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By Michael Arnold, Jonathan Delgado

In 2017, Bauer Foundation Corp. (BFC) was awarded the contract to install the deep foundations for the new 17-story Hotel Tower and the Low Rise Casino Expansion at the Seminole Hard Rock Hotel and Casino in Tampa, Florida. The site was underlain by extremely challenging Florida Limestone geology and surrounded by occupied existing buildings and infrastructure. To overcome the challenges of the difficult subsurface conditions, and to successfully complete the foundation installation without impact to the surrounding buildings and casino operation, Langan Engineering (EOR) and BFC were required to modify both the design and installation techniques during construction. The scope of work included 147 temporarily cased drilled shafts to depths up to 230 ft (70 m) below ground surface (BGS), 76 permanently cased micropiles up to 200 ft (61 m) BGS, and more than 300 augered-cast-in-place (ACIP) piles up to 125 ft (38 m) BGS. Voids and zones of high permeability in the limestone created many challenges for execution of the foundation scope including ACIP piles overbreaks of more than 400% above neatline volume, and construction induced ground subsidence/collapses adjacent to structures supported on shallow foundations. This paper will discuss site limitations, design and construction challenges, difficult geology, varied soil conditions, and lessons learned. PROJECT The project is located at Seminole Hard Rock Hotel and Casino Tampa, Florida, as shown in Fig. 1. Seminole Tribe, the owner, started the construction of a new 17-story Hotel Tower and the Low-Rise Casino Expansion at the beginning of 2017.

Jan 1, 2018

By Anthony Konya, Calvin J. Konya

The publication, RI8507, from the U.S. Bureau of Mines established an envelope equation that related scaled-distance to peak particle velocity in an attempt to predict ground vibration in the design phase of a blast. This has been further modified by Oriard, Dupont, Konya & Konya, and others to develop more refined prediction models for specific situations to obtain better predictions. While these equations can be an ideal starting point for a greenfield blasting project or a project with no given information, these equations can have errors.

Jan 1, 2018

By Henrik Schiellerup, Irene Zananiri, Johan Nyberg, Thomas Kuhn, Luis Somoza, Teresa Medialdea, Maria Judge, Pedro Ferreira, Gerry Stanley, Javier González

The GeoERA Co-Fund action is a joint contribution of 48 national and regional Geological Survey Organisations from 33 European countries “Establishing the European Geological Surveys Research Area to deliver a Geological Service for Europe (GeoERA)”. This is an ERA-NET action under Horizon 2020. The aim of GeoERA is to fund transnational projects contributing to the best use and management of the subsurface, addressing the following four themes: Geo Energy, Ground Water, Raw Materials and Information Platform. The European Commission recognises the significance of raw materials through its Raw Materials Initiative (RMI), the European Innovation Platform on Raw Materials (EIP-RM) and Horizon 2020 funding, specifically through Societal Challenge 5 – Climate Action, Environment, Resource Efficiency and Raw Materials. The GeoERA Raw Materials Theme will contribute to research and innovative developments for minerals inventory, minerals yearbook, exploration, mapping, modelling, metallogeny and critical raw materials in the pan-European framework including the sea. A major element in Europe’s long term economic strategy is to ensure security of supply for strategic and critical metals as part of the Blue Growth Strategy developing sectors that have a high potential for sustainable jobs and growth as seabed mining. The project MINDeSEA results of the collaboration between eight GeoERA Partners and four Non-funded Organizations at various points of common interest for exploration and investigation on seafloor mineral deposits. The Geological Surveys of Spain, Germany, Greece, Ireland, Norway, Portugal, Sweden and Ukraine are organisations with responsibility for coastal, marine geological investigation and mineral resources studies and mapping in their respective countries. The Non-funded participants: the Instituto Português do Mar e da Atmosfera; the United States Geological Survey; the All-Russia Scientific Research Institute for Geology and Mineral Resources of the Ocean; and the Geosciences Institute, host important databases, they have an international reputation for excellence in both science and technology, and are internationally-known experts on seafloor mineralisation and hydrothermal systems. This project addresses an integrative metallogenetic study of principal types of seabed mineral resources (hydrothermal sulfides, ferromanganese crusts, phosphorites, marine placers and polymetallic nodules) in the European Seas. The work program includes all the regional seas around Europe comprising the Atlantic Ocean, the Mediterranean Sea, the Baltic Sea and the Black Sea (Fig. 1). The MINDeSEA working group has both knowledge of and expertise in such types of mineralisation, providing exploration results, sample repositories and databases to produce innovative contributions. The importance of submarine mineralisation systems is related to the abundance and exploitation-potential of

Jan 1, 2018

By Ryan Brogden

On the 5 September 2014 a road train (tractor-trailer) with two trailers carrying ammonium nitrate was involved in a single vehicle accident on the Mitchell Highway, 30 kilometers (18 miles) south of Charleville in Central Queensland, Australia. The ammonium nitrate was being transported to a mine site for use as a blasting explosive. The truck came to rest in the creek bed adjacent to a road bridge and caught fire. The vehicle burnt for over one hour before the load of ammonium nitrate exploded. Miraculously there were no fatalities; however eight people nearby sustained injuries, some seriously. The road and rail bridge over Angellala Creek were destroyed and vehicles in the nearby vicinity were seriously damaged. The truck carrying the ammonium nitrate was completely destroyed with over 2500 pieces of debris scattered up to one thousand yards (one kilometer) from the blast site.

