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

Extensive work was done previously on the wear of grinding media and on the comminution processes operative in bal milling based on the determination of the number-size and mass-size distributions of samples of balls taken from bal mils by a specially designed device. Proof that a sample is as nearly representative as possible of the whole mass of material from which it is drawn is usually extremely difficult. This paper reports a special case in which a direct comparison was made between the number-size and mass-size distributions obtained from a sample drawn from a mil and those from the whole bal charge emptied from the mil. Exposure of the internal defects of the grinding balls caused them to develop irregular shapes after wear had reduced their diameters by about 50 per cent. As a result of the marked change in the morphology of the grinding components, an anomaly was observed between the proportion of small components collected by the sampler and that determined in the total charge. Except for this anomaly, a marked similarity was found in the data relating to the larger components in the sample and the total charge, indicating that the sample obtained by the procedure outlined is representative of the mass of the grinding charge in a mill.

Jan 1, 1989

By R. G. B. Pickering, H. H. Haase

Few innovations in the South African gold mining industry could have a more significant impact on improving profitability than non-explosive methods of mining. The far-reaching benefits of this approach are explained and the progress made through development work funded by the industry is described. Three methods are considered: impact ripping, sloting with abrasive waterjets and diamond saws, and breaking from drilled holes with waterguns and electric pulses. Of these methods, impact ripping is the most advanced and requires only minor refinements before production applications can be initiated. Although this method, based on current performance, is expected to yield considerably increased profits, it is predicted that it could perform several times better than at present with further development. The other methods of rockbreaking also show potential. Waterguns and electric rockbreaking would be attractive in unfractured rock for difficult geological conditions, and for confined areas such as gullies and development ends. Methods based on sloting could be combined with any of the other methods to enhance their effectiveness and thus yield further improvements in profitability; also, they could be used to advantage in specific applications. Al the discussed methods, therefore, deserve to be developed further.

Jan 1, 1991

By P. R. Janisch

This paper reviews the sources, production, and technology of gold in South Africa. First of al it details the geographical distribution of gold-bearing materials, together with the mineralogy and distribution of gold within those materials. It goes on to the geological origins, and to the discovery and early exploitation, of the gold deposits. The laws relating to the mining and disposal of the metal are explained, after which an outline is given of gold exploration, processing, and refining. The economics of gold production are discussed briefly, and it is concluded that, although present expertise in the financial and technological aspects of a gold-mining venture have largely reduced the risks involved, one severe risk remains: that the rate of cost inflation will not be matched by the rate of escalation in the gold price.

Jan 1, 1986

The structural design of a pavement relates to the ability of the road to carry the imposed loads without the need for excessive maintenance or rehabilitation. Current techniques for the structural design of haulage roads are empirical and based primarily on the previous experience of personnel assigned to pavement design, both in terms of the strength of the structure and the quality of the wearing course material. This has the potential for unwarranted expenditure on too thick a structure or, conversely, premature deformation leading to the need for excessive expenditure on maintenance. Furthermore, the effect of larger haulage vehicles on the structural performance of a pavement cannot be predicted. Thus, there is a need to develop a portable and practical method of structural design. This paper presents an overview of structural design methods for mine haulage roads and, through an analysis and quantification of the structural performance of existing pavements, recommends the mechanistic design procedure, together with a revised structural design and associated limiting design criteria. It is concluded that the application of the mechanistic method to a design project can reduce the costs of haulage roads construction and accrue additional benefit in terms of reduced operating and maintenance costs.

Jan 1, 1996

Proceedings of the Ninth International Symposium on Techniques for Decision-Making in the Mineral Industry, Montreal, June 1970. The Ninth International Symposium on Techniques for Decision-Making in the Mineral Industry was sponsored by The Canadian Institute of Mining and Metallurgy, McGill University and Ecole Poly technique. The programme included 71 papers on various topics, as follows: Market Analysis and Logistics Planning; Quantification of Geological Variables; Blending; Capital Investment Decisions; Mining; Financial and Economic Analysis; Search for Mineral Deposits; Market Forecasting and Strategies; Operations Research in Process Modelling; Ore Reserve Estimation; Management Information Systems; Optimization and Control of Mineral Processes. In addition to general sessions, a special feature of the Symposium was Executives' Day, which was held to provide top and middle management with a broad understanding of the usefulness of decision-making techniques and their role in the mining organization. Panel Discussions and two keynote speakers provided a review, in non-technical terms, of the areas in which decision-making techniques have proven valuable. The present volume contains 65 papers submitted for publication, along with a complete account of the Executives' Day discussion. It is broadly divided according to the above subject headings. Approximately 550 pages, illustrated. Price: $15.00; $12.00 to students, plus 50 cents for handling costs. Order now from CIM headquarters: Canadian Institute of Mining and Metallurgy, 906-1117 Ste. Catherine St. W. Montreal 110, Quebec.

