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By M. Fafard, M. Dupuis, P. Goulet, J. Bédard

Start-up of a Hall-Heroult cell is a delicate task that can affect pot performance and pot life. Modem practices for high amperage cells involve preheating the lining before the molten electrolyte is poured in. Different preheating methods and heat-up schedules are used throughout the industry, and the optimum between a short start-up and damage minimization to the cell is elusive. Direct electrical coke-bed preheating is one of the most common techniques. This practice typically results in a non-uniform surface temperature distribution and can generate detrimental thermal gradients in the cathode blocks. Numerical modeling is an invaluable tool to study this complex problem and can help improve the preheating procedures. The modeling of the mechanical response of the lining is critical to detect risks of cathode block cracking or the development of gaps where liquids could leak into. Taking into account the baking of ramming paste, the quasi-brittle nature of carbon and the contact interfaces between different materials are examples of key elements to consider. A finite element slice model of a cell was built and simulations of different electrical preheating scenarios were performed using the inhouse code FESh++ to demonstrate what can be learned through thermo-chemomechanical modeling. The potential industrial application of the model is discussed.

Jan 1, 2006

By R. Darlington, S. Ji

"High pressure die casting is a promising process to make thin-wall components with high dimensional accuracy and excellent surface quality. However, the non-uniformity is one of the important features in castings. The inhomogeneity in tensile properties and microstructural characteristics were studied for the castings with different thicknesses made by high pressure die-cast Al-Mg-Si alloys. For the local mechanical properties in the die-castings, the casting skin provided the highest, whereas the casting centre provided the lowest yield strength, UTS and elongation. The yield strength, UTS and elongation were significantly decreased towards the casting centre. The microstructural inhomogeneity is characterised by the segregation of coarse fragmented dendrites, the reduction of solute concentrations of Mg and Si, and the increase of porosity level from the surface to the centre of castings. The growth velocities of eutectic a-Al phase estimated using the Jackson-Hunt model confirm that the growth variation is larger in the thin castings than that in thick castings.INTRODUCTION Inhomogeneity is an inherent characteristic in as-cast microstructures of a variety of alloys because of their non-uniform chemistry, microstructure, defects, topology and the resultant mechanical properties in the different ranges of localization (Campbell, 2003). Generally, three types of inhomogeneities characterise casting microstructures, which include (a) the casting defects of shrinkage and gas porosity, misruns, cold shuts, inclusions, hot tears and hot spots; (b) the non-uniform microstructure from the surface to the centre of castings; and (c) the non-uniform microstructure from the dendrites grown from primary solidification and the structure formed during the subsequent eutectic solidification in inter-dendritic regions. The chemical composition and the morphology between the primary dendrites and the inter-dendritic eutectics also differ in the as-cast microstructure. Obviously, the inhomogeneity is different in the castings obtained from different casting processes."

Jan 1, 2018

By K. S. Coley, M. A. Rhamdhani, G. A. Brooks

Interfacial phenomena in high temperature reactions such as between iron alloy and slag is well documented but not fully understood. It is believed that a gradient of oxygen concentration plays an important role to the occurrence of such phenomena. This article describes the results from the continuation of the study of interfacial phenomena between Fe-Al alloy droplets and CaO-SiO2-Al2O3 slag. Materials characterization techniques involving microscopic observations, depth profiling, bulk, point analysis and were carried out. The roles of oxygen as well as other factors that contribute to the interfacial phenomena were evaluated. The results and their implications to steelmaking will be discussed.

