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By Richard W. Markley

A centralized online data acquisition system has been developed by the U.S. Bureau of Mines Pittsburgh Mining and Safety Research Center for rapidly digitizing, storing, and processing experimental signals originating up to 1100 feet away from a central computer. This system, which services seven laboratories, is currently based on a CDC System 17 1/- computer with 56K of semiconductor memory, four disk drives (one shared online with a CDC 1700), two magnetic tape drives, high-speed A/D hardware, and other input/output peripherals. The laboratories are linked to the central computer by 15-pair cables and signal conditioners and to the computer's communications controller by modems and current loops. The A/D throughput rate is approximately 30,000 samples per second (9 bit plus sign resolution) and permits scanning about 30 instruments once every millisecond for up to 100 seconds, being limited only by disk capacity. The laboratories serviced by this facility conduct explosions research and include such facilities as an Experimental Coal Mine Explosion Facility (45 channels), a Constant Volume Combustion Laboratory (4 channels), and a Simulated Coal Mine Laboratory (15 channels). Personnel support includes one systems analyst, two applications analysts, one operator, and a hardware technician. The system has performed adequately for burst-type data acquisition, but due to a lack of long-term reliability (24 hours) of the real-time multiprogramming operating system and unpredictable power failures, slow phenomena signals are generally digitized and stored offline. This latter data is input to the computer through peripherals such as a high-speed paper tape reader, or high-speed asynchronous communications ports. Processing of data is done either in real-time (as soon as data is collected) or in batch mode. Smaller batch jobs are run on this computer, and all others are transmitted by means of the system's high-speed UT 200 terminal simulator to a CDC-6000 series computer.

Jan 1, 1977

By E. G. De Coriolis

THE development of huge production facilities and of new or improved processes for manufacturing magnesium from its raw sources has been an outstanding achievement of this war. Furthermore, at least one new method has reached a stage of pilot production that offers promise. Its potentialities seem to indicate that a reduction in cost and simplification or elimination of problems incident to the use of at least one of the present processes are quite within the realm of possibility. Although magnesium of very high purity (99.9 per cent and higher) is obtained, and the rate of recovery reasonable (60 to 70 per cent), the ferrosilicon reduction process is open to a serious objection, which at the time its use was proposed was thought to be sufficient to raise some doubts as to its success, at least on a high production basis. The temperature range at which the reaction is carried out-namely, 2100° to 2150°F.-is very close to the failure temperature of the material of which the retort is made. It is so close that for a time it was assumed it might make commercial use of the process an impossibility. However, at the time under discussion, the demand for magnesium was so great that it was felt by those who had to go ahead and produce this essential metal that the emergency warranted their taking a chance on this process. Subsequent developments have fully justified the soundness of their decision. Fortunately for the war effort, when the plants were put into operation it was discovered that although the retorts did collapse in rather short periods of time, as predicted, they could be blown back into operable shape by application of high-pressure air. This practical method of operation so relieved the situation that the problem disappeared. Nevertheless, if the process had not been successful, or the production of magnesium by the electrolytic process had not been able to keep pace with demands, our war program would have been seriously impaired. "FIRELESS COOKER" PROCESS For this reason a program was set up and assigned for the development of a new method that had been suggested to the War Production Board in 1941. It is believed justifiable in terming the method "new" for several reasons: (1) while utilizing the same (ferrosilicon) process as the Pidgeon, hence involving similar reactions, the type of retort or furnace is essentially different, (2) the method of operation, reaction temperatures, etc., differ materially, and, most important of all, (3) the problems to be overcome in making the process successful were not and could not have been anticipated by anything previously known about the Pidgeon process. As will be shown later, the briquetting process, the condenser, the furnace lining

Jan 1, 1945

By D. J. Carney, R. R. Burt, E. J. Whittenberger

Hardenability (multiplying) factors for carbon, mongonese, silicon, chromium, nickel, and molybdenum have been developed for hypereutectoid low-alloy steels in which bainite is the first subcritical transformation product. These factors permit the calculation of 95, 80, and 50 pct martensite hardenability from chemical composition when steels with spheroidized structures are quenched from 1475°, 1525°, and 1575°F. The strong contributions to hardenability of the less expensive elements, silicon and manganese, suggest their use to obtain additional hardenability in hypereutectoid low-alloy steels. DURING the past decade a number of investigators'"11 have carefully developed information which permits calculation of the hardenability of medium -carbon low-alloy steels from chemical composition and grain size. These data have been especially valuable in developing less costly low-alloy steel compositions with equivalent or Improved

