Magnetic Separator Method And Apparatus

Abstract

Radial magnetic field is applied in tube from a source surrounding tube. Magnetic field is applied in either a static, pulsating, or alternating mode. A first baffle divides tube inlet into feed inlet receiving fluidized material and surrounding coaxial passage receiving wash fluid. A second baffle spaced downstream of the first baffle divides tube outlet into tailings discharge and surrounding coaxial concentrate discharge. Magnetic and magnetizable particles are attracted outwardly between baffles from central fluidized material stream and leave as a concentrate discharged with wash fluid. Nonmagnetic particles in central fluidized material stream leave tailings discharge. Fluid stream within tube has no outward radial components and may have inward radial components.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of our pending application Ser. No. 676,297 now abandoned, filed Oct. 18, 1967.

Description

BACKGROUND OF THE INVENTION

This invention relates broadly to apparatus and method for separating magnetic or magnetizable particles from nonmagnetic, or relatively nonmagnetic, particles. More specifically this invention relates to apparatus and method for separating magnetic or magnetizable particles from nonmagnetic, or relatively nonmagnetic, particles in a fluidized stream of a mixture of said particles by means of a radially applied magnetic field established about said fluidized stream.

The prior art does not embody the features nor offer the advantages of the present invention as enumerated below:

1. The particular magnetic field geometry having, within the applied field region, radial and angular components and no longitudinal components, tending to outwardly accelerate the magnetic or magnetizable particles, thereby to prevent, or at least minimize, flocculation of said magnetic or magnetizable particles and consequent entrapment of nonmagnetic particles.

2. Suitability for gaseous as well as liquid media.

3. Flow pattern of fluid stream having no net radial outward component, and preferably a net radial inward component tending to confine nonmagnetic particles to a central area.

4. No moving parts in the separation zone.

5. High capacity.

6. Minimum space requirements.

7. Adjustability of magnetic and fluid forces, allowing a wide range of materials to be treated in any one machine.

8. Ability to treat ferromagnetic or weakly magnetic particles.

9. Adaptability for use with cryogenic magnets, superconductor magnets, more conventional AC and DC electromagnets, as well as permanent magnets.

10. Feed and wash fluid inlets at one end of device, and concentrate and tailings discharges at opposite end of device.

SUMMARY OF THE INVENTION

One of the objects of this invention is to provide improved method and apparatus for separating magnetic or magnetizable particles from nonmagnetic particles or from relatively nonmagnetic particles.

Another of the objects of this invention is to provide improved method and apparatus for continuously and efficiently separating magnetic or magnetizable particles from nonmagnetic, or relatively nonmagnetic, particles in a stream of a mixture of said particles.

Other and further objects of this invention will become apparent during the course of the following description and by reference to the accompanying drawings and the appended claims.

We have discovered that the foregoing objects can be attained by continuously passing a fluidized stream of feed material into a central circular inlet passage of a separating tube, by continuously passing a stream of wash fluid into an annular circular inlet passage surrounding the feed inlet, by establishing either a static, pulsating or alternating magnetic field about a separating zone in the separating tube to attract magnetic or magnetizable particles from the feed stream into the wash stream, by withdrawing tailings from a central circular discharge and by withdrawing magnetic or magnetizable concentrate from an annular circular discharge surrounding the tailings discharge.

DESCRIPTION OF THE DRAWINGS

FIG. 1 represents a view in perspective of the separating column and three of the four pole pieces of the surrounding magnet, the magnet being partially broken away to show the separating column, and the wall of the separating column being partially broken away to show the interior construction thereof, the magnet windings being omitted for purposes of clarity, and the fluid streams within the separating column being indicated diagrammatically by arrows.

FIG. 2 represents a view in plan of the magnet showing the disposition of pole pieces, the magnet windings being omitted for purposes of clarity, further showing a transverse cross section of the separating column taken along the line 2-2 of FIG. 1.

FIG. 3 represents a view in vertical section of the separating column and magnet, taken along the line 3-3 of FIG. 2.

FIG. 4 represents diagrammatically a system employing the separating column and the surrounding magnet.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Magnetic separator 1 is seen as comprising separating column 2 surrounded intermediate its ends by magnet 3.

