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By Johne Jesus Mol Peixoto

Utilizando um modelo físico de um reator RH em escala 1:7,5, simulou-se o processo de injeção de material dessulfurante na câmara de vácuo, buscando evidenciar a influência da vazão de gás e da diferença de densidade entre as fases sobre o tempo de residência e sobre o tamanho das gotas de escória arrastadas pelo metal, parâmetros essenciais para uma estimativa da taxa de dessulfuração. O aumento na densidade do fluido similar ao aço resultou em considerável prolongamento no tempo de residência e diminuição do diâmetro médio das gotas de óleo arrastadas. Para a solução salina (NaCl) como fluido de circulação, observou-se que a redução da vazão de gás aumenta o tempo de residência das partículas de dessulfurante. Tais resultados sugerem que existe uma vazão ótima de gás para alcançar maior eficiência de dessulfuração no RH, isto é, maior tempo de residência do material dessulfurante e arraste de gotas de escória de menor diâmetro.

Oct 30, 2017

By Jr. Taylor

The following heats of solution have been measured in 1.160 molal H2SO4 at 25° C: AH298, kcal./mole Be(c) + 77.44(H2SO4?47.849 H2O) H2(g) + BeSO4 (soln) -92.83 ± 0.11 BeSO4 ?(c) + 77.44 (H2SO4?47.849 H2O) BeSO4(soln) -16.45 ± 0.02 BeSO4?2H2O(c) + 77.44(H2SO4?47.849 H2O) BeSO4?2H2O(soln) -5.395 ± 0.019 BeSO4?4H2O(c) + 77.44 (H2SO4?47.849 H2O) BeSO4?4H2O(soln) 1.513 ± 0.010 Combining these data with other experimental results and data taken from National Bureau of Standards information yielded the following heats of formation at 298° K:

Jan 1, 1966

By H. D. Kessler, F. A. Crossley, J. J. Rausch

The titanium-rich corner of the system Ti-AI-V has been studied to determine the phase relationships in the temperature interval 600° to 1200°C. Metallographic examination of long time isothermally annealed specimens was the principal method of investigation. TWENTY-SIX alloys in the region 1 to 22 pct A1 and 2 to 11 pct V, and the temperature range 600° to 1200°C, were studied as part of a program on phase relationships and transformation processes of titanium alloy systems. Experimental Procedure Preparation of Alloys—Materials used in the preparation of alloys were high purity Bureau of Mines sponge titanium (103 Bhn), 99.7 pct pure V chips obtained from the Electro Metallurgical Div., union Carbide and Carbon carp., and 99.71 pet pure A1 in the form of granulated shot from Aluminum cO. Of The alloy ingots, weighing l5 g, were melted in a nonconsumable tungsten electrode arc furnace un-

Jan 1, 1957

By R. A. L. Drew, F. Jalilian, M. Jahazi

Joining of superalloy Inconel 61 7 with a foil interlayer using transient liquid phase bonding (TLP) technique was studied. Inconel 617 is a solid solution, Ni - Cr - Co- Mo alloy with an exceptional composition of high temperature strength, oxidation, carburization resistance and thermal stability. In this investigation, two bonding temperatures, 1065°C and 1150°C, and two interlayer thicknesses with joining times varying from 5 minutes to 24 hours were employed. Experiments were carried out using nickel base interlayer (A WS BNi-3) with boron as the melting point depressant (MPD) element. Joints were characterized using optical microscopy, SEM, FEG-SEM, EBSD, XRD and microhardness. The results indicated that the rate of elimination of the liquid phase with increasing the bonding temperature, holding time and decreasing the thickness of the interlayer increased. The main precipitates in the diffusion layer had platelike and blocky morphologies for both bonding temperatures and all holding times.

Jan 1, 2006

By Marcos Vinícius Fonseca Ferreira

Questões socioambientais têm maximizado a permuta entre o uso de materiais sintéticos para o uso de materiais naturais. A fibra de fique disposta no presente trabalho na forma de tecido, extraída do folha da planta do fique (Furcraea Andina) demonstra grande potencialidade como reforço de compósito polimérico. Nos corpos de prova para os ensaios, as camadas de tecido foram misturadas à resina epoxídica DGEBA/TETA e justapostas sob pressão em um molde retangular metálico à temperatura ambiente por 24 horas. A quantidade de tecido de fique nos corpos de prova gerados, foram de até 5 camadas, cortados a partir das dimensões matriciais, seguindo a norma ASTM D256. Testados e após analisados por microscopia de varredura eletrônica (MEV). Pode-se notar o aumento significante da resistência ao impacto de acordo com o crescimento numérico de camadas fibrosas que reforçaram o compósito. Tal performance pode ser associada ao mecanismo de fratura, gerada da interação entre o tecido de fique e a matriz.

