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By Joseph E. Pogue

In 1920, 531 million barrels of crude petroleum were coi~sumed in the United States. As imposing as this figure is, the fact that the domestic consumption of crude petroleum has increased at an average rate of 10 per cent. a year for the past decade is more striking. Will this rate of increase in demand continue? If so, the year 1930 will call for 1260 million barrels of petroleum—a staggering volume. On the other hand, may we expect the demand for petroleum to grow as rapidly as it did when the automotive industry was having its most phenomenal expansion? If not, to what extent will the growth of oil requirements decrease? When and to what degree will the petroleum industry become affected by the economic law of diminishing returns? Obviously, this matter requires careful analysis, especially as both national and industrial planning must be predicated upon present estimates of the requirements of the future. The purpose of this paper, accordingly, is to project, as closely as present limitations of knowledge permit, the course of the demand for petroleum in the United States over the next ten years. At first, the problem of estimating the future of a demand as complex as that for petroleum might appear insoluble. Fortunately, hon~ever, therc are several scientific methods of approaching the problem, centering around a study of rates of industrial growth, which lend considerable hope that the requirements of the immediate future in this field may be approximated with sufficient closeness to have practical value as a basis of action. Growth oF Petroleum Demand The demand for crude petroleum is the resultant of the demands for the products made jointly from this substance—gasoline, kerosene, gas and fuel oil, and lubricating oils. The demands for these have grown at

Jan 1, 1923

By Kenneth B. Ray, George R. Gardner

The application of wet cleaning processes for the beneficiation of bituminous coal has created in some localities a problem in the recovery and disposal of fine solids in the washery water. The maximum allowable concentration of these solids in the washery circuit that is consistent with satisfactory operation of the cleaning units remains a controversial point. It has, however, been generally recognized for a number of years that some degree of control should be exerted over the concentration of such material. Early methods of control involved intermittent or continuous discharge of a portion of the plant slurry into near-by streams or settling ponds, and this persisted even after the adoption of settling tanks or cones. The practice is not always economical, for two reasons: first, because of the waste of coal, and, second, because it is sometimes difficult and expensive to obtain an adequate supply of water. The latter condition often is aggravated by chemical treatment of the make-up water that is necessary to prevent excessive corrosion of plant equipment. The modern approach to this problem has been the adoption of continuous thickening devices. However, because such equipment occupies considerable plant space and is somewhat expensive to construct, the practice of loading these thickeners beyond their rated capacity is widespread, therefore often the performance of such units is not altogether satisfactory. In recent years, European washeries have increased the rate of settling of the fine coal from the slurry by the addition of specially prepared starch solutions. These reagents cause flocculation of the solid particles and thereby increase the rate of sedimentation. The first important work on the flocculation and clarification of coal slurry was done by Henry, who developed the Henry process and used it successfully in Belgian preparation plants. Soon after the initiation in Belgium, the process was introduced into England, where subsequent, investigation developed similar processes, which were successfully used in

