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By Johannes Moeljono, Werner Wenzel, Heinrich Wilhelm Gudenhau

As an important mechanism for increasing production of the suction-draft-sinter process, it has been shown that gas permeability through the sinter layer plays an important role. Methods to increase production rates have been indicated and suggestions for carrying out the process have been made to improve the rate of production, reduce the fuel consumption, and at the same time obtain a uniform sinter. Laboratory experiments were conducted at the Institute for Ferrous Metallurgy of the Technical University at Aachen to illustrate these methods. Methods of Increasing Gas Penetration Through Sinter Layers The following are of fundamental importance in determining the process cycle during the sintering of iron ores: 1) Generation of maximum temperature, since its form and range determine sinter quality. 2) Propagation velocity of the temperature maximum which controls the attainable output. 3) The convective heat transfer which influences the velocity of travel of the temperature maximum.

Jan 1, 1974

By E. Martinez

The effect of ultrasonic energy transmitted through a liquid on chrysotile asbestos was investigated. Ultrasonic energy was effective in fiberization of chrysotile crudes as well as standard grades of milled asbestos fibers. Treated samples of several grades of milled fibers had increased wet bulk volumes and decreased settling and filtration rates compared to untreated fibers. Ultrasonics may be a method for fiberization of chrysotile without decreasing length or use of chemical additives that alter surface properties. Cavitation of the liquid on the surface of fiber bundles is believed to be the cause of the fiberization. It was found that ultrasonic energy greatly increased the rate of precipitation of latex on asbestos. When chrysotile asbestos fibers require additional opening or fiberization, the usual method employed is some type of high speed impact or grinding to open the fibers and produce a larger surface area. These methods always cause some degradation in length due to breaking of fibers. In addition, the efficiency of mechanical methods decreases as the diameter of fiber bundles decreases. Chemical methods have been proposed and it is claimed that fiberization down to individual fibers of 200-300 A diam is possible with some wetting agents. However, large amounts of reagent are required, approximately EDWARD MARTINEZ is with Central Research Laboratories, American Smelting and Refining Co., South Plain-field, N.J. TP 63H226. Manuscript, Aug. 12, 1963. Discussion of this paper, submitted in duplicate prior to Mar. 15, 1964, will appear in SME Transactions, September 1964, and AIME Transactions, 1964, vol. 229. 50 pct of the weight of fiber treated, and some of the wetting agent remains on the surface of the chrysotile and cannot be removed by any solvent which does not destroy the asbestos.' This investigation was directed at determining whether ultrasonic energy transmitted through a liquid would be effective in fiberizing chrysotile asbestos. Samples of asbestos crudes and commercially milled fibers were treated; settling and filtration rates of treated and untreated milled fibers were obtained. EQUIPMENT A Westinghouse Corp. ultrasonic cleaning system WEHH was used in this investigation. See Table I for a breakdown of this ultrasonic unit. RESULTS AND DISCUSSION Fiberization of Chrysotile Crudes: Samples of chrysotile crudes were pulled apart with tweezers so that coarse bundles of fiber approximately 1/16 in. in diam were obtained. The bundles were put into a bottle with 200 ml of methanol and the mixture placed into the ultrasonic tank for 30 min at a power output of 1200 w. The test was repeated using water instead of methanol. During the irradiation it was noted that the surfaces of the bundles were being fiberized. The liquid eventually became cloudy with dispersed solids. Fig. 1 is an electron micrograph of the fibers, some reduced to unit dimensions, and a fine material released by the ultrasonic energy. The platy particles in Fig. 1 were identified by electron diffraction and differential thermal analysis as brucite, Mg(OH)2, which must have been intergrown in the chrysotile crudes. Electron micrographs of bulk specimens of chrysotile have shown a fine material filling the interstices between tubular fibers.2,3 Electron diffraction patterns of the fine material collected after ultrasonic treatment indicate that it is amorphous. After decanting the solution, bundles of chrysotile remained somewhat decreased in diameter. Continuing the ultrasonic irradiation of the remaining material resulted in additional fiberization. The opening of the fibers occurred in both methanol and water. Cavitation of the liquid by the ultrasonic energy is undoubtedly responsible for the fiberization. When sound waves are transmitted through a liquid at a

