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By Brian J. Gorva

The key objective of forming a cartel is to increase profits to members of the cartel by taking the following action: a) control output; and b) control price. However, while attempting to obtain monopoly profits the cartel members have to contend with costs associated with cartelization and such costs include the following: political costs; the cost of coordinating output and price; organizational costs (such as cheating); and administrative costs (such as the cost of attending cartel meetings). The objective of commodity exchanges is to provide an open, free market where buyers and sellers may openly complete transactions and pricing information can be immediately disseminated. These transactions include the following: a) to provide facilities for "hedging", or transferring price risk from buyers and sellers of physical commodities to "speculators" through the medium of buying and selling futures contracts, and b) taking physical delivery of metal on due dates.

Jan 1, 1983

By James C. Cobb

Middle Pennsylvanian (Desmoinesian) coals of certain areas of the Illinois and Forest City Basins contain epigenetic sphalerite and associated minerals in veins, clastic dikes, cleat, and other small-scale structural features. The presence of sphalerite in these coals records information about the geology of coals and coal basins, and represents a potential source for zinc as a byproduct of coal production. Origin of Sphalerite in Coal The origin of sphalerite in coal suggested by Cobb (1) involves sphalerite precipitation from zinc-bearing ?Na-Ca-Cl brines upon contact with sources of sulfur in the coal bed, e.g., pyrite, H2S, and organic sulfur. These brines were essentially at the temperature of the host coals as determined by fluid-inclusion thermometry and vitrinite-reflectance studies. The migration of these brines into coal beds may have been caused by compaction of sediments due to continued sediment loading of the coal basins. Zones of high permeability such as sandstones and the coals themselves presumably acted as conduits for the movement of the brines. The open spaces where sphalerite was deposited resulted from minor deformation associated with differential compaction and cleat formation enhanced by volume shrinkage during coalification.

Jan 1, 1982

By Bo R. Arvidson

High-energy product permanent-magnet materials of rare-earth cobalt alloys are being used in applications where space or weight are at a premium cost. New applications like friction-free bearings are also made possible. However, such magnet materials have not been commercially used in magnetic separators until now due to the high cost for the overall magnetic flux generation relative to commonly used ceramic magnets or AlNiCo magnets. The design of the new high-intensity permanent- magnet roll separator (PERMROLL) takes advantage of the unique properties of rare-earth cobalt magnets rather than just substituting for conventional magnet materials now in use for magnetic separators. Hence, the new generation of high-intensity magnetic-roll separators has some unusual characteristics that make known magnetic separation applications more economically attractive, and even expands the magnetic separation technology area to include applications for which no other feasible methods are presently known.

Jan 1, 1983

By Leon D. Keller

Hydraulic concentration of minerals has been practiced for a good many years. Until recently, however, the practice has been limited to a multiplicity of small pockets and relatively low tonnages and flows. The adaptation of the SiphonSizer to the concentration and classification of magnetite has changed this concept. Some fifty commercial units are currently in operation on magnetite, varying in size from 16 ft diameter circular unit to a 25 ft by 100 ft rectangular unit. Additional units up to 38 ft diameter are under construction. Depending upon the application in the flowsheet, upgrading-varies from 0.75% to 14% Fe in a single stage. To those not familiar with taconite processing, the importance of the struggle to economically remove as much silica as possible may not be fully appreciated. These figures pertaining only to transportation may be thought-provoking. If a 10,000,000 ton per year plant could reduce the silica content of their concentrate by 17, a savings in boat freight alone would amount to 100,000 tons at $2.00 per ton annually.

Jan 1, 1963

By Kiran B. Chaudhuri

The Kivcet process is technologically the most advanced of the new lead smelting processes which have been developed over the past decade construction of the first commercial scale Kivcet lead smelter which has been designed by KHD Humboldt Wedag for Sociedad Complejo Metalurgico de Karachipampa is at present nearing completion in Bolivia. Some of the measures taken to minimise emission of harmful elements as well as methods employed to minimise energy consumption in the design of the smelter, are presented. Results of recent testwork which have added to the flexibility of the process are summarised.

Jan 1, 1982

By B. Petkof

Olivine has been an accepted industrial mineral for the last 50 years. Its initial acceptance was based on the recognition of its refractory properties by European research workers in the middle to late 1920's. Initial U.S. olivine production began in the early 1930's in North Carolina and continues there today. Olivine also is produced in the State of Washington and in other countries.

