Search Documents

By M. S. Diederichs, G. Walton

"Developments in understanding the brittle fracture of rock over the past two decades ultimately led to the acceptance of a cohesion-weakening-friction-strengthening model as an appropriate strategy for the modelling of spalling using a continuum approach. This strength model has been used to replicate observed failure depths and geometries for a number of case studies in the literature, most notably the AECL Underground Research Laboratory in Manitoba. One thing which these case studies typically ignore, however, is the influence of rock dilatancy on the evolution of brittle failure. Physically, this phenomenon is the volumetric expansion of the rock due to fracture opening; numerically, this phenomenon is captured by the flow rule, which is often characterized by the dilation angle, ?. Accurately modelling rock dilatancy in conjunction with strength evolution is necessary both to predict the magnitude and distribution of ground displacements, as well as the exact depth and shape of the fracturing zone. Both of these factors can have significant implications for support design. This paper is focussed on presenting some of the recent developments in this field in the context of a number of numerical modelling case studies. Initially, a new model for the dilatancy of brittle rock is presented, as well as some representative data and model parameters for different rock types. Next, several case studies of highly stressed tunnels and shafts are presented. The results of continuum numerical models are presented to demonstrate the ability of the back analyses to match observed in-situ measurements and obtained. The predictive capabilities of the material model are also highlighted for cases where sufficient “a priori” information (such as laboratory compression testing data) are available. The issues of model nonuniqueness and strain-localization/bifurcation are also addressed."

Jan 1, 2015

By M. B. Kime

"A set of experimental batch leaching tests studied the effect of pH, time, temperature, and stirring speed on the relative Cu, Co, Ni, and Fe leaching yields of an oxidized copper-cobalt ore sample in an aqueous hydrochloric acid solution. The results were statistically analyzed and modelled using the structural equation modelling method. Models showed that Cu, Co, and Ni leaching yields were strong functions of the leaching time and leaching temperature, whereas the Fe leaching yield depended on the leaching temperature, stirring speed, and pH. Under optimum leaching conditions yields were 99.8% Cu, 82.4% Co, 91.3% Ni, and 30.6% Fe.RÉSUMÉ Une série d’essais expérimentaux de lixiviation en bâchée ont été menés pour étudier l’effet du pH, de la durée d’attaque, de la température et de la vitesse de brassage sur les rendements relatifs de lixiviation du cuivre (Cu), du cobalt (Co), du nickel (Ni) et du fer (Fe) d’un échantillon de minerai de cuivre-cobalt oxydé dans une solution aqueuse d’acide chlorhydrique. Les résultats ont été analysés et modélisés statistiquement à l’aide de la méthode de modélisation par équation structurelle (SEM, de l’anglais structural equation modelling). Les modèles ont montré que les rendements de lixiviation du Cu, du Co et du Ni dépendaient énormément de la durée d’attaque et de la température de la lixiviation ; le rendement de lixiviation du Fe, quant à lui, dépendait de la température de la lixiviation, de la vitesse de brassage et du pH. Dans des conditions optimales de lixiviation, les rendements étaient de 99,8 % pour le Cu, de 82,4 % pour le Co, de 91,3 % pour le Ni et de 30,6 % pour le Fe. INTRODUCTIONThe Katanga province in the Democratic Republic of Congo hosts the northwestern part of the Central African Copperbelt. This region abounds with large, rich deposits of sulfide and oxidized copper-cobalt ores. In general, the main valuable minerals present are malachite (CuCO3Cu(OH)2) and heterogenite (CoO(OH)). Common impurities found in heterogenite are Cu, Ni, Si, Al, Mn, and Fe. The substitution of Co by other cations (e.g., Cu, Ni, and Fe) has an influence on the crystallinity of heterogenite (Deliens, 1974). In general, well-crystallized varieties of heterogenite have lower impurity contents, whereas amorphous heterogenite types usually contain more impurities (Thys et al., 2009). Further, in heterogenite, Co can occur in the 2+ and 3+ oxidation states. The gangue generally consists of quartz (SiO2), talc (Mg3Si4O10(OH)2), kaolinite (SiO2·Al2O3·2H2O), limonite (Fe2O3·3H2O), and goethite (FeO(OH)). Oxidized copper-cobalt ores are often treated by hydrometallurgical methods, whereas sulfide ores are often treated by flotation or pyrometallurgy, depending on their grades. Hydrometallurgical methods typically entail selectively dissolving the metals of interest (Cu, Co, and Ni) in aqueous solutions (leaching), transferring the dissolved metals to an organic solution, and retransferring these to a second aqueous solution (solvent extraction). Copper and nickel are readily dissolved in an acidic aqueous media. In contrast, cobalt is difficult to dissolve, especially if it is present in the third oxidation state; however, this species becomes soluble after it is reduced to Co2+ (Mwema, Mpoyo, & Kafumbila, 2002; Kime & Makgoale, 2016)."

