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By Ahmad Ghahremaninezhad, Noelene Ahern, Yeonuk Choi

Arsenic (As) is a toxic element and is a major contaminant in the extraction processes of some metals (e.g. gold and copper). Due to the toxicity of arsenic species, its removal from As-containing streams from extractive metallurgy processes and safe disposal is absolutely necessary. For nearly complete removal of waste arsenic species from metallurgical process streams, it is required to have arsenic in its pentavalent state (As5+ species). This study presents an oxidation process for arsenic species with air or oxygen gas as oxidant. Activated carbon (AC) or other carbon based materials are used to catalyse the oxidation reaction. Air or oxygen gas is the only consumed reagent which makes the economy of the process very attractive. The oxidation reaction can be carried out at ambient conditions (room temperature and atmospheric pressure) in less than 24 hours.

Jan 1, 2014

By K. Nagai

The Asian projects are now in their second terms after the five-year first terms. Ultrafined-grained steels were developed in lab-scale and/or in practical process. Basic approach has been performed to explore the evolution mechanisms of ultrafine-grained microstructures. There have been investigated two approaches to make the ultrafine grains: the "recrystallization route" and the transformation route. In the "recrystallization" route, heavy deformation at low temperature is necessary for the ultra-refinement. In the transformation route, making the high density of ferrite initiation sites in the deformed austenite, especially of the heavily compressed austenite structures, is essential for the ultra-refinement, and further hindering the ferrite growth is also inevitable to utilize the high initiation rate. Strength and toughness are dramatically improved by the ultra-refinement. Fatigue property is also excellent. The poor uniform elongation can be enhanced by the design of the second phase dispersion. At the same time the application has been also pursued from various viewpoints of engineering to take advantages of the ultrafine-grained steels. Bridge, ship, construction, automobile and other high strength parts are being attempted for the application.

Jan 1, 2004

By Francisco Tamargo

"This paper refers to a new process for the full recovery (above 98%) of zinc and other valuable metals (Pb, Ag, Au) accompanying zinc in its concentrates while iron is separated as a marketable product free of any harmful impurities and suitable for sale to the cement industry. The process has been especially designed to achieve the following goals: maximizing the recovery of zinc and those valuable metals that are present in most zinc concentrates (lead, silver, gold); allowing the recovery of other valuable metals such as indium or germanium that could be present in some zinc concentrates; avoiding or minimizing the need for residue disposal in safe areas as it is the common practice nowadays in the zinc industry. Finally, the process achieves the previously related goals at a competitive cost, in line with the existing more efficient operations while using conventional equipment working under atmospheric conditions. The new process can be easily implemented in those smelters using the jarosite or goethite processes as well as in those smelters using direct leaching as a part of the processing facilities. A study has already been conducted on the use of jarosite in the cement manufacturing process, in the raw mix preparation as well as for a set controller. It shows that use of clean jarosite in the manufacture of ordinary Portland cement can result in improved quality of the clinker. Jarosite showed compatibility to influence the burning characteristics of the cement raw mixes. The presence of SO3 bearing mineral phases such as natrojarosite showed the suitability of clean jarosite for use as a set controller in cement production.INTRODUCTION Iron is by far the most abundant impurity accompanying zinc in its concentrates, and consequently, iron residue disposal is a major environmental concern for many zinc smelters in the world. This is especially true during the last 30 years when environmental restrictions became more and more strict. Much research work has been carried out during the last 30 years to try to find a solution for this important issue, but with little success. Only the jarofix process represents a partial solution to this problem as jarofix is stored nearby the smelters with certain limitations as a non-contaminant residue. However, it does not avoid the need to dispose of an important amount of residues every year, representing an environmental liability. Meanwhile, the number of countries limiting or banning the disposal of iron residues generated by the zinc smelters is growing, so that the solution to this problem is becoming an urgent matter right now. At the same time, the lack of appropriate available land for iron disposal is also a major concern in many cases."

Jan 1, 2016

By L. E. Gutiérrez

A new filtration model based on porous media transport theory is presented. It predicts capacity and final moisture content in the filtered cake as a function of design and operational variables at the plant. FilterSim® is the computer code where this new model is programmed. Application of FilterSim® to ten-month operation of an industrial copper concentrate filtration plant is shown on a daily basis and using a single set of internal parameters for the whole period. Average error is less than 5%, both in capacity and moisture estimation. FilterSim® abilities to optimize industrial filtration plants as well as to estimate future budgets are illustrated with several real examples.

