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By A. B. Hooker, Ilsley. L. C.

"Several writers have called attention, in the technical press, to the possible failure of flame safety lamps in coal-dust laden atmospheres. Such writers question the safety or a flame lamp that has been proved only in atmospheres containing methane, believing that the resistance of the lamp to explosion would be lessened it coal dust constituted a part of the explosive mixture.If this be true, it follows that any series of tests devised to prove the safety of flame lamps for use in gaseous and dusty coal mines should not only embrace tests in mixtures containing various proportions of methane, but also in some of the tests the effect of adding coal dust to the explosive gaseous mixtures should be investigated.Some attention has been given this question by investigators, but the more common practice has been to make all tests in gas and air mixtures only, using methane when it was readily available. Apparently the English Accident Committee (1879-1886) who conducted tests upon 250 different lamps did not use coal dust in their tests. The first British requirements for the testing of safety lamps, issued as a result of the Coal Mine Act of 1911, made no mention of tests with coal duet.The Austrian Fire-damp Committee (1890) conducted a series of tests in which coal dust was used in some of the tests. In certain tests, the addition of coal dust apparently lowered the resistance of the lamp 1 meter per second. The Belgium investigators, Messrs. Watteyne and Stassart, conducted a series of tests in 1904 in which coal dust was used in a few tests without any marked difference in safety."

Dec 1, 1920

By William C. Cooley

SUMMARY A review is presented of the state of development of high pressure water jet equipment and of large impact hammers for rock tunneling. Information from the U.S.S.R. is based on published literature and three personal visits. Applicable papers which were presented at the International Symposium on Jet Cutting Technology in Coventry, England in April 1972 are reviewed. Data are presented on continuous jet systems, pulsed water cannons, and hydraulic-powered impact hammers with respect to the specific energy of rock breakage and potential application in tunneling machines. INTRODUCTION It has been estimated that the cost of underground excavation during the period 1970-1979 in 15 countries of the Organization for Economic Cooperation and Development will be over $54 billion, an increase of 104% over the period 1960-1969. It is expected that 55% of the tunneling construction will occur in hard rock (Ref. 1). Present tunneling machines are generally limited to soft and medium-hard rock. When used in hard rock, the cost of replacing mechanical cutter bits is high. Therefore there is a need for improved rock fracture methods which can be applied economically in tunneling machines for hard rock. Water jets and mechanical hammers are two

Jan 1, 1997

By M. Hochenhofer

Due to economic aspects and environmental regulations recycling of slag and waste from ferroalloy production became a very important issue for the companies during the last years. The treatment of slag depends prior on the composition, especially on their content of valuable metals and impurities. The final aim should be a total re-use of these materials in the industry e.g. cement industry, pig-iron production etc.. Therefore, to reach the required physical and chemical properties for a further use, possibilities of a metallurgical treatment have been investigated. The conditioning of slag with a high V-, Mo- and P-content via reducing metal bath showed to be one alternative. To determine the optimal process parameters, practical investigations with different slag compositions and thermodynamic calculations were carried out.

Jan 1, 2006

The structural design of a mine haul road involves the determination of cover thickness requirements above the in-situ or sub-grade material. The specification of these layerworks is a critical component in the overall road design process. Poor design often leads to premature failure of the road, safety is often compromised and productivity and equipment service-life will certainly decrease. Historically, the California Bearing Ratio (CBR) cover-curve design method has been widely applied to the structural design of mine haul roads. More recently, established mechanistic design principles have superceded the CBR approach to haul road design, using a multi-layer model to represent the various road structural layers. The structural design and associated layer thickness requirements are then determined following a maximum strain criterion. This paper develops a case-study evaluation of the CBR cover-curve and mechanistic design methodologies and through a comparative analysis of layerworks and materials, highlights how improved structural design can be achieved mechanistically.

