Search Documents

By E. J. Roberts

The theory is developed that the tons ground through a given mesh per day in a wet ball mill is proportional to the percent plus that mesh in contact with the balls and the net power applied to the balls at this point. A grindability test is described. DURING the course of a study of the fundamentals of classification in 1937, the need for a more basic understanding of the action of a ball mill became acute. Unless one knows how classification affects grinding, one cannot hope to effectively improve on classification. The methods of evaluating grinding efficiency that depend on surface developed were studied but soon discarded for two reasons: 1. There was no apparent method which could be generally used to give a reliable figure for the actual new surface developed as a result of grinding. Subsequent papers have not changed this conclusion. 2. The practical evaluation of grinding in the main ore dressing applications was in terms of the percentage retained on a screen which passes 90 to 99 pct of the material and not in terms of surface area. The Probability Theory With the background of our experience in the field of closed-circuit grinding, together with the papers of Lennox,1 Gow,2 Gaudin,8 Fahrenwald,4 Coghill, and others, the approach of the theoretical physicist was then tried. The thought was somewhat as follows: When one grinds in a ball mill, a given expenditure of power leads either to a certain number of point to point blows per hp-hr or to a certain distance of line contact per hp-hr, depending on whether the action of the balls is considered to be cascading or rolling. It is also assumed that the balls actually come together on each blow or during the roll. Then a volume of slurry will be covered per minute which is some function of the size of the particle being considered (see fig. 1). All particles coarser than this size will be reduced through this size. This volume of slurry contains a certain weight of ore, depending on the percent solids and the density of the solids. If we fix the percent solids and the density of the solids and let w be this certain weight of ore in the volume covered, then, in mathematical terms, what we have just postulated is, w —— 8 hp (a) dt If W is the total weight of ore present in the mill, then we can write. W w/8 hp (b) W dt and if C is the cumulative percent plus the size chosen at the start of the time interval dt, w w c/dt W 8 hp x c (c) wc But wc/100 is the weight plus the size chosen which at 100 wc the close of time dt is finer than that size, and W is the decrease in the percent plus of the whole mass of ore or —dC. Then, —W dC/dt 8 hp x C. (d) In other words, the mesh tons ground through a given size per unit of time is proportional to the hp and the percent plus the mesh. A crude analogy would be to picture a 1-ft-wide steam roller going down the road at 1 ft per sec. If we place one egg on the road per square foot, one egg will be smashed per second. If we place a dozen eggs per square foot, a dozen eggs will be crushed per second. Similarly, if all the particles in w are plus the mesh, i.e., C=100, we should have a maximum rate of reduction. If only 10 pct of them are plus the mesh (C=10), we would have only one tenth the maximum rate; if only 1 pct are plus the mesh, the balls have a hard time finding anything to work on. This is where the term "probability theory" comes from. The chances of the balls crushing a particle through a given mesh depends directly on the concentration of particles coarser than this mesh in the general pulp in the mill. Giving W the units of tons and dividing equation (d) through by W, we obtain -dC hp ----- = k---— C [1] dt ton where k is a constant for any one size of particle, density of solid and moisture content of pulp. Eq 1 is the rate equation for a first order reaction and says that the rate of decrease of the percent plus a given mesh with time is directly proportional to the hp per ton applied to the body of ore and to the percent plus the mesh in the ore mass as a whole. Since it is a differential equation, it only

Jan 1, 1951

By F. G. Jones, R. D. Pehlke, H. E. Gardner

The solubility of nitrogen in liquid Fe-18 pct Cr-8 pct Ni-0. 7 to 2.3 pct A1 alloys has been measured up to the solubility limit for the formation of aluminum nitride in the temperature range 1600° to 1700°C uszng the Sieverts' method. The solubility of nitrogen in 18-8 stainless steel increases with increasing aluminum content. Based on a nitride composition, AlN, the standard free energy of formation of aluminum nitride from the elements dissolved in liquid 18-8 stainless-steel alloys has been determined to be: ?G° = -42,500 + 20. IT in the range from 1600° to 1700° C. EVANS and pehlke1 have measured the equilibrium conditions for the formation of aluminum nitride, AlN, in liquid Fe-A1 alloys. The present study extends that work to the more complex solvent, liquid 18 pct Cr-8 pct Ni (18-8) stainless steel. Recent work by Small and pehlke2 has dealt with the effect of fourth-element additions on the solubility of nitrogen in 18-8 base alloys. They found the effect of aluminum additions, up to 0.74 pct, on the solubility of nitrogen to be small. The present study covered the range from 0.74 to 2.28 pct aluminum, and by extending the composition range may be used to better define the effect of aluminum on the nitrogen solubility in these alloys. EXPERIMENTAL PROCEDURE The Sieverts' method was used to measure the equilibrium solubility of nitrogen gas in liquid 18-8 stainless steel alloys containing 0.74, 1.49, 1.93, and 2.28 pct Al. The solubility was measured as a function of the nitrogen gas pressure at temperatures of 1600°, 1650°, and 1700°C. The apparatus used is the same as described by Small and Pehlke.2 The 100-g melts were made from Ferrovac-E high-purity iron, Crucible Steel Co.; 99.95 pct Cr, Union Carbide Corp.; 99.9 pct Ni, International Nickel Co.; and 99.99+ pct Al, Aluminum Co. of America. The aluminum was charged at the bottom of the crucible, surrounded by nickel and iron. The chromium was packed into the interstices to minimize vapor transport of the aluminum during initial melting. The hot volume of the system, measured for each melt with argon, ranged from 45 to 55 standard cu cm with a temperature coefficient of —8 x 10-3 cu cm per °C. The melt temperature was measured with a Leeds and Northrup disappearing-filament type optical pyrometer sighted vertically downward on the center of the melt surface. The temperature calibration of the system by Small and pehlke2 was assumed. Two problems are involved in determining the solubility product of a solid, metal nitride phase in liquid iron alloys. These are: 1) establishing the point of departure from Henrian behavior at the solubility limit of the metal nitride phase; and 2) determining the composition of the solid nitride which is precipitated. Determination of the solubility product of AlN was made by admitting small amounts of nitrogen into the reaction bulb until the deviation from Sieverts' law was clearly evident in the form of a pressure halt. To obtain the solubility product at several temperatures during one run the following procedure was used: 1) add increments of nitrogen to determine the Sieverts' law line at the lowest desired temperature; 2) continue to add nitrogen to precipitate a small amount of the nitride phase; 3) increase the melt temperature 50°C to dissolve the precipitated nitride; 4) repeat step 2 until either a nitride formed or the system reached ambient pressure; if a nitride formed at 1650°C, the sequence was repeated at 1700°C. The composition of the precipitated phase was checked by an X-ray diffraction pattern obtained from powder scraped from the surface of the solidified 1.93 pct A1 melt. RESULTS AND DISCUSSlON Solubility Measurements. Fig. 1 is a typical nitrogen-absorption curve obtained from measurements on a 1.93 pct A1 alloy. Since the initial absorption of nitrogen follows Sieverts' law the nitrogen solubility is plotted as a function of the square root of the pressure of nitrogen gas in the reaction bulb. The results of the solubility measurements for all alloys studied are summarized in Table I. The slope of the Sieverts' law line for each alloy was determined. Since this is also the solubility of nitrogen at 1 atm pressure of nitrogen gas, the latter designation is used for the data. It should be noted. however, that in most cases the value lies above the solubility limit for AlN. Fig. 2 shows the effect of aluminum on the solubility of nitrogen at this reference pressure and as a function of melt temperature. The solid portions of the lines represent attainable solutions; the dashed regions lie above the limit for precipitation of AlN.

