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By D. V. Doane, G. A. Timmons, W. G. Scholz

Molybdenum of high purity can be produced by direct dissociatiott of commercial molyhdenm disulfide in vacuo at 1600° to 1700°C (2910° to 3090°F). The Product is lower in oxygen than commercially available molybdenzdm powder. Analyses of ingots arc-cast from commercial molybdenum powder, hydrogen-re-cluced from animonium molybdate, and from thermally dissociated molybdenum disulfide indicate that the levels of chemical impurities in these ingots are similar. Equipment now in operation will produce 100-lb hatches of powder product. The paper describes development of processing equipment, control of processing varzahles, handling of the product, and evaluatiotl of the melal produced. MOLYBDENITE (molybdenum disulfide) can be decomposed by heat in the absence of oxygen to produce elemental molybdenum and sulfur, which is evolved as a gas. The temperatures required for the dissociation are above 1370°C (2500°F); the sulfur must be continuously withdrawn to permit the reaction to proceed to completion. This is accomplished by continuous evacuation of the thermal dissociation chamber and condensation of the gaseous sulfur in another part of the system. Cognizance of the fact that the dissociation takes place in two steps is important in controlling the process. Basically, the molybdenite dissociation process has two potential advantages as a method of produc- ing pure molybdenum: 1) The materials entering into the process contain little or no oxygen. Since the process is carried out in vacuum at high temperature, the quantities of interstitial oxygen, nitrogen, and hydrogen in the product should be very low. 2) The process is more direct than the commercia1 method of producing high-purity molybdenum. In the conventional process, molybdenite is roasted to molybdic oxide, the oxide is purified first by sublimation, then by conversion to ammonium molybdate, and finally, the molybdate is reduced in a hydrogen atmosphere (usually in two steps) to the metal lic molybdenum powder. This paper presents a description of the stages in scaling-up of the dissociation equipment and an account of attempts to evaluate the molybdenum produced by thermal dissociation, rather than a report of a fundamental study of the dissociation reaction. Since little has been written on the subject, it is appropriate, before detailing the development of the process, to review briefly the research that has been conducted over quite a period of years. LITERATURE SURVEY The first accounts of the possibility of thermal dissociation of the mineral molybdenite were re-

Jan 1, 1962

By D. N. Sutherland

The cassiterite flotation circuit at the Renison concentrator has operated with increasing levels of automatic control since late 1981. The circuit operates at high levels of recycle which make it difficult to control manually so that the initial control strategy was to stabilize the mass flows around the circuit prior to circuit optimization. Control of the air supplies to the flotation banks was introduced to achieve this stabilization and initial results indicated that some success has been achieved, as indicated by improvements in the overall circuit performance and reduction in the stream variabilities. These improvements were gained through control of the major recycle to the roughing stage which dominates the circuit behaviour. Feed-forward control of collector addition has also been introduced successfully, but attempts to control the final concentrate grade have been less satisfactory. This work is continuing and the objective of current activity is to include the three cleaning stages in an overall circuit control scheme as a first phase of metallurgical optimization of the operation.

Jan 1, 1984

By John B. Baker, Bernard B. Betty, H. F. Moore

Fox several years there has been in progress in the Materials Testing Laboratory of the University of Illinois an investigation of creep and fracture of lead and lead alloys. In the course of this investigation it has been shown that the phenomenon of creep occurs in part at the grain boundaries of lead and lead alloys. To study the occurrence of creep and the development of fracture within crystalline grains, two series of tests of single crystals of lead have been carried out. The first of these, a preliminary series, by Mr. Betty, has been described.1,2 The second, pursued by Mr. Baker for his doctoral dissertation, was carried out under the direction of Professor Moore, with the assistance of Prof. G. L. Clark in the X-ray work, and the cooperation and advice of Mr. Betty. This paper is based on the test data obtained in this second series. Single crystals of a very pure commercial lead have been prepared, some of them tested to measure creep, others tested to fracture under long-continued steady load, and still others tested under cycles of repeated tension. An interpretation of the test data of these single-crystal tests is offered, which is a combination of parts of several well-known theories. SPECIMENS The single-crystal specimens were made from a piece of very pure commercial lead sheathing. A spectroscopic analysis of one of the single crystals showed the presence of 0.005 per cent Bi, 0.0001 per cent Cu and 0.0003 per cent Ag. Preparation.-The Bridgman method of casting single-crystal speci¬mens was used.3 The specimens were cast to the shape and size shown in Fig. I (dimensions in Fig. 4c) in a duralumin mold. Molten lead does not stick to duralumin. Fig. 1 shows the mold and the blast flames for heating. After the mold had been heated to the temperature of molten

