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By C. A. Rowland, R. C. Nealey

Until recently there were very few dry grinding rod mills used. The early installations performed as anticipated. In the last seven years a number of dry grinding rod mills have been made, most of which have been used for grinding iron ore. The recent installations have not operated as anticipated in accordance with practices learned from wet rod milling. The paper does not establish any definite rules for the application of dry grinding rod mills but does attempt to establish some guidelines that can be followed. The paper reviews a number of flowsheets describing the problems encountered and some of the solutions found. Completely dried compared to partially dried feed is reviewed. Problems encountered in scaling up from pilot plant to production-size mills are described. Rod sizing, effect of rod length, rod bending, rod breakage, and rod tangling are discussed. While wet grinding rod mills have been used for 50 years to grind ores and make specifications sands, dry grinding rod mills have only recently come into significant use in the mineral industries. Among the materials now being processed in dry grinding rod mills are (1) lead sinter, lead slag, and limestone; (2) iron ore; (3) silica; (4) cement clinker; and (5) coke. Because the application of wet grinding rod mills was well understood at the time that dry grinding rod mills were introduced, the criteria and guidelines for selecting the former were carried over to the selection of the latter - in some cases with the anticipated results, but in many cases not. It is the purpose of this paper to describe, through a series of flowsheets, some of the recent problems encountered with dry grinding rod mills, to point out the solutions to these problems, and to set forth some guidelines for the selection and application of these mills. When dry grinding rod mills came into use, the following facts about their wet grinding counterparts were already well established: (1) The performance of large-sized mills can be accurately predicted from the performance of rod mills 5 or 6 ft in diameter. Wet grinding mills as large as 14 ft in diameter (inside shell) by 20 ft long with rods 19.5 ft long can operate satisfactorily.

Jan 1, 1970

By E. T. Laker, John C. Loretto

This chapter deals with the process piping aspects of moving slurries in mineral processing plants and the transportation of slurries such as tailings and concentrates over longer distances. The basic data required to select the process piping is given together with an example of line sizing and material selection. Alternative piping materials are discussed together with pumps and pumpbox design and the types of valves and other fittings available to the process piping designer. The long distance transportation of slurries is briefly discussed and a number of references given on this, including papers on actual installations.

Jan 1, 1978

By Lucien F. Trueb

The microstructure of explosion-bonded pairs of similar and dissimilar metals has been investigated by electron microscopy. A review of the specific problems encountered and the methods used for obtaining surface replicas and thin-film transmission specimens of the bond interface is given. The bond area is mainly characterized by continuous and practically diffusionless metallurgical bonding. The very large shear stresses induced along the collision front of the plates being joined causes extreme grain elongation and a symmetrical pattern of subgrains in the bonding direction. The bond zone is also characterized by a very high density of dislocations and pressure-induced twins. Localized heating occurring during the cladding process can result in partial re-crystallization or the formation of thin layers of molten material. The force of precisely controlled explosions causing a high-velocity impact between metal plates has been used for several years to achieve metallurgical bonding between an extremely wide variety of metals. This method essentially consists of accelerating a plate to high velocity toward a stationary plate by a detonating explosive. Since the restrictions to bonding are not those encountered with conventional nethods, it becomes possible to bond pairs of metals having widely different mechanical properties that are immiscible or form brittle intermetallic compounds. Many applications of such composite metals are found in the field of corrosion protection as well as numerous other fields; for example, explosion bonding is being applied for fabricating the materials used by the United States Mint in the new sandwich-type coins. The primary condition for establishing a metallurgical bond is that absolutely clean metal surfaces be brought together. Any metal exposed to the atmosphere is covered with oxides, adsorbed gases, and other contaminants; even a very forceful impact of two such surfaces is not sufficient for bonding. Cowan and Holtz-man,"' who reviewed the dynamics of colliding plates in detail, showed that in order to achieve a good bond the explosion conditions must be chosen in such a way that the plate collision velocity is less than the sonic velocity, in which case no oblique shock waves are attached to the collision front. A pressure wave is then generated ahead of the collision line, and the material forming the colliding surface of each of the plates flows forward and is ejected in the form of a spray, the so-called jet. The dynamic elastic limit of the metals must be exceeded so that there is sufficient plastic deformation. At the point where the jet formed by the junction of the inner surface layers of both plates separates from the combined plates, the material experi- ences a very high shearing strain and the pressure can reach several hundred kilobars. This process strongly influences the microstructure of the bond zone as will be seen later. Behind the collision front, uncontami-nated layers of internal material are brought together under high pressure and are thus metallurgically bonded. I) STRUCTURE OF EXPLOSION BONDS The different types of explosion bonds that can be obtained depend on the explosion conditions, and have been investigated by Cowan and Holtzman,1'2 Holtzman,3 Klein; Bahrani and crossland,' and Buck and Horn-bogen. The preferred kind for practical applications is the so-called wavy bond, typical examples of which are given in Fig. 1 showing light micrographs of various metal-to-metal interfaces. In forming this type-- of bond the collision energy is mainly expended in jetting, the formation of waves, and localized melting. Beyond the crest of the waves, eddy-shaped areas are observed in which the two metals are mixed in a complex pattern of streaks. Cowan and Holtzmanl first proposed that this wavy pattern is analogous to periodic eddy shedding in the flow of a viscous fluid around an obstacle (Von Karman's eddy street). The mass of metal ahead of the stagnation point, which is associated with the jet and has forward momentum, plays the role of an obstacle and the eddies created in the flow of solid metal around the stagnation point are preserved in the final clad specimen. This idea has been reviewed more recently by Klein4 and the variables involved in the wave formation have been discussed in some detail by Bahrani and crosslands and Buck and Hornbogen.6 Several studies of the structure of explosion bonds by light metallography have already been published.1-6 Aside from the waviness and the eddies which were mentioned above, the most striking characteristic of the area in the vicinity of the bond interface is a very considerable longitudinal grain deformation which appears to be strongest at the metal-to-metal boundary and dies out as one moves away from it. Large twins are often observed within the deformed grains, and molten areas are found in the center of the eddy-shaped structures situated beyond the crest of the waves. The large hydrostatic pressures and shear stresses occurring at the interface modify the mechanical and chemical properties of the bond zone. Increases in hardness in this area have been reported by various authors.396 The defects along the interface can also cause a local increase of the chemical reactivity and thus might be expected to boost the etching rate. However, the effects of this preferential etching cannot be observed by light microscopy due to its inherently limited resolution power. The same limitation precludes the observation of morphological features directly along the bond interface as well as the interface itself. Furthermore, no information can be gained by light-

