TECHNICAL FIELD

[001] The present disclosure relates to beneficiation systems and methods, and in particular systems and methods for grinding and classifying aggregate material.

BACKGROUND

[002] A grinding and classification system includes a grinding circuit for reducing the size of a raw aggregate material and a classification circuit for sorting the ground aggregate material into a finer product stream for further processing and a coarser stream. Optionally, the coarser stream may be recirculated back into the grinding circuit to further reduce the particle size.

[003] The above systems may be modelled around a set of initial parameters (e.g. expected composition of raw materials, required product flowrates, required product aggregate size, etc) prior to on site installation and operation.

[004] However, such systems may be inefficient if, for example, the modelled parameters are not an accurate representation of the real working conditions of the system (e.g. the modelled composition of raw materials is not correct, or if the raw material composition changes over time), or if the required parameters change during operation of the system (e.g. during operation scale-up/down). Given the nature of grinding and classifying processes, such inefficiencies can significantly increase the amount of resources such as energy or water required for operations, or increase the wear experienced during operations, resulting in increased operating costs and environmental impact.

[005] Separately, changing parameters during actual working conditions may be problematic given the inertia in the above systems. That is, given the amount of raw material being processed, changing parameters in one area of the system can have adverse consequences in another area of the system. There is, therefore, a delicate balance in improving the system as a whole.

[006] Any reference to or discussion of any document, act or item of knowledge in this specification is included solely for the 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 specification is concerned.

SUMMARY OF THE INVENTION

[007] In a first aspect, the present disclosure provides a system for grinding and classifying an aggregate material, comprising: a grinding apparatus for grinding the aggregate material to reduce a particle size of the aggregate material; a cyclone in a feedback loop with the grinding apparatus for classifying the aggregate material into a plurality of streams including an overflow stream and an underflow stream; and a control system including one or more control sensors to collect data associated with a characteristic of: the aggregate material, new aggregate material introduced into the system, and/or one or more of the plurality of streams, wherein the control system uses the data to adjust one or more process parameters of the system.

[008] In an embodiment, the cyclone may be downstream of the grinding apparatus. In an embodiment, the cyclone may be in an indirect feedback loop with the grinding apparatus.

[009] In certain embodiments, the cyclone forms part of a cyclone cluster.

[010] In an embodiment, the underflow stream is recycled into an inlet of the grinding apparatus and the overflow stream is transported downstream for further processing.

[011] In an embodiment, the characteristic of the aggregate material is a characteristic of the aggregate material transported to the cyclone or a characteristic of the overflow stream, and is selected from: a particle size; a flowrate; a water content; a pressure; and/or a density.

[012] In further embodiments, the characteristic is a characteristic of the new aggregate material, the underflow stream, or any other stream within the system, and is selected from: a particle size; a flowrate; a water content; a pressure; and/or a density.

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

[014] In an embodiment, the grinding apparatus is a semi-autogenous grinding (SAG) mill.

[015] In certain embodiments, a feed to the grinding apparatus includes water to maintain a desired aggregate density for grinding. [016] In an embodiment, the grinding apparatus is a wet ball mill and the cyclone is a hydrocyclone.

[017] In an embodiment, the system further comprises a trommel screen on a discharge end of the grinding apparatus.

[018] In certain embodiments, the trommel screen is equipped with an array of panels with rectangular openings, for scalping oversized aggregate material and ball scats (i.e. grinding media that has worn such that they are no longer efficient) out of the feedback loop and reporting the undersized aggregate material to a storage tank.

[019] In certain embodiments, water spray is added above the trommel screen, for preventing the blockage by aggregate material and adjusting the aggregate concentration of the cyclone feed.

[020] In certain embodiments, oversized aggregate material and grinding media scats retaining on the trommel screen are removed out of the feedback loop and discharged into a scats bay.

[021] In an embodiment, the system further comprises a ball retaining plate between the discharge end of the grinding apparatus and the trommel screen.

