WO2008037343A1

WO2008037343A1 - Method and device for separating magnetisable materials from a solids mixture

Info

Publication number: WO2008037343A1
Application number: PCT/EP2007/007859
Authority: WO
Inventors: Oliver Pikhard
Original assignee: RWTH- Rheinisch-Westfälische Technische Hochschule Aachen
Priority date: 2006-09-28
Filing date: 2007-09-10
Publication date: 2008-04-03
Also published as: DE102006046356A1

Abstract

The invention relates to a method and a device for separating magnetisable materials (17) from a solids mixture (2), said method comprising the following steps: the solids mixture (2) is applied to the upper side of a separation surface (6), and a magnetic field is generated by at least one magnetic field generator (11, 11a, 11 b) provided beneath the lower side (13) of the separation surface (S) in such a way that the magnetic field moves at least temporarily with a component oriented parallel to the separation surface (6). The device according to the invention comprises at least one percussion element (12) for hitting the separation surface (6).

Description

Method and device for separating magnetizable substances from a mixture of solids

The invention relates to a method and a device by which the magnetizable substances can be separated from substances which are not or only weakly magnetizable substances and can be separated from a solid mixture. By means of such methods or devices, the so-called magnetic separation can be carried out, wherein the different magnetic susceptibility of different materials is utilized.

British Patent No. 2498, filed on 04.02.1908, discloses a separating device in which a mixture of solids for separating the magnetisable portion is first passed over an at least almost vertically arranged plate, behind which an electromagnet generates a magnetic field. This vertically arranged partition plate is displaced by a mechanical lever arrangement in a swinging motion. Under the influence of gravity, the mixture of solids trickles over the separating plate, on which the magnetizable particles are first held. As a result of the gravitational force and the oscillating movements, the magnetisable particles migrate along the separating plate and are thus removed from the magnetic field. The non-magnetizable particles undergo an acceleration in the direction opposite to the magnetic field due to the oscillatory movements of the plate, so that they can be separated from the magnetizable material due to their different trajectory by means of a separating vertex. In this known device, only a single magnetic field is used for the separation, which is constant in the polar direction. As a result, the magnetizable particles are brought into a constant orientation corresponding to the constant magnetic field. Since the magnetizable particles remain in the magnetic field or at least accumulate there, their separation from the separating plate is relatively problematic. For this reason, it is only possible to work with a very weak field strength, which limits the achievable accuracy of the separation as well as the output, especially for small and very small material particles. It is also disadvantageous that the energy introduced into the material by the oscillating movement of the separating plate is not optimally utilized, since the energy is distributed over the entire surface of the plate into the material.

Another known method is the magnetic separation by means of Wechselpolanordnung according to the model of Laurila. Here, the solid mixture for separating the magnetizable portion is placed on a drum, inside which magnets are arranged with alternating polarity. The poles are arranged so that an alternating field is generated over the circumference of the drum. By rotation of the magnet system inside the drum or by moving the drum at standstill of the magnet system, the particles are moved relative to the magnetic poles and thus placed in a rotational movement. Frequently, the magnet system is arranged eccentrically in the drum, so that a removal of the magnetizable material takes place by a distance from the magnetic field.

A disadvantage of this method is that the material is only put into a rotary motion under certain circumstances. Among other things, this depends on the rotational speed of the drum or the magnet system, the particle size spectrum of the feed material and the roughness of the drum surface. Separation of the non-magnetisable particles is mainly due to the influence of gravity and inertial forces. The construction of this device is problematic because the drum made extremely accurate must be in order to ensure the desired uniform drum wall thickness with high mechanical stability, without the magnetic force loss is too large due to a too thick drum wall.

Another device for magnetic separation is known from the already 1919 filed English Patent No. 152 549. In this lifting device, the solids mixture for separating the magnetizable portion is applied to a vibrated table by means of an eccentrically mounted shaft, over which rotates a rigid drum provided on its surface with ribs engaging in the solid mixture. Inside the drum, a stationary magnet system is arranged, which generates a constant and relative to the table always the same aligned magnetic field.

