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By A. Policard

The bodies of mammals possess a very efficient mechanism for ridding themselves of inhaled dust. When the lung is healthy this mechanism works very well, and dust is quickly and completely expelled from the lung either by the respiratory tract or the lymphatics. The mechanism, however, is easily upset, and slight alterations in the condition of the ciliated epithelium or the circulation of lymph are sufficient to interfere with it, therefore the second mechanism comes into play and the dust is fixed and immobilized in some part of the lung. This, however, is not a real cleansing process, since the lung becomes a dust-trap, and may become'pneumokoniotic. The mechanism is protective at first, but later, when the accumulation of dust is considerable, it gives rise to trouble. The lung cannot become, so to speak, a physiological dust-trap, and still retain its normal structure and function; pneumokoniosis begins, which is essentially a disease due to the mechanical presence of large amounts of inert foreign material.

Jan 1, 1947

By D. J. Murdock, Wyslouzil, I. M. Flint

The highly competitive nature of the international iron ore market has forced producers to improve the quality of their pellets. The demand for low-acid pellets suitable for direct reduction has resulted in an increase in the number of plants utilizing reverse froth flotation for silica reduction. Column flotation is being favored for this service because of low capital and operating costs and improved metallurgical performance compared to conventional flotation cells. This paper describes the benefits of column flotation and discusses some important aspects of circuit design.

Jan 1, 1995

By E. Barsky

The composition of multi-component materials is proved to be unambiguously determined by the composition uncertainty parameter (composition entropy). At the same time, every component, depending on its content, introduces a certain value into this parameter. Quality criterion of multi-component separation is determined by the total change of this parameter for all products obtained as a result of the separation process. This parameter can unambiguously estimate both multi-product separation and complicated schemes of modern beneficiation plants. It can be used to estimate binary mixtures separation, too. During the optimization of multi-product separation, another problem arises, which is not peculiar to binary mixtures. In this case, the total efficacy depends on the order of separation boundaries, as well. In the present paper, a specific example of initial product separation into seven products by six boundaries is investigated. It is clear that with respect to a single boundary, two products only can be obtained. In this case, the separation optimum is shown to correspond to the separation of boundary-class particles equally into both products. We have also established that from the point of view of entropy, the maximal possible separation efficacy corresponds to equiprobable composition of the initial mixture, i.e., the fine product quantity in the material to be separated is equal to that of the coarse product. Three groups of experiments were carried out. In the first group, the boundaries were consecutively specified from the finest to the coarsest one. In the second group, the boundaries were set vice-versa, i.e., consecutively from the coarsest to the finest one. In the third group, no sequence was observed. At every separation stage, a boundary was specified in such a way that the separated material composition was as close as possible to equiprobable one relative to this boundary. Total efficacy was different in all the three cases. In third group of experiments, its value is the highest, which confirms the advanced supposition. The obtained results are phenomenological, ? they can be applied to any processes of solid, liquid and gaseous materials separation.

Jan 1, 2014

By E. B. Wright

THE property of Falconbridge Nickel Mines, Limited, is in Falconbridge township, approximately thirteen miles northwest of Sudbury. From the mine and townsite, a gravel road leads to Sudbury and a branch line of the Canadian National railway to Sudbury Junction. The ore deposit is at the southeastern corner of the 'Sudbury Basin'. It lies in a sheet-like mass, striking in an east-west direction, between norite to the north and greenstone to the south. The general attitude of the ore-body is vertical, but with frequent variations in dip of as much as 10° to the north or south. The deposit is very irregular in outline, the width varying from a few feet to eighty or ninety feet. In the vertical plane, rolls are frequently encountered. Gouge is very often present at one or both ore contacts. The norite to the north shows much jointing. The chief ore minerals are pyrrhotite, pentlandite, and chalcopyrite. The nickel content of the ore is usually double the copper content, average assays ranging from 2 to 2.5 per cent nickel and 1 to 1.5 per cent copper. The ore is of three main types: massive, breccia, and disseminated. The breccia ore, the most common type, consists of sulphides containing rounded inclusions of highly-altered country rock, which, in places, are so large that sorting is necessary in the stopes. In the norite, the breccia ore may grade into disseminated sulphides, which frequently are sufficiently concentrated for profitable mining. In places in the breccia ore, concentrations of solid sulphide masses occur. Until early in 1935, all mining at Falconbridge was by shrinkage scoping, but this method was found to be less and less suitable as greater depth was attained. When mining had reached the 1,000-foot level, ore drawn from large shrinkage stopes was found to have been diluted as much as fifty per cent by sloughing of the wall-rocks, caused by increased rock pressure and insufficient support. It was apparent that this method of stoping was un-suitable and -Mr. E. J. Martin was engaged to superintend the introduction of a method of cut-and-fill stoping.

