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By S J Riley

The cover (cap) over the tailings pit at Nabarlek uranium mine must be structurally stable as it will act as a barrier to radon gas emission and have to contain other long-lived radionuclides. Structural stability is primarily an issue of erosional stability in the context of a design life of thousands of years. The primary agent of erosion is fluvial, dominated by rainwash, overland flow, filling and gullying in the local area. Other agents of erosion are of less concern although biogenic agents of erosion (eg termites and windthrow) may enhance fluvial activity. Several methods may be used to assess erosional stability. They fall into two main categories, namely erosion modelling and geomorphic modelling. The former is illustrated by the Universal Soil Loss Equation in which parameters describing aspects of the geotechnical and hydrological properties of the rehabilitated surface are used as input for the modelling of erosion rates. The latter is illustrated by estimates of gully and valley erosion using empirical models. Estimates of the erosion rates and stability of the Nabarlek cover are presented. The two main techniques are complementary and it is argued that rehabilitation design must make use of both approaches when estimating erosion and geomorphic stability. More recent developments in geomorphic modelling using numerical techniques incorporate both approaches.

Jan 1, 1994

By J. Partinen

Drying is a unit process which has numerous applications in metallurgical process industry. Kumera Technology Center, being a worldwide equipment and process supplier, has developed sophisticated solutions for both direct and indirect drying. In conventional direct drum drying, the energy is taken from combustion of fossil fuels, requiring energy input and emitting considerable amount of off gases. In modem copper smelters, thermal energy from the off gases is recovered in waste heat boilers making the steam available. Using that steam as the energy source for concentrate drying, the total volume of off gases can be considerably reduced and releasing of harmful combustion gases into the atmosphere can be avoided. Kumera Technology Center has recently developed and promotes a new steam drying process for drying of copper concentrates. In the development of the new dryer, Kumera's approach has been to combine the best properties of both the steam dryers and the drum dryers. In the design special attention has been paid to overcome problems of excessive wear and clogging and to reduce the required maintenance operations. In this paper the environmental issues and energy consumption related to both direct and indirect drying processes are discussed. The estimated operation costs and emission levels are compared, based on calculations and the data collected from industry. Finally, the development project of the Kumera Steam Dryer is briefly reviewed

Jan 1, 1999

By A. R. Farkoosh, K. Korgiopoulos, McGill University, O. Rodop, L. A. Villegas Armenta

"New generation of Al-Mg-Si alloys with thermally stable dispersoids that prevent recrystallization and grain growth during hot deformation are currently used in automotive components requiring good formability. Alloy chemistry controls the phase formation especially age-hardening precipitates, dispersoids, and primary intermetallic which have pronounced effect on grain structure, strength and formability. In this work, thermodynamic calculations have been used to predict the effects of varying levels of Si (0.5-1.5wt%), Mg (0.5-1.5wt%) and Mn (0.1-2.5wt%) on phase selection. Thermodynamic calculations have been performed in equilibrium and non-equilibrium conditions via the FactSage™ software using the FTlite database. Selected compositions have been cast, heat treated, extruded and characterized through scanning electron microscopy with energy dispersive spectroscopy and electron channeling contrast imaging techniques. The calculations showed that at the hot deformation temperature of ~540 oC, exceeding certain Mg and Si levels would lead to retained *-Mg2Si intermetallics and Si particles at the grain boundaries in addition to a-Al-(Mn,Fe)-Si. It was found that retained *-Mg2Si phase which adversely affects formability can be avoided for Si+2Mg levels lower than 2.3wt%. FactSage calculations also showed that increasing Mn from 0.5wt% to 1wt% leads to an increase in the amount of dispersoids (from 1wt% to 2wt%) that can potentially slow down recrystallization and grain growth during hot deformation and improve formability. Calculations at room temperature also show that for an alloy with 0.7wt% Mg, excess Si beyond 0.7 wt% promotes the precipitation of Si clusters in the Al matrix that accelerate natural age-hardening. Results were confirmed by experimental investigation.INTRODUCTIONAluminum alloy 6082 (Al-Mg-Si) is used in the automotive industry because of its high strength, and good weldability (I. J. Polmear, 2006). The alloy is age-hardenable through the precipitation of ß-Mg2Si and its precursors, and the recrystallization is usually inhibited by Mn- and Cr-containing dispersoids formed through high temperature heat treatments (I. Polmear & Couper, 1988). However, it is known that minor changes in alloy chemistry (Mg/Si ratio) can have significant influences on the ductility and formability of these alloys by altering phase selection and the resultant microstructure (Gupta, Lloyd, & Court, 2001; McQueen & Celliers, 1997; Zajac, Hutchinson, Johansson, & Gullman, 1994). For automotive applications where wrought alloys (usually extrusions) are cold-formed to produce suspension components, the chemistry of the alloys and the extruded structure are of crucial importance as they determine the formability at room temperature (Asensio-Lozano, Suárez-Peña, & Vander Voort, 2014). In this study, thermodynamic calculations along with experimental investigations were carried out on the Al-Mg-Si system to understand their phase formation and precipitation hardening as a function of alloy composition."

