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By L. C. IlsLey

Explosives have been fired electrically for several decades. Mountains have been tunneled, deep shafts sunk, extensive coal and metal mine workings excavated and, in times of war, railroads, buildings, bridges, and fortifications have been destroyed by means of electrically fired explosives. Modern engineering depends so much on explosives that their safe and efficient handling and especially their detonation are of prime importance to all those connected with the use of explosive agents. Electric shot-firing is only one method of igniting explosives, but it is rapidly spreading and because of certain inherent safety features should be encouraged. Data collected by the Bureau of Mines indicate that in the United States a large percentage of the blasting in quarries, shafts, and tunnels, and from 15 to 25 per cent of the blasts in mining operations, are set off electrically. The Bureau of Mines is interested in electric shot-firing because of its use in mining, and especially because electric methods, when properly applied, are undoubtedly safer than other methods commonly used.

Jan 1, 1926

By F. B. TOUCH

This bulletin deals with a topic that is exceedingly wide, and will doubtl~ be under consideration and discussion so long as there are enough known deposits of oil and gas remaining in the earth to make their revelopment profitable. The Bureau of Mines has repeatedly called attention to the importance of protecting oil or gas sands from the encroachment of water, and the purpose of this paper is to summarize existing knowledge of methods and devices. Water may gain access to an oil-bearing formation from several sources-from water sands above or below those. containing the oil, or by encroaching through the oil sands as the oil is withdrawn. In short, it may enter a well from the "top, bottom, or side." Such ingress of water is a most serious detriment to the recovery of oil from the ground. As the art of drilling and developing oil properties has progressed, increasing thought, labor, and money have been expended on various methods, devices, and equipment for arresting the migration of water from its normal subsurface position into the porous strata containing valuable oil or gas accumulations. At an early stage in the oil-field development of California, it became evident that considerable modification of accepted drilling practices was necessary in order to meet the conditions imposed by the poorly consolidated shale, clay, sand, and bowlder beds penetrated, as well as the hard layers of sandstone and calcareous shale, which vary greatly in thickness, hardness, and frequency. These hard streaks are commonly called " shell," and are so reported in the well logs. As deeper and deeper territory was prospected, drillers from the older fields of the Ea,st, as well as from Texas and Louisiana fields, took part in the operations. Xhe practice evolved was thus based on the wide experience of a most cosmopolitan group of men who, considered as a group, were not hampered by being limited to the knowledge of the practice at any one locality.

Jan 1, 1918

By Oliver C. Fursman

This work was conducted to determine the feasibility of producing aluminum-silicon alloys in a pit-type, three-phase electric-arc furnace. Two carbon-lined furnaces were used in the tests. The power input ranged from 120 to 240 kw. in the small furnace and from 420 to 460 kw. in the large furnace. Energy consumption ranged from 5.3 to 11.5 kw.-hr. per pound of alloy produced and electrode consumption, from 240 to 510 pounds per ton of alloy produced. A wide range of crude aluminum-silicon alloys was produced by direct smelting of clays or similar aluminum silicate raw materials, using hogged fuel or wood chips as the major source of carbon in the furnace charge, and silicon of high grade was produced by smelting quartz. The aluminum content of the aluminum-silicon alloys ranged from 15 to 55 percent. Alloys produced from a white opaline-silicate clay were relatively free of iron, titanium, and other impurities. Those produced from western fire clays and kyanite, although richer in aluminum, contained considerable amounts of impurities. The purity of the alloys depended largely on the composition of the raw materials.

