Spiral wound membrane element

Abstract

A spirally wound filtration membrane element has a scroll surface that includes at least two concentric, axially displaced regions, at least one of which is sealed and at least one of which is unsealed. Such membrane elements can be produced by a winding process followed by a trimming or cutting step that produces the concentric, axially displaced regions. The seal can be applied before, during or after the trimming or cutting step.

Description

[Technical field]

[0001] The present invention relates to spirally wound membrane elements and methods for making them. [Background technology]

[0002] Reverse osmosis (RO), nanofiltration, and ultrafiltration membranes are commonly configured as spirally wound membrane elements or modules. The spirally wound configuration allows a large amount of membrane area to be packed into a small volume.

[0003] A typical spirally wound filtration element includes a central permeate collection tube, around which one or more membrane envelopes and feed spacers are wound to form a spiral bundle. The membrane envelope includes two portions of membrane sheet sandwiching a permeate channel spacer. The membrane sheets forming the membrane envelope are sealed along three edges and open at a proximal edge where the membrane envelope meets the central permeate collection tube. The spiral bundle has scroll faces at opposite ends. The spiral bundle may be partially or fully enclosed within an outer container or wrap, typically comprising a fiberglass or tape wrap.

[0004] FIG. 1 illustrates the difference in the feed flow path between a conventional axial-flow element (FIG. 1a) and an element designed for radial flow (FIGS. 1b and 1c). In an element designed for axial flow as shown in FIG. 1a, the feed is directed into the inlet side 201 of the spiral bundle (shown unwound for illustrative purposes), passes through the feed spacers, and flows between the windings of the membrane envelope in a direction generally parallel to the central permeate collection tube 2, as indicated by arrows 150, where it is concentrated and removed as a retentate from the outlet side 210 of the scroll face. The permeate, i.e., the portion of the feed that permeates through the membrane and into the membrane envelope, proceeds in a spiral inward direction between the membrane sheets toward the permeate collection tube 2. The permeate then enters the permeate collection tube 2 and is removed through the permeate outlet 24.

[0005] Establishing a radial flow of the feed through the membrane has advantages. For example, the flow within the element can be designed to reduce fouling or peeling. In a traditional RO element with axial feed flow, the pressure drop within the permeate spacer causes the flow (and splitting near the membrane surface) to be highest in the region adjacent to the permeate tube. At the same time, water permeation through the membrane causes the feed concentration to be highest at the end of the element where the feed exits the element. Peeling is typically first evident at the corners where these two regions are partially co-located. In contrast, the flow through a radial flow element can be arranged to have the highest concentration of feed placed around the periphery of the element, so that it does not overlap with the regions of highest flow and splitting. Also, when evaluated with similar flow and recovery, a radial flow element can be designed to have a higher feed flow velocity than a traditional element of the same size and feed spacer thickness, resulting in increased mixing and therefore reduced both peeling and fouling. Summary of the Invention [Problem to be solved by the invention]

[0006] A typical radial flow pattern is illustrated in Figures 1b and 1c. As shown in Figures 1b and 1c, the feed proceeds spirally outward between the windings of the membrane envelope in a radial direction that is primarily perpendicular to the permeate tube. In Figures 1b and 1c, arrows 151 correspond to the feed flow direction, which is radially outward, such that the concentrate is removed from the outlet side 210 or from the distal end 211. Alternatively, the feed flow direction may proceed in the opposite direction, i.e., spirally inward, in which case the arrows in Figures 1b and 1c would be in the opposite direction. The radial flow can be at least partially facilitated by allowing the feed to enter through only a portion of the scroll face, such as by using a sealant to selectively seal only a portion of the scroll face and block other portions. For example, a sealant may be applied to the radially outer portion of the scroll face, but not to the radially inner portion closer to the tube. In that case, the feed can only enter the spiral bundle through the unsealed radially inner portion. Conversely, the radially inner portion can be sealed but the radially outer portion cannot be sealed, thereby allowing the feed fluid to enter only through the radially outer portion of the scroll face. The problem with this sealing method is that it is difficult to precisely control the application of the sealant to only the intended portions of the scroll face. [Means for solving the problem]

