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[Pumps: oil-well: plunger: essential parts, G26, 130; 74, 828 improved type, 74, 846 leakage, 74, 837 operating cycle, 74, 833 Uren design, G26, 145 sucker-rod failures, G26, 136 sucker-rod stress, 74, 835 sucker rods, 74, 830, 832 tubing, 74, 833 tubing difficulties, G25, 138; 74, 836 Olivite, 73, 337 valve and seats, 74, 832 Punching: Monel metal, 78, 86 nickel, 78, 86 Punjab. See Indian Empire. PUPIN, M. L biography, M26, 113 John Fritz medalist, 1931, M81, 499 recipient of Washington Award, M28, 155 PURDY, R.: Discussions: on Relative Efficiencies of Domestic Fuels in Relation to Their Costs and Their Advantages 108, 353 on Uses on Coal in the Ceramic Industry, 108,389,398]

Jan 1, 1936

Jan 1, 1965

By Frederic P. Dewey

(New York Meeting, February, 1912.) By the old method of determining platinum in ores and bullion, the silver-alloy first obtained in the regular course of assay is parted in strong sulphuric acid and the residual metal weighed. This is re-alloyed with silver by a second cupellation and parted in nitric acid, the residual metal being again weighed. Any difference shown between the two weighings is assumed to be, and is called; platinum. Sometimes it is so, and if any considerable amount of platinum be present, there will be a decided difference between the two weighings; but a slight difference is no real evidence whatever of the presence of platinum. On the other hand, the second weight may equal or possibly exceed the first, even when traces of platinum are present. Again, other members of the platinum group may go into solution in nitric acid more or less. If present, these would be called platinum and escape detection. The method does not provide any direct tests whatever as to the presence or absence of platinum. It is often indecisive, and sometimes jives erroneous results. It is, therefore, quite unsatisfactory. Being called upon many times to determine platinum in a wide variety of materials, particularly when present in very small amounts, I have realized the disadvantages and defects of this old method. In an article on the solubility of gold in nitric acid, 1 I have briefly outlined a method of gathering a little gold out of a solution containing much silver, which furnishes the basis of

Apr 1, 1912

By R. Salter, C. K. Chase

Although Asarco's Silver Bell Unit, 40 miles west of Tucson, Ariz., is known primarily for copper production, molybdenite is also produced as a byproduct in the 8000 tpd flotation mill. The Silver Bell ore comes from two pits approximately two miles apart. Copper mineralization is essentially chalcocite resulting from two to three-fold secondary enrichment in a highly altered zone. A typical porphyry copper deposit, Silver Bell ore is of medium hardness. The ore consists of about one part molybdenum to 65 parts of copper. In the copper concentrate which is the starting point for separate molybdenum recovery, the ratio is also one part molybdenum to 65 of copper. Molybdenum mineralization is primary. Enrichment is not evident but it is notable that the molybdenite is more common in the more siliceous, harder rocks. The actual molybdenite occurs as diversely oriented flakes of fairly constant grain size, mostly in fractures associated with quartz veins. Most of the mineral appears unoxidized; secondary coatings on the molybdenite flakes are fortunately rare. In May 1962 a modified, improved version of the molybdenite circuit was put into operation.

Jan 7, 1964

By Donald J. Knight

HEAT Treatment at 1500' F of a mild steel containing 0.1 pct C, in an atmosphere which is oxidizing to both carbon and iron, results in the progressive oxidation of the metal surface with little or no change in the carbon content of the underlying metal. Further heat treatment of the scaled metal in either a neutral atmosphere or in a vacuum may or may not result in the decarburization of the metal depending upon the physical nature of the scale. It is apparent that if a continuous layer of oxide is present on the steel surface, the reaction OScale + Cmetal Cogas cannot progress since the SO formed gas would be unable to leave the oxide/metal interface. Thus, in order for the reaction to progress, the oxide must be cracked or porous. Vacuum heat treatment at 1500" F of samples with a thick continuous oxide scale showed no decarburization of the steel. However, when cracks were introduced mechanically into the scale prior to the vacuum heat treatment notable decarburization of the metal resulted and a structure as shown by Fig. 1 obtained, i.e., reduction of the crack walls to ferrite. With reference to the diagram of Fig. 2, it would appear that a mechanism of the following type takes place. Carbon atoms arriving at an oxide/metal/void interface, such as 'A', Fig. 2(a), can combine with oxygen atoms from the scale and leave the reaction site as Cogas thereby reducing the oxide to metal. On a greatly magnified scale, Fig. 2(b),this will appear as a ferrite projection along the crack wall. Carbon atoms entering this projection can react with oxygen atoms at point 'C', which is a new interface, and so on leading to a progressive growth of the ferrite along the crack wall and to the surface, Figs. 2 (c) and 1. It would appear that the only means by which thickening of the ferrite film can take place is by a diffusion of oxygen through the ferrite film to react with carbon at the newly formed ferrite/ void interface. Since the diffusion rate of carbon is reportedly much greater than that of oxygen, and since there is a low probability factor of oxygen and carbon atoms arriving simultaneously at the same site on the ferritehoid interface, there will be a tendency for more rapid lengthening than thickening of the ferrite layer, as is observed.