Jan 1, 1969

By A. G. McGregor

DURING the past 5 years, five new copper-smelting plants have been built and put into operation in the State of Arizona. The monthly copper output from these plants averages from 5,000,000 to 18,000,000 lb. Previously, there never was as much activity in copper-smelting plant construction in the same length of time in all the rest of the world. Naturally, in this amount of work, some new problems were met and new features in plant design and. equipment developed. Some of these features are described in this paper. CONCENTRATE HAULING, UNLOADING AND SAMPLING SYSTEM (a) Concentrate Car The International Smelting Co. has provided at its plant at Miami specially designed cars for hauling the concentrates from the mills of the Inspiration Copper Co. and the Miami Copper Co.. The car has a bottom that is readily made tight to hold flotation concentrates and is quickly and cheaply unloaded. Figs. 1, 2 and 3 show views and details of the car. The main feature of this car is the slot in the bottom throughout its length, which is closed by means of short planks that overlap like ship-lap as shown by Fig. 1. At one end of the car an iron gate operated by a screw and hand wheel is provided, which clamps or presses the planks together, making the bottom tight. A removable tapered plug rests vertically over this gate when the loading of the concentrates at the mill commences.

Jan 8, 1916

By D. C. Shelton

This paper discusses the metallurgical testing procedures and their applications at the laboratories and mills of Pima Mining Co. The author shows, using discussions and case histories, that routine sampling and evaluation of daily and monthly data can be as valuable as thorough laboratory investigations and mill test work. A great deal of valuable information can be made available this way. This paper discusses laboratory and mill metal-lurgical testing procedures and their applications at Pima Mining Co., located about 25 miles southwest of Tuscon, Ariz. The Company, incorporated in 1951 (the year the orebody was found) in California to operate the Pima mine, is jointly owned by Cyprus Mines Corp., Utah Contruction and Mining Co., and Union Oil Co. Milling started in December 1956. The main Pima orebody is a contact metamorphic vein of copper-bearing hornfels with an average dip of 45° to the south with an east-west strike. The hanging and footwalls are quartzitic pyroclastics (arkosite) containing some sulfides. Barren igneous intrusions are also present. Conglomerates and alluvial wash cover the deposit to a depth averaging about 200 ft. The principal copper mineral is chal-copyrite. Native copper, chalcocite, and minor amounts of chrysocolla and other copper minerals are also present, together with sphalerite and some molybdenite. Generally, it has been noted that the ratio of chalcocite to chalcopyrite is higher in the lower grade ores, while as the grade increases, there are only minor amounts of chalcocite. Open pit mining is employed at Pima, using both trucks and an inclined skiphoist system. A detailed description of Pima Mining Co. operations was presented by Spaulding et all. More recently another orebody to the north and east of the present pit has been discovered and will be placed in operation within a few years. This ore is of a porphyritic rather than a lode nature since values are disseminated in both igneous and metamor- phosed sedimentary rocks. The new orebody is expected to be harder and cleaner than the present deposit. The views expressed in this article are those of the author and do not necessarily reflect those of Pima Mining Co. nor of the profession in general. PlMA MILL The following outline of milling practice is presented to furnish a background for later chapters of this report wherein specific problems will be detailed and analyzed. Run of mine ore is crushed in three stages, using conventional equipment to 85% minus 1/2-in. for feed to two 10 x l6-ft rod mills operating in open circuit. Each rod mill discharge is split between two 10% x 13-ft ball mills in closed circuit with three 20-in. cyclones. In addition, a 7 x 12-ft ball mill with one 20-in. cyclone receives part of the discharge from one of the rod mills. This equipment was manufactured by Allis Chalmers and Equipment Engineers. The cyclone overflows are combined, sampled and, after joining the regrind cyclone overflow, are distributed into 12 10-cell Fagergren 66-in. flotation machines. The primary rougher concentrate produced

