A mineral processing apparatus

Abstract

A mineral processing apparatus (10) for at least partially separating iron-containing compounds in the granular material from non-iron-containing compounds, the apparatus comprising a coil of electrically conductive material (100); a fluid flow pipe (40) arranged to carry a slurry comprising water and the granular material through a passage through the centre of the coil (100); an electrical supply (130) configured to supply a time-varying voltage of a given form between a first and a second end of the coil; and a settling tank (160) arranged to receive the slurry from the fluid flow pipe.

Description

A mineral processing apparatus

[0001] The present invention relates generally to a mineral processing apparatus and a method of at least partially separating iron-containing compounds in a granular material from non-iron-containing compounds, and finds particular, although not exclusive, utility in improving the relative proportion of iron oxide in a material.

[0002] Iron oxides, and other potentially valuable iron-containing compounds, often exist in combination with many other less desirable compounds and / or elements, such as silica. In order to make use of the iron-containing compounds, it is necessary to separate the iron-containing compounds form the less desirable materials. Known methods for achieving this require large amounts of energy. It is therefore desirable to provide an apparatus and method for separating iron-containing compounds from non-iron-containing materials.

[0003] In a first aspect, the present invention provides a mineral processing apparatus comprising a coil of electrically conductive material, the coil including a passage therethrough; a fluid flow pipe passing through the passage, the fluid flow pipe arranged to carry a slurry comprising water and a granular material to be processed, the granular material comprising iron-containing compounds; an electrical supply configured to provide a time-varying voltage between a first end of the coil and a second end of the coil, the time-varying voltage being described by a function V(t), defined for any time t as the greatest value of V1(t), V2(t) and V3(t), where

[0004] V1(t) = V0[sin(2πft + p sin(2πft + q sin(2πft + r))) – k];

[0005] V2(t) = V0[a sin(2πf(t – δ1) + p sin(2πf(t – δ1) + q sin(2πf(t – δ1) + r))) – k]; and

[0006] V3(t) = V0[b sin(2πf(t – δ2) + p sin(2πf(t – δ2) + q sin(2πf(t – δ2) + r))) – k],

[0007] and where V0is a predetermined constant amplitude, f is a predetermined constant frequency, a has a value between 0.5 and 1.5, b has a value between 0.5 and 1.5, p has a value between -0.5 and 0.5, q has a value between -1 and 1, r has a value between -0.5 and 0.5, δ1has a value between 0.274 / f and 0.374 / f, δ2has a value between 0.630 / f and 0.730 / f and k has a value between -5 and 5; and a settling tank arranged to receive the slurry from the fluid flow pipe, wherein the apparatus is configured to at least partially separate iron-containing compounds in the granular material from non-iron-containing compounds, with the iron-containing compounds settling to the bottom of the settling tank, in use, for collection thereof.

[0008] It has been found that, as a result of the electromagnetic fields to which the slurry is subjected as it passes through the coil, stratification of the constituent material of the slurry occurs when it is left to settle in the settling tank. For instance, iron-containing compounds form clumps that sink to the bottom, and other materials such as aluminium oxides collect in a discrete layer in the fluid (slurry) above the base and below the surface. Other materials collect into layers at other vertical positions in the fluid. In this way, unwanted material that does not sink to the bottom of the tank may be removed and / or the material that does sink to the bottom of the tank may be collected, resulting in a material that comprises a higher percentage of iron-containing compound than the initial granular material. That is, the apparatus may be used to purify a granular material comprising iron-containing compounds.

[0009] The function V(t) may give rise to a waveform comprising a repeating series of curved peaks, each peak being separated from an adjacent peak by a sharply pointed trough at which the gradient dV / dt is discontinuous.

[0010] The series of curved peaks may comprise three peaks. Alternatively, the series of peaks may comprise two sets of three peaks, for example comprising a first set of three peaks, for which the variables a, b, p, q, r, δ1and / or δ2have a first set of values, followed by a second set of peaks, for which the variables a, b, p, q, r, δ1and / or δ2have a second set of values. It is contemplated that the series of peaks may comprise more than two sets of three peaks.

