WO2017109676A1

WO2017109676A1 - Apparatus and method for removing magnetic material from

Info

Publication number: WO2017109676A1
Application number: PCT/IB2016/057789
Authority: WO
Inventors: Michael FULLAM
Original assignee: Flsmidth A/S
Priority date: 2015-12-21
Filing date: 2016-12-19
Publication date: 2017-06-29
Also published as: CA3007985A1; ZA201803240B; CA3007985C; AU2016376031A1

Abstract

An apparatus and method for removing a magnetic material from a grinding circuit, the apparatus comprising: a screening device configured for separating undersized material from oversized material; an outfeed table, at least a portion of the outfeed table being positioned below the screening device, the outfeed 5 table being operatively configured for receiving the oversized material from the screening device and for spreading the oversized material into a layer of oversized material; and a magnetic device, at least a portion of the magnetic device located above the outfeed table, the magnetic device being operatively configured for removing the magnetic material from the layer of oversized 10 material.

Description

APPARATUS AND METHOD FOR REMOVING MAGNETIC MATERIAL FROM

GRINDING CIRCUITS

FIELD OF THE INVENTION

The present innovation relates to apparatuses and methods used to remove magnetic materials from grinding circuits, for example in the mining and minerals industries.

BACKGROUND OF THE INVENTION

The mining and minerals industries utilize various devices to separate valuable minerals from host contaminants after extraction from the earth. Initially the ore preparation procedure typically involves crushing ore from several feet in size down to approximately 1 -3 inches in a crusher (e.g. gyratory, cone or jaw crushers). The preliminary crushing step is typically followed by one or more stages of grinding to reduce the ore to an average size of less than 1 mm

(generally between 75 and 300 microns). The grinding stage typically utilizes large rotating cylindrical mills (e.g. ball or semi-autogenous grinding ("SAG") mills) containing grinding media such as spherical steel balls. The balls are in a constant tumbling motion due to the rotation of the mill. The ore is typically fed into one end of the mill, it progresses through the grinding chamber and is discharged from the opposite end. As the ore progresses through the mill the grinding media impacts the material resulting in fracture and breakage of the individual pieces of ore into smaller particles.

The tumbling motion of the grinding media results in the fracture of the grinding media (e.g. the steel balls). Additionally, mechanical abrasion will wear the grinding media surface causing a reduction in size of the grinding media. The result of this process is generation of various shapes of steel which are significantly smaller than the original spherical ball. A new grinding ball will typically range from 3 to 5 inches in diameter. The broken or worn ball components can be as large as a hemisphere of the original ball or fragments having dimensions of less than 1/4 inch. Depending on the mill design, these fragments will discharge with the mineral/crushed material and report to downstream equipment.

The ball fragments cause numerous problems in ore processing facilities. Most notably such fragments increase wear on downstream equipment within the grinding circuit, for example on pumps, piping and valves. The costs associated with maintenance downtime and equipment rebuild can be substantial.

Secondly, such fragments negatively impact mill efficiency (i.e. lower throughput). The circuit design for most grinding operations is such that a large portion of the fragments that discharge the mill will return with the new feed to the grinding circuit. As a result, a substantial build-up of fragments can occur in the grinding mill occupying volume that would otherwise be filled by mineral slurry. This loss in active mill volume can de-rate the mill capacity by as much as approximately 10%. Furthermore, the small mass of the fragments does not provide a sufficient impact force to effectively fracture the mineral particles in the mill. Third, the recovery of precious metals by downstream gravity concentrators is reduced and downstream upgrading (tabling) is less efficient. For example, the steel particles report in very high proportions to a gravity concentrate, such as a Knelson concentrate, which recover heavy particles. The amount of unwanted steel in a Knelson concentrate typically varies from 15%-45%.

It will be clearly understood that any reference herein to background material or information, does not constitute an admission that any material, information, forms part of the common general knowledge in the art, or is otherwise admissible prior art.

