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By L. M. Gochioco

The U.S. coal industry is under-going dramatic changes to meet the challenges of the keenly competitive fuels market. The application of innovative technologies is needed to improve safety and to increase productivity in order to make coal more competitive as a fuel. As more coal companies shift into capital intensive longwall mining, there is a clear need to invest more in exploration before mine plans are made. Coal seam anomalies may create adverse mining conditions. The early detection of these anomalies could make the longwall mining safer and more productive through improved planning. A standard exploratory drilling program can provide only limited geologic information. The seismic reflection technique can be used to detect coal seam anomalies and is effective in reconnaissance surveying. Recent advances in the quality of coal seismic data have increased the success rate of seismic surveying. Therefore, surface seismic surveys, coupled with selective drilling, will come to play an integral role in coal exploration in the 1990s.

Jan 1, 1990

By M. R. Peterson

The U.S. Bureau of Mines has investigated new methods for increasing the selectivity in flotation by creating and regulating reagent concentration gradients within flotation columns at steady-state operation. Gradients were generated and traced in a water-only system with the use of fluorescent dyes, and the effects of various operating parameters on these gradients were investigated. From this investigation, it was found that both gradual and steep gradients could be generated in the froth cleaning zone, and that these gradients could be changed through the manipulation of both physical and chemical operating parameters. The application of reagent-gradient control to mineral systems could improve both flotation grade and recovery in commercial flotation operations without the use of additional flotation circuitry.

Jan 1, 1992

By J. B. Hiskey, V. M. Sanchez

Electrochemical oxidation of arsenopyrite (FeAsS) has been investigated as an attempt to gain a better understanding of its dissolution chemistry. Rest potential measurements, cyclic voltammetry and constant potential experiments were conducted in the pH range from 8 to 12 in the absence and the in the presence of cyanide. A two-step reaction sequence is suggested by the electrochemical measurements. The initial step is described by: [FeAsS+6H20=Fe(OH)3+H2AsO3- +S°+7H++6e] The second step involves the oxidation of the arsenite and sulfur according to the following reactions: [H2As03-+H20=HAsO24-+3H++2e and S° +4 H2O=SO4-+3H++6e] Stoichiometric determinations confirm that 14 electrons are involved in the overall reaction.

Jan 1, 1992

By Luis R. Bittencourt

Research efforts have been made to characterize a refractory Brazilian bauxite ore composed basically of gibbsite, kaolinite and quartz. Detailed polished-section microprobe analysis of the unbroken ore has been used to describe the liberation characteristics and the association between mineral phases. The linear grade distributions for selected particle size fractions were determined by means? of a particular implementation of King's Random Fracture Model that uses the exponential model for the distribution of linear intercepts through both dispersed (kaolinite) and continuous (gibbsite) phases. The corresponding volumetric grade distributions were then determined by means of a constrained optimization technique for the solution of the transformation equation. Batch flotation experiments were carried out to determine the kinetics for particles of different sizes and the results correlated with the liberation spectrum for each size class.

Jan 1, 1991

By G. Keizer

Cortez Gold Mine (C.G.M.) is located in Lander County, Nevada, approximately 80 miles southwest of Elko, Nevada. It is accessed via Nevada State Highway 306 south from Interstate 80. This operation is a joint venture between Placer Dome U. S. Inc. (60% operator) and Kennecott Corporation (40%). The claims which supply oxide and refractory ore feed to the Cortez milling facility are located in both Lander and Eureka Counties. These include the Cortez and Horse Canyon deposits all operated by C.G.M. Joint Venture. Other deposits outside the C.G.M. claim area include; Fire Creek, Buckhorn, Gold Bar and Tonkin Springs. These deposits all occur along the Battle Mountain/Eureka Trend.

