FIELD

[0001] This disclosure relates to a hydrocyclone that forms part of a mineral processing system. In particular, the invention relates, but is not limited, to a mining system including a f lat bottom hydrocyclone. This disclosure also relates to a method for incorporating a f lat bottom hydrocyclone into a primary g rinding circuit for use in the mineral processing industry.

BACKGROUND

[0002] After iron ore is removed f rom a mine, there are a number of steps involved in processing the extracted ore. These steps may include screening the ore to separate fine particles and then crushing, grinding and separating the iron ore and other valuable metals or minerals out f rom the remaining waste materials, known as gangue. The process of reducing the ore in size and separating the valuable components from the undesired materials is known as ore benef iciation.

[0003] Grinding is normally a subsequent step after an ore crushing process, and is an important part of the preparation work for mineral sorting. Grinding has two main purposes: to break open the ore rock crystals so that the minerals inside can be accessed (and then separated from the mixture); and to produce mineral filler, which is f ine inert mineral matter.

[0004] Primary grinding is the f irst stage of the grinding process and involves two main instruments, a grinding apparatus and a classif ier. The grinding apparatus grinds feed material to a smaller size, and the classif ier divides the ground products into desired and undesired products. From here, the undesired material is returned to a grinder mill for re-grinding.

[0005] The grinding process accounts for approximately 45-55% of the energy consumption for a plant associated with the beneficiation process. This becomes an increasing, non-obvious problem in processing ores, particularly mag netite, that have lower ore grade (generally 25-40% Fe) due to the presence of impurities. Further processing is therefore required to reject the impurities in magnetite ores, making it costly to produce a commercially suitable concentrate for steel smelters.

[0006] The energy used in grinding is considerably influenced by the eff iciency of the classification operation. Therefore, increasing the classification eff iciency is crucial to optimising the operational costs of the grinding process and subseq uently, the whole plant. Increasing the classification eff iciency can also mitigate overgrinding and the generation of slime, which can lead to loss of valuable minerals and, in large quantities, cause degradation of downstream equipment. In addition, the increase of classification eff iciency helps to decrease the circulating load and consequently increase the milling throughput.

[0007] In conventional and small-scale processing plants, spiral classif iers are often used. A spiral classif ier is an eff icient classif ication apparatus, requiring less power and lower maintenance costs. However, owing to the smaller capacity but larg er layout required of spiral classifiers, they have been widely displaced over the past few decades by hydrocyclones.

[0008] Hydrocyclones are used to separate components f rom a f lowing mixture. Each of the components can take the form of a solid, liquid or gas. The separation typically involves isolating a heavier matter from a liquid. However, the process can include the separation of two components of the same state of matter. For example, two liquids can be separated f rom a mixture, based on the relative densities of each of the liquids. Solids can be separated out through size or particle density.

[0009] In the mining industry, hydrocyclones have been used to separate components from a feed or run-off material. Typically, hydrocyclones are used to separate desirable materials f rom a run-off slurry and are a commonly used classification apparatus in a mineral grinding process. Conventional hydrocyclones have a separation chamber, an input pathway for the feed material into the chamber, and two output pathways for the different components. The shape of a conventional hydrocyclone is a cylinder positioned above and in communication with a conical section.

[0010] Hydrocyclones use the f luid pressure of the flowing mixture to generate centrif ugal force and cause a number of vortexes to form in the chamber. These vortexes move the heavier material to the edge of the chamber and then down to the bottom of the chamber. Typically, there is an outlet positioned in the lower half of the hydrocyclone where this matter can be discharged. Conversely, the lighter material is pushed towards the top of the chamber and typically exits through an outlet found there.

[0011] The success of a process using a hydrocyclone for separation may be attributed to the design of the hydrocyclone, the shape and weight of the materials to be separated and the process parameters, including the speed and pressure of the f eed material. [0012] A conventional hydrocyclone, with a cylindrical section and conical section, is the most common type integrated into mineral processing as it is believed to be the most suitable separator. For example, in a Semi-autogenous (SAG) mill or ball mill grinding circuit, the cut size is often at around 37-75pm, hence a conventional hydrocyclone is capable of handling the classif ication process required. Furthermore, a conventional hydrocyclone provides a f ine material which is, typically, benef icial and desirable.

[0013] However, for an Autogenous (AG) mill circuit (for instance), it is not commonly appreciated that the cut size often increases to 106-150pm, and sometimes even higher. This higher cut size can affect what is referred to as the separation or cut point of the hydrocyclone. The cut point is the size of particle which would be subjected to an equal amount of centrif ugal force and drag force, and the point in which the particle has a 50% chance of exiting the hydrocyclone through the overflow or underf low. When a conventional hydrocyclone is employed in this type of circuit, it can lead to a number of non-obvious problems.

[0014] For example, if more f ine material is misplaced to a cyclone underf low, this can lead to an increase of circulating load and the possibility of overgrinding. This can in turn lead to restriction of the milling throughput due to a high charging load in the mill caused by high circulating load . Roping, and other associated problems, f requently occur due to high feed density caused by high circulating load as well, resulting in coarse particles being conveyed to f urther downstream. Roping is an operational issue where an abundance of solid materials is discharged from the hydrocyclone overf low causing the air core of the spiral shape of the centrif ugal f orce to collapse and the underf low discharge to resemble a rope. This can lead to damage of the downstream equipment and, in some situations, can cause a widespread breakdown across the whole production line.

[0015] Bearing this in mind, the present inventor(s) have developed an improved system and method with higher eff iciency and higher cut accuracy for primary grinding circuit.

[0016] Any reference to ordiscussion of any document, act or item of knowledge in this specif ication is included solely forthe purpose of providing a context for the present invention. It is not suggested or represented that any of these matters or any combination thereof formed at the priority date part of the common general knowledge, or was known to be relevant to an attempt to solve any problem with which this specif ication is concerned.

