US3489280A

US3489280A - Magnetic separator having field shaping poles

Info

Publication number: US3489280A
Application number: US524782A
Authority: US
Inventors: Arlo F Israelson; Robert F Merwin
Original assignee: Eriez Manufacturing Co
Current assignee: Eriez Manufacturing Co
Priority date: 1966-02-03
Filing date: 1966-02-03
Publication date: 1970-01-13
Anticipated expiration: 1987-01-13
Also published as: DE1257701B; GB1140794A; FR1510384A

Description

MAGNETIC SEPARATORHAVING FIELD SHAPING POLES Filed Feb. 5. 1966 1970 A. F. ISRAELSON ET AL 2 Sheets-Sheet 1 w ENTOR 3am rus w Jan. 13, 1970 A. ISRAELSON ET AL 3,489,280

MAGNETIC SEPARATOR HAVING FIELD SHAPING POLE S Sheets-Sheet 2 Filed Feb. 5, 1966 INVENTOR ARI-0 E ISRAELSON cML MA United States Patent 3,489,280 MAGNETIC SEPARATOR HAVING FIELD SHAPING POLES Arlo F. Israelson and Robert F. Merwin, Erie, Pa., assignors to Eriez Manufacturing Co., Erie, Pa., a corporation of Pennsylvania Filed Feb. 3, 1966, Ser. No. 524,782 Int. Cl. B03c 1/14 U.S. Cl. 209-223 6 Claims This invention relates generally tomagnetic separators and more particularly to drum type magnetic separators for separating magnetic material from nonmagnetic material in wet or dry form.

In the fields of magnetic separators many different types of magnetic separators have been developed and are currently in use to recover and concentrate ferromagnetic materials.

Some of these separators are powered by electromagnets; however, since the advent of the ceramic permanent magnets, it has become economically practical to use magnetic separators powered by these materials.

Improvements in these separators have been hampered by specifications that were established, based upon the design of the first successful electromagnetic separators. Originally, it was considered practical and advisable to measure the fields in magnetic drum separators, at a distance of two inches from the rotating drum shell. Then an average of these measurements was taken and drums were classified by these averages. For example: 650 gauss drum, 750 gauss drum, and so forth. As time has passed, users have specified higher and higher flux densities, until more recently specifications are being written, in some cases, for drums with a 1200 gauss rating.

In the meantime, magnet designers have been somewhat frustrated by the insistence of users that the two-inch gauss line must be observed, when it is an established fact that magnetic field gradient is more important than overall fiux density. In other words, the force of magnetic attraction varies as the product of the field intensity and the field gradient. Which is to say that if there are two magnetic drums, each with a flux density of 3000 gauss at the shell surface, but, as a result of design ingenuity, one drum has a flux density of 1200 gauss at two inches the other with 1200 gauss at one inch then the latter would attract magnetic particles with much greater force.

Disregard of this proven principle is especially wasteful when it is recognized that throughout the mining industry the slurries to be separated are never more than three-quarter inch or one inch deep adjacent to the face of the magnetic drum separator.

To design and build permanent magnetic drum separators, incorporating the very desirable high gradient field configuration and with ample magnetic intensity, has been considered difficult and excessively expensive. With conventional designs and existing permanent magnetic materials so much ordinary permanent magnetic material had to be used to compensate for flux leakage that space was not available within the drums and, if the newer high strength materials were used, costs would be prohibitive.

Apparatuses of the magnetic type for separating or segregating magnetisable and nonmagnetisable materials from a mixture or stream of such materials are well known. An example of such a separator is shown in Patent No. 3,168,464. Applicant has discovered that by placing repelling magnets between the magnetic poles of a drum separator such as shown in the said patent, that the fields of magnetic force from the magnetic poles are reshaped and strengthened in such a manner that a more powerful and more effective magnetic force is exerted on the particles being separated therefore a much more efiicient separating is accomplished.

ice

It is accordingly, an object of the invention to provide an improved magnetic separator.

Another object of the invention is to provide an improved magnetic separator which is simple in construction, economical to manufacture and simple as well as etficient to use.

Another object of the invention is to provide a magnetic separator made of spaced permanent magnets having interpoles of repelling magnets spaced therebetween and means to direct a stream of materials to be separated past the said poles.

