Search Documents

By Luther Wagoner

HAVING given in a former paper1 the results of assays of sea-water, bay-mud, dredgings from San Francisco bay, etc., and' believing it might be interesting to extend the work to include' some deep-sea dredgings, I procured from the Smithsonian Institution six samples taken by the U. S, steamer Albatross, and marked as follows

Jan 9, 1907

By Walter S. Weeks

The process of cooling air by allowing it to expand and do work in an engine is well known, but the theory of obtaining cold air by free expansion without the aid of an engine operating with cutoff has been little discussed. Case I If compressed air is allowed to expand to the atmospheric pressure through an orifice in an air line that is supplied by a running compressor, no cooling results except the negligible one due to the JouleThompson effect, which will not be considered in this discussion. The effect of moisture will also be neglected. Symbols P1 Absolute pressure in pipe line, lb. per sq. ft. P3 Atmospheric pressure, lb. per sq. ft. V1 Volume occupied by 1 lb. air in pipe. V3 Volume occupied by 1 lb. air at P3. C, Specific heat of air at constant volume, B.t.u. per lb. per deg. F. C, Specific heat at constant pressure, B.t.u. per lb, per deg. F. T1 Absolute temperature of air in pipe, deg. F. T8 Absolute temperature of air outside after expansion and mixing and coming to rest. j Mechanical equivalent of heat (778 ft. lb.) R Gas constant for air, ft-lb. per deg. F. = 53.3. Formulas Consider 1 lb. of air moving out of a pipe. The air behind it does work on it to the extent of P1V1 ft-lb. This work is really done by the thrust of the piston of the compressor and does not come from any energy that exists in the air in the pipe. The pound of air contains

Jan 1, 1937

By Walter S. Weeks

THE process of cooling air by allowing it to expand and do work in an engine is well known, but the theory of obtaining cold air by free expansion without the aid of an engine operating with cutoff has been little discussed. Case 1 If compressed air is allowed to expand to the atmospheric pressure through an orifice in an sir line that is supplied by a running compressor, no cooling results except the negligible one due to the Joule-Thompson effect, which will not be considered in this discussion. The effect of moisture will also be neglected. Symbols P1 Absolute pressure in pipe line, lb. per sq. ft. P3 Atmospheric pressure, lb. per sq. ft. V1 Volume occupied by 1 lb. air in pipe. V3 Volume occupied by 1 lb. air at P3. Cv Specific heat of air at constant volume, B.t.u. per lb. per deg. F. Cp Specific heat at constant pressure, B.t.u. per lb. per deg. F. T1 Absolute temperature of air in pipe, deg. F. T3 Absolute temperature of air outside after expansion and mixing and coming to rest. J Mechanical equivalent of heat (778 ft. lb.) R Gas constant for air, ft-lb. per deg. F. = 53.3. Formulas Consider 1 lb. of air moving out of a pipe. The air behind it does work on it to the extent of P1V1 ft-lb. This work is really done by the thrust of the piston of the compressor and does not come from any energy that exists in the air in the pipe. The pound of air contains

Jan 1, 1937

By W. F. Sullivan, J. R. Coleman

The use of radioisotopes in obtaining basic information on large scale industrial processing is illustrated with two examples. The first is concerned with the operating characteristics of a kiln scrubbing tower and the second with those of a Hardinge ore mill. The examples show the advantages associated with the industrial use of tracers as well as the limitations. The Atomic Energy Commission regulations governing the use of radioisotopes in this manner are also discussed. The nuclear properties of radioactive isotopes have provided a new technique for obtaining basic information on large scale industrial processing. A small portion of the process stream is made radioactive by mixing with a suitable radioisotope or by irradiation in a nuclear reactor. The "tagged" portion is then part of the normal process stream and can be followed by detection and measurement of the associated radioactivity. The advantages of radioactive tracing over other forms of tracers are well known, and include such factors as chemical similarity, capability of precise determination of very small quantities due to the high sensitivity of detection apparatus, and the absence of foreign element contamination of the final product. This report will illustrate two applications of the use of radioactive tracers in large scale industrial processing which have provided information that would have been hard to obtain by other means. The first is concerned with the operating characteristics of a kiln scrubbing tower and the second with those of a Hardinge ore mill. ATOMIC ENERGY COMMISSION REGULATIONS Atomic Energy Commission approval can be obtained by qualified personnel if the proposed quantity of radioactivity does not exceed AEC's standards for