Jan 1, 1982

By J. H. Rowland, R. A. Thomas, III, C. D. Litton

Atmospheric monitoring systems (AMS) are required when using air from conveyor belt entries to ventilate working sections in U.S. underground coal mines. AMS technology has the potential to increase fire safety mine-wide, but research is needed to determine the detection and response times for fires of a variety of combustible materials. To evaluate the potential of an AMS for fire detection in other areas of a coal mine, a series of full-scale fire experiments were conducted to determine detection and response times from fires of different combustible materials that are found in U.S. underground coal mines, including high- and low-volatility coals, conveyor belts, brattice materials, different types of wood, diesel fuel, and a foam sealant. These experiments were conducted in the Safety Research Coal Mine (SRCM) of the U.S. National Institute for Occupational Safety and Health (NIOSH) located in Pittsburgh, PA, using a commercially available AMS that is typical of current technology. The results showed that through proper selection of sensors and their locations, a mine-wide AMS can provide sufficient early fire warning times and improve the health and safety of miners.

Jan 1, 2016

By W. L. Freyberger

In many papers concerned with fundamentals of the froth flotation process, authors have considered the contents of a flotation cell to be comprised of two immiscible phases, the froth and the pulp. I (Of course, each of these phases is in turn made up of several solid phases plus air and water.) This generalized concept of the flotation system can be extended by considering the cell contents to include two phases: an extracting phase, the air bubbles plus the collector, which removes a selected mineral component from the second phase, the ore pulp. Thus, there is an analogy between a flotation system on the one hand, and chemical extracting systems, such a solvent extraction system or a leaching system, on the other hand. Such extracting systems may be operated in cocurrent or countercurrent fashion. This paper includes first a brief discussion on the general nature of cocurrent and countercurrent operation as applied to froth flotation, and then presents the experimental results of flotation of a specular hematite ore by each method, using a tall oil fatty acid as collector. Cocurrent Flotation A conventional flotation circuit involving roughing, scavenging, and cleaning flotation is illustrated schematically in Figure 1. In such a circuit the col¬lector, or extractant, and new feed ore enter together at the head of the rougher circuit, and flow cocurrently to the scavenger circuit where more collector is added. According to this practice, sufficient collector is added to the head of the rougher (and scavenger) so that the final tailings are of low enough grade to be discarded. Since the flow of collector and ore is cocurrent, the process consists of single stage contact between the extracting phase and the ore pulp. If the scavenger concentrate is recycled to the head of rougher, the overall circuit has some of the characteristics of countercurrent flow. In such a case part of the extractant (collector) is added at the discharge end of the circuit, and may

Jan 1, 1971

By Apostolos Vrakas, Georgios Anagnostou

"INTRODUCTION The small strain assumption routinely made in tunnel analyses remains sufficient from an engineering point of view as long as convergences do not exceed 10%. More specifically, small strain theory assumes that deformations are so small (in relation to the size of the underground opening) that any geometric change in the continuum can be disregarded (Fig. 1a). In fact, however, the geometry is updated during loading (or unloading) according to large strain theory and thus equilibrium and stiffness are evaluated on the deformed configuration of the continuum (Fig. 1b).In problems involving large deformations, where the undeformed and the deformed tunnel geometry differ significantly, small strain theory leads to erroneous and sometimes even nonsensical results (i.e. it can predict wall displacements even greater than the excavated radius under conditions of very low stiffness and strength, high in situ stress and low support pressure). This can easily be verified from the widely applied relationships for the ground response curve. For example, in the ideal case of linearly elastic behaviour, the convergence of an unsupported opening equals (1+?) s0 / E (where E, ? and s0 denote the Young’s modulus, Poisson’s ratio and initial isotropic stress, respectively) and is greater than 100% for E < (1+?) s0. Although convergences are less than 10% in the great majority of tunnelling projects, very large deformations may take place when tunnelling through weak rocks under a high overburden (Fig. 2). This paper will first present a very simple and practicable way to account for large strains, based entirely on the results of routine small strain analyses, and will subsequently show the importance of addressing large strains in tunnel analysis and design with reference to three typical case studies of tunnelling in squeezing ground."

