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By Hannu Penttila, Harrison R. Cooper, Olli Mattila

Two approaches to automated operation in metallurgical processes involve the conventional analog control or, more recently, digital control. The expanding use of digital controls applied to process automation is a comparatively new development. Several current technical reports describe digital control systems in concentrator grinding control, 1, 2, flotation, 3 and smelter operations. 4,5 The principle factors influencing trends to digital control are:

Jan 10, 1976

By W. A. Griffith

The fundamental principles and modern techniques of experimental planning and data analysis, applicable to any type of research, are particularly important in flotation experimentation. Since they constitute the modern science of experimentation, they should be among the working tools of any scientist, research engineer, or plant operator engaged in flotation investigates. This chapter is a review of these principles and techniques. Equipment and procedures for the actual conduct of experiments will not be discussed here since these subjects are well covered elsewhere in this volume. Neither will any attempt be made to impart a working knowledge of statistical methods of data analysis since this would be impossible in the space allotted, and many excellent texts are available to the diligent inestigator.1-4 The objective here is simply to interest the reader in the application of statistical techniques to flotation experimentation by illustrating their utility in situations frequently encountered, and to point out the principles of experimental planning necessary for their proper use. Any conscientious metallurgist engaged in flotation experimentation or operations is well aware of the inherent complexity of the flotation process, and of the often frustrating difficulties this introduces into experimentation. The raw materials normally treated by the process are complex both physi- cally and chemically, and often highly variable even when from the same source. The flotation process itself is characterized by a very large number of potentially important process variables. Many of these are beyond the con- trol of the metallurgist, and some cannot even be measured quantitatively with available instruments. Those which can be measured and controlled with reasonable precision often produce effects which are intricately interrelated. Not only are the variables many, but the physical and chemical mechanisms by which they function are imperfectly under stood. To compound the difficulty, experimental techniques are relatively crude. Controls are not very precise, and the human factor looms large in most flotation experiments. These situations lead inevitably to experimental data of a relatively low degree of precision or reproducibility. Some are inclined to think that these conditions are unique to flotation experimentation. They are not. The experimental problems met by the agronomist, the biologist, the social scientist, and others are equally complex. Investigators in these fields pioneered in the development of methods for handling just such situations by proper experimental planning and the application of statistical methods in the analysis of data. Their pioneering work has grown into a well established modern science of experimentation which has spread into every field of science. This science is based upon statistical

Jan 1, 1962

By Sidney A. Swensrud

Much has been said and written about uneconomic and evil marketing practices in the oil industry, including such factors as loaning of equipment, price cutting and secret prices, commercial discounts, abuses of credit cards and coupon books, and so forth. It is not my purpose here to add to the discussion of those problems, but rather to attempt a discussion of some of the more basic factors in the general distribution economies of the industry. The economics of distribution in the oil industry cannot be regarded apart from the general economics of the industry as a whole. The attempt to regard them as separate has led many people into the fallacy of believing that the responsibility for the apparent evils in the marketing end of the business lay entirely at the door of the marketing end. Such a view fails to take cognizance of many underlying factors; we can only expect to understand the distribution economics of the industry if we understand its general economics. We must realize also that the oil industry today is essentially the gasoline industry. The oil industry may be said to have begun about 60 years ago. At the outset it was concerned chiefly with the manufacture and sale of kerosene, lubricating oils and greases. Gasoline was then a most obnoxious by-product. The early oil-marketing company was engaged almost exclusively in refining and marketing—it did not concern itself with production but bore the relation to it merely of a purchaser. It may be said that the urge of marketing development in those days, therefore, came from the refining and marketing end of the business. The raw material had not yet begun to exert its enormous pressure, nor had the producer of crude oil acquired a direct interest in the sale of the ultimate finished products. Since then great changes have taken place. With the development of the automobile came a vast new demand for the raw material from which gasoline could be made. No longer could the refining and marketing companies be indifferent to the source of that raw material, particularly in view of the pessimistic outlook then presented as to the probable quantity of oil in existence. And despite the complete overturning of those early estimates, made before the bounty of nature and the skill of

