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By A. More, J. M. Míguez, J. Bullón

In 2000 Ferroatlantica started a project with the aim to develop a new casting machine for silicon and other ferroalloys. Until now, it has been cast more than 25.000 tons of silicon for the chemical and metallurgical market. This system has improved the process yield, productivity and product quality which place?s Ferroatlantica at the top of technology development in this field. After the first presentation of the Ferroatlantica?s casting machine at Infacon X, we would like to show the improvements in the control which have permitted us to increase the lifetime of the copper and to obtain, at the end of the machine, the right product size for the customer avoiding the current necessity of crushing and sizing the lumpy metal. Furthermore, we have improved the system in relation to the obtaining of smaller granulometries at the end of casting machine. Not only is this kind of machine cost competitive for special silicon applications but also for other normal ferroalloys with different specifications of size and thickness.

Jan 1, 2007

By David Mitchell, Daan Delport, Frik Marx, Mike Shapiro

The use of copper cooling elements to enhance refractory lining life in pyrometallurgical vessels is common in modern furnace design. Copper elements typically incorporate a base panel with cast in cooling passages and an integral extended surface (formed of pins, fins or similar) onto which suitable refractory material is cast. The metallic, conducting parts are located towards the cold face of the lining, with the refractory material interposing between the coolers and the process. The coolers are designed to arrest wear of the refractory material by freezing a layer of slag or partially reacted material onto the hot face, thereby rendering the lining inert to further attack [1]. These coolers have achieved success in new furnaces and relining of existing vessels. The freeze layer is prone to mechanical damage during operational and process instability. The coolers must be capable of extracting the additional heat flux under upset conditions to facilitate rapid self-repair of the freeze layer and prevent further refractory wear in the intermittently exposed areas. However, operational experience has shown that the high heat flux capabilities of the copper coolers have some disadvantages, especially in processes producing vapours which form corrosive compounds when condensing onto the cold surfaces of the coolers. When corrosive conditions develop, the entire composite will fail due to loss of structural integrity, and as a result of leaks from the cooling water passages. This paper describes recent developments in the approach to the design and manufacture of copper cooler panels customized to achieve specified heat fluxes and temperature profiles, thereby reducing the formation of corrosion mechanisms in applications with corrosive gaseous environments and enhancing refractory lining life. Condensation formation prevention is achieved by adjusting the geometry of the cooler and selection of suitable materials of construction.

Jan 1, 2007

By V. I. Zhuchkov, L. A. Smirnov, E. I. Arzamastsev, A. A. Babenko

A brief analysis is given for state-of-the-art of manganese and chromium ferroalloy production in Russia and their consumption by metallurgy plants. The main causes of low output of manganese and chromium ferroalloys, and ways to resolve the issue of ferroalloy production development are considered.

Jan 1, 2004

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

The energy consumption and recovery of chromium are important economic factors in ferrochrome production. Outokumpu has a lot of experience of the reduction behavior of the sintered pellets in industrial-scale furnaces and also on the grounds of numerous laboratory and pilot-scale investigations. Sintered pellets have shown a superiority over lumpy ore and briquettes made of the same chromite grade. The good performance of the pellets has also resulted in investigations on the reasons for such a performance. In this study, the factors affecting pellet behavior in smelting furnace were investigated. This study is divided into two sections, i.e. the investigations were on the factors affecting solid state reduction and on the factors affecting reduction under melting. These tests were performed by means of thermo gravimetry and by smelting tests. The correlation between the pellet characteristics and reduction behavior was shown and its influence on industrial-scale furnaces was discussed. Factors worth of consideration are for instance, the extent of oxidation during sintering, slag formation and chemistry in respect of molten state reduction, and the grain size of the chromite mineral in the raw material in respect of kinetic reasons (retention time in smelting).

