Search Documents

By C. F. Gates, H. J. Ramey

Recent literature shows that pronounced increases in oil recovery can result from the use of miscible systems in recovery operations. This literature also points out certain problems associated with maintaining miscibility, e.g., compositional changes resulting from alterations in pressure and temperature or from zone dilution. The purpose of the work described in this paper was to study miscible zones for possible use in waterflooding operations and examine the manner in which these zones break down. The fluid system selected for study was oil—terNary-butyl alcohol—water, which, because of its narrow range of miscibility, is ideally suited for investigation in short, linear systems. The laboratory-observed effects on oil recovery and zone stability of a number of variables are reported. Among the variables investigated were miscible zone size, viscosity ratio, length of travel, and interstitial water saturation. Results obtained with this system show that interstitial water adversely affects recoveries because of premature phase break. Salinity of the water further aggravates Ais situation. This effect, although pronounced for this system, would probably occur in any fluid system containing an alcohol. As expected, viscosity ratio has a decided influence on recovery efficiency and zone stability. The results also show that use of a suficieno zone size, even though the system has poor phase characteristics, yields higher oil recoveries than are obtained from straight water floods. Length-of-travel studies showed a square root relationship between zone growth and path length for favorable viscosity ratios. No such clear-cut dependence was observed under unfavorable viscosity conditions. INTRODUCTION As new oil reserves have become increasingly more difficult and expensive to find and develop, the oil industry has devoted more and more time and money to finding more efficient methods for exploiting known reserves. The increasing number of water floods is one manifestation of this attempt to improve oil recoveries from existing fields. Since considerable quantities of oil are by-passed by the waterflood process, it is only a partial answer to the problem. The search continues. Of late, several proposed processes have received the critical attention of investigators. Among them are gas drives, in situ thermal reactions and miscible displacements. The present paper is concerned with miscible displacements in conjunction with water floods. Recent literature1- reports that, under proper conditions, oil recoveries from LPG floods, propane sweeps, condensing gas drives, etc., approach 100 per cent of the oil in place in the region contacted by the flood. This literature also points out some of the problems associated with these processes, one of the main ones being the maintaining of miscibility. Compositional changes resulting from pressure and temperature variations or from zone dilution give rise to phase breaks and loss of miscibility, the conclusion being that, after loss of miscibility, much of the beneficial influence of the zone is lost.' The results of the subject work show that, if sufficient zone material exists ahead of a phase interface, considerable improvement in oil recovery can be obtained. In order to increase our understanding of the behavior of miscible systems as they degenerate into immiscible processes, a laboratory system having rapid deterioration characteristics was needed. The fluid system oil—ter tiary-butyl alcohol (TBA)—water possesses these properties and was the system investigated. Although these fluids are different from those generally employed in miscible studies, an understanding of their behavior can be applied to other miscible slug processes. However, under conditions where mass transfer maintains a miscible system through multiple contacts, e.g., enriched gas drive or high pressure gas drive, the observed behavior of alcohol zones would not be applicable. The variables of interest were zone size, viscosity ratio, length of travel, initial water saturation, rate and core characteristics. Of these, only the effects of the following on zone breakdown and oil recovery are reported in detail: (1) zone size, (2) path length, and (3) initial water saturation. The effects of viscosity ratio and core characteristics are discussed in conjunction with other variables. Although initial water saturation is not envisioned as important to the phase behavior of hydrocarbon systems, e.g., LPG, it is important in alcohol systems. The properties of the fluids and cores used are given in Table 1. As previously stated, this fluid system was selected because of the limited range of miscibility

By B. K. Miller, George E. Moore

THE Missouri fire clays are here divided into plastic and semiplastic clays occurring as widespread bedded deposits in east central Missouri and flint and diaspore clays occurring as isolated "sink-hole" deposits in the north central Ozark region. Visual inspection was the first method used in clay prospecting. Thin overburden, hard sandstone "rimrocks," and the occurrence of diaspore float made this method particularly applicable in the flint and diaspore fields. The first drilling tool used was a hand auger. One man can drill 25 to 50 ft. per day at a cost of about 35 cents per foot. Holes can be drilled to a depth of 150 feet. Spud drills are often used where the over burden is hard. This drill uses a slotted earth socket bit. A two-man crew can drill about 100 ft. per day at a cost of about 35 cents per foot. Mechanically powered auger drills have been used extensively in wildcat drilling in the past few years. This type of drill furnishes a continuous set of cuttings. The practical depth limit with this drill is 50 to 60 ft. Two men can drill 300 ft. per day at a cost of about 20 cents per foot. Core drilling is used mainly to prove a known clay deposit. A two-man crew with a No. 22 Sullivan drill can drill about 30 to 40 ft. per day in soft clay, at a cost of about $1.25 per foot.

