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By B. Salt, R. Sullivan, E. Roos, M. de Vries, K. McKenna, L. R. Nelson, M. J. N. Uys, P. Jacobs, E. Munnik, P. Lewarne

A review is presented of the furnace cooling system design and operating developments since the initial furnace start up in January 2001 of the Chambishi DC-arc furnace to produce ferrocobalt alloy. The furnace operating conditions present a number of challenges to the furnace designers and operators in particular to provide a sustainable lining that can withstand the highly corrosive siliceous slag (roughly 50% SiO2). This is exacerbated by the dual requirement to operate this slag in a relatively highly superheated state (?T ? 400°C when tapped at 1550°C) to ensure that the ferroalloy can be tapped (estimated 1370°C alloy liquidus temperature) prior to atomisation. The core design challenge occurs at the alloy-slag interface, where a single refractory type cannot simultaneously meet the dual requirement of both adequate alloy and slag corrosion compatibility. Progression by the fourth furnace campaign to involve a retrofit of the bath sidewall to Hatch high-intensity, water-cooled, copper Waffle coolers and tapblocks is described. This involves operation of the entire slag bath, the slag-alloy interface and a portion of the alloy within a more chemically compatible refractory/slag (and possibly at times even an alloy) freeze-lining. Due to the high furnace power density employed (up to 500 kW/m2 hearth area) coupled with the large slag superheat needed, the resulting imposed peak bath sidewall heat fluxes are substantial, especially in the alloy (typically averaging 170 kW/m2), and on occasion have exceeded 1000 kW/m2. The performance of the Hatch Copper Waffle coolers under such aggressive process pyrometallurgical conditions is described. Aspects of the design and especially operating strategies to effect sustained production at up to 38 MW power input are also discussed.

Jan 1, 2004

By S. Kamalpour

It has been observed that the productivity of ferromanganese furnaces, and the stability of metal and slag compositions, vary considerably according to the type of coke used as reductant. However, the desired properties of coke for optimum furnace performance are not well understood. In this investigation, the behaviour of four cokes, which exhibited a wide range of performance in ferromanganese production, was investigated by means of laboratory simulations of reducing conditions in the furnace. The Stationary Charge in Controlled Environment (SCICE) technique was used to simulate the conditions in the furnace shaft. Batches of raw materials, mixed in the same proportions as used in practice, were heated at fixed rates to 900, 1100 and 1300°C then cooled. The mass loss was used as a measure of the degree of reduction. Conditions in the lower part of the furnace were simulated by means of melt-reduction experiments in which lumps of coke were drilled out to form crucibles in which enriched ferromanganese slags were reduced at 1500 and 1550°C then cooled. An examination of the raw materials and the cooled, reacted charges using a variety of analytical and characterization techniques enabled the sequence of reaction and changes in morphology of the raw materials to be followed. This enabled an understanding of the behaviour of the cokes during reduction to be developed, which was then used to explain the observed performance of the cokes in practice. By relating the observed behaviour of the cokes in the laboratory tests to measurable properties of the unreacted cokes and to their observed performance in practice, it was shown that to achieve high productivity and good furnace performance, cokes should be selected to have moderately high reactivity towards CO2 (Boudouard reactivity) relative to conventional iron blast furnace cokes.

Jan 1, 2004

By I. Jauhari, F. Stober, D. Fowler, B. O. Wasmund, T. Miraza, C. Nichols, A. Taofik Hidyat, K. Said

