Search Documents

By J. Moema, L. Mampuru, M. Phasha, D. Mkhonto

The global liquified natural gas (LNG) storage market size is projected to reach USD17.5 billion by 2025. Currently, owed to its high toughness, tensile strength, and excellent weldability, the 9% nickel steel is the most used in building infrastructure for cryogenic applications such as the construction of tanks and pipes for storage and transportation of LNG. However, this alloy is not readily available because of its complex production process and high cost. This provides an opportunity for suitable alternative materials to build infrastructure for cryogenic applications. Among strong contenders is the Fe-Mn based alloys, which have sparked global interest due to their desirable properties such as relatively lower density, low cost, high toughness and strength, due to a high manganese (Mn) content. These attractive properties render Fe-Mn based alloys preferred candidates to replace traditional steels in engineering applications in which strengthweight ratio is critical. In response, as a build-up to designing and developing austenitic Fe- Mn alloys, the present study employed density functional theory (DFT) based first-principles computational materials modelling technique to investigate the structural, thermodynamic, and magnetic properties of binary Fe-Mn alloy composition in competing FCC, HCP, and BCC crystal structures. Using this approach, it was possible to unravel the key underlying elastic properties that are directly correlated to experimental tensile strength and high toughness in binary Fe-Mn alloys. Besides successfully validating the existing experimental data, the current predicted properties and the deployed approach will serve as a benchmark from which further alloying required to improve other properties will be conducted.

Mar 4, 2025

By H. A. D. Kirsten

The structural competence of mesh- and fibre-reinforced shotcrete was investigated in two series of tests on full-scale panels. It was found that uniformly distributed loading was marginally less demanding than point loading, mesh reinforcement was superior to fibre reinforcement, Dramix fibre and Melt Extract fibre were similar in reinforcing characteristics, and 30 mm to 35 mm was an optimum fibre length. Furthermore, the consistency of the fibre content could not be assured on practical mining sites, and an average fibre content of about 1,5 per cent was the maximum that could be obtained for fibre lengths not exceeding 35 mm. Also, owing to its greater flexibility, shotcrete reinforced with diamond mesh was preferable to fibre-reinforced shotcrete in mining excavations subject to squeezing conditions. In view of the difficulties associated with assuring the consistency of the fibre content in mining applications, it appears that the sophisticated attributes of fibre-reinforced shotcrete can be effectively exploited only in civil-engineering applications in which quality assurance is subject to explicit contractual control. Load-deflection curves, together with measurements of compressive stresses in the surfaces of some of the panels, enabled the ultimate flexural strength of reinforced shotcrete to be rigorously formulated, and rigorous design procedures for shotcrete subject to bending and direct thrust to be developed. The application of the procedures is demonstrated in a practical design case in which the moments and thrusts in a tunnel lining are determined in a numerical analysis of the interaction between the lining, the surrounding rock, and the rock-reinforcing system.

Jan 1, 1992

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 I. Ashmole

The dimension stone industry is not widely known or appreciated within the mainstream mining industry. This is in spite of the fact that the industry has grown at an average of over 7% per annum since 1980, and is estimated to now have a global turnover in excess of US$ 60 Billion per annum. Production technologies, particularly in the developed world where labour costs are high, have developed rapidly over the past two decades. Aligned with this, there has been a significant trend in adoption of a more professional mining approach in the exploration for and operation of dimension stone quarries. In fact, in the experience of the authors, mining a dimension stone deposit successfully if often more challenging from a mining engineering point of view than many conventional surface mines. This paper gives an overview of the industry and then proceeds to discuss best practice in exploration for dimension stone and to outline the latest technologies applied in mining of dimension stone. These technologies are varied and the specific combination of technologies applied in any given quarry is determined by both the physical properties of the material as well as the influence of geology which significantly impacts on the recovery of saleable material and hence the economics of the quarry.

