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By E. K. Landis

The question of magnetic concentration is assuming considerable importance, and the efficiency of the different concentrating-machines is widely discussed. As the amount of iron left in the tails must vary with commercial requirements, and with the nature of the minerals in the tails, the writer feels justified in calling attention to some points often overlooked. In almost every such commercial operation a point is reached beyond which it does not pay to go, the material saved by further operations being obtained at a cost too great. The amount of iron left in the tails from concentration must depend, therefore, upon the cost of crushing, the size to which the ore is crushed, the nature of the minerals in the gangue, and the nature of the ore itself. Some ores are so intimately mixed with their gangue that a large loss of iron in the tails is unavoidable. In many cases the gangue contains hornblende, pyroxene, serpentine, etc., which carry considerable iron as silicate, or otherwise combined, and this iron a magnetic machine cannot extract, since the minerals themselves are not magnetic. It is evidently unfair to charge the machine with this loss of iron; and hence a satisfactory test of any such apparatus would require that the iron present in the ore as magnetite should be determined, and the proportion in the tailings of such iron only should be the measure of the loss, as compared with theoretical efficiency.

Jan 1, 1892

By L. D. Jaffe, M. R. Norton, J. H. Hollomon

IN the practical heat-treatment of steel the decomposition of austenite usually occurs during cooling rather than at constant temperature. Nevertheless, the course of this decomposition has generally been studied only isothermally. Isothermal studies are not only simpler experimentally, but have the great theoretical advantage that one of the variables, temperature, is constant. It is the purpose of this paper to outline the principles that govern the relations between isothermal and anisothermal? decomposition of austenite, to present and systematize the available experimental information, and to indicate the gaps in the existing knowledge. Some of the experimental information is the result of new work. § Most of it is derived from scattered data in the literature. Many of these data were obtained incidentally in the course of research on other subjects and their significance has not been pointed out and perhaps not understood. It is hoped that this paper will aid future planning of more extensive research on anisothermal decomposition. METHOD In order to study the relations between isothermal and anisothermal decomposition, it appears fruitful to view anisothermal decomposition as taking place at a series of constant temperatures1 (except for the martensite reaction, which does not occur isothermally to an appreciable extent). When the time the steel is at each temperature is finite, the over-all amount of the reaction is considered to be the sum of the amounts occurring at each of the successive temperatures. During continuous cooling or heating, the time the steel is at each temperature and the difference between successive temperatures can be considered to approach zero. The over-all amount of transformation will then be given by integration over the range of temperatures involved. This point of view is advantageous in that it considers anisothermal transformation to be a series of isothermal transformations. The problem thus becomes one of determining the effect of partial decomposition at any given temperature upon subsequent decomposition at another temperature. Single Anisothermal Reaction Consider a phase brought to a temperature at which it is unstable, held there until it has partially transformed, and then brought to another temperature at

Jan 1, 1946

By J. H. Hollomon, L. D. Jaffe, M. R. Norton

In the practical heat-treatment of steel the decomposition of austenite usually occurs during cooling rather than at constant temperature. Nevertheless, the course of this decomposition has generally been studied only isothermally. Isothermal studies are not only simpler experimentally, but have the great theoretical advantage that one of the variables, temperature, is constant. It is the purpose of this paper to outline the principles that govern the relations between isothermal and anisothermalt‡ decomposition of austenite, to present and systematize the available experimental information, and to indicate the gaps in the existing knowledge. Some of the experimental information is the result of new work.§ Most of it is derived from scattered data in the literature. Many of these data were obtained incidentally in the course of research on other subjects and their significance has not been pointed out and perhaps not understood. It is hoped that this paper will aid future planning of more extensive research on anisothermal decomposition. Method In order to study the relations between isothermal and anisothermal decomposition, it appears fruitful to view anisothermal decomposition as taking place at a series of constant temperatures1 (except for the martensite reaction, which does not occur isothermally to an appreciable extent). When the time the steel is at each temperature is finite, the over-all amount of the reaction is considered to be the sum of the amounts occurring at each of the successive temperatures. During continuous cooling or heating, the time the steel is at each temperature and the difference between successive temperatures can be considered to approach zero. The over-all amount of transformation will then be given by integration over the range of temperatures involved. This point of view is advantageous in that it considers anisothermal transformation to be a series of isothermal transformations. The problem thus becomes one of determining the effect of partial decomposition at any given temperature upon subsequent decomposition at another temperature. Single Anisothermal Reaction Consider a phase brought to a temperature at which it is unstable, held there until it has partially transformed, and then brought to another temperature at

