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By Donald J. Olson, Thomas J. Lutzenberger, John Ramage

The North Shore Inline Interceptor, Phase IA tunnel is a 8,550-meter (28,000-ft) interceptor tunnel currently being constructed by Traylor Bros./Frontier-Kemper, Joint Venture, using a 9.8-meter (32-ft - 4-in) diameter Robbins tunnel boring machine (TBM). This tunnel is being driven in Silurian age dolomite approximately 91.5 m (300 ft) below ground surface. Significant water inflows were encountered when the tunnel drive penetrated the thinly-bedded Waubakee Formation. Flow increases approaching 0.75 cu m per min per 30 m of tunnel (200 gpm per 100 ft) have occurred in this formation. After driving approximately 2,285 m (7,500 ft) of tunnel (200 m full face in the Waubakee Formation), total flows exceeded 12 cu m per min (3,200 gpm) with about 5.7 cu m per min (1,500 gpm) entering the tun¬nel from the 200 m (600 ft) of exposed Waubakee Formation. Additional water control measures consisting of increased pumping capacity, increased water treatment capacity, surface grouting ahead of the tunnel, grouting ahead of the tunnel face and panning to improve the working environment for installation of tunnel support, were implemented to deal with the large water inflows. Currently (January 24, 1989), 3,400 m (11,000 ft) of tunnel has been driven, total water inflows are in the range of 11.7 cu m per min (3,100 gpm) with only 6.8 cu m per min (1,800 gpm) inflow from about 1,220 m (4,000 ft) of tunnel driven full face through the Waubakee Formation.

Jan 1, 1989

By Laurence M. Demers, Douglas C. Kuhn

It has been suggested that radicals on the surface of dust particles are key chemical factors in the pathophysiology which results from the occupational inhalation of coal and silica dust. In addition, oxygenated derivatives of arachidonic acid (eicosanoids) have been implicated as important biochemical mediators of mineral dust-induced lung disease through their role in bronchial and vascular smooth muscle reactivity, inflammation, and fibrosis. Therefore, we assessed eicosanoid production by the rat alveolar macrophage (AM) exposed in vitro to mineral dusts with varying surface chemical characteristics in order to determine if radicals associated with the mineral dub1 could influence the production of pro-inflammatory mediators in the lung environment. Rat AM were exposed to freshly fractured or "stale" bituminous coal dust, as well as untreated silica or silica calcined to 500°C and 1100°C. Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) levels in incubation medium were determined by specific radioimmunoassay. When AM were exposed to freshly fractured coal dust, PGE2 and TxB2 production were markedly increased. In contrast, exposure of AM to "stale" dust significantly reduced PGE2 and TxB2 production. In vitro exposure of AM to untreated silica resulted in a significant increase in PGE2 and TxB2 production compared to control. However, exposure of AM to silica calcined to 1100°C resulted in eicosanoid levels which were not significantly different from control. These findings suggest that radicals associated with respirable coal and silica particles may play a key role in the ability of mineral dust to activate AM eicosanoid production.

Jan 1, 1991

Zirconium chloride is of great commercial importance as starting materials for production of ZrO2, Zirconium metal and other Zirconium compounds from its main resources (Zircon Sands). The present study concerns with preparation of pure ZrO2 from Zircon by direct chlorination technique. Different parameters affecting the chlorination process are studied viz. carbon, chlorine flow rate temperature and time. The chlorination extent is determined from the loss in weight and chemical analysis of reaction products. The maximum chlorination extent -92% are achieved at 1100°C for 30 min. Zirconium oxide is produced from the collected zirconium tetrachloride either by calcination at 900°C or by hydrolysis in water in presence of RCI with a purity = 99%. Evaluations of the products of the process are investigated microscopically and by X-ray diffraction. The apparent activation energy of the chlorination of Zircon is determined to equal 36 kJ/mole.

