Apparatus and method for performing magnetic separation

Abstract

A magnetic separator comprising a conveyor system configured to drive a conveyor element in a running direction, and a cooperating magnetic component arranged in proximity to the conveyor element. The magnetic component comprises a magnetic body having rows of magnets oriented transversely relative to a longitudinal axis of the magnetic component, the longitudinal axis being aligned generally parallel to the running direction of the conveyor element. The polar axis of each magnet is aligned generally parallel to the longitudinal axis and consecutive rows of the magnets are arranged so that like magnetic poles of the magnets face and repel each other to establish zones of alternating magnetic polarity. Elongate separator plates may be sandwiched between consecutive rows of the magnets. Also provided is a method for separating magnetically susceptible particulates from a mixture using the separator. The mixture may, for example, comprise Run-of-the-Mine, crushed ore, mining waste or slag.

Description

[0001] APPARATUS AND METHOD FOR PERFORMING MAGNETIC SEPARATION

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] This application claims priority from South African patent application number 2022 / 13909 filed on 22 December 2022, which is incorporated by reference herein.

[0004] FIELD OF THE INVENTION

[0005] This invention relates to the separation of magnetically susceptible particulates from mine tailings, Run of the Mine (ROM), crushed ore, paste and other types of mixtures.

[0006] BACKGROUND TO THE INVENTION

[0007] Mining is an important industry across the globe. An important aspect of mining is the separation of valuable material from valueless material. Separation may be required before and after processing of raw (“virgin”) materials in mining. Separation techniques may, for example, find application in the separation of components of ROM, crushed ore or mining waste. Separation of pre-processing materials and post-processing materials is encompassed. ROM is unprocessed mined material or ore in its natural state, consisting of the soil and rock of overburden, minerals, middlings, contaminants and impurities. Mining waste is typically created as a byproduct of mining operations. Mining waste refers to material extracted from the ground and processed during the ore-processing and enrichment phases of the mining process which remains after the valuable materials have been withdrawn. Mining waste has low to no economic value and is considered as unusable mineralised material. Efficient separation of valuable material from valueless material is an issue faced at all stages of the mining process.

[0008] Mining waste products and crushed ore or ROM can include a combination of fine suspended materials, including dissolved metals which can be valuable. Mining waste products can also include reagents, chemicals, and inorganic and organic additives. Such mining waste can present itself in the form of rock waste or processing waste, aqueous solutions, particulate emissions, water treatment sludge, metallurgical slag, and so forth. Mining waste in the form of rock waste often does not contain a metal concentration of economic interest weighed against the considerable effort to extract and separate such valuable metals from the surrounding waste products.

[0009] Mining waste is regularly stored near a mining production site since transporting it to another site may not be economically viable. Mining waste is often stored in the form of slurry in large manmade embankments, commonly referred to as tailings dams. Other mining waste or materials susceptible to reprocessing or further processing through mining processes include crushed ore, ROM and paste. Tailings are the waste materials left after the target minerals or metals have been extracted from the ore and consist of crushed rock, water, trace quantities of target metals and the additives used in processing. There are different types of tailings and they may, for example, result from the processing of iron ore, copper, manganese, chromium ore, mineral sands, platinum group metals (PGMs), ferrochrome, cassiterite, cobalt, nickel, and the like.

[0010] Since the process of product extraction in mining operations is never entirely efficient, the accumulation of heaps of tailings at mines is becoming an increasing environmental concern.

[0011] Current techniques and physical separation methods employed in the mining industry for the processing and separation of valuable materials from the mixture of raw materials or mining waste include flotation, gravity separation, centrifugal separation, magnetic separation, density separation such as reflux classifier, shaking tables, and various other techniques. Separation is used either for removing valuables from gangue (the commercially valueless material in which ore is found) in a slurry, or for removing impurities (contaminants) from a wanted material. The selection of a certain separation technique is based on the properties or qualities of the materials one wishes to extract such as weight, magnetism, density, etc. A combination of these techniques may also be employed to firstly separate the metal or mineral from the waste and secondly to separate components of the recovered material from one another. A consequence of inadequate separation and refining during the processing stage is the accumulation of mining waste.

[0012] Waste recycling or reuse processes for reprocessing mining waste include similar separation methods and techniques to those mentioned above. These reprocessing or additional processing methods and techniques face similar technical and economic challenges to those faced in the original extraction and separation processing steps. An inherent shortcoming of gravity separation is the considerable loss of tailings which occurs when the method is of the density type. An inherent shortcoming of existing methods and systems for magnetic separation is that some metals require a high magnetic flux for separation especially when separating paramagnetic minerals. Most magnetic separators achieve a maximum magnetic flux field of approximately 1 .5 tesla (15 000 gauss) on the direct magnetic surface with only approximately 1.1 tesla (11 000 gauss) exercised on the magnetic or paramagnetic particulates. This weak attraction potential results in a low yield of valuable materials and leaves relatively large amounts of valuable material remaining in the mixture after separation. Accordingly, existing methods and systems for magnetic separation exhibit lower economic feasibility since the cost of incorporating sufficiently strong magnets or electromagnets is too high. Existing methods and systems also do not provide for adjustments to be made to the magnetic flux field depending on the material that the system aims to attract, and often provide a constant magnetic flux field despite applying the system to variable materials and metals, i.e. existing methods and systems are not target specific. A further drawback of existing methods and systems is that magnetically susceptible particulates are not easily agitated loose from the flowing slurry as it runs through the separator, making the particulates more difficult to separate from the surrounding gangue in the slurry.

[0013] Current methods used to process, reprocess, separate and extract precious metals, paramagnetic materials and other magnetically susceptible values from gangue in a slurry, tailings, crushed ore, ROM and paste may accordingly be insufficient to extract economically feasible quantities of such desired materials.

[0014] The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application.

[0015] SUMMARY OF THE INVENTION

[0016] In accordance with an aspect of this invention there is provided a magnetic separator comprising a conveyor system configured to drive a conveyor element in a running direction, and a cooperating magnetic component arranged in proximity to the conveyor element; the magnetic component having a length defined by a longitudinal axis aligned generally parallel to the running direction of the conveyor element; and the magnetic component comprising at least one magnetic body having an array of magnets; wherein rows of magnets in the array are oriented transversely relative to the longitudinal axis of the magnetic component, with the polar axis of each magnet aligned generally parallel to said longitudinal axis; and wherein at least one pair of consecutive rows of the magnets are arranged so that like magnetic poles of the magnets face and repel each other, thereby to establish zones of alternating magnetic polarity along the magnetic body.

[0017] The conveyor system may comprise a belt conveyor system and the conveyor element may comprise a conveyor belt. The cooperating magnetic component may comprise a conveyor bed. The conveyor bed may be arranged to support the conveyor belt.

[0018] In certain embodiments the invention may provide a magnetic separator comprising: a belt conveyor system configured to drive a conveyor belt in a running direction; and a conveyor bed arranged to support the conveyor belt, the conveyor bed having a length defined by a longitudinal axis aligned generally parallel to the running direction of the conveyor belt; the conveyor bed comprising at least one magnetic body having an array of magnets; wherein rows of magnets in the array are oriented transversely relative to the longitudinal axis of the conveyor bed, with the polar axis of each magnet aligned generally parallel to said longitudinal axis; and wherein at least one pair of consecutive rows of the magnets are arranged so that like magnetic poles of the magnets face and repel each other, thereby to establish zones of alternating magnetic polarity along the magnetic body.

