METHOD AND APPARATUS FOR PROCESSING MAGNETITE
20220008935 · 2022-01-13
Inventors
Cpc classification
B03C1/10
PERFORMING OPERATIONS; TRANSPORTING
C02F1/488
CHEMISTRY; METALLURGY
B03C1/30
PERFORMING OPERATIONS; TRANSPORTING
B01D33/00
PERFORMING OPERATIONS; TRANSPORTING
C02F11/15
CHEMISTRY; METALLURGY
International classification
B03C1/30
PERFORMING OPERATIONS; TRANSPORTING
B01D33/00
PERFORMING OPERATIONS; TRANSPORTING
B03C1/10
PERFORMING OPERATIONS; TRANSPORTING
Abstract
A method of dewatering magnetite to <10% w/w moisture content, including the step of extracting water from the magnetite by virtue of the magnetism of the magnetite, whereby the magnetite pulls together under magnetic attraction thereby squeezing water outwardly and away from the magnetite.
Claims
1. A method of dewatering magnetite to <10% w/w moisture content, comprising: the step of extracting water from the magnetite by virtue of the magnetism of the magnetite, whereby the magnetite pulls together under magnetic attraction thereby squeezing water outwardly and away from the magnetite.
2. The method of claim 1, further comprising the step of using a magnetic drum to cause the magnetite to compress itself toward the drum, thereby expelling water from the magnetite.
3. The method of claim 2, wherein the drum is arranged such that the magnetite material peels away from the magnetic drum under gravitational force after expelling water.
4. The method of claim 3, wherein the magnetite is fed along a belt filter which allows water to drop downwardly from the magnetite and through the belt filter.
5. The method of claim 3, wherein the belt filter is a vibrating belt filter.
6. An apparatus for dewatering magnetite, comprising: a magnetic drum arranged to cause the magnetite to compress itself toward the drum, thereby expelling water from the magnetite.
7. The apparatus of claim 6, further comprising a conveyor belt filter arranged such that magnetite conveyed along an upper surface of the belt filter will compress itself downwardly under magnetic attraction within the magnetite such that water is expelled from the magnetite and drains through the conveyor belt filter.
8. The apparatus of claim 7, further comprising a vibrator for vibrating the conveyor belt filter.
9. The apparatus for dewatering magnetite of claim 5, wherein the apparatus is configured to achieve a target moisture content of less than or equal to 10% w/w.
10. A method of dewatering magnetite to <10% w/w moisture content, comprising: the step of extracting water from the magnetite by virtue of the magnetism of the magnetite, whereby the magnetite pulls together under magnetic attraction thereby squeezing water outwardly and away from the magnetite.
11. A method of dewatering fine magnetite concentrate to ≤10% w/w moisture content, comprising discharging the dewatered magnetite from a magnetic drum, and further dewatering the magnetite using a conveyor belt filter arranged such that the magnetite conveyed along the upper surface of the belt filter will compress itself downwardly under magnetic attraction within the magnetite such that water is further expelled from the magnetite and drains through the conveyor belt filter.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] A preferred embodiment of the invention will be described, by way of non-limiting example only, with reference to the accompanying drawings in which:
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[0055]
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DETAILED DESCRIPTION
[0065] With reference to
[0066]
[0067] In the example depicted, the step of using a high pressure grinding roller 10 crushes the magnetite from a feed particle size distribution of at least 80 mm to a feed particle size distribution of 8 mm. More preferably, the step of using a high pressure grinding roller 10 crushes the magnetite from a feed particle size distribution of at least 80 mm, 100% passing (F.sub.10080 mm), to a feed particle size distribution of 8 mm, 100% passing (F.sub.1008 mm).
[0068] In the case of one particular make/model of machine, the step of using a high pressure grinding roller 10 may include using the high pressure grinding roller 10 with 2.4 m diameter×2.2 m wide roll operating at 4 N/mm.sup.2 pressure and 2.7 m/s roll speed.
[0069] The method may further include the step of using a dry screen 12 to generate a consistent product, and the step of using a dry magnetic separation unit (DMS) unit 14 to discard non-magnetic materials. The dry magnetic separation unit 14 may have a composite fabrication drum to avoid overheating caused by an eddy current phenomenon in a steel drum.
[0070] Turning to
[0071] In another aspect, there is provided an apparatus for processing magnetite iron ore, including a dry magnetic separation (DMS) unit 14 having a composite fabrication drum, the dry magnetic separation unit 14 being for discarding non-magnetic materials.
[0072] In
[0073] In
[0074] Turning to
[0075] With reference to
[0076] The mill 24 may be in the form of a High Intensity Grinding mill (HIGmill). The mill 24 may be arranged in the apparatus without any feedback path to the mill 24.
