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By Wayne L. Worrell

Thermodynamic data for the stable carbides and oxides of chromium, molybdenum, and tungsten have been critically eualuuted and are used to determine the stable condensed phases at 1 atm total pressure in each metal-carbon-oxygen system. Pourbaix-Ellingham diagrams have been constructed and are used to estimate the minimum temperatures neces.see)*y to oblain these metals by corbolhermic redlrction under reduced pressures. USING recently reported data for the carbides and oxides of chromium, molybdenum, and tungsten, the stable phases in the Group VI metal-carbon-oxygen systems at specific temperatures and pressures can be determined. The thermodynamically stable regions in each metal-carbon-oxygen system can be completely pictured using a Pourbaix-Ellingham diagram in which the two coordinates are oxygen potential (-RT In Po2) and temperature. Worrell and chipman' have described and constructed such diagrams for the metal-carbon-oxygen systems of vanadium, columbium, and tantalum. Downing2 has used similar diagrams to provide a description of the reactions in submerged arc furnaces. One of the examples which he cited was the Cr-C-O system; however, an improved diagram is presented in this paper using recently obtained data for the carbides of chromium. Although some of the oxides and carbides of the Group VI metals exist over slight ranges of composition,3 all solid phases are represented as stoi-chiometric compounds in the subsequent diagrams. Any error introduced into the calculated equilibria by neglecting the compositional variation of these phases is less than the uncertainty in the thermodynamic data. In a Pourbaix-Ellingham diagram for a three-component system, the phase rule requires that at equilibrium four condensed phases specify a point, three condensed phases determine a line, and two condensed phases define an area. To obtain a well-defined area at high oxygen potentials and teniperatures, the initial carbon to oxygen mole ratio is specified to be more than sufficient to reduce the oxide but not enough to convert all the metal to carbide. Thus, the lowest regions in the subse- quent Pourbaix-Ellingham diagrams represent areas in which the metal and its carbide are the stable condensed phases. Cr-C-O SYSTEM A) Thermodynamic Data. To simplify the subsequent calculations, all thermodynamic data are presented in the form of linear Gibbs-energy-of-formation* equations which were derived for the temperature range 505° to 2000°K and are reasonably accurate over the entire temperature ranges of the diagrams. The thermodynamic data for the compounds occurring in the Cr-C-O system are summarized in Table I. Several volatile chromium oxides have been reported,4 but their influence is negligible in the Cr-C-O system. Thermodynamic data for CO and CO2 were taken from the compilation of Coughlin.5 The only solid chromium oxide sufficiently stable to exist below 1800°K in the Cr-C-O system is Cr2Os.11 The Gibbs-energy-of-formation equation for Cr2O3 was obtained by revising the data tabulated in Coughlin,5 using the heat of formation of ah' and the high-temperature thermal data for chromium.7 In 1953 Richardson8 re-evaluated the original work of Kelley and coworkers,9 who measured the thermodynamic properties of the chromium carbides. However, the high-temperature equilibrium results of Boericke9 yield values for ?G°f of Cr2O3 which are 2 kcal more positive than the accepted data. His results for the chromium carbides are based on the same questionable equilibria. Gleiser10 recently determined the Gibbs energy of formation of Cr3C2 and the equation in Table I was calculated from her data and the thermal data of Kelley and coworkers.9 Thermodynamic data for the Cr7C3 and Cr23C6 carbides were obtained by combining the Cr3C2 data

Jan 1, 1965

By Ernst A. Hauser

A few years ago an Indian native of British Columbia drew the attention of white men,' to a deposit of a claylike material on King Island, at the mouth of Dean River just opposite Hunter Island in the Pacific Ocean (Fig 1 ) . The native claimed that this natural product, which is found not in solid form but either as a paste or as a thick, viscous liquid, exhibited exceptional healing properties not only for various types of skin irritation but also for internal ailments. He pointed out that the natives had been using this material very successfully for generations. Since then, systematic surveys have revealed that the deposit, covered by a humus layer of varying thickness, is far more extensive than had originally been assumed. The product as mined today is of puttylike consistency and of greenish color. If exposed to air it dries rapidly, forming a slightly gray, rather brittle product, which does not permit redispersion to its original consistency. When the natural product is rubbed on the skin, however, the presence of coarse, sandy material is revealed.

Jan 1, 1952

By G. H. Tausch, T. A. Huber

Very encouraging progress has been made ill the develop-ment of the permanent-type well completion which decreases considerable the cost of completions and workovers and aid-in the acquisition of reliable reservoir information at low cost. Completion and remedial operations are performed with tool,; which pass through the well tubing. Perforating and plug-hack operations can be done with the tubing in place and do not require pipe-handling equipment. Because of the many advantages afforded by this method, development work is going forward in anticipation of ultimately being able 10 use it to perform all usual well completion and workover operations. Effort is also being directed to the development of a more permanent type of lift equipment suitable for use with the permanent-type well completion. INTRODUCTION The permanent-type well completion in one in which the tubing and well-head are set in place only once in the life of the well and the completion or remedial work is performed through the tubing with a tubing-type perforator. a retrievable tubing extension. and other wire-line tools. This new type completion has made possible the saving of one to two days' rig time in the completion of each of several hundred wells During the last two years, and use of equipment developed for this type of completion has resulted in a 75 per cent reduction in cost. of certain types of workovers. In addition. the more reliable indication of the commercial value of a reservoir and the more accurate general reservoir information made Possible promise to be of even greater value in oil recovery than the reduction of costs for completions and workovers Recently. several well.. were worked over by using the retrievable tubing extension suspended on a swab line to plug back with cement and then perforating a higher producing interval with the tubing-type perforator, thus opening the way for complete through-the-tubing workovers which may be performed without pipe-handling equipment or mud. Those items attendant to the use of pipe-handling equipment and mud. such as hoard matting rig substructure. and pits. were also eliminated. There are indications that the elimination of drilling mud during completion and workover operations will frequently give increased well productivity, as plugging of the perforation. will not occur. It ii now possible to perforate selectively small sections of the producing interval and to test a well through these sections prior to perforating more interval. The perforating of additional interval will not entail the costly operations of killing the well and pulling tubing, nor will the old or the new perforations be plugged. The productivity of .mall sections of a reservoir and the actual gas-oil or oil-water contacts may now be determined economically under flowing condition.. Selective completions can be made in this manner to delay gas and water problems and bring about maximum oil recovery. At the present time, gas lift appears to offer the greatest potentialities for artificial lift in the permanent-type well com"letion since it can provide full-open tubing to accommodate the through-the-tubing tools and it may be ultimately developed into a fairly permanent type of lift. With precent-day pas-lift equipment. valve or mandrel failure necessitates occacio11al removal of the tubing. thereby reducing to some extent the permanence of the completion. New gas-lift valves are now