[0011] At least one peak within the series of peaks may have a height (i.e. maximum voltage) different to the height of another peak within the series of peaks. Furthermore, the temporal spacing between at least one pair of adjacent peaks within the series of peaks may be different to the temporal spacing between another pair of adjacent peaks within the series of peak.

[0012] Each peak being asymmetric about a vertical axis passing through the maximum point thereof. This may mean that the absolute value of the gradient dV / dt is greater, on average, on one side of the maximum point than the other, such that the peak appears slanted or skewed. For example, as time t increases, V(t) may increase relatively rapidly to a maximum value and then decrease relatively slowly to produce a peak that appears slanted to the left.

[0013] The shapes, relative heights and the relative temporal spacing of the peaks within the series of peaks may be the same each time the series of peaks is repeated.

[0014] The amplitude V0may be in the range 0.5V to 41V and the frequency f may be in the range 2kHz to 13.3kHz. This may correspond to an effective frequency (the reciprocal of the average time between successive pulses, as measured from peak voltage to peak voltage, which may be approximately equal to 3f) in the range 6kHz to 40kHz.

[0015] The amplitude and frequency may be determined, by the apparatus, so as to maximise the current delivered. The amplitude and / or frequency may vary over time in order to keep the current at a maximum. The timescale over which the amplitude and / or the frequency may vary may be substantially longer than 1 / f.

[0016] The variable p may be equal to -0.5, -0.4, -0.3, -0.2, -0.1, 0, 0.1, 0.2, 0.3, 0.4 or 0.5. The variable q may be equal to -1, -0.9, -0.8, -0.7, -0.6, -0.5, -0.4, -0.3, -0.2, -0.1, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1. In another example, the variable q may be equal to 0.75. The variable r may be equal to -0.5, -0.4, -0.3, -0.2, -0.1, 0, 0.1, 0.2, 0.3, 0.4 or 0.5.

[0017] The variable a may be equal to 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4 or 1.5. In another example, the variable a may be equal to 0.96. The variable b may be equal to 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4 or 1.5. In another example, the variable b may be equal to 0.93.

[0018] The variable δ1may be equal to 0.274 / f, 0.284 / f, 0.294 / f, 0.304 / f, 0.314 / f, 0.324 / f, 0.334 / f, 0.344 / f, 0.354 / f, 0.364 / f or 0.374 / f. The variable δ2may be equal to 0.630 / f, 0.640 / f, 0.650 / f, 0.660 / f, 0.670 / f, 0.680 / f, 0.690 / f, 0.700 / f, 0.710 / f, 0.720 / f or 0.730 / f.

[0019] The variable k may be equal to -5, -4, -3, -2, -1, 0, 1, 2, 3, 4 or 5. In another example, the variable k may be equal to 0.82.

[0020] The electricity supplied may have a voltage in the range 0.5V to 41V, a current in the range 150A to 600A and an effective frequency in the range 6kHz to 40kHz.

[0021] The coil of electrically conductive material may comprise a wire and / or a hollow conductive pipe (referred to hereinafter as the coil pipe). The coil may have between 30 and 100 turns; in particular, between 40 and 90 turns; more particularly, between 50 and 80 turns. The wire and / or coil pipe may have an (uncoiled) length of at least 6m. For example, the wire and / or coil pipe may have a length of approximately 10m and may be formed into a coil having 56 turns.

[0022] The coil may be wrapped in a clockwise direction from the first end of the coil to the second end of the coil, as viewed downstream along the fluid flow pipe, in use. Alternatively, the coil may be wrapped in an anti-clockwise direction.

[0023] The wire and / or coil pipe may comprise copper. The wire and / or coil pipe may include an outer coating comprising an electrical insulator, the outer coating configured to prevent short circuits between adjacent coil windings.

[0024] The wire may have a diameter of between 1mm and 10mm; in particular, between 2mm and 8mm; for example, approximately 4mm.

[0025] The coil pipe may have a diameter of between 6mm and 32mm. Here, the diameter of the coil pipe is taken to be the outer diameter of the coil pipe. The coil pipe may have a pipe wall thickness of between 0.2mm and 2mm; in particular, between 0.4mm and 1mm. For example, the coil pipe may have a diameter of 8mm and a pipe wall thickness of 0.6mm.

