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By J. G. Wiese

Reagents are added to the flotation process of Merensky Reef ores to achieve specific functions that enable the separation of valuable minerals from gangue minerals on the basis of the difference in their surface properties. However, due to the complexity of the process, the various interactions that occur as well as the incomplete liberation of the ore and range of minerals present, it is difficult to quantify the behaviour of each of the reagents. More specifically, changes made to achieve a particular outcome may have secondary effects that can override the desired effect. If all the effects and interactions can be accounted for, it is possible to manipulate reagent suites and obtain better overall metallurgical performance. This paper discusses the effect of the addition of copper sulphate at different operating points of the recovery of the sulphide minerals. Batch flotation tests indicated that the recovery of chalcopyrite was not affected when operating conditions were varied, whereas pentlandite recovery was strongly affected by the point of reagent addition, and pyrrhotite recovery was enhanced by copper sulphate addition, irrespective of the point of addition, with the extent being dependent on the ore source. Floatable gangue was activated by copper sulphate in the presence of the dithiophosphate collector. Froth stability was also affected by copper sulphate addition.

Jan 1, 2007

By Augustine O. Orumwense, Micheline Boisclair

"The use of stirred mill to complement tumbling mills in grinding fine grained minerals is increasingly becoming an attractive processing option. Parameters such as agitation speed, grinding media type and size, feed pulp density, and grinding time were studied in order to elucidate their impact on stirred milling. Test results showed that the parameters have a profound effect on stirred mill efficiency and operating cost. A comparative test with a tumbling ball mill was also made and the specific energies of both mills in fine grinding were analyzed. A difference of over 40% in energy savings particularly when the product size is smaller than 20 µm was obtained with the stirred mill.INTRODUCTIONIn industrial processes where very fine and ultrafine particles are required such as in chemical, ink, food, paint and lacquer, pulp and paper, plastics, pharmaceutical, metallurgical and ceramic industries, the use of stirred mills for grinding is well established. Mineral processing plants are gradually shifting focus to the use of stirred mills for fine grinding and /or regrinding purposes as the target liberation size gets very small. A number of plants processing finely/sparsely disseminated ores are known to have adopted stirred milling technology for their fine grinding needs (Enderle et al., 1997; Harbort et al., 1999; Gao et al., 2000; Davey, 2003 & 2006; Pease et al., 2006).There are different kinds/designs of stirred mills available on the market but, all can be divided into two sub groups namely fluidized and non-fluidized types. The non-fluidized stirred mills consist of Tower mill, Vertimill, Sala agitated mill (SAM), and ANI-Metprotech (SVM). These mills are characterized by their low-speed and the use of fairly coarse grinding media size, 3 – 20 mm. Hence, they are mostly suitable for relatively coarse grinding application. The fluidized type includes the Isamill, Netzsch mill and Stirred mill detritor (SMD). These mills have a characteristic high agitator speed, use fine grinding media size of 0.5 – 5 mm, and are employed in very fine grinding operations. The superior fine grinding capability of stirred mills is attributable to two main process parameters, which are the use of fine grinding media and a high mill speed."

Jan 1, 2008

By Prosper Lamothe

El presente texto describe los distintos métodos y criterios empleados en la valoración de yacimientos o activos mineros de Chile, asimismo se realiza un análisis comparativo de los distintos métodos para explicar las distintas distorsiones, errores, riesgo e imprecisiones de cada uno de ellos. En este sentido, las empresas son concientes de los riesgos y el impacto que tienen en el valor comercial, los modelos de estimación de recurso y las reservasmineras. mineras. Por ello, las opciones reales son actualmente la técnica que permite valorar y controlar en cierto modo la cobertura de riesgo del negocio.

