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By N. Naude, W. P. Roux

Fine particle beneficiation plays an ever-increasing role in mineral processing plants and it seems that technology can’t keep up with the challenges involved in the treating of these fines. The REFLUX™ classifier has proven itself able to treat high tonnages of fine material, especially in the coal industry. There are various fine ore applications that can benefit from such a process, yet laboratory and pilot-scale tests on many of these ores show poor efficiencies and recoveries. A better understanding of the design, operation and mechanisms of the REFLUX™ classifier is required to determine if and how it fits into these applications. The mechanisms in gravity separators are very complex due to the complex hydrodynamics, and the REFLUX™ classifier is no exception. The mechanisms of these systems are usually described through theoretical single particle-models that are hard to verify through analysing the feeds and products of these processes. To verify these models the movement of individual particles must be measured, which is not an easy task. In this paper the separation mechanisms in the incline channels of the REFLUX™ classifier were investigated with high-speed videography. A small lab scale model of the incline channel was constructed for this purpose. It was possible to capture and track the trajectories of particles under certain conditions and match these trajectories with theoretical models. The resuspension of particles, clustering and streaking was also observed and captured. Keywords: REFLUX™ classifier, particle trajectory, beneficiation, high-speed videography

Jan 1, 2020

By M. Gericke

The microbial leaching of metal sulfides is now an established biotechnological technology. Over the past 25 years, refinements in the engineering design of bioleaching processes have paralleled advances in our understanding of the diversity and role of the micro-organisms driving the process and the mechanisms by which micro-organisms enhance metal sulfide oxidation. Commercial success started with the treatment of refractory gold concentrates using mesophilic micro-organisms, followed by the development of tank bioleaching processes for the treatment of base metal concentrates. This was, initially, a mesophilic process with limited potential for recovery of copper from chalcopyrite concentrates due to slow rates and low copper extractions. The exploitation of thermophiles represents a major breakthrough in the development of bioleaching technology for the treatment of chalcopyrite-containing ores and concentrates. This development also opened the route to heap bioleaching of chalcopyrite ores, which is now a major focus of research programmes and piloting campaigns. This paper reviews the historical development of minerals bioleaching processes and gives an update on the current status of commercial tank and heap bioleach operations around the world.

Jan 1, 2009

By A. F. Mulaba-Bafubiandi

Pseudomonas spp was isolated from mine water and tailings samples collected from mining effluents and mine dumps in the Gauteng and Northern provinces of South Africa respectively. Adsorption properties of Pseudomonas spp were then tested for the removal of Cu and Co initially from their synthetic sulphate solutions, subsequently from effluents derived from metallurgical operations. The effects of experimental conditions such as pH, temperature, time, volume and metal concentration on the efficiency of the biosorption process were studied. Absorption of 45% Cu (pH 6, 37°C, 24 hours) and 40% Co (pH 6, 37°C, 24 hours) was observed from solutions with low concentrations (0.07 M). A maximum of 73% and 65% of Cu and Corespectively were recovered from the mine water samples derived from effluents.

Jan 1, 2009

By F. M. Ramadhan, M. R. Pratama

Monitoring open-pit mine road conditions has become very critical nowadays. There are several benefits to in conducting research on this field such as opportunity to improve truck’s speed which directly influences truck’s productivity. This research aims to provide a semi real-time, and sensors-based automatic road damage detector that predicts the road quality through road damage exact location tracing, road damages auto-classification, and real-time instruction in the form of work order format to mining road maintenance, and repair authorities through mobile apps and maintenance unit’s in-cabin display. It will also provide the maintenance/repair activity performance evaluation via integrated dashboards. The artificial neural network algorithm is applied during the process of data training regarding classifying road damages and severities which resulted in a valid model. The road damage classification model has a precision level of 80.5% in predicting whether the road is damaged or not. Using this approach, we are expecting to visualise a road quality map of all active roads on mine site.

