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By RAY LYMAN WILBUR

SINCE boyhood I have had a keen interest in mining engineering. To see the prospector with his pack outfit and his pan, followed by the assayer and the trained engineer, has always had -something of the lure of romance for me. It is appropriate that the American Institute of Mining and Metallurgical Engineers should hold a general meeting in California, since this State has long been a home of mining engineering. Here, after the early open methods of mining, it has been necessary for the universities to train men in geology and mining, so that the earth could be penetrated and the rich ledges opened. In the eighty years in which the mines of California have been offering experience to the miners of the world, we have seen mining engineering evolve from a comparatively simple art, covered largely by rule of thumb, into a complex group of specialties, each utilizing the very latest discoveries in the various fields of physical sciences. Mining, too, has become a great business requiring large financial support and the most careful handling. Those mining engineers who have applied new processes in special fields have thus been able to give a wide-flung range to their activities in all parts of the world. The hand of nature in distributing minerals over the surface of the earth has compelled the mining engineer to become a modern pioneer, facing the heat of the tropics as well as the frozen regions of the north. There has been a marked cosmopolitan aspect to mining engineering, since the engineer had to go wherever the prospector discovered favorable leads. This has meant dealing with the harshest of conditions, the handling of labor of all sorts, the control of sanitary conditions, and relations to all forms of transportation. Naturally this has called on some of the very best minds in all countries to unlock the stores of hidden wealth. To make them available for civilization has been the job of the mining engineer.

Jan 1, 1929

By R. J. Brison, O. F. Tangel

The development of a new method of mineral separation was sponsored by the International Salt Company, which requested Battelle Institute to investigate means for improving the quality and appearance of rock salt from the Company's Detroit mine. Although developed specifically for removing impurities from rock salt, the general method may be applicable to other separation problems. The principal impurities in rock salt from the Detroit mine are dolomite and anhydrite which represent 2 to 5 pct of the weight of the mined salt. In the size range from 1/4 to M in. (the range of primary interest in this project) the impurities are only partially liberated from the halite in normal production. Further size reduction to improve the liberation of impurities is not practicable in view of the market requirements for the coarse grades of rock salt. Laboratory separations in heavy liquids showed that, to improve the quality and appearance of the rock salt substantially, it would be necessary to remove not only free gangue particles but also a large proportion of the locked-in particles. Because rock salt is an inexpensive commodity, a low-cost process was required. Gravity methods were, of course, considered. The heavy-liquid separations indicated that a split at an effective specific gravity of 2.2 to 2.3 would be required. (The specific gravity of pure halite is 2.16.) Heavy-media separation was investigated but had the disadvantages that it was necessary both to operate with saturated brine and to dry the cleaned salt, and that the cleaned salt was darkened by the magnetite medium. Air tabling was tried but did not give the desired separation. It soon became apparent that established methods would not provide a satisfactory solution and work was undertaken on the development of a new process to solve the problem. PROCESS DEVELOPMENT Preliminary Experiments: At the start of the investigation, an analysis of the problem indicated that the diathermacy of rock salt—that is, its ability to transmit radiant heat—might form the basis for an efficient separation process. Under this theory, the impurities might be selectively heated by radiant heat. The particles could then be fed over a belt coated with a heat-sensitive substance so that the warm impure particles would adhere preferentially to the coating. After the initial experiments, made by heating the rock salt with an infrared lamp and separating the product on small sheets of resin-coated rubber, proved encouraging, a small continuous separation unit was set up. This comprised 1) a simple heating unit consisting of a vibrating feeder covered with aluminum foil and an infrared lamp mounted above the feeder and 2) a separation belt 6 in. wide and 36 in. long. A sketch of the device is shown in Fig. 1. Results with this apparatus confirmed the fact that a good separation was possible. It was apparent, however, that a considerable amount of experimental work would be needed to develop the scheme to a practical and economical process. The Process: Basically, the process consists of two main steps: 1) selective heating by radiation and 2) separation of the heated particles on a heat-sensitive surface. Because neither of these steps had previously been utilized commercially in mineral processing, it was necessary to do basic research on both aspects. Factors studied in the investigation included type of heat source, design of heating unit, design of separation belt, selection of heat-sensitive coating, removal of heated particles from the belt, contact between particles and coating, and maintenance of the heat-sensitive surface. Part of the experimental work was carried out on a small-scale unit consisting of the 36x6 in. belt and auxiliary apparatus, and part on a larger unit. For simplicity, discussion of work on both of these units is grouped together. SELECTIVE HEATING Radiant-Heat Source: The essential requirements for a radiant-heat source were 1) that the radiant heat be in a wave length range which is effectively absorbed by the impurities but not absorbed appreciably by the rock salt and 2) that it be dependable, practical, and economical. Selection of a heat source of suitable wave length range was one of the first considerations. It is well known that pure halite is highly transparent to radiant energy in wave lengths from 0.3 to 13 microns. However, the available data on infrared transmission by dolomite and anhydrite, particularly in the range below two microns, were not complete enough to serve as a reliable basis for selection of a heat source. Although it may have been possible to obtain sufficient data on infrared transmission and absorption to enable one to select the best heat source, a more direct procedure was used. This consisted simply of exposing the crude rock salt to each of several types of radiant-heat source on the small continuous separation device. The heat sources investigated, approximate source temperature used, and calculated wave length of maximum radiation are tabulated in Table I. Of the two types of tungsten-filament lamps investigated, both the short wave length photoflood lamps and the longer wave length infrared lamps were satisfactory from the standpoint of selectivity

