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By M. H. Harris

A solution has been obtained to the problem of calculating flow into a cased and perforated well. Equations describing the idealized system were solved by numerical analysis techniques on a high-speed digital computer. Computer experimentation indicated that the results are within 3 per cent of the exact solution. Computed results are presented as an apparent skin effect, on a series of dimensionless working curves. Productivity ratios can be rapidly calculated from these data for the wide range of wellbore and reservoir properties actually encountered in field practice. Any reasonable vertical unisotropy ratio can be included in the computation. Productivities can be calculated for wells perforated in a regular pattern, a single horizontal plane or a vertical line on one side of the casing. Solutions for asymmetrical perforation patterns can he easily obtained from the working curves. Solutions for flow into sells completed with a horizontal notch are also provided. Results show that productivity can be increased by extending perforation penetration. This is especially true for shallow penetrations. The highest productivity is obtained when perforations are arranged in horizontal planes, as opposed to a vertical line on one side of the casing. Four or five perforations in one plane will approach the maximum productivity. The effect of perforation hole diameter is small, and is rioticeable only in shallow penetrations. INTRODUCTION The perforating method of well completion has been successfully and widely used in most producing areas. In the past, the desired perforation results were achieved by simply shooting numerous large holes in the casing. A perforating scheme for an area, or particular well, was established by evaluating two types of experimental data: the well flow index and the productivity ratio.' 3 The well flow index test is a means of determining the relative flow capacity of perforations in a linear system. This test also gives information on the perforation size, shape and hole damage which can be expected under well-bore conditions. However, relative flow data from this test cannot be accurately tarnsformed into the radial wellbore system. Thus, no true indication of the productive capacity of a perforated well can be obtained from the well flow index test. A well productivity ratio is derived from electrolytic models built to simulate perforated wells. Available productivity ratio data 2,3 are limited in that all important variables are not extensively evaluated. For example, data are limited to well radii of 3 and 6 in., and to maximum perforation penetration of 1 ft. Practically no information is available on the pattern of flow into a perforation. The effect of various perforation patterns on well productivity has not yet been determined and the effect of perforation diameter has not been thoroughly studied. Also, it will be shown that this type of electrolytic model data is probably in error by as much as 10 per cent or more. Modern completion techniques such as limited-entry perforating, single-plane fracturing, steam and hot air injection and chemical consolidation of incompetent formations all rely on injection and/or production from a limited type of completion. These completions may consist of several high-capacity perforations or a horizontal notch which is equivalent to an infinite number of perforations in one plane. Proper design of these new completion techniques requires, in part, accurate estimates of a well's productive capacity. Data on perforated and notched well productivity have been determined in this investigation. Results are presented as a function of the pertinent variables. Equations describing the idealized system were solved by numerical analysis techniques on a high-speed digital computer. DESCRIPTION OF PROBLEM PRACTICAL APPLICATION The computed results can be applied to wells which meet several general specifications. An external drainage radius of the well must be known or assumed, but the well need not be drilled on a regular pattern. The well must be cased and cemented through the entire producing interval. And, the casing must be perforated with one or more horizontal planes of perforations. The perforation pattern itself must conform to three geometrical requirements. 1. The perforations in a plane must divide the plane into equal angular segments (Fig. 1). Four perforations per plane would be 90" apart. 2. Perforations in a plane must be directly above or beneath perforations in adjacent planes. For two shots per plane, perforations would lie in the BB' plane (Fig. 1). 3. Horizontal planes must have equal vertical spacing and be separated from the top and bottom of the formation by one half the spacing interval. Single planes of perforations should be in the middle of the formation. This is shown in Fig. 2 where h is the formation thickness in a single plane conlpletion or the spacnig interval in a multiple plane completion. The spacing interval at the top and bottom of the formation may vary somewhat without causing an appreciable error in the productivity calculation if the formation is reasonably thick and there are many horizontal planes of perforations. A special provision has been made to calculate the productivity ratios of wells with uneven spacing intervals, or for the case where a single plane of perfora-

