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By A. Kondratiev

A structurally-based viscosity model for fully liquid silicate slags has been developed and applied to the Al2O3-CaO-‘FeO’-SiO2system at metallic iron saturation. The model links the slag viscosity to the internal structure of melts through second nearest neighbour bonds concentrations taken from the quasi-chemical thermodynamic model. This viscosity model describes experimental data over the whole temperature and composition ranges within the Al2O3-CaO-‘FeO’-SiO2system at metallic iron saturation and can now be applied to other industrial slag systems.

Jan 1, 2004

By M. Verri

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Jan 1, 2009

By H. G. Oltmann

The equilibrium nitrogen solubility in the CaO-SiO2system was studied by a slag-gas equilibration technique, in graphite crucibles at 1823K under a CO-N2 atmosphere. The nitrogen content of the slags was determined by the Kjeldahl method. A reliable technique was used to obtain an initial nitrogen content in the master slags, from the addition and pre-melting of silicon nitride. Reduction of silica by graphite was found to occur during the equilibration experiments, resulting in compositional changes of the slags. The results were extrapolated to equilibrium by kinetic evaluation of the data. The nitrogen solubility showed good agreement with the result of Suito and Sano, while Fruehan?s results were lower. However, the results of the present study do not support the maximum nitrogen solubility values found by Sano.

Jan 1, 1999

By A. More, J. Bullón

Metal casting is one of the most important operations in ferroalloys factories. After the tapping of the furnace and the depuration of the metal, the preparation for customers with cooling, crushing and sizing begins. In total production costs, this contains around 8 % of the total cost of the metal, depending on the value of the fines and other important parameters. From an investment point of view, this represents around 20% of the total capital for a new furnace. Casting onto a water-refrigerated copper plate is not new for molten metals. In steel, continuous casting machines are normal in every factory. Water granulation casting exists at some ferroalloys plants. However, the majority of plants and production technology still use the technology of lumping, crushing and sizing. This technology is time consuming, produces fines and requires a relatively large work force. In 2001, Ferroatlantica put into operation a new water-cooled copper casting-machine, which seems to be a very convenient solution to solve all these problems. It is in operation at a silicon factory; the same place where the new ELSA electrode was developed for silicon metal production. This paper describes our experiences using it.

Jan 1, 2004

The mining industry worldwide is currently facing a significant restructuring process. In most underground mines, widespread mechanization of the mining processes increases production while reducing staff numbers. At the same time, mining depths as well as the lateral spread of the mine workings are increasing. This ever-changing mining environment requires sophisticated solutions for the design and operation of underground mines. In fact, a reduced number of mining engineers is taking responsibility for everincreasing mine operations. This applies not only to the excavation of the minerals, but also to all other aspects of the mining operation, including health and safety, disaster management, and mine rescue organization. Most mining engineering graduates entering the industry lack experience in mine emergency management. Young engineer trainees must learn mine emergency management and rescue work in addition to their normal training experience on the job. Often, and unfortunately, emergency and rescue training at different mining companies is not carried out to the highest level and standard and with the best possible training outcomes. The tasks and challenges a young engineer faces while being trained in a new position do not leave much room for additional training in mine rescue and emergency management. At the same time, experienced, ?old hands? are retiring and cannot easily be replaced due to limited graduation numbers. Strategies are being developed at mining universities worldwide to train mining engineering students in handling mine emergency situations and to provide hands-on experience for managing potential accident and disaster scenarios underground. Two of these strategies, from the USA and from Central Europe, are presented in this paper. These specific strategies have to be seen under special consideration of the local and regional boundary conditions, but might serve as case studies for mining schools and universities in other countries.

Jan 1, 2014

By N. Henderson, J. Weyer, J. F. Brune

"The mining industry worldwide is currently facing a significant restructuring process. In most underground mines, widespread mechanization of the mining processes increases production while reducing staff numbers. At the same time, mining depths as well as the lateral spread of the mine workings are increasing. This ever-changing mining environment requires sophisticated solutions for the design and operation of underground mines. In fact, a reduced number of mining engineers is taking responsibility for everincreasing mine operations. This applies not only to the excavation of the minerals, but also to all other aspects of the mining operation, including health and safety, disaster management, and mine rescue organization.Most mining engineering graduates entering the industry lack experience in mine emergency management. Young engineer trainees must learn mine emergency management and rescue work in addition to their normal training experience on the job. Often, and unfortunately, emergency and rescue training at different mining companies is not carried out to the highest level and standard and with the best possible training outcomes. The tasks and challenges a young engineer faces while being trained in a new position do not leave much room for additional training in mine rescue and emergency management. At the same time, experienced, ’old hands’ are retiring and cannot easily be replaced due to limited graduation numbers.Strategies are being developed at mining universities worldwide to train mining engineering students in handling mine emergency situations and to provide hands-on experience for managing potential accident and disaster scenarios underground. Two of these strategies, from the USA and from Central Europe, are presented in this paper. These specific strategies have to be seen under special consideration of the local and regional boundary conditions, but might serve as case studies for mining schools and universities in other countries."

