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By George A. Guess

The making of contracts for the purchase of ores is a business which the metallurgist usually understands better than the miner. Companies in the custom ore business often employ an ore buyer who is aware of the class of ore which the smelter needs, and is thoroughly conversant with the business. The miner on the other hand makes ore contracts but seldom, and it is often only after a settlement has been made that he realizes the meaning of the terms of the contract under which he has sold his ores. He has expectations usually greatly in excess of the amount 'net proceeds' shown at the bottom of the settlement sheet. Seldom does the occasional shipper really know his contract. A somewhat similar parallel is to be found in insurance policies. We all have insurance policies; we never know the conditions contained in them until after the fire. The clauses in the policy are for the protection of the Insurance Company. An Insurance Company has no friends.

Jan 1, 1926

By Kostas Fytas

Acid mine drainage (AMD) is a serious environmental problem that preoccupies the Canadian Mining Industry. Considerable amounts of money are spent every year in an effort to prevent or reduce the acid mine drainage phenomenon. AMD occurs when sulphide minerals (ex. pyrite) contained in rock are exposed to air and water and subsequently oxidize to produce low pH water. This acid effluent has the potential to mobilize any heavy metals contained in the rock. Coating the sulphide minerals with silicates is a new promising technology to reduce AMD. Pyrite is treated with a solution containing H2O2, sodium silicate and a buffering agent. H2O2 oxidizes a small part of pyrite producing ferric iron (Fe3+) ions. These ions subsequently react with the silicate ions to produce ferric hydroxide-silica that precipitates on the pyrite surface producing a passive coating. This silicate coating can protect the grains of pyrite from oxidation. This paper presents a series of experiments that confirm that silicate coating can considerably reduce AMD.

May 1, 2001

By L. I. Kiss, S. Perron, S. Poncsák, A. Perron

Aluminium industry has an increasing interest in the diminution of the energy consumption of the Hall-Heroult process by the reduction of the anode bottom covering with gas. Electrically isolating carbon-dioxide bubbles, produced at the anode, increase the ohmic resistance of the cell. As the gas production rate is determined by the applied current density, anode covering can be decreased only by a faster evacuation of the gas from the inter-electrode space. Among others, the inclination and curvature of the anode bottom promotes the release of the bubbles and thus decreases the mean value of the covering. Indeed, anode, insert in the molten cryolite bath has a square shape with horizontal bottom. However, inhomogeneous anode consumption, electro-erosion, bath circulation and the inclination of the bath-metal interface modify this shape gradually during electrolysis. Anode bottoms become inclined with rounded comers. This concentrates the gas generation to the center zone of the anode. As the bubble layer cannot be observed directly because of the hostile environment and the opacity of the bath, real scale air-water systems are used to study the impact of the anode geometry on the anode covering and the bubble induced flow. However, the physical properties of such a system are different than that we can found in the real cells. A simulator using the Lagrangian description of the bubble layer has been built and presented in earlier papers. This tool was used to investigate the effect of the anode inclination on gas covering and bath velocity, for both C02-cryolite and air-water system. Results obtained for the second system were compared to experimental data .

Jan 1, 2006

By Fathi Habashi, Ernesto Bourricaudy, Fouad Kamaleddine

Ilmenite occurs in black sand at the mouth of great rivers as in India, or as massive deposits like in Quebec Province in Canada. It is unsuitable for processing into pigment or for metal production because of its high iron content and its low grade. Pyrometallurgical and hydrometallurgical methods have been developed to cope with this problem which resulted in the production of two commercial products that became known as synthetic rutile and Sorelslag. Attempts are also underway to produce TiO2 pigment directly from ilmenite. This report presents a newly developed process called the Magpie process, which enables the production of high-grade synthetic rutile (over 95% TiO2) from low grade ilmenite (10-12% TiO2). Naturally, if such process is applied for low-grade ore it can be applied with advantage to high grade material as well.