Jan 1, 1967

By G. E. Anderson

THE Asientos-Tepezala district is in the north of the State of Aguascalientes, about 30 miles north of the city of Aguascalientes, the capital. The district is reached by a standard-gage railway on the west side through the junction, Rincon de Romos, which is on the main line of the National Railways of Mexico from El Paso to Aguascalientes. The terminal is Tepezala. On the east side a narrow gage connects Asientos with the junction, San Gil, on the main line, Asientos to San Luis Potosi. Tepezala on the west side of the Asientos hills is about 2 miles from Asientos on the east side. The area between the two mining centers is separated by a low subued divide which forms the central part of the hills. The district is in a group of isolated hills surrounded by characteristic bolson plains. The hills rise above the surrounding plains about 6500 to 10,000 ft.; the highest peak is Alta Mira. The two mining districts lie somewhat upon the flanks of the hills at about the same elevation, 7200 ft. The district is an old one and has been known since early in the 17th Century when the mines were worked by the Franciscan Monks. Their mining operations which were limited to the oxidized ore above the water level, consisted chiefly in extracting silver from the Santa Francisca vein. To judge from the old workings and the remains of surface plant, the operations were on a large scale. By modern mining operations since about 1900, the various mines of the district have been one of the principal sources of ore for the smelter located at Aguascalientes.

Jan 2, 1926

By Carl R. Christiansen, James J. Scott

Advance mine planning, coupled with good mining practice, can be employed to develop underground space in stone mines for future industrial usage. To assure the developer the maximum return on his investment, initial planning should consider all aspects of the commercial operation, including surface layout, mining, and underground industrialization. The modular concept of mining to compartmentalize the space offers several advantages over conventional methods. Some expenditures can be considered as mining costs with a reduction of profit from stone production while lowering the capital requirements for conversion for usable space.

Jan 1, 1977

By A. H. Daane, B. J. Beaudry

The Sc-Ti system was studied by thermal, metal-lographic, and X-ray methods. Scandium was found to transform at 1334 °C from a (hexagonal) to ß which was concluded to be bee since a continuous series of solid solutions is formed between ß scandium and ß titanium at elevated temperatures. There is a minimum in the solidus at 51 wt pet Ti and 1300°C, a monotectoid at 1050°C and 49 wt pet Ti, and a eutectoid at 875°C and 91.5 wt pet Ti. The maximum solubility of titanium in a scandium is 13.5 wt pet at the monotectoid temperature, while the maximum solubility of scandium in a titanium is 6.5 wt pet at 875°C. SCANDIUM, a member of Group 111 A of the periodic table, and now called a rare-earth metal,' has become of interest recently due to its low density (2.99 g per cc) and relatively high melting point (1539°C).Spedding,' et al. have described a method of preparation of pure scandium metal and have made a study of its basic properties. Since scandium is approximately 10 to 12 pet smaller in at. diam than the other rare earths while its electronegativity and valence are the same, a knowledge of its alloying behavior in contrast to these elements should be very helpful to fundamental alloy theory. Since scandium is quite scarce and difficult to prepare in pure form, its use as a structural material by itself seems quite unlikely. However, its use in special cases as an alloying addi- tive to other low-density materials is a possible application; the Sc-Ti system was chosen for this reason and for others of fundamental interest. Scandium was suspected of having a high temperature bee form as do some of the other rare-earth metals.3'4 Since titanium has a high-temperature bee form, a continuous series of solid solutions at elevated temperatures between ß scandium and ß titanium would prove the existence and structure of the high-temperature form of scandium. The existence of a continuous series of hexagonal solid solutions at room temperature was predicted by Burkhanov and Savitskiy,5 but Hias shown to be incorrect in early X-ray studies. EXPERIMENTAL METHODS Materials. The metals employed in this investigation were crystal bar titanium and distilled scandium prepared by the method described by Spedding,2 et al. The major impurities are listed in Table I in PPm. Alloy Preparation. All the alloys examined were initially formed in a nonconsumable electrode are-melting furnace under an atmosphere of purified helium or argon. A curve based on the observed weight loss of 0.6 pet* when titanium was melted

