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By Patricia Dillon

EHS Management Standards Communication and Reporting (8) ! Establish processes for internal and external communications ! Designate responsibilities for communication with COI ! Report as defined by senior management ! Report annually to employees, shareholders, COI on EHS and social performance Community Rights and Public Consultation (9) !Identify COI?s and establish process to hear concerns !Acknowledge and respond to complaints !Support local communities !Plan for closure and conduct public consultation !New projects include identification of COI?s, concerns to be considered in design

May 1, 2004

By J. E. Dutrizac, R. J. C. MacDonald, J. B. O'Reilly

"Sometime around 3000 B.C., primitive metallurgists working in the mountainous regions of Asia Minor bordering on the Black Sea (Pontus) produced a soft, easily fused metal today known as lead. It appears certain that the first metal was made by reductive smelting of galena, but whether this recovery arose by the accidental inclusion of galena in the stones of a fire hearth or whether it occurred as a consequence of simple pyrometallurgical experiments on a series of interesting ""stones"" will likely never be known with certainty. The properties of galena, high metallic lustre, great density and facile cleavage, must have excited the ancients, and such ""stones"" would have been the object of primitive testing111 - Shortly after the discovery of lead, the ancients found that the controlled oxidation of this metal at elevated temperatures yielded smaller amounts of a more interesting material, silver. Again, it is uncertain if the production of silver by primitive cupellation techniques was the result of a fireside accident or the consequence of a deliberate experiment, but the important fact is that silver was produced shortly after the discovery of lead. The techniques for making lead and silver spread gradually throughout the entire civilized world, likely as a result of both technology diffusion and independent rediscovery. The physical properties of lead could not have been overly attractive to the ancients, but silver was a different matter altogether. The gleaming white lustre and relative immunity to oxidation quickly assigned silver to the precious materials category, a status it still enjoys. In early times, argentiferous galena was inevitably processed only for its silver values; lead was generally an unwanted byproduct and was frequently discarded as litharge (PbO) during the cupellation process. The silver was eagerly sought, however, and resulted in considerable mining activity culminating in the famous Athenian silver mines at Laurium at the southern end of the Athenian peninsula."

Jan 1, 1999

By F. W. Wellmer

"I would like to comment on the classification scheme of ore reserves based on geestatistical and economic parameters as proposed by Wober and Morgan in the CIM Bulletin, January 1993.In principle, a classification system that combines quantitative data for levels of confidence and errors with economic expectations must be welcomed. I would like to point out, however, two aspects of the proposed classification system which might create ambiguities, and therefore problems, by working with two levels of confidence and two kinds of block sizes. A normal classification scheme reflects the information density, the highest reserve category such as class A, or proven, or measured reserves having the highest density. This is not necessarily the case in the scheme of Wober and Morgan (1993), unless the definitions are amended.I. Assuming, as the authors do, that the estimation errors show an approximately normal clistribution, at the 95% confidence level, the standard deviation has to be multiplied by about 2 for the error and, at the 84% confidence level by about 104. Reserves (or resources) with the same or even higher information density than class A reserves, which at the 95% confidence level would not fulfill the required economic criteria at the threshold level, i.e. not qualify as ""ore"" at all, could be retained ""on paper"" to class B reserves by just multiplying the standard deviation by the factor 104 instead of 2, thereby narrowing the error.This statistical ambiguity was partly inherent in the old German classification scheme which used varying confidence levels and errors (GDMB 1956; Jahns 1959). In the new German scheme, which was later adopted in Austria in a moclified version, the level of confidence was therefore fixed at 90070 for all reserve categories (Wellmer 1983; ONORM 1989)."

Jan 1, 1993

By H. Somekawa

The fracture toughness and deformation structures an AZ31 magnesium alloy processed by equal-channel-angular extrusion (ECAE) were investigated. The average grain sizes of as-ECAE and annealed-ECAE alloys were 4.0 and 16.3 µm, respectively. The plane-strain fracture toughness, Kip, in as-ECAE and annealed-ECAE were estimated to be 27.3 and 23.5 MPam1/2, respectively, by stretched zone analysis. The fracture toughness indicated higher value with grain refinement. From optical microstructural observations in samples after fracture toughness tests, although deformation twins were observed in annealed-ECAE, no deformation twins were observed in as-ECAE. From TEM observations, the dislocations on basal and non-basal planes were activated in as-ECAE. With grain refinement, the activations of dislocations on both basal and non-basal planes were possibly related to the reduction in formation of deformation twins in as-ECAE. In addition, in comparison with direct extruded process, ECAE process was more effective method to improve the fracture toughness in magnesium alloys.

