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By L. Zhou, J. Qiu, M. Tang, J. Wang, G. Dai

Coal spontaneous combustion in longwall gobs is a major concern in coal mines. In comparison to other hazards, this phenomenon is difficult to detect. Fifteen factors influencing coal spontaneous combustion in longwall gobs were identified from the literature. The logical relationships between these factors were evaluated and quantified by decision-making trial and evaluation laboratory (DEMATEL) and interpretive structural modelling (ISM) methods. A four-level hierarchical structure model was established. The research shows that combining DEMATEL and ISM can reveal the key factors that influence coal spontaneous combustion in longwall gobs and establishthe interactions and relationships among these factors. The results can provide the basis for preventing and controlling coal spontaneous combustion in longwall gobs.

Jun 10, 2024

"Chairman: Mr. K. F. LaneRapporteur: Mr C. T. ShawPapers:Design of crushing plant flow sheets by simulation by T. GurunThe impact of transportation networks upon the potential supply of base and precious metals from Sonora, Mexico by P. de V. Harris and D. E. EurestyProfitability sensitivity analysis of a mining venture by C. A. Beasley and E. P. PfleiderTechnological innovation and its potential effect on the opening of new gold mines in South Africa by N. C. JoughinMr Turgay Gurun, in presenting his paper, indicated that this simulator was no purely theoretical exercise, but that the model had been used in the design of crushing plants of capacities ranging from 3 000 tons per day to 66 000 tons per day, and that recently the design of a plant of capacity of 99 000 tons per day had been studied.The crushing plant simulator was an independent portion of a much more comprehensive simulator for the design of a. complete recovery plant. It would be possible to use each section of this simulator on its own, and simulators would be designed to cover flotation concentrates, cash flow analyses of the entire project, and so on.Each simulator would be backed by a comprehensive data bank. For example, the crushing plant simulator was backed by such a data bank which included the performance and cost data from five manufacturers for an average of 30 items of process and materials handling equipment each. This meant that data preparation involved generally less work than would be required for a manual calculation. On average, data preparation for one run took 30 minutes and three minutes of computer time on an IBM 360/40 completed the run. The model could be valuable as a design tool in that it allowed the designers an opportunity to make a thorough examination of many alternative designs. It was also of value to plant operators as it could be used to predict the consequences of operating decisions.This paper generated much interest and there were numerous questions and contributions, so many, in fact, that the discussion had to be cut short.It was pointed out by Mr K. F. Lane that crushing plants represented a very large capital investment. A plant designed for 40 000 tons per day at 98 per cent efficiency might well in practice be run at 50 000 tons per day at, say, 83 per cent efficiency. He asked how, therefore, their design could be investigated without building economic criteria into the model? The author conceded that this was a tender point. He would have liked to have given facilities for more variability of the metallurgical information. He pointed out, however, that while there was no overdesign for conservatism built into his system, some overdesign was inevitable as the performance characteristics given by the manufacturers were generally conservative. Also, in his system, if lower recovery was allowed for, the system would nut through more tonnage."

Jan 1, 2014

By F. Yang, S. S. Long

Mixed fatty acids, such as oxidised paraffin soap, are frequently used as a substitute for oleic acid in flotation of scheelite in China. Not only because it is cheaper than oleic acid, but also because it is superior in flotation performance to oleic acid. This superiority is generally attributed to the mixed fatty acids' synergistic effect. In this paper, the synergistic effect of oxidised paraffin soap was investigated. We found it mainly consists of a series of saturated fatty acid salts, with six to nineteen carbon atoms. All the contained fatty acids were classified into four groups based on their chain length to make the research work practical. Also, the groups were labelled as 1, 2, 3, and 4 in order. The research was simplified into studying the synergistic effect of four equivalent collectors, instead of fourteen fatty acids. It is justified by the fact that neighbouring fatty acids are expected to have a similar flotation performance. The synergistic effect of the four groups of fatty acids was studied by single-mineral flotation with single groups, binary mixtures, ternary mixtures, and the full component, as collector respectively. The flotation performance index and synergy value were introduced to evaluate flotation performance and synergistic effect of groups, respectively. The results show that the mixture 1+2+3 has the strongest synergy of all followed by the mixtures 1+3 and 2+3. The mixture 3+4 and 1+2, on the other hand, have negative synergy. The synergistic effect of mixtures of groups indicate that being consecutive in length and a broad range of lengths are vital for fatty acids to enhance synergy. Group 3 is fundamental for the collecting action of 733 oxidised paraffin soap in the flotation of scheelite. The fatty acid soap in group 4 is not suitable for flotation due to its low solubility. Keywords: Mixed collectors, synergistic effect, scheelite