Separating column 2, having inlet end 4 at the top thereof and outlet end 5 at the bottom thereof, comprises an elongated tubular element 6 having a circular transverse cross section and arranged with its longitudinal axis vertical. A solid rod 7, having a circular transverse cross section, is suitably mounted (by means not shown) within the tubular element 6, and extends downwardly from inlet end 4, terminating in a conically tapered portion 8 in the region of magnet 3, the longitudinal axis of said rod 7 coinciding with the longitudinal axis of the tubular element 6.

A first tubular baffle 9, having a circular transverse cross section, is suitably mounted (by means not shown) within the tubular element 6, coaxial with said tubular element 6 and the rod 7. Baffle 9 extends downwardly from inlet end 4, and terminates above magnet 3, the lower end of baffle 9 being tapered inwardly towards the inner diameter thereof as shown by the numeral 10. It will be seen, then, that two circular coaxial annular passages are formed at the inlet end 4 of the separating column 2, one a feed inlet passage 11 and the other a fluid inlet passage 12 surrounding the feed inlet passage 11.

A second tubular baffle 13, having a circular transverse cross section, is suitably mounted (by means not shown) within the tubular element 6, coaxial with said tubular element 6, said baffle 9 and said rod 7. Baffle 13 extends upwardly from outlet end 5, and terminates in the region of magnet 3, the upper end of baffle 13 being tapered outwardly toward the outer diameter thereof as shown by the numeral 14. It will be seen, then, that two coaxial passages are formed at the outlet end 5 of the separating column, one a circular tailings discharge passage 15, and the other a circular annular concentrate discharge passage 16 surrounding the tailings discharge passage 15.

The space inward of magnet 3 between tubular element 6 and the inner ends of baffles 9, 13 define a separating region. Here particle and fluid pathways are permitted to intermingle and cross over each other between feed and fluid inlet passages 11, 12 and tailing and concentrate discharge passages 15, 16.

Tubular element 6, and the other components of separating column 2 including tubular pipes 9 and 13 and rod 7, are constructed from nonmagnetic materials such as copper, brass, certain stainless steels, glass, resins, etc.

Ideally, the magnetic field generated by magnet 3 should have the following characteristics:

1. In the applied field region (viz, the region lying between the top and bottom surfaces of magnet 3), the magnetic force field will be substantially uniform at any fixed radius about the longitudinal axis of separating column 2. In other words, the strength of the force on a magnetic particle caused by the magnetic field at various points each located the same radial distance from the longitudinal axis of the separating column 2 (or from the vertical axis of magnet 3) will be substantially the same, regardless of the position of said points along the separating column 2, within the applied field region of magnet 3.

2. In the applied field region, the magnetic field pattern will be two dimensional (i.e., planar) and either static, pulsating or alternating, and substantially without components longitudinally disposed relative to separating column 2, except that with an applied field region of less than infinite length there will be some longitudinal components adjacent and beyond the edges of the applied field region (i.e., adjacent and beyond the top and bottom surfaces of magnet 3). The force on a magnetic particle will thus also have no longitudinal components in the applied field region.

3. In the applied field region, the strength of the magnetic field will increase as the perpendicular distance from the longitudinal axis of separating column 2 (or from the vertical axis of magnet 3) increases. This increase in magnetic field strength may, for example, be linear with the increase in the above-mentioned distance.

As is often the case, ideal conditions may be difficult, if not impossible, to attain in every respect. It has been found, in practice, that a magnet 3 which generates a satisfactory magnetic field having substantially the foregoing characteristics may be of the quadrupole type comprising a square iron yoke 17 and four symmetrically arranged iron pole pieces 18, the faces of the said pole pieces 18 lying parallel to the longitudinal axis of separating column 2 along equipotential surfaces of the magnetic field. It will be understood that magnet coils are wound on the pole pieces 18, these coils having been omitted for purposes of clarity. These magnet windings or coils are so disposed on the pole pieces 18 and suitably interconnected that, when the windings or coils are connected to a source of either direct, pulsed, or alternating current as noted below, adjacent pole pieces 18 acquire opposite polarity. Thus, in the illustrated quadrupole magnet 3, two opposite pole pieces 18 will be North or N poles, and the other two opposite pole pieces 18 will be South or S poles. This opposing polar arrangement remains unchanged regardless of the character of current used to excite magnet 3 windings or coils. However, it should be understood that when using alternating current, the polarity of the N poles will alternately become S poles and the S poles, N poles.

