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By Wesley Alves Quintão

O projeto criado e aqui apresentado teve por objetivo atender as necessidades da empresa em relação às metas de economia de energia e adequação ao mercado atual e para isso foi estudada uma maneira de gerar economia de gás com o desligamento de pilotos de ignição e também eliminar atrasos mecânicos no processo de acendimento, purga e estanqueidade do forno de reaquecimento Stein, através do uso de recursos da automação, eliminando dispositivos eletromecânicos garantindo velocidade de informação, economia comprovada de gás e maior confiabilidade no sistema de monitoramento do processo.

Aug 17, 2017

By M. J. Leeuwner

Computational fluid dynamic (CFD) modelling is used to research the complex flow structures that exist in a hydrocyclone. By simulation of a two phase (water and air) flow system, the internal flow and multiphase interactions are investigated. The suitability of CFD modelling as a design tool is further evaluated by examining the effect of varying device dimensions. Three hydrocyclone geometries, used in previous studies, are specified. A transient simulation approach, which employs the Reynolds Stress Model as turbulence model and the Volume of Fluid model as multiphase model, is followed. Results are validated qualitatively against experimental measurements from the previous studies. Keywords: CFD modelling, hydrocyclone, Reynolds stress model, multiphase flow

Jan 1, 2008

By Navarro Torres V. F

Los métodos de modelación con elementos de frontera y finitos son una óptima herramienta que se utiliza para previsiones de la estabilidad de explotaciones y se realiza con el método de cámaras y pilares. En ese sentido, el presente texto analiza el comportamiento de las tensiones y deformaciones en la explotación de cámaras y pilares, utilizando métodos de elementos de frontera y elementos finitos en la explotación selectiva de vetas angostas sub-horizontales. Para ello, emplea el criterio de rotura de Mohr- Coulomb de modelo elástico, donde se aplican los programas computacionales que usan elementos de frontera y elementos finitos. La aplicación práctica del análisis de estabilidad de cámaras y pilares en la explotación de vetas angostas subhorizontales, se realiza en la mina de wolframio de Panasqueira de Portugal.

Sep 14, 2009

By F. Estrada

El presente estudio revela la geología del yacimiento diseminado de cu-mo de almacén de Ica. Este depósito porfirítico, inicialmente estuvo compuesto de microgranito y pórfido cuarcífero, los cuales son relacionados con los procesos de alteración y mineralización del depósito. Posteriormente, estos eventos intrusivos de postmineralización están representados por un enjambre do diques de composición decítiica, pórfido diorítico cuarcífero y andésitico. Asimismo se describe el proceso de mineralización y la distribución de este mineral, la alteración hidrotermal y el zoneamiento de la mineralización-alteración.

Nov 20, 1972

By Ernesto Kausel

El presente texto describe la acción de microorganismos en el proceso de oxidación de diversos minerales. Los microorganismos en cuestión son el Thiobacillus Ferroxidons y el Thiobacillus Thioxidans. Asimismo, las aplicaciones de estas bacterias en el futuro se puede desarrollar a través de la fabricación de H2S04 a partir del azufre elemental, la lixiviación de minerales sulfurados y la regeneración de soluciones de sulfato ferroso.

