Spiral-type membrane element and method for manufacturing the membrane element

Abstract

The objective is to provide a spiral membrane element that reduces waste generated by used spiral membrane elements and saves introduced resources by changing the outer peripheral end of the membrane leaf to a structure that makes it easy to dismantle, while also allowing for easy recovery of the permeation-side spacer. [Solution] The spiral membrane element comprises a plurality of membrane leaves having a permeable side spacer interposed between opposing separation membranes, a double sealing portion that seals both axial ends and an 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, wherein at least one of the outer peripheral ends is not fixed to the folded portion on the inner surface of the separation membrane leaf and the outer peripheral tip of the permeable side spacer.

Description

Technical Field

[0001] The present invention relates to a spiral membrane element capable of easily recovering members with relatively little contamination (for example, a permeate side spacer and a central tube) even after long-term use and the progress of contamination of members on the supply water side, and a method for manufacturing the spiral membrane element.

Background Art

[0002] The structure of a typical spiral membrane element includes a plurality of membrane leaves having both-side sealing portions and an outer-periphery sealing portion that seal both axial ends and an outer-periphery end of the permeate side spacer interposed between opposing separation membranes, a supply side spacer interposed between the membrane leaves, and a perforated central tube (also referred to as a "collecting water pipe") around which the membrane leaves and the supply side spacer are wound. Usually, three sides of the permeate side spacer are sealed with an adhesive, and separation membranes are adhered to both surfaces thereof. At the outer-periphery end of each membrane leaf, the ends of the opposing separation membranes are adhesively joined, and the outer-periphery end of the permeate side spacer is disposed inside thereof, forming an outer-periphery sealing portion.

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

[0004] The method for treating used membrane elements after replacement is a major issue. Landfill disposal has the problem that the volume of the disposal site that can be treated is limited, and since membrane elements are mostly made of plastic materials and are not decomposed underground, there is also the problem that they remain underground semi-permanently. For this reason, it is desired to reduce waste caused by used membrane elements as much as possible. This is the same even when incineration disposal is performed.

[0005] On the other hand, incineration releases CO2, a greenhouse gas, which poses challenges from an environmental perspective. Membrane elements are made from plastic materials derived from crude oil, a valuable fossil resource, and used elements can also be considered a valuable carbon resource. Therefore, there is a need to recycle used elements into plastic materials.

[0006] Technologies for reusing used membrane elements include, for example, structures that allow the reuse of the outer casing of spiral-type membrane elements (Patent Documents 1-2), structures that allow the reuse of anti-telescopic materials (Patent Document 3), and structures that allow the reuse of the central tube (Patent Document 4).

[0007] 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.

[0008] On the other hand, Patent Document 5 proposes a method for reusing used spiral membrane elements of a conventional structure, which involves removing the separation functional layer of the RO membrane element with an acidic aqueous solution or the like to regenerate it into a UF membrane, which is a porous support. However, the regeneration method described in Patent Document 5 cannot regenerate the used spiral membrane element into the same RO membrane element as before regeneration, and therefore cannot restore the original separation membrane function. [Prior art documents] [Patent Documents]

[0009] [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]

[0010] The components on the permeate side come into contact with the filtered permeate water, resulting in relatively little contamination even after use. For example, even if one attempts to recover the permeate side spacer as a recyclable material, the separation process is extremely cumbersome because it is located inside the adhesively sealed membrane leaf. While it is possible to remove each one by hand, this is very time-consuming and costly. Therefore, there is a need to facilitate the dismantling of used membrane elements and make it easier to recycle the permeate side spacer as a material.

[0011] Therefore, the object of the present invention is to provide a spiral-type membrane element and a method for manufacturing the spiral-type membrane element, which can reduce waste and conserve introduced resources by changing the outer peripheral end of the membrane leaf to a structure that is easy to dismantle, and which can also easily recover the permeation-side spacer. [Means for solving the problem]

[0012] The above objective can be achieved by the present invention as described below.

[0013] [1] A spiral membrane element comprising two opposing separation membranes, a permeable spacer provided between them, a double sealing portion that seals both ends of the two separation membranes and the permeable spacer in the axial direction (A1), a plurality of membrane leaves having outer peripheral ends parallel to the axial direction (A1) of the separation membranes and the permeable spacer, a supply-side spacer interposed between adjacent membrane leaves, and a perforated central tube around which the membrane leaves and the supply-side spacer are wound, A spiral-type membrane element in which, at least one of the outer peripheral ends, the folded portion of the inner surface of the membrane leaf and the outer peripheral tip of the permeable spacer are not fixed to each other.

