EP0729789A1 - Magnetic separator - Google Patents

Abstract

Magnetic material is separated from non-magnetic material by a magnetic separator with a sloping and / or curved separator plate (13) which is porous and has an air supply device (15) on the side of the plate remote from the material being sepd., to blow air through the plate. A magnet system (5) forms a magnetic flux and is pref. located within a drum (T), which forms the separator plate may by rotatable. The flux passes through part of the drum circumference. Porous material is pref. a sintered material, partic. sintered bronze or ceramic.

Description

The invention relates to a magnetic separator with an inclined and / or curved cutting plate, to which the material to be separated is applied and through which a magnetic flux is maintained in order to separate the magnetic material from the non-magnetic.

Typically, the cutting plate is a drum, possibly rotatable about a horizontal axis, inside which there is a fixed magnet system, which causes the magnetic flux through part of the circumference of the drum, and has a feed device which essentially separates the material to be separated applies the highest point of the drum casing.

In such separators, an electric or permanent magnet is accommodated in the interior of the drum in such a way that magnetic forces act, for example, from the area of the drum apex to the lower area of the drum, through which the magnetic material is separated.

The good consists of granular or lumpy material that is partly magnetic (actually: magnetizable) and partly non-magnetic (actually: not magnetizable). The magnetic particles adhere to the rotating drum due to the magnetic field generated in the drum and do not fall off the drum until after the rotation they have reached the point at which the magnetic influence has essentially disappeared. The non-magnetic particles are naturally not influenced by the magnetic field and fall off the drum when they reach the underside of the drum.

The vagina plate can also be a flat structure such as tape, belt, cloth or the like. be that is moved substantially transversely to the direction of movement of the goods, so that the magnetic part of the goods is taken off the conveyor belt and thus separated.

For the separation of foreign iron parts (nails, screws, iron shavings), which only make up a small percentage of the total good, it is also known to use fixed sheath plates, which are preferably firmly connected and encapsulated with the magnet system. Due to the small amount of magnetic material, it is possible to remove the iron parts adhering to the cutting plate only from time to time while the system is at a standstill.

Such devices have been known for a long time and have essentially proven themselves. However, there are materials that are difficult or impossible to separate with satisfactory results. These include, in particular, very fine-grained and powder-like materials, since the influence of the surface forces (adhesive forces) grows disproportionately both with one another and with respect to the cutting plate as the particle size shrinks. Other materials that cause problems are those that show strong particle cohesion.

• 1. Die magnetischen Partikel können durch die an der Scheideplatte anhaftende Schichte der nicht magnetischen Partikel nicht mehr zur Oberfläche der Scheideplatte gelangen und werden daher nicht so festgehalten, wie es für eine saubere Abscheidung notwendig ist. Es gelangt daher magnetisches Material in die Sammelvorrichtung für nicht magnetisches Material.
• 2. Durch das Anhaften des nicht-magnetischen Materials an der Scheideplatte gelangt solches Material in die Sammelvorrichtung für die magnetischen Partikel oder sogar, wenn es im Falle eines Trommelscheiders, mit der Trommel weiter mitwandert, wieder zurück in den Aufgabebereich, wo es als permanente Unterschichte die Trennqualität weiter verschlechtert.

There are materials, such as aluminum oxide, magnesium oxide, chrome powder, corundum, which, from a certain fineness, usually less than 50 µm, have a negative angle of repose and adhere strongly to the vagina plate, which causes two undesirable effects:

• 1. The magnetic particles can no longer reach the surface of the cutting plate due to the layer of non-magnetic particles adhering to the cutting plate and are therefore not retained as is necessary for a clean separation. Magnetic material therefore gets into the collecting device for non-magnetic material.
• 2. Due to the adherence of the non-magnetic material to the cutting plate, such material gets into the collecting device for the magnetic particles or even, if it moves along with the drum in the case of a drum separator, back into the application area, where it acts as a permanent lower layer the separation quality deteriorated further.