Jan 1, 1939

By H. R. Stahl

The disseminated lead district of Southeast Missouri lies 70 miles south of St. Louis. The only metal of economic importance in the ore is lead, but minor amounts occur of iron, zinc, copper, cobalt, nickel, silver and cadmium. These minor metals, as might be expected, tend to concentrate in both the flotation and table middlings. In the past, some zinc has been recovered by differential flotation. The silver and cadmium tend to associate with the zinc, and some recovery is made of these two metals at the smelter. The lead occurs as galena, or lead sulphide. The minor metals are also present as sulphides. The presence of oxidized lead is suspected, but has not been definitely proved. The gangue is chiefly dolomitic limestone, with small amounts of sandstone and shaly glauconitic and chloritic minerals. The ore contains about 3.25 per cent lead, occurring as galena disseminated through the gangue. Some of the galena is very finely disseminated, and the mineral in the gravity tailings, or chat; is seldom or never in the free state. The method of treatment of the ore has been evolved over a period of 75 years; hence probably is not far from correct. The milling processes have tended toward simplification during the past 15 years, but recoveries have never been sacrificed for the sake of simplicity. In many cases, simplification of flowsheets has led to better recoveries and operating economies. A simplified flowsheet is shown in Fig. I. The St. Joseph Lead Co. operates four mills in the Flat River district, with a normal total capacity of about 21,000 tons per day, divided as follows: Federal mill, 11,000 tons; Leadwood mill, 4500 tons; Desloge mill, 3400 tons and Bonne Terre mill 2400 tons. The methods of concentration used at these plants are similar in principle; they differ mainly in details and in the type and size of the equipment used. The process of concentration may be divided into five main steps; i.e., dry crushing, wet grinding, classification with its attendant desliming, tabling and flotation. A brief description of these processes will be given, noting important differences in the various plants, and also noting the more important changes or developments of the past few years. Dry Crushing The run-of-mine ore is hoisted in skips, the capacity of these skips ranging from 23/4 tons to 81/4 tons. At the Desloge plant, the ore is hoisted in 2-ton mine cars on self-dumping cages. All ore is hoisted at shafts adjacent to the various crushing plants, no ore being transported on the surface. Primary breaking at all the mills is accomplished with 9E Telsmith breakers. Preliminary screening is provided ahead of most of these crushers, either by station-

Jan 1, 1943

By G. W. Jarman

The purpose of this paper is to present briefly a description of some of the special methods of separation or concentration, either singly or in combination with others, and to give certain operating data and examples. Explanation of the usual methods of large-production mill treatment, such as flotation or wet tabling, or of chemically treating industrial minerals, is not included in the scope of this paper, although one of these methods might be, in certain instances, augmented by one or more of the special methods that will be enumerated herein. Description of these special methods will be centered on magnetic separators, electrostatic separators and air flotation or air tables. Magnetic Sepaeatohs In general, separation is achieved by exerting upon a particle some kind of force opposed to gravity, either directly or at an angle. For example, in the Wetherill or cross-belt type of magnetic separator some particles are lifted vertically from the others because they have been exposed to a force to which they respond more readily than particles of lesser magnetic susceptibility. Of course, there is a limitation to this vertical rise, for the particle must be of a high enough susceptibility to receive a magnetic force greater than the 980 dynes per gram of gravitational urge. To overcome this limitation, the induction type of magnetic separator was developed, so that it is only necessary to instill, say, 30 to 60 dynes per gram instead of the 080, to cause a deflection away from the vertical in falling, and that deflection can be used advantageously when falling by inserting a dividing knife-edge. The induction magnetic separator (Fig. 1) has become a fairly well known method of concentrating and purifying. For example, abrasive grain was among the materials that did not respond to the previously best known type of magnetic separator, such as the Wetherill type, and the development of the induction magnetic separator in the plant of a

Jan 1, 1942

By Lo-Ching Chang, K. M. Goldman

The kinetics and mechanism of transfer of a constituent across a slag-metal interface are fundamentally important because many metallurgical processes involve the existence of a slag phase and a metal phase. Industrial processes seldom proceed to equilibrium, and information of the rates and modes of reactions are therefore often of greater practical importance than equilibrium data. A study of the kinetics of sulphur transfer across a slag-metal interface under reducing conditions will contribute a great deal toward a better understanding of desulphurization in the blast furnace process. The general principles existing in the transfer of a constituent, such as sulphur, across a slag-metal interface can be extended to similar transfer phenomena in other metallurgical processes. The present paper will demonstrate how such studies will lead to fruitful results from both the practical and theoretical standpoints. EXPERIMENTAL METHOD The apparatus used was, simple. A graphite crucible 15/8-in. id, a wall 1/8-in. thick, and a depth of 4 in., was packed in an outer fused silica tube with powdered magnesia. The crucible assembly was rotated at a speed of 235 rpm inside an in- duction coil. A charge of 250 g of Armco ingot iron was introduced into the graphite crucible and melted by induction heating. The melt was held at a desired temperature for 3-5 "'in., aftcr which 7.5 g of granular ferrous sulphide was added and the bath was held for another 3-5 mi11. A metal sample was then taken by means of a fused silica tube and a rubber suction bulb. Immediately after the metal sample was taken, 30 g of a prefused and crushed slag were introduced. The slag reached the ternperature of the furnace in 1 to 1 1/2 min. Slag

