Search Documents

By F. J. Sotillo

The objective of this investigation was to determine the feasibility of using a high-pressure roll mill (HPRM) to improve the separation efficiency of dolomite from apatite in downstream operations when treating high-dolomitic pebbles. High-dolomite samples from four phosphate mines were used for the test program. The research work plan included sample characterization studies; INSTRON tests to develop preliminary crushing data; high-pressure roll mill evaluations to determine crushing parameters, such as feed rates, rolls speed and gap, and applied torque, pressure and energy; and screen, microscopy, and flotation studies to assess dolomitelapatite separation efficiency. The results of the HPRM tests show that commercial products for all four mines can be obtained. Recoveries of 74-82% of the P2O5 and rejections of 46-83% of the MgO were reported with an specific energy consumption of 0.2-0.5 of that of a laboratory rod mill.

Jan 1, 1998

By J. H. Wernick

IN temperature-gradient zone-melting1 a molten zone is moved through a solid or across a solid surface by the establishment of a temperature gradient. This technique has both practical and fundamental aspects. One practical application is to make p-n junctions for semiconductive devices, particularly for devices in which the junctions are desired within the semiconductor. From a fundamental point of view, the technique is being investigated as a method for determining diffusivities in liquid alloys, and preliminary diffusivity results have been reported by the writer." In this paper, the effects of crystal orientation, temperature, and molten zone thickness in temperature-gradient zone-melting, and the bearing of these effects on diffusivity measurements and n-p-n junction formation are discussed. Experimental Procedure An effect of crystal orientation was noted in early experiments. To facilitate its study, movements of wire zones across a surface, rather than through the body of a single crystal, were observed for various surface planes and travel directions. The experirr-entai setup is illustrated in Fig. 1. The graphite end-section for the high temperature heater has an apron about 1/16 in. above the upper surface of the crystal. This apron insures that the surface temperature of the block is equal to or greater than the temperature within the block at every point, Thus, the zone does not penetrate the block and convection in the liquid is minimized. The experi-through a block is shown in Fig. 2,

Jan 1, 1958

By Marco D. Boscardin, Paul A. Roy, Kevin J. DiRocco, Andy J. Miller

The North Shore Connector Project for the Port Authority of Allegheny County involves TBM mining a pair of subway tunnels through soil and rock under the Allegheny River and a narrow city street. Along the tunnel alignment are a historic building on shallow foundations and modern buildings on deep foundations, one constructed directly over the alignment during the latter phases of design. This paper provides an overview of the general site conditions, and technical basis for excavation support and tunneling decisions. Deformation limits, ground improvement, monitoring and mitigation plans, geotechnical baseline report development, and risk management will also be discussed.

Jan 1, 2007

By A. Desbiens, M. Maldonado, R. del Villar, Aguilera. R.

This work details the application of a multiple model approach to estimate frother concentration in flotation processes. The methodology consists of identifying a set of linear dynamic models representing the effect of gas rate on the collection-zone gas holdup at different known frother concentrations (calibration step). An adaptive law is then obtained using Bayes' rule to evaluate the conditional probability that each model represents the observed system behavior. In this way, a frother concentration estimate is calculated as a weighted sum of model probabilities and their associated (known) frother concentrations. Experimental results conducted in a two-phase system using Dowfroth250C are promising. Modeling and analysis for MIBC frother are also provided.

Jan 1, 2009

By Ron Ketterling

Donna Summer wrote and recorded a song in 1983 with Michael Omartian called, “She Works Hard for the Money.” The song was inspired by her encounter with an exhausted rest room attendant, Onetta Johnson, who is mentioned in the song by name, and featured on the album’s back cover. ISEE President James Daley, in the May/June 2019 in The Journal of Explosives Engineering discussed the Six Pillars related to the ISEE. We will use the Internal Processes pillar to frame this discussion. The Internal Process Pillar includes five separate sub-committees – we will see how this concept applies to both ATF Explosives record-keeping compliance and business process compliance in general. We will discuss electronic and paper record keeping, what works and what doesn’t. We’ll review record keeping in light of those five sub-committees: Audit, Awards, Constitution, Ethics and Planning. You’ll come away with concrete steps you can use to improve your record keeping processes. This paper will show you how to make the hard work of inventory management and ATF record keeping work hard for you.