Preferably, the faces of pole pieces 18, as viewed in plan, will be hyperbolic and extend longitudinally parallel to each other. However, the hyperbola may be approximated by a circular arc for ease of fabrication. Such a magnet 3 is available from Pacific Electric Motor Co. of Oakland, California, their Model No. 4SF-4-18L1. Although this magnet is designed mainly for direct current excitation, it has also been found satisfactory for particle separation when connected to pulsed and alternating current sources.

As shown in the several figures, vertically arranged separating column 2 extends through the center of horizontally disposed magnet 3 and is surrounded by pole pieces 18, the longitudinal axis of separating column 2 registering with the vertical axis of magnet 3.

Other geometries of magnetic field may be suitable and permit a satisfactory separation in separating column 2. Also, other means of obtaining a satisfactory magnetic field may be employed in lieu of the wound-core electromagnet 3, depending upon the strength of the magnetic field required, such as:

1. Permanent magnets,

2. Superconducting magnets,

3. Conductor windings arranged to establish the desired magnetic field and operated in or out of a cryogenic environment, with or without iron pole pieces.

Magnets, permanent or electrically energized, may be bipolar or may have more than the four poles of the illustrated quadrupole magnet 3. It will be understood that the greater the number of poles (i.e., the closer the number of poles approaches infinity), the more rapidly will the magnetic force field increase radially from the center of the magnet. For example, in a quadrupole magnet, the force on a magnetic particle increases linearly with the radius perpendicular to the longitudinal axis. In a sextupole magnet, the force field increases as the cube of the radius. In an octupole magnet, the force field increases as the fifth power of the radius and so forth as additional poles are added.

A system utilizing magnetic separator 1 is shown diagrammatically in FIG. 4. Hopper 19 holds the material to be fractionated into magnetic or magnetizable and nonmagnetic fractions. The said material should be in a form capable of flowing through various conduits as hereinafter described, that is to say, the said material should be fluidized. This may be done by mixing such material in comminuted form with a fluid such as water to form a suspension or slurry, mixer 20 being installed in hopper 19 and operated to prevent the said material from settling in the hopper 19.

Conduit 21 communicates between the bottom of hopper 19 and feed inlet passage 11 at the inlet end 4 of separating column 2. Pump 22 is installed in conduit 21, taking suction from that portion of conduit 21 connected to hopper 19 and discharging to that portion of conduit 21 leading to separating column 2. Suitable valve means, such as gate valve 23, is installed in conduit 21 whereby to open or close the said conduit 21. Conventional flowmeter 24 may also be installed in conduit 21.

Conduit 25 communicates between a source of wash fluid (which may, for example, be the same as the fluid employed to fluidize the material being fractionated, viz, water), and the fluid inlet passage 12 at the inlet end 4 of separating column 2. Pump 26 is installed in conduit 25 to pump the fluid to the separating column 2. Suitable valve means, such as valve 27, is installed in conduit 25 to open or close the same, and a conventional flowmeter 28 may also be installed in conduit 25.

Adjustable power supply 29 is provided to energize magnet 3 from a source having a predetermined current characteristic of either direct current, pulsed current or alternating current. Power supply 29 preferably includes means for varying magnetic field intensity and means for varying the frequency of the pulsed or alternating current up to about 400 Hz. These three current characteristics will cause magnet 3 to produce either a static, a pulsating, or an alternating magnetic field, within the separating region of column 2.

The choice of power supply 29 current characteristic, and thus the magnetic field mode, is based largely on predetermined characteristics of the magnetic or magnetizable material to be fractionated and the behavior of particles of such material in the various magnetic field modes. Generally, when using the same type of magnet 3 structure, paramagnetic particles are best separated in a static magnetic field, weak ferromagnetic particles preferably in a pulsating magnetic field, or alternatively, in a static magnetic field, and highly ferromagnetic particles in preferably an alternating magnetic field, or alternatively, in a pulsating magnetic field. It should be understood that this arrangement is not inflexible. Other combinations of particle magnetic properties and magnetic field modes may be used to affect said separation, if desired. For example, particulate magnetite (highly ferromagnetic) may be separated from a mixture of magnetite and gangue in a static magnetic field.

The operation of the preferred embodiment will now be described.