Jan 1, 1947

By L. D. Jaffe, M. R. Norton, J. H. Hollomon

In the practical heat-treatment of steel the decomposition of austenite usually occurs during cooling rather than at constant temperature. Nevertheless, the course of this decomposition has generally been studied only isothermally. Isothermal studies are not only simpler experimentally, but have the great theoretical advantage that one of the variables, temperature, is constant. It is the purpose of this paper to outline the principles that govern the relations between isothermal and anisothermalt‡ decomposition of austenite, to present and systematize the available experimental information, and to indicate the gaps in the existing knowledge. Some of the experimental information is the result of new work.§ Most of it is derived from scattered data in the literature. Many of these data were obtained incidentally in the course of research on other subjects and their significance has not been pointed out and perhaps not understood. It is hoped that this paper will aid future planning of more extensive research on anisothermal decomposition. Method In order to study the relations between isothermal and anisothermal decomposition, it appears fruitful to view anisothermal decomposition as taking place at a series of constant temperatures1 (except for the martensite reaction, which does not occur isothermally to an appreciable extent). When the time the steel is at each temperature is finite, the over-all amount of the reaction is considered to be the sum of the amounts occurring at each of the successive temperatures. During continuous cooling or heating, the time the steel is at each temperature and the difference between successive temperatures can be considered to approach zero. The over-all amount of transformation will then be given by integration over the range of temperatures involved. This point of view is advantageous in that it considers anisothermal transformation to be a series of isothermal transformations. The problem thus becomes one of determining the effect of partial decomposition at any given temperature upon subsequent decomposition at another temperature. Single Anisothermal Reaction Consider a phase brought to a temperature at which it is unstable, held there until it has partially transformed, and then brought to another temperature at

Jan 1, 1947

By F. C. Schora, H. P. Meissner

Both a graphical and an analytical technique are presented for calculating stream compositions and temperatures in adiabatic staged systems in which solids travel countercurrently to a gas stream. Such a system might be a tower containing several plates, on each of which the descending solid is fluidized by the rising gas stream. Examples are presented in which chemical reactions occur, including the oxidation of SO, by a solid catalyst and the gaseous reduction of iron oxides. COUNTERCURRENT staged processes involving reactions between solid and gas streams are becoming more common. These operations are generally carried out in a series of beds of fluidized solids, with each bed or "plate" acting as a stage. Fig. 1 is a schematic diagram of such a series of stages located in a column, down through which a solids stream moves from stage to stage counter to a rising gas stream. Typical reactions carried out in such systems are the dehydration of aluminum trihydrate, the calcining of limestone, and the gaseous reduction of iron oxides. Calculation of the performance of these counter-current systems rapidly becomes more complex with increases in the number of stages and in the number of chemical reactions occurring. Calcula-tional procedures for isothermal operations of such systems have been described.4 Actual tower operations, however, are generally adiabatic, and in consequence far from isothermal. The object here is to present both graphical and analytical techniques applicable to such adiabatic towers operating continuously and in steady state. In this introductory discussion, the graphical techniques presented are of the McCabe-Thiele type, rather than of the Pon-chon type. In all the examples presented, it will be assumed that both thermal and chemical equilibrium are attained in each bed. The assumption that the gas and solid streams leaving each bed are at the same temperature as the bed is in accordance with the familiar behavior of actual fluidized solid systems. Chemical equilibrium, on the other hand, is not necessarily attained in any given stage between these two streams, even with deep beds, since reaction rates may be slow. In the last section of this paper, discussion is presented of methods suitable for use when chemical equilibrium is not attained. The adiabatic tower in Fig. 1 has "n" stages numbered from 1 to n, starting with the bottom stage as number 1. In analyzing this tower's performance, it is important to express gas flow rates in terms of a key component or element which remains completely within the gas stream throughout the tower. Similarly, solid flow is best expressed in terms of a key compound or element which remains within the solid phase throughout the tower. Thus, in burning limestone with a hot flue gas, the gas flow might be expressed as G, the pound mols of nitrogen flowing through the tower per unit time, while solid flow might be expressed as S, the pound atoms of calcium in all forms in the solid stream per unit of time. Defined in this way, both G and S are constant throughout the tower. The enthalpy of the gas and solid streams are now best expressed in terms of these key components. That is, the gas stream enthalpy H is expressed as Btu in the total gas per mol of the key component in the gas. Similarly, the solids stream enthalpy h is expressed as Btu in the total solid stream per pound mol (or pound atom) of the key component in this stream.

