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By J. D. Lubahn, R. P. Carreker, J. G. Leschen

THE formation of slip bands in crystalline solids undergoing plastic deformation has recently been treated as a problem of nucleation and growth.1 A simplified theory was developed and shown to be qualitatively consistent with certain experimental observations reported in the literature, such as the frequent failure of slip bands to traverse the entire crystal, the effect of specimen diameter and temperature on the yield stress, and the occurrence of incubation periods in the deformation of suddenly loaded crystals. The theory further predicts the appearance of transients in the rate of strain of a crystal when the applied stress is suddenly changed from one constant value to another. A transient consists of a discontinuous change in the strain rate followed by a gradual approach to a steady-state value. Such transient behavior apparently has not been recognized in previous experimental work. The preliminary experiments reported in the present paper were undertaken to confirm the existence of the predicted transients and thus to determine whether a more detailed treatment of the nucleation theory of slip might be theoretically and experimentally fruitful. EXPERIMENTAL PROCEDURE A simple creep apparatus was assembled as shown in Fig 1. Very little insulation was used on the furnace in order to facilitate rapid changes of temperature. Temperature was measured with a thermometer placed in the center of the furnace and was [ ] controlled by adjusting the Variac setting. The specimens were cold-headed in split-cylinder grips. The strain was measured as total elongation by a dial gauge sensitive to 1/10,000-in. movement of the weight pan. Since the specimen gauge lengths were

Jan 1, 1948

By U. Paakkinen, P. Eerola

In connection with theoretical studies of the dynamics and control of the flotation process, flotation cells and circuits at the Pyha- computer control of selective Cu - Zn - Fe sulfide flotation in the latter half of 1969. In this paper, the practical conclusions of these studies, conducted through simulation techniques, are summarized. The application of these results for control purposes implies a knowledge of the dependence of the flotation rate coefficients and the grade of concentrate on several factors, including aeration rate, froth depth, and reagent consumption. The relationships found in laboratory and plant scale tests are described. Off-line optimization studies, based on the relation- ships, are also described. The proposed steps in executing the computer control schedule are presented. In the first stage, a stabilizing control will be carried out using feed-back loops. A feed-forward control system which utilizes simple process models will also be tested. After these elementary stages, a proposed mathematical model of the circuit will be checked out and implemented with computer- run, plant-scale process tests. Off-line simulation will be continued in advance development of the control system. As a final step in the program optimal control of the process will be carried out through this model.

Jan 1, 1969

By G. M. Ritcey

Purification of solutions can involve various treatment methods. In the normal sequence of metals recovery by hydrometallurgy, the ore is initially prepared for leaching by grinding to the desired optimum mesh size as dictated by the leaching parameters. Following leaching and liquids- solids separation, the resultant solution is ready for purification. The use, or introduction of solvent extraction into a plant, can be either a major or a minor part of the metal recovery process as shown by the following list where solvent extraction is normally considered: a) recovery of a metal by a simple leaching of the broken ore, e.g., copper from dump leaching where there are only the three main steps of leaching, solvent extraction, and electrowinning (1);

Jan 1, 1978

By Sylvia Whitehead, G. M. Schwartz, J. N. Gundersen

Sylvia Whitehead (Petrologist, The Broken Hill Propriety Co. Ltd., Melbourne, Australia) — Examination of thin sections of jaspilites from numerous banded iron formations in Australia has revealed no evidence to suggest that silicate minerals have formed by reaction between magnetite and silica. Textural relations indicate that part of the magnetite crystallized very early in the history of the rocks, probably during diagenesis, and remained stable under conditions of metamorphism altering only to hematite or limonite under conditions of oxidation and weathering. Many jaspilites also contain later magnetite which is almost certainly of metamorphic origin. Wherever magnetite is present in quartz rich bands containing little or no silicate or carbonate, it is very fine grained and occurs generally as isolated, well formed octahedral crystals or as small crystalline aggregates. These show no evidence of corrosion or reaction with the quartz even in rocks where adjacent bands contain silicate minerals of moderate to high metamorphic grade. Concerning the silicate minerals, it is reasonably certain that bands of very fine grained stilpnomelane

