WO2008123770A1

WO2008123770A1 - Process to separate steel-containing parts from a metal-slag waste stream, using a high-gradient magnetic separation unit

Info

Publication number: WO2008123770A1
Application number: PCT/NL2008/000098
Authority: WO
Inventors: Jan Andreas Groothoff
Original assignee: Recco B.V.
Priority date: 2007-04-04
Filing date: 2008-04-04
Publication date: 2008-10-16
Also published as: EP2150349A1; KR20100016055A; CN101678361A; ATE531456T1; NL1033644C2; CN101678361B; EP2150349B1

Abstract

A process to separate steel-containing parts from a metal slag waste stream, comprising the following steps: - the feed of a metal slag waste stream generated during steel production, particularly stainless steel or tool steel production; - the dosed feed of the metal slag waste stream to a first high gradient magnet station, with the aid of a transport element; - the pulling-out of steel-containing parts from the waste stream, through the action of the magnetic field generated by the first high gradient magnet station; - the use of a breaking units to refine the steel-containing elements separated by the first high gradient magnet station, in a broken refined fraction, in which the steel-containing parts are at least partially freed of slag; - the separation of the broken refined fraction at least into a concentrate of steel-containing parts and a residual fraction.

Description

Short description: Process to separate steel-containing parts from a metal-slag waste stream, using a high-gradient magnetic separation unit.

The invention concerns a process to separate sufficiently pure steel-containing parts from a metal slag waste stream using a high gradient magnetic separation unit, in particular, the separation of sufficiently pure stainless steel-containing parts from waste streams generated during stainless steel production. For these purposes, Λsufficiently pure part' will mean a part, at least 80% of which consists of the steel in question.

Various de-ferrising units are known within the current state of technology. For example, a de-ferrising unit as per NL-C-I .023.923 is known, which comprises a magnetic station with a magnetic drum over which the whole or part of the waste stream is passed. The magnetic drum consists of a drum that rotates during operation, with a magnetic element with a semi-circular cross-section, fixed inside it. The position of the magnetic element in the drum can be adjusted. A vibratory feeder discharges its load on a section of the outer circumferential wall of the magnetic drum. There is an air gap between the feeder and the drum. The magnetic field generated causes the iron-containing waste parts to attach to the drum directly from the discharge point of the feeder, and these iron-containing waste components remain attached to the drum by action of the magnetic field, and are thus transported past a specific point of the magnetic drum, after which they are released through the action of gravity. The remaining waste parts fall down much earlier. A partition plate may be placed under the drum, to separate out and remove the part- fractions that are separated in this manner.

The disadvantage here is that such deferrising units are not suitable to handle slag waste streams generated during stainless steel production. The results obtained while handling such slag waste streams are far from satisfactory. Attempts to improve the result by using a high-gradient magnet inside the drum, particularly of more than 0.9 Tesla, in most cases causes almost all the transported waste components to remain attached to the drum. Such magnets are so powerful that they attract almost everything and they continue to attract objects in all positions along the outer circumference wall of the drum, in other words, even in places where the magnet is not touching the inner circumference wall. The slags and the steel thereby form a cake around the drum. Furthermore, the unit has very limited versatility in use.

The aim of the present invention is to remedy the above- mentioned disadvantages at least partially, or to provide a usable alternative. In particular, the invention aims to provide a process that uses a high gradient magnetic separation unit, suitable for handling metal slag waste streams generated during steel production, particularly the separation of sterile slag components of (slightly magnetic) stainless steel-containing parts.

This aim is achieved using a process as per Claim 1. The first step in this process is a metal slag waste stream feed generated during steel production, particularly, stainless steel or tool steel production. The next step is the dosed feeding of the metal slag waste stream to the first high gradient magnet station using a transport element, whereby the steel-containing components are drawn out of the waste stream by action of the magnetic field generated by the first high gradient magnet station. The steel-containing parts separated-out by the first high gradient magnet station are refined by a breaking unit into a 'broken refined fraction' , in which at least some of the slag is removed from the steel-containing parts in a type of breaking process. The refining is done for example, in an autogenous breaking process, wherein the steel-containing components are forcefully impacted against a wall, thereby separating the slag from the steel. The broken refined fraction is finally separated-out into a concentrate of sufficiently pure steel-containing components, and a residual fraction. The process has proved excellently suitable for the dry-process recovery of stainless steel scrap from very moist stainless steel slag. The residual product can still be used for special civil applications, especially after mixing in a little FeSO₄, particularly 2-3%. It has been possible to achieve a maximum recovery of high- value stainless steel metals from a metal slag waste stream, whereby a minimum residual fraction of metal remains in the slag, namely, less than 0.5%. Using the selected process, the slag can achieve a good grain distribution to make it suitable for use in special civil projects. The high gradient magnet separation unit thereby guarantees that only the sufficiently steel-containing fraction is further refined to release the steel. Around 65-75% of the slag from the waste stream is removed after the first high gradient magnet station, and therefore unnecessary refining is prevented. As a result, the end-product is largely able to retain its critical grain distribution.