[0077] In one form, the cyclone 22 is arranged to divert approximately 25% of material to bypass the mill 24. The cyclone 22 may be arranged to divert finely ground material around the mill to prevent overgrinding feed material, and thus reducing the overall mill power consumption. The mill may be configured to operate in a comparable low energy grind mode, where difficult particles are allowed to pass through the open circuit configuration at above the target grind size to be processed and/or discarded through later processing steps.
[0078] As shown in
[0079] In one particular form, the downstream deslime thickener is arranged to deslime material from the mill 24 and from the upstream cyclone 22 overflow at a rise rate to discard silica and non-magnetic materials at relatively low magnetic material losses compared to mass loss. Specifically, the downstream deslime thickener 26 may be arranged to deslime material from the mill 24 and from the upstream cyclone 22 overflow at a high rise rate of 8-10 m/h to discard silica and non-magnetic materials at relatively low magnetic material losses compared to mass loss.
[0080] The downstream deslime thickener may be arranged such that an overflow from the downstream deslime thickener 26 is diverted to a tailings storage facility 28 whereas an underflow from the downstream deslime thickener 26 is fed onward for further processing.
[0081] Also as shown in
[0082] In another aspect, there is an apparatus for processing magnetite iron ore, including a mill 24 for grinding ore particles, wherein the mill 24 is in the form of a High Intensity Grinding mill (HIGmill).
[0083] With reference to Module 5C shown in
[0084] The high grade concentrate thickener 36 is arranged to divert overflow to the tailings storage facility 28 and to feed underflow to a filter feed tank 38. All material from the regrind mill 34 is fed to a magnetic separator 40 which diverts non-magnetic material to the tailings storage facility 28 and feeds magnetic material to one or more deslime thickeners 42.
[0085] The one or more CCD deslime thickeners 42 are arranged to divert overflow to the tailings storage facility 28 and to feed underflow to the filter feed tank 38. The apparatus includes a cyclone separator 44 arranged to feed overflow to said one or more deslime thickeners 42, and to feed underflow to said screen 32 for screening. The apparatus provides accordingly a product upgrade circuit whereby percentage by mass content of iron is able to be increased to guarantee a specific grade.
[0086] In one form, the apparatus may provide a product upgrade circuit whereby percentage by mass content of iron is able to be increased to guarantee a grade of at least 67% by weight content of iron (Fe).
[0087] The high grade concentrate thickener 36 may be able to provide a high grade magnetite product, for example 25% of total product at a Fe grade of at least 68%.
[0088] The product upgrade circuit is able to minimise additional grinding by processing only 15-20% of material fed to the cyclone separator 44 and ensures a final concentrate product is at P.sub.98 of 45 μm (screen) to achieve target grade of at least 67% Fe and less than 6% SiO.sub.2.
[0089] With reference to
[0090] The method may include the step of using a magnetic drum 48 (see
[0091] There is also disclosed an apparatus for dewatering magnetite, including a magnetic drum 48 arranged to cause the magnetite to compress itself toward the drum 48, thereby expelling water from the magnetite.
[0092] The apparatus may include a conveyor belt filter 50 arranged such that magnetite conveyed along an upper surface of the belt filter 50 will compress itself downwardly under magnetic attraction within the magnetite such that water is expelled from the magnetite and drains through the conveyor belt filter 50.
[0093] More preferably, the apparatus is configured to achieve a target moisture content of less than or equal to 10% w/w.
EXAMPLE
1. Glossary
[0094]
TABLE-US-00001 TABLE 1 Glossary of Terms Abbreviation Definition BBWi Bond Ball Work Index CCD Counter Current Decantation CHF Concentrate Handling Facility COS Coarse Ore Stockpile CWi Crushing work index DMS Dry Magnetic Separation dt/h dry tonnes per hour DTR Davis Tube Recovery F.sub.80 Feed Particle Size Distribution - 80% passing Fe Iron FORTESCUE/FMG Fortescue Metals Group Ltd G Gauss g/t grams per tonne HPGR High Pressure Grinding Roll kg Kilograms km Kilometre kW Kilowatts kWh/t Kilowatt hours per tonne μm micrometres m Metres m.sup.3/h Cubic metres per hour mFe Magnetic Iron mm Millimetre Pa Pascals Mtpa Million tonnes per annum dMtpa dry Million tonnes per annum O/F Overflow O/S Oversize P.sub.80 Product Particle Size Distribution - 80% passing P.sub.98 Product Particle Size Distribution - 98% passing ROM Run of Mine rpm Revolutions per minute SiO.sub.2 Silica t/h tonnes per hour t/m.sup.2h Tonnes per square metres per hour, referring to specific settling rate TSF Tailings Storage Facility U/F Underflow U/S Undersize VS Variable Speed VSD Variable Speed Drive w/w Weight/weight WMS Wet Magnetic Separation
2. North Star Stage 2 Plant
[0095] The Stage 2 plant is designed to process 62.5 Mtpa ROM feed at a DTR MR of 32% to produce 20 dMtpa magnetite concentrate product containing 67.1% Fe and 5.6% SiO.sub.2 at a nominal P.sub.80 of 30 μm, with a magnetic Fe recovery of 100% (in comparison to lab DTR testwork results of the ROM feed).
