WO2003051544A1

WO2003051544A1 - Structured-surface packs for multi-phase separators

Info

Publication number: WO2003051544A1
Application number: PCT/EP2002/014086
Authority: WO
Inventors: Martin Roos; Markus Oles; Bernhard Schleich
Original assignee: Degussa Ag
Priority date: 2001-12-19
Filing date: 2002-12-11
Publication date: 2003-06-26
Also published as: DE10162457A1; AU2002358675A1

Abstract

In separators used in thermal technology the components are isolated by means of a mass transfer via a fluidic phase interface. Said interfaces are e.g. vapour-liquid interfaces during distillation, gas-liquid interfaces during absorption and liquid-liquid interfaces during extraction. The interfaces are usually produced by the dispersion of a fluidic phase using a supply of energy provided by means of mixers, pumps, fans or distributors. Packs such as bases, dumped packing or structured packing are used to obtain or renew the interfaces. Phase separation processes of this type can be optimised e.g. by improving the apparatus that is used. The invention therefore relates to packs for multi-phase separators, which have an artificial surface structure consisting of elevations and indentations, whereby the surface of said packs is poorly wettable. The advantage of the inventive packs is that deposits take substantially longer to form on them than on conventional packs. For packs that are used in particular in extraction apparatus, such as e.g. packing, or auxiliary coalescence agents in the form of plates, the poor wettability of the surface of the inventive packs aids the thorough mixing and subsequent isolation of the phases.

Description

Surface-structured internals for multiphase separators

The present invention relates to internals for multiphase separators, which have an artificial, surface structure of elevations and depressions, as a result of which the surfaces of these internals are poorly wettable, a process for their production and a multiphase separator and a method in which they are used.

In separation devices of thermal process engineering, the components are separated by mass transfer over a fluid phase interface. These are e.g. B. vapor-liquid interfaces in the distillation, gas-liquid interfaces in the absorption and liquid-liquid interfaces in the extraction. These interfaces are usually produced by dispersing the one fluid phase by means of energy input via stirrers or distributors. The preservation or renewal of the interfaces is done via internals such. B. floors, packing or structured packings.

In many applications, it is desirable that the internals are wetted by the dispersed phase (e.g. distillation packs). The Rachig company offers e.g. B. Packings made of polymers that can be completely wetted by a hydrophilizing surface treatment of aqueous solutions.

However, some applications also require that these parts are not or poorly wettable. These are e.g. B. internals for extraction apparatus (e.g. packs, plate coalescence aids, etc.). It is important that this poor wettability applies to the disperse phase. In the case of a disperse aqueous phase, the internals should be hydrophobic. In the case of a disperse organic phase, hydrophilic (lipophobic) internals are preferred. In the following, only the hydrophobic variant is referred to, although both are meant.

It is known that in order to achieve poor wettability of a technical surface with water, the surface must have a very hydrophobic surface. Such hydrophobized internals are known. However, these hydrophobized internals have the disadvantage that the hydrophobicity is lost relatively quickly through adhering material. State of the art according to EP 0 933 388 is that an aspect ratio of> 1 and a surface energy of less than 20 raN / ra is required for self-cleaning surfaces. The aspect ratio is defined as the quotient of the height and the width of the structure. The aforementioned criteria are realized in nature, for example in the lotus leaf. The surface of the plant formed from a hydrophobic wax-like material has elevations that are a few μm apart. Water drops essentially only come into contact with these tips. Such water-repellent surfaces have been widely described in the literature.

CH-PS-268 258 describes a method in which structured surfaces are produced by applying powders such as kaolin, talc, clay or silica gel. The powders are fixed on the surface by oils and resins based on organosilicon compounds (Examples 1 to 6). However, this patent does not describe what the grain size distribution is and how the particles are introduced into the matrix.

EP 0 909 747 AI teaches a method for producing a self-cleaning surface. The surface has hydrophobic elevations with a height of 5 to 200 μm. Such a surface is produced by applying a dispersion of powder particles and an inert material in a siloxane solution and then curing. The structure-forming particles are thus fixed to the substrate by an auxiliary medium.

