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By C. A. Rawlins

In an underground mine the ingress of heat can generally be attributed to two sources (Rock exposure and artificial mechanisms). The heat load relating rock exposure is subdivided into stoping [~40%] and haulages [~20%]. Rock is exposed to the ambient air and as a mine increases in depth the VRT (Virgin Rock Temperature) increases which leads to more heat ingress underground. To counter the heat ingress, especially in low-seam stoping areas of a deep level mine, air is, a) cooled artificially, b) the amount of rock exposed is reduced in the back areas of a stope by backfill applications, and c) ventilation air is used more efficiently. The heat reduction within a stope due to placed backfill could amount to ~50% for operations mining at a mean rock breaking depth of about 4500 mbc (metres below collar). Unfortunately, due to backfill transport methods, the physical fluid properties and application methods adopted, additional heat is induced into the air. The heat ingress due to backfill application could amount to as much as 25% of the overall in-stope heat load. This heat influx, seen as a negative aspect of backfill operations, is nevertheless overshadowed by the overall in-mine heat load reduction capability of about 20% attainable. The in-stope benefit [~50%] attainable from backfill operations could be increased with the incorporation of a heat exchange (cooling) methodology to offset the additional heat ingress into the surrounding air of a deep underground mine.

Jan 1, 2003

By T. Proietti, L. Mongiovì, L. Simeoni

Reliable estimates of the kinematic characteristics of movements are obtained by using a statistical model SSM. This model represents a useful tool for the management of alert and alarm systems. L'élaboration des données du déplacement médian d'un modèle statistique SSM opportun fournit des estimations fiables des caractéristiques cinématiques du mouvement. Le modèle peut être ainsi utilisé pour la gestion des systèmes d'alarme. Die Bearbeitung von Bewegungsdaten anhand eines geeigneten statistischen Modell SSM ergibt vertrauliche Abschätzungen der kinematischen Eigenschaften der Bewegung. Das Modell kann also für das Management von Alarmsystemen verwendet werden.

Jan 1, 2003

By J. A. Cruise

With the end of the official apartheid legislation in the early 1990s, South Africa was heralded as a non-racial country. However, racial awareness has been reintroduced into the country with the Affirmative Action and Black Economic Empowerment legislation. Gender and racial transformation are the current order of the day. All organizations are required to reflect in their make-up the demographics of the population as soon as possible. Scorecard shave been drawn up to measure the rate of transformation for gender and race in organizations. The mining industry in South Africa has been in the forefront of this transformation legislation and scorecards. This paper seeks to show the effect of gender and racial transformation on mining engineering education and professionalism by analysing the changing demographics of graduating mining students at both the South African universities offering a degree in mining engineering, the professional registration of mining engineers with the Engineering Council of South Africa (ECSA), and the membership of the Southern African Institute of Mining and Metallurgy (SAIMM), the vocational institute for mining engineers. It also demonstrates the absurdity of gender and racial quotas based solely on the demographics of the current population of the country. This paper shows the degree to which mining engineering has transformed in both gender and race.

Jan 1, 2011

By Rajib K. Mohapatra, K. Vizaya Kumar

In any manufacturing organization internal logistics plays a vital role in improving and maintaining the productivity. In Ferro Alloys manufacturing organization where there is huge input of raw material in terms of ore, reductants and variety of fluxes amounting to about four times of the mass of alloy produced need to be handled from yard to furnaces , internal logistics requires utmost attention. Any deviation or mismatch between stock and requirement will affect furnace operation. Though the activities are being outsourced by most of the organization, these require close monitoring. This communication presents an optimization model which can work as a ready reference for the manager to decide upon the material quantity and the furnace to be fed with an objective of minimizing the cost of handling and zero production loss.

Jan 1, 2007

By R. J. Forzatti

The production of sulphuric acid from sulphur generates heat. The majority of this heat is recovered as steam and is often used to generate electricity. Heat not recovered as steam is rejected to cooling water systems. The design of the turbine, condenser, and cooling water systems impacts the overall water, energy, and environmental footprint of the plant. This review considers a conceptual 2000 t/d sulphuric acid plant with several alternative cooling water systems. The review utilizes Hatch?s 4 Quadrant sustainable design tool to compare the alternatives on both an economic and a weighted sustainability scale.