Jan 1, 1965

By Howard A. Meyerhoff

IN western Argentina, in the Province of Mendoza and the Territory of Neuquén, there is a series of solid bitumen deposits which are claimed to be the most extensive in the world. In a linear belt 500 km (311 miles) long, roughly paralleling the axis of the Andes but occupying a variety of positions with respect to the orogenic structures, more than 100 outcrops have been reported. Approximately 70 of these have been prospected, and some mining has been planned or attempted for about half this number. Limited tonnage, high sulphur content, inaccessibility, labor shortages, and disastrous fires have taken a heavy toll among these operations, and in 1947, only 4 deposits were being actively mined, but 8 more were being explored and developed with a view to placing them in production. Inasmuch as these deposits are currently yielding a substantial fraction of Argentina's limited domestic supply of solid fuels, a brief account of the deposits and of the small industry based upon them will provide a commentary on Argentina's fuel problem. CHARACTER OF SOLID BITUMENS The solid bitumens of Mendoza and Neuquén are petroleum derivatives, as is indicated by the following ultimate analysis: [CONSTITUENTS PER CENT Hydrogen6.8 Carbon82.4 Nit.rogenI.6 Oxygen2.7 Sulphur2.2 Ash4.3 100.0] In physical appearance they bear a close resemblance to coal and are commonly called carbón. Their specific gravity has an extreme range of 1.10 to 1.777 in 36 samples weighed, but the average is between 1.14 and 1.24. The material is black, lustrous to dull, with blocky to sub-conchoidal fracture. Though brittle, the purest material is softer than anthracite and exhibits slightly more cohesion. This bituminous material is generally known as asfaltita or asphaltite, but definitive chemical studies indicate that the term asphaltite or grahamite can be applied correctly only to the exceptionally pure material of the Auca Mahuida district in Neuquén. Some other name should be used for the chemically variable bitumens found in all other districts, and the designation "asphaltitic pyrobitumen" has been proposed by Carlos A. S. Piscione.1 At the present time these bitumens, are finding favor as solid fuel and as a gas-producing medium. They yield heat values of 8650 to 9750 cal,2 or 14,500 to 16,750 Btu per pound, and in consequence of their excellent heating qualities and the scarcity of imported coal, they are marketed as far away as Buenos Aires at a price of go to 95 pesos, or approximately $22 to 23, per metric ton. In burning, the material swells and decomposes into solid, fluid, and gaseous fractions which burn violently though nonexplosively. Its combustibility has been responsible for disasters and virtually complete destruction at Mina La Esperanza and Mina Santa Marta, and for minor mishaps elsewhere, as at Mina Escondida in August 1947.

