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By A. L. Barnes, A. M. Rowe

A heat transfer study was made of hot gas injection into oil shale through wells interconnected by vertical fractures. This analysis involved the simultaneous numerical solution of a nonlinear, second-order partial differential equation that describes two-dimensional conduction heat transfer in oil shale and a nonlinear first-order partial differential equation that describes convection heat transfer in the fractures. Three nonlinear, temperature-dependent coefficients were used in this work; they are thermal conductivity, thermal capacity and retorting endothermic heat losses of oil shale. Vertical fractures were considered to be of finite height. Although vertical conduction heat transfer was not considered, an estimate of the error resulting from this limitation was made. The effects of injected gas temperature, injection rate, system geometry, cyclic injection and time upon retorting efficiency were investigated. Results from this study show that the rate of retorting oil shale is a direct function of both injection temperature and rate, and the theoretical producing air-oil ratio:(AOR) is an inverse function of temperature. Retorting rates are constant until "breakthrough" of the 700 F isotherm at the producing well, assuming constant injection parameters. Retorting rates for bounded systems are higher than the analogous unbounded systems and likewise AOR's are less. The use of an alternating injection-soak routine with high injection rates is less efficient than continuous injection at lower rates. These results indicate that injection temperatures on the order of 2000F or greater may give theoretical AOR's in the economic range. INTRODUCTION Over half of the known oil shale reserves are located in the U.S., and most of them lie in the Piceance Creek basin of Western Colorado. The Colorado oil shale outcrops on the edges of the Piceance Creek Basin. At the outcrops the shale beds are relatively thin, from 25 to 50 ft thick. In the center of the basin the oil shale is as great as 2,000 ft thick and is covered with 1,000 ft of overburden. It has been estimated that there are over 1,000 billion bbl of oil in shales having an oil content over 15 gal/ton in this basin. Oil shale does not contain free oil but an organic matter called kerogen. Kerogen yields petroleum hydrocarbons by destructive distillation. It must be heated to approximately 700F, at which temperature it decomposes into shale oil, gases and coke. The U.S. Bureau of Mines and, more recently, oil companies have conducted considerable research on surface retorting methods to economically recover oil from this shale. Another approach to exploit the oil shale deposits, in particular that portion having 1,000 ft of overburden, is to retort the oil shale in place and produce the liquid and gaseous hydrocarbons through wells drilled into the shale. Some research has been done on this approach.l,2 There are several variations to the in situ retorting approach. These variations fall into one of two groups, depending upon the geometry of the system: (1) retorting in a highly fractured or broken up matrix; (2) retorting from single fractures between production and injection wells. The latter is the group studied. Several investigators,3-6 using various assumptions, have studied flow of heat through horizontal systems. The objective of this work was to make a heat transfer study of in situ retorting oil shale by hot gas injection through wells interconnected by single vertical fractures of finite height. The oil shale thermal conductivity, thermal capacity and retorting endothermic heat losses were considered to be functions of temperature. A knowledge of the

Jan 1, 1969

By William P. Blake

This camp is just now startled by the alarming suggestion that unless there shall speedily be an appreciation in the value of silver, and a decrease in the cost of salt, it will be prudent business policy to close the Alice mines and mills until the conditions of production are more favorable. Such an event would be a great blow to the prosperity of Butte. It would throw some hundreds of men out of employment, and it might lead to the adoption of the same policy by other companies, which, like the Alice, have not been able to pay dividends to their shareholders for a long time. The question arises, and becomes emphatic: If, under the present adverse conditions, the mines and mills cannot be made to pay a proper profit, why should they continue to be worked ? The owners mentally ask: Shall we go on exhausting our mines, pouring out a stream of silver for the maintenance of the community, and the support of the rail ways, or shall we husband our reserves, withdraw the miners from our slopes, and wait for more favorable conditions ? This is the impending question, and all concerned dread to meet and answer it. Let us briefly review the situation and forecast, if possible, what the solution of' the problem will be. It must be understood that the discussion does not include, or refer to, the immense copper-producing interests of the camp, which may or may not be upon a very much more satisfactory basis. It will be confined chiefly to the operations of the Alice company, sta tistics of which are at hand, without involving the other silver com panies in the conclusions beyond those inevitable from well-known facts, patent to all. There are at present in Butte and in its vicinity in the principal mills an aggregate of 290 stamps dropping upon silver-ores: Alice,...........80 stamps. Moulton,. .........40 " Lexington,...50 " Silver Bow,.........30 " Blue Bird,..........90 " The Alice mills at present, with their 80 stamps, devour, in round numbers, from 100 to 120 tons a day. The actual amount

