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By R. F. Frantz, T. P. McNulty

The upper-level mineralization of the din Buttes, Arizona copper orebody consists primarily of dilute copper silicate impregnation in fault clay and throughout the altered limestone hostrock. Cuprite and native copper are minor with true chrysocolla rare. Owing to the high calcium carbonate and to the hydrogen ion exchange capacity of the clays, acid leaching would be economical only with cheap acid available. Leaching of the silicate copper with reagents other than sulfuric acid is slow and incomplete unless the ore is first heated to disorder the mineralized grains and to reduce partially the contained copper. Following heat treatment, 70 to 90 percent of the nonsulfide copper can be dissolved in aqueous anrmonium carbonate. Recovery of a pregnant solution by counter-current decantation is effective provided ammonium carbonate solution is added to the washing stages in order to oppose adsorption of dissolved copper by clays in the residue. Thermal stripping of the pregnant solution permits recovery of ammonia and carbon dioxide while precipitating copper either as oxide or carbonate. The research program was carried from batch tests through continuous miniplant operation to a five-month campaign in a 20 TPD continuous pilot plant. Pilot plant results, the relationships among key varibles, and a detailed flowsheet are given.

Jan 1, 1973

By Robert B. Smith

The South Texas Mineral Trend is now estimated to contain uranium reserves of 150 million pounds U308 . Within the past year, an estimated 10 million pounds U308 have been added to this gross reserve. It is probable that a similar amount has been identified in previously unknown orebodies that, as yet, have not been delimited or announced. Exploration that was limited in the past to a narrow band containing only the known trend has now expanded into older sediments updip and into younger units towards the coast. Uranium host formations are also now being explored at a considerable depth and distance eastward from known deposits. Only about 30 percent of the potential uranium host rocks in South Texas have been adequately explored. Geology The South Texas uranium deposits are confined mainly to sediments of the Tertiary system. Reserves are divided almost equally between the Whitsett Formation of the Jackson Group, the Catahoula Formation, and the Oakville Formation. A minor amount of the reserves occurs in sands of the Goliad Formation which may be either in the Tertiary or Quaternary Epoch. Figure 1 is a geologic column of the South Texas uranium host formations. These producing formations are marked with a mine symbol but there are also several prospect symbols that denote potentially favorable uranium host formations both younger and older from the producing formations. It is generally accepted by most workers in South Texas that the source for the uranium is the volcanic ash that is abundant within several of the formations. Likewise, the required reductant is considered to be hydrogen sulfide gas, derived from deeper seated hydrocarbon accumulations, that emanate upward along fault zones into favorable host-rock sand units. Within this basic framework of source, host, structure and hydrocarbons is where most of the reserves have been discovered and where most of the current exploration is either concentrating or expanding. Structure in South Texas is predominantly faults. Swarms of faults exist in zones paralleling the coast and running from the Rio Grande to the Sabine River. These faults are usually growth faults with the down-dropped block on the coastward side. Displacement may range from a few feet to a few hundred feet. Dips are near vertical in the younger rocks at the surface but become flatter as the fault cuts older beds in the subsurface. A map of the oil and gas fields in South Texas indicates a correlation between these fault swarms and accumulations of hydrocarbons. It is not coincidental that the known uranium trends closely follow the hydrocarbon accumulations and the faults swarms, all of which supports the theory of uranium concentration by groundwater movement through volcanic ash-rich beds into favorable host rocks impregnated with reducing hydrogen sulfide gases that migrate upward along fault planes from hydrocarbon accumulations. History Newcomers to South Texas are often amazed that active entry is possible in a district that has produced uranium for over 20 years. Understanding the conditions and occurrences of the past would explain why the opportunity still exists for companies not now active in South Texas to become active. Uranium was discovered in the middle 1950's in sandstone units of the Jackson Group at Tordillo Hill in Karnes County. This discovery was followed by a rush involving most of the major uranium exploration companies as well as several of the not-so-major. Those western prospectors who were used to numerous outcrops and neat land subdivisions were further discouraged by the small size and low grade of the deposits. Then after a brief blast, they left South Texas as they found it and returned to the richer diggings of New Mexico and Wyoming. Susquehanna Western was the only one to stay and develop mines in the area. Eventually they discovered enough ore along the Jackson outcrop to warrant constructing a small mill. They managed, with limited budget and diligent effort, to find enough ore to keep the mill going and eventually expanded into exploration in other formations. By the late 1960's, Susquehanna was mining from both the Jackson and Oakville deposits. About this time, the oil companies began to enter the uranium industry and found, that because of sound forward planning, they controlled the uranium on vast tracts of acreage. At this time, which was more than ten years after discovery, there was so little literature on South Texas uranium deposits that the oil companies began following the known trends and off-setting known orebodies. This, and a few kicks on some well gammaray logs, lead to the discovery of new areas in formations that previously had n o uranium discoveries. Still, the following of the trend as it crossed from one formation to another was the main geologic guide. Nowadays, we in South Texas feel that science has entered into the quest to discover new orebodies. The work of Galloway has indicated new pathways to explore. The understanding of multiple stages of oxidation and reduction has created some doubt about areas drilled in the past and abandoned. The expanded use of oil well logs and geochemical prospecting has lured the more progressive exploration companies off the mineral trend and into unexplored areas. Prognostication The fact that uranium exploration in South Texas has been active for only the past ten years is not an indication that South Texas is not a major uranium district. The geology of the South Texas uranium deposits as described here serves only to indicate that similar geology extends in all directions from the known mineral trend as can be seen on Figure 2.

