NICKEL LATERITES
characteristics, classification and processing options
Charles ButtAugust 2007
CUBA
INDONESIA
AUSTRALIA
LATERITES SULPHIDES
NEW CALEDONIA
PHILIPPINES22oN
22oS
NICKEL DEPOSITS: LATERITES AND SULPHIDES
NICKEL LATERITE
• Regolith, derived from ultramafic rocks, that contains commercially exploitable reserves of nickel (and, commonly, cobalt)
i.e., an economic term, implying high grades and/or tonnages of Ni-rich material
• ultramafic rocks, >~2500ppm Ni Peridotite: 40-90% olivine + pyroxene Dunite: >90% olivine ophiolite, komatiite; layered intrusives (all ± serpentinized)
NICKEL SUPPLY: LATERITES AND SULPHIDES
A: Hydrous Mg-Ni silicate deposits (~35% of total resource)
Altered serpentines, népouite, “garnierite” in saprolite High grade: global mean 1.53% Ni Moderate to high relief; savanna, tropical rainforest
B: Smectite silicate deposits (~15% of total resource)
Clays (e.g., nontronite) in upper saprolite and pedolith Low grade: global mean 1.21% Ni Low relief; savanna, semi-arid
C: Oxide deposits (~50% of total resource)
Fe and minor Mn oxides, in upper saprolite and pedolith Low grade: global mean 1.06% Ni Most environments
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CLASSIFICATION OF NICKEL LATERITES
EAST PINARESCuba
Photo: Mick Elias
Oxide
GORONew Caledonia Oxide; some hydrous silicate
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CAWSEWestern Australia
Oxide
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CRBs021-01
Ni %0.08
0.20
1.26
0.46
0.47
0.19
0.25
Co %0.04
0.07
0.04
0.15
0.16
0.09
0.12
MgO %1.0
0.3
1.1
0.08
29.4
39.5
42.3
Fe %7.6
8.5
44.1
18.1
7.2
5.8
8.3
SiO %2 70.8
82.3
35.9
72.3
26.7
28.3
36.6
DuricrustMottled and
plasmic clays
Ferruginoussaprolite
Saprolite
Saprock
Bedrock
Mn oxides
ShearSilica
Mg discontinuity
CAWSE
Magnesite
Serpentinizeddunite
Shear
Mn oxides
OXIDE NICKEL LATERITE PROFILE: CAWSE
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PRINCIPAL NICKEL MINERALS
OXIDE DEPOSITS
Goethite Fe oxide (Fe,Al)O.OH 2% Ni, 0.2% Co Asbolan Mn oxide (Co,Ni)Mn2O4(OH)2.nH2O 16% Ni, >4% Co Lithiophorite (Al,Li)Mn2O4(OH)2.nH2O 1% Ni, ~7% Co
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PLATEAUNew Caledonia
Hydrous silicate; minor oxide
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PLATEAUNew Caledonia
Hydrous silicate
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CIRCENew Caledonia
Hydrous silicate “garnierite” ore
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C RC LEM EC R B s0 0 4-0 0
0
10
20
30
40
50
Verm iform and pisolitic dur icrust
Red plasm ic clay
Ferruginoussaprolite
Saprolite
Peridotite bedrock
N i %0.3
0.9
1.4
2.0-3.0
2.3
2.5
3.0
0.3
Iron c rust P iso liths
Red lim onite
Yellow lim onite
E arthy ore
Soft sapro lite
O re w ith boulders
Rocky ore
Fresh peridotite
D epth (m )
G arnierite
after Troly et a l., 1979
HYDROUS SILICATE (GARNIERITE) – OXIDE PROFILE
Oxide
Ni lizardite Serpentine (Mg,Ni)3Si2O5(OH)4 6.1% Ni Népouite 32.8% Ni 7Å garnierite 15.1% Ni Nimite Chlorite (Ni,Mg,Al)6(Si,Al)4O10(OH)8 16.9% Ni 14Å garnierite 3.3% Ni Falcondoite Sepiolite (Ni,Mg)4Si6O15(OH)2.6H2O 24% Ni Willemseite Talc (Ni,Mg)3Si4O10(OH)2 27.1% Ni 10Å garnierite 19.9% Ni Pimelite 15.7% Ni
HYDROUS NI-MG SILICATES
PRINCIPAL NICKEL MINERALS
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BULONGWestern Australia
Smectite silicate
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MURRIN MURRINWestern Australia
Smectite silicate
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MURRIN MURRIN Smectite silicateWestern Australia
magnesite
Photo: Martin Wells
SMECTITE SILICATE PROFILE
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SMECTITE DEPOSITS
Nontronite Smectite Na0.3Fe2(Si,Al)4O10(OH)2.nH2O 4% Ni
Minor goethite, asbolan
PRINCIPAL NICKEL MINERALS
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PROCESS ORE PRODUCT COMMENT
Smelting1859, New Caledonia
Hydrous silicate Ferro-nickelmatte
Energy intensive; (smelting ~1600ºC)
Caron process
Reduction & ammoniacal leach1944, Cuba
Oxide; hydrous silicate (Mg <4%)
Ni oxide; Ni briquettes Energy intensive (reduction ~700ºC) low Co recovery
High pressure acid leach (HPAL)1959, Moa Bay, Cuba
Oxide; smectite (Mg <4%)
Ni briquettes; electronickel; oxide, sulphide, carbonate
Less energy intensive. Plant & process problems
Enhanced high pressure acid leach (EPAL)
Hydrous silicate Ni-Co hydroxide Atmospheric leach after HPAL
Acid heap leach H2SO4
Atmospheric leach
H2SO4
HCl/MgCl2
Oxide; smectite
Oxide; smectite
hydrous silicate
Ni-Co hydroxide Lower capital cost;
Lower recoveries
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PROCESSING OPTIONS FOR NICKEL LATERITES
Oxide(or smectite)
Transition
Hydrous silicate
(after Elias 2001)
PROCESSING OPTIONS RELATIVE TO DEPOSIT TYPE
Hydrous silicate ore(“garnierite”; serpentine)Too costly for smectite
e.g., tumbling of boulder ore
1400 - >1600ºC; high energy cost
SiO2/MgO <2 or >2.5= ferronickel
SiO2/MgO 1.8-2.2= matte
~77% of total production in 2000 33% or less of new capacity
NICKEL LATERITE PROCESSING
Smelting
FEED
P ROCEESS
Drying
Upgrading
Reduction roast
Smelting
Converting
P RODUCT
Fe-Ni or Ni matte90% recovery
Ni: >2.0%Co: 0.04%Fe: 20%MgO: 25%
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High grade oxide ore, some hydrous silicate; tolerates more Mg than HPAL. Too costly for smectite.