Jan 1, 2006

By E. Ghali, J. F. Dorion

This paper presents the results of on-going investigations on the influence of corrosion on the performance of support systems in selected underground gold mines. Rock support is exposed to various conditions that can be aggressive. Samples of corroded support were analysed using SEM and photomicrography to determine the main corrosion forms. Tests are on-going in controlled corrosion chambers to qualify and quantify the impact of rock and minerals particles on steel corrosion. As more data become available these relationships can lead to useful information on the choice of support systems and reliable estimates of their longevity.

Jan 1, 2011

By S. M. Bulatovic, D. M. Wyslouzil, K. R. Rawlings

"The suitability of a new organic reagent DS20 as a depressant for oxidized and carbonaceous pyritic lead-zinc ore from Nanisivik Mines Ltd. has been evaluated in the laboratory and in the plant.The depressant DS20 is a mixture of Lignosulphonate-Dextrin-Quebracho and was developed specifically for depression of highly oxidized and carbonaceous pyrite.The laboratory test work indicated that the poor metallurgy resulting from the oxidized ore could be improved to normal plant performance by the addition of the DS20 depressant with the existing plant reagents. The laboratory data suggested that lime consumption could be reduced when using DS20.In this paper, the development work and the plant trials with DS20 are described.INTRODUCTIONNanisivik Mines Ltd. treats approximately 2000 tonnes per day of lead-zinc massive sulphide ore, containing currently 1% Pb and 9% Zn. The concentrator operations have been described previously (1,2) and typical metallurgical performance is detailed in Table I.The concentrator flowsheet (Figure No. 1) and the standard reagent scheme (Table No. 2) demonstrate the relative simplicity of treatment of this coarse grained ore.A recently discovered satellite orebody - Area 14 - containing 2% Pb and 12% Zn was brought into production in October 1983. This ore had been oxidized to varying degrees by ground water; the pyrite mineralization was found to be very fast floating and a carbonaceous constituent present in higher than normal proportion also affected flotation. The simple high lime addition could not control the pyrite, and very low grade lead concentrates resulted; zinc metallurgy was also affected by this oxidized condition (Table 3)."

Jan 1, 1986

By W. Andrew Falls

Although we have yet to reach the midway point in the decade, the copper concentrate market has already witnessed some of the most volatile swings in history, moving from record high treatment and refining charges in 1991-92 to historic lows, in real terms, during the past year. What has been the cause for such volatility? By and large the swings can be attributed to factors of supply and demand in the "custom" copper concentrate market. For example, two relatively recent events which had a major impact on the supply-demand balance were the shutdown of the Bougainville copper mine in Papua New Guinea in 1989 due to rebel insurgency and the startup of the La Escondida mine in Chile in 1992. The first event, threw a balanced to slightly surplus concentrate market into a substantial deficit, forcing treatment terms down as smelters, caught short by the loss of concentrate supplies scrambled to cover their positions. The second event, brought over 300,000 mt per year of new copper in concentrate to the market, more than reversing the losses from the Bougainville shutdown. In combination with other additions to mine capacity via new mines or expansions, the custom concentrate market moved into a huge oversupply in 1991-92 and many mines found themselves unable to place uncommitted tonnage. But even this event was quickly overcome by the use of underutilized capacity at non-traditional buyers, such as those in the C.I.S., Zambia, or those which were not traditionally buyers of custom materials. All of this has happened in the space of five short years, a mere snapshot in the history of the market. I'll return to these points a little further on, but first I would like to review the fundamentals which govern the copper concentrate market.

