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By S. Sakurai

"Gravitational force is an external body force acting on underground structures. It should be noted that gravitational force cannot be replaced with the surface traction vector (Cauchy stress) which is an internal force. This fact should be properly taken into account in a numerical analysis of underground structures, particularly for structures such as vertical shafts, tunnels, and caverns constructed at great depths. It is obvious that the gravitational force must be conserved at all times.In conventional numerical analyses, the initial state of stress of the ground medium is firstly calculated under the gravitational field. This means that the gravitational force is replaced with stress (surface traction vector), and after that only the initial stress is considered in the calculation of the stresses and displacements of the structure. It should be noted that the initial stress is Cauchy stress consisting of a surface traction vector, while the gravitational force is a body force acting on the mass of the materials. This computational approach may be acceptable for elastic problems because the principle of superposition is valid for elastic materials. However, this approach becomes questionable for elasto-plastic materials because there is no guarantee that the principle of superposition is valid for them.Furthermore, another problem exists in elasto-plastic analyses: The stress state in a plastic zone must satisfy a yielding criterion such as that of Mohr-Coulomb. In order to make the stress state satisfy the criterion, an excess stress beyond the yielding criterion should be transferred to an elastic zone existing outside of the plastic zone. This seems to always be possible, because an elastic zone always exists, no matter how large of a plastic zone appears. In some cases, however, the excess stress cannot be transferred to the elastic zone because the gravitational force must be conserved. Therefore, it is obvious that the magnitude of stress around underground structures may become large and surpass the yielding criterion at great depths where a large gravitational force exists.In this paper, it is demonstrated that in a conventional elasto-plastic numerical analysis of a vertical shaft at a great depth, all the stress components around the shaft become very small, even though a large gravitational force exists. This strange result may be due to the fact that the gravitational force is not properly taken into consideration in the numerical analysis."

Jan 1, 2015

By Andre Vien, Jean-François Dupont

"Over the past several years, Svedala has developed a continuous charge monitor (CCM) for tumbling mills. It consists of a strain gauge embedded into a rubber lifter and associated electronics. This paper describes the installation and use of such a device on a SAG mill at the Holt-McDermott Mine. Comparison to measured static volumetric load and bearing pressure and inclusion of the measurement into a control strategy and its potential for condition monitoring is discussed. INTRODUCTIONWhile the measurement of load is very important in all kinds of grinding applications, the biggest benefits are expected from AG and SAG milling. This is what motivated Holt-McDermott to take a closer look at this problem, with a view to optimizing SAG mill performance.In many cases, the SAG mill control problem can be stated as maximizing throughput while avoiding a volumetric overload, with the other constraints (e.g. power, grind size, upstream/downstream equipment constraints, etc.) playing a less important role. This is certainly true at Holt-McDermott where the SAG mill is the production bottleneck about 90% of the time, and anything that can be done to increase SAG mill throughput will have a significant impact on operating profit.Although the goal of maximizing throughput while avoiding volumetric overload is simple to state, it has proven to be much more difficult to achieve. The mineral processing industry has expended a great deal of time and effort to devise control strategies in the pursuit of this objective. While much progress has been made, there is still room for considerable improvement. Across the industry it is probably fair to say that overloads occur relatively infrequently, but the real losses accrue as a result of the tendency to run rather conservatively."

Jan 1, 2001

By V. Falmagne

The mining sequence at Noranda?s Bell-Allard mine calls for two mining fronts retreating toward a central pillar known as the Retreat Zone between pyramids A and C. It is clear from numerical modelling and rock mass characterization that the induced stress level in the pillar will exceed the rock mass capacity. A mining plan was developed including the re-dimensioning of stopes in the Retreat Zone, additional ground support and instrumentation in order to ensure the safety of the workforce and to maximize ore recovery while minimizing production delays. The mining strategy consists in allowing the rock mass to fracture and fail progressively while maintaining control of the existing openings with the appropriate support. A systematic analysis of rockbursting and caving hazards was conducted for all accesses and stopes in order to plan ground support and instrumentation needs.

