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By I. V. Samarasekera, E. B. Hawbolt

A review of recent work being conducted at the university of British Columbia on the modeling of the microstructural evolution during the hot rolling of steel is presented. A mathematical model of heat transfer was developed to describe the thermal field in a slab during rough and finish rolling. The model for rough rolling, discussed in this review, also simulates the growth of oxide scale on the slab surface. To quantify the heat transferred from the slab to the work rolls, instrumented samples of MSI3O4 L stainless steel, 0,05 per cent carbon steel, and 0,05 per cent carbon steel with 0,025 per cent

Jan 1, 1995

By D. G. Krige

Recent publications have demonstrated the important role that can be played by a priori information of the grade levels, variability, and spatial patterns in adjacent or nearby areas in improving the quality of grade estimates for virgin or sparsely drilled areas. A research project was therefore conducted involving the collection and analysis of extensive sampling and borehole data from 7 reefs on some 30 Witwatersrand mines. This paper shows that the 'equivalent' log variance for the two-parameter lognormal model provides a good basis for the study and comparison of the levels and behaviour of relative variances. The trends of these against the corresponding log areas were found to form distinctive patterns, which are useful for these purposes. The patterns for the Basal, Vaal, Carbon Leader, and Main Reef Series form a reasonably close group, whereas those for the V.C.R.(particularly where the facies are mixed), B Reef, and Kimberley-Elsburg Reefs (particularly for narrow channel widths) do not always conform. The patterns shown by underground chip samples are also compared with those obtained from borehole cores. It is shown how this information can be used to improve the borehole valuation of new mines and of virgin areas in existing mines.

Jan 1, 1993

By J. W. Latilla, J. J. van Wijk

In late 1997 a request was received to assist with determining the powered support unit (shield) load capacities for the planned 2 seam short wall. This project had a number of aspects which made it attractive to utilize numerical modelling in conjunction with other more conventional design tools in the design of the shields. Amongst these were: The 2 seam panels were to be laid out about 25 m below the previously short walled 4 seam, the 4 seam had in turn been over-mined by the 5 seam long wall, the proposed face height of the 2 seam short wall was 5.5 m while the 4 seam had been mined at 4 m. The top seam in the area (5 seam) had been mined at between 1.5 and 2.2 m high, the face conditions with about 95 m of broken material applying dead weight loading to the 2 to 4 seam inter-burden septum were hard to predict and cyclical loading due to the presence of strong sandstone bands in the 2 to 4 seam inter-burden. The basic thrust of the study was to take the known, and successful, situation (4 seam short wall) and carry out comparative modelling to enable prediction of likely 2 seam conditions. Some two dimensional aspects studied were: 5 m goaf hanging up behind shields, stresses in beams to determine likely first goaf roof span, stresses in cantilever beams to asses cyclical loading due to sandstone bands in the interburden being loaded by the overlying goaf and stresses on chain and crush pillars adjacent to the goaf edge. Three dimensional aspects that were investigated included: Load distribution along face for close goafing and 5 m goaf hang-up and load in a 1 m wide rib modelled in the position of the powered support units. From the modelling it was possible to determine the optimal shield leg capacity of the new 2 seam equipment. These outputs were used when drawing up the technical specifications for manufacture of the new equipment. The face was successfully commissioned in August 2002. Fin 1997, requête fut faite pour aider à la détermination des capacités de charge pour l’unité de soutènement mécanisée (bouclier) pour la couche 2 courte taille en projet. Certains aspects de ce projet le rendaient intéressant pour utiliser la modélisation numérique en même temps que d’autres méthodes conventionnelles pour la conception des boucliers. Parmi ces aspects se trouvaient : Les panneaux de la couche 2 devaient être placés environ 25 m au dessous de la couche 4 courte taille ; la couche 4 avait été remplacée par la couche 5 longue taille ; la hauteur de taille proposée pour la couche 2 courte taille était 5.5 m, tandis que la couche 4 avait été exploitée à 4 m. La couche supérieure de la région (couche 5) avait été exploitée entre 1.5 et 2.2 m de hauteur ; il était difficile de prédire les conditions de taille, avec environ 95m de matériaux cassés ajoutant une charge morte à la plaque de séparation entre les couches 2 et 4 et un chargement cyclique causé par des bandes de grès dans l’entre-fardeau 2-4. L’idée principale de l’étude fut de prendre la situation connue et réussie (couche 4 courte taille) et de faire une modélisation comparative pour prédire les conditions probables de la couche 2. Certains des aspects à double dimension qui furent étudiés étaient : Un accrochage de remblai de 5m derrière les boucliers ; contraintes dans les poutres pour déterminer le premier intervalle probable entre remblai et toit ; contraintes dans les poutres en porte-à-faux pour évaluer le chargement cyclique causé par les bandes de grès dans l’entre-fardeau qui est accablé par le remblai et les contraintes sur les piliers par chaîne et d’écrasement adjacents au bord du remblai. Aspects à trois dimensions qui furent étudiés : Distribution de la charge le long de la taille pour les remblais proches et l’accrochage de remblai de 5 m et la charge dans une nervure de 1 m de large modelée dans la position des unités de soutènement mécanisées. La modélisation a permis de déterminer la capacité de portée optimale du bouclier du dispositif nouveau pour la couche 2. Ces résultats furent utilisés pour dresser les spécifications techniques pour la fabrication de l’équipement nouveau. La taille fut commissionnée avec succès en août