Jan 1, 1963

By W. M. Peirce, E. A. Anderson

A FEW metals have been known since the dawn of history. Many have been prepared in quantity only within the present century. Zinc falls into an intermediate category, although there is some evidence of its existence in elemental form in Greece as early as the third or fourth century B.C. Nevertheless, the first important use of zinc antedates the earliest records of civilization. This first use was in the alloy, brass, which is roughly one third zinc. This continues to the present time as one of the major uses of the metal. The first production of brass, in light of present knowledge, was perhaps one of the 'most romantic and fortuitous of technical discoveries. Copper, the major constituent of brass, had been given to man by Nature in the native state; that is, as lumps of fairly pure copper. The art of melting and working it had been learned. But zinc does not occur as the metal in Nature and even if some early metallurgist happened to heat zinc ore with a reducing agent, the reduced metallic zinc passed off as vapor and was lost. Doubtless some early coppersmith, melting copper in accidental contact with zinc ore, reduced the zinc, and the vapor was absorbed by the molten copper. Its color, hardness, and other properties were thus wonder- fully changed. And so the earliest metallic form of zinc, as nearly as we can deduce, existed in the alloy brass. Probably knowledge of the kind of rock with which to heat copper to change it to brass, the best

Jan 1, 1953

By A. T. Yu

From the very beginning when an ore body is blocked out, till the last ton of mineable ore is shipped to the smelter, consciously or not, a mining engineer is incessantly wrestling with the materials- handling problem. In the mine and the plants, over the haulage routes, and at the shipping terminals, his fundamental responsibility is to see that each ton of ore and/or waste is extracted, processed and moved easily and economically. Success or failure of many a mining enterprise often rests principally with the judicious and effective application of existant materials-handling technique or its innovation. Time and again, key innovations in practicing techniques have turned a losing venture into a successful and profitable one.

Jan 6, 1967

By Joseph F. Shirley, Harry K. Burke

On January 9, 1964, the molybdenite extraction circuit at the San Manuel concentrator was switched from the sodium hypochlorite-ferracyanide process to the present process described in this paper. This moment was the culmination of over three years of laboratory and pilot plant test work. COPPER CONCENTRATOR Even though San Manuel's molybdenite plant begins with the thickened copper concentrates, it is necessary to describe briefly the copper sulfide circuit, because San Manuel's excellent molybdenite recovery actually begins with the primary grinding of the ore.

Jan 3, 1965

By R. R. Spencer, C. A. Campbell, R. J. Marcotte, A. S. Kromer, P. H. Ostlender

Calumet Div. of Calumet & Hecla Inc. is engaged primarily in mining, milling, and smelting the native copper ores of northern Michigan. The copper occurs in fragmental tops of lava flows and in certain interbedded felsitic conglomerates of Pre- Cambrian age. The most famous native copper ore- body in world history is the Calumet conglomerate, which outcrops between the villages of Calumet and Laurium for a distance of about 2 miles. The Osceola lode parallels the conglomerate lode and is mineralized for about 3 miles. Horizontal distance between the two is 750 ft. In 1932 the price of copper dropped to 54 per lb. Coupled with the high cost of obtaining copper from extreme depths, this low price made the venture un- profitable, and the mining unit was abandoned. After the shaft pillar copper was removed from several of the conglomerate shafts in a retreating operation, the mine was allowed to fill with water. In post-depression years, when the price of copper stabilized at about 12¢, Calumet Div. found it profitable to operate its remaining mines on other lodes, as well as its tailings reclamation plants.