Jan 1, 1962

By D. G. Westlake

Levine has concluded that prismatic slip in titanium is controlled by two distinct thermally activated processes in the temperature ranges O° to 220°K and 220" to 300°K. We feel that his evidence is not convincing. He has drawn a curve through the plot of activation volume u* vs temperature T with a break at 22WK, Fig. 2. We believe that considering the possible experimental error apd the fact that there are only four points between 4° and 196°K, one could be justified to represent these points by the smooth curve we show as a solid line in Fig. 12. Levine believes that (8rf/aT)+ is discontinuous at 220°K, but he hints that he recognizes the possible doubt. We doubt seriously that the results shown in Fig. 1 indicate a discontinuity at 220°K. Certainly if he were justified in drawing a straight line through only four points on Fig. 2, we are even more justified in drawing straight lines through the seven points between 77" and 297°K on Figs. 1 and 3, because a straight line touches all seven of his circles. If his measurements of t were so precise that his decision to draw two curves in Fig. 3 is valid, then the experimental technique is deserving of further mention. We have drawn a smooth curve through the results in Fig. 3 and used this and the curve in Fig. 12 to obtain the values of shown in Fig. 13. Finding continuous is a contradiction of Fig. 4, which deserves comment itself. Levine obtained the solid circles in Fig. 4 using Fig. 2 and a smooth curve through the points shown in Fig. 3. We have replotted these solid circles in Fig. 14. We submit that there is no basis for his two straight lines (dashed in Fig. 14), and therefore have superimposed the curve that we believe is indicated. Certainly, there is reasonable doubt that a discontinuity in dH/dT exists at 220°K, even when one accepts Fig, 2. Furthermore, if one draws the straight lines indicated by least-squares treatments of the results presented as open circles in Fig. 4, their intersection is at about 196°K, not at 220°K as shown. Thus the alleged agreement between Figs. 3 and 4 with respect to "break" temperatures is not apparent. In Fig. 9, Levine has drawn a straight line very much different from the one indicated by a least-squares treatment. Obviously, he has done this because he recognized that H = 0 when T = 0. He is consistent in drawing the low-temperature curves in

Jan 1, 1968

By Herbert Clark Hoover, Lou Henry Hoover

As stated in the preface, the nomenclature to be adopted for weights and measures has presented great difficulty. Agricola uses, throughout, the Roman and the Romanized Greek scales, but in many cases he uses these terms merely as lingual equivalents for the .German quantities of his day. Moreover the classic language sometimes failed him, whereupon he coined new Latin terms adapted from the Roman scale, and thus added further confusion. We can, perhaps, make the matter dearer by an illustration of a case in weights. The Roman centumpondium, composed of zoo librae, the old German ceniner of 100 pfundt, and the English hundredweight of 1112 pounds can be called lingual equivalents. The first weighs about 494,600 Troy grains, the second 721,900, and the third 784,000. While the divisions of the centumpondium and the centner are the same, the Libra is divided into 12 unciae and the pfundt into 16 unizen, and in most places a summation of the units given proves that the author had in mind the Roman ratios. However, on p. 509 he makes the direct statement that the centumpondium weighs 146 librae, which would be about the correct weight if the centumpondium referred to was a ceniner. If we take an example such as " each centumpondium of lead contains one uncia of silver", and reduce it according to purely lingual equivalents, we should find that it runs 24.3 Troy ounces per short ton, on the basis of Roman values, and 18.25 ounces per short ton, on the basis of old German. If we were to translate these into English lingual equivalents of one ounce per hundredweight, then the value would be 17.9 ounces per short ton. [ ]

