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By W. F. Lorch

Growing use of deionised water in surface coating techniques by w. F. LORCH Production engineers in the metal plating, paint, plastics-coating and printed circuit industries are increasingly aware of the cost of sub-standard or blemished items which have been poorly processed. An area where quality control can quickly produce higher efficiencies is in the choice of suitably purified water for making up solutions, for rinse baths and 'drag-out' baths, for cleansing lines and electrophoresis tasks, for maintaining electrolyte density and hence consistency, and for facilitating the recovery of valuable minerals. The author of this article examines the general problems of using nonpurified water, and shows how purified water has become accepted by the principal surface coating industries to improve processes and effect economies.

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 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 K. O. R. Gebhard

Direct reduction-are we moving in the right direction? by K. o. R. GEBHARD INTRODUCTION Numerous forecasts predict a rapid growth rate for direct-reduction processes. The figures quoted are so impressive that many a top manager must fear that he will fall behind in technical development if he does not base a substantial part of his future steelmaking for mass production on direct reduction.

Jan 2, 1974

By T. Groenewald

Potential applications of thiourea In the processing of gold by T. GROENEWALD, Ph.D. (Rand), D.I.C. (Imperial College) (Visitor) The aqueous chemistry of gold(l) that has found practical application is mainly the chemistry of the anionic complexes involving ligands such as cyanide. sulphite, and the halides. The one potential exception is the cationic gold(I)-thiourea ion. While many laboratory studies have been made during the past decade. the application of thiourea in the processing of gold is only now reaching the development stage. While thiourea is relatively inexpensive. recent interest has probably been spurred mainly by the novel technology that could arise out of the cationic properties of the gold-thiourea ion. This review outlines the chemistry of gold and thiourea. and discusses the possible use of thiourea in the processing of gold with respect to dissolution. solvent extraction. ion exchange, electrowinning. electroplating. electroless deposition. electro-etching, and electropolishing.

Jan 6, 1977

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 C. H. Wyndham, N. B. Strydom

Discussion C. G. Hinds (Member): The climatic chamber at Kloof Gold Mine was built to the design referred to in the paper presented by Professor Wyndham and Dr Strydom. As no suitable underground facilities existed for the acclimatization of labourers at the rate required, mining operations would have been severely restricted had there not been a climatic room timeously built on surface. The climatic room can accommodate 120 labourers per 4-!-hour shift. The standards laid down by the Human Sciences Laboratory were and still are being adhered to as strictly as possible. Through a shortage of European personnel the recommended degree of white supervision could not be adhered to and the use of Bantu assistants with a minimum education of Standard 8 was introduced. This is considered to have met with sufficient success to warrant acceptance as policy. The climatic room was brought into operation on the 1st September, 1967, i.e. two months after stoping at Kloof was commenced. The figures quoted herein therefore pertain to the period between that date and the 31st March, 1969, when the main shaft and the main surface fans were commissioned. The areas worked were sited between 5016 ft and 6 365 ft below surface. Virgin rock temperatures ranged between 92°F and 99°F. Stopes are cleaned by hand lashing. During the 20 months of stoping prior to the commissioning of the main shaft, mining operations at Kloof were effected through the Harvie Watt shaft of the Libanon Gold Mining Company Limited. In this period 10 452 Bantu labourers were acclimatized in the following categories: Experienced workers 7 326 New to the industry 2 086 Re-acclimatized 1 040 It will be noted that during the period, labourers 'new to the industry' averaged 22 per cent of the intake. This percentage fluctuated from time to time and reached 42 per cent. (The present percentage is 60.) The greatest number acclimatized during anyone month occurred in February, 1969 when 1234 Bantu were treated. The greatest number of Bantu acclimatized during any 8-day period was 411. As many as four X 41/2 hour shifts were run in 24 hours. The number of men found to be heat intolerant over the period of 20 months was 33 out of a total 9 412 Bantu. The following tabulation illustrates the history of the build-up of manpower and the climatic conditions under which they worked: The average dip of the reef is 35°. The number of heat stroke and heat exhaustion cases during the period of 20 months under most difficult ventilation conditions was Nil.

Jan 10, 1969

By M. G. Atmoret

It seems to me to be particularly appropriate that this topic should be discussed at the first prize-giving function of this kind. As you know, this presentation of awards to young mining engineers and metallurgists is to be an annual event, and never before in the dynamic and rapidly changing climate of the South African metallurgical industry has it been more necessary for young, and perhaps older, practitioners to consider the future of their profession and their role in the industry. I look forward with interest to the time, five to ten years from now, when I shall recall my crystal-gazing of tonight to see how far wrong I have been.

