Method for forming a high-gradient magnetic field and a substance separation device based thereon

Abstract

A method of creating a zone of high-gradient magnetic field in a Kittel open domain structure is disclosed. The method is based on a magnetic system of an open domain structure type and is embodied in the form of two substantially rectangular constant magnets which are mated by the side faces thereof, whose magnetic field polarities are oppositely directed and the magnetic anisotropy is greater than the magnetic induction of the materials thereof. The magnets are mounted on a common base comprising a plate which is made of a non-retentive material and mates with the lower faces of the magnets, thin plates which are made of a non-retentive material, are placed on the top faces of the magnets and forms a gap arranged above the top edges of the magnets mated faces. A nonmagnetic substrate for separated material is located above the gap.

Claims

1. A method of creating a zone of a permanent, high-gradient magnetic field in a Kittel open domain structure, the method comprising: providing two permanent magnets, each of the permanent magnets having an upper side, a lower side, and a lateral side with the lateral sides of the permanent magnets joined together, the permanent magnets having directions of magnetic field polarity being opposite to one another, a magnetic anisotropy of the permanent magnets essentially exceeding the magnetic induction of a material of the permanent magnets, mounting the permanent magnets on a common base comprising a soft magnetic material that is connected to the lower sides of the permanent magnets, wherein, on the upper side of the permanent magnets, magnetic soft plates with a uniform thickness that are substantially thinner across a length thereof than each of the two permanent magnets are placed to form a narrow gap located immediately above upper edges of the joined lateral sides of the permanent magnets, and wherein the magnetic soft plates facilitate the permanent, high-gradient magnetic field at the narrow gap by increasing a gradient of the magnetic field of the permanent magnets.

2. The method of claim 1, wherein the thin plates are made of vanadium permendur.

3. The method of claim 2, wherein the narrow gap between the magnetic soft plates has a width in a range of 0.01-1.0 mm, the gap being located symmetrically about a plane, along which the lateral sides of the permanent magnets are joined.

4. The method of claim 1, wherein the narrow gap between the magnetic soft plates has a width in a range of 0.01-1.0 mm, the gap being located symmetrically about a plane, along which the lateral sides of the permanent magnets are joined.

5. The method of claim 1, further comprising: moving a material via a substrate along a direction perpendicular to the longitudinal axis of the gap.

6. The method of claim 5, wherein the substrate is a horizontal plate connected to a generator of mechanical oscillations.

7. The method of claim 1, wherein the permanent magnets are made of neodymium-iron-boron, samarium-cobalt, or iron-platinum.

8. The method of claim 1, further comprising: providing one or more additional permanent magnets, identical to the permanent magnets, wherein the lateral sides of three or more additional permanent magnets and permanent magnets are joined in series to form two or more narrow gaps located immediately above upper edges of the joined lateral sides of the additional permanent magnets and permanent magnets.

9. The method of claim 1, wherein the permanent magnets have a substantially rectangular shape.

10. The method of claim 1, wherein a ratio of the thickness of the magnetic soft plates with respect to a thickness of the two permanent magnets is about 1:25.

11. The method of claim 1, wherein a ratio of the thickness of the magnetic soft plates with respect to a thickness of the two permanent magnets is about 1:50.

12. The method of claim 1, further comprising: providing a non-magnetic substrate for the material being separated above the narrow gap, wherein the thickness of the magnetic soft plates is 0.01-1.0 mm.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an illustration of the Kittel open domain structure of two magnets,

(2) FIG. 2 presents a schematic diagram of the magnetic force lines in the Kittel open domain structure,

(3) FIG. 3 presents a schematic diagram of the magnetic force lines in the magnetic system according to the present invention,

(4) FIG. 4 is a graph showing the variation in the horizontal component of the magnetic induction nearby the edges of the joined magnets in the Kittel open domain structure,

(5) FIG. 5 is a graph showing the variation in the horizontal component of the magnetic induction nearby the edges of the joined magnets in the magnetic system according to the present invention,

(6) FIG. 6A is an illustration of the of the magnetic system according to the present invention, and

(7) FIG. 6B is an illustration of part of the magnetic system in accordance with one or more embodiments of the invention,

(8) FIG. 7 is a graph showing the dependence of the magnetic field induction in the gap zone, on the distance from the surface of the plates, and

(9) FIG. 8 is an illustration of the magnetic system in accordance with one or more embodiments of the invention.

DETAILED DESCRIPTION

(10) The disclosed device (see FIG. 6) consists of two magnets 1 and 2 of a predominantly rectangular shape, with opposite directions of magnetization (shown by arrows in the figure). The magnets are made of a material with a much greater magnetic anisotropy than the induction of a material of magnets, such as neodymium-iron-boron, iron-platinum or samarium-cobalt, for example.

(11) In experiments sintered neodymium-iron-boron magnets were used with a remnant induction of about 1.3 T, an intrinsic coercive force of magnetization of about 1300 kA/m, and a maximum energy product of about 320 kJ/m.sup.3. The size of magnets was 255050 mm.

