Method and device for magnetic selection of powder containing magnetic material

Abstract

To provide a method and a device for magnetic selection of a powder containing a magnetic material which has a small number of processes and a simple device configuration and can sufficiently remove metals from the powder.SOLUTION: A method for magnetic selection of a powder containing a magnetic material includes: a dispersion step in which the powder containing the magnetic material is dispersed by a dispersant to obtain a dispersion liquid; a flow splitting step in which the dispersion liquid is split into a first flow and a second flow; a magnetic material recovery step in which the magnetic material contained in the dispersion liquid is attracted by a magnetic force to be drawn to the second flow and recovered along the second flow; and a non-magnetic material discharge step in which a non-magnetic material contained in the dispersion liquid is discharged along the first flow.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for magnetically separating powder containing magnetic material. [Background technology]

[0002] The so-called black mass obtained by heat treatment of electrodes of lithium-ion batteries that have been used or discarded as defective products during production contains magnetic materials such as nickel, cobalt, iron, etc., and non-magnetic materials such as aluminum, copper, etc. Conventionally, in order to produce recycled electrode materials using black mass, the magnetic and non-magnetic materials contained in the black mass are separated and the elements required for the recycled electrode materials are recovered.

[0003] For example, Patent Document 1 describes a method for separating fine particles in which a powder containing magnetic material is dispersed in a liquid and the magnetic material is magnetically separated from the powder by a magnetic separator. The magnetic separator in Patent Document 1 has a magnetic pole part equipped with a coil that magnetizes a plurality of iron balls inside a tube, and while the plurality of iron balls in the magnetic pole part are magnetized, a suspension liquid is fed to the magnetic pole part, the magnetic material in the suspension liquid is attracted to the magnetized iron balls and removed, and the suspension liquid from which the magnetic material has been removed is discharged, after which the plurality of iron balls in the magnetic pole part are demagnetized, washing water is fed to the magnetic pole part, and the magnetic material magnetized to the iron balls is discharged together with the water.

[0004] However, the magnetic sorting method of Patent Document 1 has a problem in that it requires a large number of flow paths and many processes, such as magnetizing and demagnetizing the iron balls and feeding the suspension and washing water, and therefore takes a long time for sorting.

[0005] Patent Document 2 describes a magnetic sorting method for removing coarse crystal grain powder from magnetic powder. The magnetic sorting method of Patent Document 2 uses a magnetic sorting device to perform a first sorting of magnetic powder falling from a pulverizer into nano crystal powder, amorphous powder, and coarse crystal grain powder using a magnet, and then the amorphous powder and coarse crystal grain powder are conveyed on a conveyor while being heat-treated with a heater to crystallize the amorphous powder into nano crystal powder, and then the powder is conveyed over an adsorption roll to cause the nano crystal powder to fall and the coarse crystal grain powder to be adsorbed to the adsorption roll, thereby performing a second sorting of the nano crystal powder and the coarse crystal grain powder.

[0006] However, the magnetic separation method of Patent Document 2 has a problem in that the apparatus is large-scale and complicated since it is equipped with a conveyor, an adsorption roll, a peeling wall, and the like.

[0007] On the other hand, in the process of manufacturing electrodes using black mass as a precursor, if the precursor contains metal particles, the deposits in the electrode may grow into dendrites (needle-shaped crystals), causing an internal short circuit and resulting in a fire. For this reason, there is a demand to thoroughly remove the metals that cause short circuits from the black mass. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2002-224586 A [Patent Document 2] JP 2017-98454 A Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in consideration of the above-mentioned problems in the conventional art, and has an object to provide a method and apparatus for magnetic separation of powder containing magnetic material, which has few steps, a simple device configuration, and can sufficiently remove metals from the powder. [Means for solving the problem]

[0010] The means for solving the above problems are as follows. (1) The magnetic separation method of the present invention comprises the steps of: A dispersion step of dispersing a powder containing a magnetic material with a dispersant to obtain a dispersion liquid; A flow dividing step of dividing the dispersion into a first flow and a second flow; a magnetic material recovery step of attracting magnetic materials contained in the dispersion liquid by magnetic force, drawing them to the second flow, and recovering them along the second flow; a non-magnetic material discharge step of discharging non-magnetic material contained in the dispersion liquid along the first flow; Equipped with.