Jan 1, 1979

By Harlan A. Walker

ROCK-DRILL steel has an important bearing on costs in many mining operations, both directly and indirectly. Direct factors include such items as shop expense, steel consumed per ton of ore produced, cost of distribution and the dust hazard. The latter, although no specific amount may be assigned to it, is an ever-present problem, and is receiving increased attention as the science of mining progresses. Indirectly drill-steel performance affects consumption of compressed air, maintenance of drills and drilling speed. The latter, in turn, increases or retards the tempo of mining and development. These factors, while not all inclusive, are preponderant in their importance. Thus it is evident that in an extensive operation drill-steel expense may run to many thousands of dollars and that thoughtful research leading toward more efficient practice is warranted. EXPERIMENTAL WORK During the late spring of 1939, experiments were undertaken at Homestake in reducing changes in drill-steel gauge from 1/8 in. to 1/16 in. [ ] In drifts and crosscut headings mounted machines were set up and holes were drilled with 1/8-in. bit-gauge changes and other holes a few inches

Jan 1, 1940

The annual world production of minerals approximates 1,700,000,000 tons, over 90 per cent. of which consists of coal and iron. Of this amount about two-thirds is used within the countries where the minerals are produced and one-third is shipped to other countries. The movement of most of these minerals, though, shows a rather remarkable concentration. For instance, manganese moves from three principal sources and converges at four or five consuming centers; chromite and tungsten move from two principal sources. The United States is more nearly self-sustaining in regard to mineral commodities as a whole than any 'other country on the globe; but the interests of conservation - call for an international viewpoint in the handling of our mineral resources., There is perhaps as much need of specializing in mineral output as there is of specializing in manufacturing. The thought that every country on the globe should be self-sustaining in regard to mineral supplies is of somewhat the same order as the thought that every family should produce all its own raw materials rather than take advantage of the more favorable conditions existing elsewhere and so specialize in human effort. Extension of international control of minerals seems to offer possibilities of loss and gain-loss through a considerable sacrifice of national trade .and a narrowing of the field for private initiative in trade; gain through the possibility of attaining certain ends which are attainable only by international agreement, such as an allocation of supplies which will be to the advantage of the greater number of nations rather than to the advantage of the few that are strong enough to dominate the situation. The interests of conservation clearly require international control. Moreover, the lesson of the war points to the necessity of overhauling old international understandings and machinery, even though such a task would encounter great difficulties, not the least of which lie in the persistence of human habits and inertia. Whether the time has come to establish a league of nations with economic control can be determined only by our individual and collective answers to the question whether we are willing to make the necessary economic sacrifices, individually and nationally, in the interest of world harmony. The mineral industry should fully understand that, with international control, efforts to promote export will need to be modified and curtailed; that expansion of our trade in many lines will mean equivalent loss of trade to other nations; that the almost universal conception that expansion of foreign trade is a meritorious aim and end in itself, without regard to its effect on other countries, will need revision.