[022] In certain embodiments, the ball retaining plate has an array of slots for allowing the aggregate material to pass through and holding the grinding media within the grinding apparatus.

[023] In an embodiment, the grinding apparatus grinds the aggregate material with a grinding media. In such embodiments, the grinding media may be any material which assists in the crushing or grinding of the aggregate material in the grinding apparatus. For example, the grinding media may be a ball, pebble or rod made of a material with a hardness higher than that of the aggregate material. The grinding media may have a predetermined size for providing optimal grinding efficiency.

[024] In an embodiment, the system further comprises an automated feeder for providing the grinding media to the grinding apparatus. [025] In an embodiment, the grinding apparatus outputs the aggregate material to a storage tank, and the aggregate material is transported from the storage tank to the cyclone.

[026] In certain embodiments, the aggregate material is pumped from the storage tank to the cyclone.

[027] In an embodiment, the new aggregate material is introduced into the storage tank and mixed with the aggregate material.

[028] In certain embodiments, the cyclone acts as a pre-classification step for sorting the new aggregate material (mixed with the aggregate material in the cyclone input) and allowing suitably small aggregates to the overflow stream without grinding. In such embodiments, overgrinding is minimised and grinding efficiency is improved.

[029] In an embodiment, the control system is adapted to: retrieve the data from the one or more control sensors; compare the data to a model to predict an outcome; and use the predicted outcome to adjust one or more process parameters of the system.

[030] In an embodiment, the control system adjusts the one or more process parameters to achieve a desired characteristic of the overflow stream.

[031] In an embodiment, the one or more process parameters include one or more dynamic process parameters.

[032] In an embodiment, the dynamic process parameters are selected from one or more of: a grinding media recharge rate from an automated feeder for providing a grinding media to the grinding apparatus; a grinding media charge ratio in the grinding apparatus; a water addition into the grinding apparatus; a power draw of the grinding apparatus; a new aggregate material flowrate to the system; a new aggregate material particle size to the system; a new aggregate material flowrate to a storage tank; a water addition into the storage tank; an aggregate material flowrate to the cyclone; a feed density of the aggregate material to the cyclone; a feed pressure of the aggregate material to the cyclone; a water spray on a trommel screen on a discharge end of the grinding apparatus; and/or a number of active cyclone(s) in a cyclone cluster including the cyclone.

[033] In an embodiment, the process parameters are adjusted whereby: the grinding media provided from the automated feeder comprises about 18-32% of the grinding apparatus by volume; the grinding media provided from the automated feeder replaces a calculated average unit consumption of grinding media and maintains a desired grinding media charge ratio; the water addition into the grinding apparatus maintains a grinding slurry concentration of about 70- 85%; the feed pressure of the aggregate material to the cyclone is maintained at about 180-250 kPa; the feed density of the aggregate material to the cyclone is maintained at about 35-50%; a classification efficiency of the cyclone is maintained at about 40-45% at 45 pm; a circulation load of the cyclone is maintained at about 200-500%; and/or the number of active cyclone(s) in the cyclone cluster is adjusted depending on the aggregate material flowrate and feed pressure.

[034] In the above embodiment, the grinding media charge ratio is the ratio of the bulk volume of grinding media to the working volume of the grinding apparatus, and the grinding slurry concentration defines a concentration of aggregates within a slurry that is being grinded by the grinding apparatus. In certain embodiments, the grinding media charging frequency is in shift of 12 hours.

[035] In certain embodiments, the process parameters are adjusted whereby the cyclone overflow P80 (80% passing) size is around 35-50pm by adjusting the cyclone feed density and feed pressure.

[036] In an embodiment, the process parameters include one or more static process parameters.

[037] In an embodiment, the static process parameters are selected from: one or more physical parameters of the cyclone; one or more physical parameters of a grinding media; and/or one or more physical parameters of the grinding apparatus.