Jan 1, 2017

By O. G. Olvera, D. G. Dixon, E. Asselin, L. S. Quiroz

Dissolution rates of chalcopyrite (CuFeS2) were calculated using electrochemical impedance spectroscopy (EIS). The calculated dissolution rate decreased by a factor of 3.2 after the electrode was passivated. The results presented in this work indicate that the reduction of Fe3+ was the rate-controlling step for fresh CuFeS2 electrodes while the transport of cations within the passive film limited the dissolution rate for the passivated electrode. The transfer of cations at the electrode/electrolyte and passive film/electrolyte interfaces did not affect the dissolution rates of the fresh and passivated CuFeS2 electrodes, respectively. The catalytic effect of pyrite (FeS2) on the dissolution of CuFeS2 continued after the passivating treatment. The contact of fresh and passivated CuFeS2 electrodes with different FeS2 particles resulted in increased dissolution rates, due to an increase in the reduction rate of Fe3+.

Jan 1, 2014

By Wm. D. Jr. Sheldon

THIS paper presents practical data to aid in the selection of a mine ventilating fan, and outlines considerations to be made to ensure satisfactory operation and optimum efficiency of the fan. Much has been published on the general subject of mine ventilation, but the writer has found few specific data on factors and considerations which govern the selection of a fan-data which should be available to the operator if his fan is to give satisfactory service within the range of the high-efficiency portion of its performance curve and deliver the specified air capacity when operating against the anticipated range of resistance of the mine. The total quantity of fresh air furnished by the ventilation system must be adequate to provide, and to ensure at all times, safe and healthful working conditions in the mine. It is assumed that the mine operator is able to determine the air quantities required for the various parts of the mine.

Jan 1, 1941

By M. Fafard, D. Picard, J. -F. Bilodeau, G. Soucy

To simulate adequately the behaviour of a Hall-Heroult electrolysis cell, a finite element model must take into account the properties of each material. However, it has some lacking knowledge on the mechanical behaviour of materials, like the long-term visco-elastic (creep/relaxation) behaviour of cathode. A three-dimensional model is then proposed in this paper and will be ready to be implemented in the finite element code FESh++. The model was developed using the three-dimensional model based on thermodynamic of irreversible processes where the choice of the internal variables is based on a phenomenological approach. All parameters of the model are represented by constant constitutive tensors and the temperature and chemical dependencies are taking into account through scalar functions multiplying the constant constitutive tensor. The goal of the first part of this project was to determine the parameters of the threedimensional visco-elastic model at the reference state (virgin material at ambient temperature) of three different cathode materials. This paper presents the theoretical model and the results of creep tests at ambient temperature for the semi-graphitic carbon cathode.

Jan 1, 2006

By J. R. Giegerich

THE problem of dust control in metal mines has, of late years, received considerable attention. In 1932, a detailed study of dust conditions at the Sullivan mine was undertaken and, while there are no actual data available regarding conditions prior to that date, there has unquestionably been a great improvement as a result of the investigation and of the preventive methods adopted. In attacking the problem, three main factors were considered: first, and most important, how to prevent dust from being formed; second, how to depress or collect it if formed; and third-if unable to accomplish these-what precautionary measures must be adopted to prevent inhalation of this dust. Seven distinct methods of dust control are now practised at the Sullivan. Six of these are employed underground; they are tabulated below in the order of their relative importance. The seventh method is used in the crushing plants on the surface. (1) Improved ventilation (2) General use of water sprays and atomizers (3) Curtailment of secondary blasting during shift hours ( 4) 100 percent wet drilling-primary and secondary (5) Wearing of protective equipment (6) Change from carbide to electric lamps (7) Installation of dust collectors

