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By X. -P. Zhang, L. N. Y. Wong

Shale gas exploitation initiated in North America has rapidly extended worldwide. Hydraulic fracturing is an emerging field technique for stimulating the gas reservoir. The study of cracking processes, particularly crack coalescence, is vital for a successful hydraulic fracturing to enhance the gas exploitation. Experimental studies have observed that the size effects of the constituent particles are significant on the cracking behavior of the rock specimens. To further investigate the size effects, the bonded-particle model (BPM), which is based on the discrete element method (DEM), is adopted in the present research. In flaw-containing specimens, by varying the crack resolution (?= a/2R), which is the ratio of half flaw length (a) to particle size (2R), the size effects on cracking behavior under compressive loading are studied. By keeping the flaw length constant, the particle size is varied independently in the BPM analysis. Decreasing the crack resolution increases the first crack initiation stress, but it has no obvious effects on the uniaxial compressive strength. The trajectories of the first cracks and secondary cracks hence generated have a higher resolution and are well-defined in those specimens possessing a higher crack resolution. On the contrary, in lower crack resolution specimens, the macroscopic first cracks appear to be wider and less continuous. These findings from numerical simulation clearly demonstrate particle size effects on cracking behavior. Special attention should be paid to these effects in future numerical study using the bonded particle model.

Jan 1, 2015

By \/eena Sahajwalla, Alexander Blagus

This paper reports the effect of using High Density Poly-Ethylene (HDPE)/coke blends on the reduction behaviour of Mn3O4 to MnO at 1000°C. The results suggest that CH4 release increases with increasing HDPE addition. The results show that the rapid release of methane, over only the initial five minutes, limited the interaction of Mn3O4/MnO with CH4. With the devolatilisation of HDPE there was increased porosity in samples containing HDPE, assumed to be the major factor in differences of reduction rates.

Jan 1, 2011

By L. Veleva, Garcia. A., G. Perez

Aluminum is a metal used for the transmission of electricity of high voltage, in the construction industry and other areas. In atmospheric conditions aluminum forms an oxide layer (Alz03'H20) as a result of its corrosion, entering the passive state. The oxide layer can be destroyed by the presence of ions (Cr, SOx-n) developing localized (non uniform) corrosion attack by pitting, difficult for evaluation. The concepts of fractals and self-similarity were used in this study for the characterization of the development of localized corrosion. Images obtained with a scanning electron microscope (SEM) of samples of electrolytic aluminum wire that have been exposed during one year in ruralurban and marine-coastal environments of the humid tropical climate of Mexico, have been processed. The development of pitting has been studied as a function of time, making a statistics of the frequency of appearance of pits versus the area occupied by them. The data show that the distribution of the pits follows a power law. Therefore, the concept of self-similarity can be applied for the study of the phenomenon of localized corrosion, describing their development with time.

Jan 1, 2006

By L. B. Tsymbulov, L. Sh. Tsemekhman, A. N. Golov

Gipronickel Institute, JS is developing a process of continuous converting of Nicontaining copper matte and concentrates resulting in the production of blister copper and fluid NiO-containing slag in a two-zone Vaniukov furnace. The process under development is an alternative for the existing technology of blister copper production in converters, the latter being characterized with insufficient sulphur utilization, low direct copper recovery and the production of inconvenient for further processing solid slag on the basis of NiO and NiFe20 4- The results of pilot testing on processing of copper concentrate obtained from high-grade matte (HGM) separation in the two-zone Vaniukov furnace with the hearth area of 11.4 m2 are presented.

Jan 1, 2007

By F. Tanaka

Copper losses to discard slag have long impacted on the profitability of copper smelters. Businesses based on the treatment of secondary materials have also revealed that copper losses are indices of precious-metals losses. Many custom smelters are thus required to obtain more reliable controls for reducing copper losses than ever before. Mitsubishi Materials Corp. has cooperated with academic research institutes in conducting research projects on the pyrometallurgical fundamentals of copper smelting systems, including mutual evaluation of magnetite behavior between synthetic and industrial slags. The state-of-the-art pyrometallurgy has subsequently been introduced to Naoshima smelter for controlling the Mitsubishi process. The revised controls function successfully and the operational results demonstrate that avoiding the discharge of solid magnetite from the S-furnace is quite effective to reduce copper losses. Magnetite behavior has been controlled over the Mitsubishi process so as to reduce copper losses while satisfying the needs of recycling businesses growing in Japan. In-situ estimation of magnetite behavior using the absorbed heat from the melts to cooling water will also be discussed.

