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By R. M. Mashishi, T. Malehase, O. J. Okonkwo

The concentrations of selected trace elements (As, Cd, Hg, and Pb in run-of-mine (ROM) coal, discard, and coal product were investigated to assess the efficiency of beneficiation in reducing trace element concentrations and ascertain any implications regarding environmental compliance to regulatory frameworks. Samples were collected from a colliery in Mpumalanga Province twice a month for a period of 24 months. The samples were ashed to approximately 0.21 mm, then digested in a mixture of 70% HNO3 and 40% HF and analysed using inductively coupled plasma-mass spectrometry (ICP-MS). Except for Pb, the mean concentration of all elements decreased from the ROM stage to the coal product stage. The order in which trace elements occurred from the highest to lowest throughout the production chain was Pb>As>Hg>Cd. With the exception of Cd, the mean trace element concentrations in the discard were above the total concentration threshold (TCT) set for landfill disposal. The As, Hg, and Cd concentrations in the product were well below the thresholds for all land uses. However, Pb concentrations in the product coal were above legal limits, which is of concern with regard to environmental compliance and the performance and marketability of the product.

Dec 13, 2023

By C. van Buuren, R. F. Sandenbergh, P. J. Pieterse

Gold extraction from double refractory ores using conventional cyanidation has proved challenging due to the presence of carbon within the ore. Carbon particles may adsorb leached gold resulting in gold losses to tailings, i.e. preg-robbing the gold. Some of the preg-robbed gold may be recovered by the application of the HiTeCC process on CIL tailings. The process developed by Metso Outotec involves caustic conditioning of the tailings followed by high temperature desorption and simultaneous adsorption onto virgin activated carbon of the aurodicyanide. The aim of this paper was to develop a model for the HiTeCC process which could be used to support design and optimisation of the process, based on the adsorption characteristics of the preg-robbing and activated carbons. It was found that accurate experimental isotherms can be used to predict the behaviour of preg-robbing adsorbents. Comparing the sorption isotherms for preg-robbing ores and activated carbon indicated similar dependencies on temperature and ionic composition. Applying boundary layer diffusion models coupled with experimentally determined isotherms for preg-robbing ore and activated carbon, the HiTeCC process was successfully simulated at experimental and plant scale. Gold recovery of the HiTeCC process is most sensitive to the temperature of desorption and gold loading of the activated carbon, with increased temperature improving recovery. The gold loading of the activated carbon in the process should always be maintained lower than that of the normalised pregrobbing carbon gold loading to ensure favourable conditions for adsorption onto the activated carbon. Caustic conditioning stabilises adsorption and is therefore not necessary during the desorption stages of the process, but potentially improves recovery during adsorption. Keywords: Preg-robbing, refractory gold ores, HiTeCC, aurodicyanide

Jan 1, 2020

By P H. Ferreira

The mechanisation of mine development is becoming increasingly important in our South African and Southern African mines with increased emphasis on safe and efficient mining. Raise, blind and shaft boring offer mechanised solutions for excavations such as:- [reef raises stope boxholes and shaft ore passes ventilation passes and shafts chairlifts large vertical hoisting shafts (in excess of 1200 metres in depth) angled hoisting shafts (from small to large diameter bored holes)] These techniques will be discussed with reference to relevant applications and the author?s comparison between conventional drill and blast techniques.

Jan 1, 2005

By L. von Ketelhodt

Dual energy X-ray transmission (DE-XRT) sorting is a recent development in the range of sensor-based sorting technologies available today. DE-XRT is particularly suitable for dry coarse coal beneficiation in the size range -120 mm +12 mm. In this paper, we describe the technology and show the results of a number of test runs conducted on different types of coal from the USA and South Africa. The results have shown that DE-XRT is an effective technology not only for deshaling of coal and removing pyritic sulphur but also for separating coal and torbanite. The use of dry deshaling methods will be more important as water availability becomes a greater concern. DE-XRT is one such technology which will be incorporated in future dry coal processing plants.

