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By D. P. Wilkinson

Flow field design is critical to determining fuel cell performance with respect to operating conditions. Flow fields are normally designed around their maximum power operating point with the goals of maximizing performance and minimizing pressure drop between the inlet and outlet of the flow field. At lower power pressure drop is reduced, and water management and reactant distribution issues can occur over the active area as well as issues with cell to cell reactant distribution in the fuel cell stack. Flow fields have fixed flow channel geometries and fixed active areas which determine the reactant flow characteristics over the operational range of the fuel cell. In this paper we discuss some of the benefits of a new approach of changing the flow field active area with changing operating conditions. Such benefits for future fuel cell designs could include improved cell performance and stability, improved cell to cell reactant distribution, reduced low current density failure modes, and overall system advantages.

Jan 1, 2005

By Zhang. L.

Ordered intermetallic PtSb had been synthesized by arc-melted and then sintering treatment. The electro-oxidation of formic acid on PtSb was investigated at room temperature by cyclic voltammetry and chronoamperometry. The results are compared to those at a polycrystalline platinum electrode surface. It was found that PtSb intermetallic was catalytically more active than pure platinum according to the onset potential and current density. XRD and XPS technologies had been used to investigate the crystal structure and electron effect. We think formic acid decomposition on PtSb favors the reactive intermediate route and is not very much affected by the CO intermediate as compared to Pt.

Jan 1, 2005

By C. Cano

One of the main concerns within the mining industry is to minimize the impact of tailing facilities to the environment and nearby communities. Since the implementation of the first thickened tailings disposal (TTD) methodology at Kidd Creek in 1964, the thickened tailing disposal has been growing alternative disposal technology to mitigate the environmental impacts. Technical investigations on the TTD technology have been studied in detail to counteract the increasing shortage of water resources. One of the benefits observed with TTD is its resistance to potential earthquakes, particularly in zones with high seismic activity (Los Andes). TTD technology optimizes the maximum possible density for the material and generates a negative internal pore pressure in the material due to the surface and sub-surface water evaporation. This internal pore pressure should be enough to resist the pores pressure to which tailings are subject due to an earthquake action. The objective of this study is to verify the Shrinking Limit (SL) of thickened tailings during initial deposition and in the long term and the ability of tailings deposited by TTD would resist liquefaction. Fresh tailings coming from a flotation process of a copper plant concentrator were used. The samples put under cyclical three-dimensional tests associated with maximum credible earthquake magnitude range of 7.0 8.0 to develop a curve for the safety factor v/s depth for dry densities related to the maximum density obtained at the SL. At a dry density of 1.65 t/m3 liquefaction did not occur at any depth. At 90 % of dry density of 1.51 t/m3, liquefaction did not occur at earthquake magnitudes of 7.0 or 7.5 nor at any depth but liquefaction occurred at magnitude 8.0 between 0 m and 14.5 m; below 14.5 m, liquefaction does not occur.

Jan 1, 2007

By K. Sakaguchi, T. Yokoyama

"In-situ rock stress measurement was carried out in the Kamaishi mine of Iwate Prefecture to quantify the variation of the shallow crustal stress field associated with the 2011 Tohoku-oki earthquake. Stress measurement was conducted by the Compact Conical ended Borehole Overcoring (CCBO) technique, which is one of the stress relief method. The CCBO technique is the one of the suggested method of ISRM. Measurement period is from 1991 to 2014. Main results obtained in this study can be summarized as follows.The direction of the maximum principal stress did not change much before and after the earthquake. However, the directions of the intermediate principal stress and the minimum principal stress of one year after the earthquake changed from those of before earthquake. Namely, the direction of intermediate principal stress was East-West horizontally, and the direction of minimum principal stress was vertically. This state of stress is reverse fault type and was maintained for three years after the earthquake.The magnitudes of principal stresses and the vertical stress of one year after the earthquake became more than the double before the earthquake. However, the magnitudes of the maximum principal of two year after the earthquake became smaller comparing with those of one year after the earthquake. Furthermore, the magnitudes of the intermediate principal stress and the minimum principal stress of two year after the earthquake became almost same as those before earthquake, and the vertical stress of two year after the earthquake became almost equal with the overburden pressure. And the magnitudes of three principal stresses of three year after the earthquake became the same level before the earthquake."

Jan 1, 2015

By Peter A. Witt

Highland Valley Copper is a conventional truck-shovel mining and flotation concentrator operation located some 75 kilometres southwest of Kamloops, B.C. (Figure 1). The ore is located within a porphyry copper deposit and is mined at a rate of 135,000 metric tonnes per day from two separate open pits. The nearby mill produces concentrates containing 375 million pounds of copper and 5 million pounds of molybdenum metal yearly. In the Valley pit, head grades are roughly 0.40% Cu at a 0.23% Cu equivalent cut-off. The Valley pit strip ratio currently sits at 0.55:1 with waste quantities made up of separate rock and unconsolidated overburden units. From the mill, concentrates are trucked to nearby Ashcroft and then hauled by rail to ocean port facilities in Vancouver. The mine employs 950 persons and is planned to operate until 2009. The operation is a partnership between TeckCominco with a 63.9% interest, BHP Billiton holding 33.6%, and others 2.5%. Management is shared by the two principal owners and directed by a management committee.

May 1, 2003

By F. L. Pellet, S. Maiolino

"The determination of rock bolt contribution to reinforced joint shear strength is still a challenge, especially for assessing reinforced rock mass stability. For this purpose, several experimental studies have been performed during the last decades, mostly on small scale rock joint and bolt specimens. However, to accurately assess the rock bolt contribution, scale effect has to be accounted for. For this reason full scale lab tests are required as an alternative to in situ tests for which boundary conditions are more difficult to control.In this paper the results of an experimental program carried out with a large shear box, dedicated to test bolts in full scale conditions is presented. Different rock bolt diameters and different rock bolts inclination with respect to the shear plane were tested Experimental results were satisfactorily compared with an analytical model which is able to compute the contribution of the rock bolt to the shear strength of the joint as well the associated displacement of the joint. These conclusions allows us to validate the model in order to help the designer of reinforced rock engineering structures, such as slope or underground openings, to precise the optimum installation of rock bolts. INTRODUCTIONFully grouted rock bolts are commonly used for rock masses reinforcement to ensure the stability of rock slopes and underground cavities. For this purpose, the determination of rock bolt contribution to reinforced joint shear strength is of the utmost importance. During the last decades, several experimental studies have been performed to investigate the behavior of bolted rock joint. For obvious reasons, almost all the experiments were achieved on small scale bolted rock joint specimens (Bjurström, 1974; Azuar, 1977; Dight, 1983; Egger & Fernandes, 1983; Schubert, 1984; Spang & Egger, 1990; Egger & Zabuski, 1991). These studies made it possible to assess the influence of different parameters such as the bolt’s diameter, the number of bolts, the angle between the bolt and the joint, the nature of the rock, the friction and the dilatation angle of the joint. However, to accurately assess the rock bolt contribution, scale effect has to be accounted for (Vallier et al., 2010). For this reason full scale lab tests have been performed as an alternative to in situ test for which boundary conditions are more difficult to control."

Jan 1, 2015

By K. D. A. Whaley

Abstract -The Captain North Extension deposit consists of five sulfide lenses hosted in cherty and chloritic metasediment that is bounded by quartz-eye rhyolite and laminated rhyolite . Lens 2 consists of sphalerite and galena with silver-rich tetrahedrite in chert. Lens 3 contains massive pyrite, with chalcopyrite and minor gold, gradational to minor pyrite in a chloritic metasediment . The other lenses are unexplored. The sulfides occur as beds, fracture infills, and disseminated grains. Reserves are estimated at 207 555 tonnes grading 7.38% Zn, 2.76% Pb, and 91.81 g/t Ag. The deposit is isoclinally folded, dips steeply west, plunges 50 degrees south, and is faulted out to the north, where drag folding has reversed the plunge. Minor cross-faults contain talc and sericite. High sphalerite but low pyrite abundances result in poor responses to standard electromagnetic techniques. Lens 3, which contains more pyrite than Lens 2, responds better to induced polarization and allows detection. Geochemical anomalies are found in a nearby swamp and stream, but an impervious till cover inhibits the development of soil anomalies.