Mintek now offers a service for the accurate measurement and analysis of air pollution in South Africa. 'The deteriorating air quality and general degradation of the environments in industrialized and urban regions of South Africa have been of concern for more than a decade', says Mintek's Dr Johann Engelbrecht. 'The accompanying effect on health, visibility, and damage to property and the environment have prompted the public, authorities, and industry to take appropriate action. A recent study conducted by the Medical Research Council on schoolchildren in the Vaal Triangle, clearly demonstrated the relationship between the deficient quality of the air in that area, and the resultant respiratory diseases.

Jan 1, 1996

By N. P. Widodo

The ventilation measurements by tracer gas method at Pongkor gold mine show that effective diffusion coefficient, E, at straight airways indicated a similar range of measured one by the laboratory experiments which can be estimated by Taylor equation. On the other hand, E of the curved airways in the mine was estimated as larger than that of the straight ones (1.5 to 32 times than that obtained by the Taylor equation and these have been compared with the data measured in Kushiro coal mine, Japan). The curved mine airways, with small curvature against airway radius and complex velocity profile, possibly give concentration ? time curves with long tailings, thus those airway conditions could make larger E. Laboratory experiments of gas diffusion by a pulsed injection of small amount gas, into straight and curved airways, have been conducted in order to investigate a range of E in mine airways. The plots of E against Reynolds number show that the present laboratory results of straight-long airways are almost close to one calculated by Taylor equation. On the other hand, the values of E measured at curved single-direction airways were smaller than that of the straight airways, which may be due to effects by secondary vortexes flow in the curved airways.

Jan 1, 2009

By W. L. Grose, J. E. Nealy

A device developed by the U.S. Bureau of Mines for the detection and quenching of coal mine explosions suffers from the inability to discriminate between the light emitted from hydrocarbon combustion and that emitted by electrical sparks and miner's cap lamps1. Since the quenchant device is activated by an internal explosive charge, the possibility of serious injury to nearby personnel demands a detector which can reject false signals. Described herein is a detector which can provide a rapid response signal upon the emission of radiation from hydrocarbon combustion and concurrently reject spurious signals from such sources as sparks and cap lamps. It was suggested that a detector might be developed to operate on the principle of monitoring the radiation intensity emitted from two separate spectral regions and ratioing the intensities2. A series of experiments was conducted for combustion of methane-air mixtures which demonstrate the ability of such a detector to discriminate between combustion and spurious signals. Experimental Apparatus A cylindrical (3.8 in. diam by 12 in.) stainless-steel shock tube test section was used as a combustion chamber. The test section was equipped with quartz windows (2 in. diam) on either side, a piezoelectric pressure transducer, and two steel electrodes. A 10-kv capacitor discharged across the electrodes provided a submicrosecond duration spark to ignite the gas mixture within. The desired partial pressures of methane and air were obtained by using a Wallace and Tiernan 0-800 mm Hg pressure gauge with which pressures could be determined to an accuracy of % mm Hg. All tests were conducted with a total pressure of 1 atm in the chamber. To

Jan 1, 1972

By E. G. Davis

The Bureau of Mines investigated gaseous direct reduction of low-grade iron ore concentrates in a continuous fluid-bed reactor. These studies were made in a 4-inch diameter fluid-bed reactor using hydrogen alone, and oxygen-or air-reformed natural gas as the reductants. The percent reduction is directly dependent on the mole ratio of hydrogen in the reducing gas to the oxygen associated with the iron oxide in the ore. Two-and three-stage fluid bed tests were simulated by repeated continuous tests. The results showed that percent reduction of the final product was dependent on the mole ratio of the quantity of hydrogen in the gas of each stage to oxygen in the iron oxide of the initial ore feed. Reduction as high as 87 percent in the single stages and as high as 94 percent in the multistages was obtained when either hydrogen or reformed natural gas was used as the reducing gas. Magnetic separation and concentration of the highly reduced fluid-bed product yielded a high metallic iron concentrate analyzing 85 percent total iron and 80 percent metallic iron with total iron recovery as great as 90 percent. Agglomeration of the high-grade metallized concentrate produced hard pellets analyzing 85 percent total iron and 78 percent metallic iron. Green pellets, with good strength, were made without any binder in a drum pelletizer. Direct melting of the high-metallic fluid-bed product in a basic lined arc furnace produced a nearly pure iron which contained 0.09 C and 0.01 P with 95 percent recovery of the metallic iron in the metal.

