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By M. Karmis

Surface subsidence is an inevitable consequence of many underground mining operations and has been recognized as such since the fifteenth century. Damage resulting from this phenomenon ranges from simple land settlement to severe structural damage to buildings and has been witnessed in rural (Illinois, Colorado, West Virginia, Virginia, Pennsylvania) as well as in urban areas (Pennsylvania, West Virginia, Illinois, Wyoming). In fact, it is estimated that over 2 million acres of land across the United States have been affected by mining subsidence, of which 140,000 acres are in urban areas (Singh, 1978; Johnson and Miller, 1979). Further, it is estimated that during the next twenty years an additional 1.5 to 2.4 million acres of land will also be affected by mining. Subsidence prevention is not feasible, at least under the existing technologic and economic constraints of underground coal mining. Foreign experience has demonstrated, however, that subsidence can be successfully controlled if an accurate method of predicting ground movements is available. Such techniques have been developed in many coalfields, where it is currently accepted that subsidence can be predicted within ± 20 percent of the actual values. Furthermore, such movements can be translated into anticipated structural failures using established damage criteria, thus enabling appropriate precautionary measures to be implemented.

Jan 1, 1983

By L. L. Hirst

Liquid fuel oils possess certain advantages over solid fuels. Ease in handling, precision temperature control, and almost complete freedom from ash are among those considered when a liquid fuel is selected for use in industrial processing. In some instances these fuels are desirable because more heating units can e packed in a Given space where space is limited, as on snips. In other cases the' are chosen because of lower actual cost per British thermal unit absorbed, or for control of the flame to increase the capacity of furnaces, as in steel and refining.

Jan 1, 1948

By Dennis J. Grigal

The goal of the program is to develop a dust collector system mounted on a ranging drum or arm shearer which will: 1) reduce the respirable dust level of the shearer operator by at least 75 percent; 2) be easily and economically mounted on an existing shearer; and 3) will not, through modifications to the shearer, reduce its safety or productive capability. The development program consists of three phases covering the activities of the design of the dust collector system, fabricating and installing it on the ranging arm or drum shearer, and conducting underground field tests on the modified mining machine.

Jan 1, 1980

By Frank T. Greene

An investigation of the quenching behavior of coal dust-air flames was carried out. The literature relevant to coal dust-air flames was reviewed, including information on the agglomeration, sedimentation, and dispersal of dust clouds. The simple equations relating the various concentrations involved in dust flame propagation are given and their implications elaborated. It is shown that the concentration seen by a moving flame in a sedimenting dust cloud can differ significantly from the concentration commonly measured in such experiments. The known dust cloud phenomena which appeared significant in flame propagation studies were experimentally evaluated, and quenching diameters, flame speeds, and lean propagation limits for several tube diameters measured. For Pittsburgh seam coal, the Minimum Quenching Diameter (MQD) for dust between 10 and 20 µm was found to be between 0.7 and 0.8 cm, and the lean propagation for 3.2-cm tubes to be approximately 200 mg/liter. Similar MQD data were also obtained for Pocahontas and Sewell coals, Beulah lignite, and a 50-gal./ton oil shale. The effect of temperature, coal particle size, and propagation tube material were also investigated.

