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By S. R. Gilbert, B. W. Burdett, L. B. Hales

INTRODUCTION Grinding control is currently the most publicized control subject in the minerals industry. Flotation control and crushing control have not as yet received the widespread attention that grinding control has. The primary reasons for this center around the high capital costs of grinding equipment and the fact that grinding mills are extremely energy inefficient. In a typical copper concentrator the energy requirements to produce refined copper are: (1) [Total Energy Distribution (Kw-hr/yr)% Mining4.93 x 10817.3 Mineral Processing9.63 x 10833.8 Smelting and Refining13.9 x 10848.9] One-third of the total energy used for copper production is for mineral processing. A breakdown of this energy into process steps yields the following: [Total Energy Distribution (Kw-hr/yr)% Crushing and Grinding 7.16 x 108 73.8 Flotation 0.76 x 108 7.8 Materials Handling1.78 x 10818.4] It is apparent that comminution operations consume the largest proportion of the energy for processing and as such become major targets for improvements in efficiency. Unfortunately, size reduction operations are extremely inefficient. Efficiency calculations for grinding range from less than 0.1% to about 5% depending on the evaluation criteria. Because of these facts, grinding control has been and will continue to be the focus of major process control efforts. OBJECTIVES AND BENEFITS All benefits achieved as the result of grinding control are derived from modifying physical parameters which improve the efficiency of the grinding mill. These parameters include:

Jan 1, 1982

By S. R. Krom

In connection with perfecting a system of pneumatic concentration I had in view the improvement of machines for crushing and pulverizing ores. A study of the whole subject convinced me that the principle upon which the construction of the Blake crusher, and that of rolls, is based, possessed the mechanical elements which, if perfected and simplified, would make these machines the successful rivals of every other device. It is well-known that until very recently the stamp-battery held undisputed possession of the field; and mill-men and mill-builders almost universally believed that stamps would not be superseded by any other machine for fine crushing. The first step to drive stamps from the field was the introduction of rollers in the Bertrand and the Mt. Cory mills. In both of these mills the great superiority and economy of a system of crushing with rollers instead of stamps has been fully demonstrated. While perfecting the rollers, I had the fact confronting me that they had frequently been tried without success. In fact, the universal opinion prevailed that rollers could be used only for coarse, and not for fine crushing. The secret of the difficulty I discovered to lie in the imperfect and weak character of the rolls heretofore used, due to a misconception of the requirements for a machine for such work, and a failure to appreciate the advantages of continuous, rolling, crshing- surfaces, operating on the toggle-lever principle, which gives the greatest crushing pressure with the least power. expended, and the minimum of wear.

Jan 1, 1886

By Roy Thomas

SOON after the Waelz plant for the fire concentration of low-grade zinc ores was put into operation in the early part of 1929 at Katowice, it was found that the conveyor equipment for transporting the hot residue from the furnace dust chambers was inadequate. Hand tram-ming with water cooling was used for a time, but that method was injurious to the workmen as well as costly. The problem was to find some practical mechanical means of conveying flue dust at temperatures of from 450° to 600° C. as it was drawn from the dust chambers. After considerable preliminary investigation it was decided to install pneu-matic equipment for conveying the hot materials to a central mixing plant, where it would be mixed with slime and from which it would be returned to the furnace feed hoppers. The first pneumatic equipment was installed in 1930, and has been in successful operation since that time. The pneumatic method of transportation has shown a considerable saving in operating costs over the former methods of dust handling and a decided improvement in working and hygienic conditions at the plant, through the elimination of the dust hazard. Additional pneumatic equipment was installed in 1933 for conveying the furnace fume from the baghouses to the roaster plant. At the same time pick-up lines were provided for collecting the cleanings from the vertical and horizontal cooling pipes that are between the furnace dust chambers and the baghouses. The latter installation has practically eliminated a dusty and costly hand-tramming operation.

Jan 1, 1939

By William A. Hustrulid

INTRODUCTION Prior to the mid-1970's, the U.S. Radioactive Waste Disposal Program was focused on salt deposits as the geologic medium of choice, almost to the exclusion of other rock types. These efforts are illustrated by the Project Salt Vault experiment in a salt mine at Lyons, Kansas, in 1965-1967 followed by attempts to locate a repository site in central Kansas. Preliminary evaluation of other geologic media led, in 1978, to the GAIN (Geotechnical Assessment and Instrumentation Needs for Nuclear Waste Isolation in Crystalline and Argillaceous Rocks) Symposium held at the University of California (Berkeley), for the purpose of preparing a state-of-the-art document together with research needs for some of the other possible rock types. Because possible sites had not been selected, nor would they be for some time, the primary emphasis was for research and development focused on generic rocks and generic sites. A basic ground rule at that time was that the host rock formation should provide the primary containment for the waste. Also, the U.S. Nuclear Regulatory Commission (NRC) was just drafting the proposed rules regarding site suitability so that this input was not available. The collection of baseline data, conduction of some critical experiments both in the laboratory and field, and the performance of scoping studies were deemed needed. Such work was indeed undertaken; and to date, a great deal of information has been compiled and much has been learned regarding the characteristics of rock masses, rock behavior