Jan 1, 1962

By F. W. Apgar

THe valuable results that have followed the application in recent years of microscopic methods of research to problems of ore genesis have been significant, but possibly the recognition of their practical importance is not as general as might be, and while, as a scientific method of investigating ores and rocks, the advantage derived through the use of the microscope is unquestioned, its utility as an aid in solving mining problems arising during actual every-day mine examination and operation may not be fully appreciated. Perhaps the most logical method of showing some of these practical applications of the microscope will be to consider first the prospect stage of a mining venture, then the uses to which the instrument may be put during the operation of a working and developed mine, arid, finally, to discuss some of the problems of a metallurgical nature that may arise during milling and smelting the ore. The valuation of mining property as a preliminary to acquiring ownership or determining the advisability of investing time and money in an enterprise is one of the most important and delicate problems that come before the mining engineer. The many and variable factors that have to be taken into account, as, for example, the geology of the district, availability of supplies, probable mining costs, transportation facilities, and the quality of ore, require a careful balancing of costs against recoverable values. Primarily, however, a study of the local geology is of first importance, since, in a prospect with little development work, the question of character and probable quantity of the ore and its value can only be approximated with any degree of accuracy by a thorough investigation of geologic conditions, and a general knowledge of ore deposits. Unless these are favorable and pay ore reasonably certain, other factors need not be considered. The character of the outcrop, evidences of mineralizing agencies in the adjacent rocks, and geological structure, are the data of chief significance.

Jan 1, 1914

Efficient energy utilization in the electrolytic zinc process, relative to other zinc processes, is one of the reasons for its wide adoption in recent years, says John D. Siddle, zinc plant superintendent at the Bunker Hill Co., Kellogg, Idaho. Designers and operators of electrolytic zinc plants have pioneered process improvements, new equipment, and operating techniques to conserve energy. As energy costs increase it the future and competitive pressure mounts against less-efficient producers, these energy-saving improvements will he regarded as necessary for economic survival. Plant designers and operators should not lose sight of the savings in operating costs possible through intelligent utilization of all available forms of energy.

Jan 11, 1977

By Ralph E. Hartline, Wilfred Tapper

The Strataflow process for locating water entry in producing, wells is now available. This method as now practiced utilizes the fact that fluids of different salinities have different electrical resistivities. By introducing into the well a fluid of a markedly different salinity than that of the fluid being produced, a pronounced resistivity change will occur at the point of entry. By running a Strataflow survey the points of major and minor water entry may be interpreted from changes in the resistivity of fluid in the hole. Strataflow results are obtained with the well operating under almost normal producing conditions, and are a logical primary step in any workover program, having as its purpose shutting off of the water. INTRODUCTION Water production is a serious problem in many producing oil wells. It certainly increases lifting costs and in some cases presents a disposal problem. It often aggravates corrosion problems and can even endanger oil production. With accurate information to guide an effective workover program, many marginal wells could be restored to Profitable Production. The shortcomings of previous meth- ods of water entry location were recognized. The Strataflow process is the result of several years of development and field testing directed toward overcoming these limitations. It represents the continued development of a process reported by Silverman and Brown. The earlier work established the basic soundness of fresh-to-salt water resistivity contrast in delineating zones of water entry, but its application was limited by the difficulty of maintaining static balance of the well during preparation for the test. A more serious deterrent to its use, however. was its unadaptability to existing well logging service equipment and field operating methods. STRATAFLOW PRINCIPLE The general principle of the new method involves, first, conditioning the well by displacing the fluid in the bore of the well adjacent to the zone to be tested by a conditioning fluid which is miscible with the formation fluid. This displacement is carried out without interruption of the well production. The conditioning fluid must have some measurable physical, chemical, nuclear, or electrical property which is distinctive from that of the formation fluid. As the well continues to produce. formation liquid entering the well bore dilutes the conditioning fluid so that zones of entry may be determined by making a log of the property undergoing change. This general principle may be applied to indicate zones of either water or oil entry by suitable selection of conditioning fluid and proper logging equipment. The Strataflow process, as it is currently practiced for water entry location, uses fresh water as the conditioning fluid and depends for its operation upon the marked difference of electrical resistivity between this fresh water and the salty water produced by the formations. If possible. any necessary modifications of the well equipment are made a week or so before the test. The well is then returned to normal production. On the day the test is to be carried out. the conditioning water is landed at the bottom of the well and the test is made without interrupting production except for a brief period required for the conditioning water to consolidate into a continuous column extending to a point well above the test section. With this general description of the process in mind, a more detailed step-by-step description of the process will be clearer. PRELIMINARY PREPARATION OF WELL The Strataflow survey, as it is currently practiced for water entry location, is applicable only to pumping wells. Since the required electrical measurements are made by a special