The object of the invention is to create a magnetic separator which is particularly suitable for fine-grained and powder-like material and which also achieves good results with such difficult-to-separate materials.

According to the invention, the desired goals are achieved in that the cutting plate is made of porous material and that air is blown through the cutting plate towards the material.

This combination of measures ensures that the material hitting the cutting plate cannot adhere to the cutting plate but is fluidized. Within the fluidized layer formed in this way, the magnetic particles are easily and reliably drawn to the surface of the wing and held there against the forces of the air flow, while the non-magnetizable particles slide just as reliably over the cutting plate and, in the case of a drum separator, fall off when they do get into the overhanging area of the drum surface without sticking to the surface or even baking.

Cutting plates according to the invention can consist, for example, of sintered bronze, ceramic or porous plastics and can be produced by sintering or casting. It is essential that a large number of fine pores is preferred with a pore size of 5 - 200 µm, because in this way the formation of non-porous areas, to which non-magnetic material could stick again, is avoided, as well as the formation of areas with excessive flow, in which could also remove magnetic particles from the cutting plate too soon due to the air flow.

The cutting plates used in accordance with the invention have a porosity that is between 10 and 60%, preferably between 30 and 50%, where: $$\text{ε = [(ρ solid - ρ porous body) / ρ solid] x 100 [\%]}$$

In one embodiment of the invention in drum cutters, which is advantageously provided for materials that are particularly difficult to cut, the feed device for the drum separator also has a zone with a cutting plate according to the invention in its end region, which, viewed in the direction of good transport, is arranged directly in front of the drum in which the transported goods are fluidized and loosened by blowing air through the pores of the cutting plate, which forms the bottom of the transport device.

• Fig. 1 schematisch einen Magnettrommelscheider gemäß dem Stand der Technik, die
• Fig. 2 eine erfindungsgemäße Vorrichtung mit erfindungsgemäßer Zufuhrvorrichtung und die
• Fig. 3 eine erfindungsgemäße Vorrichtung mit einer unbeweglichen porösen Platte.

The invention is described in more detail below using exemplary embodiments. The shows

• Fig. 1 shows schematically a magnetic drum separator according to the prior art, the
• Fig. 2 shows a device according to the invention with a feed device according to the invention and the
• Fig. 3 shows a device according to the invention with an immobile porous plate.

In Fig. 1 a rotatable drum T is shown, on the upper vertex area 2 granular material is applied, which is partly magnetic and partly non-magnetic Particles. The feed device shown consists of a slide 3 and a baffle 4.

A magnet system 5 is provided in the interior of the drum T and is stationary and extends essentially over a half of the drum from the top to the bottom. This magnet system can consist of permanent or electromagnets and has the task of creating a magnetic flux through the drum surface in the area in which the material to be separated co-rotates with the drum, by means of which the magnetic particles are held on the drum surface.

As shown in Fig. 1, the non-magnetic material 6 leaves the drum in the area in which the possible holding forces of the drum are overcome by the combination of centrifugal force and gravity, for example in the area in which the overhang of the drum shell begins, so that with "good-natured" materials there is a dropping image, as shown in FIG. 1.

The magnetic particles adhere to the drum surface due to the magnetic flux passing through the drum surface and do not fall away from it until after the drum rotation, the individual magnetic particles 7 come into an area in which the magnetic flux is no longer sufficient around the particles to hold against the gravity and centrifugal force on the drum jacket.

In the case of the materials which are difficult to separate at the beginning, the non-magnetic material now adheres so firmly to the drum surface that it likewise only falls off in the lowest region of the drum or beyond this region, and on the other hand magnetic particles which do not because of the layer adhering to the drum get close enough to the drum surface, are already deposited with parts of the non-magnetic material, so that too 8 magnetic and non-magnetic particles with insufficient selectivity are present on both sides of the separating chute.

FIG. 2 shows a magnetic drum according to the invention, which essentially corresponds to the structure of FIG. 1.

