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By Bisweswar Das, Barada Mishra, Hrushikesh Sahoo, Swagat Rath

Banded hematite jasper (BHJ) containing 45.2% Fe, 32.64% SiO2, 0.63 % Al2O3 and 1.25 % LOI is found difficult to beneficiate either by magnetic or flotation techniques due to fine intergrowth of jasper with hematite. Phase transformation by reduction roasting with activated charcoal followed by low intensity magnetic separation to achieve a suitable iron concentrate has been attempted in this study. The mineralogy of the ore and different roasted products has been studied by X-ray powder diffraction (XRD) and scanning electron microscope (SEM) to understand the reduction mechanism. The magnetite formation is observed at 850ºC while metallic iron appeared at a higher temperature. The effects of reduction variables such as reduction time (30-270 min), temperature (750-1050ºC), and reductant (1-12 %) using activated charcoal are studied. An iron concentrate with 64.65% Fe and 55.8% recovery could be obtained under optimum conditions of temperature: 850ºC, time: 1.5 h, and reductant: 6% by weight.

Jan 1, 2014

By Tatiane Augusta Almeida dos Santos

A evolução da microestrutura de um aço inoxidável bifásico com estrutura martensítico-ferrítica (AIMF) desenvolvido pela Vallourec Tubos do Brasil S.A. foi estudada durante o tratamento térmico de revenimento através de medições in situ das frações de fase por difração de raios X. Para a liga de AIMF o revenimento é realizado para ajuste das propriedades do material e assim como ocorre com as ligas de aço inoxidável supermartensítico (AIS), este tratamento é realizado em temperaturas intercríticas. Após o resfriamento, uma quantidade da austenita revertida pode se transformar novamente em martensita enquanto outra pode permanecer retida na estrutura. Para conhecer melhor a ocorrência deste fenômeno para a liga de AIMF é essencial avaliar a sua evolução microestrutural durante o revenimento. Neste trabalho, a reversão da austenita em diferentes temperaturas de revenimento foi analisada através de difração de raios X in situ. As amostras foram também caracterizadas por microscopia eletrônica de varredura. A propriedade mecânica após diferentes condições de revenimento foi avaliada em ensaio de tração. Foi observado que há uma temperatura crítica em que a austenita revertida se torna mais estável e não se transforma durante o resfriamento subsequente.

Aug 7, 2018

By Wojciech Kasprzak, Guoxian Liang, Michel Gauthier, Mickael Dolle, Yulong Liu, Xueliang Sun, Hernando Villazon Amaris, Majid Talebi-Esfandarani, Pierre Sauriol, Thomas Bibienne, Gregory S. Patience, Delin Li, Steeve Rousselot

In the 1990s, LiFePO4 (LFP) was discovered as a cathode material for lithium ion batteries and was successfully used in the variety of devices such as power tools, E-bikes and grid accumulators. New challenges associated with use of lithium ion batteries for automotive applications demand higher performance and operating requirements, yet these requirements need to be achieved at affordable cost and without compromising vehicle safety. The advantages of LFP as a cathode material include thermal stability, limited environmental impact and potential of low cost as compared to the cathode chemistries containing cobalt. Currently, solid state and hydrothermal processes are used to synthesize LFP at the industrial scale. However, they require multiple, time-consuming steps and costly precursors. Recently, a melting-casting process to produce LFP cathode material was investigated. The motivation behind this new process is the great flexibility of raw materials including chemical makeup and particle size, and the use of lower cost, commodity chemicals, with the benefits of increased kinetics in the molten state and energy efficiencies leading to overall process cost savings. Also, if successful this process could represent a novel application of conventional casting. Melting lithium-, iron- and phosphorus-bearing precursors in near stoichiometric ratios and casting LFP material that forms around 1000 °C requires fewer processing steps.