Jan 1, 1952

By Richard Franchot

From an efficiency viewpoint, the greatest loss of energy to the blast furnace is in its failure to convert more than about a third of the coke carbon from carbon monoxide to carbon dioxide. This result has usually been ascribed to a necessity of a 2:1 excess of CO in order to reduce iron. It has, however, been proved that iron is completely reduced by equal volumes of carbon monoxide and carbon dioxide. Hence there is room for the hypothesis that vaporization, as cyanid, of accumulated alkalis is a serious primary factor limiting the ratio of ore to coke. Observed cyanid vapor concentrations and those measured by the variations of the nitrogen-oxygen ratio in the hearth gases form the basis for a quantitative explanation of the furnace action. As EVERYBODY knows, the blast furnace is a gas producer. As to the reason for this, people are not so well agreed. The significance of the fact is obvious, for the extent to which the fuel leaves the furnace as combustible gas measures poor economy in iron smelting; while good efficiency in this respect means poor gas. The furnace thus works at cross purposes. The present trend of the steel industry is toward. a primary use of the blast furnace as a gas producer with pig iron as a byproduct. Needless to say, this trend is away from improvement in iron making. The production of more and better iron in a given furnace consuming a given amount of coke would seem, at least, to involve a decrease in the relative proportion of the combustible gas. The possibility at the same time, however, of making more and better gas need not necessarily be excluded. (The more the furnace acts as gas producer, the bigger is the sulfur problem.) Whatever the object, it would seem desirable to have a, clear, comprehensive, mathematically exact estimate of why and how the blast furnace functions, to the large degree that it now does, as a gas producer. The literature does not give a definite answer to the question. That for which explanation is sought is the fact that only a minor part, usually not more than a third, of the coke carbon burned is oxidized to carbon dioxide; that the development in the furnace of the fuel energy is thus limited usually to little more than 50 per cent.; that it requires about twice as much fuel coke to make a ton of iron as is indicated by the rela-

Jan 7, 1925

By Eckley B. Coxe

IN the anthracite coal regions of Pennsylvania the custom has been to sight either at an open light (generally a mine-lamp), or at the string of a plumb-bob. If the station was intended to he a permanent one, a spud, as it is called, that is, a nail resembling a horseshoe nail with a hole in the head, is driven into the timbers over the station, or, if there be no timber, a hole is drilled in the coal or rock roof, into which a wooden plug is driven, which serves to hold the spud. The first operation in making a survey is to lay out the stations, that is, to mark the place where the holes are to be drilled for the plugs or the points on the timbers where the spuds are to be driven in. This should be done before any instrumental work is begun, as much labor can generally be spared, and the use of very short sights can often be avoided, by carefully laying out the stations beforehand. When the stations were laid out, a plumb-bob was hung from the innermost spud, which I will call No. 1, the instrument was put in position at No. 2, by plumbing down and putting a centre-pin under the spud, and then setting up over the centre-pin, and another plumb-bob was suspended from No. 3. If great accuracy was not required, a mine-lamp was set up under the plumbbobs, at No. 1 and No. 3, and the engineer sighted at them. If great accuracy was required, a lamp or some white sbface was held by an assistant behind the strings of the plumb-bobs. To work with any speed by the latter method (i. e., the accurate one), it was necessary for the engineer to have three assistants on whom he could rely even when the chaining was done afterwards; viz. : one to hold the light behind the string at No. 1, one at No. 3, and an assistant at the instrument to hold the light while levelling, reading the in

