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By T. Velea

The most widespread methods for producing metallic copper are smelting of copper sulphide concentrates (which generates various types of polluting substances) and the hydrometallurgical route which consists of leaching in sulphate and chloride media (usually employing high temperature, high-pressure and special equipments). This paper presents a process, called VEPE, which consists of oxidizing copper sulphide concentrates in weak alkaline media (Na2C03 orland NaOH solutions), under low pressure and with air sparging. The oxidized concentrate contains less than 0.4% S. Copper is recovered from the oxidized concentrate by the standard leaching-solvent extraction-electrowinning route, with a total efficiency of 98% extraction. The proposed technology could represent a good opportunity to recover copper from sulphide concentrates in a clean, simple and profitable way.

Jan 1, 2007

By T. G. Digges, C. L. Vold, M. R. Achter

A study was made of the effect of the growth conditions on the perfection of single crystals of niobium (columbium). Dislocation densities, determined by means of double-crystal diffractometer measurements , were not greatly affected by the method of crystal preparation but could be reduced by annealing treatments. However, the size, sharpness, and tilt angles of the substructures, observed with X-ray reflection macrograph, were sensitive to variations in growth procedures as well as to subsequent thermal treatments. Although the dislocation density was the same in both types, there were more low-angle bound-aries in crystals grown by zone melting than in those prepared by strain anneal. Mechanisms to account for these observations are discussed in terms of dislocation movements. A planned study of the structure-sensitive properties of refractory metals required the use of single crystals of a high degree of structural perfection and, for ease of handling, of large cross section. It appeared that the strain-anneal technique could satisfy both of these requirements. First, crystals grown in the solid state have been reported to be more perfect than those obtained from the melt.' Second, the diameters of rods which may be produced by zone melting should have a theoretical limit determined by specific gravity, thermal conductivity, and surface tension, while the diameter of strain-annealed rods is limited only by practical considerations. Previously it was shown that niobium (columbium) single crystals of 1 in. diam2 may be grown by strain anneal, compared to the 0.5 in. maximum diameter achieved by zone melting, as reported for molybdenum by Belk.3 The current research was undertaken to investigate and optimize the effect of various process variables on the perfection of 1/4 and 1/2-in.-diam niobium single crystals grown by strain annealing and to compare their perfection to those grown by zone melting. Characterization of these crystals was more conveniently accomplished by means of X-ray than by metallo-graphic techniques. EXPERIMENTAL PROCEDURE Specimen Preparation. Zone-melted crystals of 1/4 in. diam were produced by the standard electron-beam zone-melting technique. The swaged and cleaned rods were outgassed, in the solid state at a temperature near its melting point, at a rate of 12 in. per hr, and single crystals were grown by making two molten passes at 2 in. per hr. By maintaining a zone length of 4 to % in., very uniform single crystals several inches long were obtained. For the strain-annealed crystals, an induction heater was used, in preference to other types of heating, to take advantage of the good penetration of large sections. A five-turn coil, 1 in. long, operating at 10 kc and powered by a motor generator, was contained in a vacuum chamber. The rod, suspended from the upper end, was raised through the coil for both recrystallization and crystal growth. In preliminary work single crystals of the same material were also grown with single and multiturn coils powered by a 450-kc generator. A vacuum of 2 X 10-6 Torr was maintained at temperatures up to 2400°C. Starting with electron-beam-melted ingots of 21/2 in. diam, the analysis for which is given in Table I, the material was cold-swaged to the desired cross section of 1/4 and 1/2 in. diam and then recrystallized. The rods were then strained in a tensile machine and converted to single crystals by passing through the induction coil. As with zone melting, control of orientation is possible by the use of special procedures. Other investigators, see for example Williamson and smallman,4 have reported that orientation control may be achieved by a bending technique. In the present work the strained rod is partially lowered through the coil to start the growth of the crystal. Then it is removed and bent at a point in the poly crystalline portion. Finally, it is returned to the chamber and growth is continued "around the corner". This procedure has certain limitations. If the bending operation exceeds the critical strain, recrystallization may take place. Also, the amount of bending which can be imparted to the rod is limited by coil geometry, and up to now has been 10 deg. However, by repeating the bending and growing operations it should be possible to attain any desired orientation. In preparation for X-ray examination, single crystals were sectioned and planed by means of the spark-erosion technique. To obtain the maximum reflected intensity, the (110) plane was exposed for examination. They were then etched 3 to 5 min in a mixture of con-