Jan 1, 2014

By R. B. Humphrey

Cut-and-fill mining methods at the Thompson Mine have undergone significant changes since production began in 1961. Changes have been introduced in almost all aspects of the mining operation, from the original timbered chutes and air-operated slushers to the present-day bored raises, footwall ore passes and load-haul-dump units. This paper describes the evolution of mechanized cut-and fill mining methods, highlighting the changes in design for stopes and service openings, ground support methods; hydraulic filling and ventilation systems. A mechanized stoping area is described from the initial mining concept through design, development, construction and mining cycles.

Jan 1, 1979

By E. Ghali, A. D. Bas

"Treatment of oxide, e.g. roasted gold ores has received relatively less attention than sulphidic ones and recently, handling of oxide gold ores is becoming essential. In this study, the influence of roasted gold ore (RGO) slurry (at 35% solid ratio) on the electrochemical dissolution of gold has been examined using pure gold and iron oxide minerals (hematite, maghemite, and magnetite) as disc electrodes by zeroresistance ammeter mode either in one or two separate containers. The presence of slurry decreased galvanic currents, i.e. corrosion rates due to the release and increase in the amount of soluble and/or insoluble species that could retard further the anodic behaviour of gold. Higher galvanic currents were observed in two separate containers than that in one container indicating the primary importance of galvanic interactions. SEM-EDS results observed iron hydro/oxide coatings on gold surface in case of magnetite test. However, in case of RGO electrode it is not a perfect passivation, although somewhat decreasing trend was observed on gold dissolution. These findings have revealed that passivation is not only a laboratory phenomenon, but also it could be responsible for the slowdown of gold dissolution in industrial practice.INTRODUCTIONThe cyanidation of gold is an electrochemical corrosion process thus; the dissolution of gold can readily be studied by electrochemical techniques. The outcome/summary of previous electrochemical studies of gold leaching can partially be summarized as follows: Filmer (1982) and Lorenzen and van Deventer (1992) reported the negative effect of pyrite and pyrrhotite on gold leaching due to the galvanic interactions; Aghamirian and Yen (2005) studied gold galvanic corrosion in presence of sulphide mineral electrodes only in one cell using zero-resistance ammeter (ZRA) mode; Dai and Jeffrey (2006) discussed, individually, the anodic and cathodic behaviours between gold and sulphide minerals, and Azizi et al. (2010, 2011) used a bed reactor to examine the influence of sulphide minerals on gold dissolution in one and two separate cells. Accordingly, a slowdown in gold leaching has generally been attributed to the passivation phenomenon, although the indication of this phenomenon is still an undergoing debate. For instance, Mrkusic and Paynter (1970) identified the passivation as the film formation of dissolved species from calcine, Crundwell (2014) explained passivation, in the case of corrosion of metals, as the formation of a layer which is composed of a new chemical species on the mineral surface and this layer inhibits or blocks further reactions. He suggested that passivation is related to the oxidation of the metal, and the formation of a passive layer that retards the rate of dissolution by several orders of magnitude. Consequently, galvanic interactions, passivation phenomena, or combinations of them are considered significant electrochemical factors affecting gold dissolution (van Deventer, Reuter, Lorenzen, & Hoff, 1990; Azizi, Petre, & Larachi, 2012). It is important to note that generalizing the influence of a mineral/metal on gold dissolution may not be correct in all cases, since contrary behaviours/results (for pyrite) have been observed (Aghamirian & Yen, 2005). Therefore, electrochemical study of gold is still a subject of research and need to be examined further in detail."

