Spacer, method for producing same, and use thereof

Abstract

The present invention relates to a spacer (11) as support insert for a membrane module, having on both sides support elements (1, 2) which are spaced apart from one another, wherein the base surfaces (3) and top surfaces (4) and possibly also the lateral surfaces (9) of the support elements (1, 2) are provided with openings (5, 6, 10), and wherein the spacing surfaces (7) between the support elements (1, 2), like the openings (5, 6, 10), are permeable to a solid, liquid or gaseous medium, for use in a pressure-operated membrane module that can have a one-piece frame / spacer unit.

Description

[0001] Designation: Spacer, process for its manufacture and its

[0002] use

[0003] The present invention relates to a support insert for a membrane module (hereinafter referred to as a spacer), a filtration device, or generally a device for separating gaseous, liquid, or solid substances using membranes for separation (membrane module). Furthermore, the invention relates to the production and use of such a spacer and to a module or device comprising one or more such spacers.

[0004] Such spacers of membrane modules, as they are also known from US 5 254 259 A and DE 10 2014 100 659 B4, are used in a variety of membrane technology applications, for example in devices for pressure-retarded osmosis or forward

[0005] Osmosis applications, in devices for pressure-driven processes such as micro-, ultra-, nano- and hyperfiltration as well as for reverse osmosis processes, in devices for concentration-driven processes such as pervaporation, gas separation, dialysis, in devices for thermally driven processes such as membrane distillation and thermoosmosis as well as in devices for electrically driven processes such as electrodialysis, reverse electrodialysis, electrofiltration and in fuel cells.

[0006] The spacers are arranged either between two membranes or between a membrane and a membrane carrier, with the membrane(s) or the membrane carrier resting on the spacer so that the membrane on one side of the spacer is held at a distance from the opposite membrane or membrane carrier. The passages in the spacer are designed such that they form at least one flow path between at least one edge side and the front and / or back side of the spacer so that, for example, a liquid can flow along or across (perpendicular) to the membrane surface or membrane carrier surface and onto the membrane surface(s) on the other hand. This allows, for example, a liquid flow to be introduced into the spacer from the edge side, distributed over the membrane surface(s) and guided through them.The reverse process is also possible, in which a liquid flow entering through the membrane surface(s) is guided via the passages into the spacer to its edge side.

[0007] For the above-mentioned applications, it is known from the prior art to use technical woven, knitted, or nonwoven fabrics, for example, made of plastic threads or fibers, as support inserts or spacers for the respective membrane modules. The fluid flows through the cavities formed between the individual threads or fibers of the woven, knitted, or nonwoven fabric.

[0008] For example, EP 2 292 307 A1 discloses a membrane filter module in which a porous spacer material is arranged between a membrane and a membrane support plate. The spacer material consists of a nonwoven fabric that keeps the adjacent membrane at a distance from the surface of the membrane support plate, creating a flat flow path for the filtrate fluid through the nonwoven fabric between the membrane and the membrane support plate.

[0009] However, nonwovens, woven fabrics, knitted fabrics, and the like, when used as support inserts or spacers for membrane modules, usually have too low a liquid volume flow rate or too high a flow resistance. Depending on the discharge pressure of the liquid flowing through the spacer, strong fluctuations in flow resistance or volume flow rate sometimes occur. In particular, increasing discharge pressure is accompanied by a rapid drop in volume flow rate. All of this has a detrimental effect on the applications mentioned above, since the efficiency of the respective processes depends on the highest possible volume flow rate.

[0010] US 2008 / 0290031 A1 discloses a spacer for filter modules, which is arranged between two layers of a filter medium and comprises a substantially flat, structured sheet material with upper and lower projections. The upper and lower projections define an upper and a lower support surface for the layers of the filter medium, with the projections rising from the upper and lower surfaces by means of wall sections and terminating in upper sections. The upper and lower projections are spaced apart from each other in a direction parallel to the surface of the sheet material.

