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By Benjamín Leiding Valdés

"Ante la demanda industrial del cobre en el desarrollo minero, se hace necesario revisar su proceso de producción y repercusión a nivel mundial y peruano. Por tanto, el objetivo del texto describe algunos aspectos de su rentabilidad desde 1947 hasta la actualidad. De acuerdo a este último año de estudio, EE.UU. mantiene el liderazgo de producción con 29%, Chile, ocupa el segundo lugar con 14%, Rodesi, en el tercero con 12% y el cuarto lugar lo disputan Rusia y Canadá. Así, la producción norteamericana de cobre al igual que la chilena se ajusta a las demandas de consumo, mientras que la de los tres países restantes va en ascendencia. De otro lado, la mejoría de precio a nivel mundial, permitió que el conjunto de los demás países restantes ocupe el 18% de la producción, destacándose entre ellos Perú, Japón y México, seguidos de Unión de Sud África, Felipinas, Yugoeslaviay Chipre con más de 40 mil toneladas de producción de cobre. Asimismo, de acuerdo al aprovechamiento del plan de extensión, la distribución de la producción mundial del cobre primario ha mejorado tanto que en 1956 sobrepasó el consumo, aunque mantuvo su auge de precio. Sin embargo, en 1958 dicha situación cambió por el agotamiento de las reservas, ocasionando un perjuicio para los primeros países productores y un aumento para los últimos. En este sentido, los pequeños productores se convierten en las fuentes de producción de la última década, ubicando a Chile y Perú como los principales productores en América Latina. La producción chilena proviene en un 90% de su gran minería y en el 10% de su mediana y pequeña minería y sus principales mineras son Chuquiquimata en Antofogasta, El Teniente en O' Higgiins y El Salvador en Atacama. Mientras que la producción cuprífera peruana se ha duplicado en los últimos 10 años, sobrepasando las 65 mil toneladas por año. La gran minería de cobre en el Perú se inicia en los últimos años a través de la explotación del yacimiento minero de Toquepala, perteneciente a la Southern Perú Copper Corporation, estimando una reserva de 500 millones de toneladas de minerales de 1% de cobre por mes. La minería mediana peruana de cobre se encuentra en las minas de Cerro de Pasco y Morococha, en Junín, donde los minerales son concentrados y posteriormente fundidos en La Oroya. En conclusión, tanto Chile como Perú se constituyen como los dos más grandes productores de cobre sudamericanos que contribuyen al abastecimiento del mineral en este continente como en Europa, Estados Unidos y Norteamérica, no solo por sus reservas sino por la bondad de sus yacimientos. ."

Jul 20, 1959

By Peter Zhang

Shield recovery in a longwall move is normally conducted from tailgate to headgate. However, if the face is wide and the immediate roof is weak, difficult conditions with considerable roof sag, excessive shield load, and local roof falls could occur as the shield recovery proceeds to the middle of the face, causing delays in shield recovery. The situation could be aggravated when a pre-driven longwall recovery room is employed. Alternatively, a bi-directional approach for shield recovery, i.e. shield recovery starting from the middle of the face towards both tailgate and headgate, can alleviate the roof sag significantly by quickly withdrawing the shields towards the lower abutment pressure zones at the headgate and tailgate sides. In this case, the bi-directional shield recovery approach was used in a longwall move for a 1450 ft wide face under weak roof conditions. Shields were successfully withdrawn within five days without experiencing significant roof sag. The time-dependent roof-to-floor convergence, shield pressure, and roof conditions were monitored during shield recovery. 3-D finite element modeling was conducted prior to longwall move to evaluate the difference between a uni-directional and a bi-directional shield recovery during a longwall face move. Vertical stress, yield zone in and around the recovery room, load on the shields, and convergence at the center of the shield canopy were obtained from computer modeling, and compared with the data from field monitoring. Finally, the advantages of the bi-directional shield recovery are discussed.