Jan 1, 1984

By F. R. Hensel

Up to the present time few attempts have been made to produce hard nonmagnetic materials by heat treatment of austenitic steels. The usual result has been to cause them to pass into the martensitic stage, thus destroying to a great extent the typical austenitic properties, since this involves a transition of a portion of the iron from a face-centered to a body-centered type of atomic arrangement. High-strength nonmagnetic materials such as might be provided by properly hardening austenite are required in the electrical industry for different machine parts. In Europe nonmagnetic retainer rings for restraining the end-turns of the rotor windings in turbo-alternators have been developed as a special application of high-strength austenite. In testing1 a 28,000-kva. three-phase Siemens turbogenerator running at 3000 r.p.m. at full load current, the losses in the short-circuit test were 450 kw. for the magnetic ring and 286 kw. for the nonmagnetic, and the difference should be attributable to the magnetic ring. The differences in temperatures during the same test are given in Table 1 and these show the advantage of a nonmagnetic over a magnetic retainer ring. Hardening in this case was obtained by cold working, such as hammering, rolling or some means for stretching the steel while at a temperature near 500" C. One means for stretching2 is to rotate the forged or rolled ring in a centrifugal machine so as to develop within it stress higher than

Jan 1, 1931

By A. R. Calawa, T. C. Harman, M. Finn, P. Youtz

A study has been made of the growing, annealing, and diffusion parameters in PbSe, Pb1-ySnySe, and Pb1-xSnxTe. Single crystals of these materials have been grown using the Bridgman technique. For all of the above materials the as-grown crystals are p type with high carrier densities. To reduce the carrier concentration and increase the carrier mobility, the samples are annealed either isothermally or by a two-zone method. From isothermal anneals, the liquidus-solidus boundary on the metal-rich side of the stoichiometric composition has been obtained for some alloys of Pb1-xSnxTe and on both the metal- and seleniunz-rich sides for PbSe and alloys of Pbl-ySnySe. In Pbo.935 Sno.065 Se carrier concentrations as low as 5 x1016 Cm-3 and mobilities as high as 44,000 sq cm v-1 sec-1 at 77°K have been obtained. Inter diffusion parameters mere also studied. The ddiffusion experiments mere identical to the isothermal or two-zone annealing experiments except that the samples were removed prior to complete equilibration. The resulting p-n junction depths were determined by sectioning and thermal probing. Inter diffusion coefficients for various temperatures were calculated for both PbSe and Pb0.93Sn0.0,Se. RECENTLY, there has been considerable interest in the PbTe-SnTe and PbSe-SnSe alloys with the rock salt crystal structure. The unusual feature of these systems is the variation of energy gap EG with composition. Several investigations1-3 have shown that EG for the lead chalcogenides decreases as the tin content increases, goes through zero, and then increases again with further increase in tin content. The possibility of obtaining an arbitrary energy gap by selecting the composition is an especially attractive feature of these alloys for applications involving long-wavelength infrared detectors and lasers. In addition, some unusual magneto-optical, galvanomagnetic, and thermomag-netic effects should occur for alloys with low band gaps. If uncompensated low carrier density crystals can be obtained, then a small carrier effective mass, a large dielectric constant, and the resultant high carrier mobility should yield enormous effects at low temperature in a magnetic field. The relative variation of the energy gap with pressure should also be very large for these low gap materials. The primary purpose of this paper is to provide some information concerning the preparation of low carrier concentra- tion, high carrier mobility, and homogeneous single crystals with a predetermined alloy composition. I) DETERMINATION OF ALLOY COMPOSITIONS In all of the work described in this paper, the composition of lead and tin chalcogenides in the alloys was determined by electron microprobe analysis. Separate X-ray spectrometers are used to make simultaneous intensity measurements of the Pb La1 and Sn La1 lines emitted by the sample under excitation by a beam of 25 kev electrons focused to a spot about 2 µm in diam. These intensities are compared to the intensities of the same lines emitted by standards under the same conditions. The standards used are the terminal compounds of each pseudobinary system, i.e., PbTe and SnTe for Pbl-xSnxTe alloys, PbSe and SnSe for Pbl-ySnySe alloys. The composition of the sample is then obtained from theoretical calibration curves which relate the weight fractions of lead and tin in the alloy to the measured ratios of X-ray intensities for the sample and the standards. The lead and tin calibration curves for each alloy system were calculated by using corrections for backscattered electrons,4 ionization,5 and absorption,6 and assuming that the atom fraction of tellurium or selenium in the sample and standards is exactly +. Results obtained by using the microprobe are in good agreement with those obtained by wet chemical analysis. II) CRYSTAL GROWTH FROM THE VAPOR Early work on the vapor growth of PbSe was carried out by Prior.7 He used small chips of Bridgman-grown single crystals as the source material and frequently converted the whole charge of a few grams into one crystal. In the present work, vapor growth occurred using a metal-rich or chalcogenide-rich two-phased alloy powder as the source material. Small, nearly stoichiometric crystals are formed on the walls of the quartz tube. The procedure will now be described in detail. Initially, a 100-g charge containing (metal)o.51(chalco-genide)o 49 proportions or (metal)o.49(chalcogenide)o. 51 proportions of the as-received elements in chunk form are placed in a fused silica ampoule. After the ampoule is loaded, it is evacuated with a diffusion pump and sealed. The sealed ampoule is placed in the center of a vertical resistance furnace. The region containing the ampoule is heated to about 50°C above the liquidus temper-ature for the particular composition used. After about one-half hour at temperature, the elements are reacted and the molten material homogenized. The ampoule is quenched in water. The quenched ingot is crushed to a coarse powder for vapor growth experiments and to a fine powder for the isothermal annealing experiments which are discussed in a later section. Vapor growth experiments were carried out using the powdered, metal-rich or chalcogenide-rich alloys

