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By F. Rosenblum, P. Spira

"A correlation has been established between the oxygen demand of Brunswick Mining and Smelting ore and flotation results at the bench, pilot plant and operating plant scale. A method of dete""1llining the aeration requirement of sulphide ores on the basis of this correlation is presented. It is shown that abraded iron from grinding media plays an important role in aeration and flotation. Laboratory grinding must therefore be conducted under controlled conditions with suitable grinding media in order to obtain the true aeration requirement of the ore.A method of evaluating aerator efficiency, also based on oxygen demand measurements, has been used successfully at Brunswick Mining to design pilot plant and full-scale aeration systems.1. IntroductionPre-flotation aeration of sulphide pulps has been practiced in the Noranda Group for many years to help in the depression of pyrite and pyrrhotite and to promote chalcopyrite and/or galena. Recently, two out of three parallel circuits at the Brunswick Mining and Smelting Corp. Ltd. concentrator have been converted on a test basis to a new flowsheet incorporating aeration as a basic step. Among other benefits, a substantial decrease in the middlings load has been achieved as a result of improved pyrite rejection. There has been increasing interest in other organizations in the potential advantages to be derived from' aeration in terms of improved metallurgy and/or decreased reagent consumption."

Jan 1, 1978

By S. Jeon, T. H. Kim

"Understanding the frictional properties of discontinuities is crucial to ensure the stability of underground structures. In particular, the frictional behavior at depth depends on the complex interaction among mechanical, hydrological, thermal and chemical characteristics and their coupled effects. In this study, a series of triaxial compression tests were carried out to investigate the behavior of rough shear surface of synthetic rocks. The frictional behavior showed little variation at different confining and water pressures. The test results were analyzed using Coulomb’s failure criterion. In addition, numerical analysis was carried out using PFC2D to simulate the test.INTRODUCTIONUnderstanding coupled behavior of rock at depth is of great importance in design, construction and operation of underground structures such as a disposal facility of radioactive waste, hot dry rock geothermal system and oil reservoir. In particular, many uncertainties are involved in characterizing deep rock mass deformation in the designing process and interactions among fluid flow of groundwater, high temperature and stress disturbance should be considered. Many independent studies have been carried out to investigate the thermal, hydro, mechanical and chemical coupled effects in numerical and experimental methods. They include the researches by Lockner, Summers, Moore and Byerlee (1982), Jafari, Amini Hosseini, Pellet, Boulon and Buzzi (2003), Tembe, Lockner and Wong (2010), Lee, Lee and Jeon (2012), Indraratna, Premadasa, Brown, Gens and Heitor (2014)."

