US2156125A - Method of wet magnetic separation - Google Patents

Description

April 25, 1939. Q 'PAYNE 2,156,125

METHOD OF WET MAGNETIC SEPARATION Filed March so, 1937 2 Sheets-Sheetl 15 E E l April 25, 1939. c. Q. PAYNE METHOD OF WET MAGNETIC SEPARPTION 2 Sheets-Sheet 2 Filed Mach 30, 1957 YNE INIVIENTOVR (ma /v05 Q.

' Patented Apr. 25, 1939 UNITED STATES PATENT- OFFICE 1 Claim.

This invention relates to a method of wet magnetic separation of ores and minerals, especially those which are finely divided, and is applicable to the separation both of strongly and also of feebly magnetic minerals.

An important object of the invention is to control the gravitational and electrostatic forces which tend to interfere with magnetic attraction exerted on the particles while they are underlO going separation. This is accomplished by feeding the mixed particles in the form of a water diluted feed-stream into a water filled tank, then thickening the feed-stream as it descends to a submerged magnetic field in the tank by removing a practically clear-water over-flow from the top of the tank and at the same time regulating the descent of the thickened pulp by controlling the,

areas of the discharge outlets for the separated products at the bottom of the tank so that the velocity of descent through the magnetic field will be sumciently reduced for the deflection of feebly magnetic particles while passing therethrough.

Other objects and advantages of the-invention will appear as the description proceeds.

The accompanying drawings show two forms of magnetic separators for carrying out my improved method.

Fig. 1 is a vertical section of a separator which uses a single magnetic field on two flux circuits.

Fig. 2 is a vertical. section on the line II-II of Fig. 1.

Fig. 3 is a horizontal section with parts broken away on the line III-III of Fig. 1.

Fig. 4 is an enlargedperspective view of portions of interleaved magnetic and nonmagnetic rotor disks, having. open longitudinal grooves along their circumferences.

Fig. 5 is a perspective view of a modified form 0 of magnetic and nonmagnetic disks with longitudinal grooves filled with nonmagnetic material.

Fig. 6 is a vertical section through a modified form of a double-pass separator along the line VI-VI of Fig. 8 having superposed electromag- 5 nets, each having two magnetic fields on a single fiux circuit.

Fig. 7 is a horizontal section along the line- VII-VII of Fig. 6.

Fig. 8 is a longitudinal sectional elevation on the line vm vm of Fig. 6. 1

Ores and minerals, especially when finely divided as in the case of clays, slimes, or those crushed to pass about one hundred mesh screen or finer, present serious difiiculties to their mag- 'netic separation .when they are in the dry state.

. GIGS.

This may be briefly explained as due toenmeshment or clotting. It may becaused either by absorption of moisture from the atmosphere, or by impressed forces such as an electrostatic charge between minerals of different composition when they are moved upon each other. In either feed and wash-water to hasten the passage of the ore through the magnetic field.

The purpose of the method of wet separation herein set forth is to greatly enlarge the scope and value of inductive magnetic separation by permitting ores to be treated which have not In all cases however, free use is made of This method while capable of exerting the utmost attracting force upon the feed-stream as it passes through the submerged magnetic field-gap is also able to control the velocity of descent of the latter and therefore also the separating force, by eliminating the feed water by overflowing it as it enters the tank in which the separation takes places. Dealing in this way with the regulated speed of subsidence of fine particles in water. it is possible to attract and separate, more easily, those feebly magnetic minerals such as iron silicates, hornblende, biotite, garnet, etc. which can only be acted on when fine, by careful adjustment between the attracting and separating forces. Freedom of motion of the particles among themselves is thus assured, and their effective.

weight is reduced by the amountof water which they displace. In effect their resistance to separation is thus reduced when submerged. It also permits those tiny occluded and middling par ticles to be'defiected and separated to a much greater degree than has heretofore been possible by means of dry separation.

In the form of magnetic separator illustrated shaft II below the'electromagnets. The shaft I1 is driven from a pulley I8. The laminated diskrotor I3 forms the armature of the electromagnets and serves also as a separating drum on which the material to be separated is fed from a 'water filled hopper I9 placed above it. The

rotor I3 revolves between concentric faces of the pole pieces I2 with substantially equal gap on each side in order to balance the magnetic attraction of the pole pieces. The width of the field gap between the pole pieces i2 and rotor 93, in which the separation takes place, is regulated to suit the size of the particles to be separated and is as narrow as practicable to reduce the reluctance of the magnetic circuit. The electromagnets it) are connected to the current supply so that one yoke will convey. only north magnetism to one pole piece, while the other yoke conveys only south magnetism to the other pole piece. In this way a single magnetic field is .formed upon two flux circuits as shown by the broken lines and arrows in Fig. 3. The thickness of the magnetic disks 4D and nonmagnetic disks 4i forming the rotor I3 will depend upon the size of the ore particles to be separated. They are provided with horizontal grooves 42 along their circumference in order to increase their holding power by means of. the highly convergent magnetized points at the groove intersections as well as at the groove and disk edges themselves, as shown in Fig. 4-. These horizontal grooves may be closed by means of nonmagnetic strips B3, as shown in Fig. 5, where it is important to give the rotor a smooth outer surface. The horizontal grooves may also be left open as shown in Fig. 4 where itis desirable to afford some support for the particles undergoing separation as they are carried through the field-gap. The rotor shaft I1 is supported in stufiing-box bearings 20, which are attached to nonmagnetic cheek-plates 2I at each end of the rotor. These fit water tight to the ends of the pole pieces I2 and with the pole pieces form the central portion of the tank'in which the separation takes place. It is desirable to protect the surface of the rotor and the faces of the pole pieces with chromium or cadmium plating to prevent rusting. The hopper I9 forming the upper part of the water tank is detachable and has its upper edge surrounded by a continuous trough 22. the overflow from the dilute feed pulp to be collected and discharged to one side. Above the main hopper is a smaller partly submerged V- hopper 23 which is supported upon the upper edge of the main hopper. This smaller feed hopper 23 is of about the same length as that of the rotor, and a plate 24 underlies its discharge opening. The plate 24 deflects the feed-stream of materials to be separated which is discharged in thin sheets 24a towards both sides of the main hopper and enables the feed-water which is introduced with the ore str'eam, to rise and overflow the top of the main hopper as practically clear water while the thickened pulp descends in a. disseminated cloud through the upper part of plates 25 and 26 and is fed to the charged rotor This enables I3 which revolves in the direction shown by the arrow in Fig. 1. The nonmagnetic particles descend along the stationary side of the field gap and fall vertically 28 when they are released and discharged as they approach the neutral plane of the rotor where all attractive force of the rotor ceases,

' owing to reversal of polarity. They are then deflected at a divergent angle from the non-magnetic particles and fall vertically on the other side of the division plate into, a separate hopper 29 thus efiecting their separation from the latter. I

A brush or scraper 30 serves to dislodge fine steel particles sometimes present in the ore and carried past the neutral line. The receiving hoppers 27 and 29 are bolted water tight to the bottom of the tank which contains the disk rotor.- At the discharge ends of these hoppers plug-cocks 3| and 32 are located whose openings can be closely regulated. By varying the openings of these valves 3| and 32 the separated products obtained from the thickened feed-pulp can be discharged either slowly or else rapidly from the separator as the necessity of the material undergoing separation may! require. As a further means of regulating and equalizing the velocity 1' of the downward water current through the fieldgap it is advisable to provide bafiles 33, 34 in the upper part of each of these hoppers.

When the field coils of the electromagnets have been energized to secure the required magnetic I- fiux across the field gap, the rotor is caused to revolve in the direction shown by the arrow..

The material to be separated is then fed below the water level of the main hopper tank by means of the small distributing V-hopper 23. The material is thus enabled to free itself more readily from the feed-water which accompanies it and the greater part of the feed water discharges over the top edge of the main tank into the trough 22 as practically clear water. In some cases where the finely ground material is very much diluted, it may be advisable to employ an intermediate settling tank in order to thicken the pulp before feeding it to the separator; In certain cases as in treating clays, it may also be advisable to add an electrolyte to the separator feed tank, such as sodium chloride or caustic starch, in order toremove cloudy suspensions and to hasten the settling of the fine particles. As they descend, the particles are collected by the guide plates 25 and 26 and are fed upon the rotor I3. The magnetic particles are attracted and held to the charged edges and points of the rotor until they are carried over the edge of the division plate 28.

The nonmagnetic particles on the other hand pass through the field-gap without being deflected, and are collected in a separate hopper whose discharge rate is controlled by means of the plugcock 32. of feed, the speedof the rotor and strength of the fieldpboth the attracting and the separating forces can be brought under closer control than has heretofore been possible, especially in the case of finely divided ores and minerals.