In particular the process further comprises the step to separate-out a concentrate of steel-containing parts from the fraction refined by the breaking unit using at least a second high gradient magnet station, after sifting the refined fraction into a fine part-fraction and a coarse part-fraction in a sifting unit. The fine part-fraction is then transported along the second high gradient magnetic station for separating-out the concentrate of steel- containing parts. It is greatly advantageous to re-transport the coarse part-fraction back to the breaking unit for further reduction. Preferably, the coarse part-fraction may be sent along a third high gradient magnet station for further separation of a concentrate of steel-containing parts.

Through this continuous refinement/sifting process, a continuously larger amount of slag is separated-out, thereby constantly making the steel-containing parts cleaner/more pure. In addition, during refinement in for example, a breaker, certain austenitic metal parts gradually magnetise and can therefore ultimately be collected via one of the high gradient magnet stations.

The high gradient magnet stations may be of different types and for example, may be designed as a high gradient drum magnet station, or as a high gradient overband magnet station.

It is however preferable that the first high gradient magnet station along which the initial waste stream is fed should be of the type with a rotating drum and a high gradient magnet fixed inside it, whereby the drum and the magnet are arranged along a free falling path of the metal slag stream.

The second high gradient magnet station along which the fine part-fraction is transported should preferably be of the type with an endless overband and a high gradient magnet installed between the same, whereby the overband and the magnet are installed above a transport medium.

The third high gradient magnet station along which the coarse part-fraction is transported may be either of the overband type or of the drum type. It is also possible to use both types in combination, linked one after the other. Further preferred models are mentioned in the dependent claims.

The invention also concerns the use of a process according to the invention, as well as a high gradient magnet separation unit for the implementation of this process. The high gradient magnet separation unit contains a transport element for the feed of, for example, a slag waste stream generated during stainless steel production. The transport element discharges on a high gradient magnet station, especially one of the type with a rotating drum with a high gradient magnet (more than 0.95 Tesla) fixed inside it, which extends along a part of the internal circumference of the drum. On leaving the transport element, the waste stream receives an initial falling path, through the action of gravity. The magnet station should preferably be installed in such a position along this initial fall path that steel-containing components are drawn out of the aforesaid initial falling path by action of the magnetic field generated by the magnet station. Thus for example, stainless steel as well as stainless steel-containing slag components can be separated from the other slag components that are generated during stainless steel production. Thus it is possible, during the separation process, to separate-out and remove the other slag components at an early stage, so that these slag components are kept out of further refinement processes. Thus, for example, there is no longer a need to crush all the slag components into smaller particles, but only those slag components that contain stainless steel. This saves cost and time, and produces a greater final percentage of pure metal concentrate. In addition, the residual pure slags can be used as raw material.

In a variant of this, adjusting controls are provided to adjust the magnet station and the transport element to each other in various operating positions. It is advantageous to quickly and easily adapt the unit using the adjusting controls to match the characteristics of the magnet station to a specific waste stream that has to be processed. For example, the average particle sizes of the waste, adhesion characteristics, percentage of metal-containing components, etc. All of these affect the performance of the magnet station and this can now be anticipated by modifying the position of the magnet station in relation to the transport element. The adjustment of the position with respect to each other may be done once, for example, when the high gradient magnet separation unit is tested or is used for the first time. It is also possible to regularly adapt the setting to the circumstances. It is advantageous, using the adjusting controls, to determine the optimum operating condition by installing the strongest possible magnets in the magnet station, while later, during testing and/or operation, one may try to determine the optimum position of the magnet station in relation to the transport element.

The position change may consist in increasing or reducing an initial air gap between the falling path and the magnet station and/or the direction of this air gap, in other words, the transport element is at a different angle with respect to the magnet station, or that the magnet station is in a different position along the falling path. An example is a stepless adjustment between the bottom feeder and the top feeder of the waste stream through the transport element in relation to the magnet station.