Jan 1, 1981

The day after I reached New York, on January 30th, John Ryan of Anaconda told me where they wanted me to go. Late in 1916 the Russian Czar, desperate for money and supplies with which to carry on his unhappy share In the first World War, sent emissaries to the United States to see if our great mining companies might be interested in trying to find mines and to bring them to production in the millions of acres of the Imperial Estates in Russia and Siberia. It looked like a long chance as no one knew whether or where there might be important ore bodies. Even if they found them it might be a hopeless task to equip them under wartime conditions But the American copper companies had plenty of money and they were used to taking risks. They made a supersecret agreement with the Czar's deputies to send an exploring expedition to Russia at once I never learned the names of the other companies but Anaconda was to man- age the venture. Horace Winchell, then the leading mine geologist In the United States, was to be in charge of operations. Charles Janin, an eminent placer and dredge expert, was to study chances for producing gold and platinum. Though at 33 years of age I was much younger than the others, I was chosen to hunt for copper and other valuable metals. Charles Boynton, a business man who had lived in Russia and had married an attractive Russian woman, was to join the party and carry on any necessary financial or diplomatic affairs. He had gone on ahead to arrange for our reception Finally a graduate student from Ann Arbor named Steinberg was to go along as Interpreter. We soon found out that if his Russian was no better than his English his interpretlng couldn't be trusted too much I knew nothing about the millions of square miles In Russia and Siberia, and even less about what mineral deposits might be found, but I was delighted at the prospect. I was treading on air for the few

Jan 1, 1976

By Juh W. Chen

A process for recovery of energy from waste coal fines was investigated. The process, which was developed through laboratory, bench, and pilot plant scale experiments, consists of mechanical cleaning followed by high temperature oil agglomeration and pelletization. The process can produce a quality product under an economically and environmentally acceptable condition. Waste coal fines with ash less than 35: and HHV greater than 6,000 BTU/1b have been upgraded to a product with less than 15% ash and HHV Greater than 11,500 BTU/lb. A computer model has been developed to optimize the processing costs and to perform economic evaluation of specific sites. Ultimately tine model can be utilized to establish a priority listing for a region in assisting the determination of reclamation strategy.

Jan 1, 1983

By T. W. Johnson

The United States Bureau of Mines, in cooperation with the Natural Gas Department of the American Gas Association, has been studying actively for the past-several years the flow of natural bas through high--pressure pipe lines.4 This report deals with that part of the study involving the design of pipe-line, systems consisting of lines laid parallel to each other. The lines are deferred to as the original line and the parallel line. The paralleling line may or may not extend the entire length of the original line; however, the parallel line is, connected at its two ends to the original line. As a result of the large expansion of the natural-gas industry almost all markets within economic distance from the developed gas fields have at least one pipe line supplying them with natural gas. Small increases in the consumers' demand for natural gas can be met usually by increasing operating pressures, but any marked increase in demand necessitates paralleling sections of the existing systems. It is believed that to a large extent future

Jan 1, 1934

By Vitor de Oliveira Campos

Vários resíduos gerados nos processo siderúrgico são fonte de ferro e podem ser reciclados e reintegrados de volta ao ciclo produtivo do ferro. Exemplos incluem pós de coletores e despoeiramento, carepas e lamas. Estes materiais são geralmente classificados como rejeitos e são descartados em aterros a um alto custo, mas adquirem um valor significante quando reciclados e reutilizados apropriadamente. O presente estudo consiste em demostrar a viabilidade da utilização destes resíduos em um processo de mini sinterização, plantas de sinterização produzindo até 1 milhão de toneladas por ano. O produto obtido apresenta propriedades químicas e físicas adequadas para carregamento direto no alto-forno, para utilização como nucleante na sinterização, ou como refrigerante no convertedor. O balanço do zinco e dos álcalis é de extrema importância para viabilizar um sínter final com qualidade requerida e será analisado neste estudo. Conclui-se que a utilização dos resíduos citados é economicamente viável e o estudo de caso apresentado neste trabalho comprova o benefício com retorno significativo.

Aug 1, 2018

By S. S. SHINDE, P. C. JIKAR, N. B. DHOKEY

Mill scale is an oxide waste product of steel mills, containing around 70 percent iron and other allied impurities. In the present context, a dynamic prototype counter-current reactor (CCR) was used for the experimentation and simulation of a particle bed using the discrete element method (DEM). Mill scale was pulverized to ASTM mesh range 140 (106 μm)/+ 270 (53 μm) and oxidized in a CCR to make a single oxide Fe2O3 phase by maintaining the required thermodynamic conditions, such as pure oxygen at 1,100 °C. This oxidized powder was then subjected to a reduction reaction in the CCR, with gas mixture (H2:N2) ratio of 1:4 at 875±5 °C for filling degree, fd , and reactor revolution, ω, ranging from 5.38 to 16.14 percent and 2 to 5 rpm, respectively. A creeping fluid flow condition (Re < 1) and natural heat convection (Gr/Re2 >> 1) were maintained during the solid–gas reaction, and the particle-bed behavior was quantified by Froude number for the optimum operating window. The simulation was validated with the experimental results of reactor reaction product by X-ray diffraction (XRD) and scanning electron microscope (SEM) images.

