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By William Kelly, F. H. Armstrong

The object of this paper is to describe the electric equipment at the iron-ore mines of Penn Iron Mining Co., Vulcan, Mich. and of Republic Iron Co., Republic, Mich.; to give the results of tests; and to discuss the methods in use from an operating as well as from an efficiency standpoint. Electricity was introduced at the Penn mines for pumping, hoisting, and compressing air in the spring of 1907, upon the completion of a hydro-electric plant built by that company on the Menominee river about 4 miles from the mines. This plant was described in a paper1 presented before the Lake Superior Mining Institute. A paper2 presented at a meeting of the same Institute describes some of the operating features, and the safety devices of the electric hoist at the Curry shaft were briefly described in the Proceedings of the First Co-operative Safety Congress held under the auspices of the Association of Iron and Steel Electrical Engineers at Milwaukee, Wis., Sept. 30 to Oct. 5, 1912. Generating PoweR Plants After the success of electrical operation was assured, a second set of water wheels and generator was installed at the falls, for which provision had been made in the original design and in the construction of the foundations, and later three additional wires were added to the main transmission line, doubling its capacity and reducing the line loss. The general conditions of this installation are particularly favorable for hydro-electric operation. In the neighborhood of three-fourths of the power used is for mine pumping, which in the main is regular and continuous. For air compressing, power is used for about 18 hr. a day for five days, and 9 hr. for one day in the week, though occasionally when shaft sinking is going on a very small amount of compressed air may be

Jan 1, 1915

By F. E. Buch

THE Smelter is designed for a production capacity of 10,000 short tons of blister copper per month, when operating on the present concentrate grade. The Smelter lay-out is shown in Fig I. The major units of equipment comprise two reverberatory furnaces, three 13 by 30 ft Peirce-Smith converters, two straight line casting machines, one being served by a 13 by 30 ft holding furnace and the other by a ladle tilting quadrant, two converter ,aisle cranes and two converter blowers. The plant is compact and the general arrangement of standard gauge railway tracks and conveyor belts provides for a smooth flow of incoming materials and metallurgical products. Concentrate is received by conveyor belts and fluxes in standard railway trucks. The local track system is covered by an electric trolley locomotive. The Smelter treats a wet (10 pct moisture) flotation concentrate containing approximately 53 pct total copper and 0.9 pct oxide copper. The predominating minerals are chalcocite, chalcopyrite and bornite accompanied by small quantities of malachite and cuprite. The gangue is highly siliceous and requires limerock as a flux. Metallurgy would be straightforward were it not for the necessity for eliminating k bismuth which occurs as an impurity in the ore along with the copper. Directly or indirectly most of the Smelter problems can be traced to the necessity for bismuth removal. Copper recovery, based on new copper treated, averages 97.5 pct. GENERAL DESCRIPTION Flotation concentrate, containing to pct moisture, is conveyed from the filter plant to the smelter storage bins by conveyor belts, the material being weighed in transit by a revolving drum type of weigh-hopper manufactured by Samuel Denison and Son, Ltd. The weigher consists of a steel drum with dished ends carried on a horizontal shaft and rotated by an 8 hp squirrel-cage motor through a worm and spur reduction gear. A feed mouth in the drum permits of filling and discharging. The whole unit is supported on a framework resting on weighing levers, which in turn connect to transfer levers, thence to an indicator of the steelyard type situated 16 ft from the centre line of the drum. The indicator is of the "Denison" patent equilibrium controlled ticket stamping type, insuring mistake-proof records by a combination of electrical and mechanical movements which prevent the operator from printing until the cover enclosing the steelyard is closed and until the poise-weights have been set correctly to the weight of the hopper and contents. The machine is capable of weighing 30 short tons at a time but the usual load is 28 tons. After obtaining the gross weight the drum is rotated and discharged into a receiving bin situated below it. The empty drum is weighed and the net weight re-

