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By Z. Leng

"After detonation of the explosive, the final blast-induced damage area around the blast-hole falls into three categories, namely crushed zone, fractured zone, and elastic deformation zone. This paper presents a modified model to calculate the size of crushed zone around a blast-hole in drill-and-blast, with the hoop compressive stress and cavity expansion effect taken into account. The material in the crushed zone was assumed to be a granular medium without cohesion, but with internal friction. On this basis, the formula for crushing zone radius was derived. The proposed approach was verified with tests reported in the literature and the simulated results from SPH-FEM coupled models. A full statistical analysis was also carried out, and the predicted values were found to be in better agreement with the test results compared with other models. A sensitivity analysis of the modified model showed that the size of the blast-induced damage area is mainly affected by the following factors: rock mass properties, in situ stress, and borehole pressure. In particular, the roles of borehole pressure and in situ stress are discussed. Finally, suggestions are made on how the size of the crushing zones can be decreased. IntroductionOver the past decades, drill-and-blast has become the most commonly used technology in rock excavation. It is well known that in rock mass fragmentation with explosives, the annular rocks around the blast-hole are converted into fines. The formation of these fines consumes a significant part of the energy of the detonation, which in general is ignored in the determination of the efficiency of detonation (Glatolenkov and Ivanov, 1992; Furtney et al., 2012). Many studies show that only 20–30% of the total explosive energy is effectively used in fragmenting the rock, and up to 50% of the energy generated by conventional charges is wasted in overcrushing of the crushed zone and the inner part of the fractured zone (Ouchterlony et al., 2004; Sanchidrian et al., 2007). How to control the crushed zone to enhance the effective utilization of explosive energy, reducing the unit explosive consumption and the engineering cost, is therefore of great significance."

Jan 1, 2016

By A. Pareek, V. S. Masampally, V. Runkana

Mineral processing plants, in general, consist of comminution and separation circuits. Rougher flotation is considered as the heart of the separation circuit with concentrate grade and mineral recovery being the key productivity and quality parameters that affect the downstream operations and profitability. Online prediction of these parameters can help improve process performance in real-time. Past efforts to predict flotation cell performance have focused on building physics-based or machinelearning (ML) based models. Although physics-based models are popular in process design applications, ML models are more appropriate for online monitoring, control and optimisation due to their lower computational requirements. Deep learning (DL) is gaining prominence nowadays for application in industrial operations where a large amount of data is available. We have developed a DL model based on long short-term memory (LSTM) neural networks to forecast the two key performance indicators (KPIs), namely, mineral recovery and concentrate grade in a mineral processing plant. Rougher feed characteristics such as mineral grade and particle size distribution, upstream measurable disturbances such as throughput of the comminution circuit and pulp density, and control variables such as aeration rate, pH, and collector addition rate are considered as explanatory variables to train the model. The model was tested with data from an industrial mineral processing plant. For real-time dynamic predictions, the trained model appropriately accounts for mismatch in measurement frequency of real-time process data and off-line laboratory analysis data. Such a time series model can be used as a state observer in model predictive control techniques for optimal control of unit operations in a mineral processing plant. Keywords: Mineral processing, flotation, time-series, dynamic modelling, deep learning

Jan 1, 2020

By Daniel W. Kappes, Pierre F. X. Mousset-Jones

"In this paper a discussion is presented of a program designed to produce a 40-day production forecast for an underground stoping system.The program is intended to be a tool for the operations department in an underground mine, and is designed to utilize data readily available from production reports. Brevity of data input, ability to revise slope conditions easily and the accuracy of starting stope status are stressed. Applicability of the program to a wide variety of sloping methods makes the program potentially useful in a large number of mines.The general functions of the program subroutines, and input and output lists are discussed. An example is also given of a stope in operation for a three-day period, which shows how the program can handle production irregularities as they arise."

Jan 1, 2014

By M. Kumral, Y. A. Sari

Underground mining operations tend to have higher operating costs than surface mines. When metal prices decrease, profitability is jeopardized due to the high costs. Therefore, mining management harnesses new practices that increase operational efficiency. One way to manage this challenge is to invest in new mine planning practices. Stope layout optimization as a part of underground mine planning aims to identify a portion of the orebody in the form of production volumes (stopes) to maximize profit under roadway and stope dimension constraints. In this paper we propose a novel approach based on identifying ore-rich areas of the deposit and prioritizing their extraction through an iterative heuristic clustering approach. The proposed approach is compared with and validated by an exact method through a small mining example. The heuristics produced nearly identical results in a very short time. Finally, a case study was carried out using a larger data-set. The cluster-based iterative approach generated nearoptimal stope layouts in a computationally effective manner.

