DE102014018481A1 - Ceramic filter membrane and filter module - Google Patents

Abstract

The invention relates to a ceramic filter membrane for filtering a fluid (50) which is produced according to the following steps: A providing a flexible support structure (1, 5, 8); B impregnating the carrier structure with a ceramic-containing slip mass (12); and C curing the slip mass (12) to the ceramic flat filter membrane (20), which is designed as a flat filter membrane, and a further filter membrane with finger pores and a ceramic filter module.

Description

Technical area

The present invention relates to two variants of filter membranes, as well as a filter module.

Ceramic planar membranes, so-called flat filter membranes, are known per se. These can be z. B. over extrusion or even a complex Foliengießtechnologie be made with downstream embossing and laminating. For reasons of cost, however, planar membranes are predominantly made of polymers which have distinct disadvantages in terms of chemical and thermal resistance as well as mechanical strength compared to ceramic membranes. In addition to flat filter membranes and winding membranes are known, which, however, can not be used for all applications due to the given geometry. In particular, when it comes to filtering in a confined space, no winding modules can be used.

State of the art

The EP 1 954 382 A1 discloses a flat filter module with a microporous polymer membrane layer.

The EP 1 284 251 A1 discloses a flat filter module with evenly stacked flat filter modules.

In addition, ceramic filter elements are known which are not planar, but are formed as a winding membrane.

Based on the aforementioned prior art, the object of the present invention is a filter membrane which is easy to produce, and to provide a filter module in a compact design and with high mechanical strength.

The present invention solves this problem by a filter membrane having the features of claim 1 or 3 and by a filter module having the features of claim 11.

Disclosure of the invention

• A Bereitstellen einer biegsamen faserhaltigen Trägerstruktur;
• B Tränken der Trägerstruktur mit einer keramikhaltigen Schlickermasse;
• C Aushärten der Schlickermasse zu der keramischen Filtermembra.

A ceramic filter membrane according to the invention for filtering a fluid is prepared according to the following steps

• A providing a flexible fibrous carrier structure;
• B impregnating the carrier structure with a ceramic-containing slip mass;
• C curing the slip mass to the ceramic filter membrane.

The ceramic filter membrane is characterized in that it is designed as a flat filter membrane.

By soaking the fibrous carrier material, the slurry material penetrates into the fibrous structure and settles on the surface of the fibers. The slip is present as a more or less viscous mass on the fiber. A ceramic membrane of this variant has hitherto been described only as a wound membrane. The filter membrane according to the invention, in its new shape as a flat filter membrane, allows any adaptation and shaping of the filter membrane to customer specifications with regard to shape and geometry which roll form of a wound membrane has hitherto not been possible. In this case, the filter membrane membrane is brought into shape in the production and is present after firing as a thin solid ceramic structure.

By using fiber-containing material of the support structure, it can be observed that a fibrous pore shape is not only superficially present but has remained behind in the ceramic material of the flat filter membrane due to the higher penetration depth of the ceramic-containing constituents into the support material. In this case, the cured ceramic has a similar microscopic structure as the fiber structure of the carrier material. Since no other methods are known to date for providing such a structure in a ceramic material, when a fibrous carrier structure is used, this can be a clear indication of a product using the aforementioned production steps.

Alternatively, a ceramic filter membrane according to the invention may have finger pores. A filter membrane with finger pores has hitherto not been known and represents an alternative to the aforementioned ceramic filter membrane with the fibrous structure.

Advantageous embodiments of the invention are the subject of the dependent claims.

• A Bereitstellen einer biegsamen porösen Trägerstruktur;
• B Tränken der Trägerstruktur mit einer keramikhaltigen Schlickermasse;
• C Verringerung der Löslichkeit von keramikhaltigen Bestandteilen in der Schlickermasse; und
• D Aushärten der Schlickermasse zu der keramischen Filtermembran.

The ceramic filter membrane with the finger pores can be produced by a so-called phase inversion. This manufacturing method comprises at least the following steps:

• A providing a flexible porous support structure;
• B impregnating the carrier structure with a ceramic-containing slip mass;
• C reducing the solubility of ceramic-containing ingredients in the slip mass; and
• D hardening of the slip mass to the ceramic filter membrane.

A porous support structure may consist of fibers, wherein a fiber structure with fiber spaces in the sense of the present invention is also understood as a porous support structure.

A ceramic-containing slip mass may preferably have polymer constituents which are homogeneously dissolved in a solvent. These polymer constituents in turn have ceramic particles which are dispersed in the polymer constituents or homogeneously distributed. In phase inversion, the solubility of these ceramic-containing polymer constituents is preferably lowered, resulting in precipitation of these ceramic-containing polymer constituents.

The polymer material of the polymer components are preferably selected from the following materials: cellulose, polyvinyl alcohol and / or polyvinylpyrrolidone or other water-soluble common polymeric binders.

By lowering the solubility of the ceramic constituents, in particular, these abovementioned polymer constituents can infiltrate from the slip into the pores or fiber interspaces of the support structure. By infiltrating the constituents, in particular the ceramic-containing polymer constituents, before curing into the porous support structure, after hardening in step D, a ceramic flat filter membrane with high mechanical strength and high porosity remains.

