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By R. M. Hays

Prior to use of this model siphon finisher, the only means of evaluating metallurgical performance of the siphon finisher was by pilot plant studies. These are costly and require large quantities of material. A model siphon finisher and a test procedure which permits the evaluation of siphon finisher metallurgical performance has been developed. Metallurgical results between the model siphon finisher and pilot plant or commercial units show fairly good correlation. The upgrading of magnetic taconite concentrates by hydraulic concentration has been practiced for several years. In the 1940's, Braund1 used a multistage upflow classifier to upgrade magnetized magnetic concentrates. In present taconite plants, the SiphonSizer, marketed by Dorr-Oliver, Inc., has been particularly suitable for upgrading magnetic concentrates. When the hydraulic SiphonSizer is used to upgrade the concentrates in the finishing portion of the overall flowscheme, the unit will be called a siphon finisher to distinguish this application from classification. Prior to this work the only means of evaluating the metallurgical performance of the siphon finisher was by pilot plant studies which are costly and require large quantities of material. Therefore, it was desirable to develop a model siphon finisher and a test procedure which would simulate siphon finisher performance and require only small samples of material. This model would permit the evaluation of small samples such as drill core samples and be useful in evaluation of commercial siphon finisher design and performance. THE SIPHON FINISHER The siphon finisher, as shown in Fig. 1, is a tank equipped with a system of water jets which distribute the hydraulic water uniformly across the bottom of the vessel with an energy release for agitation in the teeter bed. The feed to the siphon finisher is intre duced through a feed well in the center of the unit. The silica and middling particles overflow a peripheral weir into the overflow launder. The magnetite fraction is discharged by a siphon or a modulated discharge valve. The siphon or the discharge valve is usually operated automatically by a float assembly which is responsive to the depth of the teeter bed. Various interface sensing devices have also been

Jan 1, 1968

By Walter C. Lawson

THE first plans were made in 1930 for the mining by open-pit methods of the low-grade disseminated ore body now known as the Morenci open pit. It was not until 1937, however, that final plans were completed and the decision reached to go ahead with the actual development. Many advances were made in open-pit mining equipment during that period of seven years, therefore the ways and means of attack actually used were very different from those originally contemplated. Diesel-operated bulldozers, big trucks, full-revolving electric shovels and electric churn drills constitute the major equipment finally purchased for this modern stripping operation. Neither the bulldozers nor the big trucks were considered in the early operating plans, for at that time bulldozers had not been used in mining operations and the trucks as yet were undesigned. The full-revolving shovel and the churn drills were not new developments in open-pit equipment, but both had undergone remarkable manufacturing transition, emerging far more efficient and far more dependable than their predecessors. Even the ordinary drilling steel had been fundamentally changed. It was now threaded so that the dulled cutting bits could be detached and replaced, thus eliminating the costly transportation of long bars to the drill shop for resharpening. The decision to use trucks in the preliminary stripping operations was based on the desirability of this type of transportation to economically prepare the pit for rail haulage, coupled with the success that the contractors had had with them on other big excavation jobs. There are at present no plans for the use of trucks beyond the preliminary work, inasmuch as rail haulage will give lower costs after roadbeds and benches are once established. For many years to come, both ore and waste haulage will be over favorable grades. The average length of ore haul between the pit and an assembly yard will be about two miles. From there the crushers will be 1 1/3 miles with a connecting track grade of 0.4 per cent. The upper ore benches of the pit will be reached from the yard by a series of four switchbacks over a ruling grade of 4.0 per cent compensated for curvature. Tracks to the dumps will be on 0.2 per cent grades.

Jan 1, 1938

By G. Sachs, E. J. Ripling, J. J. Lynch

INTRODUCTION General IT is general practice to evaluate the strength properties of a particular metal from its stress-strain [(S1 - E1]) curve obtained by means of a conventional tension test. Such a stress-strain curve, Fig I, illustrates two important properties of a metal, its ability to strain harden, and its ability to withstand a certain limiting stress, the "fracture stress,"[ (s'r)], and a certain limiting strain, the "ductility" [(e1)], before it fails by separation. These two fracturing characteristics are the coordinates of the point of fracture in Fig I. In the case of a metal which necks in a tension test, both the fracture stress and the ductility (measured in a tension test) are dependent upon (a) the shape of the neck and (b) average values of the stresses and strains over the cross section at the moment of fracture. However, for the purpose of this investigation, these average quantities, rather than the actual values, may be considered for reasons of simplicity. It appears that the conclusions also hold true if the analysis were carried out for actual values of fracture stress and ductility at the locus of failure. In this paper, the effects of straining (at room temperature) by various methods on [ ] the above metal characteristics, which were determined by subsequent tension tests will be discussed. According to our present knowledge, any such prestraining results in a stress-strain curve (in subsequent testing by tension), Fig 2, the general shape, or flow characteristics, of which can be derived from the original stress-strain curve of the unstrained metal minus a certain portion exhausted by the initial straining. This phenomenon is called strain hardening, and may be measured by the magnitude of the cut-off, or the "effective strain," from which the new curve must start in order to coincide in its plastic branch with the original stress-strain curve.

