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By K. Morikawa, K. Asano, J. Yoshitomi

The quality requirements for ladle shrouds have become stricter year by year to the pursuit of higher productivity and improved quality in the continuous casting of steel. The ladle shrouds must be sufficiently durable under severe conditions, such as operation without preheating and during several sequential castings. The consideration is that ceramic fibres, which have been applied in shrouds for thermal insulation during casting, could pose a risk to the worker's health. We realized materials for the ladle shrouds which show high strength and low elasticity. At the same time pursuing effective insulation, a coating which contains no fibres (Foaming Coat) has been developed, replacing the conventional one containing fibres. These materials are durable under conditions of repetitive use and consequently satisfy the customer's demands. The ladle shrouds which were improved in this way have achieved an excellent durable life in hot service of three times that of conventional ones. This paper reports the recent technological developments in ladle shrouds as well as their performance under hot operating conditions.

Jan 1, 2004

By Y. Masuda, Y. Nakamura, K. Haraguchi, A. Taniguchi, K. Arita

Availability of the elements originating from steelmaking slag for various marine phytoplankters including purely cultured strains and natural populations was tested in land and shipboard laboratories. The results obtained demonstrate that, although their solubility was not uniform among different slags, dissolved iron, silicate and phosphate from the slag stimulate phytoplankton growth. No negative effect of the slag addition on their growth was observed at lower dose, e.g. less than 200 mg/l. Since most coastal waters are the hypernitrogenous environment due to anthropogenic load of ammonium, the slag can be an ideal source of silicate and phosphate, which restore the hyper-nitrogenous condition into truly eutrophic condition with balanced Redfield ratio. In so-called HNLC (high-nitrate low-chlorophyll) oceanic areas such as the Southern Ocean and the subarctic North Pacific, where iron is almost only limiting factor of the phytoplankton growth, the slag could also be a source of iron and enhance CO2 fixation by phytoplankton photosynthesis. (Key words: carbon deposition in deep-sea, marine environmental remediation, phytoplankton, slag as a source of iron, phosphate and silicate.)

Jan 1, 2004

By Leibniz University, D. Zapf

"The demand for gas storage operations with high withdrawal rates and operation modes different to a seasonal storage regime requires a more detailed rock mechanical consideration of thermal induced stresses in the vicinity of the caverns. This means that the change of gas temperatures during operation and the consequences of these temperature changes on the stressing of the salt rock mass must be taken into account in the rock mechanical dimensioning. Within the rock mechanical calculations a loading history, i.e. a pressure versus time dependency, has to be defined. As rock salt has a time dependent material behavior stress redistributions in the rock salt mass take place even under constant internal pressure conditions. Therefore not only withdrawal and filling periods but also the duration of phases with nearly constant internal pressure is significant for the resulting state variables. Within the paper the differences and consequences for the rock mechanical recommendations are discussed. As a result it can be concluded that recommendations with respect to minimum operation pressure as well as for maximum withdrawal rates can be answered only in connection with the respective time intervals."

Jan 1, 2015

By N. Hiroyoshi

In the leaching of chalcopyrite with sulfuric acid solutions, the copper extraction rate reaches a maximum at a given redox potential. This article reviews our studies on the determination of the optimum redox potential for chalcopyrite leaching. Shaking flask and column leaching experiments for a chalcopyrite concentrate were performed under various conditions, and the results were analyzed using a normalized redox potential defined from a reaction model assuming the formation of an intermediate CU2S from chalcopyrite. Factors, such as metal ion concentrations, solid/liquid ratio, and presence of iron-oxidizing bacteria, caused significant variations in the copper extraction versus time plots. However the copper extraction rate versus normalized redox potential plots were independent of the above factors and the copper extraction rate reached a maximum at the normalized redox potentials around 0.43. Converting the normalized redox potential to the solution redox potential gives the optimum redox potential for chalcopyrite leaching as a function of cupric and ferrous ion concentrations. This semi-empirical equation can be used to predict the optimum redox potential during leaching operation, and is useful to design the redox-controlled heap leaching for chalcopyrite.

