WO2015052368A1

WO2015052368A1 - A method and a device for separating weakly magnetic particles

Info

Publication number: WO2015052368A1
Application number: PCT/FI2014/000025
Authority: WO
Inventors: Niklas Erik Tomasson TÖRNKVIST; Pekka Suominen
Original assignee: Magsort Oy
Priority date: 2013-10-10
Filing date: 2014-10-06
Publication date: 2015-04-16

Abstract

A device for separating weakly magnetic first particles, for example hematite particles, from mixture (112) comprising the first particles (113) and nonmagnetic second particles (114) is presented. The device comprises equipment (101, 102) for producing magnetic field and for moving the mixture so that mutually opposite polarity portions (N, S) of the magnetic field sweep the mixture in a sweeping direction and thereby deflect the direction of movement of the first particles towards the sweeping direction and away from the direction of movement of the second particles. The deflected direction of movement of the first particles makes it possible to receive the first and second particles with separate collectors.

Description

A method and a device for separating weakly magnetic particles

Technical field

The present disclosure relates to a device and to a method for separating particles having positive magnetic susceptibility from mixture comprising the particles and nonmagnetic other particles. The particles having the positive magnetic susceptibility can be for example hematite, ilmenite or pyrrhotite.

Background

The increase in demand for commodities as a result of development occurring in many countries has led to a search for occurrences of economic concentrations of a wide variety of minerals and elements including but not limited to iron oxides, gold, copper, platinum, palladium, nickel, silver, titanium, manganese, and magnesium. Many occurrences of such elements and minerals have become economically recoverable due to the development of low cost mineral processing systems, such as those based on magnetic properties of minerals, for economically separating the elements of interest. For example, iron ores are rich in iron oxides that include magnetite Fe₃0₄, hematite Fe₂C>3, goethite FeO(OH), limonite FeO(OH) n(H₂0) and siderite FeCCb. Typically, the iron extraction process includes enriching the iron ore. The enriching process entails separation of the iron ore from unusable materials. Because most of the iron ores are magnetic in nature, the separation process is performed using magnetic separation techniques with the aid of which the iron ores are purified to a stage from where other metallurgical processes can be used to obtain pure iron.

Typical magnetic separation processes cannot be used for separating paramagnetic materials such as hematite Fe₂C>3, ilmenite FeTi03 and pyrrhotite that has a repeating unit Fei_-xS where x is from 0 to 0.2. Since the paramagnetic materials are only weakly magnetic, many conventional separation methods based on magnetic properties of minerals cannot be used for separating paramagnetic materials from other mining materials.

One process suitable for separating hematite is known as magnetation. In this process, the material comprising hematite is crushed and mixed with water to create slurry. The slurry is then pumped through magnetic separation chambers to separate hematite. Commercial interest in this process stems from the possibility of extracting additional iron from tailings supplied by existing mines, thus increasing the yield of the mines. Although the above-mentioned magnetation can be used to separate hematite, the magnetation has its shortcomings. The magnetation requires a large setup involving machines for mixing the crushed material with water to create slurry and for pumping the slurry through the magnetic separation chambers. Requirement of a large setup increases the costs of performing the separation process. The costs are also high because magnetic flux densities significantly over 1 T are needed in the magnetic separation chamber and thus there is a need for powerful electromagnets which require a high capacity electric current supply and sufficient cooling. This, in turn, leads to an increase in the costs of iron produced from iron ore enriched using the magnetation. Further, the magnetic separation chambers through which the slurry is passed need continual cleansing for functioning efficiently. The continual cleansing leads to high maintenance cost of the magnetation setup.

Summary

The following presents a simplified summary in order to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying and non-limiting embodiments of the invention.

In accordance with the invention, there is provided a new a device for separating first particles having positive magnetic susceptibility from mixture comprising the first particles and nonmagnetic second particles. The first particles can be, for example but not necessarily, hematite, ilmenite or pyrrhotite and the second particles can be for example quartz sand. A device according to the invention comprises:

- magnetizing equipment for producing magnetic field acting on the mixture, and

- carrier equipment for carrying the mixture so that the mixture is adapted to move with respect to the magnetic field.