Jan 1, 1931

By C. A. Pierce

UNDERGROUND operations of the United States Potash Co. at its mine near Carlsbad, N.M., have been continuous since the property was opened about five years ago. Approximately one million tons of potash has been mined and two shafts have been sunk, each to a depth of about 1000 ft. Outstanding in the company's operations is the fact that not a single blasting accident has occurred during the aforesaid period. The purpose of this paper is to describe the blasting practice that has made possible the achievement of this accident-prevention record. The mining method employed in extracting the thick horizontal bed of potash may be described as a double-entry room-and-pillar system. Mine development is kept well in advance of extraction operations, and a three years' supply of ore, at least, is always available. Limits of the orebody have not been determined, and in the present system of mining headings are advanced by a "shortwall" method. This was the first potash ore bed developed in the United States. The nature of the deposit, therefore, was unknown, and it was deemed expedient to outline a conservative mining policy. Later, when more is known about the deposit and certain control ascertained, a "longwall" panel retreating method may be found advisable. The necessity for a domestic supply of potash became a national issue previous to and during the World War. The United States Govern-ment came to realize that this country should not be dependent upon foreign sources of potash, and began extensive explorations in many parts of the country, seeking an orebody that would meet the exacting require-ments of the domestic market. The Department of Interior, through the Geological Survey and Bureau of Mines, made every effort to determine the location of potash deposits and encouraged their exploitation by private capital. Through the combined efforts of the Department of Interior and private industry, the deposit now being worked by the United States Potash Co. was discovered and brought into production.

Jan 1, 1936

By R. D. Parks

DESPITE the handicap of reduced production in many districts, the mining industry in 1938 forged steadily ahead toward solution of its minor technical problems and has of-defected major advances in several fields. In California hydraulic mining for gold, shut down for forty years, will shortly be resumed following revision of restrictive laws. Disposal of hydraulicked ground is to be regulated by settling dams so as not to interfere with agriculture. Gold mining has been aided also by the development of a new high-efficiency dry amalgamator which applies the Ramsay mercury separator to the original de Phily process. Based on the principle that crushed ore will follow a rod into a mercury bath, this simple device is primarily adapted to dry areas and is to be available in small, multiple units suitable

Jan 1, 1939

By J. D. McClung

INTRODUCTION The ever increasing demand for coal sues that meet exacting specifications has made necessary the installation of thousands of dollars worth of crushing equipment by the coal industry. At one time the operator at- tempted to recover as much lump as possible but today he is confronted with the necessity of crushing to facilitate the mechanical cleaning process and to meet the demand for a variety of uniform sizes. As a matter of fact, about 65 percent of the coal mined in the United States today goes through preparation plants where it is crushed and cleaned. One becomes more aware of the importance of the art of comminution when it is realized that practically all of the operations in mining are involved in comminution in one way or another. Whether the coal is mined conventionally or by continuous miners it is separated from the solid by a breaking, ripping or milling action which essentially amounts to a comminution operation. Even degradation resulting from material handling from the mine working face to the preparation plant might in a broad sense be so classified, Then of course crushing is usually necessary in the plant before the coal is ready to be marketed. THEORY Despite the various comminution operations there is a lack of satisfac- tory information concerning the fundamentals of crushing and their relation to the variable factors associated with the operation. There are certain laws and theories on mechanical reduction, such as those of Rittinger, Kick and Bond that are helpful and useful. The difficulty in developing exact mathematical relationships for specific crusher applications is due to the many variable physical characteristics found in coal. Hardness, as measured by the Hardgrove grindability index, is one parameter that has been used for years to determine the resistance of coal to comminution. While the coal properties as measured by grindability are complex, recent work has shown that a high correlation exists between the grindability of some coals and their petrographic analysis. Early research on the hardness of petrographic entities from an Illinois coal2 demonstrated that durain was the hardest constituent followed by clarain, vitrain and very soft fusain. Other research demonstrated that, for different size fractions of the same coal, a wide variation in hardness commonly exists. For example, the fines in about half of 39 coals studied were softer than their corresponding coarse sues while most of the remaining coals were uniformly hard in all sizes. A few coals contained fines which were harder than their coarser constituents. These variations in hardness give insight into the heterogeneous nature of coal.

