1. Development of the TATI Activox ® BMR Ammonia Recovery Circuit D.A. van den Berg (Hatch), P. Mar é (Hatch), G.J. Nel (Norilsk Nickel)

2. 2 Agenda Introduction –Background to TA ® P –TA ® P flow sheet Selection of SX neutralizing reagent –General SX neutralizing reagent options –Benefits of ammonia recovery for TA ® P Ammonia recovery technology –Traditional lime boil process TA ® P ammonia recovery process –Vibrating mills –Reaction tanks –Stripping column and design Conclusion and key benefits Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion

3. 3 Tati Activox ® Project Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion

4. 4 The Tati Activox ® Project (TA ® P) Greenfields project for Activox hydrometallurgical plant located outside Francistown, Botswana Process tested at HDP (demo plant) Uses Activox ® technology to treat nickel sulphide concentrate. Ammonia recovery eased key location challenges Project indefinitely suspended mid 2008 with detailed process design complete and construction underway. Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion Feed Conc506 000 dt/a Ni4.2 - 5.3% Cu2.7 - 5.1 % Co0.11 - 0.18 % Fe47% Productt/a Nickel metal25 000 Copper metal22 000 Cobalt carbonate640

5. 5 The Tati Activox ® Plant

6. 6 SX Neutralizing Reagent Selection General Factors which were considered: 1.What are the by-products created and how are they handled? Marketable? Safe disposal? 2.What is the transportation requirements for the reagent & by-product? 3.What is the impact on plant water balance? 4.What is the impact on overall plant process conditions (impurities)? Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion

7. 7 Typical Reagent Options for pH control in SX Ammonia –Supplied as anhydrous liquid –Ammonium sulphate can be crystallised for fertilizer Sodium Hydroxide –Supplied as 50% solution or pellets –Sodium sulphate can be crystallised for detergent filler, pulp & paper or glass industry Sodium Carbonate –Supplied as anhydrous solid –Similar sodium sulphate product Location –No local market for ammonium sulphate or sodium sulphate by-product Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion

8. 8 Indicative Reagent Supply Costs Quicklime is by far the cheapest alkali Ammonia recovery uses “cheap” base to recover more expensive ammonia Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion Sodium Hydroxide (NaOH) Ammonia (NH3) Sodium Carbonate (Na2CO3) Quicklime (CaO) Increasing Cost R150 /t R6500 /t

9. 9 Tati Neutralising Reagent Selection for SX No.ReagentRequired Reagent (Kg per t acid) 1Ammonium hydroxide 347 kg ammonia prt ton acid 2Option 1 with 90% ammonia recovery 34.7 kg ammonia and 515 kg lime per ton acid 3Sodium hydroxide408 kg/t 4Sodium carbonate1081 kg/t Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion Ammonia recovery has significantly less ammonia reagent costs

10. 10 Traditional Ammonia Recovery The lime boil process: Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion Lime Slaking Cooling Water Cooling Water Cooling Water Lime Slurry Feed Slurry Steam Ammonia and Water Vapour Lime Boil Reactors Condenser Ammonia Product Tank Quicklime+ Water

11. 11 Traditional Ammonia Recovery Advantages –Only need reaction tanks and condensers (and slaking equipment) –Ammonia make-up by adding ammonium sulphate to lime boil feed or anhydrous ammonia to recovered ammonia. Disadvantages –Gypsum Scaling –Lime Slurry Dilution –Energy Intensive Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion

12. 12 TA ® P Ammonia Recovery Process Vibrating mills Reaction tanks Steam stripping, condensing, make-up Barren slurry to tailings, process water recovered Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion

13. 13 Vibrating Mills CaO(s) + H2O(l) = Ca(OH) 2 (s) (NH 4 ) 2 SO 4 (aq) + Ca(OH) 2 (s) = CaSO 4 (aq) + 2 H 2 O (l) + 2 NH 3 (aq) Reaction mills

14. 14 Reaction Tanks CaSO 4 (aq) + 2 H 2 O(l) = CaSO 4.2H 2 O(s) Gypsum formation

15. 15 Steam Stripping NH 3 (aq) = NH 3 (g) Ammonia stripping

16. 16 Steam Stripping Theoretical stages plotted on McCabe Thiele (Confirmed by ASPEN modelling, Stuart Bradbury of PPT) Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion

17. 17 Ammonia Stripping Column Design Demo plant Small (6” diameter) column 10% tray efficiency duration operation TA ® P Design Design for 15% tray efficiency –Larger column diameter and tray spacing –Typical efficiency (for dual flow trays) is 20-40%, but reduced due to slurry environment. Design for reduced steam consumption –Higher L/V ratio than demo plant to reduce steam requirements –Discharged into flash cooler to recover steam live steam requirement reduced by 30% Gypsum handling –Includes seeded reaction tanks to reduce scaling in stripping column –Included full redundant train to increase availabilities Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion

18. 18 Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion Plant Layout : Quicklime Silo Stripping Columns Flash Reboilers Reaction Tanks Vibrating Mills Condensers Note: Mills, reaction tanks and stripping column have a duplicate train (interchangeable)

19. 19 Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion Summary of Key TA ® P Ammonia Recovery Benefits As compared to other neutralising reagents: –Reduced reagents costs –Flexibility in reagent make-up (anhydrous ammonia or ammonium sulphate crystals) As compared to traditional lime boiling –Gypsum scaling is abraded off vibrating mill walls –Seeded reaction tanks promote crystal growth –Quicklime added directly to feed slurry, no slaking required, no water dilution. –Exothermic slaking energy captured in feed slurry –Reduced steam requirements

20. 20 Conclusion The TA ® P ammonia recovery circuit incorporates technologies resulting in the following advancements over the traditional lime boil process: higher quicklime utilisations improved plant availabilities lower energy requirements improved management of gypsum scale. Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion

21. 21 Thank-you Pieter Mare (Hatch) Gerhard Nel (Norilsk Nickel) Introduction Reagent Selection Ammonia Recovery TAP Ammonia Recovery Conclusion Questions?