Jan 1, 1997

By O. B. Bucklen

The Coal Research Bureau of the School of Mines at West Virginia University, using a modified design of a Russian flotation device, was able to obtain a clean coal product containing 7.64 percent ash with 94 percent yield and 97 percent coal recovery. This favorable performance was obtained with the semi-pilot scale flotation cell operating as a simulated three stage unit on slurry taken from the fine coal circuit of a coal preparation plant. This experimental device, consisting of a sheet metal cyclone-like unit mounted on a U-shaped uplift pipe, uses a combined flotation and cyclone action to beneficiate the minus 14 mesh partially cleaned feed product. In addition to providing comparable analytical results, the airlift-cyclone possesses other attractive features among them being a low capital expenditure, utilization of moderate plant floor space, efficient "operation on high density feed slurry, and absence of moving parts.

Jan 1, 1964

By P. R. Desam, J. D. Miller, A. Datta

The flow behavior of bubble-particle aggregates in separation tanks is important for many flotation systems, particularly for wastewater treatment. These aggregates can be considered as the dispersed phase in a continuous liquid phase of water and the flow characteristics determine the efficiency of the bubble separation process. In this work, a general methodology for the computational fluid dynamics (CFD) simulation of a bubble separation tank is described. This system is analyzed by Eulerian-Lagrangian approach. The momentum transfer from the dispersed phase to the continuous phase is quantified using the Particle-Source-In Cell (PSI-Cell) method. With CFD simulations, the effectiveness of different tank design parameters are evaluated in terms of the extent of bubble separation.

Jan 1, 2000

By R. L. Grayson, Y. J. Wang

An integrated approach to the management of underground coal mine production and cost is presented. A conceptual model for objectively analyzing an underground mine to obtain lower cost and higher productivity from operations is outlined. The model is designed to provide mine managers with a quantitative, decision-assisting methodology that can be used in formulating timely responses to fluctuations in operations. It consists of a productivity fore- cast component, routine use of current resource consumption factors, a linear programming scheduling component, a manpower loading analysis, and an inventory control component. The model is applied to an underground coal mine.

Jan 1, 1990

By J. H. Kempton

The scrutiny given to model predictions of pit-lake water quality has focused attention on the uncertainty associated with long-term predictions. Although comparison of probabilistic predictive modeling of water quality in existing pit lakes indicates that short-term predictions can bracket most parameters, uncertainties in wall-rock reactions and the stability of groundwater composition and climate remain unquantified. This overview of the uncertainties associated with longer-term predictions is presented as support for those considering policy decisions that must be made in the absence of reliable estimates of future conditions.

Jan 1, 1998

Diesel Particulate Matter (DPM) is considered carcinogenic after prolonged exposure. With increasing use of diesel-powered mining equipment in underground mines, miner?s exposure to DPM has been increasing. Most studies on the issue has been DPM control measures with few studies on diesel exhaust propagation patterns after leaving the tailpipes. This study uses computational fluid dynamics (CFD) to investigate the airflow pattern in an underground metal/nonmetal mine for a single heading. Several high DPM concentration areas are identified in the study and common practices for compliance are suggested. Airflow and DPM distribution are compared between blowing and exhausting face ventilation systems. Suggestions are also provided for the protection of miners in the face area.

Jan 1, 2009

By D. Robert Weir

The complex mineralogy of the Porgera resource has a pronounced effect on process selection for the recovery of refractory gold and silver. Intimate association of gold with pyrite necessitates a high degree of sulphur preoxidation in order to achieve acceptable levels of gold recovery. Acid pressure oxidation has been demonstrated to be the only commercially proven process capable of achieving the required level of pyrite oxidation. Gangue mineralization dictates preconcentration of the sulphides to limit the acid consuming capacity and carbon dioxide generation during oxidation. However, the relationship between concentrate sulphur grade and gold recovery to concentrate ultimately governs the optimum degree of sulphide preconcentration.

Jan 1, 1986

By Sangwhui Cho

In comminution processes including crushing, grinding and pulverizing, the efficiency of the comminution system is very low. Since the early 1980s, research has been conducted to increase the efficiency of pulverizing mills. Additionally, the application of microprocessors and Personal Computers to process control have come into general use. Given appropriate models of the process and control algorithms, these systems can economically control comminution processes. The ring-roller type mineral pulverizer is known as an energy saving mill. In this study, a control strategy to increase the efficiency of this type mill is explained.