Jan 1, 1968

By Paul A. Bailly

Around 4500 B.C., the Pharaoh of Egypt ordered a military campaign to the Sinai Peninsula and the shores of the Red Sea, to search for copper deposits which Egypt needed for jewelry, vases and weapons.5 To my knowledge, this is the first recorded expedition aimed at the discovery of minerals. The diligent Egyptian soldier-prospectors made discoveries through visual detection and manual effort, the approach which has given us the bulk of our mines to date. In the Rio Tinto District of Spain where Roman miners followed the Phoenician traders, we find the first evidence of discovery of hidden ore bodies in the absence of mineralized outcrops. This is how Joralemon 13 describes these Roman discoveries to the southwest of the Rio Tinto hills, under the flat plain of Seville:

Jan 6, 1979

By P. A. Boeck

(San Francisco Meeting, September, 1915) THE thermal insulation of high-temperature equipment for industrial purposes is a subject that has not received from engineers and designers the attention its importance deserves. This may be attributed to a number of causes: In the first place, heat flow is a rather difficult factor to measure under the working conditions of an industrial furnace, and until the comparatively recent introduction into certain operations of the heat balance sheet, with a systematic attempt to account for the discrepancies in the totals, the various causes of heat losses and the reasons for their existence were not brought to light. Moreover, such rapid advancement and radical changes in the design of equipment, especially in metallurgical lines, have occurred that practice has apparently outdistanced the theory of design. In the modern tendency toward greatly increased size of units, effort has seemingly been made to utilize the heat of fuel gases without proper. attention having been paid to conserving heat energy and confining it strictly to the points of maximum activity. The systematic study of the thermal properties of structural materials, which is being carried out by various government bureaus and also by a number of technical societies, is forming the basis for more intelligent and consistent work in the economically important subject of prevention of fuel waste.

Jan 8, 1915

By Joseph Kuti

ROOF SUPPORT DEVELOPMENTS IN LONGWALL (1) European longwall mining technology developed towards its modern form in relatively deep mines. With increasing depth the stability of openings driven for ventilation, travel or transport becomes paramount in mine design considerations. As a result the number of roadways and entries, as well as their width must be a minimum. (1) Another important aspect of European mining is the high density of mineable seams, as opposed to the wide lateral extension of a single seam in the U. S. A. Multi-seam mining requires strict planning and near 100% extraction, since with increasing depth, the effect of remnant pillars can be devastating. As a result the face layout of a modern European longwall panel is based on single panel entries of moderate width and great height. The mode of extraction is generally a mixture of the advance and retreat system which is called a 2-system. It is obvious, therefore, that the supports developed for the entries and for the intersection areas are more complex than those in the U. S. A.

Jan 1, 1981

By Ernest A. Hersam

The advantages of the tri-axial diagram in representing the composition of slags and silicates are well appreciated by many metallurgists. Prof. H. M. Howe* has pointed out the application of a fourth variable, in connection with the diagram, and has called attention to the usefulness of the general systern of tri-axial representation. In the discussion of Prof. Howe's paper, Mr. Firmstone† indicated how certain distances could be measured directly by projection. Prof. R. H. Thurston,‡ as early as 1877, had made use of a typtic model and of triangular diagrams, with contour-lines, rekrresenting varying physical properties corresponding to varying chemical composition. Still earlier, Prof. J. Willard Gibbs§ had used the diagram in similar work; and other scientists were thought by him to have preceded him in its use. During the period of nearly a quarter-century, following these early publications, there has been an ever-increasing use of graphic methods in numerous branches of scientific work, stimulated, in part, by the possibility of representation by three co-ordinates upon plane-surfaces. Yet the number of possible co-ordinates for graphic representation has always been, and always must be, insufficient to express many facts which are shown mathematically; while, without graphic representation, the involved nature of mathematical expression often fails to facilitate and promote research. The coming into use, therefore, of the fourth co-ordinate, permitting representation by four variables, marks but the beginning of some lines of research which could not well advance without this aid.

