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By R. J. Watson

In an earlier paper, Ehrenburg and Watson1 published the develop ment for a potential function by which it is possible to obtain the electric potential at points on the surface of the ground when a current I passes between two electrodes and the subsoil is composed of parallel, homogeneous layers. In view of the continued interest in the resistivity method of electrical prospecting, the author has considered it desirable to publish the results of a number of theoretical studies making use of this potential function, and also the results of a considerable number of tests with models designed to show the soundness of the mathematical theory. It is hoped that these results will prove how erroneous the various empirical rules for depth determination may be. It has always seemed puzzling to the author that one can find, in papers published comparatively recently, statements upholding empirical rules for depth determination, and attributing most of the irregularities of resistivity curves to vertical discontinuities in resistivity in the subsoil. It would indeed be fortunate for the geophysical investigator if such a simple rule held. However, numerous investigators have proved both theoretically and by the success of their field work that such a rule does not hold, even by a "rough approximation" in many cases. On the other hand, as is shown in the development to follow, if the underground conditions are favorable it is possible for such empirical rules to give a satisfactory depth determination. Authors should be more careful about making such sweeping statements about the accuracy of these empirical rules because the relative simplicity of the field work places the method in the hands of any interested experimenter, and he is likely to become completely disgusted with the method after he has made several obviously wrong interpretations by empirical rules. There are simple and rapid methods for finding out whether the ground beneath the electrodes is sufficiently similar to the conditions

Jan 1, 1934

By A. B. Cook

Gas cycling is generally considered a much less efficient oil recovery mechanism than water flooding. HOWever, recoveries from some fields have been exceptionally high as a result of gas cycling. Recovery from the Pick-ton field, for example, was calculated to be 73.5 perceni of the stock-tank oil originally in place. In evaluating pressure maintenance projects, determining how much of the recovery is due to displacement by gas and determining how much is due to vaporization of the imrnohile oil in the flow path of the cycled gas is very difficrilt. Even though most of the oil is recovered by displacetr~ent, the success of a project may depend on the amount of oil vaporized. A limited number of experiments have heen performed with a rotating model oil reservoir that simulates gas cycling operations and allows a separation of the oil from, tile free gas flowing into the laboratory wellbore at reservoir conditions, thus revealing which is displaced oil and which is vaporized oil. It Iras been determined that the amount of varporizatio'n is .significant if proper conditions exist These experiments show that oil vaporization depends on pressure, temperature, volatility of the oil and amount of gas cycled. Increases in each of these conditions increase the volume of oil vaporized. Data from six experiments affecting vaporization are presented to illustrate reservoir condition that range from favorable to unfavorable. 111 these eaperitnenis recovery by vaporization ranged from 73.6 to 15.3 percent of /he immobile oil (oil not produced by gas displacerrlt). INTRODUCTION Between 1930 and 1950, gas cycling was a popular. oil recovery practice. especially for the deeper reservoirs. Later, with many case history-type studies published for both gas cycling and waterflooding, it was generally believed that waterflooding was far superior to gas cycling, even when gas cycling was conducted as a primary production procedure by complete pressure maintenance. A good example illustrating the advantage of water-flooding over gas cycling is given in a paper by Matthews' on the South Burbank unit where gas injection was followed by waterflooding. The author concluded in part that "Early application of water injection, without the intervening period of gas injection, would have recovered as much total oil as ultimately will be recovered by waterflooding following the gas injection, and total operating life would have been shortened". This appears to be a logical conclusion. However, it should not be applied to all fields. Pressure maintenance with gas in the Pickton field, as reported by McGraw and Lohec;' will result in a much larger percentage of oil recovery than was obtained in the South Burbank unit. The great success in the Pickton field resulted partly from vaporization of the immobile oil in the flow path of the cycled gas. The amount of vaporization is related to the following conditions: volatility of the oil as reflected by the APT gravity of the stock-tank oil; reservoir temperature; reservoir pressure during gas cycling; and the amount of gas cycled. Therefore, the U. S. Bureau of Mines is investigating these effects on vaporization in a research project using a model oil reservoir. Three different stock-tank oils having 22, 35 and 45" API gravities are being used as base stock to synthesize reservoir oils. Experiments are being performcd to determine vaporization at 100, 175 and 250F and at 1,100, 2,600 and 4,100 psia. This is a progress report showing the results from six experiments. Other Bureau of Mines reports"- concerning vaporization are listed. LABORATORY EQUIPMENT AND PROCEDURES The equipment ' consists of an internally chromium-plated steel tube packed with finely sifted Wilcox sand. The tube is approximately 44 in. long and has an ID of 13/4 in. The sand section contains approximately 570 ml of voids, has a porosity of 32 percent, and a permeability to air of 4.3 darcies. A unique feature of the laboratory reservoir (Fig. 1) permits the tube part to rotate at 1 rpm while the outlet and inlet heads are held stationary. The outlet end contains diametrically opposed windows to permit observatlon of the flowing fluids, and two valves, one on the top and the other at the bottom. Oil and free gas. when being produced simultaneously, can be separated by manipulating the two valves to keep a gas-oil interface in view through the windows. Thus, only gas is produced through the top valve and only oil flows through the bottom valve. The laboratory equipment was designed to study vaporization. Therefore, a uniform reservoir was made using dry sifted sand as opposcd to using a consolidated sand core with interstitial water. Furthermore. the reservoir was tilted to minimize fingering of gas. This tilting also in-

