Search Documents

By V. Barranco, K. Yliniemi, A. Hubin, B. P. Wilson, D. Janas, M. Lundström, P. Hannula

Typical copper electrorefining electrolyte contains tens of grams of copper, some nickel and a wide variety of impurities. Some of these impurities comprise trace amounts of dissolved precious metals like Ag, Pd and Pt that currently are not fully exploited. This study presents an electrochemical method to recover precious metals via a combined electrodeposition-redox replacement (EDRR) process, where energy is used only to deposit copper during the ED-step, while the RR-step relies on the spontaneous replacement of copper by the precious metals (i.e. cementation). In order to conduct the recovery successfully, process parameters such as deposition potential (EDE), deposition time (tDE), redox replacement time (tRR) and the number of cycles (n) was adjusted. Investigations performed in synthetic electrolyte (40 g/L Cu, Ag = 10 ppm) proved the possibility to recover a high purity silver. Short deposition times (tDE) were found to result in small Cu particles that provided a suitably high surface area for silver cementation. In addition, experiments performed in real industrial electrolytes containing 44 g/L Cu and 54 ppb Ag (Boliden Harjavalta, Pori), demonstrated that EDRR could attain Ag recoveries of between 46–67% in an energy efficient, additive-free manner. INTRODUCTION The raw materials used in the state-of-art primary and secondary copper smelters contain mainly base metals, but also notable amounts of Ag, Pt and other precious metals. These valuable metals distribute mostly into the copper matte during the pyrometallurgical treatment (Tirronen et al., 2017) and end up into the cast anodes. During the electrorefining stage, metals more noble than copper such as gold and platinum, are not dissolved but enrich into the anode slimes. In contrast, silver may dissolve slightly and thus, minor chloride addition is used to retain silver in the slime as sparingly soluble AgCl. Moreover, other metals less noble than copper may also dissolve, such as nickel. Therefore the electrolytes used in electrorefining typically contain substantial amounts of copper, nickel and even arsenic as well as minor metals such as antimony and bismuth. In the Boliden electrorefinery these were reported to be in the magnitude of 51.2– 60.4 g/L of Cu, 10.9–15.8 g/L Ni, 7.2–15.9 As, 0.2–0.4 Sb and 0.1–0.4 Bi with an associated sulfuric acid concentration of 139–155 g/L (Lehtiniemi et al., 2018). Copper is the most noble of the dominating base metals in the electrolyte and is thus deposited on the cathode as 99.99% purity LME-A grade. Anode slimes are collected and subjected to precious metals treatment e.g. via pressure leaching—selenium recovery— Doré smelting—Ag refining—Au/Pt/Pd leaching and reduction process (Ludvigsson & Larsson, 2003). The Pori refinery, operating in Finland since 1941, not only produces 133 000 t Cu cathode and 2300 t nickel sulphate annually but also 66 t silver, 4.6 t gold and palladium and platinum (in year 2017).

Jan 1, 2019

By C. H. Stockwell

THE Eastern Townships of Quebec have been the chief Canadian source of chromite. Production, however, has never been large and, except for a period of steady but small output between 1894 and 1909, mining has been active only in war time. The known deposits are too small or too low grade to compete with overseas sources in normal times. During the last war, shipping difficulties and a greatly increased demand in the United States resulted in high prices and a ready market for low-.grade material. The Quebec chromite industry flourished and played an important part in relieving the wartime shortage. Shipments in 1918 .amounted to 15,600 tons of crude ore and 6,400 tons of concentrates. At the outbreak of the present war it was natural to turn again to the Quebec field as a possible source of this strategic mineral. Some of the old properties have since been opened by private and government money and some new deposits have been found. Total mill capacity is 750 tons per day, as compared with 200 to 300 tons in 1918. During 1940, 1941, and 1942, about 85 chromite deposits were examined by the Geological Survey in a belt 100 miles long and up to 7 miles wide. A part of this belt, about 35 miles long, in which the geological features ?were not well known, was mapped on a scale of 1/2; mile to an inch.? Small ..areas around some of the deposits were mapped in detail, on scales of 20 to 200 feet to an inch. Some geophysical work was done but did not result in the discovery of ore. Prospecting by stripping and trenching was then undertaken and chromite ore was uncovered at several localities. The above work was done by the writer and by J. W. Ambrose, who has kindly contributed his results for incorporation in this paper. Y. O. Fortier actd as assistant in the geological work and, in 1942, was in charge of a sub-party engaged in geological mapping. The author is indebted to H. C. Cooke and J. W. Ambrose for reading the original manuscript and for offering many helpful suggestions for its improvement.

