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By T. W. Healy, M. S. Moignard

The use of electrokinetic or zeta-potential phenomena in studies of the properties of mineral sulphides has increased greatly over recent years. This review aims to examine and discuss the body of literature on the subject of electrokinetic properties of sulphides in a comprehensive and critical manner. Although the review covers the period from 1925 to 1975, it is only in the past ten years that researchers have been fully aware of the implications and problems of chemical reactions, notably oxidation and precipitation reactions, on the surface properties of sulphide minerals. These papers are discussed in more detail than the earlier publications. A table containing a list of determinations of iso-electric- points and points-of-zero-charge of mineral sulphides, and the methods employed in obtaining these results, is presented.

Jan 1, 1976

By A. T. Weber, G. T. Adel

Earlier studies on the hydrodynamic interactions between fine particles and air bubbles have shown that fine particle flotation can be improved by using small air bubbles. In the present work, microbubbles ranging in size from 70 to 250 microns have been used in a flotation column for the processing of fine coal. The performance of the microbubble column has been studied as a function of wash water addition rate, aeration rate, feed rate and column length to diameter (L/D) ratio. The information collected from these tests has been used to analyze column behavior and to develop scale-up criteria. The results of this investigation suggest that mixing within the column may not be as significant as bubble size and residence time in determining column performance. Improved recovery can be obtained by decreasing bubble size which increases the flotation rate constant, and also by increasing L/D which increases residence time for a fixed column volume. The increase in residence time with L/D is due to a decrease in the volumetric flow rate of wash water with column diameter.

Jan 1, 1988

By Bill Sayer

Cadman, a wholly owned subsidiary of Heidelberg Cement, is a leading supplier of sand and gravel as well as ready mix concrete in the greater Seattle area in western Washington State. Cadman's aggregate mine is located in North Bend, 34 miles east of Seattle, WA, and consists of a "Lower Pit" and an "Upper Pit." In 2005, Cadman planned the upgrade of the North Bend mine operation as follows: Upper Pit (Figure 1): 1. Crushing Plant, Stacker and Stockpile 2. Storage Reclaim Belt Feeders 3. Feed Conveyor 4. Downhill Overland Conveyor Lower Pit (Figure 2, Photo 12): 1. Radial Stacker 2. Storage Reclaim and Truck Load-out

Jan 1, 2008

By S. K. Sahoo, S. K. Sharma, A. Yadav, B. Behera, G. S. P. Singh

A field representative modeling of the gob behavior is critical for the understanding of the associated mechanics of strata behavior in longwall workings. The findings of theoretical models and laboratory tests on the simulated gob material have shown the strain hardening behavior of the gob material. The double-yield material model, which is a built-in constitutive model in FLAC3D, has significant potential to simulate the gob compaction process as it represents materials which undergo irreversible compaction in addition to shear yielding. Apart from this, several researchers have attempted using modified elastic model or applied nodal force in reaction to the strain in the gob area as per the well-known theoretical relations to meet this requirement. Although these models can simulate the mechanical response of the gob for subcritical and critical extraction widths, they do not apply to supercritical extraction width as the gob stress may exceed the in situ stress level in such cases. For overcoming these limitations, a standard approach has been developed and validated in this paper, which can be used for simulating the gob behavior in supercritical longwall workings as well. The complete study is divided into two stages wherein the laboratory scale compression test on the simulated gob material has been numerically replicated to develop preliminary confidence followed by a parametric study of the double-yield constitutive parameters for a rational estimation of their values in different conditions. The calibrated model has been used for verifying its results by plane strain modeling of two different longwall workings, using well-established empirical and analytical findings and field observations. The approach suggested in this study can be used for the efficient modeling of the gob behavior of longwall panels under varying geo-mining conditions without compromising the accuracy of the numerical model. The meticulously validated model can be helpful in rational estimation of stress redistributions around the gob area apart from load transfer on the barrier pillar.