Jan 1, 2007

By M. Suzuki, T. Shiomi, M. Nakada, K. Tsutsumi

Mold powder plays an important role in the continuous casting process for high quality steel production. It is well known that mold powder entrapment causes surface defects in steel sheet and the high viscosity of mold powder prevents the entrapment of mold powder in molten steel in ultra low carbon steel. This paper deals with the entrapment of mold powder caused by suction by Karman?s vortex in a laboratory experiment. At first the effect of the viscosity of oil and interfacial tension between water and oil was investigated in a water model experiment. Then hot model experiments were carried out by mold powder and molten steel. The amount of mold powder entrapment was affected by the viscosity and the interfacial tension between molten steel and mold powder. As a result, the following equation of the mold powder entrapment was obtained. m=1.06*107?-0.255?m-s-2.18 The amount of mold powder entrapment decreased when the viscosity and interfacial tension increased. But the effect of viscosity was larger than that of interfacial tension in the case of the industrial mold powder when the viscosity was under 0.5 Pa.s, interfacial tension was from 1200to 1300 mN/m.

Jan 1, 2004

By T. F. J. Hälbich

Namakwa Sands aims to conserve environmental resources and prevent or minimize environmental impacts from its operations. The challenge faced by Namakwa Sands is the rehabilitation of the arid winter rainfall Strandveld and lowland Succulent Karoo vegetation zones affected by its mining activities. Extensive experimentation with different rehabilitation methods resulted in the development of an effective rehabilitation programme. The use of topsoil as a seed bank and shade-cloth as windbreaks have significantly aided the rehabilitation process. The aim of the programme is to stabilize the soil environment so as to allow the germination and development of the local plant species. The ability to control wind erosion is critical to the success of the rehabilitation effort. A programme of biodiversity audits has been started to measure the recovery of plant species in the rehabilitated area. The principle of continuous improvement, coupled to site-specific rehabilitation studies, is applied to enhance the rehabilitation programme.

Jan 1, 2003

By P. K. Sahoo, C. R. Ray, S. S. Rao

This paper deals with various factors affecting the strength of chromite briquettes which plays a vital role in the smelting of charge chrome / ferro chrome production. Appropriate briquetting parameters like molasses and lime binder level, molasses quality, particle size distribution and segment condition etc. are essential to guarantee quality briquettes in the successful use of briquette and chromite ore fines. In developing a technology for briquetting of chromite ores, it is important not only to study the grain size characteristics of the chrome ore fines but also to make an informed choice of the type and quality of the binder and the condition for producing a physically and chemically competent green and cured briquette. This paper also describes the effect of strength of briquettes on various parameters of charge chrome production as the use of quality briquettes in the production of high carbon ferrochrome alloys has a number of operational, metallurgical and economic advantages. It is also a requirement for submerged arc furnace operation that the charge be adequately porous to allow gaseous products of the reduction reaction to escape from the furnace charge burden without hindrance. Otherwise, furnace material would erupt causing electrodes and furnace other equipments damage and risking the safety of the work force. The briquette, because it replaces lumpy charge but has an advantage of smaller size, allows for an uniform and porous charge so that the ascending gaseous products can escape freely. Finally this paper deals with furnace operational results with varying proportion of briquettes having same strength.

Jan 1, 2007

By J. A. Bakken, G. Sævarsdóttir, H. Pálsson, M. Þ. Jónsson

The role of the electric arc in the consumption of electrodes in submerged arc furnaces has long been debated. The hostile environment in the furnace does not make direct measurement feasible, so simulation has been used to evaluate the arcs contribution to the erosion. Magnetofluiddynamic (MFD) electric arc simulations and a cathode / anode sub-model developed in order to provide boundary condition to the arc model have been used for this purpose. The cathode / anode sub-model provides current distributions and cathode / anode fall voltages for the arc and temperature distribution for the electrode surface, which is paramount to the erosion rate which in turn is calculated from the Clausius Clapeyron equation and the Hertz Knudsen formula for the vapour transport. In the case of high-current industrial AC arcs, arc currents are typically ~100 kA, phase voltages ~100 V and total furnace power ~10 ? 60 MW. The results show that although enormous amounts of material is evaporated, much of it recondenses on the surface. Furthermore the results show that the arc erosion increases strongly with the arc current. If a single arc is present its contribution to erosion is close to the actual total erosion in the furnace. Results from this analysis indicate that there are possibly more than one arc present in the crater, in which case less than 40% of the total erosion would be due to the arc, the rest is chemical erosion.

