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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. Crude forms of hydrometallurgy were practised hundreds of years ago Lower grade and more complex ores, e.g. Ni laterites

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slide1

Council for Mineral Technology

Developments in the hydrometallurgical processing of base metals and uranium

24 February 2009

Dr. Roger Paul

General Manager: Technology

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

Introduction
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

Outline
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

Escondida Sulphide Leach: Chile
mintek nicico s 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 55°C

Cu dissolution: 60% (200 - 300 days)

Mintek: NICICO’s Sarcheshmeh Mine, Iran
other
Pacific Ore’s BioHeapTM process

Completed a 4 500 t pilot heap facility, inner Mongolia

Microbial assisted leaching of low-grade, copper mineral sulphide (whole) ores

Geobiotics’s GEOLEACHTM process

Low-grade, copper mineral sulphide (whole) ore

Mesophiles, moderate and extreme thermophiles

Planning demonstration heap at Quebrada Blanca Mine, Chile

Other
outotec s hydrocopper

Au

Cu(I) oxide

Leach

Solution

Purification

Reduction

Cu conc.

Cu metal

Chlorine

Caustic

Ag

Chlor-Alkali

Electrolysis

Melting &

Casting

Brine

Leach residue

Hydrogen

Cu product

Outotec’s HydroCopper®

HydroCopper® Process Block Diagram

outotec s hydrocopper8
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

Outotec’s HydroCopper®
outotec s hydrocopper9
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 AG’s mine in Karajan, Armenia

Outotec’s HydroCopper®

Demonstration Plant in Pori, Finland

galvanox tm

Cu concentrate + Pyrite

Autoclave

Leach

L / S

SX / EW

Cathode

Neutralization

Tailings

GalvanoxTM
galvanox tm11
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, 80°C (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

GalvanoxTM
sepon process flow diagram

Cu concentrate

Leach

Acid & Fe(III)

L / S

SX / EW

Cathode

Flotation

Autoclave

Neutralization

Solids

Tailings

Sepon Process Flow Diagram
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

Sepon
teck cominco s 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

Teck Cominco’s CESL Process
morenci flowsheet

Cu conc.

Slurry

Feed

Water

Super Fine

Grinding

Heap / Stockpile /

Tank Leaching

Lean Bleed

  • Conditions:
  • 150-160°C
  • - 200 psi O2

Pressure

Leaching

Coolant

Streams

Flash

Let Down

Solution

Extraction

L / S

EW

SPLS

L / S

Wash

Water

WPLS

(optional)

Neutralization

Precious Metals

Leaching / Recovery

Lime

Tailings

Cu cathode

Ag, Au

Morenci Flowsheet
freeport mcmoran s 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

Freeport - McMoran’s Morenci
tati nickel flow diagram
Tati Nickel Flow Diagram
  • Treating lower grade Ni-sulphide concentrate
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 >99.8% 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

Tati Nickel Approaches
slide23

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

slide26

Laterite: Cost Comparison (Rusina)

Cost Comparison as presented by Rusina

slide27

Goro Process Selection

  • Pyromet route: drying (ore 50% mositure); selective reduction/smelting: high CAPEX and energy; poorer Ni and Co recoveries
  • Relatively low saprolite:limonite 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

cyanex 301
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
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

Goro: innovative approaches
ravensthorpe atmospheric and hpal
Ravensthorpe: Atmospheric and HPAL

Shipped to Yabulu

for refining

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

Laterites: Heap Leach Developments
costs various process options
Costs: Various Process Options
  • Why considering heap leaching when it is expected that it might be a challenge?
caldag european nickel
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, <1% Co, 7% Mn
co production projects in drc zambia
Co market increased from 35 to 60 ktpa due to demand

Price increased from US$20 to US$50

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 Co:impurity levels

Transport costs of reagents and products high: products aimed at as high as possible Co content

Co production – Projects in DRC, Zambia
oxidative precipitation using air so 2
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

Oxidative Precipitation using Air/SO2
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)

Solvent Extraction
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

Classical Precipitation
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 IBC’s 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

Ion Exchange: Co purification
uranium
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
bpc vs ms stage performance

Equilibrium line - Isotherm

Feed (PLS) concentration

BPC vs MS – Stage Performance

Improved efficiency with marginal increase of capital cost

NTU ~ 2

Operating Line O:A <1

NTU ~ 4

Org

g/l

Operating line O:A = 1

Raff Concentration

Aqueous g/l

Bateman

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

RIP - Metrix
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

Hydromet Challenges
thank you
Thank you

www.mintek.co.za