Jan 1, 1967

By F. W. Newhall, L. N. Plein

During the latter part of the year 1931, the Republic mine of the Republic Steel Corporation, at Republic, about 4 miles south of Brownsville, Pa., was mining coal along four rib or fracture lines. One of these lines, the west butt rib line, was retreating towards a concrete-lined air shaft, 320 ft. deep, which had been sunk in 1911 for ventilation purposes. With the normal rate of mining at that time, it was expected that this rib line would pass the shaft in three or four months and the shaft would then be abandoned and allowed to cave. Realizing the opportunity presented for the study of an unusual case of ground movement, the question of conducting the study was presented by the junior author to thechairman of the Institute's committee on Ground Movement and Subsidence, Mr. George S. Rice, who presented the matter to Mr. G. H. Morse, General Manager of the Northern Mines, Republic Steel Corporation, and he agreed to cooperate with the Bureau of Mines in making the study, the results of which arc presented in this paper. Acknowledgments are due to Mr. Morse for his full cooperation in this work and to Mr. G. S. Rice and Mr. J. W. Paul, both of the U. S. Bureau of Mines, for their advice and guidance during the course of the work. The authors are indebted to Mr. B. F. Herbert, mining engineer, Northern Coal Mines, Republic Steel Corporation, who assisted in all the surveys, and Mr. W. H. Smith, draftsman, U. S. Bureau of Mines, who prepared all illustrations for publication. Geologic Conditions The shaft is at Merrittstown, which is about one mile northwest of Republic. The topography in the immediate vicinity of Merrittstown consists of rolling country dissected by the meanders of Dunlap Creek and its tributaries. The surface slopes of the hills are gentle and their average gradient is less than 6º. The area at the point where the study was made lies on a hillside sloping towards the southwest, the gradient, varying from 1º to 14º. Fig. 1 shows contour lines at 5-ft. intervals on

Jan 1, 1936

By L. N. Plein, F. W. Newhall

During the latter part of the year 1931, the Republic mine of the Republic Steel Corporation, at Republic, about 4 miles south of Brownsville, Pa., was mining coal along four rib or fracture lines. One of these lines, the west butt rib line, was retreating towards a concrete-lined air shaft, 320 ft. deep, which had been sunk in 1911 for ventilation purposes. With the normal rate of mining at that time, it was expected that this rib line would pass the shaft in three or four months and the shaft would then be abandoned and allowed to cave. Realizing the opportunity presented for the study of an unusual case of ground movement, the question of conducting the study was presented by the junior author to thechairman of the Institute's committee on Ground Movement and Subsidence, Mr. George S. Rice, who presented the matter to Mr. G. H. Morse, General Manager of the Northern Mines, Republic Steel Corporation, and he agreed to cooperate with the Bureau of Mines in making the study, the results of which arc presented in this paper. Acknowledgments are due to Mr. Morse for his full cooperation in this work and to Mr. G. S. Rice and Mr. J. W. Paul, both of the U. S. Bureau of Mines, for their advice and guidance during the course of the work. The authors are indebted to Mr. B. F. Herbert, mining engineer, Northern Coal Mines, Republic Steel Corporation, who assisted in all the surveys, and Mr. W. H. Smith, draftsman, U. S. Bureau of Mines, who prepared all illustrations for publication. Geologic Conditions The shaft is at Merrittstown, which is about one mile northwest of Republic. The topography in the immediate vicinity of Merrittstown consists of rolling country dissected by the meanders of Dunlap Creek and its tributaries. The surface slopes of the hills are gentle and their average gradient is less than 6º. The area at the point where the study was made lies on a hillside sloping towards the southwest, the gradient, varying from 1º to 14º. Fig. 1 shows contour lines at 5-ft. intervals on