Jan 1, 2004

By Nima Nabavi

Shovels and excavators have significant blind spots due to their large sizes, increasing the chances of collision with other surrounding equipment such as haul trucks, loaders, and dozers. While a camera surveillance system is very useful in preventing collision, it can benefit from two additional features: (i) the ability to display the distance of the closest object within the view, and more importantly (ii) the ability to warn the operator if objects are getting too close. After a comparison between few different technologies, it is explained how these features can be provided by integrating rugged pulsar radar sensors with a camera system. The specific radar technology is already field proven in the harsh mining environments. Motion Metrics International Corp. has developed this exact product, which combines its 4-camera surveillance system (ViewMetricsTM) with a series of rugged radar sensor elements, named ViewMetricsTM-Radar. The radar system employs intelligent CAN bus communication to reduce wiring, hence improving hardware reliability with built-in troubleshooting features. A USB connection is the only hardware bridge between the radar sensors and the embedded computer. As such, an existing ViewMetricsTM system can be easily upgraded to ViewMetricsTM-Radar. As addition of new interfaces to the cab could result in operator distraction, this paper explains how ViewMetricsTM-Radar reduces distraction compared to other radar collision prevention systems.

Oct 1, 2009

By B. R. Neufeld, M. G. Heximer, S. J. Roach, W. G. Van Luven, D. G. Reynolds

"Teck Metals Ltd. operates an integrated zinc-lead complex at Trail, British Columbia, Canada. In the zinc plant, zinc concentrates are roasted to produce calcine, which is then processed in the leaching circuit for zinc recovery. Calcine is first dissolved at pH <2.0. This is followed by a precipitation stage using additional calcine that removes iron as a ferric hydroxide precipitate which is recycled to the lead operations. It is during this pH adjustment that impurities, notably arsenic, antimony and germanium, are co-precipitated with ferric hydroxide which is the primary removal phase for these elements. Recent processing conditions have resulted in lower iron inputs to the leaching circuit and this has resulted in insufficient co-precipitation of key impurities. This paper summarizes the influence of iron concentrations on impurity removal using laboratory and plant scale surveys, and emphasizes key specification limits for the primary iron removal circuit.INTRODUCTIONThe Sulphide Leach Plant (SLP) at Teck Metals Ltd., Trail Operations produces a zinc sulphate electrolyte from three different zinc bearing streams:1. Calcine, primarily containing zinc oxide, from the roasters2. Zinc electrolyte from the Oxide Leach Plant (OLP) is produced by leaching zinc oxide fume from the pyrometallurgical lead smelting operations3. Zinc slurry from the Zinc Pressure Leach (ZPL) autoclaveThe feed sources are blended and introduced to the iron removal process to precipitate iron in the form of a hydrolyzed iron precipitate which is recycled to the lead smelting operation. Along with iron, impurities, namely arsenic, antimony, germanium and silica, also co-precipitate; this process acts as the primary removal step for these elements. Following iron removal, the electrolyte is further processed in the zinc dust purification circuits. Cadmium and copper are removed in the cold stage circuit via zinc dust cementation, followed by cobalt cementation in the hot stage circuit."

Jan 1, 2016

By Dillon. Patricia

Business Growth ?Coal ?Targeting 30 million tonnes by 2013 compared to 19 million tonnes produced in 2009 ?Expanding Energy Business unit (Oil Sands) ?Copper -Strong growth potential for existing operations and development projects ?New gold strategy recently launched ?New markets for zinc Need to retain existing and attract new employees to support growth Engaged Employee ?Has a positive attitude towards the organization and its values ?Is a person who is fully involved in, and enthusiastic about, his or her work Engaged employees are more likely to stay with the organization.

May 1, 2010

By Michael S. Moats, Addin Pranowo, Gerardo R. F. Alvear F., Nigel Aslin

The toxicity of arsenic is well known and documented. However, the presence of arsenic in copper electrorefining anodes and electrolyte is critically necessary to produce high quality cathode. Arsenic as well as antimony and bismuth concentrations vary depending on their relative concentration in the anode copper received from the smelter. This paper will discuss the behaviour and benefits of arsenic in copper electrorefining and the detrimental effects of antimony and bismuth on cathode quality and tankhouse performance. This will include the minimization and mitigation of problems associated with arsenic, antimony and bismuth including cathode contamination, floating slimes, scaling and anode passivation.

