Search Documents

By William E. Ford, Edward Salisbury Dana

This section includes one distinct group, the Stibnite Group, to which orpiment is related; the other species included stand alone. Pyr., etc. - In the closed tube melts and gives a dark red liquid when hot and a red- dish yellow solid when cold; in the open tube (if heated ver slow? ) sulphurous fumes, and a white crystalline sublimate of arsenic trioxide. B.B. on ciarcoaTburm with a blue Hame, emitting arsenical and sulphurous odors. Soluble in caustic alkalies. Artif. - Realgar is frequently noted as a sublimation product from furnaces roasting ores of arsenic. Crystals are produced when arsenic sulphide is heated in a sealed tube with a solution of sodium bicarbonate. Obs. - Realgar occurs usually in veins associated with silver and lead ores. It has been found in volcanic regions as a sublimation~duct. It has also been noted as a deposit from hot spring waters. It is often rtasociate wlth orplment. It occurs at Felsi5bBnya, Kapnik and NagyAg, Hungary; Allchar, Macedonia. Binnental, Switzerland, in dolomite. In the United States, at Mercur, Utah; in the Norris Geyser Basin, Yellowstone Park, as a deposition from the hot waters. Found at the Monte Cristo millin district, Snohomish Co., Washington: the namerealga7 is from the Arabic, Rahj af gh&r,powder of the mine. Use. - Was used in fireworks to give a brilliant white light when mixed with saltpeter and ignited. The artificial material is now used for this purpose.

Jan 1, 1922

7133. Clewell, D. H. The Gravimeter. Prec. and Trans. Texas Acad. Science 1941, Austin, Tex., vol. 25, 1942, pp. 86-88. Static gravimeters, unastatized and. astatized, are considered to be the most practical for oil exploration. One gravimeter is described using a beam whose moment about a pivotal axis is elastically balanced. Magnetic or electric fields are deemed unsatisfactory for balancing gravitational force because they cannot easily be kept constant. The gravimeter described is capable of detecting a change in altitude of 3 inches and a change in latitude of about 150 feet. V. S.

Jan 1, 1944

By Wen-long Zhan, Zhe Ning, Jun-hong Zhang, Teng-fei SONG, Zhi-jun He, Qing-hai Pang

In order to investigate the influence of granularity on the gasification property of coke after microwave irradiation, comparison of ordering of carbon structure and internal microstructure of granular coke before and after microwave pretreatment was carried out. It is shown in X-ray diffraction results that the diffraction intensity of the coke sample significantly increased after 40 s irradiation under 264 W microwave power, which indicated the decrease in reactivity of coke.

Mar 1, 2017

By G. J. W. Kor, F. D. Richardson

The sulfide capacities a1 1500°C of slags in the systern CaO + CaF, +Al2O3 have been measured by bringing samples into equilibrium with gas mixtures made from CO + CO2 + SO, + N2. The capacities are negligzble both JOY CaF, and CaF, + Al2O3 melts but when lime is present even at 20 wt pct capacilies as high as 30 x lom3 can be obtained. The results have yielded information concerning the liquidus at 1500°C and fluoride-oxide melts in general. The slags used in electroslag refining contain substantial amounts of calcium fluoride. Robinson and Grainger' report that good results can be obtained by using slags of the approximate composition 70 wt pct CaF2 + 30 pct Al2O3. It has also been reported2 that a mixture of 50 pct CaF2 + 30 pct A12O3 + 20 pct CaO makes a good slag for general use. In view of the fact that very low sulfur contents are claimed for ingots produced by the electroslag process. studies have been made of the sulfide capacities [c, = wt pct S (PO2/Ps2)1/2 at 1500°C. of slags consisting of pure calcium fluoride, and of its mixtures with lime and/or alumina. These studies have also provided information on the phase diagrams. The slags were brought into equilibrium with gas mixtures prepared from NZ + CO + CO2 + SO2. Because CaFz is volatile and also easily hydrolyzed. measurements were made of its loss in weight in various flowing gas mixtures. EXPERIMENTAL Procedure. The apparatus and procedure were the same as described previously. Both platinum and iridium crucibles were used (height and inner diameter about 1 cm), but those made from iridium were stronger and able to withstand a greater number of experiments. In each experiment two crucibles were set in an alumina support and 1 g of slag mixture was divided between them. The materials from each crucible were analyzed separately after being brought to equilibrium with the gas, and then quenched in the water-cooled end of the reaction tube. Materials. Alumina and lime were prepared as de-scribed previously.4 Calcium fluoride was obtained by igniting Analar calcium fluoride in a platinum boat at about 800°C in a stream of pure dry nitrogen: the product was cooled in a desiccator. The slags were produced from mixtures of the powdered constituents, these being melted together in the course of each equilibrium experiment. The sulfur analyses and the X-ray diffraction meas- urements on the solidified slags were made as described previously.4 From the latter it appears that the CaF2 contained less than 0.5 mol pct CaO. RESULTS Values of (ps2/po2) for the Gas Mixtures. The re-sults have been represented in terms of (ps, /Po,)"? for the various gas mixtures used. The va1;es of this function at 1500°C are listed in Table I: they were calculated from the data cited previously for calculations at 1350°C 4 Weight Losses with CaF, and CaF, + CaO. The re-sults of the weight loss measurements* at 1500°C for