Jan 1, 2018

"INTRODUCTION In recent years, there has been increasing focus on environmental and social impacts of the extractive industries, climate change and resource scarcity. The concept of the circular economy aims to replaces the “take-make-dispose” economic model with one that eliminates waste of all kinds and is restorative by design. Such closed-loop systems implicitly aim to reduce the quantity of primary extracted materials entering the economy, thereby affecting supply and demand dynamics, hence mining industry economics. For the metals industry, the ability to engage in, or adapt to the circular economy can be heavily affected by industry structure and geographical factors. Eco-efficiency initiatives that reduce waste and environmental impact may help the mining and metals industry align with some of the goals of the circular economy. This paper focuses on base metals, and explores case studies in copper, lead and zinc. It analyzes primary and secondary metal production, and recycling. It examines company structures and how these affect engagement with the circular economy. CIRCULAR ECONOMY PRINCIPLES Ellen MacArthur Foundation (2012) describes the circular economy as “an industrial system that is restorative or regenerative by intention and design”, which “replaces the ‘end-of-life’ concept with restoration”, and “aims for the elimination of waste through the superior design of materials, products, systems, and, within this, business models”. The concept is systems focused. For materials such as metals, a series of loops are considered, including maintenance of devices, reuse, refurbishment and recycling. Potential methodologies to achieve circular economy outcomes include disassembly and reassembly of manufactured goods, leasing rather than buying major appliances, and converting to renewable energy sources. The circular economy is partially aligned with the principles of eco-efficiency, which relate to reducing the environmental impact per unit of a material produced. PRIMARY AND SECONDARY METAL PRODUCTION Base metals (copper, lead, zinc and nickel) are essential ingredients in modern economies and are key commodities produced by the global mining industry. Metal production can be categorized as primary or secondary. Primary metal comes from the processing, smelting and refining of metal content extracted from ores, while secondary production comes from metals recovered from recycled streams (e.g. recycled lead-acid batteries, copper wire scrap, etc.). Metals are stored in natural, anthropogenic in-use and anthropogenic waste stocks. An example of the stocks, flows and processes associated with global copper extraction and use is shown in Figure 1."

Jan 1, 2018

By D. E. Cameron

"INTRODUCTION Grade control requirements for base and precious metal projects are an important input to both conceptual and feasibility mine plans. It’s the author’s experience that grade control input is insufficient at these critical stages. The few exceptions are a stimulus for this paper. A significant portion of CRC’s practice has involved assisting operations to solve grade control issues which were finally recognized as contributing to negative production variances. Even in operations perceived to be successful, deficiencies in grade control are often masked by measures taken by an operation to compensate a deficiency in one area with outperformance in another. The advantages in having a realistic and adequate grade control plan developed at an early project stage by a geologist(s) with considerable operations experience are manifold. It’s important for the geologist to prepare clear inputs into the mine plan backed by detailed supporting information in usable, flexible formats. When the decision is made to advance a project, the exploration team passes its model to a mine planner. The team doesn’t usually provide a detailed grade control plan with the block model, thus the planner tends to treat grade control as an activity to be rolled into a broader operating category. The consequences of highly compartmentalized mine planning can be severe in the long run. Once a plan is tabled, and especially once production begins, it is very difficult to improve grade control outside the fixed parameters of the operation. Major fixes tend to be costly in terms of time and dollars. Implementing needed changes to the grade control practices and culture in an established mine can present almost insurmountable difficulties. Hypothetical examples of grade control planning are presented to illustrate the author’s points. The diagrams are conceptual and schematic; any resemblance to actual deposits is coincidental. BEYOND 50¢/TON In more than a few cases, grade control cost is buried in a subcategory of mining cost with little more consideration than a plugged number. It is possible to do a word search in 43-101 Technical Reports on advanced projects and without finding reference to “ore control” or “grade control”. The idea is to reach the orebody by the shortest and least expensive means, achieving production and investor payback at the earliest possible occasion. This entails a low stripping ratio pit or a decline ramp with sills on ore to prepare the first stopes. The processes to achieve the target production, one of which is grade control, will fit into this framework. After all, there is a block model and the planner can see the grade and tons in each block. The exploration geologist whose responsibility was to bring a large percentage of the deposit into mineral resource owns the model and has released it to planning. Now comes the planning stage. Mine geologists haven’t been hired yet and they will be phased in with production. What could go wrong? Larger companies may have the geologists with operating depth who will be inserted into the mine planning discussions, but it’s not a given. Junior companies must often delegate the conceptual and detailed planning tasks to consultant groups. Is a senior-level grade control review part of the scope of work for the mine planning? If a good grade control plan is in place before the mine geology team is staffed, a key element of success is assured."

