Search Documents

K. W. Turner, Sail Francisco, Cal. (communication to the Secretary*): The recent papers in the Transactions by Vogt,' Lindgren2 and Weed: on ore-deposits that have formed as a direct result of igneous intrusions, show that deposits of this class are widely distributed over the world, and are occasionally of commercial value. This is especially true if we consider under this head all deposits in the zone of contactrnletamorphism, the origin of which may be ascribed to the gases and vapors generated by the heat of the intrusive rock. Mr. Smith's description of the Chillagoe garnet-formations containing copper, leads one to regard these depoaits as of contactrmetamorphic origin, although he gives certain reaeons for supposing them to be of igneous origin.

Jan 1, 1904

By Christoph Pichler

A special desulphurization slag accrues during the processing of iron ore to steel, which is needed to generate high quality steel. Sulphur removing is done by different technologies, but the most common one is the generation of a high sulphur containing slag by sulphur affine elements. Currently, this desulphurization slag is partly recycled, however, huge amounts are still dumped. To utilize this desulphurization slag for future purposes, a recycling process must be established. Therefore, first characterization of this material started some years ago at the Chair of Nonferrous Metallurgy, Montanuniversität Leoben. Subsequent trials in lab scale size were performed, also some investigations for different treatment steps were evaluated, starting with a parameter study in a hot stage microscope at various gas-atmospheres. Finally, the developed recycling process concept was verified in pilot scale trials to confirm the new recycling technology. Due to the successful treatment process, also a patent was applied.

By Rakam Lama Tamang, Michael J. Byle, Stephen Ernst

"For various reasons, dredging may become necessary in front of existing bulkhead walls, either for channel deepening or for environmental remediation of contaminated sediments. The removal of sediments at the base of bulkhead walls removes support for the toe of the wall that must be assessed. Evaluation of this impact can be problematic for aging bulkheads for which no design or construction records exist. This paper will address the steps that should be taken in investigation and analysis to assure proper assessment and means to address uncertainties and gaps in information. The steps include pre-investigation data review, field inspection, geotechnical and geophysical investigation tools, parametric analysis and design tools. Examples from several bulkhead assessment projects will be provided that include a variety of conditions and tools for application. The focus of the paper will be on the integration of technologies to assess bulkhead geometry, geotechnical properties and stability, structural safety and constructability issues with removal of support, and means of temporary and permanent stabilization for environmental applications.IntroductionBulkheads and quays have existed as long as there have been waterfront activities. Some of the earliest date back to 1200 B.C.E.(Raban, 1987), however in the United States few predate the eighteenth century. Most extant bulkhead structures, and all steel sheet pile bulkhead walls date from the early 20th century or later. These structures function to protect the shore from erosion, support landside activities, and serve as place to moor and offload vessels. Regardless of the age or usage of existing bulkheads, it is essential to assess and protect them if needed where removal of soils on the water side of the bulkheads is planned to dredging.Waterfront BulkheadsExisting bulkhead structures can be classified into two types: Cantilevered, and anchored. Cantilevered walls are completely supported by the soil on the water side, while anchored bulkheads are supported both by the soil on the water side and anchorage on the land side (Figure 1). Walls may be constructed of timber, steel, or concrete. Timber walls may be lagging with soldier piles, cribbing with soldier piles, or timber sheeted such as Wakefield walls (Figure 2). Steel bulkheads are most commonly constructed using sheet piling comprised of interlocking A or Z shapes, though some historic walls were constructed with flat sheets. Precast concrete sheet piling has also been used in construction of bulkhead walls. Anchorage may be provided by steel bars or tendons attached to deadmen, sheet piling, driven piles, or earth anchors."

Jan 1, 2017

By José Flávio Viana

A redução do custo de fabricação do aço tem como ponto importante o refino secundário, seja com a utilização do Forno Panela, aquecimento químico ou borbulhamento de argônio. A qualidade e tempo de formação da escória sintética tem relação direta com o custo do tratamento. As escórias sintéticas sinterizadas produzidas pela Tecnosulfur contribuem significativamente para a redução do custo total de tratamento do aço nesta etapa.