The reduction of the solubility of the ceramic-containing polymer constituents in the slip mass can be achieved in particular by adding a non-solvent in which the ceramic-containing polymer constituents are insoluble. It may be z. B. act water.

The ceramic-containing polymer constituents of the slip mass can have at least 10% by weight, in particular 40 to 75% by weight, of oxide-ceramic-containing, carbide-ceramic-containing and / or nitride-ceramic constituents both in the case of the flat filter membrane and the filter membrane with the finger pores.

The material of the support structure is, especially at temperatures below 2000 ° C, combustible. After removal of the carrier structure remain in the ceramic cavities, which correspond to the structuring of the support structure.

The ceramic filter membrane may preferably have a height of less than 5 mm, in particular a height of less than 1 mm. This corresponds to a preferred dimensioning of a flat filter membrane. The height is the smallest dimension compared to the length or the width of the flat filter membrane.

The ceramic filter membrane can advantageously have a fluid-conducting structure, in particular a single-layer row of channels arranged next to one another. This may particularly preferably be a single-layer row of side-by-side channels. Some or all channels are preferably terminally closed. Said channels may in a particularly preferred embodiment have a maximum channel diameter of less than 1 mm.

• A Bereitstellen einer biegsamen Trägerstruktur;
• B Tränken der Trägerstruktur mit einer keramikhaltigen Schlickermasse; und
• C Aushärten der Schlickermasse zu einer keramischen Flächenstruktur;

wobei die keramische Flächenstruktur mit der keramischen Filtermembran übereinander gestapelt und stoffschlüssig miteinander verbunden sind. Selbstverständlich kann die Abfolge aus Flächenstruktur und Flachfiltermembran mehrfach wiederholt werden, so dass eine Stapelstruktur entsteht.A filter module according to the invention comprises a ceramic filter membrane and a ceramic surface structure, for spacing and for supplying a fluid to be filtered and / or for discharging a permeate from the filter module. The ceramic filter membrane and / or surface structure are produced by at least the following steps:

• A providing a flexible support structure;
• B impregnating the carrier structure with a ceramic-containing slip mass; and
• C curing the slip mass to a ceramic surface structure;

wherein the ceramic surface structure with the ceramic filter membrane stacked one above the other and are materially interconnected. Of course, the sequence of surface structure and flat filter membrane can be repeated several times, so that a stack structure is formed.

As a result, a filter module in flat design can be realized in multiple layers. The filter module is characterized by a high filter efficiency.

Advantageous embodiments of the filter module are the subject of the dependent claims.

The ceramic filter membrane of the filter module can advantageously have a multiplicity of channels arranged side by side with channel tracks in a first propagation direction and the ceramic surface structure can have a multiplicity of channels arranged next to one another in a second propagation direction. The flat filter membrane can be aligned relative to the surface structure so that the two aforementioned propagation directions about a stacking direction extending axis offset from each other, in particular by an angle of 90 ° (± 5 °) offset from each other, are.

The height of the ceramic filter membrane of the filter module in the stacking direction can be at least twice as large as the height of the surface structure in the stacking direction.

The filter membrane of the filter module is formed as a flat filter membrane according to claim 1 or as a filter membrane according to claim 3.

According to the invention, the use of the filter membranes of the invention according to claim 1 or 3 and in particular in their arrangement in a filter module according to claim 11, for filtering process water, drinking water treatment, surface water treatment, wastewater treatment and recycling, for filtration applications in the food and beverage industry and the chemical industry and biotechnology and medical technology, in particular for blood filtration, and in automotive applications, in particular for water / oil separation.

Brief description of the drawings

Preferred embodiments of the invention will be explained in more detail with reference to the following figures. Show it:

1 : Sectional view of the structure of a first support structure;

2 : Sectional view of the structure of a second support structure;

3 : Sectional view of the structure of a third support structure;

4 Fig. 1: sectional view of the structure of an intermediate product in the production of a first filter membrane;

5 Fig. 1: sectional view of the structure of an intermediate product in the production of a second filter membrane;

6 : Sectional view of the structure of an intermediate product for a permeate plate or for a ceramic surface structure for producing a first filter module;

7 : Sectional view of the structure of the first filter membrane;

8th : First sectional view of a first filter module;

9 FIG. 2: a second sectional view of the first filter module perpendicular to the first sectional view of FIG 8th ;

10 : Sectional view of the first filter membrane as part of the first filter module;

11 : schematic representation of a fibrous carrier structure; and

12 : Schematic representation of a surface of a ceramic filter membrane with finger pores.

In membrane technology different filter membranes are used, which u. a. can be differentiated according to geometries or materials. So are u. a. Flat filter membranes known, which are formed as a sheet. In addition to flat-filter membranes, hollow-fiber membranes or wound membranes (wound sheet) are also known. The first filter membrane described below is designed according to the invention as a flat filter membrane. The initially shown in the prior art serrated or wavy flat filter membranes are initially made flat and then designed z. B. embossed in wave or trapezoidal shapes.

The first filter membrane designed according to the invention as a flat filter membrane, on the other hand, can be produced in such a way that free shaping can take place depending on the desired customer geometry. The flat filter membrane can also have a wave-shaped, trapezoidal, rectangular or zigzag-shaped cross section, without requiring a separate shaping step for this purpose. The flat filter membrane can be formed both as a flat or curved sheet. The bending or bends of the fabric as well as the cross section may be irregular and may be variably adjusted during manufacture.