Jan 1, 1957

By Linda Lee, R. E. Reed-Hill, C. R. Smeal

Four fcc metal surfaces, etched to make them responsive to polarized light, have been studied with an electron microscope. Jones'prediction that these surfaces are grooved has been verified. Optical-goniometer measurements made on commercially pure nickel indicate that the groove walls are poorly defined (100) facets. Surface mientations close to either 4001 or {ill).- show no extinctions on the polam'zid-light microscope. An explanation is offered for this orientation dependence. It has also been deduced that polarized-light extinctions on a grooved cubic-metal surface should not be used directly in crystallographic-orientation determinations. The nature of the etching solutions that produce these surfaces is considered. A cubic-metal surface may be made responsive to polarized light in two basic ways."' In one, an anodic film, believed anisotropic, is formed on the surface. A plane-polarized-light beam, at normal incidence, should be reflected from this type of film with an ellipticity that varies with grain orientation. Under crossed polarizers of a polarized-light microscope, each grain may be distinguished from its neighbors by a difference in reflected-light intensity. An alternate treatment,' more generally applicable to cubic metals and of principal concern here, involves etching of grain surfaces. The characteristic features of this surface were first deduced by Jones3 from light-microscope observations. She concluded that, in general, grain surfaces were furrowed so that light was reflected from two parallel sets of etched facets. A grooved surface produces elliptical polarization of a plane-polarized beam because the beam does not strike groove walls at normal incidence. Jones also observed that the furrows must have faces inclined to each other by approximately 90 deg, since the light returns along the incident path, and that a grooved surface should show four maxima and minima of reflected-light intensity during a 360-deg stage rotation of the polarizing microscope. Positions of maximum extinction were predicted to occur when groove axes were parallel to either polarizer or analyzer vibration directions. Because of the limited resolving power of Jones' optical microscope, her deductions were primarily indirect. Proof of the correctness of her conclu-sions, as demonstrated by the electron microscope, will be given as well as evidence concerning the crystallographic nature of the etch furrows and the types of etching solutions that produce them. EXPERIMENTAL PROCEDURE During a comprehensive study of hot plastic deformation in nickel and nickel alloys, an etch was evolved that produced a surface with an excellent polarized-light response on Nickel 200 ("A" Nickel). The etching solution and associated metal-lographic procedures are given in Table I. In evaluating this etch, a study was made of the topological features of the etched surface and their relation to the underlying crystalline structure. As part of this investigation, large crystals (2 mm average diameter) were grown in a 1-cm-sq Nickel 200 specimen. After the surface was etched, the crystallographic orientations of ten grains were determined by the standard back-reflection Laue technique of Gren-inger.4 Maximum extinction positions during a microscope stage rotation were also measured for the ten grains. Groove-wall positions on the surfaces of the ten grains were measured with a two-circle optical goniometer. The technique was essentially that of Barrett and Levenson.5 Several grain surfaces were photographed with a Philips Model 100A electron microscope. All specimens were replicated with collodion, or collodion backed with formvar and chromium shadowed at 18 to 20 deg. The basic material was Nickel 200. However, an electron-micrographic study was also made of surfaces developed by polarized-light etches on other fcc metals (90-10 a brass, Monel 400, and lead). All etching procedures are given in Tables I and 11. EXPERIMENTAL RESULTS Fig. 1 shows typical electron micrographs of three different fcc metal specimens and an optical micrograph of a fourth. All photographs show a grooved structure corresponding closely to Jones'3 predictions. Also, as noted by Jones, extinctions were always observed when groove axes were either parallel or perpendicular to the microscopes' vertical cross hair. The symmetry of the grooves, with respect to the twin boundaries in Fig. 1, implies that furrows have a crystallographic basis. The coarse-grained Nickel 200 specimen was used to study this basis. Facet Orientation. The poles of the ten Nickel 200

Jan 1, 1964

By Ralph Hultgren, Prodyot Roy

Manganese vapor pressures from 1250° to 1500°K were measured by conventional Knudsen and torsion-effusion methods in twelve Fe-Mn alloys with compositions from 9 to 80 at. pct Mn. The Knudsen re-sults agveed approximately with previous measurements found in the literature which indicated the solutions were nearly ideal. However, except for the higher manganese compositions, the initial torsion readings indicated much (up to 50 pct) higher vapor presszcres than the Knudsen method. These high readings decreased steadily with time. The results are interpreted as due to depletion of surface concentration of manganese during evaporation. Thus the initial torsion readings are the most nearly correct and Knudsen methods on alloys are to be regarded with suspicion unless it can be demonstrated that diffusion rates are rapid enough to replenish surface concentrations depleted by evaporation. For the lowest manganese contents and highest temperatures, depletion causes initial torsion readings to be too low. FEW thermodynamic data are available for alloys of the high-melting transition metals due primarily to experimental difficulties at the high temperatures involved. Measurement of vapor pressure is one of the most promising techniques to be applied to this problem. From the vapor pressure of a component of an alloy phase, its activity or its partial molar Gibbs energy can be directly calculated. From measurements over a sufficient range of temperatures and compositions the partial and integral Gibbs energies, enthalpies, and entropies may be determined through Gibbs-Duhem integration. For solid phases of variable composition, which commonly are found in alloys, measured vapor pressures are low because of depletion of the surface concentration of the more volatile component as it is selectively vaporized. Diffusion from the interior tends to restore the depleted concentration. The seriousness of the effect depends on the relative rates of diffusion and vaporization. Although depletion has been recognized as a factor,' direct measurements of its rate are lacking and quantitative estimates of its effect on measurements are uncertain. In the present work the vapor pressures above a series of Fe-Mn alloys have been measured by the torsion-effusion method. This method permits a measurement of the vapor pressure of manganese as soon as the sample comes to temperature and continuously throughout the run. The rate of decline of the apparent vapor pressure measures the rate of depletion and the torsion reading at zero time should be correct. At high manganese concentrations (70 and 80 at. pct Mn), the torsion reading remained nearly constant; surface depletion was negligible. There was a slow drop in measured pressure due to bulk loss of manganese from the sample. However, for lower manganese contents, especially at high temperatures, the depletion effect was considerable and the apparent vapor pressure decreased steadily with time. For these alloys the Knudsen method should give pressures which are too low. The measurement of pressure in the Knudsen method cannot be made until enough manganese has been vaporized to be weighable. The Knudsen result is therefore an integrated average between the initial and final vapor pressures. To verify this, conventional Knudsen measurements were also made with results in approximate agreement with previously published Knudsen measurements for these alloys. As expected, for the lower manganese contents the initial torsion readings of pressure were as much as 50 pct higher than the Knudsen. THE APPARATUS The apparatus, shown in Fig. 1, is capable of operating to temperatures up to 2000°K. A vacuum of 5 x 10"6 mm Hg can be maintained. Temperatures were measured to +3° by a W-Re thermocouple placed in the dummy cell, N. The torsion cell consisted of two alumina crucibles with holes in their covers. They were placed in the molybdenum holder shown suspended from the torsion wire. Rectangular torsion wires (1 by 4 mm) were found to have superior sensitivity and less residual distortion than circular (2-mm-diameter) wires. The precision of angular measurement was found to be *0.025 deg; the variation is no doubt due to temperature fluctuation and vibration. For the Knudsen experiments the alumina cell was set on the support, N. SAMPLE PREPARATION 800-g samples were prepared by melting together electrolytic iron and electrolytic manganese and pouring the melt into a water-cooled copper mold. Melting and pouring were done under a helium at-