Apr 1, 1956

By Samuel Shallcross

THE principal function of the Bell limestone mine, of the American Lime & Stone Co., at Bellefonte, Pa., is to supply raw material to the company's modern rotary kiln plant at Bellefonte. Because mining costs are naturally higher than many open quarries with more favorably lying strata, it cannot compete, except to a limited extent, in the markets for road material and fluxing stone. In the broad sense, mining does have an advantage over the average open quarry when the end products are designed for and controlled by process and final inspection for the exacting demands of the industrial and chemical markets. Approximately 80 per cent of the output of the Bell mine is sold in the industrial and chemical markets. And as higher standards are set each year for construction and agricultural work, the remainder of the mine output goes to these two classes. Mining produces more fines than open quarries, and these fines are difficult to market; on the other hand, owing to absence of contaminating clay and impure rock, a greater percentage of the output of a mine is marketable. Because of the great production of fines, rotary kilns for lime burning are necessary when the stone must be mined. In 1921 the American Lime & Stone Co. operated 19 quarries and 72 lime shaft kilns spread over an area of 40 miles between Bellefonte and Altoona, Pa. At that time the line-production capacity of the 72 kilns amounted to approximately 700 tons per day. After 15 years the company operates three rotary kilns and six shaft kilns, with a combined output of approximately 500 tons of lime per day, concentrated in its single Bellefonte plant (Fig. 1). Its only stone-producing plants are now the limestone mine at Bellefonte and a construction-stone open quarry at Union Furnace, near Tyrone, Pennsylvania.

Jan 1, 1936

Surface mining of coal is widely condemned as a despoiler of the countryside and wastrel of land and natural resources. Yet the fact has been as widely ignored that the ingenuity of those engaged in developing the methods and equipment utilized in surface mining have made several hundred million tons of coal available for utilities and industry which could never have been mined by any other method. While doing this, the surface mining companies have recovered nearly 100% of the coal in the mining area instead of approximately 50% as is common in underground methods. Efficiency has been increasing constantly, thereby maintaining low cost to the customer. Mining has provided economic health in many areas by virtue of the direct payrolls and by the attraction of other industries to enjoy low cost, dependable fuel supplies. Surface mining of coal generally falls into two categories: contour mining, which is the result of mining in hilly or mountainous terrain where the hillside or slope limits the width of the area which can be surface mined; and area mining, which results from the surface of the land being approximately parallel with the coal seam so that a wide area may be mined in a succession of pits or open cuts.

Jan 10, 1972

By Morris A. Dodd

The nodulizing process described converts finely divided zinc calcine into a dense purified nodule. These zinc nodules are suitable for direct use in zinc reduction furnaces, especially the horizontal retort type, for the production of metal or American process zinc oxide furnaces for producing lead free zinc oxide. The basic reactions are carried out in a rotary kiln fired with fuel oil or natural gas. The combustion gases travel countercurrent to the flow of the zinc bearing material. Volatile impurities are carried out of the kiln with the combustion gases and a small portion of the finely divided feed material. The gases are cooled and the larger solid particles are separated from the stream before the resultant fume is collected in a conventional cloth filter baghouse. The fume collected can be further processed by conventional wet processes for the recovery of metallic values such as lead and cadmium. In order to nodulize the calcine properly it is elevated to a point of incipient fusion. The agglomerated material falling from the kiln is cooled and then sized by passing through a screening and crushing system consisting of a jaw crusher and a roll crusher in closed circuit with a vibrating screen.

Jan 1, 1970

By Stanley M. Miller

For rock or soil materials assumed to be generally isotropic and homogeneous, seepage theory and analytic geometry can be used to develop a mathematical technique for estimating the steady state, pie-zometric drawdown to a slope face. The resulting parabolic drawdown curve is a function of slope angle and the height of the original water table above the slope toe. When the slope is cut at a rate faster than that which allows a steady state to be attained, a non- steady state analysis approximates the transient drawdown. Monte Carlo simulation provides realizations of possible drawdown curves that can be included in slope stability risk analyses.