By L. Burris, C. H. Stockman, I. G. Dillion

Zone melting is a purification process in which separation of impurities is effected by slowly moving a narrow melted zone through a bar of solid material. Equations are presented which 1—predict the concentration profiles after successive passes of the zone and 2—give the limiting distribution of solute along the bar after an infinite number of passes of the molten zone. These equations take into account the effect of normal freezing in the last zone length. These equations were solved numerically using an electronic computer, and the concentration profiles are presented as a function of the solute distribution coefficient and the ratio of molten zone to total bar length. ZONE MELTING is a purification process in which separation of impurities is effected by slowly moving a narrow melted zone through a bar of solid material. Separation occurs if the solid freezing from a solution at any moment has a composition different from that of the liquid from which it is freezing. Solutes which lower the freezing point will tend to remain in solution and will be moved in the direction of zone travel. Solutes which raise the freezing point will preferentially freeze out, and they will be moved in a direction opposite to that of zone travel. After repeated unidirectional passage of a molten zone through a bar of material, impurities will be concentrated in the ends of the bar. A limiting concentration gradient will be reached in the bar after a large number of passes of the molten zone. Both the magnitude of this limiting concentration gradient and the rate of movement of solute in any pass depend on the zone length and on the equilibrium concentrations of solute in the liquid and solid phases. The basic theory of zone melting was thoroughly covered by Pfann.1 The purpose of this paper is to extend the theory of zone melting by presenting 1—equations which relate the concentration profiles in successive passes of the zone and 2—equations which give the limiting distribution of solute along the bar after an infinite number of passes of the molten zone. These equations take into account the effect of normal freezing* in the last zone length concentration of a given solute in the solid to the concentration of the same solute in the liquid. Analytical methods for determining the concentration profiles after any pass have been developed by Lord2 and Reiss. The method developed by Lord does not take into account normal freezing in the last zone and also becomes very complicated when the number of passes becomes large. The method developed by Reiss enables the direct calculation of the complete concentration profiles (including that in the last zone) after any pass for values of k close to unity (0.9 < k < 1.1). Both methods are useful and provide valuable insight into the zone melting process. The equations given in this article are based on the same assumptions used by Pfann. These are: 1—uniform composition in the liquid, 2—negligible diffusion in the solid, 3—constant distribution coefficient, 4—constant length of the liquid zone (except at the ends), and 5—solubility of the solute in the melt is not exceeded at any point. Equations for Concentrations in Successive Passes For a melted zone of length 1 at the left-hand end of a bar of uniform unit cross-section, the amount of solute in the liquid is J0Cn-1(x) dx [1] where the subscript is the number of the pass. Cn-1(x) represents the concentration (expressed as weight per unit volume) obtained in the previous

Jan 1, 1956

By J. J. Gilman

Examination showed that characteristic cleavage step patterns are observed on the cleavage surfaces of undeformed, slipped, bent, twinned, compressed, and indented zinc crystals; and the effect of temperature is discussed. Dimples were seen to produce cleavage steps in a treelike pattern in otherwise undeformed crystals. The steps seem to originate when cracks intersect screw dislocations. IT has been known for a long time that the path of fracture in polycrystals may be discontinuous (see Jaffe, Reed, and Mannl for review). Recently, Kies, Sullivan, and Irwin2 have proposed, and given evidence, that crack propagation is discontinuous within individual crystals as well. Other evidence has been given by Low.&apos; When discontinuous cracks within a crystal join together to make a macrocrack, the lamellae between each set of two cracks are torn somewhere, forming small cliffs. These cliffs appear as lines when the cleavage surface is observed microscopically.4,5 The lines have been called vein, tree, and riverlike markings by various authors, and they have sometimes been mistaken for fissures. The descriptive term cleavage steps is used in this paper. Cleavage steps vary in height over a wide range of values, from molecular dimensionsG to lor. and larger. Kies, Sullivan, and Irwin,2 as well as George,&apos; have shown that the gross cleavage step patterns for plastics, polycrystalline metals, and for mono-crystals are sometimes similar. Thus, they depend mostly on the mechanical variables that prevail during cleavage and are relatively insensitive to the structure of the material. For example, parabolic markings2,7,8 sometimes result when cracks open up ahead of, and not coplanar with, the main crack front. If the advance crack has the same velocity as the main crack, their intersection line is a parabola, otherwise it is a hyperbola or an ellipse. The patterns are strongly affected by differences in crack velocities. This results in chevron patterns which point to the place of origin of the main crack. It is the purpose of this paper to demonstrate the existence of a mechanism of cleavage step formation which is a continuous rather than a discontinuous process. Also, certain characteristic step patterns are described, and the strong effect of temperature is shown. The specimens were zinc monocrystals (grown from 99.999+ pct pure metal). These were cleaved at room temperature and at — 196°C. Results and Discussion Cleavage step patterns are highly variable from point to point on a given specimen, as well as from one specimen to another. Although the patterns shown in the photographs are typical, they have been selected for graphic illustration. Figs. la and lb compare undeformed crystals that were cleaved at —196 °C and room temperature, respectively. Cleavage at room temperature (Fig. lb) resulted in a higher density of high steps (dark black lines) and enhanced the visibility of the fine background markings. Deformation by simple slip caused no marked change in the step patterns until the glide strain reached about 1.0. But, as Fig. lc shows, the density of high cleavage steps was greatly increased by large glide strains. Corrugations lying perpendicular to the slip direction may also be seen in Fig. lc. These are caused by deformation bands. The cleavage resistance of the crystal of Fig. lc was very high compared to undeformed crystals (estimated by the force on a needle required for cleavage). Striking and varied cleavage step patterns were observed on bent crystals. Two characteristic patterns that were observed on crystals bent at 25°C, and cleaved by reverse bending at —196°C, are shown in Figs. 2a and 2b. The first, Fig. 2a, consists of V-shaped lines similar to the parabolas of other materials2,7 Fig. 2b shows a pattern that is the equivalent of Fig. la, consisting of faint background lines with a few higher step markings. Cleavage of bent crystals at room temperature resulted in Figs. 2c and 2d. Now, the cleavage step lines show a strong tendency to follow one of two perpendicular paths. In Fig. 2c (bent once), many of the cleavage step components that lie parallel to the bend axis are assembled into irregular lines. In Fig. 2d (bent twice), the cleavage steps again tend to consist of two perpendicular components, but neither of the components is assembled into lines. Also, the step density is higher.