Mar 1, 2018

By J. L. Wilson

"Many modern concentrators with VSD driven SAG mills still rely on the control room operator to manually adjust the speed in reaction to increasing bearing pressure. All too often, the problem with this strategy is by the time the operator reacts with a sudden speed increase, the SAG Mill is likely already on its way to loading up. To assist the new operators, the SAG Mill at B2Gold’s Fekola Mine in Mali needed a robust control that could handle load changes and unmeasured disturbances with minimal operator intervention. With modern Distributed Control Systems (DCS) powerful enough to run advanced control, they often have Model Predictive Control (MPC) blocks built in or available as an “add-on” license, and thus MPC can be readily implemented within the modern concentrator with a relatively low added capital cost. This paper discusses an implementation of two single output MPC controllers to control the SAG Mill at Fekola. This was implemented using the existing signals and advanced control blocks available to the installed DCS.INTRODUCTION Many modern concentrators with VSD driven SAG mills still rely on the control room operator to manually adjust the speed in reaction to increasing bearing pressure. All too often, the problem with this strategy is that by the time the operator reacts with a sudden speed increase, the SAG Mill is likely already on its way to loading up. The next step the operator may take may be to cut back the feed rate, or production until the SAG is once again stable. With this sudden reaction comes an abrupt change in SAG rotational speed and power consumption that sends a surge of material down the circuit as the mill suddenly ejects more pulp. Furthermore, choosing a higher rotational speed can lead to higher than normal liner wear as the cataract overshoots the toe of the charge and impacts the liners. After start-up at B2Gold’s Fekola Gold Mine in 2017, the SAG mill was being controlled manually. The SAG rotational speed was adjusted manually by the operator in step changes depending on whether the SAG bearing pressure was increasing, decreasing or stable. During this time of manual control, the SAG fresh feed rate was also adjusted to a tonnage setpoint with a PID controller. Generally, the SAG fresh feed rate setpoint was kept at a target value, but then the feed rate was throttled back if the SAG mill or grinding circuit showed signs of overloading. The extra challenges were that the operators had limited experience and were concurrently learning how the plant operated. Also, they were also occupied with managing situations in the rest of the plant. Often their attention was drawn away from the SAG mill and during that time, the SAG Mill would load up before they could react."

Jan 1, 2019

By D. G. MacBeth

Most belt scales on the market are factory calibrated to minimum accuracy figures of 0.1% - 0.2% at several load points. However, if the same belt scale is not properly installed and maintained on the customers conveyor then the scale will not measure up to the claims of the manufacturer or to the requirements of the operator.

Jan 1, 1975

By H. C. Cooke

THE gold mining industry, in Canada as in other countries, has passed through trying times in the past year. The strains and stresses of war have drawn away much of its man-power, both from the labour and the management. The urgent needs of the war machine have greatly curtailed the amounts of steel and explosives that can be allotted to the mines; and the loss, by enemy action, of supplies of such essential things as rubber, bids fair to reduce operations still further, if not cripple them entirely in time. And, as if these difficulties were not enough, war on the psychological front has been declared on the gold mines. Earnest supporters of the war effort, well-meaning theorists, and perhaps others whose intent is less disinterested, have all combined to clamour against the continuance of gold mining. We have been asked, what is the use of taking gold out of one hole in Canada to put it into another in Kentucky. We have been assured that gold will never again have any value, except for filling teeth. We have been repeatedly adjured to look at Germany, how well it has got along without gold. We have been told that it is unthinkable, when this nation is girding her loins for war, that labour and materials should be diverted to this useless effort. Gold miners should be diverted to the base-metal mines, where they can produce something of real value to the war effort; or to war factories; or, in fact, almost anywhere, so long as they are got out of the gold mines. And, what has made the situation even more disturbing, it has seemed as if all this clamour might be convincing governments. In fact, as you all know, the government of the United States did actually take the step of ordering its gold mines to cease operations. Fortunately, however, for Canada, the facts that no large favourable effects resulted from that action, and that, in Canada, gold mining is a much larger part of the national economy than in the United States, have caused our government, so far at least, to avoid this drastic step. In talking about this, however, let me emphasize that I have no more inside information on the subject than any of you. Like Will Rogers, all I know is what I see in the papers.