Jan 1, 2016

By M. B. M. Monte, M. L. Torem, E. R. Pecanha, A. G. Merma

The recent literature has unveiled the potential use of microbial strains in mineral bioprocessing. This study presents the use of a Gram-positive bacterium (Bacillus subtilis) as bioreagent for hematite flotation. The bacterium presents the ability to modify the properties of mineral surface (electrophoretic mobility and hydrophobicity). It was studied the electrokinetic behavior of hematite particles, before and after the interaction with the bacterial cells. The results revealed a shift of the isoelectric point (IEP) of the hematite after interaction with bacterial cells, suggesting a chemical adsorption mechanism. Moreover, after bacterial conditioning, the zeta potential curve of hematite presented high values in the alkaline pH range. The hematite and the bacterial surfaces presented contact angle values around 27.4° and 41.0°, respectively. According to the results, the B. subtilis strain was capable of modifying the hematite surface, and after interaction the hematite surface presented a contact angle value around 46.0°. The flotation tests were carried out in a modified Hallimond tube. The experiments revealed a significant increase in hematite flotability using the Gram-positive strain as bioreagent. The tests pointed out a maximum recovery of hematite in the presence of 600 mg/L and pH 5. Therefore, the results from this study showed the potential use of the B. subtilis strain as a biocollector for hematite flotation, and its possible application in the mineral flotation industry.

Jan 1, 2016

By A. Jafarnia

Aluminum alloys are frequently grain refined during solidification in order to promote the formation of an equiaxed grain structure in the casting. The application of Ti-based grain refiners and/or Ti containing master alloys for improving mechanical properties may result in formation of Al-Ti based intermetallics. Although the grain refinement produces many desirable qualities in aluminum castings such as improved castability and mechanical properties, the addition of Ti to Al-Si foundry alloys may lead to the formation of some undesirable intermetallic particles such as AlTiSi and cause a number of operational problems such as nozzle blockage due to segregation and agglomeration of aluminide particles within the nozzle. There are several questions to be clarified when minor amount of Ti is added to Al-Si alloys. They include nucleation and growth of AlTiSi particles, their morphologies and orientation relationships with aluminum matrix and the dissolution of these intermetallics during the course of solidification and/or post solidification treatments. The current study was initiated to study the process and possible mechanism of aluminide dissolution and the related phenomena such as segregation and agglomeration. It reports the results found during reheating of laboratory prepared Ti-added A356 alloy at three temperature ranges of below solidus, mushy zone and above liquidus.

Jan 1, 2004

By H. Hejny

Given the current status of political discussion in Europe about raw materials issues, the sustainable development of the extractive industry and the reduction of its environmental and societal footprint are among the key topics in this discussion. In this context, the European Commission approved the EO-MINERS project (Earth Observation for Monitoring and Observing Environmental and Societal Impacts of Mineral Resources Exploration and Exploitation). The overall aim of EO-MINERS is to bring into play EO-based methods and tools to facilitate and improve interaction between the mineral extractive industry, authorities, and the society in view of its sustainable development while improving its societal acceptability. Developing generic, standardised and reliable EO-based products to monitor the environmental and societal footprint of mining projects is the way chosen by EO-MINERS to improve this interaction, along with the organisation of tripartite meetings gathering all relevant stakeholders. The project uses existing EO knowledge and carries out new developments on three demonstration sites (Sokolov lignite mining area, Czech Republic, Witbank coal field, South Africa, Makmal gold mine, Kyrgyzstan) to further evaluate and demonstrate the capabilities of integrated EObased methods and tools in monitoring the environmental and societal footprints of the extractive industry during all phases of a mining project, from the exploration to the exploitation and closure stages. It contributes providing reliable and objective information about affected ecosystems, populations and societies, to serve as a basis for a sound ?trialogue? between corporate stakeholders, governmental organisations and societal stakeholders. The project already developed a set of consolidated indicators based upon previous knowledge about mining-related issues along with interviews of national, regional, and local stakeholders. These indicators reflect known environmental and societal issues at mining sites as well as the interest of various relevant stakeholder groups. The process described in the EO-MINERS project ? policy assessment > indicator identification > choice of suitable EO tools able to serve monitoring task > monitoring by EO tools > making available objective information for fair dialogue among stakeholders ? is generally applicable to all stages of a mining project. The key to success will be the right choice of indicators addressing the problem and subsequently the right choice of suitable EO tools and finally the willingness of all stakeholders to find a common solution. To this end, the EO-MINERS project organises site-specific ?trialogue? workshops at each demonstrations site, which aim to provide relevant information in adequate quality to the stakeholders as common ground for discussions. Local stakeholders, including mining companies, regulatory bodies, and community representatives are invited to participate in these workshops where the relevance of the developed EO-based products to environmental and societal impact assessment will be discussed. The presentation will discuss results obtained during these trialogue workshops, as well as the success and difficulties and reluctances encountered. The project will further indicate ways and means how the EO products and other project results may be used for monitoring purposes in all phases of a mine.