Jan 1, 1938

By Cailing Zhen, Jian Pan, Deqing Zhu, Xianlin Zhou, Yanhong Luo, Guixiang Huang

The grate-kiln process has been widely applied for oxide pellet production with the quick development of steel industry in China, but ring formation takes place which adversely affects the productivity and properties of fired pellets. Rotary kiln at high temperature seems a black box, and ring formation is difficult to measure directly by current technology. It’s of great importance to monitor ring formation during firing of pellets. Therefore, a method for estimating the thickness of ring formation in rotary kilns was studied, based on working out theoretically the relationship between ring thickness and the outside surface of the kiln, according to steady-state heat transfer across a cylinder, which provides a soft-sensing technique for ring formation at high temperature, and achieves stable pellet production .

Jan 1, 2015

By William Kohan

The industrial grinding process has undergone changes to better address the market and economic needs. Fine grinding of dry materials has developed to the point where classifying linings and fine ball charges improve mill efficiencies. Roller mills as well have wide acceptance due to their power efficiencies. The mill, by its nature, cannot provide the specific particle size or range of sizes which are required for further processing or final use. Therefore, various separators are operated in conjunction with the mill to control particle size. The sizing device helps minimize over grinding and control top size. Rising energy costs combined with increasingly tighter quality specifications have led to increasing study of the grinding and separation process.

Jan 1, 1985

Threshold blasting involves the use of small amounts of high explosive to break and fragment hard rock without having to evacuate mining personnel. The method is easily assimilated and effective in rockbreaking, but requires rigid control on drilling, charging and timing. Current underground trials are aimed at fine-tuning the amount of explosive energy and blast hole geometry to allow the firing of multiple sets of shot holes in a continuous manner. Through correct procedures, the after-blast fumes, dust and fly rock can be contained so as to provide a safe working environment. Threshold blasting hugely reduces the volumes of explosives used in mining and brings to maturity the potential of the process begun by Alfred Nobel when he introduced nitroglycerine, and later dynamite, to mining. Its key contribution is its enabling of continuous mining operations with well understood and relatively low cost technologies. The use of batch blasting, employing large burdens holds the greatest potential for delivering high flow rates of ore at minimal cost. There is good potential for rapid evolution of the concept.

Jan 1, 2002

By C. K. C. K. Gupta

The rare earths in elemental form are required for a variety of scientific and technological purposes. They are not easily obtained in this form, due to the great chemical stability of the rare-earth compounds and the strong tendency of elemental metals to react with everything they come in to contact with, especially at high temperatures. Beginning in the 1950s, when sufficient quantities of separated rare earths became available, as the result of intense research and development, three processing routes were developed to accomplish the preparation of all 16 naturally occurring rare-earth elements. They are chemical reduction of the halide intermediates, the oxides and electrochemical reduction of chlorides and oxide-fluoride mixtures. Not all the processes are effective with all the rare earths. In spite of the celebrated similarity of trivalent rare earths, the physical properties of individual rare-earth elements are sufficiently different that a variety of techniques are required for their preparation. The development of reduction processes for the rare-earth metals are covered in this paper, with focus on the oxide reduction routes. The strong reliance of effective reduction processes on the fundamental science of reduction reactions is highlighted.