Jan 1, 1938

By J. Chipman, T. Fuwa

The effects of various elements on the activity coefficient of carbon in liquid iron have been studied by two experimental methods: 1) equilibration with controlled mixtures of CO and CO2; 2) the solubility of graphite in the melt. Activity coefficient of C is increased by Al, Co, Cu, Ni, P, Si, S, and Srz. It is decreased by Cr, Cb, Mn, Mo, W, and V. THE thermodynamic properties of the iron-carbon binary system have now been fairly well established, although some uncertainty remains with respect to the exact location of some of the phase boundaries. The activity of carbon in ferrite and in austenite has been measured in the classic researches of R. P. smith' while similar measurements by Richardson and ~ennis, and by Rist and chipman3 have established the values of the activity of carbon in liquid iron up to 1760°C. On the other hand, our knowledge of the effects of alloying elements on the activity of carbon in dilute solutions is restricted to Smith's experiments on systems Fe-C-Mn and Fe-C-Si in the austenitic range and to some more recent experiments of schwarzman4 in the a range. In addition there have been a number of determinations of the effects of various elements on the solubility of graphite in liquid iron, and from these the corresponding effect in saturated solution may be obtained. The purpose of the present study was to extend the investigation of the liquid system to include the effects of alloying elements upon the activity coefficient of carbon, principally in dilute solutions. Equilibrium measurements were made on the reaction C + co, = 2 CO (g) The prepared mixture of CO and CO,, diluted with argon, flowed over the surface of the liquid metal which, after several hours' exposure to the gas, was quenched and anqlyzed. As in the earlier experiments, the principal experimental difficulty was in the deposition of carbon on the parts of the furnace at temperatures slightly below that of the metal bath. In order to minimize this difficulty, the ratio (Pco)2 /PCo2 was restricted to values not much higher than 100 atm, and correspondingly the carbon concentration in the metal seldom exceeded 0.30 pct. EXPERIMENTAL METHODS The method and apparatus were essentially the same as used by Rist and Chipman.3 The gaseous mixture consisting of highly purified CO, CO,, and argon, each controlled by a flowmeter, was led into the furnace and passed over the surface of the liquid-iron melt which was heated and stirred by high-frequency induction. One slight modification was made in that a molybdenum susceptor was placed outside the crucible for the sake of uniformity of temperature and to combat the tendency of carbon to precipitate on the crucible wall. Pure alumina crucibles approximately 25 mm ID were used. The charge consisting of about 30 g was made up of electrolytic iron, the alloying element to be added, and enough graphite to supply slightly more or less than the anticipated equilibrium carbon concentration. All metals used were of high purity. Metallic chromium, columbium, and vanadium were from special lots supplied by the Electro Metallurgical Co. Tin, copper, molybdenum, tungsten, cobalt, and nickel were of purest commercial grades. The electrolytic iron, after being cut to the proper size for charging, was prereduced by hydrogen at 850° to 1000°C to remove surface oxidation. The oxygen content of the reduced material was 0.002 pct. This treatment made it easy to control the carbon content of the initial melt. The charge was melted under the gas mixture to be used for the entire run. In some earlier melts the charge was melted under a stream of argon, but in this case some alumina was reduced from the crucible, and the aluminum thus absorbed in the melt was subsequently oxidized with the formation of a solid film of alumina on the surface of the melt. AS another safeguard against film formation, overheating of the bath was carefully avoided. All runs were made at a temperature of 1560°C. Under experimental conditions a charge of pure iron picked up 0.17 pct C in 3 hr and 0.23 pct C in 6 hr under an atmosphere for which the equilibrium concentration of carbon is 0.27. It is clear that the time required to reach equilibrium from an initially carbon-free melt would be very great. For this reason each experiment was started with a melt of known carbon concentration not far above or below the expected equilibrium value, and each melt was held at temperature for a period of at least 5 hr. Under such circumstances it was possible to chart the approach to equilibrium from both high-carbon and low-carbon materials. Temperature was controlled by frequent optical observation and adjustment and the metls were timed in such a way that the final 2 hr occurred during a time when electric power was steady; for example, 2 to 4 pm or after 11 pm. In melts containine volatile metals such as copper, tin, and mangane\e the time of holding was decreased somewhat in

