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By G. T. Lapidus, J. Trejo-Gallardo

A phenomenological model is presented for leaching silver from silver sulfide contained in mineral particles with ammoniacal thiosulfate solutions of copper in stirred reactors. Experimental results were used to adjust the kinetic parameters of the model, such as the reaction order and velocity. The incorporation of the cuprous sulfide-silver sulfide equilibrium at the reaction interface allowed the prediction of the conversion limits for different reagent concentrations. The information obtained from the reactor model was later integrated into a heap leaching simulation, whose results adequately describe tendencies observed in column tests, with respect to variations in copper and thiosulfate concentrations. Comp

Jan 1, 2005

By M. Uszko

The climatic area in which Poland is located requires heating the ventilation air at intake shafts during the winter season. Air heating of the intake shaft should ensure safe operation of hoisting devices; while at the same time it also affects the conditions of the mine environment. The paper presents the issues of shaft heating in coal mines in terms of the mining law, the effect on the conditions of the mine environment and heating technology solutions used in the mines of Kompania Weglowa S.A. (KWSA).

Aug 1, 2013

By P. H. Rodriguez

The aquatic hazard classification system of the OECD and EU requires that sparingly soluble metal substances (SSMS) be tested using the OECD Dissolution/Transformation protocol in order to quantify the release of the ecotoxicological relevant species (dissolved ions). The SSMS category contains massive forms of metals, which due to their low solubility and slow transformation characteristics are a special case. The main factors that produce the release of metal into solution are exposed surface loading, pH, and stirring rate. The classification system at present prefers the use of mass loading as opposed to surface loading, in which case the amount of metal released will primarily be a function of the pH, and mass loading. Within the framework of the European Copper Voluntary Risk Assessment, coordinated by the European Copper Institute, we have proposed and developed a methodological procedure in which we demonstrate that surface area is an intrinsic property of a SSMS and we link the exposed surface loading to the toxicity reference value in order to obtain an aquatic hazard classification for massive metals. As example, the aquatic hazard classification for copper massive will be discussed. This approach is recommended for metal massives and metal powders.

Jan 1, 2007

By Yong Kang, Bingyuan Yan, Dandan Zheng, Xiaochuan Wang, Dengfeng Su, Dongyang Li

"According to the characteristics of rock mass and the directional cutting technology of water jet, a new idea of light shock controlled blasting with water jet slotting was put forward. Based on the fracture mechanics theory and the stress wave theory, the mechanism of damping with water jet slotting was analyzed. On the basis of the above, the evolution law of the pressure wave and displacement field during the blasting were simulated by FEM software ANSYS/LS-DYNA. The result shows that: the oriented slot plays a good role in orientation during the blasting, and makes the energy generated by gas released by the explosives gather at the tip of the oriented slot, which makes it easier for the main crack to expand along the oriented slot and indirectly reduce the stress effect on the protected object. Meanwhile, the energy of the seismic wave is reduced while transmitting through damping slot. Finally, compared with the normal blasting with damping ditch, the maximum acceleration is reduced by 15.62%, the maximum velocity is reduced by 52.99%, and the maximum displacement is reduced by 68.32%. INTRODUCTIONIn recent years, with increasing demand for energy and space, an increasing number of underground projects have been under construction. Drilling-blasting method, as a traditional main method for rock excavation, is still an indispensable means in the engineering construction. As is known, blasting vibration will cause the deformation and unstable of the existing building structures, so how to reduce the influence on the existing building structures caused by the blasting vibration has become the focus. Traditional shock absorption measures mainly include three kinds: the first one is pre-splitting blasting, the second measure is to change the parameter of explosive filling, and the last one is to excavate damping ditch between the protected object and blastholes. However, engineering practices show that: the protected rock may be damaged in the process of pre-splitting crack construction by blasting, the second measure is difficult in operating, and the third measure is troubled by large work quantity (Song Guangming, 1999; Lou Jianwu, 2004; Lou Jianwu, 2005; Li Xibing et al., 2008)."