Jan 1, 1902

By Max Roseler

THE CHAIRMAN (WILLIAM KELLY, Vulcan, Mich.).-Some 8 or 9 years ago I was at Daiquiri, only a. few miles east of Firmeza, where there are deposits of iron ore of the same general character. There is a great conical hill, perhaps 800 or 1,000 ft. in height and the ore deposit appears to be somewhat in a canoe shape on one side of the hill. The mining has been done by quarrying the ore in benches. These are called levels and to go to the 10th level it was necessary to take mules and ride to the top of the hill, which was to me an upside down arrangement of numbering levels and a novel method of entering and viewing a mine. A little copper ore can be seen in places, and not being a geologist I thought the deposit might possibly be a gossan, but none of the geologists who have written on the subject approve of this hypothesis and the great question seems to be what part, if any, the limestones have played in the origin of ore; whether these deposits are replacements of limestone and whether they are contact ,deposits between the limestone and the other rocks. Examinations have been made by many eminent geologists and the problem has been discussed vigorously on both sides. The deposits are exceedingly interesting from a commercial standpoint and although they have been studied for a number off years the origin of the ore is still a difficult and somewhat controversial question. J. T. SINGEWALD, JR., Baltimore, Md.-I have had the privilege of visiting these deposits and have been very much interested in this paper, of Dr. Roesler's; having been on the ground, I can easily appreciate the difficulties under which he labored in attempting to work out the geology of that region, and he certainly deserves considerable credit for the way in which he has deciphered the geological relations of the Firmeza district. There are several points in his paper 1 ,would like to discuss; first, in regard to the geological interpretations. His differs from previous interpretations in the relative age of the diorite and the granite, but you will note that Prof. Lindgren suggests the probability. that those two rocks are very closely of the same age, and Prof. Kemp actually suggests, although he does not-accept the idea, that the granite is probably later than the diorite, so that there seems to be no particular reason

Jan 4, 1917

Albin, B. R Billings, Mont. '28 Amster, Nathan L . , 25 Broad St, New York, N. Y. '28 Bache, Jules S 42 Broadway, New York, N. Y. '28 Barrett, C. P 5338 Harper Ave, Chicago, Ill. '28 Baum, Frank G Hobart Bldg., San Francisco, Cal. '28 Bayless, Ron. William S Russ Bldg , San Francisco, Cal. ' 28 Bean, Louts H., V.P., Dwight P. Robinson & Co, Inc 125 E. 46th St, New York, N Y. '23 Beatty, Ross J 1105 First National Bank Bldg., Chicago, Ill. '28 Benwell, Oswald F 205 Colorado National Bank, Denver, Colo. '28 Beymer, Albert S., V.P., Keystone National Bank Pittsburgh, Pa. '28 Bingham, Charles W 1542 Hanna Bldg, Cleveland, Ohio. '28 Blumenthal, Hugo 44 Pine St, New York, N. Y. '28 Boettcher, Charles Ideal Cement Bldg., Denver, Colo. '28 Bowlus, Thomas H Iola, Kans. '28 Bragg, E. B Carmel, Cal. '28 Brown, Colvin B Chamber of Commerce, Washington, D. C. '28 Burt, Maxwell Struthers Southern Pines, N. C. '28

