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By Takeo Oki

A new suspension electrolysis method has been developed, which enables without any gas or dust pollutants a direct anodic extraction of zinc from zinc sulfide concentrates, while simultaneously oxidizing sulfide sulfur to elemental sulfur. The investigations were performed in a laboratory scale electrolytic cell with suspended zinc sulfide concentrate particles with or without graphite powder additions in dilute sulfuric acid electrolyte. By regulating the redox potential of the electrolysis system in combination with some additions, for example [Fe3+/Fe2+, MnO 4/MnO2, MnO 2/Mn2+ or MnO 4/Mn2+], the anodic dissolution reaction of zinc sulfide has been accomplished effectively without evolution of hydrogen sulfide. Under optimum conditions the anodic current efficiency of zinc dissolution ammounted up to 95 %, while sulfide sulfur was converted nearly completly to the elemental form. Purification by removal of sulfur and other impurities gives a zinc sulfate solution suitable for electrolysis to cathode zinc.

Jan 1, 1975

By Mahiyar Nasarwanji, Jonathan K. Hrica, Jonisha P. Pollard, Lydia M. Kocher, Brianna M. Eiter

Within the metal/nonmetal mining sector, fall-related incidents account for a large proportion of fatal and nonfatal injuries that occur in mining in the United States. However, the events and contributing factors leading up to these incidents have not been fully investigated. To help provide a clearer picture of these factors, an analysis of imminent danger orders issued by the U.S. Mine Safety and Health Administration (MSHA) from 2010 through 2017 at both surface and underground metal/nonmetal mine sites revealed that most orders are associated with fall risks. Of these cases, 84 percent involved the workers not using fall protection, fall protection not being provided or the improper use of fall protection. Fall risks for workers most frequently occurred when standing on mobile equipment, performing maintenance and repairs on plant equipment or working near highwalls. In most cases, a single, basic, corrective action — such as using fall protection — would have allowed workers to perform the task safely. Overall, these findings suggest that a systematic approach is needed to identify, eliminate and prevent imminent danger situations. Furthermore, to protect mineworkers from falls from height, frequently performed tasks requiring fall protection should be redesigned to eliminate the reliance on personal fall protection.

By E. H. Smith

St. Joe Minerals Corp., a subsidiary of Fluor Corp., treats high-grade gold, silver, and copper ore at its El Indio plant at an altitude of 4 km in the Chilean Andes. The ore is complex, being a mixture of massive pyrite-enargite and quartz, both containing very fine gold and silver. Treatment produces a copper flotation concentrate containing high levels of gold, silver, and arsenic, and also dore bullion. Part of the flotation concentrate is roasted to remove the arsenic content, and arsenic trioxide is collected as a by-product.

Jan 1, 1987

By Eric Ohl

Due to the world's ever increasing minerals and energy demands, process plants have to cope economically with ever growing throughput rates. This trend has accelerated the development of high capacity vibrating screens. Screens with screening areas of 30 to 50 square meter (322 to 540 square feet) and width of 5.5 meter (18') are technically possible and are being used presently with great success. This paper will concern itself with the general aspects of large screen design, by using modern technology and the latest findings with regards to fatigue strengths relative to the laws of vibration. It also will investigate the technical and economical limits of such designs.

