AU2017200577B1 - Magnetic Ore Separator - Google Patents

Abstract

A separator for magnetic materials combining magnetic attraction and cyclonic action. Magnetically susceptible material such as magnetite or haematite is introduced into a cyclonic chamber in either an air stream or water stream. A rotating magnetic shell around the chamber attracts the magnetic material to the walls of the chamber where it builds up until it falls under its own weight or is sucked out of the chamber. As the material rotates about the chamber, non-magnetic impurities move to the surface of the magnetic material and are removed by the fluid flow.

Description

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Magnetic Ore Separator 2017200577 30 Jan 2017

FIELD OF THE INVENTION

[0001] The present invention relates to an ore separator, in particular an ore separator using a combination of magnetics and a cyclone to separate ores such as magnetite and haematite either wet or dry.

BACKGROUND TO THE INVENTION

[0002] The present invention provides a means for separating magnetically susceptible material using low intensity magnetics. Whilst the invention is described below in use with magnetite and haematite, it is to be understood that the invention can be used to separate a wide range of material that is weakly magnetically susceptible.

[0003] At present the preferred process to concentrate magnetite ore is to use wet drum magnetic separators. Typically several circuits are used with the ore being crushed finer at each stage and with the ore needing to be dried before crushing. Whilst effective, this process requires a lot of equipment, energy and water to operate. Often large volumes of water are not available in the vicinity of magnetite deposits necessitating the transport of the ore to a remote processing plant for concentration. This roughly doubles the amount of material that needs transporting and can render a mine uneconomical.

[0004] Haematite is a readily abundant ore used for the production of iron. Haematite is usually found mixed with other materials, typically silicon based and requires refining before it can be fed into a blast furnace to produce iron. As haematite is only weakly ferromagnetic, separation is usually performed by froth floatation. This process requires large volumes of water, making it infeasible or expensive in regions without ready access to water. Some separation techniques have been developed using magnetics, but have needed to incorporate very high intensity magnetics (> 50,000 Gauss) with their inherent expense and operational issues. Known magnetic separators have also relied on water to suspend the ore and products.

[0005] Cyclonic separation, using either air cyclones and hydro cyclones is well known for the separation of ores. For ferromagnetic materials, attempts have been made to increase the efficiency of cyclones by the addition of magnetic fields to the 2 2017200577 29 Jun2017 cyclone chamber. Notably Coutere et al in US Patent 6,355,178 provide a cyclone with sequential magnetic fields in upper and lower regions of a cyclone separator. Whilst some benefit has been shown with such systems, their adoption has been low due to the marginal improvements that they offer over conventional cyclone systems.

[0006] The object of this invention is to provide a cyclone with enhanced separation performance for magnetically susceptible material, or at least provides the public with a useful alternative.

SUMMARY OF THE INVENTION

[0007] The invention provides a separator for magnetic material comprising a separation chamber surrounded by a magnetic shell of discrete magnets, wherein the separation chamber and magnetic shell rotate with respect to each other.

[0008] Preferably the discrete magnets are arranged two dimensionally with the poles of adjacent discrete magnets non-aligned.

[0009] The separation chamber may be stationary and the magnetic shell rotates., or the separation chamber rotates and the magnetic shell is stationary.

[0010] Preferably the separation chamber and magnetic shell are cylindrical or frustoconical; the separation chamber may be pre-charged with a bed of magnetic material [0011] The magnetic material may be introduced into the separator in an air stream ora water stream.

[0012] The magnets may be electromagnet.

[0013] 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

[0014] Preferred features, embodiments and variations of the invention may be 3 2017200577 30 Jan 2017 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.

[0015] Figure 1 shows a magnetic separator according to a first embodiment of the present invention with a cylindrical chamber in a cutaway perspective view.

[0016] Figure 2 shows a cutaway view of the separator from side on.

[0017] Figure 3 shows a bed of magnetically susceptible material being formed in the separator.

[0018] Figure 4 shows the bed of material growing.

[0019] Figure 5 shows the material being extracted from the separator.

[0020] Figure 6 shows the rotating cylindrical magnetic shell of the separator.

[0021] Figure 7 shows the rotating frustoconical magnetic shell of a second embodiment of the separator.

[0022] Figure 8 shows a magnetic separator according to a second embodiment of the present invention with a frustoconical chamber in a cutaway side view.

DRAWING COMPONENTS

[0023] The drawings include the following integers. 10 magnetic separator (first embodiment) 20 motor 21 motor pulley 22 drive pulley 30 body 31 bottom bearing 32 top bearing 34 stationary separation chamber 35 feed inlet 36 gangue outlet 4 40 rotating magnetic shell (cylindrical) 2017200577 30 Jan 2017 41 shell body 42 magnets (first polarity orientation) 42’ magnets (second polarity orientation) 50 product collector 51 collector mouth 52 collector output 60 restrictor 70 clump of separated ore 80 further separated material 210 magnetic separator (second embodiment) 212 body 214 ore inlet 216 product outlet 218 gangue outlet 220 drive pulley 222 motor pulley 224 motor 230 stationary separation chamber 232 vortex finder 240 rotating magnetic shell (frustoconical) 242 body 243 magnet mounting holes 244 magnets (first polarity orientation) 244’ magnets (second polarity orientation) 246 lower flange 248 upper flange 250 lower bearing 252 upper bearing 254 inner bearing