Jan 1, 2003

By R. D. Beck

The minerals industry needs the support of al sections of the population if it is going to be able to supply the new materials required for future development. It will achieve this support only if its image is good. Perceived images of the minerals industry are examined in respect of history, technology, environment, safety, education, and economics. Concern is expressed about the low technological image of the industry and the declining number of students enrolling in minerals-related disciplines. It is concluded that it is the professionals, through institutes like The South African Institute of Mining and Metallurgy, who must take the lead in improving the image of the minerals industry. The Presidential Address gives data to support this thesis; data that, is hoped, can be used in efforts to educate people about the minerals industry.

Jan 1, 1991

By R. Haldenwang, R. Erasmus, P. T. Slatter, R. P. Chhabra

Notches are used routinely for measuring the flow rate of water with free surface flows. As far as can be ascertained, no work has been done to investigate the performance of these flow rate measurement devices for non-Newtonian suspensions. The Flow Process Research Centre at the Cape Peninsula University of Technology has investigated the flow rate of kaolin and bentonite suspensions from a tank for two notch shapes, namely rectangular and triangular, and for 3 different concentrations of each suspension. The notches were calibrated using water and then the kaolin and bentonite suspensions were tested in them. The rheological characterisation of the fluids was done with a Paar Physica MC-1 rotary viscometer fitted with a cup and roughened bob. Analysis of the results shows a significant increase in discharge coefficient with increase in concentration, and the discharge coefficient has been correlated to the yield stress. This is the first such study, and further investigation is needed to confirm and extend these findings.

Jan 1, 2007

By R. du Preez

Tati Nickel is currently operating a hydrometallurgical demonstration plant in Botswana, using the Activox® process developed by LionOre Technology to produce nickel cathode and a cobalt salt from a sulphide concentrate. Cobalt is extracted using Cyanex 272. This reagent also extracts all the iron, aluminium, copper, zinc, and manganese from the nickel stream. Versatic 10 carboxylic acid is then used as extractant to recover nickel from the stream, separating it from calcium and magnesium, and upgrading it to provide a suitable advance electrolyte for nickel electrowinning. However, the selectivity of Versatic 10 for nickel over calcium is limited, and gypsum formation in the extraction circuit is a problem when attempts are made to maximize the recovery of nickel. Mintek has developed a synergistic system with Versatic 10 for improved separation of nickel from calcium and magnesium. Laboratory testwork was conducted on the raffinate of the cobalt solvent extraction circuit to optimize the Versatic 10/Nicksyn? (Mintek synergist) system to be employed. Extraction and stripping parameters suitable for this stream were optimized in the laboratory and then applied on the demonstration plant. A commercial batch (0.5 tons) of Nicksyn? reagent was produced for the demonstration plant. The laboratory testwork results and the demonstration plant performance are discussed in detail in this paper.

Jan 1, 2007

By L. C. Woollacott

A computer-aid is described that is designed to calculate steady-state material balances for ore-dressing circuits. The program determines the material balance from a specification of the process condition. No mathematical models or data adjustment techniques are employed. As such the program complements existing simulation and material balance 'smoothing' packages. The process condition is specified using performance indicators. These are significant parameters in the industry with which all practising mineral processors are very familiar. The program employs an equation-oriented technique for material balancing and so has had to deal with the difficulties peculiar to that approach.

Jan 1, 1987

There are presently no suitable underground mine production scheduling optimisation models available for application to sublevel stope mining. Scheduling underground production for maximum return is therefore still a manual process, which generally involves scheduling production from the next available highest cash flow stope within the operational constraints of the project. In most mining operations, the scheduling problem is too large and complex to guarantee truly optimal results through manual scheduling. This paper reviews some general optimisation studies that have been proposed for underground hard rock mining. Furthermore, an example of a mixed integer programming model is presented for a small conceptual sublevel stoping operation. Comparative results of a schedule generated by a mixed integer programming (MIP) production scheduling model and a manually generated model on a nine stope example is presented. Results indicate that the potential benefits of the MIP production scheduling model for the purpose of maximising NPV are significant. Finally, a new constraint was formulated to limit multiple exposures of fill masses for use in an existing MIP production scheduling model. Testing of the formulation took place on the central stope of the nine stope example, which showed that the formulation performed its task without breaking other operational constraints.