The magnetizing equipment and the carrier equipment are adapted to produce the magnetic field and to carry the mixture, respectively, so that mutually opposite polarity portions of the magnetic field are adapted to sweep the mixture in a sweeping direction and thereby deflect the direction of movement of the first particles towards the sweeping direction and away from the direction of movement of the second particles so that the deflected direction of movement of the first particles intersects the sweeping direction. The deflected direction of movement of the first particles makes it possible to receive the first and second particles with separate collectors.

As each particle of the mixture can be repetitively swept by the portions of the magnetic field having the mutually opposite polarities, the magnetic force caused by the sweeping is directed to each of the first particles many times. Therefore, there is no need for so high flux densities which would otherwise be needed for separating the first particles from the mixture. The magnitude of the magnetic force directed to a particle under consideration is proportional to the product of the following: d³, χ, B, and dB/dx, where d is the diameter of the particle, χ is the magnetic susceptibility of the material of the particle, B is the magnetic flux density, and dB/dx is the gradient of the magnetic flux density. In accordance with the invention, there is provided also a new method for separating first particles having positive magnetic susceptibility from mixture comprising the first particles and nonmagnetic second particles. A method according to the invention comprises:

- producing magnetic field acting on the mixture, and - moving the mixture with respect to the magnetic field,

The producing the magnetic field and the moving the mixture with respect to the magnetic field are carried out so that mutually opposite polarity portions of the magnetic field sweep the mixture in a sweeping direction and thereby deflect the direction of movement of the first particles towards the sweeping direction and away from the direction of movement of the second particles so that the deflected direction of movement of the first particles intersects the sweeping direction.

A number of exemplifying and non-limiting embodiments of the invention are described in accompanied dependent claims.

Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in connection with the accompanying drawings.

The verbs "to comprise" and "to include" are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality. Brief description of figures

Exemplifying and non-limiting embodiments of the invention and their advantages are explained in greater detail below with reference to the accompanying drawings, in which: figure la shows a schematic side view of a device according to an exemplifying and non-limiting embodiment of the invention for separating particles having positive magnetic susceptibility from nonmagnetic particles, figure lb shows a schematic top view of the device illustrated in figure la, figure lc shows a schematic view of a section taken along a line A-A shown in figure la, figure 2 illustrates a device according to another exemplifying and non-limiting embodiment of the invention for separating particles having positive magnetic susceptibility from nonmagnetic particles, figure 3 illustrates a device according to an exemplifying and non-limiting embodiment of the invention for separating particles having positive magnetic susceptibility from nonmagnetic particles, figures 4a and 4b illustrate a device according to an exemplifying and non-limiting embodiment of the invention for separating particles having positive magnetic susceptibility from nonmagnetic particles, and figure 5 shows a flowchart of a method according to an exemplifying and non- limiting embodiment of the invention for separating particles having positive magnetic susceptibility from nonmagnetic particles.

Description of exemplifying embodiments Figure la shows a schematic side view of a device according to an exemplifying and non-limiting embodiment of the invention. Figure lb shows a schematic top view of the device. Furthermore, figure lb shows schematically mixture 112 which comprises first particles having positive magnetic susceptibility, χ > 0, and nonmagnetic second particles. The first particles can be, for example but not necessarily, hematite, ilmenite or pyrrhotite and the second particles can be for example quartz sand. In figure lb, the first particles are presented as white circles one of which is denoted with a reference number 113 and the second particles are presented as black circles one of which is denoted with a reference number 114. Figure lc shows a schematic view of a section taken along a line A-A shown in figure la. The section plane is parallel with the xz-plane of a coordinate system 199. The device comprises magnetizing equipment 101 for producing magnetic field acting on the mixture 112 and carrier equipment 102 for carrying the mixture so that the mixture is adapted to move with respect to the magnetic field.