Jan 1, 1943

By Paul C. McWilliams

This Bureau of Mines report analyzes data on the physical properties of quartzite rock from the Crescent mine, Coeur d?Alene mining district, Kellogg, Idaho, to demonstrate the use of multivariate techniques. After regression, factor, component, cluster, and discriminant analyses are discussed, these techniques are applied to the Crescent mine data. Three appendixes contain some of the required mathematical and statistical detail plus heuristic examples of three multivariate techniques --component, cluster, and discriminant analysis.

Jan 1, 1978

By R. Brown, A. J. S. Spearing, M. Treinen, M. Theisinger

The mining and use of coal creates a significant amount of waste material that needs to be safely disposed of. It is likely that in the medium term, the Environmental Protection Agency (EPA) in the U.S. will categorize all such products as a new category – special waste. This would make the materials subject to many of the requirements for handling toxic waste, which will complicate the disposal of such products and significantly increase the disposal costs. Underground disposal would, therefore, seem to be the obvious solution, especially if the placed material can have low or no permeability, so that water table pollution does not present a serious long-term issue after placement. Significant additional advantages could be derived from this backfilling, including the reduction or elimination of surface subsidence, increased extraction, reduced surface waste disposal footprint and the elimination of explosion-proof seals in worked out areas. The research using a specific coal waste product as a typical example proved that the method of placing the backfill at a high density with low permeability is technically viable, but it must be made more cost effective and the other potential benefits quantified and costed in order to present a true comparison.

Jan 1, 2010

By Dan Preston, Shane Yanagisawa, Robert Marshall, Don Deere

Geotechnical Baseline Reports often estimate the number of cobbles that will be encountered in terms of volume or weight. These estimates are practically impossible to verify in the field. ClaroVia Holdings in conjunction with Frontier Kemper Constructors Inc. developed Digital Geologist 2.0 to classify and count cobbles discharged from an EPB TBM at the RSC7 project in Burbank, CA. The system worked by using two stereoscopic laser sensors with a global shutter to scan and count cobbles at 12 frames per second. Results of the effort are revealed along with lessons learned and paths for improvement.

Jun 13, 2023

By Christopher Mark

Knowledge of in situ stresses is fundamental to many studies in earth sciences, and coal mine ground control is no exception. During the past 20 years, it has become clear that horizontal stress is a critical factor affecting roof stability in underground coal mines. The theory of plate tectonics and the World Stress Map (WSM) project has been extremely helpful in explaining the sources and the orientations of the horizontal stresses observed underground. Recently, WSM geophysicists studying deep-seated stresses have developed a model of how stress magnitudes vary with depth in the crust. They have devoted relatively little attention to near-surface stresses, however. This paper explores the relationships between deep-seated and shallow in situ stresses in several of the world?s coalfields, using a data base of more than 350 stress measurements from underground coal mines. The analysis indicates that distinct regional trends exist, corresponding roughly to the regional stress fields identified by the WSM. The paper presents equations for estimating stress magnitudes that were developed by treating depth and elastic modulus as independent variables in regression analysis. The magnitude of the horizontal stress increases with depth, at rates that range from 0.8 to 2.0 times the vertical stress, just as the WSM ?critically stressed crust? model predicts. Overall, it seems that the stress regimes encountered in underground coal mines are closely linked to those that exist deep in the earth?s crust.