Jan 1, 2008

By V. van der Merwe, C. W. Siyasiya

"A petrochemical company experiences premature thermal fatigue failure of the casting moulds used in catalyst production. The aim of the project was to find an alternative alloy that would outperform the current low-alloy cast steel used for the moulds. Based on their thermo-fatigue properties, 3CR12 ferritic stainless steel and H11 tool steel were chosen for testing and comparison with the currently used BS3100 B7 cast steel. Samples of each material were subjected to temperature cycling in a Gleeble 1500TM thermo-mechanical processing simulator, followed by surface analyses. The main parameters derived from the test work were the total true strain, the hot strength of the materials, and the number of cycles to failure. Additionally, the coefficient of thermal expansion for each material was measured using a Bähr dilatometer. H11 tool steel yielded the best performance by way of having the fewest surface cracks, the lowest total true strain per cycle, the most cycles to failure, the highest hot strength, and the lowest coefficient of thermal expansion.IntroductionThe Catalyst Manufacturing Plant (CMP) is a dusty environment with temperatures higher than ambient. Molten mill scale (magnetite, Fe3O4) is tapped from the electric arc furnace into the casting moulds at temperatures close to 1600°C. After 10 seconds the magnetite is quenched with a water spray for 50 seconds to a minimum temperature of 400°C. Sometimes there is residual water in the pans from the cooling fog process (water sprays) in the empty mould. In a typical plant, the factory produces 40–44 batches a day containing between 150–300 moulds, depending on the time required for the specific batch (Buchholz, 2014). The typical batch in the CMP usually weighs about 6 t. The thickness of the tap, speed of the casting belt, and tilting angle all affect the number of moulds per batch.One of the main problems faced during the molten mill scale casting is the premature failure of the casting moulds. Cracks initiate on the surface of the mould, which is in contact with the hot catalyst, and propagate into the interior of the mould. Cracks are generally concentrated in the middle area of the mould where the catalyst makes first contact with the mould, and which experiences the highest temperature fluctuations. This suggests that the cracks are caused by thermal fatigue during the casting process."

Jan 1, 2016

By I. Ashmole

From the point of view of the environmental impact created, dimension stone mining is a relatively benign industry. There are no emissions besides those of the diesel powered earthmoving equipment utilised in its extraction and a small amount of blasting gases. Contamination of water resources is only likely in the event of petrochemical spillages from storage facilities and equipment, and these can largely be either prevented or cleaned up effectively. The major environmental impacts are of a visual nature, while in sensitive areas, habitat destruction and the destruction of archaeological heritage may become significant impacts. The dimension stone industry has grown at an average rate of over 7% per annum since 1986, and is forecast to continue growing at this rate for the foreseeable future. The cumulative environmental impact of the industry will thus become more significant over time. This paper discusses the environmental impacts of dimension stone mining and recommends effective means for dealing with the practical aspects of reclamation and mine closure in dimension stone mining within the context of environmentally responsible business practices. The discussion focuses mainly on the operations of the Finstone Group in Southern Africa, which are considered to be world leaders in the application of environmental management within the dimension stone mining industry, although reference is also made to other situations which the authors have encountered at dimension stone quarries around the world.

Jan 1, 2008

This paper presents recent advancements in the MillMapper software technology, developed and used for thickness gauging of liners of cylindrical grinding mills used for mineral comminution. MillMapper uses calibrated laser scanner data captured inside a mill to determine thickness at several million points on all liner surfaces with millimetre accuracy. The paper is structured as follows. First, a review of the technology and its numerous advantages over existing techniques and the value it adds to operations are presented. These are followed by discussion of recently-implemented innovations, including improved visualisation and inspection tools, automatic ball charge volume measurement and automatic mill liner volume/weight measurement. Results from its application at several sites in Australia are presented throughout.

Jan 1, 2007

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

Exxaro installed their first ultra fines treatment plant at Leeuwpan Coal mine. The plant is now fully operational and results already show that the plant has great potential. The plant was designed and installed by DRA. Several challenges were faced during the installation due to the space constraints in the Leeuwpan plant. Efficiency tests were conducted on both modules after commissioning and showed very promising results. A lower ash product with a higher yield can be produced with the fine coal dense medium cyclones compared to the spirals previously employed.