Jan 1, 1965

By H. I. Aaronson, S. Toney

When the component grains of .ferritic hicrystals of an Fe-1.55 pct Si alloy are disoriented through an angle "6 " about a conzmon [ll0] axis, the tendency for preferential growth of austenite crystals along the grain boundary during transformation at elevated temperatures is small when 11 deg, but increases rapidly at larger angles. This type of orientation-dependence indicates that grain boundary diffdsion promotes preferential growth along large-angle boundaries. Morphological differences between austenite crystals formed at small-angle [1101 and [loo] boundaries suggest that precipitate morphology can be dependent on the dislocation structure of the boundary. ThE morphology of precipitate crystals nucleated at a grain boundary can be significantly affected by the structure of the boundary.' The limited amount of experimental evidence available in the literature indicates that the morphological effects of boundaries made up of arrays of dislocations, such as subbound-aries and small-angle grain boundaries, are different from those of boundaries having essentially disordered structures, i.e., large-angle grain boundaries. On the basis of indirect evidence, it has been concluded that large-angle grain boundaries give rise to the formation of grain boundary allotriomorphs (crystals which nucleate at grain boundaries, and grow preferentially and more or less smoothly along them)2 in the proeutectoid ferrite and the proeutec-toid cementite reactions in plain-carbon steels, and apparently also in many non-ferrous alloys.' At small-angle grain boundaries in a plain carbon steel, on the other hand, ferrite crystals were found to take the form of primary side plates. Similarly, Guinie, loys. Primary sideplates formed at a subboundary with a constant orientation tend to be parallel to only one, or occasionally two matrix habit planes, and a marked change in the orientation of the boundary is accompanied by a change in the habit plane. Previous studies on the morphological effects of grain boundary structure were performed on poly-crystalline aggregates. Information on the disorien-tation of the pairs of grains forming the boundaries at which the various morphologies appeared in these specimens was largely either qualitative or semi-quantitative. Precipitate morphologies accordingly could not be accurately and systematically correlated with grain boundary structure, and thus theories which have been proposed for the various morphological effects could not be satisfactorily tested. This investigation was undertaken in an attempt to remedy these deficiencies by studying the morphological effects of grain boundary structure with a method in which the boundaries are formed by matrix grains whose disorientations are known and controlled with reasonable accuracy. EXPERIMENTAL PROCEDURE The crystallographic requirements of this study were fulfilled by means of oriented bicrystals of silicon-iron. Disorientation of the component ferrite crystals was carried out about common, major crystallographic axes through angles ranging from 1/2 to 44 deg. The silicon content was low enough SO that the bicrystals could be partially transformed to austenite by heating to elevated temperatures. The silicon-iron used had the following initial composition: 1.55 pct Si, 0.04 pct C, 0.0031 pct N, 0.17 pct Mn, 0.020 pct S, and 0.002 pct P. The alloy was obtained in the form of 0.036-in. sheet. The procedures employed to prepare seed crystals in strips of this sheet, to reorient the seeds, and to grow them into bicrystals are essentially those described by Dunn and Nonken and aynes." The characteristics of the bicrystals are given in Table I. The "bicrystal type" indicates the crystallographic plane parallel to the broad faces of the strip in both grains and the crystallographic direction which was parallel to the long edges of the strip in both grains prior to disorientation. The angular disorientation of the grains, 8, which was performed about the direction normal to the plane of the broad faces of the strip, was measured between the [ 00l] directions. Orientation of the grain boundary, , was taken as the angle between the plane of the grain boundary and a plane containing the axis of disorienta-

Jan 1, 1962

By C. W. Binckley, F. R. Burgess, E. R. Haymaker

A method of establishing stabilized back-pressure curves for gas wells producing from formations of extremely low permeability is presented. Actual well performance under many different operating conditions is shown by the stabilized back-pressure curve. By use of the method. it is possible to conduct back-pressure tests with a critical-flow prover on wells that stabilize slowly, and save approximately 88% of the gas ordinarily vented to obtain satisfactory test data, with a great reduction in time required for testing. INTRODUCTION The reasons for establishing dependable back-pressure curves on gas wells have been pointed out by previous publications. The publication most referred to. of course, is the United States Bureau of Mines Monograph 7, titled "Back-Pressure Data on Natural Gas Wells and Their Application to Production Practices". The technique generally established therein has been accepted and used by many engineers; and, when proper tests are conducted, the results can be used for the analysis and solution of several practical problems concerning field operation and development. Even where formations of low specific permeability are encountered, the determination of a well's actual performance by the back-pressure test method permits the engineer to analyze many problems in individual well operation and also to predict necessary future field development. Such problems as the determination of the ability of a well to produce into a pipe line at a predetermined line pressure, the design of gas gathering systems and meter settings, and the determination of the time and the number of wells required to be drilled to meet future market obligations, can be solved, in part., by the use of a reliable back-~ressure curve. In addition, the computed well delivery rates determined by data from backpressure tests ordered by state regtilatory bodies, when compared with the true back-Pressure curve, permit the operator to ascertain whether such data represent unstable or relatively stabilized delivery rates for given pressure conditions of the well. The technique of back-pressure testing, as described in this report, was developed by Phillips Petroleum Company engineers from data obtained during a testing program that started in 1944 and has been continued to date. Three hundred and eleven back-pressure tests were conducted on 299 wells located in the southern part of the Hugoton Field. The gas-bearing zone is composed of several dolomitic formations of the Permian Age; the important ones are the Herington, Upper Krider, Lower Krider, and Winfield. The average bottom-hole temperature is approximately 91 °F.. and the initial wellhead shut-in pressures range from 400 to 440 psig. The spacing pattern is 640 acres per well with each well located near the center of the section. The range of back-pressure potentials on wells tested was from 500 to 23,000 Mcfd. All gas wells were acidized, and the quantity of acid used, expressed in 1574 hydrocloric acid, varied from 12,000 to 22,000 gallons per well. The quantity and concentration of each treatment depended on the stage, the formation being treated, and experience gained from previously completed wells. The gas in the Hugoton Feld is a "dry" gas. It has a gasoline content of approximately 0.25 gallons per thousand cubic feet, as determined by charcoal test, and its specific gravity averages about 0.71 as compared to air (air = 1.00 at 60°F.). Of the wells tested, 71 were completed with 7" casing, 3 with 9 5/8" casing, and 1 with 6%" casing set on top of the upper producing formation with the well bore through the gas bearing formations being open hole. Two hundred and twenty-four were completed with 5 1/2'' O.D. casing set through the gas bearing formations and perforated. For the purpose of establishing reliable back-pressure curves in the area, Phillips Petroleum Company personnel has computed data on the basis of 24-hour flows per point. Early in the program, many tests were actually permitted to flow 24 hours to obtain data for each plotting point, at great expense in man power and time. Presently, however, such tests have been replaced by tests of short duration flows which can be made to effect results that correspond to the tests obtained by flows of much longer duration. METHOD When a gas well producing from a reservoir of low permeability is opened for production through a constant size orifice, both the rate of flow and working pressure decline. first at a high rate and later at a lower rate until after several hours the decline becomes difficult to ascertain. In this paper the rae of flow and working pressure are considered to be stabilized when it becomes difficult to observe changes in working pressure during a period of three hours by the use of a deadweight pressure gage. Stalibization of pressure in the literal sense is never obtained in a producing gas well. In formations of low permeability. such as those in the Hugo-ton Field, most wellhead working pressures approach stabilization closely enough to be used satisfactorily in the determination of a back-Pressure potential curve after flow periods of 24 hours. We shall therefore describe the backpressure curve calculated from ohserved rates of flow and working pressure at the end of 24-hour flow periods.