Jan 1, 1950

By J. C. Martin

Stmplified equations are developed for the flow of fluids in gas drive reservoirs in which the effects of gravity can be neglected. The results show that the pressure distribution is governed by a nonlinear heat flow type of equation, and the saturation distributions are related to the pressure by the same equations QS those developed by Muskat for the average pressure and saturations in gas drive reservoirs. Unrler certain conditions the equation for the pressure can be approximated by the linear form of the heat flow equatlon. This equation tk analogous to the equation for the pressure in single-phase compressible flow The analysis reveals that the equation for the pressure in n~ultiphase flows can be obtained directly from the equation for the pressure in slngle-phase flows by simply replacing the single-phase compressibility by the total compressibility and the single-phase mobility by the sum of the mobilities of all the fluids present. Perrine's method of pressure buildup analysis for multiphme flows is based on these same substitutions. Thus, the development presented in this paper constitutes a theoretical justification for Perrine's method of pressure buildup analysis. One of the most difficult problems associated with the production of oil is the determination of the flow of the fluids within the reservoirs. One purpose of this paper is to present the development of simplified equations for the flow in gas drive reservoirs. The other purpose is to present some of the needed theoretical foundation for the methods currently being used in the analysis of multiphase pressure buildup data. The analysis presented in this paper makes use of a partial linearization of the equations governing multiphase flows. It is felt that the process of linearizing or partially linearizing the nonlinear equations of multiphase flows can lead to useful results since this process has proved extremely valuable in the study of other fields of science and engineering where nonlinear equations are encountered. Pressure buildup data of shut-in wells have been used for many years to estimate the static reservoir pressure. These data have also been used in studying the aver- age permeability both away from and close to the well-bores. The majority of the buildup data are obtained from wells producing two or three fluids. As yet the theoretical foundations for the methods of buildup analysis used in connection with rnultiphase buildup data have not been established. A number of methods of analysis of pressure buildup data have been developed." Most of these methods apply only to single-phase flows, and almost all of the theoretical analysis is confined to single-phase flows. Perrine' developed a method of analysis for rnultiphase flows from the method for single-phase flows of Miller, Dyes, and Hutchinson.' He did this by simply replacing the single-phase compressibility by the multiphase compressibility and replacing the single-phase mobility by the sum of the mobilities of the fluids in the rnultiphase flows. Obviously, such a procedure lacks a certain amount of theoretical justification, and such practices can lead to erroneous results. Fortunately, Perrine's results have a theoretical justification, and this justification is presented in the following discussion. It is assumed that gravitational effects and the cornpressibility of the rock can be neglected. Under these assumptions the equations governing the simultaneous flow of gas, oil and water in porous media areo* The preceding equations can be expanded into the following expressions.

By Peter F. Weiss, H. Riedler, I. M. Moschitz, A. Olsacher, G. B. Fettweis

CONTENTS : 1. NATURAL FACTORS Geology Petrography and Rock Mechanics Mining System Orientation Rock Bolting System Movability of the Ore Grain Size Distribution Permeability Contamination Value of the Ore Hydrology 2. TECHNICAL FACTORS Height Length and Width Drawing Areas Time Factor Water Predrainage Surf ace Draining Underground Draining Advancing Slitting Sequence of Development Initiation of the Caving Process Drawing Rate 3. SPECIFIC MINING RULES Advancing Development Drawing Rate Interruption of Drawing (Water Distribution, Concentration of Mud, Dilution) Blasting 4. CONTROLS Safety Controls for Operation Computerised Drawing Control Structure of the Computer Program Hard Ware Print Outs 5. SUMMARY 6. ACKNOWLEDGEMENTS 7. REFERENCES Under the heading "Development System for Block Caving under Severe Conditions" a report was presented to this congress regarding a magnesite mine using block caving for several years. On account of the experience gathered in this mine and the results of far reaching exchange of experience, as well as under due consideration of the international literature it is tried to systematically list and briefly discuss the following factors that have to be considered for development and draw control of block caving. 1. NATURAL FACTORS It is self evident that this implies all those circumstances given by nature and which cannot be altered by man. Any mining activity is subjected to those and the success is depending on how far technology can be adjusted to those conditions. Geology Deposits of considerable thickness with rather steeply inclined flat-faced contacts are optimal for block caving. While vertically there is practically no limitation- for the deposit, theoretically, the smallest horizontal basis apt for operating block caving is the minimum area necessary to get the rock to completely cave in by undercutting and drawing. Practically, only consider- ably bigger main dimensions are found, mainly because of technical factors (machinery and equipment) and economic factors (cost ratio of exploration vs. development, danger of contamination).