Jan 1, 1983

By J. Herbst, J. Groppo, A. Noble, R. Q. Honaker

"Coal and coal byproducts produced annually contain a sufficient amount of rare earth elements (REEs) to meet current U.S. demand. The REEs exist in the form of minerals, ion-adsorbed elements associated with clays, and chemically bonded elements within the organic coal matrix or host mineral. Researchers at three universities collaborated to evaluate the effectiveness of existing physical and chemical concentration processes for the recovery of the REEs. The efforts found that physical separation processes can increase the total REE content in the thickener underflow material collected from a Central Appalachian coal cleaning facility from around 300 ppm to values greater than 17,500 ppm on an ash basis. Leaching followed by solvent extraction was found to be the most effective to recover the REEs from coarse middlings materials collected from multiple coal basins, as indicated by recovery values exceeding 80 percent. Based on material characterization data and process evaluations conducted for several potential feed coal sources, economic recovery of the REEs will require byproduct production of both clean coal and REE concentrate using a process flowsheet that is unique for each source. IntroductionRecent studies initiated by the National Energy Technology Laboratory showed that U.S. coals contain significant amounts of rare earth elements (REEs), suggesting that rare earth minerals (REMs) and/or REEs can be produced as byproducts (Ekmann, 2012). According to the report, the richest source of REEs is the Central Appalachian coal. At present, there are 208 coal preparation plants located in the region consisting of areas within the states of West Virginia, Kentucky, Pennsylvania, Virginia, Alabama and Tennessee, with a total capacity of 166,495 t/h, or more than 1 Gt/y (Fiscor, 2014). If only a portion of these plants are retrofitted with advanced separation processes, the U.S. coal industry would become a significant producer of REE concentrates as byproducts. An inherent advantage of becoming a byproduct producer of REEs is that no mining cost needs to be part of the production cost."

Jan 1, 2017

By Shani Engelbrecht, Belinda McFadzean, Avuyile Wali, Natalie Shackleton, Vratislav Malysiak

Frothers play a crucial role in sulphide and PGM ore flotation recovery, and AECI Mining Chemicals studies on PGM ores have shown significant flotation kinetic increases with the optimal frother-collector combinations. Using Senfroth 200 as the industry baseline, remarkable kinetic increases were observed with AECI Mining Chemicals developed frothers in the first concentrate. Even in the worst-case scenarios, 4E PGM recovery increased by 5% at a slightly higher concentrate grade. It is important not to limit frother dosage to a fixed value. Instead, enough frother should be added to maintain a stable bench float, measuring the dosages by frother volume before and after tests. Frothers can be specialized blends and their importance should not be underestimated. The results produced by formulating and innovating frothers to address specific industry challenges have been encouraging. Testing a frother on a plant scale does not have to be as daunting as with collectors, enabling the identification of the best frother-collector combinations at an industrial scale. AECI Mining Chemicals bench scale testwork has motivated plant-scale trials that have successfully transitioned to commercialization. This paper compares the results from metallurgical and froth stability tests and shows that occasionally frothers that have a less stable froth can have improved valuable mineral recoveries, while still exhibiting better drainage for reduced entrainment and mass pull. It was shown that caution should be used when relying only on simplified froth stability tests in the evaluation of new frothers.

Feb 1, 2025

"A carefully planned laboratory test program is the foundation for the successful development of a sulfide flotation process. In this paper, the development of a copper-molybdenum flotation process is described. However, the concepts discussed can be applied to most sulfide flotation systems and to many industrial minerals projects as well. Each step is examined, beginning with sample procurement and covering sample preparation, flotation test preparation grinding, scoping flotation tests for reagent scheme selection, rougher flotation parameter evaluation and cleaner circuit evaluation, through to locked-cycle testing and pilot plant design and operation. Ore variability and modeling to determine the response of various ore types to the optimum conditions established is also examined.IntroductionA carefully planned laboratory test program is essential for the successful development of any sulfide flotation process. These programs usually begin with a series of batch tests on several ore type composites to evaluate appropriate reagent schemes and delineate optimum rougher flotation conditions, such as primary grind size, flotation pulp density, flotation pulp pH and retention time. Cleaner parameters such as regrind size requirements, cleaner pH, pulp density and number of stages are then defined. Semicontinuous locked-cycle tests are performed using the parameters established in the batch tests to determine the effect of middling streams recirculation on flotation performance. The data generated and the experience gained in the locked-cycle tests may be used to design and operate a continuous pilot plant if relatively large amounts of concentrate are required for further process development, such as optimization of byproduct molybdenum production from bulk copper-molybdenum concentrate.A comprehensive ore variability program is undertaken to determine the response of various ore types to the optimum conditions established. These ore variability programs often test hundreds of samples in standardized batch rougher and cleaner tests to ensure that the orebody is well understood.This article describes the development of a copper-molybdenum flotation process, but the concepts discussed can be applied to most sulfide flotation systems and many industrial minerals projects. The block flow diagram in Fig. 1 provides an overview of the development process."