By A. Kaufman

More than 3 trillion gal of water are used annually by the mineral industry. Of this, approximately 21/2 trillion gal are recirculated, the rest constituting intake water. The major users are natural gas processing plants and phosphate rock, sand and gravel, and iron ore producers. Water was used by the mineral industry for mining (6%), processing (64%), cooling and condensing (27%), and miscellaneous uses such as boiler feed and sanitary purposes (3%). Whereas total water use is dependent on the quantity of material processed and on the particular process requirements of an industry, recirculation is dependent on processing, as well as cooling and condensing requirements, quality of new water intake, and the necessity for treating new and discharged water. Consumed water, on the other hand, is dependent on the quantity of water recirculated, and temperature and humidity in the area. Based on this analysis, an increase in water use by the mineral industry of 21/2 times by 1985 is forecast. Wster intake, however, will only rise 62%, because of a substantial increase in recirculation. In one report of a special series concerning the water resources of the United States, the Senate Select Committee on National Water Resources, 87th Congress, estimated that water demand would double by 1980 and triple by 2000.' In view of the possible water deficiencies that might result from such expanded usage and the need for research guidance, the Bureau of Mines organized and carried out a statistical canvass of water use in the mineral industry for calendar year 1962. The data used in this paper, unless otherwise noted, are derived from that canvass.' The efforts in this paper are devoted toward summarization of the canvass and analysis of the data. SOME DEFINITIONS Intake: Water introduced from an external source for the first time into a given mine or plant regardless of quality. Intake water is also called new water, water withdrawn, or makeup water. Fresh Water: Water suitable for cooking and drinking. Saline Water: Water containing more than 1000 parts per million of dissolved solids. Contaminated Water: Water not suitable for domestic use, but excluding saline water. Recirculated Water: Water reused to conserve intake water. Solutions that are recycled primarily because of fixed metallurgical practices, such as copper leaching solutions containing sulfuric acid, are excluded. Gross Water Used: Recirculated water plus intake water. Also called total water used. Consumed Water: Water that is lost by evaporation, as well as water lost in product. Seepage and transferred water are not considered consumed. The use of either intake or recirculated water may result in consumption. However, because of difficulties in measuring consulmption, consumed water is defined as the residual between intake and water discharged from the mine or plant. Mineral Industry: For the purposes of this paper, mineral industry includes all metal and nonmetal surface and underground mines and their associated processing plants, as well as custom mills, coal washing plants and associated mines, petroleum and natural gas well drillers, natural gas processing plants, and secondary recovery operations. WATER USE IN THE MINERAL INDUSTRY Water used by the mineral industry constitutes a relatively minor fraction of the water withdrawn by all users. Data compiled by the U.S. Geological Survey in 1960 indicate that water withdrawals, exclusive of that used to generate hydropower, approximate 99 trillion gal annually.3 Our data indicate that water withdrawals by the mineral industry comprise only 1% of this total, or 2% of the water withdrawn by industrial users. Use by Industry: Water used by various mineral industries is shown in Table I. The table indicates that close to one-half of the gross water used by the mineral industry in 1962 was used by natural gas processing plants, followed by sand and gravel, phosphate rock, and iron ore producers. The largest aggregate users of water are also the largest users per dollar of product. For example, Fig. 1 shows that the natural gas processing and phosphate rock industries are very large users of water per dollar of product. Their recirculation per

Jan 1, 1968

All branches of our profession may look back 'with pride upon the patriotic service rendered by engineers during the war. That war has been won. The mortal danger which it threatened has been averted. But the effects of the torture inflicted by it still remain, a fever in the blood of the body politic. Fever begets delirium and, unless its course be checked, has a tendency to produce convulsions. The only safe course is to take immediate steps to allay the fever. The seat of the present trouble is industrialism; as production is at the foundation of civilization, a diseased condition there carries pain and consequent unrest into every member of the organism. Who shall supply the cure? Quack doctors, nostrums in hand, rush forward from all directions promising to perform miracles. But sane men know that no miracles, though invoked by star gazers of purest intention, will prevent or accelerate the orderly operations of the laws of nature and of human life. Delirium must be controlled by the firm, gentle hand of intelligent, sympathetic authority. Fever must be allayed first by removal of all poisons from the system, then by consistent ministration of cooling, quieting restoratives, then by simple, wholesome nourishment. Nature will, under such treatment, supply the permanent cure.

