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By Thomas P. Meloy

A brittle solid broken by crushing or impact, results in a mass size distribution curve having a straight line segment when plotted on log-log paper. Depending on the mineral, the slope of this straight line segment ranges from a maximum of one for materials like glass and quartz to values of one half or less. Theoretical derivations of the size distribution, such as the Gaudin-Meloy model, yield a slope of one and only one. When the Gaudin-Meloy model is modified to assume that not all cracks terminate on a preexisting surface, the new model predicts that size distribution slopes, depending on the type of brittle solid, will be less than one. There is a measurable physical parameter that will predict the slope. In addition the model predicts that particles from such a size distributions will have negative corners and peaks - indentations. Moreover the model predicts that particle shape will systematically change with decreasing particle size. Finally, this new physical model of comminution may be experimentally tested.

Jan 1, 1995

By J. D. Miller, C. L. Lin

As the techniques and resolution for three-dimensional spatial analysis have advanced in the last decade, it is now possible to map in detail the microstructure of multiphase materials in three-dimensional digital space. In this regard, three-dimensional X-ray microtomography offers a unique imaging capability. Spatial resolution on the order of 10 µm can be achieved with the use of microfocus X-ray generators. Recently, a state-of-the-art cone beam X-ray microtomography system was installed at the University of Utah for the quantitative analysis of multiphase materials in three dimensions. This facility was designed to obtain 2,048 by 2,048-pixel reconstruction over a 10-mm diameter, while also allowing for the imaging of somewhat larger (40-mm) objects. The system is capable of handling high-density materials, even materials having a density as high as 8.0 g/cm3. This unique, one-of-a-kind instrument can be used to obtain three-dimensional spatial reconstruction for many applications, such as three-dimensional liberation analysis, pore structure analysis of particle beds during filtration and the air-void system of concrete structures. The utilization of X-ray microtomography not only allows for the quantitative analysis of multiphase systems but also allows, for the textural characterization and determination of phase continuity. This paper presents information regarding the current use of this new facility and a review of potential applications for the advanced analytical system. Key words: Cone beam X-ray microtomography, Three-dimensional analysis, Material characterization

Jan 1, 2003

By P. Somasundaran, D. R. Nagaraj, Jing Wang

Polysaccharides have been widely used as depressants in mineral processing for decades. They constituent one of the most abundant family of biopolymers. However, only a small number of them have been used by industry so far because of a general lack of understanding of interactions between these polymers and minerals. In this work, adsorption tests, electrophoretic mobility measurements, microflotation and fluorescence spectroscopic tests were performed along with computer simulation to explore the mechanistic aspects of guar gum adsorption and conformation on talc as a function of relevant variables such as ionic strength, pH, solvent composition and polymer molecular weight. From microflotation tests, it was found that talc hydrophobicity decreased markedly due to the adsorption of guar gum even at very low concentrations and reached a plateau below moximum adsorption. Guar gum adsorption on talc was found to be not affected significantly by changes in solution conditions such as pH and ionic strength, ruling out electrostatic force as controlling factor for adsorption. Fluorescence spectroscopic studies showed no evidence of the formation of hydrophobic domains at talc-aqueous interface. Also urea, a hydrogen bond breaker, reduced the adsorption of guar on talc. All of the above results suggest that one of the main driving forces for guar adsorption on talc is hydrogen bonding in preference to electrostatic or hydrophobic force. This information should help toward designing reagents of optimum molecular architecture for efficient depression, dispersion or other such surface modification of particles.

Jan 1, 2005

By W. G. Pariseau, S. C. Schmelter

The destabilizing effect of water pressure on rock-mass stability is examined quantitatively by the finite element method. A coupled code that accounts for the simultaneous effects of rock-mass deformation and transient fluid flow is used for this purpose. The traditional soil-mechanics assumption of an incompressible fluid is shown to be untenable for the analysis of porous, fractured rock slopes. A Mandel-Cryer effect, whish is a transitory but elevated and potentially destabilizing water pressure following a cut, was not observed.