SUMMARY

[0017] In one form, a hydrocyclone is disclosed, the hydrocyclone comprising: a body having a chamber; an inlet in communication with the chamber, the inlet configured to receive a processed material from a grinding apparatus; a f irst outlet associated with the chamber, the f irst outlet conf igured to return a f irst stream to the grinding apparatus; and a second outlet associated with the chamber, the second outlet conf igured to convey a second stream f rom the hydrocyclone, wherein at least part of a surface forming the chamber is substantially f lat to cause a directional change in the processed material present in the chamber.

[0018] In an embodiment, the processed material includes magnetite ore.

[0019] In an embodiment, the surface is approximately located at the bottom of the chamber.

[0020] In an embodiment, the surface is substantially f lat to improve the classif ication efficiency in the mineral processing system.

[0021] In an embodiment, the classif ication eff iciency is above approximately 40%.

[0022] In an embodiment, the classif ication eff iciency is above approximately 50%.

[0023] In an embodiment, the classif ication eff iciency is above approximately 60%.

[0024] In an embodiment, the particle size associated with the classification efficiency is approximately 106 pm.

[0025] In an embodiment, the hydrocyclone is conf igured to process up to approximately 750 to 900 cubic metres per hour.

[0026] In an embodiment, the surface is orientated transversely to one or more further walls of the chamber.

[0027] In an embodiment, the surface is orientated perpendicular to the one or more further walls of the chamber.

[0028] In an embodiment, the directional change includes a substantially perpendicular directional change.

[0029] In an embodiment, the directional change includes two substantially perpendicular directional changes. [0030] In an embodiment, the hydrocyclone produces a separation due to the directional change of the material against the surface of the chamber whereby: i) particles above approximately 300pm are generally directed towards the first outlet; and ii) particles below approximately 300pm are generally directed to the second outlet.

[0031] In an embodiment, particles above approximately 0pm to below approximately 200pm are generally directed to the second outlet.

[0032] In an embodiment, particles above approximately 0pm to below approximately 150pm are generally directed to the second outlet.

[0033] In an embodiment, the surface is orientated perpendicular to the one or more further walls of the chamber.

[0034] In an embodiment, the directional change includes a substantially perpendicular directional change.

[0035] In an embodiment, the directional change includes two substantially perpendicular directional changes.

[0036] In an embodiment, the body includes one or more (separate) sections.

[0037] In an embodiment, the one or more sections are arranged to form a column. In an embodiment, the one or more sections are stacked on top of one another to form the column.

[0038] In an embodiment, the one or more sections are wider than they are long er. In an embodiment, width of the one or more sections is def ined transversely to a longitudinal axis of the one or more hydrocyclones.

[0039] In an embodiment, the one or more sections are sealed against each other.

[0040] In an embodiment, the one or more sections include at least two sections that are different sizes.

[0041] In an embodiment, the one or more sections includes a f irst section and a second section that are longer than a third section. In an embodiment, length is def ined in a longitudinal direction along the hydrocyclone. In an embodiment, the longitudinal direction extends in a vertical direction.

[0042] In an embodiment, the f irst section and the second section are of the same length.

[0043] In an embodiment, the f irst section is longer than the second section. [0044] In an embodiment, the one or more sections are configured to be interchanged to obtain a selected particle size.

[0045] In an embodiment, the f irst outlet is located in the lower portion of the chamber. In an embodiment, the f irst outlet is located in the surface of the chamber.

[0046] In an embodiment, a spigot or apex is located in the lower portion of the chamber. In an embodiment, the spigot or apex is located in the f irst outlet. In an embodiment, the spigot is located in the side wall of the f irst outlet.

[0047] In an embodiment, silicon carbide is applied to the surface. In an embodiment, silicon carbide is applied to the spigot.

[0048] In an embodiment, the density of the processed material varies f rom 30% to 60% solid material.

[0049] In an embodiment, the working pressure of the processed material is between 40kPa and 90kPa.

[0050] In an embodiment, the density of the processed material varies f rom 30% to 55% solid material. In this embodiment, the working pressure of the processed material is between 50 to 90 kPa. In this embodiment, the grinding apparatus is an autogenous or semi-autogenous mill.

[0051] In an embodiment, the density of the feed material varies f rom 35% to 60% solid material. In this embodiment, the working pressure of the processed material is between 40 kPa and 60 kPa. In this embodiment, the grinding apparatus is a ball mill.

[0052] In a further form, a mineral processing system is disclosed including : a grinding apparatus conf igured to receive feed material and output a processed material; and one or more hydrocyclones, each of the hydrocyclones comprising: a body having a chamber; an inlet in communication with the chamber, the inlet configured to receive the processed material f rom the grinding apparatus; a first outlet associated with the chamber, the first outlet configured to return a first stream to the grinding apparatus; and a second outlet associated with the chamber, the second outlet conf igured to convey a second stream from the one or more hydrocyclones, wherein at least part of a surface forming the chamber is substantially flat to cause a directional change in the processed material present in the chamber.

[0053] In an embodiment, the surface is approximately located at the bottom of the chamber.

[0054] In an embodiment, the surface is substantially f lat to improve the classif ication efficiency in the mineral processing system.

[0055] In an embodiment, the classif ication eff iciency is above approximately 40%.

[0056] In an embodiment, the classif ication eff iciency is above approximately 50%.

[0057] In an embodiment, the classif ication eff iciency is above approximately 60%.

[0058] In an embodiment, particle size associated with the classification eff iciency is approximately 106 pm.

[0059] In an embodiment, the feed material to the grinding apparatus includes new feed material and recirculated feed material.

[0060] In an embodiment, the new feed material includ es material unprocessed by the grinding apparatus.

[0061] In an embodiment, the new feed material to the grinding apparatus is above

750 wet metric tons/hour (wmt/h).

[0062] In an embodiment, the new feed material to the grinding apparatus is above

1000 wet metric tons/hour (wmt/h).

[0063] In an embodiment, the new feed material to the grinding apparatus is above

1250 wmt/h.

[0064] In an embodiment, the processed material that leaves the grinding apparatus is separated into oversized and undersized particles using a mechanical screen.

[0065] In an embodiment, the undersized particles are directed to the inlet of the one or more hydrocyclones.

