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By D. R. Dolinar

The fall of small pieces of rock between roof bolts causes over 80 pct of the ground fall injuries in underground coal mines. Roof screen, if installed on the bolting cycle, can significantly reduce the number of these injuries. As the surface of the roof fails, the screen will have to retain the broken rock without failing or excessive deformation. Welded wire screen is the most common type of screen material used for roof surface control in underground coal mines. The load-deformation characteristics and the load capacity of welded wire screen were evaluated in the laboratory in a specially built test frame. In the frame, the square screen sections were held in place by bolts and bearing plates at the four corners while a center load was applied to the screen. The parameters evaluated included the wire gauge and configuration, the bearing plate loads and bolt spacing. The wire gauge of the tested screen was 4, 6, 8, 9 and 10. Maximum screen capacities for both load and displacement were developed for each of the wire gauge sizes along with the screen stiffness. This information can be used for screen selection and for the evaluation and determination of screen performance. DISCLAIMER: The findings and conclusions in this report have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.

Jan 1, 2009

By M. Abdellatif

Keywords: Magnesium, pyrometallurgy, Mintek Samples of crude magnesium produced by the Mintek Thermal Magnesium Process were refined in two stages. The first stage consisted of co-melting of batches of the crude metal and MgCl2-KCl flux (cleaning), followed by stirring at 30 rpm for 30 minutes and settling of the sludge (mixture of molten salt and solid impurities) from the magnesium melt. The operating temperature was 680?730°C. Most of the contained calcium and significant proportions of iron and silicon were transferred into the sludge phase, which left a metal containing, on average, 950 ppm Si, 470 ppm Fe, and 230 ppm Ca. In the second stage, small-scale refining tests were conducted on cleaned samples from the first stage, as well as on crude magnesium. FeCl3 was used as the refining agent. These tests were carried out at 715?760°C with various amounts of the refining agent. The refined metal was suitable for the production of various magnesium alloys, particularly AZ91D.

Jan 1, 2006

By J. E. Chilton, T. Mal

Methane monitoring at the mine face is essential to assure a safe work environment in underground coal mines. Machine-mounted methane monitors must be used to continuously monitor methane levels during mining. Monitors used on mining machines must be approved by MSHA and properly maintained to provide protection for workers (30 CFR 75.342). To provide protection the instrument must give accurate readings of current methane levels. Accuracy is maintained by calibrating the instrument with a standard gas at least once every 31 days. Instrument “response time” determines how quickly measurements will change to reflect current concentrations. At present there are no criteria for measuring the response time for a ma-chine-mounted methane monitor while underground. This study examined a procedure for measuring the response time of a machine-mounted methane monitor. Response times were measured using methanometers obtained from three different manufacturers. The effects of the measurement technique and methanometer sensor head design on response time measurements are investigated. Techniques for reducing variation in response time measurements are discussed.

By Jorge Oviedo

La planta de lixiviación, extracción por solventes y electrodeposición (L-SX-EW) de Southern Perú es una operación hidrometalúrgica dedicada a la lixiviación ácido – bacteriana de los botaderos de mineral de baja ley de la Mina Toquepala, para la producción de cobre catódico de la más alta pureza. En ese sentido, el presente trabajo describe la evolución del sistema de control y supervisión de esta planta minera en Cuajone. Para ello, dicha planta debe tener una actualización constante de sus sistemas de control y ser capaz de cambiar con la velocidad a la que avanza la tecnología de Control de Procesos. Asimismo, debe contar con personal calificado que permita el desarrollo y modernización de los sistemas sea continuo y no dependa solo de expansiones y ampliaciones ejecutadas por especialistas externos. De forma que este software de supervisión, no solamente considera la capacidad de operar la planta, si no debe ser una ayuda tanto para el operador como para brindar información en la correcta toma de decisiones.

Aug 25, 2002

By Luis Magallanes-Hernández

"Industrias Peñoles, S.A. de C.V. (Peñoles) in Mexico, is a major silver producer. The Peñoles Mining Division has eight Mining Operations and in seven of them, flotation is used to concentrate the metal and mineral values. Common metals and minerals values are: metallic gold and silver, gold-silver alloys, silver sulphide minerals (acantite, pyrargirite, argentite, proustite); lead sulphide mineral, galena; zinc sulphide mineral, sphalerite; and copper sulphide minerals (chalcopyrite and bornite).In the last years, a special emphasis has been given to using modal analysis to identify ore mineralogical limitations, in order to direct efforts into key areas where opportunities exist to improve the metallurgical results.This work aims to share Peñoles mineralogical and metallurgical results, through presenting, discussing and drawing conclusions on these results; as well as pointing out areas where more work is needed to improve the Concentrator´ performance.PEÑOLES BACKGROUNDPeñoles´s mission is to add value to non-renewable natural resources on a sustainable manner. It was established in 1887, and it is a mining group with integrated operations in smelting and refining non-ferrous metals, and producing chemicals. Peñoles is the world’s top producer of refined silver, metallic bismuth, and sodium sulphate, the leading Latin American producer of refined gold, lead, and zinc.Peñoles Mining Division is integrated into eight mining business, located on five different states in Mexico. Metal productions for the Mining Division during 2003 were: 343 thousand gold ounces, 48.4 million silver ounces, 81.3 thousand tons of lead, 235.1 thousand tons of zinc, and 10.6 thousand tons of copper."