Jan 1, 1961

By W. T. Isbell

In the Parkes process of lead refining, after desilverization has been completed by means of the addition of zinc, there remains in the lead from 0.5 to 0.6 pct zinc. At this stage in the refining operations virtually all impurities are reduced to refined lead specifications except zinc and antimony. All excess copper, nickel and cobalt have been removed by the zinc additions. The silver remaining should not exceed 0.1 oz per ton. It then remains only to remove the zinc and antimony in order to produce refined lead. At the Herculaneum plant of the St. Joseph Lead Co., practice formerly was to complete the refining by means of oxidation in a reverberatory furnace. This process consisted of heating the lead to 1400O to 1500OF and allowing it to come in contact with excess air passing over the surface of the lead and periodically agitating the bath of lead with air. This procedure not only resulted in the loss of zinc but of a considerable quantity of lead converted to the oxide in the form of dross and fume. The fume, collected in the baghouse, together with the dross was returned to the blast furnace, thus adding appreciably to the circulating load on the blast furnace and refinery. In addition, operation and maintenance of the reverberatory furnace were expensive and required the performance of disagreeably hot and somewhat hazardous work. The process of dezincing with high vacuum was developed at this plant as a substitute for the oxidation process and finally led to lower operating costs, the practical elimination of dross and fume and the direct production of metallic zinc, which is very suitable for re-use in the desilverization process. Essentially this process consists of subjecting the lead to high vacuum, in a kettle provided with means for heating, a bell-shaped member open at the lower end so constructed that it can be immersed in the molten lead, and means for evacuating the interior of the bell and for sealing an agitator. Metallic zinc is thus produced and collects on the upper cooled part of the bell member. This metallic zinc is periodically removed and re-used in the desilverization process. The process is quite simple. It is conducted at a low temperature, thus permitting the use of iron equipment, and shows a material saving in refining costs over the old method. Equipment and Its Uses Degincing Machine.—The equipment employed in this process consists of a dezincing machine, a steel kettle of 120 tons capacity, a vacuum system and equipment for handling the dezincing machine (Fig 1). The dezincing machine consists of a compact assembly, suitable for handling with an overhead crane, consisting of a treating chamber and the agitating mechanism. Treating Chamber.—The treating chamber is a bell-shaped shell (4), similar in shape to a hemispherical kettle with a lid

Jan 1, 1949

By K. Mukherjee

A quasi-thermodynamic calculation is presented for estirt~ating vacancy Parameters in fcc metals. For fcc metals the equilibrium vacancy concentration at the melting point can be approximated by a constant mole fraction. The Gibbs free energy of formation of the vacancies can then be expressed as a simple function of the absolute melting temperature alone. From this description the formation energy Ef, the vibrational entropy Sv, and the formation volume of a vacancy can be calculated in terms of known thermodynamic parameters. The calculated values are in good agree-rnent with available experimental results. IT appears that many of the physical parameters associated with lattice defects can be empirically related to thermodynamic melting parameters.'-7 Besides the implicit correlations between melting phenomenon and point defects, the melting temperature itself at atmospheric pressure can be used as a reference temperature for the purpose of comparison of vacancy concentrations in a given crystal class. The concentration at the melting point then corresponds to the maximum vacancy super saturation in the crystalline state at a fixed pressure. For pure fcc metals such as Au, Cu, Al, Ag, Pb, and Pt the mole fraction of vacancies at the melting point8 is of the order of 10*"3 to 10"1. The equation expressing the equilibrium vacancy concentration at the melting point contains three parameters: the formation energy, the vibrational entropy, and the absolute melting temperature, see Eq. [2]. Since these three parameters cover a wide range of values8 in the above-mentioned metals, it can be assumed that in other fcc metals, for which no reliable data are available, the mole fraction of vacancies at the melting point most likely lies in the range 10~3 to lO"4. This is then the basis of the calculations described in this article. Within this range the mixing entropy can be linearized and the vibrational entropy, the formation energy, and the vacancy formation volume can be calculated in terms of known thermodynamic constants. 1} LINEARIZATION OF MIXING ENTROPY The Helmholtz free energy of a crystal containing n vacancies at the melting point can be writteng as where Ef, T,, k, and S, are the formation energy of a vacancy, the absolute melting temperature, Boltz-mann's constant, and the vacancy formation entropy, respectively. After applying Stirling's approximation in Eq. [l] and minimizing with respect to n where (n/N), is the equilibrium vacancy concentration in mole fraction at the melting temperature at 1 atm pressure. If instead of setting (6~/6n) = 0 immediately after Stirling's approximation in Eq. [I], the configurational partition function is simplified, then some useful and significant results can be obtained by utilizing the experimental inforrnation After applying Stirling's approximation and rearranging is plotted as a function of (n/N) in Fig. 1. The points, not all of which are shown, are fitted by a straight line substituting from Eq. [5] into Eq. [I] and minimizing with respect to n combining Eqs. [6] and [2] It must be emphasized that Eq. [7] is only a crude approximation based on an oversimplified model of