Jan 1, 2016

By Charles T. Holland

The tonnage produced on mechanized automated retreating longwall faces in the United States is growing rapidly. This time last year some 14 faces were operating, and in addition to that, three were known to be down looking towards revision or repairs before being placed back in service. These, it is believed, are now in service. It is estimated at the present time, therefore, that somewhere between 20 and 25 faces are being operated in the country. A survey made last year by the School of Mines, West Virginia University, indicated that longwall mining in general has been beset with a great many problems, some more serious than others. The problems that we propose to discuss here are those pertaining to roof and floor trouble in the tailgates. Longwalls are operating in this country at the present time under an overburden ranging from 200 feet to nearly 3000 feet. Main and tailgate entries are operating in panels of up to five each, with the width of the pillars between these entries varying from 20 to 50 feet. Face lengths are running from 270 feet to 670; actually a face 800 feet long should be possible. The most economical face is often spoken of as being around 450 feet.

Jan 1, 1969

"Use of the Bond Work Index to size industrial grinding equipment was widely known. Bond also described its application for measuring grinding circuit efficiency. Bond Work Index efficiency has been widely used by industry, but until now without concise standard methods, or a formal guideline, for doing so. The Bond Efficiency Sub-Committee of the Industrial Comminution Efficiency work group of GMSG has produced such a guideline, which follows. It covers the methods and provides examples of how to calculate the Bond Work Index Efficiency of most industrial grinding circuits. Bond Work Index testing equipment and methods are also provided. The next steps are: (1) to establish standard reference testing materials and one or more laboratories to serve as bases for reference testing; (2) to establish the accuracy of relative circuit Work Index Efficiency determinations; and (3), to develop and provide a public data base of industrial comminution circuit Bond Work Index Efficiencies. OUTLINE Introduction and Background Part 1. Determining the Bond Efficiency of a Grinding Circuit Method Demonstration/Example Calculations Bond Work Index Testing Equipment and Procedures Accuracy of Comparative Circuit WI Efficiency Determinations (under development) List of Symbols Part 2. Data Base of Bond Grinding Circuit Efficiencies (under development) References Annexes: A1. The Bond Crushing WI Test Equipment and Procedure for Bond Efficiency Determinations (Revised March 26, 2015) B1. The Bond Rod Mill WI Test Equipment and Procedure (Revised March 26, 2015) C1. The Bond Ball Mill WI Test Equipment and Procedure (Revised March 26, 2015) Introduction and Background Please see the references and slide presentation “Bond Efficiency SLC (rev3)-print.pdf.” This efficiency determination applies to most brittle materials in their naturally occurring (un-scalped) size distributions being treated in size reduction circuits down to a product sizing of approximately eighty percent passing 70 µm (see below). Unusually shaped materials (e.g. mica) should be regarded with caution. Part 1. Determining the Bond Efficiency of a Grinding Circuit Method In the plant: • Define the circuit for which the WI efficiency is to be determined • Procure samples of the circuit feed and product • Obtain the power draw of the size reduction equipment at the drive pinion(s) • Obtain the circuit throughput rate (dry tonnage) In the laboratory:"

Jan 1, 2016

By Rogerio Martelli

Rolamentos autocompensadores de rolos são a normalmente aplicados em caixas de mancal de Correias Transportadoras nas industrias de mineração. Um dos problemas enfrentados pelos usuários são as repetitivas falhas de rolamentos aplicados nestas posições. Na SKF descobriu-se que os rolamentos autocompensadores de rolos vedados são a melhor aplicação para resolver os problemas típicos encontrados nestes equipamentos. A solução fornecida, nestes casos, é o que a SKF chama de Tríplice Barreira de Proteção, que tem como objetivo combater a principal causa de falhas que é a contaminação por partículas minerais e na presença de umidade. Em uma mina de cobre do Peru esta solução foi implementada e totalmente padronizada para todas as correias transportadoras e os resultados alcançados superaram as expectativas.