[0014] Here, the "folded portion on the inner surface of the membrane leaf" includes a folded form of a continuous separation membrane and a form in which the outer peripheral side end portion is an outer peripheral side sealing portion.

[0015] [2] The spiral membrane element according to [1], wherein the folded portion on the inner surface of the membrane leaf is formed by folding a continuous separation membrane.

[0016] [3] Among the plurality of membrane leaves, at least one (preferably one) outer peripheral side end portion constitutes a first outer peripheral side sealing portion in which the ends of the separation membrane and the outer peripheral side tip of the permeate side spacer are sealed (with an adhesive), or The spiral membrane element according to [1] or [2], which constitutes a second outer peripheral side sealing portion in which the ends of the separation membrane are sealed (with an adhesive) without being fixed to the outer peripheral side tip of the permeate side spacer.

[0017] [4] The continuous separation membrane of the spiral membrane element according to [2], wherein a fold position is provided so that when wound around a central tube, the outer separation membrane distal from the central tube is longer than the inner separation membrane proximal to the central tube.

[0018] [5] The spiral membrane element according to [2], which has a protective member that abuts against the folded portion of the continuous separation membrane.

[0019] [6] The spiral membrane element according to [5], wherein the protective member has a lower rigidity at the central portion (which abuts against the folded position) than at other portions.

[0020] [7] The permeate side spacer in the membrane leaf having the first outer peripheral side sealing portion has a tear processing portion over the entire width (for example, in a direction parallel to the central tube) on the outer peripheral side of the center (for example, at a position closer to the outer peripheral side sealing portion than the central tube).

[0021] [8] All of the outer peripheral side ends of the plurality of membrane leaves, except for the permeation side spacer, constitute an outer peripheral side sealing portion where the ends of the separation membranes are sealed (with an adhesive), the spiral membrane element according to [1].

[0022] [9] A method for manufacturing the spiral membrane element according to any one of [2] to [7] above, A folding separation membrane forming step of forming a concertina with a single separation membrane, interposing a supply side spacer between the folded separation membranes, and forming a j-th folded separation membrane (j = 1 to n); A permeation side spacer preparation step of fixing, along the longitudinal direction (width direction) of the central tube (for example, by fusion or an adhesive), a first permeation side spacer located at the lowermost part at the start of the winding operation and a plurality of i-th permeation side spacers (i = 2 to n) wound from a position above it; A membrane leaf forming step of sequentially sandwiching a j-th separation membrane with a supply side spacer interposed between the i-th permeation side spacer and the (i + 1)-th permeation side spacer, interposing a permeation side spacer between the opposing separation membranes, and forming a plurality of membrane leaves having both side sealing portions and an outer peripheral side end portion with both side end portions in the axial direction (A1) sealed; An outer peripheral side sealing portion forming step of sealing the ends of the separation membranes (for example, with an adhesive) together with or excluding the outer peripheral side tip of the permeation side spacer to form an outer peripheral side sealing portion; A winding step of winding the membrane leaf around the central tube and fixing it (for example, by a double-sided tape, fusion, an adhesive, etc. provided on the surface of the i-th permeation side spacer in contact with the central tube); A method for manufacturing a spiral membrane element including. The outer peripheral side sealing portion forming step may be performed during the winding step or after the winding step.

[0023]

[10] The method for manufacturing a spiral membrane element according to [9], including a step of providing a protection member at a position that becomes the fold portion of the separation membrane (excluding the separation membrane at the outer peripheral side end portion that becomes the outer peripheral side sealing portion) before or during the folding separation membrane forming step.

[0024]

[11] A method for disassembling the spiral membrane element described in [1] to [8] above and recovering the permeable spacer and the central tube, The process involves cutting the used spiral membrane element in the radial direction to remove the sealing portions on both sides, or removing other components (permeation-side spacer, separation membrane, and supply-side spacer) while leaving the central tube, (Optionally) The process of removing the membrane bundle bonding sections at both ends from the intermediate water collection section of the central pipe, The process involves removing the outer sealing portion of the membrane leaf after excision, separating the separation membrane and supply-side spacer from the central tube while leaving the permeation-side spacer, Methods that include...

