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By M. S. Shishvan, J. R. van Duijvenbode, L. M. Cloete, M. W. N. Buxton

Geochemical and mineralogical datasets from Tropicana Gold Mine, Australia, have been used to define ore fingerprints. VNIR/SWIR spectral data were represented by four normalised wavelength regions and were clustered to form spectral classes. Sequentially, these spectral class proportions within a block and collocated XRF data were clustered to form material types (fingerprints). The material types were related to an Equotip-BWi correlation. These correlations can be used to extrapolate a hardness signature and generate a BWi proxy for different blocks. The combined fingerprints and BWi proxy can assist as a tool for enhancing the prediction of comminution behaviour. They can explain specific domain-related hardness variations. For example, one material type could be separated into a softer (~15-18 kWh/t), and harder (>20 kWh/t) material blend. This was accomplished using the commonly overlooked VNIR region at 605 nm. This outcome has significance for blending strategies.

Sep 1, 2021

By B. Kweto, W. Legodi, C. van Buuren, R. F. Sandenbergh

Biooxidation, and especially the BIOX® process, is a viable, economical and environmentally attractive process to liberate gold hosted in refractory sulfides by oxidatively leaching the sulfides as soluble sulfates. The moderate to high cyanide consumption during the subsequent cyanidiation of the washed biooxidation residue is probably caused by the retention on the solids of labile sulfur species formed during the multi-electron oxidation process of sulfide to sulfate. In this work the nature and mode of transport of the cyanicides in the products from the mesophile BIOX® process, as well as that of the combined mesophile and thermophile bioxidation process, were considered and strategies to reduce cyanide consumption evaluated. It was found that labile sulfur species were the major cyanide consumers in the mesophile biooxidation product, forming predominantly thiocyanate during cyanidation. The transfer of labile sulfur species was only marginally decreased by more intensive and thorough washing of the biooxidation products with warm and hot water, intense stirring and warm caustic leaching. A major reduction in cyanide consumption was however achieved by using a combined mesophile and thermophile biooxidation process. Keywords: Biooxidation, refractory sulfide gold ores, cyanide consumption

Jan 1, 2020

By E. Schoeman

Ion exchange resins were investigated for the effective recovery of platinum, palladium, and gold from a pregnant cyanide heap leach solution. Screening results indicated that strong-base anion exchange resins proved to be most effective in the recovery of these metal cyanides. Gold was selectively recovered with the use of Minix, while effective recovery of gold, platinum, and palladium over the base metals, copper, and iron, was achieved with Amberlite PWA-5. Successful elution of these metal cyanides was possible from both Minix and Amberlite PWA-5, using a 2M potassium thiocyanate solution at ambient temperature. Acidic thiourea was unable to elute platinum from either Minix or Amberlite PWA-5. Effective elution of palladium and gold were, however, achieved with use of acidic thiourea. Using these results, two conceptual flow diagrams for the recovery of these metals from cyanide solutions are proposed.

Jan 1, 2012

By I. Bock

This presentation describes a technique under development referred to as Selective Blast Mining. The technique involves millisecond sequential blasting. It applies to mines where the gold bearing conglomerate band is clearly demarcated, and separated from the waste rock in the foot and hanging wall. The width of the conglomerate band should be less than ± 0,7 metres. A research program was initiated in August 1994 by Drs RE. Robinson and I.E. Bock. The objectives were to develop new blasting methods that can reduce: ? the losses of gold in narrow reef stoping. Losses of gold can be as much as 10-15% ? and to introduce selective mining to reduce ore dilution with waste rock.

Jan 1, 1996

By J. R. Percival, L. Ip, M. D. Piggott, S. J. Neethling

Component wear due to particle-laden flow is a significant challenge in the minerals processing industry in the handling and transportation of abrasive mineral slurries. Studying wear through experimentation is time-consuming and expensive; therefore possessing the ability to accurately simulate, understand and predict wear in these complex environments is highly desirable. The ability to predict wear is important in both the design of equipment in order to maximise the performance over the wear life of the components, as well in minimising potentially costly and dangerous failures and unscheduled maintenance.. Particle-induced wear is a complex problem, requring an understanding of coupled fluid-solid motion, geometry deformation in response to fluid-solid behaviour, moving geometries and wear modelling. Although the literature demonstrates that rebounding particles and changes to surface profiles can have a significant effect on subsequent wear rates and patterns, the challenge of implementing a model to account for this effect in complex geometries has been addressed by only a few authors in the literature. This paper describes a new wear simulator, leveraging fluidity, an open-source, massively parallel, finite element based CFD simulator capable of unstructured adaptive meshing. The wear simulator includes the ability to model particle-laden flow using representative Lagrangian particles and dynamic remeshing of geometry in response to wear and component movement. These capabilities are demonstrated using wear and the associated dynamically deforming boundaries within a Coriolis tester arm, with the results comparing favourably with the experimentally observed wear patterns. Keywords: CFD, wear, two-phase flows, anisotropic mesh adaptivity, boundary deformation

