council for mineral technology - mintek · 1.head grade 2.waste dilution 3.degree of weathering...
TRANSCRIPT
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UG-2 ore variability5 June 2009
Dr MAW Bryson, Mr N V Ramlall, Mr A McKenzie, Mr P Morgan (DRA)
Council for Mineral Technology
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Outline
Presentation Outline
1. Variability drivers
2. Database examples of UG-2 variability
with respect to flotation & milling
3. Concluding remarks
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Project feasibility studies
Geological reserve(discount
geological losses)
Mining method
Metallurgical work
Factors•Comminution loss
•Flotation loss
Converting into a reserve
1. Scoping tests
2. Pre-feasibilityØ Variability study
3. FeasibilityØ Bulk sample study
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1. Head grade
2. Waste dilution
3. Degree of weathering
4. Degree of alteration
5. Blasting and mining methods
6. Proximity to geological features
Ø Footwall rock types i.e. IRUP, PEG, PRX, ANS, etc
Ø Faults
Ø Intrusions
Ø Lineaments
7. Geographical location i.e. Western/Eastern Limb
Drivers of variability in UG-2 ores
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Consequences of variabilityØ Important for determining metallurgical parameters like recovery and
grade across a deposit
Ø Important for determining the payback period for a mine
Ø Milling rates for e.g. waste dilution can reduce throughput by 40 %
Ø Possible to identify problematic/good areas in a deposit
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Variability methodology
Sam
plin
g M
etho
dolo
gy
Metallurgical testw
ork
Cost versus complexity of study
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Examples
Examples of three Eastern Limb UG-2 ores
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Ore No.1
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Ore No.1 cont…
0
1
2
3
4
5
≤78 >78<82 >82<86 >86<90 ≥90
4E Recovery/ [%]
Freq
uenc
y of
occ
uren
ce Composite recovery 83 %
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Ore No.2Zone
compositesZone drill cores
Bulk composite
Zone composites
Bulk composite
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Ore No.2 cont…
0
1
2
3
≤87 88 89 90 91 92 93 ≥943E Recovery/ [%]
Freq
uenc
y of
occ
uren
ceBulk composite recovery 93 %
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Ore No.3
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Ore No. 3 cont…
0
1
2
3
4
5
≤74 >74<78 >78<82 >82<86 >86<90 ≥904E Recovery/ [%]
Freq
uenc
y of
occ
uren
ce
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Examples
Examples of two Western Limb UG-2 ores
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Ore No.4
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Ore No.4 cont…
Site B composite recovery 84 %
0
2
4
6
8
10
12
14
≤74 >74<78 >78<82 >82<86 >86<90 ≥903E Recovery/ [%]
Freq
uenc
y of
occ
uren
ceSite A Site B
Site A composite recovery 75 %
Site B composite recovery 84 %
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• Site A and Site B were characterised into altered an unaltered samples
• The presence of large amounts of talc, chlorite, serpentine, amphibole
and mica indicate some degree of alteration
Ore No.4 cont…
0123456789
10
≤70 >70<74 >74<78 >78<82 >82<86 >86<90 ≥903E Recovery [7 min]/ [%]
Freq
uenc
y of
occ
uren
ce "Altered samples" "Unaltered samples"
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Ore No. 5 – Area composite
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Ore No. 5 – Area composite cont…
0
1
2
3
≤75 76 77 78 ≥793E Recovery/ [%]
Freq
uenc
y of
occ
uren
ce
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Ore No. 5 - Lithologies
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Ore No. 5 – Lithologies cont…
0
10
2030
40
50
60
7080
90
100
Pyroxenite Anorthosite Iron-rich upperpyroxenite
Pegmatoidalpyroxenite
Lithology
3E R
ecov
ery/
[%]
Central zone Eastern Zone
Lithology composite recovery 73 %
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Milling variability
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UG2 ROM Size Ditributions
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
80.0%
90.0%
100.0%
0.01 0.10 1.00 10.00 100.00 1000.00
Size,mm
%w
t Pas
sing
Milling Variability cont…
Variable top size
Size/ [mm]
%w
t Pas
sing
UG-2 ROM Size Distribution
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Western LimbØ Ore body Variability affects grind and therefore recovery
Ø Example- Typical finite recovery-grind curve
82
84
86
88
90
92
35 45 55 65 75 85% -75 m
Fini
te R
ecov
ery/
[%]
μ
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Eastern Limb• Waste rock generally harder than on Western Limb; and higher variability
encountered• Example- Eastern Limb ‘waste fraction’ effect on ROMB grinding
efficiency
• Indicates 40 % slowdown in breakage at high waste levels!
0.0
0.2
0.4
0.6
0.8
1.0
1.2
25 30 35 40 45
% Waste in feed
Rel
ativ
e sp
ecifi
c ra
tes
of
brea
kage
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UG2 Grinding cont…•Bi-modal nature of ore is significantly affected by variations in ‘waste’ dilution
5
10
15
20
25
30
35
10 100 1000 10000 100000
Size/
Wor
k In
dex/
[kW
h/t]
Footwall Chromatic reef
[μm]
Point of cross over reflecting more energy for liberating at grain size
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Grind Variation- Typical Western Limb UG2
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
1 2 3 4 5 6 7 8 9 10 11
Sample ID
Com
posi
tion/
[%]
Reef Pyroxenite Norite Other
73.91.026Composite71.90.9121178.61.145976.31.053877.01.088767.40.957670.71.070571.41.078469.41.030377.21.283271.81.081173.50.98175.31.01910
(Control)
Actual% -75 µm
Relative Grindκn/κcontrol_avg
Sample №
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Concluding remarks• Allocate more resources to understand the inherent variability in a
deposit
• Formulate a standard metallurgical variability methodology
• Use the methodology to understand what factors control variability
within a deposit
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