Jan 1, 1947

By Paul M. Tyler

The term "milling" as applied to nonmetallic minerals often refers merely to pulverizing without preliminary beneficiation. As applied to dimension stone, it embraces all the gteps involved in shaping and giving the desired finish to blocks. Processes such as sawing, planing, rubbing and polishing seem far removed from milling as the term is used in ore dressing, nevertheless they involve the element of concentration, for only 25 to 50 per cent of the gross quarry output may leave the mill as finished products after imperfect stone has been culled and the rough blocks trimmed. On the other hand, numerous nonmetallic minerals have to be concentrated in much the same manner as low-grade ores. Engineers and machinery manufacturers have begun to recognize more clearly the opportunities awaiting them in the nonmetallic field and have brought with them the methods and equipment developed in metal-mining camps, occasionally with little modification. General Economic Considerations Approximately one-half of the total value of the mineral production of the United States represents mineral fuels, and the other half is about equally divided between metals and nonmetals, the nonmetals recently having become relatively more important. In terms of volume the domestic output of nonmetallic minerals other than fuels is more than 10 times the annual output of metals. Considered on the basis of industrial utility and general commercial and military significance, moreover, the flow of nonmetallic mineral products is quite as needful to our national integrity and well-being as is that of metals, fuels, or other basic materials. Despite their importance individually and as a group, the nonmetallic mineral industries differ so widely in essential characters and economic environment that producers thereof have been slow to develop a community of interest among themselves or with the metal-mining fraternity. A spirit of change is in the air, rule-of-thumb methods soon may be relegated to limbo, and new methods—especially time-tested ideas borrowed from ore-dressing practice—are being introduced. A faithful record of plant practice in certain of these fields, however, must register

Jan 1, 1935

By G. W. Poling

Chemical and physical properties of thiol collectors are re-examined to compare the prospects,of heavy metal-thiolate or disulphide surface reaction products acting as actual collector species. Recent evidences for the existence and importance of each of these types of adsorbed species on sulphide minerals are also discussed. A conclusion is reached that partial coverage by chemisorbed heavy metal thiolate is often sufficient to confer practical levels of hydrophobicity and floatability. Only on a few highly conducting and "noble" sulphides does adsorbed disulphide-type collector oxidation product appear to be significant.

Jan 1, 1976

By Arthur Taggart

A GENERAL awakening of interest among mill men concerning the mechanical efficiencies of their crushing machines is evident from a perusal of the recent files of mining publications. Considering the large part of the power bill which must be debited to the crushing department, such. interest is natural. When, however, the articles on the subject are read, the only statement upon which the writers agree is that fine grinding consumes a large amount of power, and that the machine which, from a concentration standpoint, offends as a slime producer is, for that reason, a serious offender in wasting power. When the mill man attempts to find a method for measuring the power wasted, or to compare the efficiency of one machine with that of another for the same work, he is confronted with a choice of methods which lead to conflicting results. There are two reasons why the work of crushing is not more generally understood. In the first place, experimental data are difficult to obtain; and in the second place, before these data can be put in general form certain assumptions must be made. A difference in these assumptions by different investigators has led to conflicting conclusions. This conflict has resulted in the proposal of two laws. The first of these is the so-called Rittinger's law, which is variously stated as follows: . "The work of crushing is proportional to the reduction in diameter."-R. H. Richards: Ore Dressing, p. 304 (1903). "The Work required to crush rock is very nearly proportional to the reciprocals of .the diameters crushed to."-A. Del Mar: Engineering and Mining Journal, vol. xciv, No. 24, p. 1129 (Dec. 14, 1912). "The Work done in crushing is proportional to the surface exposed by the operation, or better expressed for this purpose, the Work done on a given mass of rock is proportional to the reciprocal of the diameter of the final product, assuming that all the mass has been reduced to one exact size, which is only theoretically possible."- A. 0. Gates: Engineering and Mining Journal, vol. xcv, No. 21, p. 1039 (May 24, 1913).

