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By D. F. Howarth, F. F. Roxborough

Some important aspects of the design of rock-cutting systems remain relatively unexplored. Two areas of practical significance in this context form the subject of this paper: cutting in jointed or fissured rock, and groove-deepening. A series of controlled laboratory experiments on the performance of disc cutters in jointed rock showed that the spatial and geometrical configuration of jointed rock masses needs to be taken into consideration in the design of mechanized rock excavating systems. One series of experiments showed that, under favourable geometric conditions, the energy required to cut in a jointed rock mass is at least half that required to cut otherwise intact rock. Groove-deepening-the progressive deepening of a groove by successive passes of a cutter-is a potential operational feature with most mechanized rock-excavating systems. Laboratory experiments revealed an important fundamental cycle of events associated with disc cutters when progressively deepening a groove in intact rock. Furthermore, in contrast to pick cutting, groove-deepening by discs is shown to be an efficient operation and one that should not necessarily be avoided. This can be directly attributed to increased interaction between the disc cutters as the result of an increase in magnitude of the lateral forces generated as a groove is deepened.

Jan 1, 1982

By S R Grano

A fundamental model, which considers the subprocesses of particle collection by bubbles in flotation, is applied to two comprehensive flotation surveys in the rougher stages of C3 concentrator, PT Freeport Indonesia. The flotation surveys focused on the collection of: ? cell-by-cell and size-by-size metallurgical, ? cell hydrodynamic, and ? pulp and surface chemistry information. The two surveys were conducted at significantly different feed tonnages, giving rise to significantly different feed particle size distributions, pulp densities and mean pulp residence times. A series of model simulations are performed with the aim of quantifying changes in copper recovery, on both a size-by-size and unsized basis, with changes in values of the hydrodynamic parameters and hydrophobicity of the copper sulfide mineral. This was carried out in an effort to identify the most promising route to increase overall copper recovery in roughing. It was found that by increasing the hydrophobicity of the copper sulfide mineral surfaces it became possible to optimise cell hydrodynamics, which targeted increased fine (-12 µm) copper sulfide mineral recovery but without adversely affecting coarse (+150 µm) copper sulfide mineral recovery.

Jan 1, 2007

By D. L. B. Pollnow

Tinplate, and electrolytic tinning at the Iscor works, Vanderbijlpark by D. L. B. POLLNOW, B.Sc. (Chem.), M.Sc. (Met.), D.Se. (France) The paper first describes tinplate as a product, dealing with its structure and its advantages to the packaging industry. It then describes Iscor's electrolytic tinning line, which is one of the largest Halogen units in the world. Details are given of the process and of the equipment used.

Jan 1, 1977

The 86th Annual General Meeting of the South African Institute of Mining and Metallurgy was held in Kelvin House, Johannesburg, on Wednesday, 17th August, 1983. Professor A. N. Brown (President) was in the chair, and declared the meeting open at 16h05. This account of the proceedings includes only those matters that are not reported under the heading `Annual report and accounts' elsewhere in this issue.

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 M. C. van Blerck

This paper reviews the current mining taxes in South Africa, discussing the recommendations of the Mantis Technical Committee, the measures already implemented, and the future outlook. It is concluded that the tax burden imposed on individuals and on the corporate sector should be reduced, and that the taxation of al economic sectors should be neutral. The reforms implemented in 1989 and 1990 are expected to continue, and it is thought that, if the State commits itself to tax neutrality and reduces the ordinary rate of company tax to 40 per cent, the rate of mining taxes will also be lower. Ring-fencing is expected to be reduced further and the rules for capital safe-havens to be refined.

Jan 1, 1990

Report M161 Improved recoveries of gold from auriferous calcines and pyrites by fine milling. Report M171 The development of a versatile computer programme for the evaluation of batch flotation results. Report M178 The reduction of chromite in a transferred-arc plasma furnace. Report M179 Optimization of an inductively coupled plasma by the simplex method. Report M182 A techno-economic evaluation of five routes for the comminution of gold ores in South Africa. Report M183 The determination of molybdenum and tungsten in resin by X-ray-fluorescence spectrometry. Report M184 The analysis of silicates, ores, slags, and other materials by X-ray-fluorescence spectrometry. Report M188 Determination of relative sensitivity factors for use in spark-source mass spectrometry.

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 H. M. Friede

A short survey is given of the Iron Age smelting sites and smelting furnaces that have been found in South Africa. An attempt is made to classify South African smelting furnaces by the inclusion of functional characteristics such as the numbers and positions of tuyeres. An affinity is suggested between the Venda (eastern Transvaal) type of furnace and an East African type. The principles of the smelting process in South African Iron Age furnaces and the characteristics of the smelting products are discussed. Results of metallographic and chemical analyses of 19 iron specimens found at South African sites are given and compared with those from sites in Zimbabwe-Rhodesia, Mocambique, and Nigeria. The carburization and steeling of iron during primitive smelting and forging are discussed.