Jan 1, 2020

By R. T. Tshikhudo

Nanotechnology can provide solutions to many of the world?s socio-economic challenges. The application of nanomaterials for water treatment and analysis, point-of-care diagnostics and targeted drug delivery systems or devices could improve the quality of life for people in developing countries. Gold colloids have a long history (dating back to the 4th century AD) and are particularly well known for their aesthetic appeal and their therapeutic properties. Since Faraday published a report on the synthesis and properties of colloidal gold in 1857, a reasonable insight into the nature of gold sols (nucleation, growth and kinetics of coagulation) has been developed. Considerable attention has been drawn during the past few decades to the development and optimization of methods for the preparation of gold nanoparticles. In nanoscience and nanotechnology today, gold nanomaterials appear to be the most widely used material by both academics and industrialists. This is due to the extraordinary properties of gold nanoparticles (e.g. optical, catalytic, and magnetic?they are also known to act as strong Raman enhancers and may also amplify fluorescence under certain circumstances). Mintek, through Project AuTEK and the DST/Mintek Nanotechnology Innovation Centre (NIC), has been at the forefront of the development of new industrial uses for gold. Mintek?s gold nanotechnology programme focuses on the development of gold-based nanostructured materials and their applications in health, water and other related areas. While few projects use gold nanoparticles for water treatment and analysis, Mintek?s gold nanoparticles are widely used in the health sector. For example, gold nanoparticles are engineered and produced in large quantities as systems for targeted drug delivery. They are also used as tools for advanced rapid diagnostic tests. Both optical and electrochemical rapid diagnostic methods are developed for the human and animal health sectors for point-of-care testing. This paper gives a brief introduction and overview of gold nanotechnology, and desrcibes the development of some of Mintek?s gold nanoparticle targeted drug delivery systems and lateral flow point of care prototype devices.

Jan 1, 2009

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. P. Naudé

Mechel, a large, integrated steel, stainless steel, and ferroalloy producer in Russia is committed to upgrading its facilities to world class pyrometallurgical process and environmental practice. Yuzhural Nickel currently uses shaft furnaces to produce a matte containing iron, nickel and traces of cobalt. This rather old technology is thermally inefficient and is characterized by high operating costs. Mechel has investigated suitable equipment and processes to upgrade the plant, and awarded a contract for the construction of a 12 MW DC smelter, located near the town of Orsk, to Bateman Engineering Projects in June 2008. The selection of DC furnace technology for laterite smelting can be considered as a strategic highlight for the pyrometallurgical treatment of low-grade lateritic ores, and could be the first industrial-scale implementation of this technology. This project has been designed to achieve multiple goals including the demonstration of the process and associated equipment technology at commercial scale, to confirm the scale-up design parameters of the forthcoming 2 x90 MW, twin electrode DC furnaces, and to prove the environmental emission superiority of closed furnaces. It also provides a valuable operator training platform. This paper deals with the process design, key technology building blocks and design features which have been incorporated to produce a pyrometallurgical vessel capable of (i) resisting slag superheat and chemical aggressiveness, (ii) process fine material without pre-agglomeration, (iii) achieve high nickel recoveries and(iv) being tolerant to the variations in chemical composition of laterite ore. The approach to increasing campaign lives between partial and complete rebuilds, through the use of composite furnace module (CFM) technology originally developed and patented by the University of Melbourne, is also followed in more detail. Unfortunately, results from hot commissioning and lessons learned from initial operation are not available because the project completion has been delayed due to the worldwide downturn in demand for commodities. Keywords DC furnace, ferronickel laterite smelting, corrosive slag, coppercooler technology.

