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By J. M. Wempen

Booster fans in underground coal mines are often located using the concept of a neutral point. Normally, intake airways are maintained at higher absolute pressure than return airways; therefore, air leaks from intake to return. By adding a significant pressure force to a region of a ventilation system, booster fans installed in a return airway can increase the pressure in the return so that air leaks from return to intake. This is commonly referred to as recirculation. The neutral point occurs at the location in the system where the pressure difference between [ ] the intake and the return airway is zero. At this point, there is no leakage or recirculation. Ideally, placing a booster fan near the neutral point minimizes leakage and recirculation. However, in practice, the position of the neutral point is not static and it changes as the ventilation system parameters change. Booster fans have the potential to increase the capacity and efficiency of coal mine ventilation systems. However, these fans add a significant pressure source to ventilation systems and can create areas where the pressure in the intake is less than the pressure in the return causing recirculation. In systems with multiple booster fans, there may be multiple recirculation paths and, as the capacity of these fans increases, recirculation is more likely to occur.

Jan 1, 2012

By T. Orser

In 2010 Newmont made the decision to purchase a 42 foot (ft) Semi-Autogenous Grinding (SAG) mill from Metso and a 28 Mega-Watt (MW) Gearless Mill Drive (GMD) from ABB for the Conga Project in Peru. The test and study work showed that a single line 42 ft SAG mill circuit gave the most favorable project economics in comparison to an equivalently powered single line 40 ft SAG mill circuit. This paper does not address the process design or the project economics, but instead focuses on the key aspects of the SAG mill design, GMD design and the associated component manufacturing. This paper also addresses, where applicable, the potential reliability differences between the initially proposed 40 ft SAG mill and the finally accepted 42 ft SAG mill.

Jan 1, 2012

By M. Maldonado, J. A. Finch

"A flotation bank consists of a serial arrangement of cells. How to optimally operate a bank remains a challenge. This article reviews three strategies for optimizing bank performance: air profiling, mass-pull (froth velocity) profiling and Peak Air Recovery (PAR) profiling. These are all ways of manipulating the recovery profile down a bank, which may be the property being exploited. Mathematical analysis has shown that a flat cell-by-cell recovery profile maximizes the separation of two floatable minerals for a given target bank recovery when the relative floatability is constant down the bank. Available bank survey data is analyzed in respect to recovery profiling. Possible variations on recovery profile to minimize entrainment are discussed.INTRODUCTION Flotation is used to separate valuable minerals from each other and from gangue. To reach a target metallurgical performance, usually assessed in terms of concentrate grade and recovery, feed is passed through stages such as roughing, cleaning and scavenging. All these stages comprise serial arrangements of flotation cells known as banks, lines or rows. Although a bank is the simplest interconnection of cells in a circuit, i.e. the tails of one cell is the feed to the next cell down the bank, how to operate each flotation cell in a way that the whole bank performance is optimized remains a challenge. Significant efforts have been made towards understanding the effect of operating variables on the flotation performance of an isolated cell (Lynch et al., 1981; Finch and Dobby, 1990; Gorain et al., 1998). However in the case of banks the variables that can be manipulated increase with the number of cells in the bank and the problem of how to manipulate them to achieve optimum performance is difficult even disregarding variation in ore characteristics (Lynch et al., 1981, p. 16). In general, the more manipulated variables available the better for optimization purposes, however without clear guidance how to effectively use them it becomes an “embarrassment of riches”."

Jan 1, 2012

Newmont Mining Corp. has been producing gold from the Carlin Trend for more than 45 years. Naturally, the focus, scale and complexity of the operations have changed considerably during this time. Newmont discovered and developed the Carlin Main orebody that is located about 32 km (20 miles) north of Carlin, NV. The property was developed as a one-mine, one-gold mill treatment plant operation, which produced about 6.2 t/a (200,000 oz/year) of doré gold bars. The initial mine, mill and gold refining facilities were relatively small in comparison to today?s standards. The milling circuit used the Merrill-Crowe zinc precipitation process to recover dissolved gold and prepare a concentrated precious metal ?precipitate? to be melted into a doré bar for sale.

