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By Z. Zhang, Zongshu Zou, Nan Wang

"Thermodynamic calculation is applied to make an investigation on the equilibrium phase relations and liquids of CaO-SiO2-Al2O3-FeOx system for different temperatures. The calculated results with FactSage6.1 show that the effect of temperature on the the equilibrium phase relations and liquidus of CaO-SiO2-Al2O3-FeOx system and its sub-systems is appreciable. The liquid phase regions enlarge with increasing temperature from 1573K to 1873K, while the primary phase fields reduce distinctly.IntroductionThe main oxide components of vitrified bottom ash slag are CaO, Al2O3, SiO2, Fe2O3, MgO, and Na2O, accounting for more than 90% of the bottom ash by weight[1]. During slag processing, the knowledge of thermodynamic properties and liquidus temperature in the related slag systems is highly required [2, 3], which is not yet available. Through literature survey [4-6], it is clear that the systematic information on the concerned complex slag system is scarce. So far the engineers in the field have to make assumptions of the thermodynamic properties of the simplified oxide system, without taking into consideration the interactions of the different oxide components, which hinders the development of the slag valorization and utilization. In order to provide thermodynamic properties for the application of the vitrified bottom ash, the six-component oxide system (CaO-MgO-Al2O3-SiO2-FeOx-Na2O) is highly required. A preliminary phase diagram of the CaO-MgO-Al2O3-SiO2-FeOx-Na2O system can be obtained from extrapolation of the thermodynamic functions of constituent subsystems such as CaO-SiO2-FeOx-MgO, CaO-SiO2-FeOx-Al2O3, CaO-SiO2-Na2O-MgO and CaO-SiO2-Na2O-Al2O3. In this work, the equilibrium phase relation and liquidus of CaO-SiO2-FeOx-Al2O3 system, one subsystem of the concerned complex slag system, are calculated and the effect of temperature is also discussed."

Jan 1, 2012

By D. T. White

"Metallurgical extraction processes often call for the heating of aqueous slurries. Indirect heat exchangers are generally not feasible for service with high yield stress slurries because of low heat transfer rates. It is more appropriate to heat the slurry by direct contact, typically with steam as the heating medium. Although having a long and successful history, direct-contact heat transfer to aqueous slurries has been used without the support of pilot plant research. This paper provides results of the needed research, the work being done at a scale large enough to enable direct scale up to commercial operations. A pilot plant heater was constructed and tested to develop an understanding of the slurry heating process and to ensure that commercial scale heaters were appropriately sized.INTRODUCTIONPressure Leaching OperationsPressure leaching operations are often used to oxidise sulphide gold ores, or for extraction of nickel and cobalt from laterite ores with sulphuric acid. Where there is sufficient sulphur available, the exothermic pressure oxidation reactions can be self sustaining at temperatures as high as 225 ºC, without having to preheat the feed slurry. At lower sulphur levels, slurry preheating is required. This is typically achieved by utilising the flash steam released from the slurry letdown stages and contacting this directly with cold incoming slurry ahead of the autoclave. The vessels where this slurry-steam contact is made are known as heaters or condensers, with the number of pre-heat stages varying, depending on how much heat is evolved in the oxidation reaction (Mason, 1990).In nickel laterite pressure acid leaching processes, which operate between 245 and 270 ºC, the only significant exothermic reactions are those associated with dilution of sulphuric acid in the leach. As a consequence, slurry preheating with flash steam is always used commercially. In practice the number of flash steam preheating stages required varies from 1 to 3, driven by a number of factors, including other uses for flash steam and the upper temperature limit at which preheated slurry can be pumped. A diagram of a typical pressure acid leach train is shown in Figure 1.For pressure acid leaching operations and at low sulphur levels in pressure oxidation, boiler generated direct steam addition to the autoclave is required to sustain the reaction temperature. For this reason it is imperative that the flash steam – slurry heat transfer is efficient and the slurry temperature approaches that of the flash steam closely."