The material to be fractionated into magnetic or magnetizable and nonmagnetic or relatively nonmagnetic, fractions is maintained in a fluidized state in hopper 19. Thus, the said material in comminuted form is held in suspension or a slurry with a fluid such as water.

Valves 23 and 27 are opened, magnet 3 is energized, and pumps 22 and 26 are set in operations.

In this manner, a stream of fluidized material is continuously withdrawn from hopper 19 and pumped into feed inlet passage 11 of the separating column 2 and, at the same time a stream of wash fluid (water in the example under discussion) is continuously pumped into fluid inlet passage 12 of the separating column 2. Ideally, the streams of fluidized material flowing through separating column 2 should have no radial components or vectors directed outwardly and away from the longitudinal axis of separating column 2.

As the stream of fluidized material travels through the applied field region of magnet 3, the magnetic or magnetizable particles are attracted from the centrally moving stream of fluidized material and, under the influence of magnet 3, these particles travel outwardly of the longitudinal axis in the separating region of column 2 into the annular moving stream of wash fluid which carries the said magnetic or magnetizable particles longitudinally of separating column 2. The radial outwardly directed magnetic forces outwardly radially accelerate the magnetic or magnetizable particles from the longitudinal axis of separating column 2, thereby tending to mitigate or prevent flocculation of the magnetic particles, and consequent entrapment of other particles. The centrally moving stream of fluidized material, containing substantially only nonmagnetic, or relatively nonmagnetic particles, leaves the separating column through the tailings discharge passage 15. The magnetic or magnetizable particles comprising the concentrate are carried by the wash fluid out of the separating column through concentrate discharge passage 16. In the foregoing manner the material under treatment is fractionated into magnetic and nonmagnetic, or relatively nonmagnetic, fractions.

It may be desirable, under some circumstances, to establish flow conditions within separating column 2 such that the stream of wash fluid has a radial component or vector directed inwardly and towards the longitudinal axis of separating column. This tends to improve the efficiency of separation by more positively confining the nonmagnetic or relatively nonmagnetic, fraction to the central stream of fluidized material, thereby preventing the same from being scattered into the stream of wash fluid and concentrate discharge passage 16 because of collisions between the solid particles or erratic movement in the fluid caused by the shape of the nonmagnetic, or relatively nonmagnetic, particles. This flow condition may be obtained, for example, by maintaining tailings discharge passage 15 at a lower pressure than concentrate discharge passage 16, as by connecting tailings discharge passage 15 to the suction side of a pump while concentrate discharge passage 16 is not so connected, or by connecting tailings discharge passage 15 to the suction side of a pump taking greater suction than another pump having its suction side connected to the concentrate discharge passage 16.

The flow condition mentioned in the preceding paragraph may also be obtained by operating pump 26 at a higher pressure than pump 22. Moreover, this method may be combined with the method of the preceding paragraph to obtain the said desired flow condition.

When separating weakly magnetic or magnetizable fractions from nonmagnetic fractions, it may be desired to use a longer applied field region (i.e., longer vertical dimension of magnet 3) than when separating strongly magnetic fractions from other fractions. The longer applied field region permits the weakly magnetic particles to remain under the influence of the magnetic field for a longer period of time and to be displaced sufficiently for separation despite their reduced radial acceleration and velocity.

When separating weakly magnetic or magnetizable fractions from nonmagnetic fractions, it may also be desired to use stronger magnetic fields than when separating strongly magnetic fractions from other fractions. This method may also be combined with the method of the preceding paragraph to obtain the desired separation.

When separating higher ferromagnetic or stronger magnetizable fractions from weaker ferromagnetic or nonmagnetic fractions, it is desirable to increase the frequency of the alternating or pulsating magnetic field as ferromagnetic susceptability decreases. For example, a frequency of about 5-10 Hz. may be used for powdered metallic iron, about 10-25 Hz. for magnetite, and so or up to about 400 Hz. for the weakest ferromagnetic material. This method may also be combined with any of the methods of the preceding paragraphs to obtain the desired separation.

It will be understood that instead of the water hereinabove mentioned as the fluidizing medium and wash fluid, other liquids and gases may likewise be employed for the same purpose.

It may be desired, for certain materials to make adjustments to the flow rates as well as to the strength and/or frequency of the magnetic field, thereby to adjust fluid drag forces and magnetic forces to effect a desired separation.

