GB2066108A

GB2066108A - A magnetic separator

Info

Publication number: GB2066108A
Application number: GB8039877A
Authority: GB
Original assignee: Kloeckner Humboldt Deutz AG
Current assignee: Kloeckner Humboldt Deutz AG
Priority date: 1979-12-12
Filing date: 1980-12-12
Publication date: 1981-07-08
Also published as: ZA807799B; DE2949855A1

Abstract

A magnetic separator comprises a rotatable body 16 with means for producing a magnetic field, which attracts particles from a mixture carried by a conveyor device 28 which extends beneath and along the axis of body 16. The attracted particles are scraped off by a stripper 26 and are fed to one or more collectors 27. The size of the gap between body 16 and device 28 may decrease along the direction of flow of the solids so that particles of successively weaker susceptibility are attracted; a number of corresponding collectors (36-41, Figure 3 not shown) may be provided. Device 28 may be an inclined chute, an endless conveyor belt, a vibrating channel or, as shown, an air conveyor channel. <IMAGE>

Description

SPECIFICATION A magnetic separator The invention relates to a magnetic separator, more particularly for separating a dry solids mixture into fractions according to magnetic susceptibility and having a pivotally arranged rotating body in the region of a stationary separating region through which there is a magnetic flux, the material to be dressed being fed to this rotating body in the direction of its axis.

Magnetic separators of the type stated are normal- ly implemented as so-called roller or drum separators and depending on the type of material to be separated are operated either by the discharge or lifting process (see for example "Aufbereitungs Technik", Journal for Dressing Solid Raw Materials, published by Verlag Siir Aufbereitung, Wiesbaden, Series 3 (1962), Volume 9, pp. 400 to 418).

In these separators the feed material is fed in the direction of rotary movement of the roll or drum, the movement of the material being in the direction of the peripheral lines of the roll or drum.

Departing from this prior art the proposal of supplying the material in the direction of the axis of the drum via the surface of the magnetic drum separator can be gathered from German Offenlegungsschrift No. 2650528 on page 8, last paragraph.

From German Offenlegungsschrift 2307 273 a magnetic separator is known in which the material is supplied axially of the rotating body with the aid of a conveyor device arranged beneath the rotating body.

This magnetic separator however corresponds generally to a crossbeltseparator having a rotating follower or entrainment element which has a lattice structure.

In the case of an entrainment element or this type with a lattice structure formed as a matrix, problems arise, as is known with regard to the cleaning-off process. This process requires considerable expense, such as providing blasting nozzles. Moreoever, particularly during dry separation, the swirling up of the dust which is to be expected when using fairly large blasting energies might be a hinderance and also might make it doubtful that the cleaning off would be satisfactory.

It is an object of the present invention to solve the above problems.

According to the present invention there is provided a magnetic separator comprising a body rotatable about an axis and adjacent to a separating region which is arranged to be exposed to magnetic flux, a feed and/or conveyor device for moving material to be separated, the device being positioned beneath the rotatable body and extending in the direction of the axis, the device forming a clearance with the surface of the rotating body.

A refinement of the invention provides for the feed and/or conveyor device to be matched in the clearance, approximately to the curvature of the rotating body.

This embodiment has the advantage that the clearance has an approximately equal width over the entire breadth of a cross-section. As a result, with the pre-condition of equal magnetic forces in the separating region, the effect of the magnetic separating forces on particles of equal size and magnetic susceptibility throughout a cross-section of the clearance is approximately the same. The resulting separation is therefore optimized both qualitatively and quantitatively.

In another refinement of the invention, provision is made furthermore for the clearance height to decrease in the direction of the flow of material.

The advantages of th is measure is that when the material is let into the relatively high region of the clearance only those proportions of the material which have the greatest susceptibility are attracted at first. Then, out of the flow of material which has been thinned out in this way, proportions of material each having a lower susceptibility are drawn off at a lower point in the clearance as transportation progresses through the clearance. Finally in the lowest part of the clearance, shortly before leaving the separating region various proportions of material having the very lowest susceptibility are attracted and drawn off. Finally, the non-magnetic material is discarded.