Jan 1, 2008

By Rob Morrison, Andrew Scott

"Long before a modern mine commences operations it has already become a wealth of information. After start up, it can generate enormous quantities of data – especially with semi-automated data acquisition by instrumented mine equipment. Much of this data is of limited use for evaluation of (potential) performance unless it links in some way to the site business model.An underlying reason for this waste of data is that the different cultures, financial, technical, community, environmental, etc, not only have many areas of interest but also have very different conceptual models by which they evaluate performance.It is too ambitious to attempt to bring all of these cultures together – in a single step. However, the success of the Mine to Mill ™ project has demonstrated that substantial operational value can be added by using a more integrated approach to comminution. The next logical step is to integrate measured data and then to track performance from ore body model to saleable product and waste disposal.The path from resource to product also represents a path from very sparse, highly variable data to much more detailed measurement and more representative sampling. However, in both cases the data collected is usually strongly focused on the technical requirements – not on the business model.This paper emphasises the difference between data and information. There is considerable potential for confusion between the two as both data and information are often expressed as numbers. For the purpose of this paper, data and information are distinguished by their uses.A data point (or datum) is a measurement. By way of contrast, information provides a basis for decision making."

Jan 1, 2003

By J. L. Coburn

The Huari-Huari ore body is located in Southern Bolivia, at an elevation of approximately 3,800 meters above sea level. The ore is a complex massive sulfide, slightly marmatitic sphalerite, in a fault fissure filled hypo- thermal vein in Paleozoic shales and quartzite-altered sandstone. The sphalerite has common associations with pyrite and quartz and is frequently intricately intergrown with stannite, chalcopyrite, and pyrrhotite. The sphalerite also contains numerous inclusions of pyrite, marcasite, galena, boulangerite, jamesonite, quartz, arsenopyrite, and cassiterite. A research program was undertaken to develop a flowsheet for the recovery of separate silver, zinc, and tin concentrates by selective flotation. Based on this experimental work and subsequent flowsheet development, engineering and construction of a 500 metric ton per day concentrator was undertaken. This paper describes the process that was developed for the Huari-Huari ore and the unique aspects of the Huari-Huari concentrator.

Jan 1, 1977

By G. Ellie, D. F. Coates

"The mining of coal in thick and inclined seams is difficult, and there are only a few countries in the world that are really interested in the problems associated with their exploitation. In France a considerable amount of investment has been made in the mechanization of systems appropriate for such conditions.For seams inclined up to 50 degrees, of normal thickness, a new system was introduced in 1967. It consists of a longwall advancing to the rise with walking props, a shearer and hydraulic backfill. During the first two years the panel productivity was an average of 25 TN/MS, and they foresee the possibility of reaching an average of 30 TN/MS.A system for thick beds, both horizontal and inclined, is in p•rocess of being mechanized. In 1969 they started with a method consisting of a longwall in a footwall slice, or sub-level drifts with walking props, and caving and drawing up to a height of 20 m of coal. Recent experiments with a shearer have produced panel productivities between 9 and 11 TN /MS, and there is hope that with experience an average of 16 TN/MS will be obtained.In 1964 a method was initiated for beds inclined from 60 to 90 degrees, based on a mechanical cutter designed by the collieries in Lorraine. An overhand slice of 4.2 m in height is taken with a drum cutter mounted on the end of a boom. Hydraulic fill is placed at the completion of a slice. The face productivity, which has been from 13-20 TN /MS, can be perhaps increased to an average of 22 TN/MS. For those companies with important reserves in inclined and thick seams, these French systems may be worth the trouble of examining in some detail."

Jan 1, 1972

By John E. Lens

How much trouble can narrow vertical fissures in bedrock cause on a shallow bedrock site? Enough trouble so end-bearing H-piles range between 8 and 100 feet long in a single pile cap and tiebacks range from 40 to over 100 feet long within a 10 foot wall span. Sloped bedrock surfaces also complicated the tieback installation as the drill casing followed the sloped rock surface while drilling and caused unanticipated bending (and sometimes breaking) of the drill string. Warned via pre-construction rock probes and cores reaching over 80 feet deep at the Winooski, Vermont project site, the design and construction team expected anomalies in pile driving and tieback drilling due to fissures in the bedrock filled with soil and weathered-rock. The degree of abruptness in the variability in the rock surface, and its impact on pile driving and tieback drilling were less predictable. Close monitoring of pile and tieback installation, redesign of pile caps, and lengthened tiebacks overcame these anomalous fissures. This paper shares the lessons learned for overcoming these geologic challenges to benefit designers, contractors bidding the work, and ultimately, the owner, with lower contingencies.