Jan 1, 1969

By J. J. Frawley, W. J. Childs

The dynamic nucleation of supercooled bismuth and Bi-Sn alloys has been studied over a frequency range of 15 to 20,000 cps. For low-frequency vibration, a minimum vibrational energy was required for enhancement of nucleation. Above this critical energy, the dynamic supercooling was less than static supercooling showing that vibration promoted nucleation. The amount of dynamic supercooling continued to decrease with increasing vibrational energy until a minimum or threshold value was reached. This minimum value of supercooling for nucleation remained constant joy all further increases in vibrational energy. For higher frequencies, similar results were observed. This behavior has been related to the necessity of cavitation for dynamic nucleation. When a liquid is cooled to a temperature below its equilibrium melting point, the solid phase is more thermodynamically stable. However, for solidification to occur, a two-step process, nucleation and subsequent growth of the solid phase, must occur. When a liquid is supercooled, that is cooled below the equilibrium melting point, the controlling process for solidification to begin is the rate of nucleation. Once nucleation has occurred, the solidification process is controlled by the rate of growth. Nucleation can be induced by two factors: either by a catalyst or by the use of mechanical shock. Numerous investigators1-4 have studied the effect of nucleation catalysis but much less systematic study has been made of nucleation by mechanical shock waves. The influence of vibrations on grain size in castings and ingots has been studied by many authors but no clear understanding of the mechanism or accurate prediction of the effect has been presented.5 It would be intuitively expected that the further the departure from equilibrium (i.e., the greater the supercooling), the easier it would be to induce nucleation. This has been quantitatively demonstrated both by walker6 and later by Stuhr,7 that the greater the degree of supercooling the easier it is to nucleate by a shock wave. Stuhr also attempted to obtain the mechanical energy required for nucleation of bismuth as a function of supercooling. He vibrated a crucible containing supercooled metal at low frequencies and various amplitudes and noted the corresponding dynamic supercooling obtained. The amount of supercooling was inversely proportional to the mechanical energy applied. Limitation of his experiment was the problem of the confinement of the liquid in the crucible without splashing and minimizing other unwanted modes of vibration. Tiller et al.8,9 did similar work on tin and Sn-Pb alloys using an electromagnetic stirring device. Their conclusions were that the magnitude of the magnetic field strength did not affect the amount of undercooling at which nucleation was initiated. While conclusive experimental results have been lacking to explain this effect of mechanical vibration on inducing nucleation, a number of theories have been proposed. Two of these theories are discussed below. 1) The Change in Melting:- Point Locally Due to the Change in Pressure (Clapeyron Equation). According to Vonnegut10 the most plausible explanation for the nucleation of a supercooled melt by cavitation is the effect of changing the melting point by a change in pressure. For materials where the volume decreases on solidification, an increase in pressure raises the melting point; for materials which expand on solidification, the melting point is raised for a decrease in pressure, i.e., rarefaction. Using the Clapeyron equation, the melting point of a metal can be calculated as a function of pressure. If it is assumed that the equation can also be used to calculate the temperature of nucleation of a supercooled melt as a function of pressure (i.e., the temperature of heterogeneous nucleation will increase with pressure at the same rate as the melting point), the amount of supercooling required for nucleation will be constant at all pressures as shown in Fig. 1. It is obvious that an isothermal change which results in an increase in melting point results in an equal increase in supercooling. This increase in supercooling may now be sufficient for nucleation. A pressure of 80,000 atm was calculated, using the Clapeyron equation, as the pressure required to increase the temperature of nucleation of nickel by 200°C. According to Lord Rayleigh,11 this very large pressure could be generated for a very brief period of time by the collapse of a cavity. This pressure wave is radiated in all directions from the collapsed cavity. If the temperature of the melt is slightly below its equilibrium melting temperature at atmospheric pressure, stable growth can follow; that is, once nucleation occurs, growth becomes the main driving force of the solidification process. This proposal has been extended to water which expands on freezing by assuming that nucleation occurs during rarefaction following the pressure pulse. This negative pressure pulse should follow immediately after the positive pressure pulse with its magnitude approaching the critical tensile strength of the liquid. The negative pressure developed during this period would raise the melting point of water and thus promote nucleation. Hunt and jackson12 have suggested this for water. Similarly, it could be postulated that bismuth which also expands on freezing could be nucleated during the negative pressure pulse. 2) Nucleation by a High-pressure Phase. An extension of the Clapeyron equation to systems where density decreased on freezing at atmosphere pressure has been proposed by Hickling.13 The phase diagram for water initially shows the well-known decrease in

