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Multi-Stage Crushing versus AG/SAGmill and HPGR

Walter Valery and Alex J ankovicMetso Minerals Process Technology Asia-Pacific

Crushing and Grinding 2004

29 March 2004



© Metso Minerals, Inc. 2004 Multi-Stage Crushing versus AG/SAG mill and HPGRDate 29 March 20042

Presentation Outline

• Fundamental Considerations• Case Study - Optimum crushing product

size• Case Study - Circuit/Scale Comparison• Stirred Milling Potential

• Conclusion




Fundamental Considerations

• Efficiency of comminution is less than 1% !• NO!

• Efficiency of comminution should be based on sum of strainenergy and the surface energy.

• Baseline for assessing should be energy determined fromsingle-particle fracture experiments.




Schonert ranking

• Single particle compression, 100%• HPGR 80%

• Crushing 50%• Milling 30%




Fuerstenau & Vazquez-Favela, 1997

Single particlecomminution

Confined particlebed grinding

Ballmilling

Energy sink 1 1.5-3 3-10




Fuerstenau & Vazquez-Favela, 1997

• HPGR are more efficient than ball mills at low reductionratios, but lose advantage at high reduction ratios.

Energy expended(kWh/t)

Relative energyexpenditure

Ball mill 1.7 1HPGR 1.0 0.59Single-particle roll mill 0.7 0.41




Lo, 2000

• The magnitude of efficiencies varies depending on productsize.

E

f f i c i e n c y




In Practice Efficiency means:

• get the target rock into a place where it will be broken

• apply a force large enough to break it• discharge the products• do all of the above at a high rate




How do they compare?

Crusher Mill HPGR

• Getting rock into right place good bad good

• Apply force to break good good excellent

• Discharging products good good good• Doing it at high rate bad good good




SAG Mills




Ball Mills




How detailed is our understanding?




How detailed is our understanding?




High Pressure Grinding Rolls (HPGR)

Fixed roll

Feed

Moveable rollOil cylinders

Product

Nitrogen cylinder




Published HPGR potential

• The most energy efficient comminution machine• No grinding media cost

• Preferential breakage/liberation• Conditioning for downstream ball milling




Bond ball mill work index reduction after HPGROre Crusher

Type

HPGR

SpecificGrindingForce

(N/mm 2)

Rolls Speed

(m/s)

Bond Work

Index

(kWh/t)

Level of

Significanceof WIReduction

(%)Pyritic Gold CRC 17.4Ore HPGR 1.5

4.34.65.25.46.17.47.4 *

0.380.381.500.690.383.000.380.38

17.917.016.716.416.416.015.815.7

9795989999

>99>99>99

Siliceous CRC 15.6Gold Ore HPGR 2.7

7.50.380.38

15.313.8

93>99

Bauxite CRC 18.3HPGR 1.4

5.80.380.38

17.919.1

<90<90

Lamproite CRC 22.0HPGR 1.3

10.30.380.38

22.021.9

<90<90

Haematite CRC 16.1HPGR 3.5

9.50.380.38

16.115.7

<90<90

After I. Stephenson, 1997




Effect of HPGR Processing on WI of PyriticGold Ore

15

16

17

18

19

0 1 2 3 4 5 6 7 8HPGR Specif ic Grinding Force (N/mm²)

B o n

d W o r

k I n d e x

( k W h / t )

Conventional Rolls

HPGR Roll Speed = 0.38 m/s



HPGR Roll Speed = 3.00 m/sLeast squares fit to HPGR





Effect of HPGR Processing on WI of HematiteOre


14

15

16

17

18

0 1 2 3 4 5 6 7 8 9 10HPGR Specific Grinding Force (N/mm²)

B o n

d W o r k

I n d e x

( k W h / t )

Conventional Rolls

HPGR




Published HPGR limitations

• High capital cost (60 t/h unit ~ A$ 2M and 2000 t/h unit ~ A$ 10M)

• High maintenance cost (high wear)

• Low availability (long down time)• Requires ancillary equipment (feed preparation, dry processing, dust

extraction/control, de-agglomeration, screening)

• Perceived high risk




Latest about HPGR

• Potential applications are steadily increasing• Reliability increased significantly:

- wear life of studs on roll surface have increased significantly- improved availability of cheek plate and shoulder protection

• Wear increases dramatically with feed size

• Secondary crushed feed required• This technology is mature for treating hard competent andabrasive rock in the minerals industry




Multi-Stage Crushing versus AG/SAG mill andHPGR

• Grinding cost consist of:- Capital

- Maintenance materials- Power- Labor- Consumables




Total comminution costs - After Koivistoinen et all, 1996




Option 1: Three stage crushing + ball mills

Primarycrusher

Stockpile

SecondaryCyclones

Secondary ball mill

Muckpile

Primary ball mill

PrimaryCyclones

Secondarycrushing

Tertiary

crushing

Screening




Option 2: SAG + Ball Mill

SAG

Primarycrusher

Stockpile

Cyclones

Ball mill

Muckpile




Option 3: HPGR + ball mills

Primarycrusher

Stockpile

SecondaryCyclones

Secondary ball mill

Muckpile

Primary ball mill

PrimaryCyclones

MMD

HPGR




620 t/h throughput

Option Equipment Estimated Operating Power Draw

Total power drawMajor equipment costOperational cost

1

1 x Primary crusher = 0.1MW1 x Secondary crusher = 0.2MW2 x Tertiary crusher = 0.75MW