Sep 1, 2021

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 E. M. W. Skinner

Various models of near-surface kimberlite pipe emplacement have been proposed over the years. These include a top-down, phreatomagmatic model, a bottom-up, embryonic pipe model and three top-down explosive dyke models. AU of these models consider kimberlites as essentially the same rock type. However, different kimberlites have different pipe shapes and contain different rock types with very specific mineral assemblages and textures and therefore are likely to have been emplaced by different processes. Some authors have considered local geological differences as the principal reason for the contrasting geology but others argue that, while geological differences might contribute locally the petrographic peculiarities of particular kimberlites may be due mainly to inherent compositional differences specifically in the ratios of juvenile CO2 and H2O.

Jan 1, 2010

By P. T. L. Koh, M. P. Schwarz

A series of parametric studies were carried out for a flotation cell using computational fluid dynamic (CFD) modelling to determine the local response of hydrodynamic performance measures to change in operating conditions. As an example, an Outotec cell was used to carry out the response analysis. The hydrodynamics of the flotation cell has been previously investigated by laboratory measurements presented by Schwarz et al (2019), and a CFD model of the cell was developed and validated using these measurement data (Schwarz et al., 2019). In this work, parametric studies have been performed by modelling the flotation cell at different stirring speeds and gas flowrates, varying above and below standard conditions. Predictions of void fraction, bubble size, bubble surface area flux and particle–bubble collision rate are presented showing the effects of increasing and decreasing stirring speed and gas flowrate around the base case. Generally, the total gas holdup in the flotation cell was found to increase with increasing gas flowrate. The bubble diameter was found to decrease with increasing stirring speed and increase with increasing gas flowrate. The collision rate increased with both stirring speed and gas flowrate. The parametric results show that there is a correlation between the bubble surface area flux Sb which is affected by stirring speed and gas flowrate, and the particle–bubble collision rate. With the collision rate as an indication of flotation collection, it is also possible to show that cell performance can improve more by increasing stirring speed than by increasing gas flowrate in a situation where everything else remains constant. The CFD results can form the basis for a Response Surface Method (RSM) analysis which can then be used for automated optimization of cell performance. Keywords: Flotation kinetics, computational fluid dynamics, bubble surface area flux, particle-bubble collision rate

Jan 1, 2020

By K. Andres

This paper presents the vibrating mill technology and summarizes the grinding principle of ultra fine grinding. In addition, a variety of operations is described and the benefits of these different operating modes? product size and efficiency are specified. A case study of an industrial application is presented to show the integration of vibrating mills into grinding circuits. The primary focus is the overall process scheme of this technology, the installation and operating costs, as well as the design parameters required for best performance. The vibrating mill can be used in a wide range of applications for process engineering duties. For a wide range of applications, from soft to extremely hard products, which require ultra fine grinding, surface activation or homogenization, the vibrating mill is well proven. Due to its easy operation, versatility and operation efficiency, the PALLA? vibrating mill gains in importance in the mineral processing industry. Keywords: Coal, comminution, grinding, mineral processing

Jan 1, 2010

By H. Lieberwirth, M. Klichowicz

The comminution at grain size level for the liberation of valuable minerals usually requires the highest size-specific energy. Therefore, the full understanding of the comminution process at this level is essential. Models based on the Discrete Element Method (DEM) could be a helpful tool for this purpose. In those, the mineral microstructure, which has a dominant influence on the fracture behaviour, can be described in great detail. One major concern, however, is the missing representativeness of simulated models. In this study, a method to overcome this limitation is presented. The authors show how a realistic microstructure can be implemented into a particle bed comminution simulation using a two-dimensional Bonded Particle Model (BPM). The improved algorithm based modelling approach is exemplarily compared to an equivalent real experiment. Thereby, the focus is set on the analysis of the interfacial breakage and the capability of the simulation to reproduce the experimental results. The comparison of the results shows that simulations at grain size level allow a more detailed evaluation of the fracturing behaviour. This is of special interest as the aim of comminution in mineral processing is not only the size reduction of coarse particles, but an efficient liberation of the valuable components. Hence, simulations with automatically generated real mineral microstructures will help to further improve the efficiency of ore processing. Keywords: Discrete Element Method, grain modelling, particle bed comminution, realistic synthetic

Jan 1, 2020

By I. du Plessis

The metallurgical response of a difficult to treat coal and an easy to treat coal orebody were investigated in terms of the coal yield and the coal quality in a basic coal recovery flowsheet. The purpose of this paper is to show trends and derive principles for the treatment of different coal types. This investigation entailed using the LIMN simulator to simulate the metallurgical response by varying the plant operational parameters. The controllable plant variables investigated were: ?Cyclone size ?Screen and hydro-cyclone cut points ?Medium cut density ?Feed particle size distribution.

