Search Documents

By T. L. Loucks, E. T. Guerrero

Pressure drop characteristics in a system composed of two adjacent concentric regions of different permeability were studied. The differential equations for continuity of mass flow in the two regions were solved using the Laplace transformation and the necessary boundary conditions to give the pressure distribution in the composite reservoir, the resulting equation for pressure drop at the inner boundary was evaluated for a variety of composite reservoirs and compared with the results for a uniform reservoir. From this study it was found that under certain conditions the permeability in both zones, as well as the size of the inner zone, can be determined from the pressure drop curve. INTRODUCTION The theory for the pressure distribution and pressure build-up behavior of a well producing a single, slightly compressible fluid from infinite and finite homogeneous reservoirs was presented by Hornerl and Miller, Dyes and Hutchinson.2 Extensions on this original work to provide improved and extended interpretations and better agreement between theory and observed results have been made by Matthews, et a1,3 van Everdingen,4 Gladfelter, et al5 Stegemeierand Matthews,6 Hurst and Guerrero,7 and Perrine.8 More recently Lefkovits, et al,9 studied pressure build-up behavior in bounded reservoirs composed of stratified layers. Houpeurtl0 has suggested various approaches to the general problem of variable permeability and porosity but presented no analytic solutions for particular permeability variations. Albert, Jaisson and Marionll studied the finite composite reservoir and presented numerical solutions to the unsteady-state case and an analytical solution valid only for large times. They also studied the so-called pseudo-steady state for several examples of radial permeability variations. Very similar examples have been treated in the unsteady state with application to pressure build-up by Loucks in an unpublished manuscript. More recently Hurst12 has presented the complete point-sink solution (valid for all times) for the infinite composite reservoir. He applied these solutions to interference between oil fields along with an even more elegant application of his explicit solution to the material-balance equation including water influx. Mortada 13 approaches the same application by avoiding the point-source limitation but gives the solution for the aquifer region which is valid only for large times. Hopkinson, Natanson and Temple14 have treated both the finite and infinite composite reservoir obtaining the pressure distribution for the inner zone valid for large times. This paper presents a theoretical study of the pressure distribution in an infinite composite reservoir composed of two adjacent concentric regions of different permeability. The object was to determine the manner in which pressure drop at the inner boundary of a composite reservoir depends upon time, the permeability of each zone and the size of the inner zone. Expressions for the pressure distribution in both zones are developed which take into account the radius of the sink and are valid for small times as well as large times. It was felt that an understanding of the pressure drop behavior in various composite reservoirs would be of assistance in the interpretation of some pressure build-up curves which do not behave according to the theory derived for uniform systems. Often the region surrounding the wellbore is either more permeable or less permeable than the reservoir because of the various drilling and completion practices. The effects of reduced permeability due to drilling-fluid invasion and of increased permeability due to fracturing or acidizing need to be more carefully defined. Therefore, an equation for the pressure drop in a composite reservoir was developed, and the effects of both the permeability in each zone and the size of the inner zone were studied. STATEMENT AND SOLUTION OF PROBLEM BOUNDARY CONDITIONS AND ASSUMPTIONS The physical system studied was a composite

By W. E. C. A. B. Eustis

(Read at the Philadelphia Meeting, February, 1878.) IN September last I had my attention called by Mr. R. G. Leckie to a deposit of nickel in the township of Orford, province of Quebec. In many ways it has proved to be a subject of great interest. As this ore is, as far as I can learn, entirely new in mineralogy and metallurgy, it has seemed to me that it would be a matter of interest to the Institute to have laid before it, in a short paper, the peculiarities I have met with in studying it. This deposit of nickel was first described by Dr. T. Sterry Hunt, our President, in the Geology of Canada, 1863, p. 738, in the following terms : "The general diffusion of nickel throughout the magnesian rocks of the Quebec group has been already noticed. It has, however, never been met with in any considerable quantities in these rocks, although workable deposits of its ores may reasonably be looked for

