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By Suresh K. Bhatt

Although overall worker productivity for U.S. underground coal mines is available, productivity by mining method and seam thickness is not. Mining technology has gone through dramatic changes in the past decade, and the industry has experienced a lack of accurate productivity Figures addressing these changes. This information is of great interest in planning for future mining systems as thick and shallow coal seams currently being mined are depleted and exploitation of thinner, deeper, and better quality seams is considered to partially meet the requirements of the 1990 Clean Air Act Amendments. In a cooperative program, the U.S. Bureau of Mines obtained raw mine level production and related data from U.S. Energy Information Administration for 1989 and 1990 and performed the needed statistical analysis. Base criteria, parameters, and salient results of the mine productivity analysis are presented in this report.

Jan 1, 1994

By D. W. G. White

The surface tension of zinc has been determined by the sessile-drop method in a progvam emphaszzing detailed experimental care. The surface tension oj. the pure metal was measured over a range of ternperature from the melting point (419.6"C) to 540°C. At the melting point, the suvface tension of zinc was found to be: 1) 99.99+ pct Zn - 757.0 5 dynes per cm 2) 99.999+ pct Zn - 761.0 5 dynes per CI 3) 99.9999 pct Zn - 76'7.5 5 dynes pev cna From experiments carried out in a closed, isothermal cell, the temperatuve coejyicient of the surface tension (6y/6T)p, , of zinc xas found not to be negative but to be postiue. A positive tenzperatre coefficient indicates a greater depee of order in the surface than in the body of the lquid. Houlezer, by delibevately inducing continuous zaporization, a temperature coefficient of su)face tension with a negative slope can be produced. The work reported herein was undertaken as part of a larger program of fundamental research on the properties of molten zinc and zinc alloys. This program grew out of a continuing interest at the Mines Branch in the behavior of liquid metals in the foundry and of a desire on the part of the zinc industry for reliable basic data. The work was originally begun in cooperation with the Consolidated Mining and Smelting Co. Ltd., Trail, B.C., and was subsequently continued from 1960 to date in association with the Canadian Zinc and Lead Research Committee and the International Lead and Zinc Research Organization. Although the surface tension of liquid zinc has of course, been measured before, as Table I and Fig. 1 demonstrate, there is not good agreement among the existing values. Such disparities arise because sources of experimental error are insufficiently controlled. This situation places the reader in doubt. One result may be correct within narrow limits—even fortuitously—yet, because there is not agreement between several values, none can be accepted with conviction and all become suspect. It seemed, therefore, in the circumstances, that there was room for further work embodying considerable emphasis on experimental care in order that, within a small margin of error, an accurate value might be obtained. It was in this spirit that the work was undertaken. METHOD The sessile-drop method -as adopted for this work. In this method, when applied to liquid metals at elevated temperatures, the outline of the meridional section through a drop resting freely on a horizontal surface is recorded photographically. Certain parameters

Jan 1, 1967

By Barry W. Klein

The U.S. economy was considerably stronger in 1976 than in 1974 or 1975. Real gross national product (GNP) rose sharply in the first quarter of 1976 and then increased at a more moderate rate for the remainder of the year. The unemployment rate fell until June and then increased for moat of the remainder of the year, finishing at the same rate as it had started the year. The inflation rate continued to decline in 1976. Reasons for the relatively low rate (compared with those of 1974 and 1975) included small increases in food prices and only moderate increases in energy prices. Total U.S. output measured in terms of GNP increased 11.6% in 1976. Real GNP in 1972 constant dollars rose 6.2%. Inflation as measured by the implicit price deflator increased 5.1%. In real terms, gross private domestic investment for residential structures rose 22.7% in 1976 after declining 14.7%a in 1975; State and local Government expenditures increased 1.4% in 1976; and personal consumption expenditures for services rose 4.5%. The Federal Reserve Board (FRB) index of industrial production increased 10.2%.