Jan 1, 1963

By TENNEY C. DeSOLLAR

TRADITION tells us that the earliest use of Alabama iron was to make shoes for the horses of General Andrew Jackson and his men during the first part of the nineteenth century. The first recorded incident in the making of iron was the request of U. S. Indian Agent Benjamin Hawkins "that a crew of blacksmiths be sent to the Creek Nation in the lower Mississippi territory." These frontiersmen made up the first body of pioneer iron makers in the territory. The first known blast furnace was built by Joseph Heslip in 1818 at Russellville, named after Major William Russell, who was General Jackson's chief of scouts. The Tannehill furnace was built in 1830 in what is now Tuscaloosa County and its ruins, as shown above, can be seen today.

Jan 1, 1937

By W. A. Burns

Vertical flow is an important mechanism in many petroleum reservoirs. Yet no adequate method has heretofore been proposed for determining the in-situ vertical permeability in a reasonable length of time. Core measurements of vertical permeability do not necessarily represent effective in-situ values. Cores may be representative of only localized pockets of high or low permeability, and total reliance on cores might cause one to overlook the presence of vertical fractures altogether. Conventional single-well tests, interference tests, and pulse tests commonly are used to determine horizontal transmissibility, khh/u, but generally are not designed to measure vertical trans-missibility or other groups containing vertical permeability, ku. A new well test described here provides a measure of in-situ vertical permeability as well as the previously measurable horizontal permeability. This "vertical test" determines the vertical diffusivity, kv/gcu, and horizontal transmissibility, khd1/u (where dl is the length of injection or production perforations). The test is basically a short-term interference or pulse test normally lasting less than a day. Conventional down-hole equipment is used between two isolated sets of perforations in the same well, as shown in Fig. 1. A "layer-cake" description of a reservoir can be obtained by running two or more vertical tests in the same well, each over different vertical intervals. Each test can be analyzed for the effective vertical and horizontal properties of the interval tested. In addition, a vertical well test can determine the effective- ness of a shale barrier or tight zone by testing across it. Field use to date of vertical testing has confirmed its utility in reservoir description. Mathematical Basis Interpretation of vertical tests for ku and kh is based on comparison of measured pressure response with computer-generated response. Pressure behavior during a vertical test in a homogeneous, anisotropic, infinite-acting reservoir (infinite in radial extent and bounded in both directions vertically) is given by the diffusion equation for slightly compressible fluids with negligible gravity effects.l A schematic diagram of the problem is presented in Fig. 2, and an analytic solution, based on the image

Jan 1, 1970

By W. C. Peters, M. W. Pullen, C. A. Bays

During the past three and a half years considerable improvement in the techniques of solution extraction of salt has been made by the use of wells which are cross-connected by hydraulic fracture at the base of the salt. Fracture is initiated by the application of hydraulic pressure. Underreaming and perforating techniques are used to control initiation. The fracture is then extended by continuous pumping until a pressure communication is obtained. Pressure communication is followed by washing-through to obtain a low-pressure connection. Well construction using non-shrinking cements that will bond with the salt and with associated strata is essential to the process. The connecting procedure described permits solution to attack the salt deposit from its base upward, thereby permitting greater recovery, fewer well repairs, better saturation of brine, and overall economy of development and operation. The fracture method of cross-connection requires special pumping of the fluid and is limited by present experience to initial well spacings up to about 1200 feet. The method has been used in bedded salts and is applicable for wells in salt domes. Since spring of 1956, new developnents in salt extraction wells have followed procedures substantially different from those in prior use. Although multiple well systems, connected either by the natural consequence of the solution process or by undercutting under protective pads, have been used previously, the past three and a half years have brought about new designs and new operation procedures based on cross-connection of the wells using hydraulic fracture. To date these techniques have been applied largely in the bedded salt deposits of Michigan, Ontario, Ohio, West Virginia, and New York. To the writers' knowledge they have not been used in salt dome wells. The methods have not yet been in use for a sufficient period to permit any statistical comparison with the older methods. It is evident from experience to date that the methods result in higher recoveries, lower capital and operating costs, better saturation of produced brine, reduced well maintenance and repair, and in considerably fewer production units to insure