Jan 1, 1969

By S. Sumski, M. B. Panish, R. T. Lynch

The liquidus isotherms in the gallium-rich corner of the Ga-Al-P phase diagram have been determined from 1000" to 1200°C and at I100°C the corresponding solidus isotherm was obtained. A simple thermody-namic treatment which permits calculation of the solidus and liquidus isotherms is discussed. A technique which was previously used for the growth of GaxAl1-xAs was used for the preparation of solution epitaxial layers of GaxAl1-xP and ALP. An approximate value of 2.49 i 0.05 ev for the band gap of Alp at 300°K was obtained and the ternary phase data were used to estimate a value of 36 kcal per mole for the heat of formation 0f Alp at that temperature. The Gap-A1P crystalline solid solution is one in which there exists the possibility of obtaining crystals with selected energy gaps, within the limits imposed by the energy gaps of Gap and Alp. Such crystals are of considerable interest because of their potential value for optoelectronic and other solid-state devices. Furthermore, it has been amply demonstrated for GaAs and GaP,'-7 that device, or bulk materials grown from gallium solution generally have more efficient radiative recombination than materials prepared in other ways. This presumably due to the lower gallium vacancy concentration in such material.= Small crystals of GaXAl1-xP and A1P have been grown from solution,8-10 and A1P has been grown from the vapor," but neither have previously been grown by liquid epitaxy. In this paper we present the ternary liquidus-solidus phase diagram of the Ga-A1-P system in the region of primary interest for solution epitaxy, and discuss the thermodynamic implications of that phase diagram with particular reference to the liquidus and solidus isotherms in the gallium-rich corner of the GaxAl1-xP primary phase field and to the A1-P system. Several measurements of the absorption edge of GaxAl1-xP crystals have been made and the width of the forbidden gap of A1P has been estimated from these measurements. EXPERIMENTAL The differential thermal analysis technique used to determine the liquidus isotherms and the optical measurements used in this work are similar to those described previously12 for the Ga-Al-As system, ex- thermocouples in the thermopile for added sensitivity. The materials used were semiconductor grade Ga, Gap, and Al+ The composition and temperature range at which DTA studies could be done was quite restricted. The upper temperature was limited by the chrome l-alumel thermopile to about 1200°C, and the highest aluminum concentration to about 5 at. pct by low sensitivity caused by the reduced solubility of Gap with increasing aluminum concentration in the liquid. DTA studies were not possible at 1000°C and below because of the low sensitivity caused by low solubility of Gap in the Ga-A1-P system. The cooling rate for these studies was about 1°C per min. No heating studies were done because of limited sensitivity. Supercooling probably does occur, but our experience with other 111-V systems indicates that it is no greater than about 10 to 15.c. Solid solubilities were determined by analyzing epitaxial layers of GaxAl1-xP grown from the liquid, with an electron beam microprobe. The layers were grown on Gap seeds by a tipping technique in which the layer is grown over a short-temperature range (20" to 50°C) on the seed from a solution of known composition. The tipping technique reported by Nelsson1 for GaAs could not be used, particularly for solutions containing appreciable amounts of aluminum, because of the formation of an A1203 scum on the liquid surface. A system was therefore designed, which would effectively remove the oxides mechanically, so that uniform wetting and crystal growth could occur. This tipping technique has already been described in detail." The best control over the composition of the re-grown layer was obtained when the tipping was done at a temperature which corresponded to the temperature of first formation of solid for the solution being used. Generally, therefore, a solution was prepared by adding the amounts of Ga, Gap, and A1 required to yield a solution which would be completely liquid above the tipping temperature with solid precipitating below that temperature. For most of the work reported here, the 1100°C isotherm of the ternary was used. It was generally necessary to heat the solution to 50" to l00. C above the tipping temperature to dissolve all of the Gap in a reasonable length of time. The epitaxially grown layers were used both for optical transmission measurements to aid in the estimation of the way in which the absorption edge changed with aluminum concentration, and for the electron beam microprobe analyses to provide data for the determination of the solid solubility isotherm. RESULTS AND DISCUSSION Liquidus Isotherms in the Ga-A1-P Ternary Phase Diagram: Thermodynamic properties of the system. The only thermal effect studied in this work was that

