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By B. J. Coetzee, P. W. Sonnendecker

The quality control of a two-stage coal washing process involves several complex components that need to be modelled accurately, to enable autonomous control of the process. The first objective is to develop a method to track the material through the washing process, while ensuring accurate washing prediction models are used. This was achieved through a digital twin model of the Grootegeluk 1 coal processing plant. The model is the amalgamation of manipulating and combining of data-sets from the plant historian, geological wash tables, and mining dispatch servers. This information is then used to control and set the processing medium densities of all 15 modules on the plant, 10 modules in the primary wash and 5 modules in the secondary wash. This controller has been successfully implemented and controlled the plant for 10 days.

Aug 2, 2022

By D. Mkhwanazi

The purpose of the project was to optimize load haul dump (LHD) machinery use as they were spending too much time doing what they should not be doing. During the investigation, the author found that the machine's actual availability was 86% and the utilization ranged between 30% and 42%. This shows that the availability of the machine has met its target. Therefore the main problem was with the LHD utilization and that is what the project focuses on. To satisfy the objectives, the author firstly studied the existing mining data like the key performance indicators (KPIs) in order to analyse the machine's availability and utilization; this is what gave direction to the problem. Secondly the author did a literature review on mines with similar problems. This gave the author ideas on what to look at in approaching such a situation. Thirdly, the author gathered information on what the LHDs are doing on a daily basis by doing a time study. This gave the author an idea of how long it took the LHDs to complete a specific task. The author also interviewed operators and their supervisors in order to find the best practice work. This helped in identifying the problem areas when comparing the best practice work with what the LHDs are actually doing. According to the project results, it was found that the LHDs are underutilized due to shortage of drivers and the long distances the LHDs have to travel for material loading and refuelling. The author recommended that the machine utilization should be improved by training more operators in order to eliminate the 'no operator' downtime; the cost arrangement of this recommendation is included in the report. The author also recommended that the travelling time should be reduced by using tractors instead of LHDs when long distances need to be travelled for material loading. Another recommendation for reducing travelling time was to bring the mobile fuel tank closer to a section; the cost arrangement for this recommendation is also included in the report. Keywords Optimizing, LHD utilization, LHD availability, key performance indicators (KPI), shortage of drivers, long distances, mobile fuel tanks.

Jan 1, 2011

By H. Lagendijk, I. J. Reinecke

Mintek was contracted by Oriel Resources plc in 2004 to conduct a preliminary assessment study on smelting ferronickel from the large but relatively low grade Shevchenko nickel ore deposit in Kazakhstan. A detailed feasibility study (?DFS?) was awarded to Bateman BV following promising results from the preliminary assessment study (?PAS?) and small-scale pilot plant test work. As part of the DFS, a total of 450metric tons of ore was collected from three different locations in the deposit and shipped to Mintek. After sampling, the bulk sample was prepared for smelting. This comprised crushing, screening and calcining with each step done separately for the three different lots. The chemical composition of the ore from the deposit is relatively high in silica and therefore falls out of the MgO to SiO2 range that is normally processed by pyrometallurgical means to produce ferronickel. The main objective of the testwork was to demonstrate that a method could be found and successfully applied to smelt these siliceous ores and produce an acceptable nickel-containing alloy. A 2-m ID DC arc furnace was installed with a twin-cathode (electrode) configuration to replicate the proposed commercial-scale furnace and also incorporated an advanced design of water-cooled copper panels in the lower furnace sidewalls to withstand the aggressive nature of the high SiO2-containing slags. The reductant used was a high-volatile coal from Karaganda in Kazakhstan. The reductant addition was adjusted to achieve a 90% recovery of nickel. In the assessment of the process metallurgy, some deviation from equilibrium conditions was observed. This deviation is ascribed to the intermittent existence of a smelting bath partially covered with feed during the testwork. Optimization of smelting conditions should result in the metallurgy (slag metal equilibrium) being closer to the theoretical predictions and make the production of a 20% nickel alloy possible at 90% nickel recovery. The solution for the successful processing of these siliceous ores was found in the attainment of the necessary operational stability through the control of arc length, operating temperature, open-bath smelting conditions and flux additions of up to 10% dolime for the most siliceous of the three ore types. The test work carried out by Mintek provided the basis for the process flow sheet and engineering design of the DC arc smelting furnaces for the Shevchenko Nickel project.