Jan 1, 1961

By Robert Thomas

DURING the past 20 years the advantages of reinforced concrete as a substitute for timbering in so-called permanent mine openings have been fully recognized, and its use has become almost general practice in the larger mines. The term "permanent mine openings" is used advisedly and is assumed to embrace such openings as ventilation shafts, material shafts and main hoisting shafts, with their adjacent stations, ore pockets, etc. In the concreting of such openings, the actual cost as compared with that of timbering has been of secondary consideration, the support of large openings, elimination of fire hazards, and prevention of inter-ruptions to production being the primary objectives. The ultimate economy, however, of lining such openings with concrete when they are to remain in use during the entire life of the mine, and especially when they are in bad ground, will seldom be questioned. During this 20-year period there have appeared in engineering publi-cations a number of interesting articles on the use of concrete in mines, nearly always describing some specific project of major proportions, such as the concreting of ore pockets, large stations or main hoisting shafts. Such articles are unquestionably of interest, since the projects require considerable engineering thought, not only in the method of excavating large openings, but in their engineering design as well. Concreting of main hoisting shafts, particularly when this is done with the least possible interruption to production, provides some interesting problems. The concreting of haulage drifts of the dimensions commonly found in mines, on the other hand, soon develops into a routine operation, there-fore it is with some hesitancy that the author attempts to prepare an article on this subject. The writer can recall only one article on the concreting of mine haulageways, although several articles have been written concerning the concreting of tunnels considerably larger in dimensions than those required in general mine practice.

Jan 1, 1936

[Executive J. V. W. REYNDERS, Chairman WILLIAM H. BASSETT E. DEGOLYER I-I. C. BELLINGER RICHARD PETERS, JR. Finance GEORGE OTIS SMITH, Chairman H. A. GUESS F. JULIUS FOHS Admissions GEORGE D. BARRON, Chairman DAVID LEVINGER P. A. MOSMAN H. K. MASTERS J. A, SINGMASTER Alternates F. G. BREYER C. W. HAMILTON F. E. PIERCE]

Jan 1, 1928

Who's Who in Mineral Engineering - The 1978 Membership Directory of the Society of Mining Engineers of AIME