Jan 1, 2010

By Y. Zhang, F. Zhu, Y. Zhao, L. Dong, Y. Li

In order to obtain a more suitable separation medium for fine coal, in this paper a pulsed fluidised bed was used to measure the pressure fluctuation, density characteristics, bubble diameter and rising velocity of Geldart A and B particles in the bed by controlling the pulsation frequency and gas velocity, in order to study the fluidisation effect and two-phase distribution of the bed. The results indicated that with the increase of pulsation frequency, the breakthrough point on the fluidisation characteristic curve caused by particle adhesion disappeared, and there was an optimal frequency, which made the minimum fluidisation velocity of particles reach the minimum. In addition, the bubble rising velocity was also simulated. The relationship between them was established using a model, and the error was within 5%. This provides an effective way to predict the bubble velocity, study the distribution of bubble phase, and improve the stability of bed density. Keywords：Frequency, flow velocity, pressure fluctuation, bed density, bubble

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 D. Burrows

Traditionally, characterisation of the mineralogy and textures of ore and rock samples were based on observations of hand specimens and thin sections using an optical microscope. The extent of the data collection was limited by the available tools and thus variations in mineralogy and texture were generally not described by quantitative data. These qualitative to semi-quantitative approaches, even though well established over the years, resulted in variable observations and data sets. The data were unlikely to be representative of a sample and limited statistical validity meant the results could not be reliably used in modern digital mining design and planning. With recently developed SEM based quantitative mineralogy tools and the corresponding methodologies, ore textures can be quantified and compared numerically. The numerical data can not only enhance the understanding of an orebody in geological terms, but can also be used in the creation of metallurgical models for mine and mineral processing design and simulation. These capabilities provide valuable inputs to risk assessment studies and the evaluation of mineral projects.

Jan 1, 2007

By S. G. Mgenge, J. D. Steenkamp

Tronox Namakwa Sands operates two ilmenite smelters for the production of high-titania slag and low-manganese pig iron. Slag or metal is tapped from one of two product-specific, bi-level tap-holes. In this paper the refractory design specific to the tap-hole refractory layout is described, as well as practices for slag and metal tapping and refractory maintenance. Further developments planned are briefly described.

Jan 1, 2014

By K. H. Berget, V. Andersen, H. Tveit, R. Jensen

This paper presents some of the work carried out in order to improve the tapping process in silicon production, with special focus on the environmental and the safety standards. Some of the modelling work that has been done to improve the understanding of the process is described, together with the resulting implementation to improve tapping standards.

Jan 1, 2014

Geologists in some underground gold mines collect grab samples from broken ore piles or trucks as a method of grade control. It is often known as muck sampling. Generally, the goal of grab sampling is to try and reconcile the mined grade at the ore source to the predicted grade and/or predict the mill feed grade. The mass of the sample collected is limited by health and safety issues, as well as the capacity of the laboratory to process the samples within a given timeframe. In general terms, grab sampling is known to be problematic because samplers tend to over sample the fines, and/or pick out high-grade fragments; surface sampling of piles does not test material within the pile; muck piles in development drives/faces are likely to be zoned due to the blasting sequence; high or low-grade material may preferentially segregate in the pile during mucking; the five percent mass reject size of the material in muck piles is very large from underground blasting; some correlation usually exists whereby the larger fragments are enriched or depleted in the critical component of value; and the average error made in estimating the true stockpile grade is likely to be high. The method is prone to chronic fundamental sampling, grouping and segregation, delimitation, and extraction errors. Substantial warnings must be given with respect to the use of grab sampling for grade control in gold mines. The method may appear to work sometimes, which can be attributed to a fine gold particle sizing and more disseminated distribution. As with all sampling methods, its appropriateness must be determined by ore characterization and heterogeneity testing to ensure the method suits the ore type.