[038] In an embodiment, the one or more physical parameters of the cyclone include a cone angle, a cyclone body diameter, a column height, an inlet diameter, a vortex finder diameter, and a spigot diameter; and/or the grinding apparatus is a ball mill: and the one or more physical parameters of the grinding media include a ball diameter, a ball material composition, and/or a ball material hardness; and/or the one or more physical parameters of the ball mill include a ball mill liner profile, a trommel screen openings shape, a trommel screen opening size, a ball retaining plate height and a ball retaining plate slot width.

[039] In an embodiment, the process parameters are adjusted whereby: the cyclone cone angle is about 13 degrees; the cyclone body diameter is about 400mm; the cyclone column height is about 460mm; the cyclone inlet diameter is about 109mm; the cyclone vortex finder diameter is about 150mm; the cyclone spigot diameter is about 100-120mm; the ball diameter is about 20-27mm; the ball material composition comprises about 0.2-22% chromium; the ball material hardness is about 63-65 HRC; the ball liner profile is a wave profile with dimensions of about 150mm/130mm bump/hump with 80mm plate thickness; the ball retaining plate is 374mm in height and 15mm in slot width; and/or the rectangular openings of trommel screen is about 22mm long and 16mm width.

[040] In an embodiment, the control sensors include one or more of: a flow meter, a weightometer, a density meter, a pressure sensor, and a particle size analyser.

[041] In an embodiment, the control sensors include one or more of: a flow meter for water addition into the grinding apparatus; a flow meter for water spray on a trommel screen on a discharge end of the grinding apparatus; a flow meter for new aggregate material into a storage tank of the system; a flow meter for water addition into the storage tank; a weightometer for ball charge into the grinding apparatus; a flow meter between the storage tank and the cyclone; a density meter between the storage tank and the cyclone; a pressure sensor in the cyclone, or in a cyclone cluster including the cyclone; a flow meter of the overflow stream; a density meter of the overflow stream; a particle size analyser of the new aggregate material; a particle size analyser of the aggregate material conveyed to the cyclone; and/or a particle size analyser of the overflow stream.

[042] In an embodiment, the aggregate material is a magnetite ore.

[043] In a second aspect, the present disclosure provides a method for grinding and classifying aggregate material in a circuit, comprising: grinding an aggregate material in a grinding apparatus to reduce a particle size of the aggregate material; classifying the aggregate material with a cyclone or cyclone cluster into a plurality of streams including an overflow stream and an underflow stream; and using a control system including one or more control sensors to collect data associated with a characteristic of the aggregate material, new aggregate material introduced into the circuit, and/or one or more of the plurality of streams and using the data to adjust one or more process parameters.

[044] In an embodiment, the cyclone or cyclone cluster is in a feedback loop with the grinding apparatus and the underflow stream is recycled into an inlet of the grinding apparatus.

[045] In an embodiment, the method further comprises a step of providing grinding media to an inlet of the grinding apparatus using an automated feeder. [046] In an embodiment, the grinding apparatus outputs the aggregate material to a storage tank, and the aggregate material is transported from the storage tank to the cyclone.

[047] In certain embodiments, the aggregate material is pumped from the storage tank to the cyclone.

[048] In an embodiment, the control system compares the data to a model to predict an outcome, and uses the predicted outcome to adjust the one or more process parameters to achieve a desired characteristic.

[049] In an embodiment, the control system automatically adjusts a dynamic process parameter to achieve the desired characteristic.

[050] In an embodiment, adjusting the dynamic process parameter includes: increasing or decreasing a flow rate of water into the grinding apparatus; increasing or decreasing a recharge rate of grinding media from an automated feeder for providing a grinding media to the grinding apparatus; increasing or decreasing a power draw of the grinding apparatus; increasing or decreasing a flow rate of new aggregate material to a storage tank, increasing or decreasing a particle size of new aggregate material to a storage tank; increasing or decreasing a flow rate of water into the storage tank; increasing or decreasing a flow rate of the aggregate material to the cyclone; increasing or decreasing density of the aggregate material to the cyclone; increasing or decreasing feed pressure of the aggregate material to the cyclone; and/or increasing or decreasing an amount of active cyclone(s) in the cyclone cluster including the cyclone.

