end of the central tube 5. An outer fitting 15 is provided on the outer periphery of the wound body R. The upstream end component 10 and the downstream end component 20 can be integrated with the wound body R by winding the FRP into the outer fitting 15 on the outer periphery of the wound body R.

[0089] (Recycle method)

[0090] Figure 4A This is a top view illustrating an example of the process of cutting off the sealing portions 11 on both sides. Figure 4B This is an unfolded diagram showing an example of the process of cutting off the sealing portions 11 on both sides, and it is a diagram showing one of the membrane leaves L unfolded.

[0091] The method for recycling the membrane element E of the present invention is, for example, as follows: Figures 4A-4BAs shown, the process may include cutting off at least two side seals 11 of the used membrane element E. Here, the two side seals 11 typically include opposing separation membranes 1 and a permeation-side spacer 3 between them. In this process, as... Figure 4A As shown, when cutting off the sealing portions 11 on both sides, the two ends of the supply side spacer 2 in the axial direction A1 are cut off.

[0092] Through this process, such as Figure 5 As shown, a structure is obtained in which the cut membrane leaf L' and the supply-side spacer 2' are wound around the central tube 5' on the cut-off end side. It should be noted that... Figure 5 The diagram shows a structure in which the upstream end component 10 or the downstream end component 20 is removed after the sealing portions 11 on both sides are cut off.

[0093] In this process, at least the two sealing portions 11 on both sides can be cut off from the main body of the membrane element E, or the ends of the central tube 5, the upstream end component 10, or the downstream end component 20 can be cut off simultaneously. That is, the ends of the central tube 5 can also be retained without cutting off the central tube 5. It should be noted that in this embodiment, an example is shown where the two sealing portions 11 on both sides, the two ends of the central tube 5, the upstream end component 10, and the downstream end component 20 are cut off.

[0094] As a method for removing the two side sealing portions 11, examples include cutting along the cutting line C1 to remove the two ends of the winding body R containing the two side sealing portions 11 and the two ends of the central tube 5 from the body of the membrane element E; or cutting only the winding body R without cutting the central tube 5 to separate the two ends of the winding body R containing the two side sealing portions 11 from the body of the membrane element E. The upstream end component 10 and the downstream end component 20 can also be removed simultaneously or separately.

[0095] When the sealing portions 11 on both sides of the used membrane element E are cut off, the width is preferably 50 mm or less, based on the length of the separation membrane 1 in the axial direction A1. In addition, based on the length of the separation membrane 1 in the axial direction A1 before cutting, the length of the separation membrane 1 after cutting is preferably 87% or more of the length before cutting.

[0096] like Figure 5 As shown, the cut-off end can be easily peeled off from the adhesive portion 13 by applying an impact force in the direction of the arrow. Specifically, one of the cut-off ends is placed on a support platform 32 with a hole 32a having a diameter slightly larger than the outer diameter of the central tube 5. With the clamp 31 mounted on the central tube 5' at the end, an impact force is applied to the clamp 31. At this time, the clamp 31 can be any structure capable of transmitting the impact force to the central tube 5', but in order to prevent damage to the central tube 5', it is preferable to have an inset portion 31a that is in contact with the inner circumferential surface of the central tube 5'.

[0097] The adhesive portion 13 is bonded to the downwardly widened tapered portion 5b. By applying an impact force to the clamp 31, a peeling force is generated at the interface between the central tube 5' and the adhesive portion 13, making the interface easily peeled off. The central tube 5' on the other side, which has been cut off, can also be separated in the same way. The separated and recycled central tube 5' on the end side becomes a petroleum resource and can therefore be mainly used for chemical recycling.

[0098] On the other hand, after removing the outer part 15, the outer peripheral sealing part 12 is removed by unfolding the membrane leaf L on the main body side, making it easy to separate the components and allowing the remaining parts of the through side spacer 3, the supply side spacer 2, and the central tube 5 to be used for recycling.

[0099] (Other implementation methods)

[0100] (1) In the previous embodiments, an example was shown where the central tube 5 did not have a divisible structure, but in the present invention, as Figure 6A As shown, the central tube 5 may also have a separable structure at a position closer to the center than the adhesive portion 13. In the illustrated example, the central tube 5 has a separable fitting connection portion 5c at a position slightly closer to the center than the adhesive portion 13. Preferably, the separable structure is located closer to the center than the adhesive portion 13 and further outward than the openings 5a at both ends of the central tube 5.

[0101] When the central tube 5 has a separable structure, with both ends of the central tube 5 retained, after cutting off the slightly central side of the two sealing portions 11, the end-side central tube 5' can be separated from the central portion 5* of the central tube 5, and thus... Figure 6B As shown, the end-side central tube 5' can be separated from the cut-off end and recovered. This end-side central tube 5' can be reconnected to the central portion 5* of the central tube, etc., so the end-side central tube 5' and the central portion 5* of the central tube can be reused.

