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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 M. Pierce, E. Karampinos

"One of the main challenges in the numerical modelling of ground support in underground excavations is to reproduce the performance of the sequential installation of the reinforcement while capturing the rock mass behaviour of an advancing face in 3D. The 3D modelling approaches used to simulate the progressive advance of excavations are mostly continuum and often cannot reproduce the rock mass failure mechanisms. The 3D discrete element method (DEM) can better reproduce structurally controlled rock mass failure mechanisms and can explicitly represent the reinforcement elements. This paper builds on previous work that reproduced the structurally controlled squeezing conditions in an underground hard-rock mine using 3D DEM and the in situ behaviour of reinforcement under pull conditions. It addresses important issues on the way reinforcement is explicitly introduced in discrete element models. A pseudo-3D model is employed to overcome the computational restrictions and time limitations of a 3D modelling approach. The work focuses on the scaling of the material properties of the ground support elements when the thickness of the model is not equal to the out-of-plane spacing of reinforcement. It demonstrates the scaling methodology based on the type of the modelled reinforcement elements used and investigates the significance of this approach. The advantages and disadvantages of this approach with respect to 2D and 3D methods are discussed. The results are compared with field data and previous modelling work done at the mine. IntroductionNumerical models can provide significant insight into the anticipated behaviour of underground excavations. The modelling of ground support, however, is not a trivial exercise. An effective representation of ground support in underground excavations should capture the behaviour of both the rock mass and the support elements. When numerical models are used for design purposes, the complexity of the problem requires significant time and expertise (Sweby, Dight, and Potvin, 2016).At a laboratory scale, numerical models have successfully reproduced the results of laboratory tests on rockbolts by explicit modelling of the bolt, the borehole, and the grout. Chen and Li (2015) used a continuum FLAC3D (Itasca Consulting Group Inc., 2012) model to simulate the mechanical behaviour of D-bolts as observed experimentally. Grasselli (2005) used a 3D finite element code to model the behaviour of fully grouted rods and expandable bolts under shear."

Dec 1, 2018

By E. Wroth, D. G. Krige

Written contribution E. Wroth* (Visitor): The technical aspects of the assistance scheme which IS provided for in the Gold Mines Assistance Act, 1968, and certain consequential amendments to the Income Tax Act, 1962, are explained by Dr Krige. The object of this contribution is to explain the working of the Gold Mines Assistance Act (hereafter referred to as the 'Assistance Act') for the benefit of those concerned with the tax and assistance assessments of gold mining companies. The views expressed do not necessarily reflect the Revenue Department's interpretation of the legal provisions involved. 1. MINES WHICH QUALIFY FOR ASSISTANCE 1.1 The assistance scheme is applied on a selective basis. Mines which qualify for assistance are defined in the Assistance Act as 'assisted gold mines'. The requirements for classification as an assisted gold mine are that: (i) the mine be a producing gold mine; (ii) it would be likely to close down within eight years if not assisted; and (iii) with State assistance its life would be appreciably prolonged and there would be a significant increase in production of gold or uranium, or of both gold and uranium. 1.2 A mine is only considered for classification as an assisted gold mine on application. Such applications must be made to the Mining Leases Board through the Government Mining Engineer. Classification of a mine as an assisted gold mine is at the discretion of the Minister of Mines who acts in consultation with the Minister of Finance and has regard to the recommendations of the Mining Leases Board. 1.3 The Minister of Mines will impose conditions subject to which a mine is to be classified as an assisted gold mine. The most important will be that the mine must immediately lower its operating pay limit, as normally calculated, by a percentage fixed by the Mining Leases Board and conduct its future mining operations in accordance with the average grade of its ore reserves determined on the basis of such lower pay limit. l.4 The Minister will fix the date as from which classification as an assisted gold mine is to be effective. So long as the mine has operated on the basis of the lowered pay limit for at least three months during the particular year of assessment, he would normally fix the effective date as the first day of the year of assessment.