Jan 1, 2014

By H. Sekimoto, T. Matsuoka, K. Yasuhara, M. Ota, S. Akutagawa

A magnetic anisotropy sensor is used for nondestructive measurement of stress on surfaces of a ferromagnetic material, such as steel. The sensor is built on the principle of the magneto-strictive effect in which changes in magnetic permeability due to deformation of the material is measured in a nondestructive manner, which then can be translated into the absolute values of stresses existing on the surface. This technique was applied to measure stresses of H-beams used in tunnels. The results show that this method could be one of the promising technologies for non-destructive stress measurement for safe construction of underground structures. Une sonde magnétique anisotropique est utilisée pour des mesures non-destructives de stress sur la surface d' unmétal ferromagnétique, comme l'acier. La sonde est construite sur le principe de l'effet magnéto-strictif dans lequel les changements dans la perméabilité magnétique due à la déformation du metal est mesurée avec une manière non-destructive, qui peut être alors traduite en valeurs absolues des stress existants à la surface. Cette technique a été appliquée pour la mesure de stress des poutres en H utilisées dans les tunnels. Les résultats montrent que cette méthode peut être l'une des technologies promet tantes concernant les mesures non-destructives de stress pour des constructions sûres de strcutures souterraines. Ein magnetischer Anisotropie-Sensor wird für die zerstörungsfreie Messung von Spannungen an Oberflächenvon ferromagnetischen Materialien wie z.B. Stahl verwendet. Der Sensor kann Änderungen in der magnetischen Durchlässigkeit auf Grund von Verformungen des Materials erkennen, die dann in Absolutwerte der Spannungen an der Oberfläche umgerechnet werden können. Die Methode wurde auf Messung von Spannungenvon H-Balken in Tunnels angewendet. Ergebnisse zeigen, dass dies eine vielversprechende Methode für diezerstörungefreie Messung im Tiefbau ist.

Jan 1, 2003

By V. Jovicic, J. Likar

The knowledge of the geological sequence and hydrological conditions in the area of portals was the basis for the design of the entry of the highway into tunnel Trojane. Mudstone, claystone and sandstone dominate the rock layering, which is tectonically reworked and contains structural anomalies. The complexity of the sequence makes it impossible to survey all the relevant features along the full 3km length of the tunnel. Sudden and frequent transitions between litological sequences impose potential instabilities and make the excavation of the tunnel particularly difficult. The initial survey established the zones of potential failures. These were monitored using topographic survey and inclinometers with an aim to make further geotechnical analyses more reliable and adjusted to the ground conditions. The analyses of the wall construction and the results of the monitoring showed that the design of the retaining wall was adequate. La connaissance de la séquence géologique et des conditions hydrologiques dans l'aire des portails a été la base pour la planification de l'entrée de l'autoroute dans le tunnel Trojane. Le schiste, l'argilite et le grès dominent la couche rocheuse qui est tectoniquement transformée et contient les anomalies structurales. A cause de la complexité de la séquence, il est impossible de revoir toutes les particularités le long des 3 kilomètres de la toute longueur du tunnel. Les transitions soudaines et fréquentes entre les séquences lithologiques imposent l'instabilité potentielle et font l'excavation du tunnel particulièrement difficile. La revue initiale a été établie sur les zones où il existe l'éboulement potential. Elles étaient contrôlées à l'aide de la revue topographique et de l'inclinomètre pour que les analyses géotechniques suivantes soient plus sûres et adaptées aux conditions du sol. Les analyses de la construction des murs et des résultats du contrôle ont montré que la planification du mur réteneur était correspondante. Der Autobahneingang in den Trojane Tunnel war projektiert auf Basis von der Kenntnis der geologischen und hydrogeologischen Bedingungen in dem Portalgebiet. Das Gebiet besteht aus dem Tonstein und dem Sandstein. Die Schichten sind tektonisch verformt und sind deswegen sehr heterogen. Die anfaenglichen Untersuchungen haben die Zonen von den potentiellen Bruechen definiert. Weitere geotechnische Analysen waren fitted an reale geologische Bedingungen durch das Monitoring der potentiellen Bruchzonen, welches aus den topographyschen Messungen und Inklinometerdaten entstand. Die Analyse des Wandbaues und die Resultate von dem Monitoring haben erwiesen, dass die Wandprojektierung entsprechend war.