[0102] Specifically, one of the cut-off ends is placed on a support platform 32 with a hole 32a having a diameter slightly larger than the outer diameter of the central tube 5. With the clamp 31 installed on the central tube 5' on the end side, an impact force is applied to the clamp 31, thereby separating and recovering the cut-off end side central tube 5'.

[0103] The divisible structure of the central tube 5 is not particularly limited, but a fitting structure with an anti-rotation part is preferred. Figures 7A to 7C This illustrates an example of a mating structure for such a central tube 5. In Figure 7AIn the example shown, the fitting connection portion 5c of the end side of the central tube 5' has a protrusion, and the central portion 5* of the central tube 5 has a guide groove and a recess, so that the fitting connection portion 5c can be pressed in, and the protrusion can be locked in the recess for fixation.

[0104] exist Figure 7B In the example shown, the fitting connection portion 5c of the end side of the central tube 5' has a protrusion, and the central portion 5* of the central tube 5 has an L-shaped guide groove and a recess. Therefore, if the protrusion is pressed into the fitting connection portion 5c along the guide groove and rotated, the protrusion can be locked in the recess and fixed.

[0105] exist Figure 7C In the example shown, the fitting connection 5c of the end side of the central tube 5' has an external thread structure, and the central part 5* of the central tube 5 has an internal thread structure, so the fitting connection 5c can be rotated and screwed together.

[0106] (2) In the previous embodiments, an example was shown where the outer diameter of the main body of the central tube 5 was larger than the outer diameter of the top end of the central tube 5. However, in this invention, as... Figure 8 As shown, the outer diameter of the main body of the central tube 5 can also be equal to or less than the outer diameter of the top end of the central tube 5.

[0107] In this case, by providing a cone portion 5b in the central tube 5 to suppress the increase in the outer diameter of the main body of the central tube 5, the volume of the filling separation membrane 1 is maintained, thereby suppressing the reduction of the effective membrane area.

[0108] Specifically, such as Figure 8 As shown, a stepped portion with an outer diameter smaller than that of the top end of the central tube 5 is provided. Starting from this stepped portion, a tapered portion 5b is formed that expands in diameter towards the center in the axial direction A. The tapered portion 5b ends with an outer diameter equal to or less than that of the top end of the central tube 5. In other words, the central tube 5 has a top end tube portion, a stepped portion with a reduced outer diameter, a tapered portion 5b whose outer circumference expands towards the center in the axial direction A from the stepped portion, and a main body portion that extends continuously from the end of the tapered portion 5b and has an outer diameter equal to or less than that of the top end tube portion.

[0109] Even with such a structure, because it has a tapered portion 5b with an expanded diameter on the central side facing the axial direction A, the adhesive portion 13 can be easily peeled off by applying an impact force from the top end of the central tube 5 after cutting off the top end of the central tube 5 containing the stepped portion, making it easier to separate and recycle the central tube 5 during recycling.

[0110] Furthermore, by shortening the fitting portion of the interconnect used to mount the connecting membrane element E, the thickness of the tapered portion 5b of the central tube 5 can be ensured. In this case, the inner circumferential surface of the tapered portion 5b of the central tube 5 preferably also has an inclination angle of the same degree as the inclination angle θ of the tapered portion 5b.

[0111] [Potential for Industrial Applications]

[0112] The spiral membrane element according to the present invention provides a spiral membrane element that improves the durability of the adhesion between the membrane leaf and the central tube, and makes the separation and recycling of the central tube easier during recycling. The central tube can be recycled in a cut or split state; in the cut state, it can be used for chemical or material recycling, and in the split state, it can be reused. In either case, the central tube is easily separated and recycled, thus making the spiral membrane element useful as having a structure conducive to recycling.

Claims

1. A spiral membrane element comprising: a plurality of membrane leaves having a permeation-side flow path between facing separation membranes; and a perforated center pipe in which the membrane leaves are wound while a supply-side flow path is provided between the membrane leaves, wherein the spiral membrane element has a bonded portion in which both end portions in the axial direction of an inner peripheral side end portion of the membrane leaves are bonded to the center pipe, and in a region of at least a portion of the bonded portion, a tapered portion in which an outer peripheral surface of the center pipe is expanded toward the central side in the axial direction is provided.

2. The spiral membrane element according to claim 1, wherein in the entire region of the bonded portion, the tapered portion in which the outer peripheral surface of the center pipe is expanded toward the central side in the axial direction is provided.

3. The spiral membrane element according to claim 1, wherein an inclination angle θ of the tapered portion satisfies tan θ = 0.005 to 0.

1.

4. The spiral membrane element according to claim 1, wherein the center pipe has a structure capable of being divided at a position on the central side from the bonded portion. ​ ​ ​ ​ ​

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