[0026] A coolant may be circulated through the coil pipe. In this way, the temperature of the coil pipe may be regulated to counter heating caused by the dissipation of electrical power therein. The coolant may be, or may comprise, water. It is to be understood that the mineral processing apparatus may comprise additional components required to facilitate the circulation of coolant through the coil pipe. For example, the mineral processing apparatus may comprise one or more of a coolant tank, a coolant pump, a heat exchanger and coolant hoses for carrying the coolant to a first end of the coil pipe and carrying it away from a second end of the coil pipe.

[0027] The coil pipe may comprise a lining on an inner surface of the pipe wall, the lining comprising an electrical insulator for preventing unwanted conduction of electricity through the coolant.

[0028] For the avoidance of doubt, the coil pipe discussed above is entirely separate from, and not in fluid communication with, the fluid flow pipe.

[0029] The mineral processing apparatus may further comprise a return loop connected between a second end of the fluid flow pipe and a first end of the fluid flow pipe, the return loop arranged to return the slurry from the second end of the fluid flow pipe back to the first end of the fluid flow pipe for recirculation through the fluid flow pipe, before it reaches the settling tank.

[0030] In this way, the slurry can be repeatedly passed through the passage through the coil and thereby be subjected to the electromagnetic fields produced as a result of the time-varying voltage for a longer period of time. The slurry may be circulated through the fluid flow pipe and the return loop for a fixed period of time.

[0031] The return loop may not pass through the passage within the coil.

[0032] The return loop may comprise a pump configured to pump the slurry from the second end of the fluid flow pipe to the first end of the fluid flow pipe.

[0033] Either the return loop or the fluid flow pipe may comprise a first valve configured to permit entry of the slurry thereinto prior to the recirculation process. Similarly, the return loop or the fluid flow pipe may comprise a second valve configured to permit exit of the slurry therefrom after the recirculation process has been completed. It is to be appreciated that the first and second valve may be the same valve.

[0034] The fluid flow pipe may be formed of steel, iron, polyvinyl chloride (PVC), high density polyethylene (HDPE) or any other suitable material.

[0035] The settling tank may be any tank suitable for receiving the slurry from the fluid flow pipe and containing it while it settles. The settling tank may have an open top, or a removable top, so that unwanted material that floats at the surface, or in a layer below the surface, or remains suspended may be removed without draining the settling tank.

[0036] The settling tank may comprise drainage means, through which at least some of the contents of the settling tank may be drainable. For example, the drainage means may comprise a valve, located at any desired height of the tank side wall, that may be openable to allow the contents of the settling tank to flow out of the settling tank, for example under the influence of gravity. Alternatively, the drainage means may comprise a lip and / or opening towards the top of the settling tank so that the contents thereof may be poured away by tipping or tilting the settling tank. It is contemplated that the drainage means may comprise a drainage pump configured to pump the contents of the settling tank out of the settling tank. The drainage means may comprise a drainage channel, pipe and / or outlet arranged to deliver the contents of the tank to a particular location.

[0037] The apparatus may include a magnet for collecting the iron-containing compounds from at least some of the contents of the settling tank. For example, the magnet may be arranged in a drainage channel, pipe or outlet, to collect iron-containing compounds remaining in the contents of the settling tank as it is drained therefrom. Alternatively, the magnet may be located in, or removably introducible into, the settlement tank for collection of iron-containing compounds from the contents thereof.

[0038] The mineral processing apparatus may additionally comprise a mixing device configured to mix the granular material with water to form the slurry. The mixing device may be configured to mix the granular material with water at a predetermined ratio.

[0039] The mineral processing apparatus may additionally comprise means for producing a granular material from a non-granular material, for example by crushing, grinding or milling the non-granular material.

