Search Documents

By William E. Bruce

Percussive drill calibration experiments performed by the Bureau of Mines on two drills are described. The use of a linear velocity transducer to determine piston velocity, blow frequency, and piston stroke length is discussed. Data are presented on the relationships between maximum work rate and feed air pressure. Penetration rates in nine rock types were measured for the same two drills. Physical properties of the nine rock types are presented in tabular and graphical form to show relationships between penetration rates and physical properties. Finally, conclusions are drawn as to the potential use of these data to predict percussive drilling rates.

Jan 1, 1970

By J. G. Groppo

Laboratory settling and filtration testing was conducted on wet processed fly ash in order to determine the applicability of conventional dewatering techniques to reduce the moisture content prior to drying. Settling tests showed that acceptable clarity (<1.5 g/l suspended solids) could be achieved after as little as 6 minutes of settling. After settling to a consistency of 40 weight % solids, continuous laboratory vacuum filtration testing produced a cake containing below 20% moisture with throughput exceeding 150 lb/ft2/hr.

Jan 1, 1997

By T. Tamagawa

A gaseous chlorination process for hydrometallurgical treatment of a chalcopyrite concentrate was investigated. The overall process is visualized to consist of low temperature chlorination-selective oxidation, followed by aqueous chloride leaching and SX-EW for producing electrolytic copper, elemental sulfur and ferric oxide. In this article, the chlorination phase of the processes is described. Initially, the chlorination behavior of chalcopyrite-concentrate micro-pellets was investigated using a small batch-type fluidized bed reactor. The optimum conditions thereby established was used in continuous chlorination tests. The chlorinated products thus prepared were used in the selective oxidation phase of the investigation.

Jan 1, 1999

By William Hodder, Ehsan Alavi, Nader Ghasempour, Daniel Cressman

The Don River & Central Waterfront Coxwell Sanitary Bypass Tunnel (CBT) Project in Toronto will extend approximately 10.5 km from Ashbridges Bay Treatment Plant west under Lake Shore Boulevard, north under Bayview Avenue and east through the Don River park area to the Coxwell Ravine Park. The tunnel is currently being mined by using a shielded dual-mode tunnel boring machine (open and close) capable of operating in EPB mode and lined by using a precast concrete segmental tunnel linear with an internal diameter of 6,300 mm and external diameter of 6,900 mm. The CBT is expected to be excavated mainly through shale bedrock of the Georgian Bay Formation, at approximately 50 meters deep. The tunnel crosses a buried bedrock valley in two locations, in the southern portion of the alignment, adjacent to the Don River, and at the northern portion of the alignment approaching the CX-1 shaft. In these two locations, the bedrock cover is expected to be less than 6 meters. The risk of encountering weathered bedrock, significant ground water inflows or surficial soil deposits through these buried valleys was identified during the design phase. The contract required the TBM to be designed with the ability to probe drill ahead of the TBM and convert to EPB mode if necessary, to cross this area. This paper will discuss the additional exploration that was performed by the contractor to identify the extent of this buried valley, the plan going into the zone of potential weathered shale, and the actual conditions encountered.

Jun 13, 2021

By R. R. Klimpel

The use of froth flotation as a means of separating and upgrading sulfide mineral concentrates is standard industrial practice throughout the world. It is ap-parent from observing the industrial practice of sulfide mineral flotation over the last decade that progress is being made in optimizing the operating aspects of flotation. Examples of this are the availability of improved instrumentation and related computer control devices, the modification of mechanical flotation cell designs, the introduction of column cells, better reagent dosage control, blending of feed ores, increasing attention to coarse and fine particle separations, the successful introduction of new frother chemistries, etc.

Jan 1, 1989

By G. W. Phelps

This discussion deals with the geology o£ the Tennessee-Kentucky ball clay deposits; their mineralogy and chemistry; methods of finding, mining and refining; and makes observations on reserves of and future prospects for these clays. Ball clays appear in ceramic formulas for manufacture of vitreous china sanitary-ware, electrical porcelains, floor and wall tile, dinnerware and artwares(l). This type of clay is used for refractory (2) and abrasive products(3), and as a suspending agent for ceramic glazes(4), engobes(5) and porcelain enamel slips(6). Although some ball clay is imported, probably 85-90 percent of ball clay used in the USA(7) is obtained from deposits in Weakley, Henry and Carroll Counties in Tennessee(8), and in adjacent Graves County, Kentucky(9). The term "ball", as applied to clay, probably derives from former mining practice in England whereby conveniently-sized blocks of clay were cut from moist clay beds by spading(10), The expression "ball" has no other technological significance. ASTM(11) defines ball clay as "a secondary clay, commonly characterized by the presence of organic matter, high plasticity, high dry strength, long vitrification range, and a light color when fired." This, and similar(12) definitions, applies to English ball clays but is not satisfactory for many American ball clays. Geology of the Tennessee-Kentucky Ball Clay Deposits Figure 1 shows that most commercial clay areas of the eastern United States lie near the edge of the Coastal Plain; a skew-shaped configuration of its landward boundary outlines the Mississippi Embayment(13), Near the apex of this basin a broad plain, with a rolling, Bullied topography(14), dips gently westward from the Tennessee River to bluffs at the edge of the Mississippi River flood plain.