Jan 1, 2018

By Xiaolu Ye

"Comprehensive utilization of Bi and Sn from the tin-associated polymetallic tailings by “gravity separation – flotation combination process” has been studied, which was verified that the novel process is an effective method to deal with the high content pyrrhotite tin-associated polymetallic tailings. In this investigation, ore property analysis and magnetism analysis of pyrrhotite were conducted to research and develop reasonable beneficiation flowsheet. The results of ore property analysis present that pyrrhotite was not closely related to bismuth and tin minerals. Particle size analysis results indicated that pyrrhotite was mainly in the form of fine particles. The magnetic analysis results show that pyrrhotite was distribution in all the three types of pyrrhotite in a single mining area, which indicated that variable magnetism of with different crystal structure pyrrhotite. The process of “low intensity magnetic separation - high intensity magnetic separation” shown an excellent adaption for the high content pyrrhotite tin-associated polymetallic ore compared with the single flotation process based on the magnetism variable of pyrrhotite. The results of whole process test indicated that a bismuth coarse concentrate assaying 5.63% of Bi at 81.77% recovery was obtained, which treat the conditions for the Bi-S separation flotation. In addition, the content of sulfur in the tin concentrate decreased from 2.5% to 1.5%, which provided a new reference for other tin-associated polymetallic tailings. INTRODUCTION Tin has been applied extensively in catalytic chemistry, gas sensors, tin plating, and plumbing. Tin-bearing polymetallic ores have been the important deposit types to recycle tin with the rapid depletion of mineral resources. The comprehensive utilization of the associated elements has been a preoccupation for the mineral processing researchers."

Jan 1, 2018

By J. X. Zhang, F. S. Niu

"In order to accurately detect whether the collision occurs between particle and bubble in flotation process, a collision detection method of particle and bubble, which based on morphological image processing and Otsu method, is presented. First of all, it utilizes image pre-processing to optimize images, the target area and the background area are segmented by Otsu method. Then, particle and bubble are fitted to a circle combined with the least-square method. It’s convenient to obtain the coordinate information and radius. Finally, the position of all particles is extracted to an image, which achieves the particle tracking and avoids the complexity of the continuous frame image tracking.Experimental analysis shows that the relationship between the two ordinate difference d and the bubble radius r has a certain influence on the collision detection when the dripping particles are close to the bubble, when d>r, the detection accuracy is 92%;When d=1/2r, the detection accuracy is 97%;When d=0, the detection accuracy is 100%. The result indicates that this algorithm can detect the collision between particle and bubble quickly, and the working hours of manual test are saved effectively ,the best position of dripping particles close to the bubble which is taken with a CCD camera should be in the range of the particle and bubble’s ordinate difference less than half of the bubble radius.INTRODUCTIONFlotation is an important technical means to separate useful minerals from ores. The flotation process of ores and materials in the world is treated by flotation technology up to billions of tons every year, so the study of flotation process is particularly important. Raising the collision probability between mineral particles and bubbles in flotation process is one of the key factors to improve flotation separation efficiency[1]. The study indicates that[2-4] the collision probability between particles and bubbles is influenced by many factors, such as particle density, particle size bubble size, etc. The analysis of these influential factors requires a lot of experiments. Therefore, it is of great significance to design an accurate collision detection method for the research of this field."

Jan 1, 2018

By R. V. Kononko, A. Yu. Chikin, R. N. Rakhmeev, Yu. O. Fedorov

"The focus of the study is finding a solution that can help to improve diamond recovery in diamond-bearing gravity concentrates upgrading flowsheets. The purpose of the study was to develop and prove scientifically a separation method of diamonds recovery from gravity concentrates regardless of their fluorescence ability induced by X-ray radiation. Two promising recovery methods applicable to diamonds of this type are proposed, i.e. an X-ray radiometric method based on an instantaneous analysis of a secondary X-ray spectrum of separated particles, and a triboelectric method that relies on noncontact measurements of particle charges obtained during its motion in a vibratory tray. As a part of the laboratory study, X-ray fluorescence spectra of the collection of diamond crystals and main associated minerals and rocks at a particle size of -6+3 mm were produced. The analysis of the produced secondary X-ray spectra showed a significant difference between crystals, minerals and rocks within the analytical area of Ca, Fe and Zr due to the absence of calcium, iron and zircon elements in diamonds. Additionally, the scattered X-radiation level of diamonds substantially increased under the influence of X-ray radiation. Such a difference is a physical base of a new method of diamonds recovery from mineral mixtures. The laboratory study on triboelectric characteristics showed that a significant portion of diamonds gained an electric charge of a magnitude that was much higher, compared to associated minerals and rocks. The laboratory and industrial tests and the separation indicators demonstrated a high efficiency. A proposed X-ray radiometric method provides recovery of all types of diamonds regardless of X-ray fluorescence levels, with high selectivity and recovery rate of at least 98%. This proposed separation method is protected by a patent of Russian Federation (No. 2551486, “A method of X-ray radiometric separation of diamond-bearing materials”). Triboelectric separation organized in two stages (main and control) ensures recovery of up to 98-100% of diamonds at a particle size -5+2 and -2+1 mm,. More than 10 triboelectric separators successfully operate in active diamond processing plants in the Russian Federation."

