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By Y. Shiraishi, Y. Sakurai

A new method, the gliding cylinder method, was proposed as a wide range viscometer for the measurements of molten salts, slags, and glasses. The method consists of two coaxial cylinders, cylindrical bob and a vessel containing a liquid sample. There is a narrow gap between bob and vessel. When the vessel moves against the bob, the generated force on the bob consists of three types of resistance: (1) Stokes’s resistance on the bob, (2) a capillary flow resistance though an annular gap between vessel and bob, and (3) lubricating resistance in a gap. The last two can be calculated on a theoretical basis but the first cannot be estimated by a simple calculation since a wall effect did not calculate easily. However, it can be assumed that the generated force depends on both the viscosity of a liquid and velocity of the vessel. Thus, the relation between viscosity and a force at desired velocity of the vessel was measured using several standard reference materials including glycerol aqueous solutions and standard reference oils. The results depended on the magnitude of the gap between the bob and the vessel. For the wider gap, it was shown that the viscosity is a linear function of a gradient of force with respect to a vessel velocity. In contrast, if the gap is small, the viscosity depends on the gradient (of force with respect to velocity). This implies that the non-linear phenomena would occur in Stokes resistance. Though detailed analysis is in a further investigation, a calibration method can be applied to determine the viscosity by this method, because good correlation was obtained among these quantities. Viscosity of molten salts, such as NaNO3and ZnCl2was measured by this method as high temperature demonstration. Keywords: viscometer, viscosity, sphere pull-up method, fused salts, molten slags, glass melts

Jan 1, 2004

By D. G. Krige

Using chip sample data and spatial structure parameters from a large mined-out section of a South African gold mine the advantages to be gained from a regular underground borehole drilling programme have been investigated for short- and medium- to long-term planning based on block valuations. The results have been compared with the current position, which relies invariably on the extrapolation of limited peripheral sampling data from raises, gullies or stope faces. Some preliminary work has also been done regarding the implications of such underground drilling on costs used for the present pay limit calculations. The results of the study, though preliminary, show that the net advantage of advance regular underground drilling could be substantial and that a more intensive follow-up research is warranted.

Jan 1, 2003

By J. N. Van der Merwe

The data base of failed pillar cases as used by Salamon and Munro (1967) in their original analysis to determine the strength of coal pillars empirically, has been updated for this study. It is shown that the Vaal Basin and Klip River coal fields exhibit similar behaviour that differs from the failures in other areas, i.e. failure at high safety factors within a short period of time. Those collapse cases have been omitted from the new data base. Failures in the other areas that occurred after 1967 have been added. Using a technique to minimize the area of overlap between the populations of safety factors of failed and intact pillar cases, the new data base was re-analysed in conjunction with the original Salamon-Munro data base of intact pillar cases, from which the cases in the areas of weak coal were likewise eliminated. It was found that a linear formula reduced the overlap area by22%. The new formula predicts higher strength for pillars with a width-to-height ratio greater than approximately 2.0 to 3.0 and a lower strength for smaller pillars. It was also found that in order to obtain the same relative measure of stability as with the Salamon-Munro formula, the strength constant in the new formula should be within a range of 2.8 to 3.5 MPa. For most current South African coal mining conditions, using the new formula for pillar strength will result in leaving smaller pillars without sacrificing stability. The reason for this is that the Salamon-Munro formula under-estimated the strength of larger pillars and over-estimated the strength of smaller pillars. The new formula will thus result in improved reserve utilization without sacrificing stability.