SUMMARY OF THE INVENTION

An apparatus for removing magnetic material from a grinding circuit is provided. The apparatus may comprise a screening device configured for separating undersized material from oversized material; an outfeed table, at least a portion of the outfeed table being positioned below the screening device, the outfeed table being operatively configured for receiving the oversized material from the screening device and for spreading the oversized material into a layer of oversized material; and a magnetic device, at least a portion of the magnetic device located above the outfeed table, the magnetic device being operatively configured for removing the magnetic material from the layer of oversized material.

5 In an exemplary embodiment of the apparatus, the apparatus may further

comprise a frame, wherein the screening device and the outfeed table are supported by the frame. In some embodiments, the magnetic device may be supported by the frame.

In an exemplary embodiment of the apparatus, the apparatus may further i o comprise an oversize discharge located adjacent a first end of the screening device and positioned between the screening device and the outfeed table.

In an exemplary embodiment of the apparatus, the apparatus may further comprise a washing device positioned between the screening device and the outfeed table, the washing device being operatively configured to wash the

15 oversized material. In some embodiments, the layer of oversized material

comprises pre-washed oversized material.

In an exemplary embodiment of the apparatus, the apparatus may further comprise an oversize discharge located adjacent a first end of the outfeed table wherein at least at least a portion of the oversize discharge is positioned below 20 the outfeed table.

In an exemplary embodiment of the apparatus, the apparatus may further comprise a washing device positioned between the outfeed table and the oversize discharge, the washing device being operatively configured to wash the oversized material.

25 In an exemplary embodiment of the apparatus, the apparatus may further

comprise a magnetic discharge collection device, at least portion of the magnetic discharge collection device positioned below the magnetic device.

In an exemplary embodiment of the apparatus, the apparatus may further comprise an adjusting means for adjusting or tilting the outfeed table, the adjusting means being operatively connected to the outfeed table. In an exemplary embodiment of the apparatus, the outfeed table may be vertically adjustable from a horizontal plane. In some embodiments, the magnetic device may be vertically adjustable from a horizontal plane. In some embodiments, the 5 outfeed table is tiltable between approximately 0 degrees and 45 degrees from the horizontal plane. In some embodiments, the magnetic device is tiltable between approximately 0 degrees and 45 degrees from the horizontal plane.

In an exemplary embodiment of the apparatus the screening device may be comprised of a vibrating screen. i o In an exemplary embodiment of the apparatus the magnetic device may be a belt magnet.

In an exemplary embodiment of the apparatus the outfeed table may be a non- vibrating outfeed table.

An apparatus for removing a magnetic material from a grinding circuit may also comprise a screening device configured for separating undersized material from oversized material; and a belt magnet located above the screening device, the belt magnet being operatively configured for removing the magnetic material from the layer of oversized material. In some embodiments, a horizontal gap between the top portion of the screening device and the bottom portion of the belt magnet

20 is minimal. In some embodiments, the apparatus further comprises a frame, wherein the screening device is supported by the frame. In some embodiments, the apparatus further comprises a magnetic discharge collection device, at least portion of the magnetic discharge collection device positioned below the belt magnet. In some embodiments, the belt magnet is supported by the frame. In some embodiments, the screening device is comprised of a vibrating screen. In some embodiments, the belt magnet is vertically adjustable from a horizontal plane. In some embodiments, the belt magnet is tiltable between approximately 0 degrees and 45 degrees from the horizontal plane.

A method for removing a magnetic material from a grinding circuit is also

30 provided. The method may comprise the steps of separating undersized material from oversized material using a screening device; transferring the oversized material from the screening device to an outfeed table; spreading the oversized material into a layer of oversized material on the outfeed table; and removing magnetic material from the layer of oversized material using a magnetic device. In some embodiments, the method may further comprise washing the oversized material after separating the undersized material from the oversized material using a screening device but before transferring the oversized material from the screening device to the outfeed table.

In some embodiments the method may further comprise collecting the magnetic material using a magnetic discharge collection device.