Mar 1, 2021

By R. Tabanrad

This article examines the stability analysis of intake tunnels of Karun III dam & power plant. The tunnels have been excavated with a 3-dimensional and fairly complicated geometry in Pabdeh weak formation rocks at Zagros region. Due to the particular excavation geometry and inapplicability of plane-strain status, the stability of these excavations has been analyzed using both the 3D elastic software Examine 3D and the 2D non-elastic software UDEC simultaneously. The geomechanical parameters have been estimated by back analyzing the measured displacements from instruments, which were installed in the tunnels, and the parameters have been used in non-elastic numerical model. The results of the analysis show that the strains occurred in surrounding rock mass are less than the allowable failure strain and that the tunnels are stable. In addition, considering the results of non-elastic 2D analysis, the areas with unstable potentiality were identified and after the instability occurred at the areas predicted by the model , it was stopped up to the allowable strain limit through installing additional support . Bei diesem Artikel handelt es sich um eine Analyse der Festigkeit der Eingangstunnel des Damms und Elektrizitätswerks “Karoon III”.Die Tunnel haben drei Dimensionen und eine sehr schwierige Form und sind in brüchigen Felsen in “Pabedeh ,in Zagrossgebirge”eingebohrt.Aufgrund besonderer Form der Bohrung wurde ihre Festigkeit durch elastische dreidimensionale Soft-ware analysiert,die gleichzeitig die drei-und zweidimensionale unelastische Soft-ware UDEC benutzt hat.Die geometrische Parameter sind mit Ausnützung der Analyse berechneter eingesetzter Versorgungen,die in Tunnel aufgebaut sind,bewertet.Und diese Parameter sind in Zahlen-Analyse benutzt.Die Ergebnisse dieser Analyse zeigen,dass die Drücke an Felsen weniger als problematischer Grad der Drücke sind und die Tunnel fest sind.Ausserdem wurde mit einem Einblick auf die Ergebnisse der unelastischen zweidimensionale Analyse die eventuellen unfesten Teile bestimmt.Nach entstandener Unfestigkeit an diesen Teilen wurde die problematischeDrücke für Aufbau mehrere Anlagen gestoppt. Cet article examine l'analyse de la stabilité de tunnels de la prise de Karoun barrage III et centrale électrique. Les tunnels ont été excavés avec une 3 dimensionnel et compliqué géométrie dans Pabedeh que la formation faible balance à région Zagros équitablement. Dû à la géométrie de l'excavation particulière et inapplicabilite de statut de tension plane, la stabilité de ces excavations a été analysée en utilisant les deux le 3D logiciel élastique Examen 3D et le 2D logiciel non - élastique UDEC simultanément. Les paramètres du geomechanical ont été estimés en analysant le déplacement mesuré d'instruments qui ont été installés dans les tunnels et les paramètres en arrière a été utilisé dans les modèles numériques non - élastique. Les résultats de l'analyse montrent que les tensions se sont produites dans masse du roc environnante est plus petit que la tension de l'échec admissible et que les tunnels sont stables. De plus, les régions avec potentialité instable ont été identifiées étant donné les résultats de 2D analyse non - élastique, et après que l'instabilité se soit produite aux régions prédites par le modèle, il a été arrêté jusqu'à la limite de la tension admissible à travers installer du support supplémentaire.

