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By Frank X. Bellini, Marc Saidman, Allen J. Hulshizer, Anthony J. Stewart

The cooling water system for the Seabrook Nuclear Station involves 10.25 Km (33,623 ft.) of 6.7 m (22 ft.) OD hard rock tunnels, over one third of which is under and terminating over 1.6 Km (a mile) out in the Atlantic Ocean. The major excavation is accomplished by two TBM's concurrently driving the intake and discharge tunnels which by mid-January, 1981, completed 92% of the excavation. This paper presents the case history of the excavation work and describes a computer program developed to evaluate major activities of TBM excavation on a shift-by-shift basis. Details and summaries of the production efforts are computer plotted in different forms to facilitate the evaluation of production performance, trouble spots and trends.

Jan 1, 1981

By William E. Horst

Ore grindability data based on various techniques to measure comminution characteristics are used to evaluate the crushing and grinding efficiency in mineral processing operations. The importance of achieving improved comminution efficiency, in terms of energy consumption, has been emphasized by recent increases in the cost of electricity. From a theoretical standpoint, the objective of a grinding operation might be expressed as maximizing the production rate at a given grind size while minimizing the energy consumption per ton of material ground. To achieve this objective in an industrial operation presents a challenge especially in view of changes in the raw material which are normally encountered. Various procedures1-5 used to determine energy-size parameters and grindability measurements have been reported. The proposed relationships between particle size and energy consumed have much in common between many of the techniques for measuring grindability. Probably the most widely used parameter to measure ore grindability in recent years is the Bond work index6, Wi, which is defined as the kw-hr per ton required to break from infinite size to a product size of 80 percent passing 100 microns. If the breakage characteristics of a material remain constant over all size ranges, then the calculated work index would be expected to remain-constant since it expresses the resistance of material to breakage. However for most naturally occurring raw materials differences exist in the breakage characteristics depending on particle size, which can result in variations in the work index depending on grind size. Consequently work index values are generally obtained for some specified grind size which typifies the comminution operation being designed or evaluated.

Jan 1, 1975

By Y. B. He

The effect of the stability and rheological properties of magnetite dense medium on the separation performance of a 6" dense medium cyclone (DMC) is studied with the use of fine density tracers. The tests in which different size fractions of magnetite are used to prepare the dense media reveal that at low medium densities (<1.5 s.g.), the best separation is achieved when using the magnetite with intermediate particle sizes (du3.2=18 11m). At medium densities above 1.5 s.g., however, it is beneficial to use coarser magnetite. With the fine magnetite dense medium, an increase in medium density results in a decrease in separation efficiency. With the coarse magnetite, an opposite trend is observed; the separation efficiency is improved with increasing medium density. An accurate cutpoint control is critical in gravity separation. The cutpoint shift for coarse feed particles is found to decrease with increasing medium stability (density). It assumes values close to zero in a highly stable fine dense medium. When the size of the treated particles is small (<0.5 mm), the cutpoint shift is mainly determined by medium rheology. With increasing medium density, a continuous increase in cutpoint shift is observed.

Jan 1, 1993

By C. E. Jordan

Abstract. The U.S. Department of the Interior, Bureau of Mines, as part of its effort to maintain an adequate supply of minerals and metals to meet national economic and strategic needs, is conducting research on the pneumatic recovery of coarse mica. A system of crushers, screens, and zigzag air classifiers is used to concentrate coarse liberated mica particles from mica ore and from the waste tailings of abandoned mica operations. The plus 0.21-millimeter-size mica is effectively recovered by this method. The mica concentrates produced contain over 90 percent mica. The method recovered up to 78 percent of the mica in the samples. As a dry concentration method, the pneumatic-beneficiation technique may be advantageous in areas of limited water resource.