Jan 1, 2005

The compliance sampling method for coal mine dust in the United States has not changed appreciably in the last 30 years. A call for more frequent sampling with immediately available results is leading to new instruments that may supplement or replace the existing sampler. This report discusses two such instruments that provide immediate results of dust levels. The first, called the Respirable Dust Dosimeter (RDD), is designed to supplement the existing U. S. cyclone compliance sampling method. It uses the pressure drop across a filter to provide an inexpensive screening type of measurement. The RDD has been tested in the laboratory and a limited number of coal mines. Side by side testing has compared the RDD performance with personal coal mine samplers in triplicate area sample measurements. Results show that the differential pressure of specific filtration media can be an effective surrogate for respirable mass. Data show that there is a dependence on coal type and an effect of relative humidity. There also appear to be two distinct responses related to coal type. For specific coals the coefficients of determination, R2, are better than 0.9. For general use the detector tube, using laboratory generated calibration curves, can be used to estimate respirable dust levels. However, a calibration to a specific coal type may substantially improve the accuracy. Another sampler in development is called the Personal Dust Monitor (PDM). Designed to give compliance quality accuracy, the PDM uses the frequency change of a vibrating element to measure dust and give immediate feedback of results. Results of laboratory comparison of the prototype PDM sampler to personal gravimetric samplers indicate R2 values of better than 0.99 for three different coal types. Work is in progress to package the components into a person-wearable unit combined with a cap lamp system with a total projected weight of less than 1.4 kg (3 lbs).

By Benjamin Smith Lyman

THE importance of topography to geology is so commonly underrated as to deserve to be pointed out again and again. The relation of topography to the different branches of geology may be seen best by a glance at them all. Geology is well understood to consist of the observation of facts about rocks as materials of the earth (geognosy), and the explanation of those facts (geognosy). The facts to observe are : I. GEOMETRICAL, as (1) structure, including the dip and strike at different points, the size, shape, and position of basins and saddles; (2) vertical section, that is, the thickness of rock groups and of their parts ; (3) horizontal or geographical position. 11. PHYSICAL, such as texture, whether sedimentary or crystalline ; and, if crystalline, whether granitic, porphyritic, amygdaloidal, globular, or concretionary ; whether compact or granular; coarse or fine; pervious or impervious; hard or soft; firm or tender; with cleavage or without ; massive or thin ; the microscopic structure ; also whether magnetic or not ; soluble or insoluble ; fusible or infusible ; and the constituent minerals. 111. CHEMICAL that is, the composition of the rocks and of their minerals and their affinities. IV. PALAENTOLOGICAL, as what kind of fossils are in the rocks,

The discussion which followed the publication of my paper by the formert has, I think, enhanced its value. It may therefore be of interest to members of our Australasian Institute, who are not members of the Institution of Mining and Metallurgy, if I give a synopsis of the discussion.My attention was drawn to the fact that my paper did not make clear the extent of the improvement in furnace operations, which followed the use of coke of high quality; this comment applied more particularly to the lead content of slag. My failure to supply comparative figures in regard to the lead content of slag was governed by a condition which, I think, is of interest to metallurgists. As a result of industrial...

Jan 1, 1932

By E. W. Johnson

"The title of my paper is ""I 'Wonder Where The Yellow Went"". As you can readily guess, it is not related to an old-fashioned ""Pepsodent"" sales pitch! Rather, it concerns a situation which arises all too frequently in some gold milling operations, namely when actual ounces of gold production do not come up to estimated or projected ounces. The boss man scratches his head and wonders where the missing gold has gone and how it has disappeared. The problem, if one exists, is amplified if one forgets that an estimate is just that - an estimate - and not a hard fact - even though the numbers are produced by computers. And yet, from the point of view of engineering; financial and production planning and security; it is most desirable to tie together all data relating to production estimates, losses and actual production.In the course of this paper reference will be made to the term ""variance psychology"", to a few of the physical properties of gold and to the nature of its occurrence in Canadian ores, in relation to the topic under consideration. Activities which have a bearing on production estimates will be reviewed. These include: weighing, sampling, assaying, estimating residual losses and, in cyanide plants, gold precipitate production. Mention will be made of apparent, unaccounted for and unknown losses. In conclusion, I shall draw from personal experience and relate three examples of ""Where the Yellow Went''."