Jan 1, 1992

By Maria Agostina Cinellu

Some aspects of the reactivity of the two different kinds of gold(III) oxo complexes [Au2(N,N)2(?-O)2][X]2 [N,N = 2,2'-bipyridine (bipy) (1), 6-alkyl-2,2'-bipyridine (bipyR) (2), R = Me a, CH2Me b, CHMe2 c, CMe3 d, CH2CMe3 e] and [Au2(C,N,N)2(?-O)][X]2 [HC,N,N = 6-benzyl-2,2'-bipyridine (bipyR') (3), R' = CHMeC6H5 a, CMe2C6H5 b] (X = BF4, PF6) have been studied. Treatment with water converts the unsubstituted bipyridine complex [Au2(bipy)2(?-O)2][PF6]2 (1) and the cyclometallated derivatives [Au2(C,N,N)2(?-O)][PF6]2 (3) into the water soluble monomeric hydroxo species [Au(bipy)(OH)2][PF6] (4) and [Au(C,N,N)(OH)][PF6] (5), respectively. These hydroxo species, likely the intermediates in the formation of the oxo complexes, are quantitatively reverted to the latter ones by reflux in anhydrous solvents. Both kinds of oxo complexes react with PPh3 to give OPPh3, the gold(I) complex [Au(PPh3)2][PF6] and the free bipyridine ligands. The reaction of the dioxo complexes [Au2(bipyR)2(?-O)2][PF6]2 (2a, 2b, 2c, 2e) with different alkenes gives the unprecedented alkene complexes [Au(bipyR)(?2-alkene)][PF6]. The styrene adduct [Au(bipyip)(?2- CH2=CHPh)][PF6] (7) (bipyip = 6-iso-propyl-2,2?-bipyridine c) has been characterized, inter alia, by X-ray diffraction analysis. Organic products arising from olefin oxidation are also found in the reaction mixture.

Oct 1, 2003

By F. Liu, S. Rezaei, M. Muinonen, M. Barati, V. L. Lakshmanan, S. Marcuson

Canadian nickel-copper ore deposits have been a major source of nickel, copper, cobalt and precious metals for more than 100 years. The two main minerals of interest, pentlandite (Pn, (Ni,Fe)9S8) and chalcopyrite (Cp, CuFeS2), are usually accompanied by large quantities of pyrrhotite (Po, Fe1-xS). Until the 1950s, Po containing small amounts of nickel was routinely smelted as part of the valuable Ni concentrate. The rapid growth in Ni demand following the Second World War created impetus to treat the Po separately. This action would liberate a valuable smelting capacity for higher value Pn, allow for recovery of Ni locked in Po, convert the Fe to iron oxide or metallic iron pellets, and recover S as sulphuric acid or elemental sulphur. The roasting process also has the potential to produce energy due to the highly exothermic oxidation of Po. The Ni industry would then have a “waste-free” process. Both Inco (now Vale) and Falconbridge (now Glencore) developed processes and built large industrial plants for this purpose that operated with some success. But technical issues and tenuous economics were continual challenges. By the early 1980s these industrial operations were closed. Sophisticated froth flotation methods of rejecting Po were developed, and Po containing up to 1% Ni became a waste material reporting to the tailings stream. As part of a major study on possible processing methods of Po for both value recovery and waste remediation, this paper presents a historical perspective on Canadian Po tailings with regards to their generation, inventory, value, and attempts to process them.

Jan 1, 2017

By Makhlouf Boubahziz

The HNIA field is part of the Tinrhert project which consists of developing 17 fields containing essentially gas with a few small rings of oil. It is considered as one of the main fields in this project in terms of its area and the number of geological structures that has formed it. It is a wide anticline of Cambro-Ordovician age, orientated NNE-SSW and located in the South-eastern part of Illizi basin. This structure extends from Alrar-center in the North, to the North of In Amenas in the South. The area is 1350 km2. The main reservoirs forming HNIA field are the Devonian (F2, F3 and F4), Siluro-Devonian (F6) and Cambro-Ordovician. These latest are formed by 4 sandy units alternated by layers of shale and shaly silt termed from the base to the top as follow: Unit II, Unit III-3U, Unit IV-2L and Unit IV3; these units are the subject of this study. The HNIA field is essentially gas, up to day this field is at the stage of appraisal and evaluation in order to establish a development plan; therefore the main target of this study is to contribute to this frame work. The following objectives are: ?To build a structural model of the study area. ?To integrate all the sedimentological, structural and petrophysical data in order to build a 3D geological model