Jan 1, 2015

By Reinis Sipols

AGENDA ? Introduction ? Definitions and Key features ? PEA - Preliminary Economic Assessments ? PFS ? Preliminary Fesibility Studies ? FS ? Feasibility Studies ? Costs and Risks ? Cash Flow, Economic Analysis and Reporting ? Recommendations for Improved FS accuracy INTRODUCTION ? The reporting of material information on mineral deposits has been governed by NI 43-101 legislation for almost a decade. ? The investment sector depends on the independent, professional QP to provide objective observations, comments and recommendations through all levels of geological, engineering and financial evaluation until a mine construction decision has been made.

May 1, 2013

By A. Gakwaya, P. Vachon-Joannette, P. Gagnon, J. Lévesque

"Predictive numerical methods are essential tools for reduced development cost and improved high performance designs of modern aircrafts. Their use leads to savings in terms of design cycle time and experimental trials. Composite materials subjected to impact loadings demonstrate various damage modes such as matrix cracking, fiber breakage, delamination and, ultimately, fabric fracture. Composite laminates are extensively used in the aerospace industry, and their damage modeling is complex due to their inhomogeneity and anisotropic behavior. Damage evolution affects both in-service properties and performance of these composites. In this work, the drop-weight impact test has been simulated. Using a material model that accounts for both delamination and intralaminar damage, laminates response is analysed using numerical simulations based on 3-D finite-element models of the commercial code Abaqus/Explicit. Experimental and simulation results are compared, in terms of energy absorption and contact force. The obtained numerical results show good agreement with experimental data.INTRODUCTIONAs primary aircraft structures are increasingly being made from advanced fiber-reinforced polymer matrix composites and are in general exposed to a variety of impact scenarios (bird, hail, debris etc.), an understanding of the impact event and the performance of composite materials during impact is important in the development of new structures. This work is focussed on low velocity impacts that typically occur when foreign objects hit the aircraft during maintenance or other on-the-ground operations. These impacts can cause non visible damage that affect the structural integrity of the composite components. While for metallic structures, damaging impact events typically leave noticeable dents due to plastic deformation, in contrast, for high strength carbon fiber reinforced composites, they can deform elastically to strain levels exceeding 1% and the internal damage can often occur without the formation of a visible dent. The identification and effect of impact damage on the performance of the structure is thus of great concern to the aircraft industry as the durability and damage tolerance of these composite structures are strongly influenced by the size of detectable internal damage."

Jan 1, 2016

By Kazutoshi Haga, Batnasan Altansukh, Yasushi Takasaki, Mohd Yazid Bin Abdul Razak, Atsushi Shibayama