Jan 1, 2016

By M. K. Larson

"Specialized numerical modeling codes have been developed over the years to estimate ground stresses during the excavation of coal in underground mines. One of these tools, MULSIM, a displacement discontinuity boundary element code, was last developed by Zipf into a version called MULSIM/NL [USBM 1992a, 1992b]. The code was used frequently in years past, but closure of the Bureau of Mines in 1996 marked the beginning of a pause in its development. A similar tool with distinctly different treatment of overburden idealization, LaModel, was subsequently developed [Heasley 1997] and largely displaced MULSIM/NL in the literature. However, recent work modeling deep western longwall coal mines [Larson and Whyatt 2013] has demonstrated that MULSIM has distinct advantages for regions with relatively stiff and strong overburden. This work required that MULSIM be revived and updated into a version called MulsimNL/Large. Updates include larger array sizes, greater precision, greater number of materials, and the addition of a five-point, six-segment pillar load/displacement model that provides the user a more flexible coal-strength model allowing hardening and softening before a final residual strength. MulsimNL/Large has the ability to calibrate to large load transfer distances observed in some western U.S. coal mines that appear to be caused by strong, massive units in the overburden and/or floor of a coal mine. Also, it provides the ability to calibrate gob stiffness to simulate measurements or estimates of overpanel weight distribution between gob and abutment, while still maintaining load transfer distance with minor adjustments. MulsimNL/Large can easily implement material strengths calculated from various pillar strength models. The five-point model gives MulsimNL/Large the ability to easily simulate pillar behavior that is extracted from detailed pillar models, such as FLAC3D. MulsimNL/Large or similar approaches should be considered for evaluating mining layouts where stratigraphic conditions are known to cause overpanel weight to transfer to an extent significantly longer than the empirical method widely used to calculate load transfer distances in the U.S. [Peng and Chiang 1984; Mark 1987; USBM 1990]."

Jan 1, 2015

By Moussa Wone, Jeff Peterson, Filippo Azzarà, Daniele Nebbia

The DC Water and Sewer Authority's Long Term Control Plan includes tunnels, sewer separation, pumping station rehabilitation and green infrastructure to reduce combined sewer overflow (CSO) discharges to the District waterways. The Northeast Boundary Tunnel is a deep, large sewer tunnel that will reduce CSO discharges; signifi- cantly mitigate known chronic flooding in the Northeast Boundary drainage area and improve the water quality of the Anacostia River. This paper presents the unique combination of Owner and Contractor perspectives of the entire Project from conception through procurement, execution, and contract management, providing lesson learned, chal- lenges encountered, and solutions implemented to deliver the Project successfully.

Jun 23, 2024

By Linda J. Dahl

The U.S. Department of the Interior, Bureau of Mines is developing a process to selectively extract manganese from oxide ores as part of its in situ leach mining research program. The Bureau is conducting site characterization studies of two manganiferous iron-formation deposits which include: drill core, regional stratigraphic relationships from the existing geologic database, ore body geometry, geologic structure, hydrologic conditions, proximity of ore minerals to the leach fluid paths, surface subsidence potential, and data collected from laboratory leaching experiments. This information is being used to evaluate the technical, environmental, and economic feasibility of in situ leach mining of manganese for these two deposits. This paper will focus on the stratigraphy, mineralogy, ore textures, fractures, permeability, and porosity as they relate to in situ leach mining.