Jan 1, 1960

By AIME AIME

IV. THE BOUNDARY BETWEEN STEEL AND IRON. It would be well to decide on a definite carbon-content to serve as a boundary line between ingot-iron and ingot-steel, between puddled-iron and puddled-steel, and between any other varieties of wrought-iron and weld-steel. Two plans have been considered. One is to draw this line at 0.32 per cent. of carbon or its equivalent in other elements, for the reason that this carbon-content appears to correspond to the critical point, 0, in the diagrams of Roberts-Austen and Rooze-boom.8 This has the merit of corresponding to a definite physical boundary. The other plan is to draw the boundary at 0.20 per cent. of carbon, because this is a convenient place to separate the important classes " soft steel " and " half-hard steel," so that if this point was adopted "ingot-iron " would be synonymous with "soft steel," and " ingot-steel " would be the equivalent of the two classes, " half-hard steel " and " hard steel."

Mar 1, 1908

By H. C. Howarth

THIS paper gives observations on ground movement and subsidence resulting from pillar drawing in the Lick Run section of Montour No. 10 mine of the Pittsburgh Coal Co. adjacent to solid coal owned by the U. S. Bureau of Mines at its Experimental mine in Snowden Township, Allegheny County, Pennsylvania. The investigation was planned by George S. Rice, chief mining engineer of the Bureau, who arranged the necessary cooperation with Dr. L. E. Young, vice president of the Pittsburgh Coal Co. Engineers of that company placed permanent monuments on the surface to establish the boundaries of the coal owned by the Bureau and to furnish fixed points to which all levels were referred. Engineers of the Experimental mine staff then covered the ground under observation with a checkerwork of monuments made of oak pegs set into the ground at 50-ft. intervals in two directions at right angles to each other. The level of these pegs was determined first from Dec. 16 to 30, 1929; again from May 25 to June 5, 1930, and finally from July 7 to 15, 1931. Observations were then discontinued because work had been stopped temporarily in this part on Montour 10 mine.

Jan 1, 1933

By V. W. Buys, R. E. Havener

11.3-1. Basic Principles. Communications systems available for application to surface mining operations can be divided into basic categories. These are: 1. Wired systems requiring some type of metallic conductor 2. Nonwired systems, or those commonly referred to as space-radio systems. Under the heading of wired systems, telephones of the ringer type utilizing magnetos were used in the early pit operations. These are still being used in underground mining operations where calling is accomplished by ringing a code made up of short and long rings. While the standard Bell Telephone Systems have not been applied extensively in underground mining, they have been used in open pit operations but have the disadvantage of using multiple pair cables which must be installed and maintained as the mining operations proceed. They have the advantage however, that when a Bell System is installed in a surface mining operation, communication is available not only within the operation but to any point in the world through the facilities of the world-wide Bell Systems. A second type of communication available is the audio system or public address system requiring the use of a special audio cable made up of shielded pairs for the loudspeaker and microphone circuits. Audio systems have one outstanding advantage over most telephone systems in that, with a high-powered amplifier, a paging call can be heard over and above the high ambient noise conditions usually found at a surface mining operation. However, they have the disadvantage of requiring special cable which must be installed and maintained. Another type of wired communication system available for surface mining is that of carrier frequency equipment similar to that used in underground mining operations. In this system, transmission is accomplished by means of a frequency modulated carrier that travels over the underground trolley wire, the rail on which locomotives travel, and adjacent telephone wires.