Jan 5, 1968

COUNCIL The following served on Council during the year under review: Office bearers: Messrs V. C. Robinson (President), Prof D. D. Howat and Dr J. P. Hugo (Vice-Presidents), J. K. E. Douglas (Immediate Past President) and D. G. Maxwell (Honorary Treasurer). Ordinary Members of Council: Dr M. G. Atmore, Dr J. M. Bereza, H. P. Carlisle, W. W. Malan, C. E. Mavrocordatos, Prof R. P. Plewman, Dr R. E. Robinson, Dr M. D. G. Salamon, P. W. J. van Rensburg, L. W. P. van den Bosch, P. A. von Wielligh. Branch Chairmen: J. Meintjes, J. M. Meyer (Acting), J. N. Saunders (Retired). Past Presidents serving on Council: R. J. Adamson, M. Barcza, H. Britten, R. C. J. Goode, P. Lambooy, Prof J. de V. Lambrechts, Dr J. T. Mclntyre, J. F. Reid, H. Simon. Ten Council meetings were held during the year with an average attendance of eighteen and the standing committees held forty-six meetings. FINANCE The annual accounts, which are attached to this report, show an excess of income over expenditure of R5 051 compared with an excess of expenditure over income last year of R4 608. This major reversal of fortunes is due in the first instance, of course, to the increased subscriptions. There were, however, other important contributors, particularly sales of the Proceedings of the Symposium on Open Pit Mining and profits on the operation of symposia and colloquia. It would appear from a study of the accounts that there has been a substantial drop in expenditure on secretarial fees. In actual fact, however, our total expenditure on secretarial fees was higher. A portion of this expenditure was charged against the administration of the Symposium on Open Pit Mining and, in addition, the charge against the Journal accounts for secretarial fees was increased. It will be recalled that in last year's annual report it was mentioned that subsequent to the new arrangement for publication of the Journal, the expected improvement in the finances of the Journal had been slow in materialising. After a total period of 18 months there was still no sign of improvement and it was accordingly decided to end the arrangement. As a result, the drain on the finances of the Institute was considerably lessened in the second half of the year. During the course of the year Council became concerned about the rapid depletion of our accumulated funds and gave careful and detailed attention to all aspects of the Institute's financial affairs. Particular attention was given to: 1. The fact that the Institute does not have a solid financial backing and must appeal for funds every time any special event such as a symposium is held. 2. The responsibilities of the Institute to the profession and the community, with particular reference to the desirability of establishing Institute bursaries and participating in other educational activities. 3. The rapidly rising cost of living. 4. The immediate financial position of the Institute. 5. The rapidly increasing cost of publishing the Journal due to the increasing number of papers available. In the meantime the immediate financial position of the Institute has improved but as this is due largely to non-recurring or irregular items of revenue, it should not be given undue weight. After careful consideration it was decided that an appeal should be made to industry for financial assistance, which would be used to cover the cost of symposia and other unusual expenditure and also, if possible, to build up the capital resources of the Institute so that there is a solid foundation for the future. Before appealing to industry, Council wished to be quite certain that there could be no criticism of the Institute for not having done our best in a personal capacity. Furthermore, Council examined many comparative statistics, including those circulated to members, which showed that, while expenditure per member has risen at an average annual rate of 7,5% over the last fifteen years, subscription revenue per member has risen at only 3,4% per annum. It was with this background that your Council decided to raise the subscriptions. Initial approaches have been made to the big mining groups and there has been a very generous response, although the details of how financial assistance will be provided have not yet been worked out. It seems likely that some form of affiliated company membership will be the most suitable method of achieving this. When these details have been fixed, it is the intention to extend the appeal to all corners of the mining industry as well as manufacturing and metallurgical industries. It is believed that these measures will ensure that the finances of the Institute are placed on a firm foundation on which the expanding activities can be planned. The MacArthur Forrest Memorial Fund shows an excess of income over expenditure of R73 and the total fund was, therefore, increased by this amount to R4 411. The balance sheet shows that the market value of quoted shares and debentures increased during the year fron R6 540 to R9 160. The market value is now almost exactly the same as the book value. Accumulated funds now amount to R23 010 compared with R17 959 a year ago.