Jan 1, 1992

By H. Huang, R. N. Gow

"The reactivity of an enargite mineral electrode was investigated spectroelectrochemically under conditions typically found in alkaline sulfide leach solutions, with pH 11-13 and Na2S additions of 50 and 250 gL-1. A bulk enargite electrode was cycled between 0 and -1,000 mV for each set of solution conditions. Raman spectroscopy was used to determine and compare surface formations against species in mass-balanced EH-pH diagrams generated using STABCAL. Previously, it was determined that arsenic could be selectively leached under alkaline conditions at an average solution potential of -300mV, across the pH range 11-13. Operating under such conditions allowed for the selective leaching of arsenic with elemental sulfur formation. From several of the voltammograms obtained during this current testing, the formation of elemental sulfur appeared at increasingly reducing conditions with increasing sulfide concentration. At high concentrations, copper started to dissolve, possibly as a bisulfide complex, reducing the selectivity of the leach, unlike previous studies. However, the presence of the higher sulfide concentration is also anticipated to prevent passivation by consuming any surface formation of elemental sulfur. This study provides insight into the operating parameters of alkaline sulfide leaching in regards to the selectivity of arsenic leaching, as well as guidance for control of reagents and solution potential and, of course, the need for water treatment afterwards.IntroductionEnvironmental limitations on the pyrometallurgical processing of arsenic-bearing concentrates have forced operations to consider other solutions. Attempts to hydrometallurgically process enargite (Cu3AsS4) fall into two categories: the co-dissolution of arsenic and copper under acidic conditions, and the selective leaching of arsenic under basic conditions. The authors believe that the selective leaching of arsenic is more amenable because it produces a solid copper phase, preferably chalcocite (Cu2S) or covellite (CuS) that could then be processed using conventional methods already in place in the copper and gold industries. Potential leaching methods include alkaline sulfide leaching (Achimovicovica et al., 1999; Anderson and Twidwell, 2008a,b; Tongamp et al., 2009 and 2010), hypochlorite leaching (Vinals et al., 2003; Curreli et al., 2005; Mihaljovic et al., 2007), ammoniacal leaching (Gajam and Raghavan, 1983), and acid leaching (Gow et al., 2014b) with or without fine grinding to mechanically activate the enargite surface and increase normally slow leach reaction kinetics (Achimovicova et al., 1999; Balaz et al., 2000; Balaz and Achimovicova, 2006). In this study, the reactivity of enargite under alkaline sulfide leach conditions was examined."

Jan 1, 2015

By Marcos Vieira, Gil Vilela, Wanderson Silvério, Livia Faustino, Pierre Fernandes

New global industry standards and regulatory changes regarding mining tailings management are driving installation of tailings filtration plants to decommission existing tailings dams and implement dry stacking. Target of this project was to reduce ultrafine slime tailings deposition. Previous investigation at Samarco concentrator has showed a 35% decrease in tailings filtration throughput when feeding a mix of 95% flotation tailings with 5% slime tailings (compared with 100% flotation tailings), also worsening geotechnical aspects such as material workability during dry staking. Industrial trials using a proper filter aid at tailings filtration plant feeding a mix of 94% flotation tailing and 6% slime tailing (equivalent to 30% of total slime generation) have provided filtration performance maintenance (throughput and cake moisture), and dry stacking the dewatered material. Results achieved will enable life expansion of existing slime disposal structures, as well as potential life of mining extension. Furthermore, reagent chemistry influence is discussed by the light of geotechnical aspects, which has been showing improved KPIs, such as workability, compressibility and permeability.

Feb 1, 2025

One of the critical challenges facing the mining industry ? and not just in the United States ? is the looming labor shortage. A significant percentage of the industry?s professional workforce is, well, getting old, and many will be retiring in the next 10 years or so. This is not a new issue to the industry. It has been discussed at various industry meetings and conferences for many years. How does mining, with its largely negative public image, attract young people to mining schools? And, equally important, who is going to teach them? Mining schools, what?s left of them in the United States, are beginning to lose qualified faculty to retirements, and no one is available to replace them. SME addressed this issue during the keynote session at its annual meeting in February in Denver, CO. This year?s theme was ?Mining: It?s About the People.? Despite a blizzard that blanketed the city on the day most attendees were to have arrived, the meeting still attracted a record 7,202 people. And the accompanying exhibit sold 822 booths, also a record. The U.S. Department of Energy?s National Energy Technology Laboratory contracted with the National Academies? National Research Council to complete a study concerning the availability of skilled workers to meet the energy and mineral security requirements for the United States. The National Research Council, in turn, asked SME to collect and analyze workforce trends in these industries. The result of SME?s analysis is the report ?Emerging Workforce Trends in the U.S. Energy and Minerals Industries.? It is available on the SME website, www.smenet.org. Click on Government Affairs. While the report did not paint a completely dismal picture, there were some disturbing results. It concluded that within 20 years there will not be a sufficient number of skilled professionals to satisfy the labor demand. That said, the report said that most of those positions would likely be filled. However, the U.S. mining will go through a period of time when the workforce will be made up of very young and senior workers.

