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By Richard D. Dick

The Los Alamos National Laboratory was involved in an oil shale fragmentation research program in cooperation with a Consortium of industrial companies to investigate the feasibility of using modified in-situ (MIS) recovery of oil from oil shale. Field tests were conducted at the Anvil Points Mine, Colorado, in the thick oil shale beds of the Green River formation. Part of the program included obtaining data about fragmentation by instrumenting the tests with accelerometers, velocity gauges, and the CORRTEX technique (Continuous Reflectometry for Radius versus Time Experiments). Some of the rock motion data from accelerometer and velocity gauges is presented, along with some conclusions. In addition, the signal recording system is briefly explained. The CORRTEX technique is discussed, and some results on explosive performance and stem behavior using the method are discussed.

Jan 1, 1984

By George W. Sheary

Situated 45 miles west of Philadelphia and 50 miles southwest of Bethlehem Steel Company's Bethlehem plant, the integrated Grace mine facilities produce 4000 tpd of high-quality iron ore pellets. Startup of the Grace mill was in November 1958, and iron concentrates were shipped until March 1960, when the pellet plant went into operation. The underground mine, when fully developed, will hoist about 9000 tpd, including development rock. The crude ore, which has an iron content of approximately 42%, is magnetically cobbed and crushed in closed circuit with 3/4-in. slotted vibrating screens. The ore is washed and screened in the mill and the plus 1/4 in. screen product is again cobbed prior to feeding to the rod mills. Grinding is done in rod mills, and in ball mills that are in closed circuit with 30 in, cyclones, to 1% on 100 mesh and 65% minus 325 mesh. The ground ore is magnetically concentrated by three-drum permanent type finisher magnets to 67% Fe. The magnetite concentrate is pumped from the mill to a 50 ft thickener in the pellet plant. The thickened magnetite concentrate is relayed to the filters through a two-stage pump arrangement. The filter cake is fed by belt from filter concentrate bins to mixer-muller belts where it is intimately mixed with bentonite and a slight amount of water for moisture control. The fluffed concentrate then drops into balling cones. The green pellets from the balling cones are fed in a prescribed feed pattern to shaft furnaces through the use of shuttle car mechanisms. The green pellets are dried, heated to 2500°F and cooled to 1200°F as they descend through the furnace and into pellet coolers where the pellets are further reduced in temperature to 250°F. Heat is recovered in the cooling process through the use of air-to-air heat exchangers. The cooled pellets discharge on a rubber conveyor belt and are transferred to 6000-ton pellet railroad loading bin. The final pellet product consists of 90% plus 1/4 in. material (after tumble testing1) and contains 66% Fe plus 3% silica.

Jan 5, 1962

By D. S. Sanders, E. W. Witcomb

FLOTATION tests, from which the flowsheet for the concentrator was determined, were made in a pilot mill at Chuquicamata and later comparative testing of full size flotation cells was done at the Andes Copper Mining Co. concentrator in Potrerillos. The principal sulphide copper mineral is chalcocite with varying amounts of covellite, enargite, and chalcopyrite. The oxidized portion is principally antlerite, a green basic copper sulphate. The gangue minerals include quartz, sericite, pyrite, feldspars and kaolin. Chuquicamata pit ores have proved to be hard grinding. The results of the flotation and metallurgical work prove that good extraction and concentrate grade can be obtained under a rather wide range of conditions. Metallurgy In general the metallurgy of the ore requires a fairly close control of the grind to the primary rougher flotation and of the regrind of the primary rougher concentrate before cleaning. Regrinding is necessary to reduce the insoluble content of the final concentrate since a large part of the middling combinations are between the copper and silica minerals. The alkalinity of the pulps can vary between wide limits and control of the percent solids gives the desired grind. Alkalinity Control Arroyo Salado water is supplied to the concentrator head tanks. It contains about 5000 ppm of salts but test work shows no deleterious effect. Actually this water permits a decrease of as much as 1 lb of lime per ton of ore as compared to San Pedro water, which is used for leaching oxide ore. About one quarter of the water flow through the concentrator will be new water from the reservoir. The remainder will be reclaimed from the thickeners. For primary grinding and rougher flotation, new and reclaimed water are combined in the head tanks. To avoid erratic results, only new water is used in the regrind system. Milk of lime is added to the rod mill feed chute to obtain the maximum benefit of mixing with the ore. This protects the equipment from corrosion due to entrained acids and soluble copper salts. Lime consumption is 3 to 5 lb per ton of ore. Grinding and Flotation The six bin gates over each belt feeder are opened in controlled combination and sequence to keep a live bed of ore in the bin to prevent arching and to obtain mixing. The milk of lime added ahead of the rod mill is regulated to suit rougher flotation requirements. The primary promoter reagent, Aerofloat 238, is added to the 10-mesh discharge of the rod mill as it is laundered to the ball mill scoop box. The classifier overflow is regulated to produce a grind of about 12 to 15 pct +65 mesh and 60 pct -200 mesh. A secondary promoter Z-4 (aml zanthate) and the pine oil frother are added in the overflow launder where a pH of 10 to 11 is maintained. Comparatively heavy beds of froth on the

