High capacity microwave treatment of ores may be closer than previously thought

For almost 40 years engineers have explored opportunities for using microwave energy to improve the efficiency of mineral and metallurgical processes.  Given the vast energy consumption of such processes this is not a surprise  as microwave heating has long been assumed to reduce energy consumption in process engineering unit operations.  Selective heating of microwave-absorbent sulphides and metal oxides deported in a microwave-transparent gangue matrix results in differential thermal expansion of the heated phase, yielding micro-fracture around grain margins. Subsequent downstream processing may then yield higher recovery of valuable mineral sulphides and/or lower specific comminution energy, compared to non-microwave treated ore.

But while the mechanistic principles are well established, the scientific and engineering challenges of developing a commercial scale system have been immense. Typical throughputs of a large copper mine can be in excess of 5000 tph of milled ore and a microwave based treatment system would need to handle equivalent throughputs. This is at least an order of magnitude higher than any other microwave process ever built.

Last year (posting of 1st June 2017) I reported on two important papers, published in Minerals Engineering, describing how workers from the University of Nottingham, UK, and Jenike & Johanson, USA, had detailed the design, commissioning and operation of a system which was the culmination of over fifteen years of research and development activity. This resulted in a pilot-scale high power microwave treatment process, capable of operating continuously at throughputs of up to 150 tph, but crucially scaleable up to several thousand tonnes per hour.

More recent work has shown for the first time that microwave technology can be used in commercial mineral processing plants and that it can be used at significant scale with several of the largest microwave processing plants ever built being applied.  A multidisciplinary team of engineers from the University of Nottingham and Teledyne e2v have been presented with this year's Colin Campbell Mitchell Award from the Royal Academy of Engineering for developing MicroHammer, a revolutionary process for extracting copper from its ore by exposing rocks to powerful microwave energy for a fraction of a second. The team, which includes Professor Sam Kingman and Dr Chris Dodds from the University of Nottingham and Dr Ewan Livingstone, Paul Burleigh and David English from Teledyne e2v, combined their skills in microwave technology and engineering to develop the largest microwave processing system ever constructed, capable of processing up to 3000 tonnes of ore per hour.

We are very fortunate to have the team leader, Prof. Sam Kingman, at Physical Separation '19 in Falmouth next year. He will present a keynote lecture "What's cooking in mining?" which will examine the steps required to scale up such processes, will discuss the importance of the team involved and will present a strong case for understanding the value proposition for the technology being developed at the earliest stages of the project and the use of this to drive the research direction. Prof. Kingman will draw conclusions as to the steps required to see this technology in daily use across our industry - a time which he feels may be sooner than some workers may have previously thought.

Sam Kingman is a Pro-Vice-Chancellor at the University of Nottingham. He was awarded a personal chair at Nottingham in 2006, which at the time made him the youngest full Engineering Professor in the UK. He was previously the Director of the National Centre for Industrial Microwave Processing (NCIMP) which was one of the largest activities of its type in the world. In the past 12 years, Professor Kingman has published over 175 refereed journal papers and he is an inventor of over 150 patents within 29 patent families in the field of industrial microwave processing. In 2008, the work of

Professor Kingman and his group was recognised through the award of The Engineer Technology and Innovation Prize for Environmental Technology and the Environmental Prize of the Society of Petroleum Engineers and in 2011 he was awarded the Bielby Medal by the Royal Society of Chemistry, Society of Chemical Industries and the Institute of Materials, Minerals and Mining for his work to reduce energy consumption in chemical processing. Other prestigious awards include the Institution of Chemical Engineers Energy Prize in 2012 for work in microwave processing of industrial minerals and the UK Medal for Excellence in Engineering (2001). Microwave processing research at Nottingham has also been recognised by the award of the 2009 Environmental prize by the Society of Petroleum Engineers.

The very latest updates on Physical Separation '19 can be found at #PhysicalSeparation19.
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