Methods for producing structured surfaces in polymers are also known. In addition to the detailed reproduction of these structures by a master structure in injection molding or embossing processes, methods are also known which use the application of particles to a surface, such as. B. described in US 5,599,489. This method also uses an adhesion-promoting layer between particles and bulk material. For the formation of the structures, etching and coating processes for gluing the structure-forming powders and shaping processes using appropriately structured negative molds are suitable.

None of these documents describe such self-cleaning surfaces Installations of multi-phase separators can be used.

The object of the present invention was to provide internals for multiphase separators which are not or poorly wettable and avoid the disadvantages of pure hydrophobization.

Surprisingly, it was found that by equipping the internals in multi-phase separators with a surface structure consisting of elevations and depressions, the surfaces of these internals are poorly wettable.

The present invention therefore relates to poorly wettable internals for multi-phase separation apparatus according to claim 1, which are characterized in that the internals have an artificial, surface structure of elevations and depressions, the elevations on the surface of the internals a distance of 20 nm to 100 microns and have a height of 20 nm to 100 μm.

The present invention also relates to a method according to claim 10 for producing internals according to one of claims 1 to 9, which is characterized in that a surface structure having elevations and depressions is produced on the surface of the internals.

The present invention also relates to a multiphase separating apparatus according to claim 22 which has internals, which is characterized in that they have internals with structured surfaces according to one of claims 1 to 9.

In addition, the present invention relates to a method according to claim 23 for separating a multiphase system, which is characterized in that the method is carried out in a multiphase separating apparatus which has internals according to one of claims 1 to 9.

The internals according to the invention have the advantage that they are much slower Deposits due to particles or particles formed in the apparatus form than with conventional internals, since the surface structure of the internals is self-cleaning through contact with the fluid phase interface.

Especially for installations in extraction equipment, such as. B. packs or plate coalescence aids, the poor wettability of the surface of the internals according to the invention enables greater mixing or a simplified separation of the two phases.

The internals of the invention can in particular for extraction, in particular liquid-liquid extraction or for absorption, in particular gas-liquid absorption, such as. B. used in exhaust air washes.

The internals according to the invention are described below by way of example, without any intention that they should be limited to the embodiments described here.

The internals for multiphase separators according to the invention have an artificial surface structure of elevations and depressions, as a result of which the surface of these internals is poorly wettable. Such surfaces are often referred to as self-cleaning surfaces. The multiphase separators are customary separators in which the components are separated by mass transfer over a fluid phase interface, e.g. B. distillers or extractors. These phase interfaces are e.g. B. vapor-liquid interfaces in the distillation, gas-liquid interfaces in the absorption and liquid-liquid interfaces in the extraction. These interfaces are usually produced by dispersing one fluid phase in the other by means of energy input via stirrers or distributors. The maintenance or renewal of the interfaces is achieved through the internals.

The internals according to the invention in the multi-phase separators can be conventional internals, such as. B. those that are selected from the group of floors, plates, structured packings or fillings or packed beds. The internals can from the various materials known for internals, such as. B. plastics such. B. poly (vinylidene fluoride), poly (ethylene), Teflon or poly (propylene), metals such as. B. stainless steel, ceramics such. B. Al ₂ O ₃ , earthenware, glass, carbon or similar materials and composite materials. The internals according to the invention are very particularly preferably constructed from at least one material selected from the group of stainless steels or ceramics. It can be advantageous if the internals have coatings made of glass or plastic.

Poorly wettable internals are understood to mean in particular those which have an advancing and retracting angle of more than 140 °, preferably more than 145 ° and very particularly preferably more than 150 °.

The poorly wettable internals for multi-phase separation apparatuses according to the invention are characterized in that the internals have an artificial, surface structure of elevations and depressions, the elevations on the surface of the internals being a distance of 20 nm to 100 μm and a height of 20 nm to 100 µm. To achieve the self-cleaning effect, it may be particularly advantageous if the elevations on the surface of the internals are at a distance of 50 nm to 25 μm, preferably 100 nm to 10 μm and very particularly preferably 500 nm to 1 μm. In the present invention, the distance between the elevations is understood to mean the distance between the peaks or highest elevations of the elevations. It is also advantageous if the elevations on the surface of the internals have a height of 50 nm to 25 μm, preferably 100 nm to 10 μm and very particularly preferably 500 nm to 1 μm. The elevations can have a wide variety of shapes. The elevations preferably have the shape of pyramids, cones, needles, hemispheres, spheres or ridges.