By S. K. Sahoo, S. K. Sharma, A. Yadav, B. Behera, G. S. P. Singh

A field representative modeling of the gob behavior is critical for the understanding of the associated mechanics of strata behavior in longwall workings. The findings of theoretical models and laboratory tests on the simulated gob material have shown the strain hardening behavior of the gob material. The double-yield material model, which is a built-in constitutive model in FLAC3D, has significant potential to simulate the gob compaction process as it represents materials which undergo irreversible compaction in addition to shear yielding. Apart from this, several researchers have attempted using modified elastic model or applied nodal force in reaction to the strain in the gob area as per the well-known theoretical relations to meet this requirement. Although these models can simulate the mechanical response of the gob for subcritical and critical extraction widths, they do not apply to supercritical extraction width as the gob stress may exceed the in situ stress level in such cases. For overcoming these limitations, a standard approach has been developed and validated in this paper, which can be used for simulating the gob behavior in supercritical longwall workings as well. The complete study is divided into two stages wherein the laboratory scale compression test on the simulated gob material has been numerically replicated to develop preliminary confidence followed by a parametric study of the double-yield constitutive parameters for a rational estimation of their values in different conditions. The calibrated model has been used for verifying its results by plane strain modeling of two different longwall workings, using well-established empirical and analytical findings and field observations. The approach suggested in this study can be used for the efficient modeling of the gob behavior of longwall panels under varying geo-mining conditions without compromising the accuracy of the numerical model. The meticulously validated model can be helpful in rational estimation of stress redistributions around the gob area apart from load transfer on the barrier pillar.

By Robert B. Fulton, Gill Montgomery

Fluorspar is the commercial name for fluorite, a mineral that is calcium fluoride, CaF2. The name, derived from the Latin word fluere (to flow), refers to its low melting point and its early use in metallurgy as a flux. It is the principal industrial source of the element fluorine. Two other minerals, cryolite and fluorapatite, have significant fluorine content. Cryolite, sodium aluminum fluoride, Na3AlF,, is a rare mineral that has been found in commercial quantities only in Greenland. The natural material has been supplanted by synthetic cryolite for its principal industrial use in the manufacture of aluminum. Fluorapatite, Ca5F(PO3)2, is a source of phosphate for fertilizer manufacture, containing a small percentage of fluorine. Commercially mined deposits of apatite have varying amounts of fluorine, chlorine, hydroxyl, and carbonate. HISTORY Fluorspar was used by the early Greeks and Romans for ornamental purposes as vases, drinking cups, and table tops. Various peoples, including the Chinese and the American Indians, carved ornaments and figurines from large crystals. Its usefulness as a flux was known to Agricola in 16th century Europe. Fluorspar mining began in England about 1775 and at various places in the United States between 1820 and 1840. Production grew substantially following the development of basic open hearth steelmaking, wherein it is used as a flux. Use was stimulated by growth of the steel, aluminum, chemical, and ceramic industries, particularly during World Wars I and 11. Fluorocarbons entered the picture in 1931. The use of anhydrous hydrogen fluoride (HF) as a catalyst in the manufacture of alkylate for high octane fuel began in 1942. Differential flotation for separating fluorspar from galena, sphalerite, and common gangue minerals in the 1930s and the application of heavy media concentrating methods to the treatment of low grade ores in the 1940s were outstanding technological advances that facilitated increased production. Pelletizing and briquetting of flotation concentrates for use in steel furnaces and the development of flotation schemes for beneficiating ores containing abundant dolomite and barite have been major improvements in the industry. USES OF FLUORITE Fluorspar is used to make hydrogen fluoride (HF), also called hydrofluoric acid, an intermediate for fluorocarbons, aluminum fluoride, and synthetic cryolite. It is used as a flux in the steel and ceramic industries, in iron foundry and ferroalloy practice, and has many minor specialized uses. Hydrogen fluoride is produced by reacting acid grade (97% CaF,) fluorspar with sulfuric acid in a heated kiln or retort to produce HF gas and calcium sulfate. After purification by scrubbing, condensing, and distillation; the HF is marketed as anhydrous HF, a colorless fuming liquid, or it may be absorbed in water to form the aqueous acid, usually 70% HF. Synthetic cryolite, organic and inorganic fluoride chemicals, and elemental fluorine are made from hydrofluoric acid. The acid itself is important in catalysis in the manufacture of alkylate, an ingredient in high-octane fuel for aircraft and automobiles; in steel pickling, enamel stripping, and glass etching and polishing; and in various electroplating operations. The manufacture of one ton of virgin aluminum requires about 12 to 29 kg of fluorine content in synthetic cryolite and aluminum fluoride. This quantity, through improved technology and recovery practices, is being lowered significantly in countries with the most advanced technology (i.e., Australia and Sweden), while others (i.e., Surinam and South Africa), remain at the high end. Elemental fluorine is prepared from anhydrous hydrofluoric acid by electrolysis. Gaseous at room temperature and pressure, fluorine is compressed to a liquid for shipment in cylinders or in tank trucks. Elemental fluorine is used to make uranium hexafluoride, sulfur hexafluoride, and halogen fluorides. Gaseous uranium hexafluoride is used in separating U235 from U233 by the diffusion process. Sulfur hexafluoride is a stable high dielectric gas used in coaxial cables, transformers, and radar wave guides. Halogen fluorides have important applications, mostly as substitutes for elemental fluorine, which is more difficult to handle. Emulsified perfluorochemicals, organic compounds in which all hydrogen atoms have been replaced by fluorine, are undergoing investigation as promising blood substitutes. They transport oxygen and, in conjunction with a simulated blood serum, perform many functions of whole blood. With further development, these organic compounds may ultimately, in emergencies, be useful in saving lives of animals and humans during periods of acute shortages of natural blood. Inorganic fluorides are used as insecticides, preservatives, antiseptics, ceramic additives, and fluxes and in electroplating solutions, antioxidants, and many other products. Boron trifluoride is an important catalyst. Organic fluorides are volume leaders in the fluorine chemical industry. Fluorinated chlorocarbons and fluorocarbons are prepared by the interaction of anhydrous HF with chloroform, perchlorethylene and carbon tetrachloride, and are characterized by low toxicity and notable chemical stability. They perform outstandingly as refrigerants, aerosol propellants, solvents, and cleaning agents and as intermediates for polymers such as fluorocarbon resins and elastomers. Fluorocarbon resins are inert compounds that have unusually low coefficients of friction and have found a number of applications as lubricants for parts that cannot be oiled, e.g., bearings for window raising equipment located inside of automobile doors, in small electronic equipment, for the manufacture of chem-

