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By Luís Marcelo Tavares, Marko Hilden, Malcolm Powell, Grant Ballantyne, Lian Liu

The t10 relationship developed by Narayanan and Whiten has underpinned a number of the JKMRC models and the characterisation of ore competence through impact testing with the drop weight tester. This usefulness is based on a consistent relationship between the t10 value and the overall size distribution that was noted for brittle rocks. However, like all characterisation tests this should be used only when the controlling conditions apply, which in this case is single impact breakage between two metal platens and within the range of sizes in which fragment sizes are normalizable. For any other mode of breakage the relationship should be confirmed before being applied. Soft ores or bimodal ores with widely different competence between dominant components have non-typical breakage signatures. Breakage via single point impact abrasion, compressed-bed breakage, low-energy surface breakage and incremental breakage, to name some of the other breakage modes, do not obey the general t10 relationship, so their outcomes cannot be used to provide a direct comparison. Inappropriate use of the t10 parameter can result in misleading conclusions about efficiency of energy use. These issues and alternative comparison techniques are presented and discussed in terms of choosing appropriate measures of efficiency of breakage, ore competence and energy required for comminution.

Jan 1, 2014

By Charles Hardy

?POWDER METALLURGY? is the production of semiformed or fully formed metal products by compressing metal powders. It had its beginnings in the fabrication of tungsten and molybdenum bars and wire by compression, sintering, and swaging. Powder metallurgy, although still in its infancy with other metals, has shown remarkable progress in recent years. Production of Metal Powders-The first step in any powder-metallurgy process is the production of metal particles of suitable shape and size. Mechanical processes for producing metal powders, as by crushing, stamping, or grinding, are usually not suitable, as the resulting particles may cause laminations and decreased strength in the finished articles. The principal metal powders now in use on a large scale are produced by electrolysis or by reduction of metal oxides by gases.

Jan 1, 1936

By C. E. Fivaz

SYNOPSIS Tribute is paid to J.S. MacArthur and the Forrest brothers for their invention. The opinion is expressed that the successful application of their process, not only saved the gold-mining industry on the Witwatersrand from stag¬nation for an indefinite but probably prolonged period, but also made a major contribution to the economic growth of the country in the twentieth century. A background is given of the activities of prominent chemists who researched the solubility of gold in cyanide solution prior to the MacArthur-Forrest invention. An account is given of the invention and patenting of the cyanidation process, and of the golden rule that the patentees laid down for themselves, which came close to wrecking the invention. The South African gold-mining scene from the discovery of gold on the Witwatersrand in 1886 up to 1890 is sketched. An account is given of how, when unoxidized ores were first encountered, the recovery efficiency dropped alarmingly, gold shares were sold on an unprecedented scale, and doom and despondency seized the town of Johannesburg. The complete turnabout in the fortunes of the South African gold-mining industry after the introduction of the cyanidation process in 1890, the steady rate of increase in production after the Anglo-Boer War, and its effect on the South African economy are described. A brief look is taken at the effect of gold mining on secondary industry. The deportment of the gold that is not dissolved from the ore by the cyanidation process is illustrated. Some thoughts are expressed on what can be done to increase the gold recovered by cyanidation.

Jan 1, 1988

By J. D. Davis

THIS-report gives results of in investigation of the carbonizing properties of 18 coals, including 2 from Alaska, 12 from British Columbia, 3 from Washington, and 1 from Utah. Each coal was carbonized in the standard 13-inch Bureau of Mines-American Gas Association (BM-AGA) retort at 900° C. Plastic properties were determined by the Gieseler and Davis methods, and agglutinating and free-swelling properties were determined by standard methods. Expanding properties were measured in the Bureau of Mines sole-heated oven. From the results of the tests on these single coals, three coals from the Crowsnest area in British Columbia, representing Elk River Nos. 4, 9, and 10, were selected for blending with the Utah coal, which was from the Lower Sunnyside bed, Horse Canyon mine, Emery County. Lower Sunnyside also was blended with Wilkeson -Nos. 2 and 3 (Washington) coals, Pocahontas No. 3 from McDowell County, W. Va., and the Oklahoma low-volatile coal used in the blend carbonized at, the Provo, (Utah) coke plant at the time this investigation was started. Most of the blends contained 3 percent hard pitch, which is the proportion used at the Provo plant. The blends were also carbonized in 13-inch BM AGA retorts at 900° C. High-volatile B coal from the No. 3 bed, Evan-Jones mine, Lower Matanuska, Valley, Alaska, yielded poorly fused coke or char. M-bed coal from the Chickaloon mine, Upper Matanuska. Valley, Alaska, ranked as medium-volatile bituminous and coked strongly. It expanded 39.6 percent in the sole-heated oven at a. charge density of 55.5 pounds per cubic foot..