Jan 1, 1992

The effect of the chemical composition of pulverized bituminous coal particles on their physical transformation during the initial stages of combustion has been investigated. The results suggested that cenosphere formation does not require extensive thermal decomposition of the coal particles. The vitrinites in the bituminous coal softened earlier and developed larger cenospheres than the othe macerals. The coal particles swell to a higher extent during combustion than in pyrolysis; however, the cenospheres formed in the former process experienced a higher extent of fragmentation. The development of microporosity occurred predominantly after the resolidification of the swelled char particles. The type of macerals originally in the coal did not significantly affect the microporosity of the chars. Conversely, the morphology and anisotropy of the chars were strongly dependent on the maceral composition of the coal.

Jan 1, 1986

By Wayne W. Murdy

Since 1993, Newmont has been actively growing through the development of three major foreign mining operations with a fourth under construction. The first project, Yanacocha in Peru began operating in October 1993 at a time when political and business risk in that country was considered high. In 1995, Newmont began operating the Muruntau Joint Venture in Uzbekistan, the first of its kind in the CIS. In early 1996, Newmont started operating the Minahasa mine in Indonesia. Now, in early 1997, Newmont is undertaking the construction of a $1.9 billion project in Indonesia and is completing a feasibility study with our partner for the development of a gold operation in Mexico. All of these projects have been considered "risky" by most standards, and Newmont has been very successful in all of them through risk mitigation programs including utilizing strong and successful in-country partners, concentrating on developing a strong national workforce with minimal expatriate employees, utilizing World Bank, EBRD and IFC financing and building and maintaining strong ties with host governments. This paper describes in more detail, some of the risk mitigation programs that Newmont has used to successfully grow the company through development of major foreign mining operations.

Jan 1, 1997

By Don S. McCoy, W. Joseoph Schlitt, Donald B. Swanson

Introduction Contract miners have long played an important role in the minerals industry. Historically, these were individuals who worked as underground miners and were paid by the ton or the day. These hardy types still ply their trade in the industry. However, today the term "contract miner" generally refers to an independent contractor who supplies the people and equipment needed to conduct surface mining operations for an owner or lease holder. At one time or another, contract miners have probably handled virtually every mineral commodity from sand, gravel, and stone quarrying to mining uranium and precious metal ores. In today's market, though, contract mining appears to be concentrated in just a few areas. These include precious metal mines, various types of solid fuel operations, and reclamation of abandoned mines. This article covers market areas, contract mining organizations and services, and their advantages and disadvantages. Gold and silver mines Although exact figures are not available, contract mining represents a significant element in the precious metals segment of US mining. For gold and silver, the growth in contract mining appears to be paralleling the overall growth in mining activity itself. Nevada is the largest gold producer in the US. The latest available data (1985) on open pit gold/ silver mines is summarized in Table 1 (Nevada Division of Mine Inspection, 1986). These figures show that contractors mined nearly half of the ore in 1985. Total tonnage mined, of course, was much higher for both owners and contractors. Assuming an average stripping ratio of 2.5 to 1, the total daily mining rate for the contractors was more than 145 kt (160,000 st). This translates into a contract mining rate of about 36 Mt/a (40 million stpy) based on 250 operating days a year. This approximate 50-50 split between owner and contractor also appears to hold for the future. Metals Economics Group (1987) published a survey of 51 short-range and 54 long-range precious metal projects being considered throughout the US. Contacts with owners, requests for proposals, and past corporate philosophies all suggest that about 55% of the open pit operations scheduled for the near-term will be contract mined. This represents an estimated 26 kt/d (28.5 stpd) of ore. A similar assessment of the long-term projects indicates that about 12 kt/d (13,000 stpd), or just under 50% of the open pit tonnage will be contract mined. There are several reasons why gold and silver represent such an attractive opportunity for contract miners. One is that many properties are owned or leased by individuals or partnerships that are essentially entrepreneurial. Many of these owners or lease holders have minimal mining experience. They must therefore either rely on contract mining organizations, sell an interest in the project to another mining company that will become the operator, or hire an experienced management team. For about the same reason, junior mining companies also represent good prospects for contracting. This is because most junior companies focus on exploration. They would prefer to spend their generally limited funds on drilling programs. Thus, they tend to minimize additional capital requirements by using contract miners or farming out the property to another mining company. Another good reason for using contract miners is the size of the deposit. Many properties are so small that their reserves will not support the capital expenditures

