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By George O. Lower

The use of cyanides in the extraction of gold and silver is well known.1 Such extractions employ con¬centrations of cyanide in the range of 0.02-0.25 % sodium cyanide equivalent in leaching cycles of 24-48 hours and frequently longer. Copper minerals, even though minor components of precious metal ores, dissolve in these cyanide leaching solutions, consume cyanide, cause fouling of mill solutions, and thus interfere with the precipitation and recovery of gold and silver. 2,3,4 This paper presents a summary of laboratory investigations on the use of cyanide solutions as extractants for copper from various copper-bearing ore fractions. In view of the metal contents involved, it will be apparent that larger quantities of cyanide are required to extract copper than for the extraction of precious metals. In cyanide solutions of concentrations generally favorable to copper extraction, sulfide and oxide copper minerals were found to dissolve rapidly at room temperature and atmospheric pressure. For example, on products in the flotation size range, the major portions (e.g. 65-85%) of the extractable copper frequently dissolved in 2-10 minutes. At coarser grinds, e.g. 100% minus 28 mesh and 100% minus 10 mesh, 75-85% of the total copper was extracted in 30 minutes.

Jan 1, 1966

By Luís Carlos da Silva

Nos dias contemporâneos, houve uma evolução do armamento utilizado e há uma tentativa dos centros de defesa e balística de acompanhar essa evolução no desenvolvimento de blindagens cada vez mais eficientes. Essa eficiência passa tanto na leveza do material quanto na sua capacidade de proteção. Vivemos também nos dias atuais uma preocupação com questões ambientais e energéticas e é justamente, envolto nesse cenário que pesquisas relacionadas à utilização de fibras naturais (FNL’S), tem se tornado cada vez mais relevantes. Desta forma, o objetivo deste trabalho é avaliar o desempenho individual de compósitos de matriz poliéster reforçados com fibras de sisal, quando submetidos ao impacto balístico de munição com calibre de 7,62 mm. Neste trabalho foram testados compósitos reforçados com 20% e 30% em volume de fibras de sisal. Com um auxílio de um radar Doppler, foram registradas as velocidades inicial (de impacto) e residual (após a perfuração do impacto). De posse desses dados foi possível calcular à energia cinética absorvida pelo compósito e estimar à velocidade limite do projétil que essa blindagem é capaz de suportar. Os resultados após alguns tratamentos estatísticos demonstraram que o compósito em questão tem resultados similares à outras blindagens reforçadas com FNL’S, representando mais uma opção de blindagem moderna.

Oct 30, 2017

By Alexandre Iartelli

A produção de cânulas, materiais utilizados na fabricação de dispositivos médicos, é feita a partir de uma tira de aço inoxidável 304L laminado em tubos e posteriormente soldado por processo GTAW. Após esse procedimento, o tubo sofre uma série de passes de trefilação com recozimento e sem recozimento, para diminuir seu diämetro. Por fim, são realizadas as etapas de corte, apontamento e limpeza do material. Durante a trefilação, uma série de defeitos chamados “GOUGE” é encontrada, provocando altas perdas nos processos, em função das desconformidades com as especificações técnicas. Inicialmente, no intuito de caracterizar e detectar possíveis causas dos defeitos foram analisadas as características do processo, desde a soldagem até a trefilação sem recozimento. Em seguida, foram feitas análises com microscopia de varredura, para avaliar algumas características metalúrgicas do material. Como o objetivo era caracterizar o defeito, diversas causas possíveis surgiram, como a influência da corrente ou velocidade de soldagem, temperatura de tratamento juntamente com as reações do gás Amônia na geração das desconformidades, a velocidade de trefilação ou a quantidade de óleo lubrificante. Concluiu-se que o processo de soldagem não foi o causador da falha, bem como a trefilação sem recozimento. A possibilidade da causa da descontinuidade ficou com o processo de trefilação com recozimento. Assim, diversas propostas para trabalhos futuros surgiram.