Jan 1, 1960

By F. R. Cattoir

This Bureau of Mines study investigated molten salt electrorefining for beneficiating low-grade, high-carbon ferrochromium products which can be readily produced from domestic chromite concentrates. A second objective was to refine commercial ferrochromium into low-iron chromium products. Electrorefining of both types of ferrochromium in molten CaC12-NaCl-CrC12, CaCl2-MgC12-CrCl2, or KC1-LiCl-CrCl2 electrolytes produced chromium-iron products with virtual elimination of other impurity elements and some lowering of the iron content, Over 90 percent of the chromium present in the feed materials was recovered. The electrodeposited products were upgraded further by magnetic separation techniques into chromium containing less than 5 percent iron. The technical feasibility of preparing a premium chromium product from a low-grade, high-carbon ferrochromium made from domestic chromite was demonstrated. Chromium virtually free of carbon, oxygen, and silicon from high-carbon ferrochromiums was produced. In addition, the amenability of three commercial grades of ferrochromium to electrorefining and magnetic separation for preparing chromium metal containing less than 5 percent iron was determined.

Jan 1, 1969

HW Process Technologies, Inc. (HWPT) has developed a patented membrane-based ion fractionation system, which specifically separates copper from gold and silver species in a cyanide matrix. This Engineered Membrane Separation (EMS?) system was pilot demonstrated on the 82,000 liters of pregnant leach solution' (PLS) generated from tailings, via thin layer leaching, at a mine site in Durango State, Mexico. The EMS? recovered ~90% of the gold-silver cyano-complex to a 90% volume permeate (based upon an EMS? feed stream of 100% volume) while rejecting -90% of the copper cyano-complex to a \0% (by volume) concentrate. The EMS? technology combines pore-size specific electro-statically charged membranes with engineered materials of construction and application-specific operational design that reject multi-valent, ionically charged species to the concentrate and transmit mono-valent species through the membrane to the permeate. The 850 ppm Cu PLS contained approximately 0.8 gil free NaCN with, the copper cyano-omplex principally in the CU(CN)3 and CU(CN)4 forms. The gold grade of the PLS was -2 ppm Au. The ~LS calcium concentration at -700 ppm Ca was reduced to ISO ppm.Ca (± 50 ppm) by sodium cycle ion exchange pre-treatrnent prior to EMS? processing.

Jan 1, 1998

By Herman Wotruba

Mercury emissions and other environmental impacts in small-scale gold mining are a world-wide problem. "Clean" or better: "Cleaner" technologies have -apart from being environmentally sound -to guarantee a higher income and better working conditions for the miners in order to have a chance for long-term acceptance. In small scale primary gold mining in several South American countries, a number of techniques have been adapted and improved so that they not only were accepted due to their efficiency and easy handling, but they could also significantly lower mercury emissions.

Jan 1, 2003

By Reginals W. Burroughs

Diatomaceous or infusorial earth, also called diatomite; fossil meal, or kieselguhr, is derived from the lowest form of vegetable life, the unicellular alga:. It consists of the siliceous remains of extremely minute aquatic plants, which exist in both salt and fresh water. Light i~ a prerequisite to their development. These very small particles secrete silica in much the same way that molluscs secrete lime to form their shells. The diatoms at death sink to the bottom of the body of water in which they lived, and the organic matter gradually decays and is washed away, leaving the skeletons. Thousands of years are required by this means to develop bed5 of sufficient thickness to be of commercial value. The siliceous remains vary in size according to the species, but all are very minute and, as a general rule, they can be identified only under a high-power microscope. Over one thousand types have been distinguished and named. They are all composed of a hydrous or opalescent form of silica, with silica content ranging from seventy to ninety-five per cent. Magnified, they present an attractive sight, a very fragile structure with many interstitial openings known as cells. Many of them consist of two parts, defined as valves, held together by means of a girdle. Certain species, belonging to the Pinnularia family appear as a long comb, in half longitudinal section. The spaces between the teeth are the cells. This particular genus is very common in Nova Scotian deposits.