Jan 1, 2003

By J. W. Wilson, J. G. Taylor

The mechanization of haulage drilling in the gold mines of Anglo American Corporation by J. w. WILSON, Ph. D., C.Eng., M.AIME, F.!.Min.E., F.I.M.M. (Fellow), and J. G. TAYLOR, A.C.S.M., C.Eng., M.!.M.M. (Visitor) Some one-thousand kilometres of tunnels are mined annually in the gold mines of South Africa. Until two years ago, mechanized drilling on South African gold mines was not an economic proposition because of the availability of inexpensive labour and the fact that mechanized equipment developed for other mining markets could not perform satisfactorily in the tough, abrasive quartzites of theWitwatersrand System. A project team from the Technical Development Services Organisation of the Anglo American Corporation, in collaboration with various manufac turers of drill rigs and drill steel, has been concerned with the development of suitable equipment for mechanized main-haulage drilling. After two-and-a-half years of extensive testing and development of drifters, drill steels, and bits, many of the problems encountered have been sotved, and gradually jumbos mounting pneumatically and hydraulically powered drifters are being phased into production on various gold mines of the Group. A description of the development work is given, and actual operating results are recorded, together with details of the drilling and blasting techniques used.

Jan 1, 1975

By S. Swanepoel, A. V. Cherkaev, Q. G. Reynolds, M. Erwee

Ferrochrome (FeCr) is a vital ingredient in stainless steel production and is commonly produced by smelting chromite ores in submerged arc furnaces. Silicon (Si) is a componrnt of the FeCr alloy from the smelting process. Being both a contaminant and an indicator of the state of the process, its content needs to be kept within a narrow range. The complex chemistry of the smelting process and interactions between various factors make Si prediction by fundamental models infeasible. A data-driven approach offers an alternative by formulating the model based on historical data. This paper presents a systematic development of a data-driven model for predicting Si content. The model includes dimensionality reduction, regularized linear regression, and a boosting method to reduce the variability of the linear model residuals. It shows a good performance on testing data (R2 = 0.63). The most significant predictors, as determined by linear model analysis and permutation testing, are previous Si content, carbon and titanium in the alloy, calcium oxide in the slag, resistance between electrodes, and electrode slips. Further analysis using thermodynamic data and models, links these predictors to electrode control and slag chemistry. This analysis lays the foundation for implementing Si content control on a ferrochrome smelter.

Mar 14, 2024

By E. J. Margi

Deep gold exploration such as is used for Witwatersrand gold deposits is both expensive and time-consuming. This paper provides quantitative guidelines as to the economic optimum number of boreholes and deflections within each borehole for a certain reef characterized by its variability pattern and depth below surface in order to maximize the level of confidence for a fixed drilling budget or to minimize the total drilling cost for a given level of confidence. Portions of the Basal, Vaal, and Elsburg Reefs that show a wide range of variability (sample logarithmic variances of 0,63, 1,05, and 2,06 respectively) are examined at depths below surface ranging from 1000 m to 4000 m over a simulated mining property covering 7000 ha (7000 m by 10000 m). It is concluded that four intersections per borehole are optimum in al the cases considered, which cover the majority of current Witwatersrand exploration, with the exception of the highly variable Elsburg Reef at depths of 1000 m and 2000 m, where boreholes with one and two intersections respectively should be preferred.

Jan 1, 1987

By C. -I. Lee

Since the early 1970s, Korea has constructed many large-scale tunnels and underground storage caverns in response to the rapid industrial development. The rock mechanics engineers have accumulated valuable experiences in the area of underground space technologies. But they still face technical challenges in environmental and safety aspects. To discuss those challenges in Korea, a brief engineering description of underground space projects including oil and gas storage, food storage, pumped storage power plant, transportation tunnels, waterway tunnels, and radioactive waste disposal is presented. Mechanical and hydrological stability analyses of the storage caverns in Korea are also introduced. Depuis le début des années soixante-dix, le développement industriel rapide en Corée a entraîné la construction de nombreuses galeries et cavernes de stockage souterraines. Les ingénieurs de mécanique minière ont donc accumulé des expériences précieuses dans le domaine de la technologie de l’espace souterrain. Cependant, ils font toujours face à de nombreux défis techniques en ce qui concerne les aspects de l’environnement et de la sécurité. Pour présenter ces défis en Corée, l’étude présente décrit les projets d’espace souterrain, y compris le stockage de pétrole et de gaz, de nourriture, centrales de stockage pompé, tunnels de transport, tunnels navigables, et évacuation des déchets radioactifs. Des analyses de stabilité mécanique et hydrologique des cavernes de stockage en Corée sont aussi présentées. Seit Anfang der 70er-Jahre, baute Korea in Folge raschen Industriewachstums viele lange Tunnelsund unterirdische Lagerungsräume. Fachkräfte im Bereich Gesteinsmechanik sammeltenwertvolle Erfahrungen über unterirdische Raumtechnologien. Dennoch stehen sie auch heute nochvor technischen Herausforderungen im Bereich Umweltschutz und Sicherheit. Zur Erläuterungdieser Herausforderungen in Korea folgt eine kurze technische Beschreibung der Projekte zurSchaffung unterirdischen Raumes für beispielsweise Öl- und Gaslagerung,Nahrungsmittellagerung, Pumpspeicherwerke, Straßen- und Wasserstraßentunnels, als auchLagerung radioaktiven Mülls. Mechanische und hydrologische Stabilitätsanalysen derLagerungsräume in Korea werden ebenfalls dargestellt.

