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By Aurelio L. Miranda V.

Desde 1938, el estudio de La Brunquita, especie de mineral del zinc, ha conllevado diversos estudios y pruebas de flotación no solo a nivel peruano, sino internacional, a fin de determinar el procedimiento económico para su explotación industrial. En este aspecto, el objeto del presente texto señala los factores, estados problemáticos, como los resultados obtenidos durante del tratamiento del mineral en la mina de Cercapuquio. Entre los factores destacados encontramos: abundancia y ley alta del mineral, cotizaciones actuales en el mercado internacional y la labor de los técnicos. Respecto de las condiciones problemáticas que refiere las características del mineral, tenemos el difícil control rápido de la marcha de flotación, degradación del mineral e imprecisión entre el mineral y la ganga, dado el tamaño de las partículas del mineral. Finalmente, los resultados obtenidos en este proceso, muestra que para el tratamiento de pre-concentración aplicado a los minerales finos de Cercapuquio, se necesita la hidratación ya que facilita la flotación posterior del mineral. Asimismo estas operaciones de pre-concentración no solo aumentan la ley de alimentación a los molinos y la capacidad de las plantas de beneficio, sino también que modificando la composición física del mineral, mejoran las condiciones del tratamiento posterior.

Jul 20, 1956

By Jesse Puller, Ken W. Mills, Owen Salisbury

"An underground coal mine located in New South Wales has a target coal seam located 160-180 m deep directly below a 16-20 m thick conglomerate unit that has been associated with significant periodic weighting events on the longwall face. As part of the investigations to better understand the causes of periodic weighting at the mine, inclinometers capable of measuring horizontal shear movements through the full section of the overburden strata were installed ahead of mining at two locations approximately 1 km apart above the centre of two longwall panels. These inclinometers were monitored as the longwall approached each site. This paper presents the details of the installation, the results of the inclinometer monitoring at both sites, and the insights that these measurements provide for overburden behaviour about longwall panels.Horizontal shear movements were observed to develop on shear horizons that correlate closely across the two sites suggesting a mechanism that is consistent across a large area of the mine. Shear movements were observed to develop on a single horizon near the top of the conglomerate strata that was mobilised almost immediately after initial formation of the longwall goaf at a distance of 425 m ahead of the longwall face. The direction of horizontal movement was consistent with the relief of the major principal horizontal stress. As the longwall face approached each inclinometer, other horizons within the upper part of the overburden strata begin to shear with the upper strata moving toward the approaching goaf more than the lower strata. Within the last 30 m of longwall approach, tilting of the strata associated with the increase in vertical subsidence toward the extracted goaf caused a change in the style of deformation with tilting and reverse shear offsets.INTRODUCTIONLongwall mining is recognised from subsidence monitoring, surface extensometer measurements, and various other observations to cause significant disturbance to the overburden strata directly above the extracted goaf of each longwall panel. Disturbance to the overburden strata beyond the limits of each longwall panel is not so well understood. Subsidence monitoring indicates that horizontal movements beyond the edges of the extracted longwall panel are generally greater in magnitude than vertical subsidence and horizontal movements may extend up to several kilometres from the edge of the panel in some circumstances (Reid 1998, Reid 2001, Hebblewhite et al 2000, Mills 2001, Mills 2014). The mechanics of how these movements are accommodated within the overburden strata is only poorly understood and there are few direct measurements."

Jan 1, 2015

By Paul McIlroy

Costs of producing lead from various known resources in the United States are developed by the Bureau of Mines to define the future availability of domestic lead at various price levels. It is estimated that 60 million tons of primary lead (75 percent of the total resource) is available at $0.20 or less per pound; 72 million tons (90 percent of the total) is available at $0.50 or less per pound; and the 79 mil- lion ton total estimated resource can be obtained at a price or $1.82 or less per pound. The supply available at $0.20 per pound or less will meet demand for over 78 years at the 1970 annual consumption rate of 763,000 tons.