"In this study, the volatilization behaviour of arsenic (As) and antimony (Sb) from arsenicantimony bearing minerals such as tennantite (Cu12As4S13)/tetrahedrite (Cu12Sb4S13) in copper ore was investigated using a roasting process. Specifically, the thermal decomposition of tennantite and the arsenic volatilization were investigated under nitrogen and air atmosphere. The roasting experiments were performed at temperatures ranging from 500 to 1,200oC and different retention times using a laboratory electric furnace. The results indicated that over 95% volatilization was achieved at 700oC. On the other hand, when the temperature increased to 1,200oC, volatilization rate of Sb reached to 90%. Therefore, volatilization of Sb requires high temperature compared to As. It suggests that As and Sb can be separated using temperature difference. Selective removal of As is possible at 700oC, subsequently Sb can be recovered as a volatilized product by increasing the temperature to 1,200oC. Meanwhile, volatilization of Cu and Fe was not observed on these conditions. The content of As and Sb in the residues obtained from roasting at 700 and 1,200oC was less than 0.3 and 0.75 mass%, respectively. The Cu content in solid residue at 1,200oC increased to 34 mass%. The clean copper concentrate with lower amounts of arsenic and antimony was obtained from the process. INTRODUCTIONRecently, arsenic (As) and antimony (Sb) contents in copper (Cu) concentrates are increasing year by year. Arsenic and antimony are present with Cu minerals such as enargite (Cu3AsS4), tennantite (Cu12As4S13) and tetrahedrite (Cu12Sb4S13) that associate with copper sulfides [chalcopyrite (CuFeS2) and bornite (Cu5FeS4)]. They are normally concentrated by flotation and treated in copper smelters. However, treatment of copper concentrates containing high amounts of arsenic and antimony by a smelting process is difficult due to environmental implications of toxic arsenic and antimony. As demand for copper continues to grow, the need to source copper from several types of resources including those that contain high levels of As/Sb becomes necessary. Therefore, a novel processes for the treatment of As/Sb bearing Cu concentrates are required. Reviews on copper resources such as enargite, tennantite and tetrahedrite containing high amounts of arsenic and antimony are covered widely in literatures by many researchers (Padilla et al., 1998; Welham, 2001; Vinals et al., 2003; Guo & Yen, 2005; Balaž & Achimovicova, 2006a; Filippou et al., 2007; Mihajlovic et al., 2007; Lattanzi et al., 2008)."

Jan 1, 2016

By M. Alvarez-Silva, A. Uribe-Salas, J. A. Finch, M. Mimezami

The point of zero charge (PZC) of electrokinetically anisotropic minerals (chlorite and serpentine) was determined using the Mular-Roberts (M-R) titration technique, and compared to isoelectric point (IEP) obtained from electrophoretic mobility measurements. To validate the M-R technique, the point of zero charge and isoelectric point of two isotropic minerals (alumina and silica) were shown to be comparable. For serpentine and chlorite, respectively the PZC was found at pH 4.3 and 4.6, while the IEP occurred at pH 3.2 and <3. Settling tests showed that the maximum settling rate, which corresponds to aggregated particles, for chlorite was around pH 3, i.e., close to the IEP; lizardite did not show a conclusive maximum.

Jan 1, 2009

By Trygve Høy

"Important stratabound lead-zinc deposits in southeastern B. C. occur in rocks that range in age from Proterozoic Helikian to Middle Cambrian. The Sullivan deposit, and similar but smaller deposits in the Sullivan area are the only important deposits that occur in clastic rocks with little carbonate content. The highly deformed and metamorphosed Shuswap deposits, of probable Hadrynian to Helikian age, are in mixed marble, calc-silicate gneiss and pelitic schist assemblages, rocks transitional between clastics and carbonates. Deposits in younger rocks, such as the Kootenay Arc deposits in the Lower Cambrian Badshot-Reeves Formation and the Monarch -Kicking Horse deposits in Middle Cambrian dolomite, are hosted by platformal carbonate rocks.An important regional control for the distribution of deposits appears to be a northeast-trending tectonic zone that crosses the Rocky Mountains and the Purcell Mountains just south of the Sullivan area, and projects southwestward toward the Salmo camp at the southern end of the Kootenay Arc. Pronounced northeast-trending gravity and magnetic anomalies, basic volcanism of Hadrynian age (the Irene volcanics west of Creston) and a preferred alignment of Mesozoic granitic rocks indicates that the zone coincides with deep crustal structures. Within the zone are dramatic and abrupt thickness and facies changes in Hadrynian Windermere rocks and lower Paleozoic rocks, and on the east side of the Rocky Mountain Trench in Helikian Purcell Supergroup rocks, indicating that block-faulting was active intermittently within the zone from Helikian through to lower Paleozoic time. Right-lateral and reverse movements occurred on northeast-trending tear faults within the zone in Mesozoic time."