Jan 1, 1878

By F. E. Jaumot, R. L. Smith

Self-diffusion in zinc has been used as an instrument for comparison of the absorption and sectioning techniques as a means of studying diffusion. Single crystal as well as poly-crystal samples were used asanda the temperature range of diffusion extended from 200° to 415°C. For temperatures above 200°C, the data indicate that the results obtained from the absorption technique agree with those obtained from the sectioning technique. The effect on the values of the diffusion coefficient of electroplating vs evaporation as a means of applying the tracer was investigated and no significant difference observed. It was found that an excess or deficiency of tracer did not materially affect the results obtained from the sectioning technique, but invariably caused errors with the absorption technique. NEARLY all self-diffusion experiments and many alloy diffusion experiments have employed radioisotopes as the instrument for following the diffusion. Of the various techniques in which radioisotopes are applicable, the two most widely used are the sectioning and absorption techniques. In the former, the diffusion coefficient is obtained from a curve of log concentration vs the square of the mean penetration depth. In the latter, the diffusion coefficient is calculated from a knowledge of the decrease in activity at the surface after diffusion. In spite of the importance of knowing the reliability of the diffusion data and the widespread use of these two techniques, they had not been directly compared experimentally on the same samples. Thus, such a comparison was worthwhile. The specific system chosen for this comparison was the self-diffusion of zinc, since the metal was readily obtainable in high purity, single crystals were easily grown, and the anisotropic features of the diffusion added an additional factor of interest to the comparison. Self-diffusion in both single and polycrystals was investigated, since the possibility existed that grain boundaries and grain boundary diffusion might produce different effects for the different techniques. Also, the effects of electroplating vs evaporation as a means of applying the radioactive tracer, and the effects of applying an excess or deficiency of tracer material were studied. The general experimental procedures and the mathematical analyses of both techniques have been described previously in some detail, and only those points essential to an understanding of the present work will be discussed here. The mathematical analysis of the sectioning data requires only a knowledge of the solution of Fick's equation. where C,, is the initial concentration, C is the concentration at depth x, D is the diffusion coefficient, and p is the absorption coefficient of the solvent metal for the radiation from the solute. Having obtained F from the experiment, the value of z can be read from a plot of F vs In z, and D can then be calculated if is known. The necessity of knowing the absorption coefficient causes most of the criticism of the absorption technique. It is very difficult to measure accurately under the conditions existing in the diffusion experiment, but it is absolutely necessary, as will be indicated briefly later. Portions of this problem have been discussed in detail elsewhere." The difficulties involved in the measurement of the absorption coefficient arise from three principle factors: the physical characteristics of the absorber, the geometry, and complex radiation spectra. The first two are heavily dependent upon the third. If

Jan 1, 1957

By R. B. Snow

THIS paper describes a technique of polishing and etching specimens of open-hearth furnace slags or hearth aggregates for identification of the crystalline constituents-lime (CaO), tricalcium silicate (3CaO•SiO2), dicalcium silicate (2CaO-SiO2), monticellite (CaO•MgO-SiO2), or forsterite (2MgO•SiO2), with especial emphasis on the mineral merwinite (3CaO-MgO.2SiO2). With proper standardization, this identification does not require the use of the petrographic microscope. The composition of basic open-hearth slags and furnace bottoms falls, almost without exception, within systems containing CaO, MgO, "FeO," MnO and SiO2, in which the number of basic molecules so greatly exceeds the orthosilicate ratio (two molecules of base to one of silica) that free basic oxides, and combinations between them such as aluminates or ferrites, are present in cooled specimens. Orthosilicates of (CaO + MgO) are the most common in such specimens, since in nearly all cases, except premelt slags, the molecular ratio of (CaO + MgO) to SiO2 is more than 2 to r. When sufficient lime is available it combines with the silica to form dicalcium silicate (2CaO•SiO2), which contains little, if any, MgO, FeO or MnO in solid solution whereas the latter oxides combine to form the oxide solid solution known as periclase. If the lime present is insufficient to form dicalcium silicate (2CaO•SiO2) it combines with MgO to form either merwinite (3CaO•MgO.2SiO2) or monticellite (CaO-MgO•SiO2); these minerals take little if any FeO or MnO into solid solution and the remaining MgO, FeO and MnO combine as periclase. This generalization seems to be valid for basic slags and furnace bottoms, since minerals such as CaO-MnO•SiO2 and CaO-FeO-SiO2 are found only in slags in which the lime-silica ratio is less than 2 and are not observed in specimens from furnace bottoms. The identification of crystalline constituents in such materials, especially of fine crystals in the groundmass, is difficult under the petrographic microscope. They are often masked by their neighbors because of their small size in relation to the thickness of the thin section and because of the presence of opaque or colored constituents. The indices of retraction and the optical sign of the mineral are sometimes difficult to determine because of the small size or because of twinning or of inclusions within the crystal. Moreover, the positive identification of merwinite (3CaO•MgO.2SiO2) from its optical properties is usually difficult in the presence of dicalcium silicate (2CaO•SiO2). CaO, MgO, 3CaO•SiO2 and 2CaO•SiO2 in open-hearth slags have been identified for a number of years in the U.S. Steel Corporation Laboratory by the usual

Jan 1, 1947

By M. B. Mirza, F. D. Wright

Models of photoelastic material were made to simulate a mine roof that had cracked over the edge of the pillars and at the center of the span. Models were restrained from moving laterally outward so they acted as flat arches. Uniform loading was approximated by loading the models along the bottom at eight points spaced equally along the span. It was found that for models with depth to span ratios of 1:3 to 1:6, the maximum stress at the top of the center crack could be calculated directly by the following formula: Elastic stresses in mine roofs composed of sedimentary beds are usually computed by assuming that the immediate roof bed acts as a fully restrained beam uniformly loaded by its own weight and by overlying strata. Very little work has been done to analyze stresses in roof beds or beams which contain vertical (normal to the span) or nearly vertical cracks. Yet every mining engineer has walked safely under roofs that show such cracks. As far back as 1933, Bucky' made model studies of the effect of vertical cracks on the behavior of horizontal strata. He did not make any analysis of the stresses but did show that a cracked beam will stand safely under certain conditions, and also showed that a beam restrained at the ends can crack over the supports and in the middle without collapsing as long as the ends of the beam are not free to move laterally outward. The beam, or rather, part of the beam, acts like a flat arch and supports itself by pushing outward at its supports. In 1941 Evans2 treated analytically the problem of a beam cracked along so many planes perpendicular to the axis of the beam that no tensile stress can operate. He named this type of beam a "voussoir-beam" by analogy to the voussoir-arch. In 1962 ~a~cocks~ modified Evans's solution by including the effect of the shear stress component of the resultant force at the abutment. This paper gives the results of a photoelastic study of the stresses in a beam containing vertical cracks in the center of the span and over the supports. A