[0096] The main Process Plant consists of the following dry and wet plant facilities: [0097] Primary crushing [0098] Secondary crushing [0099] Tertiary HPGR crushing/screening [0100] HPGR grinding/air classification [0101] Fine grinding with magnetic separation and deslime [0102] CMS concentrate upgrade circuit [0103] Concentrate and tailings thickening [0104] Overland pipeline to port [0105] Concentrate filtration and storage facility at port.
2.1 Overall Process Flowsheet
[0106] Extensive test work programs and process modelling has been conducted over more than 5 years to establish and validate the basis of design for the process flow sheet. This testing has utilised material from diamond core drilling as well as initial mining operations.
[0107] Extensive laboratory and vendor tests has been validated and confirmed by the operation of the Stage 1 demonstration plant and the pilot plant at site configured to the Stage 2 flowsheet.
[0108] The North Star, Eastern Limb and Glacier Valley low moisture ore bodies enable a dry process using two-stage crushing, HPGRs, screening and air-classifiers, replacing the more conventional (and higher-energy) wet process of ball-milling and cycloning. The use of higher efficiency stirred regrind mills for subsequent wet processing further reduces energy consumption.
[0109] Based on operating data from the Stage 1 Demonstration Plant and extensive test work in vendor labs and at the North Star Pilot Plant, the Stage 2 Flowsheet was developed designating the plant into the following seven modular areas: [0110] Module 1—Primary Crushing [0111] Module 2—Secondary Crushing [0112] Module 3—Tertiary Crushing [0113] Module 4—Grinding [0114] Module 5—Fine Grinding [0115] Module 6—Tailings [0116] Module 7—Dewatering (Port)
[0117] The overall Stage 2 processing Flowsheet is shown in
2.2 Process Plant
[0118] The Stage 2 Process Plant is designed to process 62.5 Mtpa ROM feed at a ROM feed DTR MR of 32% to produce 20 Mtpa magnetite concentrate product containing 67.1% Fe and 5.6% SiO.sub.2.
[0119] Table 3 shows a summary of the major equipment for the Stage 2 Plant.
TABLE-US-00002 TABLE 3 Stage 2 Major Equipment Summary Installed Number Power (kW) Equipment Details of Units per unit Primary Crushers 63″-130″ (1.6 m-3.3 m) semi mobile 2 1,500 gyratory crusher for maximum feed size of 1,250 mm Secondary Crushers 1,050 kW cone crushers for maximum feed 6 1,050 size of 400 mm Screens 3.6 m wide × 7.3 m long banana screens 10 90 Tertiary Crushing 2.4 m diameter × 2.2 m wide roll operating at 4 2 × 5,100 or HPGRs 4 N/mm.sup.2 pressure and 2.7 m/s roll speed 5,700 Dry Magnetic Single drum 1.22 m diameter × 4.0 m, 3000 20 7.5 Separators Gauss Air Classifiers - Static/ 6.1 m diameter, 0.76 Mm.sup.3/h 12 2,520 Dynamic Baghouses Full size - 25,000 m.sup.2 cloth area, 6 1,056 Primary Grinding 2.2 m diameter × 2.0 m wide roll operating at 8 2 × 3,400 HPGRs 4 N/mm2 pressure and 2.0-2.2 m/s roll speed Rougher Wet Magnetic Single drum 1.2 m diameter × 3.05 m, 1150 64 11 Separators Gauss Upstream Cyclones 250 mm diameter, 8 clusters of 16 cyclones 128 N/A each Fine Grinding Mills HIGmill 5000 (2.4 m dia, 50,000 litres) 8 5,000 Deslime Thickeners 4 + 1 17 m dia CCDs 5 N/A Cleaner Wet Magnetic Triple drums each 1.2 m diameter × 3.05 m, 48 33 Separators 1000 Gauss Cons Cyclones 250 mm diameter, 4 clusters of 22 cyclones 88 N/A each High Frequency High Frequency Vibrating Multifeed 48- 88 1.8 Vibrating Screens 90MS-3 screen with three SWG48-30DF280 steel sandwich panels Regrind Mills HIGmill 5000 (2.4 m dia, 50,000 litres) 2 5,000 ReCleaner Wet Triple drums each 1.2 m diameter × 3.05 m, 7 33 Magnetic Separators 1000 Gauss Concentrate Cleaner/ 2 + 1 17 m dia CCDs 3 N/A Thickeners High Grade 26 m diameter high rate thickener 1 15 Concentrate Thickener Tailings Thickener 69 m diameter high rate thickener 3 30 Tailings Transfer centrifugal pumps 10 1,680 Pumps Concentrate Transfer positive displacement pumps 4 1,060 Pumps Concentrate Thickener 50 m diameter high rate thickener 1 30 (Port) Concentrate Filters Dewatering drums w/Vacuum Belt Filters 8 40 (Port)
3. Process Description
[0120] 3.1 Module 1—Primary Crushing (F.sub.100 1.2 m to P.sub.100 400 mm)
[0121] From the mining operations' prepared ROM fingers, ROM ore is loaded into Caterpillar 793F or equivalent rear tipping dump trucks and hauled to two gyratory type Primary Crushers. The Primary Crushers receive ore with an average F.sub.80 size of 310 mm (based on heavy ANFO blast modelling) and at an average moisture of 0.6%. Based on a design CWi of 21 kWh/t, two primary crushers are each capable to provide a crushed product with a P.sub.80 of 140-160 mm that is conveyed to downstream secondary crushing in Module 2.