Jan 1, 1967

By T. D. Lynch, N. B. Pilling

The development of a proper treatment for shells in conncction with war contracts has brought to our attention the fact that the temperature of the liquid bath in which steel is quenched has a decided influence on the speed of cooling in the case of some liquids and very little in the case of others. Widely different physical results have been obtained by the use of water spray, water immersion, and oil immersion and further experiment has shown that the quenching effect of water used as a spray or an immersion varies greatly with the temperature of the water. The present experiments were undertaken with the idea of obtaining information of a quantitative nature regarding the quenching properties of a number of liquids used commercially in hardening steel. The general features of such cooling media are common knowledge and in the literature may be found records of numerous attempts to evaluate the cooling power of a liquid when used as a quenching bath. Much, if not most, of the data given on this subject is in the form of a simple statement of the time required for a certain heated mass to cool between two arbitrary temperatures when immersed in the liquid, quite regardless of the path of the temperature change. Our own purpose has been somewhat different. We have attempted to isolate that property of these liquids having to do with their ability to absorb heat rapidly, as distinct from the behavior of a considerable mass when exposed to different thermal environments. More specifically, from the data obtained through autographically recorded cooling curves of a small standard mass quenched under various conditions, we have tried to analyze the mechanism of heat absorption by the several liquids, measure the changes in its rate as a function of the temperature of the surface of transference, and ascertain the influence of the temperature of the liquid itself upon both. Without attempting an exhaustive citation of the literature, mention may be made of some of the more important contributions, notably the pioneer work of Le Chatelier,' followed by the extensive investigations

Jan 1, 1920

By G. A. Reinhardt, H. J. Cutler

ThE Youngstown Sheet & Tube Co. has produced a large tonnage of 0.35 to 0.45 carbon forging steel, the acceptance of which was based on the physical properties of test specimens obtained by forging the original 5 3/4-in. (14.5 cm.) square bloom to a 3/4-in. (1.9 cm.) round. Annealed and tempered specimens were required. The test bars were annealed by heating from 900" to 950' C. and cooling slowly in mica. The test bars were tempered by heating to 825' to 875" C., quenching in water, and drawing to 515" to 535" C. Immediately after heat treatment, the test pieces were machined to a diameter of 0.534 in. (1.38 cm.) and tested. Very good physical properties were obtained and no difficulty was experienced in meeting the specifications called for. UlTimate Strength.. Elongation, Lb. pER Sq. In. PEE Cent.. in 4 In. Not LeEs Than Annealed specimens.............. 78,230 to 92,450. 18 Tempered...................... 120,000 to 149,350 9 After experience on this material, production of slightly higher carbon forging steel was started. The method of testing this material required that test blooms be either normalized or annealed. The normalizing consisted in heating to 850" to 900" C. and cooling in still air; the annealing, in heating to 850" to 900" C. and cooling in the furnace or in mica. From the treated bloom, the test pieces were taken either by core drilling or by sawing from points midway between the edges and the intersection of the diagonals. The cores or blocks were turned to a standard 2-in. test piece with a diameter of 0.564 in. and tested without further treatment. The physical requirements of the test pieces were: yield point, pounds per square inch minimum, 44,800; ultimate strength, pounds per square inch, 89,600 to 112,000; elongation, per cent. in 2 in. not less than 17. Difficulty was encountered as soon as work on this material was started. Many precautions and refinements were instituted but it was found very difficult to secure the required elongation.

