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

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

Jan 1, 2019

By Hairong Zeng, Matthew Baumann, Shahram Tafazoli, Edmond Chow

Measurement of rock fragmentation has evolved from a completely subjective and manual process to a statistically objective and semi-automated process. However, ultimately, the vision is to achieve a statistically representative and fully-automated process. From the blast optimization perspective, it is critical to receive reliable rock fragmentation results quickly to incorporate into the planning of subsequent blasts. Since manual rock fragmentation measurement methods tend to be time consuming, a fully-automated method is the practical way to meet these requirements.

Jan 1, 2012

Flotation works very well for particles that are typically in the range 20 to 150 µmin diameter, for base metal ores. In this range, it is possible to get quite high recoveries in conventional flotation machines. Outside this range, the recoveries decline progressively, whether it be with the very fine or the coarse end of the size spectrum. In this paper, the reasons for the drop-off in recovery are briefly reviewed, together with strategies for future work. Recent progress in the author's laboratory will be described. These include the Concorde Cell, which takes advantage of the high dissipation rates in the shock wave created when a gas-liquid mixture reaches supersonic velocities. The environment thus created is very beneficial for the flotation of ultrafines. For coarse particles, the reasons for the drop-off in recovery can be related to the highly turbulent nature of the pulp in a conventional flotation cell. To improve recovery, it is necessary to find a way of bringing particles and bubbles into contact in a quiescent environment. A new process for coarse particle flotation will be described, in which a fluidized bed is created in the flotation cell. The flow conditions are very gentle, and the high solids concentration leads to rapid rates of capture of the particles. Experimental results are presented. It is apparent that the maximum floatable size for coal and minerals can be increased by a factor often over the limits found in current practice. Advances

Jan 1, 2009

By D. W. Duncan, A. Bruynesteyn

Acidic mine waters containing solubilized uranium have been observed in many uranium and some copper mines. In every case, the sulphide and iron oxidizing bacterium, Thiobacillus ferrooxidans, was also present. This bacterium provides the ferric iron required to oxidize u+4, both by oxidizing available ferrous iron and by oxidizing pyrite or other available sulphide minerals. This latter oxidation also provides sulphuric acid and may increase extraction by exposing more uranium. The enhancement of bacterial activity and the results of some field tests are discussed.

Jan 1, 1971

By D. R. Spears

As part of its mission to develop technology to assure a continuing supply of minerals, the US Bureau of Mines has investigated the flocculation of a Stillwater, MT, chromite ore. The ore was flocculated at different solids contents and at different stirring speeds to determine the importance and effect of hydrodynamic factors. In acidic and basic pH, the chromite ore was flocculated with high molecular weight polyacrylamides differing in the degree of hydrolysis. Polyacrylamides were found to bind to chromite ore particles through hydrogen bonding. The anionicity of the polymer and the pH affected the degree of polymer-particle interaction, which in turn affected polymer conformation at the surface. A polymer conformation with many loops and tails was used to explain high flocculation efficiency. It was found that such a conformation could compensate for poor hydrodynamic conditions.

Jan 1, 1992

By S. Kelebek, E. Yalcin

"Diethylenetriamine (DETA) and/or triethylenetetramine (TETA) are reagents that can generally be categorized under ""flotation modifiers"". These polyamines are known to be effective for the deactivation/depression of pyrrhotite that is present in Canadian nickel-copper sulphide ores in large quantities. Recent bench scale testing on some of these complex ores indicated that chalcopyrite flotation can also be adversely affected under certain conditions involving polyamines, which may be taken to be an evidence of their specific affinity towards chalcopyrite. In general, DETA shows no significant depressant action on chalcopyrite while TETA's promotion of hydrophilicity for this mineral has been observed even in the presence of xanthate. This prompted an investigation on thermodynamic equilibria involving these polyamines and copper ions. Results serve a useful purpose to identify conditions for deactivation phenomena. CuDETA2+ and CuTETA2+ chelates as products of sequestration have large predominance areas covering a wide range of redox and pH conditions, where copper xanthate species are not stable, especially in the presence of TETA."