DETAILED DESCRIPTION OF THE INVENTION

[0024] The following detailed description of the invention refers to the 5 2017200577 30 Jan 2017 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 present invention provides a separator for magnetically susceptible material combining a cyclone and a rotating magnetic shell around the cyclone. The invention includes several embodiments, with the separation chamber being either cylindrical or frustoconical and the ore to be separated transported in either an air stream or water stream. The separator has been found to be successful separating either magnetite or haematite to a high level of purity. A separator with a cylindrical body and using an air stream will be discussed primarily for convenience. The other embodiments will be discussed from the point of view of their differences to the first embodiment.

[0026] GENERAL DESCRIPTION ...

[0027] A magnetic separator 10 according to a first embodiment of the present invention is shown in a cutaway perspective view in Figure 1 and closer up in the side view of Figure 2. The separator comprises a cylindrical body 30 with an internal stationary cylindrical separation chamber 34. Feed material enters the separation chamber via feed inlet 33 either in an air stream and is separated (by means discussed in detail below) into product which leaves under suction via outlet 52 of product collector 50 and gangue which leaves under suction via gangue outlet 36. Restrictor 60 limits the cross sectional area of the separation chamber to limit the volume of fluid flow. The product collector 50 surrounds the restrictor 60 and provides a mouth 51 set in from the walls of the separation chamber. Surrounding the separation chamber is a magnetic shell 40 mounted via bottom bearing 31 and top bearing 32. Drive pulley 22 allows the magnetic shell to be rotated via a drive belt (not shown) from motor pulley 21 driven by electric motor 20.

[0028] Figure 6 shows a perspective view of a complete rotating magnetic cylinder 40 in isolation. The magnetic cylinder comprises a cylindrical body 41 made from a non-magnetic material such as aluminium in which is embedded 4 columns of magnets 42 capable of producing a magnetic field of a few thousand Gauss each. The magnets are separated and disposed in columns to allow for flow of material through the 6 2017200577 30 Jan 2017 separator. To avoid continuous walls of material being formed between the magnets, the magnets are arranged such that adjacent magnets have opposite magnetic poles facing outwards. This is most relevant for magnets within a column as they are in close proximity, but is also beneficial for the rows of magnets around the shell. Magnets with a first pole facing outwards are denoted in Figure 6 by the numeral 42 and those with a second pole facing outwards by the numeral 42 ‘.

[0029] The operation of the separator 10 can be appreciated with the aid of Figures 3 to 5 which show a cutaway side view of the separator. For the sake of representational convenience the action of the separator is shown only for a single magnet. The remaining magnets operate in the same manner.

[0030] Crushed ore is first suspended in an air stream (not shown) to form a feed and then tangentially fed into the bottom of the chamber separator 34 via inlet 35. The feed develops a rotational (cyclonic) action spiralling up the chamber. The magnetically susceptible ore is attracted from the feed towards the magnets of the rotating magnetic shell, with some ore being magnetically “captured” to form a clump of separated ore 70 adjacent magnet 42. The remaining feed continues upwards, interacting in a similar way with the other magnets. The non-magnetic material in the feed will be unaffected by the magnets and continue upwards and out of the chamber via gangue outlet 36. As the magnetic shell 40 is rotated the clump 70 will remain attracted to magnet 42 and rotate in unison with it, being dragged across the inner surface of the chamber 34. Some non-magnetic material may also be captured by the clump 70. As the clump 70 is dragged around the chamber, the magnetic ore particles will adopt a random spiking motion forcing any trapped non-magnetic material to the surface of the clump where it can be carried away by the upwardly spiralling feed.

[0031] As more feed passes through the separator, the clump of separated ore 70 will continue to grow with further separated material 80 until it either falls under its own weight or is sucked into the mouth 51 of the collector 50 and removed via collector output 52.

[0032] The above description applies to strongly magnetic ore such as magnetite. For ore that is only weakly susceptible to magnetic fields such as haematite, the separator is first primed with magnetite to produce a clump of separated ore 70 which serves to concentrate the magnetic field. As subsequent feed of haematite can then be 7 2017200577 30 Jan 2017 separated to form a clump of further separated material 80 which will eventually fall under its own weight or be sucked into the mouth 51 of the collector 50 and removed via collector output 52.

[0033] A second embodiment of the separator is show as 210 in Figure 8 which includes a frustoconical separation chamber 230 and a corresponding frustoconical rotating magnetic shell 240 which is shown in isolation in Figure 7.