Jan 1, 2012

By Thomas R. Bur

The patterns of variation of the 21 anisotropic elastic constants with direction arc presented for all of the symmetry systems that are normally expected to occur in rocks and in the constituent minerals. The exception, which is not discussed, is the triclinic system for which no elastic constants are available. Variations are shown for rotations about the principal axes by means of polar graphs. These include graphs for all of the n-fold symmetry axes possible for elastic symmetry and thus make it possible to visualize variational patterns for rotations about any n-fold axis. Variations throughout space are shown by means of equal area projections for the only constants (those relating axial stress to axial strain) that are uniquely defined by a single closed surface. For those unfamiliar with the compliance (Sij) and stiffness (cij) coefficients, the variations that can be shown by Young's modulus (E), Poisson's ratio (v), and shear modulus (G) are also given.

Jan 1, 2012

"Silver is traditionally recovered in base metal smelters (lead and copper), or as a by-product of other precious metals (gold and/or PGM's). This paper presents the results of non-conventional techniques to recover silver from complex materials. The PLATSOL® process has been developed to recover, in one step and without the use of cyanide, base metals (copper, cobalt, nickel) and precious metals (gold, PGM's) from sulphide concentrates too low in grade to enter the mainstream extraction processes. Silver is only partially recovered in solution with gold and the PGM's during the PLATSOL® process. However, the silver minerals are transformed into silver chloride, which can then be recovered from the PLATSOL® residue using conventional techniques. Some South American silver concentrates contain levels of impurity (mostly arsenic) so elevated that the penalties incurred significantly affect the process economics. The present results have shown that a low temperature calcination process transforms the concentrate into a product well suited for traditional recovery treatments. Metallurgical details will be provided, as well as the results of mineralogical studies that helped clarify the process mechanisms.IntroductionSilver occurrences in nature are very diversified, and, therefore, primary silver is produced as a by-product of many base metal and precious metal operations [1], as well as a co-product of most gold ores. However, difficulties can arise when high temperature processes are used for refractory gold ores or copper concentrates, or when the silver concentrate contains impurity elements such as arsenic that trigger high penalties."

Jan 1, 2012

By Tracy T. Morris, Luis G. Navaro

"Anodic copper slimes produced during the electrolytic refining of copper are routinely batch leached to remove copper. At the Amarillo Copper Refinery, an atmospheric leaching process was converted to an autoclave pressure leaching system to improve the removal of copper, reduce the consumption of oxygen, improve leaching times and enhance tellurium recovery. The benefits of pressurized versus atmospheric leaching of slimes were soon realized by obtaining the desired level of decopperization in a shorter time and with lesser quantities of reagents. The autoclave was designed and constructed with a unique oxygen injection system that enables good control of the leaching process and with no plug-ups. Other features include a mass measuring system that balances the quantity of slimes to be leached to the desired final solution concentration based on initial feed concentrations. The end result was a more efficient and controllable leaching process for removing copper from anode slimes.IntroductionThe electrolytic refining of copper consists of an electrolytic cell filled with a sulfiiric acid based electrolyte and pairs of copper anodes and cathodes. When a current is applied, copper in the anode dissolves and is plated onto the cathode. Impurities within the anode that are more noble than copper do not dissolve and end up at the bottom of the cell and are referred to as slimes. Gold and silver are the main slimes constituents of interest because of their monetary value, but there typically are significant quantities of selenium, tellurium, lead, antimony, arsenic, bismuth, nickel, silica and tin. Copper is also present, usually as a metallic or as a reactant with tellurium, selenium, oxygen or sulfur and can range from 10 to 30% of the slimes fall."

Jan 1, 2012

By Norman Paley

A blasting project was undertaken at the Teck Alaska Red Dog Mine in 2005 to 2007 to determine the extent that using electronic detonators could increase Semi-Autogenous Grinding (SAG) mill throughput. The results of that project were reported at the 2010 ISEE Annual Conference. This paper is a postscript to that project and provides the fragmentation resulting from the implementation of a 15% pattern expansion using electronic detonators.

