Search Documents

By José Fagundes Junior, Cleudson dos Santos Rego, Bruno Bastos da Silva Murad, Vitor Borlot Borba

Since the startup in 2002, the Hot Strip Mill at ArcelorMittal Tubarão has increased gradually the coil output as the customers demand new and more resistant dimensionally challenging (thinner and/or wider) steel grades. As a critical feature for customer applications, improvements have been carried out aiming a higher thickness performance and reduction of internal losses while still meeting the more restrict tolerances booked by the customers. This paper presents the recent thickness performance evolution since 2017 and the main actions deployed to improve it.

Oct 1, 2019

By Mingming Zhang, Udaya Bhaskar Kodukula, Marcelo Andrade

The physical and chemical properties of sinter feed are important factors that determine the productivity and quality of sinter product. In this study the feasibility of treating sinter feed by high pressure grinding rolls (HPGR) is investigated for selective cracks generation exploiting weak zones along grain boundaries of poor quality iron ores without generating much fines. The pre-treated sinter feed was characterized for size distribution, surface area, contact angle, and SEM analyses. The characterization results indicated that surface area of the pre-treated sinter feed sample increased about 20%. Pot-grate sintering tests results also indicated improvement on cold permeability, sintering yield and productivity, sinter Tumbler index, and low temperature degradation index (LTD) after HPGR pre-treatment.

Mar 1, 2018

By B Shi, Y Li, L Ma, F Zhou

Subsurface fires are a common threat to coal mining, as spontaneous combustion of coal can potentially result in gas combustion and explosion. Fire-proof techniques, such as grouting, foam, or colloid injection, are not in a position to function ideally, due to the limited coverage and stopping the extinguishment substance from reaching the fire location. Liquid nitrogen, as a kind of all-submerged fire prevention or extinguishing method, can rapidly extinguish fires, thus preventing gas explosion and minimising extinguishment time. Injecting liquid nitrogen through boreholes is an important way during the period of mine catastrophe. But liquid nitrogen is not effective enough in infusion; technical issues restrict the development and utilisation of liquid nitrogen fire prevention and extinguishing technology. Immediate infusion of liquid nitrogen is usually associated with ‘air slug’ (the balloons and bubbles in the pipeline which hinder the flow of low-temperature liquid), which blocks pipelines for liquid nitrogen injecting. Another issue is that the pipeline tends to be damaged due to freezing, which undermines the injecting efficiency of liquid nitrogen and its application result. In order to solve the problems of the low efficiency and some other related field issues in liquid nitrogen perfusion, the ground–underground high efficiency liquid nitrogen injection technology were developed. Implementation of liquid nitrogen infusion techniques in Chinese coalmines achieved the goals of fire prevention and air-cooling. The technique presented in this paper is efficient in absorbing heat, and consequently, displacing oxygen and combustible gases. Field tests at Rujigou and Yangchangwan Coalmine justified the efficiency of the technique. By using this technique, there was no waste left behind, which may impede the subsequent production. The presented technique is of great benefit to the social, economic, and environmental aspects of mining operations, and will have broad applications in fire prevention for large-scale coalmines.CITATION:Zhou, F, Shi, B, Li, Y and Ma, L, 2015. Key techniques and engineering applications of stereoscopic liquid nitrogen infusion for coalmine fire prevention, in Proceedings The Australian Mine Ventilation Conference, pp 291–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By J Rock, K Bambrook

