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By H. L. Monroe

Meramec Mining Co., owned 50% by St. Joseph Lead Co. and 50% by Bethlehem Steel Corp., is engaged in mining, concentrating and pelletizing iron ore from the Pea Ridge Mine which is located about 75 miles southwest of St. Louis. The Pea Ridge orebody lies under some 1300 ft of limestone, dolomite, shale, and sandstone. It runs from east to west for about 1/2 mile and varies in width up to a maximum of around 600 ft. The orebody dips about 80" S. The ore is high grade magnetite with some local zones of specular hematite. The Precambrian country rock is rhyolite porphyry.

Jan 12, 1965

By A. F. Giamei, E. J. Freise

A discussion of the various factors affecting the accuracy of volume fraction determination by the direct comparison X-ray diffraction method is presented. To minimize errors introduced by nonrandomization effects such as preferred orientation and large grain size, as well as errors introduced by statistical effects, an iterative mathematical analysis is introduced. This analysis is applied to all observable diffractio~ spectra from a given specimen by means of computer techniques and is statistically superior to the standard direct comparison technique which utilizes only one or tm sets of intensity spectra. The computer program also presents a graphical interpretation of- the results which enables the investigator to visualize and readily assess the scatter in volume fraction estimates caused by deviations from randomness. Finally, the iterative analysis is applied to experimental data collected from a series of plain carbon steels in both the as-received and spheroidized conditions to determine the volume fraction of cemen-tite present in each case. The results show markedly good agreement with chemical analyses for all spheroidized specimens. In theory, quantitative X-ray diffraction is a power-ful analytical technique for precise determination of the volume fractions of various phases present in a multiphase poly crystalline aggregate. There are two generally used methods; both utilize the fact that the intensity of a diffraction line of a particular phase is a function of volume fraction of that phase present in the aggregate. The more common method is the so-called internal standard technique where a known amount of standard substance is mixed with the aggregate containing the unknown. The resulting ratio of the intensity of a particular diffraction line of the unknown to the intensity of a diffraction line from the standard is used to find the weight fraction of unknown material by reference to the intensity data obtained from a previously prepared set of standards containing the same amount of standard material. The details of this technique are outlined in standard works on X-ray diffraction.' The disadvantages of the technique are that it requires the use of powder specimens and that the powder mixture must be homogeneous near the surface to the maximum effective beam depth. The alternative technique is the direct comparison method in which the ratio of the intensity of a diffraction line of a phase in the aggregate to the intensity of a second-phase diffraction line yields the ratio of the volume fractions of each phase present. This method has been applied most extensively to the determination of the percentage of retained austenite in martensitic steels and to determining the amounts of hcp and fcc allotropic modifications in pure cobalt5 and the amounts of hexagonal and rhombohedra1 modifications in graphite.8 This method is applicable to bulk as well as powder aggregates and is the technique which will be considered in the following text. It is the purpose of the present communication to show that by combining the results of X-ray diffrac-tometry with the use of high-speed digital computers the results of the direct comparison quantitative X-ray analysis technique can be optimized by using all of the data available on a diffraction pattern. THEORETICAL DISCUSSION In optimizing any quantitative X-ray diffraction experiment, the problem of accuracy vs time to collect and analyze the experimental data arises. For any method to be practical, it is required that both experimental and analytical procedures are reasonably short. In most of the previous work performed by the direct comparison method, intensity data from only one or two sets of peaks were used to calculate the volume fraction of phases present in the aggregate. Consequently, rather long-time experimental measurements are required to assure that the intensity data are sufficiently accurate to justify the use of one or two sets of data. By using computer techniques to analyze the experimental data it becomes feasible to use all of the available data on a diffraction pattern. By so doing, the time spent in measuring any one diffraction maxima can be appreciably reduced. Although this results in poor counting statistics for any one maxima, the number of data points available for analysis is greatly increased. Based on the above discussion, it will be assumed that a continuous scanning counter-diffractometer technique will be used to collect intensity data from a two-phase mixture. The integrated intensity of the ith diffraction line from the a phase in the aggregate is given by:'" where is the volume fraction of the a phase, The various quantities in Eq. [la] are angular independent while those in [lb] depend on the hkl spectrum of a particular phase. The meaning of the individual quantities in Eqs. [la] and [lb] are given in Appendix 1. It is convenient at this point to outline briefly the factors which will affect the measured intensity of any one hkl spectrum. a) Extinction effects arise from two independent experimental conditions. Primary extinction arises from a high degree of crystal perfection and results in spectra having lower intensity than predicted by Eq. [I]. Any treatment, such as powdering, which reduces