Jan 3, 1919

By James A. Crookston, William D. Fitzpatrick

Committee C-8 of the American Society for Testing and Materials defines refractories as "material, usually nonmetallic, used to withstand high temperature," and it defines the term refractoriness thus, "in refractories, the capability of maintaining the desired degree of chemical and physical identity at high temperatures and in the environment and conditions of use.” The ability to withstand high temperatures is critical to classifying a material as a refractory. However, as the foregoing definition of "refractoriness" implies, the refractory material may be subjected to and is expected to resist not only high temperatures but a variety of other destructive forces incidental to its use. These include abrasion, impact, thermal shock, chemical attack, and high level loads at high temperatures. The various industrial applications of refractories represent an infinite variety of combinations and degrees of severity of these destructive forces, including high temperatures. Naturally, such a variety of application conditions leads to a need for a wide variety of refractory products to satisfy those conditions. The number of refractory products available is great enough that some form of classification is necessary to a discussion of refractories. Refractories may be classified in several ways, but the most suitable one is based on their general compositions and to lesser degrees on their physical condition and distinctive properties. The primary types of brick include aluminosilicate brick (fire clay and alumina), basic brick (magnesia and chrome ore, alone and in various combinations), silica brick, insulating brick, and special refractories (carbon, SiC, ZrO2, zircon, borides, and nitrides). Brick is, of course, preformed and usually is heat treated at high temperatures before use, but in some instances is unburned and/or chemically bonded, including the relatively new class of tar-bonded magnesia and/or dolomite brick. In addition to preformed refractories, another broad category includes the so-called specialty refractories, which are usually made in the same types as itemized for brick-bonding mortars and high temperature cements, hydraulic setting castables or refractory concrete, plastic firebrick, and ramming mixes. Refractory grains, such as fire clay and high alumina calcines, dead-burned magnesite and periclase, and dead-burned dolomite are also considered refractory products. Bricks are also classified on the basis of physical dimensions, as standard sizes and special shapes. The standard sizes are those which are of definite shape and design and are designated as 228.6 x 114.3 x 63.5 mm (9 x 4 ½ x 2 ½ in.) and 228.6 x 114.3 x 76.2 mm (9 x 4 ½ x 3 in.) straights and series. Bricks of nonstandard sizes are referred to as special shapes. These come about as a result of a particular need for a given furnace or for a particular application. Types and Classes of Refractories Fire Clay Refractories Classification: Fire clay refractories, as the name implies, are composed essentially of fire clay and/or calcined fire clay in varying proportions. The ASTM Standard Classification of Fireclay and High Alumina Refractory Brick, C27-70 (reapproved 1976), gives five classes of fire clay brick designated as super-

Jan 1, 1983

By S. R. Elliott

THE Spies mine is located in the eastern half of the northwest quarter of section 24-43-35, near the village of Iron River, Mich., and is operated by The Cleveland-Cliffs Iron Co. Speaking generally, the jasper hanging walls of most of the deposits in the Iron River district dip at a steep angle and are exceedingly strong, standing without caving, even after mining has been continued for years and after large excavations have been made. The ore is fairly hard and tough and contains no slippage faces. It occurs in large masses, which are often egg shape, with the smaller end down, and can be mined in, open stopes without the use of timber. The common system employed in the district is the shrinkage stope, or some modification of it. The Spies system was developed to utilize the advantages of the open-stope method and to avoid the disadvantages of the shrinkage stope. The Spies shaft was sunk to such a depth that the bottom, or third level, was in rock at a short distance below the bottom of the orebody, the shape and extent of which had been previously determined by diamond drilling. This is shown in plan and by the ore contours at the first, second, and third levels in Fig. 1, and in section in Figs. 2 to 7. In order to provide the necessary mills and raises, three parallel crosscuts were driven on 25 ft. centers on the bottom level. Drifts on the second and first levels were driven to the orebody and followed the foot wall in a southerly direction to the end of the ore. In crosscut 3, Fig. 1, raises 30, 40, 50, and 60 were carried up on the foot wall and holed into the second level, and were ultimately carried up and holed into the first level. These foot-wall raises carry the pipes and ladders, provide a means of ventilation, and furnish safe communication to all working places in the stope.

