WO1993008919A1

WO1993008919A1 - Magnetic disc separator

Info

Publication number: WO1993008919A1
Application number: PCT/NL1992/000196
Authority: WO
Inventors: Rintje Boersma
Original assignee: Envimag B.V.
Priority date: 1991-11-08
Filing date: 1992-11-06
Publication date: 1993-05-13

Abstract

The invention relates to a device for removing magnetic particles from a liquid, comprising a container (53) provided with a disc (61) provided with permanent magnets and drivable in rotation, wherein the field generated by the magnets extends into the container, and wherein the disc extends partially above the liquid level, and wherein a device (66) is arranged above the liquid level for carrying the magnetic particles outside the field generated by the magnets. The disc is preferably disposed outside the container. This has the advantage that removing the particles from the magnet can take place more conveniently because the particles are not situated in the direct vicinity of the magnet but a, naturally, short distance therefrom. The forces necessary for carrying the magnetic particles outside the magnetic field are thus much smaller.

Description

Magnetic disc separator.

The invention relates to a device for removing magnetic particles from a liquid, and at least one magnet, the field of which extends into the container.

Such devices are known, for example from US-A-2915186.

In this known device permanent magnets are placed in the container and the liquid flow passing through the container is regularly interrupted in order to remove the collected magnetic particles from the magnets. This is a time-consuming procedure which cannot be applied continuously.

The object of the present invention is to provide such a device which can be used continuously.

This object is achieved by a disc provided with permanent magnets that is drivable in rotation, wherein the field generated by the magnets extends into the container, and wherein the disc extends partially above the liquid level, and wherein a device is arranged above the liquid level for carrying the magnetic particles outside the field generated by the magnets.

According to a preferred embodiment the disc is arranged outside the container.

This has the advantage that removing the particles from the magnet can take place more conveniently because the particles are not situated in the direct vicinity of the magnet but at a, naturally, short distance therefrom. The forces necessary for carrying the magnetic particles outside the magnetic field are thus much smaller.

The invention will now be elucidated with referen- ce to the annexed drawings, in which: fig. 1 shows a partially broken away, schematic perspective view of a test arrangement of a first embodi¬ ment of the present invention; fig. 2 shows a partially broken away schematic perspective view of a variant of the first embodiment of the invention; fig. 3 shows a partially broken away schematic perspective view of a second embodiment of the invention; and fig. 4 is a sectional view of the embodiment depicted in fig. 3.

The embodiment according to fig. 1 is formed by a base 18 on which is arranged a container 19. The latter has a rectangular section and a long length relative to the width. The container is also high relative to its width. The container is provided with a bottom plate 20 with a non-planar form, to which later reference will be made. The container further comprises two side walls 21, 22 respectively and two head end walls 23, 24 respectively.

Arranged above the container is a shaft 25 which is mounted on either side in bearing blocks 26, 27 respec¬ tively arranged on either side of the container. Each of the bearing blocks 26, 27 respectively is arranged on the base 18 by means of a console 28, 29 respectively. On the shaft 25 is arranged a round disc 30 in which are arranged permanent magnets 33 ordered in two circles 31, 32. The permanent magnets 33 are magnetized in the direction of the shaft 25. Arranged for driving the disc 30 is an electric motor 34 which is fixed to the base 18 via a console 35. The electric motor 34 is coupled to the shaft 25^* by means of a coupling 36.

Arranged on both sides of the disc are scraping members which are each formed by a plate 37, a cutting edge 38 of which touches the plate, and wherein the plate 37 further extends downwards at an incline. The plates 37 are each provided with two standing edges 39. Both plates 37 are fixed to the base 18 by means of an adjustable yoke 40.

The shape of the bottom plate 20 is adapted to the shape of the disc 30 so that the distance between the bottom plate and the disc is always small.

A partition 41 is arranged in the container 19, wherein an inlet opening 42 is formed between the partition 41 and the end wall 24 for feeding the liquid from which the magnetic particles must be removed. On the outlet side the bottom plate 20 transposes via a threshold 43 into an inclining portion 44 which leads to an outlet duct 45.

A valve 46 is arranged for maintaining a constant water level. The valve 46 is fixed to a shaft 47 which is rotatably mounted in the walls 21, 22. The valve is formed by a first plate 48 and a second plate 49 which enclose an angle of approximately 90°. The mass of the valve 46 and the dimensions thereof are chosen such that a fixed liquid level is always maintained in the container 19. When there is a danger of this fixed liquid level being exceeded the valve 46 will open more, while if this liquid level threa¬ tens to become too low the valve will close.

The operation of this device is such that the motor 34 drives the disc 30 in rotation, this such that it rotates in the direction indicated by the arrow 50. At the same time liquid from which the magnetic particles will be removed is supplied via the inlet opening 41. This liquid enters the container 19 and thus comes within a short distance of the magnets 33 which are received in the disc 30. The distance between the side walls 21, 22 of the container herein plays a large part because the total volume of liquid must be carried into the vicinity of the magnets 33 in order to guarantee the greatest possible likelihood that the magnetic material comes within the sphere of influence of the magnets. For this purpose the magnetic particles must come so close to the magnets that the magnetic forces exerted by the magnets cause the par¬ ticles to move towards the magnet and to adhere onto the surface of the magnet.

Because the disc rotates, the magnets are moved out of the liquid, wherein the magnetic material remains adhered to the magnet. The magnets then pass the scraping member 38, wherein the magnetic material is scraped off the magnets and carried away via the plate 38. It is possible herein that the scraping member is arranged as close as possible against the disc so that the residual layer of magnetic material is negligible, although it is equally possible for the scraping member to be fixed at a short distance from the disc. It is otherwise noted herein that the thickness of the disc - to enable scraping action - is as constant as possible.

