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By D. Ackerman, S. Cole, G. Langefeld, I. Parker

The removal of gravel from the seabed using a hydraulic mining tool is a complex multi-phase problem that cannot be analysed using traditional continuum based simulation techniques. One potential approach is to simulate the behaviours of the solid phase via the discrete element method and the liquid phase via finite volume based computational fluid dynamics. The interaction between the phases is accounted for by Eulerian coupling. The feasibility of using the combined computational fluid dynamics-discrete element method to simulate gravel entrainment from an idealized seabed is evaluated. The simulation results are validated using experimental data. It is concluded that while the current approach appears feasible, further work needs to be done to improve the accuracy of the simulation and to evaluate the approach?s ability to model more complex behaviours.

Jan 1, 2007

By J van Rooyen, S. Archer, M. Fox

The use of dilute sulphur dioxide (SO2) gas mixtures for the oxidation/precipitation of manganese has been explored widely in recent years. The technical merit of the concept is well proven and implementation of the technology on commercial scale is imminent. This paper reviews the technology of manganese removal by means of dilute SO2 gas mixtures and highlights some of the challenges associated with its implementation on industrial scale. A brief review of the technology is presented; the review considers both the mechanism and chemistry of manganese oxidation/precipitation with dilute SO2 gas mixtures. The impact of variables such as temperature, pH and SO2 concentrations on the manganese removal process is assessed. Challenges associated with implementation of the technology on industrial scale are discussed. Gas dispersion is highlighted as a critical design consideration.

Jan 1, 2007

It is desirable to have a model, or method, for major project development, which will enable flexible modelling of separation circuits. This ability improves the understanding of circuits and how they should be operated, especially in a design phase, where various options are evaluated and decisions are made on the required number of stages and configuration. This paper describes existing gravity separation circuit modelling theory and concepts, as defined by Holland-Batt1 (separation window, separation efficiency and proportionality of efficiency). The crux of the paperis the application of numerical analysis to fit raw separation data by means of a modified Bézier-Spline. The paper proposes an alternative to the theory developed by Holland-Batt that provides more flexibility in the modelling of separation stages and curves, which include S-shaped curves. The paper proposes a solution to the challenge of continuously extrapolating data, and the first difficulty normally encountered, which is the fitting of an appropriate empirical formula to raw data.

Jan 1, 2007

By R. Hoare

TSG Consulting works with many of the major global mining companies using simulation modelling as an integral component in their development team's processes to determine which combination of infrastructure options, operating performance and operating rules best achieve project goals. All systems can be divided into a series of subprocesses. Conventional management and design practices focus on the optimisation of these system components. However, the interaction between subprocesses means that improvements made to the individual components do not necessarily translate into total system performance improvement. TSG Consulting advocates a `total integrated system approach' to understanding the behaviour and performance of complex interacting systems. In a constraint-based integrated set of processes, the instantaneous system capacity is limited by the subsystem component capacity that is the bottleneck at that point in time. Additionally, real world stochastic and dynamic influences tend to have knock-on effects across subsystem boundaries. This necessitates the requirement for simulation modelling to develop and validate solutions that are sufficiently robust to deliver sustainable outcomes. The key to maximising production is to understand the causes and effects the inherent variability has on component performance, subprocess performance and most importantly, the total integrated system performance. The correct use of simulation modelling techniques allows study teams to evaluate the relative merits of different capacity enhancement proposals. Put simply, when done well, simulation modelling provides a quantitative and rational process to enhance the knowledge and insight needed to make informed decisions.

Jan 1, 2007

By R. Venter

Uranium in the tetravalent state has very low solubility in acid and alkaline solutions and needs to be oxidized to the hexavalent state to become soluble. In acid leaching of uranium the uranium is oxidized by ferric iron, which in turn is reduced to ferrous iron. The reduced iron needs to be oxidized to the ferric form to allow the uranium dissolution reaction to proceed. This paper considers the known and proven oxidants used in acid leaching of uranium. These include manganese dioxide, sodium chlorate, hydrogen peroxide, ferric iron, oxygen and sulphur dioxide/air (oxygen). The reaction chemistry of each oxidant as well as the practical applications are considered and discussed. All the oxidants discussed work adequately in acid leaching of uranium and it is possible to engineer solutions for the use of the oxidants in acid leaching on plant scale. The availability and supply of the oxidant as well as the cost and environmental impact of the oxidant plays a major role in the selection of a suitable oxidant. The location of the plant will also have an impact on these issues.