Jan 1, 1963

By L. S. Darken, H. A. Wriedt

THE constitution diagram of the iron-copper system derived by Daniloff' exhibits, at the iron-rich end, phase fields similar to those of the iron-carbon diagram. At 1484° 1094°, and 850°C there are, respectively, a 6-y-L peritectic, a y-E-Lperitectic, and a a-y-E eutectoid. The phase designated E is copper-rich, containing 4 pct Fe or less according to the temperature. The composition of copper-saturated ferrite (a-solid solution) has been determined previously only twice as a function of temperature. By electrical conductivity measurements, Buchholtz and Köster2 found 3.4 pct Cu in ferrite at a eutectoid temperature of 810°C. They represented the composition of saturated ferrite by the equation, log (%Cu) = 4.32-4125 (1/T) Gregg and Daniloff3 reported that Köster later modified his opinion, raising the indicated eutectoid temperature to 833 °C and the copper content of eutectoid ferrite to 3.7 pct. The literature contains several indications4-7 that the work of Köster and his co-workers is not reliable. Norton,8 using an X-ray method, found that 1.4 pct Cu dissolved in ferrite at the approximate eutectoid temperature of 850°C and that the solubility decreased to about 0.3 pct at 700°C. Below 700°C his experimental data show almost no change in solubility. These findings, although inconsistent with the work of Ruer and Goerens4 and of Smith and Palmer,7 have been used generally since their publication. In investigations involving the observation of arrests in temperature during continuous heating or cooling the precise location of the eutectoid temperature has been obscured by a large hysteresis. The more reliable work 579 where the results are not effected by this hysteresis indicates a eutectoid temperature between 840° and 850°C. The foregoing discrepancies, along with a few observations in this Laboratory relating to the precipitation of copper from ferrite, prompted us to rein-vestigate the lower temperature portion of the Fe-Cu system. In this investigation the solubility of copper in ferrite was obtained by the chemical analysis of high-purity iron equilibrated with copper-silver alloys. This method eliminated the necessity for retaining by a quench the physical state of the specimen existing at the equilibration temperature. EXPERIMENTAL The reaction of the iron with the copper alloy was

Jan 1, 1961

George L. Heath, South Lake Linden, Mich. (communication to the Secretary): In presenting some notes on the "Heine's Blue Test" Mr. Smith expresses a preference for fresh standards and a cheaper bottle; but this is rather a reversion to the old method, since I devised in 1897 the newer method of preparation and preservation of' permanent standards, which were not used with any success in the original method. Many busy western assayers no doubt value a method for preparing a permanent set of standards in air-tight glass-stoppered bottles, whose use brings the method as near perfection as one could desire as regards rapidity of color-reading and avoidance of unnecessary work. Mr. Smith notes that his color-readings were compared with an electrolytic assay of another ore-sample, and that my electrolytic assays were made on the " blue test" solution from colorimetric assay. He omits, however, reference to the fact, showing the advantage of my procedure, that the next column in table of

Jan 1, 1901

By J. F. Myers, F. M. Lewis

C. G. McLACHLAN*-I have read this paper with considerable interest and wish to congratulate the authors on the care with which they carried out their experiments and for the detailed sizing data they have presented. 011 the other hand I do not feel that these data establish their contention that "with other factors the same, the work accomplished in a fine crushing rod mill is directly proportional to the rotating speed." My reason for making this statement is that their conclusion is based on the percentage of minus 65 mesh material produced at each of the speeds at which their tests were run. The rod mill is, however, not a fine grinding machine and therefore figures based on minus 65 mesh production are figures outside the range at which it operates to best advantage. Further, if rod mill performance is to be judged on the production of such material it should have been established that a rod mill will produce it as effectively as a ball mill. To check this last point I have gone over some of the rod and ball mill grind-ing figures for our Waite-Atnulet operation and find that the ball mill at that property produces more minus 65 mesh material per horsepower than the rod mill. Moreover, this comparison is even more favorable to the ball mill if it is limited to minus 100 mesh production. It therefore seems to me that the most satisfactory basis on which to try to com-pare the performance of the rod mill in the present case is by taking a weighted average of all the new surface produced per horsepower. W. H. Coghill3 has published data which can be applied to the sizing figures presented by the authors, and if this is done the units of new surface per horsepower produced in the Tennessee tests are as follows: Admittedly the increment of increase in new surface per horsepower shown in the foregoing figures is not great, but its trend is nevertheless definitely in favor of slower speed operation, for the conditions under which these particular tests were run. I also feel that some information regarding liner contour should have been given as I think it will be found that a mill which is equipped with liners which lift the rod load can be run at a slower speed than a mill in which the liners are comparatively smooth. J. F. MYERS and F. M. LEWIS (authors' reply)—The position taken by Mr. McLachlan is to be respected even though we are all aware of the faults of surface considerations. As he points out. the increment of increase is very small. It is so small in fact that for all practical purposes it does not conflict with the conclusions of the paper. The authors appreciate Mr. McLachlan's comprehensive study of the data.