In the exemplifying device illustrated in figures la-lc, the magnetizing equipment 101 comprises rotatable elements 103, 104, 105 and 106. As illustrated in the section view shown in figure lc, each of the rotatable elements 103-106 comprises permanent magnets having radially directed magnetic axes. In figure lc, one of the permanent magnets of the rotatable element 104 is denoted with a reference number 115. The permanent magnets can be embedded to a support matrix made of non-ferromagnetic material for example aluminum. A part of the support matrix of the rotatable element 104 is denoted with a reference number 116 in figure lc. In this exemplifying case, each rotatable element further comprises a ferromagnetic core and a support band for supporting and protecting the permanent magnets. In figure lc, the core of the rotatable element 104 is denoted with a reference number 117 and the support band of the rotatable element 104 is denoted with a reference number 118. The support band can be made of for example carbon fiber or metal. In the exemplifying device illustrated in figures la-lc, the carrier equipment 102 comprises a conveyor belt 109 driven with an electrical motor 119. The longitudinal direction of the conveyor belt 109 is substantially parallel with a rotation axis of each of the rotating elements 103-106. The conveyor belt is adapted to receive the mixture 112 from a feed box 120 and to move the mixture so that the mixture is a distance away from magnetizing equipment producing the magnetic field, i.e. the mixture does not touch the rotatable elements 103-106. The direction of the movement of the conveyor belt 109 is depicted with an arrow 130 in figure lb. The device comprises advantageously a support structure 121 with the aid of which it is possible to adjust the vertical, i.e. the z-directional, distance between the conveyor belt 109 and the rotating elements 103-106.

The rotatable elements 103 and 105 constitute first co-axial rotatable elements which are driven with an electrical motor 122, and the rotatable elements 104 and 106 constitute second co-axial rotatable elements which are driven with an electrical motor 123, as shown in figure lb. The first and second rotatable elements are adjacent to each other in the transversal direction of the conveyor belt 109, i.e. the in the x-direction of the coordinate system 199. The first and second rotatable elements are adapted to rotate in mutually opposite rotational directions as illustrated with arrows 124 and 125 in figure lc. It is also possible that all the rotatable elements 103-106 are driven with only one motor and with a power transmission arrangement comprising gear wheels, a chain and chain wheels, and/or a belt and belt pulleys. In some cases, where the mutually adjacent first and second rotatable elements are sufficiently close to each other, it may suffice that only the first, or the second, rotatable elements are rotated because the adjacent second, or first, rotatable elements are rotated due to the magnetic interaction between mutually adjacent rotatable elements.

When the rotatable elements are rotating as illustrated by the arrows 124 and 125 shown in figure lc, mutually opposite polarity portions of the magnetic field are adapted to sweep the mixture 112. A loop line 138 shown in figure lc illustrates an exemplifying flux line of the magnetic field produced by the rotatable element 104. A part 128 of the loop line represents such a portion of the magnetic field which has polarity so that the field acting on the mixture 112 is substantially upwards, i.e. in the positive z-direction of the coordinate system 199. Correspondingly, a part 129 of the loop line represents such a portion of the magnetic field which has opposite polarity so that the field acting on the mixture 112 is substantially downwards, i.e. in the negative z-direction of the coordinate system 199. The magnetic field produced by the rotatable elements 103 and 105 sweeps the mixture 112 in a sweeping direction illustrated with an arrow 127 shown in figures lb and lc. Correspondingly, the magnetic field produced by the rotatable elements 104 and 106 sweeps the mixture 112 in a sweeping direction illustrated with an arrow 126 shown in figures lb and lc. As illustrated in figure lb, the sweeping magnetic field produced by the rotatable elements 103 and 105 deflect the direction of movement of a first portion of the first particles obliquely towards a first longitudinal edge of the conveyor belt 109. Correspondingly, the sweeping magnetic field produced by the rotatable elements 104 and 106 deflect the direction of movement of a second portion of the first particles obliquely towards the second longitudinal edge of the conveyor belt 109. The deflected directions of movement of the first particles make it possible to receive the first particles at collectors 131 and 132 as illustrated in figure lb. The second particles whose direction of movement is not deflected are received at a collector 133.

