‘The biological (if not the aesthetic) value of remembering Is not that it allows one to reminisce about the past but that it permits one to calculate coldly about the unknown future’ Colin Blakemore
The Institute has always considered it well worthwhile to produce an issue devoted to student projects. These are a requirement in the final year and an important component of university training to expose the prospective graduates to research procedures. Inevitably they will be exposed to research in their careers as participants, sponsors or users. These projects have to be undertaken at the final year when examinations are looming, and time does not permit the same level of detail expected from a postgraduate researcher. The limited number that can be published is a selection from a large number with some attempt to cover the main university departments that contribute to mining and metallurgy. I started my perusal of the papers with that of Louise Bircumshaw et al., on the mathematical modelling of the biochemical leaching of refractory pyretic concentrates.
I had covered only the first few paragraphs when I started to read much more carefully. I was dealing not with a quick student project, but an outstanding and uniquely comprehensive analysis of all the parameters of the mechanism and kinetics of a complex and important process. The use of micro-organisms for the leaching of waste dumps containing sulphides to recover base metals was commonplace in the 1970s. Serious work was started in South Africa to develop a microbiological process to dissolve the pyrite and arsenopyrite which surrounded the gold in the refractory gold ores. The first commercial process to replace the old roasting process for such ores was at the Fairview mine in Barberton.
The first processes showed the possibility of significant improvements and excited the attention of the major mining houses and the chemical engineering, metallurgical and microbiological research facilities in South Africa and around the world. For decades thereafter one could not avoid a paper on the mechanism and modelling of the bioleaching process at any of the conferences and colloquia on hydrometallurgy. In the bioleach there was much meat for the hungry mathematical modellers.
There were several reaction mechanisms proposed and the rate controlling parameters were many and complex. This attention was far from being unimportant. The cost and efficiency showed much room for improvement even though bioleaching was way ahead of other methods for recovery of gold from refractory ores. In due course, the proven plant technology provided a springboard for South African mining houses to gain a foothold in many refractory gold deposits around the world. The comprehensive model proved elusive. It was mathematically complex and multifaceted. No wonder I was fascinated to find the very convincing comprehensive model put together in a student’s project report in this issue. The mathematics is, for me, formidable but the paper is excellently written, concise, precise and easy to follow and, in my view, a milestone in hydrometallurgy.
There is work to be done in confirming the validity of the model in more than the two experimental examples reported n this paper. In status it goes far beyond what might be expected from a final year student project. It matches many other prestigious transaction papers that we have published. But student training is often not the only reason for these projects. They can initiate and promote future work and future sponsorship, maybe leading to postgraduate centres of excellence. We have not heard the last of bioleaching. There are many metals and low-grade waste heaps still to be tackled. Then there is the possibility of waste coal dumps, anaerobic digestion of organic waste for bio-methane and bio-reduction of sulphates and sulphides. All of which are grist to the mill of such mathematical modelling.
My delight at the first paper must not belittle the quality of the other presentations... The paper by R.L. Pienaar on single level mining at Koffiefontuin is also a mammoth piece of work for a final year student and I am sure is of great interest to the mining community. I am not in a position to comment on its status as a contribution towards future postgraduate efforts but I am sure that all methodologies aimed at economic evaluation will be of relevance in the light of the complexity of mining economics.
The next paper I looked at, however, was one that awakened a great deal of my interest. This was the paper by J.M. Lottering et al. on the use of online reflectance spectrometry to evaluate the performance of an electrostatic separator for separation of minerals in beach sands. It brought memories of my first contact with mineral sands separation when working on the exploitation of the beach sands at Umgababa on the South Coast. The impression I obtained of the electrostatic separators was that their performance depended more on the phase of the moon than scientific principles or voltage and conductivity.
This paper also fascinated me by the use of an on line method of doing quantitative mineralogy using reflectance spectrometry to replace the tedious chemical and mineralogical methods that were used in the 1950s. This student’s project must surely lead to online methods for control of the temperamental electrostatic separators used in the ever increasing number of beach sand operation plants. One thing we did learn in the early days was the importance of thin layers of impurities on the surface of the particles. Perhaps the reflectance technique can respond to such films. In a similar vein the use of the Hopkinson pressure bar is described by L. Bbosa et al. This apparatus was developed nearly a century ago and is surprisingly simple in theory and in practice, and I am surprised that it has not been widely used in comminution research.
Some interesting results were achieved using uniform stones from a road stone quarry: rounded pebbles break more readily than sharp angular stones when subjected to a series of sub-critical impact blows. What would be very interesting is to use this equipment on heterogeneous specimens to identify how the valuable minerals such as gold are liberated after impact breakage. The remaining two papers deal with corrosion testing of silicon carbide and the impact of aluminium additions to steel on continuous casting. Both are significant contributions in an area of physical metallurgy where we need many more research personnel. Certainly I derived much benefit from this issue of the Journal. I hope many in industry did likewise and my congratulations go to the students and departments involved. R.E. Robinson APRIL 2006
- Written by R.E. Robinson
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