Jan 1, 1970

By Strathmore R. B. Cooke, Emert W. Lindroos, Norman F. Schulz

DURING the course of an investigation of the effects of various starch products on hematite and quartz in regard to their separation by' flotation, it was found that whereas most starches flocculated suspensions of hematite in water, they did not flocculate similar suspensions of quartz. However, a derivative of whole corn starch containing approximately one tenth aminoethyl group (--CH2CH2NH2) per glucose unit proved to be an exception. This aminoethyl starch was a very good flocculant for both hematite and quartz, and also possessed the property of depressing both minerals in cationic flotation tests. In view of the widespread use of starch as a flocculating agent of solids in tailing water, pulps, and for coal slimes, ore and various other purposes in sulphide and nonsulphide flotation, attention is called to the effective surface activity of aminoethyl starch in flocculating suspensions of the two minerals investigated. Test Materials The starch products employed included Globe Pearl starch No. 144 and fresh aminoethyl starch, both supplied by the Corn Products Refining Co. Dr. A. L. Elder[4] has kindly furnished a description The minerals used in the various tests are listed in Table I. Their specific surfaces were determined by the air permeability method, which gave results reproducible to within plus or minus 3 pct. Surface areas obtained by krypton adsorption were greater than the air permeability values by a factor of 2.0 for quartz and 62.4 for hematite. Starch Adsorption on Mineral Surfaces Starch adsorption data were obtained by agitating for 1 hr measured volumes of neutral starch solutions of known concentrations with weighed quantities of finely divided mineral of measured specific surface. The mineral then was separated from the pulp liquor by centrifugation and the residual starch content determined by chemical analysis. The analytical procedure consisted of oxidizing the starch with an excess of dichromate in acid medium at elevated temperature and titrating the excess dichromate by the ferrous ammonium sulphate-potassium permanganate method. Analytical results were reproducible to within less than 1 pct. Adsorption data obtained in unbuffered solutions near the neutral point are plotted in Fig. 1. The adsorption on either mineral was far greater for the aminoethyl starch than for the Pearl starch. Flocculation The degree of flocculation was determined for a given pulp by measuring the time required for the supernatant liquid to reach a certain degree of clarity. This was accomplished by passing a standard light beam through the pulp, contained in a glass settling tube, and measuring the time required after agitation ceased for the intensity of the transmitted beam to reach a predetermined value. Starch reagent was added to each pulp in small uniform increments, and the settling time was determined after each such addition. Increase in pulp liquor volume due to the added starch reagent was ignored in these tests. Pulps were maintained at or near neutrality.

Jan 1, 1952

By Orville R. Lyons

THE continuous vacuum filter, whether it be a vertical or horizontal disk, inside or outside drum, when properly applied is a very effective device for dewatering fine solids. Because of the number of variables that affect its performance, however, it is not possible to obtain consistently maximum moisture reduction in an operating plant. This paper presents a method for determining the average cake moisture and the variations in cake moisture to be anticipated when dewatering fine solids by continuous vacuum filters under normal operating conditions. Previous investigators1,2 have found that certain factors influence filter performance, drum or disk diameter, speed of rotation, percentage of immersion, and the percentage of solids in the feed influence capacity. Blinding of the filter cloth reduces effective vacuum, produces a wetter cake, and may decrease capacity. Reduced vacuum or improper adjustment between vacuum and blowing portions of the cycle will produce a wetter cake and also may decrease capacity. Widely fluctuating feed tonnages will adversely affect cake moisture and capacity. Flocculation, when properly applied, increases capacity and reduces cake moisture. Without flocculation, the slimes are the first particles sucked to the filter medium, which becomes partially blinded in consequence. With flocculation, the flocs act as coarse particles and the filter medium is not blinded. Overflocculated pulps, although filtering well, may yield wet cakes. Average Particle Size and Cake Moisture A method for predetermining the surface moisture content of coal filter cakes was published in 1949; but this method could not be applied to coals deficient in —200 mesh material or to fine mineral concentrates. Test data obtained for geared-weight types of vibrating screens4 and for centrifuges5 used to de-water coal provided definite correlations between the average particle size of a dewatered cake and the surface moisture content of the cake. It was thought that this same method of correlation should be applicable to filters, whether dewatering fine coal or fine mineral concentrates. To develop a correlation or correlations between average size of cake and cake moisture, the author collected data for filtration operations from as many sources as possible. In a considerable number of instances the information was provided by plant preparation engineers,"-" a few of the tests were on a laboratory scale: and the remainder of the data was obtained from published articles.10-17 Table I contains size-consist and miscellaneous data for coal filter cakes, and Table II contains the same data for mineral concentrate filter cakes. Fig. 1 shows the relationships existing between the average particle size of the cake and cake moisture (surface moisture for coal and total moisture for minerals) when dewatering fine solids by a variety of makes and types of filters. Average particle size is calculated by averaging the linear openings of the various pairs of screens used in the screening test, weighted in accordance with the percentages of material in the various fractions.

