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By Richard E. Otoo, Evan J. Owen, Virginia T. McLemore

Disruption in critical minerals supply chains has resulted in the evaluation of various types of mineral deposits for critical minerals potential. Much of the study on critical minerals focuses on occurrence and characterization, but little research has addressed what concentrations of critical minerals in a mineral deposit are required to make an exploration target into an operating mine. Understanding the cut-off grades of ore deposits being actively mined is one criterion to determine if concentrations in an exploration target are high enough. Cut-off grade is defined as the minimum amount of mineral contained in a ton of ore that is sent to the processing plant. Among many factors, cut-off grade depends upon the size and type of the deposit and mining operation, the processing technique, and market prices. This research does not aim to define cut-offs for determining if a mineral deposit is economic. Rather, it defines estimates of concentrations of critical minerals that could be considered good enough for further exploration. For example, ~2% total rare earth oxide (TREO) is the cut-off grade for Mt. Pass carbonatite, but 500 ppm TREO could be an exploration target for coals.

Feb 1, 2025

Several major impediments threaten the successful delivery of tunnel and under-ground construction projects. In addition to technical design and construction risks associated with tunnel projects, many of which are well understood, budgetary pressures, funding constraints and the complexity of procuring, administering and executing multiple concur-rent projects in a large program could also have a catastrophic impact on the program?s objectives. Contributing factors often include poorly managed design, procurement, construction, managerial, organizational, market and stake-holder risks, as well as nonconforming inputs or outputs to the costs and schedule, or any other potential inabilities to deliver the required or desired results. A strategy to prevent ?failure? of a project requires a proactive and holistic approach to risk management. Through planning, identification, analysis, management, monitoring and control of the project?s risks (both threats and opportunities), attention to management of risk will in-crease the probability and impact of positive events and decrease the probability and impact of events adverse to a project?s objectives.

By Z. Konstantinovic, M. Ahrens

Due to the large installed electrical power and the large number of electric drives in minerals and mining plants power factor compensation and harmonic filtering has always been an important issue. For the design of harmonic filter and power factor compensation installations several approaches can be taken. The paper describes different concepts and their advantages and analyzes special requirements and design considerations for minerals and mining plants. It also highlights areas where problems can occur and which points need to be addressed carefully. Optimized designs and solutions are discussed in case studies and the resulting energy savings and benefits for the plant operation are shown.

Jan 1, 2007

By M. D. Loy

In addition to products available from private vendors, many useful programs are developed at universities - in fact, many of these programs led the way to commercial development. Other projects are assigned to consultants with backgrounds in system design and mining. Both types of development have led to programs that can be acquired for the cost of a tape or disk. This paper highlights several underground mining packages. These programs consist of: ? USBM model-developed by the United States Bureau of nines. ? PSU model-developed by Pennsylvania State University. ? VPI model-developed by Virginia Polytechnical Institute and State University. ? NUS model-developed by NUS Corp.

Jan 1, 1987

By David Crouthamel, Raymond Henn

"The need to fill the void space or annulus created between an excavated tunnel or shaft and the final lining system has long been a requirement in underground construction. Most of those types of voids are created as a result of employing the two pass tunneling lining method. Filling of this void is called backfilling. For many years the materials used as backfill were primarily reinforced and non-reinforced concrete, sanded grout, neat cement grout, or blown-in sand/pea gravel. However, in the past 20 years the use of cellular grouts/cellular concrete as the backfill material has greatly increased. Most cellular grout is made of a mixture of water, Portland cement (with or without the addition of fly ash), a foaming agent and admixtures such as a water-reducer or superplasticizer.It is the authors’ preference to use the term cellular grout as opposed to cellular concrete since by ACI Concrete Terminology an ACI Standard (ACI CT 13), concrete contains aggregates. Normally cellular grout does not contain sand (finite aggregate), but almost never contain course aggregates.The authors believe there are several reasons for this increased use of cellular grout as backfill, such as:• The increase utilization of the various trenchless tunneling methods. Tunnels constructed using trenchless method tend to be smaller in size, excavated diameter or cross sectional area. Making man-entry for placing backfill from inside the secondary liner, utilizing pre-installed grout posts, more difficult if not impossible. It is these workspace restrictions that are the drivers as to when to utilize grout ports installed during the pipe/liner fabrication versus grout delivery pipes installed within the void/annulus space.• The ability of cellular backfills to be pumped and flow longer distances.• The unit weight of cellular grouts can be controlled by mix design and generally can range from 560 Kg/m3 (35 lbs/CF) to 1040 Kg/m3 (65 lbs/CF)."