Jan 1, 1981

By H. T. Kennedy, S. G. Dardaganian, J. L. Clanton

This paper presents equilibrium ratios measured on oil and gas samples taken from the Kelly-Snyder field at the reservoir temperature of 128°F. From these data smoothed curves were constructed for the reservoir fluid up to the bubble-point, 1,874 psia. A material balance calculation, based on the use of equilibrium ratios instead of the usual solubility and shrinkage meayr~rements is made on the field and compared to the con\.entional method. DETERMINATION OF EQUILIBRIUM RATIOS The equilibrium ratios, or K values were obtained by recombining separator samples of oil and gas taken when the reservoir was above its bubble point, and thus represented the reservoir fluid before any change had occurred due to the evolution of gas. The well sampled had a gas-oil ratio of 617 cu ft of high pressure sepalator gas per barrel of separator oil. and a bottom-hole temperature of 128°F. Samples were brought to equilibrium by agitating for 24 hours in a thermostat, maintained at the proper temperature within 0.2ºF, mercury being added when necessary to maintain the pressure constant. Samples of oil and gas were then taken by constant pressure displacement, and analyzed by low temperature frac-tionation. Equilibrium ratios were determined at 128°F and 500, 800, 1,000 and 1,400 psig. At the latter pressure, there were indications that the gas samples were contaminated with small quantities of oil, and only data taken at the first three pressures were included in Fig. I. This figure has been extended to higher and lower pressures by the use of the Fluor charts for 3,000 psi convergence pressure, on which the experimental points fit well. MATERIAL BALANCE EQUATIONS The possible errors involved in conventional material balance equations have been analyzed by Muskat1. Where the errors occur in field measurements, or in obtaining effective averages from variables such as gas-oil ratio and pressure, they will evidently be involved in any attempt to estimate the content of the reservoir. On the other hand, substantial errors may be introduced in conventional material balance calculations by: (1) the neglect of the amount of oil dissolved in gas at high pressures and temperatures in the reservoir, but which condenses under separator conditions; (2) the assumption that the separation of oil and gas in the reservoir may be duplicated by a differential liberation in the

By Paul E. Melancon, Vincent C. Kelley, Dale F. Kittel

Uranium of the Grants region occurs predominantly in continental sandstones of the upper part of the Jurassic Morrison Formation, but significant lesser deposits are found in limestone of the Jurassic Todilto Formation and in black shale of the Cretaceous Dakota Formation. The deposits are disseminations that form runs ranging from a few hundred tons to several million tons. The ore consists mainly of uraninite, uraniferous carbonaceous material, coffinite, and such secondary oxidized minerals at tyuyamunite, carnotite, and uranophane. In sandstone, the ore runs were locallized by mudstone, interstitial carbonaceous material, and primary sand channel trends. In limestone, ore deposition was related to folds and fracture zones. The great bulk of production has come from the Ambrosia Lake mines in the Grants district and the Jackpile and Paguate mines in the Laguna district. The ores, which generally have been 0.20 to 0.30 per cent U3O8, are treated at mills operated by Kerr-McGee Corporation, Homestake-Sapin Partners, and The Anaconda Company, all in the Grants district. In 14·years after discovery in 1950, the deposits had yielded concentrates valued in excess of $800,000,000. Since deposition of the Jurassic host rocks, a geologic history involving tilting, faulting, erosion, changing ground-water environments, and oxidation has considerably influenced the existence and character of the deposits. It is evident that their ongm is not simple. However, a degree of agreement appears probable for a pre-Dakota age for the original ore runs, and, at Ambrosia Lake, two principal stages of ore formation, separated by Laramide faulting, are recognized. All earlier ores have been modified by Quaternary oxidation, solution, and enrichment during which time much secondary tyuyamunite, metatyuyamunite, carnotite were formed.