Jan 1, 1952

By Stanley D. Michaelson

THE selection of the proper size of grinding mill for a given installation has long been a subject of discussion by mill manufacturers, consulting engineers, and their clients. It would be presumptuous for the author to propose a simple cure-all. Instead this paper describes a method that has been used over a period of years to determine mill size with a reasonable degree of accuracy. Furthermore, this method claims no theoretical background, for ball milling, as practiced today, is still an art. The selection of the proper size and type of mill must, therefore, be made on an empirical basis. A ball mill, in order to grind, must deliver power through its grinding media to the material to be ground. Assuming that a mill is properly supplied with grinding media, ore pulp, and power, the amount of grinding done is closely proportional to the power expended. With this as a basic premise we can, for the moment, forget about type of mill (i.e., overflow, low-level mill, or other design) and base our calculation of mill size on the total power required to grind a ton of a particular ore from a given size of feed to a given size of product. When this is determined the type and size of mill, its speed, and the weight of the load of grinding media can be selected to absorb this amount of power. DEVELOPMENT OF TECHNIQUE Some years ago, W. L. Maxson, F. Cadena, and F. C. Bond, working in the Minerals Research Laboratory of Allis-Chalmers Co., Milwaukee, developed and described a laboratory technique for comparing grindability (or relative ease of grinding) of various ores at different mesh sizes of grind.1 Additional papers2 have described the work done since that time, and the most recent paper3 summarizes results for hundreds of tests on many ores and materials. The essentials of the testing method are: a I a by 12-in. laboratory mill operating at a constant speed of rotation, using a constant volume of ore, and a constant ball load having a relatively constant grinding surface. Tests are run at 250 per cent circulating load with the feed, circulating load and products screened on calibrated Tyler standard screens. Certain ores from operating mills, representing various mineralogical types, were selected for reference and designated "standard ores." In most cases, detailed studies of the grinding circuits were made when samples of mill feed were taken for grindability tests. Each analysis formed a basis for comparison of the grindability in the laboratory with actual power requirements for a particular grinding circuit. In addition, a critical study was made, to evaluate the differences in the various grinding circuits so that two or more field installations having different layouts (single-stage grinding, two-stage grinding, or others), and using mills of various diameters operating at various speeds with differing circulating loads, etc., could be compared. Large-scale tests by mill operators complemented by laboratory investiga-

Jan 1, 1945

By J. S. Aronofsky, H. J. Ramey

Potentiometric model studies of the five-spot water flood to determine the influence of mobility ratio upon injection or production histories are described. The results suggest a method for the correlation of data from field pilot tests for the estimation of an effective mobility ratio and its effect upon field water floods. The effect of the well spacing-to-well radius ratio upon production histories is presented. A method of accounting for this factor is suggested. The influence of injection (or production) rates and injection and production well pressures upon production histories is shown. The five-spot well pattern was investigated for water-to-oil mobility ratios of 0.1 to infinity. INTRODUCTION It has been well established that mobility ratio has an important effect upon flood patterns.1,2,3,4,5 It should be equally apparent that injection and production histories must also be influenced by mobility ratio. However, none of the articles referred to above mention the importance of being able to predict the effect of well pressures (or injection rates) during the entire time history of a waterflood operation. A complete description of production histories (the terms "injection" and "production" are synonymous for the steady-state model under consideration) would provide values for well pressures and interface positions at any time for a specified injection rate. conversely, if the waterflood problem is specified in terms of a constant injection well pressure, then it would be desirable to know the injection rate and interface positions at any time. This paper describes the results of potentiometric model studies which were used to analyze the influence of mobility ratio on injection or production histories. A method is presented for calculating production histories over a range of ratios of well spacing-to-well radius. The basic method described in this paper to evaluate production histories is to: (1) determine interface position as given in Ref. 1, and (2) measure electrical current and voltage drop for each interface position. It should be mentioned that the current state of knowledge on flood patterns as affected by mobility ratio shows that significant discrepancies exist between the results of various investigators2,3,4,5. It is beyond the scope of this paper to discuss the reasons for such discrepancies. However, the method of determining production histories presented in this paper could be applied to any of the swept-area patterns presented in the literature. All results given in this paper are based on a set of swept areas obtained by the potentiometric method. Potentiometric analyzer technique is adequately described in the literature, but the basic assumptions involved in work of this nature bear repetition. It is assumed that: 1. A distinct oil-water interface exists in the reservoir; only water is mobile in the region behind the interface (water zone) and only oil is mobile in the region ahead of the interface (oil zone). 2. There is a fixed mobility value, (k/µ) w associated

Jan 1, 1957

By J. S. Bryner

In the study of metallographic specimens in the electron microscope, there is need for a method of locating the same field in both the light microscope and the electron microscope. This need arises chiefly from the fact that in the electron microscope the magnification and degree of resolution are so much higher, and the field so much smaller than in the light rnicroscope that it is often difficult, if not impossible, to identify positively what is being observed. The difficulty is increased by the fact that, because a transparent film replica of the metal surface must be used in the electron microscope, micro-constituents can be identified not by their color but only by their texture and contours. For these reasons it is desirable to obtain a series of photographs showing the same field in both microscopes in order that the appearance of common microstructures and micro-constituents in the electron microscope may be identified and catalogued for future reference. The need for a method of locating the same field in both microscopes arises also when it becomes desirable to enlarge in the electron microscope for more detailed study a particular interesting structure observed in the light microscope. Using the standard polystyrene-silicalJ replica technique, in which the silica film replica is fished from the ethyl bromide on a 1/8 in. diam zoo-mesh specimen screen, the possibilities of locating a particular area on the film in the electron microscope are rather remote. The desired structure may be obscured by the wires of the specimen screen or unrecognizable at the high magnification. A solution to the problem would be provided if a specially designed specimen screen, containing an opening which could be absolutely identified and quickly located in the electron microscope, could be fastened to the silica film replica in such a position that the desired field on the specimen would be located at the identifiable opening in the specimen screen. The design for such a specimen screen, a method for producing it, and a technique for fastening it to the silica film replica are described below. Description OF Method The Specimen Screen A simple design for a specimen screen containing an opening easy to identify and locate in the electron microscope is one with two lines of openings at right angles in the form of a cross. Such a screen is shown in Fig I. The opening at the center of the cross is identified easily and can be located quickly in the light microscope and in the objective image of the electron microscope. The specially designed specimen screens for this work were produced in quantity by electroforming. On both sides of a polished strip of copper I X 3 X 1/8 in., twenty patterns of the cross of openings were punched with a diamond point micro-hardness tester, using a load of magnitude