Jan 1, 1974

By B. D. Pandey, M. S. Kim, B. S. Kim

The recovery of Sn from used Pb-free solder (Sn, 3~4 % Ag, < 0.9 % Cu, < 1.2 % Pb) has been investigated by electrorefining in sulfuric acid solutions containing small amount of hydrochloric acid. This involved preparation of the anode material by melting and casting the used solder followed by refining. During electrorefining, dendritic tin was deposited on stainless steel cathode. Increasing the amount of hydrochloric acid up to 0.3 mol /L in the electrolyte enhanced the current efficiency to 92.2 % and the enrichment ratio of silver to 94.3 % in the anode slime which was otherwise 84.7% and 81.6 % in absence of HCl, respectively. The electrolyte containing hydrochloric acid has also prevented the precipitation of tin oxide in the bath. In the scale-up experiment using 1.6 kg anodes, 84.3 % current efficiency and close to 100 % Ag enrichment ratio were obtained, while the purity of electro-refined tin was over 99.9 %. The energy consumption of the winning process was found to be 0.151 kWh /kg-Sn which is competitive as compared to commercial tin electrorefining processes.

Jan 1, 2014

By Felipe Sombra dos Santos

Este trabalho tem por objetivo principal sintetizar e caracterizar nanopartículas de ferro de valência zero (nFVZ) para degradação de substâncias recalcitrantes, através de Processos Oxidativos Avançados. A primeira etapa consiste na sintetização nFVZ, através da reação utilizando reagentes ferrosos, com o agente redutor borohidreto de sódio, em condições controladas (pH, temperatura e velocidade de agitação do sistema). Agentes complexantes e dispersantes, como o ácido cítrico e o etilenoglicol, respectivamente, foram utilizados durante a sinterização para avaliar a variação da formação do tamanho das partículas obtidas. A caracterização foi realizada através dos ensaios de distribuição de tamanho de partículas, microscopia óptica interfacial e microscopia eletrônica de transmissão (MET). Foi observado que a concentração de ácido cítrico de 0,009 mols e o volume de 100 mL de etilenoglicol, mostraram-se como os melhores valores obtidos. Todavia o ácido se tornou um interferente na reação ao ser utilizado com o SDS. Os resultados da microscopia eletrônica de transmissão comprovam que as partículas obtidas estão na escala nanométrica.

Aug 16, 2017

By T. Haubold, K. Ortner, T. Jung, D. Roth-Fagaraseanu, C. Mattern

Application of integrally bladed disks (blisks) is of increasing interest in compressors of aero engines. Blisks are preferred due to their potential for size and weight reduction, for increased performance and for reduced manufacturing costs compared to conventionally bladed disks. Erosion of the blisk aerofoils in service reduces engine performance, and can result in short shop visit cycles. This significantly increases the life cycle cost of these components, particular when considering that eroded aerofoils can&apos;t be exchanged easily for blisks during refurbishment. Shop visit cycle times can be extended and maintenance costs can be reduced through the application of an effective protective coating. The ongoing development of an erosion resistant coating and deposition process suitable for coating complex blisk geometries is described here. The coating is a multilayered W /TiB2 system exhibiting superior erosion resistance compared to known single- and other multilayer concepts. A modified sputter process is used to enable coating even of blisk geometries with shadowed surface to competitive recurring cost.