Sep 12, 2005

By B. L. Averbach

THE rolling process may be considered as a case of a nonhomogeneous plastic flow. In such a heterogeneous deformation there is no direct general solution, and the plastic deformation varies from point to point as a function of the coordinates. It is practicable to determine these plastic strains only at the conclusion of the rolling process, and the local strains can be studied by observing the deformations produced in a suitably placed grid system. Strains at the surface of a bar after rolling have been reported by MacGregor and Coffin,' but the strain distributions within the bar have not been previously observed. Siebel² has investigated the plastic deformations resulting from wire-drawing by splitting the wire along its axis, milling a grid coordinate system on the inner plane surfaces, and binding the .wire together so that it would pull through a die as a single unit. This method was possible because of the rotational symmetry of the die. In the rolling process, however, such a system was not readily applicable. This paper describes another method of including a grid system, and reports some preliminary data on the plastic rolling strains within a square bar. Experimental Procedure 2.1 mm wide (144 network squares per sq in.) was punched from a thin lead sheet with a steel die and supported in a brass mold by thin copper wires. Pure tin was then poured around the grid to form a solid bar, with the network securely imbedded at. a given position. This bar was then machined to a square 15.2 mm (0.60 in.) wide, and then radiographed. The lead grid was quite adherent and sufficiently ductile to follow the deformation of the bar faithfully. The network lines also remained sharp enough to maintain a high radiographic contrast, and the tin bar, with the grid included, could withstand considerable deformation at room temperature without splitting at the interface. In order to fill the mold, it was necessary to cast the tin at 260-280°C and during pouring the lead grid was supported at short intervals to prevent warping. Some shrinkage cavities were encountered, but only bars which were free of shrinkage in the network region were used. This method is similar to the one employed by Steinberg" in an investigation of the strain distribution in a tensile specimen. Before rolling, the machined bars were radiographed in two directions to obtain accurate initial dimensions of each square and to observe whether the grid was straight and correctly positioned. The rolling was performed in a small hand mill with 2 in. diam rolls at room temperature, and a 20 pct reduction based on the original height was employed. The rolls were clean and no lubricant was used. Halfway through the bar, at the center of the network, the rolls were reversed and the bar extracted. These bars were then radiographed again

Jan 1, 1951

By L Torckler, R L. Brathwaite

At Neavesville gold-silver (electrum) mineralisation occurs in steeply-dipping zones of intense fracturing, brecciation and quartz veining within rhyolitic pyroclastics, carbohaceous shales and andesites. Hydrothermal alteration extends over an area of greater than 3 by 1.5 km. In rhyolitic tuffs, highly silicified zones containing quartz-adularia-illite assemblages are flanked by less silicified assemblages composed of albite, illite-montmorillonite and chlorite. The mineralogy and sequence of alteration are comparable with the alteration zones which envelop the steam-producing fissures of the active Wairakei and Broadlands geothermal fields. Primary fluid inclusions in quartz from five fissure veins in the Neavesville field show maximum homogenisation temperatures ranging from 220 - 260¦C and salinities of 0.0 - 1.1 wt per cent NaCl equivalent, which cover a similar range to actual measured temperatures and salinities in geothermal fluids at Wairakei and Broadlands. The age of the rhyolitic pyroclastics and related alteration and mineralisation is probably Pliocene and Neavesville therefore represents a fossil geothermal system. The intensely fractured zones containing the gold-silver mineralisation were probably produced by hydraulic fracturing generated by accumulation under pressure of hydrothermal fluid in blind fault zones. Study of fluid inclusions indicates that hydrothermal quartz associated with electrum was deposited under boiling conditions. High grade electrum mineralisation at Graces workings appears to be localised by reaction of hydrothermal fluid with sedimentary marcasite in black shale.

