Integrated piloting of a thermophilic nickel-copper bioleaching process

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Integrated piloting of a thermophilic
nickel-copper bioleaching process Presented at
the SAIMM Hydrometallurgy Conference 2009 held in
Muldersdrift, Gauteng 24-26 February 2009 by John
Neale Biotechnology Division, Mintek
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The BioMinE project

• Biotechnology for the Minerals Industry in Europe
• Integrated Research and Technology Development
  project
• November 2004 October 2008
• 37 participating partners
• Overall budget 17.9-million
• EC contribution 11.6-million

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Minteks contribution to BioMinE

• Coordinator of the largest Work Package
  Bioleaching
• Development of integrated bioleach-based
  processes for the recovery of base metals from
  complex, low-grade sulphide concentrates
• Target resource Aguablanca nickel-copper
  concentrate
• Extensive bench-scale bioleach testing
• Integrated bioleaching and metals recovery
  pilot-plant campaign
• Most of Minteks RD effort was aimed at the
  bioleaching of chalcopyrite
• Chalcopyrite passivates in sulphate medium at
  35C
• Higher operating temperatures
• Finer grinding
• Addition of catalysts
• Redox control

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Bioleaching of base metal concentrates

• Early 1990s
• BioNIC integrated piloting and feasibility study
  (BHP Billiton)
• Mesophiles, moderate thermophiles (35-45 C)
• Late 1990s
• Kasese commercial bioleach plant for cobalt
  extraction from pyrite (BRGM)
• Mesophiles (35-40 C) 1,000 t/a of cobalt
  cathode
• 2001
• Demonstration plant and feasibility study for
  chalcopyritic copper, zinc and lead concentrate
  (Mintek/BacTech)
• Moderate thermophiles (45 C) 1 t/d of copper
• 2003
• Commercial demonstration plant for chalcopyrite
  concentrate containing arsenic (Alliance Copper)
• Thermophiles (70-78 C) 20,000 t/a of copper

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Demonstration and commercial plants
Kasese, Uganda
BioCOP, Chuquicamata, Chile
Mintek-BacTech, Mexico
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Aguablanca Mine, southern Spain

• Open-pit nickel-copper sulphide mine
• Located 80 km north of Seville, in southern Spain
• Owned by Lundin Mining Corporation
• Treatment plant commissioned in 2005
• 1.7 million tonnes of ore per annum

• Bulk concentrate 7.3 Ni, 6.9 Cu
• Concentrate shipped to a smelter
• Underground expansion being evaluated based on
  increased resource base

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Objectives and scope of work

• Proposition is to extend Aguablanca treatment
  plant with addition of a bioleaching and
  metals-refining facility
• On-site metal production
• Increase realized metal value
• Phase 1 test work
• Concentrate characterization
• Bioleach amenability testing
• Phase 2 test work
• Open circuit bioleach miniplant operation
• Bench-scale solution purification and metals
  recovery tests
• Phase 3 test work
• Integrated pilot plant testing
• Additional bioleach optimization tests
• Conceptual engineering study
• Preliminary economic evaluation

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Conceptual process flowsheet
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Concentrate description

• Reground to a d90 of 10-12 µm
• 28.9 Fe
• 24.4 S2-
• 6.29 Cu
• 5.24 Ni
• 6.28 Si

• 23.7 pyrite (FeS2)
• 20.7 pyrrhotite (Fe(1-x)S)
• 18.5 chalcopyrite (CuFeS2)
• 14.5 pentlandite ((Fe,Ni)9S8)
• 21.6 silicates

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Bioleach amenability tests

• Effect of temperature
• Three-stage continuously operated reactor system
• 6-day residence time
• 10  feed solids concentration
• Particle size of d90 10 µm

Microbial culture Metal extraction () Metal extraction ()
Microbial culture Cu Ni
Mesophiles (35 C) Moderate thermophiles (45 C) Thermophiles (70 C) 30 65 95 76 99 99
Single-stage reactor at 3-day residence time
Thermophiles at 70 C required for chalcopyrite
bioleaching
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Bioleach amenability tests
Effect of grind size
Operating conditions Cu extraction () Cu extraction () Cu extraction () Ni extraction () Ni extraction () Ni extraction ()
Operating conditions R1 R2 R3 R1 R2 R3
3-stage, 70 C, 10 µm, 6 days 3-stage, 70 C, 20 µm, 6 days 1-stage, 70 C, 35 µm, 3 days Batch, 70 C, 35 µm, 6 days 83.5 72.4 52.9 72.8 92.0 82.0 - - 95.1 90.7 - - 98.7 96.3 87.7 98.1 99.3 97.4 - - 99.4 97.4 - -
R1/2/3 Reactor 1/2/3
Regrinding to 10 µm a prerequisite for high
copper extractions
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Preliminary specifications for downstream plant