Jan 1, 1980

By G. M. Swinkels

It is generally accepted, that oxygen is a necessary reagent for the flotation of galena with xanthate. Recent measurements have shown (1) that under plant conditions oxygen may be in a short supply to the extent that it limits the rate of flotation. Thus, it becomes important to define the exact role of oxygen and establish a model for the rational design and control of flotation separations, involving oxygen as a reagent. All theories or, the flotation of galena assign oxygen the role of an oxidant. However, they disagree on a number of questions: 1) Is the galena or the xanthate being oxidized? 2) Is a lead dixanthate or dixanthogen the actual collector? 3) Is the oxidation process in which oxygen participates of a chemical or an electrochemical nature? The last question arises from the observation (2) that an anodic bias as well as oxygen will make a galena surface hydrophobic in the presence of xanthate. Theories which are based an the premise that the influence of oxygen is of an electrochemical nature offer elegant models of galena flotation. However, full advantage has not been taken of available electrochemical techniques to discriminate between theories and this is the area towards which this research has been directed (3).

Jan 1, 1970

By J. P. Morgan

The Vesta Preparation Plant of the Jones & Laughlin Steel Corporation is located on the Monongahela River, eight miles south of Brownsville, Pennsylvania. This plant is capable of cleaning 2400 NT/hr of a mixture of Pittsburgh seam high volatile coals from the Vesta and Shannopin mines to produce a metallurgical coal of 6.75% ash and a steam coal containing 14% ash. Heavy media vessels are utilized to upgrade the coarse coal while launders and tables. handle the -1/4" fraction of the raw coal feed. Cleaned -coal goes to boot classifiers where the +48 mesh material settles and is removed by bucket elevators. This 1/4 x 48 mesh material is then sent to centrifugal driers for dewatering. As designed, the minus 48 mesh fraction overflows the boot as a 7 to 8% solids slurry and is recovered by cyclones and a thickener and dewatered by filtration. The-products of the heavy media circuit, the launder-table-boot-drier circuit and the cyclone-thickener-filter circuit are combined to constitute the shipped metallurgical coal. This Vesta-Shannopin mix is combined at J&L&apos;s Pittsburgh and Aliquippa Works with purchased low and medium volatile coals for the production of metallurgical coke.

Jan 1, 1962

By Roy A. Koski

This paper describes variations in feed characteristics, preparation techniques, response to induration and product quality in pelletizing magnetite concentrates, earthy hematite ore fines, and specular hematite concentrates in grate kiln systems. The Cleveland-Cliffs Iron Company manages plants processing these various materials on the Marquette Iron Range in northern Michigan. The operations include the Humboldt Mining Company, Marquette Iron Mining Company, Empire Iron Mining Company and the Pioneer Pellet Plant. The combined output of the operations is approximately 9,000,000 long tons per year. The Humboldt Mining Company, owned by Ford Motor Company and Cliffs, produces pellets from a specular hematite concentrate. The Empire operation, which processes magnetite ore, is owned by Inland Steel Company, McLouth Steel Corporation, International Harvester and Cliffs. The Pioneer operation, which processes earthy hematite ores, is a joint venture of Republic Steel Corporation, McLouth Steel Corporation, Bethlehem Steel Corporation and Cliffs. The Marquette Iron Mining Company, owned by hones and Laughlin Steel Corporation, International Harvester, Wheeling-Pittsburgh Steel Corporation and Cliffs, produces pellets from specular hematite concentrate at the Republic Mine and Eagle Mills Pellet Plant. With the exception of the Eagle Mills plant, the operations employ the grate-kiln pelletizing system. Descriptions of the Empire, Pioneer and Republic operations, which have a combined capacity of 7,200,000 tons per year, are given in the paper.