By S. A. L. Read

"The intact rock constant, mi, is one of the three basic input parameters required for the widelyused Hoek-Brown failure criterion. Values for the constant should ideally be determined by statistical analysis of laboratory test data. In this paper the influence of the inclusion or exclusion of tensile test data on derived values is discussed. We firstly investigate the relationship between direct tensile strength (DTS) test values and Brazilian tensile strength (BTS) test values based on a literature search, finding that the correlation between the two test types is DTS = 0.9*BTS, independent of the lithology being tested. Secondly, using the shear strength database of Douglas (2002), we examine the influence of confining pressure range and the inclusion or exclusion of DTS and BTS test values on calculated values of mi.Chief amongst the influences was the exclusion of tensile data in the calculation procedure, particularly when the Hoek triaxial confining stress range requirement (?3?max = 0.5?c) was not satisfied. Based on a reasonable 1:1 relationship between R (the ratio of unconfined compressive to tensile strength), use of actual tensile data in the calculations for the Hoek brown failure criterion is considered to be a simpler and more robust approach to the use of a tensile cutoff based on empirical criteria such as that of Fairhurst (1964). We advocate the fitting a failure curve using compressive and tensile test data as the most reliable means of calculating mi, while at the same time satisfying requirements as originally advocated by Hoek relating to the appropriate triaxial confining stress range (?3?max = 0.5?c) and sufficient (>5) evenlyspread data points. In the absence of triaxial data the use of R provides a practical means of obtaining estimates of mi that are more robust than guideline values."

Jan 1, 2015

By M. Maldonado

This work details the application of a decentralized control strategy to a pilot flotation column working with a two-phase system (water-air). The process is represented by a multivariable system composed of three inputs and three outputs. The selected control variables are the froth depth, the air hold-up and the bias rate, whereas the corresponding manipulated variables are the set-points of the local flow controllers of tailings, air and wash water. All controlled variables are estimated using electrical conductivity based techniques. In particular, the results of a new method for estimating the bias rate, based on the measurement of the volumetric fraction of wash water under the interface, is presented. This method reduces the coupling problem associated to the bias estimation as a difference between feed and tailing water rates. Moreover, the nominal system transfer matrix can be represented by an upper triangular matrix, in such a way that the closed-loop system stability reduces to the stability of the independent control loops. The experimental results show that the closed-loop system performance, particularly that of the bias rate loop, is strongly dependent on the air flow rate, reaching in some cases the saturation point of the controller.

Jan 1, 2007

By Nagahiro Saito, Takashi Nishimura, Takamichi Ichikawa, Akio Fuwa

"Yttria-stabilized zircohia (YSZ) has high potential to be used as solid-oxide fuel cell (SOFC) electrolyte. However, the high efficiency of SOFC has not been yet achieved due to the high internal resistance of bulk electrolyte. The resistance becomes lower with the decrease in the electrolyte thickness. Thus, the decrease in electrolyte thickness leads to lower internal resistance. . The aim of this study is as follows: (a) to prepare the thin films of YSZ by inductively-coupled RF plasma-enhanced metal organic chemical vapor deposition (PEMOCVD) process using Zr(t-OC4H9)4,Y(DPMh and oxygeil, and (b) to reveal the relationship between the structural characterizations and the process parameters.1. IntroductionYttia-stabilized zirconia (YSZ) has, been widely used as not only heat-resistant materials but also the components in automotive oxygen sensors, electrolytes of solid-oxide fuel cell (SOFC)(1)(2) and the buffer layers for the high-temperature superconductor because of its low thermal conductivity, good mechanical properties and high ionic conductivity. However, it is said that the internal resistance of the bulk electrolyte is too high to be appropriate as a solid electrolyte for high-efficient SOFC. The authors believe that the thin YSZ electrolyte can give a high performance to characteristics SOFC, since the internal resistance becomes lower with the decrease of electrolyte thickness. Thus the process technology to prepare YSZ thin films is desirable and must be established.In recent years, the YSZ thin films have been reported by chemical vapor deposition (CVD), thermal CVD using metal chlorides (MC) of ZrCl4 and YC(3)(4), thermal CVD using metal organic compounds (MO)(5)(10) Zr(t-OC4H9)4 and Y(C11H19O2)(11) and plasma-enhanced (PE) CVD using MO. Here, these methods are called MCCVD, MOCVD and PEMOCVD. MCCVD has two disadvantages; a large quantity of chlorinated impurities in deposited films and high processing temperature (> 1273K). This high processing temperature leads to damage of substrates in particular, so the application of this technology is limited. On the other hands, the processing temperature by MOCVD becomes and is lower. Unfortunately, the accurate vapor pressures of these metal organic compounds have not been, known so: that it is difficult to control the composition and the film thickness by MOCVD method well. Moreover, the large amount of carbonic compounds in the films prepared by MOCVD method is produced. However, plasma-effect has been reported to decrease large amount of the carbonic impurities by PEMOCVD. However, PEMOCVD has many reaction parameters in plasma processing; the geometry of experimental apparatus, radio frequency, electronic power input and so on. Thus, the general understanding about the relationship among reaction parameters, the composition and crystal structure of thin deposit film by this method has not yet been established."

