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.
Agenda
•
– Location of Tati
– TA®P Flowsheet
– Demo Plant Autoclave
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
•
Autoclave Design Review
– Different Oxygen Mass Transfer Coefficients
– Prudent Option Selected
– Autoclave Design Modified (5 vs. 4 Comp)
•
•
Design Modification
Evaluation
– Design Concerns
•
•
•
Final Agitator
Design
Conclusions
Introduction
•
•
Demo Plant Test Work
CSTR modelling
CFD modelling
Final Agitator Design
Conclusions
Where is Tati?
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
Basic Process Flowsheet
TATI ACTIVOX® PROCESS FLOWSHEET
WASH WATER
ORE
Introduction
Autoclave
Design
Review
COPPER SOLVENT
EXTRACTION
ACTIVOX ®
ULTRA-FINE
GRINDING
SOLID LIQUID SEPARATOR
SOLID RESIDUE TO PLATINUM
GROUP ELEMENTS RECOVERY
COPPER RAFFINATE
COPPER ELECTROWINNING
RELEACH
Design
Modification
COPPER
PRODUCT
AMMONIA
STRIPPING
FIRST STAGE IRON REMOVAL
Evaluation
SECOND STAGE IRON REMOVAL
AMMONIA
Final Agitator
Design
QUICKLIME
COBALT
PRECIPITATION
NICKEL ELECTROWINNING
Conclusions
COBALT SOLVENT
EXTRACTION
NICKEL SOLVENT
EXTRACTION
SODIUM
CARBONATE
COBALT
PRODUCT
AMMONIA
RECOVERY
STEAM
NICKEL
PRODUCT
TAILINGS DAM
Demo Plant Autoclave
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
Autoclave Design
Review
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
• 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
P
k L a  381.397 
V 
0.76
• Two options:
– Increase power to C1 agitators or,
– Increase the number of C1 agitators
• Autoclave design modified from five compartments
to four
Autoclave Design
Review
Introduction
Why remove a compartment?
Autoclave
Design
Review
• Increased power per agitator:
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
– 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
Design Modification
Introduction
Autoclave
Design
Review
Slurry Feed
Pipes
Quench Water
Inlet
Flash Recycle
Pipes
Slurry Overflow
Weir
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
Baffles
8 Blade
Rushton
Turbine
Oxygen
Sparger
Evaluation
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
Design Concerns to be Evaluated:
1.
2.
3.
4.
5.
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
Validity of Empirical Correlation Demo Plant Test Work
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
• Measured P/V > empirical correlation
(2.6kW/m3 vs. 1.4kW/m3)
• Subsequent runs were carried out
• Significant Ni recovery drop off below
1.4kW/m3
Validity of Empirical Correlation –
Test Results
Comparatively Consistent
Recoveries
Introduction
Autoclave
Design
Review
Design
Modification
%
Recovery
Evaluation
Final Agitator
Design
Conclusions
1.4kW/m3
Gassed power per unit volume [kW/m3]
Drop in Metal Recovery –
Theoretical CSTR Evaluation
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Cumulative Mass Fraction Exiting
Compartment
1.0
0.9
0.8
0.7
0.6
0.5
Inflection point
0.4
105 min
0.3
0.2
0.1
0.0
0
100
200
300
400
500
Time [min]
Conclusions
CFD Results
Theoretical values for 2 CSTRs in series
Theoretical values for 1 CSTR
Hot Spots –
CFD Analysis Velocity Profile
Feed and flash discharge pipe section
Introduction
Autoclave
Design
Review
Design
Modification
All Agitators – Same Rotation
Velocity
Magnitude,
m/s
3.00
View
2.50
Evaluation
Middle Agitator – Reverse Rotation
1.50
Final Agitator
Design
Conclusions
0.50
0.00
Brick Lining Wear –
CFD Analysis Velocity Profile
Introduction
Autoclave
Design
Review
Velocity
M agnitude,
m/s
7.00
6.00
Design
Modification
4.00
Evaluation
Final Agitator
Design
2.00
Conclusions
0.00
Residence Time Comparison –
Agitator Rotation Direction
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
Cumulative Fresh Feed, wt%
Residence Time Comparison –
Agitator Rotation Direction
110%
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Reverse Rotation
Same Rotation
Same Rot mean residence time = 105.38 min
Rev Rot mean residence time = 105.95 min
0
200
400
Residence Time (min)
600
800
Final Agitator Design
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
•
•
•
•
•
Eight blade Rushton turbine
Increased blade height
186kW VSD motor
69% - 2.8kW/m3
85% - 3.4kW/m3
Conclusions
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
1. Reducing the number of compartments (5 -4) should
have negligible impact on metal recovery
2. Commercial design finalised with 3 agitators in the
1st compartment
3. Well mixed 1st compartment – 7.2 turnovers/min
4. Theoretical residence time of C1 same as modelled
CFD residence time
5. Expect a uniform reaction extent and temperature
through the compartment
6. Weir wall allowed for between agitators 2 and 3 to
allow for a 5 compartment scenario to be run if
required
Thanks
Introduction
Autoclave
Design
Review
Design
Modification
Evaluation
Final Agitator
Design
Conclusions
•
•
•
•
Norilsk Nickel
Hatch – ATG
Pieterse Consulting
Hatch – Africa