[0019] The magnetic body may further comprise at least one elongate separator plate arranged or sandwiched between consecutive rows of repelling magnets in the array. The separator plate may be oriented transversely relative to the longitudinal axis of the conveyor bed. The magnetic body may comprise a plurality of such separator plates arranged generally parallel to one another. The separator plates may be arranged in a regularly-spaced series along the length of the magnetic body, with each plate extending across a breadth of the magnetic body. The separator plates may also be referred to as accelerator plates or fins.

[0020] Each separator plate may abut the two rows of magnets between which it is arranged. In certain non-limiting embodiments the separator plate may have a thickness in a range from about 1 mm to about 30 mm, optionally from about 2 mm to about 4 mm, optionally from about 2.5 mm to about 3 mm.

[0021] The conveyor bed may further comprise a back plate. The back plate may be positioned on a side of the conveyor bed opposite a portion of the conveyor belt configured to be fed with the mixture of particulate materials, so that the magnetic body separates the back plate from the conveyor belt. The back plate may abut the magnetic body. The back plate may have a thickness in a range from about 20 mm to about 50 mm, optionally about 30 mm. The back plate may be substantially non-magnetic. Without limitation thereto, the back plate may be made from stainless steel. The back plate may be made of a composite non-magnetic material.

[0022] The magnetic separator may include a washing apparatus for washing a slurry or other feed mixture conveyed on the conveyor belt during operation.

[0023] The magnetic separator may further include a feed apparatus for feeding the slurry or other feed mixture onto the conveyor belt in a mixture loading zone. The feed apparatus may be configured to be adjustable. The feed apparatus may be configured to be set at an adjustable distance from the conveyor belt.

[0024] The magnetic separator may further include a material clearing apparatus for removing magnetically susceptible and paramagnetic particulates from the conveyor belt in a particulates recovery zone. The material clearing apparatus may comprise one or more scrapers. The material clearing apparatus may comprise at least one water spray bar in conjunction with one or more scrapers.

[0025] Typically, the running direction of the conveyor belt is towards the particulates recovery zone. Particulates attracted by the magnets may be carried in a sludge adhering to the belt towards this zone, where they can be cleared from the belt by the material clearing apparatus.

[0026] The belt conveyor system may be configured such that the conveyor bed and conveyor belt have an operatively inclined orientation. The incline may be adjustable.

[0027] The magnetically susceptible or paramagnetic particulates may include substances selected from the group consisting of iron, copper, manganese, ferrochrome, chrome, magnetite, haematite, PGMs, and other precious metals.

[0028] A non-magnetic sheet may be provided between the conveyor bed and conveyor belt. Without limitation thereto, the non-magnetic sheet may be made of stainless steel.

[0029] The magnetic separator may comprise a plurality of magnetic bodies instead of just one. At least a portion of one such body may be constructed as described above. For example, it may include rows of magnets having alternating polarities. Other portions of said magnetic body (or entire lengths of other bodies) may have rows of magnets packed in a unipolar orientation.

[0030] Certain embodiments of the magnetic separator may be configured to operate in an inverted orientation compared to the embodiment described above. Thus, they may be configured such that the separation of the particulates takes place on the underside of the conveyor belt instead of on top of the belt.

[0031] In such embodiments, the feed apparatus may comprise a separate conveyor belt configured to serve as a feeder belt running through a pick-up zone underneath the conveyor belt of the separator. In use, magnetically susceptible particulates carried on the feeder belt are attracted up onto the underside of the conveyor belt of the separator. The magnetic separator may include an adjustment mechanism configured to adjust a magnetic field exerted through the conveyor belt. The adjustment mechanism may be configured to set variable inclinations of at least one of the magnetic bodies relatively to a running plane of the conveyor belt.

[0032] The magnetic separator may include a chute apparatus positioned underneath at least a part of the conveyor belt, for catching and channelling particulates and other material that falls off the belt so that it can be collected. A pivotable vane or splitter may be positioned inside the chute apparatus, for splitting or channelling different components of the falling particulates or other material into different collection zones.

[0033] The conveyor belt may have tripping formations spaced along its length. The tripping formations may, for example, comprise crosswise elongate cleats or bumpers.

[0034] The disclosed magnetic separator may be suitable for separating components of wet or dry mixtures comprising magnetic and magnetically susceptible particulates, less magnetic particulates, feebly magnetic particulates and non-magnetic particulates.

[0035] According to a further aspect of the invention there is provided a method for separating magnetically susceptible particulates from a mixture, the method comprising: operating a belt conveyor system to drive a conveyor belt in a running direction around a conveyor bed arranged to support the conveyor belt; feeding at least a portion of the mixture onto the running conveyor belt in a mixture loading zone; conveying the mixture on the conveyor belt proximate the conveyor bed, from the mixture loading zone to a particulates recovery zone; and at least partially clearing the particulates from the conveyor belt in the particulates recovery zone; wherein the conveyor bed has a length defined by a longitudinal axis aligned generally parallel to the running direction of the conveyor belt; wherein the conveyor bed comprises a magnetic body having an array of magnets, the magnets in the array being oriented transversely relative to the longitudinal axis of the conveyor bed, with the polar axis of each magnet aligned generally parallel to said longitudinal axis; and wherein at least one pair of consecutive rows of the magnets are arranged so that like magnetic poles of the magnets face and repel each other, thereby to establish zones of alternating magnetic polarity along the magnetic body in the running direction; and wherein the step of conveying the mixture on the conveyor belt proximate the conveyor bed comprises conveying the mixture past at least some of the zones of alternating magnetic polarity of the magnetic body, thereby to cause the particulates to roll or tumble along the conveyor belt.

[0036] The method may further include conveying the mixture past at least one elongate separator plate arranged or sandwiched between consecutive rows of repelling magnets in the array of magnets. The separator plate may be oriented transversely relative to the longitudinal axis of the conveyor bed. The separator plate may abut the two rows of magnets between which it is arranged.

[0037] The method may include conveying the mixture past a plurality of such separator plates arranged generally parallel to one another and in series along a length of the magnetic body in the running direction, each separator plate extending across a breadth of the magnetic body.

[0038] The conveyor bed may be inclined or horizontal and the method may include running the conveyor belt upwardly along the incline from the mixture loading zone to the particulates recovery zone.

[0039] The method may further include washing the mixture. The step of washing the mixture may comprise spraying a washing fluid onto the mixture as it is conveyed upwardly along the incline from the mixture loading zone to the particulates recovery zone, thereby to cause the washing fluid to flow downwardly along the conveyor belt, counter-currently to the upwardly running direction of the conveyor belt and conveyed mixture.

[0040] The step of feeding the mixture onto the running conveyor belt may comprise feeding it onto the conveyor belt as a slurry. The step of feeding the mixture onto the running conveyor belt may instead comprise feeding the mixture onto the conveyor belt as a dry material.

[0041] The step of feeding the mixture onto the running conveyor belt may comprise magnetically attracting at least a portion of the mixture onto an underside of the conveyor belt.