Jan 1, 1968

By Prince Lazarovich Hrebilianovich

I was asked by the chairman of one of the Sessions on Employment Problems to talk about the viewpoint of the foreign workingman. I am not a workingman. I have never done what a work-hand might call an honest day's labor; that is, I have never been in a factory or manufacturing plant or in a mine, though in truth, hard work and I are well acquainted. I was a soldier, am an engineer, have long been actively interested in the most important waterway construction in the near East, have served politics and diplomacy, written books and lectured at universities. My knowledge of the foreign workingman in this country comes from the fact that my own compatriots here at various times came to me and appealed for advice and help, and last year I was asked by the employment manager of a corporation to undertake a welfare job at one of their plants. I went out, saw the plant, talked with the superintendent and outlined certain of my ideas which he personally heartily approved, but which did not find favor with those higher up. I approach the subject of the foreign workman's point of view with the understanding that the industrial employer's effort is for the maximum of efficiency. I am conversant with labor conditions abroad both in industry and agriculture. What I have learned of industrial conditions in America as they affect the foreign immigrant has been chiefly gathered from the cases referred to of foreign workmen who from time to time have come to me with their troubles. In the course of those investigations, in order to give whatever help or advice was possible, I have been impressed with the fact that the great United States industries evidently had not yet sufficiently recognized the value of studying the conditions of the workingman in the lands of his origin across the seas. A careful study of that which could be called the moral element in connection with its foreign labor would give industry a knowledge of the man's reason for coming, what grievances he brings with him, his hopes for a future, and the peculiar character of his capacities. The employer would thereby be enabled to meet the man, to be helpful to him, to aid him and at the same time promote industrial efficiency, inasmuch as a workman who believes that he is being dealt with humanly and squarely is contented and satisfied and will give willingly, and even with pride, the best that is in him; justice and a 'air deal is all the man wants.

Jan 1, 1918

By R. H. Heinen

Introduction Drilling is the initial operating step In open pit mining. It goes hand-in-hand with the blasting operations to ensure adequately broken material for the excavation equipment employed. The drilling effectiveness is highly dependent on the quality of the drill evaluation. This discussion will center on the parameters that are needed to evaluate drill requirements for a new mine The procedure that is generated can, however, be used to evaluate whether to expand existing operations and replace existing equipment. Methods of breaking ground, other than blasthole drilling and blasting, such as ripping, will not be discussed. The importance of correct drill evaluation extends to the other facets of open pit mining. Inadequate fragmentation, the direct result of poor drilling and blasting techniques, results in oversized, hard digging for the excavating equipment. The result is higher secondary blasting costs, reduced excavation efficiencies, higher excavation costs, higher road repair costs, and higher haulage equipment costs. The main objective of evaluating drill fleet requirements, therefore, is to determine the equipment needed to minimize the operational constraints, caused by blasthole drilling, on other facets of open pit mining at the lowest cash flow costs.

Jan 1, 1979

By B. S. Norris, Charles R. Austin

IN a recent paper the authors1 discussed the reactions to tempering of hypereutectoid steels quenched from 1000° C., as revealed by studies on changes in hardness, electrical resistivity, coercive force and metallographic characteristics. The data, which related specifically to tempering temperatures of 550°, 650° and 710° C., for varying periods up to 125 hr., permitted the following important conclusions: 1. The rate of softening of the steels at the temperatures examined differed markedly although the steels were of "similar" general chemical composition. 2. The temperature of maximum softening spread over a range from about 650° C. to the eutectoid inversion. 3. The divergence in behavior was ascribed, at least in part, to a profound difference in tendency to graphitization on annealing at subeutectoid temperatures. 4. The node of spheroidization of the cementite, as revealed by metallographic studies, also varied considerably in the different steels. The purpose of the present investigation is to pursue further the study of the difference in behavior of the steels on tempering over a wider range of temperature. To this end the following features have received particular attention: 1. Comparison of temperatures of maximum softening of the various steels when the quenched samples were tempered for 5 hr. and for 75 hr. followed by furnace cooling and by quenching in water. 2. Determination of the effect of quenching temperature, prior to tempering, on the rate of softening. Quenching temperatures of 1000° and 850° C. were used in the investigations. 3. Examination of the microstructures obtained with the various heat-treatments employed.

