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By F. W. Jessen, G. F. Sears

Cavities in massive salt for the purpose of storage of liquid hydrocarbons have assumed a prominent position in recent years. This paper describes a program to facilitate leaching operations for the formation of specifically shaped storage cavities. Various forms and sizes of cavities may be possible through use of the techniques developed. INTRODUCTION The creation of large under ground storage facilities for natural gas and liquified petroleum gases has been practiced for many years. Use of cavities obtained through solution of salt for this purpose is a fairly new and novel approach, but has gained increasing importance due mainly to the economics of this type of mining operation opposed to hard rock mining or surface and pit storage.1 The idea of controlling the shape of any cavity dissolved from massive salt has not been a prime consideration of companies engaged in the formation of storage space. This has been due mainly to an insufficient knowledge of the mechanics of the leaching process and a dearth of published information dealing with both the desirability and ease of control possible for this type of operation. Two distinct advantages are readily ascertainable. From a stability standpoint (i.e., the ability of the completed cavity to withstand stress imposed by overburden pressure and lateral tectonic stresses) a controlled cavity may be generated which will yield the most favorable attitude to these external forces and remain in operable use for longer periods of time.2 A second advantage is that for a given volume, a sphere (which is one controlIed shape possible) represents the minimum surface area exposed. This may become more important in the future when dealing with refrigeration and product losses in underground cavities. The basic solution mining process, without regard for controlling the final shape, is quite simple in that the equipment and materials required to dissolve a cavity in a salt dome or layered salt section are a source of fresh water, a circulating pump, several strings of tubing and a means of disposal of the return brine. To add control measures involves the use of an inert blanket material above the position at which solution proceeds. Initially the annulus of the largest wash pipe is filled with this blanket down to the top of the proposed cavity. The bottom of the proposed cavity is determined by the depth of the original drilled hole or a blanking plug. The blanket material is added incrementally in stages and displaces the water in the enlarging cavity downward. Where the blanket material has displaced the water, no further solution takes place. The rate at which to add this controlling blanket material so as to be able to form specifically shaped cavities of any particular size is of considerable importance. THE PROBLEM It is desirable to have as much information as possible as to the behavior of the mining operation since visual observation obviously is impossible. It would be advantageous, for example, to have a step-by-step program showing how much salt is to be removed, at what rate and the time required. This type of program would facilitate procurement of surface equipment and provide for proper management of manpower requirements, as well as yield a host of intangible benefits. As mentioned earlier, only rule-of-thumb estimates were available until recently and made this type of pre-planned operation haphazardous at best. Recent work3-' has done much to clear up the ambiguities and inaccuracies attendant to solution mining of salt and has helped to place the operation on a more scientific basis. This study attempts to correlate much of the information thus far developed into a complete mining program; to extend the idea of controlled solution mining to include not only spheres, but solid conic sections of the ellipsoidal variety; and to refine the computation of the rate of removal of salt during the various stages of mining. Dommers3 and IIemson4 made extensive laboratory

Jan 1, 1967

By Anson Hayes, John Chipman

The quality of sheet and strip products made of rimming steel is closely related to the structure and chemistry of the ingots. The variation in composition throughout the ingot, as affected by segregation, is of great importance, as are also the form and distribution of the voids that result from the gases evolved. It is because of this importance that the considerable literature in this field has accumulated. No attempt is made in the present paper to compile a bibliography of the excellent work that has already been done, as this has been adequately covered in the many excellent reports on the heterogeneity of steel ingots prepared by a joint committee and published by the Iron and Steel Institute.' From time to time, in any field of investigation new tools and new technique are developed, which make further progress possible. In the field with which this paper is concerned, this is true. The development of the vacuum-fusion method as a means of following oxygen segregation, and a technique for obtaining the volume and composition of the gases evolved during solidification, have opened the way to obtaining data by means of which some considerable progress has been realized in developing more of the detailed mechanisms of solidification and segregation in rimming-steel ingots. General Theory of Segregation The basic cause of segregation lies in the fact that the impurities are less soluble in solid than in liquid iron. The solid that forms from the impure liquid is more nearly pure than the liquid itself. If solidification proceeds slowly enough, or if the liquid and solid phases are maintained in contact with one another for a sufficient time, a condition of equilibrium is set up, which may be represented by a phase diagram. Portions of the