Jan 1, 1947

By L. T. Stanley

A method is described whereby the behavior of the front is approximated when gas is injected into a thick reservoir having reasonably homogeneous properties. The method is applied to the Abqaiq field of Saudi Arabia. The producing member is the Arab-D, a high-permeability calcarenite which has no continuous betlding planes. Field performance indicates the injected gas to be partially miscible with the reservoir oil because gas volume factors experienced are lower than those predicted by the gas law. Eqlrilibril~m calculations confirnz ihis and also show that the volume factor may vary appreciably, depending on the relative quantities of oil and gas in contact in the reservoir; consequently, volutnetric balances are made for the purpose of determining the behavior of the gas volume factor during injection history. The effect of gravity segregation on position and shape of the gas front is approximated by dividing the producing section into three zones vertically and tracing the movement of the average interface in each zone, with counterflow of oil and gas taking place betweell zones behind the front. This results in a gas front that advances more rapidly along the top of [he formation than along the base, producing an "umbrella" effect in cross section that becomes more pronounced as the front progresses. The calculations cover the gas-injection period of Abqaiq field history through 1958, and the position of the gas front is plotted at one-year intervals. Finally, some comparisotls between the calcrlated fronial position and the gas-oil contact as Measured by neutron logs are made. INTRODUCTION Fig. 1 is a structure contour map of the Abqaiq field. For analytical purpcses, the field has been divided into two areas designated A and B, as shown on the map. Gas injection into Area A was begun in early 1954 into two wells located near the crest of the structure on the north-south axis of the anticline. During the period covered by this paper, the average injection rate has been 122 MMscf/D with a maximum sustained rate of 160 MMscf/D. The reservoir pressure has been maintained at 2,450 psig since start of gas injection. The reservoir originally was undersaturated but, prior to pressure maintenance, the pressure was drawn below the bubble point in most of the Area A section, creating an in-place free-gas saturation of 8 per cent at the crest of the structure. The average critical gas saturation is 13 per cent established by laboratcry core tests. That the entire reservoir remained below critical gas saturation prior to gas injection is borne out by the fact that none of the crestal wells have exhibited high gas-oil ratios during production history. The Area A reservoir is a carbonate section about 200-ft thick having average porosity and permeability of the order of 22 per cent and 500 md, respectively. The productive horizon is the Arab-D member of Jurassic age and is encountered at an average depth of

By O. P. Chisholm

The most noticeable change in lead smelting over the past few years has been the increase in the smelting rate of lead blast furnaces. For several years a great deal of attention has been paid to the preparation of the blast-furnace sinter charge but more recently the plan has been to incorporate- almost the entire makeup of the blast-furnace charge, excepting coke and scrap iron, at the sintering machines. Formerly, sintering machines were used primarily for removing, sulphur and for agglomerating finely divided material both sulphide and oxide in character. Limestone flux usually was so proportioned that a relatively large amount was added to the furnace charge direct. This procedure was also followed with oxidized ores, which were purposely crushed coarse' so that they would be adaptable for direct smelting on the furnace charge. In later years it has been the tendency in western smelters to include practically all of the limestone and oxidized ores in the sinter charge. This has been somewhat more costly because fine crushing is required for sintering purposes and because these oxidized materials were given additional processing through the sinter plant. The addition of such oxidized materials to the usual charge to be sintered, brought about, in certain instances, a deficiency in heat ordinarily supplied by the sulphide constituents of the charge. This heat deficiency has been remedied by the addition of carbonaceous fuel, in the form of finely crushed coke breeze, or in a few instances by the addition of zinc retort-plant residues. The enhanced gold price has stimulated the mining of crude siliceous ores throughout the Western States and in the smelting of such ores more limestone is required for fluxing. Shipments of gold-bearing pyritic concentrates to Western smelters have increased, and the combination of increased silica, limestone and pyrite has increased the percentage of slag, which, in itself, is an aid in .securing smoother and more rapid smelting in the blast furnace. By the addition of these substances, the percentage of zinc in the slag has been appreciably lowered. at many plants, with resultant benefit to smelting speed at the blast furnace. This increase in slag formation with lowered zinc content has caused also perceptible lessening of the amount of lead on the charge and this has benefited the blast-furnace smelting. Although a satisfactory sinter is fundamental in increased rate of bullion production per furnace, there has been a trend over the list four or five years to decrease the percentage of coke and increase the percentage of scrap iron and limestone on the blast-furnace charge. As a result of these changes in practice certain blast furnaces, without any mechanical change, have doubled or tripled their tonnages. For furnaces whore the volume of air is recorded, records show decidedly larger air volumes with a comparatively small increase in air, pressure, or, none at all.

