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By Joseph L. Margin

From a stubborn start to record setting performances in little over a year, that is the story of the English Running Tunnel Boring Machines. The program to transfer technical information on these highly advanced machines from builder to user will be discussed as a vital link to this accomplishment. Some interesting features of these machines will be covered as well as a recounting of the various conditions that were encountered during these drives and how they were resolved.

Jan 1, 1991

Enhance Fine Particle Flotation by Hydrodynamic Cavitation Difficulties in fine particle flotation are well documented. Microbubble flotation has been found to greatly improve the recovery of fine particles and in situ gas nucleation by hydrodynamic cavitation incorporated in the design of modern flotation machines has shown great performance in fine particle flotation and potentially in coarse particle flotation. In this presentation, we will provide an overview on gas nucleation by hydrodynamic cavitation and its role in fine particle flotation with focus on the progress made in our research laboratory. Hydrodynamic cavitation was achieved and the critical role of dissolved gases in the liquid was elucidated by visualisation in a high intensity agitation cell. The in situ gas nucleation on fine particles by hydrodynamic cavitation was identified by zeta potential distribution measurement in model systems. Gas nucleation by hydrodynamic cativation was found to effectively aggregate hydrophobised fine particles thereby leading to enhanced flotation kinetics. This is an abstract only. No full paper was prepared for this presentation.

Sep 13, 2010

The reliability of mining systems is generally low due to their harsh working conditions. Currently, efforts for improving mining system reliability are often made in isolation. This practice could substantially limit the effectiveness of the efforts on overall reliability improvement of the mining system. To enhance the overall reliability of mining systems, an integrated improvement approach is necessary. In this paper, we developed a framework for integrated mining system reliability improvement to address this issue. In this framework, there are five major components including data integration, business process integration, hardware integration, software integration, and analysis/decision integration, but we only focus on the integrated reliability analysis which is important to the analysis/decision integration. The reliability analysis considers the interactions between machines, and the impacts of design, operation, maintenance, automation and working environment on the overall system reliability. These multiple interactions present a big challenge to accurate reliability prediction. In this paper, we for the first time systematically investigated integrated reliability analysis approaches for dealing with this challenge using novel models and methods, including covariate hazard models, intelligent reliability prediction approach, and complex system modeling methods. While these models and methods have found some successful applications in other industries, they in general have not been effectively used for the reliability analysis of mining systems. Our study results show that the system integration approach is applicable to mining systems and can be used for developing a computer aided integration system for the implementation of the integrated reliability improvement approach.

Aug 1, 2013

By D. Tao

The adverse effects of clay particles on coal and mineral processing processes such as gravity separation, flotation, filtration, and thickening are well known in the mining industry. In particular, the presence of ultra-fine clay particles deteriorates froth flotation performance, which has been attributed largely to slime coatings that inhibit bubble attachment and to adsorption of the frother and/or collector by the clay particles. The present study was conducted to evaluate the performance of clay binding agents developed by Georgia-Pacific Resins, Inc. in enhancing coal and mineral flotation performance. Mechanical and column flotation tests were carried out using coal and potash samples. Process parameters investigated include slurry solids percentage, impeller rotation speed, binder dosage, collector dosage, etc. Flotation results show that use of GP reagents significantly enhanced flotation efficiency under different conditions. The required binder dosage and conditioning time was about 1 lb/t and 0.5-1 min, respectively. More significant improvements in process performance were observed at higher solids percentage and higher impeller rotation speed.

Jan 1, 2006

By J. P. Wilson, T. Cook, H. Kling

The Tessenderlo-Kerley Leachprocess has been shown to be effective in the removal of residual copper from molybdenite concentrates. Concentrates of varying mineralogy, including those containing relatively large amounts of chalcopyrite, have been successfully leached on laboratory and pilot plant scales. The lixiviant system is ammonia andammonium bisulfite with air / oxygen addition. An abrasive is added which greatly enhances the kinetics, and it is subsequently screened out and reused. The dissolved copper is easily recovered using existing technology. Extraction profiles, reagent consumptions, and mineralogical data are presented.