[0042] The step of at least partially clearing the particulates from the conveyor belt may comprise a process selected from the group consisting of:

[0043] • scraping the particulates off the running belt with a scraper;

[0044] • spraying the particulates off the running belt, optionally by using a spray bar spraying a washing fluid onto the particulates;

[0045] • allowing the particulates to fall off an underside of the running belt; and

[0046] • any combination of the above processes. The step of at least partially clearing the particulates from the conveyor belt in the particulates recovery zone may include collecting the particulates in at least one chute apparatus positioned beneath the conveyor system. Collecting the particulates in the chute apparatus may comprise channelling different components or portions of the particulates into different zones of the chute apparatus.

[0047] The method may include adjusting a magnetic field exerted through the conveyor belt by inclining the magnetic body relatively to a running plane of the conveyor belt.

[0048] Corresponding embodiments of the components of the magnetic separator, as described above, are also applicable to the disclosed method of separating magnetically susceptible or paramagnetic particulates from a mixture.

[0049] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

[0050] BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In the drawings:

[0052] Figure 1 is a three-dimensional view of a first embodiment of the disclosed magnetic separator;

[0053] Figure 2 is a sectional side view of the magnetic separator of Figure 1 ;

[0054] Figure 3 is a top view of the magnetic separator of Figure 1 ;

[0055] Figure 4 is a partial top view of a magnetic body of the magnetic separator of Figure 1 ;

[0056] Figure 5 is a schematic illustration of magnetic field intensity or flux density generated by the magnetic body of Figure 4;

[0057] Figure 6 is a schematic three-dimensional cut-away view of a second embodiment of the disclosed magnetic separator which operates in an inverted orientation relatively to the first embodiment; Figure 7 is a schematic side view of the magnetic separator of Figure 6 performing a process to separate magnetic particulates from less magnetically susceptible and non-magnetic particulates;

[0058] Figure 8 is a schematic cross-sectional side view of the magnetic separator of Figure 6, showing its main magnetic body in a lowered or flat configuration; and

[0059] Figure 9 is a schematic cross-sectional side view of the magnetic separator of Figure 6 showing its main magnetic body in an inclined configuration.

[0060] DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

[0061] Two exemplary embodiments of a magnetic separator are described below. The disclosed magnetic separator finds application in the separation of magnetically susceptible values from gangue or other unwanted materials in slurries or mixtures of dry materials. It may be suitable for numerous separation applications, including, for example, the removal of magnetically susceptible impurities (contaminants) from feed mixtures containing wanted materials, or the removal of magnetically susceptible particulates or steel bodies from crushed ore, ROM, mining waste, slag or “virgin” or raw mixtures or feeds.

[0062] Referring to Figures 1 to 5, an embodiment (1) of the disclosed magnetic separator comprises a belt conveyor system including a closed loop conveyor belt (2), a set of pulley rollers (3a; 3b), and a conveyor bed (4). The belt conveyor system is configured to drive the conveyor belt (2) in a running direction (A) rotating around the set of pulley rollers (3a; 3b).

[0063] The conveyor bed (4) is arranged to support the conveyor belt (2) between the pulley rollers (3a; 3b). The conveyor bed (4) has a length defined by a longitudinal axis aligned general parallel to a running direction (A) of the conveyor belt (2). The conveyor bed (4) comprises a magnetic body (5) and a back plate (6). The magnetic body (5) is shown in hidden detail in Figures 1 and 3, being positioned beneath the conveyor belt (2).

[0064] The running direction (A) of the conveyor belt (2) may be from a mixture loading zone (7) towards a particulates recovery zone (10). The magnetic separator (1) may include a feed apparatus (8) mounted above the mixture loading zone (7). In use, the feed apparatus (8) may be operated to deposit a slurry or other mixture containing magnetically susceptible particulates (including magnetic, paramagnetic or feebly magnetic particles), as well as non-magnetically susceptible particles, onto the conveyor belt (2) in the mixture loading zone (7). The magnetic separator (1) may further include a material clearing apparatus comprising a scraper (9), mounted in the particulates recovery zone (10) of the belt conveyor system. A leading edge of the scraper (9) may be biased against the conveyor belt (2) during operation so that a sludge of magnetically susceptible particulates is lifted off the conveyor belt (2) by the scraper (9) as the conveyor belt (2) passes beneath the leading edge of the scraper (9). The scraper (9) may be mounted to extend across the breadth of the conveyor belt (2). Other suitable clearing means (not shown) may be used instead of a scraper (9) or supplementary to it, such as a wiper, sprayer, blower or suction device.

[0065] The magnetic separator (1 ) may further comprise a washing apparatus (11 ) for washing the slurry or other mixture as it is conveyed by the conveyor belt (2). The washing apparatus (11) may be situated between the mixture loading zone (7) and the particulates recovery zone (10) of the belt conveyor system. The washing apparatus (11) may include a sprayer for spraying a washing fluid such as water onto the slurry or mixture, to wash away feebly magnetic or non-magnetic mineral gangue or other unwanted particulates. The sprayer and belt conveyor system may be configured such that the washing fluid flows in a direction generally opposite to the running direction (A) of the conveyor belt (2).

[0066] As best seen in Figures 3 and 4, the magnetic body (5) may comprise an array of individual magnets (12) arranged into rows (15). The arrow B in Figures 3 and 4 shows how the rows (15) of magnets (12) are oriented transversely or crosswise relative to the longitudinal axis of the conveyor bed (4) and the running direction (A) of the conveyor belt (2). Furthermore, the polar axis of each magnet (12), i.e. its axis extending between its north and south poles, is aligned generally parallel to the longitudinal axis of the conveyor bed (4) and the running direction (A) of the conveyor belt (2).

[0067] Figure 4 shows detail of the magnetic body (5). The magnetic poles of the magnets (12) are indicated by the reference letters “N” and “S”, respectively representing the north and south poles of the magnets (12). As can be seen, consecutive rows (15) of magnets (12) are arranged so that like magnetic poles (N-N and S-S) of the magnets (12) face and repel each other. This arrangement may be expected to establish linear zones of alternating magnetic polarity progressing in spaced-apart fashion along the length of the magnetic body (5). These transverse linear zones of alternating polarity may be referred to as pole pieces.

[0068] Figure 5 illustrates, schematically, how magnetic field intensity or flux density generated by the disclosed magnetic separator (1) may be configured across the magnetic body (5). The configuration of the disclosed magnetic separator (1) enables the magnetic field intensity or flux density provided by the array of magnets in the magnetic body to be generally constant along each transverse pole piece of the magnetic body, that is, across the width of the magnetic body. This results from the orientation of the magnets (12) relative to the running direction (A) of the belt (2). The magnetic body (5) generates lines of substantially equal magnetic field intensity or flux density extending across substantially the entire width the magnetic body (5). Consequently, the particulates and other materials on the belt will, almost without exception, pass over a high spot of magnetic intensity as the material flows over the magnetic body.

[0069] By contrast, if the linearly-extending poles of the magnetic body were instead to be arranged longitudinally, that is, parallel to the running direction of the conveyor belt (instead of transversely to it as presently taught), then the magnetic field intensity or flux density provided by the array of magnets would not be constant across the width of the magnetic body. This would have an undesirable effect that dead spots or weak spots would be present between the poles, extending longitudinally in the running direction of the belt, which could allow material to not be caught and to run directly to the tailings. Furthermore, the magnetic field intensity or flux density could be expected, in such longitudinal arrangements, to reduce toward the sides of the array of magnets. This would limit the ability and effectivity of the magnetic body to attract the magnetic and paramagnetic particulates and draw them towards the particulates recovery zone.