[051] In an embodiment, the control system identifies process inefficiencies of a static process parameter for adjustment to achieve the desired characteristic.

[052] In an embodiment, adjusting the static process parameter includes: identifying cyclone part(s) with an unoptimised physical parameter(s), including the cyclone cone angle, the cyclone body diameter, the cyclone column height, the cyclone inlet diameter, the cyclone vortex finder diameter, and/or the cyclone spigot diameter, and replacing the cyclone part(s) with optimised cyclone part(s); identifying grinding media with an unoptimised physical parameter(s), including ball diameter, ball material composition, and/or ball material hardness, and replacing the balls with optimised balls; and/or wherein the grinding apparatus is a ball mill, identifying an unoptimised physical parameter(s) of the ball retaining plate height and openings, the grinding apparatus liner profile, and the trommel screen opening shape and size. [053] In an embodiment, the aggregate material is a magnetite ore.

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

BRIEF DESCRIPTION OF THE DRAWINGS

[055] Various preferred embodiments of the present disclosure will now be described, by way of examples only, with reference to the accompanying figures, in which:

Figure 1 illustrates a schematic diagram of a grinding and classification system according to an embodiment of the invention; and

Figure 2 illustrates an example of a trommel screen and ball retaining plate for use with a grinding apparatus in the form of a ball mill in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[056] Figure 1 illustrates a schematic flow diagram of a grinding and classification system according to an embodiment of the invention, including a grinding apparatus in the form of a ball mill 2, a cyclone 7, and a control system 11 . Aggregate material, grinding media (in the form of hardened grinding balls), and water are introduced to an inlet 15 of the ball mill 2, respectively from an underflow stream of cyclone 7, an automated feeder 1 (shown as a grinding media bin and automated conveying system), and a water stream 13. As shown, the cyclone 7 forms a feedback loop with the grinding apparatus; however it is noted that this is not necessary in every embodiment of the invention - the aggregate material may also be provided from an external source. In the ball mill 2, the aggregate material is ground down for certain residence time in the ball mill 2 and then passed through a trommel screen 3 to separate a finer, ground aggregate material to a storage tank 5 for further processing. The coarse aggregate material and/or ball scats (i.e. grinding media worn such that they are no longer efficient) may be returned to the ball mill 2 for further grinding by a reverse spiral in the ball mill 2 (see Figure 2) and the oversize aggregate material/scats retained on the trommel screen 3 will be rejected to a scats bay 12. As shown in Figure 2, the trommel screen 3 may be positioned adjacent to a ball retaining plate 4 for retaining the grinding balls within the ball mill 2. [057] The ball mill 2 may be operated in batches or as a continuous process, and may be any mill which utilises hardened balls to grind material into a finer state including, for example, a semi-autogenous grinding (SAG) mill or a vertical mill. In further embodiments, it would be appreciated that other grinding apparatuses may be used for a similar result.

[058] The ground aggregate material is transported to a tank 5 for storage and, when appropriate, the stored aggregate material is pumped via pump 6 to the cyclone 7 for categorisation into a fine overflow stream and a coarse underflow stream. The overflow stream is stored in a tank 8 and pumped via pump 9 downstream for further processing. The coarse underflow stream may be returned to the ball mill 2 for further grinding. Whilst only one cyclone 7 is shown in Figure 1 , in further embodiments, a cyclone cluster may be formed with multiple cyclones.

