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By M. S. Shishvan, J. Sattarvand, R. S. H. Meij

Navigating miners during an evacuation using a smart evacuation technology can significantly decrease the evacuation time of an underground mine in case of an emergency. This paper presents a mathematical programming model to calculate the most efficient escape path for each miner as a critical component of the smart evacuation technology. In this model, the total evacuation distance of the crew is minimised and scenarios with blocked pathways, and stamina categories for the miners are simulated. It was found that all the tested scenarios are technically feasible. Using the feature that filters out blocked pathways has no downsides, as safer routes are calculated, and there is no penalty in the computation time. The paper also discusses the social and technical issues that need to be overcome before the algorithm can be implemented as an actual escape solution.

Sep 1, 2021

By S. A. Villalobos, F. A. Villalobos, and L. E. Aguilera

Rockburst events have been a serious problem for many years in many mines worldwide, and in particular at El Teniente mine in Chile. El Teniente is the largest copper mine in the world, located in the Andes Cordillera where high stress levels are present due to intensing mining activity in addition to complex geology. Consequently, the study and management of the rockburst threat are necessary. In this work, the case of the Diablo Regimiento (DR) mine within El Teniente is studied. The energy capacity of dynamic support systems is determined for different tunnel geometries based on two kinetic methodologies, using data from DR. Initially, rockburst potential is determined by means of a stress analysis around different tunnel geometries through the boundary elements method. In the first methodology a yielding zone (YZ) is estimated for each excavation geometry using the finite element method FEM. The second methodology involves the definition and determination of a critical strain energy (SE) around each excavation geometry using a FEM numerical analysis. In both cases, peak particle velocity PPV is estimated by a scaling law, which is subsequently adjusted due to tunnel amplification effects. According to the results, and knowing the working energy capacity applied in DR mine, it was found that the values of energy capacity for the rock dynamic supports were better estimated by the YZ-PPV approach than by the SE approach.

Sep 1, 2022

By D. F. Caicedo, I. A. Brum, L. A. Betancourt

Ferricyanide ()()*is one of the most stable cyanometallic complexes present in the gold mining effluents. This cyanocomplex is hard to degrade by natural attenuation and generates a negative impact on aquatic environments. Although free cyanide (CN-) can be obtained by acidifying the solution, the CN- is lethal for all forms of life. The oxidation of ()()* in a typical photocatalitic system was evaluated with the addition of H2O2. To verify the degradation, chemical parameters, such as free cyanide, the formation of ammonia, nitrate, and total iron were analysed at the end of the process. The degradations obtained were up to 70% in a heterogeneous photocatalysis system with TiO2, and a low rate of dissociation was observed by photolysis. The best result was achieved with the H2O2 and TiO2 photocatalytic system, and the stoichiometric concentration was about 2.5 times less than the peroxide used in the real gold mining industry, reaching 83% degradation. The photocatalytic process obtained less toxic byproducts than the original synthetic ferricyanide used as mining wastewater. Keywords: Cyanide, heterogeneous photocatalysis, titanium dioxide, UV radiation, gold wastewater

Jan 1, 2020

By N. Hamlef

In this study, the effects of heat treatment on phase formation and surface morphology of the Cr-Pt coated system are investigated using X-ray diffraction and electron microscopy techniques. The CrPt andCr4Pt (Cr3Pt - A15 type) phases were formed after heat treatment of the coated samples. Heat treating at 1000°C renders a distinct island coating morphology that is non-continuous in nature. A diffusional model is proposed for this coated system with regards to the surface morphology formation after heat treatment.

Jan 1, 2014

By D. F. Malan, R. P. Els

The limit equilibrium model, used in displacement discontinuity codes, is a popular method to simulate pillar failure. This paper investigates the use of physical modelling to calibrate this model. For the experiments, an artificial pillar material was prepared and cubes were poured using the standard 100 mm × 100 mm civil engineering concrete moulds. The friction angle between the cubes and the platens of the testing machine was varied by using soap and sandpaper. Different modes of failure were observed depending on the friction angle. Of interest is that significant loadshedding was recorded for some specimens which visually remained mostly intact. This highlights the difficulty of classifying pillars as failed or intact in underground stopes where spalling is observed. The laboratory models enabled a more precise calibration of the limit equilibrium model compared to previous attempts. Guidelines to assist with calibration of the model are given in the paper. The limit equilibrium model appears to be a useful approximation of the pillar failure as it could simulate the stress-strain behaviour of the laboratory models.