It will be noted that, along the vertical axis of magnet 3, the field strength and magnetic force on a particle are zero, regardless whether the field is static, pulsating or alternating. Also, as heretofore mentioned, the field strength closely adjacent the vertical axis of magnet 3 will be less than the field strength further removed therefrom and closer to pole pieces 18. The function of rod 7 is dual in that it prevents the incoming stream of fluidized material from entering the separating column 2 along the vertical axis of the magnetic field and also brings the said incoming stream of fluidized material to a region of greater magnetic force strength.

In the following examples, reference to material percentages shall be understood to mean percent by weight, unless expressed in other terms.

EXAMPLE 1

The following example illustrates the efficiency of the above-described embodiment in effecting a separation of particulate magnetite from an ore slurry in an alternating magnetic field. Pertinent dimensions of the apparatus shown in FIG. 1 were:

Inside diameter of separating column 2 3.5 inches Inside diameter of baffle 9 1.75 inches Inside diameter of baffle 13 2.25 inches Diameter of rod 7 0.625 inches Height of magnet 3 16 inches Diameter of central openings in magnet 3 4 inches Distance between baffles 9 and 13 2 inches Rod 7 terminating at baffle 13 Top edge of magnet 3 was 0.5 inches below baffle 9.

A feed slurry of water and 25 percent ore solids comprising 42.5 percent magnetite and 57.5 percent silica as discharged from a classifier, 70 percent minus 325 mesh, was fed through the separator magnetic field at a velocity of 6 ft./sec. (39g.p.m.). Wash water was supplied at a rate of 40 g.p.m. Magnet 3 was energized with 25 Hz. current which generated an r.m.s. field intensity of 3,500 gauss at the pole face. The following results were obtained in a single pass separation: ---------------------------------------------------------------------------

% Weight % Magnetite % Magnetite Distribution __________________________________________________________________________ Solid feed Material 100.0 42.5 100.0 Concentrate 43.1 93.7 95.0 Tailings 56.9 3.7 5.0 __________________________________________________________________________

EXAMPLE 2

The following example illustrates the efficiency of the above-described embodiment in effecting a separation of particulate ilmenite from an ore slurry in a static magnetic field. Dimensions of the apparatus shown in FIG. 1 were the same as in example 1.

A feed slurry of water and 25 percent ore solids comprising 70 percent ilmenite and 30 percent silica as fed to shaking tables, 65 mesh +325 mesh, was fed through the separator magnetic field at a velocity of 6.5 ft./sec. (42.2 g.p.m.). Wash water was supplied at a rate of 40 g.p.m. Magnet 3 was energized with direct current which generated a static magnetic field intensity of 10,000 gauss at the pole face. The following results were obtained in a single-pass separation: ---------------------------------------------------------------------------

% Weight % Ilmenite % Ilmenite Distribution __________________________________________________________________________ Solid Feed Material 100.0 70.0 100.0 Concentrate 60.5 98.2 85.0 Tailings 39.5 26.5 15.0 __________________________________________________________________________

EXAMPLE 3

The following example illustrates the efficiency of the above-described embodiment in effecting a separation of particulate magnetite from an ore slurry in a static magnetic field which is produced by a shorter magnet than in the previous examples, and a tailings stream velocity which is greater than that of the concentrate stream. Pertinent dimensions of the apparatus shown in FIG. 1 are the same as example 1, except that the height of magnet 3 was 4 inches and the distance between baffles 9 and 13 was 3.5 inches.

A feed slurry of 26 percent ore as discharged from a rod mill, minus 10 mesh plus 0, was fed through the separator magnetic field at a velocity of 2 ft./sec. (13 g.p.m.). Wash water was fed at 5 ft./sec. (100 g.p.m.). Concentrate stream velocity was 3.8 ft./sec. (56 g.p.m.). Tailings stream velocity was 4.6 ft./sec. (57 g.p.m.). Magnet 3 was energized with direct current which generated a static magnetic field of 5,000 gauss at the pole face. The following results were obtained in a single pass separation: ---------------------------------------------------------------------------

% Weight % Magnetite % Magnetite Distribution __________________________________________________________________________ Solid Feed Material 100.0 69.1 100.0 Concentrate 82.7 81.5 97.5 Tailings 17.3 10.0 2.5 __________________________________________________________________________

It will be noted from the above data that a rather precise separation of the magnetic or magnetizable particles from the other particles is obtainable. However, in some applications less precision of separation is acceptable as, for example, in the removal of iron from a coal-processing stream. In such installations it may be desired to modify the above-described embodiment to meet these requirements. This has the added benefits of reducing overall costs and simplifying construction.

