JPH0712407B2 - Metal filter element for separating particles from gas and method of making the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is made of a thin material,
And the filter holes are configured in a circular or slot shape,
TECHNICAL FIELD The present invention relates to a metal filter element for separating particles from a gas and a method for manufacturing the same.

[0002]

2. Description of the Related Art A filter device having such an element is
It is known from German Patent DE 3800457. The filter element proposed therein is designed in the form of a foil and has round holes, the cross-section of which may be eccentric from circular, for example lens-shaped. In this filter element, the dust-containing gas is diverted towards the filter holes, some of the particles not being able to follow the streamlines or only to a limited extent on the basis of their mass. A filter cake gradually forms around the filtration holes, hindering the filtration of dust particles. This foil-shaped filter element is not suitable for all application cases due to its slight mechanical stability. Returning to sheet metal instead of metal foil, "Photoetching" and "electroforming" applied to perforate the foil.
The method of "electroforming" cannot be applied.
As a reference value for photoetching, it is important that the pore size be equal to or greater than the thickness of the material. Pore sizes larger than 100 μm, which are necessary for gas purification, cannot be produced by photoetching when the material thickness is greater than 1 mm. When applying electroforming, it is disadvantageous that the pores grow and block rapidly during the filtration process as the thickness of the filtration element increases.

From DE 3726076 A1 is known a filter element consisting of a steel foil for separating particles from a gas and a method for producing the filter element, which is rod-shaped and shaped on the surface of the filter element and in its pores. A coating layer with / or platelet-shaped oxides is formed to prevent flaking of the coating layer from thin steel foils, especially at elevated temperatures. Even in the case of this filter element made of steel foil, its slight mechanical stability is disadvantageous when the filter medium produced therefrom is subjected to strong mechanical external forces.

From US Pat. No. 4,795,560 is known a metal filter element for a net-making machine which is operated under pressure for papermaking, the holes or slots of 50 to 800 μm of which are laser-based. It is punched in a thin metal plate of about 8 mm. Such a thick metal sheet is hardly suitable for the above-mentioned class of filter elements for gas separation,
Moreover, it is uneconomical.

Furthermore, from DE 40 24 168 A1 is known a coating of a metallic object, ie a catalyst carrier, different from the above-mentioned classes, which coating is PV.
D method (Plasma-Vapor-Depositio)
n), in which the glass-ceramic layer is made into two layers. In this case, it is disadvantageous that the coating requires relatively high equipment costs.

[0006]

In order to avoid the drawbacks of the prior art, the object of the present invention consists of a thin metal sheet.
The object is to find and propose a method for producing a metal filter element having a small filter hole and an improved mechanical stability compared to the thickness of the sheet.

[0007]

This problem is solved by the features of claim 1 with respect to a metallic filter element. Specific embodiments of the filter element are described in claims 2-4. A suitable method of manufacturing the filter element is described in claim 5.

The filter element according to the invention has a very good service life and stability. A closed dust cake layer is produced after a very short dust cake formation period, in which the pressure drop increase is not linear, with a very slow linear increase in pressure drop. In this case, the increase in pressure drop is clearly determined by the thickness of the dust cake layer, rather than by the type or size of the filtration holes.
A proportion of 5 to 15% of the area of the filter holes guarantees the formation of an already closed dust cake layer, which is also formed on unperforated or unslotted surfaces. As a result, the largest possible filtering surface is used for the dust cake that is constructed, so that the increase in dust cake layer thickness and thus in pressure loss is limited to a minimum. This provides reliable use of this filter element at high temperatures and high working and pressure differences. The filter element is self-supporting, requires no other support and ensures a low pure gas dust concentration.

Surprisingly, when using the production method according to claim 5, relatively small filter holes are also produced in such metal sheets whose thickness is several times the hole diameter or the slot width of the filter holes. Gas from the thin plate,
Suitable filter elements can be produced, in particular for separating dust from hot gases.

[0010]

The present invention will now be described in detail with reference to the drawings.

1 to 16 are black and white prints of photographs of a metal filter element 1 produced by the method of the present invention, and FIGS. 1 to 6 show a filter element having a slot-like filter hole 21, and FIGS. Reference numeral 16 denotes a filter element having a round filter hole 20.