Aug 17, 2017

By Mariana Peixoto

Muitos componentes de ferro fundido ficam expostos a altas temperaturas quando em serviço, podendo ocorrer a decomposição da perlita através da difusão do carbono da cementita para as lamelas de grafita, resultando em alteração microestrutural e degradação das propriedades mecânicas. A influência que a temperatura e o tempo de exposição têm sobre a microestrutura de um ferro fundido cinzento foi avaliado em amostras de quatro ferros fundidos de mesma base, com diferentes percentuais de cromo e molibdênio. Ensaios de banho de sal a uma temperatura de 500ºC foram realizados em corpos de prova com diâmetro de 10 mm. Os ensaios foram realizados com tempos de exposição a esta temperatura, após homogeneização térmica do material, de 0, 1, 2 e 4 horas. As análises metalográficas evidenciam a ocorrência da decomposição da perlita. Adicionalmente foram realizados ensaios de microdureza, a qual se mostrou sensível às alterações microestruturais geradas pela temperatura elevada. O ferro fundido com maior percentual de cromo e molibdênio apresentou melhor estabilidade da microestrutura para as condições ensaiadas.

Aug 17, 2017

By Kássio Nogueira Cançado

A perda de temperatura das barras de aço no intervalo entre a saída do forno e a entrada do laminador é fator determinante no processo de laminação e na qualidade do tubo produzido. O estudo feito tem como objetivo modelar matematicamente o resfriamento destas barras durante o transporte entre o forno e o laminador, permitindo avaliar a temperatura mínima necessária para desenfornamento e também o máximo tempo de transporte sem comprometer o processo de laminação, possibilitando um melhor setup dos equipamentos reduzindo os custos de produção. Os resultados obtidos com o modelo matemático de resfriamento foram comparados com valores reais de temperatura coletados através de campanhas de medições com termopares instalados em uma barra e com medições de pirômetro. Valores de temperatura foram coletados com termopares em barras de 270, 230 e 180 mm de diâmetro. As medições com pirômetros foram feitas em barras de 180 mm de diâmetro. O modelo de resfriamento apresentou para todos os casos erro relativo às medições inferiores a 3%.

Aug 17, 2017

Flotation testing has been done at laboratory scale on hematite mineral and ore samples using stage additions of various hydroxamates. Chemisorption of hydroxamate species onto the hematite surface was inferred from the results, possibly involving both the undissociated hydroxamic acid and hydroxamate ion as maximum recovery occurred close to the pKa of the hydroxamic acid. Flotation testing on a specular hematite ore containing 40 per cent Fe and 42.5 per cent silica gave highest iron grades in concentrate at pH 6, in contrast to published data which suggested pH 9 as the optimum value for ore processing. Using octyl hydroxamate, a rougher concentrate assaying 67 per cent Fe at 51 per cent recovery was obtained using four stage additions of 50 g/t at pH 6. For lower grade concentrates still meeting the chemical analysis for pigment grade micaceous hematite (minimum Fe assay 60 per cent) iron recoveries of 80 per cent were possible for stage additions of 50 g/t octyl hydroxamate in the pH range 6-8.