Jan 1, 2012

By H. Moslemi

Metal sulphides are usually semiconductor and their electrical conductivity is low; therefore they are sources of electrons and promote electrochemical reactions. This phenomenon is of significant importance in sulphide flotation. The formation of a hydrophobic surface on the sulphide minerals is the result of various electrochemical reactions. Potential difference in the mineral-liquid interface plays an important role in the kinetics of the reactions, and consequently, on the flotation behaviour of sulphides. The value of the potential difference is influenced by different oxidation-reduction reactions at the interface area, and is measured by a two-electrode system in which an electrode is applied as reference electrode. In this study, we attempted to measure open-circuit potentials of pyrite, pyrrhotite, and steel electrodes with respect to the reference electrode. To verify the results, two reference electrodes, saturated calomel and gold, were used. Time-potential relations with respect to both reference electrodes show that the potential of both pyrite and pyrrhotite increases with time; however, this trend decreases for steel except when at pH 12. The results show a potential drop by an increase in pH value, except for steel, for which the opposite holds. This paper discusses galvanic interactions between minerals and grinding media in the grinding circuits, as well as among other minerals in the flotation processes.

Jan 1, 2012

By Å. Partapuoli, M. Henriksson, P. Wikström, J. Worth, G. Adolfsson

The control of AG mills fed by ores with harder and softer components can be challenging due to the sensitivity of the mill to the ratio of hard to soft components. The mills at LKAB’s iron ore operations are generally well controlled, but there are periods when the throughput falls off dramatically, due to a loss of mill filling. As the ore is upgraded in the sorting plant through magnetic separation prior to milling, this presents an opportunity to manipulate the feed blend in advance. In order to assess this opportunity, a fullscale mill charge was dumped and assayed by size to quantify the build-up of competent waste in the mills. This was supplemented by pilot and locked-cycle laboratory tests at a wide range of feed blends in order to facilitate the development of an appropriate multi-component AG mill model. This paper reports the experimental campaign requirements and methodologies, as well as the major outcomes from analysis and modelling exercises using the industrial, pilot and laboratory multi-component data.

Jan 1, 2012

By Don Deardorff, Ke Yang, Yingcai Han, Ken Sorensen, Robert Kruger, Mark Petersen, Diane Fiorelli, Larry Goldfarb, Kathryn Petek, Kwabena Ofori-Awuah

Design of deep foundations for lateral loads requires an understanding of soil-foundation-structure response during loading. Lateral loads on a deep foundation (piles) could be due to earthquakes, winds, waves, and/or machine vibrations. Over the years, analysis of response of piles due to lateral loads evolved from closed-form solutions to p-y methods to strain wedge to finite element/finite difference modeling. Although analysis of lateral response of piles and shafts is routinely performed, there is no single guidance document and/or standard for design and testing. Several different analytical methods are available for the analysis, and the resulting design can result in significantly different responses which can create confusion. This is especially true for analyzing and designing piles in potentially liquefiable soils with lateral spread issues under seismic conditions.This guidance document is intended to assist geotechnical engineers, pile designers, and contractors in analysis, design, and testing of piles and drilled shafts for lateral loads. This document discusses the background of different analytical and testing procedures and presents the recommended methods for analysis, design and testing of piles for lateral loads.Chapter 1 defines the different kinds of lateral loads to which a single pile or pile group may be subjected. This first chapter also presents different types of piles used to resist lateral loads.Chapter 2 discusses geotechnical issues related to lateral pile design such as liquefaction and lateral spreading and other non-seismic issues. Also addressed in Chapter 2 is geotechnical site characterization (as related to lateral loads) in terms of site investigation, in-situ testing, geophysical testing, laboratory testing, and estimation of soil/rock properties.Chapter 3 discusses the background and available analytical methods and tools for the analysis and design of single piles and drilled shafts. Several methods of analyses from closed-form elastic solutions to the finite element/finite difference solutions and their applicability are discussed. Available commercial computer software packages for analyzing single piles and drilled shafts are also presented.Chapter 4 expands the discussion of single piles and drilled shafts into the analysis and design of pile groups. In addition, group effects, resistance of pile caps, results of previous experimental and analytical studies, and available analysis tools and software for pile groups are discussed.Chapter 5 presents the issue of lateral resistance of piles and drilled shafts as discussed in different national and international building and non-building codes. A summary of extensive research on several codes are presented to facilitate the compliance with different codes.Chapter 6 discusses structural design issues of individual piles and drilled shafts such as depth of fixity.Chapter 7 discusses soil structure interaction issues related to kinematic and inertial effects due to seismic loading and available methods of analyses.Chapter 8 discusses and presents the typical procedures for the lateral load testing of piles. This guideline was developed as an aid to the practicing engineer in providing information, direction and commentary on the lateral design of deep foundations. Although all reasonable effort has been made to accurately compile the material and information contained herein, no warranty is made with regard to any such material or information and the Deep Foundation Institute assumes no responsibility for any possible errors or any direct or indirect result of the use of any such material or information. It is not intended that this document address every factor affecting lateral design for every situation. Therefore it is the responsibility of the person utilizing information from this document to confirm that it is appropriate and correct for their situation as well as to understand and properly apply