Jan 1, 1965

By N. F. Neumann, A. W. Schlechten

Metal chlorides were formed by reacting metal oxides and calcium chloride; the effect of additions to the reaction mixture was studied. It was found that by use of proper additions, metal chlorides could be prepared from mixtures that were not reactive under ordinary conditions. ManY recent metallurgical developments involve the use of chlorine or chlorides as primary reagents; good examples are found in the production of ductile zirconium and titanium by reduction of their chlorides with magnesium. Various methods of preparing metal chlorides are used and many others have been proposed. Some chlorides are formed by the direct combination of a metal or alloy with chlorine. Other processes react chlorine and metallic oxides; carbon or other reducing agents are usually employed to reduce the metal oxides and so promote chlorination. Metallic chlorides have also been produced by the exchange of chlorine between metal oxides and a chloride, such as sodium chloride. This type of reaction was the basis for the old process of chloride roasting in which metal ores were roasted in the presence of salt. Soluble chlorides thus formed

Jan 1, 1959

By C. E. Mills

The Verde mining district is in Yavapai County, in north-central Arizona. Jerome, the principal town, has a population of 6000 and the two important mines of the district—the United Verde and the United Verde Extension—lie almost within its limits. Perched high on the southwest side of the Verde valley, at elevations of 4800 and 5500 ft. (1463 and 1676 m.) respectively, both mines have long tunnels from their lower levels through which the ore is hauled to the smelters. Clarkdale, the smelter town for the United Verde mines, lies in the Verde valley 4.1 miles (6.5 km.) distant in an air line from Jerome and at an elevation of 3560 ft. The two towns are connected by the standard-gage railroad of the Verde Tunnel and Smelter R. R., a subsidiary of the United Verde Copper Co. This road is 11 miles long and has a compensated grade of 4 per cent. At Clarkdale it connects with the Verde valley branch of the Santa Fe railroad. Clemenceau, the smelter town for the United Verde Extension mine, lies 3.5 miles (5.8 km.) in a southeasterly direction from Clarkdale, at an elevation of 3420 ft. It is connected to the Verde Valley branch of the Santa Fe railroad at Clarkdale by the Arizona Extension R. R., a subsidiary of the United Verde Extension Mining Co. The portal of the haulage tunnel, at an elevation of 3757.5 ft., is also connected with the smelter town by 4 miles of standard-gage track belonging to the same company. In the vicinity of Jerome, the great southern escarpment of the Arizona plateau forms the northeast side of the Verde valley. The general level of this escarpment, or "rim" as it is called, is about 4000 ft. above the Verde River. A corresponding elevation is reached only by the highest peaks of the Black Hills, which bound the valley to the southwest. Two lava-capped mesas, known as "Mingus" and "Woodchute mountains," form the culmination of the Black Hills. That part of the Old Black Hills mining district which lies between their crests and the Verde River is now known as the Jerome, or Verde, mining district. If the smelter towns are not included, a strip about 7 miles long by 3 miles (11 by 5 km.) wide, embraces practically all of the properties belonging to the Jerome district. T-bis strip lies parallel to and along the side of the Verde valley from First View, 2 miles northwest from Jerome, to the

Jan 1, 1925

INCREASING realization that pouring and ingot-mold practices involve many factors of fundamental importance to ingot quality and general steel-mill operations has caused these phases of steelmaking to become major concerns of operators and metallurgists engaged in control of quality and costs. Methods of pouring steel from the ladle into the ingot molds have some direct effects on ingot quality. The mold itself governs solidification and dimensions of the ingot and in so doing exerts some very tangible influences not only on ingot quality but also on product yields and general steel-mill processing. In addition, practices are employed' in the handling of molds during daily open-hearth operations that are important to quality and production costs. Therefore, pouring and mold practices must be considered highly specialized and important steps in steel-mill operations. MOLD DESIGN Mold design is difficult to discuss in a precise manner because it varies greatly throughout the industry, both in theoretical concepts and practical application, and few well developed data are available. Most ingot molds are designed to meet conditions peculiar to a given plant wherein quality standards are dictated by end-use requirements, which may differ considerably, even for the same grade of steel. The mold designer must also consider the equipment available to process ingots and the product obtained from them. Such equipment, used for stripping, heating, blooming and finishing operations, is seldom, if ever, exactly the same in any two steel plants. Thus, pronounced contrasts in mold designs can be expected to continue, even among plants making strictly comparable types of product, particularly because some producers are just beginning to realize the benefits possible from specialized designs. Certain fundamentals are used in mold design but even these

Jan 1, 1951

By Daniel R. Stewart, Ralph R. Sacrison

The function of the geological engineer is to assist in mine planning and operations by collecting, interpreting, and applying geologic data to the solution of engineering problems. The geologist supports this effort by collecting additional geologic information specifically useful to the engineer. This use of geologic information reinforces the value of mine geology to the mining process beyond the traditional role of orebody definition. Work discussed includes: evaluation of caving strategies at the Climax and Henderson mines, support definition and slope stability at the Climax mine, and some uses of geology in cavability estimation for the Mount Emmons project.

Jan 1, 1984

By K. M. Rolls, R. M. Rose, H. B. Shukovsky

Studies of the phase structure, critical current density, and resistive critical magnetic field of a 45 pct Nb-55 pct Zr superconducting alloy after final-size heat treatments are reported in this paper. A combination of optical metallography, X-ray diffraction, and electrical-resistivity measurements were used to determine the phase structure. Superconductivity measurements, made with heat-treated wires, are correlated with microstructure. Although no quantitative relationship between microstructure and critical current density is found, it is shown that SINCE Kunzler1 as well as Berlincourt, Hake, and Leslie2 first described the high-field, high-current-density superconductivity of Nb-Zr alloys, it has be- the critical current density is highest when the microstructure is finely divided by fibering, coring, precipitation, or fine-scale phase dispersions. The resistive critical field is very sensitive to the compositions of the phases present. Since the alloy investigated here is near the maximum resistive critical field for the Nb-Zr system, any phase decomposition results in a lower H,. Elimination of the effects of cold work lowers H, also. A possible interpretation of the latter in terms of internal surface superconductivity is suggested. come apparent that the resistive critical field and the current-carrying capacity of such alloys are, in large measure, dependent on composition and processing. The resistive critical magnetic field (Hr) for low current densities has been found to increase progressively with zirconium content until a flat maximum is reached between 50 and 65 pet Zr.3 For any single composition, a characteristic maximum value of H, is attained by heavily cold-drawn wire.4 critical current density (J,) depends not only upon cold work but also, apparently, upon microstructure. Heat treatments of cold-worked wires generally

Jan 1, 1965

By D. W. Fuerstenau, G. D. Gumtz

Use of the discretized batch-grinding model for the simulation of locked-cycle grinding tests from batch-grinding data is illustrated. The simulated results were compared with actual locked-cycle experimental data for the dry grinding of dolomite. To illustrate the utility of this simulation method, a number of relationships between operating and performance parameters were generated, including relations between batch grinding and the Bond test, the production rate and the circulating load, and the production rate and the product size. A large amount of testing is done each year in the mineral industry for use with grinding unit cperations, and much of the experimental test data is obtained by the tedious locked-cycle testing procedure. In addition to being experimentally complex and requiring large amounts of sample, the very nature of the locked-cycle experiment yields results that cannot readily be interpreted. The attempts that have been made to model comminution systems during the last few years may provide a better and simpler way to obtain and analyze grinding test data; these models involve elements of both fitting to "model equations" and deterministic representations.1-1 The traditional engineering design techniques for comminution systems have relied mainly upon large amounts of industrial operating data that have been correlated with locked-cycle grinding data.',' Bond's empirical mill-design procedure involving locked cycle testing remains the most generally available method to this day. The purpose of the present paper is to show how much more useful data can be obtained from a simple batch-grinding experiment that provides information which subsequently can be utilized with population balance models of the grinding process to simulate locked-cycle behavior. These simulation results can, of course, be used in Bond's general design scheme. However, the combination of batch-grinding tests and the population balance model allows many more conditions to be considered than do single laboratory tests under specific locked-cycle conditions. The use of these simulation techniques for prediction of locked-cycle behavior represents one of the first practical applications for the simulation method in comminution.

Jan 1, 1971

By Stanley D. Michaelson, Norman Weisis

The purpose of beneficiation is to increase the economic value of an ore by elimination of waste rock or by separation of minerals that require separate reduction, without destroying the physical and chemical identity of the minerals. Flotation has replaced older methods of beneficiation to a very great ex- tent, nearly entirely in the case of the copper, lead, and zinc minerals and less completely in the case of such other minerals as iron, coal, and titanium. Flotation is also used to recover barite, fluorspar, feldspar, cement rock, spodumene, vermiculite, silica, beryl, and potash in the nonmetallic field, and cobalt, vanadium, germanium, antimony, mercury, molybdenum, manganese, nickel, gold and silver, cadmium, and bismuth for metals. The rapid growth of flotation to pre-eminence cannot be attributed to its low cost, because gravity, magnetic, and electrical methods may in some cases cost only half as much. But for ores containing finely disseminated minerals, these other methods are successful only in exceptional cases, for example the magnetic taconites or titanium-bearing sands. For low grade ores with coarse texture or spotty mineralization the advantages of low-cost gravity methods and highly efficient flotation are often combined, as in the beneficiation of coal and some ores of lead and zinc, phosphate, tungsten, and manganese. When an ore is responsive to either flotation or non-flotation concentration, or to combinations of the two, the choice depends upon cost of the process only when dealing with ores of low value; in other cases it is dictated by either the process efficiency or the product specification. Generally speaking, flotatio.1 is so efficient as compared with other methods of concentration that process cost is rarely an important factor in its selection. It is said, "The metal in the mill tailing has already been mined." Once the mining cost has been paid it doesn't increase total costs very much to do a thorough job of milling. With the exception of the few types of ores that are not amenable to flotation, the chief reason for preferring electrical and gravity methods to flotation may lie in the specification of the product. Flotation demands fine grinding, and specifications may not permit this with many nonmetallic ores or coal. Another reason is the size of investment-where capital is hard to obtain or the life of the property is short, the justification for a flotation plant may not exist, and one must be content to skim off the cream. y not exist, and one must be content to skim off the cream. Gravity processes often cost less than flotation because a large part of the waste rockcan be rejected without costly grinding, no chemicals are required,

