Inlet screen for spiral-wound membrane elements and spiral-wound membrane elements

Abstract

The application provides a water inlet screen for a spiral membrane element and the spiral membrane element, which comprises a plurality of transverse wires (1), a plurality of longitudinal wires (2) and a support part (3), the transverse wires (1) and the longitudinal wires (2) are staggered to form cells, the water inlet screen comprises a plurality of matrix-arranged cells, the support part (3) is arranged at the intersection of the transverse wires (1) and the longitudinal wires (2), the transverse wires (1) and the longitudinal wires (2) are connected to the support part (3), the height of the support part (3) is greater than the thickness of the transverse wires (1) and the longitudinal wires (2) of the cell, the support part (3) is used for contacting a membrane sheet of the spiral membrane element, and the transverse wires (1) and the longitudinal wires (2) are in different planes in the thickness direction of the water inlet screen.

Description

Technical Field

[0001] This application belongs to the field of membrane separation technology, and specifically relates to an inlet separator for spiral wound membrane elements and a spiral wound membrane element. Background Technology

[0002] High-pressure membrane separation technologies (such as nanofiltration and reverse osmosis) play a crucial role in seawater and brackish water desalination, industrial wastewater treatment, and high-quality reuse of municipal sewage. The membrane elements used in high-pressure membrane separation technology can be spiral wound membrane elements, which include membrane sheets, feed gas separators, product gas separators, and a central product pipe. The feed gas separator is typically made of a high-molecular-weight polymer (such as polypropylene) and consists of a periodically repeating diamond-shaped mesh formed by two layers of interwoven wires. The feed gas separator is a vital component that separates adjacent membrane sheets, supporting them, creating flow channels, and enhancing mass transfer.

[0003] However, the inlet screens in the existing technology have two drawbacks:

[0004] (1) Local dead zones exist, which exacerbate membrane fouling. For example, dead zones are easily formed at the junctions of mesh fibers, which makes it easy for pollutants to accumulate. Microorganisms can easily attach and multiply in the dead zones, further blocking the flow channels, resulting in decreased flow field uniformity and increased membrane fouling rate.

[0005] (2) Due to the obstruction of water flow by the baffle configuration, the pressure drop in the flow channel (pressure loss from the feed water side to the concentrate side) is relatively large, resulting in high system energy consumption. In existing technologies, the pressure drop in the feed baffle is generally between 150 and 400 Pa / cm (at an inlet flow velocity of 0.12 m / s). Especially after membrane fouling, the flow resistance is even higher, and the pressure drop can reach more than four times the pre-fouling level, leading to even higher energy consumption. During long-term operation, excessively high pressure drop can damage the membrane element, causing seepage. Both of these defects severely affect the working efficiency of the membrane element and reduce its service life. Summary of the Invention

[0006] This application aims to provide an inlet separator and a spiral wound membrane element for use in spiral wound membrane elements, in order to solve or alleviate at least one problem existing in the prior art.

[0007] This application provides an inlet screen for a spiral wound membrane element, comprising multiple transverse wires, multiple longitudinal wires, and a support portion. The transverse and longitudinal wires are arranged in an alternating pattern to form cell sections. The inlet screen includes multiple matrix-arranged cell sections. The support portion is disposed at the intersection of the transverse and longitudinal wires, and both the transverse and longitudinal wires are connected to the support portion. The height of the support portion is greater than the thickness of the transverse and longitudinal wires in the cell section. The support portion is used to contact the membrane sheet of the spiral wound membrane element.

[0008] In the thickness direction of the inlet mesh, the transverse mesh wires and the longitudinal mesh wires are located in different planes.

[0009] In at least one possible implementation, the cross-sectional shape of the support is triangular, quadrilateral, pentagonal, hexagonal, circular, elliptical, or irregular.

[0010] In at least one possible implementation, the support portion is prismatic, and the cross-sectional shape of the support portion is rhomboid.

[0011] In at least one possible implementation, the ratio of the outer circle diameter of the support portion to the height of the support portion is less than or equal to 0.8 and greater than or equal to 0.5.

[0012] In at least one possible implementation, the cross-sectional shape of the transverse mesh wire and / or the longitudinal mesh wire is circular, elliptical, triangular, quadrilateral, pentagonal, hexagonal, or irregular.