Jan 1, 1961

By A. S. Nowick, E. S. Machlin

One of the main criteria used to rate the heat-resisting properties of alloys is stress rupture.' During a stress-rupture test a tensile specimen is held under a constant load at a constant temperature until it fractures. The chief measurement made during this test is the time requird for rupture at the specific test stress and temperature. It was found empirically from a series of stress-rupture tests at a constant temperature that when the logarithm of the time for rupture is plotted against the logarithm of stress a straight line is obtained within experimental error This method of showing stress-rupture data has been adopted by many investigators and the NACA.' By interpolation and extrapolation from these plots, values of the stresses required to rupture the specimens (the rupture strengths) in 10, roo, and 1000 hr are obtained for specific temperatures. Alloys are then rated for a particular application on the basis of their rupture strengths at the rupture life that most nearly represents the application. Inasmuch as stress rupture is an important criterion in rating heat-resisting alloys, it would be advantageous to know the quantitative dependence of the time lor rupture on stress, temperature, composition, and structure. In order to obtain this information, an investigation was made at the NACA Cleveland laboratory during the spring of 1945. The theory of rate processes was used because it has been found to apply to certain processes such as chemical reactions, viscous flow, and creep that occur at a definite rate for given conditions. It was thought that stress rupture was such a process. An equation was derived that gives, for a given composition and structure, the dependence of the time for rupture on stress and temperature. The investigation is part of a general program to provide information that will lead ultimately to the development of better alloys in order that the efliciency and power output of gas turbines used in aircraft propulsion can be increased. Theory The theory of rate processes will first be discussed as a general theory. It will then be shown that if stress rupture of heat-resisting alloys can be treated as a rate process, certain equations must be satisfied. Later sections will then show that these equations are satisfied. General Theory of Rate Processes The theory of rate processes5 developed by Eyring and others has been applied to chemical reactions as well as to other processes such as viscosity of liquids and diffusion. In every case in which rate-process theory can be applied, there is a small subdivision, so that the macroscopic process is the net effect of all the small processes. This smallest subdivision is called the "unit process." For example, in a chemical reaction the unit process is

Jan 1, 1948

By A. S. Nowick, E. S. Machlin

One of the main criteria used to rate the heat-resisting properties of alloys is stress rupture.' During a stress-rupture test a tensile specimen is held under a constant load at a constant temperature until it fractures. The chief measurement made during this test is the time requird for rupture at the specific test stress and temperature. It was found empirically from a series of stress-rupture tests at a constant temperature that when the logarithm of the time for rupture is plotted against the logarithm of stress a straight line is obtained within experimental error This method of showing stress-rupture data has been adopted by many investigators and the NACA.' By interpolation and extrapolation from these plots, values of the stresses required to rupture the specimens (the rupture strengths) in 10, roo, and 1000 hr are obtained for specific temperatures. Alloys are then rated for a particular application on the basis of their rupture strengths at the rupture life that most nearly represents the application. Inasmuch as stress rupture is an important criterion in rating heat-resisting alloys, it would be advantageous to know the quantitative dependence of the time lor rupture on stress, temperature, composition, and structure. In order to obtain this information, an investigation was made at the NACA Cleveland laboratory during the spring of 1945. The theory of rate processes was used because it has been found to apply to certain processes such as chemical reactions, viscous flow, and creep that occur at a definite rate for given conditions. It was thought that stress rupture was such a process. An equation was derived that gives, for a given composition and structure, the dependence of the time for rupture on stress and temperature. The investigation is part of a general program to provide information that will lead ultimately to the development of better alloys in order that the efliciency and power output of gas turbines used in aircraft propulsion can be increased. Theory The theory of rate processes will first be discussed as a general theory. It will then be shown that if stress rupture of heat-resisting alloys can be treated as a rate process, certain equations must be satisfied. Later sections will then show that these equations are satisfied. General Theory of Rate Processes The theory of rate processes5 developed by Eyring and others has been applied to chemical reactions as well as to other processes such as viscosity of liquids and diffusion. In every case in which rate-process theory can be applied, there is a small subdivision, so that the macroscopic process is the net effect of all the small processes. This smallest subdivision is called the "unit process." For example, in a chemical reaction the unit process is

Jan 1, 1948

By J. W. Leonard

Breakage, handling and treatment techniques that result in the placement of greater quantities of coal in fixed volume haulage units such as ships, railroad cars, trucks, mine cars, shuttle cars and scoops can do much to increase productivity by improving bulk density to reduce delivered cost, surprisingly enough, only in steel industry by-product coking has this subject been investigated and applied to practice, where as much as 20% or more productivity has been achieved. Research at UK Mining using popular coal mine loading cycle simulators shows that for typical Central Appalachian mining conditions a 10 to 20 percent gain in bulk density can produce a 15 to 30 percent increase in the loading cycle time of fixed volume shuttle-car/scoop based mining systems.

