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By Geoffrey Gilbert

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

Jan 1, 1924

By Arthur Crowfoot

Page IntRodUction ................... The Round Table in Lake Superior Practice .........420 Early Use of Revolving Round Table in Butte District...... Use oF the Round Table at GREat Falls foR Sand-Slime Feed ., . The Round Table for Fine Slime........,.... Construction of Slime Plant at Great Falls..... '..... 424 Tests on Wood, Linoleum, and Cement Decks.........426 Central Feed Apron Removed ....'......... Re-treatment of Round-Table Tailing........... Determination of Conditions for Round-Table Treatment of Slimcs ... 430 Variation in Slope of Round-Table Deck........ ,... The Steel-Frame Cement-Deck Round Table ........ Tests on Cement and Canvas Dock Surfaces ..: ..... Conoidal Deck Round Tables............. Results with Sand-Slime Feed on Conoidal Deck....... Conclusions from Preliminary Tests on Conoidal and Conical Decks ... 446 Discussion of Results of Four-Day Test on Conical and Conoidal Decks . 452 Discussion of Results of Eight-Day Test.......... Qualitative Sampling of Concentrates Across Conical Deck.... Summary of Slime-Plant Practice............ Suggested Flow Sheet for Slime Classification and Treatment.... Conclusion...................467 Introduction The principal object of this paper is 60 presest, data on the development of the revolving convex round table as a concentrator for the through 0.07-mm. slimes from the ores of the Butte district, although some brief notes on the earliest recorded use of this type of concentrating table in the ore-dressing plants of the Lake Superior region and of the Butte district are also presented. The revolving convex round table belongs to the class of concentrating tables known as film-sizing. tables, these tables using the relative transporting power of a film, or thin sheet of water, as it flows over a quiet inclined surface, to separate the minerals of a sorted product. The grains of heavy mineral move down the slope of the table deck slowly, or, in some cases, not at all, after the initial force of the feed entry VOL. XLIX.—27

Jan 1, 1915

By Morris Muskat

A theory is presented for calculating the performance history of complete water-drive systems producing from idealized stratified formations. The general equations are applied to systems where the permeability stratification is either of the exponential or linear type. Calculations were carried through for different degrees of permeability stratification, but with special emphasis on the effect of the mobility ratio between the produced oil and the invading water on the resultant performance. These results are also expressed graphically as curves for the initial water breakthrough recovery, for the different degrees of stratification, as a function of the mobility ratio, and of the composition of the produced fluid stream as a function of the cumulative oil recovery. For several typical cases the latter has also been plotted as a function of the cumulative oil and water throughflow. The general result is that when the mobility of the oil is lower than that of the invading water the channelling tendency resulting from the permeability stratification becomes aggravated as the higher permeability zones become flooded out. Situations of this type would obtain when producing low gravity or highly viscous oils. Conversely, if the mobility of the oil is high compared to that of the invading water, the flooding of the high permeability zones will lead to a retarding and choking effect, and the gross bypassing phenomena will be partially suppressed. These conditions would correspond to those of flooding high gravity or low viscosity oils. A discussion is given of the various basic assumptions made in the analysis, including that of ignoring the stripping phase of the production history as implied by relative permeability concepts. INTRODUCTION The physical ultimate recoveries from oil reservoirs are basically determined and limited by the physical oil displacement processes associated with the reservoir producing mechanism. In practice, however, the economic ultimate recoveries are further limited by the mobility of the reservoir fluids and the uniformity and continuity of the producing formation. In fact, it is the differential depletion between the component parts of the composite reservoir which ultimately determines the total recovery at the time of field abandonment. While this observation applies to both the solution gas drive and gravity drainage mechanisms, in which use is made only of the energy contained within the original oil-bearing reservoir, it is of even more paramount importance under operations wherein the energy associated with extraneous fluids provides the ultimate oil expulsion mechanism. Whether the invading fluid is the water from an edgewater drive, water injected for pressure maintenance, gas injected for pressure maintenance, or gas returned to the formation in a cycling program, it is often the continuity and uniformity of the producing section which will control the economic efficiency of the operations. The importance of the problem of reservoir non-uniformity does not, of course, lessen its complexity or the difficulties of its solution. In fact, these are inherently such that the concept of a "general" solution is virtually meaningless. About all that can be reasonably hoped for is the analysis of specific and well-defined types of non-uniformity which may give some degree of approximation to actual reservoir conditions. Since variations in the nature of the reservoir which depend only on the position along the streamlines will not lead directly to major differential depletion development within the reservoir, the types of non-uniformity considered thus far have involved stratification assumptions. That is, the producing section has been replaced by a multi-layer "sandwich," each uniform areally, and differing from the others only in its basic physical constants as to thickness, porosity and permeability. The fluid motion in the composite system is thus approximated by a parallel superposition of the independent fluid movements in the individual strata. For the specific application to cycling operations the theory of the effect of permeability stratification has been developed for both discontinuous' and continuous types of permeability stratification. Among the latter, treatments have been given of systems in which permeability distributions are governed by exponential, linear' or probability3 functions. In all these studies complete dynamical equivalence was assumed between the injected dry gas and the displaced wet gas. The overall effective permeability of each stratum was therefore considered as constant and independent of the degree of invasion of the injected fluid. In the case of the displacement of oil by water, the assumption of dynamical equivalence between the water and oil will be strictly valid only by accident. Even if the oil viscosity should be the same as that of the water, the effective permeability to the oil in the presence of the connate water will in general be quite different from that of the water behind the water-oil interface flowing past the trapped residual oil. As a result the effective permeability for the stratum as a whole and rate of water invasion will change with time as the intrusion continues. The differential fluid motion in the individual strata will thus also vary with time. Qualitatively, it is easy to predict the resultant effects. If the permeability to viscosity ratio of the invading fluid exceeds that of the fluid displaced, the stratification and bypassing effect of the perme-