Jan 1, 1949

By C. Dean Starr

The physical basis of the equation correlating electrical conductizlity and temperature coefficient of resistance of solid solution alloys has been inzlestzgated and the nature of the constants evaluated. It is shaun that the same form of correlation is valid irrespective of the magnitude of the temperature coefficient. However, the effect of therma1 expansion and change in resistivity with temberature nust be considered when the magnitude of the temperature coefficient of resistance is near zero. In a comprehensive literature survey conducted at the Armour Research Foundation in 1950, it was found that a linear relationship exists between the electrical conductivity, K, and the temperature coefficient of resistance, a, for solid solution alloys. This was expressed by the equation where B, a constant, depends on the solvent metal but not the solute. A continuing investigation by Hansen, Johnston, and Parks showed this equation was generally appropriate for Cu, Ag, Au, Pd, Pt, and Co base binary solid solution alloys as well as for many ternary alloys of copper over a range of conductivities and temperature coefficient of resistances from 0.02 to 0.60 reciprocal pohm cm and-0.00015to0.004Q per 0 per "C respectively. Eq. [I] was not always valid for alloys that exhibited a change in state (magnetic to nonmagnetic) or for alloys that had a temperature coefficient of resistance near or below zero. For example, in nickel alloys, a simple linear curve as predicted by Eq. [l] was not obtained when the conductivity was plotted against the temperature coefficient of resistance. Hansen suggested that deviations observed were caused by transitions from a ferromagnetic to a nonmagnetic state. Subsequent and more extensive data by ronin on Ni-Mn alloys confirmed Hansen's postulate. While both states independently showed a linear relationship between K and a, the value of B was different for the two states. In some copper and gold base alloys, as well as the platinum and palladium alloys investigated by Hansen, the conductivity did not extrapolate to zero at zero a as demanded by Eq. [I]. This deviation can be readily corrected by simply adding a constant to Eq. [I.] whence Eq. [2] shows the K decreases as a decreases but that K has a positive value when a = 0 which is observed for commercial solid solution alloys as well as the experimental alloys tested by Hansen. While other methods of correlation of electrical properties have been made such as the one by Starr and Wang3 who found a linear relationship between resistivity and temperature coefficient of resistance for Ni-Cr-Al-Cu alloys, the data, in general, can also be correlated by a form of Eq. [2]. Thus, Hansen's empirical equation has considerable merit. The objective of this paper is to determine the physical basis for this equation and to examine the region near zero a in more detail. ELECTRICAL CONDUCTIVITY VS TEMPERATURE COEFFICIENT OF FU3SISTANCE The resistance of a metal or alloy is defined as

Jan 1, 1963

By B. H. Caudle, A. B. Dyes

In a recent publication' it was shown that wells with a free surface in a homogeneous gravity-drainage reservoir have a hyperbolic decline with index n '. This paper reports efforts to extend this theory to practical field cases. As a first step in making the extension, a large number of lease production curves from gravity-drainage fields in the stripper stage were fitted with the general hyperbolic decline equation, q/q, = 1/(1 + y) y and n in each case being determined by statistical methods. It was found that this equation is reliable for decline curve extrapolation for periods up to at least 25 years. The resrilts obtained were disturbing in the sense that values for the index, n, were often smaller than one, which fact leads to the prediction that a well would produce all infinite amount of oil in infinite time. A theoretical investigation based on the results of the previous paper provides a suitable explanation for these low values of n. It suggests that these are obtained if production occurs from two or more layers of diflerent permeabilitv and thicktress or two lnyers having different skin effects. It is predicted that as the more permeable layers are exhausted, the index of decline, n, will rise from a value smaller than 2, to n = 2. A practical method is given for fitting the general hyperbolic decline Eq. 6 to production decline data. When this method is used, the index of decline observed in gravity-drainage reservoirs in the stripper stage when wing only data over early years 01 decline usually agrees quite closely with that determined using data over 25 years or more. This indicates that the hyperbolic decline equation is reliable for predicting behavior of such reservoirs. A method is also suggested for taking into account any changes in the value of the index INTRODUCTION As a result of both experimental work with models and theoretical deductions, it was recently concluded' that wells having a free surface in a homogeneous reservoir producing by pure gravity drainage should have a hyperbolic decline with n = 2. The present report details efforts to extend this work on ideal homogeneous reservoirs to actual field cases. It should be remembered that both the previous work and the present extension are based on the assumption that the reservoir is at very low pressure, and hence, nearly all the potential available for driving fluid to the well is the gravity head. Attempts to apply conclusions of this study to reservoirs which have considerable pressures supplementing the gravity drive may lead to difficulty. WELLS WITH NO FREE SURFACE In a dipping gravity-drainage reservoir such as that shown in Fig. 1, some of the down-dip wells have no free surface. The previous study' showed that the up-dip wells, which have a free surface, should follow Eq. 1. The following approximate analysis, of a type which was justified experimentally for up-dip wells in the work just mentioned, leads to results for the down-dip wells.