For such purposes, inlet end 4 of magnetic separator 1 may be modified by removing tubular baffle 9 and preferably rod 7, although under certain circumstances rod 7 may be retained to perform its functions as described above. A flowing stream comprising the feed materials is applied to inlet end 4 of separator 1. Magnet 3 provides the same type of magnetic field as noted above. Baffle 13 is also as noted above, that is, it is located in outlet end 5 to provide tailings discharge passage 15 and concentrate discharge passage 16, the latter preferably having a cross-sectional area of about 10 percent of the total discharge area. The wash fluid system 24-28 supplying wash fluid to inlet end 4 is deleted entirely.

The magnetic or magnetizable particles in the feed stream are attracted into its outer region by the magnetic field as the stream flows through the magnetic field. Concentrate in the outer region of the feed stream flows through passage 16 and tailings or the remaining inner portion of the feed stream, flows through passage 15. Feed stream flow rate, magnetic field intensity including frequency when using pulsating or alternating fields may be varied to achieve the degree of separation desired.

Claims

We claim:

1. Method of separating magnetic or magnetizable particles from a material comprising magnetic or magnetizable particles and other particles having magnetic or magnetizable values less than said particles to be separated, said method comprising:

a. establishing a flowing stream comprising said material,

b. establishing a stationary magnetic field along a separating region of said stream from a source completely surrounding the stream, said magnetic field having a flux pattern which produces substantially only radial separating forces within the separating region, said radial forces having substantially no longitudinal components and diverging perpendicularly from the stream flow axis with increasing magnitude substantially equally in all radial directions about said axis, thereby to attract magnetic or magnetizable particles flowing through the magnetic field into an outer portion of the separating region, and

c. separating said outer portion of said stream from an inner portion as the magnetic or magnetizable particles leave the separation region.

2. Method as in claim 1, further comprising:

d. varying the flow rate of said feed stream to control the amount of magnetic or magnetizable particles attracted into the outer portion of the separating region.

3. Method as in claim 1 wherein the magnetic field intensity in step (b) is static.

4. Method as in claim 1 wherein the magnetic field intensity in step (b) is pulsating.

5. Method as in claim 1 wherein the magnetic field intensity in step (b) is alternating.

6. Method as in claim 1, further comprising:

e. varying the intensity of the magnetic field to control the amount of magnetic or magnetizable particles attracted into the outer portion of the separating region.

7. Method as in claim 1 wherein the magnetic field intensity in step (b) is pulsating or alternating, and further comprising:

f. varying the pulsating or alternating frequency to control the magnetic susceptibility of the particles attracted into the outer portion of the separating region.

8. Method as in claim 7, further comprising:

g. varying the intensity of the magnetic field to control the amount of magnetic or magnetizable particles attracted into the outer portion of the separating region.

9. Method of separating magnetic or magnetizable particles from a material comprising magnetic or magnetizable particles and other particles having magnetic or magnetizable values less than said particles to be separated, said method comprising:

a. establishing a first flowing stream comprising said material,

b. establishing a second flowing stream of fluid in contact with said first flowing stream,

c. establishing a stationary magnetic field along a separating region of said streams from a source surrounding the second flowing stream, said magnetic field having a flux pattern which produces separating forces directed perpendicularly from the flow axis of said first flowing stream, thereby to attract magnetic or magnetizable particles flowing through the magnetic field from said first flowing stream into said second flowing stream, and

d. separating said first flowing stream from said second flowing stream after said magnetic or magnetizable particles leave the separating region.

10. Method as in claim 9, further comprising:

e. varying the flow rate of said first flowing stream to control the amount of magnetic or magnetizable particles attracted from the first flowing stream into said second flowing stream.

11. Method as in claim 9, further comprising:

f. varying the flow rate of the second flowing stream relative the first flowing stream to confine said other particles of material to the first flowing stream as it leaves the separating region.

12. Method as in claim 9, further comprising:

g. said first and second streams flowing parallel to each other.