[0040] In a second aspect, the invention provides a method of at least partially separating iron-containing compounds in a granular material from non-iron-containing materials, the method comprising the steps of: providing a granular material comprising iron-containing compounds; providing the mineral processing apparatus of the first aspect; mixing the granular material with water to form a slurry; passing the slurry through the fluid flow pipe; simultaneously applying a time-varying voltage between a first end of the coil and a second end of the coil, the time-varying voltage being described by a function V(t) defined for any time t as the greatest value of V1(t), V2(t) and V3(t), where

[0041] V1(t) = V0[sin(2πft + p sin(2πft + q sin(2πft + r))) – k];

[0042] V2(t) = V0[a sin(2πf(t – δ1) + p sin(2πf(t – δ1) + q sin(2πf(t – δ1) + r))) – k]; and

[0043] V3(t) = V0[b sin(2πf(t – δ2) + p sin(2πf(t – δ2) + q sin(2πf(t – δ2) + r))) – k],

[0044] and where V0is a predetermined constant amplitude, f is a predetermined constant frequency, a has a value between 0.5 and 1.5, b has a value between 0.5 and 1.5, p has a value between -0.5 and 0.5, q has a value between -1 and 1, r has a value between -0.5 and 0.5, δ1has a value between 0.274 / f and 0.374 / f, δ2has a value between 0.630 / f and 0.730 / f and k has a value between -5 and 5; passing the slurry from the fluid flow pipe into the settling tank; and collecting the iron-containing compounds from the settling tank.

[0045] The granular material may comprise grains having a size of less than 0.5mm. In particular, the grains may have a size of less than 0.2mm. Providing a granular material may comprise forming a granular material from a non-granular material, for example by crushing, grinding and / or milling the non-granular material until it comprises, for instance, grains having a size of less than 0.5mm, in particular, less than 0.2mm. Where the granular material is formed from a non-granular material, the size of the grains may be selected based on the porosity of the initial non-granular material.

[0046] The granular material comprising iron-containing compounds may mean that the granular material includes chemical compounds containing the element iron. In particular, the iron-containing compounds may be iron oxides, such as haematite (Fe2O3) or magnetite (Fe3O4).

[0047] Separating the iron-containing compounds from non-iron-containing materials may include sorting grains including iron-containing compounds from those that do not include iron-containing compounds; physically breaking down the grains to separate iron containing compounds from non-iron-containing materials to which they are physically attached; and / or breaking down bonds to separate iron-containing compounds from non-iron-containing material to which they are chemically bonded. The non-iron-containing materials may be any materials not containing the element iron, and may be referred to as waste material, unwanted material or gangue.

[0048] Mixing the granular material with water to form a slurry may involve mixing the granular material with water at a particular predetermined ratio. For example, this ratio may be 200g of granular material per litre of water. Where the granular material comprises a high proportion of silica, caustic potash (KOH) may also be mixed with the granular material and water to form the slurry. It has been found that this may help to break down silica-ferric bonds.

[0049] The method may further comprise the step of returning the slurry from a second end of the fluid flow pipe back to a first end of the fluid flow pipe for recirculation through the fluid flow pipe, before it reaches the settling tank.

[0050] The fluid may be continually recirculated through the fluid flow pipe for a predetermined period of time. The period of time may be, for example, between 35 and 60 seconds. However, longer times may be necessary for less porous granular materials.

[0051] The method may comprise leaving the slurry in the settling tank to settle, so that stratification of the materials in the slurry can occur, with the iron-containing compounds sinking to the bottom of the tank, prior to the step of collecting the iron-containing compounds. The method may further comprise removing unwanted material that remains suspended, or has stratified, in the settling tank. This may be effected by draining off the fluid in the tank at selected vertical positions within the tank, so as to remove particular layers.

[0052] The step of collecting the iron-containing compounds from the settling tank may comprise using a magnet to magnetically attract the iron-containing compounds thereto. Alternatively, and / or additionally, the step of collecting the iron-containing compounds may comprise draining at least some of the contents of the settling tank and collecting the iron-containing compounds left at the bottom of the tank.

[0053] The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

[0054] is schematic representation of a mineral processing apparatus;

[0055] shows an example waveform of a time-varying voltage V(t);

[0056] is a table showing the results of assays carried out during testing of the method according to the second aspect.

[0057] The present invention will be described with respect to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. Each drawing may not include all of the features of the invention and therefore should not necessarily be considered to be an embodiment of the invention. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

[0058] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that operation is capable in other sequences than described or illustrated herein. Likewise, method steps described or claimed in a particular sequence may be understood to operate in a different sequence.

[0059] Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that operation is capable in other orientations than described or illustrated herein.