[0013] In at least one possible implementation, the cross-sectional shape of the transverse mesh wire and / or the longitudinal mesh wire is rhomboid.

[0014] In at least one possible implementation, in the thickness direction of the inlet mesh, a pair of edges of the rhombus are located at the middle position of the transverse mesh wire or the longitudinal mesh wire.

[0015] In at least one possible implementation, the transverse mesh wires and the longitudinal mesh wires have the same cross-sectional shape and size.

[0016] The circumscribed circle diameter of the transverse or longitudinal mesh wire / the circumscribed circle diameter of the support portion is less than or equal to 0.7 and greater than or equal to 0.5.

[0017] In at least one possible implementation, for each cell, the length of both the transverse and longitudinal mesh wires is 1 mm to 4 mm.

[0018] The embodiments of this application also propose a spiral wound membrane element, which includes the inlet screen described in any one of the above technical solutions.

[0019] By adopting the above technical solution, and by making the height of the support part greater than the thickness of the transverse and longitudinal mesh wires of the cell, the support part can support the membrane surface, so that the transverse and longitudinal mesh wires do not contact the membrane surface, thereby reducing the resistance to water flow, reducing the pressure drop difference in the flow channel, and extending the service life of the membrane element. Attached Figure Description

[0020] Figure 1 A schematic diagram of the inlet screen of a spiral wound membrane element according to an embodiment of this application is shown.

[0021] Figure 2 A schematic diagram of the structure of a cell of the inlet screen of a spiral wound membrane element according to an embodiment of this application is shown.

[0022] Figure 3 A comparison diagram is shown showing the pressure drop difference per unit length of the inlet screen according to an embodiment of this application and a comparative example inlet screen.

[0023] Figure 4 A graph showing the decrease in membrane flux over time in a membrane fouling test is presented, comparing the feed screen according to an embodiment of this application and a comparative feed screen.

[0024] Explanation of reference numerals in the attached figures

[0025] 100 Inlet Separator

[0026] 1. Horizontal mesh

[0027] 2. Longitudinal wire mesh

[0028] 3 Support section Detailed Implementation

[0029] To more clearly illustrate the above-mentioned objectives, features, and advantages of this application, specific embodiments of this application are described in detail in conjunction with the accompanying drawings in this section. Besides the embodiments described in this section, this application can also be implemented in other different ways. Those skilled in the art can make corresponding improvements, modifications, and substitutions without departing from the spirit of this application; therefore, this application is not limited to the specific embodiments disclosed in this section. The scope of protection of this application should be determined by the claims.

[0030] like Figures 1 to 4 As shown, an embodiment of this application proposes a spiral wound membrane element, which includes an inlet screen 100 and a membrane sheet. The inlet screen can be wound into a cylindrical shape, and the membrane sheet can be wound around the inlet screen.

[0031] The inlet mesh 100 includes transverse wires 1, longitudinal wires 2, and a support 3. The transverse wires 1 and longitudinal wires 2 are arranged in an alternating pattern to form, for example, diamond-shaped cells. The support 3 can be positioned at the intersection of the transverse wires 1 and longitudinal wires 2. The inlet mesh includes multiple cells arranged in a matrix. Both the transverse wires 1 and longitudinal wires 2 can be connected to the support 3, thereby fixing the transverse wires 1 and longitudinal wires 2 through the support 3.

[0032] The transverse mesh 1 and the longitudinal mesh 2 are staggered vertically in the thickness direction of the membrane element. That is, in the thickness direction of the feed mesh, the transverse mesh 1 and the longitudinal mesh 2 are on different planes. The spiral wound membrane element formed in this way can promote turbulence, reduce flow dead zones, increase the shear force on the membrane surface, and enhance the antifouling ability.

[0033] Optionally, within the same cell, the transverse mesh 1 can be located radially outside the spiral wound membrane element of the longitudinal mesh 2.

[0034] The height h of the support part 3 can be greater than the thickness of the horizontal mesh 1 and the vertical mesh 2 of the cell. That is to say, both ends of the support part 3 protrude from the surface of the cell, so that the support part 3 can contact the upper and lower membrane surfaces of the diaphragm and the support part 3 plays a supporting role.