Jan 1, 1962

By C. D. King

THE key to maximum production of ingots for the war effort is maximum production of pig iron. For any given furnace and ore, the most important single influence on blast-furnace production is the quality of the furnace coke. It is generally recognized that undoubtedly deterioration of Pittsburgh coking coals will be accelerated by the depletion of some of the better grades of coal; the extension of mine mechanization, with attendant degradation of coal quality; and the opening of new coal fields, some of which are known to be fairly high in sulphur. All of these factors, contributing as they do to higher ash and sulphur, and not infrequently to inferior quality of coke, made it desirable that an extensive study be undertaken to determine the effect of washing some coals that closely approximate the average chemical composition of coking coals to be expected in the future by the subsidiaries of the United States Steel Corporation in the Pittsburgh district. It was deemed advisable to study the improvement obtained by washing such coals and to determine the need for supplementing the existing coal washery at Clairton to assure continued maximum production of pig iron from presently available furnace stacks. The existence of the coal washer at Clairton made it possible to conduct tests on coals used in raw form and on similar coals after washing. This study covers an investigation of the quality of furnace coke as affected by washing coking coals, and is confined to the use of IOO per cent high-volatile Pittsburgh seam coals from Fayette and Greene Counties in the manufacture of furnace coke. It covers the improvement in chemical and physical properties as well as the degree of uniformity in coke obtained by washing these coals, and includes the effect on blast-furnace production and practice. The test period involved is four months; the plants, Clairton by-product coke plant, and the Carrie No. I and No. 2 blast furnaces at Rankin, Pa., Carnegie- Illinois Steel Corporation. Clairton By-Product Coke Plant And Coal Washer The Clairton by-product coke plant carbonizes 30,800 net tons of coal daily in 22 batteries containing 1482 ovens. Three oven sizes are used, commonly known as wide, medium, and narrow types, recognizing the difference in oven width. These ovens also differ in height and length. The present coal washer has a daily capacity of approximately 14,000 tons, leaving 16,800 tons to be carbonized in raw form. Washed coal is used on all the narrow ovens and on three of the six batteries with ovens of medium width, raw coals being used on all the remaining ovens. The customary arrangement is

Jan 1, 1944

By I. M. Bernstein

The steady-state creep behaviov of zirconium and zivcaloy-2 was examined in the temperature vatlge 520° to 620°C A1 low stresses the creep rates were cimracterized by a linear stress dependence; at highev stresses the stress dependence was much more pronounced. Temnperature-cycling tests yielded values for the aclivation enevgy for creep. Various tlzeories were examined in the ligltt of- the experimental re-sults and it mas concluded that the low-stress creep behavior is the result of the stress-direcled diffusion of vacancies along gain boundaries. It has been observed,"&apos; usually under conditions of high temperature and low stress, that creep deformation can occur for which the steady-state creep rate is linearly dependent on the applied stress. For magnesium and certain magnesium alloys, Harris and ones&apos; and ones&apos; have argued that this type of creep occurs by mass transfer as a result of the stress-induced generation and migration of vacancies, along a gradient defined by the stress direction. Jones&apos; demonstrated that the rate-controlling diffusion path is sensitive to grain size and temperature, and that by suitable control of these variables creep could occur by vacancy diffusion either predominately along grain boundaries or through the lattice. Recently, Jones3 suggested from an examination of limited high-stress data for zircaloy-2, composition in Table I, that significant diffusion creep could occur at low stresses, at least between 375" and 500°C, controlled by grain boundary vacancy diffusion. This process could have an important implication in assessing the role of zirconium alloys as a structural or cladding material in certain classes of nuclear reactors, since it predicts creep deformation far in excess of any estimates based on extrapolating slip creep data from higher stress levels. If the diffusion creep process occurs it should be possible to describe the total steady-state creep rate of zirconium and its alloys as the sum of two terms, Eq. [I]; the first term relates to a slip creep process important at high stresses and which is manifested by a much more pronounced dependence of creep rate on stress4 than diffusion creep and the second to a process controlled by mass transfer,5&apos;6 dominant at low stresses: where A and BI are parameters which can depend on structure, Ql and Q2 are the activation energies for the particular creep process occurring, and n describes the sensitivity of the creep rate on stress. It is the purpose of this paper to present some direct experimental evidence in support of this view. It is recognized that other analytical approaches have been proposed to explain data of this kind and these will also be discussed. 1) EXPERIMENTAL PROCEDURE Flat creep specimens (gage length 1 by 0.25 by 0.02 in. approx) were prepared from cold-rolled, argon-remelted, crystal bar zirconium and cold-rolled commercial-grade zircaloy-2, the analyses of which are given in Table I. The specimens were annealed at a pressure of < 10-5 Torr at temperatures from 625" to 675°C for 2 hr and slow-cooled. This treatment produced stable grains of average size (defined here by the average linear intercept) of for zirconium and -4xin. (-10 p) for zircaloy-2. The specimens were tested in a dead load tensile creep rig. The stress was maintained constant by adjusting the applied load after approximately each 1 pct of strain. The specimen temperature was controlled to better than +1°C. This system had a small thermal lag, so that rapid temperature changes were possible. To minimize corrosion, the specimens were tested in high-purity (99.95 pct) argon, further dried,