Jan 1, 1989

By Greaves M. C, Amos M. D

A study was made of the instrumentation and technique of atomic absorption spectroscopy developed by Walsh of the Commonwealth Scientific and Industrial Research Organisation (C.S.I.R.O.), Australia.The method was evaluated for the determination of silver in lead sulphide concentrate. The precision of the procedure developed is equal to that of the uncorrected fire assay method and the accuracy is greater.Brief mention is made of the use of this technique for the determination of silver and other elements in ores and concentrator products.INTRODUCTIONThe fire assay method, although accepted on a world-wide basis as the umpire method for the determination of silver in ores and concentrates, is freely recognized as yielding results which are lower than actual due to unavoidable losses.King (1934) investigated the influence of the cupelshape, size and material on silver losses during cupellation. Using 100 mg silver prills he recorded silver losses ranging between l. and 10 per cent under extreme conditions and averaging approximately 2 percent under conditions which might be considered normal. Guerin (1957) made a detailed study, under carefully controlled conditions in a furnace similar to that described by Esdaile (1952), of the effect of temperature on silver losses during cupellation. He concluded that if cupellation were carried out at 840°C., then the amount of lead retained by the silver prill was insignificant and that the silver losses were governed by the equation: Y = 0·055 XO.74where X = the final weight of the silver priIl (mg)and Y = the silver lost (mg)

Jan 1, 1961

Discussion of the paper Of ROBERT H. BEDFORD and WILLIAM HAGUE, presented at the Salt Lake meeting, August, 1914, and printed in Bulletin No. 92, August, 1914, pp. 1807 to 1816. W. L. SAUNDERS, New York, N. Y. (communication to the Secretary *) . -Messrs. Bedford and Hague have given us a very interesting and practical paper. No better excuse for such a paper could be desired than the statement made that the expense of drilling. in this mine is one-third of the cost of delivering the ore at the mill. This statement. should be written in red letters, because it applies to a great many mines besides the one referred to and because it is generally true that in a mining plant, as also in papers read before the Institute, more attention by fat is given to the metallurgical side of mining than to the excavation of the ore, and no study of the excavation work is properly made that does not involve a careful inquiry into the merits of the rock drill used. Next in importance to the selection of a good rock drill, in a case where the actual drilling cost is one-third the cost of delivering the ore, is that. the drill should be maintained in order and kept up to its highest efficiency. The best rock chill may run down in efficiency through accidents, wear, or other conditions which are sometimes beyond supervision or control. The machine is usually in the hands of men who know how to get workout of it, not men who know how it works. The best drill runners are not machinists,. but miners. They could not tell you how the valve operates or the principle of the rotation, but they know how to get the work done. A testing machine, particularly the type described in this paper, may he of the greatest value in maintaining a uniform state of efficiency.

Jan 11, 1914

By F. H. Gilpin

SINCE Noah pitched his ark within and without with pitch, the use of asphalt in human endeavor has been increasing-for Noah's pitch was asphalt. Asphalt is a bituminous material found in nature, either pure or admixed with smaller or greater quanti-ties of mineral and non-mineral materials, or obtained by the refining of crude asphaltic-base petroleum under proper methods of control. Native or "natural" asphalts are scattered through-out the world, though the commercial value of the various deposits varies greatly, depending upon both their accessibility and magnitude and the quality of the material found. It is an acknowledged fact that such asphalts have been produced through natural causes by practically the same application of tempera-ture and pressure as are used in the modern refining of crude asphaltic-base petroleum. The best known of all the native asphalt deposits are those of Trinidad Lake in the Island of Trinidad, British West Indies, and of Bermudez Lake in Vene-zuela. Asphalt from Trinidad Lake, after refining to remove organic and some inorganic diluents, contains approximately 35 per cent, of inorganic residue, and the asphalt thus produced must be fluxed with lighter asphaltic or semi-asphaltic base oil to make it com-mercially utilizable. The refined asphalt obtained from the Bermudez Lake deposit contains from 4 to 6 per cent. of inorganic material which cannot be removed. This asphalt, also, must be fluxed to produce com-mercial products. Small quantities of similar materials are available in other locations. The best pure native asphalt' is known as. gilsonite and is mined in com-mercial quantities in the State of Utah. In numerous places in the United States, particularly Oklahoma and Kentucky, there are deposits of sand¬stone and limestone impregnated with bitumen, which are known as rock asphalts. These rock asphalts may be used, particularly in the paving industry, either as found or by slight fluxing; from some deposits the asphalt is extracted and marketed commercially.