[0060] It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

[0061] Similarly, it is to be noticed that the term “connected”, used in the description, should not be interpreted as being restricted to direct connections only. Thus, the scope of the expression “a device A connected to a device B” should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. “Connected” may mean that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with each other but yet still co-operate or interact with each other. For instance, wireless connectivity is contemplated.

[0062] Reference throughout this specification to “an embodiment” or “an aspect” means that a particular feature, structure or characteristic described in connection with the embodiment or aspect is included in at least one embodiment or aspect of the present invention. Thus, appearances of the phrases “in one embodiment”, “in an embodiment”, or “in an aspect” in various places throughout this specification are not necessarily all referring to the same embodiment or aspect, but may refer to different embodiments or aspects. Furthermore, the particular features, structures or characteristics of any one embodiment or aspect of the invention may be combined in any suitable manner with any other particular feature, structure or characteristic of another embodiment or aspect of the invention, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments or aspects.

[0063] Similarly, it should be appreciated that in the description various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Moreover, the description of any individual drawing or aspect should not necessarily be considered to be an embodiment of the invention. Rather, as the following claims reflect, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

[0064] Furthermore, while some embodiments described herein include some features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form yet further embodiments, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0065] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practised without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

[0066] In the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

[0067] The use of the term “at least one” may mean only one in certain circumstances. The use of the term “any” may mean “all” and / or “each” in certain circumstances.

[0068] Where a variable is described as having a value between x and y (x and y being a lower bound and an upper bound respectively), it is to be understood that that variable may in fact have a value falling within a narrower range of values completely encompassed by the range of values between x and y. In particular, reference herein to a variable having a value between x and y, where x and y are given to a certain number of decimal places, may mean that the variable has a value between w and z, where w and z are any two numbers having the same number of decimal places as x and y and satisfying the inequality x ≤ w < z ≤ y. For example, if x and y are integers, w and z may be any two integers satisfying the inequality. Alternatively, if x and y are given to one decimal place, w and z may be any two integer multiples of 0.1 satisfying the inequality.

[0069] For the avoidance of doubt, reference herein to a variable having a value between x and y may mean that the variable may take the value x or y; that is, the upper and lower bound are included in the range.

[0070] The principles of the invention will now be described by a detailed description of at least one drawing relating to exemplary features. It is clear that other arrangements can be configured according to the knowledge of persons skilled in the art without departing from the underlying concept or technical teaching, the invention being limited only by the terms of the appended claims.

[0071] is schematic representation of a mineral processing apparatus 10. The mineral processing apparatus 10 includes a fluid flow system comprising a fluid inlet 20, a fluid flow pipe 40 and a fluid outlet 60. The fluid inlet 20 is connected to a first end of the fluid flow pipe 40 via a first three-way valve 30. A second end of the fluid flow pipe 40 is connected to the fluid outlet 60 via a second three-way valve 50. A return loop 70 is connected between the third port of the second three-way valve 50 and the third port of the first three-way valve 30. The direction of fluid flow in each part of the fluid flow system, in use, is indicated by the solid arrows 90.

[0072] A coil 100 of conductive copper pipe is arranged around the fluid flow pipe 40 such that the fluid flow pipe 40 passes through a passage through the centre of the coil 100. Electrical connections 110, 120 connect the two ends of the coil 100 to an electrical supply 130. It is to be appreciated that, while the coil 100 inis formed of copper pipe, the mineral processing apparatus of the present invention may use a coil formed of any suitable conductive material.

[0073] In use, a slurry comprising water and a granular input material enters the fluid flow system via fluid inlet 20 and the first three-way valve 30. The slurry then flows along the fluid flow pipe 40, passing through the coil 100 as it does so, until it reaches the second three-way valve 50. Initially, the second three-way valve 50 is arranged to direct the slurry into the return loop 70 to be recirculated back towards the first three-way valve. Once a predetermined amount of the slurry has entered the fluid flow system, the first three-way valve may be actuated to close the fluid inlet 20 and direct the slurry from the return loop 70 back along the fluid flow pipe 40 so that the slurry repeatedly passes through the coil 100. A pump 80 pumps the slurry round the return loop 70 to ensure continuous circulation of the slurry through the fluid flow pipe 40 and return loop 70.

