TECHNICAL FIELD

[001] The present disclosure relates to beneficiation systems and methods, and in particular a modular system for beneficiating a ferrous ore and a method of using such a system.

BACKGROUND

[002] Iron ore is a raw material from which metallic iron can be extracted, typically in the production of steels or other ferrous-containing alloys. In Australia, the vast majority of iron ore exports are high-grade hematite, also referred to as direct shipping ore (DSO), due to the ease of separating the gangue materials and refining the metallic iron with conventional methods.

[003] In contrast, lower-grade ores such as magnetite are not as favoured due to the presence of certain impurities, requiring more sophisticated and extensive processing to produce the metallic iron. These impurities can include silica, phosphorous, sulphur and aluminium. As a result, these lower-grade ores are typically not cost effective to produce metallic iron due to increased capital and maintenance costs compared to DSO.

[004] Accordingly, the inventors have sought a system for beneficiating a ferrous ore that could increase the cost effectiveness of producing metallic iron.

[005] 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

[006] In a first aspect, the present disclosure provides a modular system for beneficiating a ferrous ore, comprising: a primary crushing module including a primary crusher for receiving and crushing the ferrous ore into a ferrous aggregate; a first grinding and classification module for receiving the ferrous aggregate, including a first grinding mill for grinding the ferrous aggregate, and first classification equipment for classifying the resultant product into at least a first fine aggregate stream; a first separation module including first separation equipment for receiving and separating the first fine aggregate stream into at least a first ferrous aggregate stream; a second grinding and classification module for receiving the first ferrous aggregate stream, including a second grinding mill, and second classification equipment for classifying the resultant product into at least a second fine aggregate stream; and a second separation module including second separation equipment for receiving and separating the second fine aggregate stream into at least a concentrated ferrous aggregate stream.

[007] In an embodiment, the at least one quality of one of the modules is selected from one or more of: a product quality of an input or an output; and/or an equipment operating variable.

[008] In an embodiment, the product quality of the input or the output is selected from: an aggregate stream iron content; an aggregate stream particle size; an aggregate stream water content; and/or an aggregate stream flowrate.

[009] In an embodiment, the equipment operating variable is selected from: a charge ratio in a grinding mill; a water content in a grinding mill; a grinding mill rotation speed; a feed density to a classifying cyclone; a feed pressure to a classifying cyclone; number of operational classifying cyclones; a separation rate of a separating equipment; energy consumption of a grinding, crushing, classifying, or separating equipment; and/or water consumption of a grinding, classifying, or separating equipment.

[010] In the above embodiment, the charge ratio of the grinding mill is the ratio of a bulk volume of grinding media to a working volume of the grinding apparatus.

[011] In an embodiment, in the first grinding and classification module, the first classification equipment classifies the resultant product into at least two streams including the first fine aggregate stream and a recycle stream for further grinding by the first grinding mill.

[012] In an embodiment, the first classification equipment includes a cyclone with an overflow stream being the first fine aggregate stream and an underflow stream being the recycle stream.

[013] In an embodiment, the cyclone is a hydrocyclone.

[014] In an embodiment, the hydrocyclone has a flat bottom. [015] In an embodiment, the first classification equipment includes a screen upstream of cyclone to separate fine aggregate particles to the cyclone and coarse aggregate particles to a secondary crushing circuit for further crushing and recycle to the first grinding mill.

[016] In an embodiment, the secondary crushing circuit includes a high-pressure grinding roll (HPGR).

[017] In an embodiment, the secondary crushing circuit includes a cone crusher.

[018] In a particular embodiment, the secondary crushing circuit includes both a high-pressure grinding roll (HPGR) and a cone crusher.

[019] In an embodiment, in the second grinding and classification module, the first ferrous aggregate stream is received by the second classification equipment and classified into the second fine aggregate stream and a coarse stream for regrinding by the second grinding mill.

[020] In an embodiment, the second classification equipment includes a cyclone with an overflow stream being the second fine aggregate stream and an underflow stream being the coarse stream for regrinding.

[021] In an embodiment, the cyclone is a hydrocyclone.

[022] In a particular embodiment, the hydrocyclone is a flat bottom hydrocyclone.

[023] In an embodiment, the hydrocyclone is a conical hydrocyclone.

[024] In an embodiment, after regrinding, the coarse stream is recycled to an inlet of the second classification equipment.