Jan 1, 1968

By R. Fahn

Bentonites are best suited for the preparation of acid activated clays with efficient adsorption properties. They are weathering products of acid volcanic ashes and natural deposits are spread worldwide. The main constituent of bentonite is aluminum hydrosilicate montmorillonite with a high ability to swell. Physical and Chemical Properties of Montmorillonite The clay mineral montmorillonite is named after its place of discovery, near Montmorillon in southern France. The structure of this clay is shown in [Fig. 1]. The montmorillonite crystal consists of about 15-20 silicate plates. Each silicate plate is composed of three layers. The central one is formed by aluminum or by ferric hydrate octahedrons, the two outer ones consist of silicon dioxide tetrahedrons. In the presence of water, the montmorillonite crystal swells and water molecules become deposited between individual silicate layers. Two types of natural bentonites are known: the Western type, which is a natural sodium bentonite (high swelling grade), and the Southern type, an alkaline earth or calcium bentonite (low swelling grade). Southern bentonites have efficient adsorption properties of their own. They are called natural active earths or fullers earths. Acid Treatment of Bentonite Under the influence of a mineral acid, the exchangeable alkaline earth ions of bentonite are substituted by hydrogen ions. Moreover, depending on the acid concentration, temperature, pressure, and reaction time, a more or less pronounced leaching process takes place. Thereby Al-, Fe-, and Mg-ions are extracted from the octahedron layers. This results in a change in the crystalline structure of montmorillonite and in an increase of its specific surface area and porosity, as shown in [Fig. 2].

Jan 1, 1983

The co-operation of the members of the Institute is earnestly sought by the Committee on Nominations, recently appointed by the Board of . Directors, in its work of formulating a ticket for officers and places falling vacant in the Board of Directors in February, 1916. The Committee must present the official ticket of nominations to the Board of Directors at its October meeting. Members are, therefore, urged to send promptly their nominations for officers and Directors in order that the Committee may have an opportunity to give them full consideration. The officers to be elected at the annual meeting in February, 1916, are: One officer, known as Director and President. Two officers, known as Director and Vice-President. Five officers, known as Director; The attention of members is called to Articles V and VII of the Constitution, and to By-Law XIII, which reads as follows: "The geographical districts to be considered by the Committee on Nominations shall he as follows, until otherwise ordered by the Board. District No. 1. New England, New York, and New Jersey, excepting New York City and district., which is provided for in the Constitution. (N. B.-New York City and district is designated District 0.) District No. 2. Pennsylvania. District No. 3. Ohio, Indiana, Illinois, Iowa, and Missouri. District No. 4. Minnesota, Wisconsin, and Michigan. District No. 5. Montana, North and South Dakota, Wyoming, Nebraska, Kansas, Washington, Oregon, Idaho, and Alaska. District No. 6. California and Nevada. District No. 7. Utah, Colorado, Arizona, and New Mexico. District No. 8. Louisiana and Texas. District No. 9. Other Southern States and District of Columbia. District No. 10. Mexico. District No. 11. Canada."

Jan 7, 1915

By M. E. Wadsworth

The chief value of a paper like this consists in its statistical tables, putting on record material useful to future inquirers. The data here given have been compiled from time to time as far back as 1874, and subsequently brought up to date. Much of the data could only be procured by personal inspection of the catalogues, as for example those relating to the Lawrence Scientific School, which were taken at that time from the catalogue of Harvard University, on file in the University Library, by the present writer, then an instructor in that institution. These tables of statistics were first prepared for publication by the present writer in 1888-1890 and published in his "Report to the Board of Control of the Michigan College of Mines " (Michigan Mining School) for 1886 to 1890. Later they were revised, enlarged and brought down to date in his reports to the same Board for 1890-92; and since that time they have been, at his request, revised, greatly enlarged and kept up to date by Mrs. Frances H. Scott, the efficient Librarian and Secretary of the Michigan College of Mines. Great credit is due to her for her devotion to this work and her untiring efforts to have the statistics complete as far as possible. The accompanying running commentary is given simply as a string to hold these statistics together, and in order to call attention to a few points. In compiling any tables like those accompanying this paper, one is confronted by serious difficulties, some of which render these results only approximate. In order to insure greater correctness and fullness in the statistics to be published the writer's reports for 1890-92 were sent to the president of every college, university, and technical school in the country, so far as known. Accompanying this was a personal letter which asked of each one his aid in correcting any errors, and in giving fuller statistics. But relatively few answers were obtained, and subsequently from one to many letters have been sent to each institution not formerly reply-