[0122] At the on-stream utilisation of approximately 76.5% (6700 h/a), each primary crusher will nominally process 4,630 t/h of material and have a design throughput rate of 6,600 t/h. This extra capacity allows for mining to feed each primary crusher (and subsequent downstream secondary crushers) from a 50/50 split ratio up to a maximum 60/40 split ratio.
[0123] Refer to
3.2 Module 2—Secondary Crushing (F.sub.100 400 mm to P.sub.100 80 mm) Secondary Crushing aims to reduce the size of the Primary Crusher product prior to sending the material to the Coarse Ore Stockpiles (COS). Six cone type Secondary Crushers each operate at a nominal throughput rate of 1,540 t/h with an on-stream utilisation of 76.5%. Ore is discharged from the crushers at a P.sub.80 of 40 mm to 45 mm and is sent to the COS. The COS consists of four stockpiles that allows the material to be stacked according to target mass recovery ranges (low, medium and high). A moving average time lag of data from on-line magnetic analysis will assist the radial stacker to direct the crushed material to the corresponding piles.
[0124] The COS serves as a break point between the upstream Modules 1 and 2 (on-stream utilisation of 76.5%) from the rest of the plant which operates with an on-stream utilisation of 84.5% by providing up to 12 hr of live storage prior to requiring dozers to push the material forward for downstream processing. Four apron feeders under the COS fine-tune the blend to ensure a uniform mass recovery feed to the downstream Module 3.
[0125] See
3.3 Module 3—Tertiary Crushing (F.sub.100 80 mm to P.sub.100 8 mm) Tertiary crushing by HPGR was introduced to the North Star 2 flowsheet to allow a consistent, fine feed to primary grinding. Secondary crushed ore from the coarse ore stockpile (F.sub.100 80 mm) is fed to the HPGR crushing circuit to generate a minus 6 to 8 mm product. Four crushing HPGRs are closed with ten dry double deck banana screens to generate a consistent product. For the 20 Mtpa concentrate production flowsheet, 8,340 t/h ore exits the screen undersize at a P.sub.80 of 4.2 mm after being passed through the Module 3 HPGRs 2.25 times and crushed from a feed F.sub.80 of 43 mm.
[0126] The screen undersize is then fed to twenty dry magnetic separation (DMS) units to effectively discard silica and non-magnetic materials prior to being sent to further downstream primary grinding. The flowsheet top size of 8 mm has been selected based on IBO plant data and testwork. Consequently, the DMS operation will process the 32% MR feed over a 3000G rare earth type dry drum and reject 17% of the total mass (primarily silica and other non-magnetics) with a low magnetics loss of 1.5%. Refer to
[0127] For the 20 dMtpa concentrate production flowsheet, DMS rejects equates to 10.5 dMtpa material with a nominal composition of 16.3% Fe and 51.8% SiO.sub.2 being sent to dry tails stacking. See
3.4 Module 4—Primary Grinding (F100 6-8 mm to P.sub.80 60-100 μm) Eight HPGRs in grinding service operate in closed circuit with air classification to produce a P.sub.80 of 80 μm product to feed the wet plant. The HPGR product discharge is targeting 20% by mass of the discharge product to be ≤80 μm when receiving a feed with a BBWi of ≤20.8 kWh/t and operating at a circulating load of 490%.
[0128] Minus 6 mm Module 3 product material is conveyed with recirculated HPGR ground product to the Air Classifier Feed Bin. Ten air classification systems operate in parallel to remove fines generated from the HPGR product targeting a P.sub.80 circa 80 μm. For each AC system, ore is withdrawn from the base of the AC feed bin by a variable speed air classifier vibratory feeder to provide a constant feed rate to the Static Separators.