Jan 1, 2007

By G. van Aswegen

Large structures in mines (faults, dykes, pillars, abutments) fail when the load exceeds the strength. If the loading system stiffness (LSS, also referred to as the ‘local mine stiffness’) is lower than the stiffness of the structure the failure will be unstable. The greater the difference between these stiffnesses, the greater the energy release during unstable failure. A method has been formulated by which the LSS is established through cost-effective numerical modelling while insight into the structure stiffness (source stiffness - SS) is provided by apparent stiffness, a parameter based on the empirical relation between seismic moment and radiated seismic energy of small seismic events from the area/volume of interest. By plotting LSS vs SS a ‘stiffness diagram’ is constructed that is useful for seismic hazard ranking of different structures. A comparative back-analysis of the Dagbreek fault in Welkom, South Africa, (source of the 1990 Matjhabeng earthquake) and two other nearby faults confirm the applicability of the method. An extension of the method, where ‘hazard magnitude’ is used as a measure of the LSS, allows a ‘stiffness diagram’ to be constructed using seismic data only. Les larges structures dans les exploitations minières (failles, dikes, piliers, culées) s’écroulent lorsque la charge dépasse la résistance. Si la raideur du système de chargement (LSS, aussi appelé la « raideur de la mine locale ») est plus basse que la raideur de la structure, l’éboulement sera instable. Plus la différence est grande entre ces deux raideurs, plus l’énergie dégagée pendant l’éboulement instable est grande. Une méthode a été formulée selon laquelle le LSS est établi par modélisation numérique rentable, tandis que la raideur de la structure (SS – raideur de la source) est établie par la raideur apparente, un paramètre basé sur la relation empirique entre le moment sismique et l’énergie sismique radiée de petits moments sismiques dans l’aire/volume en question. On trace le « diagramme de raideur » en relevant les deux mesures (LSS et SS), ce qui est utile pour classer les risques sismiques de structures différentes. On vérifie l’applicabilité de la méthode en comparant la faille de Welkom, Afrique du Sud (foyer du séisme de Matjhabeng en 1990) avec deux autres failles proches. Une extension de cette méthode, dans laquelle on utilise la « magnitude du risque » comme mesure du LSS, permet de construire le « diagramme de raideur » avec des données sismiques seulement. Große Strukturen in den Gruben (Verwerfungen, Dämme, Pfeiler, Auflager) scheitern, wenn die Last die Stärke übersteigt. Wenn die Steifheit des Ladesystems (LSS, auch bezeichnet als `lokale Grubensteifheit’) niedriger ist als die Steifheit der Struktur wird der Bruch instabil. Je grösser der Unterschied zwischen diesen Steifheiten, desto grösser die Energiefreigabe während des instabilen Bruches. Es wurde eine Methode formuliert, durch die das LSS durch eine kosteneffektive numerisches Modell erstellt wird, während ein Einblick von der offensichtlichen Steifheit in die Struktursteifheit (Quellensteifheit - SS) gegeben ist, ein Parameter der auf der emipirischen Relation zwischen seismischem Moment und ausgestrahlter seismischer Energie von kleinen seismischen Ereignissen vom Interessens-/Volumenbereich basiert. Durch das Kartograpahieren der LSS in Bezug auf die SS wird ein `Steifheitsdiagramm ' konstruiert, welches für seismische Gefahrklassifizierung der unterschiedlichen Strukturen nützlich ist. Eine vergleichende Postanalyse der Dagbreek Verwerfung in Welkom, Südafrika, (Zentrum des Matjhabeng Erdbebens 1990) und in zwei anderen nahe gelegenen Verwerfungen bestätigen die Anwendbarkeit der Methode. Eine Verlängerung der Methode, in der die `Gefahrengröße' als Maß für das LSS verwendet wird, gestattet, daß ein `Steifheitsdiagramm' konstruiert wird, welches nur seismische Daten verwendet.