Jan 1, 1950

By H. S. Price, J. C. Cavendish, R. S. Varga

This paper presents a new technique for solving some of the partial differential equations that are commonly used in simulating reservoir performance. The results of applying this technique to a simple problem show that one obtains accurate pressure values near wells, as well as accurate pressure pdients, which can be explicitly calculated. The method is completely rigorous in that convergence of the discrete numerical solution to the continuous solution for both pressure and pressure gradient is established. High-order, piecewise-polynomial approximations are used near the wells where pressure gradients are steep, while low-order, piecewise-polynomial approximations are used elsewhere to reduce greatly the calculation time. This combination is shown to give a uniformly good approximation to the solution. These approximations, obtained by using a Galerkin process with suitable Hermite subspaces, are shown to be theoretically and numerically superior to the usual approximations obtained from standard finite-difference techniques. Not only are much greater accuracies obtained, but computer times are also greatly reduced. The application of this technique to multiphase flow problems (e.g., single well coning problems) would have considerable practical interest, but such extensions of this technique with full mathematical rigor have not been made as yet. However, the numerical methods presented here are general, and in principle extend to multidimensional, multiphase flow. Moreover, the preliminary results given in this paper are sufficiently encouraging that we feel the effort in attempting these extensions is justified. INTRODUCTION The problem of obtaining accurate pressure distributions and pressure gradients around wells is of considerable importance in the numerical simulation of reservoir performance. The most common approach to solving this problem is to use finite difference techniques (see McCarty and Barfield9 or Peaceman and Rachfordl0). This approach, however, has many disadvantages, the major one being that many grid points are generally necessary for accurately describing the pressure distribution and the pressure gradient around wells. This need for a fine grid results in large computer times and often in prohibitively high costs. Besides investigating the method of finite differences, some authors, such as Welge and weber17 and Roper, Merchant and Duvall,13 have considered a combination of analytical and numerical techniques with some success. These approaches, however, are all nonrigorous and quite often cannot even be applied. In this paper, we present a numerical formulation of high-order accuracy, based on the Galerkin method, for solving this problem. We treat here only the partial differential equation that describes steady-state, single-phase flow. However, the methods presented are general and in principle extend to multidimensional, multiphase flow. Specifically we treat special cases of the problem in two dimensions described by: where G is a rectangle (with sides parallel to the coordinate axis) with boundary ?G, ?/?n denotes the outward normal, and y and B are non-negative constants such that y + B > 0.

Jan 1, 1970

By C. E. Mills

Studies of ground movement and subsidence resulting from mining operations cover a broad field. It is also a very important consideration and one that eventually affects nearly every mining operation of any extent. The damage to surface buildings, removal of mine surface plants and replacements of main hoisting shafts must reach an astounding expenditure were these cost figures available over a period of years. Were the subject one of mathematical formula and dependent only on the angle of draw of the walls or country rocks, the problem would be relatively simple. Consideration must be given to depth and extent of workings; structural conditions of the orebodies and enclosing country rock; physical properties of these same rocks, including schistosity, bedding, jointing, slips, dikes, faults, and other structural weaknesses. The method of mining, extent of openings, supporting pillars, and amount of moisture or water underground are other pertinent factors. With such a large number of variable factors, it is apparent that the subject of subsidence is one that must be based largely on experience and results at other mines where conditions are somewhat comparable. In presenting this paper, it is the intent to describe the progressive results of past ground movements at the United Verde, to bring out physical conditions largely responsible for this movement, but to refrain from theorizing on the ultimate extent of subsidence resulting from future mining operations. Geology and Structure1 The ore deposits of the United Verde are of the massive sulfide, schist-replacement type. A structural anticline formed by the intrusion of diorite between bedding planes of steeply dipping and severely folded greenstones and porphyry localized the deposit of sulfide. The mineralized zone is of great horizontal extent varying from 200,000 to 400,-000 sq. ft., and extends from the surface to the lowest levels at a steep dip of from 50° to 75. The irregular interfingering of the sulfide with