Jan 1, 1986

By L. W. Hamel

"DUST CONTROL - GRANISLE COPPER LIMITEDINTRODUCTIONGranisle. Copper Limited is located in the north-central region of the Province of British Columbia, approximately 200 road miles north-west of Prince George. Mill startup was in November, 1966, at a rate of 5,000 tons per day, expanded to 13,000 in 1973. The primary crushing rate is 1,200 tons per operating hour, and the secondary 750, and they can be operated jointly or separately.DUST COLLECTION SYSTEMS There are seven dust collection systems ventilating the crushing and grinding complex. The individual pickup points are depicted on Figure 1 -""Crushing Plant Flowsheet"", and Figure 2 - ""Concentrator Flowsheet"", e.g. 1A, 1B, 3C, etc.System No. 1 - Primary Crusher The feed rock box of the Allis-Chalmers superior 42-65 primary crusher is ventilated by 19,000 CFM of air exhausted directly to atmosphere by a Sturtevant 426 M fixed discharge fan.No. Dust Pick Up Point CFM lA Crusher Feed Rock Box 19,000System No. 2 - Primary Crushing and Screening System No. 2 ventilates the primary crushing and screening equipment. A total of 19,000 CFM of air is exhausted by a Sturtevant 426 M fixed discharge fan through a Howden Type S - size 75 cyclone locally modified for wet scrubbing."

Jan 1, 1976

By E. M. Frizzell

Development of mobile crusher systems for surface mining, allowing extension of continuous conveyor haulage systems into the pit, is traced from its introduction to the present. Variations in configurations are reviewed, and the compelling reasons for using mobile crusher systems are explored.

Jan 1, 1983

By Michael J. Rinker, P. A. Tibble, M. Wiseman, R. V. Nicholson

Tailings, from an active copper-zinc operation, containing about 10% sulphur were investigated to assess the onset of acid production and potential lime requirements for treatment of drainage. Oxygen consumption rates were measured over two years to verify spatial and seasonal variations in sulphide oxidation rates. Shallow cores were collected to assess the quality of tailings porewater and to characterize solids that had been subjected to oxidation and depletion of neutralization potential (NP) for several years. Oxygen consumption data were used to quantify rates of NP depletion and onset of acid drainage from the near- surface tailings. Based on measured oxygen consumption rates and identification of NP remaining in the tailings, future lime use in the treatment plant was expected to rise significantly without mitigation. Geochemical modeling calculations were calibrated with observed oxygen consumption rates and the model results agreed well with actual lime use in the waste water treatment plant during operations. The modeling also demonstrated the benefits of lower lime demands and treatment costs after closure as a result of construction a soil cover on the acid generating tailings.

Jan 1, 2000

By A. C. Legg, M. T. Malema

Keywords: Pyrometallurgy, flash, smelting, furnace, nickel, copper, Botswana BCL Limited operates the only Flash Smelting Furnace on the African continent, at Selebi-Phikwe, situated in north-eastern Botswana. The furnace was commissioned in 1973 and produces a high-grade sulphide matte containing nickel, copper and cobalt, which is shipped to refineries in Zimbabwe and Norway for further processing. This paper outlines the recent process improvements and plant expansions that have resulted in a capacity increase from 40 000 to 60 000 tons per annum of metal production.

Jan 1, 2006

By Derek J. Penrice

The Caltrain Downtown Extension (DTX) project will extend commuter and future statewide high-speed rail service into the Transbay Transit Center, which will be located in the business district in downtown San Francisco. The DTX project includes 1.5 miles of underground construction, comprising complex sections of mined and cut-and-cover tunnel. As part of the DTX preliminary engineering process, development of appropriate contracting practices, including contract packaging, procurement methods and contract terms for the underground construction, has been initiated. This paper provides a summary of the evaluations undertaken, preliminary conclusions reached, and proposed next steps to promote industry interest and maximize bid competition.

By J. S. Stachulak

The Diesel Emissions Evaluation Program (DEEP), a research consortium formed in 1997 by Canadian mining companies, labour unions, and provincial and federal government departments, completed its work by mid-2006. This program, in which Vale Inco participated with both direct funding and in-kind contributions, investigated the ability of currently available technology to significantly reduce underground concentrations of diesel particulate matter (DPM) with high efficiency and low maintenance over a long-term period (years of life).While DEEP?s testing showed that engine maintenance is a critical component for lowering DPM, it was clear that reduction of DPM to the very low target levels of ~0.05 mg/m3 was not possible with maintenance alone. The best candidate technology for achieving low DPM levels was particulate filter systems. Furthermore, successful deployment of such systems was highly dependent on removing them from having to rely on human intervention for their regeneration. The search continues within Vale Inco to identify a reliable and rugged system.