Thus, a flat filter membrane, which is formed as an irregularly curved sheet having a corrugated or folded cross-section, can be realized by the method steps according to the invention. A flat filter membrane is characterized by a width to height ratio of greater than 5: 1, in particular greater than 7: 1. It can be bent, but does not have a full winding.

The first filter membrane is produced by applying a ceramic-containing slip to a flexible support structure to form an intermediate product.

The slurry contains, preferably as the main constituent, an inorganic substance from which the ceramic-containing membrane layer is formed in the course of production. A preferred inorganic substance may be an oxide ceramic-containing substance, in particular Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Y ₂ O ₃ and / or SiO ₂ or a substance containing no oxide ceramics. In principle, all the aforementioned ceramic-containing compounds can be used as the inorganic substance. Other particulate ingredients may also be included as in the above-described examples of slip.

The aforesaid inorganic substance may be dissolved, colloidally or in the form of a slurry in a solvent, e.g. As water present. The water is to be understood in this context as a solvent or carrier and not as part of the slurry.

In addition to the aforementioned inorganic substance, a polymer may additionally be present in the slip, which is preferably homogeneously dissolved. The polymer is preferably one or more of the following polymer compounds, in particular cellulose, polyvinyl alcohol and / or polyvinylpyrrolidone or other water-soluble common polymeric binders.

The flexible support structure, on which the slip is applied, is formed fibrous. An exemplary fiber structure is shown in FIG 11 shown. This representation is only schematic. There are also real fiber structures which can differ greatly from this idealized representation. The slip mass wets the surface of the fibers of the carrier material after it has been applied. The fiber spaces are not completely filled. Rather, it is a coating of the fiber surface. The coating may be irregularly thick and be particularly dominant at fiber crossing points. Overall, however, under microscopic observation of the surface of the flat filter membrane, z. B. by a SEM image, nor a fiber structure can be detected.

Subsequently, the intermediate product is subjected to a curing process leaving at least the ceramic material with a fibrous structure. This can be z. B. done in a kiln. In this case, the support structure is preferably burned.

The abovementioned support structures can particularly preferably be produced from a combustible material, more preferably from an organic and / or synthetic material, preferably with or from, in particular natural, fibers, in particular cellulose or cotton, preferably paper and / or at least one polymer , The abovementioned carrier structures can also have individual material layers made of a combustible fabric, mesh and / or nonwoven.

A filter membrane with comparable structure is from the DE 10 2012 012 941 A1 known. However, this filter membrane is configured as a single-layered wound membrane.

Particularly suitable is a flat filter membrane for filtering fluids with a high content of inorganic or organic solids or with high viscosity. Here winding membranes can partially clog.

The shape of the ceramic flat filter membrane in the cured state depends inter alia on the shape of the support structure. Therefore, in 1 to 3 some carrier structures shown. These are only exemplary embodiments.

The basic structure of the carrier structure consists of a flat layer or flat layer, to which a structured or profiled layer is applied. The connection of the structured z. B. wavy and flat layers can be realized by means of a ceramic adhesive which is applied to the crests of a corresponding corrugated layer. Also alternative connection methods such. B. punching or fusing, z. As in polymer or polymer fiber layers, can be used. Based on this basic structure, further flat membrane geometries can be realized.

1 shows a first support structure 1 , The support structure 1 has three layers of material, with a flat central position 2 and an upper and a lower wavy layer 3 and 4 , The corrugated layers are connected to the middle layer. This can be done by welding, gluing or otherwise.

Alternative to the wavy shape of the layers 3 and 4 , Each layer or all layers may also have a zigzag shape, a trapezoidal shape or a rectangular folding.

2 shows a second support structure 5 with a level location 6 and a wavy layer 7 , These two layers are interconnected as in the previous example.

3 shows a third support structure 8th comprising a corrugated center layer 9 and two flat layers 10 and 11 above and below the corrugated center layer 9 are arranged.

On the support structure then a ceramic-containing slip is applied. The 4 to 6 show different intermediate structures, which result after slip application.

4 shows an intermediate in the preparation of a first filter membrane. Starting from the in 2 illustrated second support structure 5 becomes a liquid ceramic-containing slip 12 as a layer on the support structure 5 applied. Of course, an analogous order can also be applied to the in 1 and 3 represented or applied to further alternative support structures. In 4 The slip is from the outside on the support structure 5 introduced. In the 2 and 4 shown carrier structure has elongated inner channels 13 on. The surfaces of the support structure 5 which are arranged on the outside are the surfaces which have the support structure to the environment and not the surfaces which the inner channels 13 limit. On these outer surfaces of the slip 12 applied. In the same way, the slip can also be applied to serrated, trapezoidal or other layers of a similar support structure and settle there on the fibers of the respective layers.

5 shows an intermediate in the production of a second filter membrane which is structurally similar to the first filter membrane. In this embodiment, the slip is 12 into the inner channels 13 the support structure 5 brought in. This forms inside the channels 13 a layer off. In this case, the ceramic-containing slip is preferably on the fibers of the corresponding layers 6 and 7 the support structure from.

