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By Andrew Wetherelt

Blast vibrations are of paramount importance in a society where ever increasing development is putting more stringent requirements on their control. Increasing civil development and more complex extraction scenarios make the trade off between proficient vibration control and productivity difficult to ascertain. Historically, reduction of induced vibrations levels was achieved through a reduction of MIC’s leading to smaller but more frequent blasts in order to meet extraction targets.

Jan 1, 2007

By Fernanda de Lima Menezes

O biodiesel, obtido a partir de um éster e um álcool na presença de um catalisador, é produzido pela reação de transesterificação e tem como coproduto a glicerina. A produção de biodiesel da Petrobras Biocombustível tem, em uma de suas etapas, a lavagem dos produtos para remoção do catalisador básico, metilato de sódio, por meio da reação de neutralização com ácido clorídrico. Devido a essa prática, a glicerina obtida é acidificada e contêm resíduos de cloretos, o que leva à corrosão localizada dos aços utilizados em determinados pontos do processo de produção. Dessa forma, o presente trabalho avaliou a resistência à corrosão do aço austenítico 317L e do aço lean duplex 2304, em meio de glicerina acidificada contendo cloretos. Todas as medidas foram conduzidas a 64ºC, visando simular as condições de operação da empresa. Para o estudo em questão, utilizou-se as técnicas de potencial de circuito aberto (OCP), polarização potenciodinâmica e microscopia eletrônica de varredura (MEV). As análises mostraram que o aço AISI 317L obteve menor potencial de pite que o SAF 2304, logo foi menos resistente. Por meio do MEV foi possível confirmar a presença dos pites, sendo que as cavidades presentes no aço AISI 317L foram mais numerosas e profundas que as observadas no aço SAF 2304.

Jan 16, 2018

By Francisco Necy Alves Júnior

Os aços inoxidáveis superduplex (AISD) aliam boas propriedades mecânicas e resistência à corrosão, possuindo um vasto campo de aplicação na indústria petroquímica. Geralmente, os reparos dos equipamentos são realizados por soldagem, sendo importante a seleção de parâmetros. É de suma importância a obtenção do teor adequado de ferrita no metal de solda, sendo que a variação da energia de soldagem pode influenciar de forma direta a microestrutura e resistência à corrosão. Logo, este trabalho teve como objetivo avaliar os efeitos provenientes da variação de parâmetros de soldagem nas características do AISD UNS S32750. Foi avaliado o balanço de fases, relacionando esse efeito com a resistência à corrosão. Foram realizadas soldagens em chapas pelo processo TIG autógeno em 3 níveis de energia de soldagem (5, 10 e 18 kJ/cm), variando a corrente e velocidade de soldagem, de modo a obter 5 condições e a possibilidade de analisar as variáveis-resposta com essas variações isoladamente. A análise da microestrutura foi realizada por microscopia ótica e o teor de ferrita foi quantificado pela utilização de duas técnicas: ferritoscópio e quantificação por imagem. Foram realizados ensaios de temperatura crítica de pite para análise de resistência à corrosão. Concluiu-se então que o acréscimo de energia pela variação da velocidade de soldagem acarretou no aumento no teor de ferrita, ocasionando a redução da temperatura crítica de pite, sendo estes observados na fase ferrítica.

Aug 7, 2018

By S. W. Robertson, M. T. Golela, S. Mxinwa

South Africa has one of the largest Cr-related industries in the world and generates large amounts of Cr-containing smelter dusts. It is normal practice to scrub Cr from the furnace off-gas in water, and to recover the Cr by adsorption, followed by recycling of the loaded adsorbent into the furnace. A study was conducted to find a low-cost adsorbent that is capable of removing sufficient Cr from the solutions generated by scrubbing. The test work focused on the evaluation of different clay minerals (attapulgite, bentonite, and kaolinite) as adsorbents for Cr. Cr(VI) could only be adsorbed after prereduction with e.g. ascorbic acid (ASA). An 80% removal of Cr(VI) could be achieved from a solution containing 20 mg/L Cr using bentonite clay after reduction with ASA. Attapulgite and kaolinite adsorbed less than 55% Cr after reduction with ASA. Both ASA and ferrous salts were found to be suitable reducing agents. The use of acid mine drainage (AMD) was also investigated as a low-cost alternative reducing agent, as AMD usually contains iron. The Cr(VI) reduction potential of the AMD was determined by redox titration against a solution containing 50 mg/L Cr(VI). Studies show that AMD can potentially be used as a reducing agent in a Cr removal process if it is available on site.

