RU2324542C2 - Magnetic separator with ferrite and rare-earth permanent magnets - Google Patents

Abstract

FIELD: mechanic.

SUBSTANCE: magnetic separator with permanent magnets contains ferromagnetic element for closing the circuit between the two magnetic poles, as minimum. The poles are made from a ferrite magnet, in the lower part, and from rare-earth magnets, in the upper part, which is the surface of inlet and outlet of the magnetic lines of force. The relation between the effective magnetic length of the ferrite magnets and the rare-earth magnets is 2:1; the preferable materials are strontium ferrite for the first and iron-boron-neodymium for the second.

EFFECT: increase in efficiency of separator pull of ferromagnetic materials with high or low form-factor, and materials with high or low, and, sometimes, very low magnetic permeability.

8 cl, 6 dwg

Description

The invention relates to magnetic separators with permanent magnets and, more specifically, to a separator equipped with permanent magnets made of ferrite and rare earth elements, capable of enhancing and optimizing the effect of attraction of various ferromagnetic materials. The present application relates, in particular, to pulley-type separators, however, it is obvious that the above also applies to other types of magnetic separators (drums, plates, tapes, etc.) that can be equipped with the permanent magnets described here.

It is known that magnetic separators are used in those applications where it is necessary to attract and separate (separate) ferromagnetic materials of any shape and size from a mixture of materials. The separator’s ability to attract depends both on the magnetic field that it can generate (intensity and gradient), and on the intrinsic induction of the separated object, which is determined by its form factor (for example, the sphere has the worst form factor) and its degree of magnetic permeability.

For more than forty years, attractive chains (i.e., permanent magnets) made of ceramic materials such as barium ferrite and, even better, strontium ferrite have been known. These magnets have average internal and residual magnetic energy and are capable of attracting ferromagnetic materials with a large form factor and / or medium high magnetic permeability within a certain distance.

Later, in the last 15-20 years, other attractive chains began to be used, made of sintered materials with high internal residual magnetic energy, known as rare-earth elements (samarium-cobalt, iron-boron-neodymium). These magnets can attract within a relatively short distance, but with great efficiency, even materials with a low form factor and / or medium low and very low magnetic permeability. Their effectiveness, however, is concentrated within a few tens of millimeters.

Thus, it is an object of the present invention to provide a magnetic separator that overcomes the limitations of known separators. This goal is achieved by means of a separator in which each magnetic pole is made of ferrite magnets in the lower part in contact with the ferromagnetic element for connecting the circuit between the poles, and of rare-earth magnets in the upper part, which is the input / output surface of the magnetic field lines.

The main advantage is the combination of the magnetic characteristics of the permanent magnets of the two types described above (ferrite and rare earths) in such a way that they make them complementary and, thereby, increase the attractiveness of both high or low form factor ferromagnetic materials and materials with high and low, and sometimes very low, magnetic permeability.

Thus, the attraction distance of such magnets is significantly increased, and the separator can operate with a capacity that is almost twice the performance of such a separator with rare earth magnets, and with a very high separation quality compared to the average low efficiency of such a separator with ferrite magnets.

Another significant advantage lies in the very simple structure of such attracting chains, which makes it easy to manufacture and use them in separators of any type.

Other features and advantages of the separator of the present invention will be apparent to those skilled in the art from the following detailed description of one embodiment of the invention with reference to the accompanying drawings, wherein:

Figure 1 is a view in cross section of a pulley-type separator according to the prior art with ferrite magnets.

Figure 2 is a cross-sectional view of a pulley-type separator according to the prior art with rare earth magnets.

Figure 3 is a cross-sectional view of a prior art separator with ferrite and rare earth magnets of the present invention.

Figure 4 is an enlarged schematic view showing details of the structure of the attracting chain according to the present invention;

FIG. 5 is a plan view of a first possible polarization arrangement for the separator of FIG. 3.

Fig.6 is a top view of a second possible arrangement of polarities for the separator of Fig.3.

As shown in FIG. 1, the permanent magnet pulley 1 essentially consists of a ferromagnetic cylinder 2 around which ferrite magnetic masses 3A are applied, while the cylinder 2 is surrounded by a protective casing 4 of non-magnetic material (e.g., stainless steel), which is preferably filled fixing resin. This assembly is fixed by means of end flanges to a drive shaft or an idle shaft, as a result of which it can preferably be used as a drive roller for a conveyor 6 provided with rails 7 on which the material 8 is transported.

The size H1 indicates the effective working height of the layer of the processed material, and its illustrative value for a pulley with a diameter of 400 mm H1≅80-90 mm for ferromagnetic particles with a medium-high form factor and good magnetic permeability.

Figure 2 illustrates a pulley, similar in shape and size to that described above, with 3B magnetic masses with rare earths, in which the working height H2 is 40-50 mm for ferromagnetic particles with a medium low form factor and low magnetic permeability and within 30 mm from the active surface - for particles with very low magnetic permeability.