Oct 30, 2017

By S. F. Willey

Difficulties encountered in justifying replacements for overage mobile mine equipment at the Gay mine are common to most mining operations. More critical management reviews, resulting from ever rising capital expenses, increased such difficulties. These increased difficulties are especially apparent to those who are primarily operators and are not statisticians, mathematicians or computer men. The Gay mine is located 17 mi east of the town of Fort Hall in southern Idaho. This open pit operation annually supplies the J. R. Simplot Co. and the FMC Corp. with 1.5-2.0 million tons of phosphate ore. Stripping ratios average approximately three bank cubic yards of waste per ton of ore mined. The mobile mine equipment fleet consists of ten 24-cu yd scrapers; twenty-one 30-50-ton end-dump trucks; four 3%-4%- cu yd shovels; fifteen dozers in the D-8 and D-9 classes; and three road patrols. Equipment replacement is based on the results of evaluations made on individual units.

Jan 9, 1972

By Harold W. Lipper

Helium production and shipment reached new peaks in 1.361. The Bureau of Mines produced 727 million cubic feet, 13 percent more than the 1960 record, and shipped 552 million cubic feet, 16 percent more than the 1960 record. Production exceeded demand for the third successive year, enabling the Bureau of Mines to add 174 million cubic feet to the volume stored underground for future use. At the end of 1961, the total volume of helium in underground storage in the Clifside gasfield was 44-7 million cubic feet. Contracts to implement a long-range helium conservation program were completed with four companies, obligating all the contracting authority of $47.5 million a year made available by the Congress. The four companies will finance, build, and operate helium extraction plants to recover from natural gas an annual average of 3.1 billion cubic feet of helium that would ordinarily be wasted when the helium-bearing natural gas is used for fuel.

Jan 1, 1962

Hang ventilating air curtains so that they can be installed, moved, opened and closed more easily than curtains that are spadded or nailed in place. Approach Low-leakage plastic curtains fitted with grommets along the top were threaded onto a steel cable which is suspended from roof bolt plates. The system was tested in two mines. How It Works The curtains are threaded onto a steel cable which is suspended from roof bolt plates by S-shaped hooks. See Figure 1. The outby end of the cable is reeled off a hand operated winch; the inby end of the cable is anchored to a roof bolt plate by means of a cable grip and an S-shaped hook. To install the curtains the following procedure is used. First, the winch is located at least 5 feet outby the last open cross-cut. The base of the winch can be secured to the mine roof with short roof bolts, only about a foot long.

Jan 1, 1978

By Delciane Porfiro, Tiago de Mattos Serodre, Antônio Eduardo Clark Peres, Valdirene Gonzaga de Resende

The evaluation of the effect of the addition of carbon nanotubes (NTCs) directly to a etheramine on the flotation recovery of the quartz at pH 10.5 was carried out by means of microflotation tests in Hallimond tube. The quartz flotation was evaluated using 0.1% (w/v) etheramine solution with different percentages of carboxylic functionalized NTCs. The increase in the percentage of functionalized NTCs increased the flotation recovery to a maximum and from this it was observed a reduction of the recovery of the mineral. Pure etheramine and etheramine with the NTCs were characterized by FTIR spectroscopy and thermal analysis. FTIR spectra of both pure etheramine and etheramine with NTCs clearly showed peaks with the same wavelengths and diagnostics of the cation etheramine and acetate anion. Thermogravimetry indicated that the etheramine + NTCs-COOH mixture lost approximately the same weight percentage over a larger temperature range. In addition, the interaction of the nanotubes with the etheramine caused them to decompose at a lower temperature.

Oct 3, 2019

By K. P. Plucknett, Z. Memarrashidi

WC-Co ‘hard metals’ are widely used in a variety of industrial applications due to their resistance to abrasive wear, in addition to their high hardness and toughness. However, in contrast to their mechanical properties, the corrosion response of these materials is relatively poor. In the current work the corrosion mechanisms of two WC-Co cermets are analysed, with 10 and 30 vol. % of the Co metal binder, in a 3.5 wt.% NaCl aqueous solution. The assessment of corrosion involved a variety of electrochemical measurements, including open circuit potential, potentiodynamic polarisation and cyclic polarisation, together with systematic analysis of the post-corrosion solution chemistries using inductively coupled plasma optical emission spectroscopy. The corrosion potential and current density were determined, following Tafel extrapolation, allowing the calculation of the corrosion rates. It is demonstrated that continuous dissolution of the cobalt phase occurs during corrosion, which is a result of poor cermet passivation behaviour, and this response increases with the amount of binder in the cermet.