Jan 1, 1898

To THE BOARD OF DIRECTORS AND MEMBERS OF THE AMERICAN INSTITUTE OF MINING AND METALLURGICAL ENGINEERS. GENTLEMEN Like every other significant activity in the United States today, the work of the Institute has been affected by and adjusted to the prosecution of war against Germany, .Japan and their satellites. As the elaborate engines and materiel of modern mobile warfare are made, for the most part, of metals and other minerals; and are powered by mineral fuels, the industries -represented by the A.I.M.E. are of primary and vital importance. Of some 29 critical materials officially listed by the War Production Board, 24 are minerals. An alternate for one of the others, rated as a nonmineral, is to be made principally from petroleum. This alludes, of course, to rubber. The procurement of tremendous quantities of such raw materials and the effective processing, fabrication, and utilization of them depend on members of those branches of the engineering profession represented by the A.I.M.E.

Jan 1, 1943

By Barnabus Bryan

THE normal statistics of supply and demand of petroleum and its products have little more than local influence on the market movements of oil securities. The two major reasons for this condition might be called the technique of production and the technique of refining. The speed of improvement in each and the complete lack of control of their, inter-relation have resulted in overproduction of both crude oil and gasoline in the face of immense in-crease in demand. The trouble with oil securities has been that of the mushroom radio companies, where too frequent changes have killed the possibility of profits. It is a case of too much efficiency. During the past ten years there has been continual talk of wasting reserves of crude oil. This has been based on "present methods of production." Yet the methods of ten years ago in the oil industry are as antiquated today as the kerosene lamp.. The fear of famine has transformed the industry. The refiner, through the cracking process, has doubled the gaso-line output from a barrel of crude oil, thus doubling reserves and changing a current undersupply into oversupply. When the automobile driver desires he can again double reserves and transform want into abundance by demanding an automobile which will deliver twice as many miles per gallon of gasoline. Entirely apart from refining and in complete dis-regard for its needs, the oil producer has forged ahead at a pace too rapid for his own good. The science of geology has developed with experience and' lavish expenditure into a constant danger to profits in the production of oil. Two and one-half per ;cent of the producing wells in the United States are yielding one-half of the oil, while their flush production is used as an excuse to force down the price of crude oil until 200,000 wells must be abandoned or produce at a loss. The fabulous yield of the new high-pres-sure fields enables the fortunate owners to make a profit regardless of the price of oil. Such a condi-tion is unhealthy from the standpoint of oil itself and as a national policy. It is manifestly absurd to suppose that such a condition can endure for a gen-eration. There will come a day when the sequence of discovery will be temporarily broken, and at that time the consumer will be forced to pay heavy interest on the foolhardy policy of today.

Jan 6, 1927

MOWRY BATES, ? Tulsa, Okla.-In the first part of this paper the author says: "In an unpublished paper on Water Problem in the Augusta Field, S. K. Clark reaches the following conclusions: (1) That the great amount of water present is bottom water, occurring in the Varner sand, the main producing or the 2500-ft. horizon. (2) That the only striking connection between structure and water is in the area of the marked