Apr 1, 2004

By K. Ebrahimi-Nasrabadi

The dependence between the extent of conversion of cryptocrystalline magnesite to caustic magnesia was studied experimentally in the temperature range of 400?1200 °C and for calcination times up to 8 h. A TGA?DTA analysis showed that decomposition begins at temperatures as low as 340 °C and is completed at 600 °C. Measurements of specific surface area (SSA), iodine adsorption number (IN), crystallite size, and loss on ignition were carried out to characterize the product quality. It was found that while all the parameters are dependent on the extent of calcination, densification of the product caused by grain coarsening affects their final values. As a consequence, SSA and IN went through a maximum with time. The study showed that high quality caustic calcined magnesia can be produced in a narrow range of temperature (600?650 °C) and time (1?4 h). Medium quality caustic calcined magnesia can be made within a wider range of parameters.

Aug 1, 2013

By Éric Létoumeau, Julie Fournier, Sylvain Caron, Yves Breau, Martin Plante, Dominique Girard, Luc Tardif, François Robichaud

"Since 1999, COREM (formerly the Centre de Recherche Minérale) has conducted and coordinated research and development activities for a consortium of mining companies that uses the benefits and advantages of collaborative pre-competitive research. In particular, COREM’s “In Situ Optimization Group” is involved in the development and implementation of modem information technologies related to process optimization and control.The POP Project was launched in order to increase and consolidate the use of such technologies applied to mineralurgical and metallurgical processes. To ensure a successful transfer to the industry, there are a number of essential activities that have to be undertaken. These activities have been identified by COREM’s members and are grouped into three main modules:- R&D Module: research and development in universities and research centres;-Technology Transfer Module: integration of new tools into the POP Software, industrial applications and technical support;- Training Module: education of new engineers in universities and continuing education of plant personnel through on-site workshops.This paper outlines the opportunities that led to the definition of the POP Project, presents its main objectives and describes its main modules. The main features of the POP Software are outlined, the first applications at COREM’s member plants are presented and, finally, future developments are discussed."

Jan 1, 2002

By D. B. Dreisinger, A. A. Gunaratnam

A pressure oxidation (POX)-hot cure (HC)-lime boil (LB) process is used in industry to recover silver from refractory gold sulfide ores containing minerals such as pyrite and arsenopyrite. Pressure oxidation is used to oxidize minerals and liberate occluded gold particles. As such, iron goes into solution and under acidic and high temperature conditions often precipitates as basic iron sulfate (BFS). BFS consumes excess lime during neutralization prior to cyanidation. Therefore, a hot cure stage is required to re-dissolve BFS back into solution. BFS re-dissolution consumes acid and produces ferric sulfate. In the presence of silver, these conditions favor the slow formation of silver jarosite. Silver jarosite is refractory to cyanidation, and must be broken down prior to cyanidation. This is done in the lime boil to produce a cyanide-soluble silver hydroxide. A study was conducted to investigate parameters that affect the precipitates that form in each stage of the POX-HC-LB process.

Jan 1, 2017

By J. Tuominen

Outokumpu Direct-to-Blister Flash Smelting is currently in operation in two smelters, a third one is under construction and a fourth one is in the design phase. The two smelters in operation are the Glogow 2 smelter of KGHM Polska Miedz S.A. in Poland and the Olympic Dam smelter of BHP Billiton in Australia. The Outokumpu Direct-to-Blister smelter of Konkola Copper Mines Plc. in Zambia is under construction and the new smelter of Glogow 1 is under design and waiting for final go-ahead decision. Additionally, the Garfield smelter of Kennecott Utah Copper Corp. makes blister copper out of matte in a Flash Converting furnace. A similar operation is under construction for Y anggu Xiangguang Copper Co. in China. The slag cleaning process, which is needed to clean the slag of the Direct-to-Blister Flash Smelting Furnace, has different requirements depending on the feed to the flash furnace. These differences are discussed in the paper. The differences between the processes and slag produced are discussed as well as the metallurgical requirements for slag cleaning. The Direct-to-Blister process, where the blister copper is produced directly from concentrate in one step, requires at least a partial treatment of the slag in an electric slag cleaning furnace. The existing impurities determine the specific requirements of the actual cleaning process. The different processes are discussed in the paper. The newest developments of Outokumpu Technology Oy for electric slag cleaning furnace design are presented as well as the characteristics which the furnace shape gives to the process.