Jan 1, 1962

By W. H. Schacht

IN THE Lake Superior District, the air indoors must be heated continuously during eight months of the year and occasionally during the remaining months. Incident with mining in this district, therefore, there is need for heating many of the buildings connected with these operations. In addition to the mine buildings, that is, shops, engine, houses, offices, change houses, etc., such public buildings as schools, library, and theater, when close to the mines, are often supplied from the mine heating mains. At the Copper Range Company's mines, Champion, Trimountain and Baltic, the heating surface thus supplied from the mine mains is over 50,000 sq. ft. (4645 sq. m.) which requires a steam consumption, at times, of 18,000 lb. (8165 kg.) per hour, or the equivalent of a rate of over 50 tons of coal per day (were live steam used). This figure is based on a consumption of 1/3 lb. per square foot of heating surface during the coldest weather, and provided the system is not wasting steam by blowing it to the atmosphere or into the return line on account of leaky traps, which so often is the case. Under the latter conditions, steam consumptions of three to four times the above rate are not uncommon. This shows that the cost of heating is of enough importance to be given serious consideration, especially at this time of rising prices of fuel. The power and heating value of exhaust steam are appreciated by most engineers, and its application for such purposes is general. At our stamp mills, the exhaust from the stamps is used to operate low-pressure turbines, thus reducing the former water rate per horsepower developed by more than 50 per cent.

Jan 8, 1920

By Augustus Locke

The paper has two parts: the field argument and the microscopic argument. The field argument indicates that either the deep chalcocite has replacea sulfide of extraordinarily easy replaceability or it is hypogene. The microscopic argumentindicates that this sulfide, if it existed, must have been hypogene bornite; that this bornite must so excel known bornite in replaceability as to constitute a new variety; that the existence of this new variety is wholly unsupported by evidence; and that the deep Butte chalcocite is therefore hypogene. IN 1900, when the public first heard of "secondary enrichment" the Butte chalcocite seemed clearly supergene. Mining, through successive regions of leached capping, bonanza sulfide, and sulfide less rich, had paused at lean bottom levels which, though chalcocite-bearing, suggested the waning of copper. The deepest chalcocite, at 1500 ft., was yet too shallow to disturb the supergene hypothesis. But, with deeper mining, lean levels yielded to fat ones. Here and there they showed, within the same vein, an inverted distribution, chalcopyrite above and chalcocite below. To the miners' astonishment, they carried chalcocite, unaffected by cross faults, on an independent course to the depth of 2500 ft. The pattern of ore distribution, hitherto revealed only in fragments, was now appearing in perspective, and, in the depth of the chalcocite, was beginning to make Butte differ from all districts where the chalcocite is indubitably supergene. The idea of hypogene origin at length came into favor; by 1913, when Sales1 advocated this origin, the argument had become a powerful one. This argument rested on field evidence; but, already, there was beginning to emerge microscopic evidence not included in this arugment. Especially pertinent was the proof that (1) The deep chalcocite lies in-mixed with bornite, often microscopic; (2) the deep chalcocite often replaces bornite; and (3) replacement of bornite by chalcocite is accom-

