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Materials World magazine
3 Aug 2015
Philip Grey

Mineral processing technology has stagnated, and the field is in need of further investment to efficiently unlock vital natural resources, argues Philip Gray.

Let’s find a new way to process ore

Over my lengthy professional life in the extraction of metals from ores, there has been a noticeable rise in the cost of production due to energy consumption that is notable in two areas in particular – liberation of metal-containing minerals before separation by gravity and flotation.

Ores in which minerals are present in ever-finer crystal forms have to be used to meet rising demands in quantity and reductions in head contents. Energy consumption for finer grinding has soared.

Rising costs for energy consumption are reflected in increases in deposit cut off grades, which increase the capital requirements for new mines and processing sites. The expected return on capital investments may reduce as desirable amounts of the potential product have to be left underground.

How might we improve our energy bills? The progress that a great many of the technologies that we used over the past 10-20 years has been outstanding in medical and pharmaceutical applications, all forms of worldwide electronic communications, travel by air, sea and road, and agriculture, to name a few. Each of these advances has been made possible by the fundamental research that has broadened basic knowledge and thereby provided a new platform by which technology for daily use could make big improvements.

That is, except in ore processing. Our starting material is parts of the Earth’s crust that contain enhanced content of the metals we need. Before we mine these ores they may have been subjected to millions of years of deposition, heating, cooling, pressure and contact with various liquids, yet the common practice in our industry is to use information from core drilling derived from chemical analysis and optical microscopy to plan the process and plant.

The widest contact I have had has been in the extraction of zinc from concentrates through the successive processes of horizontal distillation, vertical retorts, imperial smelting blast furnace and roast, leach and electrolytic winning. It is true to say that the daily production rate for all these processes is commonly variable, which is frustrating for plant and business management. Some of these variations can be related to the chemical analysis of the ore, but often they cannot and processors try to select, from their experience, those ores and concentrates that seem to respond best.

I believe it is time to embark on some fundamental research studies on ores at the atomic and sub-atomic level. As with all research, it cannot be forecast what the result will be, or how that result will benefit future technology, but the experience in many technologies, as listed above, has been revolutionary. Ores have had very long and varied experiences in formation and it seems logical to expect that research can identify such. It may be time to target process planning of primary ore treatment to being element orientated instead of mineral orientated.

Nationally, the UK is much concerned with energy and there is now a cabinet minister whose brief is energy.

The metal extraction from ores is a consumer of energy on a big scale and governments have an interest in helping the extraction industry.

Metal extraction is not a major feature of industry in the UK, but it is in the interests of many UK companies that are managing and financing operations around the world.

About Philip

Philip Gray HonFIMMM FREng graduated in metallurgy at the Royal School of Mines, in London in 1947. After four years researching thermal extraction at AERE Harwell, he was employed by CSIRO, in Australia, on hydrometallurgical extraction of uranium, followed by 16 years with Rio Tinto at Avonmouth on Zn/Pb smelting. As an independent consultant, he assisted with thermal and hydro projects in many countries until 2000. He was President of the IMM from 1984-5 and appointed FREng in 1984. He was awarded the Futers Gold Medal in 2013.