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By J. J. Taute, G. Chisakuta, P. Bwando, G. Mitshabu

"BASF Mining Solutions have developed a new generation of copper solvent-extraction reagents that offer significant benefits over the existing reagents available to the industry today. Initial laboratory studies and pilot-plant trials have shown that these new reagents offer the benefits of a dramatic increase in resistance to degradation and are nitration-proof. This paper details a recent pilot-plant campaign at a commercial solvent-extraction plant. The main focus was to evaluate the copper/iron selectivity, copper recovery and net transfer of the new reagent compared with the conventional oxime reagents. The new reagent displays similar copper recovery and net transfer capabilities from typical agitation leach solutions. The pilot-plant results show a step change improvement in copper/iron selectivity in comparison with the existing modified and non-modified hydroxyoxime reagents used on the commercial plant. INTRODUCTION Copper solvent extraction (SX) from an acidic aqueous solution is typically accomplished using a hydroxyoxime extractant (Jergensen, 1999; Kordosky, 2000; Szymanowski, 1993). There are three hydroxyoximes from which all standard formulations are derived: 5-nonyl salicylaldoxime (NSAO), 5-dodecyl salicylaldoxime (DSAO) and 2-hydroxy-5-nonyl acetophenone oxime (HNAO). In the case of NSAO, it is necessary to use equilibrium modifiers in order to increase the copper stripped from the extractant (Kordosky & Virnig, 2003). Blends of DSAO, NSAO and HNAO are used to cover a wide spectrum of conditions (Kordosky, 2008). Use of modified aldoximes and reagent blends over the last 30 years has influenced the way copper producers and equipment manufacturers have approached the operation of copper plants. Existing solvent-extraction reagents cater for typical pregnant leach solutions (PLS) of copper mining systems which do not have significant effects on the reagent. Table I illustrates the range of copper concentration, pH values, temperature and iron concentrations for different leaching operations. As conditions become increasingly aggressive (i.e., higher PLS temperatures in primary sulfide leach or high iron content), current reagents become less capable of functioning according to expectations. One example is the effect of high iron (Fe3+) concentration in PLS and operating SX to achieve high copper recoveries. The ferric is partially chemically extracted and is transferred to elctrowinning (EW) during the stripping stage. To avoid a build-up of iron in electrolyte, which negatively affects current efficiency, a bleed of electrolyte is required. This bleed leads to excessive consumption of reagents, such as cobalt added to the EW process, and thus increases operational cost."

Jan 1, 2015

By E. Córdova, A. Anani, W. Nyaaba

Optimization of panels, haulage fleet, and waiting area involves deterministic and low-fidelity methods and experiential knowledge. The process is challenging because coal recovery and operational capabilities must be considered in the solution. The approach in this manuscript comprises the development of an integrated stochastic simulation model of a coal room-and-pillar system that addresses these challenges. The decision variables evaluated are panel width, number of shuttle cars, and change-out time (COT). The results show that the mine should implement the shortest possible COT, decreasing the cycle time and thereby increasing productivity and continuous miner (CM) utilization. The highest productivity and CM utilization for a fleet size of three shuttle cars is found in the 15-entry panel width. For the evaluated fleet sizes, the 19-entry panel width is optimal for the four and five shuttle cars. Among the three variables studied, panel width and fleet size had the most significant effects (5% increase) on the CM productivity, cycle time, and utilization.

Apr 2, 2022

By J. Pelders, G. Nelson

"Fatigue is a significant concern in the mining industry as it is a causal or contributing factor in many incidents and accidents. Fatigue can be caused by work- and non-work-related factors. There is a lack of information about associations between demographic and other non-work factors, and fatigue. This study aimed to assess associations between demographic, work, living, and socioeconomic conditions, and lifestyle characteristics, and fatigue at a platinum smelter in South Africa. Eight interviews with management and two focus groups with production workers were conducted, and 75 questionnaires were completed by production and other workers. Both work- and non-work-related factors were considered to be causes of fatigue. These factors included overtime, shift work, high workloads, activities performed outside of work, age, race, housing tenure, diet, sleep disorders, stress, and job satisfaction. In general, higher levels of fatigue were reported by younger participants, those who rented accommodation, ate less healthily, had a sleep disorder, and those with high levels of stress and low job satisfaction. As various demographic, lifestyle, and wellness-related factors were associated with fatigue, both work and non-work contributors should be addressed in fatigue management plans. BackgroundFatigue may be defined as ‘a state of impaired mental and/or physical performance and lowered alertness arising as a result of, or a combination of, hard physical and mental work, health and psychosocial factors or inadequate restorative sleep’ (BHP Billiton, 2005). Williamson et al. (2011) define fatigue as a biological drive for recuperative rest. Sleepiness and fatigue are related, and the terms are often used interchangeably. However, sleepiness, more specifically, can be defined as sleep propensity, or a person’s tendency to fall asleep (Hossain et al., 2003; Shen, Barbera, and Shapiro, 2006).Increasing levels of fatigue and sleepiness are associated with lapses in attention, errors, response slowing, fluctuations in alertness and effort, and impaired attention, working memory, long-term memory, decision-making, and creativity (Alhola and Polo-Kantola, 2007; van Dongen and Dinges, 2000). Fatigue is also associated with adverse effects on mood and impulsive behaviours (Alhola and Polo- Kantola, 2007; Minkel et al., 2011; Schwarz et al., 2013). It is a significant concern in the mining industry as it is commonly identified as a causal or contributing factor in many accidents and injuries (Schutte, 2009). Fatigue can also lead to long-term health problems, including digestive problems, heart disease, stress, and mental illness (Shaw, 2003)."