Jan 1, 1947

By C. D. Williams, C. E. Ells

The susceptibility of quenched and aged Zr-2.5 wt pct Nb alloy to embritt2ement during irradiation has been examined for a number of solution temperatures and aging times. Material quenched from temperatures approximately 40°C below the transus has high tensile ductility, and this ductility is insensitive to aging at 500°C or to irradiation. If, however, the material is quenched from temperatures above the transus it becomes highly susceptible to loss of ductility either from aging at 500 or from irradiation. Inter granular failure is characteristic of the materials having low ductility. The distribution of the equilibrium phase is found to control the susceptibility to embrittlement by restricting 6 grain growth during heat treatment and thus influencing crack propagation. IN zirconium, as in titanium, -stabilizing alloy additions are used to obtain high strengths via quench and age heat treatments, and the Zr-2.5 pct Nb alloy has been developed1 because of its strength advantage over the Zircaloys. Early in the development of the Zr-2.5 pct Nb alloy the problem of 13 embrittlement was appreciated, and for this reason the solution temperature was chosen below the p transus.' In the course of irradiation studies on quenched and aged Zr-2.5 wt pct Nb alloy it was found' that irradiation introduced an important aspect of p embrittlement, riz., material quenched from the phase and aged 24 hr at 500°C was severely embrittled by moderate doses of neutron irradiation. This effect had not been studied in titanium alloys. In titanium the metallurgical features leading to 0 ernbrittlement were found to be structures with: a) coarse a platelets at the grain bondaries, b) finely dispersed a uniformly distributed throughout the (0) matrix,6 c) Widmanstatten a-13 with more than 50 pct P, d) the presence of some metastable p transformation products,3 and e) large prior -phase grain size.5 Alternatively, the presence of a uniform distribution of coarse a was conducive to high ductility and a structure largely of equiaxed a was very dctile. The detailed mechanisms of the embrittlement have not been worked out for all of these conditions, although weakness at either a-matrix boundaries or prior p grain boundaries have been prominent in the eculation. It was proposed that acicular a might act as a mild notch, and low ductility has been associated with easy fracture along its boundary.' There have been two opposing suggestions for the source of the high ductility associated with equiaxed a phase. JaffeeB proposed that this a would accept a large por- tion of the oxygen, thus increasing the ductility of the matrix, whereas after study of a Zr-Nb-Cu alloy Weinstein and oltz proposed that the a phase, softer than the martensitic matrix, acted to blunt cracks formed in the matrix. In the present work we have studied the effect of neutron irradiation on the ductility, particularly the P embrittlement, of the Zr-2.5 wt pct Nb alloy. By a variation of solution temperature and aging time a variety of metallurgical conditions have been examined, and a range of resultant ductilities obtained. The ductility has been related to the material microstructure and mode of fracture. EXPERIMENTAL The alloy used in the present work came from two separate ingots fabricated into rod of 3/8 or i in. diam, Table I. For both batches the P transus temperature was approximately 890° C. Most of the heat treatments were done directly on lengths of the j} in. diam rod, after which the tensile test specimens were machined. Quenching was achieved by dropping rods from a dynamic vacuum into water, the cooling rate estimated to be 2 100°C per sec. For aging the rods were encapsulated in evacuated silica tubes. Round tensile test specimens, with gage diam and length 0.160 and 1.0 in., respectively, were used throughout and pulled at room temperature or 300°C on Instron tensile machines, at a crosshead speed of 0.05 ipm. Specimens were irradiated in the NRX and NRU reactors, in facilities described in previous publications.'0 The metallurgical conditions examined have been: All tensile test specimens were machined with axes in the axial direction of the swaged rod. Although the specimen had a degree of preferred crystallo-graphic orientation with basal plane normals both parallel with and perpendicular to the tensile axis, the material was comparatively isotropic." The techniques of thin foil examination in the electron micro-

Jan 1, 1970

By W. H. Bassett

ALTHOUGH brasses and bronzes have been made for ages, a systematic study of their physical properties has been carried out only during the years of the present century. Among these properties may be included those which are to be detected by means of microscopic examination; in other words by the science of metallography. The earlier workers in this field, both in this country and abroad, gave their attention to steel. When the senior author explored the situation in 1902, there was little encouragement to be found in undertaking the study of the non-ferrous alloys. A start was made, and the metallography of the brasses and bronzes, as well as of the copper-nickel- zinc alloys developed materially under his direction. Annealing experiments were begun in 1902, and in the succeeding years the effect of temperature, and the influence of previous working, on the grain size of brass were studied. The conclusions so well known and widely published today were largely reached during those earlier years. In 1905 the first complete annealing series were made. By this it is meant that brass and copper sheet, 5 B & S Nos. hard, was machined into tensile test specimens, then annealed under accurate control for 30 min. at temperatures up to the melting point of the material. Various determinations were made, including tensile strength and elongation in 2 in. There rapidly followed similar series on all of the copper-zinc alloys from 100 to 60 per cent. copper, on the bronzes, cupronickels, and on copper-zinc-nickel alloys. At this point there was published by Grard, in October, 1909,1 the very comprehensive and complete work on the tensile properties of cartridge brass, 90-10 copper-zinc, and electrolytic copper. The excellent photomicrographs in that paper illustrated the changes in structure produced by cold rolling as well as by annealing at different temperatures, but where Grard's work was confined to copper and to two alloys, the investigations in this laboratory have been over the entire fields of the commercial copper-zinc alloys, copper-tin alloys, representative copper-nickel and copper-nickel-zinc alloys as well as aluminum bronzes and others of a more special nature.

