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779Australasian Mining and Metallurgical Operating Practices

1. Concentrator Manager, Concentrator, Birla Nifty Copper Operation;2. AAusIMM, Metallurgist Superintendent, Concentrator, Birla Nifty Copper Operation;3. General Manager, Operations,Birla Nifty Copper Operation;4. Environmental Manager, Operations, Birla Nifty Copper Operation;5. Environmental Officer, Operations, Birla Nifty Copper Operation;6. Senior Geologist,Mining, Birla Nifty Copper Operation;7. Graduate Geologist, Mining, Birla Nifty Copper Operation;8. Occupational Health and Safety Manager, Operations, Birla Nifty Copper Operation;9.

Occupational Health and Safety Officer, Operations, Birla Nifty Copper Operation;10.

Human Resources Officer, Operations, Birla Nifty Copper Operation;11.

Mining Manager, Mining,Birla Nifty Copper Operation;12. Contract Mining Engineer, Mining, Birla Nifty Copper Operation;13. Underground Manager, Mining, Birla Nifty Copper Operation;14. Geotechnical Engineer,Mining, Birla Nifty Copper Operation;15. Human Resources Superintendent, Operations, Birla Nifty Copper Operation;16. Senior Metallurgist, Concentrator, Birla Nifty Copper Operation;17. Graduate Metallurgist / Metallurgical Technician, Concentrator, Birla Nifty Copper Operation;18. Metallurgist, Concentrator, Birla Nifty Copper Operation;19. MAusIMM, Metallurgist,Concentrator, Birla Nifty Copper Operation;20. Metallurgist, Concentrator, Birla Nifty Copper Operation;21. Senor Metallurgist, Concentrator, Birla Copper Operation.

Birla Nifty Copper Operation

A D I T Y A B I R L A M I N E R A L SL I M I T E D

INTRODUCTION

OverviewThe Birla Nifty Copper Operation (BNCO) is ownedand run by Aditya Birla Minerals Limited, an AustralianStock Exchange (ASX)-listed company, and part owned by Hindalco Industries Ltd, which is part of the AdityaBirla Group in India. The Nifty site is located in the GreatSandy Desert in the East Pilbara of Western Australia,approximately 1250 km north of Perth, 350 km east ofPort Hedland and 70 km west of Telfer; it is 300 m abovesea level. Figure 1 shows an aerial view of the operation.A production summary is given in Table 1.

The site generally experiences a mild winter and a verywarm summer with monsoonal activity. The ambienttemperature range is 2.5°C to 47.5°C, with an average

of 313 mm rain per year and an annual evaporationrate of 4161 mm. There is an average of 40 days withprecipitation events per year.

HistoryThe Nifty Copper deposit was discovered by Mark

(Nifty) Neville MLC, a geologist employed by WesternMining Corporation who went on to be the independentMember for the Mining and Pastoral Region ofWestern Australia. Nifty Neville was then part ofthree undertaking regional geochemical and fieldreconnaissance in October 1982 as part of the ThrosselRange Project, initiated in 1979. The project was aconceptually driven exploration program to assess and

M Bateman 1, D Price 2, S Roesler 3,M Robinson 4, R Wardman 5, G Hall 6,A Agarwal 7, C Rushby 8, K Brown 9,P Sithambaram 10 , V Utete 11 ,M Sexton 12 , T Cheaib 13 , R Alivio 14,S Taylor 15 , A Adem 16 , N F Pulle 17 ,M Biven 18 , P James 19 , A Ciluzzo 20

and T Huynh 21

c/- Nifty Copper Great Sandy DesertLevel 3, Septimus Roe Square256 Adelaide Terrace, Perth WA 6000

www.adityabirlaminerals.com.au

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Australasian Mining and Metallurgical Operating Practices780

BIRLA NIFTY COPPER OPERATION

explore for stratiform copper and lead-zinc resourceson the western and south-western basin margins of thePaterson Basin (Carver, 2004).

The exploration team travelled from Wittenoon toWoodie Woodie before heading east into the desert,skirting around the south side of the Throssel ranges.The party was travelling north, taking lag geochemicalsamples at 100 m intervals along each sand dunecorridor. After arriving at what was to be Nifty corridor,the party started sampling from the east. It was gettinglate in the afternoon and the party was pushing forwardto check a thumbprint aeromagnetic anomaly whensome outcrop was noticed on rising ground to the north.Despite some of the party wanting to call it a day andset up camp, the outcrop was examined and evidenceof sulfides prior to oxidation and leaching was found.Samples were found to be very high in copper andother base metals. Nifty was discovered (Carver, 2004).

The teams lived out of the back of Toyotas for

18 months while 22 000 samples were collected fromthe Patterson Basin, culminating in the pegging of StateAgreement exploration license E1SA. The discovery ofNifty ranks as one of the best exploration success stories

in Australia, where fundamental, persistent fieldworkdriven by first-class conceptual geological thinkingdelivered an outstanding discovery (Carver, 2004).

WMC commenced an open pit, heap leach, solventextraction (SX) and electro-winning (EW) operation onthe relatively high-grade part of the oxide mineralisationin 1993. Open pit mining operations ceased in June 2006and heap leaching operations ceased in January 2009.