In a special embodiment, the high gradient magnet is a permanent magnet based on at least one of the lanthanide elements, namely a neodymium magnet (more than 0.95 Tesla on the circumference/drum) .

The transport element may be a vibratory feeder, for example. This ensures that the waste components arrive at the magnet station already released through vibration, dosed and distributed.

In one embodiment, there is a wear-and-tear-free plastic, driven belt, which is guided around at least the high gradient magnet of the high gradient magnet separation unit. If the unit contains a drum type magnet station, the belt will be passed over the rotating drum of the same. The plastic material of the driven belt is wear-and- tear-proof enough to resist the effect of the abrasive steel- containing components, and on the other hand, the components do not remain stuck to it. Specifically, the belt may be made of PE or PU.

The invention will be further explained on the basis of the attached drawing, in which:

Figure 1 provides a schematic view, in perspective, of an embodiment of a high gradient magnet separation unit as per the invention; Figure 2 contains a schematic view, in cross-section, of figure

1;

Figure 3 contains a flow diagram of a preferred embodiment using a process as per the invention; Figure 4 shows a possible layout of a high gradient magnet separation unit for the execution of the process as per Figure 3;

Figure 5 contains a view, in perspective, of a variant of figure 4;

Figure 6 is a top view of figure 5;

Figure 7 is a variant of a unit in figure 1; and

Figure 8 is a further variant of the unit in figure 1.

Figure 1 shows the high gradient magnet separation unit in its entirety, indicated by the reference figure 1. The unit 1 contains 2 vibration feeders installed next to each other. The vibration feeders 2 are fed from above with a metal slag waste stream via a vibration feeder 3 that extends transversely over the vibration feeders 2. The vibration feeder 3 in its turn is fed with the metal slag waste stream via a conveyor belt 4. The metal slags are already sorted on the basis of pieces with a cross-section less than or equal to 20 mm. This may be done using a straining unit (not shown) which may or may not be mobile. The vertical positioning of the vibration feeder 3 on the bottom vibration feeders 2 ensures that the waste stream is directly dosed over the entire breadth of the underlying vibration feeders 2. This was found necessary to ensure proper separation, and the advantage is that the unit 1 can be made more compact.

The unit 1 also includes two magnet stations 5, each having a rotating drum 7 with permanent neodymium magnets 8 fixed within the same. The magnet station 5 is installed at an angle under the relevant vibration feeder 2 along a falling path that receives the waste stream 9 through the action of gravity, after vibration by the vibration feeder 2. During operation, the steel-containing components are drawn out of the falling waste stream 9, by action of the magnet field 10. The steel-containing parts are drawn against the rotating drum 7, past the segment where the neodymium magnet 8 is located, and only then released so that they can be dropped freely. A partition plate 12 installed under the magnet station keeps the steel- containing parts 13 separate, after they have been separated-out of the "clean" part 14 of the waste stream.

According to one aspect of the invention, adjusting controls have been provided for the mutual adjustment of the magnet station 5 and the vibration feeder 2 (see fig. 2), in various operating modes. Of these, adjusting controls 20 have been provided for the mutual vertical adjustment of the drum 7 and the vibrating feeder, 2.

Adjusting controls 21 have also been provided for the mutual horizontal adjustment of the drum 7 and the vibrating feeder 2. Finally, adjusting controls 22 have been provided for adjusting the angle at which the vibrating feeder 2 is installed. The adjusting controls 20, 21, 22 may consist for example, of screw spindles, hydraulic or pneumatic setting cylinders, that grip the suspension points of the .drum 7 and/or the vibratory feeder 2. These adjusting controls can advantageously prevent almost all the parts of the waste stream 9 from adhering to drum 7. In each case, it is easily possible to set the most optimum operating mode, whereby only relevant steel- containing components 13 are drawn out of the waste stream 9, and transported past the separation plate 12. In practice, the setting will be such that an air gap is left between the falling waste stream 9 and the drum 7, so that the steel-containing parts 13 have first to be drawn out sideways from the falling waste stream 9, before they come to rest against drum 7.

The vibration feeder 2 is made of non-magnetisable material, for example stainless steel, at least on its discharge side. This advantageously prevents the very powerful neodymium magnet 8 from being able to magnetise this part of the vibration feeder 2, which could lead to an undesirable burr formation of steel-containing parts in that part of the vibration feeder 2. The vibration feeder 2 also has a friction-reduction coating, for example of polyurethane. This prevents the waste stream 9 from adhering to the surface of the vibratory feeder 2, and therefore contributes to the reliability of the dosed supply of the waste stream to the magnet station 5.