[025] In an embodiment, the first separation module and the second separation module include a magnetic drum separator and a desliming elutriation column.

[026] In an embodiment, the first separation module includes a magnetic drum separator.

[027] In an embodiment, the second separation module includes a desliming elutriation column. [028] In an embodiment, the second separation module includes a magnetic drum separator and the desliming elutriation column.

[029] In an embodiment, the desliming elutriation column is connected in series and downstream of the magnetic drum separator.

[030] In an embodiment, the second separation module includes two desliming elutriation columns.

[031] In an embodiment, the two desliming elutriation columns are connected in series.

[032] In an embodiment, the system further comprises a dewatering module for receiving and removing water from the concentrated ferrous aggregate stream to produce an iron concentrate.

[033] In an embodiment, the dewatering module includes a concentrate thickener and/or a filter press.

[034] In an embodiment, low iron tailings streams produced by the first separation module and/or the second separation module are concentrated in a tailings thickening stage and are discharged into a tailings dam.

[035] In an embodiment, the ferrous ore is a magnetite ore.

[036] In an embodiment, the magnetite ore is a low grade magnetite ore.

[037] In an embodiment, each module includes a single input.

[038] In an embodiment, each module may be individually optimised to enhance at least one quality of one of the modules. For example, in certain embodiments, a particular module may be maintained, repaired, or replaced with a different corresponding module without effecting the processing of any other module, with the intent of enhancing performance in particular module, or any other module, or both.

[039] In a second aspect, the present disclosure provides a method for beneficiating a ferrous ore, comprising: installing a modular system for beneficiating a ferrous ore in accordance with any one of the preceding claims; and using a control system to collect data associated with an aggregate stream in the modular system and using the data to enhance at least one quality of one of the modules.

[040] In a third aspect, the present disclosure provides a grinding and classification module for use in beneficiating a ferrous aggregate, comprising: a grinding mill for grinding the ferrous aggregate, and classification equipment for classifying the ferrous aggregate after grinding into a fine aggregate stream and a coarse aggregate stream, wherein the coarse aggregate stream is fed to a crushing circuit in a feedback loop with the grinding mill, for further crushing and recycle to the grinding mill, wherein the crushing circuit includes a high-pressure grinding roll (HPGR).

[041] In an embodiment, the crushing circuit further includes a screen for separating finer particles of the coarse aggregate stream to the HPGR and coarser particles of the coarse aggregate stream for further crushing elsewhere.

[042] In an embodiment, the coarser particles are crushed by a circuit cone crusher.

[043] In an embodiment, the coarser particles crushed by the circuit cone crusher are recirculated back to the screen for further separation.

[044] In an embodiment, some or all of the coarse particles from the screen are discharged into the grinding mill.

[045] In a particular embodiment, the abovementioned screen is a dry single deck screen.

[046] In an embodiment, the crushing circuit further includes a screen for separating fine particles to be returned to the first grinding mill and coarse particles for crushing by the HPGR.

[047] In an embodiment, the coarse particles crushed by the HPGR are recirculated back to the screen for further separation.

[048] In a particular embodiment, the abovementioned screen is a dry double deck screen.

[049] In a particular embodiment, the crushing circuit includes both a dry single deck screen and a dry double deck screen. [050] In an embodiment, a portion of the coarse particles crushed by the HPGR is recirculated back to the HPGR as a feed. Preferably, this recirculated portion provides sufficient fine particles such as to protect the HPGR grinding surface in use. In certain embodiments, this HPGR grinding surface may be an HPGR tyre. In an embodiment, the HPGR tyre is a hardened surface applied to the periphery of the grinding rolls of the HPGR to protect a centre portion of the grinding rolls. In further embodiments, the HPGR grinding surface may include grinding studs.

[051] In an embodiment, the crushing circuit includes a bypass cone crusher installed in parallel with the HPGR to operate as a bypass to the HPGR. This embodiment may be particularly useful for maintaining smooth operation of the grinding and classification module during HPGR shutdown/maintenance, or when the HPGR is operating at or over capacity.

