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By Larissa Mitie Ihara

Foram encontrados vários casos de falha de engrenagens de redutores de grande porte, aplicados em turbogeradores em usinas de cogeração. Este trabalho tem como objetivo a análise de falha dessas engrenagens bihelicoidais. Engrenagens operam sob condição de carregamento cíclico variável, logo seus principais modos de falha são fadiga de contato e por flexão de dentes. A engrenagem estudada, fabricada em aço 18CrNiMo7-6, foi utlizada em campo e apresentou fratura em dois dentes. Realizou-se uma análise de espectrofotometria para confirmação da composição química do material base. Uma análise microestrutural foi realizada utilizando microscopia óptica, revelando que a microestrutura corresponde a martensita com austenita retida. Foi feito um perfil de microdureza no plano transversal do dente, que indicou uma camada cementada efetiva de 2.150 µm e dureza de 715 HV0.1 na superficie. Foi feita uma fractografia macroscópica para determinação das caracteristicas da fratura, o que permitiu identificar marcas de praia e deltas de rio. Aliado a isso, foram feitas imagens por microscopia eletrônica de varredura, determinando o local do início da trinca. A partir dessas evidências, pôde-se concluir que o mecanismo de falha predominante foi fadiga por flexão de dente.

Aug 17, 2017

By Robert F. Calman

OUTLINE FIVE EXAMPLES OF GOLD-LINKED FINANCINGS 1. Financing the Lupin Mine • Sale of Cdn $40.0 million of 12% preferred shares and Cdn $40.0 million of Gold Purchase Warrants @ $595 per ounce. 2. Financing the Copper Range acquisition • Borrowing 100,000 ounces from a Canadian chartered bank @ US$307 for five years. 3. Financing the Round Mountain expansion • Borrowing up to US $80.0 million in dollars, convertible into gold, repayable over five years from a group of North American banks. 4. Financing the Tenneco Precious Metals Division acquisition •Sale of SFr 110.0 million of ten year 3-718% bonds with warrants to buy 132,000 ounces of gold at US $560. 5. On Forward Sales, Puts and Calls • Gold, Silver, Canadian Dollars, Swiss Francs THE FINANCIAL RULES AT ECHO BAY 1. Never bet the company 2. Equity is the primary form of capital for a gold mining company 3. On debt 4. The Yardsticks for Corporate Decisions 5. Financial Community Relationships 6. Dividend Policy No Text Available Tables Follow

Jan 1, 1990

By V. F. Hollister

Four conditions are commonly accepted as being needed for the development of native sulphur deposits in sedimentary rocks : (1) ample sulphate-bearing evaporite, normally anhydritic; (2) proximity to petroleum deposits; (3) a hydrodynamic system of communication between these two; (4) a stratigraphic or structural trap to prevent escape of the sulphur and sulphur -bearing reaction products. When any of these requisites are absent, apparently no significant residual bio-epigenetic sulphur deposit will form. These requirements are, however, satisfied in some areas, which include both the Triassic and Devonian evaporites of northeastern British Columbia.

Jan 1, 1977

By Enrique Roy Dionisio Calderon

O presente trabalho mostra a concepção de um modelo que permite gerar uma superfície de mínimo consumo de redutor (carbono) em Altos-Fornos. No seu desenvolvimento foram consideradas as condições de equilíbrio das reações de redução, os balanços de massa e de energia e parâmetros operacionais. Sua aplicação à redução em Altos Fornos é exemplificada para situações reais, baseada em banco de dados operacionais de uma usina siderúrgica. Foi possível, a partir de planos de corte nestas superfícies, gerar diagramas binários do tipo CR-RD (Consumo de Redutor-Fração de Redução Direta), com possibilidade de serem gerados “on-line” no processo. Dentre os resultados obtidos, destaca-se a identificação de inviabilidades termodinâmicas importantes do forno. Dentre elas o modelo permitiu, através de seus “outputs” gráficos, prever e acompanhar o fenômeno de “gelada de forno”, conferindo desta forma maior segurança operacional ao processo.