Jan 1, 1972

By B. Das

Most coals are susceptible to spontaneous heating which in turn creates problem to mining, storage and transportation of coal. It is impossible in actual practice o eliminate spontaneous heating but spontaneous combustion can effecively be controlled through a clear understanding of its mechanism and the factors affecting it. There are altogether six stages in the process of spontaneous combustion. This includes the water adsorption stage and six oxidation stages: chemi-sorption (upto 70°C), decomposition of peroxygens (70°C-150°C), oxy-coal formation (150°C-230°C), combustion initiation (230°C) and active combustion (> 230°C). Heat is produced in all these stages. On the other hand heat is also dissipated so that some equilibrium temperature is reached. If this temperature exceeds a certain critical value (generally about 70°C), coal oxidation may advance to spontaneous combustion. The major factors influencing spontaneous combustion of coal are: coal rank, maceral composition,, water, mineral matter, joints and fissures, seam depth and thickness, mine Layout, method of ventilation, etc. Susceptibility is high for low rank coals and generally decreases with increase in rank. Of the macerals, the exinites are generally most susceptible, the inertinites least and the vitrinites somewhere in between. Water plays a major role on the spontaneous heating of coal, assisting in someways and inhibiting in other. Unrecovered coal in the gob (generally in thick seams) is a major source of fire hazards and this is specially important in shallow mine. Proper design of mine ventilation system can substantially reduce the risk of mine fire. Panel layout and load transfer can affect the development of induced cracks which in turn influence spontaneous heating. Finally, the difference between the spontaneous heating of coal in a seam and that in storage or transportation is mainly due to the change in moistured content, air circulation through the coal and coal fragmentation. These aspects have been analyzed in this paper with a view o reducing the risk of spontaneous combustion.

Jan 1, 1986

By T. H. Combs

Increased productivity in the U.S. underground coal industry has taxed pre-existing conveyor belt haulage systems. The usual remedies are costly and can disrupt production. A reduction in the belt feeder discharge rate on mobile haulage sections results in more uniform loading and reduces the spillage vulnerability. An investigation is made to determine the effect, if any, on shuttle car discharge time arising from lower feeder discharge rates. A five-section, underground mine is visualized, and belt spillage is introduced. The sectional feeder discharge rate is progressively lowered until spillage is precluded. At each level, the simulated spillage is measured and compared to the loss in face production. Methods of predicting the loss in face production from lower feeder discharge rates are discussed.

Jan 1, 1993

By R. K. Mehta

Stirred ball mill feed used for ultra-fine grinding application requires fine size separation step in order to avoid over-grinding. This paper presents the selectivity curves obtained for oil shale and complex sulfide are using 460 mesh (30 micron) Derrick vibrating screen. Interestingly, the selectivity curves generated from the experimental data were monotonic increasing selectivity for oil shale but not monotonic increasing for sulfide ore. These non-monotonic increasing selectivity curves were similar to the mechanical air separator fishhook selectivity curves described by Luckie and Austin. A 2 stage classification in series model describing the fishhook selectivity curve has been used in proposing the classification mechanism for fine vibrating screens when heterogeneous multicomponent sulfide are undergoes size separation.