Jan 1, 1944

By Kevin B. Doyle

"Canada now supplies 23 per cent of the world demand for potash. Although potash is produced by many countries, Russia and Canada have the greatest reserves and capability to supply the future substantial demand over the next decade. It is estimated that demand will grow from 38,000,000 mt KCl in 1975-76 to 60,000,000 mt KCl in 1985-86. Current firm expansion plans and development underway in the world will move Russia to the forefront in supplying this demand growth. Russia will move from supplying 40 per cent of world demand in 1975 to supplying as much as 52 per cent in 1981. Canadian deposits suffer from natural disadvantages, such as high costs and risks of mine development and operation, and high-cost transportation to international markets, but experience has shown that these natural barriers can be surmounted to effectively compete in these international markets. However, Canadian potash is losing out in the race to supply the growth in the world potash demand over the next ten years because of artificial barriers raised through the unhealthy environment created by the current battle between different levels of government and the industry over resource taxation and legislation."

Jan 1, 1976

By S. K. Sharma, Sanket Bacchuwar, Prabal Kumar Agrwal, G. V. Rao

"Iron ore processing industries play a vital role in the Indian economy. At present Iron ore of around +64% Fe is used for production of Iron through blast furnace. To produce +64% Fe from low/medium grade ores, crushing & beneficiation is compulsory. But during these processes, large amount of slime is generated. It is estimated that 18% -25% of tailing is generated during the processing of iron ore. The iron ore slime is discarded because of its particle size and chemical composition not being suitable as feed to the blast furnace. Although the fines/slimes can be agglomerated to larger particle, the alumina to silica ratio which is normally more than one pose serious problem during sintering process and subsequent smelting in blast furnace. The alumina content in the slime needs to be reduced for it to be used as the feed for blast furnace. The sample assayed 61.40% Fe, 7.68% SiO2, and 1.52% Al2O3, LOI 2.63% and all other elements were found in critical limit. A series of 27 tests were conducted by using a spiral for optimisation of process parameters to produce a pellet grade concentrate from the stacked slimes obtained from Kirandul. This paper deals with the optimisation studies of various parameters of a spiral concentrator and helps to utilize the fines from tailing ponds.INTRODUCTIONReserves of high-grade iron ores are diminishing all over the world at an alarming rate. As a result, alternative ways of augmenting and conserving precious and non - renewable natural resources are being seriously considered. One such attractive option is the recovery of metal values from slimes / tailings. Iron ore tailings containing around 48 - 60% Fe are generated from the iron ore washing plants and are disposed into tailing ponds without any further utility. These tailings in the form of slimes are not suitable in iron and steel making due to the presence of higher amount of gangue constituents. Several beneficiation techniques have been tried from time to time to reduce the gangue so that the beneficiated products could be effectively used."

Jan 1, 2016

By A. B. Morrow

Consulting engineers are well aware of large variations in plant operating cultures between countries, companies, and even within sites and operating crews. These operating cultures must be considered when designing Advanced Process Control (APC) applications in order to maximize utilization rates and return on investment. Designs must be driven by an understanding of the totality of unit operations. Economic factors, equipment constraints, management philosophy, maintenance department responsiveness, instrumentation reliability, operating crew skills and teamwork, and individual operator concerns are all important and must be considered during application design. A general approach to incorporating operating culture considerations into APC application design is described. A case study for an iron ore concentrator plant is presented.