Aug 17, 2017

By Henrique Dias Gatti Turrer

O projeto Minas-Rio da Anglo American iniciou suas operações em agosto de 2014 e tem capacidade para produção de 26,5 milhões de toneladas naturais por ano de pellet feed. O sistema contempla a exploração e concentração da jazida localizada no município de Conceição do Mato Dentro (MG), bombeamento do concentrado por 529 km até o município de São João da Barra (RJ), onde ocorrem a filtragem, estocagem e embarque do produto final através de navios. Desde a concepção do projeto até os dias de hoje, diversos estudos foram realizados objetivando-se entender o comportamento das diferentes litologias de minérios nas etapas de processamento mineral. Desses, os mais relevantes focaram nas duas principais litologias do depósito: o itabirito resultante da intemperização da matriz (IF) e o próprio saprólito (IT). Os principais pontos de investigação foram o comportamento dos mesmos perante as etapas de cominuição e concentração. O objetivo desse trabalho é apresentar uma revisão bibliográfica das diversas comparações de desempenho perante a cominuição dessas duas litologias. Além disso, são apresentados e discutidos resultados inéditos do desempenho na flotação quando concentrado separadamente ou como uma mistura. Os resultados disponíveis na literatura mostram que, ao contrário do que se imagina, o itabirito natural não apresenta consumo energético significativamente maior nas etapas de cominuição. Os testes de flotação, por sua vez, mostraram que o desempenho é diferenciado, em função do grau de liberação dos mesmos.

Aug 16, 2017

By G. Rajesh

Mathematical modeling of bioremediation has gained importance as it is used as an optimization tool for the remediation process involved in contaminated sites. The bioremediation of Cr(VI) has been studied taking into consideration the initial Cr(VI) concentration Cr(VI)ini, bacterial growth substrate concentration (S), maximum growth rate (µmax), yield coefficient (Y), half saturation constant (Ks), and inhibition constant (KI). As the enzymatic reaction is also affected by initial substrate concentration (Sini) and Ks, different ratios of (Ks/Sini) are analyzed. As the inhibition constant (KI) is not constant for all the enzyme reactions and it varies with Cr(VI)ini, the correlation between (KI) and Cr(VI)ini is developed. A set of differential equations pertaining to bioremediation of Cr(VI) has been solved using FORTRAN 90 program adopting the model developed. The results are verified with the experimental data from the literature and a good correlation has been obtained between the experimental data and the model predictions. Keywords: bioremediation, hexavalent chromium, mathematical model, inhibition kinetics

Sep 1, 2012

By L. Yuan, J. H. Rowland, R. A. Thomas, D. Bahrami

Blasting is the main method of production in many non-coal underground mining operations and produces multiple toxic gases as a result. The Mine Safety and Health Administration (MSHA) requires mine operators to measure the level of toxic gases in mines as frequently as necessary to ensure they are below regulatory safety limits. The current practice uses portable gas monitors to check the concentrations of toxic gases after a fixed post-blast time. This paper studies the application of a gas monitoring system in the return entry of a limestone mine to determine a safe re-entry time. The National Institute for Occupational Safety and Health (NIOSH) conducted such a monitoring program in a limestone mine from September 2016 through May 2018. NIOSH/PMRD (Pittsburgh Mining Research Division) is endeavoring to develop workplace solutions to improve detection of and reduce the risk of hazardous conditions. This study showed that the use of gas monitoring in the return air can be a useful tool at the mine operator’s disposal to detect and reduce the risk of hazardous conditions and also to reliably estimate the re-entry time. INTRODUCTION Underground miners are at risk of overexposure to toxic gases from various sources. Production blasting operations using explosives in underground mines are a source of multiple toxic gases that could be harmful and even fatal to humans if prolonged exposure occurs beyond the safe limits. According to Code of Federal Regulations, Title 30, Part 57.5002 [1], metal and nonmetal mine operators must conduct gas, mist, and fume measurements as frequently as necessary to determine the adequacy of control measures to protect miners from overexposure to harmful gases. MSHA will inspect mine operators’ activities to verify the evidence of such measurements [2,3]. Continuous gas monitoring in the return air is an effective way to make sure that toxic gas concentrations at the working areas are kept below the regulatory limits before the return of miners. Toxic gases can enter the mine atmosphere from different operations, such as welding, combustion, and blasting. The main gases produced from blasting are carbon monoxide (CO), carbon dioxide (CO2), nitric oxide (NO), and nitrogen dioxide (NO2). Other gases are produced in small amounts and, therefore, were not considered for this study. Related regulatory and recommended exposure limits of CO, NO, and NO2 gases are summarized in Table 1 [4].