The elevations can be structures applied to the surface or can be elevations between recesses that have been made in the surface. The indentations can be introduced into the surface in particular by embossing or molding. In a particularly preferred embodiment of the internals according to the invention, the elevations and depressions are formed in that the internals have particles on their surface.

Particles which can be used are particles which comprise at least one material selected from silicates, doped or pyrogenic silicates, minerals, metal oxides, silicas. Have metals or polymers. Preferably particles are used which have a particle diameter of 0.02 to 100 μm, particularly preferably from 0.2 to 50 μm and very particularly preferably from 0.3 to 30 μm. The surfaces of the internals according to the invention have the individual particles on the surface preferably at intervals of 0 to 10 particle diameter, particularly preferably at intervals of 2 to 8 particle diameter, in particular from 4 to 8 or 2 to 3 particle diameter.

The particles can also be present as aggregates or agglomerates, whereby according to DIN 53 206, aggregates are understood to be flat or edge-shaped primary particles (particles) and agglomerates of primary particles (particles). As particles it is also possible to use particles which aggregate from primary particles to form agglomerates or aggregates with a size of 0.2-100 μm.

It can be advantageous if the particles used have a structured surface. Particles which have an irregular fine structure in the nanometer range on the surface are preferably used. The fine structure of the particles is preferably a jagged structure with elevations and / or depressions in the nanometer range. The elevations preferably have an average height of 20 to 500 nm, particularly preferably 50 to 200 nm. The distance between the elevations or depressions on the particles is preferably less than 500 nm, very particularly preferably less than 200 nm.

As particles, in particular as particles which have an irregular fine structure in the nanometer range on the surface, those particles are preferably used which contain at least one compound selected from pyrogenic silica, aluminum oxide, Have silicon oxide, pyrogenic silicates or powdered polymers or metals. It can be advantageous if the particles used have hydrophobic properties. Particularly suitable particles are, inter alia, hydrophobicized pyrogenic silicas, so-called aerosils.

It may be advantageous if the internals have particles that have hydrophobic properties. The hydrophobic properties of the particles may be inherent due to the material used for the particles. However, hydrophobized particles can also be used, which, for. B. by treatment with at least one compound from the group of alkylsilanes, perfluoroalkylsilanes, paraffins, waxes, fatty acid esters, functionalized long-chain alkane derivatives or alkyldisilazanes, have hydrophobic properties.

The internals according to the invention are preferably produced by the method according to the invention for producing these internals. In this method, a surface structure, which has elevations or depressions, is produced on the surface of the internals. Standard internals, as described above, can be used as the starting material for producing the internals according to the invention.

It can be advantageous if the surface of the internals is at least partially hydrophobized. This partial hydrophobization of the surface can e.g. B. by treatment with at least one compound from the group of alkylsilanes, perfluoroalkylsilanes, paraffins, waxes, fatty acid esters, functionalized long-chain alkane derivatives or alkyldisilazanes.

Depending on the intended use of the internals, it can also be advantageous if the surface of the internals is hydrophilized. This can be the case in particular if the internals are to be used in an extraction apparatus in which disperse organic phases are to be separated. Due to the hydrophilization, particularly high retraction angles for the organic phases are achieved and thus a particularly good self-cleaning effect or particularly poor wettability is achieved. The surface can in particular be treated with at least one compound from the group of Alcoholates of transition metals, the chelates of transition metal alcoholates or alkoxysilanes, are at least partially hydrophilized.

The surface structure can be created on the surface of the internals themselves. This can e.g. B. done in that a surface structure is generated by applying and fixing particles on the surface of the internals. The particles can be applied and fixed by gluing, embossing, rolling or storing on or in the surface of the internals. Various newer fixing or embossing methods, which are not to be described in more detail here, can be found, inter alia, in patent applications DE 10129116.7, DE 10138036.4 and DE 10134477.5.