Jan 1, 1972

By Jinjing Dua, Jun Zhua, Kuiren Liub, Bin Wang, Xiaolei Wua

V-Ti-Fe as hydrogen storage alloy was prepared by reducing metal oxides with a metallothermic reduction method. The deoxidation process of the V-Ti-Fe alloy was performed by electro-deoxidation and vacuum induction melting method, respectively. The results showed that the content of oxygen impurity can be controlled at about 0.2wt% after electrolyzing for 240min. Both the maximum values of hydrogen absorption capacity and the effective hydrogen desorption capacity are 2.65wt% and 1.01wt%, respectively. The deoxidization effect of vacuum induction melting process is more remarkable, with Ce as the reducing agent. It is found that Ce addition is beneficial for reducing the componential segregation, promoting the hydrogen absorption activation of V-Ti-Fe alloy. When m(Ce)/m(alloy) is up to 5%, the oxygen content has been reduced to 0.05wt% and the maximum hydrogen absorption capacity and the effective hydrogen desorption capacity are up to 3.36wt% and 1.85wt%, respectively.

Jan 1, 2015

By D. R. Lentz, J. A. Walker

"Abstract -The Flat Landing Brook Zn-Pb-Ag deposit of the Bathurst Mining Camp occurs within a narrow thrust-bound nappe containing felsic volcanic and volcaniclastic rocks of the Tetagouche Group. Within the host nappe, the Tetagouche Group is represented by the Nepisiguit Falls Formation and the overlying Flat Landing Brook Formation. The Nepisiguit Falls Formation is divided into two members: quartz- and quartz-feldspar-phyric volcaniclastic rocks ± minor lavas (Grand Falls member), and aphyric, fine-grained volcaniclastic rocks (Little Falls member). The Flat Landing Brook Formation consists of aphyric rhyolite flows and interbedded pyroclastic rocks. Several gabbroic intrusions occur in both the footwall and hanging-wall sequences. These gabbros locally cut out the mineralized horizon at shallow levels, and are considered to be feeders to tholeiitic basaltic flows (Forty Mile Brook member) of the Flat Landing Brook Formation. The Flat Landing Brook deposit has many of the characteristics typical of volcanogenic massive sulfide deposits occurring within the highly productive Nepisiguit Falls Formation in the eastern part of the Bathurst Mining Camp. Mineralization occurs within or at the top of the Grand Falls member and comprises four or more massive to semi-massive sulfide lenses that vary in thickness between 3 and 5 m. Massive lenses are laterally gradational to, or underlain by, zones of disseminated sulfides up to 38 m thick. The deposit contains an estimated resource of 1.7 Mt grading 4.9% Zn, 0.94% Pb, and 19.54 g/t Ag to a depth of approximately 150 m. From 150 to 300 m below surface, mineralization is low grade and mostly disseminated. However, below 300 m, ore-grade (>10% Pb+Zn) massive sulfide lenses have been intersected over mineable widths. Oxide facies iron formation overlies and (or) grades laterally into the sulfide lenses. The oxide facies has strong positive Eu anomalies and gently sloping rare earth element (REE) profiles suggesting that it was formed from relatively hot acidic fluids that had interacted with felsic volcanic rocks in the footwall. In contrast, the silicate facies iron formation that is more distal to sulfide accumulations has very weak positive Eu anomalies and gently sloping REE profiles, suggesting either cooler hydrothermal fluids or dilution of the hydrothermal component by detrital material. Hydrothermal alteration has affected most footwall rocks. Most notably, albite-destructive alteration has resulted in Na2O depletion, whereas mass addition of K2O is manifested in the formation of sericite (white mica). In more intensely altered quartz- and feldspar-phyric volcaniclastic rocks of the Grand Falls member, feldspar destruction is accompanied by chlorite alteration, producing quartz-phyric rocks similar to those in the footwall of many Bathurst Camp deposits."

Jan 1, 2006

By A. J. Plumpton

Centrifugal air classification and li-quid-phase sedimentation are the principal methods of industrially sizing materials of dimensions smaller than those handled by screens. Increasing application of materials such as composites and high performance ceramics has furthered the need for closely-sized, fine, industrial mineral and synthetic products of controlled properties. Sedimentation can be used to separate very small sized particles but introduces problems of liquid-solid separation, de-agglomeration and drying. Some of the advantages and limitations of centrifugal air classification will be discussed and laboratory and plant measurements using centrifugal machines will be presented to support the discussion.

