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By J. N. Van der Merwe

"Platinum is a highly valuable resource, its safe and economic extraction is paramount. The success of platinum mining by the bord and pillar method depends heavily on a comprehensive and dependable pillar design method. Pillars need to be large enough to safely support the load and small enough to avoid loss of resources. A critical evaluation of current pillar design systems used in narrow-reef platinum mining was undertaken using practical experience from a large feasibility-stage platinum exploration project, supplemented by observations from several platinum mines in Zimbabwe. An extensive literature survey was undertaken in order to determine the current status of design systems. Through this approach, the shortcomings of current pillar design systems are highlighted. Areas are proposed for further research to obtain a better understanding on how additional factors influence pillar system stability. The exploration work highlighted how rock mass classification methods can be utilized in determining the overall strength of pillars. Current pillar design systems for narrow-reef platinum mining consider width-to-heightratio (usually with different exponents for width and height) and the strength of the pillar material. However, there are many more important factors that are not considered and which have a bearing on pillar system stability. An in-depth study of these parameters with a view to establish effective narrow- reef platinum mining pillar design systems needs to be undertaken. IntroductionPillars have been used as a means of support since the early days of mining. Pillarsupported mining methods such as bord and pillar require a reliable design system for them to be successful. This paper presents an evaluation of the current hard-rock mining pillar design systems as applied to a practical large-scale narrow-reef platinum mining feasibility study. It is vital to have a dependable pillar design system for economic and sustainable mining. Using an extensive database collected from the project, the pillar strength formulae were tested and several discrepancies noted. This necessitates the establishment of more reliable pillar design systems. In narrow-reef platinum mining, large compressive stresses accompanied by geological and geotechnical factors contribute to pillar instability. A well-formulated pillar design system is required that accounts for such factors so as to minimize pillar failures."

Jan 1, 2017

By M. Karsten

Platinum mines in the Bushveld Complex are located in areas with a high geothermal gradient. This means that, compared to, for example, gold mines of the Witwatersrand region, high rock temperatures are encountered at relatively shallower depths. Thus air cooling and refrigeration need to be considered at early stages in mine development. Another factor that influences air cooling and ventilation requirements is the use of trackless diesel equipment for loading and hauling broken rock. At shallower depths it will be more cost-effective to locate the cooling and ventilation equipment on surface, whereas for deeper mines the more cost-effective option is to locate cooling equipment underground. For intermediate depths, trade-off studies need to be undertaken to determine the optimum mix between more cooling and less air or more air and less cooling, as well as the optimum location for this cooling equipment. Factors that are taken into account include power requirements, positional efficiency, and additional infrastructure requirements. Traditionally the approach has been to ventilate ?all of the mine all of the time?. However, with increasing power costs and growing pressure to ensure sustainability, this strategy must be modified to apply ventilation and cooling on demand. In other words, both cooling and ventilation equipment should be operated only when needed and should be adjusted to the demand at the time. Obviously there will be areas that will need to be ventilated (and cooled) continuously (for example, for dilution of flammable gases), but this can be built in to the overall strategy. In addition, in devising ventilation on demand (VoD) strategies, occupational criteria relating to exposure to gases, noise, and heat need to be taken into account. This paper discusses options available for implementing energy-efficient ventilation and cooling systems and suggests ways of changing traditional thinking in the overall ventilation and cooling of mines. Efficient ventilation and cooling designs can play a major role in improving sustainability and reducing energy costs and carbon footprint.

Jan 1, 2012

By J. A. Maritz, D. F. Malan

Pillar strength is affected by pillar shape, but this has largely been ignored in past research studies. Bord-and-pillar layouts are typically designed using empirical strength equations developed for square pillars. Owing to the poor quality of pillar cutting, many hard-rock pillars have an irregular shape and it is not clear how this affects pillar strength. Furthermore, the strength of rectangular pillars in comparison with square pillars is also difficult to quantify. The ‘perimeter rule’ is widely adopted for rectangular pillars, but its applicability for pillars with irregular shapes has never been tested. We used numerical modelling in this study to investigate the effect of pillar shape on strength. An analytical limit equilibrium model of a square and a strip pillar also provided useful insights. For slender pillars, the strength of a long rib pillar is essentially similar to that of a square pillar. In contrast, for rib pillars with a large width to height ratio, there is a substantial increase in strength. The study found that the perimeter rule should not be used for irregularly shaped pillars. Displacement discontinuity modelling, using a limit equilibrium approach, is proposed as an alternative to determine the strength of these pillars.