Jan 2, 1923

By P. D. Merica

IN connection with other investigations on the properties and characteristics of chilled iron car wheels, the question as to the best range of annealing temperatures was raised. Chilled-iron wheels are cast with a chill against the tread and the inside of the flange, the remainder being in sand. The composition of the metal is so chosen that under these conditions the tread and inside of the flange will show white iron to a depth of from 5/8 to 7/8 in. (15 to 22 mm.), the remainder of the wheel becoming graphitized or gray. In order to relieve the stresses set up during cooling under such drastic conditions, the wheels are stripped from the mold, while still red hot, piled in a soaking pit, and allowed to cool very slowly from their temperature at stripping. Obviously the most suitable temperature for this annealing is the highest at which no formation of graphite occurs within the white tread and at which the wheels can be stripped from the molds. Inasmuch as no direct determinations have been made of the temperatures at which the' formation, of graphite takes place in white iron of compositions used in car wheels upon annealing, it was considered worth while to determine these temperatures as a means of establishing the maximum temperatures at which the annealing of the wheels may be carried out. In the course of this work, some incidental observations were made which are of interest in connection with the theory of graphitization in white iron. The literature on the subject of the formation of graphite both during cooling at casting and upon annealing is very extensive and can be best studied by reference to a comprehensive discussion of the subject by Hatfield. 1 Perhaps the most important contributions of previous investigation are the following: 1. Whether a given mass of molten iron becomes white, mottled, or gray upon casting, depends on its composition and its rate of cooling through the temperature range of solidification and immediately below.

Jan 7, 1919

By Wm. B. Price

The work of Leon Guillet concerning the effect of nickel on the structural properties of brass is checked. The best value for the coefficient of equivalence t, that is, the amount of zinc replaced by 1 per cent. of nickel, is shown to be-1.1 per cent. The best hot- and cold-working nickel silvers, varying in nickel content between the limits of 4 and 18 per cent., are tabulated and plotted diagrammatically. Also, some data are given showing a comparison between the physical properties of a hot- and cold-working low copper-nickel silver, and a commercial cold-working nickel silver containing approximately 8 per cent. more copper. THIS investigation of low copper-nickel silvers was undertaken to check the work of Leon Guillet on special brasses and to determine, more accurately, the effect of the addition of nickel on the microstructure of the binary alloys of copper and zinc. It was hoped that the results could be successfully applied to the practical production of low copper-nickel silvers. To explain the results of his investigations on special brasses, Leon Guillet evolved his conception of "fictitious compositions." He states,1 in his general conclusions, that on the introduction of a small amount of a third metal to a copper-zinc alloy, it enters into solid solution with the normal constituents up to saturation, but by so doing it brings the ternary alloy into a state microscopically equivalent to a binary copper-zinc alloy of fictitious composition, and physically more nearly like the latter than the brass containing copper-zinc in the ratio actually present. The physical properties of the ternary alloy, when compared to the same properties of an actual brass of the fictitious composition, are modified by the natural properties of the third element. Beyond the point of saturation, a special constituent appears and the above generalization no longer holds.