Jan 3, 1924

By T. D. Mueller, H. Dykstra

This paper describes a method for obtaining compositions of gas and oil phases in equilibrium with each other at a given reservoir temperature and pressure as lean or enriched gas is injected into a reservoir oil not in equilibrium with the gas. The method is based on calculation of equilibrium constants, K, from the equation log Kp = A + B F, where p is pressure and F is component characterization factor. A and B are constants that vary with a composition parameter. The paper explains how A and B could be determined with a minimum amount of data. The method consists of calculating equilibrium constants as a function of liquid composition and using the K's to calculate changes in compositiort of injection gas as it successively contacts original resetvoir oil at the gas-oil front and the change in composition of reservoir oil as it is successively contacted by the injection gas in the vicinity of an injection well. An iterative process is required. Two examples of the method are given which show how oil and gas compositions and properties are calculated with the aid of a computer. INTRODUCTION The calculation of recovery from lean-gas or enriched-gas injection into a saturated or under-saturated reservoir oil requires a knowledge of how phase properties change in a reservoir between injection well and producing well. To determine the phase compositions or properties experimentally would be difficult and time consuming, especially if one wanted to look at the effect of various injection gas compositions. For some fields an engineer would want to make preliminary calculations on the economics of gas injection before he makes the decision to spend a corrsiderable sum of money for laboratory work to obtain the necessary fluid properties. A method for calculatine compositions and properties based on a minimum of laboratory data is described. The minimum amount of data required is injection gas and reservoir oil composition and injection gas solubility as a function of pressure for an undersaturated oil, or the compositions of mixtures of reservoir fluid with two or more enriched gases, which mixtures have a bubble-point pressure that is the same as the expected average displacement pressure. On the other hand, if the economics appear to be attractive, more laboratory data can be obtained in the form of equilibrium constants for three or more mixtures of the reservoir fluid and injection gases. The method is based on the calculation of K's from the equation, log Kp = A + B F, where K is equilibrium constant, p is pressure and F is component characterization factor. This method of plotting K data by means of the above equation is described by Hoffman, Crump and Hocott.1 A and B are constants that vary with a composition parameter. It is shown how experimental data are used to determine how A and B vary with composition. BASIS OF METHOD EQUILIBRIUM CONSTANTS Equilibrium constant (K) data are required for this method. The K of each component is obtained from an equation that gives the product of K and pressure as a function of component characterization factor. The characterization factor F = b(l/Tb — l/T), where b is a constant characteristic of a given component, Tb is the boiling point in OR at atmospheric pressure of the given component, and T is the temperature of the system in OR. This method of plotting K data is described by Hoffman, Crump and Hocott.l The straight-line equation of the log Kp - F plot is log hp = log Kop +BFi, where Kop is at F =0, i designates the component, and B is the slope of the line. The factor F can be

Jan 1, 1966

By J. Leja, J. H. Schulman

FROTH flotation is usually effected by the addition of a collector agent and a frothing agent to an aqueous suspension of suitably comminuted mineral ores. The action of collectors is to adsorb onto the surfaces of minerals to be separated, sensitizing them to bubble adherence. The action of frothers has, in the past, been accepted as that of froth formation only, brought about by a lowering of the air/water interfacial tension. Substances capable of producing froth are classed1a,b according to their relative capacities for production of froth-volume and froth stability in the simple frother-water system. The purpose of this paper is to show that the surface active agents acting as frothers become effective only when there is a suitable degree of molecular interaction taking place between collector molecules and frother molecules at the air/water and solid/ water interfaces. Further, the discussion will demonstrate that the actual mechanism of adherence of an air bubble to a suitably collector-coated particle is due to the molecular interaction collector-frother. This leads to the formation of a continuous interfacial film of associated molecules, anchored to the mineral by polar groups of the collector, and enveloping the whole bubble. The tenacity of adhesion mineral-to-bubble results from the strength and the visco-elasticity of this mixed film.

Jan 2, 1954

By E. Buehler, H. J. Levinstein

The temperature ranges in which the three inter-metallic phases in the Nb-Sn system form have been determined and the composition and structure of two of the three phases has been established. The kinetics of the formation of Nb3Sn in cored wire samples has been studied in the temperature range of 800° to 1050°C. From 800°to 950°C the rate of formation increases by four orders of magnitude. The rate-controlling step for the formation process in this temperature range appears to be the diffilsion of tin through NbSn. At higher temperatu~es a change occurs in the mechanism of the formation process such that up to a temperature of 1050°C the rate of formation of Nb3Sn does not increase above the rate observed at 950°C. For temperatures helow 950°C the current-carrying capacity of the wire increases with increased percent reaction reaching a maximum value when the formation process is 90 to 95 pct complete. The maximum current-carrying capacity obtainable in this temperature range is independent of the temperature. Above 950°C tlze current-carrying capacity obtainable in the wire decreases with increasing temperature of formation. A model is proposed which accounts for the ohserved behavior. RECENTLY, Buehler et a1.l reported the results of an investigation of the process variables which influence the superconducting properties of Nb3Sn-cored wire. These results indicated that at least four variables affect the properties of the manufactured wire. These include composition, particle size of the starting powder mix, temperature of heat treatment, and time of heat treatment. In order to understand completely the role of these variables, it is necessary to have an accurate knowledge of the phase equilibria in the Nb-Sn system. At the present time, phase-equilibrium diagrams for the Nb-Sn system have been published by a number of investigators.2-5 The diagrams differ as to the number of phases present, the composition of the phases, and the temperature range of stability of the phases. The present investigation was undertaken in order to resolve these differences. Since the investigation of Buehler et al. demon- strated that the length of time at the temperature of heat treatment affected the superconducting properties of Nb3Sn, it is apparent that it is necessary to understand the kinetics of the formation process as well as the equilibrium conditions before a complete understanding of the system is possible. As a result, the kinetics of formation of the various phases in the system were also studied in this investigation. EXPEFUMENTAL PROCEDURE Diffusion couples and sintered powdered compacts were employed in the phase-diagram investigation. The diffusion couples were made by filling 1/8-in.-ID monel-sheathed niobium tubes with tin. The monel sheath was employed to facilitate drawing.' The tubes were then drawn to a tin-core diameter of 32 mils. Samples approximately 3 in. long were then cut from the drawn composite. The tin was drilled out of the ends to a depth of 1/4 in. and niobium-wire plugs were inserted into the ends and peened over. The monel was removed by etching in concentrated nitric acid, after which the samples were sealed in evacuated quartz bulbs and heat-treated in a resistance-wound tube furnace. The samples were quenched into ice water upon removal from the furnace. The diffusion couple samples were examined metallographically employing a chemical etching solution consisting of 10 ml of saturated chromic acid per g of NaF. In addition, two anodizing solutions were used for phase-identification purposes. The first was the picklesimer7 solution; the second consisted of equal parts by volume of 30 pct H2O2 and concentrated NH4OH to which 1 g of NaF was added per 25 ml of solution. The anodizing conditions for the second solution were 2 v and 100 ma with a tin cathode. The powdered compacts were made by pressing previously mixed powders of 99.9 pct pure Sn and 99.6 pct pure Nb supplied by the United Mineral Co. into cylinders 3/8 in. in diameter by 1/2 in. long. The cylinders were then sealed in quartz tubes and heat-treated in the same manner as the diffusion couples. The samples were examined metallographically and by X-ray diffraction techniques. Since it was desirable to be able to correlate the kinetic data with current-carrying capacity, the type of specimen chosen for this part of the investigation had to be a compromise between the optimum system for studying kinetics and one which was suitable for making current-carrying capacity