Jan 1, 2012

By S. Ragab

The objective of flotation models is to predict the recovery rate of minerals from a flotation cell. In this paper a CFD?based flotation models is presented. The model uses first order rate equation, and the collision frequency is estimated using Abrahamson [1] model with input from CFD two-phase simulations. Spatial distributions of dissipation rate and air volume fraction (also called void fraction) are determined by the two-phase hydrodynamic simulations. Knowing these parameters throughout the machine is essential in understanding the effectiveness of different components (rotor, stator or disperser, jets) on the flotation efficiency. Not only the average pulp recovery rate can be estimated but also the regions of high/low recovery rate can be identified. The CFD-based flotation model presented here can be used to determine the dependence of recovery rate constant at any locality within the pulp on particle diameter, particle specific gravity, contact angle, and surface tension.

Jan 1, 2012

By Gustavo Quiquia Mucha

El presente texto describe la gestión social desarrollada por la Compañía Minera Milpo, basada en una consultaría previa, libre e informada sobre la exploración minera. Para ello, se incorpora el marco ideológico y metodólogico, cuyos principios se encuentran en el Convenio 169 de la OIT sobre pueblos indígenas y tribales en países independientes, los cuales han sido incorporados en las estrategias y líneas de intervención social de Compañía Minera Milpo S.A.A. en sus proyectos de exploración minera responsable.

Jan 1, 2012

By N. Plint, M. Potgieter

The Anglo Platinum Mogalakwena North concentrator was one of the first three hard rock mineral processing applications to utilise a HPGR circuit in preference to a SAG milling circuit. This was driven by the extreme competence of the ore that had given rise to throughput issues on the original South Plant. Despite more than adequate capacity and performance of the individual comminution units, the circuit has struggled to obtain full design capacity. A thorough review of the integrated performance of the circuit revealed a wide range of bottlenecks and underutilised parts of the circuit arising from design issues. Interestingly, the major opportunities lie in materials handling issues and mismatch of loads about the circuit. This paper presents the high-level outcomes and the associated opportunities, and is pertinent to all HPGR circuit designs.

Jan 1, 2012

By E. Herrera, L. Mariscal

"Ilo Copper Smelter operates since 2007 with an ISASMELTTM furnace as a single smelting unit (1,200,000 tpy) associated with two Rotary Holding Furnaces for separation of matte and slag, and which directly produces a discard slag. Southern Peru continually has been improving the slag chemistry of its ISASMELTTM furnace in order to reduce copper losses, given its big economic impact due to large slag mass generation. The present paper describes the influence of the CaO, Al2O3 and magnetite content in the slag of the ISASMELTTM furnace correlated with the SiO2/Fe ratio and its liquidus slag. Also it defines the best slag chemistry and operating practice in order to reduce the copper losses without compromise the bricks life of the furnace.INTRODUCTIONIlo Copper Smelter of Southern Peru (Grupo Mexico) is located on the southern coast of Peru, and treats mainly copper concentrates produced in its own mines (Toquepala and Cuajone).The modernized smelter was commissioned in 2007 and operates with an ISASMELT™ furnace as a single smelting unit (1,200,000 tpy), which is associated with two Rotary Holding Furnaces (RHF) for separation of matte and slag. This slag is directly sent to the dump. Figure 1 shows the smelter flow diagram.The ISASMELT™ process is a bath-smelting process using a single lance. The lance tip is immersed into a molten slag bath contained within the stationary, vertical, refractory-lined ISASMELT™ furnace. The injection of oxygen-enriched air, through the lance into the slag results in a highly turbulent molten bath. Feed material falling into the turbulent bath from above reacts rapidly, resulting in extremely high productivity for a relatively small bath volume."

Jan 1, 2012

By Metehan Erdogan, Orhan Gökçe Göksu, Ishak Karakaya

"An experiment (mixture) design was created to optimize the process parameters of the electrochemical reduction of CaW04 to W in molten CaCl2-NaCl eutectic mixture. Temperature, applied voltage and the length of Kanthal wire winding of the CaW04 pellets were selected as the process parameters that were allowed to vary between the predetermined minimum and maximum values. The rates of the electrochemical reductions were interpreted from the variations of current and total charge vs. time graphs under different conditions. The analysis pointed out that 640°C and 2.81 V resulted in the fastest reduction. Itwas seen that the effect of Kanthal wire winding on the output current was less pronounced when compared to the other two parameters.IntroductionFFC Cambridge Process [1] has been applied to a number of metal oxides in laboratory experiments to produce metals. In nearly all of these studies, the electrolysis temperature was around 900°C, the electrolyte was pure CaCl2 or CaCl2 containing salt solutions and the anode was graphite. However, it was recently shown that the electrochemical reduction process of metal oxides in CaCl2 containing electrolytes at the mentioned high temperatures was not suitable for tungsten production [2], It was reported that as soon as WO3 contacts CaCl2, the following reaction occurs:"