Jan 1, 1927

By Joseph L. Gillson

BRAZIL has had an industry based on ocean beach deposits of heavy minerals containing monazite, zircon, rutile, and ilmenite for well over 40 years, but except at the very earliest period, prior to 1906, and again during World War 11, has this industry been at all comparable in size with similar operations in other countries. Limiting factors have been neither a lack of reserves nor lack of markets (except for zircon). Although poor local transportation and shipping facilities have handicapped the development in Brazil, these conditions were perhaps equally bad (when mining operations started) in the Indian State of Travancore, and in New South Wales and Queensland, Australia, in which states the principal production of beach deposits of heavy minerals has occurred. The outstanding restraints on the Brazilian industry have been the lower quality of the Brazilian minerals, the relative small size of individual deposits that were known until recently, the lack of interest of Brazilian investors in mining ventures, and the unfavorable climate for investment of foreign capital under Brazilian mining law. The lower quality of the minerals is indicated by the fact that the Brazilian monazite carries only 5 to 6 pct Tho2*, and the ilmenite 561/2 pct TiO2, whereas the corresponding Travancore minerals carry 9 pct Tho, and 60 pct TiO, respectively. The Brazilian zircon is a dirty brown color (which can be removed readily) as compared with the gleaming whiteness of the Australian zircon. An inadequate market for the abundant zircon that will be available in any operation in Brazil is certainly a heavy restraint, since otherwise it could be an important byproduct. The oxide of zirconia, baddeleyite, that has come from Brazil is from other sources.' Since the Brazilian beach sands carry only a little rutile, that mineral has not been available as a valuable byproduct to help finance the operations. Substantial tonnages of rutile have been exported from Brazil. The sources of this mineral are stream placers and residual deposits over gneisses in the States of Goyaz, Minas Geraes, Ceara, etc. (Leonardos,' and Chambers". With these handicaps, Brazilian production from beach sands has been marginal, and there has been only one consistent producer. This is a company, originally French, which was called Companie de Franco-BrazilliCne, but, with the downfall of France in 1940, became Brazilian under the name Monazita e Ilmenita do Brasil ("Mibra"). This company has operated several deposits in the vicinity of Guara-pary, in the State of Espirito Santo. Its office and plant has been at Guarapary. Recently a company called, "Fomil" (Fomento Monazita-Ilmenita) started operations. This company was organized by the Foote Mineral Co. of Philadelphia, and such share as a foreign company can hold under Brazilian law has now been acquired by the Lindsay Light and Chemical Co. of Chicago. When the writer went to Brazil in the fall of 1940, he found that no general survey of the beaches had been made except for a thorough study of part of the area by Abreu.4 The paper by Miranda6 had not then been written. The federal Geological Survey and Department of Mines knew only of the existence of the deposits in Espirito Santo south of Vitoria, and had a hazy idea that others might be found north of Vitoria. One deposit in Bala was known in Rio, but the larger one at Guaratiba was not known, although a Frenchman had prospected