Jan 1, 2000

By S. Haggarty, R. Walton

Barrick's growth and development plan will add three major new mines during 2005 including the Lagunas Norte Project in the La Libertad Province of Peru, the Veladero Project in the San Juan province of Argentina, and the Tulawaka Mine in north¬western Tanzania. Lagunas Norte and Veladero are similar in that they are both green-field open pit deposits at elevations over 4,000 meters above sea level, with two stage crushing and heap leaching followed by Merrill Crowe zinc precipitation for precious metal recovery. Operating sites will each generate in excess of 700,000 ozs Au per annum with commissioning and full scale operation planned during the third and fourth quarter of 2005. Details with regards to regional geography, development schedule, production and process specifics for Lagunas Norte and Veladero will be discussed in this presentation providing an overview for the respective properties.

Jan 1, 2005

By R. B. Ellestad

Introduction Lithium has been known since 1817, when it was discovered by the Swedish chemist, Arfvedson, while working in the laboratory of Berzelius on the chemical analysis of the mineral petalite, LiAl(Si205)2. Development of the chemistry of lithium proceeded slowly, following the early work of Davy, Gmelin, Bunsen, and Matthiessen. Approximately seventy years elapsed before lithium products assumed any commercial importance, and for a considerable period it was a' very minor industry. Their chief early use seems to have been in medicine, and in the production of lithiated water. Other more important uses were gradually discovered, and the industry has had a slow but steady growth. Chemistry Lithium is classified as an alkali metal, along with sodium, potassium, rubidium, and cæsium. Like these, it is a silvery-white metal, which can be cut with a knife; it is harder than sodium, but softer than lead" It is remarkable in having a density of only 0.53 gram per cubic centimeter, which makes it the lightest metal. On ignition in air, it burns intensely to form chiefly lithium monoxide, Li2O. Like the other alkali metals, lithium reacts vigorously with water to form hydrogen and lithium hydroxide. The later is a strong base, and reacts with acids to form salts. The salts of lithium are in general analogous to those of the -other alkalies, but many of them have unique properties. For example, lithium chloride and bromide are extremely hygroscopic, and have a very high water solubility. Lithium fluoride, phosphate, and carbonate, on the other hand, are all relatively insoluble, unlike the corresponding sodium and potassium compounds. In this instance, lithium exhibits its frequent tendency to resemble the alkaline-earth group of elements (calcium, strontium, and barium). Many of the special and valuable properties of lithium are related to the extremely small size of the lithium ion.

Jan 1, 1948

By S. Makni

Flotation is a complex process in which many mechanisms come into interaction. In this paper, an approach to model these mechanisms in order to predict size-by-size flotation performances is presented. The estimation of the collection efficiency of particles takes into account the serial sub-processes of particle-bubble collision, attachment and detachment. The model was applied to an industrial plant and yielded satisfactory results whereby the actual flotation performances could be correctly predicted. Furthermore, the flotation model allowed investigating the possibility of improving flotation performances by a split flotation feed in comparison to the actual single-stage process.

Sep 1, 2012

By William L. Crentz

This Investigation of the preparation characteristics of the coals in Armstrong County, Pa., is the third in a series of Bureau publications by counties appraising the practicability of upgrading marginal deposits to metallurgical standards. Earlier investigations covered the washing characteristics of the coals occurring in Cambria County, and the principal reserves remaining in Indiana County. In Armstrong County, the Upper Freeport bed is the major source of production, the Lower Kittanning bed being of secondary importance. The Lower Freeport bed is mined to some degree, but it is usually too thin and spotty in occurrence to support large-scale operations. The remaining production is taken from the Pittsburgh, Middle Kittanning, and Upper Kittanning beds, but the quantities are insignificant. Table 1 shows the county's coal production) by beds, during 1948. The coals of Armstrong County are not generally considered to be of metallurgical quality because of the high sulfur content. The raw coals usually analyze more than 2 percent sulfur, and more than 4 percent sulfur is not uncommon, especially in the Lower Kittanning bed.