Jan 7, 1978

By L. J. Health

Synthetic rock with predictable porosity and permeability has been Prepared from mixtures of sand, cement and water. Three series of mixes were investigated primarily for the relation between porosity and permeability for certain grain sizes and proportions. Synthetic rock prepared of 65 per cent large grains, 27 per cent small grains and 8 per cent Portland cement, gave measurable results ranging in porosity from 22.5 to 40 per cent and in permeability from 0.1 darcies to 6 darcies. This variation in porosity and permeability was caused by varying the amount of blending water. Drainage-cycle relative permeability characteristics of the synthetic rock were similar to those of natural reservoir rock. INTRODUCTION The fundamental behavior characteristics of fluids flowing through porous media have been described in the literature. Practical application of these flow characteristics to field conditions is too complicated except where assumptions are overly simplified. The use of dimensionally scaled models to simulate oil reservoirs has been described in the literature. 1-3 These and other papers have presented the theoretical and experimental justification for model design. Others have presented elements of model construction and their operation. In most investigations the porous media have consisted of either u ncon soli da ted sand, glass beads, broken glass or plastic-impregnated granular substances—materials in which the flow behavior is not identical to that in natural reservoir rock. The relative permeability curves for unconsoli-dated sands differ from those for consolidated sandstone. The effect of saturation history on relative permeability measurements is discussed by Geffen, et a1.4 Wyga15 has shown quite conclusively that a process of artificial cementation can be used to render un consolidated packs into synthetic sandstones having properties similar to those of natural rock. Many theoretical and experimental studies have been made in attempts to determine the structure and properties of unconsolidated sand, the most notable being by Naar and Wygal.6 Others have theorized and experimented with the fundamental characteristics of reservoir rocks. This study was conducted to determine if some general relationship could be established between the size of sand grains and the porosity and permeability in consolidated binary packs. This paper presents the results obtained by changing some of the factors which affect the porosity and permeability of synthetically prepared sandstone. In addition, drainage relative permeability curves are presented. EXPERIMENTAL PROCEDURE Mixtures of Portland cement with water and aggregate generally are designed to have certain characteristics, but essentially all are planned to be impervious to water or other liquids. Synthetic sandstone simulating oil reservoir rock, however, must be designed to have a given permeability (sometimes several darcies), a porosity which is primarily the effective porosity but quantitatively similar to natural rock, and other characteristics comparable to reservoir rock, such as wettability, pore geometry, tortuosity, etc. Unconsolidated ternary mixtures of spheres gave both a theoretically computed and an experimentally observed minimum porosity of about 25 per cent.7 By using a particle-distribution system, one-size particle packs had reproducible porosities in the reproducible range of 35 to 37 per cent.6 For model reservoir studies of the prototype system, a synthetic rock having a porosity of 25 per cent or less and a permeability of 2 darcies was required. The rock had to be uniform and competent enough to handle. Synthetic sandstone cores were prepared utilizing the technique developed by Wygal.5 Some slight variations in the procedure were incorporated. The sand was sieved through U. S. Standard sieves. A 18-20 sand denotes that the sand passed the Number

Jan 1, 1966

By B. E. Warren

Jan 1, 1965

Organization Place Date 1917 American Institute of Architects Philadelphia., Pa. Dec. 26-29 American Society of Mechanical Engineers New York City. Dec. 4-7 American Mining Congress State Chapter Phoenix, Ariz. Dec. 26-29 1918 American Society of Civil Engineers New York, N. Y. Jan. 22-25 American Institute of Mining Engineers New York, N. Y. Feb. 18-21

Jan 12, 1917

By H. T. Kennedy, S. M. Avasthi

An equation developed for gaseous hydrocarbon mixtures predicts molal volumes with an average absolute deviation of 0.73 percent when applied to 264 natural gas and condensate systems including 2,043 PVT points. Another equation developed for liquid hydrocarbon mixtures predicts molal volumes with an average absolute deviation of 1.12 percent when applied to 346 crude oil systems including 1,759 PVT points. Both equations require composition of the mixture to be expressed as mole fraction of methane through heptanes-plus, hydrogen sulfide, nitrogen and carbon dioxide, together with the characteristics of the heptanes-plus fraction in addition to the temperature and pressure. The equations cover wide ranges of the variables involved, and their accuracy is considerably better than that of other available methods. The equations were differentiated to allow calculation of the coefficients of isothermal compressibility and isobaric thermal expansion. (In this paper the coefficient of isothermal com-pressibility and the coefficient of isobaric thermal expansion will be expressed as compressibility and thermal expansion coefficient, respectively.) Equations to calculate these quantities are presented. INTRODUCTION Calculations of reservoir performance for petroleum reservoirs require accurate knowledge of the volumetric behavior of hydrocarbon mixtures, both liquid and gaseous. Compressibilities are required in transient fluid flow problems, and thermal expansion coefficients are important in thermal methods of production. An accurate laboratory investigation of the PVT behavior of each reservoir fluid encountered would be costly and time consuming. For this reason various correlations for predicting fluid properties have been developed and recorded in recent literature. Correlations have been presented in the form of graphs, tables and equations. Since an increasing number of studies are being conducted with the aid of electronic computers, recent efforts have been directed toward development of correla-tions suitable for computer programming. Application of computers permits the use of more complex correlations which otherwise are not feasible. Moreover, methods for predicting reservoir performance, particularly those based on the compositional material balance, depend upon the capability of accurately expressing the molal volumes and other fluid properties as functions of pressure, temperature and composition. The coefficient of isothermal compressibility c is defined by