In some embodiments, the spreading the oversized material into a layer of oversized material on the outfeed table comprises adjusting the angle of the outfeed table from the horizontal plane.

Other details, objects, and advantages of the invention will become apparent as the following description of certain present exemplary embodiments thereof and certain present exemplary methods of practicing the same proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of an apparatus for removing magnetic material from a grinding circuit are shown in the accompanying drawings. It should be understood that like reference numbers used in the drawings may identify like components.

Figure 1 is a perspective view of an exemplary embodiment of the apparatus for removing magnetic material from a grinding circuit.

Figure 2 is a perspective right side view of an exemplary embodiment of the apparatus for removing magnetic material from a grinding circuit. Figure 3 is a perspective left side view of an exemplary embodiment of the apparatus for removing magnetic material from a grinding circuit.

Figure 4 is a perspective top view of an exemplary embodiment of the apparatus for removing magnetic material from a grinding circuit.

Figure 5 is a perspective front side view of an exemplary embodiment of the apparatus for removing magnetic material from a grinding circuit. Figure 6 is a perspective view of an exemplary embodiment of the apparatus for removing a magnetic material from a grinding circuit.

Figure 7 is a flow chart of an exemplary grinding circuit showing one exemplary position of the apparatus.

Figure 8 is a perspective view of an exemplary embodiment of the screening device.

Figure 9 is a perspective view of an exemplary embodiment of the magnetic device and the outfeed table.

Figure 10 is a perspective view of an exemplary embodiment of the frame.

Figure 1 1 is a perspective view of an exemplary embodiment of the magnetic device.

Figure 12 is a picture of an exemplary embodiment of the apparatus installed during testing. Figure 13 is an overhead picture of the outfeed table during operation and testing. Figures 14A and 14B are pictures of the magnetic material which was recovered during testing of the apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Figures 1 -6 depict exemplary embodiments of an apparatus for removing magnetic material from a grinding circuit. As shown the apparatus may contain a screening device 10, an outfeed table 20 and a magnetic device 30. The screening device 10 is configured to separate undersized material from oversized material. At least a portion of the outfeed table 20 is positioned below the screening device 10 so that the outfeed table 20 can recieve the oversized material from the screening device and therafter spread the oversized material into a layer. At least a portion of the magnetic device 30 is located above the outfeed table 20 and is configured so that magnetic material which is present in the layer of oversized material on the outfeed table 20 can be removed. In some embodiments, the outfeed table is non-vibrating. The screening device 10 ahead of the outfeed table 20 is advantageous in that such an arrangement provides a higher efficiency of magnetic material removal, as the layer of oversize material can be thin.

The outfeed table 20 is advantageous in that in some embodiments it is stationary (i.e. - non-vibrating) and spreads out the oversize material into a layer thereby allowing more efficient and easier collection of magnetic material via closer magnetic attraction by the magnetic device 30 thereby requiring a smaller or lesser powered magnetic device 30 to be used.

Additionally, the outfeed table 20 allows the magnetic device to be placed in closer proximity to the oversized material without risking the screening device 10 damaging the magnetic device 30 and resulting in a more efficient magnetic material recovery from the oversize material layer. For example, the outfeed table 20 can spread out the oversize material into a layer thereby allowing more efficient and easier collection of magnetic material via closer magnetic attraction by the magnetic device 30 thereby requiring a smaller or lesser powered magnetic device 30 to be used. In an exemplary embodiment, there may be an oversize discharge 40 located adjacent to a first end of the screening device 10 for collecting oversize material as is passes off of the first end of the screening device 10. An oversize discharge 40 may also be positioned adjacent to a first end 24 of the outfeed table 20 for collecting additional oversize material as is passes off of the first end 24 of the outfeed table 20.

One or more washing devices 50 (e.g. a spray header) may be positioned e.g. on or above the screening device 10, between the screening device 10 and the outfeed table 20 and/or between the outfeed table 20 and the oversize discharge which is positioned adjacent to a first end 24 of the outfeed table 20 for collecting additional oversize material as is passes off of the first end of the outfeed table 20. The washing devices are operatively configured to wash the oversized material. Washing the oversized material is advantageous in that it reduces contaminants on theoversized material which allows for better quality and more desirable magnetic material being collected by the magnetic device 30. Washing the oversized material also increases the value of the product due to a low contaminant level.