Jan 1, 1968

By L. A. Weakly

The Viburnum ore trend is the largest, single known ore body of lead in the world. Four well-known mining companies operate in the trend, which is approximately 64 km (40 miles) long and up to 610 m (2,000 ft) wide, located some 121 km (75 miles) southwest of St. Louis, MO. Total production from the mines for 1979 was 33 kt/d (36,000 tons) of ore or 472 kt/a (520,350 tons) of lead and coproduct metal. The district is the number one producer of lead, providing 90% of the United States&apos; output with its coproducts, zinc ranking second, and copper and silver both ranking sixth in total US output. Mining is done in a stratiform deposit approximately 305 m (1,000 ft) in depth with the host rock principally dolomite. Ore is mined in large open stopes by the method commonly referred to as room-and-pillar mining. Mining methods and equipment are fairly similar, with the mines classified as trackless, all mining equipment operates on rubber tires. This paper will present a description of the different methods and equipment used to move ore from the active heading underground to the ore shaft for hoisting to the surface. Basically, three methods are incorporated: front-end loader and truck haulage combination; front-end loader and truck, with main line track haulage combination; and front-end loader and truck, with conveyor haulage combination. The logistics of each system, such as method of use, equipment specifications, ore handling rate, and those cost figures that could be made public, will be included.

Jan 1, 1983

By J. L. Swedlow, M. L. Williams

Two standard techniques for assessing fracture initiatlon in sheet specimens involve measurements of 1) the applied load of fracture which, via linear fuacture mechanics, is used to find the fracture tough/less SC (or SIC), and 2) the velative displacement of fracture of the opposite free faces of the crack (COD). In the past, the quantitative association between these two parameters has not been determined in detail, owing to the mathematical difficulties of computing. the stress and strain fields in the combined elasto-plastic flow near the crack. Using a numerical technique Irecently developed and applied to a 7075- TO&apos; aluminum plane stress specimern, the two parameters noted have been determined and associated quantitatirely. CONSIDERABLE effort has been expended in selecting a rigorous yet practical manner for predicting fracture. The usual point of departure is the modified Griffith criterion in which the mechanism of energy dissipation is reflected in Sc (or SIC), the parameter of "fracture toughness". Sc. differs from the surface energy used by Griffith in perfectly brittle fracture in that it includes the effect of plastic flow in the vicinity of the crack tip. Because plastic flow alters the stresses and displacements predicted from the usual linear theory of fracture mechanics, and because analysis of the nonlinear stress-strain field has presented great obstacles: only estimates of several pertinent quantities have heretofore been available. Nevertheless, two parameters have often been measured experimentally althougll usually just at the point of fracture. These are the energy release rate, or fracture toughness 9, (or I,), and the crack-opening displacement (COD). Such observations have been used in connection with frarture criteria and have been most helpful in design, although their application requires care with respect to changes in geometrical configuration from that upon which the criteria were based 1,2 Recently, however, a reasonably accurate and comprehensive method for analyzing the elasto-plastic flow has been devised and applied to plane stress specimens having arbitrary octahedral stress-strain curves.3 It thus becomes feasible to compute, albeit numerically, both the fracture toughness and crack opening as functions of the applied tensile loading on a typical specimen geometry. As a result, it is now possible to associate these two parameters quantitatively, and thereby to associate data obtained by one method with data pertaining to the other. ELASTIC ANALYSIS For the case of linear elasticity, it is relatively easy to deduce the connection between various measures of crack deformation. Using, for example, the singularity analysis, it is found that the leading term of the Airy stress function x f°r symmetrically applied loadings on an isotropic medium is

Jan 1, 1968

By Sidney L. Wise, Walter Strache

While the installation of mine bulkheads to retain water under high pressure is by no means a rarity, the following points which arose in the designing and placing of two of these bulkheads may be of interest: The Hibernia magnetite mine, located about 40 miles west of New York, in the State of New Jersey, is partly fillcd with water. This mine is located on an ore lens, the outcrop of which is over a mile long. The ore has been mined from this lens from the surface to a depth of more than 1,500 ft. It was held desirable to separate the old workings from the new, and to allow the former to fill to the 850-ft. level. Two weak places existed between the new and old workings below this Ievel: namely, a temporary bulkhead on the 10th level and a rock bulkhead of indeterminate thickness on the 16th level. When the matter of allowing the old workings to fill was investigated, the fact was developed that if these old workings were filled, the bulkhead on the 10th level would be subjected to a water pressure of about 50 lb. per square inch, and that 200 lb. per square inch would act on the 16th-level bulkhead. As the above-mentioned barriers were not deemed of sufficient strength to permit of these pressures, it became necessary to design and install new bulkheads. Design As the 16th-level bulkhead was required to withstand a pressure of 200 lb. per square inch, it presented some difficulties. A careful consideration of the various types of mine dams now in use led to the adoption of a design of the form of a truncated wedge. In this, the pressure side of the dam is of greater area than the hack, so that the resultant action is similar to driving the wedge. By cutting generous skewbacks in the walls, roof, and floor, this type in reality becomes an invisible arch. The wedge feature tends to compress the materials in the bulkhead, thereby adding to its imperviousness.