Jan 1, 1999

By Henrique Garcia Pereira

In a large scale mining project, the global feasibility study must take into account the interdependence of three sub systems: the geological subsystem, represented by the orebody model; the technological subsystem, consisting .of mining and ore dressing models; and the economic subsystem, including the selling price of final product, production costs and investments. In cases where the ore is heterogeneous, the interdependence between geological and technological subsystems may be assessed by a Data Analysis technique such as Correspondence Analysis (CA). This technique was applied by David and Dagbert (1975) on examples of data from geochemistry and geology. In the approach used in this paper, CA is used to create the basic framework for defining different types of ore. The final definitions of ore types take into account the mi¬ning method and the results of applying beneficiation processes to the ore.

Jan 1, 1982

By Bhaskar B. Thapa, Michael T. McRae, Michael J. Teske, Richard M. Nolting

Packer test data and tunnel in?ow observations are used to show that the distribution of equivalent hydraulic conductivity obtained for a rock mass from borehole packer testing will be biased if the orientations of the planned tunnel and testing borehole differ. Furthermore, test results show that the distribution of equivalent hydraulic conductivity is different in various geologic sub-units at the same site. The impact on in?ow of the major uncertainties, including conductivity, head and specific yield, is illustrated to be amenable to a combined analysis using Monte Carlo simulation.

Jan 1, 2003

Changes have been made in the Bulletin, Section I., for this month ; Personal and Employment columns have been added, and a Forum, in which will be included letters and discussions of general interest to members of the Institute ; live news and new matter have been inserted near the front; lists of officers and committees are placed next to the technical section, while standing matter and other information which is interesting chiefly when sought for, has been segregated as much as possible. Members are urged to co-operate with the Editor by sending in news items of themselves and others, and by giving some of their spare time to this department each month.

Jan 4, 1913

By Kumar Vikram

Rich reserve of prime quality limestone in east khasi hills of India and abundant quantity of low-cost fuel (Natural Gas) in Bangladesh made Lafarge Surma cement limited a joint venture company of Lafarge France and Cementos Molins Spain to envisage an integrated cement plant at Chatak District-Sylhet) a bordering town of Bangladesh. Since April 2006 the single flight 17 km Long Belt Conveyor (LBC) built by M/S Larsen & Toubro Ltd. (L&T), ECC Division an engineering and construction company of India, is feeding limestone/shale to the Lafarge Surma cement plant. This engineering marvel was created on a turnkey basis with technology support of M/S Aumund France

Jan 1, 2008

By R. Houot, C. Leschevin, G. Gillet

In mineral processing, conventional magnetic separators are equipped with traditional magnetic circuits (magnetic iron yoke with copper coils or iron-clad solenoid) that develop magnetic fields of less than 2 T'. For minerals of low magnetic susceptibility, use of these circuits has many disadvantages. Only a separator with a superconducting magnet can contribute to solving the problems and produce a high magnetic field. This paper presents and describes a magnetic separator having a superconducting magnet with integrated closed circuit for helium liquefaction. The system generator and maintenance are simplified by extensive automation realized by a versatile program- mable autocontrol unit. A comparative study if the results on concentration and purification of different raw materials with the new and with conventional separators is described.

Jan 1, 1987

By Peniti Niskanen

Outokumpu metals & Resources (OMR) is a sub-group of Outokumpu Oy. OMR is a Mining and Metallurgy group of about 75 companies in 16 countries. The main activities are exploration, mine development and, mining and metallurgical processing of base metals.

Jan 1, 1996

By R. B. Inturi, R. G. Reddy

Solid-state reduction of roast Movat chromite ore with carbon was carried out as a function of the C/FeO ratio at temperatures ranging from 800°C to 900°C. The reduction was studied using thermogravimetric analysis (TGA). A two¬stage mechanism consisting of the reduction of FeO with carbon monoxide and the regeneration of CO by the oxida¬tion of carbon with CO2 was proposed. The rate-controlling step is the carbon oxidation reaction. A kinetic equation, that of random nucleation, was proposed. The activation energy for the reduction was determined to be 55,800 J/mole and is compared to those activation energies determined for other chromite ores.