Jan 1, 1970

Throughout 1992 Pasminco conducted field trials of the Mobile Miner MM130 at Broken Hill. The goal was to develop the machine to achieve acceptable reliability and establish production rates.

Jan 1, 1993

By G. W. Murrie, W. P. Diamond, S. W. Lambert

A geologic study of the Mary Lee Group of coalbeds in the Black Warrior coal basin was undertaken to examine coal stratigraphy and determine regional trends and extent of the coalbeds. The area investigated encompasses 835 square miles in Jefferson, Walker, and Tuscaloosa Counties, Ala. More than 700 core logs were used to construct a structure map, coal, interval, and overburden isopachs, and cross sections. There is evidence that structure affected sedimentation. Coalbed isopachs indicate the Mary Lee Group was deposited in fluvial-deltaic and low-lying coastal plain environments. The Mary Lee coalbed is the only coalbed which is continuous throughout the area, commonly with two benches which have a combined thickness of 2 to 12 feet. The Mary Lee coalbed changes rank in the basin from high- through medium- to low-volatile coal. The methane gas potential of the Mary Lee Group coals is estimated to be greater than 1 trillion cubic feet. There is an excellent correlation between the orientation of surface cleats with those measured underground in the Mary Lee coalbed. The face cleats roughly parallel the axes of the area's folds and trend northeast-southwest.

Jan 1, 1976

By Joseph Kuti

ROOF SUPPORT DEVELOPMENTS IN LONGWALL (1) European longwall mining technology developed towards its modern form in relatively deep mines. With increasing depth the stability of openings driven for ventilation, travel or transport becomes paramount in mine design considerations. As a result the number of roadways and entries, as well as their width must be a minimum. (1) Another important aspect of European mining is the high density of mineable seams, as opposed to the wide lateral extension of a single seam in the U. S. A. Multi-seam mining requires strict planning and near 100% extraction, since with increasing depth, the effect of remnant pillars can be devastating. As a result the face layout of a modern European longwall panel is based on single panel entries of moderate width and great height. The mode of extraction is generally a mixture of the advance and retreat system which is called a 2-system. It is obvious, therefore, that the supports developed for the entries and for the intersection areas are more complex than those in the U. S. A.

Jan 1, 1981

By W. S. Ayres

I AM well aware that this subject is not strictly in the line of mining engineering, yet as it is a subject with which mining engineers at times have something to do, I have thought, perhaps, it might not be wholly out of place to communicate to the Institute something of the method used in determining deflection, and of its final issue. Having felt a need of some simple formula for determining the deflection of girders of uniform cross-section under any load, I have been led through the counsel of Mr. Frederick J. Slade, to whom I am indebted for many suggestions, to undertake a labor of which I shall in this paper give only some of the most important features. The results arrived at agree with those obtainable from the received formula; of Weisbach, Rankine, and others, but the expressions given by these authors, and by all others that I have at hand, are of such a form that they are not easily applied by those whose higher mathematics have become rusty from disuse, and they require, moreover, too much labor in their application to be of practical value. The general formula that I have adopted is similar to that given by Rankine, and is deflection = [mWl3 -El], in which l is the span, W the total load, E the modulus of elasticity, I the moment of inertia of the uniform cross-section of the girder, and m a factor depending for its value on the mode of distribution of the load. The problem then is to find the value of this factor m in the formula, and for some distributions of the load it leads to a number of mathematical difficulties. In this place I shall consider first the girder to be loaded symmet-

