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By Peter A. Rona

Hydrothermal mineralization along slow-spreading oceanic ridges and rift -zones that comprise more than half the global length of the seafloor spreading center system is related to anomalous physical and chemical conditions acting within the geologic settings that characterize early and advanced stages of opening of an ocean basin. Mineralization in the early stage of opening is represented by the Atlantis II Deep of the Red Sea. There, hypersaline hydrothermal solutions discharging as density stratified brines into an axial basin, have formed the largest massive sulfide deposit (70 x 106 metric tons) known at a spreading center. Mineralization at the advanced stage of opening is represented by two types of sites: (1) oceanic crust on the wall of a rift valley; and (2) oceanic crust exposed on the wall of a transform fault zone. The first type of site is the TAG Hydrothermal Field, located on a wall of the rift valley of the Mid-Atlantic Ridge at the top of the basaltic layer of oceanic crust. Evidence is presented for multi-stage, high- and low-temperature hydrothermal activity that produces Cu, Fe, and Zn enrichments within the thin sediment column and stratiform interlayered deposits of manganese oxides, iron oxides, hydroxides and silicates, on the seafloor. The second type of site occurs along walls of transform fault zones of the equatorial Mid-Atlantic Ridge and Carlsberg Ridge, which exhibit stockwork-type Cu-Fe sulfide mineralization

Jan 1, 1985

By P. C. Kapur

A principal first-order and a minor summation term contribute to the solution to the discretized batch-grinding equation when formulated in cumulative retained mode. Depending on the inter relations hips between the selection and breakage parameters, the minor term may be advantageously modified in a number of ways. The reduced grinding equations thus obtained are solved by iterations to give relatively simple solutions which are tested against experimental data. The irn-plications and advantages of the reduced grinding equations are briefly discussed. In many instances, the trajectory of the particle-size distribution in a batch mill may be extracted from a set of particle mass balance equations as follows

Jan 1, 1971

By R. S. Adhikari

It is necessary to assess the physical and functional conditions of highway bridges at regular intervals to ensure they still meet their service requirements. Currently, this condition assessment is mainly performed through visual inspection, which has been identified with several limitations (e.g. the timeconsuming assessment process and heavy reliance on inspectors? personal experience). In order to overcome these limitations and enhance the current inspection practice, this paper presents a novel method for automated bridge condition assessment using a hybrid sensing system. Under the method, existing conditions of bridge components are first captured with a stream of point clouds and color images. Then, the bridge components and the defects inflicted on the components are detected utilizing their visual patterns. The detection results are mapped to the point cloud. This way, the 3D information of the components and defects can be retrieved. The bridge condition assessment can be made effectively through the 3D visualization of this information before carrying out any on-site detailed evaluations.

Aug 1, 2013

By T J. Wilton, K A. Broadhurst

The United Kingdom, although a relatively small island, has a wealth of mineral deposits, coal, granite, limestone, gypsum, lead, florspar, etc. Coal is a major source of energy with 71 opencast coal sites, 52 using explosives. Many of these sites are in rural areas, the average area worked being 250 acres. The smallest is 35 acres, the largest 2,000 acres, but only 600 acres can be operated at any one time.

Jan 1, 1981

By X Dahe

SLon vertical ring and pulsating high gradient magnetic separators (VPHGMS) possess the advantages of high efficiency and high reliability in beneficiating weakly magnetic minerals. In recent years, models SLon-2250, SLon-2500, SLon-3000 and SLon-4000 have been developed. This paper gives several examples of their applications in oxidised iron ore and ilmenite processing flow sheets to improve iron and ilmenite recoveries.CITATION:Dahe, X, 2017. Recent development and application of SLon vertical ring and pulsating high gradient magnetic separators in the iron ore and ilmenite processing industries, in Proceedings Iron Ore 2017, pp 461–466 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By R. Cameron

The growing use and acceptance of electric vehicles (EV), as evidenced by the record sales of over 750 thousand vehicles in 2016 and a current global EV stock of 2 million vehicles, is putting pressure on sourcing raw materials such as cobalt, and to a lesser extent, nickel. Global supply is poorly diversified, with 50– 60% of global cobalt production sourced solely from the Democratic Republic of Congo (DRC). One potential source for cobalt and nickel are low-grade nickeliferous pyrrhotite tailings, of which 50–100 million tonnes are present in the Sudbury area alone. This paper presents the extraction of cobalt and nickel from this material using a combination of flotation and bioleaching technologies. The findings of a high-level techno-economic analysis of the proposed processing flowsheet are presented.