Jan 1, 1969

By Thomas R. Smith

This paper covers oil shale resources in those countries that border the Pacific Rim. The major known resources around the Pacific Rim occur in the Western United States, Australia, the People's Republic of China, (PRC) and the Thailand/Burma region. The location of these deposits is shown in Figure 1. In 1965, the U.S. Geological Survey estimated world oil shale deposits of over 4 quadrillion tons having a potential oil yield of over 2 quadrillion barrels. If all this were extracted, it could meet the world's entire energy needs far into the future. However, the Survey also estimated the spent shale waste could cover all of the surface of the world to a depth of about 10 feet. Thus, for this and many other technical and economic reasons, it does not appear to be feasible to develop a large portion of the world's oil shale resources in this century; nor will shale in itself solve our energy problems. Nevertheless, shale oil and other ' synthetic fuels are expected to play an important role in new energy supplies in the longer term. WHAT IS OIL SHALE OR SHALE OIL? The term "oil shale" is sometimes a misnomer, in that the rock is often more of a limestone or siltstone than a shale. The common link between resources termed “oil shale" is that they all contain an insoluble substance cal led kerogen (which is from the Greek words for waxmaking). Kerogen is a form of organic carbon derived from a variety of plants ranging from algae to higher plants. When heated sufficiently, the kerogen generates hydrocarbons called shale oil, a form of synthetic crude oil that in most cases is lower in hydrogen content than conventional crude oil. The amount of oil in oil shale is relatively small --roughly 10 percent (by weight) in the richer shales. To upgrade this synthetic oil to usable products, additional processing is necessary. This brief sketch gives an idea of what this different, but significant, form of hydrocarbon is like. ENVIRONMENTS OF DEPOSITION Most oil shale deposits fall into three environments of sediment deposition: 1ake (called lacustrine), sea (marine) and river (fluvial-deltaic). In each case, the deposition of oil shales took place in quiet water environments where plant life, particularly algal plants, could flourish and, after dying, be deposited in unoxygenated water where the kerogen precursors would be safe from destruction by oxidation. The oil shales that were deposited in large lake basins (lacustrine) have attracted the most attention for development over the years. They often have multiple seams, deposited in a cyclic nature with extensive areal distribution and rapid vertical changes in kerogen content. Grades are moderate to high, ranging from 80 to 200 liters per tonne. Rundle in Australia and the Piceance Creek Basin in Colorado are examples of this type. Both deposits represent large volumes of oil shale in small areas which could provide the large volume of feedstock needed for future commercial operations. The stratigraphic sections of these two deposits feature thick oil shale seams with average grades of 80 - 125 liters/tonne conducive to both open pit, and underground operations. However, the rock strength of the Rundle shale is not sufficient to - support underground mining. On the other hand, the Colorado deposits, being more carbonate in nature, are sufficiently strong to support either type of mining depending on the overburden to ore ratio. These latter types of deposits will likely provide the first target for development of a commercial industry. The marine type is characterized by extensive areal distribution with relatively thin seams. The grades are generally low to moderate, ranging from 50 to 120 liters per tonne. The marine oil shales are common worldwide, and their attractiveness for mining is dependent on the overburden to ore ratio. Because of their widespread areal distribution, their in situ resources can be quite large. The Toolebuc Formation in Central , Queensland, Australia is a good example of this type of deposit being 7-10 meters thick over an extensive area. The Julia Creek deposit with its favorable overburden-to-ore ratio is being studied for possible development. In a fluvial-deltaic environment, there are many small lakes or bogs associated with rivers in which a very pure type of oil shale called torbanite could form. Torbanites are very high grade containing up to 75 percent hydrocarbons. The known occurrences are generally small lenticular deposits associated with coal seams. Even with the high grades, it is not likely that any of the known deposits would warrant commercial development because of their small size. The torbanite deposits in New South Wales, Australia were processed prior to World War I1 near the town of Glen Davis. However, today's known resources of this type are not large enough to warrant a commercial plant.

Jan 1, 1982

By M. J. Sinnott, H. B. Probst

AN extensive survey of the factors which affect austenite grain growth has already been made.' These factors are temperature, time at temperature, rate of heating, initial grain size, hot-working, alloy content, ofheating,initialand rate of cooling from the liquidus-solidus temperature. In the present work, a vacuum-melted temperature.electrolytic iron was used and the variables studies were temperature, time at temperature, and prior ferrite grain size. Other factors were maintained constant. The iron used in this study was vacuum-melted electrolytic iron of nominal composition of impurities of 0.07 wt pct. It was supplied as a ½ in. round cold-drawn bar. This iron was tested in three conditions: as-received, annealed 6 hr at 1200°F, and annealed 6 hr at 1600°F. Samples were ? in. disks cut from the bar. The prior anneals were carried out in vacuum and the isothermal treatments were carried out in vacuum-sealed Vycor tubing. The thermal etch technique was employed to determine the austenite grain size. Prior to sealing the test specimens, one surface of the sample was polished metallographically. This surface, after heating, was examined to determine the austenite grain size, since the austenite boundaries are revealed by thermal etching. This is essentially the only technique available for measuring the austenite grain size of low carbon steels or pure irons without altering the composition. It has been shown to yield results that are in agreement with other methods used for determining austenite grain sizes.' The specimen size was quite large compared to the grain size measured, so inhibition of growth due to size effects is probably negligible. After vacuum sealing, each sample was placed into a furnace at temperature and at the completion of the run was quenched into a mercury bath. The growth temperatures used were 1700°, 1800°, 1900°, and 2000°F controlled to -~10"F. Growth times were varied from 10 to 240 hr. The long times were used in order to eliminate the nucleation and growth effects occurring during the initial transformation. Time was measured from the introduction of the capsule into the hot furnace to the time of quench. Grain-size measurements were made with the use of a grain-size eyepiece of a microscope. By determining the number of grains per square millimeter at X100 and taking the square root of the reciprocal of this number, the average linear dimension of the grains was determined. Figs. 1 and 2 are plots of these data as a function of time and temperature for the various conditions investigated. The variation of D, the linear dimension of the grains, was assumed to follow the equation3 D = A tn. The curves of Fig. 1 were obtained from the data by the use of the least-squares method of analysis. Fig. 1 is for the growth of the as-received stock and Fig. 2 is for growth after prior treatments. Differentiating the foregoing equation gives an expression for the rate of growth dD/dt = G = nAtn-1 = nD/t. Both D and G as functions of t are given in Table I. It should be noted that G is a function of time; the growth rate is rapid at early stages and decreases with increasing time. Since increasing temperature increases the growth rate, it has been common practice to use the empirical relationship G = Go e-Q/RT to relate temperature to growth rate. The growth rate customarily has been taken at constant values of D on the basis that the rate of growth is related to the boundary surface tension and this is measured by the curvature of the boundary. At constant D values, the growth rate is a function of time and temperature. The growth rate can be related however to temperature at constant time, and this has the advantage that under these conditions the growth rate is a function only of temperature. Obviously the Q values, activation energies, obtained for each assumption will not be the same and the question of which is the more correct is a moot one, since the assumed exponential relationship in either case has no particular theoretical significance. By plotting G, at constant grain size, vs 1/T, the activation energy over the temperature range of 1800" to 2000°F is found to vary from 30,000 cal per mol at the smaller grain sizes to 50,000 cal per mol at the larger grain sizes. The 1700°F data do not correlate with the data at higher temperatures. The activation energies for the 1200" and 1600°F prior annealed materials were calculated as 50,000 and 62,000 cal per mol, respectively, using the reciprocal time to a given grain size as a measure of the growth rate. Plotting G, at constant times, vs 1/T yields an activation energy of 12,300 cal per mol for the tem-