Jan 1, 1999

By J. P. Wilson

The Tessenderlo-Kerley Leach process has been shown to be effective in the removal of residual copper from molybdenite concentrates. Concentrates of varying mineralogy, including those containing relatively large amounts of chalcopyrite, have been successfully leached on laboratory and pilot plant scales. The lixiviant system is ammonia and ammonium bisulfite with air / oxygen addition. An abrasive is added which greatly enhances the kinetics, and it is subsequently screened out and reused. The dissolved copper is easily recovered using existing technology. Extraction profiles, reagent consumptions, and mineralogical data are presented.

Jan 1, 1999

Rio Tinto has embarked on a journey to use automation to improve the performance of its surface mines. The driver for automation is to improve the accuracy and consistency of mining processes and less to do with cost savings through labour reduction. A key task in most surface mines is blasthole drilling. The degree to how well this is done cascades through the downstream mining process. It impacts scheduling, excavation, slope stability, material handling, beneficiation and final product blending. Improved blasthole drilling was identified as an objective that has a significant business case in most of Rio Tinto's surface mines. This paper describes Rio Tinto's drill enhancement project that has developed a robust system for automating most of the functions on a Terex SKSS16 drill rig. Automated drilling is currently being used in production at the West Angelas iron ore mine in the Pilbara region of Western Australia. A description of the essential elements of the drill automation system is given together with an overview of how automated drilling is performed remotely from the mine office. A review of some of the benefits of the enhanced drill system is given together with the future plans to extend the functionality of the automated drill and the expected benefits.

May 1, 2010

By Jin Kim, Jerry C. Tien

Water is still the most economical and popular means of controlling dust underground. It is a process that captures dust by bringing water droplets into intimate contact with coal particles. Wetting agents, also known as surfactants, can be added to greatly facilitate such a process since they tend to reduce the interfacial tension between the coal particles (usually hydrophobic) and the liquid. The surfactants used in the study were first chosen on the basis of their HLB (Hydrophile-Lipophile Balance) value, and later tested in order to select the right type and amount of surfactants to give the best performance. Both static and dynamic tests were later conducted using different types of surfactants to examine their respective wetting effectiveness on coal particles. Experimental results show close correlation with the theoretically calculated collection efficiency that is based on a horizontal tunnel and a solid-cone water spray.

Jan 1, 1993

By Dietrich Gross

This paper describes an advanced oxy-fuel combustion technology for re-melting aluminum that significantly reduces energy consumption and emissions. This oxy-fuel combustion technology developed by Jupiter Oxygen is a patented process for combustion of fossil fuels with pure oxygen while excluding air, thereby creating an undiluted high flame temperature and increased efficiency for process heating in industrial furnaces. This unique process has led to improved heat transfer and longer residence time while maintaining the same process temperatures as with air combustion. The energy efficient combustion process allows aluminum companies to operate at a substantially lower cost due to a dramatic fuel savings of up to 70% for natural gas and waste oil (1). The results of more than 10 years of day-to-day experience utilizing the Jupiter Oxygen Corporation oxy-fuel combustion technology licensed to Jupiter Aluminum Corporation in the aluminum re-melting business are discussed.