Jan 1, 2012

Despite two large projects represented in the keynote docket, the mood of the 2011 SME Arizona Conference was summed up best by Ferol Baker, general manager of New Mexico Copper Corp. (a wholly owned subsidiary of Themac Resources Group), ?In the past, it seemed like you couldn?t go to a conference like this without hearing about one big new greenfield project after another. Now what you see is companies doing internal expansion or small-scale brownfield development.? Overall, the tone of this year?s meeting, held at the J.W. Marriott Resort at Starr Pass in Tucson, AZ, was upbeat, yet practical. From the keynote and luncheon addresses to the six panels of sessions, the projects described were positive about the future, yet focused on the details required to make those projects come to fruition.

Jan 1, 2012

By Yotamu Hara, Animesh Jha

"High Curie temperature and large magnetic anisotropy make cobalt an important magnetic material for power engineering applications of magnets operating above ambient. It is also an essential constituent of modem lithium - cobalt oxide batteries, without which modem electronic gadgets will be functionless. Both these applications of cobalt save energy and reduce C02 emission. Ironically, however the production of cobalt from copper and nickel smelting in the world remains one of the least energy efficient process. The paper analyzes the energy balance, material and process chemistry of overall cobalt recovery and the waste generated, which entail the process limitations. We discuss a novel approach for the reduction of sulphide minerals with CaS04, permitting better separation of metals from slag and generating higher concentrations of S02. Such an approach may seem to be an alternative energy efficient option for processing and further purification of cobalt in metallic form. The results are discussed in the context of process thermodynamics and reaction kinetics for Coalloy production.IntroductionCopper sulphides bearing minerals are predominantly associated with iron and cobalt sulphides minerals. Carrollite (CuC02S4) is a mineral that has both copper and cobalt sulphides [1,2], which may also contain FeS, by substituting either Cu2+ or Co2+ ions in mineral lattice. On smelting copper - cobalt - iron sulphide concentrates, some parts of the cobalt often partition to matte at preferentially low oxygen potential by forming eventually an alloy phase with copper, however a significant fraction is often lost into an oxide slag rich in iron and silica. The slag heaps accumulated in the Copperbelt region in Zambia from last 60 years of mineral processing and metal extraction is reported to be 0.3 to 2.6 wt% of cobalt element, which is high [3]. Cobalt is also available in smaller concentrations in the copper smelting and converter slag, as reported in the investigations on the recycling of such slag materials using leaching with ammonium salt [4], iron chloride [5], and sulphuric acid [6], and solvent extraction [7].The recovery of cobalt from slag, irrespective of the techniques researched so far, does not seem energy efficient because the molten slag at 1300°C is quenched by losing thermal and chemical energy. The quenched slag is again reheated to above room temperature for leaching and above liquidus for carbothermic reduction of residual cobalt oxide. For example, in Mintek DC arc smelting [3], 80% of cobalt and 95% nickel are recovered by expending 600 kW per tonne. Assuming that the mineral carrollite is the starting phase, the univariant calculations for the Co-Ca-Si-S-0, Fe-Ca-Si-S-0, and Co-C-Si-S-0 systems are shown in Figure la, lb, and le, respectively at 1573 K."

