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By W. D. Blackburn

If there is a single key to managing a mineral extraction company, it is the control of productivity. American labor costs, in general, tend to be in the range of 10%-15% of total costs. American coal mining labor costs, however, exhibit ranges of 30%-60% of total costs. Is it any wonder that the industry finds itself at a competitive disadvantage? When labor costs take as much as sixty cents of every dollar of revenue, there is little room for profitability. The American coal mining industry must set as a long range goal the reduction of labor costs to the 10%-15% range of total costs in order to be competitive.

Jan 1, 1986

By N. Greninger

The Bureau of Mines conducted a laboratory study of the measurement of the water and rock dust (RD) contents of synthetic mine-type coal dust (CD) mixtures using a commercial unit for measuring water content and several prototype radiometric units for measuring the RD content. The RD content ranged from 50 to 100 wt pct and the added water (AW) ranged from 0 to 15 wt pct. The total water (TW) content (intrinsic (IW) and AW) of a small dust sample could be readily measured automatically by essentially untrained personnel using a commercial unit. The RD content of a sample containing only IW could readily be measured by moderately trained personnel using several radiometric units. With gamma-ray devices, about 300 g of sample is needed. With the improved beta-ray device, about 25 g of sample is needed. With dry mine dust samples, the estimated RD error range for gamma-ray devices is 0.8 to 2.3 pct and 0.5 to 1.0 pct for beta-ray devices. However, the radiometric measurement of RD content was questionable if the dust mixture also contained AW or if it was uncertain whether the dust mixture contained AW.

Jan 1, 1988

By Thomas J. Blalock

The volumetric determination of uranium according to the method of Sill and Peterson (6),3/ which uses cerate oxidimetry after the separation of interferences such as sulfides and cupferrates, has been used for some time by the Bureau of Mines and gives satisfactory results for many of the samples tested. However, in those instances where the uranium content did not exceed a few tenths of 1 percent and iron was present in the range of 10 to 40 percent (as Fe203),4/ the method was cumbersome and unreliable. The need for a more accurate procedure for the determination of small amounts of uranium in the presence of large amounts of iron, such as in shale or black sands, prompted this investigation. The Bureau desired that materials containing as little as 60 p.p.m. of uranium be assayed within reasonable limits of accuracy. One of the primary aims of this work has been to eliminate, as far as possible, the necessity for repeated cup ferron extractions.

Jan 1, 1960

By A. J. Stosick, J. R. Hoffman, E. Rudy, St. Windisch

The binary alloy system Mo-C zoas investigated by means of X-ray, metallog/aphic, thermoanalytical, and melting-point techniques on chemically analyzed specimens. The system, Fig. 39, is characterized by three congruently melting, intermediate phases, Mo2C, n MoCi-x, and aMoC1-,, of which only Mo,C is stable at temperatures below 1650°C. Substoichio-metrzc (~32.5 at. pct C) dimolybdenum carbide undergoes a homogeneous sublattice order-disorder transformation at temperatures of approximately 1400°C, whereas hyperstoichiorrletric compositions undergo a discontinuous Phase change. The order-disorder transitions in the Me, C phases are discussed in terms of the structural changes involved in the transformation processes and the absence of long-range sublattice coherency in stoichiometric or hyperstoiclziomet-ric compositions attributed to the impossibility of obtaining long-range order in a linear chain of alternating carbon atoms and vacancies. From the experimental phase relutionships and the known thermody-namic data for Mo2 C, limits for the free energies of formation for the high-temperature phases r) MoC1-, and aMoC1-, are deriued and found to be in good agreement with data previously obtained from phase equilibria in ternary metal-carbon systems. IN the course of studies of the high-temperature phase relationships in ternary systems of refractory transition metals with carbon,' a number of inconsistencies found in previous work necessitated a reex-amination of some of the related metal-carbon binaries. A reassessment of the binary system data also seemed

Jan 1, 1968

By E. L. Atkinson, G. W. Leach

The paper discusses the reasons for the introduction of load-haul-dump (LHD) units into Greenside Colliery, and the circumstances leading to the replacement of conventional mechanized equipment on a trial basis in the mining operations on No. 2, 4, and 5 seams. An outline is given of the factors governing the selection and introduction of these units into coal mining, and the associated mining and engineering aspects involved in the optimization of their use. Operating statistics comparing the performance of conventional and LHD equipment are included.