These methods are briefly described below:

In DE 10129116, the particles are introduced into the surface of the polymer during the spinning process after the polymer melt has emerged from the spinneret by means of a gas stream. The particles are fixed to the polymer fibers by solidification of the polymers. Fixation methods are similar to those skilled in the art, in which the particles are introduced into a viscous surface or applied to a viscous surface, and the viscous surface solidifies by cooling, evaporation of solvents or by chemical reaction.

DE 10134477 describes a method for producing self-cleaning surfaces with a self-regenerating self-cleaning effect, in which a suitable, at least partially hydrophobic surface structure is created by fixing particles on a surface by means of a carrier, a mixture of particles and binder being used as the carrier. Of course, the use of a carrier that does not contain any particles is also conceivable, which then corresponds to a normal adhesive process. In analogy to the method mentioned in the application DE 10134477.5, the particles having an at least partially hydrophobic surface can be replaced by at least partially hydrophilic particles depending on the intended use.

Particles can be used as particles which are at least one material selected from Silicates, doped or pyrogenic silicates, minerals, metal oxides, silicas. Have metals or polymers. Preferably particles are used which have a particle diameter of 0.02 to 100 μm, particularly preferably from 0.2 to 50 μm and very particularly preferably from 0.3 to 30 μm.

The particles can also be in the form of aggregates or agglomerates, in accordance with DIN 53 206 being understood as aggregates of primary particles (particles) which are arranged flat or edge-to-edge, and agglomerates of primary particles (particles) which are connected at points. As particles it is also possible to use particles which aggregate from primary particles to form agglomerates or aggregates with a size of 0.2-100 μm.

As particles, in particular as particles which have an irregular fine structure in the nanometer range on the surface, those particles are preferably used which have at least one compound selected from pyrogenic silica, aluminum oxide, silicon oxide, pyrogenic silicates or powdery polymers or metals. It can be advantageous if the particles used have hydrophobic properties. Particularly suitable particles are, inter alia, hydrophobicized pyrogenic silicas, so-called aerosils.

It may be advantageous if the internals have particles that have hydrophobic properties. The hydrophobic properties of the particles may be inherent due to the material used for the particles. However, hydrophobized particles can also be used be the z. B. by treatment with at least one compound from the group of alkylsilanes, perfluoroalkylsilanes, paraffins, waxes, fatty acid esters, functionalized long-chain alkane derivatives or alkyldisilazanes, have hydrophobic properties.

It is also possible within the scope of the method according to the invention that the particles on the surface of the internals are provided with hydrophobic properties. In this case too, the particles are preferably provided with hydrophobic properties by treatment with at least one compound from the group of the alkylsilanes, perfluoroalkylsilanes, paraffins, waxes, fatty acid esters, functionalized long-chain alkane derivatives or alkyldisilazanes.

In another embodiment of the method according to the invention, the surface structures are also produced on the surface of the internals themselves. In this embodiment of the method according to the invention, the surface structure can be produced by changing the surface of the internals.

The shaping or structuring of the surface can be done by embossing / rolling or at the same time in the macroscopic shaping of the internals such. B. casting, injection molding or other molding processes. The corresponding negative forms of the desired structure are required for this.

Negative forms can be used industrially e.g. B. with the Ligatechnik (R. Wechsung in Mikroelektronik, 9, 1995, p. 34 ff.). Here, one or more masks are first produced by electron beam lithography with the dimensions of the desired elevations. These masks are used to expose a layer of photoresist by means of deep X-ray lithography, whereby a positive shape is obtained. The gaps in the photoresist are then filled by electrodeposition of a metal. The metal structure thus obtained is a negative form for the desired structure.

In a further embodiment of the method according to the invention, the surface structure is produced as a film or on a film which is on the surface of the Internals is transferred. The production of such films is e.g. B. in EP 0 933 388 or more specifically described in DE 10138036.4. The structured surfaces described in DE 10138036, the structure of which is formed by elevations, are distinguished by the fact that adjacent elevations are connected by ridges which have a lower average height than the elevations connected by them. In DE 10138036.4 z. B. a process for the production of structured surfaces by molding a negative shape onto an unstructured surface, in which the negative shape has a surface made up of parts of spheres or rounded truncated pyramids and valley-shaped incisions between the spherical parts. The ridges connecting the surveys achieve a significantly higher stability of the structures. Any other negative form with which surveys of the required dimensions can be produced can also be used. The embossing can be done by embossing or rolling or, in the case of macroscopic shaping of the internals, by casting, injection molding or in mold decoration (IMD) onto the surface.