Mar 1, 2019

The nature of metallurgical engineering?applying and optimising chemical and physical processing of ores into useful materials?is reviewed. Important trends that shape the context in which metallurgical engineers practise are identified ? increased global production of primary metals, declining prices, environmental constraints, and increased property requirements of materials. A successful department of metallurgical engineering is one which employs a team of academic leaders to develop graduate engineers who are productive across the full range of metallurgical processing. Keywords: metallurgical engineering, primary metals, commodity prices, processing

Jan 1, 2003

VERSLAG- REPORT No. 1365 STUDIES OF INCIPIENT FUSION IN THE SYSTEM CHROMITE- MgO- Al2O3-SiO2-C 5th January, 1972 Investigator: N. A. Barcza SYNOPSIS A fundamental study was made of twelve chromite ores by use of a thermobalance under atmospheric and reducing conditions. It was found that their thermal behaviour under atmospheric conditions can be related to the mineralogical composition of the chromite spinel and the gangue. The overall mechanism of reduction with solid carbon over the temperature range of 1 200 to 1 500°C was shown to be diffusion of carbon through the reaction product. The effects of additions of fluxes and variations in particle size on the kinetics and mechanism of reduction were determined. It was shown that carbon monoxide does not reduce chromite ore up to temperatures of 1 550 °C, and it can therefore be eliminated as the diffusing reducing species. However, the reaction product of reduction, namely a mixed carbide of iron and chromium, was shown to be an effective reducing agent for chromitc ore, while also facilitating the transport of carbon. VERSLAG - REPORT No. 1380 AN ELECTROCHEMICAL MODEL FOR THE LEACHING OF URANIUM DIOXIDE 10th January, 1972 Investigators: C. R. S. Needes, M. J. Nicol SYNOPSIS A correlation between the rate of leaching of UO2 and the electrochemical properties of the oxidant concerned has been derived. This correlation is found to be borne out by experimental results. Certain effects observed in UO2 leaching and hitherto unexplained have been clarified in terms of an electrochemical mechanism. Experiments have shown that the mixed potential of a UO2 electrode gives a measure of the rate of dissolution of UO2. Its significance to commercial practice is discussed. CONCLUSIONS (I) The dissolution of UO2 in the presence of a number of oxidants can be explained in terms of an electrochemical mechanism. (2) The mixed potential of the UO2 electrode is a measure of the rate of UO2 leaching. This principle could be used in the control of industrial leaching operations. (3) A simple treatment has provided a mathematical basis for a fundamental correlation between the rate of U02 dissolution and the chemical properties of the oxidants concerned. This relation has been found to agree well with experimental results. (4) A number of phenomena occurring during the leaching of UO2, hitherto not explained in a satisfactory manner, have now been clarified in terms of an electrochemical mechanism.

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

In this study we explore the use of a novel numerical modelling approach to study the effect of pillar reinforcement on pillar stability. Case studies in the literature indicate that tendons, strapping of the pillars, and shotcrete or thin spray-on liners are commonly used to reinforce pillars. No clear methodology exists to select the type of support or to design the capacity of the support required, however. This has led to ongoing collapses in some mines in spite of heavy support being used to reinforce unstable pillars. A limit equilibrium model with confinement on the edge of the pillar was used to simulate the interaction of the support with the failing pillar. The model correctly predicts that an increase in confinement will lead to a decrease in the extent of pillar failure. As the displacement discontinuity boundary element method allows for the efficient solution of largescale bord-and-pillar layouts, the effect of pillar confinement can now be studied on a mine-wide scale. Accurate calibration of the limit equilibrium model is, however, required before this method can be used for the design of effective pillar support.