In 1998, the Nifty operation was purchased byStraights Resources Limited, from which AdityaBirla Minerals Limited acquired the operation andsurrounding exploration tenements in March 2003.Following the completion of a feasibility study,underground development was commenced in January2004 to exploit the sulfide resource via an explorationdecline from the open pit. First sulfide was intersectedin February 2005. Construction of the concentratorcommenced in October 2004, with the first concentrateproduced in March 2006.

Operating strategy, constraints, innovationand future plansAditya Birla Minerals Limited looks towardscreating genuine copper investment opportunities byexemplifying safe and environmentally friendly copperexploration and production. As the mine is depleted ofprimary stopes and ventures into secondary and tertiarystopes, copper production strategy will be to producecopper at current volumes. The current strategy isaround increasing throughput rate and flotation circuitcapacity for the treatment of lower-grade ores tomaintain copper production. As a result, projects are inplace in an effort to prepare for the lower feed grade.Current and future projects are listed below.

Major projects completed at the concentrator include: • commissioning of the paste plant • increasing mill throughput

2010 - 2011actual

2011 - 2012plan

Ore mined underground (Mt) 2.2 2.3

Ore sourced open pit (Mt) N/A N/A

Ore milled (Mt) 2.4 2.2

Head grade Cu (%) 2.76 2.75

Head grade Au (g/t) N/A N/A

Copper produced (t) 58 034 58 748

Gold produced (oz) N/A N/A

TABLE 1Production summary.

Concentrator

Open Pit

Paste Plant

SXEW Plant

Leach Pads

Tailings

FIG 1 - Aerial view of the mine site.


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• processing information database installation • lime slaker installation.Future projects at the concentrator include:

• increasing capacity of the flotation circuit • increasing mill throughput

•

improving consistency of feed rate and grade withthe installation of a stacker • improving production at the paste plant.

GEOLOGICAL DESCRIPTIONWMC Resources Ltd discovered Nifty in the 1980susing regional ironstone sampling and reconnaissancegeology. Malachite staining of an outcrop and Cu-anomalous ironstones from dune swale reconnaissancesampling were the initial indicators (Figure 2). Thiswas followed by lag sampling on a 500 m by 50 mgrid that detected a 2.5 km by 1.5 km Cu-Pb anomaly.Secondary Cu mineralisation was intersected inpercussion drilling in mid-1981, with high-gradeprimary ore (20.8 m at three per cent Cu) discoveredin 1983 (Carver, 2004).

Nature of mineralisation, stratigraphy andgeneralised orebody morphologyMineralisation is hosted in a plunging syncline ofcarbonaceous and dolomitic shales of the upperBroadhurst Formation. The depositional age of theBroadhurst Formation is constrained to between1132±21 Ma and 816±6 Ma. Interpretation of the localstratigraphy proposes that the mine sequence consistsof the footwall beds, Nifty Member, pyrite marker bed and hanging wall beds (Figures 3 and 4). Thefootwall beds consist of chloritic and pyritic shales.The Nifty member is subdivided into the lower unit(LCU), intermediate shale (SH), upper unit (MCU)

and upper shales. The lower unit contains a 15 - 30 mthick package of interbedded fine-grained, pale grey,dolomitic mudstone and blue-black, carbonaceousshale. Separating the lower and upper units is a

prominent 1 - 4 m thick bed of dark-grey to black, very

fine-grained, chloritic shale. The upper unit (20 - 40 m)has a similar composition to that of the lower unit andconsists of alternating beds of laminated carbonaceousshale and dolomitic mudstone.

FIG 2 - Local geology at Nifty, showing locations ofthe discovery samples (Carver, 2004).

Range Symbol Description

>240 m USH Uppershale; black carbonaceous shale

20 ‐40 m UCB

20 ‐60 m HWS

5‐7 m PMB Pyrite marker bed; up to 40% pyrite25 ‐50 m ISHU

10 ‐25 m ISHL

20 ‐40 m MCU

5‐20 m BAC

2‐10 m SH Shale; carbonaceous shale15 ‐30 m LCU

>100 m FWS

Lower carbonate unit; algal limestone with siltstone and shale interbeds strongly overprinted by silica‐dolomite alteration. Unit can be strongly mineralisedFoot wall shale; a series of interbedded caronaceous shales and siltstones with occasional carbonate units

S u

l f i d e s

S u

l f i d e s

Barren algal carbonate; a massive to wavy laminated, silica‐dolomite altered. Algal micrite limestone.

Upper carbonate bed; calcareous rocks ranging from argillaceous siltstones to micrites, often interbedded with thin beds of carbonaceous shale.

Hanging wall shale; planar interbedded carbonaceous siltstones and shales. Pyrite becomes more common towards the base.

Upper interbedded shale unit; thick series of interbedded siltstones and shales.Upper carbonate unit (UCU) 1‐1.5 m thick; lies within the ISHU and consistently has strong silica dolomite alteration

Lower interbedded shale unit; a strongly silica‐dolomite altered algal carbonate with minor shale interbeds. This unit hosts the majority of the sulfide minerlisations

Middle carbonate unit; a strongly silica‐dolomite altered algal carbonate with minor shale interbeds. This unit hosts the majority of the sulfied mineralisation.

FIG 3 - Generalised Nifty stratigraphic column.

FIG 4 - Generalised Nifty cross-section.