Jan 1, 2010

By T. Tamenti

The purpose of the project was to conduct a feasibility study to determine if the current operating bottom dump trucks that haul coal should be replaced with rear dump trucks. The engineering availability of the bottom dump trucks was lower than targeted while the operating costs are the highest of all coal haulers within the Anglo Coal opencasts. To determine if it is feasible to replace the current bottom dump trucks with rear dump trucks, a production profile simulation was conducted to determine the number of rear dump trucks that would be required to meet the annual coal hauling requirements. The total capital and operating costs of these rear dump trucks were also determined using a total cost of ownership model. These were compared with the current costs of the bottom dump trucks to determine if it is financially feasible to replace the bottom dump trucks with rear dump trucks. Having considered the capital outlay that would be required to replace the bottom dump trucks with rear dump trucks as well as their respective operating costs, it was concluded that the current bottom dump trucks should be replaced with rear dump trucks. Other factors were considered in coming to this conclusion.

Jan 1, 2007

By P. Gauvillé

The key driver for choosing a circulating fluidized bed (CFB) boiler is the ability to burn a wide range of fuels with highly efficient combustion while meeting low emission requirements. Reduced sorbent and water consumption compared with pulverized coal (PC) plants and the ability to deal with corrosive fuel constituents while still meeting local regulations make a CFB boiler-based power plant particularly attractive. CFB-based power generation is particularly relevant in coal mining areas. During mining, a portion of the roof and floor material may be extracted along with the coal seam in order to create adequate working height for the equipment and miners. Therefore, run-of-mine coal which comes directly from the mine contains impurities. The raw coal can undergo a washing or screening process in order to improve its quality by reducing the ash content in the fuel in order to sell it on the export market or to comply with domestic customer requirements. The coal discarded from the washing process usually has a high ash content and difficult mechanical properties resulting from the initial properties, the mining, and the coal cleaning processes. It can contain a large volume of stones or can be very fine as a result of the washing treatment. To create value from burning this discarded coal, the boiler supplier has to meet several technical challenges in developing the appropriate design. This paper highlights the performance achieved with Alstom's CFB boilers developed for power generation over the last two decades to extract value from discarded coals. Emile Huchet Power Plant is the first 125 MWe CFB unit developed for burning coal slurries (called schlamms in France). The Emile Huchet discarded coal fuel is a very fine high-ash residue with an average particle diameter by mass (d50) of around 80 µm as received from the washing plant. The paper describes the performances and the basic design of the CFB boiler to manage such a fine fuel. The performances of two other CFBs of approximately 300 MWe output in operation in the USA and PR China are also mentioned to demonstrate the capability of this technology to burn either low-volatile bituminous or anthracite waste coals. The significant issues experienced during commissioning are reported, and the conceptual choices for burning such fuels are mentioned.

Jan 1, 2012

By R. Van Deventer

The BIOX® process was developed for the biological pre-treatment of refractory gold ores and concentrates ahead of conventional cyanide leach gold recovery. Rights to the process are currently with BIOMIN Technologies SA, a subsidiary of Gold Fields Limited. There are currently eight operating installations worldwide employing the process on a commercial scale. EKATO is a company specializing in developing new or optimizing existing mixing applications. EKATO has acquired a vast amount of expertise in agitation over its 75 year history. In a joint research project the reactors of the BIOX® process were characterized from the aspect of their mixing performance. BIOMIN is constantly testing new mixing solutions and reviewing potential vendors to increase the efficiency of the BIOX® process. EKATO?s intention was to qualify as an approved vendor for supplying agitation equipment to the BIOX® process. A two step approach was planned: In phase one of the project EKATO would develop an alternative agitation solution to the established option, exhibiting at least similar performance levels. In phase two potential possibilities to improve the overall design would be developed. This paper focuses on phase one and addresses the systematic approach applied by EKATO in characterizing the mixing processes. Mixing tasks were assessed individually applying basic theory and scale-up and -down rules to the individual tasks. Testing with model systems was done at the EKATO technology center in Schopfheim, Germany, on scales of 50 liters and 1 m³. The results showed that the ISOJET-B impeller design showed promising performance under BIOX® reactor conditions. Scale-up with the ISOJET-B was done in order to apply it in the 21 m³ live volume test reactor at Fairview mine in South Africa. At Fairview tests were performed using model systems and eventually under real plant conditions with BIOX® slurries. The results were a success and confirmed that the scale-up factors determined during the testing at EKATO?s technology center could be substantiated in the ?model scale? 25 m³ reactor. Testing under the actual process conditions showed that all design parameters were within the desired range to be considered an excellent leaching performance. This successful joint development shows the importance of a close cooperation of technology licensors or end-users and equipment suppliers. It is vital for understanding all factors influencing the mixing performance of processes. Exercises such as this will provide equipment suppliers and plant operators more confidence in managing further scale ups at ever larger engineered plants.