Jan 1, 1941

By T. W. Guy

During the past three years the Surface Preparation Committee of the American Mining Congress Coal Operators' Committees has been collecting data on dewatering and drying washed coal, and on screening coal in representative plants in the Eastern and Central bituminous fields. Because of wide variations in bed moisture, such data can be compared only after deducting the bed moisture. It was found that practically every company used a different routine for moisture sampling and determinations. Some reported the moistures as total moistures, others as surface moistures, air-dried moistures, or oven-dried moistures. For most of the reports it was necessary to estimate, from a consideration of the bed moisture and other data available in a given case, corrections to be made in order to obtain surface-moisture figures as a common basis for comparison. At any plant, and regardless of bed moisture, the percentage of surface moisture remaining in a product when the dewatering, or a given stage of the dewatering, has been completed, is the real measure of what has been accomplished. The descriptions and data given with Fig. 1 show that surface-moisture figures show relationships that would not be shown by total moistures. Therefore bed moisture should be deducted, or, if more practicable, the surface moisture of the products should be measured direct. A preparation engineer finds one per cent, or even a part of one per cent, of surface moisture a very important consideration in the results of his efforts to find the most effective and economical methods of reducing and controlling the surface moisture in his products within the required limits. Therefore it is important for him to have accurate measurements of surface moisture with minimum uncertainty as to whether they sometimes include less than the surface moisture and at others all of the surface moisture plus an unknown part of the bed moisture. The Problem We know that pieces of coal have a capacity for holding water: (1) inside themselves, which is a natural characteristic of the bed from

Jan 1, 1938

By T. W. Guy

During the past three years the Surface Preparation Committee of the American Mining Congress Coal Operators' Committees has been collecting data on dewatering and drying washed coal, and on screening coal in representative plants in the Eastern and Central bituminous fields. Because of wide variations in bed moisture, such data can be compared only after deducting the bed moisture. It was found that practically every company used a different routine for moisture sampling and determinations. Some reported the moistures as total moistures, others as surface moistures, air-dried moistures, or oven-dried moistures. For most of the reports it was necessary to estimate, from a consideration of the bed moisture and other data available in a given case, corrections to be made in order to obtain surface-moisture figures as a common basis for comparison. At any plant, and regardless of bed moisture, the percentage of surface moisture remaining in a product when the dewatering, or a given stage of the dewatering, has been completed, is the real measure of what has been accomplished. The descriptions and data given with Fig. 1 show that surface-moisture figures show relationships that would not be shown by total moistures. Therefore bed moisture should be deducted, or, if more practicable, the surface moisture of the products should be measured direct. A preparation engineer finds one per cent, or even a part of one per cent, of surface moisture a very important consideration in the results of his efforts to find the most effective and economical methods of reducing and controlling the surface moisture in his products within the required limits. Therefore it is important for him to have accurate measurements of surface moisture with minimum uncertainty as to whether they sometimes include less than the surface moisture and at others all of the surface moisture plus an unknown part of the bed moisture. The Problem We know that pieces of coal have a capacity for holding water: (1) inside themselves, which is a natural characteristic of the bed from