A narrow (200-300m) zone of amphibolite facies metamorphic rocks underlies the Papuan ophiolite near the Musa-Kumusi divide, SW of Popondetta, Oro Province. The amphibolite rocks are bounded up-section, to the NE, by peridotite and gabbro of the ophiolite; and down-section, to the SW, by mafic greenschist, which in turn overlies blueschist facies mafic schists of the Emo Metamorphics.Amphibole compositions within the narrow contact zone show a strong chemical zonation which reflects a steep thermal gradient, with maximum temperatures >800¦C at the peridotite contact. The zonation is recorded in Ti content and A-site occupancy, relative to Al'¦

Jan 1, 1994

By D. Thibault, A. Akhiate, M. Brochu, E. Braud

Cast martensitic stainless steels, 13%Cr-4%Ni, having carbon contents between 0.018 wt% and 0.067 wt% were normalized, air quenched, and tempered at two different temperatures (550°C and 610°C). Their microstructures were characterized by optical microscopy and X-ray diffraction (XRD). Macro and microhardness, tensile strengths, and impact resistance were quantified for each material and condition. Results show that the prior-austenite grain size is constant through the materials but the percentage of reformed austenite, contained in the martensitic matrix, depends strongly on the material chemistry and on the tempering temperature and on its duration. It is observed that, independently of tempering conditions, an increase in carbon content increases the material hardness and tensile strengths, whereas the elongation remains constant. In contrast, the results of Charpy type impact toughness tests show a different trend. The material containing the average carbon content (0.034 wt%) is significantly tougher than the two other alloys. Surprisingly, the toughness of the steel containing 0.034 wt% carbon was found independent of the reformed austenite content. It is thus concluded that carbon and reformed austenite contents are not the only parameters affecting the toughness of these steels.

Jan 1, 2014

By Angela Binder, Oliver Langefeld

"The future of mining will be characterized not only by the application of modern technology, but also by the harmonization of economic, environmental and social issues. These areas set major future challenges which are complex and demand extensive knowledge. As an example, mining of highly complex orebodies for the supply of often critical raw materials, needs to consider technically demanding and cost-intensive extraction issues. The amount of tailings, which need to be stored, increases with the amount of ore mined. Therefore, the negative impact on environment and society increases. Hence mining becomes expensive with regard to all three aspects: economy, environment and society. In view of a sustainable mining practice this challenge should be used as an opportunity. The positive impact should be maximized for present and future generations. The objective is to create and use the mining openings in an optimum way related to sustainability. The approach of Blue Mining, which focuses on energy and ergonomics in the field of Sustainable Development, enhances the closure planning by recommending subsequent usage of such openings for energy storage. The approach fosters among others the implementation of the 7th Goal for Sustainable Development defined by the United Nations with the assurance of access to affordable, reliable, sustainable and modern energy for all. The usage of underground storage increases the stability of solar and water power usage, which are otherwise unreliable. Blue Mining embeds these issues in the main planning effort long before groundbreaking. This approach involves experience from past and current projects. This paper introduces the concept of Blue Mining with respect to post-mining utilization of a mine for energy storage. Methods and perspectives are presented with examples covering best-practices and lessons-learned."

Jan 1, 2017

By Charles H. Kline

Industrial minerals are the Cinderella of the mining I industry. Often considered as just dirt by traditional hard-rock miners and oil drillers, these products nonetheless comprise the second largest segment of the industry and the fastest-growing one. With annual sales of $5.7 billion, industrial minerals make up 22% of the dollar value of U.S. mineral consumption. By contrast, metals account for only 11%. Fuels, of course, are dominant, representing 67%. The dollar values of production and consumption for the three segments of the industry in 1968 are shown in Table I. The growth rate of industrial minerals is shown in Table II. From 1953-1968, the current-dollar value of all U.S. mineral production increased at the average annual rate of 3.8% while that of the gross national product increased at 5.9%. Industrial minerals are the only segment of the mining industry that approached the growth of the overall economy in this period, with production values increasing 5.1% a year and apparent-consumption values 5.6% These data, expressed in current dollars, include the effects of inflation. The growth in U.S. industrial minerals production is even more striking when expressed in indexes of physical production. As shown in Table III, production of all U.S. industries increased by 4.1% a year from 1953 to 1968. The growth in production of stone and earth minerals just matched this figure. By contrast, the average annual increase for oil and gas was 2.2%: for metals, 1.6% : and for coal, only 0.6 %.

