Method for regenerating membrane elements and membrane modules

Abstract

The present invention provides a method for regenerating membrane elements that does not require altering the structure of the membrane elements to be regenerated, reduces waste generated by used membrane elements and saves introduced resources, and restores separation function, as well as a membrane module using the resulting regenerated membrane elements. [Solution] A method for regenerating a membrane element, comprising the steps of: cutting off at least the sealing portions on both sides of the used membrane element; unfolding the membrane leaf after cutting and cutting off at least the sealing portion on the outer periphery of the membrane leaf; replacing at least the separation membrane of the unfolded and cut membrane leaf with a new separation membrane; and forming a sealing portion on both sides and an outer periphery of the replaced membrane leaf to seal both axial ends and the outer periphery end, thereby obtaining a regenerated membrane element.

Description

Technical Field

[0001] The present invention relates to a method for regenerating a membrane element for manufacturing a regenerated membrane element by using a part of a used membrane element, and a membrane module using the obtained regenerated membrane element.

Background Art

[0002] The structure of a typical spiral membrane element has a plurality of membrane leaves having both-side sealing portions and an outer-periphery-side sealing portion in which a permeation-side spacer is interposed between opposing separation membranes and both-side end portions and outer-periphery-side end portions in the axial center direction are sealed, a supply-side spacer interposed between the membrane leaves, and a perforated center tube around which the membrane leaves and the supply-side spacer are wound.

[0003] As a result of such a spiral membrane element being used and undergoing deterioration over time and contamination of the membrane surface, its performance deteriorates over time. Regarding contamination of the membrane surface, it is possible to physically wash away contaminants by increasing the flow rate on the supply liquid side by flushing cleaning or chemically clean by chemical cleaning, and a certain degree of recovery is possible. However, since there is a limit to the recovery, it is necessary to replace the membrane element itself.

[0004] The treatment method for the used membrane element after replacement is a major issue. In the case of landfill disposal, there is a problem that the volume of the disposal site that can be processed is limited, and since the membrane element, which is mostly made of a plastic material, is not decomposed underground, it remains in the ground semi-permanently. Therefore, it is desired to reduce the waste caused by the used membrane element as much as possible. This is the same even in the case of incineration disposal.

[0005] As a technology for reusing a used membrane element, for example, there are those having a structure in which the exterior of a spiral membrane element can be reused (Patent Documents 1 to 2), those having a structure in which an anti-telescope material can be reused (Patent Document 3), those having a structure in which a center tube can be reused (Patent Document 4), and the like.

[0006] However, all of these technologies require a change in the structure of the spiral membrane element from the conventional structure, making it impossible to reuse used spiral membrane elements that have been used until now.

[0007] On the other hand, Patent Document 5 proposes a method for reusing conventional spiral-type membrane elements by removing the separation functional layer of the RO membrane element with an acidic aqueous solution or the like, and regenerating it into a UF membrane, which is a porous support. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2000-15063 [Patent Document 2] Japanese Patent Publication No. 2012-183527 [Patent Document 3] Japanese Patent Publication No. 2008-149322 [Patent Document 4] Japanese Patent Application Publication No. 11-267467 [Patent Document 5] Japanese Patent Application Publication No. 11-156169 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the regeneration method described in Patent Document 5 has the problem that it is not possible to regenerate a used spiral-type membrane element as the same RO membrane element as before regeneration, and therefore the function of the original separation membrane cannot be restored.

[0010] Therefore, the object of the present invention is to provide a method for regenerating membrane elements that does not require changing the structure of the membrane elements to be regenerated, which reduces waste generated by used membrane elements and saves introduced resources, and which also restores the separation function, as well as a membrane module using the resulting regenerated membrane elements. [Means for solving the problem]

[0011] The above objective can be achieved by the present invention as described below.

[0012] [1] A method for regenerating a membrane element, which involves using a portion of a used membrane element to manufacture a regenerated membrane element, The used membrane element comprises a plurality of membrane leaves having a permeable-side spacer interposed between opposing separation membranes, and having both side sealing portions and an outer peripheral sealing portion that seal both axial ends and the outer peripheral end; a supply-side spacer interposed between the membrane leaves; and a perforated central tube around which the membrane leaves and the supply-side spacer are wound. A step of removing at least the sealing portions on both sides of the used membrane element, The process involves unfolding the excised membrane leaf and excising at least the outermost sealing portion of the membrane leaf, A step of replacing at least the separation membrane of the membrane leaf after unfolding and excision with a new separation membrane, A process to obtain a regenerated film element by forming a double-sided sealing portion and an outer-circumferential sealing portion that seal both axial ends and the outer-circumferential end of the replaced film leaf, A method for regenerating membrane elements containing [the specified element].

[0013] According to the membrane element regeneration method of the present invention, since the structure of the used membrane element to be regenerated is the same as that of the conventional structure, there is no need to change the structure of the membrane element, and the separation membrane, which is difficult to restore in the state of the membrane element, can be replaced with at least a new separation membrane. For this reason, the separation function can be restored while reusing at least a portion of the other components. In addition, since at least a portion of the components can be reused, the amount of new plastic introduced is reduced, thus saving valuable petroleum resources. As a result, it is possible to provide a membrane element regeneration method that does not require changing the structure of the membrane element to be regenerated, reduces waste and saves introduced resources caused by used membrane elements, and restores the separation function.

[0014] [2] When replacing the new separation membrane, the regeneration method of the membrane element according to [1], wherein the supply-side spacer is replaced with a regenerated supply-side spacer from which contaminants have been removed by cleaning or a new supply-side spacer.