Jan 12, 2017

By J. H. Kelley

In this paper, we show that the methane emission and the dust generation in under-ground mining currently and in the future pose operational, health and safety conditions which adversely Impact face productivity and worker satisfaction. One solution is the use of a dual-aircourse system of ventilation. In this concept, one aircourse captures and exhausts to the surface the dust generated and the methane emitted in coal/mineral fragmentation while a second aircourse provides workers with cleaner air for breathing and comfort. Various dual-aircourse configurations adapted to the Variable Wall Miner are analyzed and compared with conventional mining in gassy seams, indicating a marked reduction in the required air quantity and the number of aircourses.

Jan 1, 1996

By J. J. Antony

As the first wave of precious metal heap leach closures and reclamation projects occur, a number of companies are being hit with costly surprises. While this paper refers specifically to U.S precious metal projects, it could be conceptually directed at copper leach operations and acid rock drainage (ARD) problems on an international basis. ARD is Mother Nature's version of heap leaching, only with different products and timing. Although many precious metal deposits tend to be small in comparison with some base metals systems (porphyry copper deposits), adjacent or nearby discoveries have extended the operating lives of numerous precious metal mines. Now, depleted reserves, several years of relatively depressed precious metals prices and some properties with technical difficulties have resulted in numerous mine closures. As a result, our industry is getting a diverse and comprehensive initial look at mine closure and final reclamation. The situation has been further complicated by the evolutionary trend in regulations and their enforcement and increasing public and political awareness of all environmental issues. Concurrent (proactive) vs. deferred (reactive) reclamation and a realistic early appraisal of ultimate reclamation and closure requirements, not just regulatory compliance, need to be a part of project design. The U.S. and Canada are the current fertile testing grounds and have set the design, regulation and closure standards for the next wave of operations in Latin America, the CIS (?), etc.

Jan 1, 1994

By L. G. Hendrickson

Direct-reduction processes for converting iron ores to metallic iron in the solid state have been available for some time; and whenever scrap becomes expensive, there is a new wave of interest in these processes. It is well established that direct reduction, coupled with electric-furnace steelmaking, is a technically viable method for making steel and in some circumstances is economically competitive with the conventional blast-furnace--basic-oxygen-process (BOP) route to steel. This raises a number of interesting questions, several of which could be of great interest to the coal and ore mining industries. For example, what are the quality requirements of the raw materials for direct-reduction--electric-furnace steelmaking? Would they be different from the present requirements for blast-furnace--BOP steelmaking? Other questions relate to how much steel will be made by the direct-reduction route in the future. The quality questions can be discussed with a fair degree of certainty, but a prediction of the amount of steel that will be produced by the direct-reduction--electric-furnace route is beyond the scope of this paper. However, an attempt will be made to identify some of the factors that will influence whether there is a swing to direct reduction and the rate at which it may occur.

Jan 1, 1978

By Christoph Schulte-Schrepping, Bou-Young Youn, Rolf Breitenbücher

"The main requirements of two-component grouts are a high workability and sufficient stability against sedimentation with a retention time of more than 72 hours, as well as a rapid strength development im-mediately after grouting. Component A usually consists of OPC, water, bentonite, and retarding agent. Component B, a liquid accelerator, is added to Component A during grouting at the end of the shield tail. Current investigations on different compositions of Component A showed a high workability lasting for at least 72 hours. The workability could be extended with increasing amount of the retarding agent to a certain degree. An increase of the bentonite content improved the stability of the mix, but had a negative impact on the flowability respectively the workability of Component A. High compressive strengths could be rather achieved by an adapted mixing ratio of Component A and B than by increasing the amount of the accelerator. Thereby, the interactions and compatibility of the selected constituents play an essential role. INTRODUCTION In mechanized tunneling with segment linings, the annular gap between segment ring and soil must be filled instantaneously with an adequate grouting mortar. The main functions of the annular gap grouting are to stabilize the tunnel lining and to minimize settlements of the ground surface at the same time. Thereby, two contradictory requirements are demanded on annular gap grouts: On the one hand a high workability and sufficient stability against sedimentation, on the other hand a rapid strength develop-ment immediately after grouting. Besides single-component grouts, which achieve the necessary stiffen-ing by dewatering into the surrounding soil, two-component grouts are used, especially in cohesive soils with a very low permeability. Basically, annular gap grouts are almost exclusively defined on empirical basis. Fundamental studies about the constituents and composition of the grout as well as the related achievable properties are still missing so far. Therefore, it is necessary to investigate the material-specific correlations regarding the relevant parameters of annular gap grouts – workability and flowability, stability of the mix as well as strength development – in comprehensive experiments. Based on the knowledge gained from the investigations, it should also be possible, to perform the grouting material according to a real design concept and thus, to ensure an adequate grouting in prac-tice considering the geological and hydro-geological conditions."