"Hanwha Mining Services was approached by Glencore Coal to provide a series of (trial) demonstration blasts at its Clermont coalmine. The intent of the project was to trial a bulk explosive product that would be able to provide sufficient energy for the ground type encountered without production of post-blast fume. Three blasts were loaded using the patented XLOAD bulk explosives with a density of 1.00 g/cc. XLOAD bulk products are water resistant explosives that can be loaded at densities much lower than traditional (generic) water resistant heavy ammonium nitrate – fuel oil (ANFO) or pumped blends with significantly reduced risk of fume. In addition, these products have detonation characteristics that generally deliver a higher heave partition than conventional bulk products and hence improve muck pile looseness and digability.The priority key performance measures included the absence of fume from blasting, being at least cost neutral and providing similar if not improved shovel dig rates. The design for the initial blast took a conservative approach to ensure the key blast outcomes of fume control and fragmentation were achieved.The second blast used the same pattern dimensions as the benchmark bulk product used in this area to provide a cost neutral comparison with the benchmark products that had been used over the prior six months. This resulted in a 20 per cent lower powder factor than would have otherwise been used. To test the suitability of XLOAD, this shot was slept for over two weeks between loading and firing in geology where the sleep time is typically kept to a few days to minimise the fume risk.The third blast utilised a slightly larger drill pattern to push the capabilities of XLOAD and provide a cost neutral comparison between the trial product and the traditional benchmark products. All three blasts were fired with no fume observed, no recordable incidents and good fragmentation. Shovel productivity from all three of the trial blasts was excellent with higher average instantaneous dig rates being recorded (average six per cent improvement against the instantaneous dig rates recorded for the benchmark blasts).Citation:Rock, J and Bambrook, K, 2016. Controlling Blast Related Fumes with Unconventional Explosives, in Proceedings Ninth AusIMM Open Pit Operators' Conference 2016, pp 39–49 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 15, 2016

The Savage River open cut magnetite mine is located in rugged terrain in densely rain forested northwest Tasmania. The mine and concentrating plant are both in the Savage River valley. Pickand Mather Incorporated (PMI) operated Savage River as an open cut magnetite mine between 1966 and 1996. Acid rock drainage (ARD) was first noted in the last ten years of the operation, leading to elevated concentrations of heavy metals downstream of the mine. When operations ceased in 1996, PMI returned the mine to the Tasmanian Government along with a remediation fund of $11.4 million. At that time, the assessed cost of remediation was in excess of $120 million. As a result of the ongoing ARD contamination and to facilitate both a new operation and effective remediation, Goldamere Pty Ltd negotiated an agreement with the Tasmanian Government in 1996, which resulted in the Goldamere Act and the Goldamere Agreement. The agreement has allowed Australian Bulk Minerals (ABM) to remediate the Savage River mine in conjunction with the Tasmanian Government while re-invigorating a previously closed mine by providing ABM with an indemnity against past pollution. ABM can configure its mine and waste planning activities to maximise remediation benefits without fear of future litigation for past mistakes. The effect to date has been the development of a long-term strategy to remediate the Savage River and short-term remediation works such as water management, which provide benefits to the ecosystem. After five years, the Savage River is no longer significantly impacted by ARD for 30 kilometres downstream and trout are now reported within the reaches of the mining lease. The arrangements between ABM and the Tasmanian Government are an example of a genuine WIN WIN situation where co-operative environmental management of the site results in significant improvements and where the æregulatorÆ and the æminerÆ are working together to achieve mutually beneficial goals. The end result is a significant benefit to Tasmania.

Jan 1, 2003

By B. Westin, G. Voicu, C. Daoust

Orogenic gold deposits represent a major class of deposits that are found in various rock types of various ages. Those deposits show a strong structural control that usually complicates their interpretation at the regional and deposit scales. The Rosebel Gold district located in Surinam (South America) is hosted in a Paleoproterozoic greenstone belt of the Guiana Shield, and has been recently classified as one of those orogenic gold deposits. The gold district comprises eight distinct deposits located along three different structural trends and within different rock types. The mineralization is undefonned and shows a strong structural control characteristic of orogenic gold deposits. All the deposits of the Rosebel Gold district have been subject to a detailed structural analysis that has led to the elaboration of a new structural model for the whole gold district, which is now differing considerably from the previous models. This characterization had direct implications at three different scales. 1- While the older models were considering some areas of the property as gold-barren, the new structural model has led to recent exploration campaigns which have revealed positive results. 2- At the deposit scale, the comprehension of the various vein systems and of the folding of the host rocks has helped the establishment of optimized drilling campaigns. 3- At the mining scale, the comprehension of the architecture of the veins helps for the elaboration of optimized mining method. This study thus shows that the structural analysis of orogenic gold deposits is critical, and should be a priority for exploration and production in any mine.