Jan 1, 1978

By S. W. Marcuson, P. J. Mackey

The Canadian non-ferrous mining and metallurgical industry has made great strides in environmental protection during the past half century. The path taken by the copper-nickel smelting industry in reaching today’s level is traced in this paper. Following the practice at early copper smelters in Wales and in the US, Canadian smelters originally used tall stacks to disperse furnace of-gases. This was the normal mode of operation and was accepted by society and by Government. Gradually, Government regulations required fixation of sulphur dioxide emissions and Canadian companies responded with significant technical developments to achieve this result. The initial development in Canada of the first new technologies such as the Cominco Flash Suspension Roaster and the Freeman Flash Smelting Process - both representing early versions of the modern established flash smelting technologies - and then later technologies such as the Inco Flash Smelting Process and the Noranda Process, both of which continue to this day, are discussed in this paper in terms of their contributions to the development of environmentally friendly plants. The evolution of these and other technologies is also discussed. Some comments regarding how the industry will face the future are also included.

Jan 1, 2015

By M. Cohen, S. A. Kulin

AT a recent symposium on thermodynamics in physical metallurgy1 two opposing theories of the austenite-martensite transformation were presented. Both theories agreed that this type of reaction involves a nucleation process which requires activation and that the activated nuclei develop into the well-known martensite plates with tremendous speed. However, there were essential differences in the two points of view concerning the nature of the nucleus and the mechanism by which the nucleus propagates. According to Cohen, Machlin, and Paranjpe,' the nucleus is a strain center with sufficient elastic energy to initiate a cooperative displacement among the atoms of the parent phase when a sufficiently low temperature is reached. This displacement propagates as a wave in shear-like fashion to transform the austenite into martensite without benefit of diffusion. On the other hand, Fisher, Hollomon, and Turnbull3 regard the nucleus as a solute-poor region (in the austenite) of a size which becomes supercritical relative to coherent growth into martensite when an appropriately low temperature is reached. This growth process is taken to be an atom-by- atom transfer from the receding austenite lattice to the advancing martensite lattice through the coherent interface that exists between the two phases. The present paper is not conceded with the divergent views as to the nature of the nucleus but describes some critical experiments which differentiate between the two proposed mechanisms of propagation. Fisher' has summarized the latter issue in the following way: According to the cooperative displacement theory, the speed of formation of mar-tensite plates should not be decreased by lowering the temperature, and martensite should form with extreme rapidity at very low temperatures; whereas with the alternate growth process, the speed of the martensite transformation should be retarded at very low temperatures, decreasing to zero at the absolute zero. The atom-by-atom growth mechanism predicts a marked slowing down of the reaction rate with decreasing temperature because the rate of self-diffusion in the austenite is involved in this picture. For example, Fisher, Hollomon and Turn-bull5 estimate that the activation energy for this growth process in steel is (0.34)2(0.36)* times the activation energy for self-diffusion in y-iron. The two most recent determinations of the latter quantity are 67,900" and 74,2007 cal/mol, which may be averaged as 71,000 cal/mol. This, in turn, gives a value of 3000 cal/mol for the activation energy of the atom-by-atom process, and hence the rate of growth should vary as e 8,000/RT where R is the gas constant

Jan 1, 1951

By Donald C. Strimbeck

The Bureau of Mines, U.S. Department of the Interior, is conducting research and development on a coal-burning gas turbine. This work includes the development of (1) turbine blades resistant to coal ash erosion, (2) equipment to feed coal under pressure to a turbine, (3) an efficient combustion system, and (4) equipment to remove coal ash from the gases that drive the turbine. Initial emphasis is being placed on testing the first turbine ever equipped with blades designed specifically for use with coal as the fuel. Operating tests with this turbine are now in progress. This paper describes the Bureau's coal-burning gas turbine development program and progress on this operating test.