Jan 1, 2009

By M. Misra

The coral contaminated with plutonium at Johnston Atoll UA) was subjected to gravity and flotation separation processes at the Soil Washing Laboratory (SWL) and also at the Johnston Atoll UA) site. Tests were conducted with the contaminated coral fractions referred to as the "HP-l" ( hot particles) and the "sludge". The gravity process tested was centrifugal gravity separation and the flotation processes were conventional Denver mechanical flotation and tall column flotation. Flotation tests were conducted using both fresh and sea water. Industrial fatty acid (anionic collector) was chosen as collector to make plutonium-enriched particles hydrophobic. The use of flurosilicic acid and sodium silicate made the clean coral hydrophilic. The results show that each of the processed when tested with appropriate size fraction and operating conditions resulted in passing the success criteria. It was possible to obtain more than 80% weight of the original coral as "clean sand" having activity below the JA site "soil screening level" of 13.5 pCi/gm. The field tests spiked with plutonium particles showed remarkable success. The effect of depressants, flotation medium and the coral pretreatmentis described. Finally, a flowsheet developed by the University of Nevada, Reno to treat 8000 tons of HP-l pile presently stored at JA is presented.

Jan 1, 1996

By V. N. Kolesnikov

The Sikhote-Alin part of the Circum-Pacific Ore Belt is characterized by wide distribution of Sn, Pb, Zn, W; Au, Ag, and other mineralization. This mineralization is regionally associated with the Late Cretaceous-Tertiary East Sikhote-Alin volcanic belt where it overlaps the Taukha accretiollary-wedge terrane of the Early Cretaceous age. The Pb-Zn deposits of the Dalnegorsk ore district may be grouped into the skarn (about 80%) and vein types. The skarn deposits are of major commercial value. Their geological position is controlled by the carbonate units located within tectonic melange of the Taukha terrane. Some other lithological and tectonic factors also play a significant role ill distribution of the mineralization. The ore bodies are traced to the depth of 1000-1500 m below the surface, having a pipe-lens shape and vertical zonation. Major minerals of the ores are galena, sphalerite, pyrrhotine, chalkopyrite, hedenbergite, quartz, and calcite. The minor elements of the Pb-Zn mineralization are cadmium, silver, bismuth, and copper. The paper describes relationships between mineral suites and minor element contents in the ores, as well as their significance for processing the ores. The metallurgy applied allows high recovering of the major components (Pb -93.9%; Zn -91.4%). However the tails contain some minor components that may be of commercial interest.

Jan 1, 1998

By Jon C. Volkwein

The Bureau of Mines, Foster-Miller Inc., and Beaver Creek Coal Co. have evaluated the ability of a new system to ventilate a 40-ft-deep cut. A remote-control continuous-mining machine, in a 7-ft-thick seam, with exhausting brattice was fitted with an improved sprayfan system plus additional forward and reverse pointing sprays. Static and dynamic tests using tracer gas were conducted in a full-scale model and under-ground to measure the effectiveness of exhaust face ventilation for various deep-cutting mine and spray configurations. When compared to a lO-ft primary ventilation brattice, the extended-cut spray system consistently provided better face ventilation at all configurations up to and including a 40-ft brattice setback. The system also provided good dust protection and visibility for the machine operator. Another safety advantage is the elimination of the need to set temporary roof supports to maintain the ventilation brattice.

Jan 1, 1985

By L. Bbosa

Positron Emission Particle Tracking (PEPT) and the Discrete Element Method (DEM) are used to investigate Power Draw in a laboratory scale tumbling mill. The mill is run dry in batch mode at different speeds using mono-size charge of glass beads, and is mounted along with a torque transducer to measure power. Particle tracking information from PEPT is used to reconstruct the motion of glass beads and infer the overall charge behavior, while DEM is employed to simulate particle motion and interaction, with collision mechanics calculated using the Hertz-Mindlin contact model. For PEPT and DEM data, the product of torque and average angular velocities in discrete cells are accumulated to obtain mill power. This method is found to be within statistical agreement with measured power for all tests. Spatial distributions plotted from this approach highlight the regions of the mill that draw the greatest power. A second technique to obtain Power Draw from DEM data which sums particle forces against the mill geometry is similarly found to accurately predict mill power with lower statistical error. Keywords: Power Draw, PEPT, DEM

Sep 1, 2012

By John A. Dunn

The history of underground coal mining has developed through the years from a manual digging and loading process to the highly mechanized pro- cess that it is today through the use of electric power. Mine power systems have closely followed the continued pattern of improvement and mechanization, through necessity and the application of technological advances, At the beginning electric power used in coal mines was confined to haulage. Since d-c power was better suited to traction drives, mine power systems naturally developed using direct current. During this development, a number of street railway systems were in service, using 550 volts, and it was natural that mine trolley systems went in at 550 volts. As machines for mining operations developed and the number of operating mines increased, a safety hazard developed through the use of 550 volts. Most regulating agencies opposed the use of 550 volts, and after a time the maximum voltage permitted was limited to 300 volts hot line to ground. Up until this time most mines had operated with one central generating station, which served utilization power to the whole mine. Power demands were not very great and transmission losses were within reasonable limits.

