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By L. Holappa

Ferroalloy production is an energy-intensive industrial sector with significant CO2 emissions. In this paper the current situation in ferroalloy processes is discussed from the standpoint of global environmental issues, trends and development. Progress and data of ferroalloys production are frequently compared with the steel industry, which is a closely related sector and the main user of ferroalloys. Emission factors of processes and electricity production are examined as well as possibilities and future scenarios of how to diminish CO2 emissions. As a part of this study a questionnaire was submitted to experts in the field of ferroalloys worldwide to survey opinions on the ferroalloy industry today and in the near future (2020). Eighteen questions concerning raw materials, energy, environmental aspects, by-products and economic aspects were responded to by seventeen experts, the answers were analysed and conclusions were drawn. Keywords Ferroalloys, energy, CO2 emissions, electricity, sustainability, questionnaire.

Jan 1, 2010

By A. Patri, D. S. Nimaje

Wireless sensor networks and wireless communication systems have become indispensable in underground mines. Wireless sensor networks are being used for better real-time data acquisition from ground monitoring devices, gas sensors, and mining equipment, whereas wireless communication systems are needed for locating and communicating with workers. Conventional methods like wireline communication have proved to be ineffective in the event of mine hazards such as roof falls, fires etc. Before implementation of any wireless system, the variable path loss indices for different workplaces should be determined. This helps in better signal reception and sensor node localization, and also improves the method by which miners carrying the wireless devices are tracked. This paper proposes a novel method for determining the parameters of a suitable radio propagation model, which is illustrated with the results of a practical experiment carried out in an underground coal mine in southern India. The path loss indices, along with other essential parameters for accurate localization, have been determined using the XBee modules and ZigBee protocol at 2.4 GHz frequency.

Jan 1, 2015

An efficient and portable mathematical model has been developed for simulating heat transfer in six-in-line slag-resistance-heating electric furnaces for smelting sulphide ores to produce base metals and platinum group metals. This model is a steady-state one relating furnace conditions and performances to various control and input parameters. Some transient effects occurring in electric furnaces are neglected for computation efficiency. This article describes the model development and modelling results. The present model is capable of predicting: (i) temperatures at various locations in a six-in-line furnace, such as slag bath, matte bath, solid charge, freeboard space, freeze lining, cooling water, and air gaps between solid material components, etc. (ii) freeze lining thickness, (iii)smelting rate, and (iv) heat loss rate, etc. A typical feature of the model is that it is easily portable to different application platforms and sufficiently efficient with execution times less than a few seconds. Therefore, it is possible to apply the model for online prediction and control of heat transfer and freeze lining thickness in industrial electric furnaces.

Jan 1, 2011

By J. Trckova, P. Prochazka

Physical models from equivalent materials satisfying geometrical and physical similarity have been constructed. A special technology of simulating the excavation of an opening at the front part of a tunnel and of measuring the deformation at the tunnel face was applied. The results yielded by the physical models were used to formulate constitution relations in the numerical solution. This coupled modelling enables us to predict the behaviour of tunnel structures more accurately. On a construit des modèles physiques, réalisés en matériaux équivalents et répondant aux conditions de ressemblance géométrique et physique. Sur ces modèles, on a utilisé une technologie intéressante de simulation du forage du tunnel et de la mesure de déformation du front de taille pendant le forage en progression. Les résultats donnés par les modèles physiques ont été utilisés pour formuler les relations de constitution dans la solution numérique. Une telle construction de modèles combinés permet de prévoir plus précisément le comportement de la structure du tunnel. Es wurden physikalische Simulierungsmodelle aus äquivalenten Werkstoffen konstruiert, welche die Bedingungen der geometrischen und physikalischen Ähnlichkeiten erfüllen. Bei diesen Modellen hat man die interessante Simulationstechnologie des Tunnelvortriebs sowie die Verformungsmessung beim Tunnelabbaustoß während des Vortriebsvorgangs eingesetzt. Die Ergebnisse der physikalischen Simulation wurden zur Formulierung von Konstitutionsrelationen in der numerischen Lösung genützt. So eine kombinierte Simulation erlaubt eine genauere Prognose des Benehmens der Tunnelstruktur.