Jan 3, 1922

By W. W. Anderson

John Griffen—The author has called attention to an important phase of coal cleaning since there has been considerable loose thinking regarding efficiency formulae and particularly inaccurate application of ones that have been advanced. The unanimous acceptance of an efficiency formula has been prevented because the issue has been beclouded by the fact that the objective of cleaning—-the control of chemical characteristics of the coal such as ash or sulphur content—is attained by an indirect rather than a direct method. The indirect method is usually to effect separation according to differences in specific gravity. Such separation relies on the fact that the desired chemical qualities are roughly inversely proportional to the specific gravity of the particles being separated. However, the sulphur content of the materials found in raw coal usually exhibit a far from straight line relationship with their specific gravities. Mr. Anderson meets this issue squarely by basing his formula on the efficiency of separation according to specific gravity only. It is true that machines that effect primarily a specific gravity separation are in no way directly influenced by the chemical analysis of the materials being handled and it can be argued that it is illogical to measure their efficiency by any criterion other than that of separation according to specific gravity. For the moment, let us accept this basis and analyze the application of the efficiency conception and formula proposed by Mr. Anderson under conditions which he has not considered but that will readily be found. Let us take the separation shown in his table III as an example. He terms this an example of a high order of quantitative efficiency. We will show the weight distribution of the various gravity fractions as between clean coal and refuse in table XV. Only in the gravity range of 1.50 to 1.70 has material been misplaced and, on the assumption that the cleaned coal and refuse are equal in weight, Anderson shows a quantitative efficiency of 99 pet. The gravity of separation is 1.60 and one third of the 1.50 to 1.60 sp gr fraction is misplaced in the refuse while one third of the 1.60 to 1.70 sp gr fraction is misplaced in the cleaned coal. Let us now see what effect the gravity distribution of the total products has on the quantitative efficiency calculated by his formula. Still using the data in table

Jan 1, 1951

By W. W. Anderson

John Griffen—The author has called attention to an important phase of coal cleaning since there has been considerable loose thinking regarding efficiency formulae and particularly inaccurate application of ones that have been advanced. The unanimous acceptance of an efficiency formula has been prevented because the issue has been beclouded by the fact that the objective of cleaning—-the control of chemical characteristics of the coal such as ash or sulphur content—is attained by an indirect rather than a direct method. The indirect method is usually to effect separation according to differences in specific gravity. Such separation relies on the fact that the desired chemical qualities are roughly inversely proportional to the specific gravity of the particles being separated. However, the sulphur content of the materials found in raw coal usually exhibit a far from straight line relationship with their specific gravities. Mr. Anderson meets this issue squarely by basing his formula on the efficiency of separation according to specific gravity only. It is true that machines that effect primarily a specific gravity separation are in no way directly influenced by the chemical analysis of the materials being handled and it can be argued that it is illogical to measure their efficiency by any criterion other than that of separation according to specific gravity. For the moment, let us accept this basis and analyze the application of the efficiency conception and formula proposed by Mr. Anderson under conditions which he has not considered but that will readily be found. Let us take the separation shown in his table III as an example. He terms this an example of a high order of quantitative efficiency. We will show the weight distribution of the various gravity fractions as between clean coal and refuse in table XV. Only in the gravity range of 1.50 to 1.70 has material been misplaced and, on the assumption that the cleaned coal and refuse are equal in weight, Anderson shows a quantitative efficiency of 99 pet. The gravity of separation is 1.60 and one third of the 1.50 to 1.60 sp gr fraction is misplaced in the refuse while one third of the 1.60 to 1.70 sp gr fraction is misplaced in the cleaned coal. Let us now see what effect the gravity distribution of the total products has on the quantitative efficiency calculated by his formula. Still using the data in table

Jan 1, 1951

By T. W. Guy

THE increased moisture due to water¬spraying for coal dust control is of interest even for mines from which the coal is to be wet-washed before screening, because in many cases wet coal dust materially decreases the loading efficiency of men an equipment at the faces. It also causes serious increase in the normal wear and deterioration of all equipment with which it comes in contact. It is important to the consumer if it increases his as-receive moisture. No attempt will be made in this paper t cover the entire subject of water-spraying of coal for dust control. It will be confine to discussion and data on (r) percentages c dust in bituminous coals, (2) moisture increases due to spraying for dust control in mines or plants by methods which have proven satisfactory for periods of one to five or more years, and (3) a few suggestions for research. SIZE AND PERCENTAGE OF COAL DUST The U. S. Bureau of Mines1 classifies a coal dust all bituminous coal passing 20-mesh sieve (0.0328 in. square opening; The percentage of such dust to be found is ROM coal, of course, varies widely wit. the characteristics of the seam, and with the methods used in the mining and in the preparation of the coal. ROM screen analyses of 12 U. S. coals selected at random from personal files given in Table I show: A few other screen analyses examined indicating 40 pct or more of 2o-mesh X o dust in 3/8 in. X o-sizes were not included because of uncertainty that they were representative. The number of results in Table I is not sufficient to give a reliable estimate of the average, or of the range to be expected, but it indicates that in every case the coal dust is a relatively large percentage of the total ROM coal, and, of course, a progressively larger percentage of resultants as the larger sizes are separated for marketing.