Jan 1, 1952

By T. S. Spicer, C. C. Wright, R. G. Bowman

IN recent years considerable publicity has been given to the problem of atmospheric pollution by fuel-burning equipment. Legislation has been stimulated and smoke ordinances have been enacted, the provisions of which show a definite trend toward stricter control of the emissions not only from the stacks of industrial fuel users but also from the chimneys of domestic consumers. As a result of war conditions, some slackening in the enforcement of these ordinances may be noted, but this is only a temporary expediency caused by the changes necessary in the distribution of the nation's fuel supplies and difficulties in securing the necessary equipment. Previous trends may be expected to continue in the postwar period. Largely because of the consumer demand for automatic heat, but partly because of the legislation against smoke emission, there has been a marked increase in the use of domestic underfeed stokers with the past decade. When correctly adjusted and operated, these units reduce the smoke emission materially, so that even the high-volatile bituminous coals may be burned with little or no emission of objectionable smoke. Unfortunately, however, the use of the domestic underfeed stoker introduces another problem; namely, fly-ash. PRODUCTION OF FLY-ASH The term "fly-ash" is a misnomer, since the fly material is generally a mixture of small carbonaceous particles varying from green coal to coke, and inorganic particles ranging from fluffy ash to small particles of fused clinker. For want of a more comprehensive name, however, the term fly-ash is used throughout this paper to include all the fly material. Even with hand-fired furnaces a certain amount of fly-ash is produced, which necessitates periodic cleaning of the boiler flues or furnace radiator, the smoke pipe, and occasionally the chimney itself. With stoker operations the amount of fly-ash is increased many fold, because of the higher velocity of air travel through the fuel bed. Frequently the amount of this fly-ash attains such proportions as to constitute a definite nuisance to the householder and his neighbors and distracts very materially from the otherwise automatic or semi-automatic performance of the stoker. Virtually all the boilers and hot-air furnaces marketed in the domestic field

Jan 1, 1944

By Frank T. Weems

The basic operating properties of the DorrClone are discussed and certain metallurgical applications which exploit these properties are presented. An effective method of controlling the consistency of the DorrClone underflow is described. THIS paper presents in a general manner some of the applications of the DorrClone (Dutch States Mines cyclone) in the metallurgical and heavy chemical fields. Technical or mathematical analyses of the design factors and of the mechanism whereby the cyclone effects its separation have been capably treated in a series of previous papers.'-' Engineering and operational aspects of a few installations and laboratory tests have been chosen to emphasize the unique classification characteristics of the DorrClone and to illustrate its utility in certain difficult situations. Its use in coal washing and heavy-media operations are not considered. Some 25 or more industrial installations and applications of the DorrClone in the metallurgical fields are operating at present, ranging from single trial units to complete batteries composed of a multiplicity of units. The data were obtained in part from some of these, and in part from operations of units at the Westport Mill, the laboratories and testing plant of the Dorr Co. at Westport, Conn. The DorrClone was developed, in principle, by the research dept. of the State Mines, Limburg, Holland, during World War 11. Its first use was to dewater a —50 micron sand used as a dense medium in coal washing. The metallurgical wet cyclone was first publicized by Driessen and Yancey and Geer.6 ince then the cyclone has been studied as a means of de-watering, heavy media concentration, and fine size classification. The DorrClone is shown in Figs. 1 and 2. pulp to be treated is pumped through the feed nozzle, A, into the feed cylinder, B. The feed nozzle is of rectangular cross-section, the outermost edge being tangent to the feed cylinder walls. Feed shims, C, may be attached to the innermost walls to adjust the open area of the feed nozzle available to entering pulp. The tangential injection of feed under pressure supports the vortex action of the pulp that has been detained in the cyclone; the centrifugal forces of this vortex throw the coarse particles to the walls of the cone, D, where they collect and pass downward and out through the adjustable apex opening, E. The fine particles contained in most of the water that entered with the feed pulp move to the inner spiral of the vortex and flow out through the vortex finder, F, contained in the orifice plate, G, which forms the top of cyclone chamber. The overflow pulp may then spray freely into a spray chamber, H, surmounting the cyclone or pass directly into a 90' elbow, I, of somewhat larger diameter than the vortex finder. Installation Where more than one cyclone is to be installed, best overall efficiency and ease of control are obtained with equal distribution of both pulp volume and weight of solids among the cyclones, and with the same pressure being maintained at each cyclone feed nozzle. Fig. 3 is a suggested arrangement for feeding two or more cyclones in parallel. Feed pressure control: Under normal operating conditions it is not unusual for some surge to exist in the feed that is to be sent to the cyclone. As will be discussed later, surges in the solids content of the pulp are usually not of great operational consequence, but surges in feed volume are a problem. Several systems have been devised for absorbing surges in feed volume, each involving a surge tank. If the surges are small and fairly rhythmical, a tank of sufficient size might be installed to dampen out