Jan 1, 1968

By J. B. Coher, M. B. Bever

COLD work destroys long-range order, as was first observed by Dehlinger and Graf.1 Dahl2 showed that the mechanical disordering caused by cold work produces changes in those properties that are affected by long-range order. The existence of order has a marked effect on tile manner in which an alloy deforms and therefore on its mechanical properties.L' The relation between order and deformation behavior however, is only beginning to be understood. Seemann and G1ander4 suggested that cold work reduces an ordered alloy to a kind of gruel of antiphase domains. According to Cottrell,5 superdis-locations and pairs of dislocations in a slip plane connected by a strip of anti-phase domain boundary provide deformation mechanisms which do not change the state of order. In general, however, slip may be expected to produce new domain boundaries and destroy order if dislocations move on intersecting planes or cut through existing domain boundaries. The yield strength of an ordered alloy may pass through a maximum with decreasing domain size.5"7 The reduction of domain size resulting from cold work may, therefore, lead to a maximum in strength properties. Flinn8 suggests that dislocations can climb by short-range diffusion during deformation and thus can generate domain boundaries not only on slip planes, but also on other planes which will be those with the lowest domain-boundary energy. It has long been known that the rate of strain hardening of an alloy in the ordered state is larger than in the disordered state.3'9 Also the slip bands in ordered CU3, AU10 and Ni3Mn" are finer than in the disordered alloys. The stress which causes initial yielding in Cu,Au passes through a maximum with decreasing domain size.6'12 A maximum has also been observed in the hardness of ordered Ni3Mn as a function of strain.' These observations suggest, but do not prove, that domain size reduction occurs during deformation. According to Fisher13 slip destroys short-range order and thus the strength of an alloy is related to the degree of short-range order present. Rudman and Averbach14 and Averbach et a1.,15 demonstrated that cold work reduces short-range order in copper-gold and gold-silver alloys. Destruction of long-range and short-range order by cold work implies slip on an appreciable fraction of planes. Yielding of an alloy in which short-range order exists or antiphase domain boundaries are present should be discontinuous because the first dislocations moving across the slip plane meet with the largest resistance.5 Such discontinuous yielding has been observed in CU3AU6,16 and Cuzn.l7 This phenomenon, however, can also be explained by mechanisms not involving order.b The published investigations of the effects of cold work on alloys with long-range or short-range order have not been covered thoroughly in reviews of order-disorder phenomena. These investigations, therefore, will be listed here. They have been concerned with strength properties> 2,3,6,8,9,12,16-21 electrical resistivity,2,4,18,19,21-26: thermoelectric power, magnetic properties,2,18,21,26 and X-ray strain'1,2,14,15,27,28 The slip systems and the appearance of the microstructure after deformation in ordered and disordered alloys have also been investigated. 6.10.ll,l7,23,29,30 The alloys used in these investigations were copper-gold. 1-4,6,9,10,14,16,18 23-26,28,29 copper-zinc. L7. 19. 20,30 nickel-manganese,2 11,21 iron-aluminum. iron-nickel,' copper palladium,4,18,22 gold-silver.4,18,22 and palladium-silver-copper.4 In the work reported here. the changes in properties of polycrystalline Cu3Au were investigated as functions of strain in wire drawing and rolling. Specimens were heat treated before deformation

Jan 1, 1961

By Chung Yu, Wang

CHINA can he roughly divided into three metallogenetic province: North China, the Yangtze Valley, and South China. In North China the old Pre-Cambrian schists and gneisses are represented by the abundance of quartz mines in which sporadic occurrences of copper, lead, zinc, gold, and silver are sometimes found in subordinate quantities. Along the Yangtze Valley and in Central China, extending eastward as far as Shantung, are found here and there intrusions of dioritic rocks, in which occur the famous contact deposits of iron ore, besides which minor quantities of copper. lead, and zinc are also found. In South China the igneous intrunsions are of granitoid type in which, or in the vicinity of which, occur in certain regions immense deposits of antimony, tungsten, tin, and mercury. Broadly speaking. most of the famous coal mines are now situated in regions north of the Yangtze River, in which occur also the sedimentary deposits of iron in contradistinction to the contact deposits of iron along the Yangtze Valley.

