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By F. T. Cawood, T. Chikande, H. R. Phillips

Underground mines require electricity to operate both the main surface fans and auxiliary systems, with primary ventilation systems typically accounting for approximately 40–60% of the mine’s overall electricity consumption. The primary reason for this considerable expense is that most underground ventilation systems are designed for peak demand, regardless of the actual demand, which is commonly dictated by diesel equipment usage in trackless mining operations. Most platinum mines on the Great Dyke in Zimbabwe tend to operate their ventilation systems at this peak level, despite the mine’s air quantity being well in excess of the ‘true’ ventilation needs. This is due to a lack of appropriate ventilation controls. The authors designed and installed a ventilation-on-demand system at one of the bord and pillar platinum mines to minimize the use of redundant air in underground operations. Fourth industrial revolution techniques were applied to the environmental monitoring and tracking systems thereby optimizing air quantity demands. The mine managed to reduce its annual power consumption by 23% through the implementation of manual control and time-of-day scheduling levels of the ventilationon- demand concept. There was also a 6% productivity improvement, mainly attributable to an increased face time as a result of the significant reduction in the re-entry period following a blast. This paper introduces a novel concept of ventilation optimization through digital transformation targeting mainly room and pillar platinum mines. A system was designed, installed, and commissioned, though there is currently an ongoing optimization process to harness the full benefits such as productivity enhancement, reduced power costs, and improved worker health.

Dec 13, 2022

By G. E. Blight

Several aspects of the behaviour and properties of backfills consisting of cemented cyclone underflow tailings are illustrated by means of examples, and guidelines are given on the optimization of the performance of cemented fills. The stretch characteristics of the geofabric used to contain freshly placed backfill are described, as well as the relationship between these characteristics and the forces acting on retaining barricades. The properties required to achieve a self-supporting, stable free face in cemented backfill are explored, and a graphic relationship between stable height and shear strength is presented and compared with that for uncemented (classified) tailings. After a description of the characteristics of Witwatersrand quartzite gold-tailings backfill and commonly used cements, the process of drainage and air entry into backfill is outlined. Following this, the early-age gain in strength and the shear-strength characteristics, as well as the compressibility characteristics of cemented backfill, are described. Two phenomena that are potentially damaging to cemented backfill are seismic effects (or blasting acceleration) and the closure that takes place during the curing of cement. Investigations show that neither of these phenomena is actually significantly deleterious to gold-tailings backfill: liquefaction does not Occur as a result of seismicity, and hydration of cemented fill is not significantly impeded by closure.

Jan 1, 1996

By H. Brüggemann

The exploration of deposits generates geological data which are suitable for creating a preliminary tectonic and stratigraphic model. Linked with the topographical map and analysis data from exploration drillings, this information forms a numeric representation of the deposit. The following example demonstrates an expert system which connects chemical quality requirements and quarrying criteria, and develops a quarrying strategy based on the calculated model. Additional constraining factors like process technology, quarrying methods, landscape protection regulations, etc. are included. The goal is to guarantee a long-term, homogeneous material flow from the quarry at acceptable production costs - even in the case of an extraordinarily inhomogeneous deposit. In order to fulfil this requirement it is necessary to consider a large number of rules, criteria and instructions which can be structured as an expert system and programmed with LISP at a comparably low cost. The chosen strategy is not necessarily final, but can be changed any time by altering or varying the framework of conditions. The output consists of a block-working sequence which best satisfies the set requirements for appropriate points of quarry opening.

Jan 1, 1987

[Council for 1993/94 President Dr H. Scott-Russell President Elect J.A. Cruise Vice Presidents Senior D.A.J. Ross-Watt Junior P.D.K. Robinson Immediate Past President J.P. Hoffman Honorary Treasurer J.A. Cruise]