Jan 1, 1951

By Joseph L. Gillson

BRAZIL has had an industry based on ocean beach deposits of heavy minerals containing monazite, zircon, rutile, and ilmenite for well over 40 years, but except at the very earliest period, prior to 1906, and again during World War 11, has this industry been at all comparable in size with similar operations in other countries. Limiting factors have been neither a lack of reserves nor lack of markets (except for zircon). Although poor local transportation and shipping facilities have handicapped the development in Brazil, these conditions were perhaps equally bad (when mining operations started) in the Indian State of Travancore, and in New South Wales and Queensland, Australia, in which states the principal production of beach deposits of heavy minerals has occurred. The outstanding restraints on the Brazilian industry have been the lower quality of the Brazilian minerals, the relative small size of individual deposits that were known until recently, the lack of interest of Brazilian investors in mining ventures, and the unfavorable climate for investment of foreign capital under Brazilian mining law. The lower quality of the minerals is indicated by the fact that the Brazilian monazite carries only 5 to 6 pct Tho2*, and the ilmenite 561/2 pct TiO2, whereas the corresponding Travancore minerals carry 9 pct Tho, and 60 pct TiO, respectively. The Brazilian zircon is a dirty brown color (which can be removed readily) as compared with the gleaming whiteness of the Australian zircon. An inadequate market for the abundant zircon that will be available in any operation in Brazil is certainly a heavy restraint, since otherwise it could be an important byproduct. The oxide of zirconia, baddeleyite, that has come from Brazil is from other sources.' Since the Brazilian beach sands carry only a little rutile, that mineral has not been available as a valuable byproduct to help finance the operations. Substantial tonnages of rutile have been exported from Brazil. The sources of this mineral are stream placers and residual deposits over gneisses in the States of Goyaz, Minas Geraes, Ceara, etc. (Leonardos,' and Chambers". With these handicaps, Brazilian production from beach sands has been marginal, and there has been only one consistent producer. This is a company, originally French, which was called Companie de Franco-BrazilliCne, but, with the downfall of France in 1940, became Brazilian under the name Monazita e Ilmenita do Brasil ("Mibra"). This company has operated several deposits in the vicinity of Guara-pary, in the State of Espirito Santo. Its office and plant has been at Guarapary. Recently a company called, "Fomil" (Fomento Monazita-Ilmenita) started operations. This company was organized by the Foote Mineral Co. of Philadelphia, and such share as a foreign company can hold under Brazilian law has now been acquired by the Lindsay Light and Chemical Co. of Chicago. When the writer went to Brazil in the fall of 1940, he found that no general survey of the beaches had been made except for a thorough study of part of the area by Abreu.4 The paper by Miranda6 had not then been written. The federal Geological Survey and Department of Mines knew only of the existence of the deposits in Espirito Santo south of Vitoria, and had a hazy idea that others might be found north of Vitoria. One deposit in Bala was known in Rio, but the larger one at Guaratiba was not known, although a Frenchman had prospected

Jan 1, 1951

By L. S. Panyity

The inception of this paper may be traced directly to the various discussions of another paper by the writer1 wherein certain indefinite beliefs and opinions were emphasized as to the relative importance of total sand porosity and the actual size of the openings between the grains. Since publication of that paper it has been possible to study various methods of sand analyses and results that have been obtained under different conditions and actual operations in the field. The purpose of this paper is to indicate the value of screen analysis, especially in areas where repressuring by means of water-flood, air or gas is being used in the partly depleted fields. Sand samples have been analyzed for porosity, saturation and grain size. They are mainly from the Bradford water-flood area, where a great reliance has been put upon such analyses, and where many data are available, A few sand studies are included from fields other than the water-flood area, in order to indicate the possibilities of screen analysis in any field. Examples of various conditions are given in Figs. 1 to 7, which show the porosity, saturation and grain-size analyses of submitted cores or drill cuttings. The generally accepted methods of delineating such sand studies on cross-section paper, known as "core charts" has been employed; with the exception that a method of representing grain size has been evolved which is believed to be the best adapted for this purpose. It differs from the block diagrams generally used, in the employment of a linear section. Percentage of grain-size is represented by the subdivision of a given distance, where the total length represents the whole sample of rock chunk, while the subdivisions indicate the percentages of grains of the different sizes that will pass through the various sieves, through which the samples of crushed sand are sorted to determine the size and amount of the components that make up the aggregate. Thus, on Fig. 1, under the heading of Grain Size, the first samples are composed of grains of the following sizes: 16 per cent. through 120-mesh sieve; 33 per cent. through 150-mesh; 25 per cent. through 180-mesh; 26 per cent, through 200 mesh; a total of 100 per cent. A minus sign is placed before

Jan 1, 1931

By S. K. Bradford

(Pittsburg Meeting, March, 1910.) FOR years past I have traveled in quest of promising mining-properties, over almost impassable mountain-trails to remote places in the mining-regions, usually, many miles from an assay-office. If, upon examination, the formation and the ore-deposit appeared favorable, a quick determination of the value of my samples was necessary, in order that I might take intelligent action with reference to the acquisition of the property. A journey with my samples to civilized regions often meant weeks of delay, and perhaps loss of opportunity. How many, under similar circumstances, have returned with their assay-results from such a journey, only to find that some audacious speculator had " optioned" the property ! True, a first payment could have been made and the chances taken on the results; but experience has taught that rich-looking ore is not of necessity valuable. Personally, I would not hazard a ten-dollar bill on any property without first determining by assay the value of the ore. To carry the usual complete assay-paraphernalia over such mountain-trails was impracticable by reason of the loss of time involved, the great expense of transportation (charged according to weight), and the fact that a few such trips would almost certainly wreck the outfit. For these reasons I began a process of elimination and substitution which finally enabled me to carry, in an ordinary 26-in. valise, sufficient apparatus and supplies for, say, 100 assays of adequate commercial accuracy. My final outfit was as follows: APPARATUS. Small hammer; steel mortar (2.5 in. wide, 3 in. high, with stand sawed off flat, so that it can be used as an anvil and for