As a result, the selectivity of the magnetic separator can be set and consequently optimized when separating the dry solids mixture into fractions in accordance with their susceptibility using very simple means.

In a further refinement of the magnetic separator, further provision is made for the surface of the rotating body to be profiled. Such profiling, which preferably has rotational symmetry, serves to produce inhomogeneityofthe magnetic field so as to provide locally high field gradients and bring about an increase in field strength in the clearance towards the axis of the rotating body.

In a further refinement, provision is made for the magnetic separator to have at least one collecting device for the magnetic material which is extracted at the side, laterally adjacent the rotating body. In addition, it is advisable to have an arrangement in which the collecting device has subdivisions for accommodating different fractions.

This arrangement has the advantage that magnetically different fractions can be collected separately of each other and can therefore be extracted separately.

This refinement is also uncomplicated, easily surveyed, can be implemented at low cost and easily monitored during operation.

In a further refinement, provision is made for a stripper element to be arranged adjacent to and preferably above the collecting device.

This stripping device prevents the build up of magnetic material at the surface of the rotation body in a manner known per se, for example due to magnetic remanence.

The uncomplicated and effective functioning of this stripping element is assisted by virtue of the surface of the rotation body being impermeable to the material and/or carrier media and the surface is also preferably smooth.

A preferred refinement of the magnetic separator provides for the feed and/or conveyor device to be formed as a chute.

By the term "chute" is meant a channel having a gradient preferably having a smooth base through which the material flows under the influence of acceleration due to gravity. If, necessary, the flow of material can be assisted - as known per se - by vibration. In the case of a magnetic roll separator, the pole of the magnetic system arranged beneath the roll may be formed directly as a chute for example.

In further advantageous refinement the feed and/ or conveyor device is formed as an endless conveyor belt.

Such refinement has the advantage that it may be set up using conventional components, it is also relatively uncomplicated and low in cost and moreover has the advantage of optimum controllability.

On the other hand, the feed and/or conveyor device may also be provided as a vibro channel.

And, finally, the feed and/or conveyor device may be formed as an air conveyor channel.

The embodiment as an air conveyor channel has the special advantage that the feed material is loosened by the air and moved round in the layer, thus providing the best possible method of bringing each particle into the optimum efficiency region of the magnetic system in the separating region.

In addition, in a further advantageous refinement it is possible to provide the magnetic separator either in the form of a magnetic roll separator or a magnetic drum separator.

A particularly advantageous embodiment of a magnetic drum separator in accordance with the invention is one in which the magnetic system is equipped with superconducting coils which are arranged inside the drum, together with a cryostat.

Finally, in a further refinement, the rotation body may have the shape of a cylindrical or conical body and is in each case elongate.

The length of the body has an advantageous effect on the length of the residence time of the material in the operating gap.

Preferred embodiments of the present invention will now be described by way of example with reference to the accompanying drawings of which: Figure 1 shows a sectional view of a magnetic roll separator according to a first embodiment of the present invention; Figure 2 shows a sectional view of a magnetic drum separator according to a second embodiment ofthe present invention; Figure 3 shows a partially sectional side view of a magnetic drum separator having a chute as a feed and conveyor device; Figure 4 shows a side view of a magnetic separator having an endless belt as the feed and conveyor device; Figure 5shows an end view of the magnetic separator of Figure 4; Figure 6 shows a side view of a magnetic separator having a feed and conveyor device in the form of a vibro channel; and Figure 7 shows a side view of a magnetic separator having an air conveyor channel.

In the magnetic roll separator shown in Figure 1, an induction roll 1 rotates between magnetic poles 2 and 3 in the direction of the arrow 4. The two magnetic poles 2 and 3 are connected together magnetically by means of an iron yoke 5 and are excited by the coil 6. At a spacing beneath the roll 1, a feed and conveyor device 9, can be seen arranged in the direction of the axis 8, this feed conveyor device being covered in a layer 10 of material. The device 9 forms a clearance "A" with the surface region 11 of the roll 1 in the separating region 12, the surface region 11 also extending in the direction of the axis 8.Magnetic material 13 becomes adhered to the magnetized roll 1, said material having been raised out of the material layer 10 by the magnetic forces of attraction within the separating region 12 and accumulated magnetically at the surface 11 of the roll 1 in the form of a precipitation.