Jan 1, 1952

By V. H. Gottschalk

Sponge iron is a product resulting from the reduction of an iron oxide below the temperature at which the product melts. Commercial grades usually contain 80 to 95 percent metallic iron, 2 to 5 percent unreduced iron oxide, and an amount of siliceous gangue material depending on the pur.ity of the are used for reduction. The reducing agent may be gaseous or solid, and a large variety of procedures have been proposed for bringing the reducing agent into reaction with the iron oxide. Of the proposed procedures, the one that has the distinction of having been in continuous commercial operation for the longest time, from 1911 to date, was developed at a ceramic plant in Hoeganaes, Sweden, and yields? a product that has an enviable reputation as furnace feed wherever special, high-quality steels are made.

Jan 1, 1948

This volume constitutes the Survival Subsystem portion of the final report for the Coal Mine Rescue and Survival System (CMR&SS) program, which was conducted by the Westinghouse Electric Corporation under contract to the United States Bureau of Mines (Contract Number H0101262 dated June 17, 1970). The program was directed by the Special Systems Department of the Westinghouse Baltimore, Maryland, facility. The basic objectives of the CMR&SS program were to develop and test hardware to determine the efficacy of a variety of coal mine rescue and survival concepts and techniques. These concepts were drawn from two major sources: the Request for Proposal from the Bureau of Mines1 and the final report on the Mine Rescue and Survival Study conducted by the National Academy of Engineering2 (NAE).

Jan 1, 1971

By A. F. Marques

The Azores islands are located on a triple junction where the American, African (AFR), and Euroasian (EUR) plates meet. The Mid-Atlantic Ridge (MAR), oriented N-S, represents two branches of the T; an E-W branch defines the EUR/AFR boundary called the Terceira Rift. The nature and structure of this plate boundary, as well as the dynamics of the interaction of tectonics and volcanism remain unconstrained. The Azores plateau is seated on a mantle domain of anomalously low seismic S-wave velocities, and gravity and geoid anomalies, where the apparent thick crust is thought to relate to larger degrees of melting initiated at greater depths [1]. The cause of these anomalies is controversial but many authors consider the presence of an anomalously hot/wet enriched mantle probably supplied by a plume [2]. The geochemistry of the subaerial and most submarine lavas from the plateau reinforces the plume model beneath the Azores [3-4]. The origin, size and present location of the plume is under debate but an area near Terceira is the favoured plume centre [5]. [ ] SEAFLOOR HYDROTHERMAL SYSTEMS IN THE AZORES AREA (36ºN ? 40ºN) More than 150 active and fossil hydrothermal systems are known in the oceanic seafloor [6]. Many more are yet to be found on vast oceanic areas that haven?t been explored [7]. Ever increasing knowledge shows that modern seafloor hydrothermal systems can be hosted in felsic to ultramafic rocks, vary in size and shape and exhibit diverse amounts of sediment cover

Jan 1, 2011

By C. H. Larsen

A 9-month study of the uses of wire rope associated with U. S. underground coal mining is reported. Rope applications are broken down into hoisting and nonhoisting applications where "hoisting" refers to transport in vertical and inclined shafts. The former receives the greatest emphasis since it represents the most critical rope application from the stand-point of production and safety. The discussion of hoisting practice includes aspects related to the mine operators as well as those related to the equipment builders and wire rope manufacturers. U. S. state and Federal laws regulating hoisting and wire rope use are also presented and discussed. Canadian and other foreign hoisting practice and laws are included. The state of the art in electromagnetic nondestructive inspection of hoist ropes is presented. Capabilities and use of one Canadian electromagnetic device are discussed in great detail. Conclusions are drawn regarding the present state of wire rope and hoisting technology in U. S. coal mines. Recommendations are made for improving rope practice, in general, and hoisting, in particular, consistent with greater safety.