[0025]

[12] The method of

[11] , further comprising the step of removing the exterior material (FRP) provided on the outer circumference of the used spiral membrane element. [Effects of the Invention]

[0026] (1) With the spiral membrane element described in [2] and [3] above, many membrane leaves are composed of a continuous separation membrane, and the outer sealing portion is reduced, thereby minimizing the work required to remove the permeation-side spacer from the used membrane element. (2) With the spiral membrane element described in [4] above, the continuous separation membrane can be wound around the central tube, and the fold positions can be adjusted so that the outer membrane distal to the central tube is longer than the inner membrane proximal to the central tube, thereby suppressing the occurrence of folds in the separation membrane when each membrane leaf is wound around the central tube. (3) The spiral membrane elements described in [5] and [6] above provide protection for the folded portion and stabilize the folding position. The folding position of the sealing portion on the outer circumference of the membrane leaf is stabilized, making manufacturing easier. The membrane leaf is less prone to wrinkling when wound. (4) With the spiral membrane element described in [7] above, a tearing section is formed near the outer peripheral sealing section of the permeation-side spacer. Therefore, by pulling the outer peripheral sealing section of the membrane leaf or the separation membrane away from the central tube after both sealing sections have been removed, the tearing section is torn, and the separation membrane and supply-side spacer can be easily separated from the central tube, leaving the permeation-side spacer in place. (5) With the spiral membrane element described in [8] above, the outer sealing portion is bonded to the separation membranes, except for the permeation-side spacer, so the separation membrane and supply-side spacer can be easily separated from the central tube, leaving the permeation-side spacer, by hooking and winding the outer sealing portion of the membrane leaf or the separation membrane. (8) Because contamination of the permeable spacer during dismantling work can be minimized, it is suitable for use as a raw material for material recycling or chemical recycling. [Brief explanation of the drawing]

[0027] [Figure 1A] This is a perspective view showing a partially disassembled membrane element of Embodiment 1. [Figure 1B] This is a perspective view showing a key part of the membrane element of Embodiment 1 with a portion cut out. [Figure 1C] This figure illustrates the membrane element of Embodiment 1 and its modified form. [Figure 1D] This figure shows an example of a protective member at the tip of a membrane leaf. [Figure 1E] This figure illustrates the membrane element of Embodiment 2 and a modified example. [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 3A] This is a diagram showing an example of a tear-processed area, with one of the membrane leaves unfolded. [Figure 3B] This is a schematic diagram showing an example of perforation processing as an example of a tear-resistant section. [Figure 3C]This is a schematic diagram showing an example of a half-cut process as an example of a tearing process. [Figure 4A] This figure shows an example of a method for manufacturing the membrane element of Embodiment 1. [Figure 4B] This figure shows an example of a method for manufacturing the membrane element of Embodiment 1. [Figure 5] This is a schematic diagram showing an example of the segmented structure of the central tube. [Figure 6] An example of a planar cross-sectional view of a membrane element is shown. [Modes for carrying out the invention]

[0028] (Spiral-type membrane element) The spiral membrane element E of the present invention (hereinafter simply referred to as "membrane element E") comprises, as shown in Figures 1A and 1B, a plurality of membrane leaves L having permeation-side channels between two opposing separation membranes 1, and a perforated central tube 5 in which the membrane leaves L are wound while interposing supply-side channels between the membrane leaves L. Typically, the permeation-side channels are formed by permeation-side spacers 3, and the supply-side channels are formed by supply-side spacers 2. In Embodiment 1, in the membrane leaf L, the two separation membranes 1 and the permeation-side spacers 3 form a double-sided sealing portion 11 in which both ends facing the axial direction (A1) are sealed with adhesive. Also, as shown in Figure 1A(b), one of the outer peripheral ends L1 of the separation membrane 1 and the permeation-side spacer 3, which are parallel to the axial direction (A1), is fixed with adhesive d to the ends 1e, 1e of the two opposing separation membranes 1 and the outer peripheral tip 3a of the permeation-side spacer 3, thereby forming an outer peripheral sealing portion 12. As shown in Figure 1A(c), with the exception of the configuration shown in Figure 1A(b), the folded portion L2 on the inner surface of the membrane leaf L and the outer tip 3a of the permeable spacer 3 are not fixed to each other.

[0029] Furthermore, both ends of the permeable spacer 3 facing the outer peripheral sealing portion 12 are directly fixed to the central tube 5 with adhesive, at least avoiding the opening 5a.

[0030] 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 E generally has an outer covering material 15 on the outer circumference of the winding body R, as shown in Figure 1A(a). A used membrane element is referred to as a used membrane element UE.