Jan 1, 1911

By G. T. Murray

The aging behavior of a Cu-Ti (3.2 at. pct Ti) alloy has been followed by electrical resistivity, hardness, and metallographic changes. The resistivity data indicate two principal processes, the first causing a sharp decrease in resistivity, and the second, which occurs over a long period of time, a much smaller rate of decrease. Lamellar nodules, Widmanstätten platelets, and homogeneous continuous precipitation was observed. The Widmanstätten platelets grow at the expense of the latter. When this study was initiated, little information was available on the aging behavior of copper-base titanium alloys. Several articles'-3 that appeared in the early 1930's showed that these alloys could be strengthened by precipitation, but a detailed study was not made. Within the past year, however, two other more comprehensive studies4'5 have been reported in the literature, one consisting primarily of an investigation of mechanical properties, the other

Jan 1, 1961

By J. J. Tietien, R. O. Clough

A technique previously used to prepare alloys of InAs1-xPx and GaAsl-x Px, miry: the gaseous hydrides arsine and phosphine, has been extended to grow single -crystalline GaAs 1-x Sb x by replacing the phos-phine with stibine. Procedures were developed for handling and storing stibine which now make this chemical useful for vapor phase growth. This represents the first time that this series of alloys has been grown from the vapor phase. Layers of P -type GaSb and GaSb-rich alloys have been grown with the carrier concentrations comparable to the lowest ever reported. In addition, a p-type alloy containing 4 pct GaSb exhibited a mobility of 400 sq cm per v-sec which is equivalent to the highest reported for GaAs. RECENTLY, interest has been shown in the preparation and properties of GaAs1-xSbx alloys, since it was predicted1 that for compositions in the range of 0.1 < x < 0.5, they might provide improved Gunn devices. However, preparation of these alloys presents fundamental difficulties. In the case of liquid phase growth, the large concentration difference between the liquidus and solidus in the phase diagram, at any given temperature, introduces constitutional supercooling problems. It is likely that, for this reason, virtually no description of the preparation of GaAs1-xSbx by this technique has been reported. In the case of vapor phase growth, problems are presented by the low vapor pressure of antimony, and the low melting point of GaSb and many of these alloys. In previous attempts1 at the vapor phase growth of these materials, using antimony pentachloride as the source of antimony vapor, alloy compositions were limited to those containing less than about 2 pct GaSb. This was in part due to the difficulty of avoiding condensation of antimony on introducing it to the growth zone. A growth technique has recently been described2 for the preparation of III-V compounds in which the hydrides of arsenic and phosphorous (AsH3 and pH3) are used as the source of the group V element. With this method, GaAs1-xPx and InAs1-xPx have been prepared2&apos;3 across both alloy series with very good electrical properties. Since the use of stibine (SbH3) affords the potential for effective introduction of antimony to the growth apparatus, in analogy with the other group V hydrides, this growth method has been explored for the preparation of GaAs1-xSbx alloys. In addition to GaSb, these alloys have now been prepared with values of x as high as 0.8. In the case of GaSb, undoped p-type layers were grown with carrier concentrations equivalent to the lowest reported in the literature. Thus it has been demonstrated that, with this growth technique, all of the alloys in this series can be prepared. EXPERIMENTAL PROCEDURE A) Growth Technique. The growth apparatus, shown schematically in Fig. 1, and procedure are virtually identical to that described2 for the growth of GaAs1-xPx alloys, with the exception that phosphine is replaced by stibine.* HCl is introduced over the gallium boat to *Purchased from Matheson Co., E. Rutherford,N+J. transport the gallium predominantly via its subchlo-ride to the reaction zone, where it reacts with arsenic and antimony on the substrate surface to form an alloy layer. The fundamental limiting factors to the growth of GaAs1-xSbx alloys from the vapor phase, especially GaSb-rich alloys, are the low melting point of GaSb (712°C) and the low vapor pressure of antimony at this temperature (<l mm). Thus, relatively low antimony pressures must be employed, which, however, imply low growth rates. To provide low antimony pressures, very dilute concentrations of arsine and stibine in a hydrogen carrier gas were used. Typical flow rates (referred to stp) were about 4 cm3 per min of HC1 (0.06 mole pct)+ from 0.1 to 1 cm3 per min of ASH, (0.002 to 0.02 mole pct), and from 1 to 10 cn13 per min of SbH3 (0.02 to 0.2 mole pct), with a total hydrogen carrier gas flow rate of about 6000 cm3 per min. Although no precise data on decomposition. kinetics exist, it is known4 that stibine decomposes extremely rapidly at elevated temperatures. However, the high linear velocities attendent with the high total flow rate (about 2000 cm per sec) delays cracking of the stibine until it reaches the reaction zone and prevents condensation of antimony in the system. To improve the growth rates of the GaSb-rich alloys, growth temperatures just below the alloy solidus are main-