Jan 1, 1979

By A. J. Goss, M. Tanenbaum, W. G. Pfann

THE purification of two metals, antimony and tin, by zone refining is described, and a reciprocating method of passing molten zones through a straight ingot, which effects a considerable economy of time and apparatus, is discussed. Antimony has been used extensively as a doping agent in germanium and silicon. More recently, it has become important in the preparation of new semiconducting compounds such as InSb, GaSb, and AlSb. High purity is especially necessary in this latter use, since the antimony may comprise as much as 80 pct by weight of the compound. Antimony is generally available in a commercial form of about 99.8 pct purity. Column 1 of Table I is a typical emission spectra analysis of commercially available 99.8 pct antimony. Zone refining has been quite successful in increasing the purity of such samples. Columns 2 to 4 of Table I are analyses of an ingot of the antimony of column 1 after the passage of seven molten zones in an atmosphere of nitrogen. The ingot length was 9 1/2 in.; the mean zone length was 2 in.; convection was the only means of stirring. The column headings are sample locations in inches from the leading end of the ingot. The results illustrate both the merit and a limitation of zone refining. It is seen that four of the five impurities—nickel, arsenic, lead,

Jan 1, 1955

By Charles M. Stone, Dale S. Preece

Introduction The Strategic Petroleum Reserves (SPR) is a national program dedicated to storage of large quantities of crude oil in leached salt caverns in the Texas-Louisiana gulf coast area. The program has required storage in existing caverns at each site and includes plans to leach new ones. The structural stability of each cavern depends on the behavior of the surrounding salt. In the past cavern stability has been predicted based on experience with other caverns in the vicinity. With the development of good non-linear finite element structural computer programs, it is possible to predict stability before the cavern is created. An important step in verifying the applicability of these predictive methods is comparison of analytical and field data. The analytical data come from finite element analyses of a specific cavern where the laboratory determined material properties and an approximation to the cavern geometry are used as input. These comparisons have been made for caverns in the Bayou Choctaw Dome (Louisiana) and Eminence Dome (Mississippi) with reasonably good correlation being obtained between measured and predicted volumetric response of the caverns. This paper discusses 1) the acquisition of material properties, 2) the finite element program SANCHO, and 3) the comparison of analytical and field data for each of the caverns.

Jan 1, 1982

By K. Cothern, S. Novack, D. A. Johnson, R. Borden, S. Pavlou

A procedure is presented for ranking hazardous waste sites for remedial decisions, and an example with application to mining waste sites is discussed. Typical contaminant concentrations are calculated from field data. Exposure indices that compare these measured concentrations with allowable limits are then computed. The limits are selected to protect both the health of humans (for both carcinogen and noncarcinogen effects) and the health of key organisms in the ecological food web. The additive exposure index for a site, defined as the sum of all contaminant-specific exposure indices, is then used in ranking the sites and assigning each a priority for remedial action. One key source of uncertainty in the process is the estimation of a typical site concentration from data that include values reported as "below certified reporting limit" (BCRL). This uncertainty is compounded in the additive exposure index and therefore may have a substantial effect on the assignment of remediation priority. A general approach is presented for incorporating consideration of BCRL data into uncertainty evaluation when assigning remediation priority designators to hazardous waste sites.