Jan 1, 2011

By Hasini Wijayaratne

Anode cover material, a mixture of crushed electrolyte and alumina, is a crucial part of an aluminium reduction cell because of its important role in maintaining overall heat balance. However, until recently little attention has been given to understanding or controlling its composition and quality. The thermal conductivity of anode cover material determines the extent of the heat loss from the top of the cell. This will change as a function of the granulometry and composition of the applied cover as well as over time as the cover material consolidates on top of the cell. The ability to measure or predict the thermal conductivity of fresh and ageing cover is an important tool for managing cell heat balance. Recent studies have shown that granulometry or more correctly, voidage is likely to be the predominant determinant of thermal conductivity of anode cover materials. We have developed equipment to measure the thermal conductivity of granular cover material and tested the relative importance of composition (ratio of alumina to crushed electrolyte) and granulometry/voidage on cover thermal conductivity. In general, our results confirm that granulometry is the dominating factor. Generally, high voidages contribute to lowering the thermal conductivity especially when particles are mostly fine. However the relationships between granulometry, voidage and thermal conductivity are complex due to the varying nature of heat transfer between particles. Aging of granular cover material occur during cell operation forming a consolidated crust due to exposure to heat and fumes over time. Structure and thermal behaviour of this consolidated crust is also important in understanding the overall properties of cover. This paper presents the outcomes of laboratory studies conducted in order to understand the thermochemical behaviour of anode cover material and in particular, the role of fines in anode covers mixtures.

Jan 1, 2011

By Douglas Martinazzi

O processo de soldagem por fricção com pino consumível (Friction Hydro-Pillar Processing- FHPP) um método de reparo no estado sólido que consiste no processamento termomecânico de um pino metálico em alta rotação e inserido em um orifício criado no material a reparar. O pino é pressionado com uma força axial e o aquecimento resultante do atrito dos materiais é suficiente para garantir a plastificação dos mesmos promovendo o preenchimento do orifício e a união dos componentes. Este trabalho é centrado na análise da distribuição de inclusões não metálicas do tipo Sulfetos de Manganês (MnS) presentes em juntas soldadas produzidas por esta técnica com a aplicação de diferentes forças axiais. Micrografias da zona termomecanicamente afetada (ZTMA) foram realizadas por microscopia ótica em amostras polidas e sem ataque para registrar as inclusões. Essas micrografias foram avaliadas via análise de imagens visando a determinação de quantidade, tamanho e área ocupada pelas inclusões nas juntas em juntas soldadas. O mapeamento identificou a distribuição e o tamanho médio das inclusões em função das forças axiais. Concluiu-se que a região analisada é potencialmente crítica no que diz respeito a tenacidade à fratura, uma vez que foi observada uma quantidade considerável de inclusões fragmentadas de dimensões reduzidas.

Aug 7, 2018

During 2009 the technical services staff at Barrick Gold Corporation's Australian Business Unit conducted a review of their five underground mines that utilise pastefill as the backfill component for these operations. Of the five mines reviewed three use dry tailings and two use wet tailings plants. The primary aim for these reviews was to determine whether pastefill was the right option to be used, and if not, what where the alternatives. The reviews undertaken focus on several areas including, paste plant operation, reticulation and barricade techniques, the geotechnical requirements for pastefill in regards to the current mining methods, the consideration of alternative methods, capital and operating cost histories compared to initial estimates, and a cost benefit analysis of pastefill against other mining methods. The main benefits from the use of pastefill is increasing the extraction of the resource, reducing or eliminating the need to leave pillars. In some mines the use of pastefill is geotechnically driven, to manage high stress environments or mining induced seismicity. A third benefit of using pastefill in some circumstances is that it reduces dilution, however it is considered that this is not a valid argument for most of the mines reviewed. At two mines no alternative to pastefill was determined, whilst differing extraction and filling strategies were potentially identified at the other three mines. The reviews developed cost benefit curves for those sites that had alternative mining methods to assist in determining whether pastefill is the right option to use for any particular stope. At the grades typically mined in each operation, pastefill was the preferred option to use. In all mines, pastefill was determined to be the best option at this time.