Jan 1, 1953

By C. S. Smith, L. Guttman

It is shown, from a study of geometric probabilities, that the average number of intercepts per unit length of a random line drawn through a three-dimensional structure is exactly half the true ratio of surface to volume. Since the surfaces can be internal or external, the area of grain boundary or of the interface between any two constituents in a micro-structure can be measured. Other metric relations are tabulated that may be of use in studies of the microstructure of polycrystalline, cellular, or particulate matter generally. IN many fields of scientific investigation the structure of cellular aggregates or random arrays of discrete particles imbedded in some matrix is observed on a two-dimensional section and inferences are drawn therefrom as to the real structure in three dimensions. The biologist's microtome slice, the petrologist's thin section, and the metallurgist's plane polished and etched sections are common examples, although the problem is a general one. Scientists have commonly limited their thinking to the same dimensionality as their structures, and the few attempts that have been strictly three-dimensional in character have been laborious and noteworthy. From a metallurgical standpoint it is often of considerable importance to know, in addition to the volume fraction of two or more components in an alloy, the amount of two-dimensional interface between crystals. Such grain boundaries (which may separate either two identical crystals differing only in orientation or two crystals differing in structure, and possibly also in orientation) have a determining factor upon the mechanical behavior. It is at these boundaries that melting commences, that stress-induced corrosion occurs, and that various precipitates (harmful or otherwise) first appear. The boundary is doubtless of equal importance in nonmetallic crystalline aggregates such as rocks, ceramics, and concrete, and the biologist is deeply concerned with the area of cellular membranes. Many synthetic cellular foams involve similar structural problems. The very term structure usually implies the presence of interfaces and a complete understanding of structure involves nothing but an analysis of the geometrical, metrical, and topological relations between the various interfaces (zero, one and two-dimensional) that exist in a three-dimensional structure. Even systems lacking sharp physical interfaces often have interrelated gradients of composition or velocity (as cored crystals or turbulence cells) in which a neutral surface can be treated as a two-dimensional interface. In an earlier paper by one of the authors' the question of cell shape was considered in terms of simple topological principles without regard to physical dimensions. The determination of the actual size of grains in two dimensions is carried out in a routine fashion in innumerable metallurgical laboratories (see, for example, the ASTM standard methods of grain size determination2), though this is done merely to check the uniformity of a product and has no relation to the actual three-dimensional shape or size of the grains. Some authors have discussed the three-dimensional problem but only on the basis of assumptions as to idealized grain shapes.:'-' Quantitative measurements of microstruc-tures to obtain the volumetric relations of various phases have been carried out by petrographers for many years and are of increasing popularity among metallurgists." The present paper will show how, on the basis of no assumptions other than randomness of sectioning (usually realizable in experiment), it is possible to learn a great deal about the three-dimensional structure. The relations to be derived will generally be used on random arrays of cells or other particles, although they are equally applicable to ordered arrays and even to isolated objects of complex shape provided that suitable random sections can be made. Total Area of Interfaces in a Sample Consider a typical microstructure of a single-phase polyerystalline metal, such as that shown pres- in Fig. 1. The plane cross section shown contains a network of lines which subdivides the area into two-dimensional cells. The lines, of course, represent merely the intersection of the two-dimensional plane of sectioning with the two-dimensional interfaces between adjacent three-dimensional cells. The structure also contains points at which two or more lines intersect: in three dimensions the points are, of course, lines. In the more general case there may be in three dimensions isolated particles surrounded by a single interface without contact with others, and both two and one-dimensional features which do not necessarily connect with others. On the two-dimensional section these will appear as areas delineated by a closed line (as at a and b, Fig. 2), as isolated lines

Jan 1, 1954

By W. L. Crentz, E. E. Donath, D. Doherty

IN 1948, the United States used nearly six million barrels of petroleum products every day. Although substitution of synthetic fuels for the natural petroleum product is not here yet, large quantities of special-purpose coal will be required in ever-increasing volume as the domestic production of oil from other sources fails to meet demand and the production of synthetic fuels begins. Petroleum economists do not agree as to when the shortages of domestic oil will appear; but the increasing per capita consumption of oil, coupled with a constantly growing population drawing on a potential domestic oil supply estimated to be 85 billion barrels, sooner or later will result in demand exceeding domestic supply. When this situation comes about, the excess demand will be either eliminated by curtailment of consumption or the demand met by increasing importation of foreign oil or by the production of synthetic fuels. The first recourse would definitely retard the heretofore unbroken rise in American living standards, while dependence upon a foreign oil supply during a war or other emergency would be dangerous. On the other hand, the enormous coal reserves in the United States, plus sizable deposits of oil shale, indicate adequate means of augmenting a diminishing domestic oil supply. Some idea of the impact of an expanding synthetic liquid fuels program on the coal-mining industry may be gathered when it is considered that to supply just half of our present-day petroleum needs synthetically from coal would increase the coal output by about 500 million tons annually, using an 11,900 Btu bituminous coal as the plant feed. If either a subbituminous coal or lignite were used, the quantity required would be materially increased. Synthetic Fuel Processes: The principal synthetic fuel processes using coal as a raw material are the Bergius, or coal-hydrogenation process, and the Fischer-Tropsch, or gas-synthesis process. These two processes not only produce different end products, but the preparation of the coal used in each presents its own individual problem to the coal-preparation engineer. The hydrogenation process brings together a mixture of dry, finely powdered coal, catalyst, and heavy oil to form a paste. Addition of hydrogen under rather high pressure and temperature conditions brings about transformation of the coal to a liquid product, from which a high-grade gasoline and other motor fuels may be obtained. The Fischer-Tropsch process requires the production of synthesis gas, a mixture of carbon monoxide and hydrogen. At the Bureau of Mines Louisiana, Mo., demonstration plant, this gas is being made by reacting dried pulverized coal with carefully controlled volumes of oxygen and superheated steam. After purification and in the presence of the proper catalyst and suitable conditions of pressure and temperature, the hydrogen and carbon monoxide components of the synthesis gas react to form motor fuel. The two processes are not competitive but rather com-