Jan 1, 2003

By G. Coetzer

"Prior to operating a non-recovery coke pilot plant oven, it was essential to ascertain coal cake stability during the loading of a 1 m3 (1 m × 1 m × 1 m) coal cake into the cold pilot-plant oven by a pusher mechanism. Previously established laboratory-scale compaction parameters, to obtain coal cakes with sufficient stability, were employed during the loading tests of the coal cakes. Two different coals were evaluated, namely Waterberg semi-soft coking coal (sscc) and Oaky North hard coking coal.It was demonstrated that lower applied compaction forces (14%) can be utilized during 1 m3 compaction, in comparison to laboratory-scale tests, to obtain similar wet cake densities, owing to differences in the effect of frictional forces. Wet cake densities for Waterberg sscc improved slightly (3%) to 1.13 t/m3 when utilizing 79 t/m2 applied force for a 1 m3 coal cake, in comparison to laboratory-scale tests. Similar results were obtained for Oaky North hard coking coal, with a 6% density increase to 1.27 t/m3 at a similar applied force. Porosities decreased by 13% and 32% for Waterberg sscc and Oaky North coal, respectively, when 1 m3 compaction was compared to laboratory-scale tests. An opportunity exists to further decrease the porosities of Waterberg sscc during compaction, whereas acceptable compaction parameters were achieved for Oaky North hard coking coal. Most major vertical cracks and the partial collapse of coal cakes were mitigated, and high-stability coal cakes were obtained that could be successfully loaded into the pilot-plant coke oven by a pusher mechanism.Factors contributing to the instability of the coal cake during loading into the oven, such as vertical cracks, are (i) the cubic geometry (1 m3) of the coal cake, (ii) friction exerted by the oven floor, and (iii) mechanical problems, such as a misalignment between the pusher machine feeder plate and the oven floor. IntroductionOperation of the stamp-charging horizontal 1 t electrically heated coke pilot-plant oven at Exxaro Resources requires coal cake stability during the loading of a 1 m3 compacted coal cake into the oven. In this case, a pusher plate is utilized to push the coal cake into the oven over the oven floor. This is in contrast to a ‘spoon’ or bottom plate feeding mechanism as found in industrial horizontal coke ovens. The pusher plate loading mechanism dictates that the coal cake should possess high stability and inherent strength owing to frictional forces exerted by the oven floor. In order to obtain a coal cake of acceptable stability for the 1 t coke oven, various compaction parameters need to be verified and established."

Apr 1, 2019

By J. E. Dickinson, J. L. Sutherland, J. Zhou, M. J. Cole, K. P. Galvin

Interest in early gangue rejection has grown substantially in the minerals industry to reduce energy and water consumption arising from excessive comminution. Recent developments in coarse-particle flotation have proven successful by promoting a quiescent hydrodynamic environment to limit particlebubble detachment and by helping to convey more buoyant particles to the overflow. Current approaches also benefit from upstream classification to remove the finer particles ahead of the coarse-particle flotation. In this study, coarse-particle flotation was investigated experimentally using a novel hybrid gravity-flotation system called CoarseAIR™ that exploits the hydrodynamic advantages of the Reflux® Classifier. The system consists of a lower fluidised bed housing, with a system of inclined channels above. The inclined channels enhance the segregation and hence rejection of intermediate through to relatively coarse particles containing little or no surface liberation. This approach overcomes the need for pre-classification, while offering strong transport of coarse particles made buoyant through their attachment to air bubbles. The paper explores the strong relationship between the solids transport to the overflow and the input gas flux, showing firstly the potential for significant mass rejection at the relatively low gas fluxes, and robust performance in terms of recovery across the full range of gas fluxes. Keywords: Flotation, inclined channels, coarse particle flotation, Reflux Classifier