Jan 1, 1949

By E. R. Haymaker, C. W. Binckley, F. R. Burgess

A method of establishing stabilized back-pressure curves for gas wells producing from formations of extremely low permeability is presented. Actual well performance under many different operating conditions is shown by the stabilized back-pressure curve. By use of the method. it is possible to conduct back-pressure tests with a critical-flow prover on wells that stabilize slowly, and save approximately 88% of the gas ordinarily vented to obtain satisfactory test data, with a great reduction in time required for testing. INTRODUCTION The reasons for establishing dependable back-pressure curves on gas wells have been pointed out by previous publications. The publication most referred to. of course, is the United States Bureau of Mines Monograph 7, titled "Back-Pressure Data on Natural Gas Wells and Their Application to Production Practices". The technique generally established therein has been accepted and used by many engineers; and, when proper tests are conducted, the results can be used for the analysis and solution of several practical problems concerning field operation and development. Even where formations of low specific permeability are encountered, the determination of a well's actual performance by the back-pressure test method permits the engineer to analyze many problems in individual well operation and also to predict necessary future field development. Such problems as the determination of the ability of a well to produce into a pipe line at a predetermined line pressure, the design of gas gathering systems and meter settings, and the determination of the time and the number of wells required to be drilled to meet future market obligations, can be solved, in part., by the use of a reliable back-~ressure curve. In addition, the computed well delivery rates determined by data from backpressure tests ordered by state regtilatory bodies, when compared with the true back-Pressure curve, permit the operator to ascertain whether such data represent unstable or relatively stabilized delivery rates for given pressure conditions of the well. The technique of back-pressure testing, as described in this report, was developed by Phillips Petroleum Company engineers from data obtained during a testing program that started in 1944 and has been continued to date. Three hundred and eleven back-pressure tests were conducted on 299 wells located in the southern part of the Hugoton Field. The gas-bearing zone is composed of several dolomitic formations of the Permian Age; the important ones are the Herington, Upper Krider, Lower Krider, and Winfield. The average bottom-hole temperature is approximately 91 °F.. and the initial wellhead shut-in pressures range from 400 to 440 psig. The spacing pattern is 640 acres per well with each well located near the center of the section. The range of back-pressure potentials on wells tested was from 500 to 23,000 Mcfd. All gas wells were acidized, and the quantity of acid used, expressed in 1574 hydrocloric acid, varied from 12,000 to 22,000 gallons per well. The quantity and concentration of each treatment depended on the stage, the formation being treated, and experience gained from previously completed wells. The gas in the Hugoton Feld is a "dry" gas. It has a gasoline content of approximately 0.25 gallons per thousand cubic feet, as determined by charcoal test, and its specific gravity averages about 0.71 as compared to air (air = 1.00 at 60°F.). Of the wells tested, 71 were completed with 7" casing, 3 with 9 5/8" casing, and 1 with 6%" casing set on top of the upper producing formation with the well bore through the gas bearing formations being open hole. Two hundred and twenty-four were completed with 5 1/2'' O.D. casing set through the gas bearing formations and perforated. For the purpose of establishing reliable back-pressure curves in the area, Phillips Petroleum Company personnel has computed data on the basis of 24-hour flows per point. Early in the program, many tests were actually permitted to flow 24 hours to obtain data for each plotting point, at great expense in man power and time. Presently, however, such tests have been replaced by tests of short duration flows which can be made to effect results that correspond to the tests obtained by flows of much longer duration. METHOD When a gas well producing from a reservoir of low permeability is opened for production through a constant size orifice, both the rate of flow and working pressure decline. first at a high rate and later at a lower rate until after several hours the decline becomes difficult to ascertain. In this paper the rae of flow and working pressure are considered to be stabilized when it becomes difficult to observe changes in working pressure during a period of three hours by the use of a deadweight pressure gage. Stalibization of pressure in the literal sense is never obtained in a producing gas well. In formations of low permeability. such as those in the Hugo-ton Field, most wellhead working pressures approach stabilization closely enough to be used satisfactorily in the determination of a back-Pressure potential curve after flow periods of 24 hours. We shall therefore describe the backpressure curve calculated from ohserved rates of flow and working pressure at the end of 24-hour flow periods.

