AUSTRALIA ORIGINAL COMPLETE SPECIFICATION INNOVATION PATENT Invention Title: Mineral Processing Method Name of Applicant: Iluka Resources Ltd Actual Inventor: Hackney, David Clifton Address for service: WRAYS Ground Floor, 56 Ord Street West Perth WA 6005 Attorney code: WR The following statement is a full description of this invention, including the best method of performing it known to me:- - 2 Mineral processing method Field of the Invention The present invention relates to a mineral processing method for use in relation to dry mining. 5 Background Art The beneficiation of minerals and in particular, heavy minerals from sand deposits has historically involved dry mining (for example, by mechanical excavation) and the upgrading of these mineral sands using screening and gravity concentration techniques. The way in which these processes have been utilised within the 10 mineral sands industry has fundamentally remained unchanged from its inception. Historically, mineral sand operations upgraded the run-of-mine ore at the wet concentrator prior to the transport of a heavy mineral concentrate to a mineral separation plant for further upgrading. Mineral sand deposits are becoming far more challenging from a capital 15 investment, mining and beneficiation perspective due to deposits becoming smaller, deeper, on occasions lower in grade, higher in unwanted materials and more remote. Dry mining mineral sands operations are known to include the use of a mining unit plant and primary processing plant, commonly referred to as a wet concentrator 20 plant. The objective of the mining unit plant is to prepare the mined ore for treatment in the wet concentrator plant. The main method of separation within the mining unit plant is typically by size difference through a scrubbing and screening circuit. A mining unit plant design range can typically vary from 250 tph to 1400 tph. The plant generally consists of a dump hopper, a rotating scrubber/screen, a 25 secondary screen, a water circuit and the associated sump and pumping systems, although depending on the nature of the mined material, not all of these systems may be present. The systems help to liberate the sand, heavy mineral and clay from the ore. While the oversize material (+2.5 mm) is returned to the mine void, -3 the slurry of sand, heavy mineral and clay is transported to the wet concentrator plant for upgrading. The wet concentrator plant serves to recover and concentrate the heavy mineral. The process relies on the varying density differences and magnetic susceptibilities 5 that exist between the valuable and waste materials. The wet concentrator plant is primarily a gravity concentration (and magnetic at some operations) beneficiation plant. The fine materials (also known as slimes or clays) contained within the mining unit plant slurry are removed in the wet concentrator plant using cyclones (and a desliming overflow surge bin on some operations). The fine 10 materials are densified using thickeners and returned with the wet concentrator plant barren tailings to the mining void or a tailings storage facility. The coarse material (sand) and heavy minerals are processed through a series of gravity concentrating spiral stages to separate the contained heavy mineral from the unwanted tailings (primary, scavenger, middling, cleaner and recleaner spiral 15 stages). On some operational sites, the resultant concentrates are subjected to magnetic fractionation using wet high-intensity magnetic separators (WHIMS). The WHIMS magnetics (predominantly ilmenite) are disposed of to tailings, sold or sent for further processing. The WHIMS non-magnetics are further upgraded using up-current classification and spirals. The final high-grade heavy mineral 20 concentrate is rich in rutile and zircon. It is then dewatered using dewatering cyclones with the resultant product being stockpiled awaiting transport by truck to a mineral separation plant. Different operations use different modes of transport (conveyors, haulage vehicles, pumps) but in essence the operational philosophy is the same. The 25 processes have large amounts of unwanted clays and sand (and oversize in some operations) being transported to the wet concentrator plant. In turn, once the unwanted sands and clays have been rejected by the processing stages at the wet concentrator plant they have to be returned to the mining voids at great expense. 30 The mining unit is mobile and acts along and moves with the mine face. As the mine face progresses, the distance between the mining unit and the wet -4 concentrator plant increases, thereby increasing the infrastructure and power required to transfer the mined slurry from the mining unit to the wet concentrator plant and to transfer the waste from the wet concentrator plant back to the mining unit. These increases have serious impacts on the viability of mineral deposits. 5 With mineral sand deposits becoming smaller and more remote, haulage distances (pumping/conveying/trucking) between mining operations and wet concentrators has significantly increased. Increased amounts of sand, water and tailings must be transported between mining operations and the concentration plants contributing to infrastructure capital and operational costs. 10 Whilst it is known to make wet concentrator plants modular to facilitate moves in line with movement of the mining unit, wet concentrator plants must be dismantled into their individual modules (thickeners, process water dams, piping, associated foundations, surge bins, desliming cyclones stacks etc) in order to be moved which consequently is an extremely time consuming and costly exercise. Further, 15 the utilisation of the operation is significantly hindered due to the operational time lost during these moves. Wet concentrators are normally designed for a particular feed grade (e.g. 10 % heavy minerals) and as the feed grade of a deposit diminishes, a concentrator becomes underutilised, thereby decreasing the efficiency of the mining process. 20 Whilst it would be desirable to feed a wet concentrator with material of a constant grade, this is not always possible. An issue facing the mining industry generally is the lack of electrical power near mineral deposits. With conventional processing systems, where sand and slimes are pumped to and from wet concentrators, the power demand can be great. The 25 high power demand means existing power grids may not be able to meet demand. The costs associated with power grid upgrades in order to meet demand can run into tens of millions of dollars. Further, the capital and infrastructure costs of a mining operation affect the overall profitability of the operation.