Feb 12, 2024

By Nobuharu Isago, Atsushi Kusaka, Kosuke Kawata

"Rock tunnels suffered severe damage from recent large earthquakes in Japan, despite the empirical knowledge that tunnels tolerate earthquakes better than surface structures. Seismic design for rock tunnels have therefore become a fascinating subject for many tunnel engineers. However, even basic behavior, including deformation mode and loading magnitude for hard-rock TBM tunnels and conventional ones during earthquake, has not been fully understood due to lack of actual seismic data; while EPB and slurry TBM tunnels take account of seismic design in Japan if needed. This study conducted a dynamic measurement in an actual road tunnel constructed in rock. The strongest aftershock of “the 2011 off the Pacific coast of Tohoku Earthquake” (Mw = 7.1) occurred during the measurement, providing precious data to examine deformation mode of the tunnel. Considering the acquired data, numerical analysis was also performed to calculate loading magnitude to cause fatal fracture of tunnel lining during earthquake.INTRODUCTIONLarge earthquakes can pose serious risks even for rock tunnels, as evidenced by large earthquakes in the past. In the large earthquake in Japan in 2004 (Mw = 6.6), some tunnels suffered severe damage including collapse of their permanent lining (Mashimo 2005), even though the tunnels were constructed in ordinary ground conditions except for fault, fracture zone, portal area, etc. To mitigate such risks, mechanical behavior of tunnel lining during earthquake should be clarified; however, even basic mechanical behavior including load-bearing capacity of the tunnel lining against earthquake is not fully understood.Numerous damage modes were actually observed due to various ground conditions (eg. Wang et al. 2001; Mashimo 2005). Among them, major tunnel damage caused by earthquakes can be grouped into three main modes as shown in Figure 1, excluding extremely unusual conditions such as a tunnel located on a stratum boundary where the stratum stiffness varies significantly. TYPE-I shows flexural failure or crack by bending moment at shoulders; TYPE-II indicates compression failure or flexural compression failure at crown; and TYPE-III illustrates compression failure at sidewall, mainly observed on tunnel that was constructed using steel ribs and lagging method. These damage modes, Type-I, II and III, are predominantly caused by shearing, horizontal compressing and vertical compressing deformations of the surrounding ground, respectively (Kusaka et al. 2011; Asakura et al. 2001)."

Jan 1, 2016

By Diego Pacheco Wermuth

O presente trabalho apresenta os resultados do estudo e aproveitamento de cinzas leves da queima de carvão mineral em termelétrica, como reforço para o Compósito de Matriz Metálica de cobre. Foram estudados diferentes percentuais de cinzas leves como reforço para o cobre, sendo misturados estes pós através de misturador “duplo v”, compactando os pós em diferentes pressões e sinterizando os corpos de prova obtidos pela compactação. A amostra sinterizada que apresentou a maior dureza entre todos os corpos de prova sinterizados, atingindo 89 HV, foi utilizada como base para a formulação e obtenção de novos corpos de prova, que foram estudados sob condições de moagem dos pós por moinho de bolas e moagem de alta energia. A fabricação do compósito seguiu os padrões industriais do processo de Metalurgia do Pó, como a mistura e moagem dos pós, compactação dos pós e sinterização em atmosfera controlada. Foi realizado o estudo das propriedades mecânicas do compósito formado por cobre e cinzas leves, que comprovou o aumento da dureza para 122 HV. Este trabalho proporciona uma nova aplicação para as cinzas leves, utilizando estes resíduos de usinas termoelétricas como matéria prima para reforço mecânico na composição de peças à base de cobre na indústria metalúrgica.