Jan 1, 2014

By Robert B. Parsons

"This article is based on a paper presented by Jim Scott at the 1988 annual convention of the Prospectors and Developers Association of Canada. The paper suggests a number of factors that might be taken into account in negotiating royalty terms.IntroductionRoyal ties are a part of mining life in Canada. They are used by many kinds of individuals in many kind s of situations. Prospectors commonly take royalty interests back when they transfer claims to development companies. Mining companies disposing of undeveloped (or sometimes even developed) properties are often paid at least in part by royalties. Royalties are even used by institutional investors with no other connection with the resource industry.Such different royalty holders have different investment goals, different cash flow requirements, and different risk / return preferences. These differences have given rise to a number of different royalty type s. These types range from the simplest cents-per-ton royalty (where the operator pays a royalty at a fixed rate per ton milled) to net smelter return or ""NSR"" royalties (where the royalty is based on a percentage of the operator&apos;s NSR) all the way to net profit interest or ""NPI"" royalties (where the royalty is based on the operator&apos;s bottom-line net profit),The fundamental difference between the many royalty types is in the risk/ return relationship. The cents-per-ton royalty, for example, is relatively risk-free. Of the many economic factors which affect a mine, the only one which will affect the royalty holder is the amount of ore physically milled. On the other hand, the potential for significant gains under a cents-per-ton royalty is also very limited. The royalty holder will not share in any increases in the market price of the end product or any cost reductions achieved by the producer."

Jan 1, 1988

By MacKenzie Dickson

"INTRODUCTIONGold is found in many natural states, native nuggets, loose grain in river sands, veins in rock, as well as associated with sulphides, oxides, etc., disseminated more or less minutely.Its high value in recent years has spawned new technologies to win values from sources once considered too lean for commercial recovery. Cyanide leaching from fine milled ore or tailings, from upstream recovery operations, coupled with adsorption onto relatively coarse granules of activated carbon, concentrate the gold enough to be converted to bullion by time-honoured methods.The carbon granules are fragile. Size degradation in handling must be minimized not only to prevent loss of gold on fine fragments of carbon that could pass with the barren tailings, but to maintain adsorption efficiency. Besides, the granulated carbon itself is costly. Circular Vibroscreens are winning acceptance for dewatering carbon granules thanks to their gentle yet effective performance in gold recovery systems around the world. The system at Equity Silver is illustrative.BackgroundEquity Silver Mines Ltd., Houston, British Columbia, first began production in September 1980. In 1984, a feasibility study showed that additional gold and silver could be economically recovered through cyanide leaching of the flotation tailing.Although the carbon-in-pulp (ClP) or carbon-in-leach (CIL) process is commonly used for extracting precious metals from slurries, the use of circular vibrating screens, and Vibroscreens in particular, for the carbon circuit is an innovation that cuts costs.Rectangular vibrating screens have been the conventional separation mechanism of choice across North America. In contrast, the use of Vibroscreens has been proven to be less costly for the initial purchase and installation. Also, these circular vibrating screens require less power and less space. A description of Equity Silver Mines&apos; process shows how these screens have been successfully integrated into the system."

Jan 1, 1989

By Robert B. Parsons

"This article is based on a paper presented by Jim Scott at the 1988 annual convention of the Prospectors and Developers Association of Canada. The paper suggests a number of factors that might be taken into account in negotiating royalty terms.IntroductionRoyal ties are a part of mining life in Canada. They are used by many kinds of individuals in many kind s of situations. Prospectors commonly take royalty interests back when they transfer claims to development companies. Mining companies disposing of undeveloped (or sometimes even developed) properties are often paid at least in part by royalties. Royalties are even used by institutional investors with no other connection with the resource industry.Such different royalty holders have different investment goals, different cash flow requirements, and different risk / return preferences. These differences have given rise to a number of different royalty types. These types range from the simplest cents-per-ton royalty (where the operator pays a royalty at a fixed rate per ton milled) to net smelter return or ""NSR"" royalties (where the royalty is based on a percentage of the operator&apos;s NSR) all the way to net profit interest or ""NPI"" royalties (where the royalty is based on the operator&apos;s bottom-line net profit),The fundamental difference between the many royalty types is in the risk / return relationship. The cents-per-ton royalty, for example, is relatively risk-free. Of the many economic factors which affect a mine, the only one which will affect the royalty holder is the amount of ore physically milled. On the other hand, the potential for significant gains under a cents-per-ton royalty is also very limited. The royalty holder will not share in any increases in the market price of the end product or any cost reductions achieved by the producer."