[0015] By replacing with a regenerated supply-side spacer from which contaminants have been removed by cleaning or a new supply-side spacer, the function of the supply-side spacer, which was difficult to restore in the state of the membrane element, can be restored.

[0016] [3] The regeneration method of the membrane element according to [1] or [2], wherein the used membrane element has an exterior material, and after cutting off the both-side sealing parts, the exterior material is removed.

[0017] After cutting off the both-side sealing parts and removing the exterior material, even in the case of a structure in which the exterior material is integrated with the end members, the exterior material can be easily removed.

[0018] [4] The regeneration method of the membrane element according to any one of [1] to [3], wherein the central tube of the used membrane element is replaced with a regenerated central tube whose length has been adjusted by cutting or a new central tube.

[0019] After cutting off the both-side sealing parts, the permeation-side spacer and the separation membrane after replacement have a shorter length in the axial direction, but by replacing with a regenerated central tube whose length has been adjusted by cutting or a new central tube, it can be used as a central tube of an appropriate length for the regeneration of the membrane element.

[0020] [5] A membrane module including a membrane element and a vessel for housing the membrane element, wherein the membrane element is a regenerated membrane element in which a part of the used membrane element is utilized and the length of the separation membrane in the axial direction is shortened, A membrane module in which one or more of the regenerated membrane elements, which are more than the number of the used membrane elements housed, are housed in the vessel.

[0021] According to the membrane module of the present invention, even when using a regenerated membrane element with a reduced axial length of the separation membrane, since one or more regenerated membrane elements are accommodated in the vessel than the number of used membrane elements accommodated, a decrease in the total membrane area can be suppressed. And, as the regenerated membrane element with a reduced axial length of the separation membrane, at least a permeate-side spacer, and if necessary, those obtained by reusing a feed-side spacer or a central tube can be used. As a result, it is possible to provide a membrane module that can use a regenerated membrane element obtained by reusing at least the permeate-side spacer while suppressing a decrease in the total membrane area.

[0022] [6] The membrane module according to [5], wherein the regenerated membrane elements are connected by an interconnector having an anti-telescoping function, or the regenerated membrane elements having an anti-telescoping function are connected by an interconnector.

[0023] When the regenerated membrane elements are connected by an interconnector having an anti-telescoping function, there is no need to attach an anti-telescoping material to the regenerated membrane element, and a structure advantageous for suppressing a decrease in the total membrane area can be achieved. Also, even when the regenerated membrane elements having an anti-telescoping function are connected by an interconnector, by reducing the thickness of the anti-telescoping material of the regenerated membrane element, a decrease in the total membrane area can be suppressed.

Effects of the Invention

[0024] According to the method for regenerating a membrane element of the present invention, it is possible to provide a method for regenerating a membrane element that does not require changing the structure of the membrane element to be regenerated, can reduce waste resulting from used membrane elements and save introduced resources, and can restore the separation function.

[0025] The present invention provides a membrane module that can use a regenerated membrane element, which at least has a permeable spacer reused, while suppressing a decrease in the total membrane area. [Brief explanation of the drawing]

[0026] [Figure 1A] This is a perspective view showing a partially disassembled example of a membrane element that is the target of the membrane element regeneration method of the present invention. [Figure 1B] This is a perspective view showing a cutaway section of an example of a membrane element to which the regeneration method of the present invention applies. [Figure 2A] This is a plan view showing an example of the process of removing the sealing portions on both sides. [Figure 2B] This is a diagram illustrating an example of the process of removing the bilateral sealing portion, showing one of the membrane leaves unfolded. [Figure 3] This is a diagram illustrating an example of the process of removing the outer periphery sealing portion, showing one of the membrane leaves unfolded. [Figure 4A] This is a diagram illustrating an example of the process of replacing a separation membrane with a new one, showing one of the membrane leaves unfolded before replacement. [Figure 4B] This is a diagram illustrating an example of the process of replacing a separation membrane, showing one of the membrane leaves being replaced in an unfolded state. The dashed lines continuous with the separation membrane indicate the state in which the separation membrane is folded. [Figure 5A] This is a perspective view illustrating an example of the process of replacing a separation membrane with a new one, showing how one new separation membrane and a supply-side spacer are inserted into multiple permeation-side spacers. [Figure 5B] This is a perspective view illustrating an example of the process of replacing a separation membrane with a new one, showing multiple new separation membranes and supply-side spacers inserted into multiple permeation-side spacers. [Figure 6A] This is a plan view showing an example of removing the end portion of a regenerated film element that has formed a sealing portion, and it shows the state before removal. [Figure 6B]This is a plan view showing an example of removing the end portion of a regenerated film element that has formed a sealing portion, and it shows the state after removal. [Figure 7A] A cross-sectional view showing an example of a regenerated membrane element and interconnect used in the membrane module of the present invention. [Figure 7B] This is a cross-sectional view showing an example of a key part of the membrane module of the present invention. [Figure 8A] A cross-sectional view showing another example of a regenerated film element and interconnect used in the film module of the present invention. [Figure 8B] This is a cross-sectional view showing another example of a key part of the membrane module of the present invention. [Figure 9A] A cross-sectional view showing another example of a regenerated film element and interconnect used in the film module of the present invention. [Figure 9B] This is a cross-sectional view showing another example of a key part of the membrane module of the present invention. [Figure 10] This is a diagram illustrating another example of the process of removing the outer periphery sealing portion, showing one of the membrane leaves unfolded. [Figure 11A] This is a diagram illustrating another example of the process of replacing a separation membrane, showing one of the membrane leaves unfolded before replacement. [Figure 11B] This is a diagram illustrating another example of the process of replacing a separation membrane, showing one of the membrane leaves being replaced in an unfolded state. The dashed lines continuous with the separation membrane indicate the state in which the separation membrane is folded. [Modes for carrying out the invention]

[0027] (Method for regenerating membrane elements) The present invention relates to a method for regenerating membrane elements, which involves manufacturing a regenerated membrane element using a portion of a used membrane element. The target membrane element is a spiral-type membrane element.