Jan 1, 2020

By C. Bester, G. M. Rohde

A major challenge in the mining sector is the responsible management and efficient storage of mine residue. Over recent years numerous tailings dams have experienced unintended spills and failures, with severe consequences for the mining industry, the environment, local communities, and the regional economy. The fourth industrial revolution (4IR) is impacting society due to increased interconnectivity, processing speed, and automated technologies. This paper explores whether 4IR technologies have the potential to mitigate risks associated with tailings dams. Experts in the field of tailings dam operational management were surveyed to determine their view on the risks associated with tailings dams and the potential of 4IR technologies to mitigate these risks. The survey found that a majority of experts believe that certain 4IR technologies have the potential to reduce the risks associated with tailings dam failures.

May 27, 2025

By L. Roux

This review was initially motivated by the author’s own experience in attempting to reconcile run-of mine production tons with the Coal Resource and Reserve estimation of mineable, in-situ tonnages. The primary scientific measurements and observations that are collected during exploration at the beginning of the value chain will have a profound effect on the future of the mining operation. Due diligence must be exercised during the planning of a new mine and during the life of an existing mine. The comments provided by the technical and economic assessment group of Venmyn Deloitte confirmed the need for this critical review. They found the reporting of Coal Resources in South Africa to be inconsistent. This was particularly problematic in the Waterberg Coalfield in Limpopo Province. In this coalfield there are two types of coal deposit present. The first is comprised of the thick intercalated, cyclic coal and shale/mudstone sequences of the Volksrust Formation. This overlies multiple coal seams within the Vryheid Formation, each of which is thick enough to be extracted as an individual raw coal unit. On the other hand, the interbedded coal and shale seams of the Volksrust Formation require beneficiation to separate the coal from the shale. The review examines practices and methods, investigates alternatives, provides checks and balances, and tests these against actual production reconciliations. In conclusion, the best estimates of the mineable, in-situ tonnage will be obtained from the air-dry raw material density. These estimates should be adjusted afterwards to allow for free moisture content. The adjustments are derived from reconciliation data. The greatest contributing factor to the over-estimation of Reserve tonnages is the moisture content of the raw material. This fluctuates significantly under varying conditions in situ, as well as upon exposure to the natural environment. The air-dried density of the raw material includes inherent (structurally bound) moisture within the matrix. It provides credible tonnage estimations of raw material available while also providing an indication of voids within the volume of material being assessed. The calculated solids percentage can be used to adjust the specific gravity, which is determined via the Archimedes principle. This will supply a representative estimate of the material to be mined.

Nov 1, 2021

By V. A. Myazin, M. V. Korneykova, A. V. Svetlov, V. G. Minenko, D. V. Makarov, A. L. Samusev

The paper discusses the treatment problem of mine (waste) water for enterprises of the Russian Arctic. The wide range of relevant pollutants, financial resources, the availability of land for the construction of a treatment plant, waste generated during the treatment process are some of the factors controlling current and future process design solutions. All mining operations have adopted water treatment and water quality monitoring solutions, however there is no single approach to the problem and each industry participant operates within the scope of its available resources. The range of existing and emerging methods is extensive — from using constructed wetlands for the deposition of mineral nitrogen compounds in settling ponds, reagent deposition and chemical coagulation in exhausted mine workings, and filtering dams on the surface to retrofitting existing mine drainage treatment plants with the adoption of the electrochemical coagulation process. Methods of wastewater treatment from heavy metals, oil products, and nitrogen compounds are demonstrated in the example of two industrial facilities in the Murmansk region. It was found that the use of electrochemical coagulation provides effective treatment of mine water from NO3, NO2, Ni, Fetotal and petroleum hydrocarbons (the degree of purification from 50.5-99.7%), the use of phytotreatment system provides wastewater treatment from ammonium ions and nitrite ions by 53-84%, nitrate ions - by 22%. Keywords: Industrial water treatment, treatment flowcharts, settling ponds, constructed wetlands, reagent sedimentation, chemical coagulation, electrochemical coagulation