Jan 1, 2010

By A. C. Mulholland

The electrical control of three-electrode submerged-arc furnaces suffers from a number of complexities, mostly due to the nature of the furnace electrical circuit providing power to the furnace where the three electrodes are interconnected within the furnace through the molten metal bath. This gives rise to what is known as the interaction effect 2, where variations in one electrode?s current can cause comparable changes to the currents in the other electrodes, particularly in larger furnaces with low power factor. Resistance-based control of the electrode penetration has largely alleviated these problems, since the resistance encountered by each electrode is predominantly dictated by the length and conductivity of the current path from the electrode?s tip to the molten metal bath, which acts as the three-phase circuit?s floating neutral point. Hence resistance changes due to tip position or conductivity changes beneath one electrode do not affect the resistances beneath the others, effectively decoupling the control of the individual electrodes1. Although resistance-based control is therefore generally accepted as superior to current-based control for the regulation of submerged-arc furnace electrode penetration, a few furnace operators still prefer to use current control under specific furnace conditions. This paper presents the results of analysing the performance of both current and resistance-based control in typical scenarios encountered on industrial furnaces, taking into account a number of factors including electrode penetration, power distribution, efficiency and asymmetry of the electrode currents. In order to accomplish this, three typically encountered scenarios were simulated. The results obtained show that resistance control provides more benefit in all cases, however, the uneven electrode current distribution generated by resistance control when electrodes are on top stops may cause some concern if baking of the electrodes is required in this scenario.

Jan 1, 2009

By R. L. Machunda, A. M. Rugaika, D. D. Mdachi

Sedimentary and igneous rocks are the two primary sources of phosphate that are mined and beneficiated to fertilizer. During the beneficiation process, phosphate is lost into the tailings. We investigated phosphate concentrations in tailings dumps at Minjingu mine, Tanzania using energy-dispersive X-ray fluorescence spectrometry to quantify the chemical compositions. The phosphate content in the tailings varied from 12.91% phosphorus pentoxide (P2O5) in Tailings 2 to 19.61% in Tailings Dump 1. The naturally occurring phosphate concentration in rocks ranges from 3% to 35%, and phosphate tailings from various locations with P2O5 concentrations as low as 6.46-12.65% have been beneficiated to commercial fertilizer. Our investigation revealed that phosphate concentrations in Minjingu tailings may be sufficient to be recovered for commercial applications. Suitable recovery methods are discussed, and we recommend that beneficiation should be performed to minimize the loss of phosphate into tailings. Further research is needed to identify the optimal beneficiation methodology.

Aug 8, 2024

By R. H. Matjie, J. R. Bunt, A. C. Collins, J. C. van Dyk, C. A. Strydom

South African coal discards derived from feed coal for thermoprocesses pose human health and environmental problems and incur high disposal costs. These issues need to be resolved. Coal fines and a coal fines/ K2CO3 blend were combusted at 700°C in a laboratory rotary kiln to produce ashes containing metakaolinite (Al2O3.2SiO2) and illite/muscovite/orthoclase amorphous materials. The blend ash and coal fines ash, containing 18% K2O and <1% K2O respectively, were leached with water and with 1 M and 8 M NaOH at 80°C for 4 hours using a solid to liquid ratio of 1:5. The 8 M NaOH leach yielded 17% sodalite (Na8Si6Al6O24(OH)2) formation through SiO32-, Al(OH)4-, and Na+ precipitation in the leached ashes. The 1 M NaOH leach yielded no sodalite. X-ray fluorescence analysis of the original ashes and leached ashes showed low Al and Si dissolution efficiencies due to the sodalite formation. Sequential NaOH leaching resulted in the highest potassium dissolution efficiency of 89% for the ashes of fines/K2CO3 blend and 59% for the fines. It may be possible to increase the ash-derived zeolite concentration by using even higher NaOH concentrations (12–20 M NaOH) during leaching. Sodalite derived from coal ash could possibly be utilized for water purification in industrial applications, or as molecule separators. The potassium-containing liquid could be used in fertilizer manufacture.