May 3, 2023

By A. F. Silva, R. Dockendorff, J. M. Girao Sotomayor, V. F. Navarro Torres, C. Castro

This paper shows the importance of performing probabilistic analyses in open pits, especially for mine planning, which can lead to more efficient ore extraction and meeting the acceptability criteria for safety in mine slopes. Three-dimensional stability analyses were performed to evaluate the future geometry of a large open pit for iron ore extraction in Brazil. The strength parameters of the lithologies were calibrated using ruptures in the pit walls. After determining the factors of safety (FoSs) from the calibrated parameters, probabilistic analyses were performed using the total range of values of each parameter under different field conditions to verify the reliability of the initial analysis. In this sense, it was possible to plot the probability of failure (PoF) and the FoS on the graph of slope height versus slope interramp angle (IRA) for the future pit in each lithology. IRA recommendations are made for two scenarios: (1) the best scenario: dry without ubiquitous joints and (2) the worst scenario: the water table at 10 m depth with ubiquitous joints in the most unfavourable direction. The results show that probabilistic evaluation is an important tool for establishing alert mechanisms in slopes that can be termed stable.

Jul 2, 2022

By G. T. G. Emere

The Johannesburg Branch of The South African Institute of Mining and Metallurgy was officially inaugurated at a General Meeting held in Kelvin House on Monday, 18th January, 1988. In addition to nominating committee members, Mr G. T.G. Emere delivered a presentation on the Barbrook gold-mining project, which is currently in the development phase some 40 km east of Barberton.

Jan 1, 1988

By H. M. Friede

Discussion of the above paper by A. SIFF The steely nature of the Iron Age objects mentioned in Dr Friede's paper point to two hypotheses. (1) The African iron workers were conversant with the art of direct steel manufacture. (2) They were less knowledgeable of the art of the production of carbonless iron. In this context I cannot but quote T. A. Wertime.

Jan 1, 1980

By M. J. Nicol

On page 51, the equation numbered.... On page 52, the equation numbered .... On page 53, the arrangement of the equation.... Canadian reports Asbestos by G.O. Vagt.l0 pp. Chromium by D. G. Law-West. 6 pp. Iron and Steel by T. R. Mclnnis. 15 pp. Titanium and Titanium Dioxide by M. A. Boucher. 7 pp. Vanadium by D. Shaw. 7 pp.

Jan 1, 1984

By R. G. B. Pickering

Successful management of mining operations depend on the accurate and reliable measurement of performance as a monitoring instrument in a feedback and control loop. However, when changes are being considered, the probable effect of the change on bottom line results requires different measuring techniques incorporating an in depth understanding which can identify hot spots in the operation which exhibit strong sensitivity to change. The CSIR's Division of Mining Technology has therefore been devoting a considerable effort to the establishment of techniques which enable changes to be analysed in terms of their impact on the two key parameters describing mine performance, i.e. profitability and safety. This paper describes these techniques, outlines their application to some example situations and discusses planned enhancements. The first section of the paper addresses the profitability model, and this is followed by a section considering the mine safety model.