Jan 1, 2015

By Gerardo Fuentes

Arsenic extraction from Chilean copper concentrates up to nearly 99% was achieved, using hydrothermal reactions. Arsenic appears in nature in more than 200 mineral species, being arsenopyrite (FeAsS), enargite (Cu3AsS4), and tennantite (Cu12As4S13) the most common species. In addition, arsenic is present in a large amount of copper concentrates, produced in northern Chile. Medical statistics show that in northern Chile, the amount of cancer to the lung, skin and bladder are the highest in the country. The latter situation, demonstrates the importance of studying metallurgical processes that do not generate atmospheric pollution. The hydrometallurgical processes such as hydrothermal treatment in autoclave reactors, do not produce gaseous emissions. On the other hand, the arsenic remains in solution from where it can be transformed in scorodite by widely known methods. Previous works about hydrothermal treatment of enargite have shown the feasibility of transforming the enargite of the copper concentrates into chalcocite or mineral species of the chalcocite family such as djurleite, digenite and for this reason enrich the concentrate in copper and pass the arsenic to solution. For this research, two Chilean copper concentrates were used, concentrate 1 with 5.5% arsenic and concentrate 3 with 1.8% arsenic. These concentrates were subjected to a complete chemical and mineralogical characterization. Later these concentrates were carry out to batch tests of hydrothermal treatment. Also, these concentrates were subjected to grinding to have different particle sizes. For the hydrothermal tests, a liter capacity Autoclave Engineer reactor was used. Characteristic of this reactor was the maximum temperature 350°C, 5000 PSI pressure, and 900 rpm agitation speed. Kinetic tests were carried out with the two concentrates maintaining the same solid: liquid relationship, the same agitation velocity and the variables studied were treatment temperature, time of reaction, concentration of copper in the solution and grain size of the concentrates. The conclusions of the study indicated arsenic extraction of the order of 93.98% from the concentrate 1 and arsenic extraction of the order of 98.74% from concentrate 3. After the hydrothermal treatment, the solids and solutions were characterized chemically, by electron microscopy and X ray diffraction. Also the solids were characterized by grainsize through a particle size analyzer (MICROTRAC). Results of batch treatment shows that arsenic can be release almost completely from real copper concentrates using this hydrothermal process and the next stage will be a scale up process in order obtain results for pilot plant design. INTRODUCTION Arsenic is an impurity that appears associated with copper minerals forming enargite, tennantite, tetrahedrite, and that due to the pyrometallurgical treatment either in conversion or roasting furnaces, it goes into the atmosphere together with the sulfur dioxide. A great quantity of literature can be found to eliminate arsenic or try to separate arsenic from copper. The methods used are mainly leaching processes with or without pressure (Padilla, Jerez & Ruiz, 2015) with different reagents like chloride media (Herreros, Fuentes, Quiroz & Viñals, 2003) or chloride media with sulphuric acid (Riveros & Dutrizac, 2008) or sodium hypochlorite (Mihajlovic, Strbac, Zivkovic, Kovacevic & Stehernik, 2007). It is known too that Chile is the first copper producer in the world and a great quantity of its minerals are in the north of the country, in Antofagasta.

Jan 1, 2019

By Roland Hunt

This paper deals with the practical problems as sociated with blasting a heated pillar remnant. This pillar remnant was the final stage in the blasting of a multi-stag e pillar blast. Production from the previous stages had produced burning sulphide ore, resulting in high rock temperatures in the final unblasted stage. This is an account of how, under difficult conditions, the pillar remnant was blasted.

Jan 1, 1977

By T. McCallum, B. Wellbrook, T. Ratnaweera

Leaching of copper (Cu) concentrates produces elevated concentrations of Cu and acid, which makes solvent extraction (SX) processing more challenging. Maintaining extraction targets can be more difficult with higher pregnant leach solution (PLS) grades, and variability of PLS Cu and acid can lead to increased chemical iron transfer. Diluting concentrate leach feeds with an existing heap leach inventory makes SX processing easier. However, considerations about how much to dilute and where to distribute the flow into the SX configuration must be carefully evaluated, given their impact on metallurgical performance. In this paper, characteristics of a concentrate leach feed are discussed, along with considerations for processing by SX. Also reviewed are pilot plant results of concentrate leach distribution into SX and plans for commercial testing. INTRODUCTION Hydrometallurgical processing of copper concentrates continues to gain interest from the industry. Treatment by smelting and electrorefining continues to dominate, accounting for ~80% of global copper production, but is faced with its own challenges (Li et al, 2017). The case for increased hydrometallurgical processing has been discussed as high grade ore deposits are diminishing, capital costs for smelting are high, and the environmental aspects present challenges for sustainable practice. The hydromet copper industry is also turning a corner as easily leachable copper oxide deposits are depleting, and excess SX-EW capacity exists in certain regions. The transition to hydrometallurgical processing of copper concentrates will take a bit of effort as leaching of copper sulfides is difficult and byproduct credits must be considered. Various POX leaching processes have been studied and proposed to the industry as viable practices. Of the many processes, commercial use has been practiced with the Mount Gordon Copper Process, total and partial pressure oxidation by Freeport-McMoRan at their Bagdad and Morenci, Arizona complexes, the Sepon Copper Process in Laos, and the bioleach BIOCOP™ process in Chile (Dreisinger, 2016).

Jan 1, 2019

By K. Madi, E. Yeugo Fogaing, S. Forest, M. Boussuge, L. Massard, M. Huger, Gaultm C.