Jan 1, 2003

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

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

Jan 1, 2004

By L. R. Nelson

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 of operating 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 atomization. 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 tap blocks 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 D. Govender

Theoretical flotation models suggest that there is a positive relationship between bubble-particle collision rates and turbulent kinetic energy dissipation. Fine particle flotation performance is generally enhanced by increased collision frequency and hence higher energy dissipation. Contrarily, increased turbulence in the rotor-stator region is related to higher detachment frequency of the coarser size range. Therefore, the optimal modes of recovery for the 'fine' and 'coarse' size classes appear to be diametrically opposed. Industrial applications have previously confirmed that applying greater power to flotation slurries yields significant improvements in fine particle recovery. However, recovery of the coarser size class favours a different flotation environment. An improvement in the flotation kinetics of the fine and coarse size classes, provided there is no adverse metallurgical influence on the intermediate size ranges, is obviously beneficial to the overall recovery response. Managing the local turbulent kinetic energy dissipation, and hence the power imparted to the slurry, offers the benefit of targeting the particle size ranges exhibiting slower kinetics. FLSmidth recently introduced the practical implementation of this concept. In principle, it decouples flotation regimes where fine and coarse particles exhibit preferentially recovery. In the case of naturally aspirated machines (Wemco®), it is referred to as Hybrid Energy Flotation? and incorporates at least three phases: > Standard flotation machines (standard energy input, rotor speed (r/min), rotor size/type) at the beginning of the row, where flotation is typically froth-phase limited and operational and set-up parameters have a limited influence on the recovery > Higher-powered flotation machines (high rotor speed, high-power rotor size/type) at the end of the row to improve fine particle recovery > Lower-powered flotation machines (low rotor speed, low power rotor size/type) to enhance coarse particle recovery. A CFD-based flotation model is used to highlight the effect of turbulent dissipation energy on attachment and detachment rates. Preferential collection zones for fine, and 'coarse' particles are predicted for both forced-air and naturally aspirated machines. The greater predominance of UG2 ore types, coupled with the skewed feed distribution of platinum group metals (PGMs) to the finer size fractions, suggests that PGM flotation circuits are not designed for optimal recovery across the size distribution. The application of the hybrid energy concept to PGM flotation offers a possible shift towards a more efficient flotation circuit solution through a managed distribution of energy.

Jan 1, 2013

The Skorpion process comprises three processing steps, atmospheric leaching in sulphuric acid, zinc solvent extraction and electrowinning to produce special high grade zinc. The major mode of impurity transfer was attributed to crud runs in the solvent extraction circuit. Crud may be described as a heterogeneous, partly inorganic, partly organic mass of material which accumulates predominantly at the interface between organic and aqueous solutions. The paper describes the route causes of the crud formation in the solvent extraction circuit and optimisation strategies which are being followed to prevent impurity excursions in electrowinning. Keywords: zinc oxide, solvent extraction, crud formation, colloidal silica

Jan 1, 2007

Keywords: Pyrometallurgy, furnace, Lonmin, platinum, PGM, UG2 Lonmin, earlier than any other primary platinum producer, had to deal with the concentrating and smelting of UG2-rich ores and concentrates respectively. Smelting was performed at a fairly modest scale compared to its industry peers in the Platinum Group Metals (PGMs) industry, and was focused on smelting concentrates obtained through low mass pulls while still maintaining high recoveries at its concentrators. Lonmin gradually smelted larger quantities of UG2 concentrates. Initially two 2.3 MW Infurnco furnaces were commissioned in 1982, followed by three 5 MW circular 3-electrode Pyromet furnaces in 1991. Deep electrode immersions and moderately high hearth power densities were used in all the designs. Lonmin decided to continue with circular furnace technology when it planned its new high-intensity No. 1 Furnace. Neither Lonmin nor the technology supplier and EPCM company foresaw the challenges that scale-up would bring when applied to the smelting of UG2-rich concentrate blends. Superimposed on the high chromite content, was the low base-metal loading, mineralogical difficulties, and fine particle size that came with milling of all concentrates (especially UG2 and recycle materials within the smelter). Through a process of fundamental diagnoses of furnace run-outs and wear patterns observed during repairs, the main challenges operating this high-intensity furnace were identified as sulphur vapour corrosion of the copper coolers, uneven and unpredicted movements of refractory bricks with associated copper cooler lift and matte tap-block movement, the formation of three-phase ?mushy? zones, high refractory and tap-hole wear rates, uncertainty in matte level and associated insufficient matte buffer height, and high furnace operating temperatures. These factors seldom worked in isolation and will be explored in more detail in the paper. The variability in furnace feed characteristics led Lonmin to re-design Furnace No. 1, to invest in back-up furnace capacity, and to invest in improved monitoring and control. These improvements consisted of online and high-frequency off-line feed chemistry and mineralogy monitoring, online pressure monitoring of water-cooled circuits, an alternative matte liquid level measurement in the furnace, and electrode immersion estimation. Improvements were also made at the converters by installing and utilising optical spectral analysis of the converter flame to characterise converter behaviour and achieve the desired iron end-point for white matte. This paper also briefly discusses the current and future expansion plans, as well as ancillary operations at the smelter such as flue-gas handling and materials handling.