Jan 1, 1994

By K. B. Owusu, W. Skinner, R. K. Asamoah, J. Karageorgos, M. Zanin, C. Greet

High Pressure Grinding Rolls (HPGR) are mostly used prior to pelletising processes to increase the specific surface area (SSA) of iron ore concentrate. For expressing SSA, the Blaine index is utilised as one of the most important dimensional properties of iron ore pellet feed. ISO 21283 is a standard test method that explains the manual of Blaine air-permeability apparatus for determination of this parameter. In this standard, the disaggregation method is based on passing the minus of 1 mm samples from the 0.150 mm sieve. The disaggregation process has an effective role on the results of Blaine airpermeability test especially for regrinding HPGR products. In this research, firstly the Blaine index of samples was measured without disaggregation. Following this, disaggregation was done by passing the minus of 1 mm samples through three sieves with different dimensions, 0.150, 0.090 and 0.045 mm, separately, and the Blaine index was calculated for each one. Finally, lab-mill with rubber balls, called Jar mill, was investigated as another option. Screen analysis and image analysis with SEM were performed to evaluate the effects of the sample's disaggregation on the size distribution and agglomeration of samples. The results showed that the disaggregation method with sieve size 0.150 mm, according to ISO 21283, was not applicable for HPGR products because the particles were still stuck together. In addition, the disaggregation method with the sieve size 0.045 mm or with Jar mill offered reasonable results. Keywords: Disaggregation, Blaine index, specific surface area, regrinding HPGR, ISO 21283, Jar mill

Jan 1, 2020

By H. Mulder, M. C. Bekker

The objective of this paper is to describe the research followed in creating a generalized, readiness assessment tool for mining projects. We start by highlighting the need for the assessment tool and then progress towards explaining the methodology followed during the study. The selection and finalization of the list of elements, sections, and categories that make up the unweighted values are described, followed by a summary of the weighting process applied. The outcome of this process is a weighted readiness assessment tool for mining project studies. The main benefits of the tool are that it will guide decision-makers and project managers through the definition phases of the project and improve the likelihood of project success.

Jul 2, 2022

A decision by joint-venture partners Anglo American, Gencor, and the Industrial Development Corporation to proceed with the expansion of the Columbus Stainless Steel plant in Middelburg will contribute significantly towards the economic growth that South Africa needs so desperately. The expanded facility, expected to come on-line in 1995, will be the largest single-plant producer of stainless steel in the world, and the company will rank sixth overall in world production.

Jan 1, 1993

Cutting strong rock with a drag bit assisted by high-pressure water jets By M. HOOD. B.Sc. Hons. (Min. Eng.). B.Sc. (Mech. Eng.). A.M.I.M.M. (Visitor) Experiments are described that led to the discovery that coherent high-pressure water jets directed immediately ahead of drag bits while they are cutting strong rock reduce the magnitudes of the forces on the bits significantly. Tests were carried out to assess the effects of the pressure of the water jets on bit-cutting performance. The pressure was varied between 10 MPa and 50 MPa, the water flow rate being a constant 30 I/min. Over this pressure range, the force on the bit was reduced to the extent that the depth of cut of the bit was at least doubled with the point of impingement of the jets optimized. Forces on the bit were found to be particularly sensitive to the point of impingement of the water jets relative to the bit. The optimum configuration was found to be with two jets, one directed towards each corner of the bit and impinging on the rock approximately 2 mm ahead of the leading edge of the bit. Experiments in which a drag bit and high-pressure water jets were used to cut strong abrasive quartzite in the underground mining situation have demonstrated a potential increase of up to five times in the average depth of cut due to reduction of the forces on the bit. The results from the underground tests indicate that the life of the bit is improved significantly - by a factor of approximately two - when highpressure water jets are used.

Jan 11, 1976

By J. H. van Dalen, P. J. Brandt, F. W. Wessels

A maximum of ten process streams (Merrill barren solutions) can be monitored sequentially with this on-line analyser, and gold concentrations as Iow as 0,005 mg/I can be determined. The design is a further development of the Tell-tale analyser constructed by the Corner House Laboratories during the period 1965-69. The barren solution is preconcentrated automatically by solvent extraction, the solvent being a solution of I per cent Aliquat 336 in di-isobutyl ketone. An aqueous-to-solvent ratio of 40: I is maintained. The extracted gold in the organic phase is determined by flame atomic absorption, each analysis taking approximately II minutes. The long-term reproducibility of the absorbance readings over a 24-hour period of repetitive sampling of four simulated process streams varied from 6,9 to 4,1 per cent relative standard deviation for gold concentrations of 0,0 I to 0,05 mg/I.

