Non-nesting, non-deformable patterns for spiral-wound elements

Abstract

Prevents nesting of adjacent spacer layers and blockage of feed space during element winding. A membrane for use in a spiral wound permeable membrane system has spacing features deposited on the surface of the membrane, the spacing features configured to prevent nesting of spacers when wound into a spiral.

Description

Technical Field

[0004] ,

[0001]

[01] Technical Field

[02] The present invention relates to a permeable membrane system used for separating fluid components, and particularly to a spiral wound permeable membrane element.

Background Art

[0002]

[03] Background Art

[04] The spiral wound membrane filtration elements known in the art include a laminated structure including a membrane sheet adhered to or around a porous permeation carrier, which creates a path for the fluid passing through the membrane to move to the central tube. On the other hand, this laminated structure is wound in a spiral around the central tube and is itself separated by a porous supply spacer so that the fluid flows axially through the element. This supply spacer is necessary to maintain a free and uniform axial flow within the laminated structure, but this also causes restrictions in the axial flow path and pressure drop, and also creates regions where the flow is restricted and contacts the membrane, which significantly contributes to membrane fouling through biofouling, scale formation, and particle capture.

[0003]

[05] Improvements to the design of spiral wound elements have been disclosed by Barger et al. and Bradford et al., according to which islands or protrusions directly deposited or embossed on the outer side of the membrane, i.e., on the working surface, are used instead of the supply spacer. This configuration is advantageous in that it minimizes obstacles in the flow path while maintaining a space for the axial flow through the element. Also, since this eliminates the need for a porous supply spacer as a separate component, the manufacture of the element is simplified. U.S. Patent Application Publication No. 2016 - 0008763 - A1, named "Configuration of Improved Spiral Wound Element", teaches applying a printed pattern directly on the back surface of the working surface of the membrane sheet or on the surface of the permeation carrier.

[0004]

[06] The following references, each incorporated herein by reference, may facilitate the understanding of the present invention: U.S. Patent No. 3,962,096, 4,476,022, 4,756,835, 4,834,881, 4,855,058, 4,902,417, 4,861,487, 6,632,357, and U.S. Patent Publication No. 2016-0008763-A1. [Overview of the project]

[0005]

[07] Disclosure of the invention

[08] Embodiments of the present invention provide a membrane for use in a spiral-wound permeable membrane system, comprising a membrane having spacer features deposited on the surface of the membrane, wherein the spacer features are configured to prevent nesting of spacers when the membrane is wound up in a spiral. The spacer features may be arranged to overlap when the membrane is wound up in a spiral.

[0006]

[09] In some embodiments, the separated features may include a plurality of substantially parallel line segments spaced apart from one another by non-uniform spacing. A first portion of the plurality of line segments may form a pattern by being spaced apart from one another by non-uniform spacing, and the other portions of the plurality of line segments may include repetition of the pattern. The first portion may extend at least 6 inches from the first to the last line segment. The first portion may extend at least 12 inches from the first to the last line segment. The amount of variation in spacing may be less than 15% of the average distance between adjacent separated features.

[0007]

[10] In some embodiments, the separated features are separated from each other and at non-uniform angles It may include multiple line segments oriented non-parallel to each other. The first portion of the multiple line segments is oriented at non-uniform angles to each other to form a pattern, and the other portions of the multiple line segments include repetitions of the pattern. The pattern may extend at least 6 inches from the first line segment to the last. The pattern may extend at least 12 inches from the first line segment to the last. The amount of change in angle may be less than 15% of the average angle of the feature relative to the pattern.

[0008]

[11] In some embodiments, the separation feature may include a first plurality of line segments arranged on the surface parallel to each other in a first grid, and a second plurality of line segments arranged on the surface parallel to each other in a second grid, wherein the first plurality of line segments do not intersect with the second plurality of line segments, and the first plurality of line segments are positioned at an angle other than 0 degrees with respect to the second plurality of line segments. The angle is at least 1 degree but may not exceed 45 degrees. The angle may be 45 degrees. Each of the first plurality of separation features may be separated from any adjacent first plurality of separation features by no more than one-quarter inch. Each of the first plurality of separation features may be separated from any adjacent first plurality of separation features by no more than one-tenth inch.

[0009]

[12] In some embodiments, the separated feature may include a plurality of curved segments that are separated from each other by non-uniform separation distances determined and measured along at least one path traversing the separated feature.