Jan 1, 1977

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 K. W. Falconer

The Witbank-Middelburg Branch of The South African Institute of Mining and Metallurgy celebrated 100 years of coal mining in the Witbank area with a function held at Douglas Colliery on the 5th December, 1989. Two hundred guests associated with the industry attended the occasion, at which Mr A.A. Sealey, Chairman of Rand Mines, Coal and Base Minerals Division, unveiled a plaque presented to the municipality.

Jan 1, 1990

By R. E. Robinson

On 18th November, 1991, the Department of Chemical Engineering at the University of the Witwatersrand, Johannesburg, held a display of posters to review their R & D activities. Although not a new concept, this series of presentations was the first time that the Department of Chemical Engineering at Wits had undertaken as comprehensive a review in this particular format. It turned out to be a most worth-while exercise, and the many visitors must have been impressed with the quality of the presentations.

Jan 1, 1991

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 G. G. Stanley

Mechanisms in the autogenous mill and their mathematical representation by G. G. STANLEY, B.Sc. (Eng.) (Wits.), M.E. (Queensland), Ph.D., (Fellow) The special characteristics of the autogenous mill are stated, and a suitable type of model for the mill is presented. Details of the test plant and experimental techniques for obtaining the data for model development are next given. followed by a discussion of the methods developed for the computation of the model parameters, namely the appearance matrix, the abrasion and crushing breakage-rate functions, and the discharge-rate function. Examples of results obtained with the model are given, and finally there is a brief account of confirmatory work on a fullscale autogeneous mill.

Jan 11, 1974

By D. R. Hardman, J. W. Oberholzer

Based on information supplied by South African collieries to the Coal Mining Laboratory of the Chamber of Mines since 1978, the paper outlines the general performance of the continuous miners used and gives the results more-detailed studies of the cutting, loading, and transportation processes. On average, the continuous miners produced coal at a rate of 76 t per operating hour, which, at an average machine availability of 67 per cent, resulted in a production of 51 t per total hour. The cutting rates varied between and 250 t/h but, owing to machine and system inefficiencies, the overall production rate varied between 92 and 48 It is concluded that, if the collieries concentrated on improving their machine utilization procedures and operating practices, they could increase the overall production from their continuous-miner sections.

Jan 1, 1987

By R. A. Plumbridge

I am deeply honoured by your invitation to address your great Institute on this centenary occasion. Mining is a cyclic industry that continuously faces enormous challenges as it wrests the treasures of the earth from an often reluctant mother nature. Throughout the ages, those challenges have demanded great skill from mining men and women, who are required to blend a mixture of robust determination with art and science. Pioneer Miners and Scientists It is not surprising therefore that the first blush of euphoria surrounding the discovery of gold on the Witwatersrand quickly gave way to consternation about the need to increase the metallurgical recovery of gold from the then readily identifiable conglomerate. The rugged pioneer miners had to turn to scientists for their salvation.

Jan 1, 1994

By F. H. Deist, H. D. Small, J. D. Austin, L. F. Duvel

The development and application of a computer system to aid in the planning of production in mines by F. H. DEIST, L. F. DUVEL, J. D. AUSTIN, and H. D. SMALL Published in the Journal, December 1972. Discussion by J. W. WILSON and R. W. HAZELL Although the Mine Planning Simulation Programme was originally developed as an aid to coal-mine planning, its extreme flexibility has enabled us to simulate gold-mine planning with equal facility. The initial application of the Mine Planning Simulation Model was in a small area of a large Free State gold mine where the primary aim was to assess the applicability of the programme to the gold-mining situation.

Jan 12, 1972

By G. van der Westhuizen, F. E. du Plessis

Ticor South Africa operates a dry mill at the town of Empangeni in the province of KwaZulu-Natal on the east coast of South Africa. The dry mill processes a non-magnetic mineral stream constituting rutile, leucoxene and zircon as major minerals, and minor quantities of ilmenite and other non-valuable minerals. For plant control and optimization, continuous ‘real time’ information about the mineral and chemical compositions in various plant streams is required. The current practice is to take samples at regular intervals and submit them for mineralogical(grain counting) and chemical analyses. However, these methods are time consuming, and in the case of manual grain counting, tedious and operator dependent. Until now an on-line or real-time instant mineral quantification system, which will be of great value in a plant operations environment, has not been available. Blue Cube Systems has developed a mineral quantification system using spectral mineral analysis. It measures and quantifies the composition of mineral samples instantly, providing consistent data in real time. A series of process stream samples from the dry mill mentioned above were used to evaluate the Blue Cube Systems instant mineral quantifier. This article will •describe the procedure of setting up and evaluating the Blue Cube Instant MineralQuantifier equipment •present its results, and •discuss the intended applications.