Jan 1, 2003

By Z. Lin, M. Isac, R. I. L. Guthrie

The kinetic and thermodynamic efficiencies of chromium recovery from the slag in an AOD process during the slag de-oxidation period with ferrosilicon is a complex process affected by slag basicity, temperature, the dissolution kinetics of the reducing agents, and intermixing of the slag/metal/alloy addition phases within the vessel. The present work focused on a study and simulation of the fluid dynamics and mixing behaviour of ferrosilicon additions in the AOD process for the production of stainless steel. In order to visualize the mixing behaviour, a two dimensional slice model of an AOD vessel was first built and filled with ZnCl2solution and then covered with silicone oil in order to represent the bulk liquid steel and slag phases, respectively. The injection of argon/oxygen process gases was simulated using air or helium. Particle trajectories and intermixing of the phases was monitored with a high-speed camera. To simulate the 75FeSi additions, glass spheres were used. A three-dimensional version of the AOD model was then constructed in order to confirm the adequacy of the slice model. Similar particle mixing behaviour was observed. Both models demonstrated that the ascending gas/liquid plume created two asymmetric mixing zones: a smaller rapidly re-circulating mixing zone adjacent to the side-wall locating the tuyere(s), and a larger mixing zone in the main part of the vessel. The process efficiency during the reduction period is governed by the thermal behaviour of ferroalloy as well as the mixing efficiency in the main large mixing zone. To enhance the recovery efficiency for chromium, small Fe-Si particles are suggested, given their wide distribution within the slag phase, and their large interfacial areas and rapid melting times for Cr2O3reduction from the slag. Keywords; modelling, ferrosilicon, chromium oxidation, AOD steelmaking.

Jan 1, 2004

By George J. Karcas, Raimo Kuusisto, Pertti Pekkala

Ongoing Outokumpu development in Solvent Extraction and Electrowinning Technology, involving all aspects of process chemistry, equipment and control, extends over a period of close to 30 years. The development in SX started with molybdenum and rhenium, continued with zinc, manganese, cobalt and nickel and is now focusing on copper. The OutoCompact VSF? SX concept, which has been recently introduced, is a honed version of earlier VSF? technology. The Outokumpu VSF? ("Vertical Smooth Flow") SX package includes the DOP ("Dispersion Overflow Pump") units, the Spirok Mixers, the OutoCompact Settlers including their DDG ("Dispersion Depletor Gate") fences and tank farm equipment such as the LOS ("Loaded Organic Scrubbing") tank as well as the CEP ("Copper Electrolyte Purifying") tank. Although the VSF? SX package can be implemented according to several optional lay-outs, the so-called Track version has lately been introduced to the advantage of new plants. The new OutoCompact SX technology decreases the footprint of future VSF? plants. The lay-out, including plant size flexibility, have further been improved by Outokumpu?s new OutoReverse settler technology. Two of several SX plants currently under construction rely on reverse settlers in order to maximize their performance. The Outokumpu EW technology includes process know-how as well as proprietary equipment. The copper EW package consists of permanent stainless steel cathodes based on wax-less technology and lead anodes utilising polymer concrete cells with the double contact bus bar system and ventilation hoods fitted for efficient mist control. The lifting of cell hoods, as well as cathode washing, is done by the cathode pulling crane. Proper electrolyte flows and matching current density further ensure high productivity of LME grade copper cathodes.

Jan 1, 2005

By A. P. Squelch

The question of what stress condition exists in the hangingwall of tabular stopes remains topical and largely unanswered. Limited field data exist to quantify the situation and provide calibration for investigative computer modelling exercises. Work conducted in1989 and 1990 under a Chamber of Mines Research Organization (now the CSIR: Division of Mining Technology) programme of research into the behaviour and benefits of backfill may assist with this situation. The original work was motivated by the premise that the improved hangingwall stability in backfilled panels (identified by rockfall accident analyses) is due to a change in the hangingwall stress regime. Current, largely theoretical, studies into mechanisms of stope hangingwall behaviour and support interaction could benefit from considering these data. Keywords: Backfill, horizontal stress, stope hangingwall, hangingwall stability, support interaction.