Jan 1, 1956

By W. A. Ver Wiebe

The year 1938, with a production of 58,784,250 bbl. from 18,790 wells shows a slight recession from the high peak of oil production reached the previous year, when slightly over 68 million barrels of oil was marketed. The previous high peak had been reached in 1917 with a total of 45,451,000 bbl. Another still earlier peak was reached in 1904, during which year slightly less than 5 million barrels was produced and sold. The production of gas, on the other hand, probably reached a new peak during 1938 with a total of over 60 billion cubic feet. This peak, however, was not the highest peak, for during the year 1908 over 80 billion cubic feet was produced. Between these two high peaks the production dropped down to 16 billion cubic feet in the year 1921. The number of wells drilled during the year totals 1569. This figure is somewhat lower than the figure given in several trade journals because it does not include wells that were deepened or recompleted in a different geological horizon. Nearly three-fourths (or 1107) of the total number of wells were completed as commercial oil wells (915 in western and 192 wells in eastern Kansas). The commercial gas wells completed number 50, of which 4 are in eastern Kansas and 46 in western Kansas. The remaining 412 completions include 130 dry holes in eastern and 282 dry holes in western Kansas. Based on daily potential capacity, the new discoveries of the year accounted for 70,000 bbl. of new oil for eastern and 1,220,000 bbl. of new oil for western Kansas. It is interesting to note in this connection that the number of wells completed in the state rose gradualIy to a first peak in 1904, when 2782 were drilled. The number dropped off rapidly to 368 three years later, but rose to the second and highest peak in 1918 when 4671 wells were completed. In the period between 1904 and 1912 more gas wells than oil wells were completed. Between the high peak of 1918 and the somewhat lower peak in 1937, the low point was reached during 1931, with the completion of only 470 wells. In the matter of new pools discovered, Kansas again ranks high. The exact number depends somewhat upon the interpretation of a new area whether it should be called a new pool or a long extension of an

Jan 1, 1939

By W. A. Ver Wiebe

The year 1938, with a production of 58,784,250 bbl. from 18,790 wells shows a slight recession from the high peak of oil production reached the previous year, when slightly over 68 million barrels of oil was marketed. The previous high peak had been reached in 1917 with a total of 45,451,000 bbl. Another still earlier peak was reached in 1904, during which year slightly less than 5 million barrels was produced and sold. The production of gas, on the other hand, probably reached a new peak during 1938 with a total of over 60 billion cubic feet. This peak, however, was not the highest peak, for during the year 1908 over 80 billion cubic feet was produced. Between these two high peaks the production dropped down to 16 billion cubic feet in the year 1921. The number of wells drilled during the year totals 1569. This figure is somewhat lower than the figure given in several trade journals because it does not include wells that were deepened or recompleted in a different geological horizon. Nearly three-fourths (or 1107) of the total number of wells were completed as commercial oil wells (915 in western and 192 wells in eastern Kansas). The commercial gas wells completed number 50, of which 4 are in eastern Kansas and 46 in western Kansas. The remaining 412 completions include 130 dry holes in eastern and 282 dry holes in western Kansas. Based on daily potential capacity, the new discoveries of the year accounted for 70,000 bbl. of new oil for eastern and 1,220,000 bbl. of new oil for western Kansas. It is interesting to note in this connection that the number of wells completed in the state rose gradualIy to a first peak in 1904, when 2782 were drilled. The number dropped off rapidly to 368 three years later, but rose to the second and highest peak in 1918 when 4671 wells were completed. In the period between 1904 and 1912 more gas wells than oil wells were completed. Between the high peak of 1918 and the somewhat lower peak in 1937, the low point was reached during 1931, with the completion of only 470 wells. In the matter of new pools discovered, Kansas again ranks high. The exact number depends somewhat upon the interpretation of a new area whether it should be called a new pool or a long extension of an

Jan 1, 1939

MAY began with a general strike of the bituminous and anthracite coal miners in the United States in progress, while in Great Britain about three quarters of a million workers became idle by a lockout, caused by a dispute respecting the question of the rights of management in their shops. The employers opened their shops on May 3 to men wishing to resume work, but few availed themselves of the opportunity. Up to this time the statistics had been showing a little increase in the rate of employment in Great Britain and business conditions were considered to be improving. From Russia came reports that the results of the famine had not been so bad as had been prophesied, which is not to say that they were not grievous. In prognostications such things are habitually overesti-mated. Seeding for the new crop has now begun in Russia, with hopes for better results than last year. However, the general economic situation in Russia steadily becomes worse. We had advices during May to the effect that the Soviet Government had decided to abolish the gold ruble even as a theoretical calculating unit and substitute a "goods index." This idea would be somewhat on the lines of Professor Fisher for stablizing the dollar, and there may be a chance to see how it will work in practice. There was a contradictory report from Russia, however, that it had been decided to revert to the gold basis. This is the more plausible report, for if there be anything to be deduced from economic theory and history the present paper rubles will completely collapse and return to gold basis will ensue simply because the people will refuse to sell their goods on anything else. The civil war in China came to a head during the first week in May when General Wu-Pei-fu crushed the forces of General Chang Tso-lin around Pekin. The victor declared his intention to be to reunite the North and the South and in course of time to arrange for a constitutional convention. We probably do not under-stand the conditions in China, but recent events do not appear to have solved the grave difficulties there, though they may be a step toward it. However, the immediate outlook does not appear good, General Chang having retired to the north and declared the secession of Manchuria and Mongolia.