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The upper shales (Figure 3) consist of dark-grey to black, laminated, carbonaceous shale with thin to massiveframboidal pyrite seams and blebs, disseminated veryfine-grained framboidal pyrite and minor dolomiticmudstone. Overlying the Nifty member is the pyritemarker bed, which consists of 5 - 7 m of framboidalpyrite in carbonaceous shale. Above the pyrite marker bed is a 20 - 60 m thick package of carbonaceous andpyritic shales of the hanging wall beds and 20 - 40 mfinely laminated dolomitic and calcareous silty shaleof the upper carbonate bed (modified after Anderson,1999). Figure 4 shows the generalised Nifty cross-section.

Ore type description – metallurgical focusThe copper mineralisation is contained within a synclinestructure. Historically, the near-surface materialcontained generally oxidised copper minerals such asazurite and malachite, then a minor transitional zoneprior to a significant underlying chalcocite zone. Atdepth, the mineralisation is unweathered (or fresh) andis chalcopyrite. The oxide, transitional and chalcocite- bearing ores were treated through a heap leach operationwhich has since been put onto care and maintenance.

The chalcopyrite is quite coarse-grained, varying froma minimum of 50 mµ diameter up to very large grainsof several millimetres in diameter.

Within the ore zones there occurs fairly narrow bandsof interbedded shale. These are generally graphiticin nature and free floating and tend to contaminate

the copper concentrate. It is within these zones thatconcentrations of deleterious gangue elements such asfluorine (as fluorapatite) and uranium occur. The effectof these free-floating graphitic minerals was noted to be assessed through variability testing in the feasibilitystudy test work program.

The large grain sizes of the chalcopyrite allow arelatively coarse grind size for the Nifty sulfide to stillachieve the design metallurgical response in termsof copper recovery and concentrate grade. The lackof significant quantities of competing minerals suchas pyrite and base metal sulfides within the ore zone

allows for a relatively simple flotation circuit.

MINING OPERATIONS

OverviewThe current mining operations at Nifty consist of asingle underground mine, which produces copper oreutilising the mechanised technique of longhole openstoping with paste fill in order to maximise extractionfrom the economic deposit. The operational cut-off forthe mine is approximately 1.2 per cent Cu, dependingon economic modelling.

Geotechnical descriptionThe in situ ground conditions at Nifty are good to fair.The underground mine utilises paste fill (paste with tails

and Minecem) in order to achieve close to 100 per centmining extraction of the economic orebody. In general,the stoping parameters used at Nifty are 25 m by 25 m,with some double stoping applied (25 m by 50 m) wheregeotechnical conditions permit.

In response to several paste fill issues, a number ofstrategies are being pursued to improve the quality ofthe paste fill and allow for safely optimal ore extraction.The company has recruited additional members tothe technical services team. External consultants have been engaged to provide technical support to the pastefill system. Paste fill walls are being monitored forfailure and results are being applied to future designs by means of pressure cells and piesometers. Modellinginformation is retrieved to ascertain the safety andstrength of barricades. Actions to be completedinclude:

•

development of a paste fill management system • enhancing quality control systems with new testingand monitoring equipment for use in the laboratoryand in the field, including a unconfined compressivestrength machine, point load tester, penetrometersand vanes

• increasing quality testing in order to furthercharacterise the paste fill product

• investigating alternative binder materials that willfurther optimise the paste fill system

• updating training of all stakeholders.Each stope is systematically cable-bolted in the crown,

drawpoints and slots. Development intersectionsare systematically cable-bolted and wide drives areassessed for cable-bolting requirements.

Mine planning practices and proceduresThe Indian financial year (1 April to 31 March) is used asthe basis for reviewing/updating mining inventory andlife-of mine-planning. The long-term mine planningfunction is carried out using Mine2-4D and EPS. Thisgenerally fits in with the resource and productiongeology functions on-site, both of which are carried outwith the use of Datamine Studio.

Due to the skills shortage experienced in the industryover recent years, much of the long-term planning forNifty has been carried out using consultants and/orcontractors. Recently, there has been a concerted moveto bring the long-term planning function in-house andon-site. For the financial year 2012/2013 this has begunand remains ongoing.

Short-term mine planning, including developmentdesign and drill and blast design, is carried out on-sitewith the use of Surpac and RingKing. Microsoft Excel isused to create short-term plans and schedules (weekly

and three-month rolling) although, together with themove to in-house and on-site long-term planning, theshort-term planning activities will increasingly use or be supplemented with EPS and Mine2-4D.


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Mining process and equipmentNifty utilises a mining method of longhole open stopingwith fill. Mine control records production data withthe use of PitRam. Pump stations located in the mineinclude SP2, SP10 and 21 mono. These stations house86 configured and 103 configured monos which pumpapproximately 80 m 3/s from the mine.

Production from the mine is sent to the surface utilisinga crusher conveyor system from a central locationunderground (16L). The mine has a mobile fleet of 7 ×60 t Atlas trucks (6020), 1 × 0010 Toro, 1 × 1700 Cat and4 × 2900 Cat loaders. There are also 3 × D420 Tamrock jumbos, 3 × Solo 7 Tamrock longhole rigs, 1 × Cabolt 7-5Tamrock rig, 3 × IT28G and 2 × Volvos. Maintenance ofall fixed and mobile plant in the mine is done in-house,with planned shutdowns utilising additional contractpersonnel if required.

The primary ventilation circuit at Nifty is throughthe use of twin 450 kW, twin 275 kW and four 90 kWfans. Fresh air through the decline and a single raise bore from the surface deliver air into the mine, withexhaust air then removed through two return air risesand two escapeways to the surface. Table 2 summarisesthe mining equipment list.