[0011] US 2007 / 0175812 A1 discloses a spiral-shaped separation membrane element intended to reduce the pressure drop of a feed-side channel and to be less susceptible to clogging in the feed-side channel. The separation membrane element comprises one or more separation membranes, one or more feed-side channel components, one or more permeation-side channel components, and a perforated hollow core tube around which the separation membranes, the feed-side channel components, and the permeation-side channel components are wound. The feed-side channel component is a mesh formed by fusion bonding (also called a spiral-wound element).

[0012] Finally, DE 10 2014 100 659 B4 describes a spacer for a membrane module characterized by support elements formed on the front and back of the spacer, which serve as support surfaces for a membrane or membrane carrier and which have through-openings. Flow paths between the edge sides and the front and back of the spacer serve to guide and distribute liquids. All of these spacers or support elements known from the prior art still require improvement in terms of their performance. This means that the throughput of liquids, gases, or solids to be separated (volume throughput) is still unsatisfactory. Fluctuations in flow resistance and thus in volume throughput occur. A pressure building up in the module amplifies the drop in volume throughput as the delivery pressure increases.

[0013] Additional problems arise with the handling and installation of the spacers known from the state of the art, which ultimately result in a reduced volume flow through the module and thus a loss of efficiency. This is particularly evident with spacers made of woven, knitted, or nonwoven fabrics made of a wide variety of materials. In these cases, the membranes do not lie flat or evenly against or on the spacers, which, given the low thickness of these materials, can lead to uneven or wavy membrane surfaces, for example, and thus to a loss of volume flow. Attaching the membranes to the spacer is also often problematic, especially in these cases.

[0014] Nonwovens, knitted fabrics, woven fabrics and the like consist of individual fibers or threads that are connected to one another to form a textile fabric either by tangling, stitching or via a system of intersecting, alternating warp and weft threads. The relative arrangement of the individual fibers and threads to one another is not rigid, however, but can be subject to continuous changes or shifts, for example in the event of fluctuations in the delivery pressure of the liquid flowing through the support insert. The displacement of the threads or fibers relative to one another simultaneously leads to a change in the flow cross-section of the passages formed between the threads or fibers and consequently to the described fluctuations in flow resistance or volume throughput. In the woven, knitted fabrics and nonwovens known from the prior art, all threads or fibers have a curved orwinding course, so that the contact surfaces between the support insert and the membrane on top are rounded due to the curvature of the fiber and thread sections that form the contact surface for the membrane. The rounded transition from the actual contact surface to the interior of the support insert, i.e. to the passages, sometimes has very shallow angles. When pressure is applied to the membrane in the direction of the support insert (the spacer), this results in the membrane deforming under the influence of pressure and clinging to the rounded fiber or thread sections. This greatly increases the membrane contact surface and at the same time reduces the volume throughput through the membrane, since at those points where the membrane is in direct contact with the support insert, no liquid can be transported through the membrane. The disadvantage of this is that the active membrane surface and thus the effectiveness of the membrane is greatly reduced.

[0015] The object of the present invention was therefore to provide a spacer that is suitable for a wide variety of applications and that largely avoids the disadvantages of the prior art or at least improves its properties. This applies in particular to increasing the volume throughput.

[0016] This object is achieved by a spacer according to claim 1. Advantageous embodiments of the invention are specified in the subclaims.

[0017] The inventors started from their earlier invention DE 10 2014 100 659 B4 and were able to further develop and improve it in various respects, whereby in particular the main objective could be achieved, namely the generation of a maximum flow or volume flow rate while minimizing the pressure loss during use of a membrane module according to the invention.

[0018] The spacer according to the invention is characterized by a maximum of open and thus permeable areas. A preferred volume ratio of closed to open areas of the spacer is 30% (closed) to 70% (open areas). Both sides of the spacer have raised support elements, which are arranged in a grid pattern on each side and are arranged on horizontally running grid threads. These threads are spaced apart from one another and form the base of the spacer. Raised support elements on both sides are preferably arranged in a grid structure on this base. The support elements can be arranged with a wide variety of geometries. The horizontally running grid threads are held together in two dimensions (x / y plane) by the base surfaces or by the sides of the open base surfaces of the support elements arranged on both sides, ultimately forming a basic network or a basic grid as the basis of the spacer.