Aug 1, 2013

By Jakob Janzen

This paper demonstrates that the introduction of a Battery Energy Storage System (BESS) into an isolated diesel generator based grid has the potential to reduce the electricity cost and deliver a good return on investment. Energy storage also allows for increased renewable energy penetration, into the isolated grid, that further reduces the electricity cost. The isolated power system studied includes several diesel generators of different sizes. The typical operating pattern is for the generators to be run at 80% to 85% of their power rating to deal with load fluctuations. Operating the diesel generators near their full power rating, however, improves their efficiency, in this case, while the frequency and load control can be carried out by the BESS. Operating the diesel generators near their full power rating reduces the number of generators which need to be operating to support a given load. As a result, the improved efficiency of the diesel generators and reduced maintenance cost, for operating fewer machines, are the reason for the savings.

Aug 1, 2013

By Ernest A. Hodgson

WHEN excavations are made, at depth, in hard brittle rock structures, as in certain mines in India, in South Africa, and in Ontario, the pressure due to overburden, together perhaps with inherent geologic strain, tends to become concentrated in the walls of some of these openings and the rock bursts, often closing the adjacent drifts and scopes and presenting a serious menace to the miners. Where the rock is much fractured and faulted, the danger is greater, since the pressures tend to shift without warning from point to point, sometimes within a few hours. Attempts have been repeatedly made to find some physical property of the rock which will change with pressure, which can be measured for rock 'in place' in the mine, and which will give an indication of the state of strain, thus warning of an approach to bursting conditions. Some of the properties tested have been the speed of propagation of elastic waves in the suspect rock, variations in temperature due to pressure changes, rate of closure of openings or shifts along fault planes, strain gauge measures, and others. Each of these has proved unsatisfactory for the purpose. The most promising method so far proposed has been the study of the very faint, sub-audible snaps (microseismims) which are produced in rocks under pressure. Such a study has been in progress at Lake Shore Mines since May, 1942. Instruments designed to pick up, amplify, and record the microseismims were perfected and a programme of observing, using the microseismic method, has been carried through with persistent diligence and at considerable expense. In 1943, experience with the method in a pillar section on the west side of the Lake Shore mine gave much promise of predicting bursts. A very heavy burst on January 29th of that year occurred in the exact section of the mine covered by the instruments, and the records indicated a measure of prediction. In response to repeated requests for information, a number of reports were given out, among others a radio talk by the writer over CJKL (Kirkland Lake), which was reported in full in the Northern News . Also, a detailed account of the occurrence was given in an illustrated paper by the writer (l).

Jan 1, 1945

By A. Mykytiuk, I. E. Puddington, W. D. Macleod, F. W. Meadus

"A laboratory-scale continuous procedure for the up-grading of naturally occurring tin ores, based on the principle of spherical agglomeration, is described. High recoveries are indicated. A proposed second stage suggests useful fractionation steps.IntroductionA LABORATORY-SCALE batch process for the upgrading of a tin ore using the principles of spherical agglomeration has already been described (1). This procedure consisted of milling, for about an hour, a precrushed ore with at least 200 per cent water, 0.2 per cent of a reagent such as tall oil (to render the de-sired ore particles hydrophobic) and about 3 per cent of a viscous petroleum oil. The feed material passed an 8-mesh Tyler sieve, and the percentages of re-agents are based on the dry weight of the feed. Du-ring the grinding, the hydrophobic particles transfer into the oil phase to produce coherent semi-solid bodies while the gangue stays preferentially in the aqueous phase. The concentrate can be separated from the gangue easily by a mechanical operation. Using an ore containing about 0.3 -0.5 per cent tin, grades of from 1.5 to 7.0 per cent were obtained by varying the pH of the system. Recoveries fell from about 80 per cent to as low as 50 per cent as the grade in-creased."