Jan 4, 1919

By T. K. Prentice

ABSTRACTED AND REVIEWED BY E. W. DAVIS,* MEMBER A.I.M.E. THE January-February number of the Journal of the Chemical Metallurgical and Mining Society of South Africa is made up entirely of a discussion of Ball Wear in Cylindrical Mills. Following the principal paper by T. K. Prentice are several remarkably pertinent and carefully prepared discussions. Few persons in this country would be likely to see this publication, and since the information presented is new and of current interest, it seems desirable to abstract and review this publication for the benefit of the members of the A.I.M.E. The purpose of the investigation is stated in the first two paragraphs of Prentice's paper, as follows: Early in 1941, The Chamber of Mines Steel Products, Limited, initiated a series of tests under semi-working scale conditions to determine, if possible, those physical and chemical properties of a ball which make it resistant to wear when used in a cylindrical mill as a grinding medium, with the primary object of incorporating those beneficial qualities in the balls being produced at their works. This paper describes the tests carried out and discusses the results obtained. From these results it was possible to formulate a new theory relating to ball wear in cylindrical mills. This theory is presented in the second portion of this paper. PRACTICAL BALL-MILL TESTS IN A CYLINDRICAL MILL Part I of the paper begins with a discussion of the methods used for the manufacture of grinding balls in South Africa. The following paragraph is of particular interest. The cast steel ingots, 4 ¼ - in. square by 3 ft. 6 in. long, are re-heated in a gas-fired sloping stationary-hearth furnace and then rolled in a six-pass continuous mill into 2 5/8 in. round billets. Some of these billets are then removed and cut into suitable lengths for forging into 4 in., 3 ½ in., 3 in. or 2 ½ in. balls by means of three Drop and two Beché hammers, but the greater number, whilst still at about 1,000 ºC., pass directly into a set of scroll rolls which produce, in an ingenious manner, finished 3 in. balls direct from the 2 5/8 in. billets. Except in special cases, all balls are allowed to cool in the atmosphere and are not water quenched. Details of the Tests In order to enable the reader to evaluate properly the results and conclusions in the rest of the paper and in the discussions following the paper, most of the information presented by the author under this heading is quoted: ….. The testing unit was a nominal 30 in. diameter and 18 in. long centre discharge Denver Ball Mill. The ore pulp to the ball mill comprised a small portion of the normal feed to one of the fourteen City Deep 5 ft. 6 in. X 22 ft. tube mills, and the grinding media consisted of the balls under test plus other balls to give the desired load. The running time of the test-mill was divided into approximately equal periods of five days 13 ½ hours each. The usual procedure was to examine and make up the load

Jan 1, 1944

By J. E. Campbell, G. D. Calkins, N. M. Ewbank, M. Pobereskin, A. Wesner

GRINDING for size reduction affects the economics of many processes and products. It is essential as the first step in many industrial processes and is also a finishing step for materials with properties depending on particle size, such as talc, cement, and silica sand. Intermediate and fine grinding are vital operations in the U. S. cement industry, which is producing more than 250 million bbl of cement per year.1 Wear of the grinding media is a large part of the grinding operation cost. Problems encountered in grinding cement are so complex that evaluation of efficiency and economy of grinding media is difficult.2 It has been especially difficult to evaluate the relative effectiveness of different types of balls because there are no good testing techniques.

Jan 12, 1957

By J. P. Carson

(Read at the Wilkes-Barre Meeting, May, 1877.) THE works of the Tula Iron Company are in the Republic of Mexico, State of Jalisco, twenty-eight leagues southwest of Guadal¬ajara, ten leagues northwest of the town of Sayula, through which passes the projected line of the Mexican National Railroad. Its geographical position would be about: latitude, 20° 10' N., longi¬tude, 4° 35' W. of Mexico City. The surrounding country is a roll¬ing plateau, 6000 feet above the sea, enjoying the most magnificent climate in the world, the average temperature being about 70°. The works were commenced in 1850 by a company with very small capital, having not the least idea of the undertaking. They soon fell into the hands of the money-lenders, and after changing

