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By L. A. Vermeulen

A simple argument shows that it is impossible for the flight of a rod in contact with a litter bar in a rotary mill to be initiated at that point on the upside of mill rotation when all the forces acting on the rod are in equilibrium. The argument was confirmed experimentally in a study showing that the lift of litter bars is a function of their height, that the rod velocity at the point of departure has a significant radial component, and that the subsequent flight of a rod is along a parabolic trajectory as predicted by elementary mechanics. A quantitative account of the observed effects, which is based on a dynamic theory of the sliding interaction between rods and litter bars, revealed interesting properties of the motions of rods down the surfaces of litter bars when the latter are in uniform circular motion during the rotation of a mill.

Jan 1, 1985

By B. R. Broekman, D. W. Penman

SYNOPSIS This paper traces the developments in flotation practice at Anglovaal's Prieska Copper Mine, with em¬phasis on the depression/deactivation of lead and zinc. A depressant system was devised to accept feed material that was once regarded as untreatable. Of particular interest is the long-term downward trend of concentrator working costs in real terms. This trend follows the classic Experience Curve, which relates production costs to cumulative experience. It is felt that the experience-curve concept has important implications for the mining industry in general.

Jan 1, 1991

By By the staff of Gold Fields of South Africa

A diamond-drilling programme conducted from 1971 to 1973 by the Phelps Dodge Corporation revealed three complex sulphide ore-bodies in the highly folded Namaqualand mobile belt on the farm Aggeneys, some 65 km west of the small town of Pofadder on the road to Springbok in the northwestern Cape. Of these, the Broken Hill occurrence is the most promising.

Jan 1, 1980

By H. V. R. Von Rahden

The expertise of the industrial mineralogist has not always been sufficiently used in decision-making in the minerals industry in South Africa. The mineralogist can make a contribution at al stages of the exploration programme, from the time of discovery of a geological target area, through metallurgical testwork and pilot-plant studies, to the production of a saleable product. This indicates that the activities of the industrial mineralogist should be more closely integrated with those of the exploration geologist and the extraction metallurgist in order to provide management with a meaningful picture of the economic potential of an ore deposit.

Jan 1, 1997

By B. A. Dukas

The diamond-drilling machine has for many years been the most important exploration tool In the search for and subsequent evaluation of Witwatersrand-type ore deposits. With a view to increasing the range of services that can be provided and, at the same time, counteracting rising drilling costs, new techniques are continuously being developed. Many of these techniques have equal application in surface and in underground exploration. This paper reviews drilling techniques such as non-coring pilot holes and deep wire-line drilling, as well as the design of core-barrels and drilling bits to cater for the specific nature of the job on hand. Special drilling fluids and aluminium rods to assist in normal drilling operations are also discussed. Special mention is made of a bore hole's natural tendency to deviate in a certain direction. The factors that cause deviation are used to the advantage of controlled drilling techniques.

Jan 1, 1983

By A. Koursaris, Y. N. Turan

A series of experiments was caried out in a vacuum-induction furnace to investigate the solubility of nitrogen in stainless steel type 3100S. Melts were made under constant and variable partial pressures of nitrogen so that the absorption of nitrogen from the atmosphere could be examined. Additions of nitrogenized ferochromium were made to give high nitrogen contents in the steel. Nitrogen contents of up to 0,16 wt per cent were obtained under gaseous atmospheres. With additions of nitrogenized ferochromium, nitrogen contents of up to 0,525 wt per cent were obtained. Comparisons of the later value with existing data indicate that the equilibrium concentration of nitrogen was reached for the experimental conditions used.