Jan 1, 2015

By John C. Machisak

THIS CHAPTER of the Minerals Yearbook relates to employment data and injury experience in the metal, nonmetal, and quarrying industries. Combined statistical data on the mineral industries as a whole can be found in volume Ill. Each industry in the chapter is shown separately, and no attempt has been made to combine and show an overall picture. The voluntary reporting of data on injuries and employment by operators of metal and nonmetal mines and quarries has contributed substantially to the promotion of safety in these industries. Data on injury and employment in the clay mining and milling industry are included for the first time. Table 6 contains data for clay mines only for 1955 and for clay mines and mills for 1956. The clay-mill figures are included with other nonmetallic mills in table 5. The information for norunetallic mills was compiled and published for the first time in the 1955 issue of this report.

Jan 1, 1958

By J. R. Campbell

During the past few years, the writer has had occasion to take several excursions into the realms of the washability of beds 3 and 4 of the Pocahontas coal and the proper handling of these coals in prepared sizes Fig. 1.—Washability curve for 4 by 2½-in. egg, PocahoKtas coal. Note that definite break occurs at about 1.60 sp. gr., and washing at this gravity removes all heavy rock and slate, amounting to about 5 per cent. Curve 2 indicates a bony coal, and washed egg coal might not have a good appcarance, and would be condemned by visual inspection, although it would be well prepared mechanically. to attain the greatest realization for the operator and yet produce a market product acceptable to the consumer. Preparation is not new in the southern field, but some new angles have presented themselves in recent years on account of the progress of mechanical preparation. Mechanical methods are entirely devoid of the five senses given to

Jan 1, 1931

By Alfred E. Schwaneke

A versatile torsion creep tester was instrumented with electromechanical and servomechanical components to operate automatically and unattended, producing digital printed outputs. The apparatus uses an electrical system for applying torsional stresses, and a unique angular transducer as a null detector operating a servocontrolled strain measuring system with the digital readout. The tester is designed to measure the creep in single-crystal or polycrystalline zinc, zinc alloys, magnesium, magnesium alloys, or other metals and alloys. Applied stresses may be varied from zero up to 2,000 psi in the outermost fibers of a 1/8-inch-diameter, 4-inch-long specimen. Strain readings to 0.001 degree, equivalent to a strain of 2.73 X 10-7, may be made automatically from one every 5 seconds to one per month. The apparatus has provisions for programed temperature control and special atmospheres or vacuum operation. A discussion of applications of the system to other mechanical testing apparatus is included.

Jan 1, 1970

By Forrest T. Moyer

The safety record of the mineral and mineral-fuel mining and processing industries in 1965 was improved slightly, as indicated by the reduced injury-frequency and severity rates. The overall operating activity was higher in 1965 as measured by the gains in the number of men working and in the total man-hours of worktime. Injury Experience.-The rate of occurrence of all disabling work injuries in the mineral industries was 17.65 per million man-hours in 1965. This overall rate comprised frequencies of 0.28 for fatal and 17.37 for nonfatal work injuries, of which both were slightly better than the corresponding rates of 0.29 and 17.53 in 1964. Fatalities totaled 537; 5 less than in 1964. However, the total of 32,982 nonfatal injuries was 575 higher than in 1964. This larger number of nonfatal disabilities was offset by the increased worktime so that the nonfatal frequency rate decreased in 1965.

Jan 1, 1967

By L. M. Cathles, H. R. Spedden, E. E. Malouf

Fluid flow through an igneous rock formation will occur mainly through fractures. A non-diffusing or slowly diffusing tracer (such as .5µ silica spheres identifiable under electron microscope) will arrive at a monitor well when enough fluid has been injected to displace the volume of water in the flow fractures between the injection and monitor wells. A rapidly diffusing tracer (such as NaC1)-will diffuse into the matrix blocks and so a volume of tracer nearly equal to the total fluid volume contained in the rock formation between injection and monitor wells must be injected before significant diffusing tracer arrival will be noted. The flow fracture porosity is typically one hundred times smaller than the total porosity of an igneous formation. The shift between diffusing and non diffusing tracer arrivals, together with the diffusional characteristics of the tracers, can define the diffusional accessibility of the matrix blocks of an igneous formation. A field test of these concepts and the problems encountered will be described.