[0129] The air-classifier system is a three product separator, comprised of Static and Dynamic Separators. The Static section separates a “coarser fines” cut from the air classifier which is then air conveyed to the dynamic separator. Within the dynamic separator, the fines is further refined targeting an exit product to the baghouse at a P.sub.80 of 80 μm and a top size of <2 mm. The coarse material discharging from the static and dynamic sections of the air classifiers are combined and sent to the HPGR Grinding Feed Bins.
[0130] The dynamic classifier product (P.sub.80 80 μm) fraction is recovered via a baghouse system and transported via covered conveyors to six, agitated Coarse Slurry tanks, where process water is added to slurry the fines to a solids density of 50% w/w. The slurry is then pumped to two agitated RMS Feed Tanks, where it is further diluted to a solids density of 30% w/w before being fed to the Rougher Wet Magnetic Separation Circuit. Refer to
3.5 Module 5—Fine Grinding (F.sub.80 80 μm to P.sub.80 35 μm)
[0131] Module 5 consists of the wet concentration plant as depicted in
[0132] The Module is further subdivided into the following: [0133] Module 5A—consists of rougher wet magnetic separation (WMS) and cyclone classification [0134] Module 5B—consists of fine grinding and desliming [0135] Module 5C—consists of cleaner wet magnetic separation (WMS) and a concentrate product upgrade circuit
[0136] Within Module 5A, air classifier fines from Module 4 are pumped at a solids density of 30% w/w to the Rougher WMS (RMS) units. The RMS units are single drums with ceramic ferrite magnets operating at a magnetic intensity of 1150 G. For the 20 dMtpa concentrate production flowsheet, the RMS units reject 38% of the total mass to tails while limiting magnetic Fe (mFe) losses to 1.8%. The RMS cons are sent to hydrocyclones to remove fines material <P.sub.80 of 35 μm (laser) prior to being sent to stirred mills that are designed to grind to a product size P.sub.80 of 35 μm (laser). Consequently, 25% of the material sent to the hydrocyclones is sent to overflow and bypasses the stirred mills to reduce power consumption due to overgrinding.
[0137] Within Module 5B, open circuit stirred mills are used for grinding hydrocyclone underflow at a F.sub.80 of 105 μm (screen) to produce a product P.sub.80 of 35 μm (laser) and consuming 9 kWh/t of power. The fine ground product is then combined with the hydrocyclone overflow and sent to the de-sliming circuit.
[0138] A 2-stage de-slime circuit operates at high rise rates (8-10 m/h based on O/F) to allow significant removal of low density, high silica content solids (up to 22% mass at 59 to 63% SiO.sub.2 concentration) while limiting mFe losses to 1.5% prior to being sent to the CMS circuit. For the 20 dMtpa concentrate production flowsheet, five CCDs are proposed (4 in parallel followed by 1 in series) for the de-slime circuit due to their smaller diameter and subsequent lower water consumption.
[0139] Within Module 5C, the de-slimed product from Module 5B is pumped at a solids density of 20% w/w to the Cleaner WMS (CMS) units. The CMS units are triple drum Stephenson types with ceramic ferrite magnets operating at a magnetic intensity of 1000 G. For the 20 Mtpa concentrate production flowsheet, the CMS units reject 13% of the total mass to tails while limiting magnetic Fe (mFe) losses to 0.6%.
[0140] Depending upon the ore body being processed, the Cleaner Concentrate will be in the 64-67% Fe range. Testwork has indicated significant decrease in Fe grade in size fractions >45 μm for both the North Star and Eastern Limb deposits. Hence, the remaining portion of Module 5C is collectively known as the Concentrate Product Upgrade circuit where processing steps are employed to ensure the final concentrate product is at a P.sub.98 of 45 μm (screen) in order to achieve the final product grade target of 67.1% Fe and 5.6% SiO.sub.2.
Equipment within the Upgrade Circuit Includes: [0141] Cons cyclones—overflow contains approximately 60% of the inlet cleaner cons mass at a P.sub.80 of 24 μm (laser) and is sent to the CCD cleaners; [0142] High Frequency Vibrating screens—underflow contains approximately 60% of the inlet cons cyclone U/F is sent to the High grade concentrate thickener; [0143] High grade (HG) concentrate thickener—further upgrades the High Frequency Vibrating screen U/S in a high rate thickener to a product grade of 68-69% Fe; [0144] Regrind Mills—regrinds High Frequency Vibrating screen O/S at a F.sub.80 of 69 μm (screen) to produce a product P.sub.80 of 26-30 μm (laser) and consuming 12.2 kWh/t of power; [0145] Recleaner wet magnetic separators—process regrind mill product at a solids density of 20% w/w through RCMS (Recleaner wet Magnetic Separation) units consisting of triple drum Stephenson types with ceramic ferrite magnets operating at a magnetic intensity of 1000 G. The RCMS units reject 16% of the total mass to tails while limiting magnetic Fe (mFe) losses to 1.5%. [0146] CCD cleaners—process cons cyclone O/F and RCMS cons in a 2-stage de-slime circuit operating at high rise rates (8-10 m/h based on O/F) to allow additional removal of low density, high silica content solids (up to 8% mass at 45% SiO.sub.2 concentration) while limiting mFe losses to 1.1%.