Jan 1, 1982

By R. Baker

A novel electrochemical half-cell and corresponding working electrode were designed to evaluate the electro-catalytic activities of catalysts in an environment close to that of an operating proton exchange or polymer electrolyte fuel cell (PEMFC). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were employed using the novel cell to characterize various methanol electro-oxidation parameters that contribute to the overall reaction on a fuel cell anode. The effect of temperature on methanol oxidation kinetics was examined in the potential range of 0.31 to 0.65V (vs. NHE). The data was collected in the temperature range of 20 to 80°C. Based on the experimental analysis and literature data, an equivalent circuit model (ECM) for methanol oxidation was proposed and was used to fit the EIS experimental data. The experimental data and ECM electrochemical data was used to extract electrochemical kinetic parameters for methanol oxidation such as the exchange current density, Tafel slope, and energy of activation for the reaction. Kinetic data, especially at different temperatures, is very limited in the literature.

Jan 1, 2005

By S. Khoshkhooei

In this research, the effects of rare earth elements addition on thermal fatigue behaviors of AZ91 alloy were studied. Repeated heating and cooling cycles were applied on the samples at 170°C and 210 °C to develop thermal fatigue cracks, Crack growth mechanisms and microstructural influences were investigated by optical and scanning electron microscopy (SEM) as well as energy dispersive X-ray spectroscopy (EDS), Thermal fatigue behaviors were improved successively by addition of up to 2-wt% RE, This improvement is attributed to consummation of the aluminum of the melt by precipitation of the needle shape Al 11 RE3 phases, This process reduces the volume of Mg17Al12 phases and consequently decreases the brittle Mg/Mg17Al12 interfaces which are the main reason of weak thermal properties of the alloy at rather high temperatures, Further additions of RE, however, reduced the thermal shock resistance of samples by increasing in the mean length of the brittle needle shape phases.

Jan 1, 2005

By Kathy S. Kalenchuk

Damages have been observed in shafts, backfill infrastructure and the slick line at the Leeville Mine. Shaft damage (shearing and spalling of the concrete liner) is attributed to mine-induced rock mass deformations concentrated where regional faults intersect the shafts. Aggregate bin, mixer station and conveyor drive damage (shotcrete shearing, heave of concrete floor slabs and bending of a vertical steel beams) is attributed to rock mass squeezing induced by elevated magnitudes of the vertically orientated major principal stresses. Separation of the slick line has occurred do to extension of the stressshadowed rock mass immediately above the mined out areas. Three-dimensional numerical models have been developed and calibrated to simulated rock mass deformations with magnitudes similar to those believed to have produced the observed damages. By stepping through the mine sequence, models reproduce deformations at the same mining stage as when damage has occurred. Calibrated models have been used to forward project further damage over the remaining mine life.

Jun 1, 2012

By S. M. Fatemi-Varzaneh

The AZ31 magnesium alloy is considered as a promising alloy in various applications and industries. Furthermore, to design a proper hot working process (rolling, forging and extrusion), the assessment of hot working behaviour of the alloy is necessitated. Accordingly, the hot deformation behaviour of AZ31 alloy was studied through hot compression testing method. The latter was carried out in a wide range of temperature (523 K to 783 K) and strain rates. The obtained true stress-true strain curves and final microstructures were examined and a partial melting was realized at 740 K. It was concluded that the presence of liquid did change the deformation mechanisms thereby affecting the flow behaviour.

