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Solvent extraction design consideration for the Tati Activox® Plant

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

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Solvent extraction design consideration for the Tati Activox® Plant

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  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

  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 conditionsScaling Conditions for Scaling • Super-saturation of Ca2SO4.2H2O • 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 conditionsScaling (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 conditionsScaling (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 conditionsCorrosive 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 conditionsCrud 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 conditionsCrud 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 conditionspH Control • pH Control in Co and Ni SX circuits • Extraction stages – NH4OH • Stripping stages – H2SO4 • 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. 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. Design Issues related to multiple SX trainsPlant layout Figure 5.1 Miller Side Feed Design

  15. Figure 5.2 Mixer Interconnecting pipeFigure 5.3 Settler internals Design Issues related to multiple SX trainsSettler design

  16. Design Issues related to multiple SX trainsOrganic 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

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