Since the separation of the first particles from the mixture is based on directing magnetic forces to the first particles, the separation is most effective to those of the first particles which are most free, i.e. least hindered by other particles, to move in response to the magnetic forces. Those of the first particles which are located topmost on the trail of the mixture on the conveyor belt 109 are inherently those of the first particles which are most free to be moved by the sweeping magnetic fields. The freedom of all the first particles to move can be increased by agitating the mixture so as to cause the first and second particles to be stirred on the surface of the conveyor belt 109. When a particle belonging to the first particles is e.g. bouncing due to the stirring, the particle is free to be moved at least a short distance by the sweeping magnetic field. When the sweeping by the magnetic field and the bouncing occurs sufficiently many times, the particle under consideration is shifted a sufficient distance in the sweeping direction of the magnetic field. The separation process can be tuned by adjusting the rotational speeds of the rotatable elements 103-106, by adjusting the speed of movement of the conveyor belt 109, and by adjusting the strength of the magnetic fields acting on the mixture. In the exemplifying case illustrated in figures la-lc, the strength of the magnetic fields can be adjusted by adjusting the vertical distance between the rotatable elements and the conveyor belt. The vertical distance is advantageously so long that the first particles do not stick on the rotatable elements. The peak value of the magnetic flux density acting on the mixture can be for example from 0.01 T to 0.5 T. The support band 118 can be designed to be so thick that a particle belonging to the first particles does not get captured by the rotatable element even if the particle were thrown towards the rotatable element due to the agitation of the mixture.

The exemplifying device illustrated in figures la-lc comprises advantageously an agitator 110 for agitating the conveyor belt 109 so as to cause the first and second particles to be stirred on the upper surface of the conveyor belt. In this exemplifying case, the agitator 110 comprises ferromagnetic elements adapted to agitate the conveyor belt in response to being shaken by the magnetic field produced by the magnetizing equipment and alternating with respect to the ferromagnetic elements. The ferromagnetic elements can be for example flexible wires or strips of ferromagnetic material which are shaken by the magnetic field alternating with respect to the wires or strips and which in turn agitate the conveyor belt. In figure lc, one of the ferromagnetic elements is denoted with a reference number 111. Figure 2 illustrates a device according to another exemplifying and non-limiting embodiment of the invention for separating first particles having positive magnetic susceptibility from mixture 212 comprising the first particles and nonmagnetic second particles. Figure 2 shows a schematic view of a section taken from the device in the same way as figure lc shows the schematic view of the section taken along the line A-A shown in figure la. The device illustrated in figure 2 comprises magnetizing equipment 201 for producing magnetic field acting on the mixture, and carrier equipment 202 for carrying the mixture so that the mixture is adapted to move with respect to the magnetic field. In this exemplifying case, the carrier equipment 202 comprises a conveyor belt 209 for moving the mixture 212 in the y- direction of a coordinate system 299. The magnetizing equipment 201 is adapted to produce the magnetic field so that mutually opposite polarity portions of the magnetic field are adapted to sweep the mixture in a sweeping direction which is depicted with arrows 226 in figure 2. The sweeping magnetic field deflects the direction of movement of the first particles towards the sweeping direction and away from a direction of movement of the second particles, i.e. away from the y- direction of a coordinate system 299.

In the exemplifying device illustrated in figure 2, the magnetizing equipment 201 comprises an electromagnet 207 that has a multiphase winding 208. The electromagnet 207 produces the above-mentioned sweeping magnetic field when multiphase alternating electrical current is supplied to the multiphase winding 208. A loop line 238 illustrates an exemplifying flux line of the magnetic field produced by the electromagnet 207. In this exemplifying case, the multiphase winding 208 is a 3-phase winding and the multiphase alternating electrical current is 3-phase alternating electrical current. The 3-phase winding can be in principle similar to a stator winding of a 3-phase alternating current electrical motor. It is also possible that a device according to an exemplifying and non-limiting embodiment of the invention comprises one or more rotatable permanent magnet elements such as the rotatable elements 103-106 shown in figures la-lc and also one or more electromagnets such as the electromagnet 207. The one or more rotatable permanent magnet elements can be on one side of the conveyor belt and the one or more electromagnets can be on the other side of the conveyor belt.