The most important difference is that the drum shell 1 is made of porous material and that an excess pressure is maintained inside the drum by the supply of compressed air by means of an air supply 15, through which air continuously flows through the porous drum shell, as indicated by the arrows L is indicated in Fig. 2 in some circumferential areas.

This radially outward air flow, which extends over the entire circumference of the drum, results in the above-mentioned fluidization of the material fed in and thus the desired selectivity when separating.

FIG. 2 also shows a feed device 9, which in the example shown is an oscillating conveyor. The vibrations loosen the material to be separated, which is further reinforced in the end region 10 of the vibratory conveyor 9 by the following measure according to the invention: in the end region 10, the bottom 11 of the vibratory conveyor has a fluidizing plate 16 which, like the cutting plate 13 according to the invention, is porous and, for example consists of the same material as the drum shell 1.

A wind box 12, to which compressed air is supplied, is arranged below the fluidizing plate 16. The resulting overpressure in the wind box 12 creates a permanent air flow through the fluidizing plate 16, as indicated by the arrows L in this area, as a result of which it is already on the product before it hits it Magnet drum comes to an intensive loosening and fluidization of the goods.

3 shows a stationary embodiment, for example for foreign iron deposition. A cutting plate 13 according to the invention is tightly connected to a permanent magnet all around to allow air to be blown into the area between the magnets and the cutting plate, so that the magnet forms the walls of a wind box.

Magnetic particles stick to the cutting plate and are removed from time to time after the flow of material has been interrupted. In order to facilitate this, the cutting plate can be pivoted about an axis 14.

The invention is not limited to the example shown, but can be modified in various ways. It has been shown that for different types of goods or mixtures, the measure according to the invention does not require the drum to be rotated, since the non-magnetic material glides over the stationary drum surface and falls off in the area of the beginning overhang, while the magnetic material along the Drum surface slides and only drops in the area of the end of the magnet device 5.

The size of the pores and the selected material can easily be determined by a person skilled in the art knowing the invention and the envisaged field of application. Sintered materials are preferred because of their extremely fine pore structure and high porosity. Whether it is sintered metal or sintered ceramic materials depends on their magnetic and mechanical properties.

Claims (6)

Magnetic separator with an inclined and / or curved cutting plate (13) onto which the material to be separated is applied and through which a magnetic flux is maintained by means of a magnet system (5) in order to separate the magnetic material from the non-magnetic one, characterized in that that the cutting plate (13) is porous and that an air supply device (15) is provided on the side of the cutting plate facing away from the material, through which air is blown through the cutting plate (13). Magnetic separator according to claim 1 with an optionally rotatable drum (T), inside of which is the fixed magnet system (5), which causes a magnetic flux through part of the drum circumference, and with a feed device (3, 9), which is to be separated Applies well essentially to the highest point of the drum shell, characterized in that the cutting plate is designed as a drum shell (1) which is permeable to air in the radial direction and that the air supply (15) is arranged inside the drum (T). Device according to claim 1 or 2, characterized in that the cutting plate (13) or the drum casing (1) consists of sintered material, in particular sintered bronze or ceramic. Apparatus according to claim 1, 2 or 3, characterized in that the cutting plate (13) or the drum casing (1) has a porosity ε which is between 10 and 60%, preferably between 30 and 50%, where: $$\text{ε = (ρ solid - ρ porous body) / ρ solid x 100 [\%].}$$

Device according to one of claims 1 to 4, characterized in that the pore size of the cutting plate (13) or the drum jacket (1) on the surface facing the material is 5 - 200 µm. Device according to one of claims 2 to 5, characterized in that the feed device (9) has a bottom (11) which, at least in the region (10) which faces the drum (T), has a fluidizing plate (16) which how the cutting plate (13) is porous and consists, for example, of the same material as the drum shell (1), that a wind box (12) is arranged below the fluidizing plate (16) and that in this wind box by supplying compressed air by means of an air supply ( 15) A pressure above ambient pressure is maintained.

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