Jan 1, 1936

By J. P. Denny

The constitution of the Ga-In system was determined by thermal methods. An experimentally determined metastable equilibrium line (an extension of the indium-rich liquidus) was obtained. The various alloys were studied metallographically using polished samples obtained by a casting method. These low melting alloys required a special dry-ice assembly to maintain a suitable temperature. RECENT interest in alloys that are liquid at room temperature has led to rather extensive investigation of gallium-base alloys. Widely distributed over the earth, gallium could be produced in substantially larger quantities than at present, if a significant demand existed.' One study' has established its presence in 12 out of 14 zinc blends, in all of 15 aluminum ores, in 4 out of 12 manganese ores, in 35 out of 91 iron ores, and in all of 7 magnetite ores. It occurs as a rule in minute amounts, however, leading to high extraction costs. Recent quotations run from $2.50 to $7.50 per g. During the course of the present investigation, portions of the system Ga-In have been redeter-mined, and the results of this study are presented herein. Thermal and metallographic methods have been employed. Lecoq de Boisbaudran, the discoverer of gallium, conducted the first investigation" on Ga-In alloys in 1885. The temperatures of incipient melting, and of completion of melting, were determined at four alloy compositions. In 1936, Hansen' constructed a eutec-tic-type phase diagram for the system Ga-In, based on . work. The existence of a Ga-In compound was regarded as improbable by Hansen, and subsequent investigations are in agreement. French, Saunders, and Ingle3 conducted a more complete study of the system in 1938, using thermal methods. Their phase diagram is a eutectic type, containing a unique concave-upward liquidus. The solid-solution range of gallium in indium was reported as 9.5 pct by weight, and that of indium as less than 1 pct, at the eutectic temperature. The eutectic composition, determined as being bracketed by the compositions showing a true horizontal at the eutectic temperature (16°C), was reported as 76 5-0.5 pct Ga and 24 i 0.5 pct In. Experimental Procedure The preparation of Ga-In alloys is simplified by the low melting points involved. Various compositions were prepared by melting in pyrex tubes, using a cover of distilled water or parafin to prevent the alloys from wetting the glass wall. In all cases, the melts were homogenized. by stirring. Where possible, both cooling and melting curves were determined. The extensive undercooling of gallium was found to prohibit a satisfactory cooling-curve analysis of gallium-rich alloys, however, and transition points on the gallium side of the eutectic could be determined only by melting curves. The inverse rate method of thermal analysis proved to be most satisfactory and was used to a great extent. Various heating and cooling rates were used, ranging from 0.2" to 5.0°C per min. Low temperature melting analyses were conducted within a constant temperature bath, maintained at about 70 °C. The alloys were solidified (under water or paraffin) within a pyrex tube, using dry ice; the tube was then sealed within a cold Dewar flask, the unit transferred into the constant temperature bath, and periodic temperature readings taken. The high temperature melting-curve determinations and all cooling-curve determinations were made in a vertical tube furnace. At near-eutectic compositions, the furnace was placed within a refrigerated room held at —20°C. Accordingly, the furnace on cooling approached —20°C asymptotically and permitted the determination of those phase transitions occurring below room temperatures. Temperatures were measured with a 30-gage iron-constantan thermocouple, immersed directly in the alloy. To prevent contamination of the melt, the leads and junction were coated with Lucite, applied by painting with a solution of Lucite in ethylene dichloride. Electromotive force measurements were made with a Leeds and Northrup precision potentiometer, type 8662. The couples were calibrated against the boiling point. of water and, at lower temperatures, against a calorimeter thermometer having a Bureau of Standards certificate. The melting points of gallium and indium used in the present investigation were determined as 29.-77° and 156.1°C, in good agreement with previously reported values of 29.78°C° and 156.4"C.' The spec-