Jan 1, 1939

By Anson Hayes, John Chipman

The quality of sheet and strip products made of rimming steel is closely related to the structure and chemistry of the ingots. The variation in composition throughout the ingot, as affected by segregation, is of great importance, as are also the form and distribution of the voids that result from the gases evolved. It is because of this importance that the considerable literature in this field has accumulated. No attempt is made in the present paper to compile a bibliography of the excellent work that has already been done, as this has been adequately covered in the many excellent reports on the heterogeneity of steel ingots prepared by a joint committee and published by the Iron and Steel Institute.' From time to time, in any field of investigation new tools and new technique are developed, which make further progress possible. In the field with which this paper is concerned, this is true. The development of the vacuum-fusion method as a means of following oxygen segregation, and a technique for obtaining the volume and composition of the gases evolved during solidification, have opened the way to obtaining data by means of which some considerable progress has been realized in developing more of the detailed mechanisms of solidification and segregation in rimming-steel ingots. General Theory of Segregation The basic cause of segregation lies in the fact that the impurities are less soluble in solid than in liquid iron. The solid that forms from the impure liquid is more nearly pure than the liquid itself. If solidification proceeds slowly enough, or if the liquid and solid phases are maintained in contact with one another for a sufficient time, a condition of equilibrium is set up, which may be represented by a phase diagram. Portions of the

Jan 1, 1939

By George Packard

THE shaft of the Raven. mine, at Butte, Mont., is an incline 1,700 ft. in length and dipping at various angles. At the top the dip is 70° from the horizontal, but this is gradually flattened until at the 300-ft. level the inclination is only 47°. This angle continues to the 1,100-ft. level, below which it, curves with a 125-ft. radius to 78°. In addition to these variations in dip, the shaft does not lie in the same vertical plane, with the result that the hoisting rope not only rubs at intervals on both the hanging- and foot-walls, but presses strongly against the west, dividers near the collar, while 300 ft. below it runs close to the east end plates. The early operators used no idlers, and wall plates cut 6 in. deep y the rope resulted. Later operators first attempted to overcome the excessive friction, and the wear of rope and wall plates, by introducing solid cast-iron idlers, 3 in. in diameter. To allow for the travel of the rope from side to side some of these had to be 3 ft. long and were very heavy. Judging from the appearance of the old idlers of this type found at the mine, they often failed to turn in the bearings, which is not surprising when it is considered that they would have to make 1,000 rev.. a minute under ordinary hoisting conditions. The next rolls were made of wood, 6 in. in diameter, with an iron band about each end, and a pintle of 1-in. round steel driven in at the ends to serve as a shaft. These wore rapidly, and were soon replaced by rolls made from water pipe, 5 or 6 in. in diameter, cut to the desired length and fitted with a wooden cylinder into which the pintle was driven. Where the idlers were used on the hanging-wall of the shaft the original bearing was simply a piece of 2 by 1-1 in. strap iron, 10 in. long, turned up at the end in a circle of 18 in. in diameter to receive the shaft. A small hole served for oiling, and common black oil was generally used, although filtered oil from engine bearings and compressor bearings was also used. When the rolls were to be placed on the foot-wall the bearings were made from two pieces of 1 by 3 in. steel, 6 in. long. A half circle was cut on the flat side of each piece and the two half circles together formed a bearing. Oil holes were provided, and in some cases holes were bored through the two pieces so that they could be screwed or spiked to the wall plates.

Jan 8, 1914

By S. J. Matas, R. F. Hehemann

The existence of two distinct forms of bainite—upper and lower bainite—in hypoeutectoid steels is confirmed by a systematic study of the structure of the product resulting from this mode of austenite decomposition. The transition between these two forms occurs at about 650° F regardless of the alloy content of the steel and their structural differences can be interpreted in terms of the kinetics of carbide precipitation from supersaturated ferrite. In the past few years, a renewed interest has been displayed in the kinetics and mechanism of the bainite reaction in steels. Several rather divergent models for the transformation mechanism have evolved from these studies,'-' however, it is difficult to evaluate these models critically on the basis of the existing experimental data. In particular, a more detailed knowledge of the structure of bainite should be helpful in providing a framework for the construction of an appropriate model. Metallographic studies7-l4 have led to a recognition of at least two distinct forms of bainite—frequently termed upper and lower bainite. Although the morphology of bainite changes with reaction tem- perature, there appears to be a relatively sharp transition between the two forms. This occurs in a narrow temperature range near 650° F. Transformation at temperatures below about 650° F results in the presence within the bainite of small plates of carbides oriented at an angle of 60 deg with respect to the direction of growth of the plate, while at higher temperatures carbides are oriented parallel to the growth direction. There is no generally accepted view regarding the significance of this structural transition. Some authors feel that carbides precipitate from austenite at all reaction temperatures1' while others claim, at least for low-temperature bainite, that carbides precipitate from supersaturated ferrite.14.15 It was recognized many years ago that the nature of the carbide in bainite depends on the reaction temperature. The carbide hase in upper bainite is unmistakenly cementite.16-19 The exact nature of the carbide in low-temperature bainite is less certain. Magnetic measurements of lower bainite reveal no cementite Curie point21'22 and dilatometric studiesz0 produce total expansions which are larger than those predicted on the basis of a ferrite-plus cementite structure. These effects have been attributed to the