Jan 1, 2000

By Ben L. Seegmiller

INTRODUCTION Site characterization using oriented borehole core is the subject of this paper. Borehole core is a standard source of data for rock mechanics investigations. Oriented borehole core provides data whereby the geometric orientation of various geologic discontinuities (faults, joints, bedding, etc.) may be determined. The orientation and strength characteristics of discontinuities are important in many engineering investigations and in particular, in slope stability analyses. In heavily vegetated or soil covered situations, oriented borehole core may provide the only means of assessing the subsurface planes of weakness which characterize the site. The purpose of this paper is to briefly describe various methods or orienting core, core characteristics which may be logged and the methods of processing and using the data for site characterization.

Jan 1, 1977

By Jindrich Fiala, Jirí Kout

The paper contains knowledge that have been achieved when the problem of airflow temperature and humidity changes prediction in mine airways was investigated. The substance of physical processes has been consistently applied. The methods of dry-bulb and wet-bulb temperatures calculations can be applied in any type of mine airway. The exceptionality of auxiliary ventilated airways is in the original solution of so called losing air flowing when a ventilation pipe is leaky. The combination of aerodynamics and thermodynamics solutions enable to determine climatic conditions on projected workplaces with a sufficient accuracy.

Jan 1, 1991

By G. Reed Marchant

In 1967 the US Congress passed the "Clean Air Act." This act was amended in 1970. As a result it soon became obvious that American industries were going to have to make significant changes in their methods of operation to be able to comply with quickly developing federal regulations. One of the first regulations developed was on sulfur dioxide. For this reason, the nonferrous smelting industry was immediately affected by these new regulations. This is true because the smelting process produces sulfur dioxide as a natural product of combustion when the sulfur-bearing ore is oxidized to purify the metal. The federal government's approach for setting standards included public hearings at which government, industry, and private citizens were allowed to make comments. For this reason, it was apparent to Kennecott's Metal Mining Div. that it was desirable to make a maximum effort in working with the agency to see that correct input was provided at the hearings to assist the government in setting fair and realistic standards. It was also obvious that more complete monitoring would be required. It soon became apparent that the efforts required input from many levels of the corporation from the chief executive to the plant operators. In order to accomplish both the administrative and the technical needs, an organization was needed that could respond quickly to these needs, obtain information from diverse sources, and bring it to focus in an organized approach to the problem.

Jan 1, 1979

By B. J. Arnold

A coal's size distribution clay content and moisture content can affect its handling behavior. But the combined effects of these properties and the effects of other properties are not known. Research underway at CQ Inc.'s (formerly EPRI's) Coal Quality Development Center (CQDC) and at Iowa State University (ISU) will answer these questions as part of a four year project to develop a coal handleability index for utilities to use when specifying coals. This paper will present preliminary data from the first year of the project, which focused on obtaining data on the chemical and physical properties of carious coals and their measured handling properties. Additionally, size, ash and moisture analyses and shear test data for several coals used at one power plant will be presented along with correlations between these physical and chemical properties and the measured handling properties. These data lead to the conclusion that while moisture content is the most important variable, the amount of -44 µm (-325 mesh) coal fines is a significant factor in determining coal handling behavior.

Jan 1, 1992

By R. L. Jones, D. D. Runnels, D. P. Dupon, D. J. Cline

To establish meaningful remediation goals and monitoring programs in areas disturbed by mining and associated industries, it is desirable to determine the natural concentrations of metals that existed in these areas prior to being disturbed. In mineralized areas, multiple natural populations of metals and associated components may be present. This paper describes a method for characterizing the natural background chemistry by means of probability distribution dia¬grams. The method can be applied to water, soil and other natural materials. In a study of a complicated hydrogeologic system at the Kennecott Utah Copper North and South Operational Areas near Salt Lake City, UT, probability distribution diagrams were used to differentiate between natural background waters and waters impacted by human activities. The probability distribution diagrams allowed a component-by-¬component interpretation of the chemistry of ground¬water and surface water over a large geographic area. Natural chemical background populations and anthro¬pogenic effects were identified Although the method is illustrated for mining-related sites, the same approach can also be used for other natural and anthropogeni¬cally impacted sites.