By Mariana Peixoto

Muitos componentes de ferro fundido ficam expostos a altas temperaturas quando em serviço, podendo ocorrer a decomposição da perlita através da difusão do carbono da cementita para as lamelas de grafita, resultando em alteração microestrutural e degradação das propriedades mecânicas. A influência que a temperatura e o tempo de exposição têm sobre a microestrutura de um ferro fundido cinzento foi avaliado em amostras de quatro ferros fundidos de mesma base, com diferentes percentuais de cromo e molibdênio. Ensaios de banho de sal a uma temperatura de 500ºC foram realizados em corpos de prova com diâmetro de 10 mm. Os ensaios foram realizados com tempos de exposição a esta temperatura, após homogeneização térmica do material, de 0, 1, 2 e 4 horas. As análises metalográficas evidenciam a ocorrência da decomposição da perlita. Adicionalmente foram realizados ensaios de microdureza, a qual se mostrou sensível às alterações microestruturais geradas pela temperatura elevada. O ferro fundido com maior percentual de cromo e molibdênio apresentou melhor estabilidade da microestrutura para as condições ensaiadas.

Aug 17, 2017

By J. P. McGee

The Bureau of Mines is doing research and development work on a coal-fired gas turbine plant initially developed by the Locomotive Development Committee, (LDC) of Bituminous Coal Research, Inc. The Bureau is redesigning the turbine blading and some of the auxiliary equipment, and is reerecting, the plant at the Morgantown (W. Va.) Coal Research Center. The present goal is a 1,500-hour run at virtually the same operating conditions used by the LDC in their final 1,100-hour test with the turbine. This will allow the Bureau to properly evaluate the new blade design. Erosion of the turbine blades (particularly the roots) by ash in the hot gases from the combustion of coal was the most serious problem in extended operation in earlier experimental work. New blades made of Stellite6 are being fabricated for the stator and rotor, and armored wear strips of titanium carbide will be inserted in the blades at the areas of probable maximum ash velocity and concentration. The trailing edges of the rotor and stator blades are being thickened and thinned, respectively, to induce the ash to travel to the casing and prevent it from returning to the base of the rotor blades. The first stage rotor and second stage stator blades are being removed to provide an annular space for maximum quantities of coal ash to centrifuge to the casing. Additional blades will be added to most of the rows in the stator to stop secondary flow of dust-laden gas toward the rotor. A contract has been awarded for fabrication of the new blades. The 1,500-hour run will be started as soon as the new blades are installed.

Jan 1, 1962

By João Geraldo Alves

A qualidade interna das placas obtidas no lingotamento contínuo é afetada pelas características do escoamento do aço líquido no distribuidor. O modelamento matemático é uma ferramenta muito utilizada para estudar o escoamento do aço líquido e a eficiência do uso de modificadores de fluxo na separação de inclusões do aço no distribuidor. O objetivo deste trabalho é determinar, através da modelagem matemática, uma configuração de barragem e dique que possa proporcionar uma melhor qualidade do aço lingotado. Essa modelagem utiliza recursos do software comercial ANSYS CFX, que é um software baseado no método dos volumes finitos para a solução de problemas da dinâmica dos fluidos computacional (CFD – Computational Fluid Dynamics). A utilização de barragens e diques permitiu uma melhora significativa nas condições de escoamento do aço, o que possibilitará uma melhor flotação e separação das inclusões, com um aumento no tempo de residência do aço no distribuidor, quando comparados com o projeto do distribuidor atualmente em uso.

