I first met
Philip Gray in the mid-1980s when he presented an interesting lecture to the final year mineral processors at Camborne School of Mines on the limitations of comminution and flotation in the processing of complex sulphide ores. At that time he was President of the
Institution of Mining and Metallurgy (IMM) and was an independent consultant, working, amongst other things, with
Prof. Noel Warner of the University of Birmingham on the
Warner Process for smelting zinc and lead from low-grade ores. Following on this theme some 20 years later, he presented a keynote lecture at
Pyrometallurgy ’07 in Falmouth, highlighting the natural advantages of pyrometallurgy in the processing of ores. He argued that reactions are much faster at high temperatures than they are in slurries or aqueous solutions, and mineral characteristics are lost in melts, making the reactions controllable by known universal thermodynamic and kinetic laws. Separation by differential melt solubility or volatilisation permit recoveries that are impossible by mineral processing methods. Since that time he has remained a strong advocate of the Warner Process and although now, at 88 years of age, he is retired, he still has a keen interest in the minerals industry, so it was a privilege to discuss with him his career and thoughts on mineral processing.
Philip Gray graduated in 1947 with an ARSM and BSc in Metallurgy from the Royal School of Mines, London, and has been engaged in the extractive metallurgical industry ever since. His distinguished career has covered all the disciplines in his chosen field, including research and development, engineering and design, business development and consulting.
Following his first role as a Research Officer at the Atomic Energy Research Establishment, he continued his R&D activities at the Commonwealth Science and Research Organisation in Melbourne, Australia from 1951 to 1955 where he worked on hydrometallurgical methods of extracting uranium from Australian mineral deposits. In 1955 Philip returned to the UK and joined the Research and Development section of the Imperial Smelting Corporation at Avonmouth, and became Technical Manager in 1971.
From 1978, he became an independent metallurgical consultant engaged by many mining companies worldwide. Apart from working with Professor Warner he was involved with Research and Development into extracting rare earths. He was elected President of the IMM in 1984, and in the same year was made a Fellow of the Royal Academy of Engineers. In 2013 he was awarded The Institute of Materials, Mining and Minerals
Futers Gold Medal, for outstanding services to the international minerals industry, an accolade he shares with another of my interviewees,
Tim Napier-Munn.
He has been a great advocate of the Warner Process and I asked him what it is about the Warner Process that he finds so attractive? Did he think it will ever be seriously adopted by the industry? When Noel Warner first came up with this process for recovering zinc and lead from mixed sulphide concentrates, Philip hailed it as novel and feels that it still is. Using the sphalerite mineral to be desulphurised by metallic copper and then recycling the copper mattes for desulphurisation by air to generate heat is “a neat idea” as it vaporises zinc to be condensed using the Imperial Smelting Furnace technology. It also recovers lead and copper if present. Operating at around 1000C the processing dynamics are very fast compared with flotation and electrowinning.
He remembers how Noel got a pilot plant built and operated in the University of Birmingham, but not greatly to the University’s pleasure! However it demonstrated that the closed circuit could be worked on a big scale, and a number of people were attracted to come and see it, but enthusiasm was not overwhelming. Philip feels that this response was to a considerable degree based on long established industry opposition to all things new, and also due to there being some defects in the process - it cannot reduce zinc oxide to metal and therefore take feed that is part oxidic; the design and running of a plant with a recycling matte flow in the circuit would be most difficult since the matte circuit must have some means of raising it to maintain continuous circulation - this has still not been suggested. Although he still admires the novelty of the Warner Process he now accepts that it “probably won't fly” and believes that Noel has arrived at that conclusion too.
During his long career, Philip must have seen great changes in the minerals industry. He says that when he thinks back over his 60 years or so to his student days the fundamentals of recovery of concentrates from ore feed has not changed at all! “The ore is crushed, ground to get as much liberation as possible and then sulphide minerals collected by froth flotation and sent to the smelter for metal recovery. The presumption in this is that the information from chemical analyses with some identification of main minerals under optical microscopy is sufficient information to decide the flow sheet”.
He sometimes feels regret that the ore-body on which flotation was first developed and used was Broken Hill where much of the zinc mineralisation is marmatite with a high iron content and many of the crystals are “as large as peas”. Liberation is not difficult but smelters are not best pleased with the iron. He acknowledges that during his time in the industry there have been big advances in the size and sophistication of grinding and flotation equipment, but this has not stopped the cost and energy consumption of liberation and flotation soaring for many productive plants for recovery from ore.
Philip recently had a short article published in
Materials World with some interesting and radical ideas on refining the extraction process. He discussed how materials research has delved into the depths of rearranging atoms and molecules to generate materials with extraordinary physical properties. “If we can rearrange a material’s atoms to find new associations that are different to its better known properties, then should we not look to rearrange desirable and undesirable elements to extract them more efficiently?”
I asked him if he could elaborate on this. “We now have in the UK a monthly publication,
Materials World, from IOM3, providing side by side articles on minerals and ore processing with articles about materials made using new knowledge which has been applied by reconstructing atoms to produce quite remarkable properties; e.g. graphene. This seems to me how the atomic structure of minerals might be changed to make recovery of wanted elements selected for recovery. Research, please!”
He says “I imagine that ore be brought to the surface or, perhaps, attacked in situ, so that mineral surfaces are exposed (quite a different requirement from separating a whole clean mineral particle for collecting by flotation or gravity and processing for element recovery). I would imagine that this might need application of energy to 'shuffle the atoms up a bit'. This is where there should be a substantial reduction in energy requirement and cost for very fine grinding and flotation compared with the present with, hopefully, higher recovery of specified elements. One should thereby be able to justify an ore treatment using energy in quite large quantities; note that energy is now cheaper. It seems to me that selecting specific elements for recovery is likely to be more economic than selecting impure minerals for poor recovery in the next step.” He said that we are provided today with nearly everything which is capable of doing for us much more useful services than only a few years back. “This has generally been possible from fundamental research work in the laboratory carried out only for the purpose of establishing new knowledge, not for the purpose of improving technology - but this can follow by using the new knowledge”.
“The general guideline is that basic research has in the last relatively few years taken almost every practical technology a large step forward. As examples of such we can list medical and pharmacological practices (the recent news that the incident of new Ebola cases in W Africa has taken a steep fall); all uses of IT for transmission, computers ( a really staggering advance over the past ten years- note what nearly all of us have in our pockets); the provision of energy for industrial and domestic use; the utilisation of more efficient farming methods and crop and stock nutrients; the use of minor elements (e.g. the rare earths) for gaining greater sensitivity in information projection in all forms of IT; all aspects of aircraft design and use. We can go on citing many more technologies which have leapt forward from the foundation of research to add knowledge. I would cite ore processing as one (I hope not the only one) that has still to start.”
It is apparent that, although having been retired for some time, Philip still has a great interest in the minerals industry, and he told me that he keeps in touch as best he can by reading journals and occasional email chats with me and others in our profession. It was a pleasure, as always, to talk to him, and I wish him and his wife Joan a very peaceful 2015.
It would also be interesting to have the views of blog readers on Philip's comments on research. Do we need more blue-sky research to develop mineral processing?
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