Jan 1, 1970

By W. David Tyler

Any mining or engineering-construction excavation that extends below the water table must be dewatered. In many situations, the ground is of low permeability or the workings extend only a short distance below the water table. So water removal can be handled easily and economically by using mobile centrifugal pumps. However, there is an increasing number of mines that have a continuous high flow of water into the workings. Controlling this flow can significantly increase the cost of ore production. Successful implementation of any major dewatering scheme will ultimately rely on a clear understanding of the local geology. This understanding is necessary before an interpretation of ground water conditions can be made. It will dictate which dewatering methods are feasible. Once the geology and the ground water system are known, the scope and timing of the dewatering measures can be varied with the mine plan. Ground water modeling can assist in optimizing the dewatering system, though the precise objective of each model should be clearly defined. Production wells must be sited and drilled so that individual well efficiencies are high. Any lost efficiencies will translate into higher operating costs. Each well must be designed for maximum long-term control of the water table, and pumps sized to operate under continually changing heads. Finally, the investment in each production well must be protected during the mining process.

Jan 1, 1991

By M. W. Bartley, Hugh M. Roberts

SUBSTANTIAL deposits of Bessemer hematite have been found recently by drilling beneath Steep Rock Lake, Ontario, which is situated in the northern part of the Lake Superior Region. It will be practicable to divert the waters flowing into this lake and develop open pits on the upper part of two large ore bodies by damming off and pumping out the water in the part of the lake in which they occur. Ultimately, the bulk of the ore will be mined by underground methods. Owing to the generally massive nature of the rocks in the area, no underground flows of major consequence are anticipated after diversion of the lake. The Steep Rock deposits are attributed in origin to hydrothermal replacement. They were formed, for the most part, along an unconformable, brecciated contact between the Steep Rock limestone and an overlying younger volcanic series. The replacing solutions came in as igneous after-effects, following upon the intrusion of basic igneous rocks that invaded the hanging-wall volcanics. It is believed that this took place in a geological period roughly equivalent to late Middle Huronian, which was the period when the most extensive iron-bearing rocks of the Lake Superior Region were formed. Comparison is made with other deep-seated iron-ore bodies in the Lake Superior Region, the origins of which are ascribed in the discussion to hydrothermal replacement.

Jan 1, 1943

By John Chipman

DESPITE the rapidity of chemical reactions at steelmaking temperatures, deoxidation reactions cannot be expected to reach equilibrium immediately after addition of a deoxidizing agent. A considerable period of time may be required merely to obtain complete mixing of the deoxidizing element throughout the volume of steel to which it is added. Evidence in the literature indicates that in some cases the time is long compared with that allowed for completion of the experiment or for teeming of the heat. The great turbulence observed during the filling of the ladle is no guarantee of complete dispersion on a fine scale throughout the heat. During the process there are initially certain volume elements which are high in deoxidizer and others which retain substantially their original oxygen content. Mixing consists of the subdivision and ultimate destruction of these liquid segregates through the process of shear and elimination of concentration gradients by diffusion. The shear process does not continue indefinitely and a quiescent state may be reached in the ladle before all volume elements of divergent deoxidizer and oxygen content are completely eliminated. In furnace deoxidation the time required for complete mixing may be very long unless continuous stirring is employed.' In Fig. 1, let the circle represent one small volume element of aluminum-rich metal surrounded by oxygen-rich steel in which no stirring movement remains. Further mixing requires inward diffusion of oxygen and outward diffusion of aluminum, resulting in precipitation of A12O3 in the diffusion zone. It is important to note that such a precipitate may itself interfere with the diffusion process. Moreover, if the precipitate forms as a film with even minimal mechanical strength, it may interfere not only with diffusion but with shear as well, thus stabilizing compositional differences in volume elements of greater than microscopic size. A film surrounding such a volume element would have little or no ability to rise or to sink unless it enclosed a liquid whose density differed from that of the ambient. Consider now the effect on the overall composition of the melt. Fig. 2 represents the A1-O equilibrium at the temperature of the bath. High-aluminum elements of composition X may exist alongside high-oxygen elements of composition Y in such proportions that the average composition 2 has a much higher A1-O product than that corresponding to equilibrium. The A1-O product supposedly corresponding to equilibrium at 1600 °C was found by Wentrup and Hieber2 to be 10-10, by Hilty and crafts3 to be 2 X 10-9 and by Gokcen and chipman4 to be 2 x 10-14. Only the last named investigators approached equilibrium by means