Jan 16, 2018

SULPHUR is a very well known mineral and apparently is produced in many places. It is engendered from an unctuous earthy and powerfully hot substance so that it is considered among experienced workers to bear a resemblance to the element of fire. This is called by these same men the masculine seed and the prime agent of Nature in the composition of metals. Because of its great dryness and heat it has, as experience shows, affinity with fire, which is easily introduced in it when brought near. And once introduced the fire is quenched only with difficulty before its unctuousness is wholly consumed. Although it shows itself to us of such a hot and dry nature, we must not think that sulphur is a substance so pure that it can stand by itself or that in order to attain its form it has no need of its portion and part of moisture like every other mixture. This is shown to us by its easy fusion, in which it resembles the metals. This thing is found in many places and in many varieties of color; some are white, others yellow and orange, and some others between gray and black. They also say that some red is found. It does not occur in that arrangement of veins like other minerals, but most liberal Nature makes whole mountains of it as is seen in the Aeolian islands, [26] near Sicily, in Etna or Moncibello which is the island of Sicily, at Pozzuoli, in the territory of Rome, in the Sienese domain at San Filippo, and in many other similar places. It is a substance that has a very strong odor and is most unpleasant to smell. It is very fixed in its substance so that it is never corrupted by time, by boiling, or by the moisture of water. For although it may stand in water a long time it never becomes soft nor does it ever decrease or increase in weight. It is brittle and easily crushed very fine. It is said that a trace of garlic rubbed on the mortar helps anyone who wishes to reduce it to impalpability. Its ores have a form more like earth than like stone although they some¬times have the color of a certain soft rock. The places where it is found are easily recognized by the great odor that they give out and by the very hot baths that often spring forth near it. What I have already told you about quicksilver that is contrary to the

Jan 1, 1942

By Renxing Li, Yongyong Gong, Yufeng Cheng, Zhenxing Yin, Xin Cao, Qijie Zhai

"The influence of electric current pulse (ECP) on the solidification structure of SUS430 ferritic stainless steel (FSS) was investigated in the current study. The technology of ECP has been widely used to improve the properties of metals with relatively low cost. The parallel electrodes were inserted into the free melt surface to constitute a current loop. The different influences of three parameters on solidification structure were studied by changing the peak current value, frequency and treating time respectively. The results indicated that the ECP significantly increased the number of equiaxed grains of SUS430 FSS. The as-cast structure without ECP treating was almost wholly columnar, while the number of equiaxed grains of the specimen, which was treated 3min with a peak current of 400kIA, increased to 2698 in the observed surface. To get the best refinement, an optimum range of these three parameters is required and the peak current value plays the most important role.IntroductionFor the lack of nickel resource and the pressure of environment protection, ferritic stainless steel is increasingly adopted to replace the austenite stainless steel because of its low nickel content and good mechanical properties. SUS430 steel is a typical example with excellent performance and relatively low price to replace the application of austenitic stainless steel[1-3]. This type of steel with high thermal conductivity coefficient, low expansion coefficient, good oxidation resistance, excellent stress corrosion resistance and other fantastic characteristics is often used to make components which need to have resistances for atmosphere, water, steam and oxidizing acid corrosion[4]. Since the developing of columnar grains and low toughness at high temperature, its products are easily crinkled and cracked during the subsequent rolling process[5]. The application of ferritic stainless steel is limited by these defects[6-8]."

Jan 1, 2012

By Xiaoming Wang

This paper describes a new magnetic separator integrating dynamic permanent magnetic force, gravity and flow dynamics to enhance the quality of the iron concentration. This equipment can increase the grade of concentrate by controlling the formation of magnetic agglomerations to reject most gangue. Test results indicates that the compound force field separator can be applied in improving the quality of iron concentrate and has a wide range of potential market applications. Keywords: magnetic separator, compound force field, rotating magnetic system, magnetite concentration

Sep 1, 2012

By J. H. Brown

"THE need for continuing education has been recognized only in fairly recent years as a major concern of the engineering profession. Formerly, it was acknowledged that engineers were required, at least informally, to follow the professional literature and to give some attention to new technical and technological developments. However, those relaxed days, when progress could be followed in a casual or incidental evening of reading, have disappeared in these days of mushrooming information. The engineer is now in the position of the man trying to control the flow from a fire hydrant with a child's pail. Our problem is that of developing an effective flow system -be it trough, hose, pipe or a bigger pail.The first step in achieving an effective means for continuing the education process is to realize that the need for the system is really an outgrowth of an increasingly sophisticated society. It is merely one more symptom of that society; others would• include the facts that new engineering graduates are more highly trained than those of several years ago, that graduate schools are now the norm and that even some fairly recent technologies are becoming outdated. There-fore, let us examine the education-al systems from which the bulk of the increasing sophistication has grown."