Jan 1, 1964

By T. R. Strombotne

The purpose of this report k to document a contract undertaken by TSA Systems, Incorporated for the United States Bureau of Mines to develop a commercially available source of a continuous, working,, level detector for the measurement of radon daughter products in various working environments. The basic radon measuring technique was devised by Robert Droullard and Robert Holub and has been applied here. For further details or purchasing information contact: TSA Systems, Incorporated 4919 North Broadway Boulder, Colorado 80302

Jan 1, 1982

By R Schmitt, Y Ghorbani, I McElroy, N J. Bolin, M Parian

Aitik is a large copper porphyry type deposit located in northern Sweden, currently exploited at an annual rate of approximately 45 Mt. The ore’s exceptionally low head grade of 0.25 per cent Cu and varying degrees of hardness across the entire deposit pose challenges to the two fully autogenous grinding lines, each of which comprises a primary autogenous mill in series with a pebble mill. The variability in ore grindability frequently leads to fluctuations in mill throughput. Within the framework of a geometallurgical approach, the present study investigated the relationships between ore grindability and modal mineralogy. For this purpose, drill core samples from different lithologies were subjected to Boliden AB’s in-house grindability tests. This fully autogenous laboratory-scale test generates a grindability index mainly related to abrasion breakage, which is a significant breakage mechanism within autogenous mills. The test results suggested divergent degrees of grindability within and across the selected rock types. A combination of scanning electron microscopy, X-ray powder diffraction, and X-ray fluorescence analyses was performed for the grinding products and bulk mineral samples. The resulting mineralogical and elemental properties were subsequently correlated to the parameters from the grindability tests. It was shown that the main mineral phases, such as plagioclase, quartz, and micas, correlate well with the grindability indices. Similar correlations were found regarding the sample’s chemical composition, attributable to the main mineral phases. A further inverse correlation was established between the sample’s calculated average Mohs hardness and the grindability indices. Moreover, mineral liberation information provided by scanning electron microscopy was associated with the parameters mentioned earlier. The identified relationships between grindability, modal mineralogy, and element grades may help Boliden develop a predictive throughput model for Aitik based on the mine’s block model.

Aug 24, 2022

By W. C. Hagel

Previous inuestigators have repovted unusually low H* and Do values for self-dzf@szon in certazn bcc metals, e.g., chromium nnd y -uvanium. It has been postulated that this is nn experimental crl -tetion for the existpnce of a four -atom ring meclzanzsm, mid there could be. zmpovtant theoretrcal Implicatlons. By utilizing a precise sectioning technique with Cr51 as the tracer, self-dzffi-lsion measurements in large grains of 99.99-pct Cr were extended from 1200° fo 1600"C. A least- squares analysis of the data yields that D 0.280 exp (-73,20U/RT) cm2 sec-'. These AH* and Do unlues are not anomalous; there is little reason to believe that n vacancy mechanism is not opevatiue. Apparent differences at lower temperatures may result from preferential diffusion along short-circuititing paths and/or sample contamination. WITH continued technological effort, chromium and chromium-base alloys should ultimately become useful high-temperature structural materials. Accurate measurements of self-diffusion coefficients in the pure metal are necessary for a quantitative understanding of sintering, grain growth, creep, and other related rate processes. However, two conflicting determinations have been reported.* Using an Since careful diffusion studies normally yield Do values ranging from 0.1 to 10 cm2 sec-l, the Paxton-Gondolf results require independent experimental corroboration before an undue amount of speculation arises to explain the apparent anomaly. As discussed by Nowick6 and clearly shown by Hoffman and Turn-bull7 for self-diffusion in silver, a low AH* and Do can arise from preferential diffusion along grain boundaries or other short-circuiting paths. The most reliable data come from high-temperature measurements where volume effects predominate. Following a precise sectioning technique developed for determining silver diffusion in the intermetallic compound AgMg8 and cation diffusion in the corundum oxide Cr2O3,9 the purpose of this study was to measure true volume diffusion in high-purity, large-grain samples at higher temperatures than considered previously. Another point of interest is the frequent proposal10-12 that chromium undergoes an allotropic transformation between 1375" and 1800°C where the diffusion data might then show a discontinuity. I EXPERIMENTAL 1) Sample Preparation. The highest purity (99.997 pet) Cr currently available is produced by reduction of chromium tri-iodide. Three pounds of the resulting crystal bar were shipped in a sealed container with a complete chemical analysis from the vendor.* In conformity with the procedure used for

Jan 1, 1962

By Z Hu

The technique of reclaiming disturbed land by use of a hydraulic dredge pump (HDP) (which is a set of hydraulic machines for earthwork), termed 'digging deep to fill shallow has been used in the reclamation of subsidence areas in Chinese coal mines. This paper discusses the operational principle of the technique and summarises its reclamation procedures, which are being used in current reclamation practice. The soil condition reclaimed by the HDP was studied. The results showed that the pioneer crops to be planted in the reclaimed soil should be the ‘pulse’ family crops, and that improvements to the reclaimed soil and the HDP technique itself are needed. Bused on the analysis of the previous technical processes, a new rational technical model for the HDP reclamation method is presented in this paper.