Jul 30, 2018

By O. P. Arora, M. Metzger, G. R. Ramagopal

The rates of grain boundary and general corrosion were surveyed by an approximate method. Quantitative differences between their variations with the strength or cupric ion content of the acid yielded large variations in their ratio, highly selective intergranular attack being observed only under specific chemical conditions. The boundary corrosion rate increased with the copper content of the aluminum; this was attributed to an autocatalytic effect similar to the one shown for general corrosion. High- purity aluminum in hydrochloric acid exhibits striking intergranular corrosion and other structure-dependent corrosion phenomena of fundamental interest. The behavior is highly sensitive to the metallurgical and chemical conditions, the significance of many of which has not been established. The features of the intergranular-corrosion phenomenon, first described by Rohrman,l are summarized in the remainder of this paragraph. Strong attack normally occurs only at high-angle grain boundaries.&apos; Usually 15 to 25 pctHCl is used to obtain a high rate, but this has also been obtained with weaker (7 to 15 pct) acid either by adding cupric or ferric ion to the acid3-5 or by passing an anodic current (-0.1 ma per sq cm).2,3,5,6 The two latter corrosion conditions produce strong attack of low-angle boundaries after certain heat treatments 2-4,5,7 The susceptibility of high-angle boundaries is influenced by the grain-boundary segregation of iron atoms; this increases the slow (µ per month) attack in 10 pct HCl8 but diminishes the rapid (mm per month) attack in 20 pct Hc14 (the present and most previous investigations deal with rapid attack). That segregation of elements other than iron affects intergranular corrosion has not been demonstrated, although analysis of data for iron alloys indicated that at least one other element must be considered.9 Intergranular attack occurs over a wide range of purity although it begins to become obscured above several hundred parts per million (ppm) total im- purities by the severe general corrosion which accompanies the higher iron contents and which is associated with the presence of a second phase or an inhomogeneous distribution of the dissolved iron.4,6,10 The variation of intergranular-corrosion rate with heat treatment1&apos;3-6&apos;"10 can be explained in some cases in terms of the distribution of the iron impurity but is not in general adequately understood. The present work dealt with two questions not previously considered in detail. The first proceeded from the view that the extent to which a special behavior is associated with the boundaries is indicated not by the intergranular corrosion rate alone but by the ratio of the intergranular to the general corrosion rate. A comparison of the two rates was therefore made for one lot of aluminum in acids of varying strength and metallic ion content. The second question was the effect of the copper content of the aluminum. For general corrosion, it has long been known that copper ions introduced into the acid by corrosion of the solid solution are reduced on the aluminum as patches of elemental copper which enhance the corrosion rate by providing cathodes of lower hydrogen overvoltage than were originally present.&apos;&apos;-&apos;3 Since the copper patches remain themselves unchanged, their action is "catalytic", and since they are products of corrosion, the effect is "autocatalytic." This phenomenon is significant at copper levels much lower than previously suspected, even at those typical of high-purity aluminum, as the authors have shown in a previous paper.l4 The present work shows that copper content affects intergranular corrosion. With polycrystalline specimens, truly quantitative rate measurernents are not readily made for intergranular corrosion or for general corrosion in the presence of rapid intergranular attack, and previous work in this field has tended to be qualitative. The present study made use of a simple procedure which provided fair approximations to the quantitative corrosion rates and fitted the purpose of surveying the behavior over % wide range of conditions and displaying certain large effects. The approximations involved in this work were usually outweighed by the experimental scatter, which tends to be substantial in a system as sensitive as this one. I) EXPERIMENTAL A. Material. The material procured, Table I, represented three low copper (1 to 3 ppm) lots, two of "normal" copper content (21 and 22 ppm), and two