Jan 1, 1914

By Rebecca Mae Summer

Increasing urbanization and industrial activity require increased supplies of sand and gravel. This means expanded surface mining and despoiled land near population centers. Highly competitive land use demands justify serious consideration of premining planning for multiple land use and reclamation concurrent with mining. 1-5 Formulating solutions to environmentally and economically sound uses requires a comprehensive approach based on properties of the natural resource base--geology, soils, and water. A study of sand and gravel mining within Pleistocene-Holocene fluvial deposits in Colorado County. Texas [(Fig. 1)] illustrates how physical limitations imposed by the resource base are determined.6,7 Data from drillers, logs of water wells, test boreholes, field observations, and laboratory analyses are used to evaluate these physical controls. Knowledge of the thickness and composition of overburden aids in developing optimum reclamation and revegetation plans. Most of the overburden in the study area [(Fig. 2, 3)] is a clayey mud with variable amounts of silt and fine sand. A comparative textural analysis of overburden and native soil is used to assess changes incurred by mining and for evaluating other physical characteristics, e.g., ability to support crops, permeability. and shrink-swell potential. Textures are correlated with soil types found in the area [(Table 1)] to get an approximation of probable surface properties expected from these mined materials. Results of textural analyses [(Table 2)] indicate that separating topsoils from overburden during mining is not necessary because the range of overburden textures is about that of native soils. However, more data is needed on nutrient deficiencies to evaluate fertilizer requirements for successful revegetation.*6

Jan 1, 1979

By Roswell H. Johnson

The principle of sliding or graduation in royalties is accomplished either by the block, period, cumulative, or class method. The block method calls for a very low royalty rate on all oil produced up to a certain amount. This amount would normally be that which is believed to suffice to repay the cost of the well. A higher rate would be charged after the well is making a profit. This method, common in many industries, is peculiarly inadaptable to any industry such as this where the productivity per day of the units gradually and inevitably decreases. This, for reasons given later, is because it forces an early abandonment of the well and so offends against conservation. In the period method, the royalty rate is changed by some definite amount when the well produces less than a specified quantity per day or other given unit of time. While simple to explain, it operates badly because a great deal is made to depend upon a small reduction in production, whereas the reduction as a matter of fact declines rather erratically owing to the exigency of lease management, connecting of tankage, and vagaries of the gaugers. These disadvantages are obviated by the cumulative method. In this method, all the production less than a certain amount per week has one rate of royalty, or none at all, and the oil produced in excess of that amount pays an additional rate of royalty. In the long run the calculation is probably no greater than with the period method, for simple tables will be published and printed in the oil papers that can be cut out, enabling quick readings to be made. Even without the table the calculation is easy with the few royalty rates, two or three, which would be used. In this method, the amount paid in royalty declines gradually, rather than suddenly as in the period method. The following reasons might be advanced for the adoption oi cumulative royalties: 1. To distribute the burden in accordance with the capacity to pay. This principle is a unique one in business, although familiar in taxation. This is because it does not distribute reward in proportion to efficiency.

Jan 1, 1916

By C. B. Foraker

THE Magma mine, of the Magma Copper Co., at Superior, Pinal County, Arizona, is 68 miles east of Phoenix and 21 miles west of Miami, Arizona, on highway U. S. 180. TEMPERATURES AND UNDERGROUND WATERS Surface Temperatures.-The average surface dry-bulb temperature at Superior is 72.4°; wet-bulb, 57.4°; with an indicated relative humidity of 38 per cent. The average yearly rainfall from 1921 to 1936, inclusive, was 18.74 in. The maximum condition of the atmosphere is in June, July and August, and the minimum is in January and February. The surface temperatures, of course, influence the temperatures of the down-cast shafts; however, the variation between winter and summer causes a difference of only 2° to 3° in the stopes and working places that are not close to the intake shafts. Average atmospheric conditions are shown in Fig. 1. Rock Temperatures.-Rock temperatures on the deeper levels of tile mine are as follows: LEVEL DEGREES LEVEL DEGREES 2000 109 3200 127 2250 112.5 3400 130 2550 116 3600 134 2800 120 3800 137 3000 124 4000 140 There appears to be no difference in rock temperature for any particu-lar horizon of the various formations or in the vein. Water encountered is always the same temperature as the rock from which it flows, and for this reason it is thought that the water is heated by the rock; not the rock by the water. The country rock apparently has been heated by the various intrusions, perhaps the vein itself, and has not yet had time to cool off. The geothermal gradient (Fig. 2) as indicated by the rock tem-peratures given above is 1 1/2 ° per 100 feet.