[0035] Reference Figure 2 The transverse mesh 1 can be located above the longitudinal mesh 2. Supported by the support portion 3, the transverse mesh 1 can be close to the upper membrane surface but not in contact with it. The longitudinal mesh 2 can be close to the lower membrane surface but not in contact with it. The upper and lower membrane surfaces are separated by the support portion 3, thereby forming a flow channel between them.

[0036] Within the same cell, the angle between the transverse mesh 1 and the longitudinal mesh 2 is between 90 and 150 degrees. The diagonal of the cell can extend along the axial direction of the spiral wound membrane element.

[0037] The horizontal mesh 1 of adjacent cells can be interrupted by the support part 3, and the vertical mesh 2 of adjacent cells can be interrupted by the support part 3.

[0038] The support portion 3 can be columnar. The cross-sectional shape of the support portion 3 can be triangular, quadrilateral, pentagonal, hexagonal, circular, elliptical, or irregular. Optionally, the support portion 3 can be prismatic, and its cross-sectional shape can be rhomboid. In the thickness direction of the inlet mesh, a pair of edges of the rhombus are located at the middle position of the transverse mesh 1 or the longitudinal mesh 2, so that the water flow encounters less resistance when passing through the edges of the transverse mesh 1 or the longitudinal mesh 2. The diagonal of the cross-section of the support portion 3 can extend along the axial direction of the spiral wound membrane element.

[0039] Furthermore, the support part 3 can be prismatic, and the height h of the prism can be from 26 mils to 34 mils. Optionally, the height h of the prism can be 26 mils, 28 mils, 31 mils, 34 mils, etc.

[0040] For each cell, the lengths of the transverse wires 1 and longitudinal wires 2 of the inlet mesh can both be between 1 mm and 4 mm. This size of transverse wires 1 and longitudinal wires 2 results in a cell size that is moderate and provides good anti-fouling performance.

[0041] Furthermore, the outer diameter d1 of the support part 3 and the height h of the support part 3 satisfy the following relationship: 0.5≤d1 / h≤0.8.

[0042] The cross-sectional shape and size of the transverse wire 1 and the longitudinal wire 2 can be the same. The circumscribed circle diameter d2 of the transverse wire 1 or the longitudinal wire 2 and the circumscribed circle diameter d1 of the support part 3 satisfy the following relationship: 0.5≤d2 / d1≤0.7.

[0043] Below, using the feed water separator of the spiral wound membrane element of this embodiment as an example, and a diamond mesh feed water separator of the same height and the same mesh unit size but without columnar support as a comparative example, hydraulic tests and membrane fouling tests are conducted to test and compare the pressure drop difference per unit length of the flow channel and the antifouling effect of the present invention and the comparative example.

[0044] First, using deionized water as the feed water, identical commercial reverse osmosis membranes were placed in two parallel membrane tanks of the cross-flow filtration device. The feed water separators of this application (example and comparative example) were placed on the two membrane sheets respectively. The feed water flow rate was adjusted to 0.12 m / s, and a hydraulic test was conducted. The pressure drop difference in the flow channel was measured and divided by the flow channel length to calculate the pressure drop difference per unit length of the flow channel. Subsequently, the deionized water was replaced with a mixed solution of 50 mmol / L Na₂SO₄ and 50 mmol / L CaCl₂, and a membrane fouling (scaling) test was conducted at a constant pressure of 1 MPa for 300 minutes.

[0045] Reference Figure 3 In hydraulic tests, the pressure drop difference in the flow channel can be compared. The pressure drop difference per unit length of the inlet baffle in this embodiment of the invention is 140 Pa / cm, while the pressure drop difference per unit length of the comparative example is 172 Pa / cm. The pressure drop difference per unit length of the inlet baffle in this application is reduced by 18.6% compared to the comparative example.

[0046] Reference Figure 4 In the membrane fouling (fouling) test, the relative membrane flux can be compared over time. Figure 4The dots in the diagram represent the relative membrane flux of the embodiments of this application, and the squares represent the relative membrane flux of the comparative examples. Relative membrane flux refers to the ratio of the membrane flux at a certain point in time to the initial membrane flux. In membrane fouling tests, the slower the relative membrane flux decays, the less membrane fouling occurs, indicating a better antifouling effect of the feed screen under the same conditions. The membrane flux decay rate of the feed screen embodiments of this invention is significantly lower than that of the comparative examples. When the filtration time reaches 300 minutes, the membrane flux of the embodiments only decays by about 40%, while the membrane flux of the comparative examples decays by 67%, indicating that the feed screen of this invention has a better antifouling effect.