Jan 1, 1956

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 K. E. Barrett

Exxon owns a uranium mill and holds two mining leases in Live Oak County, Texas, about halfway between San Antonio and Corpus Christi. The properties make up the Felder Uranium Operations which was reopened earlier this year. Exxon held an oil, gas, and other minerals lease on the J. C. Felder tract, which was adjacent to a relatively shallow uranium discovery by Susquehanna-Western, Inc. on the Marrs-McLean lease immediately south of the Felder property. Drilling in 1967 and 1968 confirmed the presence of reduced uranium mineralization in the basal sand unit of the Oakville formation on the Felder tract, which formed the major part of the roll-front deposit. In 1969 Exxon and Susquehanna-Western, Inc. entered into a sale and purchase agreement which provided for Susquehanna to mine and process Felder ore and purchase recovered uranium. Susquehanna moved an alkaline-leach mill from Wyoming, erected it on the Ray Point property, and placed it into operation late in 1970. Susquehanna mined and processed ore from the Felder and McLean properties through March 1973. Susquehanna ceased operations in March 1973. Exxon then acquired the mill and mill property. Exxon also purchased the mineral rights to the McLean lease, re-negotiated a mining lease for that property, and carried out shut-down programs for the mining and mill areas in the fall of 1973. The project was put on a standby basis until late 1973, when Exxon initiated mine feasibility studies for the project. MINE PLANNING EVALUATION The feasibility study for reopening the Felder Project began in late 1975 and was not completed until late 1976. I will discuss several areas of the feasibility study that required additional work prior to making the decision to renew operations. Ore Reserves Preparations for estimating the ore reserves began with the re-evaluation of more than 1500 natural radioactivity logs from exploration and pre-development drilling that had been completed on the property. These gamma ray logs of non-core rotary drill holes were the principal source of data used in making the estimate. Chemical assays of cores from the deposit were also used in the reserve determination. Electric resistivity and self-potential logs were made along with the gamma ray log. In December 1975 an additional core drilling project was undertaken to confirm the in-place density and radiometric equilibrium characteristics of the ore deposits. Comparison of chemical assays of cores with the U308 values calculated from the logs showed that the unoxidized ores were in radiometric equilibrium. In contrast, cores from anomalies occurring in near surface, weathered, and oxidized zones were in radiometric disequilibrium. Several important decisions were made in developing a mine plan or schedule of production from the Felder and McLean ore bodies. Disposal of Produced Mine Water: The ore bodies of the Felder Uranium Project occur at a point below the ground water table. The ore zones to be mined must first be dewatered to allow removal of mineralized material. In the open pit operations, this is accomplished by maintaining a perimeter ditch around the periphery of the open pit, allowing the interior of the pit to drain and collect into a sump and be pumped from the mine. In addition to anticipated water production from future mining operations, approximately 200M gallons of water was contained in three open pits left from prior mining operations. In two of these existing pits, the water was to be removed and disposed to allow for planned backfilling of waste material into these pits. The third pit would also have to be drained to allow continued mining of an area left from the prior operations. Essentially no ground water information was available for this area. The only data available was water production history from Susquehanna's mining operation. Two water wells were drilled early in 1976 on the Felder lease for use in obtaining hydrological data. A long term draw-down test was performed by pumping one water well and measuring water level drawdown in both the pumped well and the observation well. From these data, values for permeability and storage coefficient were calculated. These data were then used in modeling the aquifer to allow calculation of water influx into the mining area versus time. Once a schedule of water production, including the stored volume in the existing pits was calculated, alternate solutions for disposal were evaluated. The first system evaluated was a series of deep injection wells. The wells were designed to inject at a depth of approximately 3500 feet. Again very little information concerning reservoir characteristics of the receiving sand units was known. Using assumed values for reservoir permeability and storage coefficients, an injection well system was designed to allow for disposal of produced mine water. The biggest

Jan 1, 1979

By Raymond B. Ladoo, C. A. Stokes

Bruce C. Netschert—It is unfortunate that the authors of this paper consider it necessary to begin with an expression of concern over possible false interpretations of the word "economics." In their preoccupation with the definition of economics, they have adopted a definition of mineral economics which is, to say the least, unduly narrow. Just as the broad field of economics is not confined to a study of the profitability of business concerns, but includes the problems of production, distribution, and consumption as they pertain to society as a whole; so an inclusive definition of mineral economics should not be confined to the determination of the profitability of mineral-producing and processing enterprises, but should include the significance of the unique characteristics of mineral resources as raw materials for the use of society. Such features as the exhaustibility and localized, haphazard occurrence of deposits, the existence of a secondary (scrap) supply, and the increasing cost of operation during the life of a mining enterprise are obviously factors which concern those businesses which are producing mineral raw materials, since they partially determine the profitability of such enterprises. They are also of concern to society as a whole, however, as characteristics of one of the basic elements of the economic system. In the last analysis, the contribution which mineral economics can make as a means of determining and guiding social policy with respect to the production and utilization of mineral resources is perhaps more important than its use as a basis for determining the cost accounting procedure of individual firms. The list of "economic factors peculiar to the industrial minerals" which the authors present is in reality an application of such a broad definition of mineral economics. An inconsistency appears, however, in the inclusion of items 8 and 9 in the list. As this writer sees it, the point in question is: What influences do the characteristics of industrial minerals have on the characteristics and operating procedures of industrial mineral enterprises which are not present in the metallic mineral field? In answering this question with items 8 and 9, Messrs. Ladoo and Stokes do not recognize that there are two distinct types of differences between the two fields of enterprise. There are, on the one hand, important basic economic distinctions due to inherent economic characteristics of industrial minerals which do not pertain to metallic minerals. On the other hand are those characteristics of the industrial mineral enterprises peculiar to them alone, but which are superficial and temporary, in that they may be changed or eliminated at the discretion of the managers of those enterprises. The lack of adequate research and development in industrial mineral production, processing, and marketing (item 8) is not due to an inherent characteristic of industrial minerals. It is true that one may perhaps describe the field of industrial mineral enterprise in terms of such a deficiency, just as one could, until recently, point to a similar lack of research and development in the coal industry; but unless it can be shown that the deficiency has been wholly or partially due to the very nature of industrial minerals themselves it is not an "economic factor peculiar to the industrial minerals" but a temporary characteristic peculiar to the industry. In the writer's opinion, the authors have not demonstrated that the former relationship exists. Similarly, item 9, the "influence of technologic developments," is also not inherently peculiar to industrial minerals. Nowhere in the discussion of this item do the authors mention anything that is not equally applicable to the field of metallic minerals. This is not meant to imply that the specific technologic developments which the authors list are of equal significance in both fields. It does mean that such a statement as, "technological advances together with new consuming areas to provide markets make deposits commercially valuable which once were of no interest" cannot be considered as an argument that technological developments have significance in the field of industrial minerals alone. In considering the problem of stockpiling, the authors note that the stockpiling of nonstrategic materials might be desirable if future wartime needs could exceed domestic production capacity, but dismiss this as hardly adequate to justify such stockpiling. The problem, however, can be stated in broader economic terms, i.e., the real costs (as distinguished from the money costs) of prewar versus wartime production. In other words, it might well be that the labor and capital required to produce a given amount of a certain mineral raw material could be used more efficiently in another industry. In such a case it is obviously advantageous to stockpile the material in prewar times rather than forego the benefits of additional production in another line of endeavor during wartime under conditions which demand the optimum use of all resources, including manpower and capital. To the writer's knowl-

Jan 1, 1951

By Raymond B. Ladoo, C. A. Stokes

Bruce C. Netschert—It is unfortunate that the authors of this paper consider it necessary to begin with an expression of concern over possible false interpretations of the word "economics." In their preoccupation with the definition of economics, they have adopted a definition of mineral economics which is, to say the least, unduly narrow. Just as the broad field of economics is not confined to a study of the profitability of business concerns, but includes the problems of production, distribution, and consumption as they pertain to society as a whole; so an inclusive definition of mineral economics should not be confined to the determination of the profitability of mineral-producing and processing enterprises, but should include the significance of the unique characteristics of mineral resources as raw materials for the use of society. Such features as the exhaustibility and localized, haphazard occurrence of deposits, the existence of a secondary (scrap) supply, and the increasing cost of operation during the life of a mining enterprise are obviously factors which concern those businesses which are producing mineral raw materials, since they partially determine the profitability of such enterprises. They are also of concern to society as a whole, however, as characteristics of one of the basic elements of the economic system. In the last analysis, the contribution which mineral economics can make as a means of determining and guiding social policy with respect to the production and utilization of mineral resources is perhaps more important than its use as a basis for determining the cost accounting procedure of individual firms. The list of "economic factors peculiar to the industrial minerals" which the authors present is in reality an application of such a broad definition of mineral economics. An inconsistency appears, however, in the inclusion of items 8 and 9 in the list. As this writer sees it, the point in question is: What influences do the characteristics of industrial minerals have on the characteristics and operating procedures of industrial mineral enterprises which are not present in the metallic mineral field? In answering this question with items 8 and 9, Messrs. Ladoo and Stokes do not recognize that there are two distinct types of differences between the two fields of enterprise. There are, on the one hand, important basic economic distinctions due to inherent economic characteristics of industrial minerals which do not pertain to metallic minerals. On the other hand are those characteristics of the industrial mineral enterprises peculiar to them alone, but which are superficial and temporary, in that they may be changed or eliminated at the discretion of the managers of those enterprises. The lack of adequate research and development in industrial mineral production, processing, and marketing (item 8) is not due to an inherent characteristic of industrial minerals. It is true that one may perhaps describe the field of industrial mineral enterprise in terms of such a deficiency, just as one could, until recently, point to a similar lack of research and development in the coal industry; but unless it can be shown that the deficiency has been wholly or partially due to the very nature of industrial minerals themselves it is not an "economic factor peculiar to the industrial minerals" but a temporary characteristic peculiar to the industry. In the writer's opinion, the authors have not demonstrated that the former relationship exists. Similarly, item 9, the "influence of technologic developments," is also not inherently peculiar to industrial minerals. Nowhere in the discussion of this item do the authors mention anything that is not equally applicable to the field of metallic minerals. This is not meant to imply that the specific technologic developments which the authors list are of equal significance in both fields. It does mean that such a statement as, "technological advances together with new consuming areas to provide markets make deposits commercially valuable which once were of no interest" cannot be considered as an argument that technological developments have significance in the field of industrial minerals alone. In considering the problem of stockpiling, the authors note that the stockpiling of nonstrategic materials might be desirable if future wartime needs could exceed domestic production capacity, but dismiss this as hardly adequate to justify such stockpiling. The problem, however, can be stated in broader economic terms, i.e., the real costs (as distinguished from the money costs) of prewar versus wartime production. In other words, it might well be that the labor and capital required to produce a given amount of a certain mineral raw material could be used more efficiently in another industry. In such a case it is obviously advantageous to stockpile the material in prewar times rather than forego the benefits of additional production in another line of endeavor during wartime under conditions which demand the optimum use of all resources, including manpower and capital. To the writer's knowl-