Jan 1, 1992

By J. DeYoung

Weak demand for metals and consequent low metal prices resulted in continuation of the depressed state of US mineral exploration activity through 1983. Data collected by Resources for the Future Inc. and The Pennsylvania State University for a cooperative study on mineral exploration activity indicate that US exploration in 1983 fell by as much as 25% from 1982 levels. Precious metals remained the focus of most exploration efforts, as gold and silver prices remained attractive compared to base metals. Reports of 1983 domestic exploration and development activities in several industry journals indicates that about 85% to 90% of those projects were directed primarily at gold and silver. Gold exploration included work by several companies on Carlin- type disseminated gold deposits in Nevada, geological prospecting and drilling in the Wenatchee Gold Belt in Washington, and interest in lode and placer gold properties in California, especially by several small Canadian firms. Precious metals exploration projects were also reported in Alaska, Arizona, Colorado, Montana, New Mexico, Oregon, South Dakota, and Utah. There was also tome precious metal exploration activity in the eastern US. Development continued at the Ropes gold mine near Ishpeming, MI, and companies explored historic gold-producing areas in the Southeast. Some exploration for nonprecious metals took place last year. Stratabound copper-silver deposits were examined in western Montana, and US Borax continued exploring molybdenum resources in the Misty Fjords area in Alaska. Work on these projects during 1983 may have been stimulated by time limits on the availability of certain federal lands for exploration more than by projected improvements in metal markets. During 1983, several papers were published on mineral exploration strategies and the future of US exploration. David Watson of Raymond Kaiser Engineers, in a paper presented at the 1983 AMC Mining Convention, forecast increased exploration activity for gold and silver because of world economic conditions. He added that antimony, manganese, chromium, graphite, mercury, tantalum, tin, and barite are also likely targets based on their limited domestic reserve availability. He cited concern over reported subsidized mineral production by foreign producers and US regulatory and land-planning policies as retarding mineral exploration activity. Douglas Cook of Freeport Exploration Co., at the same meeting, presented a paper that showed that a 1950-75 period of vigorous exploration has been followed by a period where acquisition has replaced exploration as the predominant means of acquiring new mineral properties. At a December IIASA conference on "The Economics of Mineral Exploration," in Vienna, Austria, A. Rose and R. Eggert of The Pennsylvania State University pointed out that recent exploration decisions tend to rely more on evaluating production costs and comparing them with existing deposits, rather than on return of

Jan 5, 1984

By Alexandre Silva Guimarães

Este trabalho avaliou a purificação de níquel em relação aos contaminantes cálcio e magnésio a partir de soluções sintéticas sulfúricas simulando os licores industriais obtidos pelo processo de lixiviação sob pressão de minérios lateríticos de níquel. O uso de Cyanex 272 (20% v/v) se mostrou ineficiente na purificação do licor em decorrência das extrações simultâneas de magnésio e níquel e pela baixa seletividade do Cyanex 272 em relação ao cálcio (extrações inferiores a 10%). A adição de 5% v/v de ácido naftênico ao Cyanex 272 (20% v/v) provocou a extração conjunta de magnésio e níquel e extrações insignificantes de cálcio (inferiores a 0,5%). A mistura de 20% v/v de Cyanex 272 com 20% v/v de D2EHPA, em pH = 4,5, é passível de promover a purificação do licor frente ao níquel, pelo fato desta combinação de reagentes extrair cerca de 50% de cálcio, 48% de magnésio com baixos teores de níquel (em torno de 10%), podendo-se utilizar dois estágios de contactação para se obter no mínimo 80% de níquel purificado em fase aquosa.

Aug 7, 2018

By Filipe Sathler

O projeto CR298 se iniciou no final do segundo semestre de 2014 quando o Coque Rate (CR) médio era de 351,0 kg/t. A meta definida foi de atingir média mensal de CR de 298 kg/t em dezembro de 2016, permitindo aumento de produção com alta taxa de injeção de carvão PCI, porém, com baixo Fuel Rate, garantindo competitividade de mercado. Sendo assim, foi desenvolvido e divulgado um novo modelo mental de operação, processo, manutenção e gestão, envolvendo toda a área de Redução, Utilidades e Aciaria. Várias premissas técnicas foram estabelecidas com um plano de ação detalhado para garantir estabilidade no processo dos altos fornos de forma a obter este resultado. A meta foi atingida antes mesmo do planejado: CR 291,3 kg/t em Maio de 2016 e em 2016 a média anual foi de 297,0 kg/t, com Fuel Rate de 484,4 kg/t.

Oct 30, 2017

By Fred H. Lightner

The feasibility evaluation of the Borealis project of Houston International Minerals Corporation (HIMCO) was initiated in October of 1980. The operation of the Borealis Mine and heap leaching plant began in late 1981. In order to achieve the rapid development schedule several items were necessary: 1) Pre-planning of environmental requirements and early study of key issues. 2) Adoption of conservative design criteria. 3) Coordination and cooperation between HIMCO and regulatory agencies. 4) Adoption of specialized engineering and construction procedures. 5) Careful evaluation of owner project management philosophy.