Jan 1, 2007

By J. D. Noll

Elemental carbon (EC) is used as a surrogate for regulating the exposure to diesel particulate matter (DPM) of underground metal/non-metal miners. EC was chosen as a surrogate because EC is selective to DPM and is a major component of DPM. Using EC as a surrogate also gives one the advantages of no sampling artifacts and being able to sample at all locations in the mine. Currently, EC represents DPM well in underground mines. Some control technologies have been shown to possibly alter the relationship between DPM and EC and characteristics of DPM. Therefore, future work will investigate the relationship between DPM and EC as new control technologies are implemented.

Jan 1, 2002

By Hugo de León Carvalho Cedro

O presente trabalho tem como objetivo avaliar os efeitos da degradação da superfície de lentes de contato via métodos ópticos. Sendo biomateriais, as lentes estão em contato direto com estruturas sensíveis do corpo humano e seu uso surge da necessidade de reduzir enfermidades, propiciando melhora da acuidade visual e proteção ocular. Outro aspecto relevante é que as lentes se tornam uma nova estrutura refrativa de entrada da luz no globo ocular, e desse modo devem manter características de transmitância compatíveis com a córnea. Com o uso das lentes, é esperado uma degradação natural das propriedades ópticas e superficiais da mesma. Para avaliarmos essa degradação, foi planejado um experimento com um ensaio de degradação. O ensaio de degradação visa comparar o efeito de diferentes soluções simuladoras sobre a superfície das lentes tóricas: solução extrema de acetato de potássio 5% pH5, solução fisiológica usada pelo fabricante do tipo Boston Simplus multiação e solução de água ultrapura obtida de um dispositivo milli-Q (controle). O efeito da degradação foi analisado através do estudo das variações da topografia e da transmitância da lente.

Oct 30, 2017

Stripping of Fe (III) from D2EHPA Using Different Reagents The common way to extract Fe(III) from an organic solvent is by using concentrated acidic solutions. The stripping of Fe(III) from organic solvent Di-2-ethylhexyl phosphoric acid (D2EHPA) by hydrochloric acid (HCl) solutions has been found to increase with increasing the acid concentration. However, the use of a concentrated acidic solution such as 6 M HCl can degrade the organic molecules. In this research, to increase the efficiency of Fe(III) stripping from D2EHPA, effect of some acids, salts and buffer solutions was studied. Influence of Tri-butyl phosphate (TBP) as modifier on the Fe(III) stripping operation was also investigated. According to the results, the best Fe stripping recovery was achieved in the presence of low acid concentration and the salts which was 72.4 per cent oxalic acid, 70 per cent ammonium oxalate and 75 per cent buffer of oxalic acid and ammonium oxalate. The results also showed a better recovery in the presence of the buffer rather than the salt. Finally, increasing the concentration of TBP, HCl and H2SO4 resulted in a higher stripping efficiency of Fe(III). However, in the presence of oxalic acid and its salts increasing the reagent concentration did not increase the stripping efficiency and at this condition, the recovery of iron remained constant.

