Project Status: Complete
Project Participants: BHP Billiton, CSIRO, Curtin University of Technology, Newmont, Rio Tinto, University of Queensland, Xstrata, Anglo Platinum, Rustenberg Platinum Mines
Project Leader: Malcolm Powell (University of Queensland)
This project built on the highly successful foundation project and identified and tested ways to reduce the total comminution energy at existing mine sites by 20 percent or more. Specific demonstration projects were targeted, along with areas that were identified as requiring further development in order to capitalise on the outcomes of the foundation work.
The original base version of the Unified Comminution Model (UCM) was expanded to include incremental damage and two major modes of abrasion. This was tested against pilot mill data. A 1.8 metre diameter abrasion mill was constructed, allowing it to be used as a new abrasion testing device.
The JK Rotary Breakage Tester (JKRBT) and the University of Erlangen mini-breakage tester were used to characterise the breakage of three ore types over a wide range of energy – from very low surface damage to incremental breakage to single hit breakage, and on a wide range of rock sizes from 50 microns to 50 millimetres. These unique data sets of breakage over wide energy ranges and rock sizes are challenging the existing best breakage models and will form the best input yet available to mechanistic comminution models. Findings are that the current models are inadequate and do not hold over this wide range of conditions. Further research is required to study alternative models.
Three-dimensional Discrete Element Method (DEM) simulations were used to analyse the dry particle flow in tower and ball mills. Results showed that tower mills are potentially more energy-efficient than ball mills. However while ball mills are likely to be less-efficient in energy terms, they are also going to be very "forgiving" in terms of tolerance to variations in ore feed size distribution and hardness.
A world first slurry model has coupled fluid flow (Smoothed Particle Hydrodynamics) and solids flow (DEM) and has been used to analyse the slurry flow in the tower mill. The same technique has been applied to the pilot mill, with outcomes of direct relevance to mill operation and slurry flow control.
Fine ore particles have been included in the simulation of a laboratory-size ball mill to explore what these do to the flow and what breakage environment they experience. This is computationally extremely challenging and the first study of its type. Results will open the door to fundamental grinding simulations and studies of the micro-environment in milling devices – getting to the core of energy transmission.
A DEM study of the separation performance of double-deck banana screens led to interesting insights. Using realistic non-round particles gave an opportunity to seriously explore industrial-scale screen performance in much more detail than is possible with traditional testing techniques – although good quality survey and wear measurements will be essential for verification of the DEM models.
PhD student Zeljka Pokrajcic won the "2010 Vittorio de Nora Prize for Environmental Improvements in Metallurgical Industries" awarded by The Minerals, Metals, and Materials Society. She attended the award ceremony and presented her work in Seattle in February. Dr Pokrajcic has been researching ways to minimise the energy usage of crushing and grinding (comminution) circuits. Her approach
involves reducing the mass of material in the comminution circuit by rejecting coarse-sized, commercially worthless material before milling, as well as using more efficient crushing and grinding equipment. She also used modelling and ore characterisation technology developed at the JKMRC.
Three CSRP-funded students completed their research: Zeljka Pokrajcic (PhD), Fiesal Musa (PhD), and Mike Larson (Masters).
Other significant outcomes from this project include: