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By R. Hogg, D. W. Fuerstenau

Based on a simplified model for the motion of particulate materials in horizontal, rotating cylinders, approximate expressions have been derived relating the power consumption of a tumbling mill to its dimensions and speed of rotation and to the amount and nature of the charge. The basic assumptions underlying the model are that there is no slip between the charge and the mill shell, that the free surface of the charge remains essentially planar during rotation, and that there is no transfer of momentum from the material flowing down the free surface back to the mill shell. The relationships formulated from this model have been shown to be in excellent agreement with experimental results taken from the literature. While the requirements of the model are most clearly met at low speeds of rotation, the results appear to be valid even for speeds up to 70-80% of the critical speed. Poorer agreement between theory and experiment is found when the charge consists of relatively large particles (balls) and when the filling of the mill exceeds 50% of the available volume. Qualitative explanations of these deviations have been offered.

Jan 1, 1973

By H. Sato, R. J. Lipp, I. Iwasaki, K. A. Smith

Selective desliming holds much promise for upgrading low-grade, finely disseminated iron ores that are not readily amenable to conventional flotation. The process is extremely sensitive to the presence of calcium and magnesium ions that are in process water or are released by constituent minerals. The effects of these two alkaline earth ions on quartz were compared through streaming potential measurements, flocculation and cationic flotation tests, abstraction tests and scanning electron microscope studies. Calcium ion, adsorbed as CaOH+, and magnesium ion, attached by heterocoagulation as Mg(OH)2 precipitate, were responsible for the flocculation of quartz suspension and for the depression in cationic flotation of silica in alkaline pulp solutions. Magnesium hydroxide coating could be removed, similarly to adsorbed calcium ion, by complexation with EDTA and polyphosphates.

Jan 1, 1980

By T. Tanaka, H. Kiuchi

The combination of the following two exothermic reactions was studied with the purpose of recovering H2 from H2S formed in acid leaching of sulfide ores, direct reduction of metal sulfides with H2 or desulfurization of crude oils: In the kinetic study of the recovery of H2, the reaction rate was measured by the two methods of single-stage and circulation blowing of H2S through molten Pb in the temperature range of 550 to 750°C. The experimental results showed that the rate determining step is in the chemical reaction itself and also that this reaction is accelerated markedly by the addition of a trace of Ni, which may be responsible for the catalytic action of Ni dissolved in molten Pb. In the experiments where Pb metal was produced, PbS was oxidized in a stream of atmospheric N2 containing 0.5 to 20 vol-% 02 or in the same 02 partial pressures as in N2 though under reduced pressures in the temperature range of 400 to 800°C. It was found from these experiments that the formation of PbSO4, basic sulfates and PbO are suppressable to yield Pb metal alone above 750°C and for 02 concentrations of less than 1 vol-%. Vapor of PbS was thought to take an important part in the Pb formation mechanism, and the probability thereof was demonstrated thermodynamically.

Jan 1, 1978

By Philip R. Whitney

Deposition of manganese oxides is of common occurrence in streams of the north-eastern United States. Manganese entering the stream in solution in ground water is oxidized and deposited in the stream, primarily as oxide coatings on detrital materials. Prevalence and thickness of the coatings increases with increasing particle size in the coarse sand and gravel range. A number of metals of economic and environmental interest are enriched in these coatings. Samples of 8 to 16 mm pebbles were obtained from two streams in the Shawangunk region of southeastern New York State, an area of know71 Pb/Zn/Cu mineralization. The pebbles were leached to remove the oxide coatings and the resulting solutions analyzed for Mn, Fe, Pb, Zn, Cd, Cu, Co, and Ni. Trace-metal/Mn ratios in these streams are generally one to two orders of magnitude higher than regional background values. Profiles of trace- metal/Mn ratios along the streams show considerable detail; contributions of metals from tributaries are sharply reflected in the metal content of the oxides. The potential advantages and disadvantages of using coated stream gravel for geochemical prospecting and environmental studies are discussed in the light of these and other data.

Jan 1, 1976

By Robert M. Dreyer

Although lateritic ore deposits are relatively flat-lying, surficial ore bodies, the evaluation of lateritic bauxite and nickel deposits is among the most difficult problems confronting an economic geologist. Laterite is a soil formed under tropical conditions resulting in the concentration, within the soil zone, of certain trivalent metals-principally iron and aluminum, but also, locally, nickel and manganese. The soil zone is divided into two parts: (a) the true soil or lateritic zone and (b) the zone of partially altered bed rock or saprolite. Whereas bauxite generally is confined to the lateritic zone, some nickel deposits occur in both the laterite and saprolite zones. The evaluation of bauxite and lateritic nickel deposits thus has both similarities and differences. These ores have been formed by supergene, soil-forming solutions moving downward through zones of widely varying permeability within the weathering rock. Because the permeability varies widely, both vertically and laterally, the extent of weathering may vary greatly within short distances. Because the weathering process varies widely, the degree of metal concentration may also vary widely. It is not at all uncommon for a laterite to change, within a few centimeters, from a virtually valueless rock to a high grade ore. Moreover, the depth of weathering, and hence the depth and form of the ore profile, vary greatly. Obviously, for this type of deposit, a few grab samples or a few drill holes are virtually worthless. The evaluation of such a deposit requires a sophisticated statistical study based on thousands of carefully selected samples. As a rule of thumb, the cost of evaluating a large bauxite or lateritic nickel deposit will be about one cent per ton of ore in the ground. Thus, the cost of evaluating a several hundred million ton deposit may be considerable.

Jan 8, 1978

By Lester Woolsey

THE State Department can be of assistance to Americans in the petroleum business directly and indirectly. During the past few months, at the Arms Conference, it had a large hand in dealing with affairs indirectly affecting the oil problem. The conference has somewhat relieved the emphasis on naval strategy in relation to oil supply by limiting the number of naval vessels or the fleets of the Great Powers and in maintaining the "open door" in the Far East in respect of the development of the natural resources of that region by defining that policy in a nine-power treaty. The largest competitors of the. United States in the petroleum field are parties to that treaty. The Department of State also has stood steadfastly for the principle of equal opportunity in the Dutch East Indies, Mesopotamia, and Persia. The Department of State has been of indirect assistance in connection with oil problems by insisting on the recognition of treaty rights and other guar-antees, such as most-favored-nation clauses, and mandate provisions. I am not speaking as a representative of the Depart-ment of State, as L now have no connection with that institution, but my experience of several years as a member of the department and my practice since my resignation have given me opportunity to see the department from both the inside and the outside, and to measure its limitations as well as its resources.

Jan 7, 1922

By Richard E. McElvain, I. Cave

The selection of centrifugal pumps for mill discharge duty should be based on the total circuit concept. The practice of operating the mill circuit based on limitation of the pump can result in losses in one day which would offset the pump cost. Operating data from 25 grinding circuits have been reviewed and comparative results on added mill capacity have established advantages far beyond the less significant maintenance costs with increased circulating load and better cyclone operation. Mill discharge pumps should be selected on the following basis: i) Best available design for wear performance ii) Size to provide best economic life iii) Liner material best suited to circuit conditions Pump efficiency is a secondary consideration because power consumed by pumps is small compared to mill power input. Energy dissipated in mill pumps is contributing to comminution of ore.

Jan 1, 1982

By James F. Lewis

THE hematite iron ore mines east of the Hudson River are confined to a strip of country ten to fifteen miles wide, commencing on the south, near Fishkill, running northeast through Dutchess County, and striking the southeast corner of Columbia County, extending into Litchfield County, Conn., known there as the Salisbury mines, cropping out again at and near West Stockbridge, Lanesboro, and Cheshire, Mass., also in Bennington County, Vermont. The ores are found in beds or deposits and in veins, with a limestone ledge on one side and slate on the other, from six to thirty feet from the surface. Portions of it are quite solid, called rock ore, but

Jan 1, 1877

By Irwin Remson

Some unique hydrogeologic issues are inherent in the problems of siting, designing and licensing a mined geologic high-level nuclear waste repository. The problems involve hydrogeologically unfamiliar rocks for which little proven technology has been developed, long containment periods, elevated temperatures, and externally-imposed management constraints. In evaluating the existing national program, it should be recognized that hydrogeology is only one aspect of the total nuclear waste disposal problem, that the use of multiple barriers requires that the hydrogeologic system be considered in its entirety as a total system, and that engineering modifications can improve the isolation capabilities of certain barriers. Important research questions involve the mechanics of transport through dense fractured and unfractured rocks, methods for measuring vertical hydraulic conductivity, and a variety of geochemical questions. Current expectations for "high quality data" from either in situ or laboratory testing are unrealistic, and a modified approach to repository hydrogeology is needed. The dilemma is that the hydrogeological characteristics that make a potential host rock more satisfactory for respository siting are the same characteristics that are difficult to characterize and make the particular site more difficult to license. Finally, evaluation of the containment potential of any candidate site will become meaningful only with detailed underground exploration, mapping and testing in the host rock formations at the repository levels.

Jan 1, 1984

By Thomas M. Drown

THE means relied on to attain uniformity in Bessemer steel may be enumerated as follows : I. The appearance of the flame. II. The appearance of the slag. III. The spectrum of the flame. IV. Examination of the steel itself. At present, I wish briefly to bring forward a few considerations with reference to the last two mentioned, namely, the conditions favoring the employment of the spectroscope and examination of the steel. From the amount of careful investigation which has been devoted to the examination of the Bessemer flame by the spectroscope, both on the part of scientists and practical metallurgists, one might reasonably expect some results definite and satisfactory in their nature, first, as regards the nature of the flame, and second, as to the practical value of the spectroscope as a guide in conducting the process. We find, in fact, however, that uncertainty and confusion still exist. In Germany, where this subject has received the greatest attention, it is now very generally conceded that manganese is the cause of the well-known groups of dark bands that characterize the Bessemer spectrum. Nor is it easy to see how we can avoid accepting this conclusion, when Wedding and Von Lichtenfels have produced the manganese spectrum and found it to correspond closely with that shown by the Bessemer flame. But it is evident, on a moment's reflection, as Roscoe has recently brought forward, that manganese cannot be the only cause of the Bessemer spectrum, for we notice the characteristic bands quite as

By Waldemar Lindgren

I. Character of the Deposits, 226: Principal Features, 226 (Form, 227; Posi tion, 227 ; Constituent Minerals, 227 ; Exceptions, 228) ; Literature, 228 ; Geo graphic Distribution, 230 ; (California, 230 ; Idaho, 231 ; Arizona, 233 ; British Columbia, 233; Northwest Territory, 234 ; Mexico, 234; Other Countries, 235). 11. Origin oF the Deposits, 236 : Contact-Metamorphism, 236; Caw of Contact Metamorphism, 237 ; Similar Deposits of Different Origin, 240; Genetic Classifi cation, 240 ; Relation of Pegmatite- Veins to Ore-Deposits, 242. I.—Character of the Deposits. 1. Principal Features. In many schemes of classification and description the term contact-deposit has been somewhat loosely applied to all accumu-

Jan 1, 1902

By J. Landau, A. Dim, R. Houlihan

Recent developments in the application of solvent extraction in hydrometallurgical processing make it desirable to reassess the present state of availability of suitable equipment for these applications. The range of solvent extraction applications now includes very large scale applications with a modest demand on separation performance (the treatment of some base metals) and applications in which the decisive factor is a very high requirement on separation performance. The extraction column to be described in the present paper is of the type in which mechanical energy is provided for the two- liquid system inside the column. The active elements for this are reciprocating sieve plates designed and mounted so as to uniformly load the driving mechanism, to eliminate vibration of the plant, to have sufficient control over the degree of dispersion of the dispersed phase, and to reduce axial mixing effects, which are highly detrimental to the separation performance of production-scale plant. The operating features of the reciprocating-plate column will be illustrated mainly by experimental results obtained on a 4" diameter column in the extraction of uranyl nitrate with TBP. Some mechanical features of the operation of reciprocating-plate columns will also be discussed.

Jan 1, 1973

By J. H. Johnson, H. J. Schock

The cases of no auxiliary ventilation and ventilation with tubing were mathematically modeled, using a turbulent dispersion model. The Scooptram® used to load is modeled as a variable-speed, variable-strength source of pollutants moving in and out of the dead-ended drift. Model predictions are compared to experimental measurements. A parametric analysis was performed to determine If a relationship existed between C02 and NO levels. It was concluded from this analysis that when modeling a load-haul-dump cycle, it is necessary to use a model that can predict changes in source strength as well as source location. Carbon dioxide was used as a tracer to calibrate the model since, knowing the fuel flow rate, it is possible to calculate C02 production. The model was then verified after this calibration process using additional experimental results. With the calibrated model, it is possible to predict pollutant concentrations at any location in the heading using an engine map and the previously calculated flow field.

Jan 1, 1984

By F. R. Hensel

THE alloy under discussion is a nickel-silicon bronze and is one of many age-hardening or precipitation-hardening FIG. I.-EFFECT OF QUENCHING AND AGING TEMPERATURES ON HARDNESS OF TWO TYPICAL NICKEL-SILICON BRONZES, NO. 2351 AND No. 2362. copper-base alloys. The hardening con-stituent is a nickel-silicon compound.1 The quenching temperature necessary to pro-duce hardening by a subsequent aging treatment is a function of the composition and extends from about 700'C. to ()50'C.; the aging temperature range extends from 400° to 600°C. The work carried out by the authors of this paper was confined to cast alloys having compositions within the ranges of 1.5 to 3.00 per cent Ni; 0.4 to 0.75 per cent Si; balance, copper.

Jan 1, 1940

By G. Herget

Finite-element analysis of slopes and a field trial of a slope support system have shown that a considerable potential for excavation reduction exists if slopes are designed with variable slope angles with depth, and if artificial support systems are made an integral part of the slope design. A cost analysis has shown that the savings for a straight 500 ft. high slope with artificial support can amount up to $900 per foot of horizontal pit extension. Horizontal stresses and displacements can be overestimated by up to 100% by employing a two-dimensional finite-element analysis instead of a three-dimensional one. Stress magnitudes differ considerably when comparing results from slope models subjected to a gravity stress field with slope models subjected to high horizontal stresses. Because the latter case appears to be predominant for open pits, slope stability analyses have to be adjusted accordingly. A field trial measuring peak accelerations and displacements has shown that the use of pre- shearing for termination bench blasts, in cases of already heavily fractured ground, can be more detrimental than beneficial.

Jan 1, 1972

By L. C. Uren

THE resistance to flow of mixtures of gas and oil in passing up through the flow tubing of oil wells operated by gas-lift or by natural flow is a factor in oil-recovery technic that has received but little attention. Yet accurate design of a tubing installation for a particular set of conditions, where operation is by either of 'these methods, is impossible without quantitative data on the pressure loss suffered by the oil-gas mixture in its passage through the well tubing to the surface. Because of lack of such information, petroleum production technologists have been compelled to approach this problem by "cut-and-try" methods, which, doubtless in many cases, has resulted in the installation and use of tubing too large or too small for most efficient utilization of the expansive force of the gas used in lifting the oil. Impressed with the necessity for information of this character, the authors have conducted a series of tests with large-scale apparatus in the petroleum engineering laboratories of the University of California, designed to be productive of data that would afford a means of attacking the problem of flow-tubing design on a more scientific basis.