-5 The preceding discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia, 5 as at the priority date of the application. Throughout the specification and claims, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. 10 Disclosure of the Invention Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications. The invention also includes all of the steps, features, compositions 15 and compounds referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features. The present invention is not to be limited in scope by the specific embodiments described herein, which are intended for the purpose of exemplification only. 20 Functionally equivalent products, compositions and methods are clearly within the scope of the invention as described herein. The entire disclosures of all publications (including patents, patent applications, journal articles, laboratory manuals, books, or other documents) cited herein are hereby incorporated by reference. 25 In accordance with the present invention, there is provided a mineral processing method, the method comprising the steps of: - 6/1 dry mining an ore body with a mining unit and removing oversized material to provide a mineral stream; treating a mineral stream to increase the concentration of minerals in said stream and provide an upgraded mineral stream, wherein the mineral 5 stream is treated in a mobile treatment plant comprising at least one stage of gravity separation; and transferring the upgrading mineral stream to a primary processing plant wherein the mineral stream comprises zircon and the step of: treating a mineral stream to increase the concentration of minerals in said 10 stream and provide an upgraded mineral stream comprises increasing the concentration of zircon in the mineral stream. The mining unit moves with the moving face of the mine and advantageously, the mobile treatment moves in response to the movement of the mining unit. Said mobility of the mobile treatment plant minimises the distance between the mining 15 unit and the mobile treatment plant, unlike prior art methods where the distance between the mining and the primary process plant increases with movement of the mine face. Advantageously, the mobile treatment plant decreases the volume of material transported between the mining unit and the primary processing plant and 20 between the primary processing plant and the mine void. Reductions in material volumes translate to the use of smaller pipelines and pumps, or conveyor or haulage systems and lower electrical and fuel demand. The mobile treatment plant may be provided with skids, wheels or tracks to confer mobility. Alternatively, the mobile treatment plant may be lifted and 25 transferred to a vehicle to confer mobility.
