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By H. Haas

European coal mines are facing a very difficult situation. Despite a steadily increasing world energy consumption, the sales of European coal mines have been going down and production has to be adapted. The reason is the collapse of energy prices aided by the decreasing rate of U.S. $ to Deutschmark in the last few years. The problems are not due to the development of European mines themselves. Assured energy supplies are an important condition for the health of a nation's economy. Contribution of domestic energy production ensures some degree of independence from world market fluctuations as to supply volumes and price, and maintaining jobs and should be achieved within the framework of economic constellations. Governmental energy programs are planned towards meeting this end.

Jan 1, 1989

By J. R. Gaw

Recent events pertaining to U. S. energy needs and development of alternative energy fuel resources have made the American public more aware of past and present coal mining operations, and their impacts on the nation's economy and environment. This awareness has developed rapidly due to increased government involvement and consequent media coverage. This is true particularly in the Western states and in Texas. One of the consequences of this increased public awareness is public concern over the perceived and real consequences of mining operations. Emphasis has been placed on potential releases of toxic and hazardous substances, and possible carcinogens. The result of this public concern is a mounting effort at both state and Federal levels to promote stricter laws regulating the mining industry.

Jan 1, 1992

By Todd R. Taubert, Kenneth L. Bickel

The U.S. Bureau of Mines (USBM) pioneered the development of disposable filters for reducing diesel particulate emissions from permissible mining machines. The USBM is now evaluating filter media that can withstand the high exhaust temperatures on nonpermissible machines. The goal of the evaluation is to find an inexpensive medium that can be cleaned or disposed of after use, and will reduce particulate emissions by 50 % or more. This report summarizes the results from screening tests of a lava rock and woven fiberglass filter media. The lava rock media exhibited low collection efficiencies, but with very low increases in exhaust back pressure. Preliminary results indicate a collection efficiency exceeding 80 % for the woven fiber media. Testing of both media is continuing.

Jan 1, 1995

By Alexander Sutulov

It is calculated that since the beginning of last century, which practically coincides with the beginning of the Industrial Revolution, our civilization has consumed around 239.5 million tons of copper (see: Table 1). According to the most pessimistic projections of today, with only a 2.5% annual growth rate in demand, we are bound until the end of this century to consume another 200 million tons of copper in remaining 17 years. A recent study made by US Bureau of Mines (1) indicates that the proven ore reserves of 150 major operating mines and about 120 deposits sufficiently explored for development and feasibility studies accumulate a total mass of 49.3 billion tons of ore, assaying an average of 0.82% Cu and containing around 324 million tons of recoverable copper. Consequently, there is a high grade of probability that the bulk of our future ore supplies, for our demand of, say, next 25 years will cane precisely from these mines. The interesting point in USBM study is that it indicates the recoverable byproduct content of these ores and which is: 118.2 million troy ounces of gold 2277.4 million troy ounces of silver 7.1 million tons of lead 24.7 million tons of zinc 1.3 million tons of nickel 3.1 million tons of molybdenum 765 thousand tons of cobalt, and 720 thousand troy ounces of platinum. This information gives us a relatively reliable profile of our future ores for next 25 years, and thus makes possible evaluation of byproduct credits in our future copper mining and producing activities.

Jan 1, 1983

By C. L. Karr, D. L. Meredith, D. A. Stanley

The U.S. Bureau of Mines is currently investigating ways to combine the learning capabilities of genetic algorithms with the process control capabilities of fuzzy logic. Fuzzy logic has been successfully used for controlling a number of physical systems. However, the selection of acceptable fuzzy membership functions has generally been a subjective decision. In this paper, high-performance fuzzy membership functions are learned using a genetic algorithm, a search technique based on the mechanics of natural genetics. The membership functions learned by the genetic algorithm provide for a more efficient fuzzy logic controller than the membership functions selected by the authors for the liquid level system considered. The approach to developing genetic algorithm-based fuzzy logic controllers is demonstrated on a liquid level controller.

Jan 1, 1990

By E. S. Cheney

Minter (1990) has provided an excellent summary of the sedimentology and theories of origin of the Witwatersrand paleoplacer Au/U deposits. However, recent stratigraphic, metamorphic and structural-tectonic research is radically changing the concepts about the Witwatersrand that now occur in most textbooks, review articles and North American minds. Presently, these concepts are biased by the past sedimentological research so well described by Minter. Specifically, the Witwatersrand Supergroup is Archean, does not occupy a depositional basin and is significantly metamorphosed and deformed. Thus, many of its sedimentary features, including the mineralogy of its ores, have been modified. The importance of the Witwatersrand ores cannot be overestimated. Since their discovery in 1886, they have produced 52% of the gold mined in all of human history (Pretorius, 1989).