Nov 25, 2010

By Jéssica Sobrinho Lopes

No presente artigo objetivou-se, principalmente, promover a síntese e caracterização de biofilmes ecológicos elaborados a partir do amido de batata doce e da crueira de mandioca, utilizando como plastificantes o glicerol e o sorbitol. O amido da batata doce foi obtido através de descascamento, trituração, filtração, decantação e secagem, respectivamente; enquanto a crueira de mandioca foi obtida por doação. Os biofilmes foram confeccionados na proporção de 3 gramas de amido/100 gramas de solução filmogênica, e 30 ou 40 % de plastificante em relação à massa de amido, as soluções foram aquecidas e agitadas à 80ºC, depositadas em placas Petri, e secas em estufa à 50ºC por 24 horas, e à temperatura ambiente. As amostras de biofilmes foram analisadas quanto aos aspectos visuais, solubilidade em água, teor de umidade, resistência química e Espectroscopia de Infravermelho por Transformada de Fourier (FTIR). Obteve-se 18,16% de rendimento na extração do amido; solubilidade em água e teor de umidade variando, respectivamente, entre 0,03-0,12, e 2,79-11,812%; os filmes mostraram-se insolúveis em clorofórmio, acetona e álcool; e as reações foram confirmadas através de Espectroscopia de Infravermelho por Transformada de Fourier.

Oct 30, 2017

By J N. Farrell

Metallurgists frequently use a small number of large samples to characterise expected mill performance, with the a priori assumption that these few samples are representative of the entire deposit. Geometallurgical sampling is becoming more prevalent as a way to use many smaller samples to indicate the expected recovery as part of the Mineral Resource or Ore Reserve estimation.The evaluation of magnetite deposits involves specialised approaches to sample preparation, sample analysis and resource estimation. The sampling protocol for magnetite deposits will typically include the use of Davis Tube analysis. The Davis Tube is a mini-pilot plant that is used for determining the mass magnetic recovery from a small amount of sample ground to a specific size. The magnetic concentrate may then be analysed and together with the mass magnetic recovery, may be used to simulate the expected mill recovery. The magnetite sampling protocol is specific to each deposit, and is typically designed around a specific metallurgical flow sheet.During resource modelling, the mass magnetic recoveries and concentrate grades may be estimated directly or assigned to a block model using regressions with other chemical constituents. For estimation, the concentrate grades are weighted to account for the different mass magnetic recoveries of each sample and the impact of these differences on the concentrate estimates.

Sep 5, 2011

By Honggang Zhong, Xin Cao, Qijie Zhai, Hongmei Song, Congsen Wu, Cheng Zhang, Jingzheng Ye

"The influence of superheat on the solidification structure and ferrite/austenite phase transformation of a novel lean duplex stainless steel (DSS) was investigated on a setup, which designed to thermally simulate the continuous casting process. The results showed that the macrostructure of the samples all exhibited chill zone, columnar zone and equiaxed zone. The distance from chill zone to position of columnar to equiaxed transition (CET) moved from 51.0 mm to 39.8 mm with an decrease of superheat from 70 °C to 10 °C, and that the grains in the chill zone tended to be finer. In equiaxed zone, the fme and uniform grains were observed when superheat higher than 40 °C; while, coarse grains were found in samples poured at low superheat. Generally, the volume fraction of ferrite increased along the dendritic growth direction, and stabilized in equiaxed zone. The high superheat decreased the volume fraction of ferrite in equiaxed zone, while it had indistinctive influence on chill zone and columnar zone.IntroductionDuplex stainless steel with approximately equal volume of ferrite and austenite, offering an attractive combination of corrosion resistance and mechanical properties. [ l]. The production of DSS, worldwide application in structural engineering[2] and petrochemical industry[3], have increase by more than 100% in the latest decade[4]. But due to the sharp prices increase of nickel and chromium, lean duplex stainless steels which have lower contents of alloy elements were developed. They perform well in both mechanical and corrosion resistance[S, 6] and even have TRlP(Transformation Induced Plasticity) effect[?]. Nonetheless , the mechanical properties of DSS was affected greatly by the solidification structure, such as columnar to equiaxed transition (CET), grain size and phase content[8]. So, the solidification behavior of stainless steel was investigated widely"