Ore control and reconciliation proceduresThe cut-off determination for development andstope block ore is 0.5 per cent Cu and 1.2 per cent Curespectively. The ore grade is controlled on a daily basisvia software tracking of ore haulage and stope sampling.The sampling allows for an updated geological blockmodel. One sample is collected per production stope ona continuous 12-hour rotation. The samples are crushedto achieve a size of approximately 3 mm, then split,pulverised and sent to the laboratory for assaying. Daily,weekly and monthly reconciliations are performed toassess stope performance. Ore extraction from stopesand development is planned on a daily basis as per therequirements and constraints of the concentrator.

Innovation and improvementIn 2011, Nifty received a new fleet of 60 t Atlastrucks, which replaced the old fleet of 50 t Toro

trucks. Currently there are also plans to increase theventilation capacity/circuit in order to accommodatenew extensions to the mine.

PROCESSING OPERATIONS

Mineralogy and characterisationChalcopyrite is the dominant copper mineral with traceoccurrences (


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between the LCU and MCU units, extending across theentire deposit but at varying thickness (it tends to bethicker at the western margins). Graphitic shale occursmostly in the hanging wall, although some does occurin the footwall. Any over-breakage from the hangingwall will result in increased levels of carbonaceousmaterial in the plant feed; carbonaceous materialconsumes reagents and is naturally floating, resultingin low-grade concentrate and low copper recovery inflotation. The graphitic material tends to occur in arelatively consistent layer across the orebody. Stopesmined against the hanging wall will, therefore, tend tocontain more graphitic material than stopes within theorebody and adjacent to the footwall. It is interestingthat the monthly mineralogical investigationsconducted by Australian Laboratory Services (ALS) donot report carbonaceous minerals, only carbonates suchas dolomite, magnesite and siderite.

Pyritic shale generally occurs in the footwall and tendsto have a framboidal crystal structure. Framboidalpyrite generally is a reactive form of pyrite due to agranular, irregular surface. In some operations, organicmatter packs into the irregular surface, making thepyrite hydrophobic such that it readily reports to thefroth concentrate. This can occur during processing(especially grinding), where graphite can be pushed intoor smeared into the indentations on the pyrite surface.Euhedral and anhedral pyrite, formed at a later stagein the geological development of the deposit, tends tooccur within the ore zone but rarely with chalcopyrite.Pyrite is not logged or used to classify ore types. Thelocation of production stopes therefore influences thevariability of ore feed to the plant.

Process descriptionCommissioning of the Nifty sulfide concentrator beganin March 2006. Run-of-mine (ROM) ore was trucked tothe surface ROM pad, crushed through a jaw crusherand fed directly into the mill. The underground gyratorycrusher was commissioned in 2007, with crushed oreconveyed to the surface and discharged into a 100 tcapacity surge bin from which ore is fed directly to the

semi-autogenous grinding (SAG) mill. This arrangementallows for several options to feed the concentrator. Thegrinding circuit comprises a SAG mill and ball millwith classifying cyclones and a flash flotation machine.Cyclone overflow is directed to rougher and scavengingflotation machines to recover the copper minerals. Therougher and scavenger concentrates are upgraded inthe cleaner flotation circuit to approximately 25 percent Cu. The final copper concentrate is thickened andfiltered prior to dispatch by road to Port Hedland, fromwhence the concentrate is shipped to the smelter. AdityaBirla Mineral Limited has a long-term agreement for

sale of copper concentrate with smelters in India.The concentrator flow sheet is shown in Figure 5. The

processing equipment and consumable lists are givenin Tables 4 and 5 respectively.

Plant overview The grinding circuit is configured to enable ore to befed straight from underground and/or from the upperROM crusher. The ROMs are operated to meet andcontrol copper grades and production.

The grinding circuit comprises a SAG mill that is opencircuit and a ball mill operating in closed circuit witha cyclone cluster and flash flotation machine treatingore at a rate about 350 t/h, with a ball charge of up to13 per cent by volume. Classification is carried out by acluster of six cyclones. Currently there are four 650 mmdiameter cyclones and one 500 mm diameter cyclonefitted, with options to run five 500 mm cyclones. Thefive 500 mm diameter cyclones were retrofitted inplace of 650 mm diameter cyclones as part of a trial toimprove classification efficiency.

All the cyclones are of CAVEX design supplied byWeir Minerals. Two 650 mm diameter cyclones arerequired for operation at a time, each with 150 mm

ceramic spigots and an average operating pressure of60 kPa. The target cyclone overflow density is 38 percent solids and the underflow typically is 75 per centsolids with a circulating load of 250 per cent.

Item Number, size, manufacturerand installed power

Comminution

SAG mills 1×

5.5 MW SAG millSecondary ball mills 1 × 2.5 MW overflow ball mill

Flotation

Flash flotation 1 × SkimAir SK240 cell

Roughers/scavengers Rougher 1 × 70 m 3 tank cell (TC70),Scavenger – 5 × 70 m 3 tank cells(TC70)

Cleaners Rougher cleaner 3 × OK-8 cells

Cleaner scavengers Scavenger cleaner 6 × OK-8 cells,recleaner 3 × OK-3 cells

Concentrate thickeners 16 m concentrate thickener

Concentrate filters Andritz filter press

TABLE 4Concentrator equipment list.

Item g/t

125 mm grinding media 900

50 mm grinding media 560

Slaked lime 1461

Xanthate 246

Frother 98

Flocculant 14Antiscalant 18

TABLE 5Concentrator consumables/reagents list.