Jan 1, 1969

Traditional fine-grinding mills in mineral processing rely on the use of steel medium for particle size reduction. The IsaMill (a horizontal stirred mill with a 3, 000-L net chamber volume and a rated motor power of 1,120 kW) has successfully adopted a novel product-separator design, which has led to a major revision of medium use in fine grinding. The IsaMill separator has successfully operated with a wide variety of medium types, such as silica sands, river gravel, smelter slag, run-of-mine ore fractions and steel shots, with sizes ranging from 0.5 to 10 mm. Great flexibility in the IsaMill operations has been achieved for processing feed as coarse as 120 µm to a product as fine as 5 µm. This paper discusses the performance of two inert grinding media in the IsaMills that are used at Mount Isa Mines Ltd. for the processing of galena- and sphaleritebearing ores to below 10 µm. They are the copper reverberatory furnace slag (CRFS) and the heavy-medium plant rejects (HMPR). A methodology was also demonstrated for comparing the medium performance and for scaling up the IsaMills from a 1.5-L laboratory batch mill to a full-scale 3,000-L mill.

Jan 1, 2002

The 6th International Mine Ventilation Congress (IMVC) was held May 17-22,1997, in Pittsburgh, PA. This marked the second time that the IMVC was held in the United States. The first congress, organized in 1975 by the Mine Ventilation Society of South Africa, was held in Johannesburg. Since then, the meetings have been held every four or five years, with the 1979 meeting being held in Reno, NV. This was followed by Harrogot, England, in 1984; Brisbane, Australia, in 1988; and Johannesburg, South Africa, again in 1992. The IMVC provides an international forum in the field of mine ventilation for the purpose of sharing technology and experience. The meetings are attended by ventilation engineers, academics, consultants, government employees and vendors interested in mine ventilation. As was evident from this meeting, significant progress has been made in the field of mine ventilation. However, disasters continue to occur around the world and long-term health problems continue to affect workers. So there is a need for further improvements in ventilation technology. The highlight of the conference was the technical sessions in which more than 80 papers were presented by authors from more than 20 countries. In addition to the technical sessions, the conference featured field trips to a number of mine properties throughout the United States. Five short courses were offered on topics ranging from respirable-dust control to mine fires and explosions. The conference also featured a trade show. It exhibited the latest advances in ventilation equipment, computer application software, consulting and engineering services, and health and safety equipment.

Jan 1, 1997

By R. C. Oberth, C. F. Lee, E. M. Taylor

INTRODUCTION Underground siting of nuclear power stations is drawing increasing attention in various parts of the world. Scandinavian countries took the early lead in this field because of their experience in the design and construction of underground hydroelectric stations and industrial plants, and because they have near-surface rock formations which are ideally suited for hosting large underground caverns. The world&apos;s first underground nuclear facilities were built in Norway (Halden) and Sweden (Agesta) and were commissioned in 1959 and 1963 respectively. Figure 1 summarizes the main features of these and two other small-scale European facilities. (1-4) American utilities and regulators are also for a variety of reasons assessing the benefits and penalties of underground siting. A recent study by Sandia Laboratories (contracted by the Nuclear Regulatory Commission (NRC) focussed on identifying potential safety benefits of underground siting. (5) Although the study concluded that underground plants would have improved containment for some accidents, as well as better external protection, NRC, in assessing the overall benefits and penalties, decided not to impose mandatory underground siting for nuclear stations. In June 1976, the California Legislature enacted a law which directed the California Energy Commission (CEC) to examine the issues concerned with underground siting of

Jan 1, 1979

By V. C. Kelessidis

Demand for multifunctional drilling fluids continuously increases. In the quest for more hydrocarbons, drilling has extended to deep water areas (now in excess of 2.000 m) and to very deep wells (now in excess of 6.000 m). In these extreme conditions, low temperatures, as low as 1-5°C on the sea bed, high temperatures, in excess of 200°C, and high pressures, more than 1.000 bars, in the bottom of the well, are frequently encountered. In these harsh environments, synthetic oil and oil based drilling fluids are used, but the former are expensive while strict environmental requirements have limited the use of the latter. Thus, drilling industry has turned back to water based drilling fluids which use bentonite as primary viscosifier and as a fluid loss control additive. However, in conditions of high temperatures, bentonite suspensions gel and loose their exceptional low temperatures properties, thus, additives are needed to overcome such problems. In this article we review these challenging drilling environments and establish the requirements for the multifunctional drilling fluids. Our research indicates that demand for continuing use of bentonite by drilling fluid industry is strong. Furthermore, we bring forward the opportunities for new additive development which can expand the operational ranges of bentonite suspensions.