Mar 30, 2023

By M. Matabane, T. Khati

"Accurate delineation of the contact between a kimberlite pipe and country rock at production level depths is a challenge due to limited geological data. Geological information is obtained from widely spaced diamond core boreholes which are drilled either from surface or from higher mining levels within the pipe. Kimberlite pipe/country rock contacts are notoriously irregular and variable, further reducing the confidence in contact positions defined by the drill-holes. At Finsch Diamond Mine (FDM), the opportunity arose to further improve the confidence in the contact positions relative to the planned slot (end) positions of each sublevel cave tunnel during the development stage of these tunnels. As a result, the accuracy of the 3D geological model has improved.The use of diamond drill core for this purpose is expensive due to site establishment requirements. The lengthy time taken during site establishment also delays the development of tunnels and support cycles, thereby extending the completion dates. FDM has reduced delays during development by adopting percussion drilling, in conjunction with gamma ray logging. The S36 drill rig is mounted on a moveable platform and does not require a costly and lengthy site establishment. The holes are generally drilled (0°/flat) on grade elevation, and these holes could also be drilled from the rim tunnels (developed in waste) into the kimberlite pipe. A single-boom production drill rig is normally used to drill holes about 20 m in length.On completion of the contact delineation drilling, gamma logging of the holes is conducted using the GeoVista geophysical sonde (or probe) to log the natural gamma signature of the dolomite/ kimberlite contact. The advantage of this tool is that the readings are continuous within centimetre intervals, and due to contrasting characteristics between kimberlite (rich in clay minerals) and dolomite, the contact position can be determined accurately. The better definition of contact positions also adds value to tunnel stopping distance in terms of developing the tunnel’s slot at the optimum distance from the contact (easier blasting of longhole rings, avoidance of contact overbreak and premature waste ingress, and other matters relating to extraction of ore from these tunnels). This method is highly successful and has reduced development costs (on-time completion), improved definition of the pipe’s contact position for geological modelling, improved blast design, and mitigated early waste ingress by maintaining the contact’s integrity."

Feb 1, 2019

By M. Mbonami, R. Pretorius, J. Miller, P. Kyony, B. Nel, N. Mautsa

Challenges due to the formation of stable froth in acid leach systems is common at many copper and Ccbalt producers. Stable froth affects downstream process, critical equipment, and operational parameters. In severe cases the froth present safety and environmental risks and increased operational costs. Solids reports in the pregnant leach solution, accumulates, and clogs launders resulting in a potential costly safety and environmental risk. Solvent extraction is operationally affected by crud formation, organic solvent and extractant losses, reduced mass transfer due to the solids carried downstream. This article reviews the generally inadequate mechanical and hydraulic solutions of froth elimination employed over the years. The recent introduction of a chemically based solution able to eliminate froth problems that can potentially turn around the situation for those who adopt the technology.

Jan 1, 2023

By C. Yi, M. Onifade, B. Genc, S. Dineva, T. Zvarivadza, M. Khandelwal

Deep level hardrock mining faces increasing challenges from elevated in situ stresses and associated rockbursts. This study aims to develop a systematic framework for evaluating destress blasting effectiveness, with a focus on deep Swedish hardrock mines. The methodology integrates a critical review and adaptation of global best practices: advanced numerical modelling (static and dynamic simulations), field-based rock fracture monitoring using ground penetrating radar and borehole imaging, and application of rockburst prediction criteria including the strain energy storage coefficient (F), brittle shear ratio, and burst potential index. Geostatistical simulations, machine learning models, and industrial internet of things-based, real-time monitoring are proposed to enhance predictive accuracy, model calibration, and operational adaptability. Key findings show that effective destress blasting evaluation requires multi-modal integration of numerical outputs, field observations, microseismic trends, and uncertainty quantification, accounting for site-specific geological variability and dynamic stress redistribution. The study advances the field by proposing a predictive, feedback-driven evaluation framework tailored for deep Swedish mining conditions, capable of improving proactive rockburst risk management. It offers both practical tools for mining practitioners to optimise stress management, reduce seismic hazards, and enhance excavation safety, and academic foundations for future refinement of destress blasting models, geotechnical monitoring strategies, and adaptive design protocols. This research contributes to safer, more efficient deep mining operations by bridging gaps between theoretical modelling, empirical monitoring, and real-time, data-driven blast design optimisation strategies.