Jan 1, 1949

By Robert M. Grogan, Gill Montgomery

Fluorspar, the commercial name for fluorite, is a mineral composed of calcium fluoride, CaF,. Its valuable properties are due to its content of fluorine, and it is the principal commercial source of that element. The name is derived from the Latin word "fluere," to flow, because the mineral has a low melting point and is used in metallurgy as a flux. Cryolite is a sodium aluminum fluoride, Na,AlF,. It is a rare mineral which has been found in commercial quantities in only one place in the world, Greenland. Small amounts of it are shipped from stock in that country, and its place in industry has been taken over almost completely by synthetic cryolite. Because of the relative unimportance of cryolite, discussion of it has been relegated to a short section at the end of this chapter, which is principally concerned with fluorspar. History Fluorspar was used for ornamental purposes by the Greeks and Romans, who fashioned such things as vases, drinking cups, and table tops from it. Various peoples including the Chinese and the American Indians carved ornaments and figurines from large crystals. Its usefulness as a flux was known to Agricola (1564), who wrote about it in 1546. Mining began in England about 1775 and at various places in the United States during the period 1820 to 1840. Production became substantial following the development and widespread adoption of the basic open hearth method of making steel, in which fluorspar is used as a flux. After that, production and usage were stimulated by growth in the steel, aluminum, chemical, and ceramic industries and were accelerated by World Wars I and II. Fluorocarbons entered the picture in 193 1 and the use of anhydrous hydrogen fluoride (HF) as a catalyst in the manufacture of alkylate for high octane fuel blends began in 1942. The development of the froth flotation process in the late 1920s, a differential flotation scheme for separating fluorspar from galena, sphalerite, and common gangue minerals in the 1930s, and the application of heavy-media concentrating methods to the treatment of low grade ores in the 1940s were outstanding technological contributions that enabled increased production of fluorspar concentrates. In recent years the development of pelletizing and briquetting processes for making flotation concentrates into gravel-size particles for use in steel furnaces and the development of more efficient and selective flotation schemes for treating crude ores containing abundant dolomite and barite have been major improvements in the industry.

Jan 1, 1975

By V. T. Stringfield, H. H. Cooper

ONE of the earliest investigations of ground water in Florida was made in 1513 when Ponce de Leon arrived at St. Augustine in search of the Fountain of Youth. The history of the development of the water resources of the State shows that the large artesian reservoir that underlies Florida was discovered in the latter part of the last century. Part of that history is given by L. C. Johnson' who states that the first successful artesian well in Florida was drilled at St. Augustine between 1880 and 1882. After the City of Jacksonville failed to obtain a flow of artesian water at a depth of nearly 400 ft and abandoned the drilling, R. N. Ellis, City Engineer, and L. C. Johnson, using Johnson's knowledge of the geologic structure of the artesian reservoir, estimated correctly that artesian water could be obtained at a depth of about 500 ft. Thus began the development of the large artesian system in the northeastern part of the State. In 1908, the Florida Geological Survey issued its first report on the ground water of central Florida. More recent reports give the results of investigations that have been in progress in cooperation between the Florida Geological Survey and the U. S. Geological Survey since 1930. As a result, the ground-water geology and hydrology of Florida are now so well known that ground-water problems such as confronted early investigators no longer exist. However, new problems arise and new discoveries are made as the demand for more ground water increases with the development of the State. Water-Bearing Formations Descriptions of the geologic formations and a map showing their distribution at the surface are given in a recent report by Cooke.' The geologic formations that yield the ground-water supplies in Florida represent only a small part (about 1000 ft) of the total thickness of the sedimentary rocks (more than 15,000 ft) that underlie Florida. The water-bearing rocks that yield fresh water include more than two dozen formations that range in age from Eocene to recent. The Eocene formations, which consist chiefly of limestone, are the oldest and the deepest of the formations in Florida that yield fresh water to wells. In 1944, on the basis of a study of the foraminifera, the Applins -ivided the limestone of Eocene age into six formations, which are as follows, from top to bottom: Age or group Formation Jackson Ocala limestone icAvon Park limestone Claiborne -j Tallahassee limestone aLake City limestone Wilcox Salt Mountain limestone xOldsmar limestone The Ocala limestone and the underlying formations of Claiborne age, along with some of the overlying limestone of Oligocene and Miocene age, constitute the principal source of water in Florida and southeastern Georgia and generally may be regarded as forming one artesian aquifer or water-bearing unit. This aquifer is referred to in this paper as the Floridan aquifer, a name proposed by Parker.' In part of Seminole County alone more than 1000 flowing wells yield water from the Floridan aquifer. A yield of 6500 gpm, or about 9.5 million gal per day, by natural flow from a well penetrating the aquifer at Jacksonville, Florida, was observed in 1942. A yield of about 7000 gpm by natural flow was reported for a well 1390 ft deep at St. Augustine in 1887. The largest yield reported from a pumped well penetrating the aquifer is 7500 gpm, or about 10.5 million gal per day. The aquifer is also the source of some of the large springs, such as Silver Springs, whose discharge, according to measurements made by the U. S. Geological Survey, has ranged from 526 to 1350 sec-ft, or from 340 to 872 million gal per day. The top of the Ocala limestone, as represented by contours in Fig. 1, indicates in a general way the geologic structure of the formations that comprise the Floridan aquifer. The Ocala is at or near the surface in the areas represented by shading in the northwestern part of the peninsula and also in an area in western Florida adjacent to Alabama and