- 6/2 In accordance with the present invention, there is provided a mineral processing method, the method comprising the steps of: dry mining an ore body with a mining unit and removing oversized material to provide a mineral stream; - 7/1 treating a mineral stream to increase the concentration of minerals in said stream and provide an upgraded mineral stream, wherein the mineral stream is treated in a treatment plant on skids, wheels or tracks, comprising at least one stage of gravity separation; and 5 transferring the upgrading mineral stream to a primary processing plant wherein the mineral stream comprises zircon and the step of: treating a mineral stream to increase the concentration of minerals in said stream and provide an upgraded mineral stream comprises increasing the concentration of zircon in the mineral stream. 10 It is advantageous to provide a mobile treatment plant with as small a footprint as possible. It will be appreciated that this may be assisted by the utilisation of spirals with high turns and small footprints, for example, a quad start 12 turn spiral. It will be appreciated that the greater the number of starts on a spiral, the smaller the footprint of the spiral is likely to be. 15 Preferably, the step of: treating the mineral stream to increase the concentration of minerals in said stream and provide an upgrade mineral stream, comprises the step of: reducing the mass of the mineral stream by 30 %. 20 More preferably, the step of: treating the mineral stream to increase the concentration of minerals in said stream and provide an upgrade mineral stream, - 7/2 comprises the step of: reducing the mass of the mineral stream by 50 %. Preferably, the mineral stream comprises minerals and waste material wherein the waste material comprises coarse material and fine material. Preferably, the 5 coarse material has diameter greater than 53 pm and the fine material has -8 diameter less than 53 pm. More preferably, the coarse material has diameter between 53 pm and 2.5 mm. The mineral stream may further comprise water. Preferably, the step of: treating a mineral stream to increase the concentration of minerals in said 5 stream and provide an upgraded mineral stream, comprises the step of: removing at least a portion of the fine material from the mineral stream. Preferably, the step of: removing at least a portion of the fine material from the mineral stream, 10 comprises the step of: removing fine material from the mineral stream such that the fine material remaining in the treated mineral stream remains below a critical level. It will be appreciated that the determination of the critical level will be influenced by many factors and will be related to the maximum amount of fine material that 15 can be carried in process waters without compromising separation efficiencies. Preferably, the step of: removing at least a portion of the fine material from the mineral stream, comprises the step of: removing at least 90 % of the fine material from the mineral stream. 20 More preferably, the step of: -9 removing at least a portion of the fine material from the mineral stream, comprises the step of: removing at least 95 % of the fine material from the mineral stream. Preferably, the step of: 5 treating a mineral stream to increase the concentration of minerals in said stream and provide an upgraded mineral stream, comprises the step of: removing at least a portion of the coarse material from the mineral stream. In one form of the invention, the step of: 10 removing at least a portion of the coarse material from the mineral stream, comprises the step of: removing between 20 and 85 % of the coarse material from the mineral stream. In a second form of the invention, the step of: 15 treating a mineral stream to increase the concentration of minerals in said stream and provide an upgraded mineral stream, comprises the step of: removing at least 50 % of the waste material from the mineral stream. In a third form of the invention, the step of: -10 treating a mineral stream to increase the concentration of minerals in said stream and provide an upgraded mineral stream, comprises the step of: removing at least 70 % of the waste material from the mineral stream. 5 The primary processing plant may comprise cyclones, thickeners, multi stages of spirals, screens and/or magnetic separators. The upgraded mineral stream may be transferred to the primary processing plant by any means known in the art including trucks, conveyors or pipes. It will be appreciated that the treated mineral stream may not be transferred 10 directly to the primary processing plant and may be stockpiled prior to treatment at the primary processing plant. The stockpile may be drawn down on by the primary processing plant as required. Primary processing plants are normally designed for a particular feed grade, for example, 10% heavy minerals. A 1000 tph primary processing plant, designed for 15 this feed grade, would have an output of about 100 tph. As the feed grade of a deposit diminishes, the primary processing plant becomes underutilised. The inclusion of a mobile treatment plant operating at 2000 tph treating, for example, a 5 % heavy mineral feed could produce 1000 tph at 10 % grade at a yield of 50 %. Advantageously, the cost of building a 2000 tph mobile treatment plant to produce 20 1000 tph of feed at the designed feed grade is significantly cheaper than the building of a 2000 tph primary processing plant. The mobile treatment plant comprises gravity separators such as cyclones, thickeners, spirals and/or screens. In preferred forms of the invention, the mobile treatment plant comprises high capacity spirals and/or up-current classifiers. 25 The mobile treatment plant may further comprise thickeners, fed bins and water tanks.