Jan 1, 1915

By G. G. Waddell, T. J. Crocker, S. S. M. Chan

A successful engineering structural design often depends upon a thorough understanding of the material properties of the structure. It is no exception when designing a supporting system for stable underground openings. For this reason, studies were made in the deep mines of the Coeur d&apos;Alene mining district to obtain engineering properties of rocks and rock masses immediately surrounding underground openings. In this paper, data concerning laboratory tested physical properties of rocks and in-situ deformation behavior of rock masses from the Galena, Lucky Friday, and Silver Summit mines of the district are presented. Interpretations of the data so obtained and suggestions for the use of the results of the investigations as design criteria are also outlined.

Jan 1, 1973

Discussion of the paper of L. C. MORGANROTH, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 93, September, 1914, pp. 2345 to 2352. D. T. DAY, Washington, D. C.-I would like to hear some further detail as to the California deposits. L. C. MORGANROTH, Pittsburgh, Pa.-We have examined the California deposits at various times; I have been over practically all of them myself. These deposits are all of the massive variety. While it is possible that it could be mined and used for metallurgical purposes, it is not feasible because it costs too much. At the present time magnesite which is mined in California is used in the making of plaster, or by the paper trade. Careful figures show that if the California magnesite could be delivered to Atlantic seaports in the crude state at not over $4 a gross ton, and assuming that it would give the same results as the Austro-Hungarian magnesite, it would be cheaper to use the latter. It is also more difficult to dead-burn the massive magnesite, for while it starts to give up its gas readily, the difficulty consists in driving off the last few per cent., and unless this is driven off the magnesite will absorb C02 from the air, so that in a few months it may have 10 or 12 per cent. DAVID T. DAY.-How is the Austro-Hungarian supply at the present time ?

Jan 4, 1915

By Frederick C. Langenberg

A method is presented for computing the solubility of nitrogen in molten alloy steels. Examples are given to illustrate the procedure, and comparisons are made between predicted and measured nitrogen solubilities. THERE is an increasing use of nitrogen as a major alloying element in steels, or as a partial substitute for other alloying elements. Nitrogen is a potent austenite stabilizer, and Cr-Mn-low Ni-N steels, or even Cr-Mn-N steels, are being considered

Jan 1, 1957

By Allan Gibb

The ores of copper are usually associated with minerals containing arsenic, antimony and bismuth. Whatever the means adopted for extracting the copper, these metals are usually found, to a greater or less extent, in the product. There is, however, usually some elimination in the various metallurgical operations to which the ores are subjected, and some attempt is made here to determine the degree to which this elimination is effected.

Jan 1, 1903

By Clemens Catesby Jones

The substance of this paper, now amended and altered in form for its present use, was the basis of a private report prepared under professional engagement.* A private report is necessarily objective, and deprived of the scope and technicality of a scieintific treatise—which accounts for the prevalence of drawings and succinct mathematical statements rather than full descriptive details in a paper reproduced from data, of which all the original working-notes have been destroyed. In a practical sense the Hudson river valley clay-deposits owe their present existence to the protection afforded by the rock-formations on which they are supported, and, instead of being uniform in depth or continuity, are subject to the irregularities of the rugged masses which preceded and are now concealed by them. The only available information concerning these deposits contained in previous public reports or maps furnished at best a mere photograph of the surface, and as now apparent this was misleading or unreliable. It was the object of this investigation to determine in a practical manner the location, form and extent of all the clay-deposits at present existing in the lower Hudson river valley, and to ascertain with a

Jan 1, 1900

By AIME AIME

MINING men in general- are a roving lot but not so Selwyn G. Blaylock. Immediately after graduation from McGill in 1899 he went to the Trail smelter and he is there today though he spent three or four years of his early professional life at other British Columbia mining centers. Either he sensed the great possibilities of the company of which he is now vice-president and general manager, or it sensed his; more probably both. Certainly the association was a happy and fortunate one.