The existing PT Aneka Tambang (Antam) ferronickel smelter located at Pomalaa, Indonesia consists of two RKEF lines with reduction furnaces nominally rated at 17 MW and 18 MW, respectively. The low power densities and heat fluxes allowed both furnaces to operate with falling water film shell cooling systems. The furnace campaigns comprised a 5-yearly cold shut -down for metal taphole area rebuild and a 10-yearlysidewall and hearth perimeter repair. Towards the end of these campaigns the furnaces would typically be operated at below nominal power due to excessive sidewall temperatures. In January 2001 Hatch performed a smelter study which proposed options which indicated the possibility of a single furnace operation for the smelter, elimination of lime addition and transition to shielded-arc operation with associated efficiency and throughput gains. This paper discusses the process of uprating the second?line furnace capability from 18 MW to 32MW following the decision by Antam to implement the recommendations proposed by Hatch. It will cover the development of scaled-up furnace design basis by Hatch and Antam with the enabling application of Hatch cooling and binding technology. To optimise the capital cost and maximise Indonesian supply content and post installation support, the scope was carefully and clearly divided between Hatch and Antam. The challenges, set backs and valuable learning experiences gained during the implementation of the retrofit include; ?The support and re-use of existing roof system and challenges presented in re-use of existing crucible support steel. ?Training and technical assistance for Antam operators to perform refractory and copper cooler installation and maintenance of crucible integrity technologies. ?Hearth integrity during start-up and development of an initial charge and start-up procedure to achieve planned thermal expansion of the hearth prior to bath formation ?Implementation of a sidewall hold-down system within the refractory sidewall due to space constraints ?Existing furnace foundation reinforcement to overcome lateral forces on furnace piers during crucible support steel expansion ?Conversion of an open-loop gravity feed cooling water system to a closed loop pressurised system with integrated emergency gravity feed and backup system ?Existing water treatment system and pumping system improvement and modification to meet copper cooling system requirements ?Integration of the new instrumentation control system designed by Hatch to increase performance of the furnace monitoring system and operation ?Uprate transformer capacity from 25 MVA to 40 MVA to meet with requirement of Shielded- Arc Furnace Operation.

Jan 1, 2007

By P G. Gaylard

The minerals Industry carries out over US$ 2 billion of R&D annually. The R&D is performed at three levels ? in house research facilities; on a one-on-one basis with a research provider; as syndicated (collaborative) research. The key to a successful R&D programme is project selection. It is suggested that at this time of ?bounty? for the minerals industry the research portfolio should contain some ?blue sky? but potentially long term significantly beneficial projects. This said, the projects should align the technical concepts with the business imperatives. AMIRA has found the ?Road Map? concept has assisted in defining areas for R&D. Examples of this methodology using a Copper Road Map developed by AMIRA for the copper producers operating in South America is presented. The benefits derived from syndicated research are also discussed.

Jan 1, 2007

One of the most important factors leading to the success of a cement plant is its location. A multicriteria decision-making method is used to rank alternative plant locations. The set of criteria is established and corresponding criteria should be established for each case study, although this multicriteria decision-making approach has broader applicability. In this paper, the analytic hierarchy process (AHP) with 5 criteria is used to develop a location evaluation hierarchy for an alumina?cement plant in East Azerbaijan province of Iran. Five alternatives for the plant location are evaluated. The main criteria are transportation, water supply, power supply, fuel supply and land. Other criteria have the same importance as these five alternatives. The alternatives are ranked by a multicriteria method and the best site is proposed. Keywords: plant location; multicriteria decision-making