Jan 1, 1966

By Chee Theng

"Mining professionals are a resilient lot. Sure, copper prices are dismal, permitting processes seem interminable and the top mining companies are shedding jobs like a Shetland sheepdog sheds hair. All the more reason to hone technical skills, reconnect with old contacts and get one’s finger on the pulse of the industry.More than 400 did just that in the balmy sunshine and among the saguaro cactus of the Tucson venue of the SME Arizona Conference.Giving the keynote speech was Patrick Merrin, vice president at Hudbay Minerals (see box), while the luncheon speaker was University Distinguished Professor Mary Poulton, director of the Lowell Institute for Mineral Resources at The University of Arizona.“Attendance was great, especially given the copper price,” said Ta Li, vice president of business development at Tetra Tech and 2001 SME President. “The luncheon speaker was one of the better ones in recent years. Her talk contained a lot of fresh ideas, and practical versus theoretical concepts.”Talk about values, not economicsPraise was unanimous for Poulton, who gave a thought-provoking talk on “The New Face of Mining: The Culture Change for Compatible Mining.” Corporate social responsibility has been embraced by the metals mining industry, and it’s being done right, she said. “So why do we have more conflict? Why are there more protests? Why does permitting take longer and longer?” Poulton made a case for an approach based on compatible, rather than sustainable, mining to present a new face of mining that can be compatible with communities, cultures and the environment, and still be profitable. When the mining industry starts to talk about compatibility between what it is doing and what “me,” as the consumer, wants, what “we,” as citizens of a community, want, and what’s good for the “world,” we’re going to see the next culture change happen, she concluded."

Jan 1, 2015

When Caterpillar announced that it had purchased Bucyrus for $8.8 billion, it was billed as the next great chapter in the history of mining. Surely, when the history books are written, it will be remembered as a deal that changed the face of the mining equipment sector, and it could well be a major milestone in the path toward autonomous mining in the future. In the short term, the deal is a clear indication that the world?s largest equipment maker is bullish on the mining sector. The purchase of Bucyrus allows Caterpillar to expand its mining interest to six product segments (underground, surface extraction, large mining trucks, surface material handling, hauling products and growth markets) with 16 product lines to serve the mining industry. But the commitment doesn?t end there. According to Steve Wunning, president of Caterpillar?s resource industries group, which includes Cat?s global mining division, the commitment to mining goes far beyond the acquisition of Bucyrus.

Jan 1, 2011

By A Kleinitz, J Halilovic, K Trappitt

Mine operators use grade control to determine the destination of each block of material in the mine. In polymetallic mines, grades are best expressed in dollars: the Net Smelter Return, NSR, per tonne. To estimate NSRs, geologists working on grade control develop models for each geometallurgical domain in the mine. These models may incorporate observations on the mineralogy and grain sizes of the material being examined. The site’s mill operators contribute to the models by providing geologists with statistical analyses that relate assay results and mineralogical compositions to metallurgical parameters, such as the rates of recovery of each economic metal to each of the concentrates produced, and the compositions of those concentrates. The team responsible for sales and marketing of the site’s products contributes to the NSR models by providing details of the costs of shipping concentrates to smelters and refineries; and by providing figures that are specified in the smelter contracts, such as the payability of the metals in each concentrate and the fees charged by the smelter. The mill operators also provide, for the NSR models, equations to estimate the rates of recovery of deleterious materials to each concentrate. Deleterious materials comprise mostly halogens and amphoteric elements, both of which reduce the efficiency of smelters. Furthermore, deleterious materials such as antimony and arsenic may be poisonous to people and to the environment. The sales and marketing team provide specifics of the penalties that smelters impose upon deleterious materials. These penalties may reduce NSRs by tens of percent, possibly to levels below the cut-off grade. Thus, in the blocks that are subject to grade control, mine geologists monitor not only the concentrations of economic metals, but also the presence and abundance of deleterious materials. The preparation and maintenance of models, to estimate NSRs and to assess changes in the levels of potentially toxic materials to be mined, requires close and continuing consultation between corporate departments. There must be strong communication of mine geologists with the mill operators; with the people who market the mine’s concentrates; and, should there be a risk of encountering toxic levels of deleterious materials, with the mine’s health, safety and environmental officers. This co-operation could require radical changes in the structure of many organisations. However, experience suggests that such changes can significantly improve the profitability of a mine.

