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By Sang-Beom Lee

For thermodynamic prediction, the deoxidation equilibrium of aluminum in Fe-36%Ni alloy was studied with a cold crucible under Ar gas atmosphere at 1773K. For the deoxidation reaction in liquid Fe-36%Ni base, i.e.: A12O3(s) = 2A1 + 3O The interaction parameters and the equilibrium constant between aluminum and oxygen in liquid Fe-36%Ni alloy are given in the following: eo Al = -3.8, roA1=0.9, eAl° = -6.4, rAl° = 700, rAIAIo = 3.1, roA1o = 833 within the composition range of [Al] < 1 mass%. The temperature dependence of the equilibrium constant was obtained in the range of 1773K < T < 1973K by using reported data and present results as follows: log KAo= 0.58-24463.7 / T The deoxidation equilibrium with aluminum in Fe-36%Ni could be thermodynamically well described in the range up [Al] < 1 mass% with first and second order interaction parameters as well as the equilibrium constant determined in this study.

Jan 1, 2002

By K. D. Bulin

"An interesting brief history review of shovels as the primary excavating tool will permit the reader to see that immeasurable development and resources have preceded the shovel excavators which today are used extensively throughout the mining industry. With this as a background, the shovel manufacturer has the ability to utilize his resources best in those areas of shovel development in which the maximum benefits of increased reliability, performance and ease of maintenance will improve the operating rewards to the user of the equipment. The author explains the function of the shovel as a part of the material handling system. A detailed description of those areas of the shovel in which the most recent developments and major improvements have been implemented in the manufacture of the shovel excavator arc included."

Jan 1, 1973

By John Nagy

Results of initial research by the Bureau of Mines are given on the dust explosion hazard of float coal and on the related factors of occurrence, rate of production, sampling techniques, transport, and deposition of float coal. Tentatively, it is suggested that where float coal deposits prevail, a mini-mum of 80 percent incombustible be maintained in the top 1/8-inch layer to neutralize the explosion hazard of the surficial coal deposit.

Jan 1, 1965

By Tao Xuea

Gold frequently occurs in nature in the form of a gold-silver alloy. Thus, investigation of the electrochemical behavior of gold-silver alloys in cyanide solution has practical significance. In this paper, the potentiodynamic method is used to determine the anodic polarization curves of gold-silver alloys (Au-10% Ag and Au-50% Ag) in cyanide solutions. To facilitate the interpretation of the results, complementary experiments conducted in NaOH solution in the absence of cyanide are also reported. The results for the Au-Ag alloys are compared with the polarization behavior of pure gold and pure silver. With the aid of potential-pH diagrams for the Au- and Ag-CN-H20 systems and electrochemical kinetics concepts, the dissolution mechanism of gold-silver alloys, the effect of the presence of silver on the cyanidation of gold, as well as the factors which control the anodic reaction rate are clarified.

Jan 1, 1998

By Hasini Wijayaratne

Anode cover material, a mixture of crushed electrolyte and alumina, is a crucial part of an aluminium reduction cell because of its important role in maintaining overall heat balance. However, until recently little attention has been given to understanding or controlling its composition and quality. The thermal conductivity of anode cover material determines the extent of the heat loss from the top of the cell. This will change as a function of the granulometry and composition of the applied cover as well as over time as the cover material consolidates on top of the cell. The ability to measure or predict the thermal conductivity of fresh and ageing cover is an important tool for managing cell heat balance. Recent studies have shown that granulometry or more correctly, voidage is likely to be the predominant determinant of thermal conductivity of anode cover materials. We have developed equipment to measure the thermal conductivity of granular cover material and tested the relative importance of composition (ratio of alumina to crushed electrolyte) and granulometry/voidage on cover thermal conductivity. In general, our results confirm that granulometry is the dominating factor. Generally, high voidages contribute to lowering the thermal conductivity especially when particles are mostly fine. However the relationships between granulometry, voidage and thermal conductivity are complex due to the varying nature of heat transfer between particles. Aging of granular cover material occur during cell operation forming a consolidated crust due to exposure to heat and fumes over time. Structure and thermal behaviour of this consolidated crust is also important in understanding the overall properties of cover. This paper presents the outcomes of laboratory studies conducted in order to understand the thermochemical behaviour of anode cover material and in particular, the role of fines in anode covers mixtures.