By P. Kohler, T. D. Sampson, T. H. Tunley

The Metsep Process for the separation and recovery of zinc, iron, and hydrochloric acid from spent pickle liquors by T. H. TUNLEY, B.Sc. (Ch em. Eng.) (Visitor), P. KOHLER (Visitor), and T. D. SAMPSON, Pr. Eng., B.Sc. (Chem. Eng.), B.Econ. (Visitor) A spray roaster has been installed in the Johannesburg area for the treatment of spent liquors from a variety of small pickling operations. A new process was developed for the processing of the liquor that is contaminated with zinc chloride, and a commercial plant was built incorporating this process. An ionexchange plant separates the zinc from the iron chloride, and a liquid-liquid-extraction plant converts the zinc chloride to zinc sulphate and recovers the hydrochloric acid.

Jan 5, 1976

By P V. Savage, T Glück, RCA Minnitt, C Bothma

Manganese Metal Operations ?Manganese Metal Company (MMC), a subsidiary of Samancor BHP Billiton, has two production facilities for electrolytic manganese metal in South Africa and produces a range of about 44 Mn metal products. ?The company is accredited with ISO 9000 and uses Six SigmaTM for continuous improvement. ?The control of the process relies on the effective functioning of approximately 250 different control loops at 50% automation.. ?Approximately 50000 samples are analysed every month. ?There are pyro, hydro and physical unit operations for the production of electrolytic manganese metal flake and value added products ? [ ]

Jan 1, 2005

A number of issues relating to the computational aspects of pillar design are addressed in this paper. The computation of average pillar stress values is important when attempting to establish criteria for pillar design and in the analysis of the stability of tabular pillar layouts. One of the default ?classic? numerical methods that are used to determine pillar stresses is the displacement discontinuity method. In many instances it is not clearly understood that this approach does suffer from some limitations, particularly in relation to the fact that in coarse element simulations, the simulated average pillar stress (APS) can depend on the chosen mesh size. The nature of this error is highlighted in this paper and some strategies are suggested to bound the magnitude of these errors. It is demonstrated as well that the popular linear stiffness approximation to pillar or seam compressibility does appear to allow reasonably accurate estimates of the average pillar stress when either the pillar height is varied or when the seam modulus differs from the host rock modulus. A practical implication of this study is that if the seam modulus is noticeably lower than that of the host rock, such as for coal seams, it is important to use a linear stiffness constitutive model for the pillars rather than a ?rigid? pillar assumption. This added complexity seems unnecessary, however, when simulating hard rock pillars in mines where the seam modulus is very similar to that of the surrounding rock.

Jan 1, 2011

By G. B. Lundstrom

SYNOPSIS For some time, Vaal Reefs South has operated blindhole borers successfully as an integral part of the mining cycle of operations. To date, over 13 000 m of mechanized boxholing has been completed, and from time to time impressive performances have been achieved. The paper describes the machines, the modus operandi, and the structure of the boring organization at the Mine, with some of the results recorded. The Mine recently took delivery of two new machines with interesting design features. The introduction and early experiences with these two machines are also described.

Jan 1, 1985

By X. M. Prevost

A computer system to store, retrieve and process coal borehole and analytical data together with other geological, geographical or topographical information is described. As a result of the large volume and variety of data stored since its inception in 1979, as well as the basic versatility of the system, the National Coal Data Base has been performing a number of new tasks for which it was not originally designed. As considerable sets of data are used on almost every project, the use of statistical application programs has become an important processing tool.

Jan 1, 1987

Many industries base their decisions on the assaying of tiny analytical sub-samples. The problem is that most of the time several sampling and sub-sampling stages are required before the laboratory provides its ultimate assays using advanced chemical and physical methods of analysis. As long as each sampling and sub-sampling stage is the object of due diligence using the Theory of Sampling it is likely that the integrity of the sought after information has not been altered and the generated database is still capable to fulfil its informative mission. Unfortunately, more often than not, unawareness of the basic properties of heterogeneous materials combined with the unawareness of stringent requirements listed in the theory of sampling, lead to the conclusion that massive discrepancies may be observed between the expensive outcome of a long chain of sampling and analytical custody, and reality. There are no areas that are more vulnerable to such misfortune than sampling and assaying for trace amounts of constituents of interest in the environment, in high purity materials, in precious metals exploration, food chain, chemicals and pharmaceutical products. Without the preventive suggestions of the theory of sampling serious difficulties may arise when making Gaussian approximations or even log-normal manipulations in the subsequent interpretations. A complementary understanding of Poisson processes injected in the theory of sampling may greatly help the practitioner understand structural sampling problems and prevent unfortunate mistakes from being repeated over and over until a crisis is reached. This paper presents an overview of the theoretical, practical and economic difficulties often vastly underestimated in the search for quantifying trace amounts of valuable or unwelcome components.