Jan 1, 2011

By S. M. Chentouf, M. Jahazi, N. Bombardier, T. Belhadj

The main limiting factor in the commercial expansion of superplastic forming (SPF) of thin sheet aluminum alloys is the extent of cavitation phenomenon that takes place during the processing. The severity of the cavitation process is mainly dependent on the uniformity of deformation (i.e. level of local thinning) during processing. In the present paper, correlations are made between thickness variations in several formed sheets and the characteristics of the cavities observed in the material. The 1.4 mm thick 5083 aluminum alloy sheets were hot pre-formed at around 450°C for 4 min and then air-cooled. Opto-digital and Scanning Electron Microscopy were used to examine the microstructure and analyse the cavities. Also, grain size measurements were carried out for different location in the SPF formed piece. The surface and volume fractions of the cavities were measured with the aid of metallography image processing (MIPTM) on as-polished samples prior to etching. The results are analyzed in terms of the influence of applied strain and microstructure conditions on the propensity to cavitation of the alloy.

Jan 1, 2015

By J. D. Patsey

A computer program has been developed for use by the mining engineer for analyzing drum-type hoists prior to the modification of an existing system or the designing of a new one. Its use permits the preliminary evaluation of a system before seeking the technical assistance of mine hoist designers and manufacturers. Compatible with an IBM-PC, the user-friendly program accepts a variety of data and can analyze hoisting systems for any balance state. The extensive program can be used to: (1) calculate skip capacity to yield a desired production rate; (2) solve for required drum face width; (3) select a permissible wire rope from a menu of 50 available rope types: (4) estimate total horsepower of the hoist plant; and (5) estimate power cost. An example of the model's use in evaluating a hoisting system will conclude the paper.

Jan 1, 1986

By Garg. D.

Premixed bronze powders are widely used to produce a wide variety of P/M components including bearings and bushings by the powder metal industry. The physical and mechanical properties of sintered bronze components such as dimensions, strength, microstructural characteristics, and sintered density are well known to change with sinlering furnace design, particle size distribution in powders, green density, preheating and sinlering time" and temperature, and protective atmosphere flow rate. " However, not much is known about the effect of protective atmosphere composition on physical and mechanical properties of sintered bronze components; This paper describes effects of protective atmosphere composition and sintering temperature on physical and mechanical properties of sintered bronze components

Jan 1, 1996

By G. P. Gladis, R. H. Atkinson

Palladium has been used for jewelry for many years, particularly in conjunction with gold. This use increased in amount during the war, as palladium and gold were only moderately used for war purposes while demands for platinum and some of the other members of the platinum group were so great that their use in jewelry was prohibited. Palladium hardened with a small percentage of ruthenium has the necessary technical properties and appearance for good jewelry, and it is sufficiently rare to be desirable for luxury items—at least I00 times as rare as gold. Although both visual and spectro-photometric examination demonstrated that the color of Palladium was almost the same as that of platinum, a few jewelers found the surface of palladium, even after some polishing, rather dark in areas that had been repeatedly heated during the soldering necessary to assemble certain types of handmade ornaments. This phenomenon is not to be confused with the thin, bluish oxide film that can be produced by heating in air over the range 400' to 800°C., as that film is easily reduced by dipping in warm 5 per cent formic acid or in warm methanol. It was suspected that the difficulty arose from heating in atmospheres that were alternately oxidizing and reducing, as Wise and Vines1 had found that this opened the grain boundaries of palladium and palladium-silver alloys in the same manner as in pure silver, as reported by Martin and Parker.2 This damage is caused by the reaction between oxygen in solid solution in the metal, acquired when heated under oxidizing conditions, and hydrogen diffusing in from subsequent heating under reducing conditions; the steam cannot diffuse out and therefore builds up sufficient pressure to disrupt the metal near the surface. Copper and various other metals can be damaged similarly, but platinum is nearly immune; therefore the problem was new to the platinum jeweler. Sulphur in the fuel gas also can cause trouble but did not appear to be dominant in the present instance. Metallographic examination of both pure palladium and ruthenium-palladium showed that the usual torch using oxygen and city gas as normally operated did in fact cause the surface and subsurface damage that had been observed, and also disclosed that a reducing flame caused more damage than an oxidizing flame and was very damaging even in the absence of any intentional swing in atmosphere from oxidizing to reducing (Fig. 7); besides the surface damage, there was serious loss of ductility. A full explanation of the mechanism of attack is not evident at the moment, but may be allied to the attack that occurs on heating catalytically active metals in nonequilibrium atmospheres.