Jan 1, 1991

By P. N. H. Bhakta, X. P. V. Lei

The U.S. Bureau of Mines developed an alkaline oxidative pretreatment to increase the recovery of gold from refractory sulfide ores containing arsenopyrite (FeAsS) and/or pyrite (FeS2). Pretreatment of a low grade ore containing 0.4% FeAsS, 3.5% FeS2, and 2.74g/mt Au with 1.2m NaOH, 40 psig o2, 100° C, and 4 hr in a 2-L autoclave resulted in 94 to 96% sulfide oxidation. cyanidation of the pretreated residue resulted in 88% Au extraction compared to <20% Au extraction for untreated ore. Cyanide consumption was 0.25 kg NaCN per metric ton of ore. A flowsheet for treating sulfidic low-grade gold ore is proposed.

Jan 1, 1990

By K. R. Gardner, P. B. Altringer, R. H. Lien

The Bureau of Mines, U. S. Department of the Interior, is investigating biological and chemical reduction of selenate and selenite from waste waters. A mixed bacterial culture, isolated from agricultural waters, removed selenium from four oxidized cyanide solutions from precious metals operations containing 0.6 to 30 ppm Se and 13 ppm CN. Up to 85% selenium removal was attained using bacteria under controlled batch conditions in a 3-L stirred tank reactor and in small-scale continuous tests conducted in a rotating biological contactor (RBC). Fe(OH), reduction of the selenium reduced the effluent concentration to 0.02 ppm Se; however, the reagent costs were prohibitive. A final processing scheme may involve a combination of biological and chemical treatments.

Jan 1, 1991

By Bradley S. Van Gosen, Anjana K. Shah, George M. Bedinger, Donald I. Bleiwas, Karl J. Ellefsen

"Ancient and modern coastal deposits of heavy mineral sands (HMS) are the principal source of several heavy industrial minerals, with mining and processing operations on every continent except Antarctica. For example, HMS deposits are the main source of titanium feedstock for the titanium dioxide (TiO2) pigments industry, obtained from the minerals ilmenite (Fe2+TiO3), rutile (TiO2) and leucoxene (an alteration product of ilmenite). HMS deposits are also the principal source of zircon (ZrSiO4), from which zirconium dioxide (ZrO2) is obtained for uses mostly in refractory products. Sometimes monazite [(Ce,La,Nd,Th) PO4] is recovered as a byproduct mineral, sought for its rare earth elements, and thorium (Ault and others, 2016; Sengupta and Van Gosen, 2016; Van Gosen and Tulsidas, 2016).HMS are sediments containing dense (heavy) minerals that accumulate with sand, silt and clay in coastal environments, locally forming economic concentrations of the heavy minerals (Fig. 1). Economic (mined) HMS deposits include Holocene sediments on modern coasts, such as examples in India and Brazil, as well as coastal deposits formed by transgressions and regressions of the seas during intervals in the Quaternary, Tertiary and Cretaceous, such as in Australia and the southeastern United States. Economic deposits typically contain heavy-mineral concentrations of at least two percent. Individual heavy minerals are commonly defined as minerals with a specific gravity greater than approximately 2.9 g/cm3. These minerals are generally resistant to chemical weathering and physical degradation and thus survive well in fluvial and coastal environments. Heavy minerals in coastal HMS deposits may include, in order of general abundance, ilmenite, leucoxene, rutile, magnetite, zircon, staurolite, kyanite, sillimanite, tourmaline, garnet, epidote, hornblende, spinel, iron oxides, sulfides, anatase, monazite, cassiterite and xenotime. Of these, ilmenite, leucoxene, rutile and zircon are the primary economic minerals. Garnet, monazite, cassiterite and xenotime are occasionally recovered as byproducts. The heavy minerals as a suite typically make up no more than 15 weight percent of a deposit and usually much less. Quartz and clay minerals form the bulk of the sediment. The geology of HMS deposits and examples of significant districts are summarized in Van Gosen and others (2014) and Hou and Keeling (2016)."