Aug 17, 2017

By Zihe Ren, Edouard Asselin, Marcus Tomlinson, Tianbi Zhang, Jing Liu

"Raman spectroscopy is used to quantify the extent of disorder in the carbonaceous matter associated with preg-robbing ores. Previous studies of Goldstrike ores showed that the height and width of the peaks for the “D” (disordered) and “G” (graphite) bands, the so-called “Raman ratio” had a strong correlation to the preg-robbing value (PRV) measured for various ore samples. A brief literature review on Raman spectroscopy as it applies to preg-robbing ores is presented. Further, recent studies, presented here, have shown no correlation between the Raman ratio and the PRV for a wide variety of ores. This suggests that the extent of organic carbon crystal disorder is not the main factor in determining preg-robbing characteristics.INTRODUCTION Valuable base metals, such as nickel, cobalt, molybdenum, vanadium and tungsten, are used in a wide range of important technological applications. The demand for many of these metals has increased significantly over the last few decades, driven especially by economic expansion in Asia generally and China in particular. This has led in turn to a large growth in the output of mines in order to satisfy this increasing demand, as shown by the data in Table 1 (USGS, 1994, 2014). These data reflect an even longer trend of growth of these metals, with nickel, for example, showing an average rate of 5.3% per year from 1980 until 2015 (International Nickel Study Group, 2017). This rapid and sustained rate of growth means that annual mine outputs for nickel, tungsten, molybdenum and vanadium have had to double roughly every 11 to 14 years, whilst cobalt mine output has had to double roughly every 7 years, over the period from 1994 until 2014. With the average working life of a nickel mine being between 17 and 22 years (Statista, 2017), this means that from the time a nickel mine opens until it closes, the industry needs to find the equivalent of another three or four mines of a similar output to satisfy this relentless growth in demand for the metal."

Jan 1, 2017

By M S. Manono, K C. Corin

The optimisation and process developments surrounding the beneficiation of Cu-Ni-PGM ores is of fundamental importance when considering the continued rise in global demand for these precious metals. The selective sequential flotation of these ores is accompanied with various processing challenges such as the successful separation of the Cu-Ni-PGMs from non-sulfide naturally floatable gangue and pyrrhotite. Reagents such as sodium iso-butyl xanthate (SIBX) and sodium carboxymethyl cellulose (CMC) have proven to significantly improve the selectivity of the flotation process in their respective roles. The use of recycled water with abnormal inorganic electrolyte concentrations can modify the selectivity of these reagents, as ions may adsorb onto minerals such as pyrrhotite, thereby hindering or promoting the hydrophocity and floatability of pyrrhotite. Process water quality effects on the behaviour of pyrrhotite may have negative or positive influence on the recovery and grades of the wanted Cu-Ni-PGMs as valuable minerals associated with pyrrhotite such as pentlandite may be affected in like manner. Thus, the impact of concentrator process water quality on the behaviour of pyrrhotite needs to be determined. In this study synthetic process water at various ionic strengths was investigated against various CMC dosages to understand the behaviour of pyrrhotite during the flotation of a Cu-Ni-PGM Merensky ore in a batch flotation cell. This study showed that pyrrhotite grades increased with an increase in CMC dosage for fixed ionic strengths whereas the recoveries of pyrrhotite increased with an increase in ionic strength until 3SPW, then a trend of a decrease in recoveries was seen with 5SPW resulting in the lowest pyrrhotite recoveries. Furthermore, this study showed that moderate CMC dosages of 100 g/t resulted in the highest pyrrhotite recovery for all four ionic strengths of synthetic process water tested. It can be said that to maximise value recovery from Cu-Ni-PGM ores, understanding the behaviour of pyrrhotite against degrading water quality and reagent suites could be of paramount importance given the sensitivity of pyrrhotite to oxidising chemical conditions.