Jan 1, 1951

By M. C. Flemings, T. Z. Kattamis

Dendrite morphology and grain size were studied in bulk samples of iron and nickel base alloys under-cooled up to 300°C. In the alloys studied, dendrite morphology gradually changes with increasing undercooling from the usual dendritic structure to a structure composed of cylindrical dendrite arms. At a critical undercooling of approximately 170°C in these alloys there is an abrupt transition to a fine-grained structure of spherical morphology. Final dendrite-arnz spacing of melts nucleated at less than the critical undercooling decreases with increasing undercooling and with decreasing distance from a chilled surface. Grain size of melts nucleated at greater than the critical undercooling decreases similarly with these factors. It is concluded that structure coarsening, with reduction of surface area as driving force, is the principal mechanism determining final dendrite-arm spacing in melts nucleated at small undercoolings and grain site in melts nucleated at large undercoolings. IN solidification of highly undercooled melts, nuclea-tion and growth of the solid is accompanied by a rapid release of latent heat of fusion. The heat release is sufficiently rapid in bulk specimens that it takes place essentially adiabatically with respect to the surroundings; hence the specimen heats up ("recalesces") to some maximum recalescence temperature. For bulk liquid metals and alloys, a simple thermal balance shows the undercoolings obtainable in bulk samples are not sufficient to lower the maximum recalescence temperature below the equilibrium solidus temperature. Hence, some liquid always remains at the end of recalescence; this liquid must solidify by rejection of heat to the surroundings. Metals, including iron and nickel base alloys, normally freeze with only a few degrees of undercooling. In general, nucleation begins on impurity particles present in the metal, at a "heterogeneous nucleation temperature" that is quite close to the equilibrium liquidus temperature. Very small droplets of metal can be undercooled considerably before nucleation occurs,1-4 presumably because subdivision of the liquid reduces the probability of solid impurity in a given droplet. Following early work on metal droplets,' a series of studies has shown that it is possible, without great difficulty, to undercool bulk samples of many metals and alloys. Undercoolings obtainable are approximately two tenths of the melting point for nickel, iron, copper, and other metals and alloys.5-9 Specimen sizes have generally been in the range of 50 to 500 g. Studies on undercooling to date have been concerned primarily with techniques of undercooling and with nucleation and growth kinetics. Only limited consideration has been given to dendrite morphology in under- cooled alloys. One such study, in bulk Cu-Ni alloy,8 showed that at small undercoolings a typical dendritic structure was obtained. At undercoolings the order of 175°C the structure of a Cu-40 pct Ni alloy became "ray or starlike", and a dense network of subbound-aries appeared. At still larger degrees of undercooling, of the order of 250°C, the structure became more random and included an ensemble of globular forms. Comparable results were obtained by walker10 on Cu-Ni alloys, and by Kamenetskaya et al.11 in research on Cu-Ni, Sb-Bi, Fe-Ni, and Fe-Cr alloys. In this work, study was made of the processing parameters influencing dendrite morphology and grain size in undercooled alloy melts. Experiments were specifically designed to show the effects of coarsening ("ripening") during solidification on final casting morphology. EXPERIMENTAL PROCEDURE Apparatus used was patterned after that of Walker,10 Fig. l(a). Melting was by induction under reduced pressure of helium. Two different types of crucible materials were used; there was no difficulty in obtaining substantial undercooling in both types of materials. Alumina crucibles were used for the bulk of the runs made, with a glass coating separating the metal from the crucible walls. Other runs were made using fused silica crucibles with or without slag coating. A graphite susceptor was employed around the crucible to aid in melting and to reduce melt stirring. The major portion of the experimental work was on

Jan 1, 1967

By C. S. Matthews, P. Hazebroek, H. Rainbow

It ha been suggested that lormation fractures created by well stimulation treatments will adversely affect sweep-out efficrency in injection operations. Fluid-flow model studies involving vertical fractures of various lengths and fluid systems of various mobility ratios have been carried out to study this subject. In addition, limited data have been obtained on one model containing a horizontal fracture. It was found that relatively long and highly conductive fractures (not generally obtained fracturing operations) were required to affect the sweep-out efficiency substantially. In a given case in the field an approximate distinction can be made between the presence of long conductive fractures and shorter or less conductive ones. This is done with pressure build-up analyses along with data on the relationship of fracture length and conductivity to well productivity. This type analysis shows that usually the fractures induced are either short or of limited conductivity and therefore do not damage sweep-out efficiency. INTRODUCTION Improved well productivity and in-jectivity can frequently be exploited in injection operations. Higher total throughput can yield improved economics. On occasion, the achievement of an increased productivity or injectivity in specific wells can bring about a more uniform sweep of the reservoir. Higher rates can be exploited particularly in water floods of "depleted" reservoirs where a rapid "fill-up" is desired and where low pressures contribute to low well productivity. The creation of fractures local to the wellbore is an excellent means for achieving these objectives. Even though fracturing has been employed in some floods with success,1"3 there still seems to be some reluctance to employ this tool for fear of undue damage to the flood pattern and ultimate recovery. We therefore need to examine the influence which fractures of varying length may have on flood performance and then determine the length of fractures which obtain in the field with conventional fracture treatments. A substantial influence of fractures on the recovery obtained at breakthrough of the injected fluid has been presented by Crawford and Collins for equal fluid mobilities for the line-drive pattern.4,5 In addition, the influence which a fracture has on the production performance after breakthrough and on the ultimate recovery warrants consideration in reaching a conclusion concerning the use of induced fractures in flooding operations. This report presents this type of data for the five-spot injection pattern for several fluid mobilities. In arriving at some conclusion concerning the fracture lengths obtained in field operations we must examine the performance characteristic most affected by the fracture. This is the change in the flow system as reflected in the change in productivity and pressure build-up behavior. A study of these changes is also presented in this report. RESERVOIR ANALOGS The X-ray shadowgraph technique, employing miscible displacement in porous models, has been used in the study of the influence of fractures on pattern sweep-out efficiency. The X-ray shadowgraph procedure is described in detail in an earlier report8. Fractures were represented by leaving the proper portion of the model surface exposed to either injection or production. This assumes the fracture resistance to be negligible compared to that of the formation. Actually the flow resistance in propped fractures obtained in the field is sometimes not negligible so that the results with this model indicate the maximum influence of the fracture. Two types of models were necessary to represent vertical fractures in a five-spot flood. These pattern elements are illustrated in Fig. 1. In studying the influence of the horizontal fracture, only one well spacing length to thickness ratio of 50 was used. The pool unit of a Carter Electric Analyzer was used in studying the influence of fractures on productivity and build-up behavior. The square drainage system of a well was represented by a network of 576 elements of equal volume and resistance. One-fourth of this drainage area was studied as a model unit using a network of 144 condensers and resistors. Vertical fractures were represented by a shunt directed from the well perpendicular to the drainage boundary. Horizontal fractures were represented by a circular shunt. Resistance of a shunt was varied in representing different conductivities for the fractures. FRACTURE DIRECTION AND LENGTH The direction at which a vertical fracture extends into the formation and its length and conductivity influence the sweep behavior. The two