~700ºC; high energy cost
Complex pyrometallurgical - hydrometallurgical process; high energy cost with lower recoveries than smelting and PAL.
No new plants anticipated
NICKEL LATERITE PROCESSING
Caron process
FEED
P ROCEESS
Reduction roast
Grinding, drying
Leach ammoniacal CO3
Cobalt separation
Ni carbonate precipitation
P RODUCT
Ni:94% recovery
Ni: 1.8%Co: 0.1%Fe: 25-40%MgO: <12.0%
Co:90% recovery
Calcining
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Oxide or smectite ore, low Mg and Al to reduce acid consumption
Upgrade oxide by screening to remove barren silica
High capital costs, with new plants having numerous teething problems in plant and process.
Product options include sulphides: Murrin2, Halmahera hydroxide: Ravensthorpe, Vermelhocarbonate: Cawse
NICKEL LATERITE PROCESSING
High pressure acid leaching
FEED
P ROCEESS
Leach H2SO4
Ore preparation
Acid plant
S
EnergyWash/neutralize
SX-EW or precipitateP RODUCT
Ni:94% recovery
Ni: 1.3%Co: 0.13%MgO: <5.0%
Co:90% recovery
240-270ºC; lower energy costcf Caron process
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Murrin Murrin
NICKEL LATERITE PROCESSING
Atmospheric leaching
FEED
Oxide ore (but, potentially, any ore type, including low grade hydrous silicate)
P ROCEESS
Agitate, heat and leach H2SO4
Ore preparation
Acid plant or excess from HPAL
S
EnergyWash/neutralize
SX-EW or precipitateP RODUCT
Ni (Co) hydroxide~80-90% recovery
Ravensthorpe, Gag Island: oxide, serpentine saprolite (hydrous silicate)Sechol: oxide, saprolite
Enhanced high pressure acid leaching (EPAL); 80-105ºC
Sechol/Jaguar tested HCl/MgCl2 leach at 80-105ºC. Process could also yield MgO and magnetite concentrate as products. Trial discontinued
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NICKEL LATERITE PROCESSING
Heap leaching
FEED
Potentially, any ore type, including low grade hydrous silicate and rejects
P ROCEESS
Heap, irrigate for 12-18 months
Ore preparation
Acid plant or excess from HPAL
S
EnergyWash/neutralize
P RODUCT
Ni (Co) hydroxide ~80% recovery
SX-EW or precipitate
Caldag, Nornico - oxide; Murrin Murrin - smectite
Crush; upgrade by screening to remove barren silica
Neutralize using low grade saprolite ore
Suitable for smaller deposits; low capex and opex
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From top of Heap 2 looking at Çaldağ mountainDemonstration precipitation plant
European Nickel plc 2006
200 m20 km
Çaldağ Heap Leach project, Turkey
Çaldağ
Izmir *
Istanbul
50 km
*
HPAL Atmospheric leach
Heap leach
Capital expenditure
$17-22 $13-16 $8-12
Operating expenditure
$2.50 $2.50 $2.50
$US/lb Ni
Source: Minara Resources, 2006
PROCESSING OPTIONS FOR NICKEL LATERITES
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NICKEL LATERITE PROCESSING: Summary and conclusions
1: Nickel laterites form ~ 75% of known Ni resources
2: By 2010, over 50% of Ni will be derived from NiL
3: Three main ore types: oxide, hydrous silicate, smectite; all products of humid weathering, ± later modification
4: “Traditional” processing (smelting, Caron) is generally very energy intensive
5: HPAL plants use less energy but require high capital expenditure and are yet to be fully optimized; best suited to large deposits
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6: Acid leaching at lower temperatures and ambientpressures offer lower capital expenditure (but lower recovery). Suited for treating lower grade ore and small or remote deposits
7: Better mineralogical characterization is needed tooptimize grade control, beneficiation and processing
NICKEL LATERITE PROCESSING: Summary and conclusions (continued):
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