Jan 1, 2003

By K. Yathavan

Fracturing of rock at low stress levels can be a source of unexpected problems in rock engineering: • the resulting instability can be a safety hazard; • in very brittle rocks it may be associated with violent failure of the rock and strainbursting (rockbursting); • it usually leads to an unexpected requirement for rock support, with time and cost implications; • in rock boring projects, it may result in fracture of the rock ahead of the bored face and in the walls of the bore behind the face. This may lead to cutter head vibration, increased cutter wear and consequently decreased performance and increased costs. Examples of situations in which fracturing of rock at very low stress levels has been observed will be described. This will include details or estimates of the in situ stress magnitudes and the rock strengths involved. La brisure de roche sous faibles contraintes peut être l’origine de problèmes inattendus en génie minier : • L’instabilité résultante peut devenir un danger • Elle peut provoquer des éclatements violents des roches fragiles • Elle nécessite souvent une infrastructure de soutien de la roche, ayant des implications sur les coûts et les délais • Les forages de la roche peuvent provoquer une brisure de celle-ci au niveau de la surface forée mais ainsi à l’intérieur de la roche, causant parfois des vibrations et une fatigue de la tête de forage, induisant une baisse de performance et un accroissement des coûts. Nous avons décrit ci-après des exemples de situations de brisure de roche sous faibles contraintes. Cette description comprend des détails ou des estimations des forces et des contraintes impliquées. Cette étude représente la base du travail de recherche effectué sur le phénomène. ißbildung im Gestein unter niedrigen Stressbedingung kann eine mögliche Ursache sein für unerwartet auftretende Probleme in der Felsmechaniklehre: • Die resultierende Instabilität stellt ein mögliches Sicherheitsrisiko dar; • In sehr sprödem Gestein kann es verbunden sein mit einem plötzlichen und gewaltsamen Zerfall des Gesteins; • In den meisten Fällen ist eine nicht eingeplante Gesteinsabstützung erforderlich, und damit ein Zeit- und Kostenaufwand verbunden; • Bei Bohrungsprojekten kann es dazu führen, daß es während des Bohrvorganges zu einer Rißbildung im Gestein hinter und vor der gebohrten Felswand kommt. Dies kann Bohrkopfvibrationen, eine erhöhte Bohrkopfabnutzung und folglich eine Bohrleistungssenkung, sowie Kostenerhöhung zur Folge haben. Das Phenomen von Gesteinsrißbildung unter niedrigen Stressbedingung wird anhand von einigen dokumentierten Beispielen erörtert. Diese beinhalten zudem Details oder Schätzungen bezüglich der Stärke des in situ Stressfeldes, sowie der gegebenen Gesteinsstärken. Die mit diesem Beitrag dokumentierten Ergebnisse formen eine Grundlage zur weiteren Forschung dieses Phenomens.

Jan 1, 2003

By T. J. Goff, G. M. Denton

Mintek has developed the EnviroplasTM process for the treatment of solid wastes from the metallurgical industry, especially steel plant dusts, without requiring agglomeration to produce inert slag and at the same time recover metal values such as nickel, chromium and zinc. The products that are generated in the plasma-arc process are usually a metal and a non-toxic slag, which are tapped from the furnace in liquid form. The metal is mainly composed of chromium, nickel and manganese. During the production of stainless steel between 30 and 70 kg of dust and fine waste is generated per ton of steel. Mintek has successfully processed around 1000t of AOD/EAF dust on a toll treatment basis in order to recover the contained Cr and Ni. The metal produced contained 18.5 per cent Cr, and 5.5 per cent Ni. All slag samples tested conformed to US EPA regulations for disposal. The chromium and nickel recovery to metal was 90 and 98 per cent respectively, on a once through basis i.e. no baghouse dust recycle. Slag tapping temperatures varied between 1650°C and 1750°C. The average actual energy requirement excluding furnace heatlosses of smelting steel plant dust with anthracite as reductant was 1.36MWh/ ton of dust. The total mass of feed reporting to the off-gas stream was 10 per cent. The average ZnO content of the fume was 35.5 per cent.