Jan 1, 2018

By Yuliy Rubinstein

"The paper presents a analysis of the history and the trends of development of flotation apparatus. The laws of their evolution are stated and the place and role of column flotation are indicated. It is demonstrate development and different design of column apparatus. The major parameters of column cell such as diameter and height are discussed. Options are proposed on optimization of hydrodynamic characteristics of columns with large-capacity cells. High efficiency of columns with cell height of 4-6 m is shown on examples of coal preparation. A new generation of multi sectional column cells has been developed. In the cells are zones with different aerohydrodynamic parameters: combined in the machine are co-and counter- counter flows of phases. The transition from single-chamber column to multi-sectional apparatus makes it possible to create favourable hydrodynamic and aeration regimes in each section of the column dependent on the pattern of material distribution by floatability. Efficiency of application different designs column apparatus uses shown on the example of enrichment of various non-ferrous metals ores and coal. The principles of mathematical simulation of the flotation process are developed. A scaling-up procedure for column cells was based on flotation macro- and micro- dynamics simulation.INTRODUCTIONColumn flotation is considered to be one of the most significant achievement in the field of mineral processing in the end of last century. We cannot but agree with this statement but would like to understand what underlies this success. History of the flotation column can not be considered in isolation from the development of flotation apparatus on the whole. It can be argued that the first attempt to switch from oil flotation to the use of bubbles during flotation was performed Bessel brothers in 1877 (Berlin patent 42 class 22, July 2) and in 1886 (Berlin patent 39,369 May 12). According to these patents, the crushed ore was mixed with oils , hydrocarbons and water. Then the pulp received in this way was heated up to boiling . Air bubbles and steam formed during boiling facilitate the flotation of ore particles coated with oil (first patent) or bubbles been generated by the reaction of lime with acid (second patent). The evolution in the design of the flotation apparatus incorporates the following key stages. Further development is connected with the Francis Elmore’s idea to use gas bubbles received at water electrolysis (UK, 13578; 1904). This method was not introduced then, but much later, in our time and on the essentially new technical basis it found a use for sewage treatment (electroflotation). Gas bubbling under vacuum patented also by Elmore (UK, 17816; 1904) obtained a practical use. It should be noted that the method did not lose its importance till now. The design of the camera has been surely optimized (Glembotskii etal, 1963). A year later A. Macquisten (UK, 26712) developed pressure (compression) flotation. Thus, the H.Sulman, H.Picard, D. Bell’s (US, 853120, May 29, 1905) basic patent and the adjoining T. Goover’s patent 1910 (US, 953746) formed the basis of the first and most important element of modern flotation: flotation with air bubbles sucked in from the environment. In 1914, J.Callow received a patent for on an apparatus where air was sparged through the porous false bottom of the cell ( US, 1104755). Woolen fabric folded four times was fixed on a perforated metal frame to be used for air sparging (Gaudin, 1932). The following year Durrel created the prototype of the injection (ejector) apparatus. The jet aerator made it possible to significantly reduce the size of the bubbles, in comparison with the filter cloth. An apparatus with slurry pre-aeration in an airlift prior to feeding into separation cell was developed Wagner in 1917 (US, 1235083). And finally, the first column apparatus with a counter-current of slurry and air was developed by M. Towne and S. Flynn in 1919(US, 1,295,817). ("

