Original Research Paper Trends in comminution driven by energy Robin Batterham Australian Academy of Technological Sciences and Engineering, GPO Box 4055, Melbourne, Victoria 3001, Australia article info Article history: Received 31 March 2010 Received in revised form 4 November 2010 Accepted 12 November 2010 Available online 26 November 2010 Keywords: Energy Communication High pressure grinding rolls Stirred mills abstract The consumption of energy in comminution processes is approximately 2–3% of the worlds’ total energy demand. There is clear room for improvement. This paper follows a presentation given at the 4th Asian Particle Technology Symposium that suggests significant improvements are possible by the use of high pressure grinding rolls, a new design of stirred mills and a new approach to circuit design. Ó 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved. 1. Context Formal projections of energy use for the world are well estab- lished. The most recent projections from the International Energy Authority (IEA) suggest a 40% increase in demand between 2007 and 2030 with coal use rising most in absolute terms is shown in Fig. 1 [1]. Whilst there is widespread agreement that emissions must be reduced, and be reduced quite significantly, the underlying trait that is driving energy consumption upwards appears to be some- what unstoppable. We have a strong growth in population and at the same time an increase in economic activity in developing coun- tries together with a world population that is urbanising. Accepting the IEA projections, we can now turn to comminution and note that there are estimates [2] suggesting that comminution is of or- der 2–3% of the worlds’ total energy consumption. This even of it- self would be enough to warrant significant research to reduce the energy consumption of comminution. Along with the pattern of increasing demand for minerals, and hence an increasing energy demand, there is also the challenge of falling grades. If we use copper as an example, we note in Figs. 2 [3] and 3 [4] that the trend of decreasing grade is not simply one of recent years, it has been established for hundreds of years. Without a drastic change in the processes for extracting copper, there seems an inevitability of power requirements increasing because of the falling head grades. A drastic change might include in place leaching of block caved ore, but this is still a long way from routine commercial application. Whether mining is underground or above ground, comminution still plays a major part in the energy consumption of mining, as shown in Fig. 4 and noted in the Canadian Benchmarking Report in 2006 [5]. Fuerstenau (Fig. 5) [6] has made general calculations of the ef- fect of grade and recovery on energy for copper production. Taking the likely decrease in head grades and increasing demand in cop- per and other minerals, we can expect that the 2–3% of world en- ergy that is used in comminution will be maintained, despite the drastic increase overall in world energy consumption. Clearly the demand for new comminution techniques with sig- nificantly lower energy consumption is timely and necessary. 2. Opportunities in energy efficiency A recent study by Adair at The Julius Kruttschnitt Mineral Re- search Centre (JKMRC) at the University of Queensland [7] has indi- cated it should be possible to reduce direct energy usage in comminution circuits by of order 30% through energy efficient circuit design and equipment placement. Mill power consumption has of course been thoroughly researched for many years, but circuits have not been designed in the past to optimise energy consumptions per se. One promising line is to comminute and separate in multiple stages, allowing rejection of gangue materials at coarser sizes rather than grinding all material to final liberated size. This follows from de- tailed work, indicating that liberation of valuable minerals follows a different size distribution to the gangue minerals [7]. Equally there is significant indirect and embodied energy savings possible by redesign of circuits to minimise the usage of grinding media and mill liners. These of course embody indirect energy from the iron and steel production processes. All in all the estimate from Prof. Adair is that it may be possible to save up to 50% of energy via a different approach to comminution circuit design. This is a significant challenge and one in which a 0921-8831/$ - see front matter Ó 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved. doi:10.1016/j.apt.2010.11.007 E-mail address: president@atse.org.au Advanced Powder Technology 22 (2011) 138–140 Contents lists available at ScienceDirect Advanced Powder Technology journal homepage: www.elsevier.com/locate/apt