Jan 1, 1966

By S. Avalos, J. M. Ortiz, W. Kracht

Semi-autogenous grinding mills are intensive energy consumers. Current models base their energy consumption inference on operational variables and feeding ore characterization. While they provide adequate design guidelines, they are not suitable for real-time energy forecasting dealing with gaps in operational dataset and up/downstream process bottlenecks. This work explores the capability of Gated Recurrent Units to learn the semi-autogenous grinding mill consumption behaviour. Gated Recurrent Units are trained to forecast different time-support consumptions under a time-series operational dataset. The results show high performance on small supports (30 minutes) to capture local variability and long-trends while larger time supports (8 hours) can only capture time-trends but not local variability. The proposed technique seems promising for further research and implementation on real mine cases since the input variables are low-cost and easy to obtain. INTRODUCTION Current changes in the Chilean energy matrix (Román-Collado, Ordoñez, & Mundaca, 2018), from fossil fuels to renewable energies, have impacted different industries and particularly the mining sector. Solar energy incorporation into greenfield/brownfield projects will help reducing costs and will lead to rethink foundational paradigms (production and processing strategies) (Pamparana et al., 2017). Also, integration of new space-time predicting tools together with automated real-time updating models are some of the main challenges in the geometallurgical framework (Ortiz et al., 2015; van den Boogaart & Tolosana-Delgado, 2018). Those contexts encourage and demand the development of tools capable of predicting the energy consumed by mining systems, being comminution the greatest energy consumer with an average close to 50% of the entire mine consumption (Cochilco, 2013). In comminution, the semi-autogenous grinding mill (SAG) represents the largest energy consumer (~10 nominal each SAG). Theoretical and empirical energy consumption models (Jnr & Morrell, 1995; Morrell, 2004; Silva & Casali, 2015) base their inferences mainly on feed/product size distributions, SAG sizing, bearing pressure, feed hardness, water addition and grinding charge level, and commonly assume steady-state and work isolated from up and downstream processes. While those techniques provide adequate design guidelines, they are not suitable to predict hourly, daily or even weekly energy consumptions on interconnected comminution circuits where upstream/downstream bottlenecks lead SAGs to operate below designed regimes. Forecasting energy consumption is required by short-term energy management, medium and long-term planning energy consumption, designing the nominal capacity of renewable energy sources, among other. Also, when models are input-sensitive and some of those input measurements are expensive and/or time consuming, model robustness suffers when real-time predictions are required.

Jan 1, 2019

By Bong Sun You

AZ31 magnesium plate of 300mm in width and 40mm in thickness was produced by horizontal continuous casting machine, and its microstructures were analyzed on the surface and in the plate interior. The defect formation on the surface and subsurface, such as side cracks, buckling, pores and segregation, was very sensitive to the casting condition and processing parameters. Especially, casting speed and secondary cooling were the most dominant parameters to control the solidification behavior of magnesium melt, for example the position and shape of the solid/liquid interface in the mould. The cyclic marks on the surface were obvious because the plate were drawn by 4-step cycle and can not be removed. The average grain size of as cast plate measured as 50-65µm at the near surface and 300-400µm in the center of the plate was relatively small because secondary cooling water was applied to control the surface quality resulting in rapid solidification of the melt in the mould.