[0034] Similar to the separator 10 of the first embodiment, the separator 210 comprises a cylindrical body 212, separation chamber 230, bottom ore inlet 214, product outlet 216 at the bottom and gangue outlet 218 at the top. Surrounding the stationary separation chamber 230 is rotating magnetic cone 240 driven via drive pulley 220, motor pulley 222 and external motor 224. Drive belts between the pulleys are not shown. The body 212 of the separator holds lower bearing 250 and upper bearings 252 which in turn support rotating magnetic cone 240 via lower flange 246 and upper flange 248. The magnetic cone comprises a body 242 with four columns of magnets 244 and 244’ disposed at 90 degree intervals about the cone, two columns of which are visible in the figures. Again, the magnets are preferably arranged with adjacent magnets in both columns and rows having opposing polarities facing outwards.

[0035] The operation of the magnetic separator combines 3 separate aspects to separate the paramagnetic material from gangue. Any of these aspects will provide separation by themselves, however it is preferred to combine the three aspects to maximise separation efficacy.

[0036] A first aspect of the invention is a cyclonic action. Feed suspended in air enters the inner cone 230 at the bottom where it is widest. The feed spirals towards the top of the cone with increasing velocity as the diameter of the cone decreases separating the heavier ore and leaving the gangue to discharge via the product outlet 216.

[0037] In a second aspect the converging cone walls increase the strength of the magnetic field in the centre of the cone, thus separating the lower grade feed as it reaches the top of the cone.

[0038] The most significant aspect of the separator is the rotating magnetic field 8 2017200577 30 Jan 2017 produced by the rotating magnetic cone 240. As the feed spirals around the internal cone 230 the paramagnetic material will be drawn to the surface of the internal cone adjacent to the magnets. This material will then be drawn around the internal cone as the magnetic cone rotates. Further material will be attracted and columns of material will grow adjacent to each magnet. The columns will grow towards the centre of the cone allowing them to be drawn into the vortex finder by suction or the columns will collapse under their own weight and fall into the vortex finder. The columns of material are effectively dragged across the surface of the cone and in doing so are being constantly agitated. This allows entrapped gangue to bubble to the surface of the columns and be drawn away by the spiralling air flow. By having discrete magnets and arranging them in four columns air flow through the separator is maintained as the columns of material grow adjacent to each magnet.

[0039] The drawings show a working prototype separator with a 100mm diameter cone which can handle 60kg/hr of feed material. Good results have been found using a feed material with a d50 of 50pm, concentrating a feed of 35% magnetite to a product containing 60% magnetite. A magnetic field of 500 Gauss at 25 mm is used which can be readily achieved with rare earth magnets of 25mm diameter. The magnetic cone rotates at 150rpm. The design can readily scale to a 200mm diameter cone which can handle 500kg/hr, a 300mm cone which can handle 2,500kg/hr and beyond.

[0040] Both separators 10 and 210 effectively separate magnetic material. The conical separator 210 is preferred in some situations due to the intensifying magnetic fields as the cone converges which effectively collects magnetic material entrained with non-magnetic material. If a purer collected product is desired then the cylindrical separator 10 is preferred.

[0041] The reader will now appreciate the present invention which provides a magnetic separator using air to transport material. The separator provides a low cost option, in terms of both capital and operating costs, in comparison to traditional separation techniques and being able to operate without water will enable economic recovery of ore in new fields which would otherwise not be feasible.

[0042] The preferred embodiments shown and described above have operated with a finely crushed ore suspended in an air stream. With different feed and collection mechanisms as are well known in the art the separators can also work with ore 2017200577 30 Jan 2017 9 suspended in a water stream. The use of an air stream is preferred as it allows for operation in locations without abundant water supply.

[0043] The reader will now appreciate the present invention which provides a separator to efficiently separate magnetic material using low intensity magnetics. Advantageously the separator can operate using either air or water to transport the feed material.

[0044] The separator lends itself to mechanical, electrical and magnetic equivalent or near equivalents which can produce the same or similar results. For example in the preferred embodiment the separation chamber is stationary and is surrounded by a rotating magnetic shell. In alternative embodiments the separation chamber rotates and the magnetic shell remains stationary. In other embodiments the magnetic shell comprises differing arrangements of magnets. In still further embodiments the rotating magnetic shell is achieved by means of electromagnets which may also be switched in sequence. The shell and chamber may also take alternative shapes with varying results.

[0045] 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.

[0046] 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.

Claims (9)

1. A separator for magnetic material comprising a separation chamber surrounded by a magnetic shell of discrete magnets, wherein the separation chamber and magnetic shell rotate with respect to each other, and wherein the discrete magnets are arranged two dimensionally with the poles of the discrete magnets non-aligned in both circumferential and axial directions.

2. A separator as in claim 1, wherein the separation chamber is stationary and the magnetic shell rotates.

3. A separator as in claim 1, wherein the separation chamber rotates and the magnetic shell is stationary.

4. A separator as in claim 1 wherein the separation chamber and magnetic shell are cylindrical.

5. A separator as in claim 1 wherein the separation chamber and magnetic shell are frustoconical.

6. A separator as in claim 1 wherein the separation chamber is precharged with a bed of magnetic material

7. A separator as in claim 1, wherein the magnetic material is introduced into the separator in an air stream.

8. A separator as in claim 1, wherein the magnetic material is introduced into the separator in a water stream.

9. A separator as in claim 1 wherein the magnets are electromagnets.