Jan 1, 2018

By A. Singh, M. Ntlhane, V. Ross, M. Dlame

"Fine valuable particles are often lost to flotation tailings streams due to inefficient collection by air bubbles as well as passivation of surfaces by oxidation and slimes. The application of high-shear hydrodynamic cavitation devices (HCDs) to overcome this problem has already proven to be a considerable success in the industry. This paper details the results of further investigations that were undertaken at Mintek to better understand the mechanisms involved when preconditioning feed slurries in an HCD. By promoting inter-particle attrition and conditions of high shear within the reactor, cleaning of particle surfaces is enhanced as well as the formation of superfine (nano) bubbles which are believed to aid their agglomeration and subsequent collection by normal sized bubbles. In order to broaden the envelope of understanding with regard to application of the technology, rather than tailings material as investigated earlier, a Platinum Group Mineral (PGM) UG2 ore from the Bushveld Complex in South Africa was used in this study. The results of a series of batch flotation tests in a 10L Denver cell are presented, being conducted after the feed has been subjected to different methods of preconditioning. It was demonstrated that the preconditioning significantly improved the flotation kinetics of the PGMs, the optimum being obtained after around 20 passes through the reactor. This was accompanied by a much enhanced recovery-mass pull relationship and a significant improvement in the grade-recovery response. Significantly, the selectivity between the PGM and the deleterious chromite (expressed as Cr2O3) gangue more than doubled under these conditions. Modelling of the PGM data by means of the modified Kelsall model indicated that both the fast and slow floating rate constants were improved.INTRODUCTIONIt is well known that the flotation recovery of fine and ultrafine particles, typically less than 10 micron in size, is a challenge (Yoon et al., 1989; Miettenin et al., 2010). Although these particles are typically well liberated, due to their very low mass and inertia, the collision efficiency with air bubbles is low as a result of the inability of particles to penetrate the liquid streamlines around bubbles. Hence the probability of contact is often regarded as the ratedetermining step in flotation of ultrafine particles. Introducing more power into conventional flotation machines is likely to solve only part of the problem, as conventional mechanisms are effective only to a point in terms of shear and micro-turbulence. Further challenges are posed by the treatment of low-grade or oxidised tailings dump material, where valuables are passivated due to prolonged exposure to the atmosphere or slimes. Over the years, various mitigating strategies have been investigated, including the use of dissolved air flotation (Martinez-Gomez et al., 2013; Calgaroto et al., 2015), shear flocculation (Subrahmanyam and Forssberg, 1990), seed or carrier flotation (Tabosa and Rubio, 2010), sonication to clean particle surfaces (Aldrich and Feng, 1999; Newell et al., 2006), high intensity conditioning (Bulatovic and Salter, 1989; Chen et al., 1999; Tabosa and Rubio, 2010), and various electrochemical approaches such as changing Eh in order to promote formation of dixanthogen, dissolution of oxidation products by lowering the pH, activation by sulphidisation (Newell et al., 2006; Becker et al., 2014), and the use of alternative collectors."

Jan 1, 2018

By Francisca San Martín, Martin Rudolph, Willy Kracht, Tomás Vargas

It has been shown that bacteria Acidithiobacillus ferrooxidans can be used to depress pyrite in seawater flotation at natural pH, which opens the possibility for its use as an alternative to lime to depress pyrite in copper sulfide flotation. In order to have a better understanding of the mechanisms involved in pyrite depression with A. ferrooxidans, an exploratory experimental campaign was carried out, including attachment density and contact angle measurements, and the effect of adding bacteria before or after collector. Biodepression of pyrite improves when increasing pH from 3 to 8, with a decrease in recovery from 92% to 36%. This increase in depressing capability is accompanied by an increase in attachment density, from 2.58×108 bacteria/g to 1.99×109 bacteria/g at pH 3 and 8, respectively, suggesting that the mechanism of depression is related to the attachment of bacteria to the pyrite surface. It was observed that the conditioning sequence with collector and bacteria influences the biodepression capacity of A. ferrooxidans. Having as a reference a value of pyrite recovery equal to 97%, when using only xanthate in seawater flotation at pH 8, the effect of both conditioning with bacteria-followed-by-xanthate and xanthate-followed-by-bacteria were assessed. When bacteria were added before the collector, the recovery of pyrite decreased to 36%. On the other hand, when bacteria were added after collector, the recovery was 64%, showing that biodepression of pyrite with Acidithiobacillus ferrooxidans is more efficient when the conditioning is carried out first with bacteria. The contact angle values show that there is little effect of the second component added to the system, i.e., if pyrite is first conditioned with bacteria, the contact angle does not change significantly once the xanthate is added (bacteria-followed-by-xanthate). The same was observed when the conditioning sequence was xanthate-followed-by-bacteria.