Jan 1, 1971

By Bernard Lewis

During the past 10 years the technical investigations conducted by the Explosives Division of the Mine and Explosives Bureau of the Bureau of Mines have been described in a series of summarizing reports prepared by Wilbur I. Huff, consulting explosives chemist of the Bureau. These reports covered the…

Dec 1, 1947

The key aspects of process metallurgy that distinguish platinum group metal (PGM) concentrate smelting from that of other base metal sulphide concentrates are presented. These differences include considerably higher input chrome and magnesia contents that directly raise the slag liquidus temperature and have the potential to increase accumulations of refractory spinels. Most importantly, the higher processing temperature required for PGM smelting, and the resulting very high matte superheat lead to considerably more onerous smelting conditions than those typical of other smelting operations. This has presented challenges to furnace design and integrity, especially when coupled with the progressive intensification of smelting, involving doubling, and then redoubling, of furnace power input over the past 20 years. These power increases have been enabled by increasingly more advanced furnace cooling and structural technologies. Key technologies include strong constant-force spring-loaded bindings acting in three dimensions to minimize infiltration of superheated matte into brick joints, and robust well-cooled tapholes for reliably tapping the superheated matte. The result has been substantially improved productivity, and reduced smelting capital cost outlay per unit of production. A significant challenge that was not anticipated, presented itself in the form of insidious corrosion of the furnace lining, and especially high-intensity copper cooling elements. Investigation of corrosion in related industries eventually identified 'chloride-accelerated sulphidation', and this term has been retained as it generically describes the most pertinent aspects of the accelerated low-temperature wear of copper coolers observed in PGM smelting. In addition to discussing the corrosion mechanism, this paper describes a number of solutions that were developed jointly by Anglo American Platinum and Hatch to address the copper corrosion problem. First, new monitoring technologies allowed furnaces to be operated more safely for a longer period of time. Second, a system for replacing corroded coolers from outside the furnace during a fast 'hot' shutdown minimized the impact on furnace operating factor and hearth life. Finally, a corrosion-resistant graphite-protected cooler design significantly improved furnace campaign life, and heralds a more lasting solution to cooler corrosion in PGM furnaces.

Jan 1, 2012

By Henry Kreisinger

Some of the investigations conducted by the Bureau of Mines have for their object the collecting and disseminating of information regarding methods by which the fuels of the country may be most efficiently used. As the analysis of flue gases tends to develop better methods of firing, which in turn reduces waste of fuel, the Bureau of Mines in this bulletin presents for the benefit of those in charge of boiler plants and all other persons interested detailed information on methods of sampling and analyzing flue gases, and on the utilization of the analyses in promoting boiler-room economy. This bulletin is intended to be a companion to Technical Paper 80,a and is written in plain and nontechnical language, as far as possible, so that it may be readily understood by persons who have not had the advantage of a technical education. Whenever possible, illustrations of apparatus and methods of handling have been used rather than elaborate descriptions.

Jan 1, 1915

By S. K. R. Iyengar

This report presents the results of a study to develop optimal designs for light-weight mine roof supports for use in underground coal mines. A load capacity of 196 kN (22 tons) and a height adjustable between 1.829 m (72 inches) and 2.438 m (96 inches) were taken as the design parameters and the design goal was a unit weighing less than 22.3 kg (50 lbs). Three alternative design concepts were explored, viz. mechanical, hydraulic, and hydro-mechanical and a total of 13 designs analyzed in detail. Steel, aluminum alloy and composites were the main potential construction materials investigated for suitability from structural, life, and safety and other considerations. The designs considered most promising for development were: (i) the mechanical screw-pin type using telescopic tubes and a fine adjustment screw thread section (ii) the all-hydraulic type, of steel, aluminum alloy or aramid graphite construction (iii) the hydro-mechanical design using telescopic tubes and a short stroke hydraulic cylinder for fine adjustment It is shown that by using realistic mathematical models for stress and deflection calculations, it is possible to reduce prop weight to the design goal. The analysis presented for all-hydraulic props is applicable to hydraulic cylinders on all mining equipment and similar machinery. This report includes the computer program and user's guide for analyzing hydraulic cylinders as well as a cross-indexed bibliography on structural composites.