Jan 1, 1948

By C. B. Manula, R. Venkataramani, T. V. Falkie

A linear programming model has been developed to solve a production planning problem for a multi-plant stone operation serving several customers. The factors considered are production capacities, inventory restrictions, demand requirements, and available stone reserves. The objective function to be optimized is the total annual net returns from the quarry operations. For the purposes of model testing, annual stone sales from each plant were divided monthwise, productwise, and assigned to a market. The concept of assigning demands to market sectors and not to any particular plant creates the self-correcting interplay between the plants and the markets. Along with the inventory restrictions, and ending inventory requirements, this interaction enables the model to minimize the external diseconomics. The model was tested against an operating prototype and a number of alternative problems were also considered. Finally, the basic linear programming model has been enlarged by the addition of another dimension and the problem has been derived in a decomposition format.

Jan 1, 1972

By R. F. W. Pease, R. A. Ploc

A scanning electron microscope with a resolving power better then 100Å has been developed for the direct examination of surfaces. This instrument was used to study iron undergoing oxidation at 500°C. It was found that the electron current in the scanning electron microscope was low enough (about 10-atrzp) to have no observable effect on the growth of the oxide. "Armco " iron, when oxidized, exhibited an oxide film whose thickness and whiskey population varied with pain orientation; but purer iron, when oxidized, exhibited no such pain dependence and whisker occurrence appeared to be caused by impurities. UNTIL recently most surfaces of opaque specimens could either be studied with a light microscope or, if higher resolution was required, by viewing a replica of the surface in a transmission electron microscope. Direct electron microscopy of a surface has, in general, proved difficult owing to excessive foreshortening and the poor image quality obtained. The scanning electron microscope, however, offers an alternative method of directly viewing a surface without these disadvantages. At low magnification it offers a much larger depth of focus than the light microscope, and at high magnifications it offers much higher resolution (about 100Å). PRINCIPLE OF THE SCANNING ELECTRON MICROSCOPE A schematic diagram is shown in Fig. 1. The electron optical system consists of a gun followed by a series of lenses which focus the electron beam onto the surface of the specimen. The beam is scanned in a rectangular raster across the specimen surface and, by amplifying the secondary electron current from the 'pecimen, a picture of the specimen surface is built UP sequentially on the face of the display cathode-ray tube. The magnification of such a system is given by the ratio of the scan amplitude on the display cathode-ray tube to

Jan 1, 1965

Jan 1, 1954

By Frank N. Speller

Jan 1, 1934

By H. D. Newell

Jan 1, 1938

By H. D. Newell

Jan 1, 1938

By John C. F. Randolph

(Read at the Amenia Meeting, October, 1877.) Tits establishment being now in full working order, it has seemed of considerable professional interest to collect together, in a concise form, the various points as to its plan, method of dressing, and equipment. The data contained in this paper have been largely drawn from the able paper of E. Kutscher, constructing engineer. of the works, contained in the Zeitschrift fur Berg-Hütten-und Salinenuesen im Preussischen Staate, 1873, supplemented by some personal memoranda made while the works were under construction and by memoranda on the works appearing in various German technical papers from their completion up to date. This is probably the largest dressing works in the world devoted to the beneficiation of argentiferous lead ores, and it is doubtful if any establishment for the concentration of mineral of any description can compare with it in size. As showing the final practice adopted in an old and very conservative mining region, in which the concentration of ores has been a matter of constant practice and experiment for a very long period, these works are of peculiar interest. The fact that the Clausthal ores strongly resemble a very large and abundant class of ores found in the United States has always attracted the attention of American mining engineers and mine owners to the methods employed in dressing and smelting them. The study of their methods of concentration of ores has, however, always been full of difficulty,

Jan 1, 1878

By F. E. Rizzo, L. R. Bidwell, D. F. Frank

THE use of galvanic cells for the determination of oxygen activities has spread rapidly since the suitability of calcia-stabilized zirconia as a solid electrolyte material was first demonstrated by Kiukkola and Wagner.' In many of these investigations:-7 including several at ARL, the free-energy changes for various oxidation-reduction reactions involving the oxides FexO, NiO, and Cu2O have been measured as a means of assuring that a cell apparatus is functioning properly. As a result, a large quantity of data pertinent to the calculation of the high-temperature standard free energy of formation (?GO) of these oxides has been accumulated. AGFexo has been carefully measured in many independent investigations, using a variety of techniques, and consequently is accurately known. chipmans has used this informa-

