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By S. J. Buckler

Many metallurgical processes use submerged gas injection to increase the contact area between gas and liquid phases in order to promote faster overall reaction rates. The work presented in this paper is part of an experimental investigation to measure the gas-liquid interfacial area available in bubble plumes within molten metal baths. Measurements of the nitrogen absorption rate during submerged injection into molten iron baths have been used to estimate the interfacial areas of the bubble plumes. A theoretical model was used to predict the superficial nitrogen transfer rate under mixed liquid phase mass transfer -interfacial reaction control. The interfacial area was calculated by dividing the overall nitrogen absorption rate by the superficial rate. Reasonable agreement was obtained between the interfacial areas measured in our laboratory with data from a comparable system reported in the literature. The experimental results were compared with the predictions of three theoretical models and one empirical correlation. The models of Turkdogan (3) and Zhao and Themelis (5) gave the best agreement with our data.

Jan 1, 2004

By J. P. Rajot, H. Mouzannar, M. Bost

"The design of rock foundations may need to evaluate shear strength of rock-concrete interface by performing laboratory direct shear tests. A series of tests were carried out on specimens for different values of the spacing free of encapsulating material about the shear plane and different values of normal stress. Different kinds of failure were observed and not necessarily at the rock-concrete interface. The spacing free of encapsulating material appeared to be of significant influence on the test results. A mechanical analysis is presented which illustrate the influence of the loading conditions in the direct shear box on the failure mechanism. INTRODUCTIONThe design of rock foundations subjected to significant lateral loads requires defining the value of the shear strength of the interface between rock and cast in place concrete. Verifying the stability against sliding of strip footings subjected to inclined loads (SETRA, 2009) or concrete gravity dams (CFBR, 2013) are common examples where design modelling approaches imply the shear strength, sometimes the deformation behavior, of the rock-concrete interface, more or less assumed as a failure plane.Defining the behavior of rock-concrete interfaces relates to tribology. Many studies have been conducted to improve the representation of this behavior (e.g., Johnston & Lam, 1989; Kodikara & Johnston, 1994; Gu, Seidel & Haberfield, 2003; Saiang, Malmgren & Nordlund , 2005; Fishman, 2008; Eltervaag, 2013; Gutierrez, 2013), raising many questions. The behavior appeared to be influenced by many factors such as the geometry of the interface which is not planar, the roughness of the natural rock, the rock mineralogy and the concrete formulation. In addition, the study of the shear strength of rock-concrete interfaces involves considering the two different deformation behaviors of both rock and concrete. Finally, the observed failure mechanism is strongly influenced by the initial cohesion due to adhesion between the two materials when concrete is directly cast onto rock."

Jan 1, 2015

By Christina Graf

A synthesis of colloidal gold shell particles with a silica core is described. Small gold nanoclusters were attached to the functionalized surface of colloidal silica particles. Reductive growth and coalescence of these clusters lead to the formation of a closed gold layer. By variation of the thickness of this gold layer and the radius of the shell it is possible to adjust the plasmon resonance of the gold shell particles over the whole visible and infrared region of the spectrum. The optical properties of the particles made are in good agreement with theoretical calculations for coreshell particles. Due to their low polydispersity these gold shell particles form in solution large crystals with submicron lattice constants. It is also possible to produce hollow gold shells by dissolution of the silica core. A new method to coat the silica core gold shell particles with an additional outer silica shell is also presented. This allows due to a reduction in the Van-der-Waals forces to make more permanent dried crystals and facilitates functionalization of the particles for use in various photonic applications.