Jan 1, 1982

By Rudineli Demarque

Este artigo apresenta um estudo das características metalúrgicas, geométricas e microestruturais da soldagem TIG autógena aplicada em chapas de um aço AISI 304, o processo autógeno tipo cordão sobre chapa foi utilizado com a finalidade avaliar o comportamento deste aço quando submetido a ciclos térmicos distintos. A soldagem foi automatizada, na posição plana, e realizada com controle de velocidade com a finalidade de regular a energia adicionada ao material soldado. As variáveis de entrada foram a velocidade da tocha de soldagem TIG, e a corrente setada na máquina de solda. Foram avaliados os efeitos da variação da energia de soldagem sobre as características metalúrgicas do processo, sobre as características geométricas (penetração e largura) do cordão se solda, microestrutura, espaçamento dendrítico e microdureza da seção transversal da junta soldada. Os resultados indicaram uma forte influência sobre a geometria da junta soldadas, aumento de 28,5% na largura, 59,6% na profundidade e 44,6% na área, além de alterações microestruturais, aumento de 100% na quantidade de ferrita d, 12% na microdureza e 51,69% no espaçamento das dendritas no metal de solda, Além disso observaram-se ausência de defeitos nos passes isolados sobre as chapas.

Oct 30, 2017

By D. T. Peters, S. Floreen

The age hardening behavior of an Fe-8Ni-13Mo alloy was studied after the matrix had been varied to produce either ferrite, cold u~orked ferrite, or nzassive nzartensite. The aging behavior of the cold worked ferrite and murtensite structures were very similar. The martensite aging kinetics were much different from those observed in earlier studies of aging of maraging steels, even though the martensite wzatri.r had the same dislocation structure as those found in maraging steels. The results suggest that the previously observed precipitation kinetics of maraging steels ?nay have been controlled by the nucleation be-haviov, which in turn were dictated by the alloy compositions and the resultant identities of the precipitating phases. IT is well known that the rate of precipitation from solid solution depends not only on the degree of super-saturation, but also on the density and distribution of dislocations in the matrix structure. These imperfections often act as nucleation sites, and may also enhance atomic mobility. 'Thus, the presence of dislocations is important since the type and distribution of precipitates may be determined by them. The precipitate density and morphology in turn affects the mechanical properties of the alloy. A number of studies have been devoted to the precipitation characteristics in various types of maraging steels.'-" These are iron-base alloys containing 10 to 25 pct Ni along with other substitutional elements such as Mo, Ti, Al, and so forth, that are used to produce age hardening. The carbon contents of these steels are quite low, and carbide precipitation is not believed to play any significant role in the aging reactions. After solution annealing and cooling these alloys generally transfclrm to a bcc lath or massive martensite structure characterized by elongated martensite platelets that are separated from each other by low angle boundaries, and that contain a very high dislocation den~it~.~~~~~~~~-~~ Age hardening is then conducted at temperatures on the order of 800" to 1000°F to produce substitutional element precipitation within the massive martensite matrix. Most of the aging studies to date have revealed several common traits in these alloys, regardless of the particular identity of the precipitation elements. Generally hardening has been found to be extremely rapid, with incubation times that approach zero. The agng kinetics, at least up to the time when reversion of the martensite matrix to austenite begins to predominate, frequently follow a AX/~~ = ktn type law, where x is hardness or electrical resistivity, t is the time, and k and n are constants. The values of n are frequently on the order of 0.2 to 0.5, which are well below the idealized values of n based on diffusion controlled precipitate growth models. Finally, the observed activation energy values are typically on the order of 30 kcal per mole, and thus are well below the nominal value of about 60 kcal per mole found for substitutional element diffusion in ferrite. The common explanation of these observations is that the precipitation kinetics are controlled by the massive martensite matrix structure. Thus, the absence of any noticeable incubation time has been attributed, after ~ahn," to the fact that the precipitate nucleation on dislocations may occur without a finite activation energy barrier. The low values of the activation energy are generally assumed to be due to enhanced diffusivity in the highly faulted structure. If this explanation that the precipitation kinetics are dominated by the matrix structure is correct then one should observe a distinct difference in lunetics between aging in a martensitic matrix and aging the same alloy when it has a ferritic matrix. Such a comparison cannot be made with conventional maraging compositions, but could be made with the alloy used in the present study. In addition, the ferritic structure of the present alloy could be cold worked to produce a high dislocation density so that one could determine whether ferrite in this condition would age similarly to martensite. EXPERIMENTAL PROCEDURE The composition of the alloy used in this study was 8.1 pct Ni, 13.0 pct Mo, 0.10 pct Al, 0.13 pct Ti, 0.012 pct C, bal Fe. The alloy was prepared as a 40 lb vacuum induction melt. The heat was homogenized and hot forged at 2100°F to 2 by 2 in. bar, and then hot rolled at 1900°F to $ in. bar stock. The aging lunetics were followed by Rockwell C hardness and electrical resistivity measurements. Samples for hardness testing were prepared as small strips approximately 2 by $ by 4 in. thick. Electrical resistivity was studied on cylindrical samples approximately 2 in. long by 0.1 in. diam. The method for making the alloy either martensitic or ferritic was based on the fact that the alloy showed a closed y loop type of phase diagram. At high temperatures, above approximately 24003F, the alloy was entirely ferritic. Small samples on the order of the dimensions described above remained entirely ferritic after iced-brine quenching from this temperature. In practice, a heat treatment of 1 hr in an inert atmosphere at 2500°F followed by water quenching was used to produce the ferritic microstructure. These samples were quite coarse grained and usually en-