Jan 1, 1950

By Auguste J. Rossi

We cannot expect, within the limits of this paper, to treat this subject exhaustively, but will endeavor, in the following, to present it in as concise a manner as is consistent with a clear exposition of its importance. Ores of titanium, titaniferous iron-ores (that is, iron-ores containing a notable amount of titanic acid, TiO2,, say not less than 5 per cent., generally 10 to 20 per cent., and frequently more, up to 40 per cent. or thereabout), occur all over the world in immense quantity, " in mountain masses," constituting in some localities, as in Sweden, Norway, Canada, the Adirondacks (N. Y.), in North Carolina and other States of the Union, the geological formation itself, the igneous rocks having, in many places, been so permeated with the metallic oxides as to justify their being called iron-ores. As a rule they are Bessemer ores, quite free from phosphorus and sulphur, though not invariably so. When the percentage of titanic acid is very high, that of the iron is low, but the proportions do not necessarily vary in the same ratio; that is, a rich ore may contain more titanic acid than one lower in iron. The percentage of iron varies, being as low as 35 to 36 per cent. in real ilmenite. It is more generally not less than 50 to 55 per cent., reaching often an average of 58 to 60 per cent., and as high as 63 to 65 per cent. It is obvious that if these ores were to be considered in the same light as other iron-ores, equally rich in iron, they would form an excellent stock for blast-furnaces for years to come, as their supply might be called inexhaustible, and they could

Jan 1, 1903

By F. George, W. Tice, M. Salkind

It was found that Al-A13Ni could be readily cold rolled perpendicular to but not parallel to the whiskers. Reductions of more than 98 pct were achieved without cracking by rolling perpendicular to the whiskers, whereas extensive edge cracking was noted after only 15 pct reduction when rolling parallel to the whiskers. The longitudinal and transverse tensile strengths were nearly doubled, and the longitudinal yield strength more than tripled by cold rolling 50 pct in a direction perpendicular to the whiskers. The whiskers exhibited some waviness (elastic bending) as a result of cold rolling, but at very high reductions (greater than 75 pct) whisker fracture and misalignment became significant. A fine dislocation substructure in the matrix consisting of cells attached to the whiskers was pro -duced by cold rolling. Most of- the substructure was readily removed by a 1-hr anneal at 500°C. Cold rolling was found to substantially reduce the thermal stability of the microstructure at 610°C but did not affect the stability at 500°C. FIBER and whisker reinforced composite materials promise significant improvements in properties over conventional materials. Before they find wide use, however, it will be necessary to understand the response of these highly anisotropic materials to common metalworking processes. Most of the nonmetal-lic fiber reinforced materials have very low elongations (a few pct or less) in the direction of fiber alignment. Thus, metalworking techniques such as rolling and forging would not be as broadly applicable to these materials. This investigation was initiated to determine how a composite system consisting of Al3Ni whisker reinforced aluminum responded to rolling, what changes in the microstructure occurred, and the effect of deformation on the mechanical properties. The composite material studied was produced by unidirectional solidification of the A1-Al3Ni eutectic alloy'-7 and consisted of 10 pct by volume of aligned whiskers of Alai in a matrix of aluminum. It should be pointed out that this system is not representative of all composite materials, and the results will therefore not be universally applicable. The A1-Al3Ni system is characterized by: 1) A strong fiber-matrix interfacial bond 2) A ductile matrix 3) A sufficiently low fiber content to allow significant plastic flow between fibers 4) Strong, completely elastic whiskers (tensile strength 400,000 psi, elastic modulus = 20 X 106 psi.1 These factors allow the material to be readily rolled perpendicular to the fibers. If the fiber-matrix bond were not strong, such a weak interface could fail during rolling. A measure of the ability of a composite to be rolled in the transverse direction can be obtained from noting the transverse tensile behavior. In the case of Al-Al3Ni,2 there is considerable ductility (15 to 30 pct). In the case of boron filament reinforced aluminum, for example, the transverse elongation is less than 1 pct,8 and the material could probably not be cold rolled as readily in that direction. EXPERIMENTAL PROCEDURE 3-in. diam ingots of A1-A13Ni eutectic were unidi-rectionally solidified in graphite crucibles. The starting materials consisted of 99.99+ pct pure nickel and aluminum, and the pure eutectic ingots were made with 6.2 wt pct Ni. The unidirectional solidification process (described in detail elsewhere1-3) consists of preparing a master heat of eutectic composition, remelting, and withdrawing the ingot vertically downward through the heat source at a controlled rate so that plane front solidification proceeds upward at a constant velocity. The resulting microstructure consists of 10 pct by volume of whiskers of very high aspect (length to diameter) ratio. The fiber lengths have not been measured because of the difficulty of detecting fiber ends9 but exceeds 104. There is some possibility that the fibers may be continuous within one grain. Flat sheet specimens 2¾ in. sq and approximately 0.2 in. thick containing whiskers parallel to the plane of the sheet and to one edge were used for this study. A1-A13Ni exhibits either a rod-like (high solidification rates) or a blade-like (low solidification rates) whisker morphology,1,3 and both types were studied. Rolling was accomplished using a two-high rolling mill at a speed of approximately 10 fpm. The rolling direction was either parallel to or perpendicular to the direction of growth (direction of whisker alignment). Reductions of from 0.002 to 0.03 in. per pass were used with the most common value being 0.005 in. per pass. Cold rolling of Al-Al3Ni to more than 98 pct reduction in thickness was accomplished with no intermediate anneals. In addition. a series of speci-mens was cold rolled 97 pct with a 1-hr, 500°C anneal in air after each 50 pet reduction. Tensile testing was accomplished using a Tinius-lsen four screw testing machine. Flat sheet specimens + in. wide and between 2 and 2; in. long with the thickness dependent upon rolling reduction, were used. The gage section was in. wide and 1 in. long. Strain was measured using a clip-on LVDT extensome-