May 3, 2023

By G. de Tomi, G. C. Teodoro, E. Rodovalho, T. M. El Hajj, J. A. S. Tenório

The selection of an underground mining method stems from a multivariate analysis that considers geomechanical, geological, economic, and operational parameters. Even after identifying the most compatible method, there is no assurance that the mining company will achieve the best performance. The geological complexity of some deposits requires adaptations of methods described in the literature to obtain more selectivity and reduce mining waste. There are some studies on geometry of underground structures, but a methodology that describes an adaptation of a room-and-pillar mining method for ore bodies with down-dip varying from 20° to 25° is novel. The present work aimed to reduce dilution by adapting the traditional room-and-pillar mining method (TRP) to inclined ore bodies. This new method is entitled short-hole room-and-pillar (SHRP). The equations that measure the dilution are defined according to the geometry of stopes and openings. The results comprise comparative analyses of the operational and planned dilutions to measure the performance of the SHRP method. The average operating dilution of the SHRP method was more than five times lower than the planned dilution according to the TRP method. Low operational dilution indicates high selectivity of the method and its potential to reduce underground mining tailings.

Sep 9, 2024

By A. Muller

The magnesia-carbon refractories used in the ConArc process experience severe wear as a result of the varying slag composition during the blowing phase. This work determines the basicity range in which minimum as well as maximum refractory wear was experienced by the magnesia-carbon refractories during service. In order to determine an optimum slag composition, the crucible test in an induction furnace was used. The magnesia-carbon refractory bricks were cut into cylindrical crucibles to which a synthetic slag in the form of pellets was added. The basicity (B2) of the slag was varied from 0.5 to 3. Tests were done at 1 600°C for one hour. Apart from the crucible test in an induction furnace, visual inspection and SEM analysis were also done to investigate the corrosion mechanism. FACTSage® predictions about the interaction between refractories and slag were also done. These predictions were compared to the actual results attained. It was found that the extent of corrosion by slag attack decreases as the basicity increases. The most severe corrosion of the MgO-C refractories occurred at a basicity of 0.5 whereas the optimum basicity is above 2.0. SEM analysis indicated severe slag attack at the lower basicities with no visible refractory-slag interaction at higher basicities. TheFACTSage® predictions supported most of the actual findings. Keywords Magnesia-carbon, ConArc, blowing phase, slag resistance, induction furnace, crucibles.

Jan 1, 2011

By S. T. L. Harrison, A. Kotsiopoulos, M. D. Maluleke, E. Govender-Opitz

In the extraction of base metals from printed circuit boards (PCBs) using bioleaching, the accumulation of metal ion stress in solution has been shown to inhibit the microbial regeneration of ferric iron. This poses a challenge for the development of this technology for e-waste treatment. The paper explores the application of a microbial immobilisation system in a two-stage bioleaching system consisting of a chemical leaching reactor in series with a microbial ferric iron regenerating reactor to mitigate microbial inhibition and to enhance base metal extraction. A mixed microbial culture dominated by L. ferriphilum, L. ferrooxidans and At. Caldus was maintained over a period of two months in the presence of polyurethane foam which acted as the biomass support particle. Microbial metabolic activity of immobilised cells and their tolerance to inhibitory Cu ions was investigated. Results showed that immobilised microbial cells maintained higher ferrous iron oxidation activity compared to planktonic cells in the presence of increasing Cu2+ concentrations up to 6 g/L. This presents an opportunity for microbial immobilised systems to be adopted in two-stage bioleaching system. Keywords: Bioleaching, microbial immobilisation systems, microbial inhibition and ferrous iron oxidation

