US3503504A - Superconductive magnetic separator - Google Patents

Description

March 31, 1970 J. D. BANNISTER SUPERCONDUCTIVE MAGNETIC SEPARATOR 2 Sheets-Sheet 1 Filed Aug. 5, 1968 M Ua w un MP M U WP FIG. 4

//v VEN TOR 1.2 BANN/STER ATTORNEY J. D. BANNISTER SUPERCONDUCTIVE MAGNETIC SEPARATOR March 31 1970 Filed Aug. 5, 1 968 2 Sheets-Sheet 2 R Du U L S ENTRANCE IN VENTOR J. D. BANN/STER 8V ATTORNEY United States Patent O 3,503,504 SUPERCONDUCTIVE MAGNETIC SEPARATOR John D. Bannister, Summit, N.J., assignor to Air Reduction Company, Incorporated, New York, N.Y., a corporation of New York Filed Aug. 5, 1968, Ser. No. 750,162 Int. Cl. H01f 7/22; B03c 1/02 U.S. Cl. 209-223 20 Claims ABSTRACT OF THE DISCLOSURE System employing a superconducting magnet for separating magnetic and nonmagnetic components. A preferred embodiment takes the form of an ore separator in which the magnetic element is a thin panel of normally conducting material which encloses an array of super conductive magnetic coils. The panel is maintained at cryogenic temperatures by liquid helium circulating between the coils. A rotating disk serves to move a. slurry comprising magnetic and nonmagnetic components adjacent to the magnetic panel, where the magnetic components are deflected by the magnetic field, permitting the nonmagnetic gangue to move out through one exit channel. The magnetic components clinging to the disk are subsequently moved out of the magnetic field by further rotation of the disk, and are washed oif of the disk and removed through a separate exit channel.

BACKGROUND OF THE INVENTION This relates in general to magnetic processing of minerals, and more particularly to the separation of weakly magnetic constituents from a slurry containing mine tailings.

Various techniques using conventional iron core magnets have long been employed to separate magnetic minerals from the gangue. In current practice, for example, taconite ore is crushed and wet-ground to form a slurry from which the strongly magnetic fraction comprising magnetite is picked up by low intensity magnetic separators, which may, for example, be rotating drums containing conventional magnets of either electric or permanent types having fields within the range 600 to 900 gauss. The nonmagnetic gangue and weakly magnetic iron constituents are discarded in the tailing.

Conventional magnetic separators function inadequately for the reclamation of the weakly magnetic ores from the tailings, so that the latter are economically lost. The reasons for this are as follows. Conventional magnetic separators have the inherent disadvantage of being limited to field strengths of about 20,000 gauss, which is the limit of the magnetic saturation of the iron core required to control the field. Because of this, the maximum field strength attainable with iron-core magnets is strictly limited, and the gap between the pole pieces of the magnet is necessarily narrow, restricting the volume of material sifting through, and leading to clogging.

Accordingly, it is the principal object of the present invention to substantially improve the magnetic processing of minerals, particularly the weakly magnetic types, by the employment of super-magnets of a type not heretofore used for this purpose.

More specific objects of the invention are to provide high intensity magnetic separators which are characterized by substantially increased space for processing material subject to the magnetic field, thus accommodating a greater volume flow of material with less clogging.

A further object is to provide a magnetic separation system having better dynamics of the slurry stream then prior art processes.

Brief description of the invention These and other objects are achieved in accordance with the present invention in a device employing one or more superconducting coils for the magnetic processing of minerals, more particularly weakly magnetic minerals such as are usually discarded in the tailings of magnetic separators of the prior art types. Such a device may take the form of a panel comprising a superconducting coil or coils sandwiched between parallel plates of normally conducting material, forming a closed segment in which the coil or coils are maintained in a cryogenic environment. Ore containing weakly magnetic constituents passes in a slurry past the faces of the panel. The weakly magnetic constituents are attracted to and held adjacent the panel by the magnetic lines of force emanating from its face. The concentrated magnetic ore is later removed from the magnetic field by mechanical means, while the residual gangue passes from the device with the slurry.

