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By G. Sommer, R. P. Chaix, G. T. W. Ormrod

Recent developments in the instrumentation and automation of uranium-processing plants by G. SOMMER, Ing. (Grad.) (Visitor), G. T. W. ORMROD (Visitor), and R. P. CHAIX, B.Sc. (Visitor) The paper discusses work at the National Institute for Metallurgy on the evaluation of measuring techniques for the automatic control of free acid in leaching. of the ratio of ferric to ferrous ion in leaching, of pH in liquid-liquid extraction. and of uranium in loaded solvent. Commercially available instruments. and the modifications that have been made to adapt them to South African uranium plants, are also described.

By A. W. S. Schumann

SYNOPSIS The most economic exploitation of South African coal resources requires sustained study of the balance between known resources and the predicted rate of consumption, against the background of the development of other sources of energy in South Africa and relevant developments elsewhere in the world. A number of the major issues which would arise in such a study are discussed, including the need for a standardized South African definition for coal resources, the merits of sectoral forecasts of consumption compared with global forecasts, the encouragement of a higher recovery from reserves, and the development of an export market for South African coal.

By G. R. Marchant, B. K. Loveday

A mathematical model has been developed for flotation circuit simulation. This model was designed to investigate the effect of varying the circulating loads and to determine whether an improvement in overall efficiency could be gained by a size separation prior to flotation. Model parameters were obtained by regression to plant data. Highly correlated parameters in the model were combined to reduce the number of parameters so that the need for excessive data gathering was eliminated. Mass balance smoothing was used to obtain a consistent data set for regression. The results of the simulation indicate that for the same grade of concentrate, an increase in copper recovery of 0.6 per cent may be possible by increasing the circulating loads. The results of the simulation also indicated that recleaning of the plus 200-mesh material may be beneficial.

By P. J. D. Lloyd

This fascinating paper deserves study by all who are interested in the economics of gold production. The argument in the paper that price is determined by the balance between supply and demand may be thought to be obvious. However, correlation analysis presumes causality, and there is some evidence in the paper to suggest that causality is absent in this market.

Jan 1, 1984

By B. K. Loveday

There are certain ores that can be treated without upgrading (e.g., gold and uranium ores), and upgrading needs to be considered only for fairly low-grade ores of this type. If the grade is very low, treatment will not be economic even with upgrading, and there is therefore a limited range of ore grades for which upgrading is suitable.

Jan 1, 1980

By T. N. Huffman

Ancient mining and Zimbabwe T. N. HUFFMAN*. Ph.D. (Illinois) (Visitor) Ancient gold mining and Zimbabwe have been commonly associated for over a hundred years, either in terms of an exotic colony for gold export or as an African state based on the East Coast trade. The stratigraphy and radiocarbon dates from Zimbabwe and the known sequence for the Rhodesian Iron Age demonstrate that Zimbabwe was built after AD. 1000. A review of the evidence for ancient gold mining shows a similar antiquity, and a complementary rise in prosperity in Arab settlements on the East Coast indicates that gold was not extensively mined until the eleventh century. Large quantities of imported articles at Zimbabwe indicate the extent of trading during the fourteenth and fifteenth centuries, and the origins of Zimbabwe probably lay in an overflow of wealth from the gold trade during the twelfth and thirteenth centuries. Zimbabwe was abandoned by the sixteenth century because of environmental factors.

Jan 1, 1974

The role of research and development In the South African gold-mining industry Presidential Address given by M. D. G. SALAMON, Fellow, Dipl. Eng. (Mining) (Hungary), Ph.D. (Durham) The decision of the gold-mining industry in 1974 to embark on a major ten-year research and development programme was widely publicized at the time. In choosing a subject for this address, I felt almost obliged to use this opportunity to give an account of the progress of this undertaking. On reflection, however, I felt that a simple progress report would not suffice. It seemed important that the programme should be shown in persepective, and that its aims should be outlined to the mining and metallurgical engineering community, many of whom are vitally concerned with the well-being of the gold-mining industry.

