FIELD OF THE INVENTION

[0001] The present invention relates to a magnetic separator for extracting haematite from crushed ore.

BACKGROUND TO THE INVENTION

[0002] To date no dry magnetic separator for haematite is known, primarily due to the low magnetic susceptibility of haematite.

[0003] The present applicant is also the applicant for Australian Patent No

2017325592 which discloses a planar magnetic separator which works with magnetite, but has been ineffective in separating haematite as the device produces an insufficient magnetic field. Whilst the magnetic field of the separator could be increased by the use of stronger magnets, suitably strong magnets are not readily, if at all, available.

[0004] The object of this invention is to provide a separator with a strong enough magnetic field to extract haematite to alleviate the above problems, or at least provide the public with a useful alternative.

SUMMARY OF THE INVENTION

[0005] In a first aspect the invention provides a separator for extracting magnetic material from a suspended stream of weakly magnetic material and non-magnetic material, comprising a planar chamber with an inlet port, an outlet port and a tailings port, and a first magnetic assembly and a second magnetic assembly rotating in planes on either side of and parallel to the chamber, the magnetic assemblies drawing the magnetic material towards the outlet port whilst leaving non-magnetic material to exit the chamber by the tailings port, wherein the separator further comprises a yoke to magnetically connect the first magnetic assembly with the second magnetic assembly.

[0006] The first and second magnetic assemblies may rotate in the same direction as the suspended stream, or in the opposite direction to the suspended stream.

[0007] The magnetic assemblies are rotated by a shaft, and the shaft may be magnetically isolated from the yoke, magnetically coupled to the yoke or the shaft nay form the yoke. [0008] The magnetic and non-magnetic material may be suspended in an airstream, or suspended in a water stream.

[0009] Preferably the suspended stream includes strongly magnetically susceptible material to help increase the strength of the magnetic field.

[0010] It should be noted that any one of the aspects mentioned above may include any of the features of any of the other aspects mentioned above and may include any of the features of any of the embodiments described below as appropriate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows.

[0012] Figure 1 shows a magnetic separator system according to a first embodiment of the invention from a first perspective view.

[0013] Figure 2 shows a magnetic separator system according to a first embodiment of the invention from a second perspective view.

[0014] Figure 3 shows a chamber assembly of the magnetic separator system in isolation.

[0015] Figure 4 shows the magnetic assemblies of the chamber assembly in isolation.

[0016] Figure 5 shows a single magnetic assembly in isolation.

[0017] Figure 6 shows the chamber assembly in isolation with its front cover removed to reveal the chamber within.

[0018] Figure 7 shows the chamber assembly with both covers removed to show the relationship between the chamber and a magnetic assembly.

[0019] Figure 8 identifies the different areas of operation of the chamber assembly. [0020] Figure 9 shows a magnetic separator according to a second embodiment of the invention.

[0021] Figure 10 shows a magnetic separator according to a third embodiment of the invention.

[0022] Figure 1 1 shows a chamber body according to a fourth embodiment of the invention.

DRAWING COMPONENTS

[0023] The drawings include the following integers.

10 magnetic separator system

12 support

14 drive motor

16 gear box

18 pulley

20 magnetic separator

22 pulley

24 shaft

26 bush

31 first magnetic assembly

32 second magnetic assembly

40 plate

41 , 42 magnets

43 hubs

44 yoke

50 chamber assembly (first embodiment)

51 direction of rotation

52 front cover

54 rear cover

56 chamber body

57 chamber

58 chamber wall

60 ore inlet

61 air flow direction 62 tailings outlet

64 haematite outlet

80, 81 capture regions

85 transport region

90 dislodgement region

220 magnetic separator (second embodiment)

224 shaft

231 first magnetic assembly

243 hubs

320 magnetic separator (third embodiment)

324 shaft

331 first magnetic assembly

450 chamber assembly (fourth embodiment)

451 direction of rotation

454 rear cover

456 chamber body

457 chamber

458 chamber wall

460 ore inlet

461 air flow direction

464 haematite output

470 air flow valve

480, 481 , 482 capture regions

490 dislodgement region

DETAILED DESCRIPTION OF THE INVENTION

[0024] The following detailed description of the invention refers to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts. Dimensions of certain parts shown in the drawings may have been modified and/or exaggerated for the purposes of clarity or illustration.

[0025] The separator of the invention comprises a chamber through which crushed haematite ore is transported by air, and rotating magnetic disks on either side of the chamber to capture the haematite from the air stream to separate it from tailings. Although the two disks are rotating, a magnetic circuit is made between them with the aid of an axial yoke passing between the disks. This allows a strong magnetic field to be produced in the chamber between the magnetic disks suitable for extracting haematite from crushed ore.