Jan 1, 1888

By W. O. Philbrook, H. W. Hosking, N. B. Melcher

A simple and inexpensive mercury-tracer method has been develohed to study rates and Patterns of gas flow in blast furnaces. A Pulse of mercury is injected into the hot blast, and its arrival at the sampling Point is recorded by an electronic circuit that measures resonant absorbtion of ultraviolet light by mercury vapor in the gas aspirated .through the detecting. cell. A rapidly developing interest in blast-furnace technology in recent years has created a strong demand for precise knowledge of the rates and patterns of gas movement through the stock column. Classical fluid-flow theory cannot supply the desired information because the complexity of the blast-furnace situation precludes the accurate determination of many of the parameters required for solution of the equations. In fact some of the terms employed in fluid-flow treatments become almost meaningless under blast-furnace conditions. The void fraction of the stock column, for example, varies widely from place to place and is affected by the segregation of charge materials, attrition of lumps during descent, and channeling. Gas density varies with changes in local pressure, temperature, and composition, while viscosity varies with temperature and composition. Even if mean values for these functions were acceptable, they would be either impossible or extremely difficult to determine with a high degree of accuracy since the value of the mean for all gas properties would depend upon the flow distribution itself. Attempts to study gas movement by the pitot-tube determination of kinetic pressures have met with little acceptance. Reproducibility of results is extremely difficult to achieve in a situation where alignment of the tube orifice with respect to the flow direction in tortuous channels cannot be guaranteed. Because of these difficulties it would appear that progress can be achieved only with a direct method of measuring gas velocities and determining the shape of flow paths through the stock. The establishment of such a method is described in this paper. SELECTION OF METHOD Direct measurement suggests the use of a tracer by means of which the progress of a "parcel" of gas can be followed through the furnace. Several requirements must be met before any selected material can be considered a suitable tracer. First of all, it must be a substance not normally present in blastfurnace gas or dust; otherwise its presence in a gas sample will have little significance. It should be volatile at temperatures normally existing within the furnace, to ensure that it will travel with the gas, as a gas. It should possess special properties enabling its presence in the gas to be detected readily, and it should not undergo exchange reactions with any material normally present within the furnace, including refractories and coke as well as all components of the metal and slag. Radioactive materials naturally are considered because their radioactivity renders them susceptible to detection. However, of the many radioactive materials available, almost all are eliminated from final consideration by their unsuitability in terms of other properties. Radioactive silicon, carbon, calcium, phosphorus, and many others have been considered and discarded, either because they are not volatile over the whole range of significant temperatures, or because they could be expected to undergo exchange reactions with burden or refractory materials. Others which might be suitable in terms of these properties are eliminated because of a low activity, short half life, or the necessity for fragile counting apparatus. Of the many elements available in radioactive form, perhaps radon is the only one suitable for blast-furnace gas-flow studies. This has been used in several investigations1-4 with considerable success. The use of radiotracers has certain inherent disadvantages. One is the cost. An appreciable sum must be allowed for materials each time a test is made. Also, special methods of handling must be employed, and very often the progress of an investigation must be governed by the availability of isotopes and the delivery arrangements that can be made for them. An advantage is immediately gained if the tracer material can be a substance which can

Jan 1, 1960

By F. W. Jessen, James N. Howell

The accumulation of paraffin deposits in tubular goods has been recognized as a major production problem since the inception of the petroleum industry. This problem is not limited to any particular geographical area nor is it limited to a specific type of crude oil.' Generally speaking, "paraffin" deposition pertains to the deposition of any predominately organic material in flow lines, and possibly even at the sand face, which would hamper the production of oil. In some fields, a continuous effort is required to remove deposits of paraffin and in order to accomplish this, many unique methods have been devised. The best solution to this problem, however, is to prevent the formation of such deposits. One method which has been tried in a number of fields is the use of plastic pipe. The purpose of this investigation is to compare the relative effectiveness of several plastic materials to aid in the reduction or prevention of paraffin accumulations in surface flow lines. COMPOSITlON OF PARAFFIN DEPOSITS By definition, paraffin deposits are those materials which are insoluble in crude oil at the prevailing producing conditions of temperature and pressure. Such deposits1 s usually consist of small particles of petroleum wax intermixed with resins, asphaltic material, and crude oil. They may also contain a variety of foreign materials such as sand, silt, water, various metal oxides, sulfates and carbonates of iron. barium, and calcium. The petroleum waxes deposited in flow strings usually consist of both a "hard" and a "soft" wax fraction. These waxes are largely aliphatic hydrocarbons with smaller amounts of aromatic and naphthenic compounds. Nathan' has classified the hard and soft wax fractions. The aliphatic hydrocarbons present are those of high molecular weight with high melting points. Reistle3 pointed out that these high molecular weight compounds first separate from the oil due to a sharp decrease in solubility as the melting point increases. The identification of the resins and asphaltic materials rests, at present, on an arbitrary solubility procedure. Under certain conditions, materials which are insoluble in pentane (ASTM D-893) are defined as resins and asphalts. Subgrouping of these materials is made on decreasing solubility in benzene and carbon disul-fide. Shock' found some correlation be-tween the solvent response and the pentane insoluble content of paraftins: higher pentane insoluble fractions are less soluble in any of the commonly used commercial solvents. PARAFFIN CONTROL METHODS The methods used in oil fields to prevent and remove paraffin accumulations can be grouped into four general classes: (1) operative methods, (2) physical methods, (3) chemical methods, and (4) combination of any of these. Operative methods attempt to prevent the formation of paraffin deposits while the other methods are concerned primarily with the removal of these deposits. Plastic coated pipe has been used for a number of years to prevent cor- rosion in wells, and in manv instances paraffin deposits have -been greatly reduced. Field observations have indicated that plastic coated pipe not only reduced paraffin accumulation but in some cases eliminated deposition completely; however, data are needed to demonstrate the relative effectiveness of plastic materials. Deposition Apparatus The pipe used to determine the effect of velocity on rates of deposition was %- and 2-in. nominal diameter, and 5 ft in length. Steel, butyrate, rigid PVC, kralastic resin-type plastic pipes, epoxy coated pipe, PVC lined glass fiber pipe, and aluminum pipe were tested. Steel pipe was used as a control. Fig. 1 is a schematic diagram of the apparatus showing the relative position of the separate units making up the equipment. In order to facilitate the installation and removal of the test pipes in the apparatus, O-ring seals capable of sustaining pressures of 50 psi were provided at each end. Test pipes were submerged in a cold water bath maintained at or below room temperature by circulating water through copper cooling coils packed in ice. A hot water bath equipped with immersion-type heaters, stirrers, and a thermoregulator was used to maintain the temperature of the oil prior to introduction into the piping manifold. The capacity of the oil reservoir was 30 gal. A 33-gal/min centrifugal pump, capable of producing turbulent flow velocities in the test pipes, was used to circulate the oil through the system when using %-in. pipe; and a 70-galjmin centrifugal pump was used in later tests using 2-in. pipe. A by-pass arrangement made it pos-