[0028] Figure 1A is a perspective view showing a partially disassembled example of a membrane element targeted by the membrane element regeneration method of the present invention, and Figure 1B is a perspective view showing a partially cut-out main part of an example of a membrane element targeted by the membrane element regeneration method of the present invention.

[0029] Specifically, the used membrane element UE in question, as shown in Figures 1A to 1B, for example, comprises a plurality of membrane leaves L having a permeable-side spacer 3 interposed between opposing separation membranes 1, and having both side sealing portions 11 and an outer peripheral sealing portion 12 that seal both ends in the axial direction A1 and the outer peripheral end, a supply-side spacer 2 interposed between the membrane leaves L, and a perforated central tube 5 around which the membrane leaves L and the supply-side spacer 2 are wound. First, this used membrane element will be described.

[0030] (Used film element) Used membrane elements include those whose function as a membrane element cannot be expected to be restored even after chemical cleaning, for example, and specifically refer to the following conditions: (1) Even after repeated chemical cleaning (on-site or off-site cleaning), the amount of permeate is 50% or less of the initial value and the permeability of salts is 10% or more (salt blocking rate is 90% or less); (2) When comparing the weight of a membrane element with that of a new one, even after repeated chemical cleaning (on-site or off-site cleaning), the weight has increased by 25% or more of the initial value due to accumulated deposits, and the contaminants have not been removed.

[0031] Any known spiral-type membrane element can be used as a used membrane element UE, as it comprises a plurality of membrane leaves L having permeable-side spacers 3 interposed between opposing separation membranes 1, and having both side sealing portions 11 and outer peripheral sealing portion 12 that seal both side ends in the axial direction A1 and the outer peripheral end, a supply-side spacer 2 interposed between the membrane leaves L, and a perforated central tube 5 around which the membrane leaves L and the supply-side spacers 2 are wound.

[0032] 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, and the membrane element UE generally has an outer covering material 15 on the outer circumference of the winding body R, as shown in Figure 1A.

[0033] The membrane element UE is provided with two sealing portions 11 on both sides and one sealing portion 12 on the outer circumference to prevent mixing of the supply-side channel and the permeate-side channel. As shown in Figure 1B, of the sealing portions, the two sealing portions 11 on both sides are sealed with adhesive at the ends of two sides on both sides of the membrane leaf L in the axial direction A1. The outer sealing portion 12 is sealed with adhesive at the end of the outer circumference tip of the membrane leaf L. The region enclosed by the opposing separation membrane 1, the two sealing portions 11 on both sides, and the outer sealing portion 12 on the outer circumference becomes the permeate-side channel, which is connected to the opening 5a of the central tube 5.

[0034] Furthermore, as shown in Figure 1B, the present invention may have a central sealing portion 13 in which the perforated central tube 5 and the base end of the membrane leaf L are sealed with an adhesive. In this example, the wound body R has the membrane leaf L and the supply side spacer 2 wound around the central tube 5 via such a central sealing portion 13. The adhesive is not particularly limited, and any conventionally known adhesive such as a urethane adhesive or an epoxy adhesive can be used.

[0035] In a typical membrane element UE, as shown in Figure 1A, an upstream end member 10, such as a seal carrier, is provided on the upstream side of the winding body R, and a downstream end member 20, such as an anti-telescopic material, is provided on the downstream side. These upstream end members 10 and downstream end members 20 may be integrated with the winding body R by wrapping FRP, which serves as the outer covering material 15, around the outer circumference of the winding body R.

[0036] In a typical 8-inch diameter spiral membrane element, approximately 15 to 30 membrane leaves L are wound around it. When using the membrane element UE, it is housed in a pressure vessel, and the supply fluid 7 is supplied from one end face of the membrane element UE.

[0037] As shown in Figure 1A, the supplied feed 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 concentrated liquid 9 from the other end face of the membrane element UE. In addition, the permeate 8 that has permeated the separation membrane 1 as the feed liquid 7 flows along the supply-side spacer 2 flows along the permeate-side spacer 3 and then flows into the interior of the central tube 5 through the opening 5a and is discharged from the end of the central tube 5.

[0038] The supply-side spacer 2 generally serves to ensure a gap for evenly supplying fluid to the membrane surface. Such a supply-side spacer 2 can be made of, for example, a net, knitted fabric, or a textured sheet, and can be used as needed with a maximum thickness of approximately 0.1 to 3 mm. Spacers are installed on both sides of the separation membrane 1, but it is common to use different flow channel materials: the supply-side spacer 2 on the supply liquid side and the permeate-side spacer 3 on the permeate liquid side. It is preferable to use a coarse, thick net-like flow channel material for the supply-side spacer 2, while using a fine-mesh woven or knitted flow channel material for the permeate-side spacer 3.