Jan 1, 1989

By V. Cvetkovic, L. Zou, L. Jing

"Sorption process plays a significant role for solute retardation in rock fractures. In this paper, for the aim to investigate the effect of sorption on solute transport in a single rough fracture, a 2D model of representative single rock fracture was built and its roughness was statistically characterized based on the measured data of rock surface topography by laser scanning. A Finite Volume Method (FVM) code was developed to solve the Navier-Stokes (NS) equations and transport equation for numerical modelling the process of fluid flow and solute transport in the rock fracture model. Two groups of simulations were conducted: with and without the consideration of the sorption process with different average flow velocities. The results show that the surface roughness increased the complexities of flow fields, and the non-linear sorption process plays a significant role in the retardation of solute transport through rock fractures. The sorption process caused an obvious lagging time in both the solute concentration fields (plumes) and corresponding breakthrough curves. This lagging time increases with the distance from the inlet boundary, and relatively decreases with the increase of mean velocities. INTRODUCTIONFluid flow and solute transport in fractured rocks is an important research topic for performance and risk assessments for rock engineering projects concerning geo-environment safety, such as radioactive waste disposal, mining, geothermal extraction, reservoir engineering and other contaminant transport processes in geosphere (Berkowitz 2002).The solute transport in the rock fractures mainly involve the advection, surface sorption, matrix diffusion, dispersion, radioactive decay and chemical reactions, governed by general transport equations (e.g. Bodin et al., 2003). Among these transport phenomena, the sorption on the fracture walls can alter solute migration between the fractures, and play an important role in natural retention of solute transport (Weber et al., 1991; Wels et al., 1998; Kumar 2007; Dai et al., 2012). The aim of this study is to investigate the effect of sorption on the solute transport in a single rock fracture with rough surfaces. More complex transport processes, such as matrix diffusion, dispersions, radioactive decay and chemical reactions, are not included in this study."

Jan 1, 2015

Applications of proven real time, through-conveyor elemental analysis technology and benefits achieved will be discussed using case studies in base metals, iron ore and phosphate operations. PGNAA (Prompt Gamma Neutron Activation Analysis) technology and its background in minerals applications and applications which are expected to further improve its utilization will be reviewed. Short payback through operational benefits such as removal of waste from feed, increased feed grade and overall improved productivity will be demonstrated based on results achieved at several processing operations. PGNAA technology is most applicable to conveyed flows as it is unaffected by belt speed, particle size, segregation/layering, mineralogy or dust. As a transmission method able to penetrate in excess of 500mm of rock it provides extremely representative results continuously measuring through the full conveyed cross section and reporting results typically on one to five minute accumulated increments to the control room. Multi-elemental results and moisture content are used for active process control: diverting conveyed flow increments(bulk sorting), blending ore types in plant feed, and providing advance warning of significant quality changes to the downstream plant operators (e.g. flotation). Elements of interest may include deleterious components as well as target metals. Ore feed quality measurements are also useful in metal accounting, ore reconciliation and real time feedback to mining operations. Further benefits can result when combined with other technologies such as particle sorters, to upgrade diverted increments of subeconomic material to achieve higher feed grades and lower deleterious content to the main process. Measurement of elements (e.g. silica) which correlate with ore hardness or grinding characteristics can be used to moderate feed rate to grinding mills to prevent overload, hence optimizing grinding performance and reducing energy and grinding media consumption. Pebble flows can be analysed and uneconomic increments diverted to prevent recirculating flows consuming mill capacity unnecessarily. This also increases average feed grade.