Jan 1, 1920

By John M. Kelly

New Mexico produced 39,751,868 bbl. of oil in 1941 and ranked seventh among the oil-producing states. Its 1941 production established an annual record, exceeding the 1940 record year by 854,498 bbl. The average daily production for the year was 108,909 bbl. The average daily non-marginal well allowable for New Mexico on Jan. I, 1941, was 36 bbl.; at the close of the year it was 43 bbl. The average daily pipe-linc runs were approximately 3 per cent less than the allocations of the New Mexico Oil Conservation Commission, which followed closely the recommendation of the United States Bureau of Mines in setting the daily outlet demand. The production in Lea County was 34,333,448 bbl.; Eddy County, 5,009,354 bbl.; and northwestern New Mexico (San Juan and McKinley Counties), 406,306 barrels. The total number of completions in the state was 402, of which 301 were oil wells, 19 gas wells, and 82 dry holes. Drilling during 1941 was 68 per cent of 1940, and the ratio of dry holes to producers, I to 4, was the greatest since 1935. Of these dry holes 43 were drilled in proven fields and 39 were wildcats. One new oil field and one new gas field were discovered as a result of the 1941 wildcatting program. However, numerous extensions were made to the existing fields, which, although they were called extensions to proration areas, were in reality field discoveries, being on separate geologic structures. Southeastern New Mexico Lea County The Monument field was the largest producing field in Lea County, with 6,973,808 bbl. It was closely followed by the Eunice field, with 6,644,181 bbl.; Vacuum field, with 4,800,608 bbl. and Hobbs, with 3,624,159 bbl. Hobbs field, however, still has the largest total recovery, this being 97,407,929 bbl. at the end of 1941. The new oil-field discovery in Lea County during 1941 was the Salt Lake field, T. 20 S., R. 33 E. The discovery well was Leonard-Welch State No. I, NW. NW. of sec. 18, T. 20 S., R. 33 E. This well was drilled to a total depth of 3103 ft. and was completed for an initial production of 250 bbl. per day pumping. The oil is 26" gravity and the producing horizon is in the San Andres limestone of Permian age. The discovery well was completed on June 22, 1941, and since that date four more producers have been completed, with no failures. The area is about 10 miles north-west of the Lynch pool, to which the oil from this field is being trucked because there is no pipe-line connection. The greatest drilling activity during 1947 was in the Maljamar field of western Lea County, with 62 completions, 59 being oil wells and 3 dry holes. The limits of this pool are now being defined on the north and south but to date have not been defined either to the east or west. The total number of 40-acre oil-producing units in the field at the close of the year was 158. On April I, 1941, a pressure-maintenance project was installed at the southern end

Jan 1, 1942

By John M. Kelly

New Mexico produced 39,751,868 bbl. of oil in 1941 and ranked seventh among the oil-producing states. Its 1941 production established an annual record, exceeding the 1940 record year by 854,498 bbl. The average daily production for the year was 108,909 bbl. The average daily non-marginal well allowable for New Mexico on Jan. I, 1941, was 36 bbl.; at the close of the year it was 43 bbl. The average daily pipe-linc runs were approximately 3 per cent less than the allocations of the New Mexico Oil Conservation Commission, which followed closely the recommendation of the United States Bureau of Mines in setting the daily outlet demand. The production in Lea County was 34,333,448 bbl.; Eddy County, 5,009,354 bbl.; and northwestern New Mexico (San Juan and McKinley Counties), 406,306 barrels. The total number of completions in the state was 402, of which 301 were oil wells, 19 gas wells, and 82 dry holes. Drilling during 1941 was 68 per cent of 1940, and the ratio of dry holes to producers, I to 4, was the greatest since 1935. Of these dry holes 43 were drilled in proven fields and 39 were wildcats. One new oil field and one new gas field were discovered as a result of the 1941 wildcatting program. However, numerous extensions were made to the existing fields, which, although they were called extensions to proration areas, were in reality field discoveries, being on separate geologic structures. Southeastern New Mexico Lea County The Monument field was the largest producing field in Lea County, with 6,973,808 bbl. It was closely followed by the Eunice field, with 6,644,181 bbl.; Vacuum field, with 4,800,608 bbl. and Hobbs, with 3,624,159 bbl. Hobbs field, however, still has the largest total recovery, this being 97,407,929 bbl. at the end of 1941. The new oil-field discovery in Lea County during 1941 was the Salt Lake field, T. 20 S., R. 33 E. The discovery well was Leonard-Welch State No. I, NW. NW. of sec. 18, T. 20 S., R. 33 E. This well was drilled to a total depth of 3103 ft. and was completed for an initial production of 250 bbl. per day pumping. The oil is 26" gravity and the producing horizon is in the San Andres limestone of Permian age. The discovery well was completed on June 22, 1941, and since that date four more producers have been completed, with no failures. The area is about 10 miles north-west of the Lynch pool, to which the oil from this field is being trucked because there is no pipe-line connection. The greatest drilling activity during 1947 was in the Maljamar field of western Lea County, with 62 completions, 59 being oil wells and 3 dry holes. The limits of this pool are now being defined on the north and south but to date have not been defined either to the east or west. The total number of 40-acre oil-producing units in the field at the close of the year was 158. On April I, 1941, a pressure-maintenance project was installed at the southern end