Jan 1, 2019

By W. Kobal

The extraction of nickel (Ni) and cobalt (Co) from the laterite deposit of Ramu nickel-cobalt Project in Papua New Guinea was performed in this study. Chemical analysis by Inductively Coupled Plasma (ICP-AES) atomic emission spectrometer, SPS-3000 (Seiko Instruments (Inc.), shows the ore contains 48% Fe, 1% Ni, 0.1% Co, 1.8% Al, 0.14% Mg, and 0.8% Mn. Characterization by X-ray diffraction (XRD) analysis of the laterite ore obtained from the mine site shows the ore contains 70 to 80% goethite (FeOOH), assuming Fe content of 48% is mainly from geothite. The main leaching parameters investigated include; slurry temperature, leaching time and sulphuric acid (H2SO4) concentration to evaluate nickel and cobalt extraction. For all experiments, 10g batch samples are put into 300 ml beaker containing 100 ml of sulphuric acid of varying concentrations (1M, 2M, 4M). During the leaching period, 5 ml slurry samples are withdrawn at different times and filtered to obtain filtrate for ICP analysis to monitor nickel and cobalt extraction. Solid samples at the end of all tests are also obtained by filtration and after drying, XRD and ICP tests are performed to monitor nickel and cobalt contents. According to the test results performed at normal atmospheric pressure, over 99% of nickel and over 50% cobalt were extracted into solution within 120 min at 95ºC in 2M H2SO4 solution. Similar results were obtained when only temperature was reduced to 90ºC, but cobalt extraction increased to over 70% when leaching time was increased to 240 min. Further reduction in temperature to 80 and 60ºC resulted in reduction of nickel and cobalt extraction. At the end of each leaching test, magnetite was seen to attach to magnetic stirrer. The study showed nickel can be completely leached into solution but cobalt only up to 70%. Keywords: atmospheric pressure, sulphuric acid leaching, nickel laterite

Sep 1, 2012

By D Pateman, F de Fredrick

The Bentley underground mine, which is located 60km north of Leonora, Western Australia, is owned and operated by Round Oak Minerals Pty Limited. A high-grade Zn-Cu Volcanogenic Massive Sulphide (VMS) orebody, Bentley was discovered in 2008 with production commencing in 2012. Long-hole open stoping is employed to mine the steeply dipping ore body, and in recent years the Avoca method has been adopted. This requires all development in a particular area of the mine to be completed prior to stoping commencing in a bottom up sequence. Voids are commonly backfilled with loose Run-of-Mine (ROM) waste loose rockfill (LRF); or alternatively cemented rockfill (CRF) can be used. Stopes in the 3860 AOS and 3900 AOS panels were located below previously extracted Avoca zones, with LRF situated immediately above them. These high-grade stopes were originally designed with rib and sill pillars to maintain control of the existing backfill during extraction. Due to changing factors over time, including mining economics, alternative options to achieve full extraction of the stopes were reviewed, including: • Mining small successive full height stopes which would involve drawing a blanket of LRF down with the extracted ore (stoping under waste); • Stabilisation of the existing LRF above the stopes and implementing a primary/secondary stoping sequence, with the primary stopes backfilled using a cement fill. An assessment of these options was undertaken which determined that the second full extraction method was the most beneficial to the operation, and could be achieved using a cement grout (Minova’s FB200 grout) to stabilise the LRF in conjunction with implementing a sequence where the primary stopes would be backfilled with cemented aggregate fill (CAF). Footwall drives were developed adjacent to the rockfilled stopes, allowing for the installation of horizontal grouting conduits, as well as providing access to the top of the planned 3860 and 3900 level stopes for the placement of CAF. An interval at the base of the previously rockfilled stopes was grouted at multiple horizons to achieve the required thickness, with a comprehensive quality assurance/quality control (QA/QC) process undertaken. Primary stopes were CAF backfilled via an arrangement of downhole winzes, linking the top of primary stopes to cross-cuts developed off the associated footwall drives. CAF was delivered underground through an open reticulation network that was extended to the specific levels. Overall the successful implementation of the revised mining method effectively increased ore recovery while maintaining control of overbreak and dilution, providing significant financial upside. This was achieved while maintaining effective controls in light of the changes to the risk profile. Stabilisation of the existing rockfill has allowed the extraction of stopes to full height, including the originally designed sill pillars, representing an average 23% increase in ore tonnes on the initial design, with dilution from the stope crowns averaging less than 1%. The use of CAF in association with primary/secondary stoping, eliminating the need for rib pillars, has yielded an average 47% increase in ore tonnes compared to the base case mine design.