Jan 1, 1877

By F. Keller, J. D. Edwards

THE anodic treatment of aluminum presents problems of scientific as well as of commercial interest.1-3 Of particular interest is the fact that, during the anodic oxidation process, the oxide continues to form at the metal-oxide interface under any oxide previously formed. This has led to speculation as to the mechanism involved in the formation of the relatively thick oxide coatings that are used commercially for decorative or protective purposes. Furthermore, the ability of certain types of oxide coatings to adsorb dyes and other substances has stimulated research to determine the actual structure of these adsorptive coatings. It has been found that anodic oxide coatings on aluminum are composed essentially of aluminum oxide. They are formed by the action of oxygen ions penetrating to the metal surface during the electrolytic oxidation treatment. These coatings can be formed in a number of different electrolytes, as for example, those which contain sulphuric acid, chromic acid, oxalic acid, or boric acid. These are the commonest and most useful electrolytes employed commercially. Except for certain specific conditions of formation, the coatings in general have been found to be amorphous alumina, as far as can be determined by X-ray or electron-diffraction methods. Anodic oxidation processes can be arranged in three rather general classes if they are grouped in relation to the solvent action of the electrolyte on the coating.4 In the first class, the electrolyte has little or no solvent action on the coating that is formed. In general, coatings produced under such circumstances are nonporous and non- adsorptive. In the second class, the electrolyte exerts an appreciable solvent action on the coating. These coatings are porous and adsorptive. Finally, for the third class, the electrolyte tends to dissolve the coating about as rapidly as it is formed. This action produces electrolytic brightening or anodic polishing of the aluminum surface and at most leaves only a very thin film of oxide. The nonporous and nonadsorptive type of oxide film is represented by the coatings that are formed when solutions of boric acid are employed as the electrolyte. It is especially significant that these impervious films are formed in electrolytes that exert little or no solvent action on the coating. Where a boric acid electrolyte is used, the coating tends to form rapidly, with the result that the flow of current is soon reduced to substantially zero. This indicates that the growth of the coating has stopped. As a rule, the thickness of the coating is roughly proportional to the voltage employed for formation and the coatings of this type are exceedingly thin. In an electrolyte of this type, the coating has a high resistance when the aluminum is made anode; consequently, any current that may flow (leakage current) is very

Jan 1, 1944

By DeVerle P. Harris

Risk for most mineral investments is greater than that of average business ventures, because the physical and economic characteristics of the mineral deposit are never known with certainty. Inasmuch as the merits of a potential mineral investment cannot be fully appraised without consideration of the impact to the investor of the possible unfavorable events associated with the adoption of the project, methods of risk analysis are important in project evaluation and investment selection. The conceptual framework for risk analysis and the means by which some of the recommended practices might be implemented are examined. In addition to the normal business risk due to market forces, the physical and economic characteristics of the mineral deposit are never known with certainty, for only partial or indirect information is available, such as data from drill cores or surface and underground workings. Consequently, risk for most mineral investments is greater than that of average business ventures. Inasmuch as the merits of a potential mineral investment cannot be fully appraised without consideration of the impact to the investor of the possible unfavorable events associated with adoption of the project, methods of risk analysis are important in project evaluation and investment selection. This paper examines the conceptual framework for risk analysis and means by which might be implemented some of the recommended procedures. Utility Theory A discourse on risk and its impact upon investment selection quite often leads the reader into the concept of utility theory, for utility theory is a device constructed by economists to measure the satisfaction an individuai receives from a good; in the case of investment analysis, that good is the outcome of an investment. It briefly is reviewed here to describe the reaction of the individual to risk and as a stepping stone to other techniques more suited to risk analysis at the level of the firm. Utility theory proposes that an investor possess a utility map (curve), such as indicated in Fig. 1, which indicates the value in utiles of potential monetary rewards to an individual with some specific endowment of resources. Points on this map are obtained from the following relationship:

Jan 1, 1971

By Fiona M. Doyle, Christopher R. Lubeck, Michael C. Chin

The fundamentals behind a novel approach for creating inorganic/polymer hybrids are described. The binding of +2 charged ions, specifically Cue-and Cat+, to ionic functional groups is explored through UV-Vis spectroscopy and zeta potential measurements. The novel approach uses an electric field to drive ions into a functionalized polymeric matrix, thereby inducing the precipitation of calcium phosphate species. Scanning electron microscopy images of the resulting composite illustrate the results of these precipitations with two distinct morphologies observed.

Jan 1, 2003

By Lovitt M

Ora Banda Gold Mine is located in the Eastern Goldfields of Western Australia. Mining is carried out underground by sublevel open sloping resulting in large open stopes. A Mass Blast of approximately 250 000 tonnes was carried out in July 1994 to recover a rib pillar between two stopes, and the crown pillar between the underground mine and the abandoned open pit above. Strategic development within 50 m of the blast consisted of two ventilation shafts and the main decline. This development required careful design and prediction of the blast results. This paper describes the design of the blast, the prediction of the likely effects, the measures taken to reduce the risk to important development, and the results of the blast.

Jan 1, 1995

By T. W. Wlodek, Zygmunt Kowalczyk

In the period from 1946 to 1964, the annual output of co al from Polish mines increased from 4 7.3 to 117.35 million tons. In this paper, the methods of bringing about this increase in productivity through the building of some twelve new collieries (producing some 15 million tons annually) and the modernization, reconstruction and extension of some thirty-six older collieries are discussed.

Jan 1, 1967

By Martial P. Corriveau

Almost everyone agrees that coal and oil shale are the only fossil fuel resources in which the United States is self-sufficient. Of the two, only coal has a technology sufficiently developed to be of intermediate term benefit. Since it takes at least 20 years to bring advanced technology into practice, it seems logical that the major focus on energy developments should be aimed at coal. Meanwhile, we need to trade-off between actions to meet our immediate needs and the various political regulations and social demands that are disrupting the coal industry and the industries dependent upon it. The largest single user of coal is the electric power generation industry. Over 300 million tons of coal are presently being consumed each year. In view of the 5-to 7-years lead time to bring in a base-load fossil-fuel fired generating station, our requirements for double this tonnage in 1980 are already well forecast; that is, if the coal companies are allowed to mine and the utilities are allowed to burn the coal.

Jan 2, 1974

By C. M. Rule, A. K. Anyimadu, L. Knopjes

Ongoing development work on ultra-fine grinding for various applications at the Group?s concentrators has been conducted by Anglo Platinum over the last few years. Current potential applications for mainstream grinding and concentrate grinding are the subject of a group-wide research and development programme. The first 10 000-litre 2.6 MW IsaMill was jointly developed by Anglo Platinum, Xstrata Technology and Netszch for installation at the Western Limb Tailings Re-treatment project in Rustenburg, South Africa. The unit was commissioned in late 2003/early 2004, and has operated in an intermediate concentrate regrind application successfully since. This paper describes the operational performance to date, as compared with the original duty specifications and objectives. The first mainstream M10 000 IsaMill with a 3 MW drive will be operational in November2006 at the Potgietersrus Platinum (PPL) ?Platreef? Sandsloot Concentrator in South Africa?s Limpopo Province. Key Words: Western Limb Tailings Re-treatment Plant, IsaMilling, Platreef, Platinum, Palladium, PGMs, tailings.

Jan 1, 2006

By C. A. Silva

Ladle change-over, during continuous casting of steel, initiates transient flow in the tundish which influences the inclusion content and degree of mixing between two consecutive batches of steel. The mixing behavior in the tundish during this period is determined by the casting rate and the ratios of: inflow to outflow during the refilling period; and, the low liquid level relative to the nominal level in the tundish during the transiency. A 3:10 scale water-model of a typical one strand slab caster was operated in conjunction with a tracer technique to characterize the velocity fields for several combinations of these parameters. Steady operation, a limiting case of the transiency, provided a basis for comparison. High-order moments -- skewness and kurtosis -- of the residence time density function have been utilized as signature elements associated with a particular residence-time distribution for the system. A simple mathematical model incorporating the above parameters as well as a characteristic Peclet Number was successful in simulating the features of the transient period.