Jan 1, 1923

By N. Mungan, J. L. Thompson

Laboratory displacement tests were performed to study oil recovery elficiency by gravity drainage in fractured systems under miscible conditions. The porous media used were cylindrical Berea and Blue Jacket sandstone cores containing a number of well-defined, artificially formed, vertical and subvertical fractures. Butane and Soltrol 130 were the two miscible fluids used. The purpose of the study was to examine the influences of the displacement rate, fracture density, fracture orientation, fracture permeability, matrix permeability, crossflow, core length and connate water on the oil recovery. It was found that displacement rate, matrix permeability and the subvertical fractures affected oil recovery most. The critical flow rate, based on the matrix permeability, was found to be a significant factor in the process. For displacement rates below the critical flow rate, the oil recovery efficiency appeared to be unaffected by the density of the subvertical fractures. At the high displacement rates, the fracture density becomes important, with the recovery being the most efficient in the core having the greatest number of the subvertical fractures. The magnitude of the fracture permeability, the fracture orientation, the core length and the connate water have little effect on the oil recovery efficiency. INTRODUCTION Gravity drainage under miscible conditions from relatively thick reservoirs can be a very efficient recovery process, especially at low flow rates where the gravity forces are dominant and, consequently, the adverse viscous fingers associated with the unfavorable viscosity ratio are minimized or eliminated. Such a process might involve injection of an LPG or some solvent bank at the crest and then driving the bank with dry gas. For some favorable combination of reservoir temperature, pressure and oil composition, there may be no need to inject any solvent bank, since enrichment of the dry gas by the light ends of the crude creates an in-situ solvent bank. Slobod and Howlett2 have studied the effects of gravity segregation in vertical unconsolidated porous media under miscible conditions in the laboratory. The main variables in their study were the viscosity ratio, the density differences and the rate of flow. In this study, the objective was to find the influence of fractures on gravity drainage under miscible conditions. A greater number of related variables were also studied. LABORATORY STUDY CORE DESCRIPTION Displacement tests were performed mostly in cylindrical Berea sandstone cores. In a few cases in which a much lower matrix permeability was desired, Blue Jacket sandstone cores were used. The vertical fractures were formed by cutting the cores with a thin circular blade or by parting them along a bedding plane. The vertical fracture plane always contained the axis of the cylindrical core. The subvertical fractures, cut with a saw, were inclined 45' from the horizontal. The line of intersection between the planes of the vertical and subvertical fractures was parallel to the circular faces of the cores in all cases except one, as depicted by VF3HF-2 in Fig. 1. Fracture geometry of the other cores is also given in Fig. 1. Tables 1 and 2 give the physical properties of the solid and fractured cores, respectively. The suffixes and prefixes shown for each core have been used throughout the paper so that the reader may discern the fracture geometry from the core numbers.