Mar 15, 2021

By J Herd, J Rowe, M Cutbush, d F. Aziz

WearApp provides expertise for assessing the degradation of removable screening media panels on vibrating screens right in a user’s pocket. Through the WearApp application, users can simply take a picture of a panel using their mobile, enter some basic information and have the application assess the wear to provide a recommendation for whether the panel needs to be replaced. Where traditional mechanisms for assessing panel wear only measure a few points across the panel face and rely on having personnel with specialised knowledge available to perform the assessment, WearApp uses deep learning models to analyse the entire panel face and support the user to make an informed decision. The application works through analysing a panel image and using a model to automatically detect the corners of the panel. Given the known dimensions of the panel, this enables the application to calibrate the pixel size against a known reference. A second set of models then detect the apertures and measure their dimensions. With the aperture dimensions defined the application assesses the wear of the panel through referencing a stored 3D model of the aperture. Finally, the data from each aperture is collated and the wear of the entire panel face defined. Since WearApp performs measurement of the entire panel face, it also allows the user to perform a more detailed analysis of the panel’s wear profile. Where typically, the panel wear is only measured in a few locations, WearApp’s analysis enables users to visualise the panel wear across the entire panel face, identifying areas of high wear that could be leading to premature panel replacement. Additionally, because the entire panel face is measured the change in screening efficiency can be calculated accurately for the worn panel, even taking into account the impact of aperture pegging by small rocks.

Sep 1, 2024

By J. Armstrong, J. Bourgeois, S. Warren

The application of statistical analysis software programs has proven useful for investigation of rockfall runout distance along a designed slope. Rockfall modeling programs are continually being upgraded with more sophisticated analysis tools, such as the use of the rigid body versus lump mass models. Engineers at mine sites utilizing the software may have varied experience related to these models, their associated input parameters, and how to interpret the generated results. To address this concern, researchers at the Spokane Mining Research Division (SMRD) of the U.S. National Institute for Occupational Safety and Health (NIOSH) investigated the influence of slope height, slope angle, slope material, and rock size for both rigid body and lump mass models in a 2-D statistical analysis program. Based on a literature search and industry input, specific ranges common to that of an open pit mining environment were chosen for each of the input parameters to determine 90% rock runout distance as well as their sensitivity to change. Data collected from this numerical analysis and simulation will be compared to empirical rockfall data gathered through the duration of the Highwall Safety project conducted by NIOSH from 2022–2026.

Mar 2, 2022

By Herman W. Hill

This report summarizes research into the root causes of failures in mine power systems which impact safety and reliability. Abnormally low fault currents, due to arcing faults, self-excited systems, and fallen trolley wires are examined and quantified. The reliability of components which are critical for safety is studied, as well as reliability of components which are crucial to the mining pro cess. Failure rates are found through in-situ tests, accelerated life tests, studies of mine maintenance, and fault-tree analysis. Reliability data is used to predict fatalities and lost-time accidents through computer-aided fault-tree analysis. Analytical support tasks reported include the deriving of trailing-cable ampacities under cyclic loading, and the measurement of connected ground beds.

