m3-12 r rajamani s latchireddi

7/27/2019 m3-12 r Rajamani s Latchireddi

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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


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Industrial SAG Mill


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Components of grate discharge mill

FeedTrunnion

MillShell

Grate PulpLifter

DischargeTrunnion

FeedTrunnion

MillShell

Grate PulpLifter

DischargeTrunnion


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Impact

Attrition

ImpactImpact

AttritionAttrition

Field of Breakage


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Charge Motion


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Flow through Grate and Pulp

Lifters


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Charge Motion using DEM

Simulations


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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


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Gap between Lifters

(current practice)

6


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Lifter Design

(since 1998)

Ball release

22


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Charge Motion of 38x24 ft

SAG Mill fitted with 60 shelllifters


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Top hat (7 degrees)


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25 degree release angle


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Collahuasi Mines

Original lifters : 6 degree release angle

First change : 17 degree release angle Millsoft online simulation : 30 degree

release angle

Production increase : 11%


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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


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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%


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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


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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


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20 % ball load, 30 % critical speed

Measured Power - 301 Watts

Predicted Power - 294 Watts


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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


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SAG Mill Simulation Graphics

View from feed end of mill

Angled end view #1

Angled end view #2

Angled end view #3

Side view


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Isometric view of charge motion within the containing

cylindrical shell and lifters.


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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.


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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


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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

m3-12 r rajamani s latchireddi

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