Jan 1, 2011

By N. Gatelier, T. You, J. C. Kandel

ABSTRACT: Underground hydrocarbons storage is a very specific domain for the designer. He is usually free to adjust the section, shape and layout to cope with the geological and geotechnical conditions. This paper presents a panorama of the geotechnical design of mined underground storage caverns, then lists a number of uncommon features encountered in a storage excavated in Sydney, Australia, the Elgas LPG project that had to face major non-isotropic conditions with numerous local variations, impacting on the achievement of the design profiles. Changes in geotechnical design methodology and practice are examined through this project, now in operation, which will have lasted altogether almost ten years. KEY WORDS: underground storage, geotechnical engineering, stability, methodology, design. ZUSAMMENFASSUNG: Die untertaegige Speicherung von Kohlenwasserstoffen unterliegt in der Planung sehr spezifischen Bedingungen. Der planende Ingenieur hat bei der Dimensionierung und Formgebung der Speicherhohlraeume gewisse Freiheiten, muss jedoch vorgefundene geologische und geotechnische Bedingungen beruecksichtigen. Der vorliegende Beitrag gibt zunaechst einen allgemeinen Ueberblick ueber die geotechnische Planung von bergmaennisch aufgefahrenen Speicherhhohlraeumen. Darueber hinaus werden Besonderheiten betrachtet, mit denen das Elgas LPG-Speicherprojekt in einer bergmaennisch aufgefahrenen Kaverne in Sydney, Australien konfrontiert war. Hierbei ging es um die Beruecksichtigung anisotroper Bedingungen mit zusaetzlichen Heterogenitaeten im Gestein und den daraus erwachsenden Schwierigkeiten, die geplante Hohlraumform zu verwirklichen. Ueber einen Zeitraum von fast 10 Jahren, in denen das jetzt in Betrieb befindliche Projekt unterschiedliche Betriebsphasen durchlaufen hat, wurden verschiedene geotechnische Entwurfsverfahren auf ihre Anwendbarkeit geprueft. SCHLUESSELWOERTER: Untergrundspeicherung, Geotechnik, Stabilitaet, Entwurfsverfahren, Planung. RESUME : Le stockage souterrain d’hydrocarbures est un domaine très spécifique pour le concepteur, car celui-ci dispose d'une large liberté pour adapter les sections, les formes et les implantations aux conditions géologiques et géotechniques de l’environnement choisi. Après un panorama de la conception géotechnique des stockages souterrains d’hydrocarbures par la méthode dite des cavités minées, l’accent sera mis sur un certain nombre de particularités rencontrées lors du projet de stockage de GPL de Elgas à Sydney en Australie, creusé dans de très fortes conditions d’anisotropie du massif rocheux, avec de nombreuses variations locales et toutes les implications que cela peut avoir sur le maintien des formes. L’évolution des approches méthodologiques géotechniques durant la dizaine d'années de développement de ce projet depuis les premières études jusqu'à l'exploitation actuelle est également présentée. MOTS-CLEFS : stockage souterrain, géotechnique, stabilité, méthode, conception.

