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By M. A. von Below, I. C. Robinson

A mineral economic analysis of South Africa's mineral-beneficiation industry, comprising both economic theory and case studies, suggests that the domestic market has proved to be a more effective vehicle for promoting the establishment of advanced beneficiation projects than the availability of domestic raw materials. Although the domestic market plays an important role in the promotion of beneficiation by providing a secure outlet for sales, its most vital role is in the development of technological and marketing know-how that may give South African beneficiated products the competitive advantage required to penetrate export markets. The real wealth of a country lies primarily in the skills of its people rather than in its natural resources, and the domestic market plays a pivotal role in the development of these skills.

Jan 1, 1990

By Siemag Transplan GmbH

At the Hansa Mine in Dortmund, Germany, coarse run-of-mine coal, up to 60 mm in particle size, has been brought to the surface hydraulically from a depth of 850 m since November 1977. Hoisting is done by a three-chamber pipefeeder, by means of which up to 400 t/h can be lifted. The pipefeeder operates without problems, and has so far shown itself to be efficient and reliable. Vertical hoisting can be carried out by water supplied from the surface, from underground, or from a surface water supply in combination with minewater from underground. Water that flows into the mine, which would in any event have to be pumped to the surface, can be utilized for hoisting operations. The energy costs per ton of coal for a lifting height of 850 m vary between 41 and 62 South African cents, and therefore lie within the range of costs that apply to conventional hoisting.

Jan 1, 1980

By H. M. Wells

The influence of economics on the design of mine shaft systems by H, M. WEI.LS, Pr. Eng., M.Se. (Fellow) The purpose of this paper is to review some of the more important economic criteria that must be taken into account when planning the number, type, size, and distribution of the shafts, or shaft systems, required to exploit a block of payable ore. The postulated philosophy governing the selection of design parameters is that of optimization of the financial return per rand of venture capital employed for the project as a whole. While this criterion may not necessarily satisfy the investment objective under all circumstances (as, for instance, where risk limitation is important), it does serve to place the relative economic advantages and disadvantages of specific design features, which may sometimes be in opposition, into correct perspective with respect to the overall economics of the project under the prevailing economic climate at the time of the investigation.

By G. C. Howell, H. A. D. Kirsten

The mining-induced effects around narrow tabular stopes have traditionally been evaluated in terms of elastic continuum analyses. An understanding of the phenomenological behaviour of the rock surrounding deep-level gold mines has accordingly been developed on the basis of such analyses. However, elastic analyses do not afford reliable representations of the behaviour of rock in which failure may occur on discontinuities. This paper describes investigations that show how the stress and stiffness characteristics of a rockmass are affected under such circumstances for representative ranges of values for the relevant parameters (depth, span, support stiffness, field stress ratio, and discontinuity strength). These investigations afford a substantially different understanding of the mechanical behaviour of rock that is subject to failure. Instead of forming an arch across the abutments, the rock in the hangingwall bears directly across the stope onto the footwall and, instead of being subjected to tension, the nether hangingwall is clamped in compression in the horizontal direction.

Jan 1, 1993

By N. Birtek, R. P. King

The washability characteristics of fine South African coals were measured and were found to be well characterized by an M-curve having the equation Z = aQb exp(cQ) x dQ, where Z is the ash content per 100 units of total feed and 0 is the mass yield. Parameters a, b, c, and d were determined for 23 different samples of coal from important coal seams in the main South African coalfields in the size range 0,0025 to 1 mm. The relationship between ash content and relative density was determined and correlated by means of two linear relationships. This characteristic behaviour was explained in terms of the liberation of macerals and the different association between the mineral mater and the two major macerals vitrinite and inertinite. The results obtained in this study can be used to calculate the expected performance of an ideal separation process, and can also be used as input for the simulation of real beneficiation plants. An example is worked through in detail to illustrate the method of calculation.

