1. Solvent extraction design consideration for the Tati Activox® Plant I. Cronje (Hatch), E. Robles (Hatch), G Nel (Norilsk Nickel)

2. 1. Aim of presentation Design considerations and challenges faced during design of the SX circuits for the TA®P Unique process conditions of the TA®P Multiple SX trains Integrated fire management plan

3. 2. Background TAP® commercialisation of Norilsk Nickel Activox® process Demonstration plant (1:170) Phoenix mine site, NE Botswana Activox ® process - UFG & autoclave pressure leach

4. 3. TA®P Flowsheet Feed506 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 carbonate639

5. 4. Design Issues related to TA®P conditions Process conditions in SX circuit dependant on: Ore type Leach conditions & reagents Type and sequence of processes Design requirements due to unique TA®P conditions: Reduce & minimise impact of scaling Equipment selection for corrosive solutions Minimising of crud formation & control Reliable pH control

6. 4. Design Issues related to TA®P conditions Scaling Conditions for Scaling Super-saturation of Ca 2 SO 4.2H 2 O Tati concentrate, pyrrhotite ore with Ca, Mg and Mn Addition of limestone to control pH in Fe removal Co and Ni SX circuits prone to scaling Excessive scaling results in: Reduced processing & production capacity Increased energy requirements Increased downtime & maintenance cost

7. 4. Design Issues related to TA®P conditions Scaling (cont.) Design approach to reduce scaling: Adjustment of Process parameters Dilution of Co PLS liquor with 5 % filtered raw water Temperature control of Co PLS pH control to reduce Ca co-extraction Piping design Material selection has an influence on scale formation FRP minimises adhesion of scale Pipe spools designed for easy removal & descaling

8. 4. Design Issues related to TA®P conditions Scaling (cont.) Cleaning and maintenance Spare extraction mixer-settler unit in Ni SX plant Train layout optimized to ensure access to equipment Removable lids on mixer tanks, inspection hatches on settler roofs Special nozzles for hydro-blasting from tanks Use of synergists Combination of reagents to enhance mass transfer and kinetics Novel concept, not widely implemented in industry Ni-Ca synergist tested at demonstration plant Considerable improvement in Ni-Ca separation and marginal improvement in Ni extraction to be weighed up against increased cost

9. 4. Design Issues related to TA®P conditions Corrosive solutions Material selection has a large influence on capex; requires careful consideration TA®P design relies on addition of chlorides to enhance Cu extraction Tests from demo plant showed SAF 2205 - metal components in contact with solution FRP tanks & settlers with SAF 2205 internals

10. 4. Design Issues related to TA®P conditions Crud formation Conditions for crud formation Ingress of solids/chemical precipitates/insects into solution Degradation products from extractant Effect of crud Reduced settler capacity Reduced phase disengagement Excessive organic entrainment Organic loss

11. 4. Design Issues related to TA®P conditions Crud formation (cont.) Crud control & prevention PLS Clarification Settling ponds prior to SX Removal of degradation products Isolation of SX mixer-settlers from external environment Water purification pH control Crud treatment

12. 4. Design Issues related to TA®P conditions pH Control pH Control in Co and Ni SX circuits Extraction stages – NH 4 OH Stripping stages – H 2 SO 4 Tight pH control in Co SX and Ni SX to prevent co- extraction of metals Organic coating and/or scaling of probes can affect reliability of pH measurements Dedicated pH pot at feed end of settler connected with pipe to lower settler wall Cascading pH control to minimize reagent flowrate fluctuations and timely identification of pH deviations

13. 5.Design Issues related to multiple SX trains Optimising plant layout Minimise footprint Ensure easy access for maintenance Safe separation distance (Fire plume analysis) Settler selection & design Minimise turbulence; ensure sufficient coalescing surface & ensure sufficient time for phase disengagement Insufficient design may result in organic entrainment and subsequent organic cross-contamination (loss of organic) Minimise organic cross-contamination Organic carry-over from one SX circuit to the next Detrimental effects include: process upsets; reduced efficiency; metal loss & off spec product Effect reduced by proper selection of organic removal equipment

14. 5.Design Issues related to multiple SX trains Plant layout Figure 5.1 Miller Side Feed Design

15. 5.Design Issues related to multiple SX trains Settler design Figure 5.2 Mixer Interconnecting pipe Figure 5.3 Settler internals

16. 5.Design Issues related to multiple SX trains Organic recovery equipment

17. 6. Mitigation of Fire Risks Integrated fire suppression system Hazardous area assessment Fire & explosion modelling Fixed automatic foam-water deluge External automatic foam protection of vessels, tanks etc. Manually operated foam protection for internals of vessels Manual yard hydrants along perimeter of the plant

18. 7. Conclusions Process considerations related TA®P SX circuits Reduced scaling Minimise crud formation & control Efficient pH control Design considerations related to Multiple SX trains Optimising plant layout Suitable settler selection & design of internals Organic recovery strategy to minimise organic cross- contamination Mitigation of fire risks

19. 8. Acknowledgements Norilsk Nickel Africa (Pty) Ltd. Hatch Africa (Pty) Ltd. Graeme Miller Multi-disciplinary SX Design Team from Hatch Brisbane Office

20. pH Control

21. Organic equipment recovery

22. Comparison of SX Circuits

23. Fire Plume analysis Basis for layout Area of fire, volume and type of fuel, climatic and wind conditions, prsence of other assets and public access Plant layout – to reduce impact of fire escalation and increase ease of isolation & containment SX area divided into zones with bund and sump to overflow to emergency dump ponds

24. Plume analysis