Jan 1, 1951

By R. L. Lewis

A simple method for estimating the steady-state water quality of a pit lake is presented. The steady-state concentration of a conservative chemical constituent in a pit lake is shown to be a simple function of the inflow rate, the evaporation rate and the inflow concentration. An analytical method is presented for estimating the equilibrium ground water-inflow rate for use in water-quality predictions. The time required to reach chemical steady state is estimated using an iterative mass-balance model. Mine operators should find the methodology useful for planning and screening regulatory applications where conservative estimates of pit lake water quality are desirable.

Jan 1, 2000

By C. D. M. Chisholm

IN discussing stope filling, or backfilling, at the Sullivan mine, at Kimberley, B.C., a brief description of the problem will first be presented. The Sullivan orebody is a replacement in quartzite, with the ore con-forming, for the most part, with the bedding. The dip of the vein, apart from local irregularities, averages about 15 degrees near the outcrop in the southwest section of the mine, and steepens to almost 40 degrees at the northeast end of the mine. The thickness varies from a few feet to over 200 feet at the widest sections. The mineable length along the strike has averaged about 4,000 feet between the 4,600 and 3,900 levels-the section under discussion in this paper. To date, 28,000,000 tons of ore have been mined by the room-and-pillar method. Prior to 1930, all ground opened up had been supported by ore pillars, left during mining operations. From that time, the recovery of the ore from these pillars has been given serious consideration. Backfilling, as being carried on today, is the result of this study and is being done for two reasons: (1) to allow extraction of the ore pillars, and (2) to minimize subsidence of the hanging-wall rock, except where forced caving is found desirable. PRELIMINARY DEVELOPMENTS LEADING TO BACKFILLING When the Sullivan orebody was first opened up, early in the century, there appeared to be low-grade sections of the vein sufficient in extent to serve as permanent support for the roof. However, as mining extended into sections of the vein that showed continuous ore over greater areas, wooden cribs, filled with waste and low-grade ore, were erected. In some stopes, these cribs were as large as 40 ft. by 100 ft. in plan and from 50 ft. to 60 ft. in height, but it was soon realized that this method of support was inadequate. As mining progressed, it was found necessary to leave ore pillars, which eventually became the sole system of support. At first, these pillars were left at irregular intervals, but later they were laid out at definite locations on the mine plans, and these locations were adhered to as closely as mining would permit.

Jan 1, 1941

By I. I. Bethcherman

Introduction 1.-lmportance of Physical Nature of Condensates The metals of commercial interest which have reasonably high vapour pressures below 1,200° C. are mercury, cadmium, sodium, zinc, magnesium, lithium, and calcium. With the exception of mercury, these metals occupy high positions on the electrochemical series and form compounds with very high negative free-energies of formation. It is highly desirable that such metals should not be produced in a form which is finely divided, on account of their reactivity with atmospheric gases. Powders of magnesium, calcium, and even zinc (blue powder) are dangerous to handle and cannot be coalesced by simple melting techniques. Vaporization in vacuo forms a convenient method of handling and purifying the alkaline earth metals in particular and a previous paper by the authors dealt with some of the factors controlling the separation of metals by this technique (12). An essential part of the operation is the condensation of the vapour to produce a massive deposit which may be conveniently melted and handled by established metallurgical techniques. This investigation sought to determine the conditions affecting the nature of solid condensates.

Jan 1, 1951

By Ross W. Smith

Microorganisms are increasingly finding use in mineral processing and hydrometallurgy both for the enhancement of mineral engineering operations and for the remediation of mineral industry wastes. Some of the applications, such as biologically assisted leaching of sulfide ores and biooxidation of refractory sulfide gold ores, are established commercial processes. Others, such as the use of organisms for the removal of heavy metal ions from dilute aqueous streams, are nearing commercial application. Other uses of microorganisms are potentially possible. These include use of microorganisms in leaching non-sulfide ores, the flocculation or flotation of minerals and remediation of toxic chemicals discharged from mineral engineering operations.

Jan 1, 1993

By S. A. Allen

The Eufaula bauxite district of Barbour and Henry Counties in southeast Alabama covers an area approximately 14 miles long, 6 miles wide at the eastern extremity near the Chattahoochee River, and 10 miles wide at the western end near the east fork of the Choctawhatchee River (see figs. 1 and 2). The long axis of this polygon bears a little south of east.

Jan 1, 1949