Jan 1, 1928

By W. Jomaa, V. Songmene, O. Mechri, Laval Université, P. Bocher, J. Levesque

"A 2D finite element modelling (FEM), based on pure Lagrangian approach, is developed for studying the serrated chip formation during high speed machining (HSM) of 7075-T651 alloy. The solution was achieved using a commercial software package, ABAQUS/Explicit v6.13. The Johnson-Cooke (JC) constitutive equation is used to describe the work material behaviour. Moreover, the JC damage equation is implemented into the FEM to take into account for the shear localization during the serrated chip formation. Modified Coulomb friction model has been used to characterize the sliding/sticking effects on the tool-chip interface with the friction coefficient and shear flow stress determined by force calibration and machining data, respectively. The proposed FEM is validated using experimental data obtained in HSM of 7075-T651. The FEM was able to predict accurately serrated chip morphology. The intensity of chip segmentation was found to increase with cutting speed.INTRODUCTIONHigh speed machining (HSM) is one of the most used processes for manufacturing aircraft parts with aluminum alloys. For aluminum alloys, the use of HSM increases metal removal rate and reduces the formation of built up edges and burrs. However, it was found that serrated (also named segmented or sawtooth chip) and discontinuous chips can be produced during HSM of some high strength aluminum alloys, such as 7075-T6 alloy (Rao & Shin, 2001). Many parameters were found to affect the segmented/discontinuous chip formation during the machining of aluminum alloys.There are two cases in which the serrated chip can forms: the first is when machining hardened materials (Morehead, Huang, & Luo, 2007), and the second, when machining ductile materials with a cutting speed higher than a critical value (Barry & Byrne, 2002). Different theories and models were developed in order to explain the formation mechanism of such kind of chips. According to Astakhov (2006), the segmented chip formation is attributed to variations in stress and plastic deformation states, and resulting temperatures on the cutting zone. Liyao et al. (2013) stated that the segmented chip formation was mainly attributable to adiabatic shear instability/catastrophic strain localization. Others (Vyas & Shaw, 1999) suggest that the fracture/crack propagation mechanism is at the root of chip generation."

Jan 1, 2016

By G. Deschênes

In an earlier study (Deschênes et al., 2009), gold and silver were shown to be efficiently extracted from samples taken from the Kupol Mine in Russia using lead nitrate in a cyanide leach system. In the current study, a com-parison of the technical and economic merits of a new technology called CANMET enhanced leaching process (CELP) was made with the cyanidation/acidification-volatilization-recycling (AVR) process using eight metal-lurgical variability samples, as well as a large composite sample, which was to represent the initial two years of Kupol mill feed. The composite sample leach feed assayed 33.4 g/t Au and 289 g/t Ag. The metallurgical results from the large composite sample demonstrated that CELP produced very similar gold and slightly higher silver leach extractions compared to the conventional cyanidation/AVR leach conditions at 1/2 the cyanide concentra-tion (1,000 ppm NaCN in CELP vs. 2,000 ppm for cyanidation/AVR leach conditions). It was estimated that the total cost per ton was approximately the same for the two technologies (total cost of CELP with the use of Merrill-Crowe at $46.48/t, with cyanidation/AVR at $46.13/t). However, the implementation of CELP would eliminate a capital expenditure of approximately $5 million for an AVR system based on a 2005 feasibility level cost estimate. Eight variability samples used to confirm the composite sample results showed that, on average, the gold leach extractions with CELP and the conventional leach conditions were very similar, but the average silver leach extraction was 2.1% higher for CELP. Furthermore, CELP silver leach extraction was 4.6% higher on average compared to conventional cyanidation for the four mid-grade variability samples evaluated. The decision was made to remove AVR cyanide recovery from the flowsheet and implement CELP at Kupol. The ability to use the conventional leach equipment with CELP and simplify the flowsheet was also a factor, given the remote location of the Kupol Mine.