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FIG 5 - Flow sheet of the concentrator at Birla Nifty.


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The cyclone underflow can be diverted between the ball mill and SAG mill by adjusting a dart plug in thecyclone underflow distribution box to relieve excessiveflows to the ball mill or to allow continued productionat a lower rate if the ball mill is off-line for any reason.A portion of the cyclone underflow is also directed to

a SkimAir SK240 flash flotation cell. Concentrate fromthe SK240 gravitates to the concentrate trash screen andreports directly to final concentrate. Tailing goes to the ball mill feed box.

The flotation circuit is run to optimise copperconcentrate grade at ~25 per cent Cu and to maximiserecovery of copper, which is generally in the range of92 to 94 per cent recovery. There is a total of six 70 m 3 Outotec tank cells, one rougher cell and five scavengercells.

The main flotation cells are operated with levelcontrol in a two-two-one configuration. Each cell is a70 m³ tank cell fitted with a donut launder, providinga surface area of 7.94 m 2 and launder lip length of17 m. The concentrate generated by the rougher cell ispiped to the rougher cleaner feed hopper. The rougherconcentrate is upgraded to final concentrate gradein the rougher cleaners, which consists of three OK8conventional cells.

The cleaner cells have front launders only, providinga lip length of 2.4 m and surface area of 4.1 m 2 foreach cell. Concentrate is piped to the concentrate trashscreen and tailing reports to the scavenger cleanerfeed hopper. The pulp level (froth depth) of all cellsis controlled using a ball float and angle transmitterarrangement working with a pinch valve. A bank of sixOK8 cells in a three-three configuration comprises thescavenger cleaner stage.

The flotation concentrate streams are directed to theconcentrate trash screen to remove wood pulp and trashand then pumped to the Frothbuster located on the16 m diameter concentrate thickener. The Frothbusterde-aerates the slurry and, in conjunction with theconcentrate thickener feed well design, prevents frothon the surface of the thickener, which would otherwise

result in loss of concentrate in the overflow waterstream that reports to process water.The Andritz press plate and frame concentrate

pressure filter has 2 m by 2 m plates. There are 52 plates,providing a total filtration area of 208 m 2. Filter cycletimes range between 18 and 20 minutes and between13 and 16 t of concentrate is filtered each cycle. Theconcentrate is dewatered to a moisture content ofcirca 9.5 per cent (or as required). The main focus offiltration is to produce a product that is suitable forsale and transport. The upper moisture is set by thetransportable moisture limit.

Process control and metallurgical accountingOperation and plant optimisation at the Niftyconcentrator is aided by the use of OsiSoft’s Pi

Process book. The plant itself is controlled via a Citectsupervisory control and data acquisition (SCADA)system, which relays all data points to Process bookfor data analysis and visualisation. To improve plantperformance a number of moisture, density and flowanalysers are installed throughout the plant. The mostsignificant of these is the Outotec on stream analyser(OSA) that uses X-ray fluorescence. The analysersamples across the flotation circuit, ensuring targetrecovery and concentrate grades are achieved. AnOutotec particle size indicator (PSI) monitors the feedsize distribution for flotation performance and tails/concentrate streams for settling control in the respectivethickeners.

Tailings storage and water managementFlotation tailing gravitates from the last scavenger cellinto the feed well of the 24 m diameter tailings thickener.The tailings are thickened to 65 per cent solids andpumped to the paste plant or, when not producingpaste backfill, to the tailings storage facility (TSF). Theuse of flocculant in the paste filter feed has enabled useof the full tailings for generating paste by increasingthe filtration rate and matching tailings tonnage to thecapacity of the filter.

Concentrate logisticsThe filter capacity ranges from 440 t/d (dry) to amaximum of 1050 t/d (dry), with a daily average of675 t (dry). The concentrate is trucked from site to

the storage facility at Port Hedland using road trains.Between four and ten trucks are used depending onshipping requirements to maintain stock levels onsite and at port. Generally, parcels of 18 000 t (wet) ofconcentrate are shipped on a monthly basis, dependingon production. Concentrate produced is shipped toHindalco Copper’s Dahej smelter in India and refinedas per the take-off agreement.

Innovation and improvementsTwo of the most significant process improvements have been the implementation of the lime slaker and the mill

upgrade to increase throughput and process efficiency.The use of lime instead of caustic as a pH modifier hasproven to be a very successful process improvement,impacting both grade and recovery the depression ofpyrite and improving float stability.

In early 2009 it was decided to concentrate onincreasing the mill availability and productivity anda project was implemented to increase the throughputrate. The mill throughput rate had plateaued andimprovement was tapering off after commissioning, so astudy was conducted to evaluate mill performance andways of improving efficiency. The following measures

were put in place to change grinding efficiency: • The SAG mill speed was increased closer to critical

speed by changing the pinion gear, giving anapproximately 4.8 per cent speed increase.


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• The SAG mill lifter bar angles were decreased to 15 ° to allow greater impact at the toe of the charge. TheSAG mill ball size was increased from 100 mm to125 mm.

• The SAG mill charge volume was decreased. • The surface area of the pebble ports was increased to

increase the release of hard material.This has allowed the concentrator to increase

production and throughput rate each year to maintaincopper production for the life-of-mine.