Jan 1, 1962

By H. C. Fuller

Rhodonite, a manganese silicate, occurs as an important component of extensive veins in the San Juan district of Colorado. Recent work by the Bureau of Mines has demonstrated that typical ores of the area can be upgraded to about 30-percent manganese content. Because of their siliceous nature, such concentrates require further processing to convert the manganese into more usable forms. The investigation described in this report demonstrates the technical feasibility of producing silicomanganese from a rhodonitic concentrate by electric smelting methods. The rhodonitic concentrate used in the smelting research was prepared by dry high-intensity magnetic separation of ore from the Silver Queen vein. The concentrate contained 29 percent manganese, 2 percent iron, and 41 percent silica. The principal minerals in the concentrate were 35 percent rhodonite, 30 percent rhodochrosite, and 25 percent quartz and chalcedony. Limestone was used as the flux and coal was used as the reductant. These minerals were crushed and screened to minus 1/2-inch plus la-mesh size.

Jan 1, 1962

By G. N. Maniar

G. W. Healy (union Carbide Metals Co.)-The author&apos;s paper is a useful contribution to the store of maps of chemical activities of oxides in multi-component slag systems. It is also a good example of the utility of the Gibbs-Schuhmann technique for calculating activities in a system where that of one of the components has been measured. This paper Koh and Caugherty. This plot is reproduced by alor in X-ray Metallography. Because of this nonlinearity, preparation cf suitable standards and/or correction for absorption and enhancement are essential in microanalysis. However, our objection is not the conclusion that Dr. Aaronson has arrived at nor the technique he has used; but only to the foot-note credited to V. Macres. The level of chromium that he was concerned with (less than 3 pet) is so low that the deviation of uncorrected Cr-curve will be negligible. Besides Dr. Aaronson has used chromium intensity from martensite and set it equal the bulk chromium content of the alloy. Using this chromium-intensity as a reference, he has calculated the amount of chromium in the ferrite. This amounts to the same as using an internal standard. Since the chromium content in austenite and ferrite are almost the same, enhancement due to iron in both will be the same and therefore does not need to be corrected. together with the author&apos;s recently published one1 on the CaO-FeO-Fezo3 system will be most helpful to others learning to apply Schuhmann&apos;s method, which merits a far wider application than it has received to date and should greatly aid our understanding of equilibria between metal and oxide phases. As shown by okcen" its use may even be extended to sections of systems with any number of oxides. I have some questions as to the selection of equilibrium constants made by Dr. Turkdogan. He has chosen one for the formation of Fe2O3 from FeO and oxygen which gives Fea3 activities 50 pct higher

Jan 1, 1963

By P M. Hetherington, F A. Pym, M P. Murphy, K E. Crook

Consultants in the mining industry have the opportunity to visit interesting deposits all over the world. Each deposit has its own set of challenges to face when it comes to defining and understanding the deposit geology and the economics to make it viable for extraction. Some of the challenges can include appropriate data capture, sampling techniques, structural characteristics, geochemistry, geophysics, lithology definition, and economic boundaries. It is essential that the practices used at each deposit (eg drilling, sampling, geological modelling, resource estimation etc) are documented and the results obtained are robust and defensible. The Competent Person is not always aware of instances where their resource estimation practices have not been substantiated. ‘You don’t know what you don’t know’ is a phrase frequently used during a mineral resource audit. Technical work to substantiate drilling, sampling, density, assaying, geological modelling and estimation processes is not always completed. Audited Competent Persons often comment: • ‘I was unaware that this was required.’ • ‘I have not had training in this area and do not know how to complete the checks required.’ • ‘This is how we’ve always done it.’ Examples of audits where it was found that geological practices were not substantiated are examined here. A discussion is included on why substantiation of these practices is important, and potential reasons as to why there are instances of unsubstantiated processes and practices are discussed.