13. Method as in claim 9, further comprising:

h. the direction of flow of said first and second flowing streams being substantially vertical.

14. Method of separating magnetic or magnetizable particles from a material comprising magnetic particles and other particles having magnetic or magnetizable value less than said particles to be separated, said method comprising:

a. establishing a first flowing stream comprising said material,

b. establishing a second flowing stream of fluid, said second flowing stream having an annular transverse cross section extending completely around and contacting the transverse periphery of said first flowing stream,

c. establishing a stationary magnetic field in a separating region of said streams from a source surrounding the transverse periphery of said second flowing stream, said magnetic field having a flux pattern which produces separating forces directed radially outwardly from the flow axis of said first flowing stream, thereby to attract magnetic or magnetizable particles flowing through said magnetic field from said first flowing stream into said second flowing stream, and

d. separating said first flowing stream from said second flowing stream after said magnetic or magnetizable particles leave the separating region.

15. Method as in claim 14, further comprising:

e. the transverse cross section of said first flowing stream being circular,

f. the transverse cross section of said second flowing stream being a circular annulus coaxial with said first flowing stream.

16. Method as in claim 15, further comprising:

g. said magnetic field being established substantially uniformly at a plurality of symmetrically spaced points around the transverse periphery of said second flowing stream.

17. Apparatus for separating magnetic or magnetizable particles from a material comprising magnetic or magnetizable particles and other particles having magnetic or magnetizable values less than said particles to be separated, said apparatus comprising:

a. elongated conduit means having an inlet end, an outlet end, and a separating region spaced between said ends,

b. said inlet end of the conduit means adapted to receive a flowing stream comprising said material,

c. baffle means disposed within the outlet end of the conduit means and extending downstream from the separating region, said baffle means defining a concentrate discharge passage aligned coaxially with an outer portion of the separating region and a tailings discharge passage aligned coaxially with an inner portion of the separating region,

d. means for establishing a stationary magnetic field within the separating region from a source thereabout, said means having a magnetic field with a flux pattern which produces substantially only radial separating forces within the separating region, said radial forces having substantially no longitudinal components and diverging perpendicularly from the stream flow axis with increasing magnitude substantially equally in all radial directions about said flow axis, and

e. whereby magnetic or magnetizable particles flowing through the magnetic field are attracted into the outer portion of the separating region and discharged through said concentrate passage, and whereby the remaining particles are discharged through the tailing passage.

18. Apparatus as in claim 17 wherein means (d) comprises:

f. permanent magnet means having a plurality of radial poles with convex faces disposed in opposite adjacent polarity about the separating region for producing the radial separating forces of said magnetic field.

19. Apparatus as in claim 17 further comprising:

n. means for supplying said flowing stream of materials to the inlet end, and

o. control means operatively associated with means (n) for varying the flow rate of said stream.

20. Apparatus as in claim 17 wherein means (d) comprises:

g. electrically energized magnetic field producing means having a plurality of effectively radial poles with convex faces disposed in opposite adjacent polarity about the separating region for producing the radial separating forces of said magnetic field.

21. Apparatus as in claim 20 wherein means (g) includes:

h. means for varying the intensity of the magnetic field.

22. Apparatus as in claim 20 wherein means includes:

i. means for producing a static magnetic field intensity.

23. Apparatus as in claim 20 wherein means (g) includes:

j. means for producing a pulsating magnetic field intensity.

24. Apparatus as in claim 23 wherein means (j) includes:

k. means for varying the frequency of the pulsating magnetic field intensity.

25. Apparatus as in claim 20 wherein means (g) includes:

i. means for producing an alternating magnetic field intensity.

26. Apparatus as in claim 25 wherein means (l) includes:

m. means for varying the frequency of the alternating magnetic field intensity.