Jan 1, 1878

By R. H. Jacoby, V. J. Berry

When dry gas is injected into a reservoir containing a volatile crude oil, a significant amount of the reservoir liquid phase may become vaporized. The resultant rich gas phase, when subsequently produced, con-tributes to tank oil production. This contribution assumes greater importance, the more volatile the oil in-olved. Oil recovery may be sub-stantially greater than that predicted by conventional frontal-drive methods, which do not consider the vaporization equilibrium between the reservoir oil phase and the injected gas. A calculation method has been (developed to account for vaporiza-. tion of the reservoir liquid phase during gas-injectiorz operations, and for the tank oil production which results from this factor. Recovery performance calculations are presented for a reservoir containing a highly volatile oil. Tank oil recovery is calculated to be about twice that predicted by the use of the conven-rional frontal-drive equations. In contrastto usual pressure maintenance performance results, in which the gas-oil ratio rises at an increasing rate after gas breakthrough, the pre-dicated gas-oil ratio rises rapidly to about 12,000 scf/bhl and then rises much less rapidly. During gas inje-tion, most of the reservoir liquid phase contacted is evaporated by the dry injection gar. The gas-oil ratio during this period is dependent upon reservoir pressure. The higher the operating pressure, the lower the gas-oil ratio. The predicted behavior i., in accordance with laboratory PVT tests made to .simulate the vaporization behavior. In addition to recovery performance predictions, results of the calculation procedure include complete wellstrearn composition data of value in the design of gasoline plant facilities often used in con-rrction with gas-injection operations. INTRODUCTION In the cycling of gas-condensate reservoirs, dry gas is injected to maintain reservoir pressure during wet gas production and to thereby eliminate or reduce ultimate loss of liquids due to retrograde condensation within the reservoir. Gas injected into crude oil reservoirs has a dual function. It displaces oil to the producing wells and at the same time serves to partially or fully maintain reservoir pressure. Oil shrinkage which would occur upon pressure reduction is thereby minimized or eliminated. Accepted calculation methods are available'= for predicting recovery performance of either gas-condensate reservoirs or crude oil reservoirs which are being subjected to gas injection. In gas-condensate reservoirs, any retrograde liquid formed does not flow, and it is necessary to account only for the vaporization equilibrium between this liquid and the injected gas. Conversely, in normal crude oil reservoirs, both the oil and gas phases flow, but it has not been considered necessary to account for any vaporization of the reservoir liquid which might occur upon contact with the dry injection gas. Recently, high shrinkage reservoir fluids known as "volatile oils" have been found in increasing amounts. These oils are characterized by tank oil gravities above 4.5" API, solution gas-oil ratios above 1,000 scf/bbl, and reservoir volume factors above two. Special techniques have been devised for predicting depletion performance of reservoirs containing such oils.74.5.1; One of the characteristics of reservoirs producing volatile oils is that the reservoir gas phase carries a significant amount of oil which is recoverable as stock-tank liquid. This unusual vaporization be-havior implies that an appreciable amount of reservoir liquid would be vaporized upon contact of the oil with dry injection gas. In a gas-injection operation, tank oil recovery would he obtained not only through frontal displacement of the reservoir liquid by the injected gas, but also through production of the rich gas phase. This means that not only are improved methods needed to predict recovery of such oils from reservoirs undergoing gas injection, but it would also be expected that high oil recoveries might be obtained by such operations. When relatively dry gas is injected in to a volatile oil reservoir, phase equilibrium between the injected gas and the reservoir oil will tend to bc established. Initially the most volatile components, such as propane, the butanes and the pentanes, will account for most of the material transferred from the oil phase to the gas phase. As the partially stripped oil phase is contacted with additional dry injection gas, the heavier intermediate components, such as the hexanes, the heptanes and the octanes, will gradually transfer to the gas phase in increasing amounts. This is because the supply of lighter components in the oil phase dwindles due to the stripping action of the injected gas. This stripping action will usually continue to be effective down

Inflation, tight money and keen competition spur companies to consider advanced material handling systems capable of reducing cost per ton of moving ore, waste or men and supplies. Since transportation charges account for an average of about 25% of the total delivered price of a product, then this cost center may actually determine the economic value of a new deposit. This being so, it is interesting to note that of the 1.4 billion tons of revenue freight carried by all Class I carriers of the nation in 1967, over 247 million tons or 17.5% were industrial minerals or products dependent on industrial minerals, i.e., glass, gypsum board, brick, etc. Because most bulk commodities have a comparatively low market value and are usually classified for lower than normal freight rates, railroads rely on large volumes and better equipment utilization to effect an equitable return. It is for this reason that the unit and shuttle train concept came into being. The average rate per ton-mile of all materials hauled by rail in 1968 was 1.31 cents. The low rates existing for industrial minerals contributed to this low average as did unit and shuttle train rates.