Jan 1, 2012

By K. Lillkung, O. Forsen, J. Aromaa

"The dissolution rates of Pt, Pd and Rh in 250 g/L NaCl solution were calculated from the current densities determined by polarization curves and potentiostatic measurements measured with wire electrodes at atmospheric pressure. The results achieved with the two methods were similar. The dissolution rates at the corrosion potential were in the order of few nanometers per hour. The polarization curves indicated that to achieve dissolution rates required for economical operation on an industrial scale, the samples need to be polarized to higher potentials. When polarized to higher potentials, the metal dissolution rates were in the order of micrometers per hour. As the Tafel slopes of the metal dissolution region are fairly steep, the potential affects the dissolution rate greatly. Based on the activation energies, the dissolution reactions were controlled by a charge transfer step.IntroductionPlatinum group metals (PGM) have some very unique properties such as their inertness, giving excellent corrosion resistance, and a high melting point. At the same time, these factors make the refining of these metals very challenging. The main applications where PGMs are used are different catalytic converters, mostly in automotive catalysts. The used catalysts are also an attractive secondary source of PGMs. The exact concentrations of PGMs in catalysts vary widely depending on the manufacturer, the age and the capacity of the catalyst. The concentration of Pt in a new catalytic converter range from 300 to 1000 ìg/g, Pd from 200 to 800 ìg/g and Rh from 50 to 100 ìg/g [1]. Precious metal catalysts usually consist of a coat of the metal supported on ã- alumina. The recovery of metals from automotive catalysts has received much attention during the last few years [1-3]. In the near future, the use of PGMs in fuel cells is predicted to increase the amount of secondary PGMs available [4]."

Jan 1, 2012

By William Reisz

The explosives and blasting industry has a commendable safety and security record, especially over the last several decades. This is due in large part to our newer technologies, better training and education, engineering practices, corporate initiatives, our professional organizations, and whether we like to admit it or not - our regulatory agencies.

Jan 1, 2012

By H. J. McQueen

Pyro-reduction of ores to metal products developed markedly through the industrial revolution into the great depression. Nineteenth century resource and environmental sustainability were haphazardly improved by many process changes, although the motivation was primarily reduction in labor, feed stocks and fuel. Some notable achievements were coke and hot air for blast furnaces (later from waste heat stoves), puddling of wrought iron and steel ingot production with convertors advancing into oxygen use and continuous slab, billet and strip casting. Although advances in one sector were often counteracted by fall-backs in others, there was progress in that the resource consumption and pollution per unit of production was decreased. Improvements in the 2 decades following WW2 were mixed but popular notice of environmental hazards forced governments to legislate pollution controls and initiate steps in resource conservation. The energy crisis of the 1970’s saw an industrial energy-saving campaign and legislation of technology assessment procedures. Up until mid 18th Century, the training of iron masters depended on apprenticeship with some formalized knowledge from medieval books such as those of Biringuccio (1540) and Agricola (1556). The advances were very slow partly due to absence of scientific concepts of the smelting process. Nevertheless, some iron masters succeeded in improving the process and described procedures to instruct others. With the surge of steam power and the reverberatory puddling process for ductile wrought iron (WI), machinery changed from wood (iron strap reinforced) to WI machinery. With the clarification of the reduction and oxidation mechanisms by Cavendish and Lavoisier (~1780), productivity in iron production surged. The mechanical testing and microscopy of Kirkaldy (1862) spurred understanding of processing and properties of WI and steel. The various forms of C in steels were determined by chemists at the end of the 19th Century. It also became possible to control metal and slag chemistry in the open hearth furnace. But understanding of the transformations during heat treatment of steel only came in the first decades of the 20th Century.

Jan 1, 2012

By A. D. Pienaar

The aqueous chemistry of niobium and tantalum compounds with hydrofluoric acid is a mature field of investigation. In contrast, very little attention has been paid to reactions of these compounds in non-aqueous environments. Similarly, reactions of elemental fluorine with niobium and tantalum compounds have received little more than cursory attention in literature. This work discusses the isothermal reaction kinetics derived from thermogravimetry, using a less redundant approach than is currently the standard. We also discuss the most likely kinetic models for this reaction.

Jan 1, 2012

By Lv Guozhi, Niu Liping, Liu Yan, Zhang Zhiqi, He Jicheng, Zhang Ting’an, Dou Zhihe