[059] The illustrated grinding and classification system further includes a control system including a control hub 11 in communication with sensors SO, S1 , S2, S3, S4, S5, S6 and S7. It will be appreciated that sensors SO, S1 , S2 ,S3, S4, S5, S6 and S7 have been represented as an example only - certain implementations of the invention may include one or more sensors in these locations, or in other locations in the grinding and classification circuit. These sensors are designed to collect data associated with certain characteristics of the aggregate material as it progresses through the grinding and classification circuit, for example, flowrate, density, pressure, water content and/or stream particle size.

[060] The purpose of the control system is to collect the data of the characteristics of the aggregate material and use this data to adjust one or more process parameters of the system for optimising certain aspects of the grinding and classification process. It would be appreciated that these characteristics of the aggregate may change over time, for example, as harder ore is extracted from a mine site. These process parameters may be dynamic process parameters, including measurable characteristics of the processes or process streams, and/or static process parameters, including physical parameters of the equipment used in the system.

[061] In particular, the control system can be used to adjust the process parameters to achieve a desired characteristic in a certain stream, to reduce the energy or water required for operations, and/or to reduce the wear on machinery. These adjustments may be made in-situ by the control system, or the control system may identify proposed adjustments for further consideration. [062] Optionally, the system may be a wet system, such that the ball mill 2 is a wet ball mill and the cyclone 7 is a hydrocyclone. In such a system, the sensor S1 may include pressure, particle size, flowrate, and/or density sensors to determine whether the hydrocyclone 7 is operating within predetermined optimal operating parameters. If it is not, the water flowrate 13 to storage tank 5, and/or the number of active hydrocyclones 7 in a cyclone cluster, and/or a new aggregate material stream 10 flowrate to the storage tank 5 may be changed to adjust the characteristics of the aggregate material stream from the storage tank 5 to the cyclone 7. While not shown, the new aggregate material stream 10 may also be introduced before or after pump 6. The measurements of sensor S1 may further be used to adjust the amount of water used in wet ball mill 2 and optimise the process per unit of water.

[063] The following examples are described in relation to a system and method for grinding and classifying an aggregate magnetite ore, and how the control system may adjust process parameters to improve the process. However, it will be appreciated that these examples may extend to different types of aggregate materials.

Example 1

[064] In a first example, the control system can seek to adjust for an aggregate magnetite particle size of the overflow stream by operating the system and collecting particle size data at sensor SO, S2 or S3 (i.e. sensor SO, S2 or S3 includes a particle size analyser). This data can be transmitted to control hub 11 which may then control one or more process parameters in order to adjust the overflow particle size at sensor S2 or S3. For example, if the overflow particle size is too coarse, the control hub 11 may increase the flowrate of the dilution water stream 13 into the storage tank 5, increase flowrate to cyclone 7, increase number of cyclones 7 operational in a cyclone cluster and/or increase the ball charge from the automated feeder 1 to the ball mill 2, such that the aggregate material is ground to a reduced particle size. Alternatively, if the overflow particle size is finer than expected, the control hub 11 may decrease the flowrate of the dilution water stream 13 into the storage tank 5, decrease flowrate to cyclone 7, decrease number of cyclones 7 operational in a cyclone cluster and/or decrease the ball charge from the automated feeder 1 through use of sensor S7 (i.e. sensor S7 includes a weightometer) to the ball mill 2, such that the aggregate material is ground less in the ball mill 2, which would reduce the energy and/or water requirements for operating the ball mill 2.

Example 2 [065] In a further example, the control system can be focused on controlling the rate of aggregate magnetite ore provided to the ball mill 2 from the underflow stream of the cyclone 7. This can be achieved by, for example, detecting the flowrate, density and/or average particle size at sensor S0/S1 and measuring or modelling the expected characteristics of the cyclone 7 underflow stream. Optionally, this modelling may be based on a comparison of historical data comparing the flowrate, density and/or average particle size at sensors SO, S1 and S2. The system may then adjust the amount of grinding media from automated feeder 1 in-situ such that the ball mill 2 operates with a predetermined optimal grinding media ratio in the mill.