Jan 1, 2016

By F. Osmond, R. Kelly

"Malcolm Knowles, the famous adult educator once wrote: ""What a challenge we in human resources development face if we are to avoid the obsolescence of our workforce. I can foresee this challenge requiring that we reconceptualize (...) and redefine the role of HRD, away from that of managing the logistics of conducting training activities to that of managing a system of learning resources"".The context in which this was written surrounds the subject of adult education and the need for business and industry to change its approach to the treatment of adults as learners. In explaining what &apos;managing a system of learning resources&apos; means, Knowles refers to line supervisors and managers as the most ubiquitous resources for day-in and day-out employee development. In many organizations training has been largely a staff rather than line responsibility. Even where trainers reported to line management, it was still seen as a staff function performed by a few specialists.This change referred to by Knowles places a much heavier responsibility on line supervisors and managers for the development of their personnel than has traditionally been the case. Managing that change - handing over the responsibility to the line organization - is the supreme challenge for the HRD function.Just why is this change necessary? Because too often, the learner does not effectively use on the job what he or she learned in the classroom. In fact, learners often discard new methods and revert to the older ways. The reason training does not stick is that the systems for training and work management are most often separate entities and while one may support the other, they need to be a single integrated system in order to ensure the transfer to the job effectiveness of training and some real value for the training dollars.Because much training can be wasted, steps have to be taken to ensure that it fulfills its intended purpose. The effective and continuing application of knowledge and skills that learners acquire can only be realized when line supervisors and managers are at the centre of the training system.This paper describes how such a systemis being developed at the Iron Ore Company of Canada (IOC) as a functional training program is introduced. The following text provides background information on the IOC - who they are and where they are located, a definition of functional training, an evaluation of the suitability of this approach for adults in industry, a description of how the program is being implemented at IOC and some observations that have been made as this change is experienced."

Jan 1, 1995

By E. N. Durussel

"The Fox Mine has been producing copper/ zinc ore since 1970 at a rate of approximately one million tons per year, and until 1978all production was derived from longhole open stopes. In June 1978, a trial stope using bighole mining methods was started to eliminate the development of two sublevels between 400 level and surface. The trial proved to be successful, and bighole mining is now an accepted mining method for both stopes and pillars at Fox Mine.When production blasting was started in the first stope, the biggest problem encountered was the production of large amounts of sulphur dioxide gas as a result of secondary sulphide dust explosions. This gas generation resulted in lost production time and caused minor damage to underground installations to the blast level, and to the headframe. Sulphur dioxide generation has been noted in secondary drawpoint blasts and, on rare occasions, in drift rounds.This paper discusses the occurrence of the sulphur blasts and the practices and precautions used to prevent their reoccurrence at Fox Mine.IntroductionThe Fox minesite is located 30 miles southwest of Lynn Lake, Manitoba. With production startup in 1970, Fox Mine is owned and operated by Sherritt Gordon Mines Limited.The Fox orebody occurs as a large lenticular zone of semi-massive sulphides approximately 1,500 feet long and 15 to 100 feet wide running east and west. Dipping 70 degrees to the north, the orebody tends to bottom out at the 3200-foot level and reaches to within 15 feet of surface."