[0066] In an embodiment, the recirculated feed material includes processed material that has been separated by the one or more hydrocyclones and/or oversized particles that have retained on the mechanical screen.

[0067] In an embodiment, the processed material includes magnetite ore. [0068] In an embodiment, the surface is orientated transversely to one or more f urther walls of the chamber.

[0069] In an embodiment, the surface is orientated perpendicular to the one or more further walls of the chamber.

[0070] In an embodiment, the directional change includes a substantially perpendicular directional change.

[0071] In an embodiment, the directional change includes two substantially perpendicular directional changes.

[0072] In an embodiment, the one or more hydrocyclones includes at least two hydrocyclones.

[0073] In an embodiment, the one or more hydrocyclones includes at least five hydrocyclones.

[0074] In an embodiment, the one or more hydrocyclones includes ten hydrocyclones.

[0075] In an embodiment, the ten hydrocyclones include at least five hydrocyclones that are operational.

[0076] In an embodiment, the number of operational hydrocyclones is based on a predetermined feed rate.

[0077] In an embodiment, the grinding apparatus and the one or more hydrocyclones are arranged in a feedback loop.

[0078] In an embodiment, the grinding apparatus and the one or more hydrocyclones are arranged in communication with a mechanical screen in the feedback loop.

[0079] In an embodiment, the mechanical screen is a vibrating screen.

[0080] In an embodiment, the mechanical screen is a trommel screen.

[0081] In an embodiment, the body includes one or more sections.

[0082] In an embodiment, the one or more sections are arranged to form a column. In an embodiment, the one or more sections are stacked on top of one another to form the column.

[0083] In an embodiment, the one or more sections are wider than they are longer. In an embodiment, width of the one or more sections is defined transversely to a longitudinal axis of the one or more hydrocyclones.

[0084] In an embodiment, the one or more sections are sealed against each other. [0085] In an embodiment, the one or more sections include at least two sections of different sizes.

[0086] In an embodiment, the column includes a f irst and second section that are longer than a third section. In an embodiment, length is def ined in a longitudinal direction along the one or more hydrocyclones. In an embodiment, the longitudinal direction extends in a vertical direction.

[0087] In an embodiment, the column includes a f irst and second section that are of the same length.

[0088] In an embodiment, the column includes a f irst section that is longer than a second section.

[0089] In an embodiment, the one or more sections are conf igured to be interchanged to obtain a selected particle size.

[0090] In an embodiment, the f irst outlet is located in the lower portion of the chamber.

[0091] In an embodiment, the f irst outlet is located in the surface of the chamber.

[0092] In an embodiment, a spigot or apex is located in the lower portion of the chamber.

[0093] In an embodiment, the spigot or apex is located in the first outlet.

[0094] In an embodiment, the spigot is located in the side wall of the f irst outlet.

[0095] In an embodiment, silicon carbide is applied to the surface.

[0096] In an embodiment, silicon carbide is applied to the spigot.

[0097] In an embodiment, the one or more hydrocyclones produce a separatio n due to the directional change of the material against the surface of the chamber whereby: i) particles above approximately 300pm are generally directed towards the first outlet; and ii) particles below approximately 300pm are generally directed to the second outlet.

[0098] In an embodiment, particles above approximately 0pm to below 300pm are generally directed to the second outlet.

[0099] In an embodiment, particles above approximately 0pm to below 150pm are generally directed to the second outlet.

[00100] In an embodiment, the grinding apparatus may be an autogenous mill or a semi-autogenous mill. [00101] In an embodiment, the grinding apparatus may accept a feed material with a Pso of 100 to 200-mm.

[00102] In an embodiment, the autogenous mill has a cut size of 106 to 150 pm.

[00103] In an embodiment, the semi-autogenous mill has a cut size of 37 to 75 pm.

[00104] In an embodiment, the density of the processed material varies f rom 30% to

55% solid material.

[00105] In an embodiment, the working pressure of the processed material is between 50 to 90 kPa.

[00106] In an embodiment, the grinding apparatus is a ball mill.

[00107] In an embodiment, the grinding apparatus is configured to accept a feed material with a Pso of 10-25 mm.

[00108] In an embodiment, the ball mill has a cut size of 37 to 75 pm.

[00109] In an embodiment, the density of the feed material varies f rom 35% to 60% solid material.

[00110] In an embodiment, the working pressure of the processed material is between 40 kPa and 60 kPa.

[0011 1] In an embodiment, a hopper is arranged in the feedback loop between the mechanical screen and the one or more hydrocyclones.

[00112] In an embodiment, the vibrating screen is a double deck vibrating screen.

[00113] In an embodiment, the mineral processing system assists in reducing the particle size of the feed material f rom a Pso of 100-200 mm to a Pso of 100-200 pm. In this embodiment, an autogenous mill or a semi-autogenous mill is utilised in the mineral processing system.

[00114] In an embodiment, the mineral processing system assists in reducing the particle size of the feed material from a Pso of 10-20 mm to a Pso of 100-200 pm. In this embodiment, a ball mill is utilised in the mineral processing system.

[00115] In a further form, a method for processing minerals is disclosed, the method including the steps of : processing a feed material in a grinding apparatus to produce a processed material; conveying the processed material to one or more hydrocyclones; separating components f rom the processed material into a f irst stream and a second stream using one or more hydrocyclones, wherein part of the material has a directional change to separate the streams; returning the f irst stream the grinding apparatus; and conveying the second stream downstream forf urther processing.

[00116] In an embodiment, wherein the step of processing the feed material includes processing magnetite.

[00117] In an embodiment, the method f urther includes the steps of : the processed material entering a body of the one or more hydrocyclones, the body having a chamber, wherein at least part of a surface of the chamber is substantially flat to cause the directional change in the processed material present in the chamber; the processed material undergo the directional change when coming into contact with the surface.

[00118] In an embodiment, the directional change provides a coarser material being directed to the first stream compared to the second stream.

[00119] In an embodiment, the method f urther includes the steps of : conveying the processed material f rom the grinding apparatus to a mechanical screen; subjecting the processed material to a classification step; conveying the remaining processed material to a hopper; mixing the remaining processed material with water; and pumping the processed material to the one or more hydrocyclones.

