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 O 2 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/m 3 – 4.7 kW/m 3 –Outside range of commercial autoclaves –Agitator mass and bending moment – shell stress Increased number of agitators: –P/V between 2.3 kW/m 3 – 2.9 kW/m 3 –Within the range of existing autoclaves Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

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

9. Evaluation Design Concerns to be Evaluated: 1.Validity of Empirical Correlation 2.Drop in Metal Recovery 3.Hot Spots 4.Brick Lining Wear (swirling under the impeller) 5.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/m 3 vs. 1.4kW/m 3 ) Subsequent runs were carried out Significant Ni recovery drop off below 1.4kW/m 3 Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

11. Validity of Empirical Correlation – Test Results Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions % Recovery Gassed power per unit volume [kW/m3] 1.4kW/m 3 Comparatively Consistent Recoveries

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

13. Hot Spots – CFD Analysis Velocity Profile View All Agitators – Same Rotation Middle Agitator – Reverse Rotation Feed and flash discharge pipe section 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/m 3 85% - 3.4kW/m 3 Introduction Autoclave Design Review Design Modification Evaluation Final Agitator Design Conclusions

18. 1.Reducing the number of compartments (5 -4) should have negligible impact on metal recovery 2.Commercial design finalised with 3 agitators in the 1 st compartment 3.Well mixed 1 st compartment – 7.2 turnovers/min 4.Theoretical residence time of C1 same as modelled CFD residence time 5.Expect a uniform reaction extent and temperature through the compartment 6.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