Jan 1, 1993

By D. R. Willmer, E. J. Haas

As national and international health and safety management system (HSMS) standards are voluntarily accepted or regulated into practice, organizations are making an effort to modify and integrate strategic elements of a connected management system into their daily risk management practices. In high-risk industries such as mining, that effort takes on added importance. The mining industry has long recognized the importance of a more integrated approach to recognizing and responding to sitespecific risks, encouraging the adoption of a risk-based management framework. Recently, the U.S. National Mining Association led the development of an industry-specific HSMS built on the strategic frameworks of ANSI: Z10, OHSAS 18001, The American Chemistry Council’s Responsible Care, and ILO-OSH 2001. All of these standards provide strategic guidance and focus on how to incorporate a plan-do-check-act cycle into the identification, management and evaluation of worksite risks. This paper details an exploratory study into whether practices associated with executing a risk-based management framework are visible through the actions of an organization’s site-level management of health and safety risks. The results of this study show ways that site-level leaders manage day-to-day risk at their operations that can be characterized according to practices associated with a risk-based management framework. Having tangible operational examples of day-to-day risk management can serve as a starting point for evaluating field-level risk assessment efforts and their alignment to overall company efforts at effective risk mitigation through a HSMS or other processes.

Jan 1, 2016

By Gooday PE, Brech GE

Ore reserve categories used by Pancontinental Mining fall into one of three fundamental groupings: Geological In Situ Reserves Mining Reserves Production Estimates The first of these describes the total reserve within stated parameters without implication as to its mineability. The second is that part of the Geological In Situ Reserve which is considered mineable under a specific mining plan. The third is the Mining Reserve adjusted with appropriate dilution and recovery factors and thus represents the best estimate of the tonnage and grade of production. This practical three category system mirrors the standard steps traditionally taken in ore reserve estimation and readily conveys the basis of the estimates. An important, but secondary classification can be added to qualify the level of confidence in these estimates using the terms: Proved (or Measured) Probable (or Indicated) Possible (or Inferred) These terms can be applied to any of the fundamental groupings, but it is generally implicit that the level of detail required to produce meaningful Mining Reserves or Production Estimates would require the basic Geological Reserve to be at a Proved or at least Probable level of confidence. The application of these classification systems by Pancontinental is illustrated by reference to the Paddington Gold Project. The methods of calculation are described including the use of geostatistics. Reconciliations of actual production with predictions from reserves are carried out monthly and annually. To date there has been an excellent correlation with Production Estimates, based on both manual and geostatistical calculations.

Jan 1, 1987

By B. W. Gandrud

In 1927 Coghill5 showed that there is considerable liberation of the iron oxide mineral from gangue when the Alabama red iron ores are ground to a size suitable for classification and tabling, but that there is not sufficient to make possible a high extraction and a high grade of concentrate. Coghill states: High extraction and high grade of concentrate cannot be obtained without grinding to a size comparable with flotation or cyanide practice. If grade of concentrate be sacrificed the grinding need not be so severe.

Jan 1, 1934

A model of dense medium cyclones is developed based on balancing the terminal velocities of the discrete particles due to the centrifugal force against a random turbulent eddy velocity. An expression of the form P - or Q _ 1 100 e."A where P is the partition number., is a function of cyclone efficiency, particle size and density differential between the particle and medium, and is the slurry spilt, is developed and may be used for regressing plant partition data. The above model provides an understanding of peculiarities of the partition curve such as asymmetrical tails, elevation of the cutpoint and elevation of the d50 with increasingly fine feed. The effect of feed variables such as particle size, medium viscosity and changes in spigot or vortex finder diameter is shown. A means of convoluting the partition curve with various feed washabilities is discussed together with how the above may be used to evaluate plant performance for a variety of feeds.

Jan 1, 1987