Jan 1, 1949

By J. N. Hummel

The methods of electrical prospecting, which employ contact electrodes to produce an electric field in the ground, furnish information concerning the constitution of the material beneath the surface, as indicated by the distortion of this artificially produced field and anomalies therein. To reveal the distortion of such field of known character, it is only necessary to measure qualitatively the direction of the field, using sensitive compensation methods. In such a case, the survey is relatively simple, and that is an important factor from a practical point of view. The distortion of the normal field thus determined permits an easy interpretation and gives approximate information as to the subsurface conditions, without the necessity of a thorough theoretical knowledge of the electrical field. The true field of application of the equipotential lines and search-coil methods, which are based on this principle of directional determination of the electrical field in the ground, is that of search for deposits of economic minerals for the mining industry, although they can also be used in solution of other problems; for example, in the determination of the strike of anisotropic beds. The distortion of the electric field as represented by the picture of equipotential lines or other measured curves is striking only when bodies having conductivities different from that of the country rock are embedded in the underground, or when the underground is anisotropic. It is obvious that methods based on such a simple principle and capable of solving directly many of the practical problems of mining geology have found a widespread application. However, these methods are unable to furnish any information as to the presence, depth and physical properties of layers in the underground, which have different conductivities, but are parallel, or only slightly inclined, to the surface. Where such conditions exist in the underground, the picture of the field

Jan 1, 1932

These pages may be used as order sheets. Mark the number desired opposite title of pamphlet wanted, add your name and address, tear out the sheets and mail them to us. Single orders 25 c. Pamphlets 10 c. each in lots of three or more. Pamphlets 5 c. each in lots of fifty or more. These prices prevail for orders for pamphlets of the same or different titles, when cash accompanies order. The pamphlets listed on the following sheets are advance copies printed to facilitate discussion at the meetings of the Institute. They are offered for sale at the reduced prices given above as long as the supply lasts. This list is published in the Bulletin in order that members may have the first opportunity to secure pamphlets, which sometimes are in such great demand that the supply is exhausted before the wants of members can be supplied. The following list includes only a fraction of the pamphlets that have been published by the Institute. Any other paper published by the Institute may be obtained for the price of $1, except those published in Volume XXXI, which are rare. The Institute is still selling back volumes of Transactions at reduced prices, but some of these volumes are becoming rare and members who desire to complete their sets of these very important books on mining and metallurgy are advised to send in their orders as soon as convenient. The attention of members is also called to the bibliographical index of the science of ore deposits contained in the Emmons Volume which is selling at $3 in paper and $4 in half morocco. The Posepny Volume is already exhausted and members who do not get in their orders for the Emmons Volume at the present reduced price may soon find themselves unable to obtain it on such favorable terms.

Jan 8, 1917

By D. A. Martin, Laird Crocker, W. I. Nissen

The Federal Bureau of Mines has developed a process for removing SO2 from stack gases. The process comprises absorption of SO2 in an. aqueous solution of sodium citrate, citric acid, and sodium thiosulfate, followed by reaction of the absorbed SO2 with H2S to precipitate sulfur and regenerate the citrate solution for recycle. A pilot plant was operated at The Bunker Hill Co. lead smelter in Kellogg, Idaho, to assess the feasibility of using the process for flue gas desulfurization. Nominal capacity of the pilot plant, which treated .tail gas from the lead smelter sintering furnace, was 1699 standard meters cubed per hour (15 degrees celsius) of 0.3- to 0.7-percent-SO2 gas yielding about 272 net kilograms of sulfur per day. The pilot plant was operated for about 4500 hours and produced more than 45 net tonnes of sulfur. The operation demonstrated that (1) more than 95 percent of the SO2 could be removed from the lead smelter sintering furnace tail gases, (2) regeneration of the citrate solution with H2S and precipitation of sulfur in conventional stirred vessels was readily controlled and highly efficient, (3) the precipitated sulfur could be continuously recovered as a 99.5-percent-pure product by kerosine flotation and melting, and (4) the 77- to 79-percent-H2S gas used for sulfur precipitation could be readily produced from pilot plant product sulfur, natural gas, and steam. Projected operating costs, including capital charges, for a citrate plant, installed at a 118 000-tonne-per-year lead smelter and treating 49 271 standard meters cubed per hour of lead smelter sintering furnace tail gas, are estimated to be $384 per tonne of sulfur.

