DE10359813B4 - Process for working porous metallic asymmetric membranes or filter media - Google Patents

Abstract

method for processing porous, metallic asymmetric membranes or filter media, characterized that parts of the membrane or the filter medium by means of a Laser welding machine thermal treated, wherein the end face of the membrane or the filter medium seals by fusion by thermal treatment and performs the thermal treatment by laser welding under inert gas.

Description

The The present invention relates to an improved method of processing porous, metallic membranes or filter media.

membranes or filter media are known in different designs and materials. When Materials are used, for example, ceramics or metals. In this context, membranes or filter media are understood to mean partially permeable structures. at least for a component of a woman touching her Fluids permeable, for other components are impermeable. Typical applications therefor For example, the ultrafiltration and microfiltration or Cross-flow filtration, as well as cake-forming filtration on filter cartridges. More detailed descriptions can be found e.g. in Melin, Rautenbach, Membrane method, Springer Verlag, Berlin 2003 (Textbook 1).

In the DE 89 10 844 U1 describes the welding of homogeneous sintered metal bodies from the outside with a blasting process (electron beam, laser) in a vacuum. In WO 00/10685 A it is disclosed to weld filter media by means of inert gas welding.

Furthermore, asymmetrically constructed, porous, metallic membranes or filter media are known which correspond in their construction to the ceramic membranes or filter media. Explanations can be found, for example, in the textbook 1. In general, they have a coarsely porous sintered metal molding, which ensures the necessary mechanical stability. Applied to it is a relatively thin, finer sintered metal coating, which accomplishes the filtration. The pore diameters here are about 20 μm to 3 μm for the coarsely porous part and about 1 μm to 0.05 μm for the fine porous part. The metals used are, for example, iron, nickel, alloys such as stainless steels, bronzes or brass. These devices are illustrated, for example, in Textbook 1 and Li, Stöcker, metallic membranes extending areas of use for sintered metal filters, European Process Engineering, May 2001, pp. 70-71 and are incorporated herein by reference 1 shown schematically. Typical fields of application for these membranes or filter media are the concentration and / or purification of dispersions or suspensions, the cell separation of fermentation effluents and the recycling of heterogeneous catalysts as also in Textbook 1 and Li, Stöcker, metallic membranes extend areas of use for sintered metal filters, European Process Engineering, May 2001, p. 70-71

Around to use such a filter medium, for example as a membrane for microfiltration it is advantageous to coat the fine layer e.g. inside a sintered metal tube apply to a medium to be filtered defined with a high speed and higher pressure than on the outside direct the tube and withdraw the filtrate from inside to outside. The speeds in the interior of the tube are here at about 0.5 to 6.0 m / s and the pressure difference between inside and outside of the pipe is usually about 0.2 to 10 bar. Here it is essential, the metal membrane so integrate into a module that no significant narrowing of the flow path done to an unwanted Counteract pressure loss. Furthermore, one strives to this separation unit because the desired high chemical or thermal stability exclusively made of metal. In particular, attempts are made to avoid elastomer seals.

• 1. Beim Einschweißen einer innen beschichteten Metallmembran in einen Lochboden kann nichtfiltriertes Produkt über die Stirnseite der asymmetrischen Metallmembran auf die Filtratseite gelangen (2a)
• 2. Beim Verschweißen einer innen beschichteten Metallmembran mit einem Rohr von der Rück- bzw. Filtratseite bleibt ebenfalls ein Weg für nichtfiltriertes Produkt über die Stirnseite auf die Filtratseite offen (2b)
• 3. Beim Verschweißen einer außen beschichteten Metallmembran mit einem Rohr von der Vorder- bzw. Produktseite wird die feine, dünne Schicht durch den hohen Energieeintrag so geschädigt, dass Risse entstehen, die ebenfalls zu einem Weg für nichtfiltriertes Produkt auf die Filtratseite führen.