Jan 1, 1978

By Vaughan R. Voller

"The wide range of length and time scales found in solidification processes are outlined and discussed. Methods for Direct Microstructure Simulation (DMS) are introduced. Key features in sharp interface and phase field models are presented. Concepts in micro-macro solidification modeling are covered. Basic details of microstructure and segregation models are provided. A description of a recent segregation micro-macro model is presented in detail.IntroductionA solidification process involves the containment of a liquid region, which, due to cooling, transforms over time to form a fully solid product. The development of the solid microstructure and the segregation of solute components during this transformation are controlled by phenomena that occur across a wide range of length and time scales. A ""successful"" model of a given solidification process needs to account for these phenomena. Standard models of solidification employ a discrete grid of node points and associated volume elements in the special domain, with a discrete time step to track the transient changes of nodal values, describing the composition and microstructure. Through the use of such models significant progress has been made towards a complete understanding of solidification process and phenomena (see the conference proceedings in Refs [1-9]). As solidification models become more sophisticated, however, they all run into the problem of resolving the full range of disparate space and time scales.Two approaches can deal with this problem1. Direct Microstructure Simulation (DMS) where the grid size and time step are chosen to scale with the smallest length and time scales of the given problem.2. Micro-macro modeling where the grid size and time step scale with the macroscopic process scale and phenomena at smaller scales are accounted for via sub-grid modeling and volume averaging.Currently full DMS of solidification is beyond the reach of available computer power and the application and development of micro-macro models is an important and critical research area."

Jan 1, 2001

By J. H. East

THE RIFLE, COLO., oil-shale project of the Bureau of Mines was a facet of the re-search and development activities conducted under the Synthetic Liquid Fuels Act (Public Law 78-290) of April 5, 1944. The principal objectives were to devise efficient methods to mine and retort oil shale and to refine shale oil into usable products, at a total cost low enough that shale oil could supplement the domestic supply of petroleum at competitive prices. The Rifle project included three major divisions: (1) Mining, (2) retorting, and (3) refining. The major functions of the mining program were to supply oil shale to the retorts, to devise mining procedures, and to develop an under-ground-mining method by which oil shale could be produced safely at an unusually low cost per ton. The selected mining procedures and direct mining costs were demonstrated by sustained test runs.

Jan 1, 1964

By Bruce Bryant

Silver ore was discovered at Aspen in 1879, but the district did not reach full production until 1888 after lawsuits were settled and railroads furnished less expensive transportation to the outside world. The boom years were 1888-92; production declined thereafter. From the middle 1920's until 1950, the Midnight mine in the Richmond Hill district furnished most of the output in the Aspen quadrangle. Since 1950, little mining has been done at Aspen. The metals produced were silver, lead and zinc. Native silver dissolved from the sulfide ores was redeposited by waters circulating as deep as 300 m below the land surface, resulting in great secondary enrichment of many of the deposits. Over 100 million ounces of silver were produced in the Aspen quadrangle. Low-grade lead-zinc deposits remain between the old workings locally, and data available suggest that primary ore below levels mined is also of low grade. The ore occurs in the Mississippian Leadville Limestone and the lower part of the Pennsylvanian Belden Formation in sites that were made favorable for deposition by a number of stratigraphic and structural factors.

Jan 1, 1982

By AIME

NEW YORK'S largest hotel, the Pennsylvania, will be filled with mining and oil men and metallurgists the third week of February when some 3000 AIME members, their wives, and guests will gather for the Institute's 1948 Annual Meeting-its 166th general meeting. Except for the usual Sunday afternoon and evening sessions of the Mineral Industry Education Division at the Columbia University Men's Faculty Club, the big assembly will be under one top and members will not this year have to consult compass and map to find their next session. Possibly enervated by the stupendous effort of the Anniversary Celebration last spring and the plethora of highly successful fall meetings, the various committees have been a trifle slow in arranging their social and technical programs, but in mid December as we go to press there is already much to report indicative of substantial fare and high interest. The definite timetable schedule will appear in the February M&M.