Jan 1, 2020

By M. Saghaeian, R. Hejazi, V. Sheikhzadeha, A. H. Baladastian, A. Dehghani Ahmadabadi

This paper describes research done to remove apatite (phosphorus) from hematite ultrafine (70% finer than 25 micron) concentrate, recovered by electromagnetic separators at the FST Tailing Recovery Plant located in Chadormalu Iron Ore Complex through reverse froth flotation. As a result, iron and phosphorus content in magnetic concentrate (flotation feed) were 53.52% and 0.58%, respectively. Therefore, to increase the Fe content and decrease the P content of the sample, reverse flotation tests were applied. Chemical reagents used in this research consisted of sodium silicate as a depressant, sodium hydroxide and sodium carbonate as pH regulators, Alke & Dirol as fatty acid collectors and MIBC as frother. Process parameters including dosages of collectors, depressant and frother, preparation times of depressant and collectors, steps and time of frothing and pH range were selected. After doing flotation tests, in optimum condition, dosages of collectors were 1200 g/t, depressant 1200 g/t, pH in the range of 9.5 to 10, preparation time of collectors in the first step was eight minutes and at the other steps, four minutes; the number of frothing steps 4 and frothing time in each stage was three minutes. In this case, it was observed that the amount of phosphorus in the final concentrate was reduced to 0.05%, the Fe content increased from 53.52% to 61.66% and the Fe recovery achieved was 82.21%. Keywords: Iron ore, hematite ultrafine concentrate, iron and phosphorus content

Jan 1, 2020

By J. Pelders, F. Magweregwede, S. M. Rupprecht

Increased depths of conventional gold and platinum mines, longer travelling times as working places move further from the shaft, and ancillary activities taking place in the mining cycle reduce the useable time spent at them workface. Current shift lengths of 8 hours 20 minutes may no longer be adequate ton complete required mining activities.The impact of mineworker commuting times on shift work is also not well understood. The aim of this research was to draft a framework to optimize shift cycles in order to maximize productivity, health, safety, and wellness in the South African mining sector. The framework was informed by a review of the literature, case studies at a local gold mine and platinum mine, and a workshop with industry experts. The findings indicate potential advantages of extended shift lengths and continuous operations, such as improved productivity, asset utilization, and employee morale. However, concerns included fatigue and the associated safety hazards, particularly when working longer shifts, night shifts, and numerous consecutive shifts. Job demands, personal factors, and commuting times are further considerations when scheduling shifts. The ideal shift system for the mining sector should holistically consider and balance operational requirements, health and safety, and employees’ and their families’ requirements, and suit the unique needs of each operation. Changes in shift cycles will require a structured change management process, which involves all stakeholders, and could help to enhance the viability of the South African mining sector.

Aug 1, 2021

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

Opencast coal mining is responsible for the greatest area of land disturbance across all of the commodity types in South Africa. Many thousands of hectares have been rehabilitated to date and, although rehabilitation performance is not always measured or reported, a significant database, spanning 24 years, has now been analysed to identify the main shortcomings holding back rehabilitation sustainability across the industry. Data from 48 different collieries with rehabilitation performance scores measured from 2000-2024 were analysed. A standardised assessment framework was implemented at all 48 collieries, focusing on aspects of land capability, soil fertility, landscape form and drainage, vegetation species composition and basal cover, implementation of maintenance programmes, and prevalence of invasive alien plants. The findings show that, although invasive species management, plant species composition, and plant basal cover are often adequate, the implementation of aftercare and maintenance programmes (influencing soil fertility) and deficiencies in overall landform design and drainage systems are most significant in preventing overall rehabilitation progression and self-sustainability. Integrating these during design and rehabilitation execution, followed by intensive maintenance (especially in the first five years post-topsoiling and seeding) will be key for the overall industry performance to improve to acceptable levels. The database is biased towards collieries that actually do undertake rehabilitation and that do measure it, hence the actual industry performance is likely worse than what is presented. Due to the substantial hectarages involved and the main post-mining land uses being grazing and crop production, the industry cannot afford to keep perpetuating deficiencies in achieving the foundational aspects of rehabilitation that would pave the way for sustained economic future use.