Jan 1, 2008

By Brian Patrick, Norman Bell, Mark Schoenfield, Thomas Weber, Dietrich Gross

"The reduction of carbon dioxide emissions and the resultant greenhouse gas affect is hampered by the fact that all fossil fuels contain copious quantities of carbon. Process tweaking can keep the amount of carbon dioxide to a minimum but cannot significantly reduce the amount of carbon dioxide generated. The very nature of utilizing fuels requires that they be burned to release the heat required for the various processes. Reduction of metal oxides to manufacture or modify pure metals, generation of power, transportation and many other forms of fuel usage result in much of the generation of man made carbon dioxide. Oxyfuel is a unique contributor to carbon dioxide emissions. While creating higher concentrations of carbon dioxide the total volume of carbon dioxide generated is reduced. This paper will examine the unique characteristics and potential of oxyfuel that make the generation of lower volumes of carbon dioxide possible.Nearly ten years ago a commercial application of oxy-fuel was installed at Jupiter Aluminum Company in Hammond, Indiana. This process was funded and developed by Dietrich Gross CEO. This aluminum remelt facility now runs completely on oxy-fuel and has continuously for over ten years. This has reduced the melt rates to as low as 750 BTU per pound in continuous melting periods."

Jan 1, 2009

By Tuomas van der Meer, Jukka Tanninen, Annukka E. Mäkinen, Mika Martikainen, Laura M. Nevatalo

The mining industry consumes huge water volumes and the waste streams typically contain sulfate, which has caused problems to many operations around the world. Discharge of sulfate to fresh waters is being restricted as the sulfate load increases salinity and causes problems when sulfate is reduced to toxic H2S by natural bacteria. To reduce fresh water consumption, internal water recycling had become a necessity in metallurgical processes. However, the recycling causes accumulation of sulfate and other components in water, causing problems to process performance and increases scaling in piping and equipment. Few technically feasible water treatment processes exist in the market that can be applied to decrease sulfate concentration below gypsum saturation level: biological sulfate reduction, membrane separation, ion exchange, evaporation and chemical precipitation. Some of these technologies are effective for treating wastewater, but there is typically a highly concentrated sulfate fraction left requiring still further treatment. Outotec has developed a sulfate removal solution, Outotec Ettringite process, which allows flexible control of residual sulfate concentration, thereby opening doors for increased water recycle within processes and control of the sulfate in discharged waters. In this article the results and benefits of this novel process along with examples of operating costs are presented.

Jan 1, 2014

By B. Spigarelli

Carbon dioxide sequestration by conversion to carbonates has become a promising option for CO2 storage. Experiments were conducted to determine the feasibility of CO2 sequestration at ambient conditions using a Ca-rich industrial waste in a carbonate solution. The Ca-rich industrial waste used in this study was lignite fly ash. Fly ash was chosen because it is cheap, available near large CO2 point sources, already in powder form, and reactive due to amorphous properties. In the experimental set-up, CO2 absorption was inferred by monitoring feed and exhaust gas CO2 concentrations. The addition of an alkali to a fly ash-distilled water solution provided a 50% increase in CO2 absorption of the solution. Absorption time also increased by 50% compared to a fly ash-distilled water solution. TGA analysis was used to determine the extent of CO2 sequestration in the carbonate form. At a liquid to solid ratio of 20:1, the conversion of ?free? calcium to carbonates was 75%. A CO2 balance on the system concluded that at the current operating conditions 42% of the total CO2 fed to the system was sequestered in the carbonate form. SEM-EDS analysis of the fly ash particles before and after reaction with CO2 indicated that the carbonate compound being formed was calcium carbonate. The analysis identified rhomboidal structures on the surface of the fly ash particles after reaction with CO2, but not before. These rhomboids are characteristic of calcium carbonate formation and they had higher Ca, C, and O concentrations than the host spheres, suggesting calcium carbonate formation.

Jan 1, 2012

By P G. Bourke, A Yáñez, G J. Jameson, N M. L Kupka

The kinetics of fine and ultrafine particles in conventional mechanical flotation cells are limited (Feng and Aldrich, 1999; Trahar, 1981; Wang et al, 2016). Accordingly, even limited recoveries with such machines require long residence times. Theoretical investigations into the rate of capture of fine particles by flotation, have indicated that a key parameter is the rate of shear in the fluid surrounding the bubbles and the particles. Achieving fast flotation rates of ultrafines requires a new method of bringing the particles and bubbles into contact, utilising the beneficial properties of highly dissipative flows to break through the water boundary layer. In 2010, a new type of flotation cell known as the Concorde Cell was described, in which bubbles and particles are brought together in a sonic shock wave (Jameson, 2010). Earlier research had shown that when a dispersion of fine bubbles in liquid passed through a converging nozzle at the local speed of sound, the resulting shock wave downstream generates a mass of even finer bubbles in the flow as it passes through the shock wave. The fluid within the shock wave is highly turbulent, and an environment is created that is very favourable to particle-bubble collision and capture. In this paper, we briefly describe the Concorde Flotation Cell and give examples of its use.