Jan 1, 2006

By Chas. Y. Clayton, Francis B. Foley, W. E. Remmers

DuRing the summer of 1919, the late Dr. Henry M. Howe, then Chairman of the Division of Engineering of the National Research Council, organized a committee to obtain a better insight into the behavior of carbon steels under the influence of various treatments by a proper control of the time and temperature factors. During part of 1919 and 1920, work in connection with this investigation was carried on at Dr. Howe&apos;s laboratory at Bedford Hills, N. Y. During 1921 there was an enforced hiatus in the work, occasioned by the illness which resulted in Dr. Howe&apos;s death in 1922. At that time one of the present authors compiled the results of the work which had been done and this was published in 1923.&apos; Following the publication of this work, it seemed desirable to carry on in the same manner an investigation of steel of C 0.75 per cent., which steel had not been as fully treated as had the other steels of C 0.34 and 0.52 per cent., used in the published work. Furthermore, certain unusual results have been obtained in the treatment of C 0.52 per cent. steel by quenching and drawing, and repetition of this part of the work seemed advisable. This has been done during the past year at the School of Mines and Metallurgy of the University of Missouri at Rolla, Mo., by a cooperative undertaking of the School and the Bureau of Mines, working in conjunction with the Committee on Heat Treatment of Carbon Steels of the National Research Council. The present paper is a report of the results obtained in this work.

Jan 1, 1926

By G. H. Roybal

Humic-acid-rich deposits exist in Arkansas, Florida, Louisiana, New York, North Dakota, Michigan, Minnesota, Texas, and Wyoming (Burdick, 1965) and in New Mexico (Shomaker and Hiss, 1974). New Mexico humic deposits are associated with coal in the northwestern part of the state where humate and weathered coal are presently mined. Discussion of the humic -acid industry in New Mexico requires an understanding of complex terminology and coal geology. TERMINOLOGY Humic material is not a pure substance so an ambiguous and complex terminology is in use by geologists, chemists, soil scientists, agronomists, and producers. Material mined for its humic-acid content is an extremely variable mixture of base-soluble humic, fulvic, and ulvic acids and their salts, formed during partial or complete decay of organic matter. This decay releases a high-molecular-weight organic material which is darkly colored, partly colloidal, and weakly acidic.

Jan 1, 1985

By Érica Castilhos

Defeitos internos do tipo trinca off-corner são um dos principais problemas relacionados à qualidade em tarugos de aços especiais lingotados continuamente. Este tipo de defeito é bastante crítico, pois além de se apresentar de forma descontínua no tarugo e, consequentemente na barra laminada, não é detectável pelos equipamentos de inspeção em linha usualmente utilizados para garantir a qualidade final do material. Neste trabalho, foram avaliadas amostras de barras laminadas de um aço baixo carbono com e sem a presença do defeito do tipo trinca off-corner a fim de estabelecer um método que permita avaliar a criticidade da trinca. Estes resultados foram relacionados com os principais fatores que influenciam na formação deste defeito, proporcionando alterações de processo com o objetivo de minimizar a sua ocorrência.

Jul 30, 2018

By Marcelo Moreira Furst Gonçalves

A qualidade superficial dos produtos lingotados continuamente está ligada diretamente aos estágios iniciais de solidificação do aço no molde. Nessa etapa do processo, os parâmetros e estratégias de oscilação são decisivos para a obtenção de produtos com qualidade superficial adequada. Assim, foi desenvolvido na Usiminas um sistema computadorizado para monitoramento dos parâmetros de oscilação do molde, de modo a fornecer subsídios para um melhor entendimento do processo. Este sistema monitora, em tempo real, o eixo vertical e as oscilações nos eixos horizontal e transversal, mesmo com baixas amplitudes. O sistema desenvolvido possibilita a obtenção dos dados com alta precisão, de forma totalmente automática e a realização de pós-tratamento de forma a se obterem valores relativos ao processo de lingotamento e funcionamento do molde.

Jul 30, 2018

By Markssuel Teixeira Marvila

A Capilaridade, definida como um fenômeno de atração e repulsão, que ocorre no contato de líquidos com um sólido, fazendo com que este líquido se desloque sobre a superfície sólida, é um dos parâmetros primordiais para analisar a durabilidade de argamassas de múltiplo uso. Neste contexto quatro traços de argamassas, dosadas em laboratório e industriais com diferentes níveis de consistência, foram utilizadas para avaliar a correspondência entre as normas brasileira NBR 15259 (ABNT, 2005) e europeia UNI EM 15801 (2010) para cálculo do coeficiente de capilaridade. Os resultados indicam que mesmo seguindo procedimentos bastante divergentes ambas a normas proporcionaram valores de coeficiente de capilaridade para todos os traços estudados. Assim sendo fica comprovada a equivalência técnica das duas normas estudadas para obtenção do coeficiente de capilaridade.