(12) The magnets 1 and 2 are joined together along a plane 3 and and their lower sides placed on a basis 4 in the form of a plate made of soft-iron material, for example, with a thickness of 5-25 mm.

(13) On the upper sides of the magnets 1 and 2, thin plates 5 and 6 are located which are made of a magnetic soft material with high magnetic saturation induction, their thickness being 0.01-1.0 mm. The thickness of plates 5 and 6 should be chosen depending on the required magnitudes of the magnetic induction and the optimum field gradient for the separation of real substances and materials. The plates 5 and 6 are located on the upper sides of the magnets 1 and 2 with a clearance forming a narrow gap 7 which is 0.01-1.0 mm wide immediately above the upper edges 8 and 9 of the magnets 1 and 2, as a rule, symmetrically relative to a plane 3. Immediately above the gap 7 there is a non-magnetic substrate 10 for the placing of the material being separated 11. The substrate 10 can be made as a horizontal plate, for example, connected to a generator of mechanical oscillations. The substrate can also be made as a thin non-magnetic, band 14 (of polyester, for example) and be provided with means to move the band 15 along a direction perpendicular to the longitudinal axis of the gap 7 (the band and its moving means are shown in FIG. 6B). The substrate 10 can be provided with means to displace it a distance of 0-5 mm from the surface of the plates 5 and 6. The plates 5 and 6 are connected to the means 12 and 13 for moving them along the upper sides of the magnets 1 and 2 in order to regulate the width of the gap over a range of 0.01-1.0 mm.

(14) The device makes it possible to create strong magnetic fields with a magnitude of the product BB of more than 4.Math.10.sup.11 mT.sup.2/m at a distance less than 10 m from the surface of the plates 5 and 6, forming the gap. Thus, for a particular embodiment of the device, where vanadium permendur plates with a thickness of 0.20 mm are being used and the gap width is 0.05 mm, the tangential component of the magnetic field induction exceeds 4.0 T. Furthermore, the peak width of the magnetic field tangential component can be regulated by the width of the gap 7.

(15) FIG. 7 shows the dependence of the magnetic field induction on the distance from the axis perpendicular to the plane of the plates 5 and 6. The origin of coordinates in FIG. 7 corresponds to a point in the center of the gap 7 at the level of the plates 5 and 6. At a distance of 0.10 mm from this point the gradient is 4.1.Math.10.sup.6 mT/m, and at a distance of 0.01 mm 1.2.Math.10.sup.8 mT/m, while the product BB is 4.2.Math.10.sup.11 mT.sup.2/m.

(16) The experimental examination of the possibility to separate paramagnetic substances using the disclosed device was carried out on a mixture of substances with different paramagnetic susceptibility. The results are presented in the following table.

(17) TABLE-US-00001 TABLE 1 The separation of a mixture of substances with different paramagnetic susceptibility Substance Susceptibility [ .Math. 10.sup.6] Distance [mm] Dysprosium sulfate 92760 1.900 Europium chloride 26500 0.700 Copper chloride 1080 0.100

(18) The separation process was conducted as follows: The mixture of the substances presented in the table above, was placed on a thin polyester band, which was located at a fixed distance from the plates 5 and 6. Then the band was moved above the surface of the plates along a direction perpendicular to the longitudinal axis of the gap 7. The particles of dysprosium sulfate, which possess the greater magnetic susceptibility, were separated from the mixture, when the distance between the band and the plates 5 and 6 was about 1.90 mm, while the other particles of the mixture continued to move on together with the band. Then the separated particles of dysprosium sulfate were removed from the band, the distance between the band and the plates 5 and 6 was decreased, and the separation process was continued.

(19) The table presents the magnitudes of distances from the band to the surface of the plates 5 and 6, which correspond to the separation of all the components of the paramagnetic substances mixture.

(20) On the basis of the magnetic system with two magnets according to the invention, a more productive magnetic separator can be created, as a composition of two or more analogous magnetic systems. Each system should be formed by a serial joining of the faces of the three or more magnets, with separation zones in the vicinity of two or more gaps formed by the plates above the upper edges of the mating faces, as shown in FIG. 8. In a system of four magnets and three separation zones, a three-stage separation of substances could be executed during one passage of the band with substances being separated.

(21) Thus, embodiments of the invention makes it possible to create strong magnetic fields with a very high magnitude of the product BB, i.e. of more than 4.Math.10.sup.11 mT.sup.2/m, at a distance less than 10 m from the surface of the plates forming the gap. The device makes it possible to regulate the shape and gradient of the magnetic field in the zone of separation. In practice, the invention can be used for the separation of paramagnetic substances and materials from diamagnetic ones, for division of paramagnetic substances and materials in terms of the magnitudes of their paramagnetic susceptibility, and for division of diamagnetic substances and materials in terms of the magnitudes of their diamagnetic susceptibility. The substances can be both in the form of powders and in the form of colloidal solutions and suspensions.

BIBLIOGRAPHIC DATA

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