EP0434556B1 - High intensity wet magnetic separator - Google Patents

Abstract

The separator comprises at least one separator unit constituted by a chamber where the product to be treated flows from the top downwards and means for creating a magnetic field perpendicular to the flow direction of the product to be treated. <??>In order to reduce the weight, the size and the cost of the separator and to reduce its energy consumption, permanent magnets (12), optionally associated with pole pieces (14), are used for creating the magnetic field and means (34) are provided for moving the said magnets, and optionally the pole pieces, between a first position where the magnets or the pole pieces are intimately applied against the walls of the said chamber (10) and a second position such that the magnetic field in the chamber (10) is sufficiently low in order that the magnetic particles can be removed from the chamber by a stream of washing liquid. <IMAGE>

Description

The present invention relates to high intensity magnetic separators working in the wet and consisting of at least one separation chamber traversed from top to bottom by the product to be treated, in the form of a liquid or pulp containing in suspension the particles to be separated, and magnets or coils creating in the chamber a magnetic field whose lines of force are perpendicular to the direction of flow of the product to be treated; the separation chamber can contain a matrix formed of grooved plates, balls, expanded metal, iron wool, etc. through which the product to be treated circulates.

Separators of this type with discontinuous operation have a cyclical operation: in a first phase, the product to be treated is circulated in the separation chamber in the presence of the magnetic field; during this phase, the magnetic constituents of the product are fixed on the walls of the chamber and / or on the elements of the matrix, while the non-magnetic particles are entrained by the liquid phase of the product and collected in a first collector. In the second phase, the supply of the product to be treated is cut off, the magnetic field is removed and the magnetic products are extracted from the separation chamber by washing with a pressurized liquid which is generally water. On these devices, we use generally coils, to produce the magnetic field, so that it is possible to cancel the latter during the washing phase. However, it has been proposed to use permanent magnets on filters of this type intended to purify liquids sparingly loaded with magnetic particles and which do not require frequent cleaning. On these filters, the separation chamber is constituted by a cassette which can be replaced, when it is clogged, by a clean cassette possibly after dismantling the magnets. This type of filter is not suitable for the treatment of products loaded with magnetic particles.

In continuous-running separators, several separation chambers are grouped to form an endless ring or chain and are moved continuously relative to the pole pieces, which are fixed, perpendicular to the magnetic lines of force. During their movement, the chambers pass successively through a separation zone, a rinsing zone and an evacuation zone of the magnetic constituents. The supply of the chambers is carried out in the separation zone, practically over its entire length. At the exit of this zone, where the magnetic field is still intense, a rinsing liquid is circulated in the chambers to remove the grains of non-magnetic constituents retained by magnetic flocculation. In the evacuation zone which follows the rinsing zone and where the magnetic field is, practically none, the magnetic products are extracted from the chambers by washing with water under pressure. These devices are heavy, bulky and expensive and since the magnetic field is produced by electromagnets, their consumption of electrical energy is high.

It has been proposed in the literature to replace electromagnets with permanent magnets on the latter type of device, but these proposals have received no practical application, since the intensity of the magnetic field that can be produced with permanent magnets being limited, the existence of the clearance which it is necessary to provide between the walls of the separation chambers and the magnets or the pole pieces to allow their relative displacements would not have made it possible to achieve the performances sought for this type of devices.

The filter described in document EP-A-0341824 which discloses the preamble of claim 1 has the same drawback: the clearance which is provided between the magnets and the faces of the filter element, to allow the magnets to move parallel to said faces , limits the performance of the filter and makes it unsuitable for conventional applications of high intensity magnetic separators.

The object of the present invention is to allow the use of permanent magnets, in place of electromagnets, in high intensity magnetic separators working in wet conditions and, by this means, of reducing the weight, the size and the cost of these devices and reduce their energy consumption.

The magnetic separator object of the present invention comprises at least one separation chamber where the product to be treated flows from top to bottom and permanent magnets, possibly associated with pole pieces, and is characterized in that means are provided for producing a relative displacement of the magnets, respectively of the pole pieces, and of the separation between a first position where the magnets, respectively the pole pieces, are intimately applied against the walls of the separation chamber and a second position where the magnets, respectively the pole pieces, are distant from said walls and the magnetic field in said chamber is low enough that the magnetic particles can be removed from the chamber by a current of a washing liquid, said relative movement comprising a movement of the magnets, respectively of the pole pieces, transversely to said walls.