"CuCr alloy can be extensively used as contact materials in integrated circuit, electrodes, electric contact and high strength conductor. We proposed thermit reduction-electroslag remelting method of preparing the large scale CuCr alloy. But there are pores and oxide inclusions in CuCr alloy prepared by thermit reduction process. This paper studied mainly the effects of ratio of reactant and additive on the inclusion type and their occurrences in CuCr alloy. The slags and CuCr alloy were characterized respectively by XRD and SEM. The results show that when the additive is Na3AlF6, the slag consist of Al2O3 and Cr. When the additive is CaF2, the slag consist of Al2O3, Cr, CaF2 and CaAl4O7. The inclusions in CuCr alloy are mainly Al2O3 and pores which disperse in Cu-rich zone and Cu-Cr phase interface. When 5% CaF2 and 5% KClO3 are added, there are fewer pores and inclusions, and the more better microstructure.1 IntroduceCuCr alloy is the contact terminal material with an eximious properties[1,2], which gradually replaces CuBi alloy becoming the first choice for contact terminal material in the medium and high power vacuum switch after the 1970s. The traditional preparation methods of CuCr alloy mainly contain powder metallurgy, infiltration process and vacuum electric arc melting methods. But the above methods exist some shortcomings, such as poor product quality, high cost of production, processes complex ect[3-9]. CuCr alloy is made by the thermit reduction self-propagating method, which uses CuO, Cr2O3 and Al as raw material to get the high-temperature melt, and then casts to manufacture CuCr alloy ingot, which response equation follows as:"

Jan 1, 2012

By M. Sripathy, K. V. Sharmal

"The conventional fiber reinforced plastic does not participate in the plastic deformation or enter the large plastic deformation state during collision. On the other hand, sandwich structure allows more plastic deformation, which improves the energy absorption efficiency. The objective of this study is focused on the investigation of the crushing of sandwich structure made from sisal / coir / bamboo/ glass fabrics as reinforcement and with polyester resin to form the composites skin and with polyurethane foam as the core. Experiments were conducted, showing that the underlying crushing mechanism of sandwich structures is very different from that of solid-section thin-walled structures. When a sandwich is subjected to crushing, the core deforms in the shear mode and the face bends independently. The damage is through the width zone of crushed foam core accompanied by a residual crushing in the foam. It is shown that such damage causes a significant reduction of compressive strength. Results show that glass/polyester and bamboo/polyester skin based sandwich structures have superior compressive strength. Coir /polyester based sandwich structure come next to glass/polyester sandwich structures in this aspect which is then followed by Sisal /polyester based sandwich structures.IntroductionCellular polymeric foam sandwich structures are often employed in shock mitigating applications. The cellular polymeric foam has several favorable properties, such as, low density, relatively high strength-to weight ratio and a significant degree of crushability. This high crushability is the result of the large void ratio in such materials, which also facilitates the collapse of cell walls via bending and buckling [1]. A few feasibility studies on FRP sandwich panels show that the panels efficiently provided high mechanical performance for minimum weight [2]."

Jan 1, 2012

By F. M. Wang, J. P. Lin, G. Y. Tang, H. C. Zhou, Y. F. Liang, F. Ye

"Fe-6.5%Si alloy is a very excellent soft magnetic material compared with conventional Si steel (Si content ~ 3.5%), especially in high frequencies with reduced iron losses and noises. But it is hard to be fabricated due to its brittleness at room temperature. Dynamic electropulsing is applied to the cold rolled Fe-6.5%Si sheet during tensile deformation. Mechanical and microstructural properties are investigated with different electropulsing and strain rate. It is found that the yield stress decreases and the elongation increases dramatically with the application of dynamic electropulsing. It is indicated that the work hardening could be reduced with the dynamic electropulsing during deformation, which provides a promising way to fabricate this alloy sheet much easier.Introduction Fe-6.5%Si (weight percent, same as below) alloy has more excellent soft magnetic properties compared with conventional silicon steel (Si content ~ 3.5%), such as higher resistivity, higher permeability, near zero magnetostriction, etc. and exhibits much lower core losses and noises [1]. However, Fe-6.5%Si is very brittle at room temperature and hard to be fabricated in strip by conventional hot-cold rolling process [2]. This lack of low-temperature ductility has been generally attributed to structural ordering ofB2 and D03 phases [3]. Several methods have been developed to avoid its brittleness, such as chemical vapor deposition (CVD) [4], rapid quenching [5, 6], dipping and diffusion [7, 8], direct powder rolling (DPR) [9], etc. However, hot-cold rolling method is still of interest for industrial applications. In our previous work, this alloy can be cold rolled after certain thermomechanical process and heat treatment [10-13]. The cold rolled sheet exhibits some extent of ductility [11]. However, side cracks are common for the rolled sheet, it is very necessary to improve the ductility of this alloy by other technical applications."

Jan 1, 2012