Mixing System Design for the Tati Activox ® Autoclave

1. Mixing System Design for the Tati Activox® Autoclave Marc Nicolle, Mark Bellino – Hatch Africa (Pty) Ltd. Gerhard Nel –Norilsk Nickel South Africa (Pty) Ltd. Tom Plikas, Umesh Shah, Lyle Zunti – Hatch - Ltd. Herman J. H. Pieterse – Pieterse Consulting, Inc.

2. Agenda • Introduction • Location of Tati • TA®P Flowsheet • Demo Plant Autoclave • Autoclave Design Review • Different Oxygen Mass Transfer Coefficients • Prudent Option Selected • Autoclave Design Modified (5 vs. 4 Comp) • Design Modification • Evaluation • Design Concerns • Demo Plant Test Work • CSTR modelling • CFD modelling • Final Agitator Design • Conclusions Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

3. Where is Tati? Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

4. Basic Process Flowsheet Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

5. Demo Plant Autoclave Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

6. Autoclave Design Review • Autoclave design review in Canada • Over 75% of Ni is recovered in C1 • Concern on the original O2 mass transfer coefficient used to size the agitators in C1 • This indicated a lower agitator power requirement than the empirical correlation • Two options: • Increase power to C1 agitators or, • Increase the number of C1 agitators • Autoclave design modified from five compartments to four Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

7. Autoclave Design Review Why remove a compartment? • Increased power per agitator: • P/V between 3.9 kW/m3 – 4.7 kW/m3 • Outside range of commercial autoclaves • Agitator mass and bending moment – shell stress • Increased number of agitators: • P/V between 2.3 kW/m3 – 2.9 kW/m3 • Within the range of existing autoclaves Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

8. Design Modification Slurry Overflow Weir Flash Recycle Pipes Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions Quench Water Inlet Slurry Feed Pipes Baffles Oxygen Sparger 8 Blade Rushton Turbine

9. Evaluation Design Concerns to be Evaluated: • Validity of Empirical Correlation • Drop in Metal Recovery • Hot Spots • Brick Lining Wear (swirling under the impeller) • Residence Time Comparison Method of Evaluation • Point 1 – Testwork • Point 2 – Theory • Point 3, 4 & 5 – CFD analysis Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

10. Validity of Empirical Correlation -Demo Plant Test Work • Measured P/V > empirical correlation (2.6kW/m3 vs. 1.4kW/m3) • Subsequent runs were carried out • Significant Ni recovery drop off below 1.4kW/m3 Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

11. Comparatively Consistent Recoveries % Recovery Gassed power per unit volume [kW/m3] 1.4kW/m3 Validity of Empirical Correlation – Test Results Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

12. Inflection point 105 min Drop in Metal Recovery – Theoretical CSTR Evaluation Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

13. View All Agitators – Same Rotation Middle Agitator – Reverse Rotation Feed and flash discharge pipe section Hot Spots – CFD Analysis Velocity Profile Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

14. Brick Lining Wear – CFD Analysis Velocity Profile Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

15. Residence Time Comparison – Agitator Rotation Direction Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

16. Residence Time Comparison – Agitator Rotation Direction Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

17. Final Agitator Design • Eight blade Rushton turbine • Increased blade height • 186kW VSD motor • 69% - 2.8kW/m3 • 85% - 3.4kW/m3 Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

18. Conclusions • Reducing the number of compartments (5 -4) should have negligible impact on metal recovery • Commercial design finalised with 3 agitators in the 1st compartment • Well mixed 1st compartment – 7.2 turnovers/min • Theoretical residence time of C1 same as modelled CFD residence time • Expect a uniform reaction extent and temperature through the compartment • Weir wall allowed for between agitators 2 and 3 to allow for a 5 compartment scenario to be run if required Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

19. Thanks • Norilsk Nickel • Hatch – ATG • Pieterse Consulting • Hatch – Africa Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions