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By Y. Jeong, K. Kim

Excess water can lead to instability and even failure in tailings storage facilities (TSFs). Simply reducing the amount of water in TSFs could be the best way to ensure the safety of nearby communities. In this case study we investigated the effects of reducing the water content in tailings slurry at a copper-cobalt-zinc mine in Mexico. An environmentally friendly polymer was used as a drag reduction agent (DRA) to offset the increase in solids percentage. The potential effects of the increased solids concentration on the tailings transportation system were also assessed. A series of ‘what if’ studies was conducted to assess whether adding the polymer would allow the solids concentration to be increased without changing the pressure loss in the tailings pipeline. The studies entailed conducting pipe loop tests to investigate these changes under various solids/ polymer concentrations and then constructing a computational fluid dynamics (CFD) simulation model using the test results. The validated model was used to determine the optimal polymer percentages needed to maintain the same pressure loss under baseline (30% solids) conditions, and to assess the potential risks (clogging, increased erosion rates) to the pipelines. The potential water savings were found to be significant, varying from about 1.852 Mm3/a at 35% solids to 3.915 Mm3/a at 45% solids.

Dec 13, 2023

By K. B. Le Bron, T. van Aard

The empirical pillar strength formulae have been widely, and in most cases successfully, applied to design underground pillars for mines in the Bushveld Igneous Complex (BIC). This paper presents the case for combining the empirical method with numerical modelling when it comes to crush pillar stability analyses. The benefits include an understanding of potential failure mechanisms, which may then be accounted for in the designs. In addition, the impact of weak layers, such as shear zones, the impact of the dip of the orebody, differences in layouts, such as holing widths and the presence of advanced strike gulleys (ASGs) immediately adjacent to the crush pillars, and stress regime (k-ratio) may be studied using numerical modelling, as it is not accounted for in the empirical method.

Mar 5, 2025

OFS Branch Committee Meeting held in the Committee Room at the Welkom Club at 4.15 p.m. on Wednesday, 5th March, 1975. Progress in mineral dressing The National Institute for Metallurgy and the South African Institute of Mining and Metallurgy are to hold a symposium on 17th and 18th September, 1975, entitled 'Recent Progress in Mineral Dressing'. INFACON 74 This book of over 300 pages is a record of the First International Ferro-alloys Congress, which was held in Johannesburg from 22nd to 26th April, 1974, under the auspices of the Ferro Alloy Producers' Association of South Africa, the National Institute for Metallurgy, and the South African Institute of Mining and Metallurgy. NIM reports Report no. 1595 Preliminary tests on low-grade brecciated fluorspar ore from the Ottoshoop district. (5th Nov., 1973, declassified April 1975). Report no. 1612 Flotation tests on sulphide-bearing high-grade brecciated and wad ores. (20th Mar., 1974, declasl>ified April 1975). Report no. 1643 Further tests on low-grade brecciated fluorspar ore from the Ottoshoop district. (12th Jul., 1974, declassified April 1975). Report no. 1654 The determination of osmium in platiniferous media. Report no. 1689 The determination, by atomicabsorption spectrophotometry, of arsenic, selenium, tellurium, antimony, and bismuth on ion-exchange restns. Report no. 1715 Flotation tests on various types of ore from the Ottoshoop district Report no. 1730 The chromitite from the Marico occurrence, western Transvaal, its alteration, and possible reasons for its refractory nature. Report no. 233 A chemical and mineralogical study of microlite from the N oumas pegmatite. 24th Geomechanics Colloquy The above Colloquy is to be held on 2nd and 3rd October, 1975, in the Salzburg Congress Hall. Rosenhain centenary The centenary of the birth of WaIter Rosenhain (1875-1934) will be celebrated by an international conference to consider how physical metallurgy has contributed to engineering practice. Iron and steelmaking The Centre de Recherches Metallurgiques (CRM) and the Verein Deutscher Eisenhiittenleute (VDEh) are jointly to hold the International Meeting on Iron and Steelmaking 1976 in Brussels from 17th to 18th May and in Diisseldorf from 20th to 21st May, 1976. International Symposium on Mine Surveying The III I.S.M. is being held in Leoben, Austria, from 28th June to 3rd July, 1976. Book review Tenth International Mineral Processing Congress. 1973. London, The Institution of Mining and Metallurgy. 1208 pp. £20. Particles A course on particle characterization and a symposium on experience in the applications of particlesize analysis will be held during the last week of July in Pretoria and Johannesburg. A.S. & T.S. Trust The A.S. & T.S. Trust was formed on 24th March, 1972, to mark the Golden Jubilee year ofthe Associated Scientific and Technical Societies, with the object of advancing science and technology in South Africa. Second International Congress of Engineering Geology The Proceedings of the above Congress, which was held in Sao Paulo, Brazil, from 18th to 24th August, 1974, are now available.

Jan 6, 1975

By G. Akdogan, M. Tadie, A. Tapfuma

The Southern African region contains abundant gold tailing heaps that are an environmental concern due to dust pollution and chemical contamination of nearby water bodies. Nevertheless, these heaps contain gold with potential to be extracted for financial gain. In this study, the feasibility of extraction of gold from a Witwatersrand gold tailings using glycine was investigated using a two-level full factorial design. Effects of variables such as glycine concentration at levels of 0.5–1.5 M with a solid–liquid ratio of 50–200 g/L were investigated. Although the solid–liquid ratio used in this study was below the industrial norm, it provides a starting point for investigating the applicability of this technology. To enhance the gold extraction, potassium permanganate pretreatment and copper ion addition were adopted. The results revealed that 91.4% gold extraction was achieved after 24 h pre-treatment of the tailings using 2 g/L potassium permanganate followed by subsequent leaching using 1.5 M glycine at pH 12, with 50 g/L solid–liquid ratio and 2 g/L copper ions. Statistically, the solid–liquid ratio and potassium permanganate pre-treatment of the tailings were found to be significant at 95% confidence interval, whilst interactions of copper ions and glycine concentration were significant factors. The work demonstrates that potassium permanganate pre-treatment prior to glycine leaching of low-grade secondary gold resources, such as tailings, can be beneficial. Furthermore, the methodology developed in this work provides an opportunity for further investigation of the recovery of gold hosted in complex mineralogical matrices.

Apr 14, 2024

By L. A. Maseko

"As part of the mining engineering curriculum, students are required to be placed in industry for vacation work or work-integrated learning (WIL). In this paper we review work-based placement as done at the four South African mining schools: the University of Johannesburg, the University of Pretoria, the University of the Witwatersrand, and the University of South Africa.Key aspects of past and current WIL (pre- and post-graduation) practices that may need attention are highlighted for consideration by all universities that provide professional qualifications. Work-directed theoretical learning, problem-based learning, project-based learning, workplace learning, and simulated work experiences are discussed as legitimate approaches to WIL.Regardless of the choice each institution makes, commitments of universities, preparedness of university teachers, and the desire for equity and excellence will play an important role in the provision of WIL.DefinitionsAccredited Qualification: a qualification awarded on successful completion of an accredited programme.Advisory Boards (or Committees): are essential infrastructure for a WIL curriculum that is built on the integration of the workplace and the university. This requires the collaboration of experts from both environments. Workplace advisors are critical to the success of the academy as they embody expert knowledge of the ‘real world’.Assessment: the process of determining the capability or competence of an individual against standards by evaluating performance.Category: a mode of registration defined in or under the ECSA Act which has a distinctive purpose, characteristic competencies, defined principal routes to registration, and educational requirements.Experiential learning: (in South Africa sometimes used synonymously with work placement or cooperative education) is a term used with a great variety of meanings in the international literature. More broadly, it may refer to learning that has meaningful learner involvement. It is the process of generating meaning from direct experience. In the international literature, experiential learning is learning through reflection on doing, which is often contrasted with rote or didactic learning."

Dec 1, 2018

By V. Quezada, Á. Astudillo, L. Valásquez, M. Garcia

Seawater has become a viable alternative for different uses in copper hydrometallurgy. In this paper we review the main physical and chemical characteristics of seawater and how these influence copper production. Reliable data on the use of continental water are reported, and the current use and consumption of seawater in the Chilean mining industry is analysed, indicating the main areas of use and the main problems encountered. Additionally, the influence of the elements in seawaterthat have the most influence on the extractive metallurgy of copper are considered. The Chilean copper mining industry currently consumes approximately 4.1 m3/s of seawater, which corresponds to 25% of the total water used. The use of seawater for the leaching of copper sulphide minerals, such as chalcopyrite, is beneficial because it provides 20 g/L of chloride, thereby improving copper dissolution kinetics.

Jul 5, 2023

By M. C. Bekker, T. Govindasamy

The potential benefits of implementing the Last Planner System (LPS) on mining infrastructure projects were explored through two case studies in the South African mining industry. The first part of the study involved measurement of the impact of LPS through earned value techniques on secondary project data. The second part sought to establish the lean construction success factors leading to improvements in construction performance. This was done by means of a research questionnaire distributed to the project owner’s teams, contracted parties, and the LPS facilitators. The results revealed a positive correlation between LPS application and planned percentage complete. However, the performance achieved during the LPS pilot was not sustained. The success factors and benefits considered most evident in the case study pilot differed among the three stakeholder groups. The findings are expected to guide construction stakeholders to better define performance measures and focus on factors required to make LPS implementation more effective in the South African mining sector.

Feb 12, 2024

By R. J. Quevedo, Y. A. Sari, S. D. McKinnon

The large scale of cave mines leads to many challenges, including operational logistics and geomechanics design. In current practice, pillar stability assessment relies almost exclusively on stress analysis. However, stability is also affected by other factors including those related to operational aspects of the mining method, the effects of which are difficult to account for during the design stages. In this paper we present a case study of the application of a machine learning approach to evaluate the influence of these operational factors on pillar stability at the Chuquicamata underground cave mine in northern Chile. Due to the likely multi-factorial damage process leading to collapses and considering the different pillar conditions, a tree-based machine learning method was used and analysed to improve the understanding of the relative importance of the various contributing factors. Unlike stress analysis methods, it does not require any a priori knowledge of failure mechanisms, nor the calibration of associated controlling parameters. The proposed random forest model predicted pillar collapses with 80% accuracy despite limited samples to model from. The main contributing factors to collapses were found to be related to available pillar volume, cave front geometry, and time under abutment stress conditions. The effects and interactions of such factors were also studied, showing that careful and improved control over operational conditions can significantly reduce the likelihood of pillar collapses. These conclusions could not have been obtained from stress analysis alone, illustrating the complementary nature of conventional stress analysis and machine learning approaches.

Mar 14, 2024

By P. Cowx, L. Els, P. Smith, R. Nordhagen

"Tapping operations at ferroalloy smelters generate a significant amount of fume. Effective capture of fumes is required to meet the obligations of environmental, as well as occupational, legislation.A study was completed on an existing fume extraction system at a ferromanganese furnace tapping area. The area under consideration included the tap-hole, launder, and ladle area. The study consisted of site test work as well as computational fluid dynamics (CFD) modelling to identify and evaluate solutions.Site test work and observations during furnace operation provided a baseline of system performance as well as input parameters for CFD modelling. Gas flow rates and energy contents from each extraction area were measured. Photographs and video footage were taken to evaluate areas of fume leakage.The CFD study was firstly validated against site observations to ensure the accuracy of input parameters. Thereafter several modification concepts were modelled and suitable combinations were investigated to ensure robust solutions. The following concepts were considered:•,Air curtains•,Ladle hood aspect ratio and position•,Increase of ladle extraction volume•,Extension of the length of the tapping garage structureThe paper presents the results of a performance test on a working ferromanganese tapping area fume extraction system and the results of CFD modelling as compared to site test results. Upgrade options are evaluated and an integrated robust upgrade of the system described."

Jan 1, 2014

By E. R. Leeman

INTRODUCTION The first references in the literature to the so-called C.S.I.R. 'doorstopper' strain cell were made in 1964 1,2,3,4. These were the climax of nearly two years of experimental and developmental work with the instruments and the operating techniques involved. Since that time numerous field measurements have been made with 'doorstoppers' and they have been developed to a stage where they are in commercial production and are being supplied to users throughout the world. No detailed description of the latest 'doorstopper' equipment has, however, appeared in print and this paper is written to bring the literature up to date in this respect. The triaxial strain cell was developed three years ago 5, 6, 7 and was first described at the First Congress of the International Society for Rock Mechanics in Lisbon in 1966 8. Since that date laboratory tests and-particularly important-field tests 7' 9 have demonstrated the validity and practicality of the instruments and techniques. These instruments have also been developed to a stage where they have been released for commercial production. In this form they are very different from those described two years ago and a full description of them at this stage seems to be justified. THE INFORMATION SUPPLIED BY 'DOORSTOPPER' AND TRIAXIAL STRAIN CELLS Both the 'doorstopper' and triaxial strain cells were designed specifically to determine the absolute stress in rock using an overcoring stress relieving technique. They were not designed to measure changes in stress. They may, however, be used for the latter purpose provided the glue which is used to stick the strain gauges to the rock is known to possess sufficiently stable strain-time characteristics as not to affect the accuracy of the results during the time the measurements are made. The 'doorstopper' was designed primarily to measure the major principal stress in situations where its direction and those of the two other principal stresses were either known or could be assumed. For example, at great depth in undisturbed virgin ground, it is reasonable to assume that the maximum principal stress is vertical and that the other two lie in a horizontal plane. The borehole in which the 'doorstopper' is installed would thus be drilled in the horizontal plane parallel to one of the minor principal stresses, the direction of which would either have to be assumed or determined as described later. The stresses measured would be the vertical major principal stress and the principal stress acting in a horizontal plane normal to the borehole axis. It is possible, as will be shown later, to obtained the complete state of stress using 'doorstoppers'. In this event, it is necessary to make measurements in three boreholes drilled in any three known directions to each other and relative to a system of three orthogonal axes. The triaxial strain cell was designed to determine the complete state of stress in a single borehole drilled in any direction in any stress field. At first glance it would appear to supersede the 'doorstopper'. This is not necessarily true since there are

By J. F. Brand, J. C. van Dyk, F. B. Waanders

"Syngas from Africary’s Theunissen underground coal gasification (UCG) project will be used for power production and synthesis of liquid fuels and commodity chemicals. However, some of the coal components, especially condensable water, oils, tars, inorganic trace elements, and a small fraction of fly ash and particulate matter, make their way to the surface via the production well and can cause adverse impacts on downstream processes. Africary’s standard design incorporates a cold gas clean-up system that relies on relatively mature techniques based on highly effective wet scrubbers and acid gas removal (AGR) systems such as Rectisol®, but with the downside of low energy efficiency and waste water generation. In this paper, novel technologies for removing contaminants and species separation from the hot (T > 300°C) raw syngas are compared. Comparisons are made between supersonic gas separation (SGS), Ranque–Hilsch vortex tube (RHVT), vortex gradient separation (VGS), and inertia vacuum filtering (IVF), and a vortex-based gas separation concept is proposed for UCG applications. IntroductionImpurities in gasification feedstock (coal, biomass, waste, etc.), especially sulphur, nitrogen, chlorine, and inorganic mineral matter, often end up in the syngas and can cause adverse impacts on downstream processes. Africary’s standard design incorporates a cold gas clean-up system that relies on relatively mature techniques based on highly effective wet scrubbers and acid gas removal (AGR) systems such as RectisolR, SelexolR or aMDEAR; but with the downside of low energy efficiency and waste water generation.Hot (T > 300°C) gas clean-up technologies are attractive because they avoid cooling and reheating of the syngas stream. Some available warm gas cleaning technologies include traditional particulate removal devices such as cyclones, candle filters, membranes, and molecular sieves. The warm gas desulphurization process technology developed by RTI LLC (2018) requires hot syngas to remove sulphur and has become commercially ready. Many other hot gas cleanup systems are still under development, given the technical difficulties caused by extreme environmental and operating conditions."

Jan 1, 2018

By L. A. Cramer

There are a couple of dozen junior platinum mining companies coming into existence in Southern African and most intend to mine, concentrate the PGM?s in a flotation product and sell the concentrate to one of the major producers in South Africa. The price they will receive for their product and hence the return they achieve for their investment will depend upon the large number of factors that influence the market for such a product. Unfortunately the number of buyers is severely limited as it is dominated by the two major local producers, Impala Platinum and Anglo Platinum. Furthermore the current smelting technology has limited capacity for UG2 concentrates and high nickel concentrates will quickly fill any available base metal refining capacity. Few if any overseas buyers can compete for the bulky flotation concentrate produced. This paper will explore those factors such as metal recoveries, metal prices, operating costs, capacity constraints, deleterious elements, transport issues, metal premiums and discounts that are in play, types of flotation concentrates, processing capital costs, PGM grades, etc and their impact up on what smelters and refiners might be prepared to pay for such PGM concentrates. Ultimately simple graphs and equations can be developed for probably payment terms for such concentrates. Those who negotiate well will move to the higher return section of the envelope and those who use the concentrator facilities to produce the most saleable combination of flotation concentrates will enhance their returns. A deep and firm understanding of the issues surrounding this market is necessary in order to negotiate the best possible price for the seller.

Jan 1, 2008

By M. de Beer

The conversion of carbon-containing feedstock into liquid fuels can proceed via the Fischer-Tropsch synthesis, which is catalysed using supported cobalt catalysts. These catalysts contain noble metals to facilitate the reduction of oxidic cobalt species in the catalyst precursor to metallic cobalt, which is the catalytically active species for the Fischer-Tropsch synthesis. This is thought to occur via hydrogen spillover, i.e. the diffusion of atomic hydrogen over the support from the noble metal to the oxidic cobalt moieties. Noble metals may also affectthe dispersion of cobalt in the active Fischer-Tropsch catalyst. The economic aspect of the addition of noble metals to the Fischer-Tropsch catalyst is discussed.

Jan 1, 2014

By J. H. Viljoen, C. H. Graan, N. B. Strydom, J. S. Greyson

M J Martinson (Fellow) There is everywhere a lamentable dearth of quantitative information on occupational factors affecting the health and safety of mineworkers, and as the authors point out in their introduction underground lighting is one of the factors which has received little attention in South Africa prior to this welcome paper. Since the authors are to some extent pioneering, it is perhaps inevitable that the paper should raise more questions than it answers, but nevertheless it provides a provisional yardstick against which the need for, and success of, remedial action may be judged. Before commenting in detail on a few aspects of the paper it may be worthwhile to summarize the statutory provisions relating to underground lighting, contained in Chapter 15 of the Regulations promulgated in terms of the Mines and Works Act 27 of 1956. Chapter 15 is entitled `Lighting, Safety Lamps and Contraband', but in the context of the present paper only four simple regulations need be noted: firstly, no person shall work or travel in an unilluminated part of a mine unless he carries a light ; secondly, adequate stationary lights shall be provided at stations and certain other localities in shafts, winzes and places used for winding; thirdly, mechanically propelled conveyances shall be provided with an effective bright light shining in the direction of travel; and fourthly, moving machinery to which personnel have access shall be illuminated so as to be clearly visible. In all four regulations the standard of lighting to be provided is wholly subjective, and under these circumstances the wide inter- and intra-mine variations in light intensity disclosed by the study are hardly unexpected. Nevertheless the data presented in the authors' Table I raise three points (1) Is there any evidence that the 19 mines visited during the survey are representative of the 45-50 large gold mines in South Africa, or that the shafts selected are representative of the respective mines? Mine managers would scarcely be human were they not to offer better lit working places for the survey; perhaps the use of a scaling factor (e.g. tonnes or transit mineworkers per shift, kilowatts, etc.) for each working place might have helped to put the figures in perspective. (2) Looking at two of the more numerous - and probably important - of the ten working places included in the survey, i.e. stations and tips, one is struck by the marked. skewness of both intensity distributions (with higher frequencies at the lower intensities) and the abrupt cut-off in both cases just short of pitch darkness. Thus, of the 45 meaned readings recorded at 26 tips no less than 19 fall in the lowest range of 0,1-0,9 1m/ft2, with but one tip in total darkness; of 46 readings on 26 stations, 7 fall in the lowest range and none is in total dark-'1 ness. Although a light with an intensity in the range 0,1-0,9 1m/ft2 may satisfy the regulations, it is certainly arguable that in some situations it may be safer to have no light at all. (3) In view of the skewness referred to above, one wonders how meaningful are the `total average light intensities for (the gold mining) industry' quoted in Table I, which the authors compare with illumina¬tion levels found in other countries. Looking at tips again, one notes that 34 out of 45 meaned intensity readings fall below the `total average' for tips, and only 10 exceed it. From this it may be concluded that a few well-lit working places included in a `total average' may conceal a plethora in Stygian gloom. In their discussion the authors make fleeting reference to the effect of underground lighting on productivity and accident rates, without however quoting any South African experience in this regard. Intuitively it seems highly likely that better lighting (in the widest sense) would improve productivity and reduce accidents, and of course it is in these areas that the mining industry might seek economic justification for providing better lighting. It is all the more regrettable therefore that these factors were not studied simultaneously with the present investigation, especially at the Psychological Division of the Human Sciences Laboratory has recently published a study on underground accidents in the gold mining industry without making any reference whatsoever to lighting as a causal factor. In the event neither of the two studies enables us to make an economic appreciation of the situation, and this seems to be a classic example of a situation where some dovetailing of research effort would have greatly increased the useful return. On the effect of lighting on accidents, it may be noted that in 1939 Mickel presented some very interesting statistics to the Mine Managers Association of the Transvaal2, on the improvement in accident rates which followed the random issue of electric cap lamps to native mineworkers in the Hercules Section of E.R.P.M. the previous year. Based on a 12 month trial period in which 250 000 shifts were worked with carbide lamps and (contemporaneously) 307 000 shifts with cap lamps, the incidence of major accidents (at least one day in hospital among men using carbide lamps was 1,15 accidents per 1000 shifts, while the incidence of minor accidents (requiring dressing only) was 11,52 per 1 000 shifts. The corresponding figures for men using cap lamps were 0,79 and 7,31 accidents per 1 000 shifts respectively, representing a reduction of over 30 per cent in both major and minor accidents. While these figures are obviously dated - only men using cap lamps were issued with hard hats, for instance - they do indicate a need for similar research today.

Jan 1, 1971

By N. Theron, R. F. Meeser

The global emphasis on conserving energy resources has led to the adoption of hybrid power systems in vehicles. Optimally applied, hybrid systems can save up to 40% on fuel costs. To optimally manage a hybrid vehicle's energy flow it is necessary to know, in real time, all the energy requirements to complete a given route. The energy consumption depends mainly on the vehicle mass, speed profile, and route topography. Of these, the topographic profile is the one factor that is only route-dependent and not influenced by the vehicle or driving styles. The heading vs. distance profile is also an example of a route characteristic not influenced by the vehicle or driving style. In this study the topographic and heading profiles are used to identify routes, and are easily measured by means of digital barometric pressure and compass sensors. Correlations between the current route and previously travelled/stored routes are performed based on their topographic and heading profiles in a point-by-point manner. Above-ground tests were first performed using a road vehicle and six routes to evaluate the system. The system consistently and correctly identified a 20 km route within the first 4 km. It also proved to function correctly in underground tests through the implementation of an instrumented hand-held surveyor's wheel. This system finds direct practical application in optimizing the energy management of an underground hybrid locomotive used by the mining industry in South Africa, but can also be of benefit in applications where route identification is required and using GPS is not feasible.

Jan 26, 2023

By T. Nesane, S. S. Mnyakeni-Moleele, L. C. Murulana

The effectiveness of two synthesized ionic liquids, 1-(benzyloxy)-1-oxopropan-2-aminium 4-methylbenzenesulfonate (1-BOPAMS) and 4-(benzyloxy)-4-oxobutan-1-aminium 4-methylbenzenesulfonate (4-BOBAMS), were evaluated for mild steel corrosion inhibition in 1.0 M hydro-chloric acid solution, using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and gravimetric techniques. Organic moieties responsible for the adsorption process on mild steel surface were investigated using Fourier transform infrared spectroscopy (FTIR). Gravimetric analysis revealed that the inhibition efficiency of 1-BOPAMS and 4-BOBAMS increased with concentration, with maximum inhibition values of 90.32% and 97.91%, respectively, at the highest concentration of the inhibitors. Gibbs free energy (ΔG°ads) values indicated a strong interaction between the mild steel surface and the molecules of the ionic liquids, and that the adsorption process was spontaneous. These values also show that the inhibitive nature of ionic liquids against mild steel corrosion is caused by a mixedtype of adsorption film formed on the steel surface. The Langmuir adsorption isotherm was used to describe the adsorption of ionic liquid molecules onto the mild steel surface. Polarization curves showed that 1-BOPAMS and 4-BOBAMS have a similar effect on both the anodic and cathodic half-reactions, indicating that they prevent the dissolution of mild steel through both physical and chemical process. Nyquist plots were defined by incomplete semicircle capacitive loops, showing that the charge transfer mechanism controls the corrosion of mild steel in acidic solution.