The exemplifying device illustrated in figure 2 comprises advantageously an agitator for agitating the conveyor belt 209 so as to cause the first and second particles to be stirred on the upper surface of the conveyor belt. In this exemplifying case, the agitator comprises ferromagnetic elements adapted to agitate the conveyor belt in response to being shaken by the magnetic field produced by the electromagnet 207. In figure 2, one of the ferromagnetic elements is denoted with a reference number 211.

Figure 3 illustrates a device according to an exemplifying and non-limiting embodiment of the invention for separating first particles having positive magnetic susceptibility from mixture comprising the first particles and nonmagnetic second particles. The device comprises magnetizing equipment 301 for producing magnetic field acting on the mixture, and carrier equipment 302 for carrying the mixture so that the mixture is adapted to move with respect to the magnetic field. The magnetizing equipment 301 is adapted to produce the magnetic field so that mutually opposite polarity portions of the magnetic field are adapted to sweep the mixture in a sweeping direction which is depicted with an arrow 326 in figure 3. The sweeping magnetic field deflects the direction of movement of the first particles towards the sweeping direction and away from the direction of movement of the second particles. The moving path of the first particles is depicted with a curved arrow 340, and the moving path of the second particles is depicted with a curved arrow 341.

In the exemplifying device illustrated in figure 3, the carrier equipment 302 comprises a sliding surface for allowing the gravity force to move the mixture. The magnetizing equipment 301 comprises a wheel provided with permanent magnets which produce the above-mentioned sweeping magnetic field when the wheel is rotated according to an arrow 330 shown in figure 3.

Figures 4a and 4b illustrate a device according to an exemplifying and non-limiting embodiment of the invention for separating first particles having positive magnetic susceptibility from mixture comprising the first particles and nonmagnetic second particles. The device comprises magnetizing equipment 401 for producing magnetic field acting on the mixture, and carrier equipment 402 for carrying the mixture so that the mixture is adapted to move with respect to the magnetic field. In this exemplifying case, the carrier equipment 402 comprises a conveyor belt 409 for moving the mixture in the positive y-direction of a coordinate system 499. The magnetizing equipment 401 comprises a plurality of bar-shaped permanent magnets whose magnetic axes are substantially perpendicular to the conveyor belt 409. As shown in figures 4a and 4b, the permanent magnets are positioned obliquely with respect to the moving direction of the conveyer belt, i.e. obliquely with respect to the y-direction of the coordinate system 499. As shown in figure 4b, the north- pole "N" of every second of the permanent magnets is towards the part of the conveyor belt carrying mixture and the south-poles "S" of the rest of the permanent magnets are towards the part of the conveyor belt carrying mixture. When the mixture is moved by the conveyor belt 409, the magnetic field produced by the permanent magnets sweeps the mixture in a sweeping direction which is depicted with an arrow 426 in figures 4a and 4b. The sweeping magnetic field deflects the direction of movement of the first particles towards the sweeping direction and away from a direction of movement of the second particles, i.e. away from the y- direction of a coordinate system 499. The moving path of the first particles is depicted with a curved arrow 440, and the moving path of the second particles is depicted with a curved arrow 441.

Figure 5 shows a flowchart of a method according to an exemplifying and non- limiting embodiment of the invention for separating first particles having positive magnetic susceptibility from mixture comprising the first particles and nonmagnetic second particles. The method comprises the following actions:

- action 501: producing magnetic field acting on the mixture, and

- action 501: moving the mixture with respect to the magnetic field, The producing the magnetic field and the moving the mixture with respect to the magnetic field are carried out so that mutually opposite polarity portions of the magnetic field sweep the mixture in a sweeping direction and thereby deflect the direction of movement of the first particles towards the sweeping direction and away from the direction of movement of the second particles so that the deflected direction of movement of the first particles intersects the sweeping direction.

In a method according to an exemplifying and non-limiting embodiment of the invention, the magnetic field whose mutually opposite polarity portions sweep the mixture is at least partly produced with one or more rotating elements each comprising permanent magnets having radially directed magnetic axes. In a method according to an exemplifying and non-limiting embodiment of the invention, the magnetic field whose mutually opposite polarity portions sweep the mixture is at least partly produced with one or more electromagnets each having a multiphase winding supplied with multiphase alternating electrical current.