Jan 1, 1970

By M. E. Wadsworth, I. B. Cutler

Coprecipitation of anionic and cationic polyelectrolytes has been applied to floccula-tion of several mineral systems. Results obtained in a study of the flocculation of kaolinite and hematite suspensions of polycationic and polyanionic electrolytes are presented. Greatly increased settling rates were observed following precipitation of positive and negative polyelectrolytes on the surface of finely divided minerals in aqueous suspension. The ratios of polycationic to polyanionic electrolytes required to produce maximum sedimentation have been shown to correspond closely with the equivalence points obtained by light scattering studies of systems containing the positive and negative polyelectrolytes by themselves. DISPERSION of colloids has been of interest to surface chemists for many years. Flocculation studies have been employed to evaluate the limits of colloid stability. In water suspensions, colloids become unstable and flocculate when the ( potential, the potential of the kinetic solvation sheath, falls to a value at which van der Waals forces may act to draw the particles together. This may happen through an adjustment of the pH of the suspension or by addition of a salt. Optimum conditions for rapid formation of large flocs are found in the region of minimum ( potential. In addition to these well known considerations, colloids in water suspensions are known to be flocculated by certain large organic macromolecules. These polyelectrolytes in some cases minimize the i potential and in other instances increase the attractive forces by supplying sites for hydrogen bonding.' Use of organic polyelectrolytes in flocculation of mineral colloids has increased rapidly in recent years. These materials are now recognized as indispensable aids to fluid-solid separations in many extractive metallurgical operations. They have been found to increase both the settling rate in thickeners and the filtration rate of filters. In the elucidation of the characteristics of these organic reagents as floc-culants in this laboratory, it was discovered that interaction of certain polyelectrolytes had a surprisingly good effect on flocculation of mineral colloids. Experimental Procedure: The anionic flocculants used in this study were Lytron 886 and 887, produced by Monsanto Chemical Co. Both reagents are copolymers of vinyl acetate and maleic anhydride. Lime is added to Lytron 886, whereas Lytron 887 is all organic. These reagents possess two carboxyl groups for each acetate group and are therefore anionic in character. The cationic reagents used were the Peter Cooper Co. 1-X and 2-X glues. The structures are not definitely known, but the re- agents are amines and are cationic in character. The glues were prepared in the chrome-alum form. Both types of reagents may be classified as polyelectrolytes in that they are high molecular weight polymers and ionize in water. All data presented are in terms of sedimentation rate, measured in 250-ml glass-stoppered graduated cylinders. With suitable precautions such measurements are fairly reproducible and provide a sensitive means for selecting important parameters such as pH, reagent concentration, and floc size and density.2 Agitation was standardized with five complete end over end cycles of the suspensions in the stoppered graduated cylinders.

