Search Documents

By R. W. Barbaro

The limitation of sulfur dioxide in power plant emissions dictates that sulfur in coal be reduced to the lowest possible level before combustion so as not to aggravate the emission control problem at the stack. For coal fired power plants, the methods in practice to achieve low sulfur coal include mining areas with relatively low sulfur. reducing sulfur in the mined coal through preparation techniques and blending high and low sulfur coals. A prerequisite to the successful implementation of any of these practices is the knowledge of the spatial distribution and the capability to predict sulfur values in a coal seam.

Jan 1, 1988

By P. Songfack

In this work, the slurry flow in the ball mill is solved with Navier-Stokes' equations and the marker and cell technique (MAC), which tracks the fluid-free surface. Considering different planes in the radial and axial directions, this numerical approach leads to the direct calculation of the slurry velocity profile, mill holdup, and volumetric flow in the ball charge and pool. The MAC technique takes as input, the results of a direct three-dimensional simulation of the motion of grinding media, and in turn, provides a detailed knowledge of the hydrodynamics of slurry flow through the porous structure of ball load. This technique is a new approach to the mass transport problem that overcomes the limitations of indirect studies such as residence time analysis and holdup measurements.

Jan 1, 1994

By N. Damiano, J. Noll, C. Zhou, J. DuCarme

"Preventing machine-related injuries is one of the major safety concerns in underground coal mines. Severe injuries and fatalities occur when a miner is struck, crushed, or pinned by mining equipment such as a continuous mining machine (CMM), shuttle car, or a scoop. Proximity detection systems (PDSs) have been applied in mining to reduce these types of injuries and fatalities. All of the PDSs that are currently approved by the Mine Safety and Health Administration (MSHA) for use in underground coal mines are magnetic-field based and could be affected by metallic objects such as trailing cables. Researchers from the National Institute for Occupational Safety and Health (NIOSH) investigated the influence of trailing cables on the performance of PDSs. In particular, the magnetic field coupled from proximity system generators to a de-energized trailing cable were characterized. The results show that significant energy can be coupled from the proximity system generators to a trailing cable when there is a closed loop in the cable. The effect on PDS performance from the magnetic field radiated around an energized trailing cable was also quantified for different current amplitudes in the cable. It is shown that the magnetic field caused by the electric current in the trailing cable mainly consists of a 60-Hz signal and its harmonics which cause little interference to the PDS. The results presented in this paper can help PDS manufacturers to design better systems that are more immune to these effects. INTRODUCTION An average of 250 injuries occur every year during operation of Continuous mining machines (CMMs), and 43 miners have been killed by striking or pinning accidents involving CMMs in the U.S. from 1984 to 2015 (Mine Safety and Health Administration, 2015). In addition, there have been 10 fatal accidents involving mobile haulage equipped with trailing cables from 2000 to 2015 (Noll et al., 2017). In response to these fatalities and injuries the Mine Safety and Health Administration (MSHA) promulgated a regulation in 2015 requiring the use of a proximity detection system (PDS) on all CMMs except full-face machines and proposed a regulation in 2016 which would require a PDS on other mobile underground equipment. Current PDSs approved for underground use are magnetic-field based. The PDS contains machine-mounted magnetic field generators that create fields around the machine. The other part of the PDS is a miner-wearable component (MWC) that reads the flux density of the generators. These systems use the magnetic field strength readings from the MWC to determine whether a miner is at a safe distance from the machine. A stable magnetic field is essential for the accuracy of the system."

Jan 1, 2018

By I. O. Otunniyi

The natural hydrophobic response flotation method for beneficiation of printed circuit board comminution fines (PCB CF) still requires many studies to further basic understanding of the process and the flotation traits that the PCB CF presents. Varying particle size distribution (PSD) and water recovery under the scheme show that higher mass pull, obtained at the finer PSD, gave lower water recovery but higher value loss. The reverse also holds: the least mass pull at the coarsest PSD used, -106 + 75 µm, gave the highest water recovery per unit mass pull with the highest reverse recovery. This is unlike what obtains in primary resources processing, where higher water recovery is often with increased fines entrainment. The reverse recovery loss here is, therefore, more due to entrapment with the heavy mass pull characteristic of the method than to the entrainment of value with water. Other peculiarities of the system observed are discussed, with the goal of improving the performance of the process, and broadening the general knowledge of flotation systems.

By M. A. D. Azevedo

The effect of pulping reagents on the flotation de-inking of laser printed wastepaper was investigated with regard to the removal efficiency of toner and mineral filler particles for different pH values. These results show that caustic pulping causes the toner to be released from the fibers at larger particles sizes. On the other hand, acid pulping not only causes the toner to be released at smaller particles sizes but also increases the concurrent flotation removal of mineral filler particles. It was experimentally observed that the froth generation and stability during flotation were improved for acidic pH values.