Jan 1, 1980

By Jerome F. Kuzmick

Many investigations have been made on the effect of the variables of pressure, sintering temperature and sintering time on the physical and microstructural charactcristics of metal-powder compacts. Severa1 such investigations have indicatcd that pressure is the least important of these three factors in an attempt to secure a dense. strong compact by a simple coltl-pressing and sintering procedure. However, it was felt that a further study of the effect of pressure on pressed and sintered metal powder compacts might prove interesting, for the following reasons: In work done in the past on the effect of pressure, temperature. arid time, the, metal-powder compacts were subjected to long sintering periods, and temperatures right up to the melting point of the metal were applied. It was thought that pressure might exert a more profound effect under short-time simtering and within narrower ranges of temperature. such as normally would be applied in large-scale production of metal-powder parts. 2. It was hoped that something further might be learned of the nature of the bond in pressed and sintered metal-powder compacts. 3. It was thought that interesting infor mation concerning the work-hardening effect of pressure on the crystal structure. of sintered metal-powder compacts would be obtained. Procedure Rectangular bars, 2 by 1/2 by 1/4 in. were molded from the following metal powders: Atomizcd till powder, 325-mesh Atomized aluminum powder, 325-mesh Reduced copper powder, 100-mesh Electrolytic iron powder, 100-mesh Atomized 70-30 brass powder, l00-mesh The, till powder was molded at various pressures up to 40 tolls per sq. in. This was the maximum, because at higher molding pressures there was considerable extrusion of tin into the die wall, jamming the die plungers. The tin specimens were not -in tered, as this phase of the work was- done merely to see how much a very sold metal could be compressed. The aluminum powder was compressed at various pressures up to 50 lons per sq in. Higher pressures could not be used because of extrusion into the die wall The compacts were sintered one hour at 000 in pure dry hydrogen. The copper powder was molded at vari-ous pressures up to 96 tons per sq. in. One set was sintered at 750°C., another at 050 C. for one hour in pure dry hydrogen. The electrolytic iron powder was molded at various pressures up to 00 tons per sq. in. and sintered, one set at Soo°C and one set at 1300°C for one hour in pure dry hydrogen. Extra 325-mesh specimens were also prepared to study the effect of reduced particle size on grain structure. The brass powder was molded at various pressures up to 96 tolls per sq. in. and silltered for one hour. one set at 65o°C. and one set at 800°C, in pure dry hydrogeu.

Jan 1, 1945

By D. R. Dolinar

Geogrids can be used as surface control on both the roof and rib in underground mines to prevent the fall of small pieces of rock and material from between the primary supports. The use of screen material such as geogrid can significantly reduce the number of ground fall injuries caused by these small rock falls. Because of the potential for reducing injuries through the use of screen, the National Institute for Occupational Safety and Health (NIOSH) has conducted tests on screen materials including geogrid to determine their support characteristics and identify parameters that can affect their performance with respect to maintaining broken or failed rock. A specially designed test frame installed in the NIOSH Mine Roof Simulator (MRS) has been used to evaluate the load and stiffness characteristics of the screen material. Two types of geogrids with various designs have been tested-a polyester yarn and a polypropylene grid. The load-displacement characteristics of these grids were determined and the load capacity and stiffness were calculated through 20in of displacement. The load capacity and stiffness of the geogrid in general are shown to be related to the ultimate tensile strength of the screen material.

Feb 27, 2013

By Shane Baker

Cementation Foundations Skanska Ltd encountered many significant challenges in designing and constructing the foundations for the LNG (Liquefied Natural Gas) tanks and associated structures at the Isle of Grain, Kent, UK. With LNG cargo ship levels fixed by the adjacent English Channel, the platform could not exceed critical thickness in order to achieve final grade level, so a safe and efficient working platform for construction equipment on extremely poor alluvial soils was designed and installed. The detailed pile design also required particular analysis of the pile group behaviour and considered seismic load cases not usually associated with UK pile design. Continuous flight auger (CFA) piles were the chosen foundation solution and design was verified through preliminary and working pile tests both axially and horizontally. Contaminated land and existing foundations from a previous oil terminal meant that removal of spoil was extremely costly so specific measures were taken to minimise the off-site disposal. The management of a package of general Civil Engineering in addition to the piling scope, coupled with an unrelenting production program has forced a raising of the bar for this foundation technique.

Jan 1, 2006

By Jon C. Volkwein

The Bureau of Mines and many member companies of the Industrial Sand Association have been working in several areas to reduce personal exposure to respirable dust. Areas investigated include ventilation, modification of hardware, moisture addition to the product, and improved housekeeping practices. Ventilation systems have been devised and shown to contain 100 pct of a tracer gas released within the hood. An industrial clean air island has been developed and shown to reduce dust levels 90 pct at the opera- tor's position, Modification of hardware on a bag filling machine has been demonstrated to reduce dust 83 pct at the machine operator's lapel. This particular development has been termed a significant advancement in the state-of-the-art of bag filling by industry representatives. Addition of moisture to dried product materials has been tested with results showing dust reductions of 90 pct are possible!, Control of the moisture addition method still needs refinement and costs may be prohibitive. Dust sampling results clearly show the benefits of housekeeping practices such as building cleaning and vacuum sweeping. Rotation of work schedules is also effective for reducing personal exposure.