Jan 1, 1996

By F. L. D. Cloete, A. K. Haines, T. D. Sampson, T. H. Tunley, W. A. M. te Riele

The recovery of zinc from pickle liquors by ion exchange A. K. HAINES. Ph.D. (Visitor) T. H. TUNLEY. B.Sc;.(Chem.Eng.)(Visitor), W. A. M. TE RIELE. pr, Eng.. Ph. D. (Visitor), F. L. D. CLOETE. M.Sc. (Chem..Eng.)(Visitor), and T. P. SAMPSON. Pr. Eng.. BSc, (Chem.Eng,). B. Econ. (Visitor) Picklers and galvanizers in and around Johannesburg are encountering an ever-increasing problem in disposing of spent liquors from their hydrochloric acid pickling baths. Particularly troublesome is the zinc-contaminated liquor that is produced as a result of the clean-up of rejects from the galvanizing operation. Because of the volatility of zinc chloride. this liquor presents difficulties when processed in a conventional pyrohydrolysis acid-recovery unit. The paper describes the Metsep Process. developed by the National Institute for Metallurgy and Woodall-Duckham S.A. (Pty) Ltd. which involves the use of continuous ion exchange for the separation of the zinc from the pickle liquor. and the use of liquid-liquid extraction for the conversion of zinc chloride eluate to salable zinc sulphate. A description of laboratory and pilot-plant tests is given. and the approach used in the design of a full-scale continuous- ionexchange plant is outlined.

Jan 11, 1973

By R. E. Gürtunca, D. J. Adams

Writen contribution by J.F.Curtls The subject mater of the paper is interesting in that, instead of 'numerical modeling based on elastic theory' being used for the prediction of energy release rate (ERR) in relation to various types of stope support, including backfil, use is made of stresses in the backfil in an atempt to corect the numerical modeling. Authors' reply to J. F. Curtis We thank Mr Curtis for his contribution to our paper. First of al, it should be emphasized that the object of the paper is not to address the validity of ERR as a tool for the assessment of seismic events or rockbursts, but to determine an in situ modulus for the rockmass with the aid of backfil measurements. Writen contribution by T.R. Stacey Although the authors of the above-mentioned paper have presented some good and interesting information, the title of the paper, and the recommendation that such an in situ modulis should be used for calculations of energy release rate (ERR), are viewed with some concern. The reasons for this concern are as follows. Authors' reply to T.R. Stacey Dr Stacey's comments on our paper are appreciated; we should like to address his concerns as follows.

Jan 1, 1991

The Annual General Meeting of the South African Institute of Mining and Metallurgy was held in Kelvin House on Wednesday, 22nd August, 1979. Dr M. G. Atmore (President) was in the chair and declared the meeting open at 16h00. Obituaries President: It is my sad duty to announce the death of the following Members of the Institute : Brigadier R. S. G. Stokes, Honorary Life Fellow and Past President ; J. A. Arthur, C. L. Cartwright, R. B. Greaves, A. A. Haynes, G. Ross, M. W. Richards, W. T. Stobart, E. Veres, G. V. White, and A. G. Williams, Life Fellows; A. J. H. Pole, D. T. McMurray, P. G. O. Pretorius, A. E. D. Rubidge, A. M. Seccombe, and R. R. Uren, Fellows; R. E. Oltman, R. B. Richardson, and G. P. Rundle, Members; S. F. Dench and S. van Wyk, Associates. As a mark of respect to the memory of the deceased, and in sympathy with the bereaved, please rise and observe a few moments' silence. Minutes President: May we confirm the minutes of our last Annual General Meeting, which was held on 23rd August, 1978, as published in the November issue of the Journal? Agreed.

Jan 1, 1979

Exxaro installed their first ultra fines treatment plant at Leeuwpan Coal mine. The plant is now fully operational and results already show that the plant has great potential. The plant was designed and installed by DRA. Several challenges were faced during the installation due to the space constraints in the Leeuwpan plant. Efficiency tests were conducted on both modules after commissioning and showed very promising results. A lower ash product with a higher yield can be produced with the fine coal dense medium cyclones compared to the spirals previously employed.

