Transcript Paul - saimm - SAIMM
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
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
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
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 CuFeS 2 )
Maximum temperatures: up to 55 °C
Cu dissolution: 60% (200 - 300 days)
Other
Pacific
Ore’s BioHeap TM process Completed a 4 500 t pilot heap facility, inner Mongolia
Microbial assisted leaching of low-grade, copper mineral sulphide (whole) ores
Geobiotics’s GEOLEACH TM
process Low-grade, copper mineral sulphide (whole) ore
Mesophiles, moderate and extreme thermophiles
Planning demonstration heap at Quebrada Blanca Mine, Chile
Outotec’s HydroCopper
® Au Cu(I) oxide Cu conc.
Leach Chlorine Chlor-Alkali Electrolysis Caustic Leach residue Solution Purification Ag Brine Hydrogen Reduction Cu metal Melting & Casting Cu product HydroCopper ® Process Block Diagram
Outotec’s HydroCopper
® Atmospheric Leaching
Concentrate (CuFeS 2 ) 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): S 0 , hematite or goethite
Outotec’s 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 AG’s mine in Karajan, Armenia – Demonstration Plant in Pori, Finland
Galvanox
TM Cu concentrate + Pyrite Autoclave Leach L / S Neutralization Tailings SX / EW Cathode
Galvanox
TM Atmospheric Leaching
Primary copper sulphide (CuFeS 2 ) concentrates leached in acidic, iron sulphate medium
Enhanced dissolution kinetics achieved by means of pyrite (FeS 2 ) as catalyst
Copper recoveries of 98% in 4 h residence time; more typically, 20
h, 80 ° C (depending on extent of FeS 2 S 0 formation
Compatible with SX / EW recycle)
Used in combination with high-pressure autoclave for acid, heat and Fe(III) generation
Enhanced enargite (Cu 3 AsS 4 ) dissolution kinetics also achieved with FeS 2 as catalyst
Arsenic converted into environmentally stable scorodite
Sepon Process Flow Diagram
Cu concentrate Acid & Fe(III) Leach Cathode L / S SX / EW Flotation Neutralization Tailings Solids Autoclave
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 (CuFeS 2 )
Main difference with respect to Galvanox TM process:
Galvanox TM : CuFeS 2 treated in atmospheric leach Equipment size, capital and operating costs not linked to primary copper sulphide content of feed
Sepon: CuFeS 2 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 Copper Project, Laos
CESL Process Flowsheet
Teck Cominco’s CESL Process
Pressure Leaching
Can treat nearly all copper concentrates (incl. CuFeS 2 ) (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 Hidrometal úrgica Carajás (UHC) prototype plant recently completed (10 000 tpa Cu cathode). Near Caraj ás, Brazil where Vale operates Sossego copper mine
UHC Project, Brazil
Cu conc.
Water
Morenci Flowsheet
Slurry Feed
-
Conditions: 150-160 °C - 200 psi O 2 Super Fine Grinding Pressure Leaching Flash Let Down Lean Bleed Coolant Streams Heap / Stockpile / Tank Leaching Solution Extraction L / S EW SPLS Water L / S Wash Lime Neutralization Tailings WPLS (optional) Precious Metals Leaching / Recovery Ag, Au Cu cathode
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
Bacon, 2004
World Nickel Resources
Tati Nickel Flow Diagram
Treating lower grade Ni-sulphide concentrate
Concentrate Tailings
Milling Activox Leach Solid-liquid separation Copper SX PGE Recovery Copper EW
PGE Cu
Iron Removal Cobalt SX Nickel SX Ammonia Recovery Cobalt Precip Nickel EW
Co Ni
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
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
Laterite: Simple Process Routes
Malachite Consulting
Laterite: Simple Process Routes
Bacon, 2004
Laterite: Cost Comparison (Rusina)
Cost Comparison as presented by Rusina
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
Fe 3+ and Cu 2+ to be removed efficiently prior to SX –
Bacon, 2004
cause oxidation of reagent (regeneration of reagent part of flowsheet)
Water H 2 SO 4 SO 2 CaCO 3 H 2 SO 4 HCl Water Water HCl
Goro Process Flowsheet
Limonite ore Saprolite ore Feed preparation Pressue acid leach CCD Partial Neutralisation IX Cu removal Primary SX: Ni & Co recovery IX: Zn removal Secondary SX:Co/Ni separation NiCl 2 pyrohydrolysis Tailings Raffinate Ca(OH) 2 CaCO 3 Final Neutralisation Tailings impoundment at Mine Na 2 CO 3 Co precipitation Liquid effluent NiO CoCO 3
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
Ravensthorpe: Atmospheric and HPAL
Beneficiated Limonite ore Elemental S Beneficiated Saprolite ore Preleach Acid plant: H2SO4 HPAL Atmospheric leach CaCO 3 CaCO 3 Jarosite precipitation Primary neutralisation CCD Tailings O/F Secondary Neutralisation
MgO
Ni and Co MHP
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
Costs: Various Process Options
Why considering heap leaching when it is expected that it might be a challenge?
Caldag: European Nickel
Heap leaching: Caldag laterite contains low clay content 3 leach phases: neutralisation (Mg leaching) (35 kg/t H 2 SO 4 ), primary (116 kg/t H 2 SO 4 ) and secondary leaching (377 kg/t H 2 SO 4 ) Primary leach intermediate product 33% Ni, 1.5% Co Secondary leach intermediate product 25% Ni, <1% Co, 7% Mn
Caldag: European Nickel
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, Na 2 CO 3
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
Oxidative Precipitation using Air/SO
2
Oxidative precipitation of Fe and Mn using air/SO 2 received much attention from various institutes
Very attractive process option, as SO 2 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
Solvent Extraction
Purification of Co stream: DEHPA for Zn, Mn, Ca
Ca extraction will result in gypsum precipitation in strip circuit when using H 2 SO 4 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 Na 2 SO 4 environmental issue is an
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)
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 Na 2 CO 3 :
Environmental issue – produce dilute Na 2 SO 4
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
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
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
Bateman Pulsed Columns
(BPC)
Mixer/Settlers Extraction Efficiency Entrainment Moving parts Maintenance Footprint Solvent vapour loss Safety Staged Lower for cost-effective # of stages Poorer High High Large Higher Higher fire hazard BPC Continuous High Improved Low Low Small Lower Much lower
BPC vs MS – Stage Performance
Improved efficiency with marginal increase of capital cost Org g/l
Equilibrium line - Isotherm NTU ~ 2 Operating Line O : A <1 NTU ~ 4 Operating line O : A = 1
Feed (PLS) concentration Raff Concentration Aqueous g/l Bateman
Olympic Dam – recovery of Uranium by BPcs
Uranium One: BPCs Klerksdorp
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 2m 3 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
Metrix Demonstration Plant
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 H 2 SO 4 needs to be neutralized and dumped
Thank you
www.mintek.co.za