Jan 1, 2010

By G. van der Westhuizen, F. E. du Plessis

Ticor South Africa operates a dry mill at the town of Empangeni in the province of KwaZulu-Natal on the east coast of South Africa. The dry mill processes a non-magnetic mineral stream constituting rutile, leucoxene and zircon as major minerals, and minor quantities of ilmenite and other non-valuable minerals. For plant control and optimization, continuous ‘real time’ information about the mineral and chemical compositions in various plant streams is required. The current practice is to take samples at regular intervals and submit them for mineralogical(grain counting) and chemical analyses. However, these methods are time consuming, and in the case of manual grain counting, tedious and operator dependent. Until now an on-line or real-time instant mineral quantification system, which will be of great value in a plant operations environment, has not been available. Blue Cube Systems has developed a mineral quantification system using spectral mineral analysis. It measures and quantifies the composition of mineral samples instantly, providing consistent data in real time. A series of process stream samples from the dry mill mentioned above were used to evaluate the Blue Cube Systems instant mineral quantifier. This article will •describe the procedure of setting up and evaluating the Blue Cube Instant MineralQuantifier equipment •present its results, and •discuss the intended applications.

Jan 1, 2003

By T. Szendrei, S. Tose

The fracturing and movement of rock that occurs in the vicinity of a stemmed borehole charge in open pit mining operations are described by examining the effects of the emitted stress waves – shock and elastic – and the expansion of high-pressure detonation product gases. Three principal modes of momentum transfer to fractured rock are identified, all linked to gas expansion work. This work can be delivered radially (burden), axially (stemming), and in the collar zone (cratering). Flyrock is generated under unusual combinations of blast parameters and rock properties. Although infrequent and seldom predictable, the generation of flyrock can nonetheless be interpreted and modelled in terms of the principal mechanisms of rock projection described in this study. The physical processes underlying these principal mechanisms are identified and will permit the development of predictive models for flyrock velocities.

Dec 13, 2023

By S. A. Hosseini, O. Asghari

"Recoverable mineral resources assessment has become a standard geostatistical application in the mining industry, with various geostatistical techniques currently available. This investigation aimed to improve the prediction at the Sungun deposit and to obtain mineral resource models capable of handling (i) the change of support from drill-hole composites to selective mining units (SMUs), (ii) the multivariate nature of the ore control selection criteria that involves both copper and molybdenum grades; and (iii) the local uncertainty on the true (unknown) grades. The solution presented in this paper is to use direct block-support sequential cosimulation in order to construct a set of alternative outcomes of the copper and molybdenum grades on block support over the deposit, with no need for storing point-support values, hence with a considerable gain in memory management and CPU time. The grade realizations so obtained are then processed to calculate the uncertainty in the mineral resources that can be recovered above given cut-off grades, both globally and on a blockby- block basis. IntroductionGeostatistical methods are widely used by mining companies to determine a resource model of the tonnage and head grade of a potential orebody, which is one of the first and most critical inputs underpinning any mining project. The prediction of the grade, tonnage, and recoverable metal for a particular mining plan and the corresponding financial forecast constitute the main technical risks in mineral resource evaluation. The conventional approach to this problem is to predict the mineral grade for constant volumes relevant to the mining plan and to base the recoverable mineral resource calculations on those predictions. Alternatively, one can directly predict the local variability in the mining block grades based on a spatial distribution model (David 1988; Rossi and Deutsch 2014). Multiple realizations can also be constructed by conditional simulation, providing a more complete representation of block grade uncertainty, as well as the uncertainty over multiple blocks. Simulation methods allow quantification of the uncertainty of the mineral resource prediction risks in downstream studies such as mine design, mine planning, or operational optimization studies; the risk assessment is achieved after applying transfer functions to the conditional simulation models (Dimitrakopoulos 2012; Rossi and Deutsch 2014)."

Jan 1, 2017

By S. Banisi, S. Zare, M. Mahmoudi, M. Maleki-Moghaddam, M. Yahyaei

As the orebodies become more complex and lower grade, there is an increasing demand from crushing circuits for a finer product. When the product from a crushing circuit does not satisfy the requirements of the downstream processes, the cost of production increases. Thus, enhancing the performance of cone crushers through optimisation of their operating factors becomes important. One of the key factors affecting performance of cone crushers is the filling of the crushing chamber during the operation. The effect of varying the filling of the crushing chamber of a cone crusher was investigated. To assess the crusher performance, parameters such as crusher capacity, power utilisation, and reduction ratio were used. Extensive plant trials were conducted to obtain samples and operational data when the crusher chamber was 50% full (half-full) and 100% full, which is 300 mm above the top of the crusher chamber (super-choked condition). The results indicated a 62% difference in the crushing capacity when the crusher was operated in a super-choked condition compared to the half-full chamber level. In the super-choked condition, the size-specific energy at 12.7 mm was 20 % lower than that of the half-full condition. The Bond ball mill work index (BBWI) of crusher product indicated that the BBWI of the product of the super choked condition is 5.6% less than that of the product of half-full condition. This can be attributed to the generation of micro cracks in particles due to increase in the interparticle breakage when the crusher was operated in the super-choked mode. Keywords: Cone crushers, crushing efficiency, crushing chamber filling