In accordance with one embodiment of the invention, the superconducting magnetic panel takes the form of a segment of a circular disk, comprising a pair of parallel copper face plates enclosing between them an array of small superconducting coils. These coils are formed from superconducting wire or ribbon, mounted in a regular array, and wound and energized in such a manner that the field strength and field gradient of the panel are maximized in the area over the slurry channel. The superconducting panel is enclosed in a hollow disk-shaped chamber which rotates about a central axial hub with respect to the magnetic segment. The ore bearing slurry is passed in a thin layer over both sides of the rotating disk-shaped chamber. The weakly magnetic ore is attracted to and held on the rotating disk by the force-field emanating from the magnetic panel. The disk then rotates the concentrate comprising ferromagnetic material out of the magnetic field, where it is removed from the disk by a wash stream.

In preferred form the superconducting coils in the magnetic panel, which are formed from ribbon comprising a deposited layer of Nb Sn, are refrigerated to about 42 Kelvin by liquid helium piped to the panel through the hub of the disk. Inside the magnetic panel, the liquid helium is circulated between the pancake-shaped coils of superconducting ribbon which are mounted on copper supports connected between the copper face plates. The coils are conduction-cooled by the liquid helium flowing in channels. The coils are insulated from the environment by several layers of superinsulation which serves to support the evacuated interior of the panel against the external pressure. The vacuum pumping lines and electrical connections to the magnetic panel pass through the hub of the disk. It is contemplated that the size and eifective magnetic field volume of this embodiment of the invention can be extended by using several magnetic segments in parallel on the same hub.

It has been estimated that, using the invention in the form of the preferred embodiment, operating on taconite tailings from which the magnetite fraction has already been removed, 60% recovery of the iron-bearing minerals can be obtained from a tailings stream in concentration.

Although a specific form of the invention described by way of example, hereinafter, relates to the separation of the magnetic fraction from the tailings of taconite ore, it is anticipated that the invention has many additional applications in other mineral operations in both metallic and non-metallic industries. A few examples are recovery of red mud (bearing iron ore) from bauxite processing, the treatment of molybdenum ores, the treatment of nickel ores, the beneficiation of glass sands, and the beneficiation of clay for use in the paper, rubber, and pottery industries.

A particular advantage to be realized in the use of the present invention is that higher magnetic fields, of the order of several tens of kilogauss and higher gradients can be generated with superconducting magnets. Moreover, the use of superconductive coils makes practical the employment of large numbers of small magnetic coils in a panel array, further increasing the field strengths and gradients available using the present invention over those available using prior art iron core magnets. Further, the use of air-core magnets, as opposed to iron-core magnets, removes the field strength limitation imposed by the magnetic saturation of the iron core. This permits wider spacing adjacent the magnetic panel, thereby substantially increasing the rate at which material can be sifted through the apparatus without substantial clogging, and facilitating the processing of fine-ground material.

In the specification and claims hereinafter, the term superconductor is applied to certain metals whose electrical resistance vanishes at a temperature known as the critical temperature, which is a function of the specific superconducting material, and which up to the present time has not been known to exceed about 20 Kelvin. A material which cannot be rendered superconducting at a given reference temperature, and which conducts normally at the temperature, is known as a normally conducting material. The phenomenon of superconductivity, including the properties and characteristics of superconductors, together with definitions and explanations of the foregoing terms and others used by those skilled in the art to describe their behavior, is set forth in detail in the literature and in textbooks, including, for example, Superconductivity by C. A. Lynton, published by Methuen & Co. Ltd., 1962.

Other objects, features, and advantages of the invention will be apparent from a study of the specification hereinafter with reference to the attached drawings.