Jan 1, 1942

By R. L. Perrine

This paper shows how stability theory can be used to optimize solvent recovery of oil. Application of the theory leads to definition of the limiting conditions required for stable displacement to occur. One of these conditions is that the size of a solvent "slug" must at least equal a prescribed minimum. The criteria to be satisfied are miscibil-ity and stability. Stability implies that no viscous fingering will occur and that mixing will be caused only by a dispersion process. Miscibility implies that complete recovery will be obtained from the swept regions. Thus, for any specified set of reservoir conditions, an optimum use of solvent is defined. INTRODUCTION The early outlook for solvent flooding as a means to increase oil recovery was very favorable. Some laboratory results indicated that a "slug" containing perhaps 2 to 3 per cent of a hydrocarbon pore volume could be successful. However, other data suggested as much as 30 per cent would be required. The difference is of considerable economic importance. A theoretical explanation for these divergent results has been advanced by the author.1,2 Stability theory defines conditions for two distinct flow regimes. In stable displacement, solvent and oil become mixed by a dispersion process, and the solvent requirement is small. On the other hand, unstable displacement can degenerate into viscous fingering. The practical result is a considerable increase in the extent of mixing and, thus, in the solvent required. The present paper shows how to use stability theory to optimize solvent recovery of oil. Oil is usually considered to be displaced by a small amount, or a slug, of solvent. Gas in turn follows solvent. Any fingering will permit contact of nearly solvent-free gas and oil, leading to immiscibility and reduced recovery. Thus, our optimum is defined by two restrictions — stable flow and miscibility. Although an immiscible solvent process could prove more profitable than any miscible process, such processes lie outside the selected definition of an optimum. The usefulness of computations based on the present work will depend on the validity of the general theory. Because the important idealizations required tend to minimize the predicted solvent requirement, the results should state correctly the limiting conditions required. Therefore, theoretical calculations should have practical value. This paper first reviews several principles that result from stability theory. The following section describes use of these ideas in relatively simple systems which symmetry makes appear one-dimensional. Of particular importance is the step-by-step design of 3 stable minimum-solvent slug. The use of stability theory in cases of multi-dimensional displacement is discussed and, finally, suggestions are given for simplified practical application of the theoretical results. PRINCIPLES OF STABILITY THEORY The use of perturbation methods to derive stability conditions has been shown by the author.l The discussion is presented in terms of the fractional concentration of solvent in the single hydrocarbon phase. Quite generally, any disturbance can be represented as a Fourier series, of which only the least stable term need be considered. Denoting this term at time t = 0 by cn,

By A. S. Malicsi, I. Iwasaki

The removal of hydrophobic coatings of flotation collectors from iron ores becomes of interest when a duplex flotation process is considered for upgrading, when a pelletizing process is considered for a concentrate floated with a fatty acid or a soap collector, or when a disposal of froth products from cationic silica flotation is of environmental concern. Ozone can oxidize organic compounds rapidly, thereby removing the hydrophobic coatings of flotation collectors. Ozone is widely used for treating and purifying drinking water, waste water treatment, and for chemicals processing (Murphy and Orr, 1975; Rice et al., 1980). Its uses in metallurgical operations, however, are very sparse (Allegrini et al., 1970; Chernobrov and Rozinoyer, 1975; Ishii et al., 1970; Iwasaki and Malicsi, 1985; Matsubara et al., 1978). Yet, its high reactivity and the absence of potentially hazardous byproducts become of interest in destroying flotation reagents adsorbed on mineral surfaces or remaining in mill water for recycle or for discharge. Duplex Flotation A duplex flotation process, as applied to oxidized iron ores, would involve a fatty acid flotation of iron minerals followed by an amine flotation of the siliceous gangue from the rougher iron concentrate. Such a process has been used in the Florida phosphate fields. Fatty acid coatings cannot be removed as readily with a simple acid or alkali treatment from iron oxide surfaces as from Florida phosphates. A combination of reagents, such as lime and quebracho, lime and alkali phosphate, or sulfuric acid and oxalic acid, has therefore been proposed. In a previous article (Iwasaki et al., 1967) , the use of activated carbon was found to be effective in removing fatty acid coatings both in the duplex flotation and the pelletizing processes. The use of ozone offers another approach to the removal of fatty acid coatings from iron oxide surfaces. To investigate the possible application of the duplex flotation process, a specularite ore from Michigan analyzing 36.5% iron was used. A 600-g (1.3-1b) sample was ground in a laboratory rod mill together with 250 g/t (0.5 lb per st) of sodium silicate to -150 µm (-100 mesh). This was transferred to a Fagergren laboratory flotation cell, and deslimed four times at 20 µm (quartz equivalent). The deslimed pulp was transferred to a laboratory conditioner, diluted to 40% solids, and conditioned with 250 g/t (0.5 lb per st) of soda ash and 250 g/t (0.5 lb per st) of oleic acid. The conditioned pulp was then transferred back to the Fagergren cell, floated until barren of froth, and the rougher froth product was returned to the cell and cleaned. The results are presented in Table 1. The cleaner concentrate at this point analyzed 45.3% Fe. The cleaner concentrate coated with fatty acid was transferred to a 2-L (0.53-gal) beaker. While the pulp was agitated with a glass T-stirrer, ozone was bubbled into the agitated pulp for 15 minutes at a rate of 10 mg/min (0.00035 oz per min) ozone (250 g/t or 0.5 lb per st 03 feed). It was observed that the pulp ceased to froth after about 10 minutes. The amine flotation of siliceous gangue from the ozonated pulp was carried out first by conditioning with a dextrin, a commonly used starch depressant for iron oxides. This was followed by flotation with a stage addition of an ether amine at increments of 100 g/t (0.2 lb per st). Three stages were required to float the siliceous gangue to near completion. The three froth products were combined and cleaned twice. When the cationic flotation Rougher, Cleaner 1 and Cleaner 2 cell products were combined, an iron concentrate analyzing 64.5% iron was obtained at an overall iron recovery of 72.8%. Pelletizing Fatty acid flotation concentrates have been pelletized successfully in northern Michigan mills. But at other locations, fatty acid coatings on iron flotation concentrates proved so undesirable in agglomeration that other methods of concentration had to be sought. For example, a sinter mix containing iron ore concentrates upgraded by fatty acid flotation resulted in decreased productivity. This occurred because the micropellets of particles with the hydrophobic coating are less tolerant of moisture. Thus, the bed permeability is lost (Beebe, 1965). The agglomeration of concentrates obtained by the fatty acid flotation alone, and the hydrophobic coatings destroyed by ozonation or by the duplex flotation process, is not expected to cause any difficulty since the surfaces of the concentrates would be hydrophilic. Removal of the fatty acid coating with activated carbon, indicated by the loss of floatability, was shown to restore the decrepitation temperature of wet balls during drying cycle (Iwasaki et al., 1967). Disposal of Cationic Silica Flotation Froths Recent demands of iron blast furnaces place the silica content of the magnetic taconite pellets at about 5%. Conventional process for magnetic taconite involving fine grinding and magnetic separation often produces magnetic concentrates analyzing in excess of 5% silica. This is due to the presence of the middling grains of siliceous gangue and magnetite. Cationic silica flotation of magnetic taconite concentrates (DeVaney, 1949) may be used to reduce the silica content. But the amine coating on siliceous gangue becomes of environmental concern when the flotation tailings are discarded in tailing ponds.