[0019] The support elements serve to support the filter membrane or both sides of the filter membranes, which rest flat and evenly on these support elements, i.e., without undesirable rippling of the membranes, as is often the case with state-of-the-art spacers. The support elements can have any desired geometry. Circular, triangular, rectangular, or square bases are preferred. The support elements as a whole preferably have the shape of a truncated cone or a truncated pyramid with the preferred bases.

[0020] To maximize the volume flow rate and minimize the flow resistance of the spacer, the support elements have through-holes, preferably with a round or rectangular cross-section. These through-holes can be located on the top and / or side surfaces of the support elements. The base surface of the support elements is preferably completely open and thus completely permeable, except for the grid threads to which the support elements are attached and the side lines of the base surfaces that connect the grid threads. The through-holes on the top surfaces of the support elements are as large as possible but are also selected to ensure a secure and even support of the filter membranes.

[0021] The area between the grid or mesh threads between the support elements is also preferably completely open and thus permeable.

[0022] In principle, the support elements located on each side of the spacer according to the invention can have different geometries (cross-sectional shape and / or size).

[0023] The support elements according to the invention are arranged on both sides of the spacer at a predetermined distance. Open areas defined by the grid threads are preferably located between the support elements. The spacing between the support elements in the x / y plane of one side of the spacer preferably corresponds to the size or edge length of the base area of ​​the support elements. The type and spacing of the support elements do not have to be identical on both sides of the spacer. The preferred arrangement of the support elements on the spacer is indicated in the drawings accompanying this description.

[0024] Preferably, the transition between that region of the support element which forms the support surface for the membrane or the membrane carrier and the adjacent regions of the support element which form the boundary of the passages is essentially abrupt. Advantageously, the transition occurs at an angle of at most 135°, in particular at most 110°, preferably of approximately 90°, wherein the information relates to the angle enclosed by the said regions. This measure prevents the supporting membrane, under the influence of pressure, from conforming to those regions of the support element which define the boundary of the passages but are not intended to be part of the support surface. The effective support surface for the membrane is thus well-defined and remains constant regardless of the pressure conditions in the membrane module, in particular regardless of any pressure fluctuations.Consequently, the active membrane area, i.e. those areas of the membrane that are not in contact with the support elements but can be freely flowed through, remains constant regardless of the pressure conditions in the membrane module.

[0025] The support elements are preferably arranged in a lattice structure, in particular a cross lattice, line lattice, honeycomb lattice or ring lattice structure. The geometry of the lattice structure is preferably adapted to the geometry of the membrane module. For example, it is conceivable to use a ring lattice structure in a cylindrical membrane module in which the membranes or membrane supports are designed as circular disks. Line lattice structures are advantageously suitable for creating linear flow paths. Honeycomb lattices are characterized by particularly high stability. Cross lattices are advantageous for essentially rectangular membranes or

[0026] Membrane support surfaces are used.

[0027] The support elements preferably have a base surface from which the support element emerges as a three-dimensional body. In order to adapt the arrangement of the individual support elements to the lattice structure of the support element with a view to the lowest possible flow resistance while simultaneously maintaining a sufficiently large contact surface, at least one of the support elements, and preferably all of the support elements, has a rectangular, square, circular, honeycomb-shaped, or triangular base surface. Combinations of different base surface shapes are also conceivable. Support elements with a triangular base surface are, for example, preferably suitable for an arrangement in a ring lattice structure. Accordingly, honeycomb-shaped base surfaces are advantageous in a honeycomb-shaped arrangement of the support elements.

[0028] The choice of the shape and / or arrangement of the support elements can also depend on the physical properties, such as the viscosity, of the fluid flowing through the membrane module. For example, cylindrical support elements promote laminar flow, whereas support elements with edges lead to turbulent flow.

