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By R. W. Lawrence

"The management of acid rock drainage( ARD) to prevent impact when tailings are disposed of in the environment requires understanding of the phenomena giving rise to acidic drainage, a rigorous evaluation of the weathering characteristics of the tailings, and the successful implementation of control measures that will be effective in the long term. This paper provides a brief theoretical background to the complex reactions taking place in mill tailings containing residual sulfide minerals which must be appreciated to enable waste characterization program to be effective in predicting the future behavior of the tailings and in designing control methods which will work. The principals and practice of prediction and control as part of an ARD management strategy will then be discussed.Paper Not Available at Time of Publication"

Jan 1, 1997

By B. K. Choi, G. E. Kim, S. Noh, T. K. Kim

Oxide dispersion strengthened (ODS) steel has been developed as the most prospective core structural material for next-generation nuclear systems because of its excellent high strength and irradiation resistance. In ODS steel, finely dispersed nano-oxide particles with a high number density in the homogeneous grains can be very attractive to achieve superior mechanical properties at high temperatures, and these favorable microstructures can be significantly changed using process parameters during the mechanical alloying procedures. In this study, the effects of mechanical alloying times on the microstructure of 10Cr-1Mo ODS martensitic steel were investigated. Pre-alloyed powders with Y2O3 powder were mechanically alloyed for various milling times using a high energy horizontal ball-mill apparatus (model: symoloyer CM20). Powder properties such as the mean particle size, size distribution, and crystallite size were evaluated. Uniaxial hot pressing was employed to consolidate the milled powders. The results of a microstructural observation after the MA and UHP processes indicated that the homogeneity of the martensitic structures was considerably increased with the longer milling time. It is thus concluded that the mechanical properties of the ODS martensitic steel are greatly dependent on the mechanical alloying times.

Jan 1, 2015

By Marc C. Bétoumay

Workplace safety, health, climatic conditions and rising oil prices are aspects that are important to the mining industry. The need for cleaner energy for underground mine vehicles is requiring serious consideration. A number of alternate energy systems offer clean solutions to diesel emissions while maintaining the current liberty of vehicle movement. This watershed article provides a broad comparison of cleaner diesel and alternative energies for underground production vehicles. Most alternate energies and clean diesel have already been tested in underground production vehicles. There are no technology gaps that would prevent the development of commercial alternative energy power plants, but in the case of alternate energies, second and third generation versions will be required to fully test for safety and operation viability. Full regulatory development is also required and could be done in parallel to power plant testing. Vehicle operation and maintenance manpower would be the same for alternate energy application as for clean diesel. Capital cost for alternate energy power plants will remain higher until the medium term. Owing to significant ventilation savings possible with alternate technologies, operating costs would be reduced.

May 1, 2011

By Chih-Huey Lin

The Au/?-Al2O3 catalyst prepared by AuCl3 impregnation is subjected to the influence of residual chlorine after an oven drying. A post-impregnation NH4OH treatment was able to eliminate chlorine, and to reduce the cluster size of Au moiety. However, the CO oxidation activity was not increased by this post-impregnation NH4OH treatment. This suggests that certain metal-support interaction (MSI) is the determining factor for the activity of Au catalysts. Thermal treatment under H2, O2 or He was attempted to increase MSI of the prepared catalyst with or without the post-impregnation NH4OH treatment. No significant activity enhancement was found but the TPD analysis suggests that a H2 treatment has a higher chance to induce MSI.

Oct 1, 2003

By Stephen C. Tadolini

"The use of a torque wrench to establish the amount of actual load developed on an expansion anchor bofting system dates back to work completed in the early 1950s. The advent of ultrasonic measurement systems and hydraulic torque wrenches has made it possible for the U.S. Bureau of Mines to perform torque-tension measurements in the laboratory and the field much more accurately. The results indicate that the amount of initial boft preload may be overestimated by amounts in excess of 45% of the expected load using torque wrenches. This inaccuracy is primarily due to the friction that occurs between the bearing plate and the head of the boft. These parameters become extremely important when the support system is being used to prevent joint members from slipping relative to each other or when the boft acts as a heavy spring to clamp two or more sections together. Methods to overcome the frictional losses are presented in conjunction with a laboratory method to determine the actual torque-tension ratios for expansion anchor and combination bolting systems.IntroductionMechanically anchored roof bolts have been widely used in the mining industry since their introduction in 1947. Estimates made in 1989 indicate that out of 85 million fixtures, approximately 49 million bolting fixtures still use applied tension to complete the reinforcement necessary to maintain stable openings. Nearly 85 million bolts are used yearly. The most widely used bolt is the resin-anchored headed rebar, followed by standard mechanical roof bolts, specialty bolts (mechanically anchored, resin enhanced fixtures) , and combination bolts . Po st-tensioned resin rebars, combination systems, and friction stabilizers make up the remaining 10% of the units used (Fig. I).For mechanical, combination, and tension rebar bolts, the bolt tension is the primary means of reinforcing the roof, but in many cases, because of poor installation procedures, the bolts are ineffective. Mine operators recognize the importance of proper installation procedures. Long-term bolt tension measurements are required in the Code of Federal Regulations (CFR)In each bolting cycle, the actual torque or tension of the first tensioned bolt installed with each drill head shall be measured immediately after it is installed. Thereafter, for each drill head used, at least one roof bolt out of every four installed shall be measured for actual torque or tension. If the actual torque or tension of any roof bolts measured is not within the range specified in the roof control plan, corrective action shall be taken."