Jan 1, 2011

By William C. Alden

A great landslide occurred on June 23, 1925, in the valley of Gros Ventre River, about 35 miles south of Yellowstone National Park (Fig. 1). The relations of the north-easterly dipping rock formations of the slide scarp and of the dam formed by the slide are shown in the diagrammatic cross-section of the valley (Fig. 2). This generalized section is based on unpublished maps and notes by Eliot Rlackwelder, in the files of the IT. S. Geological Survey. Heavy rains and melting snow in the Gros Ventre Mountains had saturated clay layers in the Carboniferous strata, which dip toward the valley at angles of 18" to 21°, consequently an enormous mass of rock at the end of the north spur of Sheep Mountain became loosened and, on the afternoon of June 23, slid suddenly down into the valley. Within a few minutes this mass of debris—estimated as 50,000,000 cu. yd.—carrying

Jan 1, 1928

By T. L. Joseph

IN connection with its investigations of the blast&apos;-furnace process, the Bureau of Mines, in coöperation with the Minnesota School of Mines Experiment Station, developed a 6-ton experimental furnace. Such a furnace was needed to determine the feasibility of producing ferromanganese from Minnesota manganiferous iron ores, a problem of national importance because of the present need for manganese in the steel industry and our small reserves of ferro-grade ores. Furnace operators are reluctant to use new or untried raw materials or to make decided innovations in practice on account of the financial hazard of experimenting with full-scale equipment. A small furnace which can be operated at a relatively low cost is particularly adapted for testing new, raw materials and for determining the feasibility of decided innovations in practice. Laboratory experiments, plus whatever information may be available, are valuable but often do not indicate the net result of changes in an operation involving a large number of interrelated variables. From time to time the coöperation of the Bureau of Mines is solicited in connection with problems involving departures from normal procedure. Under these circumstances some sort of a practical demonstration is a desirable forerunner to full-scale operations which appear feasible after small-scale tests.

Jan 1, 1928

By D. Y. Geng

Longwall mining is a relatively new mining method in the United States. Early trials in the eastern and central coal fields were not successful, mainly because, among others, the face supports did not have sufficient capacity. It was not until in the late 1960&apos;s, when the high- capacity self-advancing powered supports became available, that longwall mining was successfully reintroduced. Since then the number of mines employing the longwall method has been steadily increasing. It has reached approximately 7.5% in 1981. Currently longwall mining is used mainly in the Appalachian coal field. The seam depth ranges from 150 to 2500 ft. but mostly between 300 and 1400 ft. The seam thickness ranges from 32 to 144 inches with the majority between 40 and 100 inches. Nearly all longwall mining are in flat or nearly flat seams extracting in single slice, although one inclined and one thick seam longwall mining have been either operated or initiated in Colorado.

Jan 1, 1983

By N. Nemeth

The filter is an apparatus designed to hold the filter medium. At such a medium takes place the entire liquid-solid or gas-solid separation process. Hence, the medium is really the essence of filtration. Yet, the medium, an originally clean porous substance with trapped solids in it, is perhaps the most neglected part of filtration research. Basically three problems prevail at the medium: 1) Penetration of solids and their blinding of the medium and the influence of such blinding on the resistance to flow. ii) The behavior of the medium in long term repetitive filtration. iii) The filter effect phenomenon whereby the flow rate on filtering an apparently clear liquid through a medium decreases with time. This study undertakes to investigate these fundamental processes.

Jan 1, 1968

By J. Hilgers

Metal prices are often predicted by relying on time trend projections of various economic indicators or even the trend in price itself Thus, time is the underlying explanatory variable acting through at best, a limited selection of economic variables. The price prediction method described in this paper differs from this by analyzing hundreds of economic variables to develop a few principle components that automatically capture the fundamental changes in the economy and delete duplicate or irrelevant information. This leaves a few principle variables to describe a state-space representation of the economy which can then be used for prediction. Forecasts of the price of a metal are then made based on these principle variables.