[00120] Further features and advantages of the present disclosure will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[002] Vario us preferred embodiments of the present disclosure will now be described, by way of examples only, with reference to the accompanying f igures, in which: Figure 1 illustrates a f low diagram relating to a mineral processing system, according to an embodiment of the invention;

Figure 2 illustrates a f ront view of a conventional hydrocyclone;

Figure 3 illustrates a front view of a flat bottom hydrocyclone for use in the mineral processing system of Figure 1 ;

Figures 4(a)-(c) illustrate variations of the flat bottom hydrocyclone in Figure 3, wherein 4(a) is a f ront view of a stand ard sized f lat bottom hydrocyclone; 4(b) is a f ront view of a short f lat bottom hydrocyclone; and 4(c) is a f ront view of an extra short f lat bottom hydrocyclone; and

Figures 5 to 7 illustrate f lowdiagrams relating to the mineral processing system of Figure 1 , according to various embodiments of the invention.

DETAILED DESCRIPTION

[00121] Figure 1 provides an illustration of a mineral processing system 10i, according to an embodiment of the invention. In this regard, the use of a reference numeral followed by a lower case letter typically indicates alternative embodiments of a general element identif ied by the reference numeral in this specif ication. Thus, for example, mineral processing system 10a is similar to but not identical to the mineral processing system 10b. Further, references to an element identified only by the numeral refer to all embodiments of that element. Thus for example a reference to mineral processing system 10 is intended to include (for instance) the mineral processing system 10i, mineral processing 10a, mineral processing system 10b and mineral processing system 10c.

[00122] After iron ore is removed f rom a mine, there are a number of steps involved in processing the extracted ore. The process of reducing the ore in size and separating the valuable components f rom the undesired materials is known as ore beneficiation. These steps may include screening the ore to separate f ine particles and then crushing, grinding and separating the desired particles f rom other materials. This separation is achieved through two steps known as screening and classif ication.

[00123] Classif ication is the process of separating out particles by size based on the particle's behaviour in a f lowing material (air or water). Because classif ication can be a complicated process, the energy used during ore beneficiation is considerably influenced by the efficiency of the classif ication operation. For wet classification, the key properties are the particle's size and density. The heavier and denser particles should settle while the finer and lighter particles should be carried along more easily within the liquid. Therefore, classification eff iciency is based on how successf ul this separation between particles with these varying properties is. In other words, classification eff iciency is generally defined as the f raction (or percentage) of the feed material of a given size which is recovered in a stream. Increasing the classification eff iciency is crucial to optimising the operational costs of the grinding process and subsequently, the whole plant.

[00124] As part of the mineral processing system 10i, new feed material 100 und ergoes a crushing step (not shown). New feed material 100 is delivered to one or more crushing device(s). This new feed material 100 contains magnetite ore. The crushing device could be any one of the following: jaw crushers, gyratory crushers, cone crushers or high pressure grinding rolls. However, it will be appreciated that the crushing device is not limited to these options. The crushing device, typically, reduces new feed material 100 from a diameter up to 1200 mm to a diameter less than 350 mm.

[00125] The specif ic particle size to be conveyed to other parts of the mineral processing system 10i depends on (amongst other things) the grinding apparatus, such as grinding apparatus 200i, that is to be used within the mineral processing system 10i. If an Autogenous (AG) mill or Semi-autogenous (SAG) mill is to be used, new feed material 100 is typically crushed only by a single crusher to obtain coarse particles with a dimension up to P80 approximately 100-200 mm. If a ball mill is to be used, new feed material 100 is crushed by two or more crushers operating in parallel to obtain f ine particles with an approximate particle P80 size of 10-20 mm or smaller. The grinding apparatus 200i will be discussed in f urther detail below.

[00126] After the crushing step, the new feed material 100 is conveyed to a primary grinding circuit of the mineral processing system 1 Oi. The primary grinding circuit is the f irst stage of the grinding process and involves two main instruments, a grinding apparatus 200i and a classif ier or hydrocyclone 300i. The grinding apparatus 200i grinds the feed material to a smaller size, and the classif ier or hydrocyclone 300i divides the ground products into desired and undesired products. From here, the undesired material is returned to the grinding apparatus 200i for re-grinding.

[00127] The mineral processing system 10i may assist in reducing the ore particle size from a Pso (80% out the o utput product) of 100-200 mm (for an AG mill o r SAG mill) or 10-20 mm (for ball mill) to a Pso of 100-200 pm.

[00128] The feed material 100' that enters the grinding apparatus 200i includes new feed material 100 and recirculated feed material. The recirculated feed material includes material that has been processed by the hydrocyclone 300i and undesirable (oversized) particles that have been retained on the mechanical screen 400. The mechanical screen 400 and the hydrocyclone 300i will be discussed in further detail below.

[00129] The grinding apparatus 200i is used to grind the feed material 100' into smaller particles. Grinding has two main purposes: to break open the ore rock crystals so that the minerals inside can be accessed (and then separated f rom the mixture); and to produce mineral f iller, which is a f ine inert mineral matter.

[00130] The grinding apparatus 200i could be any one of an Autogenous (AG) mill, Semi-autogenous (SAG) mill or ball mill, or a combination of such apparatus. However, it will be appreciated that such a grinding apparatus 200i is not limited to these options. As discussed above, Autogenous (AG) mill or Semi-autogenous (SAG) mill often require new feed material 100 to take the form of coarse ore. This is because new feed material 100 forms, at least, part of the grinding media in the grinding apparatus 200i when an AG mill or SAG mill is used. The autogenous mill uses a cut size of approximately 106 to 150pm during the grinding process but this may be higher. Conversely, the semi-autogenous mill uses a cut size of approximately 37 to 75 pm.

[00131] New feed material 100 consisting of f ine ore is pref erred when utilising a ball mill. This is because a ball mill uses its own grinding media, e.g. steel grinding balls, to aid in the grinding process. The ball mill has a cut size of approximately 37 to 75 pm.