Jan 1, 1992

By T. R. Twiddle

The sequential flotation of copper, lead, and zinc in that order is practised at the Broken Hill Concentrator of the Black Mountain Mineral Development Company (Pty) Limited. The minerals of economic importance are chalcopyrite, galena, and sphalerite, with associated silver. The targets for recovery and grade in the lead and zinc circuits were reached quite readily after start-up, but the copper circuit failed to meet the performance requirements with respect to both recovery' and grade. The original circuit for copper is described, together with the subsequent investigations and modifications that were required to produce acceptable metallurgical results. Circuits for semi-bulk and bulk flotation were tried, and the effect of the oxidation state of the pulp was investigated extensively and found to be all important. Tests were conducted on the depression of lead in the cleaning circuit by the use of sodium dichromate, and on heating with the addition of sulphurous acid. The latter technique was ultimately the more successful. The proportion of fresh to recycle water entering the circuit was shown to be important. The original reagent regime was altered and augmented. A more recent problem has been the contamination of the ore with cemented backfill. The changes that this new condition necessitated are described. Success has been measured by a continuous improvement in the economics of the copper recovery.

Jan 1, 1984

By Gernot Beer, Christian Dünser, Marcos Noronha

The main findings of the joint research initiative “Numerical Simulation in Tunnelling” and a follow-on project on efficient numerical simulation models for tunnelling are presented. Die wichtigsten Resultate des Forschungsschwerpunkts „Numerische Simulation im Tunnelbau“ und einem Folgeprojekt über effiziente numerische Simulationsmethoden werden präsentiert Les résultats les plus importants du point principal de la recherche "simulation numérique dans la construction de tunnels" et un projet consécutif sur des méthodes de simulation numériques efficaces sont présentés

Jan 1, 2003

By C. A. Hunt

The problem of materials balancing is reviewed with particular reference to the minerals industry. A broad statistical framework is established that, besides extending the classical estimation problem, allows questions concerning the value of sample information to be addressed. The following are examples of such questions: How much money should be spent on sampling? Which streams in a plant should be sampled? What should be sampled? The approach adopted makes use of Bayesian analysis. The discussion includes an illustrative example involving a simple flotation circuit.

Jan 1, 1985

By G. P. N. Venter

A method of evaluating the possible effect of an industry on the environment is presented, and the method is illustrated by its application to a hypothetical problem. An analysis is offered based on an actual survey of four industrial sites in the Lydenburg area of the eastern Transvaal. The survey showed that there is a high incidence of potentially unfavourable conditions, and there is a distinct possibility that a topographically induced eddying motion will extend over the town and the industrial sites. This moving air could entrap air pollutants, resulting in high concentrations of pollutants over the town. It is concluded that none of the sites is suitable for industries that pollute the atmosphere.

Jan 1, 1978

By A. A. Oakes, P. M. C. Wilson

This paper describes some aspects of the planning of a new colliery which commenced production in the Middleburg district in 1966. An account is given of some of the problems encountered in the early years of operation and of what was done to solve them. The conclusion is reached that design of plant and machinery should be flexible to permit multiplication of units.

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 H. A. D. Kirsten

SYNOPSIS This paper describes simple calculations to evaluate the stability of hangingwall and footwall strata at the work¬ing face and in backfilled areas. It shows that the benefits of support provided by backfill can best be realized when the fill is placed as close to the face as possible. The main beneficial effects of fill are that it reduces the stope span, at the same time providing a damping effect on vibrations, and prevents the fall-out of blocks in filled areas, thus maintaining the competence of the strata.

Jan 1, 1988

By O. K. H. Steen

Significant political and economic changes have taken place in our society in the past year that are going to impact on our minerals industry, and therefore also on our members. Surely, it is not coincidence that the economic and political changes have occured simultaneously? South Africa, by virtue of its infrastructure and technology, is strategically placed to develop the potential of Africa's mineral wealth. In this address, I give my personal views on the ability of the mining industry to participate in the wider mineral resources of the African continent.

Jan 1, 1989

By B. Gilbertson

This paper presents a method that enables one to estimate the risk-adjusted discount rate. that should be used In project discounted cash-flow analysis. The risk-adjustment process is carried out via the capital asset pricing model of modern finance theory, in which the appropriate measure of risk is the beta coefficient of the project concerned. The resulting discount rate thus depends on the properties of the project Itself, and not on the nature or cost of the capital of the firm considering the investment.