[0031] The membrane element E is provided with sealing portions on both sides 11, an outer peripheral sealing portion 12, and a folded portion L2 to prevent mixing of the supply-side flow path and the permeation-side flow path. As shown in Figure 1B, the sealing portions on both sides 11 are formed by sealing two ends on both sides of the membrane leaf L in the axial direction A1 with adhesive. The outer peripheral end L1 of one membrane leaf L is configured as an outer peripheral sealing portion 12, and the other outer peripheral end L1 is configured as a folded portion L2. The internal region of the membrane leaf L becomes the permeation-side flow path, which is in communication with the opening 5a of the central tube 5.

[0032] Furthermore, as shown in Figure 1B, the present invention has a central sealing portion 13 in which the perforated (5a) 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 epoxy adhesive can be used.

[0033] In a typical membrane element E, as shown in Figure 1A(a), 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 winding FRP, which will be the outer periphery of the winding body R, around the winding body R.

[0034] 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 E, it is housed in a pressure vessel, and the supply fluid 7 is supplied from one end face of the membrane element E.

[0035] As shown in Figure 1A(a), 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 E. 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.

[0036] 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 mm 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.

[0037] The central pipe 5 can be any pipe having an opening 5a in its wall, as shown in Figure 1A(a), 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 opening 5a, flows inside the central pipe 5, and is discharged from the end.

[0038] 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 3 is required to support the pressure on the membrane from the back of the membrane and to ensure a flow path for the permeate.

[0039] 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 with resin impregnation or fused after knitting. Warp knitted materials such as tricot half knit or double denby knit made of polyester material can also be used.

[0040] 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.

[0041] 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.

[0042] 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 dismantle and recover the upstream end member 10 and the downstream end member 20. However, by cutting off the sealing portions 11 on both sides during recycling, their separation and recovery become easier.

[0043] (Embodiment 1: Folded configuration of a continuous separation membrane) As described above, in Figure 1A(b), in one membrane leaf L, the ends 1e, 1e of two opposing separation membranes 1 and the outer peripheral tip 3a of the permeation-side spacer 3 positioned between them are fixed with adhesive d to form an outer peripheral sealing portion 12. In Figure 1A(c), the folded portion L2 is composed of a continuous separation membrane 1, and the inner surface of the folded portion L2 and the outer peripheral tip 3a of the permeation-side spacer 3 are not fixed to each other, that is, they are not sealed with adhesive or the like. Figure 1C(a) shows a schematic diagram of the membrane leaf L and supply-side spacer 2 wound around the central tube 5. Both ends of the permeation-side spacer 3 that are in contact with the central tube 5 are fixed with adhesive d.

[0044] By repeatedly folding a continuous separation membrane 1 to form a membrane leaf L, and by not fixing the permeation-side spacer 3 interposed between opposing separation membranes 1 and the inner surface of the folded portion L2, only one outer peripheral sealing portion 12 is formed. As a result, when recycling the permeation-side spacer 3 and the central tube 5, after cutting both side sealing portions 11, it is only necessary to cut one outer peripheral sealing portion 12, eliminating the need to cut all the outer peripheral sealing portions 12 formed on the entire membrane leaf L as in the conventional method, thus minimizing the cutting work.

[0045] (Variations of folded form) Figure 1C(b) is a modified example of Figure 1C(a). In all folded portions L2, the inner surface of the folded portion L2 and the outer peripheral tip 3a of the permeable spacer 3 are not fixed to each other. Furthermore, in the outer peripheral sealing portion 12, the outer peripheral tip 3a of the permeable spacer 3 is not fixed, that is, it is not sealed with adhesive or the like.

[0046] (Form of the fold line) Figure 1C(c) shows a schematic diagram of the membrane leaf L and supply-side spacer 2 before they are wound around the central tube 5. The continuous separation membrane 1 is wound around the central tube 5, and a fold position L3 is provided so that the outer separation membrane 102 distal to the central tube 5 is longer than the inner separation membrane 101 proximal to the central tube 5. The continuous separation membrane 1 is wound around the central tube 5, and by adjusting the fold position L3 so that the outer separation membrane 102 distal to the central tube 5 is longer than the inner separation membrane 101 proximal to the central tube 5, it is possible to suppress the occurrence of folds in the separation membrane when each membrane leaf L is wound around the central tube 5.

[0047] (Protection of the folded-over portion) Figure 1D(a) shows a protective member P that abuts against the folded portion L2 of the continuous separation membrane 1. The protective member P is constructed such that the rigidity of the central part P1 that contacts the fold is lower than that of the other parts, for example, by being thinner than the other parts (see Figure 1D(b)). By making the rigidity of the central part P1 lower than that of the other parts, it can conform to the shape of the folded part L2, and when attached to the fold, it can stabilize the fold position. The protective member P may be made of the same material as, for example, a resin film or a separation membrane.