Jan 1, 1934

INCREASING realization that pouring and ingot-mold practices involve many factors of fundamental importance to ingot quality and general steel-mill operations has caused these phases of steelmaking to become major concerns of operators and metallurgists engaged in control of quality and costs. Methods of pouring steel from the ladle into the ingot molds have some direct effects on ingot quality. The mold itself governs solidification and dimensions of the ingot and in so doing exerts some very tangible influences not only on ingot quality but also on product yields and general steel-mill processing. In addition, practices are employed' in the handling of molds during daily open-hearth operations that are important to quality and production costs. Therefore, pouring and mold practices must be considered highly specialized and important steps in steel-mill operations. MOLD DESIGN Mold design is difficult to discuss in a precise manner because it varies greatly throughout the industry, both in theoretical concepts and practical application, and few well developed data are available. Most ingot molds are designed to meet conditions peculiar to a given plant wherein quality standards are dictated by end-use requirements, which may differ considerably, even for the same grade of steel. The mold designer must also consider the equipment available to process ingots and the product obtained from them. Such equipment, used for stripping, heating, blooming and finishing operations, is seldom, if ever, exactly the same in any two steel plants. Thus, pronounced contrasts in mold designs can be expected to continue, even among plants making strictly comparable types of product, particularly because some producers are just beginning to realize the benefits possible from specialized designs. Certain fundamentals are used in mold design but even these

Jan 1, 1951

By C. E. Wood, E. P. Barrett, T. L. Joseph

The invention of the Bessemer converter process in 1856 added great impetus to the manufacture of steel and is one of the outstanding contributions to process metallurgy. Although the process of refining pig iron by passing air through the molten metal bears the name of Henry Bessemer, it should be mentioned in passing that William Kelley of Eddysville, Ky., worked on the process as early as 1847. Kelley was granted a patent on the process in 1857, inasmuch as he was able to prove priority in discovery.' After considerable litigation in 1865 the respective interests of Kelley and Bessemer were combined. On Sept. 10, 1856, Robert Mushet of England obtained his first patent on the application of manganese to cast steel. Mushet anticipated trouble in purifying iron by passing currents of air through it: His patent specified that steel made in this way often contained flaws and was red short or cold short. Mushet understood the refining of pig iron into steel well enough to realize the difficulties likely to be cncountered from oxidation of the iron. Mushet was not only an inventor; he was also an investigator. He understood the principle of selective oxidation which takes place in the converter process, and he realized therefore that the remedy for over-oxidation was attainable if a suitable metal could be found at a reasonable cost and in sufficient quantities. His first experiments were made in small crucibles holding a few ounces of metal. Later his work was conducted on a larger scale and with complete success. Manganese had been used in making steel a quarter of a century before the converter

Jan 1, 1927

By Samuel Daniels

THE Al-Cu-Ni-Mg alloy is much benefited by heat treatment and, in such con¬dition, is preferable to the Al-Cu-Fe-Mg alloy either as cast or as heat-treated, when both are reheated to temperatures of from 400° to 600° F. and compared, cold, with respect to strength and to hardness. The main differences between the alloys do not arise until the reheating temperature exceeds 400° F., above which they gradually soften. This softening is characterized metallographically by the appearance of intragranular precipitate. The Al-Cu-Ni-Mg alloy is weakest and least hard after being reheated at 600° F., the AI-Cu-Fe-Mg alloy at about 700° F. The former starts to reharden at 700° F., the latter at 800° F. There is a tendency for both alloys to lose strength and hardness with prolongation of time at the reheating temperatures of 500° and of 700° F. The Al-Cu-Ni-Mg alloy is considerably stronger and harder than the Al-Cu-Fe-Mg alloy when both are heat-treated and reheated for long periods of time at 500° and 700° F. Although the latter can be made harder initially than the AI-Cu-Ni-Mg alloy by suitable quenching and aging, heat treatment, in general, favors the retention of this initial (strength and) hardness after reheating to a much greater degree in the Al-Cu-Ni-Mg alloy. The percentage of elongation of the two materials in any condition is very small. CERTAIN aluminum alloys have been used for pistons and other parts operating at temperatures up to 650° F. because of their lightness, high thermal conductivity and specific heat, fair strength and hardness at elevated temperatures, excellent machineability, and moderate resistance o corrosion. In the piston, the inertia forces and the bearing loading and with this the vibration are decreased. The piston head functions at a lower temperature (about 200° F. below one of cast iron), so that, because of the lessened tendency toward carbonization and detonation, higher compression ratios may be used. On the other hand, the aluminum alloys do not have the wearing and bearing qualities of cast iron; also they have a large coefficient of expansion, allowance for which must be made in the design.

