Council for Mineral Technology

An overview of HPGR testwork program at Mintek

5th June 2009

Johnny T. KalalaHead of Comminution, Minerals Processing Division, Mintek

• Introduction• HPGR’s on site at Mintek• Key questions on HPGR• HPGR testwork program

– Development/ Improvement of test procedures– HPGR operation– Flowsheets development– Modelling and simulations– Downstream benefits– HPGR control

• Conclusion

Presentation overview

HPGR is maturing to become a competitive technology in designing comminution circuits

Introduction

Motivation to implement a HPGRØ Improve Energy efficiencyØ Cost reduction by not using grinding mediaØ DebottleneckingØ Metallurgical performanceØ Differential comminution

HPGR’s on site at Mintek1. Polysius HPGR

Studded rolls

Diameter=0.250 mWidth=0.100 mTop size: 12 mm

HPGR’s on site at Mintek2. Koppern HPGR

Hexadur Rolls

Diameter= 1 mWidth= 0.250mTop size: 40 mm

Crushing in a HPGRFeed

Product

Ø Amenability of different ore type to HPGR?

Key questions

Throughput (t/h)

Ore competency

cost Morley (2006)

Ø TestingØQuantification of HPGR benefits

Does an open circuit HPGR do a better job than a modern closed circuit cone crusher for tertiary crushing duties?

Does HPGR technology provide lower energy and steel consumption?Does HPGR technology lead to better concentrate circuit grades and recoveries?

Ø Limitations of the technologyDoes HPGR technology lead to better kinetic of flotation or leaching?

1. Improved method for testingü Amount of sample to be usedü Data recordingü Sampling

2. Development of a flake competency index to characterise the competency of HPGR flakes

3. Piston die compression test to predict HPGR performance

4. Wear tests

HPGR testwork program

1. Testing: ore amenability

HPGR testwork program

1. Influence of operating variables

0

20

40

60

80

100

120

140

160

180

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00

Time [Seconds]

POWER Fixed Roller [kW] POWER Float. Roller [kW] Pressure DE [bar] Pressure NDE [bar] Gap DE [mm] Gap NDE [mm]

Typical HPGR test output

Hydraulic pressure

Power

Operating gap

I. Ore amenability

HPGR testwork program

2. Piston die compression test263g UG2 -12mm, compression at different forces

0

200

400

600

800

1000

1200

1400

1600

1800

0 1 2 3 4 5 6 7

Displacement, mm

App

lied

Forc

e, k

N

Max. Force 100kN2 500kN2 1700kN3Input Energy, Nm 85.28 574.15 2519.16Energy returned, % 7.2 23.7 48.4RR50 1.4 2.8 5.3Solid fraction 0.72 - 0.88

I. Ore amenability

HPGR testwork program

1

10

100

0.01 0.1 1 10 100Particle mesh size [mm]

Mas

s pe

rcen

tage

less

than

siz

eFeed0.18 kW/t0.33 kWh/t0.69kW/t0.89 kWh/t1.26 kWh/t1.54 kWh/t1.98 kWh/tFeed fit0.18 kW/t fit0.33 kWh/t fit0.69kW/t fit0.89 kWh/t fit1.26 kWh/t fit1.54 kWh/t fit1.98 kWh/t fit

2. Piston die compression test

Merensky ore: top size 12 mm

I. Ore amenability

HPGR testwork program

3. Development of a “ Mintek” flake competency testHPGR flake deagglomeration using a scrubber: Kimberlite oreMerensky ore flake

Kimberlite flake after deagglomeration in a scrubberCircuit used at Jwaneng

I. Ore amenability

HPGR testwork program

3. Development of a “ Mintek” flake competency test

0.010.020.030.040.050.060.070.080.090.0

0.0 2.0 4.0 6.0 8.0 10.0

Screening time (min)

% P

assi

ng m

esh

size

MerenskyGold oreKimberlite

Influence of ore type on screening kinetic

30.0

40.0

50.0

60.0

70.0

80.0

90.0

0.0 2.0 4.0 6.0 8.0 10.0

Screening time (min)

% P

asin

g m

esh

size

HP90 %-3.35 mmHP120 %-3.35 mmHP60 %-3.35 mm

Influence of hydraulic pressure on screening kinetic for a Merensky ore

I. Ore amenability

0

5

10

15

20

25

30

35

40

45

50

0 1 2 3 4 5 6

Moisture (%)

Wea

r rat

e (g

/t)

UG2 (4 N/mm2) Merensky (4 N/mm2) UG2 (2 N/mm2) UG2 (6N/mm2)

HPGR testwork programI. Ore amenability

4. Wear test

UG2 and Merensky results on Polysius studded rolls

HPGR testwork programII. Influence of operating conditions

Merensky, 1.85% Moisture, product size distribution

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8Specific press force, N/mm2

% le

ss th

an s

ize

% passing 75 microns % passing 300 microns % passing 600 microns

HPGR testwork programIII. Flowsheet development

Comminution circuit without using steel as grinding media

1 - HPGR feed2 - HPGR discharge3 - Repulper dilution4 - Flash float feed5 - Flash float concentrate6 - Flash float tails7 - Primary mill discharge8 - Primary float dilution9 - Primary float feed10 - Primary float concentrate11 - Primary float tails

HPGR

0.6 mmmesh

(-70+25) mm pebbles

AG mill Pebble mill

Primaryfloat

ROM feed

Water

Secondary float

Dewatering hydrocyclone

(-70+0.6) mmPebbles + sand

HPGR testwork program

Ø Assessing HPGR benefits as a tertiary crusher in comparison to moderncone crusher choke fed

III. Flowsheet development

Action in a cone crusher Action in a HPGR

HPGR testwork programIII. Flowsheet development

Ø Assessing HPGR benefits as a tertiary crusher in comparison to moderncone crusher choke fed

HPGR

RepulperFlash float Primary ball mill

1

23

4

105

6 7

8

9

1 - HPGR feed2 - HPGR discharge3 - Repulper dilution4 - Flash float feed5 - Flash float concentrate6 - Flash float tails7 - Primary mill discharge8 - Primary float dilution9 - Primary float feed10 - Primary float concentrate11 - Primary float tails

11

Basic Northam circuit

HPGR testwork programIV. Modelling, simulation and scale up

Objectives:

- Development of steady state and dynamic model for HPGR- Scale-up from HPGR laboratory test and compression tests- Plant surveys

HPGR testwork programV. Downstream benefits

Objectives: Quantification of HPGR downstream benefits

Ø Milling- Reduction of spec. energy consumption- Reduction of BBWI

Ø Flotation and leaching- Faster kinetic- Better recovery

Ø Mineralogy- Liberation- Quantification of microcracks

HPGR testwork program

Objectives: Improve HPGR performance by providing better control

Ø Maintain throughput by changing roll speedØ Maintain or avoid cake formationØ Control the quality of HPGR product by changing on line the split between

edge and centre productØ Maintain an autogenous layer on HPGR to minimize wear

VI. HPGR control

The future of the HPGR depends on progress made to improve the current understanding of the technology and on our ability to exploit all benefits provided.

Conclusion

Current limitations of the technology:Ø Feed top size ( ~ 80 mm)Ø Feed moistureØ Product size distributionØ Classification of HPGR productØCapacityØWear rate

• Mintek• Polysius• IMS• Comminution group, Minerals Processing

Division

Acknowledgements

www.mintek.co.za

Thank you