Jan 1, 2006

"“Developed by the CIM Sub-Committee, these guidelines are an addition to Guidelines Specific to Particular Commodities which are appended to the CIM Estimation of Mineral Resources and Mineral Reserves Best Practice Guidelines.Rock Hosted DiamondsJennifer Burgess, Consultant, Sechelt, BCNeil Buxton, WWW International Diamond Consultants Ltd.Darren Dyck, BHP Billiton Diamonds Inc., Kelowna, BCMartinus Oosterveld, (De Beers retired), Plettenberg Bay, South AfricaRichard Routledge, Scott Wilson Roscoe Postle Associates Inc., Toronto, ONMalcom Thurston, De Beers Canada, Toronto, ONPreambleDiamonds are produced commercially from intrusive rock, consisting of kimberlite and lamproite, and from alluvial and marine placer deposits. These guidelines apply to rock deposits; the term ""diamonds"" herein refers to natural diamonds; ""diamond deposits"" refers to diamonds hosted in kimberlite and lamproite rocks; and ""diamonds"" and ""stones"" are interchangeable.The CIM Best Practices General Guidelines for other commodities are also applicable to diamond deposits, however, because of diamond's distinguishing aspects, additional guidelines are appropriate as published in the CIM Guidelines for the Reporting of Diamond Exploration Results and these Best Practice Guidelines for estimating Mineral Resources and Mineral Reserves (MRMR).Diamonds differ from other minerals. Firstly, they occur as discrete particles in concentrations as low as parts per billion. Secondly, the release of diamonds from the kimberlite or lamproite host rock is a function of the excavation and treatment process. Thirdly, the value of diamonds varies from deposit to deposit and varies with stone size within a given deposit. These aspects must be considered when sampling, evaluating the resource and establishing the reserve of a depositThe product from metallic mineral mines is generally quite liquid in terms of number of potential buyers, and the commodity prices and price structure are published daily. In contrast, most diamonds are valued in the overall market context only 10 times a year in ""sights"" and the marketing of diamonds is dominated by a small number of organizations. Diamond valuation is more akin to industrial minerals valuation in that process recovery is important at the ""assay stage"", the impact on price of new goods arriving on the market must be evaluated, and product quality must be acceptable to potential buyers."

Jan 1, 2003

By Song (Bruce) Li

This paper presents a three-tier web-based GIS application that uses Java Server Page (JSP), Java Servlet and relational database to manage performance monitoring and reporting in the oil sands mining industry. It is a real-time Earth Structure Performance Monitoring System (ESPMS), which allows the user to record and store instrumentation monitoring readings as well as technical observations and instrumentation installation documentations into a complete relational database. The ESPMS introduces the advantages of precise field record keeping, due diligence, security, consistency and completeness while at the same time simplifying the task of reporting. ESPMS combines web-based Geographic Information System (GIS) mapping and data management to facilitate the collection, organization, retrieval, reporting and communication of the vast amounts of monitoring data related to mining and tailings engineering associated with site investigation and construction information. ESPMS utilizes web-based GIS technology to incorporate referenced aerial photographs, Energy, Mines and Resources (EMR) maps or AutoCAD drawings as a base map for the monitoring site. It dynamically creates and administers all instrumentation monitoring locations and reading frequencies. It enables the user to collect and manage the data associated with an unlimited number of reading events. It provides the designer with real-time monitoring data (what, why, when, how), thereby allowing them to make early adjustments to design protocols or procedures, or to take remedial action(s) regarding the subject earth structure under construction or after completion. It provides more cost-effective reporting and data sharing through the Internet. It improves security on data entry and eliminates unauthorized data changes. It allows better integration of graphics and illustrations with numerical data files. It is capable of managing the continually expanding workload resulting from new and larger structures in the oil sands or other mineral mining industries. The ESPMS facilitates easier data gathering for preparation of as-built and after-built or regulatory reports, etc. It enables quick location of the interested instruments and summarization of the performance of the instruments. It enables one to visualize performance data and QA/QC construction test results spatially on any given cross-section. Data can be exported to MS Excel for detailed analysis and to evaluate the stability of the earth structures.