The magnets, respectively the pole pieces, can be moved by means of jacks controlled by a programmable automaton, at the same time as valves placed on the supply and the evacuation of the separation chamber, to be applied on the walls of the chamber during the separation phase and be separated from them during the phase of evacuation of the magnetic constituents, the duration of each of the phases being predetermined or a function, for example, of the degree of clogging of the chamber.

The separation chamber can be constituted, in a conventional manner, by a tubular casing made of magnetic material, containing a matrix formed of grooved plates, balls, expanded metal, etc., and occupying the entire section of the chamber.

It can also be constituted by a section of tube made of an elastically deformable material, such as rubber or a plastic material, having in the normal state a circular or curved section and which is crushed between the magnets during the separation phase so to form a flat tube.

The magnets can be constituted by an assembly of elementary magnets whose direction of magnetization is perpendicular to the direction of flow of the product treated in the separation chamber. It is also possible to use a stack of magnets and flat pole pieces, the direction of magnetization of the magnets being in this case parallel to the direction of flow of the product to be treated. The pole pieces located on either side of the separation chamber may be located in the same plane perpendicular to the direction of flow of the product to be treated and of the same polarity or opposite polarities, or vertically offset by half not.

In the case where the separator has only one separation chamber, its operation is necessarily discontinuous. For continuous operation, several identical elementary units will be combined, each unit being formed of a separation chamber, permanent magnets, possibly of pole pieces, and of means for removing the permanent magnets from the chamber and applying them to its walls, and being supplied cyclically with products to be treated and washing liquid, the various units being successively supplied so as to allow continuous operation.

The various units can be fixed and be connected, on the one hand, to a supply of products to be treated and to a collector of purified products and, on the other hand, to a source of a washing liquid and to a collector of magnetic constituents, through a set of valves whose opening and closing are programmed to ensure cyclic operation of the separation units.

The separation units can also be mobile and movable between a separation zone, which is equipped with means for supplying products to be treated, and for collecting purified products, and a washing zone provided with means for distributing a liquid. washing and collecting magnetic components. In the case of a device comprising only two units, the movement can be alternative. In the general case, the separation units will be linked to each other to form an endless ring or chain and will be moved step by step, always in the same direction. We can obviously provide, several separation and washing zones, along the ring or the endless chain. According to the invention, the longitudinal movement of the units will be accompanied by a transverse displacement of the magnets when the units pass from one zone to another.

As a variant, each unit could comprise two or more chambers which would be brought successively between the magnets, in a separation zone comprising, moreover, means for supplying the product to be treated and for collecting the purified product, then distant from this zone. and brought to a washing area equipped with means for dispensing a washing liquid and for collecting magnetic components, the magnets normally applied to the walls of the chamber being in the separation zone, being periodically spaced apart to allow the chambers to be moved.

The magnets and / or the pole pieces located on either side of the separation chamber being of opposite polarities, the means used to separate them from the separation chamber must overcome the force of magnetic attraction. Part of the energy involved can be recovered during the movement of magnets or pole pieces, especially when using several units operating sequentially.

• La figure 1 est une vue en coupe verticale d'une unité de séparation conforme à l'invention, représentée schématiquement;
• Les figures 2 a et b sont des vues de dessus de l'unité de la figure 1 pendant les phases de séparation et de lavage respectivement;
• Les figures 3 a et b sont des vues de dessus, analogues aux figures 2 a et b, d'une autre unité de séparation conforme à l'invention, comportant une chambre de séparation de conception différente;
• La figure 4 montre une possibilité de réalisation du circuit magnétique d'une unité de séparation; et
• La figure 5 montre une possibilité d'association de deux unités de séparation pour assurer un fonctionnement continu.

Other characteristics of the invention will appear on reading the description which follows and refers to the accompanying drawings which show, by way of non-limiting example, some embodiments of the invention and in which

• Figure 1 is a vertical sectional view of a separation unit according to the invention, shown schematically;
• Figures 2 a and b are top views of the unit of Figure 1 during the separation and washing phases respectively;
• Figures 3 a and b are top views, similar to Figures 2 a and b, of another separation unit according to the invention, comprising a separation chamber of different design;
• Figure 4 shows a possible embodiment of the magnetic circuit of a separation unit; and
• Figure 5 shows a possibility of combining two separation units to ensure continuous operation.