Jan 1, 1969

By Lawrence Addicks

T HIS has been a most momentous year in the annals of the Institute. We have been in the midst of a situation which, were it not for the convulsions of social unrest with which life is surrounded on every side, would have attracted the attention of the world at large. I do not refer to the desperate campaign for new members. That has gone on much as usual except that, this being leap year, the annual proposal to the M. & M. Society has been omitted. Nor do I refer to the desperate situation which we found in other directions, the spread of Bolshevism, the burning of the Engineers' Club, the fact that the selling of copper appears to have become one of the lost arts. No, I speak of the great question which has to be. settled once and for all, as to whether this great Institute should adopt simplified spelling. The whole trouble started in the ranks of the California Hysterical Society. It appears, while most of the San Francisco members can read and write, several of them cannot spell. It also appears that the Secretary, in editing the Transactions, has perhaps made just a little bit too much of a point of employing the correct Stoughton idiom. At any rate, the rebels filed an amendment to the constitution, and the stage was set for civil war, with perhaps more stress on war than on civil.

Jan 1, 1920

By Y. C. Liu

Both the habit plane of martensite and the orientation relationship between the matrix and martensite platelets of different habit planes have been investigated in binary titanium alloys with molybdenum, chromium, and iron. The effect of the mode of deformation on the martensite habit plane was studied. A micrograph of an exposed mar-tensite platelet is presented. IN the study of martensitic transformation in Ti-Mn alloys,' two martensite habit planes—{334), and {344)8—were reported. The {334), habit was also observed in unalloyed titanium upon transformation,' although there is disagreement with respect to the exact indices. The other habit plane, {344),, has not been reported in martensitic transformation in any other alloys. The present investigation was made to determine whether other binary titanium alloys with P-stabil-izing elements would exhibit a crystallography of transformation similar to that of Ti-Mn alloys. Furthermore, since martensite platelets can be induced by deformation under certain conditions, it was of interest to investigate whether the mode of deformation, compressive or tensile, would influence the formation of martensite platelets on a specific plane in an alloy system which possesses two martensite habit planes. Experimental Procedure The material used for the preparation of the binary alloys of iodide titanium with molybdenum, chromium, and iron had the following purities: 99.99 pct iodide titanium, 99.9 pct molybdenum, 99.423 pct chromium, and 99.9 pct iron. The compositions of alloys listed in this paper are in nominal weight percentage. All specimens used were prepared and treated according to the procedure described in reference 1, unless stated. For the subzero temperature treat,ment the following experimental schedule was followed. After specimens had undergone the grain-growth treatment, they were quenched into an ice-water bath and were then metallographically examined. In specimens of higher alloy content, no martensitic transformation was observed. In those in which mar-tensitic transformation did occur, only specimens in which the martensite platelets existed as fine needles in localized regions were used. All specimens were reannealed 17 hr at 1200°C, quenched into ice water. and the capsule was broken. They were held in the ice water for from 5 to 10 sec, then transferred to a liquid-argon bath. This stepped quenching procedure was found to be more efficient than direct quenching into liquid argon. In the latter case, as soon as the hot specimen was immersed in the liquid argon, a protective, insulating layer of argon gas formed, and the specimen continued to glow vividly in the bath for some time. In the study of the habit behavior of martensite produced by deformation, specimens were deformed at room temperature either by compression, tension, or rolling. Martensite habit planes were determined by the two-surface analysis procedure described in reference 1. A stereographic net of 153/4 in. diam was used throughout the investigation. The method for determining the orlentation relationship between martensite and the matrix follows that used by Greninger and Troiano.' A diamond-polishing table with its auxiliaries was used in order