Jan 10, 1976

By S. L. Crouch

This paper describes a numerical procedure for the computation of the displacements and stresses induced by the mining of a tabular ore deposit in faulted ground. The numerical procedure is based on the displacement discontinuity method, which can be regarded as an application of Salamon's 'face element principle' to cases in which the reef plane is faulted into several sections, or even folded in an arbitrary way. An element of a fault is modelled in the same manner as an element of the reef, except that a fault element is allowed to undergo permanent inelastic deformation (i.e., slip) if the stresses transmitted through the fault-filling material satisfy a Mohr-Coulomb yield condition. An iterative technique for the incorporation of a Mohr-Coulomb yield condition in the general displacement discontinuity method is explained. This technique is illustrated by means of a simple example involving the mining of a flat-lying reef intersected by a fault. The displacements and stresses at selected locations along the fault are examined as the reef is mined, element by element. A consideration of the energy changes reveals that the occurrence of slip along a fault leads to a sudden increase in the energy release rate due to mining as the excavation intersects the fault. The energy release rate then falls off abruptly to a value less than that which would occur in the absence of any slip, and gradually builds up to re-establish the conditions that would exist in unfaulted ground.

Jan 1, 1979

By R. D. C. Shone

Consideration is given to the technical and economic feasibility of freeze desalination as a technique for the simultaneous provision of ice to cool deep mines and for the desalination of mine water. Freeze desalination has not been developed fully or commercially. For sea-water applications, it may not offer significant advantages over other methods of desalination but, for the unique mining application, a single dual purpose plant that produces desalinated ice could offer significant cost savings over combinations of separate desalinators and ice-makers. The current status 01 freeze desalination is reviewed, and the important aspects relating to mines are discussed. Some freezing processes that could be suitably modified are described. The possible use of conventional ice-making machines for desalinating mine water is also discussed.

Jan 1, 1987

By P. Syrjänen, Lovén. P.

Because geostatistics together with block modeling has not been studied in detail before in the rock mechanics, a two-year research program to investigate the practical use of geotechnical modeling was started in Finland in 1999. According to research work results block modeling gives good estimate of overall rock mass quality but it can not identify individual structures like faults and narrow weakness zones. Weakness zones and faults should be mapped from drill cores, surface mapping, geophysical methods etc. and manually generate 3-D structural model. Rock mechanical 3-D modeling can be used for preliminary stope dimensioning and preliminary reinforcement design. Detailed design needs rock quality mapping from drifts during excavation work. La géostatistique associée à la modélisation par blocs n'ayant pas été étudiée en détail jusqu'à présent dans la mécanique des roches, un programme de recherche sur deux ans visant à examiner l'utilisation pratique de la modélisation géotechnique a été lancé en Finlande en 1999. D'après les résultats des travaux de recherche, la modélisation par blocs donne une bonne estimation de la qualité générale de la masse rocheuse mais elle ne permet pas d'identifier les structures individuelles comme les failles et les zones géologiquement dégradées étroites. Ces zones et failles devraient être cartographiées à partir de carottes de sondages, d'une cartographie de surface, de méthodes géophysiques, etc. et générer manuellement un modèle de structure 3D. La modélisation mécanique des roches en 3D peut être utilisée pour un dimensionnement de la chambre et un plan d'armature préliminaires. Un plan détaillé nécessite l'élaboration d'une cartographie de la qualité des roches des galeries lors des travaux d'excavation. Da man früher Geostatik und Block-Modellieren in der Gebirgsmechanik nicht detailliert untersuchte, wurde 1999 in Finnland ein zweijähriges Untersuchungsprogramm in Angriff genommen. Aufgrund der Untersuchungsergebnisse ergibt das Block-Modellieren eine gute Beurteilung der gesamten Gebirgsmassenqualität, kann jedoch einzelne Strukturen wie Verwerfungen und kleine Schwachzonen nicht identifizieren. Schwachzonen und Verwerfungen müssen demnach aus Bohrkernen, oder mit Hilfe von Oberflächenkartierung, geophysischen Verfahren usw. ermittelt und danach ein 3-D-Strukturmodell manuell erstellt werden. Felsmechanisches 3-D-Modellieren ist für die vorbereitende Abbaudimensionierung und für die vorbereitende Bewehrungsplanung verwendbar. Ein detaillierter Entwurf benötigt die Kartierung der Gesteinsqualität aus den Gesteinsstrecken während der Ausbrucharbeiten.