[0147] The upgrade circuit removes approximately 7% of the inlet cleaner concentrate mass to achieve the 67.2% Fe grade with an estimated 1% magnetic losses. The HG and CCD thickener products are combined in the Concentrate Storage Tanks and subsequently pumped to the Module 7 Port via an overland pipeline.
3.6 Module 6—Tailings
[0148] Wet tailings from the RMS, CMS and RCMS are combined with overflow from the RMS Deslime and CCD Cleaner O/F streams and sent to three tailings high rate thickeners prior to pumping to a tailings storage facility (TSF). The tailings thickeners are designed to achieve an underflow density of 62% w/w solids while operating at a specific settling rate of 0.3 t/m.sup.2h and rise rate of 5 m/h. Flocculant addition has been designed to 40 g/t based on testwork and coagulant addition is being considered as a mitigating strategy for reducing the amount of residual flocculant in the process water that provides make-up water to the deslime circuits. Refer to
[0149] For the 20 dMtpa concentrate production flowsheet, 32 Mtpa solids with an estimated composition of 18% Fe and 52% SiO.sub.2 containing 19.4 Gl/a water are transported via a 7 km slurry pipeline to the TSF.
[0150] See
3.7 Module 7—Dewatering (Port)
[0151] 2,700 dt/h slurry at a density of 62% w/w solids is pumped approximately 135 km to the port. Based on testwork (Paterson & Cooke), yield stress of 1.8 Pa and plastic viscosity of 40 mPa.Math.s was used for pumping calculations. The slurry is pumped at a solids density in the range of 55% to 68% w/w, at a velocity of 1.7 to 1.8 m/s.
[0152] The port filtration facility is based on magnetic drums and belt filters, and includes a thickener, filter feed tanks, filters and ancillary equipment, as shown in
[0153] See
Notes: Process Flow
[0154] Significant novel and inventive areas to consider are combined Module 3/4, combined Module 5A/5B and Module 5C.
Module 3 Tertiary Crushing and Module 4 Grinding: The Novel Flowsheet Allows for:
[0155] Optimisation to promote the HPGR to work more to maximise the HPGR to promote micro-fissuring of the material at lower power consumption where: [0156] Inlet feed size to Module 3 can be run at top size of 80 mm preferably (and potentially to 100 mm) to reduce load on upstream secondary crushing [0157] Exit feed size from Module 4 at a P.sub.80 of 80 μm (and potentially down to 60 μm) to improve magnetic liberation and power reduction to the downstream magnetic separators and tower mills, respectively. [0158] Dry magnetic Separation occurring outside the two circuits allows for optimum size being sent to the DMS (top size of 6-8 mm) to effectively discard silica and non-magnetic materials at low magnetic losses (17% mass loss at 1.5% magnetic loss). Also, with the DMS being external to the circuits, this mitigates the effects of inlet feed ROM mass recovery fluctuations to the two independent circuits.
Refer FIG. 8.
Module 5a & 5b Fine Grinding: The Novel Flowsheet Allows for:
[0159] Optimisation of mill power by using the Upstream Cyclones as a “Power” splitter by diverting approximately 25% of the material in the cyclone overflow to the downstream de-slime thickeners. [0160] Desliming of mill and cyclone overflow Magnetite Products at high rise rates (10 m/h) to effectively discard silica and non-magnetic materials at low magnetic losses (22% mass loss at 1.5% magnetic loss (MFe)) to ensure better operating performance exiting the downstream CMS units.
Refer FIG. 9.
[0161] With reference to
Module 5c Product Upgrade Circuit: The Novel Flowsheet Allows for:
[0162] Guaranteeing Fe grade at 67+% for all ore bodies considered for the project. Typical upgrade of 64+% Fe to 67+% Fe with <10% mass loss of the feed to Module 5c (or 2-3% of original ROM feed). [0163] Upgrade circuit minimises additional grinding by only processing 15-20% of the CMS cons material and ensures final concentrate product is at a P.sub.98 of 45 μm (screen) to achieve target grade of 67+% Fe and <6% SiO.sub.2. [0164] Potential to provide a High Grade magnetite product i.e. 25% of total product at a Fe grade >68%.
Refer FIG. 10.