May 1, 2004

By S. Kelebek, Gerhard W. Heinrich, Peter F. Wells

"The review and optimization of process stages is an integral part of the program to improve the metallurgical performance of the Strathcona Mill. Improved primary grind size distributions, streamlining of rougher-scavenger circuits and increased platinum recoveries were the target of plant and laboratory scale tests. The results can be summarized as follows:• Decreasing the primary grinding cyclone vortex finder diameter for nickel/copper ore gave significant increases in overall copper recovery and improved rougher flotation selectivity.• The scavenger flotation stage in the circuit treating copper ore was found to contribute little to this circuit's copper recoveries -yet to be essential for acceptable recoveries of nickel, platinum and gold. The elimination of this stage by re-routing the tailings from the copper ore rougher into the nickel/copper ore rougher feed has lead to lower gangue recoveries to the nickel concentrate and to improved copper-nickel separation, while reducing equipment operating costs.• Surface aging effects such as oxidation are known to decrease flotation recoveries of platinum minerals such as sperrylite. The conditioning of an intermediate non-magnetic process stream with copper sulphate prior to thickening increased the platinum recoveries in the subsequent flotation stage by approximately 10%."

Jan 1, 1996

By E. Nurminen

Thermal transport properties of copper flash smelting flue dust have been investigated. Such values of the dust are needed to correctly model the process and to optimize its heat recovery performance. Dust accretions on heat recovery boiler walls may have a significant influence on the boilers heat transfer efficiency. Measurements of the thermal transport properties have been made for industrial flue dust and for pure sulphate components. The measurements have been conducted at temperatures up to 400 °C and the effect of porosity on these properties has also been investigated. The results indicate that the flue dust and the sulphate components are effective thermal insulators and the dust build-up on the boiler walls is likely to greatly decrease the heat transfer efficiency of the boiler.

Jan 1, 2007

By I. Protkova

Versa Power Systems solid oxide fuel cell (SOFC) stacks operate at intermediate temperatures 700 ? 800 °C allowing the use of metallic interconnects. Thermal expansion good matching with other stack components and cost restriction led to selecting ferritic stainless steels as interconnect material. Analytical tools and techniques were developed to understand the ferritic stainless steel behavior at high temperature while exposed to dual environment. Analytical tools such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) have provided valuable information towards describing interconnect degradation in a variety of testing conditions. Several examples are presented to demonstrate interconnect oxidation and its relation with SOFC testing results.

Jan 1, 2005

By Diego L. Romero, Joy P. Romero

"IntroductionMinerals may be classed broadly as ferromagnetic (magnetite for example), as paramagnetic (attracts to regions of magnetic field convergence) and as diamagnetic (attracts to regions of magnetic field divergence). High-intensity separators are not necessary to separate ferromagnetic minerals from other classes. Rather, low-intensity units that generate fields below 5000 gauss are adequate for this purpose. However, paramagnetic minerals, such as ilmenite, with high magnetic ""attractability"" require fields of up to 10 000 gauss; those with low attractability may require even higher fields. Table 1 shows approximate ranges of field intensities necessary to separate ferromagnetic and paramagnetic minerals from minerals of lower attractability, along with the force with which they are attracted relative to iron in a standardized magnetic field.Uniform magnetic fields, not useful for separators, are generated between flat parallel surfaces; non-uniform fields, useful for separators, arise when at least one of the surfaces is of irregular shape. The diagrams below show how magnetic lines of force align relative to north and south poles.If a particle is placed in a uniform field, it feels no displacing force unless the particle distorts the applied field assymmetrically. This is not the case in non-uniform fields which are required for magnetic separators.Magnetic fields can be generated by permanent magnets (low intensity), by electromagnets (medium and high intensity) and even by superconducting coils (100 000 gauss fields and higher), although the latter are not as yet useful in production environments .The magnetic force of attraction per unit of mass, that acts on a paramagnetic mineral such as hematite, increases in proportion to the strength of the field . Unfortunately, the highest fields attainable with electromagnets is of the order of 20 000 gauss. Fortunately, the gradient of the fie ld (that is, the degree of convergence of magnetic lines of force) is important, because the attractive force per unit mass is proportional to it also . This can be stated:"

Jan 1, 1989