6 shows an intermediate product for producing a surface structure 14 for supplying or discharging a fluid or a permeate plate for the fluid to be cleaned 20 and the purified permeate 21 , The surface structure may also be formed as a ceramic-containing filter membrane. This surface structure has a support structure analogous to the support structure 8th of the 3 on, with a wavy middle layer 9 and two flat layers 10 and 11 above and below the middle layer 9 , In this intermediate product is a layer of ceramic-containing slip 12 on at least one of the support structure to the environment limiting surface of the planar layers 10 and 11 , Due to the corrugated center layer has this surface structure 14 also channels 24 on.

The wavy middle layer 9 may be formed of any material in this embodiment, but which remains after the curing of the slurry layer. The wavy middle layer 9 can be provided as a support layer. The surface structure is subsequently also permeate plate 14 designated.

The ceramic-containing slip is then applied to the support structure. The 4 to 6 show different intermediate structures, which result after slip application.

4 shows an intermediate in the production of a first variant of a first filter membrane. Starting from the in 2 illustrated second support structure 5 becomes a liquid ceramic-containing slip 12 as a layer on the support structure 5 applied. Of course, an analogous order can also be applied to the in 1 and 3 represented or applied to further alternative support structures. In 4 The slip is from the outside on the support structure 5 introduced. In the 2 and 4 shown carrier structure has elongated inner channels 13 on. The surfaces of the support structure 5 which are arranged on the outside are the surfaces which have the support structure to the environment and not the surfaces which the inner channels 13 limit. On these outer surfaces of the slip 12 applied. In the same way, the slip can also be applied to serrated, trapezoidal or other layers of a similar support structure. It is advantageous if the slip partially in the layers 6 and 7 the support structure 5 seeped in order to achieve a firm connection of the resulting cured ceramic-containing layers with each other after curing of the slip material.

5 shows an intermediate in the production of a second variant of a first filter membrane, which is designed structurally similar to the first variant. In this embodiment, the slip is 12 into the inner channels 13 the support structure 5 brought in. This forms inside the channels 13 a layer off. Also in this embodiment, the ceramic-containing slip preferably seeps into the corresponding layers 6 and 7 the support structure, so that the channels are connected to each other after curing. In the in 5 shown first variant is by introducing the slip into the channels 13 the nominal size of these channels is reduced.

6 shows an intermediate product for producing a surface structure 14 for supplying or discharging a fluid or a permeate plate for the fluid to be cleaned 20 and the purified permeate 21 , The surface structure may be formed as a third variant of a first filter membrane. This surface structure has a support structure analogous to the support structure 8th of the 3 on, with a wavy middle layer 9 and two flat layers 10 and 11 above and below the middle layer 9 , In this intermediate product is a layer of ceramic-containing slip 12 on at least one of the support structure to the environment limiting surface of the planar layers 10 and 11 , Through the corrugated Middle layer has this surface structure 14 also channels 24 on. The wavy middle layer 9 can be provided as a support layer. The surface structure 14 , what a 6 is shown below, also permeate plate 14 designated.

7 shows a first variant of a first filter membrane 50 after passing through the manufacturing steps. This has a wavy position 15 and a planar position 16 made of hardened ceramic membrane material. Due to the wavy position 15 has the filter membrane channels 13 on which one in a first direction 80 run. The channels are through the corrugated layer 15 and the level location 16 limited and separated from each other. Thus, the filter membrane exists 50 preferably completely made of ceramic membrane material. The channels 13 can be terminal towards 80 through a closure material 27 locked. This detail will be in 10 detailed. In this case, the closure material may be a ceramic-containing mass, which the channels 13 , preferably diffusion-tight, closes.

An oncoming flow of the fluid to be filtered 20 can be done from the outside, for example parallel to the channels 12 , Then the fluid permeates 20 the wavy position 15 and the level location 16 made of ceramic membrane material and the permeate formed 21 will be on the other side of the filter membrane 50 discharged as purified fluid. On the other side of the filter membrane there is a lower pressure than in the environment in which the fluid is supplied.

Of course, the fluid to be cleaned can be directed and filtered in the opposite direction through the filter membrane at appropriate pressure conditions. In 7 is also very well illustrated the shape of the filter membrane. The ceramic-containing filter membrane 50 is rigid. However, this illustrated rigid shape can be easily realized in the production prior to curing depending on customer specifications.

In the following, a second filter membrane is also described in the context of the present invention, which is produced by a preferred method. It may be both an arbitrary filter membrane, such. B. to act a flat filter membrane or even around a winding membrane. The filter membrane according to the invention is produced by a so-called phase inversion process.

First, a support structure is coated with a ceramic-containing slip. This slip is phase inducible.

The carrier structure is preferably a porous material. The material may be fibrous, for example, wherein the fiber interstices in the context of the present invention are to be understood as pores. The abovementioned support structures can particularly preferably be produced from a combustible material, more preferably from an organic and / or synthetic material, preferably with or from, in particular natural, fibers, in particular cellulose or cotton, preferably paper and / or at least one polymer , The abovementioned carrier structures can also have individual material layers made of a combustible fabric, mesh and / or nonwoven.

However, the support structure is not limited to fibrous material but may be another porous material.