Jan 1, 2002

By W. D. Northrop

This paper gives an account of the development of a technique whereby the vertical limits of geological horizons may be identified by the use of vertical variograms on the mineral of economic interest. This information may supplement or guide the correct subdivision of the individual horizons into meaning full data sets by diligent geological observation. This process then improves the quality of the variance modelling of the gold distribution in the plane of the individual layers and therefore enables better estimates to be made into the grids or blocks of the mine model. The technique is explained by an account of the development work, which was performed, on duplicate superimposed reef horizons in the Kimberley formations. The paper then shows how the correct approach was developed to evaluate the mineralized layers in a multiple stacked conglomerate layer sequence in the Elsburg reefs of the Witwatersrand Rand System at the Target deposit. The method of categorization of resources according to confidence in the estimate is also explained. The feasibility processes carried out on the three-dimensional model, in accordance with the SAMREC code are also described. An example of the development of a reconciliation process utilizing chip sampling is also explained.

Jan 1, 2003

By Phillip M. Dight

A number of impending and actual pit wall failures have been observed and documented which have been interpreted to initiate on newly generated structural features. This infers failure through intact rock. Failure mechanisms have been postulated resulting from circumferential stress, extensional strain and brittle flexure. These will be discussed in the context of the failures and the associated monitoring. The implications of failure initiating on ?unknown? features has a significant impact for deep open pit mines where designs are based on the expected structural regime. Being able to anticipate such failures is important for design. Equally important is management of such changes as they arise. In this context, monitoring using high resolution microseismic techniques will be discussed as a means of providing early warning of such failures.

Jan 1, 2006

By M. M. Ali, C. Musingwini, R. A. Phillips

The long-term open-pit mine production scheduling problem (OPMPSP) is typically solved in two broad stages. The first stage entails optimisation of the ultimate pit limit, which delimits the economical final pit and maximises the undiscounted value of the deposit. The second stage entails optimisation of the long-term open-pit mine production scheduling, which maximises the discounted value of the deposit. The long-term OPMPSP is a type of an NP-hard problem, such as the travelling salesman problem (TSP), because it is intrinsically complex to solve since it incorporates both hard and soft constraints. Therefore, metaheuristic approaches have been used to find global optimum solutions to the long-term OPMPSP. This paper presents a metaheuristic approach utilising a dual interchange algorithm (DIA) to solve the long-term OPMPSP. The DIA is a parent algorithm which supervises two subservient algorithms, namely, simulated annealing (SA) and Tabu search (TS). The DIA selects the better solution generated in each run from the two algorithms, and simultaneously penalises the algorithm that produced an inferior solution, while rewarding the one that produced a better solution. The DIA was tested on the three-dimensional Arizona Copper Deposit (KD) dataset, which is publicly available for research purposes from the online MineLib repository. It was set to generate net present values (NPVs) in five-minute intervals and the solution improved until it plateaued at about 30 minutes of runtime. The NPVs compared favourably to those obtained on the same KD dataset but obtained over 24-hour runtimes, when solved using simulated annealing and Tabu search algorithms, and the NPV generated from the work of Muñoz (2012) using the modified TopoSort as found on the MineLib repository at the time of this study. Therefore, this paper demonstrates that DIAs can be developed and used to solve the three-dimensional long-term OPMPSP.

Sep 1, 2021

By L Singheiser, W. Willenborg, M. Mueller, K. Hilpert

The limitation of fossil fuel resources and the necessity of reducing CO2emission require an increase of the efficiency of power plants by using combined cycle power systems. Pressurized Pulverized Coal Combustion (PPCC) is a potential concept to realise these objectives. The direct use of hot flue gas for driving a gas turbine requires a hot gas cleanup to achieve corrosion prevention of the turbine blading. One of the main problems is the alkali release during the coal combustion process. Molten coal ash slag has a high potential for alkali retention which depend son the alkali oxide activity in the slag. Knudsen Effusion Mass Spectrometry (KEMS) was used to determine thermodynamic data of alkali gas species over molten coal ash slags and of alkali oxides in molten coal ash slags. The main interest of the investigations focused on the structural dependence of the thermodynamic properties of the alkalis. It was found that there is a strong correlation between the thermodynamic properties and the ratio of nonbridging oxygen to tetrahedral oxygen (NBO/T). An increase of the polymerization of the slag results in a decrease of the alkali oxide activity in the slag and thus a decrease of the alkali partial pressure over the slag. Keywords: coal ash slag, structure, alkali oxide activity, alkali vapour pressure, PPCC, KEMS.

