RU178981U1 - Magnetic separator - Google Patents

Abstract

The utility model relates to the field of powder metallurgy, namely, devices for separating waste products for the production of permanent NdFeB magnets. The technical problem, which the utility model aims to solve, is to increase the selectivity of the separation of waste products from the production of NdFeB magnets in magnetic separation. The stated technical problem is solved by the fact that in the magnetic separator, including the feeder and receivers of the separation products, the trough and the magnetic system, which is an endless conveyor belt with permanent magnets mounted on it, the trough bends around the magnetic system in the direction of its movement and deviates from it in the lower part down, and the permanent magnets are fixed on the conveyor belt with the same poles, and pole tips are installed on their opposite poles. Technical result, achievement which is provided by a combination of essential features, is to increase the selectivity of the separation of waste magnetic materials NdFeB, by creating the same conditions for magnetic separation for each particle of the separated material.

Description

The utility model relates to the field of powder metallurgy, and in particular to devices for the separation of waste production of permanent magnets NdFeB.

At present, NdFeB permanent magnets are the most popular among the others (cast, ferrite, etc.), because they have the highest magnetic parameters.

These magnets contain up to 40% of scarce rare-earth metals and cobalt, therefore, waste from their production (marriage of magnets in appearance, geometric dimensions and magnetic parameters) is reused to reduce costs.

Since NdFeB permanent magnets are manufactured using powder metallurgy technology, the waste is demagnetized, crushed to particles with a size of 0.8-1.0 mm and introduced into the processing chain for grinding operations together with a powder of fresh magnetic materials.

However, the magnetic material NdFeB interacts very actively with the surrounding air; therefore, oxygen gradually accumulates in it, which destroys the main magnetic phase of Nd ₂ Fe ₁₄ B with the formation of neodymium oxide NdO. In this case, its main magnetic parameters (residual induction Br and coercive force Нсв) decrease and its magnetic susceptibility χ increases.

The increase in the magnetic susceptibility of the NdFeB material (χ = 0.05) during its oxidation is associated with the release of iron (χ = 1100) in it during the destruction of the main magnetic phase of Nd ₂ Fe ₁₄ B. As a result, 1 mass. % NdO simultaneously forms about 2 mass. % Fe, which increase the magnetic susceptibility of the material by almost 22 units.

This fact makes it possible to separate particles of a material containing NdO above an acceptable value (0.3 mass%) by magnetic separation, since the force acting in a magnetic field on a particle of a substance is proportional to its magnetic susceptibility [1].

At the moment, various types of separators are known with adjustable values of the magnetic field in the separation zone, which are used as separator analyzers [2]. A common disadvantage of these devices is low productivity, only periodic operation and low separation selectivity.

Moreover, by the separation selectivity (Cp) is meant the ratio of the magnetic susceptibilities of the separated materials [1]:

where γ1 is the magnetic susceptibility of the less magnetic fraction;

γ2 is the magnetic susceptibility of the more magnetic fraction.

The closest in technical essence is the gravimagnetic separator, including a trench and a magnetic system located under it [3]. The magnetic system is an endless ribbon with permanent magnets mounted on it. However, it is used in the present invention to transport the magnetic fraction through the trough and is structurally capable of only separating the magnetic fraction from the non-magnetic one.

Therefore, magnetic separators are used in the separation of NdFeB materials [4], only to highlight the main high-coercive (χ = 0.05), low-coercive weakly magnetic (χ> 1000) and non-magnetic fractions (χ <10 ^-3 ). The selectivity of the separation process is about 5 × 10 ^-5 .

The technical problem to be solved by the claimed utility model is to increase the selectivity of the separation of waste products from the production of NdFeB magnets during magnetic separation. The stated technical problem is solved by the fact that in the magnetic separator, including the feeder and receivers of the separation products, the trough and the magnetic system, which is an endless conveyor belt with permanent magnets mounted on it, the trough bends around the magnetic system in the direction of its movement and deviates from it in the lower part down, and permanent magnets are fixed on the conveyor belt with the same poles, and pole tips are installed on their opposite poles.