[0048] (Embodiment 2: Folded-over form of the outer peripheral sealing portion) As shown in Figure 1E(a), one membrane leaf L is formed by fixing the ends 1e, 1e of two opposing separation membranes 1 and the outer peripheral tip 3a of the permeable spacer 3 positioned between them with adhesive d, thereby forming a first outer peripheral sealing portion 121. As shown in Figure 1E(b), with the exception of the membrane leaf L shown in Figure 1E(a), the folded portion L2 of the other membrane leaves L is configured as a second outer peripheral sealing portion 122 in which only the ends 1e, 1e of the opposing separation membrane 1 are fixed with adhesive d. Unlike Figures 1A(b) and 1E(a), the outer peripheral tip 3a of the permeation-side spacer 3 interposed between the opposing separation membranes 1 is not fixed with adhesive d. Figure 1E(c) shows a schematic diagram of the state in which the membrane leaves L and supply-side spacer 2 are wound around the central tube 5. As a result, when recycling the permeable spacer 3 and the central tube 5, after cutting the sealing portions 11 on both sides, it is only necessary to cut the first outer peripheral sealing portion 121 that is fixed to the permeable spacer 3. This eliminates the need to cut all of the outer peripheral sealing portions formed on the entire membrane leaf L, as in the conventional method, thus minimizing the cutting work.

[0049] (Modified version of Embodiment 2) In Embodiment 2, as shown in Figure 1E(b), the folded portion L2 of all membrane leaves L is configured as a second outer peripheral sealing portion 122, where the ends 1e, 1e of the opposing separation membrane 1 are fixed with adhesive d. Figure 1E(d) shows a schematic diagram of the state in which the membrane leaves L and the supply-side spacer 2 are wound around the central tube 5. As a result, there is no need for the first outer peripheral sealing portion 121 fixed to the permeable spacer 3, which further simplifies the work.

[0050] (Embodiment 3) In Examples 1 and 2, the permeable spacer 3 of the outer peripheral sealing portion 12, 121, which is fixed together with the outer peripheral end portion 3a of the permeable spacer 3, may have a tear-processed portion. In the permeable spacer 3 within the membrane leaf L, a tear-resistant section T1 is formed along its entire width (in the direction of the central tube 5) on the outer periphery (closer to the outer sealing sections 12 and 121 than to the central tube 5). Figures 2B and 3A show perforation as an example of the tear-resistant section T1, indicated by dashed lines. In the perforation shown in Figure 3B, the cut length w1 is 10 mm to 100 mm, and the cut interval w2 is 0.5 mm to 3 mm. If the cut length w1 is less than 10 mm or the interval w2 exceeds 3 mm, the tear resistance will be poor. If the cut length w1 exceeds 100 mm, the stiffness and rigidity of the permeable spacer will decrease, making it difficult to handle during assembly. If the interval w2 is less than 0.5 mm, there is a risk of breakage during assembly or use.

[0051] As shown in Figure 3A, the position of the tearing section T1 is such that the distance w0 from the outer peripheral sealing sections 12 and 121 towards the central tube 5 is within 10 mm to 100 mm, preferably within 10 mm to 80 mm, more preferably within 10 mm to 60 mm, and even more preferably within 10 mm to 50 mm. If the distance w0 is less than 10 mm, it is too close to the outer peripheral sealing sections 12 and 121 and may interfere with the adhesive application process, and if it exceeds 100 mm, the area of ​​the permeable spacer that can be reused becomes small.

[0052] (Another example of a tearing process) The tear-processed section T2 in Figure 3C is a half-cut. The depth of the half-cut is 50% to 95% of the thickness of the permeable spacer. If the cut depth is less than 50%, the tearing performance is poor, and if it exceeds 95%, there is a risk of breakage during assembly or use. The position of the tear-processed section T2 is the same as the distance w0 described above.

[0053] (Manufacturing method of Embodiment 1) The manufacturing method for spiral membrane elements includes the following steps. Here, multiple membrane leaves L are constructed from a single separation membrane 1. Figures 4A and 4B illustrate each step. (S1) A zigzag pattern is formed using one separation membrane 1. The first folded separation membrane 1_1 is constructed by folding it distally from the starting end 1sp of the separation membrane 1. Next, a fold is made (at the fold position L3 described above), and it is folded distally again to construct the second folded separation membrane 1_2. The third folded separation membrane 1_3 and the fourth folded separation membrane 1_4 are constructed by repeating this process. The end of the separation membrane 1 that serves as the endpoint is shown as 1ep. Supply-side spacers 2 are interposed inside the first, second, third, and fourth folded separation membranes 1_1, 1_2, 1_3, and 1_4, respectively. In other words, a supply-side spacer 2 is interposed between the separation membranes 1 that are folded back every other one, forming the jth folded separation membrane 1_j (j=1 to n) (folded separation membrane formation process). In Figure 4A, the number of folded separation membranes is 4(j).