Aug 24, 2022

By J Loeb, J Dampney, P Cameron

Optimisation of Blast Design and Execution must be done right the first time. It is too late after the ore is broken. Consequences of poor design and execution negatively affect productivity from load and haul through the primary crusher to processing and hence reduce mine site profits. Harnessing and utilising ‘big data’ from geology, geometallurgy, drill hole location, powder loading, blast timing, blast movement and fragmentation to close the loop in blast design and optimise the blast increases productivity across the entire value chain from Mine to Mill. As the internet of things and artificial intelligence increases the quantity of data available, being able to capture and utilise this data to advantage is a challenge. Recent advances in software and hardware together with the increased power of cloud computing allows engineers to close the blasting loop to increase mine site productivity. Numerous case studies over the years detail significant gains from implementing the innovative technologies available to Mine to Mill projects. The opportunity is available for all members of the multi-discipline teams at each mine site to actively ensure productivity improvements are realised and maintained not only in their area, or silo of responsibility but across the entire mine site. This paper refers to recent case studies which outline how significant improvements in productivity are available to all mining operations to increase mine site profitability and dividends to shareholders.

Jun 22, 2022

By J. F. Myers, F. M. Lewis

The paper reports the development of a large, slow speed ball mill closed circuited with a hydroscillator. This increased grinding efficiency 28 pct over conventional units.

Jan 1, 1950

By R. L. Grayson, W. E. Wallace, J. W. Stephens, M. D. Attfield, P. S. Brower, V. Vallyathan, M. J. Keane, J. C. Harrison

Pure respirable quartz is a known pathogenic agent for lung disease. However, for mixed dusts, neither mineralogical nor in vitro cytotoxicity assays unequivocally predict the contribution of quartz to their pathogenic potential.First, although Coal Workers' Pneumoconiosis (CWP) and Progressive Massive Fibrosis (PMF) prevalence have been found to correlate with total respirable coal mine dust exposure, and with coal rank (Attfield and Morring, 1992), epidemiological studies generally have not found the quartz component of coal mine dust as measured by X-ray diffraction or infrared spectroscopy (each of which essentially measures the mass-percent quartz in a bulk sample) to be clear predictors of CWP prevalence or incidence (Walton et al., 1971). Second, the properties which distinguish the extreme fibrogenic potential of quartz are not revealed by conventional in vitro bioassay comparison with other silicate mineral dusts. As an example, quartz and kaolin (aluminosilicate) clay in vitro cytotoxicities are comparable for lavaged primary pulmonary macrophages.The studies discussed here address these two anomalies from a general hypothesis that the pathogenic activity of respired quartz particles is associated with properties of, and interactions with, the particle surfaces. One factor in the expression of toxic activity by a particle surface is the biological availability of that surface. Anomalous lack of correlation of disease prevalence with mass percent quartz in exposures to some mixed composition respirable-sized dusts suggests that individual particle surface features, invisible by bulk sample mass analysis, may alter the biological availability of a fraction of quartz particles in a dust. For pure-surfaced mineral particles, the comparably strong prompt membranolytic activities of quartz and kaolin in vitro suggest that upon deposition of such particles in the lung there must be other interactions with particle surfaces which distinguish quartz. This might be due to toxic surface-associated sites specific to silica, or to interactions of other sites on other mineral particles which affect the biological availability of their toxic functional groups. For example, alurninol groups on clays affect the availability or activity of adjacent silanol groups. Surface activities which distinguish quartz pathogenici ty might be manifest in one or more of the sequential interactions upon deposition in the lung; first with the pulmonary surfactant system, then with extracellular and phagolysosomal enzymatic digestive processes, or with subsequent cytotoxic processes.

Dec 1, 1995

By K. Kar, M. Gautam, J. T. Jurewicz

The 10-mm Dorr-Oliver cyclone has been widely used as a personal sampler for size selective sampling of particles within the respirable range (Dp < 10 gm). Because of their inertia, the particles are unable to follow the swirling flow (outer vortex) within the cyclone. The particles migrate to the bottom of the cyclone, depending on their size, and get trapped into the inner vortex which leads to an eventual blow-off from the top of the cyclone. By measuring the size distribution of the particles in the free stream and in the collected sample, the aspiration efficiency of the cyclone can be calculated. Velocity difference between the free stream and sampling velocity. Inlet orientation, particle impaction and deposition, particle inertia and free stream turbulence result in the departure of the aspiration efficiency from unity and this, in turn, leads to inlet bias. Although the effect of inlet bias on sampling efficiency has been investigated in past, the results lack detailed information and show only some general trend. In this effort, a systematic, in-depth experimental work on the effect of inlet bias on the sampling efficiency has been undertaken using non-intrusive Laser Doppler Anemometry (LDA), Aerodynamic Particle Sizer (APS) and impactors.

