Search Documents

By N. T. Halgreen

The use of coal for combustion, carbonization, and the production of synthetic fuel is discussed briefly, highlighting the effect of certain physical and chemical properties of coal on these processes. The effect of consumer specifications of properties such as calorific value, ash content, moisture content, and size consist on the planning and operation of a mine are discussed, including the influence of coal degradation through time or mechanical means. The effects of various mining methods on these parameters and on the utilization of coal reserves are discussed.

Jan 1, 1984

By W. L. Van Heerden

In situ complete stress-strain characteristics of large coal specimens by W. L. VAN HEERDEN, B.Sc. Hons. (Pret.) (Visitor) The significance of ;n situ tests on large coal specimens is briefly reviewed. Tests aimed at obtaining complete stress-strain characteristics of large coal specimens with high width-to-height ratios are described. A formula for the relationship between strength and width-to-height ratios of coal pillars is proposed, and the influence of width to- height ratios on the deformation characteristics of pillars is discussed.

By P. F. S. Jackson, A. Strasheim

In the survey "Analysis of South African raw bullion" the distribution of trace elements within the bullion have been shown to be distinctively dependent on the extraction process. In general the amalgamation process produces the more impure bullion with respect to trace elements. Some chemical and physical explanations are given for the differences that have been observed in the raw bullion as received at the Rand Refinery. The value of the spark source mass spectrographic technique in the study of the elemental impurities in bullion is demonstrated.

By Adams. M. D.

Most of the cyanide lost in carbon-In-pulp plants is due to the reaction of cyanide with base metals and sulphides during leaching. Some cyanide is also lost in the adsorption tanks as a result of oxidative and adsorption reactions with the activated carbon. The high rates of cyanide loss in the elution and electrowinning stages are atributable to hydrolytic decomposition and anodic oxidation, respectively. However, the relative amount of cyanide lost during these two stages is small for a given amount of ore treated.

Jan 1, 1990

By G. W. Holl, E. G. Fairon

A review of some aspects of shaft design by G. W. HOLL, Pr. Eng., Associate of the Mine Managers Association of South Africa (Fellow)- and E. G. FAIRON, Pr. Eng., F.S.A.I.E.E., M.I. Cert. M.E.E., M.I.Mech. E., (Visitor) The reasons for the choice of vertical shafts in preference to inclined shafts of comparable capacity are set out, and the conclusion that the former are superior in virtually all circumstances is substantiated. The shapes of vertical shafts sunk during the past sixty years are recorded, and the shapes of those sunk during the past decade are analysed. From this analysis it is clear that circular and elliptical (and quasi-elliptical) shafts are the shafts of the future and that the rectangular shape will conceivably become obsolete. The determination of the size of shaft is discussed and it is forecast that shafts of a diameter of 13 metres and over will probably be sunk without difficulty in the years to come. The depth of the shaft is determined intrinsically by the Mines and Works Regulations applicable to factors pf safety of winding ropes and the design of the winding system. The Blair winder is the most suitable winder for hoisting rock, men, and material from a depth of, say, 3000 metres on an economic basis. Tertiary shafts will, therefore, be unnecessary in future deep-level mining projects at the limit of depth now envisaged. A few other factors relating to shaft design are described.

By A. N. Brown

Professor D. G. Krige, of the Department of Mining Engineering of the University of the Witwatersrand, received the degree of Doctor of Engineering (honoris causa) from the University of Pretoria at the Autumn Graduation Ceremony in April 1981. He was honoured an outstanding engineer for his world-renowned pioneering work in the field of statistical methods of ore valuation, or geostatistics as it has become known. Metalliferous Ore Deposits A short course on the 'Evolution of Metalliferous Ore Deposits' will be held at Rhodes University, Grahamstown, from 8th to 13th February, 1982.

Jan 1, 1981

By H. C. Voges

The use of heavy-medium separation in the processing of iron ores by H. C. VOGES. B.Sc. (Visitor) The paper discusses various aspects of the application of heavy-medium separation to the processing of hematite ore at Sishen and Thabazimbi. The two main factors to be borne in mind in the design of a plant for such beneficiation are the Iow unit value of the iron ore produced and the high separation densities required. The four factors of importance in the avoidance of high viscosity in the ferrosilicon medium are discussed in turn.

Jan 6, 1975

By D. D. Howat, J. van der Colf

Slags of the system CaO-MgO-AI2O3-TiO2-SiO2at had been reduced in graphite crucibles for selected time Intervals were fully re-oxidized so that an assessment could be made of the rate and extent to which the titanium oxide had been reduced. The derived kinetic parameters were studied as functions of slag composition and temperature. The extent of reduction after selected Intervals of treatment could be correlated with the physical behaviour of the melt (in terms of viscosity and electrical resistivity).