Jan 1, 1981

By J. P. Jylhä, A. Jokilaakso

The Outotec Flash Smelting process is widely used in primary copper production. A layer of slag on top of matte (copper–iron sulphide melt) creates a barrier through which matte droplets descend. Droplets of different sizes settle through the layer at different rates, which increases possibility of copper losses as smaller matte droplets may be removed with the slag. In this work CFD-DEM (computational fluid dynamics – discrete element method) coupling was used to simulate matte droplets settling through the slag during slag tapping. Discrete droplets and slag flow were simulated with DEM and CFD, respectively. This new approach enables tracking and solving movement and interactions of individual droplets. User-defined models were created to take coalescence and reaction kinetics into account. Coalescence created larger droplets, while the reactions decreased droplet size and increased its density. Drag caused funnelling effect, which pulled droplets towards the centre line of the descending cluster. This research is the only study known by the present authors in modelling liquid-liquid systems with the CFD-DEM coupling. Simulating coalescence and chemical reactions for discrete droplets enables more realistic simulations. However, CFD- DEM simulations are computationally resource intensive already without additional models, so a full scale industrial settler modelling still waits for further increase in computer performance. INTRODUCTION Flash smelting is a method used in copper and nickel production. In the flash smelting process, oxidation of sulphides in a concentrate is used to release energy needed to smelt the feed. In the process, copper matte is formed. Matte has copper content in the range of 55 – 70% (Sridhar, Toguri, & Simeonov, 1997), the rest is mainly sulphur and iron but has still many other impurities (Taskinen, Seppälä, Laulumaa, & Poijärvi, 2001). Oxidized iron forms iron-silicate slag while SO2 is collected for acid production (Davenport & Partelpoeg, 2015). The Outotec flash smelting furnace (FSF) can be divided in four major component: concentrate burner, reaction shaft, settler and uptake. Concentrate, flux and oxygen enriched air are injected into the reactor through the concentrate burner. The mixture then reacts in the reaction shaft forming matte and slag, which are collected in the settler, while off-gases flow out of the reactor through uptake for heat and dust recovery, and SO2 collection for H2SO4 production. The matte and slag form separate layers due to immiscibility and density difference. Raw material feed is continuous, but the matte and the slag are tapped periodically. A flash smelting furnace is depicted in Figure 1.

Jan 1, 2019

"Sink-float analysis is often used to obtain yield-ash and density partition curves in the coal industry. These provide a valuable tool for evaluating the performance of a separation process. However, for dense minerals, obtaining complete grade-recovery and density partition curves is more difficult due to the lack of heavy liquids available with the required densities. This paper examines a potential solution to this problem which is to perform batch fractionation of mineral samples in a laboratory-scale REFLUX™ Classifier using high viscosity fluidising liquids. The REFLUX™ Classifier is a gravity separation unit consisting of a system of parallel inclined channels positioned above a vertical fluidised bed. Operated in semi-batch mode, a charge of particles is fluidised from below and particles up to a certain density are elutriated from the top of the system. The fluidisation rate is then increased incrementally to fractionate the sample at progressively increasing densities. Previous work by Hunter et al. (2014) and Iveson et al. (2015) has shown that this method provides excellent agreement with yield-ash and partition curves for coal, especially when glycerol solutions are used as the fluidising liquid. This approach has now been extended to obtain the grade-recovery and density partition curves of high density mineral samples. This method has the potential to provide the minerals industry with an effective tool to evaluate the performance of unit operations separating at cut points higher than the available heavy liquids.INTRODUCTIONMeasuring efficiency and effectiveness is of key importance in the continuous improvement of mineral processing plants. For density based separation, one way the performance of a process can be evaluated is the measurement of density-based partition curves. Currently, this is done in the coal industry using the sink-float method, where heavy liquids are used to fractionate particles into discrete density intervals. However, with high density minerals such as iron ore, liquids of sufficient density are rare, and in most cases also pose serious health and safety concerns to laboratory operators. Most commercial laboratories do not perform sink-float separations above a density of about 4400 kg/m3, the maximum density of Clerici solution without operating at excessive temperatures (Koroznikova, Klutke, McKnight & Hall, 2007; Rosenblum, 1974)."