[0011] (2) The magnetic separation device of the present invention is an outer tube having a supply port for supplying a dispersion liquid of powder containing a magnetic material; A magnet disposed on the outside of the outer tube; an inner tube inserted into the outer tube and having an inlet downstream of the magnet; a recovery port is provided in the outer tube to recover a dispersion liquid containing a magnetic material that has flowed into a second flow flowing between the outer tube and the inner tube; The inner pipe is provided with a discharge port for discharging the dispersion liquid containing the non-magnetic material that has flowed into the first flow flowing inside the inner pipe.

[0012] (3) In the above-mentioned means 2, The magnet comprises a plurality of magnets arranged at equal intervals on the outer peripheral surface of the outer tube.

[0013] (4) In the above means 2 or 3, The magnets are electromagnets, and are configured to sequentially apply a pulse current in the circumferential direction.

[0014] (5) In any one of the above means 2 to 4, The plurality of magnets includes a first group of magnets and a second group of magnets arranged downstream of the first group of magnets.

[0015] (6) In the above-mentioned means 5, The first group of magnets and the second group of magnets are made of electromagnets, and are configured to apply currents with a phase shift so as to demagnetize the first group of magnets and then magnetize the second group of magnets.

[0016] (7) In the above-mentioned means 5, The first group of magnets and the second group of magnets are made of electromagnets, and are configured to sequentially apply pulse currents to each of them in the circumferential direction, and to apply currents with a phase shift so as to demagnetize the first group of magnets and then magnetize the second group of magnets.

[0017] (8) In any one of the above means 2 to 7, The magnetic separators are arranged in a plurality of stages, and the discharge port of the inner pipe of the upstream magnetic separator is connected to the supply port of the outer pipe of the downstream magnetic separator. Effect of the Invention

[0018] According to the present invention, a powder is dispersed in a dispersion liquid, the dispersion liquid is divided, the magnetic material contained in the dispersion liquid is attracted to the second flow by magnetic force, and the non-magnetic material contained in the dispersion liquid is discharged along the first flow, thereby achieving the effects of fewer steps, a simple device configuration, and sufficient removal of metals from the powder. [Brief description of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view of a magnetic separation device according to a first embodiment of the present invention. [Diagram 2] Cross-sectional view of line II-II in Figure 1. [Diagram 3] 2 is a timing chart showing the on / off operation of the electromagnet in FIG. 1. [Figure 4] FIG. 5 is a cross-sectional view of a magnetic separation device according to a second embodiment of the present invention. [Diagram 5] 5 is a timing chart showing the on / off operation of the electromagnet in FIG. 4. [Figure 6]10 is a timing chart showing the on / off operation of an electromagnet in a modified example of the magnetic separation device according to the second embodiment. [Figure 7] FIG. 5 is a cross-sectional view of a magnetic separation device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0021] <Magnetic sorting method> The magnetic separation method according to an embodiment of the present invention includes the steps of: A dispersion step of dispersing a powder containing a magnetic material with a dispersant to obtain a dispersion liquid; A flow dividing step of dividing the dispersion into a first flow and a second flow; a magnetic material recovery step of attracting the magnetic material contained in the dispersion liquid by magnetic force to the second flow and recovering the magnetic material along the second flow; a non-magnetic material discharge step of discharging the non-magnetic material contained in the dispersion liquid along the first flow; Equipped with.