[0010]

[13] In some embodiments, the separation features may be configured to at least partially support these separation features on adjacent layers as the membrane is formed in the permeable membrane system.

[0011]

[14] In some embodiments, the separation features may be located near the edge of the membrane.

[0012]

[15] In some embodiments, the interleaved features may be located across the entire surface of the film.

[0013]

[16] In some embodiments, the separated features may be closer together near the edge of the membrane than in parts further away from the edge of the membrane. The edge of the membrane may be defined as an area within 3 inches of the edge of the membrane. The edge of the membrane may be defined as an area within 1 inch of the edge of the membrane.

[0014]

[17] In some embodiments, the separating features may be made of one or more of thermoplastics, reactive polymers, waxes, or resins and deposited directly onto the film surface.

[0015]

[18] In some embodiments, the separating features may be made of high-temperature thermoplastic plastic, metal, or ceramic, formed away from the film surface, and then adhered to the film surface.

[0016]

[19] Embodiments of the present invention provide a permeable membrane system including the membrane described herein.

[0017]

[20] Embodiments of the present invention provide a water treatment facility comprising one or more permeable membrane systems described herein.

[0018]

[21] Embodiments of the present invention provide a permeable membrane system as described herein, and a water treatment method comprising passing water to be treated through the permeable membrane system.

[0019]

[22] Embodiments of the present invention provide the membrane described herein and a method for making a permeable membrane system, which includes winding the membrane in a spiral shape. [Brief explanation of the drawing]

[0020]

[23] Brief description of the drawing [Figure 1] This diagram shows an arrangement of parallel line segments with varying spacing to prevent nesting during the winding of spiral-wound elements. [Figure 2] This diagram shows line segments arranged at various angles to prevent nesting during the winding of spiral-wound elements. [Figure 3A]A diagram of the structure of a proximity separation pattern designed to prevent nesting during the winding up of a spiral winding element. [Figure 3B] A diagram of the structure of a proximity separation pattern designed to prevent nesting during the winding up of a spiral winding element. [Figure 3C] A diagram of the structure of a proximity separation pattern designed to prevent nesting during the winding up of a spiral winding element. [Figure 4A] A diagram of an embodiment of a further example of a feature. [Figure 4B] A diagram of an embodiment of a further example of a feature. [Figure 4C] A diagram of an embodiment of a further example of a feature. [Figure 4D] A diagram of an embodiment of a further example of a feature.

Best Mode for Carrying Out the Invention

[0021]

[28] Best Mode for Carrying Out the Invention and Industrial Applicability

[29] Embossing or depositing features on the surface of the membrane sheet of the spiral wound element, or on or within the permeate carrier sheet, to space adjacent membrane sheets apart provides several advantages compared to a supply spacer mesh, including more open flow channels, lower pressure drop, reduced fouling, and the ability to create a thinner supply space than what was considered practical with a mesh. The membrane sheet itself can be made of a porous polypropylene layer and is adhered to the polysulfone layer by a membrane polymer material cast onto the porous polysulfone layer. Various other materials and methods can be used to make the membrane sheet. Membrane sheets can be created that provide various degrees of removal efficiency. Microfiltration membranes are typically capable of removing substances as small as about 0.1 micron, typical of bacteria and protozoa, or other contaminants of this size, in industrial applications. Ultrafiltration membranes can have a pore size as small as about 0.01 micron and can, for example, remove viruses from a fluid source. Nanofiltration membranes can have a pore size small enough to remove divalent ions, but are thought to allow monovalent ions such as sodium and chloride to pass through. An example of the use of nanofiltration is, for example, water softening to remove calcium carbonate. Reverse osmosis typically has the smallest pore size and is sufficient to remove monovalent salts and is typically used in desalination applications. Various structures of such spacer features have been disclosed by Barger et al., and the international application PCT / US14 / 18813 by Bradford et al., which is incorporated herein by reference, discloses various methods and materials suitable for depositing spaced features on a membrane sheet. Such methods and materials can be useful for implementing embodiments of the present invention.