[0007] The present invention relates to a spiral wound filtration element, comprising: a) a central permeate collection tube having a plurality of openings along its length and a permeate outlet at one or both ends; b) a spiral bundle including at least one membrane envelope and at least one feed spacer means for creating a feed channel within a spirally wound filtration element, the at least one membrane envelope and the at least one feed spacer means being wound around a central permeate collection tube; (i) each membrane envelope comprises two portions of a membrane sheet and a permeate channel spacer means for providing a permeate channel between the two portions of the membrane sheet, each membrane envelope being sealed on each of a first edge, a second edge opposite the face edge, and a distal edge, and open on a proximal edge, each membrane envelope being attached to the central permeate collection tube such that the open proximal edge of each membrane envelope is in fluid communication with one or more of a plurality of openings along a length of the permeate collection tube; (ii) the spiral bundle has opposing first and second scroll faces at opposing ends of the spiral bundle, an exterior longitudinal surface between the first and second scroll faces, and a feed channel between adjacent exterior surfaces of at least one membrane envelope within the spiral bundle; (iii) the first scroll face includes at least two concentric axially displaced regions, at least one of said concentric axially displaced regions of the first scroll face being sealed against the feed channel, and at least one of said concentric axially displaced regions of the first scroll face being unsealed such that feed fluid can pass through the unsealed region of the first scroll face into the feed channel of the spiral bundle or concentrate can pass through such unsealed region out of the feed channel of the spiral bundle; The spiral wound filtration element is a spiral wound filtration element that further includes openings on the second scroll face, on the outer longitudinal surface of the spiral bundle, or both, for allowing concentrate to exit the feed channels of the spiral bundle or feed fluid to enter the feed channels of the spiral bundle.

[0008] The present invention also provides a method for producing a spirally wound filtration element, comprising the steps of: a) winding at least one membrane envelope and a feed spacer means for creating a feed channel around a permeate collection tube to form a spiral bundle having opposing first and second ends, an exterior longitudinal surface between the first end and the second end, a feed channel disposed between adjacent exterior surfaces of the at least one membrane envelope, and one or more openings at the second end, the exterior longitudinal surface, or both, such that a concentrate can exit the feed channel of the spiral bundle or a feed fluid can enter the feed channel of the spiral bundle; (i) the permeate collection tube has a plurality of openings along its length and a permeate outlet on at least one end; (ii) rolling, each membrane envelope including two portions of a membrane sheet and a permeate channel spacer means for providing a permeate channel between the two portions of the membrane sheet, each membrane envelope open over a proximal edge and sealed at or near each of a first edge, a second edge opposite the first edge, and a distal edge, the first edge being sealed with an adhesive strip, each membrane envelope being attached to the central permeate collection tube such that the open proximal edge of each membrane envelope is in fluid communication with one or more of the plurality of openings along a length of the permeate collection tube; b) in one or more removing steps, removing at least a portion of a first end of the spiral bundle, whereby portions of each of the membrane sheet, the feed spacer means, the permeate spacer means and the adhesive strip are removed to form a first scroll face, while leaving a portion of the adhesive strip intact along an entire first edge of each membrane envelope, said first scroll face including at least two concentric axially displaced scroll face regions; and c) sealing at least one but fewer than all of the concentric, axially displaced scroll surface areas of the first scroll face to create one or more sealed scroll surface areas, each sealed scroll surface area having a seal that blocks flow into or out of the feed channel through the sealed scroll surface area. [Brief description of the drawings]

[0009] [Figure 1a] FIG. 1 is a perspective view illustrating axial feed flow through a spirally wound membrane. [Figure 1b] FIG. 13 is a perspective view illustrating the mode of radial feed flow through a spirally wound membrane. [Figure 1c] FIG. 13 is a perspective view illustrating the mode of radial feed flow through a spirally wound membrane. [Diagram 2] 1 is a perspective view, partially in section, of a partially unwound spiral wound filtration element of the present invention; [Diagram 3] FIG. 2 is an isometric view of one embodiment of a spirally wound filtration element of the present invention. [Figure 4] FIG. 2 is an isometric view of a second embodiment of a spirally wound filtration element of the present invention. [Diagram 5] FIG. 2 is an isometric view of a second embodiment of a spirally wound filtration element of the present invention. [Figure 6a] 1 is a cross-sectional view of a portion of one embodiment of the present invention; [Figure 6b] 1 is a cross-sectional view of a portion of one embodiment of the present invention; [Figure 7] FIG. 1 is a perspective view of a membrane material adapted for use in producing the spiral wound filtration elements of the present invention. [Figure 8] 1 illustrates generally a first method of creating an adhesive seal on a spirally wound filtration element of the present invention. [Figure 9] 10 illustrates generally a second method of producing an adhesive seal on a spirally wound filtration element of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 2-5, a spirally wound filtration element 1 includes a central permeate collection tube 2. The central permeate collection tube 2 has a plurality of openings 3 (FIG. 2) along its length through which permeate enters from the membrane envelope 4 (FIG. 2), and at least one permeate outlet 24 at one or both ends for discharging the permeate.