Jan 1, 2009

By W. A. Te Riele

The National Institute for Metallurgy was the venue for a one-day colloquium on 'The Chemistry of Processes for the Recovery of Gold on Activated Carbon'. Organized by the South African Chemical Institute (Southern Transvaal Section) in collaboration with the National Institute for Metallurgy (NIM) and the South African Institute of Mining and Metallurgy, the colloquium attracted tremendous interest from the mining industry. Some 300 metallurgists, engineers, and chemists were brought up to date on advances in this technology made by scientists of NIM and the Anglo American Research Laboratories (AARL).

Jan 1, 1980

By M. Sciarone, B. Collins

The production, properties, and selection of ferrosilicon powders for heavy-medium separation by B. COLLlNS. B.Sc Eng. (Rand) (Fellow). T. J. NAPIER-MUNN. B.Sc. (Eng.). A.R.S.M. (Visitor). And M. SCIARONE. M.Se. Eng. (Delft) (Visitor). There are basically two types of ferrosilicon powder available to operators of heavy-medium plants in South Africa spherical and milled grades. The production processes are described, and the properties of the two types are examined and compared. Guidelines are given for the selection of the correct grade of ferrosilicon for any particular application.

Jan 12, 1974

By F. L. D. Cloete

he above article by E. Barnea, which appeared in the January 1978 issue of the Journal (vol. 78, no. 6, pp. 143-145), calls for comment in view of the author's claims for the novelty of his proof. He states in his article that its main purpose is to give a mathematically acceptable proof by induction of the 'recently proposed' equation

Jan 1, 1978

By M. J. Santofimia

Multiphase microstructures in steel have been intensively studied in the past years, but combining non-equilibrium phases still offers a great potential for further development of these steel grades. Thus, improved combinations of mechanical properties can be obtained with microstructures formed by bainite or martensite, in combination with retained austenite. In particular, microstructures on the basis of carbon-depleted martensite and retained austenite can be produced by the very promising production process named quenching and partitioning (Q&P). Originally, the Q&P process aimed to avoid the formation of bainite during the heat treatment. However, the process does provide the possibility for (carbide-free) bainite formation during the partitioning step, i.e. in the presence of martensite. This article evaluates this approach, considering thatthe formation of bainite from austenite is strongly influenced by the preceding formation of martensite. Although the accelerating effect of the presence of martensite during bainite formation has been observed, it is not yet fully understood, and experimental and theoretical studies are being performed in order to come to a more effective exploitation of these processes for the formation of multiphase microstructures.

Jan 1, 2013

By A. Montini, M. H. Moys

A technique for the measurement of slurry consistency inside a grinding mil is described. The rate of slurry drainage from a sensing probe mounted through the mil shell is measured and correlated with the percentage solids of the slurry discharging from the mil. The response time of the measurement(obtained on a pilot bal mil) is compared with the response time of the viscosity of the mill discharge. It is shown that the new measurement should allow much tighter control of the mil behaviour, with concomitant savings in the consumption of power and steel.