Jan 1, 2007

By E. Burdukova

Rheological measurements have found a wide array of applications in mineral processing research. Rheological properties of mineral suspensions are highly dependent on the mineral surface properties as described by DLVO theory, and the relationship between these properties and inter-particle interactions is well established. In this paper, rheological properties of mineral suspensions are used to study the differences in behaviour of isotropic talc and anisotropic zirconia minerals as a function of varying properties of the suspension medium, such as pH and polymer dosage, specifically carboxymethyl cellulose (CMC). It was found that the rheological tests when carried out in parallel with electrophoretic or point of zero charge measurements, clearly reveal differences between behaviour of the suspensions of isotropic and anisotropic minerals. These differences are further accentuated with the addition of carboxymethyl cellulose (CMC).

Jan 1, 2006

By K. S. Coley, G. A. Irons, T. Kaneyasu

"It is very important to reveal the lime dissolution mechanism in steelmaking slag, to promote its dissolution without calcium fluoride, which is now almost forbidden for use in most industrialized countries. In this research, the purpose was focused on the development of an experimental method to measure the mutual diffusivity of Ca2+ under the condition of lime dissolution into slag. By forming diffusion couples using a ""vacuum slag aspirating technique"", the method was established. The following mutual diffusivities of Ca2+, in CaO-SiO2-FeO slag systems, imitating oxygen steelmaking slag, were determined using this method:4.1*10-10 m2/s at 1400°C for 27wt.%CaO-53wt.%SiO2-20wt.%FeO slag,4.3* 10-10 m2/s and at 1400°C for 20wt.%CaO-40wt.%SiO2-40wt.%FeO slag, and 1.3*10-10 m2/s at 1250°C for 20wt.%CaO-40wt.%SiO2-40wt.%FeO slag.It was also verified that, if the basicity and ferrite content of the bulk slag are low, then a calcium silicate film forms on the lime surface, and drastically deters the lime dissolution."

Jan 1, 2004

By Michael Samis

The real option valuation method is often presented as an alternative to the conventional discounted cash flow (DCF) approach because it is able to recognize additional project value due to the presence of management flexibility. However, these two valuation methods can be separated on a more fundamental level by their differences in risk discounting. Real option valuation applies the risk-adjustment to the source of uncertainty in the cash flow while the DCF method adjusts for risk at the aggregate level of net cash flow. This seemingly small difference is the reason why the real option method is able to differentiate between projects according to each project?s unique risk characteristics while the conventional DCF approach cannot. This paper provides an overview of the real options and DCF valuation frameworks and discusses the differences in risk discounting that exist between the two methods. Using grade-school mathematics, this paper clearly demonstrates how, with real options, a unique project risk discount can be calculated which is directly linked to the project?s unique risk profile. It also highlights why the DCF method fails in this regard and shows why a call to ?increase the Risk-Adjusted Discount Rate? is an incomplete solution at best. Finally, a heap-leach project and satellite reserve development project are valued with both techniques and the difference in investment conclusions is explained in terms of the risk-discounting concepts discussed here.

May 1, 2003

By Gilles Tremblay

The legacy of orphaned/abandoned mines, with their associated environmental liability, human health concerns and the financial costs of clean up is a serious issue facing Canada. In 1999 and 2000, a number of stakeholders put forth requests to Mines Ministers to establish a joint industry-government working group, assisted by other stakeholders to review the issue of abandoned mines. The Ministers supported this initiative and asked that a multi-stakeholder workshop be organized to identify key issues and priorities. The Workshop on Abandoned Mines, held June 2001 in Winnipeg, developed consensus, guiding principles and recommendations that were presented at the Mines Ministers? Conference, September 2001. Ministers agreed on the importance of a large-scale program for the rehabilitation of orphaned/abandoned mines sites. A multi-stakeholder Orphaned/Abandoned (O/A) Mines Advisory Committee was formed and a plan was developed to study various issues relating to the implementation of remediation programs across Canada. Three task groups were formed to address the following key areas: Information Gathering; Community Involvement; and Barriers to Collaboration. The presentation will include a summary of the results of the three projects and the future work plan for the program.