Jan 1, 1968

By George Steintveit

Det Norske Zinkicompani A/S was established in 1924, on the initiative of the Compagnie Royale Asturienne des Mines. Experimental electrothermic zinc production was carried out on industrial scale for a two-year period, but the problems of electrothermic smelting were not solved. A license for the electrolytic zinc production process was then obtained from the Anaconda Copper Mining Co. A plant for electrolytic zinc production was built, near the small fjord town of Odda in Hardanger, West Norway, The production was based on zinc ore from Spain, and cheap local hydro-electric power. The plant came into operation in 1929. Annual capacity, 36,000 tons. In 1964 a long-term agreement was concluded with Boliden AB by which Det Norske Zinkkompani is secured the raw materials basis for an expansion of the annual capacity to 100,000 tons of zinc, Since World War II, the company has been pursuing extensive research and development programs. As a result, various sections have been rebuilt: nev unloading and storage facilities, a 250 ton per day Fluid Bed Roaster with contact plant, new continuous leaching system, integrating the Jarosite Residue Process, new solution purification section - upgrading the solution quality for a 600 Amp/m2 current density Tank Room operation -, installation of induction furnaces for cathode melting with casting machines and automatic stacking of slabs. Simultaneously, instrumentation, and methods of automatic control have been developed and introduced, providing conditions for optimal plant operations.

Jan 1, 1970

By Frank E. Shepard

Electric power in mining-operations is now successfully applied to haulage, hoisting, lighting and pumping; and until lately, drilling was the one department of mining in which an electric source of energy had not been introduced. Drilling by electric power has been the field for much investigation and several forms of electric-drills have been tried; but in the severe service of rock-drilling many dieculties have been encountered, and the heavy cost of repairs has caused a deep prejudice against this system of drilling. In the majority of electric rock-drills previously placed on the market, two principal factors have been considered; first, a portable electric motor usually of heavy pattern, coupled to the driving-mechanism of the drill proper by means of a flexible shaft; and second, the coupling of some form of reciprocating cross-head to a piston by means of a spiral spring, the drill-bit being fastened to the piston-rod by some suitable form of chuck with fastening bolts and nuts. In this latter form of drill, the cross-head has a fixed stroke, while the piston with drill-bit attached is allowed a variable stroke through the

Jan 1, 1904

By Franklyn W. Oatman

In order that the conditions which obtain in an oil well may be readily understood, a brief description of a typical California well and a number of the phenomena accompanying same will be given. That the necessity for the exclusion of water be realized, the effects of water intrusion, a description of methods of prevention, .and a discussion of causes of failure will be presented, followed by a summary and recommendations. Fig. 1 shows a section of a typical well which illustrates the relation of oil sands to overlying strata. It indicates a deep water sand separated from the oil sand by shale, and the proper place for the final shutting off of water. In this well a comparatively thick stratum of compact shale protected the oil from overlying water so that the operation of landing the water string was a simple matter. In some wells the protecting stratum may be only from 3 to 5 ft. thick and very careful operation is necessary in order to land the water string of casing properly and not puncture through to the oil sand. The cases just cited are common, but occasionally, after excluding overlying water, productive oil sands are drilled through in the expectation of finding more productive underlying sand, and a water-bearing stratum is tapped. In this case the problem is the reverse of the normal; water must be prevented from ascending rather than descending. A discussion of well-drilling methods is not within the scope of this paper, except such operations as pertain to shutting off of water. A brief outline of the several conditions which may accompany drilling follows. Some or all may be present in any particular case. The direct relation of these to prevention of intrusion will be discussed in detail further on. In drilling, the hole becomes more or less irregular in shape, and rough, and as the casing follows the bit into the well it does not fit snugly against the walls. As a result, water may descend between the casing and walls of the well. If a circulation pump is not used during drilling, the hole is simply punched through and the pulverized material removed from the well by means of a bailer. If circulation is maintained there is a continual flow of water down inside the casing and up around the outside between the pipe and the walls of hole. This keeps an open space around the pipe.

Jan 1, 1915

By D. N. Dietz

A method for determining average reservoir pressure is presented, which is simpler to apply than that devised by Matthews. Brons and Hazebroek. For bounded reservoirs, identical results are obtained if stabilized-flow conditions prevail. The present method yields inferior results in the transient state. The method can, with a slight modification, also be used for water-drive reservoirs. INTRODUCTION In the method proposed by Matthews, Brons and Haze-broek' for determining average reservoir pressure in a multi-well reservoir, the cumulative production (the production time of each well) enters twice: once when the buildup is plotted against In (t + t)/At to arrive at p*, and a second time when the correction, p*-p is determined with one of the several formulas for differently shaped drainage areas. Once a steady state has been attained, however, the previous production history should be immaterial. The same pressure distribution could have been arrived at after different cumulative productions of the individual wells. In principle, therefore, it should be possible to determine average pressures without referring to cumulative productions. In the following paragraphs an expression is presented for the difference between the pressure in a producing well and the average pressure of its drainage area. Then the build-up time needed to overcome this difference is indicated. CASE OF A CIRCULAR DRAINAGE AREA AND A CENTRAL WELL PRESSURE DISTRIBUTION BEFORE SHUT-IN The general differential equation of radial flow (see Muskat, Eq. 10.2) may be written In the steady state, the rate of production of the well is equal to the rate of expansion of the fluid contained in the the drainage area; thus