Jan 1, 2007

By Walter Valery, Peter Radziszewski

"The NewCrest Cadia operation boasts the largest SAG mill commissioned last June 1998. A request was made to shed some more light on possible SAG mill charge behaviour. Three different software were used to simulate SAG mill charge behaviour:Mishra/Rajamanis MillSoft DEM charge motion program, Radziszewskis agglomerated DEM charge motion program and Powell/Nuricks MillTraj outer trajectories program. The contexts simulated are: 20/30 % charge volume, 65/75/85 % critical speed using the Hi-Lo lifter configuration specified for the mill as well as a Hi-Lo 60 degre lifter face configuration. Further, lifter interval was also studied to determine the effect on power draft. Power predictions are compared with those obtained during the commissioning period.INTRODUCTIONThe NewCrest Cadia operation is located outside of Orange, New South Wales, Australia. With proven reserves of 190 million tonnes at a grade of 0.75 g/t Au, the mill was designed to process 17 Mtpa (2065 tph) of ore with an 86% copper and 73% gold recovery. The grinding circuit (Fig. 1, Table I) boasts the largest SAG mill (Fig. 2) and was commissioned last June 1998."

Jan 1, 1999

By C. H. Buck, A. J. Taylor

"In 2015 Vale’s Clarabelle Mill began the process change to enable a higher degree of Cu separation. The flowsheet modification was part of a complete divisional flowsheet change being implemented in Vale’s Sudbury Operations. This paper will centre on some of the Operational Readiness (OR) work, culminating in the commissioning of the circuit in March 2017. The emphasis will be on the implementation of an integrated test plan to prepare for the process flow change through the mill.BackgroundClarabelle Mill (CBM) began making a saleable Cu concentrate in 2006 with the installation of the Cu separation circuit. Typical separation rate was 35-40% of Cu in feed reporting to Cu concentrate based on a target Ni concentrate Cu:Ni target of 0.7-0.8. The remainder of the recovered Cu (55-60%) reported to Ni concentrate and was smelted through the Copper Cliff Smelter.In 2013 a capital project, Surface Facility Upgrade (SFU), was implemented to focus on matching the surface plants capacities with the future mine plan to maximize revenues. This was to be achieved by redistributing the metal flow, specifically Cu, through CBM to increase metal unit content through the Smelter. The amount of redistribution of Cu was determined to be based on maintaining a stable Cu to Ni ratio (Cu:Ni) in the Ni concentrate.The change in Cu:Ni ratio in the Ni concentrate would affect the Sudbury divisional flowsheet, and required process changes across the all of the surface plants. The detail that surrounds the flowsheet changes as a whole will not be discussed, but the outcome of the decisions plays a large role in the operational readiness interactions between the mill, its suppliers and its downstream customers."

Jan 1, 2018

By M. H. Pelley

To increase drill fleet capacity and meet increased ore demands at its Carol Lake Project, the Iron Ore Company of Canada initiated a program in 1975 to convert the Gardner-Denver 120 and Bucyrus-Erie 60-R rotary drill fleet from 12 1/4-inch-diameter multi-pass drilling to 15-inch-diameter single-pass drilling. This paper will examine briefly the conversion program , including some tests and results, and examine how the utilization of the 15-inch-diameter blast-holes, coordinated by a comprehensive drilling and blasting program, has improved the drilling, blasting and drilling-plus-blasting aspects of the mine operations, from both economic and operational viewpoints.