Jan 1, 1938

By Francis S. Peabody

This paper will not be a technical paper, because, although I have been in the business of mining and selling coal for 30 odd years, I am neither a mining engineer nor a practical miner. If I digress from time to time from my thesis, I must be forgiven by the expert engineers and highly technical gentlemen for whose proceedings this article is written. Waste of the wonderful store of power that the Creator placed at our disposal appears to have been the theory and the basis of our methods of extracting this power—waste from the time the coal is mined to the time it is consumed. Let us consider the prime causes of this wastage which has been the heritage of the coal mining industry. In the early days—about 150 years after " Stone Cole" was discovered in Illinois by Joliet and Marquette, and Father Hennepin noted a "cole" mine on his map—the mode of mining prevalent among farmer landowners, on whose property coal was discovered near the surface or outcropping on the hillsides, was to enter the seam by a shallow shaft or drift into the hillside and remove the coal by wedging it down until a large room was left. The roof without support would fall and our primitive coal operator would then sink another shaft or drive another drift. In these early operations only the large lumps were taken and all small pieces and screenings were left to be covered by the fall of the roof—in fact this condition prevailed in Illinois up to about 1885. Gradually the method of mining changed from the open chamber, to a single entry with rooms turned to the right and left. Later, as the demand for coal increased and the necessity for larger mines became evident, the "room and pillar" system grew to be regular practice. The room and pillar system of mining consisted of starting away from the shaft bottom or drift mouth, with a pair of entries usually 12 to 15 ft. wide and about 30 ft. center to center, one entry being used for the air intake and the other for the return air and haulage; from each entry rooms or chambers were turned, narrow at the mouth and widening

Jan 1, 1918

By Frank F. Aplan

In looking into the crystal-ball scene of minerals beneficiation for 1970 and beyond, an impartial observer becomes con- fused as to what has been done and what is possible in the way of improvements. The mining official must balance the burden which is being shouldered by the mineral industry for maintaining our environment in its pristine state on one hand, with the solid advancements made in technology and cost savings on the other hand. Then the official wonders if this is really the criterion for judging overall performance today. As a prospective engineer, Dave Bolles sees it this way: "Specialization has caused many engineers to subordinate everything to doing their job the cheapest and fastest way. In the future this won't be enough. The engineer in the mineral industry will be responsible not only for mining, concentrating and smelting, but also for the resultant wastes- the mine dumps, the tailing dams and the slag piles." (See Drift on page 63).

Jan 1, 1971

Joseph Esrey Johnson, Jr., had already achieved rare distinction as an able metallurgist, clear thinker, brilliant author, and wise consulting engineer to bankers and operators; he had achieved the essentials of a great career when dcath cut short his activities on Apr. 4, 1919, in the forty-ninth year of his age. He belonged to a family of iron blast-furnace men and mine managers. His father, Major J. E. Johnson, after serving with distinction in the Army of the North, identified himself with the iron mines and blast furnace at Longdale, Va., with which he was connected during almost his entire business life. It is significant, that, during those troublous times of reconstruction in the South, he enjoyed always the affection and respect of his neighbors and associates alike. From him his son obtained not only a thorough training in blast-furnace practice and iron mining, but great personal courage and force of character. His mother, who survives both her husband and sons, possesses rare intellectuality, humor and a tenderness and human sympathy which those who were privileged to know well J. E. Johnson, Jr., recognized beneath his exterior of aggressiveness and will power. In a recently published analysis of the qualities which characterize the world's great men, three traits stand out preeminently; viz., independence, courage, and intellectuality. Each of these characteristics J. E. Johnson, Jr., possessed in extraordinary degree. His early education was obtained under a private tutor at Longdale, and this circumstance probably enhanced a natural tendency to independence of character and individuality which, however, under the control of his unusual power of straight thinking and clear analysis never allowed him to go far astray. It has been said of him that if once he set his mind to a problem, however knotty, he scored a bull's-eye before the subject was dropped. His manner of attacking a subject involved first mastering the details of the available knowledge; then, putting this acquired information to one side, with an untrammeled mind blazing out a path of his own, so clear, so well-defined, and expressed in such simple terms that he illuminated the whole subject without distorting the original data or discussion. His two books, "Blast-furnace Construction in America" and "The Principles, Operation, and Products of the Blast Furnace, "on the iron blast furnace together form the most comprehensive, the most enlightening, and the most useful treatise on the subject ever produced in any language. But his ability did not end with the mastery and elucidation of principles enunciated by his predecessors; his own