Jan 1, 2020

By R. Letsaole, H. Mabowa, J. Sehat, J. Tshilongo, T. Rampfumedzi, N. Ntsasa, A. Mkhohlakal1

This study explores the use of co-collectors to enhance the recovery and determination of rhodium during fire assay with lead collection, followed by acid dissolution using conventional hot plate methods. Rhodium, a critical platinum group metal, poses analytical challenges due to its low natural abundance and complex chemistry. Among the co-collectors tested, palladium and tellurium demonstrated significantly improved rhodium recoveries, ranging between 100% and 120%, whereas silver resulted in poor recovery and higher error margins. These findings highlight that co-collectors can enhance the efficiency and sensitivity of platinum group metal analysis, although their effectiveness is dependent on the chemical interaction with the target element. Acid dissolution was essential to ensure complete digestion of prills prior to analysis, enabling accurate quantification of rhodium. Overall, the findings suggest that palladium and tellurium are effective co-collectors for rhodium determination in fire assay, while silver and lead flux alone are unsuitable. This work provides important insight into optimising fire assay procedures for reliable rhodium analysis, with potential benefits for platinum group metals recovery and economic evaluation.

Mar 6, 2026

By R. Singh, A. K. Dhawan, M. Dixit, H. Dev

ABSTRACT: The modulus of deformation of rock mass is an important engineering parameter required for the design of foundation of hydraulic structure and to study the interaction of rock mass and the structure at the foundation support. Different equipment and techniques are used to arrive at the design modulus value. Since any error in the estimation of modulus values results in multiplication of its effects in the analysis, it is necessary to know about the reliability of testing equipment and procedures. In the present study modulus values obtained by different in-situ equipment at different project sites have been compared. KURZFASSUNG: Der Verformungsmodul von der Felsenmasse ist technisch ein wichtiger Parameter, den man zur Konstuktion des Grunds fuer die Hydro – Tektonik, benoetigt um auch die gegenseitige Beeinflussung der Felsenmasse und der Tektonik am Traggrund zu betrachten. Verschiedene Geraete und Methoden werden angewandt, um den Ausfuehrungsmodul -Wert zu erreichen. Es ist erforderlich, die Zuverlaessigkeit der Pruefeinrichtung sowie des Verfahrens zu kennen, da irgend ein Fehler in der Abschaetzung von Modulwerten in der Analyse zu einer Vervielfachung ihrer Einwirkung fuehrt. In der vorligenden Arbeit werden die Modulwerte gewonnen aus unterschiedlichen Einrichtungen an Ort und Stelle and verschiedenen Projekt -Stellen mit einander verglichen. SOMMAIRE: Le module de deformation d’une roche est un parametre important pour la conception et realisation des ouvrages hydrauliques ainsi que pour etudier l’interaction de la roche et de la structure d’appuis de base. De divers equipments et techniques sont employes pour determiner la valeur de ce module de conception. Puisque l’effet d’une erreur d’evaluation du module devient multiplie dans l’analyse, il est necessaire de savoir la fiabilite des equipments et des methods qu’on ulilise. Dans cette etude, on a compare les valeurs des modules obtenues en employant les equipments in-situ aux sites differents de projets.

Jan 1, 2003

By M. A. Reuter, N. J. Bartie

Metals make modern societies function, and increasingly, various high purity precious and special metals endow sustainability-driving technologies with specific functionalities. These metals become heavily intertwined within products, complicating end-of-life treatment. To counteract the resulting downcycling and potential depletion of scarce resources, maximising both the quantities and qualities of materials recovered during primary extraction and recycling, processes should be a priority in the pursuit of sustainable circular economy. Adopting a process simulation approach; a digital twin for the life cycle of cadmium-telluride solar photovoltaic (CdTe PV) modules was created. The system comprises an integrated metallurgical production system that produces, among others, cadmium, tellurium, selenium, zinc, copper, and lead, all of which are required to manufacture PV modules. System-wide resource efficiency and environmental impacts are assessed using exergy analysis and life cycle assessment, respectively. Simulation of this large and complex product life cycle at a high level of detail allows for the evaluation of potential system-wide effects of various production, recycling and residue exchange scenarios aimed at maximising the sustainability of the entire system. It diminishes the need to make arbitrary choices about allocation methods for the distribution of environmental impacts in multipleoutput production systems. Furthermore, it demonstrates the key importance of metallurgy in achieving circular economy. Keywords: Circular economy, sustainability, simulation, metallurgy, CdTe photovoltaics, life cycle assessment

