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Water represents 80?85% of the volume of mineral pulp processed in flotation circuits. Imperatives for a more detailed focus on circuit water quality and its control have come from increasing requirements to use relatively impure primary water supplies (e.g. high salinity, treated sewage) and high proportions of recycle from tailings dams, thickener overflows, dewatered and filter products. An integrated methodology for examining process water quality and its effect on minerals separation has been developed coupled with minerals surface chemistry across the complete processing circuit. Unrecognised factors, including varying proportions of water streams (daily or hourly), colloidal precipitation, highly variable pH and Eh, reaction and dissolution of minerals, minerals surface layer coatings, residual reagents and their reaction products, and microbiological activity have been studied in eight mineral processing circuits. The methodology combines: solution survey and modelling; microbiological surveys; minerals surface analysis and modelling; and process response. It has been possible to match the predicted (model) pulp chemistry with that measured from surveys of the solution and mineral surfaces. Treatment methods have included: monitored and balanced stream combinations; organic species removal; flocculation and aggregation; induced precipitation; dissolved air flotation; ageing (oxidation, UV exposure); and chemical surface conditioning of minerals. Some specific achievements from the methodology applied in plant and laboratory testing, with examples from case studies, will be described.

Jan 1, 2001

By J. Dvorácek

Similar to the case of any other business venture, the activities of mining industries are profit-oriented. Nothing will stop successful businesses in their quest for new localities to be prospected for minerals of their choice, because the useful economic life of any mine is limited. Before starting the process of land acquisition, it is important for any mining company to be able to forecast the profitability of the venture. The focus of this paper has been on the prospects of success, concerning the case of the opencast extraction of aggregates for construction. A set of 70 successful and loss-making quarries was subjected to investigation. An international company owns the quarries, which are located in seven European countries. The method of discriminate analysis provided the criteria for assessing future economic performance. The same criteria served the purpose of classifying other quarries belonging to the company.

Jan 1, 2012

By N. Barton, E. Quadros

This paper addresses the prediction of groutable joint apertures, grout penetration limitations, and possible grout take volumes per cubic metre of rock, as a result of 5 to 10 MPa pre-injection pressures ahead of tunnels. Joints are obviously opened more than in the preceding Lugeon tests, and many rock mass properties can apparently be improved if stable micro-cement based materials are used. Cet article concerne la prédiction des ouvertures des fractures injectables, les limites de pénétration du coulis et les volumes injectés par mètre cube, d’après les résultats des injections à l’avant tête des tunnels sous pressions de 5 à 10 MPa. Evidemment les joints s’ouvrent plus que dans les essais Lugeon précédents. Maintes propriétés du massif peuvent apparemment être améliorés si l’on emploi des coulis a base de micro-ciment stable. Die Publikation widmet sich der Prognose injizierbarer Kluftöffnungen, Grenzwerte für Injektionsreichweiten und erreichbarer Injektionsvolumen pro Kubikmeter injizierter Fels, durch die Anwendung von 5 bis 10 MPa Vorinjektionsdrücken vor der Tunnelfront.Die Klüfte werden offensichtlich weiter geöffnet als in den vorhergegangenen Lugeon Versuchen und mehrere Felsparameter können durch die Verwendung von stabilisierten Micro-Zement basierten Injektionsmaterialien verbessert werden.

Jan 1, 2003

By R. Pickering

The purpose of this paper is to explore the application of technology to stoping systems. Technology, because for the past 100 years the South African narrow reef mining industry has battled to control working costs in a labour-intensive industry. Stoping systems, because it is the stoping method and methodology which is at the heart of the mining system. Introduce a more efficient stoping system and the mining system will look after itself. The technology applied to stoping over the past 100 years can be categorized as follows: ?The introduction of pneumatic rockdrills early this century, the cumbersome rig mounted units being replaced by smaller, lighter hand-held units which were then made easier to use with the addition of an air leg ?Scraper winches to replace gravity and shovels to move rock both in the face and the gullies were first introduced in the late 1920s ?Hydraulic props as a support method arrived in the1960s ?Some people argue that tungsten carbide inserts were equally important. There have been a number of attempts to introduce different technologies into stoping, the most recent being trackless equipment. Where the stoping layout suits the technology it has been successful. There have been too many instances where a technology has been installed because it is fashionable. At the end of the day the outcome from change in the stoping systems has to be safer and more profitable mining systems. It is the contention of the author that change is only likely to be effective if it is supported by the introduction and application of appropriate technology.

