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Mul ulti ti--Stage Cr us ushi hing ng versu versus s AG AG//SAG m i ll an d HPGR Walter Walt er Valer alery y and Alex J an ankov kovic ic Metso Minerals Process Technology Asia-Pacific

Crus rushin hing g and Grinding Grindi ng 200 2004 29 March 2004

Prese resent nta ati tion on Out Outli line ne

• Fundamental Considerations • Case Study - Optimum crushing product size • Case Study - Circu ircuit it/S /Scale cale Compa omparrison • Stirred Milling Potential • Conclusion

Fun unda dame ment nta al Consid Cons ide eratio rations ns

• Efficiency of comminution is less than 1% ! • NO! NO! • Efficiency of comminution should be based on sum of strain energy and the surface energy. • Baseline for assessing should be energy determined from single-particle fracture experiments.

Schonert ranking

• Single particle compression, • HPGR • Crushing • Milling

100% 80% 50% 30%

Fuerstenau & Vazquez-Favela, 1997

Energy sink

Single particle comminution 1

Confined particle bed grinding 1.5-3

Ball milling 3-10

Fuerstenau & Vazquez-Favela, 1997

Ball mill HPGR Single-particle roll mill

Energy expended (kWh/t) 1.7 1.0 0.7

Relative energy expenditure 1 0.59 0.41

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

Lo, 2000

y c n e i c i f f E

• The magnitude of efficiencies varies depending on product size.

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

Discharging products Doing it at high rate

good bad

good good

excellent good good

SAG Mills

Ball Mills

How detailed is our understanding?

How detailed is our understanding?

High Pressure Grinding Rolls (HPGR)

Nitrogen cylinder Oil cylinders

Feed Moveable roll

Fixed roll

Product

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 HPGR Ore

Crusher Type

Pyritic Gold Ore

CRC HPGR

Siliceous Gold Ore

CRC HPGR

Bauxite

CRC HPGR

Lamproite

Haematite

CRC HPGR CRC HPGR

After I. Stephenson, 1997

HPGR Specific Grinding Force 2 (N/mm )

Rolls Speed

Bond Work Index

(m/s)

1.5 4.3 4.6 5.2 5.4 6.1 7.4 * 7.4

0.38 0.38 1.50 0.69 0.38 3.00 0.38 0.38

2.7 7.5

0.38 0.38

1.4 5.8

0.38 0.38

1.3 10.3

0.38 0.38

(kWh/t) 17.4 17.9 17.0 16.7 16.4 16.4 16.0 15.8 15.7 15.6 15.3 13.8 18.3 17.9 19.1 22.0 22.0 21.9

0.38 0.38

16.1 16.1 15.7

3.5 9.5

Level of Significance of WI Reduction (%) 97 95 98 99 99 >99 >99 >99 93 >99 <90 <90 <90 <90 <90 <90

Effect of HPGR Processing on WI of Pyritic Gold Ore 19

18 ) t / h W k ( x e d n17 I k r o W d n o B 16

Conventional Rolls HPGR Roll Speed =0.38 m/s HPGR Roll Speed =0.69 m/s HPGR Roll Speed =1.50 m/s HPGR Roll Speed =3.00 m/s Least squares fit to HPGR

15 0

1

2

3 4 5 HPGR Specif ic Gri ndi ng For ce (N/mm²)


6

7

8

Effect of HPGR Processing on WI of Hematite Ore 18

17 ) t / h W k ( x e d n16 I k r o W d n o B 15

Conventional Rolls HPGR 14 0

1

2

3 4 5 6 7 HPGR Specific Grinding Force (N/mm²)


8

9

10

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 and abrasive rock in the minerals industry

Multi-Stage Crushing versus AG/SAG mill and HPGR

• 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 Muckpile Primary crusher Secondary crushing