Jan 1, 1920

By ERNEST W. ELLIS

MORE or less contradictory findings as to the most satisfactory feed for concentration tables of the Wilfley type is shown by the diversity of opinion among experimenters. Prof. R. H. Richards,l as a result of his work, favors classification. On the other hand the work of Messrs. Cox, Gibbins, and Porter,' of McGill University, points in general to the desirability of screen-sized feed The ore used was obtained from the West mill of the Bunker Hill and Sullivan Mining and Concentrating Co., Kellogg, Idaho, and consisted of argentiferous galena in a gangue of quartzite and siderite. The natural feed was taken from the launder supplying the Fahrenwald classifier. Classified feed was collected from each of the ten spigots of this same classifier. From the natural feed the screen-sized feed was pre- pared in the laboratory. All three types of table feed were therefore derived from the actual mill circuit of a large plant.

Jan 1, 1926

By G. W. Jones

THIS paper describes experiments in which eight test samples of gelatin dynamite were fired in three different types of apparatus and the quantity and composition of the gaseous products of detonation determined. The special dynamites were so prepared that the oxygen balance of the samples varied from -35.0 to +6.0 g. per 100 g. of explosive, including the wrapper. By means of this graded series of explosives, the relation between oxygen balance and gaseous products of detonation could be studied explicitly. The effect of varying oxygen balance on explosive strength has been discussed in another paper.1 The apparatus employed in the work described in the present paper included (1) the Bichel gage, a steel bomb of 15-1. volume; (2) the Crawshaw-Jones confined detonation apparatus, a steel cannon from which the explosive is fired into a pipe of 90-1. volume; and (3) the Hercules tank, an apparatus in which the explosive is confined in a quartz block which is placed in a steel tank of about 4500-1. volume. A full description of the apparatus is given later. VARIABLES AFFECTING COMPOSITION OF DETONATION PRODUCTS The character of the detonation products of commercial explosives is governed in part by the same factors that affect the combustion products from explosive mixtures of air with gases or vapors. In either case, combustible materials-namely, carbon, hydrogen, and sometimes sulfur-are present and combined variously. In an exploding gas mixture the combustibles are oxidized by oxygen in the admixed air, whereas with explosives the necessary oxygen is provided by oxygen-carrying materials in the explosive ingredients.

Jan 1, 1928

By Henry Hebley

IN preparing this paper it has been the aim of the writer to keep the problems of both producers and consumers in mind. Until now, no attempt has been made to familiarize each group with the other's practice and limitations. This paper is an effort to acquaint the readers with some of the factors pertaining to the problem and cost of mining and preparing steam coal, and also to the economics of producing steam with such coal. In recent years all lines of endeavor have turned to intensive mechani-zation in order to lower the unit cost of production. The average fuel consumption in steam electric generating stations has dropped in 20 years from 4.0 lb. to 1.4.1b. per kilowatt-hour; while the modern power station can generate 1 kw-hr. on a fraction under 1 lb., or 13,000 B.t.u. coal. Also, the amount produced per man has in that same period risen from 3.8 to 8.2 tons, owing to the use of modernized equipment below ground for coal cutting, drilling, shooting, loading, hauling and hoisting. Unfortunately, the rapid speed of 5 tons per minute of operation at which the coal is loaded mechanically precludes any appreciable removal of impurities at the coal face, so that the raw coal is hoisted containing a markedly higher percentage of impurities than the hand-loaded coal, which was subjected to the scrutiny of the miner during loading. Also, during the past 20 years, certain seams of coal lying close to the surface have been made economically available by the improved design of electrically operated shovels and draglines for the removal of overbur-den running as high as 56 ft. This strip coal frequently contains so much ash in the raw state (Table 1) that it would have no sales value. There-fore, coal preparation must be adopted to beneficiate the raw product. Some seams in the United States have a decreasing ash content with decreasing size, owing, in all probability, to the fact that the coal is friable while the impurities are hard, causing a concentration of the low-ash material in the fine sizes. Illinois No. 6 coal being rather hard, naturally the reverse is true.