[0074] The electrical supply 130 supplies a time-varying voltage between the two ends of the coil 100 of the form V(t), as described above in the summary of the invention. The time-varying voltage across the coil results in a time-varying magnetic field within the passage through the centre of the coil 100 and the slurry is exposed to this magnetic field each time it passes along the fluid flow pipe 40.

[0075] After a predetermined period of time, the second three-way valve 50 may be actuated so that the slurry is directed from the fluid flow pipe 40 to the fluid outlet 60, rather than into the return loop 70.

[0076] The actuation of the first and second three-way valves may be controlled by a control system (not shown), which may comprise a timer circuit.

[0077] In order to regulate the temperature of the coil 100, a coolant may be circulated through the copper pipe forming the coil 100. The coolant may be circulated through the coil 100 by a coolant system 140, connected to the coil 100 via coolant hoses 150. The coolant system 140 may comprise a coolant pump for pumping the coolant through the coil 100 and the coolant hoses 150, and a heat exchanger for transferring heat away from the coolant as it passes through the coolant system 140.

[0078] It is to be appreciated that the return loop 70, the pump 80 and the first and second three-way valves 30, 50 are optional features and may not be present. Rather, the slurry may flow straight from the fluid inlet 20 into the fluid flow pipe 40 and out the fluid outlet 60, passing only once through the coil 100.

[0079] Similarly, the coolant system 140, including coolant hoses 150, is an optional feature that may not be present.

[0080] The mineral processing apparatus 10 further includes a settling tank 160 arranged to receive the slurry from the fluid outlet 60. In use, the slurry may be left to settle in the settling tank 160. The electromagnetic fields to which the slurry is subjected as it passes through the fluid flow pipe 40 may enhance the magnetic properties of iron-containing compounds in the slurry, and may also affect the properties of the water. Consequently, when left to settle, the iron-containing compounds, such as iron oxides, may gather together in clumps 170, which may sink to the bottom of the tank 160, while other components of the granular material are stratified (i.e. form bands or layers) in the tank 160, and do not sink to the bottom. The density of the fluid (slurry), in particular the density of the water in the slurry, may be changed by the electromagnetic fields. The stratified materials may then be removed, leaving the clumps of iron-containing compounds 170 at the bottom of the tank 160.

[0081] The settling tank 160 includes a drainage channel 180 through which the contents of the tank 160 may be drained. The drainage channel 180 may be selectively openable (for example, using a valve) so that it may be closed while the slurry is settling and then opened once the stratified material has been removed. While the draining channel 180 is shown at the bottom of the tank 160, in an alternative arrangement, a drainage channel may instead be located at the top of the tank, or at a position between the bottom and the top of the tank 160.

[0082] The drainage channel 180 includes a magnet 190 around which the contents of the tank 160 pass as they flow out through the drainage channel 180. The clumps of iron-containing compounds 170 may be attracted to, and collect on, the magnet as the contents of the tank 160 are drained through the drainage channel 180.

[0083] Alternatively, instead of the magnet 190, or in addition thereto, the drainage channel may include a mesh or sieve or some other means for collecting the iron oxide clumps 170 as the tank 160 is drained through the drainage channel 180.

[0084] shows an example waveform of the voltage V(t), applied between a first end of the coil and a second end of the coil, as a function of time t. In this example, the amplitude V0is 3.12V and the frequency f is 2105Hz. The values of the other parameters are a = 0.96, b = 0.93, p = 0.2, q = 0.75, r = -0.5, δ1= 0.324 / f, δ2= 0.680 / f and k = 0.82.

[0085] As can be seen in, the waveform comprises a repeating series of three peaks, the series of peaks comprising a first peak 210, a second peak 220 and a third peak 230, each peak being smoothly curved and approximately sinusoidal in form. Each first peak 210 is separated from an adjacent second peak 220 by a first trough 250; each second peak 220 is separated from an adjacent third peak 230 by a second trough 260; and each third peak 230 is separated from an adjacent first peak 210 by a third trough 270. Unlike the peaks, the troughs are sharply pointed and the gradient of the waveform is discontinuous at the troughs.

[0086] Within each series of peaks, the first peak 210 is the highest; the second peak 220 is lower; and the third peak 230 is lower again. The first trough 250 is the shallowest (i.e. has the highest minimum point); the second trough 260 is the deepest; and the third trough 270 is slightly deeper than the first trough 250 but shallower than the second trough 260.