Jan 1, 1964

By J. E. Gillespie

Introduction Mineral wool may be defined as "rock, slag, or glass fibres made by a process of melting and blowing by steam or air, containing a minimum of oil and unfiberized material" (U.S. Bureau of Standards CS 117-44). The earliest production of the material was in Wales, about one hundred years ago. In the United States, the industry daces from 1870 when a plant, using slag as raw material, was established in Greenfield, New Jersey. It was not until 1897, however, that large-scale production was commenced on this continent at a plant in Alexandria, Indiana, which utilized rock from nearby deposits. Today, mineral wool is manufactured in many parts of the United States and Canada, the plants for the most part being in close proximity to deposits of suitable rock or to sources of slag. In the United States there are some seventy-five producers with a total annual capacity of nearly one million tons of wool. In Canada, in 1946, eleven manufacturers produced about fifty million square feet of batt-type mineral wool insulation material. Mineral wool is, perhaps, the most efficient of all heat-insulating materials and, moreover, it is fireproof, extremely durable, and insect- proof. Its high efficiency is due to the very low thermal conductivity of the fibres themselves and to the fact that the produce as marketed contains up to 90 per cent non-conducting air space. Depending on the degree of compression of the fibres in the manufactured product, the specific gravity ranges from 2 lb. to 10 lb. per cubic foot. Products Marketed Following are the principal forms in which mineral wool is marketed: Blanket. - Mineral wool with or without reinforcing on one or both sides, with various types of confining media, all suitably bound together.

Jan 1, 1948

By Keith A. Heasley, Jian Yang

"LaModel uses a laminated overburden boundary-element model and can calculate not only seam-level stresses and displacements but also surface subsidence for thin tabular deposit such as coal seams (Heasley, 1998). Up to this point in time, the material property wizards in LaModel have primarily been designed for calculating accurate stress distributions in single- and multipleseam situations, and for investigating and optimizing pillar sizes and layouts in relation to overburden, abutment, and multipleseam stresses. However, the critical input parameters that will give the most accurate seam-level stress distribution do not necessarily produce the best surface subsidence prediction. The objective of this paper is to develop a methodology for calibrating the critical input parameters in LaModel to optimize surface subsidence prediction.For optimum surface subsidence prediction, it was found that the gob convergence (as defined by the final gob modulus) and the overburden stiffness (as defined by the lamination thickness) were the two most critical parameters that needed to be calibrated (Heasley, 2016). By calibrating numerous panels with various widths and depths, a formula that provides the optimum final gob modulus to use for subsidence prediction was developed. Also, three different empirical formulas for optimizing the lamination thickness as a function of overburden depth and/or the panel width to- depth ratio were determined for the three cases: supercritical panels, and subcritical panels with and without offsets. Further, if the user has measured data for subsidence factor and angle-of draw, the optimum final gob modulus and lamination thickness can be determined from the measured data. These new subsidence prediction formulas are being implemented into new material wizards in LaModel.INTRODUCTIONIn the past few decades, with the increased need for highly productive mining techniques, full extraction mining methods have been increasingly employed in the U.S. coal mining industry. These total extraction mining methods, which include both longwall mining and room-and-pillar retreat mining, normally cause immediate roof caving and the associated surface subsidence. These methods can be highly productive and cost-effective, but the associated surface subsidence can cause damage to surface structures and negatively impact the surface environment (Peng, 2008). Therefore, a reliable program for predicting the surface subsidence associated with full extraction mining is required for appropriately engineering and managing the surface subsidence impacts of full extraction mining."

Jan 1, 2016

By L. A. Haas

S02 reduction with CO was studied in an integral flow reactor at a nominal flow of 0.5 liter per minute. Reactant gas contained 3 percent SO2, 6 percent CO, and the balance He. SO2 conversion was determined for three different types of catalysts. The first consisted of 16 commercial catalysts used for various chemical syntheses. Only the commercial catalysts which contained transition metals in alumina removed more than 30 percent 80a at temperatures below 510° C. Two other types of catalysts were prepared in the laboratory either by pelletizing equal amounts of powdered alumina and transition metal oxides or by impregnating commercial alumina tablets with transition metal ions. Regardless of preparation techniques, Cr and Fe in alumina were the two best catalysts. The observed results suggest that an intermediate (SCO) is formed by the interaction of surface metal sulfides and carbonyls. Alumina then catalyzes the interaction of SCO with S02 to form the end products (sulfur and carbon dioxide). Over 80 percent S02 was removed at 460° C with 2 grams alumina impregnated with 2.5 percent iron.