On the front side, the falling path of the waste stream 9 is limited by a collection plate 30. Lead-through space has been provided between the collection plate 30 and the drum 7. The collection plate 30 is to prevent (heavy) parts from the waste stream from moving too far away from the drum 7. The collection plate 30 guides these parts back if so desired, so that they can again be pulled-up by the neodymium magnet 8. The collection plate 30 can be adjusted in various operating positions with respect to the magnet station 5, using the adjusting controls 31. This may consist of moving the collection plate 30 horizontally, or changing the angle rotation of the collection plate 30.

The invention also relates to a process for the separation of steel-containing parts from a metal slag waste stream, using a high gradient magnet separation unit. Figure 3 shows a flow diagram of such a process. Here, a slag waste stream is loaded in a hopper 36 using a loader 35. From there, the waste stream goes to a mobile straining unit 37. This strains parts less than or equal to 15 mm, specifically, less than or equal to 10 mm. The larger parts are transported to storage facility 38 for further treatment. The smaller parts that are strained out are transported to a high gradient magnet separation unit 39. Preferably, this is a high gradient magnet separation unit as described above in figures 1 and 2. However, the adjusting controls are not strictly required here, and may even be left out if so desired. As described above in figure 1 and 2, the unit 39 pulls out the steel-containing parts out of a falling waste stream using a neodymium magnet station that is arranged with a slope under a vibration feeder. The rest of the waste stream is moved to a storage facility 40 as "clean" slag. The steel-containing parts drawn from the waste stream (around 20%) are transported to a breaking unit 41, specifically, formed by a vertical impactor. A vacuum cleaner 42 has been provided to remove the dust generated during the reduction. The reduced stream of steel-containing components is then transported to a second straining unit 43, with a setting to strain-out any particles exceeding a few millimetres, for example 1 mm. The strained-out fine fraction is transported to a storage facility 44 as "clean" slag. The parts larger than 1 mm will either be removed as steel-containing concentrate 45 that can be offered again if so desired to the high gradient magnet separation unit 39, or may be removed to the storage unit 46.

Figure 4 shows a possible layout of figure 3. One can see that suitable transport elements have been provided between the various stations, in the form of conveyor belts and/or vibration feeders for example.

A second high gradient magnet station may also be used instead of or in addition to the second strainer unit. Specifically, if the air humidity of the waste stream is too high, this offers advantages because it will no longer be possible to properly strain out particles not exceeding a couple of millimetres. It is also possible to replace the second straining unit by a "windshifter" . In this, separation is done on the basis of specific weight, whereby the final dust particles are blown off and collected or sucked out of a falling stream. The compressor of the vacuum cleaning system may be used for this purpose. Figure 5 and 6 shows a convenient model of a high gradient magnet separation unit for the execution of a process as per the invention. The unit contains a bunker 51 via which a metal slag waste stream, specifically, of 0-15mm metal slag is transported via a conveyor belt 52 to a vibration distributor 53, which in turn feeds two high gradient magnet stations 54. The magnetic concentrate

(steel-containing parts) separated by the high gradient magnet station will be transported by a conveyor belt 55 to a special vertical impact breaker 56 where slag will be broken away from the parts. The breaker 56 is also equipped with one or more pressure guns for the periodic breaking open of lumped parts, if necessary. Nonmagnetic parts leave the magnet stations 54 via a belt 65 and come to rest on a collection belt 60. The high gradient magnet stations 54 are preferably so adjusted that only those components that contain <0.5% steel will be placed on the collection belt 60.

After the breaker 56, the material (the broken, refined fraction) will be placed on a conveyor belt 57 with direct dust suction 66 at the start of belt 57. The conveyor belt 57 feeds a fine strainer of the type 58, which is specially set-up for straining up to a couple of millimetres, particularly 3mm, under relatively wet conditions .

The strained-out coarse part-fraction (also called overgrain) including the coarse metal parts contained therein, particularly those between 3-15mm will leave the strainer 58 via a belt 64, and will return to the breaker 56 in order to be further refined there. On the way, this strained coarse part-fraction will become a concentrate of steel-containing parts, or of sufficiently pure metal, specifically, containing >80% steel, via a high gradient magnet station 63, which can be adjusted, extracted and placed in a collection container 68.