Jan 6, 1922

By J. H. Wernick

IN a study of the rate of decomposition of %-in. cubes of limestone, dolomitic limestone, and dolomite in a sweeping nitrogen atmosphere, Joseph, Beatty, and Bitsianes&apos; found that the zone of calcination advanced at substantially a constant rate at a given temperature. The purpose of this paper is to show that their data indicate at least two processes occurring when the above carbonates decompose. It is suggested that there are two processes occurring consecutively, one the limiting process in a given temperature range and the other the limiting process over another temperature range. The data of Joseph and co-workers have been extended by use of the Arrhenius equation, Eq. 1, a relation beween the velocity constant k of a reaction and the absolute temperature T. d In k A &apos; dT Rr2 A is the activation energy in calories per mol (additional energy that must be added for an average molecule to react), and R is equal to 1.986 cal

Jan 1, 1955

By E. D. Hummer, J. A. Younkins. J. P. Proctor

Comparatively little has been published relating practical experience with the control of the solid content of washery water systems that must be "closed." A "closed" system is one that for some reason may not be cleaned by the emission Of any effluent Of high &apos;&apos;lid &apos;content to be rep1aced by &apos;lean water in Order to hold the solid content of the waste water within reasonable bounds for efficient washing. It is the Purpose of this Paper to describe practical experience with such a water system and to present data that it is hoped may be of some use to those who are faced with a similar problem. The washery clarification system described comprises three thickeners and three filters, and although it is admitted that each of the fields of water settling and thickening and filtration offers a wide scope for investigation, the authors are not attempting to present the answers to these problems but to set down the results of some experience along these lines, making no claims as to the ultimate solution of the problems in hand. The subject of water clarification has vast ramifications; for example, the science of flocculation as applied to water settlillg and filtering opens up fields of wide possibilities of which as yet little is known. A comparatively recent entry into the field of water treatment, which may offer possibilities of practical application, is the use of "wetting" agents such as "Aerosol." General Arrangement of Water System So that the reader may obtain a comprehensive picture of the factors concerned in the control of a closed water system, it is necessary to give a brief description of the washing plant that is serviced by the water system to be described in the following pages. As we are not primarily concerned with the washing plant in detail, only a brief description of the flow of coal as it relates to the water system will be given here. For a more detailed account of this type of washer, the reader is referred to earlier papers,1,2 The washer, which handles o to 4-in, raw coal (750 tons per hour) is an American Rheolaveur plant of two complements; the coarse coal or sealed discharge plant and the fine coal or free discharge plant. The sealed discharge plant (Fig. I) consists of twin 48.in. primary launders, each having two washing boxes, supplemented by one 32-in. rewash launder, which also has two washing boxes. "Push" water for washing and conveying coal in these launders is supplied from a constant-head tank under pressure head of 10½ ft. at the point of introduction at the feed end of the launder. This tank also supplies water for upward or vertical currents used in the Rheolaveur or washing boxes. Each box discharges into a sealed boot elevator (Fig. I).

Jan 1, 1942

By William B. Senseman

FOR reasons well known to mining engineers, wet grinding is quite universal in plants having to do with the extraction of metallic values from crude ores. In the processing of the nonmetallic and industrial minerals, dry grinding is the more common method. The crude materials usually contain less moisture than is required for wet grinding and the products usually are marketed in dry form; most of them as powders. To grind wet, therefore, would entail the addition of water and an expense for drying the product, which is not justified. Furthermore, the material would be a dried cake that would still have to be pulverized or disintegrated before use. For producing fine products, air separators have largely replaced the earlier practice of sizing with screens and bolting reels. Mills in which the air-separating feature is an integral part of the design are now commonplace. Mill designs are many and air systems have developed along various lines, but for the purpose of this discussion, only the fundamental idea need be emphasized the idea of using air for sizing and removing pulverized material from a grinding mill. About 20 years ago, when the use of mills equipped with air separation had become common practice, heated air or gas was introduced to such a system for the removal of moisture. The purpose of this discussion is to outline the developments and trends that have followed this experiment. It is an important development, for mills equipped with air separation are now universally used for pulverizing not only nonmetallic and industrial minerals, but a great variety of other materials. All such mills are essentially the same. Dried material is pulverized, removed by an air stream, trapped in a cyclone collector, and relatively clean air from the cyclone is returned through a fan to the mill. There is no theoretical need for a vent from the system. The practical need is to vent the air that leaks into the system, and, since the cyclone is not 100 per cent efficient as a dust collector, this vented air carries some dust with it. The initial attempt. at drying was made on a system like that described, by the addition of a furnace. The minus pressure within the mill draws hot gas from the furnace. Infiltration air, along with the drying gases and evaporated moisture, is vented as before. The first application was made to a mill used for pulverizing coal. The coal contained very little moisture, so very little drying effect was needed for the success of this experiment. Actually, some calculated efficiencies of over 100 per cent were obtained before due allowance was made for the conversion of mill power into useful heat. When moisture is low,, the heat obtained from the conversion of mill power is an appreciable part of that required. That drying can be effected in the short time interval available in a grinding mill of this type is better understood by visual-