[0070] Depending on the particular application for which the magnetic separator (1) is to be used, the magnets (12) of the magnetic body (5) may be high grade or low-grade magnets. In certain embodiments, for example, the magnets (12) may be made from (or may include) rare earth elements, ferrite, or magnetite. At least some of the magnets (12) may comprise neodymium magnets, also known as NdFeB, NIB or Neo magnets, or samarium cobalt magnets, also known as SmCo magnets. However, standard anisotropic ferrite magnets, ceramic magnets, or iron magnets may also be suitable for applications which do not demand a high magnetic field intensity, such as the extraction of ferrochrome, magnetite, or ferro silicone.

[0071] At least some of the magnets (12) in the array may each have approximate dimensions in the following ranges:

[0072] • length (I): 5 - 65 mm;

[0073] • width (w): 20 - 200 mm; and

[0074] • height / depth (d): 20 - 200 mm; wherein: the length (I) of a magnet (12) is measured parallel to the longitudinal axis of the magnetic body (5), i.e. parallel to the running direction of the conveyor belt (2); - the width (w) of a magnet (12) is measured parallel to the breadth of the magnetic body (5), i.e. transversely to the running direction of the conveyor belt (2); and

[0075] - the depth (d) of a magnet (12) is measured through the depth of the magnetic body (5); i.e. through the height or thickness of the magnetic body (5) and perpendicularly away from the conveyor belt (2).

[0076] In certain embodiments, and without limitation to the examples given, at least some of the magnets (12) may each have an approximate ratio of dimensions of length x width x depth selected from the group consisting of:

[0077] • 10 x 22 x 22;

[0078] • 40 x 65 x 65;

[0079] • 60 x 80 x 80;

[0080] • 45 x 65 x 67.5;

[0081] • 60 x 85 x 87.5;

[0082] • 25.4 x 100 x 150;

[0083] • 25.4 x 50 x 150;

[0084] • 55 x 75 x 100;

[0085] • 25.4 x 105 x 155; and

[0086] • 30 x 105 x 155.

[0087] In preferred embodiments, the above ratios may represent dimensions expressed in millimetres (mm); however, it will be appreciated that other dimensional units are feasible depending upon the scale of the apparatus, provided the above ratios are maintained.

[0088] Magnets (12) having dimensions in these ratios may provide a magnetic flux field or magnetic pattern which is advantageous compared to other dimensional permutations. The described features may enable the zones of alternating magnetic polarity and linear zones of concentrated magnetic field intensity or flux to pass through or penetrate the material of the conveyor belt (2) and attract magnetically susceptible particulates to the belt (2).

[0089] The magnetic field intensity or flux density provided by the array of magnets (12) in the magnetic body (5) may operatively exceed 1.8 tesla (18 000 gauss). It may range from about 1.8 to about 2.5 tesla (18 000 to 25 000 gauss), as measured immediately above the conveyor bed (4) (below the conveyor belt (2)).

[0090] The magnetic field intensity or flux density penetrating through the conveyor belt (2) from the magnetic body (5) may exceed 1.4 tesla (14 000 gauss). The field intensity may range from about 0.7 to about 2.0 tesla (7 000 to 20 000 gauss), as measured on the upper, carrying side of the conveyor belt (2) in its operative condition, i.e. on the side of the conveyor belt (2) that is opposite the side which faces the conveyor bed (4).

[0091] To reduce the gauss rating or magnetic flux achieved through the conveyor belt (2), it is feasible to either use a thicker conveyor belt or to add one or more non-magnetic sheets between the magnetic body (5) and the conveyor belt (2). These sheets may be made of stainless steel, for example. This has an effect similar to increasing the “air gap” or “air spacing” between them, and reduces the magnetic intensity or strength achieved through the conveyor belt (2) so that a required strength can be set or adjusted according to the prevailing requirements for achieving separation. For example, an embodiment of the disclosed magnetic separator that is suitable for separating ferrochrome can be set to start at approximately 0.5 tesla (5 000 gauss) measured at the surface of the conveyor belt, but because both the ferrochrome and the slag can be magnetic at 0.15 tesla (1 500 gauss), for example, the strength may need to be reduced to approximately 0.09 tesla (900 gauss) so that only the more magnetic ferrochrome is caught and the less magnetic slag is then discharged.

[0092] Multiple elongate separator plates (13), also referred to as accelerator plates or fins, are arranged or sandwiched between the consecutive rows (15) of repelling magnets (12) in the array. Like the rows (15), the separator plates (13) are also oriented transversely relative to the longitudinal axis of the conveyor bed (4) and the running direction (A) of the conveyor belt (2). Therefore, the separator plates (13) are oriented generally parallel to the arrow B in the drawings.

[0093] The separator plates (13) are typically arranged generally parallel to one another in a regularly- spaced series progressing along the length of the magnetic body (5), with each separator plate (13) extending transversely or crosswise across the breadth of the magnetic body (5).

[0094] Each separator plate (13) may abut the two rows of magnets (12) between which it is arranged.

[0095] In certain non-limiting embodiments, each separator plate (13) may have a thickness in a range from about 1 mm to 30 mm, optionally from about 2 mm to about 6 mm, optionally from about 2.5 mm to about 4 mm. Thicknesses in these ranges can promote penetration of the magnetic field through the conveyor belt (2). Thinner plates permit higher field intensity but may be disadvantageous insofar as they can reduce penetration of the field through the belt (2).

[0096] In certain non-limiting embodiments, at least some of the separator plates (13) may each be made entirely or partially from mild steel or permendur. The steel may have an iron content of about 98%. At least some of the separator plates may instead, or in addition, be made entirely or partially from alternative alloys depending on the acceleration required, that is, the concentration or focusing of the magnetic field and the tripping force required to be applied to the magnetically susceptible particles.

[0097] In other non-limiting embodiments, at least some of the separator plates (13) may be made entirely or partially from one or more non-magnetic materials. The use of non-magnetic materials may be suitable to control the effective “air gap” or “air spacing” between magnets when the magnetic separator is used for certain applications.

[0098] Each separator plate (13) should advantageously be thoroughly cleaned before the magnetic body (5) is assembled, i.e. before each separator plate (13) is fitted into place between the rows of repelling magnets (12) which it is designed to separate. All oxidation on the steel should be removed. Cleaning can be carried out with the aid of a surface grinder or polisher.

[0099] As best seen in Figures 1 and 2, the belt conveyor system of the magnetic separator (1) may be configured such that the conveyor belt (2) and the conveyor bed (4) are operatively inclined, although it will be appreciated that embodiments with a horizontal orientation also fall within the scope of the invention. Embodiments with the inclined configuration are advantageous in that they allow the water or other washing fluid sprayed onto the slurry by the washing apparatus (11) to flow down the inclined conveyor belt (2), passing over and through the slurry or other mixture as it is carried upwardly on the belt (2) along the incline. This action promotes washing of the slurry or other mixture as the water flows counter-currently to the direction of travel of the magnetically susceptible particulates being carried up the incline. In certain embodiments, the incline of the conveyor bed (4) and the conveyor belt (2) may be in a range from about 5° to about 60° to horizontal. By way of example, an incline of about 10° may be suitable for separating Cr particles, an incline of about 12° to 15° may be suitable for separating Fe particles, an incline of about 30° may be suitable for separating ferrochrome particles from a slurry, and an incline of 45° may be suitable for separating Fe particles from a dry mixture.