Jan 1, 1980

By Franz E. Pawlek

Synopsis This is a summary of investigations in the field of pressure leaching carried out at the Institute for Extractive Metallurgy of the Technical University of Berlin-West during the last seven years. The efficient dispersion of gas in a liquid and its dissolutions as well as the events at the phase boundary when leaching ZnS are reported. At the end two examples are given for the use of pressure leaching in the processing of smelter by-products. INTRODUCTION About 20 years ago, experiments were independently started in Canada and in Berlin on the subject of dissolving sulfidic ores without preliminary treatment by means of leaching under increased oxygen pressure. In Canada ammoniacal solutions were mainly employed, and F. A. Forward and his co-workers were successful in applying this process on a large industrial scale1, 2. This process is used in Fort Saskatchewan to produce about 15,000 tons of Ni per year. In Berlin, investigations were started on leaching with acid solutions3, 4. This process had also been used on a large industrial scale in the D.S.A., but the choice of unfavourable working conditions led to great difficulties, and to giving up this process for industrial use. Later on in Berlin work was carried out especially on the kinetics of pressure leaching 5, 6, 7, 8, 9 and its applications to the processing of smelter by-products, in particular of mattes and speisses10, 11, 12, 13, 14. The dissolution of ores and by-products can be subdivided into four steps: 1. the efficient dispersion of the gas, so that its dissolution occurs over as great a surface area as possible, since only the dissolved oxygen reacts with the solid, 2. the suspension of the solid, so that the entire surface can take part in the reaction, 3. the phase boundary reaction, 4. the removal of the reaction products. The first two steps belong to the field of process engineering and will be discussed from this point of view. The aim of these experiments15 was to find out first of all the limits of efficiency of self-sucking stirrers in solutions of low viscosity with regard to the mass transfer. In addition, the effect of ultrasonics in the same reaction system was studied. The experiments were carried out in a lucite container as shown in Fig. 1. Four baffles of 0.1 d width were in the stirring vessel. The height of these baffles was adjustable. For every experiment one litre of liquid was used. An infinitely variable direct current motor, which was fixed with a hollow shaft, served as the driving power for the stirrer.

By P. Kind

Design criteria and recent developments in large-capacity Wemco flotation cells by P. KIND, Ph.D. (Clausthal), B.Sc. (Visitor) The scaling-up of the large flotation cells that have been developed during the past few years has been based on hydrodynamic considerations and has resulted in a 500 ft3 cell unit. Plant results on a porphyry copper ore show that the 500 ft3 unit is equivalent to the previously used 300 ft3 model.. . Plant tests on the use of 300 ft3 flotation cells for the recovery of phosphate, particularly from the coarse size fractions, are also described.

Jan 3, 1976

By S. Khoshjavan

In this investigation, the effects of different coal chemical properties were studied to estimate the coal Hardgrove Grindability Index (HGI) values index. An artificial neural network (ANN) method for 300 data-sets was used for evaluating the HGI values. Ten input parameters were used, and the outputs of the models were compared in order to select the best model for this study. A threelayer ANN was found to be optimum with architecture of five neurons in each of the first and second hidden layers, and one neuron in the output layer. The correlation coefficients (R2) for the training and test data were 0.962 and 0.82 respectively. Sensitivity analysis showed that volatile material, carbon, hydrogen, Btu, nitrogen, and fixed carbon (all on a dry basis) have the greatest effect on HGI, and moisture, oxygen (dry), ash (dry), and total sulphur (dry) the least effect. Keywords coal chemical properties, Hardgrove Grindability Index, artificial neural network, back-propagation neural network.

Jun 1, 2013

Fig. 4 and 5 of the paper 'The analysis of ventilation and cooling requirements for mines' by J. van der WaIt, E. M. de Kock, and L. K. Smith are positioned incorrectly in the February issue (J.B. Afr. Inst. Min. Metal., vol. 83, no. 2, Feb. 1983). Extractive metallurgy of zinc At a professional development seminar to be held in Montreal (Canada) from 18th to 22nd April, 1983, specialists from industry and university will discuss the extractive metallurgy of zinc from ore to finished metal with special emphasis on the theory and practice of modern technology.

Jan 1, 1983

By S. Botes, H. van der Merwe

While the refractory lining contains the process on a steady-state basis, the tap-hole must provide a channel for transport of molten materials at discreet intervals, with thermal cycling as routine. The tap-hole introduces a discontinuity in any lining, and this fact can lead to failure in the region around the tap-hole before general lining failure occurs. Hence there is a need for a rapid and reliable tap-hole repair technique that can be readily implemented in conjunction with all types of linings. The UCAR®V Repair supplied by GrafTech is a durable solution capable of repairing all types of lining designs and has been extensively utilized in the ferroalloy industry. More than 20 UCAR®V Repairs have been successfully performed in South Africa alone. This paper describes the system in general and reviews recent repairs and their unique challenges.

