the influence of feed properties on cyclone performance and
TRANSCRIPT
J.A Wates Fraser Alexander, South Africa
H. Venter Fraser Alexander, South Africa
A. O’Callaghan Fraser Alexander, South Africa
J. Tucker Consulting Metallurgist, South Africa
The influence of feed properties on cyclone performance and stacking of underflow
0
10
20
30
40
50
60
70
80
90
100
1 10 100 1000
Perc
enta
ge P
assi
ng
Particle Size Distribution
SPCU - FEED PSD - April 2012 - December 2012
Feed density
0.00%
5.00%
10.00%
15.00%
20.00%
25.00%
30.00%
1.700
1.750
1.800
1.850
1.900
1.950
2.000
2.050
30 35 40 45 50 55 60 65 70
% M
ass
Sp
lit
Un
de
rflo
w R
D
Spigot Diameter mm
Underflow RD Mass Split
Technical Conclusions •Feed PSD most significant variable and highly variable
•There is an best fit vortex finder and spigot size 135/55 and
feed pressure of 160 kPa
•For a given U/F RD, Barrel extensions and pressurization
improve split. Throttling also improves split.
•Stacking angle improves with increasing u/f RD but is
inversely proportional to split.
•The split to underflow can be increased by decreasing the cyclone cut
point. Decreasing the cut point increases the percent passing 75
micron.
•The permeability decreases as the percentage passing 75 microns
increases.
•The permeability measured at 25% passing 75 micron is just high
enough to achieve a permeability of 10 times higher than the overflow.
•The maximum percentage passing 75 microns should therefore be
limited to 25%.
Operational Conclusions
Volume=Mass discharged*split/in situ dry density
Mass discharged
0%
5%
10%
15%
20%
25%
U/F Vol split
On-site measuredsplits
Cyclone 1 Cyclone 2 Cyclone 3 Cyclone 4 Cyclone 5 Cyclone 6 Cyclone 7 Cyclone 8 Overall
UF(1.6 - 1.7) 7% 3% 6% 2% 2% 0% 2% 0% 3%
UF(1.7 - 1.8) 22% 48% 22% 36% 35% 24% 25% 33% 30%
UF(1.8 - 1.9) 64% 45% 68% 60% 56% 69% 68% 62% 62%
UF(1.9 - 2.0) 7% 5% 4% 2% 8% 7% 6% 5% 5%
UF (RD 1.8+) 71% 50% 72% 62% 63% 76% 74% 67% 67%
0%
10%
20%
30%
40%
50%
60%
70%
80%
% F
req
uen
cySummative - UF Density
0
50
100
150
200
250
300
350
400
450
500
60 65 70 75 80
Yie
ld s
tre
ss
SOLIDS CONCENTRATION BY MASS %
5%
15%
25%
35%
45%
Harties
Buffels
0
50
100
150
200
250
300
350
400
450
500
0% 10% 20% 30% 40% 50%
Yie
ld s
tre
ss P
a
% Passing - fines below 75microns
Yield stress against % passing on specific Solids Concentration
65
67.5
70
72.5
75
77.5
0
50
100
150
200
250
300
350
400
450
500
0% 10% 20% 30% 40% 50%
Yie
ld s
tre
ss P
a
% Passing - fines below 75microns
Yield stress against % passing on specific Solids Concentration
65
67.5
70
72.5
75
77.5
Volume=Mass discharged*split/in situ dry density
Mass discharged
•Single stage cyclones cannot be expected to cut cleanly at 75 microns.
The cut point must be set above 75 microns to meet the requirements.
•Where feed conditions vary significantly, as they often do in practice,
mass split to underflow will be about 50% of the percentage passing
75 microns in the feed. This can be increased marginally by cyclone
modification and management.
•Based on the rule of thumb, the practical mass split for the case history
described in the paper (for an average feed of 75% passing 75 micron)
would is around 15% by mass.
•By fine tuning the operations we have been able to achieve a maximum
of 17% without losing too much underflow to the basin.
Practical Conclusions
0
50
100
150
200
250
300
350
400
450
500
1 3 5 7 9 11 13 15
Yie
ld S
tre
ss P
a
Gradient 1:x
Bulyanhulu Range
Flow rate : 1900 tpd Bulyanhulu : 3000 tpd
0
5
10
15
20
25
30 35 40 45 50 55 60 65 70 75
BE
AC
H S
LO
PE
%
SOLIDS CONCENTRATION %
SOLIDS CONCENTRATION VS BEACH SLOPE
80% minus 75 micron
20% Minus 75 micron
60% Minus 75 Micron
Segregation boundary
Acknowledgements
• Co-authors
• DRD
• Anglo Gold Ashanti
• The Fraser Alexander team