Jan 1, 1948

By R. E. Shinkosk

This paper outlines the development of a program for increasing the life of woolen bags used for filtering Dwight-Lloyd gases by treating the bags and gases with hydrated lime. Methods and apparatus are described for determining alkalinity of dusts, acidity and breaking strength of bag cloth. Procedure and results, based on several years of operation, are presented. DURING 1939, additional facilities were constructed in the Dwight-Lloyd Blast Furnace and Baghouse departments at the Selby, California, Plant of the American Smelting and Refining Co. In order to handle adequately the increased volume of gases from the resultant increase in production, it was necessary to increase gradually the amount of water used for cooling gases ahead of the sinter machine baghouse. As a result of this increased water cooling, the average bag life dropped from 27 months in 1939 to 14 months in 1941. (Table I). This drop in life meant an increased. bag cost, as well as lower recovery of dust and some curtailment of operation. During 1941, it was found new bags showed as high as 0.3 pct acidity* after two weeks of opera- tion and as much as 2.0 pct acidity after some months of operation. This high acidity was present in spite of the fact that free oxide or relative alkalinity of the unburned dust ran from 5 to 6 pct. In view of these circumstances, a twofold program was started in Nov. 1941.t Part one of this program consisted of vigorously dipping all new bags in a weak lime solution, containing 50 lb of hydrated lime per 50 gal of water. Part two consisted of feeding fine, dry, hydrated lime into the gas stream intake of the sinter baghouse fan. Apparatus for feeding this lime is shown in fig. 1. All baghouse chambers are shaken in rotation about once each hour. On alternate hours, the baghouse operator places 50 lb of hydrated lime (one sack) into the lime feeder, starts feeder and immediately starts the bag shaking machinery. The rate at which lime is fed is set to coincide with the approximate time necessary to shake all sinter bag-house chambers, or about 15 min. It is felt this method of lime addition is most effective for getting lime into the woolen bag fabric. The amount of lime so fed averages about 600 lb per day. The amount of lime fed per day is varied to keep a minimum relative alkalinity of 9 pct in the unburned sinter dust. A daily dust sample is taken for alkalinity by allowing dust to accumulate in a sample pipe over a 24-hr period. This sample pipe, placed in any chamber cellar, is 2 in. in diam, 4 ft long, is sealed on the inner end, and capped on the outer end. It has a 1/2 in. slot cut for 18 in. along the tip end. This slot faces upward and allows the pipe to fill gradually with dust as bags are shaken. Breaking strength of bags has, in most cases, been the deciding factor in bag replacement. Bags that normally test 100 psi breaking strength when new are replaced when they test under 35 lb. The method for determining breaking strength is shown in the description accompanying fig. 2. Since the start of the liming program in 1941, bag life has increased from 14 months to an average of over 23 months, with a consequent material decrease in bag cost per year. Acidity, as per cent sulphuric acid, may be determined by means of a Beckman pH meter as follows: From a piece of bag cloth. which has been thoroughly cleaned of dust, a 5 g sample is weighed on a balance. Cut the sample into fine pieces and place in a 400 cc beaker. Add 100 cc (measured) of distilled water and stir vigorously. Filter on suction funnel, holding cloth pulp in beaker with a stirring rod. Wash cloth sample and filter wash water four additional times, each time with 20 cc distilled water, the last time squeezing cloth pulp over funnel. Discard pulp and rinse funnel and filter paper. Pour wash solution jnto measuring graduate and make up to exactly 300 cc with distilled water. Place into clean 600 cc beaker and measure the pH on meter. The per cent acid in bag cloth is read from the following table:—

Jan 1, 1951

By G. Austin Schroter

ALTHOUGH there is now an extensive literature on the bleaching clays, not a great deal of material is to be found concerning the geological fea-tures of these deposits and their bearing on problems of exploration and development. At the same time, chemical and crystallographic research on the clay minerals during the past few years has laid a suitable founda-tion upon which to base conclusions of economic value drawn from field observations. All of the criteria and deductions herein presented are based upon extensive field work by the senior author, both in the United States and Canada, and when subjected to the ultimate tests of development and exploitation they have held up remarkably well, despite the fact that many of these conclusions apparently have not been reviewed in the litera-ture heretofore. The nomenclature of the bleaching clays is rather confusing in the light of present-day commercial standards and has even led to litigation." The old term "fuller's earth" is largely based upon trade usage and the definition of the term therefore is dependent upon the changing standards of commerce. For statistical purposes the Bureau of Mines81 classes as "fuller's earth" all natural bleaching or filtering claylike materials that possess high adsorptive capacity without previous chemical treat-ment or activation. Conversely, the so-called activated or acid activated clays are now generally recognized as any clay mineral or mixture of the clay minerals whose adsorptive capacity has been developed to commercial standards by chemical or physical treatment. Therefore, without attempting to propose any additions to the nomen-clature of bleaching clays, this paper will refer to naturally adsorptive clays and activable clays, respectively, for the two types indicated.