Jan 1, 1990

By W. S. Weeks

In coursing the ventilating air through a mine it is often necessary to restrict a comparatively open split in order that it may carry exactly the desired quantity of air. Such a restriction is known as a regulator, and usually takes the form of a partition with a hole in it. The quantity of air circulating is controlled by the size of the hole or orifice. For example, it is desired to force a quantity q I cu. ft, per min. through split a (Fig. 1) and the quantity q2 through split b. It requires a pressure of 2 in. water to force the desired quantity through a, and a pressure of 1 in. to force the desired amount through b. The pressure drop between points A and B must be 2 in and a pressure of 1 in. must be destroyed in split b. This is done by inserting a regulator in b, which causes the velocity to increase in the orifice and results in a change from pressure-head to velocity-head. If the air, after passing the orifice, is slowed down in a turbulent manner, all of the velocity-head does not change back into pressure-head, so a permanent loss of static pressure results. A classic formula for computing the area of an orifice to destroy a certain amount of static pressure has been handed down from early days: 0.0004Q a =2 This formula is based on the assumption that all velocity-head in the orifice is "destroyed;" that is, does not reappear again as either velocity-pressure or static pressure. The derivation of the formula is as follows: h = head lost in regulator in fect of air. v = velocity in regulator in fect per second. q = quantity circulating in cubic feet per second. Q = quantity circulating in cubic feet pcr minute. a = area of orifice in square feet.

Jan 1, 1928

By J. Grumer

Nine dust and gaseous inhibitors of propagating coal dust-air flames (lean, stoichiometric, and rich) were evaluated in a newly developed 15-cm-id, 3.6-meter-long instrumented flame duct, under conditions such that wall quenching was virtually absent and the dust concentration was temporally and spacially uniform to within about t5 percent. Listed roughly in order of increasing efficiency, the inhibitors evaluated were rock dust (calcium carbonate), powdered oyster shells (calcium carbonate), Halon 1301 (trifluorobromomethane), Halon 1211 (difluorochlorobromomethane), sodium chloride, Super-K (potassium chloride), regular-grade fire extinguishant powder (sodium bicarbonate), Purple-K (potassium bicarbonate), and Monnex (potassium bicarbonate combined with urea). Experiments were extended to clouds containing 1 and 2 volume-percent of methane. The inhibition of lean, stoichiometric, and rich methane-air flames without coal dust was also examined in a few instances; results agreed with those obtained for coal dust-air flames.

Jan 1, 1971

By J. Donald Rimstidt, Jeanette K. Jerz

Acid mine drainage is a major environmental problem worldwide. A key to remediating this problem is understanding the rate and mechanisms of the complex, multistep pyrite oxidation reaction under geologically relevant conditions. Because many waste piles are not submerged, a large amount of pyrite oxidation actually occurs in air. We have designed a Barcroft-manometer reactor to measure the rate of pyrite oxidation in air as a function of relative humidity and oxygen partial pressure. The reactor consists of two chambers joined by a manometer. Each experiment occurs at constant temperature, initial oxygen partial pressure, and relative humidity, although these variable can be changed between runs. Oxygen consumption was measured and pyrite oxidation rates were calculated from those data. Initial data indicate that rate of pyrite oxidation by oxygen in humid air is much faster than the rate of oxidation by oxygen in solution. The rates determined by this study can be used to develop better remediation techniques for acidic mine waters.

Jan 1, 2000

By F. J. Longworth

FoR a number of years an intensive study has been made to improve the blast-furnace practice at Copperhill not only as to cost% but to provide a good grade of gas for the acid plants. This study took us back to the fundamentals of successful pyrite smelting; namely, a blast furnace working on a clean sulfide ore, free from fines, and the use of quartz high in silica as a flux. In 1919, the quality of the flux was improved and its effect on the metallurgy was very marked. To improve the practice further, it was necessary to work out some method of treatment for the sulfide fines and the siliceous and refractory ores, other than in the blast furnace. A series of milling tests indicated that these products could be successfully treated by differential flotation, and in 1922 plans were made and a flotation plant built. It was estimated that the flotation plant would deliver to the smelter 40 to 50 tons of concentrates per day; the problem was what to do with these concentrates. It was out of the question to attempt to smelt them in a blast furnace because of the dust losses and because our practice demands a charge free from fines for satisfactory operation. There is no custom smelter in the vicinity to which concentrates may be sold, pending the time when the tonnage will be sufficient to warrant roasters and a reverbatory furnace. Sintering and nodulizing were investigated but neither method fitted into our scheme of metallurgy. A close study of the converter practice was then made to see if some method could not be evolved to smelt this tonnage of concentrates in a converter without preliminary treatment. At that time, the converter installation consisted of two 12-ft. Great Falls converters, which were handling 12 to 14 per cent. matte. The heat balance of the converters working with 12 to 14 per cent. matte was more than sufficient to smelt the contemplated tonnage of concentrates but the mechanical difficulties of feeding fines into the Great Falls converter made the use of this type of converter impractical. While there was no opportunity to experiment with the Pierce-Smith converter, equipped with a Garr gun, theoretically it seemed practical