Jan 1, 2007

By Jean-François Doyon

Les aspects environnementaux des activités minières d?exploitation réalisées sur le territoire québécois sont encadrés par divers cadres légaux, réglementaires ou autres (directive, politique, guide) tant au niveau provincial que fédéral. Ces cadres s?appliquent à l?un ou l?autre des trois grandes étapes du projet, soit lors de l?étude d?avant projet, pendant l?exploitation ou à la cessation des activités d?exploitation. Comme la réglementation environnementale est de plus en plus nombreuse, ces dernières années, cette présentation vise à exposer les principaux cadres provinciaux et fédéraux actuellement en application au Québec pour le secteur minier et à en dégager les particularités. ABSTRACT The environmental aspects of mining activities carried out across Quebec fall within the scope of various legal, prescribed or other frameworks (directives, policies, guides) at provincial and federal levels. These frameworks apply to one or another of the three major steps of a project: preliminary design, mining and closure. As the number of environmental regulations has greatly increased during the past few years, the object of this presentation is to state the main provincial and federal frameworks currently applicable in Quebec for the mining sector and to identify their special features.

Nov 1, 2002

By Alan L. Sangster

Abstract -Auriferous, bedding-parallel veins occur in zones of carbonaceous, argillaceous and sulfidic turbidites in the Lower to Middle Cambrian sandy flysch of the Goldenville Formation. The ?34S values for vein and wall-rock arsenopyrite and pyrrhotite, and for regional pyrite and pyrrhotite, are highly positive. The values are similar to those from Cambro-Ordovician sediment-hosted deposits of other types, and display trends that increase upward in the stratigraphic sequence. The similarity in composition of vein and wallrock sulfides indicates a seawater-sulfate source for sulfur, derived from the enclosing rocks at the time of vein formation. The upward increase in ?34S values is consistent with closed system sulfate reduction in the anoxic portion of a stratified water-column. Published ?18C and ?18O values for Meguma Group vein carbonates are unlike those of other gold-vein carbonates, but are similar to those of diagenetic-metamorphic carbonates from the Meguma Group and elsewhere. These data indicate that the source for the vein-related sulfides and carbonates may be the host strata; possibly the arsenic and gold were derived from the same source.

Jan 1, 1992

By H. Kuboyama

The synergistic effects of polymer additives such as gelatin and polyethylene glycol) (PEG) and Cl- on Cu electrodeposition have been investigated by measuring the polarization curves for Cu deposition, by rotating ring-disk electrode technique and by AC impedance measurements. The cathode potential for Cu deposition was greatly polarized in solutions containing both Cl- and gelatin or PEG, showing evident synergistic effect of polymer additives and Cl- on Cu deposition. The cathode potential was shifted to the less noble direction with increasing the concentration of Cl- in solutions containing polymer additives and showed the maximum polarization at Cl- concentration range between 0.1 and 1 mmol/L. The rotating ring-disk electrode technique revealed that Cu deposition in solutions containing small amounts of Cl- proceeded with initial formation of adsorbed intermediate CuClad. The Cole-Cole plots obtained by AC impedance techniques suggest that the reduction of CuClad is suppressed by polymer additives. The morphology of Cu deposited from solutions containing both PEG and Cl- showed the compacted surface composed of smaller grains due to an increase in the overpotential for Cu deposition.

Jan 1, 2007

By Jacek Paraszczak

As the deposits located closer to the surface are getting depleted, more and more Canadian mines produce ore from considerable depths. Deep mining represents a number of serious challenges including high rock temperature. Conventional diesel powered loadhaul- dump machines and trucks so widely used in metal mines constitute an additional source of heat and noxious gases. Due to this, they have a substantial adverse impact on a quantity of fresh air required and a cost of ventilation, particularly since the mines have to meet more and more stringent regulations in this respect. In this context, the paper examines possible alternatives for diesel powered equipment, both these commercially available as those at the stages of prototypes or under development. They are reviewed with regards to their principles, required infrastructure, stage of technology development and its progress. The questions of their flexibility, practicality and economic viability are also addressed. Following the above a potential for their implementation and possible benefits (if any) in the conditions of deep Canadian mines is discussed. The paper concludes with short to medium term predictions concerning the most promising drive alternatives for vehicles destined to operate in deep metal mines.