Jan 1, 2005

By S. J. Baumgartner

The ferromanganese industry is under pressure to deal with the slag arising from the production of ferromanganese, which is discarded in landfills or slag heaps. This material poses an environmental and health risk to surrounding ecosystems and communities, and disposal costs are increasing. Ferromanganese slag contains an appreciable amount of residual manganese metal, which can be exploited. Previous work has shown that the slag can be leached fully, while rejecting the silica to a residue. The methods that were investigated to recover manganese from the leach solution included hydroxide precipitation to upgrade the leach solution followed by manganese carbonate precipitation to produce a pure manganese carbonate product or a manganese carbonate furnace feed material, which would be recycled to increase manganese recoveries in the production of ferromanganese. In addition, electrowinning of electrolytic manganese dioxide from the leach solution was studied. The methods were compared in terms of selectivity, costs, and product quality. Co-recovery of the leach residue, which is a potential cement additive, is discussed. Among the methods investigated to upgrade the pregnant leach solution, hydroxide precipitation utilizing ammonia to adjust the pH appears to be the most effective in removing major impurities such as iron, aluminium, and silica to less than 1 ppm. The manganese carbonate and impure manganese carbonate furnace feed products met quality specifications. However, although the production of these materials was technically viable, the large amounts of base reagent that were required to raise the pH, and the associated high operating costs, rendered the process uneconomic. An optimization study was therefore carried out with the primary objective to determine the ideal acid amount to be utilized in the waterstarved digestion stage, thereby decreasing acid and base consumption while optimizing the quality of the pregnant leach solution, and producing a leach residue that contained <1% Mn. The outcome was an economically viable process. Additional benefits included an increase in the manganese content of the impure manganese carbonate furnace feed material, and a substantial reduction in the dilution of the pregnant leach solution, thereby maintaining high manganese concentrations that rendered the solution viable for electrowinning of electrolytic manganese dioxide, the production of which yielded a current efficiency of 74%.

Jan 1, 2014

By M. Kumral, Y. A. Sari

Underground mining operations tend to have higher operating costs than surface mines. When metal prices decrease, profitability is jeopardized due to the high costs. Therefore, mining management harnesses new practices that increase operational efficiency. One way to manage this challenge is to invest in new mine planning practices. Stope layout optimization as a part of underground mine planning aims to identify a portion of the orebody in the form of production volumes (stopes) to maximize profit under roadway and stope dimension constraints. In this paper we propose a novel approach based on identifying ore-rich areas of the deposit and prioritizing their extraction through an iterative heuristic clustering approach. The proposed approach is compared with and validated by an exact method through a small mining example. The heuristics produced nearly identical results in a very short time. Finally, a case study was carried out using a larger data-set. The cluster-based iterative approach generated nearoptimal stope layouts in a computationally effective manner.

Mar 1, 2021

By L. Rademeyer, P. Mazzoni, C. Kubank, F. Brown

The Corridor Sands deposits of heavy mineral sands represent the largest known economic resource of titanium dioxide minerals. The West Block of Deposit 1 alone contains Measured and Indicated Mineral Resources of 1.7 billion tonnes containing 4.14 per cent ilmenite, estimated in accordance with the JORC standard, sufficient for at least the first 20 years of mining. Total mineral resources are estimated to be approximately 17 billion tonnes at 5 per cent Total Heavy Minerals (THM). Test work was undertaken on the West Block of Deposit 1 over a period of two years in order to develop the process flow sheet to bankable standards. Geological, mineralogical and metallurgical test work was integrated from a pre-feasibility stage to the full bankable stage. The process flowsheet was developed with the central objective of the production of saleable products, of consistent quality and acceptable to the respective end-markets. The aim of this paper is to describe the way in which the various challenges for the project have been addressed by using integrated geological and mineralogical information, which has resulted in the development of a complete flow sheet. The process confirmed that material within customer specifications could be produced, once various metallurgical parameters were understood. This flow sheet development progressed from laboratory test work through to full field trials at pilot plant scale on large consignments of mineralized material. The flow sheet was developed to such a standard as to be used with confidence for both engineering design and cost estimates, and to determine the recovery factors to be used in financial evaluations. Keywords: Corridor sands, Flow sheet, Pilot plant Titanium dioxide

Jan 1, 2003

By B. Clermont

Ball mills are usually the largest consumers of energy within a mineral concentrator. Comminution is responsible for 50% of the total mineral processing cost. In today?s global markets, expanding mining groups are trying to optimize mill performances. Since comminution is concerned with liberating valuable minerals for recovery in the separation process, it is crucial to run the mills at the best operating conditions which lead to good liberation at competitive throughputs with minimum costs (energy and wear). The high availability of the equipment is also essential to maximize production and profit. To reach this key objective, continuous and reliable information about the mill operation is vital. An innovative tool which can deliver information about in-mill dynamics has been developed by Magotteaux. It can provide online and accurate measurements of the degree of grinding ball fill and pulp position for timely decision making and actions. This tool could be used on its own or linked to an automatic grinding ball loading system named Magoload. Therefore, ball load could be kept constant by using direct measurement. This article describes the Sensomag and presents some of the major improvements that can be achieved with it. Some other promising avenues are still to be explored. Keywords: Comminution, process control, process optimization, process instrumentation, online analysis.