Jan 1, 1952

By Sherwin F. Kelly, Bela Low, William B. Creagmile

Electrical methods and instruments for geophysical exploration have been almost exclusively applied, during these years of development of the art, by a few companies specializing in this field. The control of patents, the cost of the instruments and the general lack of published information on details of field procedure and office interpretation have given these owners a monopoly in carrying out electrical surveys. The development of the Megger Ground Tester1 seems likely to change this situation, and to enable mining engineers and geologists, without special training in geophysics, to carry out simple reconnaissance electrical surveys. Nevertheless, the need for such special training and experience in planning surveys and interpreting their results remains, and probably i always will remain, indispensable for a successful outcome. The unique thing about, the Megger Ground Tester, which gives rise to this hope for its general use, is its simplicity of operation. The four binding posts of the instrument are connected by insulated wires to four stakes driven into the ground at appropriate points. The crank of the Megger is then turned, and the resistance of the ground between the two inside stakes is read directly, in ohms, by the deflection of a pointer over a scale. The apparatus is shown in Fig. 1. Fundamentally, the principle of operation is that of determining the resistance of a four-terminal conductor, as applied by Frank Wenner to the measurement of earth resistivity. "A four-terminal conductor is a conductor provided with two terminals to which current leads may be connected and two terminals to which potential leads may be connected. The resistance of such a conductor is the difference in potential between the potential terminals divided by the current entering and leaving

Jan 1, 1932

By Axel Hultgren

IN ingots of silicon-killed carbon steel made without addition of - aluminum, transparent spherical or nearly spherical inclusions, up to about 0.15-mm diameter, are generally present. They may be glassy or crystallized, wholly or partially. In steels of high carbon contents they consist of silica,4,12 in steels of lower carbon contents arid, in consequence, higher oxygen contents, of iron-manganese-silicate with higher iron and manganese contents the lower the carbon content. Small silicate inclusions, about 0.01 mm or smaller, may occur, just as sulphide inclusions do, in portions that have been the last or nearly the last to freeze,10,12,17 this location being verified by primary etching.10 Hence, it may be concluded that they have separated from liquid steel that has become enriched in oxygen through segregation during freezing. Silicate inclusions with a diameter larger than about 0.02 mm appear, at least in ingots of moderate size, to be distributed at random in relation to the primary structure and therefore may be assumed to have existed as droplets in the liquid steel before freezing started at the point in question. The average size of such large inclusions has been found to increase toward the axis17 and their amount to increase from the top downward in the axial region .2,10 It has been assumed that this accumulation is a result of the droplets being brought down by the slowly settling metal crystals.2 It has been suggested that large silicate inclusions generally form,6 or may form," by coagulation of smaller ones, or by small drops being caught by larger ones during the rising of the latter.9 The occasional occurrence of a large inclusion surrounded by a swarm of small ones has been taken as a proof of this mechanism but, as suggested later, may be explained in another way. It has been pointed out that an inclusion droplet in the liquid steel may grow at the expense of an adjacent one, which implies diffusion of soluble inclusion-forming elements in the liquid steel.15 Further, it has been pointed out that, on cooling in ladle or mold, the metal-silicate equilibrium is displaced in the direction of separation of silicate. Thus inclusions may grow in size and amount.2,3,8,12,13,17,19,20 The exposure of the liquid steel to the oxygen of the air during tapping and pouring, and the consequent reaction, has been mentioned as a source of the formation of inclusions19,20 but this possibility has not received particular attention. Further, the admixture of furnace slag during tapping' or of refractory material from various sources1,20 has been considered. The inclusions due to the latter may be recognized, however, through their resistance to hydrofluoric acid, imparted by the alumina content. Silicate inclusions, are often referred to as. the natural and inevitable product of reaction on adding silicon or silicon

Jan 1, 1948

By E. A. Anderson

In 1918 the American Society for Testing Materials held a symposium2 on what was then known as season cracking. The sessions included six papers, all on brass. During the ensuing 26 yr., many new workers have come into the field and several other metals have been found subject to failure by stress-corrosion cracking when the right combination of stress and environment is achieved. It is not surprising, therefore, that the present symposium has brought forth 29 papers covering alloys of seven important metals. The phenomenon of stress-corrosion cracking is not necessarily confined to these seven metals. Dix3 has stated, "Indeed, it is probable that ingenious investigators can find solutions which will stress-corrosion crack any known metal or alloy." Mears, Brown, and Dix4 have indicated that stress- corrosion cracking failures are not necessarily limited to metals but may include the plastics. It is to be expected that the increase in the number of metals known to crack in service and the general emphasis on such failures at a symposium such as this will alarm many to whom the subject is un- familiar. Such alarm is not justified by the record. It is true that stress-corrosion

Jan 1, 1945

By Chester S. Conrad

SEVERAL years ago Pittsburgh Consolidation Coal Co. intensified efforts to combat the hazard of mine fires. The program consisted of three parts in the order of likely accomplishment: 1) Purchase and installation of newer and more practical fire fighting equipment. 2) Establishment of trained fire fighting teams at every mine plant. 3) A drive to remove the causes of mine fires. Experimentation with alternating current on section equipment is a major development in this part of the program. Use of alternating current to power mining equipment had been recognized as being most practical from the standpoint of safety. A means to re- place the d-c traction motor is all that has delayed complete section mechanization with a-c power.