[0039] The central pipe 5 can be any pipe having openings 5a around its circumference, as shown in Figure 1A, and any conventional pipe can be used. Generally, when used in seawater desalination or wastewater treatment, the permeate water that has passed through the separation membrane 1 flows towards the central pipe 5 through the permeate-side flow path formed along the permeate-side spacer 3 interposed between the opposing separation membranes 1, then flows into the central pipe 5 through the openings 5a, flows inside the central pipe 5, and is discharged from the end.

[0040] The permeate-side spacer 3 is installed between opposing separation membranes 1 in the membrane leaf L, as shown in Figure 1A, when RO membranes or NF membranes are used in applications such as seawater desalination and wastewater treatment. This permeate-side spacer is required to support the pressure on the membrane from the back surface of the membrane and to ensure a flow path for the permeate.

[0041] To ensure such functionality, it is preferable that the permeable spacer 3 is formed by a tricot knitted fabric, and more preferably that the tricot knitted fabric is reinforced by resin impregnation or fusion treatment after knitting.

[0042] As the separation membrane 1, various porous membranes can be used, but a composite semipermeable membrane having a separation functional layer on the surface of a porous support is preferred. As the porous support, one having a polymer porous layer on one side of a nonwoven fabric layer is preferred.

[0043] These composite semipermeable membranes are called RO (reverse osmosis) membranes, NF (nanofiltration) membranes, or FO (forward osmosis) membranes depending on their filtration performance and treatment method, and can be used for ultrapure water production, seawater desalination, brine desalination, and wastewater reuse.

[0044] Examples of exterior materials 15 include various sheets, films, tapes, etc., and fiber-reinforced plastic (FRP) may be used for reinforcement as needed. In a structure in which the upstream end member 10 and the downstream end member 20 are firmly integrated by the exterior FRP, it is difficult to disassemble the membrane element UE, but in the present invention, these can be removed when cutting the sealing portions 11 on both sides without disassembly.

[0045] (Process of removing the sealing portions on both sides) Figure 2A is a plan view showing an example of the process of removing the sealing portions 11 on both sides, and Figure 2B is an unfolded view showing an example of the process of removing the sealing portions 11 on both sides, with one of the membrane leaves L unfolded.

[0046] The present invention's method for regenerating a membrane element includes, for example, the step of removing at least the sealing portions 11 on both sides of the used membrane element UE, as shown in Figures 2A and 2B. Here, the sealing portions 11 on both sides typically include opposing separation membranes 1 and a permeable-side spacer 3 interposed between them. In this step, as shown in Figure 2A, it is preferable to remove both ends of the supply-side spacer 2 in the axial direction A1 when removing the sealing portions 11 on both sides.

[0047] This process yields a membrane leaf L1 in which the opposing separation membrane 1 and the permeation-side spacer 3 are bonded only at the outer peripheral sealing portion 12 of the three sealing portions at the ends of the membrane leaf L, as shown in Figure 3. At this time, one or more membrane leaves L1 may be fixed (bonded, etc.) to the central tube 5 via the permeation-side spacer 3. In this case, the inner peripheral ends of one or more permeation-side spacer 3 may be fixed to the central tube 5, and furthermore, the inner peripheral ends of one or more other permeation-side spacer 3 may be further fixed to the inner peripheral end of a permeation-side spacer 3 fixed to the central tube 5. In other words, all permeation-side spacer 3 may be directly or indirectly fixed to the central tube 5. Note that if both ends of the supply-side spacer 2 are cut off, the length of the supply-side spacer 2 in the axial direction A1 can be made to match the length of the permeation-side spacer 3.

[0048] In this process, it is sufficient that at least the sealing portions 11 on both sides are removed from the main body of the membrane element UE, and at the same time, the ends of the central tube 5, the upstream end member 10, or the downstream end member 20 may also be removed. In other words, it is possible to leave the ends intact without cutting the central tube 5. In this embodiment, an example is shown in which the sealing portions 11 on both sides, both ends of the central tube 5, the upstream end member 10, and the downstream end member 20 are removed.

[0049] Methods for removing the double-sided sealing portions 11 include, for example, cutting along the cutting line C1 to remove both ends of the wound body R including the double-sided sealing portions 11 and both ends of the central tube 5 from the main body of the membrane element UE, or cutting only the wound body R without cutting the central tube 5 to separate both ends of the wound body R including the double-sided sealing portions 11 from the main body of the membrane element UE. It is also possible to remove the upstream end member 10 and the downstream end member 20 simultaneously or separately. Alternatively, methods such as cutting to remove the entire ends of the wound body R including the double-sided sealing portions 11 may also be used.

[0050] When removing the sealing portions 11 on both sides of the used membrane element UE, the width is preferably 50 mm or less, based on the length A1 in the axial direction of the separation membrane 1. Furthermore, it is preferable that the length of the separation membrane 1 after removal is 87% or more of the length of the separation membrane 1 before removal, based on the length A1 in the axial direction of the separation membrane 1 before removal.

[0051] (Process of removing the outer sealing portion) Figure 3 is an unfolded view showing an example of the process of removing the outer peripheral sealing portion 12, and shows one of the membrane leaves L1 from which the sealing portions 11 on both sides have been removed.

[0052] The present invention's method for regenerating a membrane element includes, for example, the step of unfolding the excised membrane leaf L1 and excising at least the outer peripheral sealing portion 12 of the membrane leaf L1, as shown in Figure 3. In this embodiment, an example is shown in which the outer peripheral sealing portion 12 is cut along the cutting line C2. Here, the outer peripheral sealing portion 12 usually includes opposing separation membranes 1 and a permeable spacer 3 interposed between them. Furthermore, "unfolding the membrane leaf L1" refers to opening the wound membrane leaf L1 so that it can be easily cut, and it is not necessarily required to flatten the membrane leaf L1.