Jan 1, 2016

By S. T. Hall

The authors have previously described a method of enhancing the magnetic susceptibility of pyrite by a mild alkaline oxidative pressure leach (Hall et al, 1985). This finding was successfully applied to enhance the magnetic desulfurization of an Eastern Canadian coal (Hall and Finch, 1984). This paper reports on enhancement of the magnetic susceptibilities of iron-containing sulfides (arsenopyrite, chalcopyrite and marcasite) upon similar treatment. It also explores the application of this pretreatment in the magnetic separation of fine sulfides from oxides and other sulfide minerals. In the latter case galvanic interference effects have a serious impact on the potential use of this method.

Jan 1, 1985

By R. Bhaskar

The objective of the project was to optimize the ventilation parameters of a continuous miner underboom scrubber to further control. the amount of airborne dust discharged during mining, to further reduce the exposure of face personnel for an exhaust brattice ventilation system, and avoid recirculation of contaminants at the face. This research was performed in an underground coal mine in Utah. The tasks included preliminary face ventilation evaluation and optimization of the scrubber system to eliminate recirculation of the scrubber discharge air. Airflow tests were conducted on the currently used dust control system and the modified scrubber system. Tracer gas tests were performed to evaluate face ventilation effectiveness. Confirmatory tests of the scrubber system under actual operating conditions, modifications to the scrubber system, and a comparative evaluation of the scrubber system vs. the existing system were performed. This paper presents the results of the airflow pattern tests and the respirable dust levels in the modified scrubber system and the existing system. The optimized face ventilation parameters and the developed operating guidelines may provide the benefits of dust reduction, better face ventilation, and improved visibility.

Jan 1, 1994

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 Corale L. Brierley

The effect of hydrogen peroxide (H2O2) on growth and respiration of Thiobacillus, thiooxidans, and Thiobacillus ferrooxidans, organisms involved in acid leaching of copper sulfide minerals and uranium oxides, was examined. Oxygen uptake and growth by T. thiooxidans were inhibited after contact with 0.82 mM H2O2. Inhibition of oxygen uptake by T. ferrooxidans occurred at 8.24 mM H2O2, and growth was inhibited after 6 hours exposure to 2.06 mM H2O2. Higher concentrations of H2O2 can be used without detriment to thiobacilli if it is dissipated prior to reaching the oxidation pond or dump surface. INTRODUCTION In recent years, hydrometallurgical processes for recovery of metal values from low-grade ore minerals have played an increasingly important role. Dump leaching of low-grade copper waste materials in the western United States now yields 11.5% of the total U. S. copper production. Although scavenger operations in uranium leaching have been successful, the state-of-the-art of in-situ

Jan 1, 1977

By J. G. Groppo

Eastern U.S. oil shale contains approximately 10 to 12 gallons of oil per ton and 7 to 10 percent pyritic sulfur. Physical beneficiation of these low grade shales using froth flotation provides a high grade material which will make extraction of oil more economically attractive. The Alabama oil shale used in the present study contained 16.46 percent organic carbon and 14.5 gallons of oil per ton as determined by Fischer assay. Liberation size of the kerogen was estimated at 10 /-Lm. &apos;Ken-Flote&apos; column flotation technology provided a high grade concentrate containing as much as 60 percent organic carbon, however, carbon recovery was about 60 percent. Carbon recovery was improved to 75-85 percent while maintaining concentrate grades in excess of 40 percent carbon by providing longer retention time in the column which facilitated effective bubble-particle collision and attachment.

Jan 1, 1993

By M. Guzman, M. Romero, S. Bravo-Thais, M. Flores

The phytoremediation method is proposed to recover valuable metals from polluted soils. In this sense, the objective of this research is to determine if it is possible to use native plants in the recovery of precious metals from abandoned mining liabilities. The tailings samples containing Au and Ag were acquired from the northern region of Peru. Two native plant species, Stipa Ichu and Cortaderia Nitida, were used. Results show that Au was recovery around 19% (1.52 mg/Kg) and 25.43% (1.78 mg/Kg) by using Stipa Ichu and Cortadeira Nitida, respectively. Besides, Ag had a better recovery in the Stipa Ichu reaching a value of 6.83% (0.628 mg/Kg); in contrast, Cortadeira Nitida had an efficiency of 3.6% (0.814 mg/Kg). Bioaccumulation, bioconcentration and translocation factors were calculated by determining the concentration of precious metals in the roots and aerial parts of each plant. Results show that Stipa Ichu had a greater capacity of hyperaccumulated Ag compared to Au; while Cortaderia Nitida tended to have a better performance for Au. In conclusion, both plants are recommended for phytoremediation of mining liabilities.