Oct 1, 2003

By A. L. Hinde, H. Dong, J. T. Kalala

"The High Pressure Grinding Roll (HPGR) is gaining acceptance in the mineral processing industry and has become a competitive technology in reducing the specific energy consumption in Mineral processing plants. The amount of samples required for HPGR amenability testwork and HPGR wear tests is usually high and often cannot be available at early stage of projects were only a few drill cores are available.Although HPGR was initiated from small scale piston die compression tests, the development of small scale piston die test to predict the performance of HPGR has been slow.The objectives of this paper was to present the designs, operating procedure of piston-die press and operating conditions which have resulted in similar particle size distribution obtained from a piston die test and HPGR Labwal unit starting from the same feed size distribution. Testwork were conducted using a 2 MN piston-die press and a Labwal HPGR unit on major South African ore types, viz, gold, platinum and iron ores. The results obtained show that piston-die test can generate data to predict energy consumption, product size distribution, and even to evaluate the edge effect."

Jan 1, 2012

The control of carbon concentration in a counter current carbon absorption circuit is critical to optimise gold recovery. MINTEK has developed a carbon movement controller to address this potentially problematic area in gold extraction. This controller reduces operator interaction by automating carbon movement. Elution schedules are entered into the control system, which then moves the carbon through the circuit into the first adsorption tank until enough carbon is available for elution. This is done while maintaining the specified carbon profile within the circuit. MINTEK has also developed an online-carbonconcentration- meter to measure carbon concentration in pulp. The meter uses an ultrasonic measurement technique. Long term testing has shown the measurement to be robust and require minimal maintenance. Results from a gold mine in South Africa’s well known Witwatersrand gold producing area has shown a decrease in soluble gold loss between 30 - 50% when the controller was used.

Jan 1, 2014

By Min-Sung Kang

Excavation and earthmoving equipment mostly operate in accident-prone areas. These areas normally have rollover, confinement, and fall or may be considered harmful work areas due to demolitions and sewage removals. It is inevitable that excavation and earthmoving systems should be developed to secure the safety of operators through unmanned and remote control systems. Therefore, this research proposes a system that enables excavators to be unmanned and remote controlled without any renovation, remodeling, change, or transformation by applying attachable and separable mechanism and modules. Moreover, this research proposes the sensor module to evaluate the dynamic status without processing remodeling or transformation the existing hydraulic drive excavation system by adopting the easy attachable and separable mechanism. The study verifies this proposal based on observed possibility and feasibility through the experiments.

Aug 1, 2013

By M. R. Julien

"The geomechanical behavior of rocksalt shows very distinctive features. The response of this most ductile of all low porosity rocks is dominated by inelastic processes that are strongly time- and historydependent. These characteristics must be taken into account when analyzing underground openings. Different constitutive models have been proposed and used for this purpose, and this paper presents the general formulation and applications of one of these. The SUVIC model relies on a unified approach with internal state variables producing mixed hardening to represent the inelastic behavior, which lead to specific solutions for plasticity and creep. The model equations have been implemented into a finite element code to perform numerical analyses. Simulations results are presented to show that this model captures essential aspects of rocksalt behavior under simple and complex laboratory testing conditions. Simulations are also conducted to analyze the response of underground openings. INTRODUCTIONPredicting the response of man-made excavations in rocksalt can be quite a challenge as it requires a reliable constitutive model to represent the material behavior. This softest of all low porosity rocks shows a highly non-linear inelastic behavior, very sensitive to history and rate effects (e.g. Senseny et al., 1993; Cristescu & Hunsche, 1997; Julien, 1999; Wittdke, 2014). The many deformation (micro) mechanisms acting locally in rocksalt make the construction of appropriate constitutive equations quite complex. Nonetheless, there have been significant progresses made over the last two decades or so; many of these developments have been included in a series of specialized Conferences Proceedings (Ghoreychi et al., 1996; Aubertin & Hardy, 1998; Cristescu et al., 2002; Wallner et al., 2007; Bérest et al., 2012)."