Apr 25, 2025

By C. O’Donova, E. Adam, L. A. Torres-Cruz

High-profile failures of tailings dams illustrate the significant safety challenge they pose. The decant pond of such facilities plays an important role in their mechanical stability. This study investigates the feasibility of using public multispectral data collected by the Sentinel-2 satellite mission to monitor the area of the decant pond. The Sentinel-2 mission has a revisit time of 5 days and the data used herein has a spatial resolution of 10 m/pixel. We considered two water-detection metrics: the normalized difference water index (NDWI) and the near-infrared (NIR) reflectance. Implementation of the method at a South African platinum tailings dam illustrates the capabilities and limitations. Public, sub-metre resolution true-colour imagery served as validation data. There is good agreement between pond area measurements based on Sentinel-2 and the validation imagery. These results suggest the feasibility of using Sentinel-2 data to supplement the monitoring of the decant pond.

Apr 2, 2022

By R. M. Mashishi, T. Malehase, O. J. Okonkwo

The concentrations of selected trace elements (As, Cd, Hg, and Pb in run-of-mine (ROM) coal, discard, and coal product were investigated to assess the efficiency of beneficiation in reducing trace element concentrations and ascertain any implications regarding environmental compliance to regulatory frameworks. Samples were collected from a colliery in Mpumalanga Province twice a month for a period of 24 months. The samples were ashed to approximately 0.21 mm, then digested in a mixture of 70% HNO3 and 40% HF and analysed using inductively coupled plasma-mass spectrometry (ICP-MS). Except for Pb, the mean concentration of all elements decreased from the ROM stage to the coal product stage. The order in which trace elements occurred from the highest to lowest throughout the production chain was Pb>As>Hg>Cd. With the exception of Cd, the mean trace element concentrations in the discard were above the total concentration threshold (TCT) set for landfill disposal. The As, Hg, and Cd concentrations in the product were well below the thresholds for all land uses. However, Pb concentrations in the product coal were above legal limits, which is of concern with regard to environmental compliance and the performance and marketability of the product.

Dec 13, 2023

By B. Genc, C. Gous

Spontaneous combustion during coal mining operations is a major problem that affects the health and safety of workers and causes environmental problems. The phenomenon is associated with the presence of coal, coal shale, and pyrite. In 2020, a premature detonation incident occurred at an iron ore mine where the waste material contains black carbonaceous shale units known to be associated with pyrite. The spontaneous combustion propensity and properties of samples of the black carbonaceous shales from the mine were examined and compared with samples from the Witbank Coalfield. The spontaneous combustion liability indexes of these samples were correlated with X-ray fluorescence (XRF) and proximate and ultimate analyses using linear regression. The Wits-Ehac Index classification results show that the samples were between medium and high risk. The linear regression analysis showed very poor correlations between the Wits-Ehac Index results and the XRF and proximate and ultimate results. The most valuable relationship found is between the presence of relatively high sulphur (greater than 3%) and ground reactivity with nitrate-bearing explosive emulsion.

Jun 5, 2023

By T. Nghipulile, M. Moys, M. Bwalya, H. Simonsen

The quest for efficiency in comminution is an ongoing concern as comminution usually constitutes a major cost component in the metal production industry. Such improvements can be made by circuit optimization or development of more efficient equipment. A novel crusher, known as the rotary offset crusher (ROC), promises to deliver in this space. The ROC was invented in 2002 by Michael Hunt, Henry Simonsen, and Ian Sinclair, but failed to garner enough support to progress to production. The original design concept was recently rekindled, and a laboratory version of the crusher has been built and commissioned at the University of the Witwatersrand. The crusher is simple in design, with two cylindrical discs that are parallel to each other, and, as the name implies, there is an offset between the vertical axes of the discs. The top disc has a conical section on its lower face, and this creates a crushing zone between the opposite faces of the two spinning discs. Centrifugal motion transports particles through the crushing zone. Batch experiments have been conducted with quartz at various crusher settings (discs offset, rotational speed, and vertical exit gap) for various feed size distributions. The indications so far suggest that the disc speed is a key factor affecting the performance. Size reduction ratios as high as 11 were recorded from experiments with quartz at a speed of 830 r/min.

