CN216170662U

CN216170662U - Filter media construction

Info

Publication number: CN216170662U
Application number: CN202121010497.7U
Authority: CN
Inventors: S·范登迪杰克; A·戈克斯; J·德贝尔德梅克
Original assignee: Bekaert NV SA
Current assignee: Bekaert NV SA
Priority date: 2021-05-12
Filing date: 2021-05-12
Publication date: 2022-04-05
Anticipated expiration: 2031-05-12

Abstract

A layered filter media structure (10) comprising at least a) a first wire mesh, b) a first layer (12) comprising a non-woven web of metal fibers, c) a second layer being a woven dutch weave, d) a second wire mesh. The layered filter media construction has the advantage of improving bubble point pressure after multiple cleanings.

Description

Filter media construction

Technical Field

The present invention relates to a layered filter media construction suitable for filtration purposes.

Background

The filter materials currently available for filtration applications and in situ cleanable filter media conveniently comprise a ceramic membrane layer secured to the surface of a porous sintered metal powder or the surface of a metal fiber matrix material. However, the high pressure drop in the direction through the filter layers is a considerable disadvantage, because of the high pressure of the filter layers and the strong mechanical support, which results in additional energy being required for the filtration process. Furthermore, repeated backwashing of these filter layers is difficult and, after all, the ceramic layer is rather brittle, which has a negative effect on the durability. The metal mesh also serves as a backup mesh to keep filtration efficiency at a minimum. The filter media construction after cleaning was tested using the bubble point method. The backup web should ensure the foaming pressure. On the other hand, such a backup net should have no or little effect on other properties of the filter media structure, such as the performance in a backflow test (also referred to as a 10L/min test).

SUMMERY OF THE UTILITY MODEL

It is an object of the present invention to avoid the disadvantages of the prior art.

It is another object of the present invention to provide a filter media structure suitable for microfiltration without causing high pressure drop in the direction through the structure.

It is yet another object of the present invention to provide a filter media construction that allows for repeated backwashing.

According to a first aspect of the present invention, there is provided a layered filter media structure comprising at least a first wire mesh, a first layer, a second layer, and a second wire mesh. Wherein the first layer comprises a non-woven web of metal fibers and the second layer is a woven dutch weave.

The dutch weave is formed by cross weaving tightly joined small diameter corrugated wire between non-corrugated and non-joined large diameter wire. The high density of the metal filaments in the dutch weave gives them a higher mechanical strength. The dutch weave according to the present invention may be a plain dutch weave, a twill dutch weave, a reverse dutch twill weave, or a reverse dutch weave.

The plain dutch weave has a porosity of between 10% and 25%, a coarse opening of about 100 μm, and a minimum opening of about 5 μm. The dutch weave according to the present invention is preferably a plain dutch weave including high flow alternatives. The high flow rate plain dutch weave is defined in terms of a special calculated plain dutch weave wherein the porosity of all weaves is guaranteed to be 40% by calculation.

According to the utility model, the nonwoven web of metal fibers may be in a green state, i.e. it is not sintered. Preferably, however, the nonwoven web of metal fibers has been sintered.

The weight of the first layer is preferably 300g/m²To 600g/m²And thus its thickness is limited to the range of 0.05mm to 0.15 mm. Generally, the pressure drop across the filter is proportional to its thickness. In this case, the limited thickness of the first layer limits the pressure drop generated to an acceptable level. The nonwoven web of metal fibers may have a porosity that may be less than 90%. The first layer comprises metal fibers having a diameter of less than 10 μm.

Further, the first layer may include a first sublayer and a second sublayer. Wherein the first sub-layer may have a porosity of less than 55% and the second sub-layer may have a porosity of not less than 80%. The first sub-layer comprises metal fibers having a diameter of less than 3 μm, for example less than 2.5 μm, for example 2 μm, and the second sub-layer comprises metal fibers having a diameter of at least three times the diameter of the fibers in the first sub-layer. The first sub-layer having a lower porosity determines the grade of the filter, i.e. the size of the particles that are mostly still able to pass through the filter. Due to the greater porosity of the second sublayer, the degree of pressure drop over the second sublayer is significantly lower than over the first sublayer. The total pressure drop across the filter media construction is approximately equal to the finite pressure drop across the first sublayer. The inflowing fluid is able to expand in the second sublayer as soon as it passes through the first layer.

In order to obtain a porosity difference between the first and second sub-layers, the first sub-layer is sintered and compacted separately and beforehand. Only thereafter can the sintered and compacted first sub-layer come into contact with the second sub-layer and a second sintering operation is carried out to sinter the fibres in the second sub-layer and to bond the two layers together.

The first layer can be obtained by a cold isostatic pressing operation. For the compacting operation of the first layer, an isostatic cooling operation is preferably used, since this operation enables a homogeneous filter medium to be obtained. However, isostatic cool operation may result in a slightly rough surface, rather than being flat and smooth. Isostatic cooling is preferred here, wherein pressure is applied from one side of the layer, and wherein the other side of the layer is placed on a flat and smooth support, in order to obtain a flat and smooth surface.

Preferably, a wire mesh is secured as a support to the first and second layers. Most preferably, a first wire mesh fixed to the first layer is located at the inlet side and a second wire mesh fixed to the second layer is located at the outlet side. The meshes of the first wire mesh are smaller than the meshes of the second wire mesh. The wire diameter of the first wire mesh is smaller than the wire diameter of the second wire mesh. The first wire mesh and/or the second wire mesh may be calendered wire mesh.

In addition to the function of support, the first wire mesh has another function and advantage. The first wire mesh creates some turbulence in the incoming fluid, which improves the anti-fouling properties.