[0011] One or more membrane envelopes 4 and one or more feed spacer means 11 are wound around a central permeate collection tube 2 to form a helical bundle 23. Spiral wound filtration elements having membrane envelopes and feed spacer means wound around a central permeate collection tube, as well as methods for making such elements, are well known and are described, for example, in U.S. Pat. Nos. 4,792,401; 5,275,726; 8,142,657; 8,661,648 and WO 91 / 11249, among many other references, all of which are useful in the present invention. The assembly of spiral wound filtration elements will therefore only be briefly described.

[0012] An embodiment of the membrane envelope 4 is illustrated in Figure 2. The membrane envelope 4 includes two membrane sheets 5 (the two membrane sheets 5 may be substantially rectangular, including square) and a permeate spacer means 6. The two membrane sheets 5 may be formed from a single larger sheet that is typically folded along a proximal edge 10 with a feed spacer means 11 therebetween. In some embodiments, multiple membrane sheets, such as a bellflower leaf design, are formed by also folding the single larger sheet along a distal edge 9.

[0013] The membrane sheet is or includes a sheet of membrane material, such as a nanofiltration, reverse osmosis or ultrafiltration membrane material, and the membrane sheet may be an asymmetric or symmetric membrane material having a discriminating layer and a supporting layer. Examples of discriminating membrane materials include cellulose acetate, polysulfone, polyethersulfone, polyamide, polyvinylidene fluoride and the like, but the discriminating layer is preferably a polyamide thin film formed through interfacial polymerization. The supporting layer in an asymmetric membrane may include, for example, a nonwoven fabric, a fibrous web, or a woven fabric, as described in U.S. Pat. Nos. 4,214,994, 4,795,559, 5,435,957, 6,156,680, 7,048,855 and 8,591,684. Most preferably, the membrane is a composite comprising a thin film layer on a porous ultrafiltration support layer which is itself supported by a nonwoven web, such as that described in US Pat. No. 4,277,344.

[0014] The permeate spacer means 6 creates a permeate channel between the two membrane sheets 5 of the membrane envelope 4 such that permeate passing through the membrane sheets 5 enters the membrane envelope 4 and flows in the permeate channel to the central permeate collection tube 2. The open proximal end of the membrane envelope 4 is in fluid communication with one or more of the multiple openings 3 along the length of the central permeate collection tube 2 such that the permeate in the permeate channel of the membrane envelope 4 can flow into those openings. The permeate spacer means 6 may be a sheet of material separate from each of the two membrane sheets 5 such as a mesh, knit or woven fabric that forms a flow channel, one common form being a tricot knit. In other embodiments, the permeate channel between the membrane sheets may be formed by extrusion, embossing or otherwise structured to provide multiple continuous paths for flow between the membranes. Examples of permeate spacer materials include polyethylene, polyester and / or polypropylene.

[0015] Alternatively or additionally, the permeate spacer means 6 may be integrated into one or both of the membrane sheets 5, for example in the form of raised areas extending into the permeate channels. Such raised areas may for example be or include raised dimples, raised ridges and the like, which may form any pattern and / or may be randomly arranged in each case to separate the two membrane sheets 5 to form the permeate channels.

[0016] The membrane envelope 4 is sealed on a first edge 7, a second edge 8, and a distal edge 9. The first edge 7 is sealed with an adhesive forming an adhesive strip 70 (FIGS. 6a and 6b) that preferably runs parallel to the first edge 7 and extends inwardly therefrom. Preferably, the width of the adhesive strip 70 is large enough to allow the membrane envelope 4 to be trimmed within the adhesive strip 70 to generate concentric axially displaced regions of the first scroll face 20 (such as regions 30, 31, and 301 in FIGS. 3-5), as described more fully below. The second edge 8 and the distal edge 9 can be sealed in the same manner, using an adhesive to form adhesive strips (such as adhesive strip 72 in FIGS. 6a and 6b) that run parallel to and extend inwardly from the corresponding edges. Alternatively, either the second edge 8 and / or the distal edge 9 can be the folded sides of a larger membrane sheet that is folded to form the two membrane sheets 5 of the membrane envelope 4, with the crease creating a seal in such a case.