Jan 1, 1962

By S. W. Poole, J. A. Rosa

THE object of this investigation was to determine the distribution of chemical elements within a large, killed alloy-steel ingot, by sulphur printing and quantitative chemical analysis. With regard to segregation in steel ingots, the factors of melting practice, pouring temperatures, mold design, etc., and the mechanics of solidification and its attendant functions, have been the subject of intensive study over a period of years by many investigators. Notable among these is the Sub-Committee of the No. 5 Committee of the British Iron and Steel Institute. For an exposition 0f the many problems awaiting the researcher on the heterogeneity of steel ingots, the methods of attacking these problems, together with some of the answers, the reader is referred to the nine reports and numerous papers of that committee and its membership. STEELMAKING DATA Melt.-The heat was made in a 70-ton direct arc-type basic electric furnace. Furnace charge consisted of nickel-chromium-molybdenum steel, most of it in the form of heavy mill scrap. All of the scrap was charged cold. The standard double-slag method was employed, the heat being finished under a strong carbide slag. Aluminum was used as the deoxidizing agent. Tapping temperature, as observed with an optical pyrometer, was 3000°F. Detail of Mold and Ingot Size.-Details of the ingot mold and the ingot itself are given in Fig. I. Teeming.-Teeming temperature of the subject ingot as observed with an optical pyrometer was 2830°F. The ingot was top-poured directly through a 1 ½ in. nozzle and required 7 min., 44 sec. to fill up to the hot top. An additional 2 min., 30 sec. were required to fill the hot top. The ingot was stripped hot and charged with the remainder of the heat into an annealing furnace. There it was given the standard annealing cycle used for these ingots. Subsequent heat-treatments are described elsewhere in this paper. SECTIONING AND PREPARATION FOR SULPHUR PRINTING Because of previous favorable experience in sectioning ingots up to 21 ½ in. square with an oxyacetylene torch, it was decided to use this method to section the subject ingot. The ingot was preheated to 900°F. for 12 hr. It was then placed on a steel bed in a horizontal position so that the longitudinal axis was level and parallel to the track of the motor-driven torch carrier. Two cuts were made, one 2 in. above the longitudinal axis and the other 2 in. below. The time required to make each cut was approximately 75 min. The cutting operation is shown in Figs. z and 3. The 4-in. thick slab was mmediately charged into a furnace standing at 1200°F.

Jan 1, 1944

The Western World's gold reserves now exceed 23,000 mt (750 million oz), 65% of which exist in South Africa. Although several major mines are reducing production or closing because of depletion of reserves, new mines or expansions of existing mines are coming on-stream which will maintain an annual production of 684 mt (22 million oz) of gold well into the 1990s. These new operations by the South African mining industry represent the largest expansion since the opening of the Witwatersrand gold fields in 1886. Included in three new mines being opened is that of Anglo American Corporation's Elandsrand plant, their fir& new gold venture in South Africa in seventeen years. Current average grade of South African mines is 8.2 g Au per mt (0.24 oz per st); and while the cost of the Elandsrand 135,000 mt (149,000 st) operation, including mine development, was about $314 million, it is estimated that the cost of a comparable operation started today and completed in the mid-1980s would be of the order of $480 million. New mines to exploit low-grade ore bodies are, therefore, likely to be few in number, and further expansion will undoubtedly be in the form of extensions to existkg operations where cash flow can be used to finance development. The authors' first monograph, "Gold and Silver Cyanidation Plant Practice," devoted a section to South African cyanide plant operation; and it is believed that this new volume would not be complete without a description of Elandsrand, South Africa's newest gold plant. The Elandsrand mine is adjacent to Anglo American's Western Deep Levels on the Far West Rand. The decision to go ahead with the development was taken in mid-1974 from the results of exploration drilling carried out over a period of .lo years. Results of 17 bore holes and 68 intersections of the Ventersdorp Contact Reef had indicated a gold-.bearing reef less than one meter thick at a depth of 1,800 to 3,000 meters (5,900 to 9,840 ft). Preliminary studies indicated a mine of 900 km (560 miles) of underground workings would yield 725,000 kg (23. 3 million oz) of gold from 60 million mt (66 million st) of ore to be milled over a period of 34 years. Eventually, when the mine is in full production, the total hoisting capacity will be 300,000 mt per month (331,000 st) for a milling capacity of 225,000 mt per month (248,000 st). The Elandsrand surface facilities have been built on a low range of 0 hills to take maximum advantage of the 10 slope in transporting ore