Jan 1, 2016

By Kari Niiranen, Andreas Boehm

LKAB (Luossavaara-Kiirunavaara AB) is operating underground iron ore mine, with three beneficiation and pelletizing plants in Kiruna, Northern Sweden. The wet low intensity magnetic separation (WLIMS) is regarded as the crucial part of silicate mineral separation from the ore. The Kiirunavaara iron ore deposit shows a rather low content of silica (ca. 2.3 to 3.3 % SiO2) but the silica grade is expected to increase in the deeper parts of the deposit. This can be problematic in the case of DR pellet quality with an average silica grade under 0.75 % SiO2. A laboratory scale methodology was developed for the systematic characterization of the ore for mineral processing with the focus on silicates at the Institute of Mineral Processing, University of Leoben. This methodology is combining mineralogical, geochemical and process mineralogical characteristics. Automated mineralogy (QEMSCAN) was used to study the modal mineralogy, the distribution of silicate minerals in different particle size classes after comminution, the deportment of silicon (Si) between various silicates and degree of liberation and intergrowth of magnetite and silicates. Based on the mineralogical investigations, actinolite, phlogopite and even quartz and albite are the predominating SiO2 bearing minerals in the ore. The important result of the investigations was the discovery of two separate subtypes within the high silica ore type B2 based on their mineralogy and mineral processing characteristics. The crucial part of the investigations of intergrowths and liberation of magnetite results was the magnetic separation tests carried out with the Davis magnetic tube. The binary intergrowths of magnetite and the silicate minerals (mostly actinolite) are the most common type of mineral association discovered. The significant characteristics in the intergrowths of magnetite and actinolite are the fine-grained magnetite inclusions in actinolite which may end up increasing the SiO2 grade in the magnetite concentrate despite magnetic separation.

Jan 1, 2016

By T. Bhambhani, O. Yavuzkan, D. R. Nagaraj

"Cu ore bodies commonly contain oxide Cu at the surface, with sulfide Cu content increasing with depth. The recovery of oxide Cu minerals by flotation is a longstanding challenge in the minerals industry, especially for high acid-consuming ores which would not be economical for direct acid leaching. Current practice of oxide Cu recovery involves sulfidization (often using controlled potential sulfidization or CPS) using NaSH (or Na2S) followed by flotation using traditional sulfide collectors. CPS has shown to improve recovery of oxide Cu but has the following limitations: a) HSE issues with NaSH, b) high consumption of NaSH, and c) inability to recover certain oxide Cu minerals because they are refractory to sulfidization. The oxide Cu flotation is further complicated by the presence of certain non-sulfide gangue minerals which adversely impact both recovery and selectivity.Over the past eight decades, numerous collectors have been proposed and evaluated for the direct flotation (i.e. without sulfidization) of oxide Cu minerals, the most researched of which is alkyl hydroxamate. While there are numerous publications dealing with the fundamentals of interaction of alkyl hydroxamates with single minerals, there are few publications which discuss the practical aspects of alkyl hydroxamate use in ore flotation, particularly their use with sulfidizing agents. Case studies in this paper include methods to identify optimum combinations of sulfidizing agents and oxide collectors to maximize recovery for various types of ores. It was observed that some ores do not require any sulfidization, while others require at least partial sulfidization to improve efficacy of AHX. Depending upon the ore type and mineralogy, recovery improvement in the range of 5 to 15% units, over and above that achieved with CPS, has been observed with the use of AHX. For ores requiring high dosages of NaSH, it was shown that AHX can be used to reduce the NaSH consumption significantly. The challenges associated with the presence of non-sulfide gangue minerals in oxide copper ores are included, and the use of modifiers to alleviate the associated problems and enhance the performance of AHX is discussed."