Jan 1, 1999

By B. Unver

Effective strata control is a prerequisite for maintaining an efficient mining operation. If the strata in the vicinity of an opening are not controlled effectively, it is impossible to perform a safe, efficient and economical operation. In this paper, the reasons and outcome of instability problems observed in roadways opened in clay and marl at the Bolu Colliery of Yeni Çeltek Establishment are investigated. Roadways under examination were located in a syncline causing high residual tectonic stresses. Factors affecting the instability have been studied thoroughly by examining geology and tectonics of the area, establishing convergence measuring stations to understand in situ behaviour of supports and laboratory tests to determine engineering properties of samples taken from nearby convergence measurement stations. As a conclusion, a new production strategy and a new support system are recommended to maintain stability.

Jan 1, 1999

The coal-based power generation industry faces increased pressure from all sectors to improve its environmental performance. This is due to increased awareness of and concerns regarding greenhouse-and acid-gas emissions, toxic metal releases (to both air and water) and water availability. A methodology to assess this industry?s environmental performance is needed. Such a methodology should assess all environmental impacts accurately, recognizing the irspatial and temporal dependence, and taking into account the social acceptability of technologies employed. Here, we develop a methodology to determine the environ-mental impact associated with solid wastes generated by this industry, and apply this to the specific case of ash management. More specifically, the case study compares the environmental footprint of an ash deposit for a number of operational water management scenarios. The methodology considers leachate generation processes from ash impoundments to obtain a time-dependent concentration profile of mobile constituents at the interface between the ash impoundment and the surrounding environment. This leachate prediction modelling is subsequently linked to plume dispersion modelling tools to determine the fate and transport of leached components, predominantly salts, into groundwater. Together, these provide a measure of the extent to which a land mass is affected by leachate migration from the deposit. To determine the exact boundary between regions of acceptable and unacceptable risk to the environment, we use Ecological Risk Assessment concepts. In this way it is possible to obtain a time dependent affected land footprint which could be used as an indicator of the environmental impact of solid waste management practices. This information can be included in a set of environmental criteria which form the basis of an overall environ-mental impact assessment, using tools such as Life Cycle Assessment (LCA). The value of LCA is that its structure is consistent with accepted models of environmental decision making, where different approaches to valuation in impact assessment assist in prioritizing impacts on the basis of their perceived significance. The proposed ?affected land footprint? metric represents a significant improvement over current LCA impact indicators for solid waste management practices. Keywords: Environmental Impact Assessment, Environmental Risk Assessment; Life Cycle Assessment; coal ash; leachability; salinity

Jan 1, 2002

By Marco Barla, Mariacristina Bonini, Giovanni Barla

ABSTRACT: The paper describes the characterisation studies of Tectonised Clay Shales at laboratory and in situ scale. The interest relates to tunnelling under squeezing and swelling conditions, in Italy, along the Apennines. The results of monitoring during full face excavation are presented in conjunction with numerical modelling. RESUME: Cet article présente la caractérisation, à l'échelle du laboratoire et in situ, des Argiles Chaotiques. L'attention est portée sur le creusement, dans ces milieux gonflants, des tunnels, dans les zones montagneuses des Appennini, en Italie. Enfin, on présentera les résultats de la modélisation numérique et la comparaison de ces derniers avec les mesures effectuées in situ. KURZFASSUNG: Die Arbeit beschreibt die Charakterisierungsstudien von tektonisierten Schiefertonen, sowohl im Labor als auch vor Ort. Das Interesse gilt dem Tunnelbau unter Quetsch- und Schwellbedingungen in Italien entlang der Apenninen. Die Überwachungsergebnisse des ganzflächigen Ausbruchs werden mit numerischen Modellen präsentiert.

Jan 1, 2003

By D. S. Dihalu

A generalization of Gy?s model for the fundamental sampling error introduced the new ?parameter for the dependent selection of particles?, denoted as Cij. This allows for modeling deviations from the ideal situation where the selection of a pair of particles is composed of two independent selections. The generalized model potentially leads to more accurate variance estimates in the case of clustering of particles, differences in densities or sizes of the particles or repulsive inter-particle forces. A straightforward and practically applicable method is needed for the determination of this parameter for miscellaneous mixtures in industrial settings. In this contribution, the feasibility of using digital image analysis to determine this parameter Cij, will be demonstrated. Line transect sampling of a digital image was used to construct a transition probability matrix. A new algorithm to derive quantitative estimates for Cij will be presented and discussed. The applicability was verified by a photograph of zirconium silicate particles of sizes typical for industries dealing with pharmaceutical, food/feed, and environmental applications. Conditions affecting the practical applicability are identified and potential pitfalls will be discussed, including e.g. how a potential unrepresentative surface can affect the quality of the estimate of Cij.