Short description of the drawings FIG. 1 is a showing in cross section of a magnetic ore separator in accordance with the present invention;

FIG. 2 is a showing in side section along the line 2-2 of the ore separator of FIG. 1;

FIG. 3 is an enlarged cross sectional showing of a stationary hollow sector 15 of FIG. 1;

FIG. 4 is a side sectional showing of the stationary hollow sector 15 of FIG. 3, along the line 44 of FIG. 3;

FIG. 5 is a further enlargement, in cross-section, of a portion of the inner magnetic panel 19 of FIG. 3; and

FIG. 6 is a side sectional showing of the portion of the inner magnetic panel 19 shown in FIG. 5, with one of the copper cover plates removed.

Detailed description of the drawings The principles of the present invention can best be described with reference to the specific embodiment shown in cross-section and side section in FIGS. 1 and 2, respectively, which is designed to operate on the tailings of a conventional taconite ore separator. The drawings are intended for purposes of illustration and are not to scale. For processing by the latter, the ore has initially been crushed and wet-ground to form a slurry, from which a fraction comprising largely magnetite has been separated out by low intensity magnetic separators. These separators (not shown) are rotating drums containing conventional magnets, of either electric or permanent types, having fields which are of comparatively low intensity, of the order of 600 to 900 gauss. The nonmagnetic gangue and weakly magnetic iron, including hematite and similar iron metals from the taconite processing, are descarded in the tailings.

The system of FIGS. 1 and 2 includes a cylindrical drum 1 in which is mounted a rotating disk-shaped chamber 2, the periphery of which moves between the upper slurry entrance 3, in which the tailings of the taconite separator are received in a moving stream, and a pair of exit channels 4 and 5, where the magnetic residue and the gangue are drawn off separately. The heart of this system is a stationary sector 15 including an inner magnetic panel 19 which is mounted inside of the disk 2 in such a manner that it remains in a stationary position in the right-hand lower quadrant during rotation of the disk. Sector 15 comprises a hermetically sealed, evacuated chamber enclosing an insulated cryogenic environment in which is mounted an array of superconductive coils 16 in a panel 19 of normally conducting material (see FIGS. 3 and 4). The coils are disposed to generate a magnetic field having lines of force which are substantially normal to the plane of rotation of disk-shaped chamber 2.

Referring in detail to FIGS. 1 and 2 of the drawings, housing 1 is a hollow cylindrical drum comprising, for example, a steel shell /2 inch thick, having an abrasion resist-ant inner coating of hard rubber or the like 0.2 inch thick. The housing 1, in the present illustrative example, forms a cylindrical inner cavity 12 feet in diameter and 4 inches deep, except for the centrally disposed hub portion 12 which is 1 foot in diameter and 4 feet deep. The housing 1 includes an entrance channel 3 which projects upwardly in a direction approximately tangential to the curved upper periphery of the housing 1. Channel 3 provides an elongated rectangular mouth of 1 ft? cross sectional area designed to accommodate the infiowing stream of slurry. Leading out of the lower end of housing 1 are a pair of channels, including one ore exit 4 for the magnetic residue, and a gangue exit 5. The latter, approximately the same size as channel 3, is centered at an angle of about moving in a clockwise direction around the periphery of the housing from the center of the slurry entrance 3. Exit 5 projects out in nearly a radial direction from the housing, and is designed to be in nearly a straight-line path below the slurry entrance 3. The ore exit chanel 4, approximately the same size as the others, is removed around the periphery of the housing 1 in a clockwise direction so that its center line forms an angle of about 45 with that of the gangue exit 5.