Jan 1, 1938

By Y. H. Hatzor, D. Bakun Mazor

"A new model for thermally-induced block displacement in discontinuous rock slopes is being explored inside a Controlled Climate Laboratory (CCL). The model is based on a hypothesized wedging mechanism that takes place inside the filled tension crack of a discrete block that rests on an inclined plane. Irreversible block sliding is assumed to develop in response to climatic thermal fluctuations and consequent contraction and expansion of the sliding block material. While an analytical expression for this model is already available, we are exploring the possibility of obtaining such a permanent, thermallyinduced, rock block displacement, under fully controlled conditions in the laboratory, to enable effective analysis of the sensitivity of the mechanism to geometry, mechanical properties, and temperature fluctuations.A large scale (approximately 0.5 m3 in volume) model consisting of four blocks has been installed in the CCL. The CCL permits accurate control of atmospheric temperature (?0.5 °C) from 6 °C to 45 °C. Harmonic temperature function is planned in advance and is controlled by a computer program throughout the experiment process. The minimum length of the temperature cyclic period for thermally-induced block displacement is calculated here based on the existing analytical model.Due to the fact that this experiment is still in progress, preliminary results will be available in the next few months. The obtained results may explain sudden triggering of rock slope failures that are not correlated with common failure triggers such as seismic activities, pore pressure build-up, or freezing and thawing of water inside rock joints."

Jan 1, 2015

By H. R. Barnhurst

It would be a difficult matter to trace from the beginning the very few improvements made in the burning of fuels prior to 1860. Donbtless the crossing of the sticks of wood in building a mood fire early appealed to our savage ancestry as a means of expediting its effectiveness for their crude culinary purposes. Stones and andirons came later in assisting the admission of air to the under part of the fuel bed, while beacons and cressets, utilized metal bars as supports for the same purpose. It is probable that Tuba1 Cain owed his success to the use of bellows making possible the use of mixed fuel and charge upon a hearth. With the development of working in cast iron, grate bars came in, and they are still with us doing duty in every household and almost every art where heat is a factor. Little was done beyond these crude methods prior to 1860. With the advancement of knowledge came the fuel-gas producer, a natural child of the retorts employed in supplying illuminating gas. It is only within the last 15 years that the conclusion became general that complicated systems for saving heat would not remedy deli-. ciencies in its primary development, and within that time there has been great advancement in the means of producing initially a fire of high effciency, so that to-day we are moving rapidly toward both high development and high absorption, with the resultant of high efficiencies. In studying the subject of the availability of pulverized coal as a fuel, it may occur to ask, why has this not come up earlier? This, question would be naturally prompted by recalling the fact that Thomas Crompton's English patents upon his methods were issued to him nearly 40 years ago. A conclusive answer to this, however, is that Crompton at that time had very crude facilities for making what was at best a very imperfect pulverization of the coal, arid the expense of preparation mas very great. He does not seem to have been aware of the advantage of a thorough drying of the coal in the

Jan 1, 1914

By Bruce N. McIver, Leo Casagrande

Similarities are noted in the practices and problems of constructing dams to impound mine tailings, fly ash, and chemical wastes. The comparison of a typical tailings dam with a conventional water-retaining earth dam shows that the former is inherently less stable and can be susceptible to cracking, liquefaction, erosion, and frost action, as illustrated by examples. Several methods are presented for building safe tailings dams using either the coarse fraction of the tailings or local soils, the important factor in each method being proper compaction of the material. The safety of existing tailings dams can be improved by flattening the overall slope, preferably by adding berms, or by decreasing the height. Where neither remedy is possible, the installation of electro-osmotic tie-backs is suggested. Dumps of mine spoil can be stabilized economically by compacting the material in layers along the toe to form a dam.