Jan 1, 1970

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 E. P. Barrett, T. L. Joseph

The large iron-ore producers on the Mesabi Range are able to maintain the silica in their shipping products at from 8 to 10 per cent. by mixing ores of various grades, some assaying 4 per cent, silica and some as high as 18 per cent. silica. For each ton of 4 per cent. silica ore mined, a ton of 14 per cent, silica ore can be mined and mixed with it and the average grade maintained at 9 per cent. This mixing operation has made possible the utilization of large quantities of ore too lean to be used alone, and herein lies the advantage of the producers who operate a number of mines at the same time. As the grade of the ore from one of the properties falls off, a little high-grade ore from another property can be mixed with it and the average maintained, while if one property alone were being operated all of the ore below grade would be left behind. This mixing operation, however, can continue only as long as there is high-grade ore available for mixing with the high-silica ores and, while the tonnage of iron ore in the Mesabi Range is still enormous, the tonnage of high-grade ore suitable for mixing with any quantity of low-grade ore is being rapidly depleted. Obviously, if an 18 per cent. silica ore can be reduced by concentration methods to 12 per cent. silica, considerably more of it can be utilized with a given amount of high-grade ore. The operators on the Mesabi Range recognize this situation and are energeticdly endeavoring to reduce the silica in their concentration plants because every unit of silica that can be removed by concentration is a conservation of their high-grade ores. More Elaborate Processes Will Be Needed At the present time there are thirty-seven concentrating plants on the Mesabi Range, and about one-third of the total ore shipped is beneficiated in these plants. In about one-half of these plants no reduction is made in the silica but the moisture or structure of the ore is improved. The washing process is by far the most important method for the removal of silica, and it is interesting to observe that the tonnage of "wash" ore during the past five years has shown practically no increase although the total tonnage of ore shipped has increased. This is due to the fact that the available tonnage of wash ore is being depleted and the amount

Jan 1, 1930

By B. D. Smith, K. H. Coats

Experiments in which calcium chloride displaced sodium chloride from four cores showed the extent of asymmetry in the resulting effluent concentration profiles. These results provided a check on how validly the mixing process is modeled by a differential (i.e., not finite-stage) capacitance mathematical model. The effluent concentration profile from two consolidated cores exhibited considerable asymmetry, while two unconsolidated cores yielded nearly symmetrical profiles. All runs resulted in breakthrough of the 50 per cent concentration significantly before one pore volume was injected. In addition, velocity appreciably affected the effluent concentration profile from a Torpedo sandstone core. The differential capacitance model matched the data significantly better than a simple diffusion model. The capacitance model allows determination of the amount of dead-end pore space in a porous matrix and the effect of velocity on the rate of diffusion into this space. An experimental program yielding insight into the physical validity of the capacitance effect is described. INTRODUCTION Axial dispersion — the mixing accompanying the flow of miscible fluids through porous media — has been the subject of many relativeiy recent studiesl-13 and a comprehensive review of the topic has been given by Perkins and Johnston.14 This dispersion is of practical interest in studies of the miscible displacement process, fixed-bed chemical reactors, and the adsorption of solutes from a flowing stream onto the surface of a porous medium. In the latter case, the effect of dispersion must be considered when adsorption parameters are determined from the nature of concentration profiles. In general, early studies of dispersion assumed applicability of a simple diffusion equation and were concerned with correlation of the experimentallv determined "effective" diffusion coefficient with system properties over a large range of the latter. Recent have been concerned with the deviations between the asymmetrical effluent concentration profiles observed and the symmetrical ones predicted by the diffusion model. In the present study, effluent concentration profiles were obtained from consolidated and unconsolidated cores. These profiles were compared with those predicted by a differential (i.e., not finite-stage) capacitance model. Solutions to the simple diffusion model, for three sets of boundary conditions, were compared with one another and with the experimental profiles. SUMMARY OF PREVIOUS WORK The reader is referred to Perkins and johnston14 for an extensive review of studies of dispersion in porous media. Many investigators have employed the simple diffusion model characterized by Eq. 1 below: The dispersion coefficient D for unconsolidated systems is correlated by u is interstitial velocity and dp is particle diameter. Since heterogeneity of the sand pack affects the mixing, this equation is also expressed as where a is proportional to the degree of heterogeneity and is about 3.5 for random packs of unconsolidated sand.l4 Eq. 3 holds for 2 For a Do homogeneous (regular) type of packing, should be 1 or less.6 Aris and Amundson6 and Carberry and Bretton consider o to be the number of particle lengths per mixing cell in the finite-stage model. Data from consolidated cores indicate dp to be about 0.36 cm for outcrop rocks, Torpedo sandstone having a reported value of 0.17 cm.15 For v /Do less than about 2, the effect of molecular diffusion must be considered and the total dispersion coeffi-