Jan 1, 1951

By E. E. Donath, W. L. Crentz, D. Doherty

IN 1948, the United States used nearly six million barrels of petroleum products every day. Although substitution of synthetic fuels for the natural petroleum product is not here yet, large quantities of special-purpose coal will be required in ever-increasing volume as the domestic production of oil from other sources fails to meet demand and the production of synthetic fuels begins. Petroleum economists do not agree as to when the shortages of domestic oil will appear; but the increasing per capita consumption of oil, coupled with a constantly growing population drawing on a potential domestic oil supply estimated to be 85 billion barrels, sooner or later will result in demand exceeding domestic supply. When this situation comes about, the excess demand will be either eliminated by curtailment of consumption or the demand met by increasing importation of foreign oil or by the production of synthetic fuels. The first recourse would definitely retard the heretofore unbroken rise in American living standards, while dependence upon a foreign oil supply during a war or other emergency would be dangerous. On the other hand, the enormous coal reserves in the United States, plus sizable deposits of oil shale, indicate adequate means of augmenting a diminishing domestic oil supply. Some idea of the impact of an expanding synthetic liquid fuels program on the coal-mining industry may be gathered when it is considered that to supply just half of our present-day petroleum needs synthetically from coal would increase the coal output by about 500 million tons annually, using an 11,900 Btu bituminous coal as the plant feed. If either a subbituminous coal or lignite were used, the quantity required would be materially increased. Synthetic Fuel Processes: The principal synthetic fuel processes using coal as a raw material are the Bergius, or coal-hydrogenation process, and the Fischer-Tropsch, or gas-synthesis process. These two processes not only produce different end products, but the preparation of the coal used in each presents its own individual problem to the coal-preparation engineer. The hydrogenation process brings together a mixture of dry, finely powdered coal, catalyst, and heavy oil to form a paste. Addition of hydrogen under rather high pressure and temperature conditions brings about transformation of the coal to a liquid product, from which a high-grade gasoline and other motor fuels may be obtained. The Fischer-Tropsch process requires the production of synthesis gas, a mixture of carbon monoxide and hydrogen. At the Bureau of Mines Louisiana, Mo., demonstration plant, this gas is being made by reacting dried pulverized coal with carefully controlled volumes of oxygen and superheated steam. After purification and in the presence of the proper catalyst and suitable conditions of pressure and temperature, the hydrogen and carbon monoxide components of the synthesis gas react to form motor fuel. The two processes are not competitive but rather com-

Jan 1, 1951

By P. G. Sprang, S. Rosen

The Y-Al- C ternary phase diagram for the com -position range from 55 to 100 at. pct Y and for a temperature of 950°C has been constructed from metallographic and X-ray diffraction data. The significant features of the isothermal section which is presented are the small solubility of aluminum in the binary Y3C phase and the presence of a ternary carbide phase with a small homogeneity range around the composition Y3AlC. The similarity in structure and composition between these two carbide phases is discussed in the light of the misci-bility gap which exists between room temperature and 1300°C, which was the temperature range studied. THE occurrence and stability criteria of ternary T3BC, carbide phases having the L'12 structure and the general formula T3BCx have been discussed in detail by stadelmaier1 and more recently by the present authors., Stadelmaier found many representatives of these phases formed between the T metals Mn, Fe, Co, and Ni and the B metals Mg, Al, Zn, Ca, Ge, Cd, In, Sn, Hg, T1, and Pb. The present authors reported on a new series of iso-structural carbide phases formed between the T metals of the Sc group and the B metal, aluminum. These new phases are unique in that many of the Sc group elements form stable binary carbide phases which occur about the composition T3C and which crystallize with a structure similar to that of the T9BCx ternary carbide phases. Furthermore, these binary and ternary phases are found to coexist in equilibrium with each other. The similarity in structure and composition between, for example, Y3C and Y3AlC in the light of the mis-cibility gap which had been found to exist between these two phases indicated a need for a more thorough knowledge of the phase relations which occur in alloys based upon these compositions. Consequently, an investigation of the phase equilibria in the yttrium-rich portion of the Y-A1-C phase diagram was undertaken. The limiting Y-A1 binary diagram determined by Lundin and Klodt3 and the results of Spedding et al.4 governing the Y3C phase were used as guides in , constructing the diagram. EXPERIMENTAL Alloys weighing about 10 g were prepared by arc-melting powder compacts made from the various components on a water-cooled copper hearth using a tungsten electrode in a gettered argon atmosphere. Good homogeneity was obtained by melting the alloys three times. The purity of the yttrium used was 99.9 pct (0.07 pct rare earths). The purity of the aluminum and the carbon was 99.99 pct. The results of chemical analysis on five representative alloys showed that losses during the alloying process were predominantly carbon losses and that in no instance did the measured concentration of this component differ by more than 3 at. pct from the intended composition. For this reason the alloy compositions which are reported are those of the charges prepared for melting. Three alloys which were analyzed for copper, tungsten, nitrogen, and oxygen compositions showed that no contamination had occurred either during casting or during the subsequent annealing treatments. For the major part annealing treatments were carried out on specimens which were placed in