- 11 In one form of the invention, the step of: treating a mineral stream to increase the concentration of minerals in said stream and provide an upgraded mineral stream, wherein the mineral stream is treated in a mobile treatment plant, 5 is repeated in a subsequent mobile treatment plant. It is believed that the use of subsequent mobile treatment plant would be particularly advantageous in the processing of low grade ores. In one form of the invention, the mineral stream comprises heavy minerals. Heavy minerals are known to include, rutile, ilmenite leucoxene, other altered 10 titanous minerals, zircon, garnet, magnetite, monazite and staurolite. Preferably, the step of: treating a mineral stream to increase the concentration of minerals in said stream and provide an upgraded mineral stream, comprises recovery of greater than 90 % of the minerals present in the mineral stream. 15 More preferably, the step of: treating a mineral stream to increase the concentration of minerals in said stream and provide an upgraded mineral stream, comprises recovery of greater than 94 % of the minerals present in the mineral stream. More preferably, the step of: 20 treating a mineral stream to increase the concentration of minerals in said stream and provide an upgraded mineral stream, comprises recovery of greater than 97 % of the minerals present in the mineral stream. The present invention ensures full utilisation of assets by increasing the effective front end capacity of the primary processing plant, whilst maintaining output. The - 12 present invention may further lead to the use of smaller primary processing plant per unit volume than mineral processing methods of the prior art. Brief Description of the Drawings The present invention will now be described, by way of example only, with 5 reference to one embodiment thereof, and the accompanying drawing, in which: Figure 1 is a schematic flow sheet showing how a method in accordance with the present invention may be utilised in the processing of heavy minerals. Best Mode(s) for Carrying Out the Invention By way of example, the method of the present invention is described in the 10 context of the treatment of heavy mineral deposits, although such should not be seen as limiting the generality of the foregoing description. The present invention may be applied to any mining operation which transports unwanted materials to and from a mining stage and a first primary processing stage. The typical mining unit plant is a mobile feed preparation scrubbing and screening 15 circuit and primarily consists of: a front end loader dump hopper and feed system including a scalping screen; transfer conveyors; a scrubber and 40 mm rotating screen; 25 mm and 2.5 mm double deck vibrating screen; an oversize conveyor; a high pressure water circuit; and a pumping transfer circuit. It should be appreciated that the above configuration may vary at different mining sites. 20 In a typical mining unit plant, trucks deliver and deposit the run of mine feed material onto stockpiles located in close proximity to the mining unit plant feed hopper. These blended materials are reclaimed by front-end loader/s and fed into the feed hopper, which is mounted over a variable speed belt feeder. The belt feeder introduces the feed to a conveyor and transfers the material to a 300 mm 25 shaking scalping screen. The scalping screen oversize material is discharged into a ground bunker from - 13 where it is loaded by front end loader and trucked to the pit. The scalping screen undersize product gravitates to a second conveyor, which transfers the material to a high-pressure water spray slurry box, which directs the material into a scrubber which is fitted with a 40 mm screen. The oversize from the screen reports to the 5 oversize conveyor while the undersize gravitates to a sump from where it is pumped to a double deck screen fitted with 25 mm and 2.5 mm panels. The undersize from the 2.5 mm screen panel deck reports to the wet concentrator plant feed sump/pump while the oversize material (+2.5 mm and +25 mm) is conveyed to the oversize stockpile. The scrubber-trommel oversize material is 10 transported to the oversize stockpile via the final oversize conveyor for removal by front end loader and truck back to the pit. The wet concentrator plant is primarily a gravity (and in some cases magnetic) beneficiation plant which consists of: de-sliming cyclones; thickener/s; surge bin; fines/clay disposal pumping; spiral and up-current-classifier circuits; linear screen 15 (only on plant with WHIMS); low intensity magnetic separator (only on plant with WHIMS); wet high intensity magnetic separator (WHIMS); heavy mineral concentrate stockpiles; sand tailings disposal/pumping; and water management system. The wet concentrator plant receives feed from the mining unit plant and produces 20 a mineral concentrate, a sands tailings and densified fines. The sand tailings and fines are disposed of separately or combined after being returned to the mine. The -2.5mm slurry (including heavy minerals, sand and fines) generated by the mining unit plant is pumped to a cluster of desliming cyclones. The cyclone underflow reports to the primary spiral constant density surge bin which 25 incorporates fluidisation water at the base of the sump. The bin is designed to facilitate the overflow of water which reports to the thickener. The cyclone overflow (nominally -53 pm) is mixed with flocculant and reports to the thickeners. A portion of the thickener overflow is utilised as dilution water for the desliming cyclone sump/pump, while excess thickener overflow reports to the process water 30 dam. Thickener underflow is combined with the de-watered wet concentrator plant sands tailings and pumped to the tailings disposal system which yields a - 14 densified co-disposed product and recovered water stream, which is returned to the thickener/s. The primary spiral feed is pumped with the addition of dilution water at a nominal solids feed rate of 400 tph (varying from plant to plant from 200 tph to 1400 tph) 5 and pulp density of 35 % solids (varying from plant to plant from 30 % - 45 %) to the primary spiral separators consisting of 8 banks of 8 triple start MG 6.3 spirals (-2.1 tph/start). Four products are generated by the primary spirals: concentrate 1 (super concentrate) reports to the recleaner spiral feed pump, concentrate 2 reports to the cleaner spiral feed pump, the middling to the middling 10 spiral feed pump and the tailing to the scavenger spiral feed pump. The scavenger spiral feed pump delivers the feed material to the 6 banks of 12 triple start MG6.3 spirals. The scavenger spirals produce three products: concentrate reports to the middling spirals feed pump, the middling returns to the scavenger spirals via the scavenger feed pump and the tailing to the final tailings 15 pump. The middlings spiral feed pump delivers the feed material to the 3 banks of 12 triple start MG6.3 spirals at a nominal 30% solids. The middlings spirals produce three products: concentrate reports to the cleaner spirals feed pump, the middling returns to the middlings spirals via the middling feed pump and the tailing to the 20 scavenger spiral feed pump. The feed to the 3 banks of 12 triple start MG 6.3 cleaner spirals is delivered from its feed sump/pump at -30 % solids, the middlings being re-circulated back to the cleaner spirals feed sump/pump, concentrate reports to the re-cleaner spiral separators sump/pump. The tailing reports to the middling spiral feed 25 sump/pump. The feed to the 4 banks of 12 twin start HG10 re-cleaner spiral separators are delivered from the feed sump/pump at -35 % solids, the middlings being re circulated back to the re-cleaner spirals sump/pump. The tailings from the re cleaner spiral separators gravitate to the cleaner spiral separators feed -15 sump/pump while the concentrate is pumped to the linear screen (nominally 850 micron aperture). Oversize reports to a tailings sump while the undersize material (-850 pm) gravitates to a Low Intensity Magnetic Separator (LIMS) to remove highly susceptible magnetic material prior to magnetic separation with Wet High 5 Intensity Magnetic Separators (WHIMS). The LIMS magnetic fraction reports to tailings. The LIMS non-magnetic fraction is pumped to the primary WHIMS stage consisting of three wide-rotor WHIMS. The primary WHIMS magnetic fraction is pumped to the secondary WHIMS via a densifing sump/pump. The secondary 10 WHIMS magnetic fraction is pumped to tailings while the non magnetics from the primary and secondary WHIMS is classified to remove fine silica using an up stream classifier. The up-stream classifier overflow is pumped to 2 Banks of 6 double start MG6.3 spirals via a sump/pump and de-watering cyclone. The concentrate from these spirals joins with the classifier underflow, the middlings 15 returns to the overflow scavenger spiral feed pump and the tailing gravitate to a tailings sump/pump. The combined scavenger spiral tailings, overflow scavenger spiral tailings, linear screen oversize and LIMS magnetics are pumped to tails dewatering cyclones. This thickened cyclone underflow is combined with the thickened fines from the 20 thickener underflow and pumped to the tails disposal system. The dewatering cyclone overflow gravitates to the thickener feed wells. The high-grade up-stream classified underflow fraction is combined with the overflow scavenger spiral concentrate and pumped to dewatering cyclone. The cyclone underflow reports to dewatering cyclones. The resultant dewatered 25 product reports to a heavy mineral concentrate stockpile awaiting transport to a mineral separation plant. Heavy mineral concentrates (rutile, zircon, ilmenite etc) are further processed into their respective products, using dry processing technologies (primarily magnetic and electrostatic technologies). The mineral separation plant is normally centrally located (for example, in the nearest major 30 town or port) and can receive concentrates from more than one mining operation.