Jan 1, 1970

By M. A. Goudie

The deposits occur in a large salt basin of Middle Devonian age. The potash, the final deposit in the salt basin, results from several interrupted cycles of evaporation and dessication. The deposits are extensive, and, at first glance, relatively undisturbed. With more and more wells being drilled, it has now become evident that salt solution has played a large part in changing the original deposits, resulting in some cases in partial to complete removal of the potash and the underlying halite. The most dominant factor in the removal of salt by solution appears to have been tectonic movement and consequent faulting, probably of relatively minor dimensions but of major importance. Evidence which indicates the tilting of the evaporite basin to the north and northwest is shown by the changing pattern of the basin during succeeding eras of potash deposition. The potash minerals of most importance economically are sylvite and carnallite. Reserve calculations indicate that 6.4 billion tons of recoverable high grade potash in K2O equivalent exist in the basin. The Devonian salt basin, which contains the Saskatchewan potash deposits, extends from just east of the foothills in Alberta, north as far as the Peace River area, across Saskatchewan and into Manitoba as far east as Range 10 west of the First Meridian and south into Montana and North Dakota (Fig. 1). The basin is closed everywhere except to the northwest. The known potash deposits are confined almost entirely to the Province of Saskatchewan, with the exception of a small area in western Manitoba bordering the Saskatchewan boundary. The following discussion will concern only the Saskatchewan part of the basin. The evaporite series in the basin is defined as the Prairie Evaporite Formation of the Elk Point Group, of Middle Devonian age. Recent work done by potassium-argon dating methods has indicated an Upper Middle Devonian (Givetian) age of from 285 to 347 million years for the potash. The Elk Point Group consists in ascending order of the Ashern, Winnipegosis, and Prairie Evaporite Formations. The Ashern formation, with an average thickness of 30 ft, sometimes called the Third Red Bed, consists of dolomitic shales and shaly dolomites. The Winnipegosis, is a reef-type dolomite, usually with good porosity, and in many cases oil-staining, although to date no production has been obtained. The thickness varies from 50 to 250 ft. The Prairie Evaporite formation, varying from 0 to 600 ft in thickness, consists of halite with interbedded anhydrite and shale, with considerable amounts of potassium salts in the upper part of the formation. The potassium salts are chiefly chlorides, although very minor occurrences of sulfates have been re- ported. The anhydrite beds do not appear to be continuous, although generally one or two bands of anhydrite underlie the lowest potash zone and are used as marker horizons. The shale occurs as seams interbedded with the salts, as large irregular inclusions in the salts and as very fine particles in intimate mixture with the salts. The Prairie Evaporite Formation is overlain by the Second Red Bed member, the Dawson Bay Formation and the First Red Bed Member of the Manitoba Group, listed in ascending order. The Red Beds are shales which vary in color from red to green, maroon, grey, grey-black, and reddish purples. They serve as marker horizons for coring the potash. The Second Red Bed averages 14 ft in thickness, the First Red Bed 35 ft. The Dawson Bay Formation, which everywhere overlies the First Red Bed and the Prairie Evaporite Formation in the area under discussion, is a reef type of carbonate, in some places limestone, in others limestone and dolomite, with vugular to pinpoint porosity averaging 130 ft in thickness. In some parts of the area, it has a salt section near the top of the formation, usually with interbedded shales and limestones. In other parts of the area, it is waterbearing and the salt is absent. Detailed mapping has indicated that the areas in which the Dawson Bay is water-bearing are areas which have been disturbed by faulting. Where the Dawson Bay is salt-bearing, the porosity has been plugged by salt. The total thickness of the salt varies from between 600 to 700 ft in the center of the basin to zero at the northern edge of the basin (Fig. 2).* The salt-free area in the center of the Province is believed to have resulted from removal of salt by solution. Evidence from several wells suggests that salt removal has been a continuing process from the time of deposition to the present day. One well drilled between the Quill Lakes for potash information encountered

Jan 1, 1961

By L. A. Mekler

THE recirculating furnace is primarily a heating apparatus of the convection type in which the heat-absorbing surfaces are heated by a mixture of fresh products of combustion and a portion of the combustion gases that have already given off a part of their heat in their previous passage over the heat-absorbing surfaces. In its basic conception, the recirculating furnace can be considered as a closed thermal system in which the heat-absorbing surfaces are .constantly swept by a fixed quantity of products of combustion at a given initial temperature with the gases being constantly returned to the furnace and reheated before they again enter the heating zone. Gases equal in amount to that produced by the fuel burned to reheat the circulating gases are constantly ejected from the system to the stack. The recirculating furnace is the most suitable apparatus for heating by convection where low furnace temperatures must be maintained and where only a small portion of the available heat is taken out of the gases, particularly where the maximum allowable furnace temperature is low and where the final temperature of the gases is only a few hundred degrees below their initial temperature. In such cases, recirculation not only provides a method of reducing the rather high combustion temperatures of the fuel when burned without a large amount of excess air, but, by returning to the furnace the heat content of the gases at their final temperature, recovers a large portion of heat that otherwise would have been lost through the stack.

Jan 1, 1928

By Persifor Frazer

The '(author's edition" of the following paper, "subject to re vision," was received by him, and copies sent to Professor Geikie and others about two weeks before the date of the meeting at which it was to be read. A telegram, and subsequently a letter (both of which unfortunately arrived too late), apprised the present writer that the Director General objected to certain views ascribed to him as the reverse of those which he really held. These views, however interesting, had no very important bearing on the object of the fol lowing notes, which, as must be evident, are devoted to the conside ration of the close analogies between the Welsh and American rocks. Without being able, therefore, to account for the circumstance which Professor Geikie has mentioned, it is thought better in the present revised edition to omit all allusion to Professor Geikie, or Mr. Peach, or their views, except in this place, where I desire to thank them for their courtesy during the time which I had the pleasure of spending in their society. It appears sufficiently throughout the body of the paper that the writer had not the slightest intention of entering the controversy, which was about to commence, concerning the proper horizons of the St. David's rocks, for many reasons; and amongst others because he did not feel that a sojourn of a few days in a difficult region, which had been already studied by many of the foremost geologists of England, would warrant him in adding to the literature on the sub ject. The discussion of the analogies between these rocks and those of the Eastern Appalachians, which he has studied for twelve years, of which eight were spent in the service of the Second Geological Survey of Pennsylvania, was much more to his taste as it was more within his ability, and if he has added anything to the evidence of these analogies, the paper, however imperfect, will not have been written entirely in vain. Right or wrong, he assumes the entire responsibility of what follows.