Jan 10, 1969

By T. K. Prentice

The January-February number of the Journal of the Chemical Metallurgical and Mining Society of South Africa, 1943, is made up entirely of a discussion of Ball Wear in Cylindrical Mills. Following the principal paper by T. K. Prentice are several remarkably pertinent and carefully prepared discussions. Few persons in this country would be likely to see this publication, and since the information presented is new and of current interest, it seems desirable to abstract and review this publication for the benefit of the members of the A.I.M.E. The purpose of the investigation is stated in the first two paragraphs of Prentice's paper, as follows: Early in 1941, The Chamber of Mines Steel Products, Limited, initiated a series of tests under semi-working scale conditions to determine, if possible, those physical and chemical properties of a ball which make it resistant to wear when used in a cylindrical mill as a grinding medium, with the primary object of incorporating those beneficial qualities in the balls being produced at their works. This paper describes the tests carried out and discusses the results obtained. From these results it was possible to formulate a new theory relating to ball wear in cylindrical mills. This theory is presented in the second portion of this paper. Practical Ball-mill Tests in a Cylindrical Mill Part I of the paper begins with a discussion of the methods used for the manu- facture of grinding balls in South Africa. The following paragraph is of particular interest. The cast steel ingots, 4¼ in. square by 3 ft. 6 in. long, are re-heated in a gas-fired sloping stationary-hearth furnace and then rolled in a six-pass continuous mill into 25/8 in. round billets. Some of these billets are then removed and cut into suitable lengths for forging into 4 in., 3¼ in. , 3 in. or 2½ in. balls by means of three Drop and two Beche hammers, but the greater number, whilst still at about 1,000, pass directly into a set of scroll rolls which produce, in an ingenious manner, finished 3 in. balls direct from the 25/8 in. billets. Except in special cases, all balls are allowed to cool in the atmosphere and are not water quenched. Details of the Tests In order to enable the reader to evaluate properly the results and conclusions in the rest of the paper and in the discussions following the paper, most of the information presented by the author under this heading is quoted: The testing unit was a nominal 30 in. diameter and 18 in. long centre discharge Denver Ball Mill. The ore pulp to the ball mill comprised a small portion of the normal feed to one of the fourteen City Deep 5 ft. 6 in. X 22 ft. tube mills, and the grinding media consisted of the balls under test plus other balls to give the desired load. The running time of the test-mill was divided into approximately equal periods of five days 13½ hours each. The usual procedure was to examine and make up the load

Jan 1, 1947

By T. K. Prentice

The January-February number of the Journal of the Chemical Metallurgical and Mining Society of South Africa, 1943, is made up entirely of a discussion of Ball Wear in Cylindrical Mills. Following the principal paper by T. K. Prentice are several remarkably pertinent and carefully prepared discussions. Few persons in this country would be likely to see this publication, and since the information presented is new and of current interest, it seems desirable to abstract and review this publication for the benefit of the members of the A.I.M.E. The purpose of the investigation is stated in the first two paragraphs of Prentice's paper, as follows: Early in 1941, The Chamber of Mines Steel Products, Limited, initiated a series of tests under semi-working scale conditions to determine, if possible, those physical and chemical properties of a ball which make it resistant to wear when used in a cylindrical mill as a grinding medium, with the primary object of incorporating those beneficial qualities in the balls being produced at their works. This paper describes the tests carried out and discusses the results obtained. From these results it was possible to formulate a new theory relating to ball wear in cylindrical mills. This theory is presented in the second portion of this paper. Practical Ball-mill Tests in a Cylindrical Mill Part I of the paper begins with a discussion of the methods used for the manu- facture of grinding balls in South Africa. The following paragraph is of particular interest. The cast steel ingots, 4¼ in. square by 3 ft. 6 in. long, are re-heated in a gas-fired sloping stationary-hearth furnace and then rolled in a six-pass continuous mill into 25/8 in. round billets. Some of these billets are then removed and cut into suitable lengths for forging into 4 in., 3¼ in. , 3 in. or 2½ in. balls by means of three Drop and two Beche hammers, but the greater number, whilst still at about 1,000, pass directly into a set of scroll rolls which produce, in an ingenious manner, finished 3 in. balls direct from the 25/8 in. billets. Except in special cases, all balls are allowed to cool in the atmosphere and are not water quenched. Details of the Tests In order to enable the reader to evaluate properly the results and conclusions in the rest of the paper and in the discussions following the paper, most of the information presented by the author under this heading is quoted: The testing unit was a nominal 30 in. diameter and 18 in. long centre discharge Denver Ball Mill. The ore pulp to the ball mill comprised a small portion of the normal feed to one of the fourteen City Deep 5 ft. 6 in. X 22 ft. tube mills, and the grinding media consisted of the balls under test plus other balls to give the desired load. The running time of the test-mill was divided into approximately equal periods of five days 13½ hours each. The usual procedure was to examine and make up the load

Jan 1, 1947