Jan 1, 1964

By C. W. Thompson

The two-way belt conveyor for coal mine service simultaneously carries coal from faces and transports men and supplies into the mine, largely eliminating the necessity for rubber-tired supply and man haulage equipment and the necessity of maintaining additional headings. SINCE 1920 use of belt conveyor transportation has increased steadily, and capacity in tons per hour per unit has increased at about the same ratio. Belt conveyor systems for simultaneous two-way material transportation have been widely discussed, but heretofore have proved impractical for specific operations. Studies of a proposed means of disposing of wash-ery waste on the return trip of a main haulage conveyor, as yet uninstalled, led to the application of two-way belt haulage to Weirton's underground supply and mantrip problems. Except for a single-tracked main haulage entry, Weirton mine is essentially a full-belt haulage operation with attendant problems of supply and man-trip haulage that could not be handled with conventional belt conveyors during the regular work shift. It was necessary, therefore, to maintain rubber-tired haulage equipment and haulageways serving multiple-shift continuous operations. The conventional underground belt conveyor is primarily intended to transport coal from working faces to surface. Belts are usually reversed to haul men to face areas at the start of the working shift or to transport supplies. The two-way belt conveyor for coal mine service is not yet offered for sale as a unit by any manufacturer and must be built on order. This conveyor, with return run traveling parallel but opposite in direction to the outgoing or coal haulage run, permits not only haulage of coal from faces, but simultaneously permits transportation of men and supplies into the mine at any time, see Figs. 1 and 2. This eliminates, to a great extent, the necessity for rubber-tired supply and man haulage equipment and the maintenance of additional headings. Unlike conventional installations the return belt is in the open for inspection and maintenance. It is less subject to edge wear, since it runs on regular troughing idlers, see Fig. 3. The only points where the edge of the belt can rub are at the drive unit and the tail units where improved design should eventually eliminate edge wear entirely. Individual conveyor sections are lighter, since all that is needed is a tubular stringer on each side to carry troughing idlers only, no cover plates being necessary. The return run is carried on an assembly identical to that carrying the coal haulage run. These assemblies are definitely easier to handle and are cheaper than installations for the same length of conventional belt conveyor. The four pipes required for the complete conveyor frame may serve only as supports, or, with proper couplings, may be used for mine water discharge line, pressure line for face spraying, telephone cable conduit, or any other purpose requiring a pipe line, see Fig. 4. Additional expense, if any, for the increased number of pulleys needed to turn the belt over for the return service is more than offset by reduced expense for rubber-tired supply and mantrip haulage. The two-way belt haulage system is confined to a single heading on intake air, isolated from all other headings by stoppings on each side, and open for air circulation only at the main haulage way and at the faces. One additional heading, also on intake air, is maintained as an emergency rubber-tired haulage way, all other headings being center-posted and used as airways only until retreat work begins. This method, of course, can and should be used with any belt conveyor, since it provides two independent intake airways for escape in case of fire on the belt or elsewhere. Belt heading is heavily timbered even under good top conditions and space between the two runs permits center posting for the full length