A disadvantage of this device is that it does not allow a clean separation, especially in very fine or powdery solid mixtures. The interparticle forces that occur with very fine grain mixtures can not be overcome hereby, which favors a faulty discharge. Also, with fine powders or dusts, the trajectory of the individual particles is significantly lower due to the air resistance increasing with the specific surface. Therefore, the distance between the table and the drum mounted above it must be very small, which in turn causes the risk of clogging. In addition, depending on the iron content, blockages may also occur in this device due to the formation of so-called "iron beds", that is, by agglomeration of iron filings in the magnetic field.

For the separation of pulverulent or fine-grained solid mixtures, all previously known magnetic separation devices and magnetic separation processes are at most poor or not at all suitable. Grains in this grain size range are difficult to separate because of their irregular grain shape and large specific surface area. The current state of the Technology in the field of fine grain separation attempts to separate by grain shape, grain size and / or density. The treatment of the materials by means of magnetic separators leads to no separation success, since in this particle size range, the interparticle forces in the material are too large.

As an alternative to the separation principle of magnetic separation, one also knows the principle of eddy current separation. As a result, however, only electrically conductive parts or solid particles of electrically non-conductive parts or particles are separable. A separation of magnetizable particles from non-magnetizable particles is not possible with the eddy current separation, which is a significant difference from the principle of magnetic separation. Eddy current separating devices are known, for example, from US Pat. No. 5,860,532 A or DE 39 06 422 C1. In this case, an alternating magnetic field is generated by means of eccentrically mounted rotors on which permanent magnets are arranged. The alternating magnetic field is used in the eddy current separation for the separation of electrically conductive, non-magnetizable components from a solid mixture. In the alternating magnetic field eddy currents are induced in the electrically conductive parts, which in turn build up their own magnetic fields, which are directed opposite to the generator magnetic field. Thereby, these electrically conductive particles can be separated from the remaining mixture, i. are separated from the electrically non-conductive particles. A separation of the magnetizable parts of the present solid mixture is not feasible with such aggregates, and therefore they are not suitable for carrying out the method according to the present invention.

The object of the present invention is to improve the known devices and methods of magnetic separation in such a way that the abovementioned disadvantages are overcome and a precise separation of magnetizable particles can be carried out quickly and effectively even with very fine-grained and powdery material mixtures. This object is achieved by a method according to claim 1 or by a device according to claim 15. Advantageous embodiments and modifications of the invention will become apparent from the respective dependent claims.

It is essential in the solution according to the invention that the solid mixture is first applied to the upper side of a separating surface such that a magnetic field is generated by at least one magnetic field generator provided below the underside of the separating surface such that the magnetic field is at least temporarily aligned with a component directed parallel to the separating surface moved and that one or more impact element (s) is hit against the separation surface. Although depending on the nature of the solid mixture already a stroke may be sufficient, is preferably beaten several times against the release surface.

The solution is based on the idea that for the desired separation of the magnetizable particles from the non-magnetizable particles, the forces acting between the particles must be overcome, which inventively by the deliberate introduction of shear, frictional and compressive forces in the to be separated Material takes place. For this purpose, a combination of magnetic forces with a targeted introduction of impact pulses in the material to be separated is proposed.

The main advantage of the method according to the invention is that even mixtures of very small and very small particles can be separated particularly effectively. This achieves a high separation efficiency and a very precise separation or a high degree of purity with the relatively fast and easy to carry out process.

The strong interparticle forces acting in particular in the disperse range with grain sizes below 10 μm are composed of van der Waals forces and electrostatic forces. In addition, formal coherent bonds and liquid bridges are forces that can lead to agglomerations in the entire grain size range. Solid-state bridges between individual particles can also occur. To separate the magnetizable particles from the non-magnetizable or only less magnetizable particles, these aforementioned forces must be overcome.

The force difference required for this purpose is generated according to the invention by a magnetic field generator attracts the material mixture and moves with the moving magnetic field, while additionally beaten by means of a striking element against the material mixture carrying separation surface. The occurring acceleration of the non-magnetizable particles against the magnetic force and the gravity by the impact is greater than that of the magnetizable particles that remain in the magnetic field. Due to the moving magnetic field, the solid mixture to be separated is constantly redeployed, so that additional friction and shear forces act on the material and lead to the separation of magnetizable and non-magnetizable material in the magnetic field.