By M. U. Ozbay, D. R. Lougher

An in-situ experimental programme was carried out to improve the understanding of the rockmass and pillar behaviour in moderately deep hard-rock mines. The experiments were carried out at Impala Platinum mines and consisted of precise levelling measurements in the footwall of the reef, stress measurements in pillars, convergence measurements in the stope, and petroscope observations in pillars. The results were analyzed using a computer program in an attempt to quantify the characteristic behaviour of the rockmass as well as the pillars. The measured off-reef displacement data were found to co11fonn to the trends obtained from elastic modelling and the correlation could be improved by modelling the small pillars with reduced modulus to simulate yielding' of the pillars. The stress strain curve obtained from analyzing the in situ results, showed that a 6x 3 xl m pillar yields without significant load shedding at peak stress levels of approximately 208 MPa. The closure measurements confirmed that the mechanism of yielding is mainly that of pillars punching into the foundations. Slight to moderate sidewall fracturing and slabbing might be contributing to yielding, but to a much lesser degree than the former mechanism, as the petroscope observation revealed the existence of an intact region beyond 0,6m from the pillar sides.

Jan 1, 1995

1. USSR co-operation International Mining, the London-based publication, has received USSR Government approval to publish a Russian language edition for circulation in the Soviet Union. 2. Mintek publications Special Publication no. 11. World chromite resources and ferochromium production, by M.H. Silk. 1988. 160 pp. South Africa RlOO including postage; elsewhere US$lOO including postage. Application Report 4 The development and implementation of novel refining processes for the platinum-group metals (including the refining of anode slimes). 1988. 16 pp. Report M249D The acid activation of local clays including solid-liquid separation, by P.M. Cole and G.F. Lahoud. First issued Mar. 1986, reissued Apr. 1988. 46 pp. ReportM250D The production of refined feromanganese in a transfered- arc plasma furnace, by A.F .S. Schoukens and M.Ford. First issued Mar. 1986; reissued Apr. 1988.23 pp. ReportM257D Extraction of gold from eastern Transvaal concentrates by roasting and cyanidation, by J.J. Robinson. First issued Apr. 1986; reissued Apr. 1988. 55 pp. ReportM267D The recovery of gold from backfil by gravity separation, by R.N. Guest. First issued Jun. 1986; reissued Apr. 1988. 18 pp. ReportM285D Autogenous miling of kimberlite, by D.I. Hoyer. First issued act. 1986; reissued Apr. 1988. 11 pp

Jan 1, 1988

By M. W. John, I. D. Matthews

SYNOPSIS This paper describes the process adopted for the recovery of gold from a dump originating from clean-up operations at Durban Roodepoort Deep Gold Mine. The gold-bearing dump material was refractory in nature, not being amenable to cyanidation because of the high level of carbonaceous material present. The laboratory tests on the material involved particle-size and chemical analyses, a mineralogical examination of the material, preliminary tests, and optimization of the process for the treatment of the dump material. The preliminary tests included tests on roasting, flotation, pre-leaching, adsorbent-in-leach, and blinding. Of these options, carbon-in-leach showed the greatest potential. The rate of gold dissolution, the rate of gold adsorption by the carbonaceous material, and the ratio of carbon to pulp were then investigated. It was determined that the ratio of carbon to pulp necessary to yield a reasonable gold recovery resulted in a carbon loading that was not high enough for economic elution and regeneration. A process incorporating washing of the carbon with cold acid between adsorption cycles was tested, and reasonable gold recoveries and carbon loadings were obtained. Durban Roodepoort Deep Gold Mine piloted the conceptualized process and determined that it was economically feasible. Two Browns tanks on site were modified, and an acid-wash tank was installed. The capital outlay for the plant was recovered within some 3 months.

