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By R. Guest

Reichert cone concentrators are used successfully in many applications, but have as yet not found favour in the gold mining industry on the Witwatersrand, because, for optimum operation, the cones need to have specially designed feed-preparation and circuit details. In addition, good liberation of the valuable minerals is essential. Gravity tests, in which a pilot plant was used on refractory gold ore, showed that 94 per cent of the gold could be extracted after gravity concentration and preferential grinding, roasting, and cyanidation of the concentrate, whereas 96 per cent could be extracted by flotation followed by the same preferential treatment. However, the capital and operating costs for gravity separation are expected to be considerably lower than those for flotation.

Jan 1, 1982

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 J. D. Austin, D. G. Kringe

Rates of return realized on investments in the gold mines of the newer goldfields outside the Witwatersrand were calculated and analysed over various time intervals and on various bases. It is shown that these rates of return are strongly correlated with changes in the gold price and cannot be equated with the returns that are expected when investments are made, and that the changes in gold price also affect the rates of return on the Johannesburg Stock Exchange as a whole. These correlations are used, together with a limited application of the Capital Asset Pricing Model, to suggest the expected levels of threshold returns in real terms for new mining projects, for projects on existing mines, and for share valuations.

Jan 1, 1980

Blasting in a gold mine has to satisfy the following set of techno economic conditions: good fragmentation, minimum stopped width, minimum number of rock falls, cost effectiveness. Results of a comparative study of the performance of a Low Density Anfo (LDA) and a conventional Anfo (ANFEX) are discussed. LDA appears to be more cost effective. The same borehole volume can be charged with material of reduced specific gravity. The velocity of detonation (VOD) is increased in the case of LDA resulting in more breakage as a result of shock energy than from the energy in the gas phase. This leads to less damage to the excavation and more favourable breakage of the excavated rock. As a result the overall economics of the mining operation is improved.

Jan 1, 1995

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 H. C. Voges

An account is given of the tests being conducted by Iscor on the following processes for the beneficiation of coal fines: froth flotation, gravity separation, heavy-medium separation, and pneumatic and column flotation. The coals used in the tests came from the Durnacol, Tshikondeni, Grootegeluk, and Hlobane collieries. The problems involved in the dewatering of fine products are stressed. From a theoretical study of the efficiencies that should be possible for a hypothetical South African coal, it is concluded that future fines-beneficiation plants in South Africa may use standard heavy-medium cyclones for coal down to 1 mm in size, fines heavy-medium separation for the 1 mm to 450 µm fraction, and column or pneumatic flotation for the minus 450 µm fines.

Jan 1, 1991

Two column flotation cells have been installed as single-stage rougher cleaners at Batu Hijau. The objective was to provide additional residence time in the cleaner circuit to maintain maximum recovery during high mill throughput and high feed grade periods. Installation of the columns has allowed the relatively coarse, well-liberated rougher concentrate and the relatively fine, low-grade scavenger concentrate to be treated separately, improving metallurgical performance in the cleaner circuit. Plant results show that the columns produce a high-grade concentrate at an average stage copper recovery of approximately 80 per cent. There is also indication of increases in both overall plant copper recovery and final concentrate copper grade. In addition, the operability and stability of the cleaner circuit has greatly improved.

Jan 1, 2007

By K. C. Mills

The objective of this work was to provide process engineers with values of the physical properties of various slag systems involved in high-temperature processes. Software that calculates the thermo-physical properties of slags from chemical composition is available on the www.pyrometallurgy.co.za website. This paper outlines the principles underlying the various models available in the program. The software calculates the following properties of crystalline, glassy, and liquid slags (where appropriate) as a function of temperature: heat capacity, enthalpy, density, viscosity, thermal conductivity, electrical conductivity, and surface tension. We hope, in the future, to update the program to (i) add new models as they become available, (ii) remove any ?bugs? discovered in existing programs, and (iii) provide guidance on the limitations of individual programs.

Jan 1, 2011

By I. C. R. Gilchrist

A principal requirement in the design of a backfill transportation pipeline is the accurate prediction of the values of key slurry flow parameters. Input variables, such as particle size and solids concentration, are usually determined by the load-bearing requirements of the placed fill. It is therefore necessary to identify the optimum conditions of transport for a particular combination of input variables. This paper critically reviews the methods available to predict the values of flow parameters in slurry pipeline systems in the light of experimental data generated at a test facility. Particular reference is made to rod milled waste and deslimed tailings transport systems and, in the case of the former, it is shown that both pumping and load-bearing requirements can be optimized.