Jan 1, 1953

By Richard Kastner, Emilie Vanoudheusden, Fabrice Emeriault, Jacques Robert

INTRODUCTION The subway line B of Toulouse (France) has been realized with three different tunnel boring machines (TBM) techniques: Contracts 2 and 5 are excavated with earth-pressure balanced TBM, Contract 4 with a slurry shield TBM, and Contract 3 with a compressed-air TBM. The first three machines are around 7.7 m in diameter, while the last one is 5.3 m. Moreover, a small part of the line (50 m) has been excavated by a conventional method. The tunnels run through the Toulouse molasses, composed of hard sandy clay with pockets and lenses of dense sand. Geotechnical investigations have shown that in these formations, K0 is greater than 1, around 1.8 at a depth of 25 m (Serratrice,2005) and that geotechnical characteristics are homogenous on the whole layout (? =22 kN/m3, Su = 300 kPa, c' = 30 kPa, F' = 32°). The water table is found between 2 and4 m below ground level. As geology, stratigraphy and tunnel cover (between 10 and 20 m) are almost identical, a comparison of movements induced by the excavation by each of the four excavation techniques is possible. This paper presents the soil mass movement measures in the case of the conventional excavation method and in the case of TBM sections. It shows how tunneling parameters may explain the different surface movements observed during excavation. For the sake of simplicity, only the results of Contract 2 (earth pressure balanced TBM)will be presented. MONITORING Monitoring for the Conventional Method Section For the conventional method section (Vanoudheusden et al. 2005) the mass soil movements are measured with two inclinometers and one multi-point extensometer borehole with automatic data acquisition (Figure 1). The monitoring devices include

Jan 1, 2007

By R. M. Kear

Strategic and tactical planning are both required in the mining industry but have completely different objectives and require different environments. If these are not fully understood, then the best value for a mining operation may not be realized. This paper examines the differences in these approaches and how they interface in the mining environment. The objectives, content, skills required and the implied management issues for these two components are examined with the hope that this will assist management and the planning teams in defining their respective roles and expectations. The opinions are those of the author based on his experience on several mining operations and projects.

Jan 1, 2006

By J. Fu

"Since it was first identified in 1817, selenium has received considerable interest. Native selenium and a few selenium minerals were discovered several decades later. With the increasing number of selenium minerals, the occurrence of selenium minerals became the focus of much research. A great number of selenium deposits were reported all over the world, although few independent selenium deposits were discovered. Selenium is obtained mainly as a byproduct of other metals, and is produced primarily from the anode mud of copper refineries. This paper presents a comprehensive review of selenium minerals, as well as the treatment of copper refinery anode slimes for the recovery of selenium. Our focus is on the selenium minerals, including their discovery and occurrence, and the distribution of selenium resources. In addition, the main methods of recovering selenium from copper anode slimes are summarized. IntroductionSelenium (Se) was first observed in 1817 in a laboratory (Greenwood et al., 1984). The discovery of selenium was made by the Swedish chemist J.J. Berzelius and J.G. Gahn, who isolated selenium from a red residue in sulphuric acid from pyrite mined at Fahlun, Sweden. Selenium was named from the Greek word selene (moon), since it resembled tellurium, which had been discovered a few years earlier and named from the Latin word tellus (Earth).After the first observation of selenium in the laboratory, selenium received considerable interest. In 1954, E.P. Kaiser pointed out that Se is enriched in sulphide ores and often associated with Bi, Co, Sn etc. (Kaiser 1954). In 1959, Hawley and Nichol investigated selenium in Canadian sulphide minerals, and presented the content of selenium in sulphide from several deposits of different types. They also proposed that Se is enriched in lowtemperature hydrothermal pyrite (Hawley and Nichol, 1959). The thermodynamic conditions for forming native selenium and selenium minerals in sedimentary rocks were discussed, as well as geochemical behaviour of selenium near the oxidation zones of sulphides in the 1970s (Howard III, 1977; Zhu et al., 2003). Zhu et al. examined the morphology, features, and genesis of native selenium from Yutangba, Enshi City, Hubei Province, China in 2004, and pointed out, from the different forms of native Se, that selenium can be activated,transformed, remobilized, and enriched at sites such as in the unsaturated subsurface zone or in the saturated zone (Zhu et al., 2005). The transport and deposition of selenium in felsic volcanic-hosted massive sulphide deposits of the Yukon Territory, Canada was studied and reported by Layton- Matthews et al. (2005)."