Jan 1, 1952

By K. Reinhardt

The idea of burning blast-furnace gases directly in gas-engines, instead of under steam-boilers, as had previously been done, was first put into practice barely ten years ago, almost simultaneously in Great Britain, Germany and Belgium. The pioneers of this movement made their first experiments with small engines. After these experiments had given satisfactory results, and it had been shown that the thermal value of the poor blast-furnace gases, in spite of defective scrubbing, could with safety be directly transformed into mechanical work in the gas-engine, there very soon arose a considerable demand for gas-engines of large power, similar to the large steam-engines employed in metallurgical works. In face of these sudden requirements, the gas-engine builders were placed in a difficult position; for up to that time the gas-motor was considered as suitable for small engines only, and it was generally believed that the limit of size had been attained with 100 to 150 effective h.p. in a single cylinder. Manufacturers of gas-motors, however, did not underrate the advantages offered by this new field for their manufactures, and it so happened that in Germany the Berlin-Anhaltische Masch-inenbau-Gesellschaft, of Dessau, was the first to undertake the construction of a 600-h.p. two-cycle gas-engine, with two cylinders of the Oechelhauser-Junkers type, for the Hoerder Mining & Smelting Company. The engine was started in 1898, and, with a few improvements and alterations, is still working satisfactorily. This engine worked with astonishingly high effciency, considering the period. The builders were therefore

Jan 1, 1907

James GayleY, New Pork City (communication to the Secretary*) :—The main thing that is sought after in this matter is that all purcliases shall be made by analysis. This is done already in special lines, as in the manufacture of various grades of steel in which phosphorus, silicon and sulphur are specified within narrow limits, and I quite agree with Mr. Cook that specifications, which are over-rigid in unessential particulars, should be avoided, as they defeat their own purpose because unreasonable requirements permitting no variation are practically not fulfilled, and it is impossible to specify grade

Jan 1, 1905

By O. L. Culberson, J. J. McKetta

INTRODUCTION The equilibrium constants for methane and for water, and for ethane and water have been calculated from experimental data for the two binary systems.2,3,11,12 These constants are for the two-phase systems for the temperature range of 100" to 340°F and the pressure range of 200 to 10,000 psia. The constants for ethane are greater than those for methane. Equilibrium constants for a natural gas from a natural gas-water system6 are about the same as those for methane. Equilibrium constants for water in all three systems are very nearly the same over the greater part of the range of temperatures and pressures studied. In ideal solutions, the vapor-liquid equilibrium constants for a component should be the same in all such solutions at a given temperature and pressure.5 Few solutions are ideal, and consequently the use of generalized constants often leads to error in situations where they do not actually apply. In decidedly non-ideal systems, it is desirable to have equilibrium constant data for the specific system. Vaporization equilibrium constants may be calculated either by thermodynamic methods or from experimental vapor-liquid equilibrium data. In the thermodynamic calculation. the equilibrium constant K may be shown to be" K = fP,/fl'..........(1) where fPi is the fugacity of the pure component i at the given temperature and at the vapor pressure of the pure component, and fp is the fugacity of pure i in the gaseous state at the temperature and total pressure of the system. At best the thermodynamic calculation results in a K applicable to ideal solutions. Equilibrium constants calculated from Equation (1) have been found to have only limited agreement with experimental values, even though the solutions for which they were calculated approached ideality."'" If the more volatile component is at a temperature above its critical, the accuracy of the equilibrium constant for the component is made more doubtful by the use of the vapor pressure term under such conditions. In order to make the thermodynamic calculation on a component above its critical temperature, one must resort to one of the empirical methods of extrapolation of the vapor pressure to conditions above its critical point.13 Application of the thermodynamic equilibrium constant then to the methane-water or the ethane-water systems would be risky since the systems are non-ideal, and the methane and ethane are above their critical in most petroleum operations. ETHANE-WATER SYSTEM In the temperature range of from 100° to 340°F and for pressures up to 10,000 psia, the vapor-liquid equilibrium data 'References given at end of paper. Manuscript received in the office of the Petroleum Branch March 16, 1951.