Jan 1, 2003

By C. Botha

The South African democratically-elected government instituted policies and legislation that are intended to bring about change and transformation in the country and have drastically affected different industries, among others, the mining industry. The Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA) and the Broad-based Socio-economic Empowerment Charter (Mining Charter) were introduced in order to redress previous inequalities and to promote women's employment in the mining industry. This research evaluates the practical implementation of the MPRDA and the Mining Charter with specific reference to women in underground mining. A quantitative research paradigm was used. Data were collected through a process of a face-to-face interview surveys utilizing a structured questionnaire. The research setting was limited to the platinum-mining industry in the area of Rustenburg in the North West Province. The study population consisted of 195 available women working undergound at the mine. It is clear from the findings that mining companies are facing major challenges in their attempt to incorporate women in underground mining activities. Company policies regarding these issues must be firmly in place; however, the challenge lies in the translation of these policies into practice. In this regard, managers will have to play a leading role in the successful phasing in of women into the underground mining arena.

Jan 1, 2012

By N. C. Gay

The quantitative evaluation of the performance of fill materials placed in gold mine stopes is achieved by (i) measurement of the in-situ load- displacement, or stress-strain, characteristics of the materials; (ii) an objective comparison between the observed fill performance and that predicted from suitable computer modelling techniques; and (iii) objectively comparing conditions in backfilled and conventional stopes. Considerable problems have been experienced with the development of sufficiently robust instrumentation which can be installed within filled pad- docks and give reliable information over a long period of time. However, at most mines where backfill performance is being monitored, it has been possible to correlate stress measurements within the filled paddocks with strain measurements adjacent to the paddocks. The resultant stress-strain curves agree relatively well with those determined in the laboratory. Measurements in the hangingwall strata of filled and unfilled stopes indicate that the placement of fill does reduce the amount of inelastic convergence due to bed separation. Moreover, in some stopes, the rate of convergence with respect to face advance does reduce to that of the theoretical elastic convergence. Quantification of changes in the conditions at the stope face due to placement of fill has proved difficult. Observations indicate that, provided the fill is placed close to the face (- 5 m), and adequate temporary face support is used, conditions in filled panels are superior. In addition, in filled panels the damage caused by a rockburst in the stope and, particularly, in gullies is generally much less than would be expected in an unfilled stope. To quantify these improvements, parameters such as stope height, face advance and the frequency of falls of ground are being monitored.

Jan 1, 1988

By M. F. Handley

This paper covers in situ stresses in the Earth?s crust prior to any man-made disturbances, such as mining. It introduces the Southern African Stress Database, which contains primitive stress measurements obtained from locations spread all over southern Africa. The measured stress data shows large variability without any visible trends, except a relationship with increasing depth. The stress database is reviewed briefly, establishing means to measure the variability or dispersion in the measurements, and showing that the dispersion is not as much a result of experimental error as it is a feature of primitive stress. The paper demonstrates from the beginning that the state of stress in rock is highly variable, but that there are well-defined maximum and minimum limits to all the stress components in rock. Formal error analysis is introduced to check the consistency of the database and to separate out a database of consistent stress measurements for use in a primitive stress model. The aim is to provide a picture of primitive crustal stress based on objective stress measurements together with interpretations of how the primitive stress can be affected by the five main influences; namely, depth, rock mass properties, tectonism, isostacy, and erosion. Four elementary models for primitive stress are introduced and compared with the measured data. It is quite clear that none of the elementary models is sufficient to describe the data. In the absence of a better model, this paper suggests a generic model based on the Hoek-Brown failure criterion and the consistent stress database, since it incorporates the variability in the stress tensor that is likely to be encountered underground all over southern Africa. Rock engineers should take every opportunity to obtain local primitive stress data at every mining operation and civil engineering project, and to adjust the proposed model accordingly Keywords primitive stress, Southern African Stress Database, error analysis, generic primitive stress model.

Jun 1, 2013