Jan 1, 1965

By Yang Tsang Woo

I will endeavor to describe the methods of silver-mining and smelting employed by the natives in Mongolia. Modern methods have been applied there, but with little success; and, since they are familiar to most members of the Institute, I will simply mention that the failure was due to the high price of coke used in smelting the ore in modern furnaces, and to the unsuitable mill-machinery employed for concentrating the galena, which is finely distributed in the ore. The Jehol silver-mines are situated about 45 miles NE. of Jehol, the capital of Mongolia. They embrace two mines, 5 miles apart,—the Ku Shan Tze mine and the Yen Tung Shan mine. They were first worked by natives 50 years ago, about the time when mining was so flourishing in other parts of the world,—for instance, in California and Australia. The upper part of the vein is galena mixed with iron-stone, and is 2 to 4 ft. thick. At lower levels the vein is composed of silver-lead ore running between quartz-porphyry walls. Limestone, talc and black shale, colored by graphite, are found in other parts of the mine. Crystalline limestone is found 1 mile NE. of Ku Shan Tze. Granite is encountered in the Yen Tung Shan mine. Mining.—The native method of working the mines is most primitive. The same method may have been employed a thousand years ago. A small inclined shaft, 4 ft. by 4 ft., is sunk in the vein-stuff where the appearances are most favorable. Another shaft is sunk 20 or 30 yds. away, for ventilation. The shaft follows the vein in a zigzag fashion in whatever direction the vein appears to be richest. Timber is used only in soft ground. Where the ground is hard, the roof is cut into an arch-form. In some places, instead of using ladders, steps are cut in the rock, just wide enough to hold one foot. The deepest native workings are 400 ft. below the

Jan 1, 1903

By William L. Fink and

Although age-hardening in an aluminum-base alloy containing magnesium was observed by Alfred Wilml as early as 1911, it was not until 1919 that a theory of the mechanism of age-hardening was proposed. Merica, Waltenberg and Scott12 studying the age-hardening characteristics of Duralumin at the National Bureau of Standards, came to the conclusion that age-hardening of this alloy is caused by the precipitation of CuAl2, which is less soluble at the aging temperature than at the solution heat-treating temperature. It was postulated that the initially precipitated particles were of fine colloidal dimensions but that they gradually grew in size. Maximum hardness was assumed to be attained when the particles reached a critical size. This theory was at first received skeptically, since it was a widely accepted view at that time that the solid solution state should represent the hardest state of an alloy. Shortly thereafter, Jeffries and Archer proposed their well-known slip interference theory.&apos;13 They suggested that age-hardening was accomplished by the precipitated particles acting as keys interfering with slip along crystallographic glide planes. They showed that this mechanical theory led direct,ly to the assumption that maximum hardening would be produced by particles of a critical size, which they suggested would have a diameter approximately 10 times that of the aluminum atom. This contribution amplified and explained so rationally the age-hardening theory of Merica, Waltenberg and Scott that wide acceptance resulted. Objections to Simple Precipitation Theory From time to time certain experimental facts have been cited against the simple precipitation theory. The first of these was the discovery by Fraenkel4 that, although the electrical resistivity of Duralumin decreased during aging at higher temperatures (from 100&apos; to 250&apos; C.), it increased during aging at ordinary temperatures. This was not in accordance

Jan 1, 1940

By William L. Fink and

Although age-hardening in an aluminum-base alloy containing magnesium was observed by Alfred Wilml as early as 1911, it was not until 1919 that a theory of the mechanism of age-hardening was proposed. Merica, Waltenberg and Scott12 studying the age-hardening characteristics of Duralumin at the National Bureau of Standards, came to the conclusion that age-hardening of this alloy is caused by the precipitation of CuAl2, which is less soluble at the aging temperature than at the solution heat-treating temperature. It was postulated that the initially precipitated particles were of fine colloidal dimensions but that they gradually grew in size. Maximum hardness was assumed to be attained when the particles reached a critical size. This theory was at first received skeptically, since it was a widely accepted view at that time that the solid solution state should represent the hardest state of an alloy. Shortly thereafter, Jeffries and Archer proposed their well-known slip interference theory.&apos;13 They suggested that age-hardening was accomplished by the precipitated particles acting as keys interfering with slip along crystallographic glide planes. They showed that this mechanical theory led direct,ly to the assumption that maximum hardening would be produced by particles of a critical size, which they suggested would have a diameter approximately 10 times that of the aluminum atom. This contribution amplified and explained so rationally the age-hardening theory of Merica, Waltenberg and Scott that wide acceptance resulted. Objections to Simple Precipitation Theory From time to time certain experimental facts have been cited against the simple precipitation theory. The first of these was the discovery by Fraenkel4 that, although the electrical resistivity of Duralumin decreased during aging at higher temperatures (from 100&apos; to 250&apos; C.), it increased during aging at ordinary temperatures. This was not in accordance