Jan 1, 2010

By E. H. Myrhaug, K. Aasly, T. Malvik

Quartz is one of the main raw materials for the carbothermic production of ferrosilicon and silicon metal. The ideal process is written: SiO2 + 2C = Si + 2CO The real process is much more complicated, depending on the quality of the raw materials. Several research projects have been carried out on quartz for the (Fe)Si process during the last 50-60 years. One of the important properties that have been discussed in this review is the volume expansion that takes place between 850 °C to 1000 ºC and explosive disintegration for some quartz types. No final and definite conclusions have been made but several reasons have been mentioned: The influence of the phase transformation to tridymite, which takes place within the same temperature interval, has been discussed in several papers. Alkali impurities have been mentioned as a critical factor for this transformation to take place. Other researchers have mentioned mica impurities as a critical factor for the behavior of the quartz at these temperatures. Studies of fluid inclusions in quartz was reported in some papers focusing on the volume expansion of these during heating as a source of explosive disintegration, especially along planes of healed micro fractures that often contain vast numbers of such inclusions. Several methods for investigations of the important properties of quartz have been presented and these provide a good basis for the further research on quartz raw materials.

Jan 1, 2007

By D. O’Connor, A. Pytlik, D. J. Corbett

The resistance of yielding rockbolts to multiple impact loads was tested by means of a drop hammer. The methodology was based on the ASTM D7401-08 standard as well as the requirements specified for rockbolts by Luossavaara-Kiirunavaara Aktiebolag (LKAB – a Swedish mining company) and the Safety In Mines Research Advisory Committee of South Africa (project number GAP 423). During the tests, the loading force and bolt elongation were measured with a sampling frequency of fs = 19.2 kHz. In order to analyse the phenomena involved, the tests were recorded using two independent high-speed video cameras (600 and 1000 frames per second) and one thermal camera (128 frames per second). The tests demonstrated that all the samples transferred double the gravitational potential energy of Ep = 50.85 kJ from the impact load of mass m = 2825 kg and impact velocity of v = 6.0 m/s without failure. Damage to the bolt-resin contact in the upper anchoring zone of the bolt in the steel tube occurred after subsequent impacts. As a result, the macro-deformed bolt exhibits additional yield, and its operation following the shearing of the resin bond is similar to that of a ‘cone bolt’. Only one test resulted in damage to the threaded bolt rod-nut coupling, during the fourth impact; however, no damage to the bolt-resin contact zone was observed.

Nov 6, 2023

By R. Heuberger

South Africa?s Mining Industry operates in an uncertain world. The industry is buffeted by problems regarding retrenchments, unemployment, low productivity, rising costs, volatile exchange rates, commodity prices and government regulations. With these uncertainties facing the decision makers, what does applied technology offer the industry?s management? Modelling languages with risk analysis have been available for decades, but in the past their use has been very expensive, requiring large mainframe computers and lots of computer time. Today, PCs and laptops have incredible power, which makes interactive risk analysis affordable and viable for all enterprises, whether small or large. ?What is risk analysis? ?What is Monte Carlo simulation? ?What kinds of computer models need to be created to use risk analysis and Monte Carlo simulation effectively? This paper addresses these questions and illustrates, with a practical example in the mining industry, how risk analysis techniques can be used to support decisions in the climate of uncertainty.

Jan 1, 2005

By F. P. Hassani

Today, mine backfilling has become an integral part of mining operations, both from a local and overall ground control point of view, and as regards mining techniques and environmental considerations. During the past decade, substantial research has been carried out to contribute to the better understanding of the mechanisms involved in mine backfill behaviour. This work involved analytical, experimental and numerical studies at different scales. Accordingly, this work has been aimed at developing backfill design guidelines for actual working conditions. Backfill design for deep mining conditions is complex and requires understanding of various elements. The most important of these elements are: backfill inherent strength parameters, backfill placement method, stope geometry and interaction between backfill and host rock. The mobilization of backfill strength parameters controls the backfill behaviour and thus, its failure mode. It is believed that the governing boundary conditions and backfill-rock interaction influence the backfill strength mobilization significantly. Accordingly, the interaction between backfill and host rock is an influential factor in overall backfill behaviour under applied loads. The focus of this research is to investigate the backfill-rock interaction, considering a nonlinear behaviour for both backfill and rock mass. Assuming typical stope geometry, the FLAC code was used to model the complex boundary condition associated with narrow vein mining conditions and to simulate the backfill behaviour. A comprehensive numerical study was conducted and the results obtained were compared against field observations. The analysis of findings provides qualitative results, which can be used for backfill design. Keywords: Numerical modelling, backfill, deep mining, non-linear behaviour, rock mechanics, backfill behaviour, narrow vein mining.