By Howard I. Smith

POTASH is of prime importance as a plant food and is also widely used in industry. The term "potash was applied to a crude pearlash obtained by evaporating, in iron pots, solutions leached from plant ashes. Later it included caustic potash obtained by treating pot ashes with lime, and now it is applied generally to various compounds of potassium used by agriculture and industry. Herein it applies to the theoretical equivalent in potassium oxide (K20)--a compound never found in nature or manufactured in commerce but generally used as a common denominator for comparison of all potassium compounds. Potash was made from plant ashes at an early date, but potassium in mineral form was not noted until 1797, when it was identified in leucite.3 The importance to plant life of potash in the soil was first recognized by von Liebig3 and his published reference thereto appeared in 1840. In 1843, potash was discovered in the brine of a well drilled for salt near Stassfurt. HISTORY OF THE AMERICAN POTASH INDUSTRY Among the colonists reaching Virginia in 1608 were men from Poland skilled in making potash from wood ashes19 and records show that the production of potash was begun in other colonies also, soon after their establishment. The American product entered the trade in 1635, and at various times since that date the production of potash for industry has been subsidized by the Government or protected by tariffs. The production of potash from wood ashes reached its peak in 1825. Beginning in 1823, a cheaper product, sodium carbonate, made by the Leblanc process, was substituted for much of the potash used in industry. Production rapidly declined after the Civil War, when the forests most productive of potash had become depleted and labor had become

Jan 1, 1949

By Lyman Johnson

Single crystals qf copper in "single slip" orientatiorzs have been deformed in compression. During defortnation all of the independent deformation parameters have been measured. These parameters consist of thefive strain components and three components descrihing the lattice rotation. By a finite strain analysis these pararmeters , forrming a deformation gradient martrix, are related to the amounts of slip on each of the twelve slip systems. The results show that the amount of secondary slip is about equal to the amount of primary slip. This is an order of magnitude larger than has been believed previoutsly. ACCORDING to early theory and experiments, when a single crystal of a fcc metal is deformed in tension or compression it should deform by slip on only one slip system until the stress axis reaches a symmetrical orientation.' However. the observation of a large increase in the secondary dislocation density during ..single slip" makes it clear that some slip does occur on secondary systems. Knowledge of the amount and distribution of this secondary slip is essential to a complete understanding of the mechanisms of single-crystal deformation. Ahlers and Haasen 2 and Mitchell and Thornton1 have tried to detect the amount of secondary slip in single crystals of silver and copper, respectively. Each simultaneously measured the angle A, between the tensile axis and the primary slip direction and the length 1 of a gage section of the specimen after incremental amounts of deformation in tension. The measured A, was then compared with the theoretical single slip angle hp. given by sin Ap = j sin . hO where ?o was the initial angle between the tensile axis and the primary slip direction and lo was the initial gage length. In both sets of experiments a small but systematic difference between ?e and ?p was found. This difference must be due to the occurrence of secondary slip. However, as Mitchell and Thornton1 pointed out. nothing quantitative can be said about the amount and distribution of this secondary slip from the measurements that they made. The reason that no quantitative conclusions could be made is because no unique solution for the distribution of slip on the twelve fcc slip systems can be determined from only two measured deformation parameters such as A and 1. There are, in fact, eight independent macroscopic deformation parameters that can be measured when a single crystal undergoes a homogeneous deformation. Physically these can be thought of as the five finite strain components and the three angles describing the crystal lattice rotation. All eight of these parameters were measured by Taylor4,5 for aluminum deformed in tension and compression. At that time the concern was to show that slip occurs on {111 (110) systems in fcc metals, and the mathematics were not available to determine what slip distributions were compatible with the measurements. In this paper the mathematics6,7 are developed that allow the slip distribution to be determined from these measurable macroscopic deformation parameters. The analysis is applied to the measurements of the strain and lattice rotation of copper single crystals deformed in compression. The results show that the amount of secondary slip is an order of magnitude larger than had previously been thought. CRYSTALLOGRAPHIC DESCRIPTION OF A HOMOGENEOUS DEFORMATION The deformation of a solid body can be represented by a transformation matrix F that transforms the un-deformed state into the deformed state. Consider a vector X connecting two material points in the unde-formed material and the vector x connecting the same two material points after deformation, where both vectors are referred to the same set of Cartesian axes. The final vector x is related to the initial vector X by the equation: X = FS. [2] Eq. [2] can be considered as the equation defining F, which is called the deformation gradient matrix. Its components are: If the deformation is homogeneous, the transformation is linear and the components of F are constants. Using subscript notation, if P is the unit vector in the initial direction of a material line, the components of the unit vector p in the direction of the same material line after deformation are given by:

Jan 1, 1970

By R. F. Mehl, C. E. Birchenall

R. E. Hoffman and D. Turnbull—The authors have presented evidence which they have interpreted as indicating that the rate of self diffusion is not intrinsically more rapid at grain boundaries than within the grain. Grain-size effects which apparently exist are attributed rather to impurities concentrated at the grain boundaries. In view of our own experiments and the existing evidence, we believe that the support for this hypothesis is not convincing. We have in progress an investigation in which the rate of self diffusion of silver is being measured over an extended temperature range in both single-crystal and polycrystalline specimens. The results of the single-crystal experiments and some preliminary data on fine-grained polycrystalline specimens have already been reported:' and it is anticipated that a complete report will be published in the near future. The self-diffusion coefficient of large-grained polycrystalline silver (1 grain per sq mm) has previously been measured by Johnson" between 730" and 940°C. The diffusion coefficients which we have measured in single crystals (210 plane normal to diffusion direction) agree within experimental error with values calculated from an extrapolation of Johnson's curve down to temperatures as low as 500 °C. However, it has been demonstrated that the overall self-diffusion rate in fine-grained polycrystalline specimens (initial grain size of 0.003 cm) becomes measurably larger than the overall rate in a single crystal at a temperature of 600°C, and the discrepancy between the two rates becomes greater as the temperature is further decreased. In fact, it has been possible to obtain satisfactory penetration curves for polycrystalline specimens using the sectioning technique at temperatures as low as 400°C. At this temperature, the penetration is 50 to 100 times greater in the polycrystalline specimens than in a single crystal. Fisher" has developed an analysis whereby the ratio of the rate of the unit diffusion process at the grain boundary to the corresponding rate within the grain can be calculated from the penetration curves and an assumption as to the width of a grain boundary. This analysis applied to our data indicates that the unit process at the grain boundary is faster by a factor of 10' at 475°C when the grain boundary width is taken to be 5. The silver used in most of these experiments was obtained from the Handy and Harmon Co. and listed as 99.97 pct pure. Preliminary experiments on 99.999 pct silver from the Jarrel-Asch Co. indicate a grain-size effect of the same order of magnitude as in the less pure silver. Nominally, these purities are as good, at least, as that of the carbonyl iron used by the authors, but of course if an impurity effect does exist its magnitude might be very dependent upon the nature of both major and minor constituents. The authors have cited the work of other investigators who have found no grain-size effects. Neither Steigman, Shockley and Nix" nor Maier and Nelson8 were able to correlate self-diffusion coefficients of copper with grain size. However, all their measurements were performed at or above 750°C; and on the basis of our work with silver, no grain-size effect would be expected at temperatures above about 0.7 of the absolute melting temperature unless the grain size were exceedingly small. Likewise, in the investigation of the self diffusion of lead by Seith and Keil,14 the lowest temperature at which the diffusion coefficient was measured in polycrystalline specimens was 207°C, which is still sufficiently high so that the lack of a grain-size effect is not surprising. Finally, in those experiments on iron from which they concluded that there was no grain size effect, Drs. Birchenall and Mehl seem to have no information as to the actual grain sizes immediately prior to and following the diffusion anneal. Without this information, we believe that their own experiments offer little support for their hypothesis. F. S. Buffington, I. D. Bakalar, and M. Cohen—The results given in this paper agree in order of magnitude with those tentatively reported by us.27 However, significant differences exist in the two sets of data, and it may be well to make an explicit comparison. The diffusion studies at M.I.T. were conducted on somewhat higher purity iron (99.98 pct Fe) than the grades used by the authors, but this is undoubtedly not the answer. Fig. 4 shows the diffusion results of both laboratories for the gamma phase, omitting the authors' data on the commercial steels, while fig. 5 presents a similar comparison for the alpha phase. The divergence is much more marked in the latter case than in the former. In connection with the M.I.T. determinations, all of the runs in the gamma range and those above 800 °C in the alpha range were conducted with specimens having a relatively thick (0.002 cm) electrodeposit of radioactive iron. This practice minimizes any possible error due to extraneous diffusion that may occur during the heating to and cooling from the operating temperature. An exact solution of Fick's law for these boundary conditions was used in calculating the diffusion coefficients. At a later time, three runs were made below 800°C, using very thin electrodeposits similar to those of the authors, and the points fell considerably below the values expected from the extrapolation of the results based on the specimens with the thick deposits (compare dash-dot line in fig. 5). However, in the runs with the thin deposits, deviations of 100 pct were found between the individual specimens, whereas the maximum deviation with the thick deposits was less than 25 pct. Accordingly, it is not known at the moment whether the M.I.T. points below 800 °C should be given as much weight as those above 800°C. If this were done, the frequency factor would be of the order of 400 cm2 per sec, which is quite high. In other metals, the frequency factor for self diffusion lies between about 0.1 and 10 cm2 per sec. As the points below

Jan 1, 1951

By Robert H. Richards

THE Institute of Mining Engineers has shown so much interest in the educational problem of profitably combining theory and practice, that it seems especially appropriate to lay before its members the methods and aims of the mining laboratory of which I have charge, and in which one form of combination of hand with head work is now being tried. If anything may be contributed toward the solution of this problem by the discussion which follows, my purpose mill be attained. Whether it was wise or not to establish a mining school so far from the principal mining centres, does not now enter into the question. Given, a mining school already begun, how shall it be made most efficient in developing engineers who are trained to think for themselves as well as versed in the works of others ? This is the question with which we have had to deal. In considering the bearing of this laboratory work upon the students' preparation, it will be convenient to take it up under five different heads: 1. The methods and aims of the laboratory. 2. The advantage to students of having a part, at least, of their practical work in the curriculum of their school. 3. The advantage to be derived by mine; and works. 4. Degree of accuracy which may be attained in working ores on a small scale. 5. Reslts of work in the laboratory. 1. The Methods and Aims of the Laboratory.—During the May meeting of 1873, held in Boston, I had the privilege of reading before you a paper stating the plan; and aims of this laboratory. Since that time me have been constantly following out those plans, and are more than ever convineed that me are working in the right direction. We do not feel that the time we have spent has been in any sense thrown away. Perhaps the aims of the laboratory can be most clearly shown by illustration. Many young engineers have school thinking that they know everything. They go to the works, and expect to teach the superintendent something and the men a good deal, regardless of the fact that it is this spirit that has prejudiced workmen against schoolmen. They are often more trouble than they