Jan 1, 1993

By Jack V. Hill

A unique type of grinding mill liner has been developed by Waagner-Biro A.G. of Austria. This liner system, termed an angular spiral lining (.ESL), was, successfully tested by Magma Copper Company's San Manuel concentrator in both their 10 Ft x 10 Ft (3.05m x 3.05m) and 12 Ft, 6 In x 14 Ft (3.81m x 4.27m) grate discharge wet grinding ball mills. Magma Copper's savings in power and grinding balls justified conversion of more than half of their twenty-six ball mills to the ESL system.1,2 The ASL system was provided by the Capitol Castings Division of Midland Ross Corporation, the exclusive licensee for such conversions. Capitol Castings proposed the following as expected benefits from installation of an ASL system in an 18 Ft x 21 Ft (5.49m x 6.40m) overflow discharge wet grinding ball mill at the Pinto Valley Operation of Cities Service Company: "(a) Reduction of power consumption per ton of ore milled = 12%, (b) Increased throughput = 6%, (c) Reduction of ball consumption = 6%."

Jan 1, 1982

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 Phillip O. Tyree, R. A. Metz, Joseph W. Mussey

Bio-epigenetic sulphur deposits occur in Pecos, Reeves and Culberson counties of far West Texas. Sulfate reducing bacteria, utilizing hydrocarbons as energy, transformed gypsum into replacement limestone and hydrogen sulfide. Hydrogen sulfide, retained in the pores of the replacement limestone, was subsequently oxidized by highly oxygenated groundwaters, and native sulphur precipitated. West Texas sulphur was first recognized at surface exposures by William P. Blake, a geologist attached to the Captain Pope Military/ Scientific Expedition of 1854. Attempts were made in the early 1900&apos;s to mine these sulphur vent exposures by a retort method, but the ventures met with little success. In 1967, Duval discovered a large sulphur deposit near some of the old sulphur works in Culberson County. Duval also expanded reserves in a small sulphur deposit in Pecos County. The Frasch process, developed for producing sulphur from Gulf Coast salt domes, proved successful in West Texas type sulphur deposits also. However, modifications of the process were necessary to provide economical and efficient sulphur recovery from the varied ore occurrences. West Texas conditions and logistics require the ultimate in productivity to be competitive in the domestic and foreign sulphur markets. Several companies, in addition to Duval, are producing or have produced sulphur in West Texas. As of June 1, 1984, a total of 29.87 million mt (29.4 million long tons) of sulphur had been produced west of the Pecos River. Duval corporation has produced more than 88 percent of that total.

Jan 1, 1992

By J. C. Ashby

Electric utility response to certain amendments of the Clean Air Act has resulted in a production of several types of alkaline coal combustion byproducts. Alkaline combustion byproducts are gaining increasing usage for acid mine drainage mitigation as research leads to a better understanding of their beneficial applications. Since January of 1997, Mettiki Coal Corporation has been injecting alkaline flue gas desulfurization material from Virginia Power&apos;s Mt. Storm Unit #3 wet limestone scrubber into abandoned portions of the active Mettiki mine. This paper provides an overview of the key design, transportation, regulatory, and environmental issues faced in the project.

Jan 1, 1998

By A. V. Castelli

Since the record year of 1981 through 1985 the tonnage of weighting materials (barite and other heavy minerals) used in drilling fluids has decreased an estimated 49%. As in the past, barite still makes up over 90% of the minerals used for weighting materials in drilling fluid. Domestic production of barite has decreased 69% since 1981 and imported barite has made up over 50% of the total barite consumed since 1982. See Figure 1 for usage of barite. The number of operating grinding plants has decreased from 69 in 1982 to 39 at the end of 1985. With the decrease in demand of weighting materials for drilling fluids and an over capacity of grinding existing, prices for weighting materials have decreased dramatically. Although the American Petroleum Institute has not changed any of the specifications for barite, some users have initiated their own new specifications and have proposed to have them included in the API specifications. The exploration for and development of oil and gas dictates the level of weighting material used in the drilling fluids industry. Most forecasters do not foresee (or predict) increases in the level of drilling until the 90&apos;s. The primary or unground barite produced in the U.S. mines has a difficult time competing with imported barite due to the location of the mines. These mines are located in North Central Nevada, with small tonnages being produced in California, Missouri, Illinois, Montana and Washington. The major reason, is the difference in transportation costs from the mines versus ocean freight rates from the foreign ports to the major area of use, the U.S. Gulf. Since 1981, the production of primary barite has decreased from 2,849,000/ST (2,584,596/MT) in 1981 to an estimated 890,000/ ST (807,403/MT) in 1985(1). If it were not for the use of unit trains by some producers the production of primary barite in the U.S. would have probably declined another 20% in 1985. During the same period, of the total amount of barite consumed in the U.S., imported barite ore increased from 417, in 1981 to 65% in 1985. The major exporting countries to the U.S. during this period were China 46.27, Morocco 15.27., Chile 10%, Peru 8.4%, India 7.9%, Mexico 5.4%, Thailand 3.9% and Ireland 2.3%.