Jan 1, 1978

By J. H. McKibbon

THE metallurgical industry has purchased more than sixty per cent of the industrial gas cleaning equipment installed in Canada. This includes cyclonic collectors, scrubbers, cloth filters and Cottrell Precipitators. These are the principal types of equipment which are used commercially for the cleaning of gases which result from the processing of iron, nickel, copper, lead, zinc, gold, gypsum and aluminum ores. The recovered dust, which usually contains metal values, is returned to the process. The cost of the equipment is thus economically justified. This is in contrast to other industries, such as those involving steam power generation, asbestos, cement and lime production, where, though dust collection equipment is extensively used, it is installed primarily for nuisance abatement. Communities are becoming more and more conscious of air pollution, new and more stringent legislation is being enacted, and, for other than economic reasons the smelting industry will eventually be required to install more efficient gas cleaning equipment. This paper

Jan 1, 1962

By F. J. MacPherson, A. C. Caron

"Cassiar Asbestos Corporation Limited is at present B,C.'s only asbestos mining company, and has been actively engaged in the management and operation of the Cassiar Mine since the early 1950's. The Cassiar operations are located between 3,500' and 6,600' elevation in a secluded mountainous area of northern B.C., approximately 100 miles by road southwest of Watson Lake in the Yukon Territory. Climatic conditions in this area range from mild warm in the summer, to extremely cold during the long winter period.The minesite itself is located over a mile above sea level at the top of McDame Mountain, where year round 24 hours per day miners extract the chrysotile ore from the surrounding waste by standard open pit techniques. The ore body dips into the mountain at about a 45° angle, and as the mining progresses, larger stripping ratios are required. Waste to ore ratio this year will be more than 10 to l whereas only a few years ago ratios of 3 or 4 to l were possible. After drilling, blasting, and loading by shovel onto trucks, the asbestos ore is transported to the Primary Crushing Plant for crushing prior to transport by aerial tramway more than three miles to the Concentrator and Mill in the valley below, where the fibre is extracted from the barren host rock serpentine and milled into numerous grades for shipment to asbestos users round the world. The major air usage is associated with the milling process, presently requiring over 500,000 CFM, with future requirements expected to exceed 840,000 CFM by the end of the decade."

Jan 1, 1976

By H. O. Lien

Among the known iron deposits in Canada, many are of low grade and require beneficiation to produce an acceptable blast-furnace feed. Some of the deposits have never been considered for commercial exploitation due to the lack of a suitable concentrating process. A number of deposits of this type are located in Northern Ontario. The problem in upgrading these deposits is three fold. Firstly, the iron occurs as a mixture of magnetite and hematite. Secondly, the grain size of the material can be fine to very fine. Thirdly, the complex mixture of gangue minerals, which consists invariably of silica, flaky silicates and carbonates, slimes excessively on fine grinding. Algoma's efforts to concentrate these iron-bearing materials culminated in the development of a "Selective Flocculation and Desliming Process" employing slimes removal as the sole beneficiation technique. The process was applied successfully in the laboratory using two stages of grinding and a total of seven deslimings. Prior to the removal of slimes, the iron-bearing fines were selectively flocculated from a thoroughly dispersed pulp using a modified starch as flocculant, Sodium silicate was employed as dispersant. An attempt was made to optimize some of the process variables using material from one specific iron formation near the town of Geraldton in Northern Ontario. The preparation of the starch proved most critical. This matter, and the method used to evaluate the degree of breakdown of the starch molecule, are therefore discussed in some detail.

Jan 1, 1978

By Fathi Habashi

New technology first introduced by Nippon Steel Corporation at Kitakyushu in Japan in 1976 now used at a number of plants in other countries, known as dry quenching of coke, uses nitrogen in a closed circuit to avoid environmental emissions. In addition, heat is recovered in the form of steam, from the red-hot coke. In steel plants oxygen is used extensively and therefore by-product nitrogen from air liquefaction can be effectively utilized in this way.