Jan 1, 2014

By M. Görnerup, A. Kapilashrami, Seetharaman. S., A. K. Lahiri

Simultaneous reduction and foaming of chromium-rich slag have been studied in a laboratory furnace equipped with X-ray image analysis. Reduction of the metal oxides by graphite generated CO, which caused the melt to foam. The slag composition continuously changed due to reactions and dissolution of lining. Gas generation rate, foam height, and gas bubble size were studied and correlated to slag composition. Viscosity increased significantly during the experiments due to a change in slag composition. Bubble sizes varied little during the progress of reactions but differed considerably for different slags. Bubble sizes were largest for V2O5 containing slag, which is contrary to the general understanding that the presence of strong surface active agents reduces the bubble size. The foaming index did not follow expected trends for bubble size and viscosity, suggesting that foaming index is not a suitable parameter for discussion of foams under dynamic conditions. Keywords: slag, foaming, dynamic conditions

Jan 1, 2004

By M. Moys

The use of temperature measurements for unusual applications in the analysis and control of column flotation and milling is discussed. This is followed by a review of some of the authors current research in the application of the discrete element method to the modelling of particulate processes, specifically milling, fluidized beds and chute flow.

Jan 1, 2005

By W. J. Errington

The Isasmelt process was developed at Mount Isa Mines Limited in Queensland, Australia in collaboration with CSIRO, the Australian Government research organisation. Originally developed for primary lead smelting, culminating in the construction of a 60,000 tonnes per annum lead smelter at Mount Isa, this technology now also provides a major part of the current 200,000 tonnes per annum copper smelting capacity at Mount Isa. A programme is now in place to expand copper production to 250,000 tonnes per annum. The technology has also been applied to secondary lead smelting at Britannia Refined Metals, a MIM subsidiary company, where a 30,000 tonnes per annum lead plant based on battery scrap feed has been operating since 1991. Mount Isa Mines Limited decided to license the technology in1988, and copper smelting plants utilising Isasmelt technology are now operated by Cyprus Miami Mining Corporation in the USA and by Sterlite Industries in India. In addition, the technology was adopted by AGIP for smelting copper/nickel concentrates in Australia. Union Miniere are currently constructing an Isasmelt furnace to smelt and convert copper-containing materials at their plant at Hoboken in Belgium. This paper discusses these developments and also some likely future developments which include the application of the technology for continuous copper and nickel converting and applications in the treatment of zinc-containing residues.

Jan 1, 1997

By V. Coetzee

In 1992, a paper was compiled highlighting a common-sense approach to electric smelting at Impala Platinum. Since then, the smelter complex has undergone considerable changes. Mineral economics, UG2 exploitation, and changing environmental legislation have enforced numerous process upgrades, yet a common-sense approach has always been adopted. This document details the major changes in the smelter complex at Mineral Processes (Minpro) over the past 15 years, and provides the rationale for the changes. Keywords: Pyrometallurgy, furnace, PGM, platinum, nickel, copper, electric smelting, six-in-line, Peirce-Smith, Impala Platinum.

Jan 1, 2006

By S. E. Olsen, M. Tangstad, G. Tranell, K. Berg, S. Gaal

In this study, the reduction behaviours of MnO and SiO2containing slags by solid carbonaceous materials was investigated in both small and larger-scale laboratory experiments. Five types of carbonaceous material were investigated: 2 graphites, industrial coke, anthracite and eucalyptus charcoal. The effects of the reductant type/properties on the reduction kinetics, metal composition and metal yield, have been quantified. Results show that the reduction rate is highly dependant on the type of carbon used. It was found that the reductant type significantly influenced the SiO2reduction while it did not seem to have a large effect on the MnO reduction. This may be due to the different CO2and SiO reactivities of the materials.