Jan 1, 1990

An International Ferro-alloys Congress, arranged by the Ferro Alloy Producers' Association of South Africa, the South African Institute of Mining and Metallurgy, and the National Institute for Metallurgy, will be held in Johannesburg, South Africa, in April 1974. The technical programme, occupying five days, will cover the following topics in relation to all ferro-alloys: 1. Burden preparation, blending, pelletization, handling, reducing agents. 2. Electric smelting furnaces-design, operation, management,- smelting optimization, shop practice, refractories. 3. Mineralogy, reduction behaviour, smelting reactions, slags. 4. Automation, Pollution control. 5. Applications, trends in comsumption, trends in composition specifications. There will be no parallel sessions. Papers in the above topics are invited; review papers will also be welcome. Proposed titles and abstracts in not more than 200 words should be submitted before the 30th of November, 1972, to The Chairman, Programme Committee, INFACON 74, Private Bag 7, AUCKLAND PARK, South Africa. The abstracts will be considered during January 1973, and papers accepted for the Congress must be submitted in final form before the 31st of July, 1973. The proceedings of the Congress will be published as a special volume. There will be a series of post-Congress tours to ferroalloy plants and other places of both technical and scenic interest. A full ladies' programme will be arranged. The First Circular, giving further details, can be obtained from: The Secretary of the Organizing Committee, INFACON 74, Private Bag 7, AUCKLAND PARK, South Africa.

By R. Tinsley

Project-finance risk assessment is mature and approached systematically. Mining industry due diligence remains fragmented with specialists addressing different aspects of the project such as reserves/JORC, environmental impact, commodity market, even financial analysis/ modelling. Each professional has a natural tendency to believe that the risk factors they have examined are the key ones necessary to be reviewed, as if their review will stand in isolation from others in the way a project materialises. By first laying out the project risk categories and risk matrices, this paper examines the due diligence process with a keen eye to the risk assessment and overlap/interaction. Some cross fertilisation of due diligence techniques from other industry sectors is placed into the mining context. Six case studies are then presented with regards to due diligence features in each project's feasibility review or financial information/ offering memorandum. A power case first shows the differences between the due diligence expectations of banks versus bond financings. Then some Australian and Indonesian mining development cases are analysed to see the due diligence learning points. Some of these were project/due diligence failures. The conclusion focuses on the value of a systematic risk assessment for project evaluation, all from the project-finance perspective.

Jan 1, 2007

By W. P. Channon, J. B. See

The reduction of fluxed and non-fluxed manganese, ores by ferromanganese silicide by W. P. CHANNON, B.Se. (Eng.), M.Sce. (Eng.) Wits. (Visitor) and J. B. SEE, B.Sce. Hons., Ph.D. (New South Wales), M.I.M., M.I.M.M. (Member) In South Africa, medium-carbonferromanganese is produced by the silicothermic reduction of slags containing MnO. Because of its importance in the production of refined ferromanganese, a study was made of the reaction between a premelted South African Mamatwan manganese ore and various ferromanganese silicide reducing alloys, with and without fluxing agents. Because the reaction is highly exothermic, temperature appeared to have little effect on the rates of manganese transfer to the metal and silicon transfer to the slag, and an apparent equilibrium was rapidly approached. Limits were determined for the favourable effects of fluxing additions, and manganese recoveries were found to decline as the ratio of CaO to MgO decreased as a result of the addition of basic flux. The recovery of manganese passed through a maximum, and subsequently decreased for variations in the ratio of alloy to ore. The results obtained, when used in conjunction with other physicochemical data related to this slag-metal system, suggest optimum slag compositions for the efficient manufacture of medium-carbon ferromanganese from Mamatwan ore.

Jan 3, 1977

By C. L. E. Swartz, I. J. Barker, J. H. Schubert

A dynamic simulator of the leaching and adsorption cascades of a gold plant was developed and used to compare the effect of various disturbances on the overall efficiency of the plant. These comparisons show which disturbances most critically need to be controlled to optimize plant performance. The simulator was based on an existing gold plant. Dynamic and steady-state data were collected on the plant and were used in the modeling of the process. Simple dual-rate models are used to describe the leaching and adsorption processes. Mole-balances of various species take into account the changes of concentrations in the leach, and also the movement of pulp and carbon up and down the adsorption cascade. Fluctuations in the flow rate, density, and cyanide concentration of the feed to the leach have a negative effect on the efficiency of the leach, while carbon attrition was found to be an important factor in decreasing the efficiency of the carbon-in-pulp (GIP) section. Badly regulated transfers contribute towards the decreased efficiency of the GIP section, but overflows and carbon leakage have only a limited long-term effect. Various carbon profiles and transfer schemes were studied, and the results indicated that a slightly heavier loading at the bottom of the cascade is beneficial, while the type of transfer is relatively unimportant.