As shown in Figure 8, in an exemplary embodiment, the screening device 10 is a vibrating screen. In other embodiments the screening device can be other well known types of screens in the art, for example static screens or sieve bend screens. As shown in Figure 8, the vibrating screen 10 may contain a vibrator (or motor) 13 for exciting or moving a screen 12. Typically the vibrator 13 is mounted on a mounting plate 14 across the screening device 10. The screening device may also contain feet 18 and spring feet 19 attached thereto. In some embodiments, the screening device may contain a washing device 50, for example a spray header, for washing material as it is screened and before it passes onto the outfeed table 20.

As shown in Figure 1 1 , in an exemplary embodiment, the magnetic device 30 is a belt magnet. In other embodiments the magnetic device can be other well known types of magnets in the art, for example a drum magnet. As shown in Figure 1 1 , the belt magnet 10 has a first longitudinal rail 34 and a second longitudinal rail 36. As shown rollers 37 are disposed between the longitudinal rails 34, 36 at the first end 38 and second end 39. A belt 31 may be disposed between the longitudinal rails 34, 36 and is rotatable (via a drive device 32) around the rollers

37. In some embodiments, the magnetic device 30 can be supported by the 5 frame 100. In other embodiments the magnetic device 30 can be suspended above the outfeed table 20. The use of the belt magnet is advantageous in that the belt magnet removes coarse scats (i.e. - metallic material). Grinding media generally breaks by spalling of the grinding ball. As the scat recirculates in the grinding circuit, it further breaks into smaller pieces. Thus it is advantageous to i o remove the scats at the coarsest size possible. An additional advatage is that the belt magnet presents its magnetic effect over a large surface area of the outfeed table 20 with a thin layer of slurry, allowing a long residence time for pick up of the magnetic material.

As shown in Figure 9, in an exemplary embodiment an outfeed table 20 has a 15 first side 21 , a second side 22, a front end 28 and a back end 29. The outfeed table may also contain a liner plate 23. In an exemplary embodiment, the liner plate is made of ultra high molecular weight polyethyline ("UHMW"). The UHMW may assist in providing a wear resisitant surface and allows a low coefficient of friction for the magnetic material. In other embodiments, other like materials well

20 known in the art may be used as all of or part of the liner plate 23. As further shown in Figure 9, the magnetic device 30 is positioned above (but adjacent and close to) the outfeed table 20. By positioning the magnetic device close to the outfeed table 20, more magnetic material is able to be collected by the magnetic device 30.

25 Figure 10 depicts an exemplary embodiment of the frame 100 which may support one or more of the screening device 10, the magnetic device 30 and the outfeed table 20. In the embodiment shown in Figure 10, the frame contains skid beams 102. One or more vertical beams 104 may be attached to the skid beams 102. Horizontal tie beams 106 and/or cross braces 108 may be used to provide

30 structural rigidity to the vertical beams 104. The frame may also contain feed chute legs 17 for supporting the feed chute 16 on the frame 100 and or screening device 10. Figure 7 depicts a flow diagram of a typical grinding and gravity separation circuit. In operation, an apparatus for removing a magnetic material from a grinding circuit may be placed at e.g. location 200. The apparatus detailed herein (as shown in Figures 1 -6 and 12 and 13) was trialed on the screen oversize of an existing Knelson feed screen. The oversize in the trial was pre- screened at 2 to 6 mm. During the trial the apparatus was operated continously (24 hours per day, 7 days a week) with a feed rate of approximately 2 TPH with a + 2 mm feed and a 2-6 mm screen aperture installed on the apparatus. The trial resulted in an actual magnetic material recovery of 2 by 50 gallon drums per shift which would equate to an estimated plant wide magnetic material recovery of 10% of total plant grinding media. If two of three screen oversize streams were treated the magnetic material recovery would be expected to be higher. As shown in Figures 14A and 14B, visually, the recovered magnetic material was clean, and was not a large gold carrier. Gold grade smeared onto the metallic material was only -0.3 g/t. A sample of the magnetic material (e.g. scrap steel) recovered during the trial was shipped back to the grinding media supplier and although the oxide (rust) component was higher than normal scrap steel, the steel was suitable for use as scrap.