Jan 1, 1980

By H. E. Cross

Metallurgical considerations in the automation of gold-recovery plants By H. E. CROSS. Pr. Eng., B.Sc. (Eng.) Hons. (Fellow) The advantages of the automation of gold-recovery plants are examined. The various sections of a gold-recovery plant are analysed, and the extent to which instrumentation can usefully be employed is described. INTRODUCTION The scope of this paper is restricted to the ore-treatment and recovery plants on Witwatersrand gold mines. To extend the field to plants that process base metals and industrial minerals would result in a paper that would be too lengthy. However, the subject matter of this paper is applicable to most mineraldressing and recovery plants and will, it is hoped, be a foundation on which to build somewhat more sophisticated control systems required in the base-metals field.

By A. Bain

The use of plastics in the coal mining industry is making slow progress whereas these materials could make a greater contribution to safety, to a reduction of working costs and to the higher productivity of mine workers. Possibly the reluctance to experiment with the new material of our age is due to the low profit margin of coal mining. This note has been prepared to present a brief survey of what has been done in the last few years and to mention some of the investigations the author has made and is making in an attempt to develop more use of plastics in the industry. Some of the plastics used on the mines have taken their place in the industry in the same manner that they are used in everyday life while others have been introduced because there has been a need for them. New uses and applications are being developed and these are the ones that are most interesting. The plastic that is specially developed to give the maximum benefit and not the one that is a modification of some other everyday product is the next development in the field. Many manufacturers are keen to promote such investigation but are not aware of the problems the mines wish to solve and therefore it is only through management itself that this development can be carried out. This note deals with plastic material under three headings: (a) Plastic as the superior material, and briefly describes how plastic has replaced a few major items which are better when made from plastic. (b) Plastics of necessity, being a short summary of how plastics had to be introduced because of laws and conditions making it a necessity. (c) Development of new ideas, being briefly some of the ideas being developed overseas and some of the ideas being tried by the author. Plastic items in common use such as in housing, electric cables, laboratory equipment, awnings, nylon bearings, locomotive brake linings, etc. being well known are not discussed. PLASTIC AS THE SUPERIOR MATERIAL Plastic belting underground Following a fire in a belt road in England resulting in the deaths of many workers, and subsequently a fire accompanied by fatalities in a belt road in a mine in this country, a law was introduced which states that only flameproof belting is to be used underground. This ruling forced the mines to use P.V.A. belting as no other was available. This belting has non-inflammable characteristics that are superior to rubber. Due to the high tension on long-distance belts used today the need for stronger belting material called for something better than cotton and the answer to this was nylon. Nylon also has the ability to withstand dry-rot which reduces the life of a belt very quickly.

By B. Rohrmann

The paper deals briefly with the history of vanadium, and its uses, price movement, and world resources. It then describes the titanomagnetite ore of the Bushveld Complex, and the production of vanadium from this ore at Highveld Steel & Vanadium Corporation Limited, giving details of the various processes used, including the roast-leach, rotary-kiln, electric-smelting, shaking-ladle, and basic-oxygen-furnace operations. The paper concludes with a very brief account of the treatment of Highveld slags in Europe for the production of vanadium pentoxlde and ferrovanadium.

Jan 1, 1985

By P. Greenfield

The German steelmaking industry has come up with a novel solution to the problem of waste plastics-grind them into particles and use them in the steelmaking process. Plastics make ideal agents for removing oxygen from iron ore in blast furnaces, and save on oil and coal as well. The aim of replacing heavy oil and coal with plastics in blast furnaces is to use them as reducing agents as well as an additional energy source.

Jan 1, 1996

By D. W. Horsfall

The coal-preparation techniques used in South Africa over the past ten years are reviewed, the term preparation being taken to refer to processes involving beneficiation techniques. The success of the preparation methods adopted can be gauged from the fact that, although South African coals are generally of a fairly low quality, the country is producing coals both that are used locally for the raising of steam and for metallurgical purposes, and that compete successfully on world export markets.

Jan 1, 1980