[0026] Four embodiments of the invention are presented, in the first three

embodiments the airflow carrying the ore is in the opposite direction to the rotation of the magnetic disks, and in the fourth embodiment the airflow carrying the ore is in the opposite direction to the rotation of the magnetic disks. The first embodiment is presented in greater detail; the remaining embodiments are presented mainly by reference to its differences to the first embodiment. Typical dimensions and operating parameters are discussed in relation to the fourth embodiment.

[0027] A magnetic separator system 10 incorporating a magnetic separator 20 is shown from two different perspective views in Figure 1 and Figure 2. The system 10 generally comprises the separator 20 and drive motor 14 mounted on support frame 12. The motor drives the separator via gear box 16, and pulleys 18 and 22. Not shown are well known upstream and downstream components for supplying the ore to be separated in an airstream to the ore inlet 60 and collecting the separated haematite from haematite output 64 and tailings from tailing outlet 62. The magnetic separator 20 comprises a chamber assembly 50 according to a first embodiment, and first magnetic assembly 31 and second magnetic assembly 32 which are driven in unison to rotate adjacent the front cover 52 and rear cover 54 of the chamber assembly.

[0028] The chamber assembly 20 and is components are presented in Figure 3 to Figure 8. Figure 3 shows the chamber assembly 20 in isolation from the rest of the magnetic separator system 10; Figure 4 shows the magnetic assemblies 31 and 32 in isolation; Figure 5 shows the second magnetic assembly 32 in isolation; Figure 6 shows the chamber assembly 50 in isolation with its front cover removed; Figure 6 shows both covers 52, 54 removed to show the relationship between the chamber assembly 50 and the magnetic assembly 31 ; whilst Figure 8 identifies the different regions of operation of the chamber assembly.

[0029] The chamber assembly 20 comprises a chamber body 56 fitted with front cover 52 and rear cover 54 to define a chamber 57 within. Ore to be separated enters the chamber in an airstream via ore inlet 60 from which haematite is caught between the first and second magnetic assemblies 31 , 32 as they rotate and is transported to haematite outlet 64. Tailings pass through the chamber and out via tailings outlet 62. The magnetic assemblies 31 , 32 are mounted to shaft 24 via hubs 43 and bushes 26. The shaft 24 is mounted on bearings 28 (seen in Figures 1 and 2) and driven via pulley 22.

[0030] The magnetic assemblies 31 and 32 shown in isolation in Figures 4 and 5 include a series of magnets 41 , 42 mounted on plates 40. Yoke 44 helps complete the magnetic circuits between opposing magnets. The magnets 41 on the first magnetic assembly 31 are organised such that their magnetic poles are orientated oppositely to the magnetic poles of the opposing magnets 42 on the second magnetic assembly 32, i.e. a magnet with a north pole facing inwardly on one assembly is positioned opposite a magnet with a north pole facing outwardly on the other assembly. Various

arrangements of magnets may be used to achieve this, preferably an arrangement where both magnetic assemblies are identical and rotationally offset from each other to align the poles is used. The yoke 40 includes a hollow centre and the hubs 24 of the magnetic assemblies are mounted by non-magnetic bushes to the shaft 24 to give a non-magnetic gap between the magnetic assemblies and the shaft used to rotate them. This allows the magnetic flux to pass easily between the two plates and prevents flux leakage to other parts of the machinery via the shaft 24. The second and third embodiments of the invention have different shaft and yoke arrangements, and are discussed further below.

[0031] The operation of the separator is best appreciated with the aid of Figure 8. The dashed lines show magnetic regions defined by the outlines of the magnets 41 on plate 31 which are sitting below the rear cover 54. These regions will rotate through the chamber 57 in the direction shown by arrow 51. As the regions rotate they will perform different functions. After the ore enters the chamber in an airstream via ore inlet 60 it will pass over capture regions 80, 81. The airflow direction is indicated by arrow 61 and is opposite to the rotation 51 of the magnetic regions. As this region is part of a magnetic circuit it will have a high magnetic flux and capture the magnetically susceptible haematite from the ore airstream. The tailings will continue moving with the airstream and exit the chamber via the tailings outlet 62. Once the capture regions 81 , 82 have rotated out of the airstream they will become a transport region 85, moving the captured haematite to the dislodgement region 90 in which the haematite comes in contact with an internal wall 58 of the chamber. The haematite will build up against the wall, and as the magnet 41 moves away will fall out of the chamber via haematite outlet 64.

