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The use of a time series variogram as an aid in controlling the quality of a product was pioneered by Pierre M. Gy and is described. The ability to analyse and interpret covariance relationships time series data is possible using the variogram. The concept of stream heterogeneity allows sources of variability in process streams to be identified and isolated. Principally this is distributional heterogeneity that is due to a short range effect of segregation in the process stream related to size or composition distribution of the material on a local scale and due to a long-range change in the size and grade of the material stream. The variogram is simply a tool for representing these sources of variability in a way that is explicit, allowing identification of the source and providing important insights to temporal continuity between samples. This paper describes the chronologically related large-scale variability in an iron ore process stream (%Fe), and illustrates the control and mitigation of variability at various stages within the process using a variogram. Three main sources of variability are identified including the random variability V[0], the process variability V[1], and the variability due to cyclical phenomena V[cyclic], arising from human routine or mechanical defects. These sources of variability can be represented on the control chart that provides the plant superintendent with insights as to the sampling capability of the systems in place. Maintaining levels of variability within customer specification limits requires that production systems be controlled without overcorrecting for the trends in changing quality. This can be done only by representing the limits of control relative to the limits of specification on a control chart. Where the specification limits encroach on the control limits, one or the other, or both, may need to be changed; specification limits that constrain the control limits lead to reactive decision making that is expensive and stressful for plant operators.

Jan 1, 2008

By Francisco Coutinho Dornelas

Este artigo pretende contribuir na compreensão da produtividade de mão de obra por meio de análise do setor de produção de aço da América Latina. A discussão teórica fundamenta-se em Tangen (2005), que demonstra como o termo produtividade embora muito utilizado é vagamente definido e mal-entendido e que o conceito mais largamente aceito é a relação entre saída (output) e entrada (input). Nesse contexto, realizou-se um estudo com setor siderúrgico da América Latina com dados do ano de 2015. A pesquisa foi realizada entre Março e Agosto de 2016 com os principais gestores de engenharia industrial e/ou de recursos humanos das empresas, onde se procurou identificar relação entre a produção de aço bruto (saída) e a mão de obra empregada diretamente envolvida no processo de produção, isto é, equipes de operação e manutenção, do quadro próprio e de terceiros, excluindo-se todo o demais efetivo bem como o pessoal afastado por férias e por outros motivos, acrescido de horas extraordinárias trabalhados no período, medido em termos de t/FTE. Os resultados mostraram uma produtividade mediana de 1534 t/FTE, variando dependendo de a empresa ter rota integrada ou semi-integrada e produtora de aços planos ou longos. A contribuição deste estudo reside na proposição de uma metodologia de cálculo de produtividade de mão de obra na produção de aço, possibilitando comparação entre diferentes segmentos desta indústria, outras empresas e regiões do mundo, além de permitir acompanhar sua evolução ao longo do tempo.

Oct 30, 2017

By Jürgen Antrekowitsch, Thomas Griessacher

"Heavy metal containing residues are typically hazardous wastes because on the one hand, a deposition gets more and more complicated and on the other hand, the large amounts of metals like Zn, Cu, Fe and Pb represent a significant value. Thus, a post-treatment of these materials with the recovery/recycling of the metals and stabilization of the waste is not only ecological but often also economical. The therefore typically applied recycling processes utilize pyrometallurgical steps, where carbon or carbon monoxide from fossil coal and coke is used as a reducing agent, which results in large amounts of CO2 emissions. An alternative option is the application of a hydrogen-rich gas emitted in biomass utilization processes as a carbon-neutral reducing agent. Investigations in a retort process which were done at different temperatures and times showed excellent results concerning the achievable reduction rates and final contents of the heavy metals for various residues.IntroductionNowadays heavy metal containing residues like electric arc furnace dust (EAFD), dust from cupola furnaces, waelz slag, etc. are declared as hazardous wastes in a growing number of countries due to the leachability of the heavy metals in these residues. For that reason it is no longer possible to landfill these materials or use them for road construction or disposal works. Some land filling activities, carried out until now, have only been realizable because of some process modifications or cost intensive post-treatment steps of these residues. But the disposal capacities for such materials are decreasing, therefore increasing the prices. The second point for the growing disposal limitations is the stringent environmental legislations and regulations, which restrict the number and amounts of materials which can be dumped [1 – 5].From the other point of view these heavy metal containing residues usually have high contents of zinc, lead, iron, etc., which represent a significant value and therefore a big potential to recover these metals. This is why in recent years the number of recycling processes and the amount of recycled heavy metal containing residues have continuously increased. These recycling processes have the target to recover the valuable metals from the residual materials in the form of a saleable product as well as the stabilization of the slag produced in these processes [5, 6]."