Jan 12, 1919

By George E. Kruger, William F. Butler

The less developed nations maintaining a free enterprise economy (to which this chapter is addressed) have real and substantial opportunities to lay a foundation for general economic progress by using their mineral resources. Most of these nations have mineral resources which could be developed. By seizing these opportunities, nations seeking rapid economic development can secure a source of foreign exchange earnings to finance the imports needed for growth and, at the same time, increase the technical knowledge and well-being of an important part of their population. History clearly shows the manner in which most of the currently industrialized nations have used mineral resources to support their development. Indeed, few nations have managed to achieve a high level of income without a firm base of mineral resource development. The main exceptions appear to be the Netherlands, Switzerland, Denmark, and New Zealand, and the last two have based their prosperity on a highly efficient agriculture. Economic growth in the United States, the United Kingdom, Canada, France, Germany, and Russia was importantly based on the use of indigenous mineral resources. Despite this record of accomplishment through mineral development, many of the currently less developed nations are not taking advantage of the opportunities available in the mineral field. Restrictive laws or practices in many such nations operate effectively to prevent development of mineral resources. This failure to grasp real opportunities for development is based on a series of arguments that the mineral field offers few substantial and attainable advantages. Among these, the following propositions appear the most important:

Jan 1, 1964

By John H. Ratcliffe, Hans T. Lundberg

In airborne gravity surveys effects of acceleration and irregular movements of the aircraft must be balanced out or overcome. The gradient of vertical gravity is recorded, therefore, by using two masses instead of one. As the amplitude variations are infinitesimal and difficult to measure accurately, at of gradient during flight is positive or negative. The positive portions of the pattern can then be indicated and contoured. Even with these simplifications, the source of energy must be exceptionally stable. General Principles: In the conventional gravimeter the weight of a standard mass is determined at a number of selected points within the survey area. In most systems weight is determined by comparing the gravity pull with extension or torque produced in a wire spring. The instruments employed are sensitive to the slightest movement; they cannot be used on a moving platform unless velocity is kept strictly uniform.

Jan 8, 1959

By G. K. Manning, W. E. Few

WORK on the effect of vacuum heat treatment of 0.040 in. diam sintered and wrought molybdenum wires has been sponsored by the Office of Naval Research at Battelle for the past several years. An electrical resistance furnace' capable of maintaining a vacuum of less than 0.1 micron of mercury at temperatures as high as 4000 °F was used for heat treating the wires. Early in the work, it was found that the introduction of a few microns pressure of oxygen into the furnace resulted in a rapid increase in the oxygen content of the wire specimens and the appearance of a discrete oxide phase. Subsequent elimination of the oxygen atmosphere caused the disappearance of the oxide phase. This was used to determine the solid solubility of oxygen in molybdenum over the temperature range of 2000" to 3000°F.2 It was observed that, with the disappearance of the oxide phase, the wires regained some ductility. Single-phased wires possessed from 5 to as much as 40 pct elongation in 2 in. Later, attention became centered on determining the cause of this wide range in ductility. Wires containing less than 0.002 pct C, less than 0.0007 pct 0, less than 0.0005 pct N, and less than 0.00003 pct H exhibited the erratic ductility noted above. These percentages represent approximately the limit of accuracy of presently available methods of analysis and thus it became apparent that chemical analysis would be of little help in the study. A number of possible explanations for the wide range in ductility were suggested during the course of the work. It was first suspected that variations in the grain size of the recrystallized wire specimens might be responsible. Wire from several lots of material was available. One of these lots tended to develop very large grains when recrystallized, the others all developed an ASTM grain size of 3 to 4 when heated above 2700°F. No correlation between grain size and ductility could be found. It was thought that back diffusion of oil from the diffusion pump might cause contamination of the wire, principally with carbon, but when wires were treated without cooling the cold trap in the pumping system,

Jan 1, 1956

By Richard H. Terhune

The use of water-cooled breast-jackets or cinder-tap blocks is a great convenience in lead-smelting, even when siliceous slags are made. If the charges are at all basic it is almost imperative. Jackets of riveted wrought-iron or steel are expensive; those of cast-iron are liable to crack; those of bronze are costly and not durable, being easily penetrated by tapping-bars or destroyed by streams of matte impinging against them. To overcome these objections I introduced at the Hanauer works, in April, 1886, castjackets of steel, which have been in constant use since that time and are to-day as good as new. These jackets were made for us by the Chester Steel Castings Company, of Chester, Pa., at a cost of ten cents a pound at the works of that company. The metal is 5/8-inch thick, and the jackets were cored and tapped for l1/2-inch bushings, affording two large holes for the removal of dirt and incrustations. The same holes are used for feed- and discharge-water through 3/4-inch pipe. I hope the successful introduction here of cast-jackets of steel will lead to their more extended use in all branches of metallurgy where water-cooled surfaces are severely taxed, and where the size and thickness of the castings are not unfavorable to the production of a sound article, impervious to water and of high tensile strength.