Oct 1, 2016

By D. R. Spears, C. E. Jordan

The U.S. Bureau of Mines examined the influence of turbulence on the fine bubble flotation of fine-sized (minus 40 micron) galena in order to improve flotation efficiency. Fine bubble flotation was carried out in a spinning-disk flotation cell and was compared to results obtained from flotation in a conventional cell at equivalent agitation levels. An automated electrochemical technique was used to monitor the turbulent velocity distributions of the fluid within the cell as a function of time and position. The velocity profiles were used to increase the precision of the fine particle, turbulent flotation model. While improved flotation response was obtained with intense agitation, the effect of bubble size was small. These results matched the model&apos;s predicted response for fine particle flotation.

Jan 1, 1989

By T. W. Beck

Drilling into coal mine roof strata to install roof bolts has the potential to release substantial quantities of respirable dust. Due to the proximity of drill holes to the breathing zone of roof bolting personnel, dust escaping the holes and avoiding capture by the dust collection system pose a potential respiratory health risk. Controls are available to complement the typical dry vacuum collection system and minimize harmful exposures during the initial phase of drilling. This paper examines the use of a bit sleeve in combination with a dusthog- type bit to improve dust extraction during the critical initial phase of drilling. A twistedbody drill bit is also evaluated to determine the quantity of dust liberated in comparison with the dust-hog-type bit. Based on the results of our laboratory tests, the bit sleeve may reduce dust emissions by one-half during the initial phase of drilling before the drill bit is fully enclosed by the drill hole. Because collaring is responsible for the largest dust liberations, overall dust emission can also be substantially reduced. The use of a twistedbody bit has minimal improvement on dust capture compared with the commonly used dust-hog-type bit.

Jan 1, 2014

By Francisco A. Fonseca

The Carajás Hills are in Brazil&apos;s Eastern Amazon, between the Araguaia and Xingu rivers, and parallels 5° and 7° Latitude South. A location map is given in Fig. 1. It is an area of low mountains (maximum altitude 900 meters), covered by the Amazon rain forest. Annual average temperature is 25°C, ranging from 31°C (maximum) to 19°C (minimum). Annual rainfall averages 2,000mm. Although it rains throughout the whole year, heavy rains occur from December through March. At the beginning of the 20&apos;s, Brazilian explorationists made brief geological descriptions of the area. Due to the thick soil, scarce fresh rock outcrops and the tropical forest covering a completely unpopulated area, detailed geological studies were difficult and reconnaissance expeditions were limited to the river margins.

Jan 1, 1982

By Clark J. Gilbert

The mining method at the Cannon mine uses heading and bench stopes, which are subsequently backfilled with cemented high-strength fill before pillar removal. The dimensions of the pillars are 7.3 m wide by 19.8 to 28.9 m high (24 ft by 65 to 95 ft). They require careful blasting in order to not damage the rock, compromising pillar strength and complicating later removal. Additionally, the proximity of dwellings makes vibration control a must for good neighbor relations. A blast monitoring study was conducted in order to optimize bench blasting practices to maximize fragmentation, reduce costs, and to minimize wall damage and ground vibration. The Cannon mine is a joint venture between Asamera Minerals (US) Inc., a 92% owned subsidiary of Gulf Canada Ltd., and Breakwater Ltd. Asamera is the operator. The mine is located at the south end of Wenatchee, WA, a town of roughly 45,000 people on the eastern flanks of the Cascade Mountains. Gold is the primary product at the mine. The rock is extracted using a sublevel end-slicing method on 15 m (50 ft) lifts, with subsequent backfilling and pillar removal. The stope widths, dictated by rock conditions at 7.3 m (24 ft), are the same in the primaries as in the pillars, or secondaries.

Jan 1, 1990

By W. K. Tolley

The U.S. Bureau of Mines (USBM) is currently investigating the electrochemistry of mineral flotation. A significant need in this area is greater reliability of sensors. The USBM is testing electrolytic methods to clean and condition redox-sensing electrodes to improve the reliability and extend the service life of these instruments in the harsh physical and chemical environment of mineral processing slurries. A novel method for removing scale from fouled electrodes has been developed that includes anodic polarization to 1.2 V versus the Ag/AgCl reference potential, followed by brief potentiodynamic conditioning. Laboratory results show that this technique removes calcarious deposits from gold sensing electrodes and returns the electrode to useful service within approximately 10 min. Mechanical abrasion to remove the scale is thereby avoided.