Oct 30, 2017

By Edward M. Downs

This paper is a brief review of the lubrication requirements of enclosed gearing on earth moving equipment, particularly as they apply to intermediate and large draglines and shovels used in open pit mining operations. It discusses the requirements of spur, helical and herringbone gearing in both horizontal and vertically mounted applications. The effects of base stock, oil viscosity, additive treatment, quantity of oil and method of application are considered. In addition, a newly designed circulating oil system for enclosed swing gear cases and the reasons for its development are discussed.

Jan 1, 1968

Predict the spontaneous combustion potential of a coal, using an expert system computer program. Background Approximately 15% of underground coal mint fires in the United States are attributed to spontaneous combustion. These spontaneous combustion fires frequently occur in worked-out or abandoned areas of a coal mine, This makes the control and extinguishment of the fire difficult and often requires large sections of the mine or even the entire mine to be scaled for long periods of time. A prior knowledge of the self-heating potential of the coal can be useful in preventing spontaneous combustion fires through the use of aggressive monitoring and control measures at existing coal mining operations, and in the planning oh new mines. Many factors can affect the spontaneous combustion process in a mine, including the self-heating potential of the coal, ventilation, geologic factors, and mining conditions and practices. Various test methods have been used to evaluate the relative self-healing potential of coals, including crossing point temperature and adiabatic heating methods, and oxygen adsorption techniques. However, these tests arc usually time-consuming and difficult to conduct, limiting their use to laboratories.

Jan 1, 1992

By Liming Yuan, John C. Edwards, Gene F. Friel, Robert A. Franks

Diesel fuel fire experiments were conducted in NIOSH’s Pittsburgh Research Laboratory’s (PRL) Safety Research Coal Mine (SRCM) to determine the critical air velocity for preventing smoke rollback. Such information is necessary for the preplanning and implementation of ventilation changes during mine fire fighting and rescue operations. The fire intensity varied from 50 kW to 300 kW depending upon the fuel tray area. Airflow in the 2 m high and 2.9 m wide coal mine entry was regulated during the course of each experiment; measured upwind from the fire as an average over the entry cross-section with an ultrasonic airflow sensor; and recorded dynamically with a mine monitoring system. The extent of smoke reversal was monitored with light obscuration monitors, ionization smoke sensors, and visual observations. Experimental results for the critical air velocity for smoke reversal as a function of fire intensity compared very well with model predictions based upon a computational fluid dynamics (CFD) fire dynamics simulator.

By G. S. Bartlett

The theme of this Colloquium, survival strategies, not only conveys a sense of urgency but also takes cognizance of the fact that, as in the political arena, tough decisions have to be made and acted upon in the years to come. It is therefore appropriate that the SAIMM, as spokesman for the metallurgical industry, should be dealing with these issues at this time, and I wish to commend the organizers of this Colloquium for focusing on a mater as important as the future of this great industry. In view of this, I regard it as an honour and privilege to officiate on this occasion, where the best of South Africa's brain power in the metallurgical field will be harnessed with a view to moulding strategies for survival.

Jan 1, 1993

By W. W. Adams

"The main purpose in the compilation of accident statistics is to reveal conditions that may result in injury to persons or property so that remedial measures may be applied. For practical reasons it is usually found necessary to restrict inquiry to conditions which actually have caused personal injury, and to omit those which nay, but have not yet, resulted in damage, Fortunately or unfortunately, there is a sufficient number of the former to indicate the existence of hazards so numerous as to require all of the attention which the industry can devote to the subject.Two years ago, the Bureau of 'mines, in cooperation with the National Safety Council, undertook an intensive campaign to obtain more complete and satisfactory information regarding mine accidents than had theretofore been available. Since 1911 the bureau had been receiving annual summaries from all companies operating metal mines, showing, in a general way, the number and causes of accidents that occurred during the preceding year and the number of men employed at the mines. Monthly summaries of fatal accidents at coal mines were received from the state inspectors, showing the number of deaths attributed to each of 22 main causes of accidents, Information for individual coal mines was not furnished.While this information, nation-wide in scope, is indispensable because it epitomizes the progress or retrogression in the industry as a whole, and serves as a background of specialized studies, yet certain classes of acci¬dents, for example, those that are more or less peculiar to specific districts or mines, require an analysis in greater detail than is possible on the sole basis afforded by the annual summaries.The need for more specific information was realized some years ago in the State of Pennsylvania in connection with the administration of the workmen's compensation law, The mining industry is well acquainted with the val¬uable studies of accidents, particularly nonfatal accidents, in the mines of that State being conducted by Mr. Rush N. Hosier."