Mounted inside of the cylindrical housing 1 is a disk shaped chamber 2, formed, for example, of a thin shell of hard rubber, or alternatively, hard rubber on a steel shell, or the like. Chamber 2 is 11 feet 9 inches in inner diameter and 2 inches across the interior. At its center, it is shrunk onto two axial steel hollow drive shafts 2a, 2b, each 9 inches in diameter and having a Mr inch wall thickness. Shaft 2a extends 6 inches out from the center of the left-hand face of disk-shaped chamber 2, and shaft 2b extends 12 inches out from the center of its right-hand face. Projecting drive shafts 2a, 2b are mounted to revolve, causing disk-shaped chamber 2 to rotate about the short axis through its center. The drive shafts 2a, 2b may ride, for example, between systems of ball or roller bearings 7a, 7b and 7c, 7d, respectively, which are respectively interposed between the inner wall of housing 1 and the outer surfaces of shafts 2a, 2b, and between their inner surfaces and the outer surface of bearing pipe 11. The latter is of stainless steel, 6 inches in diameter, having a wall inch thick, projecting an axial distance of, say, 16 inches in each direction from the longitudinal axis of the disk 2.

Sealing means 8a, 8b are interposed between the bearings 7a, 7b and 7c, 7d and the drive shafts on each side, to seal the interior chamber of the housing 1 and to protect the bearing 7 from the abrasive slurry. This may take the form, in each case, of a mechanical seal, well known in the art.

Disk 2 is disposed to revolve about the axis at its center by means of a drive sheave 6, which is fixed to the right-hand end of the hollow drive shaft 2]) The drive sheave 6 is connected through a conventional system of gears (not shown) to a conventional motor drive (not shown), which drives the disk 2 to rotate clockwise, in the present model, at a rate of, say, 16 revolutions per minute, so that the peripheral portion of the wheel moves at a linear velocity of about 5 feet per second, comparable to the rate of flow of the slurry in entrance channel 3, as will be discussed hereinafter.

Inside of the revolving disk-shaped chamber 2 is fitted the stationary hollow sector 15, which is shown in detail in cross and side section, respectively, in FIGS. 3 and 4, and which is a salient feature of the presently described embodiment. Hollow sector 15, which is shaped to fill approximately one quadrant of the disk-shaped cham ber 2, the latter revolving freely with respect to it, comprises a stainless steel outer shell having walls .040 inch thick. These enclose a chamber, rectangular in cross-section. 1 /2 inches across the interior, 5.5 feet along each of the radial edges, and feet, approximately, along the peripheral edges, defining a pair of matched semicircular sector plates a and 15b, disposed with their principal surfaces parallel to each other. The inner edge of the hollow sector '15 is centered on an inwardly curved closure plate 11a formed of stainless steel /2 inch thick, which is 6 inches across and extends about 90 around the interior of the pipe 11 (see FIG 1). The closure plate 11a includes a plurality of openings into which are hermetically sealed conduits for evacuating the hollow inner space of sector 15, conduits leading to and returning from a source of liquid helium, and conduits leading to and returning to a source of power, as will be explained hereinafter.

Symmetrically positioned inside of the outer shell provided by hollow sector 15, is an inner magnetic panel 19 formed of normally conducting material which is de signed to accomodate in sandwich fashion an array of superconductive coils 16. On the exterior, panel 19 is shaped similarly to hollow sector 15, but somewhat smaller, comprising a pair of panel plates 19a and 1% which are 5.4 feet on each of their radial edges, 9.5 feet around the periphery, .250 inch thick, and spaced with their inner surfaces .1 inch apart.

The space between the outer shell comprising walls 15a, 15b of the hollow sector 15 and the parallel inner plates 19a, 19b of magnetic panel 19 is filled with superinsulation 18 which may comprise, for example, sheets of aluminized Mylar .(Registered trademark of E. I. du Pont de Nemours & Co.) film, having a thickness of, say, /2 mil, tightly packed together. In addition to insulating the inner space, this serves to hold the inner chamber 19 in place, and keeps the hollow sector 15 from collapsing. The hollow sector 15 is evacuated to a pressure of, say, 10* millimeters of mercury through a duct 17 leading to a vacuum pump 17a, and is then hermetically sealed.