Feb 1, 2023

By R. Gorakhki, R. Stafford, A. Jung

Geosynthetic clay liners (GCLs) have been used widely as an alternative for compacted clay liners and covers in mine waste applications. The high swelling of bentonite particles in the GCL creates a uniform barrier layer that results in low permeability of water and mine waste leachate. GCLs must provide sufficient internal and interface shear strength stability, especially if GCLs are used in steep slopes under high normal loads. Peel strength is a common parameter that is typically correlated to internal shear strength properties of GCLs. The relationship between internal shear strength and peel strength of GCL at normal stresses of 287, 575, 862, and 1724 kPa is evaluated in this study. The data in this study was compared with the peel strength-internal shear strength relationships found in literature. The study concludes that the relationship between peel strength and internal shear strength is unique based on manufacturing, needle-punching density and the method with and without heat treatment of the geotextile end fiber bundles.

Feb 1, 2023

By M. Guzman, S. B. Thais, M. F. Obispo, M. R. Arribasplata

One of the greatest environmental issues related to the development of the mining activity is the generation of Acid Mine Drainage (AMD). Many methods have been developed for AMD treatment, being wetlands a good option for heavy metal removal. In this sense, the implementation of artificial wetlands for the treatment of mining effluents would seem to be an environmentally friendly alternative. In this paper, we present the results on the elimination of heavy metals (Cu, Zn, Pb and Fe) using two Peruvian native species such as Schoenoplectus californicus (C.A. Mey.) and Phragmites australis (Cav.) Trin. Ex Steud. The results show that Schoenoplectus californicus preferentially removes copper (82 and 90%), lead (88 and 92%) and iron (28 and 69%), whereas Phragmites australis removes copper (68 and 87%) and zinc (53 and 95%). Likewise, it is observed that the Schoenoplectus californicus mainly retains the ions in its root, copper (89%), zinc (84%) and iron (76%). While the Phragmites australis accumulates iron (62%) and copper (74%) in the steam and root part respectively

Mar 2, 2022

By J. N. Cox

Coal preparation is based on the properties of noncombustable materials (impurities) in coal being different from the organic constituents. The most commonly used property difference is density, via its affect on settling rates; and either gravitational or centrifugal forces can be used to remove impurities. However, examination of various particles settling rate correlations shows that at smaller sizes, particle drag becomes a very important factor. Classification, based on differential settling rates, becomes impractical and some property other than density must provide the basis for fine coal cleaning. Froth flotation and agglomeration employ differences in surface properties to clean coal. These methods are very successful except that the oxidized surface of a pyrite particle is somewhat hydrophobic and will tend to be collected with the organic portion of the coal. Surface property cleaning techniques have not been very effective in rejecting sulfur, except for two-stage flotation.

Jan 1, 1984

By M. Z. Rashad

The purpose of this paper was to compare the covariance and multiquadric functions in same mining and geological applications. The basic principals of the two techniques are covered briefly. Similarities and dissimilarities of the covariance and multiquadric functions are discussed geometrically, mathematically and practically. A 14 by 16 kilometer square area in Baharia Oasis, Western Desert of Egypt, was selected for a detailed comparative test. The gravity anomalies of forty-eight test stations were computed by using the data of sixty-three control stations. The results indicated that the covariance function is quite better than the multiquadric one. On the other hand, the multiquadric function more simple in computation than the other one, which needs to precalculations such as semivariogram and covariogram. Moreover, multiquadric equations are based on geometrical and physical considerations rather than covariance functions.

Jan 1, 1990

By Georgene Renner

Due to disturbance of their traditional roosts, caves and tree hollows, more than half of the 44 bat species found in the United States and Canada now live in abandoned and inactive underground mines. The North American Bats and Mines Project was created two years ago by Bat Conservation International Inc. (BCI) in Austin, TX and the Bureau of Land Management (BLM) in response to the issue of mine closure and bat habitat. The partnership provides national coordination among government and private agencies and the mining industry to minimize the loss of bats living in mines. It also trains land managers on how to conduct cost-effective mine assessment and closure to protect both bats and people.

Jan 1, 1996