clement chibwana
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High temperature heap leaching of chalcopyrite:
Method of evaluation and process model validation
Clement ChibwanaMetallurgist, Base Metals Technology-CPY Project 13th July 2012
BM Technology - CPY Project Team
Disclaimer
Slide 2
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Bioleaching process to increase rate of sulphide mineral leaching
Fe2+
Fe3+
Cu2+
H+
O2, CO2
diffusion through micro-poresair flow
migration or flow throughliquid film
reaction with mineral grains
absorption of oxygen & CO 2 into liquid film
solution phase solid phasegas phase
reaction with secondary sulphur
SO42-
BacterialGrowth
Bioleach Process: Catalytic effect enhancing oxidation rates of ferrous iron & sulphur by oxygen
- High solution Eh & fast leach kinetics
- Heat generation by oxidation of pyrite achieving high temperatures
solution flow
Slide 3Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Development strategy to scale-up from laboratory to commercial heap
Slide 4
Accurate, reliable simulation
Validated computer model
Design Parameters for Commercial Scale Heap
Understand Microbial Ecology: Optimisation of Inoculation & Microbial Growth Rates
6m Columns
Simulation Columns
Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Inoculation strategy to achieve microbial succession
Time
Tem
pera
ture
ChalcopyriteLeaching Zone
10 oC
45 oC
32 oC
68 oC
50 oC
25 oC
65 oC
Moderate
thermophiles
50 oC
High temperature
mesophiles
35 oC
Low temperature
mesophiles
Thermophiles
Sulfolobus metallicus
Metallosphaera sp.
Archaea JTC 1/2Ferroplasma JTC
Acidithiomicrobium & Acidimicrobium sp.
Acidithiobacillus caldus
Leptospirillum ferriphilum
Acidithiobacillus ferrooxidans
Acidithiobacillus thiooxidans
Sulfobacillus disulfidooxidans
Sulfobacillus MAD
60 oC
Slide 5Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Simulation column construction
Slide 6Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Simulation column operation: loading & unloading
Slide 7Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Sulphide mineral distribution of the chalcopyrite o re showing copper source ratio’s (CSR)
Slide 8Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Gangue mineral distribution of thechalcopyrite ore
Slide 9Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Simulation column Pregnant Leach Solution (PLS) pH & Eh profiles
Slide 10
400
500
600
700
800
900
1000
1,0
1,5
2,0
2,5
3,0
0 50 100 150 200 250 300 350
Pot
entia
l vs
SH
E /m
V
pH
Leach Period /days
PLS pH PLS solution potential
Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Simulation column oxygen utilisation
Slide 11
0
10
20
30
40
50
60
70
0 50 100 150 200 250 300
% O
xyge
n U
tilis
ed
Time (days)
Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Simulation column mineral extraction and temperature profiles
Slide 12
0,0
1,0
2,0
3,0
4,0
5,0
6,0
7,0
8,0
9,0
0
10
20
30
40
50
60
70
80
90
100
0 50 100 150 200 250 300
Air
and
Liqu
id fl
ow /
Kg.
m-2
.hr
Ave
rage
Tem
pera
ture
/°C
Pyr
ite O
xida
tion
/% C
oppe
r E
xtra
ctio
n /%
Leach Period /days
Average Temperature Pyrite Oxidation Copper Extraction Air flow Liquid flow
Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Microbial population change in solution as a function of ore temperature : simulation column
Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012 Slide 13
Simulation column energy balance
Slide 14
0
10
20
30
40
50
60
70
80
-80
-60
-40
-20
0
20
40
60
80
100
0 50 100 150 200 250 300
Tem
pera
ture
(oC
)
Ene
rgy
per
unit
volu
me
(W
/m3)
Time (days)
Energy at Top Energy at Bottom Energy Accumulation Energy Generated Column Temperature
Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Simulation column temperature profile
Slide 15Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Process model fit to extraction & temperature profi les of the simulation column
Slide 16
0
10
20
30
40
50
60
70
80
0
10
20
30
40
50
60
70
80
0 50 100 150 200 250 300
Ave
rage
Col
umn
Tem
pera
ture
(de
g C
)
Cop
per
Ext
ract
ion
(%
)
Leach Period (days)
Calculated Copper Extraction
Measured Copper Extraction
Calculated Average Temperature
Measured Average Temperature
Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Process model fit to oxygen utilisation
Slide 17
0
10
20
30
40
50
60
70
80
90
0 50 100 150 200 250 300
Oxy
gen
Util
isat
ion
(%
)
Leach Period (days)
Calculated Measured
Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Process model fit to net acid consumption results
Slide 18
-10
-8
-6
-4
-2
0
2
4
6
0 50 100 150 200 250 300
Net
Aci
d C
onsu
mpt
ion
(kg
/t)
Leach Period (days)
Calculated Measured
Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Progress since IBS 2007
Slide 19Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Pilot heap : 500 000 kT Ore
Slide 20Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Hot zones of heap 9-15m depth
S
1
4
23
6 5
789
N
S
EW
Slide 21Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Pilot heap 3D temperature profiles
3 m 6 m 9 m
15 m 18 m
November 1 2007: 5 days irrigation to low flowrate (between 10 &14 m3/h)
Slide 22Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