Jan 1, 2014

By H. J. McQueen

Aluminum was hot worked at 400 - 500°C and strain rates (e ) of 0.004 -0.1s-1, under reversing strains (c) of 0.5 to 0.2 or 0.5 to 0 and also advancing from 0.5 to 1 or 0.5 to 5. Under similar test conditions for different parts of the strain paths, the average measured flow stresses are found to agree with each other. In the forward and backward strain path tests, the almost identical steady state plateaus affirm the occurrence of dynamic recovery (DRV). On reversal of strain direction at constant e , there was generally negligible Bauschinger effect. In specimens annealed at 400°C, static recrystallisation (SRX) was followed microstructurally. mainly by disappearance of elongated grains with serrated boundaries because the new grains were only little a finer than the old due to low strain energy. The only influence of reversing strain path observed was the effect of change of grain boundary area as grains elongated or returned towards equiaxed. In optical microscopy, elongated grains with serrations and deformation bands confirmed DRV in forward path specimens. In reverse path specimens, equiaxed grains were gradually restored with retention of serrations and bands. In low magnification polarized optical microscopy, grain alignment increased with strain for forward path specimens; whereas it decreased in reverse path ones, supporting DRV. Orientation imaging microscopy (OIM/SEM) revealed that elongated grains are broken up as deformation bands rotate during the forward path and that grains return to equiaxed appearance on backward straining. Comparative studies using optical microscopy in polarized light (POM), OIM/SEM and transmission electron microscopy (TEM) revealed that while subgrains remain equiaxed and constant in size and character during the forward and backward paths, the fraction of low angle facets decreased while that of high angle grain facets increased with increasing strain; these are coupled with a fairly low fraction of medium angle boundaries. The results contribute to the understanding that dynamic recovery in aluminum maintains sub-boundaries with low misorientation but as grains elongate and more subgrain become adjacent to grain boundaries the fraction of high angle boundaries rises (with backward straining it was vice versa).

Jan 1, 2007

By Edward Martinez

Due to its unique properties, chrysotile asbestos is used in many diversified applications. In recent years, a better understanding of the structure and properties of chrysotile has evolved due to the research efforts of many investigators. A summary of the results of some of these investigations is given. An attempt is made to show the relationships between the properties of chrysotile and its crystal structure. Examples taken from the literature are cited in which methods have been developed for modifying the properties to improve the performance of asbestos in some applications. These include the effect of pH on the positive zeta potential and the addition of sodium silicate to improve filtration characteristics. The dehydroxylation and formation of forsterite when chrysotile is heated are also discussed.

Jan 1, 1966

By G. Titichoca

Modification of the blasting process considers that any increase in the energy consumption generates greater benefits if done in the later stages (associated with a larger decrease in energy consumption). Therefore, although the blasting cost is doubled, generating a greater proportion of fines in addition to a weaker ore (because with greater loads and appropriate distribution of explosives a greater number of internal cracks is generated), the reduction of the unit cost that occurs in the grinding stages (SAG and ball mills) generates a positive balance in the overall size reduction process. Codelco Chile, Division Andina, has developed an extensive experimental plan to evaluate the concept of blasting modification applying greater energy. This was implemented in two stages, each including a specific mine sector: La Union and Don Luis. This paper reviews the experience of implementing such blasting modifications at the La Union mine and its impact on the design concepts and the operation of the SAG mill plant

Jan 1, 2007

By W. Dingley, G. R. Hoey

"AbstractWear of six types of grinding balls was compared with and without corrosion inhibition in grinding Ni-Cu sulphide and hematite ores in laboratory ball mills. Forged steel balls (Rc 60 to 65) and three types of white cast iron balls (Rc 50 to 65) were susceptible to corrosive wear and two types of stainless steel balls [AISI Type 440C (Rc 65) and AISI Type 302 is; 35)] were relatively immune. The relative wear rates of the five types of hard balls (Rc 50 to 65) were dependent on the corrosivity of the ore. Ranking of the hard balls with respect to wear resistance was consistent for the sulphide and hematite ores in the presence of corrosion inhibition, whereas their ranking was different for the two ores in the absence of inhibition.The electrochemical potential of the grinding balls was measured during grinding and was found to be a useful measurement for assessing the susceptibility of an alloy to corrosive wear. Reduction of ball wear for forged steel and white cast irons with corrosion inhibition was concomitant with a shift of ball potential to less active values. Ball potentials in the presence of inhibition were indicative of non-corroding metal surfaces.IntroductionA PREVIOUS STUDY by the authors (1) showed that corrosion inhibitors - sodium nitrite, sodium chromate and sodium metasilicate - reduced wear of forged steel grinding balls by up to 49% in grinding Ni-Cu sulphide ore. Although the mechanism of wear reduction was not elucidated, it was concluded that corrosion must play a significant role in the wear of grinding media. Remark and Wick (2) of Battelle Pacific Northwest Laboratories have also evaluated corrosion inhibitors for the reduction of metal wear using abrasive and n on- abrasive te sting procedures. Their research was sponsored by 16 companies throughout the world. Preliminary results indicated that anodic inhibitors prevent from one-fourth to one-half of the loss due to corrosion."