Jun 27, 2025

By DeVerle P. Harris, David E. Euresty

"Potential metal supply refers to metals to be produced from as yet unknown deposits. Naturally, to measure potential supply requires, among other things, inference to the number of deposits, their tonnage, and their grade Thus, probability distributions were constructed for each 400-square mile cell in Northern Sonora, Mexico. A computer system was developed that simulated the occurrence of deposits for each cell, exploration for the deposits, and their exploitation. Evaluation was performed for each deposit by discounted cash flow analysis.An objective of this study was to explore the effect of the transportation network and required road or railroad construction upon potential supply. Consequently, the evaluation system was designed to consider the spatial location of a simulated deposit to the existing transportation network and the market destination. The construction of linkages to connect the deposit to existing transportation arteries as well as the carrying of the concentrates to the intended market were simulated. in terms of cost. The selection of the path took into account the existing terrain. This was done by digitizing topographical maps and representing the topography of the area by an orthogonal grid of elevations. The optimum route was selected by dynamic programming, meeting a prescribed gradient constraint. The potential supply of each cell was determined, allowing for the infrastructure effect."

Jan 1, 2014

By D. Skelton

The Renard kimberlite cluster is located in the Monts Otish region of Quebec, Canada. A Canadian National Instrument (NI) 43-101 compliant resource statement for the Renard kimberlites 2, 3, 4 and 9 and the Lynx kimberlite dyke was first issued in 2008 followed by a Preliminary Economic Assessment and the development of a conceptual mine plan. Following a successful drill program in 2009 that greatly expanded the amount of kimberlite in Renard 2, a revised resource statement was issued in December 2009 comprising 23 million carats of Indicated Mineral Resources and 13 million carats of Inferred Mineral Resources, a threefold increase on the previous estimate. The project is currently the focus of a second Preliminary Economic Assessment and it is expected that a full feasibility and permitting program will commence in 2010 leading to the creation of Quebec&apos;s first diamond mine by 2013.

Jan 1, 2010

By C. M. D. Majola, K. E. Langerman

Energy efficiency is a cost-effective way of both bolstering energy security and limiting the harmful effects of energy use on the environment. Mining is an inherently energy-intensive activity, and the 2008 revision of South Africa’s National Energy Efficiency Strategy (NEES) set a target of a 10% reduction in energy consumption by 2015 for the mining sector. In this study, we investigate the effectiveness of the NEES in improving energy efficiency in the South African coal mining sector by surveying energy intensity at a number of operations, and analysing energy efficiency trends and energy use by process and energy carrier at an underground coal mine in Mpumalanga. Most mines surveyed exhibit an increase in energy intensity over time. At the case study mine, the increase was primarily due to increased energy use in the beneficiation and discard reclaiming processes. Trends in energy consumption are a poor reflection of trends in energy intensity, as a decline in energy consumption is most easily achieved by reducing production. A more appropriate metric for energy efficiency at coal mines is energy intensity, defined as energy use per unit of saleable product, relative to a multi-year baseline. The evidence suggests that the NEES has been ineffective in promoting energy efficiency in South African coal mines. We propose that greater success could be achieved by monitoring and reporting on energy intensity at the process level, and by incentivizing energy efficiency gains.

Sep 6, 2023

By D. Visser

This paper is based on the Townlands Ore Replacement Project whereby the concept of conventional sinking of one large diameter shaft was declined and replaced with three smaller raise bored shafts. A wire line geophysical survey was done and the results indicated that a single shaft larger then 4 m diameter unsupported would not be suitable. The shafts were placed 28 meters apart measured from centre to centre. To ensure that the skin to skin pillars between the shafts remained regular and to minimise any deflection, the pilot holes were drilled with the Rotary Vertical Drilling System. The different shaft sinking methodologies are discussed explaining the risk associated with each method.

Jan 1, 2009

By D. Visser

This paper is based on the Townlands Ore Replacement Project whereby the concept of conventional sinking of one large diameter shaft was declined and replaced with three smaller raise bored shafts. A wire line geophysical survey was done and the results indicated that a single shaft larger then 4 m diameter unsupported would not be suitable. The shafts were placed 28 meters apart measured from centre to centre. To ensure that the skin to skin pillars between the shafts remained regular and to minimise any deflection, the pilot holes were drilled with the Rotary Vertical Drilling System. The different shaft sinking methodologies are discussed explaining the risk associated with each method.

Jan 1, 2009