Jan 1, 1943

By I. C. Edwards, G. E. Agar

INTRODUCTION Many research efforts over the past years have been devoted to the study of energy consumption in comminution and the characteristics of the broken material. The old "laws" have been superseded by more general methods of analysis1,2,3 but these methods have not received much attention outside the laboratory. The work to be described here was done in order to obtain scale-up information on wet rod milling of sylvinite. EXPERIMENTAL A 30 x 51 in. Denver rod mill with a scoop feeder was used for these tests. Ore was fed from a variable speed screw conveyor into the feed box along with saturated brine. The mill was filled to approximately 45% of its volume with 2400 lbs of a mixed rod charge. The minimum possible feed rate was 2.5 tph and the practical maximum for this mill was 8 tph. Individual tests were run by setting the solid feed rate, then adjusting the brine flow rate to give the desired pulp density. After steady state, as evidenced by constant discharge pulp density, had been reached, samples of the discharge were taken at 15-minute intervals. These samples were filtered, washed with alcohol, dried, then screened on Tyler screens using a Ro-tap shaker. The sylvinite feed was regular plant feed that had been scalped at 20 mesh and was tapped from the coarse ore bins. It had been previously passed through a roll crusher set at 3 inches and after scalping was essentially minus 1 in. plus 20 mesh. RESULTS The screen analysis of samples from each series of tests was plotted on double logarithmic scale paper to determine the reliability of the series. In some cases, a faulty sample or screening procedure dictated that the results of one test be discarded. The criterion is a simple one — if the slope of one plot was noticeably different from the others in the series, it was discarded. The only cases that caused difficulty were those in which the brine was not thoroughly displaced from the solids. When this occurred agglomerates were easily identified on the screens and the whole of the sample was retained on 3 or 4 screens. There were no border line cases. The number N given in Table 1 is the number of size analyses that were pooled to form the data shown in Fig. 1. While examining the reliability of the sizing and sampling by plotting the data, it became apparent that there was no significant difference between grinds made at 50 and 60% solids. For the analysis given here, these tests were regarded

Jan 1, 1967

COUNCIL OF ECONOMICS OF AIME Formerly Mineral Economics Division Established as a Division December 15, 1948 Established as a Council February 26, 1957 Douglas Donald, Chairman Sheldon Wimpfen, Vice-Chairman (Mining) A J Phillips, Vice-Chairman (Metals) E Connaughton, Vice-Chairman (Petroleum) J S Vanick, Contact AIME Director A H Lindley, Jr Secretary-Treasurer Lehman Brothers 1 William Street New York 4, N Y COUNCIL OF EDUCATION Formerly Mineral Industry Education Division Established as a Division January 15, 1932 Established as a Council February 26, 1957 L E Shaffer, Chairman J D Forrester, Vice-Chairman O Cutler Shepard, Past Chairman , Contact AIME Director

Jan 1, 1959

By H. R. Cooper

Beginning from the point of view that process control of ore flotation can be approached by on-line analysis of processing behavior, an equation was developed which has characteristics useful for a multi-variable feedback loop. The application of this equation to optimizing control with a data acquisition system will be discussed in Part 11. OBJECTIVE OF CONTROL The purpose of developing a feedback method for concentrator control is to provide a means for determining ore processing behavior in order that data describing the ore can be used to make appropriate changes in control conditions while the ore continues to flow through the flotation circuit. In absence of simple linear relationships between pairs of variables in the flotation process, attention is directed to the need for a generalized relationship which possibly would incorporate all pertinent variables. It would be possible to apply such an equation to the control of variables in a concentrator in real time according to operational requirements as ore gradually changes in quality and processing behavior. To meet this objective, it is necessary to define relationships describing flotation performance in terms of performance variables capable of being measured on-line, either with on-line instruments and analyzers or with manual methods lending themselves to quick determination of meaningful information. Relationships derived to meet this objective form a model for the flotation process. The evaluation of flotation parameters of the ore and the execution of control on the basis of the derived information while the ore is continuing through the process would constitute a feedback control system. Data for the following control and performance variables can be made available: 1) ore feed rate, 2) collector addition rate, 3) lime addition rate, 4) pulp density, 5) assay or multiple assays in feed, tails, or concentrate sufficient for material balancing, 6) particle size distribution in flotation feed, 7) froth height, and 8) frother addition rate. Other process variables, such as flotation air input and mechanical agitation intensity, are usually not considered as control variables and were not taken into account in this analysis. Other data, such as that describing the ore, would be useful for concentrator process control. However, information of this type (such as ore hardness, grain size of the mineral, chemical species of the mineral, and ore surface properties) being not presently measurable in the on-line sense, has the effect of causing disturbances in the system which can be detected only indirectly. The process control system being sought must recognize disturbances by their effect on measured performance followed by determining control changes to compensate for them in meeting the objectives of improved performance (perhaps higher throughput, maximum return, etc.). A suitable model for the process having capability of recognizing the effects of ore disturbances should provide the means for introducing proper compensation through control changes. This would be done by processing on-line data with the model to calculate coefficients reflecting ore characteristics. This procedure can only be applied in a typical flotation system when on-line data can be processed at faster rates than the usual rate at which the ore in flotation feed takes on significantly different characteristics. For example, material balance data can be accumulated in approximately 5-min intervals using on-line X-ray fluorescence analysis. The flotation system time constant might be 15 min including grinding. Ore changes having time constants longer than 1 hr could be accommodated using on-line feedback control by this procedure. FORM OF A FLOTATION MODEL A suitable form for mathematical expression of the flotation process is an equation involving rates, when each of the components entering into the separation can be treated independently by a rate equation. A first-order, kinetic rate equation can be written on

