SPACER WITH MIXING ELEMENTS, PARTICULARLY FOR MEMBRANE MODULES

Abstract

The invention relates to a spacer with mixing elements, particularly for membrane modules. The spacer comprises a three-dimensional net with mesh (1) having the shape of polygons with number of sides n≥5, with at least one pair of sides made of support beams (2) which are not in contact with one another, parallel to one another, preferably inclined from the axis defining the direction of the flow, each of which fits in the volume of a cylinder and is in contact with the surface of membranes (4), with at least one pair of vertices of the sides made of support beams (2) is connected with one another by means of two connectors (3) comprising mixing elements which are not in contact with the surface of both membranes (4) and forming between them an angle β<180°, each of the connectors (3) fits in the volume of a solid formed by twisting a cylinder along its longitudinal axis by 90°, the spacer having, at least on part of its surface, mixing elements fixed in the net mesh, each of which is made of two beams (101) of the height of 0.1-10 mm, preferably 0.3 mm, being support points of the membrane (103), which are in contact with the membrane (103) and comprise side edges of a polyhedron being a mesh of the net and are connected by at least two connectors (102a) and (102b), intersecting at an angle (γ) in the range of 0-180°, preferably 30°, or interweaving in at least one point of a flat projection on a plain defined by axes of the beams (101). The spacer makes it possible to minimize fluid flow resistance and operate with a high linear flow velocity in constant conditions.

Claims

1. A spacer with mixing elements, in particular for membrane modules, having the shape of a three-dimensional net with mesh in form of polygons comprising a three-dimensional net with mesh (1) having the shape of polygons with the number of sides n≥5, having at least one pair of sides made of support beams (2) which are in contact with two membranes placed on both sides of the spacer and are not in contact with one another, with the height (H), equal to the distance between the membranes, in the range of 0.1 to 10 mm and the length L of 0.1 to 10 mm, parallel to each other, each of which fits in the volume of a cylinder and is in contact with the surface of membranes (4), with at least one pair of the vertices of sides made of support beams (2) is connected with one another by two connectors (3) comprising mixing elements which are not in contact with the surface of both membranes (4) of the membrane module and form between them an angle β<180°, whereas each connector (3) fits in the volume of a solid formed by twisting a cylinder along its longitudinal axis by 90°, and the relation (z) of height (h) of connectors (3) to the height (H) of support beams (2) fits in the range of 1:1000 to 1:1.2, the spacer having mixing elements arranged at least on a part of its surface and fixed in the net mesh.

2. The spacer according to claim 1, comprising a mixing element made of two beams (101) of the height of 0.1-10 mm, being support points of the membrane (103), which are in contact with the membrane (103) and constitute side edges of a polyhedron being a mesh of the net and are connected by at least two connectors (102a) and (102b) of the length ratio of (102a) to (102b) in the range of 1:5 to 5:1, intersecting at an angle (g) in the range of 0-180°, or interweaving in at least one point of a flat projection on a plain defined by axes of the beams. (101).

3. The spacer according to claim 1, wherein the beams (101) of the mixing element have the shape of a solid belonging to a group comprising an ellipsoid, sphere, polyhedron, torus, or a segment of one of these solids.

4. The spacer according to claim 1, wherein connectors (102a) and (102b) in the mixing element are not in contact with the membrane (103).

5. The spacer according to claim 1, wherein connectors (102a) and (102b) of the mixing element are made of multi-filament yarn or a monofilament.

6. The spacer according to claim 1, comprising a three-dimensional net with hexagon-shaped mesh (1).

7. The spacer according to claim 1, comprising a warp knitted fabric with hexagon-shaped openwork, wherein each of the openwork bars formed by weave meshes constituting support beams (2), fits in the volume of a cylinder with the shape of the base similar to a circle or an ellipse, each connector (3) fits in the volume of a solid formed by twisting a cylinder with the shape of the base similar to an ellipse along it longitudinal axis by 90°.

8. The spacer according to claim 1, wherein support beams (2) have the shape of a solid selected from a group comprising an ellipsoid, sphere, polyhedron, torus, or a segment of each of these solids.