Jun 1, 2013

By MARK J. VANARELLI

Estimating groundwater inflows in rock deep tunnels is critical to the safety of personnel constructing the tunnel and the cost of construction. This paper presents two case studies for estimating steady-state groundwater inflows into deep rock tunnels. The case studies included the Chattahoochee and Nancy Creek tunnels. In this paper, statistical methods were applied to packer test data obtained from exploratory borings during geotechnical site investigations. A semi-empirical procedure was utilized for estimating groundwater inflows into these deep rock tunnels. It is the most widely used method/procedure in the tunnel industry. The Chattahoochee and Nancy Creek tunnels are deep rock tunnels which exhibit radial flow conditions. For the radial flow condition, a statistical analysis presented in this paper indicates that the semi-empirical procedure works well; however, variations in the procedure and/or an insufficient amount of testing could lead to underestimations of the inflow quantities. Packer test data plotted in histograms were observed in all cases to be log-normally distributed for the radial flow condition. Modeling using Monte Carlo simulations was observed to be an effective tool for removing irregularities in the distribution of the data and incorporating high-end permeability data to derive reasonable groundwater inflow estimates. This paper is based on the PhD thesis entitled “Improvements to the Current State of the Practice in Steady-State, Groundwater Inflow Estimates into Rock Tunnels based on the Application of Statistical Analysis Methods of Packer Test Data obtained from Exploratory Borings During Geotechnical Site Investigations.”

Oct 9, 2020

By Richard A. Levins

The imposition of non-market regulations, such as the proposed SO2 standards for coal combustion, will typically lead to less efficient (thus more costly) production in a free enterprise system. For the coal industry these increased costs will occur in several ways, among which are mining less accessible low sulfur reserves and transporting low sulfur coal to distant markets. There are, of course, social benefits of reducing the S02 emissions from the use of high sulfur coal. The social benefits include decreased health risks, reduced damages to property, and certain unmeasurable benefits associated with the aesthetic appeal of clean air. Proponents of Federal S02 standards argue that the benefits gained from reduced emissions will exceed the costs borne by the coal industry and society in general in meeting the regulations. The purpose of this paper is to investigate the degree to which costs of meeting future energy demands from coal will change under different sulfur standards. No attempt is made to estimate the benefits of imposing regulations. Specifically, the impact of SO2 standards on the private costs of meeting regional coal demands, the competitive positions of the nation's major coal producing regions, the degree to which strip mining as opposed to underground mining will be feasible, the amount of coal being processed, and the amount of coal transported over major rail routes will be analyzed.

Jan 1, 1976

By J. A. Dos Santos

"INTRODUCTION Dramatic reduction in energy use and environmental impact can be achieved with sandwich belt high angle conveyors that serve as the vital link in any IPCC (In-pit Crushing and Conveying) system. These high angle conveyors are not new at all, but have not found wide use in IPCC systems where they can realize the greatest advantage. Reduced energy consumption and environmental impact, with IPCC systems, was already realized in the 1970s. With the bulk material haulage limited to conventional open trough conveyors the most direct path out of the open pit was precluded, requiring low angle spiral ramps and/or deep slots and/or tunnels through the high wall of the open pit. These excavations, to accommodate the low angle limitations, represented undesirable impact on cost and on the environment. Against this backdrop, a major study in 1979 sought to develop high angle conveying systems that could continuously haul the mined bulk material directly out of the pit, along the high wall – the shortest distance between the two end points. Between 1979 and 1982, that study developed sandwich belt high angle conveying systems that utilized all conventional conveyor equipment including smooth surfaced rubber belts that could be continuously scraped clean. These systems had all of the positive features of conventional conveyors but overcame the angle limitation. By hugging the bulk material between two belts, the material’s internal friction could be developed to facilitate conveying at any high angle up to 90 degrees (vertical). After an intense testing period (about one year) on the first large scale prototype system, commercialization began in 1983 with the installation of a 60 degree incline system at a western United States coal mine, elevating 2000 t/h of coal to a train load out system. It did not take a long period of scrutiny and acceptance before this high angle conveyor found use in the most rugged requirements of an IPCC system. This was only the second commercial sale, and after more than 150 commercial installations, it remains arguably the most significant high angle conveying system. In 1984, a copper mine in Serbia, already using pit perimeter crushing and conveying, decided to move their primary crusher deep into the pit and to use a sandwich belt high angle conveying system to elevate the ore continuously, directly out of the pit, along the high wall to the pit perimeter where it then transferred to a conventional conveyor for the remaining haul to the plant. The system had significant features including 2000mm wide belts that elevated 250mm coarse ore, at 4000 t/h, over six 15-meter high benches for a total 90 meters of net lift. The system was able to reduce the truck haulage fleet by ten 200 ton trucks realizing great cost savings, zero emissions to the air and greatly reduced traffic congestion in the pit. The system operated successfully until 2002 when the mine shut down. Many successful sandwich belt high angle conveyors followed with the current count of commercial installations at more than 150. Despite the great success with this system, its use has not been repeated as part of an IPCC system."