Jan 1, 1995

By Steve R. McCutcheon, Cees R. Van Staal, John P. Langton, Leslie R. Fyffe

The volcanic-dominated Tetagouche Group in northern New Brunswick contains numerous massive-sulfide deposits and intimately associated metalliferous sediments. The massive sulfides are generally hosted by Llanvirnian-Llandeilian volcaniclastic sedimentary rocks of the Nepisiguit Falls, Patrick Brook, and Boucher Brook formations. These formations are intercalated or closely associated with rhyolitic-dacitic flows and/or domes, and minor continental tholeiites of the Flat Landing Brook Formation. Pyroclastic rocks are relatively scarce in the silicic volcanic complex. Tuffites and epiclastic sandstones, of the Nepisiguit Falls and Patrick Brook formations, respectively, generally occur along the fringes of the silicic volcanic complex. The flows and tuffites are intruded by quartz- and feldspar-phyric rhyolite (porphyry) dykes, sills, and domes. Although the volume of the silicic volcanic complex is large, evidence for a previously proposed collapsed-caldera model is lacking. On the basis of host-rock type and stratigraphic position, the sediment-hosted massive sulfides have been divided into three groups: the Brunswick-, Caribou- and Halfmile Lake-type deposits. Syngenetic feeder pipes and asociated alteration zones are generally not present beneath the Caribou- and the Halfmile Lake-type deposits and, if present at all, are poorly developed underneath the Brunswick-type.

Jan 1, 1992

By R. T. Erskine

"IntroductionIn this paper it will not be possible to cover all details of the reagent systems at Brunswick Mining and Smelting but it is hoped that a description of the evolution of these systems will be of some benefit. The concentrator of Brunswick Mining and Smelting located near Bathurst, New Brunswick was originally designed as a 3,000 ton per day operation but before construction commenced was uprated, with 4,500 tons per day being treated by the summer of 1964. Development of the open pit at another ore body five miles away was initiated in 1965 and additional concentrator and crusher facilities went into operation in September, 1966. Present total daily throughput is over 8,000 tons per day. The ore at Brunswick is very high grade but mineralization is very fine grained and requires grinds generally over 75% minus 400 mesh for liberation. The amount of surface exposed using grinds of this order understandably requires great quantities of reagents, Reagent mixing systems for the original concentrator allowed only for batch mixing and were very expensive in labour cost especially.During the first three years of operation total number of men employed in reagent handling reached a peak of four men per shift and six men on dayshift unloading cars for a total of 22 men. At present only one man is employed on shift, and four men on dayshift take care of unloading and mixing reagents, a total of 8 men. The man on shift is almost entirely occupied with checking feeder operation, flow rates, and head tank levels. Most commonly used reagents are tabulated in Fig. 1 showing average monthly and daily requirements in the Brunswick operation as well as pounds per ton of mill feed as found in 1969. It is very obvious that with over seventeen tons each of lime and soda ash and six tons of copper sulphate used each day, opening of bags and mixing batches of solution is an inefficient undertaking."

Jan 1, 1970

By René G. del Villar, Jules Thibault, René del Villar

"Some key control variables of industrial processes, associated with product quality, often cannot be measured directly or frequently enough to establish adequate control. In such cases, it is possible to use available measurements to provide a prediction for these process variables and use them in a control strategy, thereby giving rise to what is now commonly called a softsensor.In some industrial grinding circuits, the on-line particle size analyzer is shared between various sampling points. Therefore, for a given location, the actual measurement is only available every 10 to 20 minutes, a delay which is unacceptable for automatic control purposes. To alleviate this problem, a softsensor based on an artificial neural network has been investigated. First, the structure of the neural network and different schemes for the training process are analyzed. Then, the performance of the neural network softsensor is compared with other inferential methods such as ARMA models and Kalman filters.IntroductionGRAHM, French acronym of the Research Group on Computer Applications in the Mineral Industry at Laval University, began in 1990 a research project on Knowledge Based Automatic Control (KBAC). This project, sponsored by a consortium of eight mining companies and the federal and provincial governments, seeked to screen advanced (knowledge-based) methods for data processing (filtering, mass balancing, etc) and automatic control (model-based) for their use in the mineral processing operations and the transfer of the project results to the sponsor companies.In parallel to more academic research work, a number of case-studies have been undertaken with the cooperation of partner companies. Among such works, a very successful one has been the design and installation of a new control strategy for one of the Kidd Creek (Falconbridge Ltd.) grinding circuits. This project was related to the evaluation of a number of control strategies and the implementation of one of them, as selected by the plant management, in the concentrator.A total of sixteen control schemes were evaluated on one of the dynamic phenomenological simulators developed at GRAHM, a trademark of this research group [ l]. The calibration of the simulator models was done based on industrial data gathered by GRAHM and Kidd Creek personnel. Then, the simulator was used to test the performance of various PID-based control schemes, designed to achieve the control objectives set by the Kidd Creek personnel. The best scheme proposed called for controlling the cyclone overflow particle size by manipulating the water addition rate to the cyclone feed box and the circulating load by manipulating the circuit ore feed. The particle size analyzer (PSI-200) available for monitoring the product size, was unfortunately shared (multiplexed) among various streams of the plant, which meant a 14 min delay between two consecutive readings for any particular stream. This induced the plant personnel to choose an alternative control strategy, one which controlled the cyclone feed density instead of the cyclone overflow particle size."