Jan 1, 1957

By Charles T. Malcomson

In the United States, improvements in methods of combustion have made possible the use of the smaller sizes of anthracite. This coal is now being reclaimed from the culm banks accumulated by the miners in the more prodigal years. To-day the freshly mined "slush" is segrega,ted and stored against the time when, through briquetting or some other means, it may be utilized as a commercial fuel. For many years Europe has achieved enviable results in the conservation of her small coal by briquetting. This profitable industry, first placed on a commercial basis in France in 1842, has grown to such magnitude that the production during 1913 exceeded 36,000,000 short tons. Briquets produced in Great Britain are used principally for steam purposes and the greater part of the output is either exported or taken by the Admiralty. On the Continent the briquets are sold in all branches of the coal trade. The French railways consume from 16 to 40 per cent. of their fuel in briquet form, and in Germany the lignite briquets (of which 20,000,000 tons were produced in 1913) are as familiar and interesting to the American traveler as the huge porcelain stoves in which they are burned. It is not strange, therefore, that aggressive and far-sighted promoters heralded this means of converting our ubiquitous coal waste into revenue. To the superficial student the briquetting process seemed so simple as to make success easy. It is for this reason principally that the path of the industry in America has been strewn with failures. The rash enthusiast had either not worked out the mechanical problems involved or had failed to grasp the local conditions under which the briquets must be made and sold. It may be confidently stated, however, that in spite of the many vicissitudes through which it has passed, coal briquetting is now an accomplished economic success in this country, and as a profitable adjunct to the coal industry it has come to stay. Several valuable contributions relating to coal briquetting are found in the Transactions. Charles Dorrance, Jr., has sketched briefly the history of the anthracite briquetting plants from the time of Loiseau's pioneer plant down to that of the Lehigh Coal & Navigation Co. at Lans-ford. Since then this phase of the industry has remained practically at

Jan 1, 1915

By I. R. Kramer

A delay time for yielding in cold-worked face-centered-cubic metals was found. Slip on (123) planes was observed. Glide on these planes occurred during the delay-time period before slip starts on the (111) planes. AN important approach to the study of the anchoring and blocking of dislocations is available through the delayed-yield phenomenon which has been observed in body-centered and hexagonal close-packed metal by several investigators. Clark and his associate1-5 showed that a delay time for yielding is present in mild steels and fine-grain molybdenum. Type 302 stainless, SAE 4130 normalized, SAE 4130 quenched and tempered, and 24s-T aluminum aid not have a delay time. Kramer and Maddin6 studied the delay-yield effect. in metal single crystals. While they found a delay time in body-centered-cubic metals none could be found in the face-centered-cubic metals. Later7 a delay time was found in hexagonal close-packed metals. cottrell8 has proposed an explanation for the difference in the yield phenomena of b.c.c. and f.c.c. metals based upon the anchoring of edge dislocations by the proper types of impurity atoms (C and N). In the body-centered-cubic lattice the interstitial atoms are near a cube edge and can interact with an edge dislocation, while in a face-centered-cubic lattice the distortion around an interstitial atom is of spherical symmetry and cannot anchor a screw dislocation which has practically no hydrostatic component. Cottrell's theory seems to account rather well for the behavior of body-centered-cubic . metals. EXPERIMENTAL PROCEDURE The apparatus used in these experiments is essentially of the same design as described previously.' Single crystals 1 in. long and having a diameter of % in. were placed in a pendulum which consisted of a bar 8 ft long designed with a crystal holder to accommodate the specimen at low temperatures. This portion of the apparatus was supported on fine molybdenum wires. A bar of the same diameter and length comprised the other portion of the apparatus. This bar was supported on a set of roller bearings arranged around the periphery of the bar to allow accurate alignment. This bar was propelled by means of a spring-loaded gun and allowed to strike the lead bar in front of the single-crystal specimen. SR-4 type A-8 resistance strain gages were cemented to the specimen and the strain measurements were obtained by amplifying the strain-gage output by means of a high-gain preamplifier. A tektronix 545 oscilloscope was used together with a polaroid camera to record the strain and time sweep. An Ellis Associate Bridge was used to calibrate the strain gages and calibration readings were obtained before each test. The sweep of the time signal was initiated by means of a miniature thyraton which was fired when the two bars came into contact. The single-crystal specimens were cut from single-crystal bars about 12 in. long, grown by a modified Bridgman technique. The aluminum crystals were made with material of 99.99 pct purity while the purity of the copper was 99.999 pct. A cut-off wheel was used to prepare the specimens which were then machined to the desired length. The two opposite faces of the specimen were parallel to each other and perpendicular to the axis of the specimen. The specimens were compressed 1 pct. No machining followed thereafter. In some cases prestraining was carried out in liquid nitrogen by impacting the specimens directly in the apparatus so that subsequent observations could be made without allowing the specimen to warm up to room temperature. The single crystals were compressed 1 pct at room temperature in a hand press without much control of the rate of deformation. In some cases specimens were recompressed to obtain the desired length change. As far as could be determined in these experiments this factor did not seem to influence the results. The SR-4 strain gages were glued with a cellulose type cement onto the specimen surface and baked at 45°C for 12 hr. As a check on the baking treatment gages were allowed to dry at room temperature. All delay time tests in this paper were conducted in a liquid nitrogen bath at -195°C. A schematic delay time oscilloscope trace is shown in Fig. 1. At point B the elastic stress wave caused by the impact reaches the strain gage on the specimen. The portion BC is the elastic strain. In this investigation the strain at point C was used to calculate the critical resolved shear stress by multiplying by the proper modulus depending upon the orientation of the single-crystal specimen. The time between C and D is the delay time portion of the curve. This portion of the curve is fairly flat but does have a definite microstrain associated with it. After the point D is reached the specimen deforms rapidly and the strain reaches a maximum at E. Following this, depending upon the length of the bar behind the specimen, the strain remains constant for a period and then decreases when the reflected elastic wave returns from the end of the pendulum bar. A permanent plastic strain is recorded on the oscilloscope trace and also measured by a strain-measuring bridge. The strain, E p,