Jan 1, 1981

By Geoffrey Gilbert

A study of specimens shows that the key to both oxidation and enrichment at Duck-town is the behavior of pyrrhotite, which is in part dissolved and in part replaced by marcasite. Enrichment takes place chiefly at the expense of marcasite. THE material that forms the basis of this paper was collected in the spring of 1922, during a ten-day visit to Ducktown by the writer in the company of Prof. L. C. Graton. The time available for the work was far too short to allow anything like a thorough study of the deposits, and structural and stratigraphic questions, though they have an important bearing on the origin of the primary ores, were necessarily left untouched. Attention was focussed on the zone of oxidation and enrichment; and by devoting most of our time to the upper levels, open pits, and old workings, and examining the deeper levels only thoroughly enough to obtain a fair idea of the nature of the primary sulfide ore, we were able to make a reasonably complete survey of the various orebodies. With this field work for a background, the writer later made a study, in the Harvard laboratories, of the specimens obtained during the visit. As some of the facts brought to light by this study appear to be new, it seems worth while to set forth the outstanding features and a proposed explanation of them. Much of the Ducktown material that is obviously of greatest significance, as regards oxidation and enrichment, is soft and crumbly. Notwithstanding the desirability of gaining from such material all possible information as to its mineral composition and textural relationships, but little has heretofore been learned regarding it; but, by suitable preparation of this material in connection with the present study, it has been possible to examine it under the microscope without any disturbance of its texture and about as satisfactorily as if it were hard, fresh ore. The information thus gained has contributed measurably to the results set forth in this paper.

Jan 3, 1924

By E. D. Fields, R. W. Sayers, M. C. Tippett

The Duval Corp. porphyry copper deposits at Copper Canyon and Copper Basin, though widely separated, form an econornic unit requiring integrated exploitation. Contrasts in mineralization, host rocks, and mode of occurrence present unique mining and milling problems. Mixed oxide-sulfide ore is treated in extensive dump leaching facilities in both areas. Complex Cu-Au-Ag ore is treated in a 4000-tpd mill at Copper Canyon. In both areas, hypogene metallization occurs within large aureoles of metamoiphism and hydrothennal alteration related to quartz monzonite intrusions of mid-Tertiary age. Supergene processes fitrther altered the rocks and enriched the hypogene protore. At Copper Canyon, hypogene copper and iron sulfides with gold and silver occur in fractures, as partial replacement of favorable beds, and as disseminations in Paleozoic sedimentary rocks. The lower part of the Pennsylvanian Battle formation was a particularly favorable host. Metallization occurs to a lesser extent in quartz monzonite. Metal zoning is well-developed. The deposits at Copper Basin consist principally of supergene copper minerals in arenites of the Cambrian Harmony formation. Oxidation of hypogene copper and iron sulfides in tactite zones has formed at least two commercial deposits; intersections of fractures with favorable beds exerted important ore controls. Recently, the Copper Canyon and Copper Basin properties of Duval Corp. have been added to the list of porphyry copper mines in Nevada, marking the first new copper open pit in this state in 15 years. The properties are situated in the Battle Mountain