Aug 24, 2022

Recent U.S. mine disasters identified a need for improved training of miners in escape from mine fires and explosions. Researchers at the National Institute for Occupational Safety and Health?s (NIOSH) Spokane Research Laboratory (SRL) have designed fire-escape training software for use in a mine-safety training course. The software allows four trainees to work together in a virtual world via a computer network. Trainees responded favorably and showed a marked improvement in locating the proper evacuation routes on subsequent trials. In collaboration with the Pittsburgh Research Laboratory (PRL), a more elaborate fire evacuation scenario is being developed. Further study is needed to confirm that virtual training will translate to improved safety outcomes in the real world. Keywords: virtual reality (VR), safety, training, mining, mine fire evacuation

Jan 1, 2009

By A. Singh

"Flotation of fine (< 10 µm) minerals is a challenge exacerbated by the emerging practice of fine grinding flotation feed to better liberate targeted minerals; however, the ability of conventional flotation cells to float liberated fines remains questionable. The Gold Ore solution using Mach reactors was tested at Mintek, South Africa, and showed an ~180% increase in the Kelsall kfast factor, a projected recovery improvement of 4% for the Mach-reactor case, and final concentrate grade twice that of conventional flotation. Theory, pilot plant results, and key aspects of plant design, supplemented by operational plant observations after commissioning, are discussed.RÉSUMÉ Le procédé de flottation de minerais fins (< 10 µm) pose de grandes difficultés, lesquelles sont aggravées par la pratique émergente de l’alimentation du circuit de flottation avec des mailles de broyage très fines pour mieux libérer les minéraux ciblés ; la capacité des cellules de flottation classiques à flotter les fines de minerais libérées reste cependant discutable. La solution proposée par la société Gold Ore, qui utilise des réacteurs Mach, a été testée à Mintek, en Afrique du Sud ; elle affichait une augmentation d’environ 180 % du facteur kfast développé par M. Kelsall dans son modèle de flottation, une amélioration prévue de la récupération de 4 % dans le cas du réacteur Mach, et une teneur finale des concentrés deux fois plus importante que celle obtenue avec la flottation classique. Sont débattus dans cet article la théorie, les résultats générés par l’usine pilote ainsi que les principaux aspects de la conception de l’usine complétés par des observations relatives à l’usine en activité après sa mise en service."

Jan 1, 2018

By A. Singh

"The flotation of fine minerals less than 10 µm in size is an age old challenge spanning both the precious metal and industrial mineral sectors across a range of commodities. This problem has been brought into sharper focus by the emergence of the practice of fine grinding of flotation feed to effect better liberation of the targeted minerals. However, the ability of conventional flotation cells to effectively float the liberated fines remains questionable. In order to overcome this problem, Gold Ore postulates the “Bringing the Mountain to Mohamed” hypothesis which comprises the steps of gas nucleation on particle surfaces, aggregation of particles and levitation of aggregates. Testing of this hypothesis at Mintek, South Africa, showed a ~180% increase in the Kelsall kfast factor coupled with a projected recovery improvement of ~4 % for the Mach Reactor case coupled with a final concentrate grade of ~2 times that of conventional flotation. These fundamentals were then extrapolated to plant scale with Mach Reactors installed on the flotation feed at Platmin’s Tailings Scavenger Plant (TSP) with the objective of scavenging the fine minerals lost to tailings by the main plant. This paper details the theory, pilot plant results as well as key aspects of the full scale plant design supplemented by operational plant observations after commissioning. This game changing application is regarded as being pivotal to future flotation plant design whilst providing the technology leverage required for the survival of mineral operations in an economically unfriendly environment.INTRODUCTION - THE CONUNDRUM OF FINE PARTICLE FLOTATION“If the mountain won't come to Mohamed then Mohamed must go to the mountain” is an age old saying written into the book of proverbs in 1670. Legend has it that Mohamed promised his people that he would summon a mountain to come over to him so that he could offer up his prayers from its summit. After numerous attempts at moving the mountain went in vain, Mohamed, quite unabashed, said “Well if the mountain will not come to Mohamed, then Mohamed will go to the Mountain.” In this analogy, Mohamed is a fine particle <10 µm and the mountain is a bubble within a flotation system. The age old challenge is how to bring these two together to achieve attachment?"