Jan 1, 1971

By Manuel Gomez

A general prediction model for the Hardgrove grindability index was constructed from 735 coal samples using the proximate analysis, heating value, and sulfur content. The coals used to develop the general model ranged in volatile matter from 12.8 to 49.2 percent, dry basis, and had grindability indexes ranging from 35 to 121. A restricted model applicable to bituminous coals having grindabilities in the 40 to 110 range was developed from the proximate analysis and the petrographic composition of the coal. The prediction of coal grindability within a single seam was also investigated. The results reported support the belief that mechanical properties of the coal are related to both chemical and petrographic factors of the coal. The mechanical properties of coal may be forecast in advance of mining because the variables used as input to the prediction models can be measured from drill core samples collected during exploration.

Jan 1, 1970

By Jeanne A. Zimmer, Andrew B. Cecala, Edward D. Thimons

The Bureau of Mines performed a study to determine optimal locations for longwall face methane monitoring equipment. Longwall face ignitions continue to be a concern to the U. S. coal mining industry. Gains in ignition control technology have been somewhat negated by advances in longwall productivity. More reliable, heavy-duty longwall face systems generate higher production rates and increase methane liberation rates. These rates will likely continue to rise in the future as further coal production increases occur. Efforts will continue in the areas of methane drainage, methane containment, and methane dilution. In addition, more effective face methane monitoring is needed. As technology continues toward automated longwall panels, the importance of monitoring for methane at the shearer becomes even more significant. Since the primary face ignition source is the shearer mining machine, the Bureau ran tests to determine the best location to take methane readings on the shearer. This information, in conjunction with data obtained from field studies, provides a knowledge base for selecting optimum face methane monitoring locations. INTRODUCTION Face ignitions are a concern for many U. S. longwalls and will continue to be until better control technology can be developed or until reliable and accurate knowledge can be provided as to when an explosive concentration is present. Figure 1 shows the number of reported U. S. underground longwall ignitions from 1980 to 1990. The number of longwall panels have remained relatively constant over this time period with 89 reported in 1980, compared to 96 in 1990. In spite of technological improvements in mining over the past decade, no significant reduction in the number of longwall face ignitions has occurred. One factor contributing to this is that the U. S. coal industry is mining gassier seams causing methane liberation rates on the average to be higher (Trevits, 1991; Grau, 1987). Another factor is the development and implementation of more reliable, heavy-duty longwall face systems that are generating higher production rates and higher methane liberation rates. Additionally, the average panel width in 1991 was 714 ft; a 44 pct increase from 1980 when faces averaged a width of 495 ft (Merritt, 1992). Increases in panel width also impact total face methane emissions. [ ] There have been substantial advances in control technology in the areas of methane drainage, methane containment, and methane dilution. In some mines, efforts to drain methane in advance of mining have proven effective, but geological conditions often preclude this approach (McCall, 1984; Ely, 1989). In other cases, ventilation air quantities of over 100,000 ft3/min and face velocities of over 1,000 ft/min have been implemented on longwall panels. Other operations have implemented anti-ignition spray systems which use water sprays behind each cutting bit to quench the hot streaks created from cutting noncoal materials (Courtney, 1990). Other control techniques, such as the modified shearer clearer system and ventilated drum, have been used to increase the amount of turbulence and ventilation around the cutting drums, thus reducing methane levels (Cecala, 1986; Divers, 1987).

