Development of the TATI Activox

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Development of the TATI Activox BMR Ammonia
Recovery Circuit
D.A. van den Berg (Hatch), P. Maré (Hatch), G.J.
Nel (Norilsk Nickel)
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Agenda

• Introduction
• Background to TAP
• TAP flow sheet
• Selection of SX neutralizing reagent
• General SX neutralizing reagent options
• Benefits of ammonia recovery for TAP
• Ammonia recovery technology
• Traditional lime boil process
• TAP ammonia recovery process
• Vibrating mills
• Reaction tanks
• Stripping column and design
• Conclusion and key benefits

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
3
Tati Activox Project
Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
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The Tati Activox Project (TAP)

• Greenfields project for Activox
  hydrometallurgical plant located outside
  Francistown, Botswana
• Process tested at HDP (demo plant)
• Uses Activox technology to treat nickel sulphide
  concentrate.
• Ammonia recovery eased key location challenges
• Project indefinitely suspended mid 2008 with
  detailed process design complete and construction
  underway.

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
Feed Conc 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 640
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The Tati Activox Plant
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SX Neutralizing Reagent Selection

• General Factors which were considered
• What are the by-products created and how are they
  handled?
• Marketable?
• Safe disposal?
• What is the transportation requirements for the
  reagent by-product?
• What is the impact on plant water balance?
• What is the impact on overall plant process
  conditions (impurities)?

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
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Typical Reagent Options for pH control in SX

• Ammonia
• Supplied as anhydrous liquid
• Ammonium sulphate can be crystallised for
  fertilizer
• Sodium Hydroxide
• Supplied as 50 solution or pellets
• Sodium sulphate can be crystallised for detergent
  filler, pulp paper or glass industry
• Sodium Carbonate
• Supplied as anhydrous solid
• Similar sodium sulphate product
• Location
• No local market for ammonium sulphate or sodium
  sulphate by-product

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
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Indicative Reagent Supply Costs
R6500 /t
Sodium Hydroxide (NaOH)
Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
Ammonia (NH3)
Increasing Cost
Sodium Carbonate (Na2CO3)
Quicklime (CaO)
R150 /t

• Quicklime is by far the cheapest alkali
• Ammonia recovery uses cheap base to recover
  more expensive ammonia

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Tati Neutralising Reagent Selection for SX
No. Reagent Required Reagent (Kg per t acid)
1 Ammonium hydroxide 347 kg ammonia prt ton acid
2 Option 1 with 90 ammonia recovery 34.7 kg ammonia and 515 kg lime per ton acid
3 Sodium hydroxide 408 kg/t
4 Sodium carbonate 1081 kg/t
Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion

• Ammonia recovery has significantly less ammonia
  reagent costs

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Traditional Ammonia Recovery

• The lime boil process

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
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Traditional Ammonia Recovery

• Advantages
• Only need reaction tanks and condensers (and
  slaking equipment)
• Ammonia make-up by adding ammonium sulphate to
  lime boil feed or anhydrous ammonia to recovered
  ammonia.
• Disadvantages
• Gypsum Scaling
• Lime Slurry Dilution
• Energy Intensive

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
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TAP Ammonia Recovery Process

• Vibrating mills
• Reaction tanks
• Steam stripping, condensing, make-up
• Barren slurry to tailings, process water recovered

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
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Vibrating Mills
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Reaction Tanks
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Steam Stripping
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Steam Stripping

• Theoretical stages plotted on McCabe Thiele
• (Confirmed by ASPEN modelling, Stuart Bradbury of
  PPT)

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
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Ammonia Stripping Column Design

• Demo plant
• Small (6 diameter) column
• 10 tray efficiency duration operation
• TAP Design
• Design for 15 tray efficiency
• Larger column diameter and tray spacing
• Typical efficiency (for dual flow trays) is
  20-40, but reduced due to slurry environment.
• Design for reduced steam consumption
• Higher L/V ratio than demo plant to reduce steam
  requirements
• Discharged into flash cooler to recover steam
• live steam requirement reduced by 30
• Gypsum handling
• Includes seeded reaction tanks to reduce scaling
  in stripping column
• Included full redundant train to increase
  availabilities

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
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Plant Layout
Stripping Columns
Note Mills, reaction tanks and stripping column
have a duplicate train (interchangeable)
Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
Condensers
Flash Reboilers
Reaction Tanks
Quicklime Silo
Vibrating Mills
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Summary of Key TAP Ammonia Recovery Benefits

• As compared to other neutralising reagents
• Reduced reagents costs
• Flexibility in reagent make-up (anhydrous ammonia
  or ammonium sulphate crystals)
• As compared to traditional lime boiling
• Gypsum scaling is abraded off vibrating mill
  walls
• Seeded reaction tanks promote crystal growth
• Quicklime added directly to feed slurry, no
  slaking required, no water dilution.
• Exothermic slaking energy captured in feed slurry
• Reduced steam requirements

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
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Conclusion

• The TAP ammonia recovery circuit incorporates
  technologies resulting in the following
  advancements over the traditional lime boil
  process
• higher quicklime utilisations
• improved plant availabilities
• lower energy requirements
• improved management of gypsum scale.

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
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Thank-you

• Pieter Mare (Hatch)
• Gerhard Nel (Norilsk Nickel)

Introduction Reagent Selection Ammonia
Recovery TAP Ammonia Recovery Conclusion
Questions?