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By R. C. Urquhart, D. D. Howat, R. I. L. Guthrie

Heat losses from ladles during teeming by R. C. URQUHART, M.Eng. (McGiII), Ph.D. (Visitor). R. I. L. GUTHRIE, B.Sc. (Eng.) (London), A.R.S.M., Ph.D., D.I.C. (Visitor), and D. D. HOWAT, B.Sc. (Glas.), Ph.D. (Fellow) In an investigation of the loss of temperature by liquid steel during a teeming operation, a numerical technique was used to calculate the heat flows and the rate of temperature drop over the entire teeming operation. The calculations show that, before teeming, approximately 50 per cent of the heat loss is into the ladle wall at the level of the metal. As teeming progresses, the amount of heat lost by radiation to the wall above the metalline increases. The effect of variables, such as initial metal temperature, the preheat of the ladle and ladle cover, and delays, on the rate of temperature loss by the metal were determined.

Jan 11, 1973

The Grants register 1979-1981, edited by Roland Turner. London, MacMillan, 1980. (Available from Geonicla Publications, P.O. Box 31487, Braamfontein 2017 at R31,37; price to libraries R28,33.) Buyer's guide. Pretoria, South African Bureau of Standards, 1980. (Available free of charge from the Director General, SABS, Private Bag X191, Pretoria 0001.) SABS specification on gold alloys. World coal resources, by Bernardo F. Grossling. London, Financial Times, 1980. 160 pp. $D.S.155. Resources policy, a quarterly journal publish d in March, June, September, and December. Annua subscription: £40. Diamond jubilee 1980 The Associated Scientific and Technical Societies was established in 1920 primarily to 'promote the interests of Scientific, Professional and Technical Societies, the advancement of knowledge in Scientific and Technical subjects, and to uphold the professional status of such Societies,' and to 'represent corporately the views of Scientific, Professional and Technical Societies and the members thereof'. In this manner the strength of unity

Jan 1, 1980

By D. J. Bosman

The impoved densification of sludge from neutralized acid mine drainage. by D. J. BOSMAN, B.Sc., (Member) The paper describes an investigation aimed at finding a solution to the accumulation of acid mine drainage in the old workings at Coronation Collieries, Kromdraai. The problem involved the neutralization of the acid in the water, without the large volumes of sludge and the large amounts of dissolved solids that usually result from neutralization. Pilot-plant work on the site using a limeneutralization process developed at Bethlehem Steel Corporation (U.S.A.) showed this to be a feasible method. A sludge of 22 per cent density was obtained under optimum operating parameters. The amount of suspended solids in the overflow water was very high, but this does not give rise to concern because the full-scale plant at Kromdraai will practise secondary sedimentation by running the thickener overflow through large dams with a theoretical retention time of 25 days. An analysis of the theory underlying the process is also made.

Jan 4, 1974

By G. Gafner

The paper gives the reasons for the development of a gold alloy of 990 fineness with good colour, durability, and mechanical properties, and explains why titanium was chosen as the alloying metal. Methods are described for the alloy?s production, solutionizing, and age-hardening. Mechanical properties are given as a function of deformation, age-hardening time, and temperature for three different starting states, and these properties are compared with those of some standard 14 and 18 ct jewelery alloys and pure gold. The effects of various salts and fluxes on the composition of the alloy after heat treatment at 1150, 800, and 500°C are discussed. These indicate how alloy scrap can be refined to pure gold, and how solutionizing and agehardening can be conducted without the use of vacuum equipment. The results of wear tests indicate that the alloy is more durable than normal coinage and jewelery alloys. Tips are given on the grain refining, soldering, and casting of the alloy.

Jan 1, 1989

By D. Duncanson, R. J. Davidson, C. G. S. Schmidt, G. A. Brown, J. D. Taylor, N. W. Hanf