Jan 1, 1970

By M Chen, G H. Wang, J R. Zhou, P Yan, W B. Lu

Blast vibration analysis is one of the important topics in the control technology of blast vibration damage. Nowadays, blasting vibration safety standards are based on both the particle velocity and the frequency of vibration and they have been adopted widely and internationally. However, the analysis on vibration frequencies is less studied compared to investigations of peak particle velocity. For the vibration induced by a spherical charge in a viscoelasticly infinite rock mass, an expression of vibration spectrum taking into account the damping effect of rock mass is inferred. Then the attenuation laws of dominant frequencies and centroid frequencies are compared theoretically. For the case of cylindrical charge, dynamic finite element method (DFEM) software of LS-DYNA is employed to analyse the attenuation laws of characteristic frequencies. The research demonstrates that, no matter whether it is a spherical charge or a cylindrical charge, there is a local mutation or fluctuation at some distance when the blast proceeds, while the centroid frequencies conform to a smooth attenuation law. Both the multipeaks structures of vibration spectra and the decay rate difference between high- and low-frequency components contribute to the mutation or fluctuation investigated in this study. Additionally, an increase in longitudinally sonic velocity or the quality factor of rock mass produces an increase in the vibration frequencies, whereas an increase in blast source diameter or the rise time of blast load produces a decrease in vibration frequencies from a spherical charge. In borehole blasting, there is a positive correlation between the vibration frequencies and charge diameter, whereas there is a negative correlation with charge length. And altering the initiation plan will change vibration frequencies to various degrees. Finally, theoretical analysis results were validated by the empirical data from field experiments of Fengning pumped storage power station.CITATION:Zhou, J R, Lu, W B, Chen, M, Yan, P and Wang, G H, 2015. A further study on the attenuation laws of blasting vibration frequency, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 673–682 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By Madhu G. Ranade

A statistically designed pot grate- kiln test program was conducted to determine the agglomeration process variables necessary for increasing the low temperature disintegration resistance (LTD) and reducibility (R40) of magnetite-based Empire acid pellets. The ASTM tumble index and compression strength were to be maintained at an acceptable level. Six process variables, bentonite addition level, preheat time and temperature, firing time and temperature, and cooling rate, were investigated within the constraints of the Empire plant. The bentonite addition level and firing temperature had the largest effect on pellet properties. The results of this program were verified during a pl ant trial. The target firing temperature at the Empire Plant has been decreased for increasing the LTD and R40 of commercially produced Empire pellets