Jan 1, 2010

By V. Vallyathan, Xianglin Shi, N. S. Dalai

While Cr(VI) is a known carcinogen, the underlying biochemical mechanism is still not fully understood (1). In a pioneering study Jennette (2) utilized electron spin resonance (ESR) spectroscopy to demonstrate that a long-lived Cr(V) species is generated during the reduction of Cr(VI) by microsomes in the presence of NADPH. Later Wetterhahn and co-workers (3, 4) showed that incubation of chromate with isolated rat liver mitochondria causes the reduction of Cr(VI), as well as the formation of a Cr(V) species. Analogous Cr(V) species have also been detected in the reduction of Cr(VI) by other cellular systems such as Hanserulla polymorphared (5) and blood cells (6, 7). All these as well as other studies (8-12) have suggested that this Cr(V) species plays a significant role in the mechanism of Cr(VI) toxicity. Thus far, however, the chemical structure of this dominant Cr(V) species formed in cellular systems has not been identified, and this observation provided an impetus for the present investigation. Another reason for undertaking this study was that some recent reports (10-16) suggest that hydroxyl ('OH) radicals may also play an important role in the mechanism of Cr(VI) toxicity. In particular, it has been shown that OH radicals are formed in reactions between Cr(V) species and H2O2 (13-16), and that the radical yield depends on the chemical structure of the Cr(V) species (15). For example, while Cr(V)-diol complexes efficiently generate OH radicals, another Cr(V) species, the tetraperoxochromate (CrO3/8) ion, does not (15). Thus in the present study, we focused our attention on the following: (a) structural identification of the Cr(V) species generated in the reduction of Cr(VI) by subcellular as well as cellular systems, using microsomes, mitochondria, and Escherichia coli; (b) possible detection of OH radical in the same systems since there is no earlier report of chromium-mediated generation of 'OH radicals in a cellular system; (c) possible involvement of molecular oxygen in chromium-related OH radical generation since a recent report (17) indicated that Cr(VI) mutagenesis is strongly oxygen dependent; and (d) elucidation of the mechanism of OH radical formation in these systems.

Mar 1, 1992

By J. Rao Mokka

Extensive exploration has resulted in delineation of a massive sulfide district on the north flank of the east-central Alaska range. The district covers approximately 400 square miles and contains numerous stratiform; transported and some replacement type sulfide deposits ranging in size from less than 1 million tons to 20 million tons. Five types of ores were sampled for the study. Mineralogical analysis revealed that the minerals are too fine grained for conventional grinding and beneficiation. Hydrometallurgical studies were con-ducted using ferric chloride as a lixiviant. Ore microscopic studies as well as electron microprobe analyses of minerals in the raw samples and leach residues explained the low recoveries for certain elements as well as sources of impurities that need to be eliminated from the process streams.

Jan 1, 1991

By Y. C. Guan

The leaching kinetics of chalcopyrite in ammonium iodide solutions with iodine has been studied using rotating disc. The variables studied J include the concentrations of lixiviants, rotation speed, pH of the solution, reaction temperature, and reaction product layer. The leaching rate was found to be independent with the disc rotating speed. The apparent activation energy was measured to be about 50 kJ/mole from 15°C to 35°C, and 30.3 kJ/mole from 35°C to 60°C. Experimental findings were described by a kinetic model, and the overall rate was found to be: (formula)

Jan 1, 1997

By Olusegun J. Ilegbusi

"A two-fluid model is used to calculate flow and heat transfer characteristics of a plasma jet. This model accounts for both gradient-diffusion mixing and unmixing that may result from pressure-gradient-body-force imbalance in the system. The unmixedness is considered to be essentially a Rayleigh-Taylor kind instability. Separate transport equations are solved for the plasma and ambient gas velocities, temperatures and volume fractions. The two fluids allowed to exchange mass, momentum and energy through empirical interaction parameters. The empirical coefficients are first established by comparison of predictions with available experimental data for shear flows. The model is then applied to an Argon plasma jet ejecting into stagnant air. The predicted results show the significant build-up of unmixed air within the plasma gas, even relatively far downstream of the plasma torch. By adjusting the inlet condition, the model adequately reproduces the available experimental data on the temperature profile.IntroductionPlasma jets have important applications in materials processing, some of which include spray deposition, melting and refining, heat treatment and materials synthesis. In a typical reactor, the hot plasma stream entrains a surrounding gas and the resulting heat and mass transfer and the condition of operation of the torch, determines to a large extent, the performance of the unit. The entrainment may prevent uniform mixing and produce regions of unmixed hot/cold gases and non-uniform deposits as a result of insufficient melting of deposit in cold regions. This phenomenon may also affect chemical reaction rate in plasma systems for NOx reduction in exhaust gases.The study of plasma phenomena is often conveniently divided into three parts namely, the plasma torch, the plasma jet and analysis of the particles carried in the jet. The present work concerns processes occuring in the near-field of the plasma jet i.e. just downstream of the torch."