Jan 1, 1990

This paper presents a quantitative approach to the problem of determining design capacity and field dimensions of underground coal mines using room- and-pillar mining systems. In evaluating these design variables, relationships among mining costs, number of production sections in mines, location of central shafts, mine field dimensions, section production, mine output, and cost of production losses due to underground man-traveling are analyzed. Thereby the unit cost of coal is expressed as a function of the design variables as well as input parameters such as seam angle, seam thickness, seam depth, underground traveling speed of men, mine recovery and plant recovery. The problem is then formulated as a nonlinear optimization model in terms of minimizing the unit cost of coal subject to a set of constraints and solved analytically for flat seams and numerically for inclined seams. Sensitivity analysis of the variables is also included in the paper.

Jan 1, 1987

By P. J. Lloyd

Society is fully justified in its concern about the environment, but that concern may, at present, be too uncritical It is, for instance, essential to establish that there is a valid environmental impact, and that there is truly a causal link between a human activity and an observed shift in environmental conditions. In establishing these, it inessential to recognize that scientific proof offers consistency, but that it can never provide completeness. Thus, no amount of scientific endeavour can ever prove that mitigation of the effects of human activity will be perfect. Society normally expresses its concern through legislation. The existing legislation in South Africa is reviewed, and it is found that [>legislation regarding water is probably too stringent to be effective, >legislation regarding air and land use is probably too lax, >all the environmental legislation is too fragmented to be efficient, and the Department of Environmental Affairs is hamstrung by inter-departmental rivalry. ] It is accordingly concluded that, if means are to be found for ensuring adequate mitigation of environmental impact in the face of ongoing economic development, it is necessary to establish a Judicial Commission on Environmental Affairs advised by, but given greater powers than, the departments currently active in environmental maters. This Commission should be charged with creating, perhaps over a decade, a body of legislation that would guide development while protecting the environment in its widest sense.

Jan 1, 1994

By B. N. Soutar

The design and operation of a double- V compartment vertical-flow settler by B. N. SOUTAR, B.Sc. (Mech. Eng.) Wits. (Visitor) This paper describes the development of a vertical-flow settler for underground pumping installations in the mines of Gold Fields of South Africa Ltd. The recommended settler employs the principle of 'dynamic filtration': the solids that are in suspension in mine water are filtered through a stable horizontal bed of flocculated particles, a technique that was established in about 1958.

Jan 3, 1977

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 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 A. R. Barnes, C. W. P. Finn

The prereduction and smelting characteristics of UG-2 ore were studied and compared with those of Winterveld chromite ore. The UG-2 ore proved more reducible, and substantial prereduction (over 70 per cent reduction after 30 minutes at 1250oC) was obtained. No difficulty was experienced in the production oh high-carbon ferrochromium alloy containing 48 to 50 per cent chromium. Calculations of the energy balance show that UG-2 chromite has lower total energy requirements (both on the basis of unit of ferrochromium produced and of total chromium content). More than 50 per cent of the energy required for reduction can be supplied outside the smelting furnace.

Jan 1, 1983

By G. J. McDougall, M. J. Nicol, O. L. Wellington, R. G. Copperthwaites, R. D. Hancock

X-ray photoelectron spectroscopy showed that the adsorption of gold cyanide on carbon in the presence or absence of electrolytes and acids proceeds by the same mechanism. Although the identity of the gold cyanide adsorbate is not known, the mechanism appears to have an initial adsorption stage that involves the adsorption of an ion pair: Mn+[Au(CN)-2]n where Mn+ is a metal ion (for example Na+, K+ and Ca2+) that has a lower solubility than the Au(CN)-2 anion in the adsorption medium, followed by a reduction step in which either a sub-stoichiometric Au(CN)x surface species or a cluster-type compound of gold is formed.

Jan 1, 1980

This report describes the investigational work on the development of a fire-assay method capable of concentrating, in a button of nickel sulphide, all six of the platinum-group metals present in samples of ores, concentrates, and mattes. In the method adopted, the sample is fused with a mixture of sodium carbonate, sodium tetraborate, nickel carbonate, and sulphur. The nickel sulphide formed during fusion collects the noble metals and carries them to the bottom of the crucible. The nickel sulphide button is dissolved, and the noble metals are isolated and determined. The coefficients of variation range between 1,0 and 4,9 per cent for the various platinum-group metals when they are present in concentrations between 0,3 and 75 p.p.m.