Sep 13, 2010

By J. N. Van der Merwe

"A major shortcoming of the statistical back-analysis of coal pillar strength is that it relies on the asmined pillar dimensions, not taking into account time-related pillar scaling with subsequent reduction in pillar width. The paper describes an investigation where the rate of pillar scaling was applied to the pillars in the databases of failed and unfailed pillars. The reduced pillar sizes were then used in the same method of statistical back-analysis that had been used in the past.This resulted in an equation for pillar strength which predicts significantly greater pillar strength than the previous statistical analyses, which is similar to the strength which had been found earlier by direct testing of large specimens underground. It is concluded that the lower strengths found by previous statistical analyses are due to the incorrect pillar width being used and that by adjusting the pillar sizes to compensate for scaling, more credible results that correspond to direct testing are obtained.As the newly derived strength equation is time-dependent, it follows that the safety factors and probabilities of failure are likewise time-dependant. An equation to determine the probability of failure is also developed. This results in the safety factor being close to unity at a probability of failure of 50%, which is aligned to statistical expectation. IntroductionSince the Coalbrook mine disaster, caused by massive pillar collapse, there have been several attempts at analysing and defining the strength of coal pillars. It was realized in the very beginning that performing classical strength tests on coal specimens in a laboratory and then transferring those results to real coal pillars could not be successful. The scatter of results is one problem and, more seriously, there is a size effect (at least for small specimens) that made the transformation of strength results to much larger coal pillars underground all but impossible.Two main schools of thought then emerged. Some researchers preferred to perform direct strength tests on large specimens underground, while others relied on statistical back-analysis of failed and unfailed pillar cases, attempting to determine the differences in size and shape that would allow a satisfactory prediction of failure. The latter school of thought resulted in the method that was widely accepted by the South African coal mining industry, described in the landmark publication by Salamon and Munro (1967)."

Jul 1, 2019

New Zealand has often been quoted by metallurgists and others as one of the countries in which Tellurium is found, and locally it has been recorded that appreciable quantities of tellurium have been met with in the Thames and surroundingdistricts. However, specimens containing tellurium which have been obtained on this field have not been preserved and their scarcity today points to the fact that tellurium is not here abundant.To ascertain its distribution, analyses and assays have been made by the author on a large number of ores, the results of several of which are given below.The presence of any considerable percentage of tellurium has an important bearing on the metallurgical treatment of ores in which it is found.

Jan 1, 1901

By Miguel Pimentel

El presente trabajo describe el proceso implementado por la minera Yanacocha para el tratamiento de las aguas de exceso a través de la Tecnología de Membranas (EMS- Engineered Membranes System) o proceso de Osmosis Inversa, conocida también por las siglas en inglés de RO (Reverse Osmosis). El proceso RO tiene por objetivo tratar la solución barren proveniente de la planta de Merrill-Crowe para reducir el contenido de cianuro, así como los metales disueltos y otras sustancias como nitratos y nitritos en la solución.También, busca clarificar el agua tratada para cumplir con las exigencias que establece el Ministerio de Energía y Minas (MEM) y el Banco Mundial (IFC) en cuanto a límites de descarga permisibles. Una vez alcanzados los niveles establecidos, y con la aprobación del área interna de Control de Calidad, el agua tratada se descarga al medio ambiente.

Sep 12, 2005

Flotation Circuit Optimisation - Towards More Sustainable Practice

Sep 13, 2010

By John A. Franklin, Tom C. Palangio, Norbert H. Maerz

WipFrag systems I and II have become the world standard in photoanalysis systems to measure fragmentation. Mines, quarries and excavating contractors can now easily measure blast results and track the progress of optimization efforts. This technology was developed and evolved to allow automatic measurements of the size distribution of patiicles on moving conveyors, in truck boxes and on crusher feeds. Production machinery can now be controlled by photoanalysis results and multiple cameras allow various locations to be monitored by a single system. Blast designs can be monitored on a shot by shot basis. Changes in delay times, explosives, patterns and hole sizes can be quickly evaluated. Along with this measurement capability has come a heightened awareness of the importance of “optimum size” and uniformity of particles for lowest cost production and material handling efficiency. In the past, savings in the “drill / blast” cycle of the operation were sometimes overshadowed by downstream production costs related to fragmentation. Now total production costs can be compared with fragmentation sizes which will immediately show the trend towards optimum size for economical production. No cost reduction program can be complete without this critical information.

Jan 1, 1997

By Joseph Javes Aramburú

El presente texto describe la optimización del circuito de molienda y clasificación de la planta de hierro, el cual comprende un molino de barras y de bolas. El proceso se inicia con la exploración geológica, se determinan las reservas probadas y probables, y se establece la forma de explotarloLa eficiencia de la molienda está en función del volumen útil del molino a diferentes volúmenes de llenado que permite determinar los parámetros óptimos de la operación.