The separation unit shown in Figures 1 and 2 consists essentially of a separation chamber 10 placed between two permanent magnets 12 of opposite polarities. Each magnet is integral with an L-section armature 14, the two armatures forming a closed magnetic circuit with the magnets and the chamber 10, when the magnets are applied to the opposite walls of the chamber 10, as shown in the figure. 2 a.

The separation chamber consists of an envelope made of a non-magnetic material, of rectangular section and open at its two ends. It is filled with vertical grooved plates or other elements, such as bars, steel wool, etc ... made of soft magnetic material which create in the gap magnetic field gradients allowing the magnetic particles of the product to be treated to fix on said elements.

At its upper end, the chamber 10 is connected to a pipe for supplying the product to be treated 16, through a solenoid valve 18, and to a pipe for pressurized water 20, through a solenoid valve 22. A collector 24 is placed under the chamber 10 and connected to two conduits 26 and 28, through solenoid valves 30 and 32, respectively, which make it possible to direct the products collected in two different directions.

Cylinders 34 make it possible to move the magnets and the armatures perpendicular to the large faces of the chamber 10 and to maintain the magnets applied to the latter (FIG. 2 a) or separated from them (FIG. 2 b).

This separation unit operates as follows: in a first phase, the magnets 12 are applied to the large faces of the chamber 10 (FIG. 2a), the valves 18 and 30 are open and the valves 22 and 32 are closed. The product to be treated, in the form of pulp, circulates from top to bottom in the chamber 10, between the vertical plates. The magnetic particles are subjected to attractive forces which deflect them towards the plates and hold them there. The purified product is collected in the collector 24 and evacuated through the conduit 26. In a second phase, the magnets are moved away from the chamber (FIG. 2 b), the valves 18 and 30 are closed and the valves 22 and 32 are open. The magnetic particles which are no longer subjected to the action of the magnetic field are then entrained by the pressurized water circulating in the chamber 10 and discharged through the conduit 28.

The duration of the first phase can be predetermined, in particular if the content of the product to be treated in particles magnetic varies little over time. Alternatively, the transition from the first to the second phase can be done when the degree of clogging of the chamber, evaluated for example from a measurement of the flow rate or of the pressure drop, reaches a predetermined value.

The magnets must be separated by a sufficient distance so that the magnetic field in the chamber 10 is practically zero, the lines of force of the magnetic field of each magnet then closing in on themselves through the air gap formed between the magnet and chamber 10 and the associated armature.

The magnets 12 are constituted by an assembly by bonding of elementary magnets with samarium-cobalt or with neodymium-iron-boron, the direction of magnetization being perpendicular to the large faces of the chamber 10. As a variant, each magnet 12-armature assembly 14 could be replaced by a stack of magnets 40 and pole pieces 42, as shown in FIG. 4, the direction of magnetization of the magnets being parallel to the direction of flow of the product to be treated in the chamber 10 (arrow F ).

Figures 3 a and b show another embodiment of the separation chamber. This is here constituted by an elastically deformable tube 110, made of rubber or plastic, which normally has a circular section (FIG. 3 b) and takes a flattened shape. when it is compressed between the magnets 12 (Figure 3 a). Preferably, the tube will be filled with a material, such as steel wool, which can be compressed elastically without great effort so as not to hinder the deformation of the tube and its return to the original shape. Wires of soft magnetic material arranged longitudinally or braided to form a tubular sheath could be embedded in the thickness of the wall of the tube to create magnetic field gradients on the inside of the tube. Figure 3a corresponds to the separation phase, the magnets being brought together and crushing the tube 110; in the washing phase (Figure 3b) the magnets are spaced from each other, and the tube has resumed its circular shape.