Plates 19a and 19b, and the closed ends of the inner panel 19, are formed of copper inch thick. For preferred operation, this may comprise a copper manufactured by the American Metal Climax Company under the trade name OFHC brand copper, of which the analysis is specified on page 6 of their brochure entitled OFHC Brand Copper at Work, a case book of applications, Amex Publication OF/66-2780. The copper, in a preferred embodiment, should have a resistivity ratio within the range 100:300, where the ratio represents the resistivity at room temperature divided by the resistivity at 42 C. It will be understood that other normally conducting materials, such as, for example, aluminum, or alternatively, gold or silver, are useful for the purposes of the present invention, instead of, or in addition to, copper. The function of the normally conducting panel 19, in addition to providing a mounting for the superconductive coils 16, is to prevent instability in the superconductive coil due to what is known in the art as flux jumping.

Referring again to FIGS. 3 and 4, one of the enclosing A inch thick copper inner shell plates 19a, 19b, which are fastened together in a press fit, is removed to reveal an ordered array of pancake-shaped superconducting coils 16. Each pair of coils 16 is mounted on one of the copper posts 16a, which pass through the thickness of the inner shell 19a, 19b, the ends being integrally fixed in the panel sidewalls. This is more clearly shown in FIGS. 5 and 6 which are detailed showings of the arrangement of the coils 16 in the magnetic panel 19. In the present example, coils 16 which are 2 inches in diameter and .1 inch thick, are mounted in rows as shown in FIGURES 3, 4, 5 and 6 of the drawings, parallel to each of the radii of the quadrant sector. In the present example, each of the coils is formed of ribbon comprising a thin film of superconducting material such as, for example, Nb Sn or niobium titanium, which has been diffused onto a substrate. This may comprise a stainless steel or Hastalloy (registered trademark of Union Carbide Corporation) substrate, /2 mil thick and .05 wide and having a silver coating, processed to form superconductive ribbon in the manner described in detail, for example, by E. R. Schrader and E. Kolondra in an article entitled Analysis of Degradation Effects in Superconductive Niobium Stannide Solenoids, RCA Review, vol. XXV, September 1964, and which is known as RCA Development No. R-602l4 Niobium-tin Superconductive Ribbon.

A portion of the panel array of FIGS. 3 and 4, including the pancake-shaped coils 16 of superconductive ribbon, mounted on copper posts 16a and arranged in regular rows, is shown schematically in detail in the enlarged cross section in FIG. 5, and in the enlarged sidesection in FIG. 6 of the drawings. The coils are set in double layered pairs, the winding in each case being from the center outward, with cross-over from one layer to the other being made at the center post 160, the two ends being wound clockwise and counterclockwise, respectively, to form the upper and lower coils. Alternate coils are wound in opposite directions, the electrical cross-over being made from one pair of coils to the next, at the periphery of the first upper layer coil, and at the periphery of the next under layer coil, etc.

All of the coils are connected in series to minimize the current requirement of the power supply and supply busses. The coils are connected in rows, and crossovers from row to row are made at alternate ends of the rows. The coils are wound in a manner to give a pattern of alternate north and south poles on each face of the panel, which will give the maximum magnetic force field over the volume of the slurry passage.

It will be noted that the force on a weakly magnetic particle in a magnetic field is defined by the following equation:

F =kVHdH/ dy where: F=force k=volume susceptability of particle V: particle volume H=field strength, and

dH/dy :field gradient It will be seen by reference to FIG. 6 that a direct current of, for example 300 amperes passes from the 3 watt source of power 24 through the input trunk lead 21, traverses the series-connected circuits in the panel 19, and returns to source 24 through trunk conduit 22. The potential drop between the input conductor 21 and output conductor 22 is, for example, 0.01 volt. Starting from trunk line 21, the current traverses the first pair of coils, passing downward through the thickness of the panel, and in a reverse direction, returning upward through the thickness along the next pair of coils. In this manner, the current conducting path proceeds down one row of coils, and back the next, the last coil of the last row being connected to the output through the trunk line 22. In the example under description, the fiow of current generates in panel 19 a high intensity magnetic field of the order of 35 kilogauss through the thickness of the copper panel, providing areas alternately poled positive and negative, so that the panel is characterized by areas of steep field gradient.