Jan 1, 2011

By Alex Doll, Derek Barratt

"There is a number of comminution tests commonly used in the mining industry. Many of the tests are used for a particular grinding model or mill sizing program and are incompatible with other tests of different models. This paper provides an overview of the commonly used grinding and crushing tests, which models (or practitioners) use a particular combination of tests and draws some relationships between the incompatible tests based on the DJB Consultants Inc. database of projects.Case studies will demonstrate similarities and differences between major mining districts with some comments about homogeneous and heterogeneous behaviour within the grindability results.INTRODUCTIONThere are a number of bench-scale grindability tests in use for sizing and predicting throughput for grinding circuits. Part of the reason for this variety is there are a number of different grinding models in use in the Industry, and those models operate using incompatible test results as input (Doll and Barratt, 2008).By using the database of testwork in the DJB Consultants, Inc. (DJB) Millpower 2000 database (see Table 1), some of the more commonly used tests are compared and relationships will be drawn."

Jan 1, 2011

By Luke Keeney, Stephen Walters

"The start up of a new mining and metallurgical facility is a crucial step in the life of any mining project. The mining industries record is poor when evaluating processing plant operation relative to design capacity predictions made during feasibility studies. Multivariate geometallurgical orebody characterisation, using principle component analysis, is a method developed for improving predictive processing performance models during feasibility stages of mine development. This paper outlines the application of multivariate geometallurgical characterisation to the Cadia East deposit located in New South Wales, Australia. Cadia East is a low grade high tonnage copper-gold porphyry system in advanced stages of feasibility analysis. A dataset of ~32000 measurements and 150 comminution parameters (A*b and BMWI) has been used to develop class-based characterisation and modelling methodologies. The results of this study outline the development of class-based ore characterisation and provide a technique for analysing and interpreting large and complex geometallurgical datasets for prediction and optimisation of processing performance. The results enable sophisticated population modelling to be conducted which displays deposit scale processing variability, aiding circuit design specifications and predictions during feasibility studies.INTRODUCTIONA feasibility study is the major technical report on which the decision to proceed to production and on which financing is based (Shillabeer & Gypton, 2003). The mining industry’s record is not very good when actual construction time, costs, and operating performance are compared to the projections made in feasibility studies (Ballard, 1983; Gypton & Ward, 2000; Gypton 2002). A study by McNulty (1998) found that of 41 mineral processing and chemical plants built between 1965 and 1995, only 56% achieved design capacity within two years of commissioning and three were closed after failing to achieve design capacity within 36 months of start up (Shillabeer & Gypton, 2003). McNulty (1998) related this underachievement and failure of start up performance to the use of innovative process technology without appreciating and managing technical risk. Factors contributing to technical risk include inadequate pilot plant testing, scaled up prototype equipment without backup, design flaws and poorly understood complex process chemistry."

Jan 1, 2009

By Richard C. Moore

The U.S. Bureau of Mines contracted a study to review the air and water monitoring requirements of five Federal environmental acts (the Federal Water Pollution Control Act, the Safe Drinking Water Act, the Clean Air Act, the Surface Mining Control and Reclamation Act, and the Resource Conservation and Recovery Act) and to compile information on the currently available monitoring instruments. A literature review of the acts and their associated regulations was conducted to determine applicability to the mining industry as well as any air and water monitoring requirements. In addition, an industry search and literature review was performed to assess the instrumentation available to comply with the monitoring regulations. Based on this research, the instruments are classified by general applicability to air, surface water, or ground water monitoring, then catalogued by monitoring parameters. A discussion is provided on recommended and innovative monitoring techniques.