Jan 1, 1992

By T. Krumins, L. Zunti, R. Frischmuth

"Titanium and titanium alloys are commonly selected for pressure oxidation autoclave vent piping and pressure control valve components, as well as autoclave internals and other process piping. In the autoclave vent application, titanium ignition risk is controlled by limiting oxygen concentration, and preventing high gas velocity gas impingement on surfaces. Oxygen concentration is dependent on the autoclave pressure and temperature operating conditions and therefore oxygen concentration and the associated titanium ignition risk is dependent on standard operating procedures, process control interlocks and permissive conditions. It is not uncommon for these standard controls to be deficient during atypical operating conditions, or for operations to deviate from the operating procedures, increasing the potential for a titanium ignition incident. Titanium ignition risk caused by elevated oxygen concentration in autoclave vent systems can be reduced with the introduction of an online autoclave overpressure calculation and the configuration of associated interlocks and permissive conditions. INTRODUCTION High temperature pressure oxidation (>190°C) is a well recognized and versatile metallurgical oxidative pre-treatment process commonly used to liberate gold from refractory sulphide ores and concentrates before conventional leaching with cyanide. Titanium and titanium alloys are highly corrosion resistant in pressure oxidation process conditions and are therefore commonly selected as materials of construction for many components including: autoclave internals, agitators, process piping, and components in autoclave vent systems. Operations that anticipate or have experienced aggressive corrosion in the vent system often have little choice in material selection other than the use of titanium (Krag & Henson, 1992). Titanium is not suitable for use with elevated oxygen concentrations and is considered a restricted material because of its high pyrophoricity and combustion propagation properties (Beeson, Smith, Stewart, 2007). Several serious incidents have occurred in which titanium materials have ignited in autoclave applications (Zawierucha, McIllroy, Million, 1995). In autoclave vent applications, titanium ignition risk is reduced by preventing elevated oxygen concentrations, maintaining low gas velocities, and minimizing the potential for gas impingement on surfaces. Oxygen concentration in the autoclave vapour phase and vent system is dependent on the autoclave operating pressure and temperature conditions and therefore titanium ignition prevention controls typically include process interlocks and operating procedures based on the selected nominal design operating conditions. However, it is not uncommon for these controls to be deficient or for operations to deviate from the nominal operating conditions over time, increasing the risk of titanium ignition. The introduction of an online calculation of autoclave overpressure and a maximum target autoclave pressure as well as associated process control interlocks and permissive conditions can alert the autoclave control room operator and prevent an elevated oxygen concentration from developing, and therefore reduce titanium ignition risk in autoclave vent systems."

Jan 1, 2016

By Mark Cadzow, Rodney Lamb

CARBAD is a recently developed Australian process for the recovery of gold and platinum group metals (PGM). The process relies on the selective agglomeration phenomena of the gold and PGM to capture the mineral in a carbon-hydrocarbon media. The precious minerals are then extracted from the loaded media by a solvent gold room process producing a relatively pure concentrate. The media is then reformed and recycled. The process development from batch test work to a 5 t/h commercial scale CARBAD plant is discussed. The operation and results of processing a variety of ore types at several alluvial and hardrock gold mines is examined. The operating and capital costs for the CARBAD process shows that it is significantly less than that the conventional CIP/CIL. The environmental safety of the process is a major feature where precious metal deposits are located within urban environments or within wilderness areas.

Jan 1, 1989

By M. Z. Emad, M. U. Khan

"Coal mines opting for longwall mining or its variations rely on the main and tail gates for production. Stability of these entries or crosscuts is crucial in coal mining operations. Roof or strata failure can be fatal, may lead to property loss and delay in production. Failure of the gates depends upon many factors including the mining method, panel dimensions, pillar width, mine depth, caving rate, dimensions of gates and roof strength properties. In Pakistan coal is mined through a variation of longwall mining method with almost no mechanization while using timber as a primary support. Timber support as chock is very useful in coal mines especially in overhanging face. Similarly gate entries and coal faces are supported by chock supports throughout their length. In this paper the stability of the longwall gate is assessed for a typical coal mine in Pakistan by using finite element code. Numerical modelling considerations for gate entries are discussed. A model parametric study is performed for key factors. The results showed that the existing mining practice is not suitable and there is a need to review the mining approach. INTRODUCTION Main and tail gate entries leading to longwall mining panel play a crucial role in production cycle. Failure of any of these may lead to loss of life, property and production delays. The stability of gate entries depends primarily on the nature of loading and stresses incurred. It is relatively easier to assess the ground response to production for common longwall mining panel. In thin-seam coal mines the gate entries are generally supported throughout their length by timber made chock supports. The tailgates receive huge deformations and stresses during the mining and backfilling cycle. The chock supports are required to take care of rock falls leading to blockage of entries causing production delays and loss of capital. A number of supports are available for supporting the gate entries (Hoek and Brown 1980; Brady and Brown 1985). The support system can be selected based on load-deformation characteristics including the yielding behavior, pre- and post-yielding behavior (Barczak, 2003). The principal of support selection is that the support characteristics must match the ground response in order to maintain the gate entries (Mucho, et al., 1999). It has been observed that thin-seam mining (<1 m) is very challenging and it is necessary to develop an understanding of ground mechanics before the selection of an efficient support system Dolinar (2003). The chock supports have been tested for load-deformation characteristics in the laboratory (Barczak 2003). But the ground and support interaction, response and loads must be assessed for individual site. This can be accomplished by in-situ testing and observations at few locations. The generated data is generally insufficient for complete understanding. Numerical models can combine the data generated in the laboratory and on-site to fulfill the requirements."