[0017] As shown in Fig. 2, the feed spacer means 11 create feed channels between adjacent exterior surfaces of the membrane envelopes 4 in the spiral bundle 23. Each feed channel is a conduit through which the feed flows between and in contact with the membrane envelopes 4, where a portion of the feed is concentrated due to permeation into the membrane envelopes 4 and is directed (as a concentrate) to a concentrate outlet. The feed spacer means 11 may be a separate sheet, such as an extruded diagonal net, for example as described in US Patent No. 6,881,336. Alternatively or additionally, the feed spacer means 11 may be integrated into one or both of the membrane sheets 5 in the form of a raised area extending into the feed channel.

[0018] The proximal end 10 of the membrane envelope(s) 4 is attached to the central permeate collection tube 2, typically by glue, although mechanical fastening methods can be used. When the feed spacer means 11 separates from the membrane envelope 4, it is sandwiched by the membrane envelope 4, and the membrane envelope 4 and the feed spacer means 11 are wound around the central permeate collection tube 2 to form a helical bundle 23.

[0019] The spiral bundle 23 has an outer longitudinal surface 22, a first scroll face 20 and a second scroll face 21 on an opposite end of the spiral bundle opposite the first scroll face 20. After winding, the first scroll face 20 corresponds to a first edge 7 of the membrane envelope 4 and the second scroll face 21 corresponds to a second edge 8 of the membrane envelope 4. The designations "first" and "second" are used arbitrarily herein to identify scroll faces and particular edges of the membrane envelope, and no chronological relationship or priority is intended between them by this identification.

[0020] The first scroll face 20 includes concentric, axially displaced regions (such as regions 30, 31, and 301 in FIGS. 2-5). By "axially displaced" it is meant that at least two adjacent concentric regions are axially offset, i.e., located at different positions or heights along an axis parallel to the permeate tube. There is at least one inner region 30 and at least one outer region 31. "Inner" refers to radially inward and "outer" refers to radially outward. An inner region, such as inner region 30, may extend axially outward relative to an outer region, such as outer region 31, as shown in FIGS. 3 and 6. Conversely, an outer region, such as outer region 31 (FIGS. 2-5), may extend axially outward relative to an adjacent inner region, such as inner region 30, as shown in FIG. 4. The average axial offset between adjacent concentric axially displaced regions may be, for example, at least 1 mm to 2 cm. More preferably, the average axial offset may be greater than 2 mm, or even greater than 2.5 mm, or even greater than 5 mm. The average axial offset may be, for example, up to 2.5 cm, or up to 1 cm. Each concentric axially displaced region may comprise, for example, greater than 5% of the total scroll face area of ​​inlet scroll face 20.

[0021] The axial displacement between adjacent concentric axially displaced regions of the first scroll face 20 creates a wall (reference numeral 97 in FIGS. 3-6) at the boundary between those adjacent axially displaced regions. The wall 97 is the exposed side of the more axially outwardly extending region and describes the surface region of the first scroll face that extends axially outward from the adjacent region. The wall 97 may have a height equal to the axial displacement. The ridge or wall 97 is preferably perpendicular to the adjacent concentric axially displaced regions of the first scroll face 20 (regions 30, 31, etc.), but may be at another angle thereto. Preferably, the wall is no more than 45 degrees from the vertical, more preferably 15 degrees.

[0022] It is preferred to provide just two concentric axially displaced regions in first scroll face 20, although more may be provided if desired. Figure 5 illustrates an exemplary embodiment having three such concentric axially displaced regions 30, 31 and 301.

[0023] The axially displaced region of first scroll face 20 can be created in a number of ways. In a preferred process, the concentric axially displaced region (such as regions 30, 31 and 301 in Figures 2-5) is created via a cutting or trimming operation, where the helical bundle 23 is formed having a first end, and first scroll face 20 is created by cutting or trimming the first end to create the concentric axially displaced region.

[0024] Referring to FIG. 6a, lines 55 and 55' represent the longitudinal extent of the spiral bundle 23 (and the unmodified starting scroll face) after winding and before such cutting or trimming operations. Lines 56 and 56' represent the longitudinal extent of the adhesive strips 70 and 72, respectively, after winding and before such cutting or trimming operations. (Both shaded areas (hashed and dotted) correspond to the areas of the adhesive strips initially, but only the areas of the hash marks remain after the cutting operation.) In the embodiment shown in FIGS. 6a and 6b, the cutting or trimming operations are performed in both the inner region 30 and the outer region 31. The cutting or trimming operations may be performed in a single step or in multiple steps. When performing the cutting or trimming operations, the removed material typically includes each membrane sheet 5, the feed spacer means 11, a portion of the permeate spacer means 6, and typically a portion of the adhesive strips 70, while at least a portion of the adhesive strips 70 remains intact. The scroll face 20 is formed by the inner and outer regions 30 and 31 and the wall 97.