Jan 1, 2010

By R. Dekkers, J. Plessers

The feasibility of using hydrogen to obtain clean steels is investigated. High hydrogen contents are generally considered as detrimental due to the risk of flakes, bubbles and breakouts during casting. Hydrogen can nonetheless be removed by degassing of the steel. The results of industrial campaigns, where total oxygen content and hydrogen content were monitored, are presented. High resolution microscopy of inclusions and laboratory experiments on the rate of inclusion removal by CaO-Al2O3 slags at different partial hydrogen have been carried out. So far, evidence that hydrogen may influence inclusions or the steel cleanliness is not clear. Keywords: hydrogen, cleanliness, inclusions.

Jan 1, 2004

By A. de Meyer

Zincor experienced significant losses of metallic zinc to dross during the melting of zinc cathode plates. In this study five factors affecting the formation of dross are identified from literature. Dross from both the plant and that produced in the laboratory is characterized using XRD. An empirical model, based on laboratory-scale investigations, was developed to quantify the effect these factors on their own or in combination with each other has on the amount of zinc loss to dross. The predictive capability of the model is evaluated based on the laboratory-scale investigations. Predictions are made on the effects that heat treating the cathode plates prior to melting, increasing the cathode plate thickness, washing and drying prior to melting, and loading the furnace in a controlled manner have on the amount of zinc loss to dross. Keywords: Zinc, dross, optimize, smelter, yield, losses, empirical, model, XRD.

Jan 1, 2010

Ferrochrome is the major chromium source for stainless steel production, and submerged-arc furnaces (SAF) are most commonly utilised to smelt chromite ores into ferrochrome by using suitable carbonaceous reductants such as coke. Because of the complexity of feed structure and electrical-thermal-chemical interactions, there exist large gradients and wide distributions of temperature, mineralogy and other process variables in the furnace. This leads to various zones in the furnace, and different reduction mechanisms. Control of the furnace is thus often difficult due to the complicated physical and chemical situations in the furnace. The temperature profile in the submerged arc furnace has a great influence on the reduction rate and the production efficiency. Therefore, the energy generation through electrical arcs submerged in the solid feed and its distribution within the packed bed play an important role. In the present paper, an overall process model is illustrated to simulate inter-linked transport processes of fluid flow, heat transfer and reduction kinetics within the submerged arc furnace. The application of reaction kinetic data to simulate the chromite pellet/lumpy ore reduction with CO gas is presented and further adjusted to provide a submodel for a flow and heat transfer simulation for the packed bed by using computational fluid dynamics (CFD) technique. The comprehensive process model is aimed to simulate materials and gas flow, temperature and energy distribution throughout the furnace system. A preliminary model for gas flow and temperature distribution for the upper part of a 20 MW furnace (the packed bed) for high carbon ferrochrome production has been developed under simplified conditions. The integration of the reaction kinetic model into process simulation, and the future vision for a more comprehensive process modelling are discussed. It is expected that better understanding of the furnace insights through process modelling will help process optimisation and furnace control.