The technical result, which is achieved by a combination of essential features, is to increase the selectivity of the separation of waste magnetic materials NdFeB, by creating the same conditions of magnetic separation for each particle of the separated material.

The utility model device is shown in FIG. 1. The magnetic separator operates as follows. The powder of the material to be separated 2, through the hopper 1, enters the feeder 3, in which it is captured by the magnetic field of the magnet 4 and, under its influence, moves after the magnet along the non-magnetic groove 7. The movement of the magnet is provided by a conveyor belt 6, on which it is rigidly fixed. Pole tip 5 serves to create a uniform magnetic field in the working area on the surface of the gutter.

In the lower part of the separator (during the reverse movement of the conveyor belt), the trough deviates downward from the line with a pole tip. As a result of this, the gap between the permanent magnets and the particles of the material begins to increase and the magnetic field acting on the particles of the material begins to weaken. Falling particles of separated material are collected in receivers 8.

The main elements of the proposed utility model, determining its essential features and providing the necessary technical result, are:

- Permanent magnets mounted on the conveyor belt with the same poles and having pole tips on opposite poles.

- a gutter enveloping the magnetic system and deviating downward from the bottom.

Permanent magnets 4 in this design provide not only the transportation of magnetic material through the gutter, but also form the working zones of the magnetic separator, which moves in space according to the law specified by the shape of the gutter.

During the reverse stroke of the material particles (in the lower part of the separator), two forces act on them: magnetic force and gravity.

The specific magnetic force (magnetic acceleration) f acting on a unit mass of a particle in air (Fig. 1) is [1]:

where μ ₀ is the magnetic constant;

χ _h - magnetic susceptibility of a particle of a substance;

H is the magnetic field strength;

gradH is the gradient of the magnetic field in the direction from the source of the magnetic field B (in this case, the pole tip).

If the specific magnetic force (magnetic acceleration) is higher than the gravitational acceleration g, then the particle will be pressed against the surface of the gutter. If on the contrary, the particle will fall down.

In this case, as can be seen from formula (2), the point of incidence of a material particle does not depend on its mass, but is determined only by the ratio of the parameters of the magnetic field created by the permanent magnet and the magnetic susceptibility of the material particle. As a result of this, particles with a lower magnetic susceptibility will fall first (in a magnetic field with a higher intensity).

To increase the selectivity of the magnetic separator, it is necessary that the difference in the magnetic parameters of the permanent magnets forming the magnetic system is minimal, because, basically, it will determine the selectivity of the separation process in the proposed utility model.

The pole pieces 5, made of soft magnetic material, are necessary to create a uniform working zone of magnetic separation. The best option would be to create with their help a working area across the gutter with a width comparable to the average particle size of the material being separated. Currently, there are various designs of pole pieces, ensuring uniformity of the magnetic field at the level of 0.001%, for example, in the working volumes of medical tomographs [5].

The installation of all permanent magnets on the conveyor belt of the separator with the same poles is necessary to prevent magnetization of particles of the material being separated to each other. Unlike other magnetic materials, NdFeB permanent magnet waste products are particles with a magnetic texture. Like any rare earth magnet, they can only be magnetized along the direction of the texture.

Once in a magnetic field, even if it is not magnetized, the particles rotate with a texture along the line of magnetic field induction, in this case vertically (Fig. 2). At the same time, the polarity is formed in them strictly in accordance with the polarity of the permanent magnets that form the magnetic system, and, like any magnets placed in parallel and with poles in one direction, they begin to repel each other. In reality, the particles of material stand in one line across the trench (Fig. 2) at a certain distance from each other.

The non-magnetic trough 7 serves not only for transporting the material to be separated, but also, by its downward deflection, sets the law of variation of the magnetic field strength (H gradH) in the working area of the magnetic separator, which in this device is always located on the surface of the trough and moves along it.