Jan 1, 1993

By W. Rall, A. J. Birkle

The effect of fast-neutron irradiation on the micvo strcture of a common reactor pressure-vessel steel, A212 Grade B, was studied using thin-foil transmission electron microscopy. The dislocation density of the irradiated material is considerably greater than that of the nonirradiated control material. Annealing studies indicated that dislocations and hardness ill the irradiated material annealed out—as docs the radiation-induced embrittlement according to other- investigators— at temperatures STEELS in nuclear reactors are affected by neutron irradiation. In the American Society for Testing Materials (ASTM) A302B and A212B steels commonly specified by designers for reactor vessels, between 650° and 800°F. However, the dislocations and hardness in control samples cold-worked to 9 and 70 pct did not anneal out readily, and a high dis -location density was observed, even after a 1-hr anneal at 850°F. Based on the hypothesis that cllrster defects, rather than the increased dislocation density, are primarily responsible for mdicltiotz-iudziced e)nbriftlen7ent, reconzmendations are made for reducing the susceptibility to such ernbrittlement. exposures at a temperature of 550°F or lower to neutron dosages encountered during a 20- to 30-year life (-3 X 10'' nvt, >1 mev) may increase the nil-ductility transition temperature (NDT) as much as 300" or 400".'9 Therefore, to prevent brittle failures in reactor structures, extreme caution is required to reduce thermally induced stresses during all reactor shutdowns and startups when the temperature is below the NDT of the pressure vessel.

Jan 1, 1964

By A. Pinches, R. Winby, P. J. van Staden, M. K. Rhodes, P. C. Miller

This paper is a progress report on the commercialization of using bioleaching for base-metal concentrates. The paper focuses on bioleach processes for recovering copper from chalcopyrite and nickel/cobalt from pentlandite/pyrrhotite. Data is discussed from pilot-plant trials in which an overall recovery >95% was obtained for the bioleaching of copper from chalcopyrite. The pilot plant was operated in closed circuit with solvent extraction and electrowinning circuits for final metal recovery. For the bioleaching of nickel and cobalt from pentlandite/pyrrhotite, an overall recovery of 97% was achieved. Precipitation routines were used to produce a final nickel/cobalt product. The pilot plants were capable of treating a few kilograms of concentrate per day. Prominent features in the design of a 1-t/day (1.1-stpd) copper-bioleach demonstration plant for the treatment of chalcopyrite concentrate are discussed. The plant, which is now under design, will be constructed and operated based on the results obtained from the laboratory pilot-plant campaigns. Issues of scale-up for the demonstration plant, together with integration into upstream and downstream processing, are also addressed. Independently derived capital and operating costs are presented for a possible commercial plant. These cost studies indicate the principle economic issues in considering the application of bioleaching to the extraction of base metals. The benefits of bioleaching complex concentrates that are not amenable to physical beneficiation and economic treatment by conventional smelting are highlighted. Issues, such as the environmental aspects, that illustrate the benefits of bioleach technology are given.

Jan 1, 2000

By C. H. Herty

Almost every metallurgist who has given the Howe Memorial Lecture has had a personal contact with the distinguished gentleman to whose honor this hour is devoted. Unfortunately for me, such personal contacts were not possible. However, in the preparation of a thesis on the open-hearth process, one of my earliest tasks was to make a survey of the literature, and it was from Professor Howe's Metallurgy of Iron and Steel that I drew a number of references to previous work which formed the foundation for my reading. In his volume there is such a complete exposition of the then current thought on the subject of slags and on their role in the elimination of phosphorus from steel that I feel no hesitation in discussing in this Howe Lecture the subject of "Slag Control." In the present era of close specification, the drive for uniformity of product, and the close inspection of the product and of the cost sheet, the utmost efforts must be made to control the steelmaking variables to the best advantage of the steel producer. One of the major variables is the slag in the furnace and its effect upon the composition and quality of the metal. What advantages are to be gained from slag control? In the broad sense the advantages must be tremendous, because the very foundations of good steel melting are based on "shaping up" the slag to a point where, with proper temperature, the heat is ready for the final additions. Every melter works toward these ends through his experience with innumerable heats of steel. The elimination of undesirable constituents such as phosphorus and sulphur is entirely a matter of slag composition and physical nature, a point well known for over half a century. The role played by the slag in assisting in proper heat transfer from roof and flame to the steel has been equally well known. In more recent years there has come the problem of oxygen control in the more accurate gauging of additions for making high-grade rimmed steel for the new strip mills, and in the deoxidizing additions for grain-size control and cleanliness of forging steels, both carbon and alloy. In this problem the oxidizing characteristics of the slag are of prime importance.