Jan 1, 1946

By G. P. Gladis, R. H. Atkinson

Palladium has been used for jewelry for many years, particularly in conjunction with gold. This use increased in amount during the war, as palladium and gold were only moderately used for war purposes while demands for platinum and some of the other members of the platinum group were so great that their use in jewelry was prohibited. Palladium hardened with a small percentage of ruthenium has the necessary technical properties and appearance for good jewelry, and it is sufficiently rare to be desirable for luxury items—at least I00 times as rare as gold. Although both visual and spectro-photometric examination demonstrated that the color of Palladium was almost the same as that of platinum, a few jewelers found the surface of palladium, even after some polishing, rather dark in areas that had been repeatedly heated during the soldering necessary to assemble certain types of handmade ornaments. This phenomenon is not to be confused with the thin, bluish oxide film that can be produced by heating in air over the range 400' to 800°C., as that film is easily reduced by dipping in warm 5 per cent formic acid or in warm methanol. It was suspected that the difficulty arose from heating in atmospheres that were alternately oxidizing and reducing, as Wise and Vines1 had found that this opened the grain boundaries of palladium and palladium-silver alloys in the same manner as in pure silver, as reported by Martin and Parker.2 This damage is caused by the reaction between oxygen in solid solution in the metal, acquired when heated under oxidizing conditions, and hydrogen diffusing in from subsequent heating under reducing conditions; the steam cannot diffuse out and therefore builds up sufficient pressure to disrupt the metal near the surface. Copper and various other metals can be damaged similarly, but platinum is nearly immune; therefore the problem was new to the platinum jeweler. Sulphur in the fuel gas also can cause trouble but did not appear to be dominant in the present instance. Metallographic examination of both pure palladium and ruthenium-palladium showed that the usual torch using oxygen and city gas as normally operated did in fact cause the surface and subsurface damage that had been observed, and also disclosed that a reducing flame caused more damage than an oxidizing flame and was very damaging even in the absence of any intentional swing in atmosphere from oxidizing to reducing (Fig. 7); besides the surface damage, there was serious loss of ductility. A full explanation of the mechanism of attack is not evident at the moment, but may be allied to the attack that occurs on heating catalytically active metals in nonequilibrium atmospheres.

Jan 1, 1946

By S. Weinig, J. Winter

The grain boundary adsorption of solutes as a function of bulk concentration and solution temperature was studied using internal-frictimz techniques. From the variation of the cor-responding energy of activation for the Phenomenon, the inter-actior2 energy between a solute atom and a high-angle boundary was calculated. Interaction energies in the range of 0.3 ev were obtained, and were used to obtain the actual concentration of solute at the grain boundary. In corroboralory creel, studies the direct grain boundary contribution to the total creep strain was measured. It was found that the interface creep varied with the type and magnitude of the solute adsorbed. Subscribing to the theory of their being energetically favorable sites at the grain boundary for solutes of both Positive and negative size deviations, ternaries were investigated in Which solutes of both types were present. A marked increase in the resistance to grain boundary creep was manifested. THE major difficulty which has been encountered in investigations of the grain boundary segregation of solutes has been the lack of a sufficiently sensitive method of measuring the amount of adsorbed solute at the boundary. For the general case of a high-angle boundary, no direct method of measuring the adsorption at the boundary has been found to date. Internal friction has been used in several studies of grain boundary adsorption1-3 and although it is somewhat indirect, it was demonstrated to have the necessary sensitivity. In this investigation the authors have used internal-friction techniques in conjunction with a study of the grain boundary contribution to the total creep strain. As both parts of the investigation were performed on the same specimens it was possible to combine a highly sensitive technique with a somewhat more direct method in order to obtain information about the adsorption phenomenon. From internal-friction studies the rate of increase of the activation energy was observed to be a function of the difference in size between the solute and solvent atoms. It was proposed that if Gibbs' adsorption isotherm is considered, i.e., where r is the excess solute at the boundary, c is the bulk concentration, and ay/ac is the change in grain boundary energy with bulk concentration, then AH b/ac must vary in the same way as ay/ac and therefore In this way a relative measure of the grain boundary adsorption of solutes is directly obtainable from in-ternal-friction studies. If the previous work in the field of grain boundary adsorption of solutes is examined, certain apparent information is desirable if the phenomenon is to be understood. The most important questions that must be asked are as follows: 1) Is the adsorption of solutes at the grain boundary an equilibrium process? 2) Can the Mott model of the grain boundary be used as a basis of setting up an elastic interaction between the grain boundary and solute atoms? 3) Is it possible to obtain an exact measure of the excess solute at the grain boundary as a function of temperature and bulk concentration rather than merely a relative measure of the adsorption 4) Are the conclusions obtained from an indirect method such as internal-friction studies meaningful in considering gross grain boundary effects such as creep? EXPERIMENTAL PROCEDURE The material used in this investigation was Bureau of Mines "superpurity" titanium (79 Bhn—1500 kg