27. Apparatus for separating magnetic or magnetizable particles from a material comprising magnetic or magnetizable particles and other particles having magnetic or magnetizable values less than said particles to be separated, said apparatus comprising:

a. elongated conduit means having an inlet end, an outlet end, and a separating region spaced between said ends,

b. first baffle means disposed within the inlet end of the conduit means and extending downstream to the separating region, said first baffle means defining within said conduit means adjacent the inlet end thereof a feed inlet passage adapted to receive a first flowing stream comprising said material and a wash fluid inlet passage adapted to receive a second flowing stream of wash fluid,

c. second baffle means disposed within the outlet end of the conduit means and extending downstream from the separating region, said second baffle means defining within said conduit means adjacent the outlet end thereof a concentrate discharge passage adapted to discharge a third flowing stream and a tailings discharge passage adapted to discharge a fourth flowing stream,

d. said concentrate discharge passage and said wash fluid inlet passage being substantially aligned with respect to each other longitudinally of the elongated conduit means,

e. said tailings discharge passage and said feed inlet passage being substantially aligned with respect to each other longitudinally of the elongated conduit means,

f. means for establishing a stationary magnetic field within the separating region from a source positioned such that the second flowing stream is interposed between the first flowing stream and said source, and

g. whereby magnetic or magnetizable particles flowing through the magnetic field are attracted from the first flowing stream into the second flowing stream and are discharged through the concentrate passage with the wash fluid in a third flowing stream, and whereby the other particles are discharged through said tailings passage in a fourth flowing stream.

28. Apparatus as in claim 27, further comprising:

h. said means (f) applying a magnetic force to said magnetic or magnetizable particles in a direction substantially perpendicular to the longitudinal axis of said elongated conduit means.

29. Apparatus as in claim 27, further comprising:

i. said elongated conduit means being arranged with its longitudinal axis vertical.

30. Apparatus as in claim 27, further comprising:

j. rod means mounted coaxially within said inlet end and extending into the separating region, said rod means having a circular transverse cross section, whereby the feed inlet passage has a circular annular transverse cross section.

31. Apparatus as in claim 27, further comprising:

k. means for supplying the first flowing stream to means (b), and

l. control means operatively associated with means (k) for varying the flow rate of the first stream.

32. Apparatus as in claim 27, further comprising:

m. means for supplying the first and second streams to means (b), and

n. control means operatively associated with means (m) for varying the flow rate of the second stream relative the first stream.

33. Apparatus for separating magnetic or magnetizable particles from a material comprising magnetic or magnetizable particles and other particles having magnetic or magnetizable values less than said particles to be separated, said apparatus comprising:

a. a first hollow elongated tube having an inlet end, an outlet end, and a separating region spaced between said ends,

b. a second hallow elongated tube disposed within the inlet end of the first tube and extending downstream to the separating region, said second tube defining within the first tube adjacent the inlet end thereof a central feed inlet passage adapted to receive a first flowing stream comprising said material and an annular wash fluid inlet passage surrounding the central feed inlet passage, said wash fluid inlet passage being adapted to receive a second flowing stream of wash fluid,

c. a third hollow elongated tube disposed within the outlet end of the first tube and extending downstream form the separating region, said third tube defining within the first tube adjacent the outlet end thereof a central tailings discharge passage adapted to discharge a third flowing stream and an annular concentrate discharge passage surrounding the central tailings discharge passage, said concentrate discharge passage being adapted to discharge a fourth flowing stream,

d. said concentrate discharge passage and said wash fluid inlet passage being substantially aligned with respect to each other longitudinally of the first tube,

e. said tailings discharge passage and said feed inlet passage being substantially aligned with respect to each other longitudinally of the first tube,

f. means for establishing a stationary magnetic field within the separating region from a source positioned such that the second flowing stream is interposed between the first flowing stream and said source, and

g. whereby magnetic or magnetizable particles flowing through the magnetic field are attracted from the first flowing stream into the second flowing stream and are carried out of said first tube through the concentrate discharge passage with the wash fluid in a fourth flowing stream, and whereby the other particles are carried out of the first tube through the tailings discharge passage in a third flowing stream.

34. Apparatus as in claim 33, further comprising:

h. said first tube being arranged with its longitudinal axis vertical.

35. Apparatus as in claim 33, further comprising:

i. said means (f) applying a magnetic force to said magnetic or magnetizable particles in a direction substantially perpendicular to the longitudinal axis of the first tube.

36. Apparatus as in claim 33, further comprising:

j. said first, second and third tubes each having a circular transverse cross section,

k. said second and third tubes each being mounted to said first tube coaxially therewith.

37. Apparatus as in claim 36, further comprising:

l. said means (f) generating a magnetic force substantially uniformly at a plurality of symmetrically spaced points around the transverse periphery of the first tube.