The development of a cyanidation route for the treatment of gold-plant gravity concentrates is described. This work was carried out as a natural consequence of earlier improvements to the recovery of gold in the gravity sections of existing gold plants. Concern about the environmental aspects of the conventional amalgamation process was further motivation in the development of an alternative procedure. It was found that the partial pressure of oxygen in solution was the most critical reactionrate determining factor. The rate of gold dissolution was shown to be controlled by the reaction rate below approximately 25°C and by diffusion above that temperature. Thus, the efficiency of pulp agitation and oxygen partial pressure permitted a high degree of control over the rate of gold dissolution. The use of oxygen rather than air significantly increased the dissolution rate of both gold and silver. The solubilities of sodium, calcium, and potassium aurocyanide complexes under simulated reaction conditions were studied, and it was established that the values for the sodium and calcium complexes were limited, requiring the use of lower pulp densities and higher reaction temperatures for the treatment of very high-grade concentrates. The presence of excessive amounts of tramp iron in such concentrates of up to 25 per cent by mass was found to result in poor gold dissolution owing to the cementation of gold under certain reaction conditions. The maintenance of high oxygen partial pressures, together with high cyanide concentrations, high pH levels, and the presence of calcium in the system, all aided in passivating the tramp iron. Copper, gold, and iron were shown to be the main cyanide-consuming elements. Optimum gold dissolution was obtained in a closed bench-scale reactor incorporating a flotation-machine type of agitator for effective pulp agitation and oxygenation, the oxygen being recirculated. The reactor was designed to operate under a very small positive pressure. After reaction times of 2 to 6 hours at temperatures in the region of 30°C, both the gold and the silver dissolution averaged 99,S per cent. In the case of very high-grade concentrates, it was shown that gold could be floated in the same reactor by drawing off the flotation concentrate through a port in the reactor. A flotation recovery of 87,4 per cent of the gold in 3,9 per cent by mass was obtained. The recovery of osmiridium from cyanide-leach residues and the electrowinning of gold from the pregnant liquors were also considered as processing aspects in the treatment of gold-plant belt concentrates. Final table tailings with a gold concentration of 10to 12 gft were obtained. The results of the investigation strongly suggested that an alternative cyanidation route for the treatment of gold-plant concentrates was technically feasible, provided the system included effective agitation and oxygenation. In the case of lower-grade concentrates, cyanidation followed by the electrowinning of gold appears to be the simplest route, while, for high-grade concentrates, flotation and smelting of the concentrate followed by cyanidation of the flotation tailings are suggested. The use of oxygen rather than air for sparging the pulp would depend largely on the grade of material to be treated. A preliminary comparison of the costs related to the amalgamation and cyanidation processes for the recovery of gold from such concentrates indicated very similar capital and operating costs. It was concluded that other considerations, e.g. toxicity, safety, and lower labour requirements, were more important than such small cost differences. Furthermore, the 'opening' of the gold-plant gravity circuit, which would be made possible by a cyanidation route, would further reduce the operating costs because of the subsequent decrease in the tonnage to be treated.

Jan 1, 1978

By R. M. Stroh, D. F. H. Grave

In this paper ventilation planning methods are discussed, with particular reference to the application of computer techniques to the solving of the many problems associated with the forecasting of ventilation and refrigeration requirements in mines of high production rates going to depths and rock temperatures higher than previously experienced. The use of the Starfield-Dickson programmes for calculating heat flow into airways and advancing stopes is demonstrated in the case of ventilation planning on a large mine extending to a brief depth of over 3 km below the surface. The possible effects of new mining methods on ventilation requirements in the future is briefly discussed.

By R. I. Klintworth

The multi-reef area of Cooke 3 Shaft provides a unique mining challenge on account of the very thin middlings between the pay bands and the marginal values of the reef. It is uneconomic or impractical, because of the excessive heights, to mine the middlings using conventional stoping methods. The development of suitable mining methods is discussed with particular emphasis on the control of water inflow and the policy of not jeopardizing or sterilizing other reef horizons by the mining method implemented. No definite solution is currently available, but with the aid of instrumentation, computer analyses and mechanized mining equipment, the mine continues to attempt to maximize extraction and profits.

Jan 1, 1988

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 A. Smith

After the introduction of mechanized bord-and-pillar development at Dumacol in 1958, pillars were being developed at a much faster rate than they could be extracted by hand loading methods. Efforts were therefore made to increase the rate of pillar extraction by mechanization. Following two partially successful mechanized stooping trials in 1964 and 1971, it was decided that mechanized pillar extraction with 1 m3 cable-reel front-end loaders should be introduced. The first section to employ the new equipment started production in May 1979, and the mine now has four mechanized pillarextraction sections in operation. Considerable improvements in production, productivity, safety, and percentage extraction have been achieved.