A significant advantage of the proposed method is thus in the targeted introduction of forces to increase the difference in forces required to separate the smallest particles. Due to the temporal and local separation of stratification and separation phase, the separation effect increases many times. In conventional dry-working magnetic separators, on the other hand, separation takes place only by the force difference between the magnetic force, on the one hand, and the force resulting from the kinetic energy of the particles, on the other hand. Even at very high particle speeds, no similar difference in force is achieved as in the method according to the invention.

The invention is fundamentally suitable for the separation of all fine to ultrafine granular material mixtures which contain magnetizable constituents and dried present. A particularly advantageous application is the preparation of dried abrasive slurries, the aim being the recovery of the metallic materials and the non-metallic grinding wheel parts. So far, abrasive sludge is usually pressed together with turnings into pellets, wherein the pellets to 80-90% consist of turnings to have the necessary stability. By separating the metallic constituents from the dried grinding sludge, however, they can be pressed into pellets immediately and without turning chips. In addition, advantageously, the thus separated grinding wheel components can be processed. Further fields of application may be, for example, in industries where it is important to produce high-purity powders, for example in the medical industry, food industry, raw material processing, abrasive production. Depending on the field of application, both the magnetizable and the non-magnetisable particles can be re-integrated into a raw materials cycle.

Expediently, the magnetic separation is preceded by other classification stages, since a preceding fractionation and pre-enrichment have a positive effect on the separation result.

It is particularly advantageous if the polarity direction of the magnetic field is changed at regular or irregular time intervals, so that a moving alternating magnetic field results. The magnetizable particles in the magnetic field themselves become permanent magnets which align themselves in the magnetic field according to the magnetic field lines. The moving magnetic field or alternating magnetic field therefore causes the magnetizable particles to move according to the movement frequency of the magnetic field and to rotate when changing the polarity. This rotation in turn means that non-magnetizable particles of magnetizable particles can be sheared off more easily. In addition, the solid mixture applied to the separating surface is loosened by the rotary motion and brought into a fluid-like state, the prevents non-magnetizable particles from being trapped by magnetizable particles, which also increases the accuracy of the separation. Preferably, the method of the invention is applied to mixtures of solids consisting of very small particles. In this case, a particularly effective separation is achieved with powdered or granular solid mixtures containing particles whose average diameter is between 1 .mu.m and 5 mm, in particular between 3 .mu.m and 1 mm. Particularly preferred particle sizes have an average diameter of 10 .mu.m to 300 .mu.m. Nevertheless, the method according to the invention can also be used with material mixtures which contain larger particles or parts. Here, too, an improved and thus more effective separation is achieved compared to the previously known methods in terms of purity and Ausbringleistung.

It is particularly favorable if the at least one impact element is hit from below against the underside of the separating surface. Repeated blows are preferably carried out against the separation surface in order to support the loosening of the solid mixture to be separated particularly effective.

According to a particularly preferred embodiment of the invention it is further provided that a plane of an at least partially, preferably completely flexible material is used as the separating surface. In this way, the impact energy can be introduced into the material mixture located on the flexible separation surface in a particularly effective manner, and the force difference required for the separation of very small particles is particularly great. It should be chosen as thin as possible, but still sufficiently stable parting plane.

Furthermore, it is particularly advantageous if the impact element is used to carry out a striking movement impinging obliquely against the separating surface, which impacting on the separating surface is directed perpendicularly to the separating surface Movement component and has a parallel to the separation surface directed movement component. As a result, the loosening of the solid mixture thereon is effectively supported, especially in horizontally aligned parting surfaces.

The effectiveness of the separation can be further increased by being beaten with the impact element or with the impact elements during the movement of the magnetic field and thus during the movement of the solid mixture against the separation surface, so that there is a superposition of the forces acting on the solid mixture or impulses comes.