Jan 1, 1981

By A. T. Iannacchione

Underground limestone mines typically use the room-and-pillar method of mining in the generally flat-lying limestone formations. In some cases the dip may exceed 5° which can result in unique roof instability problems. Stability may be further exacerbated by the presence of horizontal tectonic stresses. Field studies and numerical model analyses are combined to assess the affect of the dip in various stress conditions. The results showed that where the horizontal tectonic stresses are sufficient to cause intact rock failure, increasing dip results in increased failure potential. The effect of the dip is greater when the maximum horizontal stress is parallel to the dip. Two case studies are presented and evaluated against the findings of stress analysis results. The study showed that the empirical rules of orienting headings parallel to the maximum stress are generally applicable to dipping excavations, except when mining in the up-dip direction. The importance of accurately determining the orientation of the maximum horizontal stress is emphasized because the window of favorable orientations relative to the stress is small.

By Ry Stone

To maintain longwall continuity, NRE Wongawilli Colliery extracted the approximately 20-year-old Thompson Mains and in doing so, 20 roadways were holed into during longwall retreat. The orientation of these roadways with regard to the longwall face varied between (i) a parallel alignment where the entire roadway was simultaneously subjected to a significant increase in vertical stress on holing and (ii) a more favorable high angle of alignment, meaning that only a portion of the roadway was subjected to an increase in vertical stress on holing. In addition, the longwall holed into and was recovered in one of the existing roadways. The geotechnical environment presented several additional challenges during longwall retreat. The orientation of the stress field resulted in a major horizontal stress notch on the maingate and an elevation in the major horizontal stress in front of the longwall face during the retreat up to an adjacent goaf edge. The presence of geological structure zones also resulted in both swings in the major horizontal stress direction and increased levels of roof deformation. The gate road support designs were based on commonly accepted strata management techniques and principles. The support designs in the hole-through roadways were based on empirical design models generated from (i) aconceptual geomechanical model of pre-driven hole-throughand recovery roads and (ii) a worldwide database on pre-driven hole-throughand recovery roads. Imperative to the success of extracting the panel was a sitespecific strata management process. In this regard, consideration was given to the following: roof displacement monitoring in the gate roads (in particular, Longwall (LW) Acceleration Position), roof-to-floor convergence monitoring in the hole-through roadways, the ability of the mine to limit downtime prior to and during holing by utilizing an Authority to Mine (ATM) type process, and the use of Trigger Action Response Plans (TARP).

Jan 1, 2012

By A. Sandberg, M. Nzotta, Du Sichen, N. N. Tripathi, K. Beskow

The present study was carried out to investigate the impact of slag refractory lining reactions on the formation of inclusions during ladle treatment of steel. The experiments were conducted on an industrial scale in the ladle at Uddeholm Tooling AB in Hagfors, Sweden. The inclusion chemistry and population during ladle treatment were studied along with the composition of the ladle glaze, taken from the ladle lining. The inclusions in the steel were classified into four groups according to the Swedish standard SS 111116. SEM/EDS analyses were carried out to identify the phases present in both the inclusions and the ladle glaze. The number of inclusions in the steel before deoxidation was found to increase with the ladle age, i.e. the number of times the ladle had been in use. A similar increase was also found after vacuum degassing and before casting. A great portion of inclusions before casting was found to be supplied by ladle glaze. This observation was further confirmed and explained by thermodynamic analysis. The present results show that ladle glaze is a major source of inclusions in the ladle at Uddeholm Tooling. Keywords: Slag/ refractory/ lining?reactions, ladle glaze, inclusions, inclusion chemistry, ladle treatment