[0029] As explained, the support elements are arranged in several, preferably two, planes. Particularly advantageous is the arrangement with a lattice structure offset from one another in the respective planes. Such an arrangement is characterized by particularly low flow resistance. The term "arrangement in one plane" in this case refers not only to the arrangement in one plane in the strictly mathematical sense, i.e., in a plane spanned by two straight lines, but also to other two-dimensional arrangements of the support elements, such as in a curved plane, on a cylindrical surface, or the like. The top and bottom sides of the spacer are considered two different planes.

[0030] To form the spacer as a coherent unit, the support elements of different levels are connected to one another according to a further advantageous embodiment of the invention. The connection can be made either directly or via spacer elements.

[0031] According to a further advantageous embodiment of the invention, the support elements or the spacer are made entirely of metal, ceramic, and / or plastic, in particular of a polymeric plastic, for example, polypropylene. The choice of material for the support elements can be determined, among other things, depending on the application area of ​​the membrane module and / or the physical and chemical properties of the fluid flowing through the membrane module.

[0032] Depending on the geometry, material and arrangement of the support elements as well as the overall structure of the spacer, different manufacturing processes can be considered.

[0033] One possible method is injection molding using an injection molding machine, in which the material, preferably plastic, is plasticized in an injection unit and injected into an injection mold. The cavity of the mold determines the shape and surface structure of the finished workpiece. Injection molding is particularly suitable for large-scale production and is the preferred manufacturing method for the spacer, which is preferably made of plastic (e.g., polypropylene).

[0034] Alternatively, the spacer can be manufactured by compression molding, particularly by deep drawing or thermal drawing. Various variants of compression molding are conceivable, such as compression molding using molding tools, compression molding using active media such as gases or liquids, or high-speed molding. These processes are particularly advantageous for forming the support elements in different planes from a film-like or thin, plate-like material, with at least parts of the starting material advantageously forming an intermediate layer that connects the support elements to one another. Similarly, stamping processes can also be used, in which the support elements of the spacer are formed from a starting workpiece using stamping tools.

[0035] Preferred is production by selective laser sintering, i.e., by a 3D printing process in which spatial structures of the spacer are produced by sintering a powdered starting material. This process is particularly suitable for complex, particularly multi-layered support inserts with multiple levels.

[0036] Stereolithography processes can also be considered, in which the workpiece is built up layer by layer from computer-generated CAD data using grid points that materialize freely in space. This process is also particularly suitable for complex, particularly multi-layered support inserts that are to be manufactured from a polymer plastic.

[0037] Similarly, a fused deposition modeling process can be used, which builds up a workpiece layer by layer from a meltable plastic. The process involves liquefying a wire-like plastic material by heating and then solidifying the material by cooling after application. The material is typically applied by extrusion using a heating nozzle that can be freely moved within the production plane.

[0038] Alternatively, a multijet modeling process is also conceivable, in which the workpiece is built up layer by layer using a print head with several linearly arranged nozzles.

[0039] According to an advantageous embodiment of the invention, the thickness of the support insert (spacer) (between the cover surfaces of the support elements) from front to back is between 0.3 mm and 5 mm, in particular between 1.6 mm and 2.5 mm.

[0040] According to a further advantageous embodiment of the invention, the thickness of a plane is between 0.2 mm and 2 mm, in particular between 0.3 mm and 1 mm, particularly preferably between 0.4 mm and 0.7 mm.

[0041] According to a further advantageous embodiment of the invention, the distance between two adjacent planes (corresponding to the thickness of the grid threads) is between 0.05 mm and 1 mm, in particular between 0.1 mm and 0.4 mm.

[0042] According to a further advantageous embodiment of the invention, the diameter or edge length of the base area of ​​a support element is between 1 mm and 5 mm, in particular between 1.4 mm and 2.5 mm. This also preferably applies to the distances between the support elements on one side.

[0043] According to a further advantageous embodiment of the invention, the diameter or the edge lengths of the through opening are between 0.2 mm and 4 mm, in particular between 0.5 mm and 1.5 mm.