Jan 1, 1960

By B. K. Mishra, P. Patnaik, B. C. Tripathy, I. N. Bhattacharya

Cobalt is an essential metal considering its numerous industrial applications. The demand for the metal is increasing due to its wide range of use in, for example, rechargeable batteries and as an alloying element in super alloys. Cost effective production of Co is critical. Electrowinning from aqueous sulphate solutions is the preferred technology available for the production of Co. Attempts are being made to produce uniform, smooth and bright deposits of cobalt metal. Use of organic additives in the electrolytic bath improves current efficiency and deposit morphology of the metal. We investigated the effect of quaternary amines TEABr, TPABr and TBABr during cobalt electrowinning from aqueous sulphate solutions. Among the additives studied, TEABr yielded the best results. Smooth and bright deposits of cobalt were obtained at low concentration of TEABr (10 mg/L) maintaining a very high current efficiency of 99.6%. X-ray crystallography indicated that (100) is the most preferred plane of crystal growth.

Jan 1, 2014

By Lori Kormos, Jhonny Carrión De la Cruz, Dominic Fragomeni, Elizabeth Whiteman, Jorge Oliveira

"Process diagnosis, flowsheet design and optimisation are most effectively and efficiently achieved through the use of metallurgical testwork combined with more modern quantitative mineralogical techniques. Integration of the mineralogical data in testwork programs provides a resolution that cannot be obtained from assays alone and can direct the flow of work to result in optimized conditions more quickly than would otherwise be possible. At Xstrata Process Support (XPS), QEMSCAN (Quantitative Evaluation of Materials by Scanning Electron Microscope) and EPMA (Electron Probe Micro Analyser) information can be employed to diagnose specific issues in a plant or lab scale test and are routinely combined with other metallurgical data sets to benchmark performance, design and optimise flowsheets. Representative sampling protocols for ore bodies or test products, the use of geometallurgical unit classification and high confidence metallurgical test programs are key components of the strategy. Two case studies from Xstrata Zinc’s Antamina Mine and Concentrator in Perú, and Xstrata Nickel’s Nickel Rim South Mine in Sudbury are described to show how the use of quantitative mineralogy were used to diagnose a plant issue and how the data can be integrated into metallurgical programs to assist mineral processing engineers to design and optimise flowsheets.INTRODUCTIONOver the past decade, there has been a shift away from metallurgical testing that employs only chemical assays to quantify performance; the use of empirical observation in order to optimise a flowsheet; and the extraction of bulk samples for testing or piloting. The integration of geological information into the planning and execution of testwork programs including the use of quantitative mineralogy has improved the overall quality and predictability of metallurgical programs. At the same time, improvements to metallurgical testwork protocols such as rigorous statistical assessment of results, the use of factorially designed experimental strategies (DOE), and replicate flotation with appropriate quality controls, has improved the confidence level in these results.Process diagnosis, which utilizes quantitative mineralogy, can clearly define the root cause of the metallurgical issue. Whether used on its own to diagnose an issue or in combination with other metallurgical testwork, the use of mineralogical data has become the standard in the mining industry."