In operation, material or slurry is fed onto a screening device 10. The material may be fed onto the screening device via a feed chute 16. The material may then be separated by the screening device 10 into oversized material (which stays on top of the screen 12) and undersized material which passes through the screen 12. The oversized material can be washed using a washing device 50 on the screen 12. The oversized material can be conveyed off of a first end of the screening device 10 into an oversize discharge 40. In an exemplary

embodiment, the oversized material can be washed by a washing device 50 (e.g. between the screening device 10 and the outfeed table 20) before it is conveyed onto the outfeed table 20. The oversized material on the outfeed table 20 (which may be pre-washed oversized material) can be spread into a layer on the outfeed table 20. To assist with spreading of the oversized material on the outfeed table

20, the outfeed table 20 may be vertically adjustable from a horizontal plane (H). In some embodiments, the outfeed table 20 is tiltable between approximately 0 degrees and 45 degrees from the horizontal plane (H). In order to keep the magnetic device 30 as close to the outfeed table 20 as possible when it tilts or adjusts, the magnetic device 30 may also be vertically adjustable from a horizontal plane (H). In some embodiments, therefore, the magnetic device 30 is also tiltable between approximately 0 degrees and 45 degrees from the horizontal plane (H). In some embodiments, an adjusting means 70 is used to adjust the outfeed table 20. In an exemplary embodiment, the adjusting means may be comprised of e.g. studs 72 and hinges 74.

The magnetic device 30 operates where at least a portion of the magnetic device 30 is above the outfeed table 20. In operation the magnetic device 30 collects magnetic material from the layer of oversized material on the outfeed table 20. A magnetic discharge collection device 60 may be positioned at least partially below the magnetic device 30. The magnetic discharge collection device 60 collects magnetic material. Such magnetic material may include one or more of the following: iron (Fe), nickel (Ni), or cobalt (Co), Magnetite (Fe304), Ulvospinel (Fe2Ti02), Hematite (aFe203), llmenite (FeTi02), Maghemite (YFe203), Jacobsite (MnFe204), Trevorite (NiFe204), Magnesioferrite (MgFe204), Pyrrhotite (Fe7S8), Greigite (Fe3S4), Troilite (FeS), Goethite (aFeOOH), Lepidocrocite (vFeOOH), Feroxyhyte (5FeOOH), Awaruite (Ni3Fe) or Wairauite (CoFe). In some embodiments the magnetic discharge collection device 60 contains a protective cover 62 for preventing magnetic material spray or discharge and/or a collection bin 61 for storing or collecting the magnetic material.

In an alternative embodiment of an apparatus for removing magnetic material from a grinding circuit, the apparatus may comprise a screening device 10 configured for separating undersized material from oversized material and a belt magnet located above the screening device 10, the belt magnet being operatively configured for removing the magnetic material from the layer of oversized material. In an exemplary embodiment, the belt magnet is placed very close to the screening device 10 so that there is a minimized horizontal gap between the top portion of the screening device and the bottom portion of the belt magnet. A method for removing a magnetic material from a grinding circuit is also provided. In an exemplary embodiment, the method includes separating undersized material from oversized material using a screening device 10;

transferring the oversized material from the screening device 10 to an outfeed table 20; spreading the oversized material into a layer of oversized material on the outfeed table 20; removing magnetic material from the layer of oversized material using a magnetic device 30. In an exemplary embodiment, the step of spreading the oversized material into a layer of oversized material on the outfeed table includes adjusting the angle of the outfeed table 20 from the horizontal plane (H).