Jan 1, 1940

By G. Austin Schroter

ALTHOUGH there is now an extensive literature on the bleaching clays, not a great deal of material is to be found concerning the geological fea-tures of these deposits and their bearing on problems of exploration and development. At the same time, chemical and crystallographic research on the clay minerals during the past few years has laid a suitable founda-tion upon which to base conclusions of economic value drawn from field observations. All of the criteria and deductions herein presented are based upon extensive field work by the senior author, both in the United States and Canada, and when subjected to the ultimate tests of development and exploitation they have held up remarkably well, despite the fact that many of these conclusions apparently have not been reviewed in the litera-ture heretofore. The nomenclature of the bleaching clays is rather confusing in the light of present-day commercial standards and has even led to litigation.76 The old term "fuller's earth" is largely based upon trade usage and the definition of the term therefore is dependent upon the changing standards of commerce. For statistical purposes the Bureau of Mines81 classes as "fuller's earth" all natural bleaching or filtering claylike materials that possess high adsorptive capacity without previous chemical treat-ment or activation. Conversely, the so-called activated or acid activated clays are now generally recognized as any clay mineral or mixture of the clay minerals whose adsorptive capacity has been developed to commercial standards by chemical or physical treatment. Therefore, without attempting to propose any additions to the nomen-clature of bleaching clays, this paper will refer to naturally adsorptive clays and activable clays, respectively, for the two types indicated.

Jan 1, 1940

By W. C. Weslow

AN extended program devoted to the development of a matrix for holding diamonds of a size and. kind not heretofore generally used is being carried on by the Carboloy Company, and this paper describes the part of the development that affects mining and its allied industries. Labora-tory and field work so far has indicated the following: 1. Tungsten carbide and cobalt form the most desirable known matrix material for the holding of diamonds for drilling work. 2. Industrial bort diamonds in sizes and of a class not generally heretofore acceptable and therefore less expensive can be successfully held in this cemented carbide matrix. 3. In exploratory drilling, the combination of bort diamonds, impreg-nated throughout a matrix of tungsten carbide and cobalt, when fabri-cated onto drilling crowns, is an indicated economic substitute for drilling crowns in which the diamonds are set by hand, mechanically or by casting. 4. This impregnated type of drilling crown or bit has definite possi-bilites of revolutionizing the drilling of blast holes, particularly in the harder formations. This will be brought about by the development of high-speed light-weight rotary equipment using an impregnated diamond bit to replace the percussion drill now in general use. (The development of this rotary equipment is well past the laboratory stage at this time.) 5. That the use of a rotary bit is a preventive measure in the fight against silicosis. The development of this product was started by G. F. Taylor at the Research Laboratories of the General Electric Co. It was early recog-nized that it had possibilities in the drilling field and the present product is the result of considerable experimental work with other powdered metals as well as with tungsten carbide and cobalt.

Jan 1, 1940

By Robert Franke

(Butte Meeting, August, 1913.) IN view of the prominence which the conical mill has attained in the fine-crushing field .within the few years since its introduction, the following comparison with its more mature forerunner, the Chilean mill, based on extensive tests, is submitted in the interest of the milling profession. Soon after designing the concentrating plant of the Miami Copper Co. in 1909, the Hardinge conical mill made its appearance in the milling forum. . Its possibility as a suitable crushing device for the plant was well recognized, but in view of the lack of commercial demonstration, at the time, as to capacity, efficiency for desired product, and the still more uncertain factors of cost of maintenance and power consumption, it was deemed that the immediate adoption of this machine throughout the plant would be a hazardous undertaking. For these reasons it was decided to equip the majority of the immediately required units of the plant with Chilean mills, the fine-crushing proficiencies of which were better known, and one section with Hardinge mills, to serve as a test unit for the guidance of future installations and replacements. Thereby, after 1.5 years' operation with both types of mills, a thorough test as to metallurgical efficiency and cost economy has been obtained. The conical mill used in these tests is the 8-ft. Hardinge pebble mill, having a cylinder 22 in. in length. The cylindrical portion of this mill is lined with cast-iron liner plates, and the conical extensions with silex bricks bound together by cement. Each. liner plate carries a projecting lifter, the function of which is to increase the height of drop of the lifted material. Danish No. 5 pebbles, obtained from the coast deposits of Denmark, are used for the grinding charge. The Chilean mill used is a fast-running, 3-roller, 6-ft. Saturn mill, with screens of 0.037-in. opening. The feed to these mills is the oversize of Callow screens having 0.029-in. openings, which. follow rolls crushing to 0.5 in.