Jan 1, 1976

By R. S. Botsford

SPECULATION as to when and under what conditions mining may be resumed in Russia by foreign interests is becoming more interesting. Circumstances have changed so completely that all new projects must give careful consideration to the conditions as they exist at this time. For example, it is now estimated that a certain copper company in Russia can produce copper and put it on board ship at seaboard for 8 1/2c. per lb., crediting the copper with the value of precious metals contained. It is further estimated that in some places gold can be produced at a cost of about one-half of its value; platinum can be produced even more advantageously. Transportation, which is absolutely necessary for mines of coal, iron or manganese ore, as well as for an industry consuming either coal or coke, is not so essential for the operation of a gold or platinum dredge when the dredge has once been put into operation; after that, food is the principal material for which transportation must be provided. During 1922 the operators in the Urals, who had combined in a so-called platinum trust, expected to produce about 2340 lb. of crude platinum but the amount actually recovered during that season was reported as only 1620 lb., most of which came from hand workings; Nicolo Pavda had the principal dredges in operation during that year. In preparation for 1923 operations, about $400,000 worth of repair parts were obtained in England. At least two American-built dredges and one Putiloff dredge are reported in operation at Nicolo Pavda and it is supposed that most of the better dredges in the platinum district are now working.

Jan 12, 1923

By T. W. Guy

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

Jan 1, 1938

By R. B. Campbell

One of the three power plants that will be in the Curecanti Unit of the Bureau of Reclamation's Colorado River Storage Project is the power plant at Morrow Point Dam. Presently under construction, the Morrow Point Power Plant is between Gunnison and Montrose on the Gunnison River in west-central Colorado. (Fig. 1). Morrow Point Dam will be a thin, double-curvature, concrete-arch dam, 465 ft high and will impound 120,000 acre-ft of water. Two 60,000-kw hydroelectric generators will be housed in an underground power plant in the left abutment just down- stream from the dam. The power-plant chamber will be an unlined opening 205.5 ft long, 57 ft wide and 65 to 134 ft high. The arch-type roof with a rise-to-span ratio of 1 to 4 will be supported with rock bolts and chain link fence. A description and discussion of the design considerations for the power-plant opening and rock bolt design are given by William H. Wolf, Gilbert L. Brown, and Ernest D. Morgan in "Morrow Point Under- ground Powerplant," ASCE Power Division Specialty Conference, Denver Colorado, August 18-20, 1965. The Morrow Point site is in a moderately active region of mild earth- quakes, as evidenced by recent earthquakes in 1960 and 1962. Therefore, the Bureau of Reclamation undertook an investigation of the effects on the underground power-plant chamber when subjected to an earthquake. The art of earthquake engineering has been directed primarily at developing methods of analyzing the nature of ground surface motions and designing surface structures to resist damage from vibrations impressed on the structure by the ground motions. The mechanism of straining an underground cavity by an earthquake