In a method according to an exemplifying and non-limiting embodiment of the invention, the mixture is moved with a conveyor belt. In a method according to an exemplifying and non-limiting embodiment of the invention, the mixture is moved by allowing the gravity force to move the mixture along a sliding surface.

In a method according to an exemplifying and non-limiting embodiment of the invention, the mixture is moved with a conveyor belt and the longitudinal direction of the conveyor belt is substantially parallel with a rotation axis of each of one or more rotating elements which produce the magnetic field whose mutually opposite polarity portions sweep the mixture. In a method according to an exemplifying and non-limiting embodiment of the invention, the rotating elements comprise at least one first rotating element and at least one second rotating element so that the first and second rotating elements are adjacent to each other in a transversal direction of the conveyor belt and rotate in mutually opposite rotational directions so as to deflect the direction of movement of a first portion of the first particles obliquely towards a first longitudinal edge of the conveyor belt and the direction of movement of a second portion of the first particles obliquely towards a second longitudinal edge of the conveyor belt.

In a method according to an exemplifying and non-limiting embodiment of the invention, the mixture is moved with a conveyor belt and the longitudinal direction of the conveyor belt is substantially perpendicular to directions of magnetic axes of a multiphase winding of each of one or more electromagnets which produce the magnetic field whose mutually opposite polarity portions sweep the mixture.

A method according to an exemplifying and non-limiting embodiment of the invention further comprises agitating the mixture. The mixture can be agitated for example with the aid of one or more ferromagnetic elements shaken by the magnetic field alternating with respect to the ferromagnetic elements. In a method according to an exemplifying and non-limiting embodiment of the invention, a peak value of the magnetic flux density acting on the mixture is from 0.01 T to 0.5 T.

In a method according to an exemplifying and non-limiting embodiment of the invention, the material of the first particles is material selected from a group consisting of: hematite, ilmenite and pyrrhotite.

The non-limiting, specific examples provided in the description given above should not be construed as limiting the scope and/or the applicability of the appended claims.

Claims

What is claimed is:

1. A device for separating first particles having positive magnetic susceptibility from mixture comprising the first particles and nonmagnetic second particles, the device comprising: - magnetizing equipment (101, 201, 301, 401) for producing magnetic field acting on the mixture, and

- carrier equipment (102, 202, 302, 402) for carrying the mixture so that the mixture is adapted to move with respect to the magnetic field, characterized in that the magnetizing equipment and the carrier equipment are adapted to produce the magnetic field and to carry the mixture so that mutually opposite polarity portions of the magnetic field are adapted to sweep the mixture in a sweeping direction and deflect a direction of movement of the first particles towards the sweeping direction and away from a direction of movement of the second particles, the deflected direction of movement of the first particles intersecting the sweeping direction.

2. A device according to claim 1, wherein the magnetizing equipment (101) comprises one or more rotatable elements (103-106) each comprising permanent magnets (115) having radially directed magnetic axes so as to produce at least a part of the magnetic field acting on the mixture, the mutually opposite polarity portions of the magnetic field sweeping the mixture in response to rotation of the one or more rotatable elements.

3. A device according to claim 1 or 2, wherein the magnetizing equipment (201) comprises one or more electromagnets (207) each having a multiphase winding (208), the one or more electromagnets producing at least a part of the magnetic field whose mutually opposite polarity portions are adapted to sweep the mixture in response to being supplied with multiphase alternating electrical current.

4. A device according to any of claims 1-3, wherein the carrier equipment (102, 202, 402) comprises a conveyor belt (109, 209, 409) for moving the mixture in a longitudinal direction of the conveyor belt.

5. A device according to any of claims 1-3, wherein the carrier equipment (302) comprises a sliding surface for allowing gravity force to move the mixture.