Planned upgrades in the flotation circuit are currently being developed via an engineering study. Works willinclude the installation of a second rougher flotationcell and an increase in the cleaning capacity withthe installation of other cleaner cells. The additionalflotation capacity due to the addition of another roughercell will have a number of benefits including:

• increased stability in the cleaning circuit by extrarecovery up front

• decreased effect of head grade spikes on the rest ofthe circuit

• increased overall recovery by increasing the lengthof time for material to be recovered.

Installation of a coarse ore stacker is under way inorder to minimise the variation in the feed to the mill.This will help to achieve stability in the flotation circuit,which will further minimise the loss of copper into thetails stream.

The processing strategy is one of continuousimprovement to increase both efficiency and product-ivity in the plant to and maintain copper productionas the resource and underground grade decrease,maximising life-of-mine and copper production.

CHEMICAL PROCESSING OPERATIONSThe copper oxide operation commenced in 1993 under adifferent owner and was suspended (placed under careand maintenance) in January 2009 after approximately15 Mt of ore had been leached using a heap leachingprocess and the solutions treated through a SX/EW

circuit to produce copper cathode. The SX/EW circuit iscurrently under care and maintenance. Approximately15 Mt of ore is stacked on the leach pads, with anestimated copper grade of ~0.5 per cent.

The initial capacity of the plant was 16 500 t/a ofcathode, using five Krebs SX mixer/settler units and102 EW cells. In 1998, the plant capacity increasedto 25 000 t/a of cathode with the addition of four SXunits (three Krebs type and one standard type) andan additional 46 EW cells. Rectifier capacity was alsoincreased from 4.6 MW to 7.5 MW.

One of the major issues associated with the treatmentof material was the imbalance between the harderores, the coarser ores and the weathered shales. Thelatter material was of a very fine nature and unsuitablefor heap leaching itself. Coarse material was blended

with the weathered shale to produce a workable heapleaching feed. In general, if the -75 mµ component ofore or blended ore exceeds 15 per cent there may bepercolation issues under normal leaching conditions.

Mineralogy and characterisation

The current Nifty heap leach pads (HLPs) contain15 Mt at an estimated grade of slightly above 0.5 percent Cu; this equates to approximately 75 000 t ofcontained copper. The predominate copper mineralsare malachite, azurite and chalcanthite, with minorchalcopyrite, chalcocite, cuprite and native copper.Apart from the last four minerals, these are readilydissolved by sulfuric acid, with intrinsic yields in theorder of >95 per cent.

Table 6 summarises the known mineralogy in typicalNifty oxidised shale ore. Archival data indicate thatkaolinite can range up to 17 per cent of the total mass,with the combined muscovite, biotite, chlorite andkaolinite ranging up to 35 per cent. These figures areof significance in heap leaching, as phylo-silicates areextremely fine and soft, which explains the heavyclay nature observed in all of the current heaps underirrigation.

Process descriptionWMC commenced an open pit, heap leach, SX/EWoperation on the relatively high-grade part of the oxidemineralisation in 1993. Open pit mining operationsceased in June 2006 and heap leaching operationsceased in January 2009.

Chemical formula SiO 2/Al2O3 ratio

SG

Quartz SiO 2 2.62

Muscovite KAl2(Si3Al)O10(OH,F)2 1.1785 2.82Biotite K(Mg,Fe++)3AlSi3O10(OH,F)2 3.5357 3.09

Orthoclase KAlSi 3O8 3.5349 2.56

Andesine (Na,Ca)(Si,Al)4O8 2.1889 2.67

Chlorite(corrensite)

(Ca,Na,K)(Mg,Fe,Al)9(Si,Al)8O20(OH)10.n(H2O)

2.3579

Albite NaAlSi3O8 3.3115 2.62

Kaolinite Al2Si2O5(OH)4 1.178 2.6

Dolomite CaMg(CO 3)2 2.84

Calcite CaCO 3 2.71

Malachite Cu 2(CO3)(OH)2 3.8Azurite Cu 3(CO3)2(OH)2 3.83

Cuprite Cu 2O 6.1

Chrysocola (Cu,Al) 2H2Si2O5(OH)4.n(H2O)

9.4304 2.15

Native copper Cu 8.94

Chalcocite Cu 2S 5.65

Chalcopyrite CuFe S2 4.19

TABLE 6Mineralogy of typical Nifty oxidised shale.


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The process flow sheet is shown in Figure 6 and theprocess equipment list is given in Table 7.

During the period of operation, ore was fed to the jawcrusher at 300 t/h. The crushed product was sent to adouble-deck screen where the oversize was recycledto a cone crusher and the undersize proceeded tothe agglomeration drum. Sulfuric acid and waterwere mixed to create an agglomerated product. Theagglomerated product discharged onto a conveyorand was sent to a stacker, which then distributed theproduct onto the leach pad. By the end of 2008, 15 Mtwere stacked. The leaching process continued with thetop layer of each heap being leached with acidic solutionconsisting of raffinate (low copper leach solution) andintermediate copper leach solution (ILS).

The leaching process begins from the raffinate pond(SX tailings discharge), where 850 m 3/h is pumpeddown a pipe, extending from the beginning to the endof the heap pads. This irrigates the lowest producing/extracting copper pads. The discharge from these leachpads has a copper content of two to three per centcopper. The solution is diverted into the ILS ponds viathe W-drains (two pathways which travel along thefront of the leach pads to receive the discharge fromthe pads which can go to the ILS and pregnant leachsolution (PLS) ponds.