Jan 1, 2003

By F. A. Camisani-Calzolari

The latter half of the 20th century has seen the proliferation of a series of codes to address commodity needs which were brought about by rapidly advancing technologies and the globalization of markets and consumerism. This paper addresses the specific needs and the origin of this surge and presents these codes in the context they were developed. It also compares the main codes or groups of codes and elaborates upon their strengths and weaknesses. Three main categories of codes are identified, namely: codes for reporting to international agencies, codes addressing government needs and, finally, codes for the investors and the stock market. Codes governed by international agencies usually relate to strategic commodities which have highly specialized fields of usage like nuclear power generation where international cooperation is eventually the only viable approach for both the development of technologies and their applications. Codes for reporting to governments address the necessity of each state to exploit their mineral potential profitably and to secure the preservation of wealth for future generations. Reporting to investors is experiencing a considerable popularity as of late because of globalization in mining and the growing need for outside financing of mining projects, whose capital requirements are getting out of reach for the average mid-cap mining company. All these codes have advantages and shortcomings dictated by the specific circumstances under which they were developed, therefore necessitating the definition and implementation of some kind of international standard whereby investments and the spread of information across political boundaries would be facilitated. Though none of these codes might ever become international in the true sense of the word because of significantly different legislations at national level, a step that would greatly contribute to the cross-border disclosure of information would be the reciprocal recognition of competent persons by the major mining countries, including China and Russia. It is also becoming essential that financial institutions and investors be properly advised on mining projects by reporting reserves and resources in a transparent and responsible way with the relevant public disclosures being compiled by professionals who take full responsibility for their submissions. Keywords: reporting codes, mineral resources, mineral reserves, competent person, UN Framework Classification, IAEA classification, JORC Code, SAMREC Code and CRIRSCO.

Jan 1, 2003

By S. J. Lötter

Analysis of the major and minor components of raw zircon as well as plasma-dissociated zircon was undertaken using inductively coupled plasma optical emission spectroscopy (ICP-OES). Microwave-assisted acid extraction as well as flux fusion using lithium tetraborate were investigated as digestion methods. Microwave-assisted acid extraction samples were analysed with matrix-matched standards. The most successful microwave-assisted acid extractions yielded 44.3(1), 49.75(7), 78.3(3) and 90.0(7) per cent recovery for Zr, Hf, Al, and Fe respectively using sulphuric acid. In no instance was acid extraction capable of complete digestion of the sample matrix. A standard addition method was applied to the flux-fusion samples due to the high complexity of the sample matrix. Method validation for the flux fusion procedure was performed using the SARM 62 certified reference material (CRM) with acceptable recovery ranges being based on the 95 per cent confidence intervals of the CRM. Successful analyses were achieved for Zr, Hf, and Ti with apparent content of 66(6), 1.7(1) and 0.15(1) per cent respectively.

Jan 1, 2012

By J. Gummer, M. Williams, S. J. Hawksworth

A common problem encountered in British coal mines is bearing failure on conveyor system idler rollers, which on occasions has led to fires. The UK Mines Inspectorate initiated a study of such failures to assess the potential for ignition of explosive atmospheres. As part of this study HSL have developed a system to measure the temperatures generated within the bearings during controlled failure. Temperatures are measured using both infrared thermal imaging and contact thermometry. The work to date has shown that temperatures well in excess of the auto-ignition temperature of methane can occur.

Jan 1, 2003

By S. J. Frank

Ferroalloy furnaces are well known to be extremely difficult to control from a metallurgical perspective. Mostly metallurgical control is still reactive in nature, causing a significant amount of reworking and product blending to achieve a proper product specification. Despite numerous efforts towards the model based control of primary smelting operations, actual metallurgical feed forward control seems to remain elusive. One of the key reasons in the failure to model these metallurgical reactors well, is that fundamentally orientated pyrometallurgists, statisticians, data miners and control engineers very often have diverging ideas how to model these systems. Furthermore, metallurgists have often come to rely on their ability to develop empirical regression models of furnace behaviour, as they have lost their faith in the ability of thermochemical and metallurgical engineering fundamentals to accurately predict the outcomes from furnaces. This paper shows how good thermochemical modelling can be combined with proper technological and systems analysis, as well as a proper inventory model, to predict the alloy and slag chemistry with good accuracy one tap into the future, at a time horizon of typically around 4 to 6 hours. For this modelling approach, a number of tools will be used, such as data reconciliation, thermodynamic modelling using Fact Sage®, inventory and heel estimation, neural networks and statistical data exploration. Furthermore, systems identification theory will be combined with the approaches given above to develop a truly dynamic predictive model. This paper seeks to demonstrate the need for a hybrid approach, which incorporates plant data and readily accessible thermodynamic data to develop a proper dynamic model.