Jan 1, 2009

By R. E. Ray, J. W. Stevenson, J. A. Berry

Conventional concrete block plastered with a cementitious coating is the most common material used in the construction of permanent stoppings to direct airflow in underground mines in the US. All mines experience various degrees of strata convergence depending on depth of overburden, geological conditions, and type of roof support employed. Strata convergence will cause cracks and joint openings in masonry stoppings, resulting insignificant air leakage losses. Where strata convergence is severe, complete structural failure of the stopping can ultimately occur. Reconstruction of damaged or destroyed stoppings adds expensive overhead to mining operations, and even greater expenses are incurred from the additional fan horsepower required to overcome leakage losses. Ideally, a stopping should maintain high resistance to airflow while yielding to strata convergence. By properly incorporating a polyisocyanurate rigid foam material within the masonry block structure, stopping service life can be increased in mines experiencing strata convergence problems such as floor heave, roof loading, and lateral rib movement.

Jan 1, 1986

By M. Hochenhofer

Due to economic aspects and environmental regulations recycling of slag and waste from ferroalloy production became a very important issue for the companies during the last years. The treatment of slag depends prior on the composition, especially on their content of valuable metals and impurities. The final aim should be a total re-use of these materials in the industry e.g. cement industry, pig-iron production etc.. Therefore, to reach the required physical and chemical properties for a further use, possibilities of a metallurgical treatment have been investigated. The conditioning of slag with a high V-, Mo- and P-content via reducing metal bath showed to be one alternative. To determine the optimal process parameters, practical investigations with different slag compositions and thermodynamic calculations were carried out.

Jan 1, 2006

By T. G. Joseph

A strain-softening constitutive relationship is introduced that describes the post-failure stress-strain curve for rock regardless of whether the rock is intact or broken. The core of this relationship is an ?apparent friction? concept that relates the post-failure apparent cohesive and frictional characteristics of the rock to the strain. The relationship can be determined for a given rock via a series of tri-axial strength tests establishing the peak strength and corresponding strain for a range of confining pressures, together with the determination of the base angle of friction via a simple tilt test. The postulates and assumptions used in deriving this relationship are verified from results of tri-axial tests on both intact and broken rock.

May 1, 2002

By John Haviland, Richard E. Danell

"BHP Australia Coat Pty Ltd (BHPAC) operates seven large open pit coal mines in the Bowen Basin ofCentral Queensland, Australia. These mines have operated for periods ranging from 16 to 37 years. All of these mines have dipping seams to varying degrees and are facing increasing overburden removal in an effort to maintain production. To ensure the economic viability of the operations, this increased level of overburden removal must ah.0 be conducted at lower unit costs."

Jan 1, 1995

By Lutz Markworth, Wolfram Jaspers, Johannes Kottmann

PNEUFLOT® technology has been applied for the past 20 years in coal, ore and other minerals processing plants. During the last two years this technology has achieved a breakthrough with some 42 units being sold signifying a rising trend. »Humboldt Wedag Coal & Minerals Technology« has performed extensive research and development work over the last five years. The results of which were used to design a new fourth generation aerator. Humboldt Wedag, through its association with EKOF, can offer a holistic solution encompassing both flotation equipment and reagents. It is the only company in the world able to offer such a package. The association with EKOF strengthens the Humboldt Wedag product offering, especially as the company in-troduced pneumatic flotation cells to the South African market in the form of the PNEUFLOT®. Before starting pilot scale test work, a mineralogical analysis has to be carried out to determine the mineral com-position as well as the liberation grade. HW-CMT works together with independent institutes. Different reagent regimes can be tested in laboratory scale. Pilot machines, each packed in a 20? container, are available to carry out extensive test work at customers? processing plants. A group of engineers from HW-CMT is involved in the pilot test work. The flexible pilot machines are designed to cater for coal, ores and other minerals. The small feed rates of 7 ? 12 m³/h only means the pilot machines do not disturb the operation of process plants. Batch tests have to be carried out to determine the numbers of PNEU-FLOT® stages. New applications in iron ore, copper ore, platinum group minerals, rock phosphate and potash were suc-cessfully tested in the last three years. In applications where the feed material is very fine, PNEUFLOT® technology is able to achieve high recoveries with particle sizes where conventional technology failed.

Jan 1, 2007