Scavenging Flotation Tailings using a
Continuous Centrifugal Gravity
Concentrator
Hassan Ghaffari, Bern Klein
UBC Mining
Ish Grewal, Knelson Gravity Solutions
Continuous Centrifugal
Gravity Concentrators
Kelsey Jig
Falcon Model C
Knelson CVD
CVD Concentrator
•Operating Variable
•Bowl speed
•Fluidization water
•Pinch valve open time
•Pinch valve closed time
•Variable interactions
Model
Feed Rate (t/h)
CVD6-1
0.5 – 2
CVD32-1
40 – 70
CVD32-2
40 – 70
CVD42-1
70 – 100
CVD Applications
• Industrial Applications
•Density separator
•Size classifier
•Mass yields (1 to 40%)
•De-slime
–
–
–
–
Separation of iron oxides from talc
Cassiterite
Chromite
Gold and gold bearing sulfides
• Tested Application
– Scavenging rougher flotation tailings
– Scavenging cleaner flotation tailings
– Separation of ash and sulfur from
coal
Flotation
100
90
80
21.0
70
60
50
40
30
15.0
18.0
12.0
9.0
6.0
20
10
0
Distribution (%)
Recovery (%)
Recovery versus Particle Size
3.0
0.0
1
10
100
Particle Size (um)
1000
Recovery
Particle Size
Preferred Size
Scavenging Flotation Tailings
• CVD - Size enhanced density separator
• Recover coarse middling particles from tailings in small mass yield
(<5%)
– Recycle CVD concentrate to grinding circuit
– Reduce losses at coarse end of particle size distribution
– Improve overall metal recovery
• Potential opportunity
– Increase grind size
– Reduce losses at fine end of particle size distribution
– Increase grinding circuit throughput
– Reduce energy requirements
• Effectively produce narrower size distribution of liberated sulfide
minerals in particle size range where flotation is most efficient
Eskay Creek Mine
• Au/Ag Mine
• Flotation of bulk sulfide
concentrate grading 100 g/t Aueq
Eskay Creek Mine Flotation Circuit
Feed
Ball Mill
Cyclone
Hydrocyclone O/F
Flotation
Tailing
Conc.
Knelson
Conc.
Gemini Table
Conc.
Smelter
• Au/Ag Flotation
recoveries average 90%
• Variations in ore
mineralogy affect
recoveries
Pilot Scale Testing
-Lab testing
-Plant testing
UBC Center for
Mineral Processing
Sample Characterization
Sample
P80
(µm)
Au
Ag
+100 mesh
Fraction
(ppm)
(ppm)
Weight %
Au Distrib. %
S Distrib.
%
+150 mesh Fraction
LGT
130
1.9
48.3
9.3
27.9
20.6
HGT
100
3.2
39.0
5.3
10.6
10.7
Batch Knelson Tests
Sample
Mass Yield %
Au (ppm)
Au Recovery %
LGT
5.0
5.1
20.0
HGT
4.0
3.9
8.8
Lab Pilot Scale Tests Results - LGT
Test
Au (ppm)
Au Recov %
Upgrade Ratio
Mass Yield %
1
6.31
5.5
5.95
0.93
2
4.46
6.5
3.88
1.67
3
12.51
28.4
8.67
3.27
4
3.66
14.7
3.33
4.43
5
5.60
35
4.52
7.74
6
4.36
15.3
1.64
9.32
Au Grade versus Particle Size
in CVD Concentrate and Tailing
S Grade versus Particle Size
in CVD Concentrate and Tailing
5
4
Concentrate
Tailing
3
3
2
2
1
1
Size Class (mesh)
+5
0
+7
0
-5
0
-7
0
+1
0
0
0
0+
14
0
-1
0
-1
4
0+
20
0
0+
27
-2
0
-2
7
0+
40
0
0
0
-4
0
S Grade %
4
40
10
9
8
7
6
5
4
3
2
1
0
Au Recovery %
35
30
25
20
15
10
5
Au Recovery %
Au Upgrade Ratio
0
0.5
2.5
4.5
Mass Yield %
6.5
8.5
Au Upgrade Ratio
Au Grade/Recovery versus Mass Yield
Size Partition to CVD Conc.
80
Partition Number %
70
60
Test 3
Test 6
50
40
30
20
10
0
10
100
Size (µm)
1000
Eskay Creek Plant Trials
• Thickened flotation tailings
• 26 Trials
20
30
25
16
Conc. Au Eq (g/t)
Gold Eq Recovery (%)
18
20
15
10
14
12
10
8
6
4
5
2
0
0
0
5
10
CVD Masspull (%)
15
20
0
5
10
CVD Masspull (%)
15
20
Eskay Creek Plant Trials
60
50
CVD Conc
CVD Tails
30
20
10
0
-38
38
53
75
106
150
Particle Size (um)
212
300
425
Au (g/t)
40
Eskay Creek Plant Trials
6000
5000
CVD Conc
CVD Tails
3000
2000
1000
0
-38
38
53
75
106
150
Particle Size (um)
212
300
425
Ag (g/t)
4000
Eskay Creek – Plant Trial
120
100
100
80
80
60
60
40
Gold Grade.
40
Gold Rec.
20
20
0
7
10
12
15
Flot. Conc. Mass Yield (%)
0
100
Gold Recovery (%)
Gold Eq (g/t)
• Flotation of CVD Concentrate
Proposed Hybrid Flotation / Gravity Flowsheet
Feed
Ball Mill
Cyclone
O/F
Hydrocyclone
Tailings
Flotation
Conc.
Batch Knelsone
Knelson
CVD
Conc.
Gemini Table
Conc.
Smelter
Tailing
CONCLUSIONS & RECOMMENDATIONS
• Pilot scale testing indicated that the CVD was
effective at recovering metals from flotation tailings.
• The results indicated that the metal recovered was
primarily in the coarse size fractions, which would
likely contain middling particles (sulfide + silicates)
ie size enhanced density separation.
• Flotation of the reground gravity concentrate yielded
good grades and recoveries.
CONCLUSIONS &
RECOMMENDATIONS
• Continuous Centrifugal Gravity Concentrators may
have a role in hybrid flotation gravity circuits that
exploit the strengths of each technology
•
• The next step is to assess the potential for increasing
grind size to reduce losses in ultrafine fraction, reduce
energy requirements and increase throughput
• Thank You
• Acknowledgements
– Barrick Eskay Creek Mine
– Knelson Gravity Solutions
– NSERC IPS