May 3, 2023

By D. Orynbassar, N. Madani

This work addresses the problem of geostatistical simulation of cross-correlated variables by factorization approaches in the case when the sampling pattern is unequal. A solution is presented, based on a Co-Gibbs sampler algorithm, by which the missing values can be imputed. In this algorithm, a heterotopic simple cokriging approach is introduced to take into account the cross-dependency of the undersampled variable with the secondary variable that is more available over the entire region. A real gold deposit is employed to test the algorithm. The imputation results are compared with other Gibbs sampler techniques for which simple cokriging and simple kriging are used. The results show that heterotopic simple cokriging outperforms the other two techniques. The imputed values are then employed for the purpose of resource estimation by using principal component analysis (PCA) as a factorization technique, and the output compared with traditional factorization approaches where the heterotopic part of the data is removed. Comparison of the results of these two techniques shows that the latter leads to substantial losses of important information in the case of an unequal sampling pattern, while the former is capable of reproducing better recovery functions.

Aug 1, 2021

By E. Kalhan, C. Kincal

One of the biggest problems in open pit mining is slope stability. The avoidance of slope stability problems depends on a comprehensive assessment of environmental and operational factors such as geology, climate, and mining activities. In the light of these considerations, slope geometries should be determined in accordance with engineering principles. In this research, the slope stability of rock slopes in a mine opened in a gneiss geological unit has been studied. Production activities were ceased in 2019 due to the slope movements in the eastern part of the quarry. In order to safely continue the production, field works were primarily carried out. To assess slope stability, detailed discontinuity surveys were carried out on bench faces. Subsequently, kinematic and numerical analyses were employed to identify geometries that are expected to maintain stability under the prevailing geological structures and environmental constraints. Engineering geological studies such as scanline measurements in steps and investigation of potential failure mechanisms by kinematic analysis technique were carried out. Small module reactor and Q-slope rock mass classification systems were used to evaluate slope stability. Based on these classification systems potential unstable rock slopes were identified and thematic maps were created using geographic information systems. The most suitable slope geometries are suggested for these slopes. In addition, the improvement methods suggested by the rock mass classification systems were proposed for these slopes.

Sep 1, 2025

By Nicolle Krusberski

Potential errors in XRF analysis are discussed and investigated with specific reference to the analysis of ilmenite samples. A selection of ilmenite samples was chosen and prepared using two XRF preparation techniques: pressed powder pellet and unroasted fusion bead. The merits of the two methods have been discussed in this paper for ilmenite analysis by XRF. Recommendations have been made regarding the use of pressed powder pellets especially with regard to the mineralogical effects that were evidenced during this investigation. The fusion bead technique was found to be far more accurate and able to meet short turnaround requirements provided the calibration methodology used is specific to the grade of samples analyzed.

Jan 1, 2014

By E. Y. Baafi, H. Fan, W. Zeng

We present a discrete event simulator, TSJSim (Truck-Shovel JaamSim Simulator), for evaluating the stochastic and dynamic operational variables in a truck-shovel system. TSJSim offers four truck allocation strategies: Fixed truck assignment (FTA), Minimizing shovel production requirement (MSPR), Minimizing truck waiting time (MTWT), and Minimizing truck semi-cycle time (MTSCT) including the genetic algorithm (GA) optimization and the frozen dispatching algorithm (FDA) optimization rules. Multiple decision points along the haul routes for all the trucks close to the decision points were included in the model. The simulation results indicate that the trends associated with production tons and queuing time utilizing the four truck allocation strategies (MSPR, MTWT, FDA, and GA) all demonstrated similar patterns as the fleet size varied. As the system fleet size increased, the system production tons under these strategies at first increased significantly and then remained relatively constant; the queuing time relating to these strategies showed a positive relationship with the system fleet size. The bunching time decreased when the truck allocation strategies were applied in the model. In the simulated truck-shovel network system with multiple traffic intersections, by assigning the trucks at the intersections, both productivity and fleet utilization increased.