By J. J. Gilman

THEORIES of fracture in metals have been based primarily on the dependence of fracture strength on grain size. This dependence was first observed by Masing and Polanyi.l These workers, as well as 0rowan12 and Davidenkov and Wittman,' thought the grain size could be equated with the crack size in the Griffith condition for crack propagation.4 In this way they could account for the observed proportionality between fracture stress and the reciprocal square root of the grain size. The chief results of recent investigations of the fracture strength of polycrystals are summarized in Fig. 1. Low for iron,5 Petch for iron,' Greenwood and Quarrel for zinc, Petch and Zein for zinc,' and Hauser, Landon, and Dorn for magnesium'' have all found that the fracture stress of a polycrystal is proportional to the reciprocal square root of the grain size. Also, they find that, for large grain sizes, the fracture stress lies near the extrapolation of the yield-stress curve determined at small grain sizes; where measurable plastic strain precedes fracture. Low9 has gone a step further and shown that, in Range 1, the fracture stress in tension is almost identical to the yield stress in compression for a given grain size. Homes and Gouzou, 10 and Low also have shown that, in Range 2 of Fig. 1, microcracks form when the yield stress is reached, but they do not cause failure until the stress reaches a much higher value. The fact that yielding always precedes fracture suggests that fracture is induced by plastic flow. A mechanism by which this might occur was first proposed by Zener.11 He pointed out that blocked dislocations would cause stress concentrations which might cause fracture. The blocking would be caused by grain boundaries. This idea has been developed by Eshelby, Frank, and Nabarro,12 by Koehler,13 and by Stroh.14 By means of etchpits blocked dislocations have been observed in brass by Jacquet,15 in zinc by Gilman,16 and in lithium fluoride by Gilman and johnston. The blocked-dislocation theory and the experiments that bear on it have been summarized by Mott.18 One of the strong points of the blocked-dislocation theory is that it can explain the grain-size dependence of the fracture stress in a natural way. However, Low9 has pointed out that the theory is not satisfying when it is considered quantitatively. Gilman10 also has criticized the theory and presented an alternative interpretation of the relation between fracture stress and grain size. Since the blocked-dislocation theory is not the only theory that can explain in the grain-size effect, it is necessary to find other evidence either to support or deny it. In this investigation the following points were studied: 1) If blocked dislocations normally cause fracture, then the fracture stress ought to be very high in the absence of plastic glide. Is it? 2) If dislocations must be blocked in order for metals to fracture, then certain types of grain

Jan 1, 1959

Oregon State Agricultural College, School of Mines, Corvallis, Ore Available publications of the old Bureau of Mines and Geology of Idaho have lately been distributed through the School of Mines of Oregon State College As the School of Mines was abolished in the summer of 1932, all of the bulletins and publications available have been turned over to the State College Library for distribution. At present plans have not been completed for further distribution For information on available publications, address: Director of Libraries, Oregon State College, Corvalhs, Oregon

Jan 1, 1933

Engineering Experiment Station, University of Arkansas, Fayetteville, Ark. W N Gladson, Dean and Director The Engineering Experiment Station has published a number of bulletins, only a few of which are of particular interest in this directory: Bulletin 3, Arkansas coal or oil for domestic heating; 4, Road materials of Arkansas, 5, A study of Arkansas coals, 6, Portland cement materials in Arkansas; 11, Natural gas versus Arkansas coal for house heating. Circular 3, Short cuts to combustion efficiency with natural gas Address the Engineering Experiment Station for any of these publications.

Jan 1, 1933

By G. S. Hume

The production of petroleum in Canada is relatively small in proportion to the amount of oil consumed. Production figures are given in Tables 1 and 2, which show that the production in Alberta for 1934 was more than for the whole of Canada in 1933. The production of natural gas for Canada is shown in Table 3, In Turner Valley, the largest producing gas and oil field in Alberta, seven naphtha wells from the Paleozoic limestone and one crude oil well from Lower Cretaceous strata were completed during the year. Six-

Jan 1, 1935

By Ahmad Saberian

Five salt samples 20 to 40 cm tall, sealed on all sides except one, were exposed to a series of dissolution tests in various brine solutions and at different temperatures. Solvents were in the 50 to 96% saturation range and the temperatures varied between 40°F and 150°F. The collected dissolution data sets for vertical salt surfaces were analyzed and three were selected to be used for developing a general relation. After various curve fitting efforts, an empirical relation for salt dissolution rate as a function of brine temperature and salinity was developed.

Jan 1, 1985