Jan 1, 2012

By K. Fleck

Energy West Mining Company (EWMC) has implemented a geologic program for improving stability and support requirements along deep two-entry longwall gateroads at its Deer Creek Mine operations located near Huntington, Utah. Together with geotechnical monitoring and concurrent review of mine seismicity in cooperation with MTI staff, it has become possible to improve longwall layout designs for two seam extraction of the Hiawatha and Blind Canyon seams. The geologic program consists of surface and in-mine exploration drilling, surface and in-mine geologic mapping, rock mechanics testing and detailed measurements of changes in depositional and structural conditions during development of every longwall gateroad. The geotechnical program consists of underground measurements at seven locations in two neighboring mining districts located in the Hiawatha and Blind Canyon coal seams under moderate to deep cover. Within the last five years, additional measurements, including data on seismicity and face conditions, have been incorporated into the data collection program for verifying the insitu coal strength and load transfer mechanisms for improving two-seam designs and support systems. Geologic mapping results are also used to predict local stability of headgate and tailgate entries, combining mine roof mapping, stratigraphic profiles of the coal and roof, and depth-of-cover information and dual-seam mine overlays, for use by operations personnel in planning roof and rib support for the retreating longwall sections.

Jan 1, 2012

By D. Imeson, T. Grammatikopoulos, M. Aghamirian, M. Oliazadeh

"More than 70% of potash is produced worldwide by froth flotation. Flotation of potash was developed in the early 1930s. Amines are widely used for flotation of sylvite (KCl) from halite (NaCl) and insoluble materials such as clays. Amine collector is also absorbed by clays. Therefore, clays are usually separated by scrubbing and de-sliming prior to flotation. Alternatively, slimes can be floated ahead of potash flotation. Flotation recoveries of sylvite are commonly in the range of 85%, while losses can occur in slimes, flotation tailings and make-up of process brine. Ores containing free coarse-grained sylvite are generally screened, whereas both fine and coarse fractions are conditioned and floated separately. The unique features of potash flotation include solubility of sylvite in water, the size of particles floated and fast kinetics. Particles up to 2.3 mm can be floated and about 50% of flotation feed can be removed in the rougher stage in few minutes. The main challenges in potash flotation are the recovery of potash from slimes, flotation efficiency in the presence of carnallite and recovery of coarse potash grains. A review of potash flotation shows that there is still room for improvement in both coarse and fine potash flotation. The present paper reviews the most significant flotation parameters including reagent type and dosage, flotation circuits, flotation equipment size and new developments in potash flotation. The latter include new reagents, flotation technologies (Hydrofloat, Jameson and column cells) larger flotation cells and slimes flotation.INTRODUCTION Potash is the common industrial term for potassium in various chemical combinations and minerals soluble in water. About 90% of potash produced worldwide is used as agricultural fertilizers. Flotation is the main treatment process of sylvinite (KCl-NaCl) ores for recovery of sylvite (KCl). Potash concentrate should contain a minimum of 95% KCl and be relatively free from 0.2 mm KCl fines. The flotation process for beneficiation of potash ores was developed in United States and Russia concurrently in the early 1930s. In 1934, Potash Corporation of America applied flotation process in a commercial scale (Tippin R.B. and Huiatt J.L). In the initial application, halite (NaCl) was selectively floated by employing lead chloride as an activator and soap as collector. The sylvite concentrate was reported in the cell underflow."