[0022] The ratio of dispersant to powder in the dispersion liquid used in the dispersion step is preferably 20 to 75% by weight for powder and 0.1 to 20% by weight for dispersant. The powder is preferably pulverized to 50 μm or less using a jet mill or the like. If the powder has a size exceeding 50 μm, it will not be dispersed and will precipitate. As the dispersant, one or more selected from polymer dispersants (acid type, low acid value), polymer anionic dispersants, polymer polycarboxylic acid type dispersants, low molecular weight surfactants, polymer nonionic (nonionic) surfactants, and polymer anionic surfactants can be used. Examples of the polymer dispersant include the Solsperse (registered trademark) series manufactured by Lubrizol Japan Co., Ltd., such as "Solsperse 43000," "Solsperse 44000," "Solsperse 46000," "Solsperse W100," and "Solsperse W320," the TEGO (registered trademark) Disperse series manufactured by EVONIK, such as "TEGO Disperse 750W," "TEGO Disperse 755W," and "TEGO Disperse 760W," and the BYK products, such as "DISPERBYK (registered trademark)-180," "DISPERBYK-190," "DISPERBYK-194N," "DISPERBYK-2010," "DISPERBYK-2012," and "DISPERBYK-2015." Examples of the polymeric anionic dispersant include the Joncryl (registered trademark) series manufactured by BASF Japan Ltd., such as "Joncryl 60J", "Joncryl 63J", "Joncryl 70J", "Joncryl HPD-96J" and "Joncryl 6137A". Examples of polymeric polycarboxylic acid-based dispersants include "BYK (registered trademark)-154" manufactured by BYK, "TEGO Disperse 715W" from the TEGO Disperse series manufactured by EVONIK, and "SN Dispersant 5020," "NOPCO SPARSE (registered trademark) 44-C," and "SN Dispersant 5034" manufactured by San Nopco Ltd. Low molecular weight surfactants include carboxylates such as soap, sulfonates such as linear alkylbenzene sulfonates (LAS), α-sulfofatty acid methyl ester salts (MES), and α-olefin sulfonates (AOS), and sulfates such as alkyl sulfates (AS) and polyoxyethylene alkyl sulfates (AES). Examples of polymeric nonionic surfactants include the Emulgen (registered trademark) series manufactured by Kao Corporation and the Noigen (registered trademark) series manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Examples of the polymeric anionic surfactant include the EMAL (registered trademark) series manufactured by Kao Corporation and the HITENOL (registered trademark) series manufactured by Daiichi Kogyo Seiyaku Co., Ltd. In addition, antifoaming agents, preservatives, etc. may be added as necessary. The viscosity of the dispersion during dispersion is preferably 5 mPa·s to 2000 mPa·s, and for this purpose, a cellulose-based additive, a thickening polysaccharide, an alcohol, or an ether may be used as a viscosity adjuster.

[0023] The first and second flows used in the flow dividing step are preferably made of a double pipe, with the second flow being between the outer pipe and the inner pipe, and the first flow being inside the inner pipe. This is because a magnet can be placed on the outside of the outer pipe to attract the liquid between the outer pipe and the inner pipe by magnetic force. The flow rate of the dispersion liquid is preferably 10 ml to 5 L / min.

[0024] The magnet used in the magnetic material recovery step is preferably an electromagnet, which preferably generates a magnetic flux density of 1000 to 5000 gauss.

[0025] The second flow in the magnetic material recovery step contains the magnetic materials attracted by the magnetic force of the magnet, so the magnetic materials can be recovered by filtering and drying the dispersion liquid of the second flow. The first flow in the non-magnetic material discharge process contains only non-magnetic materials, and the magnetic materials that have been attracted to the second flow by the magnetic force of the magnet have been removed from the first flow. Therefore, the non-magnetic materials can be recovered by filtering and drying the dispersion liquid of the first flow.

[0026] <First embodiment of magnetic separation device> 1 shows a magnetic separation device 1 according to a first embodiment of the present invention. The magnetic separation device 1 is composed of an outer tube 2, an inner tube 3, and an electromagnet 4.

[0027] The outer pipe 2 is cylindrical and is preferably made of a non-magnetic metal such as aluminum or a resin such as polyvinyl chloride. The outer pipe 2 has a main body portion 2a on the upstream side and an expanded diameter portion 2b on the downstream side that is larger in diameter than the upstream side. The upstream end of the main body portion 2a is connected to a supply port 5, and the downstream end is connected to the expanded diameter portion 2b. The downstream end of the expanded diameter portion 2b is closed. A recovery port 6 is formed on the outer periphery of the expanded diameter portion 2b, and is configured to flow out from this recovery port 6 in a direction perpendicular to the flow of the main body portion 2a.

[0028] The inner pipe 3, like the outer pipe 2, is preferably made of a non-magnetic metal such as aluminum or a resin such as polyvinyl chloride. The ratio of the outer diameters of the inner pipe 3 and the outer pipe 2 is preferably 1:2. The inner pipe 3 is inserted inside the outer pipe 2 and supported on the inner surface of the outer pipe 2 via a stay 7. An annular gap 8 is formed between the inner pipe 3 and the outer pipe 2, forming a flow path for the second flow. The upstream end of the inner pipe 3 is located downstream of a magnet 4, which will be described later, and serves as an inlet 9 for the first flow. The downstream end of the inner pipe 3 penetrates a closed end of the enlarged diameter portion 2b of the outer pipe 2, and serves as an outlet 10 for the first flow.