[0053] This process removes the sealing portions at the three edges of the membrane leaf L, as shown in Figure 4B, resulting in a membrane leaf L2 that can separate the opposing separation membrane 1 and the permeation-side spacer 3. This allows the separation membrane 1 to be replaced with a new separation membrane 1'. Furthermore, when unfolding the membrane leaf L1 after excision, or after unfolding, the supply-side spacer 2 can be easily removed. Therefore, it is possible to replace the supply-side spacer 2 before and after excising the outer peripheral sealing portion 12.

[0054] In this process, it is sufficient that at least the outer peripheral sealing portion 12 is removed from the main body of the membrane element UE, and other materials such as adhesive tape present around the wound body R may be removed beforehand or at the same time. It is also possible to perform a step of removing the outer covering material 15 after removing the sealing portions 11 on both sides. The step of removing the outer covering material 15 will be described later.

[0055] When removing the outer sealing portion 12 of the used membrane element UE, the width is preferably 50 mm or less, based on the length perpendicular to the axial direction A1 of the separation membrane 1. Furthermore, it is preferable that the length of the separation membrane 1 after removal is 87% or more of the length of the separation membrane 1 before removal, based on the length perpendicular to the axial direction A1 of the separation membrane 1 before removal.

[0056] In this way, by setting the width of the double-sided sealing portion 11 and the outer peripheral sealing portion 12 to 87% or more of the length of the separation membrane 1 in two directions before removal, based on the length of the separation membrane 1 before removal, it is possible to make the effective membrane area of ​​the resulting regenerated membrane element RE 76% or more of the effective membrane area of ​​the used membrane element UE (87% × 87% = 76%).

[0057] (Step to replace the separation membrane) Figure 4A is an unfolded view showing an example of the process of replacing a separation membrane 1', showing one of the membrane leaves L2 before replacement unfolded. Figure 4B shows one of the membrane leaves L2 during replacement unfolded, with the dashed line continuous with the separation membrane 1 indicating the state in which the separation membrane 1 is folded. Figure 5A is a perspective view showing an example of the process of replacing a separation membrane 1', showing one new separation membrane 1' and a supply-side spacer 2' being inserted into multiple permeation-side spacers 3. Figure 5B is a perspective view showing an example of the process of replacing a separation membrane 1', showing multiple new separation membranes 1' and supply-side spacers 2' being inserted into multiple permeation-side spacers 3.

[0058] The present invention's method for regenerating a membrane element includes, for example, the step of replacing at least the separation membrane 1 of the membrane leaf L2 after unfolding and cutting with a new separation membrane 1', as shown in Figures 4A to 5B. This step yields a component in which the separation membrane 1 has been replaced with a new separation membrane 1', as shown in Figure 5B. At this time, at least the permeation-side spacer 3 is reused, but preferably, the permeation-side spacer 3 and the central tube 5, which show little deterioration due to use, can be reused. In this embodiment, an example is shown in which the supply-side spacer 2 is also replaced with a new supply-side spacer 2', but it is also possible to reuse the used supply-side spacer 2 as is or after cleaning, repairing, etc., depending on the degree of deterioration. This will be described later.

[0059] When replacing the separation membrane 1, as shown in Figure 4B, the folded separation membrane 1 is removed from both sides of the permeate-side spacer 3. In this case, one or more permeate-side spacers 3 may be attached to the central tube 5 directly or via other permeate-side spacers 3, in which case the separation membrane 1 can be removed from the outside of the central tube 5 (for example, in the manner indicated by the arrow). At that time, the supply-side spacer 2, which is not shown, can be removed at the same time as or separately from the folded separation membrane 1.

[0060] In this embodiment, as shown in Figure 5A, an example is shown where only one permeable spacer 3 is bonded to the central tube 5, but it is also possible to pre-bond the inner circumferential ends of multiple other permeable spacers 3 to this permeable spacer 3.

[0061] Next, as shown in Figure 5A, a new, folded separation membrane 1' and a supply-side spacer 2' are inserted between a plurality of permeable-side spacers 3. If the plurality of permeable-side spacers 3 are not bonded to each other, it is also possible to alternately place the members consisting of the new, folded separation membrane 1' and the supply-side spacer 2' interposed therebetween with the permeable-side spacers 3.

[0062] In the process of replacing the separation membrane 1' with a new one, it is preferable to provide adhesive means for forming a sealing portion. For example, in the example shown in Figure 5B, adhesives 4 and 6 are applied to the side of the separation membrane 1' that contacts the permeate-side spacer 3 to form sealing portions at the three edges, but it is also possible to perform heat bonding using a heat-adhesive sheet or the like. Alternatively, instead of applying adhesives 4 and 6 to the separation membrane 1', they can be applied to the permeate-side spacer 3. It is also possible to fix or temporarily attach the inner circumference end of the supply-side spacer 2' to the bent portion of the separation membrane 1'.

[0063] (The process of replacing the supply-side spacer) Regarding the supply-side spacer 2, when the sealing portions 11 on both sides of the membrane leaf L are removed, both ends of the supply-side spacer 2 can be removed simultaneously, making the lengths of the supply-side spacer 2 and the permeation-side spacer 3 in the axial direction A1 equal. Therefore, the supply-side spacer 2 can be used as is.

[0064] Furthermore, the supply-side spacer 2 can be reused as a regenerated supply-side spacer after removing contaminants through cleaning. It is also possible to replace it with a new supply-side spacer.