Jan 1, 2003

By H. El-Faramawy, A. Ahmed, M. Eissa, M. El-Fawakhry, T. Mattar, S. N. Ghali, E. M. Kotb

As a result of the depletion of high-grade manganese reserves, it has become necessary to consider the exploitation of low-grade manganese ores. The main problem of low-grade manganese ore is the low Mn/Fe ratio, which makes it unfit for the production of manganese ferroalloys. In this work, a selective reduction technique was used for smelting low-manganese ore in the presence of coke and fluxing material in an electric submerged arc furnace to obtain a rich manganese slag and low-manganese pig iron. The product slag was blended with medium-manganese ore and smelted in an electric submerged arc furnace, in the presence of coke and the fluxing agent, to produce silicomanganese alloy. The influence of reducing agent ratio, charge basicity, and charge Mn/Si ratio on the smelting process was investigated. The optimum conditions were found to be a coke ratio of, 1.35, Mn/Si ratio of 2.0, and charge basicity of 2.5. The silicomanganese alloy produced under these conditions satisfies the specifications for Si16Mn63 and Si17Mn65. The experimental results were applied on a pilot scale, producing a silicomanganese alloy with a chemical composition close to that of the standard specifications.

Jan 2, 2022

By G. Swan, E. Nordlund, P. Zhang

"SynopsisThe most widely used support design damage criterion for rockburst-prone mines is based upon kinetic energy, which is proportional to the square of the ejection velocity and is commonly expressed in terms of peak particle velocity (PPV). Field monitoring and back-analyses have shown that ejection velocities of the order of 10 m/s and higher can result from seismic events of moderate magnitude. Such velocities are much higher than those predicted using PPV obtained from scaling laws. It has also been found that the peak ground motion (i.e. PPV) on the surface of an excavation is preferentially amplified (by four- to tenfold) compared to the motion in solid rock at a similar distance from the source. However, the wave propagation and interaction processes involved within the fractured rock in generating high ground motion are very complex and are not well understood at this time.In this paper, velocity amplification was investigated by modelling the dynamic interaction between fractured rock and a free surface using a 2D discontinuum-based numerical program, UDEC (Universal Distinct Element Code). A 1D model with a fractured zone was used to represent the fractured rock. Velocity amplification, quantified by PPV, predicted at the free end of the model was 2.0–3.6 times higher than the input velocity. It was found that the wave frequency, fracture stiffness, fracture spacing, and thickness of fractured zone are the main factors that affect the velocity amplification. The results have proved that the interaction of the seismic wave and multiple fractures near the free surface strongly influences the ground motion.IntroductionSince mining-induced seismicity is almost inevitable in deep mines, ground support is generally employed to mitigate the risk of seismically-induced damage. The most widely used support design criterion for seismicallyprone mines is one that seeks to maximize the absorption of the kinetic energy (plus potential energy if a gravity component is considered) of key rock blocks. Based on this criterion, design methods for rock support were first proposed by Wagner (1984) in South Africa and later improved, among others, by Roberts and Brummer (1988) and Kaiser et al. (1996)."

Jan 1, 2015

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By A. P. I. Popoola

Laser coatings are used for a wide variety of applications. TiB2/Ni intermetallic matrix composite coatings were fabricated on Al-substrate by a high power Rofin Sinar Nd: YAG solid-state laser. The characterization of the coatings was carried out by optical microscopy (OM), scanning electron microscopy (SEM/EDS) and X-ray Diffraction (XRD). Electrochemical study of the laser coatings in 3.65 per cent NaCl at room temperature revealed that with very high weight proportion of nickel the corrosion resistance of the coatings deteriorated due the presence of AlB10 phase. 50 wt per cent TiB2+50 wt per cent Ni laser coatings exhibited the highest corrosion resistance in test solution. Keywords Corrosion, protective film, laser surface alloying, reinforcement.

Jan 1, 2011

By M. Tangstad, D. Lu, G. Tranell, S. Gaal, J. Safarian

The kinetics of MnO reduction from high carbon ferromanganese slag was investigated using a sessile drop technique at 1600 ºC. The effects of reductant type, ambient atmosphere and slag composition on the MnO reduction were illuminated. Two different types of industrial reductants (ground to a particle size of 44 to 106micron and pressed to pellets) were used as substrates for small slag droplets of varying composition, which were reacted in a CO or Ar atmosphere with the reaction studied in-situ. The cross sections of the reacted slag-carbon samples were subsequently studied by EPMA to find the extent of MnO reduction as a function of reaction time. It was found that the rate of MnO reduction is affected by both the type of reductant, the ambient atmosphere and the presence of metallic components in the slag. Higher reduction rates were obtained for charcoal than for coke as reductant while a CO atmosphere unexpectedly yielded faster MnO reduction than an Ar atmosphere. It was also found that metal prills in the initial slag will increase the rate ofMnO reduction.