Jan 1, 2004

By W. Barthel, B. A. Dippenaar, J. Malan

In its most basic form, the process of sintering is very simple, and has been in use since the turn of the previous century. However, while the basic process is simple, control of the process relies on a number of extremely complex interdependent process parameters and requires a thorough understanding of the effect of these parameters on production capacity and product quality. Further, as with many other processes, the process parameters and hence design details of visually similar installations are highly dependant on the specific feed materials. While the industry trend has been towards an increase of capacity in order to lower unit production cost, typically in Iron ore sintering plants, this approach is not always possible for other commodities because of the scale of operation. This paper seeks firstly to describe some design considerations of sinter plants; secondly, to report on results from testwork performed with a specific series Manganese ore blends; and last, to relate these results to the design of new small-scale Manganese ore sinter plants.

Jan 1, 2004

By D. M. MacHunter, M. K. Palmer

Refinement of design parameters and features has resulted in the development and commercialization of spiral separator models that offer enhanced performance for a number of application areas. Examples of recently developed spiral separator models include the enhanced performance (EP)spiral and the HC (high capacity) series. Comparative performance data for appropriate applications are presented for each of these new model spiral separators. The utilization of spiral separators providing improved performance offers significant cost and operational benefits for process plants. Examples of process flowsheet changes that have resulted from the incorporation of recently developed spiral separators include the reduction of the number of process stages and the achievement of high density tailings by the utilization of a dewatering arrangement in the spiral tailings splitter system.

Jan 1, 2003

By D. Boldini, R. Lackner, H. A. Mang

ABSTRACT: In this paper, the strong interaction between the hardening shotcrete lining and the surrounding ground in NATM tunneling is investigated by means of axisymmetric analyses, accounting for the three-dimensional nature of the excavation process. The effect of the hydration of shotcrete on strength, stiffness, chemical shrinkage as well as microcracking and creep are accounted for. For the description of the mechanical behavior of the ground, a multi-surface plasticity model is employed. The performed analyses of the excavation process provide insight into the influence of each phenomenon accounted for in the material model for shotcrete on the response of the ground-shotcrete compound structure. ZUSAMMENFASSUNG: In diesem Beitrag soll die Interaktion zwischen dem erhärtenden Spritzbeton und dem Boden auf der Basis axisymmetrischer Berechnungen untersucht werden. Derartige Berechnungen ermöglichen die Berücksichtigung des drei-dimensionalen Charakters des Vortriebprozesses. Die Auswirkung der Hydratation auf die Entwicklung der Festigkeit, Steifigkeit und der chemischen Schwindverzerrungen, sowie das Reißen und das Kriechen des Spritzbetons wurde berücksichtigt. Das mechanische Verhalten des Bodens wurde mittels eines Mehrflächenplastizitätsmodells simuliert. Die durchgeführten Berechnungen des Vortriebprozesses geben Einblicke in die Auswirkungen der Spritzbetoneigenschaften auf das Tragverhalten des Boden-Spritzbeton-Komposits. RÉSUMÉ: La stricte interaction entre le soutènement en béton projeté durcissant et le terrain dans un tunnel creusé avec la NATM est étudiée par des analyses axisymétriques, compte tenu de la nature tridimensionnelle des processus de creusement. Les effets de l’hydratation du béton sur la résistance, la rigidité et la contraction chimique, ainsi que sur la micro-fissuration et le fluage, sont mis en compte. Pour la description du comportement mécanique du terrain on emploie un modèle de plasticité multi-surface. Les analyses conduites mettent en évidence l’influence de chaque phénomène considéré dans le modèle constitutif du béton projeté sur la réponse de la structure composite terrain-béton projeté.

Jan 1, 2003

By M. Olper

The zinc recycling is assuming more and more importance. A lot of zinc secondaries and wastes are ready to be collected and converted to zinc metal. The impurities present in these materials and the technical and economical problems that some traditional ways of treating these materials are facing, call for new technologies. The EZINEX Process, a fully hydrometallurgical process industrially proven to convert oxidised zinc bearing materials directly to zinc cathodes, is an innovative process that can deal with any kind of zinc waste/secondaries in a very powerful way. In this paper the highlights of this process will be shown and discussed to demonstrate the robustness of the process and its economic viability.