[00132] The feed material 100' is termed a processed material 150, in this specif ication, once it has left the grinding apparatuses 200. However, it will be appreciated that, for example, the feed material 100' is partially processed and the processed material 150 may be f urther processed by, for instance, the hydrocyclones 300.

[00133] Afterthe grinding step, the processed material 1 50 is conveyed to a mechanical screen 400 for classifying. The mechanical screen 400 could be a rotary screen, such as a trommel screen, or a vibrating screen; however, the invention is not limited to these devices. The purpose of the screen is to separate the ground ore into multiple grades through classif ication of particle size.

[00134] In Figure 1 , a vibrating screen 400i is used as the mechanical screen. A vibrating screen is, typically, used when smaller size material needs to be classif ied. The vibrating screen 400i consists of a screen media placed on a spring -mo unted frame, where the f rame could be horizontal or on an incline. The screen media is formed of one or more layers which include a series of openings. If there is more than one layer, the openings of each consecutive layer diminish in size. The screen media is pulled tight across the f rame. When the processed material 150 is shaken throug h the vibrating screen 400i, the vibrating screen 400i separates out particles of an undesirable size. The remaining processed material 150 will contain a selected particle size.

[00135] Following the mechanical screen 400, the undesired particles can take a number of different paths. These paths are dependent on the chosen grinding apparatus 200 to be used in the mineral processing system 10.

[00136] For system 10i, when an AG mill or SAG mill is used as the grinding apparatus 200i, the undesired particles f rom the mechanical screen 400i are delivered back to a pebble crusher 700i forf urther crushing or directly returned to the grinding apparatus 200i throug h a return pathway 500i. When a ball mill is used as the grinding apparatus 200i, the und esired particles are often rejected. This is because the undesired particles from the ball mill consist of grinding media scats, extra coarse ore lumps or foreign objects.

[00137] Following the mechanical screen 400i, the processed material 150 is conveyed to a hydrocyclone 300i. The hydrocyclone 300i is a type of classifier. As discussed above in relation to classif ication, classif iers are used to separate and sort materials based off their density, shape and size. They operate by distinguishing between the various settling velocities of the different particle sizes that make up a processed material 150. The use of classifier aids in improving the quality of the product material. In one embodiment of the present invention, ten hydrocyclones 300i are used and the number of operational hydrocyclones is varied based on the feed rate thereto.

[00138] When an autogenous or semi-autogeno us mill has been utilised as the grinding apparatus 200i, the density of the processed material 150 will preferably vary from 30% to 55% solid material. In this embodiment, the working pressure of the processed material 150 is between 50 to 90 kPa.

[00139] When a ball mill has been utilised as the grinding apparatus 200i, the density of the processed material 150 preferably varies f rom 35% to 60% solid material. In this f urther embodiment, the working pressure of the processed material 150 is between 40 kPa and 60 kPa.

[00140] Classification can, to an extent, be undertaken by a spiral classif ier. However, in the present disclosure, the classif ication is und ertaken by a hydrocyclone 300i and this will be discussed in f urther detail with reference to Figures 2 and 3.

[00141] Figure 2 illustrates a f ront view of a conventional prior art hydrocyclone. The shape of a conventional hydrocyclone is a cylindrical section 270 positioned above and in communication with a conical section 250. A conventional hydrocyclone has a conventional feed inlet 210 to allow the processed material 150 to enter the cylindrical section 270, and two output pathways forthe different components. Centrif ugal forces are created f rom the entry of the processed material 150. This forces the heavier material to the walls of the hydrocyclone and down the co nical section 250, while leaving the remaining liquid spinning . The conventional vortex finder 280 keeps increasing the speed of the remaining liquid which eventually exits the hydrocyclone through a conventional overf low pathway 230. [00142] Due to the co nical shape of the conventio nal hydrocyclone, the heavier material increases in speed and hereby increases the separation eff iciency of this material. This heavier material leaves the hydrocyclone through the conventio nal underflow pathway 240. [00143] A conventional hydrocyclone, with a cylindrical section and conical section, is the most common type integrated into mineral processing as it has traditionally been the most suitable separator. For example, in a SAG mill or ball mill grinding circuit, the cut size is often at around 37-75 pm, hence the conventional hydrocyclone is capable of handling the classif ication process required. However, for an AG mill circuit (for instance), the required cut size often increases to 106-150 pm, and sometimes even higher (eg, 300pm etc). This higher cut size can affect what is referred to as the separation or cut point of the hydrocyclone. The cut point is the size of particle which would be subjected to an equal amount of centrif ugal force and drag force, and the point in which the particle has a 50% chance of exiting the hydrocyclone through the overflow or und erf low. When a conventional hydrocyclone is employed in this type of circuit, it can lead to a number of problems due to the f iner material flowing through the circuit.

[00144] For example, if more f ine material is bypassed to the cyclone underflow, this can lead to an increase of circulating load and the possibility of overgrinding . This can in turn lead to restriction of the milling throughput due to a high charging load in the mill caused by high circulating load. Roping and associated problems f requently occur due to high feed density caused by high circulating load as well, resulting in coarse particles being conveyed to f urther downstream. This can lead to damage of the downstream equipment and, in some situations, can cause a widespread breakdown across the whole production line.

[00145] Figure 3 depicts a front view of a f lat bottom hydrocyclone 300i for use in a mineral processing system 10i as described in the present invention. Compared with the conventional hydrocyclone as shown in Figure 2, a flat bottom hydrocyclone 300i is cylindrically-shaped with a flat bottom as shown in Figure 3. Flat bottom hydrocyclones have been developed , such as those found in Chinese patent No. 200620084869 and Chinese patent No. 201721898633.4. However, these hyd rocyclones suffer f rom a number of issues and (for example) are not adapted for processing magnetite. Furthermore, hydrocyclones with varied column lengths are installed in the cyclone cluster of the present invention. This allows the same hydrocyclones with different column lengths or a combination of different hydrocyclones with varied column lengths to achieve a target overf low P ₈ o size according to process requirements.