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

BRIEF DESCRIPTION OF THE DRAWINGS

[053] 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 system for beneficiating a ferrous ore according to a first embodiment of the invention;

Figure 2 illustrates a schematic diagram of a system for beneficiating a ferrous ore according to a second embodiment of the invention;

Figure 3 illustrates a schematic diagram of a system for beneficiating a ferrous ore according to a third embodiment of the invention;

Figure 4 illustrates a primary crushing module of the first, second and third embodiments of the invention;

Figure 5 illustrates a first grinding and classification module and a first separation module of the first embodiment of the invention; Figure 6 illustrates a first grinding and classification module and a first separation module of the second and third embodiments of the invention;

Figure 7 illustrates a first grinding and classification module and a first separation module of the third embodiment of the invention;

Figure 8 illustrates a second grinding and classification module of the first, second and third embodiments of the invention;

Figure 9 illustrates a second separation module of the first embodiment of the invention;

Figure 10 illustrates a second separation module of the second and third embodiments of the invention;

Figure 11 illustrates a dewatering module of the first, second and third embodiments of the invention;

Figure 12 illustrates a tailings treatment system of the first, second and third embodiments of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[054] Figures 1 , 2 and 3 illustrate schematic flow diagrams of modular systems according to three embodiments of the invention. These systems are comprised of: a primary crushing module, a first grinding and classification module, a first separation module, a second grinding and classification module, a second separation module, a dewatering module, and a tailings treatment system, and the systems will be described with reference to their individual modules.

[055] It will be appreciated that, while the three illustrated embodiments in Figures 1 , 2 and 3 utilise similar equipment in some modules, it is not necessary for every embodiment in accordance with the invention to use such equipment.

[056] That is, in each module, the equipment should be selected for its appropriateness to perform the task of the module. Each module includes a single input and may be individually optimised such as to enhance a quality of one or more of the modules. This quality may be a product quality of an output of the module, or an input of a sequential module, or an equipment operating variable used in one or more of the modules. Examples of such qualities may include: an aggregate stream iron content, an aggregate stream particle size, an aggregate stream water content, and/or an aggregate stream flowrate, a charge ratio in a grinding mill, a water content in a grinding mill, a grinding mill rotation speed, a feed density to a classifying cyclone, a feed pressure to a classifying cyclone, a number of operational classifying cyclones, a separation rate of a separating equipment, energy consumption of a grinding, crushing, classifying, or separating equipment, or water consumption of a grinding, classifying, or separating equipment.

Module 1 - Primary crushing

[057] As illustrated in Figure 4, the primary crushing module includes a ferrous ore input into the system, shown in the form of rear tipping dump trucks depositing the ferrous ore into a vessel in the form of a hopper 10 for storage. When the system is ready for operation, the ferrous ore may be transported from the hopper 10 to a primary crusher, shown in the form of a gyratory crusher 11 , for crushing the ferrous ore into a ferrous aggregate. The ferrous aggregate is then conveyed to a first grinding and classification module in stream S1 .

Module 2 - First grinding and classification

[058] Three variations of the first grinding and classification module are shown in Figures 5-7, in which the ferrous aggregate is received in stream S1 and fed to a first grinding mill, shown in the form of an autogenous mill 20, for grinding to reduce the ferrous aggregate size. The resultant material is classified by the first classification equipment, including a screen 21 which separates the fine aggregate material, which is provided to hydrocyclone 23, and the coarse aggregate material, for secondary crushing and recycle. The overflow from the hydrocyclone 23 is provided to the first separation module, while the underflow is recycled to the inlet of the autogenous mill 20. Optionally, hydrocyclone 23 may have a flat bottom which, in pilot systems, the inventors have found are able to effect a reduction of recirculation load to the autogenous mill 20 from 300-350% to 100-150%, allowing the autogenous mill 20 to operate more efficiently and steadily.

[059] In the first embodiment, illustrated in Figure 5, the secondary crushing circuit includes a cone crusher 22a.

[060] In the second embodiment, illustrated in Figure 6, the secondary crushing circuit may alternatively use a further screen 22b and high-pressure grinding roll (HPGR) 22c to achieve the secondary crushing. The HPGR 22c is therefore in a feedback loop with the autogenous mill 20. That is, for example, part of the output from the autogenous mill 20 makes its way to the HPGR 22c. The circuit may optionally also include a further crushing device, such as bypass cone crusher 22d, for maintaining smooth operation of the grinding and classification module during HPGR 22c shutdown/maintenance, or when the HPGR 22c is operating at or over capacity.