Jan 1, 2009

By N. D. Fernandes

Labour-intensive narrow reef stoping, as traditionally practised in South African gold and platinum mines, is almost unique in the modern first-world mechanized mining environment. Shortcomings of the system include the ever increasing cost of labour, a cap on achievable productivity and a poor safety record, particularly in the field of rock-related accidents. In the absence of sustainable alternative technologies, the South African mining industry has spent millions of rands improving the present system, focusing on improving workplace safety. This paper details the changes to stope support at Impala Platinum?s Rustenburg operations, and the impact on rock-related safety performance. Keywords Stope panel support, narrow reef stoping, improving workplace safety.

Jan 1, 2011

By D. F. Malan

Considerable practical knowledge and effective use of empirical evidence is required in the design of tunnel support systems. In many instances, it is unclear how individual support elements interact with fractured rock and which elements of the support system are critical in controlling and containing the movement of material proximate to the excavation. The present paper outlines a displacement discontinuity approach that allows the coupling of surface constraints, in the form of liner or mesh material, to an explicit representation of time-dependent rock discontinuity creep movements. The method is illustrated for a simple square-shaped tunnel profile in which the fracture zone is mobilized by an imposed stress field. A crucial aspect of the model is the computational treatment of the coupling between the liner material and there presentation of the fractured rock mass. This allows the response of the liner material to be assessed quantitatively in terms of the possible reduction of movement in the rock mass. The importance of installing the liner timeously after the excavation is formed is illustrated in a specific example. A number of computational difficulties in simulating liner-rock interaction mechanisms are identified.

Jan 1, 2008

By M. Z. Emad, A. Khan, N. Abbas, K. G. Li

Probability-based empirical methods were employed as an alternative approach to predicting uncertainties associated with rock mass properties. The focus was on developing probabilistic spreadsheets to forecast rock mass classification indexes. Histograms were constructed to describe the best distribution in predicting rock mass properties. The developed models also offer utility in predicting the impact of discontinuities within the rock mass on rock strength and rock mass classification systems. Statistical analyses identified volumetric joint count, joint spacing, joint frequency, and rock strength as the most influential parameters. Moreover, the statistical analysis revealed varying degrees of correlation among different rock mass properties. While some properties demonstrated significant correlations suitable for modelling, others did not align well with any correlation model. The results highlight the need for a comprehensive approach to rock mass characterization, considering multiple factors beyond volumetric joint count. Geological complexities, including tectonic activity and weathering processes, may obscure direct correlations. These results emphasize the importance of empirical modelling and detailed site investigations for accurate assessment of rock mass quality and stability in the Himalaya.

Jun 10, 2024

By S. Moolla, R. Lynch, S. Brijraj

A reliable method to locate microseismic evets is an important objective for routine mine seismic monitoring. We developed an algorithm that can automatically and reliably locate an event from a single uniaxial trace. Signals created by microseismic events are recorded as seismograms that consist of direct P- and S-waves as well as the waves reflected off the underground excavations. We take advantage of the extra complexity these reflections introduce as they make the signal more unique. In our investigation we cross-correlated unaltered synthetic seismograms against trial waveforms created from a linear combination of appropriate waveforms from a library of numerically calculated strain Green’s tensors. We use a single uniaxial synthetic seismogram to invert for the source location, six moment tensor components, and frequency. The resulting cost functions are constructed as maximal correlations at each node in the mine grid through the true source x-planes. This function is maximized by differential evolution to simultaneously yield the source parameters. Sensitivity tests such as shifting the mine plans and altering the background velocities of the media are investigated to test the robustness of the method. We contaminate the data with 40% white noise to test the resolution against simulated real recorded seismograms. The method is demonstrated using synthetic data calculated with a realistic underground 3D velocity model.