Feb 1, 2008

By M. Schwarze

SMS Meer GmbH with its COPPER PLANTS DIVISION produces a full line of systems and machines for the processing of copper. The product range includes: shaft melting furnaces, anode casting lines, horizontal and vertical casting lines, casting and rolling lines for copper wire rod and strip, cold pilger mills, planetary rolling mills as well as tube drawing equipment. The new designed shaft furnaces are the most economic way of copper melting. The CONTILANOD® system with hydraulic shear represents a breakthrough into higher production capacities and improved geometrical accuracy of anodes. The new generation of CONTIROD® lines with individual drives of rolling stands guarantee cost effective production of highest rod quality. A new horizontal continuous casting technology for the production of tube shells as feed stock for the copper tube manufacturing process ? directube® was developed and introduced into production. A first line for continuous vertical strip casting - called VERTICAST® - for higher production rates and improval quality of cold-rollable strips is in the final stage of commissioning. These innovative technologies increase product quality, reduce process costs and help for a wide use of copper in all sectors of life.

Jan 1, 2007

By G. E. Joe

"This is a panel discussion on the milling experience with large volume flotation machines in Canada. Over the past ten years, the Canadian milling industry has been characterized by treatment of ever increasing tonnages of lower grade ores. In order to treat these ores efficiently, mineral processors have been employing increasingly larger volume flotation machines. In older established mills, standard flotation cells have been replaced by the larger volume models with very apparent savings in mill floor space as noted in the Opemiska copper mill.We are pleased to hear from four mill operators with extensive experience on large volume flotation machines. They are:1. I. E. Wahn, metallurgist with Falconbridge-Manibridge, who will describe their mill experiences with the Tank cell and the Maxwell cell.2. G. M. Hughes, mill superintendent of Sherritt Gordon-Ruttan, will detail recent experience with the Agitair cell.3. J. R. Maxwell, mill superintendent of Opemiska Copper, will report on their Maxwell cell installation and operation.4. A. H. Winckers, superintendent of Development and Technical Control, Sullivan Mill, will present a paper written by H. J. Chalmers describing Cominco's past experiences with large volume flotation machine installations including Denvers, Wemcos and Maxwells."

Jan 1, 1974

By Jonathan Tsang, Ali Merati, Jonathan Beddoes

Due to economic factors, many aircraft in service today have been operating for more than 30 years even though they were initially designed with a service life of 20 years. Improved damage management models are therefore needed for use in life prediction and management of the aging fleets of aircraft. Currently, the generally accepted procedure in fatigue life prediction methodologies is to back calculate the equivalent initial flaw size (EIFS) using established long crack growth data. However, it was observed from studies carried out at the National Research Council Canada that nucleation and short crack growth constitute up to -95% of the fatigue life. As a result, it seems that the significance of the short crack regime has been underestimated and must be further investigated and fully understood before an accurate holistic life prediction methodology can be realized. Unlike long cracks, local microstructural features such as grain boundary, grain size, inter-particle spacing, and texture play dominant roles in the behavior of short cracks. An extensive study has been carried out to evaluate different crack detection and monitoring techniques in the short crack regime for AA2024-T3. The results will be presented in detail.

Jan 1, 2004

By E. M. Córdoba

The effect of the Fe3+ lFe2+ redox couple on the chemical and biological dissolution of chalcopyrite was studied. All the tests were carried out in stirred flasks with 100 mL of a ferric/ferrous sulphate solution, in the absence or in the presence of bacteria (iron- or sulphur-oxidizing) and at low (35 DC) and high (68DC) temperature. The initial redox potential was controlled between 300 and 600 m V Ag/ AgCI and silver was used as chemical catalyst. The results showed that the oxidizing action of ferric ion on the chalcopyrite was controlled, in all cases, by nucleation and precipitation of jarosites on unreacted particles. The tendency of Fe3+lFe2+ solutions towards equilibrium favours the activities of both ions to be equal. Consequently, the dissolution rate was faster at relatively low redox potentials (between 400 and 500 mY) than at high values (600 mY). In this sense, the presence of ferrous ion in the system is a key factor to control hydrolysis and precipitation of ferric ion. Unlike jarosite, the elemental sulphur produced during dissolution of chalcopyrite was porous and did not act as a diffusion barrier.