Jan 1, 2015

By M. Leijd, K. S. Forrester, M. Saxon, M. Oczlon

This paper provides an introduction to wet high intensity magnetic separation (WHIMS) and its successful application to the beneficiation of rare earth element (REE) enriched eudialyte. The analysis includes an in-depth reporting of the deportment of key elements as well as a statistical interpretation of the relative importance of operational parameters including magnetic field intensity, flow velocity, and matrix loading density. Conclusions are drawn on the relative success of the technology, potential areas for process improvement, and the research direction that continues to be investigated. Three original equipment manufacturer (OEM) technologies were subjected to a series of screening and characterization tests to identify the optimal operating parameter set to magnetically beneficiate eudialyte from Norra Kärr, Sweden. Upon the completion of the characterization test it was apparent that the Metso HGMS technology was superior with respect to REE recovery and gangue rejection for the Norra Kärr composite. The Metso HGMS was then subjected to a series of verification tests to confirm the repeatability and reproducibility of the system.

Jan 1, 2014

By Anthony McDonald, Dominic Verhelst

"Hudson Bay Mining and Smelting Co. Ltd. (HBM&S) started up a zinc plant and smelter in late 1930, employing technology of that period. The zinc plant has since converted from a roast/leach operation to a two stage pressure leach operation to eliminate sulphur dioxide emissioms. The smelter, however, is still continuing with much of the original roaster/reverberatory furnace technology. This paper reviews the process flow of the copper smelter, with some comments on past and recent changes.Smelter FlowsheetPrior to July 1993, the HBM&S smelter operation consisted of seven areas, namely feed preparation, roasters, reverberatory furnace, converters, anode casting, fuming plant, and dust collection. A simplified smelter flowsheet is shown in Figure 1. The data for tonnage of materials moving through the circuit are presented in Tables I to 4, and are representative of the time period from July 1992 to June 1993. A change in the zinc plant technology in 1993 resulted in the elimination of a zinc-bearing sulphide leach residue from the smelter feed blend, thereby greatly reducing the zinc content of slag produced in the smelter. Consequently the fuming plant and ancillary equipment, such as the drying plant, were shut down. These areas will, however, be described. With the closure of the zinc fuming furnaces all the slag from the reverberatory furnace is now discarded to stockpile.The over-all smelter metal recoveries are 96% for Cu and rn.5010 for Au and Ag. Figures 2 and 4 indicate historical production numbers of copper, silver and gold, respectively. A review of the minor element distribution in the smelter can be found elsewhere."

Jan 1, 1994

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 A. Warczok

The mechanisms and kinetics of copper oxidation and reduction have been investigated in small scale thermal gravimetric experiments as well as in laboratory pilot scale, packed bed reactors. With blister copper flowing gravitationally down through a packed bed of ceramic particles, counter-current to low oxygen containing combustion gases, the rate of oxidation was found to be very high due to the large surface area created. Similarly, reduction by flowing copper through a packed bed of charcoal lead to rapid de-oxidation. Based on these laboratory measurements, fundamental rate data have been obtained. Modeling of industrial sized packed bed reactors using the laboratory results, opened up the possibilities of developing a new, very intensive, continuous process for copper fire refining. The developed mathematical model together with a computer process simulator, allowed for the design of the industrial-pilot installation to be built and tested at the ENAMI Paipote smelter in Chile.

Jan 1, 2007

By V. V. Severov, Z. Lafhaj

The flotation separation of salt type calcium minerals is problematic, due to the similarities in their formation properties and the same active Ca2+ related site for interaction with anionic collectors and similar physicochemical characteristics such as solubility, point of zero charge, surface speciation, Ca-site density. The work was performed to achieve effective and selective separation of the calcium-minerals using pure minerals samples: four calcite, two fluorite, and two apatite samples. The effect of pure and mixing anionic collectors such as oleic and linoleic acid to different ratio (2:1; 1:1; 1:2) as well as the role of nonionic collectors on the selective separation of Ca minerals were studied. All flotation tests were performed in self-aspirated flotation cell. The results obtained with the blend of anionic collectors with the molar ratio of 2:1 show a separation between apatite and calcite at pH 5 and a ratio 1:2 at pH 9. The enhancing of separation contrast using the sodium silicate as a depressant for calcite and apatite is also examined as a function of oleate/linoleate ratio. Additionally, this paper discusses the enhancing of the selective separation of Ca minerals when anionic collectors were blended with nonionic reagents. The surface reactions in aqueous mineral suspensions and the adsorption of anionic collectors blended with nonionic reagents were studied by FTIR spectroscopy. An unexpected synergistic effect was observed for some ratios between anionic and nonionic reagents. The mixture of fatty acids and nonionic reagent showed very high flotation efficiency in comparison with fatty acid alone for the flotation of an igneous low-grade phosphate ore.