Jan 1, 2004

By C. J. Van Niekerk

The study comprised of the investigation into the sensitization characteristics of AISI 409 titanium stabilized ferritic stainless steel during low heat input welding. AISI 409 is a fully ferritic stainless steel used in catalytic converters and tubing for automotive exhaust systems due to the supposition that sensitization does not occur during low heat input welding. Two plates of 2 and 4 mm were tested for sensitization during low heat input welding. The study confirmed that chromium carbide (M23C6) precipitation occurs on the grain boundaries in the heat-affected zone with consequent depletion of Cr adjacent to the grain boundaries during welding. In the 2 mm plate sensitization occurred in the heat input range of 0.1 kJ/mm to above 0.25 kJ/mm and in the 4 mm plate sensitization occurred in the heat input range of 0.2 to 0.9 kJ/mm. Ti stabilization is ineffective at the heat inputs used in this investigation due to the rapid cooling rate through the temperature region where TiC precipitates. The presence of N was found to be detrimental since it consumes Ti on cooling, forming TiN, effectively lowering the amount of Ti available for TiC formation during rapid cooling after welding. Annealing for 5 minutes at 725°C does not improve the sensitization characteristics of the welded plate. There is a linear increase in grain size as heat input increases. The resistance to pitting corrosion decreases in the sensitized, welded plate in theheat-affected zone adjacent to the fusion line of welding. Keywords AISI 409 ferritic stainless steel, sensitization, grain growth, resistance to pitting corrosion, low heat input welding.

Jan 1, 2011

By B. P. Watson

The Bushveld platinum group metal deposits are two distinct, shallow-dipping stratiform tabular orebodies which strike for many hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2 300 m. The mining method is a variation of planar open stoping. Pillars are widely employed to support the open stopes. In the deeper levels, in-stope pillars are required to fail in a stable manner soon after being cut, and the residual pillar strength is used to stabilize the hanging wall. These pillars are commonly known as crush pillars. Little work has been done in the past to determine pillar peak and residual strengths, and pillars have been designed using experience and formulae developed for other hard-rock mines. This has led to over and undersize pillars with consequential loss of ore, pillar bursts and potential collapses. This paper describes a crush pillar design methodology, and provides design charts. Three mining environments were incorporated in the investigations, which included underground and laboratory measurements, analytical solutions, numerical model sand back analyses. The results of the study are suitable for the areas where the research was carried out, and may also be applied with caution in other similar environments.

Jan 1, 2010

By P. J. K Leeuw, E. Uludag, M. J. Nong

Efficient drill-and-blast performance is pivotal to the profitability of deep-level mines, where high operating costs and declining grades demand maximum throughput. This study investigated persistent fragmentation problems at a longhole stoping operation that suffered from simultaneous oversized rock blockages in 300 mm × 300 mm grizzlies and excessive fines. Fifty-one muckpile images from five blasted stopes were analysed with Split-Desktop. Although the overall F₈₀ was 287 mm, nominally suitable for the grizzly aperture, the Rosin- Rammler uniformity index of 0.80 revealed a highly inconsistent size distribution containing both boulders and fines. Existing drill patterns were then evaluated with the Aegis underground software, which showed negligible crack overlap at the toe owing to inadequate spacing and burden. Insufficient energy overlap between blastholes, particularly at the toe, was found to contribute to the coarse fragmentation, while excessive fines were attributed to the crushing and severely fractured zones of blastholes. Optimisation simulations demonstrated that an 89 mm blasthole diameter on a 2 m × 2 m pattern would overlap, aligning with Aegis requirements of balancing powder factor, break angle, and energy distribution. Implementing this revised pattern is expected to reduce secondary breaking, prevent ore-pass blockages, lower fines, and ultimately improve overall production efficiency. The methodology illustrates how integrated image analysis and modelling software can effectively diagnose and address fragmentation issues, particularly in underground longhole mining, where challenging blasting conditions require a balance between achieving optimal fragmentation and maintaining stope stability. This approach offers a cost-effective pathway to improving comminution performance in deeplevel mines.