Jan 1, 2003

By C. J. Alberts

The perception exists in many organizations that, once an energy management system is employed, there need not be any further adjustments to such a system. This is not true, as the field of energy management is a dynamic field, and constant feedback and adjustments are needed to enhance the efficiency of a system to the point that substantial pay-back can be obtained. It is stressed that for any energy management system to be successful, careful planning should permeate through the organization, from the top level decision-makers to the workplace. This paper describes a dynamic technique by which energy management strategies can be evaluated by viewing the effects of the strategies on the organization as a whole.

Jan 1, 1997

The Centenary Distinguished Lecture was held on Thursday, 24th March, 1994 at the Convention Centre of the Sandton Sun, Johannesburg at 20:00. Herewith the proceedings that followed. P.R. Janisch: The South African Institute of Mining and Metalurgy began life one hundred years ago tonight, and eight years (almost to the day) after the 1886 discovery of gold, which has impacted so profoundly on the course of events in our country since then. The Early Years That discovery was a mater of fortune, but not in the sense of the conventional prospector's lucky strike. Canny explorers, such as the Strubens, had been around for some years and, if George Harrison had not stumbled over the Main Reef when he did, someone else would surely have done so within months. The element of luck was that the gold-bearing rocks of the Witwatersrand actually lay exposed to sight. We now know that they are something of the order of 2,5 billion years old. Rocks of that age are usually covered by younger formations. In fact, the bulk of the Witwatersrand Basin is covered by lava, dolomite, and Karoo measures. What, one wonders, would our history have been had the Karoo, which stops at the Vaal, extended no more than 60 kilometres further north. Dr H. Scot-Russell A piece of advice attributed to Paul Kruger, the who was President of the South African Republic one hundred years ago, was the following: 'Seek from the past that which is good, and build on it for the future'. It is advice that can be applied universally and, whether deliberately or not, it must have motivated my predecessors when this Institute celebrated its 40th, 50th, and 75th birthdays. Those milestones were each marked by retrospectives, as Peter Janisch has so ably presented tonight on our hundredth anniversary. The parallels do not end there. We find ourselves in times no less daunting than those our predecessors. Next month will see the birth of a new kind of South Africa; so did May 1902, May 1919, and May 1948.

Jan 1, 1994

By A. L. Hinde, P. J. D. Lloyd, D. Hebden

The philosophy behind the design of a rougher cell for the handling of coarse feed and for the maximization of recovery within a given time is presented. The application of this philosophy in cells of 22-litre, 320-litre, and 3 m3 capacity is outlined, and the results of the process testing of these cells are given. In this testing, particular accent was placed on the recovery of water as a guide to the recovery of the finest size of particles, and the rate of recovery of various mineral species. It is concluded that a promising concept has been identified, but that further testing is needed for the firmer establishment of optimal operational parameters in a production environment.

Jan 1, 1983

By R. G. B. Pickering

Conventional mining is an excellent match of mining method and equipment. The result is guaranteed performance. Change in the form of different technology requires change in mining method until the best match is achieved. This paper covers the development of technology and mining method that has occurred in the last five years to arrive at the objective of successful mechanized mining in narrow reef platinum deposits of the Bushveld Complex.

Jan 1, 2004

By O. Korhonen, T. Leskinen

The use of large OK-16 flotation machines at the concentrators of Outokumpu Oy by o. KORHONEN and T. LESKINEN(Visitors) The development ofthe OK-16 flotation machine is described briefly, and an account is given of its use at various concentration plants in Finland. The benefits arising from the use of larger flotation machines are listed, and the technical specification of the OK-16 machine is detailed in an appendix.