Jan 1, 1979

By P. C. Schutte, N. B. Strydom, A. J. Kielblock

Three groups of unacclimatized men were subjected to five-day climatic-room procedures at wet-bulb temperatures of 29,30, and 31 C respectively. The findings indicated that individuals reach a satisfactory level of heat acclimatization for work in environmental temperature conforming to those at which they were acclimatized. It is, therefore, superfluous to acclimatize men at wet-bulb temperatures that exceed those at which they are destined to work. These methods of acclimatization can be linked advantageously to heat-tolerance testing at mines with suitable underground temperatures.

Jan 1, 1983

By A. V. Z. Brink, D. M. O’Connor

Recent research into the prediction of mining-induced seismic events by the monitoring of small microseismic events at Western Deep levels Gold Mine is described. Measurement and interpretation techniques and results are presented. It was found that the occurrence of the larger events near longwall faces on the Carbon leader reef is preceded for some hours by an increased rate of microseismic emission and spatial concentration of the microseismic events in the zone of eventual failure. The research is currently being expanded with the aim of producing a practical rockburst early-warning system.

Jan 1, 1983

By C. J. Van Niekerk, C. C. Begley

SYNOPSIS The paper opens with brief descriptions of the history, occurrence, and regional geology of South Afri¬can zinc deposits, and follows with descriptions of the resources, mining methods, and processes for the concentration of the sulphide minerals and the extraction of zinc as practised in South Africa. The end uses in the form of alloys or as salts are given in some detail. Statistics on the production and consumption of zinc in South Africa are given, and the current market situation and future prospects are discussed briefly.

Jan 1, 1991

By D. J. Adams, R. G. Gürtunca

This paper describes the results obtained from a rock-engineering monitoring programme carried out at West Driefontein gold mine, where dewatered and classified tailings have been used as backfils for local and regional support. The in situ behaviour of these backfils and the surounding rockmass were determined, and it was found that the backfil used on this mine has provided significant regional support. The underground observations also showed less rockburst damage in backfiled panels than in unfiled panels, provided the backfil had been placed properly in the stopes.

Jan 1, 1991

By M. J. Nicol, P. Balestra, E. Schalch

A detailed fundamental study has been made of the various factors that influence the partial reactions comprising the electrochemical model of the cementation of gold from cyanide solutions by zinc. The effects of cyanide concentration, pH, agitation, additions of lead, and the presence of various impurity ions on both the anodic dissolution of zinc and the cathodic reduction of gold have been investigated. The results are used to explain the influence of these variables on the rate of cementation, and possible implications of this work for plant practice are discussed.

Jan 1, 1979

By D. R. Hardman

Coal mining has been practised in South Africa for over one hundred years. The total production increased gradually in the early pat of the twentieth century, but over the past twenty years the rate of growth has been considerable. Although opencast mining has contributed largely to this increase in production in recent years, underground bordand- pillar operations still contribute slightly less than 50 per cent of the total production. The paper highlights problems arising from old bord-and-pillar workings, and an indication is given of how some of the problems have been addressed.

Jan 1, 1990

By L. Dison, J. A. Hahn, G. E. Blight

A system of artificial support for shallow mines is described, analysed, and evaluated. The system can be designed rationally to support a predetermined overburden load, and tests have shown that the design theory gives accurate predictions of strength. The support system, consisting as it does of two basic materials, reinforced granular material and reinforced cemented material, is flexible and can be varied to suit changing requirements of height and load. The system of preloading to the design load by jacking off the roof ensures that the walls are both stiff and prooftested.

Jan 1, 1982

By B. J. Ralph, I. J. Corrans, B. Harris

In the first section, a brief background to the practical and theoretical aspects of bacterial leaching is presented. Descriptions are given of present and potential methods for exploiting bacterial leaching in metal-winning. In the second section, the results of recent research are presented. The aim of this work was to obtain a greater understanding of the mechanism of bacterial leaching of sulphide minerals. Bacteria were observed to catalyse leaching reactions by oxidising ferrous ions to ferric ions, by removing protective films at the mineral surface and by depolarising cathodic areas.

By G. J. Kringe

The results of a series of measurements of accelerations and guide-roller loads made on mineshaft conveyances are given, together with the predictions of these accelerations and loads based on a computer programme. The analysis of the measurements is described, and the results of the measurements and computer predictions when compared show reasonable agreement. Some parameters that increase the guide-roller loads are identified, and their effects are studied, together with some comments on the total loads. Finally, a possible format for a design specification is discussed, and some tentative design values are given.