[0100] In other embodiments that may be suitable for processing dry mixtures of valuable and nonvaluable materials or particulates, the incline of the conveyor bed (4) and the conveyor belt (2) may be in a range from about 20° to about 60° to horizontal.

[0101] In further embodiments that may be suitable for processing wet mixtures of valuable and nonvaluable materials or particulates, the incline of the conveyor bed (4) and the conveyor belt (2) may be in a range from about 5° to about 30° to horizontal.

[0102] The magnets (12) of the magnetic body (5) typically abut the back plate (6) and may be fastened to it using bolts (14). It will be appreciated, however, that the back plate (6) may be affixed to the magnetic body (5) by other means, e.g., adhesives or welding.

[0103] A bin or other receptacle (16) may be provided below the scraper (9), into which the particulatecontaining sludge may fall and be collected as it is scraped off the belt (2) during operation.

[0104] The conveyor bed (4), magnetic body (5) and operatively upper portion of the conveyor belt (2) may each define a length and a breadth. The operatively upper portion of the conveyor belt (2) may have a length in a range from about 2 m to about 4 m and a breadth in a range from about 1 to about 3 m; optionally a length of about 3 m to about 4 m and a breadth in a range from about 1.5 m to 2.7 m.

[0105] In certain non-limiting embodiments, the conveyor belt (2) may have a thickness ranging from about 1.3 mm to about 6 mm.

[0106] The conveyor belt (2) may advantageously be equipped with straight or flat sidewalls. Sidewalls of this type may be preferable to “concertina“-type sidewalls found in some belt conveyor systems, since the latter type can allow dirt to get trapped in crevices between the sidewalls and belt, which is then not affected by the magnetic body and can be discharged to the magnetic side, thereby contaminating the product.

[0107] The conveyor belt (2) may be bare, that is, generally flat and smooth. It may be generally free from bumpers, cleats or other irregular formations installed across the width of the belt. Formations of this type can trap and carry through dirt, thereby reducing the cleaning time over the magnetic body and also contaminating the product.

[0108] The join or seam between the ends of the conveyor belt (2) should not be thick or have a step. The join should be spliced well and should have the same thickness as the belt.

[0109] The conveyor bed (4) and the magnetic body (5) may each have a breadth which approximately matches or marginally exceeds the breadth of the conveyor belt (2).

[0110] The conveyor bed (4) and the magnetic body (5) may each have a length which approximately matches the distance between the pulley rollers (3a; 3b) of the conveyor belt (2). During operation of the disclosed magnetic separator (1), the separator plates (13) may act to concentrate the magnetic field intensity or flux density associated with the magnets (12) into a series of generally linear zones oriented transversely to the longitudinal axis of the conveyor bed (4) and spaced apart from one another along the length of the conveyor bed (4). This configuration is schematically illustrated in Figure 5. The linear zones extend across the breadth of the magnetic body (5). The positioning and alignment of the linear magnetic zones may correspond generally to the positioning and alignment of the separator plates (13).

[0111] Magnetically susceptible particulates are attracted towards the carrying surface of the conveyor belt (2) by the magnetic field and pulled along with the belt (2) up the incline towards the scraper (9), while less magnetically susceptible matter in the mineral gangue is not attracted to the conveyor belt (2) and may accordingly be washed down the incline and off the conveyor belt (2) as waste or as the valuable material. As mentioned previously, in some modes of performing the invention the non-magnetically susceptible particulates are the valuable material and the magnetically susceptible particulates are required to be removed from the mixture.

[0112] Meanwhile, the spaced-apart linear zones of concentrated magnetic field intensity or flux density extending across the breadth of the conveyor bed (4), as well the changing and alternating magnetic polarity which the slurry on the conveyor belt (2) experiences as it is carried over the magnetic body (5), may be expected to cause the magnetically susceptible particulates in the slurry to roll or tumble over the conveyor belt (2) as they are conveyed upwardly on the conveyor belt (2) towards the scraper (9) in the particulates recovery zone (10). This rolling or tumbling action may be expected to promote agitation and separation of those particulates from the unwanted gangue and other material surrounding or encasing them. This action may accordingly result in a cleaner final product. By contrast, if the linearly extending poles of the magnetic body were hypothetically arranged parallel to the running direction of the conveyor belt (instead of transversely to it as presently taught), then the particulates being conveyed on the belt would not be expected to experience the tumbling or rolling effect that is achieved by the magnetic separator of the present teaching. Particulates caught by the belt would be expected to easily trap nonmagnetic material between the magnetic material, which would then be carried along with the magnetic material, thereby contaminating the product.

[0113] The magnetic separator (1) may be particularly, although not exclusively, useful for washing values from tailings, or for concentrating virgin or raw material to achieve a commercially valuable grade mineral or metal.

[0114] Moreover, the transverse or crosswise alignment of the rows of magnets (12) and accelerator plates (13), and hence of the linear zones of flux density, may inhibit or reduce the formation of striations on the conveyor belt (2) as compared against other types of magnetic separators in which the magnets (12) and flux density align along the length of the conveyor bed (4), that is, parallel to the running direction of the conveyor belt (2).

[0115] Figures 6 to 9 show a further embodiment (601) of the disclosed magnetic separator. This embodiment is distinguishable from the previously described embodiment (1) in the following main respects:

[0116] • The embodiment (601) has an inverted configuration, that is, it works upside down compared to the embodiment (1). The separation of the particulates takes place on the underside of a conveyor belt (603) instead of on top of the belt.

[0117] • The embodiment (601) includes two magnetic bodies instead of one. There is a pick-up body (605a) and a main body (605b). At least part of the main body (605b) has a construction like that of the magnetic body (5) described above, that is, the poles of its magnets alternate north, south, north, south, etc. Separator plates (607) are provided between some of the consecutive rows of the magnets. Without limiting the generality of suitable dimensions for these plates, they may each have a thickness similar to those described above for the separator plates (13). Also like the plates (13), the plates (607) may be made entirely or partially from magnetic materials, non-magnetic materials, or combinations thereof. Such materials may, for example, include mild steel, permendur, other suitable alloys or appropriate non-magnetic materials. Unlike in the case of the embodiment (1), however, the separator plates of the embodiment (601) shown in the drawings are present in only one section of the main magnetic body (605b), not along its full length. Some of the consecutive rows of magnets are arranged in direct contact with one another (not sandwiched between separator plates) while others are separated by the separator plates. It will be appreciated, however, that separator plates could be provided between every pair of rows if required for a particular application.

[0118] • As shown in Figure 7, an additional conveyor belt (651) is provided as part of the feed apparatus. This belt, referred to herein as a feeder belt, runs through a pick-up zone (653) below the main conveyor belt (603) (“separator belt”) of the magnetic separator (601). The feeder belt (651) can run codirectionally with the separator belt (603) as shown in Figure 7, or it can run transversely to it (not shown).