[0044] According to a further advantageous embodiment of the invention, the distance between adjacent support elements of a plane is between 0.2 mm and 4 mm, in particular between 0.8 and 2 mm.

[0045] The spacer according to the invention can be designed with or without edges. The edges are preferably made of solid material and have no spacer structure. As a rule, no special fastening of the spacer in the membrane module is required. The spacer is preferably manufactured as a precisely fitting insert. Spacers with and without edges are manufactured in a single work step using one of the aforementioned processes. The edges of the spacer can be of different widths as required. The thickness of the edges can be the same as, smaller than, or larger than the thickness of the spacer (DS). This depends in particular on the installation situation and the nature of the transition areas in the frame part of the module that accommodates the spacer.

[0046] The spacers according to the invention are characterized by high stability combined with high flexibility, which makes their use advantageous in all membrane modules, regardless of their geometry. At the same time, it ensures that the liquid volume flow through the spacer and the membranes adjacent to it is as high as possible, regardless of the discharge pressure of the medium to be treated, and that the flow resistance generated by the spacer is as low as possible, while still providing sufficient support for the often very thin and fragile membranes. Generally speaking, the spacer is designed in detail to match the respective membrane so that the membrane can achieve optimal performance under the specified operating conditions.

[0047] The spacers according to the invention are suitable for all separation or filtration processes that utilize pressure-driven membrane technology, such as in a plate-and-frame system. Examples include ultrafiltration, nanofiltration, and reverse osmosis. Examples of application areas and technologies include osmotic power, wound modules, and modules where aeration and humidification of surfaces play a role (e.g., fuel cells), as well as general filtration and mass transfer at interfaces.

[0048] Further objects, advantages, features, and possible applications of the present invention will become apparent from the following description of an exemplary embodiment with reference to the drawings. All described and / or illustrated features, individually or in any meaningful combination, constitute the subject matter of the present invention, regardless of their summary or reference to the patent claims.

[0049] Preferred embodiments of the spacer according to the invention are presented below, without limiting the invention thereto. The features presented and their arrangement can be freely combined, as long as such a combination promotes the purpose of the invention.

[0050] Figure 1 shows a schematic representation or schematic diagram of a preferred embodiment of the spacer spanned in a two-dimensional X / Y coordinate system.

[0051] Figure 2 shows an isometric view of the spacer according to Fig. 1 with elevations (support elements) drawn on the front and back.

[0052] Figure 3 shows a side view of the spacer according to Fig. 1 .

[0053] Figure 4 shows an embodiment of the elevations or support elements on the front and back of the spacer.

[0054] Figure 5 shows the frame-spacer composite according to the invention as an integrated component that is manufactured in one process step.

[0055] Fig. 1 shows a schematic diagram of a preferred embodiment of the spacer 11, which is spanned in an X / Y coordinate system. It is a top view. Here, X denotes support elements above the x / y plane, i.e. in the +z direction in a three-dimensional representation, and 0 support elements on the underside of the spacer, which extend in the -z direction. The lines a parallel to the x-axis represent grid threads. Two parallel threads are connected to one another via the support elements X or by their boundaries b of the base surfaces of the support elements X, which run parallel to the y-axis. The connection of the line pairs a / a is made in an analogous manner via the base surfaces of the support elements 0 on the underside of the spacer.

[0056] Fig. 2 shows the spacer 11 with the arrangement of the support elements (X=1 and O=2). The base surfaces 3 and the cover surfaces 4 of these support elements 1, 2 are provided with openings 5, 6. These openings 5, 6 can have any shape (e.g. round, elliptical, square, rectangular). The aim is to achieve an optimal compromise between the largest possible openings to maximize the volume throughput and a remaining cover surface that allows a dimensionally stable support of the membrane. In addition, the side or jacket surfaces 9 can also be provided with corresponding openings. Finally, the spacer surfaces 7 between the support elements 1, 2 are also permeable, so that the medium to be cleaned or processed (preferably a liquid with a solid content) can pass through the spacer almost unhindered and in all directions (e.g. in directions a and b).