Jan 1, 2007

By Willem C. A. van Niekerk, David A. Baldwin, Nardus Potgieter, Willie A. Gericke

Authorities that regulate environmental issues pertaining to industrial wastes in South Africa regard landfill disposal as the only effective environmental management option for slag and other inorganic by-products from the ferro-alloy industry. Metallurgical slags are widely utilised in civil engineering and construction applications in other countries in the world and in line with the overall philosophy of conserving mineral and other natural resources, these materials should be assessed for the possibility of resource recovery, recycling, reclamation, direct re-use or alternative uses. This presentation describes a risk-based approach for the assessment of by-products from the ferro-alloy industry for alternative use. Once a by-product from an industrial process has been identified for alternative use, its intended use would be defined, but it will not be possible to control its actual use or misuse in society, nor will it be possible to control its fate during the application life cycle. In the interest of protection of human health and the environment, potential risks associated with the handling and uses of a material throughout its life cycle therefore have to be quantified. The assessment has to include both human health and ecological risks and must cover the entire life cycle of a product, from its production up to its end-of-life disposal. The presentation introduces the concept of tiered risk assessment and demonstrates how this applies in the overall assessment of by-products from metallurgical industry sector for safe use in society.

Jan 1, 2007

A Life Cycle Assessment (LCA) of stainless steel production, including that of the nickel, ferronickel, ferrochromium and iron feedstocks was carried out using inventory data derived from the literature. The environmental impact categories considered in the study were Global Warming Potential (GWP), Acidification Potential (AP) and total (or full cycle) energy consumption. The effects of different sources of electricity (black coal, natural gas and hydroelectricity) were also examined in the study. The results of the LCA showed that when ferronickel is used as the nickel source, the total energy consumption for stainless steel production is approximately 50% higher than when nickel metal is used as the nickel source (75 MJ/kg cf. 49 MJ/kg). This result comes about largely because the Fe units in ferronickel have a much higher energy intensity than do the Fe units in pig iron, and the greater the use of the former at the expense of the latter, the greater is the total energy consumption. The results also showed that the production of ferronickel made by far the largest contribution (59%) to the total energy consumption for stainless steel production when this feedstock is used as the nickel source, but when nickel metal is used as the nickel source the contributions of the various stages are more evenly distributed. It was also observed that the electricity consumption of the electric furnaces used in the production of ferronickel, ferrochromium and stainless steel contributed approximately 50% to the total energy consumed in stainless steel production. Given the relatively low efficiencies associated with electrical power generation, significant reductions in the total energy of stainless steel production could be anticipated if more direct use of thermal energy was made in the ferronickel, ferrochromium and/or stainless steel smelting stages, for example by utilising bath smelting processes.

Jan 1, 2004

By B. W. Lee, P. O?Shaughnessy

The practice of manganese ferroalloy smelting has traditionally been based on utilising oxide ores which typically contain a high level of manganese. This preference for oxides has even been extended to the modification of natural carbonates into nodulized oxides. However smelting practices developed over the past 30 years have created a market for natural manganese carbonate ores, driven in part by the unique properties that this type of ore can offer. An understanding of the mineralogy of carbonate ore and its thermal properties has provided important information which enables furnace operators to take full advantage of the chemical differences. However changes to traditional operating practices have been necessary. Once furnace operations using natural and unmodified carbonate ore have been mastered, the unique chemical features of manganese carbonate ore are able to contribute, not only to new product development, but also to cost savings. The use of natural manganese carbonate ore is now a well-established aspect of the industry. The sustained increase in demand for carbonate ore worldwide over the past several years confirms acceptance of its quality. There are effectively few limits to its successful use.