Jan 1, 1993

By A. Chryss, L. Pullum

Shear-thickening suspensions abound throughout the hydraulic conveying industry; at least this is the perception of many engineers running plants where hydraulic conveying is commonplace. In reality, shear thickening behaviour is limited, in the main, to high concentrations of fine particles, including colloidal and biological suspensions, at moderate to high shear rates. In the authors? experience most cases of shear-thickening behaviour have been either simple ?coarse? particle interactions, poor instrumentation techniques, or both. In some cases these were obviously heterogeneous flows, while in others flows that were homogenous, or were thought to be homogenous. Examples, which illustrate this erroneous perception are given. However, the trend towards pastes and complex suspensions that use high concentration carrier fluids means that the underlying slurries for many of these flows may now be truly shear-thickening. Unfortunately, suspensions that might exhibit shear thickening also invariably exhibit slip, or wall-particle depletion. These separate phenomena are difficult to resolve experimentally and many observations of apparent shear-thickening behaviour are in fact obscured or convoluted by slip effects. A method is presented whereby the true flow properties of these high concentration suspensions, and hence accurate prediction of pipeline flows, can be made using a parallel plate rheometer.

Jan 1, 2007

By M. Bryson, V. Deeplaul

As a national facility, Mintek?s brief is to conduct high calibre research that allows the most effective utilization of South African resources. The research takes two different forms, with the efforts being directed at both high-risk endeavours that may lead to the development or adoption of new technologies or the reapplication of technologies to potential new operations. Starting in the 80s Mintek began developing a process to upgrade the UG2 ore and invested heavily in projects, equipment and people to service the industry. Some of the highlights of that work that has been conducted here include: ?Development of a milling and flotation process for UG2 ores ?Development of the ?Mintek Process? for maximizing PGM recovery for UG2 ores ?Conversion of the UG2 milling circuits to open circuit ?Development of a robust pilot plant facility for use in plant design studies ?Use of dense media as a waste rejection option ?Use of attritioners in flotation circuits. More recently, and with the future in mind, the following processes are being researched, some of which have already been commercially applied: ?Development of a flowsheet for Platreef ores ?Use of optical sorting technology for upgrading platinum ores ?Use of a mini-plant for reagent optimization studies. Each of the highlights listed above will be discussed in the paper.

Jan 1, 2004

It is suggested that an increase in the production from thin coal seams in South Africa is necessary, and that a substantial amount of any increase will be mined by the bord-and-pillar method. For the purpose of this study, a thin coal seam was regarded as any seam 1,5 m thick or less to the minimum thickness at which mechanized equipment can operate in bord-and-pillar workings. The equipment being utilized in thin-seam bord-and-pillar layouts includes conventional equipment, load-hauldump cars (scoops), and drum-type and Fairchild-Wilcox continuous miners. Comparisons are made of these types of equipment for bord-and-pillar mining at various seam thicknesses within the thin-seam range. The evaluations involved production rates and the cost of extraction for South African conditions, use being made of an existing computer modelling technique in the generation of production rates. The indications are that, for seam thicknesses greater than 0,9 m, drum-type continuous miners utilizing continuous haulage are the most productive and cost-effective equipment at present operating in thin-seam bord-and- pillar workings. Where seams thinner than 0,9 m are to be exploited, Fairchild-Wilcox continuous miners, particularly the Mark 22, produce the most coal at the lowest cost.