Jan 1, 1996

By P. Chu, J. A. Finch, R. Li

"Bubble size plays a key role in flotation. In this paper, we examine the possibility of using passive acoustic sending to determine bubble size. Software was developed based on Short Time Fourier Transformation (STFT) to analyze the frequency of the acoustic signal emitted from the bubble formation event. Bubble size was determined from the Minnaert frequency. The acoustic-determined bubble size responded to reagent dosage, but was less sensitive than that given by imaging. The constraints of the current acoustic approach are discussed.INTRODUCTIONBubble size is an important factor affecting flotation performance. It determines the maximum available surface area for collecting and transporting mineral particles. Of interest for process control (Gorain, Franzidis, & Manlapig, 1995), it can be determined by several techniques, such as image analysis (Grau & Heiskanen, 2002; Hernandez-Aguilar, Gomez, & Finch, 2002); conductivity (Barigou & Greaves, 1992); drift flux analysis using gas rate and gas holdup measurements (Banisi & Finch, 1994); and optical sensors (Randall, Goodall, Fairlamb, Dold, & Connor, 1989). However, all these techniques have drawbacks.Acoustic analysis of the oscillatory behaviour of bubbles to extract bubble size is another possibility (Leighton & Walton, 1987; Pandit, Varley, Thorpe, & Davidson, 1992; Al-Masry, Ali, & Aqeel, 2005; Manasseh & Ooi, 2009; Leighton & White, 2012; Spencer et al., 2012). The fundamental basis is the work of Minnaert (1933) who first correlated the bubble size with its natural frequency, Equation 1:"

Jan 1, 2016

By J. Duriez, L. Scholtès, F. V. Donzé

"Fracture propagation process in brittle rock is investigated by means of numerical simulations performed with an adapted formulation of the discrete element method. The progressive failure mechanism is simulated through the breaking of the bonds making up the cohesion between the elements constituting the simulated medium. The use of appropriate contact laws associated to a near neighbor interaction feature provide the model the ability to reproduce fundamental characteristics of brittle rock behavior such as, for example, high values of the tensile to compressive strength ratio. Great attention is given to accurately describe the properties of the pre-existing joints or faults in the model. A specific joint model gives the possibility to define a tailor-made behavior of the discontinuity surfaces without suffering from discretization bias.Compression test simulations are performed on pre-flawed samples and compared to experimental results in order to validate the numerical approach for describing the initiation and propagation of fractures in brittle rock under mode I+II loading. It is shown that the crack mechanical parameters can greatly influence the fracturing pattern, in particular its frictional properties. Overall, the numerical simulations reproduce fairly well the failure patterns that are obtained experimentally.The discrete model is then used to study mode I+III loading to give an insight into fracturing problems occurring at the scale of the continental crust. The ability of the model to support mechanically the physical modelings performed with wet clay or sandbox is shown. As an example, the model is used to track the development of a twist crack system (wrench fault) through the nucleation and coalescence of microcracks."