[00146] The flat bottom hydrocyclone has a cylindrical upper body 305i which has a feed inlet 31 Oi. The feed inlet 31 Oi is configured to receive a processed material 150 from the grinding apparatus 200i.The f lat bottom hydrocyclone 300i has a cylindrical shaped lower body 320i, wither substantially vertical outer wall(s), having a diameter smaller that the upper body 305i. The lower body 320i is formed f rom a number of sections 350i. An end wall 360i, which is substantially perpendicular to the outer walls of the lower body 320i, forms a 'f lat bottom'. The inner walls of the upper body 305i and lower body 320i form a chamber to which the feed inlet 31 Oi is coupled. A first outlet 340i provides an underf low pathway associated with the chamber and is conf igured to return a f irst stream to the grinding apparatus 200i. A second outlet 330i associated with the chamber provides an overf low pathway for classified product.

[00147] The processed material 150 enters the chamber under a working pressure. The pressure of the material creates centrifugal forces within the chamber. Centrif ugal force pushes the heavier or coarser material towards and down the walls of the chamber. The end wall 360i causes a directional change in the processed material 150 present in the chamber. That is, the end wall 360i causes the processed material 150 to substantially change in a perpendicular direction towards underf low outlet 340i. Due to the directional change of the end wall 360i, improved classification eff iciency occurs in the mineral processing system, as less fine material is directed to the underflow pathway (first outlet 340).

[00148] To explain this in more detail, the chamber has two output pathways forthe different components. The heavier particles of the processed material 150 passes through the underf low pathway 340i. The processed material 150 leaves the flat bottom hydrocyclone 300i through a spigot 370i found in the underflow pathway 340i. The spigot 370i could also be an apex under an embodiment of the invention.

[00149] To assist with a bed of coarse solids rotating and circulating on the end wall 360i, causes grooving in the end wall 360i and spigot 370i, a wear-resisting material is applied to the components to prolong their service life. In one embodiment, silicon carbide is applied to the f lat surface 360i and the spigot 370i.

[00150] The processed material 150 that leaves through the underf low pathway 340i returns to the grinding apparatus for further grinding.

[00151] The vortex f inder 380i increases the speed of the liquid and finer material that has separated f rom the heavier material. The f iner material, and any accompanying liquid, exits the flat bottom hydrocyclone 300i through the overf low pathway, via second outlet 330i. The f iner material forms the desired product of the mineral processing system 10i. The finer material is conveyed downstream to be processed f urther.

[00152] Figure 4(a)-(c) depicts various embodiments of different flat bottom hydrocylcones, according to the present invention, wherein (a) is a f ront view of a standard sized f lat bottom hydrocyclone; (b) is a f ront view of a short f lat bottom hydrocyclone; and (c) is a f ront view of an extra short flat bottom hydrocyclone. Each of these conf igurations are considered to be a f lat bottom hydrocyclone 300 as that described with reference to Figure 3.

[00153] In a similar manner to hydrocyclone 300i, each of the hydrocyclones 300a, 300b, 300c shown Figures 4(a), 4(b) and 4(c) include sections 350 arranged to form the lower body 320. The sections 350 are arranged vertically to form a column. That is, the sections 350 are stacked on top of one another to form the column. A chamber is formed inside of the column. The one or more sections 350i may be sealed against each other.

[00154] The sections 350 are configured to be interchanged to obtain a desired overf low particle size. When a coarser overf low particle size is desired, the lower body 320 can be reconfigured with the sections 350. This ability to reconfigure the sections 350 provides an advantage over conventional hydrocyclones which cannot be configured in the same manner.

[00155] The sections 350 may be different sizes. As shown in Figure 4(a), the hydrocyclone 300a includes two sections 350a, 350b of the same height/length and one section 350c of a smaller height/length. This formation is referred to as a standard f lat bottom hydrocyclone 300a. The stand ard f lat bottom hydrocyclone 300a has larg er internal volume and longer time for classif ication which helps to increase the fineness of overf low.

[00156] An embodiment can be formed by removing a short section 350c from the body 320a of the standard flat bottom hydrocyclone 300a. This conf iguration is referred to as a short flat bottom hydrocyclone 300b. A further embodiment can be formed by removing a long section 350b f rom the body 320a of the standard flat bottom hydrocyclone 300a. This is referred to as an extra short flat bottom hydrocyclone 300c.

[00157] The short f lat bottom hydrocyclone 300b and extra short f lat bottom hydrocyclone 300c produce a shorter classif ication time, shortercolumn length, and smaller tangential velocity loss. These factors strengthen the centrif ugal intensity at end wall 360b, 360c and help to reduce the proportion of f ine particles remaining in the processed material 150 that leaves the chamber through the underflow pathway 340. [00158] Figure 5 provides an embodiment of the mineral processing system 10a for improving the classif ication eff iciency in primary grinding circuit. This embodiment preferably includes an AG mill or SAG mill as the g rinding apparatus 200a. A vibrating screen is preferably included as the mechanical screen 400a. One flat bottom hydrocyclone 300i is included in the system 10a but, in f urther embodiment, multiple hydrocyclones 300 may be included . Each apparatus is employed in a feedback loop.

[00159] New feed material 100 may have a particle P80 size of 100-200 mm. New feed material 100 is conveyed to the grinding apparatus 200a. Water may be included as part of the grinding process to obtain a desired grinding density. The grinding apparatus 200a includes a mill grate. Following the grinding step, the processed material 150 is discharged from the grinding apparatus 200a through the mill grate. The processed material 150 is conveyed to the mechanical screen 400a. The mechanical screen 400a is a vibrating screen. The vibrating screen is employed with double decks, aiming at increasing the screening eff iciency.

[00160] The undesired particle sizes of the processed material 150 are returned to the crushing step. As shown in Figure 5, the undesired material is conveyed to a bin 750 and feeder 780 before being transferred into a pebble crusher 700a. The crushed pebbles then return to the grinding apparatus 200a. In an alternative embodiment, the undesired particle sizes are returned to the grinding apparatus 200a.