2 x Screens = 0.1MW1 x Primary ball mill = 4.3MW1 x Secondary ball mill = 7.5MW

12.95MW16.5 M $A

13.0 $A/t

2

1 x Primary crusher = 0.1MW1 x SAG mill = 9.0MW

1 x Ball mill = 5.5MW

14.60MW13.1 M $A

7.2 $A/t

3

1 x Primary crusher = 0.1MW1 x Secondary crusher = 0.2MW1 x Screen = 0.05MW1 x HPGR = 1.2MW1 x MMD = 0.2MW1 x Screen = 0.05MW1 x Primary ball mill = 4.0MW1 x Secondary ball mill = 6.3MW

12.15MW

14 M $A5 $A/t




1250 t/h throughput

Option Equipment Estimated Operating Power Draw Total power drawMajor equipment costOperational cos t

1

1 x Primary crusher = 0.15MW1 x Secondary crusher = 0.4MW4 x Tertiary crusher = 1.5MW4 x Screens = 0.2MW1 x Primary ball mill = 8.6MW1 x Secondary ball mill = 15.0MW

25.85MW33.3 M $A

11 $A/t

2

1 x Primary crusher = 0.15MW

1 x SAG mill = 18.0MW1 x Ball mill = 11.0MW

29.15MW

28.2 M $A6.1 $A/t

3

1 x Primary crusher = 0.15MW1 x Secondary crusher = 0.5MW

1 x Screen = 0.05MW1 x HPGR = 2.4MW1 x MMD = 0.25MW2 x Screen = 0.2MW1 x Primary ball mill = 8.0MW1 x Secondary ball mill = 12.6MW

24.15MW27.8 M $A

4.3 $A/t

2 00 h h h




2500 t/h throughputOption Equipment Estimated Operating Power Draw Total power draw

Major equipment costOperational cos t

1

1 x Primary crusher = 0.25MW2 x Secondary crusher = 0.8MW8 x Tertiary crusher = 3.0MW8 x Screens = 0.4MW

2 x Primary ball mills = 17.2MW3 x Secondary ball mills = 30.0MW

51.65MW65.8 M $A

9 $A/t

2

1 x Primary crusher = 0.25MW2 x SAG mill = 36.0MW

2 x Ball mill = 22.0MW

58.25MW56.2 M $A

5.5 $A/t

3

1 x Primary crusher = 0.25MW1 x Secondary crusher = 0.75MW1 x Screen = 0.1MW

2 x HPGR = 6.8MW1 x MMD = 0.3MW4 x Screens = 0.4MW1 x Primary ball mills = 12.5MW2 x Secondary ball mills = 25.2MW

46.30MW

48.3 M $A3.9 $A/t

C i f i l d i f




Comparison of capital and operating costs for the different circuits

0

5

10

15

20

25

30

35

SAG + Ball Mill 3 Stage Crush + Ball Mills HPGR+Ball Mills

Capital Expense (Million A$)

Operational Cost (A$/t)

C i f E ti d GHG




Comparison of Energy consumption and GHGEmission for the different circuits

0

5

10

15

20

25

30

SAG + Ball Mill 3 Stage Crush + BallMills

HPGR+Ball Mills HPGR+BallMills+Vertimills®

Energy (kWh/t)

CO2 Emission (power and steel)

HPGR + B ll Mill + Sti d Mill




HPGR + Ball Mill + Stirred Mill

Primarycrusher

Stockpile

Secondary

Cyclones

Muckpile

Primary ball mill

PrimaryCyclones

MMD

HPGR

Verti mi ll

Vertimill® potential




Vertimill® potential

0

5

10

15

20

25

30

35

40

0.01 0.1 1 10 100 1000

80% passing s ize (mm)

e n e r g y c o n s u m p

t i o n (

k W h / t )

crushing

milling

Ball mill

Vertimill ®




Closed circuit AG

Secondary CyclonesPrimary Cyclones

AG

Vertimill




Closed circuit SAG

Secondary CyclonesPrimary Cyclones

SAG

Vertimills




Open SAG

Primary Cyclones

SAG

Secondary Cyclones

Vertimill

Ball mill

Current coarse grinding



© Metso Minerals, Inc. 2004

Current coarse grindingapplications

Chino (US) - tertiary millingSAG - Ball mill- Vertimill®

Williams mine (Canada) - secondary millingMcArthur River - secondary milling

SAG - Vertimill ®

Cannington - secondary millingAG - Vertimill ®

Comminution starts here!




Comminution starts here!

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