Jan 1, 1986

By F. F. Peng, Y. Xia

In modeling of hindered-settling bed separators, the published separation mechanisms are based on differences of particle density and size distributions, without the details of complexity of particles-liquid interactions. A fluid dynamic model for the separator is developed using Euler-Lagrange approach of Computational Fluid Dynamics (CFD). Fluid motion is obtained from solving the movement of liquid governing equations. The damping effect on flow pat-terns caused by the movement of particles resulted in liquid-particle coupling is included in the model. Effects of particle size, and particle density compositions, feed rate, feed water flow rate, upward fluidizing water flow rate, etc., are simulated in the 2-D separation model. Flow pattern effects on the separation of fine particles in the separators with center downward-flow and side cross-flow feed systems are investigated.

Jan 1, 2004

By E. J. Onuscheck

Coal mine safety of the past was plagued by disasters that took the lives of thousands of miners. Through the years new mining methods, improved laws, and a commitment from the mining industry has reduced the frequency of such incidents to a minimum. History tells us that coal was mined in the early 1700&apos;s in Virginia primarily for use by blacksmiths -- most of that mining was done in the Richmond area. It was in those mines that methane was encountered; as workings became more extensive, methane explosions became more frequent. In the early 1800&apos;s the first recorded explosion occurred near Richmond, Virginia -- 40 men were killed.

Jan 1, 1985

By J. Drelich

The adsorption of oleate at the surface of titanium dioxide from aqueous solutions was examined by Fourier transform infrared (FT -IR.) spectroscopy using a germanium internal reflection element coated with a thin film of TiO2. This thin film, with a thickness of 100-200 A, was deposited on the surface of a germanium single crystal by RFIDC magnetron reactive sputtering. It was found that significant adsorption of oleate from a 0.02-0.03 mM aqueous solution on the surface of TiO2 thin film occurs at neutral pH, from about pH=5.5 to pH=7.7. Adsorption of oleate at the surface of the amorphous TiO2 thin film appeared to be reversible, involving soap-acid dimers.

Jan 1, 1997

By S. Veeramasuneni

The recent nonequilibrium electrophoretic mobility measurements by laser-Doppler electrophoresis coupled with the stability and prevalence of collector colloids in soluble-salt flotation systems suggest that the selective flotation of alkali halides is due to the adsorption of oppositely charged collector colloids by heterocoagulation. Previously reported flotation results confirm this surface charge/collector colloid adsorption model. These results also indicate that the sign of the surface charge has a significant effect on the extent of particle dispersion/aggregation. In this regard, the nature of such particle interaction forces at high ionic strengths are examined to improve our understanding of these systems. Atomic force microscopy (AFM) is now being used to directly measure the interaction forces responsible for the stability of these alkali halide aggregates observed in optical microscopy studies. Results from this study indicate that, while repulsive hydration forces exist between similarly charged hydrophilic particles, attractive forces exist between oppositely charged hydrophilic particles in high ionic strength solutions.