Jan 1, 1940

By Carl Davis

A description is given of grinding practice on the Rand and of experiments made to improve that practice. The paper includes a description of the experimental plants and methods and the results obtained. THE first tube-mill on the Rand was put into operation in May, 1904, at the Glen Deep Mine. From that time onwards, tube-mills were added to various plants, although little was known regarding the capacity of a given tube-mill when working on banket ore. Within a few years, however, the so-called standard size (length of shell 22 ft. 0 in. diameter 5 ft. 6 in.) was generally used until the last year or two. Practically the only exceptions were about 30 tube-mills having a length of 16 ft. and a diameter of 6 ft., and a few open-end mills of the roller-supported type. Most of the information obtained during the last 15 years has been obtained with mills of the standard dimensions. The adoption of the tube-mill as an accessory to the stamp mill was rapid; and where 3 tube-mills were working on the Rand at the end of 1904, 244 were in use seven years later.1 By 1910, good practice provided 1 tube-mill for 20 stamps of 2000-lb. falling weight. The horsepower of the motors driving the tube-mills had increased from. 80 to 100 and then to 125 at this date. Broadly speaking, current practice at that date aimed at a final product of which 60 per cent. was suitable for sand treatment and 40 per cent. for slime. The sand grading was +60 mesh, 6 per cent.; +90 mesh, 25 per cent.; -90 mesh, 69 per cent.; and the slime grading -200 mesh, 2 per cent.; -200 mesh, 98 per cent.

Jan 12, 1924

By John M. Crowl, L. E. Sawyer

5.3-1. General Public Resistance to Strip Mining. Surface (strip) mining is the oldest recorded method of extracting coal and other minerals from the earth. This method of mining completely alters the topography of the earth&apos;s surface, leaving an area of more or less parallel ridges or of peaked mounds of the materials which overlay the mineral seam. It destroys all original vegetation and provides materials for new type soil. During the early years the acreage mined by this method was small, land was plentiful, and with a growing young nation no thought was given to the restoration of the disturbed areas to some form of productive use. Early in the present century the development of steam shovels and drag-lines made it possible to remove thicker overburden to recover the products. With the deeper digging, the size of the disturbed areas increased. With this increase in the size of equipment and the improvement of blasting techniques, mining was expanded into more prominent locations and to areas of more valuable land. The more progressive operators became aware of the need to reclaim those areas for some productive use. Electric shovels with capacities of up to 200 cu yd and draglines with capacities of 145 cu yd, capable of uncovering products over 100 ft below the surface, are now in use. Combined with the increase in the size of equipment, the expansion of contour mining or rim stripping in the mountainous areas has focused public attention on the need for a sound reclamation program for all disturbed areas. APPEARANCE. After mining, the areas consist of varying percentages of rock, shale, slate, and soil material devoid of all plant and animal life. Unless a definite reclamation plan is carried out, many of the mined areas will remain bare for a period of years. The topography of the area is completely altered. What may have been level to rolling land in cultivation, in grass, or in timber is thrown up into a series of ridges or mounds.

Jan 1, 1968

By Anton Eilers, R. W. Raymond, O. H. Hann

THIS paper will treat of such works only as beneficiate ores directly in the mining districts. And when it is said that more than twenty

By George W. Lower, William A. Hockings, Donald A. Kaczynski

The rate of dissolution of polycrystalline metallic copper in aqueous cupric ammonium nitrate solutions in the non-film-forming region was investigated by the rotating disc method. The investigation was performed in solution concentration ranges applicable to hydrometallurgical processes. This investigation was an extension of a study on the cupric ammonium carbonate system previously reported by Smith, Lower and Hockings, in which the following kinetic model was proposed: (1) Diffusion of cupric ammine ions to the copper surface; (2) Forward reaction - first order reaction of cupric ammine ions with metallic copper; (3) Reverse reaction - disproportionation of cuprous ammine ions to metallic copper and cupric ammine ions ; and (4) Diffusion of cuprous ammine ions from the copper surface. The nitrate system was selected for this study because it simplified the determination of the ionic composition of the solutions. The variables studied were stirring speed and cupric, ammonia, and nitrate concentrations. The dissolution rate increased linearly with at low values of but exhibited increasingly negative deviations from linearity at higher values of m. The rate also increased with increasing cupric concentration but decreased with increasing ammonia and nitrate concentration. Good agreement was obtained between the experimental rate data and the proposed model. Further verification of the model was indicated by the close agreement of the diffusion coefficient calculated from the data and comparable literature values.

Jan 1, 1974