Jan 1, 1979

By M. G. Adamson, B. D. H. Phillips

This paper describes a procedure that has been found successful in the planning and execution of practical trials of mechanized-mining equipment. The procedure is illustrated by reference to development trials of a rockslotting machine with pneumatic or hydraulic drills that were conducted on South African gold mines.

Jan 1, 1978

By P. J. Kinver

The paper presents details of the costs and outputs being achieved by South African mechanized tunneling and stoping drillings. The information was gathered from various hard-rock mining and tunneling operations ranging from deep-level gold mines to shallow base-metal mines. The survey included older pneumatic rigs and the newer electro-hydraulic rigs, but excluded shaft drilling and the stope drillings that were developed recently for narrow reefs. The information presented is intended as a guide to those having to decide whether to use mechanized drillings and, if so, what type and quantity

Jan 1, 1990

By J. C. Mostert, P. N. Roberts

Electric smelting at Rustenburg Platinum Mines Limited of nickel - copper concentrates containing platinum-group metals By J. C. MOSTERT Pr. Eng.. B.Sc. (Stellenboseh). M.Sc. Met. Eng. (Fellow) and P. N. ROBERTS Pr. Eng.. B.Sc. Eng. (Rand) (Fellow) The processes involved in the smelting in an electric furnace of nickel-copper concentrates containing platinumgroup metals are described. These are concentrate drying, pelletizing, pellet drying, and flux and pellets proportioning, followed by smelting of the concentrate in a submersible-electrode electric furnace, which is discussed in more detail. The furnace matte is blown in a converter to the white-metal stage and is cast in moulds, whilst the slag is granulated, ground, and floated for recovery of valuable metals and afterwards pumped to the tailing dam.

By N. C. Joughin

Potential for the mechanization of stoping in gold mines by N. C. JOUGHIN B.Sc. Eng., Ph.D. (Rand) (Member) The basic requirements for stoping machines are identified first by examination of the mining rates and productivities attained in conventional stoping, and then by examination of a series of problem areas associated with the shape of the reefs, rockbreaking, rockhandling, and the support and design of the machines. Some of the more important machines being developed are described briefly, and their principal features are compared with the basic requirements identified in the first part of the paper. An estimate of the potential demand for the different types of machines is given.

Jan 1, 1976

By J. A. Drummond

The duties and efficiencies of a number of main and auxiliary fans were determined by standard and thermal methods. Some observations on the effect of water and dirt accumulation on fan performance were made.

By B. Rainier

This paper discusses the preparation of material for backfilling operations using hydrocyclones. Aspects dealt with include the advantages and disadvantages, material requirements, process constraints, operating systems and equipment of the backfill plant.

Jan 1, 1988

By J. N. Van der Merwe

It is shown that the safety factor as calculated traditionally by use of the tributary-area theory is not valid for high-extraction methods of coal mining. An alternative approach is suggested in which the pillar loads are calculated more realistically for the period during which pillar extraction is in progress. This safety factor, which is known as the Extraction Safety Factor (ESF), can be used in determining the effects of strong layers in the overburden on pillar sizes.

Jan 1, 1990

By A. A. Hazell

Mine management by objectives By A. A. HAZELL The author discusses the objective areas of mine management. Setting objectives is seen to be a conscious process which starts at the highest level of management. This enables clear objectives to be set at each lower management level. The methods of setting objectives in the areas of stope production, productivity and manager performance are set out in detail. In the area of manager performance emphasis must be placed on the practice of management. It is concluded from results obtained that "management by objectives" produces better than average perormances.

By D. G. Hulbert, D. Tudors, M. L. Coetzee, I. K. Craig

The paper describes how a multivariable control scheme was developed and implemented for the run-of-mine milling circuit at a gold mine belonging to Vaal Reefs Exploration & Mining Company Limited. The key variables that are controlled are slurry level in the sump, mass of material in the mil, and product size. The control scheme has resulted in reliable control of the dynamics of the plant, and has provided a good basis for the optimization of plant operation by the selection of suitable set Points.

Jan 1, 1990

By D. A. Viljoen

An account is given of the development of man's interest in the recovery and working of minerals from Palaeolithic times to the present. This is followed by a discussion of future production trends for the more important minerals, and of likely technological developments in the recovery of various minerals. The crucial importance of energy minerals is stressed, as are several other factors of significance to a flourishing minerals industry: manpower, education, financial climate, Industrial health and safety, and preservation of the environment.

Jan 1, 1979

By R. Hutchings

The paper reviews current understanding of the effect of ion implantation on the wear process, and the state-of-the-art of ion implantation as a commercially viable treatment to impart wear resistance. Ion implantation involves the firing of high-energy ions into the surface of a material, which modifies the surface properties and so causes a transition in the dominant wear mode. The process is best suited to specialized engineering applications involving critical dimensional tolerances or surface finishes, but has gained little industrial acceptance because of its poor reproducibility and the lack of a suitable method of inspection.

Jan 1, 1986