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Council for Mineral Technology General Manager: Technology

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1 Council for Mineral Technology General Manager: Technology
Developments in the hydrometallurgical processing of base metals and uranium 24 February 2009 Dr. Roger Paul General Manager: Technology

2 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

3 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

4 Escondida Sulphide Leach: Chile
Bioleaching (mesophiles) Low-grade, run-of-mine (ROM) ore with SX / EW Designed to produce tpa copper cathode Project cost: US $ 870m (includes desalination plant at Coloso) Production at plant began in 2007 Photograph: Becerra, E., Olea, A., Smithson, P. and Castillo, D., Engineering a Bioleaching Hydrometallurgy Plant To Achieve Maximum Microbial Activity, Viña del Mar, Chile, 2007.

5 Mintek: NICICO’s Sarcheshmeh Mine, Iran
Bioleaching (mesophiles / thermophiles) Pilot heaps (6 m height, t) Ore: 100% passing 25 mm, transitional (53% of Cu(T) as CuFeS2) Maximum temperatures: up to 55°C Cu dissolution: 60% ( days) Photograph: Van Staden, P. J., MINTEK.

6 Other Pacific Ore’s BioHeapTM process Geobiotics’s GEOLEACHTM process
Completed a 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

7 Outotec’s HydroCopper®
Solution Purification Reduction Chlor-Alkali Electrolysis Melting & Casting Cu conc. Leach Leach residue Cu(I) oxide Cu metal Cu product Chlorine Hydrogen Brine Caustic Ag Au Flowsheet (Karonen, J., HydroCopper® - From Concentrate to Copper Product, Outotec Research Oy, 2008). HydroCopper® Process Block Diagram

8 Outotec’s HydroCopper®
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

9 Outotec’s HydroCopper®
Presently, engineering a commercial plant for Mongolian Erdenet Mining Corporation (Mongolia) to produce tpa copper wire rod Another plant to be build ( tpa) for Zangezur Copper – Molybdenum Combine AG’s mine in Karajan, Armenia Photograph: HydroCopperTM – Ground-Breaking Technology, Outokumpu, Internet. Demonstration Plant in Pori, Finland

10 GalvanoxTM L / S Neutralization Leach Autoclave SX / EW
Cu concentrate + Pyrite Tailings Cathode Miller, K. J., Sylwestrzak, L. A. and Baxter, K. G., Treatment of Copper Sulphide Deposits – Evaluation of a Galvanox™ Versus Sepon Circuit Configuration, Alta 2008 Copper Conference, June 2008.

11 GalvanoxTM 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

12 Sepon Process Flow Diagram
Cu concentrate Flotation Neutralization L / S Leach SX / EW Tailings Cathode Autoclave Acid & Fe(III) Solids Miller, K. J., Sylwestrzak, L. A. and Baxter, K. G., Treatment of Copper Sulphide Deposits – Evaluation of a Galvanox™ Versus Sepon Circuit Configuration, Alta 2008 Copper Conference, June 2008.

13 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

14 Sepon Copper Project, Laos
Photograph: Bateman Engineering website, Internet.

15 CESL Process Flowsheet
A typical CESL copper / precious metals process flowsheet; solution to nickel and gold / silver recovery not related to Vale’s 10K plant (The CESL Process: An Environmentally Superior Alternative to Smelting, Teckcominco Brochure, Internet).

16 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 ( tpa Cu cathode). Near Carajás, Brazil where Vale operates Sossego copper mine

17 UHC Project, Brazil Autoclave and evaporator at UHC, Brazil (Photograph: The CESL Process, Teckcominco presentation, Internet).

18 Morenci Flowsheet Cu conc. Slurry Super Fine Grinding Pressure
Leaching Flash Let Down L / S Wash Neutralization Water Lime Tailings Heap / Stockpile / Tank Leaching Solution Extraction EW Feed Cu cathode WPLS SPLS Lean Bleed Coolant Streams Precious Metals Leaching / Recovery Ag, Au (optional) Conditions: °C - 200 psi O2 Flowsheet, Construction and Start-Up of the Freeport - McMoran Concentrate Leach Plant at Morenci, Arizona, Alta 2008 Copper Conference.

19 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 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

20 World Nickel Resources
Bacon, 2004

21 Tati Nickel Flow Diagram
Treating lower grade Ni-sulphide concentrate

22 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

23 Laterite Minerals Limonite, asbolite: (1-1.7% Ni, % Co) – suitable for PAL and Caron process Nontronite: (1-5% Ni, 0.05% Co) – suitable for PAL and smelting Serpentine: (1.5-10% Ni, % Co); typical 1-2% Ni – suitable for pyromet processes (ferronickel and matte smelting) Garnierite: (10-20% Ni, % Co); typical 2-3% Ni – suitable for pyromet processes (ferronickel and matte smelting, especially high C ferronickel) Bacon, 2004

24 Laterite: Simple Process Routes
Malachite Consulting

25 Laterite: Simple Process Routes
Bacon, 2004

26 Laterite: Cost Comparison (Rusina)
Cost Comparison as presented by Rusina

27 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

28 Goro Process Flowsheet

29 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

30 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

31 Ravensthorpe: Atmospheric and HPAL
Shipped to Yabulu for refining

32 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

33 Costs: Various Process Options
Why considering heap leaching when it is expected that it might be a challenge?

34 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

35 Caldag: European Nickel

36 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

37 Oxidative Precipitation using Air/SO2
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

38 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)

39 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

40 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

41 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

42 Bateman Pulsed Columns (BPC)
Mixer/Settlers BPC Extraction Staged Continuous Efficiency Lower for cost-effective # of stages High Entrainment Poorer Improved Moving parts Low Maintenance Footprint Large Small Solvent vapour loss Higher Lower Safety Higher fire hazard Much lower

43 BPC vs MS – Stage Performance
Improved efficiency with marginal increase of capital cost Feed (PLS) concentration Equilibrium line - Isotherm NTU ~ 2 Operating Line O : A <1 NTU ~ 4 Org g/l Operating line O : A = 1 Raff Concentration Aqueous g/l Bateman

44 Olympic Dam – recovery of Uranium by BPcs

45 Uranium One: BPCs Klerksdorp

46 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

47 Metrix Demonstration Plant

48 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

49 Thank you

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