Jan 1, 1999

By B Scheiner, D. A. Stanley

Introduction Treatment of ores to recover metal and mineral values results in waste materials usually in the form of dilute slurries. The US Bureau of Mines (USBM) investigated a technique for dewatering phosphatic clay waste by flocculating with polyethylene oxide (PEO) and dewatering the resulting floes on a static screen and/or trommel screen (Schemer et al., 1985). In the investigation, it was determined that PEO was far superior to polyacrylamide polymers for this type of dewatering. This paper discusses reasons for this superior performance. Comparison of PEO with polyacrylamides Dewatering experiments were conducted by adding PEO solution from a burette to a stirred clay slurry. The dewatering endpoint was characterized by rotation of the floc mass as a unit, a clear supernate, a maximum floc size, and a minimum floc volume. Additional water was removed from the floes by hand squeezing (Schemer et al., 1985). The clays investigated were sodium, potassium, magnesium, calcium, and aluminum exchanged montmorillonite and attapulgite. Nine commercially available (Superfloc) polyacrylamides were compared with PEO at two polymer concentrations. Results are summarized in Table 1. The solids content of the dewatered clays ranged between 24% and 33% and was highest for PEO-treated material. These results and the data in Table 1 indicate that PEO is superior to polyacrylamide in terms of polymer dosage required. Superflocs 16 through 128, like PEO, are nonionic and should give similar results to those for PEO if the flocculation mechanism is the same for both type polymers. Superflocs 204 through 214 are anionic with increasing anionic character from 204 to 214. Generally, the anionic polymers gave the best results for the polyacrylamides tested, but in terms of dosage they were not as good as PEO. Correlation between flocculation and dewaterability of waste slurries The overall mechanism for mechanically induced clay dewatering is not completely known, but certain observations can be made. For instance, when a polymer is adsorbed on a clay such as montmorillonite, the polymer desorbs interlayer water. Polymer adsorption is driven by favorable entropy changes associated with this water desorption. It is also known that the -CH2-CH2- links of the PEO chain are sufficiently hydrophobic to lead to physical adsorption of the polymer (Theng, 1979). For montmorillonite slurries, the sheet-like fundamental particles, called tactoids, consist of a small, variable number of aluminosilicate layers together with interlayer water and exchange ions. The flocculation process consists of adsorption of polymer on the tactoid. Loops and tails of polymer that extend into solution then adsorb on another tactoid, forming a bridge. Mechanical action, induced by hand squeezing or in a trammel, joins the bridged tactoids face-to-face and edge-to-edge to form regions of high density. Similar orientation effects are observed for the needle-like attapulgite crystals (Schemer et al., 1985). Proposed flocculation model Generally, statements concerning flocculation and dewaterability apply to both PEO and the polyacrylamides. However, PEO has additional interaction with the clay material when compared with polyacrylamides. PEO is a polymer with repeating -CH2-CH2-O- groups and interacts with montmorillonite through a water bridge whose strength is greatly influenced by the exchange ion. To obtain insight into this interaction, a series of experiments were conducted in which different ion exchange forms of montmorillonite and attapulgite clays