Jan 1, 1965

By Ikuya Takase

INTRODUCTION Since the occurrence of the first oil crisis, coun-tries of the world, especially oil-importing countries have made sustained and vigorous efforts to lessen the dependency on oil as a source of energy supply. The adoption of "Principles of Coal Policy" by the IEA Ministerial Governing Board Meeting in May, 1979 was the first formal action taken by major energy consuming countries. At the Venice Summit in June, 1980, it was agreed that production and use of coal should be doubled over the next ten years. In fact, the world coal use in 1980 showed around a 10 percent increase over the previous year. Recently, we have seen an indication that the balance of oil supply and demand in the short term have eased. But I believe that it remains vital that we continue to encourage the development and introduction of alternative energy sources. Because, from the medium and long range viewpoint the recovery of the worldwide economy will lead us to increased oil requirements and thus we will be faced with the cyclical, structural tightening situation between the supply and demand of oil. Moreover, we are still convinced that the constraint of the supply capabilities of the Middle-East nations may be increasing in the long-term, since there still remains political uncertainties among these nations. Consequently, above all, coal is viewed as an alternative energy resource available for immediate expansion of use and is given as high a priority as nuclear power. In Japan, we regard coal as the most reliable alternative energy resource to replace oil. According to the "Alternative Energy Supply Targets" approved by the Cabinet in November, 1980, the level of coal imports is estimated to approximately double by 1990, while our domestic coal production will remain nearly at the same level. The transition from oil to coal is found in the recent import levels of coal---73 mil¬lion tons in 1980, a 23 percent increase over the 59 million tons imported in 1979. There was an upsurge in steaming coal imports, reflecting the transition in feedstocks---7.2 million tons in 1980, four times over the previous year's amount. Henceforth, from the medium to long range view, the demand for coal, especially that of steaming coal is forecast to continue to grow. The timely expansion of supply capabilities is our utmost concern and should be one of the most significant goals of our comprehensive policy. The Overseas Coal Investigative Committee, a privately organized advisory panel to the Director-General of the Natural Resources and Energy Agency of the Ministry of International Trade and Industry (MITI), investigated means to secure a stable supply of overseas coal. The panel presented its interim proposals in August, 1981, recommending the diversification of coal import sources, extensive use of low rank coal, as well as enhanced international cooperation between coal producing and importing countries. THE CONTENTS OF THE COMMITTEE'S REPORT Four Points for Major Consideration In order to ensure a stable supply of overseas coal, Japan needs adequate policy measures consistent with the characteristics of coal resources and environmental requirements, giving consideration to Japan's status and the role she is expected to play in the areas. From the above, great importance should be attached to the following four points: All the components of the "Coal Chain" (Namely, the development of mine sites, construction of railroads, port loading facilities, coal shipping vessels, port receiving facilities, including coal centers and international transport facilities etc.) should be reviewed and reformed with steps taken to assure efficiency consistent with the entire coal chain system. The complete formation of a coal chain system requires such lengthy lead times and huge amounts of investment that necessary measures should be undertaken well in advance utilizing long-range projections of future demands and various economic surveys. Policy planning should be conducted taking into account of harmonizing stability and economics of the supply structure. For ensuring the long-term stability and expansion of the coal trade, international cooperation on a bilateral and multi-national basis should be encouraged. Mutual understanding and close relationships are essential to facilitate the formation of the supply system and to promote the extensive use of coal. Direction and Problems Related to Supply Stability Expansion of Supply Capabilities. World coal imports in 1979 amounted to 229 million tons, of which Japan's share amounted to 59 million tons, or one fourth of the entire amount. The imports of European and Asian countries accounted for 83 million tons and 7 million tons respectively. According to the examination of the Investigative Committee, Japan's coal requirement is estimated to be between 140-150 million tons by 1990, nearly the same level as announced in the Provisional Long-Term Energy Supply and Demand Outlook in 1979. This fore¬cast is-to be revised in April, 1982. Japan's demand is expected to be met through fiscal 1985; however, by 1990, the supply is estimated to fall short of demand, particulary, in the field of steaming coal. For the expansion of supply capability, first, mine development should be accelerated. The proposed

Jan 1, 1982

By R. W. Heckel, R. L. DeGregorio

The DeHoff method of determining the size distribution of ellipsoid-shaped, second-phase particles has been applied to the spheroidization of cementite in a eutectoid steel. The surface area of Precipitates determined from the various size fractions in the distribution was correlated with surface-area measurements based on the number of intersected interfaces on a random lest line. The precipitate particles were found to be oblate ellipsoids with an axial ratio of about 0.90. The size distributions were found to be log-normal. A method is proposed whereby the shrinkage of small particles and growth of large ones can be determined from the experimental data. The experimental data are compared to previously proposed mathematical models describing diffusion-controlled kinetics and various types of interface-controlled kinetics. The experimental growth and shrinkage rates are considerably slower than those predicted by diffusion-controlled kinetics. The best fit is obtained for a model describing interface-controlled kinetics limited by the rate of formation of cementite at the growing interfaces where the interfacial reaction rate is proportional to the solute thermodynamic activity gradient across the surface. THE subject of spheroidization of second-phase particles has been considered previously by other investigators. Livingston1 has studied the precipitation of the cobalt-rich phase from copper alloys containing 0.7 to 3.2 wt pet Co. His results indicate that the average particle size increases as the cube root of the heat treatment time in accord with diffusion-controlled kinetics.'-' Komatsu and rant' in their studies of the growth of SiO2 in a dispersion-strengthened copper-silica alloy found that the initial growth of SiO2 proceeded by diffusion-controlled growth and later stages were limited by interface-controlled growth. The values of the activation energy obtained for the interface- controlled process led them to the conclusion that the process was limited by the dissociation of SiO2 at the shrinking interface. The transition from diffusion-controlled growth to interface-controlled growth was characterized by a particle size which varied with the heat-treatment temperature. It is also interesting to note that the particle-size distribution as found by Komatsu and Grant exhibits log-normal behavior when replotted on log-probability coordinates. Dromsky, Lenel, and Ansell9 have observed the growth of Al2O3 particles having a mean free path of about 1.5 to 13 µ. Their photomicrographs indicate that the Al2O3 particle sizes were larger than those observed by Komatsu and Grant. Dromsky, Lenel, and Ansell concluded that the Al2O3 coarsened by an interface-controlled growth mechanism limited by the solution of A12O3 at the shrinking interfaces. Bannyh, Modin, and Modin10 have studied the spheroidization of a eutectoid steel (0.83 wt pet C). Their spheroidization (tempering) treatments were carried out in the range from 210o to 700°C for times between 1.5 sec and 20 hr. Measurements of mean particle size as a function of time indicated a cube root of time dependence of size at 700°C, in agreement with previous analyses of diffusion-controlled kinetics.2°7 At lower temperatures, the time dependence was less than the one-third power. It is important to note that, although mathematical models of growth* considering particle-size distribution have been available, measurements of only mean particle size have been carried out. DeHoff11 has presented a quantitative metallography technique which is applicable to the determination of the size distribution of ellipsoids of constant shape. This method is applicable to both oblate and prolate ellipsoids of all ratios of minor to major axis and is based upon an extension of Saltykov's analysis12 of the distribution of spheres of varying size. DeHoff's analysis is based upon measurements of the minor axis of the particles on a random plane of polish in a unit area. This method provides a measure of the number of ellipsoids in various size ranges per unit area. As pointed out by DeHoff, such measurements may be used to obtain surface area and total precipitate volume data. Thus, the accuracy of the distribution analysis may be checked by comparison of the surface and volume