[0029] As shown in FIG. 2, the magnet 4 is composed of a plurality of electromagnets arranged at equal intervals along the outer peripheral surface of the outer tube 2. The number of magnets 4 is eight in the embodiment, but is not limited to this, and is preferably three or more. The magnet 4 is composed of an iron core 11, a coil 12 wound around the iron core 11, and a yoke 13 extending from one end of the iron core 11 to the other end. The magnet 4 is arranged so that the tip of the yoke 13 contacts the outer surface of the outer tube 2, so that the magnetic field lines can be efficiently supplied to the dispersion liquid flowing inside the outer tube 2 without leaking. The magnet 4 can be magnetized and demagnetized by applying a pulse current by a control circuit (not shown).

[0030] Next, the operation of the magnetic separator 1 will be described. Here, the explanation will be given assuming that a dispersion liquid in which black mass pulverized to 50 μm or less is dispersed with a dispersant is used as the dispersion liquid. Black mass contains magnetic materials such as nickel, cobalt, and their compounds, and non-magnetic materials such as copper and aluminum.

[0031] The black mass dispersion liquid supplied to the supply port 5 of the outer tube 2 is divided into a second flow flowing through the gap 8 between the outer tube 2 and the inner tube 3, and a first flow flowing inside the inner tube 3.

[0032] The magnet 4 is made up of a plurality of electromagnets, each of which is magnetized by applying a current thereto by a control device (not shown).

[0033] The magnetic materials, such as nickel, cobalt and compounds thereof, in the dispersion liquid flowing inside the outer tube 2 are attracted toward the magnet 4, i.e., toward the radially outer side of the outer tube 2, by the magnetic force of the magnet 4, and move radially outward from the outer tube 2 and flow into the first flow that flows through the gap 8 between the outer tube 2 and the inner tube 3. The dispersion liquid containing the magnetic materials that flows along the first flow flows into the expanded diameter section 2b and flows out from the recovery port 6 of the expanded diameter section 2b.

[0034] On the other hand, non-magnetic materials such as copper, aluminum, etc. in the dispersion liquid flowing inside the outer tube 2 move along the flow in the outer tube 2 without being affected by the magnetic force of the magnet 4, and some of them flow into the second flow that flows through the gap 8 between the outer tube 2 and the inner tube 3, but the majority of them flow into the first flow that flows inside the inner tube 3. The dispersion liquid from which the magnetic materials have been removed (dispersion liquid containing non-magnetic materials) flowing along the first flow flows out from the outlet 10 of the inner tube 3.

[0035] The dispersion liquid containing the magnetic material flowing out from the recovery port 6 along the second flow passes through a filtration section not shown, and the filtered magnetic materials such as nickel, cobalt and their compounds are dried and recovered in a drying section not shown. The dispersion liquid, from which the magnetic materials flowing out of the outlet 10 along the first flow have been removed and which contains the non-magnetic materials, passes through a filtration section not shown, and the filtered non-magnetic materials such as copper, aluminum, etc. are dried in a drying section not shown and recovered.

[0036] <Modification of the first embodiment> In the first embodiment, a current is always applied to the magnets 4 during the magnetic separation operation, but as shown in Fig. 3, a pulse current may be applied to the magnets 4 in a circumferential direction in sequence. That is, after a pulse current with a pulse width of 1 second is applied to the first magnet 4 at the 0° position in Fig. 2, a pulse current with a pulse width of 1 second is applied to the magnets 4 at the 45°, 90°, 135°, 180°, 225°, 270°, and 315° positions in sequence, and this is repeated in sequence in the circumferential direction. This allows the magnetic material contained in the dispersion to flow into the second flow while rotating around the axis of the outer tube 2.

[0037] <Second embodiment of magnetic separation device> 4 shows a magnetic separation device 1A according to a second embodiment of the present invention. The configuration of the magnetic separation device 1A is the same as that of the magnetic separation device 1 according to the first embodiment, except for the arrangement of magnets, and corresponding parts are given the same reference numerals and the description thereof will be omitted.

[0038] The magnets 4 of the magnetic separator 1A according to the second embodiment are composed of a first group of magnets 4a and a second group of magnets 4b arranged downstream of the first group of magnets 4a. The first group of magnets 4a and the second group of magnets 4b are composed of electromagnets, and are configured to apply currents with a phase shift so as to magnetize the second group of magnets 4b after demagnetizing the first group of magnets 4a, as shown in Fig. 5.