Jan 1, 1986

By H. S. Price, R. L. Reed, J. E. Warren

The behavior of the reverse-combustion process in a linear adiabatic system is theoretically investigated by means of an idealized physical model. T his model is described by a pair of non-linear equations involving heat and mass transfer which are coupled by a concentration-dependent reaction-rate function of the Ar-rhenius type. The differential equations governing the quasi steady-state temperature and concentration distributions are approximately solved by using either physical or mathematical simplifications. It is shown that the reverse -combustion process can be mechanistically described by simple physical models whose behavior equations can be solved formally. It is further demonstrated that the derived reverse-combustion equations can be solved numerically within the error limits for the experimental data. The theoretically predicted peak temperature-flux-velocity relationship exhibits reasonable agreement with experimental data obtained from Athabasca tar sand. The principal contribution of this work lies in its usefulness as a starting point for developing a more comprehensive theory. A description of the vaporization-coking process must be obtained; then, the theory must be extended to three dimensions to include geometrical effects and heat losses. INTRODUCTION In another paper,'" he physical processes visualized as occurring during reverse combustion have been described. In this paper, the extent to which an elementary theory can account for experimental observations is determined. Theoretical results that can be used to estimate some of the behavior characteristics of importance to this process are also presented. Since it is not possible to include all the features of the combustion mechanism of which we are currently aware, the mathematical formulation refers to the highly idealized system developed herein. This simplified physical model is based on the simultaneous transfer of mass and heat accompanied by a chemical reaction: it is described mathematically by a pair of coupled, nonlinear differential equations. Similar sets of equations have been studied extensively in the field of flame propagation; an excellent review of these investigations has been published by Evans.1 FORMULATION OF THE PROBLEM It will be recalled that the experiments are performed with a thin-walled cylindrical tube that is uniformly packed with sand and oil. The system is maintained substantially adiabatic by means of heat supplied externally in such a way that the radial temperature gradient in any plane normal to the axis of the tube approaches zero. Initially, the tube is at ambient temperature, except at one end where it is rapidly heated to a predetermined temperature. When the prescribed temperature is achieved, air is caused to flow into the cold end of the tube. As the oxygen in the air stream contacts the hot oil, a localized exothermic reaction takes place. The generated heat is conducted and convected away from the reaction zone so that definite temperature and concentration profiles are rapidly established and move uniformly in a direction opposite to that of the air flow (Fig. 1). As a consequence of this mode of oxidation, all of the oxygen in the air is consumed; then, the remaining nitrogen and the gaseous combustion products sweep out all vaporized hydrocarbons and leave an immobile hydrocarbon-coke on the sand.