Jan 1, 2007

By A. A. Oakes, P. M. C. Wilson

This paper describes some aspects of the planning of a new colliery which commenced production in the Middleburg district in 1966. An account is given of some of the problems encountered in the early years of operation and of what was done to solve them. The conclusion is reached that design of plant and machinery should be flexible to permit multiplication of units.

By R. C. More O’Ferrall

The author mentions some of the problems he has encountered, together with their solutions. These include the stoping of isolated pillars, the reduction of the size of shaft pillars, the stoping of a new horizon above or below a horizon that has already been stoped out, and the mining of thick bands of reef left behind in the footwall or hanging wall.

Jan 1, 1981

By D. Limpitlaw, A. Alsum, D. Neale

"Ecological footprint analysis (EFA) was first described in 1996 as a measure of carrying capacity appropriated by human activities. EFA is a resource and emissions accounting tool designed to track the demand on the biosphere’s regenerative capacity. Ecological footprints are increasingly used as indicators of organizational and corporate environmental performance and product sustainability. There is a compelling argument to develop an EFA tool for mining companies.To determine the size of a mine’s ecological footprint, land requirements for all categories of consumption and waste discharge must be summed. This land is only made up of the ecologically productive land and water in various classes (cropland, pasture, forests etc.) required on an ongoing basis to provide all energy and material resources consumed and absorb wastes.A challenge in conducting an EFA for a mine is the shortage of accessible data. Undertaking an EFA for a corporation or individual site entails compiling consumption and emissions data (which can be used for other reporting applications). The footprint results themselves highlight the most critical aspects of an organization’s impact on the environment and provide a platform for focusing actions and for educating the workforce to improve their contribution to best-practice operations. This paper discusses the benefits and challenges of undertaking an EFA for a mining company, and provides examples of the various components of ecological footprints associated with mines, as well as showing how an EFA can be used to understand and communicate some of the impacts associated with mining activities.IntroductionFundamental biophysical and economic limits are now being experienced in many countries around the world. Herman Daly, a former World Bank economist, described this scenario as ‘uneconomic growth’, where the costs of growth exceed the benefits (Daly, 2005). This occurs when the economy’s expansion encroaches excessively on the surrounding ecosystem, sacrificing natural capital. Under such conditions the sacrificed natural capital is more valuable that the resulting economic growth. Consequently, the world faces largescale threats to sustainability and especially to the viability and continued existence of the ecosystems that support human settlements (El Zein et al., 2014). In recognition of this sustainability imperative, mining companies are increasingly concerned with their ecological footprint (EF)."

Jan 1, 2017

By F. T. Cawood

This article offers a personal and independent view on the threats to the sustainability of the South African minerals industry. It argues that if the six identified threats of insufficient spending on research and development, general standard of education, nationalization, inadequate infrastructure, Aids prevalence and labour inefficiency are not acted upon as a matter of urgency, the future of the mining industry, along with its important contribution to the economy, is at risk.

Jan 1, 2011

By R. S. J. Du Toit

SYNOPSIS This paper is based on a thesis dealing with the problem of basing the current rate at which money is collected from mine owners to pay compensation for pneumoconiosis in the future, on the current dust hazard on mines. The certification of pneumoconiotics and the incidence of pneumoconiosis are discussed against the background of existing legal provision for collecting funds for compensation. The various pneumoconiosis indices are considered. In the data analyzed, the only pneumoconiosis index common to a number of classes of mines is the time it takes to develop pneumoconiosis. Sets of dust indices and pneumoconiosis indices are computed. Expressions are derived for the time it takes to develop pneumoconiosis as a function of the dust hazard, and for the collection of funds as a function of the time available for collection. From these two expressions follows an expression for the rate of collecting funds as a function of the dust hazard.

By F. Riedel

In May 2009 a test work programme was carried out at the sorting laboratory of CommodasUltrasort in Germany which was aimed at establishing the efficiency of X- ray transmission sorting for the recovery of unliberated diamonds in a size range of +8mm. A PRO Tertiary XRT belt sorter with a working width of 600mm and a belt speed of -3mJs was used for the test work. Dual energy X-ray transmission sorting is a type of sensor-based sorting which uses an X-ray scanning system, The attenuation of the transmitting X-rays is measured at two different energy levels, Thereby it is possible to eliminate the effect of the particle thickness on the measurement result. The effective measurement results in a classification by elemental order based on the periodic table.