[0047] The inlet screen and spiral wound membrane element of this application can achieve the following beneficial effects.

[0048] (1) By supporting the membrane surface through the support part 3, the transverse mesh wire 1 and the longitudinal mesh wire 2 can be kept out of contact with the membrane surface, thereby reducing the resistance to water flow and reducing the pressure drop difference in the flow channel.

[0049] (2) By placing the transverse mesh 1 and the longitudinal mesh 2 on different planes, the flow dead zone can be reduced, the shear force on the membrane surface can be increased, and the antifouling ability can be enhanced.

[0050] It should be understood that at least some aspects or features of the above-described implementation methods, embodiments, or examples can be appropriately combined.

[0051] It is understood that, in this application, when the number of parts or components is not specifically limited, the number can be one or more, where multiple refers to two or more. For cases where the number of parts or components shown in the drawings and / or described in the specification is, for example, two, three, four, etc., this specific number is generally exemplary and not restrictive, and can be understood as multiple, i.e., two or more; however, this does not mean that this application excludes the case of one.

[0052] In this application, unless otherwise expressly stated or limited, terms such as "installation," "assembly," "connection," "linking," "joining," "linking," "abutment," "communication," "connection," "conduction," "fixing," and "fastening" should be interpreted broadly, for example, they can be direct or indirect. For instance, regarding connection, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two components or the interaction between two components, unless otherwise expressly stated or limited. For instance, regarding communication / conduction, it can be direct communication / conduction or indirect communication / conduction through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0053] In this application, unless otherwise expressly stated or limited, a component being disposed in / installed in / located in / enclosed in / placed within, inside, or within another component can be either of the following two situations: a portion or a majority of the one component is located within the other component; or the one component is completely enclosed within the other component.

[0054] Although the present application has been described in detail using the above embodiments, it will be apparent to those skilled in the art that the present application is not limited to the embodiments described herein. The present application can be modified and implemented as alternative embodiments without departing from the spirit and scope of the present application as defined by the claims. Therefore, the description in this specification is for illustrative purposes only and does not have any limiting meaning for the present application.

Claims

1. A water inlet screen for a spiral wound membrane element, characterized in that, The inlet mesh includes multiple transverse meshes (1), multiple longitudinal meshes (2), and a support (3). The transverse meshes (1) and the longitudinal meshes (2) are arranged in an alternating pattern to form cell sections. The inlet mesh includes multiple cell sections arranged in a matrix. The support (3) is located at the intersection of the transverse meshes (1) and the longitudinal meshes (2). Both the transverse meshes (1) and the longitudinal meshes (2) are connected to the support (3). The height of the support (3) is greater than the thickness of the transverse meshes (1) and the longitudinal meshes (2) of the cell section. The support (3) is used to contact the membrane sheet of the spiral wound membrane element. In the thickness direction of the inlet mesh, the transverse wires (1) and the longitudinal wires (2) are located in different planes. The support portion (3) is prismatic, and the cross-sectional shape of the support portion (3) is rhomboid. The diagonal of the cross-section of the support portion (3) extends along the axial direction of the spiral wound membrane element. The ratio of the outer diameter of the support part (3) to the height (h) of the support part (3) is less than or equal to 0.8 and greater than or equal to 0.

5. The cross-sectional shape of the transverse mesh (1) and / or the longitudinal mesh (2) is rhomboid. In the thickness direction of the inlet mesh, a pair of edges of the rhombus are located at the middle position of the transverse mesh (1) or the longitudinal mesh (2).

2. The inlet screen for spiral wound membrane elements according to claim 1, characterized in that, The transverse mesh (1) and the longitudinal mesh (2) have the same cross-sectional shape and size. The outer circle diameter of the transverse mesh (1) or the longitudinal mesh (2) / the outer circle diameter of the support part (3) is less than or equal to 0.7 and greater than or equal to 0.

5.

3. The inlet screen for spiral wound membrane elements according to claim 1, characterized in that, For each cell, the length of the transverse wire (1) and the longitudinal wire (2) is 1 mm to 4 mm.

4. A spiral wound membrane element, characterized in that, The spiral wound membrane element includes the inlet screen as described in any one of claims 1 to 3.

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