Jan 1, 1994

By Jr. McCulloch

Mining operations of Freeport Indonesia (FI) are located approximately 4 degrees -6&apos; south latitude, 137 -7&apos; east longitude in Irian Jaya the eastern most state of Indonesia (Figure I). The mines are located approximately 96 km (60 miles) from coast in the Carstenz Mountain range. The ore bodies are between 2900 and 4000 meters (9500 and 13 000 ft) elevation.

Jan 1, 1989

By R. Jin

The hydrophobicity of six coals ranked from lignite to anthracite is studied through contact-angle measurements, bubble attachment-time measurements, FTIR spectroscopy, and Hallimond-tube flotation. The preliminary study shows that the hydrophobicity of coals can be told by the bubble attachment times of coals (a kinetic criterion) or by the contact angles (an - equilibrium criterion). A general agreement between flotation response of coals and measured bubble attachment times or contact angles is observed in the present study. However, the study also shows that the hydrophobicity of coals can be predicted by FTIR spectroscopy work with proper manipulation of the spectra. Both hydroxyl and carboxyl groups in the coals are proven by FTIR work to be responsible for the change of coal hydrophobicity. A new criterion for the hydrophilicity index of coals from FTIR spectra is introduced through the study.

Jan 1, 1987

By Michael Gobla

"Since 1994 the Bureau of Reclamation (BOR) has used risk analysis to evaluate dams. Risk considers both the likelihood of failure and the expected consequences should failure occur. Risk analysis relies on the detailed formulation and critical analysis of all possible potential failure modes. Potential failure modes are formulated by describing the sequence of events that must occur to result in failure, where failure is defined as the uncontrolled release of the impounded reservoir. Failure occurs in response to loadings such as water seepage through a dam (static forces), shaking from an earthquake (dynamic forces), sudden flood inflows (hydrologic forces), or accidental overfilling (operational errors). Reclamation has, to a limited extent, applied risk analysis to inactive and abandoned mines to evaluate tailings dams, pit lakes and flooded underground mines. Case histories of potential failure mode analysis, as applied to mine impounded water, illustrate what critical technical information is needed to determine if failure is likely, what the consequences of failure are likely to be, and what are the highest risks that should be addressed first.IntroductionImpounded water and high water content wastes at mining and industrial processing sites are potential threats to public safety and the environment. Recent failures such as the TVA Kingston flyash impoundment failure in Tennessee in 2008 (4.1 million m3 or 5.4 million cu yd) release, the Mt. Poly Tailings Dam failure in British Columbia in 2014 (4.4 million m3 or 5.8 million cu yd) release, and the Samarco Fundao Tailings Dam failure in Brazil in 2015 (59 millon m3 or 78 million cu yd) release have renewed attention to this issue. Potential risks from impounded water at mining and industrial sites originate not only from tailing dams, but also from water in process ponds and conveyance pipelines, sediment retention dams, water retention dams, mine pit lakes and flooded underground mine workings.Conventional water retaining dams also have a record of failure. Notable examples of failure include Vajont Dam in Italy in 1963 (2,600 lives lost), Banqiao and Shimantan Dams in China in 1975 (171,000 lives lost), and Machhu-II Dam in India (10,000 lives lost). After the 1976 Teton Dam failure in Idaho, the U.S. Bureau of Reclamation (BOR) established a Dam Safety Program. By 1984, the agency developed and began using risk analysis methods. BOR operates and maintains an inventory of hundreds of aging dams which were designed and constructed over a period of 100 years. Many of these facilities were designed and constructed prior to the development and adaptation of modern soil mechanics in dam engineering. Diligent observational monitoring, detailed site investigations and the application of risk evaluation to the BOR dam inventory has identified many deficiencies resulting in significant demands on available funding for remediation efforts. The application of risk analysis has allowed the agency to rank sites by risk. By giving priority of remedial efforts to high-risk sites, significant improvements to dam safety have been achieved."