Jan 1, 1967

By B. D. Lichter

In a previous paper, Oelsen, Schuermann, and Hey-nertl pointed out the possibility of obtaining complete thermodynamic functions for alloy systems from calorimetric measurements alone. Specifically, if the heat content of a heterogeneous, multicomponent system is known as a function of temperature and composition, then it is possible to derive the heats, entropies, and free energies of formation of liquid phases and of solid intermediate phases of fixed composition. The authors present equations and graphical techniques applicable to eutectic systems and systems with intermediate phases without solid solubility at lower temperatures. eijering has considered possible extension of the treatment to systems with complete solid-state miscibility at lower temperatures; however, experimental difficulties practically restrict the method to systems with very limited miscibility in the solid state. The purpose of this note is to present an alternative derivation of the heats and entropies of formation of liquid phases and of solid intermediate phases from heat-content measurements alone. Fig. 1 shows three types of phase diagram to which the analysis may be applied. If the heat content is determined as a function of composition x, at temperature T, we have quite generally and the heat of mixing of the liquid is obtained directly from heat-content measurements. If the temperature T lies in a two-phase region (solid-liquid) then

Jan 1, 1967

By D. I. Bardos, A. M. Bardos, Paul A. Beck

The approximate effective silicon radii in ternary Laves phase alloys with transition elements and silicon were found to range between 1.16 and 1.21A, i.e., considerably smaller than the atomic radius calculated for elemental silicon. The atomic radii were found to increase with the size of the transition element atoms in the structure. It has been noted by Aronsson1 that silicon in solid solution in iron, cobalt, and nickel has an effective CN 12 atomic radius of approximately 1.20Å, a value very much smaller than the CN 12 radius of 1.34Å derived from the interatomic distances in elemental silicon.7 The unusually short metal-silicon interatomic distances in transition element monosilicides and disilicides have been also pointed out by various investigators.1 A similar tendency was observed by Nevitt in Cr3O type silicides.2 Recent work on Laves phases in ternary systems of silicon with transition elements4"8 suggested that extensive Laves phase fields may occur in such systems.8 It has been pointed out by Laves7 that the MgCu2 and MgZn2 type structures lend themselves particularly well for the determination of the effective radii of the component atoms. In these AB2 phases the B atoms are arranged in close packed straight lines, and their distances are related in a simple manner to the lattice parameters.8 The present work was undertaken in order to find out whether or not the B transition element in such AB2 Laves phases can be replaced to an appreciable extent by silicon. In cases where extensive substitution proves to be possible, the "average atomic radius for the B site" at various silicon contents was to be determined, and the effective atomic radius of silicon calculated by extrapolation to complete replacement of the B component by silicon. The following ternary systems were studied: Ti-Mn-Si, Ti-Fe-Si, V-Co-Si, V-Ni-Si, Nb-Fe-Si, Nb-Co-Si, Ta-Fe-Si, Ta-Co-Si, and Mo-Fe-Si. In all of these alloy systems, the Laves phase solid solutions were found to extend over a considerable range of silicon content. As previously reported,4"8 in the V-Co-Si, V-Ni-Si, and Mo-Fe-Si ternary systems Laves phases do occur, even though there are no corresponding binary Laves phases. In stabilizing the Laves phase, silicon acts as if it were decreasing the effective electron concentration of the alloy.8 A more detailed study of the boundaries of the Laves phases in the V-Co-Si and V-Ni-Si systems has been made and will be published elsewhere. In both cases, the elongated Laves phase fields extend parallel to the B-Si side of the composition triangle, clearly showing that silicon is substituting for cobalt, respectively, nickel over a wide range of compositions. The binary Laves phases NbCo2 and TaCo2 have the cubic MgCu2-type structure. It was found that, in both ternary systems with silicon, again the MgZn2-type hexagonal Laves phase is stabilized and that this phase extends to high-silicon contents. In each ternary system at least three Laves phase alloys of the composition A(B1_xSix)2 were used, x here denoting the fractional substitution of the B-transition element atoms by silicon. The alloys, listed in Table I, were prepared by arc melting in argon. Each specimen was water quenched after a homogenizing anneal of 3 days at 110(FC, except for the Mo-Fe-Si alloys, which were annealed at 1200°C. Metallographic examination showed that most of the homogenized alloys consisted of a single phase, although some had minor amounts of a second phase, as shown in Table I. X-ray diffraction patterns were prepared using an asymmetrical focusing camera of large resolution and Fe Ka radiation. The patterns were indexed, and the lattice parameters of the hexagonal Laves phases were determined from the available diffraction lines of highest indices: (213), (205), and (313). The lat-