Jan 1, 1983

By W. H. Young, P. D. Torrey

The Eastern fields comprise a distinct geological and geographical unit, located in the northern part of the Appalachian geosynclinal prov-ince. In this area are the fields of New York, producing from rocks of Devonian, Silurian and Ordovician age; the fields of western Pennsylvania, where oil and gas occur chiefly in rocks of Mississippian and Devonian age; the fields of eastern Ohio, where oil and gas are obtained from rocks of Pennsylvanian, Mississippian and Silurian age; and the fields of West Virginia, where oil and gas are produced from rocks of Pennsylvanian, Mississippian and Devonian age. Many of these fields are of great antiquity in comparison to the age of the producing areas in a greater part of this country, and consequently in most instances it is impossible to obtain accurate historical statistics. In addition, the records of many of the more recently discovered fields are either unobtainable or are not sufficiently reliable to justify their incorporation in a review of this character. Rather than overemphasize certain fields and areas, where complete records are available, when there are many other fields of equal importance for which statistical data are not available, the authors have made a tabulation of development that does not take into consideration past operations and production. The records utilized in preparing this paper were derived largely from the scout reports of several of the larger companies, which generously made them available to the authors. These were independently tabulated by counties and townships, in order to eliminate as far as possible duplications and, excepting the Clinton fields of Ohio, where many of the smaller wells have not been individually reported, they represent the most accurate information available. Market conditions in both the oil and gas industry were far from favorable during 1932 and in consequence there was a total decline in drilling in the Eastern States, which is 22 per cent less than the number of completions in the preceding year. This decline was not constant over the entire area, as is shown in Table 1. The oil fields of both New York and western Pennsylvania were the scene of renewed drilling activity, which was largely restricted to the water-flooding operations in the Bradford and Allegany fields. Practically no new operations were started, but a certain number of new wells

Jan 1, 1933

Jan 1, 1914

By Arthur Zentner

The electrolytic zinc plant of today is foreshadowed in the patents issued to Léon Létrange of Paris in 1881 and 1883l. He proposed roasting zinc blende to make the zinc soluble in water or sulphuric acid, thus obtaining a sulphate solution. His purification was apparently that used in the lithopone work of the day. For electrolyzing he proposed anodes of carbon or lead, for cathodes zinc, copper or brass. Numerous patents by other workers were taken out in the first 10 years, most of which dealt with sulphate solutions. It is easy to presume that the formation of chlorine gas in zinc chloride electrolysis caused early emphasis on sulphate work. Lack of success with this invited further work with chloride solutions. Efficient and cheaper oxidizing agents for use in the chloride processes were more generally available. Carbon anodes could be used instead of lead anodes, which were blamed for much of the early electrolyzing troubles and remained in disfavor for many years. Carl Hoepfner received his first zinc patents in 18902. He was the most persistent of those who worked with chloride solutions and met with the largest measure of success. Hc built three plants, only one of which remained in operation. This was built in 1896 at the plant of Brunner, Mond & Co., Winnington, England, now part of Imperial Chemical Industries Ltd. It leached with by-product calcium chloride from the company's Solvay alkali plant and returned to it the chlorine formed in electrolyzing. The zinc plant had a capacity of 5 long tons of zinc, said to have been doubled later, and remained in operation until 1924. No commercial plant using chloride solutions has operated since then. E. A. Ashcroft experimented in the middle nineties with chloride, alkaline and sulphate solutions on materials from Broken Hill, Australia. He built a plant with a rated capacity of 10 long tons of zinc per day, at Cockle Creek, New South Wales, in 1898. This figure was never approached nor was cyclical operation achieved. The work in the plant appears to have been largely with sulphate solutions. The plant suffered from a multitude of troubles: poor roasting, gclatinous silica, liberal use of live steam in solutions to combat the gclatinous silica with considerable

Jan 1, 1937

By W. H. W. Husband

Rock salt has been solution mined for many years in many countries. Attempts have been made in the past in Canada and various other countries to produce potash by the same method. However, only Kalium Chemicals Ltd. has been successful, possibly because the conditions in Saskatchewan are the most favorable to be found so far for the development of a solution-mining method for potash. In view of the fact that few studies of solution mining of potash have been attempted, only one company has succeeded in using the method, and no information has been released by this company, the application of solution mining of potash ore bodies has to be presented on the basis of available theory, past small-scale studies, and recent patents. A simple mining method is outlined and possible methods of recovering the potash from the brine are discussed. Dissolution data pertaining to solution mining of potash, flowsheets, and material balances are presented. The available information is brought together in a cost analysis to show capital and product costs in terms of 1966 dollars.