Jan 1, 1960

By John B. Miles

THE present period of depression in the iron industry, with the resultant close approximation of the cost of production to the selling-price of pig-iron, should make the discussion of this subject at this time not only interesting but, profitable. It is possible that it may result, in the collection of data, which when added to those set forth in this paper will clearly indicate the influence of the rate. of driving a blast-furnace upon its fuel-economy. The question is not whether an excessive rate of driving (meaning a rate definitely in excess of the average rate in the United States) results in, an increase in the fuel-consumption, but rather whether a rate considerably less than the average does not result in a marked decrease in the fuel-consumption. The commercial and metallurgical sides of. this problem must be kept separate. With a large margin between the cost of production and the selling-price of pig-iron, and a plant already in operation, it is frequently profitable to sacrifice a couple of hundred pounds of fuel per ton of pig-iron in order to secure the greater gross profits resulting from a larger tonnage. When this margin decreases with a plant in operation, or when the determination of the size of a new furnace intended for a certain production . confronts the management, a clear understanding of the effect of the rate of driving upon fuel-economy becomes necessary. If it be granted that slow driving leads to low fuel-consumption, it should he borne in mind in the design of a new plant for the production of a certain tonnage that the adoption of an economical rate of driving increases only the size of the furnace proper, whereas, due to the decrease in quantity of blast required on account of the decrease in fuel burned, the stoves, the blowing-engines, the boilers and the piping may be de-

Sep 1, 1908

By R. E. Zimmerman, Michael Sokaski, E. R. Palowitch, M. R. Geer, H. F. Yancey, W. Deurbrouck, S. C. Sun

PART 1: DENSE MEDIUM SEPARATION by M. SOKASKI, M. R. GEER and H. F. YANCEY INTRODUCTION In the early days of coarse-coal treatment by the dense-medium process in Europe, loess was one of the materials used for medium solids. Newly developed cyclones were used to reclaim and thicken :he loess suspension. On occasion, when the cyclone thickener at the Maurits mine in the Netherlands plugged, the overflow was found to be filled with clean coal free of impurity. From this observation stemmed the concept of the cyclone as a cleaning device. Development took place during World War 11 in the laboratory of the Dutch State Mines under the direction of M. G. Driessen. A 15-ton-per-hour pilot plant was in operation in the laboratory by 1945, when, in September, Driessen made the first public disclosure of the process in a paper presented to the Institute of Fuel in London. In April 1945,2 operation of this pilot plant was observed by one of the authors, who was so impressed with the potential of the cyclone process that, on his return to the United States, a research program on the cyclone was started by the Bureau of Mines immediately. This work led to an AIME paper in 1946 in which the first details of cyclone operation on American coals was made available. Commercial adoption of the cyclone proceeded in Europe, initially in the Netherlands, Germany, and France. In the United States, where coal is less costly and most of the coals are so easy to clean they respond well to simpler cleaning systems, the first cyclone plant was not built until 1961.3 As of the spring of 1967, a total of 31 commercial cy- clone plants had been installed or were under construction in the United States; this does not include eight Dynawhirlpool plants. The capacity of the cyclone plants ranges from 50 to 1300 tons per hour and totals 6600. THEORY Before discussing the theory of a dense medium cyclone, a brief description may be helpful to some readers who are not familiar with its basic operation. In a typical dense-medium cyclone, illustrated in figure 10-1, the mixture of medium and raw coal enters tangentially near the top of the cylindrical section, thus forming a strong vertical flow. The refuse moves along the wall of the cyclone and is discharged through the under- flow orifice. The washed coal moves toward the longitudinal axis of the cyclone and passes through the vortex finder to the overflow chamber.

Jan 1, 1968

By L. E. Porter

The demand for crude oil on the Pacific Coast during the year 1945. was so acute that the California crude supply had to be augmented by tank-car imports from the Texas and Rocky Mountain fields. Crude imports reached a high of 64,800 bbl. per day during June, with a total of 14,259,000 bbl. imported during the first 11 .months. The U. S. Navy also implemented the crude output from California pools by drilling and completing approximately 300 wells in the Naval Petroleum Reserve No. 1 (Elk Hills), from which an established production of 65,000. bbl. per day was reached in late February and maintained until Aug. 17, 1945, when it was reduced to its preprogram level of 15,000 bbl. per day. Even with the conclusion of the Pacific war on V-J day (Aug. 14), the military petroleum product requirements have permitted little material reduction in output of California crude to prewar rates. During the year, a total of 327-760,000 bbl. of crude was produced, or 19 per cent of the total crude production within the United States during the same period, as compared with 310,996,000 bbl. or 18.4 per cent of the nation's crude production in 1944.