This study has been carried out owing to the French research program PROMETHEREF, which aims to improve the knowledge of thermal and mechanical properties of industrial refractories at high temperature. In this frame, this paper relates a collaborative study between Saint-Gobain CREE, R&D Centre for Saint-Gobain Ceramics & Plastics in Europe (Cavaillon), the Materials Center P.M. Fourt of Ecole des Mines de Paris (Evry) and the Research Group on Heterogeneous Materials (GEMH) of ENSCI (Limoges). Data collected at high temperatures by using different means (bending tests, ultrasonic measurements,...) allows the identification of the high temperature behavior of two fused cast materials, produced by Saint-Gobain group for the glass manufacturing industry. The results emphasize the importance of the transformation of zirconia and of the viscosity of the glassy intergranular phase on the mechanical behavior. Damage under the form of microcracking caused by thermal expansion mismatch between the phases is also observed during cooling down at low temperature, when the material is elastic.

Jan 1, 2004

By P. Rosario

"Current industry practice for HPGR assessment and sizing relies on conducting a series of tests using pilot-scale machines with roll diameters of 700 mm to 1000 mm. Substantial amounts of sample are required for such pilot test programs, typically 1 to 10 tonnes of the sample is needed depending on the level of study and complexity of the resource. Collection of large quantities of representative samples during the early stage development is challenging and expensive, thus significantly hinders the HPGR technology from being incorporated into early-stage designs. A robust and reliable laboratory test is therefore needed to allow a fair consideration of HPGR for early stage projects. With support from the Canadian Mineral Industry Research Organization (CAMIRO), the NBK Institute of Mining Engineering at the University of British Columbia (UBC) developed a suite of Piston Press bench-scale tests that correlated to pilot and full scale HPGR operating information (Davaanyam, 2015; Davaanyam et al, 2015; McClintock, 2018). The Piston Press Tests (PPTs) are capable of assessing the HPGR technology at the scoping, pre-economic analysis (PEA), and pre-feasibility (PFS) stages of project development. This paper will briefly describe the theory on which the PPTs are based, and then presents a case study conducted for a copper deposit to show how the PPTs are being used for scoping and pre-feasibility level studies. Specifically, the PPTs are being used to provide information for preliminary sizing and selection of an HPGR and to assess the effect of ore variability on HPGR performance. The results are also applied to developing HPGR circuit designs and can be incorporated in simulation so that optimum design parameters can be selected.INTRODUCTION It is widely accepted that high pressure grinding rolls (HPGRs) offer a viable energy-efficient solution for the modern comminution flowsheet design. Table 1 summarizes selected examples of HPGR applications in the hard rock mining industry. The main benefits of HPGRs are energy savings which leads to lower operating costs, and its stable operating characteristics that can better cope with variations in ore hardness when compared to the conventional SAG mill-based comminution circuits."