Jan 1, 1972

By D. H. Baker

THIS REPORT presents the technique and equipment used in determining the hardness of titanium sponge. Detailed descriptions are given of the methods used in preparing test samples for chemical analysis and hardness testing, the method of melting and surfacing test ingots, and the technique of reading Brinell-hardness impressions. The arc-melting furnace described, for which engineering drawings are included, will produce from 70 to 90 double-melted buttons each 8 hours of operation. Experimental data are also presented depicting the effect on hardness of the methods of surfacing specimens, temperature of test specimens, and the effect of time at test load. These data show that surfacing of the specimen involves no critical machining operations but that the test surface must be paralleled by a relatively flat surface for contact with the anvil of the Brinell tester. The heating of a specimen to 150° C. during surfacing does not materially affect the results if the ingot is cooled to room temperature before the hardness impressions are made. The optimum time at load appears to be approximately 30 seconds, but load times of as much as 1/ ½ minutes will not cause major errors.

Jan 1, 1959

By William E. Roscoe

"Mineral exploration properties are those on which an economically viable mineral deposit has not yet been discovered. Such properties are bought, sold, optioned and joint ventured on the basis of their perceived potential for the existence and discovery of a viable mineral deposit. The intrinsic value of an exploration property is therefore based on the exploration potential. One measure of the exploration potential is the amount that can be justified to spend on exploration for a viable deposit.The appraised value method uses a cost approach to value exploration properties. It is based on the premise that an exploration property is worth the meaningful past exploration expenditures plus warranted future costs to test remaining exploration potential. Results of past exploration work are analyzed in order to retain only those past expenditures that are productive in terms of identifying remaining potential. Warranted future costs comprise a reasonable exploration budget to test that potential.INTRODUCTIONThe purpose of this paper is to describe a cost approach to the valuation of mineral exploration properties and to provide some valuation examples. The particular cost approach described is the Appraised Value Method, which is best applied to mineral properties at the exploration stage.At present there are no comprehensive regulations or guidelines in Canada which specify what approaches and methods to use for the valuation of mineral properties. In this paper, the Appraised Value Method described is one method that the writer considers to be accepted industry practice for mineral properties at the exploration stage.Mineral properties are valued for a number of reasons, including mergers and acquisitions, non arm's length transactions, pricing of initial public offering of stock, support for property agreements, litigation, expropriation, and insurance claims."

Jan 1, 2003

By K. Cybulski

Coal dust explosions still remain the main hazard in the coal mining sector, notwithstanding their relatively wide recognition compared to other hazards and the development of effective methods of prevention. Coal dust explosions are still the cause of numerous catastrophes, often leading to fatalities. Fortunately, they rarely occur, and it is for this reason that their hazardous impact is often underestimated. This problem in Poland is being exclusively solved by the Central Mining Institute, Experimental Mine Barbara. Here, basic research on the phenomenon of coal dust explosions and prevention methods is carried out, as well as investigations into the causes and circumstances of past accidents. After 15 years of no coal dust explosion accidents in Poland (1987?2002), a few coal dust explosions have recently occurred, with tragic consequences. These events have taken place not only in hard coal mines, where the presence of dangerous coal dust is the result of common production cycle, and safety measures against coal dust explosions are subject to specific regulations, but also in coal-fired power plants. This is of special concern because prior to 1987, such accidents had been been reported only for coal mines and not for coal-fired power plants. In recent years, two dust explosions occurred in Polish power facilities: the Dolna Odra and Turow power plants. In both cases, coal dust explosions occurred in the fuel supply system, but biomass dust was also involved. The explosions caused significant damage to the systems and buildings. This paper gives description and schematics of the regions of catastrophic coal dust explosions that have occurred in recent years in Poland, as well as the results of post-accident investigations, presenting the coal dust explosion hazard at the accident scene The results specify in detail the state of safety measures against coal dust explosions in light of the relevant regulations in force, including amount of deposited coal dust, content of incombustible matter in coal dust, free moisture content in coal dust, state of coal dust explosion safety zones, and state of explosion barriers. The conclusions from the site inspection and post-accident investigations presented enable us to determine locations of explosion initiation, probable ignition sources, range of explosion flames, and explosion barrier performance. A complete elimination of coal dust explosion hazard at the site of dust deposition is practically impossible to achieve. Similarly, a total elimination of ignition source, which may be related to the occurrence of other natural hazards, equipment malfunction or human errors, is impossible. The examples of tragic events that took place in Polish coal mines and coal-fired power plants highlight shortcomings and mistakes made in terms of assessment and prevention measures taken against the coal dust explosion hazard.