Jan 1, 2020

By M. Buchmann, T. Mütze, F. Heinicke

Dry air classification is a well-known technique used for decades in the cement industry to separate material in the size range of 0.01-1.0 mm. Additionally, in corresponding dry grinding circuits with effective machines such as High Pressure Grinding Rolls (HPGR), the energy consumption can be reduced compared to wet applications. These dry systems are not state of the art in minerals processing plants, but first prototypes have been installed and an increasing number of projects are starting to evaluate this option. One challenge in this field is the mineral composition of ores, which have, by far, a higher variety in density and size than those of cement. High density particles such as iron- containing ones have higher settling rates than low density silica particles of the same size. The main question to answer in this paper is how to evaluate this effect, so a quantitative method using Mineral Liberation Analyses was developed to calculate two-dimensional partition curves. Additional statistical analyses allow for isolation and quantifying the interaction of density and size, enabling engineers to consider this effect for the sizing of process plants. The paper will present the method and selective results for a compounded ore of iron and silica. Keywords: HPGR, air classification, partition curve, MLA

Jan 1, 2020

By W. C. Joughin

The science of soil mechanics is 100 years old, and rock mechanics is about 80 years old. While methods of analysis and design have been developed and have evolved over time, these are relatively young sciences. The rapid increases in computing power and new technologies have enabled more sophisticated modelling and monitoring. However, there are still many aspects of soil and rock mechanics that are not well understood. Geotechnical failures, which have major consequences, still occur. These consequences may include environmental damage, major production holdups and associated loss of revenue, damage to infrastructure, and loss of life. High-consequence events, which are rare, are more difficult to anticipate and to design for, because by their nature they involve extraordinary circumstances or conditions, often geological in nature. The risks are usually mitigated by conservative designs and monitoring. Detailed geotechnical investigations help us to understand the natural variability of soil and rock masses and identify unusual or unexpected conditions. Investigating and researching major geotechnical failures is essential to enable these unusual circumstances to be anticipated. In the past, severe unanticipated events may have been treated as natural events or ‘acts of God’. However, society now has much greater expectations and it is essential to have policies and procedures in place that enable appropriate management of these rare, high-consequence risks. A good example is the Global Industry Standard on Tailings Management (GISTM), which was introduced after the catastrophic dam collapse at Vale’s Corrego de Feijao mine in Brumadinho, Brazil. The address will explain the concepts of uncertainty and variability, and how they should be taken into account in geotechnical design. The challenges facing geotechnical engineers, mine owners, and managers will be discussed. referencing a number of real case studies.

Sep 6, 2023

By E. Marè, D. R. Groot, R. Engelbrecht, T. Coetsee

Hydrogen peroxide is often used as an oxidising agent in experimental waste electronic equipment (WEE) leaching work. However, the high cost of peroxide is a negative factor in its consideration in further process development. A few studies have reported on the efficient application of peroxide addition schedules to ensure optimum reagent consumption. Large quantities of unleached substrate material contained in WEE feed material result in a large dead volume of material in the leaching reactor. This factor necessitates fast reaction rates to enable the use of a high feed material throughput reactor to enhance overall project viability via hydrometallurgical processing. In this study the effects of hydrogen peroxide addition schedules on base metal leaching efficiency and solution temperatures were tested at laboratory scale. The results showed that overall peroxide consumption can be optimised to lower levels by matching peroxide additions to the particular feed material’s leaching behaviour. A simplified integrated model for peroxide decomposition is used to explain its effect on solution temperatures and leaching rates. Keywords: Peroxide consumption, waste electronic equipment, copper leaching, integrated model

Jan 1, 2020

By C. Gatschlhofer, A. Krammer, H. Raupenstrauch, T. Hochsteiner, A. Holzer, L. Wiszniewski

The rising demand for lithium-ion batteries, coupled with international climate targets, emphasises the need for circular economy and zero-waste recycling approaches. However, so far, no industrial-scaled solutions are available that fulfil global recovery targets. Therefore, a novel pyrometallurgical reactor was developed at the Chair of Thermal Processing Technology at Montanuniversitaet Leoben to avoid lithium slagging and recover volatile elements via the gas phase. Nevertheless, previous results show that several impact factors, including interfering elements or pre-treatment steps, strongly limit the recycling efficiency of black mass. To simulate the black mass and provide feedback on possible influences of pre-treatment steps, cathode material from production with additives of interfering elements was analysed regarding melting behaviour. The results show that formation of a further processable alloy was increased by almost 50% when pretreatment steps were excluded, indicating pre-treatment steps as a major influence to be considered within this specific recycling route.