Jan 1, 2004

By G. E. McElroy, A. S. Richardson

"Experiments in the determination of friction factors for fan-pipe installations were carried on in a Butte mine during the fall and winter of 1922-23, under a cooperative agreement between the Bureau of Mines and the Anaconda Ccpper Mining Co. The results have been summarized in a separate paper,*** and this report, which is one of several giving more detailed data, discusses the methods used and the application of the results to fan-pipe practice.The use of canvas and galvanized-iron pipe, 8 to 20 inches in diameter, with small fans, usually electrically driven blowers, is an important factor in the ventilation of metal mines and is increasing in coal mines and long tunnels. In the Matte district the standard installation is an electrically driven small blower fan and 8 to 16 inch canvas pipe.The application of available data on friction losses in sheet-metal pipe to mine installations was doubtful, and very little has been published on canvas pipe, except general statements that the friction looses are greater than in galvanized-iron pipe. Experiments by Weeks and others,**** who determined friction losses under laboratory conditions for a few typical materials used in mine equipment, supported the statements.In 1918, one of the authors (Richardson) conducted tests for the Anaconda Copper Mining Cc. on the friction losses in canvas-pipe systems and the beet type of centrifugal blower for use with such pipe lines. He obtained the average total resistance per unit of length in use, without reference to the variable conditions of the lines. The results were of great value in developing more efficient equipment for average service conditions, and indicated that average friction losses for the commercial canvas tubing then used by the company were equal to or lees than these given for galvanized-iron pipe. Later on, the particular canvas tested was discarded for a heavier and more service-material."

Oct 1, 1923

By J. A. Cruise

With the end of the official apartheid legislation in the early 1990s, South Africa was heralded as a non-racial country. However, racial awareness has been reintroduced into the country with the Affirmative Action and Black Economic Empowerment legislation. Gender and racial transformation are the current order of the day. All organizations are required to reflect in their make-up the demographics of the population as soon as possible. Scorecard shave been drawn up to measure the rate of transformation for gender and race in organizations. The mining industry in South Africa has been in the forefront of this transformation legislation and scorecards. This paper seeks to show the effect of gender and racial transformation on mining engineering education and professionalism by analysing the changing demographics of graduating mining students at both the South African universities offering a degree in mining engineering, the professional registration of mining engineers with the Engineering Council of South Africa (ECSA), and the membership of the Southern African Institute of Mining and Metallurgy (SAIMM), the vocational institute for mining engineers. It also demonstrates the absurdity of gender and racial quotas based solely on the demographics of the current population of the country. This paper shows the degree to which mining engineering has transformed in both gender and race.

Jan 1, 2011

By D Wiseman, D Weedon, T Akroyd

Models of the size specific processes of particle collision, attachment and detachment have been combined in a form suitable for analysis of a full-scale flotation plant. The model is based on a first principal approach to particle collection by bubbles. Parameters considered include particle size, bubble size, particle contact angle, energy dissipation, entrainment and froth recovery. Using data structures configured within an Excel spreadsheet using æLimn: The Flowsheet ProcessorÆ, the model has been incorporated into a description of the individual cells within a simple roughing and cleaning flotation circuit. Simulated feeds of varying particle size distribution, feed tonnage and varying mineral hydrophobicity representing different mineral phases are presented to the model to produce predicted final concentrate grades and recoveries. Practical techniques for measuring many of the parameters included in the model are now becoming readily available. However, relating the terms included for contact angle, energy dissipation, entrainment (ie water recovery) and froth recovery to measurable parameters in operating plants remain as continuing challenges for research.

Jan 1, 2004

By Tiago Ribeiro Costa

A otimização da matriz energética na produção de metais tem sido um dos tópicos predominantes mundialmente. Um dos principais consumidores ineficientes de energia, em alguns casos impactando inclusive no consumo de fornos elétricos são os sistemas de aquecimento de panelas. Buscando novas alternativas de redução de custos de energia, e redução de emissões, a White Martins encontrou uma alternativa técnica aos convencionais Pré-Aquecedores de panelas ar-gás. É o Sistema de Aquecimento de Panelas Oxicombustão com queimador Optifire, que utiliza oxigênio puro como comburente ou ar enriquecido. Comparado ao sistema ar-gás convencional, é possível promover uma economia de combustível de até 50% e redução de emissões de carbono e NOx. A tecnologia do equipamento consiste em realizar a queima estequiométrica balanceada, através da medição precisa dos gases, utilizando queimadores avançados com maior eficiência e melhorando a distribuição de calor, de forma a não gerar diferenças de temperatura entre seções. Com a tecnologia Optifire é possível inclusive o remanejamento de combustível mais nobre, como gás de coqueria em processos como aquecimento de regeneradores de altos-fornos. Este trabalho descreverá o estudo da oportunidade e dimensionamento para aquecedores de panela.