Jan 1, 2010

Book review Doyle, William S. Strip Mining of Coal; Environmental solutions. Park Ridge (New Jersey), 1976. 352 pp. $32. Surface mining of coal is still in its infancy in South Africa. The environmental repercussions following large-scale disturbance of the land surface, and the secondary effects of the disposal of waste products and effluents from mining, have not yet become apparent.

Jan 1, 1977

By R. C. Dunne, W. A. Gilbert, I. J. Corrans, K. S. Liddell

After bench-scale and pilot-plant tests in which it was shown that wet high-intensity magnetic separation (WHIMS) can achieve good recoveries of gold and uranium from Witwatersrand residues, a production size machine was installed at a gold mine. The mechanical and metallurgical performance of this machine have been satisfactory, and the economics of the process are attractive. WHIMS can be combined with other unit operations like flotation for the optimization of overall gold and uranium recoveries. This concept is shown to be relevant, not only to operations for the retreatment of tailings, but to processes for the treatment of coarser material. In the latter, there is a saving in energy consumption compared with the energy required for the fine grinding of the total feed, and a material suitable for underground backfill can be produced. Improved. more cost-effective WHIMS machines currently under development are also described.

Jan 1, 1983

This paper describes an interactive personal computer program, ENVIRON, which simulates cooling and ventilating systems on gold mines. An example of the practical application of the program is given and proposed future developments are discussed. The program consists of two main modules, HEATFLOW and VENT- FLOW. HEATFLOW calculates the heat loads and the effect of air coolers, while VENTFLOW estimates the air flow distribution. As the calculation of the heat loads requires a knowledge of the air flow and vice versa, the two modules are run iteratively until the solution converges. The program is written in Pascal and runs on any IBM-compatible personal computer.

Jan 1, 1987

By R. M. S. Falcon, L. M. Falcon

The prediction of the mechanical behaviour of South African coal on the basis of current proximate and other chemical parameters gives rise to problems, and the use of ultimate analyses and inferred maceral and rank analyses, although it has improved the situation to some extent, is still not satisfactory. In an attempt to reach a new level of understanding, this paper gives an in-depth review of the fundamental petrographic characteristics of coal and compares these parameters with the main types of mechanical performance. A two-tiered system of primary and secondary parameters is proposed for the prediction of coal behaviour. The primary or inherent parameters include rank and organic composition. The secondary or extraneous factors include such parameters as mineral mater, cracks or cleats, degree of oxidation, and size. In addition, an explanation is offered of several anomalous behavioural conditions in some South African coals.

Jan 1, 1987

If an orebody has been drilled to achieve some level of regulatory compliance, then a number of associated geological databases will exist, representing 10 000 to 100 000 m plus of core intervals. The databases usually contain data about assays, lithology, mineralisation and geophysical attributes. They will also include location information such as collar positions and downhole surveys. Obviously this data is collected by geologists for, predominantly, geologists and mining engineers. However, from a process design viewpoint process engineers usually ignore the geology where possible and rely on a small number of metallurgical test samples. Typically these test samples are sourced from convenient and available cores or from a small number of specially drilled metallurgical holes. One of the worst instances known to the author was the design of a SAG mill using only two SAG specific test results (one for each of the major ore types) while, geologically, the orebody was defined by more than 30 000 m of drilling. This paper sets out a philosophy to maximise the use of the geological data, both for process design and in preparation for the commissioning phase of projects. Geological data is used in the identification of preferred locations for metallurgical test samples, for checking the metallurgical validity of the geological ore-type definitions, where necessary developing new ore-type definitions (geometallurgical domains) and developing mathematical relationships for the estimation of important metallurgical factors across the geological database. If the estimation of factors (for example ore competence) is considered reliable enough then there is also the possibility of feeding calculated data back into the block modelling process to allow the generation of metallurgically relevant outputs in the mine plans.

Jan 1, 2007

By J. A. L. Napier

By use of a functional model of capital expenditure developed earlier, a prototype cash-flow model is formulated as a basis for the investigation of the economic consequences when the production rate of a mine is manipulated as fundamental design variable. The optimum production capacities that maximize the common economic criteria of net present value, present-value ratio, and wealth growth rate are determined. It is shown that these choices depend certain key groupings of the economic parameters, and that they have a fixed interrelationship. The basic cash-flow model is extended further to include the effects of a constrained rate of production buildup and the imposition of State taxation on generated income. An approximation to the initial tax-free period of a new mining venture is developed, and, by use of these results, the optimum choice of production level is analysed when both the buildup rate is constrained and tax is imposed. This extended model permits a comparison between the performance of existing mines and the predicted theoretical production levels for these mines.

Jan 1, 1981