[0025] In one embodiment, the inner region 30 and the outer region 31 are formed by removing a first portion of the first end of the spiral bundle 23 from a radially inward location, while leaving a portion of the adhesive strip of said first portion intact, and removing a second portion from a radially outward portion of the first end of the spiral bundle. This can be done in one or more steps. It is often preferred, but not necessary, to generate a uniform plane on each of the inner region 30 and the outer region 31. Such a plane is preferably perpendicular to the axis of the central permeate collection tube 2. Such a method may be extended to generate three or more concentric axially displaced regions.

[0026] In another embodiment, a first removal step is performed and the adhesive seal is then applied to all or a portion of the first scroll face. In a second removal step, a portion of the adhesive seal (together with portions of the membrane sheet, feed spacer means, permeate spacer means and adhesive strip) is removed adjacent to the permeate tube to form an unsealed radially inward and axially inward region of the scroll face suitable for passing the feed. In contrast to the illustration in FIG. 4, it may be preferable for this inner region 30 to have a generally inclined surface (as opposed to being flat and perpendicular to the permeate tube axis) since an inclined cut may reduce debris formed on the cut surface that may otherwise restrict flow. Also, when the radially inward concentric region 30 is axially inward adjacent to the permeate tube, it may be advantageous to have a larger width adhesive strip 70 near the permeate tube. In a preferred embodiment, the average distance of the open permeate channels between opposing adhesive strips (70, 72) near the first and second edges (7, 8) is preferably at least 1 cm less within 5 cm of the permeate tube than over other regions of the permeate spacer. Figure 6b illustrates how an angled cut surface adjacent to the permeate tube can be combined with an adhesive strip 70 that increasingly flares inwardly from the first edge 7 to promote the creation of open feed channels without tearing the adhesive strip 70.

[0027] Such a cutting or trimming step is performed without tearing the seal on the first side edge 7 of the membrane envelope 4. In a preferred embodiment where the first side edge 7 of the membrane envelope 4 is sealed with an adhesive strip 70, the cutting or trimming is performed within or outside the adhesive strip 70, as shown in FIG. 5, such that the seal created by the adhesive strip 70 remains intact.

[0028] The cutting or trimming can be performed using, for example, a knife, a rotary blade, a mill, or other useful method. In a preferred embodiment, the cutting or trimming may be performed at least in part while rotating the element relative to a cutting tool (such as a cutting tool).

[0029] An alternative method of generating the concentric axially displaced regions of the inlet scroll face 20 is to fabricate the membrane envelope 4 and / or the membrane sheets 5 in such a way that when the membrane envelope 4 is wound to form the helical bundle, it generates the concentric axially displaced regions. With reference to FIG. 7, the membrane 80 is adapted to fold along a line 81 to form two membrane sheets 5, the fold 81 forming the sealed distal edge 9 of the membrane envelope 4 when the membrane 80 is assembled into the membrane envelope. When assembled into the membrane envelope, the edges 8' and 10' generate the outlet edge 8 and proximal edge 10, respectively, of the membrane envelope. The edges 7A and 7B are displaced from each other and, when folded, generate the first edge 7 of the membrane envelope. When wound to form the helical bundle, the edges 7A and 7B generate the axially displaced concentric inner and outer regions (30, 31) of the scroll face 20.

[0030] Alternatively, two separate membrane sheets can be fabricated separately in a manner similar to that shown in Figure 7 to create displaced first edges 7A and 7B, and then formed (together with a permeate spacer means) to create a membrane envelope. Instead of fabricating a membrane or membrane sheet in such a manner, a membrane sheet can first be formed into a membrane envelope, and a first edge of the membrane envelope cut or trimmed to create edges similar to first edges 7A and 7B of Figure 7. Upon rolling, axially displaced concentric inner and outer regions (30, 31) of scroll face 20 are created.

[0031] At least one, but not all, of the concentric, axially displaced regions of first scroll face 20 are sealed to locally close the flow paths to and from the feed channel through one or more regions of first scroll face 20. It is generally preferred to seal the outer regions, such as outer region 31, and leave one or more more radially inner regions, such as regions 30 and / or 301, unsealed. A preferred type of sealant is an adhesive sealant that is applied as a liquid or emulsion and dried and / or cured to form an adhesive seal 60 on the corresponding region of first scroll face 20.