Jan 2, 1926

By W. J. Maraman, D. R. Harbur, J. W. Anderson

A device for rapidly quenching liquid metals into thin platelets has been developed at the Los Alamos Scientific Laboratory. This rapid quenching equipment is built around the technique of catching a molten drop of metal between a rapidly closing plate and a stationary plate. The design and operation of this unit are described. The closing speed of the smasher plate at impact is 12.6 ft per sec. The quenching rate for this device is controlled by the interface resistance between the plates and the platelet, and is dependent upon the heat content and density of the material being quenched. The initial quenching rate down to the freezing point of the platelet material is lo5º to 106ºC per sec. After an isothermal delay, which is poportional to the heat of fusion of the platelet material, the final cooling rate down to the temperature of the smaslier plates is l04ºto 105cº per sec. RAPID heating of metals by capacitor discharge and other methods has provided the metallurgist with a useful tool for probing into the kinetics of phase changes and the many nonequilibrium phenomena which occur during rapid temperature changes. Equally interesting studies can also be made on metals and alloys which are rapidly cooled from the liquid state.' Studies in this field have been limited, however, because the rates at which metals could be cooled were many orders of magnitude slower than the rates possible for heating. In recent years many new laboratory methods have been developed to rapidly cool metals from the liquid state to ambient temperature and below.2"4 All of these methods involve spreading a liquid drop of metal into a thin foil in a very short time. The methods developed have varied from ejecting a drop of molten metal at the inside surface of a rotating cylinder or stationary curved plate to catching a falling drop of molten metal between rapidly closing plates. The equipment which has been developed at the Los Alamos Scientific Laboratory for rapidly cooling molten materials uses the latter of these two approaches. The basic design, operation, and initial results of this rapid quenching device are given in this report. APPARATUS The drop smasher, which is now being used to obtain rapidly cooled metal foils, is shown in Fig. 1. Basically the device consists of a smasher plate which is driven by a solenoid into a stationary plate. The solenoid is activated by a drop passing through the photoelectric cell and is powered by discharging an adjustable 350-v capacitor bank with a 66-amp peak current into it. This power supply is designed so that the solenoid is powered for 2 m-sec after plate closure to minimize the rebound effect. There is an adjustable time-delay mechanism between the photoelectric cell and the solenoid. Both smasher plates have changeable inserts so that a variety of materials can be used to smash the molten drop. The shaft of the moving plate is guided in an adjustable housing which has ball-bearing walls. The cabinet shown to the left of the drop smasher in Fig. 1 contains the power supply and receiver for the photoelectric cell, the time delay mechanism, and the capacitor bank. The drop smasher can be placed inside a vacuum chamber, for use with radioactive materials, with the upper plate forming the lid, as shown in Fig. 2. On top of the vacuum lid is an induction coil, powered by an Ajax induction generator, which is used to melt drops from the end of the rod extending through the vacuum seal on top the quartz tube. OPERATION The drop smasher shown in Fig. 2 is operated in the following manner. The smasher plates are separated and the unit is lowered into the vacuum chamber using a pressurized cylinder. The induction coil, quartz tube, and lid with sliding vacuum seal are then assembled on top the vacuum chamber. A rod of the material for rapid quenching studies is connected to the rod extending through the sliding vacuum seal. The vacuum chamber is then evacuated and the desired atmosphere established. The photoelectric cell is turned on, and the capacitor bank is charged and armed. Power is supplied to the induction coil, and the rod of material for rapid quenching studies is lowered into the induction field. A molten drop forms on the end of the rod, drops off, falls through the light beam of the photoelectric cell, and is then caught between the smasher plates. .

Jan 1, 1970

By W. P. Sykes

SEVEN years ago, Dr. S. L. Hoyt1 presented a masterful discussion of the hard metal carbides and cemented tungsten carbide. His lecture summarized most of the data then available in the field; many of the details relating to the production, properties and structure of cemented tungsten carbide had never been previously published, for, in fact, this information was only then being acquired. During the intervening years, the cemented carbides have assumed a place of real importance in the commercial field, with an ever widening variety of applications due to constant improvement in the control of production technique and the unremitting search for new compositions that might better the performance of the alloys in one or another type of service. The most recent summary of production methods, properties and guides for the successful application of the cemented carbides appears in the 1936 edition of the Metals Handbook. Of necessity, much detailed information relating to structures and physical properties is not included in such a summary, and it is with such details that the present discussion is concerned. STEPS IN PREPARATION While the past 25 years have contributed a valuable store of working knowledge in the field of powder metallurgy, many of the process controls are derived entirely from experience and are not as yet finally explained by a specific physical or chemical phenomenon. For most of the cemented carbides such difficulties are aggravated by our lack of knowledge not only of the complex alloy systems involved, but also by the possible changes in structure and even in composition which may accompany variations in temperature, heating time, and furnace atmospheres. The principal steps in the preparation of these cemented carbide alloys are fairly well known, but to supply a foundation for discussion these steps are briefly outlined as follows: 1. Formation of the metal carbide in the form of powder by heating a mixture of carbon and the metal powder or oxide for several

