Transcript Slide 1

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
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
Mintek’s 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 Mintek’s R&D effort was aimed at the bioleaching
of chalcopyrite
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Chalcopyrite “passivates” in sulphate medium at 35°C
Higher operating temperatures
Finer grinding
Addition of catalysts
Redox control
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
Demonstration and commercial plants
Kasese, Uganda
BioCOP, Chuquicamata, Chile
Mintek-BacTech, Mexico
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
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:
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Integrated pilot plant testing
Additional bioleach optimization tests
Conceptual engineering study
Preliminary economic evaluation
Conceptual process flowsheet
Bioleaching
Copper
solvent
extraction
Wash
water
Solid-liquid
separation
& washing
Neutralisation
& iron
precipitation
Limestone
Nickel
hydroxide
precipitate
Limestone
Neutralisation
& iron
precipitation
Solid-liquid
separation
& washing
Gypsum
& iron
Solid-liquid
separation
& washing
Wash
water
Wash
water
Solid-liquid
separation
& washing
Neutralisation
Lime
Gypsum
& iron
Bioresidue
Wash
water
Copper
electrowinning
Nickel
precipitation
Magnesia
Mg
precipitate
Copper
cathode
Solid-liquid
separation
Concentrate description
• Reground to a d90 of 10-12 µm
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•
28.9
24.4
6.29
5.24
6.28
%
%
%
%
%
Fe
S2Cu
Ni
Si
•
•
•
•
•
23.7
20.7
18.5
14.5
21.6
%
%
%
%
%
pyrite (FeS2)
pyrrhotite (Fe(1-x)S)
chalcopyrite (CuFeS2)
pentlandite ((Fe,Ni)9S8)
silicates
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
Mesophiles (35 °C)*
Moderate thermophiles (45 °C)
Thermophiles (70 °C)
Metal extraction
(%)
Cu
Ni
30
65
95
76
99
99
* Single-stage reactor at 3-day residence time
Thermophiles at 70 °C required for chalcopyrite bioleaching
Bioleach amenability tests
Effect of grind size
Operating conditions
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
Cu extraction (%)
Ni extraction (%)
R1
R2
R3
R1
R2
R3
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
Preliminary specifications for downstream plant
• Range of batch bench-scale tests performed
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Primary iron precipitation
Solvent extraction
Secondary iron precipitation
Nickel hydroxide precipitation
Magnesium removal
• Results used to set initial operating parameters for
integrated pilot plant
Integrated pilot plant
Integrated bioleach plant performance
Eh level (mV, Ag|AgCl)
750
• Bioleach plant operated for 220 days
• Recycle loops closed
• Very stable operation
700
650
R1
600
◦ Steady redox potential
◦ Stable oxygen uptake rates
R2
R3
550
R4
500
450
0
50
100
150
200
250
• Swift recovery from process upsets
• No impact of recycle on process
performance
Time (d)
20
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
18
Oxygen Uptake rate (kg/(m 3.d))
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16
14
12
R1
10
R2
8
R3
6
R4
4
2
0
0
50
100
150
Time (d)
200
250
Effect of redox control
Feed
R1
Microbial culture
Thermophiles
70
Temperature (°C)
pH level
1.6
Redox (mV, Ag|AgCl))
430
Cumulative residence time (d)
3.0
Feed solids concentration (%)
9.8
Grind – d90 (µm)
10
R2
R3
70
1.3
550
4.5
70
1.25
580
6.0
[Fe] (g/L)
[Cu] (g/L)
[Ni] (g/L)
14.5 17.4 18.0
7.1 7.0 7.0
6.7 6.9 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
Effect of grind size
Feed
R1
Microbial culture
Thermophiles
70
Temperature (°C)
pH level
1.7
Redox (mV, Ag|AgCl))
430
Cumulative residence time (d)
3.0
Feed solids concentration (%)
9.4
Grind – d90 (µm)
20
R2
R3
70
1.4
550
4.5
70
1.3
570
6.0
[Fe] (g/L)
[Cu] (g/L)
[Ni] (g/L)
13.6 16.0 19.2
7.3 7.4 7.6
6.7 7.0 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
With redox control, a coarser grind can be tolerated
70.1
96.0
97.9
94.2
Primary iron precipitation
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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
Copper SX-EW
• Standard reagent suite
• 2 extraction stages, 1 scrubbing, 2 stripping
• 98-99 % copper extraction
• LME A-grade copper cathode produced
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
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)
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
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
Preliminary economic evaluation
Design basis
96,000 t concentrate/a
4,857 t Ni/a
5,400 t Cu/a
Bioleach +
Concentrate
n
sale
Ni(OH)2 ppt Ni-S pptn Ni SX-EW
Capex
-
61
61
66
-
10.3
12.4
11.2
US$-million/a
-
0.96
1.16
1.04
US$/lb Ni
IRR, 10 years
31%
30%
29%
33%
%
NPV, 8 %
145
203
196
239
US$-million
Opex
US$-million
Biohydrometallurgical process with production of metal and/or
metal intermediates is cost-competitive
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 %
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
Thank you
www.mintek.co.za