[0057] At the same time, the medium to be processed can flow on each side of the spacer in the x / y direction (directions a and b) and thus be distributed along and across the membrane surfaces. This means that flows in all three dimensions (x / y: along a plane and z-direction flow through the spacer) are possible.

[0058] Fig. 3 shows a side view of the spacer 11 according to Fig. 1 . Therein, DS denotes the thickness of the spacer including the support elements 1, 2 on the front and back sides, and DG denotes the thickness of the grid threads a and b, respectively, on which the support elements 1, 2 are arranged. Finally, Fig. 4 shows a preferred embodiment of the support elements 1, 2 with openings 5 ​​in the cover surfaces 4 and openings 6 in the base surfaces 3. Furthermore, openings 10 are shown in the side walls or lateral surfaces 9 of the support elements 1, 2.

[0059] Frame-spacer composite as an integrated component.

[0060] Fig. 5 shows the frame-spacer composite according to the invention as an integrated component that is manufactured in one process step.

[0061] In a particularly preferred embodiment of the present invention, the spacer according to the invention is used in a rigid frame-spacer assembly for the production of membrane modules with optimal flow for PRO operation (PRO = Pressure Retarded Osmosis). The rigid frame-spacer assembly is manufactured as an integrated assembly in a single process step (see Fig. 5).

[0062] The PRO process for energy generation using aqueous solutions with different salt contents currently uses modified reverse osmosis modules.

[0063] Reverse osmosis modules are technically designed so that there is an inlet into the module (feed) and two outgoing volume flows (retentate and permeate).

[0064] For the PRO application, two feeds (Feed 1 = brine and Feed 2 = water) and two outgoing volume flows (Outlet 1 = diluted brine and Outlet 2 = residual water) are generally required.

[0065] To enable the use of reverse osmosis modules for PRO, the "permeate side" of the modules was equipped with an additional water inlet. These measures should be considered an "emergency solution." They do not optimally guide the water-side flow rate and result in an insufficient water supply to the back of the membrane during PRO operation. This undersupply occurs particularly at diversion points, where dead zones form where the flow completely stops.

[0066] WO 2012 / 084960 A1 describes, for the first time, a module designed directly for PRO operation (2 incoming volume flows, 2 outgoing volume flows). The module is intended for use in seawater / freshwater applications. For this module, the frames are manufactured using injection molding, a spacer material of your choice is precisely cut to the frame's internal dimensions, the spacer material is fixed precisely in the center of the frame, and the membranes are glued to the inner edge of the frame on both sides. The relatively thin membranes, with a thickness of approximately 150 μm, must be glued absolutely tightly to the frame with tape (a sealing material for compensating for unevenness with an adhesive applied to both sides) and also ensure the stability of the frame to the spacer.

[0067] In conventional plate-frame designs, solid, impermeable plastic materials are used for the membrane support. The filtrate (permeate) is transported away by a spacer material (fabric, fleece, or similar) placed between the plate and the membrane. The finished plate package has a sandwich-like structure and consists of membrane + spacer + plate + spacer + membrane.

[0068] According to the present invention, the spacer or spacer structure is manufactured together with the surrounding frame in a single production step. This means that the frame and spacer form an integrated component. Through the joint manufacturing process, both elements of the component (frame + spacer) are provided with increased mechanical stability. The spacer is firmly connected to the frame. The water feed from the frame's water feed channel into the spacer interior and the opposite discharge from the spacer interior into the frame's water outlet channel can be achieved through joint manufacturing with an optimized access slot, which enables even water distribution within the spacer interior.

[0069] The membranes are then sealed to the inner edge of the frame on both sides. No sealing material or adhesive is used. The seal is completely tight. The very thin membrane does not have to provide stability for the frame-spacer assembly; rather, the frame-spacer assembly supports and secures the membrane. Unlike adhesive or welding techniques, the sealing makes it possible to tightly bond the membrane directly to the frame, even with the active side.