Jan 1, 2018

By Henry T. Mulryan

The philosophy, strategy and techniques of successful marketing of talc, differ sharply from those applied to most other mined products. Unlike non-ferrous metals, there are no commodity exchanges to facilitate the transfer of goods. Unlike iron ore and some non-metallics, assured markets by means of long term contracts are practically non-existent. Talc must be sold and sold and sold again. The normal channels of talc distribution are almost identical to those used, by the chemical industry. These consist of a blend of producer marketing staff, field technical service, and sales force; and independent chemical wholesalers. Like the term "chemicals", there is tremendous product diversity contained in the rather loose expression "commercial talc". Certain kinds of talc, processed in conventional ways, are regarded as commodities by the consumer. That is, that material from one source or supplier is considered to be effectively interchangeable with those available from a number of other areas and producers. Under such conditions, lowest delivered price, quickest delivery, and best, customer service, are the key factors in a successful sales effort.

Jan 1, 1965

By Miguel Reyes, Mathew Girman, Chenming Zhou

Modern smart mining increasingly depends on sophisticated electrical and electronic systems for improved safety and productivity. With more electronic systems being introduced underground, the mining industry faces electromagnetic compatibility (EMC) issues caused by electromagnetic energy emitted by one device adversely impacting the normal function of another. This paper provides an overview of EMC and electromagnetic interference (EMI) research for underground mining, including a review of EMI in other industries applicable to mining, published EMI research pertaining to mining applications, representative EMI incidences, related EMI legislation in mining, and mitigation strategies.

Jan 3, 2022

By J. P. Ducarme

The eastern U.S. contains vast reserves of thin seam coal deposits, particularly in the Appalachian mountain region. These typical 355 to 710 mm thick reserves are difficult or uneconomical to recover with present technology. The U.S. Bureau of Mines is developing technology that would allow nearly 100% recovery of thin seams in these mountaintop regions. This paper details the research that has been conducted on these new techniques and presents results of testing on a cross-ridge full-scale physical model.

Jan 1, 1994

By R. P. Schneider

The Chino mine, concentrator, and smelter are located in Grant County in Southwestern New Mexico. Chino Mines Company is a partnership two-thirds owned and operated by Kennecott Santa Fe Corp., and one-third owned by MC Minerals Corp. (Mitsubishi) of Japan. The Chino Ore Body The Chino ore body is a widely varied deposit of rock types and contains intrusive stocks and sediments. The stocks contain chalcocite in a matrix of quartz, mica, and feldspar. Much of the feldspar is altered to clay. Some of these stocks are enriched with native copper. The sediments contain chalcopyrite associated with gangue minerals including magnetite, pyrite, garnet chlorite, and epidote. The contact of the stock and sediment is heavily altered to chlorite and clay. The stock ores contain economic quantities of molybdenite. The operating work index of Chino ore varies from 5 to 20 kwh/ton and averages 8.5 kwh/ton. The ore head to the concentrator averaged 0.81% copper and 0.010% molybdenum. Fifteen percent of the total copper head exists as nonsulfide mineralization.

Jan 1, 1985