Jan 1, 1977

By Mari Yamamoto

Controlled thermolysis of gold(I) complex, [Au(C13H27COO)(PPh3)], at 180 °C for 5 h under an N2 atmosphere affords the new type of monodispersed spherical gold nanoparticles capped by myristate and a small amount of PPh3 ligands (average diameter 23±1.5 nm), in spite of no use of solvent, reducing agent and stabilizer. Much attention has been paid to the preparation and structure determination of transition metal nanoparticles, because of their widespread use in technological applications.1 In general, the chemical reduction of metal salts and organometallic complexes2 by the use of reducing agent is carried out to prepare gold nanoparticles. In some cases, a large amount of solvent and stabilizers such as surfactants,3 polymers4 and ligands5 are used to prevent agglomeration of particles and control the particle size. For instance, Brust et al. reported a two-phase reduction of AuCl4 - by NaBH4 in the presence of dodecanethiol as stabilizer to prepare gold nanoparticles.6 On the other hand, O?Brien et al. recently reported an one-phase preparation of gold nanoparticles by the reduction of AuCl4 - by NaBH4 in the mixture of tri-n-octylphosphine oxide and octadecylamine which act as both solvent and stabilizer, but this procedure also needs reducing agent.7

Oct 1, 2003

By K. Yamaguchi

To contribute highly efficient and environmentally conscious copper smelting process, several topics in chemistry of the continuous converting were discussed. Through the reviewing the authors' thermodynamic simulations, it is recognized that small amount and low copper content of the coexisting slag is preferable. Some discussions were added to the Takeda's diagram for Cu20-FeOx-CaO ferrite slag, and the activity curves of the constituents were derived. Thermodynamic calculations were carried out on the copper contents of the slag during the blister copper formation. The dissolution of copper in slag decrease somewhat with increasing temperature, but the effects of increasing S02 pressure and decreasing %S in copper are considerable to increase in copper content of the slag. The optimum oxygen enrichment in the supplied air, and regulation of the oxidation degree for the blister copper are important in practice. The gypsum phase separation in the calcium ferrite slag was also evaluated thermodynamically, and concluded that decreasing temperature, increasing CaO content or S02 pressure, and extensive oxidation of the blister copper tend to separate CaS04.

Jan 1, 2007

By K. Ilankoon, I. M. Saman, S. J. Neethling

In heap leaching the transport of the acid from the drippers to the surface of the ore particles is a major factor in the overall performance of a heap. This flow behaviour is complex as the flow is unsaturated and occurs along a tortuous set of inter-particle channels and connections. The particle properties such as size, shape and porosity are very important when modelling the liquid holdup and flow within heaps, since the dominant mechanisms at work are quite different. This paper investigates the effect of these particle properties experimentally on heap flow behaviour using a 1-D column leaching system consisting of non-porous glass beads with a system of actual ore particles. The similarities and differences between the two systems on flow behaviour are described using an inter-particle flow model. In addition, the applicability of positron emission particle tracking (PEPT) for laboratory column leaching will be detailed to calculate hydrodynamic dispersion in packed beds compared to more conventional residence time distribution (RTD) tests and also to obtain the time averaged rivulet flow paths through the particles of the bed for the better understanding of heap hydrodynamics.