Jan 1, 2016

By C. Ayora

The Iberian Pyrite Belt (SW Spain and Portugal) contains one of the largest reserves of pyrite in the world with mining activities dating back to prehistoric times. About one hundred abandoned mine wastes and galleries release a huge acidity and metal load to the Tinto and Odiel rivers. Once the mining activity is over, polluting discharges can persists for decades or even centuries with no specific responsible entity. In-situ passive remediation technologies are especially suitable for these orphan sites. The concept is to insert a reactive porous material in the natural flow path of contaminated surface and ground waters, and it is implemented through infiltration ponds and reactive barriers, respectively. Calcium carbonate pea-size gravel is the common alkalinity supplier to neutralize acidity and precipitate metals. These remediation systems have been traditionally implemented in coal mines. However, the acid drainages from the Iberian Pyrite Belt contain metal concentrations one to two orders of magnitude higher than those from coal mines and require special designs to avoid quick clogging or passivation (coating) of the grains of reactive material. To overcome these problems, a Dispersed Alkaline Substrate (DAS) mixed from fine-grained limestone sand and a coarse inert matrix (e.g. wood chips) was developed. The small grains provide a large reactive surface and dissolve almost completely before the growing layer of precipitates passivates the substrate. The high porosity and the dispersion of nuclei for precipitation on the inert surfaces retard clogging. However, limestone dissolution only raises pH to values around 6.5, which is sufficient to precipitate the hydroxides of trivalent metals (Al, Fe), but it is not alkaline enough to remove divalent metals. Magnesium oxide, which hydrates to Mg hydroxide upon contact with water, buffers the solution pH between 8.5 and 10. A DAS system replacing limestone with caustic magnesium oxide has been tested to be very efficient to remove divalent metals (Zn, Cd, Mn, Cu, Co, Ni, Pb) from drainage previously treated with limestone.

Aug 1, 2013

By K. Swedburg, M. Samuels

"The expansion of the concentrator at New Gold’s New Afton copper-gold mine in British Columbia, Canada, completed in 2015, included an increase in the required retention time of the cleaning circuit. On site pilot testing of a Woodgrove Staged Flotation Reactor (SFR) had shown that a high grade copper concentrate would be produced with excellent recovery. The SFR was selected rather than conventional tank cell technology based on the much smaller footprint (which rendered a separate and expensive building extension unnecessary), high concentrate grades demonstrated in testing, and the lower energy requirement. Three SFRs, each capable of taking a nominal feed of 700 cubic meters per hour were installed and commissioned 10 months after the receipt of order. The SFRs operate in series and all of the cells produce a final concentrate typically grading 32% Cu, while the overall SFR stage recovery averages 55%. The tailings from the SFRs are treated in the original conventional three-stage cleaner circuit where the remaining values are recovered in a concentrate grading 28% Cu. Design production was achieved within days of the initial start-up of the SFR circuit.INTRODUCTIONThe New Afton concentrator, located near Kamloops, British Columbia, Canada processes a copper-gold ore with a designed head grade of 0.96% Cu, 0.72 g/tonne Au, and 2.22 g/t Ag.The New Afton Mine is a block cave mining operation. Ore is undercut from the bottom up and removed at the extraction level from a grid of draw points. Ore is trammed to the ore passes by underground loader and dropped to a haulage level for transport by trucks to the gyratory crusher. From the crusher, the ore is conveyed to the mill via a 4.5 kilometre long conveyor system. Block caving was chosen for the New Afton deposit because the underground infrastructure could be built below the historical open pit of the Afton Mine (a previous operation of Teck Resources) and this method is favorable to large-scale low-cost mining.The New Afton deposit is a copper-gold, alkalic porphyry system. Hypogene mineralization is characterized by discontinuous copper sulphide veinlets and disseminations, principally chalcopyrite and minor bornite, along with pyrite as the second most dominant sulphide. Gold particles vary in size from 5 µm to 40 µm and occur as native gold and electrum, associated mostly with the chalcopyrite grains and never with the pyrite. In some instances, a second alteration phase has resulted in the copper sulphides being replaced by tennantite-tetrahedrite locally and along faults that transect the mineralized body. The design head grade of arsenic is 244 PPM, although the presence of tennantite is inconsistent and can vary from trace levels to 15% of the total copper. No arsenopyrite is present in the hypogene ores. Supergene mineralization, consisting of native copper with accessory chalcocite occurs in minor amounts along faults and highly oxidized near-surface portions of the deposit."