Jan 1, 2016

By Göksel Hızlı, Selim Ertürk, Ayşegül Bilen, Raşit Sezer, Cüneyt Arslan

The carbothermic reduction of celestite is the first step in producing many strontium products. The way materials move in the rotary kiln has an essential effect on the carbothermic reduction efficiency as well as the temperature. In this study, the reduction of celestite ore and excess carbon blend in a laboratory-scale rotary kiln was investigated. In the experiments carried out at three different temperatures, the rotational speed and slope of the furnace tube were altered, and their effects on the reaction efficiency were examined. The leachability of the reduced powders and the content of the unburned coke indicated the optimal parameters for the reaction.When the speed was increased to 10 rpm, the powders weremoremobile in the stack and could react more easily with the furnace atmosphere. According to the results, celestite can be reduced by carbon at temperatures of 1000–1200 °C, at rates of between 5% and 75%. The maximumreaction yield (75%) was obtained with a slope of 2° and a rotational speed of 6 rpm at 1100 °C.

May 7, 2020

By D. N. Madge

A description will be given of an approach to plant process automation based on the strategy of first developing an information system followed by later development of process models. The advantages of this approach over the unit process control will be outlined. Some insight will be given into the risks associated with this method. These risks can be shown to be primarily economic.' Some reference will be made to two Cominco installations in the interests of illustrating the generality of the information systems approach.

Jan 1, 1972

By R. M. Quinlan

The coal industry in the United States has undergone significant economic changes during the past six years. The price of coal remained relatively constant from 1950 to 1969 (See Figures 1 and 2). Steam coal prices tripled and metallurgical coal prices doubled from 1969 to 1974. This price structure has created a new economic environment for coal preparation. Contributing factors to these price trends include: ? Coal Mine Health and Safety Act of 1969 ? Mid-East oil embargo of 1973 ? United Mine Workers of America contract agreements ? Productivity decrease (tons per man-day basis) ? Environmental Protection Agency regulations The increased value of coal justifies additional capital investment in cleaning facilities to optimize yield. Current trends include recovery of existing slurry ponds and recleaning of refuse. Coal preparation plant product yield and quality must be evaluated in terms of the amount of capital expended and cost of operation. Therefore, it is advantageous to optimize the plant product based on clean coal selling price and rate of return on investment.

Jan 1, 1976

By C. M. McCulloch

More and more mining underground is being conducted using the longwall method. Likewise, many new surface mines use area or mountaintop removal methods. These methods can have a significant impact on surface and groundwater resources. The overall study of the effects on surface and groundwater from mining is referred to as the probable hydrologic consequences (PHC) determination of mining and reclamation. Collection and interpretation of information concerning groundwater and surface water quality and quantity, as well as detailed geologic analysis, is required to adequately define the impacts of mining. This paper discusses the present day requirements and methodology of preparing a PHC for a large mining operation in the eastern coalfields.

Jan 1, 1995

By A. Kaina

The San Luis deposit is one of the few documented gold deposits on a detachment surface. This paper presents mineralogic and geochemical data that was gathered to characterize the mineralization, classify the ore deposit, and provide details of the ore forming process. Included are data on the paragenesis; alteration-mineral assemblages major and trace element geochemistry, and fluid inclusions. The San Luis deposit occurs on the western slope of the Sangre de Cristo Mountains adjacent to the San Luis Basin about 5 miles northeast of the town of San Luis in Costillo County, south-central Colorado. Mineralization was discovered in the district in the early 17th century. Production began in 1890 on lead-silver ores from which the district took the name the old name of "El Plomo". From 1897 through 1934 gold was intermittently produced. Battle Mountain Gold Company took an option on the property in 1987 and proved on ore body comprising an eastern block that has 1,277,300 t ore at a grade of 1.68 g/t and a western block of 9,744,000 t with a grade of 1.34 g/t. Production began in 1990. A companion paper by Benson (1994) describes the San Luis district and the ore body, hence the reader is referred to this or Robert and David (1990) for details of the geology from which the following is summarized.

Jan 1, 1994

By A. G. Kim

Increasing transportation costs, clean air regulations and the decreasing availability of landfill space are factors in the increased interest in the utilization of low cost disposal sites for coal combustion residues (CCR). Inactive surface and underground coal mines can satisfy the conditions for stable CCR disposal sites, and subsurface CCR injection can be beneficial in reducing the amount of acid mine drainage (AMD) often produced at such sites. The material is expected to add alkalinity to the subsurface environment and to decrease the permeability and porosity of the buried spoil. Both mechanisms can reduce the amount of acid normally generated at a mine site. The Bureau of Mines is cooperating with an independent coal company in a test of subsurface injection of a mixture of fly ash, from conventional power plants or from fluidized bed combustion (FBC) , with AMD sludge into a reclaimed surface mine. Changes in water quality parameters and the concentration of heavy metals in water samples from wells and seeps are being used to assess the effect of CCR injection. The preliminary results discussed here indicate that improvement in subsurface water quality was related to fly ash injection and that components of the fly ash were stable in the acid environment.