Jan 1, 2009

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 F. van Heerden

The paper sketches the. management of the various phases in a cost-reimbursable, plus-fee contract. which is claimed to be the most flexible of all contracts. In this type of contract, the contractor is reimbursed for all the direct costs Incurred, plus a percentage fee to cover his profit (or overheads and profit). The client usually reserves the right to approve all drawings, equipment purchases. contract awards, technical specifications. project cheques and change orders.

Jan 1, 1982

By A. O. Filmer

A study of the dissolution of gold from a pyrite concentrate and from various calcines is reported. The percentage extraction of gold was found to decrease with increasing sulphur content in the material leached because of the porosity of the materials, and particularly because of the passivation of the anodic dissolution of gold when the gold was In contact with other conducting minerals. This is explained in terms of the current-potential curves for the oxidation of gold and the reduction of dissolved oxygen.

Jan 1, 1982

By C. G. Verkerk

The paper discusses the transport and rheological characteristics of high concentration slurries or pastes for backfill purposes. The influence of pipe size, particle size distribution, additives, coarse material and mass concentration on these characteristics is addressed.

Jan 1, 1988

By M. D. Prendergast

Research into the ferrous metallurgy of Rhodesian Iron Age societies M. D. PRENDERGAST (Visitor) Iron-working was a widespread economic activity in Iron Age Rhodesia, and merits historical and metallurgical investigation. However, the research done so far has been incidental and poorly disseminated. This paper reviews the available evidence and the ways in which it can be interpreted by archaeologists and historical metallurgists. Particular attention is paid to smelting techniques and current metallurgical research, and brief suggestions are made for future research. v074n06p254.pdf

Jan 1, 1974

By A. J. Jager, G. R. Adams

The pattern of mining-induced fractures ahead of stope faces in deep-level gold mines, as revealed by petroscopic observations, is described. It is shown that there are zones of fractured and unfractured rock ahead of the face, which are about I m wide and continue as discrete entities for at least 12 m parallel to the face and at least 5 m vertically. These zones do not form continuously as mining progresses, but develop from time to time, leaving a solid zone between the fractured zones. The maximum depth of fracturing ahead of the face depends on the rate of energy release.

Jan 1, 1980

By R. R. Mankowski

The work described here is an extension of current theory applied to obtaining the power dissipated at the wavefront of a transverse disturbance traveling along a mine hoisting cable. A previously derived empirical relation is adapted to the present problem, and is solved by use of a Lagrange-type reference frame moving with the wavefront. As a result of tie limitations inherent in the original relation, only a lower-bound for the domain of predicted power losses is defined. A qualitative assessment of conditions leading to the undesirable effects of internal frictional losses at the wavefronts are discussed in terms of the operating environment found on typical mining installations

Jan 1, 1990

By A. P. W. Briggs

Difficulties with the screening of large volumes of pulp to remove plus 600 /km material before the adsorption circuit and to retain plus 20-mesh carbon in the adsorption contactors have largely been solved, with the result that the plant can now handle its design throughput. The elution and electrowinning processes have been modified to simplify the circuit, but the regeneration of carbon remains unsatisfactory. The production of fine carbon in the plant can lead to increased gold losses, and this carbon must be collected and treated. Collection methods for fine carbon and some indications of the quantity of the carbon and its gold values are given.

Jan 1, 1983

By M. Timucin

High-temperature phase relations in the Pb-PbS system were established by the quenching of samples equilibrated in evacuated and sealed silica capsules. The liquid-miscibility gap seen in some previously published phase diagrams was not observed. The thermodynamic activities of PbS in liquid solutions of this system were derived at 1473 K from the isopiestic equilibration of samples belonging to this solution series with Cu2S-PbS melts of known PbS activities. The behaviour of Pb-PbS melts was found to be compatible with a subregular solution model. This model also made it possible to obtain an analytical liquidus for PbS that was in excelent agreement with the experimental determination.