In FIG. 1, the groove 7 is depicted deflected at the angle γ at the bottom of the separator, however, its bending shape can be any (parabola, hyperbola, etc.), depending on the range of magnetic susceptibility of the fraction to be separated from the material to be separated.

The design of the feeder can be any of the known [2], which are used for dosed supply of shared material. The material feed rate is selected empirically, based on specific requirements. With an increase in the feed rate of the material, there will be a decrease in the separation selectivity and an increase in the performance of the separator, with a decrease in the feed rate of the material, an increase in the selectivity of separation and a decrease in the separator performance.

The speed of the conveyor belt, which is also selected empirically, depends on the specific requirements for productivity and selectivity, in a similar way.

Example:

For magnetic separation, thermally demagnetized waste of NdFeB permanent magnets in the form of powders with a particle size of 0.755-1.0 mm with an average NdO content of 0.52 wt. %, which cannot be reused in the manufacture of magnets due to the high content of NdO (more than 0.3 wt.%).

The magnetic separator manufactured by Magneton JSC according to the proposed embodiment contained a non-magnetic trench made of brass with a width of 20 mm. In the lower part of the magnetic separator, the trough deviated by an angle of 15 °. In this case, the magnetic field strength on its surface fell (in a deflected section 80 mm long) from 180 kA / m to 20 kA / m.

Permanent magnets with geometrical dimensions of 10 × 10 × 20 of NdFeB material were mounted on a conveyor belt according to FIG. 1. The gap between the magnets was 10 mm. The size of 20 mm magnets was located across the conveyor belt. The number of magnets placed on the tape was 25 pieces.

The pole pieces were made of steel St10 and were equilateral triangular prisms, the upper (facing the trough) angle of which was dulled with a 0.5 mm chamfer.

The length of the conveyor belt was 50 cm. The speed of the conveyor belt was 0.48 m / s and was provided with an electric drive with a power of 50 watts.

The outlet of the feeder was a slot with dimensions of 1.2 × 15 mm, placed the largest size across the groove of the separator.

As containers for the separated products, 10 containers were used, which were under the working area of the separator according to FIG. 1. In the process of magnetic separation of 0.5 kg of material, all separated material was distributed over 10 containers, the numbering of which was carried out according to FIG. 1 from left to right.

Overall dimensions of the magnetic separator 200 × 250 × 400 mm. Weight 4.4 kg. The capacity of the magnetic separator for the material to be separated was 18.6 g / min, which corresponds to the annual productivity with 2 shift work of 4.5 t / year.

The results of magnetic separation are shown in table 1.

As can be seen from the results obtained, the use of the utility model makes it possible to increase the selectivity of separation of waste from the production of permanent NdFeB magnets to 0.24-0.82, depending on the content of NdO in them.

Information sources:

1. Tikhonov, O.N. Magnetic, electrical and special enrichment methods / O.N. Tikhonov, E.E. Andreev, V.B. Kuskov, M.V. Nikitin. - St. Petersburg: St. Petersburg State University, 2016 .-- 70 p.

2. Karmazin, V.V. Magnetic and electrical enrichment methods / V.V. Karmazin, V.I. Karmazin. - M .: Nedra, 1988 .-- 304 s.

3. US patent No. 4659457, NKI 209/40. Claim 09/30/85. Gravitymagnetic ore separators and methods (prototype).

4. RF patent No. 2082551, IPC B22F, B22F 1/00, B22F 1/00. Claim 01/13/1993. Method for the production of rare earth permanent magnets

5. Kurbatov P.A., Kuznetsova E.A., Kulaev Yu.V. Design of open-type permanent magnet systems for magnetic resonance tomographs // Electricity, 2007. - No. 7. - S. 47-52.

Claims (1)

A magnetic separator, including a feeder and receivers of separation products, a trough and a magnetic system, which is an endless conveyor belt with permanent magnets mounted on it, characterized in that, in order to increase the selectivity of separation of materials, the trough bends around the magnetic system in the direction of its movement and in the lower parts deviates downward from it, and permanent magnets are fixed on the conveyor belt with the same poles, and pole tips are installed on their opposite poles.

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