Jan 1, 1936

By E. Thomson

This type of microscopic investigation, although still in its infancy, has already found practical applications in several different phases of mining activity. The study of the transparent minerals in rocks, by means of the ordinary petrographic microscope, has for long been a very useful supplement to observations in the field, but the opaque minerals, until recently, have had to rest content with a more or less superficial determination with the hand-lens or the blow-pipe. In a great many cases, particularly where the association of metallics has been somewhat complex, this has been entirely inadequate, and the determination of these opaque minerals under the micro- scope, has opened up a new field of scientific investigation that bids fair to surpass, in practical value at least, the micro-scopic determination of the rock-forming minerals. As the details of this kind of microscopy are possibly not entirely familiar to all mining men, it might be well to outline them very briefly before dealing with the practical directions in which this method may be applied. The ordinary petro-graphic microscope, with but one extra attachment, will serve for this work. A small reflecting device, called a vertical illuminator, is inserted immediately above the objective lens. This reflects the light down to the surface of the specimen and from here the light is directed up the middle of the microscope tube to the eye. As it is desirable that the maximum amount of reflection should be secured from the surface of the section, it is first polished and set in a position perpendicular to the vertical axis of the microscope.

Jan 1, 1924

By V. L. Eardley-Wilmot

Diatomite as prepared for the market is a fluffy, white powder, remarkably light in weight-it weighs only 10 to 15 pounds per cubic foot, or one-tenth as much as sand. Being extremely porous and inert, it is in large and increasing demand for insulation and filtration purposes, as general filler, and for many other uses. Structure Structurally, diatomite is quite different from any other known commercial material. It is composed of myriads of microscopically small, siliceous shells of diatoms which belong to a group of flowerless aquatic plants called algae. When these plants die, the siliceous remains sink to the bottom of the water and form beds of diatomite. Over 8,000 species of diatoms are known, named, and tabulated. The intricate scroll-work and patterns on many of these are one of the marvels of nature, and yet so small are they that from 40 to 70 million separate diatoms may be contained in one cubic inch of material. However, the size and shape of these diatoms, which vary greatly (compare Figures 5 and 6), have an important bearing on the commercial use of the diatomite. The diatoms in the majority of the known deposits are so typical of that deposit that, after a micro-examination, an expert can usually tell not only from what part of the world, but also from what particular deposit, the sample has come.

Jan 1, 1931

By Viraj Parekh, Kinnor Chattopadhyay, Sina Mostaghel, Xiao Zhang

Electric arc furnace steelmaking is a dominant approach in North America and controlling EAF emissions is a key issue today because of stringent permit limits imposed by various regulatory bodies. In the present study, an attempt has been made to mathematically model EAF emissions, and use the models as a predictive tool for fine tuning the process. CFD modelling has been used to model various fume release scenarios, and optimize the exhaust conditions for maximum capture. Thermodynamic calculations have been used to analyze various chemical reactions which lead to the emissions of hazardous air pollutants with special emphasis on Zinc, Lead and Manganese.

Jan 1, 2015

By M. Muinonen, R. Pandher

Royal Nickel Corporation is developing the Dumont Nickel Project, a large nickel sulphide deposit located near the town of Amos, Québec. The nickel occurs as pentlandite, heazlewoodite, and awaruite. The relatively low grade ore can be processed to a very high grade nickel concentrate, containing 29% Ni. The absence of copper and precious metals in the ore renders this concentrate amenable to processing by dead roasting in a fluid-bed roaster and smelting in an electric furnace to produce ferronickel for sale to stainless steel producers. Laboratory test work and conceptual engineering design was completed to demonstrate the amenability of Dumont concentrate to produce ferro-nickel.

Jan 1, 2015

By S. Boisvert

Risk-based Inspection (RBI) addresses the challenges associated with ageing plants by focusing the inspection effort on the process equipments with the highest risk, thereby improving plant safety and reducing inspection costs. The RBI methodology is commonly used in the oil industry through the API 581 standard. Since no such standard exists in the mining and metals industry, BPR-Bechtel has developed one using inspection data from process equipments in CEZinc. Models were developed for various damage mechanisms, such as uniform corrosion and stress corrosion cracking. The equations were organized into a user friendly software that facilitates the implementation process.