Jan 1, 2023

By V. V. Getman, V. A. Chanturiya, T. N. Matveeva

Most of the Au and PGM ores in Russia are characterised by a thin mineral impregnation of noble metals in sulfide minerals, and a large variety of mineral forms that lead to high loss of precious metals with fine fractions during flotation. In modern flotation technology, the rational choice of reagents is one of the main trends for selective separation of minerals and effective metals recovery. New data on the selectivity of the thermo-sensitive polymer with specific functional groups (TMPPh) as a flocculant and collector of Au and Pt fine fractions are available. The selective modified collector (DEDTCm) for the recovery of Au and Pt from complex ores is discussed in this paper. Scanning electronic microscopy (SEAM), laser SIM and AFM microscopy, UV and IR spectroscopy were applied to study the adsorbed layer of new reagents on the mineral surface. Flotation tests of TMPPh on the gold-bearing ore of the Olimpiada deposit showed an increase in Au extraction and Au content in the concentrate of the rougher flotation. Using a combination of reagents TMPPh and ButX, the quality of the Au and Pt concentrates increased in 1.7 time with an increase in recovery up to 15 % compared with the traditional reagent mode. Testing of TMPPh polymers in flotation of Pt-Cu-Ni ore at Norilsk Nickel has shown the ability to obtain a concentrate with a higher Pt content. Recovery of platinum is 17% higher than recovery in an experiment without polymer. Application of DEDTCm helped to achieve higher technological parameters in flotation of lowgrade Rt-Cu-Ni ore. Compared to the basic mode Pt recovery was plus 13%, Pd recovery was plus 9% and the content of precious metals in the rougher flotation concentrate increased in 2,5 - 4 times. The studies have been supported by Grants of the President of RF “Scientific School of Academician V.A. Chanturiya” NSh-220.2012.5, NSh-748.2014.5. Keywords: Au and Pt complex ores, flotation, flocculation, thermo-sensitive polymer TMPPh, modified collector

Jan 1, 2020

By J. S. Contreras, E. Córdova, I. Gottreux, A. Anani, A. Ferrada

Cave mining is an underground mass mining technique. The largest projects, which are known as ‘super caves’, produce hundreds of thousands of tons of ore per day, which involves large footprints with considerable column height, and have a life of mine of over 20-40 years. These operations are typically located deep, under high stresses and in competent rock masses, making initiation and propagation of the caving process harder to manage. These challenges must be confronted by optimizing the fragmentation of the orebody to achieve smaller size blocks that will result in consistent caving and improved flow of the ore from the drawpoints. To achieve better performance from the drawpoints, preconditioning is applied to fragment and damage the material required to cave. We present a proposed design for preconditioning in underground mines, considering the challenges that these large-scale mines are already facing, based on a comprehensive analysis of current design parameters, case studies, and sensitivity analyses using numerical models.