Jan 1, 1970

By J. W. Graham

For many years the author has been cognizant of the difficulty encountered by some in treating with the water influx formulas for unsteady-state fluid flow as pertain to the material balance equation. This has particularly applied in establishing reservoir performance and identifying reservoir pressure, which to the practicing engineer has entailed a trial-and-error procedure, and for others has necessitated resorting to computing devices and reiteration processes. In retrospect this difficulty stems from the fact that reservoir pressure in the material balance formulas, as well as associated with the water influx equations, is an inexplicit term, and the work reported in the past is irrefutable. However, what will be presented in this paper is another approach to the problem, whereby the entire material balance equation will be treated by the Laplace transformation, and reservoir pressure which hereto has been inexplicit, can now be isolated by mathematical procedure to relate that parameter with all the factors contributing to its change. This is the simplification entailed, that treats first with an undersaturated oil reservoir as an integrated effect from the inception of production. The second phase pertains to saturated oil reservoirs that encompass a survey traverse. Although both methods of approach are necessarily different in aspect, the most interesting fact is that the mathematics so deduced are identical. Both the linear and radial water-drive systems are incorporated. for which an illustrated factual example is offered for the latter, treating with a saturated oil reservoir. INTRODUCTIO N What is performed in this work is the simplification of an involved computation by advanced analysis. Although such may be construed as a contradiction when one treats with higher mathematics; nevertheless, when direction is given to such an undertaking the results car. be most revealing. Likewise, it is to be mentioned that the bases for these mathematics have been developed on the expediency of the occasion. This is not to be inferred as a qualification of this work, but rather the demands frequently placed upon the author in his private prac- tice in meeting a time limit. A situation, instead of being fraught with hazards, often has given emphasis to creative thought. What will be entailed in this work is the simplification of the material balance formulas by the Laplace Transformation., Although this reveals entirely new horizons that will be given expression in a forthcoming tract, it suffices in the present instance to limit our attention to this phase of the development that treats both with an undersaturated and saturated oil reservoir. To orient the reader's thoughts as to what is involved in this simplification is the recognition that reservoir pressure, as such, is an inexplicit term in the material balance equation. This is the independent parameter that defines the total history of performance in the author's' unsteady-state water influx formulas, as well as the basis for the physical dependency of fluid behavior within the formation as prescribed in the Schil-thuis' material balance equation. Therefore, to isolate reservoir pressure, which is the most essential factor in any reservoir study, is rather a cumbersome procedure entailing either a trial-and-error calculation for the engineer; or as some prefer, a reiteration process performed on a computing device. However, once such an equation can be transcribed as a Laplace transformation, this inexplicitness so expressed can be alleviated to identify reservoir pressure as an explicit function of all the factors contributing to its change. This is the simplification encompassed, that will treat first with an undersaturated oil reservoir as an integrated effect from the inception of production, and secondly, with a saturated oil reservoir as a survey traverse. Although the two approaches are necessarily different because of the uhvsics involved. it is an interesting commentary that the mathematics are identical, showing the interdependency of the two methods. In order to acquaint the reader with this development, the simplest case will be treated first; namely, an under-saturated oil reservoir subject to a linear water drive. However, what may be construed for this example as an idealistic case is actually a most practical application in certain parts of the world, where the size of the fields are so large that radial water-drive approaches the configuration of a linear drive. Further, to avoid the repetition of much symbolism, frequent references will be made to the work of the author and an associate on Laplace Transformations3,

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 Charles R. Stewart, William W. Owens

Reservoir performance predictions based on laboratory core test data assume that fluid flow is laminar for the laboratory test. A study has been made to determine the validity of this assumption for laboratory tests on various types of porosity found in producing limestone formation. Data are presented which show that turbulence and slippage can occur during laboratory tests on hetero-geneous-type porosity limestones, thus causing serious errors in measured single-phase permeabilities and two-phase relative permeability characteristics. In single-phase flow tests it is possible to eliminate turbulence and correct for slippage or to eliminate both factors by controlling test conditions. It is not always possible to control test conditions and thereby eliminate turbulence and slippage in two-phase .flow tests. A correction method is presented which can be used to calculate the true two-phase laminar flow relative permeability characteristic even though furbulence and slippage exist. .INTRODUCTION It is customary to make use of Darcy's law and modifications of this law, together with laboratory data on formation core samples to predict the performance of producing reservoirs. Such predictions are based on an assumption that fluid flow is in the laminar or streamline region for the laboratory test. It was the purpose of this inves- tigation to determine the extent to which turbulent flow may occur in laboratory fluid flow tests on hetero-geneous porosity limestones. Considering that turbulent flow conditions might exist in some laboratory fluid flow tests, additional emphasis was placed on the development of a method to correct for turbulence when laminar flow conditions could not be attained. FLUID FLOW CONCEPTS FOR POROUS MEDIA The Influence of Pore Geometry on Fluid Flow One of the more important factors influencing fluid flow in porous media is the geometry of the pore space which includes such characteristics of the pores as size, shape, distribution, roughness, uniformity, etc. In general, oil- and gas-producing formations can be divided into two broad types on the basis of pore geometry. One has been called sandstone-type porosity media, which is characterized by a small range in pore size, uniformity in shape of the pores, smooth pore surfaces and a regular and uniform distribution of pores. The other type has been called heterogeneous porosity media and is usually limited to the dolomites and limestones. This type is characterized by a wide variation in the size, shape, and distribution of the pores and rough, irregular pore surfaces. It is therefore apparent that conditions are much more favorable for turbulent flow* in heterogeneous-type porosity media than in sandstone-type porosity media. Interrelationship Between Turbulence and Gas Slippage In studying the problem of turbulent flow in laboratory tests on porous media, it is necessary to be aware of the interrelationship between slippage and turbulence for gas flow. As a result of slippage or the Klinken-berg effecta, apparent perrneabilities to gas are greater than the true value because there is no stationary layer of gas in contact with the walls of the flow channels. Gas slippage decreases as the mean free path of the gas molecules decreases. Since the mean free path of any gas decreases with increasing density, increases in static pressure result in lower apparent gas permeabilities. However, a reduction in gas permeability can also be due to turbulence. Therefore, in studying only turbulent flow in porous media, it is necessary to hold gas density, and slippage, constant or to reduce slippage to a negligible value by operating at high static pressures. Presentation of Laminar and Turbulent Flow Data A graphical relationship between permeability and a pseudo-Reynolds number, N,, will be used to show the two types of fluid flow, i.e., laminar and turbulent. The usual graphical method for such a description has been the use of friction factor-Reynolds number charts4. On such a logarithmic diagram, the laminar region appears as a straight line having a slope of 45 degrees. As the friction factor decreases and the Reynolds number increases, the turbulent region is reached and appears as a deviation from the 45-degree slope line. However, in petroleum engineering literature resistance of por-