Jan 1, 1988

By J. J. leR. Cilliers

ABSTRACT The recently introduced concept of negative taxation complicates estimation of the distributable profit of certain South African gold mines, and an assisted mine could operate at a working loss and yet produce an overall profit for distribution amongst its shareholders. A simple diagram is presented from which the approximate working profit or loss, taxation payable or tax credit received, and the distributable profit of an assisted mine can be estimated directly for any combination of the four main variable operational factors: tonnage milled, recovery grade, unit cost and capital expenditure. INTRODUCTION The effects on the working profits of South African Gold mines caused by changes in unit working costs, recovery grade, tonnage milled and capital expenditure are readily estimated. For normal tax- and lease-paying mines the distributable profit is related to the working profit and the latter is a commonly accepted comparative measure of the profitability of an operation. However, the recently introduced concept of State assistance in the form of negative taxation1, i.e. a tax credit, for mines with a life of less than eight years complicates such estimates. A requirement of State assistance is that an assisted mine must lower its normal pay limit by 16 to 20 per cent, and it will be possible for a mine to operate at a working loss and yet produce an overall profit for distribution amongst its shareholders. In the case of an assisted mine it is therefore necessary for management to judge the effects of changes in unit costs, grade, etc., in terms of distributable profit instead of working profit. This will require repeated calculation of tax to be paid or tax credits that will be received under the numerous possible combinations of the four main variable factors. However, with the aid of the diagram illustrated in Fig. 1, it is possible to assess at a glance the practical effect of these variables on the distributable profit of an operation not subject to tax on the normal formula, or small mine formula, with sufficient accuracy to decide whether a detailed analysis is required. USE OF THE DIAGRAM From the central point 'X' in Fig. 1, a range of tonnages milled per annum has been plotted along the north-bearing axis, a series of costs per ton milled in the northwestern quadrant, recovery grades in the northeastern quadrant, and capital expenditures in the southwestern quadrant. Starting from the tonnage milled per annum, a line is drawn east and west across the two northern quadrants up to the points where it reaches the desired cost- and grade-lines. From these points two north-south lines are drawn into the southern quadrants. A further line is drawn to the east from the point where the western north-south line crosses the desired capital expenditure. Distributable profit is read off in the southeastern quadrant where this line intersects the eastern north-south line. Every possible combination of

By J. P. Gous, M. Tangstad, J. D. Steenkamp

In April of 2013 a 48 MVA submerged arc furnace producing silicomanganese was excavated in South Africa. One of the areas excavated systematically was the furnace taphole. The aim was to obtain a refractory wear profile of the tap-hole area, together with affected hearth and sidewall refractory. Subsequently, thermodynamic modelling was applied to quantify the potential for chemical reaction between refractory and slag and refractory and metal in the tap-hole area.

Jan 1, 2014

By N. du Preez, J. Christie, F. Crundwell

Precipitation is a key process in the recovery of copper and cobalt. While there is a wealth of experience in operating precipitation steps, improving their performance remains challenging. Chemically, the reaction might be controlled by reaction kinetics, be limited by oxygen mass transfer, or be at equilibrium. In this paper, we examine these different operating regimes and demonstrate how they can be identified from plant operating data, process modelling, and pilot plant test work

Jan 1, 2023

'Gee Whiz', a nationwide schools' science and technology competition, is being screened on SATY1 on Friday evenings at 18:00. Twenty-seven schools from al over South Africa are taking part in the series, which will run for 13 weeks. The participating schools were selected on the basis of their performance in the National Youth Science Olympiad and in Mintek's Minsa science competition, which has been organized on an annual basis since 1988.

Jan 1, 1991

By R. T. Muller

Contribution to the above paper by R. T. Muller (Visitor) Demands are being made and pressure is being brought to bear on employers in South Africa to narrow or eliminate the wage gap between their White and Black employees. Few thinking people will dispute the fact that a constant improvement in the wages of Black personnel is essential, but this cannot be done merely by a redistribution of income in South Africa.

Jan 7, 1974

By S. Neilson, M. G. Demmer, K. McCarogher

The Phoenix Programme takes the Mining and Mineral Processing Industry into the Science Classroom In the early years of mining, methods were crude, simple, labour-intensive, and very slow. Human resourcefulness, however, created innovations (mechanization, and computerization), that resulted in faster development, greater tonnages of ore, more efficient separation, and a superior final product. This expansion occured an ever-increasing rate, and resulted in a booming mining industry and a growing economy.