Jan 1, 1945

By J. A. Younkins. J. P. Proctor, E. D. Hummer

Comparatively little has been published relating practical experience with the control of the solid content of washery water systems that must be "closed." A "closed" system is one that for some reason may not be cleaned by the emission Of any effluent Of high &apos;&apos;lid &apos;content to be rep1aced by &apos;lean water in Order to hold the solid content of the waste water within reasonable bounds for efficient washing. It is the Purpose of this Paper to describe practical experience with such a water system and to present data that it is hoped may be of some use to those who are faced with a similar problem. The washery clarification system described comprises three thickeners and three filters, and although it is admitted that each of the fields of water settling and thickening and filtration offers a wide scope for investigation, the authors are not attempting to present the answers to these problems but to set down the results of some experience along these lines, making no claims as to the ultimate solution of the problems in hand. The subject of water clarification has vast ramifications; for example, the science of flocculation as applied to water settlillg and filtering opens up fields of wide possibilities of which as yet little is known. A comparatively recent entry into the field of water treatment, which may offer possibilities of practical application, is the use of "wetting" agents such as "Aerosol." General Arrangement of Water System So that the reader may obtain a comprehensive picture of the factors concerned in the control of a closed water system, it is necessary to give a brief description of the washing plant that is serviced by the water system to be described in the following pages. As we are not primarily concerned with the washing plant in detail, only a brief description of the flow of coal as it relates to the water system will be given here. For a more detailed account of this type of washer, the reader is referred to earlier papers,1,2 The washer, which handles o to 4-in, raw coal (750 tons per hour) is an American Rheolaveur plant of two complements; the coarse coal or sealed discharge plant and the fine coal or free discharge plant. The sealed discharge plant (Fig. I) consists of twin 48.in. primary launders, each having two washing boxes, supplemented by one 32-in. rewash launder, which also has two washing boxes. "Push" water for washing and conveying coal in these launders is supplied from a constant-head tank under pressure head of 10½ ft. at the point of introduction at the feed end of the launder. This tank also supplies water for upward or vertical currents used in the Rheolaveur or washing boxes. Each box discharges into a sealed boot elevator (Fig. I).

Jan 1, 1942

By Y. Kondo, S. Yamazaki, Z. Asaki

Thermal deco7nposition of Pyrite particles in a fluidized bed with inert gas stream was studied. Assuming that heat transfer from the surroundings to the fluidized particles controls the overall decomposition rate, rate equations for the batch process and for the continuous process were derived. In the batch experiment, a linear rate equation satisfies the experimental results and the overall heat transfer coefficient calculated from the rate constant agrees fairly well with that obtained by Leva.l1 For the continuous process, two rate equations were derived, one on the assumption of complete mixing of particles and another on the upward piston flow of particles in a fluidized bed. The former holds for a bed containing a higher fraction of decomposed pyrite realized at lower feeding rates. The latter can be applied for a bed at higher feeding rates. Thus, segregation of particles in the fluidized bed was indicated at higher feeding rates. Bed temperatures also correspond to these conditions. ThERMAL decomposition of pyrite may be represented by Eq. [I]. The pressure of diatomic sulfur gas reaches 1 atm at about 690°C. The thermodynamics,&apos; kinetics,2&apos;3 composition, and properties3-5 of decomposed products of such a reaction have been studied. Pyrite is a very common sul-fide mineral and is often accompanied with other sul-fides. It is of basic interest in nonferrous metallurgy to clarify the behavior of pyrite in the pyrometallur-gical processes of sulfide minerals of metals such as copper, lead, zinc, nickel, and so forth. Interest in this reaction increased recently because of possible elimination of arsenic from pyrite in processing highly purified iron oxide pellets. Producing elemental sulfur from pyrite, instead of sulfuric acid, also aroused interest in this reaction. It is indicated that the thermal decomposition of solid particles, such as calcium carbonate, proceeds through three major sequential steps: heat transfer, interfacial chemical reaction, and mass transfer.637 It is known that the decomposed product of pyrite is very porous2, 3 and the diatomic sulfur gas evolved can easily escape through this layer of decomposed product. It depends upon the circumstances, therefore, whether the heat transfer to the interface within particles or the chemical reaction at the interface determines the overall decomposition rate. The enthalpy change in the decomposition of pyrite is about 33 kcal per mole FeS2 which is comparable to that of calcium carbonate. The decomposition of calcium car- bonate becomes more and more dependent on the rate of transport of heat when reaction temperature increases, such as occurs in a fluidized bed.6&apos;7 It is reasonable to presume, therefore, that the thermal decomposition of pyrite, an endothermic process, carried out in a fluidized bed may be analyzed according to the heat transfer controlling model. This work intends, first, to propose a mathematical model that determines the overall rate in a fluidized bed for the decomposition process and, second, to investigate a few characteristics of the fluidized bed based upon the experimental results obtained. KINETICS OF THERMAL DECOMPOSITION IN A FLUIDIZED BED It is intended in this section to obtain rate equations for thermal decomposition of pyrite in a fluidized bed by assuming that the overall rate is determined by heat transfer from the surroundings to the particles. Both batch and continuous processes are considered. 1) Batch Process. To obtain the rate equation in the batch process, the following two additional assumptions are made. First, the temperature of preheated inert gas, tg, blown into the fluidized bed is assumed to be the same as the temperature of the fluidized bed, tf. Thus, no heat exchange occurs between the gas and particles in the bed and only the heat transfer from the reactor wall kept at tw to the particles is to be considered. Second, the decomposition is assumed to start at the outer surface of the particles and to proceed toward the center. At any given time during decomposition, undecomposed pyrite remains in the tori at a temperature: td. The decomposed shell is composed of FeS1+x whose outer surface is at tp Diatomic sulfur gas evolving at the interface is heated to tf during its escape through the decomposed shell. This is illustrated in Fig. 1. With the above-mentioned assumptions of heat transfer, we have:

Jan 1, 1969

By John W. Buch

NeaRly 25 years ago operating officials in the northern anthracite field were confronted with the problem of profitably mining virgin beds of thin coal (those 48 in. and under) or destroying them by mining underlying thick beds. To solve this problem costly hand-mining methods were replaced by cheaper mechanical methods, which eliminated the need for the lifting of bottom or the brushing of top in excessive quantities, which was essential if proper height for hand loading1 was to be provided. During this period long-face mining was an outstanding development. In its favor in comparison with any other method were the ease with which undercutting machines could be used, a differential in powder cost of about fifteen cents per ton in favor of this method over mining from a solid chamber or pillar face, and a greater production per day from a single working place, resulting in lower capital expenditures for a given total production, closer supervision and lower transportation cost. The long faces were drilled by jackhammer and undercut by machines. The coal from the cut was loaded into mine cars placed on the gangway road by means of a double-drum mechanical scraper engine and a mechanical V-type scoop. A tugger hoist was used to spot empty cars at the loading point from a supply placed at the operation by an electric mine locomotive. During loading the roof was supported by vertical wooden props paralleling the face. After the loading was completed the scraper engine and the ropes that had been used to propel the scoop in the loading of coal transferred the props to and along the face. A row of unfilled cogs was then built parallel to the new face and about 6 ft. from it. These cogs were usually made 6 by 3 ft., the longer dimension paralleling the face; they were placed on an average at 12-ft. centers. These wooden cogs were left in place and were buried later by falling roof. Attempts to remove them were never successful. When a new long face was started, the cog spacing would be increased to about 20-ft. centers. As successive cuts were made, weight would begin on the cogs, and they

Jan 1, 1940

By John W. Buch

NeaRly 25 years ago operating officials in the northern anthracite field were confronted with the problem of profitably mining virgin beds of thin coal (those 48 in. and under) or destroying them by mining underlying thick beds. To solve this problem costly hand-mining methods were replaced by cheaper mechanical methods, which eliminated the need for the lifting of bottom or the brushing of top in excessive quantities, which was essential if proper height for hand loading1 was to be provided. During this period long-face mining was an outstanding development. In its favor in comparison with any other method were the ease with which undercutting machines could be used, a differential in powder cost of about fifteen cents per ton in favor of this method over mining from a solid chamber or pillar face, and a greater production per day from a single working place, resulting in lower capital expenditures for a given total production, closer supervision and lower transportation cost. The long faces were drilled by jackhammer and undercut by machines. The coal from the cut was loaded into mine cars placed on the gangway road by means of a double-drum mechanical scraper engine and a mechanical V-type scoop. A tugger hoist was used to spot empty cars at the loading point from a supply placed at the operation by an electric mine locomotive. During loading the roof was supported by vertical wooden props paralleling the face. After the loading was completed the scraper engine and the ropes that had been used to propel the scoop in the loading of coal transferred the props to and along the face. A row of unfilled cogs was then built parallel to the new face and about 6 ft. from it. These cogs were usually made 6 by 3 ft., the longer dimension paralleling the face; they were placed on an average at 12-ft. centers. These wooden cogs were left in place and were buried later by falling roof. Attempts to remove them were never successful. When a new long face was started, the cog spacing would be increased to about 20-ft. centers. As successive cuts were made, weight would begin on the cogs, and they