Aug 1, 2013

By H. Bannach

"This paper focusses on what seem to be the leading indicators of prosperity in the minerals industry during this decade: the geographical distribution of deposits, environmental impact, capital allocation and acid consumption. There is a potential for meeting environmental criteria at a reasonable profit margin, but those with limited acid demand within economic range will face hard times to meet growing environmental concerns, resulting in additional mine closures. At the other end, those with old waste dumps who are thinking about smelting capacity additions will need capital influx at a much larger rate than ever before. All things considered, a change should be made in the way the world's copper reserves are computed, because there is a growing need to internalize these effects back to the ore blocks before a meaningful estimate of reserves becomes available.IntroductionThe copper industry has undergone several changes during the past decade, many of which were expected to take place because they rel1ect the economics of ageing mines. However, many others took place that shocked the industry because they were not completely under control. The focus of this paper is to rel1ect on those changes, and on market expectations for this decade that somehow depend on their impact.To review the prospects for new mine developments and expansions from an industry perspective to a full extent, it would be necessary to consider not only the deposits themselves, but also geographical constraints, environmental constraints, labour composition, technology development and use, the availability of capital, ownership issues, and integration within the industry. This paper, however, will concentrate on only some of the key elements that are believed to playa major role in shaping the market in the decade that has just begun. These elements, all interconnected, are:"

Jan 1, 1992

By N. W. Xu, C. Sha, F. Dai, Y. G. Zhu, B. Li

Underground caverns stability and excavatability of rock masses are of significance in geotechnical engineering, in both design and construction stages. Risks associated with underground group caverns of Houziyan hydropower station in southwestern China are growing as a result of continuous excavation-induced unloading. To improve our understanding of the underground caverns instability and resolve the complex subsurface conditions of the highly fractured rock mass, a high resolution microseismic monitoring system was established in the deep underground caverns, pursuing the relationship between the measured data about microseismic activity and excavation damage zones of surrounding rock mass. Through analyzing the tempo-spatial distribution of microseismic activity, excavation damage zones and potential risk regions in underground caverns were identified. Furthermore, the correlation between microseismic activity and pre-existing geological structures, as well as traditional monitoring was analyzed. In order to validate the correlation between seismicity and potential slip surface of underground caverns, a model was implemented into numerical code to further evaluate the deformation and stability of surrounding rock mass. The monitoring results demonstrate that microseismic events mainly occur at high stress concentration regions, which coincides with the results obtained from numerical analysis. Therefore, the comprehensive method incorporating microseismic monitoring and numerical analysis, as well as traditional monitoring and filed observation has been proven to be very promising in deformation and even instability prediction of surrounding rock mass in underground caverns subject to delineation of potential slip surfaces and excavation damage zones.

Jan 1, 2015

A line of nine self-aspirating W emco cells, part of the Rougher circuit at Division Salvador, Codelco Chile, was retrofitted to allow operation with forced air. Each cell could be operated self-aspirated or with compressed air supplied through a 4-inch line equipped with a mass flow meter. Gas dispersion was characterized for the two modes of operation. Metallurgical performance was compared under self-aspirated conditions and with different gas profiles under forced air conditions. Cell characterization demonstrated that with forced-air the cells could not evenly distribute air across the cell volume. Bubble size increased with gas velocity, as expected, with no difference between self-aspirated and forced-air operation. A systematic increase in bubble size down the bank was found. Cumulative bubble surface area flux down the bank showed no major differences between surveys. However, grade-recovery curves revealed that the highest recoveries were invariably obtained with forced air operation. Plotting concentrate mass recovery vs. enrichment ratio showed that the line performance could be controlled over a wider range when forced air was used.