Jan 1, 2010

By R. C. Schmidt

The Mont Klahoyo magnetite deposit is located about 600 km northwest of Abidjan, Ivory Coast. During an exploration period ending in 1977 an international joint venture group investigated the deposit and proved reserves of 670 million tons grading 36% iron. The deposit, occurring at the northeast end of the Baoubly-Kiriao chain of Precambrian iron formations, is associated with amphibolites, pyroxenites and gneisses of the Liberian Shield. At Mont Klahoyo occur two separate iron formations of which the lower member is the ore body. This lower member consists of a highly metamorphosed - banded quartz-magnetite iron formation in which iron silicate bands alternate with beds of quartz-magnetite. mphibolite-pyroxenites and sillimanite-cordierite-garnet gneisses form hanging and footwall rocks. The iron formation has been folded into an elongated overturned "Z" shaped major drag fold with axes trending and plunging approximately northeast. Beds are vertical or dip steeply to the southeast. The ore zone has an average thickness of 130 m and outcrops intermittently over a distance of approximately 5.5 km. Based upon detailed studies of drill cores and the results of ore dressing test work, eight stratigraphic units, identified as K-1 to K-8, are recognizable in the iron formation. Four interbedded units are low grade silicate zones (silicate facies) with the remaining quartz-magnetite units (oxide facies) repre¬senting the important ore zones of the Mont Klahoyo deposit. The ore-bearing "K" units are subdivided further, based upon their specific lithologies, iron content and concentration characteristics, into eleven ore types. The identification of these ore types is considered particularly important to mine planning and flowsheet design. A cap of oxidized materials overlies the primary quartz-magnetite iron formation but no enrichment has occurred. It is proposed that the Mont Kalhoyo iron formations were deposited, possibly chemically, in a volcanic environment as a siliceous iron formation with volcanism providing the primary source of iron and silica. Metamorphism converted the siliceous iron formation to a relatively coarse-grained quartz-magnetite-silicate iron formation.

Jan 1, 1979

By Thomas E. Howard

Recently, the mining community has begun to move toward a more prominent place in the structure of American society. Extensive press coverage of our energy problems during the past year or two has led to an increasing awareness on the part of the public of the vital role that mining must play if today's standard of living is to be maintained. It appears that mining may be emerging from a status generally characterized in the public mind as an esoteric, dirty, man-killing, land- scape-despoiling endeavor, to a new stature that may eventually become as respectable as agriculture. To be sure, we are still being criticized, as has been the lot of miners since the time of Agricola. In fact, the clamor has never been louder. Nevertheless, the public, in increasing numbers, is beginning to know it needs us. But we cannot be complacent. Our improving stature brings along with it increasing responsibility. The mineral industry will be expected to produce mineral raw materials and fuels in ever larger amounts and sell them at reasonable prices, in the face of rising labor costs, decreasing labor availability, chacging labor attitudes, increasingly stringent environmental regulation, stricter health and safety standards, and a deteriorating geo-political climate.