Jan 1, 2016

By R. Fragoudakis

AISI 4130 steel is a medium carbon Cr-Mo steel used in automotive, aeronautic and other general-purpose industries. In this study, 4130 steel fatigue specimens were carburized at 927oC to enhance the carbon content in the steel, raising it from approximately 0.30% (non-carburized) to 0.90% (carburized, oil quenched and tempered). Rotating bending fatigue tests were performed on the R. R. Moore Rotating Beam Fatigue Testing System, in order to determine the high cycle fatigue (HCF) life of 4130 steel and plot the corresponding S-N diagrams. A comparison of the results of carburized and non-carburized specimens shows that carburizing of steel: a) increases the surface hardness and b) improves the fatigue strength of the steel by at least two orders of magnitude.

Jan 1, 2010

The Carboniferous sedimentary rocks of southwestern Newfoundland merit investigation because of petroleum, salt and gypsum possibilities and indications of base metallization along the equivalent of the Horton-Windsor con-tact. In this paper, Lower Mississippian (Anguille) strata are divided into three formations: (1) the Cape John below, (2) the Snakes Bight and (3) the Seacliffs. A correlation between these formations and the Craignish, Strathlorne and Ainslie formations of the Horton group? in western Cape Breton Island is suggested. The criteria for the Anguille subdivision are essentially lithological, but preliminary study of included spore assemblages suggests more precise interformational correlations between Anguille and Horton sequences. The re-measured lower portion of the type section of the Codroy group is presented to define more clearly the stratigraphic position of numerous gypsum and limestone beds. Because of rapid facies changes within the Codroy group a simplified two-fold division into upper and lower units is proposed on the grounds of

Jan 1, 1964

By N. Parlee, V. C. Kashyap

The solubilities of nitrogen in liquid iron and liquid Fe-Ni, Fe-Mo, Fe-V, and Fe-Mo-V alloys were measured by the Sieverts method. Measurements were made at 1600° to 1800°C on binary alloys up to 20 pet Ni, 10 pet V, 10 pet Mo; and on ternary alloys containing 0 to 3 pet V with 0 to 5 pet Mo. The results on liquid iron confirm that Sieverts' law is obeyed in the range 50 to 750 mm pressure. The measured solubilities and their temperature coefficients are in general agreement with other modern authors. The logarithms of the activity coefficients of nitrogen in the binaries are approximately linear functions of the pet of alloying element. A method suggested by Wagner, Chipman, and others for predicting gas solubilities in complex alloys from solubility data on binaries was applied to the Fe-Mo-V alloys. Reasonably good agreement was obtained between calculated and experimental solubilities. NITROGEN'S solubility in liquid iron has been studied by a number of investigators. It is reasonably well established that the solubility of nitrogen follows Sieverts' law at least up to 1 atm partial pressure and that the solubility increases gradually with temperature. The solubility of nitrogen in Fe-X binary liquid systems has been investigated in only a few cases. Only the systems Fe-Cr,3-5, 7 Fe-V,3 Fe-Mn,3, 5 Fe-Ni,3, 5 Fe-Si,B, H Fe-C, L, H and Fe-P4 appear to have received any study. The only work on liquid Fe-V was done by Brick and Creevy.3 This was limited to 13.5 pet and 26.5 pet V, but no exact temperatures were recorded. No work whatsoever appears to have been done on liquid Fe-Mo alloys and even work on Fe-Ni alloys is rather scant. The work on liquid ternary systems is still more limited, and the only publication available appears to be that of Wentrup and Reif,7 who studied the Fe-Cr-Mn and Fe-Cr-Ni alloys. Rassbach, Saunders, and Harbrecht17 have reported work on the solubility of nitrogen in stainless steel but this was not a systematic study of any particular system. Commercial alloys usually contain several alloying elements. Thus, it often becomes important to be able to predict the nitrogen solubility in systems containing two or more added elements without the necessity of making measurements. Wagner,14 Chipman," Darken and Gurry," and Morris and Buehl 14 have suggested means by which this may be accomplished, and Langenberg14 has recently applied one of these methods to nitrogen solubility in complex liquid alloys. This paper reports the results of nitrogen solubility determinations on Fe-Ni, Fe-Mo, Fe-V, and Fe-Mo-V alloys and compares calculated and experimental solubilities in the ternary alloy. Attempted measurements on Fe-Cr alloys were not successful by the experimental method employed. Experimental Method The general method of solubility measurement was that of Sieverts.' The apparatus and procedure were essentially the same as used by Liang, Bever, and Floe."' The equipment consisted of a small vacuum furnace heated by a 6 kw induction unit, gas measuring apparatus, and a gas purification train. The crucibles used were Norton Alundum with alumina sand around them for insulation. The crucibles were charged with 100 to 200 g of material, about 180 g or nearly filling the crucible being found most satisfactory. Hot volumes were determined with argon and ranged from 95 to 130 cu cm (stp). Temperature measurements were made with a Leeds and Northrup optical pyrometer which was calibrated periodically against the melting point of iron in the same apparatus."-'* Good quality nitrogen, hydrogen, and argon gases were further purified and dried in standard purification trains. The sources of the high purity iron and other alloying elements used were as follows:

Jan 1, 1959

By P. A. Manohar

This paper describes an implementation of the Potts model for simulation of grain growth in 2D on a distributed-memory parallel architecture. The simulation scheme utilizes a continuous-time, asynchronous parallel version of the n-fold way algorithm. Each Processing Element (PE) carries a piece of the global simulation domain while the virtual topology of the PEs is in the form of a square grid in 2D and Torus in 3D. Different PEs have different local simulated times. Inter-processor communication is carried by the Message Passing Interface (MPI) routines. Sample results for grain growth simulation in 2D are presented for a 840 x 840 global domain size distributed over 16 PEs. The grain growth kinetics obtained in the simulation of pure, isotropic systems is in good agreement with the theory. Grain size distributions obtained in the parallel simulation are well described by the lognormal distribution, thus validating the simulation procedure. Keywords: Metropolis algorithm. n-fold way algorithm, asynchronous parallelization, grain growth

Jan 1, 2003

By Timothy J. Matthews, Timothy J. Batchler, Daniel J. McElhinney

The National Institute for Occupational Safety and Health’s (NIOSH) Mine Roof Simulator (MRS) at the Pittsburgh Mining Research Division was commissioned for operation in 1981. The MRS was originally designed for longwall shield research and was the only hydraulic press in the world with the capability to apply biaxial loads to these large structures. The results of this forty-year research program have contributed to improved performance and increased knowledge of longwall shields, mobile roof supports and hydraulic cylinders in the mining industry. Also, considerable research and development have been conducted to develop standing support technologies for the mining industry. The Support Technology Optimization Program (STOP) was developed to evaluate how these various technologies can impact and improve both ground control conditions and mine safety. Additional MRS research has included the performance of ventilation stopping walls including the development of a new testing protocol to evaluate the transverse loading capabilities under arching load conditions and evaluating the performance characteristics of welded wire screen as used in underground mine roof surface control. The NIOSH Mine Roof Simulator has been a reliable and valuable tool for the past forty years for the evaluation of safety structures used in mining, and this research has contributed significantly to the advancement toward safer mines. This paper will summarize those research results and provide a glimpse of planned future activities.

By G. A. Bole

"This paper presents a review of the literature and is an epitome of work acne and articles published by Schurecht, Robson and Andrews', in the investigation of the feasibility of making basic refractories from dolomite, was carried on successively by these men, at the Ceramic experiment Station of the Bureau of Mines, Columbus, Ohio.Scope of the work.The dolomite refractories investigation of the Ceramic Station includes a study of the many fluxes which could be used to aid in the dead-burning of dolomite and also a complete survey of the iron oxide-alumina-silica field as fluxes. The temperature of calcination and the resulting properties have been carefully investigated, and the most desirable calcines chosen for further investigation in the making of dolamite bricks. Many binders and the several methods in common use of fabricating bricks commercially were tried, and a thorough study was made of the properties of the most successful ware,Previous Investigators.Even before the World War, considerable work was done on dolomite this war greatly accelerated the efforts of the many Investigators."