Jan 1, 1994

By Jesse L. . Jr. You

Tunnels in the granitic Climax stock at the Nevada Test Site were inspected for keyblock occurrence. Thirteen relatively large pyramidal keyblocks were located in about 230 m (750 it) of tunnel. Orientations, dimensions, joint roughness coefficients, and joint compressive strengths were measured for the faces of nine keyblocks. The measurements were used to back-analyze keyblock stability to check the validity of a numerical model for keyblock behavior. A newly developed three-dimensional numerical model correctly predicted whether or not each keyblock failed in six of eight cases. The two exceptions involved stress conditions and keyblock locations that clearly violated the assumptions that underlie the stability model. The observations also allowed the effect of tunnel orientation on keyblock occurrence to be evaluated. Of the thirteen observed keyblocks, nine large blocks were found in less than 30 m (100 ft) of the Piledriver drift (which runs N56E) while only four blocks of comparable size were observed in 200 m (656 ft) of the Spent Fuel Test--Climax drifts (N61W). The orientations of the keyblock faces were checked against known discontinuity set orientations; some of the faces correlated well with mean set orientations, whi.le other faces were fringe members of sets. Stereographic techniques were used to examine the frequency of keyblock occurrence and to determine the maximum keyblock size that could be encountered with a given combination of discontinuities. Keyblock occurrence was found to be affected by tunnel orientation in a predictable way; this can be used to guide or improve tunnel design practices.

Jan 1, 1986

By G. H. Roybal, J. M. Barker

Humate mining in New Mexico is a small industry [455 m3 (16,079 cu yd) valued at $395,894 for 1983] with three mines active in 1985. Either humate (carbonaceous claystones rich in organic matter) or weathered coal ("leonardite") high in humic acid are mined. The humic acid content needed to meet consumer specifications determines which type is mined. The humate and "leonardite" now mined in New Mexico are used primarily as soil conditioners or as drilling mud additives. The potential resource for both are very extensive within the coal-bearing formations of the San Juan Basin in northwest New Mexico.