Jan 1, 2018

By G. Pahomova

"It developed an alternative to traditional flotation enrichment refractory of complex lead-zinc ores to obtain conditional lead and zinc products. The scheme involves the use of the processing method of gravitational enrichment of the primary cycle and the combined gravity-flotation-hydrometallurgical in finishing. The method has a high level of comprehensive utilization of mineral raw materials in relation to the elements that are extracted in the process of enrichment in lead concentrate, and the increase in recoverable value of processed ores. INTRODUCTION The primary source of lead are complex sulphide lead-zinc ore, lead ore actually rarer. The value of lead and zinc ores (except lead and zinc) is determined by the presence in them of a wide range of associated components: silver, contained mainly in galena; gold; bismuth in the form of its own minerals, but is associated with galena; cadmium contained mainly in the sphalerite; indium, thallium and gallium contained in sphalerite and galena; selenium and tellurium are present as impurities in the sulfide, tellurium is also found in the form of its own minerals. Of note harmful impurities antimony, which is often associated with lead sulphosalts and arsenic, having a substantially own minerals. By quality (content of lead, or the total content of lead and zinc) lead-zinc ores are divided into rich, ordinary and poor; by oxidation - to sulfide (with a lead oxides content less than 15% and zinc oxide content less than 10%), mixed and oxidized (50% oxide); the latter have a subordinate importance as a source of zinc and lead. Traditionally, the most contrasting technological properties of sulfide ores of nonferrous metals considered flotation properties, which determines the priority in the selection of flotation technology of their enrichment. Other methods of enrichment - gravity (jigging and enrichment in heavy suspensions), radiometric sorting (separation) are used as preliminary operations whose main purpose is to increase the content of lead and zinc in the ore sent to flotation, as well as the removing of part of empty rock in dumping tails prior to flotation. Effective implementation of these methods is possible at large size emphasizing in the ore of lead and zinc minerals, which is typical of the rich ores and which so far mainly worked. At the same time, non-ferrous metal ores (polymetallic, lead-zinc, copper-zinc, etc.) have a sufficiently high contrast to gravitational properties since ore minerals have a higher density compared with a rock minerals. But the gravity of the practice of non-ferrous ores enrichment is not widely used, despite its high degree of environmental safety and lower cost expensive."

Jan 1, 2018

By S. Banisi, A. R. Hasankhoei, A. R. Ghasemi, E. Razi, G. A. Parsapour

At the pelletizing plant of the Gol-E-Gohar mining and industrial company two parallel dry closed grinding circuits, each with the average throughput of 300 t/h, are used. Each grinding circuit consists of a burner, a dry ball mill (6.2 m×13 m) and an air separator. The ball mill consists of a 2 m-long drying and an 11 m-long grinding chambers. The iron ore concentrate is fed to the drying chamber by a feed chute. The first 1.35 m of the drying chamber consists of 56 flights in two rows to decrease the feed moisture from 5% to below 0.2% and the rest of dryer chamber consists of deflectors to pass the material to the grinding chamber. It was found that when the feed moisture content increased from 1.3% to 3.5%, the throughput decreased by 12% (35 t/h) indicating a low performance of the dryer. Monitoring the wear rate of flights for a period of 12 months showed that the first 0.8 m length of the flights length did not experience any wear. This means that about 59% of flights do not contribute in material distribution and drying. A DEM simulation of feed chute and the drying chamber demonstrated that due to the inappropriate design of feed chute most of materials do not get in touch with the first 0.8 m length of the drying chamber. To overcome this problem, various feed chute designs with different geometries were simulated by the KMPCDEM© software. With the aim of arriving at a proper material trajectory, where the total length of the flights are used, a new feed chute was selected. The simulation results indicated that if the height of the flights is increased from 1.60 to 2.26 m and the slope is increased from 45 to 48 degrees the material arrive at the first 0.48 m of drying chamber. In this manner, the unused part of the drying chamber decreases from 59% to 36% of the length. After installation of the new feed chute, during a period of three months the throughput increased by 36 t/h.

Jan 1, 2018

By A. Mainza, H. Hill, L. S. Bbosa

"Impact breakage is the most elementary size reduction mechanism in comminution devices. In comminution research, characterization of breakage is primarily concerned with the energy expended to cause it. The main challenges of this approach have been quantifying the actual energy requirements of impact breakage and developing mechanistic models to accurately describe the process. For engineering load analysis, fracture is characterized in terms of strengths such as yield stress and ultimate tensile stress, which govern the maximum loads specific materials can be subjected to before irreversible inelastic deformation and subsequently complete fracture occur. With this approach, the main challenge has been to elucidate the underlying mechanism, in the means that the load causes weaknesses in the material microstructure to act as sites for stress concentrations, leading to crack initiation, propagation and eventual failure. Studies dedicated to investigating particle fracture under impact loading have led to the development of several devices for conducting breakage characterization tests. These devices include the drop weight tester, split Hopkinson pressure bar, rotary breakage tester and the short impact load cell. All these have different particle loading and breakage methods, and thus can yield distinct information which can be compiled together to study a material and the nature of breakage. This work analyses the single impact breakage data obtained across the listed devices. A homogenous ore commonly known as blue stone is used for all breakage tests. The work is conducted using standard procedures specific to each device as closely as possible. Drop weight and rotary breakage tests were used to obtain hardness parameters based on an existing t10 breakage model, while split Hopkinson pressure bar and short impact load cell measurements provided properties based on conventional engineering load analysis. The results were used to highlight the significance of the loading geometry, impact mechanism and impulse on the extent of breakage."