Jan 1, 2006

By Robert R. Perron

The U. S. Bureau of Mines is engaged in many diverse programs for improving mine safety. Of particular interest to the Bureau are new and improved means for minimizing the hazard of fire which can be initiated by prolonged low energy electrical faults on trolley line systems. When a high energy fault occurs on a trolley line, wherein the current exceeds the magnitude normally drawn by legitimate loads, such as locomotives, then the circuit breakers at close-by power rectifier sets trip. Tripping of the breakers not only protects the equipment at the rectifier sets, but also disconnects the energy source from the fault and thereby minimizes the fire risk. However, the fault current is frequently of a level substantially below that required to trip the overload breakers. When the fault is a substantial percentage of the set level of the breakers, the energy dissipated by the fault is frequently sufficient to clear the system by rapidly burning itself clear. Such a fault is often short-lived and does not present as serious a fire risk hazard as a prolonged, much lower energy fault, wherein the energy level is too low to clear the system. The breakdown of a trolley line insulator, in which there was a 15 to 30 ampere fault to ground, would represent such a fault or illegitimate load and a substantial fire risk.

Jan 1, 1975

By Turgut Yalcin

"High-grade concentrates are achieved in flotation columns primarily due to the use of thick froth layers and wash water, both of which facilitate the drainage of hydrophilic minerals from the froth. However, conventional columns employ tall, non-agitated recovery sections for bubble-particle attachment that require high headroom and special gas spargers as well as imposing particle size limitations. These disadvantages can be all alleviated by carrying out the recovery part of the process in a mechanical or pneumatic cell which generate froth more conveniently and efficiently.This paper describes the combining of mechanical and column flotation in a single unit and discusses the influence of various parameters on the performance of the system.INTRODUCTIONIn a flotation process, some of the minerals lifted up to the froth phase may drain back to the pulp due to various reasons such as weak attachment of particles to air bubbles, bursting of air bubbles, agitation of froth, etc. Weakly floating and entrained hydrophilic minerals drain at a faster rate than the strongly floating minerals, and effective exploitation of such differential drainage can lead to cleaner concentrates.For a given mineral, if the rate of flotation from pulp to froth is k1 (min·1) and the rate of drainage from froth to pulp is k2 (min""1), then the net (overall) flotation rate of the mineral, k (min-1 ), will be [Lynch et al., 1981 ]:"

Jan 1, 1997

By Rolf B. Pedersen, Ana Filipa Marques, Ingunn H. Thorseth, Ingeborg Okland

"Deep sea mining of polymetallic sulphides will change the physical and chemical conditions at the seafloor by creating scars when sulphides are removed, and potentially also by deposition of mine tailings at the seafloor. These changes will impact the existing ecosystems at the seafloor in and around the mined areas. Seafloor Massive Sulphide deposits that have been exposed to oxic seawater weather into Fe-metal-oxyhydroxides. However, the rates of weathering and release of heavy metals and other toxic compounds to the environment from freshly exposed sulphides in a deep-sea environment are not well studied.During a cruise to the Arctic Mid-Ocean Ridge in the Norwegian-Greenland Sea in July 2014 we will initiate in-situ experiments investigating the microbiological and geochemical processes involved in the weathering of freshly exposed massive sulphides deposits in a natural environment. This will be done by creating scars in naturally occurring sulphide deposits and by deploying weathering experiments at the seafloor. The sites will be revisited and re-sampled in 2015. The mobility and fate of heavy metals will be one of the main concerns of the study as well as constraining the time it will take for exposed sulphides to return to the chemical state present prior to mining. In this presentation we will present the experimental framework and the preliminary results from the July 2014 cruise. This project is part of the EU funded MIDAS (Managing impacts of deep sea resource exploitation) project."