Jan 1, 2008

By R. Webster

"Daniel Krige’s influence on soil science, and on soil survey in particular, has been profound. From the 1920s onwards soil surveyors made their maps by classifying the soils and drawing boundaries between the classes they recognized. By the 1960s many influential pedologists were convinced that if one knew to which class of soil a site belonged then one would be able to predict the soil’s properties there. At the same time, engineers began to realize that prediction from such maps was essentially a statistical matter and to apply classical sampling theory. Such methods, though sound, proved inefficient because they failed to take account of the spatial dependence within the classes.Matters changed dramatically in the 1970s when soil scientists learned of the work of Daniel Krige and Georges Matheron’s theory of regionalized variables. Statistical pedologists (pedometricians) first linked R.A. Fisher’s analysis of variance to regionalized variables via spatial hierarchical designs to estimate spatial components of variance. They then applied the mainstream geostatistical methods of spatial analysis and kriging to map plant nutrients, trace elements, pollutants, salt, and agricultural pests in soil, which has led to advances in modern precision agriculture. They were among the first Earth scientists to use nonlinear statistical estimation for modelling variograms and to make the programmed algorithms publicly available. More recently, pedometricians have turned to likelihood methods, specifically residual maximum likelihood (REML), to combine fixed effects, such as trend and external variables, with spatially correlated variables in linear mixed models for spatial prediction. They have also explored non stationary variances with wavelets and by spectral tempering, although it is not clear how the results should be used for prediction. This paper illustrates the most significant advances, with results from research projects."

Jan 1, 2015

By A. Nkolele

Paper written on project work carried out in partial fulfilment of B. Tech (Metallurgical Engineering) degree Fine coal of the Goedehoop Colliery is dewatered by centrifuging before being sold. Full-scale plant tests were carried out to reduce residual cake moisture by the addition of surfactants. It is believed that by modifying the interface between the coal surface and the adherent surface water, as well as the water occluded in the cake voids, drainage is improved. Two anionic surfactants at concentrations up to 150 g/t were tested on coal of <0.5 mm size. The results demonstrate that quite high additions of surfactant (80 g/t)were needed to reduce moisture from 20 to about 17?18%. It was observed that when increasing surfactant additions at low levels, within a very narrow concentration range, the retained moisture first increased sharply only to decrease sharply immediately thereafter; this effect points to a critical surfactant concentration. Based on the obtained results, the use of surfactants cannot be recommended at this stage; further investigations under more controlled conditions are required.

Jan 1, 2004

Paper written on project work carried out in partial fulfilment of B. Eng (Mining Engineering) degree The stability of a ferrosilicon dense medium suspension is one of the most important parameters to keep under control since it determines the density gradient of the medium in the separation zone and thus directly influences separation sharpness. The stability of ferrosilicon suspensions were characterized using settling tests employing a differential pressure method. Particles smaller than 45 µm and especially the ore fines played an important role in the settling behaviour of the solids. High medium stability is favoured by ore fines, fine medium particles, and high medium densities. Keywords: dense media, ferrosilicon, dense medium stability, ore fines

Jan 1, 2002

By G. O. Oniyide, H. Yilmaz

The South African platinum mines in the Bushveld Complex (BC) have unique features that distinguish them from the gold mines. They have a higher horizontal stress closer to the surface, lower occurrence of seismic activity (caused mainly by pillar failure), and are sited in an area of high geothermal gradient. One of the future challenges of platinum mining is the increasing temperatures as the mining depth increases. High temperatures invariably bring about higher ventilation costs and require different approaches to human factors and ergonomics. Excavation stability would also be another area of concern due to increasing stresses. In this investigation, the effect of temperature on the physical and chemical properties of selected Bushveld rocks (chromitite, pyroxenite, norite, leuconorite, gabbronorite, mottled anorthosite, varitextured anorthosite, granite, and granofels) was studied by means of optical microscopy and scanning electron microscopy using energy-dispersive Xray spectrometry (SEM-EDX). The rock specimens were heated in a temperature-controlled oven a rate of 2°C /min to 50°C, 100°C, and 140°C and kept at temperature for five consecutive days. Samples were allowed to cool to ambient temperature (approximately 20°C) before image capturing. Micrographs of the specimens were taken before and after heat treatment. All the SEM samples were also subjected to heating and cooling on alternate days for ten days in order to observe the effect of repeated heating and cooling on the rocks. The results of the optical microscopy analyses showed minor physical changes in the rocks. The SEM images revealed that cracks initiating at lower temperatures extend with increasing temperature. The chemical analyses showed that the temperature range considered in this research is not high enough to induce changes in the chemical composition of rock samples.