[0022]

[30] Spacer features embossed or deposited directly onto the membrane surface differ from conventional mesh feed spacers in the manufacturing of spiral-wound elements. Spacer features can be produced in a much wider variety of shapes and patterns than can be achieved by extruded or woven mesh materials, and their spacing and orientation can also be as diverse. When manufacturing spiral-wound filtration elements using embossed or deposited features, a membrane sheet with features on half of the membrane sheet is folded to form a leaf, with one side containing the features and the other side blank, where both opposing sides are the working membrane surfaces. The spacers allow the feed solution to flow between the working membrane surfaces, so that the entire working surface of the membrane can be used for filtration. A permeate carrier sheet is inserted outside these two membrane sheets. The fluid flowing through the working membrane sheet comes into contact with the permeate carrier, and the fluid in the permeate carrier is carried to a central tube. Adhesive is applied before it is wound up around the central tube, and the process is complete. Creating the element: A line of adhesive is deposited around three sides of the outer perimeter of the sheet, starting from one end of the central tube, on either the back (non-working) surface of the woven membrane leaf, or on the permeable carrier mesh above the leaf, before returning to contact the central tube. The adhesive line serves to seal the permeable carrier and separate it from the feed / reject flow. This process is repeated for each leaf used to create the element.

[0023]

[31] Printed features are particularly important in the inlet and outlet regions of the spiral-wound element, where the regions between the features form gaps that allow feedwater to flow into the element and rejectwater to flow out of the element, and must resist the forces generated by compressing the lines of viscous adhesive during winding of the element. If the printed features are simply repeating patterns of regularly spaced lines, segments, or pillars, they can deform adjacent membrane sheets into the supply space by forces on the adhesive during winding, thereby blocking the flow path. Similarly, several patterns and gaps of features can deform all adjacent layers of the membrane, permeable carriers, and adhesives, causing them to nest between the features.

[0024]

[32] An example embodiment of the present invention can prevent blockage of the supply channel during the manufacture of spiral-wound elements by providing spacing and patterns of features that prevent collapse and deformation of the membrane film and adjacent layers. Furthermore, by providing additional support to the membrane sheet during winding to prevent nesting, an example embodiment of the present invention can prevent blockage of the supply channel without requiring any changes to the standard process used for winding spiral-wound elements.

[0025]

[33] The benefit of embodiments of the present invention is that by reducing blockage of the interlayer supply space of the spiral-wound element, flow resistance is reduced, which in turn reduces the pressure drop from the element inlet to the outlet, improving filtration efficiency and reducing energy requirements.

[0026]

[34] An example embodiment of the present invention may also benefit by promoting more uniform flow within the element and preventing potential contamination due to non-uniform flow. Irregular flow can occur within the element when several portions of the supply space are irregularly blocked, as can occur by the nesting of adjacent layers between conventional features. Irregular flow is known to create stagnant areas that lead to biological contamination and scale buildup.

[0027]

[35] Referring to Figure 1, in an embodiment of the present invention, the spacing between adjacent features is slightly varied perpendicular to the flow traversing the element, rather than uniform spacing between adjacent features. This varied spacing is periodic, and the set varied spacing occurs regularly and has a longer period, making the overall possibility of nesting less. In some spiral winding element structures, the period before pattern repetition is preferably at least 6 inches (6"), and more preferably at least 12 inches (12"). In some spiral winding element structures, the amount of variation in spacing is preferably less than 15% of the average distance between adjacent features, so as not to significantly affect the flow characteristics in the element. Varying the spacing of features reduces the possibility of nesting of patterns between continuous layers in the spiral winding element.

[0028]

[36] Referring to Figure 2, in another embodiment of the present invention, the arrangement of line segments providing spacer features has angles that vary slightly from each other from mutually parallel positions. This variation in angle is periodic, and the set varied angles occur regularly and have a longer period overall, which reduces the possibility of nesting. In some spiral-wound element structures, the period before pattern repetition is preferably at least 6 inches (6") and more preferably at least 12 inches (12"). In some spiral-wound element structures, the amount of angle variation is preferably less than 15% of the average angle of the overall arrangement of spacer features so as not to significantly affect the flow features in the element. Angles of the features Varying the degree of winding reduces the possibility of nesting patterns between continuous layers of spiral-wound elements.