Jan 1, 2016

By M. Fan, A. Hobert, W. van Dyk

Low flotation recovery and selectivity have been long-standing problems in the treatment of most ultra-fine phosphate ores. This paper investigates the improved flotation of two ultra-fine Brazilian phosphate ores from Itafos’ Arraias project. These ores are predominantly composed of quartz, muscovite, apatite and a Ca-Al phosphate. As a result of fine phosphate dissemination and associated grinding requirements, column flotation was selected for the metallurgical test program to address the inherent limitations of fine particle flotation using conventional flotation cells. Accordingly, both benchtop Denver cell and laboratory column flotation tests were conducted to optimize their respective flotation responses. Improved flotation performance was achieved using column flotation as compared to benchtop mechanical flotation. In column flotation, a P2O5 concentrate grade of 30.5-31.0% was yielded at a flotation recovery of 83.7-85.1% for the 38x0µm generated ultrafines. The benefits of Eriez’ column flotation technology realized from this study include a higher degree of selectivity, increased recovery, and reduced collector dosage as compared to bench-scale mechanical flotation.

Mar 2, 2022

By M. Fan, R. Letkiewicz, A. Hobert, J. Milbourne

Ultrafine copper, gold and silver minerals flotation has become increasingly important because of the rising demand for processing finely disseminated ores. This paper investigates the improved flotation of ultrafine ores from a Troilus Gold project. Troilus is primarily an Au-Cu deposit but contains minor amounts of Ag, Zn and Pb, as well as traces of Bi, Te, and Mo. As a result of ultrafine Cu-Au-Ag dissemination and associated grinding requirements, Eriez’ column/StackCell and Denver benchtop cells were utilized to optimize their respective flotation responses. Enhanced flotation results were achieved using column and StackCell technologies. KAX 51 and SPRI 206 collectors, Na2SO3, and ZnSO4 depressants were the primary reagents employed. In column/StackCell flotation of three main mineral deposit ore composites, the rougher-scavenger-cleaner circuit Cu, Au and Ag flotation recoveries were 90.4~95.8% at a copper grade of 13.6-17.4%, 87.5-95.1% at a gold grade of 101-145.9 g/t, and 88.6-91.8% at a silver grade of 62.6-251.4 g/t, respectively. The benefits of Eriez Column/StackCell flotation technologies include high flotation selectivity and increased recovery due to unique hydrodynamic designs. Specifically, the StackCell design facilitates high turbulent kinetic energy dissipation rates to improve fine particle recovery and incorporates countercurrent wash water to significantly reduce hydraulic entrainment of the finest size gangue minerals to the froth product.