Jan 1, 1965

By C. D. Stahl, S. M. Farouq Ali

This investigation attempts to describe and simulate the alcohol displacement process by means of a cell model, as employed in chemical engineering practice. The proposed model is more simple than previously proposed models. and utilizes parameters chosen on a theoretical basis. The model successfully reproduced the formation of the stabilized bank and the breakthrough of alcohol, the latter depending on one of the model parameters, which may be correlated with the length of the porous medium. Moreover, the effects of the phase behavior of the liquid system involved, as observed in experimental studies, were reproduced. Several variations of the basic model were devised and tested on a digital computer. These included the cases in which: (1) the actual value of fractional flow was used in cell-to-cell computations; (2) the number of cells was varied within the same run; and (3) incomplete rather than complete phase equilibrium was assumed within each cell. The proposed cell model clarifies the basic mechanism of the process. Detailed concentration profiles obtained for each cell, for instance, showed the mechanism of bank formation in relation to the phase behavior characteristics. The results obtained indicated a varying degree of phase equilibrium concommitant with changes in the velocities of the phases in an actual alcohol displacement. This condition was approximated by changing the number of cells during the simulation. Interesting information was obtained on the influence of path length on the efficiency of alcohol displacement, which has been the subject of some controversy. Certain limitations preclude the use of the proposed model as a substitute for experimental studies. The results obtained were, nevertheless, of value in interpreting the experimental results. INTRODUCTION During recent years considerable effort has been directed toward an understanding of alcohol displacement, the process whereby oil and water are recovered from a porous medium by the continuous injection of a solvent. The complex nature of the physical process involved has so far defied a complete mathematical treatment. Other methods of approach, amounting to an overall material balance, have been proposed, yielding useful information on certain aspects of the process.1-3 Taber et al, in particular, defined the displacement mechanism in terms of the phase behavior of the alcohol-oil-brine system invoIved.2 Wachmann reported a mathematical treatment of alcohol displacement subject to certain simplifying assumptions? Donohue proposed the use of a "cell model" for simulating alcohol disPlacement.5 The nature of the assumptions involved limited the utility of the model. The present work attempts to examine the variables involved in the simulation of alcohol displacement and discusses several possible versions of the basic cell model. Under certain conditions the model results are similar to the experimental results. In particular, the spontaneous formation of of the stabilized bank and the effects of the system phase behavior were successfully reproduced. PREVIOUS WORK ON CELL MODELS Cell models and the theoretical plate concept are often used in solving chemical engineering problems in which an explicit mathematical solution may be difficult or impossible to obtain. Examples of such applications occur in distillation, gas-liquid chroma tography,6 reactor technology, absorption, etc. In petroleum engineering, such a model was used by Attra7 to describe non-equilibrium gas drive, and by Higgins and Leigh ton8 to calculate sweep efficiency in water flooding. Aris and Amundsen pointed out the equivalence between the diffusion model and perfectly mixed cells connected in series.9 Deans proposed a three-parameter cell model to simulate two-component

Jan 1, 1966

By John E. Hockett

The need for basic information about the relationship between resistance to dejormatim (flow stress), temperature, strain, and strain rate, for the solution of metal-fovming problems, is pointed out. Some early attempts to satisfy the need are mentioned. A brief description of a machine called a Cam Plastome-ter is given, including the processing of results of testing in the machine. Next, a program of testing aluminum in compression over a wide range of constant true-strain rates (0.1 to > 200 sec-1) and a modevately broad range of temperatures (223° to 673°K) is described. The results of this program are presented in the form of true-stress us true-strain cuvves. The data in these curves are presented in the form of relationships between true stress and true-strain rate in sermilogarithmic and log-log form, as functions of temperatures—for several true strains. Finally, true stress, for a given true strain, is displayed as a function of log true-strain rate and absolute temperature, i.e., a surface. SINCE the publication of Hill's book1 on plasticity theory, increasingly rapid advances have been made in analytical solutions to forming problems. Methods in common use are the slab method, the uniform deformation energy method, the limit analysis method, the slipline field method, and the semiexperimental method called "visioplasticity". These approaches, and examples of their use, are covered in detail by Johnson and Melloor2 and by Thornsen, Yang, and Kobayashi.3 unfortunately, practically all of the above work has had to rely upon a number of basic assumptions, e.g., homogeneous deformation and Coulomb (sliding) friction; and virtually no dependence of the mechanical behavior of the deforming metal, upon temperature, strain, and strain rate, has been included. It is with this dependency that this paper is concerned. Loizou and sims4 looked at the above relationship for lead using both a constant compression-speed Cam Plastometer and a constant true-strain-rate Cam Plastometer designed by Orowan.5 Alder and Phillips8 investigated the relationships for aluminum, copper, and steel in the same constant true-strain-rate Plastometer. cook7 tested twelve steels at temperatures ranging from 1170° to 1473°K in the same Plastometer over a range of true-strain rates of 1.5 to 100 sec-'. The writer tested commercially pure aluminum at room temperature and depleted uranium at temperatures from 573" to 873°K at strain rates from 10-3 to 1.0 sec-1 in a Cam Plastometer designed and built at Los Alamos Scientific Laboratory.8 During the past few years the Cam Plastometer at Los Alamos has been used for a number of relatively minor experiments on brass, mild steel, duralumin, Armco iron, and depleted uranium. In this time the machine has been continually modified and improved. It was decided to utilize fully the wide range of strain rates now available with the machine by testing a material about which some information was already in the literature. Prior work on commercially pure aluminum6 appeared to deserve confirmation and expansion. So it was decided to explore the resistance to compression of this material over the currently available range of constant true-strain rates and a convenient range of temperatures. This paper is a report of that exploration. I) EQUIPMENT AND PROCEDURE The principal item of equipment is, of course, the Cam Plastometer, the working part of which is shown in Fig. 1. In this figure, an aluminum specimen may be seen between two tungsten carbide platens, in position for a room-temperature test. Above the upper carbide platen is a load cell. Output from the load cell is amplified and applied to a galvanometer in a recording oscillograph. Auxiliary equipment includes the oscillograph, the control console, a counter, and a time-mark generator. The counter is first used in adjusting the time base. Then it registers the count, of sixty pips per revolution generated by the rotating cam, in each second. These pips and the time base are also applied to galvanometers in the oscillograph. Thus, load, time, and cam position are recorded simultaneously. Heating of a specimen prior to compression is done