Jan 1, 2004

By J. Arzuúa, U. Castro-Filgueira, L. R. Alejano, F. Malan

"Pillar design for underground mining is typically done using empirical formulae or numerical modelling. Practical experience and recent literature, nevertheless, illustrate the shortcomings of these design approaches. Ongoing monitoring of pillars is therefore recommended to minimize the risk associated with these designs.In a mine where a large number of pillars are cut, different pillar strengths can be expected owing to variations in rock mass strength from area to area. This problem is compounded by the fact that in mining environments the pillars are not always cut according to the prescribed dimensions. Although the original design using either empirical methods or modelling may predict stable pillars, unstable pillars will be encountered in reality. Very conservative designs with large factors of safety may circumvent this problem, but this approach is uneconomical.A possible solution to localized stability problems may be to enhance the strength of a few unstable pillars. It may even be hypothesized that reinforcing a few critical pillars may prevent ‘pillar runs’ on a much larger scale. Rockbolting, strapping of pillars, and pillar shotcreting have occasionally been used in the past as possible solutions. It appears that these have not been successful in all cases and large collapses have occurred in spite of the pillar remedial work.The authors investigated the strapping of pillars by conducting laboratory tests on cabled rock specimens. The results were qualitatively compared to actual attempts of pillar reinforcement available in the literature, as well as additional observations in an old haematite roomand- pillar mine in Spain. Based on these results, the value of steel cabling and mesh wrapped around pillars to improve stability is demonstrated. Some cases where this approach will not be successful are also discussed."

Jan 1, 2017

By H. Hearnden

Whereas in the past, ladles were simply a means of transferring molten products from furnace tapholes to points of discharge be they casting pans or waste dumps, the ladle is now becoming a more integral and versatile piece of equipment in the pyrometallurgical plant. The drive behind this development is the need for continuous improvement in performance where better, faster and cheaper means remaining competitive in the global market. This paper will explore the technologies available for the rendering of a costly and otherwise cumbersome piece of pyrometallurgical equipment more efficient and versatile in adding value to the final product. Essentially it all revolves around heat and more importantly the loss of it when tapping. The common practice is to move the molten product to its point of discharge quickly with the minimum of interruption to prevent skulling and hence the cost associated with clearing it. The advances in Oxy-fuel burners, AC or DC ladle furnaces, converters, gas purging and high velocity, bath injection systems has increased the versatility of processes and enhanced the potential for adding value to intermediate products through down stream practices such as granulation and atomisation.

Jan 1, 2004

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 A van Jaarsveld

Environmentally-friendly, safe and cost-effective technology for stope drilling has successfully been introduced at TauTona mine. It has enabled the problem of inadequate compressed air pressure and its downgrading impact on production capability to be overcome. The paper traces the development process which culminated in the conversion of the entire stoping operation at TauTona to electric drilling. Background work which took place at other mines is also described. Statistics of performance improvements are provided. 1. Introduction Holman?s Silver series and the Seco S215 were drills that had a measurable impact on the South African gold mining industry. It is too soon to say whether Hilti will join those great names. However, there is no doubt that the introduction of electric drills into the harsh and unforgiving world of deep level gold mining is a significant development. History has shown that being the first to enter a new technology is no guarantee of long-term success. The pain and suffering which accompany the birth of anything new can deplete the energy of the innovator while at the same time creating opportunities for competitors to leapfrog him. In addition to commitment and enthusiasm, the innovator must therefore also possess, or have access to stamina and resourcefulness to overcome the unexpected difficulties which will inevitably arise. All of these were needed for the Hilti project.