Figure 3 illustrates a pulley, similar in shape and size to those described above, with mixed magnetic masses 3C according to the present invention, where, for the sake of example only, in particular, two ferrite blocks 12 with a height of about 25 mm located in contact with the ferromagnetic cylinder 2, and one rare-earth block 13, also about 25 mm high, mounted on top of the ferrite blocks 12 and in contact with them and next to the non-magnetic casing 4.

Figure 4 illustrates in detail the permanent magnet circuit of the present invention, containing at least two north-south poles 3C, each of which is made in the lower part in contact with the ferromagnetic cylinder 2 for connecting the circuit between the poles, of ferrite magnets 12 (preferably strontium ferrite), and in the upper part, which is the exit surface 14 of the magnetic field lines 15 for the north pole or the surface 16 of the magnetic field lines 15 for the south pole, from rare earth magnets 13 (p preferably iron-boron-neodymium), capable of increasing the magnetic field strength and, in particular, the magnetic field gradient.

Figures 5 and 6 illustrate, in order to give an example, two possible options for arranging the polarities in the longitudinal direction of the magnetic pulleys; in particular, FIG. 5 shows a “checkerboard” arrangement of various north-south magnetic poles, while FIG. 6 shows an arrangement with longitudinal alternating rows of north-south polarities.

To compare the indicative field strengths and field gradient that can be obtained in the three separators described above, the table below. In this table, D stands for the distance at which the magnetic field was measured, and G stands for the field gradient measured over the indicated distance range.

Distance and gradient Ferritic Rare earth Ferritic + Rare Earth D = 10 mm (Oe) 1015 2000 2500 G by 10-20 mm (E / cm) 245 820 900 D = 20 mm (Oe) 770 1180 1600 G by 20-30 mm (E / cm) 150 510 500 D = 30 mm (E) 620 670 1100 G by 30-40 mm (E / cm) 120 310 300 D = 40 mm (Oe) 500 360 800 G by 40-50 mm (E / cm) 90 160 240 D = 50 mm (E) 410 200 560 G by 50-60 mm (E / cm) 60 - 160 D = 60 mm (E) 350 - 400 G 60-70 mm (E / cm) fifty - 120 D = 70 mm (Oe) 300 - 280 G at 70-80 mm (E / cm) fifty - 80 D = 80 mm (Oe) 250 - 200 G 80-90 mm (E / cm) 40 - fifty D = 90 mm (Oe) 210 - 150

Thus, this new type of attracting chain, applied, as a comparative example, to the above pulley, unexpectedly allows to improve the characteristics of the magnets of these two types at those distances where they are less effective, while at the same time maintaining their advantageous characteristics in areas where they work better individually.

This is due, obviously, to the ability to have better performance in an area beyond a distance of 50 mm from the active surface due to a higher gradient compared to a pulley on ferrite magnets, which has problems with poorly magnetized materials; and, similarly, this is due to the ability to have significantly improved average characteristics in the zone within 50 mm due to the stronger field compared to a similar pulley on rare earth magnets.

Obviously, the above-described and illustrated embodiment of the magnetic separator according to the present invention is just an example in which many different modifications can be made. In particular, the ratio between the effective magnetic length of ferrite and rare-earth elements in each pole may differ from the 2: 1 ratio illustrated above, for example, it can be from 1: 1 to 3: 1, and, as is obvious, the number, shape and location of magnetic poles can freely change according to needs.

Claims (8)

1. Magnetic separator with permanent magnets, containing a ferromagnetic element (2) for connecting the circuit between at least two magnetic poles (3C), characterized in that each magnetic pole (3C) is made of ferrite magnets (12) in the lower part in contact with the aforementioned ferromagnetic element (2) for connecting the circuit, and from rare earth magnets (13) in the upper part, which is the input / output surface (14) of magnetic field lines (15, 16). 2. The magnetic separator according to claim 1, characterized in that in each magnetic pole (3C) the ratio between the effective magnetic length of ferrite magnets (12) and rare-earth magnets (13) is from 1: 1 to 3: 1, preferably 2: 1 . 3. A magnetic separator according to claim 1 or 2, characterized in that it consists of a ferromagnetic cylinder (2) around which magnetic poles (3C) are applied, said cylinder (2) being surrounded by a protective casing (4) of non-magnetic material filled fixing resin (5), and this assembly is fixed on the shaft so that it can be used as a conveyor (6), on which the processed material (8) is transported. 4. The magnetic separator according to claim 1 or 2, characterized in that the ferrite magnets (12) are made of barium ferrite or strontium ferrite. 5. The magnetic separator according to claim 1 or 2, characterized in that the rare earth magnets (13) are made of samarium-cobalt or iron-boron-neodymium. 6. The magnetic separator according to claim 3, characterized in that the ferrite magnets (12) are made of barium ferrite or strontium ferrite. 7. The magnetic separator according to claim 3, characterized in that the rare-earth magnets (13) are made of samarium-cobalt or iron-boron-neodymium. 8. The magnetic separator according to claim 4, characterized in that the rare earth magnets (13) are made of samarium-cobalt or iron-boron-neodymium.

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