Mar 22, 2022

By HASAN SERKAN GOKCEN, SERKAN CAYIRLI

Manufacturers have improved various stirred mill types to be well adapted to fine and ultrafine grinding applications. These stirred mills, which are operated in wet or dry conditions, may be classified as horizontal — such as AHM-horizontal agitated media mill, IsaMill and Drais mill — or vertical — such as tower mill, Vertimill, Maxmill, Stirred Media Detritor and ATR vertical agitated media mill. The main difference between vertical and horizontal structures is in their operational variations. Additionally, the scaling-up of mills is also an important parameter for selecting the suitable orientation [1]. The purpose of this study was to investigate the dry grindability of calcite powders in a vertically and horizontally orientable laboratory batch-type stirred mill. The experimental results were evaluated using stress intensity analysis. The results showed that the d50 values decreased with increasing stress energy down to a certain point and then increased for both milling orientations. Even though the optimum stress energies for both vertical and horizontal orientations were in the range of 1 × 10−3 to 5 × 10−3 Nm at 750 and 1,500 kJ/kg energy consumption, the product size was finer for the horizontal orientation at the same stress energy value.

By J. B. Rosenbaum

This report presents new findings and consolidates previously published data to provide a single reference containing a concise and comprehensive description of the Bureau's work on electrolytic chromium. Two separate systems for electrolytic-chromium recovery were developed, one designated as the oxidized system the other as the reduced system. The electrowinning of chromium metal follows the dissolution of chromium from the ore or from ferrochrome and its separation from gangue and metallic impurities. Chromite was first solubilized by pressure digestion at slightly elevated temperatures in an oxidized acid solution using Na2Cr2O7 as an oxidizing agent. Later it was found that a sodium-free electrolyte was preferable, using return-cell anolyte containing H2SO4 and Cr03 as the oxidizing agent. Gangue materials were separated from the soluble metallics by filtration; and, after the Cr+3 had been stabilized, the metallic impurities were separated as crystalline ammonium salts by vacuum crystallization.

Jan 1, 1957

By J. Visman

The water cyclone washer has a number of advantages that makes it a desirable machine for the cleaning of fine-grained and friable materials such as 1,4 x 0" slack coals. In this paper results are presented of tests carried out on a shaly coal containing a high percentage of inter-grown materials from the Minto area, New Brunswick. The tests were con-ducted in the pilot plant of the Western Regional Laboratory in Edmonton. The test results show that the cleaning characteristics of this coal can be improved by lightly grinding the recirculating middlings fraction, which constitutes approximately 30 per cent (1.45-2.00 fraction) of the raw feed. • The cleaning of 1;4 x 0" fines by water cyclones compares favourably with other coal cleaning machines and has an added advantage of being extremely simple to operate, low in capital and operating cost, and high in capacity. The application of water cy-clones dates back approximately ten years, following its development at the Dutch State Mines. ( 3) A number of papers published d

Jan 1, 1961

By Farzad Moradpouri, Kianoush Barani, M. R. Azadi

The aim of this paper is to assess the effect of microwave treatment on copper sulfide ore for ball milling and bed breakage. Liberation analysis of ground products in eight size fractions showed that microwave pretreatment liberated more chalcopyrite particles from the bed breakage product than the ball mill product. In bed breakage, microwave pretreatment caused a 2% increase in chalcopyrite liberation on average. Microwave pretreatment produces more elongated particles in ball milling and more rounded particles in bed breakage, respectively. Microwave pretreatment produces coarser chalcopyrite particles with a wide range of sizes. This effect is more significant in bed breakage compared with ball milling. Micro-flotation test results showed that in ball milling, treated and untreated materials have similar metallurgical performance and there is a little difference (1%) between the average Cu recovery values. However, in bed breakage, the average recovery for the treated materials is about 5% higher than the untreated materials.