Jan 1, 1985

By P. Rice, A. Photolo, A. C. Barnard

Introduction -Sampling Tool Project (STP) -History -Results to date -Costs -Questions

Jan 1, 2005

By M E. Dunphy, P Silversmith

The Reefton Goldfield, both historically and potentially, represents a significant gold producing camp in the Westland province of New Zealand. Some two million ounces of gold have been produced from the Greenland Group host rocks between 1870 and 1951 with the most significant producers being the Blackwater and Globe Progress mines.   Steep terrain, high rainfall, poor outcrop, widespread fluvio-glacial deposits, tertiary cover and sometimes onerous environmental access conditions have proved a challenge to conventional exploration techniques. In addition classic exploration techniques have come up against a desire to reduce exploration cycle time and exploration costs while increasing both quality and quantity of geological information.   The trial, and subsequent implementation, of Wacker sampling has proved a highly successful and effective geochemical tool currently being utilised to target, discover, and define potential economic gold mineralisation in the Reefton Goldfield.

Jan 1, 1997

By Paul Staples, Fred Woodcock, Robert Grant, Mike Cooper

"Noranda's Brunswick Mining Division, near Bathurst, New Brunswick, processes 10,500 TPD of complex Cu-Pb-Zn bearing ore. Brunswick uses conventional rod and ball milling techniques to achieve a flotation feed size of 75% passing 400 mesh. Over a two year period, testwork was performed using a Marcy pilot plant ball mill to assess the impact of several key variables on secondary grinding efficiency. Four graded mill charges were used to compare balls and slugs at 25 and 29 mm sizes. Data was evaluated by determining grinding rates using a commercially available steady state simulator. Results were critical in Brunswick's efforts to achieve finer grinds while minimizing cost per tonne.IntroductionBackgroundThe Brunswick orebody is an extremely fined grained volcanogenic massive lead, zinc, copper, silver, iron sulphide body between two metamorphosed sedimentary and felsic volcanic rock units. Pyrite content is about 60% with 20% non-sulphide minerals, mainly silica and chlorite.Size reduction at Brunswick is performed by three separate parallel lines consisting of rod mills, primary and secondary ball mill circuits, all in series. The line 3 grinding circuit is presented in Figure 1."