Jan 1, 2021

By R. Mumbi, M. Peart, E. Arinaitwe, B. Mbao, J. Zulu

Since 1925, xanthates have been widely used in sulfide flotation due to their low cost, ease of manufacture, and ability to float most value species. However, the industry's increasing need for safer and more selective alternatives, driven by low head grades, poor-quality, difficult-to-process ore with complex mineralogy, and stricter environmental regulations, has led to the development of Solvay's AERO® XR series of collectors. These custom-formulated products are based on greener chemistries and offer metallurgical benefits that are similar to or better than those of xanthates, without the safety concerns. Developed through Solvay's Flotation Matrix (FM) 100 approach, the XR series collectors are suitable for a wide range of applications, including the processing of Cu, Zn, and Cu-Ni, as well as the flotation of precious metals. This paper will highlight the differences between xanthates and XR series collectors, and present case studies of their successful commercial application at various global operations.

Jan 1, 2023

By P. J. Petit

"The complex planning required to achieve any planned production yields multiple and dissociated responses over the life of project (LOP). The customary decision-making process negates the possibilities of developing optimized and integral solutions from operating levels up to business and strategic levels. This results in an inefficient project or overall underperformance of the operation.In the project setting, disconnected trade-offs and improved performance studies become inadequate, because they are site-specific and use only a few comparative parameters. They are often based on a small data-set.Decisions taken to achieve overall objectives require the correct determination and dissemination of key performance indicators (KPIs). The KPIs indicate efficiency in operation, whereby the marginal rate of technical substitution corresponds to the rate of production. It is the necessary condition for optimization. Performance realization for sustainability follows optimization modelling, the latter often being presented with financial results such as business net present value (NPV). It considers techno-financial constraints and provides a strategic and aligned outlook of KPI decisions for an enhanced and integrated outcome.This paper explains a mining case study that is rendered efficient, and through business optimization (BO) short-term and sustainable targets are reached. Business optimization increases the NPV by 14.7%. This is achieved by challenging conventional decision-making associated with maximizing business value by including environmental externalities within the LOP."

Jan 1, 2016

By P. Mühlen, C. Nelson

Process control optimisation depends a lot on the availability of timely data from production to give operators a chance to make adjustments before potential process upsets or disruptions happen. A lot of data is already available with newer and updated machine technologies, but what about the process upsets coming from the raw materials that we use? They are natural products and therefore they are not of a stable composition or mineralogy. The production process depends on a certain chemical or mineralogical stability of the raw materials when they come to a roaster, kiln or sintering stage. Only then can the proposed reactions take place and the equipment be operated at stable temperatures. Laboratory analytical technologies have the limitation that they depend on representative samples and have a long time delay. Therefore online (real time) analysers are used nowadays in mining applications to obtain an early indication of the actual mined or to-be-processed ore. Most available technologies can only analyse inorganic content on an oxide or elemental level. Near infrared (NIR)- based online analysers can overcome that limitation and give a real time analysis of organic as well as inorganic composition, if required on a mineral level. The paper will present two case studies where the NIR online technology was successfully adapted.: a) Optimising refractory gold ore processing at the Goldstrike roaster operation b) Optimising the sinter process at a Japanese manufacturer. Keywords: Analyser, NIR, online, realtime, gold, roaster, iron ore, sinter, mineral phase analysis

Jan 1, 2020

By H. Möller, L. Mashigo, C. Gassmann

Wire-arc additive manufacturing (WAAM) is a directed-energy deposition technology that uses arc welding procedures to produce computer-aided designed parts, such as three-dimensional printed metal components. A challenge of additive manufacturing is the anisotropy. Interstitial elements play a significant role in the mechanical properties of Ti6Al4V of different grades. In this research, the mechanical properties of Grade 5 and Grade 23 Ti6Al4V were compared for this application. Samples were extracted from WAAM-produced Ti6Al4V walls in different directions (horizontal and vertical) and at different positions (top and bottom). The samples were subjected to optical microscopy and tensile and hardness tests. Grade 5 Ti6Al4V samples were found to have greater strength, greater hardness, and lower ductility, owing to the higher content of interstitial elements compared with Grade 23. The bottom samples had higher strength than the top samples, which is attributed to thermal cycling during manufacturing, resulting in different microstructures.