Jan 1, 1999

By Dario Libano, Luis Carlos Tenuta, Juliano Penteado

"Subway Line Number 4 is one of the newest additions to the Rio de Janeiro subway network. Built for the 2016 Olympic Games, the 16 km (10 mi) subway line connects the south of the city, with the famous beaches Copacabana and Ipanema, to Barra da Tijuca, west of the city, where the Olympic Village and Park are located. This new line, which is estimated to cost USD 2.2 billion, is composed of six new stations: Jardim Oceanico, São Conrado, Gavea, Antero de Quintal, Jardim de Alah (JA) and Nossa Senhora da Paz Station.Brasfond participated in the construction of foundations and retaining structures for all the stations, and each presented unique challenges. This is not surprising considering the difficulties present in a highly-dense urban environment including utilities, nearby buildings, traffic limitations and noise.Of all the stations, JA Station was the most challenging to construct. It was located in the middle of an avenue between residential high rises supported on shallow foundations as well as below sea level in sands with high groundwater. The other five stations were located in small parks and squares, with no buildings in the immediate proximity.The interaction between designer, owner, and the general and foundation contractors during execution was key in safely reducing the construction schedule. This was significant given the unforeseen construction delays the client, Linha 4 Sul JV, faced due to permitting, utility and traffic relocation so that the owner could fulfill their final goal: making the line operational by the Olympic Games. The GeologyGeologically, the state of Rio de Janeiro is formed by Pre- Cambrian crystalline basement rock. Its geological formation is very old and comprises two major orogenic cycles, a Mid-Precambrian formation, called “Transamazonian” (Proterozoic Era), and an Upper-Precambrian to Cambrian called “Brasiliano” (Proterozoic-Paleozoic). The soil structure of the city of Rio de Janeiro is represented by a core of crystalline rocks, usually granite-gneiss, covered with a layer of residual soil and/or partially weathered rock.JA Station is located in a Rio de Janeiro neighborhood called Ipanema, between the Atlantic Ocean and Lagoon Rodrigo de Freitas. Local geology is composed of a superficial soil, consisting of medium to coarse grained sands. Top of rock varied significantly from 20 m (66 ft) deep on one side of the station to 33 m (108 ft) on the other. Water is at a depth of 3 m (10 ft)."

Jan 1, 2016

By Bruno Rodrigues Henriques

O entendimento, controle e otimização do rendimento de aço líquido, em uma aciaria LD, é uma tarefa complexa e desafiadora. Qualquer projeto que se disponha a otimizar o rendimento de aço líquido irá se deparar com enormes dificuldades técnicas e operacionais. A despeito de todas as dificuldades e em função da importância do rendimento de aço líquido, uma vez que o mesmo tem forte impacto no custo de produção, toda aciaria procura manter essa variável de processo sob estrito controle. Esse trabalho se propõe a mostrar todas as etapas da condução de um projeto, desenvolvido e implantado em 2014, que tinha como foco entender, controlar e otimizar o rendimento de aço liquido. Durante o desenvolvimento do projeto, foi encontrado um total de 19 desvios e foram implementadas 23 ações corretivas. O valor do rendimento, que antes do projeto estava em torno de 91,6%, evoluiu para uma média de 93,5% em 2015 e 2016. Esse aumento de 1,9%, em média, no valor do rendimento de aço líquido, proporcionou uma expressiva redução no custo de produção na aciaria.

Aug 17, 2017

By Fernando Dellacqua Cristo

Durante o processo de desfosforação, as principais fases sólidas formadas na escória são o silicato dicálcico (2CaO.SiO2) e tricálcio (3CaO.SiO2), o fosfato tricálcico (3CaO.P2O5), e o 3CaOSiO2.3CaOP2O5 formado pela oxidação do fósforo em solução sólida com o silicato tricálcio. O objetivo deste trabalho é estudar a formação destes compostos e avaliar a influência das fases sólidas e líquidas formadas na eficiência da desfosforação. Foram analisadas diferentes composições de escórias industriais com diferentes teores de CaO e FeO. As fases presentes na escória e a sua viscosidade foram determinadas pela termodinâmica computacional utilizando o software FactSage (usando os bancos de dados GTOXID e FTOXID) e os resultados destas análises foram relacionados com a eficiência de desfosforação. A eficiência da desfosforação também foi relacionada com os diferentes modelos de relação de partição do fósforo (Lp) disponíveis na literatura.