Jan 1, 2004

By E. T. Boshoff

Paper written on project work carried out in partial fulfilment of B. Eng. (Metallurgical Engineering) The weathering of kimberlite can be accelerated with cations in solution if swelling of the kimberlite occurs in contact with the weathering medium. The type and amount of swelling clays present, along with the surface charge and cation valence, determine the degree of swelling that can occur. Crystalline swelling occurs by the incorporation of cations in the interlayer spacing of the silica sheets. Kimberlite exposed to cupric cations showed very strong weathering, indicating that this type of weathering may be considered a viable process option. Kimberlite fines generated after weathering with monovalent cations showed poor settling behaviour compared to kimberlite weathered with di-, and trivalent cations.

Jan 1, 2005

By T. Frömmer, H. Wagner

An inter-disciplinary geotechnical study has been carried out in an Austrian magnesite mine. The paper describes the how geological data, in situ and laboratory tests as well as subjective, empirical, geophysical and numerical methods have been used to identify critical areas in the mine. In einem österreichischen Magnesit Bergbau wurde in den letzten Jahren eine interdisziplinäre geotechnische Studie durchgeführt. Der Vortrag beschreibt den Einsatz subjektiver, empirischer, geophysikalischer und numerischer Methoden zur Identifikation geotechnischer Problembereiche Ces dernières années des études géotechniques interdisciplinaires sont effectuées dans une mine souterraine de magnésite en Autriche. Ce rapport trace l’application des méthodes subjectives, empiriques, géophysiques et numériques pour identifier les zones problématiques dans la mine

Jan 1, 2003

By Sverre Olsen, Kai Tang

The composition of ferromanganese slag is very important as it determines the slag/metal equilibrium relations including MnO content of final slag, melting relations and slag viscosity. The slag composition is further expected to influence the process temperature. The properties of ferromanganese slags are suitably described by its basicity and A/S mass ratios. The influence of slag basicity has been discussed in the previous papers. The present paper will discuss the effect of Al2O3 on melting relations, viscosity and MnO-content of final slag. This discussion will be based on assessed thermochemical databases and a recently developed viscosity model.

Jan 1, 2007

By L Tolmay, L Nair

Investor confidence can be compromised when one observes large discrepancies between the SAMREC reserves and the mining plan. It is therefore up to the responsible persons to ensure that all contributing factors get taken into account when determining a reserve declaration. Confounding factors could be further aggravated by large oscillations in the commodity price thus resulting in major changes to the mining plan, if the accepted price was either too optimistic or pessimistic. Additional factors that must receive our attention are, uncertainty in geological facies type, mining practices, geology and grade estimation. The paper outlines (in the authors? opinion) some of the important factors that need to be taken into account, in order to ensure proper alignment between the estimates of the life of mine (LOM) reserve grades, and the corresponding actualisation of the mining plan. These parameters provide an historical insight into what actually happens when attempts are made to implement the mining envisaged in the LOM plan. In turn these allow judicious application of discount factors that enable a realistic estimate of SAMREC reserve classification and declaration. Some of the factors that will be covered are: - 1) Flexibility of developed reserves and the ability to maintain this. 2) Mining control mechanisms and their overall efficacy. 3) The ability to extrapolate facies types and its effect on grade control. 4) The ability to control the mining mix and value variation. 5) Finding a happy medium between optimism and pragmatism.