Jan 1, 1997

By A. I. Johnson

The pegmatites of the Black Hills of South Dakota are the coarse-grained differentiates of the Harney Peak Granite. The Harney Peak Granite was intruded into the Pre-cambrian schist and quartzites and resulted in the Black Hills uplift. In the outer adzes of the granite intrusion occur the pegmatites. In the zoned pegmatites, representing the most highly differentiated portions of the parent magma, occur most of the minerals produced from pegmatites. These are of economic importance and they are the subject of this paper. The various mineral products will be taken up separately.

Jan 1, 1978

By Jerry Wang, Greg Bold, Mahmood Khwaja, Rebecca Caldon, William Simcoe

Phase III and Phase IV of the Beaver Creek Clean River Project, Albany, NY, includes microtunnel construction of 2,320 feet of 48-inch/36-inch internal diameter (ID) conveyance pipe and a 525 foot long 9.5-ft horseshoe shape roadheader excavated tunnel. Notable challenges were encountered during the construction including mixed face tunnel conditions, undocumented existing fill ground conditions that resulted in settlement during shaft construction, and unstable tunnel face conditions. This paper discusses several of the key challenges encountered during construction and selected solutions to construction sequencing and methodology to successfully complete Phase III and Phase IV of the Beaver Creek Clean River Project.

Dec 1, 2022

By Carl Hansen

Sonora Mining Corporation (SMC) operates the 6,000 tonne per day Jamestown open pit gold mine in the Mother Lode district of California. The mine has been in operation since January, 1987, and has produced approximately 7,800 kilograms of gold since start-up. The property consists of five ore bodies lying along a five kilometer stretch of the famous Mother Lode vein system. At present, only the Harvard ore body is being mined. The Harvard pit is centered around a historic underground mine of the same name that was operated from 1896 to 1916. The present ore body averages 2.5 grams gold per tonne as free milling gold and auriferous pyrite. The project consists of the open pit mine and concentrator complex in Tuolumne County, California, and a carbon-in-pulp leach plant located near Yerington, Nevada.

Jan 1, 1990

By Roland Froidevaux

The potential use of geostatistics for quantitative ore reserve reporting is shown using a simple gold case study as an example. The need of defining quantitative class limits is stressed, and a possible approach to this problem is suggested.

Jan 1, 1983

By Giovanni Osellame, Jean Habimana

"The Montreal Metro Blue Line Extension Project is part of a metropolitan Program that was launched in 2009 by the Transportation Ministry of Quebec to add additional extensions to existing metro lines in the cities of Montreal, Longueil and Laval with the intention to meet current demand and future growth within the Montreal agglomeration. Specifically the Blue Line Extension Project will add five underground stations to the East of the Montreal. The paper addresses the preparation and the implementation of a three-step geotechnical and geo-environmental investigation program and preliminary design considerations such as the selection of a preferred horizontal and vertical alignment, the selection of construction methods based on previous local experience and current industry trends, as well as preliminary sizing of underground infrastructures. PROJECT BACKGROUND An agreement between the three mayors of the Montreal Metropolitan City agglomeration, namely, Montreal, Longueil and Laval prompted the Government of the Province of Quebec to create a project office to oversee the studies of extending the existing metro network. The last extension of the existing metro network was completed in 2008 with the Laval extension, which consisted of adding three stations from the existing Orange line. The current extension Program consists of three different extensions, namely extending the Orange Line to Laval and finishing the loop, extending the Blue Line to the East of Montreal by adding five stations, and adding five stations on the Southshore of the St-Lawrence River for the Yellow Line extension. The extension program also requires the construction of an underground storage and maintenance garage located to the north-west of the existing Cote-Vertu station on the Orange line. Figure 1 shows the overall extension program with the existing network."

Jan 1, 2016

Since 1955 Gaspe Mines has produced 144 million tonnes of ore, averaging 0.87% Cu, mined from two open pits and underground workings. In 1994, four exploration drill holes discovered a buried porphyry/skarn Cu-Mo deposit at depths of between 1000 m and 1700 m below the top of Porphyry Mountain. The mineralization and alteration associated with the Porphyry mountain quartz monzonite does not outcrop. A total of 19,500 m of drilling in 12 drill holes has outlined 200 million tonnes grading 0.73% Cu and 0.08% Mo. Mineralization occurs as veins and disseminations of chalcopyrite and molybdenite. Drilling and feasibility studies continue.