Jan 1, 2018

By William Gleason

"The mining industry tends to focus on very large numbers, whether it’s talking in terms of size of deposits, tons of material mined, the equipment used or the dollars spent. The numbers associated with mining projects are often in the hundreds of millions, but sometimes it’s the little things that can have the biggest impact.Take, for example, the Rosemont Copper Project in Arizona. Owned by HudBay Minerals, the Rosemont Copper project, when in production, is expected to be one of the largest copper mines in the United States, accounting for about 10 percent of total copper production with annual production expected to be 110 Mt/a (243 million lbs/year). However, the project is currently mired in a years-long permitting process. At the 2017 SME Arizona Conference in Tucson, AZ, Kathy Arnold, director of environmental and regulatory affairs for Hudbay Minerals, spoke about the project and the efforts to get it into production.She opened her presentation with the unfortunate news that her 2017 presentation would not be that much different than the 2016, 2015 or 2014 presentations she gave to the same conference. That’s because, as of Dec. 4, 2017, the project had been in the permitting process for 3,797 days, more than 10 years. The process began when Rosemont submitted its initial mine plan in 2006 and a revised one in 2017. The official start to Rosemont Copper’s National Environmental Policy Act (NEPA) started in 2008.In June 2017, the project received its Final Record of Decision from the U.S. Forest Service, moving it a step closer to production. Yet it still faces stiff opposition from opponents while it works to secure the Clean Water Act Permit from the U.S. Army Corps of Engineers and to complete its final mine plan of operations.In her presentation, Arnold said the long process taught her many lessons, including approaching things with a different mindset. More than 130 pages worth of public comments have been collected over the years. The concerns expressed range from lighting issues to pavement to preserving land for a jaguar that was spotted on the property and named El Jefe.“A lot of things that people worry about seem to be small things, but we had to have a different mindset and be open-minded to the concerns,” Arnold said. “That is the commitment we made.”"

Jan 1, 2018

By K-O. Mickelsson, S. Töyrä, H. Esbensen

Accurate information of physical, chemical and metallurgical quality characteristics such as moisture content, iron grade and particle size are crucial for successful process control and for producing products within customer specifications. Correct moisture content of pellet feed is an important variable for successful balling of iron ore pellets and to minimize power consumption in the sintering process. Control of the filtering process in the pelletizing plant is therefore essential for both productivity and high product quality. The current measurement systems for moisture content at LKAB are based on two types of manual grab sampling, subsequently analyzed with rapid moisture determination methods. Previous studies of the measurement systems have indicated high sampling variability resulting in lowered possibilities for successful process control. The objective of the present study is to evaluate an alternative filter sampling approach and testing of on-line Infra-Red analysis (IR-analysis). On-line IR-analysis has the advantage of eliminating physical sample extraction and allowing for continuous monitoring of moisture content. However, this approach is sensitive to the surrounding environment, making careful calibration and control crucial for the quality of measurement results. Furthermore, as IR-sensors only target the surface of the conveyed pellet feed, several incorrect sampling errors need to be considered and counteracted to eliminate sampling bias and reduce the remaining measurement variability. Variographic characterization was applied to the two current grab sampling approaches of combined filtered material, to the alternative filter sampling method, and to the On-line IR-analysis. The results indicate that both the sampling of separate filters (using composite sampling and ISO-standardized moisture analysis), as well as a calibrated and well- maintained IR-sensor can improve the relative variability significantly, by lowering the total measurement system variance from 60% to 25%.

Jan 1, 2018

By Y. Foucaud, I. Filippova, L. Filippov

Flotation is the most common beneficiation route for tungsten ores, but the predominance of minerals with similar surface properties poses a real challenge. This study investigates the use of Falcon centrifugal separators for gangue minerals removal and desliming prior to flotation. A typical tungsten-bearing skarn ore (Tabuaço, Portugal) is used, containing scheelite (CaWO4) associated with dense calcium-bearing silicates (vesuvianite), fluorite, apatite and light silicates (feldspars) as gangue minerals. Two types of Falcon bowls (Falcon UF and Falcon SB) were used, prior to flotation tests with fatty acids as collectors and a combination of sodium carbonate and sodium silicate as gangue minerals depressants. This flowsheet was compared with a reverse configuration, using flotation prior to Falcon concentrator, and with a classical flowsheet, using hydrocyclone and flotation. Gravity pre-concentration and desliming with the Falcon concentrator were optimized through the design of experiments (DoE) methodology. The influences of pulp density, rotational speed, feed flowrate and fluidisation pressure (for the Falcon SB) were studied for both bowls. Results showed that the Falcon can be used as a desliming and pre-concentrating apparatus. Separation performances depend mainly on rotary speed and pulp density for the Falcon UF, whereas rotary speed and fluidisation pressure are the main parameters for the Falcon SB. With only one stage of Falcon SB, an enrichment ratio of 7.9 is obtained with a 65% WO3 recovery while 89% of apatite and fluorite are rejected, which constitutes a very good selectivity. In comparison, Falcon UF shows lower enrichment ratios, around 2.7. In terms of desliming, Falcon UF is as efficient as the hydrocyclone, while the Falcon SB is significantly more efficient. Hence, the use of Falcon SB prior to flotation improves the overall performance of the tungsten flotation route by desliming the flotation feed while pre-concentrating the scheelite. It impacts very advantageously the flotation, as most of the calcium-bearing minerals are eliminated. A Falcon SB stage prior to flotation yields a final concentrate grade of 29.7% WO3 with a recovery of only 36.8 % that should be optimized as the reagents dosages were not adapted to the pre-concentrated feed.