9. The spacer according to claim 1, comprising a monofilament or yarn of the thickness of 0.01 to 1 mm.

10. The spacer according to claim 1, comprising plastics in form of synthetic filaments, polymer block or molding belonging to a group comprising olefin plastics, halogenated olefin plastics, polyamides, polyesters, polyurethanes and methacrylate resins and polyaryl polymers.

11. The spacer according to claim 1, comprising cotton filaments.

12. The spacer according to claim 1, wherein the spacer is finished by impregnation.

13. The spacer according to claim 1, wherein the spacer is finished by impregnation in a solution of hardening polymer resin.

14. The spacer according to claim 1, wherein a surface on both sides is thickened by bringing it into contact and wetting its surface elements with a surface of a viscous binding solution.

15. The spacer according to claim 1, wherein both sides of its surface thickened by bringing it into contact and wetting its surface elements with a polymer or hardening monomer solution containing ionic groups, permanently binding with the spacer surface.

16. The spacer according to claim 1, wherein the spacer is made of a metal wire.

Description

[0046] The subject of the invention is presented in embodiments in the attached drawing in which:

[0047] FIG. 1 schematically shows a design of a fragment of a segment of the spacer, perspective view,

[0048] FIG. 2 shows an embodiment of a spacer with hexagon-shaped mesh, top view,

[0049] FIG. 3 shows a spacer with pentagon-shaped cross-section of the mesh, top view,

[0050] FIG. 4 shows a perspective view of diagram of a pentagon-shaped single mesh,

[0051] FIG. 5 shows the spacer according to the invention with pentagon-shaped mesh with two parallel walls,

[0052] FIG. 6 shows a macroscopic view of a single hexagon-shaped mesh of a spacer with two support beams and two pairs of connectors connected at the tips of the support beams;

[0053] FIG. 7 shows a fragment of the surface of the spacer in the form of an openwork warp yarn knitted fabric with mesh in form of hexagons; enlarged perspective view

[0054] FIG. 8 shows the relation of pressure drop to the linear flow velocity for various spacers,

[0055] FIG. 9 shows the relation of porosity to the thickness and design of spacers,

[0056] FIG. 10 shows the value of mass transfer efficiency coefficients in a pressure membrane module for various spacers;

[0057] FIG. 11 shows the relation of the limiting current density to the linear flow velocity for various spacers,

[0058] FIG. 12 shows a mixing element of the spacer comprising ellipsoidal beams and connectors;

[0059] FIG. 13 shows a mixing element of the spacer, wherein the connectors are not in contact with membranes,

[0060] FIG. 14 shows a mixing element of the spacer comprising beams in the shape of a prism with a rectangular base, and three connectors that do not come into contact with beams at the tips or membranes,

[0061] FIG. 15 shows a mixing element of the spacer positioned in the mesh of a three-dimensional net;

[0062] FIG. 16 shows a mixing element of the spacer positioned in the mesh of a three-dimensional net constituting the spacer; the mesh of the three-dimensional net with a mixing element was obtained from a prismatoid (104) by removing the bases and replacing two side walls with the shape of a mixing element according to the invention, thus obtaining a solid (105),

[0063] FIG. 17 shows a mixing element of the spacer used in the spacer made in the form of a three-dimensional net as an openwork warp knitted fabric,

[0064] FIG. 18 shows a graph illustrating results of a comparative experiment.

[0065] The spacer according to the invention is a three-dimensional net with meshes 1 in the shape of hexagons (n=6), with at least one pair of sides made of support beams 2 that are not in contact with one another, of the height H=0.4 mm and length L=3.0 mm, parallel to one another, inclined from the axis defining flow direction by an angle α=10°, each of which fits in the cylinder volume and is in contact with membrane surface 4. At least one pair of vertices of the sides made of support beams 2 is connected to one another through two sides made of connectors 3 being mixing elements. Connectors 3 are not in contact with the surface of both membranes 4 and form between them an angle β=120°. Each connector 3 fits in the volume of a solid formed by twisting the cylinder along its longitudinal axis by 90°, and the ratio z of the height h of connectors 3 to the height H of support beams 2 is 1:5. The spacer is made of polypropylene.