Jan 1, 1937

By Herbert Haas

GEORGE W. HAWKINS, Tucson, Ariz. (communication to the Secretary*).-The paper by Mr. Haas will no doubt be followed with considerable interest, as it covers the power-plant problem in quite a comprehensive way, including not only the usual operating costs but also the fixed charges on the investment, and for load factors ranging all the way from 25 to 100 per cent. and fuel oil ranging from $1.25 to $2 per barrel. The very fact, however, that his paper does cover such a wide range of conditions, makes it the more imperative that any conclusion drawn from his analysis be very carefully considered for any specific case, for in making such analysis the type of prime mover and size must be selected for some one condition which might not be the proper selection had some other condition been assumed as the basic one, resulting in an unfavorable comparison under all conditions except that condition assumed. From the reasons given by the author for his selection of the large turbine units, it is evident he had in mind very high load factors, ranging

Jan 12, 1916

By E. Miller, R. Geffken, K. L. Komarek

The thermodynamzc properties oJ liquid Cd-Sb alloys were investigated using the cell arrangement measurments were obtained every 2°C at a heating and cooling rate of 12°C per hr and at equilibrium every 2O0C frorn 500°C down through the stable liquidus. The S-shaped asCd US composition curve was used in the cotnposition regzon near Cd,Sb, to calculate a tempeerture-dependent inleraction coefficient from quasichemical theory. Rapid changes in a scd were observed at a transition temperature varying from 400" to 465°C depending on con/kosition. It could not be determined if the changes in aScd were discontinuous, but tlze composition dependeke of the magnitude of the change is indicative of a second-order phase transformation in the liquid. The values of the experimental changes in ASCd are in agreement with calculations from the slope of the transition temperature, using the concept that a second-ovdev phase transition occurs in liquid Cd-Sb alloys. II is suggested that the transformalion is associated with the formation of Cd4Sb3 molecules in the liquid. ThE structure of liquid alloys is the subject of many investigations. X-ray, resistivity, and thermody-namic data have been interpreted as indicating varying degrees of short-range order in the liquid in alloy systems forming inter metallic compounds. In general, the melting process is not a transition from an ordered to a completely disordered state, but some degree of order is retained in the liquid. Maximum ordering in the liquid state occurs close to the melting temperature of the compound and the arrangement of atoms becomes more random at higher temperatures. Of special interest in this respect is the Cd-Sb system. It is one of the few metallic systems which form both stable and metastable compounds when liquid alloys are cooled at normal rates. The stable system exhibits an intermetallic compound, CdSb, melting at 459"c.l A second compound, CdrSbs, has also been reported,' melting close to this temperature. The metastable system has one compound, CdsSbz, melting at 420"c.I Resistivity measurements on liquid Cd-Sb alloys close to the liquidus temperatures have been interpreted in terms of a complex ordering behavior which changes rapidly with increasing temperature.3 The resistivity-composition curve is characterized by two maxima corresponding in composition to CdSb and CdsSbz. The resistivity-temperature plots show sharp breaks for alloys in the composition range of 45 to 70 at. pct Cd on cooling through a transition temperature close to the stable liquidus. Fisher and phillips4 investigated the influence of temperature and composition on the viscosity of liquid CdSb alloys. The viscosity of some alloys increases sharply on supercooling below the stable liquidus. A maximum in the viscosity-composition curve occurs at the composition CdSb. The thermodynamic properties of liquid Cd-Sb alloys have been investigated by Seltz and ~e~itt' and Elliott and chipmane by the electromotive-force method and their results are in good agreement. However, these investigations were carried out at temperatures well above the liquidus temperatures of the alloys, and the temperature coefficients of the electromotive force, dE/dT, were obtained from experimental points for each alloy at a few temperatures considerably above the liquidus temperature. Scheil and ~aach' investigated the thermodynamic properties of this system by the dew point method in the temperature range from about 100°C above the stable liquidus down into the supercooled liquid region. They reported several anomalies, i.e., the activity of a melt on heating differed from that on cooling, and the activity increased sharply in the limited temperature interval immediately above the liquidus temperature of the stable alloy, followed by a sudden decrease below the liquidus. Values obtained on heating and cooling were not in agreement. A reinvesti-gation of a few alloys by Scheil and Kalkuhl' by the electromotive-force method failed to confirm these observations. The authors concluded that the anomalies were due to inhomogeneities in the starting alloys and they discarded their previous results. The present investigation was undertaken in order to obtain thermodynamic data close to the liquidus temperature and in the supercooled region where the anomalies were originally reported, employing the electro motive-force method. This method is quite precise and will most easily permit observations of small changes in activity and partial molar entropy with temperature. Measurements were taken every few degrees so that the dE/dT values could be calculated over the entire temperature range and small changes in the thermodynamic properties close to the liquidus temperature could be observed. I) EXPERIMENTAL PROCEDURE Specimens were prepared from 99.999+ pct Cd and Sb (Cominco). Surface oxide was removed by scraping and then melting the metals under vacuum and filtering through Pyrex wool. Appropriate amounts of the metals were weighed on an analytical balance to k0.1 mg, sealed in double Pyrex capsules under vacuum,