Jan 1, 1957

By John W. Cahn, David A. Karlyn, Morris Cohen

The massive B(bcc) — am (fcc) transformation in Cu-Zn alloys has been studied isothermally by pulse-heating the retained ß phase from room temperature to the reaction temperatures. The transformation is found to occur only in the single-phase a region of the equilibrium diagram. The massive growth rate is of the order of 1 cm per sec and is constant at each temperature, usually after a delay time of some milliseconds. The delay time depends on the reaction temperature in C-curve fashion, while the growth rate increases monotonically with temperature over the single-phase range. The absence of isothermal massive transformation in the two-phase region does not arise from slow growth rates at such temperatures, but because the reaction cannot get started there. It is proposed that the massive transjormation initiates at small preexisting a particles which have rejected zinc into the surrounding 0 matrix. Only within the single-phase region can these particles consume the excess zinc during diffusion-controlled growth and thereby accelerate to the steady-state massive growth rate. The onset of massive growth marks the end of the delay time, and the growth rate then becomes interface-controlled. These isothermal transformation characteristics explain why the usual composition range for massive-kinetic studies by quenching is so limited. The same principles can be extended to more complex alloy systems by recognizing that the single-phase region in which the massive transformation can occur may not be stable with respect to phases not participating in the reaction. MASSWE transformations are now recognized as a regular class of solid-state reactions involving no compositional change (like martensitic transformations) and no shear displacements (unlike martensitic transformations). The name was first coined by Greninger1 in 1939 to describe the coarse grains of fcc a solid solution generated via a fast reaction from the parent bcc 0 solid solution in Cu-A1 alloys. However, some 9 years earlier, phillips2 had already described a similar transformation in the Cu-Zn system. The fact that the massive a formed as a single phase during drastic quenching from the 0 region of the equilibrium diagram signified that compositional changes were precluded. and the reaction was presumed to take place as in a one-component polymorphic transition by nucleation and growth. Phillips also observed that the occurrence of the massive transformation in the Cu-Zn system was extremely sensitive to alloy composition. For example. in a Cu-37.3 at. pct Zn alloy. the ß — am (am = massive transformation product) reaction was found to predominate and was not suppressed by iced-brine quenching from the 0 region. whereas at compositions greater than 38.3 at. pct Zn the massive reaction did not appear at all. Knowledge concerning massive transformations has bee11 substantially enhanced over the years by Massalski and his coworkers; an excellent summary of his papers and the current understanding of this type of reaction has been published recently by Barrett and ~assalski." he massive transformation product grows in roughly nodular form. often with irregular boundaries but sometimes with almost planar interfaces. The latter may have simple crys-tallographic indices relative to the 0 matrix. or the indices may be complex just as in the case of mar-tensites.'1 Little is known about the existence of orientation relationships between the massive and parent phases. A striking feature of massive transformations is that the massive units start almost exclusively at grain boundaries of the parent phase and frequently propagate on a broad front across matrix grains and grain boundaries of various orientations. Because of the rapid growth rate, it is thought that the interface motion is controlled. not by long-range diffusion. but by thermally activated atom jumps across the transformation boundary.