Jan 1, 1987

By B. Ceccarelli

Many public domain programs useful in mining engineering, e.g., MULSIM, DZTAB, and EXPAREA, require tedious data input and generate pages and pages of printed output. To eliminate the tedium and to enhance the output, ETI U.S., Inc. developed GEM, Graphics for Engineering and Mining, a collection of application programs and underlying interface tools for VAX/VMS computers. This paper presents an example of how an application program in GEM enhances a specific public domain program. It describes how GEM provides automated graphics assisted input and output. The paper describes how this program uses the GEM User Interface: the 3D GKS device independent graphics, server and drivers, various mining, mathematical and statistical algorithms, the means of handling graphics, data including IGES, and the foreign language interface.

Jan 1, 1992

By G. Hargrave, K. W. Moloney, M. R. Stokes

In recent years drivage advance rates in the UK have in- creased from 35m per week in the 1980's to 100/150m per week possible today. These extended rates of advance have resulted in an increase in the potential methane, dust and heat generation at the drivage face. In order to disperse this additional pollutant load requires an increase of fresh air at the face. Although advance rates have changed, current auxiliary ventilation practice has not. UK mining law requires that the fresh air must be delivered to within 5m of the face. This has lead to the wide spread use of overlap auxiliary systems, since a pure forcing system set at this distance would lead to excessive airborne dust. UK mining law does not at present consider on-board mounted exhaust scrubber fans to constitute an effective overlap fan within mechanised drivages. In an attempt to determine whether working conditions could be safely and economically improved within mechanised drivages, a series of preliminary full scale gallery trials were con- ducted. A summary of the principal findings of these trials are presented together with an outline of a series of representative CFD simulations, scale model experiments.

Jan 1, 1997

By Arthur R. MacPherson

Este capítulo revisa las etapas que deben seguirse desde el momento de considerar la molienda autógena en el desarrollo de un nuevo depósito de mineral o en la expansión de una planta existente, hasta la compra de un molino autógeno. En este caso el término autógeno incluye: semi-autógeno, molinos de pebbles secundarios y molino de bolos (trozos), así como los sistemas de molienda autógena total. También se han incluido las alternativas por vía húmeda y seca. Antes de programar el ensayo debe decidirse cuantas muestras brutas son requeridas para calcular propiamente las posibilidades de molienda autógena del depósito. También ha de tomarse la decisión, de como y donde deben tomarse las muestras, por ejemplo: planta piloto situada en el sitio de localización de la planta o en otro lugar establecido; molienda en húmedo y/o en seco....etc. En el mismo programa del ensayo se obtendrán ciertos datos fundamentales. Los ensayos deberán incluir un trabajo suficiente. para determinar cuál de las moliendas, totalmente autógena o semi-autógena, debe utilizarse; y qué tipo produce la máxima eficacia en la potencia consumida. También, los otros datos pertinentes deben ser recolectados, como por ejemplo: potencias, tonelajes, alimentación, carga, tamaño del producto, carga circulante, etc. Si es necesaria una molienda secundaria para obtener el tamano final, la decisión de qué molienda debe emplearse (molino de pebbles o molino de bolas) puede requerirse un ensayo de trabajo adicional. Finalmente, la concentración del mineral puede jugar un papel importante en la selección del circuito y debería ser una parte del ensayo final una vez que se ha establecido la molienda. Para determinar qué tipo de molinos pueden satisfacer los requerimientos establecidos por la planta piloto, debe tomarse una escala para ciertos datos como: potencia del molino, consumo de acero, simple o doble etapa de molienda, tipo de molino secundario. Para asegurar un posterior entendimiento del depósito de mineral y sus características de molienda, deberán efectuarse algunos trabajos adicionales a pequena escala utilizando pequeñas muestras y molinos para producir unos datos comparables de molienda. También, algunos ensayos tales como medio de molienda óptimo, e índice de trabajo, deberán ser completados.