Another object of the invention is to provide an im proved magnetic separator having circumferentially spaced permanent magnets and a second set of circumferentially spaced permanent magnets spaced on a larger radius and facing the poles of the first permanent magnets with the like polarity of said second set of magnets repelling the polarity of said first set with means to direct a stream of materials to be separated between the first and second permanent magnets.

With the above and other objects in view, the present invention consists of the combination and arrangement of parts hereinafter more fully described, illustrated in the accompanying drawings and more particularly pointed out in the appended claims, it being understood that changes may be made in form, size, porportions, and minor details of construction without departing from the spirit or sacrificing any of the advantages of the invention.

In the drawings:

FIG. 1 is a longitudinal cross sectional view of a magnetic separator according to the invention showing repelling magnets inserted between poles of main magnets.

FIG. 2 is a view similar to FIG. 1 of another embodiment of the invention showing additional poles (repelling magnets) spaced on the opposite side of a path for a stream of material to be separated.

FIG. 3 is an isometric view of a magnetic assembly similar to the one shown in FIG. 1.

FIG. 4 is an enlarged view of four main poles with three repelling poles of the magnetic assembly and four outer bucking magnets in operative relation to each other.

FIG. 5 is a view of a magnetic assembly showing the field shape which would occur with the magnetic arrangement shown in FIG. 1.

FIG. 6 is a view of an assembly showing the magnetic field shape which would occur with the magnetic arrangement shown in FIG. 2.

FIG. 7 is a view of the field arrangement which would occur if the adjustable magnets were moved to the relation relatives to the poles shown in FIG. 4.

Now with more particular reference to the drawings. The drawings illustrate drum-type magnetic separators employing permanent magnets, according to the invention. The drum-type magnetic separators, according to the drawing, have been constructed specifically for recovering or separating magnetizable materials, for example in iron ore purification in concentrators or for use in second flow processes, for example for removing from coal finally ground iron magnetite. It is to be understood the permanent magnet, according to the invention, is also applicable to attractors other than separators.

The magnetic separators illustrated in the drawing are of the wet-drum type. It is to be understood, however, that permanent magnet separators, according to the invention, can be constructed as dry systems. FIG. 1 illustrates a con-current wet-drum separator comprising a drum or cylindrical shell 11 made of non-magnetic, non-magnetizable metallic material and mounted for rotation about a stationary shaft 12 on bearings, not shown, supported on a framework, not shown.

The cylindrical shell 11 is rotatably driven counterclockwise, for example, by a sprocket wheel which is in turn rotatably driven through a chain drive 17 illustrated diagramatically from an electric motor 18. The sprocket is suitably secured to one of the end plates, not shown, of the drum or shell.

The shell 11 has an exterior surface that forms a material conveyor operative as hereinafter described. A fixed permanent magnet described generally by the reference numeral 20 is mounted on the shaft 12 concentrically with the cylindrical shell 11 and interiorly thereof. The magnet comprises support members 21 provided with a hub 22 supporting a back plate 24 preferably having high magnetic permeability. Multiple pole assemblies 25-29 of alternate polarity are mounted angularly spaced on the back plate 24. These poles extend axially in the cylindrical shell or drum 11. Repelling

magnets

60, 61, 62 and 63 are placed between poles 25-29 as shown. The repelling magnets have a polarity such that the poles of the repelling magnets are adjacent like poles of the magnets 25-29. The repelling magnets practically eliminate flux leakage because of their repelling force that forces the leakage field back into the magnets 25-29. The permanent magnet 20 construction details will be hereinafter described completely. The outermost end faces of the poles are spaced radially inwardly of the inner surfaces of the rotatably driven shell 11, for example, about one-eighth of an inch or one-sixteenth or even three-eighths or larger clearance depending upon the size of the separator so that an air gap 31 is formed between the pole end faces and the shell interior surfaces.