[00161] The remaining (undersized) processed material 150 flows to a slurry hopper 600a. The processed material 150 is mixed with water or another suitable f luid in the slurry hopper 600a to form another processed material 150 before being pumped to one or more flat bottom hydrocyclones 300i. Preferably, the density of the processed material 150 after it leaves the slurry hopper 600 will vary f rom 30% to 55% solid material. Preferably, the working pressure of the processed material 150 varies from 50 kPa to 90 kPa. The process capacity for each of the one or more f lat bottom hydrocyclones 300i, in this embodiment, is approximately 750 to 900 cubic metres per hour.

[00162] The processed material 150 then passes through the f lat bottom hydrocyclone 300i. After being subjected to centrif ugal forces within the f lat bottom hydrocyclone 300i, the heavier particles of the processed material 150 pass through the underflow pathway 340i. This part of the processed material 150 then returns to the grinding apparatus 200a for further grinding. The finer material, and accompanying liquid, exits the f lat bottom hydrocyclone 300a through an overt low pathway 330i. The f iner material is conveyed downstream to be processed f urther. [00163] Figure 6 provides a further embodiment of the mineral processing system 10b for improving the classif ication eff iciency in primary grinding circuit. This embodiment includes a ball mill as the grinding apparatus 200b. A trommel screen is utilised as a mechanical screen 400b. A number of f lat bottom hydrocyclones 300i form a cluster. Each apparatus is employed in a feedback loop.

[00164] New feed material 100 may have a particle P80 size of 10-20 mm or smaller.

New feed material 100 is conveyed to the grinding apparatus 200b. In this embodiment, the grinding apparatus 200b is a ball mill. Water may be included as part of the grinding process to obtain a desired grinding density. Grinding media, such as steel grinding balls, should be added regularly.

[00165] The ball mill includ es a discharge outlet. A mechanical screen 400b is installed on the discharge outlet of the ball mill. The mechanical screen 400b takes the form of a trommel screen. The undesired material discharged f rom the trommel screen, i.e. scats, are disposed of .

[00166] The remaining processed material 150 f lows to a slurry hopper 600b. The processed material 150 is mixed with water or another suitable f luid in the slurry hopper 600b before being pumped to flat bottom hydrocyclones 30 Oi. Preferably, the density of the processed material 150 after it leaves the slurry hopper 600b will vary from 35% to 60% solid material. Preferably, the working pressure of the processed material 150 varies f rom 40 kPa to 60 kPa.

[00167] The processed material 150 then passes through the f lat bottom hydrocyclones 300i. After being subjected to centrif ugal forces within the f lat bottom hydrocyclone 300i, the heavier particles of the processed material 150 pass through the underf low pathway 340i. This part of the processed material 150 then returns to the grinding apparatus 200b. The finer material, and accompanying liquid, exits the flat bottom hydrocyclo ne 300i thro ugh an overt low pathway 330i. The f iner material is conveyed downstream to be processed f urther.

Example

[00168] A further mineral processing system 10c is provided in Figure 7. This system 10c processes magnetite ore. A combination of an autogenous mill with a vibrating screen and a pebble crusher, together with a hydrocyclone cluster, form a feedback loop whereby at least part of the material is circulated therearound. As shown in Figure 7, the mineral processing system 10c consists of a grinding apparatus 200c, a mechanical screen 400c, a slurry hopper 600c, a feed pump 800c, f lat bottom hydrocyclones 300i and pebble crushers 700c. The grinding apparatus 200c is an AG mill and the mechanical screen 400c is a double deck vibrating screen.

[00169] New feed material 100 of the feed material 100' includes broken ore from an open pit. New feed material 100 has a F80 of around 300-350 mm. New feed material 100 may be delivered to the primary crushers by a fleet of haul trucks. Preferably, the primary crushers are gyratory crushers. New feed material 100 may be delivered to the crushed ore stockpile by conveyor belts. New feed material 100 is preferably fed to the grinding apparatus 200c through the use of apron feeders and conveyor belts.

[00170] The processed material 150 is discharged f rom the grinding apparatus 200c. The processed material 150 is then conveyed to the mechanical screen 400c. The desired particle sizes remain in the processed material 150 which is then conveyed to a slurry hopper 600c. The undesired (oversized) particles are returned to the pebble crushers 700c. The processed material 150 is then pumped to the f lat bottom hydrocyclones 300i by the feed pump 800c.

[00171] The f lat bottom hydrocyclones 300i are configured in a cluster. The number of hydrocyclones in the cluster may vary and, for example, can include ten f lat bottom hydrocyclones 300i. Each of the flat bottom hydrocyclones contained in the clusterdoes not need to be operational at any one time. The number of operational hydrocyclones is based on a predetermined feed rate.

[00172] The capacity associated with each of the flat bottom hydrocyclones 300i is approximately 750 to 900 cubic metres per hour (m ³ /h). The processed material 150 can be delivered to the cluster at a cluster feed rate 4500-5400 m ³ /h to be spread amongst the hydrocyclones. This cluster feed rate can vary based on the new feed material 100 and hydrocyclone recirculatio n rate. This is because the feed material to the grinding apparatus 200c can include fresh or new feed material, which has not been processed by the hydrocyclones, and recirculated feed material that includes material that has been processed by the hydrocyclones and recirculated crushed pebbles (e.g., particles that have been retained on the mechanical screen 400c) if any.

[00173] A first stream exits the one or more f lat bottom hydrocyclones 300i through an underflow pathway. The first stream is returned to the grinding apparatus 200c f orf urther grinding. A second stream exits the one or more f lat bottom hydrocyclones 300i thro ugh an overt low pathway. The second stream is conveyed downstream forf urther processing.

[00174] In this embodiment, conventional cone hydrocyclones with a diameter of 840 mm were conf igured in the original AG mill circuit. It was found that problems would arise and, in some cases, production incidents would occur, due to the inability of the conventional cone hydrocyclones to f ully accommodate the variation of operating conditions in the primary grinding circuit. The problems observed in the conventional cone hydrocyclone und erf low included surging, roping and plugging. Notably, this occurred when the particle size distribution of conventional hydrocyclone feed material varied which happened when there were f luctuations in the AG mill grinding performance. This resulted in coarse particles reporting to downstream magnetic separators. These coarse particles could result in damage to the magnetic separator drums found downstream or block the feed pipelines of the magnetic separators, which could lead to whole line breakdown.