Jan 1, 1994

By K. Norris

The Amax Gold Guanaco mine is located in the Atacama Desert, approximately 260 km southeast of Antofagasta, Chile. The 6,000 tpd leach operation produces approximately 90,000 oz of gold, and 360,000 oz of silver per year. Production began in 1987, and the operation has been managed by Amax Gold since 1992. The mine has been plagued in the past by high operating costs and low production. Several significant changes have been made to the operations which have resulted in lower costs and higher operating efficiencies. A review of these changes is presented herein.

Jan 1, 1997

By Mike Trovant, Stavros A. Argyropoulos

"A fixed grid numerical model for phase change problems is proposed. The model solves for heat transfer and fluid flow, via the coupled solution of the energy, continuity and momentum equations. In addition, the numerical scheme accounts for temperature varying thermophysical properties and determines the shrinkage profile resulting from phase and density change. Simulations are run to determine the effect of varying model parameters and wall cooling rates on the location and shape of the shrinkage void formation in cylindrical casts. Results are shown for both aluminum and magnesium.IntroductionThe mathematical modeling of phase change processes (be they solidification or melting problems) entails solving for many interrelated phenomena. A comprehensive numerical simulation of the casting of a metal, for example, would have to account for: (a) heat transfer in both the solid and liquid portions of the metal and in the mold, (b) the release of latent heat during phase change, (c) fluid flow behavior in the liquid portion of the metal, (d) temperature induced shrinkage caused by liquid contraction and solidification contraction, and (e) the development of thermal stresses with accompanying shrinkage in the solid portion of the cast and mold. A schematic of the relationships that exist between the coupled equations which govern solidification is shown in Figure 1."

Jan 1, 1994

By K. A. Natarajan, S. Usha Padukone

"An industrial waste liquor having high sulfate concentrations was subjected to biological treatment using the sulfate-reducing bacteria (SRB) Desulfovibrio desulfuricans. Toxicity levels of different sulfate, cobalt and nickel concentrations toward growth of the SRB with respect to biological sulfate reduction kinetics was initially established. Optimum sulfate concentration to promote SRB growth amounted to 0.8 - 1 g/L. The strain of D. desulfuricans used in this study initially tolerated up to 4 -5 g/L of sulfate or 50 mg/L of cobalt and nickel, while its tolerance could be further enhanced through adaptation by serial subculturing in the presence of increasing concentrations of sulfate, cobalt and nickel. From the waste liquor, more than 70% of sulfate and 95% of cobalt and nickel could be precipitated as sulfides, using a preadapted strain of D. desulfuricans. Probable mechanisms involving biological sulfide precipitation and metal adsorption onto precipitates and bacterial cells are discussed.IntroductionIndustrial effluents from hydrometallurgical and mineral processing operations often contain high sulfate and metal concentrations posing significant disposal problems, which require urgent solution to avoid serious environmental contamination. In such waste liquors, sulfate and heavy metals such as cobalt, nickel, zinc and iron originate from the chemical or biological oxidation of exposed sulfide minerals. Reduction of sulfate and precipitation of toxic metal ions from industrial wastes is essential from the viewpoint of environmentally acceptable waste disposal and recovery of associated strategic metals.Many of these heavy metals are essential for metabolic activity of bacterial cells at low levels. But they exert toxic effects at concentrations encountered in polluted water. Removal of toxic metals through biological reduction of sulfates from industrial waste waters have been practiced for several decades. Metal remediation through common physicochemical techniques such as oxidation-reduction, chemical precipitation, filtration, electrochemical treatment, evaporation, ion exchange and reverse osmosis processes is expensive and not suitable in the case of voluminous effluents containing complexing organic matter and low metal concentrations. Further, strong and contaminating reagents are used for desorption, resulting in toxic sludge and secondary environmental pollution. Biotechnological approaches can be more efficient and cost effective for detoxification of such effluents. Biotreatment/ bioremoval offers several advantages over conventional chemical and physical treatment technologies, especially for diluted and mixed contaminants. Biological detoxification, which involves the use of microbes to detoxify and degrade environmental contaminants, has received increasing attention in recent years (Iwamoto and Nasu, 2001). In addition, valuable metals can be recovered from metal sulfide sludge (Boonstra et al., 1999)."