Jan 1, 1940

By C. H. Herty

Almost every metallurgist who has given the Howe Memorial Lecture has had a personal contact with the distinguished gentleman to whose honor this hour is devoted. Unfortunately for me, such personal contacts were not possible. However, in the preparation of a thesis on the open-hearth process, one of my earliest tasks was to make a survey of the literature, and it was from Professor Howe's Metallurgy of Iron and Steel that I drew a number of references to previous work which formed the foundation for my reading. In his volume there is such a complete exposition of the then current thought on the subject of slags and on their role in the elimination of phosphorus from steel that I feel no hesitation in discussing in this Howe Lecture the subject of "Slag Control." In the present era of close specification, the drive for uniformity of product, and the close inspection of the product and of the cost sheet, the utmost efforts must be made to control the steelmaking variables to the best advantage of the steel producer. One of the major variables is the slag in the furnace and its effect upon the composition and quality of the metal. What advantages are to be gained from slag control? In the broad sense the advantages must be tremendous, because the very foundations of good steel melting are based on "shaping up" the slag to a point where, with proper temperature, the heat is ready for the final additions. Every melter works toward these ends through his experience with innumerable heats of steel. The elimination of undesirable constituents such as phosphorus and sulphur is entirely a matter of slag composition and physical nature, a point well known for over half a century. The role played by the slag in assisting in proper heat transfer from roof and flame to the steel has been equally well known. In more recent years there has come the problem of oxygen control in the more accurate gauging of additions for making high-grade rimmed steel for the new strip mills, and in the deoxidizing additions for grain-size control and cleanliness of forging steels, both carbon and alloy. In this problem the oxidizing characteristics of the slag are of prime importance.

Jan 1, 1940

Tooele Flue-type Cottrell Treater Discussion of the-paper of A. B. YOUNG, to be presented at the New York meeting, February, 1921, and printed to accompany MINING AND METALLURGY No. 162, June, 1920. HARRY V. WELCH,* Los Angeles, Calif. (written discussion).-The basic requirement in the electrostatic process of electrical precipitation is that gases containing solid particles in suspension are forced to pass through an electrical field consisting of an insulated high-potential wire, or other type of discharge member, and a grounded plate, or other, type .of collecting member. Commercial. operation and efficiency of precipitation are secured by electrical and structural arrangements to provide the maximum value of the variable factors modifying the degree of precipitation. That is to say: 1. A unidirectional flow, of high-potential current is vastly more effective in precipitation than a high potential alternating-current flow.

Jan 2, 1921

The Elura Orebody consists of a number of parallel, vertically oriented pipe-like structures of pyrite-sphalerite-galena mineralization located at the core of a structural dome. Concentric zoning of the mineralization into an outer Siliceous, intermediate Pyritic and inner Pyrrhotitic Zone has been previously recognized and is used in routine geologic modelling of the lead, zinc and silver grades.Statistical analysis of the metal grade distribution in the orebody has confirmed the importance of the mineralogical zones in the understanding of grade trends. The gradational nature of intra-zone boundaries, especially those related to the subjective definition of the Siliceous Zone, are apparent in the statistics.