Jan 1, 1879

By J. A. Clum, R. W. Heins, T. D. Tiemann

The use of Na-montmorillonite clay hinders (Western Bentonite) in the pelletizing of iron ore concentrates is well established as is the idea that alternative binders must be found. 1-6 This note summarizes work done7 in evaluating a Wisconsin montmorillonite clay binder. The clay occurs in irregualr beds overlying the Prairie du Chien Dolomite and the St. Peters Sandstone near Hersey, St. Croix County. The raw Wisconsin clay contained 65% quartz and 35% clay minerals. The Na20to CaO ratio was 0.234. Suspension viscosity tests of the raw clay gave results only slightly better than water alone, even after treatment with activator materials. Sedimentation treatment reduced the quartz in the decantate to 5% after 240 min (four hours). Twenty minutes of sedimentation produced a decantate with 27.5% quartz which was found as effective as the 5% quartz decantate in pelletizing behavior. The 20 min decantate was used in subsequent tests. The decantate was filtered and dried at 110°(230°F). The minus 200 mesh portion of this was added directly to the magnetite concentrate. Pellets were made in a laboratory sized disc pelletizer from pastes consisting of ore concentrate, balling water (9%) and binder (clay, or clay + resins, or resins). The pastes were premixed in a Waring blender. The binders were: (1) 1% of a commercially used Western Bentonite; (2) 1 % or 3% of the Wisconsin clay (raw, or 20 min decantate); (3) 20 min decantate washed with activator solutions, (to exchange Na for Ca in the clay); (4) decantate with activator added in the balling water; (5) decantate with organic resins; (6) organic resins. Measurements of the 0.46 m (18 in.) Green Drop Number, the Dry Strength and the Fired Strength (fired at 1260°C (2300°F) for 30 min) were made. The dry and fired compressive strengths were determined on an Instron testing machine using a C-load cell and a F-load cell, respectively. The cross-head speed was 0.004 m/sec (0.1 in./min) for both. The results of each measurement were averaged for 15 pellets. A summary of those results is presented in [Table 1]. More detailed results and procedures are presented in another report.7 In addition to the effects on pellet strength due to various binders the effect of varying magnetite concentrate characteristics is noted in [Table l]. There, a few comparative data are shown for Cornwall, PA Magnetite, which has a generally liner particle size than the Black River Falls magnetite which was used for most of the tests.

Jan 1, 1979

By B. F. Oliver, C. W. Haworth

Pure tin and Sn-0.5pct Pb ingots have been frozen unidirectionally from the base. For quiescent melts that were initially undercooled, a transition from lower eqlciaxed structure to an upper columnar structure is found in the alloy ingots. Columnar to equi-axed back to columnar transitions are observed in superheated alloy ingots, but no such equiaxed band is observed impure tin. The reproducible equiaxed band is associated with a thermal undercooling followed by a recalescence. This undercooling is <5"C, whereas the critical (maximum obtainable) under-cooling for both the pure tin and the alloys used is -20°C. A similar undercooling is observed at the same position in the pure tin ingots, although in this case no clear transition in structure can be seen. The structure of the pure tin ingots is either entirely columnar or mixed columnar-equiaxed. A consideration of the detailed thermal history of the ingots indicates that the ingot macrostructures are determined by the occurrence of a local therlnal undercooling in conjunction with nuclei multiplication and transport mechanisrris. GENERALLY it is found that a pure metal ingot solidifies so as to produce an entirely columnar structure. Frequently an alloy ingot is found to have a columnar outer zone and an equiaxed central portion. Early systematic work to examine the factors controlling the formation of the equiaxed structure was reported by Northcott&apos; who showed that, for copper alloys frozen unidirectionally with a given ingot practice, the alloying element influenced the length of columnar crystals and the extent of the equiaxed structure. Northcott showed that alloys with a wider freezing range more readily produced the equiaxed structure. The nucleation process can be important in producing equiaxed structures; frequently an alloy which readily solidifies with an entirely columnar structure will produce an entirely equiaxed structure when a nucleating agent is added to the melt.&apos; The formation of the equiaxed structure was attributed by Winegard and chalmers3 to the presence of constitutional supercooling; that is, a region of liquid in front of the growing solid could have a temperature below its equilibrium liquidus temperature. Thus, with a small enough temperature gradient in the liquid, it was suggested that the presence of constitutional supercooling may be sufficient to bring about the nuclea-tion necessary for the formation of an equiaxed structure. Although this explanation is plausible, and may be relevant in many ingots, Walker has described an experiment&apos; for which constitutional supercooling seems to be an unlikely cause of nucleation. A Ni-20 pct Cu alloy, repeatedly undercooled more than 50"C, was crystallized and found to show the typical colum-nar-equiaxed structure. The separation between the liquidus and the solidus for the alloy is 40°C. Thus, in this experiment the nucleation required for the formation of the equiaxed structure must have come about in some other way than by the nucleation catalysis constitutional supercooling hypothesis. Chalmers has suggested more recently5 that nuclei (in a typical ingot) are present immediately after pouring and are prevented from redissolving by the constitutional supercooling effect. More recently Uhlman, Seward, Jackson, and ~unt&apos; have shown direct evidence using ice and organic materials that freeze dendritically that the "remelt mechanism" may be an extremely effective crystal multiplication process during the freezing of ingots under conditions involving dendritic growth. JSlia" experimentally demonstrated the detachment of dendrite arms. chernov14 has analyzed the dendrite arm detachment process as a coarsening phenomena driven by the minimization of interphase area. Katta-mis and ~lemings" working with undercooled steel melts give evidence supporting this mechanism. Mechanisms of dendrite arm detachment such as those assisted by convection are believed to be the origin of the macrostructures obtained in this study. This study makes no attempt to distinguish the relative contributions of these mechanisms. The object of the present work was to obtain accurate temperature measurements during the solidification of an ingot and to correlate these measurements with the formation of equiaxed grains in the resulting ingot structures. Similar previous work is very limited. The measurements carried out by Northcott are neither sufficiently extensive nor sufficiently accurate for any interpretation. Plaskett and winegard7 carried out experiments on A1-Mg alloys in which they observed values of the temperature gradient, G, in the liquid and rate of freezing, R (for a given alloy solute content Co), at the transition from a columnar to an equiaxed structure. They reported that equiaxed crystals were produced at values of G/G approximately proportional to the solidus composition. Similar experiments using Pb-Sn alloys carried out by £111011" showed a linear relation between G/R and the solidus composition. However, the thermocouples were in the mold wall rather than in the melt and, in one case, ingot surfaces were examined. There is ambiguity in the meaning of the values of G and R measured in all these experiments. APPARATUS AND EXPERIMENTAL PROCEDURE Alloys were prepared by induction melting 99.999 pct Sn and 99.999 pct Pb to form a Sn-0.5 wt pct Pb alloy in air in a graphite crucible and casting into a cylindrical graphite mold 6 in. long, 1 in. in diarn , and with a & in. wall thickness. This mold was mounted on a copper base through which cooling water could be