Jan 1, 2014

By J. M. Wempen

Booster fans in underground coal mines are often located using the concept of a neutral point. Normally, intake airways are maintained at higher absolute pressure than return airways; therefore, air leaks from intake to return. By adding a significant pressure force to a region of a ventilation system, booster fans installed in a return airway can increase the pressure in the return so that air leaks from return to intake. This is commonly referred to as recirculation. The neutral point occurs at the location in the system where the pressure difference between [ ] the intake and the return airway is zero. At this point, there is no leakage or recirculation. Ideally, placing a booster fan near the neutral point minimizes leakage and recirculation. However, in practice, the position of the neutral point is not static and it changes as the ventilation system parameters change. Booster fans have the potential to increase the capacity and efficiency of coal mine ventilation systems. However, these fans add a significant pressure source to ventilation systems and can create areas where the pressure in the intake is less than the pressure in the return causing recirculation. In systems with multiple booster fans, there may be multiple recirculation paths and, as the capacity of these fans increases, recirculation is more likely to occur.

Jan 1, 2012

By Agnes Ágata Fróes Martins

Placas ósseas metálicas são componentes utilizados para correção ou cura de fraturas ósseas. Em se tratando de implantes ortopédicos, é fundamental conhecer o comportamento dos materiais quando submetidos a esforços mecânicos. Para isto ensaios são realizados baseados em normas técnicas, que no caso específico de placas ósseas, são utilizadas as normas ASTM F382 e ABNT NBR 15672-2. Na execução do ensaio para determinação da rigidez à flexão, de uma placa óssea, pode existir o efeito da flexibilidade do dispositivo de ensaio. Para verificar a magnitude desse efeito, foram realizados três ensaios de flexão estático e um ensaio de flexibilidade do dispositivo de ensaio, onde o ensaio foi interrompido ao final da fase elástica. As propriedades mecânicas da placa foram avaliadas, aplicando a correção da flexibilidade do dispositivo. Os resultados mostraram que para os níveis de carregamento alcançados, as cargas de prova apresentaram pouca influência na flexibilidade do dispositivo, e consequentemente pouca influência na rigidez após os cálculos de correção.

Aug 8, 2018

By Ibrahim Yusufoglu, Cem Kahruman, Mert Zoraga

In this study, a strontium sulfate mineral (celestite) was converted to strontium oxalate in solutions containing ammonium oxalate as a reactant. The experiments were carried out under isothermal conditions. The effects of stirring speed, ammonium oxalate concentration, particle size and temperature on the conversion rate were investigated. During the conversion process, definite volumes of solutions were taken from the reactor after different reaction times for the determination of sulfate ions using ICPOES. Fractional conversions of strontium sulfate were determined at different times and fractional conversion vs time diagrams were generated. It was found that the conversion of strontium sulfate was increased by increasing the ammonium oxalate concentration and temperature in addition to decreasing the particle size. The effect of stirring speed was negligible on the reaction rate. It was observed that above 328 K, a protective layer of strontium oxalate was formed on the strontium sulfate particles. X-ray Powder Diffraction technique was used for characterization of solid substances.

Jan 1, 2014

In recent years there have been many changes in mine ownership due to the on-going rationalisation towards larger mining companies. Larger companies inevitably find it hard to manage small mining operations and in many cases smaller mines do not fit corporate resource, production and profit criteria. Smaller companies are more suited to managing these medium or small scale mines and are tendering for the purchase or lease of mines that larger companies wish to dispose of. In addition to these factors there has also been a trend (especially in Western Australia) for mines to continue operating at ever increasing depths. This in turn has led to more mines operating in high stress environments and experiencing damaging seismicity. Assessing the viability of seismically active mines from a takeover or purchase point of view should involve analysing the risk profile of every aspect on mining that could be affected by adverse seismicity. This includes assessing current and alternative mining methods, mine designs, support systems, extraction sequencing, monitoring and blasting. This paper includes discussion on items that need to be assessed when considering the purchase of seismically active mines, with experience gained from some recent studies in Western Australia. In these cases it was apparent that quantification of previous seismic history on itÆs own was a totally inadequate method of assessing minewide seismic risk potential. A more holistic approach is required, taking into account all aspects of relevant data, all the minewide effects of seismic activity and all possible means of mitigating those effects.