Jan 1, 1995

By J. H. Scaff, W. G. Pfann

The effects of impurities on the electrical properties of silicon are discussed in a companion paper by Messrs. Scaff, Theuerer, and Schumacher.&apos; It was shown that an ingot of silicon which contained boron and phosphorus in certain concentrations consisted partly of p-silicon and partly of n-silicon2 and that the common boundary between these regions was the source of a photo-voltage. These features were ascribed to the segregation of boron and phosphorus during solidification of the ingot. Because of different rates of segregation the first portion of the ingot to freeze contained a molar excess of boron over phosphorus and hence was p-silicon. The last-solidified region contained a molar excess of phosphorus and was n-silicon. This paper is concerned with the microscopic examination of such ingots. The microstructures are rather unusual in certain respects and their study has helped to show how the segregation of minor elements modifies the electrical properties of silicon. The microstructures of ingots prepared from two lots of silicon, designated 1 and 2, will be described. These lots were obtained from the Electro Metallurgical Co. Both contain 99.8+ pct silicon, but they differ in impurity analysis. For each lot will be shown the microstruc-ture of a slowly cooled ingot, for which the time of solidification is 6 min., and that of a rapidly cooled ingot, for which the time of solidification is 2 min. The ingots were prepared from 45 g charges of silicon. When an alloy freezes a cored structure is generally produced because of insufficient diffusion to remove concentration differences established during freezing. As a result of coring the first portion of a crystal to freeze is usually poorer in solute than equilibrium requires, while the last material to solidify is richer. In a columnar grain, growth is principally unidirectional and coring can produce a concentration gradient along the entire grain. By carrying the picture of the coring process from a single grain to an entire ingot in which columnar grains are aligned more or less radially, one can easily see that a composition gradient could be established between the outside and center of the ingot. This, to a considerable extent, occurs during the solidification of a slowly cooled ingot of silicon. Slowly Cooled Ingot In slowly cooled ingots of both lots of silicon, columnar grains which are approximately radial in direction and longest at the top of the ingot enclose a region in which the shapes and align- ment of the grains are considerably less regular. The central region is last to solidify and contains cavities and inclusions. The sketch of Fig 1 illustrates some of these features, as well as others which will be described below. If a polished section of an ingot is etched in a mixture of 2 parts of 20 pct HF and 98 parts of HNO3 the p-n barrier becomes visible. The overall shape of the barrier in a slowly-cooled ingot is roughly oval, as may be seen in Fig 1. The proportion of n-silicon, that is, the region enclosed by the barrier, is considerably greater in ingots of lot 1 than in those of lot 2. A sample about 34 x 1/8 X 1/8 in. was cut from a slowly cooled ingot of lot 1 with its long direction extending from the top of the ingot to the porous region. Thus its upper half was psilicon, its lower half n-silicon. A longitudinal face was polished and etched in the acid mixture. The areas of interest are identified in Fig 2. A band of parallel markings extends across the sample in the columnar region. These striae are roughly parallel to the upper surface of the ingot and cross grain boundaries with only slight deviations. They are quite distinct in the n-silicon,

Jan 1, 1950

By D Thornton, R Hodson, D Sprott

Blast fragmentation size distribution and thus blast design have been found to have a direct impact on the load and haul cycle through excavator dig time and bucket payload. Previous studies have demonstrated that by reducing the excavator dig time and increasing bucket payload, significant improvements can be made in both productivity and unit cost. Simulation work reported in the literature indicates that a 20 per cent improvement in dig time may result in only a three per cent improvement in load and haul productivity and unit cost. At the same time, a ten per cent improvement in bucket payload will directly translate to a ten per cent improvement in load and haul productivity and unit cost. Based upon these findings, extensive laboratory and field work have been undertaken in the past to correlate blast fragmentation distribution to bucket payload. In contrast, the literature reports limited studies quantifying the impact of blast fragmentation on excavator dig time. Field work was conducted at Placer Dome Asia PacificÆs Granny Smith Mine (Wallaby Pit) in Western Australia, concentrating on quantifying the impact of blast fragmentation on the dig time of a Liebherr 994 hydraulic excavator (shovel attachment with 14 m3 bucket). Fragmentation was assessed for each truck load of material using the Split Desktop system, while the excavator cycle analysis was conducted manually. Measured fragmentation P80 (fragment size at which 80 per cent of material passes) values ranged from 200 mm to 1200 mm. The field study investigated the impact of various fragmentation parameters (P20, P50, P80, cumulative per cent passing 250 mm size fraction, and uniformity index) on the average and total dig times. The results indicate that the fragmentation P80 provides the best correlation to average dig time (total dig time divided by the number of bucket passes to load a truck). The total dig time was found to be dependant upon the fragmentation P80 and the number of bucket passes to fill a truck. Monte Carlo simulation results, based upon these relationships, indicate a 26 per cent improvement in average dig time and a 12 per cent to 46 per cent improvement in total dig time (bucket passes ranging from 4 to 8), with a change in fragmentation P80 from 600 mm to 200 mm.