Astripper 14 releases the attracted material 13 from the surface 11 of the roll 1 so that it can be received by the collecting device 15.

Figure 2 shows a second embodiment of a magnetic drum separator in accordance with the present invention. The figure shows in cross-section a drum 16 having a magnetic system 17 with coils 18 arranged in fixed manner inside the drum 16. The feed and conveyor device 28 shown in section is formed as an air conveyor channel having an air channel 19 which is supplied with air through the line 20. A porous base 21 of the air conveyor channel 28, which is matched in shape to the curvature of the drum 16, has aerating air flowing through it, whereby the layer 22 of material passed along on this air is fluidized, i.e. loosened and moved round by the air passing through it.As a result, the individual particles of the material layer 22 are caught by the magnetic attraction forces within the separating region, inside the magnetic clearance "A" and drawn to the surface 24 of the drum 16 where they adhere in the form of magnetic material 25 and finally are engaged by the stripper 26 and stripped off.

The stripped-off magnetic material is accommodated and removed by the collecting device 27.

Figure 3 shows a drum separator having a drum 16 shown partiaily in section. It has a profiled surface 24 by means of which the outwardly extending field of - the magnetic system 17 is inhomogeneously distorted. The profiled tips 72 concentrate on the field lines and as a result locally high field gradients are produced in the region of these field lines. A chute 71 inclined with respect to the horizontal is arranged beneath the drum 16 as a feed and/or conveyor device such that the material fed at the point indicated by the arrow 53 trickles through the magnetic clearance "A", which tapers in the direction of transport 39, under the action of acceleration due to gravity. The stripper 26 has a negative shaping of its profile at its side which sweeps along the surface 24 and the profile tips 72 ensuring uninterrupted cleaning of the surface 24 of the drum 16. The axis of the drum 16 is designated by the number 34. It is pivotally arranged in a bearing not shown in greater detail so that the roll can be set into any desired inclination with respect to the horizontal in accordance with the position of the chute 71.

Collecting devices 36,37,38,38' and 41 collect material types I, lI, III, lila and IV. The magnetic material I has the highest suscepitbility and with the decreasing susceptibility the types 11,111 and Illa follow, while type IV is the non-magnetic material.

Figure 4 shows a magnetic drum separator having a feed and/or conveyor device in the form of an endless belt 30.

The latter is guided between the profiled rolls 31, 32; 31 32, and is then matched in the conveyor cross-section of the curvature of the drum 33, as illustrated in Figure 5 by the view in the direction of the axis 34. The material is fed at the point designated by the arrow 53.

Figure 4 also shows an extraction device 35 having separate boxes 36,37 and 38 for collecting fractions l, ill, III. The material 40 which is non-magnetic and discarded at the right end when the belt 30 moves in the direction of the arrow 39 is accommodated by a separate collecting device 41. In the view according to Figure 4, moreover, a stripper 42 can be seen which frees the drum 33 of magnetic material adhering to it. In the example shown, the width "A" of the magnetic clearance is approximately unchanged over the whole of its length.

However, the belt transport device 31, 31', 32,32' may be changed both in height and in inclination with respect to the horizontal with the aid of adjusting spindles 43, thus giving the possibility of displacing the magnetic clearance "A" in width either in parallel or at an angle, to provide a clearance of wedge shape.

Figure 6 shows a magnetic drum separator with a vibro conveyor channel 50 as the feed and/or conveyor device. The vibro conveyor channel 50 is set in oscillation in accordance with the double arrow 52 by the vibrator 51 and transports the said material shown schematically by the arrow 53 in the direction of arrow 54. The vibro channel 50 is fixed into a support, not shown in greater detail, or suspended from a ceiling by means of adjustable chain suspension elements 55, 55'. The magnetic clearance "A" can be variably set with respect to the drum 57 by adjusting the clamping elements 56, 56'.

Collecting devices 58,59,60 and 61 for fractions I, II and Ill and for non-magnetic material IV are shown merely schematically.

Finally, Figure 7 shows a partially sectional view of a magnetic drum separator with drum 62, axis 63 and bearings 64 which are indicated schematically.