Nov 1, 2002

By K. Buxmann

Climate change is a subject of growing concern. Based on the International Energy Agency, about 19% of man made greenhouse gas emissions globally are generated by the transport sector. This paper will focus on the environmental aspects of the light-weighting in transport and the resulting savings of fuel and electricity. Aluminium is an option for lightweight applications in transport, with very high benefits not only in the use stage, but also in the stage of vehicle recycling. Life cycle assessment is used to quantify the relative benefits of light-weighting specific components of cars, commercial road vehicles, buses, ships and trains. A vehicle consists of many components, which are produced by different processes and undergo different types of end-of-life operations. This document does not intend to compare a generic aluminium vehicle with a generic "heavy materials" vehicle. It rather tries to use a pragmatic approach based on specific examples of components where aluminium is used and can be used in the design of new vehicles, also taking into account future developments. The case studies in this paper are based on real cases where aluminium was used. For each component, sensitivity analyses are applied to see the impact of specific parameters such as the end-of-life recycling rate and the use stage driving distance. Significant greenhouse gas savings by the use of aluminium are demonstrated for cars and even higher ones for trucks, buses, trains and ships. In addition, the total potential benefits of light-weighting with aluminium are shown on the global level.

Jan 1, 2007

By Wataru Inagaki, Kozo Kawano, Tetsuya Ando

Cu–Ni–P alloys are the typical precipitation-hardening material. Thus, Cu–Ni–P alloys is expected to apply alternative materials for heat-exchanger tubes. Therefore, it was investigated that the effect of the heat-treatment simulated brazing on mechanical properties of Cu–Ni–P alloy in this study. The hardness of specimen as heat-treatment simulated brazing after solution heat treated (sht) was shown approximately 105 HV. The peak hardness and tensile strength of the specimen as performed aged at 498 K for 43.2 ks following the heat-treatment simulated brazing achieved at approximately 140 HV and 260 MPa, respectively. From these results, it is expected the application to higher-strength tube for heat-exchanger after brazing in a furnace. INTRODUCTION Copper prices have increased dramatically with high in recent years. At the same time, manufacturing industries are required to reduce the environment load by reducing the wall thickness of the copper tubes used in heat exchangers. High-strength copper alloys are developed for reducing the wall thickness, while achieving high strength, of the copper tubes. Moreover, excellent workability and corrosive durability are also required by these copper tubes. Furthermore, the brazing, which are carried out at about 1050 K during the assembly process of heat exchangers, leads to grain growth and re-solving of additive elements. Nomura et al. achieved a tensile strength and Vickers hardness of approximately 260 MPa and 110 HV, respectively, after aging at 723 K for approximately 36 ks. Tamagawa et al. studied that the strength of Cu–Ni–P alloy rapidly increased at about 125 HV during the cooling process after the heat brazing due to the Ni2P precipitates sized 5–10 nm. Furthermore, Inagaki et al. achieved a Vickers hardness of approximately 130 HV by aging at 498 K for 10.8 ks. In the present study, we focused on the lowest aging temperature of 498 K in the previous study, and investigating the effect of heat-treatment simulated brazing on the mechanical properties of the Cu–0.93 mass%Ni–0.24 mass%P alloy.

Jan 1, 2019

By Chr. Krause

Within the scope the collaborative research centre 599 (Medical University of Hanover, University of Veterinary Medicine Hanover, University of Hanover) the behaviour of the degradation of magnesium materials as implants are investigated by using animal experiments (rabbits). Thus extruded cylindrical pins from the magnesium alloys MgCa0.8%, WE43 and LAE 442 were implanted intramedullary in the tibiadiaphyses. The implantation duration was 3 and 6 month. After the explantation 3 point bending tests were carried out to investigate the possible changes of the mechanical properties. Clearly changes in dependence of the implantation duration could be determined. The three magnesium alloys show a decrease of the mechanical resistance with an increasing implantation time. To evaluate the degradation process, wich is the reason for the changes, micrographs and element analyses (EDX) have been accomplished after the 3 point bending tests. The micrographs show for all used magnesium alloys corroded surfaces but no preferred corrosion on the grain boundarys. The element analyses show beside a layer which is rich in calcium and phosphorus an agglomeration of rare earth elements in this layer. With these results a using of magnesium alloys as a material for implants can be announced.