A pulsed solid-state laser was used to manufacture the slot-shaped filtering holes 21, and an electron beam generator was used to manufacture the round filtering holes 20.

1 to 10 show the filter element 1 immediately after the production of the circular or slot-shaped filter holes 20 and 21 (that is, without post-treatment). 11 to 16 show a round filter hole 2
After further treatment of the filter element 1 with 0 according to the invention, i.e. after the production of the round filter hole 20, the filter element 1 is sprayed with small glass spheres (other sprays are also possible) in the example CVD method. (Chemical vapor deposition method "Chemical v
aor deposition ”) as an adhesion layer
ceramic protective layer 3 made of iC layer 30 and Al ₂ O ₃
1 (a surprisingly round peripheral wall 2 of the filtration hole 20)
2 is a map of the filter element (also coated together).

In detail, FIG. 1 shows a section of a filter element 1 in which slot areas 2 and cross rails 3 are arranged alternately. The slot area 2 is formed by a number of slot-shaped filter holes 21 (FIG. 2). At the periphery, the filter element 1 is provided with longitudinal edges 4 and lateral edges 5 as reinforcing elements. In FIG. 1, the inflow side of the filter element 1, that is, the side away from the laser beam during processing is mapped.

The filter element 1 shown in FIG. 1 can be used as a flat plate filter. However, the filter element 1 can also be formed into a tubular candle filter element by bending it longitudinally or laterally so that both longitudinal edges or lateral edges are abutted or fixed in an overlapping manner.

2 to 5 show magnified maps of the entrance surface or exit surface of the laser beam from the slot range indicated by 2 in FIG. These figures reveal how slotted filter holes can be regularly manufactured by laser beam machining. In this case, Figure 2 is on a 1:20 scale,
FIG. 4 shows, on a scale of 1:40, the face of the filter element 1 on which the laser beam is incident on the filter element during processing, and FIGS. 3 to 5 show the face of the filter element 1 on which the laser beam exits the filter element. In general, the shape of the slots is more regular on the entrance side than on the exit side, and the size of the filter holes is larger on the entrance side than on the exit side. The middle portion of the slot-shaped filter hole 21 is relatively regularly configured, as can be clearly seen from FIG. 6 (cross-sectional view).

When used as a dust filter, the narrow holes are arranged on the inflow side, so that surface filtration is exclusively performed. There is no risk of blockage. Filter element 1 according to the invention
In this case, a relatively fine filtration structure can be realized without impairing its stability.

These microstructures can be further refined by coatings, which will be discussed in more detail below, to separate fine dusts that cannot be achieved using prior art filtration elements. A filter element 1 which is suitable for

FIGS. 7 and 8 show, on a scale of 1:35, a section from a filter element with round filter holes 20. These figures show the manufacturing stage after the circular filtration holes 20 have been opened using an electron beam. The emission side of the electron beam is shown in FIG. 7, and the incident side is shown in FIG. Regarding the filter element 1, FIG. 7 corresponds to the inlet side and FIG. 8 corresponds to the outlet side.

In FIGS. 9 and 10, an uncoated filter element 1 showing the regularity of the surface of a circular frustoconical filter hole 20 is shown.
The cross-section from is shown. In FIG. 10, the formation of burrs can be recognized in the hole incident area of the electron beam.

As shown in FIGS. 11 and 12, the coating achieves a further refinement of the structure by removing irregularities in the entrance and exit areas of the round filter hole and narrowing the round filter hole 20. be able to. The coating is C
VD method (Chemical vapor deposition)
on the filter element 1 with an adhering layer of TiC per layer and a ceramic protective layer of Al ₂ O ₃ on it. Before coating, for example, sand, glass, or the like is sprayed on the filter element 1 having the round filter holes 20 to remove burrs formed by the electron beam in the hole incident range and the hole emission range of the electron beam. Material annular bulge 4 that bends inward to limit the filter holes 20
Form 0. As a result, the filter hole 20 is provided on the outlet side of the hole.
Is further reduced (as desired).

13 to 16 the cross section from the coated filtration element 1 is mapped on a scale of 1: 100 to 1: 500.

In FIG. 13, two round filtration holes 20 are recognized, the middle hole being concentrically cut and the lateral holes being eccentrically cut. The latter is common in other planes. Commonly indicated filter hole 2
In the case of, deburring and covering by filtration element 1
It can be easily recognized that the extremely fine structure can be obtained on the side of the raw material gas effective for filtration.