Jan 1, 2010

By J. Lui

Inco Copper Cliff Smelter commissioned two new Inco flash furnaces in 1991/1993 as part of its S02 abatement program. Each flash furnace is equipped with a fluid bed dryer. The ~ 12 wt% water content in the concentrate filter cake, flux, reverts and sludge is removed in the fluid bed dryer. The dry solids are discharged from the dryer together with exhaust gases into the baghouses where they are separated. The dry solids are transferred to four storage bins. In September 2003, for the first time since startup in 1991/1993, a large amount of elemental sulfur accumulation was discovered on the walls, roofs and floors of the outlet side of the baghouse chambers. Several baghouse fires were experienced during cleaning and conducting maintenance work in the elemental sulfur contaminated baghouses. Laboratory scale test work at the Inco research lab was conducted to understand the mechanism. A plant solution to minimize elemental sulfur formation was implemented with success. This paper summarizes the efforts to understand and minimize elemental sulfur formation in the baghouse chambers.

Jan 1, 2007

By W. Tse, D. Wong

Dense medium separation (DMS) is one of several preconcentration methods used for early waste rejection from run of mine ores at relatively coarse particle sizes prior to additional milling and beneficiation. DMS has been used extensively in the coal, diamond and iron ore industries but lab scale and pilot test work has demonstrated successful separation and upgrading of other minerals such as lead, zinc, copper and lithium based ores using DMS. This paper reviews historical dense media systems, results from the pilot scale Condor DMS system as well as associated laboratory heavy liquid separation (HLS) test work.

Jan 1, 2014

By Qing-Xun Low

Ni current collector has excellent electronic conductivity and mechanica, properties. However, nicke, cannot be used in H2S-containing syngas SOFCs due to sulfur poisoning and coking. Copper coated nicke, is prepared by electrochemica, deposition. XRD, SEM, and EDX techniques are used to characterize the samples. After high temperature treatment in syngas containing, the coated samples exhibit high resistance of coke formation and sulfur corrosion compared to pure nickel. Therefore, copper coated nicke, is a promising anode current collector for H2S-containing syngas SOFCs.

Jan 1, 2010

By G. S. Hume

In the transformation of carbonaceous materials, such as peat, to coals of various grades, the changes are known to be both physical and chemical and the grade of coal finally produced depends on the stage to which alteration proceeded. Those changes, which are frequently spoken of as the results of metamorphism, are due to pressure with accompanying heat and, according to the amount of metamorphism to which the sediments with the included carbonaceous beds have been subjected, there is a gradation from peat to anthracite coal, and even to graphite. The improvement in the quality of the coal as a result of metamorphism is due to an increase of the carbon content of the coal and a corresponding loss of the volatile materials. This rise in the quality of the coal according to the degree of metamorphism is well illustrated by the coals of western Canada. In the Plains area, where the deformation and the attendant metamorphism of the sediments is comparatively small, the coals are lignites, whereas in the mountains, where deformation has been severe, the coals are semi-anthracites. Sub-bituminous and bituminous coals occur in the intervening areas. The same general relationship between the quality of the coal and the degree of metamorphism holds true for the Appalachian basin of the United States, where there is a progressive improvement in the quality of the coals from west to east, that is, from an area of comparatively slight metamorphism to an area of marked deformation in the Appalachian Mountain region. But while it is true that this relationship holds in a general way, it has been found that the improvement in the quality of the coal is not always uniformly progressive, and there may be local variations such that an area containing coal with a carbon content indicating low or medium metamorphism may be surrounded by areas in which the coals are of higher grade. These local variations in many cases can be explained, and they in no way detract from the general rule that, in a region exhibiting a progressive betterment in the quality of the coal from an area of low metamorphism to one of more marked deformation, the quality of the coal, i.e., the amount of fixed carbon in the coal, may be taken as an index of the degree of metamorphism of the coal as well as of the sediments in which it occurs, It has been pointed out (') that certain coals, such as cannels, are unreliable indicators of the varying degree of metamorphism because of the nature of the material from which such coal was derived. Such coals, however, are not known in western Canada and their behaviour need not here be discussed.