Jan 1, 2004

By E. Milke, A. Arnold, B. Friedrich, A. Sydykov

CaF2is often used as a fluoride addition to the chloride salt flux in the melting of aluminium scrap. The solubility of CaF2in the chloride salt system is limited. Dissolved CaF2is considered to improve the properties of salt fluxes. Experimental investigations indicated that the solubility ofCaF2in 70 wt % NaCl/30 wt % KCl, German salt flux used in aluminium scrap melting, might be lower than expected according to literature data. The pseudo binary section CaF2-(70 wt % NaCl-30 wt % KCl) was investigated by differential thermal analysis (DTA). The determined solubility of CaF2appeared to be considerably lower than presented in the literature. The pseudo binary section calculated using thermodynamic data partially confirmed the results. DTA allowed us alsoto determine the crystallization temperature interval of the two phase eutectic consisting of the solid solution NaCl-KCl and CaF2. Keywords: aluminium recycling, phase system, salt flux, CaF2, NaCl, KCl, solubility

Jan 1, 2004

By H. Hamma, R. Fehrmann, M. Gaune-Escard, G. Hatem, S. B. Rasmussen, K. M. Eriksen

The molten salts M2S2O7and MHSO4, the binary molten salt systems M2S2O7-MHSO4and the molten salt-gas systems M2S2O7-V2O5and M2S2O7-M2SO4-V2O5(M = Na, K, Rb, Cs) in O2, SO2and Ar atmospheres have been investigated by thermal methods like calorimetry, Differential Enthalpic Analysis (DEA) and Differential Scanning Calorimetry (DSC). Fundamental thermodynamic data like temperatures and molar heats of solid-solid transition and fusion, phase diagrams, heat capacities of solids and liquids, heat of mixing, and heats of complex formation have been obtained and are reviewed here. Also EPR spectroscopic evidence of V(IV) complexes and their structure are reported and the results are discussed in relation to the mechanism of SO2oxidation by V2O5based industrial catalysts. Keywords: Alkali pyrosulfates, alkali hydrogen sulfates, vanadium pentoxide, EPR spectroscopy, complex formation

Jan 1, 2004

By R. Butcher

Mud rushes are hazardous occurrences that have occurred frequently in mines in South Africa, and have been the cause of numerous fatalities in the past. Mud rush incidents not associated with accidents are believed to be common occurrences that are not generally reported. Many such incidents are probably associated with the operation of chutes and box fronts. This paper describes the conditions necessary for mud rush occurrences, postulated mud rush mechanisms, and methods of combating the mud rush hazard.

Jan 1, 2005

By V. V. Nazimko, A. I. Hohotva, S. N. Alexandrov, V. P. Sazhnev, V. S. Zaharov

Ground behaviour in the vicinity of a roadway has been investigated using a physical model and in situ tests during a roof fall. It was discovered that behaviour of the ground is governed by irreversible displacements of adjacent rock clusters. The cluster is a short-living sector of a rock mass that moves as a solid body. For the lack of degree of freedom, the rock mass must be divided into clusters that are forced to move one after another in space and in time. These clusters permanently rearrange and reform during irreversible (inelastic) ground deformation. The crowded clusters have to yield to each other and alter their velocity and direction of movement to accommodate their motion into the excavation. Such behaviour involves uneven and irregular vertical deflection and the movement of adjacent rock blocks in the roof, sides and floor of an opening. Such movement destroys the symmetry of horizontal displacements with respect to the centre line of the opening. A set of indicators that a roof fall is imminent has been identified. Horizontal displacements and dilation must be controlled in order to maintain the stability of an underground opening. Such a state retains the self-supporting effect of the roof and contributes to rock bolts bearing capacity.

Jan 1, 2003

By L. Holappa

Ferroalloys like FeCr and FeMn are mostly produced in submerged electric arc furnaces. Typical for these processes is that the amount of slag is quite high. The role of slag for the process is thus very essential and specific chemical, physical and electrical properties are required. Slags in FeCr process are Al2O3-MgO-SiO2based with minor contents of CaO and CrOx. Slags in FeMn process are principally similar originating from silicate minerals but can have quite a large composition range depending on the manganese ore and its gangue minerals. Characteristic for FeMn process is that the slag is rich in manganese oxide up to above 30%. A common feature is that the ?ore oxides?, CrOx and MnOxin slag are not only divalent oxides but also containing some higher valent of Cr3+ and Mn3+, respectively. In FeMn production conditions the slag consists mainlyMn2+. This is a clear difference from CrOx containing slags in which both two and three valent coexists in slags in FeCr process conditions. Oxidation state of the slag depends on the ambient oxygen partial pressure and temperature in the examined process. Thermodynamics of slags in ferroalloys production are discussed in terms of phase diagrams, activities and oxidation state of chromium and manganese oxides. Further, slag properties influencing reduction kinetics and furnace operation i.e. viscosity and electrical resistivity are discussed. Keywords: review, slags, ferroalloys, ferrochromium, ferromanganese, thermodynamics, physical properties.