Aug 16, 2017

By Louis A. Panek

Tests of mine-roof models in a centrifuge show that the suspension effect due to bolting a horizontally bedded mine roof with frictionless surfaces of contact between beds depends principally on the number of bolted beds and their relative flexural rigidities, provided that sufficient bolt tension is exerted to prevent strata separations at the bolt locations. Strata separations tend to occur in the unbolted roof mainly because the beds have unequal thicknesses. "Suspension effect" refers to the transfer of part of the weight of weaker or thinner beds to the flexurally more rigid beds by roof bolts or by any other means. The factors investigated were number of beds in the bolted unit, bed thickness, modulus of elasticity of beds, length of bolts, spacing of bolts across and along the opening, bolt load, and intensity of roof load. The general principles of behavior of the bolted roof beds are explained by an approximate theory. Model test data are used to validate the theory and to obtain an expression for the "suspension efficiency". As the suspension effect actually observed in the models is smaller than that predicted by the approximate theory, the suspension efficiency in general is less than unity. Mathematical expressions are obtained for (1) the change in roof bending stress due to the suspension effect, which is needed for design of a roof-bolting system, (2) the change of roof deflection due to the suspension effect, which may be useful for evaluating the effectiveness of a roof-bolting system, and (3) the bolt load or pre-load that is required to achieve the desired reinforcing effect.

Jan 1, 1962

By Samuel Frimpong

Green house gases have become a major concern within the international community over the last two decades due to their potential link to global warming. Carbon dioxide (CO2) is the principal greenhouse gas. In the Kyoto Agreement, Canada has committed to reduce emissions by 6 % below 1990 levels by 2012. This presents a serious economic challenge to Canada and Alberta. Over the next decade, oil sands production expansion, population and industry growth and energy demand will increase CO2 emissions. Current and future CO2 emissions and their economic implications in Alberta will be critical in formulating a comprehensive and balanced policy for dealing with concerns in this area. Disposal of carbon dioxide (CO2) in land aquifers is a potentially viable option for Alberta in dealing with long-term CO2 emissions. Studies have confirmed the existence of appropriate aquifers in the Alberta Basin for CO2 storage over a long geological period. Carbon dioxide is an ideal candidate for aquifer disposal because of its high density and solubility in water at relatively high pressures. In this study, the authors develop a computer simulation model of a scaled aquifer disposal system. The scaled model consists of an injector well, aquifer environment with dominant Ca++ and Mg++ cations. Liquefied CO2 is injected at an appropriate pressure and concentration through an injector well model. The injected CO2 migrates from the point of contact between the injector well and the aquifer domain to the main regime of the latter. The rate of migration is a function of porosity, permeability, cations, aquifer fluid flow regime and CO2 injected pressure. These models are validated using flue gas data from the 546 MW Wabamum Power Plant in Alberta. The total energy requirements for aquifer CO2 disposal system are distributed between a minimum of 105 MW and a maximum of 172 MW, with a mean of 132 MW and a coefficient of variation of 10%. The results show that there is significant variability in all the energy requirements for the CO2 disposal system. The total energy requirements for the disposal system as a fraction of the total power generated by the Wabamum plant of 546 MW could be between 0.19 and 0.32. This is a very significant energy requirement and thorough analysis must be carried out to reduce this variability and energy requirements.

May 1, 2001

By Rick Coleman

PT Freeport Indonesia’s (PTFI) latest expansion has increased total mill throughput to 125kt/d (137,700 stpd). The most recent expansion included the installation of a semiautogenous mill (SAG) designed to treat more ore than any other single SAG mill currently operating in the world. Also included in the expansion were two large ball mills, rougher and cleaner flotation, including conventional and column cells, and a regrind circuit. All equipment is supported by a modern distributed control system. PTFI’s operations are located in the Ertsberg mining district of Irian Jaya’s Jayawijaya Mountains, the eastern-most province of the republic of Indonesia on the Island of New Guinea. PTFI, the operator, is owned by Freeport McMoRan Copper and Gold (81.3%), the government of Indonesia (9.4%) and private Indonesian investors (9.3%).