Jan 1, 1968

By Olaf Hondrum

CHURN drilling equipment at Bagdad consists of two Bucyrus Erie 27-T model drills and one 22-T drill with gasoline engines. The drilling tools weigh approximately 1600 lb. The holes are drilled with 7-in. bits which are heated in an oil burning furnace and sharpened in an electrically powered bit sharpener. A service truck brings the bits to the drills and takes the dull bits back to the shop. The bits weigh around 250 lb. when new and are handled by drill crews without any mechanical handling device. When the management decided to start open- pit operations in 1945 the ruggedness of the terrain was one factor that led to the purchase of the small 22-T model drill. The orebody lies on both sides of Copper Creek Canyon. The sides of the canyon are steep and are cut by numerous narrow branch gullies. The drill had to travel over roads that were narrow and steep. It proved adequate for drilling the capping formation and is still in use.

Jan 1, 1950

By J. A. Herbst

During the last decade it has been established that conventional mineral-processing control strategies based on classical control theory result in significant increases in plant throughput and operating-cost savings. It has, however, also been recognized that conventional strategies have important limitations for complex multivariable mineral-processing systems. These limitations center around the fact that single-input/single- output control linkings often result in highly undesirable interactions between controllers. During the last few years new and promising approaches to solving this problem have emerged. These approaches are based on the use of on-line dynamic models to make predictions which are useful for control decision-making. This paper presents a brief summary of the state-of-the-art for mineral-processing control in 1984. This summary is followed by a review of recent developments in model-based control strategies including those in optimal control, self- tuning regulators and decoupling control. Expected trends for the future in the control of mineral-processing operations are discussed.