Jan 1, 1958

By H. M. Beatty, T. L. Joseph, Gust Bitsianes

SUCCESSFUL blast-furnace operation depends upon securing an optimum balance between a number of important variables. This balance will vary somewhat from furnace to furnace in the same plant and with raw materials available in different plants. It is difficult to isolate the effect of any one variable unless it has a rather pronounced effect upon the efficiency of operation. The physical properties of iron ore and coke are known to affect the process, yet it is difficult to set up any definite yardstick by which these differences can be appraised. In recent years, whenever practicable, operators have taken steps to obtain better control over the absolute size and uniformity of size of the ore and coke. The size and physical character of the stone, however, have received comparatively little attention, emphasis being placed upon chemical composition, fluxing efficiency, and action as a desulphurizing agent. Since the stone occupies only about 10 per cent of the volume of the stock column, its influence upon permeability is less than that of the ore and the coke. The large pieces now used have a tendency to roll to the center and thus increase the permeability of this part of the stock column. Smaller pieces would be more effective in promoting the permeability of denser portions of the stock. The size and physical properties of blast- furnace stone are important also for reasons best understood by considering the results obtained by the crushing and the sizing of iron ore. Crushing ore to about 2 in. at Provo, Utah, and to about I in. in Alabama produced material somewhat less permeable to gases, even though sized. In spite of some sacrifice in permeability, the efficiency of the process was improved by crushing and sizing the ore, as indicated by a substantial saving in fuel and increased output. This saving in fuel is due in large measure to more thorough reduction of ore in the upper part of the furnace and to a corresponding decrease in the amount of carbon consumed prematurely above the tuyeres by the reaction CO2 + C = 2CO ? 70,080 B.t.u. [I] The physical properties of stone, its size and rate of calcination are important because they influence the rate at which C02 is released and the completeness of calcination before reaching a level in the furnace where the temperature does not exceed 1050°C. (1920°F.). Briefly, carbon dioxide from the limestone or from the reduction of ore may cause premature com- bustion of carbon above the tuyeres. Assuming that 1000 lb. of limestone is used per ton of pig iron, about 435 lb. of C02 will be liberated during calcination of a good grade of stone. If all this CO2 from the stone were to oxidize carbon prematurely, about 120 lb. would be consumed above the tuyeres in a heat-absorbing reaction. The amount of carbon thus consumed when a

Jan 1, 1942

By Guang Ping Cui

In this paper the imminent relationship between rock burst and its phenomenon with normal rock pressure and its appearance, as well as the factors of one changing into another have been analyzed. Based on this, the necessary and sufficient appearing factors of rock bursts have been put forward, and the term ''burst pressure" has been defined. According to the statistics data of tremendous rock bursts which appear in collieries in Hunan Province, the features of high frequency, great strength and shallow depth of the beginning burst have been found. There are some special structures in the coal seams, which are closely related with the burst phenomenon. A hypothesis of "star structure" has been suggested for the appearing mechanism of bursts. Inside and around this star structure the distribution rule of burst pressure and rock strength has been researched depending upon the theory of the limited stress field. A new description of the appearing causes of bursts has been raised.

Jan 1, 1984

By H. J. Ramey

A general solution is presented for the transient temperature distribution caused by radial movement of a cylindrical heat source through a homogeneous medium of infinite extent. This problem represents a highly simplified model of the movement of a combustion front during the thermal recovery of oil. Numerical solutions are presented for a heat source moving at a constant velocity, and a velocity inversely proportional to the radial location of the heat source. Numerical solutions are presented for both finite and infinite vertical thickness of the heat source, i.e., with and without vertical heat losses. The numerical solutions are used to estimate the fuel concentration needed to maintain a combustion front during the thermal recovery of oil. The sensible heat carried to the combustion front by the injected gas stream is discussed in regard to the fuel concentration. Numerical solutions for a heat source (combustion front) of finite vertical thickness indicate the field conditions that may be necessary to sustain the temperature of a combustion front above the ignition temperature of the fuel over considerable distances from an injection well. The results also have implications in regard to the quantity of heat required during ignition. The results of this computation apply to a highly idealized model of a thermal recovery process. But the results may be used as a guide in engineering consideration of the thermal recovery process. INTRODUCTIO N The thermal recovery of crude oil has received considerable attention since the publication by Kuhn and Kochl of laboratory and field tests of this method of oil recovery. Other publications2,3,4,5,6, since that time have dealt with various features of the thermal recovery of oil and have illustrated the extremely complex nature of this process. Vogel and Krueger7 described an electric analog computer designed to solve a moving heat source problem which was analogous to movement of a combustion front during the thermal recovery of oil. The heat source was maintained at constant temperature and was a cylindrical source of infinite height (no vertical heat loss) moving radially at either constant velocity, or at a velocity inversely proportional to the radial location of the heat source. Jenkins and Ramey2 presented analytical solutions to a similar heat conduction problem and pointed out the possible importance of vertical heat losses. The following presents a general solution to the transient heat conduction problem introduced by Jenkins and Ramey4 as well as numerical solutions for a wide range of conditions possibly similar to those that might exist during field operation of the analogous thermal recovery process. DESCRIPTION OF PROBLEM The problem considered in this paper is determination of transient temperature distribution caused by a cylindrical heat source of infinite or finite vertical height, moving radially through an isotropic medium of infinite extent. It is further assumed that the heat flux generated at the surface of the moving heat source may be a function of time such that the fuel concentration required may be constant, or permitted to vary, and that heat is generated at the surface of the heat source only. In regard to the thermal recovery of oil the assumption that heat is generated at the surface of the front is equivalent to assuming that the thickness of the combustion zone is infinitely small, or that the reaction rate between fuel and oxidant gas is infinite. The last assumption does not appear stringent. See laboratory information published by Martin, et al3 Under these assumptions the temperature distribution throughout an infinite medium caused by a heat source moving radially with an arbitrary velocity may be described by The heat generation function or heat flux at the surface of the source, +(t), is Note that the fuel concentration may be defined as a function of time. Eq. 1 is derived in the Appendix.