Jan 1, 2020

By C. Botha

The South African democratically-elected government instituted policies and legislation that are intended to bring about change and transformation in the country and have drastically affected different industries, among others, the mining industry. The Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA) and the Broad-based Socio-economic Empowerment Charter (Mining Charter) were introduced in order to redress previous inequalities and to promote women's employment in the mining industry. This research evaluates the practical implementation of the MPRDA and the Mining Charter with specific reference to women in underground mining. A quantitative research paradigm was used. Data were collected through a process of a face-to-face interview surveys utilizing a structured questionnaire. The research setting was limited to the platinum-mining industry in the area of Rustenburg in the North West Province. The study population consisted of 195 available women working undergound at the mine. It is clear from the findings that mining companies are facing major challenges in their attempt to incorporate women in underground mining activities. Company policies regarding these issues must be firmly in place; however, the challenge lies in the translation of these policies into practice. In this regard, managers will have to play a leading role in the successful phasing in of women into the underground mining arena.

Jan 1, 2012

By S. A. Lorentz, Y. Xu, C. Theron

The failure of tailings storage facilities (TSFs) results in the discharge of significant quantities of hazardous waste material into the natural environment. Research studies relating to slope instability have identified physical mechanisms such as rainfall-induced erosion, liquefaction, and shear failure as the main triggers. The generation of transient pressure waves and the mobilization of pre-event water in the unsaturated zone have been found to trigger shallow landslides in natural hillslopes. In this paper we review these physical mechanisms, known as groundwater ridging (GWR) and the Lisse effect (LE), from other studies. Previous researchers have explained both these phenomena through field and laboratory observations, numerical modelling, as well as conceptual discussions. These case studies demonstrate the impact of rainfall characteristics on the generation of transient pressure waves that rapidly increase the phreatic surface and change pore water suction. Reference is also made to the influence and behaviour of physical porous medium characteristics on the establishment of a continuous water phase that facilitates the transmission of an induced pressure head. However, previous studies fail to recognize the possibility that the pressure increase in pre-event water through pore air propagation could cause slope instability in tailings dams. The authors suggest that the physical properties and hydraulic behaviour of unsaturated porous tailings media make it susceptible to GWR and the LE, resulting in the creation of a potential failure plane.

Feb 2, 2022

By S. W. Jacobsz, E. P. Kearsley, N. K. Schoeman

A physical modelling approach was adopted to simulate the process of cave mining propagation at various horizontal to vertical stress state ratios, and image data was captured and used to characterize the resulting failure mechanisms. Image processing was integrated into the study to determine minor principal strains in models to identify where critical extensional strains had been exceeded relative to crack propagation. The study exhibited a scale factor magnitude of 119 using a calculated critical extensional strain value of 0.014% for the modelling material used. It was perceived that cave propagation occurred through successive parallel extensional ‘fracture bands’ in all cases, as noticed in models of prior studies, deviating from that described by the Duplancic model. Cracks tended to bisect regions of minor principal strain equal to the critical extensional strain, which suggests ‘fracture banding’ is an acceptable failure mode for brittle, rock-like materials. Moreover, it was found that models with lower horizontal to vertical stress ratios (K ratios) showed a greater degree of vertical development of the caving mechanism (at similar vertical stresses), while the vertical extent of the cave was suppressed in models with higher K ratios. Models subjected to larger vertical stresses experienced slower cave formation in latter time-steps. These models exhibited larger two-dimensional caved perimeters and areas, respectively.

Nov 30, 2022

By G. R. Drennan, N. J. Wagner, M. J. T. Sebola

The Soutpansberg Coalfield hosts South Africa's hard coking coal reserves. However, coals in this region are understudied compared to other coalfields in the country. This study characterizes the properties of fine-float fraction samples extracted from a wide diameter borehole core in the Makhado Project, Tshipise sub-basin, Soutpansberg coalfield. Conventional analyses were used to determine the coal quality, petrographic composition, mineralogy, geochemistry (including trace element and rare earth element composition), and free swelling index of samples from six coal horizons and three partings from the economic No.6 Seam. The coal samples are classified as medium rank bituminous C coals (0.88 %RoVmr, 0.92 %Rmax) and are highly vitrinitic in composition (97 vol% mineral matter free (mmf)). The samples show strong caking potential (FSI of 9). The total rare earth concentrations range between 570 and 3193 ppm in the ash samples. Preliminary analysis show all but two samples are promising sources of rare earth elements as the total concentrations exceeded the 1000 ppm cut-off grade. Further research is required to confirm these preliminary findings.