[061] In the third embodiment, shown in the Figure 7, the secondary crushing circuit may alternatively use a further dry single deck screen 22f, circuit cone crusher 22e, dry double deck screen 22b and high-pressure grinding roll (HPGR) 22c to achieve the secondary crushing. The further dry single deck screen 22f is applied to control an upper limit aggregate size fed to the HPGR 22c with the oversize fed the circuit cone crusher 22e. The dry double deck screen 22b is employed to control an upper limit aggregate size returning to the autogenous mill 20 with oversize recycling back to HPGR 22c. Oversize of the dry single deck screen 22f may alternatively bypass the circuit cone crusher 22e and return back the autogenous mill 20 directly without crushing. The secondary crushing circuit is therefore in a feedback loop with the autogenous mill 20. That is, for example, part of the output from the autogenous mill 20 makes its way to the secondary crushing circuit. The circuit may optionally also include a crushing device, such as bypass cone crusher 22d, for maintaining smooth operation of the grinding and classification module during HPGR 22c shutdown/maintenance, or when the HPGR 22c is operating at or over capacity.

[062] The inventors are not aware of previous use of an HPGR for pebble crushing in iron ore beneficiation systems similar to those described in the second and third embodiments. With particular reference to the third embodiment, the use of the HPGR 22c in feedback loop with a dry double deck screen 22b has significant advantages in a reduction of energy required for the first grinding and classification module (despite adding further devices to the system), a substantial improvement of the autogenous mill 20 and a reduced wear rate of the crushing surface when compared to traditional methods, such as cone crushing. The use of the further dry single deck screen 22f may filter out coarser particles which may be inefficient for crushing in the HPGR 22c, or may damage the grinding roll tyre surface of the HPGR 22c, and may also scalp oversize tramp metals out of the HPGR system, mitigating the damage of the grinding roll tyre surface by the tramp metals. The coarser particles of dry single deck screen 22f are reported to the circuit cone crusher 22e which is in feedback loop with the dry single deck screen 22f. The coarse particles of the dry single deck screen 22f are alternatively directly returned to the autogenous mill 20 by bypassing the circuit cone crusher 22e, which will be used as grinding media if the ferrous aggregate particle size in stream S1 is small and the autogenous mill power draw is low. The use of the dry double deck screen 22b, in feedback loop with the HPGR 22c, separates the coarser particles which return to the HPGR 22c, and the finer particles which return to the autogenous mill 20. This will allow to control the particle size of the pebbles returning to the autogenous mill 20, ultimately taking the advantages of HPGR in energy saving and throughput improvement of the autogenous mill 20. The HPGR product can be partially recycled to the HPGR feed to maintain enough fines in the feed for HPGR tyre protection, extending the HPGR tyre service life and improving the availability of HPGR. Similar advantages are also applicable for the secondary crushing circuit in the second embodiment.

Module 3 - First separation

[063] In all illustrated embodiments, the first separation module includes a first separation equipment in the form of a magnetic drum separator 24 to separate the hydrocyclone 23 overflow into a first fine aggregate stream S2, including the magnetic ferrous particles, and a tailings stream T1 .

Module 4 - Second grinding and classification

[064] As illustrated in Figure 8, the second grinding and classification module receives the first fine aggregate stream S2 as an inlet to a classification equipment, shown in the form of a hydrocyclone 30. The overflow from the hydrocyclone 30 is transported to the next module as a second fine aggregate stream S3, while the underflow is recycled to the inlet of a grinding mill, shown in the form of a ball mill 31 . After grinding, this recycle stream is provided back to the hydrocyclone 30 inlet for further classification.

[065] Optionally, hydrocyclone 30 may be individually optimised within the module to reduce the recirculation load. For example, in pilot tests, the hydrocyclone 30 cone angle was optimised from 10 degrees to 13 degrees, which reduced the recirculation load from 600-800% to 200- 500%, significantly improving the ball mill capacity and reducing the energy and water requirements for running the ball mill 31 .

Module 5 - Second separation

[066] The second separation module, illustrated in Figures 9 and 10 for the three embodiments, aims to receive and separate the second fine aggregate stream into a concentrated ferrous aggregate stream S4 and further waste tailings streams T2, T3. [067] In the first embodiment, shown in Figure 9, the module includes a magnetic drum separator 40a, to separate out any non-magnetic particles, and a desliming elutriation column 41 to concentrate the concentrated ferrous aggregate stream S4.