Jan 1, 2017

By J. James Eidel

Geological interpretations generally require projections from direct observations at the earth&apos;s surface. Crustal projections include mineral deposits as well as the geochemistry of the crust and its fluids, structure and tectonics. Drilling offers opportunities for verification of the required projections, and is thus a required step in furthering crustal understanding. Like any new science, the direct observations that drilling provides commonly generate major surprises and stimulate totally new ideas. Drilling is costly. There are many critically important scientific problems with societal and potential economic benefits in mineral deposits which have not been drilled because the holes are difficult to justify as economically sound risks for private capital. Such holes, however, are highly justifiable research goals for government because of the significant new opportunity for ore deposit insight and exploration that they afford. The earth science community is prepared with excellent drilling projects for research in mineral deposits.

Jan 1, 1985

By M. A. Qianjie

The problems of coalmine safety in china remain unsolved for decades. Starting with the description on safety status quo of coalmine in china, different existing analysis and measures discussed for the safety problem solution of coalmine china. With the consideration of system thought in mind, the author present with a unique systematic reason analysis method on such actuality--individual analysis and general analysis--each for its particular purpose. Upon such cause analysis, construction of the safety system is made clear and, solutions for such problems provided.

Jan 1, 2006

Stillwater Mining Company (SMC) has an extensive history with tunnel boring machines (TBM) at the Stillwater and East Boulder underground PGM mines in Montana. The most recent TBM used is for the Blitz Project, where a 5.5m (18ft) diameter main beam unit, commissioned in Q3 2012, is being utilized to drive a 6,975m (22,500 ft) ventilation and haulage level East of the Stillwater Mine for the Blitz expansion project. The assembly/commissioning of the TBM, institution of the planned diamond drilling program, application of ground control systems, and the current tunneling metrics will be covered.

Feb 23, 2014

By T. C. Bibb

Longwalls using shearers in seam heights of less than 1.2 m (48 inches) are relatively rare in the U.S. Westmoreland Coal Company is currently operating a shearer-equipped longwall at a cutting height of 1.17 m (46 inches) in its Bullitt Mine. This face has averaged 2795 metric tons/day of operation since its startup on April 3, 1984. Longwall productivity in thin seams is substantially impacted by equipment reliability and availability of useable working room for travel and access. This paper addresses the design criteria used in selecting this face equipment, with the goal of maximizing these two parameters. Equipment discussed includes shearers. face conveyor, shields, stageloader, and emulsion system.

Jan 1, 1985

By B. J. Sauer

Misapplication of AC induction motors for mine crusher and mill applications has long been a frustration for both the driven equipment supplier and the mine operator. Proper selection of AC induction motors is critical to providing efficient production. This paper focuses on the selection of AC induction motors for gyratory crusher, cone crusher, and grinding mill applications. The criteria for motor selection includes: proper enclosure, driven equipment torque requirements, bearing life, temperature rise, starting requirements, ambient temperature, altitude and accessory requirements.

Jan 1, 1999

By V. E. Housman

EPA&apos;s Office of Solid Waste (OSW) is developing a program, under Subtitle D of the Resource Conservation and Recovery Act (RCRA) to regulate the management of non-coal mining wastes. In May 1988. OSW produced a "Strawman", which is a working document that is precursor to a proposed rule. OSW has been working closely with environmental groups, industry, and States to solicit comments and feedback on the mining waste program. OSW currently plans to release a second "Strawman" in early 1990. A proposed rule is tentatively scheduled to be published in the spring of 1991.

Jan 1, 1990

By M. Manrique

Various pyrometallurgical methods for treating Ilmenite and Zircon concentrates are reviewed. Laboratory experiments, using a thermal plasma reactor, have been performed to evaluate: the conversion of ilmenite to TiC or TiC-Fe and the conversion of zircon to ZrC or ZrC-SiC. Results are examined and possible processing routes are identified.

Jan 1, 1996

The future phosphate rock deposits in South Florida contain a significant fraction of dolomite. The high MgO content of the rock is undesirable in the production of phosphoric acid. Several flotation schemes have been attempted to separate dolomite from phosphate rock. Alternately, Selective Flocculation process has been suggested to separate dolomite from apatite. A high MgO content rock was simulated by a 30:10:60 synthetic mixture of apatite, dolomite and silica. Single mineral selectivity was observed in the mixed mineral systems apatite-silica and dolomite-silica with Polyacrylic acid (PM) and Poly(ethylene oxide) (PEO) flocculants respectively but not realized in apatite-dolomite system with PEO flocculant. Heteroflocculation, suspected to be the major reason for loss in selectivity, was minimized by addition of a Site Blocking Agent (lower molecular weight fraction of PEO). Process parameters such as size reduction schemes, flocculant/SBA dosage, and pH were investigated to achieve the desired separation. The selectivity obtained in binary mixed mineral tests was translated into the ternary mixed mineral system, viz. apatite-dolomite-silica. In this presentation surface chemical characterization of the samples and their flocculation behavior will be discussed.

Jan 1, 1994