Jan 1, 1987

By Aladar B. Dory

INTRODUCTION Practical experience in mines with known presence of radon daughters in the mine atmosphere in Canada and elsewhere shows that a very high concentration builds up in an unventilated dead end heading. As Holaday et al1 observed, even a minimal air movement results in a drastic reduction in radon daughter concentration. It is therefore obvious that the main objective of radon daughter control in the working environment is to design the ventilation system providing an optimized flow of fresh air into the workplace, resulting in acceptable climatic conditions and achieving radon daughter concentrations resulting in exposures as low as reasonably achievable. BASIC OBJECTIVES Large mining companies, having extensive material resources and professional expertise, have utilized elaborate electrical modelling in the design of mine ventilation systems as early as 1950 (coal mining industry in Europe) and with the advance of computer modelling techniques, their utilization in ventilation systems design is on the increase. Unfortunately, these methods are usually not available to small mining companies and even the large companies might not achieve the fullest benefit from utilizing them, if proper limiting factors are not considered in the modelling. When an evaluation of a ventilation system of a mine is undertaken in literature, a measure of the amount of air supplied underground per one ton of ore mined is used as an indicator of the efficiency of the ventilation system. Yet, even the greatest amount of air forced into the mine might not result in an acceptable working environment if a proper distribution of this air into individual working places is not achieved. The volume and the age of the air are probably the two most important factors in achieving acceptable radon daughter concentrations in the workplace, but other factors also have to be considered. DIRECTOR MINE - ALCAN, NEWFOUNDLAND FLUORSPAR WORKS ST. LAWRENCE, NEWFOUNDLAND, CANADA Ventilation To illustrate the effects of the design of the ventilation system on the control of radon daughter concentration, let us review the gradual development of the ventilation system of this mine from the earlier years of its development up until its final years of operation. This mine, located near the community of St. Lawrence on the south coast of Burin Peninsula was developed in the late thirties and reached full production by 1942. Unfortunately as was customary at that time, the only source of ventilation was a natural draft. The mine was extremely wet, and no significant attention was initially given to possible health effects of dust. It was not until the mid-fifties, when a number of cases of silicosis had surfaced, that de Villiers and Windish2 observed a significant increase of lung cancer incidence among the miners in comparison to its incidence among the general population of Newfoundland. Suspicions regarding radiation as a cause of the lung cancer were expressed, but it was only in surveys taken in late 1959 and early 1960 that Windish3 and Little4 established the presence of radon daughters in the mine atmosphere in very high concentrations. Windish, de Villiers and Hurley suggested that the most likely source of the radon in the mine was the mine water which dissolved radon during its passage through the granitic country rock in the surrounding geological area. This conclusion was confirmed by analyses of water from various areas of the mine by the Atomic Energy Canada Limited laboratories. The radon values in the samples varied from 4,240 to 12,850 pCi/L5. Following the discovery of the presence of radon daughters in the mine, the company took speedy action to install mechanical ventilation for the mine. The system was not designed as a total unit, but fans were installed rather on a trial and error basis. The basic system installation began in March 1960 and was completed by 1962. It remained basically unchanged with only minor modifications until August 1973 when a wholly new, redesigned ventilation system was implemented. A schematic section of the mine and its ventilation system for the period prior to March 1960 is given in Figure "A", for the period 1960-1973 in Figure "B", and for the period after August 1973 in Figure "C". The ventilation system prior to 1960 is not known. All workings of the mine were ventilated only by natural ventilation. If any measurements of airflows at different or any times of the year ever existed, no records have been preserved. The very minimal natural ventilation was augmented by "blowing" air from compressed air supply lines and exhaust air from drills. It is known that the compressor capacities of the mine were limited and therefore no significant air movement was probably created by the "blowing".

Jan 1, 1981

By Dwayne C. Kicker, Duk-Won Park

As the use of longwall mining increases in the U.S.. there is a need to better understand the stress redistribu- tions indicative of this method. To control high stress concentrations, the yield pillar concept has been developed. A physical longwall mine model has been designed to study the effect of yield pillars in deep mining. The model in- cludes sensitive stress measuring devices, a new excavating technique, and a new model material. This study includes the use of both regular and yield pillar systems and has successfully simulated the mode of stress change in chain pillars.

Jan 1, 1986

By J. Paraszczak

With regards to the cost and profitability of a mining operation, the performance of the equipment employed is one of the key issues. Cost and profitability depend on, among other factors, the reliability and availability of the equipment. In an attempt to reduce equipment downtime, it is indispensable to collect and analyze reliable data and information on failures and maintenance actions. This paper reviews common problems encountered in this respect, with particular emphasis on the lack of uniform terminology and methodology. Recommendations concerning the standardiztion of reliability and maintainability concepts and measures are given. Regarding the benefits that the latter may bring, the paper concludes with a proposal for an industry-wide initiative in this respect.

Jan 1, 2002