Jan 1, 1968

By T. W. Watson, D. R. Flynn

,Measurements are reported for the thermal conductivity of four heat-resistant alloys which were measured at the National Bureau of Standards. Data are given for two samples of AISI Type 316 stainless steel covering a combined temperature range from -150° to + 800°C. The thermal conductivities of three samples of AISI Type 347 were measured over the temperature range from -150° to +150C. Thermal conductivity values are given for Carpenter 20 stainless steel from 100" to 800" C. Data are given for Inconel 702, in both the solution-annealed and the age-hardened condition, over the temperature range from -150" to +800C. SINCE 1958 the National Bureau of Standards, at the request of other government agencies or private laboratories, has carried out measurements of the thermal conductivity of a number of metals and alloys. This paper presents available thermal conductivity data obtained in this way on samples of four heat-resistant alloys. The data presented for Carpenter 20* stainless steel are, to the best of our knowledge, the only thermal conductivity values which have been reported for this alloy to date. Although thermal conductivity values for AISI stainless steels 316 and 347 have been reported by previous investigators, the present data are believed to be of particular interest because, for each alloy, the effect on thermal conductivity of small changes in chemical composition can be observed. The data on Inconel 702&apos; are of interest, not only for

Jan 1, 1969

By Carlos A. Aranda

The Smelting and Refining Department of Cerro de Pasco Corporation is located at La Oroya at an altitude of 3,720 meters (12,205 feet) in the Peruvian Andes. Producing lead, zinc and copper as well as twelve by-product metals and chemicals, the smelter is among the world&apos;s most complex. With the intake of high-bismuth ores in 1934, electrolytic lead refining by a modified Betts process was piloted and the plant went into commercial production in 1937 at a nominal capacity of 100 M.T. per day. After expansions in 1950 and 1963, nominal capacity has increased to 250 M.T. per day. Anodes spaced at 10.8 cm centre to centre and starting sheets are both set into the cells by overhead cranes. The asphalt-lined concrete cells are arranged in a Walker side-by-side configuration, and the electrolyte, circulating at 13 l/min./cell, is a solution of locally-produced hydrofluosilicic acid and lead fluosilicate. The corrosion cycle is limited to four days due to high impurity content of the bullion, which has successfully been treated at contents of up to 9% impurities. The cathodes are melted, drossed, and cast into blocks and pigs assaying 99.997 + % lead. The anodes with the blanket of slime adhering, are washed with electrolyte and condensate makeup water to remove the concentrated lead fluosilicate entrapped in the slimes. The slimes are then removed with high-pressure water sprays, centrifuged and sent to another plant for recovery of silver, gold, bismuth, selenium, tellurium, and antimony.

Jan 1, 1970

By E. P. Pfleide, L. W. Gibbs. J. R. Gross

A method using computer techniques is described for the comparative evaluation of truck performance over any given haul road using readily obtainable manufacturers&apos; data. An additional computer program is utilized to calculate individual cycle times for each truck and shovel combination, fleet requirements for any desired production rate, and to estimate comparative costs. The introduction of a large number of variables into the program permits management to determine the critical system factors having the greatest bearing on costs. Thus, the method described can be used not only for analysis of needs for a new surface mine but for cost improvement in existing mines where changes in truck and shovel operations are contemplated. The systems analysis approach to the solution of problems in the mining industry is gaining in industry acceptance. This is a logical development in view of the fact that a mine constitutes one of the most dynamic systems of production. In contrast with a manufacturing plant, situated in a location selected through choice and utilizing a regulated source of quality controlled raw materials, the miner must go where the ore is and he is faced with ever changing physical conditions. He is subjected to the vagaries of nature, and he can never mine the same ore twice. What is systems engineering? There seems to be no concise and universally accepted definition of the term and its meaning is still fairly local. It deals largely with trade-offs of subsystem characteristics to achieve some desired result in an overall system. This concept of suboptimization can be explained by an example. If the objective of a mining company is to produce a certain quality ore at minimum cost, the optimum operation is not achieved by minimizing all costs, since all phases of mining are interrelated. Reduction of blasting costs might well increase loading, hauling, and crushing costs out of proportion to the resulting saving in explosives. Hence tradeoffs are necessary. It is evident then that an optimum system is achieved through a blending of suboptimal components which taken together yield the desired result. OBJECTIVE For our mathematical model we will assume the existence of a hypothetical new organization called Taconite Mining Co. (TMC). TMC has made an analysis of their orebody, their proposed operation, and