Jan 1, 1968

I do not think too much emphasis can be placed upon creation of favorable climate for development of foreign mineral resources to feed the hungry maw of our industrialized nation. We have become dependent, not only upon the ten raw products indicated in Mr. Bancroft's article, but upon 71 mineral substances listed by DMPA as in short supply. Forty-four of these are metals, 9 are chemical minerals and 18 are nonmetallic minerals. Of this list only 8 are produced in any large quantity in the United States, and all are vital in peace-time industry. Even more, they are absolutely essential for defense. This represents our present needs. But if our consumption and requirements are projected over the next 25 years as is done by the President's Materials Policy Commission-The Paley Report-our future outlook becomes appalling. The divergence of consumption over production, even allowing for substitution and conservation, will widen in the future. This means our dependence upon foreign raw materials, mainly minerals, will grow. What are the chief foreign sources of minerals for our future needs? They are chiefly Latin America and the dominions and colonies of the Western European nations. The British Commonwealth countries contain in abundance those minerals which the U. S. lacks. Of 32 of the most critical minerals the Commonwealth is deficient in 7 and lacks only 1; whereas the U. S. is deficient in 18. Strikingly, our deficient minerals are abundant in the Commonwealth and several of their deficiencies are in excess in the U. S. Resources of the two nations complement each other. If Europe should be overrun by an unfriendly power that could control the destinies and resources of the European dominions and colonies, our industrial life would be placed in severe jeopardy. Therefore, I heartily endorse Mr. Bancroft's statements regarding the Point IV program, provided the program is wisely administered and implemented. It is from the underdeveloped countries, as pointed out by Mr. Bancroft, that most of our future mineral supplies will have to come. Many of the underdeveloped source countries are African colonies and dominions of Western European nations. Our present aid to Europe, therefore, is not, as many infer, a purely one-sided affair; it safeguards our future industrial development and security. Development aid directly to the underdeveloped countries through a well administered Point IV program, can do much, I believe, to safeguard our prosperity. I regard it as a wise investment for future U. S. mineral needs. Dr. Alan M. Bateman Department of Geological Sciences Yale University Mr. Howland Bancroft's article, The Broadening Road to Foreign Investment, appeared on page 666 of the July MINING ENGINEERING.

Jan 1, 1952

By W. J. Keep

Cast-iron, or pig-iron, is iron which contains all the carbon that it could absorb during its reduction in the blast-furnace. As is well-known to chemists, carbon exists in cast-iron in two distinct forms. In chemical union, as "combined" carbon, it cannot be discerned, except as it may increase the whiteness of the fracture, in so-called white iron, or carburetted iron (sp. gr. about 7.72). Carbon mechanically mixed with the iron as graphite is visible, varying in color from gray to black, while the fracture of the iron, according to the color and amount of graphite it contains, ranges from a light to a very dark gray. The specific gravity of graphitic iron is about 7.40. Silicon in cast-iron is evidently to some extent combined with the iron and the carbon ; but whether it exists also in a form corresponding with graphitic carbon, mechanically mixed with the remaining mass, is a question still in dispute, which we have not in this paper endeavored to answer. It has been the opinion of many writers on metallurgy, and many foundry men, that silicon is in every way injurious to cast-iron. Yet

Jan 1, 1889

By Richard S. McCaffery, Clarence H. Lorig, Joseph F. Oesterle, Ira N. Goff, Oscar O. Fritsche

This paper is the report of an investigation to determine the relations between the viscosity, temperature and composition of that portion of the silica-alumina-lime-magnesia system(l) within which blast-furnace slags are found. The work reported in this paper was made possible by a grant of funds from Engineering Foundation. It is a part of a project, the determination of properties and structure of iron blast-furnace slags, upon which the laboratories of the University of Wisconsin have been at work for some years. Three papers have been published, which have marked the progress of the study of iron blast-furnace slags at Wisconsin. The first,(2) Desul-furizing Power of Iron Blast-furnace Slags, discussed the solubility of sulfur in slags that contained no magnesia and discussed the viscosity. The second, (3) The Constitution of Iron Blast-furnace Slags, developed the constitutions of slags in the four-component system, silica-alumina-lime-magnesia, and pointed out an explanation of slag structure. Composition of Iron Blast-furnace Slags,(l) which was the third paper, gave a method of calculating the percentages of the various compounds present in slags when the amount of oxide was given and also an interpretation of quaternary equilibrium. Illustrations were given of the mineral composition of blast-furnace slags and some applications of composition results were shown. Because of their relative ease of measurement, the viscosity-temperature relation for slags was selected as a factor which would be useful in correlating the physical properties of molten slags to furnace operation. With this in mind the viscosities of slags whose compositions are in that portion of the quaternary system, silica-alumina-lime-magnesia, in which blast-furnace slags occur, were thoroughly investigated.