[0039] In the magnetic separation device 1A of the second embodiment, the magnetic bodies in the dispersion liquid flowing inside the outer tube are attracted by the magnetic force of the first group of magnets 4a and then further attracted by the magnetic force of the second group of magnets 4b, so that the magnetic bodies in the dispersion liquid can be sufficiently and reliably moved radially outward from the outer tube 2 and allowed to flow into the first flow flowing through the gap 8 between the outer tube 2 and the inner tube 3.

[0040] <Modification of the second embodiment> In the second embodiment, during magnetic separation operation, current is applied simultaneously to the first group of magnets 4a, and after the first group of magnets 4a are separated, current is applied simultaneously to the second group of magnets 4b. However, each of the first group of magnets 4a and the second group of magnets 4b may be magnetized and demagnetized individually.

[0041] That is, as shown in FIG. 6, a pulse current with a pulse width of 1 second is applied sequentially in the circumferential direction to the first group of multiple magnets 4a and the second group of multiple magnets 4b, and the pulse current is applied with a phase shift so as to demagnetize the first group of multiple magnets 4a and then magnetize the second group of multiple magnets 4b.

[0042] In this modified example, the magnetic bodies in the dispersion liquid flowing inside the outer tube are attracted while being rotated around the axis of the outer tube 2 by the magnetic force of the first group of magnets 4a, and are further attracted while being rotated around the axis of the outer tube 2 by the magnetic force of the second group of magnets 4b, so that the magnetic bodies in the dispersion liquid can be moved radially outward of the outer tube 2 more sufficiently and reliably, and can flow into the second flow flowing through the gap 8 between the outer tube 2 and the inner tube 3.

[0043] <Third embodiment of magnetic separation device> 7 shows a magnetic separation device 1B according to a third embodiment of the present invention. In the magnetic separation device 1B, the magnetic separation devices 1 according to the first embodiment are arranged in multiple stages (two stages in this embodiment), and are connected to the discharge port 10 of the inner pipe 3 of the upstream magnetic separation device 1a and the supply port 5 of the outer pipe 2 of the downstream magnetic separation device 1b.

[0044] In the magnetic separation device 1B of the third embodiment, the dispersion liquid from which the magnetic materials flowing out from the discharge outlet 10 of the inner tube 2 of the upstream magnetic separation device 1a have been recovered flows into the supply port 5 of the outer tube 2 of the downstream magnetic separation device 1b, so that the magnetic materials that flow out without being recovered by the upstream magnetic separation device 1a can be recovered by the downstream magnetic separation device 1b.

[0045] The upstream magnetic separation device 1a and the downstream magnetic separation device 1b are not limited to the magnetic separation device 1 of the first embodiment, but may be the magnetic separation device 1A of the second embodiment, or may be used in combination. EXAMPLES

[0046] (Preparation of Dispersion) The following raw materials and 750 parts of 1.0 mm zirconia beads (manufactured by Nikkato Corporation) were charged into a 500 mL PP container and dispersed for 60 minutes using a paint shaker manufactured by Red Devil Co., Ltd. to obtain a dispersion liquid. Black Mass: 250 copies Solsperse W100 (dispersant, manufactured by Lubrizol Japan Co., Ltd.): 25 parts Surfynol (registered trademark) AD01 (manufactured by Nissin Chemical Industry Co., Ltd., antifoaming agent): 0.2 parts Proxel (registered trademark) XL2 (manufactured by Ashbya, preservative): 1 part ·Wednesday: 348.8 copies Next, the zirconia beads were removed from the above dispersion to obtain a black mass dispersion.

[0047] In the magnetic separator 1A of the second embodiment, a vinyl chloride pipe with an outer diameter of 50 mm was used as the outer tube, and a vinyl chloride pipe with an outer diameter of 25 mm and an inner diameter of 20 mm was used as the inner tube. A pulse current was applied to the magnet at the timing shown in FIG. 5 to generate a magnetic flux density of 2500 Gauss intermittently. When the black mass dispersion liquid after the above adjustment was flowed into the outer tube at a flow rate of 1 L / mm, 38 g of Ni, Co, and their compounds were recovered per 100 g of black mass. The composition of the black mass before magnetic separation and the composition of the dispersion liquid flowing out of the inner tube after magnetic separation were analyzed by ICP (inductively coupled plasma) atomic emission spectroscopy, and the results are shown in Table 1. [Table 1] As shown in Table 1, it was confirmed that by the magnetic separation in Example 1, the dispersion liquid flowing out of the inner tube after magnetic separation had the magnetic materials Ni and Co sufficiently removed. EXAMPLES