Jun 10, 2024

By J. Stacey

There are four components to this guideline 1. Guidance on the socio-economic aspects of closure policy 2. Socio-economic closure activities mapped against the mining project life-cycle (a ?check status? tool) 3. A process guide for mine closure planning and implementation 4. Tools in support of mine closure planning and implementation How to use this guideline The four components are part of a hierarchy with: ?Overarching policy as the starting point ?The mine life cycle model as a quick process check tool ?The process guide for detailed practical planning and implementation as practical guidance ?Supportive tools as resources to address specific planning and implementation steps.

Jan 1, 2010

By J. O. Mogalanyane, N. Naudé, A. M. Garbers-Craig

The fines produced is not suitable as feed material for the subsequent rotary kiln and the electrical arc furnace. The need for briquetting the ferronickel ore is premised on the minimisation of fine particles in the rotary kiln as well as improving charge permeability in the furnace, and improving overall process safety. Briquetting may be defined as an agglomeration method in which fine particles are compressed under pressure. It consists of three different technologies: vibropressing, roller pressing and stiff extrusion. The current study focuses on evaluating the performance of ferronickel briquettes generated, using roller-pressing technology. Physical properties, chemical properties and metallurgical properties of the briquettes were used to evaluate their performance and quality. Standard ISO tests for iron ore pellets were used. Size degradation as a result of reduction was measured using the ISO 4696-1 test. The decrepitation of the briquettes at the point of entry into the rotary kiln was evaluated using the ISO 8371 test method at a temperature of 700oC. The degree of reduction was evaluated using the ISO 4695 test procedure. Average green briquette compressive strength of 559 N was reported at a moisture content of 16% with an average drop number of 19.1. Increasing the moisture content has a detrimental effect on both the compressive strength and the green briquette yield. The drop number is expressed as the number of drops until breakage, when a briquette is dropped from a 1 m height, decreased with an increase in moisture content. At a moisture content of 16% an average green briquette yield of 85.1% was reported. Keywords: Ferronickel briquettes, moisture content, curing conditions, physical properties, chemical properties

Jan 1, 2020

By B. X. Huang

Hydraulic fracturing technology is presented as a solution to improve permeability and thus solve the extraction problem of coal seam gas in low-permeability gas-bearing coal seams. Given an existing group of original cracks, the propagation of main hydraulic cracks and hydraulic wing cracks was simulated using realistic failure process analysis software. The process represents the structural transformation of hydraulic fracturing and permeability improvements caused by it. In addition, a field test for improving the permeability of gassy coal seams by hydraulic fracturing was also conducted. The propagation of the main cracks and wing cracks by hydraulic fracturing forms a network of original joint cracks, hydraulic wing cracks, and main hydraulic cracks, which improve the permeability of the coal seam. High-pressure water in the drill hole and in the main hydraulic cracks permeates the two flanks of the hole, forming the permeating water pressure. With an increase in drill water pressure and an extension of the main hydraulic cracks, the permeating water pressure on both sides of the main hydraulic cracks in the coal mass also increases. Hydraulic cracks tend to form connections through rock bridges. The extension of hydraulic wing cracks through connections in the rock bridges between the cracks transforms the rock mass to a fractured structure and improves its permeability. Hydraulic fracturing technology for improving permeability in underground conditions can increase the amount of gas drainage by a factor of 15. A stress relief area develops at a radial distance of 10-2.0 m from the hydraulic fracturing drill hole, while an area of rising stresses, called the pressurized area, develops a further 15 m away from the pressurized hole. Practice has proved the existence of the stress transfer phenomenon and the high stress area after fracturing. This kind of hydraulic fracturing technology is more effective in holes drilled from underground than in surface drill holes, with respect to costs and controllability, and is therefore the major trend in gas drainage development in coal mines.