Sep 1, 1924

By H. E. Powell

A laboratory mineral-dressing investigation was conducted by the Federal Bureau of Mines on four limonitic and four sideritic iron ores from the North Basin of the east Texas iron-ore district. The samples, composited from drill cores, were considered representative of the iron-ore reserves of the area. The objectives of this research were twofold: (1) To devise a mineral-dressing method whereby the yield from currently mined east Texas iron ores might be increased and the grade improved, and (2) to extend such treatment to include the lower grade ferruginous materials that are not amenable to beneficiation by simple washing and, therefore, are not being exploited. Of the mineral-dressing methods used in this investigation, magnetic separation of roasted are was shown to be the most effective. Results show that, by this method, a laboratory recovery of 82 percent of the iron is attainable at a grade surpassing that obtained by current plant practice and that both limonite and siderite are amenable to concentration by the process. The existence of large deposits of iron are in eastern Texas has been recognized for over 100 years. These ores were first exploited during the Civil War and were mined intermittently until about 1911. From that time until 1944 when the Defense Plant Corporation financed the erection of three blast furnaces to use these east Texas ores, production was almost at a standstill.4/

Jan 1, 1960

By Y. Ide, K. Kishitake

It is expected that an Al-Cr-N composite nitride film may have a higher resistance to oxidation at elevated temperatures than the well-known Ti-Al-N films. The formation conditions of Al-Cr-N films by a de reactive sputtering method and their properties were studied in this study. The films characterized with respect to their high temperature properties such as chemical composition, crystal structure, microhardness, wear and· friction. The crystal structure of the Al-Cr-N films changed from hexagonal phase to cubic phase with an increase in Cr content in the films. The resistivity to thermal oxidation of the Al-Cr-N films is superior to that of usual TI-Al-N films. A half of the friction coefficient in the Al-Cr-N film was obtained comparing with that in the ordinary TI-Al-N film at room temperature and the wear rate of Al-Cr-N film was 2 order smaller than that of TI-Al-N film. The Al-Cr-N films show a small friction coefficient at 500°C and then they are recognized to have good tribological characteristics.

Jan 1, 2000

By David B. Brooks, Roger L. Williams

Control of the environment is as old as mining. Engineers have always had to consider how best to deal with the surface, and the character of the surface environment always affects mining method in some way. However, if the relationship of the mine to the environment is old, today's approach is new. For one thing, land, air and water formerly could be viewed simply as obstacles to be overcome or resources to be utilized to win ore at the lowest possible cost. Now we have come to realize that these nonmineral components of the environment also are highly valuable. For another thing, environ- mental protection has become a public policy issue. Again, a special public interest in land and land use is old. From the firs(, the crown claimed extra rights in valuable minerals, and to this day a multitude of laws and regulations control-and tax-land use in every country. What is new is the detailed public attention bring given to waste management practices, whether these wastes be in the form of solids, liquids or gases, and regardless of where in the environment they appear. (It is convenient to lump all mining environmental problems, including hank fires and subsidence, together under the term "waste management," for in effect that is what they are.) As a result of these changes, the mining engineer must consider that lie is dealing with two productive resources the minerals and the remainder of the environment-and he must expect that lie will be judged not only on his efficiency in recovering the one but also on his effectiveness in protecting the other. Further, in seeking to protect the environment, the modern mining-environmental engineer has a dual role. First, there is the obvious task of finding better ways for industry to cope with waste-management problems in actual operations. Second, there is the less obvious but equally important task of helping formulate appropriate public policy objectives for the environment. Throughout; the section it is assumed that mining is an acceptable land use for the tracts under consideration. The question of whether mining will be permitted at all on these tracts is a further public-policy issue, ultimately to be resolved politically and thus, since it is beyond the scope of engineering, is not a subject that can be usefully discussed in a mining handbook. Finally, none of the statements in the section are predicated on the assumption that required waste-management measures will be privately profitable in the conventional sense. Indeed, the reverse is more likely to be the case-at least if accounts are kept so as to include all appreciable costs and a normal rate of return on investment in waste-disposal and reclamation equipment.',',' However, it is clear that improved waste management will be required of mining firms and that, to a considerable although undetermined degree, this expenditure is in the best long-run interest of both public and industry. The several studies that have attempted to quantify the impact of mining on the environment are admittedly rough but still provide enough information to indicate that there is a big job to be done. For example, something approaching 7,000 mi of stream in Appalachia alone are continuously or significantly affected