Provision is made externally of the cylindrical shell 11 for delivering a slurry or mixture of material comprising magnetizable material and non-magnetizable material to be separated by the attraction of the magnetizable material to the outer conveyor surface of the cylindrical shell 11 by the strong high-gradient type magnetic field developed by a permanent magnet 20. The material to be separated designated 35 is delivered to a chamber 36 extending longitudinally of the cylindrical shell. Water is fed into the chamber 36 through a conduit 37 so that a slurry is formed and delivered through an elongated opening 39 in the chamber 36 into a second chamber 40 formed between the drum 11 and plate 41. The water delivered through the inlet conduit 37 is held at a level 43 by suitably controlling the. delivery rate and the height of a plate 45 that defines an overflow chamber 46 so that the excess water flows through an overflow outlet conduit 48.

The material 35 moves along between the shell exterior surface and the plate 41 in contact with the shell, and in the same direction as the shell rotation, so that the magnetizable material therein is attracted to the outer surface of the shell or drum and held in position thereon. As the drum rotates the material is agitated by the magnet 20, since the successive fields formed by the assemblies are of alternate polarity, it can readily be appreciated carrying the material through a series of alternating polarity magnetic fields associated with the permanent magnet will rotate the magnetizable materials on the surface of the shell thereby permitting the non-magnetic material or tailings to fall clear of the conveyor outer surface of the shell. The non-magnetic tailings are discharged through an opening 50 into a chamber 51 and are designated generally by the reference number 52. The tailings entering the chamber 51 are discharged from this chamber through an outlet conduit 54. The magnetic material remains attracted to the outer surface of the shell until it comes into a posi. tion past the pole 29 so that the permanent magnet 20 is no longer effective and the magnetic material falls off, or it may be scraped by a scraper, not shown, into a discharge chute 55 from which it may be discharged, for example, to a container 56 as magnetic concentrate.

In the drawings FIG. 2 illustrates a wet-drum separator in which a rotata bly driven cylindrical shell or drum 60 is mounted for rotation on a stationary shaft =61 and is driven clockwise at a suitab e p eselected speed by an electric motor 62 through a chain drive 63 cooperative with a sprocket wheel 64 mounted on an end plate of the drum, not shown. The apparatus is provided with a permanent magnet 66 mounted on the shaft 61 in a stationary position and concentric with the shell 60. The permanent magnet comprises multiple pole assemblies 71-75 of alternate polarity secured to a magnetizable back plate 77 mounted depending from support plates 78 having hub 80 circumferentially of the shaft 61. The permanent magnet 66 functions in a manner similar to the magnet 20 heretofore described.

In the embodiment of the apparatus illustrated in FIG. 2 the slurry of material to be separated is provided through a supply or inlet pipe 82 to an elongated chamber 83 and fed through a delivery opening, for example a pipe 84, into a distribution chamber 85. The slurry in the chamber 85 is maintained at a level 86 by the baflle or spill-over plate 87 and the controlled rate of feed and any excess of overflow water enters another chamber 89 and is discharged to an overflow outlet pipe 91.

In this typeof apparatus the magnetic material is attracted to the strongest fields by the magnetic pole assembly 72 nearest the opening into the distribution chamber and is then agitated as the material is carried into the field of opposite polarity developed by the magnetic assembly 71 and is discharged as magnetic concentrate through a discharge chute 93 into a suitable container illustrated diagrammatically at 95. The material entering the distribution chamber 85 also flows through the chamber in the direction of the pole assembly 73 where further refining or attraction of magnetizable material takes place and the nonmagnetic tailings are discharged through an opening 97 into a chamber 98 and out through a tailings discharge outlet pipe 99.

The fixed permanent magnets 20, 6-6 heretofore generally described are constructed according to either of two constructions of permanent magnet assemblies to be hereinafter described and in which like reference numerals denote similar parts. According to the invention, the permanent magnets are constructed generally in the manner of the construction of a permanent magnet 100 illustrated in FIG. 3. The magnet 100 comprises an arcuate back plate 102 made, for example of steel and supported on support plates, for example the support plate, axially spaced on a shaft 105 and provided with

hubs

106, 107 through which a stationary shaft 105 passes.