Jan 1, 2016

By Aysan Molaei, Kristian E. Waters

"Solvent extraction is the one of the most common techniques for recovering metal ions from aqueous systems. However, it is not efficient in the extraction of low concentration metal ions from aqueous solutions. Predispersed solvent extraction (PDSE) is an alternative method for solvent extraction which implies colloidal liquid aphrons as extracting agents in order to reach higher interfacial area and lower reagent consumption. This work investigated important parameters in PDSE of nickel ions from dilute aqueous solutions by fractional factorial design of experiments. Four experimental parameters, the initial extractant concentration, initial surfactant concentration, equilibrium pH and phase volume ratio (organic to aqueous ratio) were investigated. The important parameters were determined as well as important interactions between these parameters. It was found that extractant concentration, phase volume ratio, and equilibrium pH are the most significant experimental parameters. However, the interaction between surfactant concentration and other parameters was determined as significant interactions.INTRODUCTIONNickel is one of the key components found in cars, mobile phones, rechargeable batteries, kitchen appliances, and steel industry (Anyadike, 2002). It is one of the most important metals produced by Canada which is in the five top nickel producers in the world. Despite a 24% decrease in the nickel prices from 2011 to 2014 the nickel global mine production increased by 36% between these years (U.S. Geological Survey, 2015; Nickel - Statista Dossier, 2015), which shows the increasing demand for nickel. This high demand leads producers to consider the production of nickel from low grade ores and other secondary sources such as process wastewaters. The removal of nickel ions from process wastewater is also important due to environmental considerations. Nickel is known to be a human carcinogen and it may cause serious lung and kidney problems, pulmonary fibrosis, gastrointestinal distress, and skin dermatitis if it exceeds the critical level (Borba et al., 2006; Fu & Wang, 2011)."

Jan 1, 2016

By L. I. Kiss, S. Perron, D. Toulouse, S. Poncsák, A. Perron

Bubbles play an important role in many industrial processes. In a Hall-Heroult cell, used for aluminum production, bubbles contribute to induce flow in the cell. The induced flow is important for the thermal balance of the cell as well as for the distribution and dissolution of the alumina. The existence of the bubble layer does not have advantages only. It increases the voltage of the cell and causes deformation along the cryolite-molten aluminum interface. The role of the anode inclination in the behaviour of the bubble layer as well as in the hydrodynamics of the bath is not clearly understood. In this work, the effect of the anode inclination angle on the bubble driven flow is studied in an industrial scale air-water model. The inclination angle is varied up to 5° from the horizontal. The instantaneous flow field is captured by Particle Image Velocimetry (PIV) system. The mean velocity fields were calculated by ensembleaveraging the instantaneous velocity fields measured at different time. The existence of the counter-flow in the interpolar space and the vortex in the side channel has been confirmed. Furthermore it has been observed that the effect of anode slope on the velocity field is weak.