Jan 1, 2007

By J. A. Eisele, D. L. Pool

"The Bureau of Mines has developed a particle agglomeration technique to improve the flow of leaching solution through heaps of low-grade gold-silver ores which contain clays. Benchscale experiments and industrial practice have shown that the percolation rate of cyanide leaching solution is greatly enhanced by mixing the ore with Portland cement as a binder, moistening the mixture, mechanically tumbling to form agglomerates, and aging before heap building and leaching. A slight modification ofthe technique allows its application to precious-metal-bearing tailings, which cannot normally be treated by heap leaching because they are too fine. IntroductionMany low-grade gold and silver deposits and tailing materials from former mining operations in the western United States are potential sources for precious metals. These sources are too low grade or too small to support the capital cost of a conventional cyanidation plant but have stimulated the development of lowcost procedures, such as extraction of the precious metals by heap leaching with cyanide. The Bureau of Mines has investigated methods to improve the recovery ofgold and silver by heap leaching these low-grade materials.For heap leaching to be successful, the crushed and stacked ore must have good permeability so that uniform distribution of the cyanide leaching solution through the heaps can be achieved. Some of the most difficult gold and silver ores to treat by heap leaching are those containing excessive amounts of clays, or fines generated during crushing. Excessive amounts of slimes, generally minus 50-micrometre or 270-mesh Tyler sieve size particles, in the heap feed will slow the percolation of the leaching solution, cause channelling, or produce dormant or unleached areas within the heap, resulting in long leaching periods and low extractions. In extreme cases, the clays or slimes can seal the heap and cause the leaching solution to run off the sides of the heap rather than through it."

Jan 1, 1987

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 J. H. Curran

Agenda ? Challenges of developed world mining ? Software aids for creative and practical engineering ? Rocscience software philosophy ? Rocscience suite of geomechanics programs ? Case study ? design of de-stress slot Mining Challenges of the Developed World ? Dwindling reserves ? Great depths ? Strict operating and environmental regulations ? Competition from lower cost operations in developing countries

Apr 1, 2005

By E. Ghali, C. Su, G. Houlachi

"The influence of lead ions on zinc electrowinning process was investigated by means of electrochemical noise measurements (ENMs) and cyclic voltammetry in conjunction with scanning electron microscopy and X-ray diffraction. All electrochemical experiments were performed in sulphuric acid electrolyte containing different lead ion concentrations as impurity. Lead was added in six trace levels between 0.05–0.8 mg/L in the bath. The lead content of the zinc deposits was dependent on the introduced lead concentrations. The overpotential associated with zinc electrodeposition shifted to higher values with the increase of lead concentration in the solution. An appropriate correlation was found between the different concentrations of lead in the electrolyte and the morphology of zinc deposit by ENM. The results showed that the increase of lead ion concentrations is generally accompanied with the decrease of skew and increase of kurtosis values that could be related to the morphology of zinc deposit. Effectively, the morphology changes from well-defined hexagonal platelets to large hexagonal, layered platelets and finally to non-symmetric refined crystalline structure, respectively.INTRODUCTION In commercial zinc electrowinning, zinc oxide is leached from the roasted calcine with an aqueous acid sulfate electrolyte. Then the zinc-rich solution is purified and transferred into an electrolytic cell. During electrolysis, zinc is deposited on aluminum cathode where lead-silver or pure lead is served as anode. Electrodeposition of zinc could be influenced by several parameters such as bath acidity, temperature, current density, the nature and concentration of impurities as well as additives in electrolyte. Metallic impurities play a complex role during zinc electrowinning and they can adversely"

Jan 1, 2016

By A. R. Barnes, R. Pandher, T. Shannon, P. Gover

Following the closure of the Glencore Zinc Brunswick mine, the Glencore Brunswick Smelter has transitioned to treating external feeds, and currently treats a number of secondary Pb-Zn concentrates. Processing these concentrates has in some cases been challenging due to the diverse mineralogy of the feeds. Certain feeds are difficult to ignite or show inadequate sulphur removal during oxidation on the sinter strand, while in other cases, combinations of feeds produce a sinter with unsuitable properties for further handling. This paper discusses two methods developed in collaboration with XPS Consulting & Testwork Services to characterize these feeds prior to processing them and to identify which ones are most likely to pose challenges during processing.