The ceramic-containing slip contains an inorganic substance from which the ceramic-containing membrane layer is formed in the course of production. A preferred inorganic substance may be an oxide-ceramic-containing substance, in particular Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Y ₂ O ₃ and / or SiO ₂ or a non-oxide-ceramic substance, in particular a carbidic or nitridic compound, eg. SiC, Si ₃ N ₄ or BC. In principle, all the aforementioned ceramic-containing compounds can be used as the inorganic substance. Other particulate ingredients may also be included as in the above-described examples of slip.

In addition to the aforementioned inorganic substance, a polymer is additionally contained in the slip, which is preferably dissolved homogeneously. The polymer is preferably one or more of the following compounds selected from the following polymer compound classes: polysulfone, pulylene ether sulfone, polyvinyl butyral, polyamide, polyacrylonitrile, cellulose esters and / or polyethylene.

The aforesaid inorganic substance may be applied to the support structure, preferably dispersed in a solvent, dispersed or distributed homogeneously. Subsequently, a non-solvent is added. This addition precipitates polymer components from the slurry which precipitate in the support structure and then solidify. Within these polymer constituents is the aforementioned inorganic substance, which is preferably homogeneously distributed in the polymer matrix.

For example, the slurry may be in the form of polymer components in which the aforementioned inorganic substance is distributed. be emulsified in a nonpolar solvent. This Non-polar solvents, for example ethanol and / or NMP, are part of the slip. The slurry is applied to the support structure and infiltrates the support structure. Then a non-solvent is applied. This non-solvent can, for. B. be water. By adding this non-solvent, phase inversion occurs whereby the polymer components precipitate with the inorganic substance and solidify in the support structure. The polymer matrix thus fixes and encloses the ceramic constituents on and / or in the carrier material during phase inversion.

Due to the phase inversion, a ceramic-containing surface forms with so-called finger pores. While in the pre-rubbed first filter membrane, in which a coating of the fibers of the carrier takes place, even after firing a fiber structure is superficially recognizable, the surface of the second filter membrane holes due to the finger pores. This surface structure is, for example, as a top view in FIG 12 shown. This representation is merely schematic and exemplary. As you can see on the basis of the surface structure no longer be inferred on a fiber structure of the substrate used. The distance, size and number of finger pores may vary. In a preferred variant of the second filter membrane, the finger pores have an average pore length of 1 μm to 5000 μm on average, it being possible to determine the average pore length only in the case of thicker filter membranes. For thinner filter membranes, the finger pores can also sporadically extend as an irregularly shaped channel over the entire thickness of the filter membrane. The mean pore width of the finger pores can vary in a preferred embodiment between 0.05 to 2 microns. The dimensioning of the pores is z. B. determined by mercury porosimetry and by scanning electron micrographs (SEM) recordings.

If a fiber material is used as the carrier material, the fiber interspaces are filled by the phase inversion with the inorganic material. In the production process, which is based on the first filter membrane, ie the flat filter membrane, this is not the case, but the fiber interstices remain substantially unfilled.

Subsequently, the carrier material can be removed in a firing process, whereby in addition the ceramic-containing slip is cured to a ceramic.

In addition to the different surface design of the first and the second filter membrane has the production through a phase inversion process also production technical advantages. While a sensitive drying process was necessary in the production of the first filter membrane after the slip application and before the firing process, a drying can be carried out faster and less complicated in the production of the second filter membrane.

This is because when drying in the first case, the ceramic concentration changes constantly. During concentration, local concentration agglomerations may form in which more inorganic substance is formed than in other areas. In the case of phase inversion, on the other hand, due to the preceding precipitation step, there is already a pre-consolidated, ceramic-containing structure which only changes to a slight extent during drying. As a result of the phase inversion, the previously quality-determining step of drying can be considerably simplified and handled in a time-efficient manner.

In addition, the slip may preferably have a further compound which influences the solution property of the inorganic substance. This substance may preferably be a polymer compound which increases the solubility of the inorganic substance in the solvent. Such a substance may preferably contain a conventional emulsifying and / or dispersing agent, such as. As polyvinylpyrrolidone (K90) or a polyvinyl alcohol.

With the abovementioned method, it is possible to coat or infiltrate preformed structures, in particular support structures based on plastics, cellulose, etc., of any geometry with a phase-inversion-capable ceramic-containing slurry and to produce the actual filter structure by means of a downstream phase inversion process. As a result of the firing process required for ceramics, the support structure can be burnt out without leaving any residue and the remaining ceramic-containing structure can be faithfully solidified. Such a structure of a filter ceramic is not known from the prior art.

By applying the phase inversion, it is possible to realize both individual material layers as parts of the overall filter module (eg individual corrugated webs) as well as entire filter modules, in particular also flat filter modules.

Any structures which can be realized by means of templates and are accessible for ceramic-containing slip can be realized. A complicated and complicated drying process can be omitted in the phase inversion ceramic compared to conventional ceramization, since the ceramic particles not due to their fixation in the solidified by the phase inversion polymer matrix can be flushed out. As a result, the overall structure due to the solidified polymer matrix is hardly susceptible to drying defects (such as cracks). Thus, filter elements in the form of honeycomb bodies (as a template, for example, paper wraps) can be produced simply and quickly, as well as with high process reliability.