Jan 1, 2007

By Org de Wet

This paper summarises the strategy for selection between a two module coal plant incorporating large, but less equipment, and a three module coal plant with more but smaller equipment. The two options were evaluated in terms of three main categories: ? Size ? size of the equipment and the effect on the process efficiency as well as the difference in physical dimensions of the plant to accommodate the larger equipment; ? Cost ? capital savings between a two and a three module plant, processing the same ROM (run-of-mine) tons per hour (t/hr); and ? Practicality ? in terms of constructability of the plant, safety of using larger equipment and maintainability of the equipment. Decisions that were taken to reduce the risk associated with size, cost and practicality on the chosen option of a two module plant will be highlighted.

Jan 1, 2006

By C. W. P. Finn

On 14th April, 1980, 76 delegates from industry, universities, and research laboratories gathered at the University of the Witwatersrand to attend the Pyrometallurgy Vacation School. Professor H. B. Bell, Chairman of the Department of Metallurgy at the University of Strathclyde, Scotland, was there to lead the School, along with 12 local lecturers, who had gathered at the Hotel Devonshire at 07h30 for an Authors' Breakfast. Analytical chemistry Euroanalysis IV will be held in the town of Espoo, approximately 9 km from the centre of Helsinki, from Sunday, August 23rd, to Friday, August 28th, 1981.

Jan 1, 1980

By J. A. Cruise

From 27th to 29th September, The South African Institute of Mining and Metallurgy held a Colloquium on Equipment Alternatives in Underground Mining in Johannesburg. The Colloquium, which was highly successful, was held concurrently with the 1988 Electra Mining Exhibition. Particle characterization The Fourth European Symposium on Particle Characterization is to be held in Nirnberg, West Germany, from 19th to 21st April, 1989.

Jan 1, 1988

By M. Seeger

The demographics and the growing numbers of people provide a strong signal that the demand for electrical power in Southern Africa will grow considerably over the foreseeable future. Without a steady and increasing supply of electricity development of the continent is likely to be constrained. The inventory of solar, wind, hydrothermal, geothermal and biomass resources will probably provide sources of energy for the future The parallels between extraction of natural resources in the minerals industry and the green energy industry is striking, and the well-established project development process in the minerals industry provides an ideal and useful template for comparing the establishment and development of green energy projects. The potential levels of power generation and carbon savings are described.

Jan 1, 2010

By L. Lehasa

The purpose of the project was to investigate the challenges faced by Khutala Colliery pertaining to underground road construction and maintenance. Furthermore the influence of these challenges on productivity and safety requirements were taken into consideration. The operating standards required for the construction and maintenance of the 2 seam road transport infrastructure was investigated, together with reasons why the standards of operating procedure are not met. The Code of Practice put in place by Khutala Colliery was used to view the standard operating procedures. Leading practices on underground road construction were researched. The project aims to discover the gaps that Khutala Colliery must bridge to implement enhanced practices with regards to underground road construction. During the period of study, observations were carried out to determine whether the road construction standards of operating procedure were being adhered to at all times for both road construction and road maintenance. Khutala Colliery has put in place a traffic management plan, which includes safety practices and work policies that must be adhered to while travelling on underground transport roads.

Jan 1, 2012

By N. Nišić, A. Cvjetić, V. Jovanović, D. Knežević, D. Nišić

The risks associated with operating water reservoirs and tailings storage facilities (TSFs) are different because of their different purposes, methods of construction and operation, and characteristics of the materials impounded and their flow behaviour. Regardless of the differences, these two types of structures are often put in the same category when it comes to risk assessment and the application of relevant methodologies, which may result in unrealistic outcomes. In this paper we investigate whether it is possible to apply the risk ranking methodology designed for water reservoirs to TDFs and overview the key differences between these two types of structures. We also provide a comparative analysis of the results obtained by conducting a risk assessment of the operation of a TSF, applying the method recommended by the International Commission on Large Dams (ICOLD), and analyse the results using the failure mode and effects analysis (FMEA) technique. It is concluded that a more realistic evaluation of risk levels can be obtained by adopting a systematic approach to risk assessment in accordance with the traditional risk definition on which the FMEA technique is based.