Jan 1, 2014

By Y. M. Shneerson, P. V. Zaytsev, I. V. Fomenko, M. A. Pleshkov

A thermodynamic description of the equilibrium in liquid and gas phases under specific conditions of refractory gold pressure oxidation was generated using the HKF theory. The gold behavior was considered at 190-225°C in the presence of 1-100 mg/L of chloride ion, and under oxidationreduction potential (ORP) of +700 to +1030 mV. The calculations show that the predominant form of gold(I) occurrence is [AuOH]° compared to [AuCl2]?. High ORP favors the formation of [AuCl4]? as a predominant form of gold(III). It is noted that this complex is responsible for the gold losses buildup during POX. Laboratory test results for double refractory concentrate POX are shown. The combined negative effect of (i) organic carbon of the concentrate and (ii) dissolved chlorides in POX slurry on gold recovery is demonstrated. The effects of carbonate blending to the POX feed concentrate and incomplete oxidation of sulfides on POX performance were studied. The pilot tests results of continuous pressure oxidation are also shown and generally confirm the laboratory results and theoretic dependencies. A comparison of the experimental data with the results of thermodynamic calculations is made. As a result of current research, an effective process for POX treatment of carbonaceous sulfide concentrates in the presence of chlorides was developed.

Jan 1, 2014

By C. Carlson, W. Muir

"The oxygen demand of the complex lead-zinc-iron feed at the Cyuro Anvil concentrator was determined denendent on the cyanide ion con-contration of the pulp. By redistribution of the cyanide [ ] the grinding circuit in direct proportion to the amount of surface area created, a more activated flotation feed in obtained.Monitoring the oxygen demand of the flotation feed and grinding mill discharge has proved useful in diagnosing metallurgical problems day to day operation."

Jan 1, 1976

By Manqiu Xu, Songtao Yang, Zongfu Dai, Robert Pelton

"Hydrophobic polystyrene nanoparticle suspensions were evaluated as potential flotation collectors for pentlandite. Experiments involving both clean model mineral suspensions and complex ultramafic nickel ores confirmed that conventional water-soluble molecular flotation collectors such as xanthate could be partially or completely replaced by hydrophobic nanoparticle flotation collectors. The ability of nanoparticles to induce flotation was demonstrated by floating hydrophilic, negatively charged glass beads with cationic polystyrene nanoparticle collectors. Electrostatic attraction promoted the spontaneous deposition of the nanoparticles on the glass surfaces raising the effective contact angle sufficiently high to promote the adhesion of beads to air bubbles. As little as 10% coverage of the bead surfaces with our most effective nanoparticles could promote high flotation efficiencies, whereas conventional small molecular flotation collector requires ~ 20% or higher coverage for a good recovery. Surface functionalized nanoparticles enhanced the ability for nanoparticle collectors to selectively deposit onto surfaces of the desired mineral particles in the presence of gangue. For example, poly (styrene-co-vinylimidazole) nanoparticles were designed to selectively deposit onto nickel mineral (pentlandite) in the presence of Mg/Si slime. Flotation tests of ultramafic nickel ores at Vale with these nanoparticle collectors have shown improvements in both pentlandite recovery and selectivity. On-going work includes attempts to identify specific applications where nanoparticle flotation collectors might be cost effective.INTRODUCTION Most mineral processing operations include multiple stages of froth flotation to concentrate and isolate the desired product. Before flotation, chemical collectors are routinely added to ground ore slurries, selectively binding to mineral-rich particles, increasing their hydrophobicity thus promoting selective flotation. (Fuerstenau, Jameson, & Yoon, 2007) Conventional collectors are surfactants with a short hydrocarbon tail and a head group, such as xanthate. A typical conventional collector is potassium amyl xanthate (PAX), which is a small molecule with an extended molecular length of about 1 nm. Critical characteristics of a good collector include the ability to selectively adsorb onto desired mineral surfaces and to lower the water/mineral surface energy. Despite the extensive role of flotation in mineral processing, some ores are difficult to process by flotation. For example, ultramafic nickel sulfide ore containing both valuable pentlandite and large quantities of unwanted Mg/Si slime [primarily serpentine, (MgFe)3Si2O5(OH)4] responds poorly to flotation. (Mani, Xu, Quinn, & Stratton-Crawley, 1997) Fibrous hydrophilic Mg/Si slime usually masks the surface of pentlandite (known as “slime coating”) due to electrostatic interaction (Edwards, Kipkie, & Agar, 1980) and dramatically depresses pentlandite flotation. Consequently, new approaches are required for processing these difficult ores."