[0032] The adhesive seal 60 is adapted to prevent the feed fluid from entering or exiting the spiral bundle 23 through the sealed area of ​​the first scroll face 20, thereby restricting fluid flow to only the unsealed areas. The sealant may be of the elastomeric type. Examples of useful adhesive sealants include various types of hot melt adhesives, as well as polymerizable adhesives having at least one reactive monomer, such as various one- or two-part resins or urethanes, free radically polymerizable adhesives, cyanoacrylate adhesives, and the like. In some embodiments, the seal may be bonded to a permeable or non-permeable backing layer such that the seal layer is sandwiched between the scroll face and the backing layer.

[0033] In embodiments where the concentric axially displaced regions of the first scroll face 20 are produced by cutting or trimming, the adhesive seal 60 may be applied after the cutting or trimming step, as shown diagrammatically in FIG. 8. As shown in FIG. 8, an untrimmed helix bundle 23' is formed around the central permeate collection tube 2 in step (a). The first end 20' of the untrimmed helix bundle 23' is trimmed in one or more steps (b) to produce a first end 20 of the helix bundle 23 having concentric axially displaced regions 30 and 31. As shown, the inner region 30 extends axially outward from region 31. In step (c), the adhesive seal 60 is then applied to only one of the concentric axially displaced regions of the first scroll face 20(c). As shown, adhesive seal 60 is applied to exterior region 31, but may be applied to any one or more concentric, axially displaced regions, provided that at least one such region remains unsealed.

[0034] An advantage of the present invention is that application of the adhesive seal only to intended areas is simplified and more easily controlled near walls (such as wall 97) at the boundaries between adjacent concentric axially displaced areas due to the axial offset of adjacent concentric areas of first scroll face 20. The present invention is particularly well suited for automated application of the adhesive seal by robotic or otherwise.

[0035] In another preferred embodiment, the adhesive seal may be applied to the entire first end of the spiral bundle 23, preferably after a first cutting or trimming operation that flattens the surface of the scroll face. In this embodiment, only a portion of the adhesive seal is removed during the cutting or trimming operation, leaving the adhesive seal 60 on the remaining portion of the first scroll face 20 (which has not been moved axially much). In this embodiment, the cutting or trimming operation is preferably performed by making multiple cuts, and the adhesive seal 60 is performed after the first cut and before the second or final cut. Such a process is illustrated diagrammatically in FIG. 9. As shown in FIG. 9, an untrimmed spiral bundle 23' is formed around the central permeate collection tube 2 in step (a). In step (b), the adhesive seal 60 is applied to the entire first end 20' of the spiral bundle. First end 20' of spiral bundle 23' is then trimmed in one or more steps (b) to produce first end 20 of spiral bundle 23 having concentric axially displaced regions 30 and 31, one of which (30) remains sealed with adhesive seal 60. The adhesive seal is removed from region 31 during trimming, leaving only region 30 sealed. As shown, inner region 30 extends axially outward from region 31 and retains the adhesive seal.

[0036] Alternatively, any concentric, axially displaced areas of the first scroll face 20 to be sealed can be mechanically sealed, such as through the use of appropriate gaskets or other mechanical devices fitted to seal the appropriate areas. Such gaskets may be held in place via end caps or other mechanical means.

[0037] In some embodiments, the second scroll face 21 also includes at least two concentric, axially displaced regions, including a radially inner region and at least one radially outer region, as described with respect to the first scroll face 20. In such cases, at least one such region may be sealed as described above, and at least one such region may not be sealed. In other embodiments, the second scroll face 21 has a flat surface.

[0038] A feed fluid is filtered using the spirally wound membrane element of the present invention. The unsealed area of ​​the first scroll face 20 functions as either a feed inlet port (as shown in Figs. 1a, 1b and 1C) or a concentric outlet port, depending on how the flow is directed through the element. The spirally wound filtration element 1 further includes openings on the second scroll face 21 (as shown in Fig. 1b), on the outer longitudinal surface 22 of the spiral bundle 23 (as shown in Fig. 1C), or both. The openings on the second scroll face 21 and the outer longitudinal surface 22 function as either a concentric outlet or a feed fluid inlet, again depending on how the flow is directed through the element. The flow direction is determined by the orientation of the spirally wound membrane element within the filtration system and by the location of the sealed area of ​​the inlet scroll face 20.