Jan 1, 2012

By T. S. Kagogo

The factors affecting haul truck tyre performance and the effectiveness of the management system at Rossing Uranium Mine were investigated with the aim of increasing tyre performance in terms of running hours until failure. The main objectives were to identify the types of tyre failure, their causes and cost implications, and evaluate the effectiveness of the management system. A site severity survey, weight study, and TKPH studies were conducted to determine the pit conditions, and an analysis of failed tyres carried out. The results showed that tyre performance at the mine has declined from 2009 to date, and the increase in lost value amounted to R5.7 million in 2012 alone. The main cause of tyre failure is loose rocks in the pit. The present management system in the load and haul department is not effective enough due to operational constraints it is facing.

Jan 1, 2014

Production caving started for Lift 2 at Northparkes in August 2004. In a period of less than 3 months, more than 10 000 seismic events were recorded. Events up to local magnitude +2.9 were induced near the mine during caving, with event rates of up to 500 per day. This paper documents the seismicity related to cave initiation and cave propagation during the initial production of Lift 2. The seismogenic zone of events initially moved at a rate of about 0.5 metres per day, accelerating to 2 to 3 metres per day after a few months of cave production. Seismic data analysis infers that the crown pillar between Lift 1 and Lift 2 was destressed over a vertical height of about 100 metres. As the seismogenic zone approached the crown pillar, a macroseismic episode occurred, with more than 20 events of at least local magnitude +1 occurring in a two-week period. Based on the seismicity recorded for Lift 2 at Northparkes Mines, a caving mechanics model is proposed. Comments and suggestions are made for seismic data analysis and design of seismic monitoring systems in block caving mines.

Jan 1, 2008

By J. Rabe

Tasked with developing a flow sheet for a new resource, one typically turns the experts for help. The advice of an expert can be invaluable in reducing the time and costs associated with characterizing an ore (not to mention extracting maximum information from limited samples). While guiding and optimizing a metallurgical concept study requires a certain skill set, selling a project is something different. The metallurgical specialist is usually not responsible for sharing the results of investigations with potential investors. However, the person responsible for selling the project can ensure that a metallurgical concept study is conducted thoroughly and responsibly without having the ability to do the work, while being sufficiently familiar with the metallurgical aspects to authoritatively sell the project. The process of identifying suitable process routes through to constructing a concept flow sheet and mass balance is discussed as a basic example. From basic mineralogical information and a thorough literature survey, the most likely beneficiation routes can be identified and targeted testing conducted. The final top size will depend on the required product properties (mainly grade), the selected beneficiation technology, and the ore?s liberation properties. Once the required top size has been identified, comminution options can be evaluated. Once again, literature surveys can be used to supplement concept-level comminution property information, and select possible equipment and circuit configurations. Marketing, material handling, and logistics-related information can be used to determine required dewatering technologies. At this stage, enough information is available to develop a concept mass balance and conduct basic equipment sizing..