The permanent magnet 100 comprises a plurality of pole assemblies 110-113 of alternate polarity. The even numbered

pole assemblies

110, 112 may be considered to be of north magnetic polarity and the odd numbered pole assemblies 111, 113 may be considered to be of south magnetic polarity. Each pole is formed by an assembly of a plurality of stacks of ceramic permanent magnet material arranged axially on the magnet. For example, the pole 111 comprises nine stacks, two of which are designated with reference numerals, for example the

stacks

121, 122. Each stack is made up of magnetic units 125. Each magnetic unit is in the form of a magnetic slab having a greater length and width dimension than thickness. The magnetic units are preferably made of a magnetic ceramic material and have major opposite faces defining their thickness dimension and arranged within each stack with their major faces in an intimate face-toface relationship. The stacks are arranged contiguous to each other with the magnetic units in end-to-end abutting realtionship. The magnetic units in the stacks are of equal thickness so the stacks on each pole are of equal height. The units in each stack are magnetized permanently in the same direction and in the direction of their thickness dimension which corresponds-to magnetization in a direction substantially normal to the opposite faces defining the thickness dimension of the unit.

The successive stacks in each pole assembly are arranged in a row "as illustrated in FIG. 3 and are secured to the steel back plate which has high magnetic permeability and is provided with flats, for example the

flats

130, 131 extending longitudinally of the plate on which the innermost magnetic units 125 have their faces in intimate contact therewith. These fiats are spaced angularly on the arcuate back plate and are on equidistant radii from the axis of rotation of the shaft. The flats need not have the same width when the pole pieces have different widths. In the illustrations in FIGS. 1 and 2 the pole pieces or magnetic units have the same width in all the poles. The outer units are, therefore, concentric and equally spaced radially inwardly from the inner surfaces of a cylindrical shell with which they are mounted concentrically.

The repelling

magnets

150, 151 and 152 are disposed between the magnetic units, The repelling magnets are polarized laterally as shown.

In the embodiment of the invention shown in FIG. 4, the

main poles

210, 211, 212 and 213 are fixed to the back bar 202 which is made of magnetic material and may be held stationary in the same manner as in the other embodiments of the invention. A rotating drum 232 may be driven in the manner as the drum in the preceding embodiments are driven. A stationary baifle or housing 215 is fixed generally concentric to the rotating drum 232 and spaced outward from the rotating drum a distance indicated at B. This distance is determined by the magnetic field characteristic desired in the space between drum 232 and housing 215.

The bucking

magnets

206, 207, 208 and 209 are fixed to a back bar 300 which is made of magnetic material. The bucking magnets and back bar are held in spaced relation to the fixed bafile 215. The bucking magnets and back bar 300 are rotatably adjustable and may also be adjusted toward and away from the main magnets by means of the adjusting members 220, to permit shaping and increasing or decreasing the gradient and strength of the magnetic field in the space between drum 232 and bafile 215. The stationary baffle 215 is fixed a distance B from the rotating drum and the faces of the bucking magnets will be adjusted to have a distance A of a suitable magnitude to give the proper bucking effect on the field re sulting from the main magnets. In the embodiment of FIGURE 4, Dimension B must be less than A so the ferromagnetic particles will be attracted to the main poles, rather than to bucking magnets. Also in the embodiment of FIG. 4; the bucking magnets are rotatably adjustable so that the field pattern of the main magnets can be adjusted to attract particles so they will move toward the main magnets either in the path illustrated in C or D, or any inter-mediate path, depending upon the characteristics of the materials being separated. Where the particles to be attracted are weakly magnetic, path C is preferable over D because the direction of attraction is such that more time is permitted to overcome the inertia of the moving particles. In path D the particles must change direction rather abruptly, so there is a greater chance that some weakly magnetic particles could get past the magnets. The outside repelling magnets cause a significant increase in flux density at the surface of the drum shell with realtively low flux densities in adjacent areas. It is the rather abrupt change within a short distance that is called high gradient and is so important for the attraction of magnetic particles.

The adjustment of the repelling magnets closer to or further from the main magnets is important because it permits adjustment of the field strength to accommodate variations in characteristics of ore deposits. With some ores, if the magnets are too strong, they may remove undesirable frictions.