November 30 2007: 34 days irrigation to rate 2l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 23Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
December 15 2007: 49 days irrigation to rate 4.5 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 24Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
December 25 2007: 59 days irrigation to rate 5 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 25Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
3 m 6 m 9 m
15 m 18 m
January 12 2008: 77 days irrigation to rate 5.5 l/h/m2
Pilot heap 3D temperature profiles
Slide 26Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
3 m 6 m 9 m
15 m 18 m
January 26 2008: 91 days irrigation to rate 5.5 l/h/m2
Pilot heap 3D temperature profiles
Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012 Slide 27
February 12 2008: 108 days irrigation to rate 5.5 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 28Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
February 20 2008: 116 days irrigation to rate 4.5 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 29Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
March 12 2008: 137 days irrigation to rate 1.5 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 30Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
March 20 2008: 145 days irrigation to rate 2 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 31Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
April 3 2008: 159 days irrigation to rate 3 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 32Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
April 22 2008: 178 days irrigation to rate 3 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 33Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
May 10 2008: 196 days irrigation to rate 4.5 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 34Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
May 25 2008: 212 days irrigation to rate 4.5 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 35Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Jun 5 2008: 222 days irrigation to rate 4.5 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 36Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Jun 22 2008: 239 days irrigation to rate 3 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 37Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
July 15 2008: 262 days irrigation to rate 3 l/h/m2
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 38Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
July 27 2008: 274 days. Since July 22 cut irrigation and drainage starts
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 39Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
August 7 2008: 285 days. Continuous period of drainage
3 m 6 m 9 m
15 m 18 m
Pilot heap 3D temperature profiles
Slide 40Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Mineral dissolution versus depth: Hot zone
AVG Recoveries in Hot and Cool Zones by Depth
0
10
20
30
40
50
60
70
80
90
100
Cc Cv Cp Bn CuT Pyrite
Rec
.%
HOT 0-6
HOT >6
COOL 0-6
COOL >6
Slide 41Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Conclusions
The results presented demonstrate the ability of high temperature bioleaching to effectively leach a primarycopper ore. The copper recovery achieved was 75% in a leach cycle of 283 days.
The application of the Simulation Column patented by BHP Billiton - Base Metals (US Patent No. US 7727510B2, 1 June 2010) has been demonstrated, showing that self-generation of heat from bioleaching of pyritecontained in the ore may be managed to sustain high operating temperatures (average of 70 °C).
The success of bioleaching was attributed to the inoculation strategy and the ability to achieve microbialsuccession as the ore temperature increased.
The Process Model developed by BHP Billiton - Base Metals was validated against experimental results fromoperation of the Simulation Column.
The High Temperature Heap Leach Process has been tested in a 500 kT Pilot Heap confirming that highchalcopyrite dissolutions may be achieved at heap temperatures of >50°C.
The development work by BHP Billiton – Base Metals has laid the foundation for the application of HighTemperature Heap Leaching for treatment of suitable primary copper ores.
The gangue mineral composition, crush size, and ore permeability as a function of heap height and leach time,are also critical factors that determine the heap design and leach performance.
Slide 42Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012
Acknowledgements
The high standard of work by the Mintek Biotechnology Division is acknowledged along with significant
individual contributions by Stefan Robertson (Mintek) and Heinrich Muller (Mintek), which combined to make
the test program a success.
The support work by the University of Cape Town is recognised, in particular the work carried out by Nathan
van Wyk for the molecular biology work done on the samples.
Acknowledgement is also given to Hatch Africa (Pty) Ltd and Wade Walker for the design and construction of
the columns described in this paper and for their engineering support during the operation of the column.
Slide 43Clement Chibwana, Metallurgist, Base Metals Technology –CPY Project, 13th July 2012