Jan 1, 2019

By Kazutoshi Haga, Batnasan Altansukh, Atsushi Shibayama, Ryuji Oinuma

"Recently, the arsenic grade in copper ores has been increasing year by year. Arsenic bearing minerals (enargite (Cu3AsS4) and tennantite (Cu12As4S13)) coexist with typical copper minerals such as chalcopyrite (CuFeS2). The removal of arsenic from copper ores that contain relatively high arsenic content is essential due to its adverse impact on the environment and the resulting economic consequences. In this study, arsenic removal and dissolution behaviour of Cu and As from enargite (Cu3AsS4) were investigated using ferric sulphate (Fe2(SO4)3) solutions containing sodium chloride under high pressure oxidation conditions. The effects of numerous parameters including the concentration of Fe2(SO4)3 and NaCl, temperature, total pressure, leaching time and particle size were studied while other variables such as pulp density and stirring speed were fixed at 100 g/L and 750 rpm. The results showed that more than 60% of the copper was dissolved in a 0.1 M ferric sulphate solution under the high pressure oxidative conditions, whereas the leaching rate of arsenic was less than 20%. SEM observation revealed that elemental sulphur was deposited on the surface of enargite forming a passivation layer and the residue was agglomerated. Those phenomena may cause a decrease in the copper leaching rate. It was found that more than 80% of copper was dissolved in the ferric sulphate solution in the presence of 0.34 M sodium chloride under the conditions optimized, whereas the dissolution of arsenic in the mixture did not exceed 2%. XRD analysis of the solid residues from the leaching experiments used ferric sulphate and mixtures of ferric sulphate and sodium chloride showed arsenic to be present as scorodite (FeAsO4).INTRODUCTION In recent years, there has been an increase of the arsenic (As) content of copper ores due to the gradual depletion of high grade copper ores. In some copper deposits, arsenic occurs in the form of minerals such as enargite and tennantite. The removal of arsenic in ores containing copper is critical to the production of pure copper and the management of the environmental challenges caused by the smelting process. Due to the environmental risk caused by arsenic emission and the deteriorated quality of the copper product, smelting of enargite concentrates is not an effective method for the extraction of copper (Padilla et al., 2010; Safarzadeh et al., 2014; Long et al., 2012). Therefore, a number of studies have been carried out to develop arsenic removal technologies from copper ores using various methods such as hydrometallurgy (Curreli et al., 2009; Tongamp et al. 2010), pyrometallurgy (Dalewski., 1999; Padilla. et al, 2012) and bio-oxidation (Ehrlich, 1964; Sasaki et al., 2010). Several hydrometallurgical leaching processes like sulphuric acid, alkaline sodium sulphide and sodium sulphate and ferric sulphate leaching have been developed to treat enargite ores and concentrates. The alkaline sodium sulphide leaching process has been developed for the removal of arsenic from enargite (Anderson, & Twidwell, 2008; Parada et al., 2014). The mechanism of the dissolution of arsenic from enargite in sodium sulphite solution is"

Jan 1, 2016

By T. Scully

Since early days in coal mining, it has been known that some coals and the carbonaceous materials associated with them will heat and fire spontaneously. Many theories have been advanced to account for this phenomenon, but it is only within comparatively recent years that any scientific research has been carried out to determine the causes of this heating, the conditions which bring about its occurrence, and the reason why different coals heat with a varying degree of readiness. So far, this research has not cleared up these points entirely, but a great advance has been made in our knowledge of the matter. In general, any coal will fire spontaneously, although with a varying degree of readiness, provided conditions for its doing so are favourable enough. These conditions are that the coal must be in a fine state of division, that sufficient oxygen must be present for rapid oxidation, and that the air current passing must be so small that it is insufficient to carry off the heat produced by this oxidation. Many other minor factors, however, contribute to bring about spontaneous heating, either by producing initial heat themselves or by inducing the other major conditions.

Jan 1, 1931

By F. Schulz

NA's primary smelter has continually increased its production output in the past decade, making it necessary to improve the lifetime of the casting moulds for copper anodes. The current throughput of more than 1,100,000 tonnes per year of copper concentrates amounts to an output of about 450,000 tonnes per year of anode copper at NA's Hamburg plant. The anodes are cast on a single casting wheel with 24 anode moulds. Besides the stable chemical analyses, the reproducible geometry of the anodes is an important precondition for the success of the subsequent electro-refining process. The anode moulds are subjected to thermally-induced alternating stress and side reactions with the melt. Typical signs of wear will be shown and discussed. Different processes to produce anode moulds will be introduced and the results in terms of their lifetime and the quality of the anodes themselves will be discussed. Finally an outlook is given on possible efficiency improvements.

Jan 1, 2007

By E. Sharifi

Advanced Process Control (APC) has been one of the most beneficial tools in the past decades available to minerals processing industry. Low capital cost together with significant improvements in process optimization have made APC an attractive investment option for nearly all mineral processing units. During economic downturns, importance of process optimization becomes even more relevant as metal producers tend to target de-bottlenecking and process efficiency improvements rather than large-scale capacity upgrades. APC project clearly has a lot of potential to improve process performance but there are also some pitfalls to be identified and avoided in order to achieve a desired outcome. Above all, APC project implementation is collaboration between the system vendor and user. Targets for the optimization must be agreed together with the customer and process performance must be defined before and after the optimization project. Most importantly, performance of the process must be monitored on a continuous basis during and after the project and potentially improved further. This paper discusses Outotec’s experiences from various concentrator optimization projects. Some examples are discussed in more details; however, the main target is to present general guidelines enabling a successful APC project implementation.