[0087] Between each pair of adjacent troughs, the value of V(t) initially increases rapidly, reaching a peak at a time less than half the time between the adjacent troughs, before decreasing again at a slower rate. That is, the peaks do not appear centrally between the troughs, but instead appear shifted (tilted, slanted) so that they occur to the left of the midpoint between the troughs.

[0088] The variable a determines the relative height of the second peak 220 compared with the first peak 210. Similarly, the variable b determines the relative height of the third peak 230 compared with the first peak 210. If a is set to equal 1, the first and second peaks will be the same height; if b is set to equal 1, the first and third peaks will be the same height; and if a is set to be equal to b, the second and third peaks will be the same height.

[0089] The variable δ1determines the horizontal spacing between the first peak 210 and the second peak 220, and consequently affects the depth of the first trough 250. Similarly, the variable δ2determines the horizontal spacing between the first peak 210 and the third peak 230, and consequently affects the depth of the third trough 270. It follows that the spacing between the second peak 220 and the third peak 230 (and the consequent depth of the second trough 260) is determined by the difference between δ1andδ2.If δ1is set to equal 1 / (3f) and δ2is set to equal 2 / (3f), the horizontal spacing between all peaks will be consistent and the troughs will all have the same depth.

[0090] The variables p, q and r determine the shape of each peak. If p is set to equal zero, each peak will have a shape that is symmetric about a vertical axis passing through the maximum point of the peak. The first peak 210, second peak 220 and third peak 230 will all have the same shape, regardless of the values of p, q and r.

[0091] The variable k determines the vertical displacement of the waveform relative to the V=0 axis. If the value of k is increased, the entire waveform will be shifted “down”, while if the value of k is decreased, the entire waveform will be shifted “up”.

[0092] An example of the use of the mineral processing apparatus according to the present invention is described below.

[0093] A sample of an input material containing iron ore was crushed and then ground to form a powder comprising grains of less than 0.5mm in size. The powder was mixed with water, at a ratio of 200g of powder per litre of water, to form a slurry. The slurry was circulated through the fluid flow pipe at a flow rate of five litres per minute for a total time of 35 seconds, before being passed to the settling tank and left to settle. The material that had sunk to the bottom of the tank was then collected.

[0094] A sample of the input material and a sample of the processed material collected from the bottom of the tank were both assayed, using x-ray fluorescence spectroscopy, to determine the relative proportions of different elements and / or compounds therein. The sample of the initial material contained 86.9% iron oxide (haematite, Fe2O3), with 7.0% aluminium oxide (Al2O3), 5.5% silicon dioxide (SiO2) and a number of trace elements / compounds. By contrast, in the sample of processed material, the percentage of iron oxide had increased to 94.9%, while the percentages of both aluminium oxide and silicon dioxide had decreased to 3.8% and 0.81%, respectively. In other words, the iron oxides had been refined.

[0095] is a table showing the full results of the assays carried out on the samples of the input (raw) material and the resultant (processed) material collected from the bottom of the tank.