Jan 1, 2009

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

The depletion of favourably located and higher-grade mineral deposits, combined with more favourable metal prices and higher capital costs, has stimulated research into heap leaching of lower grade ores and wastes. This has resulted in renewed interest in heap leaching of uranium ores, and in the development of processes for the bacterial heap leaching of low-grade chalcopyrite ores and the acid heap leaching of nickel laterites. A complete programme of heap leach testwork typically involves a sequence of bottle roll tests and column tests, followed by piloting on test heaps. The initial testwork is aimed at determining the amenability of the ore to heap leaching, which depends on the characteristic of the ore with respect to porosity and permeability to leach liquor, acid consumption, metal recovery and percolation. Subsequent phases of the testwork focus on the development of the process design criteria for the treatment of the ore. Basic techno-economic models have also been developed as a tool for the initial estimation of heap leach viability. Mintek has also developed in-heap monitoring probes, coupled to an operator guidance system, in order to assist the operator in achieving optimal conditions for bacterial growth and heat preservation during pilot-plant operation.

Jan 1, 2009

By A. Esterhuizen

Since 2005 Two Rivers Platinum Mine has set out on an initiative to actively monitor and control ground conditions on a daily basis, by making use of borehole cameras and pro-actively amending the support and mining strategies based on day-to-day observations of the hangingwall conditions. Today the borehole camera observations form part of the Rock Engineering Department?s daily function, and the size and frequency of falls of ground and ensuing accident rates have been drastically reduced since implementation of the system. The Two Rivers Platinum fall-of-ground management system aims to support 100% of the possible fallout thickness, based on ongoing data gathering and interpretation, thereby ensuring safety and limiting support cost.

Jan 1, 2014

By P. van der Westhuyzen

Gone are the days of stock-standard diamond beneficiation and final recovery circuits that could, with minor modifications, be adapted to treat any diamond-bearing ore source. A new era has dawned, offering the opportunity to streamline existing diamond processing operations or develop simpler, more efficient, and economical diamond processing plants, with the focus on more efficient comminution, beneficiation, and final recovery. This change in scene has been brought about by: ? The introduction, rapid development, and maturation of multiple comminution, sorting, and recovery technologies ? The need to adapt to a new standard of project approach post the commodity super-cycle phase, where optimizing existing operations and developing scalable, ?fit for purpose? new mines are fast becoming the norm in diamond processing plants in both primary and alluvial operations ? The quest for energy efficiency and lower labour costs ? More remote and inaccessible reserves (under lakes, tops of mountains etc.). This paper serves to identify some technology advances and demonstrates how these could be considered as replacements for or in combination with conventional technologies to arrive at an optimum techno-economic solution. To name a few applications/technologies: ? Comminution: conventional cone crusher, modified/specialized cone crusher, and the high-pressure grinding roll (HPGR). Although significant advances have been made in recent years, this paper only briefly covers comminution within the beneficiation circuit design ? Waste sorting: NIR (near-infrared) sorting, optical (colour) sorting, XRF (X-ray fluorescence) ? Primary concentration by combining dense media separation (DMS) with either XRT (X-ray transmissive), pulsed X-ray, jigs, or pan plants depending on the application, scale, and economics ? Final recovery of diamonds with either conventional X-ray technology, pulsed X-ray technology, or XRT. From recent studies, it can be concluded that there is no longer a standard solution, but rather the ?right? or appropriate solution. Through combining a sound knowledge of the ore source (ore dressing studies or onmine data gathering) and leveraging off the advances in technologies, one is able, through trade-off studies, to arrive at the ultimate techno-economic configuration, the ?right? solution. Emphasis is placed on maximizing diamond recoveries through appropriate technology selection and minimizing the associated costs in an effort to de-bottleneck or improve efficiencies of existing diamond processing plants, or to arrive at the ideal new diamond process plant design..

Jan 1, 2014