Jan 1, 1984

By E. T. Turkdogan, M. T. Hepworth, R. P. Smith

The permeability of oxygen in 0 iron in the tempera-ture range 700" to 900 C and in 6 iron at 1450°C was determined by the rate of internal oxidation of iron, containing -0.1 pct Al. The solubility of oxygen in zone-refined iron was determined by equilibration with hydrogen-water vapor gas mixtures at 1450" and 1510°C; oxygen solubilities , for iron in equi1ibriu.rn with molten oxide, are found to be 66 and 83 ppm for these two temperatures, respectively. The diffusivity of oxygen in iron at 14500C3 as calculated from the permeability and solubility data, is (4.1 * 0.6) x 10 "B sq cm per sec. OXYGEN is one of the most common impurities present in iron or steel, mainly in the form of oxide inclusions. In the study of many metallurgical problems concerning solid iron, it is often desirable to know with a reasonable accuracy the solubility and diffusivity of oxygen over a wide temperature range. The solubility of oxygen in solid iron has been the subject of numerous studies yielding highly discordant results as seen for example from the literature surveys made by Meijering &apos; and Schenck et a1.&apos; As shown by Kitchener et aL3 and by Sifferlen, the high oxygen solubilities reported by many investigators are the result of oxidizable impurities which are often present in iron. In addition, there have been experimental problems associated with icaccuracy of oxygen analysis of iron containing less than 100 ppm 0. A number of studies have been made on the permeability of oxygen in a and y iron using Fe-Si, Fe-Mn, and Fe-A1 alloys in the internal-oxidation experiments.1&apos;2&apos;5&apos;6 However, no direct measurements have been made of the diffusivity of oxygen in iron. In the present work two sets of experimental measurements were made: permeability and solubility studies at 1450" and 1510°C and permeability studies only in the range 700 to 900°C. In both sets of permeability measurements slab-shaped specimens containing small predetermined amounts of aluminum in solution were exposed at constant temperature to gas mixtures of hydrogen, water vapor, and argon for varying times. These specimens were quenched, sectioned, and examined for oxygen penetration by metallographic observation of aluminum oxide particles which formed. From these data, it is possible to calculate the ratio of the diffusivity of oxygen in iron, D, to the equilibrium constant K for the reaction Hz(g) * O (dissolved in iron) = H,O(g). EXPERIMENTAL Permeability Measurements at 1450°C. An ingot of vacuum-carbon deoxidized iron containing 0.086 pct A1 was prepared, using commercial "Type lO4A Plas-tiron"; after hot rolling, specimens were machined into slabs a by 2 by 2 in. The impurity contents were: S, P < 0.002 pct; C, Mn < 0.01 pct; each of all other Usual impurities < 0.004 pet. The amount of oxide inclusions in this material, determined by a bromine-methyl acetate extraction, corresponded to about 20 ppm 0 in the iron which agreed well with the results of vacuum-fusion analysis. Each specimen was annealed at 1450°C for 1 hr in purified hydrogen, polished to a smooth surface, and then introduced into a controlled oxidizing atmosphere in a recrystallized alumina tube at 1450°C. The constant temperature zone (*3"C) was about 3 in. in length. The gas composition was controlled by mixing argon with hydrogen (using calibrated constant-head flow meters) and passing the mixture through a column of a mixture of oxalic acid dihydrate and 10 pct anhydrous oxalic acid, to establish a required water-vapor content in the gas mixture. The temperature of the oxalic acid dihydrate column was controlled by a thermostat. The total gas flow was in the range 800 to 1000 cu cm per min. The exit gas from the reaction tube was passed through a weighing bottle containing a desiccant, to cross-check the degree of water-vapor saturation, which for all experiments was about 97 pct of those derived from the data of Baxter and Lansing.1 For a typical experiment, a specimen was introduced into the furnace in a stream of dry argon and hydrogen. The specimen was then rapidly raised by a Pt-Rh alloy wire into the hot zone and allowed to reach the reaction temperature, at which time the oxidizing gas mixture was introduced. The oxygen potentials employed were sufficient to oxidize aluminum but not to cause liquid iron oxide to form. After a specified time, the experiment was ended by dropping the specimen onto a water-cooled copper block at the bottom of the reaction tube. The depth of the internally oxidized zone, hereafter called the "case", was determined by sectioning the specimen at right angles to the long direction. The section was then examined under a microscope equipped with a micrometer stage. In general, the oxide particles were fairly uniform in size and distribution, forming a reasonably well-defined interface between the oxidized and unoxidized region. A typical cross section as observed at X30 is shown in Fig. 1. A thermal macroetch was used in one selected specimen to delineate the case. A cross section of a previously oxidized slab was polished and reheated at 1450°C in a hydrogen atmosphere for about 10 min. Upon quenching, the surface relief shown in Fig. 2 was produced; causes of this effect are unknown. Permeability Measurements Below 900°C. A slightly

Jan 1, 1967

By J. J. Thomas, J. H. Nead

This investigation was undertaken to determine, if possible, the relation between static and dynamic tensile tests as measured by the work required to break test specimens slowly, in a tensile testing machine, and rapidly, by means of a falling weight. It was hoped that the investigation would throw some light on the role played by ductility under different rates of application of load. In problems of design, it is usually assumed that the moduli of elasticity of all steels are equal; viz., about 30,000,000. The stress-strain diagram within the elastic limit is a straight line, as shown in Fig. 1, where OA is the curve of a hard steel and OB that of a soft steel. If the modulus of elasticity is constant, as assumed, the slope of the line OC

Jan 1, 1922