Jul 8, 2021

By M. Aatach, St. Gaydardzhiev, M. Kadiyski, E. Visariev, V. Stoilov

Detailed process oriented characterisation on representative samples from plant survey of the slag flotation plant belonging to Aurubis, Bulgaria has been realised in order to evaluate the mineralogical occurrences of Cu, Ni, Mo and Co bearing phases. The slag subjected to flotation consisted in majority of fayalite, magnetite-iron oxides and a glass-like phase. Ni and Mo have been found to be closely associated to magnetite and fayalite. The tailing from the slag flotation has been subjected to sulphation roasting followed by water leaching as a hydrometallurgical means to recover the remaining Cu, Mo, Ni and Co. Based on the various sulphation roasting conditions (acid dosage, duration, temperature) copper, nickel and cobalt were brought to solution to a different extent. Molybdenum was the most difficult to be rendered soluble due to its close association with iron, suspected to form an insoluble compound with it. Sulphation roasting performed at 350ºC has secured the best extraction degree for Cu, Mo and Co, while maximum recovery of Ni has been documented when roasting was done at 150°C. Keywords: Copper slag; characterisation; SEM; roasting; metals leaching, hydrometallurgy 16(2), 153–65.

Jan 1, 2020

By Roberto Fustos, Gonzalo Nelis, Víctor Sanhueza, René Gómez

Hang-ups are a challenging operational problem in block caving mines. They interrupt ore flow and imply hang-up removal activities, which take time, increase operational costs, and involve safety risks for workers. In block caving, the number of hangup events of mechanical arches that appear in the drawbell could be decreased if the drawbell geometry is adequately designed based on the expected rock fragmentation. Here, we compile and analyze hang-ups reported in several block caving mines to evaluate the impact of drawbell geometry, rock size, and vertical load on hang-up frequency at the mine scale. Results show that the ratios between drawbell length and d80 (dL/d80), between drawbell width and d80 (dW/d80), between drawbell volume and rock volume (VDB/VP), and vertical stress are critical parameters that define hang-up frequency. These findings confirm previous experimental studies, where a decrease in hang-up events is associated with an increase in these ratios. Additionally, these outcomes are used in a support vector machine algorithm to define categories of hang-up frequency. The results of this classification algorithm are presented in diagrams, which can be used to estimate the hang-up frequency in block caving projects.

Oct 15, 2022

By Geoffrey C. Huggins

Diagnostic: tests were performed on a production ST-5A Load-Haul-Dump machine manufactured by Wagner Mining Machinery Company to evaluate and rank order noise sources. The diagnostic evaluation indicated that the major noise sources were the transmission, the engine, and the cooling fan. This phase was followed by implementation of recommended noise control treatments, which included vibration isolation of the transmission, a transmission enclosure, an engine enclosure, and modifications of the inlet to the cooling fan. The final step in the program was an underground operational period which began on 31 August 1976 at the National Gypsum Mine in Shoals, Indiana. The noise control treatments successfully reduced the LHD operator noise exposure by 7 dB(A), thus increasing its allowable operation time by a factor of 2.7. Actual measurements made underground using noise dosimeters have indicated that, during, a typical shift, the noise control treatments have reduced the fractional exposure to an allowable level. The report discusses the mechanical aspects of the LHD, its noise sources, the treatments applied, the final levels achieved, and field experience with the noise-controlled machine.