[0065] While it is possible to replace the supply-side spacer 2 after replacing the separation membrane 1 with a new separation membrane 1', it is preferable to replace the supply-side spacer 2 when replacing the separation membrane 1 with a new separation membrane 1', as shown in Figure 5A, in order to simplify the process.

[0066] (The process of replacing the central tube) Regarding the central tube 5, when the sealing portions 11 on both sides of the membrane leaf L are removed, both ends of the central tube 5 can be removed simultaneously, making the axial length A1 of the central tube 5 and the permeable side spacer 3 the same. Therefore, the central tube 5 can be used as is.

[0067] Furthermore, when removing the sealing portions 11 on both sides of the membrane leaf L, it is possible to leave both ends of the central tube 5 intact and ultimately use a regenerated central tube cut to an appropriate length. It is also possible to replace it with a new central tube 5.

[0068] However, since the central tube 5 is less susceptible to deterioration from use, it is preferable to reuse the central tube 5 after simultaneously cutting off both ends of the central tube 5 when removing the sealing portions 11 on both sides of the membrane leaf L. Of course, if reuse is difficult due to the position of the opening 5a in the central tube 5, it is preferable to replace it with a new central tube 5.

[0069] (Process for obtaining regenerated film elements) Figure 6A is a plan view showing an example of removing the end of a regenerated film element that has formed a sealing portion, and shows the state before removal. Figure 6B is a plan view showing an example of removing the end of a regenerated film element that has formed a sealing portion, and shows the state after removal.

[0070] The present invention provides a method for regenerating a membrane element, which includes the step of forming a double-sided sealing portion 11 and an outer-circumferential sealing portion 12 by sealing both ends in the axial direction A1 and the outer-circumferential end of the replaced membrane leaf to obtain a regenerated membrane element RE. This step allows for the acquisition of a regenerated membrane element RE in which at least the separation membrane 1 has been replaced with a new separation membrane 1', as shown in Figure 6B. In this embodiment, as shown in Figures 6A to 6B, an example is shown in which, with the replaced membrane leaf wound around the central tube 5, a sealing portion is formed by solidifying adhesive, an outer covering material is provided as necessary, and then the ends are trimmed.

[0071] First, at least one separation membrane 1 is replaced with a new separation membrane 1', and a laminate LB, which is provided with adhesive means for forming a sealing portion, is wound around the central tube 5 (in the direction of the arrow in Figure 5B). The laminate LB includes a member consisting of a new separation membrane 1' in a folded state and a supply-side spacer 2' interposed therebetween, and a permeation-side spacer 3, with the members consisting of the separation membrane 1' and supply-side spacer 2' and the permeation-side spacer 3 being alternately laminated.

[0072] By allowing the adhesive to solidify while the laminated body LB is wound around the central tube 5, a wound body R can be obtained that has both side sealing portions 11' and the outer peripheral sealing portion 12 formed before trimming, as shown in Figure 6A.

[0073] Next, as shown in Figure 6B, a regenerated film element RE can be obtained by trimming both ends of the wound body R along the cutting line C3. Trimming is preferable to align the end faces of the regenerated film element RE. At that time, by trimming the central tube 5 as well, the lengths of the central tube 5 and the wound body R can be made the same.

[0074] The regenerated film element RE may be provided with a new outer covering 15, and an upstream end member 10 or a downstream end member 20 may be provided while adjusting the length of the central tube 5. New upstream end members 10 or downstream end members 20 may be used, but it is also possible to use those recovered from used film elements UE.

[0075] (The process of removing the exterior materials) In the present invention, it is preferable to remove the outer covering material 15 after removing the sealing portions 11 on both sides. This makes it easier to unfold the membrane leaf L1 from which the sealing portions 11 on both sides have been removed and to remove the outer peripheral sealing portion 12.

[0076] When the exterior material 15 includes FRP, the FRP may be directly formed on the outer circumference of the winding body R, or other members may be interposed between it and the winding body R. In either case, cutting the FRP at one or more locations along the direction of the central pipe 5 makes it easier to remove the exterior material 15. If other members are interposed, it becomes easier to remove the exterior material 15 after cutting.

[0077] When the FRP is directly bonded to the outer circumference of the wound body R, the FRP can be removed by cutting or other means. During cutting, the outer peripheral sealing portion 12 located at the outermost circumference of the wound body R may be damaged, but in the present invention, since the outer peripheral sealing portion 12 is removed afterward, this problem is less likely to occur.

[0078] (Effect of reducing CO2 emissions) In the membrane element regeneration method of the present invention, the reduction in CO2 emissions due to the reuse of raw materials is estimated to be 16% or more. The calculation was performed using reuse rates of 90%, 90%, and 50% for the permeate-side spacer, central tube, and supply-side spacer, respectively. Furthermore, the reduction in CO2 emissions was calculated based on the raw materials and manufacturing process, comparing the case where only new materials were used with the case where only recycled materials were used.

[0079] (Other embodiments of the method for regenerating membrane elements) (1) In the above embodiment, an example was shown in which the sealing portions 11 on both sides, both ends of the central pipe 5, the upstream end member 10, and the downstream end member 20 are removed in the step of removing the sealing portions 11 on both sides. However, as shown in Figure 10, the sealing portions 11 on both sides, the upstream end member 10, and the downstream end member 20 may be removed while leaving both ends of the central pipe 5. In other words, it is also possible to leave the ends intact without cutting the central pipe 5.