Jan 1, 2007

By Y. Ye, J. D. Miller, E. Pacquet, S. Gopalakrishnan

From laboratory research activities during the past five years, it is now evident that effective flotation separations can be achieved with the high-capacity air-sparged hydrocyclone. The effectiveness of the equipment has been demonstrated on a pilot-scale basis (1 tph) for a number of mineral commodities including coal, copper, gold, and industrial minerals using a nominal 5-cm x 50-cm system with separation efficiencies equivalent to those achieved by conventional flotation machines. The high specific capacity of the air-sparged hydrocyclone (100 to 600 tpd per cubic foot of cell volume for a nominal 5 cm x 50 cm system compared to 1 to 2 tpd per cubic foot of cell volume for conventional columns and mechanical machines) makes it especially well-suited for the pro- cessing of low-grade ore. As a result of these pilot-scale successes, a number of plant-scale test programs are planned for larger-diameter units to establish wear characteristics and scale-up relationships for design purposes. The status of the air-sparged hydrocyclone technology is reviewed in the present paper, including a description of the system, fundamental considerations of flotation mechanisms, general discussion regarding the effect of control variables, and the significance of feed characteristics.

Jan 1, 1988

By Caren Caldwell, Leslie Thompson

1.1 Biological Process Description Pintail Systems, Inc. (PSI) has developed and in partnership with their clients in the mining industry has applied biological remediation processes for detoxification of spent ore and process solutions from heap leach operations. Contaminants that are treated to mine closure levels or drinking water standards include cyanides (weak acid dissociable and total cyanides), thiocyanate, nitrates and heavy metals. Biological processes are both site-specific and ore-specific processes. PSI specializes in isolating indigenous microorgan­isms from spent ore and process solutions and augments them in the laboratory for enhanced bio-detoxification in the field. Bioaugmentation in the lab is a key to successful heap bio-detox in the field. In PSI's bioaugmentation processes native microorganisms are isolated from the spent ore environment and are tested for contaminant remediation capacity. A majority of the indigenous microbes will be tolerant of the spent ore environment but will not contribute to contaminant metabolism. Indigenous enrichment or biostimulation of these non-working microbes by adding trace nutrients can competitively inhibit the working microbes. For this reason PSI focuses on the bioaugmentation process where non-working microbes are discarded and the working population is enhanced through stress, mutation and exogenous enrichment before it is re-introduced to the heap and process solutions.

Jan 1, 1997

By A. Giblett, J. Shuttleworth, R. Dunne

In a previous paper (Dunne, Martins, Goulsbra, Chittenden 1997), the new gravity circuits at Telfer Gold Mine, which incor­porate Knelson centrifugal separators in both the sulphide and oxides, are described. The advantages of the new circuits over the replaced spiral ( oxide circuit) and jig (sulphide circuit) were discussed, as were the improvements in gravity gold recovety. It is of note that the installation of the centrifugal separators in themselves did not result in increased gold recovery. The realisa­tion that changes in gold room practices are required to take advan­tage of the increased fine gold recovery from the Knelson concen­trator was an important step towards improved gravity gold recov­ery. This was achieved by increasing the time taken to treat the Knelson concentrate on the shaking table in the gold room. Although this increased gold recove1y, it was found that the table tailings, especially from the sulphide circuit, still contained high values of gold. In an effort to ascertain ways in which gravity gold recovery could be fu1iher improved, a sample of the sulphide table tailings was sent to the Oretest Laboratory in Perth for testwork. The results from this program are discussed in this paper.