Jul 1, 2021

By N. Naude, R. Foisy, F. Bornman

Spiral separators have been widely accepted as one of the most flexible gravity separation devices for several decades. The International Journal of Mineral Processing, 84, pp. 118 – 132 mentioned that spirals are for treating material too coarse for flotation and too fine for dense-media separation. Powder Technology V 102, pp 244 – 252, 1999 stated that there exists a genuine need for extending the performance envelope of spirals – whether to treat finer or coarser material than the traditional size ranges. In recent times there has been an upsurge in interest, particularly in the development of newer fine gravity separators. Spiral separators for the recovery of ultra-fine particles have a unique profile, pitch and features to ensure efficient performance. The flow on the spiral trough must be controlled to minimise turbulence that will entrain fine particles in the outer section of the trough. The experimental test work showed a movement of mass from the outer region towards the centre column of the spiral, i.e., from the fine tailings band towards the concentrate. As recovery on the spiral trough is a function of mass yield and grade, the ultra-fine 7 spiral had a better recovery than the HX5. This makes the UF7 an ideal rougher spiral. Keywords: Ultra-fine particles, spiral, design, recovery

Jan 1, 2020

1. Recent books D. K. Hsiao, D. S. Kerr, and S. E. Madnick. Computer security. New York, Academic Press, 1979.276 pp. $18. W. C. J. van Rensburg and S. Bambrick. Economics of the world's mineral industries. Isando, McGrawHill, 1979. R18,95. Soviet metallurgical research 1973-1977. Vo!. 1. Subject index and author index (1963-1972). Vo!. 2. Chronological listing of titles with full bibliographical information (1960-1972). London, Scientific Information Consultants Limited (661 Finchley Road, London NW2 2HN). £24 per set. W. Hoosen. Miners' dictionary. London, Institution of Mining and Metallurgy, 1979. (Reprint.) £11 (£9 for members). G. J. Pitt and G. R. Millward. Coal and modern coalprocessing: an introduction. New York, Academic Press, 1979. 224 pp. $18. D. Stephenson. Rockfill in hydraulic engineering. Amsterdam, Elsevier, 1979. 228 pp. U.S. $45, D.fl.90. 2. NIM reports Report no. 2015 The preparation of synthetic standards for use in instrumental neutron-activation analysis. Report no. 2029 The commissioning of a 5 kW inductively coupled plasma unit for use with a 3,4-metre Ebert spectrograph. Report no. 2032 The Cancer Project: a summary of the computer-aided operation of a 48 MV.A ferrochromium furnace. Report no. 2036 The determination of thallium in ores, concentrates, and metals. Report no. 2040 A solid-state constant-current power unit for the magnetic analyser of the MS702R mass spectrometer. Report no. 2044 The separation and determination of anions by ion chromatography. Computer congress In October 1980, Japan and Australia are hosting the 8th World Computer Congress. This Congress is a triennial event conducted under the sponsorship of the International Federation for Information Processing. INFACON 80 The Second International Ferro-Alloys Congress, organized by IPFEO (Institute of Western European Ferro-alloy Producers), is to be held in Lausanne, Switzerland, on 13th to 16th October, 1980.