[068] In the second and third embodiments, shown in Figure 10, the module includes two desliming elutriation columns 40b, 41 connected in series to concentrate the concentrated ferrous aggregate stream S4.

[069] The use of a desliming elutriation column was found to be beneficial over using only traditional drum magnetic separators in improving separation efficiency, leading to less grinding required for a similar grade aggregate product or higher concentrate grade at a similar grind size. In particular, the desliming elutriation column is very effective in diverting high silica slime, non-magnetic material and poorly locked ferrous particles to the tailings steams T2, T3. This is particularly advantageous for refining magnetite ore due to the difficulties in separating silica from ferrous particles in the ore. This results in a higher quality concentrated ferrous aggregate stream S4, which requires a reduced number of steps to further purify to a metallic iron product. The use of two desliming elutriation column in series in the second and third embodiments further enhances the beneficial effect of the desliming elutriation with the first desliming elutriation column focusing on removal of high silica slime and non-magnetic material and the second on rejection of poorly locked ferrous particles.

Module 6 - Dewatering

[070] The dewatering module aims to receive the concentrated ferrous aggregate stream S4 and remove moisture from it to produce an iron concentrate S5, as shown in Figure 11 . In the first, second and third embodiments, this is achieved through the use of a concentrate thickener 50 and a filter press 52. Optionally, a filtrate thickener 51 may be utilised in series with the concentrate thickener 50 to further dewater the stream prior to pressing in filter press 52 when the density of the ferrous aggregate stream to the filter press 52 is suitably low.

Tailings treatment

[071] As shown in Figure 12, the modular system may also include a tailings thickening stage to further dewater the tailings streams T1 , T2, T3 such that they may be suitable disposed of. In the illustrated embodiments, this is achieved through tailings thickeners 60, 61 such that the tailings may be disposed of in the tailings dam 62. Example systems

[072] Example systems of the first and third embodiments of the invention were modelled and tested in accordance with an aggregate magnetite ore input having a particle size between about 0-1 .2m:

Table 1 : Comparison of First and Third Embodiments

[073] Each embodiment was optimised toward a target grade of 65% Fe in the aggregate stream after the second separation module, and less than 10% w/w moisture after the filter press in the dewatering module.

[074] While the third embodiment has additional installed power for each individual unit of equipment, the inventors found that the use of the HPGR was significantly more energy efficient than the cone crusher in the first embodiment and the aggregate size recycling to the first grinding mill after the secondary crushing was much coarser for the first embodiment. Moreover, the first embodiment had a higher recirculation rate for secondary crushing, further increasing its energy requirements and reducing the rate of aggregate throughput of the module compared to the third embodiment.

[075] Furthermore, it was found in both embodiments that the use of one or two desliming elutriation columns was effective in separating high silica slime, non-magnetic material, and poorly locked magnetite particles to concentrating the iron grade in the product and increasing the rate of concentrated aggregate throughput of the module.

System advantages

[076] The first, second and third embodiments of the modular system of the invention, as shown in Figures 1 , 2 and 3 and detailed in Table 1 , have demonstrated significant advantages in comparison to a conventional process for beneficiating a magnetite ore.

[077] In particular, the inventors have found the use of an HPGR in the first grinding and classification module to be significantly beneficial in reducing the unit energy consumption in the first grinding and classification module, and increasing the aggregate throughput in the first grinding mill. Furthermore, the use of desliming elutriation column(s) in the separation modules beneficial in separating unwanted impurities and increasing the iron content of the concentrated ferrous aggregate stream, as well as reducing the overall energy consumption. The modular system is also beneficial in that each module may be isolated and individually optimised, which would additionally increase efficiency in each subsequent module. Furthermore, the modular system with two stages of grinding and classification and separation is a shorter process in comparison with other ferrous ore beneficiating systems, with less equipment maintenance and sufficient operation flexibility to accommodate ferrous ore feed property variation and to achieve target iron concentrate quality.

[078] Throughout the description, certain processing equipment have been referenced as singular quantities of said equipment. However, it will be appreciated that the present disclosure of these described systems and modules may extend to systems and modules utilising a plurality of said equipment, which may be implemented in series or in parallel.

[079] 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.

[080] 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.

[081] 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.