Jan 1, 1991

By K. C. Sole, G. Robinson, M. S. Moats, W. G. Davenport, S. Sandoval

Global practice in hydrometallurgical production of copper cathode by electrowinning is reviewed, based on individual plant operating data for 2018. Data from 29 plants were collected, representing 38% of world cathode copper production. Similar surveys were carried out in 1997, 1999, 2003, 2007, and 2013. This survey includes analysis of historical and current data. Evolving trends in operating conditions and performance, as well as equipment design and process technology choices, are analysed and differences in operating practices with location are assessed. Examples of recent technology and operational choices to increase productivity, improve copper quality, and decrease electrical energy consumption are discussed. Significant project expansions, particularly in Africa, and the consolidation of numerous small Chinese operations are also presented. INTRODUCTION Global trends and operating practices in copper electrowinning (EW) in 2018 are reviewed and evaluated. Similar world and African surveys were carried out in 1997, 1999, 2001, 2002, 2003, 2007, and 2013 (Robinson, Davenport, & Jenkins, 1997; Jenkins, Davenport, Kennedy, & Robinson, 1999; Davenport, Jenkins, Robinson, & Karcas, 2001; Robinson, Garbutt, & Davenport, 2002; Robinson, Davenport, Jenkins, King, & Rasmussen, 2003; Robinson, Davenport, Moats, Karcas, & Demetrio, 2007; Robinson, Sole, Sandoval, Moats, Siegmund, & Davenport, 2013). Contributing operations included sites from the USA and Mexico (9), Chile and Peru (6), Laos (1), Kazakhstan (1), and Africa (9). Despite fewer contributions compared with past experience, this survey nevertheless represents 2018 copper EW cathode production of 1.76 Mt, or about 38% of world production of 4.64 Mt (International Copper Study Group, 2017). This drop in permission to contribute is attributed to the more competitive nature of the industry and unprecedented production pressures; furthermore, several operations in Australia have shut down, while large operations that are currently commissioning or ramping up to full production in Africa and Asia declined to participate. Of the Chinese operations, which represent an increasingly important proportion of global electrowon cathode copper, particularly in Africa, only Tenke Fungurume (Democratic Republic of Congo; DRC) participated in this survey.

Jan 1, 2019

By G. Van Weert

In the spring of 2010 double refractory ores from historical stockpiles were processed through Barrick's Goldstrike pressure oxidation facility, thereby providing preg robbing feeds for a variety of metallurgical testwork. This paper describes the effects of amount, type, place and time of addition of activated carbons on CIL gold recovery and shows that native carbon in plant PDX'ed discharge solids can still preg rob gold loaded activated carbon.

Jan 1, 2011

By A. Uribe-Salas, J. A. Finch, B. J. Huls

Froth depth or interface level is an important control variable in column flotation which can influence both grade and recovery. A common method of locating the level is based on sensing the hydrostatic pressure at one or more points along the column. The level indicated can be in considerable error, largely because of variations in froth and collection zone bulk densities. A portable conductivity probe has been developed to detect the position of the interface from conductance measurements across the interface. The location of the interface corresponds to the position where a large change in conductance is observed, which is primarily a consequence of the difference in gas holdup between the collection and froth zone. This probe detects the position of the interface to an accuracy of ± 5 cm. The probe can be used while the column is in operation, which allows for on-line recalibration of the level detection system. Results obtained in its application in a pilot-scale column (0.91 m in diameter) are described.