Jan 1, 1938

By Kim C. Harden

INTRODUCTION The purpose of the following discussion is to present the state of the art of solution mining. Since the economics of a mining method ultimately determines its applicability and viability this presentation shall revolve around the costs of in- situ solution mining. First the assumed physical characteristics of the hypothetical ore body are described, followed by the appropriate operating assumptions. Then after a brief discussion on the type of surface plant to be used, the assumed project time tables and costs for Texas and Wyoming are presented. Finally, the economics of in-situ uranium leaching are analyzed through the use of discounted cash flow rate of return analysis. ORE BODY CHARACTERISTICS The assumption of the ore body characteristics is probably the most variable portion of this discussion. The characteristics that have been used are based mainly on state of the art technology, however, consideration of the most common depths of ore, ore thicknesses, and permeabilities also influenced these assumptions. In addition, it is assumed that these assumptions are equally applicable to Texas and Wyoming. The average grade of the ore is assumed to be .09% U308 with no apparent disequilibrium. The average thickness of ore is 2.29 m (7.5 ft) which results in an average grade-thickness (GT) of .675. The assumed depth to the top of the ore is 121.92 m (400 ft), the ore density is placed at 1.78 gm/cc (18 cu ft/ton), the porosity is estimated to be 28% and the permeability 1 darcy. These assumed ore body characteristics are shown in Table I. In addition, it is specified that the costs to be later discussed are based on a minimum GT cut-off of 0.15. It is more common to use GT cut-offs of 0.30 to 0.50 but GT cut-offs as low as 0.15 in conjunction with a minimum grade of 0.05% U308 have been used in the past with success and is considered state of the art. The ultimate percentage of uranium recovered from the ore is left to the discretion of the reader since the costs and economics are based on pounds recovered by the surface plant. OPERATING AS.SUMPTIONS An annual production rate of 200,000 lbs U308!yr was chosen for this example. In order to maintain this production rate, based on the ore body characterized above, a flow of 4731 liter/min (1250 GPM) with a recovery solution grade averaging .039 gm U308/liter is assumed. A regular 5 spot well field pattern is used with a well spacing of 21.5 m (70.7 ft) between like wells and 15.24 m (50 ft) between unlike wells. This well spacing gives each well an area of influence equal to 232.25 sq m (2500 sq ftl. An excess wells factor of 1.17 is used to estimate additional monitor wells and well field boundary wells. Each production well is expected to yield an average flow rate of 37.85 liter/min (10 GPM). In addition it is assumed that the ore body has a good shape in that it is not tenuous and narrow but has at least an average width of 200 ft. The process chemistry required for this ore body is assumed to be based on the sodium carbonate System- Oxygen is the chosen oxidant. Sodium chloride elution followed by precipitation with hydrogen peroxide makes up the remaining portion of the process. A fluidized up-flow ion exchange system is specified. The operating assumptions are listed in Table II. Restoration of the ore body shall be assumed to be accomplished through the use of ground water flush. Other methods may be considered as having to fall within the costs estimated for a ground water flush in order to be economic. In Texas it is assumed that a high capacity disposal well (200 GPM +I is required and in Wyoming evaporation ponds covering approximately 35 acres are to be used. No specific cost has been given to restoration. Instead only the additional capital investment for restoration equipment is given. Then, one year of restoration operating expense is estimated and included as the operating expense for one year beyond the last pound of U308 produced. It is also assumed that restoration will be pursued in the mined out areas of the ore body contiguous with ongoing production.

Jan 1, 1980

By Leonard Bernstein, Harry Bartholomew

MANY of the properties of metals and alloys are structure dependent. Not the least of these is the grain structure. For example, in producing alloy bonds between silicon or germanium and gold-alloy foil at temperatures above their eutectics (which are, respectively, at 370" and 356°C) but below the melting points of the individual constituents, it was found that wetting was more complete with a fine-grain structure than with a coarse-grain structure. In cases where the assemblies were held together for long periods of time at elevated temperatures, wetting was not as critically dependent on the grain structure as was the case for shorter periods of time. When liquid phase forms, it first forms in the grain boundaries due to the fact that most of the impurities are concentrated at the grain boundaries and that most impurities tend to lower the melting point of the gold alloy somewhat. In addition, grain boundaries are at high-surface free-energy levels and are thus in a more favorable condition to initiate good wetting. A fine-grain structure will have more grain boundaries per unit area than coarse-grain structure thereby making wetting somewhat easier. To make the grain structure of an alloy sys- tem visible, a satisfactory method for differentiating between the different grains of which the system is composed must be employed. For the alloy bonding system previously described, the grain structure on the foil surface is of primary interest. Conventionally used etchants for the gold-alloy system will not adequately delineate grain boundaries in their structures. For this reason an alternate method is proposed for those cases where such a determination is necessary. Foil between 0.0005 and 0.005 in. thick has been used in this determination. The equipment used in this investigation was described in a previous publication.' Essentially, it employs a resistance-type filament which can be heated up very rapidly and cooled very rapidly. A thin refractory material is placed on top of the heating element. This refractory material may be molybdenum, tantalum, tungsten, or even ceramic but its thickness should be less than 0.010 in. to minimize the temperature gradient across it. The gold-alloy foil is placed on top of this refractory material. The temperature of the heating filament is raised to 900°C and cooled down to below 100°C in 5 to 10 sec. During this cycle, the foil can be observed to plastically deform due to its own weight. With no further chemical etching, this assembly is then viewed under a standard metallurgical microscope and the grain size measured. Fig. 1 is a Au-1 pct Sb alloy at 400X magnification and Fig. 2 is a Au-1 pct Ga alloy at 130X. This technique has proved to be an adequate means for controlling processing conditions in producing large quantities of gold alloy foil.