Jan 1, 1986

By M. D. Prendergast

Research into the ferrous metallurgy of Rhodesian Iron Age societies M. D. PRENDERGAST (Visitor) Iron-working was a widespread economic activity in Iron Age Rhodesia, and merits historical and metallurgical investigation. However, the research done so far has been incidental and poorly disseminated. This paper reviews the available evidence and the ways in which it can be interpreted by archaeologists and historical metallurgists. Particular attention is paid to smelting techniques and current metallurgical research, and brief suggestions are made for future research. v074n06p254.pdf

Jan 1, 1974

By P. R. Jochens, D. D. Howat, R. B. Atmore

INTRODUCTION The Miller chlorination process has assumed a preeminent position in the refining of gold bullion, a position it has maintained for over half a century. In the early sixties considerable interest was aroused by the idea of producing a consistently high grade bullion at the mine smelthouses themselves. However, as the use of chlorine in industrial plants is associated with considerable hazards, oxygen was considered a natural alternative, apart from bing less expensive than chlorine. Partial refining at the mine smelthouses would considerably decrease the requirements made on Rand Refinery Limited as well as indicating the possibility of reducing final refining costs. An added factor would be the purer silver chloride obtainable, after prior removal of the base metals by oxygen injection, which would facilitate the production of high-purity silver. The free energies of formation of the oxides of the metals;- silver, copper, lead, zinc, iron and bismuth indicate that, with the exception of silver, these metals should be capable of removal as oxides by oxygen injection. Rose1 had shown that during injection of gold bullion, considerable loss of silver to the boraxsilver slag occurred and, furthermore, that copper removal was not efficient and oxide attack on the refractories was severe. Plant test work2 had confirmed the difficulty of copper removal, but had shown that zinc and lead were almost completely removed. The difficulty of copper removal by oxygen injection warranted further investigation. Also, the high decomposition pressure of silver oxide suggested that by suitable control of the slag composition it might be possible to reduce to very small proportions the silver carried into the slag as oxide. The oxidation of copper by oxygen injection and subsequent dissolution of the oxide in a slag may occur according to the following reactions; Reactions 4 and 5 were considered because of the relatively high solubility of oxygen in molten silver and silver alloys. Thermodynamic data indicate that there is little possibility of any reaction involving the formation of CuO occurring at temperatures above 1 000 °C. To ensure that the operative reactions 1 and 4 take place to the maximum extent, the following factors He significant. (a) an increase in the activity of the copper in the bullion, (b) an increase in the partial pressure of oxygen in the system, (c) an increase in the activity of the oxygen in solution in the metal, (d) a decrease in the activity of cuprous oxide in the slag. From practical considerations, the operative variable most easily susceptible to control is the composition of the slag. SOLUBILITY OF COPPER OXIDES IN BOROSILICATE SLAGS Very scanty information exists on systems containing copper oxides but the indications are that slags containing considerable amounts of boric oxide would possibly prove to be the best solvents for cuprous and cupric oxides. This is attributed to the fact that the activities of copper oxides are much lower in boric oxide slags than in slags in which silica is the main network former. The number of possible slags containing boric oxide was limited by consideration of liquidus temperature, viscosity, corrosive action on refractories, volatilization, and ultimately cost (for industrial application). Slags in the systems soda-boric oxide-silica and lime-boric oxide-silica were selected paying due attention to the above limitations. Additions of 5, 10 and 15 per cent cupric oxide were made to the finely ground, premelted slags. These mixtures were then reground and 2g quantities held in re crystallized alumina crucibles at temperatures of 1150°C and 1 250°C respectively for 30 minutes. The crucibles were removed from the furnace, rapidly cooled, cut in half longitudinally, and a thin section taken from one half was subjected to microscopic examination.

By Penswick D.

From the perspective of management control, most mining operations can be represented by a hierarchy comprising four layers. The base of this hierarchy consists of the individual pieces of equipment that are used to break and transport rock. The next level comprises the coordinated interaction between different pieces of equipment, termed a process. An operation results from the bringing together of different processes within a common discipline, such as mining or hydrometallurgy. Finally, an enterprise is formed when the separate mining, concentrating and smelting business units are combined. To date, much of the literature written on the topic of mining automation has focused on the equipment level, specifically on removing the operator from production mining equipment. This focus should not, however, overshadow advances registered in automation at both the process and enterprise levels. Only at the operations level of the hierarchy has little progress been made. While automated equipment, process management and enterprise resource planning are a current reality; it is argued that the benefits from automation have, to date, been largely elusive. It is further argued that full benefits of automating other levels will only be fully achieved when this ‘gap’ in the mining automation hierarchy has been addressed and an uninterrupted, process-wide information flow across the entire operation is achieved. Furthermore, it will be reasoned that so-called vertical integration can only be achieved with an automated operational level in place. It is believed that all the necessary building blocks are in place and that the industry is ready for this development. The paper concludes by presenting a vision for what operational level automation would achieve.

Sep 1, 2001