By Lennart Wellenius

LAISVALL - ONE OF THE BOLIDEN MINES Until the Aitik Mine (2,000,000 mtpy) started in 1968 the Laisvall Mine (1,200,000 mtpy) was the biggest unit of about 20 producing mines, belonging to the Boliden Company Ltd. As shown in Fig. 1 the mines are spread over a wide area. Most of them are small complex ore mines (50,000 - 300,000 mtpy), for which reason the total mine production does not exceed 5,500,000 mtpy. When our company was invited to present a paper, Laisvall was chosen because it is the biggest European galena-mine in production today. The Laisvall Mine is situated in the county of Norrbotten, Sweden, at the eastern border of the Caledonian mountain-chain. The road distance to Slagnäs, the nearest railway station, is 60 miles. The railway between Slagnäs and BOLIDEN's smelting plant, the Rönnskär Works, is 140 miles long. PRODUCTION STARTED IN 1943 In the Autumn of 1938 a boulder was discovered, consisting of sandstone with galena, on the shore of the Lake Stor-Laisan. The boulder came from an Eocambrian sandstone formation, which is overlain by Cambrian-Silurian rock.

Jan 1, 1970

By H. l. Burghoff, A. I. Blank

The state of knowledge bearing on the stability of copper under stress at elevated temperatures is generally known to be in need of revision and extension. The present investigation, dealing with the creep characteristics of a deoxidized copper of low residual phosphorus content, is intended to contribute in some small measure toward this end. The experimental data presented herein have been correlated by methods of evaluation and interpretation familiar to those who are concerned with crecp of metals. In practice it is common, if not requisite, to use structurally stable materials at elevated temperatures. It is frequently desirable, however, to test materials under conditions that produce structural change, in order to determine the extent of such change and its effect on physical properties, thus making it possible to establish accurately the limiting conditions to which such materials may be safely exposed. The creep characteristics of the drawn copper wire of this investigation arc directly associated with its structural instability at elevated temperatures. Complete realization of this fact is essential to the evaluation of its creep resistance under various conditions. Creep results should apply to steady deformation under equilibrium conditions, but these are seldom attained in only one or two thousand hours. It will be shown that steady creep rate for copper at useful stresses does not usually begin until considerably more time has elapsed. A wholly satisfactory substitute or shortcut for extensive creep testing does not appear to be evident in the application of mathematical analyses to limited experimental data. Material A single lot of phosphorized copper wire was drawn down to 0.125-i11. diameter with a final reduction of 84 per cent. After mechanical straightening, a portion of this wire was annealed to an average grain size of 0.013 mm. in a controlled-atmosphere furnace. The composition and initial properties of the copper in these two conditions are listed in Table I. Photomicrographs of the original structure are shown in Fig. I.