Jan 1, 2015

By Ken Major, Anita Marks, Craig Sams

In 2007 Copper Mountain Mining determined that there were sufficient resources to consider reopening the Similco Mine near Princeton, BC. The mill facility that had been built by Newmont Mining in 1972 was closed in 1996 and all of the process equipment removed. The mill had been built on the west side of the Similkameen River to facilitate mining of the Ingerbelle Deposit. In 1980 construction was completed on a primary crusher and cable belt to deliver ore across the Similkameen River from the Copper Mountain deposit to the Ingerbelle mill. With the decision to restart mining of the Copper Mountain deposit, the decision was made to design and build a 35,000 tpd grinding and flotation mill near the mining operations. This paper discusses the application of historical operating data for the selection of the mills for the new grinding circuit and provides an overview of the grinding circuit design.

Jan 1, 2012

By C. B. Webber, L. S. Diaz

"The paper presents the approach taken by Craigmont Mines to grinding circuit control. A detailed description is given of a fully automatic control system which bases its control actions on the continuous measurement of particle size in the cyclone overflow stream. The control system holds a specified particle size in the cyclone overflow, and grinds rod mi 11 ore feed at increased rates. The principles of operation of the system used for continuous measurement of particle size are described, end the improvements in mill throughput and copper recovery over several months of continuous operation are presented.INTRODUCTION Craigmont Mines Limited is located in the south-western interior region of the province of British Columbia, approximately 230 road miles north-east of Vancouver, and ten miles west of the town of Merritt. A moderate climate, good roads and service facilities provided by the Canadian Pacific Railway, Inland Natural Gas Company, and the B.C. Hydro and Power Authority, have provided a very favorable mine and plant site.The preliminary metallurgical design of the Craigmont mill was based on the test results of samples obtained from the original 2500' level drift during 1959. Pilot plant runs and other research testing for design pur¬poses were conducted at the Canadian Exploration Ltd. Laboratory, at Salmo, B.C. The design flowsheet was altered in progressive stages from 2,000 to 3,000, and finally 4,000 tons per day as the ore reserves became better defined. Construction work on the 2,400' level mill site commenced in late 1960. The official opening of Craigntnt Mines Limited took place on September 15, 1961, a little over two years from the time of the metallurgical assessment of the original ore samples.Mill throughput to date has varied widely both on a daily and a monthly basis, due to the varying hardness of the mine ores. The grindability af the ore appears to be related to the oxide iron content, which varies from lows of 9% to highs of 20%. Daily tonnage has ranged from 5,000 tons per day with 10% iron in the feed, to 6,000 tons per day with 20% iron feeds."

Jan 1, 1973

By Jinsuo Zhang

Investment in coal resource development is affected by a variety of uncertain factors. Investors can make a flexible, strategic decision to achieve the value of risk implicated in those uncertain factors. Therefore, based on real-option theory, we identified key uncertain factors that affect a coal resource investment project, and revealed the formation mechanism of option value in coal resource developing investment project. Then, a multi-factor decision making model was established for a coal resource development investment project with random changes of coal price, interest rate, convenience yield and production cost. Finally, we tested the model and analyzed relevant parameters by applying living data. Our results indicate this model reflects the value of risk implicated in uncertain factors for coal resource development investment, and is able to determine a critical point of decision making change when coal price and production cost varym respectively. By means of parameters analysis, the convenience yield has a positive effect on the project value. The interest rate has a negative effect.

Aug 1, 2013

By G. G. Li

"A dynamic ventilation-modeling package, VREX, was used to simulate the mine activities through tracking the equipment movements in underground workings and determine the airflow demand for a new production scenario in a ventilation-on-demand (VOD) system. It incorporates the mine development data from a discrete event simulation and balances the ventilation network using the CANVENT ventilation solver. A case study was performed to demonstrate the capabilities of the software, evaluate the performance of the network and determine the potential energy savings for implementing VOD in a deep mine operation.INTRODUCTIONThe ventilation cost of an underground mine can be significant—up to 50% of the mine’s energy consumption could be used to run fans and provide heat/refrigeration to meet the specified production environment for workers and equipment. The VOD system has proven to be more efficient in operating the fans and supplying the amount of air corresponding to the mine activities taking place in underground workings (Hardcastle, Kocsis, & O’Connor, 2006). In order to properly solve and evaluate the VOD system, a dynamic ventilation modeling software VREX—the ventilation rules engine has been developed to simulate the mine activities and determine the airflow demand for each production scenario within an operation period (Dasys & Cameron, 2011).VREX is a decision support tool, backed by the CANVENT mine ventilation solver (Li, Kocsis, & Hardcastle, 2009), for determining the outcomes of network configuration changes over time. The software incorporates the mine development data with ventilation modeling through the discrete event simulation (DES) performed by SimMineTM. As it simulates the air requirements for different vehicles and activities, VREX can evaluate both the performance of the ventilation system and the potential economic benefits of making operational or technological changes (Pritchard, 2010). For example, the model can be used to assess the economic and environmental impacts arising from modifying regulations to support the use of electric or lower emission vehicles. The combination of DES and ventilation modeling provides a new technology to generate the production scenarios according to mine schedules and activities and to determine the potential benefits for various levels of ventilation control, such as time interval and work shift change."