[0165] As will be understood from the foregoing, an example of the invention provides an apparatus for processing magnetite iron ore, including a first high pressure grinding roller (HPGR) for crushing the magnetite iron ore into particles, and a second high pressure grinding roller (HPGR) for grinding the particles. Advantageously, the applicant has determined that energy savings are achieved by having a first HPGR which does a crushing operation and a second HPGR which does a grinding operation. It would not previously have been conceived that an HPGR could be used to reduce a feed particle size distribution of 8 mm, 100% passing (F.sub.1008 mm) to produce a product P.sub.80 of 80 μm owing to vibrations, the product being too fine, the absence of voids and chatter from the machinery. The applicant has identified viscosity in the material, an ability of the HPGR to shear iron ore material from the silica, and has applied inventiveness to arrive at an arrangement which enables significant energy and cost savings. The present invention involves an unexpected result that has been achieved by virtue of the inventors' knowledge, expertise, ingenuity and time investment.
[0166] In one form, the first high pressure grinding roller may crush the magnetite iron ore from a feed particle size distribution of at least 80 mm, 100% passing (F.sub.10080 mm), to a feed particle size distribution of 8 mm, 100% passing (F.sub.1008 mm). The second high pressure grinding roller crushes the particles from a feed particle size distribution of at least 80 mm, 100% passing (F.sub.10080 mm), to a feed particle size distribution of 8 mm, 100% passing (F.sub.1008 mm).
[0167] Advantageously, there is provided a method of processing a low moisture magnetite ore body via a two-stage HPGR circuit which allows for the optimisation of the HPGR to work from top size of 80 mm to produce a product P.sub.80 of 80 μm to reduce power consumption. A first HPGR circuit may be in closed circuit with a screen, and a second HPGR circuit may be closed with an Air Classifier/Baghouse system. The two circuits may be separated by Dry Magnetic Separation, to remove non-magnetic waste material prior to the second circuit, thus reducing the throughput and additional grinding to the second HPGR circuit.
[0168] Advantageously, examples of the present invention ensure that 67% Fe grade is achievable from 64-65 wt % total Fe magnetite feed streams with minimal mass loss by (a) removing slimes (cons cyclone) prior to further hydroseparation processing; and (b) limiting +45 micron material to <2 wt % in the final product stream via derrick screens followed by regrind mills and magnetic separators to limit oversize mass loss.
[0169] Advantageously, the present invention provides a method of dewatering fine magnetite concentrate (P80L≤45 μm or more specifically P80L of 25 μm-35 μm) to ≤10% w/w moisture content, with an apparatus for dewatering magnetite, where the dewatered magnetite is discharged from the drum and further dewatered using a conveyor belt filter arranged such that the magnetite conveyed along the upper surface of the belt filter will compress itself downwardly under magnetic attraction within the magnetite such that water is further expelled from the magnetite and drains through the conveyor belt filter.
[0170] While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.
[0171] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.
[0172] Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
EXPLANATION OF REFERENCE LETTERS IN THE DRAWINGS
FIG. 1
[0173] A Primary crushing (×2) [0174] B Secondary crushing (×6) [0175] C Coarse ore stockpile [0176] D High pressure grinding rolls (4) [0177] E Fines [0178] F Air classifiers (×10) [0179] G Bag houses (×6)-4 full size/2 half size [0180] H Mags [0181] I Oversize [0182] J Undersize [0183] K Dry screens (×10) [0184] L Coarse [0185] M High pressure grinding rolls (×8) [0186] N Dry magnetic separation (×20) [0187] O Coarse rejects stockpile [0188] P Water addition [0189] Q Coarse transfer tanks (×2) [0190] R Cyclone overflow [0191] S RMS mags [0192] T Rougher wet magnetic separation (×58) [0193] U RMS non-mags [0194] V RMS deslime thickener overflow [0195] W Cyclone underflow [0196] X Fine grinding mills (×7) [0197] Y