Jan 1, 2005

By A. Ghirian

Once cemented paste backfill (CPB) is transferred and placed into a mine stope, various coupled mechanisms will take place in the CPB material or structure. It will be subjected to strong coupled thermal (T), hydraulic (H), mechanical (M), and chemical (C) processes. Field studies have shown that the in-situ properties and performance of CPB differ from those obtained in the laboratory. This is mainly due to effects of the aforementioned coupled THMC mechanisms or processes. For a reliable and cost-effective design of a CPB structure and barricade, it is crucial to have a proper understanding of the THMC behaviour and evolution of CPB. Also, it is important to consider the effect of coupled THMC factors (e.g., self-weight pressure, drained/undrained and thermal conditions, pore pressure) while curing the CPB specimens. For this purpose, a laboratory setup is developed to investigate the properties of CPB materials. The setup is capable of curing CPB specimens (10 cm in diameter and 20 cm in height) under controlled vertical pressure (curing under stress) and various coupled THMC conditions, while continuously monitoring the evolution of total stress, pore pressure, suction, temperature, water drainage, chemical composition of the pore water and vertical deformation. Once the required curing time is achieved, the specimen can be extracted and then subjected to experimental tests of interest, such as those that determine the Unconfined Compressive Strength (UCS), shear strength parameters, saturated hydraulic conductivity and thermal properties. In this paper, we describe the developed experimental setup and present some results of the THMC behaviour of CPB under various curing stresses and rates of backfilling. The obtained results show that the THMC properties of CPB are strongly coupled due to several mechanisms, such as self-weight pressure, heat of hydration and suction development as a result of self-desiccation. The findings can assist researchers and practitioners to better understand THMC behaviour and thus design more cost-effective CPB structures.

Aug 1, 2013

By Guoxiang Chi

This paper consists of two parts: the first part describes the principles and functionality of the BsnMod program, and the second part presents preliminary application of this program to paleo-fluid flow modeling in the Anticosti Basin. The BsnMod program simulates fluid flow and heat transfer during the evolution of sedimentary basins through numerical solution (finite difference method) of three partial differential equations, which describe sediment compaction, fluid continuity, and heat conservation. It can be used to estimate the evolution of fluid overpressure, flow rate, and temperature during the basin history. The program was written in C++, works under Windows environments, and has a user interface allowing inputs in dialogues and outputs in both tabular and graphic forms. The program was applied to the Lower Paleozoic Anticosti Basin in eastern Canada. The basin history consists of a passive margin stage and a foreland basin stage. Preliminary simulation results indicate that no significant fluid overpressures were developed in the passive margin stage and during the early period of the foreland basin stage, but strong overpressures were developed within the foreland basin succession during the middle and late periods of the foreland basin stage. Fluid flow rates were generally slow, and thermal profiles were not significantly disturbed by fluid movement throughout the basin history. Potential source rocks of hydrocarbons were found in the foreland basin succession. The strong overpressures in the foreland basin succession could have been a major driving force for hydrocarbon migration from the source rocks to the underlying potential reservoir rocks.

May 1, 2001

By W. Dietzel

Fracture mechanics based techniques are used to gain insight into the phenomenon of stress corrosion cracking (SCC) and to develop guidance for avoiding or controlling SCC. From constant extension rate experiments under rising load or rising displacement conditions the susceptibility of high strength steels, aluminum, magnesium and titanium alloys to SCC and hydrogen embrittlement can be assessed. Such tests on pre-cracked specimens are also well suited for studying the mechanisms leading to SCC by employing appropriate models for the degradation of metallic materials which take into account the uptake of atomic hydrogen from the corrosive environment. Measurements of crack growth resistance curves using the crack tip opening displacement as fracture parameter can be compared with simulated R-curves obtained from modeling of the mechanism of hydrogen embrittlement. The materials investigated are a high strength steel and a magnesium alloy both exposed to environmental conditions which fostered the uptake of hydrogen.