Jan 1, 1989

By L. Wade

The advent of relatively cheap computing power has precipitated a rapid growth of computer usage in the mining industry. In order to obtain most benefit from this development a need is recognised for the future mining graduate to be trained in computer literacy. This paper outlines the type of training required and describes progress to date with such a programme at the University of the Witwatersrand. Certain challenges concerning the teaching effort are discussed.

Jan 1, 1987

By G-L. Wu, X-B. Liu, C-Y. Zhou

"The static recrystallization behaviour of Ti-Nb microalloyed high-strength steel during hot deformation was studied by conducting double-hit hot compression experiments using a Gleeble-3500 thermomechanical simulator. The effects of deformation temperature, strain rate, strain, and initial austenite grain size on the static recrystallization fraction are discussed. The static recrystallization kinetics were modelled, and the results show that the static recrystallization fraction increased with deformation temperature, strain rate, and strain and interpass time. The static recrystallization activation energy Qs was 326.05 kJ mol-1. Comparison of the experimental results and predicted results indicates that the effects of deformation parameters on the static recrystallization in multistage hot deformation are significant. The predicted results are in good agreement with the experimental results. IntroductionIn hot-forming processes, complex microstructures are often induced by multiple hot deformation mechanisms (Zhang et al., 2014; Liang et al., 2015). The softening behaviour during hot processing has generated considerable interest because component properties are influenced significantly by the corresponding microstructural evolution (Wu et al., 2010). It is well known that dynamic recrystallization (DRX); metadynamic recrystallization (MDRX), which occurs by the growth of DRX nuclei during intervals of deformation; and static recrystallization (SRX), which occurs by nucleation and growth during the intervals of deformation, can significantly alter the austenite grain size (Chen et al., 2015. Chen, Sui, and Cui, 2014; Mao et al., 2014). The long interpass times allow complete SRX to take place if the steel is being rolled above the interpass recrystallization stop temperature (Tnr), i.e. in the absence of carbonitride precipitation (Siciliano, 2000). In recent research, microalloying technology coupled with new-generation thermomechanical control processing (NG-TMCP) has proved efficient in achieving the proper balance between strength, toughness, ductility, and formability by means of a suitable combination of chemical composition and thermomechanical treatment parameters (Shukla et al., 2012; Bandyopadhyay et al., 2011). The alloying elements Nb, V, Ti are widely used in high-strength low-alloy (HSLA) steel to achieve the desired strength and toughness properties with solid-solution strengthening, precipitation hardening, grain refinement, and dislocation strengthening (Opiela, 2014; Chen and Yu, 2012). The wide applicability of alloying elements in HSLA steel is due to the fact that heat treatments are not required after forming of the parts, which results in time and cost savings."

Jan 1, 2017

1. New books 1979 Louisville Coal Conference proceedings. Epping (England), Bowker Publishing Co., 1980. 4 vols. $43.00. Proceedings of a joint meeting of the Institution of Mining and Metallurgy, the Society of Mining Engineers of AIME, and the Metallurgical Society of AIME, held in London, 27 to 30 May, 1980, by M. J. Jones (ed.). London, Institution of Mining and Metallurgy, 1981. 350 pp. £46. Economic mineral deposits, by M. L. Jensen and A. M. Bateman. 3rd ed. New York, John Wiley, 1981. 752 pp. $22.95. E & MJ intErnational directory of mining and mineral processing operations. Epping (England), Bowker Publishing Co., 1980. 1314 pp. $67.00. Physical methods in modern chemical analysis, by T. Kuwana (ed.). New York, Academic Press, 1980. Vol. 2. 432 pp. $38.25. English translations of DIN standards. Availablefrom the SABS, Private Bag 191, Pretoria 0001. Mining international year book. London, Financial Times, 1981. 730 pp. $90.00 airmail, £37.50 surface. Analytical atomic absorption spectroscopy. Selected methods, by J. V. van Loon. New York, Academic Press, 1980. 360 pp. $35.00. 2. NIM reports Report no. 1848 An electrochemical and kinetic investigation of the behaviour of gold in chloride solutions. I. The cathodic deposition of gold. (First issued 7th Jul., 1976.) Report no. 1844 An electrochemical and kinetic investigation of the behaviour of gold in chloride solutions. 11. The anodic dissolution of gold. (First issued 7th Jul., 1976.) Report no. 1846 An electrochemical and kinetic investigation of the behaviour of gold in chloride solutions. 111. The gold(II1)- gold(I) eaction on platinum and the disproportionation of gold(I). (First issued 7th Jul., 1976.) Report no. 1979 An electrochemical investigation of the behaviour of gold in chloride solutions. I V. Results obtained from Phase 2 of the investigation. (First issued 30th Jun., 1978.) Report no. 2093 The measurement of electrical variables in a submergedarc furnace. Steels for pipelines Since welding was first introduced as a method of joining pipelines, gas-pipeline engineers have taken the opportunity to increase gas pressures, and hence increase the efficiency and economy of transporting gases. Envitec '83 The International Trade Fair and Congress for Engineering in Environmental Protection - the ENVITEC '83 - will take place in Diisseldorf from 21st to 25th February, 1983.