Oct 15, 1971

By I. H. Clark

In some mining situations, backfills are not only required to be free-standing but are also expected to provide hangingwall support. It may therefore be specified that the backfill withstand a certain calculated stress within a given time. Given the materials available, the choice of backfill composition is not always straightforward, and an approach to the evaluation of cemented tailings backfill is therefore proposed. The general use of such a method will greatly assist in both the scientific analysis of the material properties for industry-wide purposes of comparison and decision-making as regards the choice of fill.

Jan 1, 1988

By R. N. Guest

The Tromp distribution curve was used in an evaluation of gravity separators treating a synthetic ore made up of silica and marker minerals of various relative densities. The results pinpoint differences in the concentration of particles of different sizes, and indicate how the grade of a concentrate is likely to vary with particle size. An increase in the feed rate increased the efficiency of the 'waterless' spiral concentrator that was tested, but the multiport spiral concentrator tested was more efficient. Both spiral concentrators were found to be more efficient than the pinched sluice and the shaking table that were tested. The method was found to be a useful way of evaluating gravity concentrators, but, for ease of analysis, care must be taken in the choice of marker minerals.

Jan 1, 1985

By N. A. Barcza

Pointing out that South Africa needs to utilize its wealth-creating activities, together with local and international investment, to further develop its industries, the address asserts that the mining and minerals industries, especially in the manufacture of beneficiated products, offer the greatest potential for South Africa to achieve its goal. As many mineral-beneficiation processes are based on pyrometallurgical routes, the address goes on to describe some historical - pyrometallurgical operations and to indicate probable developments in the future. These include growth in the fields of both precious and base metals. After discussing environmental and recycling matters, together with manpower requirements, the address concludes that the major growth in the mining and minerals industries will occur in the manufacture of steel, stainless steel, ferro-alloys (particularly ferrochromium), aluminium, and titania slag.

Jan 1, 1996

By C. J. Fauconnier

The main purpose of the paper is to determine the contribution of fluctuations in barometric pressure to flammable gas explosions in South African mines. For this purpose, the barometric-pressure patterns preceding each of the 59 major explosions in South African gold and coal mines over the past 20 years were analysed. It is concluded that diurnal fluctuations in pressure do not have a major influence on the accumulation of gas in the underground workings, but that pressure drops associated with cyclonic weather systems moving across the country over a number of days are the major factor contributing to gas explosions in mines. To illustrate some of the points made in the paper, the Hlobane Colliery explosion of September 1983 is used as a case study. In the final section, several general conclusions are drawn and recommendations put forward as to how mines should recognize and react to meteorological phenomena that may lead to an increased probability of gas explosions in underground workings.

Jan 1, 1992

By A. Koursaris, J. B. See

The influence of Iscor coke and Delmas coal on the reduction of Mamatwan manganese ore to ferromanganese was examined by use of a variation of the 'stationary charge in controlled environment' (SCICE) technique. The charges of Mamatwan ore and the appropriate reducing agent were heated to temperatures between 1300 and I600 °C and either allowed to cool immediately the required temperature had been reached or held at that particular temperature for periods of up to ... hours. The heating rate was 350°C per hour, the particle size of the ore was between 2,83 and 12,7 mm, and the particle size of the reducing agent was between 2,83 and 6,35 mm. After being allowed to cool in air, the reacted charges were examined by optical microscopy, X-ray-diffraction analysis, scanning electron microscopy, and electron-microprobe analysis. No significant difference was found between the changes observed during the reduction of Mamatwan manganese ore by Iscor coke and by Delmas coal. A hypothesis is advanced to explain the mechanism of formation of the Fe-Mn-C alloy.

Jan 1, 1979

By H. L. Monro

The individual supplies of and demands for gold that make up the total supply/demand structure in any year, together with their individual price elasticities, are used to determine the effect of forward sales on the gold price.

Jan 1, 1992

By S. J. C. L. Peeters

Geographical information systems (GISs) provide sophisticated functionalities t1tat can be used by the personnel in many aspects of the mining industry to visualize, analyse, and manipulate spatial and tabular data. This paper presents an experimental case study for Hartebeestfontein Gold Mine. It shows how data from different computer systems can be brought together into a GIS by use of the Arc/Info and ArcView programs.

Jan 1, 1996