Jan 1, 2007

By F. B. Samani, B. Stabel

The 1,000 MW Hydro Power Station Masjed-e-Soleiman (formerly called Godar-e-Landar) in Iran is under construction since 1992. The rock engineering aspects of the major underground structure, i.e. the powerhouse cavern shall be reported on in detail. The geotechnical investigations are described and results given. The results of several geotechnical analyses are presented. The designed and executed rock support is given. A description of the monitoring systems and typical measurement results obtained during and after excavation are presented. The lessons learnt during construction of the Stage-I powerhouse cavern were applied on the extension of the powerhouse cavern, which is to house an additional 1000 MW. Details regarding the unexpected behaviour of the Mudstones are given. Die 1000 MW Wasserkraftanlage Masjed-e-Soleiman (vormals Godar-e-Landar genannt) befindet sich seit 1992 in Bau. Dieser Artikel berichtet im Detail über die felsbaulichen Aspekte der Untertagebauwerke, insb. der Maschinenkaverne. Die geotechnischen Untersuchungen werden beschrieben und deren Ergebnisse wie die Ergebnisse verschiedener Berechnungen werden präsentiert. Die geplante und die ausgeführte Felssicherung wird angegeben. Die eingebauten Überwachungseinrichtungen werden beschrieben und typische Ergebnisse während des Aushubs und danach werden dargestellt. Die Erfahrungen beim Aushub der Kaverne der Stufe I wurden beim Entwurf der Kaverne der Erweiterungsstufe II, die weitere 1000 MW beherbergen wird, berücksichtigt. Details zum unerwarteten Verhalten des Schluff-/Tonsteins werden angegeben. La centrale hydroélectrique de Masjed-e-Soleiman (dénommée anciennement Godar-e-Landar), d’une puissance de 1.000 MW, est en construction depuis 1992. Un rapport détaillé sera présenté sur les aspects relatifs à la construction en enrochements de l’aménagement souterrain principal, à savoir la caverne abritant la salle des machines. Une description des investigations géotechniques réalisées y est fournie ainsi que les résultats correspondants. En outre sont présentés les résultats de plusieurs analyses géotechniques. L’ancrage dans la roche tel que projeté et réalisé est présenté. Une description des systèmes de contrôle ainsi que les résultats de mesures typiques obtenus au cours des travaux d’excavation sont donnés. Les leçons tirées lors de la construction de la Phase 1 de la caverne de la salle des machines furent appliquées à l’extension de la caverne de la salle des machines, qui doit abriter une unité supplémentaire d’une puissance de 1.000 MW. Par ailleurs, des détails sont donnés sur le comportement inattendu des argilites.

Jan 1, 2003

By C. N. Harman, N. S. S. Rama Rao

Production of Ferro-alloys through submerged electric arc furnace involves use of electric power as one of the major inputs. Hence the production by this power intensive process can be made economically more competitive if the specific power requirement for smelting each ton of the product is brought down. This becomes all the more necessary where the power cost is comparatively high, like in India. Since the day FACOR started production of Ferro Chrome in 1968, briquetted chromite fines along with lumpy ores were used as feed. Subsequently the increase in the proportion of briquettes and reduction in lumpy ore helped in increasing the use of chromite fines and also brought down the specific power requirement. Meantime FACOR had been closely watching the technical development of use of sintered pellets in Outokumpu and SRC Processes which need still lower specific power. But the high capital requirement for a pelletisation plant kept FACOR from introducing pellets feed to their Ferro chrome furnaces. So this was postponed to be adopted in future. In February 2004 in the ?1st Ferro-Alloys India?, a paper [1] was presented by Dr. Amit Chatterjee. In the questions period after the presentation of the paper there came up a discussion in which it was revealed that with the Indian high grade chrome ores it was not possible to make sufficiently strong pellets, unless a larger percentage of bentonite is used as binder. This is because the Indian high grade Chrome ores have different mineralogy of gangue content compared to low grade ores in Finland and South Africa. Higher usage of bentonite gives rise to higher slag volume and this would result in increased specific power. Since FACOR had plans to go in future for sintered pellets feed, this gave rise to a doubt on success of pelletisation for Indian high-grade chrome ores. This prompted FACOR to take up experimental production of sintered chromite pellets and use of the same in one of their existing furnaces for production of high carbon Ferro chrome. The results are encouraging and are summarized in the paper.

Jan 1, 2007