Jan 1, 1988

The relationships between backfill-transportation parameters (solids concentration, velocity, and pipe diameter) and the wear rate of backfill-transportation pipelines is well understood. However, the degree of wear experienced by a pipeline depends not only on the transportation parameters, but also on the characteristics of the solids making up the backfill, i.e. the particle-size distribution, hardness, shape, and sharpness of the particles. Therefore, unless data corresponding to the specific wear rate of the solids are available, the determination of the wear rate for pipes transporting an uncharacterized backfill is largely guesswork. This paper describes an evaluation of particle characteristics with special reference to particle sharpness so that pipe wear rates can be correlated with solids of different size distributions and sharpnesses.

Jan 1, 1993

By L. H. W. Walker

As part of an overall design of a computer based mining managerial system, the geological and mineral estates management disciplines find themselves centrally placed in terms of producing fundamental data both before and during the mining operation. Computerisation of all aspects of these fields of endeavour has come to be seen as essential for complete integration with other mining orientated disciplines. Release 1 .l. of the Anglo American system of mineral estates management has been tested and is in the process of being implemented at several Anglo American Gold Division mines.

Jan 1, 1987

By K. M. Banks

Multiple-pass hot-strip-rolling schedules of carbon steels and niobium-microalloyed ferrite-pearlite steels were simulated on a Gleeble 1500 thermomechanical test apparatus. The effects of finishing temperature, coiling temperature, and chemical composition on the as-deformed ferrite grain size and hardness of the steels were determined. Low finishing temperatures and low coiling temperatures both contributed to ferrite grain refinement. Good agreement was found for the microstructure and hardness of the steels between the as-ruled condition and the results obtained from rolling simulations. The progress of recrystalization and precipitation was followed from examinations of the flow-stress curves during the hot-rolling simulations. The flow-stress behaviour during the finishing passes was consistent with the resulting changes in final ferrite grain size. It was found that the no-recrystalization temperature, TNR, is raised by increased additions of niobium.

Jan 1, 1993

By R. L. Paul

Although it is often said that South Africa does not have suitable deposits, or the potential to develop mines on a small scale, a recent survey by the Chamber of Mines1 showed that, out of a sample of 641 producers, 41 per cent had between 10 and 19 employees, and a further 29 per cent had between 20 and 29 employees. This goes to show that minerals-related small, medium, and micro-enterprises (SMMEs) do exist, and can play an important role in the development of rural industries in South Africa. Nchaka Moloi of the Department for Mineral and Energy Affairs defined the various categories of SMMEsas shown in Table I2. An enterprise could be placed in a certain category as long as two of the variables, employees, capex or production applied.

Jan 1, 1997

Past work on the ignition of methane-air mixtures by coal-cutting picks is reviewed, with special reference to the factors that contribute to ignitions and ways of reducing them. The main conclusions obtained from this review are outlined for the following aspects: mechanisms of ignition, methane concentrations, and the roles of rock types, cutting parameters, cutting tools, and water. However, many of these factors have been investigated on a qualitative, rather than on a quantitative, basis. A considerable amount of effort over a long period has been expended in this area of research. It is shown that a number of the factors influencing ignitions by machine picks have been researched adequately, but that there is still work to be done. Research is continuing in this area, being concentrated primarily upon the ignition potential of the coal-cutting pick.

Jan 1, 1985

By P. A. Laxen, P. J. van Staden

In situ leaching tests with thiourea as the lixiviant were caried out in two worked-out stopes at the No. 6 shaft at Rand Leases Gold Mining Company. Dissolution rates of 0,9 and 0,7 9 of gold per week per 100 m2 of footwal area were achieved. A major disadvantage of the method seems to be the slow rate of dissolution of the gold, which is probably caused by poor contact and slow mass transfer between the lixiviant and the gold surfaces. Under full-scale application, the loss of lixiviant by leakage could also be a very important factor. Furthermore, the oxidation products of thiourea may 'poison' the activated carbon that is used for the recovery of the gold. The method may therefore be economically viable only in stopes that contain high values of residual gold.

Jan 1, 1989