Oct 30, 2017

By A. H. Castillejos E., F. A. Acosta G.

Filtration is widely used as a terminal refining step for metals, particularly for the casting of aluminum alloys, but still more knowledge is required to understand how several factors affect the efficiency of removal of inclusions. In this study, both, initial and long term filtration efficiencies of a ceramic foam filter have been obtained from the computed trajectories of solid particles suspended in molten aluminum. The complex structure of the foam filters is represented by a unit cell which is formed by a pair of pores with average dimensions. The fluid flow field was determined from the numerical solution of the Navier-Stokes equation, and periodic fully developed flow was assumed at the inlet of the calculation domain, as a boundary condition. This flow field corresponds to laminar flow as that found in ceramic filters operating under normal conditions. Computed initial filtration efficiencies showed that filtration efficiency decreases sharply with fluid velocity for particles larger than 30 µm, but smaller particles are better trapped at higher fluid velocities. Finally, it was found that long term filtration efficiency for particles of 8 µm decreased with time, in spite that perfect particle-wall attachment was assumed. Filter aging was considered in this study, and it was found that the distorted flow field, around the already trapped small inclusions prevented further collection.

Jan 1, 1999

By Estéfano Aparecido Vieira

O presente trabalho busca desenvolver métodos de estudo de remoção de inclusões de aço em escala de laboratório relacionando propriedades como viscosidade e composição química das escórias com a capacidade de remoção de inclusões. Com esse fim, foram desenvolvidas cinco escórias usando como referência a viscosidade da fase líquida assim como o percentual da fase líquida. As escórias foram adicionadas sobre o aço fundido e comparou-se o nível de inclusões antes e depois dos experimentos. As escórias também foram analisadas após os experimentos através da difratometria de raios-x para identificação das fazes formadas. Os resultados apontam que as escórias testadas possuem a capacidade de remover inclusões. Porém escórias com elevado teor de CaO tem maior eficiência na remoção das inclusões.

Oct 30, 2017

By Rafael Sartim

A indústria siderúrgica possui aspectos ambientais associados ao seu processo produtivo ligados em grande parte à emissão de material particulado, efluentes líquidos e geração de resíduos. A emissão de material particulado ocorre durante diversas etapas do processo produtivo, cabendo a estes a aplicação de sistemas para o controle ambiental. Em especial, a planta de sinterização possui como característica emissões primárias ligadas à exaustão da máquina, e secundárias referentes aos sistemas de captações em linhas de peneiramento, retorno de finos e pontos de transferência de correias transportadoras. Para o tratamento das emissões secundárias, a ArcelorMittal Tubarão possui um sistema de despoeiramento. Em virtude de melhorias de processo e alterações na produção, o sistema necessita de uma maior vazão para atendimento à demanda atual. Neste contexto, este trabalho se propôs a avaliar e testar a técnica de supressão de pó em pontos de transferência entre correias transportadoras para verificar sua aplicabilidade. Como conclusão, constatou-se que esta técnica é aplicável em regiões específicas com bons resultados na redução de emissão visível. Além disso, o uso do supressor reduz a quantidade de captações necessárias ao sistema complementando o controle do atual sistema de despoeiramento.