Apr 1, 2013

By Fernando Saavedra

En los sectores de mina, concentradora y planta Mofito, perteneciente a la minera Codelco Chuquimata, las redes de control exigen un aumento en los volúmenes de información de control en los equipos de operación y mantenimiento. Por ello, se plantea mejorar la disponiibilidad, confiabilidad y robustez de las redes existentes en las distintas áreas de la minera Chuquimalta a través de un proyecto que optimize dichas condiciones de las redes de control ControlNet Y EtherNet/P y así aumentar la confiabilidad impactando en la disminución de los tiempos de pérdida-producción relacionados con fallas en las redes de control.

Sep 1, 2014

By Cz. Mora, A. Pawelczyk, D. Hreniak, P. Nowak, A. Dyonizy, S. Strek, W. Strek, K. Grabas, A. Ostrowski

Globalization and a growing demand for limited raw material resources have forced changes in the approach to the supply chain. This is particularly true in the case of rare earths, which are regarded as one of the most important development indicators of modern technologies. To ensure a secure supply of commodities, the European economies have been prompted to investigate REE recovery from sources which until recently, for technical or economic reasons, were considered not sufficiently attractive. An interesting example is apatite phosphogypsum waste dumps. The REE content in these waste dumps averages around 0.5-1 %. One of the most important phosphogypsum locations in Poland is the Lower Silesia region where a phosphoric acid Chemical Plant "Wizów" operated for several dozen years. In this work, rare earths are leached from the phosphogypsum crystalline structure by a chemical treatment and can then be separated into individual chemical compounds. The technology used in these recovery tests, matches up to a coherent European raw materials policy supporting effective management of resources and promoting waste materials recycling.

Jan 1, 2014

From time to time lead, which is normally considered to be a soft ductile metal, fails by cracking. The cracks which form appear to be of two distinct types-(a) those which follow a zig-zag course around the boundaries of crystals and (b) those which follow a more direct path, frequently two systems of cracks appearing at right angles.The former appear definitely to be associated primarily with the properties of the crystal boundaries, whilst the latter appear rather to be determined by the system of stresses applied. In both cases the lead appears to be a brittle rather than a ductile metal, for the failure occurs without the large amount of deformation usually associated with the tensile breaking of lead. The latter is, however, a function of time and when lead is deformed by long applications of stress, the metal appears to- be less ductile than when the stress is applied suddenly. Thus, if a given test piece of commercial lead is broken by a stress of 1100 lb. per sq. in. in several hours, it may extend 40 to 50%before failing, whereas when broken by a stress of 500 lb. per sq. in. acting for 12 months or more it willshow an extension of only 15 to 25 %. With lower stresses still, failure would take much longer and undoubtedly lower extensions would be obtained.As the stress is lowered it is found that the marked local contraction characteristic of ductile metals becomes less noticeable, and failure, instead of being by extension of *Lecture delivered to the First 'Ordinary Meeting of the Australasian Institute of Mining and Metallurgy, 21st August, 1935.

Jan 1, 1935

Project cost control procedures and computer systems have enjoyed a successful and simple relationship over the past decade, thanks primarily to the proliferation of portable computers or PC's. Prior to the introduction of this technology, project control was largely a manual and somewhat onerous task of historical data compilations, with little time available for dynamic forecasting, staged planning, or pre-emptive cost control. Automated systems developed during this era were resident on "Heavy Iron" or mainframe computers and were expensive to maintain and operate. Use of these early systems was limited to large engineering, construction, and industrial concerns with the economies of scale and funding required for their successful application. Systems were either designed for critical path analysis or task scheduling, but rarely integrated with the other, much less cost control.