Jan 1, 1968

By Arthur E. Hall

Tax operation of "softening" in lead refining is designed, as the word implies, to separate from the bulk of the lead the elements that tend to make lead hard. These elements, which invariably are present in argentiferous lead, interfere with the desilverization, and must be almost entirely absent in refined desilverized lead. They are mainly copper, antimony, arsenic and tin. The properties utilized in accomplishing this separation are the low solubility of copper or copper sulphide in lead at its freezing-point temperature, and the greater and selective affinity for oxygen of the other elements at temperatures of the order of 700° to 900' C., or, in the prcsence of sufficient, alkali, at a temperature of about 500' C. The major problems of softening lead bullion lie in the necessary subsequent treatment of the by-products of the primary operation, which contain, either chemically or mechanically, lead or reagents that must be isolated for market or re-use. Therefore an important objective of the primary operation must be the highest practicable concentration of these elements in the by-products. Within the past three decades, during which the writer has been engaged in lead refining, the technique of softening lead bullion has had as many variations as there were lead refineries. This was the result of the variation in composition and character of lead bullion recived. The writer has received for refining shipments of lead bullion varying as widely as indicated by the following table: Sb, Per CEnt As. Per Cent Sn, Per Cent Cu. Per Cent Ag. Oz. per Ton 1.00 0.05 nil 0.05 70 0.50 2.50 2.00 0.50 200 3.50 0.50 nil 0.30 350 At times these have been received uniformly and at other times irregularly with a variation from week to week as wide as those shown. Under such conditions, establishment of a universal softening technique presented many problems. Such variations existed because refinery tolls too often were based on a ton of bullion, whatever its composition, and

Jan 1, 1937

By W. H. Adams

Virginia, a store-house of metals, is more and more a surprise to the present generation. With her enormous available mineral wealth, worked upon steadily for over a century, exploited SUEciently to demonstrate beyond question costs and values, reported upon by our most eminent scientists, written up by thoroughly earnest correspondents, we yet find her little understood by capitalists or practical men, and until very lately overlooked by the advanceguard of pioneers in metallurgy, whose restless energy conquered the wilderness of Northern Michigan years ago, and has written a new and startling history for almost impenetrable Western territories. The world is learning through the mouths of giant furnaces lately put in blast at Lowmoor, Goshen, and Roanoke, more of this wondcrful State. It is becoming plain that nearer home, amid all the surroundings of civilization, under an equable climate and with the advantage of a minimum cost for fuel and labor, there are stores of mineral, varied in character and deposited over a wide area, which exceed all ordinary calcnlations. Principal among these minerals, iron ores have been, and will probably continue to be, the leading product and the source of greatest revenue. My attention has been called during the past year to one particular section of the iron-belt, where for forty years charcoal-furnaces were successfully operated, the ores being mined in open pits, as can so frequently be seen from the Connecticut line southward into Georgia. There is, however, a significant peculiarity in the character of these deposits of Louisa county warranting special mention, as it is thought that nowhere on the earth's surface, within so moderate a distance of tidewater, can their like be fouad. Probably half a million tons of lump and wash-material have been taken from pits

Jan 1, 1884

DAVE BARTLEY and Edwin F. Gray, miners, late of Shasta County, California, young, healthy, and "dead broke," arrived at Ely, Nevada, one evening in the summer of 1900. Before rustling jobs and going to work, they decided to look around the camp, and in pursuance of this plan they visited a number of claims owned by D. C. McDonald, Justice of the Peace and pioneer of the district. Among the claims he showed them were the Ruth (named after his daughter) and the Kearsarge. Both were regarded as possible gold or silver properties. For no very definite reason the two miners changed their plan and took a lease and option to buy the two claims for $3500. After the transaction was closed and the partners were alone, Gray asked Bartley what he thought of the ground. "If she's good for anything, it's copper" was the reply; and, so far as the records disclose, that was the first time that anyone ever thought of Ely or the Robinson mining district, as it was called, as a possible copper area. There were some slight surface indications of copper, but it is probable that the fact that Bartley had just come from a copper district had something to do with his predilection for a metal that was much despised around Ely. In any event, his hunch was good, and he spoke with the wisdom of an oracle. For thirty years prospectors had sought gold and silver around the camp. Several stamp mills and cyanide plants had been put up and a hundred shafts had been sunk, but fate had been indifferent in its rewards to the optimistic owners. Copper ore would have to be hauled by wagon, 150 miles down Steptoe Valley to the Southern Pacific Railroad, and there was scant hope of finding ore that would bear this cost. W. B. Graham, who ran the general store in Ely, grubstaked Bartley and Gray, furnishing them with food and mining