Jan 1, 1977

By Paul Gottlieb

This paper reviews the status of automated applied mineralogy today and describes the history and fundamental theoretical and practical bases underpinning the development of automated systems. Details are given of the technical challenges that were faced in creating the new technology and in applying it to a range of applications. In recent years, automated mineralogy has become established as an essential enabling technology for the reliable acquisition of statistically sound comprehensive mineralogical and metallurgical data. This has had a revolutionary effect on the industrial use of such data in the study of geology, mining and mineral processing. Previously, using manual methods, it was not feasible to attempt this work because the large data sets required could not be assembled in a realistic timescale. There was a reliance on individual expert mineralogists and this was not scalable. The speed, reliability, detail and repeatability of the modern automated measurements has now made this type of analysis routine. Automated Applied Mineralogy has come of age! More than 100 systems have been installed around the World. Automated mineralogical analysers such as QEMSCAN® were originally developed as diagnostic metallurgical tools to improve mineral processing plants using samples drawn from plant surveys, bench and pilot-scale tests. They were used mainly for the assessment and auditing of size fractions of mill products, such as concentrates and tails. Subsequently, they began to be used for concentrator design and optimisation where ore characterisation was used to help understand the relationship between the feed ore and its subsequent behaviour in the plant. They are now widely used to measure exploration cores and drill chips from drilling programs to predict eventual metallurgical performance. Ore samples can be classified into metallurgical, as well as geological types, by combining mineralogical features in the ores with metallurgical properties related to grade control, separation, comminution, flotation and leaching behaviour. Three-dimensional block models of ore deposits are now being created based on processing response in addition to geological and mining properties. The development of automated systems began in Australia, the United Kingdom and Canada in the late 1970s and early 1980s. There were many technical challenges. Mathematical theories of randomness, sampling theory, image analysis and stereology were developed to ensure sample representivity so that meaningful information could be obtained. Sample preparation, presentation and measurement methods were developed to ensure that the random sampling was preserved during the measurements. Methods of automatic measurement and mineral identification evolved from the use of electron microscopes, fitted with backscattered electron brightness and energy dispersive X-ray detectors. Operational procedures were required to ensure that these instruments could accommodate a large number of samples and operate unattended for long periods of time. The new technology was progressively applied to a range of commodities and applications and new analysis methods, such as liberation measurement, were needed for metallurgical interpretation of mineralogical data.

Jan 1, 2014

By E. B. Nelson, B. W. Gandrud, B. M. Bird

"The Lewisburg No. 2 mine of the Sloss-Sheffield Steel & Iron Company is located in Jefferson County, Alabama, about 7 miles due north of Birmingham. At this point the coal from the Mary Lee seam when coked in by-product ovens yields an excellent quality of metallurgical coke suitable for use in the iron blast furnace; it is also an excellent steam coal. In mining, all three benches are worked. Coarse impurities are largely gobbed by the miners underground.In addition to giving the data obtained from screen-sizing and float-and-sink tests of a representative sample of the raw coal, this report presents the results of slotted-screen tests to show the proportions of flaky particles in selected sizes, and the results of tests to show how much coal is liberated from impurities by crushing the coarsest sizes. These data have been obtained in connection with an extensive study of coal-washing now being conducted by the U. S. Bureau of Mines and the University of Alabama, with U. cooperation of the different operators of Alabama. As the work progresses other reports will follow containing furtner data on the washability both of the Mary Lee seam and of other seams in Alabama and giving the results obtained in preparing these coals by various methods.Although a great amount of investigative work on the preparation of the Mary Lee scam was previously carried on by the various coal companies of the district, comparatively little of this information has been published. In governmental publications three references have been found. Forbes5 gives a number of sections with proximate and ultimate analyses of face samples taken in the mines. Gandrud and Britton'' show sections of this seam at Flat Creek and New Castle; they also give the specific gravity and ash contents of the partings of coal and impurities. In their paper Yancey and Fraser7 include washability studies and washing data from the Sayreton mine of the Republic Iron & Steel Co."

Jun 1, 1930

By Alfred Saulniers

El presente texto describe los cuatro mitos sobre las empresas públicas en Latinoamérica. El primer mito refiere al concepto de empresa como algo definido, donde hay una sola definición"correcta" del término puesto que se usaron diferentes enfoques (administrativo y jurídico) y por ende, se crean problemas en la evaluación del comportamiento de empresas públicas. El segundo mito señala que la empresa pública en Latinoamérica es un fenómeno post- depresión -en tanto es el resultado de la depresión de la segunda guerra mundial y estas se limitaron a generar una infraestructura mínima de apoyo a explotadores de la riqueza agrícola de la región. El tercer mito muestra que las empresas públicas son parásitos paraestatales, cuya función primordial es engullir subsidios de las aarcas públicas. El error estriba en el concepto errado del término subsidio y donde se aplica a una situación de dependencia perpetua impueta a la empresa. El último mito señala que las empresas públicas son inferiores a las empresas privadas debido a la clasificación por la naturaleza de su propiedad.

Jan 1, 1986