Jan 1, 2002

By J A. Rowland

When executing a ventilation change the mine ventilation circuit is in a state of flux throughout the entire change period with discrete mine areas both under ventilated and/or over ventilated during the change process. Whilst routine risk reduction strategies such as removing electrical power and people from the mine are commonly deployed it is wise to complete the change in the shortest practical time frame. This not only minimises the chance of unacceptable concentrations of contaminants accumulating around the mine but reduces the impedance on production activities which are routinely suspended during these change periods. This paper firstly highlights the importance of the maintenance of an accurate ventilation model and discusses issues which should be considered to assist to maintain in it a suitable state of health. Further it provides some tips on how to monitor that your model is in an acceptable state of tune so that it can be confidently deployed in the change process. Finally, it details the sequential process how a finely tuned and accurate ventilation model can be utilised to carry out major ventilation changes according to appliance pressure adjustments only and without the need to constantly measure and check resultant branch flows throughout the whole change process. Also discussed are some simple practical tips which will help ensure that the ventilation change process will go according to the devised plan on the day and in the most appropriate order including checking the efficiency and accuracy of the change, after it is completed.

Oct 12, 2022

By Mohsen Hashemzadehfini

Nowadays heap leaching has become established as a mineral processing technology for treatment of some low grade minerals such as copper, gold, and zinc, etc. Heap height, particle size, leach reagent consumption, and metal recovery are four important metallurgical parameters in a hydrometallurgical process like heap leaching. This paper investigated the effects of heap height and particle size on copper recovery as well as acid consumption. Three heap heights of 2, 4 and 6 meters and two particle size fractions of less than 25.4 mm and 50.8 mm were selected as variables in the experiments. The research results showed the inverse relation between heap height and copper recovery as well as acid consumption. Under given conditions, the copper recoveries of minus 25.4 mm ore are 78.63%, 66.27% and 52.88% higher than that of minus 50.8 mm samples for the heap heights of 2, 4, and 6 m, respectively. Both copper recovery and acid consumption increase with decreasing particle size. Keywords: heap leaching, heap height, particle size, acid consumption

Sep 1, 2012

By X Li, J Wang, D Liu, Y Liu, K Hu

"Since the adoption of open-door policy 30 years ago, rapid economic growth has resulted in serious resource depletion and environmental destruction, especially in mining areas. As an urgent response to this situation, the central government and the Ministry of Land and Resources (MLR) have adjusted policies with concrete and realistic actions for halting this trend of non-sustainable mining activities in China. æGreen Mine CampaignÆ is one of the actions implemented. In 2010, MLR announced the æGreen Mine CampaignÆ, in which existing and new mines will be evaluated against the æGreen Mine Construction StandardsÆ and certified as æGreen MineÆ if complying with these standards. The standards cover five key aspects: the considerations of science-supported resource exploitation efficient resource utilisation standardised management environmental friendliness harmonious community relationship.Every year, MLR reviews ægreen minesÆ from all provinces. Thirty seven mines, including coal, metal, non-metal, gold, chemical industry and building materials mines, passed the review and were certified as green mines in 2010. In 2011, 187 out of 194 mines that participated in the review were certified as ægreen minesÆ. These mines are viewed as good examples of sustainable mining development in China.CITATION:Liu, Y, Hu, K, Li, X, Liu, Y, Liu, D and Wang, J, 2012. The green mine campaign and sustainable mining in China, in Proceedings Life-of-Mine 2012, pp 339-342 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jul 10, 2012

By Keenneth Huachaca

Durante los últimos años, en las operaciones mineras subterráneas surgió la necesidad de contar con diversos mecanismos de control operativo orientados a la mejora de los procesos productivos. Actualmente estos mecanismos tienen muchas dificultades, principalmente en las comunicaciones, debido a la volatilidad de las labores, costos altos de instalación y daños físicos a los medios de comunicación existentes (fibra óptica, cables coaxiales y leaky feeder), lo que dificulta principalmente la extracción de datos de los equipos móviles livianos y pesados. En este trabajo se presenta un nuevo medio de comunicación que se adapta a la volatilidad de las labores mineras, tiene bajo costo de instalación y está exento de sufrir daños físicos en su trayecto, por lo que garantiza una alta disponibilidad y fiabilidad de la transferencia de información del subterráneo hacia los centros de control existentes, donde la información es procesada, a la vez que facilita la aplicación de los mecanismos de control para la optimización de los procesos productivos.

Sep 20, 2019