In one embodiment, the method may further include washing the oversized material after separating the undersized material from the oversized material using a screening device 10 but before transferring the oversized material from the screening device 10 to the outfeed table 20. In another exemplary embodiment, the method may further include collecting the magnetic material using a magnetic discharge collection device 60.

The apparatus described herein is further advantageous in that significant costs are recouped by recovering the magnetic material (i.e. - steel scrap) and thereby reducing costs spent on new grinding media. Typical economics are as follows: · Grinding ball consumption - Typical is 1 .2 kg/tonne ore (SAG/Ball circuit)

Media cost - $1 ,500/tonne

Media cost - $1 .80 per tonne ore processed

Grinding ball recovery as scrap - approximately 30%

Ball scrap price - approximately 30% of new · Net benefit $0.16 per tonne processed, or 9% reduction in media cost.

Other benefits may include decreased wear on downstream equipment within the grinding circuit, for example on pumps, piping and valves; an increase in efficiency within the grinding circuit and a decrease in the amount of unwanted materials in gravity concentrates.

It is to be understood that the form of this invention as shown is merely a preferred embodiment. Various changes may be made in the function and arrangement of parts; equivalent means may be substituted for those illustrated and described; and certain features may be used independently from others without departing from the spirit and scope of the invention as defined in the following claims.

List of Components:

10 - screening device

12 - screen

13 - vibrator

5 14 - mounting plate

16 - feed chute

17 - feed chute legs

18 - legs

19 - spring feet

i o 20 - outfeed table

21 - first side outfeed table

22 - second side outfeed table

23 - liner plate

24 - first end outfeed table

15 25 - second end outfeed table

30 - magnetic device

31 - belt

32 - drive device

34 - first longitudinal rail of magnetic device

20 36 - second longitudinal rail of magnetic device

37 - roller

38 - first end of magnetic device

39 - second end of magnetic device

40 - oversize discharge

25 50 - washing device

60 - magnetic discharge collection device

61 - collection bin

62 - protective cover

70 - adjusting means

30 72 - stud

74 - hinge

100 - frame

102 - skid beam

104 - vertical column

35 106 - horizontal tie beam

108 - cross brace

200 - location of apparatus within grinding circuit a - angle

h- horizontal plane

40

Claims

1 . An apparatus for removing a magnetic material from a grinding circuit comprising: a screening device configured for separating undersized material from 5 oversized material; an outfeed table, at least a portion of the outfeed table being positioned below the screening device, the outfeed table being operatively configured for receiving the oversized material from the screening device and for spreading the oversized material into a layer of oversized material; and, i o a magnetic device, at least a portion of the magnetic device located above the outfeed table, the magnetic device being operatively configured for removing the magnetic material from the layer of oversized material.

2. The apparatus of claim 1 , further comprising a frame, wherein the screening device and the outfeed table are supported by the frame.

15 3. The apparatus of claim 1 , wherein the screening device is comprised of a vibrating screen.

4. The apparatus of claim 1 , further comprising: an oversize discharge located adjacent a first end of the screening device and positioned between the screening device and the outfeed table.

20 5. The apparatus of claim 1 , further comprising: a washing device positioned between the screening device and the outfeed table, the washing device being operatively configured to wash the oversized material.

6. The apparatus of claim 4, wherein the layer of oversized material

25 comprises pre-washed oversized material.

7. The apparatus of claim 2, wherein the magnetic device is supported by the frame.

8. The apparatus of claim 1 , wherein the outfeed table is vertically adjustable from a horizontal plane.

9. The apparatus of claim 8, wherein the outfeed table is tiltable between approximately 0 degrees and 45 degrees from the horizontal plane.

10. The apparatus of claim 1 , wherein the magnetic device is vertically adjustable from a horizontal plane.

1 1 . The apparatus of claim 10, wherein the magnetic device is tiltable between approximately 0 degrees and 45 degrees from the horizontal plane.