Jan 1, 1937

By L. W. Eastwood

The structure of eutectics has been studied by a number of investigators, and the complexity of the structural relationship of the components has been agreed upon, especially that of the "eutectic colony," type III of Portevin&apos;s1 classification. This paper does not attempt to alter the present classifications of eutectics; rather, it discusses the relationship between the macrostructure and the microstructure of the copper-cuprous oxide eutectic, and describes in detail the mechanism of the formation and the structure of the eutectic. Further, throughout the entire discussion it attempts to point out certain misconceptions in regard to the interpretation of the observed structure of the copper-cuprous oxide eutectic, one of the so-called "eutectic colony" types, and to correlate as much as possible the work done by the writer with that done by other investigators. Of the three types of eutectics listed by Portevin,2 the eutectic colony type has presented the greatest difficulty in interpretation. Although the copper-cuprous oxide eutectic is typical of the eutectic colony type in appearance, it may not be truly representative because the copper forms about 96 per cent of the eutectic and the cuprous oxide about 4 per cent. The interpretation of the origin and structure of the "eutectic colony" given here is strictly limited, therefore, to the copper-cuprous oxide eutectic. Macrostructure Fig. 1 shows the macrostructure of the eutectic at 3 diameters, the melt having been chill-cast into an iron mold, the resulting specimen sawed into two parts and the section polished and etched with the usual mixture of hydrogen peroxide and ammonium hydroxide. This specimen contains 0.48 per cent oxygen and is only slightly hypereutectic. If such a melt is allowed to cool slowly, large macrograins will form without the columnar structure of Fig. 1 and the well-known phenomenon of liquation will occur, forming copper oxide dendrites at the top and copper

Jan 1, 1934

By P. Somasundaran

Flotation of minerals has usually been discussed in terms of solid-liquid interfacial phenomena. This paper discusses the relative importance of phenomena such as collector adsorption at other interfaces formed between the bubble, liquid and solid. Adsorption of collector ions of various chain lengths at liquid-gas and solid-gas interfaces has been obtained. The data have been analyzed under conditions corresponding to those of flotation to show the significant role of collector adsorbed on the bubble surface in determining the bubble-mineral attachment required for flotation, and consequently to suggest consideration of this role in the development of better flotation conditions. Vacuum flotation of quartz with alkyl ammonium acetate reported in the foregoing paper1 showed that the collector chain length has an effect on flotation even at concentrations below those necessary for hemi-micelle association of the hydrocarbon chains at a solid-liquid interface. This chain length effect might be explained by the following arguments: Hydrocarbon chains find it energetically favorable to be in a medium of low dielectric constant. Considering the possibility of an iceberg structure at the solid-liquid interface, such a structure would produce a region of lower dielectric constant at the solid-liquid interface than in the liquid phase, because the dielectric constant of ice is 2 to 3,2 while that of water is 80. Depending on chain length, this difference will certainly cause even individual ions to adsorb in higher quantities at the solid-liquid interface. Another mechanism to consider is the possible formation of dimers, trimers, etc and chain length would influence this formation. But, above all, the chain length effect on flotation at concentrations of low adsorption at the solid-liquid interface could be due to the significant but often-neglected role of the collector adsorption at the bub- ble surface. Collector ions or molecules are adsorbed both at the solid-liquid interface and the liquid-gas interface. Below the concentration for hemi-micelle association at the Stern plane adjacent to the surface, the bulk of the collector ions adsorbed at the solid-liquid interface are in the diffuse part of the double layer. If such systems, where there is a gas bubble coming in contact with the solid surface, are to achieve some degree of electroneutrality, those collector ions would have to migrate from the diffuse part of the double layer to the region directly adjacent to the surface during the induction period when the bubble is making contact with the solid. The time necessary for this migration would contribute to the induction period required for creation of the solid-gas interface. It seems reasonable that the induction period could be reduced sufficiently for flotation to occur if these collector ions were carried to the surface by the bubble. In an attempt to ascertain whether or not the bubble could possibly have sufficient collector ions at its surface to meet the requirement mentioned above, the adsorption density of the collector ions at the liquid-air interface was determined. For this purpose, the surface tension of alkyl ammonium acetate solutions was determined as a function of concentration. Adsorption densities of the collector at the liquid-gas interface were calculated using the Gibbs adsorption equation: where y is the interfacial tension and ri and pi are the adsorption density and the chemical potential, respectively, of the chemical species, i. Using the convention that the adsorption density of water at the interface is zero, the following relationship is obtained for the liquid-gas interface where lg refers to liquid-gas interface and RA+ refers to the alkyl ammonium ions. For dilute solutions, rf^-wri^&rfwW [3] where C is the concentration of the collector ions in solution. l?:: can now be evaluated using Eq. 3 and surface tension measurements.