Nov 30, 2022

By A. K. Singh, R. Singh, P. K. Mandal

On the basis of in situ study of pillar loading at different sites, an attempt is made in this paper to visualize the development of mining induced stress under varying geo-mining conditions. Field study demonstrated interesting interaction between size of pillar and nature of roof rock mass under the influence of increasing dimension of the excavation. Stiffness of pillars/overburden, extraction ratio and depth cover are observed to be the important parameters for the estimation of mining induced stress over the pillar. These parameters influence, both, the value of ultimate induced stress (vertical) and its range of influence ahead of the face line. Further, it is observed that the change in width/height (w/h) ratio of a pillar has got considerable influence over the nature of mining induced stress over it. Impact of highly dynamic nature of mining induced stress over the natural supports is observed to be the most serious factor for the safety of working under a hard and massive roof rock mass. On the basis of these observations, a conceptual model of interaction between the natural support and overlying strata is discussed in the paper. ZUSAMMENFASSUNG: Aufgrund ist in situ Studium von Säule Beladung an verschiedenen Stellen, ein Versuch in diesem Papier gemacht, die Entwicklung des Bergbaus vostellen sich, Spannung unter Änderung von Geo Bergbau von Bedingungen hat veranlaßt. Feld Studium hat interessante Wechselwirkung zwischen Größe von Säule und Natur von Dach Felsen Masse unter dem Einfluß von Vermehrung Dimension des excavation vorgeführt. Steifheit des Säulen Overburden, Herausziehung Verhältnisses und Tiefe sind beobachtet bedeckt, die wichtigen Parameter für die Schätzung des Bergbaus zu sein, Spannung über der Säule hat veranlaßt. Diese Parameter beeinflussen, beide, der Wert allerletzter veranlaßter Spannung (senkrecht) und sein Bereich des Einflusses voraus von der Gesicht Linie. Weiter ist, es beobachtet, daß die Änderung in Breite Höhe (W H) Verhältnis einer Säule beträchtlichen Einfluß über der Natur des Bergbaus erhalten hat, Spannung hat darüber veranlaßt. Schlag sehr dynamischer Natur des Bergbaus ist Spannung über den natürlichen Stützen beobachtet hat veranlaßt, der ernsteste Faktor für die Sicherheit des Arbeitens unter einer harten und massiven Dach Felsen Masse zu sein. Aufgrund dieser Beobachtungen, ein begriffliches Modell der Wechselwirkung zwischen der natürlichen Stütze und der überlagernde strata ist im Papier diskutiert. RESUME: En se basant sur dans l'étude de situ de chargement de pilier aux sites différents, une tentative est faite dans ce papier pour envisager le développement de creuse la tension persuadée sous varier de conditions de geo creuse. L'étude de champs a démontré l'interaction intéressante entre la taille de pilier et la nature de masse de rocher de toit sous l'influence d'augmenter de dimension de l'excavation. La raideur de piliers overburden, la proportion d'extraction et la couverture de profondeur est observée pour être les paramètres importants pour le jugement de creuse la tension persuadée par-dessus le pilier. Ces paramètres influencent, les deux, la valeur de tension persuadée ultime (vertical) et sa gamme d'influence en avant de la ligne de face. Plus, il est observé que le changement dans la largeur hauteur (le w h) la proportion d'un pilier a reçu l'influence considérable par-dessus la nature de creuse la tension persuadée par-dessus il. L'impact de nature extrêmement dynamique de creuse la tension persuadée par-dessus les soutiens naturels est observé pour être le facteur le plus sérieux pour la sûreté de fonctionnement sous une masse de rocher de toit dure et massive. En se basant sur ces observations, un modèle conceptuel d'interaction entre le soutien naturel et les couches recouvrant est discuté dans le papier.