Jan 1, 1996

By Gennaro Marino

Documented case histories are studied where data were found on the initial collapse of the overburden above the longwall panels. Under this scenario, the most controlled conditions exist for assessing the span capacity of the overburden (i.e., before failure the roof spans to fin coal abutments on two to all four sides). In an attempt to correlate theory to field observations, data are used on the overburden lithology, and the depth, width, and face advance of the panel, as well as, the subsidence conditions noted on the surface. The subsidence measured on the surface is used to determine when complete failure in the over- burden rock has occurred.

Jan 1, 1987

By M. Morin

"This paper examines the design issues associated with the integration of mineral processing within underground mining using a total systems approach. It demonstrates conceptual integrated system design options appropriate to a range of geological scenarios. Particular reference is then given to a case study of stoping in narrow base metal veins.The performance of such integrated systems in terms of productivity, economical and environmental criteria is demonstrated by means of simulation. Particular attention is given to the potential benefits to mine waste management. Processing technologies appear to offer genuine potential benefits, while underground mining methods may need to evolve further to facilitate full integration. This paper is based on industry supported research aimed at developing selective and clean underground mining systems. IntroductionTotal systems thinking is simple in principle but complex to implement. The premise is that to achieve optimum effectiveness and efficiency from a system, the complete system must be considered. Using this approach will avoid the situation where the optimization of a localized component of any system results in a negative impact on the performance of the complete system. Take for example the parts manager who reduces inventory costs without consideration of the consequences to the plant. If the plant goes down and a part is unavailable, it would then cost significantly more than the cost of having it in inventory (Ackoff, 1994).A tool for applying total systems thinking toward understanding and analyzing different mineral extraction options is the structured analysis and design techniques (SADT). Originally developed by Ross (1977), SADT is a formal systems engineering methodology (FIPS PUB, 1993) for process and enterprise modelling (Marca and McGowan, 1993). Figure 1 presents a highlevel structured analysis of the traditional or conventional metal extraction process. There are three sequential processes with several arrows entering or exiting each process. In SADT, inputs always enter from the left-hand side and exit as outputs of the process on the right-hand side. Constraints affecting the transformation of inputs to outputs enter the process from the top while resources or mechanisms enabling the transformation enter from the bottom. SADT is a hierarchical decomposition technique and further analysis is undertaken by expanding downward into each process."

Jan 1, 2003

Coal mining in Indiana is limited to the south-western portion of the state, with coal currently being recovered in 19 counties. The coal-producing area of the state covers approximately 6,500 square miles. Although most of the coal in Indiana is recovered by surface mining methods, a small percentage is recovered through underground mining. To date, 40 percent of the known coal reserves have been removed. Indiana has about 33 billion tons of identified coal reserves, of which approximately 17 billion tons are recoverable using current technology. Of this recoverable coal, about 15 billion tons are recoverable by underground mining and 2 billion tons are recoverable by surface mining methods. The State of Indiana has regulated the environmental impacts of coal mining since 1941. Indiana was the second state in the nation to pass legislation requiring mined land reclamation. Its SMCRA regulatory program was approved July 29,1982, and its Abandoned Mine Land Program was approved July 29, 1982.

Jan 1, 1992

By D. R. Tesarik, M. K. Larson, D. K. Denton, J. B. Seymour, R. L. Rains, T. J. Williams