Jan 1, 2014

To B. K. Martus I discussed several points raised by Mr Martus in my reply to Professor Krige*. Mr Martus discusses several possible interpretations of optimum South African sales, but in my paper these sales refer to the sales level that maximized the working profit of the whole South African gold-mining industry over the past eleven years. Mr Martus also seems to be under the impression that the paper deals with the future. While there may be references to the future, and some implications for the future may be obvious, the paper deals essentially with the past eleven years.

Jan 1, 1984

By J. C. Paynter

A review of copper hydrometallurgy by J. C. PAYNTER, B.Sc. (Chem. Eng.) (Visitor) Copper hydrometallurgy is discussed with special reference to the treatment of chalcopyrite concentrates under South African conditions. The following processes are described and illustrated: Sherritt Gordon's ammonia pressure leachilng, the Arbiter Process, sulphuric acid pressure leaching, roasting processes, the Cymet Process, and the ferric chloride process developed at the National Institute for Metallursy. These processes are then compared with respect to the form of sulphur produced (elemental sulphur or sulphate), the character of the iron product and the handling of different types of ore.

Jan 11, 1973

By H. J. N. Winhoff

The tailings dam at Consolidated Murchison Limited by H. J. N. WINHOFF, Ing. Grad. (Visitor) The history of tailings dam operations at Consolidated Murchison Limited is briefly recounted, and a mechanical method of dam-wall construction is described and illustrated in some detail.

Jan 12, 1973

By S. Schutte, J. Pelders, F. Magweregwede, S. Ngobese, W. Botha

A people-centric, systematic approach that involves different stakeholders is considered necessary to successfully address changes associated with modernizing the South African mining industry. In this paper we discuss the inclusion of various South African mining industry stakeholders, particularly the employees, in equipment design and development processes. Data was acquired through a literature review and inputs from South African mining industry stakeholders through focus group discussions, interviews, and an online survey. It was suggested that some of the areas that could be improved by the inclusion of employees in the process are design quality, ergonomics, equipment acceptance by the workforce, safety, efficiency, skills, insight into context of use, and early design iterations and identification of problems. Among the issues considered to be barriers to inclusion were lack of buy-in, lack of resources, difficulty in manufacturers accessing the mines, difficulties in involving too many people, intellectual property concerns, and unavailability of mine employees due to their key responsibilities. Identified critical factors in the equipment design and development process include iterative design, stakeholder participation throughout the process, needs analysis through consultation, and change management. A guideline was developed for worker inclusion in equipment design and development that could be used by the South African mining industry. The study identified several economic and social benefits of including stakeholders in the early stages of design and development. It is recommended that the South African mining industry considers using the developed guideline.

Apr 5, 2023

By W. F. Lorch

Growing use of deionised water in surface coating techniques by w. F. LORCH Production engineers in the metal plating, paint, plastics-coating and printed circuit industries are increasingly aware of the cost of sub-standard or blemished items which have been poorly processed. An area where quality control can quickly produce higher efficiencies is in the choice of suitably purified water for making up solutions, for rinse baths and 'drag-out' baths, for cleansing lines and electrophoresis tasks, for maintaining electrolyte density and hence consistency, and for facilitating the recovery of valuable minerals. The author of this article examines the general problems of using nonpurified water, and shows how purified water has become accepted by the principal surface coating industries to improve processes and effect economies.

By D. van Rensburg

Jointed rock slopes are generally stable, as there is no freedom of movement for blocks of rock. In an open- pit mining environment, blasting opens up space into which blocks of rock can fail, resulting in the common occurrence of slope failure. Prior to the blasting of a trim pattern, the immediate highwall is scaled, where loose rock material is removed by means of a mechanical scaler. As mining of the pit progresses, the height of the scaled highwall from the pit floor progressively increases. These highwalls are never scaled again for the remainder of the pit life, and time-dependant deterioration contributes to these highwalls becoming subject to rockfall and, sometimes, slope failure. This paper documents the development of a South African innovation, a remote-controlled mechanical highwall scaler, a world first for the mining industry. The scaler will enable open-pit highwalls to be scaled from crest to toe whenever the need arises. It will reduce the risk associated with highwalls and deliver on the Anglo American promise of producing safe, profitable platinum.

Jan 1, 2012