Jan 1, 2007

By Nancy E. Wilk

In 2015, more than 1.2 million deaths annually were estimated to be caused by occupational risks (WHO, 2018). In 2021, this estimate increased with the publishing of the World Health Organization (WHO) and the International Labour Office (ILO) Joint Estimates of the Work-related Burden of Disease and Injury based on data from 2000 to 2016 (WHO/ILO, 2021). These global estimates reported that each year 1.9 million people die from exposure to occupational risk factors, 81% of these fatalities resulting from non-communicable, occupational diseases. WHO/ILO notes that the health-related risk factors with the largest number of attributable deaths were exposures to long working hours followed by workplace exposures to particulate matter, gases, and fumes. The health outcome with the greatest work-related burden of deaths was chronic obstructive pulmonary disease, followed by stroke and ischaemic heart disease. In considering the 2021 data published by WHO/ILO, it is likely that the estimates are low and underestimate the true burden of occupational disease and injury. In support of that position, more recently the ILO estimated that “2.3 million women and men around the world succumb to work-related accidents or diseases every year; this corresponds to over 6000 deaths every single day” (ILO, 2022).

Jan 1, 2023

By J. Jackman

North America has been aggressively pursuing approaches to improve the fuel efficiency of vehicles, and to develop alternatives to petroleum-based fuels used in automotive applications, for over ten years, Increasing energy demand due to emerging economies, coupled with probable peaking of conventional petroleum production in the coming decades are increasing the need to reduce dependence on petroleum-based fuels for transportation, Vehicle lightweighting is seen as an important strategy to improve fuel efficiency of conventional as well as highly innovative vehicles, Magnesium has recently emerged as a serious candidate for lightweighting, as a result of lower global prices, Automotive vehicles produced in North America currently use more Mg than vehicles produced elsewhere in the world, but the amounts per vehicle are very small in comparison to other materials such as steel, aluminum and plastics, The reasons, besides price, are primarily a less-developed state of technology for Mg in automotive transportation applications and lack of familiarity by the vehicle manufacturers with the material, This paper reviews the major government-funded research programs in the USA and Canada that are dedicated to advancing the state of Mg technology for automotive applications, It provides examples of research in the areas of high-pressure and other types of castings, corrosion solutions, sheet development and other wrought applications.

Jan 1, 2006

By U. Martin

Advanced copper materials for conducting applications require an optimal combination of high mechanical strength at ambient and moderately elevated temperatures together with superior electrical and thermal conductivity. Mechanical alloying under repeated cooling of the milling vials in liquid nitrogen has been applied to produce ultra-fine grained (UFG) oxide dispersion strengthened (ODS) copper with a high yield strength at ambient temperature. In the present study ODS copper was manufactured by mechanical alloying of copper powder and 3% by volume of incoherent oxide dispersoids. During the high-energy milling a homogeneous distribution of fine dispersoid particles (diameter nearly 100 nm) can be achieved in the powder. Samples with a density of more then 97% of theoretical value were produced by uniaxial hot pressing under 650 MPa at 600°C for 20 minutes. The high yield strength at ambient temperature can be described by a linear superposition of the Orowan stress for particle hardening and of ultra-fine grain strengthening according to the Hall-Petch mechanism. Simultaneously, a best value of 75% IACS could be obtained for the electrical conductivity. The creep behaviour of ODS copper in the temperature range from 500°C to 700°C is described within the frame of diffusional creep deformation.

Jan 1, 2007

By T. Stergiou

An extensive research is being carried out on the shaft furnace operation in order to minimize down-times and reduce operational cost. The need to increase the scrap percentage on the charging mix, together with the need of cheaper spare parts has led to the investigation of alternative materials for the burner system on the shaft furnace. This system consists of a burner block and a flame holder. Traditionally these items are constructed either from SiC ? oxide bonded or SiC-nitride bonded. A lot of problems have been confronted over the past 8 years of operation. Usually, large cracks are formed on both flame holders and burner blocks. This resulted in leakage of combustion gases to the back of the lining and a quick erosion of it. Additionally, the burner blocks suffer from chemical erosion, due to the increased amount of scrap used in the charging mix and the presence of slag inside the furnace. Alternative materials such as stainless steel for the flame holder and alumina-chromia refractory for the burner block have been tested in terms of life-time and resistance on chemical erosion. Furthermore, additional changes have been made on the burner block design in order to alter the flame shape and improve the scrap melting operation.

