Christopher Greet
Transcript of Christopher Greet
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Improving copper recoveryat Xstrata Coppers Ernest
Henry Concentrator by
changing the grindingchemistry
Chris Greet, Jessica Kinal, John Twomey and Matthew Peatey
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Flow sheet
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2002-2004: Ian Wark Research Institute conducted tests on site
with the Magotteaux Mill, but encountered problems with
copper activated pyrite.
September 2004: A SAG mill feed sample tested successfully.
April 2005: Confirmation study on new SAG feed sample.
April 2006: Further confirmation study on new SAG feed sample.
April 2008: Pilot plant trial.
November 2009: Plant trail commences.
Project History
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Laboratory results:
Pulp chemistry
Media pH Eh, mV (SHE) DO, ppm EDTA Fe, % EDTA Cu, %
Forged18% Cr30% Cr
10.910.910.9
-2393110
0.00.40.6
1.60.20.2
0.080.100.09
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10.0
12.0
14.0
16.0
18.0
20.0
22.0
24.0
65.0 70.0 75.0 80.0 85.0 90.0 95.0 100.0
Cu recovery, %
Cugrade,
%
Forged 18% Cr 30% Cr
TestRecovery, % Dilutent grade
Cu Au Au, ppm Mo, ppm IS, % NSG, %
Forged18% Cr30% Cr
85.688.887.2
65.770.465.3
5.45.25.5
143615521528
18.314.47.6
38.442.349.1
Laboratory results:
Cu/Au metallurgy
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Cu rougher
cel ls 1 and 2
Cu rougher
cel ls 3 and 4
Cu rougher
cel ls 1 and 2
Cu rougher
cel ls 3 and 4
HiCr pi lot plant bal l mi l l in
closed circui t with cyclone
Main plant
Cu rougher cells 5 to 8 Cu rougher cells 9 to 12
Cu rougher cells 5 to 8 Cu rougher cells 9 to 12
Reagents
Reagents
Forged pi lot plant bal l mi l l
in closed circui t with
cyc lone
SAG mil l discharge
Rougher tai l ing
Cu rougher concentrate
Rougher tai l ing
Cu rougher concentrate
Surge
tank
Surge
tank
Pilot plant study:
Pilot plant flow sheet
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Media Parameters
pH Eh, mV (SHE) DO, ppm EDTA Fe, % EDTA Cu, %
Forged18% Cr
10.310.1
-8354
0.030.02
0.050.03
0.10.1
Pilot plant study:
Pulp chemistry
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Pilot plant study:
Metallurgical improvement
Statistical analysis of the 65 surveys of the pilot plant indicated:
2.81.8 percent increase in Cu recovery (>99 percent confidence)
1.30.8 percent increase in Cu grade (>95 percent confidence)
3.42.2 percent increase in Au recovery (>99 percent confidence)
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Do nothing.
Convert the ball mill to high chrome grinding media:
Dump and replace with an initial charge of high chrome
Realise benefits earlier
On/off trial
Logistical nightmare for a mill of this size
Media delivery at end of year
Purge by top-up
Nominally 8 months to purge the mill
Compare before and after
Supply earlier
Plant trial:
The options
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Plant trial:
Dumping a mill without a hatch!
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Media Parameters
pH Eh, mV (SHE) DO, ppm EDTA Fe, % EDTA Cu, %
Forged18% Cr
11.511.2
7598
0.61.9
0.640.27
0.660.26
Plant trial:
Pulp chemistry
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Plant trial:
Cu recovery improvement
75
7779
81
83
85
87
89
91
93
95
0.05 0.10 0.15 0.20 0.25 0.30 0.35
Feed copper grade, %
Copperrecovery,
%
Forged Chrome Linear (Forged) Linear (Chrome)
0
10
20
30
40
50
10 100 1000
Size, micron
CuD
istributioninFinalTailing,
%
Forged 18% Cr
The copper recovery increased by 2.4 0.8 percent, with greater than 99percent confidence, which would increase the potential metal value by
$12,941,000 USD per annum.
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Conclusions
The experimental approach adopted was designed to minimise risk to the
plant. In all three phases of the work it was noted that a change fromforged steel to high chrome grinding media resulted in:
A shift in the ball mill discharge Eh to more oxidising pulp potentials;
An increase in the dissolved oxygen content of the pulp; and
A reduction in the percentage of EDTA extractable iron.
The pulp chemical changes were due to the change in grinding media can
be directly linked to improved copper and gold recoveries in the
laboratory and pilot plant studies.
In the plant trial the improvement in the copper recoveries was at least1.6 percent due to improved fine chalcopyrite recovery.
The work demonstrates that using a robust laboratory schedule such as
the Magotteaux Mill can be used effectively to predict plant performance.