Jan 1, 2015

The role of ZnSO4 in activation of sphalerite (ZnS) and deactivation of lead-activated sphalerite has been investigated. Adsorption of metallic ions at the solid-solution interface, electrokinetic results for sphalerite under different chemical conditions, and thermodynamic calculations were used to elucidate the mechanisms involved. It is shown that flotation response of sphalerite in absence of activators is rather weak and that adsorption of ethyl xanthate on the mineral mainly electrostatic in nature. Zinc sulfate is found to activate the mineral but only in a narrow acidic pH range. This is attributed to the increase of zeta potential as well as the possible increase in amount of negatively charged bulk precipitated zinc xanthate. Lead ions activate sphalerite in a wide pH range and the lead activated mineral assumes a flotation behavior similar to that of galena (PbS). However, addition of ZnSO4 depresses the lead-activated sphalerite by replacing lead ions at the mineral/solution interface.

Jan 1, 1999

By G. Cailletaud, I. Guillot, D. Larouche, R. Martinez, D. Massinon

The precipitation of Al2Cu particles in a 319 T7 aluminum alloy has been modeled. A theoretical approach enables the concomitant computation of nucleation, growth and coarsening, based on an implicit scheme using the finite differences. The equation of continuity is discretized in time and space in order to obtain a matricial form. The inversion of a tridiagonal matrix allows us to determine the evolution of the size distribution of Al2Cu particles at t + dt. The fluxes of solute in-between the boundaries, as well as the ones at the boundaries, are computed in order to respect the conservation of the mass of the system. The main results of the model are compared to TEM measurements. Simulations provide quantitative features on the impact of the cooling rate on the size distribution of Al2Cu particles in good agreement with the TEM measurements. This metallurgical model is integrated into FEA software in order to perform mechanical computations. This kind of multiscale approach allows new perspectives to be investigated in the process of designing cylinder heads. It enables a more precise prediction of the microstructure, its evolution as a function of continuous cooling rates and its impact on the integrity of the structure.

Jan 1, 2015

By Jillian Spindura

This work investigates the carbothermic reduction of the complex sulphide mineral, pentlandite, in the presence of lime. The effects of change in temperature and the use of different carbon sources are studied and the role of these variables on the reducibility of pentlandite mineral is discussed. The microstructures of the heat-treated pellets are examined using X-ray diffraction and scanning electron microscopic techniques. The latter analytical method also allows any variation in the morphology and composition of the metallic phases formed, with temperature, to be considered. The kinetics of the reduction process is studied and the magnitude of the overall activation energy is determined from the plots of percentage reduction versus time.

Jan 1, 1996

In the grand scheme of things, the 9.5-t (21,000-lb) shipment of molybdenum concentrate that left Freeport-McMoRan?s Climax Mine site on May 10, 2012 was not unlike the thousands of others that have been hauled away from the site during the last century, except for the fact that this shipment marked the official rebirth of one of America?s greatest mines. For nearly two decades, 17 years to be exact, there was no production from the mine that was once the largest underground mine in the world and was so important to the Allies? effort during World War II that it was assigned the highest priority of any mine in the United States by the War Production Board. The economic recession in 1980 put an end to the mine?s success, and the Great Recession of 2008 nearly derailed the mine again. But, like the nearby town of Leadville, CO, the mine survived thanks to an investment of more than $700 million by Climax Molybdenum Co., a Freeport-McMoRan company, to bring the Climax Mine back into production.

Jan 1, 2012