Jan 1, 2012

By Mark Holdsworth

In 2002, Kennecott Utah Copper Copperton Concentrator installed an Expert Control system for optimization of their SAG and Ball milling circuits. The advanced process control has been well received and is utilized well over 95% of the time. In the years since, many lessons have been learned and many advances have been made. Improvements have produced millions of dollars of benefits and have included directly controlling feedrate with complex logic as opposed to using a bearing pressure controller, modifications to how sound is used for control, modifying logic for maximizing asset utilization and using advanced control for automating equipment restart.

Jan 1, 2012

By D. Royston

Reducing SAG Mill feed size has been a major trend in recent years. ‘Mine to mill’ strategies have reduced blasted-rock size, and in a growing number of operations reducing the primary crusher CSS and/or adding additional crushing upstream of the SAG mill have reduced rock feed size. While reducing feed size will increase SAG mill throughput, issues arise in terms of retaining charge in the mill, exposing the shell lining to impact damage, and maintaining milling performance should the pre-crush system shut down. This paper reviews the past experience on pre-crushing for SAG mills and provides an analysis of liner design (in particular grates and shell liners) for pre-crushed feed.

Jan 1, 2012

By M J. Daniel

Comminution is the science of size reduction of brittle materials. It is integral to mineral extraction and is one of the most energy intensive processes in the mining industry. There are a number of tests used to quantify the strength of ore, which are then used to size the AG / SAG mill in circuit design. The calculated energy utilized for breakage in these devices is based on the assumptions that the materials treated are of average shape and that the processing equipment is designed to break the ore as efficiently as possible under the given operating conditions. In drop weight tests, it was found that shape significantly influences the measured rock strength. Controlled experiments with variations in blends of rock shape show that mill throughput increases with the addition of weaker shaped rocks.

Jan 1, 2012

By R. Farrar

Protective canopies for conventional electric face equipment, including shuttle cars, operating in low coal (less than 48 inches) were designed, fabricated, installed and evaluated on in-mine machines engaged in regular coal mining operations. This work was performed under contract to the U.S. Bureau of Mines, Pittsburgh Mining and Safety Research Center. The canopies will support a vertical load of 18,000 pounds and provide protection against both roof falls and contact with the mine rib. Canopy configurations were established based on human engineering studies, full scale canopy mockups, and in-mine observation and consultation with mine and equipment manufacturing personnel. Overall height of each canopy is hydraulically adjustable between a minimum of 32 inches and a maximum of 40 inches. Canopy tops are open framework, welded structures, covered with expanded metal mesh. Structural members are 1 3/4-inch or 2-inch square tubing of AISI 413ON and ASTM A500 material, respectively. The canopy tops are typically supported by an understructure and upright post arrangement that is either integrated into the current operator platform or attached to the machine frame. The four upright corner posts house the hydraulic actuators. Canopy tops are elevated horizontally. Canopies are welded or bolted to the existing machines. Installation is accomplished with a minimal amount of interface modifications. No major machine design changes are required. Canopies were trial installed and load tested at the manufacturer's facility prior to installation on the in-mine machines. Canopies were installed on a Joy 14BU10 Loader, 16RB-3AH Cutter, and two 21SC Shuttle Cars, and a Galis 300 Roof Drill and 460-S Face Drill. Canopy installations were evaluated in the Jewell Ridge Coal Company No. 12 and Big Creek Tiller Mines. Operational time accumulated on the installations during evaluation ranged from 1 week to 14 weeks of two-shift operation. All five canopy designs, manufacture, and test were successfully accomplished. The five canopies met all safety requirements. Three of the five canopies were deemed to be completely successful from an operator's point of view. That is, mine management as well as the machine operator found that the canopies did not impede the operation of the machines to function with the same efficiency as before the installation of the canopies. The loader canopy, in fact, appeared to have provided a mole efficient operation of the loader by providing added safety to the operator from rib contact thus allowing him to concentrate more fully on the loading function. Operational problems were encountered with the shuttle car and the roof drill. The shuttle car canopy obstructed visibility to an objectionable amount and the roof drill canopy impeded maneuverability of the machine, more than doubling the roof bolting time.