Jan 1, 1963

By Enrique Touceda

The question as to the proper amount of total carbon that the malleable founder would prefer to have in pig iron for use in the production of air-furnace, white iron castings, must be considered from different angles, that is, whether it is desirable or advantageous from an economic standpoint to use some kind of low-carbon scrap on his mixture, or make use of pig and sprue only. Whereas silicon is the acknowledged scrap carrier in the case of cupola gray iron castings, carbon performs this role for the most part in malleable iron practice, irrespective of the character of furnace used for the production of the white iron castings. In this particular, the advantage lies with the maker of gray iron castings in that the silicon content in pig iron through a regulation of furnace temperature is under very easy control by the blast-furnace manager, whereas he has little or no control over the resultant percentage of carbon, as this is dependent on the quantity of coke in the hearth, and hearth temperature, coupled with the amount of hearth slag and its particular composition. As perhaps more than 95 per cent. of white iron castings are made in air furnaces the following statements are intended to cover that situation particularly: In the malleable process the composition of the hard iron castings (that is determined upon as best suited for the work in hand) is the one factor that must control the composition of the mixture to be used; because if the elements are not between certain definite limits individually and collectively the annealed or finished product will be unsoitable, due, perhaps, to lack of sufficient strength or because it is too hard, to machine easily. The annealed product can be divided into two classes, one of which greatly predominates, that is, by far the largest tonnage is used for machine parts where high strength and ductility are essential requisites, while a far smaller amount, light in weight and thin in section, is used for other manufactured products in which castings of any reasonable degree of strength and ductility have proved satisfactory.

Jan 1, 1927

By Roy J. Helfinstine

One of the most urgent needs in the field of coal combustion is the ability to predict the performance of a coal from knowledge gained from small-scale tests. Numerous types of analyses and tests are conducted on coal, including the proximate and ultimate analyses, heating value, varieties of sulphur, ash analysis, ash fusion temperatures, free swelling index, petrographic analysis, and Gieseler plasticity. The Illinois Geological Survey has made an intensive study of the value of these tests for judging the performance characteristics of the coal as actually utilized. To date, three reports 1 2 3 have been is- sued, and another is being prepared. The present paper briefly summarizes some of the results found in the studies.

Jan 1, 1949

By William H. Spice

Drilling activities in South Central Texas for the year 1945 continued the steady increase over the past two years, while new fields discovered for the year included four new gas fields and one field extension. In the 30 counties included in this area, which comprises district No. 1, Oil and Gas Division, Railroad Commission of Texas, 141 exploratory wells were completed, compared with 61 drilled in 1944 and 29 drilled in 1943. Of these 141 tests, 55 were field well and 86 were wildcats; 38 were completed as oil wells, S as gas and gas-distillate producers, and 95 were abandoned as dry. Atascosa and McMullen Counties were the most active in the district, accounting for 73 of the wells drilled.

Jan 1, 1946

By Jay J. Burns

TWO zinc concentrating mills are operated by the St. Joseph Lead Co. in St. Lawrence County, N. Y. The Edwards mill is operating at present only sixteen hours a day treating 400 tons daily. The metallurgy at Edwards presents no unusual problems therefore this discussion is mainly limited to the metallurgy of the Balmat ore. The Balmat mill has a capacity of 1,250 tons per day and the operating crew consists of three shift bosses each with five millmen per shift. Two crusher operators work on each of two shifts and one cleanup man on day shift. The repair crew is made up of a foreman and three repairmen, one of the repairmen being capable of taking over any operating job in the mill from shift boss down. Each millman is capable of handling the next job in line and several men in the yard crew are broken into handling the start-off job in the mill so that temporary shortages of men do not cause extensive overtime. Sphalerite, pyrite, and galena, the principal ore minerals, occur in a gangue of calcite, dolomite, and silicates, especially diopside, plus tremo-