[0039] In some embodiments, the feed fluid is contacted under applied pressure with an unsealed region of the first scroll face 20 where it enters the spiral bundle 23 through the feed channel formed by the feed spacer means 11. The feed then travels through the spiral bundle 23 into the spiral bundle 23, where a portion of the feed is permeated into the membrane envelope 4 to form a permeate, and the remainder (retentate) exits the spiral bundle 23 through a retentate outlet, which may be in the second scroll face 21, in the outer longitudinal surface 22, or both. In such embodiments, the feed fluid most preferably enters the feed channel at an unsealed interior region of the first scroll face 20 (such as region 30 in Figures 2-4) and flows in a radially outward spiral direction as indicated by arrow 151 in Figures 1b and 1c (it being understood that arrow 151 represents an idealized flow path that only approximates the actual direction of flow). The concentrate outlet may be (a) all or a portion of the second scroll face 21 (FIG. 1b), (b) the outer longitudinal surface 22 of the spiral bundle 23 (FIG. 1c), the distal end of the membrane envelope 4 and the feed spacer means 11, or (c) both. In embodiments where the concentrate outlet is along the outer longitudinal surface 22 of the spiral bundle 23, the second scroll face 21 is preferably entirely sealed to prevent the concentrate from exiting the spiral bundle 23 through the second scroll face 21. In embodiments where the concentrate outlet is a portion of the outlet scroll face 21, the interior or exterior of the outlet scroll face 21 may be sealed as described for the inlet scroll face 20. In embodiments where a portion of the outlet scroll face 21 is sealed, the outlet scroll face may include concentric axially displaced regions similar to the concentric axially displaced regions of the inlet scroll face 20 (30, 31, 301, etc.).

[0040] In other embodiments, the unsealed area of ​​the first scroll face 20 serves as a concentrate outlet. In such embodiments, one or more openings are preferably provided on the outer longitudinal surface 22, at the distal end of the membrane envelope 4 and in the feed spacer means 11, which openings serve as a feed fluid inlet. In such embodiments, an unsealed area of ​​the first scroll face 20 is provided in which the feed fluid flows in a radially inward helical direction opposite to the direction indicated by the arrows 151 in Figures 1b and 1c.

[0041] The spirally wound filtration element 1 may include various additional and optional features. End caps may be provided at either or both of the inlet and outlet ends of the element. The spiral bundle may be contained within a longitudinal casing. Such end caps and casings, when present, may include, for example, one or more ports for directing fluids (feed, permeate, and concentrate) to and from the element, be adapted to direct flow to and from specific areas of the spiral bundle, be adapted to prevent or reduce stretching, be adapted to provide mechanical protection to the spiral bundle, and / or be adapted to interface with other components of the filtration system.

Claims

1. A spirally wound filtration element, comprising: a) a central permeate collection tube having a plurality of openings along its length and a permeate outlet at one or both ends; b) a spiral bundle including at least one membrane envelope and at least one feed spacer means for creating a feed channel within said spirally wound filtration element, said at least one membrane envelope and at least one feed spacer means being wound around said central permeate collection tube; (i) each membrane envelope comprises two portions of a membrane sheet and a permeate channel spacer means for providing a permeate channel between the two portions of the membrane sheet, each membrane envelope being sealed on each of a first edge, a second edge opposite the first edge, and a distal edge, and open on a proximal edge, each membrane envelope being attached to the central permeate collection tube such that the open proximal edge of each membrane envelope is in fluid communication with one or more of the plurality of openings along a length of the permeate collection tube; (ii) the spiral bundle having opposing first and second scroll faces at opposing ends of the spiral bundle, an exterior longitudinal surface between the first and second scroll faces, and a feed channel between adjacent exterior surfaces of the at least one membrane envelope within the spiral bundle; (iii) the first scroll face includes at least two concentric axially displaced regions, at least one of the concentric axially displaced regions of the first scroll face being sealed against the feed channel, and at least one of the concentric axially displaced regions of the first scroll face being unsealed such that feed fluid can flow into the feed channel of the spiral bundle through an unsealed region of the first scroll face, or concentrate can flow out of the feed channel of the spiral bundle through such unsealed region; The spiral wound filtration element further includes openings on the second scroll face, on the exterior longitudinal surface of the spiral bundle, or both, to allow a concentrate to exit the feed channel of the spiral bundle or a feed fluid to enter the feed channel of the spiral bundle.