Jan 1, 1927

By Michael K. O’Leary, William D. Coplin

"Risks from political instability and government policies restricting equity ownership, local operations and transfers of payments affect the profitability of foreign mining ventures. More than seat-of-the-pants judgments and old-boy networks are required to anticipate these risks and to take actions appropriate to offsetting them. A system for making political forecasts, called the Prince System, and a series of charts relaying risk s to a production of key minerals will be presented.IntroductionFirm s with extractive operations outside their home country do not have to be told that political stability and government decisions play a big role in the success o f their operations. The takeover of copper firm s in Chile during the Allende administration in 1971 and the recent decision by Venezuela to reduce Reynolds Metals equity share in a smelting operation from 50% to 28% are two examples of hundreds of events that have determined the profitability of extractive operations over the past decade. Both risks and opportunities for international firms seeking to produce and market raw materials are heavily affected by political conditions. While news of political events travel much faster than in the past and host governments are more clever in shaping the risks as well as the opportunities, politics has always been part of the mining business.What has changed is the need to be more systematic in approaching the assessment of political conditions and how it affects business. The increasing costs of extractive operations, the need for long-range planning, the importance of financial arrangements and the world-wide scope of man y firm s' activities require that the assessment be updated continuously and be comparable across different countries and different types of investments. Political risk analysis, the assessment o f macro-political changes and specific governmental decision s on the operations of extractive industries needs to become as systematic and integrated into corporate decision -making as economic analysis has become over the past two decade s."

Jan 1, 1983

"A numerical procedure based on Smoothed Particle Hydrodynamics (SPH) is developed for rock blasting phenomena involving multiple intersecting joints. In this procedure, an elasto-plastic damage constitutive model has been applied in the framework of SPH to simulate yielding response of the surrounding rock medium. In this paper, a square shape rock medium with centrally located emulsion explosive in a borehole is numerically blasted with and without the presence of two diagonal rock joints. The model is simulated by assuming all four sides of the rock medium as free surfaces. The paper elaborates the propagation of stress wave, expansion dynamics of gaseous products, and development of fracture, fragmentation of the medium and dissipation of energy due to damage.INTRODUCTIONDamage prediction of rock mass and its mean fragmentation size are of important to design blast parameters for a given explosive. Current blasting practice solely depends on empirical relationships between fragmentation sizes to those blast design parameters while mathematical descriptions of the physical laws governing the process of rock blasting are limited. A constitutive relationship based on properties of explosives and rock mass is of special interest because of its capabilities in describing the key features of rock fracture and fragmentation, resulting in understanding of the physical process involved in rock blasting. It is well known that blast-induced damage and fragmentation of rock mass occur due to detonation induced stress wave and product gas driven fracture propagation. Nevertheless, the fundamental mechanism of the failure process and the behavior of rock characteristics under these two different loading are not well understood in many cases, which are closely related to growth of fractures and interaction of cracks under different loading conditions.Continuum damage mechanics is considered to be appropriate to describe the failure process under such high-amplitude stress wave. Based on this approach, several theoretical models have been developed to analyze the dynamic damage of brittle material such as rock and concrete with microstructure (Chen, 1999; Taylor et al., 1986; Wu et al., 2004; Yazdchi et al., 1996). These models are mostly based on the theory of damage mechanics or fracture mechanics with some statistical treatment to incorporate random distribution of microcracks. In the application of fracture mechanics theory, sometimes it is difficult to estimate the micromechanical parameters such as crack density and fracture toughness in different modes. In this study, damage in rock material is evaluated according to the earlier model developed by Grady and Kipp (1980), which is a fracture model coupled with a material description for stress wave propagation to predict quantitatively fracture and fragmentation under explosive loading conditions."