Oct 30, 2017

By Ricardo Rodrigues Grizotti, Laudelino Cota Fonseca Junior, Marcio Basilio Xaviere

O projeto tem por objetivo desenvolver a padronização e implantação de um Modelo de Governança de Planejamento e Gestão de Estoques de MRO (Manutenção, Reparo e Operação) bem como um Modelo de Reposição baseado em políticas e modelos quantitativos, estatístico suportado de ferramental sistêmico desenvolvido no ERP SAP da companhia que incorpora Práticas de Planejamento e Gerenciamento, para melhor determinação dos Estoques e Nível de Serviços dos Materiais de Natureza MRO visando a otimização e balanceamento dos níveis de estoque com aumento do nível de serviço; redução do stockout; oportunizar a otimização dos tamanho dos lotes de compras para cada SKU; otimização das políticas de reabastecimento para cada classe de SKU e desenvolver indicadores e desempenho para monitoramento e controle do processo de planejamento e gestão dos estoques de MRO. O desenvolvimento, construção e implantação do projeto foi pautado e realizado através do uso da Metodologia Lean Six Sigma e suas ferramentas advindas do DMAIC - (“Define”, “Measure”, “Analyse”, “Improve” e “Control”), como uma estratégia gerencial planejada, com foco nos resultados de qualidade e financeiros, com o objetivo de promover mudanças significativas na empresa, buscando sempre melhorias nos processos, produtos e serviços oferecidos aos clientes.

Oct 1, 2019

By Catia Casagrande

O processo de pelotização foi desenvolvido com a finalidade de aproveitar as partículas finas e ultrafinas geradas nas operações de exploração e beneficiamento do minério de ferro. Entretanto para atender as usinas de pelotização, faz-se necessário utilizar a moagem para adequar as características de granulometria e superfície específica das misturas de minérios de ferro às especificações da produção de pelotas. Porém os moinhos possuem alto consumo de energia elétrica, elevando o custo operacional do processo de pelotização. Frente ao cenário atual, foi realizado o trabalho para estudar a substituição à moagem (área úmida) por processo de multi prensagens. Além disso, foram misturados os minérios de ferro com carvão, a fim de reduzir também o custo da moagem deste insumo. O objetivo principal foi quebrar as partículas de mistura de minérios de ferro e carvão, e avaliar os resultados de superfície específica e granulometria deste produto comparando com o processo padrão (moagem e prensagem). A prensa de rolos de bancada e as análises físicas e químicas foram realizadas para o desenvolvimento do trabalho. Foi concluída a possibilidade de atingir granulometria e superfície específica através de multi prensagens, atendendo o processo de pelotamento.

Aug 16, 2017

By Valentín Pamo

El presente trabajo describe los procesos y equipos que permiten la extracción de metales preciosos de la refinería de Ilo en condiciones agresivas, obligando a investigar materiales resistentes a la corrosión. Asimismo, se presentan alternativas que aseguren la continuidad de las operaciones en el proceso productivo de dicha refinería.