Sep 1, 2014

By Francesco Vegliò, Luigi Toro, Francesca Pagnanelli

"Different hydrometallurgical processes have been studied in order to recover manganese(II) from oxidised minerals such as MnO2 (Vegliò and Toro, 1994). An innovative acid reductive leaching carried out in soft experimental conditions was here considered using agro-industrial wastes containing carbohydrates as reducing agents (Vegliò et al., 1998).The leaching process was investigated from a kinetic and equilibrium point of view in order to optimize the experimental conditions and obtain high purity and concentrated MnSO4 solutions.The overall leaching process (not considering the complex network of intermediate oxidation reactions of the carbohydrates in hot sulphuric acid medium (Vegliò and Toro, 1994)) can be described by the following reaction:24 MnO2 + C12H22O11 + 48 H 24 Mn2+ + 12 CO2 + 35 H2O (1)A Shrinking Core Model (SCM) was modified by a variable activation energy term to take into account both the variable reagent concentrations and the reaction rate change with respect to the manganese dioxide conversion. The influence of the particle size in the kinetic model is discussed with the support of SEM analysis and BET surface measurements before and after leaching.Manganese extraction yield was maximised (170-190 g/L) using appropriate carbohydrates and acid excesses, while impurity concentrations were kept low (Fe<10ppm and Ca<300ppm) pre-treating the ores, using hydroalcoholic leaching medium and different combinations of down-stream processes. In particular precipitation, solvent extraction and adsorption onto active carbon were tested to eliminate Fe and Ca from MnSO4 solutions."

Jan 1, 2003

By D O. Hayba

Metal-rich slurries discharged from excess-enthalpy geothermal wells at Kawerau (NZ) indicate that an efficient ore precipitation mechanism operates in some feedzones. In our conceptual model, which takes into account the relative permeabilities of liquid and gas phases in boiling fluids, a metal-precipitating liquid phase is effectively immobilised along boiling fronts, leading to the formation of highly concentrated ore. Chemical equilibrium and heat/mass transport modelling demonstrate the general applicability of this conceptual model to hydrothermal eruption environments.

Jan 1, 1995

By Guosheng Zhan

The Homestake Mine included the open cut and underground workings up to 2,484 m (8,150 ft) deep. The mine ceased mining activities in December 2001 after 125 years of operation. Pumping from the underground workings continued for 18 more months until June 10, 2003. Homestake had completed a comprehensive hydrologic evaluation on post-closure underground flooding prior to the shutdown of pumping. After closure, the mine was selected by the National Science Foundation as the site for the Deep Underground Science and Engineering Laboratory (DUSEL). An interim laboratory facility will be set at the 1478 m (4850 ft) Level. The final facility will be set at the 2256 m (7400 ft) Level or deeper. Pumping from the underground workings began on June 5, 2008 by the South Dakota Science and Technology Authority (SDSTA). During the period of June 2008 through March 2009, the pumping rate increased from 41 L/s (650 gpm) to 81 L/s (1,290 gpm) with an average rate of 60 L/s (950 gpm). As a result, the water level had been lowered more than 95 m (310 ft). It was found that the observed rebound and later decline to date is in close agreement with the model projections. Because of this, the authors of this paper reject claims of a lack of sufficient measurement devices in place and a lack of understanding of the hydrologic system at the Homestake Mine prior to shutdown of pumping in 2003 (Davis et al, 2009). Furthermore, it is believed that this validated model can serve as a useful tool for the SDSTA to manage future underground dewatering for the DUSEL operation. This paper evaluates the hydrologic conditions in the Homestake Mine area and projects the post-closure groundwater rebound and decline due to DUSEL pumping.

Jan 4, 2010