Jan 1, 1954

By Ottar Dragge, C. Danielsson, Bo Kalling

THE desulphurizing of pig iron has been accomplished with a number of different additions. The oldest and still most commonly used agent is soda, the extensive use of which commenced about 1925, when it was used principally for cupola furnace iron. More recent experience' seems to show that better results can be obtained with sodium hydroxide. The well-known desulphurizing properties of lime have also been exploited in different technical processes. Another material with even more powerful effect is calcium carbide.' The desulphurizing ability of manganese, when added to the ladle in sufficient quantity, should also be mentioned in this connection. During recent years increasing attention has been paid to the desulphurizing properties of metallic magnesium." An addition of a suitable alloy of magnesium is now in use purely for the purpose of sulphur elimination. Of the desulphurizing agents mentioned, lime is by far the cheapest, provided that the reaction can be brought about rapidly and completely. Therefore, a method that makes full use of the desulphurizing ability of lime may be able to compete with other processes. A method developed at the Dom-narfvet Iron and Steel Works (Sweden) will be described, which enables pig iron to be rapidly desulphurized to very low sulphur contents by using a burnt lime powder. as the desulphurizing agent. Lime in Older Processes In cases where lime has been used for the desul-phurization of pig iron, it has generally not been used alone, but mixed with other substances such as fluorspar, to obtain the formation of a molten slag during the process. This method has been tried by Tigerschiold,' who treated the iron with a lime-fluorspar mixture, the stirring of the iron being brought about inductively with low frequency alternating current. Very good results were obtained. A process of this type has also been suggested by R. P. Heuer, U. S. A. The principles of this method, which has been tested in Great Britain by Newell. Lanener. and Parsons." re that a mixture of lime and fluoispar is added to the hot metal in the ladle, while a powerful stream of nitrogen gas is blown into the bath to produce the required intermixing. The results of the tests were unsatisfactory, however. A similar process has been developed at The Steel Co. of Canada, according to a statement by H. M. Griffith.' Here the tests were carried out in a carbon-lined ladle provided with carbon tuyeres in the side wall for blowing nitrogen into the bath. The addition consisted of about 20 lb of a mixture of burnt lime and fluorspar per ton of pig iron. Good results appear to have been achieved. The sulphur content of the pig iron is stated to have been reduced from 0.025 to 0.050 pct down to 0.006 pct. Various methods of desulphurizing pig iron have been tried using lime powder without fluxing material for fusing. Eichholz and Behrendt7 have experimented with blowing a powdered limeicoke mixture with air into the ladle. Their results were, however, not conclusive and the experiments do not appear to have been continued. Similar experiments have been carried out at Domnarfvet, using nitrogen instead of air in order to avoid oxidation. But these attempts were not particularly successful. It appears to be difficult to achieve the required agitation by this means. The strong cooling effect of the gas on the iron is also a serious drawback. A method in many respects similar to that tried at Domnarfvet was tried by Eulenberg and Krus at the end of the 1930's. Here again desulphurization was carried out with lime alone, brought into contact with the molten iron in a rotary furnace. The temperature was kept at the required level, 1400" to 1500°C, by the introduction of a pulverized coal burner in one end of the furnace. The speed of rotating was not given. A paper by Bading and Krus states that, in one of the first experiments, the sulphur content in 56 tons of pig iron was brought down from 0.186 to 0.035 pct in 117 min, but that a considerable shortening of the time would be possible. According to later reports by Eichholz and Behrendt,' it should be possible by this process to achieve a desulphurization speed of 0.35 pct S per hr for a consumption of 6 to 10 pct limestone and 2 to 3 pct coke, as fuel exclusively. The final sulphur content is, however, not stated. Domnarfvet Method After a number of different procedures had been investigated, the tests at Domnarfvet were directed to desulphurization with lime in a rotary furnace. Before going into the practical details of the method, the theoretical aspects will be discussed briefly. If the pig iron does not contain alloying elements other than carbon, the reaction can be expressed most simply by the usual equation: FeS + CaO + C = Fe + CaS + CO [I] 4H,. ~ 34,000 cal That this reaction can be carried through to a very complete desulphurization of pig iron has been shown by OelsenD in a discussion in connection with the Eulenberg and Krus' method. He mentions two laboratory tests, in one of which the sulphur content in the pig iron at 1400°C was reduced from 0.540 to 0.006 pct after treating with 3.35 pct lime. The pig iron had a low manganese content, but other analysis is th. given. Mention also should be made of the recently published investigations by Fischer and Cohnen'" dealing with the influence of the carbon content of the iron on desulphurization with lime, although in this case fluorspar was added also. The tests show that efficient desulphurization is possible with lime in the steel bath, provided that the carbon content is sufficiently high. The temperature employed in these tests was considerably higher (1620") than that normal for treatment of pig iron. The author concludes that the product S% X C% - 0.011 at the temperature in question.

Jan 1, 1952

By E. L. Mann

Asbestos is the generic name given to a group of fibrous mineral silicates found in nature. They are all incombustible and can be separated by mechanical means into fibers of various lengths and cross sections, but each differs in chemical composition from the others. The commercial grades of asbestos consist of a spectrum of lengths and sizes and are not definitive as are most organic fibers. It is generally recognized that there are two main groups of asbestos. The first only contains the fibrous serpentine called chrysotile and comprises about 94% of the world production of asbestos. The second group contains five minerals in the amphibole series-crocidolite, amosite, anthophyllite, tremolite, and actinolite. The latter two have no commercial importance. Properties Physical The structures of asbestos fibers have been studied intensively over a number of years. X-ray diffraction patterns have been used as a means of identification and classification. Low angle X-ray scattering techniques have shown that chrysotile fibers are "hexagonally close packed" and parallel to each other, having cross-sectional diameters varying from 18Å to 300 Å units, while the amphibole fibers are many times larger in cross section, have considerably smaller surface areas, and the fibers are less symmetrical than those of chrysotile. Electron micrographs of the more common types of asbestos are shown in Figs. 1-4. Fig. 1 illustrates the softness and flexibility of chrysotile which make it suitable for textile-type products. For a number of years there was considerable controversy over the exact nature of chrysotile fiber, but the photographic evidence in Figs. 5-7 clearly show that it is tubular in structure. The curvature is the result of the mismatch in the dimensions of the silica [Si2O5] and brucite [Mg(OH)2] layers which are on the inside and outside, respectively, of a double sheet. This curvature had been predicted by Pauling (1930) years ago based on the molecular dimensions of the two component structures. In contrast to this, the structure of the amphiboles consists of two ribbon chains based on Si4O11 units separated by a band of seven cations with two hydroxyl groups attached to

Jan 1, 1983