Jan 1, 1940

By M. E. Fine, A. A. Henderson

Investigation of the tensile properties of silver based aluminum alloy crystals was undertaken because it appeared attractive for studying strengthening effects due to Suzuki locking with minimum complication. Yield drops were observed in all alloy crystals (1, 2. 3. 4, and 6 at. pct Al) after strain aging at room temperature. No yield drops were found in similarly grown and tested silver crystals. The yield effects are attributed to Suzuki locking but the major portion of the solid solution strengthening to other mechanisms. INVESTIGATION of the tensile properties of single crystds of silver alloyed with aluminum was undertaken because it appeared to be a system in which segregation at stacking faults associated with partial dislocations1 would be the dominant factor in anchoring dislocations. First, silver and aluminum have closely similar atomic sizes and thus solute atom locking of a dislocation due to elastic interactions should be unimportant. Second, while both X-ray2 and thermodynamic3 investigations show short-range ordering in silver-based aluminum alloys, the degree of local order is quite small (X-ray measurements give v = EAB - 1/2(EAA + EBB) = - 0.025 ev and thermodynamic measurements give v r -0.007 ev) and should not be important in strengthening dilute alloys. Third, the stacking fault energy of silver is probably low (as indicated by the profusity of annealing twins) and is very likely diminished further and quite rapidly by aluminum additions since the A1-Ag phase diagram shows a stable hexagonal phase at only 25 at. pct Al. Also, a careful investigation in this laboratory4 has shown that the ratio of twin to normal grain boundaries in recrystallized alloys increases with aluminum content. Thus, with minimum complication from other factors, Ag-A1 alloys seem attractive for studying strengthening effects due to segregation at stacking faults of extended dislocations. EXPERIMENTAL METHOD Single crystals measuring 250 by 5 by 1.5 mm of pure Ag (99.99 pct) and Ag-A1 alloys (A1 of 99.999 pct purity) of nominal compositions* 1, 2, 3, 4, and 6 at. pct were grown in high-purity graphite molds from the melt under a dynamic vacuum (1 x l0-5 mm Hg). The technique consisted of moving a furnace having a hot zone (which melted about 0.5 cm of alloy) over a horizontal, evacuated quartz tube con- taining the mold and alloy at a rate of 3/8 in. per hr. Chemical analysis showed roughly the first inch of the crystal to be solute poor, the last inch solute rich; and the center section uniform in composition within the sensitivity of the analytical method (± 0.2 at. pct Al). The center section of the crystal was cut into five specimens. Gage lengths of reduced cross section, measuring from 1.5 to 2 cm in length, were mechanically introduced by means of jeweler&apos;s files and fine abrasive cloth with the crystal firmly held in polished steel guides. One-third of the cross section was then removed by etching and electro-polishing, the crystals were all subsequently annealed for several days at 850°C in a dynamic vacuum (<1 x 10-5 mm Hg) and furnace cooled to 200°C. The crystal orientations were determined using the usual back-reflection Laue technique. The Laue spots were sharp and of the same size as the incident beam. However, microscopic examination showed the crystals to contain substructures with subgrains of the order of a micron in diameter. The details of this substructure are presently under investigation. Tensile testing was done with a table model Instron using a cross-head speed of 0.002 in. per min. For testing at various temperatures the following media were used: 1) 415oK, hot ethylene glycol; 2) 296ºK, air, acetone, water; 3) 273ºK, ice water; 4) 258ºK, ethylene glycol "ice" in ethylene glycol; 5) 200°K, dry ice in acetone; 6) 77ºK, liquid nitrogen. EXPERIMENTAL RESULTS A) Yield Behavior—A portion of an interrupted stress-strain curve for a 6 at. pct A1 crystal of the indicated orientation tested at room temperature is shown in Fig. 1. Initially, at (a), there is a small, gradual yield drop of about 10 mg per sq mm2. However, on stopping the test, and aging for a few minutes at (b), a sharp yield drop is found. Aging for longer times at (c) and (dl results in larger yield drops (and larger AT&apos;S). At, defined in Fig. 1, is usually larger than the yield drop by about 20 pct; however, this increase in the lower yield is transient since extrapolations of the flow stress curves join as may be seen from Fig. 1. (Both Laue and low-angle scattering photographs revealed no evidence of precipitation in a strain-aged 6 at. pct A1 crystal.)

Jan 1, 1962

By John P. Goheen

Considerable work has been done in developing a pyrometer to measure the temperature of molten brasses, bronzes, and aluminum in the crucible. On account of the high melting points and the amount of zinc and sulfurous fumes given off from molten brasses, the conditions are somewhat severe for a thermocouple of standard design; but satisfactory results are obtained with a portable pyrometer, 3 ft. (0.9 m.) of connecting lead wire, and a special 5-ft. nickel-nickel chromium thermocouple, composed of rods 1/4in. (6.35 mm.) in diameter. The lower 12 or 24 in., as desired, may be made detachable so that new tips may be connected at little trouble or expense. The portable instrument need not be of the extreme high-resistance type, as the movable parts of the galvanometer of a lower resistance instrument may be better constxucted to withstand the continuous handling such an instrument receives. Platinum-platinum rhodium thermocouples, protected with porcelain and graphite tubes, have been used, but the lag in registering the temperature is too great. It has been found that the range of temperature for various brasses is as follows: Red brasses...............2200-2250" F. (1205-1234" C.) Yellow brasses............2250-2400" F. (1234-1318&apos; C.) Bronzes..................2300-2550" F. (1260-1400" C.) A recent test with a portable pyrometer having a range of 2600" F. with a bare 1/4 in. heavy exposed couple 5 it. long and a handle attached at the upper end showed that the temperatures of molten aluminum under varying conditions in an oil-fired crucible furnace and one of the Simplex type were as follows: CRUCIBLE, OIL-FIRED FURNACE SIMPLEX FURNACE Temperature of metal in furnace....... 1540" F. (837" C.) 1530" F. (834" C.) Temperature in ladle after skimming at furnace......................... 1480" F. (805" C.) 1440" F. (784" C.) Temperature in ladle after skimming at floor near mold................... 1440" F. (784" C.) 1430&apos; F. (778" C.)

Jan 1, 1923

By John P. Goheen

Considerable work has been done in developing a pyrometer to measure the temperature of molten brasses, bronzes, and aluminum in the crucible. On account of the high melting points and the amount of zinc and sulfurous fumes given off from molten brasses, the conditions are somewhat severe for a thermocouple of standard design; but satisfactory results are obtained with a portable pyrometer, 3 ft. (0.9 m.) of connecting lead wire, and a special 5-ft. nickel-nickel chromium thermocouple, composed of rods 1/4in. (6.35 mm.) in diameter. The lower 12 or 24 in., as desired, may be made detachable so that new tips may be connected at little trouble or expense. The portable instrument need not be of the extreme high-resistance type, as the movable parts of the galvanometer of a lower resistance instrument may be better constxucted to withstand the continuous handling such an instrument receives. Platinum-platinum rhodium thermocouples, protected with porcelain and graphite tubes, have been used, but the lag in registering the temperature is too great. It has been found that the range of temperature for various brasses is as follows: Red brasses...............2200-2250" F. (1205-1234" C.) Yellow brasses............2250-2400" F. (1234-1318&apos; C.) Bronzes..................2300-2550" F. (1260-1400" C.) A recent test with a portable pyrometer having a range of 2600" F. with a bare 1/4 in. heavy exposed couple 5 it. long and a handle attached at the upper end showed that the temperatures of molten aluminum under varying conditions in an oil-fired crucible furnace and one of the Simplex type were as follows: CRUCIBLE, OIL-FIRED FURNACE SIMPLEX FURNACE Temperature of metal in furnace....... 1540" F. (837" C.) 1530" F. (834" C.) Temperature in ladle after skimming at furnace......................... 1480" F. (805" C.) 1440" F. (784" C.) Temperature in ladle after skimming at floor near mold................... 1440" F. (784" C.) 1430&apos; F. (778" C.)