The strained fine part-fraction (also called undergrain) , including the fine metal parts in the same, specifically, between 0- 3mm, leave the strainer 58 via a belt 59. Two high gradient magnet stations 61 and 62 extrude from this fine part-fraction as well, a concentrate of steel-containing parts, that is to say sufficiently pure metal, in particular, with a steel content >80%. The one high gradient magnet station is installed transversely, and the other in line with a sub-band of the strainer 58.

Non-magnetic parts (including the fine broken-off slag parts) of the fine part-fraction leave the magnet station 61, 62 via the belt 59 and come to rest on the collection belt 60. The high gradient magnet stations 61 should preferably be so adjusted that only those components that contain <0.5% steel will be placed on the collection belt 60. Thus the end products of this continuous process are as follows :

- collection bins 69, 70: 0-3mm parts with >80% steel;

- collection bin 68: 3-15mm parts with >80% steel; and

- collection belt 60: 0-15mm parts with <0.5 % steel; Obviously, other part-size ranges can be achieved by adjusting or setting the strainer unit accordingly, and/or other minimum or maximum steel content limits may be obtained by making the setting of the high gradient magnet stations more sensitive or less sensitive.

If it is found during operations that too much sufficiently pure metal is being circulated at the same time, a signal-activated return conveyor 67 may be used. By stopping the feed belt 52, there remains, at that given moment, only sufficiently pure metal in the circuit which comprises the belt 64, the conveyor belt 55, the breaker 56, the conveyor belt 57 and the strainer 58. If this is not directly collected by the high gradient magnet station 63, for example due to the strongly austenitic character of these pieces, the return belt 67 may be activated to directly collect these parts.

Figure 7 shows a. model of a high gradient magnet station 75 fed by a vibration feeder 74, which is particularly suitable for processing more moist metal slags. In practice, the moisture content of the waste streams of the metal slag to be processed may be up to 18% water. For these reasons, the magnet station 75 is now equipped with a special endless, driven belt 76, in particular of wear-and- tear proof PU or PE material, which passes over a magnetic drum 77 at one end, specifically, within the rotation of the magnetic drum 77. The magnetic drum 77 is installed along the falling path that receives a waste stream after this has been vibrated off by the vibration feeder 74. The magnetic drum 77 is self-rotating and encloses a high gradient magnet that is fixed inside it. Since the endless belt 76 is self-driving, its speed can be changed. The belt 76 has ribs 77' extending over the breadth. The version with belt 76 prevents adhesion to the drum 77. Since metal can no longer remain suspended from the drum 77, the drum 77 is prevented from deforming, which would otherwise jam the magnet station 75. This installation allows the use a high gradient magnet with a breadth greater than or equal to 1500mm, without the possible pulling of the magnetic drum during operation, into a bent shape.

Figure 8 shows a variant of this idea, in which an entire endless, driven plastic belt 80 of this type is guided over a rotating high gradient magnet roller 81. Instead of via a vibration feeder, a metal slag waste stream is now fed with a fast moving belt 82. Again, metal concentrate is drawn out of the falling parts sideways during the fall, past an underlying separation plate 83. This installation as well allows the use of a high gradient magnet of a breadth exceeding 1500mm. The magnet roller 81, over which the belt 80 is guided, is installed along the falling path that receives the waste stream if it leaves this discharge belt 82. In particular, the position of the magnet roller 81, with the belt 80 guided over the same, can be adjusted according to the feed belt 82. There are many variants, in addition to the models shown. Thus for example, instead of a neodymium magnet, one may use a different permanent magnet based on the lanthanide elements, or a high gradient magnet with a magnetic flux density exceeding 0.95 Tesla on the circumference, respectively on the magnetic drum. Thus according to the invention, this is a reliably working multi-functiona^'l high gradient magnet separation unit, which can preferably be easily adjusted according to changes in the working conditions and which can then be precisely adjusted to obtain an optimum performance so as to prevent blockages. The invention is especially suitable to the recovery of steel-containing metal parts out of slag waste streams generated during steel production, particularly stainless steel or tool steel production.

Claims

C L A I M S

1. Process to separate steel-containing parts from a metal slag waste stream comprising the following steps:

- the feed of a metal slag waste stream generated during steel production, particularly stainless steel or tool steel production;

- the dosed feed of the metal slag waste stream to a first high gradient magnet station, with the aid of a transport element;

- the pulling-out of steel-containing parts from the waste stream, through the action of the magnetic field generated by the first high gradient magnet station;

- the use of a breaking unit to break down -the steel-containing elements, separated by the first high gradient magnet station, into a broken refined fraction, in which at least some of the slag is removed from the steel-containing parts; - the separation of the broken refined fraction at least into a concentrate of steel-containing parts and a residual fraction.