Jan 1, 2010

By S. Kauchali

"Underground coal gasification (UCG) is recognized as an efficient mining technique capable of chemically converting the coal from deep coal seams into synthesis gas. Depending on the main constituents of the synthesis gas, chemicals, electricity, or heat can be produced at the surface. This paper provides a high-level graphical method to assist practitioners in developing preliminary gasification processes and experimental programmes prior to detailed designs or field trials. The graphical method identifies theoretical limits of operation for sensible gasification within a thermally balanced region, based primarily on the basic coal chemistry. The analyses of the theoretical outputs are compared to actual field trials from sites in the USA and Australia, with very favourable results. A South African coal is studied to determine the possible synthesis gas outputs achievable using various UCG techniques: controlled retractable injection point (CRIP) and linked vertical wells (LVW). For CRIP techniques, an important result suggests that pyrolysis, and subsequent char production, are important intermediate phenomena allowing for increased thermal efficiencies of UCG. The conclusion is that South African coals need to be studied for pyrolysis-char behaviour as part of any future UCG programme. The results also suggest that UCG with CRIP would be a preferred technology choice for Bosjesspruit coal where pyrolysis dynamics are important. Lastly, the use of CO2 as oxidant in the gasification process is shown to produce syngas with significant higher heating value. Introduction and literature surveyCoal is a commonly utilized fossil fuel, providing over 40% of global electricity demand and about 90% of South Africa’s primary energy needs. However, less than 20% of the known world resources are suitable for possible extraction using conventional surface and underground mining techniques (Andrianopolous,, Korre, and Durucan, 2015). Underground coal gasification (UCG) has the potential to recover the energy stored in coal in an environmentally responsible manner by exploiting seams that are deemed unmineable by traditional methods. The UCG process, if successfully developed, can increase coal reserves substantially. For example, in the Limpopo region of South Africa alone, the estimated potential for UCG gas, based on existing geological records, is over 400 trillion cubic feet (TCF) natural gas equivalent – this is about a hundred times more gas than the existing 4-TCF Pande-Temane natural gas field reserve in Mozambique (de Pontes, Mocumbi, and Sangweni, 2014)."

Oct 1, 2018

By J. Hadjigeorgiou, T. R. Stacey

This paper introduces the Quantified Value-created Process (QVP), a decision-making process for use in mine design and operation. The implementation of the QVP is founded on a ten-step rock engineering design process and a ten-step strategic planning process. The potential of this approach is demonstrated by examples of value created as a result of good research, design, and planning. The QVP is divided into two parts, namely, a ‘planning the process’ section and an ‘implementing the process’ section, and can be considered to be an extension of the risk approach. All costs, direct and indirect, associated with a significant mining decision (design, operational, investment) must be quantified in advance of committing to that decision, to determine the value that will be created in the short, medium, and long terms. Ethical values, associated with health, safety, the environment, public perception, and social aspects, may be difficult to quantify in economic terms, but must nevertheless also be considered. In contrast with a traditional risk approach, the QVP will identify the upside, and allow executives to make more informed strategic decisions. In this context it is essential to actively engage upper management in the decision process.

Feb 2, 2022

By B. Amankwaa-Kyeremeh, W. Skinner, R. K. Asamoah, C. Greet

With the continuous increase in ore mineralogical complexity coupled with decreasing head grades, there is a need for mining industries to process large tonnages of material to meet global metal demands. Smarter, cheaper techniques are required to better map ore mineralogical variations proceeding to pre-concentration (flotation) stages for higher performance and metal recoveries. This paper is aimed at briefly reviewing previous studies on different selected ore mineralogy, with the focus on their pulp chemistry, to identify relationships which aid quicker flotation feed variation monitoring. Very little published work exists linking pulp chemistry parameters to flotation feed mineralogical variation. A successful application implies maximising grades at higher metal recoveries and reducing the cost of reagent for a better performing flotation circuit. Keywords: Mineralogical variation, flotation, pulp chemistry

Jan 1, 2020

By I. Soto, E. Córdova, A. Anani

The new caving megaprojects that are planned to go into production in the next decade have scheduled horizontal developments at very high rates, which are difficult to achieve. Research has been conducted that seeks to model the construction times for underground developments to determine the feasibility of achieving the planned rates. However, these previous attempts do not consider all the operational aspects that make up the mine development cycle. Here, we present a discrete event simulation (DES) model that individualizes each unit operation of the development cycle to determine the construction rates that new projects will be able to attain. The developed model was applied to the New Mine Level (NML) of the El Teniente Division (DET). The results indicate that it would be impractical to achieve the advance rates scheduled in the original plans if the unit operations of the mine continue to be executed using the status quo. The metres developed after six years in the sections analysed can be significantly improved by changing the maintenance strategy for the equipment (457 metres increase), orepass availability (194 metres increase), and the initial planning sequence (1 598 metres increase). It is recommended that the mine implements a flexible maintenance strategy, defines a strategy to ensure and increase orepass availability to contractors, and makes use of current simulation tools for a more robust development sequence planning.