Jan 1, 2004

By A. J. Van Der Merwe, N. A. Barcza, M. Boyes, N. R. Clarke

Oriel Resources has with the support of SRK (Cardiff) and DRA and Mintek (South Africa) carried our a Definitive Feasibility Study (DFS) to recover high grade chrome ore from its Voskhod deposit very close to Chromtau that is near to Aktobe in Kazakhstan. Voskhod is a large podiform ore body that contains nearly 20million tons of chromite grading about 48% Cr2O3 and with a Cr/Fe ratio of over 3/1. Selected bore hole core samples were obtained from the confirmation drilling programme during the DFS phase of the project in 2005 for pilot plant test work to design the mineral beneficiation plant. The chrome ore is characterised by four main types, namely high grade lumpy and chip sized ore, high-grade fine ore, lower grade (subordinate) lumpy ore and lower grade fine ore. Gravity separation tests carried out by Mintek showed that the large density difference between the high grade (at over 3.7t/m3) and lower grade ore (at less than 2.97t/m3 ) should ensure very good separation in the DMS drum and DMS cyclone stages resulting in high recoveries of Cr2O3 - rich chromite ore products. Very high chrome ore grades of up to 64% Cr2O3 and Cr/Fe ratios of 4 to 1 were obtained at an 80% mass yield from selected samples of lumpy and chip ore size fractions. The overall predicted recovery from the design work on the mine and plant is expected to be closer to about 70% of the ROM (Run of Mine) feed. DRA has completed the design of the mineral processing plant to recover about 900 kt/a of chrome ore from the 1.3 Mt/a of ROM feed. The plant has been sized to handle up to 1.5 Mt/a and will also be able to address the variability in ore feed as different regions in the deposit are mined. The lumpy high-grade product and the chips size fraction is expected to grade around 48% Cr2O3 and the fine concentrate between 56 and 58%Cr2O3 The ratio of products is expected to be about 70, 15 and 15 percent respectively but will vary to some extent during the expected 20 year life of the mining operation based on including the associated adjacent Karaagash deposit together with the Voskhod deposit. The prediction of the product split from the processing plant depends on many factors such as the geology, mineralogy, mining, handling and metallurgical processing. An overall process flow model has been developed that covers the ROM ore, the various types of chrome ore feed to the mineral beneficiation plant, the projected products and the subsequent smelting of the chromite ores to produce High Carbon Ferrochromium. The model allows the optimisation of the quality of the chrome ore in terms of Cr2O3 content, Cr/Fe ratio and recovery to be studied. This information can also be evaluated in terms of the economic requirements for smelting High Carbon Ferrochromium (HCFeCr) at a given location. Oriel is planning to supply chrome ore to Ferrochrome plants mostly in China and Russia. The use of the model will assist to maximise the value of the Voskhod project to its owners and also assist the users of the chrome ore in selecting the appropriate supply quality to meet their needs for a given smelter operation. The smelting of high grade Voskhod ore requires a limited addition of about 5 to 7% quartz to flux the MgO and Al2O3 and about 25% coke as a reducing agent to produce an alloy containing from about 65 to 74%chromium depending on the Cr/Fe ratio.

Jan 1, 2007

By X. H. Zhang, J. G. Cai

This paper discusses the behaviour of large-span tunnels and caverns in hard rock in a major underground storage project. In-situ stresses were measured using hydraulic fracturing during site investigation and 3-D overcoring during construction, with both showing a horizontal stress ratio of 2-3 times the vertical stress. Rock reinforcement design was based on the Q-system combined with numerical modelling for special design cases. Tunnel design and performance were checked and monitored by in-situ instrumentation during rock excavation, including measurements of deformation, convergence, and load on rock bolts. Deformation measurements using borehole extensometers included one borehole drilled into the virgin rock before rock excavation, which provided a direct and very insightful comparison with the various deformation measurements made during rock excavation. These measurements coupled with numerical calculations have proven that the high horizontal stresses to be very favourable to the stability of the large openings.

Jan 1, 2003

By W. Valderrama, D. G. Almond

Operation of large SAG mills requires a change in the conceptual approach to grinding processes. The traditional energy consumption criteria are now enhanced with new criteria derived from the mechanical dynamics of the mill load. This new approach demands instrumentation capable of providing accurate information about the load movement and the ratio of balls and ore inside the mill. This paper discusses two new performance enhancing tools available to meet these needs.