Jan 1, 1998

By J. Loredo

In some rural regions of Peru, artisanal gold mining is currently an essential activity as it provides an important source of income. In the Huanca region (Ayacucho Department) gold deposits are not attractive for mining companies due to their reduced size, but they have enough interest for artisanal mining because of the ease and low cost of mining operations. Artisanal gold mining represents an important damage for the environment, because operations related to amalgamation processes using Hg result in special environmental problems besides the typical ones commonly associated to all mining activities. A preliminary sampling has been made in soils, materials from tailing ponds and surface water of the Acarí River, at the site of the Huanca village, according to networks specially designed for the particular conditions of the area. Studies accomplished revealed high mercury concentrations in soils and tailings. Chemical analyses of soils directly collected in the area of the active or abandoned ?quimbaletes? show mercury concentrations ranging from 15.3 mg?kg-1 to 44.2 mg.kg-1. Mercury concentrations in soils decrease as a function of distance from the before mentioned sources. Water quality of the Acarí River that flows through the area does not present important changes as a consequence of the mining and processing operations.

Jan 1, 2006

By Antonieta Middea, Rupen Adamian, Fernando F. Lins

This work presents the results obtained with aggregation of fine talc (-19 m), a naturally hydrophobic mineral, in the presence of KC1 solutions. The classical DLVO theory describes well the aggregation of talc in dilute KC1 solutions. Beyond 1 M KCI we have found indications that a non-DLVO interparticles force is operative, say an hydration (repulsive) force. This structural force could be responsible for the unexpected re-dispersion of talc suspension. However, no repulsive force (depression) has been observed in salt flotation of talc at higher ionic strength, up to 3 MKCI.

Jan 1, 1995

By Rolando V. Cuaño

For geostatistical applications, heterogeneous spatial phenomena are better modeled as mixtures of populations. However, the modeling of the constituent populations can become complex. The alternative mixture model offers a simplified approach to the w modeling problem. The model is applied and tested on the Walker Lake data set. Compared to the univariate ordinary kriging model, the alternative model generates less biased block estimates.

Jan 1, 1996

By Frederick W. Bauer

The potential worldwide "market" for metallurgical bauxite is about 94 million MT. The high degree of concentration of the alumina sector, combined with the high percentage of long-term contractual relationships, results in a small spot market with an illdefined price structure. Further segmentation occurs based on bauxite quality and alumina plant design. The potential &apos;free" market is estimated to be about 18 million MT that represent the requirements of nonintegrated alumina producers. It, too, is covered almost entirely by multi-year supply contracts.

Jan 1, 1984

By Satya Harpalani

An investigation was carried out to study the microscopic structure of coal in order to understand the phenomenon of methane migration. A Scanning Electron Microscope (SEH) was used to study the surface and pore structure of bituminous coal taken from an underground mine. Micrographs obtained showed the highly porous nature of coal which explains the large quantities of gases that remain within the pores in the compressed and adsorbed forms. These micrographs further showed that most of the pores within the coal matrix are the &apos;dead-end&apos; type and do not contribute much towards the flow of gas. The most important finding was that solid coal has a network of cracks and fractures indicating that it is these cracks that are primarily responsible for the gas flow, rather than the pores. The size and distribution of the pores within coal influence the capacity of coal to retain methane but movement of the gas molecules is the responsibility of the microfractures. Any mathematical modeling to simulate gas flow through coal must take this into account. For purposes of modeling, the structure of coal can be considered to have dual porosity. First, the gas molecules are released from the pores and there is a gradual migration towards the fractures. Once the gas reaches the fractures, its movement is eased greatly along these fractures.

Jan 1, 1987

By R. E. Hochscheid

Cyclones installed in three closed- circuit grinding systems were changed from conventional, vertical mounting to horizontal mounting with a favorable improvement in classification efficiency. In two of the installations, apex plugging problems were eliminated because horizontal mounting permit- ted the use of much larger apex orifices. Marked reduction in circulating load was accompanied by greatly reduced maintenance requirements for the cyclone and the cyclone feed pump in one of the installations.

Jan 1, 1988