2. 10. The spiral wound filtration element of claim 1, wherein the axially displaced regions of the at least two concentric circles are axially displaced from each other by an average distance of between 1 mm and 2 cm.

3. 3. A spiral wound filter element as claimed in claim 1 or 2, wherein said first scroll surface has exactly two concentric axially displaced regions.

4. 3. The spiral wound filtration element of claim 1 or 2, wherein the concentric axially displaced regions include an inner region and an outer region, the inner region being displaced axially outward relative to the outer region.

5. 3. The spiral wound filtration element of claim 1 or 2, wherein the concentric axially displaced regions include an inner region and an outer region, the outer region being displaced axially outward relative to the inner region.

6. 3. The spiral wound filtration element of claim 1 or 2, wherein axial displacement between adjacent axially displaced regions of said first scroll face creates a wall at an interface between adjacent axially displaced regions of said concentric circles.

7. 3. The spiral wound filtration element of claim 1 or 2, wherein at least one of the axially displaced regions of the concentric circles of the first scroll face is sealed to the feed channel with an adhesive seal selected from the group consisting of hot melt adhesives and curable adhesives having at least one reactive monomer.

8. 8. The spiral wound filtration element of claim 7, further comprising a backing layer adhered to said adhesive seal such that said adhesive seal layer is sandwiched between said scroll face and said backing layer.

9. 1. A method for producing a spirally wound filtration element, comprising: a) winding a permeate collection tube around the at least one membrane envelope and a feed spacer means for creating said feed channel to form a spiral bundle having opposing first and second ends, an exterior longitudinal surface between said first end and said second end, a feed channel disposed between adjacent exterior surfaces of at least one membrane envelope, and one or more openings in said second end, in said exterior longitudinal surface, or both, such that a concentrate can exit said feed channel of the spiral bundle or a feed fluid can enter said feed channel of the spiral bundle; (i) the permeate collection tube has a plurality of openings along its length and a permeate outlet on at least one end; (ii) rolling, each membrane envelope comprising two portions of a membrane sheet and a permeate channel spacer means for providing a permeate channel between the two portions of the membrane sheet, each membrane envelope open on a proximal edge and sealed at or near each of a first edge, a second edge opposite the first face edge, and a distal edge, the first edge being sealed with an adhesive strip, each membrane envelope being attached to the central permeate collection tube such that the open proximal edge of each membrane envelope is in fluid communication with one or more of the plurality of openings along a length of the permeate collection tube; b) in one or more removing steps, removing at least a portion of a first end of said spiral bundle, whereby a portion of each of the membrane sheet, the feed spacer means, the permeate spacer means and the adhesive strip are removed to form a first scroll surface while leaving a portion of said adhesive strip intact along the entire first edge of each membrane envelope, said first scroll surface including at least two concentric axially displaced scroll surface areas; and c) sealing at least one but fewer than all of said concentric axially displaced scroll surface areas of said first scroll face to create one or more sealed scroll surface areas, each sealed scroll surface area having a seal that blocks flow into or out of said feed channel through said sealed scroll surface area.

10. 10. The method of claim 9, wherein the axially displaced scroll surface regions of the at least two concentric circles generated in step b) are axially displaced from each other by an average distance of between 1 mm and 2 cm.

11. 11. The method according to claim 9 or 10, wherein in step b) exactly two concentric axially displaced regions are generated in the first scroll surface.

12. 11. The method of claim 9 or 10, wherein the axially displaced regions of the concentric circles generated in step b) comprise an inner region and an outer region, the inner region being displaced axially outward relative to the outer region.

13. 11. The method of claim 9 or 10, wherein the concentric axially displaced regions include an inner region and an outer region, the outer region being displaced axially outward relative to the inner region.

14. 11. The method of claim 9 or 10, wherein step b) creates a wall having a height equal to the axial displacement between axially displaced regions of said adjacent concentric circles of said first scroll face.

15. The method according to claim 9 or 10, wherein step c) is carried out after step b).

16. 11. The method according to claim 9 or 10, wherein step c) is carried out by applying an adhesive seal to the entire scroll face prior to step b), and a portion of the adhesive seal is removed together with a portion of the inlet end of the spiral bundle removed during step b).

17. 11. The method according to claim 9 or 10, wherein a first removal step is performed, an adhesive seal is then applied to all or a portion of the first scroll face, and a second removal step is performed, whereby a portion of the adhesive seal is removed together with each of the membrane sheet, the feed spacer means, the permeate spacer means and the adhesive strip.

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