Jan 4, 1996

By Roy J. Greenfield

The overall purpose of this research was to improve the understanding of how the post disaster seismic location system works, what determines the signal size, what is the character of the seismic noise, how well the system can detect blows from a trapped miner, and how well the source of the blows can be located. Based on an improved understanding of the system, improvements were suggested in the seismic subarray configuration, and in the system deployment procedures. An important part of this research was to become familiar with the seismic system operation and to work with the Westinghouse Electric Corporation and MSHA personnel to modify and improve the system. To accomplish this we participated in the planning, execution, and data analysis for a number of seismic field tests. Several in-mine field tests were conducted. From these tests the capabilities of an in-mine seismic system were analyzed and specifications were made for designing an operational in-mine system. Several portions of the work done on this grant were covered in previous reports. In particular the capabilities or the presently operational surface based seismic location system has been thoroughly documented by Durkin and Greenfield (1981). Portions of the location procedures and effects of mine openings on seismic signals have also previously been published. These portions or the work will only be summarized in this final report.

Jan 1, 1982

By M. Silva, G. Olivares

In a leach pile, the drainage layer or commonly known as the cover layer has been a matter of discussion due to the multiple phenomena or events that occur within it which impacts negatively the leaching process. All these events are directly related to the loss of draining capacity and irregular flow net due to an excessive compaction and entrapment of fines reducing the flow velocity which in turn cause more fines to get trapped. Over time the problem will continue to worsen rapidly and accelerating continuously like a geometric progression. When the cover layer gets to a certain level of deterioration, the only alternative to continue operating safely is to replace the entire cover material, a huge cost for any mining operation. TESRA has developed a solution to counteract the accelerated advance of the deterioration of the drainage layer. The solution consists of using large agricultural tractors coupled to a proprietary design of a heavy- duty subsoiler-ripper for deep tillage for loosening and breaking up the ground at various depth and with different legs spacing from 0.4 m or above. Also, if the ground still requires additional breaking, TESRA proposes the use of a rototiller that breaks any lumps to homogenize the ground to a certain particle size. With the subsoiler-ripper/rototiller combination equipment a layer of 0.5 m deep is properly treated to match closely the original conditions of the ground thus regaining the flow net as close as to the original seepage condition. Once the ripping is completed the subsoiler-ripper tool is replaced with another that is similar to a plow and thus continue with the installation of drainage pipes. The tool digs a Y-type profile trench allowing the pipe to sit precisely at the bottom of the trench, contributing additional lateral and lower support. This tool controls the installation depth of the drainage pipe at different inclination grades and also eliminating any irregularities that may block the flow of the leaching solution. Sometimes the obstructions block completely the flow of the solution. The main result of this methodology is the reduction of groundwater levels and at least 2% less humidity in the leaching gravel due to an increase in the draining capacity of cover. The methodology developed by TESRA applied during a couple of cycles of a dynamic leach pile has proven to be a real alternative to remedy and recuperate the cover close to its original conditions. The methodology requires only one large tractor and two accessories operated in different stages while replacing the more traditional and less efficient machinery such as the Bulldozer, Motor-grader, and backhoes.

Jan 1, 2019

By P. M. Sullivan

At its College Park Metallurgy Research Center in Maryland, the Bureau of Mines has installed and is operating a 5-ton-per-hour pilot plant for continuous mechanical separation of values contained in raw urban refuse. The entire sys tern was assembled using commercially available equipment. The process relies on multistage processing including shredding, air classification, screening, gravity concentration, and electrostatic separation. Compactor trucks deliver raw refuse collected along typical routes in metropolitan Washington, D.C., to the pilot plant. The loads are separated into concentrates of (1) light-gage iron, (2) massive metals, (3) glass, (4) putrescibles and waste combustibles, (5) paper, and (6) plastics. While some refinements remain to be made in the processing system flow-sheet, the data obtained to date have been highly encouraging, indicating favorable economics for commercial-size plants.