It can be advantageous to subsequently hydrophobize the internals that have been equipped with the surface structure. This can be done by treating the internals with the compounds specified for the hydrophobization of the particles. It can be just as advantageous if the surface or surface structure of the internals to improve the chemical resistance with an appropriate material, such as. B. Gold is coated. However, such a coating must be carried out in such a way that the surface structure is retained. Such a possibility for coating z. B. the process of chemical vapor deposition (CVD) or sputtering.

The internals according to the invention can be used in multiphase separators of the known type.

The subject matter according to the invention also includes all other methods for separating multiphase systems, which are characterized in that the methods are carried out in a multiphase separating apparatus which have internals according to one of claims 1 to 9. In particular, methods for separating a multiphase system in a multiphase separating apparatus, which have internals according to one of claims 1 to 9 preferred, in which one or more of the inlet streams of the multiphase system contain particles whose deposition on the surface of the internals is reduced or avoided due to the self-cleaning effect. Likewise, the internals according to the invention are suitable for carrying out processes for separating a multiphase system in a multiphase separator, particles forming in the apparatus, the deposition of which on the surface of the internals according to the invention is reduced or avoided due to the self-cleaning effect.

The present invention is explained in more detail with the aid of the following examples, without the invention being restricted to these embodiments.

Example 1 :

Built-ins can e.g. B. by an injection molding process in combination with a by LIGA

Process manufactured, conventional injection mold. The LIGA process is a structuring process that is based on the basic processes of X-ray lithography, electroplating and molding. The method differs from micromechanics in that the structures are not produced by an etching process in the base material but are inexpensively molded using a tool in the injection molding process. After the lithographic resist exposure (radiation-sensitive polymer) and development, the lacquer structure produced in this way is used as a form for an electroplating process in which a metal alloy is deposited in the exposed spaces. Then the lacquer structure is removed and the remaining metal structure is used for the impression tool (G. Gerlach, W. Dötzel "Fundamentals of micro system technology" Carl Hanser Verlag Munich, 1997, page 60f).

Internals made of poly (propylene) were provided with a micro-structured surface during injection molding using a tool described above. The distance between the microstructures was on average 4 μm with a height of at least 4 μm and a half-width of 2 μm. Geometrically, the structural elements had the shape of a cone.

Then the built-in UV radiation of 254 nm was removed for two minutes. set to break bonds on the surface. Then fluoroalkyl acrylate (acrylic acid 1H, 1H, HH-perfluoroundecyl ester from Lancaster) is grafted thermally onto these surfaces (grafting-from). This procedure reduced the surface energy from approximately 28 mN / ra to less than 15 raN / ra.

On this structure, with the help of an adjustable inclined plane, the angle is determined at which a drop of water is no longer rolling. The resulting roll angle of 0.1 ° is significantly smaller than without a structured surface, in which a roll angle of more than 55 ° was obtained.

The adjustable inclined plane with this structure is immersed in the water-miscible solvent n-hexane. A drop of water is applied to the surface covered by the hexane. Again, the angle at which the drop no longer rolls is determined for the applied water drop. The resulting roll angle of 0.1 is also significantly smaller than that of a non-structured surface where the angle is 20 °.

In comparison to unstructured surfaces, in the case of surfaces structured according to the invention, in hexane at the same angle of the inclined plane, a much faster rolling of the water drop from the surface was found. With an inclination of 8 ° on the inclined plane, a 10 μl drop rolled down a 4 cm distance on a structured surface in 1.2 seconds. The drop got stuck on an unstructured surface. This shows that the structured surfaces can significantly improve the effect of internals.

