An overview of HPGR testwork program at Mintek

Transcription

1 Council for Mineral Technology An overview of HPGR testwork program at Mintek 5 th June 2009 Johnny T. Kalala Head of Comminution, Minerals Processing Division, Mintek

2 Presentation overview 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

3 Introduction HPGR is maturing to become a competitive technology in designing comminution circuits Motivation to implement a HPGR Improve Energy efficiency Cost reduction by not using grinding media Debottlenecking Metallurgical performance Differential comminution

4 HPGR s on site at Mintek 1. Polysius HPGR Studded rolls Diameter=0.250 m Width=0.100 m Top size: 12 mm

5 HPGR s on site at Mintek 2. Koppern HPGR Diameter= 1 m Width= 0.250m Top size: 40 mm Hexadur Rolls

6 Crushing in a HPGR Feed Product

7 Key questions Amenability of different ore type to HPGR? Ore competency Throughput (t/h) cost Morley (2006) Does an open circuit HPGR do a better job than a modern closed circuit cone crusher for tertiary crushing duties? Testing Quantification of HPGR benefits Does HPGR technology provide lower energy and steel consumption? Does HPGR technology lead to better concentrate circuit grades and recoveries? Does HPGR technology lead to better kinetic of flotation or leaching? Limitations of the technology

8 1. Testing: ore amenability 1. Improved method for testing Amount of sample to be used Data recording 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

9 I. Ore amenability 1. Influence of operating variables 180 Hydraulic pressure Power Operating gap Time[Seconds] POWERFixedRoller [kw] POWERFloat. Roller [kw] PressureDE[bar] PresureNDE[bar] GapDE[ m] GapNDE[m] Typical HPGR test output

10 I. Ore amenability 2. Piston die compression test Applied Force, kn g UG2-12mm, compression at different forces Max. Force 100kN2 500kN2 1700kN3 Input Energy, Nm Energy returned, % RR Solid fraction Displacement, mm

11 100 HPGR testwork program I. Ore amenability 2. Piston die compression test Mass percentage less than size Particle mesh size [mm] Feed 0.18 kw/t 0.33 kwh/t 0.69kW/t 0.89 kwh/t 1.26 kwh/t 1.54 kwh/t 1.98 kwh/t Feed fit 0.18 kw/t fit 0.33 kwh/t fit 0.69kW/t fit 0.89 kwh/t fit 1.26 kwh/t fit 1.54 kwh/t fit 1.98 kwh/t fit Merensky ore: top size 12 mm

12 I. Ore amenability 3. Development of a Mintek flake competency test Merensky ore flake HPGR flake deagglomeration using a scrubber: Kimberlite ore Kimberlite flake after deagglomeration in a scrubber Circuit used at Jwaneng

13 I. Ore amenability 3. Development of a Mintek flake competency test % Passing mesh size Screening time (min) Merensky Gold ore Kimberlite % Pasing mesh size HP90 %-3.35 mm HP120 %-3.35 mm HP60 %-3.35 mm Screening time (min) Influence of ore type on screening kinetic Influence of hydraulic pressure on screening kinetic for a Merensky ore

14 4. Wear test I. Ore amenability Wear rate (g/t) Moisture (%) UG2 (4 N/mm2) Merensky (4 N/mm2) UG2 (2 N/mm2) UG2 (6N/mm2) UG2 and Merensky results on Polysius studded rolls

15 II. Influence of operating conditions 70 Merensky, 1.85% Moisture, product size distribution 60 % less than size Specific press force, N/mm2 % passing 75 microns % passing 300 microns % passing 600 microns

16 III. Flowsheet development Comminution circuit without using steel as grinding media HPGR ( ) mm Pebbles + sand (-70+25) mm pebbles Dewatering hydrocyclone 1 - HPGR feed 2 - HPGR discharge 3 - Repulper dilution 4 - Flash float feed 5 - Flash float concentrate 6 - Flash float tails 7 - Primary mill discharge 8 - Primary float dilution 9 - Primary float feed 10 - Primary float concentrate 11 - Primary float tails ROM feed Water AG mill 0.6 mm mesh Primary float Pebble mill Secondary float

17 III. Flowsheet development Assessing HPGR benefits as a tertiary crusher in comparison to modern cone crusher choke fed Action in a cone crusher Action in a HPGR

18 III. Flowsheet development Assessing HPGR benefits as a tertiary crusher in comparison to modern cone crusher choke fed HPGR HPGR feed 2 - HPGR discharge 3 - Repulper dilution 4 - Flash float feed 5 - Flash float concentrate 6 - Flash float tails 7 - Primary mill discharge 8 - Primary float dilution 9 - Primary float feed 10 - Primary float concentrate 11 - Primary float tails Repulper Flash float Primary ball mill Basic Northam circuit

19 IV. 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

20 V. Downstream benefits Objectives: Quantification of HPGR downstream benefits Milling - Reduction of spec. energy consumption - Reduction of BBWI Flotation and leaching - Faster kinetic - Better recovery Mineralogy - Liberation - Quantification of microcracks

21 VI. HPGR control Objectives: Improve HPGR performance by providing better control Maintain throughput by changing roll speed Maintain or avoid cake formation Control the quality of HPGR product by changing on line the split between edge and centre product Maintain an autogenous layer on HPGR to minimize wear

22 Conclusion Current limitations of the technology: Feed top size ( ~ 80 mm) Feed moisture Product size distribution Classification of HPGR product Capacity Wear rate 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.

23 Acknowledgements Mintek Polysius IMS Comminution group, Minerals Processing Division

24 Thank you