Jan 1, 1985

By deur R. Dippenaar

'n Kort kursus oar die teorie en praktyk van hittebehandeling is vanaf 29 Junie 1981 tot 3 Julie 1981 in die departement Materiaalkunde en Metallurgiese Ingenieurswese aan die Universiteit van Pretoria aangebied. Die kursus is dour dosente van die departement opgestel en in samewerking met 'n aantal gassprekers aDder beskerming van die Suid-Afrikaanse Instituut vir Mynbou en Metallurgie aangebied. Tunnelling The Third International Symposium on Tunnelling is to be held in Brighton from 7th to 11th June, 1982. Professional development seminars The Department of Mining and Metallurgical Engineering of McGill University is to hold the following seminars during 1981-1982.

Jan 1, 1981

SACPE has asked the Journal to bring the following points to the notice of members who are about register with SACPE. When to Apply There is no set time to apply for registration. Engineers should apply when they believe that their training has met all the requirements of Policy Statement No. 1/3. Pitfalls Remember that it is the applicants' training that must be evaluated, and this requires the avoidance in the application of vague generalities such as 'My duties were design plant including its economic evaluation' or 'I was engaged in . . Requirements An example of what is required can perhaps best illustrate the point.

Jan 1, 1982

By More-O&apos, R. C. Ferrall, J. W. Wilson

Discussion: M. D. G. Salamon* (Fellow): The theoretical principles behind the techniques of calculation used by the authors was formulated and published during the period 1962- 65. These principles, together with their practical implications, were summarized in a review paper in 1966.1 Now, in February, 1970, we have this long and comprehensive paper discussing the practical application of the theory. I think this is good progress. The large number of practical examples treated in the paper clearly demonstrates not only the skill and knowledge of the authors, but also the versatility of the techniques of analysis. I feel that the techniques described by the authors, and their improved versions, will revolutionize mine planning. I suggest that no shaft system or stoping layout should be planned in future without an adequate rock mechanics analysis. It seems that it will be progressively more difficult to white wash mistakes in rock mechanics and attribute their costly outcome to normal mining risk. We should not, however, become complacent. There is still a lot to learn and do in the future. I do not want to discuss tonight the question of further research but instead, I will raise two other problems which may hinder the future progress of practical rock mechanics. To carry out work similar to that described in the paper, mine managements require men who are capable of doing the work and who have the most efficient techniques of analysis at their disposal. As a research engineer I have been associated with the development of techniques of analysis. I can assure you that these have undergone an amazingly rapid development during the last six years. We have seen the change from the use of the electrolytic tank analogue and manual integration to the method described by the authors, that is, to the employment of the automatic network analogue and computer integration. But this is not the end. In a recent paper Prof R. P. Plewman2 and his co-authors described a completely digital technique. Here the process of calculating on- and off-reef quantities is integrated into one computer run. But these sophisticated methods of computation are useless without men to make intelligent use of them. During the last few years a new breed of mining engineers has appeared on the scene - the Rock Mechanics Engineer. I feel it is timely to call the attention of the senior members of this Institute to the fact that this new breed will succeed in carrying out its duties in a valuable manner only if we manage to attract to its ranks young engineers of the right quality. The requirements are high. The top rock mechanics engineers have to be good mine planners and they have to understand the essence of sophisticated theories. Without these attributes they will not succeed in the long term and the industry will not gain the benefit of available knowledge. To attract this quality of engineers the industry will have to ensure that rock mechanics is accepted by all concerned as a career which could lead to the top echelons of our profession. Finally, I would like to make one or two remarks concerning Part I of the paper. In Sections 3.1 and 3.2 the authors describe methods of determining the normal stress on the reef plane and the convergence distribution in the excavations. The description as given applies only to a horizontal reef. When the reef is inclined the situation is more complex since a shear component of stress on the intact reef and a ride component in the excavations must then also be determined. These can be calculated by methods similar to that described in the paper.3 The practical application of the method of calculating the released energy (Section 3.4) is in the comparison of various stoping layouts to establish an order of preference in terms of decreasing rates of energy release. To carry out these comparisons effectively, the calculations must be carried out in a manner by which the values of energy per unit area obtained are comparable. I would like to note in this respect that the method of calculation given in the paper is valid without reservation only if there is no elastic contact between the hanging and foot walls in the mined-out area. If there is contact then the calculated energy values are correct only if the mined out area is increased in small steps during the analysis. My second point in this regard is concerned with the practical method of calculation as described in Sections 3.4 (ii)-(iii). Firstly, I would like to suggest that the energy calculation should be carried out, as far as possible, by using always the same scale on the analogue. Secondly, the reading of current on a pin should be followed by the removal of that pin to obtain the corresponding reading of potential. The product of these two values will be proportional to the energy released during the mining of the small area corresponding to that pin. The method suggested by the authors tends to mask possible danger points in the layouts, since they obtain an average value for a time period, say, for six months.