Aug 2, 2022

By R Linares

For centuries, diamond's superlative properties have earned it a reputation as the 'dream' material for mankind in its search to create advanced applications. Until recently, this dream has been realized only in the use of diamond for gemstones and abrasive applications where several tons of diamonds are now used on an annual basis. The vision of having large, high quality diamond as part of a broad engineering tool-kit for many diverse high tech industries is now becoming a reality however, with the advent of early stage commercial availability of single crystal and poly crystalline CVD diamond.

Jan 1, 2010

By F. L. D. Cloete, M. C. Coetzee

This study was aimed at a comparison of the efectiveness of a new axial-flow type of mixer impeller (the Prochem design) with the traditional inclined-blade turbine. The intended application of the mixers was in carbon-in-pulp plants for the extraction of gold from cyanide-leached pulps. The first part of the project involved water and ion-exchange resin, and measurement of the power drawn by the various sizes of impeller to fully suspend the resin. The rate of reaction between the resin and the solution was measured as a function of the power input to the mixer. In the second part of the project, use was made of activated carbon, silver cyanide solutions, and ore pulps. The rate of absorption of silver from the solutions and pulps was determined, as well as the rate of attrition of the activated carbon caused by the various impellers in clear water. The Prochem design of axial-flow impeller was shown to fully suspend solids at only one-quarter of the power requireabyan inclined-blade turbine of similar size. The axial-flow pattern produced was responsible for the more uniform vertical concentration profile of suspended beads produced by the Prochem design. These measurements verified the observations of other researchers that the rate of reaction is not affected by the ;design of impeller provided that al the solids are fully suspended. The Prochem design of impeller therefore achieved the same reaction rate as the conventional turbine at a quarter of the power input. The atrition rates of activated carbon could be correlated, in terms of the energy absorbed, by the same equation for al the impellers. Higher concentrations of activated carbon increased the amount of carbon fines produced. These results emphasize the importance of designing mixers for minimum power consumption.

Jan 1, 1989

By G. R. Lane

A large opencast gold mining company in Africa had just completed a feasibility study for the expansion of the operations. A traditional net present value project valuation methodology had been used that showed a very positive net present value (NPV). The project team had conducted a qualitative risk assessment that identified and logged all potential project risks and had subjectively incorporated ?risk? via the discount rate and other assumption contingencies around gold price expectations, operating parameters etc. Management requested that an independent quantitative risk modelling approach be adopted to obtain a better understanding of the impact of risk on the overall project valuation and confidence level in the final valuation. A detailed project valuation model was configured in the Carbon Modelling Technology and the stochastic modelling module used to perform the Monte Carlo simulations. Analysis of historical operational performance data relating to actual achievements versus planned and budget determined the historical variability of the underlying parameters as well as variance to budget. This was done at a detailed level for mining rates and costs, processing rate, costs and recovery, and other operational efficiency measures. External market assumptions relating to gold price, exchange rate, and inflation were modelled and the dependency between them modelled using a copula. This case study will demonstrate the approach taken to building and populating the quantitative risk model and the overall results of the Monte Carlo simulation. The final valuation demonstrated that the project had a 44 percent probability of an NPV less than zero i.e. 44 percent chance of project finance loss.

Jan 1, 2012

By M. H. Tyeb, C. Banerjee, A. K. Majumder

The primary requirement from a hydrocyclone is the classification of the feed solid particles. Particle classification occurs inside a hydrocyclone by virtue of the relative radial distribution of the suspended particles, based on their size and specific gravity. The particle classification behaviour in a hydrocyclone is experimentally studied in this paper. The phenomenological features of the air core at different feed solid concentrations and the distribution of the solid concentrations in the hydrocyclone are also analysed by the theoretical study of flow features in a steady Rankine vortex. Semi-empirical models for predicting the hydrocyclone performance in terms of flow split ratio, and cut size have been developed using the background knowledge of convoluted hydrodynamics. In addition, to validate the classification performance of a smaller diameter hydrocyclone, the potential of the present model is extended for envisaging the same for larger diameter hydrocyclones. A comparison between the model predicted values and the measurement data shows a good match. Keywords: Hydrocyclone, classification, Rankine-vortex, air core, modelling

Jan 1, 2020