Jan 1, 1933

By Oliver Bowles

While vast quantities of limestone and dolomite are used in metallurgy, the estimated production in 1926 being 23,860,000 tons, there are many problems connected with their use which have not received adequate study. The literature of metallurgy is notably lacking in comprehensive discussions of fluxing or furnace stone. Approximately 900 lb. of limestone is used for every long ton of pig iron produced in the blast furnace, but this important constituent of the charge receives little atten. tion compared with the intensive study that has been applied to ores and fuels, the other important constituents of the charge. In an effort to elucidate some of the doubtful points, the writer has made a wide review of metallurgical literature, and has had the disappointing experience of finding not more than a paragraph or two on metallurgical stone for each two or three thousand pages of literature reviewed. Furthermore, the limited information supplied is in some instances contradictory and even absurd. For example, a correspondent in a reputable metallurgical magazine classifies magnesia and silica together as impurities in flux " that must be melted and run off as slag." From the furnace operator's viewpoint it is desirable that as complete knowledge as possible be obtained concerning the effects of chemical composition and physical character of the stone on its action in the furnace and on the quality of the metal produced. A better knowledge of these features is advantageous also to the quarry operator in that it enables him to work more intelligently in producing stone that will best satisfy the metallurgists' requirements. The following pages comprise a brief compilation of data now available. Much of the information is well established and probably acceptable to most metallurgists. On some points there is room for debate, and the chief purpose in presenting a paper at this time is to arouse discussion which will throw more light on controversial points and thus assist the author in preparing a more comprehensive and accurate discussion of metallurgical limestone problems.

By Philip Wilson

Tun mines of the Calumet & Arizona Mining Co. are situated in the Warren Mining District, Cochise County, Arizona, between Bisbee and Warren and adjoin those of the Copper Queen Consolidated Mining Co. and the Shattuck Arizona Copper Co. Paleozoic limestones of considerable thickness have been intruded by granite porphyry. A great stock of the intrusive outcrops boldly near the city of Bisbee and is known as Sacramento Hill. From this central core the porphyry has tongued out into the limestone for many thousands of feet as dikes and sills of irregular shape and variable dimensions. Churn drilling has recently developed a large tonnage of secondarily enriched copper ore in the main porphyry mass of Sacramento Hill. While some ore has been found in porphyry in other parts of the district it is relatively unimportant compared with that which occurs in the Paleozoic limestone as irregular lenses replacing favorable beds near porphyry contacts or associated with well-marked fracture zones often many hundreds of feet away from the intrusive. In a zone extending from Sacramento Hill for a distance of from 1,500 to 3,000 ft. the limestone has been extensively metamorphosed and in this contact metamorphic zone the ore occurs through a known vertical thickness of upward of 900 ft. and individual orebodies often show extension in a vertical direction of over 200 ft. At a greater distance from the intrusive stock the ore occurs as lenses of greater horizontal than vertical dimensions with an average thickness of approximately 30 ft. An exception to this rule is found in the occasional steeply dipping mineralized fractures, almost true tabular veins, which are found long distances away from the zone of contact metamorphism.

Jan 7, 1916

By H. S. Coe

ENGINEERS have long recognized the desirability of correlating the data obtained from small-scale slime-settling tests with commercial work as carried on in large tanks. This need, though most apparent in designing new installations, frequently arises also in existent plants, since a large range of experimental work can be performed without interfering with regular operation. GENERAL SETTLING PHENOMENA In order to develop rational methods of laboratory testing, it becomes necessary to study the general phenomena of settling. Since it was desired to give the public the benefit of these methods at as early a date as possible, together with the knowledge of the general principles of slime settling necessary for a clear understanding of the laboratory tests, we have ventured to discuss the subject in so far as brought out by the work which we now have under way. We realize that certain of our preliminary conclusions may be subject to modification, but it seems probable that, with but few exceptions, the general laws enunciated will cover the settling behavior of all pulps encountered in metallurgical plants. However, it must be recognized that there is still a vast amount of work to be done upon certain phases of the subject; therefore, at this time we will attempt only a discussion of the behavior of ore pulps during the process of settling or dewatering, under certain given conditions. The laws and principles controlling these conditions are not fully established, so that a complete discussion of them will not be attempted in this paper. In metallurgical practice, slime pulp consists of water, finely divided sand

