GB2040191A - Magnetic separator - Google Patents

Abstract

A magnetic separator for classifying fine-grain material by passing the material through a matrix which is located in a magnetic field in which the matrix comprises a series of laminations or plates (11) which are arranged at a spacing from each other. The surface of each plate facing an adjacent plate is provided with longitudinal grooves which are arranged to extend in the direction of throughflow of the material and with transverse grooves (13) which are arranged to extend transverse to the direction of throughflow of the material. <IMAGE>

Description

SPECIFICATION A magnetic separator This invention relates to a magnetic separator in which fine-grain material which is to be classified is passed through a matrix which is located in a magnetic field and comprises an arrangement of ferromagnetic elements.

With this type of separator which separates by means of magnetic attraction and which is designed to classify weakly magnetic minerals in particular, usually those minerals suspended in a carrier medium such as water, a very high magnetic field is produced in a separating chamber. Inside the separating chamber are located induction poles in the form of magnetizable ferromagnetic elements which distort the magnetic field as a result of their high permeability such that a high degree of inhomogeneity of the magnetic field results while forming large local field gradients. The particles which are of higher magnetic susceptibility are attracted to the induction poles in the separating chamber and accumulate there, while particles of a lesser magnetic susceptibility pass out of the separating chamber.The accumulated particles are rinsed out of the separating chamber at a later point in time.

The arrangement of the ferromagnetic elements in the separating chamber is called a matrix. The following have been suggested as ferromagnetic elements or induction poles: plates which have projecting edges running in the direction of throughflow of the material (for example British Patent Specification No. 1,054,807); profiled or shaped rods; loose spheres such as ball bearings and stacks of expanded metal.

The fill elements last mentioned are extremely good, because of their filigree structure, for classifying particles having an especially fine grain structure and which are particularly low in magnetic properties, because with the plurality of induction poles which are closely adjacent each other in the separating chamber even very small particles and particles which are few in number have the opportunity of arriving in a region of high magnetic force and thus of being retained. On the other hand however, it is difficult to rinse these retained particles out of such a matrix because the dense packing of the filler elements is an obstacle to the cleaning force of the rinsing agents. Moreover, the capacity of a separator decreases as the matrix becomes more dense, while the rinsing process is frequently the factor which determines the speed.As the filigree nature of the matrix becomes more dense so the danger of blockages and interruptions in operation of the magnetic separator increases. On the other hand, a matrix which comprises a stack of laminations or plates may be more easily cleaned but such a matrix is less effective than a filler element matrix if it is a question of retaining particles with a particularly fine grain structure and which have low magnetic properties.

The present invention aims to provide a magnetic separator which has both the advantages of a stack of laminations matrix and the advantages of a filler element matrix without having their disadvantages.

According to the invention, there is provided a magnetic separator in which fine-grain material which is to be classified is passed through a matrix which is located in a magnetic field, wherein the matrix comprises at least two ferromagnetic plates which are arranged at a spacing from each other, the surface of each plate facing an adjacent plate being provided with longitudinal grooves which are arranged to extend in the direction of throughflow of the material and with transverse grooves which are arranged to extend transverse to the direction of throughflow of the material.

The transverse grooves which are arranged in addition to the longitudinal grooves bring about shaping of the surfaces of the matrix plates similar to thorns with innumerable points or apices and edges and with a correspondingly increased concentration of magnetic lines of force at the apices and edges of the matrix plates so that the magnetic separator in accordance with the invention is able to achieve the separating quality of a separator having a filler element matrix. Nevertheless, the advantages of a separator with a stack of laminations matrix, such as its capacity, the very small danger of blockages occurring, the possibility of rinsing it out under pressure or using a jet under pressure are maintained because, in the separator in accordance with the invention, the throughflow channels remain unrestrictedly open to the material to be classified.

The invention will now be further described, by way of the example, with reference to the drawings in which: Figure 1 is an end elevation of one embodiment of a stack of laminations matrix of a magnetic separator in accordance with the invention: Figure 2 is an end elevation of a second embodiment of a stack of laminations matrix having a different distribution of grooves; Figure 3 is a section taken on the line Ill-Ill in Figure 2 showing the face of one of the plates or laminations of the matrix; Figure 4 is a plan view of a stack of laminations matrix having plates in accordance with Figures 1 or 2and3and Figure 5 shows the arrangement of a stack of laminations matrix in accordance with the invention in part in a continuously operating magnetic separatop with a rotating matrix.