Oct 2, 2025

By J. Bakken, M. Th. Jonsson, G. Sævarsdottir

A typical three-phase submerged-arc furnace for production of silicon metal and ferrosilicon has arc currents ~100 kA, phase voltages ~100 V and total furnace power ~10 - 60 MW. The arcs burn in gas filled cavities or "craters", where the main atomic components of the plasma mixture are silicon, oxygen and carbon. Two quite different simulation models for high-current AC arcs have been developed: the simple Channel Arc Model (CAM), and the more sophisticated Magneto-Fluid-Dynamic Model (MFD). These models have been described extensively and results reported at INFACON-8 and INFACON-9, respectively. The coupling between the arcs and the AC power source is described by a complete three-phase Electric Circuit Model. Recent numerical modelling studies of industrial AC arcs show that the boundary conditions at the cathode and anode are critical for the simulation results. A novel Cathode/Anode Sub-Model for high-current AC arcs that treats both cathode and anode indicates a completely different cathode behaviour than previously assumed. A cathode spot which serves a high-current electric arc is shown to be dominated by the energy impact from the arc. This leads to lower cathode fall voltage than obtained from previously developed models. The anode fall voltage is negative, as the main function of the potential barrier is to repel plasma electrons. The cathode spot is diffuse in the sense that the arc in fact contracts away from the cathode. Simulation results are compared to measurements on both industrial furnaces and smaller scale pilot furnaces. An important conclusion, supported by our arc studies, is that the arc length in silicon metal and ferrosilicon furnaces does not exceed 15 cm and the arc may burn anywhere on the electrode, not necessarily beneath the electrode tip.

Jan 1, 2004

By M. Ghoreychi, X. Daupley

ABSTRACT: The paper is devoted to two major aspects related to the abandonment of salt mines: 1)- Long-term risk associated with the mechanical instability of surface and its consequences for public security and properties. 2)- Long term dissolution and transport of salt resulting from its communication with groundwater. Basic characteristic features of salt deposits and mining methods are presented through the studies already undertaken on French mines. This analysis allows to identify major hazards encountered in different traditional salt mines and solution-mining cavities. In particular, the role of overburden (presence and thickness of salt layer in exploitation roof, presence of clayey rocks or hard rocks e.g. dolomite or anhydrite), presence of water-bearing strata and possibly natural brine levels, discontinuities, etc. are discussed. In the second part, the main features of mechanical behaviour of salt (creep, damage) as well as transfer processes of this material are presented. The influence of these aspects on the long term evolution of abandoned salt mines is then analysed. KEY WORDS: exploitation, abandonment, salt, mechanical, stability, transport, solution, brine. ZUSAMMENFASSUNG: Der Artikel bezieht sich auf zwei bedeutende Aspekte beim Salzabbau: 1)-Das langsfristige Risiko zur Bodenoberflächeunbeständigkeit und sein Einfluss über Mensch= und Gütersicherheit. 2)-Die langsfristige Auflösung und Beförderung des Salz beruhen sich auf Studien über französiche Bergbauen. Diese Analyse emöglicht es, die bedeutendesten Risiken in verschiedenen Salzgruben zu identifizieren, bzw. Traditionellen oder durch Auflösung abgebauten. Insbesondere wird die Rolle des Deckgebirges (Vorhandensein und Dicke von Salzschicht am Dach des Grube, Beisein von Tanlager oder hartem Gestein wie Bitterkalk oder Anhydrid), Beisein von wasserhaltigem Boden und/oder gesalzenen Wasserflächen, Trennflächen, usw… erötert. Im zweiten Teil werden die haupsächlichen Eigenschaften des Salzverhaltens (Kriechen und Beschädigung) beschrieben. Ihr Einfluss über das Verhalten von stillgelegten Bergwerken lässt sich analysieren. SCHLÜSSELWÖRTER: Bergwerksbetrieb, Stilllegung, Mechanik, Beständigkeit, Ausbreitung, Aussolung, Solewasser. RESUME: L’article est consacré à deux aspects majeurs liés à l’abandon d’exploitations de sel : 1)- Le risque d’une instabilité à long terme de la surface du sol et son incidence sur la sécurité des personnes et des biens. 2)- La dissolution à long terme et le transport de sel sous l’effet d’une communication avec des eaux souterraines. Les principales caractéristiques de gisements et d’exploitations de sel sont présentées en s’appuyant sur les études antérieures réalisées sur les exploitations en France. Cette analyse permet d’identifier les risques majeurs rencontrés dans différentes mines de sel traditionnelles ou exploitées par dissolution. En particulier, le rôle du recouvrement (présence et épaisseur d’un banc de sel au toit de l’exploitation, présence de terrains argileux ou de roches dures telles que la dolomie ou de l’anhydrite), présence de terrains aquifères ou de nappes salées éventuelles, discontinuités, etc. sont discutées. Dans la deuxième partie, les principaux traits du comportement mécanique du sel (fluage, endommagement) ainsi que les processus de transport de ce matériau sont présentés. L’influence de ces aspects sur le comportement à long terme d’exploitations abandonnées de sel est ensuite analysée. MOTS CLES: exploitation, abandon, mécanique, sel, stabilité, transport, dissolution, saumure.

