Council for Mineral Technology

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Council for Mineral Technology
Developments in the hydrometallurgical processing
of base metals and uranium 24 February 2009 Dr.
Roger Paul General Manager Technology
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Introduction

• Crude forms of hydrometallurgy were practised
  hundreds of years ago
• Lower grade and more complex ores, e.g. Ni
  laterites
• Metal recoveries are of increasing importance to
  be cost effective
• Metal purities more stringent for modern
  applications
• Technological advances, e.g. pressure leaching
• Major developments in materials of construction
• Environmental and energy issues around smelting
  technologies

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Outline

• Cu recovery from sulphides, low grade ores
• Ni recovery from sulphides and laterites
• Co recent developments in Africa
• Uranium higher price initiated numerous projects
• Conclusions

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Escondida Sulphide Leach Chile

• Bioleaching (mesophiles)
• Low-grade, run-of-mine (ROM) ore with SX / EW
• Designed to produce 180 000 tpa copper cathode
• Project cost US 870m (includes desalination
  plant at Coloso)
• Production at plant began in 2007

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Mintek NICICOs Sarcheshmeh Mine, Iran

• Bioleaching (mesophiles / thermophiles)
• Pilot heaps (6 m height, 20 000 t)
• Ore 100 passing 25 mm, transitional (53 of
  Cu(T) as CuFeS2)
• Maximum temperatures up to 55C
• Cu dissolution 60 (200 - 300 days)

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Other

• Pacific Ores BioHeapTM process
• Completed a 4 500 t pilot heap facility, inner
  Mongolia
• Microbial assisted leaching of low-grade, copper
  mineral sulphide (whole) ores
• Geobioticss GEOLEACHTM process
• Low-grade, copper mineral sulphide (whole) ore
• Mesophiles, moderate and extreme thermophiles
• Planning demonstration heap at Quebrada Blanca
  Mine, Chile

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Outotecs HydroCopper
HydroCopper Process Block Diagram
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Outotecs HydroCopper

• Atmospheric Leaching
• Concentrate (CuFeS2) leaching in acidic, chloride
  medium use of chlorine / oxygen
• Chloride stabilizes Cu(I) which is precipitated
  as CuO before melting
• Produce high-quality copper powder (LME A Cu
  cathode equivalent), which can be melted and cast
  in required form
• Process produces no sulphuric acid
• Can treat variety of copper concentrates (incl.
  lower grades)
• Reduced capital and operating costs with process
  plant near concentrator (transportation / storage
  needs eliminated)
• Reagents regenerated (chlor-alkali electrolysis
  step)
• Gold and silver recovered
• Closed water circulation efficient handling of
  process off-gas
• Residues (leach) S0, hematite or goethite

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Outotecs HydroCopper

• Presently, engineering a commercial plant for
  Mongolian Erdenet Mining Corporation (Mongolia)
  to produce 50 000 tpa copper wire rod
• Another plant to be build (27 000 tpa) for
  Zangezur Copper Molybdenum Combine AGs mine in
  Karajan, Armenia

Demonstration Plant in Pori, Finland
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GalvanoxTM
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GalvanoxTM

• Atmospheric Leaching
• Primary copper sulphide (CuFeS2) concentrates
  leached in acidic, iron sulphate medium
• Enhanced dissolution kinetics achieved by means
  of pyrite (FeS2) as catalyst
• Copper recoveries of 98 in 4 h residence time
  more typically, 20 h, 80C (depending on extent
  of FeS2 recycle)
• S0 formation
• Compatible with SX / EW
• Used in combination with high-pressure autoclave
  for acid, heat and Fe(III) generation
• Enhanced enargite (Cu3AsS4) dissolution kinetics
  also achieved with FeS2 as catalyst
• Arsenic converted into environmentally stable
  scorodite

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Sepon Process Flow Diagram
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Sepon

• Atmospheric / Pressure Leaching
• Secondary Cu-sulphide concentrates leached in
  acidic, iron sulphate
• Used in combination with high-pressure autoclave
  for acid, heat and Fe(III) generation
• Commercialized successfully Sepon Plant, Laos
• Could be modified for primary copper sulphides
  (CuFeS2)
• Main difference with respect to GalvanoxTM
  process
• GalvanoxTM CuFeS2 treated in atmospheric
  leach
• Equipment size, capital and operating costs
  not linked to primary copper sulphide content of
  feed
• Sepon CuFeS2 treated in high-pressure
  autoclave
• Equipment size, capital and operating costs
  directly linked to primary copper sulphide
  content of feed
• Arsenic bearing concentrates conversion into
  environmentally stable scorodite

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Sepon Copper Project, Laos
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CESL Process Flowsheet
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Teck Comincos CESL Process