Tertiary crushing

Stockpile Screening

Primary Cyclones

Primary ball mill

Secondary Cyclones

Secon dary ball mill

Option 2: SAG + Ball Mill Muckpile Primary crusher

Stockpile

Cyclones

Ball mill SAG

Option 3: HPGR + ball mills Muckpile Primary crusher

HPGR

Stockpile

MMD

Primary Cyclones

Primary ball mill

Secondary Cyclones

Second ary ball mill

620 t/h throughput Option

Equipment

Estimated Operating Power Draw

Total power dr aw Major equipment c ost Operational cost

1

1 x Primary crusher = 0.1MW 1 x Secondary crusher = 0.2MW 2 x Tertiary crusher = 0.75MW 2 x Screens = 0.1MW 1 x Primary ball mill =4.3MW 1 x Secondary ball mill = 7.5MW

2

1 x Primary crusher = 0.1MW 1 x SAG mill = 9.0MW 1 x Ball mill = 5.5MW

14.60MW 13.1 M $A 7.2 $A/t

3

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

12.15MW 14 M $A 5 $A/t

12.95MW 16.5 M $A 13.0 $A/t


Equipment


1

1 x Primary crusher =0.15MW 1 x Secondary crusher = 0.4MW 4 x Tertiary crusher = 1.5MW 4 x Screens = 0.2MW 1 x Primary ball mill = 8.6MW 1 x Secondary ball mill = 15.0MW

2

1 x Primary crusher =0.15MW 1 x SAG mill = 18.0MW 1 x Ball mill = 11.0MW

3

1 x Primary crusher =0.15MW 1 x Secondary crusher = 0.5MW 1 x Screen = 0.05MW 1 x HPGR = 2.4MW 1 x MMD = 0.25MW 2 x Screen = 0.2MW 1 x Primary ball mill = 8.0MW 1 x Secondary ball mill = 12.6MW

Total power draw Major equipment cost Operational cos t

25.85MW 33.3 M $A 11 $A/t

29.15MW 28.2 M $A 6.1 $A/t

24.15MW 27.8 M $A 4.3 $A/t


Equipment


1

1 x Primary crusher =0.25MW 2 x Secondary crusher = 0.8MW 8 x Tertiary crusher = 3.0MW 8 x Screens = 0.4MW 2 x Primary ball mills =17.2MW 3 x Secondary ball mills = 30.0MW

2

1 x Primary crusher =0.25MW 2 x SAG mill = 36.0MW 2 x Ball mill = 22.0MW

3

1 x Primary crusher =0.25MW 1 x Secondary crusher = 0.75MW 1 x Screen = 0.1MW 2 x HPGR =6.8MW 1 x MMD = 0.3MW 4 x Screens = 0.4MW 1 x Primary ball mills =12.5MW 2 x Secondary ball mills = 25.2MW

Total power draw Major equipment co st Operational cos t

51.65MW 65.8 M $A 9 $A/t

58.25MW 56.2 M $A 5.5 $A/t

46.30MW 48.3 M $A 3.9 $A/t

Comparison of capital and operating costs for the different circuits 35 Capital Expense (Million A$)

30

Operational Cost (A$/t)

25

20

15

10

5

0 SAG +Ball Mill

3 Stage Crush +Ball Mills

HPGR+Ball Mills

Comparison of Energy consumption and GHG Emission for the different circuits 30 Energy (kWh/t) CO2 Emission (power and steel)

25

20

15

10

5

0 SAG +Ball Mill

3 Stage Crush + Ball Mills

HPGR+Ball Mills

HPGR+Ball Mills+Vertimills®

HPGR + Ball Mill + Stirred Mill

Muckpile Primary crusher

HPGR

Stockpile

MMD

Primary Cyclones

Secondary Cyclones

Verti mi ll Primary ball mill

Vertimill® potential 40

Ball mill 35 ) t / h W 30 k ( n 25 o i t p m 20 u s n o 15 c y g r 10 e n e 5

milling crushing

Vertimill

®

0 0.01

0.1

1

10

80% passing s ize (mm)

100

1000

Closed circuit AG Primary Cyclones

Secondary Cyclones

Vertimill AG

Closed circuit SAG Second ary Cyclo nes Primary Cyclones

Vertimills

SAG

Open SAG

Primary Cyclones

SAG

Second ary Cyclo nes

Ball mill Vertimill

Current coarse grinding applications Chino (US) - tertiary milling SAG - Ball mill- Vertimill®

Williams mine (Canada) - secondary milling McArthur River - secondary milling SAG - Vertimill ®

Cannington - secondary milling AG - Vertimill ®

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