Processing Considerations for the Cobalt Recovery from Congolese Copperbelt Ores

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

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

3. 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

4. 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

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

6. Cobalt Intermediates

7. Cobalt Intermediates • Impurity removal prior to intermediate production

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

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

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

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

12. Cobalt Hydroxide Intermediate Cobalt hydroxide precipitation • pH 7.5 (1st stage) • pH 8 - 8.5 (2nd stage) - lime Slaked lime • Forms gypsum impurity in Co salt • Availability Milk of magnesia • No gypsum produced Caustic soda • No gypsum produced • Na2SO4 disposal considerations

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

14. Cobalt Carbonate Intermediate Cobalt Carbonate Precipitation • 1st stage precipitation using Na2CO3 Advantages • Relatively simple plant to operate and maintain • Good recoveries • Compatible to future metal production Disadvantages • Na2SO4 disposal issues

15. Cobalt Sulphide Intermediate Cobalt Sulphide Precipitation H2S - Not considered for further discussion NaHS Advantages • Low capital cost • Product purity Disadvantages • HSE issues • Low recoveries • Less desirable product

16. 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

17. Cobalt Intermediate Conclusions • CoS and CoSO4 rejected • Environmental issues to determine between Co(OH)2 and CoCO3 • Current projects preference for Co(OH)2 • 2 stage precipitation preferred

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

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

20. 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

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

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

23. 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

24. 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

25. 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

26. Thank You