Jan 1, 1980

Advances in extractive metallurgy, 1977. Proceedings of the third symposium organised by the Institution of Mining and Metallurgy held from 18-20th April 1977. London, the Institution of Mining and Metallurgy, 1977. 244 pp. £18,50. Coal preparation A meeting of the Organising Committee of the Eighth International Coal Preparation Congress took place in Moscow on 24th and 25th May, 1977. Representatives NIM reports Report no. 1906 An automated instrument for measuring the effects of impurities on cathodic-current efficiency during the electrowinning of zinc. (2nd Sep., 1977). Report no. 1908 An analysis of the replies to a questionnaire on materials of construction for ore hoppers. (16th Sep., 1977). Report no. 1913 The mechanism and rate of reduction of Mamatwan manganese-ore fines by carbon. (2nd Sep., 1977). Report no. 1914 The thermodynamics of the formation of sulphate complexes of iron (111), cobalt (11), iron (11), manganese (11), and copper (11) in perchlorate medium. (15th Sep., 1977). Report no. 1924 The composition of chromite grains from varwUB Witwatersrand reefs. (23rd Sep., 1977). Atomic absorption The Perkin-Elmer Corporation of South Africa is planning to hold an Atomic Absorption Autumn School in Cape Town from 10th to 13th April, 1978. Travel bursaries Two Atlas Cop co travel bursaries for study tours of Swedish mines may be awarded annually to young mining graduates. Stability in coal mining The First International Symposium on the above subject is to be held in Vancouver (Canada) on 5th to 7th April, 1978.

Jan 1, 1978

By V. K. Risinggård, M. Sparta

We report on the development of a finite-element method model for a pilot furnace for the production of manganese alloys. The model is a multiphysics model that addresses material flow, electrical conditions, heat transfer, and physical and chemical transformations. It is capable of studying both quasi-steady and transient states in time-dependent simulations. The model includes common charge materials and fluxes and can simulate production of both ferromanganese and silicomanganese alloys with acid and basic slags, as well as changing charge compositions. The model output provides access to the material distribution in the furnace during furnace runs, temperature profiles, current paths, energy balances, and alloy and slag production rates and compositions.

Apr 16, 2024

By H. Ogasawara

Information on rock stress is important for safe mining in seismically active ground. On a major gold mine, a few tens of crews are continuously conducting geological drilling with small pneumatic machines. However, stress measurements are not often carried out in South African deep-level gold mines. One of the reasons is the drilling diameter that overcoring requires, which is much larger than the diameters used in regular geological drilling, e.g. Boart Longyear Metre Eater, which drills AQ or BQ holes. Larger diameter holes result in slower drilling advance, more load in transportation and handling at sites, and higher cost. In order to enable overcoring in BX size (60 mm diameter), we modified the compact conical-ended borehole overcoring (CCBO) technique that has been suggested by International Society for Rock Mechanics (ISRM) and was originally designed for NX drilling (76 mm diameter). With a single overcoring, the 3-D stress tensor can be determined. We tested this modified method at a depth of about 3 km at Moab Khotsong mine in South Africa. We worked with drilling crew who usually work at geological drilling with the Metre Eater. In January 2011, we tried using regular geological drilling tools (a sequence of a normal BX bit, reamer, and rod) without success. In August and September 2011, introducing stabilizers and thin BX bits, we succeeded. We could complete a cycle of procedures necessary for an overcoring, including shaping the borehole-end conically, glueing a 16-element strain cell, and overcoring, within 2.5 hours. Only 10 cm overcoring is needed, which increases the chance of successful overcoring in heavily fractured conditions. This modified method is suitable for up-dip holes to depths of 10-15 m from tunnels, and has the potential to be widely used at the initial stage of geological exploration drilling at many localities.

Jan 1, 2012

By C. Karageorgos, J. Sakala, A. Prinsloo, B. Ngambi

The sulphide flotation circuit at First Quantum Minerals’ Kansanshi mine in Zambia produced over 100,000 t of copper in 2019. For this circuit, mineralogical analysis has shown that the majority of the copper lost is hosted in fine liberated chalcopyrite, which is a paramagnetic mineral. The objective of this work was therefore to improve fine chalcopyrite recovery in the sulphide flotation circuit at Kansanshi, using a magnetic conditioning technology to agglomerate fine paramagnetic minerals. This theoretically increases the probability of attachment during collision and therefore improves recovery. A four-month paired ‘t’ test plant trial was carried out and comprised of consecutive ON-OFF periods with and without magnetic conditioning in the rougher flotation bank of the sulphide circuit. The experimental design involved assessment of recovery by size based on daily and weekly composite samples of feed and tails, sized using both wet-screening and cyclosizer. Both the daily plant data and the sized samples showed an increase in Cu recovery with magnetic conditioning ON. A 0.56% copper recovery improvement was measured with magnetic conditioning at a 99.4% confidence level. Keywords: Flotation, fine mineral, chalcopyrite, magnetic aggregation

Jan 1, 2020