[00175] In addition, some fine particles below the cut size, which sho uld have exited via the overt low pathway of the conventional cone hydrocyclone, were exiting via the underf low pathway. This caused an increase in the circulating load and subsequently decreased the throug hput of the AG mill. Based on the original design, the cyclone overf low P ₈ o should be around 180 pm, but the actual overflow P ₈ o was only 50-70 pm, significantly restricting AG mill throughput.

[00176] In order to resolve the abnormal production conditions and improve the circulating load and throughput of the AG mill, f lat bottom hydrocyclones 300, as described above, were introduced and tested in the primary grinding circuit.

Example 1

[00177] Example 1 involved a series of comparative trials that were performed to evaluate the feasibility of the present invention for increasing classif ication eff iciency and decreasing circulating load in primary grinding circuit.

[00178] There were 14 sets of conventional cone hydrocyclones, each with a diameter of 840 mm, a spigot with a diameter of 180 mm and a vortex f inder with a diameter of 400 mm conf igured in the original cone hydrocyclone cluster. Normally, f ive to six conventional cone hydrocyclones would be running at any one time. The conventional cone hydrocyclones were run with a working pressure of 50-60 kPa. Seven f lat bottom hydrocyclones 300i, as described above, with a diameter of 840 mm, a spigot with a diameter of 150 mm and a vortex f inder with a diameter of 340 mm were installed in the cluster to replace the conventional cone hydrocyclones.

[00179] The comparative trials are carried out between the conventional hydrocyclones and the flat bottom hydrocyclones. The feed material 100 conveyed to each hydrocyclone had the same conditions, such as the particle size distribution, density and working pressure. [00180] The following table (Table 1 ) compares the analysis of each set of hydrocyclones during the trial.

Table 1 : Example 1 trial results

[00181] The trial results indicate that, compared to conventional cone hydrocyclones, the f lat bottom hydrocyclones (in the systems 10) have signif icant advantages for use in primary grinding circuits. These advantages are as follows:

• The operating status for flat bottom hydrocyclones was more stable. • It was found that spigot roping or issues with the spigot being plugged were rare and involved blockage via a foreign object.

• Flat bottom hydrocyclones in the systems 10 had a greater f lexibility to accommodate the f luctuation of the AG mill throughput and feed density.

• The underflow of the f lat bottom hydrocyclones included a significant reduction in fine material. Fine material in the underf low was reduced by 10%. This subsequently provided a better material size distribution when the f ine material reached downstream processing.

• The overf low Pso size (considered to be 80% of the particles passing through) increased by 30-50 pm in comparison to that of the conventional cone hydrocyclone.

• The circulating load for the present flat bottom hydrocyclones was 110-170%. This was red uced substantially f rom that of conventional cone hydro cyclones, where the circulating load was 250-300% forconical cyclones.

• The classif ication eff iciency for the present f lat bottom hydrocyclones is averaged at around 64%, an increase of 13% when compared to conventional cone hydrocyclones.

• The AG mill throughput increased by 10-15% with the present f lat bottom hydrocyclones.

Example 2

[00182] An advantage of replacing the conventional cone hydrocyclones with f lat bottom hydrocyclones 300 is to shift the load f rom the primary grinding circuit to f urther downstream. However, it was found that there was still a significant gap between observed between the calculated P ₈ o size in the f lat bottom hydrocyclone overf low pathway and AG mill throughput and the results that were being recorded.

[00183] In order to f urther coarsen the Pso size exiting the cluster of f lat bottom hydrocyclones 300 and increase the AG mill throughput, the standard f lat bottom hydrocyclone was modif ied to shorten the classification time for obtaining coarser particle sizes. These conf igurations have been discussed above and are depicted in Figure 4(a-c). These conf iguratio ns are referred to as a short f lat bottom hydrocyclone 300b and an extra short flat bottom hydrocyclone 300c. [00184] The comparative trials for each of the three conf igurations of the flat bottom hydrocyclone were performed in parallel within the same f lat bottom hydrocyclone cluster. Each hydrocyclone was equipped with the same diameter of 840 mm, spigot of 150 mm and vortex f inder of 340 mm. The results of Example 2 are listed in Table 2.

Table 2: Trial results for three different types of FBH

[00185] The results showed that both the short f lat bottom hydrocyclone 300b and the extra short f lat bottom hydrocyclone 300c can obtain a lower circulating load while having a lower classif ication eff iciency compared to a standard flat bottom hydrocyclone 300a. If the grinding throughput is causing a delay in the mineral processing system 10, a short or extra short f lat bottom hydrocyclone (300b and 300c respectively) may be the most appropriate configuration of a f lat bottom hydrocyclone for a primary grinding circuit. This will increase the efficiencies of the system 10 but, as will be appreciated, the system 10 as a whole needs to be considered in evaluating and adopting one of the hydrocyclones 300.

[00186] In this specif ication, adjectives such as left and right, top and bottom, hot and cold, f irst and second, and the like may be used to distinguish one element or action f rom another element or action without necessarily requiring or implying any actual such relationship or order. Where context permits, reference to a component, an integer or step (or the alike) is not to be construed as being limited to only one of that component, integer, or step, but rather could be one or more of that component, integer or step.

[00187] In this specification, the terms ‘comprises’, ‘comprising’, ‘includes’, ‘including’, or similar terms are intended to mean a non-exclusive inclusion, such that a method, system or apparatus that comprises a list of elements does not include those elements solely, but may well include other elements not listed.

[00188] The above description relating to embodiments of the present disclosure is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the disclosure to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present disclosure will be apparent to those skilled in the art f rom the above teaching. Accordingly, while some alternative embodiments have been discussed specif ically, other embodiments will be apparent or relatively easily developed by those of ord inary skill in the art. The present disclosure is intended to embrace all modif ications, alternatives, and variations that have been discussed herein, and other embodiments that fall within the spirit and scope of the above description.

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