Mar 1, 1992

By Brian FitzPatrick, Michael J. Weaver

Everyone has a role in site safety, even consultants. This paper presents a summary of how a geotechnical and environmental consulting firm, with field staff on construction and subsurface explorations sites, engaged their staff and leveraged relationships with contractors to assess the construction related risks to which its staff members are exposed. These findings were then integrated into their technical training materials for both new staff and those needing a refresher, so that safety is discussed at the same time as the technical work and not treated as a separate topic. The paper outlines the process of identifying and evaluating the construction related risks that staff members face and presents examples of how the consultant can engage contractors in the process. By doing this, knowledge can be shared and there is a better mutual understanding of the risks associated with common construction and exploration related field tasks. The work resulted in an increase in staff engagement in safety, a better understanding of the true risks that staff face in the field, better relationships with contractors, and lower safety metrics. HISTORY At Haley & Aldrich, Inc., we renewed our safety journey in May 2012. Like many others, we had concerns over injuries our staff experienced in the three previous years, and a potentially significant utility strike we experienced while excavating a trench. In 2009, 2010 and 2011 we experienced an increase in recordable injuries, including two significant injuries, which caused our Experience Modification Rate (EMR) (see note below), Total Recordable Incident Rate (TRIR), and Days Away-Restricted, and Transferred Rate (DART) to rise significantly. See Fig. 1 for details. This caused us to step back and review our approach to safety, and our “safety culture”. The rise in reportable incidents and injuries also corresponded to the beginning of a growth period for the company.

Jan 1, 2019

By Juan M. Pestana, Jeremy M. Gasser, Cuneyt Gokmen, Paul J. Sabatini, William Tanner, Daniel J. Woeste

An access pathway and working platform were designed and constructed for equipment access for a Deep Soil Mixing (DSM) pilot study over a coal combustion residual (CCR) surface impoundment (SI). The DSM pilot study was conducted to evaluate slurry mix designs and construction techniques for installing DSM columns up to 95 feet deep. Two-dimensional (2-D) limit equilibrium and 2-D finite element analyses were used to evaluate multiple failure mechanisms including: (i) bearing capacity, (ii) punching shear of mixed ground and underlying CCR, (iii) effect of fluidized DSM columns on working platform stability, and (iv) liquefaction. The analysis results were used to design ground improvement required to increase bearing capacity and stability of the CCR under the proposed equipment access route. A long-reach excavator was used to perform shallow bucket mixing and walk onto the CCR SI atop previously mixed cells following a minimum cure time and acceptance of quality control test results. Prior to mobilizing the DSM rig, a static load test was conducted to evaluate performance of the working platform. Both the access pathway and working platform demonstrated acceptable performance under the design loads during the DSM pilot study. This case study emphasizes the economic and safety benefits that can be realized by appropriately designing critical temporary work items such as access pathways and working platforms in difficult ground conditions. INTRODUCTION A Deep Soil Mixing (DSM) pilot study was conducted at a coal combustion residual (CCR) surface impoundment (SI) to evaluate slurry mix designs and construction techniques for closure design of the SI (Site). Sluicing of CCR at the facility ceased and closure will be initiated based on requirements in the final United States Environmental Protection Agency (USEPA) Rule for Disposal of Coal Combustion Residuals from Electric Utilities, 40 CFR 257, effective October 19, 2015. The proposed closure approach involves constructing a DSM containment structure (DSM Wall) to separate the SI into two areas: (i) a closure by removal area; and (ii) a consolidate and cap-in-place area. The proposed DSM Wall would retain the CCR within the consolidated closure footprint and provide a barrier between the two areas of the SI. The predominant CCR in the SI where the pilot study was conducted were fly ash and bottom ash. CCR materials in surface impoundments are generally soft and saturated as a result of being sluiced into place and can present stability and safety challenges when performing earthwork activities.