To provide the proper cryogenic environment for energizing the superconductive coils 16, the channels between the coils are filled with circulating helium brought into panel 19 through conduit 1411 (see FIGS. 3 and 4) from the source 27, which includes a compressor for providing a stream of helium at a pressure of 16 pounds per square inch absolute and a temperature of about 4 Kelvin, flowing at the rate of 15 gm./sec. Conduit 14a is surrounded by a vacuum-insulated pipe. The liquid helium is vaporized as it flows through the channels surrounding the coils 16, returning as gas through the pipe 14b to the compressor connected to helium source 27.

In operation, the separator works as follows. After the initial step in which the magnetite fraction of the crushed taconite ore has been substantially removed from the slurry by conventional magnetic separators (not shown), the tailings from these separators, including nonmagnetic gangue and weakly magnetic iron having a high component of hematite, serve as the raw materials for the separator disclosed in FIGS. 1 and 2 herein.

The slurry, as it flows into the intake channel 3, is about solid in a water carrier, of which about 9% is weakly magnetic material, including mostly hematite, and the remainder of which is nonmagnetic ganguge. The average particle size is about .375 inch. The slurry flows into the entrance pipe 3 at a mass flow rate of about 10 cubic feet per second, and at a linear velocity of about 5 feet per second, falling in a substantially even stream on the outside edges of revolving disk-shaped chamber 2, being carried partly by gravity and partly by rotation of the disk to gangue exit 5. Since the latter is located in nearly a straight line path directly below the slurry entrance 3 it is in a position to receive the nonmagnetic gangue which falls off of revolving disk 2. As the slurry reaches the area adjacent the magnetic segment 15, the magnetic material, including the hematite component, is drawn by the high intensity force field, which extends from the front to back face of the panel 15, and clings to the outside of the rotating disk 2. The rotation of the hollow rubber disk 2 removes the clinging magnetic material beyond the effective field of the magnetic sector to a point beyond the exit channel 5 and adjacent the exit channel 4 where one or more high velocity streams of water are directed against the face of the revolving disk 2, disengaging the weakly magnetic residue, which subsequently flows out through the channel 4 where it is collected for further processing. Salient characteristics of the disclosed illustrative embodiment are given in Table I.

TABLE I Characteristics of illustrative ore separator of present invention Slurry channel on each side of the panel:

Depth-inches 1.0 Panel area-square feet 24 Superconducting magnet, coils per square foot 9 Magnetic field (on a coil centerline):

At the panel-kilogauss 35 At one inch from the panel-kilogauss 7 Slurry speedfeet per second 5 Estimated concentrate output at:

60% recoverytons per hour 27 60% recovery-tons per year (235,000)

The figures in Table I are based on a number of simplifying assumptions. In the illustrative separator the magnetic force on a hematite particle is estimated at 100 times the force on a magnetite particle in a conventional separator. Use of this high force-field creates the possibility of collecting gangue with the concentrate. Thus, a useful separation in accordance with the principles of the present invention may involve multiple stages of weaker force fields. While the ratio of forces on particles of low but differing susceptibilities is constant with increasing field strength, the difference between these forces becomes larger and allows for easier adjustment of the separation parameters to effect a separation. Clearly, any given separation requires empirical adjustment of the number of stages, the slurry concentration, the particle velocity, the channel depth and length, and the force-field strength. It is conceivable that in some practical applications, separation may require stronger fields or more stages than disclosed herein, resulting in an increased superconducting ribbon requirement.

It will be apparent that the embodiment under description should be constructed to insure long-term reliability under very strenuous mechanical service. In particular, the problem of maintaining structural integrity while passing the very abrasive slurry as close as possible to the coil windings is paramount.