Jan 2, 1924

By L. A. Bromley, A. W. Petersen

The van Arkel-deBoer method for producing ductile titanium by thermal decomposition of Til, vapor and deposition on an electrically heated filament is modified by film boiling Til liquid on a heated filament, resulting in similar titanium deposition on the filament and liberation of gaseous iodine. The deposition rate is higher and the energy requirement smaller than in the van Arkel process. Many problems must be solved before the process is commercially feasible. TITANIUM of 99.9 pct purity, called ductile titanium, has been produced by a modification of the van Arkel-deBoer&apos; method. In the van Arkel-deBoer method, an electrically heated wire is suspended from two electrodes, which are placed in a container holding TiI, vapor at a low&apos; vapor pressure (usually <5 mm Hg). The vapor diffuses to the hot wire, usually maintained at 1100" to 1600°C,&apos; and decomposes according to the reaction liberating gaseous atomic iodine and depositing solid crystalline titanium on the wire. Estimations based on the data of Runnalls and Pidgeon,&apos; indicate that the rate-control ling step is the diffusion of atomic iodine away from the wire. There appears to be nearly thermodynamic equilibrium at the wire with TiI, and iodine as the main gaseous species. TiI, is almost certainly an important gaseous species in the cooler regions.&apos; The liberated iodine diffuses to a heated source of crude titanium and reacts to form more TiI, vapor, which again diffuses to the hot wire and completes the cyclic process. The foregoing process may be modified by suspending the hot wire in liquid TiI,, instead of the vapor, and obtaining film boiling. This type of boiling is characterized by the formation of a continuous film of vapor over the wire surface. Since only vapor contacts the wire sul.face, the temperature of this surface may be raised as high as desirable, within the limit of mechanical strength requirements for the wire. By properly adjusting the input voltage. the temperature of the wire may be maintained above U0C"C; and by evacuating the vessel holding the liquid TiI, and maintaining a suitable condenser temperature, the vapor pressure of TiI, may be held low. Thus, the conditions of operation of the van Arkel-deBoer method may be approximated with film boiling; and hence, it is postulated that ductile titanium may be produced by this method. Preparation of Til, There are many methods available for the preparation of TiI,; that used in this research was prepared by the direct reaction of titanium sponge in controlled amounts with liquid iodine. Although no difficulty was encountered with this reaction, it has since been pointed out that this method is sometimes dangerous and should be used with caution. The resulting TiI, was purified by distillation. First Film Boiling Experiments Apparatus: The apparatus shown in Fig. 1 was used for film boiling TiI, on short wire filaments. The current to the filament was supplied through a bank of three 5 kva transformers connected in parallel. The current was controlled by adjusting the voltage over a 0 to 67.5 v range with a 7 kva variable transformer on the low voltage side of the bank of transformers. The current and voltage were measured by Weston meters. The sealed-in-glass tungsten electrodes were hard-soldered to the filament for the film boiling of TiI,. The bottom part of the reactor, containing TiI,, was wrapped with ni-chrome heating wires to maintain the TiI, in the liquid state. An ice or liquid nitrogen trap, for solidifying I, vapor and any TiI, not condensed, was attached to the low pressure side of the air-cooled condenser. A Megavac vacuum pump was used. Procedure: A 0.010 in. diam tungsten filament was hard-soldered to the tungsten electrodes. TiI, was melted (mp 156°C) and poured into the reactor chamber; the top of the reactor chamber, containing the electrodes, was replaced. Freezing of the TiI, was prevented by controlling the current to the ni-chrome wires wrapped around the reactor with a 1 kva variable transformer. The mechanical vacuum pump was started and the system evacuated to about 2 mm Hg TiI, vapor pressure. The current to the filament was turned on and the impressed voltage slowly increased with the variable transformer. A sudden drop in current at nearly constant im-