Jan 1, 1988

By A. J. Van Rensburg, N. B. Strydom, C. H. Van Graan

The design, construction, and use of a practical ice-jacket for miners by N. B. STRYDOM, Ph.D. (Illinois) (Fellow), D. MITCHELL, Ph.D. (Rand) (Member), A. J. VAN RENSBURG, M.Sc (Poteh) (Visitor), and C. H. VAN GRAAN, M.Sc (Pretoria) (Visitor) Microclimate suits have been shown to be very effective in decreasing physiological strain in hot, wet environments, thus enabling men to work without risk in areas that would normally carry a high risk of heat stroke. In this paper, some design considerations in the development of the frozen jacket are described. Water complied with most of the desirable properties required of a coolant material for use In a microclimate suit. The Human Sciences Laboratory has developed a jacket in which ice is used as the coolant and which is designed according to the most acceptable anthropometrical characteristics. The jacket consists of an inner poncho-type waistcoat containing 28 water compartments. Over this is worn an insulating jacket, which minimizes warming of the coolant by the environment. Suitable refrigeration units have been developed to freeze the jackets underground. Laboratory tests have shown that these jackets are effective for about 2,5 hours, Irrespective of the wet-bulb environment, when men are working at a moderate rate. Jackets should, however, be used only in environments in which the wet-bulb temperature is in the range of 32,S0 to 35,S °C.

Jan 9, 1974

By S. J. van Wyk, A. S. H. Haagner

Land rehabilitation transcends the mere establishment of vegetation across disturbed landscapes; it should be conceptualised as a specialised ecological reconstruction process. This process necessitates a long-term perspective on the success of land repurposing. It requires a continuum of inputs specified and managed by a dedicated and qualified custodian to ensure the sustained economic viability and ecological sustainability of the land. Based on the authors’ combined experience and field observations over more than five decades, they advocate for an urgent shift away from traditional land rehabilitation practices toward a paradigm centred on land capability reconstruction and active stewardship. The prevailing rehabilitation culture has overly simplified the process to a mere revegetation exercise, which is fundamentally incompatible with the comprehensive requirements for sustainable land capability. While the regulatory framework provides valuable guidance for obtaining a mine’s social license to operate, a paradigm reset is essential. Mining companies must prioritise rehabilitation quality, set achievable sustainability goals, and establish clear pathways and milestones to meet relinquishment criteria. Currently, the status quo view—a model reliant on outsourced contracting and agricultural approaches—is that mine rehabilitation is a one-time intervention rather than a complex, systemic, and long-term process. This perspective presents significant challenges, as the success of ecological interventions can only be accurately assessed over extended timeframes, often spanning decades. Shortsighted rehabilitation specifications, coupled with practitioners operating within agricultural decision frameworks, frequently overlook the necessity for integrated rehabilitation expertise and the scientific foundation essential for designing and implementing effective ecological outcomes. A lack of long-term monitoring information impedes the required adaptive management of rehabilitated systems and, therefore, delays the transition towards final land use. This short approach costs the mining industry millions annually, often without recognising the inadequacies in long-term liability mitigation and the substandard ecological success achieved. The disconnect between procurement processes, the qualifications of service providers, and the unclear pathways to relinquishment can impede successful rehabilitation outcomes, frequently undermining progress toward sustainability milestones. Unless there is a fundamental reset of the land rehabilitation culture, pursuing sustainability will remain an elusive and perhaps impossible objective. Consequently, mining companies may hesitate to fully commit to sustainable land rehabilitation practices, as the prospects for relinquishment and final closure remain uncertain at best.

Apr 25, 2025

By F. Q. P. Leiding

SYNOPSIS A technique is described for measuring the change in volume in a borehole drilled in a rock mass subjected to stress and strain. It is shown that the volumetric strain or change in volume provides a practical estimate of the the stress in the rock.

A description is given of a simple, cheap device that enables the intact shear strength of rock to be determined quickly and inexpensively. Thin rock plates, prepared with a diamond saw, are tested in double shear by a linear punching action. By varying the direction of the diamond-saw cut in a number of specimens, the change in shear strength can be measured for different orientations relative to the rock fabric.

Jan 1, 1980

By A. M. Thyer

Throughout the history of mining, underground fires or explosions have killed many hundreds or thousands of people. Fortunately, the safety record has gradually improved as a result of many people’s work on improving safety standards and work practices. However, fire and explosion still remains a threat in many situations. As a result the UK Mines Inspectorate commissioned a project to study materials used underground and to develop a fire/explosion risk assessment system. Such a system has been developed, following the study of incidents, specified fire resistance criteria, and fire safety practices. The final methodology uses a series of check sheets to identify potential fuels and ignition sources, preventative measures, fire/explosion mitigation systems, and items for inclusion in emergency plans.

Jan 1, 2003