Jan 1, 1970

By J. Douglas, W. T. Ford, G. E. Henderson, I. F. Roebuck

An implicit numerical method is presented for simulating the differential and algebraic relations governing one-dimensional three-phase flow in porous media. The method is based upon compositional representation of the hydrocarbon system. Variable physical properties and water-oil capillary forces are included in the formulation; however, the effect of gravity is ignored. The effects of changing composition and mass transfer are considered through the use of known phase behavior concepts and correlations. The differential and algebraic equations and the numeric approximations to these equations are presented, and the computing algorithm is discussed in detail. This method is used to simulate a single-phase, two hydrocarbon-component gas displacement laboratory experiment. The method is also applied in simulating a solution gas drive and a gas injection problem using a reservoir oil represented as a nine-component mixture. For comparative purposes, the latter two problems also are examined with a one-dimensional volumetric model. The results of the simulation of the laboratory experiment demonstrate the relevance of this method to problems wherein the effects of mass transfer significantly enter the displacement process. The comparison of the results of the volumetric and compositional methods applied to a reservoir system illustrates not only the advantages and benefits derived from examining the hydrocarbon system composition, but also the necessity of this approach in application to a general reservoir problem. INTRODUCTION The advent of large memory, high-speed digital computers enabled reservoir engineers and mathematicians to pool their knowledge in the development of sophisticated techniques for the prediction of oil and gas reservoir performance. These techniques have progressed from volumetric and trend analysis calculations to the development of "mathematical models", or reservoir simulators. These latter models, in general, utilize finite difference approximations to the rather complex partial differential equations that mathematically describe the physics and thermodynamics of fluid flow in porous media. Many forms of this "model" type are available today, and much of the recent literature has been devoted to either improving known methods or developing new techniques for use in these prediction methods. The more advanced techniques in use at this time consist of the solution of differential and algebraic relations that describe a reservoir geometry in one, two or three dimensions and that incorporate reservoir hydrocarbon and water fluid systems that obey specified physical laws, having properties that might easily be measured in the laboratory. This type of model utilizes formation volume factors and other volumetric data, expressed directly as functions of pressure, to represent the reservoir fluid system. Experience gained with this type of simulator, commonly known as a "beta-factor model", has indicated that the approach has many outstanding defects, most of them due to the assumption that those properties measured in the laboratory completely describe the behavior of the fluid system throughout the life of the project under study. The effects of varying hydrocarbon composition and mass transfer between the phases of this hydrocarbon system must, by definition, be ignored. These defects, which may often be ignored in

Jan 1, 1970

By Norman F. Schulz

The technical excellence of separation achieved in a mineral concentration process, or any other process where two constituents of any kind are physically separated from each other, is expressed uniquely and quantitatively by the separation efficiency (E,): E. = (R - R,), where R is the percentage of the valuable constituent and R, the percentage of the waste appearing in the concentrate. The separation efficiency meets all the usual requirements of a true efficiency and is independent of the nature of the process used. It can be visualized as the percentage of the feed material that, in effect, actually undergoes complete separation while the rest of the feed is distributed randomly and unchanged into the two separation products. The problem of quantitatively assessing the results of a mineral concentration process recurs whenever one tries to decide which of two similar test results is more desirable. Although economic factors may greatly influence the eventual choice of process, they usually have very little to do with the technical excellence of a separation and are, therefore, not a consideration at this point. Concentrate grade and recovery, used simultaneously are the most widely accepted measures of performance, and if both the grade and the recovery are greater for one case than for another, the choice is simple. However, when the results of closely competitive operations are compared, it often occurs that one set of test results shows a higher grade and a lower recovery than another and the choice is no longer obvious. Laboratory investigations of a mineral concentration process applied to a given feed material can often be designed to yield successive paired values of concentrate grade and recovery over the practical range of the course of a separation process.' These results may be plotted as some combination of the cumulative values of grade, weight recovery, or unit recovery in the concentrate. The resulting correlations for two slightly different sets of conditions can then be compared qualitatively, or even quantitatively in particular cases.2 Such comparisons are not applicable, however, to individual concentration test results. The reduction of a separation test result to a single efficiency figure, preferably as a percentage of ideality, would afford the simplest and most precise means for comparing the results of competitive tests. The effective proportion of feed material that undergoes complete separation in any real concentration process, hereafter referred to as "separation efficiency," is such a figure. It is essily calculated from the usual feed and product data and can even be evaluated, in many cases, from data in publications describing various concentration processes. Mineral Concentration Processes and Their Evaluation Mineral Concentration Processes: The overall concentration process may be subdivided into a liberation process which severs the bonds between unlike mineral species, and a separation process, which sorts the resulting liberated particles into two products—a concentrate rich in mineral A and a tailing lean in mineral A. A perfect mineral concentration process is represented by the idealized scheme shown in Fig. 1 in which liberation and separation are not differentiated. The feed mixture consists of two mineral types which are completely liberated early in the process and then sorted by type. All the mineral particles of type A which respond uniquely to the selection forces acting in the ideal separator, report to the concentrate, while all the mineral particles of type non-A report to the tail-