Jan 1, 1994

By J. C. Gathje

The Robinson copper ores were mined for many years from pits containing varying ore grades, sulfide and oxide ore types, and differing mineralogy. The ores also contain gold and molybdenum values, and their recoveries are an integral part of the flowsheet development. Metallurgical responses were characterized using a standard flotation procedure. Further studies investigated primary and regrind particle sizes, reagents, and other variables. The metallurgical testing was supported by mineralogical studies. Results demonstrated a high degree of metallurgical success for flotation. Final copper concentrates ranged in grade from approximately 28 to 30% copper and copper recoveries were 89 to 95% based on laboratory and pilot plant data.

Jan 1, 1992

By Clarice L. Amaral, Ricardo Melamed

Clay-coating has been used as an environmental technology tool for the immobilization of toxic elements. The mechanisms of arsenate retention in clays suggest that not only the system pH is of fundamental importance in the process but also the character of metals and ligands that compose the electrolyte system. The goal of this study was to investigate the interactions between system pH and electrolyte ions on the retention of arsenate in an Oxisol soil. The sorption of arsenate decreases with the increase in system pH, reflecting the competitive sorption of arsenate with OH groups. Solutions containing Ca tend to favour the immobilization of arsenate in a relatively broad pH range.

Jan 1, 1998

By K. Häge

"Die Nachhaltigkeit der Braunkohlengewinnung in der öffentlichen Wahrnehmung wird nur weiter erfolgreich kommuniziert werden können, wenn durch konkretes Handeln glaubhaft gezeigt wird, dass die offenen Fragen fair und solide beantwortet werden. Dazu gehören insbesondere die neue innovative technische Lösung sowie das sensible Interessenmanagement. Die Braunkohlenindustrie hat gelernt, dass Offenheit und nicht zuletzt das beständige Bemühen um den Meinungsaustausch mit ihrem Umfeld wichtige Elemente sind. Der in Jahrzehnten erworbene Schatz an Glaubwürdig-keit ist eine Basis, auf der die Braunkohlenindustrie ihre Zukunft gestalten kann. Darüber hinaus sind politische Rahmenvorgaben erforderlich. Das öffentliche Interesse an einer sicheren und preiswerten Energieversorgung unter Einschluss der Braunkohle ist unverzichtbar. In diesem Kon-text kann dann die Braunkohle die an sie gerichteten Fragen der Ökonomie, der Ökologie und der Sozialverträglichkeit auch mit Hilfe von Indikatoren beantworten.ABSTRACTThe discussion of the sustainability of lignite mining can only be continued successfully if the indus-try acts in a practical manner and demonstrates trustworthiness by responding fairly and reliably to open questions. This includes new and innovative technical solutions as well as the sensitive management of interests. The lignite industry has learned that openness and the constant effort to exchange viewpoints within their environment are all essential elements. The credibility that has been gained over the decades is the foundation on which the lignite industry can build its future. Beyond that a framework of political guidelines is necessary. Public interest in a secure and inex-pensive energy supply that also includes lignite is indispensable. In this context, the lignite industry will then be able to answer the questions which are directed at them and concern the economy, ecology, and social tolerability also by indicators."

Jan 1, 2005

By G. France

The Blair Athol Coal Mine (BAC) is a large open cut operation in the Bowen Basin of Queensland, Australia. Current mine capacity is about 11 million tonnes per annum (Mtpa) of export coal. On-line analysis at BAC consists of two Coalscan 9500s installed directly on the output of the crusher plant and immediately before the product stockpiles, while a third Coalscan 9500 is installed on the transfer conveyor feeding the train loading bin. The two product Coals cans have a dual purpose. The first is to provide real time coal quality data directly back to the mining operations. The second is that of modeling the product stockpile with accurate on-line information. This modeling enables both production and coal quality personnel to accurately examine the coal quality of each stockpile with a degree of resolution which previously had never been achieved.

Jan 1, 1999

By T. W. Eddy

Research was conducted in which elemental mercury and its sulfide mineral (cinnabar) are removed from a copper sulfide concentrate by low temperature thermal applications. The goal of this research was to reduce, volatilize, and collect mercury vapor from concentrated smelter feed in a simulated drying environment while maintaining the chemical integrity of the residual. The study used synthesized concentrates composed of copper sulfide and mercury bearing minerals (such as cinnabar (HgS) or elemental mercury) to determine optimal residence times and temperature ranges.

Jan 1, 1996