[0119] Figure 7 illustrates the operation of the embodiment (601) of the magnetic separator. The feeder belt (651) and the separator belt (603) run closely past each other. The separator belt (603) passes through the pick-up zone (653) just above a feed mixture (655) that is brought in on the feeder belt (651). The purpose of this part of the machine is to attract all or most of the magnetic material in the feed mixture (655) and lift it off the feeder belt (651) so that it sticks to the underside of the running separator belt (603). Meanwhile, most of the non-magnetic particulates remain on the feeder belt (651) and are carried away to be collected for use or discarded elsewhere.

[0120] The pick-up magnetic body (605a) that is positioned above the feeder belt (651) provides a long magnetic field to offer maximum pick-up strength at the operating gap where the feed mixture (655) passes underneath it on the feeder belt (651). Typically, therefore, the magnets in the pickup body are packed in a unipolar arrangement, oriented either north or south since a single pole normally offers the longest effective field length. However, in certain embodiments (not shown), at least a part of the pick-up body may instead be constructed like the magnetic body (5) described previously, that is, it may include rows of magnets having alternating polarities. This arrangement can provide a higher gauss rating which could be desirable in certain circumstances, such as for the processing of specific ores.

[0121] In use of the magnetic separator (601), magnetically susceptible material that does not make it all the way to the end of the main magnetic body (605b) falls off the underside of the belt as “middlings” (657 in Figure 7). The machine is set so that these middlings drop off while the belt passes over a middlings discharge and collection zone (659). There could also be some nonmagnetic material here which was trapped or clumped with the magnetic material in the pick-up zone (653). This non-magnetic material will fall off the belt relatively quickly as the magnetic particles will tumble and turn.

[0122] More strongly magnetic particulates (661 in Figure 7) remain attracted to the underside of the separator belt (603). These materials continue along on the underside of the belt (603), running beneath the main magnetic body (605b). Eventually they reach a region of lower magnetic force where the upward pull is insufficient to hold them onto the underside of the belt (603). They fall off the belt and can be collected in a magnetic values discharge and collection zone (663). Material that sticks to the belt all the way to the end of the main magnetic body may be expected to be the purest material, i.e. the most magnetically susceptible material. This could be high grade iron, for example. The separator could be set to achieve a saleable grade using the adjustment mechanism described further below.

[0123] A chute apparatus (665) may be provided beneath the separator belt (603). Typically it is positioned below a portion of the belt which passes underneath the main magnetic body (605b). The chute apparatus (665) is configured to catch particulates that fall off the belt. A pivotable vane or splitter (667) may be provided inside the chute apparatus (665) to split or channel different components of the falling particulates into the separate collection zones. For example, the length of the middlings collection zone (659) can be adjusted by pivoting the vane (667) so that a larger or smaller quantity of less magnetically susceptible middlings will be deflected by a first side of the vane and fall into that zone according to requirements. More magnetically susceptible components will then travel further along on the underside of the belt until they fall off and are channelled by the other side of the vane (667) into the magnetic values collection zone (663).

[0124] The depicted chute apparatus (665) defines only two collection zones (659, 663), the one closest to the feeder conveyor being the middlings collection zone and the one further along being magnetic values collection zone. It will be appreciated, however, that the apparatus may be configured to define more than two collection zones depending on the type of material being processed. The mutliple zones could be defined by a plurality of different chutes, or a single chute could define three or more separate collection zones, for example, a zone for weak middlings, a zone for strong middlings, and a zone for magnetic values. The separate collection zones can be configured to feed separate conveyor belts or bins (not shown) for collecting the separated components.

[0125] As in the case of the embodiment (1) of the magnetic separator, the inverted variant (601) also imparts a rolling or tumbling action to clumps of magnetic material carried along by the separator belt (603), although in this case the rolling action takes place on the underside of the conveyor belt. As before, the rolling action is caused partly by the changing polarity of the magnets in the main magnetic body (605b) and partly by tripping formations such as cleats provided on the belt, (discussed further below). The rolling action provides a cleaning action. Less magnetically susceptible particles are broken loose or agitated out of the mixed clumps of material as the separator belt runs in the direction “A” as shown in Figure 6.

[0126] The illustrated embodiment of the magnetic separator (601) further includes an adjustment mechanism for adjusting the magnetic strength exerted through the conveyor belt (603) by the main magnetic body (605b). This mechanism allows the inclination of the main body to be adjusted and set by pivoting the main body (605b) about a horizontal hinge (669). Pivoting the main body upwardly causes a drop-off in magnetic field strength or gauss rating exerted through the belt (603) as it passes from the middlings collection zone towards a magnetic cleaning area above the values collection zone (663). Figures 8 and 9 show the main magnetic body (605b) set in two different inclined conditions. In Figure 8 the main body has been lowered so that it lies flat above the belt (603). This orientation provides a stronger magnetic attraction through the belt. In Figure 9, however, the main body (605b) has been raised into an inclined orientation in which its free end is spaced from the belt. This orientation, combined with a more distributed packing of the magnets towards the free end of the main body (consecutive rows of magnets are separated by separator plates), causes the magnetic attraction to drop off more quickly as the belt (603) runs towards the free end of the main body.

[0127] It will be appreciated that other adjustment mechanisms for varying the strength or gauss rating of the exerted magnetic field may be implemented. For example, weaker magnets could be used towards the free end of the main magnetic body.

[0128] The separator belt (603) may have tripping formations attached to it or integrated with it. For example, the belt may have crosswise elongate cleats or bumpers (671 in Figure 6) spaced along its length.

[0129] Eyelets or eye plates (673) may be provided on the top of the magnetic separator (601) so that it can be suspended over the feeder belt (651).

[0130] During use of the magnetic separator (601), the underside of the separator belt (603) travelling below the pick-up body (605a) attracts and carries magnetic material away from the feeder belt (651) and towards the main magnetic body (605b) where the poles of the magnets start to alternate.

[0131] The material is tripped and agitated by the cleats (671) as it is carried under the alternating poles of the main magnetic body (605b). This action may help to impart the desired rolling or tumbling action to the feed material carried on the underside of the belt. This provides a cleaning effect, and can help to break up clumps of the material. Less magnetically susceptible particulates may be shaken loose and drop into the middlings collection zone (659). The collected middlings can be reworked. For example, they can be crushed to liberate more of the non-magnetic material from the iron and then passed through the same magnetic separator again, or they can be blended with other material comprising non-magnetics or magnetics, depending on the targeted grades.

[0132] After passing the middlings collection zone (659), remaining material which is more magnetic than the middlings continues along under the belt until it reaches magnetically weaker regions where, for example, the raised free end of the pivoted main body is more spaced from the belt. Material that now falls off the magnet due to it not being magnetic enough to be attracted to the belt falls into the downstream region of the chute apparatus (665) under the force of gravity and is channelled through the magnetic values collection zone (663).

[0133] Without limiting the generality of suitable applications of the magnetic separator (601), the feed mixture could comprise iron-bearing gangue or iron slag from foundries or smelters. In such applications the middlings could comprise a mixture of slag and iron still bound together. If the feed material contains, for example, 40% iron and 60% impurities, the impurities will fall off into the middlings collection zone (659). Here the magnetic field strength or gauss rating exerted through the belt will have been set low enough to release most impurities and only attract the better quality particulates. These could contain 60% or more of iron, for example, allowing them to pass the middlings section and travel further towards the free end of the main magnetic body (605b) before falling off the belt.