Jan 1, 2003

By A Unlutepe

The Bosphorus Rail Tunnel Project, located in Istanbul, Turkey, aims to provide a Euro-Asian rail link, via an immersed tube tunnel crossing the Bosphorus Strait, along which will run all commuter, freight and intercity passenger trains of Turkish State Railways (TCDD), as well as the future extension to the European rail network. The total length of upgrading and new railway construction will be approximately 76 km. The main structures include the immersed tube tunnel; mechanised shield tunnels; new Austrian tunnelling method (NATM) tunnels; cut-and-cover, at-grade and retained-cut/fill structures; and some service structures. This paper discusses Phase 1 implementation of the project, one of the major transportation infrastructure projects in the world today, whose varied structures present stimulating engineering and construction challenges.

Jan 1, 2008

By C. Gherghel

The planning and operation of ventilation network systems for uranium mines require special considerations since ventilation is the primary technique of controlling ambient concentrations of radon progeny. The major environmental challenge facing the ventilation engineer is the requirement to dilute radon progeny to below the Working Level Month per year of worker exposure required by law. The application of large airflow volumes and the utilization of low residence times constitute some of the factors considered by the design engineer. Good mine planning and sequencing are also critical for protecting the health of miners. The mine ventilation must have such characteristics as flexibility, high air distribution efficiency, rapid air transit times, zero recirculation and no short-circuiting. A well established maintenance program for all ventilation appliances must be in place to guarantee control of the distribution system. Real-time monitoring systems permit assurance the adequate quality of air is delivered to working places. A case study for an operating mine is used to demonstrate how the ventilation system is successfully managed and operated using the above concepts.

Jan 1, 2009

By W. C. Phalen

"Tho the term “magnesite” is generally applied to the iron-bearing carbonate of magnesium, such as is found in Austria and Hungary, by some Austrian magnesite is referred to as bruennerite. The mineral bruennerite has become of commercial importance only in Austria. The important deposits are found in Styria, lower Austria and northern Hungary. It is of interest to know that the world's largest deposit of spathic iron ores or iron carbonate (FeCO3), occurs at Eisenerz, Styria, while the world's largest deposit of spathic bruennerite is found at Veitsch in the same province.The Styrian and lower Austrian deposits are located much nearer the Adriatic sea than are the deposits of northern Hungary; and it is from the former that most of the exported magnesite has come. They are located south-west of Vienna, and extend west from Semmering thru the Murz Valley to Tyrol. The chief deposits reckoning from east to west are those of Semmering, Veitsch, Breitenau, Trieben, Radenthein, and Dienten.The largest and most important deposit is that at Veitsch located near Mitterdorf, on the South Austrian railroad in the Murz Valley, Styria. Here the magnesite, which occurs in the form of a lens is quarried on the slope of a hill in a series of terraces about 50 feet apart. The entire work extends thru a vertical distance of 500 feet. The huge magnesite lens is nearly 4 of a mile long and over 1,000 feet in width, and probably extends to a considerable depth.The formation containing the magnesite extends eastward beyond Vienna into Northern Hungary where magnesite is quarried beyond Jolsva and Nyustya in the Gomor district. In spite of the remote location of these deposits as compared with those in Styria, magnesite was shipped from them before the war a distance of 360 miles to the port of Fiume for overseas shipments to other parts of Europe and to America.The average analysis showing the composition of the Austria-Hungary mineral is as follows:The magnesite occurs as lenticular masses in a belt of Carboniferous rocks consisting mainly of metamorphosed Shales, sandstones, conglomerates,,and limestone, It is grayish in color when fresh, and contains sufficient ferrous carbonate to blacken it when calcined. It turns brown owing to the oxide ion of the ferrous carbonate when exposed to the air. The quantity of carbonate of iron is ariable and different analyses show that it ranges up to 13 or 14%For the most part, only the sintered article has been imported into The United States. This material has achieved an enviable reputation for its uniformity both as to chemical and physical characteristics. The homogeneity of the sintered Austrian magnesite is doubtless due in part to the averaging effect of the different operations, such as crushing, dressing, sintering, And mixing, n effect which is not obtainable in mere hand samples.There is comparatively little variability in the sintered magnesite as marketed, and five analyses of this sintered magnesite as quoted by Cornu* are gas follows:"