Preferably, the moving magnetic field is generated by at least one moving magnet. This can be designed as an electromagnet or as a permanent magnet. However, it is also possible to use as a magnetic field generator at least one stationary electromagnet, which is acted upon by alternating current. In all cases, it is already sufficient if the magnetic field is moved temporarily. However, a permanent movement of the magnetic field is particularly advantageous.

If at least one moving magnet is used, it is favorable if it is moved back and forth in a straight line or arc, so that the material mixture to be separated also performs a reciprocating movement.

Alternatively, the magnet or the magnets below the separating surface can also be moved in a circle around an axis. Advantageously, this axis extends at least approximately parallel to the plane of the separation surface, whereby the movement of the solid mixture is promoted on the separation surface.

It is further particularly advantageous if two or more magnets are arranged together with at least one striking element on a rotor are, which is rotated below the parting surface about a rotor axis which is at least approximately aligned parallel to the parting surface. The impact elements are preferably arranged on the surface of the rotor in such a way that they can come into contact with the underside of the separating surface in order to be able to introduce the desired impact energy into the solid mixture. Also, a plurality of rotors may be arranged below a separating surface.

According to a particularly preferred embodiment of the invention, the solid mixture to be separated is applied to the separating surface when it is in an at least approximately horizontally oriented position, wherein the separating surface is then pivoted in an obliquely and / or vertically aligned position. During this pivoting movement, the frictional force initially acting on the particles, their movement braking frictional force is gradually reduced and with increasing inclination detachment of non-magnetizable particles also under the influence of gravity increasingly facilitated. In particular, the separating surface can also be moved beyond a vertical alignment in an overhead position.

It is also particularly advantageous if a plurality of angularly aligned separating surfaces in the form of a drum are arranged one behind the other and are rotated continuously about a common drum axis. In this way, a continuous running separation process with a continuously supplied particle flow can be carried out particularly favorably.

According to a further particularly preferred embodiment of the invention, in each case at least one rotor is moved under each separation surface of such a drum at a rotational speed which is greater than the rotational speed of the drum. Preferably, the rotational speed of the rotors is a multiple of the rotational speed of the drum, so that a corresponding number of blows are applied to them during the movement of each separation surface.

The present invention also relates to a device for separating magnetizable substances from a mixture of solids by way of magnetic separation, which is structurally simple and enables a highly accurate separation even with powdery or fine-grained mixtures of solids. The device according to the invention comprises a separation surface for receiving the solid mixture, wherein below the separation surface at least one magnetic field generator is arranged, through which a magnetic field can be generated, which is temporarily or constantly moved. Furthermore, the device comprises one or more impact element (s), which are designed for hitting against the separating surface. In particular, the method described above can be carried out with this device.

It is particularly advantageous in the apparatus when a plurality of angularly aligned separating surfaces are arranged in the form of a rotatable about a common drum axis drum, wherein under each separation surface at least one rotor is mounted, which comprises a plurality of magnets and at least one impact element, and about a rotor axis is rotatable, which is aligned at least approximately parallel to the respective separation surface. The axes of the rotors are preferably also aligned parallel to the drum axis. By rotating with the rotors magnets a moving magnetic field is generated for each separation surface in a particularly simple manner. Preferably, the striking elements are designed as projecting on the peripheral surface of the rotors impact edges, which can extend over the entire width of the rotors.

The axes of the rotors are not moved relative to the respective parting surface, thereby avoiding the problem of sticking of the particles over the magnetic poles which occurs in conventional change-over separators. All magnetizable particles are thus offset regardless of their grain size in a rotational movement through the alternating magnetic field.

Advantageously, the drum, which forms the individual parting surfaces and envelops the rotors, is formed of an at least partially, preferably of a completely flexible material, which is stretched over a plurality of at least substantially radially extending drum arms. In this case, the length of the drum arms and, associated therewith, the tension of the separating surfaces can be regulated and / or the distance between the rotor axes and the respective separating surfaces can be changed. By the adjustability of the voltage can be adjusted specifically the impact energy input. The adjustability of the distance between parting plane and rotor, serves to adjust the field strength of the moving magnetic field. In this case, in contrast to conventional Wechselpolscheidern by the clamping struts, which spans the drum over the rotors, an extremely rigid construction can be achieved even with relatively thin separation surfaces. Thin separating surfaces have the advantages that the loss of magnetic force remains low and that the impact energy can be more selectively introduced into the material mixture to be separated.