[0054] (S2) At the start of the winding operation, the first permeable spacer 3_1 located at the bottom and multiple i-th permeable spacers 3_i (i=2 to n) wound from a position above it are fixed along the longitudinal direction (width direction) of the central tube 5 (permeable spacer preparation step). In Figure 4A, four (=i) permeable spacer configurations are shown to match the 4 number of folds of the separation membrane 1. Both ends of the first permeable spacer 3_1 in the direction perpendicular to the axial direction (A1) are fixed to the central tube 5 by connecting parts d0. The first permeable spacer 3_1 and the second permeable spacer 3_2, the second permeable spacer 3_2 and the third permeable spacer 3_3, and the third permeable spacer 3_3 and the fourth permeable spacer 3_3 are each fixed by connecting parts d1 in the direction parallel to the axial direction (A1). The connecting portion d0 is secured to the other members by means of double-sided tape, fusion (e.g., ultrasonic fusion, heat fusion, etc.), etc. The connecting portion d1 is secured to the other members by means of adhesive, fusion (e.g., ultrasonic fusion, heat fusion, etc.), etc.

[0055] (S3) The jth separation membrane 1_j, with the supply-side spacer 2 interposed between the ith permeation-side spacer 3_i and the i+1th permeation-side spacer 3_i+1, is sequentially sandwiched, and the permeation-side spacer 3 is interposed between the opposing separation membranes 1, forming a plurality of membrane leaves L having both side sealing portions 11 that seal both ends in the axial direction (A1) and an outer peripheral end L1 (folded portion L2 and one outer peripheral sealing portion 12) (membrane leaf formation step). In Figure 4B, the first permeable spacer 3_1 is set lying on its side so as not to interfere with other permeable spacers, and the fourth folded separation membrane 1_4 is placed on top of the first permeable spacer 3_1. Next, adhesive d2 is applied to both ends of the fourth folded separation membrane 1_4 in a direction perpendicular to the axial direction (A1) of the first permeable spacer 3_1, and the second permeable spacer 3_2 is placed on top to form the double-sided sealing portion 11. The same procedure is repeated, and with multiple layers of formed membrane leaves stacked, adhesive d3 is applied to both ends of the first, second, third, and fourth permeable spacers 3_1, 3_2, 3_3, and 3_4 in a direction perpendicular to the axial direction (A1) to fix them around the central tube 5. The adhesive d2 applied to both ends of the uppermost separation membrane and the adhesive d3 applied to both ends of the fourth permeable spacer 3_4 may be connected.

[0056] (S4-1) The ends 1ep and 1sp of one separation membrane 1 are sealed with adhesive, either together with or excluding the outer peripheral tip 3a of the permeation-side spacer 3, to form an outer peripheral sealing portion 12 (outer peripheral sealing portion formation step). In Figure 4B, the outer peripheral sealing portion 12 is configured to be sealed with adhesive together with the outer peripheral tip 3a of the permeation-side spacer 3. In a modified example of Embodiment 1 (Figure 1A(b)), the outer peripheral sealing portion 12 is configured to be sealed with adhesive only at the ends 1ep and 1sp of one separation membrane 1. Figure 4B(S4) shows an example with eight membrane leaves L.

[0057] (S4-2) The membrane leaf L is wound around the central tube 5 and fixed with adhesive d3 provided at both ends of the i-th permeable spacer 3_i that contacts the central tube 5 in a direction perpendicular to the axial direction (A1) (winding process). Figure 4B shows a side cross-section of the element membrane wound around the central tube 5. The outer periphery sealing process may be performed during the winding process or after the winding process.

[0058] (Protective component installation process) During or before the above-mentioned folded separation membrane formation process (S1), the protective member P is applied (attached) to the folded portion of the separation membrane. For example, the protective member P is attached to the folded portion when forming a zigzag pattern with a single separation membrane. This prevents damage to the folded portion of the separation membrane when folding the membrane. In addition, by making the rigidity of the central part of the protective member P less than that of the other parts, the position of the fold can be stabilized when folding the separation membrane.