Jan 1, 1968

By C. E. Wood

THE Blast Furnace Studies Section, Metallurgical Division, Bureau of Mines, has been working for several years on the mechanism of desulphurization of iron and steel by slags. The usual assumption that desulphurization takes place by diffusion of FeS from metal into slag and subsequent reaction of this FeS with CaO to produce CaS has seemed to us inconsistent with a number of experimental results we have obtained. We undertook, for example, to determine the proportion of sulphur in a slag present as FeS. An entirely satisfactory method of doing this has not yet been evolved. The results of extraction with metallic antimony led to an interesting conclusion, however. FeS is readily soluble in metallic antimony, either physically or by chemical reaction. On the other hand, CaS was found to be insoluble. Hence it would appear that by rapid extraction of the slag with antimony we might expect to determine the distribution of sulphur between iron and calcium. The results showed that much of the sulphur was present as FeS. In some instances the extraction of sulphur as FeS was almost quantitative. For example, in a slag containing 3.8 grams Fe and 3.7 grams S, extraction removed 1.18 grams S and 2.12 grams Fe. If all the iron present in the antimony had been FeS, 1.21 grams S would have been extracted. In another slag with 8.6 grams Fe and 0.06 gram S present, 0.14 gram Fe and 0.08 gram S were extracted. This was obviously extraction of sulphur as FeS within the analytical error and showed that FeS was present either in solution or as a dispersion. Attempts to determine the solubility of FeS and CaS in slag by quenching and ultramicroscopic investigation have indicated that the solubility of FeS is very low, and that reactions in the slag are probably not to be considered as homogeneous. A more detailed report on these theoretical considerations will be made at a later date.

Jan 1, 1939

By S. M. Runke, R. G. Meara, O&apos

The Bureau of Mines has been charged by Congress to investigate processes for the production of alumina from low-grade bauxite, alunite, and clay. As one part of the program, an investigation of the application of ore-dressing methods to improve the grade of high-silica bauxite is in progress at the Mississippi Valley Experiment Station at Rolla, Mo. This paper summarizes data obtained so far and presents detailcd results of tests on four typical samples. Mineralogy of Batjxite The name bauxite originally was used to designate the dihydrous aluminum oxide (A1203.2HzO). The designation has been retained, although the existence of a specific mineral of such composition has been disproved. The term is now applied to ores of aluminum consisting of various mixtures of the minerals gibbsite (AlzOa.3H20), diaspore (A120a.H20), and boehmite (Alr-03.H20). The predominant hydrous aluminum oxide in most American bauxite, however, is gibbsite. In some instances bauxite may be amorphous mixtures of the hydrous aluminum oxides that approximate the composition of dihydrous aluminum oxide (A1203.2Hz0). The proposed name for this material is cliachite. Gibbsite and boehmite, the trihydrate and monohydrate, are soluble in a solution of sodium hydroxide at elevated temperature and pressure, whereas diaspore is practically insoluble. The solubility of these two minerals is the basis of the Bayer process of alumina extraction. All bauxites contain certain impurities, the commonest of which, in the order of their importance, are: silica, principally as a constituent of kaolinite, and to a lesser extent as quartz; iron, as hematite, limonite, and siderite; and titanium, as ilmenite, rutile and leucoxene. Minor impurities are zircon, cobalt and nickel. Bauxite is produced commercially in Arkansas, Alabama, Mississippi, Georgia and Tennessee, but the most important deposits in the United States are in Arkansas, in the vicinity of Little Rock. History of Batjxite Beneficiatjon The literature on bauxite beneficiation is limited, but the reports of Gandrud and DeVaneyl and Clemmer, Clemmons, and Stacy2 show the possibilities of flotation as a means of beneficiating bauxite. Their work has also developed reagent combinations that are satisfactory for flotation of gibbsite.

Jan 1, 1944

By R. G. O’Meara, S. M. Runke

THE Bureau of Mines has been charged by Congress to investigate processes for the production of alumina from low-grade bauxite, alunite, and clay. As one part of the program, an investigation of the application of ore-dressing methods to improve the grade of high-silica bauxite is in progress at the Mississippi Valley Experiment Station at Rolla, Mo. This paper summarizes data obtained so far and presents detailed results of tests on four typical samples. MINERALOGY OF BAUXITE The name bauxite originally was used to designate the dihydrous aluminum oxide (A1203.2H20). The designation has been retained, although the existence of a specific mineral of such composition has been disproved. The term is now applied to ores of aluminum consisting of various mixtures of the minerals gibbsite (A1203.3H20), diaspore (A1203.H20), and boehmite (A1203.H20). The predominant hydrous aluminum oxide in most American bauxite, however, is gibbsite. In some instances bauxite may be amorphous mixtures of the hydrous aluminum oxides that approximate the composition of dihydrous aluminum oxide (A1203.2H20). The proposed name for this material is cliachite. Gibbsite and boehmite, the trihydrate and monohydrate, are soluble in a solution of sodium hydroxide at elevated temperature and pressure, whereas diaspore is practically insoluble. The solubility of these two minerals is the basis of the Bayer process of alumina extraction. All bauxites contain certain impurities, the commonest of which, in the order of their importance, are: silica, principally as a constituent of kaolinite, and to a lesser extent as quartz; iron, as hematite, limonite, and siderite; and titanium, as ilmenite, rutile and leucoxene. Minor impurities are zircon, cobalt and nickel. Bauxite is produced commercially in Arkansas, Alabama, Mississippi, Georgia and Tennessee, but the most important deposits in the United States are in Arkansas, in the vicinity of Little Rock. HISTORY OF BAUXITE BENEFICIATION The literature on bauxite beneficiation is limited, but the reports of Gandrud and DeVaney1 and Clemmer, Clemmons, and Stacy2 show the possibilities of flotation as a means of beneficiating bauxite. Their work has also developed reagent