Jan 1, 1948

By Cyril S., Smith

WE cannot but marvel at the fact that fire is necessary for almost every operation. It takes the sands of the earth and melts them-now into glass, now into silver, minium or other lead or some substance useful to the artist or physician. By fire, minerals are disintegrated and copper produced; in fire is iron born and by fire is it subdued; by fire, gold is purified; by fire, stones are burned for the binding together of the walls of houses.... Fire is the immeasurable, uncontrollable element, concerning which it is hard to say whether it consumes more or produces more." Thus wrote Pliny in his "Natural History," that great collection of fact and error which constitutes the principal contemporary description of Roman technology and which until the seventeenth century was the authority most often quoted and requoted by those who wrote on metals, as on many other subjects.

Jan 1, 1940

By G. S. Beaumont

This report presents a programme of work to demonstrate the use of a surface-based centralised computer control system for the remote monitoring and control of underground conveyors in a US coal mine. The system selected for demonstration was the 'Dynalink' Micro MINOS system which is manufactured by Hawker Siddeley Dynamics Engineering Limited. The site selected was Barnes S Tucker Lancashire No. 20 Mine located near Carrolltown, Cambria County, Pennsylvania. The system concept, operating and application software was designed and developed by the. British National Coal Board. The report describes the selection of the site, specification of the system requirements, commissioning, operation and evaluation of the system under typical US mine operating conditions. Experience with the system, based primarily on the system reliability and performance of conveyor control, was favourable. Mine management personnel felt that the system had successfully achieved its objectives and were keen to expand monitoring and control to other activities.

Jan 1, 1986

By P. A. Riveros, J. Binvignat, V. M. McNamara, D. Koren

The recovery of cyanide from a gold mill solution containing high levels of copper (400 mg/L to 900 mg/L) using the AVR process was evaluated. It was determined that acidification to pH 2 to 3 provides a suitable balance between HCN generation, copper precipitation and acid consumption. A short pilot plant campaign showed that ~75% of the feed WAD cyanide was recovered while the remainder precipitated along with copper upon acidification. The acid consumption averaged 3.5 g H2SO4 per litre of solution. The copper precipitate, consisting mostly of CuCN and CuSCN, was readily separated from the solution by gravity. The volatilization of HCN in countercurrent packed columns averaged 98.7% efficiency. Reabsorption of HCN was practically 100% in NaOH solutions and slightly lower in a lime slurry. Basic volatilizer design parameters applicable to a large-scale operation were determined, including the Henry’s Law constant and the mass transfer coefficient of HCN gas.

Jan 1, 1998

By J. E. Johnson

IT is the purpose of the present paper, while not excluding chemical considerations, to deal more extensively with some of the physical and mechanical aspects of the blast-furnace process, and to point out its dependence in these respects on well-known laws. The quantity and cost of ore and flux required to make a ton of iron being determined by circumstances over which the furnace-man, under given conditions as to quality and quantity of product, has commonly little control; the principal item of cost, apart from the saving of labor, which he can aspire to reduce, is that of fuel. To determine the limits of possibility in this direction is clearly the first step in d practical inquiry; and this step is represented herewith in Fig. 1, a diagram showing the total useful effect obtained from a pound of fuel under various conditions, and thus permitting direct comparison, under any given conditions, between actual results and the maximum possible results. The following statements will explain the basis upon which this diagram has been constructed. One pound of fuel, containing 90 per cent. of fixed carbon (which represents average conditions), is taken as the unit. The degree of oxidation of the carbon is measured by the ratio of the two oxides of carbon contained in the top-gases. It is necessary to remember that a considerable quantity of carbon is brought in as carbon dioxide by the flux, and to take account of it and of its condition. It is here considered that the carbon dioxide liberated by the limestone does not affect the analysis of the toll-gases, and that the ratio of CO to CO., will remain unchanged by the addition of limestone; enough CO, being reduced by the solution

Sep 1, 1905