Oct 1, 2022

The January General Meeting of the Institute was held in Kelvin House, Johannesburg, on 15th January, 1969 at 4.30 p.m. Mr R. C. J. Goode (President) was in the Chair. There were also present eighteen Members, including Messrs F. P. Bath, H. Britten, J. K. E. Douglas, P. Lambooy, V. C. Robinson, W. T. Stobart and P. W. J. van Rensburg (Council Members), Messrs J. C. Hall, P. C. Pirow, Dr D. I. Legge, Messrs E. R. Rudolph, H. R. Reid, Dr N. Stutterheim, Messrs B. F. van der Merwe, L. W. P. van den Bosch, D. T. Watt, M. Youngworth and T. Zadkin. Two Associate Members, Dr P. R. Jochens and Mr D. A. Viljoen. Two Students, Messrs R. P. W. Henrard and D. Ossin. Sixteen Visitors, including Messrs I. Barnes, B. F. Bath, S. Botha, P. A. du Plessis, K. Edwards, Dr F. S. Fulton, Messrs H. Grant, B. Havenga, L. Kok, Dr D. Lasar, R. Sandler, C. W. Wolhuter and J. D. Young. Secretary, Mr D. C. Visser. Total present: Forty. MINUTES The President: "May we confirm the minutes of the meeting held on the 20th November, 1968, as published in the December, 1968, issue of the Journal?" Agreed. MEMBERSHIP The President: "I have much pleasure in announcing that the names of the under-mentioned candidates, having been published in accordance with By-Law 5.2.2, Council has elected them to membership of the Institute in the following grades: Members: Basil James Jackson and James Petrie Archibald. Associate Members: Ronald Creasy, Hugh Angus McCallum and John Barton Cunliff. Graduate: Hermanus Isak Johannes van der Merwe. Affiliate: Edgar Ramsay. Student: Petrus Daniel Wolmarans. MEMBERS TRANSFERRED TO A HIGHER GRADE From Affiliate to Associate Member: Neil Bradfield and Mervyn Bayard Allman. "I welcome the newly elected members to the Institute and congratulate those members who have been transferred to a higher grade." (Applause). GENERAL BUSINESS The President: "Are there any matters to raise under this heading? If not, we will proceed to the next item on the agenda which is the presentation of today's paper."

By Piotr M. Kapias

Keywords: extraction, lead refining, Pb-Tl solutions, PbCl2-TlCl solutions. The theoretical part of the paper presents an analysis of the conditions of Tl extraction from Pb using different extractants and determines the activity coefficients in liquid solutions of Pb-Tl and PbCl2-TlCl. The dependence of the solution activity coefficients upon the composition and temperature is presented in the form of Krupkowski and Krupkowski-Fitzner equations. An analysis and evaluation were made of the influence of the methods of PbCl2 introduction into a Pb-Tl solution upon the efficiency of the Tl extraction process under thermodynamic equilibrium conditions. The analysis made it possible to formulate relevant equations describing the dynamics of the process of Tl extraction from Pb under stirring conditions as well as under the extractant injection into the liquid Pb-Tl solution conditions. In the part concerning experimental work, results are given for tests on the Tl extraction process from Pb-Tl liquid solutions of initial Tl content of approximately 0.05% mass using PbCl2 or, alternatively, Cl2(g) conducted in laboratorial scale. The tests made it possible to establish the influence of time, temperature, mass and the method of introducing the extractants into the liquid upon the level of Tl extraction from a Pb-Tl solution. Labels used in the text. WT1m - TI content in metallic phase, % mass WT1s - TI content in chloride phase, % mass wpTlm - TI content in metallic phase in initial state, % mass W°Tlm - TI content in metallic phase in equilibrium conditions, % mass m°m - initial mass in metallic phase mm - mass in metallic phase mPbC12 - lead chloride mass fed to the system MPbC12-TIC1 - mass in chloride phase MPb - lead atomic mass, g/mole MT1 - thallium atomic mass, g/mole K - Nernst distribution coefficient Xi - mole friction of solution component X°PbC12 - mole friction of PbC12 in saturated solution X°T1C1 - mole friction of T1C1 in saturated solution T - temperature, K R - gas constant, J/(mole K) k - kinetic equation constant, 1/(%-min.) ?i - solution component activity coefficient e - extraction rate, %