Jan 1, 1990

By C. Cánepa

El presente estudio describe de forma comparativa algunas características similares entre las minas "Río Seco, "Raúl" y "Condestable"con el objeto de determinar la semejanza entre los procesos de su origen. En este sentido, se encontró similitud en la composición mineralógica a niveles macro y microscópico entre los yacimientos mencionados anteriormente. La mineralización en "Río Seco" presenta carácteres geométricos semejantes a los mencionados para el tipo "veta", con un desarrollo notable en el tamaño de todas las fases minerales. Asimismo la diversidad y evolución geométrica de los tipos de mineralización metálica y la transformación química de las fases minerales en cada uno de los yacimientos estudiados, indican la intervención de más de un proceso genético en la formación de los mismos.

Nov 20, 1972

By D. G. Krige

Using chip sample data and spatial structure parameters from a large mined-out section of a South African gold mine the advantages to be gained from a regular underground borehole drilling programme have been investigated for short- and medium- to long-term planning based on block valuations. The results have been compared with the current position, which relies invariably on the extrapolation of limited peripheral sampling data from raises, gullies or stope faces. Some preliminary work has also been done regarding the implications of such underground drilling on costs used for the present pay limit calculations. The results of the study, though preliminary, show that the net advantage of advance regular underground drilling could be substantial and that a more intensive follow-up research is warranted.

Jan 1, 2003

By Roberto Maldonado Astorga

El presente texto señala la implementación del modelo de gestión para las operaciones de Volcán Campaña Minera, basado en el Modelo de Gestión de Malcom Baldrige. El modelo tiene el objetivo de establecer un proceso sistemático y estandarizado que asegure la mejora contínua y en línea con la visión de la empresa que apunta al logro de la excelencia operativa. La estrategia se divide en tres módulos: Módulo de Organización, Módulo de Gestión y Módulo de Comunicación. Asimismo se busca, implementar círculos de optimización permanente, monitorear de forma sistemática la ejecución de iniciativas de mejora y seguir el impacto en los indicadores.

Nov 1, 2014

By Antônio César de Araújo Freitas

As empresas de mineração têm desafios logísticos em sua operação no dia a dia, visto o crescente volume de minério movimentado nas Usinas e Portos e pressão crescente por resultados operacionais que se traduzem na busca contínua por níveis superiores de produtividade. A tecnologia de automação dos processos produtivos e de máquinas evoluiu muito na última década, entretanto o processo da logística nos pátios de matéria prima e produtos apresenta baixo nível de automação e é baseado em informações verbais e observações visuais a respeito do nível de estoques e disposição dos materiais nas pilhas e áreas dos pátios de manuseio. Em um processo tão complexo, pequenas decisões da operação no dia a dia, que podem variar de acordo com o operador, supervisor ou turno de operação, podem influenciar a produtividade diretamente, afetando indicadores como horas paradas e deslocamento de máquinas por tonelada expedida, afetando dessa forma custos significativos na operação de uma usina ou porto. Este trabalho tem por objetivo então descrever as técnicas utilizadas para modelar os desafios de logística nos pátios de minério, descrevendo sistemas de otimização utilizados com apresentação de resultados em projetos como o de Carajás, planta da VALE que é atualmente a maior mina de minério de ferro do mundo, abordando a redução de deslocamento de máquinas, diminuição da exposição ao risco de colisão e redução de paradas.

Jul 30, 2018

By Kristen Dunlap

There are several thousand remote stream crossing structures in the Tongass National Forest in need of removal. In 2007 thirty-three collapsing log bridges, log culverts, and metal culverts no longer in use were removed with explosives. Species of salmon, trout, char, and sculpin are present in the project area. Blasting overpressures may injure or kill fish in streams and ground vibrations can damage salmonid embryos in streambeds. Regulatory agencies offer guidelines with limits for blasting induced overpressures and vibrations. However, there has been no quantification of blast overpressures in shallow streams. Methods used to predict lethal levels for various blasting applications have not been completely validated. This research provides guidance for analyzing ground vibrations and water overpressures during blasting activities in or around fish streams.

Jan 1, 2009