14 to 16, the coating 10 consisting of the adhesion layer 30 and the ceramic protective layer 31 is not only on the surface of the filtration element 1 and on the annular bulge 40 in the area of the entrance of the round filtration hole 20, It can be seen that it is also effective on the inner wall (FIGS. 14 and 15).

[Brief description of drawings]

FIG. 1 is a photograph of a filter element portion having slot-shaped filter holes.

FIG. 2 is an enlarged photograph of the filtration element of FIG. 1 at a magnification of 1:20.

FIG. 3: Magnification 1: 2 from below the filter element of FIG.
An enlarged photograph of 0.

4 is an enlarged photograph of the filtration element of FIG. 2 at a magnification of 1:40.

5: Magnification 1: 4 from below the filter element of FIG.
An enlarged photograph of 0.

FIG. 6 is a partial cross-sectional photograph of the filtration element according to FIGS.

FIG. 7 is a magnified photograph at 35: 1 magnification from above of a filter element having circular filter holes.

FIG. 8: Magnification 35 from below of the filter element of FIG. 7:
Enlarged picture of 1.

9 is a magnified photograph of a cross section of the filtration element according to FIGS. 7 and 8 at a magnification of 100: 1.

FIG. 10 is an enlarged photograph of the portion from FIG. 9 at a magnification of 500: 1.

FIG. 11: Magnification 3 of the filter element according to FIG. 7 after coating
5: 1 enlarged photo.

FIG. 12: Magnification 3 of the filter element according to FIG. 8 after coating
5: 1 enlarged photo.

FIG. 13 is a magnified photograph of a partial cross section of the filtration element according to FIG. 9 after coating at a magnification of 100: 1.

FIG. 14 is an enlarged photograph of a cross section of the portion from FIG. 13 at 100: 1 magnification.

FIG. 15 is an enlarged photograph of a cross section of the portion from FIG. 13 at 100: 1 magnification.

16 is a magnified photograph of a cross section of the portion from FIG. 13 at 100: 1 magnification.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Filter element 2 Slot range 3 Horizontal cross section 4 Vertical edge part 5 Horizontal edge part 10 Cover 20 Circular filter hole 21 Slot-shaped filter hole 30 Adhesive layer 31 Ceramic protective layer 40 Annular swelling part

Claims (5)

[Claims] 1. A metal filter element for separating particles from a gas, which is made of a thin material and has a filter hole formed in a circular shape or a slot shape, wherein the filter element (1) has a thickness of 15 to 1500 μm. CrNiMoT
i of thin metal plate, the round filtration holes (20) of the filtration element have a diameter of up to 100 μm on the inflow side or the slotted filtration holes (21) have a length of at least 100 mm on the inflow side and a maximum width Has a dimension of 150 μm,
The filter element (1) has a TiC layer (30) as an adhesion layer.
And / or Al ₂ O ₃ ceramic protective layer (3
A metal filter element for separating particles from a gas, characterized in that it has 1) and the filter holes (20, 21) are 5 to 15% of the filter element surface. 2. Filter element according to claim 1, characterized in that the slot-shaped filter holes (21) are wedge-shaped and the circular filter holes (20) are frustoconical. 3. The coating thickness of the protective layer (30, 31) is 10
3. The filter element according to claim 1, wherein the filter element has a thickness of μm. 4. The filter element according to claim 1, wherein the filter holes (20, 21) are defined by an annular bulge (40) of material. 5. A metallic filter element for separating particles from a gas according to claim 1, wherein the filter element is made of a thin material and the filtering holes are circular or slot-shaped. In the manufacturing method of 1., the filter element (1) is cut from a thin metal plate of CrNiMoTi as a material, and a circular or slot-shaped filter hole (20, 21) is formed on this material by using a pulsed solid state laser or an electron beam. For example, sand, glass or the like is sprayed on the filtering element (1) which is provided and not perforated or slotted, and the TiC layer (30) and / or Al is deposited as an adhesion layer under a vacuum by a CVD method (chemical vapor deposition method). _A method for producing a metal filter element for separating particles from a gas, which comprises coating with a ceramic protective layer made of ₂ O ₃ .