Jan 1, 1981

One of the main bottlenecks in the carbon-in pulp process for the recovery qf gold is the elution procedure, which typically requires the heading of caustic cyanide eluants to high temperatures for 16 to 24 hours. The present work demonstrates that sodium sulphide solution as an alternative eluant can effect complete elution in about 4 hours at ambient temperatures. Elution efficiencies of around 100 per cent were obtained in 4 hours with a single pass of eluant containing 0,2 M Na2S and 0,4 NaOH about 10 bed-volumes of eluant The initial rate was slow over the first hour of elution, probably because the activated carbon catalysed the oxidation of sulphide to polysulphide. Elution efficiencies of around 100 per cent were also obtained in less than 4 hours during the batch elution of carbon at liquid-to-solid ratio of about 100. Lower liquid to solid ratio resulted in the re-adsorption of gold, probably owing to the oxidation of sulphide to polysulphide, with the resultant formation of gold complexes that were eluted less readily. Improved rates of elution were obtained at higher sulphide concentrations and pH values greater than about 13. Higher temperatures increased the initial elution rate, but lowered the overall extraction efficiency, probably because of the deposition of elemental gold on the carbon. Variation of the ionic strength by the addition of NaCl had no defect on the elution, which confirms that the elution mechanism in the case of sulphide is different from that when cyanide or I1)1droxide is used as the eluant. It is proposed that the elution of gold by sulphide solutions proceeds by means of an initial step that involves the reaction of polysulphide ions with the adsorbed aurocyanide speeds, forming AuCN on the carbon and thiocyanate in solution. This step is followed by the formation of poorly adsorbed complexes with sulphide ions, such as [AUS3-2]-The presence of polysulphides, whether generated in situ by the catalytic oxidation effect of activated carbon or by the addition of elemental sulphur, reduces the elution rate and efficiency dramatically. This is probably due to the formation of complexes such as AUS-3 and AUS-2 , which have a high adsorption affinity.

Jan 1, 1994

By P. Gauvillé

The key driver for choosing a circulating fluidized bed (CFB) boiler is the ability to burn a wide range of fuels with highly efficient combustion while meeting low emission requirements. Reduced sorbent and water consumption compared with pulverized coal (PC) plants and the ability to deal with corrosive fuel constituents while still meeting local regulations make a CFB boiler-based power plant particularly attractive. CFB-based power generation is particularly relevant in coal mining areas. During mining, a portion of the roof and floor material may be extracted along with the coal seam in order to create adequate working height for the equipment and miners. Therefore, run-of-mine coal which comes directly from the mine contains impurities. The raw coal can undergo a washing or screening process in order to improve its quality by reducing the ash content in the fuel in order to sell it on the export market or to comply with domestic customer requirements. The coal discarded from the washing process usually has a high ash content and difficult mechanical properties resulting from the initial properties, the mining, and the coal cleaning processes. It can contain a large volume of stones or can be very fine as a result of the washing treatment. To create value from burning this discarded coal, the boiler supplier has to meet several technical challenges in developing the appropriate design. This paper highlights the performance achieved with Alstom's CFB boilers developed for power generation over the last two decades to extract value from discarded coals. Emile Huchet Power Plant is the first 125 MWe CFB unit developed for burning coal slurries (called schlamms in France). The Emile Huchet discarded coal fuel is a very fine high-ash residue with an average particle diameter by mass (d50) of around 80 µm as received from the washing plant. The paper describes the performances and the basic design of the CFB boiler to manage such a fine fuel. The performances of two other CFBs of approximately 300 MWe output in operation in the USA and PR China are also mentioned to demonstrate the capability of this technology to burn either low-volatile bituminous or anthracite waste coals. The significant issues experienced during commissioning are reported, and the conceptual choices for burning such fuels are mentioned.

Jan 1, 2012