Jan 1, 1972

By Frank Somogyi, Donald H. Gray

Techniques for in-situ dewatering of tailings and slimes include evaporation, decantation, drainage under self weight, drainage by surcharging, and electro-osmosis. A promising technique for increasing drainage efficiency is a vertical, wall-drain system, which can be constructed in an impoundment concurrently with deposition of slurried tailings. The vertical drains, which can be constructed from sand or from the coarse fraction of a tailings stream, greatly speed the rate of consolidation of the fine tailings or slimes. The performance of a wall drain system and the semitidy of consolidation efficiency to certain variables or system parameters are examined. These parameters include the slime deposition rate, ratio of drain to slime permeability, drain width, and drain spacing.

Jan 1, 1979

By R. J. Batterham, P. W. Roller

Granulated sinter mixes of three iron ore types were prepared with a range of water contents in a laboratory investigation. The mean diameter of the granulated mixes and the void fraction of beds of the mixes were determined experimentally. Pressure drop measurements over a range of flow rates were made in a laboratory permeameter with pressure tappings at several depths in the bed. The Ergun equation was applied to the results to determine the shape factor of the granulated mixes. Pressure readings down the bed were used to estimate the local void fraction in the bed using the Ergun equation and the calculated granule shape factors. It was found that there was a decrease in void fraction with depth in the bed. The significance of this and the variation of shape factor values with the amount of water used for granulation is examined in relation to the strength of granules of the sinter mixes. The experimental and mathematical techniques presented may be useful in interpreting the behavior of the permeability of sinter beds after ignition.

Jan 1, 1986

By E. W. Mehal, R. W. Haisty, D. W. Show

The next generation of integrated circuits will probably include circuits constructed in and of GaAs. The existence of both semi-insulating and semiconducting forms of GaAs is the fact which will bring this about. In this paper we discuss the uses and limitations of semi-insulating GaAs for integrated-circuit applications. The two main areas considered are the electrical isolation that can be achieved between components on a semi-insulating substrate and the characteristics of p-n junctions in contact with semi-insulating GclAs. A process basic to attaining integrated circuits in GaAs to fully utilize the insulating properties of the substrate is selective epitaxial deposition. This process involves the deposition of a SiO2 layer onto a The trend in integrated circuits is towards the use of high-resistivity substrates or regions to achieve component isolation. The use of SiO, layers in the oxide isolation methods and the use of sapphire substrates are examples of this idea. GaAs is also a polished surface of a GaAs substrate, etching out selected area of the SiO, film to expose a GaAs surface, and deposition only onto the exposed GaAs surface. By using this process , islands of semiconducting GaAs are deposited onto a semi-insulating GnAs substrate, the islands being electrically isolated from one another by the substrate. The deposition of both p- and n-type semiconducting GaAs can be carried out in this nzanner to form p-n junctions in the island areas. This process can also be used to produce a planav structure by deposition of GctAs through a SiO, mask into holes etched into the GaAs substrate. This Putterned Epitaxial Technology (PET) is described. very promising material for use in future integrated circuits because of the existence of both semi-in-sulating and semiconducting forms. Active devices can be fabricated in the semiconducting material, and these individual components can then be electrically isolated from one another by using semi-insulating GaAs as the substrate. Epitaxial semi-insulating GaAs can also be produced thus making three-dimensional monolithic integrated circuits feasible.' This paper describes the research aimed at developing the methods for producing both two- and three-dimensional integrated circuits in GaAs, and examines some of the properties of semi-insulating GaAs as they relate to these integrated circuits.

Jan 1, 1967