6. A device according to claim 2, wherein the carrier equipment (102) comprises a conveyor belt (109) for moving the mixture in a longitudinal direction of the conveyor belt, the longitudinal direction of the conveyor belt being substantially parallel with a rotation axis of each of the one or more rotatable elements.

7. A device according to claim 3, wherein the carrier equipment (202) comprises a conveyor belt (209) for moving the mixture in a longitudinal direction of the conveyor belt, the longitudinal direction of the conveyor belt being substantially perpendicular to directions of magnetic axes of the multiphase winding (208) of each of the electromagnets.

8. A device according to claim 6, wherein the rotatable elements comprise at least one first rotatable element (103, 105) and at least one second rotatable element (104, 106), the first and second rotatable elements being adjacent to each other in a transversal direction of the conveyor belt (109) and adapted to rotate in mutually opposite rotational directions so as to deflect a direction of movement of a first portion of the first particles obliquely towards a first longitudinal edge of the conveyor belt and a direction of movement of a second portion of the first particles obliquely towards a second longitudinal edge of the conveyor belt.

9. A device according to any of claim 1-8, wherein the device further comprises an agitator (110) for agitating a part of the carrier equipment so as to stir the first and second particles carried with the carrier equipment.

10. A device according to claim 9, wherein the agitator comprises one or more ferromagnetic elements (111, 211) adapted to agitate the part of the carrier element in response to being shaken by the magnetic field produced by the magnetizing equipment and alternating with respect to the ferromagnetic elements.

11. A device according to any of claims 1-10, wherein a peak value of magnetic flux density acting on the mixture is from 0.01 T to 0.5 T.

12. A method for separating first particles having positive magnetic susceptibility from mixture comprising the first particles and nonmagnetic second particles, the method comprising: - producing (501) magnetic field acting on the mixture, and

- moving (502) the mixture with respect to the magnetic field, . characterized in that the producing the magnetic field and the moving the mixture with respect to the magnetic field are carried out so that mutually opposite polarity portions of the magnetic field sweep the mixture in a sweeping direction and deflect a direction of movement of the first particles towards the sweeping direction and away from a direction of movement of the second particles, the deflected direction of movement of the first particles intersecting the sweeping direction.

13. A method according to claim 12, wherein the magnetic field whose mutually opposite polarity portions sweep the mixture is at least partly produced with one or more rotating elements each comprising permanent magnets having radially directed magnetic axes.

14. A method according to claim 12 or 13, wherein the magnetic field whose mutually opposite polarity portions sweep the mixture is at least partly produced with one or more electromagnets each having a multiphase winding supplied with multiphase alternating electrical current.

15. A method according to any of claims 12-14, wherein the mixture is moved with a conveyor belt.

16. A method according to any of claims 12-14, wherein the mixture is moved by allowing gravity force to move the mixture along a sliding surface.

17. A method according to claim 13, wherein the mixture is moved with a conveyor belt and the longitudinal direction of the conveyor belt is substantially parallel with a rotation axis of each of the one or more rotating elements.

18. A method according to claim 14, wherein the mixture is moved with a conveyor belt and the longitudinal direction of the conveyor belt is substantially perpendicular to directions of magnetic axes of the multiphase winding of each of the electromagnets.

19. A method according to claim 17, wherein the rotating elements comprise at least one first rotating element and at least one second rotating element, the first and second rotating elements being adjacent to each other in a transversal direction of the conveyor belt and rotating in mutually opposite rotational directions so as to deflect a direction of movement of a first portion of the first particles obliquely towards a first longitudinal edge of the conveyor belt and a direction of movement of a second portion of the first particles obliquely towards a second longitudinal edge of the conveyor belt.

20. A method according to any of claim 12-19, wherein the method further comprises agitating the mixture.

21. A method according to claim 20, wherein the mixture is agitated with the aid of one or more ferromagnetic elements shaken by the magnetic field alternating with respect to the ferromagnetic elements.

22. A method according to any of claims 12-21, wherein a peak value of magnetic flux density acting on the mixture is from 0.01 T to 0.5 T.

23. A method according to any of claims 12-22, wherein material of the first particles is material selected from a group consisting of: hematite, ilmenite and pyrrhotite.