Jan 1, 1974

By Olofsson O, Durance M-V, Villeneuve J

Modelling of the Sala Agitated Mill (SAM) using a simplified solution to the population balance approach has been carried out. The rate of breakage is modified by the mill power, providing predictions of the resulting product size distribution for different grinding conditions and mill sizes. The power of the mill is estimated by a physically derived function, using an assumption that the mill power consumption mainly arises from the ball to ball friction within the mill. The grinding efficiency, depending on the media ball size and pulp density is approximated in the model. Experimental work on grinding a complex sulphide ore using a pilot scale SAM 7.5 has been carried out. Good agreement has been found between the data from the test campaign and the simulated values. The model has also been validated with experimental data from a pilot grinding of calcium carbonate and from an industrial mill. The model is included in the USIM PAC simulation software.

Jan 1, 1995

By Homer E. Harris, William C. DeSieghardt, William A. Burgess

Under sponsorship of NIOSH, Eastern Associated Coal Corp., with the Harvard School of Public Health acting as a subcontractor, has determined for the first time the effective protection provided to working underground coal miners wearing approved half-mask dust respirators. This was done by conducting 187 man-shifts of in-mine testing in four different coal mines; included in this testing were 37 different test subjects representing 11 different job classifications and 5 different models of respirators. Presently available respirators on average provided significant protection levels to working miners even though on an intermittent use basis. However, "average" protection values were well below those achieved under laboratory conditions. Protection levels varied from man to man in a given work crew and from day to day for a given man. In addition, some of the factors affecting use and effectiveness of presently used respirators are discussed, as are areas in which improvements are needed, and the need to consider these improvements in context of a systems approach.

Jan 1, 1975

By C. O’Donova, E. Adam, L. A. Torres-Cruz

High-profile failures of tailings dams illustrate the significant safety challenge they pose. The decant pond of such facilities plays an important role in their mechanical stability. This study investigates the feasibility of using public multispectral data collected by the Sentinel-2 satellite mission to monitor the area of the decant pond. The Sentinel-2 mission has a revisit time of 5 days and the data used herein has a spatial resolution of 10 m/pixel. We considered two water-detection metrics: the normalized difference water index (NDWI) and the near-infrared (NIR) reflectance. Implementation of the method at a South African platinum tailings dam illustrates the capabilities and limitations. Public, sub-metre resolution true-colour imagery served as validation data. There is good agreement between pond area measurements based on Sentinel-2 and the validation imagery. These results suggest the feasibility of using Sentinel-2 data to supplement the monitoring of the decant pond.

Apr 2, 2022

By Wenbin Liu

A novel route for rapid synthesis of ultrafine WC-Co cemented carbides with homogeneous binder phase distribution is reported. The composite powder is produced by in situ reduction-carbonization reactions by using WO2.9, Co3O4 and carbon black as raw powders. The reaction equilibrium and phase stability are studied by thermodynamic calculations. The WC-Co composite powder is condensed by spark plasma sintering (SPS) to obtain the cemented carbides bulk. The sintering temperature is lower than that in the conventional sintering methods by 1500C, while the sintering time is remarkably reduced by 3-5 times. The high performances of the hardness and the fracture toughness are obtained. The experimental results confirm that the present processing scheme of in situ reduction-carbonization reactions and subsequent SPS sintering is an efficient way to prepare WC-Co cemented carbides, and is apparently superior to the conventional long-period techniques of preparing composite powder and cemented carbides bulk.

Jan 1, 2008

By D. E. Walsh, J. T. Hollow, H. K. Lin, J. L. Oleson

At the Fort Knox Mine, Fairbanks, Alaska, carbon fines are generated during stripping, acid washing and kiln regeneration operations. Because of their gold value, carbon fines are collected by a filter press. Samples of the carbon fines show that they consist of 20% to 30% carbon, 70% to 80% grit and 0.17 to 0.68 g/kg (5.0-19.9 oz/st) gold. About 80% of the gold values in the carbon fines used in this study are in the form of recrystallized free gold grains, with the balance being the adsorbed gold on the carbon. High recoveries of gold and carbon were obtained from the fines in laboratory tests using froth flotation, with a high rejection of the grit. More than 95% of gold and 90% of carbon can be recovered by three stages of gold flotation followed by two stages of carbon flotation. Key words: Gold recovery, Activated carbon, Flotation

Jan 1, 2003