• Pressure Leaching
• Can treat nearly all copper concentrates (incl.
  CuFeS2) (both high and low grades)
• High metal recoveries of 96 to 97 to LME Grade
  A Copper
• Reagents recycled
• Elemental sulphur (85 to 95) and hematite
• Low Capex and Opex
• Efficient / economic recovery of precious metals
• Handles common impurities well
• Net user of water (no effluent)
• Moderate energy consumption (3200 kWh / t Cu
  incl. oxygen plant)
• Construction of Usina Hidrometalúrgica Carajás
  (UHC) prototype plant recently completed (10 000
  tpa Cu cathode). Near Carajás, Brazil where Vale
  operates Sossego copper mine

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UHC Project, Brazil
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Morenci Flowsheet
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Freeport - McMorans Morenci

• Pressure Leaching
• Bagdad (Phelps Dodge) demonstration plant medium
  temperature pressure leaching of copper
  concentrate with direct electrowinning (DEW)
  (commercial demonstration, 2005)
• Morenci Western Copper concentrate mixed
  chalcopyrite, covellite, chalcocite, pyrite
• 215 000 tpa of concentrate (grade 34 Cu)
• 147 million pounds Cu produced per annum
• 97 Cu recovery
• Capital cost US 250m (incl. concentrator
  refurbishment , concentrate leach facilities)
• Commissioning / start-up 2007
• Pressure leach vessel systems, L/S, DEW, silica
  removal, construction materials working well to
  date

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World Nickel Resources
Bacon, 2004
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Tati Nickel Flow Diagram

• Treating lower grade Ni-sulphide concentrate

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Tati Nickel Approaches

• Ultra-fine milling lower temp leach
• S reports to leach residue
• Ni SX using versatic Mintek synergist
• The V10/Nicksyn system was more robust, and the
  circuit operation was simpler risk associated
  with gypsum minimised
• Higher recoveries of gt99.8 were achieved with
  minimal or no calcium co-extraction.
• The V10/Nicksyn system was operated with one
  less extraction stage, yielding higher
  recoveries. Potentially, two less extraction
  stages could be used.
• Ammonia for neutralisation
• Lime boil employing vibrating mill to limit
  impact of gypsum scaling

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Laterite Minerals

• Limonite, asbolite (1-1.7 Ni, 0.1-0.2 Co)
  suitable for PAL and Caron process
• Nontronite (1-5 Ni, 0.05 Co) suitable for
  PAL and smelting
• Serpentine (1.5-10 Ni, 0.05-1 Co) typical
  1-2 Ni suitable for pyromet processes
  (ferronickel and matte smelting)
• Garnierite (10-20 Ni, 0.05-1 Co) typical 2-3
  Ni suitable for pyromet processes (ferronickel
  and matte smelting, especially high C ferronickel)

Bacon, 2004
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Laterite Simple Process Routes
Malachite Consulting
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Laterite Simple Process Routes
Bacon, 2004
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Laterite Cost Comparison (Rusina)
Cost Comparison as presented by Rusina
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Goro Process Selection

• Pyromet route drying (ore 50 mositure)
  selective reduction/smelting high CAPEX and
  energy poorer Ni and Co recoveries
• Relatively low saprolitelimonite ratio and
  relatively low Mg-content of saprolite hydromet
  HPAL route selected
• HPAL lower CAPEX and OPEX (energy consumption
  lower no drying required)
• Higher Ni and Co recoveries
• Ni and Co products sulphide ppt considered
  direct SX more cost-effective
• Fe3 and Cu2 to be removed efficiently prior to
  SX cause oxidation of reagent (regeneration of
  reagent part of flowsheet)

Bacon, 2004
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Goro Process Flowsheet
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CYANEX 301
Extraction curves for 15 vol. Cyanex 301

• No Ca, Mg and Mn extraction
• No neutralisation required for Ni, Co extraction
• Sensitive to Cu and Fe in PLS
• Stripping with HCl

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Goro innovative approaches

• Cu removal by IX to ensure very low level
• Cyanex 301 no extraction of Mn, Mg, Ca
• No neutralisation required for Ni, Co extraction
  (for limited concentration of Ni)
• Regeneration of oxidised Cyanex 301 on site
  (oxidation limited with use of BPCs)
• Switching of sulphate to chloride medium
• IX for Zn removal to low levels
• Should currently be commissioning

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Ravensthorpe Atmospheric and HPAL
Shipped to Yabulu for refining
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Laterites Heap Leach Developments

• Existing operations Murrin Murrin (Minara
  Resources)
• Committed projects Caldag (European Nickel)
• Projects in development
• Vale Inco
• Metallica (Queensland)
• GME Resources (WA)
• Rusina (Phillipines)
• Nickelore (WA)
• RMS (PNG)
• Concerns stability of heap and associated
  percolation efficiency

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Costs Various Process Options

• Why considering heap leaching when it is expected
  that it might be a challenge?