Jan 1, 1925

By Hsing Kuang Lin

Ferric chloride leaching w.as applied to a complex sulfide ore from Tok, Alaska to dissolve zinc, lead, silver and copper. Gold in the leaching residue, as well as in the ore, is found to be refractory to the conventional cyanidation process. Roasting, pressure oxidation and elemental sulfur removal followed by cyanidation were tested to improve gold dissolution. Also tested were thiourea leaching and high-pressure cyanidation. The readsorption of dissolved gold by carbonaceous matter in the chloride leaching residue was analyzed. Based on the experimental results, factors causing difficulty of gold dissolution from the leaching residue are discussed.

Jan 1, 1989

By Ernest L. Bradley

A positive pressure ventilation system, augmented by a dewatering well curtain and underground longhole drilling, provides effective ventilation and radon control at EXXON Minerals Company's Highland Underground Mine in the Southern Powder River Basin of Wyoming. Testing different types of bulkheads, sealants, and bleeder systems has led to improvements in the basic ventilation system. Continued testing of new or different materials and equipment is expected to lead to further improvement in the ventilation program. Effective training of both miners and supervisors is essential to maintaining and improving ventilation techniques. This paper addresses the ongoing ventilation program and experience to date at the Highland Uranium Mine.

Jan 1, 1979

By M Fishwick Tapia

This paper was prepared and translated from the final report of the investigation into the Codelco Chile Salvador DivisionÆs air blast which occurred in the Inca-West area. In this section of the block cave mine, a stable arch formed covering an area of approximately 15 000 m2 . This zone subsequently collapsed producing a massive air blast. The collapse followed a series of planned extraction activities and occurred on 5 December 1999. This paper discusses the cave back arching event and the measures that were taken in order to induce the controlled collapse. This was to minimise risk to personnel, equipment and installations. The results obtained to date are presented.

Jan 1, 2000

By Edward Thomas

Yucca Mountain Overview The U.S. Department of Energy?s Yucca Mountain Project is a geologic repository project designed to receive, handle, package, transport, and emplace spent nuclear fuel and high level radioactive waste. The planned repository would be located in Yucca Mountain on the western edge of the Nevada Test Site, about 90 miles northwest of Las Vegas, Nevada, and would include both surface and subsurface areas. Yucca Mountain rock formations consist of successive layers of volcanic rocks (called tuffs) approximately 14 to 11.5 million years old, formed by eruptions of volcanic calderas to the north. With the volcanic rock the potential for methane emission is not an issue and the subsurface repository is a non-gassy (methane) classification. This paper will provide a summary of the development ventilation system design that provides fresh air for subsurface construction activities, and the emplacement ventilation system design that removes heat generated by the waste packages. The subsurface layout, illustrated in Figure 1, contains 108 emplacement drifts, one Performance Confirmation(PC) observation drift, nine intake/exhaust shafts, and three access ramps. The existing Yucca Mountain facilities, shown in bold lines in Figure 1, include a 7.8 km long, 7.62 m (25 ft) diameter U shaped tunnel that is formed by the North and South Ramps at both ends of the Exploratory Studies Facility (ESF) drift and a 1.5 km long, 5.0 m (16.4 ft) diameter Enhanced Characterization of the Repository Block drift (ECRB) that were constructed from 1994 through 1998. These drifts were used for site characterization activities and have been incorporated into the subsurface repository configuration. The unexcavated perimeter access main and exhaust main drifts are typically 7.62 m (25 ft) diameter TBM excavations and the emplacement drifts are 5.5 m (18 ft) diameter TBM excavations. The turnouts leading into the emplacement drifts are to be excavated by either mechanical, or drill and blast methods and serve as the launch chambers for the emplacement drift TBM excavations.