One thousand, two hundred cubic metres per hour ispumped from the ILS ponds to the remaining pads, withthe discharge being sent to the ILS (150 m 3 of the lower

copper content discharge) and PLS (850 m3

of highercopper content solution) ponds via the W-drains.

FIG 6 - The solvent extraction and electro-winning flow sheet.

Item Number, size, manufacturer

Mixer/settlers 8 units, Krebs

Coalescer 1 unit, 80 m 3

Circulating tank 1 unit, 289 m 3

Wash tank 1 unit, 134 m 3

Loaded organic tank 1 unit, 60 m 3

Jameson cell 1 unit, 5 m 3

Filter press 1 unit, Diemme

Acid storage 10 000 m 3

Reagent mixing tanks 2 units, 1 m 3

EW cells 146 units, 33 cathodes

Heat exchanger 1 unit

Rectifier 1 unit, 7.5 MWStripping machine 1 unit, 100 cells/day

Spintek filters 4 units, 43 m 3 capacity

Cathode sampling hole press 1 unit

Anode wash box 1 unit

Agglomerate drum 1 unit

Jaw crusher 1 unit, Nordberg C125B 150 kW

Cone crusher 1 unit, Nordberg HP300 220 kW

Double-deck screen 1 unit, Metso, 2.45 m × 6.1 m

Stacker 1 unit

Overland conveyor 1 km

TABLE 7Solvent extraction and electro-winning plant equipment list.


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Bore water is pumped in to the ILS and raffinateponds to maintain the levels due to evaporation fromthe ponds and heaps. The required addition rangesfrom 150 to 200 m 3/h. Sulfuric acid is added to the ILSponds to ensure the free acid content is maintained at2 - 4 g/L.

Solution from the PLS ponds (850 m 3/h) with a coppercontent of 2 - 4 g/L is sent to the SX plant, where theflow is diverted to two circuits consisting of mixers andsettlers (extraction and stripping settlers). Four hundredand fifty cubic metres per hour is sent to circuit A and400 m3/h sent to circuit B. The solvent extraction circuitconsists of two stages: extraction and stripping. Thecircuit is run in an organic continuous phase (higherratio of organic than aqueous in the solution), where theorganic and aqueous solution run in a counter-currentdirection to each other. The aqueous phase refers to thePLS solution and the organic phase refers to the diluent(Shellsol 2046, containing a 20 per cent concentration ofcopper extractant LIX 984N).

Both loaded aqueous solution (PLS) from the heapleach barren organic (circulating in the SX plant) at aratio of 1:1.2 (aqueous:organic) enters the mixer at thestart of the extraction stage. The mixing allows theextractant to interact with the aqueous phase (PLSsolution) and remove the copper from the aqueousphase and into the organic phase (diluent). Thismixture of aqueous and organic phase proceeds to thesettlers, where the organic phase is separated from the

aqueous phase by natural difference of specific gravity.Once separated in the settler, the organic and aqueousphases move in a counter-current direction throughthe extraction circuit. As the organic and aqueousstreams move through the extraction circuit, the coppercontent of the barren organic (10

TABLE 8Electrolyte operating parameters.


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Studies have been conducted on the leach pad materialand the following methods have been proposed toextract the remaining copper in the heap pads: • Removal of slimes: the existing leach pads are re-

mined and the copper-containing material is fedinto a hydrosizer. The problematic clay material isremoved via the overflow and the underflow thenre-stacked on the leach pads to be leached withacidic solution. The removal of the clay materialwill allow greater percolation of the acidic solutionthrough the leach pads, enabling a higher extractionof the copper from the restacked leach pads.

• Continuous vat leaching: the existing leach padsare re-mined and the copper-containing materialprocessed through a continuous vat leach wherethere is no restriction of contact between the acidsolution and the copper minerals, enabling a highextraction of the copper.

ENVIRONMENT AND COMMUNITYBNCO operates under the following licenses andcommitments: • Western Mining Corporation Limited (Throssell Range)

Agreement Act 1985 , WA State Agreement • WA Department of Environment and Conservation

(DEC) Prescribed Premises environmental operatinglicense – groundwater monitoring, tip management,wastewater treatment, emissions to air, land andwater and annual reporting

• Department of Water abstraction licenses for

3 730 000 kL for dewatering and 75 000 kL for processand potable water • National Greenhouse and Energy Reporting (NGER) • National Pollution Inventory (NPI).

Hydrocarbon management infrastructure is in theprocess of being evaluated and upgraded in order tomeet compliance with the DEC license.

There has been a commitment to improve theenvironment impact at site in several areas. Two of themain challenges that Nifty faces are the managementof the SX/EW, due to ageing infrastructure thatneeds constant work to prevent spillage, and thewater management on-site. These two areas will beconcentrated on in future works.

BNCO has invested substantially in developing amine closure plan, which will be submitted in 2012. Themain domains that require closure planning are the pit,TSF, heap leach pads and the waste rock dump (WRD).Materials characterisations of WRD, HLP and tailingshave been conducted. Erosion potential and slopestudies have been conducted in order to design a WRD batter that will support a sustainable rate of erosion. A 2ha rehabilitation trial has been constructed on the WRD

in order to test various cover designs for a final WRDlandform. Hydrology studies are ongoing in order tocalculate a final pit water level and quality at closure.