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Caldag European Nickel

• Heap leaching Caldag laterite contains low clay
  content
• 3 leach phases neutralisation (Mg leaching) (35
  kg/t H2SO4), primary (116 kg/t H2SO4) and
  secondary leaching (377 kg/t H2SO4)
• Primary leach intermediate product 33 Ni, 1.5
  Co
• Secondary leach intermediate product 25 Ni, lt1
  Co, 7 Mn

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Caldag European Nickel
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Co production Projects in DRC, Zambia

• Co market increased from 35 to 60 ktpa due to
  demand
• Price increased from US20 to US50
• Mintek evaluated many different flowsheets for
  numerous clients
• Various products targetted metal, hydroxides
  (low and high grade), carbonates, oxide
• Process options
• Classical precipitation using lime/limestone,
  MgO, Na2CO3
• Solvent extraction
• Price sensitive to the type of product and the
  Coimpurity levels
• Transport costs of reagents and products high
  products aimed at as high as possible Co content

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Oxidative Precipitation using Air/SO2

• Oxidative precipitation of Fe and Mn using
  air/SO2 received much attention from various
  institutes
• Very attractive process option, as SO2 generally
  available on site from either roaster or S-burner
• Fe can be oxidised quantitatively at relatively
  low pH values (2-2.8) within a reasonably short
  period (2 g/L within 1 hour)
• Mn oxidation done at somewhat higher pH values
  (3-3.5)
• Co losses to be minimised
• No commercial plant yet, Ruashi being
  commissioned
• Test work indicated that gas mixing, sparging and
  agitation critical
• Energy demand for agitation to be optimised

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Solvent Extraction

• Purification of Co stream DEHPA for Zn, Mn, Ca
• Ca extraction will result in gypsum precipitation
  in strip circuit when using H2SO4 as strip
  liquor, unless flowrate similar to PLS flowrate
  so that gypsum maintained below solubility level
• Strong extraction of Fe3 ? requires stripping
  with HCl
• Co SX using Cyanex 272 for Zn removal, and for Co
  recovery and separation from Ni
• More than one type of SX reagent in one circuit a
  major concern this can be designed to prevent
  contamination, but there is a risk
• Neutralisation required during purification and
  recovery of Co
• Contamination of effluent streams with dilute
  Na2SO4 is an environmental issue
• Future of SX for Co
• need to be able to produce a concentrated stream
  that will make crystallization viable, or
• neutralization by means of ammonia that could be
  recycled (lime boil an problematic operation)

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Classical Precipitation

• Precipitation with lime/limestone
• Readily available, relatively cheap
• Low grade Co (15-17 Co in dried solids)
• Mass/volume of cake cause complications when in
  loop with EW
• Transport costs/ton Co very high
• Precipitation with Na2CO3
• Environmental issue produce dilute Na2SO4
• Produce 40-50 Co product
• Can be calcined for further upgrading of product
• Precipitation with MgO
• Produced high grade Co product (40)
• Mg can be precipitated from barren stream prior
  to dumping
• Very expensive reagent
• Efficient use requires careful design
  considerations
• Impact on EW bleed can be large if reagent
  addition un-optimal

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Ion Exchange Co purification

• Purification of Co stream Zn, Cu, Ni, and more
  recently Cd
• Zn and Cu can be removed from the Co PLS stream,
  or advance electrolytes to the required levels
  (30 mg/kg in Grade A metal)
• Ni removal Dowex M4195 resin most effective
  option, but very costly
• Cd removal by IBCs Molecular Recognition product
  (10 mg/kg in Grade A metal)
• Ionex or Septor CCIX systems considered where
  resin cost high
• Ion exchange systems efficient to consistently
  achieve the required levels

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Uranium

• Revival after decades of inactivity!
• Previous technologies still valid for today
• Some new developments could make projects
  economically more viable, eg. direct SX using
  BPCs and RIP

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Bateman Pulsed Columns (BPC)
Mixer/Settlers BPC
Extraction Staged Continuous
Efficiency Lower for cost-effective of stages High
Entrainment Poorer Improved
Moving parts High Low
Maintenance High Low
Footprint Large Small
Solvent vapour loss Higher Lower
Safety Higher fire hazard Much lower
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BPC vs MS Stage Performance
Improved efficiency with marginal increase of
capital cost
Operating Line O A lt1
NTU 2
NTU 4
Org g/l
Operating line O A 1
Aqueous g/l
Raff Concentration
Bateman
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Olympic Dam recovery of Uranium by BPcs
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Uranium One BPCs Klerksdorp
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RIP - Metrix

• Mintek developed RIP for Au, base metals and
  uranium
• Currently testing 3 resins for their
  metallurgical performance in laboratory as well
  as durability in 2m3 Metrix plant
• Suitable for recovery and upgrading of uranium
  from pulps, especially where solid/liquid
  separation costly
• Kayelekera, Paladin Resources, Malawi currently
  commissioning RIP application

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Metrix Demonstration Plant
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Hydromet Challenges

• Cu chalcopyrite, especially ambient conditions,
  remains difficult especially for low grade ores
• Ni laterites a number of laterite projects to
  date have failed or performed poorly, so it
  remains a challenge to get it right
• Water availability and quality (now desalination
  plants part of CAPEX/OPEX of new plants)
• S and acid balance in world often not used where
  produced, transport costs high storage
  facilities limited
• All S used as H2SO4 needs to be neutralized and
  dumped

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Thank you
www.mintek.co.za