Jan 1, 2008

By M. Kwasniewski, M. Takahashi

Prismatic samples of a medium-grained sandstone from Slask Colliery (Upper Silesian Coal Basin, Poland) were tested under uniaxial compression, conventional triaxial compression and true triaxial compression conditions. The conventional triaxial compression tests were carried out at confining pressure (p) equal to 12.5, 25.0 and 37.5 MPa. In the true triaxial compression tests the minimum principal stress (s3) was equal to 25.0 MPa and the intermediate principal stress (s2) was 1.5, 2 and 2.5 times higher than s3. Results of the studies show that confining pressure strongly inhibited dilatant behavior of rock samples tested under conventional triaxial compression conditions; the increasing confinement resulted in the growing compaction of the rock material. The effect of dilatancy was also highly suppressed by the intermediate principal stress. While important dilatant, negative volumetric strain corresponded to the peak differential stress at low intermediate principal stress conditions, at high intermediate stresses the rock material was damaged to much lesser extent. As a result, faulting of rock samples in the post-peak region was much more violent and was accompanied by a strong acoustic effect. Les échantillons parallélépipédiques du grès à grains moyens de la mine ‘Slask’ (Bassin Houiller de Haute Silésie, Pologne) ont subi les essais de compression monoaxiale (compression simple), de compression triaxiale conventionnelle (compression triaxale de révolution) et de compression triaxiale vraie. Les essais de la compression triaxiale conventionnelle ont été effectués à la pression de confinement de 12,5, 25,0 et 37,5 MPa. Dans les essais de compression triaxiale vraie la contrainte principale minimale (s3) était de 25,0 MPa et la contrainte principale intermédiaire (s2) était 1,5, 2 et 2,5 fois supérieure de s3. Il résulte des essais que la pression de confinement inhibe fortement le processus de dilatance dans les échantillons testés dans les conditions de compression triaxiale conventionnelle; l’augmentation de la pression provoquait l’augmentation du compactage du matériau rocheux. Le phénomène de dilatance était également limité de façon significative par la contrainte principale intermédiaire. Alors que l’importante déformation volumique négative correspondait à la contrainte différentielle ultime avec les faibles contraintes principales intermédiaires, dans les conditions de fortes contraintes intermédiaires, le matériau rocheux subissait l'endommagement de façon beaucoup moins importante. En résultat, la rupture des échantillons rocheux au stade post-maximum était beaucoup plus violente et accompagnée d’un fort effet acoustique. Prismatische Probekörper des mittelkörnigen Sandsteines aus dem Bergwerk ‘Slask’ (das Oberschlesische Kohlengebiet, Polen) wurden unter der einaxialen Druckbeanspruchung, konventionellen dreiaxialen Druckbeanspruchung und der echten dreiaxialen Druckbeanspruchung geprüft. Konventionelle dreiaxiale Druckversuche wurden bei dem Manteldruck von 12,5 25,0 und 37,5 MPa durchgeführt. Bei den echten dreiaxialen Druckversuchen betrug die kleinste Hauptspannung (s3) 25,0 MPa und mittlere Hauptspannung (s2) war 1,5-, 2- und 2,5-mal höher als s3. Aus den durchgeführten Versuchen ergibt sich, dass der Manteldruck die Dilatanzentwicklung bei den Probekörpern unter der konventionellen dreiaxialen Druckbeanspruchung stark bremst; die Erhöhung des Druckes rief die ansteigende Kompaktion des Gesteinsmaterials hervor. Die Dilatanz wurde auch durch die mittlere Hauptspannung beschränkt. Während die wesentlichen volumetrischen, dilatanten Verformungen der Grenzdifferenzspannung bei den niedrigen mittleren Hauptspannungen entsprachen, bei den hohen mittleren Hauptspannungen wurde das Gesteinsmaterial viel weniger beschädigt. Im Ergebnis war der Scherbruch der Gesteinsproben im Post-Peak-Bereich viel heftiger und mit kräftigen akustischen Effekten verbunden.