Jan 1, 2014

By J. Flemming, R. O. Burt

"The Tanco pegmatite is located in the Bird River greenstone belt of southeastern Manitoba approximately 160 km northeast of Winnipeg (Figure 1). This pegmatite body was discovered in 1929 and subsequently attempts were made to exploit it for tin by Jack Nutt Mines Ltd. and later in the middle 1950's by Montgary Oil Ltd., who extensively developed but did not produce from, its lithium deposits. In 1966 systematic investigation of the pegmatite as a potential source of tantalum led to the founding of Tantalum Mining Corporation of Canada Ltd. (TANGO) in 1967 and production of tantalum concentrates from the Bernie Lake mine commenced in 1969. Tanco is currently jointly owned by Hudson Bay Mining and Smelting Co., Cabot Beryl co Inc. of Boston, and the Province of Manitoba. (Williams and others 1978, Burt 1979, Burt and others 1982), continued until the end of 1982, when, due to falling demand and prices, operations were suspended.During the 1970's Tanco had investigated the potential of the lithium orebody; carrying our research into both the concentration of the ore and into the production of lithium chemicals. However lithium chemicals were in an over-supply situation, due in part to the production from Chilean brine deposits (Buckley, 1983), and Tanco' s own plans were put into abeyance. The potential alternative market, the direct use of concentrates in the glass and ceramics industry, did not at the time justify the cost of constructing a new plant."

Jan 1, 1986

By R. Farhat

Coating systems that yield a thermally grown oxide (TGO) protective layer have been proposed as a potential method for extending the lifecycle of components exposed to high temperature corrosion. This is particularly relevant to the petrochemical industry, where any reduction in corrosion rates can yield substantial cost reductions. The primary goal of this project is to develop a coating repair procedure and to investigate the oxidation performance of the repaired location. Electrospark deposition (ESD) was used to repair spalled segments of TGO grown on MCrA1Y substrates using various electrodes possessing mixed crystal structures. Specifically, electrodes of NiCoCrA1Y (BCC-FCC mixtures) and CoNiCrA1Y (FCCBCC mixtures), were deposited and oxidized to develop the TGO using a heat treatment of 24 hours at 1000°C in air. This presentation will focus on the microstructural evolution of the base metal and ESD repair on damaged area, in both as- deposited and oxidized forms. Results of SEM and XRD analysis will be presented.

Jan 1, 2011

By D. Monder

Fuel cells are promising sources of electrical energy because of their exceptionally high efficiencies and low environmental emissions. Solid oxide fuel cells (SOFC) are high temperature, ceramic electrolyte cells, which unlike most other fuel cells, can work with a variety of fuels besides pure hydrogen, including hydrocarbons and hydrogen sulfide. In this presentation I present the models we have built for a single H2S fuelled SOFC. The goal is to model the electrochemical reaction coupled with mass transfer, fluid flow and current/voltage distribution in an yttria stabilized zirconia electrolyte fuel cell assembly operated between 750 and 850 °C. Two models of the above SOFC are discussed in this work, 1) an algebraic model derived by integrating a one-dimensional model along the thickness of the cell, and 2) a two-dimensional finite element axi-symmetric model. Important physical and kinetic parameters in the 1-D model are fitted using experimental data sets at three different temperatures and reasonable fits are obtained for the data sets at 800 °C and 850 °C. However, the third data set at 750 °C does not give a good fit using this model. We need to apply the curve-fitting to more data sets to investigate it further. The main conclusion that can be drawn from the present study is that the ohmic resistance of the cell is very high. Contact resistances are believed to be the reason behind this although there could be contributions from resistive interphases. The 2-D model also gives reasonable fits to data sets. One of the publications by the laboratory group doing the experimental work in our department presented very interesting data that shows the cell performance being a strong function of fuel flow-rate. We want to model this behaviour and will have to depend on the 2-D model as the 1-D model does not have flow-rates as parameters.