Jan 1, 1982

By Paul C. Miclea, Robert E. Murphy

The behavior of fire and airflows in a confined tunnel differ significantly from more familiar fire situations outside, due to the buoyant effect which tends to create a layer of hot smoke and gases flowing away from the fire near the crown of the tunnel, while air supporting combustion moves toward the fire beneath the smoke layer. A subway emergency ventilation system is designed to force air to flow through the tunnel, shifting the balance of heated air in the direction of the forced flow and avoiding the "back-layering" of hot gases and fumes. This paper presents a computer program, called the "Subway Environment Simulation" (SES), which can be used to predict airflows created by the emergency ventilation system. It utilizes the latest state-of-the-art analytical treatment of fires in enclosed spaces, including observations from mine fires and gas explosions. The program allows designers to reduce construction cost by identifying unnecessary ventilation shafts and by verifying fan capacities. In addition, the program allows the designers and operators to determine safe evacuation routes, in case of a train fire, by predicting the occurrence of back-layering. It can be used to determine when the ventilation system can control the direction of smoke movement to provide a clear and safe path for evacuating people and facilitate fire fighting operations.

Jan 1, 1989

By K. Osseo-Asare

Metal recovery from solution, i.e., the formation of a solid product from a purified aqueous electrolyte solution, is increasingly becoming more than a simple matter of bulk precipitation. In many cases, operating conditions must be carefully manipulated to control the rate and yield of the precipitation/crystallization process, as well as the purity and physical characteristics of the solid product. A review is presented of the underlying physico-chemical processes, with emphasis on solution and interfacial chemistry. Opportunities for the integration of hydrometallurgical metal recovery and materials processing operations are discussed.

Jan 1, 1989

By Jed H. Mosgrove

One of the most interesting of all the subjects required of persons studying the different facets of coal mining is coal mine gases. Some mine gases have been a real problem since the very beginning of underground mining, and in the early days there was insufficient knowledge to cope with them. The history of mining shows that until about the last 50 years, much work was done primarily by the hand methods which are primitive by today's standards. Miners had to contend with gases without the aid of enclosed lighting, permissible mine machinery, sophisticated testing devices, and high-pressure ventilating fans. In early days the miners were not educated about the different mine gases nor did they have the technical equipment to determine the actual composition of the deadly atmospheres they encountered. They simply applied a descriptive term to each gas or mixture of gases depending on its effect on a person or the surrounding atmosphere. The gases or mixtures of gases were then referred to as "damps," a term which was probably derived from the German word "dampf," meaning vapors or gases. The more common damps encountered were : Blackdamp A condition of the atmosphere in which a miner's light would be extinguished and in which breathing would be difficult, sometimes even resulting in suffocation. An atmosphere deficient in oxygen which could contain a combination of any of the mine gases Firedamp A flammable mixture of methane and air which would either burn or explode when ignited. White Damp A mixture of gases containing carbon monoxide, most often found in mines during fires or after explosions.

Jan 1, 1981

By M. W. Harmer, J. M. Quist

Laboratory test work, pilot plant testing and plant experience with wet, fine-mesh screens are discussed. High-frequency, low-amplitude, fine-mesh, wet screens were installed on the 6th cleaner concentrate stream. These screens produce a 60% oversize recovery split of the molybdenite concentrate that is of leached equivalent quality. The undersize stream is leached with hot ferric chloride to remove lead and copper contaminants before roasting or shipment to sulfide customers. This plant modification is a good example of using existing technology in an unconventional flow sheet to yield significant cost savings.

Jan 1, 1991

In 1990, US mine production of barite increased 54.1 %. Barite consumption, sold or used by grinding plants, increased by 27.6%. Imports were about the same as 1989. World mine production in¬creased 12.3%, according to the US Bureau of Mines. The value of domestically produced barite, fob mine, decreased 12.7%, according to the Bureau. The declared value, cif US port, of all imported crude barite during the year 1990 increased from $40.27/t ($36.54 per st) in 1989 to $40.61/t ($36.84 per st). Nevada continued to be the leading producer of barite with 82% of the total, followed by Georgia and Missouri. It is estimated that 750/c, of the domestically mined barite was used as a weighting agent in drilling fluids. The remaining 25% was used in barium chemicals, glass or as a filler. Most of the production from Missouri, Georgia and Tennessee was used in the non-oilfield sector. Of the total barite used by grinding plants and chemical manufacturers, it is estimated that 90% was used in drilling fluids and 10% in the non-oilfield sector. This includes barium chemicals and fillers in paper, plastics, and glass. Tonnage consumed in the drilling fluids market increased due to the higher average rig count during 1990. The average number of rotary rigs operating, (1010), was 16.2% more than the 1989 average of 869 in the US.