Aug 1, 2013

By K. A. Natarajan, S. Usha Padukone

"An industrial waste liquor having high sulfate concentrations was subjected to biological treatment using the sulfate-reducing bacteria (SRB) Desulfovibrio desulfuricans. Toxicity levels of different sulfate, cobalt and nickel concentrations toward growth of the SRB with respect to biological sulfate reduction kinetics was initially established. Optimum sulfate concentration to promote SRB growth amounted to 0.8 - 1 g/L. The strain of D. desulfuricans used in this study initially tolerated up to 4 -5 g/L of sulfate or 50 mg/L of cobalt and nickel, while its tolerance could be further enhanced through adaptation by serial subculturing in the presence of increasing concentrations of sulfate, cobalt and nickel. From the waste liquor, more than 70% of sulfate and 95% of cobalt and nickel could be precipitated as sulfides, using a preadapted strain of D. desulfuricans. Probable mechanisms involving biological sulfide precipitation and metal adsorption onto precipitates and bacterial cells are discussed.IntroductionIndustrial effluents from hydrometallurgical and mineral processing operations often contain high sulfate and metal concentrations posing significant disposal problems, which require urgent solution to avoid serious environmental contamination. In such waste liquors, sulfate and heavy metals such as cobalt, nickel, zinc and iron originate from the chemical or biological oxidation of exposed sulfide minerals. Reduction of sulfate and precipitation of toxic metal ions from industrial wastes is essential from the viewpoint of environmentally acceptable waste disposal and recovery of associated strategic metals.Many of these heavy metals are essential for metabolic activity of bacterial cells at low levels. But they exert toxic effects at concentrations encountered in polluted water. Removal of toxic metals through biological reduction of sulfates from industrial waste waters have been practiced for several decades. Metal remediation through common physicochemical techniques such as oxidation-reduction, chemical precipitation, filtration, electrochemical treatment, evaporation, ion exchange and reverse osmosis processes is expensive and not suitable in the case of voluminous effluents containing complexing organic matter and low metal concentrations. Further, strong and contaminating reagents are used for desorption, resulting in toxic sludge and secondary environmental pollution. Biotechnological approaches can be more efficient and cost effective for detoxification of such effluents. Biotreatment/ bioremoval offers several advantages over conventional chemical and physical treatment technologies, especially for diluted and mixed contaminants. Biological detoxification, which involves the use of microbes to detoxify and degrade environmental contaminants, has received increasing attention in recent years (Iwamoto and Nasu, 2001). In addition, valuable metals can be recovered from metal sulfide sludge (Boonstra et al., 1999)."

Jan 1, 2015

By Henry H. Roos

The productivity of the underground driller has increased 500-600% during the past 20 years. This increase is not due so much to improved percussion drills as it is to improved drill support equipment and modernization of mining methods, Efforts to mechanize drilling in mining operations were made as early as the late 1800's; and, patents on rock drill manipulating machinery date back to 1906. However, the great rush to mechanization began in the 1950's when the development of trackless mining methods gave mining engineers and equipment designers their first opportunity to create improved operating conditions for the equipment and to match the equipment with these conditions. Accordingly, this paper will summarize the developments of the past 20 years and will attempt a forecast of developments that can be expected during the next few years.

Jan 1, 1970

By R. D. Leitch

The work of the United States Bureau of Mines on stream pollution by coal-mine drainage has included a study of seasonal variations in acidity and volume of several streams in Pennsylvania. The acidity of these streams has been determined during the two or three years prior to 1930 and the results may be considered to represent "normal" low water conditions. The summer of 1330, however, was unusually dry and represents what may be termed "extreme low water conditions on these streams. This report is a comparison of the results obtained for extreme low water of 1930 and for other years. The streams investigated were Buffalo Creek in Somerset County, Indian Creek (lower 5 miles) in Westmoreland County, Little Toby Creek in Elk and Jefferson Counties, Daguscohonda Run in Elk County and West Creek in Elk and Cameron Counties. These will be treated separately in the order given. Most of the descriptive matter and physical data pertinent to the streams and drainage basins are taken from published reports of the Pennsylvania State Water Supply Commission, 1917.

Jan 1, 1931