Jan 1, 2007

By G. Lafont

Aug 1, 2013

By E. Benguerel, G. Monteith, L. Centomo, S. Pelletier

In early 2007, it became apparent that with changing concentrate feeds, the magnesium (Mg) load projected for CEZinc starting in 2009 and beyond would quadruple and overwhelm the current Mg process bleed capacity. A project was started, following design for six sigma (DFSS) standards, to select both the optimal process and to evaluate its target capacity for the Mg bleed circuit. The economic and process risks of under or over-designing while Mg reduction efforts were underway at the mines also needed to be evaluated. This paper describes the project methodology, the impact on the plant, and some potential optimizations for CEZinc's basic zinc sulphate (BZS) Mg bleed process.

Jan 1, 2008

By K. Soucek, J. Ptácek, A. Hastíková, R. Kukutsch, P. Konícek, P. Waclawik

"Cable bolts are used frequently as a secondary support system (with steel arch support) in difficult stress-strain conditions of deep coal mines. The load transfer mechanism of cable bolts depends on several factors, such as the strength, deformation and geometric properties of the bolts, resin and the surrounding rock mass so-called cable-resin-rock system (CRR system). The bonding length and bolt/borehole diameter ratio strongly influence the final bearing capacity of the CRR system.The study presents the behaviour of CRR system during a pull-out test which is usually used in the carboniferous rock mass in the Czech part of the Upper Silesian Coal Basin. A series of 28 pull out tests were performed on 3-m-long cable bolts, with various combinations of borehole diameters and bonding lengths, to understand this behaviour. Boreholes were drilled into a solid rock mass consisting of fine-grained sandstone to guarantee similar conditions during the pull-out tests. Video inspection and measurement of borehole diameters were performed to determine their quality and real diameters. Three characteristics were observed from pull-out test results: ultimate pull-out load; displacement of the end of bolt and system stiffness. Numerical modelling by FEM (Finite Element Method) was used to determine the stiffness of the CRR system for variable bolt/borehole ratios and bonding lengths each under constant load. A linear elasto-plastic model and a mohr-coulomb model were used for cable and resin-rock respectively. The results of the experiment may contribute significantly to improving of the methodology of cable bolts installation as well as the design of used cable bolts."

Jan 1, 2015

By J. E. Dutrizac, J. B. Sunstrum

"Lead was among the first metals known to man, and there are indications that lead was produced by the reductive smelting of galena in the mountains surrounding the Black Sea as early as 3000 B. C .(1). The early metallurgists soon discovered that silver could be recovered from lead bullion by cupellation techniques, and that the litharge product of the cupellation process could be reduced to give silver-free lead metal. By the Graeco-Roman era, lead-silver ores were being extensively exploited for both their silver and lead contents. Although silver was always of prime concern, a number of industrial uses existed for lead that included piping and sheeting. Subsequently, lead metallurgical practice developed steadily in different parts of the world, and was a relatively mature technology by the time of the European colonization of North America. In the United States, lead was produced on a small scale as early as 1720, and by 1800, the extensive Pb-Zn deposits of Missouri-Kansas and the upper Mississippi Valley were being developed(2). Many of the early American lead ores were low in silver, and seemed to have been worked primarily for their lead contents. Major uses of lead at the time included bullets, pipe and sheeting. During the period 1860-1890, the silver-rich galena ores of the western United States were exploited, and a number of lead smelters were operated. Although all the smelters produced lead metal, the recuperation of the associated silver and gold values was generally of prime concern. In Canada, lead deposits are abundant, and galenarich outcrops frequently attracted the attention of the early explorers and prospectors. In fact, the first record of a Canadian ore deposit seems to have been the observation of an argentiferous galena vein near Lake Temiscamingue in 17 41(3). The presence of silver-bearing lead deposits naturally attracted the attention of the mining community, and many outcrops were worked throughout the country. Because of the problems associated with transporting lead concentrates to existing American or overseas smelters, attention soon shifted to the establishment of local lead smelting facilities. The purpose of this article is to examine those early smelting efforts and to try to identify the first ""successful"" Canadian lead smelter."