Jan 7, 1913

By Norman Pilling

THE solubilities of a series of experimental alloys covering the range 0 to 100 per cent. Ni, 0 to 30 per cent. Cr have been studied under conditions of complete submersion in several fully aerated acid solutions, and in solutions containing sulfurous acid. In nonoxidizing, hydrogen-discharging acids, if the nickel content is below a certain critical amount, chromium increases the rate of solution and nickel decreases this rate; this critical content of nickel is about 13 per cent. Alloys containing more than this corrode at a constant minimum rate independent of iron, nickel or chromium contents. Austenitic chrome-nickel steels may thus have a resistance to these acids equal to that of nickel-chromium alloys. In nitric acid and in unaerated sulfurous acid rather sharp limits of attack occur which are principally dependent on chromium content. In the former the limit of attack is not related to a particular chromium content but varies continuously with acid concentration. The action of sulfurous acid on these alloys is highly dependent on the presence of small amounts of other substances in solution, and many sulfurous acid mixtures rapidly attack alloys to which the pure acid is wholly inert. The observed effects are. not compatible with Tammann's theory relating corrosion resistance to lattice structure but are believed to be concordant with current views of the electrochemical nature of corrosion.

Jan 1, 1929

By P. Bolsaitis, L. Skolnick

Vapor pressures of silver over ternary alloys of six different copper to gold ratios have been measured by means of the Knudsen effusion technique. The data obtained in the temperature range of 1330° to 1375° have been used to estimate the integral excess free energies of the ternary alloys and the activities of copper and gold. The results compare favorably to the predictions based on the electron cell model of alloys recently formulated by the authors. THE orifice effusion method for measuring vapor pressures of materials in condensed phases was first introduced by knudsen, and has since been used extensively for the determination of thermodynamic properties of condensed phases. The basis of the measurement is the effusion, through a small orifice, of vapor in equilibrium with a condensed phase. Assuming free molecular flow into high vacuum, the vapor pressure, P (in mm Hg), of the effusing species is calculated from the following equation:' where w (g) is the weight of effusing species lost during a run, t (sec) the time length of the run, A, (sq cm) the area of the effusion orifice, T ("K) the temperature at which the run is conducted, M the molecular weight of the effusing species, and k the Clausing factor, a constant that corrects for deviations from free molecular flow caused by the finite thickness of the orifice walls.17 The determination of partial and integral thermodynamic variables from vapor pressure data of ternary alloys is possible only if the vapor pressures of all but one component are negligible or can be esti-

Jan 1, 1969

By R. M. Stewart

INTRODUCTION Requirements for achieving economic slope stability in open pit mining must not only be met during the operating stages but in all preceding stages of mine development. In many operating mines little or no emphasis was ever placed on evaluating the stability of possible slopes during the exploration and planning stages. The purpose of this discussion is to emphasize the necessary considerations that should be made in all stages of development in order to achieve the safest and most economic pit slopes. The most economic slopes may not always be the safest slopes and it is incumbent upon the mine operators and engineers to achieve an optimal combination of economics and safety. The stability requirements outlined are based on the profit motive and are, therefore, practically oriented. Long-term basic research or theoretical studies are considered important only to the extent that they can be shown to have a definite payoff. Consideration will first be given to the information required for stability analysis, which can be determined during the exploration and evaluation stage, followed by further stability work necessary during the mine planning and layout stage. Particular emphasis is then placed on the operating stage in which blasting, dewatering, artificial stabilization, and slope failure are discussed. Lastly, the importance of a logical and orderly research procedure is stressed. EXPLORATION AND EVALUATION STAGE The purpose of the exploration and evaluation stage in the mining scheme is to find and delineate a potential orebody. Discovery and delineation commonly involve drilling tens and in many cases hundreds of boreholes. These boreholes, which may cost as much as $20.00 per foot of depth for a cored hole, are usually abandoned once drilling is completed. Stability evaluation for a potential open pit should begin at this stage by taking advantage of the existing boreholes. Rock and soil properties, as well as hydrologic parameters, may be obtained from both the borehole and the core. Seismic velocity and neutron probes may be used to log the borehole to obtain elastic moduli data. A borehole dilation jack may also be used to give backup information on the rock and soil elastic parameters. Use of a core orientation system can result in the determination of fault and joint frequency and distribution. Before splitting or otherwise disturbing the fresh core, qualitative evaluation