Jan 1, 1883

By Clarence A. Seyler

The technical difficulties of cutting thin sections of coal for examination by transmitted light have hitherto restricted the investigation of the important subject of the microstructure of coal to the few possessed of the requisite skill and time. Apart from this, the method fails with anthracites and other coals rich in carbon, owing to the opacity of the material. Occasional use of the method of polishing a surface, with or without etching, has been made, but it was not until Winter' published an account of his results that attention was seriously directed to the method. In May, 1923, a specimen of dull anthracite came into my hands; I tried Winter's method on it and the presence of megaspores and other vegetable structures became clearly visible. A preliminary notice was published by me;2 but I soon abandoned the use of Schulze's solution, having found that a mixture of chromic and sulfuric acids gave far better results. In the meantime Turner and Randall, in America, had independently developed the method of flame etching, as applied to anthracite, with great success. I have spent a year studying the method of chromic etching, which gives excellent results with bituminous coals and camels, as well as with anthracite. For anthracites, I have used the chromic method and Turner's method of flame etching, whichever was the more convenient or as a check one on the other. The polishing is done, according to metallurgical practice, by the use of a polishing machine and successively finer emery paper, followed by polishing on cloth moistened with a suspension of levigated green oxide of chromium, and a final rubbing on "selvyt" (a cotton velvet polishing cloth) moistened with alcohol. The polished sample is examined by reflected light with a 2/3 and 1/6 in. objective. Bituminous coals usually show considerable structure, and even anthracites show it faintly in places. The sample is then etched by immersion in a boiling solution made by adding 10 c.c. of concentrated sulfuric acid to 30 C.C. of a saturated solution of chromic acid; enough water is then added to dissolve

Jan 1, 1925

By A. N. Chirico

This paper reviews the three major distillation processes: multiple effect (LTV) evaporation, multi-stage flash distillation and vapor-compression forced circulation evaporation. Scale preventative measures are discussed for all saline water applications. Operational data is presented on the Freeport, Texas, demonstration plant, which is the first government facility to produce one million gallons per day of fresh water for a municipality. There has been much publicity concerning the water crisis that confronts many peoples today. There is little doubt that the arid regions - which include the Middle East, parts of Africa and the Caribbean — have suffered to no slight extent for the lack of this most precious commodity. But what about our own country? Government experts have extrapolated demands and flatly predict that by 1980 we will be faced with a shortage of 80 billion gal per day. The validity of this prediction has been disputed by others; however, it appears certain that there will always be a natural abundance in some areas, a shortage of supply in other areas. Distributing our total natural water resource equitably would be impossible. Transmission of water by means of aqueducts can be an expensive undertaking. The controversial Feather River Project in Calif. is an example. The estimated cost for this venture is a staggering three billion dollars. As our population continues to increase and our standard of living rises, agricultural and industrial requirements will be proportionate. What can be done to avoid a crisis? We can conserve and use our water for industrial and irrigation purposes more judiciously: we can attempt to eliminate pollution of our natural resources from sewage and industrial wastes; we can develop, while there is time, saline water conversion processes for the massive production of low cost fresh water. The scope of this paper will be limited to only the distillation type processes that are commercially feasible. The first step in making potable water is to find a source of raw material. An inexhaustible supply is provided by oceans in coastal regions, but the supply of water is more critical in the inland communities of our country. The source of raw material in these. regions is brackish well water and this must be utilized. There is a significant process difference when handling brackish water compared to seawater and this brings out an important fact: No single conversion method can be universally applied to solve all the water problems. Composition of the raw water and degree of distillate purity are factors which must be considered before a particular process is selected. Local conditions at the plant site, fuel costs, labor costs, disposal facilities, etc. are other equally important factors which must be evaluated. WATER CONVERSION PROCESSES Conversion processes commercially feasible today are: 1) multiple effect evaporation, 2) multiple flash distillation, 3) vapor compression distillation and 4) electrodialysis. The first three are distillation processes which take potable water out of the raw water, while the fourth is a membrane process which takes out the salt. In addition to the above there are a good number of other promising methods for production of potable water, many of them in the basic research stage. Freezing is another promising process with commercial potential. This process hinges upon the formation of ice crystals which are free of salt occulsions. Separation and washing of the crystals are problems that must be solved before this process can be considered commercially feasible. Freezing processes have several advantages mostly attributable to the low temperature of operation. This low temperature reduces the scaling and corrosion problems encountered in higher temperature operations. Several different freezing processes are being considered and will be tested in the pilot plant at Wrightsville Beach. One process is a flash freeze process, a second uses a secondary refrigerant such as butane for freezing, and a third process employs a secondary refrigerant particularly controlled to produce large ice crystals. Of the above processes, only the distillation processes are reliable when water of high purity is re-