Jan 1, 1929

By Leo Brewer, Gerd M. Rosenblatt

Thermodynamic calculations predict the species vaporizing from metal-oxide mixtures when reliable free energy functions, enthalpies of formation, and dissociation energies are available for the possible gaseous and condensed oxide components. Calculations of the oxygen to metal ratio in the vapor phase compared with the oxygen to metal ratio in a liquid metal saturated with oxide impurity are presented The possibility of purifying metals contaminated with oxide by vacuum melting or by distillation is discussed. Kinetic considerations affecting rates are neglected. IN recent years extensive information has been obtained on the thermodynamic stability of gaseous oxides of metals due to a variety of new types of measurement. Perhaps the greatest amount of information has come from the application of mass spec-trometry to the study of high-temperature vapors.' In many instances oxides of quite unusual oxidation states are found to be important in the high-temperature vapors. At low temperatures the standard free energy change for a reaction as given by the equation ?F° = ?H° - T?S° is determined primarily by the AH" value. However, at higher temperatures where the value of T in the T?S° term is large, the entropy term becomes equal to or greater than the AH term. At low temperatures only reactions for which AH is negative or only slightly endothermic are of importance. This restricts the main equilibrium species largely to those with completed octets or those with the principle oxidation number of the element. At

Jan 1, 1962

By R. G. Mallon, R. L. Braun

Primary copper-sulfide ore deposits that are well below the water table can be chemically mined by in-situ high-pressure leaching. The leaching is accomplished by pumping oxygen gas into the bottom of a large underground flooded column of rubblized ore. Part of the injected oxygen dissolves under the high hydrostatic pressure in the column. With a high enough injection rate, the excess oxygen gas induces a convective circulation of oxygenated solution within the rubble column, which transports dissolved oxygen throughout the system. At elevated temperatures, this results in a relatively rapid dissolution of the copper minerals. A method of calculating the leaching rates is presented. The calculation is done by means of a finite-difference computer code that couples all of the processes relating to copper leaching, convective circulation, and the injection, dissolution, and consumption of oxygen. Results of the calculation for a typical case show that over 70% of the copper can be extracted in less than six years with good efficiency in oxygen utilization.

Jan 1, 1976

By Joe L. Ratigan

INTRODUCTION Rock mechanics engineers are seldom concerned with obtaining the tensile or fracture strength of brittle rock at low mean stresses. The reason for this is two fold. Firstly, the behavior of many excavations in brittle rock is controlled by the inherent discontinuities in the rock mass. Because of the jointing and faulting, tensile strength is usually taken to be negligible. The second reason that tensile strength is seldom obtained in the laboratory is that the technology of utilizing this strength measure in design is undeveloped. Despite the fact that tensile strength of brittle rock is often ignored, there are a number of applications in rock mechanics wherein the knowledge of tensile strength is of fundamental importance. The apparent tensile strength must be known in a hydraulic fracture experiment if the state of in situ stress is to be determined from the initiation of the hydraulically induced fracture. In certain underground situations, the apparent tensile strength of intact rock beams defined by jointing or bedding planes is important in determining required rock bolting. Numerous other situations require a knowledge of apparent tensile strength including such high technology uses of underground space as geothermal energy extraction and LPG storage. Three observations are invariably made when intact rock samples are taken into the laboratory and tested to determine tensile strength. (1) The apparent tensile strength depends on the sample size (the 1 arger the specimen, the lower the tensile strength)

Jan 1, 1982

By I. Plaskin

Interaction of sulfide minerals and native metals I with reagents in flotation is largely determined by particle-surface changes resulting from action of the medium and dissolved gases. A number of early studies were devoted to the selective action of various gases on minerals.' Mc-Lachlan' paid attention to oxygen as the most active gas affecting flotation properties of sulfide minerals. Opposing views were expressed concerning the influence of sulfide oxidation on xanthate flotation: Taggart3 recognized the positive influence of oxygen, and I. W. Wark4 rejected it. Shvedovh ffered the hypothesis of partial oxidation. As to the influence of such gases as hydrogen" and carbon dioxide on mineral floatability, opinions also differed. Effect of Oxygen on Sulfide Mineral Flotation: Research on the influence of oxygen and other gases on the floatability of sulfide minerals and native metals has been carried out at the Institute of Mining of the USSR Academy of Sciences in

Jan 1, 1960