Jan 1, 1972

By B. M. Larsen, W. E. Shenk

THIS paper describes a method of reversal control of the open-hearth furnace that obtains in practice those effects considered below as essential to a completely automatic control, without appreciable interference with the natural rise and fall in temperature of the regenerative portions of the furnace system. Growing out of some studies of radiation pyrometry in open-hearth regenerators, it was developed during 1934-1938, and has been successfully applied to a number of commercial furnaces. The goal of open-hearth furnace operation is the highest rate of production of steel of proper quality consistent with good refractory life and fuel economy. This requires rapid heat transfer from furnace to charge, which in turn is dependent upon heating the furnace refractories to the highest safe operating temperature. The greater the heat input to the melting chamber, the sooner this limiting temperature will be reached, so that control methods in general that are designed to protect against overheating of refractories should help to maintain maximum fuel input and production rate. For the typical open-hearth system, with fixed regenerator capacity and with rate of fuel input usually restricted in its range of variation, our basic assumption is the idea that the only other important variable that is, the time interval between successive reversals-should also be held constant or within a small range. The present reversal control was designed therefore so that, under normal operating conditions, no arbitrary limitation is imposed other than to keep the reversal interval within the optimum time range. However, since a near approach to completely automatic operation involves protection of refractories through the balancing of furnace end temperatures as well as emergency protection against temperature peaks above some upper limit, it was also felt essential to employ, as an integral part of the control unit, a temperature-measuring instrument to register the true temperature of the refractory surfaces at some critical region in the hot ends of the regenerative zones. As the basic elements of the control, we thus have one "maximum" and one "minimum" time relay and a potentiometer recorder-controller, combined with switches and relays to operate as follows: x. Reversal normally occurs within an optimum range limited by the maximum and minimum settings to about 4 to 6 min. variation, but the actual interval usually is less variable and closer to the minimum setting. 2. The margin between minimum and maximum time is utilized, together with a "floating temperature limit" in the potentiometric control instrument, to correct any

Jan 1, 1945

AGGLOMERATION U.S. 4,067,727 - In the sintering of a charge of iron oxide ore, a fuel and a flux on a travelling grate machine, the dust problem is minimized by providing a plurality of cooling zones and by directing heated dust-laden air from a first cooling zone to the sintering zone wherein the dust is filtered from the air by the material being sintered. Air from a further cooling zone can be exhausted directly to the atmosphere. Dust removal in the cooling zone is improved by using a purging zone in which higher pressure air agitates the dust in the sintered material. This patent is a division of U.S. Patent No. 3,973,762, dated Aug. 10, 1976. F. Cappel, assigned to Dravo Corp. Jan. 10, 1978. 6 pp. (75-5). Filed: 4-1-76 (672,748).

Jan 1, 1979

By Henry A. Mather

While this device is not new in its inception, its peculiar advantages failed to be of practical utility until furnace-builders instituted the mechanical reform of supporting the upper and lower water-jackets by hanging them from an I-beam frame, independently upheld by iron columns, instead of resting the entire weight of structure on the bottom, as practice formerly prescribed. The Colorado Iron Works were among the first to build copper-furnaces of this description, and the device, illustrated herewith, has been installed by them in three recent plants,—two furnaces for the Westinghouse interests near Ely, Vermont, and one for the Grand Prize Copper Company, of Gila county, Arizona. The jack-screw supports (Figs. 1 and 2) and the familiar iron bottom of former practice are retained as integral parts of this new furnace-bottom. And, instead of resting inert on the tapfloor of the furnace-room, the jack-screws are supported on and bolted to two I-beams the length of the furnace, placed immediately beneath, and parallel to, its sides. These I-beams are bolted to, and supported by, three steel axles equipped with small flanged wheels, the whole constituting a carriage, which runs freely on a track. The entire apparatus is movable or rigid at will, for the wheels are easily braced, if the tension of the tightened jack-screws does not serve to hold the whole in position. The advantages of this design will be at once apparent to those who have had practical experience in barring furnaces provided with stationary iron bottoms. It is a well-known fact that the larger part of the time occupied in cleaning and preparing a frozen furnace for active service is necessitated by working in a confined place where the temperature is uncomfortable, and that in such case the débris must be removed from

Jan 1, 1903