Jan 1, 1990

By V. Schwinn, P. Fluess, N. Cauderlier, J. Bauer

From a strategic and economic point of view, the development of fine grain high strength steels for long distance pipelines is intensified world wide to satisfy the demand for natural gas in the future.The project related property profiles based on strength, toughness, crack arrest and sometimes resistance against HIC at defined design temperatures require an effective structural refinement using advanced steelmaking and processing in the rolling mill. The microstructure of modern line pipe steels ranges from ferritic pearlitic to ferritic-bainitic and structures where bainite is the dominant component, possibly upgraded by secondary phases. This paper illustrates microstructures and properties of recent orders on line pipe steels both for onshore and offshore application using different processing routes in the plate mill. Examples will be given for SAWL 485 offshore grades, X65 HIC and X70 HIC onshore grades, respectively. Finally, production results of a recent X80 order will be presented.

Jan 1, 2005

By J. C. Thornley, H. L. J. Drummond

"Fifty years of wear on the original carbon steel shaft of this hydro turbine necessitated repair operations in 1980. Both austenitic and martensitic stainless steels have been used individually as journal materials in separate trials on an80-inch long and 22-inch diameter radial bearing but neither one nor the other has been successful.The wear and cracking problems of the stainless steels leading to the present abandonment of both classes of stainless steel are described. In particular the dependence of the toughness of type 410 stainless steel on its tempering temperature and the susceptibility of that steel to quench cracking are highlighted because problems have been caused by both of these metallurgical factors.IntroductionAs part of a desire to improve the efficiency of a fifty-year old hydro-electric generating station on the Saint John River, the decision was made to change the journal and bearing material for the shaft bearings, which are stave-type bearings. For the initial fifty years of operation the bearings had been wooden (lignum vitae) and had run on the carbon steel shaft directly. For one of the four unit s at this station the performance of this combination has been truly excellent, and the remaining three sets of bearings had performed well. However there had been shaft wear on the units and the wear had made the shafts somewhat elliptical when a decision was made to install some sort of new journal on to three of the old shafts. [In addition to the wear on the carbon steel journals it was found that one shaft was significantly softer in the bearing area than it was immediately above the bearings (180 Vickers in comparison with 230 to 250 Vickers)] ."

Jan 1, 1985

By Muhammad Zaka Emad

ABSTRACT: Sublevel stoping mining methods with delayed backfill employs cemented rockfill (CRF) as a backfill material. It is used in underground mines to achieve ground control and reduce wall slough. In addition CRF serves to reduce development waste and provides a working surface for mining the upper levels. Efforts to optimize CRF practices have been published. This paper presents a detailed review of CRF practices in open stoping mining systems with reference to case studies. A new methodology is suggested in a simple stepwise approach, which can be adopted for site specific conditions. The need of laboratory testing and quality control program is discussed based on the published literature.

May 1, 2013

By P. J. Foster

Bowtie analysis has recently emerged as a technique of choice that can be used when looking specifically at major hazards in the mining industry. A Bowtie diagram is a graphical means of assessment that focuses on identifying all the specific causes and consequences of major events, from which all the ?pre-event? and ?post-event? control measures can be identified. From this critical control measures can be identified and monitoring/assurance systems can be established. It is this assessment of control measures and their effectiveness that replaces the more traditional evaluation of risk (using matrix-based approaches) based on the fact that risk is a function of control ineffectiveness. This is a major difference with traditional risk assessment where all too often control effectiveness is assumed. This paper summarises the Bowtie analysis process and outlines one specific case study where the technique was used on the unwanted event of a collision of a haul truck and light vehicle in an openpit mine. Although more effort is required in undertaking the assessments, control assurance provided this way will go a long way in ensuring that risk assessments and major hazard management become much more effective in practice.

Aug 1, 2013

By Michael J. Beare

Requirements of both local permitting and international fundraising are forcing increasing numbers of projects in Russia and CIS to carry out dual technical studies. The principal focus of Russian mining project design is to satisfy local regulatory requirements. However, the technical documents are not generally accepted by international banks for project finance outside Russia. Similarly, international study documents are not accepted for permitting in Russia. The purpose of this paper is to compare and contrast Russian and international approaches to mine technical studies and draw conclusions from this. The Russian design and permitting system is centered around two key statutory technical documents termed the TEO Konditsy and the TEO Project. These documents are subject to regulatory approval and are broadly equivalent to the international prefeasibility study and the feasibility study respectively. A comparison of study criteria suggests similar approaches are used for the main technical disciplines in project design by the time projects are at the point of construction, but there is divergence on environmental matters where the OVOS (Russian ESIA equivalent) differs from an ESIA in some significant areas. The key differences relate to project footprint, level of technical detailed required for baseline studies, level of public consultation, consideration and disclosure of information, labour, coverage of community and social issues and the preparation of a Social and Environmental Management System (SEMS). It has been noted that the Russian Design Institutes often leave the detailed economic analysis until after the TEO Konditsy. A common problem is design teams tend to look for ?technological solutions? without due concern for project economics. The end result of this can be mines that are overcapitalized and hence sub-optimal. It can be concluded that Design Institutes have the monopoly on Russian permitting reports and this is likely to continue. Similarly, Russian institutes generally do not prepare feasibility studies to international standards and this is likely to continue to be the case. Therefore to achieve the requirement of dual technical studies, the international consultants and Russian Design Institutes will need to cooperate on a joint work program. Key issues will be to ensure the most appropriate option studies are carried out at the right stages, that project economics are considered throughout the study, and that the environmental work program covers the additional studies necessary for the ESIA.