Jan 1, 1957

By W. G. Lidman, H. J. Hamjian

&apos; I HE fabrication of many materials from powders involves a sintering process. A mass of powder will sinter because of the excess free energy over the same mass in the densified state caused by the higher total surface area of the powder. An understanding of the kinetics and mechanism of sintering should assist in improving the properties of such materials. The present investigation conducted at the NACA Lewis laboratory deals with the sintering of chromium carbide. Dry sintering (sintering at a temperature below the melting point) was divided into two stages by Shaler:&apos; the first stage, during which the particles preserve much of their original shape and the voids are interconnected, and the second stage, during which densification occurs and the pores are isolated. The mechanism of forming interfaces between particles, or welding together of particles, has been investigated by Kuczynski2 and may be described by any one or a combination of the following mechanisms: viscous flow, evaporation and condensation, volume diffusion, or surface diffusion. The mechanism by which pores are closed or eliminated (densification) during sintering, is of interest. Grain growth observed during sintering may be attributed to the variation in the surface energies of individual grains, causing some grains to grow at the expense of others. Grain boundary migration occurs presumably by a diffusion process, therefore the rate of grain growth would be expected to increase exponentially with increasing time and temperature. Thus, for practical sintering times of less than 1 hr, a certain minimum temperature may exist at which major structural and property changes will occur. Densification and kinetics of grain growth during sintering under pressure of chromium carbide were investigated to provide additional information which will aid in describing more accurately the sintering process and the mechanisms involved. This material was selected for this study because of the current interest in high strength, oxidation resistant refractory materials, such as carbides, which are sintered to produce solid, dense materials from powders. Sintering under pressure is a process where the heat and pressure are applied to the compact simultaneously, specimens for this work were prepared by sintering under pressure at different temperatures and for various time periods. Experimental Procedure Preparation of Specimens: Chemical analysis of the commercial chromium carbide used in this investigation was as follows: Cr 86.19 pct, C 12.14 pct, and Fe 0.2 pct. X-ray diffraction powder patterns gave characteristic diffraction lines of Cr3C2 crystal structure. Powder particle size was determined microscopically and the average initial particle size was 6 microns with 85 pct between 2 and 10 microns. Specimens sintered under pressure were formed in graphite dies3 heated by induction. Sintering temperatures were measured with an optical pyrometer by sighting into a 3/8-in. hole drilled 1 in. deep at the midsection of the graphite die. A load of approximately 1 ton per sq in. was applied to the powder. The die assembly was heated in 20 min to the highest temperature (2500°F&apos;) at which no increase in grain size could be observed, and less than 2.5 min were required to heat from this temperature to the maximum temperature (3000°F). Sintering temperatures and times for the specimens of this investigation are indicated in Table I. Analysis of Specimens: Specimens polished with diamond abrasives were etched to reveal the grain boundaries with a 1:1 mixture of 20 pct potassium hydroxide and 20 pct potassium ferricyanide heated to 160°F. Representative areas of each sample were photographed at 1000 diameters. The largest diameters of all well-defined grains were measured, but only the measurements of 15 of the largest grains were averaged in order to determine an index of grain size on the assumption that they were among the first to begin growth. Densities were determined from differential weighing of the samples in air and water. The reported density values are considered correct within ±0.01 g per milliliter. Results and Discussion Metal compacts have exhibited grain growth when sintered at temperatures about two-thirds of the absolute temperature of their melting point.&apos; Grain growth also occurs during the sintering of chromium carbide and is illustrated by the micrographs shown in Fig. 1. These micrographs were prepared from specimens sintered for 90 min at temperatures ranging from 1371°C (2500°F) to 1648°C (3000°F). Average grain size and density measurements of specimens investigated are presented in Table I. The relationship between grain size and sintering tem-

Jan 1, 1954

Human progress has a visible material phase, easily discernible, that is expressed in the standard of living. This material phase, however, is only the outward expression of a spiritual or mental phase that acts as a driving force in making humanity improve both its outlook and its mode of living. The instrument of progress is the human brain. Under the urge of spiritual drive, the brain acts as a focal point to utilize the forces of nature and put them to work for the benefit of mankind. Besides intelligence, which is an innate quality, the tools of the human brain are knowledge, experience, training, initiative, and skill. Given sufficient intelligence, the human brain can make an amazing amount of progress, provided it is supplied with an adequate spiritual and moral urge and a good technical background. It is the role of education to sup- ply such a background. The material phase of human progress proceeds on a series of parallel fronts, all of them interdependent to some extent (Fig. 7). The rise of the standard of living, dependent as it is upon the manufacture and mass distribution of goods, is based essentially upon the development and utilization of the material resources of a country or land area. This development involves the extraction of mineral and organic products from Mother Earth, their transportation to manufacturing centers, their transformation into finished goods and their dis-

Jan 1, 1950

By Paul S. Parobeck, Robert A. Haney, Andrew J. Gero, Thomas F. Tomb

As a result of recommendations made in the 1988 Report of the Mine Safety and Health Administration Advisory Committee on Standards and Regulations for Diesel-Powered Equipment in Underground Coal Mines, the Mine Safety and Health Administration (MSHA) initiated a program to develop and test a diesel particulate sampling device. The sampling device employed the principles of inertial impaction to separate respirable dust into two fractions; one fraction containing particulate material having an aerodynamic equivalent diameter equal to, or greater than, 1.0 micrometer, and the other fraction containing particulate material having an aerodynamic equivalent diameter less than 1.0 micrometer. The design criteria were based on data which showed that virtually all of the diesel particulate material and very little of the mine generated dust was less than 1.0 micrometer in size. The instrument was tested in underground dieselized coal mines and in the laboratory. Comparative measurements were obtained with the MSHA designed impactor sampler, a University of Minnesota (UM) designed impactor sampler and MSHA&apos;s standard respirable coal mine dust sampler. Simultaneous measurements were also obtained with five of the MSHA and five of the UM designed impactor samplers to investigate between sampler precision. The paper discusses the design differences between the MSHA and UM impactor samplers, the precision of replicate measurement obtained with both instruments and compares measurements obtained with the respective samplers of the sub- and supermicron fractions of the respirable material.