Jan 1, 1947

By COURTNEY DE KALB

IRON ore is the cause of the present trouble in Morocco. At least three nations are interested in the outcome and private syndicates have been active. The iron deposits are found in that mountainous northern coast line known as the Rif. This is an uplift that has been cut through, by the northward drainage, representing an ancient land surface. Erosion has produced .a fiordlike coast, which circum- stance has aided contraband' traffic to the tribes dominated by Abd-el-Krim, the chief of the clan of the Beni Urriaguel, near the center of 'the north coast, opposite Alhucemas. The iron deposits are extensive in the territory of the Beni Urriaguel. They were "located," if such a term is permissible, many years ago. The first arrangements, through direct contracts with the tribal chieftains, have been reinforced by compliance with the subsequent code under the Spanish protectorate in 1914. Under those terms, the location had to be made through the Arbitral Commission sitting in Paris. These locations, or "denouncements," were made by the I-louse of Mannesmann, of Hamburg.

Jan 1, 1925

By F. W. Jessen, R. W. Durie

The development in the laboratory of mall salt cavities illustrated that the rate at which salt dissolved was affected by the rate at which fresh water was injected into the cavity. Experiments carried out with small salt cores indicated, however, that the rate of salt removal with forced convection was not significantly different from that with natural convection, provided the flow was in the laminar range. The rate of salt removal was apparently controlled by the water salinity, which was indirectly determined by the rate at which fresh water was injected. With turbulent flow at the salt surface, the rate of salt removal could be increased several-fold with the same salinity in the cavity. A quantitative evaluation of the rate of salt removal under natural convection was attempted by using techniques developed for the analogous heat convection system. The values of the rate of salt removal obtained experimentally were considerably greater than the calculated values due to surface irregularities. To determine the effect of these irregularities, the rate of salt removal was found for a smooth surface by experimentally determining the rate of salt removal as an irregular surface developed and then extrapolating this trend back to initial time. Excellent agreement between the experimental and calculated values then were obtained. INTRODUCTION Underground cavities leached from massive salt formations have been used extensively for many years for storing LPG products. The development techniques for storing methane gases in the liquid state at a low temperature leads to speculation that underground salt cavities of controlled geometry may be quite important in this field. In any case, the increasing number of salt cavities used for storage indicates an impending need for a better knowledge of the washing process to efficiently develop maximum storage volumes within specified regions. It is the purpose of this paper to discuss some aspects of -the mechanism of the dissolution of salt in the formation of cavities of controlled geometry. Although no attempt is made to resolve the problems that may be associated with the storage of methane in the liquid state in salt formations, the fact that salt cavities can be formed at reasonable cost would appear to justify investigation in this direction. Further, underground cavities have the advantage of allowing storage at higher pressures (and hence higher temperatures) than surface installations. Although the thermal conductivity of salt is somewhat higher than frozen earths, 0.017 cal/(sec) (cm)(c) for salt at 32F vs 0.005 cal/(sec) (cm) () for ice at this temperature, this disadvantage is offset by the higher storage temperature in underground cavities. For example, at atmospheric pressure, the temperature of liquid methane would be —258F. In a storage cavity at 2,000 ft, the pressure would be approximately 1,000 psia, which would allow a storage temperature of -9OF. The formation temperature would be roughly 110F at this depth, hence the total temperature differential would be 200F. Under surface storage conditions the corresponding temperature difference would be some 333 F (75 F + 258 F). The results of this difference can be compared more readily by substituting the appropriate values of thermal conductivity, temperature difference, heat capacity and density into the solution of the diffusion equation for the unsteady linear conduction of heat. For the underground salt storage, the heat flux is 15cal/(sec) (sq cm), where t is the time in seconds from the initiation of the cooling. For the surface system, and using the thermal properties of ice at the average temperature, the corresponding figure is 21cal/(sec) (sq cm). Hence, the heat losses through ice under surface conditions would be some 30 per cent higher than the underground salt storage. This ratio would vary, considerablv. Of course, for other conditions, but it indicates that an advantage over surface facilities may be obtained by storage in underground salt cavities.