Sep 9, 2007

Development of a Froth Dropback Measurement Device

Sep 13, 2010

By Syd S. Peng

Coal mine ground control is the science of the application of rock mechanics principles to coal mining operations. More acceptance of ground control techniques by the US coal mining industry has been seen in the 1980s. It has been demonstrated many times that a proper ground control design is key to a successful coal mining operation. However, numerous in-mine applications of various ground control techniques by the author indicate that cur¬rent techniques need improvement. The biggest problem in coal mine ground control is that miners are dealing with materials of rapidly varying properties and occurrence. And only the exposed surface can be identified positively. Thus, in attempting to solve the ground control problems, many unknown factors are assumed. Some of these problems deriving from such assumptions are discussed here. Coal pillars There are two types of coal pillars - barrier and chain pillars - depending on the purpose. Barrier pillars are those located between panels or sections or mines. Their objective is to isolate the mined-out effects of one from the other. Chain pillars are characteristic of room-and-pillar mining. They are designed to support the overburden load and protect the surrounding entries and crosscuts. Pillar design is the most popular and, frequently, the only ground control technique employed by coal operators for mine design. There are many pillar design formulae available (Bieniawski, 1983; Peng, 1986). Nearly all consider both size and width/height effects. Specifically, pillar strength decreases with increases in pillar size and increases with increase in the ratio of width to height. However, the manner of those changes varies with investigators. Consequently, the pillar size determined varies considerably from investigator to investigator. And the variation grows much more pronounced as the seam depth increases (Fig. 1). The question, then, is which one should be used? One may say each formula is developed for a particular coalfield. A particular formula may have been used to design a pillar, which has not failed. Does that mean it was over designed? Not necessarily, because no one can confirm its stated "safety factor." Recent case studies (Peng, 1986; Tang and Peng, 1988) show that all pillar formulae are too conservative for chain pillar design in room-and-pillar mines due to the following two problems: • Uncertainty about in situ pillar strength. All formulae employ uniaxial compressive strength of selected samples tested in the laboratory and scaled to that for underground pillars. The scaling factors are not well proven. In situ testings by Bieniawski (1969) suggested that 1.5 m (5 ft) pillars are representative of in situ pillars that, after being tested in various US coal mines, are not universally applicable. • Uncertainty about the actual loading on the pillar. The most frequently used tributary loading theory defines the loading as total overburden weight tributary to each pillar (from roofline to surface). This is too conservative when it applies to coal measure rocks. The overburden consists of layered strata of different stiffness. Many stiffer strata will self-support over small roof spans. Depending on the location of these strata above the coal seam, it will reduce pillar loading in various proportions. It follows that total structural analysis using, for instance, finite element method is more appropriate. It can take into account the interaction of roof and floor strata with coal. This has been demonstrated by Peng et al. (1986,1988) on several case studies. However, the validity of the finite element structural analysis depends on the accuracy of in

Jan 1, 1989

By C. B. Manula

This report is volume 5 of an eleven-volume final report for a Grant completed by The Pennsylvania State University for the Bureau of Mines to develop a dynamic general purpose computer simulation model for underground coal mining. The simulator developed under the Grant has a wide range of possible applications in the design and evaluation of underground coal mining systems from the standpoints of health and safety, productivity, and mine environment. The Master Design Simulator consists of nine free-standing function-oriented subsystem models linked together into an integrated, comprehensive model of an entire mining system. The subsystems comprising the Master Design Simulator include geology and reserves, methane generation, roof support, subsidence, production, rail haulage, cost, water generation, and ventilation. This volume of the final report describes the Subsidence subsystem of the Master Design Simulator. This subsystem uses the finite element method to simulate ground movement caused by an advancing mining face in an underground coal mine. The model is structured around the concept that the ground mass is a layered media of different thicknesses and material properties. Gob areas are considered to be unfilled with broken rock at the beginning of mining. After mining starts, the gob areas are filled with broken material which provides resistance to the lowering of the overlying strata. The model is tied to the Geology and Reserves subsystem, but it can also operate as a free standing routine. A case study is presented illustrating the application of the model. A detailed user's manual, including a program listing, is included in the appendices.

Jan 1, 1974

By Leon Maday, Dan L. Pecha, Jeremy Johnson, Daniel N. Adams

The Brightwater conveyance system includes 26 km of tunnels, a 130 mgd pump station, 2 km of micro tunnels, and a 2.4 km outfall. The tunnels extend from Woodinville to Puget Sound through varying soils in 1 to 7 bars of hydrostatic pressure and depths to 185 m. The tunnel diameters range from 4 to 6 m and include numerous lining systems. This paper highlights major shaft and tunnel design, including dual cellshafts, multiple pipe configuration tunnels, polymer concrete segments, and the use of a one pass lining designed to convey high pressure effluent.

Jan 1, 2005