Dec 13, 2022

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 A. Drumond, J. F. C. L. Costa, M. G. Lemos, A. L. Rodrigues, F. G. Niquini

The past decade has seen a renewed possibility of using machine learning algorithms to solve a large collection of problems in several fields. Data acquisition for mining operations has increased with the growth in sensor-based technologies, and therefore the amount of information available for mining applications has dramatically increased. Ore sorting equipment is available for separating ore from waste based on differences in physical properties detected by a real-time analyser. The separation efficiency depends on the contrast in these properties. In this study we investigate the application of machine learning models trained using data from the output of a dual-energy X-ray ore sorting apparatus at a gold mine. The particles were first hand-sorted into ore and gangue classes based on their mineralogical composition. Classification models were then used to help decide the balance between the number of true and false positives for ore in the concentrate, with a view to economic parameters, using their receiver operator characteristic (ROC) curves. The results showed AUC (area under the ROC curve) scores of up to 0.85 for the classification models and a maximum reward condition Fpr/Tpr around 0.5/0.9 for a simplified economic model.

Aug 8, 2024

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 F. Mwaura

"The aim of the audit was to determine whether the mining project environmental impact assessments (EIAs) in Kenya are undertaken according to international best practice. A sample of 50 EIA reports for the 2007–2016 period was evaluated using 18 criteria in the Environmental Law Alliance Worldwide (ELAW) guidelines. The findings showed that only two criteria were considered ‘excellent’ according to the ELAW guidelines, namely baseline environmental assessment and prediction of physical impacts. Six criteria were found to be ‘satisfactory’, including prediction of social impacts, analysis of alternative options, and impact mitigation. The reports were quite weak in terms of: consideration of all phases in the mining cycle, environmental regulatory framework, prediction of biological impacts, stakeholder consultation and engagement, integration of human right issues, and integration of climate change and cost-benefit analysis. It is therefore recommended that the Kenyan National Environment Management Authority (NEMA) should consider tightening the EIA terms and conditions in the approval of statutory terms of reference (ToR) for full-scale mining EIAs to ensure improved performance of EIA as a tool for environmental protection. IntroductionThe nexus between society and the environment has continued to generate interest because the environment is the source of goods and services that sustain the various needs of human beings as outlined in the UN sustainable development goals (SDGs) (Armstrong and Peart, 2000; Sutton 2004; Chakrabarti 2007; Strange and Bayley 2008). All the five generic categories of societal needs, namely physiological needs (food, water, clothing, medicines, etc.), residential and occupational needs (shelter, transport, energy, etc.), economic needs (tradeable goods and services), leisure and recreational needs (tourism), and cultural and spiritual needs (e.g. sacred resources and ecosystems) (Mwaura et al. 2016) are addressed by the environment. Consequently, a wide range of development sectors have been established around the world in order to address the above needs (Lederer, Galtung, and Antal, 1980; Rammelsberg et al., 2006; Noonan, 2014). All these development sectors rely entirely on the environment for their proper functioning, as shown in Table I."

May 1, 2019

By E. Keskinkilic

"Electrical steels are used in motors, power generators, and transformers for electrical applications owing to their superior magnetic properties. These properties are attributed to the presence of a significant amount of silicon in the steel composition. Silicon steels are mainly grouped into two categories: grain-oriented (GO) and non-grain-oriented (NGO). The Si content of silicon steels is generally between about 0.50% and 6.5%. Therefore, silicon steels are further classified as low-, medium-, and high- Si steels. In this paper, liquid steel processing practices for certain silicon steel grades are outlined by considering a steelmaking company that integrates a basic oxygen furnace (BOF), a ladle furnace (LF), and an RHtype degassing unit (RH). Possible problems are identified, suggestions are discussed, and conclusions are drawn on the basis of real plant data. IntroductionSilicon steels are widely used in motors, power generators, and transformers for electrical applications owing to their superior magnetic properties. They are mainly grouped into grain-oriented (GO) and non-grain-oriented (NGO) silicon steel grades. However, the differences in the properties and thermomechanical production of GO and NGO grades are outside the scope of this paper. In this study, liquid steel processing of certain silicon steels will be discussed. In the integrated iron and steelmaking process, converters are the primary steelmaking units that are used mainly for decarburization and removal of phosphorus, and for obtaining liquid steel with a specific chemical composition and suitable temperature for secondary steelmaking operations. Ladle furnaces are a type of ladle metallurgy station consisting of electrical and/or chemical heating facilities for adjusting the liquid steel temperature during alloying. Various types of vacuum units are used for decarburization and removal of nitrogen, hydrogen, and sulphur, depending on the metallurgical conditions of the vacuum units. In this study, an actual steel-production company is considered in which the primary steelmaking operation uses a basic oxygen furnace (BOF) converter with N2/Ar bottom blowing, and the secondary steelmaking operations involve (1) a ladle furnace (LF) heated by three graphite electrodes and equipped with Ar and N2 top/bottom mixing facilities, and (2) an RHtype (circulation) vacuum degassing unit equipped with a top-blowing attachment for oxygen blowing and an Ar-purging system from an up-leg snorkel."