The shape of the ceramic-containing second filter membrane depends in the cured state, inter alia, on the shape of the support structure and may be analogous to the first filter membrane also formed as a flat filter membrane. In the 1 to 3 illustrated variants of support structures can therefore also be used as embodiments in the production of the second filter membrane.

The basic structure of the support structure and the connections of the layers can be formed analogously as in the production of the first filter membrane. The support structure may be as in 1 to 3 represented and formed as previously described.

The macroscopic shape and design of individual intermediates, permeate plates and / or a corresponding second filter membrane, z. B. in curved form and with one or more Welllagen can analogous to the embodiments of 4 to 7 respectively. The difference in the production of the second filter membrane is the additional phase inversion step and the different microscopic surface structure (pore shape, pore distribution, etc.).

The different variants of the first filter membrane as well as the second filter membrane can be used to produce a filter module, which is described below with reference to 8th to 10 is explained.

8th . 9 and 10 show a filter module 25 with the first filter membrane 50 of the 7 or alternatively a form-matched second filter membrane. The filter module also shows the permeate plate 14 of the 6 which may alternatively be subjected to the additional step of phase inversion during the production thereof after the slip application.

Here are the channels 13 the filter membrane 50 and the channels 24 the permeate plate 14 angular, preferably at an angle of 90 ° to each other. However, the arrangement with a 90 ° offset is not absolutely necessary. Other angles can be chosen. The permeate plate 14 It also serves as a spacer between two filter membranes 50 and can be used to derive the permeate.

The filter membrane 50 and the permeate plate 14 also form in multiple stacking, as in 9 represented, in interaction other channels 26 out. This is due to the wavy position 15 the filter membrane 50 limited by porous ceramic membrane material and by the flat position 11 the permeate plate 14 also made of porous ceramic material.

The following is the operation of the filter module 25 explained in more detail. It should be noted that the filtering can also be done in the opposite direction, depending on the pressure gradient. These two different filtration directions are in 4 and 5 shown schematically.

Into the channels 26 between the filter membrane 50 and the permeate plate 14 the fluid to be purified is passed. The permeate penetrates the corrugated layer of the filter membrane 50 and enters the channels 13 one. There, the permeate penetrates one of the two planar layers of another permeate plate 14 , Due to the channels offset by 90 ° 24 This further permeate plate becomes the permeate from the filter module 25 dissipated. In these channels 24 There is less pressure than in the channels 26 ,

Variously constructed support structures can also lead to other structures of filter modules.

The intermediate structure of the 3 to 6 from which the permeate plate 14 is formed, is much flatter than the filter membrane 50 , The filter membrane 50 is preferably at least twice as thick as the permeate plate 14 , in particular at least three times as thick. This is in addition to the stretchability of the material also by the small thickness of the permeate 14 a bendability in the extension direction of the channels 24 reached. As a result of this flexibility, the flat-membrane membrane module can be bent to a shape predefined by the customer before the slurry material hardens, with the flat-membrane membrane module retaining this shape after curing of the slurry to form one or more ceramic membrane layers.

In 7 the flexibility of the support structure of the filter membrane or the flat filter membrane before the curing of the slurry was again shown schematically. Of course, this is somewhat reduced by adding the permeate plate. However, it is also present in a combination of the carrier structures of the permeate plate and the filter membrane.

The filter module 25 In its simplest embodiment, at least the first or the second filter membrane and one of the aforementioned Surface structures. The first and / or the second filter membrane may preferably at least one structured, z. B. wavy, layer or membrane layer and have a flat layer or membrane layer. Between these two layers channels form. The fluid to be cleaned can be introduced, for example, from the outside to the flat filter membrane and the permeate through the inner channels 13 be dissipated. The first layer of the respective filter membrane can be designed in particular as a carrier layer. It creates a mechanical strength of the filter membrane. The second layer may be formed as a separating layer for filtering the fluid to form a retentate and a permeate. The second layer can be arranged directly on the first layer.

The filter membranes can be connected to one another or to one or more surface structures or permeate plates by means of a heat-resistant adhesive. The adhesive may preferably be based on Al ₂ O ₃ . In addition, particulate inorganic additives, dispersants and polymers, such as. For example, polyvinylpyrrolidones may be included in the ceramic-containing adhesive composition. Water is preferably another component of the adhesive.

The adhesive can in addition to the connection of the individual layers of a support structure for the terminal closing of the channels 13 be used.

However, the structure of the material layer may also have a plurality of ceramic layers, such. For example, an oxide-ceramic layer and the fluid to be filtered out a carbidic or nitridic layer particularly preferably of silicon carbide and / or aluminum nitride. This can be thinner than the oxide-ceramic layer and be arranged on the oxide-ceramic layer toward the fluid to be filtered out.

The ceramic-containing slip used in the production of the first and the second filter membrane may preferably be a slip which forms a substantially oxide-ceramic membrane and / or a carbide and / or a nitride ceramic membrane. The ceramic-containing slip can be applied, for example, by means of a dipping or spraying process. The oxide-ceramic material of the hardened filter membrane and / or the permeate plate can preferably be selected from the following materials: Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Y ₂ O ₃ and / or SiO ₂ . These oxide, carbide and / or nitride ceramic materials or mixtures of these materials have an advantageous strength, so that the filter membrane and possibly also the permeate plate has good strength and pressure stability. Furthermore, the material of the filter membrane and / or the permeate plate may comprise additives, preferably in the form of alkali and / or alkaline earth metal compounds.