Jan 1, 1938

By Charles H. Fulton

Experimental work on the process was begun on a laboratory scale at Cleveland, Ohio, in 1914, and transferred to East St. Louis, Ill. in 1916, where a commercial sized furnace was in technical operation until January, 1918. The essential steps of the process are as follows: Oxidized zinc ore or roasted zinc concentrate is mixed with crushed coke and coal-tar pitch and formed into briquets 9.25 in. (23.5 cm.) in diameter and 21 in. (53 cm.) long in a manner similar to that used in the manufacture of graphite or carbon electrodes, except that much less care and time are required. The composition varies with the nature of the ore; in one case, the composition was 100 parts ore, 70 parts coke, and 18 to 20 parts pitch. These briquets maintain their form and volume during and after the distillation of the zinc. This object is gained by using coke as the matrix and coal-tar pitch as the binder; this pitch becomes coke on heating and unites the ore particle and the original coke particle into a continuous mass. The briquet is an electrical conductor but only to such a degree that it can be used as a resistor. The size of the ore, as in the present practice of zinc metallurgy, ranges from fine material, such as flotation concentrate, to coarse table and fine jig concentrate. The process is not restricted to any particular kind of ore, but is applicable to pure high-grade ores, ores high in iron, and complex zinc-lead ores, since the residue from the distillation IS held immovably in place within the briquet. In the case of complex zinc-lead ores, the distillation is conducted with a carefully regulated temperature so that a high percentage of lead is retained in the distilled briquet, which may then be smelted for its lead content. In present zinc smelting practice, the reduction fuel is from 40 to 50 per cent. of the weight of the ore. In the briquet, it is from 60 to 85 per cent. of the ore; but unless the ore is exceptionally high in residue, the distilled briquet may be used over again as coke, or as a high ash coke for fuel purposes in power production. Baked briquets are hard and tough and may be handled roughly

Jan 1, 1921

By Richard E. McElvain

The mining and other industries have grown and changed with- respect to their requirements for slurry pumps capable of handling high percentages of abrasive materials. Greater solids concentration, higher heads and pressures, and increased flow arc not possible. Today's equipment delivers up to three times the flow-tonnage and 1.3 times the head per stage as compared with pumps of ten years ago. This results in four times the requirement in size and energy. The new centrifugal pumps are capable of handling these requirements at pressures up to 4826 kPa (700 psi), with 6895 kPa (1000 psi) or more being considered for future systems. The latest pumps, functioning at four times the operating requirement on flow-head, weight eight times more than the previous equipment. Efficiency is increased slightly, to about 75 % to 85%. A testing program on equivalent units has confirmed that the added strength and specific design of heavy-duty pumps can meet demanding engineering objectives. Operating life on difficult-to-pump materials is increased from 500 to over 5000 hours of continuous operation; the ten-fold increase in pump operating time is a major design objective.

Jan 12, 1976

IT is not enough to know how to melt well and to have the bellows and charcoal for your purpose. If you wish to make small castings turn out well, on account of their thinness, it is necessary to aid the metals with unctuous and corrupting materials like tin, sublimate, arsenic, or realgar,

Jan 1, 1942

This Bulletin will be received by members at about the time the Colorado Meeting is in session. A general account, of the meeting will be printed in the October Bulletin, but it will not be practicable to publish the discussion of the papers at the Colorado Meeting until the Nov-vember Bulletin.