Jan 1, 1969

By J. Trevor Eyton

This paper addresses some of the financial risk hedging mechanisms available to a corporation contemplating entering the mining business at a significant level of investment. The approach which I have adopted is that of a case study relating to the risk hedging aspects of Brascan Limited&apos;s acquisition of 46% of Noranda Inc., formerly Noranda Mines Limited, followed by some remarks on options open to mining companies for reducing financial risks. To appreciate the rationale for Brascan committing over (Can.) $800 million to the natural resource sector, some knowledge of Brascan&apos;s parent company, Edper Investments Ltd., is required at the outset. Edper Investments, prior to acquiring a 48% interest in Brascan, controlled Trizec Corporation, one of the world&apos;s largest property companies. Edper also was involved in the financial services sector through Continental Bank of Canada and Hees International Corporation. For some considerable time prior to Edper&apos;s investment in Brascan, Edper felt a need to provide a better balance to its portfolio of property and financial services. Brascan was rich in cash, relatively unleveraged, and with important existing holdings in natural resources and consumer products. The acquisition of a controlling interest in Brascan provided an opportunity to balance Edper&apos;s portfolio of property and financial services with world class acquisitions in natural resources, supplemented by consumer products and financial services. The end result of Brascan&apos;s activities over the last few years is illustrated by the following analysis of the book value of Brascan&apos;s assets at the end of December 1983. [Can.$% Millions _ Natural Resources81748 Consumer Products 654 38 Financial Services 157 9 Other Operations895$1,717100% ] Source: Brascan 1983 Annual Report. The large emphasis on natural resources came about from the fact that for Canadians operating mainly in Canada, natural resources were attractive. We were impressed by Canada&apos;s position in the world natural resource industry as illustrated by some of the following statistics: [CommodityCanadian Estimated Production In 1983 As % of World Total Newsprint 30 Potash 21 Uranium 18 Molybdenum 17 Zinc 17 Pulp 16 Nickel 16 Saw Logs 11 Silver 8 Copper 7 Lead 6 Gas 5 Oil3] Source: U.S. Bureau of Mines and Brascan estimates. In addition, the quality of Canada&apos;s reserves looked good to us. The polymetallic nature of many of Canada&apos;s orebodies offered a hedge against risk relating to any one metal. Put another way, the by-product metal credits offered a net operating cost advantage with respect to many of the metals mined. Our energy costs also appeared to provide Canada&apos;s natural resource industries with an advantage. We considered Canadian mining expertise as amongst the world&apos;s finest, as were the exploration equipment and technology developed in Canada. In addition, Canada offered a stable political climate and one we knew. Further, we felt the Canadian Government&apos;s future role in the industry would, on balance, be benign, partly because the Canadian content of the mining industry was very high in contrast to the petroleum industry. Granted, we could find cheaper sources of copper; however, to do so would involve venturing into regions where country risks were higher.

Jan 1, 1985

By Henry S. Drinker

The Butler Mine property is situated in the vicinity of Pittston, in the Wyoming coal-field of Pennsylvania. The coal has been &apos; worked out from the fourteen-foot or Baltimore vein for a number of years on part of the tract, the old chambers remaining open as when originally abandoned. This vein outcrops on the Butler prop erty, and is nowhere more than sixty feet below the surface of the ground on the line of the cut-off to be described. Above the four teen-foot vein and about, say midway, between it and the surface of the ground, there is another small vein or rider of coal, about twelve inches in thickness. The rock between the two veins is a carbon aceous slate, about twenty-five feet in thickness. Above the smaller vein is a bed of sandstone, varying in thickness, but generally not less than from eight to ten feet. This sandstone is also carbonaceous, but the proportion of carbon is much less than in the slate below. Both rocks have been analyzed, and before the next Institute meet ing, the writer hopes to be able to furnish the exact proportions. The sandstone is overlaid with debris up to the surface of the ground. Some time during the spring of 1876, it was found that the coal left in the worked-out mine had been set on fire, and that the fire was gradually spreading. Inquiry developed the fact that the fire had originally been started by a woman, who had taken up her abode in an old tunnel leading into the workings. Owing to some delay in the early attempts made to extinguish the fire, it finally gained such headway that no ordinary means were found to be effectual. Finally, Mr. C. F. Conrad, civil and mining engineer, of Pittston, Penna., was called in as consulting engineer. He advised the making of a thorough cut through such portion of the old workings as had not been reached by the fire. It was found by survey that this cut could be limited to a length of about one thousand two hundred feet, as the vein faulted on both sides, and that the greatest depth of the cut would be about sixty feet. Subsequently it was decided to tunnel part of the way, thus saving the deepest portion of the cut. In 1856-7, there occurred a fire in the same mine. Two stone walls in V-shape running from the apex of the V towards the out crop, were built to cot the fire 06 and these walls were carried as far as the vein had at that time been worked. After the walls were finished