Jan 1, 1945

By Richard T. Newcomb

This paper considers the many problems involved in estimating rates of technical change via productivity indexes. In mining, declining ore grades complicate the measurement of progress considerably. The estimates discussed in this article were made for the United States iron mining industry by means of two techniques: a simple model of production with two inputs, and multiple regression. The results can be used to explain the relation existing on U.S. iron ranges between rates of exhaustion, technical change, output per man and the increase in capital proportions observed since World War I. Similar ob-servations can be made on the mining sector trends in the United States, Canada, and Japan. Formidable problems confront the economist attempting to estimate the influence of technological changes on the progress of mineral industries. Peculiar to these industries is the problem of how to adjust any measure of technological progress for the offsetting influence of exhaustion. Exhaustion has long been recognized in the mining industry as a critical dimension. Empirically, it is usually treated as a problem of declining grades of ore either in production or in reserves. There are studies of the trends in mining industries attempting to relate changes in input requirements to changes in grade and technology over time. Most frequently, the measure used to indicate technological progress is average labor productivity, e.g., output per man-hour. However, although such an approach has the merit of being simple and direct, it ignores the influence of other important factors of production such as capital. Without defining both the nature of technological change and of production, it can be very misleading to identify increases in labor productivity with tech-

Jan 1, 1969

By R. F. Mehl, J. K. Stanley

THE recrystallization of cold-worked metals is studied ordinarily by determining the temperatures required for complete recrystallization to occur within a given arbitrary time period, usually within 15 min. to 2 hr. The results obtained are conventionally assembled in a three-dimensional diagram relating this temperature to the amount of cold-work (percentage deformation) and the resultant grain size, though sometimes other modes of representation are employed.1 Such three-dimensional diagrams are not complete, for the number of variables exceeds the number represented. The process of recrystallization is characterized by a time-rate, a fact that is not portrayed upon ordinary recrystallization diagrams. It is known that recrystallization consists in the formation of new nuclei and the growth of these nuclei, a process that continues until the matrix is completely consumed and the original set of grains entirely replaced by the new. This knowledge is old.2 Truly heterogeneous reactions invariably proceed by nucleation and growth; the decomposition of eutectoid solid solutions provides an example about which much is known,3 and freezing, originally studied by Tammann, provides the classic example. Although recrystallization is not a heterogeneous reaction .within the orthodox meaning of the term, the mechanism of the process is the same. As in eutectoid inversion and freezing, it should be possible to study the rate of isothermal recrystallization as a function of time, and it should also be possible to analyze the isothermal reaction curve into the component rates of nucleation and growth that determine them.* Other methods, not employing the rates of nucleation and growth, have been used to represent the rates of such reactions, but these in general have been artificial and have not led to progress.4,5? The theory of recrystallization is not in advanced state; if recrystallization data were obtained, in terms of the rate of isothermal recrystallization, and in terms of the rate of nucleation and the rate of growth of recrystallized grains, and in particular if the temperature coefficients of these rates were measured accurately, an adequate theory should be more readily developed.27 Such an effort requires proper experimental technique, but especially requires suitable methods of mathematical analysis to convert measurements made upon a surface of polish into values for the rate of nucleation and the rate of growth and to combine these into a rate of isothermal recrystallization. These methods are now

Jan 1, 1942

By I. M. Roberts

THE war emergency has affected every phase of industry. The gas and coke-oven companies have sought faithfully to discharge their responsibility in this critical period and have willingly modified their operations where possible to meet the ever increasing demands made upon them. Our company made commitments for blast-furnace coke for war purposes which necessitated a reduction in coking time in order to produce the amount required to. meet the new demands. At the same time there were certain customers of long standing, who had been supplied with foundry and egg-sized coke produced on fairly long coking periods, who also were engaged in war work and whose patronage we desired to retain. Coke produced on short coking rates from the coal mixture we were then using would not have been satisfactory for these customers. The average width of our ovens is 19 ¾ in., which is a little wider than the more modern ovens of the present day. They were originally designed to give somewhat cool tops in order to produce a rich gas. This necessitates carrying the heats a little on the warm side so that the tops will be fully carbonized. A reduction in coking time, as is generally known, is accompanied by a reduction in the average size of the coke produced. This is due to the greater shrinkage that takes place at the higher temperatures required to carbonize the charges in a shorter time. The net result is that the coke is more cross fractured and longitudinally fractured and breaks up into small sizes on handling. The cokes produced from the better coking coals seem to be more susceptible to fracture at high temperatures than those from poorer coking coals. A coal mixture that produces a beautiful foundry-sized coke at 30 to 36 hr. may yield a product at 18 hr. that would be so badly fractured as to be unsatisfactory for foundry practice. COKING CHARACTERISTICS OF COALS Our problem was to find some economical innovation and develop a method that would enable us to reduce the coking time and still produce a coke satisfactory to our foundry trade. However, before discussing the results of our present operations, it might be well to present a few observations on the coking characteristics of coals in general. Most coke-oven operators carbonize a blended mixture of coals. It may consist of a single high-volatile coal with a single low-volatile coal, or of a combination of several high-volatile and low-volatile coals. Medium-volatile coals of the Eagle seam are used for the production of high-grade foundry coke. Medium and high-volatile coals are often blended with one or more low-volatile coals. The possibilities are almost infinite, but the combinations are limited by such factors as cost and facilities for handling multicoal mixtures, and by other practical considerations. Every coal has characteristics that make it blend better with a particular coal or coals in preference to others. This property has