Jan 1, 2014

By R. C. Reed, L. T. Wu, H. C. Harada, K. Kawagish, R. T. Wu

Oxidation of pure metals is a chemical reaction in which the metal loses one or more electrons, such that the atom of the metal changes from the neutral state to a positively charge ion and reacts with oxygen to form an oxide of the metal. The oxide can form as a protective and adherent scale that slows down further oxidation, or may spall off repeatedly, exposing fresh metal surface to react with oxygen. In multi-component alloy systems such as typical high temperature NiCrAlY bond coats, more than one oxidation mechanism may take place at once and thus, complicates the study of oxidation. To better understand the competition between formations of oxides of different compositions, a thermodynamic assessment is carried out to study the oxidation mechanism of a Ni-27Cr-9Al (at %) ternary alloy. Based on the assessment, it is demonstrated that the layering of different oxides can be determined, with the most stable oxide (alumina) existing directly above the metal-oxide interface and the least stable oxide (nickel oxide) locating on the outer most layer. A comparison between the calculated results and previously published experimental observations shows excellent agreement.

Jan 1, 2010

By Ö Yilmaz

In this study, the behaviour of rock mass subjected to blasting load is investigated using three dimensional finite difference numerical modelling. In the analyses, Mohr-Coulomb failure criterion has been used for the characterisation of the rock mass strength. Stresses acting on the borehole boundary have been simulated by an exponential function which reaches its maximum within a short time and then falls to zero value in a considerable time period. The strain rate effect on the mechanical properties of rock material has also been taken into account in the analyses. Four different explosive-rock mass combinations have been studied to investigate blast induced damage zone. It has been observed that proposed equation for the dynamic compressive strength of rock material fits very well to general suggestions. Results have shown that blast damage analysis model recommended with this study is successful.

Aug 1, 2013

By M. Bourassa, R. del Villar, S. St. Arnaud, J. Valenzuela

"Autogenous grinding is used quite frequently for mineral comminution as a result of its lower capital and operating costs. However, it is more difficult to control than conventional grinding, particularly when the autogenous or semiautogenous mill is the only comminution stage (i.e. no secondary grinding is available). Analysis of the control strategy used then becomes extremely important, a task that is greatly simplified by the use of an empirical dynamic simulator:This paper presents the methodology used in the development and the calibration of such a simulator for the autogenous grinding circuit of an iron are concentrator: The various steps are described: industrial data acquisition, preliminary treatment of the gathered information. and empirical modelling of the process. Finally, both the actual and the proposed control strategies are compared using simulation results.This exercise has shown that the variability of some of the controlled variables could be reduced through a better handling of the water addition and the use of filters on some of the signals used for control purposes. The reduction in variability of critical variables, such as power draw, would allow their average value to be increased without the risk of exceeding their safety values. Some advanced control techniques were also tested, with interesting results."

Jan 1, 1995

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 T. Gonzales, M. Maleki, M. Caçador, B. Climenhaga, H. Ghorbani

The campaign life of furnaces in the copper making industry is greatly affected by damage caused by normal operation cycling and abnormal conditions. Proper monitoring and assessment of the existing conditions and safe remaining life of the vessels and their refractory lining is key to prevent an unplanned early replacement. This paper presents an industry-proven refractory management program as well as a typical fitness-for-service assessment of a rotary vessel shell in order to extend the campaign life of copper making furnaces and enhance safety. The furnace refractory management system involves a comprehensive audit and monitoring program which has been successfully applied to several copper flash smelting furnaces over the past 15 years. The fitness for service assessment provides a methodology to estimate the remaining life of the steel components by evaluating the existing damage and future damage rate based on the historical survey data. The above practices can provide the operator with cost savings by extending the vessel campaign life in lieu of implementing more rigorous refractory lining and shell audits. INTRODUCTION Primary copper smelting is generally divided into two categories of flash smelting and open bath smelting. There are many different types of vessels that can be used to convert the copper concentrate to blister copper including, flash, Mitsubishi process, TSL (ISA/Ausmelt), SKS Bottom Blowing, Anode and Teniente/Noranda furnaces, reactors, and Peirce Smith converters. Each vessel has its own complex and intense environment which requires careful refractory and steel design to withstand the severe thermomechanical and thermochemical attacks within its campaign life. The campaign life of furnaces is greatly affected by damage caused by normal operation cycling and abnormal conditions. Proper assessment of the existing conditions and safe remaining life of the vessels and/or refractory lining is key to prevent an unplanned early replacement. This paper presents an industry-proven refractory management program as well as a fitness-for- service assessment methodology to estimate the remaining campaign life of copper making furnaces resulting in cost savings and enhanced safety of the operating vessels.