Jan 1, 1998

By B. R. Arvidson

Rare-earth elements have some unique properties that are used in many common applications, such as TV screens and lighters. In the 1970's, rare-earths began to be used in a new generation of magnetic materials that have very unique characteristics. Not only were these stronger in the sense of attraction force between a magnet and mild steel (high induction, B), the coercivity (He) is extremely high. This property makes the magnetization of the magnet body composed of a rare-earth element alloy very stable, i.e., it cannot easily be demagnetized.

Jan 1, 1998

By Lester F. Sanford

Located in the Santa Cruz Mountains eight miles north of the City of Santa Cruz and inland from the coast, lies a typical beach sand consisting of quartz and feldspar grains of the Santa Harguerita formation of the middle tertiary age, Reserves of over twenty-five million tons of this sand form the deposit presently being harvested by Pacific Cement & Aggregates, a Division of Lone Star Cement Corporation. The deposit ranges from 350 to 700 feet above sea level and varies from two percent passing a 200 mesh screen to ten percent retained on a ¼ inch screen (see Figure '#l) In 1929 the first sand plant went into operation at this site. It was replaced by a new plant in 1937. This plant continued operation until the middle of 1965 when replaced by the modern plant described in this paper.

Jan 1, 1967

By Robert T. Tape, Thomas G. Harper

Valley-fill heap leaches built in steep terrain over low-friction angle liner system may be unstable even though analyses indicate stable ore slopes. This paper demonstrates the potential for massive heap failure using stability analyses which consider both heap slope and heap mass failure considerations. The computations presented also reveal the sensitivity of mass heap stability to liner friction angles.

Jan 1, 1987

By M. Sengupta, N. I. Johansen, A. K. Sinha

In Arctic surface mines, frozen ground adds to the complexity of slope stability analysis. The seasonal temperature change may thaw permafrost, and this thawed ground is often unstable. A computer program, GEODYNE, was used to simulate the movement of the thaw front in bare and insulated permafrost slopes. The simulation shows that the insulation can be used on mine slopes to prevent thawing.

Jan 1, 1990

By G. R. S. Smith

In any filtration, it is primarily the filter medium (cloth) and cake filtering properties that control the type of filtration equipment used and filtration conditions. The advent of new types of filter cloths, such as the membrane cloth discussed in this paper, can result in significant changes in filtration techniques and areas of application for filtration. For many suspensions, for instance, conventional filtration is uneconomic compared to gravity separation or not filtering at all (as with product recovery from dilute streams) because the solids are very fine, are hard to retain and build up filter pressure rapidly, and once retained are hard to remove. As a result of the developments discussed here, this is no longer the case. This technique and the use of the membrane filter cloth is well established. This filtration is currently being used for white liquor filtration in twenty-four mills worldwide in the chemical recovery step of the kraft process for producing paper pulp where it is replacing gravity thickeners in new plants. Filters up to 1000 sq. ft. (100 sq. meters) are filtering large volumes of solids from hot caustic solutions. The filtration materials and techniques discussed in this paper open the way to new methods and applications for filtration in the mining industry. It is not the intention of this paper to give a vigorous analysis of the different separations, but to outline some of the ways in which this filtration technique might be used in the mining industry.

Jan 1, 1989

By Deepak Malhotra

Is operator training necessary for optimization of flotation plants? The answer is obvious-Yes. The author suggests a three-phase program for operators when new plants are built or new crews are hired in existing operations. Case examples are discussed to illustrate the benefits of operator training.

Jan 1, 1999

By M. L. Young, M. S. Klima

Hindered-settling columns are used throughout the minerals industry for both size and density separations. In this study, the performance of a continuous laboratory-scale hindered-settling column was evaluated for various particle systems. The test variables included solids composition, water rate and column height. Column performance was evaluated using partition curves and corresponding performance parameters.

Jan 1, 2000

By Gregg E. Korbin, Patrick Hamilton

INTRODUCTION The Balsam Meadow Project, presently under construction for the Southern California Edison Company, is located approximately 55 miles northeast of Fresno, in the Sierra Nevada Mountains (Fig. 1). Major components of this project include an underground powerhouse for a 200 MW unit and a high pressure power tunnel/shaft. Site exploration [ ]

Jan 1, 1987

By D. L. Petersen, C. R. Nelson, P. M. Bergson, B. K. Nelson

Membrane waterproofing systems in large tunnels cause the partial decoupling of the concrete liner from the rockbolted and shotcreted reinforced rockmass. This decoupling leads to a loose fit of the liner in the excavation when shrinkage from cooling and moisture loss occurs. This increases tensile stresses which require either the addition of reinforcing steel in excess of common European practice or the potential for liner cracking. Hot weather concrete placement and cold weather service conditions increase the magnitude of the problem, while creep of the rockmass reduces it. Contact grouting also reduces, but does not eliminate, the problem.

Jan 1, 1991