The environmental department also managesongoing issues with dingo/human interactions, wildlifemonitoring, stormwater management, scrap metal andpoly pipe recycling, and addresses the understandingof the near- and long-term water balance.

OCCUPATIONAL HEALTH AND SAFETYBNCO safety management system (SMS) is derived

from the site safety management plan (SMP). Thesafety management plan encompasses a three-element business process incorporating people, managementand process as follows.

1979 WMC explored the region for copper, zinc and lead

1981 Mineralisation first discovered; became known as the Throssell Ranges Project

1983 A high-grade primary sulfide orebody resource and secondary oxide reserve were delineated

1983 - 1992 A series of feasibility studies were completedSeptember 1992 WMC committed to develop the deposit

November 1992 Mining contracts awarded; prestripping of overburden commenced

November 1993 Nifty's first month of production

December 1997 Total production since commencement 40 000 t of cathode copper

10 November 1997 WMC announced intention to sell the operation

1998 Plant capacity increased to 25 000 t/a of cathode – additional 46 EW cells and four SX units installed

13 July 1998 Straits announced agreement to acquire the Nif ty Copper Operation

30 October 1998 Completion of Nifty acquisition by Straits, with settlement on 18 November 1998

10 March 2003 Aditya Birla Group acquired the Nifty Copper Operation

June 2006 Open pit operations shut downJanuary 2009 Leaching operations shut down

TABLE 9History and basis of solvent extraction and electro-winning flow sheet.


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The people element includes: • occupational rehabilitation • work method statements • inductions and training • incident/accident investigations and corrective

actions • roles, responsibilities and accountabilities • hazardous work activities • hazard identification and risk assessment.The management element includes:

• information and reporting • legal and legislative obligations • employee communication and involvement • management commitment and planning.The process element includes:

• procurement • design safety • inspection and testing • management of change • formal workplace inspections • industrial hygiene and atmospheric monitoring • audits and system improvement.The SMS is supported by a INX data control system.

This system provides a site-wide framework forrecording and correlating safety information, enablingthe organisation to monitor safety performance,auditing, trends, hazards and events. Additionally, thesystem provides an overview of compliance with bothstatutory and organisational requirements. This systemprovides the ability to measure performance and assistin the implementation of change management processes.

MANAGEMENT AND ORGANISATIONTable 10 lists the staffing numbers by functional section/department.

Human resources challengesThe human resources (HR) department underwent areview in 2012 and is now well-placed to capitalise onthe many opportunities BNCO offers, with a permanent

HR superintendent and HR officer in place. This is bolstered by a Perth-based corporate HR functionconsisting of a head of HR and a recruitment officer(servicing the Nifty and Mount Gordon operations).

Site HR policies and procedures are being reviewed to better align with business goals and the creation of one-and five-year strategic management plans is underway.The key to successful site based HR is taking a proactiveapproach to engaging the employee base, and the HRdepartment is committed to fostering an inclusive, bestpractice culture on-site.

The major challenges facing the HR departmentat BNCO are inherent to all metalliferous miningoperations in Australia: the attraction and retentionof skilled employees. With mega-projects beginningconstruction in oil and gas and large-scale capitalinvestment in iron ore it is difficult for base-metal-orientated companies to compete on salaries alonefor employees. While BNCO base salaries are verycompetitive, it is the lengthy mine life of at least eightyears that is a point of difference, as there is stabilityof employment and a chance to develop a long-termcareer. With a lifestyle and family-friendly eight dayson, six days off roster, BNCO is well-placed to becomean employer of choice.

The HR department uses a traditional approachto recruitment, with a combination of direct onlineadvertising, internal networks and referrals, contractors,

recruitment agencies and labour hire companies.Wherever possible HR strives to employ people direct,as that is the preferred option to long-term contractors;it is more cost effective in the long-term and builds astable employee base. The HR department is committedto internally promoting and transferring staff intovacancies whenever possible to reward loyalty andfoster a learning culture.

A six-person training team completes the BNCO HRdepartment and manages a proactive training planaimed at upskilling workers with nationally accreditedtraining, including apprenticeships, traineeships andvarious certificate I, II, III and IV courses. BNCO is well-positioned to capitalise on attracting staff who wantlong-term, steady employment and a defined careerpath.

RISK MANAGEMENTBNCO has a risk management system using a top-down model. The major risks have been identified andranked by independent insurance assessors and themanagement team. Each risk has been given a rankingand, where prudent to do so, a strategy has been put

in place to manage the risk. This allows key areas thatmay cause major business interruptions to be managed,mainly through the identification and purchase ofcritical spares.

Department Number

Administration 7

Supply/stores 16

Occupational health safety and environment 15

Engineering 221

Mining 192

Concentrator 74

Village 38

Total 563

TABLE 10Staffing numbers by functional section/department.


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Major events have been identified and strategies andprocedures have been put in place, such as a floodand cyclone preparedness procedure and a lightningprocedure which clearly state actions that need to betaken to manage the risks in such events. From this flowstandards and procedures that set out the company’spolicy, which lead down to safe operating procedures, job safety environment analysis (JSEAs) and take fives,where risks are identified and managed on all levels.

All contractors are expected to provide an occupationalhealth and safety management system before comingto site and must comply with all company policiesand standards. This includes meeting all applicableAustralian standards and guidelines.

REFERENCESCarver, R N, 2004. Nifty Copper Deposit, Great Sandy Desert

Western Australia [online], CRC LEME. Available from:.


ch07_birla nifty.pdf

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