Jan 1, 1970

By Clyde E. Williams

MORE has been said about the iron and steel situation on the Pacific Coast than has been done .about it; but perhaps as much has been done as conditions have warranted. The production of finished steel in an amount sufficient to take care of the local demand for certain sizes and shapes is an established industry on the .coast. The amount .and the variety of products, so made, changes with the demand or them which is largely dependent upon the growth in population. An increasing demand will not always increase the quantity of steel produced locally because the cost of production may rise so -high as to let in steel from the outside. The reason for this is that all of the steel made in the West comes from steel scrap, the supply of which is .limited. From the standpoint of the metallurgist, it would. be desirable to subititute pig iron for some of ' the steel scrap, but this cannot be done profitably because the pig iron now available is too expensive. In other words, the large future demand for steel and pig iron on the Pacific Coast must be supplied by reduction of ores in the West, unless we are to be content with paying high transportation costs for material produced elsewhere. ."

Jan 1, 1924

NEW MEMBERS. The following list comprises the names of those persons who became members during the month of April, 1913: BARNES, BLAKESLEE, Min. Engr Burrwood, La. BOYLSTON, HERBERT M., Cons. Met. Engr 26 Abbot Bldg., Cambridge, Mass. BUEHLER, HENRY A., State Geol Rolla, Mo. CASTO, WILLIAM H., JR., Mining Bonanza, Idaho. COHEN, MAXWELL B., Mill Operator Miami, Ariz. EVANS, MILTON R., Shop Draftsman 92 Division St., Kingston, Pa. HARPER, WALTER S., Asst. Treas 42 Broadway, New York, N. Y. JAMES. JAMES S.. Min. Engr Telluride. Colo.

Jan 5, 1913

By D. Hanson

Fox most of their practical applications metals are required to with-stand stresses of appreciable magnitude: indeed, it is because they possess the quality of resisting stress without becoming permanently deformed that they find such extensive use in the service of man. Metals and alloys must, in service, usually behave as elastic substances-or nearly so. It is not difficult to satisfy this condition at ordinary temperatures. Iron and its alloys, especially the steels, are at normal temperatures excellent elastic bodies, capable of satisfying most of the mechanical requirements of the engineer: where electrical, chemical or other properties are impor-tant, which cannot be met by steels, it is usually possible to find a non-ferrous alloy such as nickel, copper or aluminum, which will prove satisfactory. When the metals or alloys are not inherently sufficiently elastic, cold-working or heat-treatment may develop elastic properties to a sufficient extent for practical needs. By means of relatively simple, rapid tests we can measure such properties as elastic modulus, limit of proportionality and proof stress, upon which design can be based with confidence. The case of the soft metals, such as lead and tin, is well known to be exceptional. They possess no definite limit of elasticity, and the value of proof stress or tensile strength depends to a great extent on the speed with which the test is carried out. Design here must be based on other considerations than a well-established theory of the proportionality of stress and strain. It is now generally recognized that steels and non-ferrous alloys possess at temperatures not greatly exceeding that of the atmosphere, characteristics quite different from those existing at ordinary temperatures, and that they assume qualities similar to those of the soft metals. Not only have they no limit of elasticity, but the proof stress and the ultimate stress depend on the time of application of the load. Flow under load may persist for long periods of time, possibly indefinitely, and the determination of a true maximum stress becomes a matter of great difficulty.

Jan 1, 1939

By Alfred Boyles

"HEREDITY"' in cast iron has been a subject of much discussion. Numerous experimenters have found that the properties of gray iron may vary greatly without corresponding variations in composition or thermal treatment. The main structural difference in such cases is in the size and distribution of the graphite flakes and the explanations given usually attribute this difference to some chemical element not shown by ordinary analysis or to some physical factor, such as inclusions in the melt. It cannot be said that any of these theories is completely satisfactory. Much remains to be learned about cast iron and for this reason a study of the material was undertaken as a part of the program of fundamental research at Battelle Memorial Institute. A review of the literature indicated that very little systematic work had been done on the mecha-nism of freezing in cast iron. The experiments described below are largely concerned with that problem.

Jan 1, 1937

71 BROADWAY, NEW YORK, Sept. 22, 1913. CHARLES W. GOODALE, Chairman, . DARSIE C. BARD, ESQ., Secretary. Committee on Precious and Base Metals, Butte, Montana. Gentlemen The wonderful success of the meeting of the Institute held in Montana makes it necessary that some public acknowledgment should be made to those to whom this success is due. We are conscious that the securing of the great number of technical papers of lasting value and the carrying to success of most complete detailed arrangements for holding the meeting have called for several months of skilled effort on your part. The benefit of the meeting is very great and extends not only to those who were fortunate enough to be present, but to our four thousand absent members and their friends as well. To you and your associates on the Committee whose efforts have made this never-to-be-forgotten meeting possible we owe far more than can be expressed in votes of thanks. Very respectfully, CHARLES F. RAND, President.