[0070] Below you will find further explanations of the terms frame and frame-spacer assembly with regard to the PRO module structure.

[0071] With the described frame-spacer composite with sealed membranes, hereinafter referred to as "frame", frame stacks can be formed which, in conjunction with pressure pipes into which the stacks are inserted, form a PRO module.

[0072] The stacked frames form internal channels for the water supply and drainage, as well as external channels with the pressure pipe for the brine supply and drainage. The channel lengths within the module can be designed in segments of any length on the water and brine sides, depending on the PRO conditions. Within a segment, all frames are fed in parallel, and the end of the segment flow is sealed, transforming the water outlet channel of the first segment or the brine outlet channel of the first segment into the respective feed channel of the second segment. Corresponding diversions occur in all additional segments of a module.

[0073] The segmentation enables a precise distribution of brine and water in the module depending on the brine concentration and prevents the formation of “dead zones” that lead to crystallization and concentration polarization on the brine side and suppression of water flow from the water to the brine side.

[0074] The membrane support plate used in conventional modules is replaced in the inventive PRO module by a frame-spacer composite produced using 3D printing or the Freeformer. The frame and spacer are manufactured in a single printing process and form a solid, stable unit.

[0075] The spacer material is "open," offering vertical and horizontal flow options. At the same time, the spacer material has a finely structured support structure for the membranes. This support structure prevents the membranes from being forced into the spacer, even at higher system pressures of up to 150 bar.

[0076] The sandwich-like structure is reduced to membrane + spacer + membrane compared to the state-of-the-art. Due to the open structure of the spacer and the short flow paths within the spacer, the pressure drop for the permeate outflow or the PRO water feed is reduced to a minimum compared to the state-of-the-art (approximately 70% less).

[0077] The maximum operating pressure is preferably 80 bar in PRO mode. The higher pressure allows saturated salt solutions to be used, making energy generation significantly more efficient. The compact, stable design of the frame-spacer assembly also enables optimal backflow, as required for pressure-retarded osmosis. Another important aspect of the frame-spacer assembly is the seal-free connection of the membrane through sealing, laser welding, or gluing.

[0078] The frame-spacer assembly can be manufactured in any size. The spacer area can take on any geometry. It can be round, rectangular, square, or specially shaped according to requirements.

[0079] The newly designed frame offers flexible combinations for modular construction, which can be varied to suit the separation task. The frame can be used in the module design for typical cross-flow operation for membrane separation tasks (liquid systems with reverse osmosis, nanofiltration, ultrafiltration and microfiltration as well as gas separation systems) and can be equipped with one feed and two discharge lines for retentate / concentrate and permeate / filtrate. The feed can be segmented as required within the frame stack depending on the application. The frame can also be equipped with two feeds and two discharge lines and can therefore be used for dialysis, forward osmosis, pressure-retarded osmosis and similar applications. The feed and discharge lines can be segmented as required within the frame stack depending on the application.

[0080] The frame-spacer system opens up new application possibilities for membrane systems. Up to 200 or more frames are used in the modular structure.

[0081] In cross-flow operation (reverse osmosis, nanofiltration, ultrafiltration, microfiltration), the external feed can be segmented in a single stage or in multiple stages. Segment lengths and the number of segments can be planned according to the application. For permeate discharge, one direction can be selected, or both outlets can be used.

[0082] In PRO mode, the internal feed (usually water) can also be segmented. The internal segmentation can be different from the external one and is determined exclusively by the PRO flux. Furthermore, the internal feed can be set up in parallel or countercurrent to the external feed.

[0083] The reversal of the feed-in direction is possible for the external and internal feed-in.

[0084] The frame-spacer composite according to the invention is preferably manufactured using SLS (Selective Laser Sintering) or SLS-FDR (SLS Fine Detail Resolution). This is a well-known additive manufacturing process (3D printing) for producing three-dimensional structures from powdered starting materials by sintering with a laser.