Jan 1, 1932

By Robert E. Green

Experiments were performed in order to investigate the influence of magnitude of driving force, recouery, and previous heat treatment on grain boundary migration in deformed aluminum crystals. The frequency of occurrence of strain-free grains possessing Preferred crystallographic orientations was studied both as a function of heat treatment and as a function of amount of deformation of the matrix crystal. Aluminum of such composition as to exhibit precipitation-hardening behavior was used. CONSIDERABLE work has been devoted to the factors influencing grain boundary migration in metals.1'52 Aust and Rutterl-9 have studied grain boundary migration into matrix crystals containing a striation substructure, which provided a thermally stable driving force during the course of the migration experiments. These authors state that, while variations in the striation pattern were sometimes observed, it was possible to obtain reasonably uniform and reproducible striation structure by careful control of the solidification conditions. Admittedly, this source of driving force is a unique one and has served well in numerous experiments. However, although the striation substructure provides a thermally stable driving force, the subject of its reproducibility from crystal to crystal is questionable. In fact, Aust and Rutter3 attribute the scatter shown in some of their experimental points and several anomalies in boundary migration rates to variations in the substructure driving force along a single specimen. A further limitation on striation-induced driving force is that the driving force cannot be varied over wide ranges in a controlled manner. More often used as a source of driving force is the strain energy stored in a crystal during plastic deformation. This type of driving force has the disadvantage that it is not thermally stable due to recovery taking place simultaneously with the grain boundary mobility measurements. On the other hand, this strain-induced driving force is very reproducible from crystal to crystal since it is very easy to grow single crystals possessing the same purity and crystallographic orientation and then to strain them identically. In order to measure grain boundary migration rates two different methods are primarily used. Most often the technique employed is the heat-cool-etch method1' which involves thermal cycling, while the other technique, developed by Graham and Cahn11 using an X-ray diffractometer and goniometer furnace, involves continuous heating only. Thus the influence of thermal cycling vs continuous heating is a factor to be considered in grain boundary migration rate measurements, particularly in cases where the source of driving force is the strain energy stored in the deformed matrix, and recovery is likely to occur. Numerous recent investigations have shown that extremely small impurity additions to zone-refined metals exert a marked effect on grain boundary migration rates1-5, 9, 12-27 and a few have considered the effect of the distribution of impurities.28-35 The concentration of impurities and their distribution as influenced by heat treatment must also be taken into account in migration-rate studies. In the present article consideration is given to the influence of the magnitude of driving force, recovery, and previous heat treatment on grain boundary migration rates. In order to vary the driving force over a large range it was necessary to use as a source of driving force the energy stored in the matrix crystal during plastic deformation. A majority of the investigations were performed on aluminum specimens which were of such compositions as to exhibit precipitation-hardening behavior.

Jan 1, 1965

By E. Parthe, J. P. Pemsler

TWO references can be found in the literature concerning the ternary system uranium-tantalum -carbon. C. H. Schramm, P. Gordon, and A. R. Kaufmam reported in this Journal1 on the existence of the ternary carbide "UTa10C4." They also report a second face-centered-cubic carbide phase in the system U-Ta-C, which they denote as "white" phase. The publication includes a reproduction of a Debye-Scherrer powder photograph of "UTa10C4" and a list of the sin2 0 values of this compound. H. Nowotny, R. Kieffer, F. Benesovsky, and E. Laube2 report the complete solid solubility between TaC and UC with a B1 structure. Since the ternary phase "UTa10C4" lies very close to the binary system Ta-C, and the established phase Ta2C with a C27 structure had not been mentioned by Schramm et al., it was thought worthwhile to compare the patterns of "UTa10C4" with Ta2C. The strong lines of the given pattern were indexed on a hexagonal unit cell with the approximate cell parameters a = 3.09A and c = 4.93A. These are the values reported for Ta2C in the literature.3 The correspondence between reported and calculated sin2 8 values may be studied in columns 4 and 5 of Table I. The agreement is fair, but there remain weak lines which cannot be assigned to the hexagonal unit cell. The extinctions correspond to those of Ta2C, but a comparison of the calculated and observed intensities of the Ta2C lines (columns 2 and 3) with those of the corresponding lines of "UTa10C4" (column 6) show occasional deviations. To clarify this situation, four new samples were prepared. The compositions of these samples were chosen in such a way as to observe any existing ternary phase in the system TaC-UC-U-Ta. The samples were arc melted in an inert atmosphere and annealed at 1100°C for 36 to 72 hr. Compositions of the samples determined by chemical analysis are given along with the results of X-ray investigations in Table 11. The following conclusions may be drawn from these data: a) No ternary compounds occur in the section TaC-UC-U-Ta of the ternary system Ta-U-C. The "white" phase reported by Schramm et al. corresponds to a solid solution between TaC and UC. Only one three-phase field exists: C27-B1-A2. (Both tantalum and ? uranium have body-centered-cubic A2 structures.) The a uranium observed in sample 4 transformed from the high-temperature ? phase on cooling. b) The phase Ta2C with a C27 structure extends into the ternary system. "UTa10C4" is, therefore, a uranium-enriched Ta2C. Good agreement is ob-

Jan 1, 1960

By J. E. Burke

Recent investigations have elucidated many of the phenomena of the grain growth process, but have also revealed some conflicting and unexplained results. Beck and his co-workers 1,2,3 have shown that grain growth continues with continued heating at one temperature until the average grain size approaches the thickness of the specimen. Plotting the logarithm of the average grain diameter, D, against the logarithm of the annealing time, t, they find the straight line relationship given by the equation: D = Ktm [,] with possible small deviations at short annealing times. K and n are constants at constant temperature. On the other hand, Wa1ker4 finds that, in alpha brass) the rate of growth falls off more rapidly than indicated by Eq i after long annealing, so that an equilibrium grain size is approached. Burke5 showed, using Walker's data, that time and temperature for grain growth are apparently related through an activation energy, H, according to the relationship: ] where h and tz are the annealing times necessary for the average grain size to increase from Do to D at temperatures T1 and T2 and R is the gas laws constant. In the case quoted, H had the value 60,000 cal per mol. The apparent validity of this relationship, at least up to 700°C, and the approximate value of H were later confirmed by Beck3 The results obtained by Beck Kremer, Demer and Holzworth2 for aluminum and aluminum-magnesium alloys could not be satisfied by such a relationship, since the slope of the isothermal curves increased with increasing temperature. These data indicate and Beck, Holzworth and HuV ater demonstrated expcrimentally that the only apparent factor controlling the rate of grain growth at constant temperature is the grain size. While many of the phenomena have been elucidated, a reasonably quantitative explanation of the process is lacking. There exists uncertainty even as to the primary driving force for grain growth, although there is a considerable body of indirect evidence that the interfacial energy of the grain boundary is responsible.7,8,io Making implicit use of this assumption, several authors14,16 have pointed out that grain boundaries should migrate toward their center of curvature. Harker and Parkerg have advanced this concept furthest, and show that one can expect grain boundary migration to occur only when the grain faces are curved, or when they meet at non-equilibrium angles. When the face is curved toward a grain A, for example, the atoms in the surface of grain B, on the other side of the boundary7 are on the average more surromded by the atoms of their lattice than the atoms on the surface of grain A. Because of thermal motion, the atoms at the interface will sometimes be attached to grain A and