Jan 1, 1973

By Y A. Stepanyants, J Crawford

A practical field method for determining the maximum value of the intrinsic oxidation rate, Smax , of sulfidic materials in waste rock dumps is proposed. Knowledge of the intrinsic oxidation rate of sulfidic materials distributed in a dump is necessary for predictive modelling of oxidation and pollutant generation over time. The suggested method uses the fact that drilling waste rock dumps to install probes for monitoring temperature and oxygen concentration causes large volumes of air to be injected into a dump by the drill rig. By measuring the rate of decrease of oxygen concentration along the length of a borehole immediately after installation, it is proposed that Smax can be calculated at different depths. The aims of this work were: to derive a simple, practical formula for the estimation of Smax from the oxygen concentrations measured over time, based on some simplifying assumptions; to use a two-dimensional numerical model that incorporates all the necessary physical processes to model the behaviour of an aerated dump over time for a reasonable range of dump and material parameters; and to compare the results of the two approaches to assess the validity of the simple formula as a method for estimating Smax. It has been found that the technique can provide reliable estimates of Smax when the value is of the order of 10-7 kg(O2) m-3 s-1 or greater. At the lower end of the range however the radius of the zone aerated during drilling becomes an important parameter and further work has been recommended to investigate this aspect of the method.

Jan 1, 2003

By S. A. Montague

In spite of the many new insulating materials, both synthetic and manufactured, that have been put on the market since the end of World War II, and notwithstanding the many millions of dollars applied to the development of synthetic mica, natural block mica1 is still a most indispensable insulator in various electronic components. It will remain so, barring some spectacular break-through in research that might provide a substitute fully acceptable as a replacement for mica in all of its superior properties. But this is not to say the future for mica is assured, or free from serious problems. Technological advances have created problems requiring a solution to be found if future requirements are to be filled.

Jan 1, 1962

By Luis Noval Noval García

El objetivo de la ventilación es desarrollar una atmósfera saludable, segura y apta para la realización del trabajo por parte del personal. En ese sentido, el presente texto señala los gases como problemas comunes presentados dentro del ambiente minero tales como asfixia por anoxia (caso de inhalación) intoxicación, envenenamiento y muerte (letal) e inflamación y explosión (Productos). Para eliminar estos riesgos se debe eliminar las causas a través de una buena ventilación. Asimismo, es necesario conocer las propiedades de los gases, disponer de equipos para detectar su presencia y procurar los medios para eliminarlos.

Sep 1, 1984

By I. Gaballah

Decontamination of synthetic solutions of PbC12 containing 10, 100 and 1000 ppm of lead, using chemically treated barks had been studied. The percentage of !cad cations' removal from solutions depends upon the pH and the initial concentration. About 99 % of the initial lead content can be removed at pH of about 3.5, 5.5 and 6.5 for initial concentrations of 10, 100 and 1000 ppm respectively. The maximum retention capacity of the treated bark is about 83 mg of lead per gram of modified bark. Bark loaded with lead had been analyzed by Infra Red spectroscopy. It seems that lead reacts with hydroxyl groups of the phenolic constituents of the bark. On the other hand, the removal of a lead cation by the bark leads to the release of two H+. This seems to show that the removal of lead could be interpreted as an ion exchange with hydrogen belonging to the hydroxyl groups of the modified bark.

Jan 1, 1994

By Leland L. Mink

Open-pit mining is sometimes conducted in areas where the artesian pressures contained in aquifers underlying the pit's floor are great enough to cause floor heave. In order to reduce this pressure several methods are commonly used. One of these methods is a pressure relief well or depressurization wick. The wick consists of a borehole which is filled with gravel and cased at the surface. The wick is allowed to flow freely, thus reducing pressure near its location. The spacing and depth of these wicks can be determined by a simple analytical and graphical technique which considers the weight of material overlying the aquifer and the artesian force within the aquifer. An example of the technique using data from a Colombian coal mine is presented.

Jan 1, 1986

By R. F. Davis

The evaluation and selection of coals for producing metallurgical coke is indeed a com- plex process simply because coal is a complex and variable substance which is sensitive to how it is treated from the time it is mined until it is transformed into coke. A review of the the more common evaluation tests made on coal and how the test results are applied in commercial practice. Parameters used to select coal blends for wet and preheated charges should also be of interest.

Jan 1, 1980