Tailings thickeners (×3) [0198] Z To tailings storage facility [0199] Aa Overflow [0200] Ba RMS Deslime LFCUs (4×1) [0201] Ca RMS Deslime underflow [0202] Da Cleaner wet magnetic separation (×44) [0203] Ea CMS mags [0204] Fa Cyclone overflow [0205] Ga Cyclone underflow [0206] Ha Derrick screens (×80) [0207] Ia Oversize [0208] Ja Undersize [0209] Ka Regrind mill (×2) [0210] La Re-cleaner wet magnetic separation (×6) [0211] Ma CMS non-mags [0212] Na RCMS non-mags [0213] Oa High grade concentrate thickener [0214] Pa RCMS mags [0215] Qa Overflow [0216] Ra CCD cleaner LFCUs (2×1) [0217] Sa Water addition [0218] Ta Concentrate storage tanks (×4) [0219] Ua Concretrate pipeline to port [0220] Va Concentrate filter feed tank (×4) [0221] Wa Concentrate thickener [0222] Xa Port concentrate handling facility [0223] Ya Dewatering drums (×16) [0224] Za Concentrate filters (×8) [0225] Ab PW Return to OPF [0226] Bb Concentrate product to storage
FIG. 2
[0227] Cb Module 1 [0228] Db Primary Crushing [0229] Eb Module 2 [0230] Fb Secondary crushing (×3) [0231] Gb Coarse ore stockpile
FIG. 3
[0232] Hb Fresh feed from COS [0233] Ib High pressure grinding rolls [0234] Jb Dry screen [0235] Kb Oversize [0236] Lb Undersize [0237] Mb Mags [0238] Nb To Module 4 [0239] Ob Dry magnetic separation [0240] Pb Non mags [0241] Qb DMS rejects
FIG. 4
[0242] Rb From Module 3 [0243] Sb Air classifier (static/dynamic) [0244] Tb Fines [0245] Ub Mags [0246] Vb Coarse [0247] Wb Bag House [0248] Xb Transfer Hoppers [0249] Yb High pressure grinding rolls [0250] Zb Water addition [0251] Ac RMS feed tank [0252] Bc To Module 5A
FIG. 5
[0253] Cc From Module 4 [0254] Dc Module 5A [0255] Ec Cyclone overflow [0256] Fc RMS mags [0257] Gc Rougher wet magnetic separation (×58) [0258] Hc Water addition [0259] Ic RMS feed tank [0260] Jc RMS deslime thickener overflow [0261] Kc Cyclone underflow [0262] Lc RMS non-mags [0263] Mc Fine grinding mills (×7) [0264] Nc RMS Deslime LFCUs (4×1) [0265] Oc To Module 6 [0266] Pc CMS mags [0267] Qc Cleaner wet magnetic separation (×44) [0268] Rc RMS deslime underflow [0269] Sc CMS non-mags [0270] Tc Module 5B [0271] Uc Regrind mill [0272] Vc CCD cleaner LFCUs (2×1)
FIG. 6
[0273] Wc Module 5A—RMS non-mags [0274] Xc Module 5B—RMS Deslime O/F [0275] Yc Module 5C—CMS Non-mags [0276] Zc Module 5C—RCMS Non-mags [0277] Ad Module 5C—CCD cleaner O/F [0278] Bd Tailings thickeners (×3) [0279] Cd To tailings storage facility
FIG. 7
[0280] Dd Concentrate pipeline to port [0281] Ed Concentrate thickener [0282] Fd Concentrate filter feed tank (×4) [0283] Gd Dewatering drums (×16) [0284] Hd Concentrate handling facility [0285] Id Concentrate filters (×8) [0286] Jd Concentrate product to storage
FIG. 8
[0287] Kd Fresh feed [0288] Ld Module 3 [0289] Md High pressure grinding rolls [0290] Nd Module 4 [0291] Od Oversize [0292] Pd Undersize [0293] Qd Dry screen [0294] Rd Mags [0295] Sd Air classifier (Static/dynamic) [0296] Td Fines [0297] Ud Coarse [0298] Vd Dry magnetic separation [0299] Wd Non mags [0300] Xd DMS rejects [0301] Yd High pressure grinding rolls [0302] Zd Bag House [0303] Ae Transfer hoppers [0304] Be Water addition [0305] Ce RMS feed tank [0306] De To module 5A
FIG. 9
[0307] Ee Air classifier fines [0308] Fe Module 5a [0309] Ge Cyclone overflow [0310] He Module 5b [0311] Ie RMS cons [0312] Je RMS tails [0313] Ke Magnetic separator [0314] Le Upstream cyclone [0315] Me To Module 6 [0316] Ne Cyclone underflow [0317] Oe To mill feed tank [0318] Pe HIGmill [0319] Qe Mill product tank [0320] Re Overflow [0321] Se To tailings [0322] Te Water addition [0323] Ue Underflow [0324] Ve CCD1 [0325] We CCD2 [0326] Xe Deslime thickeners [0327] Ye To CMS
FIG. 9a
[0328] Ze
FIG. 10
[0339] Kf From Module 5C Part A [0340] Lf CMS Cons [0341] Mf Cyclone overflow [0342] Nf Cyclone underflow [0343] Of Oversize [0344] Pf Derrick Screen [0345] Qf Undersize [0346] Rf HG TH Overflow [0347] Sf High grade concentrate thickener [0348] Tf Regrind Mill [0349] Uf Re-cleaner wet magnetic separation [0350] Vf RCMS Tails [0351] Wf RCMS cons [0352] Xf To tailings Module 6 [0353] Yf Overflow [0354] Zf Underflow [0355] Ag CCD1 [0356] Bg CCD2 [0357] Cg CCD3 [0358] Dg Water Addition [0359] Eg CCD deslime thickeners [0360] Fg Filter [0361] Gg Feed tank [0362] Hg To Filtration Module 7