Jan 9, 1918

By C. R. Ince

THE term "differential flotation" is used to denote a flotation operation in which separation is effected between two or more minerals of the same class; e. g., lead sulfide from zinc sulfide, pyrite from blende, chalcopyrite from pyrite, chalcopyrite from blende. At present, so far as published work shows, there seem to be two theories as to the mechanics of differential flotation. The earlier and more generally accepted theory is that the so-called depressing agents alter the surface of one or more of the sulfides in the ore, either by chemical action or adsorption, so that it is no longer amenable to flotation, but that these depressed sulfides can be revived, after the unaffected sulfide has been floated, by reagents which react chemically with the altered surface and make it amenable to flotation. More recently, Professor Taggart1 has advanced the theory that slime adsorption is an important factor in differential flotation. He believes that, with the proper use of a class of agents, which he calls .dispersion agents and which include practically all the depressing agents, one can cause the slime to adsorb differentially on sulfide surfaces. A gangue-slime coated sulfide surface will act as a gangue particle and will not float. If, subsequently, an agent that will remove the gangue-slime coating is added, the sulfide again assumes its original surface and can be floated as an ordinary sulfide. This-is the basis of the slime theory of differential flotation. Timber Butte mill at Butte, Mont., is a typical lead-zinc flotation concentrator. Neihart ore, chosen for investigation in this work, is one of the custom ores treated at that mill. Practice at Timber Butte mill in February, 1928, was as follows: A combined lead-zinc concentrate was first made using 0.2 lb. per ton on the ore of potassium xanthate and 0.03 lb. per ton of Cleveland Cliffs oil after 1.5 lb. per ton of lime and 1 lb. per ton of calcium chloride has been added just before the ball mill. The concentrate was then thickened to 70 per cent. solids. Potassium cyanide to the amount of 0.3 lb. per ton and zinc sulfate in the quantity of 0.5 lb. per ton were added to the thickened pulp and the whole

Jan 1, 1929

By Walter C. Lawson

The primary objective in laying track in panel sections is to reduce the number of track laborers required. This is possible because the work is mechanized. Moreover, because the work is mechanized and each of the operations needs only a few men, and each is self-contained, the work can be carried on at night as well as in daylight; therefore, the method provides a means of preparing tracks on more than one shift. The laying of tracks in open pits and quarries in panel sections is not new but new methods have been made possible by the introduction of new types of equipment. The purpose of this paper is to describe the methods that are followed in the Morenci open pit. General Mining Operations Full-scale ore production at Morenci is about 50,000 tons daily. The normal yearly output of ore and waste is 32,000,000 tons, of which 30,000,000 tons is handled by rail haulage. This requires the building of approximately 47 miles of loading and other temporary tracks during a 12 months' period (Fig I). Broken ore and waste is loaded into 90-ton capacity dump cars with 5-cu-yd full-revolving electric shovels. Shovel banks are uniformly 50 ft high. They are blasted with churn drill holes and the broken material from a blast is loaded out with two shovel cuts, the first one being called (locally) the "splatter" cut and the second one the "clean-up" or "face-up" cut. When a shovel is making its clean-up cut, the loading track is about 70 ft from the toe of the bank and, under normal conditions, a bank is blasted against it without removing the track. It is thus evident that each track is used for two shovel cuts before relocation is necessary, inasmuch as a single position serves for both the clean-up cut prior to blasting and for the splatter cut following the blast. The normal advance of a solid bench by a single blast is 40 ft (Fig 2). Preparation OF Panel Grade In preparation of panel grades bulldozers and rooters are used for the bulk of the work and an auto-patrol road grader for the final stage. At Morenci, bulldozers have always been used for track-grade preparation, but before the introduction of the other two types of equipment grades were uneven and irregular at best, and always necessitated a big gang of track laborers to hand-block under the ties with rocks after a track was laid into place. High blocking also made poor track because of instability and caused frequent derailments. Under these conditions derailments were generally bad as re-railing became difficult. Much track was torn up and many tics broken in the process. The inadequacy of the hand-blocked track, together with the inefficiency of hand blocking, constantly pointed, to the desirability of reducing the amount of labor required, so various means were tried to improve conditions, such as wood