A well-defined energy input into the solid mixture to be separated is adjustable both by a change in the frequency of the magnetic alternating field and by a change in the intensity of impact. The inventively proposed magnetic separator concept thus has the significant advantage that due to the geometric arrangement, the separation intensity can be adjusted independently of the separation time.

According to a particularly preferred embodiment of the invention can be provided that for the removal of the magnetizable substances from the parting surfaces at least one brush is provided, the bristles always abut the drum surface even with a rotation of the drum and so remove the adhering substances. It is particularly advantageous if the brush is designed as a rotating round brush, which is pressed against the drum surface in order to improve the separation of the magnetizable particles from the separating surfaces. A particularly simple removal of the removed by the brush from the drum magnetizable particles can be achieved in that the brush is mounted on a pivotable chute, through which the magnetizable particles are also removed from the magnetic field. Alternatively, the brush can also be arranged on a pivotally mounted arm.

Further advantages and features of the invention will become apparent from the following description and the embodiments illustrated in the drawings.

Show it:

Figure 1: Schematic side view of a magnetic separating device according to the invention;

Figure 2: Enlarged view of a rotor of Figure 1; and

FIGS. 3a to 3d: simplified representation of the particle movements during the separation.

In the magnetic separating device 1 according to the invention shown in Figure 1, a powdery solid mixture 2 is fed via a vibrating conveyor 3 from above on a drum 4, which rotates about a horizontally mounted drum axis 5. The drum 4 here comprises nine circumferentially arranged successively separating surfaces 6, each consisting of a thin and flexible, but nevertheless sufficiently strong material, which over the End points 7 of nine starting from the drum axis 5 radially outwardly extending holding arms 8 is stretched.

Below each separating surface 6, a respective roller-shaped rotor 9 is mounted, which is rotatable about a rotor axis 10, which is parallel to the drum axis 5 and thus also parallel to the respective separating surface 6. The width of the rotors 9 corresponds substantially to the width of the drum 4. Alternatively, the rotors 9 may be made narrower than the drum 4. Each rotor 9 has at its periphery four over the entire rotor width extending rod-shaped permanent magnets 11, the poles are oriented alternately in radial alignment, so that when two opposing magnets 11, the north pole N and the two respectively centrally located therebetween magnet 11 of the south pole S facing outward.

In addition, each rotor 9 has two diametrically opposed edge-like impact elements 12, which also extend over the entire rotor width and protrude radially outward beyond the outer circumference of the rotor 9. They hit when rotating the rotors 9 from below against the bottom 13 of the separating surfaces 6. Thus, the rotation of a rotor 9 simultaneously leads to the moving magnetic field and to the exercise of the impact pulses at the respective separation surface 6. In the embodiment shown in Figure 1 the drum 4 counterclockwise, while the individual rotors 9 all rotate clockwise. These indicated by arrows, opposite directions of rotation lead to a particularly effective separation.

The end points 7 of the length-adjustable retaining arms 8 are in the radial direction 14 further inwardly or outwardly adjustable, whereby the distance of the rotor axis 10 and the impact edges 12 to the respective separation surface 6 and thus the introduced into the material to be separated 2 impact energy is variable (Figure 2 ). By rotating the entire drum 4 about its axis 5, the rotor 9 carrying the magnets 11 and striking edges 12 is guided under the feed stream. The powdery solid mixture 2 always falls from the vibrating conveyor 3 to the separating surface 6 of the drum 4. The material 2 is first attracted by the magnets 11 of the respective closest rotor 9 and thus enters the separation process described. The separated during the separation process from the solid mixture 2 or only weakly magnetizable particles 15 are collected in a first receptacle 16.