Jan 1, 2006

By Greg Collins

BUCKO EXPLORATION HISTORY ??1964-Discovery ??1970?s -114 holes totaling 34,000 metres drilled -vertical shaft excavated to a depth of 300 metres (1000 Level) plus 800 metres of underground development -Exploration program cancelled due to Falconbridge economic issues ??1990?S-19 holes drilled totaling 9,600 metres ??2000 -13 hole 4,600 metre exploration program by Nuinsco Res.

May 1, 2006

The tensile test results of as-cast A356.2 grain-refined alloy castings show that the tensile strength can be improved by strontium modification (`SrM'), superheating at 900°C OM, and melt thermal treatment of the Sr-modified alloy melt (`SrMTT'). Both SrM and SrMTT processes can greatly improve the ductility (percent elongation) of the as-cast alloy. During solution heat treatment at 540°C, eutectic Si particles undergo fragmentation, spheroidization, and coarsening, thereby affecting their morphology. The effects of solution heat treatment on the tensile properties of the variously treated A356.2 alloy castings can be summed up as follows: the yield strength of the castings is significantly improved after 8 h solution heat treatment due to the precipitation of Mg2Si, after which it remains more or less the same with the further increase in solution treatment time up to 80 h; the ultimate tensile strength is also greatly improved within the first 8 h of solution heat treatment and then remains at the same level thereafter, up to 80h of solution treatment. The improvement in UTS is attributed to Mg2Si precipitation, dissolution of Si within the aluminum matrix, and changes in the Si particle morphology (spheroidization). The ductility of the as-received grain refined non-modified (`NM'), grain refined and superheated at 900°C (`SH'), and melt thermal-treated grain refined (`MTT') A356.2 alloy castings can be improved considerably with solution heat treatment e.g. from ~6% in the as-cast non-modified casting to ~10% after 80 h solution treatment.

Jan 1, 2011

By Sebastian Siebert

Unmanned Aerial Vehicles (UAV) as a data acquisition platform and as a measurement instrument have become attractive for many surveying applications in civil engineering. However, their performance is not well understood for these particular applications. The specific scope of the presented work is the performance evaluation of a UAV system that was built to rapidly acquire mobile 3D mapping data for large earthmoving construction sites. Details to the components of the developed system (hardware and control software) are explained. A novel program for photogrammetric flight planning and its execution for the generation of 3D point clouds from digital mobile images is explained. A performance model for estimating the position error was developed and tested in several realistic construction environments. Results to these tests are presented as they relate in particular to large excavation and earth moving construction sites. Results and experiences with the developed UAV system are in particular useful for researchers or practitioners in need for successfully adapting UAV technology for their application(s).

Aug 1, 2013

By Yves Pépin, Sylvain Lefebvre, Dimitrios Filippou, Guillaume Hudon

"Titanium dioxide pigment plants using the so-called “chloride process” produce considerable amounts of chloride waste, which contains predominantly iron chloride. In most cases, this waste is dissolved in a weak hydrochloric acid solution and then neutralised. The metal content of the waste is dumped as hydroxide sludge, while its chloride content is lost in an effluent.Rio Tinto Iron & Titanium has developed a new proprietary process whereby pure metallic iron and chlorine gas are recovered from chloride waste by electrolysis. This process uses a two compartment cell separated by an anion exchange membrane to prevent iron cycling between its trivalent and divalent valence. The cathode is made of titanium Grade 7, while the anode is a dimensionally stable one of the type “metal–mixed metal oxide” (MMO) for the evolution of chlorine gas. The catholyte is concentrated and pH-adjusted iron-rich chloride solution originating from chloride waste. The anolyte is recirculating solution containing alkali or alkali earth chlorides such as MgCl2, NaCl, etc. Current efficiencies above 90% can be achieved at temperatures about 80°C using catholyte solutions almost saturated in iron chloride and other chlorides.In this paper, we discuss the details of this process, and how this could be integrated within a chloride pigment plant for the treatment of chloride wastes."

Jan 1, 2016