Jan 1, 1962

By H. R. Hanley, Charles Y. Clayton

One of the most important contributions to the art of electrolytic zinc production has been the aluminum cathode. This has been used in all major production since its commercial development in 1916. The literature is replete with important contributions, some of which may have been replaced by better ones, but thus far there appears no other metal to take the place of aluminum as cathode material. Credit for this innovation goes to Sherard Cowper Coles, of England. When experimenting on the extraction of zinc from Broken Hill ore at Hayle, Cornwall, in 1893, he introduced the aluminum cathode, and in 1895 obtained British Patent No. 20073. The reason for this dominant position of aluminum as cathode material in zinc sulphate electrolytes is its unique surface, to which electro-deposited metals usually do not tightly adhere. The metal must, be of high purity for best results. It is possible to develop a starting-sheet method by which thin electro-deposited sheets of cathode zinc are made and stripped from a smooth aluminum plate. Such thin sheets of cathode zinc may be used as are the copper sheets in standard electrolytic copper-refinery practice. However, complications arise because of extreme warping of the zinc starting sheet after a few hours of deposition, and thus special arrangements must be made to compensate for this abnormality. Reasons advanced for the ease with which deposits may be stripped from the aluminum surface are: (1) presence of a permanent oxide coating on the metal, (2) failure of aluminum to alloy with the deposit, (3) differences in coefficient of expansion, (4) high position of aluminum in the electromotive scries of metals. Of these reasons for nonadherence, which may have some application in general deposition, probably the oxide coating has the greatest bearing on the subject of zinc deposition. Adherence of zinc deposits has occasionally had serious effect on tonnage and production costs. Opinions have differed as to the specific

Jan 1, 1943

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 Pranav Deshpande

The wear behavior of metal matrix composites differs from that of the monolithic metallic counterparts because composite materials have multiple constituents in their structures and these constituents wear at different rates. It was observed that under low wear stresses, abrasive wear prevailed. As the wear stress increases, pullout of reinforcement occurs and both abrasive wear and wear due to pullout contribute to the overall composite wear. A model of wear taking into account both types of wear has been developed. A critical pullout wear stress was suggested for each composite. Below the critical wear stress, no pullout of reinforcement occurs. It turns out that the critical wear stress simply equals to the ratio of the interfacial strength between the matrix and the reinforcement to the friction coefficient between the reinforcement and the wear counter surface. The critical wear stress is independent of the particle size of the reinforcement. From data on wear of 53% WC composites, the equation of wear for 32% WC composites was obtained. Experimental results agreed well with the predicted wear rate of this composites. This provides an excellent verification of the wear model developed by Lin and Deshpande. Wear data from Modi et al. in the literature were also perfectly fitted with the model.

Jan 1, 2006

By Ricardo Montero

At this time, over 300 tons of Au are used in electronic equipment each year with other precious and strategic metals such as Ag, Pt, Pd, Cu, Nb, Ta, etc. After the use-phase, the electronic devices become electronic waste (e-waste); consequently it is important to consider e-waste as a secondary supply for recovery of these metals. One of the most important components is the printed circuit boards (PCBs) because the amount of their precious metals is ten times higher than rich precious metals bearing ore. This paper presents the recovery of Au, Ag, Cu and Nb from PCBs of discarded computers using leaching column technique. The amount of these metals in used PCBs was: 613 g/ton of Au, 1515 g/ton of Ag, 36 g/ton of Nb and 23.4 % of Cu. The PCBs were crushed with a hammer mill until reaching a particle size between 3.33 mm to 0.43 mm. Then, it was leached with sodium cyanide solution in a glass column using the following conditions: sodium cyanide concentration 4 g/L, flux 20 L/kg PCBs day, pH between 10.5 to 11 and leaching time 15 days. Every day, after leaching, the pregnant solutions passed through a column with activated carbon to complete the closed loop system. The following recoveries were obtained: 46.6% of Au, 51.3% of Ag, 47.2% of Nb and 62.3 % of Cu. The products obtained are: a) loaded carbon that contains the desired metals and b) processed PCBs with precious metal contents. A preliminary technical-economic study shows the feasibility to create a small-scale PCBs recycling plant. The initial investment is on the order of US$ 155 639, considering the recovered metals from loaded carbon. The internal rate of return for 10 years period (IRR) and net present value (NPV) estimated are 27% and US$ 105 926 respectively. Keywords: printed circuit boards, recovery, precious metals, niobium, leaching column