Jan 1, 2015

By G. Chahal, L. C. So, S. Faucher, S. Mostaghel, S. -Y. Oh, S. K. Lee

Slag dumping and water granulation are the most commonly used slag treatment methods in the metallurgical industries. In both processes, water is present (by desire for cooling and dispersion or as a result of rain accumulation) and thus equipment and operations are designed to minimize and mitigate the risk of steam explosions resulting from the inappropriate contact of slag with water. Slag handling practices have, therefore, never been inherently safe; even good design, operation, and maintenance are not sufficient to prevent explosions or other related injuries from occurring. For slag handling to become inherently safe, our industry must eliminate the potential contact of water with molten slag. This is today feasible with the advent of dry granulation technologies, a review of which is presented, and it thus falls to us, in the metallurgical sector, to lead the way in their final stages of development and adoption. Furthermore, while slag dumping and water granulation offer some metallurgists the means of valorizing their slag as a by-product, for most, this is not the case. The energy in slag is lost through dumping and water granulation processes, and where slag is sold as a by-product, it is for its chemical content only. Here, dry granulation processes also offer advantages including the production of by-products which hold value in both their chemical content and physical properties and heat recovery. Dry granulation, therefore, augments the methods by which slag may be valorized over traditional processing methods.

Jan 1, 2015

By R. M. Oliver

THE Falconbridge property is almost completely covered with over-burden to a depth varying from 60 to over 200 feet. This overburden consists of grave], sand, and boulder, with bands of very fine silt, and there is usually a layer of water-bearing quicksand adjoining the r:ock surface. In previous shafts sunk at Falconbridge, this water-bearing quicksand had given considerable trouble, and further difficulties were expected in sinking No. 5 shaft, due to its greater size. The method described in this paper is the one adopted in sinking this shaft, after the matter had been carefully considered. No. 5 shaft is located 2,400 feet east of the old main No. l shaft, and is sunk in norite in the hanging-wall of the ore-body, which is, however, ? practically vertical to the deepest known intersection. The greatest depths of overburden prevail on the south side, or footwall, of the ore-body, and this, together.. with the fact that the footwall is wet and more badly fractured, swayed the final decision to sink in the hanging-wall. After the shaft site had been chosen and cleared, a diamond drill was set up a few feet away and a hole bored to a depth of 405 feet to test the over-burden and character of the norite bedrock. The depth of overbudren indicated by the hole was Ill feet, with the last 10 feet water-bearing. The norite was rusted and broken up for only a few feet below bedrock. A steel sinking shield (Figure l) was assembled at the shaft location, and consisted of 5/8-inch plate, 5 feet deep, built around a frame of 6 inch by 6 inch angle-iron, and braced at the corners with the same material. Twelve-inch I-beams held the shield as rigid as possible. In order to reduce binding against pebbles to a minimum, the shield was constructed with a 1-inch batter on all sides.

Jan 1, 1938

By André Piché

"Over the last ten years, several developments have been undertaken to conceive a machine capable of carrying out simultaneously all the mining tasks in hard rock deposits: cutting, mucking, hauling, ground support and dust control.The main advantages of continuous mining over conventional drill and blast is the elimination of the cyclical nature of the actual methods. Other advantages sought are improved stability of mine openings, higher productivity, lower costs, and a cleaner and safer mining environment. Noranda has con-tributed to these developments in a major way. As a member of HDRK, Noranda participated in the development of two mechanical continuous mining machines; the TM60 and the Wirth. Noranda also undertook a development of its own based on the utilization of electricity to break rock. This technology is called plasma blasting (PBT). The concept of plasma blasting is illustrated in Figure 1.When the operating voltage is reached (18kV), the energy is released through a high current switch (500k A) into a coaxial powercable. It is then delivered to the tip of an electrode inserted into a drill hole which is filled with an electrolyte (water). When the energy reaches the electrolyte, it is instantaneously transformed into a high temperature, high pres-sure plasma that produces a shock wave capable of breaking rock(1).After initial testing of the plasma blasting technology in the lab and in the feld, two experimental platforms were constructed. The first one, a test bench, was erected at the Noranda Technology Centre in Pointe Claire, Quebec.(2)The second one is a rock breaker prototype based on a standard diesel-powered carrier (Fig. 2). Each platform was equipped with a 300 kJ pulsed-power module.In 1993, the rock breaker prototype was used for an extensive series of tests in the field. During that campaign, over 700 oversized boulders were blasted. The results of the tests demonstrated that more durable components for PBT were needed. The test bench was then used to successfully develop and test long-lasting components (probe, switch, cable, connector) that can be adapted to industrial platforms leading to the commercialization of the technology."

Jan 1, 1996