Jan 1, 1889

By V. Lessels, D. J. Buckwalter, D. H. Rose

At White Pine Copper Co.'s operation in the Upper Peninsula of Michigan, the company has been losing more than four lbs of copper in each ton of sand tailings. With an average rate of 12,000 tpd of sand going to the tailing pond daily, the company has been losing more than 14 million lbs of the red metal annually. With an eye aimed toward lessening this loss, White Pine engineers in 1959 initiated a study on techniques for recovering this "lost" copper from the sands. Inasmuch as the flotation operation was considered to be optimized, a logical approach seemed to be leaching. For various reasons ammonia, ferric chloride, acid, and biological leaching were ruled out as impracticable. This led to a consideration of cyanide leaching as practiced in the precious metals industry.

Jan 8, 1967

By M. J. Spendlove, H. W. St. Clair

An automatic surface-follower mechanism was used to measure the surface temperature and the rate of evaporation of molten zinc while undergoing distillation at low pressure. At pressures of 50 to 100 microns Hg, the rate of evaporation may be 60 to 80 pct of the theoretical maximum corresponding to the measured temperature. The rate decreases rapidly at pressures above 100 microns Hg, to only 7 pct of the theoretical maximum at 2000 microns Hg. Measured temperature gradients at the surface are in agreement with theoretical gradients calculated from the heat of vaporization, rate of evaporation, and thermal conductivity of molten zinc. THIS paper covers a series of careful measurements of the rate of evaporation of molten zinc at low pressures, undertaken as a part of a general investigation on the separation of metals by distillation.' Preliminary results on the rate of evaporation of zinc were described in a previous publication.' The results of the preliminary study are as follows: 1—The observed rates of evaporation of zinc were as high as 0.60 g per sq cm per min, corresponding to 75 pct of the maximum rate as determined by the temperature of the metal. 2—The evaporation rate was decreased from 0.30 g per sq cm per min at a pressure of 25 microns to only 0.09 g per sq cm per min when the pressure was increased to 5 mm. 3—The temperature of the surface during rapid evaporation may be 35" to 100°C less than the main mass of metal. Observed temperature gradients at the surface are consistent with those calculated from the heat of vaporization and the thermal conductivity of liquid zinc. In the preliminary experiments, the rate of evaporation was determined from the loss in weight of the metal in the crucible during the test. This was compared with the weight of the condensate. Obviously, this method was subject to error because of some uncertainty as to the period of evaporation that should correspond to the loss in weight. Furthermore, this method did not permit taking into account probable variations in the rate of evaporation during the test. A more serious shortcoming was that the temperature at the evaporating surface was not known, so the maximum theoretical rate of evaporation could not be calculated accurately. To improve the precision of rate measurements and to allow accurate measurements of the surface temperature, a refined experimental technique was developed whereby the temperature and position of the surface could be measured accurately. This was done by an automatic surface-follower mechanism that gave a continuous record of the surface temperature and the amount of zinc evaporated. These data permitted an instantaneous determination of the actual rate of evaporation and the surface temperature throughout the test. Pure zinc (99.99 pct Zn) was used in all experiments. Description of Distillation Furnace The details of construction of the distillation furnace are shown in Fig. l. The furnace is enclosed in a large quartz tube open at one end. The open end of the quartz tube is sealed by means of a water-cooled head. The entire enclosure is vacuum tight. The connection between the water-cooled head and the quartz tube is sealed by means of a rubber gasket which fits tightly against the smooth end of the tube. The metal is heated by induced current set up in the molten zinc and the walls of the graphite crucible by means of a water-cooled induction coil outside the quartz tube. High frequency current is passed through the induction coil from a 6 kw mer-