Jan 1, 2020

By G. Asbjörnsson, E. Hulthén, P. Papadopoulou, C. M. Evertsson

Crushing plant managers need to assess, manage, and communicate the environmental impact induced by their crushing plant operations as a step towards the sustainable development of the company. However, performing reliable environmental impact calculations of crushing plants can be challenging when the availability of operational and emission data is low, and when the company’s environmental expertise is not adapted and connected to plant operations (or does not currently exist). To address these challenges, this paper proposes a practical approach where the lifecycle assessment methodology (LCA) is combined with process simulations in a web-based tool. To describe what functionality such a tool should have to be incorporated into a company’s workflow, the system that surrounds a crushing plant is analysed. Further, a case study with a three-stage crushing plant is introduced to showcase how the simulated power draw results produced with the beta version of the tool can be compared to measured sensor data from the crushing plant for one operational day. The results indicate that the simulation tool can provide an adequate estimation of the specific energy for the different material fractions and give an overview of the environmental impact of the process caused by electricity and explosives consumption. Plant managers and operators can use this tool to calculate the environmental impacts of their plant and simulate how different operational strategies influence them. Keywords: LCA, environmental impact, coarse comminution, crushing plant

Jan 1, 2020

By M. Viljoen

South Africa has produced more than a third of the total gold mined throughout history and remains a major although, until recently, no longer the largest producer of gold. South African gold production peaked in 1970 with an output of 1 000 t, a major component of the western world?s gold production, with the development of the country?s economy having been based largely on this mineral wealth. The costs and difficulties of increasingly deep-level mining, coupled with increasing labour costs and the low gold price until relatively recently, have seen production fall steadily since then, with the closure of many mines including those of the Central Rand Goldfield in the mid seventies. Thus in 1998, only 464 t were produced, with 342 tons being produced in 2004. In 2006, 275 tons of gold were produced and after more than 100 years was the last year as the world?s largest gold producer. In 2008 gold production was 221 tons, making South Africa the third largest gold producer after China (292 t) and the USA (234 t). Gold production would have been lower if it had not been for massive tailings dam retreatment operations that started in the late seventies, including in the Central Rand Goldfield. Mining of a remaining deep and lower grade shallow resources has now also become a major focus and has recently lead to a rebirth of reef mining on the Central Rand Goldfield.

Jan 1, 2009

By J. N. Van der Merwe

"The probability of survival of coal pillars is a more rational indicator of stability than the safety factor. Over time, pillars undergo reduction in size by progressive scaling of the sidewalls. The probability of survival is therefore not constant but reduces over time. The rate of scaling can be quantified, and the reduction of the probability of survival as a function of time can therefore also be quantified. The paper describes the link between the factor of safety, probability of survival, and reduction of the probability of survival. Using the safety factor, probability of survival, and the time at which the probability of survival will reduce to 50% is proposed as a more rational method of evaluating pillar stability than the safety factor alone.IntroductionCoal pillar strength has long been the subject of research in South Africa and several other coal-producing countries. However, it began receiving serious attention only after the Coalbrook disaster in 1960. The most important outcomes of the initial investigations were the groundbreaking research by Salamon and Munro (1967) that resulted in the well-known power formula for pillar strength, and the work by Bieniawski (1969) that resulted in a linear formula for strength. The former approach was based on empirical back-analysis of failed and stable pillar cases, and the latter on in situ strength tests on large specimens.The Salamon and Munro (1967) formula has been widely used in South Africa and even adapted for application to hard rock pillars by researchers such as Hedley and Grant (1972).At the time of the initial work by Salamon and Munro, there were only 27 failed pillar cases suitable for analysis. It was not possible at the time to determine site- or seam-specific strength, and the result was a general formula for use in all seams in all mining districts. Since that time pillars have continued to fail and the database continued to grow – as of 2013, there were 85 cases in the database. Using the additional data, there have been a number of re-evaluations of the strength formula and it has also become possible to differentiate between the different mining seams and areas."

Jan 1, 2016