[0134] It will be understood that embodiments of the disclosed magnetic separator (1 ; 601) are suitable for many other applications. These include, for example, the separation of ferrochrome from magnetite in dry mixtures, or the removal of magnetically susceptible particulates or contaminants from other feed mixtures such as those described in the introduction to this section.

[0135] The invention also provides a method for separating magnetically susceptible particulates from mixtures such as those described above. The method comprises the steps of operating a belt conveyor system to drive a conveyor belt in a running direction proximate a conveyor bed arranged to support the conveyor belt; feeding at least a portion of a mixture onto the running conveyor belt in a mixture loading zone; and conveying the portion of the mixture proximate the conveyor bed, from the mixture loading zone to a particulates recovery zone. The method may further include at least partially clearing the particulates from the conveyor belt in the particulates recovery zone.

[0136] The conveyor bed may be as described above and the step of conveying the mixture proximate the conveyor bed may comprise conveying the mixture past the zones of alternating magnetic polarity of the magnetic body, thereby to cause the particulates to roll or tumble along the conveyor belt.

[0137] The method may further include conveying the portion of the mixture past at least one elongate separator plate arranged or sandwiched between consecutive rows of repelling magnets in the array of magnets. Advantageously, the separator plate may be oriented transversely relative to the longitudinal axis of the conveyor bed. The separator plate may abut the two rows of magnets between which it is arranged, as shown in the drawings. The method may include conveying the mixture past a plurality of such separator plates arranged generally parallel to one another and in series along a length of the magnetic body in the running direction, each separator plate extending across a breadth of the magnetic body.

[0138] As described above, the conveyor bed may be operatively inclined and the method may include running the conveyor belt upwardly along the incline from the mixture loading zone to the particulates recovery zone.

[0139] The method may further include washing a slurry or other mixture conveyed on the conveyor belt. The step of washing the mixture may comprise spraying or otherwise discharging a washing fluid such as water onto the mixture as it is conveyed upwardly along the incline from the mixture loading zone to the particulates recovery zone. The washing fluid can then flow downwardly along the conveyor belt, counter-currently to the upwardly running direction of the conveyor belt and conveyed mixture.

[0140] Typically during operation, the valuable material that is sought to be recovered will move upwardly on the conveyor belt towards the top of the inclined magnetic body, and the material washed off the conveyor belt by the flow of slurry and water will then be the rejects or tailings. This mode of operation would apply, for example, when separating out iron, which could be in the form of magnetite or haematite. Other modes of operation also fall within the scope of the invention, however. For example, PGMs are normally non-magnetic. In this case the magnetic body is used to upgrade the PGM concentrate by removing magnetically susceptible particles like chromium. The material attracted by the magnetic body, which moves towards the operatively upper end of the magnetic body, is discarded and the tailings (running to the operatively lower end of the magnetic body) are recovered as the desired product. When recovering certain minerals, different desired products could go in opposite directions, for example, when separating a mixture of iron and mineral sands.

[0141] The following is presented as an example of a separation process involving iron. A strong magnet will pull both magnetite and haematite. Magnetite is susceptible at approximately 0.15 tesla (1 500 gauss) and haematite at approximately 1.0 tesla (10 000 gauss). On a first pass at about 1.5 tesla (15 000 gauss), for example, both will be caught. A second pass can then be done at approximately 0.15 tesla (1 500 gauss) so that magnetite will move towards the top end and haematite towards the bottom end so that the two are now separated but both top and bottom are saleable products.

[0142] The step of feeding the mixture onto the running conveyor belt may comprise feeding it onto the conveyor belt as a slurry or as a dry material. The mixture may be fed onto and spread evenly across the conveyor belt.

[0143] The step of feeding at least a portion of the mixture onto the running conveyor belt may comprise magnetically attracting the portion of the mixture onto an underside of the conveyor belt.

[0144] The step of at least partially clearing the particulates from the conveyor belt may comprise scraping the particulates off the running belt. A scraper may be used for this purpose. Instead or in addition, the step of at least partially clearing the particulates from the conveyor belt may comprise spraying the particulates off the running belt. A spray bar may be used for this purpose. A washing fluid may be sprayed onto the particulates.

[0145] Instead or in addition, the step of at least partially clearing the particulates from the conveyor belt may include allowing the particulates to fall of an underside of the conveyor belt in separate zones. The step may thus include splitting components of particulates and other material falling from the conveyor belt. It may further include collecting the particulates and other material in different zones of a chute apparatus positioned beneath the conveyor belt.

[0146] The method may include a step of adjusting a magnetic field exerted through the conveyor belt by inclining the magnetic body relatively to a running plane of the conveyor belt.

[0147] In a specific application, and without limiting the generality of possible applications, the disclosed magnetic separator and method can be used to separate and extract magnetically susceptible particulates such as iron, chrome, manganese, copper or other metals from crushed ore or gangue in a slurry or tailings.

[0148] The disclosed magnetic separator may be effective for use with tailings or mining waste as well as ROM or “virgin” or raw mixtures. The invention can serve as a replacement for existing spiral separators, gravity separators, and other conventional methods and systems applied in existing mining processes.

[0149] As another example, the magnetic separator could be used to separate components of a slag mixture. Good quality iron in the mixture, suitable for melting and re-use, may be separated from impurities, tailings and other non-magnetic materials. To perform this type of separation, the slag mixture is typically first crushed and agitated, which allows the slag to come off the iron because slag is softer than iron. This promotes liberation of the slag and non-magnetics from the iron. The magnets in the separator (601) would then be used to concentrate the usable iron. Material not attracted off the feeder belt (651) would comprise the non-magnetics free of iron content or having very little iron content. This material may be suitable for use in agricultural applications, provided the majority of the iron has been removed and the values of Calcium Carbonate Equivalent (CCE) are high.

[0150] The ability to adjust the magnetic flux field may allow for efficient and cost-effective separation. Also, the disclosed magnetic separator may be more cost-effective than other devices and separation techniques insofar as certain embodiments can be run with relatively small motors, for example, a motor rated in a range from 1 .5 kWto 2 kW, or a small solar-powered motor. Moreover, the water or other washing fluid used with the disclosed magnetic separator can be recycled and re-used, thereby reducing the ecological footprint of the system as a whole. The disclosed system and method may accordingly provide a sustainable and eco-friendly (“green”) technology.

[0151] In one test, a scaled-down embodiment of the separator (601) outperformed jigs and worked without the need for any water in the feed mixture.

[0152] The foregoing description has been presented for the purpose of illustration; it is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Persons skilled in the relevant art can appreciate that many modifications and variations are possible in light of the above disclosure.

[0153] For example, and without limiting the generality of the scope of possible variants, the rows of magnets in the magnetic body of an alternative embodiment (not shown) need not consist of multiple magnets. Thus, each row may instead be formed of a single, elongate magnet extending across the breadth of the magnetic body, rather than a linear arrangement of multiple smaller magnets.

[0154] In a further example of a different variant (not shown) that falls within the scope of the invention, at least some of the abutting rows of magnets could be arranged with unlike poles facing and attracting each other. Therefore, in contrast to embodiments which employ unitary (solid) magnets extending between each successive pair of accelerator plates, it is possible instead to use multiple thinner magnets to make up bigger, composite magnets, with each composite magnet being positioned between a pair of accelerator plates. For example, two rows of abutting magnets could be provided between a pair of spaced separator plates, with the poles in those two inner rows being positioned to attract each other while at the same time repelling the two rows of magnets which surround them on either side of the two separator plates. However, it may be expected that a solid magnet would be advantageous compared to such composite embodiments insofar as a solid magnet may provide more power or magnetic intensity than two or more smaller magnets joined to one another or abutting one another.