Jan 1, 2003

By Krogerus. H., P. Jokinen, T. Lintumaa

Keywords: Pyrometallurgy, furnace, coke, smelting charge, optimization, ferrochrome The main consumer of ferrochrome is stainless steel production. Stainless steel must maintain a reasonable price against other competitive materials. Therefore, the ferrochrome price must be low enough and profitable for the producers of stainless steel. The investment and operational costs of ferrochrome production are greatly dependent on the availability of the process and the production rate. Thus the furnace size and production rate in submerged electric arc furnaces will be greatly increased in the near future. The ferrochrome production per furnace, e.g. at Outokumpu?s Tornio Works, increased from 30 000 t/a to 165 000 t/a in about 35 years. The same trend will continue globally but now much more quickly. The Outokumpu ferrochrome process at Tornio Works uses sintered chromite pellets and upgraded lumpy ore as a chromite source. Metallurgical coke is used as a reductant. Reliable smelting in a large furnace demands the correct charge composition and well-known characteristics of the charge components. The quality and electrical conductivity of cokes (normally used) has the most important role for the electrical conductivity of the smelting charge. The results of the measured electrical conductivity of different cokes and the smelting charge with many controlling factors are presented here. These measurements were performed over the years for our own purposes at the laboratory of Outokumpu Research Oy (ORC), in Pori, Finland.

Jan 1, 2006

By I. Druce, C. Li, T. Qu, J. Dong, W. Y. Xinchao, V. Nkuna

CITIC Heavy Industries has a large installed base of grinding equipment throughout Africa in different configurations, including high-pressure grinding rollers with ball mill and semi-autogenous ball crusher. The total installed power of CITIC’s mills exceeds 430 MW. In this paper, we compare several typical grinding circuits of copper in Africa with about 15 kt/d throughput based on ore properties, process selection, equipment sizing, and key equipment capital and operating costs. Actual operating performance is also introduced. The comparison for the following mine sites provides a general reference for the selection of copper grinding circuits with this approximate throughput: Kamoa-Kakula Copper Mine with high-pressure grinding rollers with ball mill circuit, and Deziwa and Sicomine Copper-Cobalt Mines with semi-autogenous ball crusher circuits

Jan 1, 2023

By Dennis Van Heerden

Southern Africa has a long history of underground hard rock mining dating back to the late 1800?s. The rock support of underground excavations has significantly changed during this period, due to improved technology, experience gained and rock support requirements by mining and geotechnical engineers. This paper examines the available underground rock support methods in Southern Africa with emphasis on the types and characteristics of: - Rock bolt types. - Rock bolt and long anchor grouts. - Thin-sprayed liners. - Sprayed Concrete. - Ground consolidations through injection methods. - Cavity and void filling with aerated cement products. [ ]

Jan 1, 2007

By Mark Coleman

Pnuematic Conveying and Process Injection Technologies have been implimented in the metals markets for the last 40 years and have consideribly improved the productivity and the performance of many processes. There have been many steps forward in handling technology and this paper seeks to consider those now offered by Clyde Materials Handling who as an established customer-driven solutions provider, which has turned its attention to supporting the Metals Market. Clyde seek to utilises its knowledge, expertise and technologies to transform the production processes of its customers, who operate in the ferrous and non-ferrous metals industries. With over 30 years experience in the process improvement industry, Clyde Materials Handling has helped their global customer base transform the way in which they operate their processes, which has enabled them to generate sustainable economic benefit and maintain their positions as leaders in their respective markets. Operators within the metals market have developed and deployed pneumatic conveying and pneumatic injection technologies. These environmentally supportive and sustain-able solutions have been used to transport raw materials within operating facilities, from storage to silo, as well as injecting these materials directly into the heart of production processes. Operators, such as Codelco in Chile, Corus Steel in the UK, and many others across the World have seen pneumatic injection solutions transform their process and costs. To inject a consistent, pulseless and accurate flow of material to a copper concentrate bath smelter, or injecting granular or pulverized coal as a coke substitute in to a blast furnace via the Tuyeres helps to increase the operational capacity, availability and productivity and reduce the cost of the operation. This paper will discuss and highlight the ways in which pneumatic conveying and injection technologies, created by Clyde Materials Handling, and applied in partnership with the customer, have helped to improve the operational performance of the production processes of operators across the non-ferrous metals markets with specific reference to applications in the Lead and Zinc Industries. With examples from Zinc Fuming in Australia, Zinc Calcine and Powder Handling in Korea, Precision coal injection to QSL and TSL Furnaces, and metered distribution of Zinc Calcine to Reactors.

Jan 1, 2008