[0032] The chamber body is preferably made from a machinable plastic such as HDPE (High Density Poly-Ethylene), and the covers from non-magnetic stainless steel. The chamber assembly is generally U-shaped providing clearance from the yoke and allowing easy removal from and insertion into the chamber to facilitate changeover.

This is an important consideration as the movement of the material through the chamber leads to abrasion.

[0033] Figure 9 shows a magnetic separator 220 according to a second

embodiment in which the shaft 224 and yoke 243 of first magnetic assembly 231 are in direct contact with each other, i.e. not magnetically isolated. This allows for a simpler construction.

[0034] A third embodiment of the magnetic separator 320 is shown in Figure 10 in which the shaft 324 of the first magnetic assembly 331 acts as a yoke.

[0035] The magnetic separator system 10, may alternatively incorporate a chamber assembly 450 according to a fourth embodiment of the invention which is shown in Figure 1 1. The fourth embodiment shares many aspects with the first to third

embodiments and will mainly be discussed with regards to points of difference. The fourth chamber assembly 450 primarily differs from the first chamber assembly 50 in that the magnetic assemblies rotate in the same direction as the airflow through the chamber as opposed to the first chamber in which the magnetic assemblies rotate in the opposite direction to the airflow through the chamber. As per the first embodiment of the invention, magnetic assemblies (not shown) are positioned either side of the chamber assembly which in this case rotate as per direction arrow 451. As before, a chamber body 456 in conjunction with rear cover 454 and front cover (not shown) define a chamber 457. Ore suspended in an airflow enters the chamber via ore inlet 460 and passes over capture regions 480, 481 and 482 (which have magnets above and below) which extract haematite from the airflow and transport it around to the dislodgement region 490 in which the haematite comes in contact with an internal wall 458 of the chamber. The airflow indicated by arrow 461 is in the same direction as the rotation of the magnetic assemblies indicated by 451. The haematite will build up against the wall, and as the magnets move away will fall out of the chamber via haematite outlet 464. The tailings exit the chamber via a tailings outlet (not shown) which sits opposite an air flow valve 470 which is open to the atmosphere and adjusted to achieve neutral air flow at the haematite output. In this embodiment the magnets rotate in the same direction as the airflow, and are matched roughly in speed to maximise capture of the haematite from the airstream. The magnetic assembly (not shown) may be as per the magnetic assemblies of any of the first three embodiments, with the drive shaft isolated from the yoke, in contact with the yoke, or forming the yoke itself.

[0036] The throughput of the system can be adjusted by scaling the various components, speeds and number of magnets. For a practical system a magnetic field strength of approximately 8,000 Gauss is sufficient to extract the haematite, with other parameters being varied to achieve the desired throughput. This has only been achievable by the yoke partially completing the magnetic circuit between the opposing magnets. The magnetic field can be further enhanced with the addition of strongly susceptible material to the ore feed such as steel shot or magnetite. This extra material is readily captured between the magnets and when in place helps maximise the magnetic field which in turn increases the capture of the weakly magnetically

susceptible haematite. The magnetic material can be easily separated downstream from the haematite output using a low strength magnetic field that is too weak to attract the haematite.

[0037] A practical system according to the second embodiment for handling a throughput of 10.7 tonnes of ore per hour with a 36% head grade has been produced.

In this system the chamber is 2,141 mm in diameter and 30 mm high, with an ore inlet 860 mm wide. Other dimensions may be scaled from Figure 9. The magnetic assemblies include circular plates 2,100 mm in diameter fitted with 48 magnets each 1 15 mm in diameter and 50 mm thick and capable of producing a magnetic field of 8,000 Gauss. A venturi fitted to a 190 mm diameter feed pipe with an air flow of 968 m ³ /hr at 10 m/s introduces ore to give an air loading of 0.3%. The dimensions of the chamber maintain a similar air speed which is roughly matched by the circumferential speed of the magnetic disks, which rotate at 48 rpm (or 5.3 m/s at their circumference). The arrangement of magnets used can hold approximately 29 grams of haematite between a pair of magnets, which is sufficient to extract all of the haematite from the airflow. A test system has been shown to recover over 95% of the haematite present in the ore feed.

[0038] Whilst the system has been described in the context of separating haematite from an airstream of crushed ore, it is also suitable for separating haematite from crushed ore suspended in a water stream, and may also be used for separating other weakly magnetic material from non-magnetic material or even strongly magnetic material from non-magnetic material.

[0039] The reader will now appreciate the present invention which provides a separator with a strong enough magnetic field to effectively extract haematite.

[0040] Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in this field.

[0041] In the present specification and claims (if any), the word "comprising" and its derivatives including "comprises" and "comprise" include each of the stated integers but does not exclude the inclusion of one or more further integers.