• Range of batch bench-scale tests performed
• Primary iron precipitation
• Solvent extraction
• Secondary iron precipitation
• Nickel hydroxide precipitation
• Magnesium removal
• Results used to set initial operating parameters
  for integrated pilot plant

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Integrated pilot plant
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Integrated bioleach plant performance

• Bioleach plant operated for 220 days
• Recycle loops closed
• Very stable operation
• Steady redox potential
• Stable oxygen uptake rates
• Swift recovery from process upsets
• No impact of recycle on process performance

• Sulphide oxidation 99.4
• Iron extraction 95.8
• Nickel extraction 99.3
• Copper extraction 95.0
• Bioliquor tenors
• 5.8 g/L nickel
• 5.6 g/L copper
• 17.9 g/L iron

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Effect of redox control
Feed R1 R2 R3
Microbial culture Temperature (C) pH level Redox (mV, AgAgCl)) Cumulative residence time (d) Feed solids concentration () Grind d90 (µm) Thermophiles 9.8 10 70 1.6 430 3.0 70 1.3 550 4.5 70 1.25 580 6.0
Fe (g/L) Cu (g/L) Ni (g/L) 14.5 7.1 6.7 17.4 7.0 6.9 18.0 7.0 7.0
Fe extraction () Cu extraction () Ni extraction () S2- extraction () 48.4 96.2 93.8 67.3 68.6 97.8 98.4 94.2 75.6 98.1 98.7 98.8
Redox control reduces the residence time from 6
to 4 days
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Effect of grind size
Feed R1 R2 R3
Microbial culture Temperature (C) pH level Redox (mV, AgAgCl)) Cumulative residence time (d) Feed solids concentration () Grind d90 (µm) Thermophiles 9.4 20 70 1.7 430 3.0 70 1.4 550 4.5 70 1.3 570 6.0
Fe (g/L) Cu (g/L) Ni (g/L) 13.6 7.3 6.7 16.0 7.4 7.0 19.2 7.6 7.5
Fe extraction () Cu extraction () Ni extraction () S2- extraction () 40.7 92.7 85.1 63.7 63.1 95.8 96.9 84.7 70.1 96.0 97.9 94.2
With redox control, a coarser grind can be
tolerated
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Primary iron precipitation

• Five reactors
• Operating temperature of 60 C
• Residence time of 5 hours
• Product recycle for seeding
• Difficult to settle/filter product
• Extent of copper loss depends on pH level
• Iron removal of 99.5 at a pH level of 3.0

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Copper SX-EW

• Standard reagent suite
• 2 extraction stages, 1 scrubbing, 2 stripping
• 98-99 copper extraction
• LME A-grade copper cathode produced

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Secondary iron precipitation

• Five reactors
• Operating temperature of 60 C
• Residence time of 5 hours
• Product recycle for seeding
• Target pH level of 5.0
• Gypsum/iron product easy to settle
• Effective copper and nickel scavenging from
  product using a cyclone
• 75 copper, 80 nickel recovery in 18 of mass
• Recycle to bioleach

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Nickel hydroxide precipitation

• Various options considered
• Single-stage process chosen
• Five reactors
• Operating temperature of 60 C
• Residence time of 5 hours
• Product recycle for seeding
• Target pH level of 7.8
• Nickel removal of 99.5
• Product nickel content between 31.6 and 47.5
• Precipitate difficult to dewater by filtration
  (60 moisture retained)

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Magnesium hydroxide precipitation

• Five reactors
• Operating temperature of 60 C
• Residence time of 5 hours
• Product recycle for seeding
• Target pH level of 9.5
• Complete magnesium removal
• Product relatively easy to filter
• Liquor recycled to bioleach process

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Conceptual engineering study

• 96,000 t/a of concentrate
• 5,400 t/a of copper cathode
• 4,857 t/a of nickel as nickel hydroxide
  intermediate
• Concentrate regrinding in a bead mill
  (Deswik/IsaMill) 14.3 kW.h/t
• Bioleach reactors 12 1,620 m3 vessels
• Three nickel recovery options considered
• Nickel hydroxide precipitation
• Nickel sulphide precipitation
• Nickel SX-EW

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Preliminary economic evaluation
Biohydrometallurgical process with production of
metal and/or metal intermediates is
cost-competitive
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Impact of low redox process

• Decreased residence time (6 ? 4 days)
• Individual bioleach reactor volume reduced to 920
  m3
• Bioleach capital cost reduced by 40
• Overall plant cost reduced by 12
• Overall operating cost reduced by 4
• IRR increased from 29.9 to 31.7

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Overall conclusions

• Long-term demonstration of thermophile-based
  bioleach process achieved
• Integrated pilot-plant operation attained
• Economic viability of biohydrometallurgical
  processes established
• Controlled low redox process for chalcopyrite
  bioleaching shows potential to reduce bioleach
  capital costs significantly
• This process has been developed to the point
  where it can be offered commercially

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Thank you
www.mintek.co.za