Jan 1, 1981

By George L. Richert

The Minas de Matahambre is situated on the north coast of Cuba, in the Province of Pinar del Rio, approximately 150 miles west of Havana. This nine is the only producer of copper in Cuba, and has been worked for the past 15 years. In 1921 the property was affiliated with The American Metal Co., Ltd., and has been worked by them since that time under the direction of Mr. D. D. Homer, General Manager. Extracts from P. D. Wilson's ?Preliminary report on the geology at Minas de Matahambre? have been freely used in this report.

Jan 1, 1929

By B E. De Gee, N Viviers, A Naidoo

In 2013 the Mopani Copper Mine Mufulira plant in Zambia embarked on a project that was aimed at improving concentrator recoveries. The project commenced with the automation of the milling and flotation circuits. This involved the installation of new instrumentation, namely measurement devices and actuators, and the connection of these to new programmable logic controllers (PLCs).The infrastructure changes were followed by the implementation of basic proportional-integral-derivative (PID) controllers on the PLCs. Supervisory control and data acquisition (SCADA) interfaces were also implemented to allow for switching between controller modes, inputting of setpoint variables and to provide a visual display for process monitoring. The final phase of the project involved the installation and commissioning of advanced process control (APC) solutions on the milling and flotation circuits. This work was carried out by Mintek over 21 on-site days. The APC solutions included the MillStar and FloatStar suites of advanced controllers.The MillStar control suite focused on stabilising the mill feed and mill discharge on the two primary mills as well as the flotation circuit feed. Mintek’s CyLas instruments, which provide a measurement of the hydrocyclone underflow angle, were also installed. The measurements were incorporated into the discharge stabilisation control on both milling circuits. The FloatStar level stabiliser controller provided flotation cell pulp level control on fourteen cells, including two columns.Performance tests showed that the Mintek APC system stabilised the mill feed and mill discharge while ensuring the process remained within operational constraints. The MillStar control system utilised the CyLas instrument to prevent roping on the hydrocyclone underflow. This was not always achieved under normal operation. Additionally, the flotation section was stabilised as a result of improved level control by the FloatStar control system.Performance comparisons showed that the Mintek control system improved the operation of the milling and flotation circuits resulting in a greater copper recovery.CITATION:Naidoo, A, De Gee, B E and Viviers, N, 2014. Implementation of an advanced milling and flotation control system at Mopani Mufulira copper mine, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 363–368 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By A E. Petts

Record iron ore prices and a renaissance of infrastructure in the Pilbara have Flinders Mines poised to move from explorer/developer to an iron ore producer. The potential of the company’s Pilbara Iron Ore Project was first highlighted by the announcement of Rio Tinto’s Caliwingina North deposit to the north and the Fortescue Metals group’s Serenity deposit in the southeast. The success of Flinders Mines’ exploration has been based on incorporating landscape studies into an existing geological framework, and using this to understand the iron-rich materials that were emplaced during the Tertiary. The development of the Delta and Eagle deposit resource models highlights this process. There are three main mineralisation styles at the project; detrital iron, channel iron and bedded iron deposits. They have textural and mineralogical similarities with comparative deposits in the region. Gaining an insight into the geological processes unique to detrital iron deposits and more distal channel iron deposits has been important to understanding the geometallurgy of the mineralisation. The model sits comfortably with other regional oregenesis models and allows a contextual framework to be developed around the timing of deposition of the Fe-rich detritus and pisolitic nodules that dominate the deposits. The exploration model also allows Flinders to explore more effectively for bedded iron mineralisation developed prior to, and since the development of the Tertiary weathering landscape.

Jul 11, 2011

By A. Warczok, C. M. Diaz, A. Bergman, T. Utigard, M. Barati

The world wide consumption of energy is steadily increasing and by 2030 it is forecasted to grow by another 50%, leading to mounting political and economic pressures. For any pyrometallurgical operation, it is therefore paramount to investigate and implement methods to decrease the use of energy. In the pyrometallurgical processing of steel, copper, nickel and other high temperature metals, a large amount of energy is lost in hot off-gases, molten slags, mattes and molten metals. Most of this energy is generally lost during the cooling and solidification steps with very little focus on energy recovery or reuse. In this paper we will quantify how much energy is contained in the various slag streams, then review previous attempts and methods employed to recover some of this energy, and finally evaluate some novel technologies that could potentially be employed.