Jan 1, 2018

By D. Milne, G. Snell

"A new method to predict stope hangingwall failure in underground excavations is proposed. This method compares movement rate for stope hangingwalls, determined from changes in strain or deformation, with changing opening geometry. This geometry is represented by the effective radius factor (ERF), a measure of relative distance to supporting abutments from an opening surface point. This strain-ERF (SERF) approach is applied to an instrumentation program for Brunswick mine near Bathurst, New Brunswick. The SERF method for this case study predicted failure at an ERF of 13.9 m and hangingwall failure actually occurred at an approximate ERF of 12.4 m.RÉSUMÉ Cet article propose une nouvelle méthode permettant de prévoir la rupture de l’éponte supérieure des chambres d’abattage dans les excavations souterraines. Cette méthode compare la vitesse de mouvement des épontes supérieures des chambres d’abattage, déterminée à partir des changements aux niveaux des contraintes ou de la déformation, à la géométrie variable de l’ouverture au jour. Cette géométrie est représentée par le facteur du rayon effectif (ERF, de l’anglais Effective Radius Factor), une mesure de la distance relative jusqu’aux appuis latéraux de soutènement à partir d’un point de la surface d’ouverture au jour. Cette approche contraintes-ERF (SERF, de l’anglais strain-ERF) est appliquée à un programme d’instrumentation pour la mine Brunswick située près de Bathurst, dans le Nouveau-Brunswick. Pour cette étude de cas, la méthode SERF prévoyait une rupture à un ERF de 13,9 mètres (m); la rupture de l’éponte supérieure s’est effectivement produite à un ERF d’environ 12,4 m.INTRODUCTIONUnderground stope design can be improved with the installation of field instrumentation. The most commonly used instrumentation for monitoring rock mass behaviour around open stopes is extensometers. The y-axis of Figure 1 represents how the changing rate of movement, measured using either displacement- or stress-type instruments, can be observed over time. The magnitude of movement measured by extensometers can give an approximation of the load on installed support (Milne, Pakalnis, & Lunder, 1996) and a changing rate of movement can indicate approaching instability."

Jan 1, 2018

"The research aimed at solving the problem of measuring instantaneous local physical quantities for multiphase flows in mineral processing, which are common in minerals industry and with significant challenges. Due to the lack of proper measurement tools currently in minerals industry, multiphase flows (such as in flotation cell) are treated as in a “black-box”. It is crucial to develop measurement technique by which the acquired processing data can be used for process optimization and control. By measuring the conductivity distribution across a measurement area, Electrical Resistance Tomography (ERT) has been adopted by many researchers to monitor and investigate many processes involving multiphase flows in other industry sectors. A compact ERT probe was built and then used to measure the conductivity distribution within a few flotation machines. In a flowing foam flotation column, the results showed that ERT can accurately measure the change of liquid content (high conductivity fluid distribution). In another part of work, based on the Green-Kubo relations, ERT can measure turbulence via the fluctuation of conductivity caused by bubbles moving through the measurement area, changing the density of the fluid. The tests with the Metso 3 m3 RCS flotation cell were also carried out for turbulence measurement under different air rates and impeller speeds. The results of flotation cell from ERT measurement showed that varying impeller speed had more pronounced influence than changing air rate. When impeller speed is increased, the size of the high turbulent zone increases. ERT is a powerful technique that has the potential to be used for a wider range of applications. The future work will be carried out with more case studies and expanded to more processes such as leaching process, high temperature flows in further downstream production chain (steel making process and alloy manufacturing process).INTRODUCTIONMultiphase flows constitute a majority of the naturally-occurring and industrially-relevant flows, especially in mineral processing. Some of the measurement techniques have been used for the study of fluid characteristics. Optical techniques such as Laser Doppler Anemometry (Kyselaa et al., 2013) and Particle Image Velocimetry (Nobach and Bodenschatz, 2009) can produce accurate measurement results with high spatial and temporal resolution, but their applications are limited to transparent flows. Hot wire probes (Amini et al., 2013) have high spatial and temporal resolution in turbulence quantification, but they are susceptible to environmental factors."

Jan 1, 2018