Jan 1, 2012

By C. J. Martin, M. P. Hay

"A methodology was developed in the mid-1980’s to predict plant performance from standard laboratory flotation tests. The technique is based on a simple, empirical kinetics model, and is tailored for use by the practical metallurgist.To date the performance of more than 20 flotation plants has been predicted, including copper, lead, zinc, phosphate, pyrite, graphite, cassiterite, platinum, nickel and various slags. The method has successfully been used to predict and size four flotation plants directly from bench-scale laboratory flotation testwork. All have since been commissioned, and have performed as predicted.The technique has now received broad acceptance within the South African mining industry, for example in the last year alone it has been used to drive flowsheet development for at least seven new plants. It is also being used to assist in the optimisation of existing operating plants.The methodology is described in this paper and verification of the methodology is presented using case studies of porphyry, polymetallic and PGM operations.INTRODUCTIONThere is considerable interest these days in the use of modelling to simulate flotation circuits, for process design and plant optimisation purposes. Although these models are proving to be useful tools for plant design and optimisation, their complexity can make them cumbersome – expensive to use and difficult for metallurgists to visualise and mentally absorb, without a background in each specific technique. In “SUPASIM” no attempt is made to measure flotation fundamentals, rather to use empirical relationships between laboratory flotation kinetics and plant performance – relationships that hold up well to validation exercises as will be demonstrated later in this paper. Although not designed to be as comprehensive as other models, “SUPASIM” is easily understood by the operating metallurgist and can be quickly and easily applied."

Jan 1, 2004

By Jochen Petersen, Caroline Muzawazi

The technical feasibility of ammonia leaching of PGM bearing Platreef flotation concentrates was investigated as an alternative method for the recovery of base metals prior to precious metal recovery. The composition of the concentrates includes 2.02% Cu and 3.17% Ni, and the major base metal minerals are chalcopyrite and pentlandite. Optimal leaching conditions were initially established in shake flask experiments to be a solution containing 4 M NH4OH, 4 M (NH4)2CO3 and a pH range between 9 and 10. These were used as base case conditions in column and batch stirred tank reactor tests, where the effects of total ammonia concentration and operating temperature were explored further. At optimal conditions nearly 100% Cu and Ni extraction were obtained in the batch stirred tank reactor, and 95% Cu and 60% Ni extraction was obtained in columns. The activation energy for chalcopyrite and pentlandite was 36 kJ/mol and 16 kJ/mol, respectively, in both reactors, indicating different reaction pathways for the two minerals. Gas-liquid mass transfer appears to be the limiting reaction step in columns much more than in tanks, and the degree of ammonia loss to air is significant. This initial test work indicates the feasibility of using ammonia leaching for this and similar materials as an alternative route to conventional smelting and refining prior to PGM recovery, but a number of technical challenges still need to be overcome.

Jan 1, 2014

By O. Lashkari

Swirled Enthalpy Equilibration Device (SEED) is a new patented Slurry-on-Demand, SoD, processing route. The semi-solid slug preparation is carried out by off-center swirling of aluminum melt in a metallic mould. As part of the current research program on the semi¬solid processing of aluminum alloys, the morphological evolution of 356 aluminum foundry alloy microstructure is reported here. Semi-solid slugs were prepared using two different pouring temperatures of 645°C and 695°C respectively. Morphological evolution of the semi-solid microstructure was characterized using image analysis through measuring of primary a-Al particle size, number density, aspect ratio and sphericity. The possible relationships between microstructural features and process parameters were also investigated. The current report covers the effect of pouring temperature on the morphology of primary a-Al dendrites and attempts are made to explain the differences between the predicted percentage primary a-Al phase and those of the actual values in the as-cast slugs.

Jan 1, 2004