Jan 1, 2014

By K. Yamaguchi

To contribute highly efficient and environmentally conscious copper smelting process, several topics in chemistry of the continuous converting were discussed. Through the reviewing the authors' thermodynamic simulations, it is recognized that small amount and low copper content of the coexisting slag is preferable. Some discussions were added to the Takeda's diagram for Cu20-Fe0x-Ca0 ferrite slag, and the activity curves of the constituents were derived. Thermodynamic calculations were carried out on the copper contents of the slag during the blister copper formation. The dissolution of copper in slag decrease somewhat with increasing temperature, but the effects of increasing S02 pressure and decreasing %S in copper are considerable to increase in copper content of the slag. The optimum oxygen enrichment in the supplied air, and regulation of the oxidation degree for the blister copper are important in practice. The gypsum phase separation in the calcium ferrite slag was also evaluated thermodynamically, and concluded that decreasing temperature, increasing CaO content or S02 pressure, and extensive oxidation of the blister copper tend to separate CaS04. 0

Jan 1, 2007

By E. Dernedde

A few studies have suggested that the rate of adsorption of hydrogen fluoride on smelter grade alumina is determined by kinetic factors. However, no performance equation for dry scrubbers has appeared in the literature so far. Experimental data from a pilot dry scrubber with co-current flow were compared with results of kinetic models of adsorption, film diffusion and pore diffusion. The pore diffusion model was deemed the most appropriate. It was transformed into a performance equation for steady-state operations of dry scrubbers by the inclusion of the alumina recirculation. Operating results of industrial dry scrubbers with co-current flow were successfully evaluated by means of the performance equation. The average fluoride content of the alumina was also estimated by using the pore diffusion model.

Jan 1, 2011

By Sylvie Lévesque, Cory Hennessey, Daniel Amariei

"In the iron ore industry, fine particles recovery is an important concern in terms of process performance and production costs. Continuous efforts are thus devoted to increase the efficiency in handling these fines.The Reflux Classifier (RC) is a relatively new technology that is mainly used in the coal and industrial minerals industries. The operating principle of this system is based on three mechanisms: hindered settling, autogenous dense medium and lamella settling. A preliminary evaluation of the Reflux Classifier technology for the beneficiation of iron ore fines was formerly done at the pilot scale using a RCTM300 unit. The good results obtained, using iron ore fines from screened spiral stream, made this technology very attractive for the iron industry. However, the high capacity of the RCTM300 unit (1–3 t/h), makes it unsuitable for R&D purposes. Thus, a smaller unit, the RCTM100, was assessed to validate the performances obtained with the RCTM300.This paper summarizes the performances obtained with the RCTM100. The challenges of the scale-down related to the adaptability of this technology to the iron ore industry are also presented. The results are compared to the RCTM300 performances, as well as benchmarked against sink-float tests. The metallurgical results on feed and products issued after the test work with the RCTM100 unit are supported by mineralogical characterization using a Mineral Liberation Analyzer.INTRODUCTIONFine particles recovery by physical separation means is a historical concern (Holland-Batt, 1992; Peukert and Wadenpohl, 2001; Srivastavaa et al., 2001; Majumder et al., 2003). Attempts to improve fine particle recovery at the laboratory, pilot and industrial scales adopting different strategies with traditional equipment or assessing new promising devices such as the MGS (multi-gravity separator), the Kelsey jig, the Yang jig, etc. (Kim, 2002; Goudreau, 2008; Kerr, 2012) have yielded variable success."

Jan 1, 2016

By Arnold Blaisonneau, Théophile Guillon, Xavier Rachez, Sylvie Gentier

"L’étude présentée ici vise à étudier l’influence, lors de stimulation hydraulique de puits dans les réservoirs géothermiques de type Enhanced Geothermal System (EGS), du comportement mécanique des zones de failles recoupant le puits sur la réponse hydraulique du réseau de fractures 3D. Dans ce but, un modèle 3D, basé sur la méthode des éléments distincts et dans lequel les zones de failles recoupant le puits sont modélisées par des fractures numériques 2D, est mis en oeuvre. Les modélisations présentées ici visent à caractériser l’influence du comportement mécanique (type de comportement, hétérogénéité) sur la cinétique de la stimulation hydraulique, ainsi que sur son effet spatial autour du puits. INTRODUCTIONPour le développement de l’exploitation géothermique de type Enhanced Geothermal System (EGS), la phase de stimulation conditionne grandement le succés du projet ; en effet, elle a pour objectif d’augmenter l’injectivité et la productivité des puits et doit permettre d’assurer la connexion entre les puits d’injection et de production garantissant ainsi la viabilité technique et économique de l’échangeur. Pour le site EGS de Soultz-sous-Forêts (France), parmi différentes techniques de stimulation, la stimulation hydraulique a été utilisée à cette fin en provoquant une augmentation irréversible de la perméabilité autour des puits. Dans ce type de réservoirs fracturés, le but des stimulations hydrauliques est de réactiver, plus spécifiquement en cisaillement, des structures hydrauliques pré-existantes (fractures, zones de failles etc.) dans le socle cristallin. La compréhension des phénomènes physiques durant la stimulation hydraulique est cruciale pour optimiser cette technologie et pour contrôler/limiter les risques associés (viabilité technique et économique des puits, sismicité induite etc.). C’est notamment le cas pour la relation entre le comportement mécanique des structures stimulées et les conséquences sur le comportement hydraulique dans un contexte tectonique spécifique."