Jan 1, 1949

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Jan 1, 1938

By Margaret Dienes, Karl L. Fetters

IT is recognized that ingot structure is important in determining the quality of finished steel. Such elements of ingot structure as the size, shape and distribution of primary crystals; the size, shape and distribution of shrinkage cavities; the degree and kind of segregation (both macro and micro); the distribution of nonmetallic impurities and gas cavities are each the result of solidification phenomena. These structural features vary with variations in ingot practice: Their control requires a knowledge of their correlation with the variables of ingot practice. The structures of full-sized commercial steel ingots have been studied extensively by the Steel Ingots Committee of the Iron and Steel Institute.1 This work has contributed much to our knowledge of ingot structure and the factors that control it. These investigations of necessity have been limited in scope because of their costliness and the great amount of time required. Studies of the structure of small steel ingots have not been very satisfactory because of the rapid rate of freezing of the ingots. Their structures are thus difficult to resolve and to interpret. Medium sizes of steel ingots in the ranges of 150 to 500 lb. do offer opportunity for study, but their cost also becomes greater and their use less expeditious. Experimental models for the study of steel-ingot structure have been made of nonferrous metals. Gathmann2 used lead-tin alloys and reported that they were satisfactory for determination of the location of the major shrinkage cavities and the "planes of weakness" resulting from the pattern of crystallization. Certain features of mold design have been illustrated by these results. Bezdenezhnihk3 has used copper and aluminum ingots similarly and has shown the effect of mold-wall thickness on the depth of columnar grains. These studies of nonferrous models have been useful, but their results have been limited because the analogy with steel ingots obviously is not a close one. Model wax ingots have also been useful in pointing out important features of mold design. Gathmann4 watched the solidification of wax ingots, through a glass-walled mold, and has reported the effects of mold type on the location of the shrinkage cavities. Segregation was simulated by using a mixture of paraffin and stearine and adding a red dye that on freezing segregated preferentially to the stearine. Brearley5 also used wax models to determine .the effects of some of the principal features of mold design. Carlsson and Hultgren6 used stearic acid to show that the columnar crystals of ingots tend to slope upward progressively from the mold wall toward the center of the ingot. As with the nonferrous ingots, the wax ingots have

Jan 1, 1943

By L. H. Reiss, J. Groult, L. Montadert

Many fields, where the reservoir is composed of sandy layers, show great complexity because of the lack of continuity which results from a particular type of seditnentation. This complexity may be a factor of prime importance in studying reservoir drainage, especially in the displacement of oil by water or gas. This paper describes work done to study this heterogeneity and its influence in the exploitation of the fields of the lower Devonian sandy shale in the Fort Polignac Basin in Algeria. Two lines of research were followed. 1. On the border of the hasin, a detailed sedimentological study established rules for the distribution of the sandy zones, which furnished hypotheses necessary for devising a geologic model of the reservoir. A certain number of sandy zones were recognized and characterized by their sedimentation. 2. In the interior of the basin, production logs deterrnined the productivity profile. Study of these point data led to a description of the distribution of oil and gas phases in the reservoir so that the continuity of different zones between the wells could be deduced. These techniques were applied to the study of the lower Devonian sandy shale reservoir of Zarzaitine. The sedimentological study guiding the correlation work, with the aid of the conventional static data (logs and cores), led to the establishment of a useful geologic model of the reservoir. Production logs, thanks to the contribution of dynamic elements, permitted corrobora-tion of the model. In particular, the logs confirmed separation, as proposed by the sedimenfological study, of two comparable sandy groups by revealing the continuity of a thin impermeable layer, invisible on conventional logs. INTRODUCTION The heterogeneity of sandstone reservoirs considerably influences the distribution of fluids, as well as their displacement in the reservoir. Rational development of a field and maximum recovery of hydrocarbons are closely tied to an exact and precise knowledge of the intern architecture. We will try to show how it is possible I refine the knowledge of the reservoir by seeking qui different and varied sources of information. Productic geology, the group of techniques which leads to idei concerning reservoir architecture and its geometric descris tion, furnishes the framework of this undertaking. Of these techniques. those used so far are qui varied. Descriptive as well as quantitative, the technique partake as much of classical geology as of reservo science. They include (1) geologic studies of the enti basin, especially a stratigraphic and sedimentologic study of the reservoir member at its outcrop, detail1 observations of cores taken from wells and, finall oriented cores; (2) interpretation of geophysical dat (3) interpretation of electric logs, nuclear and sonic lo and dipmeters: (4) petrophysical study of the reserve on samples taken from wells; (5) reservoir dynamics (stu of the production history and, in particular, interpretati of production logs); and (6) analysis of the fluids a thermodynamic studies. This incomplete list could also include (1) study the migration of the fluids, (2) geochemistry (chemi characterization of the oils), (3) regional hydrodynamii and (4) injection and detection of tracers. If most of these techniques are classic, attention i nevertheless be called to applying two of the techniql in conjunction: the study of the reservoir member its outcrop and the study of dynamic distribution fluid phases in the reservoir through use of product logs, used in the study of the sandy shale reservoirs the lower Devonian of the Fort Polignac Basin, Alge in particular, their application to the study of the 2 zaitine field where they have led to a new and satisfact model of the reservoir will be described. THE ZARZAITlNE FIELD Situated in the interior of the Fort Polignac 8 about 150 kilometers (km) north of the lower Devol outcrop, the Zarzaitine Devonian oil field was discovc On Ian. 28, 19'' (Figs. 1 and l8). It is in the fern a monocline truncated by two perpendicular fault: great throw, with a downthrown section to the north\: Erosion at the top of the structure has caused one of it to disappear. It is a reservoir with a gas cap an m coefficient on the order of 1:5, open to the aql On the northeast, with the oil zone covering an Of 106 sq km and with initial oil reserves of 222 mi

Jan 1, 1967