By B. C. H. Steele, C. B. Alcock

In choosing solid oxide electrolytes for use in the measurement of thermodynamic quantities at high temperatures, the two most important criteria are the values of the partial ionic and electronic conduc tizities. Measurements of these conducticities have been made for some Group IVA oxides and solid solutions of these oxides with CaO, Y2O3, and La2O3. The total conductivities as a function of temperature. oxygen partial pressure, and composition were determined, as well as the electromotive forces of cells in which the oxygen partial Pressures of the electrodes were between 10-7 and 10-29 atm at 1000°C. Additional factors that influence the experimental arrangements, such as the operating temperature, the appropviate cell atmosphere, and electrode kinetics, are also discussed. IT has long been recognized that galvanic cells incorporating solid electrolytes can possess many advantages for the measurement of high-temperature thermodynamic data. Unfortunately, the electrical-transport properties have only been established for a few solid electrolytes, although attempts have been made, and are still being made, to use such materials as porcelain' and magnesia.' Kuikkola and Wagner have discussed3 and demonstrated4 various applications of solid electrolytes, and, in particular, their work stimulated the electrochemical measurement of oxygen activities using cells incorporating the solid oxide electrolyte, Zr0.85Ca0.15O1.85 The excellent characteristics of this oxide electrolyte have been confirmed by the investigations of Kingery et al.5 (oxygen ion diffusion), Carter and Rhodes6 (zirconium and calcium ion diffusion), and Weissbart and Ruka7 (electronic transference number). However the observations of Peters and Mobius,8 later confirmed by Schmalzried,9 indicated that the electronic component of zirconia-based electrolytes could become significant at low oxygen chemical potentials. Under these conditions, thoria-based electrolytes have obvious advantages arising from their superior thermodynamic stability. It was known that certain thoria solid solutions possessed defect fluorite structures containing anionic vacancies (cf. Zro.85Cao.l50O1. 85), although data on their electrical properties were conflicting. Kiukkola and wagner4 concluded that thoria-based electrolytes exhibited appreciable electronic conductivity, whereas Peters and Mobius8 mentioned that the electronic conductivity only became important at high oxygen partial pressures, but gave no further details. In addition, both Kiukkola and wagner4 and Peters and Mann'" had determined the oxygen chemical potentials associated with the Fe-FeO, Co-COO, Ni-NiO, and Cu-Cu2O equilibria, and it was not known whether discrepancies in their results could be attributed to the different cell design, or the thoria-based electrolyte used by Peters and Mann. These uncertainties have been resolved during the present investigation into the measurement of low oxygen chemical potentials, and transport properties of the relevant oxide electrolytes are presented and discussed. Other experimental difficulties associated with low oxygen chemical potential measurements are also described, with particular reference to the Nb-O system. 1. THEORETICAL CONSIDERATIONS Oxide systems of potential use as solid electrolytes possess a large energy gap between the valence and conduction bands. Little is known about the defects present in these wide-gap metal oxides as a function of impurity content and deviations from stoichiom-etry, or the mechanisms by which electronic charges move in these solids. For these materials it is convenient to represent the measured conductivity as the the sum of three terms: where a, is the conductivity due to positive hole conduction (p type), and oe is the electronic conductivity due to electron conduction (n type). U there is a large concentration of ionic vacancies fixed by composition then the ionic contribution will not be a function of oxygen pressure. Although the possibility of a pressure-independent electronic component also cannot be ignored, it is likely that such a term would only become significant at very high temperatures, and in general the positive hole conduction will increase with increasing oxygen pressure, and the electron conduction will increase with decreasing oxygen pressure. It follows that the total conductivity is related to oxygen partial pressure as follows:

Jan 1, 1965

By Jonas Svensson

A new method is described for the production of cold-bonded pellets using a hydraulic binder, such as portland cement. Large-scale pilot-plant tests have proved that self-fluxing pellets of high reducibility and good handling strength can be made by the method. Blast-furnace trials have shown that the pellets are an acceptable burden material, comparable with self-fluxing sinter or heat-hardened pellets. Economic factors of commercial-scale production are discussed. The Grangcold Pellet Process—for which patents have been applied or already granted in a number of coun-tries—uses a hydraulic adhesive such as portland cement, slag cements, pozzolanic cements, etc., for the production of cold-bonded pellets. The idea of using a hydraulic binder for the agglomeration of iron-ore fines is not new. Portland cement was proposed as an adhesive for cold-bonded iron-ore briquettes in patents granted more than 50 years ago.' In a report on the briquetting of iron-ore fines, published in Stahl und Eisen in 1959; it is stated that briquettes bonded with portland cement are used on a small scale at an ironwork in Germany. According to the report, the briquettes showed excellent strength in the blast furnace although their general use was made impossible because they required a long hardening time, during which they are sticky, soft, and difficult to store and handle. The Grangcold Pellet Process has overcome this particular disadvantage by mixing the balls with a suitable amount of the balling concentrate before storing them. The pellets are embedded in the concentrated during storing in such a way that they are isolated from each other and thus prevented from sticking together to form clusters. Thanks to the embedding concentrate, the pellets are subjected to a more or less uniform pressure from all sides which does not deform them. Thus, the mixture can be stored in a stockpile or in a bin until the pellets have hardened sufficiently. The concentrate is separated from the pellets by means of screening. The concentrate is returned to the balling operation and the pellets are either shipped to the blast furnace or stored for final hardening. The binder preferred for the Grangcold Pellett Process is portland-cement clinker, ground without the admixture of gypsum in order to avoid sulfur in the pellets as far as possible. Usually a 10% binder content is used. Two-thirds of the portland-cement clinker consist of lime and the rest is silica, alumina, and ferric oxide. Thus, self-fluxing or overbasic pellets are produced with this binder if the amount of silica in the concentrate used does not exceed 4%. The Grangcold Pellet Process was developed by the mineral Processing Laboratory of the Granges Co. Work started in 1963 with batch-scale tests. In 1966, a small pilot plant was put into operation in which 1800 tons of pellets were produced using 10% of rapid-hardening portland cement as a binder. Favorable results from a blast-furnace test with this batch led to the decision to erect a larger pilot plant which went into production in the summer of 1967. Since then, approximately 100,000 tons of cold-bonded pellets have been produced, mostly with 10% gypsum-free portland cement as a binder. Several full-scale blast-furnace trials have been performed with the pellets. The results of the trials indicate that the Grangcold pellets constitute a satisfactory blast-furnace feed. An industrial plant for the production of Grangcold pellets with a rated capacity of 1.5 million tpy is now under construction at the Granges Co.'s mine at Grangesberg. The plant will come into operation in the summer of 1970. Results from Laboratory Work Pellets made from iron-ore concentrate bonded with portland cement harden slowly and their handling is very critical until they have hardened enough to loose their stickiness. It is therefore especially important to study the progress of the hardening action and the factors influencing it. This is best achieved by investigating the relationship between the compressive strength of the cement-bonded pellets and the curing time under varied conditions. The general course of this relation-

Jan 1, 1971

By K. F. Veith, R. L. Marovelli, T. S. Chen

An analytical study is made of thermal stress distribution in a thin circular disc subjected to a peripheral thermal shock at various rates of heat transfer. The problem is of importance in predicting the thermal shock response of a rock body of finite size. The theoretical analysis is based on radial heat flow by conduction in the disc and heat exchange by convection between the disc and the surroundings. The case of constant properties and plane stress is treated. Solutions of the stress distribution are presented for both cooling and heating shocks and an average stress theory is formulated. Preliminary experimental verification was obtained from the results of shock tests on thin rock discs insulated on both flat end faces so that heat exchange took place through the exposed peripheral surface. Physical properties vital to the analysis are Young's modulus, tensile strength, coefficient of linear thermal expansion, thermal diffusivity and thermal conductivity. Plots of these properties are presented. Historically, thermal energy has been used for primary rock removal throughout the ages. Although it is not widely known, the fire-setting method of thermal rock fragmentation was still in use 100 years ago in systematic underground mining operations in Scandinavia.' There, the availability of cheap labor and abundant wood fuel made the method competitive with the early blasting powders. By 1880, as high explosives replaced powder, use of the method declined and it was finally abandoned about 1885. Only 40 years ago, some experimental fire-setting methods were used for rock removal underground at Pribram and Zinnwald in Central Europe.2 Compressed air-oil burners replaced the earlier wood fuels. About 15 years ago, gaseous oxygen-oil burners were introduced in the United States and gained acceptance for difficult blasthole drilling and some quarry opera- tions. At present, there is renewed interest in the compressed air-oil burner designs. The literature included information on thermal secondary processes for rock weakening or particle liberation3,4,5,6,7,8 on thermal spallation of rock 9,10,11,12,13 and on the thermal fracture of materials other than rock. The 1955 Symposium on Thermal Fracture14 and the later work of Hassel-man, cover recent developments in thermal shock investigations on brittle ceramics. Although the number of published analytical and experimental investigations conducted on ceramic and refractory materials is large, the literature reveals that there is a lack of information on both the theoretical and actual response of rock to thermal shock. Many of the thermal shock studies on ceramic and refractory bodies are based on the case of heat transfer at the solid's surface by convection in either liquid or air. A similar heat transfer situation was adopted for a theoretical analysis of the thermal stresses in a thin circular disc subjected to a peripheral thermal shock. Experimental thermal shock tests were then conducted on rock specimens to check the analytical results. Specially insulated quartzite, basalt and taconite discs were shocked in either liquid or still air bath at various rates of heat transfer. The work was done in order to resolve the question as to whether theoretically determined tensile stresses are actually realized in a finite rock body undergoing thermal shock. Specifically, if theory predicts that the tensile strength of a rock should be exceeded in a particular type of controlled thermal shock, will fracture occur? This information is needed by Bureau researchers working on thermal and electrical rock fragmentation methods. The object of this paper is to present the main features of the theory and procedure being used in the authors' approach to quantitative prediction of rock response to a thermal shock. THEORETICAL ANALYSIS In the analysis to follow, simple geometry of a thin circular disc is considered. The disc is assumed to be isotropic, homogeneous and perfectly elastic, and to have constant thermal and mechanical properties. The effect of radiation is neglected so that heat is transferred by conduction inside the disc and by convection with its surrounding. In addition, the end

Jan 1, 1967

By K. H. Kilgren

At high formation pressures the distillate produced from a gas-condensate reservoir may be black in color. In this event the dense gas phase existing above the dew point is correspondingly dark. Volumetric phase data and an analysis of a reservoir fluid exhibiting these characteristics, together with a description of the visual equilibrium cell in which these observations were made, are presented in this paper. INTRODUCTION Previously the author, like many others in the oil and gas industry perhaps, tacitly assumed that the expressions black or dark oil system, crude oil system and bubble-point system were synonymous. Crude oil reservoir fluids are bubble-point systems and yield a black or dark stock-tank oil of relatively low API gravity. Conversely, a clear or amber colored trap distillate of high API gravity is assumed indicative of a dew point system or a gas-condensate reservoir fluid. This broad classification appears satisfactory for shallow reservoirs, but as the following study demonstrates, may be misleading when applied to deep reservoirs. Theoretically, there is no reason to exclude the possibility of producing a dark, low-gravity distillate from a gas-condensate reservoir. At sufficiently high values of pressure and temperature, heavy, dark-colored hydrocarbons may exist in the vapor state of a multi-component system. If enough dark-colored components are present in the reservoir vapor phase, the resulting condensate will be dark. The reservoir fluid investigated in the present study supports this contention. Stock-tank production was black in color and measured 29" APT gravity. From outward appearances, the liquid closely resembled a medium gravity crude oil. Experimental measurements proved the reservoir fluid was in reality a gas-condensate system. Volumetric phase data for this high-pressure system and a description of the visual cell in which the study was conducted successfully are presented in this paper. THEORY Phase behavior of a reservoir fluid can be predicted accurately with reference to a pressure-temperature phase diagram. If the reservoir temperature is lower than the critical temperature of the hydrocarbon fluid in place, bubble-point behavior will be observed. If the reservoir temperature lies between the critical and cricondentherm temperature, dew point behavior and retrograde condensation will occur. For reservoir temperatures above the cri- condentherm, only a single gas phase can exist in the reservoir regardless of pressure. Providing the composition of the reservoir fluid were known, it would be possible to predict the critical temperature and estimate the phase behavior from equilibrium relationships. However, the usual practice is to obtain a sample of reservoir fluid, subject it to varying pressures at the reservoir temperature and observe the phase behavior experimentally. The latter method was used to obtain the data reported here. WELL AND TRAPPING INFORMATION A summary of pertinent data for the well from which the reservoir fluid was sampled is presented in Table 1. This well is located offshore Louisiana. Except for the pressure which substantially exceeds hydrostatic pressure, the information does not appear unusual. Prior to the sampling program, the well was produced for 22 hours at a stock tank oil rate of 139 B/D. Average trapping conditions and gauging data for the six-hour test period that followed are summarized in Table 2. Samples of the first-stage trap gas and liquid were obtained during the latter portion of the test period. Ambient temperature remained 5 to 10F below trap temperature and presented no problem for sampling. Surface wind and moderate foaming of stock-tank oil presented some difficulty in obtaining accurate stock-tank gauges. SAMPLE ANALYSIS Compositions of the gas and liquid samples are shown in Table 3. The trap gas was analyzed by isothermal chromatography which revealed only a trace of heptane in the stream. The trap liquid was initially analyzed by low-temperature fractional distillation, yielding a bottom product of heptane and heavier components. Specific gravity of this fraction was measured and the mol weight was determined by freezing point depression. The hexane and lighter overhead gas collected during distillation was

Jan 1, 1967

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 D. A. Flanagan, P. B. Crawford

A study has been made of the feasibility of storing liquid meihane at low pressures in undergrohd caverns. Methane liquefies at — 258°F at atmospheric pressure. It is shown that the methane evaporation rates will rapidly decrease and cool the surrounding rock so that at the end of one month they would be between 50 Mcf/hr for a cavern of 25-ft radius and 700 Mcf/hr for a cavern of 100-ft radius. At the end of 10 years, the evaporation rates would be 18 and 100 Mcf/hr, respectively, for caverns of the same radii. The evaporation rates may be reduced by a factor of 2 to 10 by the application of insulation. The cost for mining the caverns is estimated to be $.75 to $1.25/Mcf of storage. This is substantially less than surface storage; it is believed to be safer and to result in lower maintenance, savings in space and savings in strategic materials. INTRODUCTION During the past few years, there has been an increasing interest in the economic feasibility of liquefying methane. Methane liquefaction is being considered for tanker transport; in addition, liquefaction is being reconsidered for shaving peak gas demands. Several articles have described natural gas liquefaction and the progress of the tanker in making trial runs from the United States to Great Britain to determine the feasibility of tanker transport. At the present time, pipelines are not designed to supply peak gas loads during extremely cold periods such as are oiten encountered in the North and Northeast. Gas is being stored in underground reservoirs en-route to its destination, but in many instances satisfactory storage in porous reservoirs has not been practical, especially along the Eastern seaboard where few petroleum reservoirs have been found. In England and other foreign countries, it is unlikely that satisfactory porous structures could be found, and it may be desirable to mine or excavate the rock to obtain storage. By storing the methane near the consumption point, product availability can be increased during periods of need. Methane liquefies at - 258OF at atmospheric pressure, and 1 cu ft of liquid methane will make about 600 cu ft of gaseous methane. Methane liquefaction for shaving peak gas demands was conducted in Cleveland, Ohio in the early 1940's. The Cleveland plant was designed to liquefy 4 MMcf/D of natural gas.' Development of several low-temperature processes has resulted in some improvements in the design of low-temperature storage vessels. Liquefied-methane storage vessels can be designed for various evaporation rates. The desired rate will depend on the reason for liquefaction. For shaving peak gas demands, the desired evaporation rates would be low, possibly between 0.2 and 1.5 per cent/day. For methane tanker transport and supply, the evaporation rates must be high and must equal the total daily rate of supply. It is apparent that the cost of storage facilities will depend on the objective and will vary appreciably. Surface storage of methane may cost between $3,000 and $20,000/MMscf, depending on the size and design. The failure of the surface storage vessels at Cleveland, with the resulting injury and loss of many lives, has caused considerable emphasis to be placed upon developing new, safer and improved methods of storing liquid methane. Storage of liquefied propane and butane in underground salt domes has been very satisfactory. The per-barrel cost of underground storage for any sizeable capacity is very small compared to the cost of surface storage for LPG mixtures. The larger the capacity of the underground storage, the less is the per-barrel cost. Numerous advantages appear to exist if liquefied methane could be satisfactorily stored underground, the principal advantages being increased safety, lower initial cost, lower maintenance cost, savings in space and savings in strategic materials. The purpose of this paper is to determine the feasibility of storing liquid methane underground in mined caverns. If a large spherical cavern is dug underground and is filled instantaneously with liquid methane, the surface of the sphere may approach the liquid methane temperature almost instantaneously. The temperature distribution for a sphere of radius r. in an infinite medium, initially at one temperature with spherical surface kept at T, from time t = 0, is given by Eq. 1.'