[0059] (Method for recovering recycled materials) The method for recovering recycled components involves disassembling the used membrane element UE and recovering the permeable spacer and central tube. (S11) This is a step to remove the outer covering material 15 provided on the outer circumference of the used film element UE, if such material is provided on the outer circumference of the used film element UE. (S12) This is a step in which the used membrane element UE is cut radially along the winding R so as to remove the sealing portions 11 on both sides, or the other components (permeation side spacer 3, separation membrane 1 and supply side spacer 2) are removed while leaving the central tube 5. (S13) (Optional) This is the step of removing the membrane bundle bonding portion 600 from the intermediate water collection portion 610. (S14) The outer sealing portion 12 of the excised membrane leaf L is removed, and the separation membrane 1 and supply-side spacer 2 are separated from the central tube 5, leaving the permeation-side spacer 3.

[0060] (Step of removing the sealing portions on both sides: S12) 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.

[0061] The double-sided sealing portion 11 typically includes two opposing separation membranes 1 and a permeable-side spacer 3 interposed between them, and is fixed with an adhesive. In this process, as shown in Figure 2A, when removing the double-sided sealing portion 11, it is preferable to remove the ends on both sides of the supply-side spacer 2 in the axial direction A1, which are closer to the center than the double-sided sealing portion 11.

[0062] As shown in Figure 3A, a membrane leaf L1 is obtained in which the two opposing separation membranes 1 and the permeation-side spacer 3 are bonded only at the outer peripheral sealing portion 12 of the sealing portions at the three ends of the membrane leaf L. In this case, one or more membrane leaves L1 may be fixed (bonded, etc.) to the central tube 5 via the permeation-side spacer 3. Also, 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.

[0063] In this process, it is sufficient that at least the sealing portions 11 on both sides are removed from the body of the used 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.

[0064] 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 body of the used 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 body of the used 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.

[0065] 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.

[0066] (Removal of the outer sealing portion: S14) If there is only one outer peripheral sealing portion 12 to which the separation membrane 1 is fixed, the outer peripheral sealing portion may be removed, and then the separation membrane 1 and the supply-side spacer 2 may be separated from the central tube 5, leaving the permeation-side spacer 3 in place. Alternatively, if a tear-processed portion T1 is formed on the permeation-side spacer 3, the tear-processed portion T1 may be torn by hooking and winding the outer peripheral sealing portion 12 or the separation membrane 1 fixed to the outer peripheral sealing portion 12, thereby separating the separation membrane 1 and the supply-side spacer 2 from the central tube 5 while leaving the permeation-side spacer 3 intact.

[0067] (separation) After recovering the separation membrane, the outer periphery sealing portion (the ends of the two separation membranes, the end of the permeate-side spacer, and the composite portion of the sealing resin), and the supply-side spacer, the process moves to chemical recycling by thermal decomposition. In order to proceed to the thermal decomposition process, it is preferable to separate the supply-side spacer, which is suitable for thermal decomposition, from the other materials (separation membrane, permeate-side spacer, and sealing resin), which are not suitable for thermal decomposition, by pretreatment.

[0068] Examples of pretreatment include crushing the recovered materials and separating them based on specific gravity using an aqueous solution. For example, the specific gravity of the supply-side spacer material is low (e.g., polypropylene resin: approximately 0.9, polyethylene resin: approximately 0.95), while the specific gravity of other materials is high (e.g., polyethylene terephthalate: approximately 1.6, fiber-reinforced plastic: approximately 1.8, urethane resin: approximately 1.2). Therefore, by using an aqueous solution with adjusted specific gravity (specific gravity: approximately 1.05) after shredding, the materials can be easily separated and recovered. Furthermore, separation can be accelerated and made more efficient by using centrifugal separation with a fluid cyclone.

[0069] (Another embodiment of the process of removing the sealing portions on both sides) The central tube 5 shown in Figures 5 and 6 has a structure that allows it to be divided at both ends in the longitudinal direction. Figure 6 shows a planar cross-section of the membrane element E. The dashed line frame in Figure 6 indicates the boundary between the membrane bundle bonding sections 600 at both ends and the intermediate water collection section 610, where the fitting section shown in Figure 5 is provided. By making the structure such that the membrane bundle bonding sections 600 at both ends and the intermediate water collection section 610 are connected by a fit, it is also possible to divide it at the point where the sealing sections 11 on both sides are cut. The fitting section does not require sealing with adhesive or the like. When winding the wound body during the manufacturing of the membrane element, torque is applied to the central tube 5, so the fitting section has a mechanism to prevent rotation in the circumferential direction. Specifically, it can be made up of a latch mechanism that can be fastened simply by pushing using the elasticity of the central tube material, a mechanism that adds rotation to that, or a screw fastening.