Jan 1, 2011

By José Ojeda

El presente texto describe los recursos alternativos para recuperar valores de los minerales oxidados de plata y plomo. Para lo cual se utiliza la floculación-flotación hidrofóbica, donde se espera que la segregación selectiva de partículas finas mejore la constante flotación y la cinética de flotación.

Nov 1, 2014

By Sam Lo Grasso, Carlos Herranz Calvo, Stuart Warren, Ted Giesing, Charles Marchesano

Mott MacDonald and Project Management Advisors are providing Technical and Project Management services for San Diego County for the Courthouse Commons Project. The Courthouse Commons Project involves the redevelopment of three downtown blocks owned by San Diego County and construction of an Inmate Transfer Tunnel between the County Central Jail and the San Diego Central Court. The tunnel will be 327 feet long, crosses the San Diego Fault and is being constructed using the Sequential Excavation Method (SEM). This paper discusses the history and procure‑ ment strategy for the project, the technical aspects of the transfer tunnel and the con‑ struction progress of the tunnel to date.

Jun 13, 2021

By Blênio Márcio Cunha Silva

A indústria siderúrgica global está buscando cada vez mais tecnologias para tornar o seu processo produtivo mais sustentável e competitivo. Uma das grandes oportunidades, já conhecida nesse setor, é a transformação dos seus resíduos em coprodutos para revenda no mercado. Por esse motivo, este trabalho tem como objetivo avaliar as características físicas e químicas de duas escórias de aciaria por meio de uma caracterização tecnológica. Uma das amostras é proveniente do forno elétrico a arco (FEA), e a outra do conversor a oxigênio (Basic Oxygen Furnace - BOF ou Linz Donawitz - LD). Para o desenvolvimento da pesquisa foram utilizadas: uma etapa de cominuição, análises de classificação granulométrica, composição química e microscopia determinativa pelo sistema TIMA-MIRA. Os resultados da caracterização permitiram identificar e quantificar os elementos químicos e fases presentes nas escórias, as quais apresentaram teores de ferro acima de 20%, teores de CaO acima de 25%, ausência de P e Na e predominância das fases CaSi, CaFe e ferrosos.

Aug 17, 2017

By M. B. McClenaghan, O. P. Lavin, Ian Nichol

"Exploration in most areas of Canada has to contend with problems posed by glacial overburden. In many areas exploration for gold has been based on the sampling of tills, frequently by deep overburden drilling, and analyses of heavy mineral concentrates. Notwithstanding the significant role that till geochemistry has played in the discovery of some important gold deposits over the last few years, increased appreciation of the nature of the glacial history and stratigraphy and the character of gold within till has led to the recognition of a number of ways whereby the effectiveness of exploration can be improved upon.In order for till geochemistry to be useful in exploration, a number of conditions must be fulfilled, including:1. mineralization, or alteration halo related to mineralization, subcropping at the bedrock/overburden interface;2. glacial erosion and dispersal of a recognizable signature of mineralization into the glacial sediments;3. preservation of glacial sediments containing this geochemical component (trace metal or mineral) at positions subsequently selected for sampling (normally drill sites);4. correct identification of specific till units and associated ice movement history;5. collection of adequately large and representative samples;6. appropriate sample preparation and processing;7. appropriate geochemical analyses; and8. correct data processing and interpretation.While we have no control over the first two geological conditions, and only limited control over till availability, we can control the quality and thoroughness of sampling, sample identification, sample preparation, analysis and interpretation. In particular attention needs to be focussed on obtaining a large enough sample to be adequately representative, an unbiased sample must be collected, together with appropriate sample processing, analysis, data processing and interpretation. It is considered that by modifying or extending existing approaches to gold exploration the chances of exploration success can be increased. In particular, analyses of both the heavy mineral and minus 63 µ m fractions of till is recommended because gold in till may occur in different size fractions."

Jan 1, 1992