Fig. 2 shows a device which is suitable for lar¬ ger-scale applications; this comprises three units 51 connected in parallel, each of which corresponds in large measure with the device shown in fig. 1. The separate units are distinguished from the device depicted in fig. 1 only in the arrangement of sepa¬ rate discharge ducts 52, each of which forms an integrated unit with the scraping plates 37.

The capacity of the motor, not shown in the draw- ing, must of course be adapted for driving the desired number of discs.

The shape of the containers is further adapted to allow space for the ducts 52.

It occurs in some processes that a magnetic sepa- ration has to take place in two separate phases of such a process. It is then attractive to apply a device for such a process wherein two devices according to the invention are applied simultaneously. Such devices can of course be disposed separately, although certainly in the case of one of the devices according to claims 13-19 it will be attractive to connect such devices in parallel and to attach the discs to a single shaft. Thus a saving in the number of drive motors is obtained while also a great saving of space results. In the embodiment shown in fig. 3 there is a container 53 which is formed by two long walls 54, 55 and two short walls 56, 57. One of the walls is provided with a protrusion 58. In order to cause the magnetic field to permeate through the wall into the container the wall will be manufactured of non-magnetic conducting material.

The container further comprises a bottom not shown in the drawing. A feed pipe 59 is arranged on one of the short sides 56 for feeding the liquid to be cleaned, while a discharge pipe 60 is arranged on the other short side for draining the liquid from which the magnetic material has been removed. Along one of the walls 55 and parallel thereto is arranged a rotatable disc 61 which extends entirely on the outside of the container. This rotatable disc 61 falls wholly within the surface of the wall 55 and the protrusion 58.

Two concentric series of permanent magnets 62 are arranged in the rotatable disc.

The rotatable disc is fixed to a shaft 63 which is mounted in a number of bearing blocks 64 and which is driven by an electric motor 65.

Further arranged at the location of the protrusion and above the edge of the container 53 is a gutter 66 which serves to remove the magnetic particles which have been removed from the liquid. To aid the transport of the magnetic particles a spray nozzle 67 is arranged which is connected to a water feed hose 68 with which a water jet 69 can be generated and which aids the transport of the material along the gutter 66.

A piece of soft iron is further fixed against the protrusion 58 which ensures that the field coming from the magnets is deformed. The operation of this device will now be descri¬ bed.

A liquid in which magnetic particles are present is supplied by means of the feed pipe 59. Magnetic par¬ ticles are also understood to include particles which become magnetic under the influence of a magnetic field, and which are also designated as magnetizable particles. Because of the narrowness of the container the liquid is carried into the sphere of influence of the magnets 62. It is noted here that the distance between the disc 61 and the wall 55, respectively the protrusion 58, is as small as possible, for example in the order of magnitude of a millimetre. The particles are there attracted by the magnetic field and moved towards the wall 55.

Due to the rotation of the disc 61 which is driven in rotation by a motor 65, the particles will then be moved in a circular path along the wall 55 and the protrusion 58, wherein the path of the magnets is followed as closely as possible. This movement proceeds until the magnetic particles reach the gutter 66 and they are moved off the disc. The vertical component of the force exerted by the magnets causes this movement. However, the horizontal force exerted by the magnets must hereby be overcome.

To aid this process use is made of a water jet 69 whereby the magnetic particles are subjected to an addi- tional force directed along the gutter 66. A soft iron plate 70 is arranged to also form the field as favourably as possible at the point of adhesion of the gutter 66.

It is likewise possible of course to apply such a configuration when the volumes to be treated in different phases are different; for the first phase for example, wherein a large volume of liquid has to be treated, a number of devices can be connected in parallel, while for instance for the second phase, wherein only a smaller volume has to be treated, one device can suffice. Also in this case all these devices can be mounted on a single shaft.

It will be apparent to any skilled person that the device can still be modified to a large degree in respect of dimensioning and embodiment.

Claims

1. Device for removing magnetic particles from a liquid, comprising a container, characterized by a disc provided with permanent magnets and drivable in rotation, wherein the field generated by the magnets extends into the container, and wherein the disc extends partially above the liquid level, and wherein a device is arranged above the liquid level for carrying the magnetic particles outside the field generated by the magnets.

2. Device as claimed in claim 1, characterized in that the disc is disposed outside the container.

3. Device as claimed in claim 2, characterized in that an element influencing the field pattern is arranged in the vicinity of the scraping device.

4. Device as claimed in claim 3, characterized in that the element influencing the field pattern is formed by a piece of soft iron.

5. Device as claimed in claim 1, 2, 3 or 4, cha¬ racterized in that the permanent magnets are manufactured from an alloy in which at least one element is present from the group of rare earths.

6. Device as claimed in any of the claims 2-5, characterized in that a flushing device is arranged for flushing the magnetic particles along the gutter.

7. Device as claimed in any of the foregoing claims, characterized in that the magnets are ordered on the disc in concentric circles around the shaft and that the magnets within such a circle are alternately polarized.

8. Device as claimed in any of the foregoing claims, characterized in that the feed and discharge means for supplying liquid to the container and carrying liquid from the container are adapted for causing the liquid to flow along the disc substantially according to a chord of the circle describing the disc.

9. Device characterized by a parallel connection of devices as claimed in any of the foregoing claims, wherein the disc of each of the devices is placed on the same shaft driven in rotation.