Sep 1, 2012

By Shijie Wang

In pressure oxidation leaching of copper anode slimes, than 65% of the tellurium is m' cxtraoted during decopperizing. About l0- 15% of the selenium is also dissolved simultane¬ously by severe leach conditions. Current operation for the treatment of the leachate is to constantly recirculate the leach solution through a bed of copper turnings. The tellurium and sele¬nium are precipitated from the leach liquor as copper telluride and copper selenide and sepa¬rated from the solution by filtration. In order to improve the reaction efficiency and reduce the process cost, viz, minimize the copper addition, cut retention time, and reduce the energy consumption; a chemical reducing agent is studied and the cementation process tested in the laboratory. In this paper, the test results are presented and the process chemistry is discussed.

Jan 1, 2003

By H. H. Uhlig

A study of passivity in chromium-iron alloys holds considerable interest, both because of the present-clay practical importance of the stainless steels, and because of the scientific importance attached to the mechanism of their corrosion resistance. Upon the discovery of the passive chromium-iron alloys in 1912, it seemed logical to attribute the observed phenomenal corrosion resistance to a thin, continuous, protective reaction product on the surface. The product was thought to be Cr2O3 or a similar oxide containing both chromium and iron. This mechanism seemed likely in view of Michael Faraday's conjecture that passive iron is not reactive in concentrated nitric acid because of an oxide on the metal surf ace. Since 1912, data have accumulated that permit a further exploration into the nature of passivity and provide a new approach to the problem. A summary of the facts lends considerable weight to a mechanism based not on physical protection of an oxide or similar compound, although such compounds may be present on the surface, but to a change in tendency of surface metal atoms to react chemically. This change in reaction tendency is ascribed to chemisorbed films that effectively satisfy residual valence forces of the metal surface, but do not appreciably disturb the positions of metal atoms in the lattice. In other words, formation of a new lattice such as that of an oxide is not a necessary condition for this type of passivity. The decreased reaction tendency of the metal by reason of chemisorbed films can thereby account for low reaction rates of the stainless steels in many media, as well as a noble galvanic potential as is observed. Substances capable of adsorbing on the stainless steels, and hence accompanying the property of passivity, are typically oxygen, nitrites or chromates, but are not in any sense limited to these. Other elements and compounds can also chemisorb, and therefore may also play a major part in the mechanism of passivity in specific media. The mechanism of passivity based on chemisorption or activated adsorption begins with the interpretation Langmuir proposed for his experiments concerning adsorbed oxygen on tungsten.' He found that adsorbed oxygen was tightly bound, remaining on the tungsten surface above temperatures at which WO3 rapidly volatilizes. The oxygen in such a state did not readily react with hydrogen even at

Jan 1, 1949

By James P. Kimball

The object of the present memoir is to pot on record some practical experiments by the writer in smelting a silicions native magnetite with no other flux than the silicates of its own gangue.' This work was undertaken in the spring of 1878 for Messrs. Naylor & Co., of' Boston, to whom I am indebted for the privilege of here communicating its results, these having hitherto only been simply announced.* So far as I am aware these are the first instances of the kind ill this country that non-calcareous; or rather non-carbonatbed, magnetite have successfully been used strictly alone as self-fluxing ores in the blast furnace; that is, without the addition of' calcareous flux in the form either of limestone, quicklime, calcareous ore, or basic (calcareous) slag. Previous to the spring of 1878, when the Chateaugay magnetic ore was first brought to illy notice. its use had been limited to Catalan forges, after " separation " at the ore bed. The blooms and billets made from it in the several forges of Messrs. Weed $ Williams, and of Mr. Williams, were well known in the trade as among the best in the market. Tile Chateaugay ore beds proving of great magnitude, and the ore exceptionally low in phosphoric acid, it commended itself for blast-furnace purposes to Messrs. Naylor & Co., who employed me to blow-in the charcoal furnace at Pittsford, Vt., on this ore in the spring of 1878, a previous trial of this ore in the same furnace in the fall of 1877 having proved abortive. This was therefore the first time that Chateaugay ore was successfully smelted in a blast furnace, although since well known as a blast-furnace ore possessing superior and exceptional qualities. The Pittsford furnace, although rebuilt in 1844, and subsequently improved by the former owner, the late J. Prichard, is one of the few furnaces of the old type with open breast (Sumpfofen) still active in this country, Its improvements 011 furnaces of the period,

Jan 1, 1881