Feb 2, 2021

By A. Singh, K. Bisaka, G. Marape, T. Mokgomola

This paper investigated the pre-concentration amenability of sovite (carbonatite) ore to enhance the grade of rare earth elements (REE) bearing minerals by rejecting calcite, and to improve total rare earth elements (TREE) recovery using gravity and magnetic separation. A high proportion of calcite affects downstream processes like leaching due to high acid consumption. Multiple flowsheets combining gravity and magnetic separation were employed to target > 60% TREEs recovery to the final concentrate and > 60% calcite rejection to the tailings. Head analysis of the feed showed the sample’s main constituents as Fe (15.61%), Ca (16.04%), SiO2 (7.13%), and lastly TREEs (1.12%). Mineralogy liberation data at 2mm top size indicated poor liberation of TREEs, with the majority of minerals displaying < 30% mass greater than 80% liberated. Grain size distribution data showed that the majority of REE minerals are fine grained and report to the < 20 μm size class. Calcite liberation mineralogy showed < 60% mass greater than 80% liberation.A combination of a single-stage shaking table with a wet high intensity magnetic separator at a magnetic intensity of 7520 G was found to be the optimum flowsheet. For a shaking table feed with P80 of 150 μm followed by tails regrind to P80 of 45 μm as feed to wet high intensity magnetic separator, the overall mass balance results showed that 60.5% TREEs are recovered to the concentrate while 63.0% calcite is rejected to the tails. However, due to the fine-grained nature of This paper investigated the pre-concentration amenability of sovite (carbonatite) ore to enhance the grade of rare earth elements (REE) bearing minerals by rejecting calcite, and to improve total rare earth elements (TREE) recovery using gravity and magnetic separation. A high proportion of calcite affects downstream processes like leaching due to high acid consumption. Multiple flowsheets combining gravity and magnetic separation were employed to target > 60% TREEs recovery to the final concentrate and > 60% calcite rejection to the tailings. Head analysis of the feed showed the sample’s main constituents as Fe (15.61%), Ca (16.04%), SiO2 (7.13%), and lastly TREEs (1.12%). Mineralogy liberation data at 2mm top size indicated poor liberation of TREEs, with the majority of minerals displaying < 30% mass greater than 80% liberated. Grain size distribution data showed that the majority of REE minerals are fine grained and report to the < 20 μm size class. Calcite liberation mineralogy showed < 60% mass greater than 80% liberation.A combination of a single-stage shaking table with a wet high intensity magnetic separator at a magnetic intensity of 7520 G was found to be the optimum flowsheet. For a shaking table feed with P80 of 150 μm followed by tails regrind to P80 of 45 μm as feed to wet high intensity magnetic separator, the overall mass balance results showed that 60.5% TREEs are recovered to the concentrate while 63.0% calcite is rejected to the tails. However, due to the fine-grained nature of TREEs, no flowsheet improved their grade.

Nov 6, 2024

By M. A. El-Sayed

"Double oxide films (bifilms) are significant defects in light alloy castings that occur when, during melt handling, the oxidized surface of the melt is folded over onto itself and then entrained into the liquid metal, encapsulating a portion of the local atmosphere. These defects create crevices in the final castings and have been shown to decrease tensile and fatigue properties, and also to increase their scatter, making casting properties unreproducible and unreliable. This paper reports on two different experiments performed to study the behaviour of such defects in Al alloys. In the first experiment and as a proxy for a bifilm, air bubbles were held in an Al-5Mg alloy melt for varying periods of time before the melt was allowed to solidify. The composition of the gas content of the bubbles was subsequently analysed using mass spectrometry to ascertain how it changed with time. In the other experiment the influence of the age of bifilms on the mechanical properties of Al-5Mg castings was assessed by holding castings in the liquid state for different times before solidification, followed by mechanical property testing and SEM and EDX studies of the fracture surfaces of tensile test bars. This research could provide a better understanding of the behaviour of double oxide film defects, and may lead to the development of new techniques by which these defects could be eliminated, or at least deactivated, in light alloy castings. Introduction One of the major structural defects affecting the reproducibility of mechanical properties of aluminium castings is the double oxide film defect (El-Sayed and Essa, 2017; El-Sayed and Ghazy, 2017). This type of defect is usually created as a result of poor filling system design. Owing to the very high reactivity of liquid Al-Mg alloy with oxygen in the air, the surface of the liquid metal can be considered to be permanently coated with an oxide film (Weigel and Fromm, 1990). As a consequence of surface turbulence, the oxidized metal surface can become folded over onto itself, but not fused, and then submerged into the bulk liquid, with a portion of the mould atmosphere being entrapped within it (Campbell, 2003; Al- Sayed, 2016; El-Sayed, Hassanin, and Essa, 2016)."