Jan 1, 2016

By Wei Zhang, Jinhong Zhang

"The adsorption of ethyl xanthate on copper sulfides, i.e., chalcopyrite, chalcocite and bornite, has been studied in situ in aqueous solutions by applying an atomic force microscopy (AFM). AFM images show that xanthate, such as potassium ethyl xanthate (KEX), adsorbs strongly on chalcocite and bornite mainly in the form of insoluble metal xanthate, which binds strongly with the mineral surface without being removed by flushing with ethanol alcohol. This adsorption mechanism is totally different from the one obtained with chalcopyrite/xanthate system, during which oily dixanthogen is the main adsorption product on chalcopyrite surface. The findings obtained from the present AFM study suggest that an AFM image analysis is a powerful tool for the study of the collector’s adsorption on mineral surface and as well the development of novel collector for copper sulfide flotation.INTRODUCTIONIn mining industry, copper sulfide minerals, i.e., chalcopyrite, chalcocite and bornite, are usually separated selectively from non-valuable gangue by froth flotation, which treats the highest throughput and produces the maximum economic outcome of any surface chemistry process. In flotation, collectors are added into the pulp (mixture of water and fine-grained minerals) to selectively adsorb onto the target mineral and render its surface with high hydrophobicity, which is generally beneficial for a strong mineralbubble attachment and thus a high flotation recovery.The adsorption of collector on mineral surface, therefore, is vital for a successful flotation process and it has been studied by applying various surface analysis techniques, such as IR (Infrared Spectroscopy), CV (Cyclic Voltammetry) and XPS (X-ray Photoelectron Spectroscopy). (Poling, 1963; Allison et al., 1972; Mielczarski et al., 1984; Leppinen et al., 1989; Kartio et al., 1996) These studies have revealed a lot of information, such as the reaction, product and mechanism, of the adsorption of chemicals on mineral surface. It is also of great interest to directly get the image of adsorbed collectors on mineral surface changing with pulp chemistry, such as pH, redox potential, ionic strength and chemical’s dosage."

Jan 1, 2016

By P. MacPhail, G. S. Dobby, I. M. Flint

"The objective of the laboratory work described in this paper has been to develop a method f or producing small gas bubbles at moderate to high gas rates in a flotation column. Small bubbles are particularly important for attaining reasonable flotation rates of fine particles. An ultrasonic aerosol generator has been employed to add frother solution directly to the gas stream. Using porous glass and filter cloth spargers, aerosol frother addition has produced bubbles at 1/2 to 2/3 the diameter of those produced by conventional frother addition to the liquid, at a lower frother consumption.IntroductionGas bubbles are generated in a flotation column most commonly by forcing gas through a porous medium called a sparger. Typical sparger material includes rubber (pierced with small holes) , fabric (such as filter cloth), fritted glass, or porous metal (steel or bronze) . Solid sparger material is suitable for laboratory use; however, for industrial applications a flexible sparger such as rubber or fabric is necessary to prevent the eventual plugging of orfices with solid particles and/ or precipitates. An exception to this is the use of a gas liquid contactor external to the column in combination with pressure release of gas in water, a method that has been demonstrated to produce very small gas bubbles. The typical objective of bubble generation for flotation column purposes is to produce bubbles with diameter of about 0.1 cm (and less) at a gas superficial velocity of 1 cm/s to 3 cm/s. In general, the smaller the bubble, the better. In man y cases, though, there is little , or nothing, gained by generating bubbles less than about 0.05 ern in diameter.Several factors affect bubble size when generated by a sparger: gas rate, orifice diameter, sparger surface area, surfactant type, surfactant dosage, and static head. At very low gas rates bubble diameter is independent of flow rate and is proportional to orifice diameter. At the moderate gas rates encountered in flotation columns bubble diameter, db&apos; is related to gas flow by: db oc vg n, where vg is superficial gas velocity (rate of gas flow per unit column area). For porous steel and filter cloth, n has a value of about 0.25 for vg between 0.2 cm/s and 2 cm/s(2). The magnitude of the effect of orifice diameter at these gas rates is unclear. The effects of frother type and concentration on bubble size issuing from a single orifice have been measur ed by Miagkovaru , shown here in Figure I(IS). The reduction in bubble diameter upon surfactant addition is due to the lowering of interfacial tension created by adsorption of surfactant at the gas liquid interface."

Jan 1, 1988