By D. F. Malan, J. C. Esterhuyse

"Mining in the Carletonville area of the Witwatersrand Basin predates 1934. Owing to the depletion of higher grade ore, the current activities focus increasingly on the extraction of lower grade secondary reefs as well as remnant extraction. Of particular interest is multi-reef remnant extraction. Numerical modelling was conducted to investigate some rock engineering aspects of remnants being understoped on a secondary reef horizon. An analysis of the stress evolution in the middling between two reef horizons indicated that a zone of high major and low minor principal stress develops between the two reefs. This indicates a high risk of violent shear failure. Some pillars were nevertheless successfully understoped in the past and a study was conducted to better understand this phenomenon. An ’extended’ energy release rate concept introduced by Napier and Malan (2014) proved to be useful for investigating this problem. It was found that bedding planes and lithology appears to play a role in the stable dissipation of energy in multi-reef remnant geometries. The study indicated that the stope convergence and the various energy components are affected by the presence, position, and properties of a bedding plane. The energy solutions are complex and sometimes counterintuitive. Care should be exercised when modelling specific cases. The modelling was nevertheless valuable as it indicated that energy dissipated on weak layers may reduce the risk of violent failure in a multi-reef mining scenario. Additional work is required to investigate if crushing on the reef plane plays a prominent role when mining these remnants. IntroductionTo extend the lives of the Witwatersrand gold mines, work is being conducted to include a larger number of remnants and pillars in the reserve base of the mines. According to Jager and Ryder (1999), a remnant is an unmined block of ground surrounded by extensive mining. Remnants are typically left because of adverse or difficult mining conditions caused by geological structures, poor ground conditions, low grade, or rockburst damage (Durrheim, 1997). In contrast, pillars are typically the result of rock engineering designs to control energy release rates (ERR) and seismicity. During the early 1900s, remnants formed by the practice of scattered mining layouts had a significant effect on seismicity. Numerous task teams were appointed during this period. As the industry expanded, the severity of rockbursting increased and the research was formalized after the 1960s. Various recommendations were made and many of these are still used as best practice today (e.g. Jager and Ryder, 1999)."

Dec 1, 2018

By N. Hanief

This research involves the investigation of phase transformations in the platinum-chromium coated system. Single-layer 0.1 µm platinum coatings were deposited via electron beam deposition on 99.98 percent pure chromium substrates. Specimens were subjected to systematic heat treatment in a vacuum furnace at 900°C for up to 20 hours. Phase formation and the changes in surface morphology were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM).Both CrPt and Cr3Pt phases are formed during heat treatment for different times at 900°C. Significant changes in the morphology of this coated system were detected after heat treatment at 900°C for 20 hours.

Jan 1, 2012

By R. Kosmicki

Wet end components of centrifugal slurry pumps used in the hydraulic transport of solids are subject to substantial erosive wear. Accurate prediction of the casing wear rate and location for a particular duty is beneficial for correct pump selection and design, maintenance planning, and elimination of emergency shutdowns. CFD multiphase simulation using the Eulerian-Eulerian approach is being applied successfully to determine the velocity fields and solids concentration in the centrifugal pump, allowing for accurate predictions of casing wear patterns resulting from sliding abrasive wear. Simulation results for various single domain and multi-domain (multistage) multiphase simulations are discussed. Emphasis is placed on results from a 3-dimensional, multi-stage transient, multiphase simulation and comparison to field data.