Jan 1, 1973

By L. Allan White

Instrumental analysis is an indispensable tool to many phases of research on rare-earth metals and their compounds; therefore, the development of new and improved instrumental techniques is essential. This report describes an emission spectrometric analytical method using direct-current carbon-arc excitation of various rare-earth-oxide mixtures. Lanthanum oxide serves the dual purpose of an internal standard and a constant major constituent. The versatility of the method was demonstrated by three different applications: (a) Analysis of complex rare-earth concentrates; (b) determination of impurities in high-purity rare-earth oxides; and (c) detection of rare-earth elements in other types of matrices, such as those resulting from beneficiation of rare-earth ores. The average error of analysis in the concentration range of 0.2 to 10.0 percent was 14.6 percent for a group of complex synthetic mixtures of rare-earth oxides. An average error of analysis in the concentration range of 0.05 to 0.50 percent was 21 percent for a group of high-purity rare-earth oxides.

Jan 1, 1959

By C D. Rose

"The primary objective of this paper is to demonstrate a different approach to predicting and verifying mechanical sampling system precision. Early in the year 2011 an experiment was conducted to evaluate the sampling precision being obtained by a three-stage falling-stream mechanical sampling system for coal owned and operated by Peabody Energy. This system collects samples from lots averaging approximately 14000 t being loaded onto rail cars at a flow rate averaging about 9000 t/h. In phase 1 of the experiment, a total of 60 increments were collected in a two day period at preassigned intervals using a cross-belt sampler located on a conveyor belt feeding a silo upstream of the sampling system under evaluation. Coal variability parameters were calculated from the resulting laboratory analysis data using the gauge-invariant fractal model developed by the author.Estimates of precision of the three-stage system as a function of the number of increments were calculated using the variability parameters determined in phase 1. In phase 2 of the experiment, duplicate samples of 30 lots of coal were taken by the three-stage sampling system, enabling calculations of the precision being achieved by the system. Phase 2 precision estimates are in reasonable agreement with those of phase 1. Conclusions drawn from the experiment include the following: Experimental variograms or the equivalent correlograms are essential in understanding sampling issues and for designing a sampling system to meet specific precision requirements. Consensus coal sampling standards provided by ISO and ASTM may be improved by treating all stages of a mechanical sampling system as æsamplingÆ rather than considering downstream sampling stages as æsample preparationÆ, to be treated in a separate part of the document. The coal industry would profit from use of methodology for routinely monitoring the overall measurement precision and the precision of the individual components of measurement: sampling, sample preparation and laboratory testing. This would not only give necessary credence to the measurement results but would also no doubt, lead to more efficient sampling system designs.CITATION:Rose, C D, 2012. Evaluation of precision being obtained by a three-stage sampling system for coal, in Proceedings Sampling 2012, pp 115-124 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 21, 2012

By John D. Foulkes

A study to categorize and characterize underground metal/non-metal mining operations from the viewpoint of telecommunication requirements and practices. The objectives were to: ? Gather and analyze data; ? Identify communication requirements; and ? Recommend systems for operational emergency and post-disaster telecommunications.

Jan 1, 1979

By Jean-Michel Rendu

On April 30, 2003, representatives of the Society for Mining, Metallurgy and Exploration, Inc.(SME) met with the staff of the Division of Corporation Finance of the U.S. Securities and Exchange Commission (SEC). The meeting was held to discuss issues related to the estimation and publication of mineral resources and ore reserves. It took place in the Washington, D.C. offices of the SEC. SEC staff members included Roger Schwall, assistant director, Division of Corporation Finance; Jill Davis, senior accountant; Roger Baer, senior mining engineer; Carl Chavez, chief mining engineer; Ron Winfrey, senior petroleum engineer; and John Murphy, senior petroleum engineer. SME committee members included JM Rendu, independent consultant and chairman of the SME Committee on Resources and Reserves; Ian Douglas, manager of deposit modeling and reserve estimation with Newmont Mining; Art Graham, director and mining engineer with Deutsche Bank Trust Company Americas; Larry Smith, chief geologist with AMEC Mining and Metals Consulting; and George MacDonald, vice president of exploration with Freeport-McMoRan Copper and Gold.