The liquid or pasty ceramic-containing slip material for forming the membrane layer may also contain ceramic particles. The ceramic material for forming the membrane layer may preferably have an average particle or particle size in the range of about 0.5 to 10.0 μm, in particular less than 5 μm.

The liquid or pasty ceramic-containing material, for example in the form of a ceramic slip, can be used as constituents, in particular particles, for example of aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), silicon carbide ( SiC), silicates, zeolites or mixtures thereof. As a result, the firing temperatures can be reduced, so that firing temperatures below 1000 ° C, preferably below 500 ° C can be achieved. The abovementioned particles are preferably contained in the slip material to an extent of less than or equal to 20% by weight.

9 shows schematically a stacking sequence of flat filter membranes 50 and permeate plates 14 which in the stacking direction 70 are arranged one above the other. The filter membranes designed as flat filter membranes can be either the above-described first filter membrane or the previously described second filter membrane.

The corresponding flat filter membrane 50 may have a width of, for example, 0.5 mm to 50 mm and a height of, for example, 0.3 mm to 5 mm and with a ceramic adhesive across the channels 13 be provided which is applied at a distance, preferably from 1 mm to 200 mm.

The corresponding permeate plate 14 may have a width of, for example, 0.5 mm to 50 mm and a height of, for example, 0.1 mm to 2 mm and with a ceramic adhesive across the channels 13 be provided which is applied at a distance, preferably from 1 mm to 200 mm.

A material layer of the first or second filter membrane in the cured state may preferably have a wall thickness of 0.02 to 1.5 mm. The layer thicknesses and their structure can be analyzed, for example, by means of GDOES spectroscopy (glow discharge spectroscopy). Slight fluctuation margins of individual devices from different manufacturers are already included in the range specifications.

An aforementioned first or second filter membrane and a filter module constructed therefrom can be used for filtering produced water, process water, water treatment, surface water treatment, wastewater treatment and recycling, filtration applications in the food and beverage industry, and the chemical industry and biotechnology. and medical technology, in particular for blood filtration, and be used in automotive applications, in particular for water / oil separation.

Produced water is a well-established term in the oil and gas industry. He called water, which in the oil and gas production, such. B. also fracking incurred. This can occasionally have higher viscosities than normal water. Even with oil extraction, z. As in oil wells and in the extraction of oil accumulate huge amounts of contaminated water. This is also referred to in professional circles as produced water.

The porosity of the fiber wall or the filter membrane can be adjusted according to the choice of materials. In a preferred embodiment, the porosity of the first layer, that is to say the carrier layer, may be 25-50% and the porosity of the second layer, ie the separating layer, may be 20-60%. Mercury porosimeters, which measure in the range below 10 nm pore size and are therefore suitable for pore size determination, are from various manufacturers, eg. B. Quantachrome Instruments and Micromeritics known.

The present invention enables the provision of a first filter membrane as a flat filter membrane by means of a flexible support structure can be brought by cost-effective shaping processes in the desired planar or structured geometry, infiltrated with a ceramic-containing slip and then cured. In this case, the predetermined by the support structure or the template shape is maintained throughout the manufacturing process. Shrinkage caused by the burning process is ignored in this analysis. This results in a cost-effective manufacturing process for ceramic flat membranes compared to the known ceramic-containing method.

The flat filter membrane as well as the second filter membrane, ie the membrane obtainable by phase inversion, can be used as a microfiltration membrane. When used as an ultrafiltration membrane or as a nanofiltration membrane, further coating systems based on aluminum oxide, zirconium oxide, silicon oxide, silicon carbide and / or titanium dioxide are necessary. For this purpose is z. B. the pore size of the resulting ceramic layer on the composition of the slurry and / or on the material of the support structure adjustable.

The present invention also allows the provision of a second filter membrane in any arrangement, such. B. as a flat filter membrane or as a wound membrane. The second filter membrane is easier to produce than the first flat filter membrane and has a novel microscopic surface structure.

The aforementioned ceramic filter membrane and the ceramic filter modules composed thereof are overall less expensive and easier to produce compared to other known ceramic-containing production method.

For the second ceramic filter membrane, in particular also improved mechanical strength can be achieved compared to the first ceramic filter membrane.

Due to the phase inversion process with the formation of the finger pores, a polymer material with finer-grained ceramic constituents, more preferably between 0.4 to 2 μm, can be used over the first ceramic filter membrane, whereby the sintering temperature can be lowered during manufacture and a higher mechanical strength is achieved. However, one can also resort to a powder with coarse-grained constituents between 2 to 20 microns. In the case of the first filter membrane, when using the polymer material with the finer-grained ceramic constituents, only the carrier fibers are coated, but in this case no homogeneous pore formation occurs.

Due to a high flexibility of corresponding support structures also very small corrugated structures with a shaft diameter <1 mm are also embossed, which can significantly increase the filter area of the above-described first and second filter membrane. The same applies to zigzag, trapezoidal or rectangular structures. Such small sized structures could not be realized with the previous methods. Therefore, such small-sized structures are an indication that it is a filter membrane according to the invention and a filter module according to the invention.