Example 3

[066] The control system may further be used to optimise the physical equipment used within the grinding and classification circuits. For example, sensors SO, S1 , S2 and/or S3 can be used to collect data on the flow, density and particle size of the overflow stream to determine whether the equipment parameters of the cyclone 7 are appropriate for the current production process to produce an overflow stream with desirable characteristics. If they are not found to be appropriate, or the results are not as expected, the system may identify that a physical optimisation of the cyclone 7 should be considered at, for example, the next maintenance phase to optimise the equipment parameters for purpose. Using the available data and comparing it to technical models, the control system could then propose adjustments to, for example, the cone angle, cyclone body diameter, column height, inlet diameter, vortex finder diameter, and/or spigot diameter that could achieve the desired characteristics in the overflow stream.

[067] Similarly, the sensors SO, S1 and S2 could be used to detect the density, flowrate and particle size of the new aggregate material, the aggregate material from the storage tank 5 to the cyclone 7, and cyclone overflow stream, and this information could be used to optimise the physical equipment used in ball mill 2, including the ball scats content, the ball diameter, the ball material composition (i.e. increasing/decreasing the ball hardness), the charge ratio, ball retaining plate height and slot width, trommel screen openings and/or mill liner profile.

Further Examples

[068] Further implementations of the control system include controlling one or more of the following dynamic process parameters: a mill power draw in the ball mill 2, for example, by measuring or modelling the cyclone 7 underflow stream and adjusting the grinding media introduced from the automated feeder 1 to achieve an optimal ball charge ratio; an average charge quantity of the grinding media indicated by a weightometer S7 in the ball mill 2, for example, by the unit consumption and the charging frequency to maintain an optimal ball charge ratio; a water content in the ball mill 2, for example, by measuring or modelling the cyclone 7 underflow stream and adjusting the new aggregate stream 10, or introducing a water stream 13 directly into the ball mill 2; a cyclone circulation load in feedback loop, for example, in response to an undesirable average particle size of the aggregate material or of the overflow stream; a feed density and/or a feed pressure of the aggregate material to the cyclone 7, for example, by adjusting the water flow 13 to storage tank 5, changing the number of active cyclones 7 in a cyclone cluster and/or the aggregate material flowrate to the cyclone 7; a cyclone classification efficiency, and/or a cyclone circulation load, for example, by adjusting the operating parameters of cyclone 7 such as the feed density and/or a feed pressure of the aggregate material to the cyclone 7.

[069] Classification efficiency is generally defined as, for example, the fraction (or percentage) of the feed material of a given size which is recovered in a stream.

[070] With the above in mind, the present grinding and classification system provides a number of advantages including: i) adjusting the parameters of cyclone 7, including cone angle, cyclone body diameter, column height, feed inlet diameter, vortex finder diameter and spigot diameter, to be suitable for the magnetite ore which has been processed by the ball mill 2; ii) monitoring the flow rate, density and pressure of the aggregate material feed to the cyclone and flow rate and density of the overflow stream to optimise the classification efficiency, or sampling the cyclone inlet/overflow/underflow and new aggregate material to measure the particle size distribution and grade to evaluate the classification and grinding efficiency; iii) adjusting the balls diameter and quantity via an automated ball feed conveyor to keep the grinding efficiency at an optimal status; iv) adjusting the shape and/or the size of the openings of trommel; v) adjusting the height and slot width of the ball retaining plate; vi) adjusting the mill liner profile; vii) changing the chromium content in the composition of balls to improve the grinding efficiency, reduce the unit consumption and improve the cost effectiveness; and/or viii) adjusting in-situ the operational parameters to cover the fluctuations of the new feed material quality.

[071] In this specification, adjectives such as left and right, top and bottom, hot and cold, first and second, and the like may be used to distinguish one element or action from 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.

[072] 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.

[073] 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 from the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. The present disclosure is intended to embrace all modifications, alternatives, and variations that have been discussed herein, and other embodiments that fall within the spirit and scope of the above description.