[0155] In a further non-limiting example of a variant (not shown), the conveyor belt could be configured to run and circulate in a planar rather than parallel orientation, in the manner of the overlapping slat carousels typically used for baggage handling in airports. Embodiments of this type of belt are less preferred than endless loop belt conveyors, however, on account of gaps being necessitated between overlapping slats, through which slurry and particulate material could be lost.

[0156] Although permanent magnets are used to construct the magnetic body of the illustrated magnetic separator, in other embodiments it may be appropriate to use other types of magnets. For example, temporary magnets or electromagnets may be used instead of or in addition to the permanent magnets, depending upon the intended application of the magnetic separator and the intensity of the magnetic field required.

[0157] It will likewise be appreciated that a plurality of discrete magnetic bodies could be provided along the length of the conveyor bed, either abutting one another or spaced apart from one another.

[0158] It will also be appreciated that in certain embodiments (not shown), the conveyor bed (and hence the magnetic body) may be arranged operatively above the conveyor belt rather than below it.

[0159] Furthermore, in certain alternative embodiments (not shown), the magnetic component need not comprise a flat conveyor bed. For example, the magnetic component may be generally cylindrical in configuration, comprising a drum encased by the magnetic body. In such embodiments, the drum may be arranged to serve as a roller pulley around which the conveyor belt may run. In certain embodiments, moreover, the drum may be arranged to serve as a drive pulley.

[0160] In other embodiments (not shown) the conveyor system need not be limited to a belt conveyor system, that is, the magnetic separator may be of the type known as a drum separator. In such embodiments, the conveyor element may comprise a drum and the cooperating magnetic component (and magnetic body) may be provided as one or more arcuate shoes positioned inside the drum. In such embodiments, the running direction of the drum and the longitudinal axis of the magnetic body (in relation to which the rows of magnets are transversely arranged) may lie tangential to the circumference of the drum.

[0161] The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention to be set forth in any claims that issue on an application based hereon.

[0162] Finally, throughout the specification, unless the context requires otherwise:

[0163] • the word “comprise” or variations such as “comprises” or “comprising” will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers; and

[0164] • the phrase “magnetically susceptible” used in reference to magnetically susceptible particulates or other materials will be understood in its broadest sense and will, without limitation, encompass reference to magnetic, paramagnetic and feebly magnetic particulates and other materials.

Claims

CLAIMS:1 . A magnetic separator comprising a conveyor system configured to drive a conveyor element in a running direction, and a cooperating magnetic component arranged in proximity to the conveyor element; the magnetic component having a length defined by a longitudinal axis aligned generally parallel to the running direction of the conveyor element; and the magnetic component comprising at least one magnetic body having an array of magnets; wherein rows of magnets in the array are oriented transversely relative to the longitudinal axis of the magnetic component, with the polar axis of each magnet aligned generally parallel to said longitudinal axis; and wherein at least one pair of consecutive rows of the magnets are arranged so that like magnetic poles of the magnets face and repel each other, thereby to establish zones of alternating magnetic polarity along the magnetic body.

2. A magnetic separator comprising: a belt conveyor system configured to drive a conveyor belt in a running direction; and a conveyor bed arranged to support the conveyor belt, the conveyor bed having a length defined by a longitudinal axis aligned generally parallel to the running direction of the conveyor belt; the conveyor bed comprising at least one magnetic body having an array of magnets; wherein rows of magnets in the array are oriented transversely relative to the longitudinal axis of the conveyor bed, with the polar axis of each magnet aligned generally parallel to said longitudinal axis; and wherein at least one pair of consecutive rows of the magnets are arranged so that like magnetic poles of the magnets face and repel each other, thereby to establish zones of alternating magnetic polarity along the magnetic body.

3. The magnetic separator according to claim 2, wherein the magnetic body comprises at least one elongate separator plate arranged between consecutive rows of repelling magnets in the array, the separator plate being oriented transversely relative to the longitudinal axis of the conveyor bed.

4. The magnetic separator according to claim 3, wherein the separator plate abuts two rows of magnets between which it is arranged.

5. The magnetic separator according to any one of claims 2 to 4, wherein the conveyor bed further comprises a back plate.

6. The magnetic separator according to any one of claims 2 to 5, which further includes at least one magnetic body having rows of magnets packed in a unipolar orientation.

7. The magnetic separator according to any one of claims 2 to 6, wherein the belt conveyor system is configured such that the conveyor bed and conveyor belt have an adjustable, operatively inclined orientation.

8. The magnetic separator according to any one of claims 2 to 7, which includes an adjustment mechanism configured to adjust a magnetic field exerted through the conveyor belt, the adjustment mechanism being configured to set variable inclinations of the magnetic body relatively to a running plane of the conveyor belt.

9. The magnetic separator according to any one of claims 2 to 8, which includes a chute apparatus positioned beneath at least a part of the conveyor belt, with a pivotable vane positioned therein.

10. The magnetic separator according to any one of claims 2 to 9, wherein the conveyor belt has tripping formations spaced along its length.

11. A method for separating magnetically susceptible particulates from a mixture, the method comprising: operating a belt conveyor system to drive a conveyor belt in a running direction around a conveyor bed arranged to support the conveyor belt; feeding at least a portion of the mixture onto the running conveyor belt in a mixture loading zone; conveying the mixture on the conveyor belt proximate the conveyor bed, from the mixture loading zone to a particulates recovery zone; and at least partially clearing the particulates from the conveyor belt in the particulates recovery zone; wherein the conveyor bed has a length defined by a longitudinal axis aligned generally parallel to the running direction of the conveyor belt; wherein the conveyor bed comprises a magnetic body having an array of magnets, the magnets in the array being oriented transversely relative to the longitudinal axis of the conveyor bed, with the polar axis of each magnet aligned generally parallel to said longitudinal axis; and wherein at least one pair of consecutive rows of the magnets are arranged so that like magnetic poles of the magnets face and repel each other, thereby toestablish zones of alternating magnetic polarity along the magnetic body in the running direction; and wherein the step of conveying the mixture on the conveyor belt proximate the conveyor bed comprises conveying the mixture past at least some of the zones of alternating magnetic polarity of the magnetic body, thereby to cause the particulates to tumble along the conveyor belt.

12. The method according to claim 11 , which futher includes conveying the mixture past at least one elongate separator plate arranged between consecutive rows of repelling magnets in the array of magnets.

13. The method according to either one of claims 11 and 12, wherein the step of feeding at least a portion of the mixture onto the running conveyor belt comprises magnetically attracting the portion of the mixture onto an underside of the conveyor belt.

14. The method according to any one of claims 11 to 13, wherein the step of at least partially clearing the particulates from the conveyor belt comprises a process selected from the group consisting of: scraping the particulates off the running belt; spraying the particulates off the running belt; allowing the particulates to fall off an underside of the running belt; and any combination of the above processes.

15. The method according to any one of claims 11 to 14, which includes adjusting a magnetic field exerted through the conveyor belt by inclining the magnetic body relatively to a running plane of the conveyor belt.

Images