Because backfill has occasionally collapsed into an active working area, posing a hazard to miners, engineers from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health and Hecla Mining Co. installed instruments in a cemented, backfilled, stope-ramp intersection at Hecla’s Lucky Friday Mine, Mullan, ID. The purpose was to measure stress and strain changes in the backfill and reinforcing members during undercut mining. The instruments were monitored for 6 months while three successive cuts were mined below the intersection. Readings showed induced loads up to 3450 kPa (500 psi) in the backfill as stope walls converged 2.5 to 12 cm (1 to 5 in). The backfill then deformed against the top and bottom plates of the 2-m- (6-ft-) long vertical rock bolts installed as reinforcement, producing loads to 177 kN (40,000 lb)on the rock bolts. We hypothesize that a compressive zone was created in the backfill that allowed the backfill to remain stable as long as the compressive zones from adjacent rock bolts overlapped. This hypothesis is presented in graphical form. Of particular interest was the effect of loading on trusses installed to augment the vertical rock bolts and wire mesh typically installed in backfill. Data from the instruments indicate that wall closure perpendicular to the vein induced loads in truss legs parallel to the vein and in the rock bolt driven through the center of the truss, but, because they are designed to function under tension, truss legs perpendicular to the vein supplied in significant support as a result of compressional forces from wall closure. Based on this study, use of trusses was discontinued, and an alternative support system of wood beams and posts was installed as needed to ensure the safety of miners working beneath the backfill in stope-ramp intersections.

Jan 7, 2001

By Ayumi Yoshioka

Os componentes automotivos em geral devem atender a especificações rigorosas de propriedades mecânicas, requisitos de limpeza inclusionária, entre outros. Enxofre e alumínio são dois elementos adicionados ao banho líquido, que têm papel importante na obtenção destas propriedades, mas que dificultam o processo de produção por lingotamento contínuo por favorecer a formação de partículas sólidas de alto ponto de fusão, que podem prejudicar a limpeza inclusionária e provocar a obstrução das válvulas de lingotamento. O objetivo do presente trabalho é analisar e classificar as inclusões de corridas do aço DIN 38MnSiVS6 em escala industrial e avaliar estes resultados em conjunto com os dados de processo de aciaria e com os resultados de simulação termodinâmica utilizando o software FactSage 6.4. Foi observado que as corridas apresentaram tanto sulfetos de cálcio quanto espinélios, mas as primeiras, associadas a uma fração líquida menor na escória, tiveram uma correlação mais perceptível com a má lingotabilidade.

Aug 17, 2017

By Joaquim Luiz Monteiro Barros

O atendimento as normas ambientais vigentes nos diversos processos das siderúrgicas no Brasil, mais do que uma exigência legal, deve ser um compromisso da empresa com os funcionários, clientes e com a sociedade como um todo. O perfeito dimensionamento do sistema de limpeza de gases e a aplicação de filtros de mangas horizontais é, com certeza, uma alternativa eficiente para solucionar de forma adequada as particularidades e necessidades dos diversos processos siderúrgicos.

Aug 17, 2017

By Alexsandro Marcio da Silva

Com o objetivo de prover informações precisas, coesas e em tempo real aos gestores da Diretoria da Usina Presidente Vargas (UPV) para a tomada de decisões, foi criado o projeto para Gestão de Indicadores de Desempenho em Tempo Real com o foco no processo produtivo e performance das áreas de Laminação (a quente e a frio), Zincagem e Folhas Metálicas. O projeto foi desenvolvido em fases, onde cada fase contemplava um determinado número de equipamentos, áreas e plantas, com visualização em drill down. Utilizando os conceitos de Data Visualization e Operational Intelligence, foi possível integrar e centralizar as informações de diversas fontes de dados, tais como, PIMS, MES, LIMS, ERP, Supervisórios, PROCOM's e entradas manuais. Padronizar as informações de controle do processo produtivo entre os gestores facilita a identificação de problemas e suas causas, e permite analisar simultaneamente várias áreas e plantas. Exibir em tempo real perdas operacionais em decorrência de desvios de processo, torna o processo de tomada de decisão mais rápido e assertivo, contribuindo para a melhoria da performance dos equipamentos, redução de riscos de falhas, e além disso aumenta a vida útil dos equipamentos e otimiza a monitoração dos processos.

Jul 30, 2018