Mixing System Design for the Tati Activox

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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.
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Agenda

• Introduction
• Location of Tati
• TAP 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
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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
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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 O2 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
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Autoclave Design Review

• Why remove a compartment?
• Increased power per agitator
• P/V between 3.9 kW/m3 4.7 kW/m3
• Outside range of commercial autoclaves
• Agitator mass and bending moment shell stress
• Increased number of agitators
• P/V between 2.3 kW/m3 2.9 kW/m3
• Within the range of existing autoclaves

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

• Design Concerns to be Evaluated
• Validity of Empirical Correlation
• Drop in Metal Recovery
• Hot Spots
• Brick Lining Wear (swirling under the impeller)
• 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
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Validity of Empirical Correlation -Demo Plant
Test Work

• Measured P/V gt empirical correlation (2.6kW/m3
  vs. 1.4kW/m3)
• Subsequent runs were carried out
• Significant Ni recovery drop off below 1.4kW/m3

Introduction Autoclave Design Review Design
Modification Evaluation Final Agitator Design
Conclusions
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Validity of Empirical Correlation Test Results
Introduction Autoclave Design Review Design
Modification Evaluation Final Agitator Design
Conclusions
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Drop in Metal Recovery Theoretical CSTR
Evaluation
Introduction Autoclave Design Review Design
Modification Evaluation Final Agitator Design
Conclusions
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Hot Spots CFD Analysis Velocity Profile
Introduction Autoclave Design Review Design
Modification Evaluation Final Agitator Design
Conclusions
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Brick Lining Wear CFD Analysis Velocity Profile
Introduction Autoclave Design Review Design
Modification Evaluation Final Agitator Design
Conclusions
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Residence Time Comparison Agitator Rotation
Direction
Introduction Autoclave Design Review Design
Modification Evaluation Final Agitator Design
Conclusions
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Residence Time Comparison Agitator Rotation
Direction
Introduction Autoclave Design Review Design
Modification Evaluation Final Agitator Design
Conclusions
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Final Agitator Design

• Eight blade Rushton turbine
• Increased blade height
• 186kW VSD motor
• 69 - 2.8kW/m3
• 85 - 3.4kW/m3

Introduction Autoclave Design Review Design
Modification Evaluation Final Agitator Design
Conclusions
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Conclusions

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

• Norilsk Nickel
• Hatch ATG
• Pieterse Consulting
• Hatch Africa

Introduction Autoclave Design Review Design
Modification Evaluation Final Agitator Design
Conclusions