Jan 1, 1952

By N. F. Schulz, H. A. Lex, J. D. Zetterstrom

A green ball of iron ore faces many perils from the time it is formed until it finally emerges from the pelletizing furnace as a hardened pellet. For instance, if the rate of heat transfer into a ball is sufficient to produce vapor from either the free or combined water more rapidly than it can escape at a tolerable pressure, the ball may split, spall, or even explode, a failure commonly known as decrepitation. To avoid such failures, one must either limit the rate of heat transfer during the drying and preheating stages, at the expense of production rates, or improve the decrepitation resistance of the green balls. The latter remedy may often be accomplished through changes in ore preparation, balling procedures, or the judicious use of binders or other additives. INTRODUCTION Pelletization has become established as an especially desirable method for the agglomeration of fine taconite concentrates and it promises to be equally satisfactory for improving the physical structures of certain natural ores. A high-quality pelletized iron ore consists of uniformly sized spheres, usually about 1/2-in. diam, which are strong enough to resist abrasion and breakage during handling and which reduce well without disintegration in the blast furnace. The unfired agglomerates, "green balls", are subject to several destructive effects that must be avoided or minimized if a high-quality product is to be obtained by pelletization. Among these are abrasion and impact deformation or breakage during handling of the wet green balls, deformation and breakage by compressive forces in the bed of ore in the pel-letizing furnace, decrepitation during drying and preheating, wind erosion, and radial cracking at firing temperatures. Moisture condensation from the warm saturated gases downstream from the drying zone on wet, cool balls may cause bed collapse if it becomes excessive. Decrepitation is defined as the sudden disintegration of green balls, usually with an audible pop, that occurs when they are heated too rapidly during the drying or preheating stages of the pelletization process. The extent of ball disintegration may vary from merely splitting off a small fragment to almost total disintegration into the original ore particles making up the ball. Such ball destruction results in a decreased yield of pellets, and the fragments, which also tend to interfere by obstructing the gas flow through the bed, must eventually be screened from the fired product and recycled. The closely related type of ball failure that sometimes occurs during the high temperature firing stage, resulting in radial cracks without fragmentation, was not considered to be decrepitation for the purpose of this investigation. Failure by decrepitation is not usually a serious problem in the pelletization of taconite concentrates. The problem is significant, however, in the pelletization of some natural ores, especially those containing hydrous iron oxides. In some instances, economicd production rates cannot be maintained if the drying and preheating rates are slowed down enough to avoid decrepitation. OBJECTIVES This investigation was undertaken to: (1) Develop a practical laboratory means for quantitatively measuring the tendency for green balls to decrepitate in iron ore pelletizing furnaces, and (2) Investigate the causes and cures of ball decrepitation. MATERIALS Two iron ores were used in the work reported here: a taconite concentrate at 90% minus 325 mesh, containing 65.0% Fe, 8.4% SiO2, and no loss-on-ignition; and a crude oxidized ore at 54% minus 325 mesh, containing 59.1% Fe, 3.6% SiO2, 1.1% A12O3, and 9.5% loss-on-ignition. For a special test of effect of particle size distribution on decrepitation, two other

Jan 1, 1967

By R. W. Raymond

The sudden death of Captain Jones, September 28,1889, became known to his fellow-members on the eve of the Ottawa meeting of the Institute; and at that meeting, Mr. Charles Albert Ashburner, of Pittsburgh, expressed with unaffected feeling and unpremeditated eloquence the sorrow of all. Mr. Ashburner subsequently undertook to revise and extend, for in in the Transactions, the remarks he had made at Ottawa; but death surprised him also, in the midst of his labors; and it has become my duty and privilege to prepare from the memoranda he left behind, the present brief and inadequate notice. To me, who knew and loved them both, this task of double sorrow recalls them both, with a peculiar sense of presence and of absence. They seem to speak from another land, not far away, yet not with human voices—like an echo and its echo. William Richard Jones was born in Luzerne county, Pennsylvania, February 23, 1839. His father was Rev. John G. Jones, a Welsh minister, who had immigrated to the United States in 1832. William was the eldest son, and his father's failing health made it necessary for him to begin early the work of self-support. At the age of ten, he was apprenticed to the Crane Iron company, of Catasauqua, and in this humble capacity entered upon the profession in which he was to become famous. Unquestionably, the thorough acquaintance with all details, acquired by working his way from the bottom to the top, was one secret of the conspicuous executive ability which characterized him in the height of his career. According to a letter from Mr. J. H. Geer, Assistant Chief Engineer of the Cambria Iron Company, Mr. Jones entered the service of that company in 1858 or 1859 as a machinist, and continued to work in that capacity until July, 1862, when he enlisted as a private in the 133d Regiment of Pennsylvania Volunteers, in which he afterwards commanded a company. The regiment was mustered out of service in 1863, and Captain Jones re-enlisted in the 194th

Jan 1, 1890