The matrices shown in all of Figures 1 to 5 comprise plates 10,11 which are arranged in parallel and at a spacing from each other, their surfaces being provided with longitudinal grooves 12 running the direction of throughflow of the material to be classified and usually arranged vertically. At an angle of 90 transverse with respect to the longitudinal grooves 12 are arranged transverse grooves 13, which may also be at a different angle with respect to the longitudinal grooves. Both the longitudinal grooves 12 and the transverse grooves 13 are preferably V-shaped in cross-section so that they may be manufactured easily.In the case of the stack of laminations matrix shown in Figure 1 and in the lower region 14 of the matrix shown in Figures 2 and 3, the spacing between the transverse grooves 13 is equal to the spacing between the longitudinal grooves 12, for example 2.1 mm, so that the grooves form a plurality of pyramids 15 each having an apex and four inclined sharp side edges. With the stack of laminations matrix shown in Figures 2 and 3, the spacing between the transverse grooves 13 as seen from the upper end of the plates to the lower end of the plates in the direction of throughflow of material is initially large and decreases downwardly towards the lower end so as to form the pyramids 15 in the lower region 14.

In this embodiment, in the upper region of the plates easily magnetized components of a grain mixture such as hemetite iron are attracted and in the lower region of the plates having a greater number of high local field gradients the components which are not easily magnetized such as impure iron for example or very fine-grain iron are attracted. The stack of laminations matrix shown in Figures 2 and 3 is also well suited to cleaning a non-magnetizable product which is to be extracted by separating out the magnetizable impurities, for example in order to clean vitreous (glassmaking) sand, which contains only traces of magnetizable impurities such as iron oxides for example.

In any case, a particle of the material which is to be classified, which travels downwardly in the base of the groove of the longitudinal grooves 12 or along the cutting edge arrives at a transverse groove 13 or a sharp edge or apex of a pyramid and is attracted there. The stack of laminations matrix in accordance with the invention has, in the lower region of the plates at least, very many areas having high local field gradients so that a magnetic separator equipped therewith has the quality of separation of a separator having a filigree filler element matrix in the lower region of the plates, and it is this region which is important, while at the same time maintaining a free throughflow cross-section and providing the possibility of rinsing out the material which has been attracted under pressure or using a jet under pressure.

In the embodiment shown in Figure 5 a plurality of matrices 16 with plates provided with longitudinal and transverse grooves are arranged inside an annular casing 17, which is rotatably mounted about avertical axis within a magnetic field, while the material to be classified is supplied to the upper end of the annular casing 17. Spacers 18 are arranged between the adjacent grooved plates 10 or 11. The plates may be tangential, radial or inclined with respect to the rotor.

Claims (6)

1. A magnetic separator in which fine-grain material which is to be classified is passed through a matrix which is located in a magnetic field, wherein the matrix comprises at least two ferromagnetic plates which are arranged at a spacing from each other, the surfaces of each plate facing an adjacent plate being provided with longitudinal grooves which are arranged to extend in the direction of throughflow of the material and with transverse grooves which are arranged to extend transverse to the direction of throughflow of the material.

2. A magnetic separator according to Claim 1, wherein both the longitudinal grooves and the transverse grooves are V-shaped in cross-section.

3. A magnetic separator according to Claim 1 or claim 2, wherein the spacing between the transverse grooves is equal to the spacing between the longitudinal grooves so that the grooves form a plurality of pyramids each having an apex and four side edges.

4. A magnetic separator according to Claim 1 or claim 2, wherein the spacing between the transverse grooves from one end of the plates to the other seen in the direction of throughflow of material is initially a large spacing at said one end and becomes increasingly smaller towards the other end of the plates.

5. A magnetic separator according to any preceding Claim, wherein a plurality of matrices is provided, each of said matrices having plates inside an annular casing which is notably mounted about an axis within a magnetic field while the material which is to be classified is supplied to one end of the annular casing.

6. A magnetic separator substantially as described herein with reference to the drawings.