Jul 1, 1924

By H. S. Fowler

The Consolidated Mining and Smelting Company has been in the business of mining and exploration since its incorporation in 1906. The Company has reports written as early as 1890. Consequently, its files contain a very large number of reports, and also of maps, of ail descriptions. REPORTS Before describing the filing of maps, a brie{ note on our general system of filing reports will perhaps clarify the discussion. Reports of a non-periodic nature, primarily those based upon examinations by field engineers, are separated from all other data and filed in what we know as the Mine Series System. Each property on which reports are written is given a serial number, known as the Mine Series Number. This serial number is assigned at the time the first report is filed and it remains permanently identified with the property, regardless of its state of activity. Our mine series numbers now total over 5,000. The serial number for a property may be found by referring to an alphabetical index of properties. MAPS We found it necessary to divide maps into two groups: (1) Maps of properties (2) Maps of areas

Jan 1, 1944

By E. Luttgen

The substance referred to in the title is the artificially prepared basic carbonate of magnesia, a compound of the carbonate with the hydroxide. It is the "block-magnesia " of commerce, the magnesia alba of the pharmacist. Its composition, though somewhat indefinite, may usually be expressed by the formula : 4MgCO3,Mg(OH)2, 5H2O; it is found to vary slightly with the details of the method of preparation. This substance has been employed recently with much reported success, as a non-conductor of heat. It is moulded to form coverings suitable for steam-pipes and their fittings and sectional jackets for boilers and cylinders; it is furnished also in forms suitable for lining refrigerators, walls and roofs of buildings, fire-proof safes, etc. It was with a view of ascertaining the efficiency of this material as a non-conductor, or, rather, its relative efficiency among the various non-conducting materials in use, that the writer made the experiments about to be described. A block of magnesium carbonate or magnesia alba exhibits some interesting physical qualities. It is a smooth, white, close-grained solid, in outward appearance resembling a block of Paris plaster. It possesses the lightness of cork, the porosity of sponge, and withal a degree of firmness and strength that, in view of its levity, is quite remarkable. To examine more closely the properties of this substance, a number of 1-inch cubes were sawed from the commercial block-carbonate, also some bricks, that is, blocks measuring accurately 2 x 4 x 8 inches, the dimensions of an ordinary brick. The cubes weighed from 2.2 to 2.7 grammes, the bricks weighed 140 to 175 grammes (5 to 6 ounces). The bricks were carefully measured and weighed, and placed in vessels containing distilled water, in which they became gradually submerged, owing to the displacement by water of the air inclosed in the structure of the magnesium carbonate. After twenty-four hours the blocks were removed from the water, dried superficially by contact with filter-paper and weighed. From the increase in weight, the volume of the water absorbed, and consequently that of the air displaced by it, were obtained. For example: a block which when dry weighed 155

Jan 1, 1887

By John Goodell

CIVIL engineers seem to number in their ranks more advocates of licensing than are found among the practitioners of other branches of the pro-fession. Licensing was not originated by civil engineers but it was forced upon them in two ways. In the first place, the civil engineering profession has hangers-on like every other profession. The first legislative result of their imperfect accomplishments with which I am familiar occurred in the far West. It was found that early irrigation works were so badly planned in some cases that not only were water rights made very uncertain but considerable sums were invested in structures and ditches which proved inadequate and occasionally complete failures. Water was too valuable to be wasted in that way and money too hard to obtain. In those sections, therefore, laws were passed many years ago which made it obligatory for the design of irrigation works and other structures utilizing water to be made by engineers who had satisfied a board of examiners that they possessed the technical qualifications to plan such works properly. The basic thought on which such laws rest is the same as that on which laws governing the licensing of boiler operators rest, namely, the safety and welfare of the public. While boiler explosions still occur and irrigation works are built which are not wholly satis-factory, these laws have helped the, public, it is gener-ally agreed.