Jan 1, 1923

By E. C. Bitzer

THE primary object of the work described in the following pages was to simplify the equipment in the separating circuit of the heavy-media process by substituting a spiral classifier for the separatory cone. Mechanical considerations were the leading attraction and the best that was hoped for on metallurgical performance was that the new vessel would give results equal to those obtained by conventional equipment. Tests have demonstrated in commercial operation on iron ore that the mechanical advantages of the spiral separator are about as predicted; also, the metallurgical performance is superior to the cone on the ores treated. Treatment of iron ore involves the separation of two products: a concentrate that sinks and a float product that contains true float material plus a controlled division of interfering middling. The middling material is heavier than the average specific gravity of the separating medium. Recent work with the spiral separator on Tri-State zinc ore showed that the middling material had to be recovered as concentrate because this fraction contained the bulk of the-zinc in the ore. It has been demonstrated that it is possible to make three products with the new separator on an ore such as this: a float tailing, a float middling, and a high grade heavy sink product. It appears from this last work that the new separator has definite mechanica1 and metallurgical advantages over any type of separating cone for treating feed that contains large amounts of material of a specific gravity close to that of the separating medium. However, either type of separator should perform equally well, metallurgically, on feed that is free of middlings. Each series of experiments with the spiral separator as required additional work to fully develop the possibilities of the machine. For this reason the paper is divided into chronological parts. History of Development A drag-type classifier was first proposed as a substitute for the cone separator by Butler Brothers technicians during the initial tests with galena medium at Crosby, Minn., in 1937. The desire for finding a substitute for the cone arose from trouble with interfering middlings and certain operating disadvantages of the cone. The possibility of using a spiral classifier was also suggested at this time by Emmett Butler and C. J. Abrams. However, inability to satisfactorily recover fine galena, which was used as a medium, terminated all development work at Crosby. During the winter of 1937--1938 investigation started on magnetic medium with concurrent s development of the inverted or closed- top cone, which was found necessary to eliminate iron-ore middlings with the float product. About

Jan 1, 1947

By R. L. Templin

In treating a cast metal by any working process such as rolling, drawing or forging, variations in the conditions present in the remelting, casting, chilling and preheating of the initial ingot will certainly have some effect on the physical properties of the final product. In considering the effects of cold working on the physical properties of metals, however, it will be assumed that these factors, being controlled according to best practice, will remain constant and therefore may be neglected. Starting with such a uniform metal ingot, the next operation in the production of wrought metal involves hot working by rolling, forging or extrusion so as to produce a slab, billet or bloom. This working must be sufficient to produce substantial grain refinement and minimize any defects occurring in the initial ingot. Even such a hot-worked product is not suitable as a starting material for determining the effects of cold working because it contains internal strains analogous to those resulting from cold working. It is necessary, therefore, to supplement the hot working with a considerable amount of cold working, followed by a proper annealing in order to obtain a material suitable for use in defining the effects of cold working on the physical properties of a metal. That is, if the effects of cold working are to be evaluated accurately it is necessary to have other effects at least constant if not absent. Such material, unfortunately, cannot always be obtained in commercial practice but the requirements just indicated certainly represent the desired goal; this goal has been attained in the treatment of some metals, one being aluminum. Factors That Must Be Considered Simultaneously with Cold Working So many other factors affect the physical properties of a metal that it is necessary to consider these factors simultaneously with cold working; their effects vary in magnitude with the amount of cold work present. The most important of these factors are: (I) chemical composition, (2) structure, (3) temperature of working, (4) character of working, (5) rate of working, and (6) methods used for measuring results. For

Jan 1, 1930

By W. H. Emmons

THIS paper is the third of a series treating of the relations of ores of the metals to igneous rocks. The first1 outlined the general problem; the second2 proposed a classification of lode ores, and showed how the distribution of the deposits is in a certain measure controlled by the contour of the roof of the parent batholith. A number of mining districts were discussed, the examples being selected chiefly from group 2 of the classification. The proposed classification of lode deposits, briefly stated, is as follows: 1. Cryptobatholithic: near hidden batholiths which have not yet been exhumed by erosion. 2. Acrobatholithic: in and near cupolas or domes of batholiths-the high points of larger underlying masses. 3. Epibatholithic: on batholiths, near their rims, but below eroded cupolas, or below the highest points of the roofs. 4. Embatholithic: among closely-spaced outcrops which probably are parts of a single batholith. The outcrops of invaded rocks predominate. 5. Endobatholithic: in and near roof pendants of large batholiths. The invading rocks predominate. 6. Hypobatholithic: in deeply-eroded batholiths, where even roof pendants, have been -eroded. Deposits of certain metals on the roofs of the batholiths are much more numerous in some positions than deposits of other metals, and the horizontal zonal arrangements of lodes of different metals are shown characteristically only in certain groups. In a large measure, also, the character of the fracturing and metallization is determined by, the-position on the roof, of the batholith.

Jan 1, 1927