Post on 02-Apr-2018
7/27/2019 m3-12 r Rajamani s Latchireddi
1/30
Simulation of Ball and Rock Charge
Motion in SAG Mills for the Design of
Shell and Pulp Lifters
R.K.Rajamani and S.Latchireddi
University of Utah135 S 1460 E, Rm 412, Salt Lake City, UT 84112
Part 1
7/27/2019 m3-12 r Rajamani s Latchireddi
2/30
Industrial SAG Mill
7/27/2019 m3-12 r Rajamani s Latchireddi
3/30
Components of grate discharge mill
FeedTrunnion
MillShell
Grate PulpLifter
DischargeTrunnion
FeedTrunnion
MillShell
Grate PulpLifter
DischargeTrunnion
7/27/2019 m3-12 r Rajamani s Latchireddi
4/30
Impact
Attrition
ImpactImpact
AttritionAttrition
Field of Breakage
7/27/2019 m3-12 r Rajamani s Latchireddi
5/30
Charge Motion
7/27/2019 m3-12 r Rajamani s Latchireddi
6/30
Flow through Grate and Pulp
Lifters
7/27/2019 m3-12 r Rajamani s Latchireddi
7/30
Charge Motion using DEM
Simulations
7/27/2019 m3-12 r Rajamani s Latchireddi
8/30
Unit Vector :
Relative Velocity :Normal Velocity :
Tangential Velocity :
Shear Velocity :
1212 PPPPe
12 VVVr
eVVrn
eVrVrVVts
21
21
DEM Algorithm
X
Y
Z
P1
P2
e
nrtVVV
7/27/2019 m3-12 r Rajamani s Latchireddi
9/30
Gap between Lifters
(current practice)
6
7/27/2019 m3-12 r Rajamani s Latchireddi
10/30
Lifter Design
(since 1998)
Ball release
22
7/27/2019 m3-12 r Rajamani s Latchireddi
11/30
Charge Motion of 38x24 ft
SAG Mill fitted with 60 shelllifters
7/27/2019 m3-12 r Rajamani s Latchireddi
12/30
Top hat (7 degrees)
7/27/2019 m3-12 r Rajamani s Latchireddi
13/30
25 degree release angle
7/27/2019 m3-12 r Rajamani s Latchireddi
14/30
35 degree release angle
7/27/2019 m3-12 r Rajamani s Latchireddi
15/30
45 degree release angle
7/27/2019 m3-12 r Rajamani s Latchireddi
16/30
Collahuasi Mines
Original lifters : 6 degree release angle
First change : 17 degree release angle Millsoft online simulation : 30 degree
release angle
Production increase : 11%
7/27/2019 m3-12 r Rajamani s Latchireddi
17/30
Allumbrera Mines(36x15 ft SAG)
Original lifters : 72 rows of 10 degree
release angle
First change : 48 rows of 25 degree release
angle
Millsoft online simulation : 36 rows of 30degree release angle
Throughput increase : 50,000 to 96,000 tpd
7/27/2019 m3-12 r Rajamani s Latchireddi
18/30
Candelaria Mines(36x15 ft SAG)
Original lifters : 72 rows of 10 degree
release angle
First change : 20 degree release angle
Millsoft online simulation : 36 rows of 35
degree release angle Throughput increase : 15%
7/27/2019 m3-12 r Rajamani s Latchireddi
19/30
Los Pelambres Mines(36x17 ft SAG)
Original lifters : 72 rows of 8 degree release
angle
Millsoft online simulation : 36 rows of 30
degree release angle
Throughput increase : 10,000 tpd
7/27/2019 m3-12 r Rajamani s Latchireddi
20/30
3D Verification with a lab Scale
Mill
0.9 X 0.14 m mill
Front face fitted with a Plexiglas plate.
50 mm grinding balls 220-260 balls
Power measured with a torque sensor
Video images comparison
7/27/2019 m3-12 r Rajamani s Latchireddi
21/30
20 % ball load, 30 % critical speed
Measured Power - 301 Watts
Predicted Power - 294 Watts
7/27/2019 m3-12 r Rajamani s Latchireddi
22/30
20 % ball load, 50 % critical speed
Measured Power - 459 Watts
Predicted Power - 461 Watts
7/27/2019 m3-12 r Rajamani s Latchireddi
23/30
20 % ball load, 70 % critical speed
Measured Power - 532 Watts
Predicted Power - 531 Watts
7/27/2019 m3-12 r Rajamani s Latchireddi
24/30
Kennecott SAG Mill Simulation
34 X 15 ft. Mill
15 degree tapered cones
33 rows of lifters 25% total filling and 12% ball filling
Mill speed 10.6 rpm
7/27/2019 m3-12 r Rajamani s Latchireddi
25/30
SAG Mill Simulation Graphics
View from feed end of mill
Angled end view #1
Angled end view #2
Angled end view #3
Side view
7/27/2019 m3-12 r Rajamani s Latchireddi
26/30
7/27/2019 m3-12 r Rajamani s Latchireddi
27/30
Isometric view of charge motion within the containing
cylindrical shell and lifters.
7/27/2019 m3-12 r Rajamani s Latchireddi
28/30
Kennecott Simulation Results
Mill power draft 3.2 megawatts per meter
length of mill.
Predicted power of 34 ft. SAG mill is 6.6megawatts.
Actual operating power draft 7 megawatts.
See charge animation.
7/27/2019 m3-12 r Rajamani s Latchireddi
29/30
3D Power predictions
Mill diameterX Mill
Length (m)
Mill filling % Mill speed( % critical)
Power drawactual
Power drawpredicted
0.25 X 0.29 50 60 76 watts 71 watts
0.38 X 0.29 50 60 209 212
0.9 X 0.14 20 31 301 294
0.9 X 0.14 20 50 459 461
0.9 X 0.14 20 71 532 531
0.9 X 0.14 30 31 393 396
0.9 X 0.14 30 50 617 624
10.2 X 4.6 25 74 7.0 mW 6.6 mW
7/27/2019 m3-12 r Rajamani s Latchireddi
30/30
3D Simulation of 40 X 20 ft. Mill
11.89 X 3.0 m mill simulated 25 % of mill volume filled with balls and
rock particles
Particle sizes: Mix of0.125m,0.10m,0.075m balls and rocks
155,000 particles in simulation
Power predicted 17,956 kW compares withobserved power 16,500 to 19,000 kW