Jan 4, 1922

By W. A. Selvig

BY plotting fixed carbon against British thermal units of coals free from mineral matter, and ranging in rank from anthracite to lignite, it is found that the coals of higher rank, from anthracite to the higher rank of the high-volatile bituminous coals, inclusive, can be separated into groups according to their degree of metamorphism by reference to their fixed carbon. Such charts show also that the coals lower in rank can be best separated into groups with respect to B.t.u., especially when plotted on the moist basis, that is, coal containing its natural bed moisture. A tentative scheme for coal classification was presented at the October, 1932, meeting of the Technical Committee on Scientific Classification, of the American Standards Association Sectional Com-mittee on Coal Classification. This scheme was sponsored by Sub-committee IV on Tentative Classification of Coals, under the chairmanship of W. T. Thom, Jr. It proposed the grouping of coals according to rank by reference to fixed carbon and B.t.u., on the basis of coal containing its natural bed moisture but free from mineral matter. This scheme proposed classifying coals into four broad classes: (1) anthracitic, (2) bituminous, (3) subbituminous, (4) lignitic.. The anthracitic class was divided into three groups designated as meta-anthracite, normal anthracite, and semianthracite. The bituminous class also was divided into three groups, low volatile, medium volatile, and high volatile. The high-volatile group was further subdivided into four subgroups according to moisture content, as follows: (1) less than 5 per cent, (2) 5 to 10 per cent, (3) 10 to 15 per cent, and (4) 15 per cent and more. The subbituminous class was divided into two groups, group, 1 including subbituminous coals having calorific values of 10,500 B.t.u. or more, and group 2 including those with less than 10,500 B.t.u. , The lignitic class of coal was divided into two groups both below 8,000.B.t.u., the one group consisting of consolidated and the other of unconsolidated

Jan 1, 1934

By I Elias, E Moya, S Chaffer

This paper is based on a case study from a mine site that operates two gyratory primary crushers. These crushers were encountering problems, which included inconsistent P80, reduced liner life tonnage and, on some occasions, catastrophic failure of the liners.As part of an evaluation process, both crushers were ‘mapped’ using a technology for condition monitoring and modelling of the crusher’s wear components. The technology provides comprehensive coverage of the crusher’s concaves and mantle at 100 mm intervals. It also automatically assesses wear rate between inspections and determines the highest wear areas. Outcomes include projected optimum reline dates at target replacement thicknesses, the identification of asymmetrical wear patterns, and the accurate measurement of open and closed (OSS/CSS) side settings.A comprehensive study was performed to optimise the performance of both these crushers at site. Over a period of seven liner service lives, the strategies to improved performance included liner analysis (concaves and mantle profile analysis), tonnes per day (t/d) and tonnes per hour (t/h) analysis, mantle reutilisation, detection and control of loose concaves, and detection and control of uneven wear and hot spots.These strategies resulted in the improved mechanical and operational performance of both crushers through concave and mantle redesign, OSS/CSS control, accurate wear forecasting plus other initiatives.As a result of these initiatives, the site now experiences benefits which include consistent product size, increased tonnes per hour (t/h) for both crushers and the liner life tonnage has doubled. Additionally, further benefits include less downtime for crusher liner maintenance and the reduced cost of inventories by mantle reutilisation.CITATION:Elias, I, Chaffer, S and Moya, E, 2015. Improvements in service life and cost reduction for gyratory primary crushers through mantle and concaves optimisation – a case study, in Proceedings Iron Ore 2015, pp 115–128 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By Z. Bibak and S. Banisi

Granular systems, i.e. particles with realistic shapes, are commonly encountered in nature and industry. While the discrete element method (DEM) is a tool for the simulation of granular flow, in most of the DEM simulation particles are assumed to be spherical. It is questionable whether results drawn from a spherical particle could be easily transferred to a non-spherical particle. Thus, obtaining a fundamental understanding of the underlying physics of granular flows is not only of academic interest, but is also highly related to industrial applications. An in-house developed DEM software called KMPCDEM ©, which was coded to handle non-spherical particles, was used to simulate the particle behaviour. In this paper, the effect of particle shape on the dynamics of particles of non-spherical and spherical shape, including algorithms for the determination of the particle orientation, the moment of inertia, shape representation, and computation time was described. The assumption of a spherical shape has been justified by the complexity of simulation and significantly higher computation time if a realistic shape for particles was used. Dynamics differences showed that findings obtained from spherical particle systems could not be readily extrapolated to non-spherical particle systems. Consequently, particle shape is an important, if not even the most important parameter to be considered in DEM simulations, and therefore has to be captured accurately if DEM is to be used as a predictive tool. Keywords: Discrete element method (DEM), granular systems, non-spherical particles

Jan 1, 2020