Jan 1, 2012

By Thomas R. Doyle

When you think of the state of Maine, you probably think of lobsters or lighthouses. The last thing you would think of is metallic mineral mining, and that is for good reason. According to the Maine Geological Survey?s website, ?no metals have been mined in Maine since 1977.? Moreover, Maine?s metallic mineral mining laws and rules, which were last rewritten in 1991, have effectively made mining in the Pine Tree State impossible. Statutory changes enacted in 2012, however, put Maine on a path to make metallic mineral mining part of the local economy in the near future. History of metallic mineral mining in Maine Currently, Maine is not a metallic mineral mining state, though that has not always been the case. The 1800s saw various mining operations in Maine, including what the Maine Geological Survey calls a ?mining boom? from 1879 to 1882, where mining of iron, silver, copper, lead and zinc expanded rapidly. Mining and mining activity in the more recent past, however, drove the debate before the state legislature when this issue was debated in 2012.

Jan 1, 2012

By David W. Tongue

This report describes the engineering work leading to the design of an underground coal mine piping system to transport approximately 2,000,000 cubic feet per day of methane gas to the surface from degasification holes drilled horizontally into the coalbed in existing coal mines. Safety instrumentation for detection of gas leaks and provisions for automatic emergency shutdown are included in the design. It also includes specifications for a safe system of handling gas, water, and drill cuttings during drilling of the horizontal holes and recommendations for compressor and metering facilities at the surface. The main pipeline is recommended to be constructed of polyethylene plastic pipe joined by a butt fusion method while lateral lines and separator and meter piping at the horizontal holes are recommended to be screwed steel piping. The materials used are to be resistant to the forces of impact exerted by falling rock. The pipelines are to be suspended from the ceiling with pipe hangers. All steel components are protected from chemical corrosion by applying protective coatings and the vertical casing to the surface is protected from electrolytic corrosion by a rectifier station. Methane gas detectors monitor the mine atmosphere to detect the presence of gas leaks and a pneumatic plastic tubing line provides for control of the safety shutdown system. Both the recommended design and the required construction procedures are in compliance with the applicable Federal codes for coal mine safety.

Jan 1, 2012

"High Pressure Grinding Roll (“HPGR”) technology is applied in a broadening range of minerals processing applications for relatively wet or moist materials. HPGR grinding of dry material or involving drying and air classification is more common, for example in cement manufacturing. A number of minerals processing plants are also operating with dry material, either due to process reasons, such as considerations of preceding or subsequent process stages, or as dictated by local conditions of arid areas and scarcity of water. The present world-wide expectation of decreasing availability of water supply urges us to look for alternatives that minimize water consumption.Recently established and envisaged future HPGR applications with dry ores have indicated that the technology of dry crushing and classification as practiced in cement and limestone grinding can be applied in minerals processing. Moreover, dry technology could very well be applied for generating a final fine product at sizes near or below 100 microns, as may be required for beneficiation by, for instance, flotation, magnetic separation or tank leaching.Dry HPGR grinding requires special attention in maintaining suitable process economics, when considering power input in grinding, drying and classification. In some cases, HPGR capacity and roll surface wear life may be negatively affected by a lack of moisture in the feed.This publication summarizes some of the features of, and experiences in dry HPGR applications. This includes design aspects of the classification system and discussion of the wear protection of the roll surfaces. The paper also includes examples of operational experiences of dry practices in minerals processing and cement plants."

Jan 1, 2012

Narrow vein mining, with enough challenge and also where the cutting edge technology can be applied, is still a very important and exciting portion of the mining industry. Based on the deposit characteristics, the most flexible mining method, cut and fill, has been being tested mining this high grade Northern Nevada property, Hollister, since the year of 2008. In the last three years, 254,000 tons of ore were hauled out of the portal and 23,000 feet of development were excavated underground with the winning of several safety and environmental awards. Together with mine geology, the essential segments include mining cycle, ground control, ventilation, grade control and backfill method in cut and fill stopes were covered in this paper.