Jan 1, 2007

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

"Chairman: Professor H. S. SICHEL Rapporteur: Miss M. I. WATSONPapers:Unrolling of Copperbelt orebodies by J. H. E. Perry and V. H. WiikAn exploration model for tabular orebodies by G. S. Koch and R. F. LinkHarmonic analysis of copper and gold occurrences in the Arbitibi area of the Canadian Shield by F. P. Agterberg and A. G. FabbriMathematical models of orebodies by M. J. Newton and A. G. Royle Estimation of lateritic-type orebodies by A. JournelIn his presentation Mr Wiik said that unrolling could be regarded as a reversal of the natural process of folding, so that the aim of an unrolling procedure would be the reconstruction of original pre-tectonic conditions. While simply formulated, this aim might not always be achieved. The geometrical relationship between points on the deformed surface and corresponding points on the original surface is process-dependent, and a true reconstruction could be achieved only if the deformation history were known in detail.In this computer unrolling procedure all these complexities were ignored. Referring to one particular marker horizon, Mr Wiik said that it was assumed in the procedure that this marker was deposited as a horizontal stratum and that it had subsequently been deformed by simple flexure-type folding.The procedure allowed the geologist to incorporate his knowledge and conception of the deposit through repeated re-contouring with dummy points. This 'manumatic' aspect of the procedure had proved invaluable, not only in resolving specific unrolling problems but also in making the system more acceptable to the geologists in general.Unrolling served towards removing what might be termed `tectonic noise' superimposed on the primary distribution patterns for regionalized variables such as metal content and orebody thickness. From this point of view, variograms derived on the basis of unrolled-plan co-ordinates should be more meaningful in terms of depositional environment than are variograms calculated from a normal map projection.Mr M. M. Oosterveld remarked that it appeared from the paper that there were problems in applying the unrolling technique to ore reserve calculation, and asked whether there were not other methods that might be used for that purpose.Mr Wiik replied that at present unrolling played only a minor role in practical ore reserve estimation within Roan Consolidated Mines, Limited. The techniques currently in use differed from one orebody to another, but in general they involved projection onto a vertical longitudinal section or a horizontal plan, with subsequent grid interpolation by means of a standard computer contouring package."

Jan 1, 2014

By C. P. S. Barnard, D. G. Krige

Objective justification on economic grounds for expenditure aimed at improving the quality of the underground working environment requires a suitable measure of any improvement in productivity that would result under routine working conditions. For this purpose, a composite production criterion is suggested, as well as its correlation under actual operating conditions with various factors directly affecting productivity and the environment. Of the environmental factors, wet-bulb temperature appears to be the major factor affecting productivity. The production data given indicate that a decrease in the wet-bulb temperature of 1OC can be expected to result, on average, in some 3 to 4 per cent increase in productivity; in the higher temperature ranges, this percentage could be much higher.

Jan 1, 1981

By M. H. Moys, J. Engelbrecht, N. Terblanche

Interface levels in flotation columns are generally measured with the aid of a pressure-sensitive Instrument, e.g. a differential-pressure cell. This paper criticizes the use of this type of measurement, and discusses other methods that are claimed to give more accurate measures of interface levels. The paper focuses on the development of methods based on the measurement of conductivity across the froth-slurry interface. These are often sabotaged by variations in the conductivity of the feed slurry, particularly when the pH of the slurry IS being controlled, e.g. In sulphide flotation. Methods of improving the accuracy and reliability of this technique are described. The result IS a robust, easy-to maintain level-control scheme that successfully rejects large disturbances in plant operation (including a 5:1 change in slurry conductivity) while controlling levels to an accuracy of I 4 cm.

Jan 1, 1992

By M. Loots, E. Van Der Lingen, S. Grobbelaar

The increased adoption of unmanned aerial vehicles (UAVs) may improve the productivity and costeffectiveness of remote sensing in the mining industry. This review’s objective is to enable stakeholders to identify possible application adoption, improvement, and innovation opportunities. The review merges a building block strategy and practical screening criteria to identify possible avenues of research to answer the review questions. After the screening process, 72 documents were included in the review. Papers were classified into four categories: exploration, development, exploitation, and reclamation. Fifteen applications were identified, the majority of which were in the exploration phase. The most often researched applications were topographic surveys, reclamation monitoring, and slope management. From the two UAV types identified, multi-rotor vehicles were the most favoured for all applications. From the eight remote sensing techniques identified, photogrammetry was the one most often used. Other techniques were limited because of complexity, cost, or the incompatibility of sensors and UAVs. The review was limited to published papers in academic journals. Future studies could aim to include empirical data on the latest UAV applications used in the mining industry.

Jul 2, 2022