Jan 1, 2007

By P. Bonadia, A. Tabereaux

Nearly all aluminium smelters are increasing the potline amperage to achieve higher aluminium production. In some instances the higher amperage operation has a significant negative impact on shortening the lifetime of aluminum electrolysis cell cathodes due to loss of the protective sidewall cryolite ledge freeze and too rapid penetration of the cell bottom refractory lining by cryolitic bath components due to the higher temperature isotherms. Thus Cathodes require careful thermal modeling of the cathode relining designs and improved refractory materials to allow greater heat loss from the sidewall to preserve a stable sidewall ledge freeze at higher amperages, and the selection of optimum refractory barrier materials to control the penetration and reaction of bath into the cathode bottom refractory and insulation lining. This requires an understanding of the reaction mechanisms and product formation for molten NaF enriched bath and alumino-silicate refractories. It is desirable to use dense, low porosity refractory fireclay firebricks, or similar materials with a sufficiently high silica content to promote the formation the mineralogical phase albite, NaAlSi3O8, that significantly increases the viscosity of the melt which slows the diffusion of reactive species in the melt and thereby retards further bath penetration.

Jan 1, 2004

By Maurizio Violo, Arjan Beqiraj, Umberto Masi

"Abstract - Four main podiform occurrences of chromite have been distinguished in the ultramafic Bulqiza massif, Albania; they are associated from the bottom to the top with: i) basal harzburgites (lower tectonite sequence), ii) dunitic lens-bearing harzbugites (middle-upper tectonite sequence), iii) layered chromitite-bearing dunites of transitional zone, and, iiii) the stratigraphically lowermost part of the magmatic section. However, only the occurrences hosted by rocks ii) and iii) are economically important.Chromite compositions similar to those of other podiform chromites are bimodal. Thus, chromites from occurrences ii) and iii) are richer in Cr than chromites from the other two occurrences. Accessory chromite disseminated throughout the massif is richer in Fe than orebody chromite, displaying similar range of the Cr/Cr+Al ratios, with accessory residue chromite matching the characteristic (Cr/Cr+Al >0.6) range of type-III Alpine peridotites. Both orebody and accessory chromites show compositional ranges correlating with host-rock compositions, i.e., the Cr-rich chromites are hosted by the most refractory ultramafic rocks. Therefore, the Cr/Cr+Al and Mg/Fetot (Cr/Fetot) ratios of chromite are useful for exploration of high-grade, metallurgical chromite ore at Bulqiza and in other massifs of similar geodynamic setting."

Jan 1, 2000

By Jeffrey D. Smith, William G. Fahrenholtz, Jose M. Soto

Interactions between A356 aluminum (Al-Si alloy) and dense fused silica (FS) riser tubes used for low-pressure casting of aluminum alloys were evaluated using a sessile drop approach. The tubes have a short service life, but cost and thermal shock resistance make them an effective solution. The main problem encountered during use is the reaction of aluminum with silica to form alumina and silicon, which causes failure. Tests have been conducted on as-fired (uncoated) and modified (coated) tubes. Experiments were carried out in a horizontal furnace at 1225°C under argon to minimize the effect of the aluminum oxide on the interactions at the alloy-silica interface. Images of the drop were acquired and contact angle values were estimated for uncoated and coated samples, but no significant differences in the contact angles were observed. Scanning electron microscopy revealed the presence of cracks at the interface between the reaction zone and the unreacted silica. The presence of reaction products (silicon in the reacting alloy and aluminum in a reaction zone between the alloy and the unaffected silica) has been confirmed using energy dispersive spectroscopy. A two layer coating system was found to be effective in reducing penetration of the aluminum alloy.

Jan 1, 2004

By J. E. Gebhardt

Advances in computational modeling provide unprecedented process simulation tools for the process engineer to examine and explore options for optimizing heap leach operations. A phenomenological model developed within a computational fluid dynamic software framework provides a general heap leach modeling tool that describes reactive dissolution and fluid flow through the stockpile. A one-dimensional form of the model is used to parameterize the kinetic leach reactions for a mixture of copper sulfide and oxide minerals against data from operational leach tests. A two dimensional version of the model provides a means to investigate the effects of irrigation rate, lift height, air injection, bacteria limitations, and other factors on recovery and pregnant leach solution concentrations. The model was calibrated for the Nifty Copper operation and ore type in order to simulate heap performance. Model simulations are reported for the chalcocitetype ore and compared to process data. The application showed that the multidimensional nature of heap leaching causes heterogeneous effects that are not always adequately described by one-dimensional models. Irrigation flow rate and aeration effects were simulated for a multi-lift heap section, and model results indicated that air injection at the base of the second lift would be required to achieve expected copper recovery under these lift height and flow conditions.

Jan 1, 2007