There has been no lack of attempts to weld such an asymmetric filter medium or an asymmetric membrane directly without pretreatment of the face with a non-porous metal part such as hole bottom or metal tube. Specifically, the following problems occurred:

• 1. When welding an internally coated metal membrane into a perforated bottom, non-filtered product can reach the filtrate side via the front side of the asymmetric metal membrane ( 2a )
• 2. When welding an internally coated metal membrane with a tube from the back or filtrate side also leaves a way for non-filtered product on the front side on the filtrate side open ( 2 B )
• 3. When welding an externally coated metal membrane with a pipe from the front or product side, the fine, thin layer is damaged by the high energy input so that cracks arise, which also lead to a path for non-filtered product on the filtrate side.

It Thus, the task turned out to be a procedurally simple To find a method which remedies the disadvantages mentioned and which allows a lasting and good separation.

Accordingly, became a method for processing porous, metallic membranes or filter media found which is characterized that parts of the membrane or the filter medium by means of a Laser welder thermally treated.

In the following, the inventive method is based on the 3 described in more detail. In this case, the membrane or the filter medium is fused at the end side so that a dense, fused metal layer (in the lower part of the 3 The exact procedure for fusing the end face by means of a laser welding device depends on the particular metallic materials present and the layer structure (thickness and pore diameter of the coarse, thick substructure and the finer, thinner In general, it should be noted that the energy input is designed in such a way that the end face is sealed and defect-free connected to the separation layer The typical shielding gases are inert gases such as argon.

Subsequently, the separating elements obtained according to the invention can be connected to other, solid metal parts by welding. Examples are in the 4a to 4d shown.

In 4a It can be seen how the sealed, internally coated tubular metal membrane by means of a laser welding ( 3 ) into the perforated bottom of a module ( 2 ) was fixed. In this context, a module is understood to be a pressure housing which receives the membrane or the filter medium and, separated by the membrane or the filter medium, generates a retentate and permeate or filtrate space and has feeds and discharges for feed, retentate and permeate ,

In 4b is shown how the sealed, internally coated tubular metal membrane by means of a laser welding ( 3 ) from the outside with a metal tube ( 2 ), which can be welded into the perforated bottom of a module.

4c shows a sealed, internally coated tubular metal membrane, which by means of laser welding from inside and outside ( 3 respectively. 4 ) with a short metal ring ( 2 ) was welded. This metal ring is itself by means of external welding ( 6 ) with a metal tube ( 5 ) welded and can be welded into the hole bottom of a module.

In 4d is an externally coated, tubular metal membrane to see, which by laser welding ( 3 ) from the outside with a metal tube ( 2 ), which can be welded into the perforated bottom of a module.

The exam whether in the sealing a sufficiently dense, fused layer has been achieved, is only after the described connection with others meaningful metal parts. The connection is sufficiently dense, if it does not allow gas through to the bubble point of the release layer. In the Bubble Point measurement is the separating layer with a liquid e.g. Isopropanol filled and then the pressure measured, at the air or nitrogen the liquid displaced from the pores of the separation layer and then gas through the Separating layer flows (visible by blistering). Is the connection (sealing and welding with a solid metal part) is not sufficiently good, this blistering occur at the compound at a significantly lower pressure.

The produced according to the invention Separators are suitable for the use in ultrafiltration and microfiltration or crossflow filtration. typical Fields of application are the concentration and / or purification of Dispersions or suspensions, the cell separation of fermentation effluents as well the recycling of heterogeneous catalysts - see also textbook 1 or Li, Stöcker, metallic membranes extend areas of use for sintered metal filters, European Process Engineering, May 2001, p. 70-71.

The inventive method offers a manufacturing technology simple way to produce Separating elements which permanently enable a good separation, because of the seal according to the invention the front end an unwanted, direct product flow from the feed or retentate side to the permeate or filtrate side can be avoided.

Especially the method according to the invention is suitable for the production of separating elements, which are easily in all-metal modules shrink wrapped can be which in turn are particularly suitable for applications e.g. at high Temperatures (100 - 300 ° C) as well in the presence of organic media, these applications alone or in combination can be realized.

Claims (2)

Process for the treatment of porous, metallic asymmetric membranes or filter media, characterized in that parts of the membrane or of the filter medium are thermally treated by means of a laser welding device, wherein the end face of the membrane or of the filter medium by means of the thermal treatment by Ver sealing and performs the thermal treatment by laser welding under inert gas. Method according to claim 1, characterized in that that the membrane thus obtained or the resulting filter medium by further welding with additional Metal parts connects.