[0070] Figures 5(a) to 5(c) show examples of the fitting structure of the central tube 5. In the example shown in Figure 5(a), the fitting connection portion 5c of the end-side central tube 5' has a projection, and the main body side of the central tube 5 has a guide groove and a recess. Therefore, the fitting connection portion 5c can be pushed in and the projection can be locked into the recess for fixation.

[0071] In the example shown in Figure 5(b), the fitting connection portion 5c of the end-side central tube 5' has a projection, and the main body side of the central tube 5 has an L-shaped guide groove and a recess. Therefore, by pushing and rotating the fitting connection portion 5c so that the projection follows the guide groove, the projection can be locked into the recess and fixed in place.

[0072] In the example shown in Figure 5(C), the fitting connection portion 5c of the end-side central tube 5' has a male screw structure, and the main body side of the central tube 5 has a female screw structure, so the fitting connection portion 5c can be rotated and screwed together. [Industrial applicability]

[0073] According to the present invention, the permeation-side spacer and central tube can be efficiently recovered from used membrane elements. Furthermore, contamination of the permeation-side spacer during dismantling can be minimized, allowing it to be used as raw material for material recycling or chemical recycling. [Explanation of symbols]

[0074] 1: Separation membrane 2: Supply side spacer 3: Translucent side spacer 5: Central tube 11: Sealing section on both sides 12: Outer peripheral sealing portion 15: Exterior materials A1: Axial direction UE: Used film element E: Membrane element R: Coiled body L: Membrane Leaf

Claims

1. A spiral membrane element comprising a permeable-side spacer interposed between opposing separation membranes, a plurality of membrane leaves having both axially sealed ends and an 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 spiral-type membrane element in which, at least one of the outer peripheral ends, the folded portion of the inner surface of the membrane leaf and the outer peripheral tip of the permeable spacer are not fixed to each other.

2. The spiral membrane element according to claim 1, wherein the folded portion on the inner surface of the separation membrane leaf is formed by folding a continuous separation membrane.

3. Of the plurality of membrane leaves, at least one outer peripheral end is A first outer peripheral sealing portion is formed in which the ends of the separation membrane and the outer peripheral tip of the permeable spacer are sealed together, or The spiral membrane element according to claim 1 or 2, wherein the ends of the separation membranes form a second outer peripheral sealing portion that is sealed without being fixed to the outer peripheral tip of the permeable spacer.

4. The spiral membrane element according to claim 2, wherein the continuous separation membrane is wound around a central tube and folds are provided such that the outer membrane distal to the central tube is longer than the inner membrane proximal to the central tube.

5. The spiral membrane element according to claim 2, further comprising a protective member that contacts the fold portion of the continuous separation membrane.

6. The protective member is a spiral membrane element according to claim 5, wherein the rigidity of the central part is less than that of the other parts.

7. The spiral membrane element according to claim 3, wherein the permeable spacer in the membrane leaf having the first outer peripheral sealing portion has a tear-processed portion along its entire width on the outer peripheral side rather than the center.

8. The spiral membrane element according to claim 1, wherein all of the outer peripheral ends of the plurality of membrane leaves, excluding the permeable spacer, constitute an outer peripheral sealing portion in which the ends of the separation membranes are sealed together.

9. A method for manufacturing a spiral membrane element according to any one of claims 2 to 7, A folded separation membrane formation step involves forming a zigzag pattern with a single separation membrane, interposing a supply-side spacer between the folded separation membranes, and forming the jth folded separation membrane. A permeable spacer preparation step involves fixing a first permeable spacer located at the bottom at the start of the winding operation, and a plurality of i-th permeable spacers that are wound from a position above it, along the longitudinal direction of the central tube. A membrane leaf formation step involves sequentially sandwiching a j-th separation membrane, with a supply-side spacer interposed between an i-th permeation-side spacer and an i+1-th permeation-side spacer, thereby interposing a permeation-side spacer between opposing separation membranes, and forming a plurality of membrane leaves having both axially sealed ends and an outer peripheral end; An outer peripheral sealing portion forming step, in which the ends of the separation membranes are sealed together with or excluding the outer peripheral tip of the permeable spacer to form an outer peripheral sealing portion, A winding step in which the aforementioned membrane leaf is wrapped around and fixed to the central tube, A method for manufacturing a spiral-type membrane element, including [the specified element].

10. A method for manufacturing a spiral membrane element according to claim 9, comprising the step of providing a protective member at a position that will become a fold in the separation membrane before or during the folded separation membrane formation step.

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