Beneath the said bearings 64 is located the air conveyor channel 65, air being conducted through its porous base 66 out of the chamber 67 in order to loosen and transport the material. The base 66 is arranged at an inclination with respect to the horizontal "H" in accordance with the angle a, the material introduced according to arrow 70 being transported in the direction of the arrow 69 via the porous base 66 of the air conveyor channel 65. The connecting piece 68 serves to supply the chamber 67 with air.

In each of the above described embodiments the gap may be altered in height or thickness and/or to provide a wedge-shaped tapering in the direction of the transportation of material 69. The alteration may be affected as desired by means of adjusting devices not shown in greater detail and left to the discretion of those skilled in the art.

The above described separators are uncomplicated and are capable of implementation with conventional components. As far as functioning is concerned, special importance is placed on the one hand on good selectivity of the magnetic separator and on the other hand on the capability of cleaning off the magnetic material which has been attracted from the surface of the rotating body without difficulty, i.e. at very low cost and with optimum efficiency.

The following advantages are also obtained by the above described embodiments: the attracted material is cleaned off from the surface of the rotating body using very simple means and completely without difficulty; the residence time of the material in the clearance and therefore within the separating region is relatively long; as a result of this, the qualitative and/or quantitative output of the magnetic separator is at an optimum; the supply of material may take place independentiy of the effects of acceleration due to gravity and of movement and/or the composition of the surface of the rotating body which is why the material can be supplied by simple means in absolutely uniform manner and optimally metered.

Claims

1. A magnetic separator comprising a body rotatable about an axis and adjacent to a separating region which is arranged to be exposed to magnetic flux, a feed and/or conveyor device for moving material to be separated, the device being positioned beneath the rotatable body and extending in the direction of the axis, the device forming a clearance with the surface of the rotating body.

2. A magnetic separator according to claim 1 wherein the rotating body is of substantially circular cross-section and in the region of the clearance the shape of the feed and/or conveyor device is approximately matched to the curvature of the rotating body.

3. A magnetic separator according to claim 1 or 2 wherein the height of the clearance decreases in the direction of motion of the material.

4. A magnetic separator according to any one of claims 1 to 3, wherein the surface of the rotating body has a profiled portion.

5. A magnetic separator according to any one of claims 1 to 4, wherein at least one device for collecting magnetic material extracted at the side is arranged laterally adjacent the rotating body.

6. A magnetic separator according to claim 5 wherein the collecting device has subdivisions for accommodating various fractions (I, II, Ill).

7. A magnetic separator according to claim 5 or 6 wherein a stripping element is arranged above the or each collecting device.

8. A magnetic separator according to any one of claims 1 to 7, wherein the feed and/or conveyor device is formed as a chute.

9. A magnetic separator according to any one of Claims 1 to 7, wherein the feed and/or conveyor device is formed as an endless conveyor belt.

10. A magnetic separator according to any one of Claims 1 to 7 wherein the feed and/or conveyor device is formed as a vibro channel.

11. A magnetic separator according to anyone of claims 1 to 7, wherein the feed and/or conveyor device is formed as an air conveyor channel.

12. A magnetic separator according to any one of claims 1 to 11, characterized in that the magnetic separator is formed as a magnetic roll separator.

13. A magnetic separator according to any one of claims 1 to 11, wherein the magnetic separator is formed as a magnetic drum separator.

14. A magnetic separator according to any one of claims 1 to 13, wherein the rotatable body is elongate.

15. A magnetic separator according to claim 14 wherein the rotatable body is cylindrical.

16. A magnetic separator according to claim 14 wherein the rotatable body is conical.

17. A magnetic separator according to any preceding claim wherein the rotatable body has an impermeable surface.

18. A magnetic separator substantially as herein described with reference to the accompanying drawings.

19. A method of separating a dry mixture of solids into fractions in accordance with their magnetic susceptibility employing a magnetic separator as claimed in any preceding claim.

20. A method according to claim 19 wherein, the surface of the rotatable body is impermeable to the solids.

21. A method according to claim 20 wherein the solids are in a carrier medium, the surface of the rotatable body also being impermeable to the carrier medium.

22. A method of magnetic separating substantially as herein described with reference to the accompanying drawings.