The filter membrane according to the invention can during its preparation of a free shaping, z. B. as a bent flat filter membrane as in 10 represented, which can be fitted in any size spaces. Such a free shaping is therefore a clear indication that it is a flat filter membrane according to the invention and a filter module according to the invention.

A clear indication of the production variant presented in the invention is also that the impression of the support structure, if this itself has a structure, in the ceramic-containing material of the filter membrane rejects. In the case of the above-described first filter membrane, this can already be determined by means of a microscopic image of the surface; in the case of the above-described second filter membrane, a sectional image of the structure is recommended. Such structures, eg. Example, as a fiber surface for paper or nonwoven, in the cured ceramic-containing membrane material are not known in the manufacturing processes of the prior art and therefore also an indication of a filter membrane according to the invention and a filter module according to the invention. No presence of a structure in the ceramic-containing membrane is of course not to be understood as an indication of the non-existence in particular of the second above-described filter membrane, since the flat filter membrane can also be prepared with a support structure of other porous materials.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1954382 A1 [0003]
• EP 1284251 A1 [0004]
• DE 102012012941 A1 [0054]

Claims (15)

Ceramic filter membrane for filtering a fluid ( 20 ), characterized in that the ceramic filter membrane ( 50 ) according to the following steps: A providing a flexible fibrous carrier structure ( 1 . 5 . 8th ); B impregnating the carrier structure with a ceramic-containing slip mass ( 12 ); C hardening of the slip mass ( 12 ) to the ceramic filter membrane ( 50 ), characterized in that the ceramic filter membrane is designed as a flat filter membrane. Ceramic filter membrane according to claim 1, characterized in that the filter membrane ( 50 ) has a fibrous surface structure. Ceramic filter membrane for filtering a fluid ( 20 ), characterized in that the ceramic filter membrane finger pores ( 101 ) having. Ceramic filter membrane according to claim 3, characterized in that the ceramic filter membrane is produced by the following steps: A providing a flexible porous carrier structure ( 1 . 5 . 8th ); B impregnating the carrier structure with a ceramic slip mass ( 12 ); C reduction of the solubility of constituents in the slip mass ( 12 ); and D hardening the slip mass ( 12 ) to the ceramic filter membrane. Ceramic flat filter membrane according to claim 3 or 4, characterized in that the reduction of the solubility of the constituents in the slip mass ( 12 ), in particular of ceramic-containing polymer constituents, by adding a non-solvent in which the constituents are insoluble. Ceramic filter membrane according to one of the preceding claims, characterized in that the ceramic-containing constituents of the slip mass ( 12 ) are at least 10 wt .-%, in particular 40 to 75 wt .-%, oxide-ceramic, carbide-ceramic and / or nitride ceramic components. Ceramic filter membrane according to one of the preceding claims 1 to 6, characterized in that the material of the support structure ( 1 . 5 . 8th ), especially at temperatures below 2000 ° C, is flammable. Ceramic filter membrane according to one of the preceding claims 1 to 7, characterized in that the ceramic filter membrane ( 50 ) has a height of less than 5 mm, in particular a height of less than 1 mm. Ceramic filter membrane according to one of the preceding claims 1 to 8, characterized in that the ceramic filter membrane ( 50 ) a fluid-conducting structure, in particular a single-layer row of side-by-side channels ( 13 ), having. Ceramic filter membrane according to one of the preceding claims 1 to 9, characterized in that the filter membrane within the ceramic material has voids in the form of fibers. Filter module comprising a ceramic filter membrane and a ceramic surface structure ( 14 ), for spacing and supplying a fluid to be filtered ( 20 ) and / or for discharging a permeate from the filter module ( 60 ), characterized in that the surface structure ( 14 ) is made by at least the following steps: A providing a flexible support structure; B impregnating the carrier structure with a ceramic-containing slip mass ( 12 ); and C curing the slip mass ( 12 ) to the ceramic surface structure ( 14 ); wherein the ceramic surface structure ( 14 ) is stacked on top of each other with the ceramic filter membrane and firmly bonded together. Filter module according to claim 11, characterized in that the ceramic filter membrane ( 50 ) a plurality of juxtaposed channels ( 13 ) with channel tracks in a first propagation direction ( 80 ) and wherein the ceramic surface structure ( 14 ) a plurality of juxtaposed channels ( 24 ) in a second propagation direction ( 90 ), and wherein the two propagation directions ( 80 and 90 ) in the stacking direction ( 70 ) extending axis offset from one another, in particular offset by an angle of 90 ° to each other, are. Filter module according to one of claims 11 or 12, characterized in that the height of the ceramic filter membrane ( 50 ) in the stacking direction ( 70 ) is at least twice as large as the height of the surface structure ( 14 ) in the stacking direction ( 70 ). Filter module according to one of claims 11 to 13, characterized in that the filter membrane as a flat filter membrane ( 50 ) according to claim 1 or as a filter membrane according to claim 3 is formed. Use of the filter membrane according to claim 1 or 3, in particular as an arrangement in a filter module according to claim 11, for Filtration of process water, for drinking water treatment, for surface water treatment, for wastewater treatment and recycling, for filtration applications in the food and beverage industry and the chemical industry and biotechnology and medical technology, in particular for blood filtration, and in automotive applications, in particular for water / oil separation.

Images