Jan 1, 1951

By J. J. McKetta, O. L. Culberson

INTRODUCTION The equilibrium constants for methane and for water, and for ethane and water have been calculated from experimental data for the two binary systems.2,3,11,12 These constants are for the two-phase systems for the temperature range of 100" to 340°F and the pressure range of 200 to 10,000 psia. The constants for ethane are greater than those for methane. Equilibrium constants for a natural gas from a natural gas-water system6 are about the same as those for methane. Equilibrium constants for water in all three systems are very nearly the same over the greater part of the range of temperatures and pressures studied. In ideal solutions, the vapor-liquid equilibrium constants for a component should be the same in all such solutions at a given temperature and pressure.5 Few solutions are ideal, and consequently the use of generalized constants often leads to error in situations where they do not actually apply. In decidedly non-ideal systems, it is desirable to have equilibrium constant data for the specific system. Vaporization equilibrium constants may be calculated either by thermodynamic methods or from experimental vapor-liquid equilibrium data. In the thermodynamic calculation. the equilibrium constant K may be shown to be" K = fP,/fl'..........(1) where fPi is the fugacity of the pure component i at the given temperature and at the vapor pressure of the pure component, and fp is the fugacity of pure i in the gaseous state at the temperature and total pressure of the system. At best the thermodynamic calculation results in a K applicable to ideal solutions. Equilibrium constants calculated from Equation (1) have been found to have only limited agreement with experimental values, even though the solutions for which they were calculated approached ideality."'" If the more volatile component is at a temperature above its critical, the accuracy of the equilibrium constant for the component is made more doubtful by the use of the vapor pressure term under such conditions. In order to make the thermodynamic calculation on a component above its critical temperature, one must resort to one of the empirical methods of extrapolation of the vapor pressure to conditions above its critical point.13 Application of the thermodynamic equilibrium constant then to the methane-water or the ethane-water systems would be risky since the systems are non-ideal, and the methane and ethane are above their critical in most petroleum operations. ETHANE-WATER SYSTEM In the temperature range of from 100° to 340°F and for pressures up to 10,000 psia, the vapor-liquid equilibrium data 'References given at end of paper. Manuscript received in the office of the Petroleum Branch March 16, 1951.

Jan 1, 1951

By Herbert A. Stein, John B. Murdock

AN analysis of perlite expansion furnaces must be based upon one consistent theory which explains how and why perlite does expand when heated. There is more than one such theory, so to establish a basis for the rest of this paper, the authors will outline one theory and the data that support it before going into the construction details of different furnaces. JOHN B. MURDOCK, Associate Member AIME, is President, and HERBERT A. STEIN is Secretary, of the Perlite Corp., Phoenix, Arizona. San Francisco Meeting, February 1949. TP 2736 H. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Jan. 3, 1949. Why Perlite Expands: Perlite is known to contain some dissolved or combined fluid, probably water, which is lost when the material is heated to fusion. It is generally agreed that when particles of this volcanic glass are heated to fusion in such a way that vaporization of this water into steam takes place at the same time as the glass becomes soft, the steam puffs up each particle into a mass of glass foam. It is a simple matter to expand perlite under a blow torch for demonstration purposes, but in commercial installations, the problem is made more complicated by the necessity of making efficient use of both raw material and fuel, and producing an expanded aggregate conforming to close specifications for size distribution and density, using many different types of perlite rock. The ability of a given operation to fulfill these requirements depends upon the proper handling of four variables. They are: (1) the nature of the perlite rock used, (2) the heating time taken to get the perlite particle up to its highest temperature, (3) the size of the particle, and (4) the maximum temperature the particle reaches. Types of Perlite Rock: Perlite may be classified in many ways, but the characteristics most easily correlated with its behavior in furnaces are its softening temperature, its effective water content, and its "liveliness." Actually there is a close correlation among these three characteristics so it is possible to describe a perlite using any one of them. Lively perlites always have low softening temperatures and high effective water contents, whereas the deader perlites have higher softening temperatures and lower effective water contents. These softening temperatures run from 1400°F to above 2000°F and the effective water contents run from over 2 pct down to 0.2 pct. Included in the category of lively glasses are the green pitchstone from the Edgar claim in Superior, Ariz., the red pitchstone on the Animas highway south of Lordsburg, N. Mex., and a gray glass from Beatty, Nevada. Examples of intermediate perlites (in order of decreasing liveliness) are the Guzman-Lobb perlite with obsidian