Aug 1, 1919

By Robert W. Bruhn

A 125 foot high steel lattice frame tower supporting a 500 kV EHV transmission line and located over the gateroads of a longwall mining operation was subjected to ground movements from the mining of adjacent longwall panels. Under an agreement with the owner of the powerline, the mine operator was required to minimize mining impacts on the transmission line. In view of this requirement, the mine operator prepared a forecast of the expected subsidence ground movements prior to the onset of mining. These forecasts, in conjunction with finite element analyses of the tower superstructure under the imposed ground movements and wind loadings. suggested that the structural capacity of the tower would probably be diminished little, if at all, by mining. Ground movements determined by survey during mining of the two longwall panels were found to be in close agreement with predictions. Strains measured in selected tower members during mining generally agreed with values calculated by the finite element analyses. The study confirmed a methodology to predict subsidence and to assess its effects on steel lattice transmission towers.

Jan 1, 1990

By Paul Wellman

A computer program is presented that may be used to calculate the bare equipment cost of the major processing units for any hot potassium carbonate gas purification system. The program is designed such that, with only minor modifications, it could be used with a variety of computer systems.

Jan 1, 1968

By W. K. Utt

This report discusses U.S. Bureau of Mines&apos; research involving modem vehicle position determination techniques in surface mining. The applications would include haul trucks, power shovels, and drilling rigs. Accurate position determination of these vehicles in near real-time is expected to result in safer and more efficient mining operations. The requirements for a vehicle position monitoring and warning system were determined. After screening several concepts, the global positioning system (GPS) and a radar positioning system were selected for further evaluation. A state-of-the-art GPS receiver was taken to a surface mine to assess the feasibility of receiving the satellite signals. A state-of-the-art radar positioning system was evaluated with regard to accuracy.

Jan 1, 1995

By D. Kang

The adsorption behavior of silver in ammoniacal solutions on to activated carbon has been studied. The parameters affecting the adsorption of silver on to activated carbon included temperature, agitation speed, concentration of cations and anions as well as that of ammonia. It was found that the adsorption of silver from ammoniacal solutions was dependent upon the initial silver concentration in the solution and other factors. The recovery of silver from ammoniacal solutions was found to be not so effective as the case with gold reported earlier. The adsorption rate was relatively slow overall, despite a rather fast initial adsorption. The apparent activation energy for the adsorption was measured to be 30.2 kJ/mol. It was believed that the kinetics of the silver adsorption on activated carbon was limited by a mixed control mechanism.

Jan 1, 1998

By Detnet Solutions

1. “Daisy-Chain” concept The term “daisy-chain” stems from the fact that when the HotShot? detonators are connected there is a chain or electrical path for electrical current to flow from detonator A to detonator B, detonator B to detonator C etc until the path is terminated by an electrical means. The “daisy-chain” concept has long been used in electronic detonator systems, historically used in Expert Explosives’ ExEx 1000 5/6 wire system and currently in use in African Explosives Limited (AEL’s) Electrodet? electronic detonator system and has been adopted as the basis upon which the “auto-programmability” of the HotShot? electronic detonator system functions. HotShot? Detonators are connected to each other in a string, completing a “daisy chain”, and during the auto-detection mode of the control equipment, it is possible for the equipment to determine the order of hookup of the detonators as well as map the entire blast layout. The auxiliary components (Row Controllers & Branch Controllers) assist the control equipment in mapping the entire blast by indicating different points on the blast, i.e. The inflection point of a row of blast holes on a closed chevron timing pattern, the beginning of row of blast holes on open chevron timing pattern and extra blast holes or extra blast rows.

Jan 1, 2004