May 1, 2009

By M. J. Nicol, T. Moyo

Ammoniacal solutions are an effective lixiviant for the oxidative dissolution of some mineral sulphides. A detailed study of the anodic dissolution of chalcopyrite in ammonium sulphate-ammonium hydroxide solutions has been carried out using cyclic voltammetry, chrono-amperometry and rest potential measurements. The role of the copper(II)/copper(I) redox couple in the oxidation process has been evaluated. Rest potentials have been found not to be affected by oxygen but to increase with an increase in initial copper(II) concentration. Pseudo-steady-state anodic current densities measured in the absence of copper(II) ions at the rest potentials obtained in the presence of copper(II) ions increase with increasing concentration of copper(II) ions, confirming the positive effect of copper(II) ions on the rate of dissolution of the mineral. Cyclic voltametric and chrono-amperometric data show that in the absence of initial copper(II) ions, the rate of dissolution in the presence of dissolved oxygen is significantly lower. These results confirm that the effective oxidant for the mineral under the conditions of the study is copper(II) and not dissolved oxygen. Coulometric measurements have been used to establish the stoichiometry of the anodic reaction at different potentials.

Jan 1, 2014

By G. L. Spence

Prevention of cuprous and cupric oxide formation on stored ETP copper rod is a major concern for copper rod and wire producers. During normal storage periods copper oxide layers can increase from less then 100 A to more then 1000 A exceeding ASTM specifications and discoloring the rod surface. Various types of corrosion inhibitors are tested and compared in effectiveness for prevention of copper oxide formation on stored copper rod. Aromatic triazole compounds are also compared to a non-azole containing compound.

Jan 1, 2007

By Richard P. Taylor, Rod Henham

Abstract - Newly discovered pegmatites distributed throughout the sub-surface environs of the Musselwhite Archean gold deposit occur as narrow dikes that intrude most of the major lithological units. The mineralogy and textures of the pegmatite dikes are characteristic of granitic pegmatites of the "Rare-Element Class"; more specifically, they closely resemble varieties of the "Complex-type" granitic pegmatites that are commonly associated with zones of tantalum mineralization. The essential minerals in the dikes comprise albite, quartz, and K-feldspar, together with lesser amounts of mica (including lepidolite), spessartine, tourmaline, and locally, spodumene. Fine-grained (30 µm to 300 µm), tantalum-bearing minerals occur in the quartzo-feldspathic matrix of the dikes as disseminations, in interstices, and in small vugs. The nature of the tantalum-bearing mineral assemblage present in individual pegmatite dikes varies from a simple mineral assemblage composed of ferrocolumbite (with around 39 wt% Ta2O5) in the most northerly dike, to more complex assemblages comprised of manganotantalite (with up to 75 wt% Ta2O5), ferrotapiolite (with up to 79 wt% Ta2O5), and microlite (with up to 76 wt% Ta2O5) that are present in dikes located several kilometers to the south and southwest. The compositional characteristics and textural relationships of the tantalum-bearing minerals in the dikes provide evidence of igneous fractionation trends that are typical of rare-element granitic pegmatites. Such trends suggest that the newly discovered pegmatites represent part of a more extensive group of cogenetic, tantalum-mineralized dikes.