Jan 1, 1949

By R. J. Brison, O. F. Tangel

The development of a new method of mineral separation was sponsored by the International Salt Company, which requested Battelle Institute to investigate means for improving the quality and appearance of rock salt from the Company's Detroit mine. Although developed specifically for removing impurities from rock salt, the general method may be applicable to other separation problems. The principal impurities in rock salt from the Detroit mine are dolomite and anhydrite which represent 2 to 5 pct of the weight of the mined salt. In the size range from 1/4 to M in. (the range of primary interest in this project) the impurities are only partially liberated from the halite in normal production. Further size reduction to improve the liberation of impurities is not practicable in view of the market requirements for the coarse grades of rock salt. Laboratory separations in heavy liquids showed that, to improve the quality and appearance of the rock salt substantially, it would be necessary to remove not only free gangue particles but also a large proportion of the locked-in particles. Because rock salt is an inexpensive commodity, a low-cost process was required. Gravity methods were, of course, considered. The heavy-liquid separations indicated that a split at an effective specific gravity of 2.2 to 2.3 would be required. (The specific gravity of pure halite is 2.16.) Heavy-media separation was investigated but had the disadvantages that it was necessary both to operate with saturated brine and to dry the cleaned salt, and that the cleaned salt was darkened by the magnetite medium. Air tabling was tried but did not give the desired separation. It soon became apparent that established methods would not provide a satisfactory solution and work was undertaken on the development of a new process to solve the problem. PROCESS DEVELOPMENT Preliminary Experiments: At the start of the investigation, an analysis of the problem indicated that the diathermacy of rock salt—that is, its ability to transmit radiant heat—might form the basis for an efficient separation process. Under this theory, the impurities might be selectively heated by radiant heat. The particles could then be fed over a belt coated with a heat-sensitive substance so that the warm impure particles would adhere preferentially to the coating. After the initial experiments, made by heating the rock salt with an infrared lamp and separating the product on small sheets of resin-coated rubber, proved encouraging, a small continuous separation unit was set up. This comprised 1) a simple heating unit consisting of a vibrating feeder covered with aluminum foil and an infrared lamp mounted above the feeder and 2) a separation belt 6 in. wide and 36 in. long. A sketch of the device is shown in Fig. 1. Results with this apparatus confirmed the fact that a good separation was possible. It was apparent, however, that a considerable amount of experimental work would be needed to develop the scheme to a practical and economical process. The Process: Basically, the process consists of two main steps: 1) selective heating by radiation and 2) separation of the heated particles on a heat-sensitive surface. Because neither of these steps had previously been utilized commercially in mineral processing, it was necessary to do basic research on both aspects. Factors studied in the investigation included type of heat source, design of heating unit, design of separation belt, selection of heat-sensitive coating, removal of heated particles from the belt, contact between particles and coating, and maintenance of the heat-sensitive surface. Part of the experimental work was carried out on a small-scale unit consisting of the 36x6 in. belt and auxiliary apparatus, and part on a larger unit. For simplicity, discussion of work on both of these units is grouped together. SELECTIVE HEATING Radiant-Heat Source: The essential requirements for a radiant-heat source were 1) that the radiant heat be in a wave length range which is effectively absorbed by the impurities but not absorbed appreciably by the rock salt and 2) that it be dependable, practical, and economical. Selection of a heat source of suitable wave length range was one of the first considerations. It is well known that pure halite is highly transparent to radiant energy in wave lengths from 0.3 to 13 microns. However, the available data on infrared transmission by dolomite and anhydrite, particularly in the range below two microns, were not complete enough to serve as a reliable basis for selection of a heat source. Although it may have been possible to obtain sufficient data on infrared transmission and absorption to enable one to select the best heat source, a more direct procedure was used. This consisted simply of exposing the crude rock salt to each of several types of radiant-heat source on the small continuous separation device. The heat sources investigated, approximate source temperature used, and calculated wave length of maximum radiation are tabulated in Table I. Of the two types of tungsten-filament lamps investigated, both the short wave length photoflood lamps and the longer wave length infrared lamps were satisfactory from the standpoint of selectivity

Jan 1, 1961

By A. N. Chirico

This paper reviews the three major distillation processes: multiple effect (LTV) evaporation, multi-stage flash distillation and vapor-compression forced circulation evaporation. Scale preventative measures are discussed for all saline water applications. Operational data is presented on the Freeport, Texas, demonstration plant, which is the first government facility to produce one million gallons per day of fresh water for a municipality. There has been much publicity concerning the water crisis that confronts many peoples today. There is little doubt that the arid regions - which include the Middle East, parts of Africa and the Caribbean — have suffered to no slight extent for the lack of this most precious commodity. But what about our own country? Government experts have extrapolated demands and flatly predict that by 1980 we will be faced with a shortage of 80 billion gal per day. The validity of this prediction has been disputed by others; however, it appears certain that there will always be a natural abundance in some areas, a shortage of supply in other areas. Distributing our total natural water resource equitably would be impossible. Transmission of water by means of aqueducts can be an expensive undertaking. The controversial Feather River Project in Calif. is an example. The estimated cost for this venture is a staggering three billion dollars. As our population continues to increase and our standard of living rises, agricultural and industrial requirements will be proportionate. What can be done to avoid a crisis? We can conserve and use our water for industrial and irrigation purposes more judiciously: we can attempt to eliminate pollution of our natural resources from sewage and industrial wastes; we can develop, while there is time, saline water conversion processes for the massive production of low cost fresh water. The scope of this paper will be limited to only the distillation type processes that are commercially feasible. The first step in making potable water is to find a source of raw material. An inexhaustible supply is provided by oceans in coastal regions, but the supply of water is more critical in the inland communities of our country. The source of raw material in these. regions is brackish well water and this must be utilized. There is a significant process difference when handling brackish water compared to seawater and this brings out an important fact: No single conversion method can be universally applied to solve all the water problems. Composition of the raw water and degree of distillate purity are factors which must be considered before a particular process is selected. Local conditions at the plant site, fuel costs, labor costs, disposal facilities, etc. are other equally important factors which must be evaluated. WATER CONVERSION PROCESSES Conversion processes commercially feasible today are: 1) multiple effect evaporation, 2) multiple flash distillation, 3) vapor compression distillation and 4) electrodialysis. The first three are distillation processes which take potable water out of the raw water, while the fourth is a membrane process which takes out the salt. In addition to the above there are a good number of other promising methods for production of potable water, many of them in the basic research stage. Freezing is another promising process with commercial potential. This process hinges upon the formation of ice crystals which are free of salt occulsions. Separation and washing of the crystals are problems that must be solved before this process can be considered commercially feasible. Freezing processes have several advantages mostly attributable to the low temperature of operation. This low temperature reduces the scaling and corrosion problems encountered in higher temperature operations. Several different freezing processes are being considered and will be tested in the pilot plant at Wrightsville Beach. One process is a flash freeze process, a second uses a secondary refrigerant such as butane for freezing, and a third process employs a secondary refrigerant particularly controlled to produce large ice crystals. Of the above processes, only the distillation processes are reliable when water of high purity is re-