[0080] When the sealing portions 11 on both sides are removed while leaving both ends of the central tube 5, the length of the central tube 5 becomes longer than the length of the axial direction A1 of the membrane leaf L2 before replacement, as shown in Figures 11A and 11B. In this case, it is possible to cut both ends of the central tube 5 after the completion of the process of obtaining the regenerated membrane element RE, or in a process prior to that. In this case, it is preferable to match the length of the central tube 5 to the length of the axial direction A1 of the winding body R of the regenerated membrane element RE, or to bring the lengths of the two closer together.

[0081] (Membrane module) Figure 7A is a cross-sectional view showing an example of a regenerated film element and interconnector used in the film module of the present invention. Figure 7B is a cross-sectional view showing an example of a main part of the film module of the present invention.

[0082] As shown in Figures 7A to 7B, the present invention is a membrane module comprising a membrane element and a vessel V that houses the membrane element, wherein the membrane element is a regenerated membrane element RE manufactured using a portion of a used membrane element UE, and the length of the axial direction A1 of the separation membrane 1 is shortened, and the vessel V houses one or more regenerated membrane elements RE than the number of used membrane elements UE that are housed therein.

[0083] In this embodiment, we show an example in which regenerated film elements RE are connected to each other by an interconnector 21 having an anti-telescopic function. Here, the interconnector 21 has an inner type that fits to the inner circumference of the central tube 5 and an outer type that fits to the outer circumference of the central tube 5, but in this embodiment, we show an example of the inner type.

[0084] Any vessel V capable of accommodating a general membrane element can be used. The vessel V may be the same as or different from the one that contained the used membrane element UE.

[0085] The regenerated membrane element RE can be any regenerated membrane element RE manufactured using a portion of the used membrane element UE, in which the length of the axial direction A1 of the separation membrane 1 has been shortened. However, the regenerated membrane element RE obtained by the membrane element regeneration method of the present invention is preferred. In this embodiment, an example is shown in which a regenerated membrane element RE is used in which the length of the axial direction A1 of the separation membrane 1 and the length of the central tube 5 are the same.

[0086] In this example, as shown in Figures 7A to 7B, if the central tube 5 of the used membrane element UE has an enlarged inner circumference as the mating portion 5b of the interconnector 21, the length of the mating portion 5b will be shorter in the regenerated membrane element RE.

[0087] Furthermore, the regenerated membrane element RE may have an upstream end member 10 and a downstream end member 20 integrally provided, and the length of the central tube 5 may be greater than the length of the axial direction A1 of the separation membrane 1. However, by using a regenerated membrane element RE with the same length as the separation membrane 1 and the central tube 5, it becomes easier to suppress the reduction in the total membrane area in the membrane module.

[0088] In other words, although the effective film area per regenerated film element RE decreases due to regeneration, the regenerated film elements RE are connected to each other by interconnectors 21 that have an anti-telescopic function. This allows for the storage of one or more more regenerated film elements RE than the number of used film elements UE in the vessel V, thereby increasing the overall effective film area of ​​the regenerated film elements RE.

[0089] As shown in Figures 7A to 7B, the interconnector 21 includes a main body 22, a flow path forming part 23, and a seal holding part 24. The main body 22 has a groove for holding a sealing member 25 such as an O-ring, and both sides of the main body 22 are inserted into the fitting part 5b on the inner circumference side of the central tube 5 of the regenerated film element RE, and the sealing state is maintained by the sealing member 25. When using an interconnector 21 with an anti-telescopic function, it is possible to use an outer type, but from the viewpoint of simplifying the structure, an inner type interconnector 21 is preferred.

[0090] The flow path forming section 23 has an opening to ensure the flow of the supply liquid 7, etc., and is formed by multiple plates arranged radially. The seal holding section 24 is formed in an annular shape and has a groove on its outer circumference for holding a seal member 26, such as one with a U-shaped cross-section. In other words, the interconnector 21 has both an anti-telescopic function and an outer circumference sealing function.

[0091] In order to accommodate one or more regenerated membrane elements RE in the vessel V than the number of used membrane elements UE that can be accommodated, the length of the regenerated membrane elements RE in the axial direction A1, i.e., the length of the separation membrane 1' in the same direction, may be adjusted when manufacturing the regenerated membrane elements RE.

[0092] For example, if the length of used film elements UE is 40 inches = 1016 mm and there are 6 of them, and the length of regenerated film elements RE is 34 inches = 864 mm, then by housing 7 regenerated film elements RE in the same vessel V, the total effective film area before and after replacement with regenerated film elements RE can be maintained.

[0093] Furthermore, when manufacturing a regenerated membrane element RE in which the length of the axial direction A1 of the separation membrane 1 is shortened, as described above, by setting the width of the two side sealing portions 11 and the outer peripheral sealing portion 12 to 87% or more of the length of the separation membrane 1 in both directions before cutting, it is possible to make the effective membrane area of ​​the resulting regenerated membrane element RE 76% or more of the effective membrane area of ​​the used membrane element UE (87% × 87% = 76%).

[0094] Therefore, it is preferable that the effective film area of ​​the regenerated film element RE in the film module of the present invention is 76% or more of the effective film area of ​​the used film element UE. Furthermore, by reducing the width when removing the sealing portions 11 on both sides or the sealing portion 12 on the outer periphery, it is also possible to make the effective film area of ​​the regenerated film element RE 80% or more of the effective film area of ​​the used film element UE.

[0095] (Other embodiments of membrane modules) (1) In the present invention, instead of providing an interconnector 21 having an anti-telescopic function, the regenerated film elements RE may be provided with an anti-telescopic function, as shown in Figures 8A to 8B, for example, and the regenerated film elements RE may be connected to each other by an interconnector 21 with a general structure for connecting the central tubes 5. In that case, the interconnector 21 may be an inner type or an outer type.