Jan 1, 1951

By Herbert A. Stein, John B. Murdock

AN analysis of perlite expansion furnaces must be based upon one consistent theory which explains how and why perlite does expand when heated. There is more than one such theory, so to establish a basis for the rest of this paper, the authors will outline one theory and the data that support it before going into the construction details of different furnaces. JOHN B. MURDOCK, Associate Member AIME, is President, and HERBERT A. STEIN is Secretary, of the Perlite Corp., Phoenix, Arizona. San Francisco Meeting, February 1949. TP 2736 H. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscript received Jan. 3, 1949. Why Perlite Expands: Perlite is known to contain some dissolved or combined fluid, probably water, which is lost when the material is heated to fusion. It is generally agreed that when particles of this volcanic glass are heated to fusion in such a way that vaporization of this water into steam takes place at the same time as the glass becomes soft, the steam puffs up each particle into a mass of glass foam. It is a simple matter to expand perlite under a blow torch for demonstration purposes, but in commercial installations, the problem is made more complicated by the necessity of making efficient use of both raw material and fuel, and producing an expanded aggregate conforming to close specifications for size distribution and density, using many different types of perlite rock. The ability of a given operation to fulfill these requirements depends upon the proper handling of four variables. They are: (1) the nature of the perlite rock used, (2) the heating time taken to get the perlite particle up to its highest temperature, (3) the size of the particle, and (4) the maximum temperature the particle reaches. Types of Perlite Rock: Perlite may be classified in many ways, but the characteristics most easily correlated with its behavior in furnaces are its softening temperature, its effective water content, and its "liveliness." Actually there is a close correlation among these three characteristics so it is possible to describe a perlite using any one of them. Lively perlites always have low softening temperatures and high effective water contents, whereas the deader perlites have higher softening temperatures and lower effective water contents. These softening temperatures run from 1400°F to above 2000°F and the effective water contents run from over 2 pct down to 0.2 pct. Included in the category of lively glasses are the green pitchstone from the Edgar claim in Superior, Ariz., the red pitchstone on the Animas highway south of Lordsburg, N. Mex., and a gray glass from Beatty, Nevada. Examples of intermediate perlites (in order of decreasing liveliness) are the Guzman-Lobb perlite with obsidian

Jan 1, 1951

By John H. Schilling

The Gabbs magnesite-brucite deposit is unique in size and is one of two magnesite deposits being exploited in the United States. It is near the town of Gabbs, which is one hundred miles southeast of Reno, in west-central Nevada. The brucite was discovered in 1927; the magnesite was found while exploring the brucite. During World War II, more than 80,000 tons of magnesium metal was produced from about 900,000 tons of magnesite ore mined from these deposits. An additional 5,000,000 tons of magnesite and 1,000,000 tons of brucite have been produced for use in making magnesia refractories and chemicals. Basic Inc., presently the only producer, mines 1.5 ± 0.25 million tons of ore and waste annually using high-selective open-pit rriethods; the ore is up-graded, calcined, and processed into a variety of products. Known reserves of highgrade (less than 5 per cent CaO) magnesite ore total more than 25,000,000 tons, and there are larger tonnages of lower-grade material; brucite reserves are small. The magnesite and brucite are in generally west-dipping dolomite of the upper member of the late Triassic Luning Formation, in the over-riding plate of the Paradise thrust fault. A great variety of dikes and a stock of Cretaceous granodiorite intrude the Luning Formation in the vicinity of the magnesite-brucite deposit. The magnesite bodies are scattered over an area of about a square mile around a prong of granodiorite which extends north from the stock. The brucite is mainly in two bodies in contact with the prong of granodiorite; at the surface and along deeper cracks the brucite has weathered to hydromagnesite and artinite. In the area of magnesite-brucite mineralization, much of the dark, fine-grained, schistose, regionally-metamorphosed dolomite of the Luning Formation has been marmorized to a lighter-colored, coarser-grained, massive dolomite that is intergrown in varying proportions with the magnesite. The magnesite and marmorized dolomite can not be distinguished visually. In addition to the two varieties of dolomite, the gangue in the magnesite and brucite bodies mainly is the various varieties of dike rock, serpentine and a variety of other "contact" minerals, and "post-ore" dolomite and calcite. The magnesite ( and recrystallized dolomite) is believed to have formed by the hydrothermal replacement of the regionally metamorphosed sedimentary dolomite; alternatively it has been suggested that the magnesite is sedimentarv and formed contemporaneously with the dolomite in an embayment of the Triassic sea. Because all the igneous rocks exposed in the immediate vicinity of the magnesite deposits appear to be younger than the magnesite, the ore-forming solutions are thought to be related to a somewhat older granite which crops out elsewhere in the area. The brucite is the result of contact-metasomatic replacement of magnesite during the emplacement of the granodiorite stock.

Jan 1, 1968

By Byron B. Morton

NICKEL-BEARING alloys are associated with petroleum in the fields of exploration, production, and refining. In the first- named field the geologist of today makes use of such instruments as the seismograph, torsion balance, and magnetometer, the selection of proper alloys and metals for the manufacture of which is an important matter. Nickel-bearing alloys are useful for parts that require resistance to corrosion or that must have non-magnetic properties. Where special co- efficient of thermal expansion are de- sired, they are obtained by using alloys high in nickel (20 to 60 per cent), since, by varying the nickel contents, alloys can be obtained ranging fro111 "Invar", with a low expansion between -40 and 175 cleg. F., to those with coefficients of expansion exceeding that of steels. The latter are obtained by additions of chromiurn to the alloys. Alloys containing 50 to 80 per cent of nickel, which possess high magnetic permeability, find application in certain instruments where this property is important.