Jan 1, 2015

By D. F. VanDine

The phases of a typical exploration program for sand and gravel resources include: (1) collection and assessment of existing information; (2) air photo interpretation and remote sensing; (3) ground investigation and mapping; (4) sampling and testing; and (5) data storage, retrieval, analysis and presentation. Depending on the purpose, time frame and funding available for the study, these phases, and the various techniques used within each phase, will vary. Once a sand and gravel deposit has been located, defined in size and quality, and found to be suitable for a given purpose, it can then be classified as a granular resource.

Jan 1, 1984

By H. Watari

In 1998, a voluntary agreement was reached between the European Commission and the European Car Manufacturers Association (ACEA) to reduce average carbon dioxide emissions of new cars to 25% below 1995 levels by 2008, Agreements have also been reached between the European Commission and the Japanese Automobile Manufacturers Association (JAMA) and the Korean Automobile Manufacturers Association (KAMA), However, the target average of carbon dioxide emissions of less than 140g/km in 2008 is a very challenging goal, Therefore, total product weight reduction is an objective for many manufacturers, This can be achieved utilizing materials possessing high strength and low weight, One material that has recently attracted interest is magnesium alloys, The magnesium alloys are expected to play an important role as next-generation materials, which have possibilities of contributing to lighten the total product weight when magnesium products can be used to replace aluminum and mild steel products.

Jan 1, 2005

By Claudio Rocha Rosales

"Peñoles is a mining group with integrated operations in the smelting and refining of non-ferrous metals, and is also a chemicals producer. Peñoles is the world’s foremost producer of refined silver, metallic bismuth and sodium sulphate and is the leading Latin American producer of refined gold, lead and zinc. The Met-Mex Peñoles Zinc Plant commenced operations in 1973 with an annual production capacity of 105,000 t/y. Year after year the production has been increased, and at present, the production capacity is 240,000 t/y. In this paper, the leaching process,particularly the operation of the jarosite circuit is reviewed ,specifying process improvements to treat high iron calcines.INTRODUCTIONThe purpose of the leaching process is to recover the metals, mainly zinc,through a series of extraction stages with sulphuric acid solutions, which progressively increase the zinc recovery. After the series of acidification stages,the solution, which is rich in iron, is sent to the jarosite circuit to separate the zinc from the iron (Garcia & Valdez, 1996).The first step of the leaching process is the neutral leach circuit which produces a zinc sulphate solution that is sent to the purification section for the removal of impurities such as cadmium, cobalt and copper, after this solution is sent to the tankhouse to feed the electrolytic cells."

Jan 1, 2016

By L. Haavanlammi

Iron is a significant component of all copper concentrates leached in the HydroCopperTM process. The metals in the concentrate are leached in a chloride solution by oxidation with cupric ions. Copper enters into the solution as a cuprous chloro¬complex. Iron dissolves at the same time in the ferrous form, but it is immediately oxidized to the ferric state. Oxidation is effected by sparging air or oxygen into the leaching reactors. Because the pH is 1 - 2.5, ferric ion precipitates as akaganeite (T<90°C) or hematite (T> 90°C). Arsenic, antimony and the main part of the bismuth co-precipitate with iron and report to the leach residue. Cupric leaching is faster than iron oxidation; thus, leaching of low-iron concentrates (secondary copper minerals) is quicker than leaching high iron concentrates (chalcopyrite). Pyrite does not dissolve during copper leaching, but is oxidized slowly at higher redox-potentials after the copper has been leached.

Jan 1, 2006