Claims

A mineral processing apparatus comprising a coil of electrically conductive material, the coil including a passage therethrough; a fluid flow pipe passing through the passage, the fluid flow pipe arranged to carry a slurry comprising water and a granular material to be processed, the granular material comprising iron-containing compounds; an electrical supply configured to provide a time-varying voltage between a first end of the coil and a second end of the coil, the time-varying voltage being described by a function V(t), defined for any time t as the greatest value of V1(t), V2(t) and V3(t), whereV1(t) = V0[sin(2πft + p sin(2πft + q sin(2πft + r))) – k];V2(t) = V0[a sin(2πf(t – δ1) + p sin(2πf(t – δ1) + q sin(2πf(t – δ1) + r))) – k]; andV3(t) = V0[b sin(2πf(t – δ2) + p sin(2πf(t – δ2) + q sin(2πf(t – δ2) + r))) – k],and where V0is a predetermined constant amplitude, f is a predetermined constant frequency, a has a value between 0.5 and 1.5, b has a value between 0.5 and 1.5, p has a value between -0.5 and 0.5, q has a value between -1 and 1, r has a value between -0.5 and 0.5, δ1has a value between 0.274 / f and 0.374 / f, δ2has a value between 0.630 / f and 0.730 / f and k has a value between -5 and 5; anda settling tank arranged to receive the slurry from the fluid flow pipe,wherein the apparatus is configured to at least partially separate iron-containing compounds in the granular material from non-iron-containing compounds, with the iron-containing compounds settling to the bottom of the settling tank, in use, for collection thereof.The mineral processing apparatus according to claim 1, wherein p = 0.2, q = 0.75 and r = -0.5.The mineral processing apparatus according to either one of claim 1 and claim 2, wherein a = 0.96 and b = 0.93.The mineral processing apparatus according to any preceding claim, wherein δ1= 0.324 / f and δ2= 0.680 / f.The mineral processing apparatus according to any preceding claim, wherein k = 0.82.The mineral processing apparatus according to any preceding claim, wherein the coil of electrically conductive material comprises a wire.The mineral processing apparatus according to any preceding claim, wherein the coil of electrically conductive material comprises a hollow conductive pipe.The mineral processing apparatus according to claim 7, wherein the coil of electrically conductive material comprises copper.The mineral processing apparatus according to either one of claim 7 and claim 8, wherein the hollow conductive pipe has a diameter of between 6mm and 32mm.The mineral processing apparatus according to any one of claims 7 to 9, wherein a coolant is circulated through the hollow conductive pipe.The mineral processing apparatus according to any preceding claim, further comprising a return loop connected between a second end of the fluid flow pipe and a first end of the fluid flow pipe, the return loop arranged to return the slurry from the second end of the fluid flow pipe back to the first end of the fluid flow pipe for recirculation through the fluid flow pipe, before it reaches the settling tank.The mineral processing apparatus according to claim 11, wherein the return loop comprises a pump configured to pump the slurry from the second end of the fluid flow pipe to the first end of the fluid flow pipe.The mineral processing apparatus according to any preceding claim, further comprising a mixing device configured to mix the granular material with water to form the slurry.The mineral processing apparatus according to any preceding claim, wherein the settling tank comprises drainage means, through which at least some of the contents of the settling tank are drainable, the apparatus including a magnet for collecting the iron-containing compounds from at least some of the contents.A method of at least partially separating iron-containing compounds in a granular material from non-iron-containing materials, the method comprising the steps of: providing a granular material comprising iron-containing compounds; providing the mineral processing apparatus of any preceding claim; mixing the granular material with water to form a slurry; passing the slurry through the fluid flow pipe; simultaneously applying a time-varying voltage between a first end of the coil and a second end of the coil, the time-varying voltage being described by a function V(t), defined for any time t as the greatest value of V1(t), V2(t) and V3(t), whereV1(t) = V0[sin(2πft + p sin(2πft + q sin(2πft + r))) – k];V2(t) = V0[a sin(2πf(t – δ1) + p sin(2πf(t – δ1) + q sin(2πf(t – δ1) + r))) – k]; andV3(t) = V0[b sin(2πf(t – δ2) + p sin(2πf(t – δ2) + q sin(2πf(t – δ2) + r))) – k],and where V0is a predetermined constant amplitude, f is a predetermined constant frequency, a has a value between 0.5 and 1.5, b has a value between 0.5 and 1.5, p has a value between -0.5 and 0.5, q has a value between -1 and 1, r has a value between -0.5 and 0.5, δ1has a value between 0.274 / f and 0.374 / f, δ2has a value between 0.630 / f and 0.730 / f and k has a value between -5 and 5; passing the slurry from the fluid flow pipe into the settling tank; and collecting the iron-containing compounds from the settling tank.The method according to claim 15, wherein the iron-containing compounds comprise iron oxide.The method according to either one of claims 15 and 16, further comprising the step of returning the slurry from a second end of the fluid flow pipe back to a first end of the fluid flow pipe for recirculation through the fluid flow pipe, before it reaches the settling tank.The method according to claim 17, wherein the slurry is continually recirculated through the fluid flow pipe for a predetermined period of time, before it reaches the settling tank.The method according to any one of claims 15 to 18, wherein the step of collecting the iron-containing compounds comprises using a magnet to magnetically attract the iron-containing compounds thereto.

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