By A. K. Mukherjee, John E. Dorn

The effects of strain rate and temperature on the critical resolved shear stress for (321)[111] slip were determined for the silver-rich CsCl type of intermetallic compound AgMg. The flow stress increased only slightly as the test temperature was first decreased below room temperature; a rapid increase in the flow stress was obtained with yet further decrease in temperature from about 250' to 4OK. The effect of both the temperature and strain rate on the flow stress over the low-temperature range could be rationalized satisfactorily in terms of the Peiwls mechanism when the deformation was controlled by rate of nucleation of pairs of kinks. IN spite of the well-documented interest of metallurgists and engineers concerning the mechanical behavior of intermediate phases and intermetallic compounds, very little definitive information is available on this important subject. As recently summarized by westbrook,1 only limited and modest progress has been made thus far in elucidating the details of the mechanism of plastic deformation for the intermetallic compounds; the available information largely concerns phenom-enological descriptions of empirical observations and experimental facts, principally with reference to poly crystalline aggregates. The present report on the elucidation of the rate-controlling mechanism for slip in the bcc structure of AgMg is part of the comprehensive program of a systematic investigation on the mechanical behavior of intermetallic compounds. The intermetallic compound AgMg has a CsCl type of lattice structureZ and is completely ordered up to its melting point of 820c3 This material was selected for our present investigation because of its simple crystal structure, moderate and congruent melting point, ordered structure persisting up to the melting point, and some solubilities of the constituent elements, which could be expected to help in the growing of single-crystal specimens. Whereas previous investigations on the properties of AgMg include hardness,*"6 slip systems,7 tensile flow stress of polycrystalline specimens,' and electrical resistivity,4 the current investigation will be directed principally at elucidating the rate-controlling dislocation mechanism responsible for slip in single crystals at low temperatures. It will be shown that the strain rate is consistent with a model involving the rate of nucleation of pairs of kinks by the Peierls mechanism for plastic deformation. EXPERIMENTAL TECHNIQUES Single-crystal specimens of the AgMg intermetallic compound were prepared and tested as follows: 1) A master alloy ingot of AgMg was produced by melting and chill casting the high-purity silver (99.995 wt pct) and high-purity magnesium (99.997 wt pct) in an induction furnace under a helium atmosphere. 2) Sections of the above-mentioned ingot were placed in a graphite mold containing a spherical cavity in which a single-crystal sphere of 1 in. diam was grown under helium by the Bridgman technique. 3) The operative slip systems were investigated at room temperature on a singlecrystal of AgMg, from measurements of the angles made by the slip traces on the two surfaces of the specimen, which were at 90 deg to each other. The investigation confirmed that the AgMg compound undergoes slip primarily in the (321) plane and in the [Ill] direction, but a small amount of secondary slip was also noticed in the (112) (111) system. No slip was observed in the (110) planes. 4) The single-crystal sphere, mentioned earlier, was oriented in a graphite mold containing a cylindrical cavity of 3/8 in. diam above the spherical receptable to give the angle xo = 45 deg between the axis of the cylindrical bar and the normal to the slip plane (321), and the angle AO = 45 deg between the slip direction [Ill] and the axis of the bar. Oriented single-crystal bar seeds were produced by melting, under a helium atmosphere, a polycrystalline bar in the cylindrical cavity above the oriented spherical seed and by growing an oriented single-crystal bar from the seed. 5) Finally, oriented single-crystal specimens were grown from these cylindrical seeds. 6) The cylindrical specimens were machined in a High-Tension Spark Cutting unit to give a 2-in. gage length. The spark-machined gage section was elec-tropolished in a bath containing 200 ml of H3PO4,

Jan 1, 1964

By W. A. Jr. Slippy, E. P. Dahlberg, R. B. Reed-Hill

A large room-temperature mechanical-hysteresis effect under cyclic tensile loading was observed in zivconium specimens prestrained at 77°K so as to form large numbers of (1121) twins. The observed hysteresis loss was a maximum when the prestrain was just under 1 pct It also depended strongly on the maximum applied cyclic stress, but only moderately on loading rate and temperature (-72°to 100°C). The phenotnena have also been studied in terms of the elastic aftereffect where the data has been found to cotlforln closely to the functional relationship between strain and time, c = -RT/a In tank ft. t to)/Zr, for strains cts large as about 10-4 This eyication can be derived directly from the strain-rate equation There may be important commercial implications to the present discovery since it appears that within rather wide limits it may be possible to obtain any desired magnitude of damping capacity in zirconium melal. The damping propevties may also be given directional characteristics. It is shown that the observed anelaslic phenomena can he explained on the assumiplion that they are the resuilt of stress-induced twin-boundary movements in which the average twin increases its thickness by only a few percent. In polycrystalline zirconium, a grain is least favorably oriented for slip when its basal plane, containing the (1130) slip directions, lies nearly perpendicular to the principle normal stress. Mechanical twinning is favored by this orientation and under simple tensile deformation at room temperature the primary twinning mode is {1012).' The (1012) twinning shear is small (0.17) so that, during deformation, twin growth does not greatly enhance ductility. At 77°K, on the other hand, the predominant twinning mode shifts to {1121), and many thin (1121) twins can form at small strains.' Twins thus nucleated can grow readily during subsequent room-temperature deformation and permit easy deformation in unfavorably oriented grains. In addition, the (1131) twinning shear is large: 0.63. These facts have lead to a process' for greatly improving the room-temperature ductility of zirconium when it contains a sizable fraction of grains with basal planes nearly normal to the stress axis. Optimum results are obtained by slightly less than 1 pct prestrain. The effect is large so that a 50 pct elongation increase is readily attained. A large room-temperature mechanical-hysteresis effect has also been observed in zirconium specimens prestrained at 77°K. The present paper is concerned with some aspects of this effect which the experimental observations strongly indicate is primarily the result of strain-induced {1121) twin-boundary movements. This clearly suggests that mechanical twins formed by plastic deformation can cause anelastic effects similar to those previously observed2 for annealing twins and twins associated with phase transformations. EXPERIMENTAL PROCEDURES All specimens were prepared from arc-melted sponge zirconium plate stock as previously described,3 which has a preferred orientation with basal planes aligned parallel to and uniformly distributed around the rolling direction. Both lonti-tudinal and transverse tensile specimens, with axes parallel and transverse, respectively, to the plate rolling direction, were cut from this plate. In a longitudinal specimen most grains are favorably oriented for slip, while in a transverse specimen a large fraction are unfavorably oriented. Prestraining at 77°K was performed in two ways. In one, annealed zirconium plate stock was cooled in liquid nitrogen and then rolled in the transverse plate direction to strains varying from 0.5 to 12 pct. Cylindrical 1/8-in.-diameter by 1-1/4-in.-gage-length tensile specimens were machined from this material. In the other, previously machined tensile specimens were prestrained in tension at 77°K between 0.2 and 3.8 pct. Type FA 25-12 SR4 strain gages were cemented to all specimen gage sections. All tests were performed on an Instron testing machine of 10,000-lb capacity. EXPERIMENTAL RESULTS Fig. 1 shows a typical two-cycle room-temperature stress-strain diagram for a specimen prestrained 0.65 pct by rolling at 77°K. The maximum stress in both cycles was 14,500 psi. Note that in the first cycle the loading and unloading curves are unsymmetrical so that a residual strain, er, remains after unloading. In the second cycle the stress-strain curves form a nearly symmetrical hystere-

