Processing Considerations for the Cobalt Recovery from Congolese

Processing Considerations for the Cobalt Recovery from Congolese Copperbelt Ores B. Swartz, S. Donegan, S. Amos Presented M. Reolon 24 – 26 February 2009

Introduction • • Increased global demand for Cu and Co Increased political stability in DRC Renewed interest Cu & Co deposits Studies and projects

Introduction Cu and Co • Agitated oxide leach of Cu & Co • Recovered from Cu SX raffinate bleed • Produce Co intermediate • Metal production if viable Aim • Introduces Co production options • Presents NPV comparison of the selected options

Cobalt Processing Options Three levels of Co recovery • Concentrate by gravity separation – not considered further • Intermediate cobalt salt • Cobalt metal Factors to be considered • Operation (safe, simple, robust) • Technical (proven, robust) • Environmental • Commercial

Cobalt Intermediates Introduction Cobalt Processing Options • Concentrates • Intermediates • Metals • NPV Comparisons

Cobalt Intermediates

Cobalt Intermediates • Impurity removal prior to intermediate production

Cobalt Intermediate Fe / Mn / (Al) removal Cu removal Al removal

Cobalt Intermediate Fe / Mn / (Al) removal Cu removal Al removal Co Precipitation

Cobalt Intermediate Single stage • Lower purity Co Two stage • Higher purity Co salt product from 1 st stage • Recycle 2 nd stage slurry to Fe / Mn precipitation

Cobalt Intermediate Four main options • Cobalt hydroxide precipitation • Cobalt carbonate precipitation • Cobalt sulphide precipitation • Cobalt sulphate crystallization

Cobalt Hydroxide Intermediate Cobalt hydroxide precipitation • p. H 7. 5 (1 st stage) • p. H 8 - 8. 5 (2 nd stage) - lime Slaked lime • Forms gypsum impurity in Co salt • Availability Milk of magnesia • No gypsum produced Caustic soda • No gypsum produced • Na 2 SO 4 disposal considerations

Cobalt Hydroxide Intermediate Advantages • Low operating costs • Little effluent disposal issues (except with Na. OH) • No toxic emissions • Relatively simple plant to operate and maintain Disadvantages • Lower product quality

Cobalt Carbonate Intermediate Cobalt Carbonate Precipitation • 1 st stage precipitation using Na 2 CO 3 Advantages • Relatively simple plant to operate and maintain • Good recoveries • Compatible to future metal production Disadvantages • Na 2 SO 4 disposal issues

Cobalt Sulphide Intermediate Cobalt Sulphide Precipitation H 2 S - Not considered for further discussion Na. HS Advantages • Low capital cost • Product purity Disadvantages • HSE issues • Low recoveries • Less desirable product

Cobalt Sulphate Intermediate Cobalt Sulphate Crystallization • Falling film evaporator • Crystallizer • Dry, bag and ship Advantage • Marketable product • Compatible to future metals plant Disadvantage • Expensive to build and operate • Co-crystallization of all impurities

Cobalt Intermediate Conclusions • Co. S and Co. SO 4 rejected • Environmental issues to determine between Co(OH)2 and Co. CO 3 • Current projects preference for Co(OH)2 • 2 stage precipitation preferred Effluent Discharge Rated Best to Worst Available Co. CO 3 not available Co(OH)2 > > Co(OH)2 > Co. CO 3 > Co. SO 4 > Co. S

Cobalt Metal Introduction Cobalt Processing Options • Concentrates • Intermediates • Metals • NPV Comparisons

Cobalt Metal Two Processes • Cathode by electrowinning • Powder / briquettes by hydrogen reduction – Not considered further

Cobalt Metal by Electrowinning Co cathode – two processes considered • Co(OH)2 redissolution – Impurity removal by filtration and IX – Co Cathode in EW • Co solution SX – Impurity removal by SX and IX – Co Cathode in EW

Cobalt Metal Conclusions • SX equal or superior to redissolution • Capital and environmental factors predominate • Recommend Co precipitation and redissolution

Cobalt Metal Introduction Cobalt Processing Options • Concentrates • Intermediates • Metals • NPV Comparisons

Comparative NPV between Co(OH)2 and Metal High level NPV on three scenarios • Co(OH)2 intermediate product • Phase 1 Co(OH)2 intermediate product, Phase 2 Cathode metal product • Co(OH)2 intermediate to cathode metal product (no intermediate product) • • Basis in Paper Capital and operating cost - comparison only

Comparative NPV between Co(OH)2 and Metal • • Significant benefits for metal product over intermediate product No significant difference between intermediate product to cathode, or direct resolution to cathode

Conclusions • • Often environmental consideration and operational complexity determine optimum route Follow less complex route in early years (Co(OH)2 production) Do not underestimate Co metal plant complexity With experience and cash flow, consider upgrade to metal producing facility

Thank You