Jan 1, 1999

By Rob Scott

Making a difference with Zinc & Health Two billion people do not get enough zinc in their diets. Every year 450,000 children die from complications arising from zinc deficiency Our Zinc Alliance For Child Health partnership with CIDA and Micronutrient Initiative, our involvement with UNICEF through the IZA and our partnership with BASF are gaining wide recognition. Sustainability at Teck ? Integrating into our Core Business Strategy Our strategy Long term goals Our approach Managing risks and finding opportunities Our progress Early reports Moving Forward Metrics and indicators

May 1, 2013

By J. Fixter, P. Prangnell, Z. Pinter, E. Eimer, B. Chehab

"High deposition rate Wire and Arc Additive Manufacture (WAAM) can provide benefits to the aerospace industry, including a reduction in lead time, reduced material waste and, through higher solidification rates, refinement of the as-built microstructure relative to a cast material. However, candidate 2xxx series high strength alloys for this process normally require a solution treatment, which is problematic for large near-net-shape components, and age hardening to achieve maximum mechanical properties. With each layer being subject to multiple thermal cycles, exploiting the thermal conditions in the WAAM process to avoid post-build solution treatment is therefore of interest. A solutionisation model has been developed for the WAAM process, based on diffusion controlled dissolution using DICTRA, which was validated through thermal simulations combined with 2D and 3D image analysis. The model has subsequently been used to simulate the solutionisation behavior during a typical WAAM thermal cycle and to explore what could theoretically be achieved by, for example, refining the starting microstructure.INTRODUCTION There is currently great interest in exploiting additive manufacturing (AM) in the aerospace sector due to several benefits it can potentially provide; including reduced material waste, shorter product lead times and greater design freedom (Herzog, Seyda, Wycisk, & Emmelmann, 2016). However, with aluminium alloys the material properties obtained are generally inferior to those of conventional high-strength wrought products; therefore more research is required to explore the potential for exploiting the unique process conditions in AM to improve the as-deposited microstructure. A range of AM techniques are now available (Debroy et al., 2018), which differ in terms of the feedstock type and power source and it is necessary to match the appropriate technology to a particular application. This generally requires a compromise between the build rate and shape resolution. Wire and plasma-arc additive manufacturing involves using an electric arc to melt wire onto a substrate, and fabricates a part by building up overlapping layers of deposited weld beads (Addison et al., 2015; Williams et al., 2015). The benefits of this process over other AM methods are the much higher deposition rates (e.g. kg’s/hour) achievable and lower capital equipment costs relative to powder bed techniques, which makes it suitable for large scale applications. However, limitations include a lower part complexity, lower solidification rates and a greater need for post-process machining (Frazier, 2014)."

Jan 1, 2018

By K. Thuro, H. Käsling, F. Menschik

"With increasing data volume, due to enhancing requirements for ground investigation programs for large construction projects, the demand for more efficient filing systems is more and more growing. Depending on the project we also have to use flexible systems to cope with varying data out of different lab and field tests.The chair for Engineering Geology at TUM is developing a web-based database solution to handle all project relevant data in a more appropriate way. We aim to optimize our data management to achieve a fast and easy way of collecting, documenting and analyzing our gained data. The second objective is to provide an easy access to our data for project partners across broadly distributed locations.This Database system consists of a PHP web interface and a MySQL database core. The current setup allows an online access via Internet (www). We are able to grant and constrain access to all data or only arrays of data with our user management system to guarantee the safety of project data and respect all rights and proprietorship. The database system is of modular design and consists of the following three base modules: module of general project data, module of laboratory data and user management module. At the current stage we are able to save and work with all usually generated specific values from unconfined compressive strength tests, brazilian tensile strength tests, point load tests, CERCHAR and LCPC abrasivity tests and ultrasonic tests. The user is able to perform a simple statistical analysis within our database (e.g. average calculation of one sample) and export data as csv or xls files for further analysis.For specific questions within projects we are able to deploy and integrate further modules in our database system. At this moment, we are developing an add on to use this database for different drill test analyses. One of the tools correlates drilling performance and drill head wear measured in the field with rock mechanical properties, and extrapolates the data to estimate the performance and wear in new projects. Today we are managing 90 projects with 550 samples and almost 1350 lab tests with the base module.In our contribution we aim to demonstrate an efficient way of data structuring using a relational database for laboratory and field testing data."

Jan 1, 2015