Jan 1, 2019

By André L. B. Bittencourt

The copper content in the waste slag represents the greatest loss in the process of Caraíba Metais&apos; Smelter. By identifying the variables responsible for copper stabilization in the slag, a minimization on these losses is expected, producing a granulated waste slag with a copper content lower than 0.7%. Statistics resourses such as control charts, Pareto&apos;s diagram and correlations curves were applied for the data obtained in the first semester of 1992. The magnetite and the calcium oxide contents in the slag of the Flash Smelter Furnace were most prominent variables. Some operational changes introduced during and after this investigation have shown good results.

Jan 1, 1994

Editor&apos;s note: Biographical information about Ihor Kunasz, president, Newmont Uzbekistan, can be found in the February 1998 issue of ME, page 94 and in the May 1996 issue, page 92. Your personal assessment of the minerals business. Gosh! When I think about what has happened to the minerals industry over the past 27 years that I have been a member of SME! There have been fundamental structural changes in the industry. And I think that SME has been quite successful in coping with these changes as well. There has been a reorientation in how the minerals industry does business. It used to be called rationalization. Today we call it reengineering. In addition, the minerals industry has become more complex and more global. Shareholders have become more vocal and demanding in the management of the business, asking for protection of their shareholders&apos; value. In the 1980s, a fundamental change was precipitated by a merger and acquisition fever in all industries, including the minerals industry. Raiders such as T. Boone Pickens put enormous demands on companies that, in turn, had to spend substantial management time to fend off the raiders. This resulted in a major restructuring of the mining houses. Today, for example, Anaconda, Kennecott and Amax are only historical names.

Jan 1, 1998

By Sean Masse

New Gold?s New Afton Mine, located 8 km (5 miles) west of Kamloops, British Columbia, is a 4.5-Mt/a (5-million stpy) block cave mine, making it the highest tonnage underground hard rock mine in Canada. The reserve is estimated at 52.5 Mt (55.9 million st) with grades of 0.65 g/t (0.02 oz/st) gold and 0.93 percent copper (2012). Commercial production was achieved in July 2012 and nameplate production was achieved ahead of schedule in September 2012, with the cave breaching to surface in 2013. The mill has a SAG and a ball mill with a froth flotation circuit.

Jan 1, 2014

By V. Falmagne

The mining sequence at Noranda?s Bell-Allard mine calls for two mining fronts retreating toward a central pillar known as the Retreat Zone between pyramids A and C. It is clear from numerical modelling and rock mass characterization that the induced stress level in the pillar will exceed the rock mass capacity. A mining plan was developed including the re-dimensioning of stopes in the Retreat Zone, additional ground support and instrumentation in order to ensure the safety of the workforce and to maximize ore recovery while minimizing production delays. The mining strategy consists in allowing the rock mass to fracture and fail progressively while maintaining control of the existing openings with the appropriate support. A systematic analysis of rockbursting and caving hazards was conducted for all accesses and stopes in order to plan ground support and instrumentation needs.

Apr 1, 2004

The perception of New Zealand as an exploration destination has improved compared with other countries. There has been a realisation that New Zealand&apos;s potential is greater than previously thought. Other countries are not as attractive as before, and explorers are looking at alternatives that are geologically prospective and politically stable. &nbsp; New Zealand is regarded as geologically prospective, especially for gold, with potential for world class deposits. It is also prospective for other metals, coal and industrial minerals. New Zealand is politically stable, and has an economy that is attractive to overseas investors. It is one of the least corrupt countries in the world, which overseas companies see as providing a high degree of certainty for investment. &nbsp; New Zealand has good opportunities for investment in gold exploration at present. Otago has been the focus for new companies and is the favoured exploration location. Otago is regarded as very prospective, and hosts New Zealand&apos;s largest gold deposit at Macraes. There is potential for other similar deposits elsewhere in Otago. &nbsp; The mineral industry previously had an excessively pessimistic view of New Zealand, which has resulted in little new investment in New Zealand for some years. Previous pessimism is turning to optimism, and there is increasing interest in New Zealand as an exploration destination by overseas explorers.

Jan 1, 1997

By R Butler

Contract m1n1ng in New Zealand developed in the coal industry and has become an element in the success of recently opened hard rock gold mines. At Martha Hill, the mining contractor is undertaking a wide range of activities from open pit mining, crushing, conveying, waste embankment construction and drainage.

Jan 1, 1991