Jan 1, 2005

By Neil Camarta

$6 Billion Dollar Education ?? Construction is like war ? you need a command and control organization ?? A strong Owner?s team is a must ?? Smaller is better ? break the project into bite size chunks ?? New technology is risky ? lots of construction and start-up risk ?? Safety can be successfully managed ?? Don?t expect contractors to ?work well together? ?? Never, ever let Mining Engineers run stuff than can catch fire

May 1, 2008

By E. Ghali

For engineering applications, magnesium is usually alloyed with one or more elements which include aluminium, manganese, rare earth metals, lithium, zinc, and zirconium. Under normal environmental conditions, the corrosion resistance of magnesium alloys is comparable or better than that of mild steel. The oxide film thickness on pure magnesium after exposure for only ?10 seconds at ambient temperature is 2.2 ± 0.3 nm. Exposure to humid air or to water leads to the formation of a thick hydrated amorphous film that has an oxidation rate less than 0.01 pm/ y. E-pH diagram and high temperature corrosion are discussed. The pH values between 8.5 and 11.5 correspond to a relatively protective oxide or hydroxide film that is more stable at higher pH. Structural applications of magnesium alloys are limited by creep strength rather than by oxidation. Active and active-passive behaviours of magnesium alloys are discussed. The pilling Bedworth Ratio values of oxide and hydroxide are 0.79 and 1.77 respectively and so the formation of Mg(OH)2 inside the oxide film could lead to the development of cracks. Microbiologically influenced corrosion and rational biodegradation of magnesium alloys are discussed because of their interest for medical care.

Jan 1, 2006

By S. Southall, F. McCaffrey, F. Stober, M. Darini

Electrode Columns are commonly used in electric furnaces to deliver current and regulate furnace power to the smelting or melting process. Hatch has developed an innovative patent-pending system for lowering ("slipping") and/or raising ("back-slipping") the electrodes through an electrode column, without requiring the release of any clamping devices. All clamping forces are applied by springs. Unlike systems employing hydraulically applied clamping forces, (e.g., water bladders) the spring system is failsafe. Its inherent simplicity virtually eliminates the need for maintenance. The Hatch system is particularly applicable to Soderberg electrodes, and comprises two axially movable slipping clamps and a stationary power clamp, each of which apply a distributed, radial clamping force to the electrode. The magnitudes of the slipping sleeves' clamping forces and sequencing of their axial movements are selected such that the slipping clamps, in conjunction with the weight of the electrode, provide slipping or back slipping without release of any clamping force.

Jan 1, 2005

By G. J. Govett

THE RESERVES of industrial minerals of the Western Plains are probably several times more valunable than all the known deposits of metallic minerals of the Canadian Shield, though sharing little of the latter's popular appeal. Because of comparatively low value per unit weight or volume, an adequate and accessible supply of industrial minerals is essential for the full development of any territory; assessment of the value of deposits should consider fully the proximity to cheap transportation, and existing and potential markets. Production statistics of industrial minerals are probably a more reliable guide to economic development than, for example, those of petroleum, and the relative importance of industrial minerals increases with growth of the population. The development of a high-volume natural deposit such as petroleum naturally favours an increase in population, and thus industrial minerals form an integral part of an expanding industrial economy. This situation is clearly demonstrated by the relationsl1ips of industrial minerals production, petroleum production, and population growth, in Alberta (Figure 1).

Jan 1, 1959

By J. A. Espinosa-Guillen, J. A. Lopez-Molina, S. García, J. A. Valencia-Quintanar