Jan 1, 1944

By W. R. Bean

Probably few, if any, of the many serious problems confronting malleable foundries have been more difficult of solution than the question as to why malleable that is ductile, black in fracture, and normal in all respects before galvanizing should, by that process, be rendered brittle, brilliantly crystalline or "white" in fracture, and of low resistance to shock. So far as we are aware, the technical literature contains no data or discussions on this subject, except two referencesl,2 of a general character. It is apparently a question that every one concerned, producer and consumer alike, has been willing to evade as far as possible. Various theories as to the cause of the deterioration have been given but such checking of these theories as we have done indicates that there was no sound basis for most of them. This work on the galvanizing of malleable was first undertaken in 1916, and has continued until the present time. We now feel that for all practical purposes we have reached a solution and are glad to be able to offer it in a form that can be readily applied to production processes. It is impossible to give here a detailed account of the early work done on this problem. A great number of tests were instituted and an enor-

Jan 1, 1923

By W. R. Bean

Probably few, if any, of the many serious problems confronting malleable foundries have been more difficult of solution than the question as to why malleable that is ductile, black in fracture, and normal in all respects before galvanizing should, by that process, be rendered brittle, brilliantly crystalline or "white" in fracture, and of low resistance to shock. So far as we are aware, the technical literature contains no data or discussions on this subject, except two referencesl,2 of a general character. It is apparently a question that every one concerned, producer and consumer alike, has been willing to evade as far as possible. Various theories as to the cause of the deterioration have been given but such checking of these theories as we have done indicates that there was no sound basis for most of them. This work on the galvanizing of malleable was first undertaken in 1916, and has continued until the present time. We now feel that for all practical purposes we have reached a solution and are glad to be able to offer it in a form that can be readily applied to production processes. It is impossible to give here a detailed account of the early work done on this problem. A great number of tests were instituted and an enor-

Jan 1, 1923

By L. J. Demer, W. W. Walker

AMONG several variables of the indentation hardness test is the effect of loading time on the measured hardness of a material. The most generally recommended duration of loading is 10sec.1-3 Although this short loading duration is undoubtedly satisfactory for harder metals, it is questionable that it is sufficient for very soft metals,4 or for certain plastics.5 The effect of duration of loading on the measured hardness of ionic crystals is largely unknown, although Onitsche and Mitsches found that the indentor (under a very low load) had not yet reached equilibrium after 60 sec in a variety of ionic crystals. To extend further the data of Onitsche and Mitsche, a systematic study was made of the effect of duration of loading for longer periods, up to 50,000 sec, on the 136 deg Dph of synthetic lithium fluoride. For comparison, less extensive tests were made on synthetic magnesium oxide and copper single crystals. The general procedure used was to indent a cleaved and polished (100) face of a lithium fluoride crystal using a Leitz Durimet microhardness tester. In certain cases, the indentor was so oriented as to align the diagonals of the 136 deg diamond pyramid indentation parallel to a (100) edge. In other cases the diagonal of the indentation was aligned at 45 deg to a (100) edge of the crystal. After indenting, the surface tested was etched in the acid etchant recommended by Gilman and Johnston.' This revealed the position of dislocation lines which intersected the surface tested. At these points of emergence were formed the usual sharp, pyramidal etch pits as shown in Fig. 1. The specific procedure used in studying duration of loading was as follows. The surface of the crystal was indented, and the load was left on the indentor for a predetermined time. This duration of loading was varied systematically from 1 to 50,000 sec. After the desired amount of time had elapsed, the indentor was removed from the crystal and the size of the resulting indentation was determined using a micrometer eyepiece. The surface was then etched to reveal the dislocation etch pit pattern around the indentation. Procedures used for lithium fluoride, magnesium oxide, and copper were similar. Preliminary studies revealed that, although an indentation was enlarged by increasing loading time, no corresponding changes occurred in the surface etch pit pattern. Since no evidence of dislocation movement was observed on the surface, it was assumed that the plastic deformation indicated by the indentor sinking into the surface was a result of dislocation movement inside the crystal. This movement was studied bf making a series of surface indentations in a crystal corresponding to various lengths of time, cleaving the crystal vertically through the indentations, etching the freshly

Jan 1, 1964