Jan 1, 1963

By R. A. Wagstaff

THE method of charging a reverberatory furnace has changed many times since smelting was introduced in this country from the old smelters of Swansea, England. The cause of the latest change at the Garfield plant has been the excessive fineness of the charge due to fine grinding in the concentration of the crude copper ores. The many desirable features of deep-bath smelting as now used at Garfield have been proved. The old method of dropping the charge through holes in the arch (known as center-feed method) causes excessive dusting which makes heavy slag and causes flue-dust losses, also rapid deterioration of the silica brickwork of the furnace through fusion .with the iron oxides from the dust. The purpose of this paper is to describe a gun feeder that was designed to overcome the disadvantages of the older methods of center feeding and still maintain the good features of deep-bath smelting with the hot finer charge. A gun feeder was designed to introduce the finely divided hot calcines under the moving gas stream of the combustion zone and still have them spread in a uniform blanket over the highly heated matte bath. The temperature of the furnace was so great that it was impossible to maintain a stationary feeder, so a movable feeder was designed that could be introduced into the highly heated zone and be withdrawn after the charge had been dropped. It was necessary to protect the nozzle of the gun with a water-cooled coil. Many different types of protected nozzles were tried, such as air jackets, water jackets and heat-resisting steel alloys, but none proved satisfactory.

Jan 1, 1932

By Oscar A. Glaeser

The purpose of this paper is to present specific applications of the fundamental principles of mine ventilation and the means that are at our disposal to accomplish the task of maintaining a healthful atmosphere in small mines and prospect openings. Need for Ventilation The range between the maximum oxygen content of normal air and the minimum safe content is extremely narrow, approximately 5 per cent. Furthermore, normal air must not be contaminated with irrespirable gases beyond definite limits, and mineral dusts are equally dangerous, although health impairment is slower. Tables 1 and 2 present the more common respiratory hazards encountered in mines. Adequate ventilation is the most effective means available to reduce or eliminate these hazards. Mechanical ventilation has reached varying stages of perfection in coal mines and in many large metal mines. The small mines and prospects rarely have a definite plan of ventilation. As a consequence underground workers are frequently exposed to health and accident hazards. The annual reports of fatalities in mines in the Western States record yearly many deaths due to asphyxiation and deaths caused by men falling down shafts and raises after being overcome by gas. At times mining operations are slowed up because there is no means of driving out the gas after blasting. For that reason only one shift is worked, or men wait from one to several hours for the "smoke" to clear out. Methane gas in varying quantities is widely distributed throughout California. It has been encountered in explosive concentrations in the coast range. It has been found on the Mother Lode and in quicksilver mines near the coast. Methane explosions have not been uncommon in underground operations and in tunneling jobs. These conditions and records indicate that there is room for improvement in mine-air conditions.

Jan 1, 1937