Jan 1, 1965

By W. V. Swarzenski

In its effort to combat waterlogging and soil salinity, the Water and Soils Investigation Division of WAPDA (West Pakistan's Water and Power Development Authority) has carried out an extensive program of test drilling andwater sampling since 1954. Data collected during the past ten years have permitted the delineation of fresh and saline groundwater zones in the Punjab Plain. Fresh groundwater containing generally less than 500 ppm of total dissolved solids is found in wide belts paralleling the major rivers and in other areas of fresh-water recharge. Locally, fresh groundwater extends to depths of 1500 ft and more. Saline groundwater occurs down gradient from sources of recharge, particularly in the lower central parts of the interfluvial areas, and presumably underlies most of the Punjab Plain. The groundwaters of the Punjab are characterized by their evolution from calcium, magnesium bicarbonate waters near sources of recharge to waters containing a dominant proportion of sodium. The highly mineralized waters of the Punjab are generally of the sodium chloride type, whereas in the Dera Ismail Khan District, sodium sulfate waters predominate. The pattern of distribution of saline groundwater zones and the observed gradual increase in mineral content, down gradient from sources of recharge, can be explained best by a hypothesis stressing the process of evaporation from the water table and solution of minerals within the alluvial aquifer. In 1954, detailed groundwater surveys in the Punjab Plain were initiated by WASID, the Water and Soils Investigation Division of West Pakistan's Water and Power Development Authority. The investigations, undertaken under a cooperative agreement between the governments of Pakistan and the United States, were aimed at the formulation of reclamation measures to improve waterlogged and saline soils, and to assess the groundwater potential of the Punjab and other areas of West Pakistan. The nature and urgency of WASID's primary task limited the exploration of the alluvial aquifer generally to its uppermost part. About 1030 test holes drilled in 47,000 sq miles of the Punjab defined the nature of the alluvium to depths of about 600 ft and yielded data on water quality to 400 or 500 ft. A report on the hydrology of the Punjab, based on the results of these investigations was published by WASID in 1963.' The present report incorporates data obtained by WASID since 1962 in a program of deep test drilling in the Punjab and the adjacent areas of Bahawalpur and Dera Ismail Khan District, permitting the definition of fresh and saline groundwater zones to depths of 1500 ft in some areas. Groundwater in the Punjab Plain is contained in alluvial deposits, predominantly sand and silt, which extend almost everywhere to depths of 1000 ft and more. The alluvium has been deposited by the Indus River and its tributaries since late Tertiary time and is contiguous with similar deposits in India. The Indo-Gangetic Plain extends from the foothills of the Himalayas to the ancient rocks of the Peninsular Shield in central India and to the ocean. Gradients are generally very low and range from about 1% ft per mile in the upper part of the plain to less than 1 ft per mile in the south and southwest. The monotony of the alluvial plain is broken by scattered bedrock outcrops in two of the interfluvial areas, Chaj Doab and Rechna Doab. The bedrock hills are projections of the northwest-trending Delhi-Shahpur Ridge that is largely buried by alluvium. The rocks of the buried ridge, presumably of Precambrian age, are essentially impermeable and define the lower limit of the alluvial aquifer in parts of Chaj, Rechna, and Bari doabs. Elsewhere in the Punjab, there are no outcrops of other consolidated rocks and their presence below the alluvium is conjectural. The principal areas of bedrock outcrops, near Kirana and Sangla, are shown diagrammatically in Fig. 1. The movement of groundwater through the alluvial aquifer of the Punjab has been described by Green-man and others.' In most of the area, the pre-irriga-tion water table sloped from the rivers downstream and toward the central axes of the doabs, indicating that the rivers were sources of groundwater recharge. As a result of seepage from irrigation canals, water levels have risen as much as 90 ft. In 1960 they were within 5 to 15 ft of the land surface and above the

Jan 1, 1970

By F. M. Smith, R. H. Moore, J. R. Morrey

Electrodiffusion in y cerium reported by Henrie has been confirmed and a Preliminary estimate made of the relative rates of electrodiffusion of iron, cobalt, and nickel. These diffuse to the anode at rates decreasing in that order. In addition, copper and manganese exhibit slow, but detectable, diffusion to the anode and molybdenum exhibits detectable diffusion to the cathode. The electrodiffusion of carbon, .zirconium, antimony, magnesium , and silicon in y cerium could not be detected. Iron and cobalt diffuse in y cerium at rates proportional to the current density and with no apparent dependence on temperature. Decreasing polarization of iron and cobalt with increasing temperature, which cancels the expected rate increase, would account for this behavior. The electrodiffusion rate of iron in y uranium and in E plutonium has been measured. Diffusion of iron is anode-directed. Tin was found to diffuse to the cathode, in y uranium, at an appreciable rate. In all of these solvent metals, negative ions diffuse to the anode and positive ions to the cathode. The potential field effect appears to account satisfactorily for these results. FROM early experimental work summarized by Jost1 and Seith,2 the driving force for electrodiffusion was attributed to the potential field acting on ions in a metal. More recently, Heuman,3 Wever,4 and Huntington5 have shown that momentum interchange between conduction electrons and mobile entities in the metal contributes to electrodiffusion. Electron momentum interchange is anodically directed and the direction of diffusion resulting from the field force is dependent upon the charge on the diffusing entity. These two effects may either reinforce or oppose each other. Glinchuk6 has pointed out that momentum transfer in defect conductors should be cathode-directed and this appears to be the case as demonstrated by wever's4 work on iron. Barnett's7 work, on the other hand, indicates that, even in defect conductors, electrons show a negative E/m ratio when accelerated with respect to the lattice and should lead to anode-directed momentum transfer. In discussing this problem, Wever and seith8 suggest that defect electrons interact preferentially with activated ions so as to allow a net movement toward the cathode while still maintaining an electron momentum transfer in the anode direction. Williams and Huffine9 and Henriel0 have demonstrated that electrodiffusion may be useful for purification of yttrium and cerium. In yttrium, Williams and Huffine note that movement of several metallic impurities toward the anode is in keeping with observations in most other metallic systems and indicates that yttrium remains a normal electronic conductor at least to 1230°C. Close inspection of their data shows, however, that oxygen, nitrogen, and the transition elements diffused toward the anode, while nontransition elements diffused toward the cathode. This suggests that potential field effects may have been appreciable. The present work was concerned with the applicability of electrodiffusion as a technique for purification of plutonium, but, because of the obvious hazard inherent in work with this metal, experiments to develop the technique were carried out using cerium and uranium. The results of electrodiffusion measurements on these metals and on plutonium are reported here. EXPERIMENTAL The metal specimens prepared for this work were 6 in. long, 1/4 to 1/2 in. wide, and 1/16 to 3/32 in. thick. The uranium specimens were machined from a bar which analyzed 310 ppm Fe and the electrodiffusion of iron was followed by spectrographic and by chemical analysis. Cerium and plutonium specimens were cut from sheet rolled from ingots obtained from molten salt-metal equilibrations during which radioactive tracers were introduced. The electrodiffusion of the tracers was subsequently determined by counting methods. The specimens were electrolyzed between nickel electrodes containing resistance heaters used to equalize the specimen and electrode temperatures, thereby reducing thermal gradients. The temperature of the electrodes adjacent to the ends of the specimen was measured with chromel-alumel thermocouples which were connected to the heater controls. The surface temperature of the specimen at a point midway between the electrodes was measured with a sapphire rod pyrometer, the output of which controlled the dc power supply. This assembly was enclosed within an evacuable chamber containing a quartz viewing window. The temperature of the specimen over its entire length could be scanned with a portable pyrometer through

Jan 1, 1965