Jan 1, 2003

By Onuralp Yücel, Süheyla Aydin, Erçin Ersundu

Turkish iron and steel sector, the base of which was established in the 1930?s, plays an important role in the industrialization and development of the country?s economy. In Türkiye this sector is the major consumer of ferroalloys. There had been a great improvement in Turkish Iron and Steel industry, especially after the 1980?sand as a result, 20.9 million tons of yearly crude steel production placed Türkiye 11th in the global steel output and 3rd in Europe. 15 % of steel produced in Türkiye is flat products, while the long products make the rest. The product composition and the general characteristics of steel production process led to an increase in ferroalloy consumption. Domestically consumed ferroalloys are especially ferromanganese, silicomanganese, and ferrosilicon. As of today, ferroalloy production capacity of Türkiye is 173,800 tons/year; 161,500 tons of which is ferrochrome with high and low carbon grades, 7,300 tons of ferrosilicochrome and the rest is ferrosilicon (5,000 tons/year). Türkiye is one of leading ferrochrome producers in the world considering the above mentioned production figures. However, this production is mainly exported since Türkiye?s stainless steel production level is modest requiring low amounts of ferrochrome. The products of iron and steel industry in Türkiye require large quantities of other ferroalloys, which make Türkiye a major importer and exporter of ferroalloys. The aim of this work is to present production, consumption, import and export quantities of: ferrochrome, ferromanganese, ferrosilicon, ferromolybdenum, ferrotungsten, ferrotitanium and ferrovanadium of Türkiye, between 1990 and 2006.

Jan 1, 2007

By K. Ford, R. Urquhart, D. Hobbs

CIS countries are home to some of the world's largest producers of chrome, manganese and silicon ferro alloys and leading suppliers to world export markets. The region's ferro alloys production is rising faster than demand from its domestic steel industry - unit alloy consumption in domestic steelmaking is in fact falling as process efficiencies improve - and there is significant spare capacity available to increase production. CIS producers enjoy certain strategic advantages in the production of ferro alloys - for example, captive ore sup-plies, low power and labour costs - but must also meet certain challenges - such as lower labour productivity and greater distance to market than some of their competitors. CIS producers are ambitious but new investment is needed to upgrade some aging plants and overhaul outdated process technologies if they are to be more competitive with the world's leading producers and address the environmental issues that are now moving up the agenda. This paper describes the structure of the region's ferro alloys industry and discusses its advantages and disadvantages by alloy and by country. It considers how the ongoing process of restructuring and new investment in the industry might move forwards, based on its strengths and weaknesses, technical and environmental factors and the strategies of the main players. It asks how the industry might maximise its substantial potential - in particular, for the production of chrome and manganese ferro alloys - and examines the implications this holds for all global ferro alloys players.

Jan 1, 2007

By Harushige Kusumi, Yuzuru Ashida, Toshiki Watanabe, Toshifumi Matsuoka

ABSTRACT: The technique of various kinds of numerical analysis offered remarkable results to explication of many rock mechanical phenomena. These techniques regarded a rock stratum as a continuum body and solved the governing equation of continuum mechanics by using finite differ-ence method, finite element method and/or others. Using numerical analysis based on continuum mechanics, however, the simulations of destruction phenomena caused by elastic waves and on the other hand, the elastic wave propagation which generated by fracturing events are quite difficult. In this paper, we express a rock stratum by a granular body model and develop a simulation tech-nique can simulate both wave phenomena and destruction phenomena at once. The DEM (discrete element method) simulation results are compared with finite difference solutions of elastic wave equation. Furthermore, we simulate Hopkinson effect by this proposed method. Hopkinson effect is famous as a destruction phenomenon caused by elastic wave propagation. ABRISS: In dieser Studie drücken wird eine Felsschicht durch ein Granularkörpermodell aus und entwickeln eine Simulationstechnik, die sowohl Wellenphänomene als auch Zerstörungsphänomene simulieren kann. Die Ergebnisse der Simulation mit DEM (Diskrete-Elemente-Methode) werden mit denen der Finit-Differenz-Lösung von Gleichungen elastischer Wellen verglichen. Desweiteren simulierten wir den Hopkinson-Effekt mit dieser vorgeschlagenen Methode. Der Hopkinson-Effekt ist als Zerstörungsphänomen berühmt, verursacht durch Fortpflanzung elastischer Wellen. RESUME: Dans cette étude, nous exprimons un lit de roches par un modèle à corps granulaire et développons une technique, permettant de simuler d'un coup le phénomène des ondes et le phé-nomène de destruction. Les résultats de la simulation DEM (méthode d'éléments discrets) sont comparés aux solutions à différence finie de l'équation d'ondes élastiques. En outre, nous simulons l'effet d'Hopkinson par la méthode proposée. L'effet d'Hopkinson est connu comme phénomène de destruction, causé par la propagation d'ondes élastiques.