Jan 1, 1999

By Nomuqhele N. Nkosi, Yasuo Yabe, Musa D. Manzi, Raymond J. Durrheim, Siyanda B. Mngadi

This study examined rock failure in brittle rocks hosting the deep gold-bearing ore bodies on scales between millimeters and kilometres. This research study is part of the International Continental scientific Drilling Program (ICDP) project, “Drilling into Seismogenic Zones of M2.0-M5.5 earthquakes in deep South African gold mines” (DSeis). The broader ICDP-DSeis project aims include the examination of the extent of damage, the stress state around the fringes of the earthquake, and the potential existence of living organisms associated with deep-level earthquakes. Nevertheless, this study focused on two seismogenic zones – the Cooke 4 mine and Moab Khotsong mine. At Cooke 4 mine, the study examined the evolution of mining-induced fractures (M1-4) occurring ahead of the stope face during the extraction of the remnant shaft pillar. These fractures were monitored and delineated by a dense array of acoustic emission sensors that allowed hypocentres to be located with decimeter accuracy. Using this acoustic emission data, the DSeis team drilled and recovered the fractures, rock breccia and gouge using a sophisticated triple-tube drilling rig.

Apr 26, 2022

By Zoltan F. Oszter

The frictional resistance to motion of a belt conveyor has always been a subject of intensive studies and research by engineers throughout the years. Numerous informations have been developed by analysing series of field tests on belt conveyors of different characteristics and carrying different materials at various capacities. Within certain limits of weight per unit length and tension, the theoretical considerations and the analysis of the field tests, both in the US and abroad, resulted in the development of similar formulas. In general these formulas are safe to use up to the following limits:

Jan 1, 1977

By Cal D. Iles

Decreasing ore grades and increasing labor and material costs have seriously eroded the economic vitality of many mining operations. Coupled with global economic stagnation and recession in the early 1980&apos;s, these conditions have forced reevaluation of operating strategies and methodologies with the objective of remaining competitive in a world marketplace. A concept offering large potential benefits is hardrock portable crushing and conveying. Implementation of this system at Duval Corporation&apos;s Sierrita open pit copper-molybdenum mine (Figure 1) has significantly reduced mining costs, becoming a major part of Sierrita&apos;s cost reduction strategy. Located 48 km south of Tucson, Arizona, the 209 000 t/d property has one portable 60x89 gyratory ore-crusher in operation with tentative plans for two additional units.

Jan 1, 1985

By Michael M. Kimberley

Gold is sufficiently valuable that concentrations as small as 1 p.p.m. may support low-cost mining. Mindful of this, Sunoco Energy Development Company (Sunedco) obtained fire-assay analyses on some sulfide-rich sandstone encountered during routine drilling. Initial fire-assay values from independent laboratories indicated some significant gold values and independent analysis by atomic-absorption spectroscopy also indicated detectable gold at economically interesting concentrations. Sunoco geologists realized the potential for spurious results inherent in both fire assaying and atomic-absorption spectroscopy. Fire assaying that relies on gold measurement by weight requires perfect separation of gold from all other elements, Imperfect separation may artificially enhance apparent gold concentrations. Atomic-absorption-spectroscopy (AAS) measurements are potentially subject to interferences from other elements. For example, Beamish and Van Loon (1977, p.4) report AAS measurements of 4 p.p.m. Au to be characteristic of completely barren soil samples when samples are prepared by standard dissolution in HC1 to form solutions of about 10,000 p.p.m. total cations (mostly Na, Ca, Mg, Al, and Fe) .

Jan 1, 1981

By S. Gundiah

Preparation of functionalized polymers from the polymerization of monomers and preformed polymers are discussed with a few illustrative examples. The methods of their characterization, with reference to their application in flocculation, are described.

Jan 1, 1987

By Da-Rong Chou

An optimum method for selecting exploratory drilling locations has been developed. The process has been modelled as a highly non-linear programming problem subject to constraints. Solution involves an iterative algorithm which converges rapidly and procedures have been developed to distinguish between local and global optima. The algorithm has been implemented as an interactive computer program which allows the user to influence directly the solution process and to evaluate the effect of any manual adjustments to the optimal solution.

Jan 1, 1984