Aug 16, 2017

By G. Shore

"The development of a DC resistivity instrumentation system for data acquisition in extreme topography yielded an unexpected bonus in the quality and information content of the type of raw data gathered. Not only were traditionally too-rough areas being investigated systematically for the first time, the unique high-density, multi-directional raw data were providing the opportunity to greatly expand the range of conductive and resistive signatures that could be accurately recognized. Using a true 3-D inversion algorithm, 3-D earth resistivity imagery began to show distinctive anomaly patterns for hydrothermal mineralization at the seldom-visited resistive end of the spectrum, successfully imaging epithermal gold systems in conditions that had defied conventional ground and airborne geophysics for years.The traditional mode of designing a resistivity survey to test a specific target concept was shown to be an unnecessary limitation on exploration thinking when a single sweep acquisition of dense, multi-directional 3-D raw data could effectively provide the all-targets “shotgun” coverage that would take 10 or 12 conventional surveys to duplicate. Exploration planning has the opportunity to move from single steps of trial and error geophysical testing to a mode of mapping everything at the outset, and then sorting out what might be of exploration interest in the results. Survey parameterization becomes the non-technical process of marking an outline on a map and declaring “survey here.” Operational and interpretational reasons for not testing where the exploration interest lies have all but disappeared. With any-terrain capabilities and unprecedented raw data density and overlap to support interpretation of complex conditions, that outline can be drawn through extreme rough terrain, including lakes, cliffs, industrial facilities, and grounded installations to test for generally unknown sub-surface features of potential interest.As more is learned about the larger-scale signatures of ore settings and the district-scale geo-electric imprint of hydrothermal processes on lithology, it appears that the only thing certain about ore signatures is their uncertainty. This is not bad news. New opportunities abound as the advanced 3-D technology allows a first effective look at the previously unexplorable rough terrain or complicated settings, and a second look at areas where older results may now be known to be non-definitive."

Jan 1, 2002

By Lloyd B. Underwood

In the event of a sudden nuclear attack upon the United States, it is imperative that vital command and control centers have a high probability of survival. One such vital facility is the North American Air Defense Command Combat Operations Center at Colorado Springs, Colorado. Known briefly as NOW, this installation when completed will be housed in large chambers excavated out of granite beneath the eastern slope of Cheyenne Mountain (Figure 1). The NORAD COC, a U. S. Air Force sponsored project, will serve as the primary collection and evaluation center for data concerning unknown aircraft, missiles, or space vehicles, which might bring destruction to North America. The data will be fed into high-speed computers and electronic equipment from outpost sources - radar, ballistic missile early warning stations and picket ships throughout the world. Electronically controlled display boards will make it possible to evaluate the tracking data instantaneously and to take appropriate defensive action1.

Jan 1, 1965

By Veena Sahajwalla

The cupola furnace is a coke-fueled shaft furnace used as a primary melting unit in iron foundries. Control of chemical composition of the iron tapped from the cupola is a key factor in productivity and quality control. In an effort to develop a control model for the cupola, a fundamental approach based on physical and chemical principles has been taken to describe the melting process. The behavior of oxidation of the solid charge in the stack of the cupola has been studied. Sulfidation of the charge materials by sulfur-bearing components released to the furnace gases from the coke has been described. Carburization of metal droplets of iron and of steel in separate molten streams has been characterized. Finally, reactions with alloying elements in the hearth (well) of the furnace have been defined. These reactions have been described in a computer-implemented model developed to predict the composition of the iron tapped from the cupola. The model has utilized the thermodynamics and kinetics of the oxidation, sulfidation, and carburization reactions, including temperature and physical aspects, in the various zones of the melting unit. The model predictions have been compared favorably with operating results.