Jan 1, 1966

By M. Cross

The main results from a programme of theoretical work on various aspects of the pelletizing operation are presented. This paper is primarily concerned with the modelling of: (i) The balling drum operation. A model is outlined which clearly demonstrates the characteristic surging behaviour of the balling circuit. It is used first in a control analysis and, subsequently, in the design and testing of various control schemes. (ii)The grate-kiln-cooler induration process. Models describing each of the constituent processes are outlined and a composite model of the whole induration process presented. The main results from each of these models are discussed.

Jan 1, 1977

By J. L. Jernegan

In the summer and fall of 1875, the author was present during a short smelting campaign at the Hall Valley works, and having had occasion to make a number of chemical analyses of the ores, fuel, and fluxes, deems that the results of the same, and also an account of the smelting operations, may be found of interest to members of the Institute. The mines and reduction works of the Hall Valley Silver—Lead Mining and Smelting Company (limited) are situated at Hall Valley, Park County, Colorado. The smelting works are located about half way from the mouth to the head of the above-named valley, and the mines high up on the mountains, near its head. The three principal mines of the company are the Whale, Leftwick, and Coldspring. They are all on different veins, running parallel to one another, with a general trend from southwest and northeast. The

By James E. Mills

In the work of exploring certain gold-bearing gravels in the American Valley, Plumas Co., California, entrusted to my charge by Prof. A. Agassiz, of Cambridge, and Q. A. Shaw, Esq., of Boston, it became necessary to sink a shaft through loose materials containing in some layers large quantities of water, and I have been compelled to devise a new method which has proved successful and may be of service elsewhere.

Jan 1, 1885

By Ernest F. Burchard

MOST of the iron ore smelted in Alabama blast furnaces is mined within Alabama, although deposits in the neighboring States of Georgia and Tennessee may be drawn upon when occasion requires. Of the four commercial kinds of iron ore, the anhydrous ferric oxide, hematite (Fe2O3) ; the hydrous ferric oxide, mostly the type commonly known as limonite (2 Fe2O33H2O) ; the carbonate, siderite (FeCO3) ; and the magnetic oxide, magnetite (Fe:3O4) ; the first two are found in abundance in Alabama, the third in less than commercial quantities, and the fourth only rarely. Both the hematite and the hydroxide are found in somewhat different forms according to their geologic environment. The Red Mountain hematite, of Silurian age, that crops out in well¬defined beds for 1.50 miles northeast-southwest and 40 miles northwest-southeast is the predominant source of ore. Only a small part of this area carries ore of commercial value; Birmingham and Gadsden are now the only centers of production. The ore is of sedimentary origin, probably altered from vast deposits of greensand mixed with calcareous, fossiliferous. marine debris. Other types of hematite not vet mined commercially are in metamorphosed rocks-red ore in slates in Columbiana Mountain and specular hematite (gray ore) in quartzite in the Talladega Hills.

Jan 1, 1938

By Michael Tenebaum

IN a previous investigation1 the authors studied the effect of pressure on the reduction of iron ores by hydrogen. With hydrogen as a reducing agent, the rate of reduction was increased substantially by increasing the pressure from 1 to 2 atmospheres. The results with hydrogen prompted the present study of the effect of pressure on reduction with carbon monox-ide and with mixtures of carbon monoxide and nitrogen. FEATURES OF REDUCTION PROCESS The gas stream in the lower part of the blast furnace always contains sufficient concentrations of reducing gases to complete reduction provided sufficient time is allowed for the reaction to proceed. Reducing gases react immediately with the iron oxide on the surface of lumps of ore. However, as the unreduced surface recedes from the easily accessible exterior of the lump, the reaction proceeds by virtue of the diffusion of the gases into and out of individual pieces. The rate of diffusion of gases, which undoubtedly plays an important role in the reduction of iron ores, depends on several factors, most impor-tant of which are: (1) molecular weight or density, (2) pressure, (3) tem-perature, (4) concentration gradient. Thus, the rate of reduction of a lump of iron ore at any temperature will depend not only on the specific reaction rate but also upon: (1) available surface of unreduced iron oxide, (2) rate of diffusion of the reducing gas to the reacting surface, (3) rate of effusion of the gaseous products of the reaction from the reacting surface, (4) adsorption of the gases on the reacting surface.

Jan 1, 1939