[0066] In another embodiment, the spacer according to the invention comprises a three-dimensional net with mesh in the shape of pentagons n=5.

[0067] In another particularly preferred embodiment, the spacer comprises a warp knitted fabric with hexagon-shaped openwork, wherein each of the openwork bars formed by weave mesh and being the beams of the spacer 2, fits in the volume of a cylinder with a base substantially shaped like an ellipse, and each of the connectors 3 fits in the volume of a solid formed by twisting a cylinder with its base similar to an ellipse along its longitudinal axis by 90°.

[0068] The spacer has mixing elements fixed in the net mesh arranged on a part of its surface, every mixing element of the spacer according to the invention is made of beams 101 in contact with the lower and the upper membrane 103, being the side edges of a polyhedron being the mesh of the net of the spacer, connected with at least two connectors 102a and 102b, which connect with beams 101 in any point of the beams 101 and intersect or interweave at an angle γ inside a figure defined by axes of beams 101 and the surface of membranes 103. Such a design means that the fluid flowing through the net is forced to flow around the mixing element in four different ways (under, over, from the left or the right side of the point where the connectors intersect of interweave). At the same time, the flow of the fluid is partitioned only to a small extent and as a result the pressure drop is not drastically increased.

[0069] In another embodiment of the spacer according to the invention, the mixing element is made of beams 101 in the shape of an ellipsoid and connectors 102a, 102b with connector to connector length ratio 102a:102b=1.0:1.0, connectors 102a and 102b are in contact with the beams 101 at the tips and the membranes 103 and intersect at an angle γ=45°,

[0070] In another embodiment of the spacer according to the invention, the mixing element is made of beams 101 shaped like a prism with a rectangular basis and connectors 102a, 102b, with the connector to connector length ratio 102a:102b 1.3:1.0, which intersect at an angle γ=35° and are in contact with beams 101, but are not in contact with membranes 103.

[0071] In another embodiment of the spacer according to the invention, the mixing element is made of beams 101 shaped like a prism with a rectangular base and one connector 102a and two connectors 102b with connector to connector length ratio 102a:102b=1.3:1.0, connector 102a and two connectors 102b are not in contact with the beams 101 at the tips or membranes 103 and intersect at an angle γ=35°.

[0072] In another embodiment of the design of the spacer according to the invention, the spacer comprises a net, wherein the mixing element is positioned in the mesh. The mesh of the three-dimensional net with a mixing element was obtained from a prismatoid 104 by removing the bases and replacing two side walls with a shape of the mixing element of the spacer according to the invention thus obtaining a solid 105. The mixing element of the spacer according to the invention comprises at least one wall of a polyhedron without bases which defines the mesh of a three-dimensional net constituting the design of the spacer. The polyhedron may be a prism or an antiprism or a pyramid or a truncated pyramid or a prism or a wedge.

In another embodiment of the design of the spacer according to the invention, the mixing elements are positioned in the mesh of a three-dimensional net which constitutes the spacer. In the embodiment, nine meshes of the net were connected, with each mesh with mixing elements obtained from a tetrahedron by removing the bases and two opposing side walls and replacing one of them with a shape of the mixing element thus obtaining a three-dimensional net.

[0073] In another embodiment of the spacer according to the invention, the mixing element was positioned in the spacer made in form of a three-dimensional net as openwork warp knitted fabric made of 20-filament polyamide yarn, wherein the bars of the openwork are beams 101, whereas two threads of the yarn connecting bars of the openwork are connectors 102a, 102b. In this embodiment, the knitted fabric is the spacer in form of a three-dimensional net comprising a mixing element with the height of beams 101 of 0.26 mm, the connector to connector length ratio 102a:102b=10:7 and an angle between connectors γ=20°.

[0074] The spacer is made of a polyamide monofilament or, alternatively, yarn of a thickness of 0.15 mm.