Jan 1, 1935

It is doubtful if the far-reaching sociological influence and effects of the last few years will be fully appreciated within the present generation, but there are certain lessons and morals already apparent from which we should profit immediately. One of these has been an insistent, though vague, feeling among engineers and men of technical training and experience, that their worth as political and economic factors is not recognized by society. This feeling has found expression first in a tendency on the part of these men to organize for the purpose of securing recognition, or to demand greater activity in their interest on the part of societies already organized. However it may be accomplished, the demand for some means of binding engineers together for purposes of self-interest and public good is in the air and will not be denied. In other words, the time is' propitious for two things: vastly increasing the membership of engineering societies, and serving that membership according to its desires. There are particular reasons why every mining and metallurgical engineer, in the United States at least, should hold membership in the

Jan 6, 1919

By E. P. Mathewson

DURING the past 35 years it has been my privilege to deal with hundreds of recent graduates from engineering schools all over the world. In consequence, I, feel that I have learned something about the training of, engineering students. In the first place, I believe that too great specializa-tion is a mistake. A student should receive general training in engineering for at least three out of the four years of the course, and any specializing that may be required should come in the fourth year. Too great emphasis can not be laid upon the fact that the four years' training does not make an engineer; on the contrary, the graduate is only fitted to enter the pro-fession. He becomes an engineer in the true sense of the word only after years of practice; the college train-ing merely shows him where to look for information and develops his intellectual powers. Some of our engineering schools have lengthened the term of study to five years and talk of increasing it still further. This, in my opinion, is a mistake. A young man who spends more than four years in college is apt to become too academic and theoretical. It is better to stiffen the matriculation examinations than to prolong the years of study in college. No matter how good the faculty may be and how carefully selected the course of study, the graduate can never become an engineer unless he has some natural qualifications for the vocation. There are one or two subjects in which most recent graduates seem to be weak; these are accounting, the command of English, and training in the writing of reports. A short course in general accounting should always be included in the curriculum. To this should be added instruction in the preparation of estimates and cost statements. In making reports it should be borne in mind that these reports are to be submitted to busy men,-and not to technical men. The busy man wants the gist of the report summarized on the front page of the report. He wants to know that if he expends a certain sum of money in a certain way, he will get certain results and make so much profit. This should be put clearly before him in short statements, free from technical terms. The details of the report can follow .at greater length; it should be remembered that the employer is not going to read these details, but will confine his attention to the summary.

Jan 1, 1923

By J. C. Cook

In solution-mining of underground salt and similar minerals, using drilled wells for access, it is desirable to monitor the lateral growth pattern of the resulting fluid-filled cavern. Therefore, a process of seismic surveying from the surface of the ground has been conceived in which the amplitudes of waves reflected from and transmitted through the soluble formation are measured. The large acoustic impedance contrast between solid and fluid should produce striking amplitude anomalies, especially if shear waves are employed, since thick fluid bodies are opaque to shear waves. Horizontally-polarized (SH) shear waves are best for preventing conversion to P waves at the numerous horizontal interfaces in the ground. Field tests to date have shown that a truck-mounted, half-ton hammer striking horizontally against the end of a trench produces usable SH-wave energy at lateral distances up to about 850 ft. Horizontally-directed explosive wave sources were effective to about 2000 ft. Conventional magnetic-tape recording and processing were used, but with the detecting geophones oriented to favor SH waves. An irregular solution cavity in bedded salt at 500-ft depth has apparently been located by SH-wave and SV-wave reflections. Further field work is planned to corroborate and extend this result. The Brine Cavity Research Group, an association of 11 chemical and salt producing companies, is supporting this work. Major deposits of salt in tabular beds lie beneath some 300,000 sq miles of land in the central and northeastern U.S. This salt is a basic source of soda ash and chlorine, and has been extracted as brine from drilled wells for about a century. During the past two decades, the U.S. solution-mining industry, following the lead of European operators, has greatly improved the extraction process through the application of engineering and science.' In 1957, the Brine Cavity Research Group, an association of 11 chemical and salt producing companies, was formed. This group proceeded to attack certain common problems through the support of research. An outstanding problem has been that of determining the shape and location of the growing solution cavities in the underground salt, so that measures can be taken to maintain operating efficiency. The problem has been partially solved by the Dowel1 sonar mapping service, which employs a pulse-echo device lowered into the cavity through the well.2 However, the working range of this equipment is at present insufficient for large cavities, and echoes are not returned from highly sloping walls nor from behind such obstructions as rock debris. Therefore, an independent means of mapping the cavity, for example, from the surface without interfering with operation of the well, would be desirable. THEORY OF THE METHOD Seismic waves are the only physical agent known to be capable of sufficient resolution and penetration to define typical solution cavities from the surface of the ground. The geometry is unfavorable: cavity widths are generally less than half their depths below the surface; resolution and lateral location of boundaries and channels to within 50 ft at depths of 500 to 3000 ft is desirable. Conventional seismic surveying, as used for petroleum prospecting, is probably not the answer: isopach mapping, for example, is not thought accurate enough to define the cavity by the slight additional delay time it would introduce (of the order of 0.005 sec for a 50 ft-thick cavity in hard Paleozoic rocks). Refraction surveying has also been considered, but seismic specialists see little promise in it for this problem. In 1957, in correspondence with industry personnel, the writer suggested a seismic method based upon careful measurement of reflection amplitudes. As Table I illustrates, seismic reflection coefficients r for typical brine-rock interfaces are considerably higher than those for typical interfaces between different kinds of solid rock. This fact can be utilized in two ways, illustrated in Fig. 1: 1) If the cavity roof is reasonably flat (which it may sometimes be since the unsaturated top brine will be in contact with an insoluble rock stratum), extra-strong seismic reflections will be received from the salt stratum where the solid has been replaced by liquid.