Feb 1, 2023

By N. S. Dalal, J. F. Mega, X. Shi, V. Vallyathan

Several studies have suggested that pulmonary toxicity to asbestos and silica may be mediated through oxidant-induced cell injury. We have reported recently that surface radicals associated with freshly fractured silica may be an imponant factor in cell injury and induction of pulmonary disease. Although the generation of oxygenated radicals in dust-cell interactions has been demonstrated, there are no data correlating the toxicity of a dust with the level of oxygen radical generation by the dust during its interaction with phagocytic cells. In the present study, we have investigated the in vitro generation of oxygen free radicals from human neutrophils and rat alveolar macrophages stimulated with freshly fractured silica, aged silica, amosite, crocidolite, chrysotilc, and a nontoxic dust, barite. Electron spin resonance (ESR) with the aid of a spin trap phenyl-N-ten-butyl nitronc (PBN) was used to measure the oxygen radicals generated during phagocytosis of the dusts. The relative toxicity index and ESR peak heights, on an equal surface area basis and normalized to barite as one, showed a direct relationship. The normalized toxicity indices and peak heights were: silica, 3.5 versus 2; chrysotile, 4 versus 2; crocidolite, 11 versus 8; and amosite, 26 versus 13. Addition of hydroxyl radical scavengers such as catalase, dimethyl sulfoxide, 1,3 dimethyl-2-thiourea (DMTU), sodium benzoate, and mannitol prevented the radical generation. Carmustine, a glutathione reductase- glutathione peroxidase inhibitor, caused a 5-fold increase in the radical generation. These results indicate that a nontoxic dust such as barite generates toxic oxygen radicals at a minimal level that can be quenched by the normal cellular defense system. For toxic dusts such as silica, amositc, chrysotile, and crocidolite, the potential for oxygen radical generation is enhanced by their surface propenies, physical dimensions, and the surface-based radical-generating redox sites. The enhanced radical generation may impair the cellular defense system, resulting in cell injury. Use of scavengers, chelators, and potentiating agents suggests the membrane-based oxidase system as the probable primary source of the radical-generating system. The data presented herein suggest the generation of oxygen free radicals as an important primary event in silica- as well as asbestos-induced cell injury.

Mar 1, 1992

By K. Osburn

South Deep Gold Mine, owned by Gold Fields Ltd., is situated near Westonaria in the Gauteng Province of South Africa and mines the conglomerate bands of the Upper Elsburg reefs (Mondeor Conglomerate Formation) of the Witwatersrand Supergroup and the Ventersdorp Contact Reef (VCR) of the Ventersdorp Supergroup. The stoping and underground developments are mechanized. The Upper Elsburg reefs are mined by a variety of mining methods, including mechanized drift and fill, modified drift and bench, longhole stoping, and low-profile mining. Optimal mine design and scheduling for deep-level mechanized mining are complex, and success is highly dependent on detailed, robust, and accurate geological and geostatistical models. Geological structures significantly influence the sedimentological characteristics, distribution, and preservation of the Upper Elsburg reefs and VCR. Accordingly, particular emphasis is placed on the generation of a mine-scale structural model that accommodates the relationships between the older north-trending fault systems (West Rand and Panvlakte faults) and younger east-trending dextral wrench faults. Results from underground mapping, borehole intersections, and highresolution three-dimensional seismic data have been integrated to produce coherent three-dimensional geological models. The Upper Elsburg reefs suboutcrop against the VCR and comprise an easterly diverging clastic wedge, thickening from the suboutcrop position, to approximately 130 m at the mine?s eastern boundary. The Upper Elsburg reefs are characterized by conglomerate and quartzite bands forming multiple, stacked, upward-fining unconformity-bounded couplets. Palaeocurrent directions are dominantly from west-northwest to east-southeast, indicating that the more proximal deposits are preserved close to the suboutcrop, with distal facies to the east. Sedimentological modelling is applied to individual stratigraphic units and caters for facies definition. This is achieved through channel width (CW) kriging and fitting of type sections to borehole and mapping data. Homogenous geological geozones for each stratigraphic unit are thus defined within individual structural blocks on the basis of those sedimentological parameters that have been found to have a positive spatial correlation to gold concentration. These geozones then serve as constraints to the evaluation of the orebody. This contribution presents a summary of the modelling processes that are currently applied in the development of high-confidence, timeously produced geological models that are essential input for mineral resource estimation and mechanized mine planning and scheduling.

Jan 1, 2014