The strongly magnetizable particles 17 remaining in the region of the magnetic field are guided into the region of a rotating brush 18 by the further rotation of the drum 4. The brush 18 first pushes the magnetizable particles 17 out of the magnetic field and deflects them into a pivotally mounted chute 19. As a result, the magnetizable particles 17 are completely removed from the region of the attractive magnetic fields and can be conducted through the chute 19 into a second collecting container 20. Instead of the collecting container 16 and 20, of course, other types of Abtransports or collection are possible, in particular the removal by means of a conveyor belt.

Due to the pivotable articulation of the lower end of the chute 19, the brush 18 is always in contact with the surface of the drum 4 and with the separating surfaces 6. The pressure of the brush 18 on the separating surfaces 6 takes place by the weight of the chute 19 and the brush 18. If necessary, however, the contact pressure can be increased by means of a tensioning device in order to improve the separation of the magnetizable particles 17 from the separating surfaces 6.

The separation mechanism will be explained in more detail below with reference to the particle movement shown in simplified form in FIGS. 3a to 3d. The round bodies represent the non-magnetisable particles 15, while the rectangular ones Body represent the magnetizable particles 17. The rotor 9 rotates below the separation surface 6 counterclockwise.

As shown in FIG. 3 a, first the magnetisable particles 17 firmly clamp the non-magnetisable particles 15 in the intermediate spaces, so that no separation takes place in this phase. Thus, all the particles 15, 17 are initially accelerated together, irrespective of their magnetizability, to the left, since together they follow the movement of the magnetic field of the magnet 11a closest to the rotor 9. The force components acting on the particles 15, 17 can be divided into a component arranged parallel to the plane of the separating surface 6 and a component arranged perpendicular to the plane of the separating surface 6. The component arranged perpendicular to the plane of the separating surface 6 is responsible for the frictional force occurring between the particles 15, 17 and the separating surface 6. The parallel to the separation surface 6 extending force component, which is greater in this position than the perpendicular force component, accelerates the particles 15, 17 to the left.

As a result of the further rotation of the rotor 9 and thus also of the magnet 11a, the particles 15, 17 continue to be dragged until an equilibrium between the accelerating force parallel to the separating surface 6 and the indirectly decelerating force, which is perpendicular to the separating surface 6, occurs. At the same time, the magnetizable particles 17 align along the magnetic field of the magnet 11a, and they are also rotated in their orientation with the rotation of the magnet 11a on the rotating rotor 9 on the separating surface 6. The particles 15, 17 finally reach a dead center, where they stop. Due to the strong deceleration, it is not possible to separate magnetic particles 15, which are located at the outer edge of the particle cluster, from the mixture.

Thereafter, the magnetic field of the magnet 11b appearing on the opposite side attracts the particles 15, 17. The acceleration of all particles 15, 17 in the direction of the emerging magnet 11b (in the figures to the right) is very large, since the force component acting perpendicular to the separation surface 6 is very small and the force component acting parallel to the separation surface 6 is very large. During this acceleration process, the kinetic energy of the particles 15, 17 increases sharply. Then the impact edge 12 hits from below against the separation surface 6 (Figure 3b). As a result of the impingement of the striking edge 12, the direction of movement of the particles 15, 17 is deflected outwards, with the particles 15, 17 moving away from the separating surface 6. At the same time, the material is loosened up at the same time, so that the non-magnetisable particles 15 previously enclosed can separate from the magnetizable particles 17 (FIG. 3c).

The magnetizable particles 17 are then attracted again by the nearest magnet 11b and again accelerated to the left. By contrast, the non-magnetisable particles 15 fly out of the magnetic field and can be separated by utilizing gravity (FIG. 3d).

Claims

10.09.2007 SC 06063 WO

claims

I. Method for Separating Magnetizable Substances (17) from a Solids Mixture (2), The following method steps are described in more detail:

the solid mixture (2) is applied to the upper side of a separating surface (6),

a magnetic field is generated by at least one magnetic field generator (11, 11a, 11b) provided below the underside (13) of the separating surface (6) such that the magnetic field moves at least temporarily with a component directed parallel to the separating surface (6),

- With at least one impact element (12) is hit against the separation surface (6).

2. The method according to claim 1, characterized in that the polarity direction of the magnetic field is preferably changed at regular time intervals.