Jan 1, 1879

By J Price, M. R. Geer, H. F. Yancey

COAL mine operators recognize coal as an abrasive material, because the wear of drilling, cutting, and conveying equipment is reflected as a cost item for replacement of parts. Similarly, industrial consumers of coal experience abrasive wear on all coal-handling equipment. Operators of pulverized fuel plants are doubtless most keenly aware of the abrasiveness of coal, because under the high contact pressures developed between coal and metal in pulverizers, abrasive wear is increased many fold. Moreover, experience in operating pulverized fuel plants has demonstrated that some coals are much more abrasive than others. Hardgrove&apos; stated that maintenance costs entailed by the wear of grinding elements is often a more important variable than the cost of the power required to pulverize different coals. Craig2 also reports that one coal may cause pulverizer parts to wear several times faster than another. It is apparent, therefore, that those concerned with pulverizing coal could profitably employ a method for estimating the abrasiveness of different coals, just as they utilize standard tests for thermal value, grindability, and ash-fusion temperature to assist in selecting the most suitable and economical coal to use in a particular plant. The objective of this investigation was to develop a test procedure that would be suitable for general use in estimating the abrasiveness of coals. However, few, if any, of the standard tests now used for evaluating the properties of coal are the product of a single investigation or the result of a single investigator&apos;s efforts. Rather, in each case, a testing procedure was devised by one investigator, used by others on a wider variety of coals, and finally refined completely as the result of the joint efforts of a number of interested people. Thus, the test procedure for estimating abrasiveness developed in the course of this work may not be refined sufficiently in its present form for general use, but it may serve as the starting point from which an acceptable test procedure can be developed. The method has been used thus far on only about a dozen coals, and there has been no opportunity to attempt a correlation between experimental results and actual plant experience. Only wider use of the procedure by other investigators and correlation with plant experience can determine to what extent the method will have to be modified to render it suitable for general application. Test Method Although the literature contains no record of an attempt to devise a method for estimating the abrasiveness of coal that could be used industrially, several investigators have tested properties of coal that are closely related to its abrasiveness. The abrasiveness of a material generally is considered to be related to its hardness, and hardness tests for coal have been employed by Heywood,&apos; O&apos;Neill," and Mathes. Also, the resistance of coal to abrasion, a property that presumably is related to the abrasiveness of coal, was measured by Heywooda and by Simek, Pulkrabek, and Coufalik.2 11 these investigators tested only individual pieces of coal. Since coal is a heterogeneous material having components of varying properties, tests of this type can yield results having little more than academic interest. Only a test method that utilizes a representative sample of coal can give results that are useful industrially. The abrasion tests used for various other materials have been considered for adaptation to testing the abrasiveness of coal. The tests used for metals,7-9 paving and flooring,&apos;" and rubber," cannot be used because coal is not sufficiently abrasive.~ The present experimental work was begun before World War II and was conducted by three research fellows"&apos;" working under a joint agreement between the University of Washington and the Bureau of Mines. After a great deal of preliminary work with a variety of apparatus and materials, a test procedure was developed which consisted of rotating a test disk 2Yz in. diam in a steel mortar containing the coal sample. The shaft carrying the test disk at the lower end and a 100-lb load on the upper end was free to move vertically. The bed of coal in the mortar was kept fluid by low-pressure air admitted through a port near the bottom of the mortar. Measurable wear on an Armco iron disk could be obtained in this test procedure, but, despite extensive efforts to eliminate them, several major disadvantages remained in this test method. First, with most coals the amount of wear on the iron disk did not exceed a few milligrams. Second, a single type of disk was not applicable for all coals. A smooth iron disk gave satisfactory results with both bituminous and sub-bituminous coals, but hardly any wear with anthracite or coke. A disk having studs or projections gave more satisfactory abrasion losses with anthracite and coke and presented no operating difficulties with free-burning bituminous and sub-bituminous coals. It could not, however, be used with caking coals because these coals formed a

Jan 1, 1952