[0048] In a modified example of the magnetic separator 1A of the second embodiment, a vinyl chloride pipe with an outer diameter of 50 mm was used as the outer tube, and a vinyl chloride pipe with an outer diameter of 25 mm and an inner diameter of 20 mm was used as the inner tube. A pulse current was applied to the magnet at the timing shown in FIG. 6 to generate a magnetic flux density of 2500 Gauss intermittently. When the black mass dispersion liquid after the above adjustment was flowed into the outer tube at a flow rate of 1 L / mm, 41 g of Ni, Co, and their compounds were recovered per 100 g of black mass. The composition of the black mass before magnetic separation and the composition of the dispersion liquid flowing out of the inner tube after magnetic separation were analyzed by ICP (inductively coupled plasma) atomic emission spectrometry, and the results are shown in Table 2. [Table 2] As shown in Table 2, it was confirmed that by the magnetic separation in Example 2, the dispersion liquid flowing out of the inner tube after magnetic separation had the magnetic materials Ni and Co sufficiently removed.

[0049] The present invention is not limited to the above-described embodiment, and the arrangement and structure of the magnets, the current application pattern, the double tube structure, and the like can be changed or modified as appropriate. [Explanation of symbols]

[0050] 1, 1A, 1B...Magnetic sorting device 1a…Upstream magnetic separator 1b…Downstream magnetic separator 2…Outer tube 2a…Main body part 2b…Enlarged diameter part 3…Inner tube 4…Magnet 4a…First group of multiple magnets 4b…Second group of multiple magnets 5…Supply inlet 6…Collection port 7...Stay 8…Gap 9…Inlet 10…Exhaust port 11...Iron core 12…Coil 13…York

Claims

1. A dispersion step of dispersing a powder containing a magnetic material with a dispersant to obtain a dispersion liquid; A flow dividing step of dividing the dispersion into a first flow and a second flow; a magnetic material recovery step of attracting magnetic materials contained in the dispersion liquid by magnetic force, drawing them to the second flow, and recovering them along the second flow; a non-magnetic material discharge step of discharging non-magnetic material contained in the dispersion liquid along the first flow; A method for magnetically separating powder containing a magnetic material, comprising:

2. an outer tube having a supply port for supplying a dispersion liquid of powder containing a magnetic material; A magnet disposed on the outside of the outer tube; an inner tube inserted into the outer tube and having an inlet downstream of the magnet; a recovery port is provided in the outer pipe for recovering a dispersion liquid containing a magnetic material that has flowed into a second flow flowing between the outer pipe and the inner pipe; The magnetic separation device for powder containing magnetic material, wherein the inner tube is provided with a discharge port for discharging a dispersion liquid containing non-magnetic material that has flowed into a first flow flowing inside the inner tube.

3. 3. The magnetic separator for powder containing magnetic material according to claim 2, wherein the magnet comprises a plurality of magnets arranged at equal intervals on the outer peripheral surface of the outer tube.

4. 4. The magnetic separation device for powder containing magnetic material according to claim 3, wherein the plurality of magnets are electromagnets, and a pulse current is sequentially applied to the magnets in a circumferential direction.

5. 4. The magnetic separation device for powder containing magnetic material according to claim 3, wherein the plurality of magnets comprises a first group of magnets and a second group of magnets arranged downstream of the first group of magnets.

6. 6. A magnetic separation device for powder containing magnetic material as described in claim 5, wherein the first group of magnets and the second group of magnets are electromagnets, and are configured to apply currents with a phase shift so as to demagnetize the first group of magnets and then magnetize the second group of magnets.

7. 6. A magnetic separation device for powder containing magnetic material as described in claim 5, wherein the first group of magnets and the second group of magnets are electromagnets, and a pulse current is sequentially applied to each of them in the circumferential direction, and currents are applied with a phase shift so as to demagnetize the first group of magnets and then magnetize the second group of magnets.

8. 8. A magnetic separation device for powder containing magnetic material according to claim 2, wherein the magnetic separation devices are arranged in a plurality of stages and connected to the discharge outlet of the inner tube of the upstream magnetic separation device and the supply inlet of the outer tube of the downstream magnetic separation device.

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