Solvent%20extraction%20design%20consideration%20for%20the%20Tati%20Activox

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

• Design considerations and challenges faced
• during design of the SX circuits for the TAP
• Unique process conditions of the TAP
• Multiple SX trains
• Integrated fire management plan

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2. Background

• TAP commercialisation of Norilsk Nickel Activox
  process
• Demonstration plant (1170)
• Phoenix mine site, NE Botswana
• Activox process - UFG autoclave pressure
  leach

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3. TAP Flowsheet
Feed 506 000 dt/a
Ni 4.2 - 5.3
Cu 2.7 - 5.1
Co 0.11 - 0.18
Fe 47
Product t/a
Nickel metal 25 000
Copper metal 22 000
Cobalt carbonate 639
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4. Design Issues related to TAP conditions

• Process conditions in SX circuit dependant on
• Ore type
• Leach conditions reagents
• Type and sequence of processes
• Design requirements due to unique TAP
  conditions
• Reduce minimise impact of scaling
• Equipment selection for corrosive solutions
• Minimising of crud formation control
• Reliable pH control

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4. Design Issues related to TAP conditions
Scaling

• 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

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4. Design Issues related to TAP
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

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4. Design Issues related to TAP 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

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4. Design Issues related to TAP
conditionsCorrosive solutions

• Material selection has a large influence on
  capex requires careful consideration
• TAP 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

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4. Design Issues related to TAP 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

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4. Design Issues related to TAP 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

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4. Design Issues related to TAP 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

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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

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Design Issues related to multiple SX
trainsPlant layout

• Figure 5.1 Miller Side Feed Design

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Design Issues related to multiple SX
trainsSettler design

• Figure 5.2 Mixer Interconnecting pipe
  Figure 5.3 Settler internals

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Design Issues related to multiple SX
trainsOrganic recovery equipment
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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

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7. Conclusions

• Process considerations related TAP 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

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8. Acknowledgements

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

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pH Control
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Organic equipment recovery
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Comparison of SX Circuits
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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

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Plume analysis