- 16 The excess thickener overflow returns to the process water dam. A process water pump draws water from the dam and supplies water to the mining unit and wet concentrator for pump makeup and dilution water. The process water pump also supplies water to the process water tank. Four pumps are connected to the water 5 tank as follows; WHIMS wash water pump, up-stream classifier water pump, LIMS wash water pump and gland water pumps. Current process flows have all coarse (+53um-2.5mm) and fine (-53um) material being pumped to the wet concentrator plant. The distance between the mining unit and the wet concentrator plant can be up to 6 km. A series of pumping 10 stations is needed to transport these slurries to and from the mine. With this process all waters are cleaned and managed at the wet concentrator plant which means all process water is pumped from the wet concentrator plant to the mining unit plant. These volumes can run in the thousands of cubic meters an hour. With the present invention, the fine material and a portion of the coarse material is 15 rejected on the mobile treatment plant which is located close to the mining operation. This results in a portion of the sand not having to be transported via the multiple pumping stations and wet concentrator plant process systems and then returned to the mine. In accordance with the present invention, and best seen in Figure 1, the mobile 20 treatment plant receives feed from the mining unit plant 12 and produces an upgraded sand fraction 14, a sand tailing 16 and densified fines 18. The sand tailings 16 and fines 18 are disposed of separately or combined and returned to the mine. The desliming cyclone underflow 24 reports to a spiral fed constant density bin 26. 25 The bin 26 is designed to facilitate the overflow of water (for high fines deposits) which reports to the mobile thickeners. The -2.5 mm slurry 20 (including heavy minerals, sand and fines) generated by the mining unit plant 12 is pumped to a de-sliming section 22 comprising at least one stack of desliming cyclones for removal of clay/slimes.
- 17 The constant density bin pumps feeds onto 20 Roche high capacity spirals 28 (HC1RS quad start spirals or Multotec HC extended spirals) with the addition of dilution water at a nominal solids feed rate of 400 tph at a pulp density of about 40 % solids (range 30 % - 55 % solids). The feed rate onto these units can be varied 5 between 3 tph and 8 tph/start depending on the separation characteristics of the ore in question. The mobile treatment plant size may be varied, for example from 240 tph to 640 tph with appropriate pumping changes. It should be noted that whilst the present embodiment describes a mobile treatment plant with a capacity of 400 tph, the mobile treatment plant could have a capacity of 2000 tph or higher. 10 The inclusion of a bank of middling or scavenger spirals to treat a middlings or tails stream off the first spirals may be provided should higher recoveries be required. The upgraded mineral stream 14 is either pumped to the primary processing plant 32 or stockpiled 34 (via dewatering cyclones or a Kisa type bucket wheel) and then trucked to the wet concentrator plant. The treatment step 15 in the mobile treatment plant maximises recovery whilst achieving a mass reduction of around 50 %. The desliming cyclone overflow 36 (nominally -53 pm) is mixed with flocculant and fed to a thickener 38 whereafter the thickened slimes 18 are mixed with the dewater rejected sand product 16 off the high capacity spirals, ready for 20 deposition in the mining void 40. A portion of the thickener overflow may be utilised as dilution water for the desliming cyclone sump/pump, while excess thickener overflow reports to the process water tank. Water recovered from the tailings disposal system is returned to the thickener/s. The mobile treatment plant is located close to the mining unit and close to the 25 tailings deposition site (preferably within 1200m). Depending on the speed at which the mining unit progresses, it is expected that the mobile treatment plant would be moved every two months to a new location approximately 1.2 km away. One of the design criteria for the mobile treatment plant is that it must be mobile to facilitate fast mine moves. The utilisation of the HC1 RS units (or Multotec HX8 or 30 10 units), which are -12 turn, result in a very tall building with a very small overall footprint.
-18 Therefore, the present invention presents the opportunity to have the primary processing plant remain fixed while the mining unit plant and mobile treatment plant move as the mining face advances. Tests have shown that on a feed grade of 12 % heavy mineral, desired recoveries 5 would be achieved at a yield of 30 % to concentrate, resulting in a rejection of 70% of the sand to tails at the mine site. On a 400 tph mobile treatment plant operation, this equates to 280 tph of sand and 420 m 3 /hr of water not being pumped to the wet concentrator plant (and returned) over a potential 6 km.