Jan 1, 1992

By D. L. Moellenberg

Under various state laws enacted mostly within the last 20 years, reclamation requirements and standards for hard-rock mining operations have been established virtually everywhere in the western United States. Unlike the uniform and detailed coal mine reclamation requirements under the federal Surface Mining Control and Reclamation Act ( "SMCRA" ) and state programs mode led after SMCRA, the various state law hard-rock mine reclamation requirements are based upon a variety of objectives, and therefore are subject to varying standards from state to state. While the diversity of reclamation requirements complicates the determination of what reclamation measures will be required at any particular mine, there are valid reasons for this diversity. There are dozens of different commodities mined in the United States, and mining methods are different for each commodity. Local natural conditions such as climate, precipitation, geology, hydrology, and biology vary widely across the county. Site-specific conditions also affect mining and reclamation methods. Also, factors such as economics, land use, and environmental protection issues receive different priorities in different states and communities within those states. State reclamation requirements in general provide the flexibility to consider site-specific circumstances, allowing operators to design and engineer the best reclamation measures for each mining site. To the mine developer or manager, reclamation requirements must be translated into design, operational, and closure measures for mine planning. Each of these measures must then be assigned additional costs to be factored into the economic decisions for a particular mining operation. On a broader level, reclamation costs must be factored into decisions such as where to invest in exploration and mine development. The purpose of this paper is to provide a summary of the state non-coal mine reclamation requirements in twelve western states. This summary comparison may be useful as a starting point in considering how local reclamation requirements will impact potential mining costs.

Jan 1, 1994

By Ilkka Haapamäki

El presente texto señala la planificación del proceso de ventilación Outokumpu en la mina Helsinki, Finlandia a través de la evaluación de las cantidades de aire. Este sistema se basa en normas locales vigentes para la higiene laboral, órdenes relativas a la ventilación de las minas, cantidades de producción de la mina, condiciones geológicas de la mina y cantidad local de sustancias producidas durante el trabajo de la mina. Asimismo se describe el layout del programa, preparación de la red de ventilación y simulación por medio de una computadora, planificación de la dirección del proceso de ventilación, control automático de la ventilación en la mina de Pyhasalmi, cálculo de costo, planes de investigación y evaluación del número personal requerido.

Oct 14, 1980

By S. Kauchali

"Underground coal gasification (UCG) is recognized as an efficient mining technique capable of chemically converting the coal from deep coal seams into synthesis gas. Depending on the main constituents of the synthesis gas, chemicals, electricity, or heat can be produced at the surface. This paper provides a high-level graphical method to assist practitioners in developing preliminary gasification processes and experimental programmes prior to detailed designs or field trials. The graphical method identifies theoretical limits of operation for sensible gasification within a thermally balanced region, based primarily on the basic coal chemistry. The analyses of the theoretical outputs are compared to actual field trials from sites in the USA and Australia, with very favourable results. A South African coal is studied to determine the possible synthesis gas outputs achievable using various UCG techniques: controlled retractable injection point (CRIP) and linked vertical wells (LVW). For CRIP techniques, an important result suggests that pyrolysis, and subsequent char production, are important intermediate phenomena allowing for increased thermal efficiencies of UCG. The conclusion is that South African coals need to be studied for pyrolysis-char behaviour as part of any future UCG programme. The results also suggest that UCG with CRIP would be a preferred technology choice for Bosjesspruit coal where pyrolysis dynamics are important. Lastly, the use of CO2 as oxidant in the gasification process is shown to produce syngas with significant higher heating value. Introduction and literature surveyCoal is a commonly utilized fossil fuel, providing over 40% of global electricity demand and about 90% of South Africa’s primary energy needs. However, less than 20% of the known world resources are suitable for possible extraction using conventional surface and underground mining techniques (Andrianopolous,, Korre, and Durucan, 2015). Underground coal gasification (UCG) has the potential to recover the energy stored in coal in an environmentally responsible manner by exploiting seams that are deemed unmineable by traditional methods. The UCG process, if successfully developed, can increase coal reserves substantially. For example, in the Limpopo region of South Africa alone, the estimated potential for UCG gas, based on existing geological records, is over 400 trillion cubic feet (TCF) natural gas equivalent – this is about a hundred times more gas than the existing 4-TCF Pande-Temane natural gas field reserve in Mozambique (de Pontes, Mocumbi, and Sangweni, 2014)."

Oct 1, 2018