Jan 1, 2019

By N. Dahata

B206 aluminum?copper alloy has a potential for wider use in the automotive industry due to its light weight and relatively superior mechanical properties as compared to aluminum-silicon alloys. The possibility of casting this alloy via Lost Foam Casting (LFC) has not been investigated in detail. Therefore, the effects of foam types (T170B standard untreated EPS and T175-brominated EPS), coating types (Styro Shield 5553 and Styro Shield 5554), copper level (4.5 wt % and 5.0 wt %) and titanium levels (0.5 wt % and 0.25 wt %) were related to fillability, microstructure and microporosity. The metal velocity in T175 EPS pattern was higher than that in T170B EPS pattern. For T175 EPS pattern, the total solidification time was 3% higher and the loss of temperature for decomposition of EPS was lower than those in the case of T170B EPS pattern. The grain size, porosity level and maximum pore size were quantified using Light Optical Microscopy (LOM) and image analysis. The casting with T175 EPS pattern showed larger grain size relative to that with T170B EPS pattern. The porosity level and the maximum pore size decreased significantly when the titanium level was increased from 0.05 wt % to 0.25 wt %.

Jan 1, 2007

By G. Plascencia, C. López, J. González, D. Jaramillo, M. A. Barrón

Air jet and molten matte interaction within a Peirce - Smith converter is analyzed during the first stages of blowing using Computational Fluid Dynamics (CFD), by means of the Large Eddy Simulation and Reynolds Stress turbulence models. Jet velocities ranging from 5 to 150 mis, which involve the bubbling and open jet regimes, were considered in 2 and in 3-D numerical simulations. As a result of the computer simulations, it was found that low velocities results in gas bubbling in the molten copper, whereas higher gas velocities results in well defined plumes. The consequence of such different behaviours results in an increment in the rate of refractory wear or in copper splashing respectively. The analysis of the results may lead to improve the design of the tuyeres currently used in copper converting. Bottom blowing of air is also explored in this work. Numerical results show a strong non-linear parabolic behaviour of the jet velocity on the average velocity of copper; which means that beyond certain jet velocity, the copper de-accelerates thus reducing its velocity. This may be due to the open nature of the jet, which prevents the momentum transfer from the injected gas to the molten copper.

Jan 1, 2007

By J. Robitaille, P. Cousin

"Agnico-Eagle Mines Ltd, Laronde Division, is a gold operation processing ore containing copper and zinc. Copper is recovered as a concentrate prior to gold cyanidation.Copper concentrate grade was improved with the implementation of an on-stream analyzer. Further improvements to the copper concentrate grade could be achieved throughefficient zinc depression.High cyanide cost linked to the copper content in the flotation circuit tails, prompted some modifications to the flotation circuit. Economics and environmental issues were considered. A Maxwell cell was retrofitted with an Outokumpu HG cell mechanism stabilizing it's operation. Secondly a flotation column was added to increase circuit capacity.This paper will address flotation circuit operation difficulties, successes and results achieved before and after modifications.RESUMELes Mines Agnico-Eagle division Laronde sont considéré comme étant un producteur d'or. Le minerai révèle toutefois des teneurs appréciables en cuivre et zinc. Un circuit de traitement combinant des étapes de flottation du cuivre et de cyanuration de l'or a été adopte. Le rejet de la flottation est lixivie pour son contenu en or.La teneur moyenne en cuivre du concentre final fut augmentée suite a l'implantation d'un système d'analyse en continu. Une séparation plus efficace de la sphalérite se devra d'être obtenue afin d'améliorer davantage la qualité du concentre produit.Le contenu en cuivre au rejet du circuit de flottation influence directement la consommation en cyanure. Pour cette raison, certaines modifications à la flottation sont devenues nécessaires. Des facteurs d'ordre économique et environnemental ont été considérées. Une cellule existante fut transformée en cellule HG d'Outokumpu, stabilisant son opération, et une colonne de flottation fut ajoutée au circuit afin d'accroitre sa capacité.Le présent document se veut une rétrospective des problèmes d'opération vécus, des solutions apportées ainsi que des résultats obtenus et de leurs implications suite aux améliorationseffectuees."