Jan 1, 1946

By Anthony Anable

THE definite trend to stricter specifications with respect to hydraulic concrete has become increasingly manifest in the last six years or so; but it remained for the vast reclamation projects of the Bureau of Recla-mation of the Department of the Interior of the last few years to focus attention on this trend, and to demonstrate how thousands of tons of concrete-making aggregates can be produced continuously and auto-matically with a control of fineness comparable with that obtained with small samples in well equipped private and governmental laboratories. Pioneer work in this direction was done, to be sure, by private com-panies, notably the Kaiser Paving Co. of San Francisco, prior to the present vast public works program. Then in 1931 came the first great aggregates-preparation plant of the Six Companies, Inc. to supply. construction materials for Boulder Dam' in Nevada, and now, in 1936, the aggregates plant of the Mason-Walsh-Atkinson-Kier Co., general con¬tractors on the Grand Coulee dam in Washington. At Boulder dam and to an even greater degree at Grand Coulee dam, sand production is recognized as probably the most important single element affecting the physical characteristics of the concrete. For in the construction of dams accurate grading of the fine aggregate has consider-able bearing on the attainment of a uniform and homogeneous concrete of a high degree of workability and placeability and, at the same time, combining high density and low cement content. Low cement content is of value not only from the standpoint of economy but also because the use of an unnecessarily rich concrete causes certain undesirable characteristics to develop. This paper will relate how at Grand Coulee dam methods that are more advanced than ever before are producing four sizes of gravel and a sand having a fineness modulus of 2.5-3.0. The design capacity is 1000 tons an hour. Significantly, the methods and equipment employed are broadly those that have been used for a generation in metallurgical mills for accurately sizing and grading both precious

Jan 1, 1936

By R. H. Sweetser

THERE are SO many conditions affecting blast-furnace results that it is hard to get satisfactory comparative data on the working of two furnaces, and much more difficult to get comparable results from the use of two entirely different fuels. The several advantages of charcoal over coke as a blast-furnace fuel have doubtless been apparent to many managers; but probably the conditions for comparative tests of the two were never so favorable as during the year 1905, at the works of the Algoma Steel Co., Sault Ste. Marie, Ontario, which comprise two modern blast-furnaces, well equipped, though of comparatively small capacity. For four consecutive months one of these furnaces was run with charcoal and the other with coke. Then the charcoal-furnace ran for a while with part charcoal and part coke; and, still later, with coke only. The ore-mixtures were about the same in the two furnaces, and, of course, all the climatic conditions were identical. The dimensions of the two furnaces, and their work with the different fuels, are given in Table I.

Jan 5, 1908

By James J. Bean

Although determining and controlling specific gravity of operating medium in a heavy-media plant manually presents no problem, there are advantages to automatic recording and control. The two installations discussed employ the usual method of measurement. Pneumatic control with band control and reset features is used to regulate dilution water and hence specific gravity. Difficulties have been mechanical in nature and associated with obtaining a proper I sample and maintaining tight air connections in bubble-tube piping:

Jan 1, 1950

By R. T. DeHoff

A theoretical development is presented which reformulates Fick's first law for diffusion in the solid state. The diffusion flux of component i in a multi-component system, Ji, is related to its local concentration, ci, and local jump frequency, ri : where a is a geometric factor and d is the jump distance. The product, ciri , is defined as the local concentration of atomic jumps for component i. The analog to Fick's second law is also derived. A solution to this equation is presented, which permits the experimental determination of the variation of atom jump frequency with composition in multicomponent systems. HISTORICALLY, the description of diffusion in the solid state has been presumed to be best approached as an application of more general diffusion laws, known as the phenomenological equations. These equations relate the flux, Ji, of the various components, expressed in atoms, grams, or volume, to the driving force involved, expressed as either a compositional or chemical potential gradient, sumption that the flux is simply proportional to the driving force is the foundation of this approach. The phenomenological equations take the form: where the concentration gradients are assumed to be the driving force, and: if the chemical potential gradient is taken as the driving force. The coefficients Dij in Eq. [1.] are the "diffusion coefficients"; the elements of the corresponding matrix in Eq. [2], the Mij, are called the "mobilities". Eqs. [I] and [2] may be considered to be definitions of these phenomenological coefficients. A formidable body of literature has been generated about these equations; this literature dates back to their original formulation for the simplest case of binary diffusion in a fluid, by Adolf Fick, in 1855.' This description has been shown to be self-consistent. However, the "constants of proportionality", the Dij or ,Mij, are not constant: they vary with composition in all but the simplest systems. Even in the case of tracer diffusion, wherein it can be shown that the diffusion coefficient is constant, the mobility, which is considered in irreversible thermodynamics to be the more physically meaningful quantity, varies with the concentration of the tracer involved.' In more complex systems, it is necessary to evaluate the entire matrix of phenomenological coefficients, as a function of composition, in order to describe diffusion locally. Further, in order to determine this matrix experimentally, it is necessary to produce diffusion couples that have different sequences of compositions; the matrix may be evaluated only at points where these "composition paths" cross.* Finally, and perhaps most

Jan 1, 1969