Dec 1, 2016

By Phil W. Welch

At first glance, the similarity between the fine grinding of cement clinker and coarse grinding done in other mineral processing industries may seem remote. However, it is interesting to note that the mill discharge fineness of cement clinker is only 70 to 90% passing 100 mesh and quite comparable to other mineral processing grinds. There is however, a greater dependence of the mill on the air separator in the finish grinding of cement clinker than in other mineral processing industries which explains why a technique to guage the balance between a mill and separator first began in the cement industry. (1) More recently an adaptation of this technique has shown its application to the processing of phosphate rock and is the central topic of this paper. First, an explanation of work done with fine grinding cement circuits seems appropriate together with a few general comments regarding cement. When unground or partially ground cement clinker enters a finish grinding mill, it is subjected to mechanical forces of impact and attrition which gradually reduce it to a range of sizes characteristic of finish cement. That is, a range of approximately 1 to 125 microns. The large proportion of superfine particles relative to the coarse and intermediate size particles is typical of portland cement particle size distribution. It accounts for the workability characteristics of plastic concrete and the early strength development of concrete which is so necessary to its successful use as a construction material. For this reason It is quite evident from quality control tests when a shortage of superfines exists.

Jan 1, 1975

By T. E. Bernard

"Refuge alternatives (RA) provide shelter to miners trapped underground during a disaster. RA manufacturers must demonstrate that their RAs meet the Mine Safety and Health Administration (MSHA) requirements for oxygen supply, carbon dioxide removal, and the management of heat that results from the RA occupants and mechanical/chemical systems. In this study, miner size and activity level were used to determine the metabolic heat rate, oxygen requirements, and carbon dioxide generation that is representative of miners in a refuge situation. A convenience sample of 198 male miners was used for the distribution of current US coal miners, and the composite 95th percentile height and weight were determined to be 193 cm (76 in) and 133 kg (293 lb). The resting metabolic rate (RMR) was determined to be representative of activity level in an RA. The highest likely metabolic heat generation ranged from 115 W to 135 W, depending on RA occupancy. The highest required oxygen supply and carbon dioxide removal were estimated to be 23 LO2/h/person (0.81 ft3/h/person) and 20 LCO2/h/person (0.71 ft3/h/person), which means the margin of safety is 50% or more when compared to the MSHA requirements. INTRODUCTION Refuge alternatives (RAs) provide shelter to miners trapped underground during a disaster. Manufacturers must demonstrate that their RAs meet Mine Safety and Health Administration (MSHA) requirements for the supply of oxygen, the removal of carbon dioxide, and the management of heat that results from the occupants and the mechanical/chemical systems in the RA [1]. These MSHA requirements were based on a standard 70 kg (168 lb) male with an assumed allocation of activity of 80% rest and 20% moderate activity level [2]. The purpose of this paper is to re-examine the metabolic heat generation and oxygen and carbon dioxide requirements of miners in an RA based on actual miner size and more realistic RA activity levels based on current RA designs. The purpose of this paper is to re-examine the Mine Safety and Health Administration (MSHA) requirements for oxygen supply, carbon dioxide removal, and heat generation. To achieve this, researchers took the following steps to estimate the metabolic demands and the associated heat generation, oxygen requirements, and carbon dioxide production. 1. Characterized the anthropometric characteristics of the miner population. 2. Described the metabolic rate profile of RA occupants. 3. Characterized the maintenance demands of RAs. 4. Summarized oxygen supply and carbon dioxide removal volumes. ANTHROPOMETRIC CHARACTERISTICS OF MINERS The weight, height, and age distributions of the adult male populations are summarized in Table 1. For each data set, the reported mean and standard deviation are provided. The 95th percentile (%ile) value for height and weight for each population was the mean plus 1.64 times the standard deviation."

Jan 1, 2017

By William C. Grady

The environmental and economic problem created by pyrite in coal are well documented. The removal of pyritic sulfur prior to, or during, utilization has been the object of considerable research, however, much of this research has proceeded without a proper knowledge of the microscopic occurrences of pyrite in coal. This paper investigates the forms, occurrences, and variations in the distribution of pyrite in major West Virginia coal scan. Twenty-nine samples from twenty-two major west Virginia coal scans were selected for this study (see Table I). The samples were selected so as to be representative of the major coal producing areas of the state. All samples, except five, were collected at active surface mines, as indicated in Table I, and all except one were channel samples. The time interval between sampling and preparation of polished microblocks varied from two months to two years, though most were prepared within three months of collection. Grinding, screen¬ing, and riffling of samples to obtain 250 grams of -20 mesh coal for microscopic analysis strictly followed ASTM procedure D2013-72.

Jan 1, 1976