Mar 22, 2022

By A. G. Galaitsis

This report summarizes the work performed under the USBM Contract No. J0245001. The purpose of this work was to expand and improve the scope and accuracy of the method developed under USBM Contract No. J0113056 for the prediction of the number of overexposed workers in the mining industry. A significant portion of the noise data were acquired during mine visits-that took place in the-course of this contract. These data were obtained with time-resolved dosimeters which among other things store a time history of the sampled noise for an eight hour work period. The remainder of the noise data have been obtained from MSHA files and from other BoM-sponsored projects. The report reviews the prediction model, discusses the model&apos;s assumptions and approximations, describes the function of the developed software, offers typical examples on the use of the software and includes plots of the newly acquired noise data records.

Jan 1, 1986

1.Assessment of methane content in coal. Given a naturally low methane content in 11 Coal Seam and the fact that the areas of the 11 Seam adjacent to the tunnelway were degassing for a very, very long time due to previous development and mining, it is conservatively estimated that the remaining in -situ methane is less than 0.5m3/tonne. 2. Continuous miner cutting rate based on the past practice. The best loading rate recorded at the past operations of Smoky River Coal was 45 seconds for a 8 tonnes shuttle car. Using these records, the maximum peak loading rate potential at the face is calculated at 0.178 tonnes per one second or 10.67 tonnes per one minute. 3. Methane release at the face. ?The actual face methane liberation, conservatively assumed at 40% of the total in situ content: 0.20 m3/tonne ?The peak cutting rate: 0.178 t/sec ?The maximum (peak) face methane release: 0.20*0.178 = 0.036 m3/sec

May 1, 2003

By E. J. Eisenach, Edward Matsen

AT the present time the Climax Molybdenum Co. is the largest molybdenum producer in the world and the operator of the largest underground mine in North America. It has grown steadily and rapidly since its beginning in 1917. Only 250,000 lb of MoS2 were produced during the first year from 1917 to 1918 when the company was formed. Operations were suspended shortly thereafter because of the lack of a market and knowledge of the uses of molybdenum. During World War I it was used as a substitute for some rare metals and for minor chemical purposes. After 5 years of intensive research and sales promotion, Climax metallurgists succeeded in finding proper applications for the newly discovered metal and the mine was reopened in 1924. Demand for molybdenum increased gradually and in 1930, 3.5 million lb of MoS2 were produced. In the meantime, research work for additional uses of molybdenum continued until it had established itself as one of the most important alloying elements in producing high quality steels. After the start of World War 11, from January 1942 to October 1953, 43 million tons of molybdenum ore were mined and 484 million lb of MoS2 were produced. Climax mine is located in Colorado, 100 miles southwest of Denver and 12 miles northeast of Leadville on the Continental Divide of the Rocky Mountains. The principal mine workings range from 11,170 to 12,000 ft in elevation. Topographically, it lies in the base of a large cirque that is surrounded by Mt. Bartlett to the north, Clinton Peak and McNamee Peak to the east and Ceresco Ridge to the south. This cirque opens to the west and to the Ten Mile Valley.

Jan 3, 1954

The sequences in alteration and mineralisation from five copper-gold porphyry systems (Taysan and Didipio, Philippines; Horse-Ivaal and Wafi River, PNG; and Goonumbla, Australia) and one gold-copper skarn system (Browns Creek, Australia) are documented in this paper. Alteration and mineralisation in all these systems reflect a common evolution from crystallisation of melts emplaced at shallow crustal levels (zoned potassic -> propylitic alteration), followed by exsolution of volatile-rich fluids from these melts (porphyry quartz ¦K-feldspar/biotite veins and local high temperature advanced argillic alteration), to a progressive cooling of the intrusion which results in associated retrograde alteration. Copper-gold mineralisation in all cases is almost exclusively restricted to the cooler retrograde events. The recognition of the temporal and spatial zonations in alteration and mineralisation in gold-copper porphyry systems has significant relevance in the interpretation of geophysical signatures, overprinting alteration, vein sequences and structural controls, and can lead to more focused and potentially more cost-effective exploration.

Jan 1, 1999