12. The apparatus of claim 1 , further comprising a magnetic discharge collection device, at least portion of the magnetic discharge collection device positioned below the magnetic device.

13. The apparatus of claim 1 , wherein the magnetic device is a belt magnet.

14. The apparatus of claim 1 , further comprising: an oversize discharge located adjacent a first end of the outfeed table wherein at least at least a portion of the oversize discharge is positioned below the outfeed.table.

15. The apparatus of claim 14, further comprising: a washing device positioned between the outfeed table and the oversize discharge, the washing device being operatively configured to wash the oversized material.

16. The apparatus of claim 1 , further comprising an adjusting means for adjusting or tilting the outfeed table, the adjusting means being operatively connected to the outfeed table.

17. The apparatus of claim 1 , wherein the magnetic material comprises iron (Fe), nickel (Ni), or cobalt (Co).

18. The apparatus of claim 16, wherein the magnetic material comprises one or more of the group consisting of: Magnetite (Fe304), Ulvospinel (Fe2Ti02),

5 Hematite (aFe203), llmenite (FeTi02), Maghemite (YFe203), Jacobsite

(MnFe204), Trevorite (NiFe204), Magnesioferrite (MgFe204), Pyrrhotite (Fe7S8), Greigite (Fe3S4), Troilite (FeS), Goethite (aFeOOH), Lepidocrocite (yFeOOH), Feroxyhyte (5FeOOH), Awaruite (Ni3Fe), and Wairauite (CoFe).

19. The apparatus of claim 1 , wherein the outfeed table is a non-vibrating i o outfeed table.

20. A method for removing a magnetic material from a grinding circuit comprising: separating undersized material from oversized material using a screening device;

15 transferring the oversized material from the screening device to an outfeed table; spreading the oversized material into a layer of oversized material on the outfeed table; removing magnetic material from the layer of oversized material using a 20 magnetic device.

21 . The method of claim 20, further comprising: washing the oversized material after separating the undersized material from the oversized material using a screening device but before transferring the oversized material from the screening device to the outfeed table.

22. The method of claim 20, wherein spreading the oversized material into a layer of oversized material on the outfeed table comprises adjusting the angle of the outfeed table from the horizontal plane.

23. The method of claim 20, further comprising: collecting the magnetic material using a magnetic discharge collection device.

24. An apparatus for removing a magnetic material from a grinding circuit comprising: a screening device configured for separating undersized material from oversized material; and a belt magnet located above the screening device, the belt magnet being operatively configured for removing the magnetic material from the layer of oversized material.

25. The apparatus of claim 24, wherein a horizontal gap between the top portion of the screening device and the bottom portion of the belt magnet is minimal.

26. The apparatus of claim 24, further comprising a frame, wherein the screening device is supported by the frame.

27. The apparatus of claim 24, wherein the screening device is comprised of a vibrating screen.

28. The apparatus of claim 26, wherein the belt magnet is supported by the frame.

29. The apparatus of claim 24, wherein the belt magnet is vertically adjustable from a horizontal plane.

30. The apparatus of claim 29, wherein the belt magnet is tiltable between approximately 0 degrees and 45 degrees from the horizontal plane.

31 . The apparatus of claim 24, further comprising a magnetic discharge collection device, at least portion of the magnetic discharge collection device positioned below the belt magnet.

32. The apparatus of claim 24, wherein the magnetic material comprises iron (Fe), nickel (Ni), or cobalt (Co).

33. The apparatus of claim 24, wherein the magnetic material comprises one or more of the group consisting of: Magnetite (Fe304), Ulvospinel (Fe2Ti02), Hematite (aFe203), llmenite (FeTi02), Maghemite (YFe203), Jacobsite (MnFe204), Trevorite (NiFe204), Magnesioferrite (MgFe204), Pyrrhotite (Fe7S8), Greigite (Fe3S4), Troilite (FeS), Goethite (aFeOOH), Lepidocrocite (yFeOOH), Feroxyhyte (5FeOOH), Awaruite (Ni3Fe), and Wairauite (CoFe).