Jan 1, 2001

By S. Avalos, J. M. Ortiz, W. Kracht

Semi-autogenous grinding mills are intensive energy consumers. Current models base their energy consumption inference on operational variables and feeding ore characterization. While they provide adequate design guidelines, they are not suitable for real-time energy forecasting dealing with gaps in operational dataset and up/downstream process bottlenecks. This work explores the capability of Gated Recurrent Units to learn the semi-autogenous grinding mill consumption behaviour. Gated Recurrent Units are trained to forecast different time-support consumptions under a time-series operational dataset. The results show high performance on small supports (30 minutes) to capture local variability and long-trends while larger time supports (8 hours) can only capture time-trends but not local variability. The proposed technique seems promising for further research and implementation on real mine cases since the input variables are low-cost and easy to obtain. INTRODUCTION Current changes in the Chilean energy matrix (Román-Collado, Ordoñez, & Mundaca, 2018), from fossil fuels to renewable energies, have impacted different industries and particularly the mining sector. Solar energy incorporation into greenfield/brownfield projects will help reducing costs and will lead to rethink foundational paradigms (production and processing strategies) (Pamparana et al., 2017). Also, integration of new space-time predicting tools together with automated real-time updating models are some of the main challenges in the geometallurgical framework (Ortiz et al., 2015; van den Boogaart & Tolosana-Delgado, 2018). Those contexts encourage and demand the development of tools capable of predicting the energy consumed by mining systems, being comminution the greatest energy consumer with an average close to 50% of the entire mine consumption (Cochilco, 2013). In comminution, the semi-autogenous grinding mill (SAG) represents the largest energy consumer (~10 nominal each SAG). Theoretical and empirical energy consumption models (Jnr & Morrell, 1995; Morrell, 2004; Silva & Casali, 2015) base their inferences mainly on feed/product size distributions, SAG sizing, bearing pressure, feed hardness, water addition and grinding charge level, and commonly assume steady-state and work isolated from up and downstream processes. While those techniques provide adequate design guidelines, they are not suitable to predict hourly, daily or even weekly energy consumptions on interconnected comminution circuits where upstream/downstream bottlenecks lead SAGs to operate below designed regimes. Forecasting energy consumption is required by short-term energy management, medium and long-term planning energy consumption, designing the nominal capacity of renewable energy sources, among other. Also, when models are input-sensitive and some of those input measurements are expensive and/or time consuming, model robustness suffers when real-time predictions are required.

Jan 1, 2019

By Gordon A. Irons, H. Y. Hwang

An impinging gas jet on a water surface was studied to understand momentum transfer in oxygen steelmaking. Depth, width and oscillation frequency of the jet cavity were measured and the splashes interpreted with Kelvin-Helmholtz instability and combined Rayleigh-Taylor and Kelvin-Helmholtz instability theory. A model to calculate separate gas and liquid velocities, applying the exact momentum boundary condition, is proposed.

Jan 1, 2004

By T. P. R. de Jong, H. Harbeck

"This contribution reports recent mineral sorting experience and lists the opportunities of the newest generation of automatic sorters with a special focus on electromagnetic detection and Xray transmission. With the available sensor resolutions and actuator systems that are available today sorting of minerals down to 2 mm size and up to 250 mm lump size is technically feasible. In industry, ore as well as coal is still hand-picked and current automation potential only utilised in a handful of specific applications. Recently a number of technological developments took place that may increase sorting potential, save mill costs and lead to lower overall tonnage costs.They are:??High speed and high resolution sorting systems based on X-ray transmission imaging??High speed on-line image processing and further development of advanced data processing??Modular multi-sensor automatic sorting units (using one or more sensors such as colour, electromagnetic and X-ray in a single device)??Sensitive electromagnetic sensors for sorting based on differences in magnetic susceptibility and electric conductivityThe above enables compact dry separation, insensitive for moisture fluctuations and at high separation sharpness, as well as “electronic” high gradient magnetic separation for larger particles. Besides conventional X-ray transmission (XRT), dual-energy XRT (DE-XRT) is now being redesigned to meet the requirements of the mining industry. The mentioned technologies provide automatic dry separation of minerals and rock as alternative for conventional processing."

Jan 1, 2005

By Werner Unland, Nick Holl

"The paper presents the engineering design and experience gained so far with a dewatering system for an open-pit uranium mine planned at Key Lake in Northern Saskatchewan.The results of hydrogeological investigations preceding engineering exhibit an extensive unconfined overburden aquifer hydraulically connected with the underlying Athabasca Formation and basement rocks, both of relatively low hydraulic conductivity. The overburden aquifer is embedded in a bedrock trough, with the deepest depression between the planned pits. The hydrogeological data were used in a numerical dewatering model simulating groundwater flow atdifferent stages of the pit development.Based on the model results, the engineering design had to provide for different pumping rates, varying between 1.0 and 0.21 ms/sec. This problem was solved by using a double line pressure system. The design concept for the complete peripheral discharge system and the well design used for 26dewatering wells are discussed.Experience with reverse-circulation techniques applied for the construction of the dewatering wells is presented. Theoretical and practical considerations which led to the constructionof wells of different diameters are discussed.The design of the in-pit dewatering system provides for seepage ditches, horizontal drains, pit-bottom sumps and inpit dewatering wells where required."

Jan 1, 1980