Jan 1, 2003

By Casley G. E, Pritchard J

A single slurry fed fluosolids roaster was chosen to replace six multiple hearth roasters in the Copper Smelter at Mount Isa as part of the overall program to increase production from 100 000 to 155 000 tonnes blister copper per annum. The paper describes factors influencing the choice of the unit, problems encountered during the commissioning and details of the present roaster operation.

Jan 1, 1974

By V. A. Chanturiya

There is an obvious disproportion in Russia gold-mining industry between the structure of gold reserves and the gold-mining techniques. The bulk of gold (over 70%) is extracted from alluvial deposit, 20%~25% from bedrock occurrences and 5%~7% from complex copper-zinc and polymetallic ores. The proved gold-bearing reserves are distributed as follows: alluvial ?19%, bedrock ?80%, the latter being sufficient to supply gold at the current production level for 100 years to come. In Russia, like elsewhere in the world, development of primary gold deposits is considered a first-priority line of development for gold-mining industry. Most of the gold-containing ores characteristic of Russian gold deposits are resistant ores with gold content varying between 3 ppm and 5 ppm usually showing quite low gold and silver recovery by cyanidation. Processing resistance of gold-containing mineral complexes is related to the presence of gold particles of submicrometric (<1.0 µm) and nanometric (10~100 nm) size, mostly asso-ciated with pyrite and arsenopyrite. Therefore switching over to processing bedrock entails a num-ber of technological problems that stem from chemical and physical resistivity of ores. The chemical resistivity can be overcome through flotation, oxidation roasting, autoclave leaching (biohydro-metallurgical oxidation), etc. The physical resistivity can be dealt with by resorting to traditional power-intensive methods,e.g. grinding to a ?40µm size, thermal treatments of sulphide concentrates and non-traditional high-energy methods of liberating the sulphides by means of power attack, e.g. electro-chemical oxidation, exposure to electron beam radiation and other methods. The modern non-traditional processes for treatment of rebellious noble metal-bearing ore, aimed at improving disintegration efficiency for finely dispersed mineral complexes are analysed. Advantages and perspectives of a new high-efficient, energy-saving and ecologically safe process of the nanosecond high-power electromagnetic pulses (HPEMP) effect are proved. The said process provides a stable increase in the valuable component recovery at lower energy consumption and production costs of the finite product at the stage of dressing rebellious gold-bearing ores and concentrated products. The experimental data prove high efficiency of the preliminary impulse treatment, thus, the increase in the gold recovery at the cyanidation stage amounted to 4%~12% from rebel-lious ores, 10%~30% from gravity concentrates, 5%~45% from flotation concentrates, 30%~80% from oil flotation tailings.

Jan 1, 2014

By Sam Warren, Antonio Marinucci, Genesis Z. Figueroa, Anne Lemnitzer

Drilled Displacement Piles (DDP) provide an ideal deep foundation solution that combines the benefits of ground improvement with traditional advantages of piling systems. This paper consolidates data from 20 construction projects in which more than 30 DDPs were installed and tested axially. High quality site exploration data (e.g., Cone Penetration Test and Standard Penetration Test) were evaluated to derive geotechnical analysis parameters. The test sites consisted of mostly mixed soil types with strongly stratified layers of sand, silt, and clay. Pile diameters ranged between 40 cm and 61 cm. Test results were compared with predictive methods developed specifically for DDPs as well as methods used in general geotechnical practice. The accuracy of the empirical methods is presented in terms of total pile capacity, pile length/diameter, and soil type. The large majority of all examined methods underpredict the in-situ pile capacities. It was also found that the difference between the tested and predicted capacity is strongly related to the level of improvement in the surrounding soil due to the piles’ installation. A general comparison between predictive axial accuracy and the observed level of ground improvement upon installation is also discussed.

May 1, 2022