Jan 1, 2012

Particles for heap leaching in conventional circuits are prepared using Cone crushers. Cone crushers are used to crush the ore to the size range between 12-25 mm for heap leaching operations. Leaching from these relatively coarse particles occurs only at the surface and in subsurface regions, which are accessible from the surface by cracks and pores. Since leaching is active in accessible areas, the method of comminution that forms multiple cracks and pores would offer an advantage for heap leach. An investigation was performed in this study to assess if the HPGR forms more cracks and pores than a Cone crusher. X-ray computed tomography (CT) was used to characterize the degree of cracks and pores formed by these two comminution devices that can be used for heap leaching feed preparation. In order to compare the effect of the comminution method on crack network generation, a bulk sample of the zinc ore was crushed by the HPGR at three different pressure settings (45, 95 and 120 bar), the sample ore was also crushed with a Cone crusher for comparison purposes. Products from the Cone crusher and HPGR experiment were then screened into five size fractions ((-25 +19), (-19+16), (-16+9.5), (-9.5+5), (-5+4.75) mm), Subsamples from the ((-25 +19), (-16+9.5), (-5+4.75) mm) size fractions were analysed. The spatial distribution of the crack network of sphalerite particles was characterized using a highresolution industrial X-ray CT system. This paper describes the use of image analysis techniques including image segmentation, which uses a combination of thresholding and other methods to characterize and quantify crack and mineral dissemination in the sphalerite particles after comminution with the HPGR and Cone crusher. The results are validated with those obtained using traditional techniques such as physical gas (with N2) adsorption, mercury intrusion porosimetry, SEM and QEMSCAN.

Jan 1, 2012

By Nirmal Weerasekara, Jochen Franke, Malcolm Powell, John Favier

Mill liners serve the dual purpose of protecting the shell from wear and transferring the rotary motion of the mill to an effective grinding action. As the liners wear, the efficiency of energy transfer changes, so there is balance between liner profile for wear and for milling efficiency. A tool that can simultaneously predict the evolution of the liner profile and the associated change in milling efficiency should prove most useful in optimal liner design. This paper presents such an approach, based on measured 3D liner profile data informing 3D DEM simulations of charge motion and liner wear modelling.

Jan 1, 2012

By F. Qi, T. Frišcic, C. Mottillo

"One of the principal goals of modern industry is to minimize the environmental impact and increase the materials- and energy-efficiency of transforming raw materials into valuable products. This paper will highlight our latest laboratory-scale research in low-energy, low-solvent reactivity of metal oxides and their conversion into popular metal-organic frameworks (MOFs), zeolitic imidazolate frameworks (e.g. Basolite® Z1200 component ZIF-8), and metallodrugs (e.g. bismuth subsalicylate, active component of Pepto-Bismol®). Mechanochemical ion- and liquid-assisted grinding (ILAG) and ""accelerated aging"" techniques will be presented, along with novel low-energy and solvent-free approaches, inspired by geological weathering processes, for converting metal oxides into metal-organic materials. INTRODUCTIONThe development of environmentally-friendly processes, which would in the same time be more materials- and energy-efficient than the existing ones, is one of the central concerns of modern chemical research. In that sense, the focus of the chemist has been mainly on the preparation of carbon-based organic molecules and adaptation of traditional organic synthesis to the recently delineated ideals of Green Chemistry. However, there is a growing realization within the chemistry community that significant energy, materials, and ecology-related benefits can be achieved and, indeed, targeted in the transformations of materials that are typically associated with inorganic chemistry and minerals processing. The principal aim of this highlight contribution is to illustrate how, through the use of approaches associated with solventfree chemistry and mechanochemistry (James et al., 2012), one can develop a clean and efficient system of chemical and materials transformations involving oxide precursors that normally belong to the realm of inorganic chemistry and mineral processing. In particular, this contribution will provide an overview of the recently developed mechanochemical and solvent-free reactivity of metal oxides towards small organic molecules. These mechanochemical reactions, including the methods of liquid-assisted grinding (LAG, Frišcic & Jones, 2009) and ion- and liquid-assisted grinding (ILAG, Frišcic, 2010), have so far provided a radically different means to construct advanced metal-organic materials (e.g. porous metal-organic frameworks, [MOFs] or metallodrugs) by rehabilitating metal oxides as precursors, eliminating the use of bulk organic solvents, and avoiding the use of high temperatures."

Jan 1, 2012