Jan 1, 1963

By A. T. Yu

On March 18, 1964, the 52,000 dwt ore carrier M/S Houn Maru called at the port of Coquimbo, Chile, on its maiden voyage to take iron ore to Japan. This marked the first time a vessel of this size ever arrived at Coquimbo, and the event promises to drastically accelerate henceforth iron ore exports from Coquimbo province. This was made possible by the use of a versatile shiploading system recently installed by Cia. Minera Santa Fe. Coquimbo has no mechanized loading facilities other than six conventional 5-ton cargo cranes. Limited space on shore further complicates the stocking problems. To make the best of what is available, a meticulously organized semi-hand-loading system has been developed through the years.

Jan 5, 1964

By M. R. J. Wyllie, Michael A. Torcaso

With the continued deep drilling of today, increasing numbers of high pressure and high temperature gas-condensate reservoirs are being discovered. Correspondingly, the ranges of properties of gas-condensate reservoir fluids are also being increased. The literature1*'." contains several excellent reviews of the property ranges in presently known condensate reservoirs. When one examines these property ranges, it becomes apparent that the need for reliable data is great if the engineer is to evaluate properly or appraise a gas-condensate reservoir. It is the purpose of this paper to present phase-behavior data that will point out some of the important variables that influence recovery from gas-condensate reservoirs produced by pressure depletion. All these variables may be resolved into two major categories: the hydroc:arbon composition of the reservoir fluid and the physical properties of the reservoir. But the variables which we will consider are those which are usually determined from well tests shortly after discovery and are, consequently, readily available to the engineer. They are as follows: (1) the producing separator gas-stock-tank liquid ratio, (2) stock-tank liquid gravity, and (3) reservoir temperature. Laboratory depletion studies have been performed on several reservoir fluids to illustrate the effect of changes in the cronsidered variables upon ultimate recoveries. The deviation factors, Z, of a series of reservoir fluids were determined experimentally to illustrate their order of magnitude and their effect upon the calculation of in-place reserves existing at high pressurcs and temperatures. The procedures followed in conjunction with the performance of these studies and their associated calculations are illustrated in Fig. 1. For the purpose of this paper, the depletion recoveries are expressed only in terms of pcr cent of initial stock-tank liquid, with the abandonment pressure assumed to be 500 psig. VARIATION OF RECOVERY WITH INITIAL PRODUCING SEPARATOR GAS-STOCK-TANK LIQUID RATIO The producing separator gas-stock-tank liquid ratio has long been one of the principal criteria in assumptions and generalized correlations' used for the estimation of ultimate recovery from gas-condensate reservoirs. Fig. 2 presents a plot of the cumulative recovery of stock-tank liquid at abandonment as a function of the initial producing separator gas-stock-tank liquid ratio. The graphical illustration represents the results of 44 laboratory depletion studies performed on actual gas-condensate fluids. These data are presented not only to illustrate the general trend of ultimate recovery increase with initial producing ratio increase but to emphasize the considerable variation in possible recovery at any given producing ratio. Table 1 presents the properties of two actual reservoir fluids chosen to illustrate the approximate extremities of producing ratios for gas-condensate systems. The fluids designated as A and B exhibited initial producing ratios of 3,400 and 114,000 scf/bbl, respectively. Fig. 3 presents a graphical comparison of the cumulative stock-tank liquid recoveries, calculated from the well-stream compositions and produced volumes for each fluid during depletion. It is to be noted that Fluid A exhibited a recovery of only 16.5 per cent when produced to an assumed abandonment pressure of 500 psig while the corresponding recovery for Fluid B was calculated to be 62.2 per cent. This difference in recovery, which exemplifies the general trend of recovery increase with initial producing ratio increase, is readily explained by consid-