Jan 1, 1991

By R. J. Pugh

The surface chemical sites on several fillers (quartz, feldspar, calcite and granite) were studied by the adsorption of well defined acid and basic probe molecules (benzoic acid, benzyl alcohol, ethyl benzoate, pyridine and benzyl amine) from cyclohexane. The results provided a wide variation of adsorption data, emphasizing the extensive range of site heterogeneity on the filler surfaces. In addition, it was shown that the acidic probes were strongly adsorbed on all of the minerals, thus indicating that the basic surface sites dominate the acidic ones. Also, through FTIR studies with vapor-phase probes adsorbed on orthoclase, it was possible to identify the nature of specific sites and the type of bonding occurring between the filler surface and the probe molecule. These types of surface analytical techniques could give useful information for predicting the adsorption functional groups on dispersants, dyes, thickeners, etc. and could lead to enhanced interfacial bonding between the filler and the matrix.

Jan 1, 1993

By K. V. K. Prasad

Solution of most engineering problems requires, in addition to vast numerical calculations, substantial use of practical judgement and expertise. With advances in applied mathematics and computer technology, the numerical aspects of problem solution have reached a considerable level of maturity. However, it is only recently that approaches like the expert systems methodology have been developed to incorporate the judgemental aspects as well. For rapid development and prototying of expert systems, expert system building tools or "shells" have become widely available. For the expert system developer, identification of the key characteristics of the problem domain and selection of the right expert system tool are of crucial importance. In this paper, the important attributes required in an expert system shell for use in the development of a mine ventilation planning expert system are discussed. These attributes are general in that most engineering problems in mining would have these requirements. Also, the results of an exercise undertaken to evaluate commercially available shells for application to mining engineering problems are presented.

Jan 1, 1989

By C. DeRossett, K. F. Unrug

Sedimentary rock fractures commonly occur in the vicinity of outcrops. Mine highwalls and highway cuts provide excellent views of these near-surface joint systems. This paper explains the origin, characterization, distribution and extent of the these joint systems with reference to the lithologic composition of the rocks. The practical implications of these joint systems on the operation of a mine are described. Included are discussions of the discontinuous deformation that results from surface subsidence, the stability of mine portals and near-outcrop underground operations, and the stability of highwalls when using highwall miners and strip operations. Some design procedures are recommended to minimize the problems encountered within mining areas having intense joint systems.

Jan 1, 1996

By Andreas G. Mueller

Gold-silver and copper-gold deposits with high-temperature wallrock alteration of Ca-Mg-Fe-Al silicates occur in ca. 3.0 Ga old greenstone belts of the Yilgarn Block, Western Australia. The deposits are hosted by amphibolite-facies komatiites, basalts and BIF, controlled by ductile shear zones and located within the contact-metamorphic aureoles of composite granodiorite-granite batholiths. Disseminated sulfides and free gold form foliation-parallel ore zones in a gangue of anhydrous silicates (garnet, clinopyroxene, olivine), hydrous silicates (amphibole, biotite) and calcite. The deposits may be classified on the basis of their dominant economic metals as: 1(1) Gold skarns with substantial silver as by-product, represented by the Marvel Loch mine (production: 2,200,000 t at 3.5 g/t Au), and characterized by the mineral association pyrrhotite, loellingite, arsenopyrite, galena, gold and magnetite. (2) Gold skarns with low silver contents, represented by the Nevoria mine (production:1,850,000 t at 3.4 g/t Au), and characterized by the mineral association pyrrhotite, chalcopyrite, arsenopyrite, gold, Bi-tellurides and magnetite. (3) Copper-gold skarns, represented by the Elverdton mine (production: 850,000 t at .7 5 Cu, 0.81 g/t Au), and characterized by the mineral association magnetite, chalcopyrite, pyrrhotite, pyrite, gold and Ag-Bi tellurides.

Jan 1, 1990