Jan 1, 1997

By M. Drozd, M. Somppi, Z. F. Yamak

"Activated carbon is used to recover gold in solution from various gold circuit designs including carbon-in-pulp (CIP), carbon-in-column (CIC), and carbon-in-leach (CIL) processes; however, the characteristics and durability of the activated carbon can vary. Handling this medium poses challenges when fine carbon losses occur in the CIP, CIC, and CIL circuit discharge. Additionally, adsorbed gold on carbon fines can be lost to the discharge. The studies in this paper aim to standardize laboratory methods for testing activated carbon qualities specific to the gold industry. The investigation focused on size distribution, platelet content, wet attrition resistance, gold kinetics, and gold loading. The results demonstrate that a 96 h attrition test and a gold loading test form a basis for ranking carbon samples based on expected economic performance of the plant. ¦ KEYWORDS Activated carbon, Carbon attrition, Carbon ball-pan hardness, Carbon evaluation, Carbon fines loss, Carbon turnover RÉSUMÉ Le charbon actif sert à récupérer l’or en solution dans diverses conceptions de circuits de broyage d’or, notamment les procédés de charbon en pulpe (CIP, de l’anglais carbon-in-pulp), de charbon en colonnes (CIC, de l’anglais carbon-in-column) et de lixiviation au carbone, ou charbon au lixiviat (CIL, de l’anglais carbon-in-leach). Toutefois, les caractéristiques et la durabilité du charbon actif varient. La manipulation de ce milieu pose des problèmes dès lors que se produisent des pertes de carbone à grain fin dans la décharge des circuits CIP, CIC et CIL. Par ailleurs, l’or adsorbé sur les fines de charbon peut se perdre durant la décharge. Les études réalisées dans le cadre de cet article visent à normaliser les méthodes de laboratoire pour tester les qualités du charbon actif spécifiques au secteur de l’exploitation aurifère. L’étude portait sur la composition granulométrique, la teneur des plaquettes, la résistance au frottement humide, la cinétique de l’or et l’adsorption de l’or, à savoir la capacité du charbon actif à adsorber l’or sur une période spécifique. Les résultats ont montré qu’un test de frottement de 96 heures et un test d’adsorption de l’or constituaient le fondement d’un classement des échantillons de carbone du point de vue économique en vue de trouver l’échantillon générant le meilleur rendement des usines. ¦ MOTS CLÉS charbon actif, dureté de la batée des billes de carbone, évaluation du carbone, perte de fines de charbon, renouvellement du carbone, résistance au carbone INTRODUCTION The use of activated carbon for gold extraction is among the most common processes in modern gold-milling plants. Although gold losses are inevitable in the milling process, operators often focus on reducing gold loss to tailings. One focus area that is important in gold recovery is optimizing the use of activated carbon and examining potential changes to realize improved economics for carbon-in-pulp (CIP), carbon-in-column (CIC), and carbon-in-leach (CIL) processes. Granular activated carbon (Figure 1) is widely used for gold extraction from slurries containing gold-cyanide complexes. This activated carbon—produced from charred coconut shells—is well suited because of its adsorption kinetics, gold-loading capacity, attrition resistance, and ability to be reactivated. The extraction process using activated carbon technology involves adsorbing gold from an aqueous leachate; the gold is dissolved using a cyanide salt and consequently a dicyanoaurate(I) ion (Au(CN)2–) is formed, as noted in equation 1."

Jan 1, 2019

By A Vakili

Dilution is associated with considerable direct and indirect costs in underground open stoping operations. As shown in previous works, an improved ability to predict dilution enables the economic risks associated with unplanned dilution to be reduced. Depending on the width of the orebody and depth of mining, the economic performance of an open stoping operation can become even more sensitive to dilution. It is shown in several well-documented studies that as little as 1 per cent of additional dilution can impose millions of dollars of lost profits per annum. Optimisation of a stoping operation is therefore largely dependent on the ability of the operation to minimise dilution. This can only be achieved through sensible analysis of past and future performance of mined stopes using the most appropriate recent available technologies and tools. This article presents a new design process that utilises advanced geotechnical numerical modelling and various other analytical tools to assist with a more robust mine design of open stoping operations. The focus of this design process is on geotechnical factors affecting dilution during the life-of-mine. A recent application of this optimisation method for a mining operation is presented in this paper as a case study. Through the application of this method and various other operational improvements, the mine was able to deliver more consistent production and lower operating costs over its life-ofmine outlook and was able to reduce dilution by up to 50 per cent and achieve sustainable record high production rates.

Mar 29, 2023

By Gabriel S. Esterhuizen

This paper addresses the need for a method to compare the effectiveness of different support systems when designing ground support in coal mines. At present, support design methods include empirical methods based on observations of past performance of installed support systems, analytical methods where the roof is typically simulated by elastic beams and numerical model analysis. The approach presented in this paper estimates the relative stability of a support design through geotechnical evaluation of the rock mass and numerical model analysis of the interaction between the rock mass and the support system. Models are used first to simulate the design performance at the expected rock conditions. The rock strength is then reduced until collapse is indicated in the model. The stability factor is then calculated as the ratio of the expected rock mass strength to the rock mass strength at the onset of collapse, and is similar to the well-known factor of safety used in engineering practice. The stability factor can be used to assist in developing a final support design by comparing the effectiveness of various support systems and the stability of excavations under various geological and loading conditions. Examples of the method?s application in three different geological settings are presented.