Jan 1, 1944

By Harold Cook

Discussion of the paper of HAROLD EARLE COOK, presented at the New York meeting, February, 1916, and printed in Bulletin No. 110, February, 1916, pp. 375 to 400. ALBERT SAUVEUR, Cambridge, Mass.-I think we must all agree with Lieutenant-Commander Cook when he says that there is a great deal of room for improvement in the annealing of steel castings and that better results would be attained if the annealing were conducted in closer agreement with scientific requirements. Whether even a carefully annealed steel casting can ever be made the equal of a steel forging of good quality is still a debatable question. Nevertheless, we all realize that very greatly improved results can be attained by careful annealing. Lieutenant-Commander Cook refers to some requirements calling for annealing steel castings above the Ac1 point. He is undoubtedly right where he says that this should be the Ac3 point. Take, for example, a steel casting containing, say, 0.35 per cent. of carbon, having a very coarse structure made up of coarsely crystalline ferrite. If this is heated just above the Ac1 point the ferrite remains, of course, just as it was before, while the pearlite is converted into a solid solution, austenite. Upon cooling, all this austenite is again converted into pearlite, or sorbite, while the coarse structure of the ferrite remains unchanged and the annealing has accomplished very little. It is therefore surprising that the requirement of annealing above the Ac1 point should appear, in these specifications.

Jan 5, 1916

By M. Albertson

The purposes of this statement are to define a problem that exists in regard to the estimation of developed petroleum reserves, to analyze the problem in an abstract manner, and to discuss it as an introduction to certain papers that follow. The problem is to devise and develop a suitable procedure to permit more accurate estimates of developed petroleum reserves. Part of the problem is to make such estimates available earlier in the life of any particular pool. The problem of securing more accurate estimates of developed petroleum reserves existed prior to curtailment of production. With curtailment, however, the problem became acute, some of the more prominent reasons being as follows: 1. The standard method of estimation depended on production-decline curves. This method is inapplicable while curtailment prevails and available methods arc insufficient. 2. The retarding influence imposed by wide open flow conditions upon overdevelopment is absent. Great losses of capital by overdevelopment can now occur before realization of the true situation occurs, or before effective steps can be taken to stop such wastage. This increases the need for early, accurate estimates. 3. Above-ground stocks have diminished and the equivalent of such supply tends more and more to be retained underground in the natural reservoirs. It becomes increasingly necessary to know accurately the amount of these stocks. To direct attention to an additional point of different nature: improved accuracy of reserve estimation can be obtained only by closer scrutiny of the factors that determine recovery. This examination and the resulting efforts to measure the effect of these factors in terms of ultimate recovery must tend to improve ultimate recovery. The statements regarding the acute nature of the problem also indicate to some extent the importance of the problem and the necessity of finding a solution. Developed reserves of the industry, and of individual opera-tors, are one of the great factors that properly should determine explora-

Jan 1, 1936

By D. I. Cameron

A graphical method has been developed and tested for separating the effects of grain boundary and lattice diffusion in polycrystalline materials. The method is based on the assumptions that for unidirectional diffusion from a plane source of radioactive material, the penetration of activity far into the specimen from the source is due solely to grain-boundary effects, and 2) pure grain-boundary penetration is described by a linear plot of log activity vs the perpendicular distance x from the source. The former is based on the fact that at any temperature the grain-boundary diffusion coefficient is always very large relative to the lattice diffusion coefficient; and the latter is based on the derivation of Fisher.1 Using these criteria along with appropriate penetration data (in this case, data for the diffusion of Cb95 in pressed and sintered UO2) one first plots the data as log activity vs x2 and as log activity vs x, as shown by curves 1 and 2, respectively, in Fig. 1. A tangent line to curve 2 for large x (curve 3) is then transferred to the x2 plot as curve 4. The subtraction of curve 4 from curve 1 yields curve 5 which represents only lattice diffusion and may therefore be related to the diffusion coefficient by using the appropriate solution to Fick&apos;s second law. It should be noted that the method has inherent inaccuracies for small and large values of x2 and only the subtraction at intermediate values can be used. For the illustrated specimen the calculated diffusion coefficient is 3.4 X 10-11 sq cm per sec at 1445°C while data using a single crystal of UO2 at the same temperature yielded a value of 2.9 x 10-11 sq cm per sec.2 The same method of subtracting grain-boundary diffusion effects to obtain lattice diffusion coefficients has been successfully used to determine self-diffusion coefficients of Th230 in polycrystal- line thoria.

Jan 1, 1962

By M. Albertson

The purposes of this statement are to define a problem that exists in regard to the estimation of developed petroleum reserves, to analyze the problem in an abstract manner, and to discuss it as an introduction to certain papers that follow. The problem is to devise and develop a suitable procedure to permit more accurate estimates of developed petroleum reserves. Part of the problem is to make such estimates available earlier in the life of any particular pool. The problem of securing more accurate estimates of developed petroleum reserves existed prior to curtailment of production. With curtailment, however, the problem became acute, some of the more prominent reasons being as follows: 1. The standard method of estimation depended on production-decline curves. This method is inapplicable while curtailment prevails and available methods arc insufficient. 2. The retarding influence imposed by wide open flow conditions upon overdevelopment is absent. Great losses of capital by overdevelopment can now occur before realization of the true situation occurs, or before effective steps can be taken to stop such wastage. This increases the need for early, accurate estimates. 3. Above-ground stocks have diminished and the equivalent of such supply tends more and more to be retained underground in the natural reservoirs. It becomes increasingly necessary to know accurately the amount of these stocks. To direct attention to an additional point of different nature: improved accuracy of reserve estimation can be obtained only by closer scrutiny of the factors that determine recovery. This examination and the resulting efforts to measure the effect of these factors in terms of ultimate recovery must tend to improve ultimate recovery. The statements regarding the acute nature of the problem also indicate to some extent the importance of the problem and the necessity of finding a solution. Developed reserves of the industry, and of individual opera-tors, are one of the great factors that properly should determine explora-

Jan 1, 1936