Jan 1, 1995

By Robert B. Parsons

"The new Ontario Liberal government introduced its first budget in October. The changes to The Mining Tax Act proposed in the budget are mean t 10 simplify the current system without any loss of revenue to the government. It goes without saying that some operators will benefit from the changes while others will pay more taxes after 1985.With regard to ongoing matters at the federal level, the proposed carve-out legislation and the issue of northern allowances are being discussed with government officials, and a small victory has recently been scored with regard 10 the laxation of certain share transactions of prospectors and grubstakers. A report on these issues is provided herein.Ontario BudgetOn October 24, 1985, Ontario Finance Minister Robert F. Nixon tabled a budget proposing several significant changes to both the Ontario Mining Tax Act and the province’s income tax legislation.Mining Tax ActA flat rate of tax and reduced processing allowances highlight proposed changes to The Mining Tax Act. The proposed changes, with a comparison to the existing system, are set out in Table I.The most significant change is the replacement of the graduated tax rate schedule with a flat 20010 tax rate. This is a welcome change for most mine operators who viewed the high rate of 30% on profit over $20 million as counter-productive.However, the flat rate of ta x may not be welcome to all operators. Generally speaking, operators with less than $ 10 million annual profit are better off under the graduated rate system, while operators with annual profit exceeding $10 million will benefit from the 20010 tax rate."

Jan 1, 1986

By N. Hwang

There has been increasing interest in the use of robotic machines, and several prototype robotic machines have been developed to automate the grit-blasting process for the purpose of steel bridge maintenance. To utilize such a robotic grit-blast machine effectively, the first consideration is automating the determination of the rust surface area to blast, on the basis of standards of practice, in a rapid manner. This study aims to propose a method to rapidly and accurately determine the rust surface area on steel bridges to blast, with consideration for the standards of practice, from images acquired via a blasting machine. The first step is to perform a color space conversion to transform the input image from a red/green/blue (RGB) color space to a hue/saturation/intensity (HSI) color space. The next step is to detect the presence of rust, using pixel-level classification via the C4.5 decision tree algorithm. Then it is necessary to confirm the blasting area by verifying whether the rust detection result satisfies the specified criteria on the basis of standards of practice. The proposed method was validated on 39 test images with various characteristics with respect to the degree of rusting and rust distribution type. The experimental results showed that the average accuracy rate of rust area classification was about 97.63%, and the success rate of the final decision of blasting area determination was 100.00% for 39 test examples. The whole processing time took an average of only 0.86 seconds per image. The preliminary results demonstrated that the proposed method not only determined whether rust was present in an image and the amount of rust but also indicated whether blasting was necessary, and, if necessary, it rapidly specified the rust surface area that should be blasted on the basis of standards of practice. The proposed method could be successfully incorporated into a robotic grit-blast machine.

Aug 1, 2013

By K. Thuro, B. Sellmeier, M. Krautblatter

"Recent rockfall events, like the Tramin rockfall at January 21st, 2014, underline the significance of a comprehensive hazard assessment. A common way of estimating the hazard along infrastructure is the performance of run-out modelling using 3D rockfall codes like Rockyfor3D or RAMMS::Rockfall (Dorren, 2010, Bartelt et al., 2013). The potential block volumes are often roughly estimated from talus material and an overview of the source area, where the magnitude assessment is usually physically and intellectually demanding. Nevertheless especially for increased magnitudes, the volume estimation is crucial in terms of hazard analysis. Mid-Magnitude-Events exceed the load capacity of the most mitigation measures and their date of failure is hard to predict. Here we define the term Mid-Magnitude-Events as block volumes between boulder falls (10-100 m³) and block falls (100-10,000 m³) (Whalley, 1984).The current contribution provides an approach of integral process analysis for a 200 m3 carbonate block above the federal road B 305 near the city of Salzburg in the Bavarian Alps, Germany. We performed detailed analysis of the critical carbonate block exposed to planar failure. The block volume and the dimensions of the failure surface were mapped in detail, due to the unique occasion of an accessible failure surface. The discontinuity persistence was recorded to assess a minimal degree of fragmentation for a potential failure scenario. A maximum degree of fragmentation was estimated due to recording of block dimensions at the talus slope resulting from frequent rockfalls.We performed parameter studies in terms of run-out modelling using the code RAMMS::Rockfall (Bartelt et al., 2013), taking the recorded data for block fragmentation into account. In our contribution, we aim to demonstrate a comprehensive approach for hazard assessment of mid magnitude rockfalls, taking detachment processes, fragmentation and run-out analysis into account."

Jan 1, 2015