Thursday, 25 March 2010

Comminution and enhanced mineral liberation

I have been looking at the final programme for Comminution ’10, and one paper from Hacettepe University in Turkey brought back memories of comminution research at CSM and Birmingham in the mid 1980s. In their abstract Ozcan and Benzer state:

"The comminution process is still governed by a large number of factors that influence the liberation of the valuable components in the ore. A better understanding of these basic factors will provide more certainty about the design of equipment in order to achieve the best liberation and energy efficiency.

The aim is to improve our understanding of the influence that breakage and the intensity of breakage has on the particle size distribution and the liberation of the valuable minerals. Liberation enhancement is sought for two main reasons. Firstly, if liberation is achieved without needing to grind particles to fine sizes, less is spent on energy. Secondly, over-grinding is not only costly, but produces fines that tend to interfere with subsequent separation processes thus making the downstream processes both inefficient and more expensive."

Over the past couple of decades great improvements have been made in comminution equipment, control and simulation, but it must never be forgotten that enhanced liberation should also be a major aim. Seventeen years ago, Keith Atkinson and I published a paper in Minerals Engineering (Volume 6 Number 7, 1993) entitled “Some observations on the fracture and liberation of mineral assemblies”. The paper considered the need to research more deeply the mechanisms of the breakage processes in comminution machines, particularly the promotion of intergranular fracture. It was shown that in order to do this control of crack propagation, and the nature and role of grain boundaries, are areas deserving most attention. I think this paper still provides food for thought, and it can be accessed on ScienceDirect.

I am sure that enhanced liberation will be discussed next month in Cape Town and that high-pressure grinding rolls will be debated in this regard. Interestingly, in the latest issue of Minerals Engineering (Volume 23 Issue 5, 2010), Vizcarra et al suggest that breakage devices utilising particle-bed breakage mechanisms (such as HPGR) do not enhance the liberation properties of metalliferous ores as many previous investigations have reported.

Currently around 140 delegates are registered for Comminution '10 and three exhibit booths are still available. One of these (#4) is in a prime location in the coffee/lunch area.

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