Although the invention has been described with reference to a specific embodiment for separating hematite and weakly magnetic ore from the tailings of a taconite separation system, it will be understood that the principles of the invention have much broader application, and that the particular materials and forms of the components disclosed may be changed to meet the specific necessities of each application. Moreover, the present inventive concept of employing a superconductive magnetic system for the purposes of separating out ferromagnetic material from non-magnetic material is not restricted to constructions employing an array of small magnets of the type shown by way of illustration; but, it is within the contemplation of the invention that for certain types of embodiments a single large magnetic configuration employing the principles of superconductivity may be preferable.

It will be understood by those skilled in the art that the scope of the present invention is not restricted to the particular structures and/ or parameters disclosed herein by way of illustration; but, that the scope of the invention is defined in the appended claims.

I claim:

1. A system for separating out desired magnetic components from material containing a mixture of magnetic and non-magnetic components, said system comprising an entrance channel for accommodating a moving stream of said mixture and a plurality of separated exit channels comprising a first exit channel accommodating streams comprising primarily non-magnetic components and a second exit channel for accommodating the desired magnetic components of said mixture, a source of electrical power, circuit means in energy transfer relation with said source constructed to generate a magnetic field between said entrance and exit channels in the path of said moving stream for diverting the desired magnetic components in said stream from entering said first exit channel, said circuit means including superconducting material arranged in an array of superconductive coils having their major faces aligned in substantially the same plane, all of said coils being interposed in a panel of normally conductive material, means comprising a cryogenic environment for bringing said superconductive material to a temperature below its critical temperature, and means for removing said diverted magnetic components from the effective area of said magnetic field to an area adjacent said second exit channel and for deflecting said magnetic components into said second exit channel.

2. The combination in accordance with claim 1 wherein each of said coils is mounted on an axis of normally conducting material.

3. The combination in accordance with claim 2 in which said superconductive coils are pancake-shaped windings formed of ribbons comprising a nonsuperconducting substrate having a superconducting layer deposited on one face of said substrate.

4. The combination in accordance with claim 3 wherein said normally conductive panel is essentially copper, and said superconducting layer comprises a principal component of Nb Sn.

5. The combination in accordance with claim 1 wherein said panel is interposed in a hermetically sealed chamber and said means for establishing a cryogenic environment includes a source of liquid helium and channel means connected to said source and respectively passing through said chamber and said panel adjacent said coils to deliver liquid helium to said coils, and further channel means for withdrawing helium gas formed in said panel, said chamber including insulating means adjacent said panel.

6. The combination in accordance with claim 1 wherein said means comprises a device rotatable in a plane substantially transverse to the direction of said field for removing said magnetic components to an area adjacent said second exit channel, and means for directing a high velocity stream of liquid onto the face of said device in a position outside of said field for Washing said magnetic components into said second exit channel.

7. A magnetic separator comprising in combination, a housing including an entrance for accommodating a slurry comprising magnetic and non-magnetic components, said housing including a pair of exits comprising an ore exit and a gangue exit spaced apart in said housing from said entrance, a moving means constructed to traverse the space interval between said entrance and each of said exits comprising a revolving disc, magnetic cans for deflecting the magnetic portion of said slurry to one of said exits While permitting the non-magnetic portion of said slurry to leave by the other said exit comprising a stationary section adjacent said revolving disc and located to deflect the magnetic component of said slurry from an area adjacent said gangue exit to an area adjacent said ore exit, said stationary sector comprising a hermetically sealed cryogenic system including superconducting material in the form of a plurality of superconducting coils disposed in an array between layers of normally conducting material to form a panel disposed within said hermetically sealed cryogenic system, said array constructed and arranged to create a magnetic force field in a direction substantially normal to the plane of rotation of said disc and means for maintaining said cryogenic system at a temperature below the critical temperature of said superconducting material.