Jan 1, 1985

Early in 1950 a new laboratory was set up to deal with problems in mineragraphy, petrology and metallography. This paper describes the equipment, the organisation and association of the laboratory with the various departments of the company, the work that has been done and future plans.At Mount Isa it was soon realised that the microscope would play a most important role in mineral dressing problems and aiding geological research.As early as 1928, R. J. Colony submitted a petrographic report on Black Star ore for Consolidated Limited; much later, in 1934-5 Dr. Grondijs published for Mount Isa Mines Limited a preliminary study of the Mount Isa orebody, followed by a mineragraphicinvestigation of mill products, and in 1937 a Study of Mount Isa Ores by H. GrondIjs and C. Schouten appeared in Economic Geology, for June-July. Other papers dealing with the petrology and mineragraphy of Mount Isa ores are appended at the end of the paper.The mill research metallurgical staff has endeavoured to incorporate mineragraphy in solving milling problems and determining the effectiveness of laboratory as well as examining minerals sent in by the geological department.For many years the amount of equipment available was limited and much of it was locally made or improvised. An improvised briquetting machine, and grinding and polishing lap gave moderate results in conjunction with an old, but serviceable, Leitz microscope. However, for more detailed and accurate work not possible with improvised equipment, many mineragraphic problems were sent to specialist in.

Jan 1, 1953

By F. San Martin, Y. Lefevre, F. Tamargo

The San Juan de Nieva smelter was commissioned in 1960 with an electrolytic zinc capacity of 15,000 t/y. After a number of minor expansions, the capacity was increased to 320,000 t/y in 1991 and will reach 440,000 t/y by August 2001. The expansion involves the construction of a 900 t/day Lurgi roaster and a new acid plant. The leaching will be fully revamped and modernised, including the construction of a new building for residue treatment and for j arosite precipitation with a separate circuit for silver-containing concentrates. The project also includes the construction of a fully automated 137,000 t/y zinc cathode tankhouse fitted with 3.4 m2 cathodes designed by Asturiana de Zinc, and based on the existing tankhouse and introducing some improvements. New melting and casting facilities, also designed by Asturiana, will be constructed.

Jan 1, 2000

By R. L. Grant

At the Eighth International Conference of the Directors of Safety in Mines Research, Sartorius and Thouzea5/ presented and discussed data obtained in explosives tests made under varying conditions of humidity. These tests showed that there was less probability of explosives failure when the humidity of the testing gallery atmosphere was high. As it is to be expected that the relative humidity of mine atmospheres where permissible explosives are used will not be identical with that of the test-gallery atmospheres, the influence of atmospheric moisture upon the incendivity of permissible explosives is of the utmost importance if decreasing humidity reduces the relative safety of an explosive. Because of this and because the question has recurred frequently in discussions of gallery testing at Bruceton, Pa., it was decided to investigate the effect of humidity and ambient temperature on the ignition of firedamp by explosives, applying the small-scale gallery methods developed at the Bureau of Mines and used earlier to study the fundamental causes of such ignitions.6 7 8/

Jan 1, 1956

By J. Weinberg

This Bureau of Mines report presents data on the changes in the use of steel in motor vehicles over the past 35 yr. Sources of supply of steel for the automotive sector have shifted from almost all domestic in the 1950's to about 50% domestic and 50% foreign in the 1980's. Downsizing, design changes, and substitution of lighter weight materials to achieve energy efficiency also contributed to the market loss of the domestic steel industry. Although plastics and aluminum have displaced some steel in motor vehicles over the years, heavy low-carbon steel is now being replaced most rapidly by lightweight high-strength steel. If the percent of domestic steel used in motor vehicles had not declined since 1950, domestic industry would have supplied 9.3 million more short tons of steel than it supplied in 1985. Downsizing and design changes accounted for 43% of the loss; steel imports, 32%; and substitution of plastics and aluminum, 25%. In 1985, the total value of market share lost by U.S. steel producers was $5.1 billion, of which $1.6 billion was lost to foreign steel producers and automobile manufacturers. Through aggressive marketing and increased efficiency, however, the domestic steel industry may be able to recapture some lost markets, as applications for high-strength steels expand, and as foreign-owned automotive plants in the United States provide fresh sales opportunities.

Jan 1, 1988