Nov 1, 2018

By Y. Ren, B. Yang

The magnetic field characteristics due to electromagnetic stirring in the secondary cooling zone of an extra-thick slab during continuous casting are numerically determined using Maxwell's equations, with particular emphasis on the distribution of magnetic induction intensity and electromagnetic force, as well as the influence of process parameters on the magnetic field. The orientation of the electromagnetic force is the same when the electromagnetic stirrers at the 30° and 60° posistions of the arc-shaped slab are powered in the same direction; otherwise, the orientation is opposite. The magnetic induction at the centre of the section of the stirrer's central axis at the 30° positio, as well as the current, frequency, and fitting formulae, are as follows: B = {0.075I.(1/A)-0.3} mT and B = {-1.75f.(1/Hz)+22} mT. The electromagnetic force and current fitting formula at the central point of the B-B section is F = {0.03168I2.(1/A2)-03.762I.(1/A)+326.7} N/m3, and the fitting formula of electromagnetic force and frequency at the centre point is divided into two segments. The first takes the form of a parabola: = {-21((f-4.3).(1/Hz)2)+970} N/m3, and the second segment is negative linear: F = {-1.65f.(1/Hz)+51.5} N/m3.

Apr 16, 2024

By R. Pipeleers

Recent experience has shown that all underground workplaces in the Campine Coalfield in Belgium will require controlled cooling within three years. Considering the socio-economic and legal importance of the climatic problems underground, IREA has undertaken studies in forecasting the climate of future workplaces, planning the necessary cooling equipment and optimizing efficiency in the existing cooling equipment. These studies are being carried out using the climate forecasting program of Bergbau-Forschung. So far, the German model has been obliged to utilize manually measured data from a few workplaces in the Campine. As the model does not fit very well with these measurements, it has been thought necessary to&apos; develop a system of continuous data acquisition and transmission. This system is being tested in the Beringen mine of the N.V. Kempense Steenkollenmijnen. In the first part of this paper the digital tranmission system is described; in the second the sensors used to collect the necessary climatic data are presented, and in the third some results are given.

Jan 1, 1987

By K. Barani, F. Moradpouri, M. Godarzi

A sampling campaign carried out on the lead flotation circuit at Lakan lead-zinc processing plant demonstrated that the Pb recovery was only about 68-69%. Characterization of the Pb flotation tailing showed that 61.4% of the Pb is in the –37 μm size fraction, which is difficult to recover by flotation. Batch flotation experiments were carried out on a plant sample of the lead flotation feed and high-intensity conditioning (HIC) was used to improve flotation recovery. The results showed that increasing the collector conditioning time from 1 to 3 minutes significantly increases the Pb recovery from 42.5% to 57.3%. Further increases in conditioning time to 5 to 7 minutes decreased the Pb recovery. With a collector conditioning time of more than 3 minutes, due to the surface cleaning effect, increasing collector and frother dosage improved the flotation selectivity and recovery, even at higher collector dosages. The Pb recovery increased from 69.1% to 79.8% with increasing impeller speed from 600 to 1250 r/min. HIC increases the flotation kinetics and greatly improves the flotation recovery and concentrate grade.

Apr 2, 2022

By G. Mahieu, L. Perez-Barnuevo, P. Barbeau-Verreault, O. Gravel

Raglan mine is a copper-nickel mining operation, part of Glencore, and located at the northern border of the province of Quebec, in Canada. The concentrator is fed by a mix of four different underground mines, thus it must accommodate periodic variations in run-of-mine mineralisation and composition. In order to concentrate nickel and copper sulphides, the flotation circuit also includes a regrind step at the cleaner stage. This leads to challenges in maintaining optimal recoveries and in diagnosing potential disturbances. This paper advocates for the combination of automated mineralogical analyses, reconciliated mass balances from diagnostic sampling campaigns and innovative multidimensional visualisation to assist in tackling these challenges. Through this approach, it has been possible to quantify the regrind step influence on the liberation of valuable mineral particles in the final flotation concentrate. The methodology also allows for virtual sieving of the products in order to track unit loss in the flotation process. The proposed analysis scheme presents an opportunity to easily diagnose flotation circuit performance based on mineralogical information. Keywords: Flotation diagnostics, multi-dimensional visualisation, mineral liberation analysis

Jan 1, 2020