Jan 1, 1965

By Charles Catlett

THE rapid development of the Portland-cement industry implies that the country is being very carefully searched for material suitable for its manufacture. Such material can be found at a great many places ; but deposits thoroughly satisfactory in chemical composition, and at the same time meeting all the other requirements connected with the economic production and profitable marketing of the product, are exceedingly few, if I may judge from the investigations which I have had to make in a number of States. The raw mixture which by its clinking and grinding forms Portland cement contains approximately 75 per cent. of carbonate of lime. This is found in nature as limestone or marl. The natural rock commonly carries either more than the required percentage of carbonate of lime (in which case it has to be reduced by suitable admixture of clayey ingredients) or less-in which case purer lime carbonate has to be added. The controlling ingredient, therefore, is carbonate of lime, or limestone of the right composition. Among the most serious difficulties is that of finding limestones low enough in magnesia to meet the exacting requirements of certain specifications. All engineers recognize that there is a limit beyond which it is not safe to let the magnesia go; but within that limit there is considerable difference of opinion. Until that difference is finally settled, no one would be willing to invest the large sum of money necessary for a Portland-cement plant, if it were not certain that the usual requirements in this particular could be satisfied. The usual limit in well-established specifications is 5 per cent. of magnesium oxide in the finished cement, but many specifications limit the amount to 3 per cent. These figures

Jan 9, 1907

By E. J. Pasierb, H. W. Paxton

Mavkers ill a diffusion couple in the iron-chromium system move towards the high chromium side indicating Dcr > DFe at the marker composition. By a combituztion of measurements of D& and D a: a function of composition, this is also shown independently. DFe is calculated as a function of composition. and shown to be in reasonable agreement with measured values by other workers. MEASUREMENTS of marker movements in diffusion couples have been used from time to time to demonstrate that a vacancy or interstitial mechanism may be operative. Since there is a possibility that ring diffusion1 may be operative in chromium, the present experiments are of interest in showing some non-ring mechanism in iron-chromium alloys around the equiatomic composition. EXPERIMENTAL PROCEDURE The movement of markers originally at the interface between 1-in. sq sections of pure Cr (6 mm thick) and outer slabs of 30 Cr-70 Fe alloy was followed as a function of time at temperatures from 1150" to 1425"C, in a Kanthal-wound furnace. Temperature control was +5°C over extended periods. The analyses of these alloys are given in Table I. Selection of suitable markers presented a considerable experimental problem; the eventual solution was to draw quartz rod down to 0.01 cm and seat this in V-grooves 0.01 cm deep on each side of the chromium prior to welding. A preliminary experiment in which the groove was machined in the alloy gave identical results. Welding was accomplished by passing a heavy current through specimens under moderate pressure in a helium atmosphere. This method produced good welds with a planar interface as shown by subsequent metallo-graphic investigation. Any markers which did not adequately fill their groove and showed subsequent contamination from the atmosphere during heat treatment were not considered reliable. The composite sample was ground and metal-lographically polished on the four sides perpendicular to the interface. Fiducial marks (deep milled slots) were made outside the diffusion zone to check on total volume change. All necessary measurements were made on a metallograph reading to +0.0005 cm. The samples were wrapped in tantalum foil and given diffusion anneals for times to 200 hr in carefully purified dry hydrogen in a sealed McDanel porcelain tube. Chromium-zirconium chips were introduced near the specimen as an additional getter. The specimens were cooled relatively slowly after the diffusion anneal to preserve the McDanel tube but no significant error in effective time at temperature was thereby introduced. At least 1 mm was ground off the surface before measurements were taken. It was observed that the grain size following short diffusion anneals was several mm and was appreciably larger in the 30 Cr alloy than in the pure Cr. No significant grain boundary penetration was present as indicated by the etch limit. The results are presented in the next section. Measurements of D were made by standard sectioning techniques with chemical analysis. Machining difficulties limited the

Jan 1, 1961

By W. A. Forbes

by the combustion of this gas as it reached the air was a familiar sight in the days when open-top furnaces were in vogue. As blast-furnace practice progressed, however, involving the use of hot blast and the development of power from the gas, blast-furnace construction was modified to conserve this gas for heating hot-blast stoves, raising steam under boilers, and various miscellaneous purposes. When the use of blast-furnace gas was extended to the driving of gas engines, the necessity for thoroughly cleaning the gas became apparent., and soon the advantages of also properly cleaning the gas for use in stoves and udder boilers became more fully recognized.

Jan 10, 1913