Jan 1, 2019

By T. Fliß

The protection of natural resources is of essential importance in times of rapidly increasing populations and resulting shortage of agricultural land. Soil and groundwater resources play a central role for the production of food or feed of any kind. The intensive agricultural and environmentally friendly use of these resources must ensure sufficient income and sustainability of life for future generations. Mining projects often represent a particularly deep intervention into ecosystems due to their size as well as the most expensive treatment processes. Conventional mines comprising of shafts and developed mining fields require the stockpiling of waste rock and in particular to potash mining, the discharge of brines from raw salt processing. In contrast, mining operations based on the solution mining method can be operated without major environmental impacts and lower security risks. While the solution mining for the production of rock salt finds application since more than 500 years, exist a procedure to produce potash using solution mining only since the 1980's. For solution mining drill holes are used to exploit the potash, launched from the surface into the deposit. The exploitation of the raw material occurs by the dissolution of the potash injecting solvents and creating so-called brine caverns. Currently, a number of mining projects in Carnallite deposits by the solution mining method are in progress around the world. Often these projects are located in sensitive ecosystems. K-UTEC project and support actual a solution mining operation of a Carnallite deposit for a Chinese customer in South-East Asia. This work comprises a comprehensive geological and geomechanical modeling as well as stability analyses. Furthermore the cavern design and brine field layout as well as the planning of the brine processing and the plant design. The present paper introduces this project as a case study. The application of a special solution mining procedure and processing design ensures an emission-free mining operation (Zero Disposal Plant). The emission-free operation is achieved by utilizing the full extent of the caverns to dispose the liquid solutions from processing. The presentation of principal salt processing and technical equipment will be rounded by information about the geology of the deposit. Since the deposit includes a number of sensitive minerals, such as Tachyhydrite and Bischofite the presentation comprise a lot of interesting items with special view at the brine field operation. K-UTEC designed and delivered a special blanket measuring system and a well cement according the request of the customer. K-UTEC, a research and engineering company with more than 60 years of experience in the sector of potash and rock salt mining, developed the world's first solution mining operation for Carnallite in Germany more than 30 years ago. In recent times K-UTEC served in different solution mining projects worldwide, with special view at the environmental impact, as well as the optimal utilization of the deposits.

Aug 1, 2013

By Jan Drzymala, Przemyslaw B. Kowalczuk

"Flotation is possible when the forces operating between a bubble and the attached particle are properly balanced. There are many forces operating in the bubble-particle aggregate. The magnitude, location and direction of the forces depend on the type of process. The simplest arrangement in flotation is when a spherical bubble is attached to a spherical particle and both are immersed in water. In such a system there are four essential forces which shape the stability of the bubble-particle aggregate. They are excess pressure and interfacial solid/liquid, solid/gas and liquid/gas forces. A proper analysis and balance of the size, location and direction of these four principal forces lead to a general equation delineating the stability of the spherical particle–attached bubble system. Specific cross sections of the system and solution of the general equation lead to different relationships including the Young formula as well as the well-known geometrical relation between contact angle, particle and bubble radiuses. The arrangement of forces in the proposed graphical representation of the Young law is different from that presently used in literature for a bubble attached to an unmovable solid particle. Many real solid/liquid/gas systems are more complex due to the presence of additional forces which change the regular curvature of the liquid/gas interface leading to advancing and receding contact angles.INTRODUCTIONThere are numerous papers (Athukorallage, Aulisa, Iyer & Zhang, 2015; Chau, Bruckard, Koh & Nguyen, 2009; Drzymala, 1994; Lubarda, 2012; Pellicer, Manzanares & Mafe, 1995; Wang, Cui, Zhou, Xu, Sun, & Zhu, 2014; Young, 1804) and books (Davies & Rideal, 1963; Defay & Prigogine, 1966; Lee, 2013; Lyklema, 2000) dealing with the solid/liquid/gas system. Many of them concern the three involved phases having the shape of a sphere or spherical cap and the formed contact angle. The contact angle is usually measured through the liquid phase and can be either smaller or greater than 90o. The essential part of these publications is a graphical representation of the system with the Young equation shown as a result of balance of only three forces that is the excess Gibbs (or Helmholz) free energy per unit area of the three involved interfaces (Davies & Rideal, 1963; Defay & Prigogine, 1966; Israelachvili, 1985) (Figs. 1a-c). The Young equation, when the gravity force/buoyancy is neglected, is:"