Jan 1, 1990

By W. S. Gillam

A need for new supplies of fresh water exists today and in many specific areas that need is urgent. One solution lies in saline water conversion, a problem complicated by cost factors. The principles involved in saline water conversion, the status of development, and the estimated costs (present and future) of several processes are presented. Among the methods discussed are distillation, electrodialysis, and freezing. In general, the costs presented are based on a standardized procedure for estimating conversion costs, permitting a valid comparison among the various processes. The need for new supplies of fresh water and the potential benefits to be derived from an abundant supply of converted water are recognized by practically everyone concerned with water problems. The water supply problem exists today; it is urgent in many specific areas in this country and also in the world, and it will become more acute in the future. One answer to the growing problem of adequate water supplies is the development of new sources. Very significant quantities of brackish underground and surface waters exist in certain areas and an inexhaustible supply of ocean water is available. Thus in many areas water resources can be extended through saline water conversion. Congress recognized the need for new sources of fresh water in 1952 and passed the Saline Water Act, Public Law 448, amended it in 1955, and in September 1958, enacted Public Law 85-883, calling for the construction of at least five demonstration plants. The program is administered by the Dept. of Interior through the Office of Saline Water, and its primary objective is to reduce the cost of converted water produced, whether it be by development of new processes or improvement of known processes. This is a most difficult problem and one that will require several years of prodigious effort. It is difficult—not because of any intricate or new chemistry, engineering, or physics involved—but because of the difficulty in converting water at low cost. Whatever the sources of the saline water, the salts which are held tenaciously in solution must be removed before the water becomes suitable for industrial or domestic uses. Saline water is a relatively simple system of salts dissolved in water. It has certain chemical and physical properties that determine the various methods by which the salts may be separated from the water. The system, although not complex, in most instances, has had countless years in which to reach equilibrium and is, therefore, comparatively stable. Because of its stability, separation of saline solutions requires relatively large quantities of energy. The unique properties of water depend on the fact that its molecules are chemically active. The chemical and physical properties of water are associated with the type of bonding involved in the water molecule. Chemical changes such as hydrolysis, or rusting of iron, involve the breaking of chemical bonds between the hydrogen and oxygen atoms. Physical changes, such as evaporation in a boiler, the melting of ice, or the viscous resistance to flow in a pipe, involve breaking of the hydrogen bonds. (The hydrogen nucleus is so small that it can attract two negative atoms.) Thus water molecules not only combine with molecules of other compounds but even with one another; e.g., each molecule may be bounded to four other molecules. Water molecules cling to the ions of dissolved salt to form water-encumbered hydrated ions and they cling to one another to form entangling networks through which hydrated ions can be propelled only by tearing the networks apart. That is one reason why considerable energy still needs to be expended in our simplest procedures for purifying water. If water molecules did not have this habit of clinging so tenaciously to other molecules, and to one another, it would be easy to push salt ions past the water molecule and get a separation. But the water would not then dissolve salt, so the problem would not exist.' Water when heated evaporates very slowly, relative to other liquids having simple molecules. Vaporization involves the separation of molecules from the liquid, and this means overcoming the attraction between molecules which is due to the hydrogen bonding. The heat of vaporization for water is high; consequently, the boiling point of water is also high. Water boils at 100" C; hydrogen sulfide (H2S) at -60" C; oxygen (02) at -183" C; nitrogen (N2) at -196" C; and methane (CH4) at-161°C, even though the latter has about the same molecular weight as water. Because of these peculiar properties of water, it exists as a liquid on earth instead of a gas such as hydrogen sulfide or nitrogen and oxygen.

Jan 1, 1961

By Scott IA, Jefferson C, Dipasquale S

This paper describes the use of modelling and simulation techniques in the analysis of the heavy medium plant at the Lead/Zinc Concentrator of Mount Isa Mines Limited. The objective of the study is to determine how to increase heavy medium plant recovery at a higher than current rejection rate in order to achieve the desired throughput through the grinding and flotation sections of the concentrator. Three options were considered: 1. Install smaller aperture preparation on screen to enable the cyclones to be fed finer materials. Install smaller diameter cyclones. 3. Maintain low viscosity medium.

Jan 1, 1987

By A. Iván, Patiño C. Francisco, Flores B. Javier, Peréz L. Miguel, Hernandez A. Juan, Trapála P. Norma, Salinas R. Eleazar, Rivera L. Isauro, G. Flores, U. Mizraim