Jan 1, 2008

A well known rock mass classification system has been altered slightly to address the issues found under remnant mining conditions. By detail study of the expected fracture patterns and local geology, the rock mass is classified to indicate the condition of the hanging wall prior to mining. The risk level of each mining step is evaluated by calculating input parameters for computer simulations from the actual rock mass condition. Seismic activity is catered for by the understanding that large event rates and large magnitude events reduce the quality of the local rock mass and that the rock mass stiffness should be adapted accordingly. A case study is presented to test parts of the protocol. Un système connu de classification des masses rocheuses a été légèrement modifié pour faire face aux questions posées par les conditions d’extraction de débris. Une étude détaillée des diagrammes de fragmentation et de la géologie locale permet de classer la masse rocheuse pour indiquer la condition du toit avant l’extraction. Le niveau de risque de chaque étape minière est évalué en calculant les paramètres d’entrée pour simulation par ordinateur à partir de la condition réelle de la masse rocheuse. L’activité sismique est prise en compte avec la réalisation que les taux de larges évènements et les évènements de large magnitude réduisent la qualité de la masse rocheuse locale et que la raideur de la masse rocheuse doit donc être adaptée. Une étude de cas est présentée pour tester des sections du protocole. Ein sehr bekanntes Gesteinsmassenklassifikationssystem wurde abgeändert um die Probleme zu behandeln die unter Restabbaukonditionen angetroffen werden. Durch detaillierstes Studium der der zu erwartenden Bruchmuster und der lokalen geologischen Verhältnisse wird die Gesteinsmasse in Hinblick auf die Konditionen der Flözoberseite klassifiziert. Das Risikoniveau für jeden Abbauschritt wird durch die Eingabeparameter aktuellen Gesteinsmassenkondition für die Computersimulation evaluiert. Für die Seismische Aktivitäten wird Sorge getragen durch das Verständnis, daß große Ereignisraten und Ereignisse hoher Größenklassen die Qualität der lokalen Gesteinsmasse reduzieren und daß die Gesteinsmassensteifheit entsprechend adaptiert werden sollte. Eine Fallstudie um Teile des Protokolls zu testen wird präsentiert.

Jan 1, 2003

By K. C. Mills, R. Thackray

A test has been devised that can predict accurately the % crystallinity developed in a slag film formed between the steel strand and the mould. The % crystallinity in the test samples was determined and compared with that for slag films formed in the mould when casting with that flux. There was good agreement between the % crystallinity in the test samples and the slag films. It was found that additions of TiO2and ZrO2had little effect on the amount of crystalline phase formed, but additions of CaO caused a dramatic increase in the amount of crystalline phase formed. Various parameters (which can be calculated from chemical composition of the flux) have been plotted against % crystallinty in the test samples. It was found that the modified (NBO/T) ratio provided the best relation with % crystallinity for the various parameters tested. There commended relation is % crystallinity=141.1(NBO/T)-284.0. Keywords: continuous casting, mould flux, slag film, crystallinity, chemical composition

Jan 1, 2004

By Hao Li, Allan Moss, Richard K. Brummer

At the Palabora Mine, the transition to caving 400 m below the bottom of the 800 m deep pit resulted in a slope failure of the North wall that began in 2003, and is still mobile. This failure can be explained by the daylighting into the cave zone of a prominent joint set. The failure was modelled by the 3-dimensional code 3DEC, which is capable of modelling the nonlinear behaviour of discontinuum materials with large displacement.

Jan 1, 2006

By S. H. Yi, J. R. Kim, Y. S. Lee

The viscosities of CaO-SiO2-Al2O3-MgO-FeO slags were measured under conditions ofCaO/SiO2=1.15–1.6, 10–13 percent Al2O3, 5–10 percent MgO and 5–20 percent FeO. Slag viscosity decreased with increasing FeO content at a fixed basicity (CaO/SiO2) of slag. Slag viscosity at low FeO (<7.5 percent FeO) exhibited a minimum value by increasing MgO content in slag. Viscosity decreased with increasing slag basicity up to 1.3 while it increased as slag basicity increased from 1.3 to 1.5. Thus, it was proposed that the driving force for the decreases of slag viscosity would be an increase in depolymerization of silicate network at C/S=1.3, while the viscous behaviour at C/S>1.3 would be increased with increasing the chemical potential of primary solid phase e.g. dicalcium silicate. A thermodynamic approach for the activity of primary solid phase in molten slags resulted in a reasonable relationship between viscosity and slag components. Therefore, it was confirmed that slag viscosity in basic slags system (C/S>1.3) could be determined by the chemical potential of dicalcium silicate. Keywords: viscosity, basicity, bosh slag, blast furnace, slag structure, FT-IR

Jan 1, 2004