Jan 1, 2003

By C. J. Badenhorst

Oxides of sulphur are corrosive and are produced when sulphur-containing fuels are burned. Sulphur dioxide (SO2) is a colourless gas with a characteristic, irritating, pungent odour. Exposure routes to the human body are mainly through inhalation and skin and/or eye contact. Symptoms of exposure to SO2 may include irritation of the eyes, nose, and throat; rhinorrhea (discharge of thin nasal mucous); choking; cough; and reflex bronchoconstriction. To protect employees against the ill health effects of SO2 exposure, they are often required to make use of respiratory protection whenever entering areas were the SO2 levels exceed the statutory limits. The use of respiratory protective equipment should always be a last resort and should be considered only after other control measures have failed to reduce occupational exposure levels to below the occupational exposure limit or whilst other control measures are being investigated or implemented. Whenever the use of respiratory protection equipment is considered, it should always be used as part of a comprehensive respiratory protection plan. It is also extremely important that all potentially exposed persons are adequately and comprehensively informed and trained.

Jan 1, 2007

By R Kroukamp

Horizontal belt filters are typically used for separation of relatively free filtering solids where good post treatment is required. He horizontal belt filter is a continuous filter with an endless cloth supported on a grooved carrier belt. The belt and cloth are driven around two rollers across a series of evacuated suction boxes. The feed suspension is introduced at one end of the filter and deliquored to produce a cake at the other end. The benefits of using horizontal belt filters are good cake washing, continuous and visible processing, fully automatic operation, flexibility, high capacity and relative high speeds of operation. If required, horizontal belt filters enable efficient counter-current washings to minimize the usage of wash liquid. The horizontal belt filter has applications in the following: [? Metal concentrates ? Mineral sands ? Tailings ? Coal ? Iron ore ? Alumina ? Chloride processing ? Nickel and Cobalt refining ? Platinum group metals ? Zinc processing ? Many other applications in the Mining and Metallurgy industries ] 2. Operating Principle of a Horizontal Vacuum Belt Filter 2.1 Cake Forming The slurry to be dewatered is evenly distributed onto the filtering surface. Gravity assists the cake formation and the feed can be introduced in multiple stages. 2.2 Cake Washing Once the cake is formed, wash liquor/water can be introduced onto the top of the cake via a wash launder or sprays. Multiple wash stages, co-current, counter-current or direct washing can be added by increasing the length of the filter.

Jan 1, 2007

The 106th Annual General Meeting of The South African Institute of Mining and Metallurgy was held in the J.C. Lemmer Auditorium, SA National Museum of Military History, 22 Erlswold Way, Saxonwold, Johannesburg on Wednesday, 13th August, 2003. Welcome The President extended a special welcome to the guests and representatives of our sister institutes and other associations, also to recipients of awards, senior members of industry, Honorary Life Fellows, Past-presidents, our Members and other guests, among them the following: Kevin Moxham, President, Association of Mine Resident Engineers Prof. Jay Barton, Vice President, The Geological Society of South Africa Dr Gus Muller, President, Institute of Certificated Mechanical and Electrical Engineers, South Africa Marius van Rooyen, President, Institute of Mine Surveyors of South Africa Benjamin Ngulube, Deputy Vice President, South African Institution of Electrical Engineers Dr Francois Malan, Chairman, South African Institute of Rock Engineering Dr Paul Jourdan, President, Mintek

Jan 1, 2003