Example 2:

Internals as described in Example 1 were dusted with soot. These model impurities were almost completely removed from the surface of the internals by water sprinkling. Soot is removed from the surface by the rolling water drops. Example 3:

Internals structured on the underside, as described in Example 1, were sprayed with water droplets from below. Compared to unstructured internals, it results in a significantly lower amount of adhering drops. The poor wettability of the surface of the internals according to the invention enables greater mixing or simplified separation of two phases.

1 and 2 show scanning electron microscopic images (SEM images) of surface-structured internals according to the invention. 1 shows the SEM image of a microstructured film with a conical structure for internals. 2 shows an SEM image of a periodic microstructure for internals.

Claims

claims:

1. Poorly wettable internals for multi-phase separators, characterized in that the internals have an artificial surface structure of elevations and depressions, the elevations on the surface of the internals being at a distance of 20 nm to 100 μm and a height of 20 nm to 100 μm.

2. internals according to claim 1, characterized in that the multi-phase separation apparatus are distillation, absorption or extraction apparatus.

3. internals according to one of claims 1 or 2, characterized in that the internals are selected from the group of floors, plates, structured packings or Füllkö fillings.

4. internals according to one of claims 1 to 3, characterized in that the elevations on the surface of the internals have a distance of 10 microns to 100 nm.

5. internals according to one of claims 1 to 3, characterized in that the elevations on the surface of the internals have a height of 10 microns to 100 nm.

6. internals according to one of claims 1 to 4, characterized in that the internals on their surface particles with an average particle diameter have from 0.02 to 100 μm.

7. internals according to claim 6, characterized in that the particles are selected from at least one material selected from silicates, doped silicates, minerals, metal oxides, silicas or polymers.

8. internals according to claim 7, characterized in that the particles have an irregular fine structure in the nanometer range on the surface.

9. internals according to at least one of claims 5 to 8, characterized in that the particles have hydrophobic properties.

10. The method for producing internals according to one of claims 1 to 9, characterized in that a surface structure having elevations or depressions is produced on the surface of the internals.

11. The method according to claim 10, characterized in that the surface of the internals is at least partially hydrophobized.

12. The method according to claim 11, characterized in that the surface is at least partially hydrophobized by treatment with at least one compound from the group of alkylsilanes, perfluoroalkylsilanes, paraffins, waxes, fatty acid esters, functionalized long-chain alkane derivatives or alkyldisilazanes.

13. The method according to claim 10, characterized in that the surface of the internals is hydrophilized.

14. The method according to claim 13, characterized in that the surface is at least partially hydrophilized by treatment with at least one compound from the group of the alcoholates of transition metals, the chelates of transition metal alcoholates or alkoxysilanes.

15. The method according to at least one of claims 10 to 14, characterized in that the surface structure is generated on the surface of the internals themselves.

16. The method according to at least one of claims 10 to 15, characterized in that the surface structure is produced by applying and fixing particles on the surface of the internals.

17. The method according to claim 16, characterized in that particles have a material selected from silicates, doped silicates, minerals, metal oxides, silicas or polymers.

18. The method according to claim 16 or 17, characterized in that the particles have an average particle diameter of 0.1 to 30 microns.

19. The method according to at least one of claims 16 to 18, characterized in that the particles have an irregular fine structure in the nanometer range on the surface exhibit.

20. The method according to claim 15, characterized in that the surface structure is generated by changing the surface of the internals.

21. The method according to at least one of claims 10 to 14, characterized in that the surface structure is produced as a film which on the surface of the

Internals is transferred.

22. The multi-phase separating apparatus has the internals, characterized in that the internals have structured surfaces according to one of claims 1 to 9.

23. A method for separating a multiphase system, characterized in that the method is carried out in a multiphase separating apparatus which has internals according to one of claims 1 to 9.

24. A method for separating a multiphase system according to claim 23, characterized in that one or more of the inlet streams of the multiphase system contain particles whose deposition on the surface of the internals according to one of claims 1 to 9 is reduced or avoided due to the self-cleaning effect.

25. A method for separating a multi-phase system according to claim 23, characterized in that particles form in the apparatus, the deposition of which on the surface of the internals is reduced or avoided according to one of claims 1 to 9 due to the self-cleaning effect.