To be able to process a product continuously, it is necessary to combine several separation units. In the general case where the washing phase is shorter than the separation phase, two units are sufficient to ensure continuous operation. The diagram of such an installation is shown in FIG. 5. The supply lines for the product to be treated 16 and for pressurized water 20 are connected to the chambers 10 ′ and 10 ′ ′ through solenoid valves 18 ′ and 18 ′ ′ and 22 ′ and 22 ′ ′, respectively. Collectors 24 ′ and 24 ′ ′ placed under the chambers 10 ′ and 10 ′ ′ make it possible to direct the products leaving the chambers towards an outlet for purified product or an outlet for magnetic product, depending on the position of a schematic selector by a pivoting flap 50 ′, 50 ′ ′. The valves 18 ′, 18 ′ ′, 22 ′ and 22 ′ ′, the selectors 50 ′ and 50 ′ ′ as well as the jacks, not shown, moving the magnets 12 ′, 12 ′ ′ are controlled by a programmable controller or a microphone -computer according to a pre-established and modifiable program so that at any time, at least one of the units is in the separation phase.

The number of units to be used in an installation will depend on the flow of product to be treated. The use of standard units reduces costs and facilitates maintenance, as a faulty unit can be quickly replaced by a spare unit.

An intermediate rinsing phase with maintenance of the magnetic field may be provided to remove the grains of non-magnetic constituents retained by magnetic flocculation.

It is understood that all the modifications which can be made to the embodiments described by the substitution of equivalent technical means and in particular the variants set out in the preamble to the description fall within the scope of the invention as defined by the claims.

Claims (9)

1. Wet process high intensity magnetic separator comprising at least one separating unit consisting of a chamber through which the product to be processed circulates downwardly and means to create a magnetic field perpendicular to the direction of flow of the product to be processed consisting of permanent magnets which may be associated with pole pieces, characterized in that means (34) are provided to cause a relative displacement of the magnets (12), respectively of the pole pieces (14), and of the chamber (10) between a first position in which the magnets, respectively the pole pieces, are closely applied against the walls of the said chamber and a second position in which the magnets, respectively the pole pieces, are apart from the said walls and the magnetic field in the chamber is weak enough to allow the magnetic particles to be removed from the chamber by a washing-liquid flow, which relative displacement includes a movement of the magnets, respectively of the pole pieces, transversely to the said walls.
2. Magnetic separator according to claim 1, characterized in that the said means to move the magnets (12), respectively the pole pieces, consist of jacks (34) controlled by a programmable logic controller or a microprocessor, at the same time as valves (18, 22, 30, 32) mounted on ducts (16, 20, 26, 28) connected to the inlet and the outlet of the said chamber (10), so that the magnets, respectively the pole pieces, be applied on the walls of the chamber during a separation phase, and apart from the said walls during a washing phase.
3. Magnetic separator according to claim 1 or 2, characterized in that the said chamber (10) consists of a tubular casing made of an amagnetic material containing a ferromagnetic matrix permeable to the product to be processed.
4. Magnetic separator according to claim 1 or 2, characterized in that the said chamber (10) consists of a section of tube made of an elastically deformable material having a circular or convex section in its normal state and containing an elastically compressible ferromagnetic matrix permeable to the product to be processed, and in that the said tube is crushed between the magnets or the pole pieces and takes the form of a flat tube during the separation phase.
5. Magnetic separator according to any of claims 1 to 4, characterized in that the said means of production of the magnetic field are made up of an assembly of elementary magnets whose magnetization direction is perpendicular to the direction of flow of the product to be processed through the said chamber (10).
6. Magnetic separator according to any of claims 1 to 4, characterized in that the said means of production of the magnetic field are made up of a stack of magnets and pole pieces, the direction of magnetization of the magnets being parallel to the direction of flow of the product to be processed through the said chamber (10).
7. Magnetic separator according to any of the above claims, characterized in that the separating unit or each separating unit comprises two chambers or more, means to move the chambers between a first zone containing the magnets and equipped with means to supply product to be processed and to collect the purified product and a second zone equipped with means to distribute a washing liquid and to collect the magnetic constituents and to bring them by turns successively into the first and the second zone and means to coordinate the movements of the chambers and of the magnets and/or pole pieces.
8. Magnetic separator according to any of claims 1 to 6, characterized in that it comprises several separating units and means (18', 18'', 22', 22'') to connect cyclically each separating unit, on the one hand, to a product-to-be-processed feed line (16) and a purified product collector (26) and, on the other hand, to a source of a washing liquid (20) and a magnetic constituent collector (28).
9. Magnetic separator according to any of claims 1 to 6, characterized in that it comprises several separating units and means to bring them by turns into a separation zone equipped with means to supply product to be processed and to collect the purified product and then into a washing zone equipped with means to distribute a washing liquid and to collect the magnetic constituents.

Images