By S. Korman, S. B. Tuwiner

THE purpose of this study is to investigate the effect of agitation upon the flotation of chal-cocite. It is believed that the concentration of collector which is required to produce a water-repellent surface upon the mineral is determined among other things by the rate of collector diffusion through an impeding film of more or less stagnant fluid. Its thickness depends upon the intensity of agitation. In the first part of this study a method is developed for determining the thickness of the fluid film upon a polished surface of synthetic chalcocite. The film thickness is then determined as precisely as possible under three readily reproducible condi-tions of agitation intensity. These determinations serve as a quantitative evaluation of agitation. In Part 2 it is demonstrated that in solutions of lime at PH 10.5 and in the absence of air or dissolved oxygen the concentration of collector required to develop water-repellency upon the surface in any given time is a function of the fluid film thickness, and that after about 10 min the relation becomes linear. This points to the possibility that the collector ions may be involved in a diffusional process through the fluid film. In Part 3 it is shown that where air is present more collector is required to produce water-repellency than for the case in which air is excluded. Next, it is shown that for the latter case the most minute amount of sodium sulphide suffices to preclude development of water-repellency. Both oxygen and sulphide are in a sense, therefore, depres- sants for chalcocite in a lime solution at PH 10.5. When oxygen and sulphide are present simultaneously there is a region of minimum critical collector concentration for water-repellency which is very markedly lower than the concentration where oxygen alone or where sulphide alone is present. Moreover, this minimum appears to be identical with the collector concentration which is required where sulphide and oxygen are both excluded. This would appear to indicate that in certain ranges of concentration of oxygen and sulphide, each cancels the effect of the other. The range of concentration of solution for this effect in solutions saturated with oxygen is a function of the agitation intensity. Thus we are led to believe that a chemical reaction involving sulphide and oxygen occurs at the surface of the chalcocite. Part 4 of this study is a further development of this idea and some of its consequences from an electrochemical standpoint, while in Part 5 the disappearance of sulphide from pulps of several minerals is noted with an indication that both dissolved oxygen and the mineral are necessary, the reaction being catalytic or pseudocatalytic. Part 1. Determination of Fluid Film Thickness The Fluid Film Concept: The hindrance to the diffusion of collector to the surface of the chalcocite is a barrier of stagnant fluid in the vicinity of the surface. It is the same barrier that limits the rate of transfer of heat, the rate of solution of dissolving crystals, or any of the other rates pertaining to chemical engineering unit operations in which the film resistance to diffusion plays a principal role.' Fluid films are present upon the surface to an extent which varies with the geometry and intensity of agitation. They result from the fact that in the region within the fluid near a surface, motion is entirely parallel to it. From the standpoint of transfer to or away from the interface the effect is as though the fluid were stagnant. Outside of the film, movement of the fluid may be streamline or turbu-

Jan 1, 1951

By S. Korman, S. B. Tuwiner

THE purpose of this study is to investigate the effect of agitation upon the flotation of chal-cocite. It is believed that the concentration of collector which is required to produce a water-repellent surface upon the mineral is determined among other things by the rate of collector diffusion through an impeding film of more or less stagnant fluid. Its thickness depends upon the intensity of agitation. In the first part of this study a method is developed for determining the thickness of the fluid film upon a polished surface of synthetic chalcocite. The film thickness is then determined as precisely as possible under three readily reproducible condi-tions of agitation intensity. These determinations serve as a quantitative evaluation of agitation. In Part 2 it is demonstrated that in solutions of lime at PH 10.5 and in the absence of air or dissolved oxygen the concentration of collector required to develop water-repellency upon the surface in any given time is a function of the fluid film thickness, and that after about 10 min the relation becomes linear. This points to the possibility that the collector ions may be involved in a diffusional process through the fluid film. In Part 3 it is shown that where air is present more collector is required to produce water-repellency than for the case in which air is excluded. Next, it is shown that for the latter case the most minute amount of sodium sulphide suffices to preclude development of water-repellency. Both oxygen and sulphide are in a sense, therefore, depres- sants for chalcocite in a lime solution at PH 10.5. When oxygen and sulphide are present simultaneously there is a region of minimum critical collector concentration for water-repellency which is very markedly lower than the concentration where oxygen alone or where sulphide alone is present. Moreover, this minimum appears to be identical with the collector concentration which is required where sulphide and oxygen are both excluded. This would appear to indicate that in certain ranges of concentration of oxygen and sulphide, each cancels the effect of the other. The range of concentration of solution for this effect in solutions saturated with oxygen is a function of the agitation intensity. Thus we are led to believe that a chemical reaction involving sulphide and oxygen occurs at the surface of the chalcocite. Part 4 of this study is a further development of this idea and some of its consequences from an electrochemical standpoint, while in Part 5 the disappearance of sulphide from pulps of several minerals is noted with an indication that both dissolved oxygen and the mineral are necessary, the reaction being catalytic or pseudocatalytic. Part 1. Determination of Fluid Film Thickness The Fluid Film Concept: The hindrance to the diffusion of collector to the surface of the chalcocite is a barrier of stagnant fluid in the vicinity of the surface. It is the same barrier that limits the rate of transfer of heat, the rate of solution of dissolving crystals, or any of the other rates pertaining to chemical engineering unit operations in which the film resistance to diffusion plays a principal role.' Fluid films are present upon the surface to an extent which varies with the geometry and intensity of agitation. They result from the fact that in the region within the fluid near a surface, motion is entirely parallel to it. From the standpoint of transfer to or away from the interface the effect is as though the fluid were stagnant. Outside of the film, movement of the fluid may be streamline or turbu-

Jan 1, 1951

By P. J. G. duToit

The continually growing shortage of skilled underground miners, the escalating costs of labor, supplies and equipment, and the indisputable example of "what can be done" by our friends in the space-travel field, seem to be catalysts that are accelerating improvements in underground mining technology. The search for an economic, automated continuous excavation method that would produce rock at the mining face in sizes suitable for automated transportation directly into the rod-, ball-, or autogenous grinding mills is continuing. New mining methods and techniques were devised and many improvements on old methods and techniques came forth at an increasing pace that reflected a widely spreading policy among mining men to shun the shackles of conservatism and to forge ahead and venture into newer ideas.

Jan 2, 1967