Jan 6, 1975

By W. A. Griffith

Fractional replication of factorial design, a general method for planning experimentation and for analysis of data obtained, is described as applied to a flotation investigation. This method leads to determination of optimum process conditions with minimum experimental effort. Its advantages over simple factorial design are demonstrated. A METHOD for planning experimentation and for analyzing the data secured will be demonstrated. This method, termed fractional replication of factorial design, employs a relatively small number of individual experiments to determine which of a large number of process variables are controlling, to determine which combination of levels of these variables is most likely to produce optimum results, and also to predict what results will be obtained with a particular combination of conditions not already tested. Although the general method is not new, having been developed by Finney in 1945,' the extent to which it can improve the effectiveness of applied research generally has not been recognized by metallurgists. The fractional replication procedure is particularly useful in flotation experimentation and an example from such an investigation will be used in the paper. However, it has equal value in any investigation in which similar experimental difficulties are encountered. In developing a flotation process for a particular mineral separation, the investigator is inevitably confronted with the following difficulties: 1—There are a large number of potentially important process variables. 2—Results of individual experiments are not highly reproducible, due in part to the difficulty in precisely controlling all the variables. 3—Considerable effort is expended in conducting individual experiments. 4—There are practical limits on the number of individual experiments which can be made. In situations of just such a type, modern statistical methods of planning experimentation and analyzing data have their greatest value. Applications of one such technique, called factorial design, to problems of this type have been described by Dorenfeld and others.'-' The simple factorial design is an efficient procedure when the investigator hopes to provide a comprehensive understanding of the effects and interrelationships of a small number of variables over a limited range. In applied research, this is seldom the main objective. Rather, the investigator usually wishes to determine which of the many potentially important variables are in fact controlling, which levels of the controlling variables will provide opti- mum metallurgical results, and what these results will be at optimum conditions. Interest in detailed trends is limited to the controlling variables and to levels in the region of optimum conditions. Simple factorial design has serious deficiencies for such objectives and is not the most efficient method of experimental design. Deficiencies of Factorial Design In a simple factorial design, an experiment must be made at every possible combination of each level of every variable, once these have been chosen and the levels of each to be included have been decided upon. As the number of variables or levels of each increases, the experimental program quickly reaches prohibitive size. For example, an investigation of only four variables, each at four levels, requires 256 individual experiments. Often upon completion of such an extensive program, it is found that one or more of the variables has metallurgically unimportant effects or that a poor estimate has been made as to the appropriate range of levels to be investigated. The result is that only a small proportion of the data obtained falls in the range of real metallurgical interest. Indeed, it frequently can be anticipated that certain combinations of levels of variables will not produce results of interest, but they still must be included so that the essential balance, or orthogonality, of the design will be retained. It may be true that factorial design will provide the greatest amount of information from a given number of experiments, but it does not necessarily follow that it will lead to the desired information with a minimum number of experiments. Much of the information provided may be of little value. Advantages of Fractional Replication The disadvantages of simple factorial design are overcome to a great extent by a modification known as fractional replication. This is a technique for sampling systematically the potential data of a full factorial experiment, that is, the data which would have been obtained if the complete factorially designed program had been completed. Only a fraction of the total array of experiments is made, but the experiments are chosen in such a way that the important advantages of factorial design and the accompanying analysis of variance are retained. The data obtained from the first group of experiments are used to determine which of several variables are controlling and which levels of these variables are most likely to produce the desired result. Unimportant variables and levels of variables then may be

Jan 1, 1956

By John D. Ridge

For mining geologists, the most important trends during 1962 have been the increased concentration of the exploratory activities of American mining companies in the United States and Canada and the greater use of the combined techniques of geology, geophysics and geochemistry in searches over larger areas for wider varieties of metals and minerals. The principal reasons for these changes in approach have been the deterioration of the political-economic climate in many areas of the globe of equal or greater geologic promise and the realization that modern exploration is most efficiently and economically conducted through the use of all available means of detecting ores in areas sufficiently large to raise to a maximum the chances of success. The attitude of certain major U.S. metal-producing companies can be shown by the officially ex- pressed positions of their principal officers. Early in 1962, Clyde E. Weed, Chairman of the Board of Anaconda, remarked that "because of unsettled conditions and disruptive influences in many of the copper-producing areas of the world, it is imperative that domestic copper-producing capacity be improved and made as efficient as possible in order to meet consumer demands at reasonably stable prices." In November, Robert G. Page, President of Phelps Dodge, pointed out that his company is not only concentrating most of its exploratory effort on this continent but is also increasing the number of metals for which it is searching. Frank R. Milliken, President of Kennecott, recently said that "most of our exploration money is going into the northern part of the Western Hemisphere."

Jan 2, 1963

By J. K. Whyatt

Assuring ground control safety in many mining and tunneling projects depends, at least in part, on an understanding of in situ stress conditions that will be encountered. Yet it is rarely practical to conduct more than a very limited number of stress measurements. Stresses along the route of a proposed excavation are typically interpolated from available measurements, often assuming a linear variation of stress with depth (or elevation). However, projects where multiple stress measurements are conducted often report more complex variations of in situ stress, usually in apparent relationship to geologic structures. These structures often include lithologies of contrasting elastic properties. A method is proposed for estimating stresses in these cases by first back-calculating regional loads from available stress measurements and then modeling the distribution of stress throughout the rock mass. The method has been successfully applied to a set of in situ stress measurements from the Coeur d’Alene Mining District of northern Idaho, USA. Results provided new insights into district stress conditions and the distribution of rockburst hazards along mine drifts and between various mines. This success should transfer readily to suitable deep tunneling projects.