Apr 1, 2021

A mineralogical study was conducted on the feed (3.51 g/t Au and ~90 g/t Ag) and four leach residue samples (assaying 0.09 to 0.19 g/t Au and 30.0 to 61.5 g/t Ag) from the Pinos Altos silver-gold deposit in Mexico to determine the cause for gold and silver losses. A comprehensive mineralogical and analytical approach including fire assay, gravity pre-concentration, ore microscopy, mineral liberation analyser (MLA) and electron microprobe was used for the current study. Results showed that gold and silver lost in the leach residues occurred mainly as inclusions in quartz and silicates (accounting for over 80% for Au and 92% for Ag of the head assays, respectively), with a minor amount in iron oxide and other minerals. The amount of liberated gold and silver is negligible. Results also showed that gold and silver particles in leach residues are mainly ranged from 1 µm to 5 µm in size, which implies that ultrafine grinding is required to improve the recoveries of these two metals. Keywords: mineralogy, gold deportment, silver deportment, silver-gold ore, leach residue, recovery improvement.

Jan 1, 2009

By I. Silin, H. Wotruba, A. Liono, I. Volobayev, Y. Rubinstein, D. Gürsel

Old, abandoned or in situ processed and storaged tailings can be a potential source of remained valuable metals and minerals. By reprocessing of tailings, it is possible not only to achieve economical profit from recovery of valuable metals, but also to reduce environmental damage caused by tailings such as generation of acid mine drainage from sulfide minerals, mobilization of heavy metals, soils and groundwater contamination. In addition, storage facilities can be successfully redesigned with modern geotechnical requirements and monitoring to avoid a dam collapse of abandoned tailings. In this case study, the processing of low grade abandoned tailings was investigated. Copper (0.15%), cobalt (0.032%) and gold (0.35 ppm) were determined as main valuable and recoverable metals. Cobalt occurs as cobaltite and cobaltiferrous pyrite, while chalcopyrite represents copper. The fine fraction of tailings below 32 μm is enriched with cobalt and copper. Preliminary test-works with initial tailings sample were aimed to recover copper, cobalt and gold. The previously tested magnetic and gravity separation could not recover the metals in a pre-concentration step. Flotation tests of the tailings sample had shown a suitability for flotation without previous regrinding of the tailings. The valuable minerals are first proposed to be recovered by collective flotation, followed by a selective circuit with production of a low grade copper concentrate and a cobalt bearing pyrite concentrate. Based on various tested collectors, amounts of sulfidisation agents and activators, a suitable reagents regime was determined and used for up-scaling by locked cycled test. Keywords: reprocessing, tailings, copper, cobalt, gold, flotation, cobaltite, cobaltiferrous pyrite

Jan 1, 2020

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 R. Dehghan, M. Zarei, A. Tohry, S. C. Chelgani

Typical depressants for selective reverse flotation of iron oxides from complex silicates do not generally show high levels of efficiency. Therefore, as a hot topic, there are several ongoing investigations in this area. The main aim of this paper is exploring the potential of using humic acid (HA) as a depressant in reverse cationic flotation of hematite from complex silicates. For such a process, the wettability and flotation behaviour of pure minerals (hematite and silicates) was investigated at pH 10 in the presence of HA and cationic collector. Adsorption mechanism of HA on these minerals was measured by zeta-potential and FTIR. Results of flotation tests showed that at the lower concentrations of HA, selective separation of silicates from hematite is beneficial, where the floatability of amphibole was higher than pyroxene. A higher separation efficiency of hematite through reverse flotation was observed in the presence of amphibole, in comparison with the presence of pyroxene. Wettability studies showed that HA has a significant effect on reducing the hydrophobicity of treated minerals with the collector. The adsorption, ZPC and FTIR test results indicated that HA was adsorbed on both silicates and hematite. However, the absorption intensity onto hematite was much higher than silicates. It was found that the adsorption mechanism of HA on hematite takes place through both strong H-bonding and ligand exchange. Keywords: Reverse cationic flotation, humic acid, iron oxide, complex silicates, surface adsorption

Jan 1, 2020