Jan 1, 2003

By M. H. Farjadi, J. Azari

Cost analysis of chrome ore reduction is one of the important issues facing ferrochrome producers in today?s competitive environment. Much of this depends on quality and various ratios in the actual ore. The latter can have a direct bearing on electricity consumption and optimum efficiency of the furnaces. While the industry has been successful in reducing costs by designing larger and more efficient furnaces, the role of the optimum blend of ore has perhaps been given less emphasis. This paper will discuss the general specification and metallurgical characteristics of various chrome ores for producing high carbon ferrochromium on industrial scale. By analysing the results obtained from smelting, including chromium recovery and energy consumption, the determining parameters in total cost of ferrochromium i.e. chrome ore; reductant and energy consumption can be optimized. Our study is based on actual experiences obtained from Faryab Ferroalloy Plant over a period of approximately three years.

Jan 1, 2004

By F. Bonnet, J. Lehmann, H. Gaye

A review of thermodynamic information and models of slags, including associated software when available, is presented. The pertinence and accuracy of these models is discussed by comparison of their predictions for various slag thermodynamic properties with the available experimental data. Practical industrial applications will be illustrated by a literature review of the dephosphorization process of ferromanganese alloys and by the description of Ti behavior during silico-manganese alloys production. This latter example will show how the thermodynamic models have been used to propose a flotation treatment at low temperature to enhance TiC removal.

Jan 1, 2004

By S. -H. Chang, C. -I. Lee, Y. -K. Lee

Based on results from triaxial compressive tests, an experimental damage model to simulate post-peak behaviours as well as nonlinear behaviours before peak strength was developed. In order to consider pre-peak behaviours, variations of elastic constants at each damage level were regressed by functions of confining pressure. In addition, post-peak behaviours were simulated successfully by using Hoek-Brown constants. As results, the experimental model could predict nonlinear behaviours, peak strengths and stiffness changes observed in experiments. Basé sur des résultats des essais compressifs à trois axes, un modèle expérimental de dommages pour simuler des comportements de poteau-crête aussi bien que des comportements non-linéaires avant la force maximale a été développé. Afin de considérer des comportements de pré-crête, des variations des constantes élastiques à chaque niveau de dommages ont été régressées par des fonctions de pression d'emprisonnement. En outre, des comportements de poteau-crête ont été simulés avec succès en employant des constantes de Hoek-Brunes. Comme résultat, le modèle expérimental a pu prévoir des comportements non-linéaires, des forces maximales et des changements de riidité observés dans les expériences. Auf Basis der Ergebnisse des dreiaxialen Drucktests wurde das experimentelle Schadensmodell, das sowohl das nicht-lineare Verhalten vor der maximalen Stärke als auch das Verhalten nach der maximalen Stärke simulieren kann, entwickelt. Um das Verhalten vor der maximalen Stärke zu berücksichtigen, wurden die Veränderungen der elastischen Konstante bei dem jeweiligen Schadensniveau durch die Funktionen des begrenzten Drucks zurückgegangen. Außerdem wurde das Verhalten nach der maximalen Stärke unter Benutzung von Hoek-Brown Konstanten erfolgreich simuliert. Schließlich konnte das experimentelle Modell das nicht-lineare Verhalten, die maximale Stärke und die Veränderungen bezüglich der Steifigkeit während der Experimente voraussehen.

Jan 1, 2003