Jan 1, 2006

By J. Gebhardt, D. McBride, C. R. Bennett, Croft. N., M. Cross

A comprehensive model of solution flow through heap leach systems requires a numerical solution with the ability to predict variably saturated-unsaturated flow through porous media domains that contain materials with spatially variable properties. The types of flow associated with stockpile leach processes lead to flow problems, such as infiltration into dry soil, drainage, perched water tables and flow through heterogeneous materials. Computational methods for modelling this class of flow behaviour are conventionally based on the classical Richards' equation. However, the governing equations are highly non-linear, difficult to solve, and require iterative numerical solution methods. The pressure-based form of the Richards' equation suffers from poor mass balance, while the mixed form can possess convergence difficulties. An adaptive transformed mixed algorithm is described, which reduces the non-linearity of the problem, optimizes the time step size, and provides a fast, numerically robust scheme that significantly reduces computation (or CPU) time. This method is shown to give fast, accurate solutions on a number of complex flow problems. The utility of this algorithm is illustrated through its implementation within the PHYSICA computational modelling software, which incidentally, provides a framework for a comprehensive heap leach model.

Jan 1, 2005

By John G. McCamis

The Maritimes Carboniferous Basin is the largest intermontane basin in the Appalachian Mountain System, occupying a total area of 57,200 square miles and containing up to 30,000 feet of late Devonian through Permian .sediments. Deposition began with continental elastics in late Devonian and early Mississippian. Marine deposition is represented by a limestone-evaporite sequence of late Mississippian age. Pennsylvanian and Permian continental rocks deposited largely in flood-plain and swamp environments complete the succession. Marine seismic data disclose several varieties of structure, both halokinetic and tectonic in origin. Recent exploratory drilling in the offshore part of the Basin encountered good reservoir rocks in the Riversdale sandstones, which also provided encouraging shows. The most likely source rocks of hydro~ arbons in the Maritimes Basin are shales in the Horton and Riversdale groups. Potential recoverable reserves of the Maritimes Basin are estimated to be 400 million barrels of oil or 7.8 trillion cubic feet of gas, based on the volume-of-sediment method of calculation.

Jan 1, 1973

By John Canterford

Quay Magnesium Limited (QMG) listed on the Australian Stock Exchange in late September 2004 having raised approximately A$30 million with the object of designing, constructing, commissioning and operating a 15,000 t/a magnesium alloy production facility in Nanjing, China, Site construction commenced in February 2005 with installation of all major components completed by the end of October 2005, Hot commissioning was simultaneously commenced with the final stages of installation, leading to the first stage of continuous ingot casting by mid November 2005, Since that time ramp-up to the name plate capacity has been undertaken, This presentation highlights some of the more significant technical and logistical hurdles that have had to be overcome in order to meet the high quality product specifications required by a range of QMG customers.

Jan 1, 2006

By L. J. Han, Y. J. Zong, S. Y. Wen, J. J. Wei

"Stress strain curves characteristics, deformation and strength properties, and failure process and characteristics of sandstone samples under different stress states were analyzed through triaxial compression tests carried on using TAW-2000 microcomputer control electro-hydraulic servo rock triaxial test system. The experimental results reveal that peak strength, residual strength, elasticity modulus and deformation modulus increase linearly with confining pressure, and failure models transform from fragile failure under low confining pressure to ductility failure under high confining pressure. Macroscopic failure forms of samples under uniaxial compression was split failure paralleling to the axis of samples, while macroscopic failure forms under uniaxial compression was shear failure, the shear failure angle of which decreased linearly with confining pressure. There were significant volume dilatation properties in the loading process of sandstone under different confining pressure, and then based on acoustic emission damage and volumetric dilatation damage the damage evolution properties of samples were analyzed, and damage constitutive model were established, realizing the real-time quantitative evaluation of samples damage state in loading process. INTRODUCTIONDamage is a phenomenon that micro defects in material under monotonic loading or reloading will lead to progressive decrease of the cohesion and damage of volume units. Many scholars at home and abroad have carried out systematic researchers on damage evolution characteristics and constitutive model of rock, and have achieved a series of remarkable results in this field. Lu Y.D. (2004) studied the complete stress-strain curve’s characteristics of marble under triaxial compression, and established the bilinear elastic-linear strain softening-residual ideal plastic damage constitutive model. Ren J.X. (2001) studied the damage evolution laws of coal and rock mass by computerized tomography triaxial loading system, realizing the quantitative evaluation of damage state. Zhang Z.L. (2011) studied the deformation and failure mechanism of strong weathered sandstone by triaxial compression test, and analyzed the damage evolution processes and established the damage evolution equations based on the density method. Li X.J. (2012) studied the microscopic damage characteristics of siltstone under triaxial compression by scanning electron microscope and digital image technology, and analyzed the statistical distribution characteristics of cracks azimuth angle, length, width. Zhou J.W. (2012) studied the strength, deformation and fracture damage characteristics of sandstone by uniaxial cyclic loading and unloading tests, and defined damage variable based on linear damage mechanics theory and acoustic emission (AE). Cao W.G. (2006) established a new damage model and a statistical damage constitutive model of rock under specific confining pressure according to the force of damaged part and undamaged part in rock on the base of statistical damage theory. Li S.C. (2014) studied the damage evolution characteristics in the whole uniaxial compression process of sandstone by electrical resistivity and AE, and proposed a status qualitative criterion for rock damage."