Jan 1, 1984

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 D. G. Krige

Using a very large number of chip-sample values from a mined-out area of the Hartebeestfontein mine and accepting these as equivalent to borehole values (also areas of 1 km by 1 km as equivalent to 'mines'), the authors apply a series of borehole-valuation procedures to these 'mines', Large undeveloped sections of existing mines are also regarded as the equivalent of such 'mines'. These procedures start with the orthodox arithmetic mean and then introduce additional information in the form of the Iog normal frequency distribution model for Sichel's 't' estimator. Knowledge of the average log-variance within mines leads to the tH estimator. The mean grade of the 'family' of mines to which a new mine belongs is then introduced via regression or elementary kriging. Next, further information on the macro spatial structure of the grade is used, together with the grades of adjacent existing mines in ordinary and simple macro-kriging procedures; finally, via the distribution model, the grade is seen as a function of the logs of the grades and their variances. These are introduced as spatial variables, and both are estimated by macro-Iog normal ordinary and simple kriging procedures with grades and variances from adjacent mines'. Comparisons are also made between macro-kriging on lognormal transformed values versus untransformed values. Conclusions are drawn on the relative importance of the various items of additional information used, on the procedures followed, and on the significance of the advantages gained

Jan 1, 1992

By C. Mueller

Automation of mining operations is pushed by cost pressure and cyclical product prices. However, until now the different types of equipment were not able to communicate electronically with each other or with central computer systems. Therefore, the International Rock Excavation Data Exchange Standard (IREDES) was launched by major players in the industry. The task of this initiative is to define a ‘common electronic language’ for easy and standardized data exchange. As in other industries, this standard is expected to have significant impact on the use of automation in general and on the markets for third party components and software. The standard’s technical architecture is open and flexible for future applications. It consists of an ‘horizontal’ structure defining ‘Application Profiles’ for different types of data sets. An additional ‘vertical’ structure (‘Equipment Profiles’) implements equipment dependent definitions for each of the applicable Application Profiles. First profiles will be available for Drill Rigs. The standard bases on the XML language thus enabling easy data exchange with commercial databases. IREDES data sets may use storage media as well as networking infrastructures for information exchange. The IREDES work is carried out by the initiative members working jointly together in the IREDES work groups. It is open for participation of all interested organizations. First prototyping applications are expected to start during 2001, the first products may be available in the following year. Key words: Mine Automation; Machine Automation; Data Exchange; Rock Excavation; Standard; Remote Control; Teleoperation; Ethernet; TCP/IP; Internet Technology; Service; Quality Assurance; Control Centre;

Sep 1, 2001

By S. Budavari

The effects of shaft pillars left in deep-level hard-rock mines during the extraction of tabular deposits were studied some time ago, resulting in the formulation of design principles and procedures, which have been used with success in the design of shaft pillars in the deep-level gold mines of South Africa. The method has not yet been utilized in the design of shaft pillars in shallow and moderately deep hard-rock mines. The purpose of the present study was to remedy the situation since a great number of deposits are worked at those depths. The object of this paper is to present governing equations for the components of stress and differential movement as derived by use of an elastic model. The pillar is taken to be circular in the plane of a horizontal deposit. On the basis of the numerical results obtained, a study was made of the distribution of the vertical strain and tilt along the axis of the shaft, and of the vertical stress along the shaft and across the pillar. In every case investigated, the most adverse geometry was taken into consideration. By use of an empirical criterion and the results of some in situ observations, the determination of pillar dimensions and differential displacement components for South African gold-mining conditions is demonstrated. Pillar dimensions for shallow and moderate depths are compared with those accepted for deep-level conditions.

Jan 1, 1986

By M. A. de Ruijter

Bracken Gold Mine ceased mining operations during February 1993. The clean-up of the gold plant, which had already commenced in September 1992, was completed in January 1994. The mine had been in production since early in 1962 but, because of a decreasing ore reserve, increasing working costs, and a relatively low gold price, closure had become inevitable. The closure had been under consideration since August 1983, when the first estimate was made regarding the amount of gold that could be recovered from the clean-up operations. Until that stage, it had been accepted that Bracken would conform to the commonly accepted idea that 0.25% of the total gold produced by the plant would be recovered during the clean-up operation. This idea was dispelled when the initial estimates indicated that the gold recovery would vary between 0.049 and 0.095%. The actual figure realized was 0.036%, showing that there is no generalforl1ula for the calculation of the amount of gold to be recovered from such clean-up operations. During the clean-up operation, Bracken became an unexpected contributor to the State's Reconstruction and Development Programme by having al the mine and plant buildings purchased and converted into a community development centre. This shortene4 the time available for the clean-up, and several of the buildings remained intact. However, the foundations and sub-soils had been sampled extensively, and it is considered that no recoverable gold was left behind.

Jan 1, 1996