Jan 10, 1913

By N. Nemeth, L. L. Sirois

The role of the filter medium in continuous-vacuum filtration and the special circumstances which influence the resistance to flow through the porous cake and filter cloth are discussed. Due to negative pressure differential, gas bubbles evolve in the slurry, constrict passages in the filter cake and medium, and further restrict flow through the tortuous channels. Filtration is a liquid-solid separation process taking place at a porous medium under a pressure differential. The liquid passes through the medium; the solids are retained on the medium as a partially dewatered cake. Filtration is far from a simple process and has been described in terms ranging from "complex" to "subtle." Because of the many variables involved, no unified filtration theory has been developed, and the filtration process is still considered very much an art. In industrial filter design, basic relationships, whether derived for idealized conditions or developed empirically, are usually adapted to suit local conditions. In the mining industry where continuous-vacuum filtration is the main dewatering process, the physical state of the concentrates and the relatively low pressure differentials permit the assumption that the cakes are noncompressible, an assumption which leads to the use of theoretically sound rate equations. Notwithstanding this simplification, there are other problems, unique in the application of vacuum to dewatering, and until now completely ignored, which demand special attention. The basics of filtration involve the capture of solids on, while permitting the flow of liquid through, a porous layer of cake and cloth. Flow is determined by the structure of the solids which make up the cake and the particles permanently attached to the cloth. The problem of this structure, essentially one of solid geometry, has been considered insoluble by Hatscheckl as early as 1907 and by Freshwater as recently as 1967. Since cake structure is determined by the slurry parameters, that problem is far too large for inclusion in this study. For theoretical considerations, uniform buildup of the filter cake must be assumed; and for efficient practical operation, the resistance of the medium must be kept constant over long periods. The latter can be achieved by careful selection of the filter cloth, since the greatest part of the total filtration resistance will develop at the cake-cloth contact. This paper discusses the role of the filter medium in continuous vacuum filtration and the special circumstances which influence the resistance to flow through the porous cake and the filter cloth.

Jan 1, 1971

By J. C. Fisher

Nucleation theory is applied to martensite nucleation in substitutional iron alloys. Composition fluctuations are neglected, and a steady rate of nucleation is predicted for any composition and temperature. The maximum rate of nucleation (as a function of temperature) is shown to be measurable only for on extremely narrow composition range, being too great or too small outside this range. A number of experimental observations, including completely isothermal transformation in some alloys and composition-dependence of M. temperature in others, are compared with the calculated behavior. IN a previous report,¹ nucleation theory was applied to the formation of isothermal martensite in an Fe-Ni-Mn alloy. The experimental observations of Cech and Hollomon² were accounted for quantitatively. It now is of interest to examine the predictions of nucleation theory with respect to martensite transformation in substitutional iron alloys of other compositions. Since Fe-Ni alloys have received considerable attention, both as to their transformation kinetics and their free energies, they will be treated in detail, although the results apply with equal validity to other substitutional alloys. In substitutional alloys, where composition fluctuations can be neglected in volumes of critical nuclear size, the rate of nucleation of martensite in subcooled austenite is¹ n - Nv exp (—W*/kT) [I] where the free energy of formation of the critical size nucleus is W* = 8192 p (?² s³) [2] In the expressions for n and W*, the symbols have the following meanings: N is the number of atoms per unit volume; v, the atomic vibration frequency; 8, a function of the elastic constants of austenite and the shear angle of martensite; , the austenite/mar-tensite inter facial free energy; and ?fc is the free energy change per unit volume accompanying the transformation. Jones and Pumphrey² have determined the austenite to martensite free energy change as a function of nickel content and temperature for Fe-Ni alloys. Their expression is ?F = 2500 C + 1.25 (1 —C)?FFc cal per mol [3] where C is the atom fraction of nickel, and ?Ffe is the free energy change per unit volume for pure iron as tabulated by Zener4 (or, equivalently, Fisher"). From Eqs. 1 to 3, it is possible to calculate isothermal nucleation rates as a function of temperature and composition for Fe-Ni alloys. The only unknown parameter is (?² s³). The best value of this parameter for Fe-Ni alloys, determined from M. temperatures in a manner to be described shortly, is (?² s³)= 9.92 (10)21 cgs units [4] Taking this value of (?² s³), C-curves for isothermal nucleation were calculated for Fe-Ni alloys of several compositions, and are plotted in Fig. 1. It is evident from Fig. 1 that completely isothermal nucleation of martensite in Fe-Ni alloys can be observed experimentally for only a very narrow range of compositions. Cech and Hollomon find that a nucleation rate of about 10' nuclei per cc per sec is as fast as they can follow dilatometrically, and a rate of about 10-1 nucleus per cc per sec is about the slowest that can be measured conveniently. If the nucleation rate is to lie between the limits 10-1 10 the nickel content of an Fe-Ni alloy must fall in the atomic fraction range 0.299 5 C 5 0.302. Nickel contents lower than 0.299 correspond to nucleation rates too great to follow, and those higher than 0.302 to nucleation rates too slow to measure in a reasonable time.* In view of the narrow corn- position range in which successful isothermal measurements can be made, it is not surprising that only one substitutional alloy has been described' that comes close to being in the proper range.

Jan 1, 1954