Mixing System Design for the Tati Activox ® Autoclave Marc Nicolle, Mark Bellino – Hatch Africa (Pty) Ltd. Gerhard Nel –Norilsk Nickel South Africa (Pty)

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

• Introduction– Location of Tati– TA®P 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

Where is Tati?

Introduction


Design Modification

Evaluation


Conclusions

Basic Process FlowsheetTATI ACTIVOX® PROCESS FLOWSHEET

ULTRA-FINE GRINDING

COBALT SOLVENT EXTRACTION

COPPER SOLVENT EXTRACTION

ACTIVOX®

SOLID LIQUID SEPARATOR

COBALT PRECIPITATION

FIRST STAGE IRON REMOVAL

COPPER ELECTROWINNING

NICKEL SOLVENT EXTRACTION

AMMONIA RECOVERY

NICKEL ELECTROWINNING

AMMONIA STRIPPING

TAILINGS DAM

ORE

SOLID RESIDUE TO PLATINUM GROUP ELEMENTS RECOVERY

RELEACH

COBALT PRODUCT

COPPER RAFFINATE

WASH WATER

SECOND STAGE IRON REMOVAL

NICKEL PRODUCT

COPPER PRODUCT

STEAM

AMMONIA

SODIUM CARBONATE

QUICKLIME

Introduction


Design Modification

Evaluation


Conclusions

Demo Plant Autoclave

Introduction


Design Modification

Evaluation


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

• Two options:– Increase power to C1 agitators or,– Increase the number of C1 agitators

• Autoclave design modified from five compartments to four

76.0

397.381

V

PakL

Introduction


Design Modification

Evaluation


Conclusions


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


Design Modification

Evaluation


Conclusions

Design Modification

Introduction


Design Modification

Evaluation


Conclusions

Slurry FeedPipes

Quench WaterInlet

Flash RecyclePipes

Slurry OverflowWeir

8 Blade Rushton Turbine

Baffles Oxygen Sparger

Evaluation

Design Concerns to be Evaluated:1. Validity of Empirical Correlation2. Drop in Metal Recovery3. Hot Spots4. Brick Lining Wear (swirling under the impeller)5. Residence Time Comparison

Method of Evaluation– Point 1 – Testwork – Point 2 – Theory– Point 3, 4 & 5 – CFD analysis

Introduction


Design Modification

Evaluation


Conclusions

Validity of Empirical Correlation -Demo Plant Test Work

• 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

Introduction


Design Modification

Evaluation


Conclusions

86

87

88

89

90

91

92

0 0.5 1 1.5 2 2.5 3

P /V kW/m3

Validity of Empirical Correlation –

Test Results

Introduction


Design Modification

Evaluation


Conclusions

%Recovery

Gassed power per unit volume [kW/m3]1.4kW/m3

Comparatively Consistent Recoveries

Drop in Metal Recovery – Theoretical CSTR Evaluation

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 100 200 300 400 500

Time [min]

Cu

mu

lati

ve M

ass

Fra

ctio

n E

xiti

ng

C

om

par

tmen

t

CFD Results Theoretical values for 2 CSTRs in series Theoretical values for 1 CSTR

105 min

Inflection point

Introduction


Design Modification

Evaluation


Conclusions

Hot Spots – CFD Analysis Velocity Profile

0.00

3.00

0.50

1.50

2.50

Velocity Magnitude, m/s

View

All Agitators – Same Rotation

Middle Agitator – Reverse Rotation

Feed and flash discharge pipe section

Introduction


Design Modification

Evaluation


Conclusions

Brick Lining Wear – CFD Analysis Velocity Profile

0.00

7.00

2.00

4.00

6.00

Velocity Magnitude, m/s

Introduction


Design Modification

Evaluation


Conclusions

Residence Time Comparison – Agitator Rotation Direction

Introduction


Design Modification

Evaluation


Conclusions

Residence Time Comparison – Agitator Rotation Direction

0%10%20%30%40%50%60%70%80%90%

100%110%

0 200 400 600 800

Residence Time (min)

Cu

mu

lati

ve F

resh

Feed

, w

t%

Reverse Rotation

Same Rotation

Rev Rot mean residence time = 105.95 minSame Rot mean residence time = 105.38 min

0%10%20%30%40%50%60%70%80%90%

100%110%

0 200 400 600 800

Residence Time (min)

Cu

mu

lati

ve F

resh

Feed

, w

t%

Reverse Rotation

Same Rotation

Rev Rot mean residence time = 105.95 minSame Rot mean residence time = 105.38 min

Introduction


Design Modification

Evaluation


Conclusions


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

• 85% - 3.4kW/m3

Introduction


Design Modification

Evaluation


Conclusions

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

Introduction


Design Modification

Evaluation


Conclusions

Thanks

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

Introduction


Design Modification

Evaluation


Conclusions

Mixing System Design for the Tati Activox ® Autoclave Marc Nicolle, Mark Bellino – Hatch Africa (Pty) Ltd. Gerhard Nel –Norilsk Nickel South Africa (Pty)

Documents

mixing system design

increased power

recovery gassed power

c1 concern

theory point

testwork point

metal recovery

significant ni recovery