[0085] Another very suitable method is the production of the composite using various types of the so-called Freeformer for plastic products, which is sold by the company Arburg in Germany and advertised on the Internet.

[0086] Polymeric plastics such as polypropylene are preferred materials for the production of the composite.

[0087] 1 support element X above the x / y plane

[0088] 2 Support element 0 below the x / y plane

[0089] 3 Floor space

[0090] 4 Cover area

[0091] 5 Opening in base area 3

[0092] 6 Opening in deck area 4

[0093] 7 Clearance area (open)

[0094] 8 edges

[0095] 9 Shell surface

[0096] 10 Opening in shell surface 9

[0097] 1 1 Spacer

[0098] DS Thickness of the spacer

[0099] DG Thickness of the grid threads

[0100] 12 frame-spacer composite

[0101] 13 Feed channel (inlet / feed)

[0102] 14 Outlet channel side

[0103] 15 Feed channel water

[0104] 16 Water outlet channel

[0105] 17 Mounting opening

[0106] 18 Membrane cover of the spacer structure (both sides; membranes sealed all around with the edge of the frame-spacer composite)

[0107] 19 surrounding frame edge to which the membrane is sealed

[0108] 20 Slot in the middle of the frame on both sides; allows supply and removal to / from the spacer interior

Claims

Patent claims 1 . Spacer (1 1 ) as a support insert for a membrane module, which has support elements (1 , 2) on both sides which are spaced apart from one another, wherein the base surfaces (3) and cover surfaces (4) and optionally also the lateral surfaces (9) of the support elements (1 , 2) are provided with openings (5, 6, 10), and wherein the spacer surfaces (7) between the support elements (1 , 2) as well as the openings (5, 6, 10) are permeable to a solid, liquid or gaseous medium.

2. Spacer (11) according to claim 1, characterized in that the ratio (the area) of closed to open areas of the spacer (11) is not less than 30%:70%, based on the total surface of the spacer (11).

3. Spacer (1 1 ) according to claim 1 or 2, characterized in that the Support elements (1, 2) are arranged in a lattice structure.

4. Spacer (1 1 ) according to one of claims 1 to 3, characterized in that the transition between the cover surfaces (4) of the support elements (1 , 2) and the spacer surfaces (7) takes place abruptly, the transition taking place at an angle of at most 135 degrees.

5. Spacer (11) according to one of claims 1 to 4, characterized in that the support elements (1, 2) have a rectangular, square, circular, honeycomb-shaped or triangular base area (3).

6. Spacer (11) according to one of claims 1 to 5, characterized in that the openings (5, 6, 10) of the support elements (1, 2) have a round or rectangular cross-section.

7. Spacer (11) according to one of claims 1 to 6, characterized in that the support elements (1, 2) on the front and back of the spacer (11) have a lattice structure offset from one another.

8. Spacer (11) according to one of claims 1 to 7, characterized in that the spacer (1) consists of metal, ceramic or plastic, in particular of polypropylene.

9. Use of a spacer (11) according to one of claims 1 to 8 in a membrane module, in particular in a pressure-operated membrane module.

10. Membrane module, in particular pressure-operated membrane module, which has a spacer (11) according to one of claims 1 to 8.

11. Membrane module according to claim 10, characterized in that the spacer (11) is in the form of a one-piece frame-spacer composite (12).

12. Membrane module according to claim 1 1 , characterized in that the spacer (1 1 ) is covered on both sides with a membrane which is sealed onto the edge (19) of the frame-spacer composite (12).

13. One-piece frame-spacer assembly (12) comprising a spacer (11) according to one of claims 1 to 8.

14. A method for producing a spacer (11) according to one of claims 1 to 8, by injection molding, laser sintering, stereolithography, fused deposition modeling, multi-jet modeling, pressure forming, deep drawing or embossing.

15. Method for producing a one-piece frame-spacer composite (12) according to claim 13 by selective laser sintering (SLS) or with the aid of a freeformer for plastic products.

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