Jan 1, 1991

By H. W. Seamon

THE data here given were obtained by 1500 tests made, by the United Verde Copper Co. to determine the most economical air pressure for the operation of hammer drills under the varying conditions of use, and to investigate the variation in drilling speed at different air pressures Twelve models of drills were used at gage pressures ranging from 40 to 130 lb. No effort was made to harmonize theory and practice; but rather to formulate empiric rules that would cover the. average variation of the results obtained. These rules on the performance of hammer drills, based on the air pressure as the main variable, however, are not necessarily of universal application, but they apparently satisfy the results obtained in this series of tests. The drilling conditions at this property vary widely; an average of twenty-one machine shifts to a 3-ft. (0.9-m.) round has been found necessary in some of the development work, while an, advance of 56. ft. has been made in seven shifts in the "oxide" ground. This range pre-eludes the adoption of one type of drill as a standard; consequently almost every kind of hammer drill sold in this country has been tested. At present, sixteen models are in use, of which two types of the heavy (150 to 160 lb.) mounted drills, one of the light mounted drill, one stoper, and two hand plugging drills are considered as standard.

Jan 1, 1921

By José Gonzales

"Una rampa es uno de los aspectos más importantes de la planificación a cielo abierto- en tanto se define como un camino con cierta pendiente que se desarrolla desde la parte superior del tajo hasta la parte más profunda del mismo. En ese sentido, el presente texto señala la ecuación que describa una rampa en 3D de un tajo abierto, a través de los parámetros constantes de diseño el desarrollo de la rampa. Entre los parámetros considerados tenemos: ancho de la rampa, pendiente de la rampa, ángulo interrampa del tajo, radio de la base superior del tajo (máxima área superior que engloba toda la fase), radio de la base inferior del tajo (mínima área de trabajo para los equipos). Una vez desarrollado el diseño de la rampa en función de los cinco parámetros anteriormente descritos, se podrá determinar mediante la codificación de un software denominados UNI-RAMP, el número de vueltas que requerirá la rampa para llegar al fondo del tajo, la profundidad total del tajo y el ángulo global del tajo. "

Dec 1, 2015

By H. Krogerus, P. Niemelä, P. Oikarinen

High carbon ferrochromium is produced by carbon reduction. No replacement for carbon as reductant has yet been developed. The reduction creates a considerable amount of CO-gas. In open and semi-closed furnaces the gas is burned when leaving the burden. In closed furnaces the formed gas is sucked out by a fan, washed and utilised as fuel. The formation of carbon monoxide is presented briefly starting from thermodynamic considerations up to solid and liquid state reduction. The volume, composition and energy content of the furnace gas are discussed, focusing on the raw materials and pre-treatment processes of the furnace feed as well as on the process equipment and control. Outokumpu has been using closed and sealed furnaces and utilising the CO-gas in its Tornio Ferrochrome Works since 1968. Today in Tornio with an annual ferrochromium production of 260 000 t CO-gas production is 186 million m3, representing 68 MWh an hour. At the same time the furnace power input is 95MW. About 98 % of the CO-gas is utilised, whereof 30% in the ferrochrome production itself. This paper focuses on the characteristics and utilisation of CO-gas. CO-gas is secondary energy, which on one hand saves primary electric and fossil fuel energy in ferrochromium production and, on the other, replaces other fossil fuels at the adjacent steel works. The characteristics of the fuel, requirements for utilisation as well as health and safety aspects are discussed. Utilisation of the gas has a high impact on the total dust and gaseous emissions and on the energy optimisation at the ferrochromium and steel works.

Jan 1, 2004