[0096] Examples of structures that provide an anti-telescopic function to the regenerated film element RE include a structure in which the anti-telescopic material 30 is bonded to the end of the central tube 5. In this case, the length of the central tube 5 may be the same as the length of the wound body R, but from the viewpoint of ensuring strength, etc., it is preferable to make the length of the central tube 5 greater than the length of the wound body R, as shown in Figures 8A to 8B, for example, and to bond the anti-telescopic material 30 to the outer circumference of the extended portion.

[0097] In the illustrated example, the anti-telescope material 30 includes an annular portion 32, a flow path forming portion 33, and a seal holding portion 34. The inner circumferential surface of the annular portion 32 is fixed to the end of the central pipe 5, and the flow path forming portion 33 has an opening to ensure the flow of the supply liquid 7, etc., and is formed by a plurality of plates arranged radially. The seal holding portion 34 is formed in an annular shape and has a groove on its outer circumference for holding a sealing member 26, such as one with a U-shaped cross-section. In other words, the anti-telescope material 30 has both an anti-telescope function and an outer circumference sealing function.

[0098] Furthermore, the interconnector 21 has a main body 22 with a groove for holding a sealing member 25 such as an O-ring, and both sides of the main body 22 are inserted into the fitting portion 5b on the inner circumference side of the central tube 5 of the regenerated film element RE, and the sealing state is maintained by the sealing member 25.

[0099] (2) In the present invention, instead of providing an interconnector 21 having an anti-telescope function, a structure in which the anti-telescope material 30 and the interconnector 21 are separate components may be used, for example, as shown in Figures 9A to 9B. In that case, the interconnector is inserted into the central opening of the anti-telescope material 30, but it is preferable to provide a locking portion 27 on the interconnector 21 to prevent the anti-telescope material 30 from moving downstream.

[0100] (3) In the present invention, it is preferable to provide a holding length adjustment mechanism upstream of the upstreammost regenerating film element RE so that the entirety of the multiple regenerating film elements RE connected by the interconnector 21 is housed and held in a predetermined position within the vessel V.

[0101] A mechanism for adjusting the holding length includes an adapter that can be connected to a dedicated adapter of the vessel located at the upstream end and can be held at the upstream end of the vessel V. Other examples include a ring-shaped or similar member that can be combined with such an adapter and interposed in the gap between the upstream end of the vessel V and the adapter, and an adjustment bolt provided at the upstream end of the vessel V for pressing the adapter toward the center. [Industrial applicability]

[0102] According to the membrane element regeneration method of the present invention, at least the central tube and the permeable side spacer can be reused, thus reducing waste generated by used membrane elements and saving valuable petroleum resources by reducing the amount of new plastic used in the manufacture of recycled membrane elements.

[0103] According to the membrane module of the present invention, a regenerated membrane element, in which at least the central tube and the permeable side spacer are reused, can be used while suppressing a decrease in the total membrane area. [Explanation of symbols]

[0104] 1: Separation membrane 1': New separation membrane 2: Supply side spacer 2': New supply-side spacer 3: Translucent side spacer 5: Central tube 11: Sealing section on both sides 12: Outer peripheral sealing portion 15: Exterior materials 21: Interconnector A1: Axial direction C1~C3: Cutting line UE: Used film element RE: Regenerated film element R: Coiled body L: Membrane Leaf V: Vessel

Claims

1. A method for regenerating membrane elements, which involves manufacturing a regenerated membrane element using a portion of a used membrane element, The used membrane element comprises a plurality of membrane leaves having a permeable-side spacer interposed between opposing separation membranes, and having both side sealing portions and an outer peripheral sealing portion that seal both axial ends and the outer peripheral end; a supply-side spacer interposed between the membrane leaves; and a perforated central tube around which the membrane leaves and the supply-side spacer are wound. A step of removing at least the sealing portions on both sides of the used membrane element, The process involves unfolding the excised membrane leaf and excising at least the outermost sealing portion of the membrane leaf, A step of replacing at least the separation membrane of the membrane leaf after unfolding and excision with a new separation membrane, A process to obtain a regenerated film element by forming a double-sided sealing portion and an outer-circumferential sealing portion that seal both axial ends and the outer-circumferential end of the replaced film leaf, A method for regenerating membrane elements containing [the specified element].

2. The method for regenerating a membrane element according to claim 1, wherein when replacing the new separation membrane, the supply-side spacer is replaced with a regenerated supply-side spacer from which contaminants have been removed by cleaning, or with a new supply-side spacer.

3. The method for regenerating a membrane element according to claim 1, wherein the used membrane element has an outer covering material, and the outer covering material is removed after the sealing portions on both sides are cut off.

4. The method for regenerating a membrane element according to claim 1, wherein the central tube of the used membrane element is replaced with a regenerated central tube whose length has been adjusted by cutting, or with a new central tube.

5. A membrane module comprising a membrane element and a vessel that houses the membrane element, The aforementioned membrane element is a regenerated membrane element manufactured using a portion of a used membrane element, in which the axial length of the separation membrane is shortened. A membrane module in which one or more regenerated membrane elements are housed in the vessel than the number of used membrane elements that can be housed.

6. The film module according to claim 5, wherein the regenerated film elements are connected to each other by an interconnector having an anti-telescopic function, or the regenerated film elements having an anti-telescopic function are connected to each other by an interconnector.

Images