Jan 1, 1971

By Robert Stefanko

With passage of the Clean Streams Act of the Commonwealth of Pennsylvania and its impact on the coal industry, considerable research has been conducted to explore various approaches to the problem, including deep-well disposal. Available drillhole data from gas and oil wells were used to develop cross -sectional maps for various portions of the state and potential disposal zones were evaluated. Bethlehem Mines Corp., faced with a severe water problem at its Marianna operation in Washington County, cooperated with the Dept. of Mining at The Pennsylvania State University in establishing a 1500-ft well into the Salt Sands for the purpose of determining the feasibility of mine water disposal. The thickness, porosity, and permeability of the formation at the well site proved to be below what had been anticipated from drillhole data. Further, subsequent hydraulic fracturing did not improve the flow characteristics of the well; pumping pressures remained in the range of 1800-2000 psig for disposing of water at the rate of 150 gpm. The legal problems of disposal at the site were very formidable. When the Salt Sands proved to be less than satisfactory, permission could not be obtained to dispose in other promising formations. The paper details many of the problems associated with the experimental well and makes an assessment of the potential for deep-well disposal of mine water. The concept of disposing of liquid industrial wastes by deep-well injection is not a new one. Brines associated with crude oil long have been disposed of in this manner, with the additional benefit of aiding secondary oil recovery. More recently, with the expansion of nuclear energy, the lethal, highly radioactive wastes which are by-products of the fission process have created severe disposal problems. During the past ten years, a variety of industries have resorted to subsurface disposal, some of the details of which are given e1sewhere.l,2 The list reveals wide variations in injection rate, pumping pressure, cost, and waste disposition. Included are successful installations in Western Pennsylvania. Enactment of more restrictive clean-water legislation in Pennsylvania recently had a great impact on the coal industry. Among its provisions was the reclassifica-tion of most mine water as industrial waste whose dis-posal is prohibited in any stream of the Commonwealth. This had the effect of accelerating research in a variety of areas, although treatment methods still retained primary interest. When a feasibility study of deep-well disposal was proposed to the Pennsylvania Dept. of Mines and Mineral Industries, the Coal Research Board (CRB) approved it. This paper summarizes the efforts on this project. Acid mine water is a chemically complex liquid. having no definite quantitative relationship among its constituents. However, it is the iron disulfide (FeS2) associated with practically all coal seams that produces the objectionable products present in acid mine water when combined with air and water. The principal contaminants are sulfuric acid (H2SO,) and ferric hydroxide (Fe(OH)2. Ferric hydroxide is a rust-colored gelatinous precipitate that coats stream bottoms and destroys aquatic life. However, other ions and bacteria are present in acid mine water in varying amounts.

Jan 1, 1971

Jan 1, 1968

By Bunting S. Crocker

Pebble grinding was used at Lake Shore Mines in 1949. A full description of experimental evidence and test plant results was published in 1952 1 and further operating details in 1954.2 In more recent years the term autogenous grinding has been coined and is now frequently seen in the technical literature. Autogenous crushing and/or grinding covers any grinding mill in which the larger of ore are made to grind the fine pieces; the crushing and grinding may be either dry or wet. This discussion deals only with wet autogenous grinding, and only in the fine grinding part of the circuit, i.e., from 6 mesh to 92 pct -325 mesh. The term pebble milling could apply to fine autogenous grinding in which the pebbles are made from the ore itself, or it could also refer to grinding with pebbles, such as flint pebbles, from a source outside the mine.

Jan 5, 1959