Jan 1, 2004

By H. Kotzé

Ticor SA began with a detailed feasibility study in 1995. The Hillendale mine (situated between Richards Bay and Empangeni) and mineral separation plant were approved in 2000. The smelter, just outside Empangeni, consists of two 36 MW DC arc furnaces that were commissioned in 2003. Experiences gained during the initial commissioning of the furnaces proved valuable in later commissioning work, as shown by the increase in ramp-up rates. The capacity of the plant is 250 kt/a TiO2slag and 145 kt/a of pig iron.

Jan 1, 2006

By M. P. Brungs, S. Haji Amini

Static dissolution of CaO into a CaO-SiO2-Al2O3slag and slags with additional fluxing agents (fluorspar, nepheline syenite and ilmenite) was studied. The slag was packed into dense CaO crucibles and heated to 1500ºC /1600ºC. After reaction, the crucible was air cooled and cross-sectioned. The development of the Ca2SiO4 phase and concentration profiles of various cations across the reaction zone were examined by Electron Probe Micro Analysis. At 1500ºC, a Ca2SiO4layer was found to form at the CaO/slag interface. No such layer was evident at 1600ºC. Ilmenite and nepheline syenite were found to be effective substitutes for fluorspar, increasing the rate of CaO dissolution.

Jan 1, 2004

By O. F. Oxtoby, J. E. Olsen, M. W. Erwee, Q. G. Reynolds

"The extraction of molten products and wastes through smelting furnace tap-holes during the tapping process is a complex procedure involving many coupled thermophysical effects. Insight into the fluid flow behaviour in such systems can be gained by using computational mechanics tools to build highfidelity models of the fluid flow and other relevant physics. Previous work using such models indicates that the nature of the flow in the tap-hole, as well as operational parameters such as the tapping flow rate, depends strongly on the properties of the material being tapped and the geometry of the tap-hole channel. Additional complications arise when multiple fluid phases (for example, slag and metal) are present simultaneously, when porous coke beds hinder flow to the tap-hole entrance, and when the geometry of the tap-hole changes over time due to cycles of wear and repair. In the present work, challenges with the coupling of phenomena such as multiphase flow and porosity into computational fluid dynamics methods for tap-hole modelling are discussed in the context of electric furnaces used for ferromanganese production. Qualitative and quantitative results of computational models of flow through tap-holes are presented and compared as a function of material parameters to determine sensitivity effects, and in response to operational parameters to determine typical process behaviour over the duration of a tap. IntroductionPyrometallurgical production using electric furnaces accounts for substantial portion of the world supply of ferroalloys and other strategic materials (Degel et al., 2015). A range of different furnace designs may be used depending on the metallurgical process, with circular three-electrode submerged arc furnaces (SAFs) powered by alternating current being the most common for commodities such as ferromanganese and silicomanganese (Olsen, Tangstad, and Lindstad, 2007).As shown in Figure 1, manganese furnaces typically operate with a deep charge consisting of an upper layer of loose burden (onto the upper surface of which is fed solid raw material), a molten slag layer partially or completely filled with unreacted carbonaceous reductant (generally metallurgical coke), and a molten metal layer which settles to the bottom of the furnace due to its high density. The solid particles present in the slag and burden layers form porous beds which hinder the fluid flow of molten process material and gases inside the furnace (Olsen, Tangstad, and Lindstad, 2007).In order to remove material from the furnace during normal operations, a single tap-hole is built into the sidewall of the vessel near to the level of the hearth. Tapping involves removing both slag and metal phases through the same tap-hole channel, which makes tap-hole design, operation, and maintenance particularly complex. In the case of processes such as ferromanganese, which operate with no external gas injection or open arcs present at the furnace electrodes, flow of material out of the tap-hole is driven primarily by the hydrostatic pressure generated by the weight of the solid and liquid phases above the tap-hole."

Jun 1, 2019

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