8. The combination in accordance with claim 7 wherein alternate ones of said coils are oppositely poled to produce a high field gradient between each of said coils and the adjacent coils of said array.

9. The combination in accordance with claim 7 wherein said stationary sector comprises a closed panel of normally conducting material including an array of coils formed of ribbon comprising a superconducting film overlaid on a nonsuperconducting substrate, the said coils being mounted in a regular array on a series of supports of normally conducting material formed integrally with said panel.

10. The combination in accordance with claim 9 wherein said hermetically sealed system includes a plurality of channels spaced apart adjacent said coils, a source of liquid helium, means for connecting said source to an intake point in said hermetically-sealed system, whereby said liquid helium circulates through said chan- 10 nels, and an exit channel for conveying said helium to return to said source.

11. The combination in accordance with claim 10 wherein said superconducting film comprises primarily Nb Sn, and said normally conducting material comprises primarily copper.

12. The combination in accordance with claim 10 wherein said superconducting film comprises primarily niobium titanium.

13. The combination in accordance with claim 10 wherein said substrate comprises primarily stainless steel.

14. Apparatus for separating a desired magnetic component from a mixture containing both magnetic and non-magnetic components comprising, a housing having an entrance for said mixture and a plurality of exits for the removal of the desired magnetic component and the remainder of the mixture; magnetic means for separating the desired magnetic component from said mixture, said magnetic means comprising an inner panel containing a plurality of superconducting magnets within an outer evacuated chamber, means to supply liquid helium to said panel to maintain the temperature of said magnets at or below the critical temperature, further means to Withdraw helium gas that is found in the panel, said magnets comprising a plurality of superconducting coils connected in series and arranged to give a pattern of alternate north and south poles to establish a steep field gradient.

15. The apparatus of claim 14 wherein superinsulation is positioned around the inner panel in said evacuated chamber.

16. The apparatus of claim 14 in which the magnetic means is located in close proximity to a movable element in said housing and generates a magnetic field which passes through at least part of said element, said mixture contacting said movable element as it passes through said housing.

17. The apparatus of claim 16 in which the movable element comprises a disk shaped chamber containing the magnetic means.

18. The apparatus of claim 14 in which the inner panel comprises normally conductive material.

19. The apparatus of claim 14 in which the coils are pancake shaped with substantially coplanar faces.

20. The apparatus of claim 14 in which the coils are formed about center posts of normally conductive material.

References Cited UNITED STATES PATENTS 939,523 11/1909 Ludwick 209-223 X 3,026,151 3/1962 Buchhold 335-216 X 3,157,830 11/1964 Matthias 335-216 3,173,079 3/1965 McFee.

3,187,235 6/1965 Berlincourt 335216 3,200,299 8/1965 Autler 3352l6 X 3,265,939 8/1966 Rinderer 335-216 3,281,737 10/1966 Swartz 335-216 3,289,836 12/1966 Weston 209214 3,394,330 7/1968 Schindler 335-216 FRANK W. LUTIER, Primary Examiner U.S. Cl. X.R. 209-22 Column Column Column Column Column Column Column Column Column Column Column Column Attest:

Patent No.

Inventor(s) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION John D. Bannister Dated March 3 97 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

line 71,

line 1, line &9,

line 27, lines #0 line 71,

line 30, line 73,

lines 5 L line 16,

line 28,

line 3M,

Edward M. Fletcher, Ir. Attesting Officer "then" should read --than--.

heading should be all caps.

the word --the-- is missing between "in channels".

the word "the" should read --that--. and 55, headings should be all caps. "descarded" should read -discarded--.

"one" shouldread --an--.

the period is missing at the end of sentence, after "2b" through 58 should have been indented.

the comma is missing after "tion" the word "ganguge"should read -gangue--.

"section" should read --sector-.

SIGNEI sewn sips-1970 WILLIAM E- W, JR. Commissioner of Patents F ORM PO-1D5O 10-69)

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