Jan 1, 2016

By N. Moelans, I. Bellemans, K. Verbeken

In this work, we present a phase field model to simulate the facetted crystallization of Fe3O4 in a quaternary FeO-Fe2O3-Cu2O-SiO2 melt under different partial pressures of oxygen. An important focus in creating more realistic phase field models is the incorporation of the thermodynamic driving forces in multicomponent multiphase-field models by coupling to thermodynamic databases. The diffusion of FeO, Fe2O3 and Cu2O is considered. The ratio of FeO/Fe2O3 at the upper boundary is in equilibrium with the oxygen fugacity of the atmosphere, while conserving Fe. Two-dimensional simulations are performed with different varying oxygen fugacity in the atmosphere. For the considered composition range, the growth velocities of the spinel crystals increase with decreasing oxygen fugacity. INTRODUCTION Crystallization of silicate melts has its applications in geology, pyrometallurgy and glass making. In pyrometallurgy, the solidification of slags influences the freeze lining behaviour (Campforts et al., 2007) and the cooling of slag after tapping (Durinck, Jones, Blanpain, & Wollants, 2008). Modeling of silicate melt crystallization is frequently done on the macroscopic level, using thermodynamic equilibrium calculations to determine the fractions of all phases as a function of temperature. The Factsage software and database package (Bale et al., 2016, 2009, 2002) already proved its usefulness in pyrometallurgical applications, for example to model the phase mixture after solidification of a stainless steel slag (Durinck et al., 2008). Crystallization of phases typically results in complex morphologies on the mesoscale, e.g. dendrites or facetted growth. On this mesoscale, the phase field concept has proved to be a very powerful tool (Moelans, Blanpain, & Wollants, 2008) for modeling crystallizing microstructures, because it can treat arbitrarily complex interface shapes with minimal mathematical complexity. In contrast to macroscopic models, the diffusion profiles and crystallization kinetics can be described as well as the morphology of individual crystals. First, Kobayashi (Kobayashi, 1993) simulated a growing dendrite in a pure undercooled metallic liquid. Then, Warren and Boettinger (1995) simulated a dendrite in an isothermal system considering a binary alloy. The extension to multi-phase systems was done by Steinbach et al. (1996). This was further extended by Tiaden, Nestler, Diepers, and Steinbach (1998) to a framework with coupled diffusion and phase field equations in multi-component systems.

Jan 1, 2019

By Hani S. Mitri

Strainbursts in brittle rock are common to deep underground mines. The state of stress at the boundary of mine openings is dictated by a biaxial stress/loading condition. This paper reports the results of a series of biaxial compression tests carried out on 100 mm cubic samples of norite rock, under different horizontal-to-vertical stress ratios. The results indicate that the biaxial compressive strength is considerably higher than the uniaxial one. It is found that the norite sample behaviour under biaxial loading mirrors field behaviour where shearing and progressive spalling of the opening boundary are observed prior to strainbursting. Sample failure is initiated by rock spalling at the sample free faces, i.e. in the plane of biaxial loading. Finally, it?s the out-of-plane shear failure mechanism that causes the sample to collapse. Shear failure takes place violently and abruptly and is accompanied with considerable audible noise.

Apr 1, 2005