Jan 6, 1976

By J. van der Walt, A. Whillier

Reference is made to the approach to mine cooling in which the service water is used as one of the means of distributing refrigeration, and attention is drawn to various engineering disciplines or functions necessary for effective distribution and reticulation of cold water from refrigeration plant. The demand for service water is intermittent, the peak flow-rates being typically two to three times the average flowrate. The refrigeration plant, on the other hand, must preferably be operated steadily throughout the day and night, with the result that a large storage dam for cold water must be incorporated into each system in order to even out the surge in demand for water. These dams should be operated as constant-temperature, variable-volume reservoirs. The conventional cascade system involving dams on each level is not the best for sending water down mines, and schemes are described that avoid the need for such dams. Reference is made to various tests that were carried out, and to several large systems that were installed. Management and organizational problems that could arise as a result of new technological developments in mine cooling are referred to, and cost figures are quoted to indicate the large potential savings, In addition to the improved environmental conditions, that can be achieved through the use of integrated water systems.

Jan 1, 1979

By J. H. Lazarus

The evolution of backfill-distribution systems for deep gold mines is examined. The status of current technology for the design of backfill-distribution systems is considered with reference to pipeline pressure gradients, pipeline wear rates, and slurry flow regimes. The effect of an increase in the relative density of the slurry on the performance of backfill-distribution systems is illustrated. Future trends regarding the design of backfill-distribution systems are discussed.

Jan 1, 1993

By C. Ringas, F. P. A. Robinson

Various theories proposed to account for microbial corrosion are reviewed as a background to a better understanding of this type of corrosion in iron-based alloys. Experimental evidence is presented to show that even stainless-steel alloys are prone to microbial attack by sulphate-reducing bacteria. The corrosive attack by the bacteria is due primarily to the hydrogen sulphide that is produced as part of their metabolic processes.

Jan 1, 1987

By L. A. Vermeulen, D. D. Howat

New distribution functions are derived to describe the size distribution of grinding elements in ball mils. The formulations are based on the assumption that abrasive as well as impactive interactions occur during bal milling-an assumption that is supported by a large body of experimental evidence. It is shown that the functions can be used in the estimation of the magnitudes of abrasive and impactive components in the total rate of bal wear. The relative magnitudes of the wear components provide a basis for optimization of the chemical and metallurgical properties of the balls in a given milling situation. However, it is contended that these quantities are also useful indicators of the relative intensities of the abrasive and impactive interactions that are operative in the size reduction of mineral particles within ball mils. These quantities can be determined for any industrial ball mil, and their magnitudes provide practical guidelines for mil operation. The theory is used in an analysis of samples of ball charges from two industrial ball mils, and it is also applied to al the data on bal-size distributions found in the literature. The qualitative correlation between the calculated values of the wear components and the reported operating conditions is good for a variety of industrial ball mils, in conformity with the hypothesis that the relative magnitudes of the wear components are related to the milling conditions.

Jan 1, 1986

By M. C. van Blerck

Since its introduction in 1956, the capital allowance has been increased and its scope widened. At present the allowance is 10% in respect of two categories of gold mine (post-1973 and other deep level mines) and 6% in respect of natural oil mines. The allowance is a significant incentive encouraging the development of new mines, to the benefit of both the fiscus and the South African economy as a whole. A strong case can be made for increasing the amount and the scope of the allowance. The Margo Report recommendation that the allowance should possibly be replaced with a system of direct grants is, in theory, neutral. However, practical difficulties exist with cash grants and there is concern with the implications elsewhere in the Margo Report that the capital allowance is excessive and that, as a consequence, such direct grants will represent an effective reduction in this incentive. I believe that the best course of action would be the retention (and enhancement) of the capital allowance and the expansion of its scope.

Jan 1, 1988