Jan 1, 2014

By von Wielligh. L., D. G. Hattingh, M. N. James, W. Thomas

"SynopsisThe process of joining materials by friction is based on generating the heat necessary to create a solid-state mechanical bond between two faying surfaces to be joined. In simple terms, the components to be joined are subjected to frictional heating between rubbing surfaces, causing an increase in interface temperature and leading to localized softening of interface material, creating what is described as a ’third body’ plasticized layer. This plasticized zone reduces the energy input rate from frictional heating and hence prevents macroscopic melting. The plasticized layer can no longer transmit sufficient stress as it effectively behaves as a lubricant (Boldyrev and Voinov, 1980; Godet, 1984; Singer, 1998; Suery, Blandin, and Dendievel, 1994). The potential for this solid-state frictional joining process to create high-performance joints between, for example, dissimilar materials with limited detrimental metallurgical impact, and reduced defect population and residual stress level, has had a very significant impact on fabrication and repair in industrial sectors such as transport. This paper presents a brief overview of the advances made within the family of friction processing technologies that could potentially be exploited in the nuclear industry as alternative joining and repair techniques to fusion welding.Modern friction processing technologies can be placed into two main categories: those that make use of a consumable tool to achieve the intended repair or joint (friction stud and friction hydro-pillar processing) and those making use of a non-consumable tool (friction stir welding). The most mature friction joining technology is friction rotary welding, where a joint is formed between original parent materials only. A new addition in this category is linear friction welding, which opens the potential for joining complex near-net-shape geometries by friction heating. The continuous innovation in friction processing over the last 25 years has led to the development of a number of unique processes and applications, highlighting the adaptability of friction processes for specialized applications for high-value engineering components.IntroductionAssessing the potential for using alternative joining and repair techniques for specific applications in a given industrial sector is informed by an appreciation of the current size and potential growth in that sector. Power generation by nuclear fission has been out of favour over the past few years, due to several high-profile nuclear incidents, e.g. the Fukushima Daiichi nuclear disaster, as well as concerns over disposal of nuclear waste and spent fuel rods. However, due to rapid increases in the demand for electricity, coupled with many fossil-fuel fired plants reaching end-of-life, there is renewed interest in installing additional nuclear capacity."

Jan 1, 2015

Book new a Book reviews Economics of the mineral industries. 4th Edition. Society of Mining Engineers (Caler No. D, Litleton, CO 80127, U.S.A.). 660 pp. Reviewer: M.A. Ford Foundry technology, by P.R. Beeley. Durban, Buterworth Scientific, 1982. R124 + GST. Reviewer: A.P. van Wyk Underground Transport Symposium. Johannesburg, The South African Institute of Mining and Metallurgy Special Publication SP 1. 300 pp. R65 (Non-Member), R55 (Member), + GST. Reviewer: C.L. Workman-navies A summary of the Project DevelopmentSymposium as presented by The Australasian Institute of Mining and Metalurgy. $A 25.00. Reviewer: D.J. van Niekerk Geology of uranium deposits. Proceedings of the CIM-SEG Uranium Symposium, September 1981, edited by T. I. I. Sibbald and W. Petruk. Quebec, The Canadian Institute of Mining and Metallurgy, Special Volume 32, 1985.268 pp. Canadian $40 members, $50 non-members (plus $3 for postage and packaging). Reviewer: M.S. Toros Crushing and grinding process handbook. Chichester (England), Wiley, 1986. £49. Reviewer: M.P. Hay O'okiep's 50th birthday The 0'okiep Copper Company Limited, situated at Nababeep s,ome 35 km from Springbok, recently celebrated its fiftieth anniversary.

Jan 1, 1987

By L. A. Balzan, M. Kalicinski, F. Nieuwenhuys

GEOSCANs on belt analysers have been widely utilised in iron ore for nearly two decades. Since the first installations in 2003, the availability of accurate and reliable grade data has become standardised across iron ore mines in the Northern Cape, where various streams are monitored continuously to ensure the optimal functioning of plants. Assmang Khumani has been at the forefront of technology adoption and has implemented 19 GEOSCANs at various locations throughout the plant, monitoring run-of-mine, stockyard feed, beneficiation plant feeds, and products. Over the years, collaborative advances in the technology have allowed for numerous benefits and gains to be made. In recent times, there has been a concerted effort on the development of analysis for phosphorus in the material flows, and based on Scantech's experience in the phosphate industry, this element has now been calibrated to achieve statistically acceptable and repeatable accuracies for real time analysis of this element on many of Khumani's GEOSCAN analysers. This paper provides an overview of GEOSCAN use at Khumani, while focusing on the development of phosphorus analysis. A case study of analysis results is presented for a range of analysers that have been calibrated for this element, as well as a discussion on the benefits obtained as a result of this analysis. Keywords: Online analysis, real-time, process control

Jan 1, 2020