Jan 1, 2012

By H. G. Iverson

The purpose of this investigation was to beneficiate the Talladega gray iron ores by flotation. A component of the problem was the determination of the degree of beneficiation possible by flotation as well as the relative selectivity of certain reagents in promoting flotation of either the iron minerals or the siliceous gangue minerals. The scope of the present investigation involved only the use of small-scale laboratory equipment. Treatment by roasting and magnetic separation was not included in this study, inasmuch as a similar comprehensive investigation was completed and the results were published by the Bureau of Mines in 1927. The results of the work on Talladega iron ores are briefly summarized in this report. In the search for efficient and economic methods of beneficiating low-grade iron ores, the flotation process is among those that are receiving considerable attention. The Talladega ores are of particular interest for a flotation study, because they contain two iron minerals (magnetite and specular hematite) that are somewhat dissimilar in their flotative response.

Jan 1, 1949

By R Lethlean

The mining industry in its drive to optimise equipment use and minimise cost simply to remain profitable in an uncertain commodity market needs to develop a greater understanding of equipment capabilities and cost. The factors influencing mobile equipment fleet cost and performance commence at the time of mine planning and continue to exert an influence over the life of the mine. These factors must be understood at the early stages of any operationÆs planning process as they continue to impact both positively and negatively on fleet performance and operating cost throughout the life of the mine. The key factors examined in this paper include: grades; rolling resistance; fragmentation and truck loading.

Jan 1, 1998

By H. J. Chen

In recent years, it has been recognized that the high horizontal stress is an important factor that contributes to a cutter roof. When the immediate roof is thinly bedded, the presence of a high horizontal stress may first cause failure on the bedding planes or weak planes, and then a cutter roof develops as the individual stratum crushes and buckles progressively layer by layer. In this study, the stress distributions in the bedding planes of the immediate roof are analyzed for an entry-pillar system in the multiple longwall panels by using the finite element method. Then the roof failure is analyzed based on the rock failure criterion and the stress distributions.

Jan 1, 1998

By S. Frimpong

Hydraulic shovels are widely used for primary production in surface mining operations. Variability in material diggability, unstructured mining environments and limited space and operator inefficiency affect the performance of these shovel excavators. Dynamic models of the hydraulic shovels are essential for understanding and improving machine performance. This paper contributes to this subject area by advancing hydraulic shovel kinematics and dynamics using the modified Newton-Euler method. A virtual simulator is developed to simulate the hydraulic shovel performance in the ADAMS environment. The simulator is validated with data on shovel geometry and the physical and mechanical properties of a formation in a surface mining environment. The results indicate that a shorter digging time increases the shovel operating power requirements, and that the required peak power increases by 100% when the digging time reduces by 50%. Simulation results also show that a shallow trajectory facilitates the digging process, with 50% reduction in peak power requirements compared to a deep one. This simulator provides a powerful tool for performance monitoring, excavation process designs and structural optimization of hydraulic excavators. This work also forms the basis for developing comprehensive simulator models for automated shovel operations in constrained mining environments.

Jan 1, 2005

By B. R. Zernich

Advances in tunneling technology, such as Earth Pressure Balance and Slurry Shield methods, have allowed the tunneling industry to construct tunnels in increasingly difficult ground conditions. In recent years, a number of civil projects including large diameter train tunnels, subway tunnels, water tunnels, sewer tunnels, and combined sewer tunnels have been successfully completed deep beneath the water table in soft ground conditions utilizing modern day Tunnel Boring Machines (TBM). With the increase in difficult ground conditions and higher water pressure comes the inherent need to utilize compressed air to gain access to the TBM?s cutterhead and cutting tools. This paper focuses on one such instance in Los Angeles, CA in which Traylor Brothers Inc. performed a cutterhead intervention by compressing the heading of an 11-foot diameter tunnel to approximately 3 bar gauge pressure. This paper focuses on the environmental controls used to manage ventilation, oxygen levels, temperature, and pressure, as well as discusses the problems associated with toxic gases and the increased risk of fire. The paper will also cover the physical science of the environment and the increased risks of performing basic job functions while in a compressed air heading.

Jan 1, 2009