By André Desbiens, Jocelyn Bouchard, René del Villar

"The metallurgical performance of the column flotation process is determined by the concentrate grade and recovery. Although the former can be continuously measured using an on-stream analyzer, the latter must be estimated by a material balance calculation based on seldom verified steady-state assumptions. Consequently, the automatic control and optimization of flotation columns should be performed using secondary variables having a strong influence on the metallurgical performance, such as froth depth, gas hold-up or bubble surface area flux and bias. The aim of this paper is to present a model-based automatic control strategy using froth depth and bias measurements obtained from virtual sensors developed at Laval University. Preliminary pilot plant results on two-phase (water– air) and three-phase system (water – minerals – air) will be presented and eventual industrial implementation of such a strategy as well as the possibility of achieving effective real-time optimization from bias and froth depth measurements will also be discussed.INTRODUCTIONFlotation columns have been widely studied and used in mineral processing for about twenty years. Although a great deal of work has been accomplished to understand the influence of different variables such as froth depth (H), bubble surface area flux (Sb) and bias (Jb) on the metallurgical performance, the measurement of some of these variables is still difficult to be performed – except at the laboratory level – because in most cases, no commercial device yet exists.As a result of this, it is almost impossible to achieve neither efficient control nor optimization of the process at the industrial level, even in open-loop operation. This paper aims at presenting a simple control strategy of froth depth and bias. Description of the sensors used to achieved measurements, preliminary pilot plant results for froth depth control, eventual industrial applications and possibilities for process optimization are also treated."

Jan 1, 2003

By Shin-ya Kitamura

Kinetic modeling is very important to understand steelmaking reactions. The coupled reaction model proposed by Prof. D.G.C Robertson is the best suited program, and therefore, the author has applied it to the various steelmaking reactions, a few examples of which are discussed. Hot metal dephosphorization occurs under non-equilibrium conditions as it takes place between the slag, which has a high oxygen potential, and the hot metal, which has a low oxygen potential. A process simulation model based on the coupled reaction model was constructed. This model considers the solid and liquid slag, liquid metal phases, and the reaction between the solid and liquid slag, besides the reaction between the liquid slag and liquid metal. Using this model, the ruling factor to increase the reaction efficiency of dephosphorization has been verified. In the secondary refining process, the values of inclusion composition calculated by the thermodynamic model, under the assumption of equilibrium with the metal composition, were found to be different from those observed in practice. A kinetic model, incorporating the reactions between slag, metal, inclusion, and refractory has been postulated, and the composition change of inclusion during treatment has been analyzed.

Jan 1, 2014

By Richard Giffen, Boris CARO VARGAS, Terrence Carroll

"This paper takes an in-depth look at the $72 million design-build Norris Cut project, which includes the replacement of an existing 54-inch waste water sewer main to Fisher Island under the Norris Cut Channel. Tunneling through one of the country’s most unpredictable geologies created unique challenges in both the design and construction phases of the project. The paper presents the geotechnical and structural design considerations for the 100-foot deep secant piled TBM launch shaft in the highly permeable Fort Thompson formation limestone and sands. The structural design effort also included the design of the tremie slab, thrust wall and design of the largely unreinforced launch shaft to resist asymmetric loading from partial ground freezing. The retrieval shaft was designed as a deep soil mixed shaft and is thought to be the deepest soil-mixed shaft in Miami. From a construction perspective, this paper discusses the unique challenges of building two shafts with two different techniques and will compare some of the constructability aspects, costs and equipment schedule-considerations related to the use of two separate techniques. INTRODUCTION Nicholson Construction Company (NCC) was awarded a $72.1 million Design-Build contract to replace an existing force main from the Virginia Key Central District Wastewater Treatment Plant (CDWWTP) under the Norris Cut Channel to Fisher Island. The location of the project is shown in Figure 1. The project involves replacing an existing 54-inch diameter pre-stressed concrete sewer force main with a 60-inch diameter fiberglass force main. Arup USA, Inc. (Arup) is the lead designer for Nicholson on this design-build project. Arup is providing design services for the TBM launch and retrieval shafts, segmental tunnel lining, the fiberglass pipe, and the horizontal directional drill component. Miami-Dade Water and Sewer Department currently owns and operates the existing 54-inch sanitary force main that transmits sewage collected from Miami Beach and Fisher Island to the CDWWTP for treatment and disposal. The existing force main was subject to a condition assessment in December 2011 which revealed structural deficiencies in the pre-stressed concrete pipeline."

Jan 1, 2016