Jan 1, 2018

By A. Mainza, I. Govender, Elbasher M. E. Ahmed

A mechanistic description of axial segregation in rotating drum flows remains an open question. Consequently, optimal mixing of grinding balls and rocks for efficient breakage, maximum production of fines, and slurry transport is seldom achieved. Experimental and numerical studies of granular mixtures in rotating drums identify alternating axial bands that eventually coarsen in the long-term limit. Most models of axial segregation are limited to binary mixtures and cannot always predict the logarithmic coarsening effects observed experimentally. A key missing factor is a robust description of the axial free surface profile that is valid across a wide range of flow regimes. We present a practical model of the axial free surface profile by linking it to readily-derived geometric features of the cross-sectional S-shaped free surface profile. A parametric study shows good agreement with experimental measurements reported in the literature and heuristically valid trends.

May 1, 2021

By H. Laitala, M. Lampi

Metso Outotec has developed a wide range of solvent-extraction technologies over decades and has introduced Metso Outotec VSF®X solvent-extraction plant. Standardized and modularized, Metso Outotec VSFX Plant provides a novel way to design, manufacture, transport, install, operate, and maintain solvent-extraction plants far better than in the past with highly sustainable and safe methods. For the customer, this means fast-track projects with savings in means of time, costs, quality, and operation. Sicomines and Metso Outotec have together implemented and commissioned a modern and efficient copper solvent-extraction plant. Plant commissioning and ramp up of the plant were fast and the plant is now operating efficiently. This paper presents Sicomines’ VSFX copper solvent-extraction project and gives a sight into operating figures for the plant.

Jan 1, 2023

By J. Petersen, T. Moyo, J. Dinga

The leaching of chalcopyrite in ferric sulfate media is notorious for its slow and inhibited kinetics. Different methods have been proposed to improve the kinetics, including the use of organic compounds as additives to the leaching media. In this study, the enhancing effect of methanol, ethanol, 1-propanol, and 2-propanol on the leaching of chalcopyrite in aerated acid ferric sulfate solutions using different reactor systems was investigated. The results revealed a clear improvement of copper dissolution by methanol and 1-propanol relative to tests with no additives under similar conditions. Operating a continuous-flow mini-column reactor yields surprisingly good results, potentially related to the maintaining of a consistent leaching micro-environment on the mineral surface. Scanning electron microscopy studies showed that the alcohols result in the removal of surface deposits formed during the anodic dissolution, potentially thus facilitating improved cathodic reduction of the ferric ion to drive the anodic dissolution.

Jan 1, 2023

By L. Tartibu, S. Assuli, P. Nkul, A. Kabimba, W. Elongo, N. Makhotla, D. F. Verwey, F. G. Ndiitwani, J. Bilali, T. Mukongo

The presence of colloidal silica negatively impacts various hydrometallurgy processes. This paper details the nature of colloidal silica, operational issues caused by colloidal silica, as well as various mitigation measures. MMG Kinsevere observed severe phase-continuity instability, increased crud formation, and reagent consumption, and reduced current efficiency in electrowinning with a deterioration in copper quality. Historical mitigation measures were initially implemented but failed to solve the problem. MMG Kinsevere successfully achieved efficient silica removal without adverse effect on the solvent extraction with the use of DEHSCOFIX® SC12 coagulant. A week into the coagulant trial, silica concentration had dropped from > 1500 mg/L to within 500 mg/L. The solventextraction plant recovered its stability and again operated at maximum capacity. Additionally, improvement was observed on current efficiency and copper cathodes quality with use of the coagulant.

Jan 1, 2023

This paper examines the new water-hydraulic (hydropowered) drill rigs that have been developed and proven in the last decade primarily in tabular, shallow-dipping, narrow-reef hard-rock South African mines. These include drill rigs for flat-end tunnel development, narrow inclined raises and winzes, large inclines and declines and longhole-based developments such as ore passes and vent raises. The hydropower technology rigs offer advantages both in safety and performance over traditional compressed-air-powered, hand-held development, and are generally more cost-effective than imported oil electro-hydraulic drill rigs. Furthermore, hydropowered rigs are inherently energy-efficient. The benefits of hydropower are discussed and a ?comprehensive development model? is presented which demonstrates that ore-bodies can be accessed in significantly shorter times. ?Localized? half level hydropower systems are introduced and a range of ancillary equipment available is listed.

Jan 1, 2012