[0075] In another embodiment, the spacer is made of polyester multi-filament yarn of the thickness of 0.05 mm.

[0076] In other embodiments of the spacer according to the invention, support beams 2 may have the shape of an ellipsoid or a sphere, polyhedron or torus or comprise segments of each of these solids.

[0077] Also, depending on the embodiment, the spacer according to the invention may be made of plastics in the form of synthetic filaments, polymer block or molding included in a group comprising olefin plastics, halogenated olefin plastics, polyamides, polyesters, polyurethanes and methacrylate resins and polyaryl polymers.

[0078] In another special embodiment, the spacer with mixing elements is made of cotton filaments.

[0079] In another special embodiment, the spacer according to the invention is finished by impregnation in the solution of a hardening polymer resin.

[0080] In another embodiment, the spacer according to the invention has both sides of its surface thickened by bringing it into contact and wetting its surface elements with a polymer or hardening monomer solution containing ionic groups, permanently binding with the spacer surface.

[0081] In a particular embodiment, the spacer according to the invention is made of metal wire.

Comparative Test

[0082] The purpose of the test was to compare the relation between pressure drop and the linear flow velocity of a fluid in an electrodialyser of the length of 70 cm (FIG. 8). The tests were based on the use of commercial spacers of the thickness of 0.35 mm and 0.4 mm, and spacers according to the invention of the thickness of 0.2 mm, 0.26 mm and 0.35 mm. The tests showed that the spacer according to the invention is characterized by flow resistance that is approximately 20% lower as compared to results observed for commercial spacers of a similar thickness.

[0083] Porosity (FIG. 9) of commercial spacers of the thickness of 0.16 mm, 0.2 mm, 0.26 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.7 mm and 0.75 mm was compared with the spacer according to the invention of the thickness of 0.2 mm, 0.26 mm and 0.35 mm. The tests showed that the spacer according to the invention is characterized by higher porosity as compared to results observed for commercial spacers of a similar thickness.

[0084] Tests were performed in a pressure membrane module with the use of commercial spacers of the thickness of 0.26 mm, 0.45 mm and the spacer according to the invention of the thickness of 0.26 mm and 0.35 mm, linear flow velocity 0.075 m/s. Mass transfer efficiency co-efficient was calculated based on the obtained results (FIG. 10). The co-efficient is a product of mass transport co-efficient and pressure drop per unit of length. The highest mass transfer efficiency co-efficient was observed for a spacer of the thickness of 0.35 mm made by knitting technology, which was a result of a relatively good mass transfer co-efficient and particularly low flow resistance.

[0085] Tests were performed in an electrodialysis module with the use of commercial spacers of the thickness of 0.35 mm, 0.4 mm and the spacer according to the invention of the thickness of 0.35 mm. Limiting current density was determined for linear flow velocity of 1, 2 and 4 cm/s and diluate salinity of 0.4 g/dm.sup.3 (FIG. 11). Tests showed that the limiting current density value in a module with spacers according to the invention is higher than is the case for a module equipped with commercial spacers of a similar thickness.

Comparative Experiment

[0086] A commercial spacer of the thickness of 0.35 mm, wherein the mixing element comprises beams 101 which are in contact with the membrane and are positioned at an angle α=90° to the flow direction was compared with a spacer of the thickness of 0.36 mm, wherein the height of beams 101 was 0.36 mm, and the length ratio of connector 102a to connector 102b was 1.0:1.0, and the angle between connectors γ was 11°. Tests were conducted in an elctrodialyser equipped with four pairs of membranes PC-SK/PC-SA, with efficient membrane surface of 4.5 cm.sup.2. The obtained results are presented in a graph (FIG. 7) which shows the relation between Sherwood dimensionless number [Sh], which describes the mass transfer coefficient, and a dimensionless power number [Pn], which describes consumption of energy for pumping the fluid.

[0087] Results obtained during the comparative experiment show clearly that the use of a mixing element according to the invention made it possible to increase the mass transfer co-efficient by approximately 40% while maintaining energy consumption at the same level.