Jan 3, 1916

Jan 1, 1932

By H. R. Stahl

The disseminated lead district of Southeast Missouri lies 70 miles south of St. Louis. The only metal of economic importance in the ore is lead, but minor amounts occur of iron, zinc, copper, cobalt, nickel, silver and cadmium. These minor metals, as might be expected, tend to concentrate in both the flotation and table middlings. In the past, some zinc has been recovered by differential flotation. The silver and cadmium tend to associate with the zinc, and some recovery is made of these two metals at the smelter. The lead occurs as galena, or lead sulphide. The minor metals are also present as sulphides. The presence of oxidized lead is suspected, but has not been definitely proved. The gangue is chiefly dolomitic limestone, with small amounts of sandstone and shaly glauconitic and chloritic minerals. The ore contains about 3.25 per cent lead, occurring as galena disseminated through the gangue. Some of the galena is very finely disseminated, and the mineral in the gravity tailings, or chat; is seldom or never in the free state. The method of treatment of the ore has been evolved over a period of 75 years; hence probably is not far from correct. The milling processes have tended toward simplification during the past 15 years, but recoveries have never been sacrificed for the sake of simplicity. In many cases, simplification of flowsheets has led to better recoveries and operating economies. A simplified flowsheet is shown in Fig. I. The St. Joseph Lead Co. operates four mills in the Flat River district, with a normal total capacity of about 21,000 tons per day, divided as follows: Federal mill, 11,000 tons; Leadwood mill, 4500 tons; Desloge mill, 3400 tons and Bonne Terre mill 2400 tons. The methods of concentration used at these plants are similar in principle; they differ mainly in details and in the type and size of the equipment used. The process of concentration may be divided into five main steps; i.e., dry crushing, wet grinding, classification with its attendant desliming, tabling and flotation. A brief description of these processes will be given, noting important differences in the various plants, and also noting the more important changes or developments of the past few years. Dry Crushing The run-of-mine ore is hoisted in skips, the capacity of these skips ranging from 23/4 tons to 81/4 tons. At the Desloge plant, the ore is hoisted in 2-ton mine cars on self-dumping cages. All ore is hoisted at shafts adjacent to the various crushing plants, no ore being transported on the surface. Primary breaking at all the mills is accomplished with 9E Telsmith breakers. Preliminary screening is provided ahead of most of these crushers, either by station-

Jan 1, 1943

By G. E. Murray

Lead blast-furnace work at Trail is unique in that this is the only plant in the world where blast-furnace smelting on a large scale for both lead and zinc recovery is carried on under one management. On this account the factors that determine economic practice differ from those of other lead smelters. In addition to this different metallurgical outlook, a great deal of structural investigation has been carried on, which has resulted in the development of a furnace which should prove of interest to all who are faced with similar problems. This description may be conveniently divided into various heads as follows: (1) General—make-up of charge, etc.; (2) structural—(a) hoods and charging methods, (b) shaft construction, (c) crucible construction; (3) handling slag; (4) handling bullion; (5) metallurgy. The Charge The Trail plant is an old one, on a congested site. As with most old plants, this limits the method of charge preparation. In general, lead metallurgists will agree that sinter when it reaches the blast furnace should contain as small an amount as possible of actual fines. There would be some difference of opinion as to the maximum size as well as of the minimum required, but to obtain the optimum condition some form of screening is indicated. This screening should take place immediately before the blast furnace if possible, and because sinter deteriorates in storage there should be as little as possible. There should also be the minimum amount of handling between the sinter machines and the furnaces. Unfortunately, at Trail the sinter must be handled considerably before it is charged to the furnace, and no feasible scheme of screening has yet been devised. Trail practice, then, demands that the sinter be a strong one physically. Dependent upon the amount of lead in it, it has been found advantageous to incorporate granulated slag into the final sinter, the amount varying inversely as the lead content. The addition of this slag makes a harder sinter, which arrives at the blast furnace in a better condition, but it entails some lack of efficiency, because desulphuriza-tion is not so rapid nor so complete.

Jan 1, 1937