Jan 1, 2008

By J. Mulenshi, J. Rosenkranz, P. Khavari, S. C. Chelgani

The geometallurgical concept has mainly been applied to primary ore deposits, starting from ore characterisation to the economic optimisation of the mining operation. However, as primary ore resources are becoming depleted and lower in grade, alternative sources need to be explored and a question of adaptability of the geometallurgical approach to the secondary resource repositories arises. The particle size distribution, chemical and mineralogical compositions of the Smaltjärnen historical tungsten tailings from physical separation in Yxsjöberg, Sweden were studied using drill core samples collected from different locations within the tailings repository in order to assess the amenability of the tailings to reprocessing. The tailings are dominated by the –600 to +149 μm particle size fraction. This fraction contains most of the elements of interest (W, Cu, S, Sn, Zn, Be, Bi and F) hosted by scheelite, chalcopyrite, pyrrhotite, cassiterite, danalite (both Zn and Be), bismuthinite and fluorite, respectively. The particle size distribution and mineralogical composition vary across the repository, suggesting a possible existence of geometallurgical domains, which require further assessment to evaluate metallurgical performance. Keywords: Historical tailings, tungsten, scheelite, geometallurgy, characterisation, mineralogy, reprocessing

Jan 1, 2020

"Chairman: Professor J. C. Griffiths Rapporteur: Mr J. P. G. PRETORIUSPapers:Mine-mill production scheduling by dynamic programming by R. J. Roman Optimization of a large mining venture by J. C. Paynter, B. K. Loveday and C. G. Robinson Economic surface mining of multiple seams by T. V. Falkie and W. E. PorterIn introducing his paper, Mr Roman said that whereas in manufacturing plants the yearly production levels were usually chosen to produce the largest annual cash flow, in a mining operation, the raw materials (ore) were exhaustible so that the production had to be scheduled to maximize the total net present worth of the operation. This optimum production schedule could be determined by using dynamic programming. The required information was readily available to management at most mines. The 'possible operating range' of production rates lay between the rate with the highest profit per ton. and that with the highest profit per year. The optimum production rate started typically at the top of this range and decreased slowly as the deposit was depleted.Dynamic programming was used to determine several production schedules for a hypothetical mine-mill complex. The effects of changes in the ore grade estimates, size of deposit and acceptable rate of interest on the production schedule were taken into account. Apart from the fact that the net present worth of the overall profits was larger than that obtained by conventional methods, it appeared from the cases studied that the amount of metal recovered was also greater.Dr it P. King commented that this was a very interesting application of dynamic programming. He pointed out, however, that the market price of the metal was likely to vary significantly and randomly during the life of the mine, and he suggested that the problem should, therefore, be reformulated as a stochastic dynamic programming problem.If the price of the metal rose to abnormally high levels, a much higher than normal production rate could be expected. The results of analyses given in Table 5 showed that the production rate was a function of market price. In his view the stochastic problem could be solved just as easily as the deterministic problem.In reply to a question by Dr King as to whether the function relating recovery to production rate (Table I) was based on real data, the author replied that it was based on the results of an analysis conducted at the Union Carbide Corporation's Pine Creek tungsten mine in California.Dr D. M. Hawkins stated that costs were incurred when the production rate was altered, for example, in appointing or laying off staff, and that in practice it may be necessary to take these costs into account in finding the optimum production rate. Mr Roman replied that, while normal administrative costs were accounted for, the additional costs incurred in appointing and laying off staff were not taken into account."

Jan 1, 2014