Jan 1, 2015

By Edouard Asselin, Tasawar Javed

This study was conducted as a part of ongoing work to characterize sulphide concentrate leach residues generated under CESL (Cominco Engineering Services Limited) and Vale pilot and demonstration plant medium temperature (150 °C) process conditions. Three different samples were analyzed. Derivative samples were prepared by extracting gypsum, sulphur and amorphous/poorly crystalline iron oxyhydroxide phases from the leach residues. Thermal behavior of the samples was studied by thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) in the temperature range 25 to 800 °C in both air and nitrogen atmospheres, with XRD analyses both before and after heating. Thermal transformation temperatures for different iron oxides/oxyhydroxides present in hydrometallurgical leach residues vary over a wide range which suggests the variable crystallinity of the phases. Raman spectroscopic analysis was carried out to help identify the type of iron phases in the residues. Furthermore, hydroxylamine hydrochloride (HaHC) and oxalate extractions were used to compare the fractionation of the amorphous/poorly crystalline iron phases in the residues. Given the compositions of the residues, any thermal events in the temperature range of 200 °C to 480 °C were attributed to amorphous/poorly crystalline iron phases.

Jan 1, 2014

By I. Farr, H. Wittens

"In 1989 and 1990 abnormally high levels of arsenic in ore from the Thompson Open Pit Mine threatened Manitoba Division's electro-nickel production. The paper will discuss our development of a flotation process to separate pentlandite and gersdorffite (the prime nickel and arsenic bearing minerals).The presentation will focus on the development of the process from conception, through lab and plant test work, to plant optimization and full scale production. The paper will conclude with the benefits and cost of the completed project.INTRODUCTIONRejection of arsenic from nickel sulphide ores was not a primary concern in the Manitoba Division until 1989. At that time increased production in the Thompson Open Pit mine, which contains high arsenic ore zones, resulted in excess amounts of arsenic in the Thompson Refinery affecting electro-nickel quality. This problem was resolved through extensive efforts by Mill personnel. The purpose of this paper is to familiarize the reader with- the Thompson Mill.- the mineralogy of the Thompson orebody.- the evolution of Ni/As separation in the Mill.- the metallurgical impacts of the separation on the Mill.- the importance of the separation to the Manitoba Division."

Jan 1, 1991

By D. S. Salonine

Aluminum alloys offer a wide range of capability with a unique combination of advantages that makes them the materials of choice for numerous products and markets. One of the most important applications is their use as the primary structure and outer envelope in aerospace vehicles. Wide and thorough studies on hot working and microstructure evolution of aluminum alloys have been made in Russia. The most important appear to be: - introducing the structure diagrams in strain rate - temperature coordinates which show areas of different microstructures (non-recrystallized, recrystallized, and mixed) after the hot deformation and the following heat-treatment for common aluminum alloys (Yu.M. Vainblat); - studying the press-effect ("structural effect" by V.I. Dobatkin); - learning the influence of hot worked substructure on aging mechanisms; conducting researches on press heat-treatment. These works allowed a deeper understanding and a better control of the mechanical behavior of aluminum products. Comparisons are made to equivalent developments in Europe and America.

Jan 1, 2004

By G. Guzman

In the framework of the optimization of Teniente Converter operation the new system of automatic flux feeding through gar-gun was implemented in the Potrerillos Smelter, Codelco Chile, Salvador Division. The control algoritm based on simple iron and silica balance adjusted by empirical coefficients was incorporated in the logical programmer. The programmer works in real time gathering information from the plant instrumentation events and introduced chemical assays of concentrate, slag and flux. Through the auto-tuning of the automatic operation the criterions of optimal flux dosage were determined. Four month of operation of the automatic flux feeding system demonstrated the stabilization of magnetite content in the slag in the narrow range from 18 to 20% and the decrease of flux consumption, corresponding to annual savings US$ 340,000. Additionally, the automatic system helps operators in the control room in fast determination of optimal fluxing and avoid the errors in flux dosage affecting the slag quality and its impact on refractory wear.

Jan 1, 2007