The filter media construction of the present invention has superior performance compared to conventional surface or depth filter media. According to the utility model, the two outer wire meshes as support meshes are subjected to the pressure differences involved. Preferably, the non-woven first layer is sintered such that particles are trapped inside the sintered fibers and gels (deformable particles) are also trapped. The dutch weave in the layered filter media construction of the present invention can provide improved bubble point pressure over long term use and after multiple cleanings. On the other hand, if any material (rigid, non-gel) comes loose, it will be trapped in the dutch weave. Preferably, the dutch weave has a high porosity, so the efficiency of the layered filter media structure is similar to that without the dutch weave.

Drawings

The following detailed description refers to the accompanying drawings in which:

FIG. 1 shows an enlarged cross-sectional view of a layered filter media construction according to the present invention.

Figures 2 to 11 show schematic views of wire mesh and dutch weave applicable to the present invention.

Detailed Description

The following description will be based on preferred embodiments of the utility model. It will be obvious to the skilled person, however, that the utility model is not limited to this particular embodiment.

Referring to fig. 1, a layered filter media structure 10 according to the present invention includes a first layer 12 formed of a sintered and compacted fiber web.

The filter media construction shown in fig. 1 can be made in the following manner. Steel fibres having a diameter of 2 μm are obtained by bundle drawing techniques, as described for example in us patent No. 3379000. The first nonwoven layer is then produced by means of a random feeding device which converts the steel fibres into a web, for example as disclosed in GB1190844 (corresponding to us patent No. 3469297). The web is then sintered and compacted by means of an isostatic cool operation at a pressure above 2000bar to obtain a porosity below 55%, such as below 50%, such as 46%. This forms the first layer 12.

As the second layer 13, a dutch weave as shown in fig. 7 to 11 may be applied. A dutch weave with high porosity as shown in fig. 9 is preferably used to form the second layer 13. Dutch-type weaving with high porosity (40% to 50%) is the most effective because of the very stable weave structure. The lotusThe openings of the basket weave are very stable and do not change with the weave conditions (e.g. stretching at the end of the roll or wire diameter variations). For example, the second layer 13 may be commercially available

And (4) knitting.

The braid is a dutch weave in which the openings between two continuous chute wire wires are smaller than the openings of the "filtering triangle". This is a dutch weave with high porosity and good adhesion. The second layer had a weight of 18712g/m2 and a thickness of about 0.30 mm.

The second layer 13 is arranged on the second wire mesh 15, and the first layer 12 is arranged with its flat surface on the second layer 13. A first wire mesh 14, which has been pre-rolled, is arranged on the first layer. The first wire mesh 14 and the second wire mesh 15 may have an alternative weave structure as shown in fig. 2 to 6. As an example, the first wire mesh 14 has been rolled to a thickness of 0.17mm and has 48 mesh openings per inch (1 inch-25.4 mm). The weight of the powder is 380g/m². The second wire mesh 15 has a thickness of 0.45mm and has 40 meshes per inch. The weight of the powder is 1220g/m²。

The layered assembly so obtained is sintered together under light pressure to obtain the layered filter media structure 10.

The layered filter media structure according to the present invention has been subjected to a bubble point pressure test and a conventional test for measuring air permeability. The bubble point values of the fibrous media and dutch weave need to be adjusted to ensure a minimum. The air permeability in the example was 1700L/dm2/min and the bubble point pressure was 1825 Pa.

It has been noted that the filter media construction of the present invention having a dutch weave has a relatively small drop in applied pressure. The pressure drop of the layered filter medium structure without the Dutch braid is 265L/dm²Min, and similar layered over with Dutch knit layerThe pressure drop of the filter medium structure is 220L/dm²/min。

The materials used in the filter media construction according to the present invention may be conventional compositions such as 316 stainless steel, alloys, inconel or nichrome. The latter component can be used for gas filtration at high temperatures.

Claims

1. A layered filter media structure (10) comprising at least the following layers:

a) a first wire-mesh net is provided,

b) a first layer (12) comprising a nonwoven web of metal fibers,

c) a second layer, the second layer being a woven dutch weave,

d) a second wire mesh.

2. A layered filter media structure as in claim 1, wherein the dutch weave is a plain dutch weave, a twill dutch weave, a reverse dutch twill weave, or a reverse dutch weave.

3. A layered filter media structure as claimed in claim 1 or 2, wherein the dutch weave porosity is in the range of 40% to 50%.

4. A layered filter media structure as in claim 1 or 2, wherein the non-woven web of metal fibers has been sintered.

5. A layered filter media structure as claimed in claim 1 or 2, wherein the first layer has a weight of 300g/m²To 600g/m²Within the range of (1).

6. A layered filter media structure as in claim 1 or 2, wherein the nonwoven web of metal fibers has a porosity of less than 90%.

7. A layered filter media structure as claimed in claim 1 or 2, wherein the first layer comprises metal fibres having a diameter of less than 10 μm.

8. A layered filter media structure as in claim 1 or 2, wherein the first layer comprises a first sublayer and a second sublayer, the first sublayer having a porosity of less than 55% and the second sublayer having a porosity of at least 80%.

9. A layered filter media structure according to claim 1 or 2, wherein the first layer comprises a first sublayer and a second sublayer, the first sublayer comprising metal fibers having a diameter of less than 3 μ ι η, and wherein the second sublayer comprises metal fibers having a diameter of at least three times the diameter of the fibers in the first sublayer.

10. A layered filter media structure as claimed in claim 1 or 2 wherein the first layer is obtainable by an isostatic cool operation.

11. A layered filter media structure according to claim 1 or 2, wherein the wires of the first wire mesh have a finer diameter than the wires in the second wire mesh.

12. A layered filter media structure according to claim 1 or 2, wherein the first and/or second wire mesh is a calendered wire mesh.