Jan 1, 1963

THE developments in construction and operation of the basic open-hearth furnace that have taken place in recent years have placed new emphasis on the vital influence played by regulation and control of the combustion system in both furnace production and furnace life. The several factors influencing flame development, such as regulation of fuel supply, air supply, air preheat, furnace draft, and furnace reversal, must be controlled closely if successful furnace performance is to be accomplished. Rugged instrumentation of distinctive design is required to sup- ply dependable information concerning operating conditions, which is requisite to proper regulation of combustion. This chapter attempts to give a practical discussion of the various features of open-hearth practice and instrumentation related to the efficient heating of the furnace, control of temperature, and protection of the furnace structure from accidental overheating. The appended references will be helpful to readers wanting a more detailed treatment of individual topics. OPEN-HEARTH FUELS The most important open-hearth fuels are listed in Table 4-1 together with their compositions and other data useful for combustion calculations. A detailed discussion of open-hearth fuels is not attempted here, but certain factors peculiar to their application to this type of process are briefly indicated on the following pages. Very often an open-hearth shop is forced by economic factors to use a fuel to which its furnaces are not very well adapted, because the general fuel-allocation scheme for the works as a whole seems to demand it. Often a variable marginal supply of coke-oven gas or tar must be consumed by the open hearth, together with another fuel such as producer gas, natural gas, or oil, to fill out total requirements. Most furnaces employ more than one kind of fuel during their useful life; however, the partial redesign

Jan 1, 1964

By D. J. McAdam, R. W. Mebs

THE technical cohesive strength of a metal means, not the interatomic forces, but the technically estimated resistance to fracture. An example of such resistance to fracture is the so-called "true" breaking stress of a tension-test specimen, the breaking load divided by the sectional area at fracture, According to the prevalent view,8 the technical cohesive strength of a metal, in any particular state as regards prior mechanical treatment and heat-treatment, is determined by a limiting value of the algebraically greatest principal stress.? In two previous papers by one of the authors,14,15 evidence was presented to indicate that the technical cohesive strength of a metal cannot be represented by a single stress value, but that it comprises an infinite number of values corresponding to the infinite number of possible combinations of the principal stresses. The technical cohesive strength thus comprises an infinite number of technical cohesion limits, each representing a specific stress combination at fracture. In the same papers, evidence was presented that plastic extension causes a continuous increase in the technical cohesive strength. Such a variation is not in accordance with the prevalent view that plastic extension first increases, then decreases, the technical cohesive strength.8 In this paper, as in the previous papers,14,15 the algebraically greatest principal stress will be designated S1, the least principal stress will be designated S3, and the intermediate principal stress will be designated S2. The technical cohesion limit under polarsymmetric tension (S1 = S2 = S3) will be termed the "disruptive stress," and the cohesion limit under unidirectional tension (S2 and S3 = o) will be termed the "severing stress." 14,15 The yield strength of a metal, according to the generally accepted theory, may be represented by a constant value of the shearing-strain energy, and hence by a constant value of the sum of the squares of the three principal stress differences. In the second of the previous papers,"' however, evidence was presented that the limiting yield stress decreases with increase in the volume stress, the algebraic average of the three principal stresses.* This influence of the volume stress becomes prominent only in the field of triaxial tension. In the two previous papers, 14,15 diagrams were presented to show the variation of the technical cohesion limit, yield stress, and ultimate stress with the combination of principal stresses and with plastic extension. Those diagrams and the resultant conclusions are derived from experimental data obtained by other investigators. They are based chiefly on results of tension tests

Jan 1, 1943