3. The method according to claim 1 or 2, characterized in that the separation is carried out in a powdery or granular solid mixture (2) containing particles (15, 17) whose average diameter between 1 micron and 5 mm, in particular between 3 microns and 1 mm, preferably between 10 .mu.m and 300 .mu.m.

4. The method according to any one of claims 1 to 3, d a d u r c h e c e n e e c h e n e, that preferably several times with the at least one impact element (12) from below against the bottom (13) of the separating surface (6) is beaten.

5. Method according to one of the preceding claims, characterized in that a plane of an at least partially flexible material is used as the separating surface (6).

6. The method according to any one of the preceding claims, characterized in that with the at least one impact element (12) is carried out a striking movement, which when striking the separating surface (6) perpendicular to the parting surface (6) directed movement component and a parallel to the parting surface (6 ) directed movement component.

7. Method according to one of the preceding claims, characterized in that the at least one impact element (12) is struck against the separating surface (6) during the movement of the magnetic field.

8. The method according to any one of the preceding claims, characterized in that the at least temporarily moving magnetic field is generated by means of at least one moving magnet (11, 11a, 11b) or by means of at least one acted upon by an alternating current electromagnet.

9. Method according to claim 8, wherein at least one magnet (11, 11a, 11b) is moved back and forth in a straight line or arcuate manner.

10. The method of claim 8, wherein at least one magnet (11, 11a, 11b) beneath the separation surface (6) is moved in a circle about an axis (10) extending at least approximately parallel to the plane of the separation surface (6).

11. The method according to claim 10, characterized in that below the separating surface (6) at least one rotor (9) comprising a plurality of magnets (11, 11a, 11b) and at least one striking element (12) is rotated about a rotor axis (10) which is aligned at least approximately parallel to the separating surface (6).

12. The method according to any one of the preceding claims, characterized in that the separation surface (6) during application of the material mixture (2) is in an at least substantially horizontally aligned position, and that the separation surface (6) thereafter in an oblique and / or vertical aligned position is brought.

13. The method according to any one of the preceding claims, characterized in that a plurality of angularly aligned separating surfaces (6) in the form of a drum (4) are arranged one behind the other and are continuously rotated about a common drum axis (5).

14. The method of claim 13 in combination with claim 11, characterized in that under each separation surface (6) at least one rotor (9) is moved at a rotational speed which is greater than the rotational speed of the drum (4), and preferably a multiple the rotational speed of the drum (4) is.

15. Device (1) for the separation of magnetisable substances (17) from a mixture of solids (2), in particular by carrying out the method according to one of the preceding claims, characterized in that it comprises a separation surface (6) for receiving the solid mixture (2), wherein below the separating surface (6) at least one magnetic field generator (11, 11a, 11b) is arranged, through which an at least temporarily moved magnetic field can be generated, and that it comprises at least one striking element (12) for hitting against the separating surface (6).

16. The apparatus according to claim 15, characterized in that a plurality of angularly aligned separating surfaces (6) in the form of a common drum axis (5) rotatable drum (4) are arranged, wherein under each separation surface (6) at least one rotor (9) mounted which comprises a plurality of magnets (11, 11a, 11b) and at least one impact element (12), and which is rotatable about a rotor axis (10) which is aligned at least approximately parallel to the respective parting surface (6).

17. The apparatus according to claim 16, characterized in that the individual separating surfaces (6) forming and the rotors (9) enveloping drum (4) made of an at least partially flexible Material consists and over a plurality of at least substantially radially extending drum arms (8) is clamped, wherein the length of the drum arms (8) and / or the distance of the rotor axes (10) to the respective separating surfaces (6) is variable.

18. Device according to claim 16 or 17, characterized in that for removing the magnetisable substances (17) from the separating surfaces (6) at least one brush (18) is provided whose bristles abut the drum surface even when the drum (4) rotates.

19. The device according to claim 18, characterized in that the brush (18) is designed as a rotating round brush which is pressed against the drum surface.

20. Device according to claim 19, characterized in that the brush (18) is mounted on a pivotable arm or on a pivotable chute (19), via which the magnetizable substances (17) can be removed from the magnetic field.