Jan 1, 2010

By O. C. Rojas, J. Sanhueza, J. C. Vargas

Empresa Nacional de Minería (ENAMI) is dedicated to the promotion of small and mid scale Chilean mining industry. Paipote, ENAMI Copper Smelter, processes a variety of mineral products as the result of this promotion. The mineral products characterize a wide variation of copper, iron, sulfur and precious metals content as well as the significant dispersion in the content of impurities, such as arsenic, antimony and bismuth. The Smelter Modernization Program, initiated in1997, introduced a series of technological and operational changes. The development of operational planning and control strategies was necessary to optimize the blending of a wide variety of concentrates and the control of metallurgical processes in order to ensure the stable operation, fulfillment of environmental regulations and the quality of produced copper anodes. A permanent optimization process carried out in the last decade led to the permanent increase of the smelting capacity and the production of anodes and sulfuric acid. Additionally, introduced improvements affected the smelter efficiency and metallurgical recovery, demonstrating the possibilities of the optimization of a small smelting facility reflected in good metallurgical and economic results. This paper presents the smelter evolution, introduced technological and process control changes as well as incorporated new reactors and equipment as a continuous process of optimization.

Jan 1, 2007

By G. Anger, J. Enser, H. Antrekowitsch, S. Koch

Homogeneous chemical composition and microstructure are always necessary, but not always attained in practice. As-cast aluminium alloys tend to have a segregation microstructure. Features of the cast structure, which affect subsequent processing or properties, can be altered by the homogenization. The main task of the Department of Nonferrous Metallurgy was to investigate the effect of homogenization treatment on precipitation hardening of aluminium alloys 6061 and 6082. The effect of the solution heat treatment (SHT) temperature on the mechanical properties was also analyzed. The homogenized and non-homogenized rolling slabs were produced according to the usual conditions and methods. The metallographic investigations were carried out on the as-cast samples, after homogenization, after the hot and the cold rolling mill, and after natural and artificial ageing. Then, Brinell hardness measurements and tensile tests were conducted on both alloys in order to examine the influence of the homogenization.

Jan 1, 2006

By W. Basuki, B. Setyotomo, L. Hakim, R. Hendrajaya

Due to high crack sensitivity of slab product of gas and oil line pipe application, its steel making process and alloy composition were evaluated and then improved to overcome its critical solidification process and reduced surface defects. The study was conducted at Slab Steel Plant Krakatau Steel. The purpose was to improve slab surface quality by reducing surface defects so that the slab surface doesn&apos;t need to be totally repaired. The method applied was by performing plant trial process, which the secondary process parameters such as alloying method and the casting parameters such as casting powder selection, metallurgical cooling, mould level control, and superheat were continuously monitored and then adjusted to the surface quality of the product. Based on the calculation of Ferrite potential of the steel, the chemical composition was designed to achieve optimum casting parameters in order to avoid high shrinkage during solidification. The results of the study are decreased surface defect quantity, and smooth casting process. The quantity of crack decreased by almost 90%. The slab surface repairing was significantly reduced from 85. % to less than 10%. These new casting parameters and developed alloy composition are then used and standardized for the mass production of the steel.

Jan 1, 2005

By G. Song

Magnesium has excellent bio-compatibility in terms of its density, strength, elastic modulus and toxicity. However, due to its poor corrosion performance, so far magnesium has not been successfully used in the human body as a permanent implant material. Nevertheless, there is a possibility to utilize the low corrosion resistance of magnesium to make magnesium into a temporary implant component that can gradually dissolve in the human body after surgical region heals. This will avoid the secondary operation to remove the temporarily implanted component and the chronic inflammatory discomfort caused by the implant. This paper is aimed at exploring the possibility of using magnesium as a degradable bio-material through investigating the corrosion behaviors of pure magnesium and surface treated magnesium in a simulated body fluid (SBF) solution. It was found that magnesium corroded rapidly in the SBF solution, resulting in vigorous hydrogen evolution and a strong alkalization effect. Hence, it is impractical to use magnesium as a permanent implanted material or even a degradable implant. However, a proper anodizing treatment can significantly improve the corrosion resistance of magnesium, and hence slower down the hydrogen evolution and alkalization processes, which will allow to control the corrosion or degradation of magnesium at a desired rate in the human body. With a controllable corrosion rate, it is believed that magnesium as a degradable implanted material will be eventually achievable.

Jan 1, 2006