Jan 1, 2016

By P. Gonzalez, C. Ariyo, L. Holappa

Oxidation state of titanium was determined in CaO-SiO2-TiOxslags in the composition range25–53 per cent CaO, 27–46 per cent SiO2, 10–55 per cent TiOxat 1873K using gas equilibration method. In the experiments, slags with different titanium oxide contents were equilibrated with a known carbon monoxide and carbon dioxide ratio. The results were used to determine the Ti3+and Ti4+contents as well as the activity coefficient ratio of corresponding oxides in the slag. The dependency of the activity coefficient ratio as a function of oxygen partial pressure was determined. Keywords: titanium, titanium oxide, activity, activity coefficient, slag iron, carbon monoxide,carbon doixide, gas, equilibrium.

Jan 1, 2004

The reality of rising electrical power costs and the haunting prospect of decreasing electrical power availability are a threat to the growth of new projects and expansion programmes that could negatively affect the sustainability of mining operations. These threats require the adoption of effective power saving measures aimed at three principal objectives: the elimination of wastage, the reduction of power usage particularly during peak demand periods and, more importantly, improving the efficiency of high power-demand processes. It is reasonable to assume that the greatest impact will be achieved by concentrating on those processes that are large electrical power consumers. For Anglo Platinum operations, mine ventilation and, currently to a lesser extent, mine cooling are two continuous processes that fall in this category. It is estimated that these may consume fifteen to thirty-five per cent of the power delivered to the shaft head-depending on the shaft&apos;s design. Mine ventilation systems suffer from inherent, historical inefficiencies that lead to excessive power consumption. Air cooling systems are designed to be energy-wise in terms of modulating refrigeration plant operation to meet the underground requirements while maximizing use of &apos;free&apos; cooling from surface conditions. Currently about ninety-five per cent of the refrigeration capacity used in Anglo Platinum mines is dedicated to surface bulk air coolers. The net thermal efficiency of these systems is compromised as mines expand in depth and on strike. Looking to the future, this practice will be complemented by more energy demanding underground cooling tactics requiring considerably higher electrical power consumption per unit ton produced. To counter this increase in power consumption, more energy-efficient systems and advantageous transient strategies such as thermal storage and the use of ice-on surface and possibly even underground-are being considered. This paper describes work currently undertaken and planned by Anglo Platinum operations to reduce power consumption by main fans during off-shift periods, the associated efforts currently introduced to reduce underground air leakage, the possibility of introducing more efficient auxiliary ventilation systems, the feasibility of thermal storage, and a brief look at energy recovery system as a means of countering the anticipated power demand associated with underground cooling. Keywords Mine ventilation, mine air cooling, energy efficiency, chilled service water, energy recovery, air wastage, fan selection.

Jan 1, 2011

By M. J. Lukhele

Paper written on project work carried out in partial fulfilment of B. Tech (Mining Engineering) degree A number of high wall mining methods were developed over the years to mine coal reserves exposed on the high walls created during surface mining. The auger mining system was initially developed in the early 1940s in the United States of America. High wall mining is a method of recovering coal from seam exposed either by mechanical excavation methods or natural erosions. This is usually associated with strip-mining (opencast) where the stripping ratio is high and uneconomical to mine using the opencast mining method. This paper discusses the surface auger mining as deployed at Rietspruit Mine Services Proprietary Limited.

Jan 1, 2002

The aim of this research was to study the absorption characteristics of thermally dried fine coal from South African collieries. After milling to ?150 µm and pressure filtration, the samples were subjected to either air drying or thermal drying at 150°C. The samples were then put into a climate box at 28°C and at three different relative humidity levels, namely 30, 60 and 94 per cent. It was found that the equilibrium moisture content of thermally dried coal at a specific relative humidity was lower than that of air dried coal. The relationship between the equilibrium moisture content and relative humidity is described by 1 ? RH = exp (-KTMen). There was no relationship between the volatile matter content and equilibrium moisture content, but there was an increase in the equilibrium moisture content of the coal with an increase in mineral content. The moisture uptake rate increased with an increase in temperature and a decrease in particle size. A model is discussed that fitted the experimental data and gave a good prediction for changes in the conditions. There was no evidence of greater moisture absorption by thermally dried coal. Keywords: Fine coal, thermal drying, drainage, South Africa, drying

Jan 1, 2002