The foregoing specification sets forth the invention in its preferred practical form, but it is understood that the structure shown is capable of modification within a range of equivalents without departing from the invention which is to be understood is broadly novel as is commensurate with the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A magnetic separator comprising:

a back bar,

spaced permanent main magnets fixed to said back bar,

and said magnets having a face spaced from said back bar,

said main magnets each having a magnetic pole adjacent its said face of opposite polarity from the pole of the main magnet adjacent thereto,

repelling magnets disposed between said main magnets,

means to direct a stream containing nonmagnetic ma terial and magnetic material in close proximity to said faces of said magnets and through magnetic fields produced by said main magnets, whereby said magnetic material is separated from said nonmagnetic material,

said repelling magnets each having a magnetic pole at each side thereof of like polarity to the pole of the main magnet at said face thereof, whereby the leakage field of said main magnets is repelling and reinforces the normal field which is forced outward toward said stream of material,

a plurality of bucking magnets being disposed in an arcuate pattern outside of said main magnets with one pole of each said bucking magnet directly opposite and facing a like pole of said main magnet.

2. The separator recited in calim 1 wherein:

said means to direct said materials into close proximity to said faces of said magnets comprises a hollow drum,

a part of said drum extending between said main magnets and said bucking magnets,

a stationary housing disposed between said drum and said bucking magnets,

said stationary housing and said drum defining a flow path for said materials.

3. The separator recited in claim 2 wherein:

means is provided for adjusting said bucking magnets rotatably in relation to said main magnets whereby the effect of said of said bucking magnets on the field of said main magnets is altered.

4. The separator recited in claim 3 wherein:

means is provided for moving said bucking magnets toward and away from said main magnets whereby the magnetic field may be made stronger or weaker.

5. The separator recited in claim 4 wherein:

one said bucking magnet is disposed adjacent each said main pole.

6. The separator recited in claim 5 wherein:

means is provided for adjusting said bucking magnets toward and away from said main magnets and to adjust rotatably in relation to said main magnets whereby the effect of said bucking magnets on the field of said main magnets is altered.

References Cited UNITED STATES PATENTS 2,088,364 7/1937 Ellis 209232 X 2,466,839 4/1949 Caldwell 209219 X 3,146,191 8/1964 Greenwald 209223 3,168,464 2/1965 Ferris 209232 X 3,209,912 10/1965 Sloan 209223 2,733,812 2/1956 Hoff 209223 SAMIH ZAHARNA, Primary Examiner R. HALPER, Assistant Examiner US. Cl. X.R.

Claims

1. A MAGNETIC SEPARATOR COMPRISING: A BACK BAR, SPACED PERMANENT MAIN MAGNETS FIXED TO SAID BACK BAR, AND SAID MAGNETS HAVING A FACE SPACED FROM SAID BACK BAR, SAID MAIN MAGNETS EACH HAVING A MAGNETIC POLE ADJACENT ITS SAID FACE OF OPPOSITE POLARITY FROM THE POLE OF THE MAIN MAGNET ADJACENT THERETO, REPELLING MAGNETS DISPOSED BETWEEN SAID MAIN MAGNETS, MEANS TO DIRECT A STREAM CONTAINING NONMAGNETIC MATERIAL AND MAGNETIC MATERIAL IN CLOSE PROXIMITY TO SAID FACES OF SAID MAGNETS AND THROUGH MAGNETIC FIELDS PRODUCED BY SAID MAIN MAGNETS, WHEREBY SAID MAGNETIC MATERIAL IS SEPARATED FROM SAID NONMAGNETIC MATERIAL, SAID REPELLING MAGNETS EACH HAVING A MAGNETIC POLE AT EACH SIDE THEREOF OF LIKE POLARITY TO THE POLE OF THE MAIN MAGNET AT SAID FACE THEREOF, WHEREBY THE LEAKAGE FIELD OF SAID MAIN MAGNETS IS REPELLING AND REINFORCES THE NORMAL FIELD WHICH IS FORCED OUTWARD TOWARD SAID STREAM OF MATERIAL, A PLURALITY OF BUCKING MAGNETS BEING DISPOSED IN AN ARCUATE PATTERN OUTSIDE OF SAID MAIN MAGNETS WITH ONE POLE OF EACH SAID BUCKING MAGNET DIRECTLY OPPOSITE AND FACING A LIKE POLE OF SAID MAIN MAGNET.