[0029]

[37] Similarly, variations in features or relative angles can be performed with other shapes such as curves, or zigzag-patterned features can also be arranged at periodically varying angles to prevent nesting of continuous layers. Examples of such variations are shown in Figure 4. Figure 4a is a diagram of a zigzag pattern with varying interior angles for each feature, and Figure 4B is a diagram of identical zigzag elements arranged non-parallel to each other. Figure 4C is a diagram of a curved feature with varying curved shapes for each feature, and Figure 4D is a diagram of curved features of the same shape but arranged non-parallel to each other. The spacing between features in Figure 4 is illustrated consistently, but features can also be arranged with varying spacing between them, as in Figure 1. The present invention intends for such various shapes and structures of features, each providing features that at least partially support features on adjacent layers when the elements are rolled up and bonded.

[0030]

[38] Conventional spiral-wound elements using extruded mesh spacers generally have very close and spaced mesh fibers, so the fibers do not deform the entire layer of membrane film or membrane, permeable carrier and adhesive, and thus do not cause blockage of the supply space, thus eliminating nesting problems between adjacent layers. Typically, the maximum mesh spacing is 8 fibers per inch, but it is more common to have 10 to 12 fibers per inch in larger elements, and more densely spaced in smaller elements. Thus the problem addressed by the present invention was not clear until a novel deposited spacing feature was introduced.

[0031]

[39] Referring to Figure 3, a further embodiment of the present invention employs a pattern of embossed or deposited features arranged in a pattern that is similar in spacing to conventional mesh feed spacers and minimizes obstruction to the feed flow. These features may include regularly arranged shapes such as circular or polygonal columns, chevrons, curved line segments, or other shapes, which are offset from each other and set at two different angles from the direction of the transverse flow of the fluid. These angles are the same but opposite in direction, e.g., +45° and -45° (Figure 3A), and can be any angle from + / -1° to + / -45° (Figures 3A, 3B). In some spiral winding element structures, the maximum spacing of any portion of such features to the nearest adjacent feature is preferably less than a quarter inch (0.25”) and more preferably less than a tenth inch (0.10”). In another embodiment, the features include an array of offset and opposing angled line segments, with spaced-out circular supports between the features (Figure 3C). Such close-spaced features are beneficial in that the features and the surrounding film sheet are substantially less susceptible to deformation during the winding process when the adhesive contacts the film. For this reason, having these close-spaced and spaced patterns along the outer periphery of the film sheet to which the adhesive is applied can be beneficial even when less densely packed and spaced patterns are employed elsewhere on the film sheet to reduce flow restrictions.

[0032]

[40] In each exemplary embodiment, the features may be continuously embossed or deposited over the entire printed surface of the film leaf, or may be embossed or deposited only along the inlet and outlet edges of the film, for example, in widths of 1 to 3 inches, to support the area to which the adhesive is applied, or may be embossed or deposited only along the inlet and outlet edges and the edges of the film, for example, in widths of 1 to 3 inches, to support the entire area to which the adhesive is applied.

[0033]

[41] The features may include, but are not limited to, a variety of materials compatible with the separation fluid and permeation carrier, including thermoplastics, reactive polymers, waxes, or resins. However, materials that are compatible with the separation fluid but not suitable for direct deposition onto the permeate carrier, including high-temperature thermoplastics, metals, or ceramics, can be pre-formed, cast, or cut to the appropriate dimensions and bonded to the surface of the permeate carrier with an adhesive compatible with the permeate carrier.

[0034]

[42] The present invention has been described in relation to various exemplary embodiments. The above description is merely illustrative of the application of the principles of the present invention, and it will be understood that the scope thereof is determined by the claims taking into account the specification. Other variations and modifications of the present invention will be apparent to those skilled in the art.

Claims

1. A membrane used in a spiral-wound permeable membrane system, A membrane comprising a membrane having separable features deposited on its surface, wherein the separable features are more closely spaced near the edge of the membrane than in portions further away from the edge of the membrane, and the separable features are arranged to overlap when the membrane is rolled up in a spiral shape.

2. A membrane according to claim 1, wherein the edge of the membrane is defined as an area within 3 inches of the edge of the membrane.

3. A membrane according to claim 2, wherein the edge of the membrane is defined as an area within 1 inch of the edge of the membrane.

4. A film according to claim 1, wherein the separated features include a plurality of substantially parallel line segments separated from each other by non-uniform separation distances.

5. A film according to claim 1, wherein the separated features include a plurality of line segments that are separated from each other and oriented non-parallel to each other at non-uniform angles.

6. A film according to claim 1, wherein the separated feature comprises a plurality of curved segments separated from each other by non-uniform separation distances.

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