2. Process as per Claim 1, in which the first high gradient magnet station is installed along a falling path which the waste stream receives by the action of gravity, after the waste stream has left the transport element on its discharge side.

3. Process as per Claim 1 or 2, wherein the high gradient magnet station contains a rotating drum and a high gradient magnet with a magnetic flux density of more than 0.95 Tesla fixed within the same, which extends along a part of the internal circumference of the drum.

4. Process as per Claim 3, further including the step of mutually adjusting the drum of the high gradient magnet station and the transport element depending on the working conditions, or the characteristics of the waste stream respectively, in various working positions .

5. Process according to one of the preceding Claims, further comprising the step of separating the concentrate of steel-containing parts from the broken refined fraction separated from the breaking unit, using at least a second high gradient magnet station.

6. Process as per Claim 5, in which prior to the step of separating the concentrate of steel-containing parts using the second high gradient magnet station, the broken refined fraction is strained by a straining unit into a fine part-fraction and a coarse part-fraction, whereby the fine part-fraction is fed along the second high gradient magnet station for the separation of the concentrate of steel- containing parts.

7. Process as per Claim 6, in which the coarse part-fraction is returned to the breaking unit for further refinement.

8. Procedure as per Claim 6 or 7, wherein the coarse part-fraction is transported along a third high gradient magnet station for separation of further concentrate of steel-containing components.

9. The use of the process according to one of the preceding Claims for recovering steel-containing metal parts from slag waste stream that arises during the production of steel.

10. Use according to Claim 9 for the recovery of steel-containing metal parts from a waste stream from the slag generated during the manufacture of stainless steel.

11. Use according to Claim 9 for recovering steel-containing metal parts from a slag waste stream generated during the manufacture of tool steel.

12. High gradient magnet separation unit for the execution of the process according to one of the preceding Claims, comprising: - a transport element for feeding the metal slag waste stream; and - a high gradient magnet station for the separation of steel- containing parts from the metal slag waste stream, whereby the magnet station contains a high gradient magnet with a magnetic flux density exceeding 0.95 Tesla on the circumference.

13. High gradient magnetic separation unit as per Claim 12, whereby a wear resistant plastic drive belt is provided, which is guided around at least the high gradient magnet.

14. High gradient magnet separation unit as per Claim 13, whereby the magnet station further comprises a rotating drum in which the high gradient magnet is fixedly positioned, and extends along a part of the internal circumference of the drum, and whereby the plastic drive belt is guided over the drum.

15. High gradient magnet separation unit as per Claim 13 or 14, wherein the plastic drive belt contains a PE or PU layer.

16. High gradient magnet separation unit according to one of the preceding Claims, wherein the magnet station is installed along a falling track which the waste stream receives through the action of gravity after the waste stream has left the transport element on its discharge side, such that the steel-containing parts are drawn out of the falling waste streams by the magnetic field generated by the magnet station.

17. High gradient magnet separation unit as per Claim 16, wherein a collection plate is provided along the falling track at the magnet station location, with a lead-through opening between the collection plate and magnet station, with adjusting controls for the mutual adjustment of the magnet station and the collection plate under various working conditions.

18. High gradient magnet separation unit as per one of the preceding Claims, whereby adjusting controls are provided to make mutual adjustments between the magnet station and the transport element discharging its load at that point, in various working postitions.

19. High gradient magnet separation unit according to one of the preceding Claims, wherein a breaking unit is provided downstream of the magnet station, for the refinement of the steel-containing parts separated by the magnet station, in a broken refined fraction, in which at least some of the slag is removed from the steel-containing parts.

20. High gradient magnet separation unit as per Claim 19, in which the breaking unit is a vertical impactor.

21. High gradient magnet separation unit as per Claim 19 or 20, wherein a second high gradient magnet station is installed downstream of the breaking unit.

5 22. High gradient magnet station as per one of the Claims 19-21, wherein a strainer unit is installed downstream of the breaking unit, for the straining out of a fine and a gross part-fraction from the broken refined fraction.

10 23. High gradient magnet separation unit as per Claim 22, wherein a transport element is provided for re-feeding the coarse part-fraction to the breaking unit.

24. High gradient magnet separation unit as per Claim 22 or 23, 15 wherein a third high gradient magnet station is provided for feeding the coarse part-fraction along, to separate further concentrate of steel-containing parts.