Jan 1, 1964

By G. J. Dickman, W. N. Thomas

The factors involved in selecting, a drive system for a grinding mill, including gearing arrangement, motor selection, and electric-supply system limitations are reviewed. Equipment costs are evaluated on a dollar per horsepower basis and starting performance is analyzed, the latter making use of a recently developed computer program. The present interest in large-diameter grinding mills and the rapidly rising cost of the drive in proportion to the cost of the mill establishes a need to explore the drive system in detail. The drive for a 7 to 8,000 hp mill will cost from $350 to $600,000 which represents nearly half the total cost of the mill package, and requires as much building space as the mill proper. Some of the drive components require a longer time to manufacture and the installation time and costs are equal to those for the mill. It is apparent that the drive has become a dominant factor in the overall mill design consideration. A new plant requires a tremendous investment in both time and money. With the high degree of competition in the mining industry, low capital cost is an exceedingly important factor in the development of a project. It is just as important, however, to insure that the equipment is going to perform satisfactorily for the anticipated life of the project without adding unplanned operating, maintenance, and replacement costs. This is the position in which the engineer or designer usually finds himself and is really one of his primary functionsestablishing a realistic compromise between cost and performance. Large primary grinding mills can represent a major portion of the cost of a plant and the drive system accounts for a substantial part of this cost. These facts justify a careful analysis of the drive requirements and all of the factors involved in ultimately arriving at the best system for the lowest cost. A number of excellent papers have been published on various aspects of mill drives. The authors have used information from these papers in making a study of a drive for a 7600-hp, 32 x 12-ft autogenous mill. This was a broad investigation, including mechanical and electrical design, layout, performance, and maintenance considerations, and overall economics leading to the selection of the optimum system for that mill. This paper was developed from the study and includes information applicable to large mills in general. For a successful and economical application, the drive must be considered as a system and all of the components analyzed to determine their effect on the system. This requires the participation of the mill designer, gear, and other mechanical component manufacturers, motor manufacturer, plant designer, and operator. A careful analysis of the mill torque requirements is first necessary to provide a basis for selection of the mechanical and electrical drive components. Because of manufacturing limitations on the size and capacity of gearing available for these low-speed applications, an evaluation of costs for various gear ratios and configurations in conjunction with motor speeds is required. Consultation with the power-supply company is necessary to determine limitations on motor-starting disturbances and to analyze operating costs on the basis of existing rate structures and low characteristics. Finally, consideration must be given to the drive arrangement and its affect on plant layout, space requirements, and location of auxiliary equipment for the selected process. There are presently three basic schemes for driving a mill. The first is a direct drive by a motor operating at mill speed with no gearing. The second is by a higher-speed motor through a trunnion-connected gear drive. The third is by a motor through the more conventional pinion and ring-gear with the option of an interposing gear box to permit greater motor speed than pinion shaft speed. [(Fig. 1.)] Several manufacturers have or are presently developing motors which drive the mill directly without the use of gears. One arrangement has the motor armature intimately surrounding the mill shell-discharge spout or extension of the trunnion journal. The motor stator is then supported independently and surrounds the shell or trunnion-mounted rotor. Another variation utilizes an independent mill-speed motor connected to the trunnion by a drive shaft and flexible couplings.

Jan 1, 1972

By C. C. Wright, T. S. Spicer, R. G. Bowman

In recent years considerable publicity has been given to the problem of atmospheric pollution by fuel-burning equipment. Legislation has been stimulated and smoke ordinances have been enacted, the provisions of which show a definite trend toward stricter control of the emissions not only from the stacks of industrial fuel users but also from the chimneys of domestic consumers. As a result of war conditions, some slackening in the enforcement of these ordinances may be noted, but this is only a temporary expediency caused by the changes necessary in the distribution of the nation's fuel supplies and difficulties in securing the necessary equipment. Previous trends may be expected to continue in the postwar period. Largely because of the consumer demand for automatic heat, but partly because of the legislation against smoke emission, there has been a marked increase in the use of domestic underfeed stokers with the past decade. When correctly adjusted and operated, these units reduce the smoke emission materially, so that even the high-volatile bituminous coals may be burned with little or no emission of objectionable smoke. Unfortunately, however, the use of the domestic underfeed stoker introduces another problem; namely, fly-ash. Production of Fly-ash The term "fly-ash" is a misnomer, since the fly material is generally a mixture of small carbonaceous particles varying from green coal to coke, and inorganic particles ranging from fluffy ash to small particles of fused clinker. For want of a more comprehensive name, however, the term fly-ash is used throughout this paper to include all the fly material. Even with hand-fired furnaces a certain amount of fly-ash is produced, which necessitates periodic cleaning of the boiler flues or furnace radiator, the smoke pipe, and occasionally the chimney itself. With stoker operations the amount of fly-ash is increased many fold, because of the higher velocity of air travel through the fuel bed. Frequently the amount of this fly-ash attains such proportions as to constitute a definite nuisance to the householder and his neighbors and distracts very materially from the otherwise automatic or semi-automatic performance of the stoker. Virtually all the boilers and hot-air