"Tills work is related with the production of tiles using wastes from mining and metallurgical industry of Hidalgo State, as raw material. These wastes present a majority particle size (60 %), minor than 53 m (mesh 270, in Tyler Series) with the following composition; 70.01 % wt. of Si02, 12.82 % wt. of Ah03, 3.80 % wt. of Fe, 0.70 % wt. of Mn, 3.98 % wt. ofK20, 3.34 % wt. of CaO, 2.50 % wt. ofNa20, 0.04 % wt. of Zn, 0.026 % wt. of Pb, 56 grams per ton of Ag and 0.6 grams per ton of Au. In this work, the partial results and experimental conditions for the preparation of some composites to produce tiles are shown. The composite that offers the best results in productions of tiles was that with 66.67 % wt. of mining waste, 26.67 % wt. of red mud and 6.67 % wt. of black mud.IntroductionTo now, mining activities carried out during more than 457 years in Hidalgo State, Mexico; has lead a great volume of wastes; which can be classified into different types, having among the more common; Acid mining water, solid transport water, elements in radical form, abandoned minerals without processing and processing minerals wastes known as burrows, being these the most abundant in the region counting with an approximated volume of 110 million of tons, presenting a fine particle size that can affect population health during windy epochs [1 -4].Form metallurgical point of view, is well known that a fundamental characterization study it is necessary to know the viability of reusing or recycling of these wastes. According this, these residues can also be considered as raw materials in other economical activities, due its Si, Fe, AI, Ca, Na and P oxides contents, its mineralogy and the distribution of chemical elements in the primary and secondary phases [1,2,5,6]."

Jan 1, 2012

By Richard L. Bullock

At the beginning of the previous chapter, variation in the types of room-and-pillar stopes were briefly identified so that the reader could begin to understand the extensive application of this mining system. These same variations will be reviewed and elaborated upon in this chapter while discussing the methods by which the material is extracted. FULL-FACE SLICING BY DRILLING AND BLASTING When the entire mineralized thickness is taken in one pass of mining, it is known as full-face slicing. There is no mineral of economic value intentionally left either in the floor or the back. Theoretically, there is no limit as to how high the face could be in a single pass. But there are practical limitations to equipment size, pillar stability, and control of local loose slabs on the face, roof, and pillars that dictate current practices. The range of face height of the 15 typical room- and-pillar mines covered in Table 8 (Sec. 1, Subsec. 7) from the Dravo report, 1974 was 1.7 m (5.5 ft) to 9.8 m (32.1 ft), the average being 5.2 m (17.1 ft). In the Gaspe copper mine, Murduchville, Que., the drill jumbos were constructed with an extendable tower for full-face mining up to 15.2 m (49.9 ft) if necessary. However, a more common practice at that mine is to take the ore in multiple slices (Hall, 1959). In many metal mines the normal practice when starting stoping is to drive a single development drift into the ore zone a distance that will allow at least four or five rooms to be opened on each side of the initial drift. Since this opening will probably serve as the main haulage drift, it should be kept as straight and as level as possible. As to the other criteria for the stope developments, it might be well at this point for the mine planner to review the remarks presented earlier (Sec. 1, Subsec. 7) on drifts, entries, and crosscuts for production. After the initial drift is driven, it should be slabbed to the full room width if it is not that wide already. Next, the future pillars should be marked on the ribs and the rooms driven between them. If the ore extends beyond the length of the initial drift and is to be mined in the normal sequence of mining, care should be taken in a random room-and-pillar system to see that the extension of the initial roadway remains straight. If pillar "spotting" is left to the shift foreman or to the miners, they probably will not realize the importance of maintaining a uniform pillar line next to the roadway, and of keeping the line straight. Invariably, a pillar will end up in the middle of the future drift extension resulting in a "dogleg" in a possible main haul- age road. While this error is not catastrophic, too much weaving in and out of pillars will certainly slow down future production haulage and needlessly increase costs. Face or Breast Drilling and Blasting Practices To drill and blast the initial advances into the rock, usually some form of cut pattern must be used. In room-and-pillar mining, when a pattern is drilled in a face and that face is the only exposed surface to which all of the rock must be broken, the pattern is known as a "face round" or "swing." The face to which the rock must be broken is referred to as a "free face." Thus the most common way to advance a room into virgin rock with only one free face is by drilling swings. If, after breaking around a pillar, taking down back, or taking up bottom, there is a second (or third) face exposed, a group of holes drilled nearly parallel to a free face and breaking to it is known as a "slab round" or "slabbing." In some mining districts it is also known as "slashing." Obviously, because two faces exposed offer less resistance to fragmentation than a single face, slabbing requires less drilling and fewer explosives than required to break the same tonnage with the same degree of fragmentation with swings. Therefore, it behooves the driller (or supervisor) to plan the combination of

Jan 1, 1982