Jan 1, 2004

By H. Hu, T. S. Golosinski

The paper reports on use of neural network algorithms to model performance and condition of mining trucks. The model inputs are selected digital data streams collected by truck Vital Information Management System, VIMS, during its operation in a mine. The models built as the result of this work allow for projection of truck condition and performance into future. As such they facilitate more efficient management of mine truck fleets. Keywords: Modelling, modeling, neural networks, mining equipment, Vital Information Management System, Intelligent Miner, mining truck

Jan 1, 2003

By Michelle Mouton, Johanna van Deventer, Jussi Vaarno

Mintek has been involved in numerous projects to remove Fe and Mn from dilute Co sulphate solutions by means of oxidative precipitation using air/SO2. Test work was done using a gas induction system, designed and supplied by Outotec. Various aspects, such as SO2 concentration, SO2 flowrate, impeller rotation speed and pH were investigated on a 2 m3 scale. Batch tests were performed using a residence time of 5 hours. Mintek has been involved in numerous projects to remove Fe and Mn from dilute Co sulphate solutions by means of oxidative precipitation using air/SO2. Test work was done using a gas induction system, designed and supplied by Outotec. Various aspects, such as SO2 concentration, SO2 flowrate, impeller rotation speed and pH were investigated on a 2 m3 scale. Batch tests were performed using a residence time of 5 hours. Impeller rotation speeds of 0-220 rpm were tested, and it seemed that speeds of between 80 and 220 rpm gave similar Fe and Mn removal rates. Co and Cu losses were generally below 1% and 5% respectively at pH 3.

Jan 1, 2007

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 B. Derin, T. Uzunoglu, O. Yücel

In this study, reduction behaviours of Turkish chromite concentrate (48 % Cr2O3, 13.30 % FeO, 18.33 % MgO, 12.37 % Al2O3, 5.76 % SiO2) and nickel oxide by Fe-C alloy in graphite crucible were investigated. In the first stage of experiments, steel scraps were melted in graphite crucibles and were saturated with carbon at 1600 °C and 30 min. In the second stage, mixtures of different amount of chromite concentrate, nickel oxide and flux additives (CaO,SiO2 and CaF2) were charged into the graphite crucible containing the Fe-C alloy and heated to 1600 °C for different reduction times (0-180 min) under argon gas. The highest Cr and Ni con-tents in alloys were found as 11.41 and 14.37 % and the highest Cr and Ni recoveries were found as 88 and94 %, respectively at 180 min.

Jan 1, 2007

By Y. Poornachandra Rao, P. C. Sudhakar, L. Malakondaiah

NBV commissioned a 27.6 MVA furnace in the year 2005. This paper explains: a)Furnace design features b)Furnace process control, Direct slag granulation c)Continuous casting, Waste heat recovery, Sintering d) Gas cleaning plant, Protection of Environment. Keywords: Furnace Equipment, SiMn Production, Casting, Heat Recovery and Low hood

Jan 1, 2007

The Skorpion Zinc Project demonstrated the viability of the production of zinc from non-sulphide (commonly called ?zinc-oxide?) ores, using the leach/solvent extraction/electrowinning process route. The success of Skorpion raised the profile of a number of other zinc oxide deposits, considered to be similar. However, a study of three such deposits demonstrates that the application of whole-ore-leaching may be limited and that the concentration of zinc, or at least the separation from acid-consuming gangue minerals, prior to leaching is essential to the successful recovery of zinc from these deposits. The recovery of zinc is dependent on an understanding of the geology of the deposit, the mineralogical association of zinc minerals with gangue minerals (Boni, 2005) and limitations of mining practice. Flow sheet development and the associated metallurgical test work to derive an economically viable treatment route from two of these deposits are discussed. Key parameters affecting zinc recovery by gravity separation and flotation are presented, demonstrating that even minor differences in mineralogy have a profound impact on zinc recovery and reagent consumption. The study also deals with the determination of appropriate design parameters through metallurgical mapping of the dense media separation process.

Jan 1, 2008