Jan 1, 1944

By T. S. Spicer, C. C. Wright, R. G. Bowman

In recent years considerable publicity has been given to the problem of atmospheric pollution by fuel-burning equipment. Legislation has been stimulated and smoke ordinances have been enacted, the provisions of which show a definite trend toward stricter control of the emissions not only from the stacks of industrial fuel users but also from the chimneys of domestic consumers. As a result of war conditions, some slackening in the enforcement of these ordinances may be noted, but this is only a temporary expediency caused by the changes necessary in the distribution of the nation's fuel supplies and difficulties in securing the necessary equipment. Previous trends may be expected to continue in the postwar period. Largely because of the consumer demand for automatic heat, but partly because of the legislation against smoke emission, there has been a marked increase in the use of domestic underfeed stokers with the past decade. When correctly adjusted and operated, these units reduce the smoke emission materially, so that even the high-volatile bituminous coals may be burned with little or no emission of objectionable smoke. Unfortunately, however, the use of the domestic underfeed stoker introduces another problem; namely, fly-ash. Production of Fly-ash The term "fly-ash" is a misnomer, since the fly material is generally a mixture of small carbonaceous particles varying from green coal to coke, and inorganic particles ranging from fluffy ash to small particles of fused clinker. For want of a more comprehensive name, however, the term fly-ash is used throughout this paper to include all the fly material. Even with hand-fired furnaces a certain amount of fly-ash is produced, which necessitates periodic cleaning of the boiler flues or furnace radiator, the smoke pipe, and occasionally the chimney itself. With stoker operations the amount of fly-ash is increased many fold, because of the higher velocity of air travel through the fuel bed. Frequently the amount of this fly-ash attains such proportions as to constitute a definite nuisance to the householder and his neighbors and distracts very materially from the otherwise automatic or semi-automatic performance of the stoker. Virtually all the boilers and hot-air

Jan 1, 1944

Discussion of the paper of LAWRENCE ADDICKS, presented at the Salt Lake meet-ing, August, 1914, and printed in Bulletin No. 91, July, 1914, pp. 1671 to 1674. JAMES H. PAYNE, Baltimore, Md. (communication to the Secretary*). -Mr. Addicks's account of the behavior of the nodulizer at Chrome on blast-furnace flue dust leads me to outline what has been done so far upon the application .of the same apparatus to fine sulphide concentrates. As Mr. Addicks states in his paper, the conditions prevailing in the test kiln at Yorktown in the demonstration I made for him upon Chrome material were strongly oxidizing; so much so that the sulphur was roasted down to less than 1 per cent. It is therefore to be expected that the first test made upon sulphide ore a short time after this, in which Ducktown green ore fines were used, did not show very promising results. Although the Ducktown ore contained only 13.52 per cent. of sulphur its gangue was quite fusible, and the intense heat generated by the oxidation of. the extremely fine sulphide particles slagged the mass, bringing about a condition approximating that of a Brückner roaster in distress. During the spring and summer of 1912, the writer kept working upon different schemes to cut clown this slagging. Two successful methods were finally worked 'out embodying opposite principles, one promoting oxidation of the finer particles and the other retarding. their oxidation. In the early part of the present year the writer succeeded in interesting the Braden Copper Co. in nodulizing, with the result that an extensive series of tests were made at Yorktown upon oil-floated concentrates covering quite a wide range in analysis. These tests led to trials in the Chrome rotary on the part of the U. S. Metals Refining Co. of Minerals Separation concentrates which they had in stock, and later to test runs to check up the Yorktown runs on Braden concentrates. The large-scale tests checked up with the Yorktown tests in every way (except fuel consumption, which was, however, correctly predicted), and led to the Braden company's decision to adopt the process at Braden. The fuel consumption upon oil-floated concentrates is not over 6 gal. per ton and in many cases is less. The action in the furnace is independent of the sulphur content, and there is actually less tendency to form nose rings in the Chrome rotary than upon flue dust. It is believed that the improvements entering into the design of the Braden kilns will cut down the nose-ring trouble to where it will no longer be a drawback to the process.

Jan 11, 1914