A modification of the design of separator described above and its application to the separation of finely divided materials into three products by means of two superposed electromagnets is illustrated in Figs. 6, 7 and 8. In this form of embodiment of my invention, bipolar electromag- In this way and byvarying the rate nets 5B and 52 are shown m Fig. 6 in their superposed position, each of which has two rotors 5|, 5m, 53 and 53a mounted on shafts 56 and 51. These are so assembled with single yokes 54 and 55 that with the aid of keepers 83 and 84 they secure two magnetic fields upon the same flux circuit generated by the electromagnets as shown in Fig. 7. In this design the iron path of the flux circuit can be made somewhat shorter in relation to the length of field-gap available for separation, than in the design shown in Figs. 1, 2 and 3. The

two electromagnets 5G and 52 may be energized to produce a clean magnetic concentrate 58 from the top electromagnet 50 and a clean tailings 59 and middlings product 80 from the bottom electromagnet 52. The two successive magnetic products may also be combined where they are to be discarded, and where the main object is to secure a clean nonmagnetic product from the crude material by means of a double pass as illustrated in Fig. 6.

The mechanical features in the form of sepa rator illustrated in Figs. 6, 7 and 8 may differ from that illustrated in Figs. 1, 2 and 3 in that the partly submerged V-hopper 6| here has a feed roller 62 underlying its discharge opening in place of plate 24 illustrated in Fig. 1. The feed rollers 62 and 62a revolve with the shaft 63 and deflect the feed-stream of the materials to be separated in such manner that it is discharged in a thin sheet 64 toward the inclined portion 65 of the main hopper. It then falls to the inclined guide plate 66 from which it is fed to the upper charged rotor 51 or 5| a which revolves in the directionshown by the arrow in Fig. 6.

The particles which are not attracted by the magnetized edges and points of disks 40 of rotors 5| and 5 la fall vertically into the hoppered opening formed by the inclined plates 61 and 68. These are supported above rotors 53 and 53a and guide the particles upon the lower charged m tors 53 and 53a. which separate the remaining magnetic particles from the material which has been fed to them. The nonmagnetic portion descends into hopper 69, while the magnetic portion of the material is discharged over the division plate 10 as the rotor 53 or 53a. loses its power of attraction at the neutral line due to reversal of polarity.

The particles 58 which have beenattracted and deflected by the energized rotors 5| or 5M.

and carried over division plate 12 may also be collected in hopper I5 along with magnetically attracted particles 60 which have been separated from the nonmagnetic particles 59 by the lower set of rotors 53 or 530 where only two separated products are desired.

The separating rotors in the form illustrated in Figs. 6, '7 and 8 may be revolved by a chain drive connecting the sprocket wheels amxed to the rotor shafts and the counter-shaft 16 which in turn is driven by the pulley 82. Feed-roller shaft 63 is drivably connected to counter-shaft 16 by means of sprocket wheel 17, an endless chain 18 and a sprocket wheel mounted on feed-roller shaft 63. Sprocket wheel I8 which is mounted on counter shaft I5 is drivably connected with rotor shaft 56 by means of a drive chain 19 and a sprocket wheel mounted on said rotor shaft. Another sprocket wheel mounted on shaft 55 serves to drive rotor shaft 51 with the aid of an endless chain and sprocket wheel 8| mounted on shaft 51. By varying the relative size of these sprocket wheels, the speeds of the various rotors may be varied to suit the nature of the material to be separated.

The principle involved in both the above described designs is, however, the same. The dilute feed-stream is fed into the top of a water filled tank and is thickened as it descends to the submerged magnetic fields by removing a practically clear-water overflow from the top of the tank. The actual separation of the nonmagnetic from the magnetic particles is accomlished by one or more energized rotors, in the tank. while the speed of descent of the thickened feedstream is controlled by varying the areas of the discharge outlets for the separated products at the bottom of the tank.

I wish it to be understood that my invention is not limited to a combination of the specific elements or to the specific structures illustrated in the drawings, but that" it includes all such variations as come within the spirit and scope of the disclosure herein and the claim appended hereinafter.

I claim:

The method of wet magnetic separation of ores and minerals containing feebly magnetic and nonmagnetic particles which consists in submerging them in a tank of water thereby reducing their eifective weight, causing the particles of ore to fall through the water and along guide plates into a submerged arcuate magnetic field gap formed between an arcuate faced pole piece and a" horizontal magnetic rotor submerged in said tank and attracting the magnetic away from thenonmagnetic particles within said gap by feeding them along the arc of said horizontal rotor in direct contact therewith in said magnetic field, substantially as and for the purpose described.

. CLARENCE Q. PAYNE.

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