"The design and implementation of grouting treatments in rock masses are procedures that require continuous adjustment of parameters and criteria to optimize the results. In this proposal we describe a set of tools that enhance decision-making for this type of jobs particularly in dam projects. The methodology is focused on hydrogeological zoning of the site and its constant update combining engineer’s experience with artificial intelligence techniques to integrate the site knowledge; as well as the evaluation of grouting results for different scrutiny scales, with special attention on the relationship between water absorption and grout consumption. INTRODUCTIONSeveral methodologies for design, implementation and evaluation for grouting rock masses have been developed for the solution of specific problems and tested in diverse geological conditions. Each of these methodologies is focused on results evaluation for different scrutiny scales (Table 1) and is employed to assist decision-making before or during the grouting process.Some methods define specifications for grouting each stage of the borehole, making theoretical, semi empirical or experience-based considerations to define basic parameters as maximum pressure, maximum volume, grouting time, flow rate, etc. Ultimately each approach aim to optimize the injection process, adjusting volumes or the grouting time required to obtain satisfactory results, reducing risk of creating new flow paths or unnecessary grout travels, and enhancing the mixture properties to achieve adequate penetrability and long-term behaviour. Some of these criteria have been widely used in dam projects, for example the concept of Grouting Based on Facts to define the maximum pressure and volume (Ewert, 1997), the GIN method (Lombardi & Deere, 1993; El Tani, 2012), or the North American standards based on Apparent Lugeon measures (Naudts, 1995; Bruce 2011); on the other hand, there are relatively new criteria that have shown good results for dam grouting as the Aperture Control Method (Bonin et al., 2012; Carter et al., 2012) or the Real Time Grouting Control Method (Stille et al., 2012)."

Jan 1, 2015

By K. C. Corin, Z. G. Song, J. Y. Liu, M. W. Zhang, State Key Laboratory of Mineral Processing-BGRIMM, J. G. Wiese

"In the present study effect of grinding media on flotation of two mineral systems have been investigated, viz. sulphide minerals (including a pure chalcopyrite and pyrite mineral, and two different base metal sulphide ores), and oxide minerals (quartz, hematite and cassiterite). It was shown that mild steel media milling produced lower recoveries in the case of chalcopyrite and pyrite, as compared to the case of milling using ceramic media. For oxide minerals, the effects of using mild steel media as opposed to ceramic media were not as significant as was for the sulphides, although, after mild steel milling, at acidic pHs their recoveries were significantly reduced. For two base metal sulphide ores, viz. Nkomati and Dexing ores, the differences resulting from different milling media , although marginal, were opposite for each of these ores.For oxide minerals XPS showed that oxides and hydroxides of iron (e.g. FeOOH) adsorbed on the surfaces of the minerals. In the case of the Nkomati ore, adding Fe2+ or F3+ ions after milling with chrome steel media resulted in reduced talc (gangue) recovery, but increased water recovery and reduced concentrate grades. Further investigations are currently in progress to examine the Fe ions effect on the talc surfaces and froth properties.INTRODUCTIONGrinding of ores is necessary to liberate the valuable minerals from its gangues to allow for their selective recovery during mineral processing such as flotation. The grinding process inevitably involves contact of the ores with the surface of the grinding device and the grinding media. Accompanied by grinding, several phenomena can occur including the grinding medium wear, formation of precipitated species on the ore surfaces, chemical reaction, galvanic effects, changes in the Eh of solution, etc. There is a considerable body of literature on the differences observed in the flotation of various ores after milling using various grinding media. Laboratory studies have used balls or rods made from mild steel, ceramic, stainless steel or chrome steel to investigate the effects of different grinding media on mineral flotation. It is found that the interactions between the ore and the grinding environment can affect flotation separation of sulphide (Wei and Sandenbergh, 2007; Bruckard, 2011), oxide (He et al., 2014) and carbonate minerals (Song, 2009 and 2010). For example, mild steel milling produces relatively high concentrations of Fe ions in the pulp, affecting the recoveries of minerals compared to the case of ceramic media. On the other hand, the stainless steel media or chrome media are reported to be beneficial to the recovery of sulphides, when compared to the cases of using mild or carbon steel media (Rey and Formanek, 1960; Peng et al., 2003a,b; Huang and Grano, 2006; Bruckard, 2011). It is not clear, however, whether these Fe ions may affect the surface properties of the minerals involved or the general pulp/froth behaviour and hence their floatability. In addition, in the study of an low-S PGE ore carried out by Miettunen et al. (2012), forged media grinding in the CO2 atmosphere led to the highest Pt and Pd grades and recoveries, but the high chrome grinding media gave lower flotation recoveries than those using the forged media."

Jan 1, 2016