Jan 12, 1987

By Janine Acasi, Robert D. Rogers, Jonathan K. Trautman, Richard C. Cronn, James H. Wolfram

The demand for phosphate will continue into the future, because phosphate is currently irreplaceable as a plant nutrient and in many chemical applications. Phosphate is not recycled, so the supply must be replenished through a process of mining and purification. The most energy intensive part of the process, separation of phosphate from the ore, requires 54 to 78% (depending on the method used) of the estimated 0.5 quads of energy consumed by the U.S. phosphate industry. This paper provides data from a project designed to determine if a biotechnology can be developed to separate phosphate from its ore. Several hundred microorganisms (both bacteria and fungi) capable of solubilization of phosphate ore have been isolated from the environment. Work is ongoing to determine the mechanism for solubilization. In addition, how these organisms could be used in a bioprocess is being investigated.

Jan 1, 1989

By S. Mathur

Oxide particles are commonly used as fillers in plastics, paper, rubber etc. (particulate composites). The successful fabrication of such composites is dependent upon the adhesive strength of the filler particles to the matrix. The compatibility of the matrix and the filler particles is generally enhanced by adsorption of surface modifiers such as surfactants and polymers at the particle-matrix interface. In order to develop a scientific basis for selection of appropriate modifiers it is necessary to understand their adsorption mechanism(s). Specifically, adsorption of polymeric additives is attributed to a combination of chemical and electrostatic interactions, hydrogen bonding and van der Waals forces. Hydrogen bonding has been suggested to be the primary adsorption mechanism for non-ionic polymers. However, a literature survey of Poly(ethylene oxide)(PEO)-oxide system suggested PEO, a non-ionic polymer, to be substrate specific. A systematic study was undertaken to investigate the adsorption mechanism(s) of a PEO on oxide particles. It was determined that strong Bronsted acid sites on the surface interact with the ether oxygen, a Lewis base, of PEO to induce adsorption. In this work characterization of PEO binding sites on oxides is reported and the mechanism(s) of PEO adsorption discussed.

Jan 1, 1997

By George Anagnostou

Time-dependent ground behavior may have important implications for the construction process or the life of a tunnel. The paper gives a concise overview of the influence of time on the deformations and the stability of underground openings, including topics such as face stability in soft ground or the time-development of pressure or deformations in squeezing or swelling rock. While keeping in mind practical questions of tunnel engineering, emphasis is placed on understanding the observed time-dependency, on the underlying mechanisms (such as pore water pressure dissipation or chemical processes) as well as on the respective inherent prediction-uncertainties and design-uncertainties.

Jan 1, 2007

By Alain A. Sonntag

This paper presents the most recent developments in KREBS technology directed towards treating higher throughputs, increasing efficiencies and providing further improvement in SX technology with a new concept: the submerged launder. Industrial plants built in the last past few years and using these improvements are described.

Jan 1, 1989

By R. Freer

Recent developments in expanded PTFE membrane filter cloths offer high flow rates and sub-micron particle removal. These high strength, industrial grade filter cloths can be tailored for tubular filters, leaf filters and rotary vacuum drums. Filtration techniques using tubular filters make possible filtration of difficult slurries with the elimination/reduction of filter aids and chemical additives. This paper describes principles of surface filtration, applying the membrane filter cloth and comparisons to gravity separators. Benefits to the mining industry include clear effluent, enhanced solids recovery and accelerated cost payback.

Jan 1, 1996

By V. A. Leach, Lokan. K. H., S. B. Solomon, R. S. O’Brien, L. J. Martin, K. N. Wise

INTRODUCTION The development during 1979 of a relatively small, but high grade (10,000 tonnes uranium at an average grade of 2 per cent), uranium ore body at Nabarlek in the Northern Territory, Australia offered an excellent opportunity to obtain detailed radiation data for an open cut mine operating during the dry season. The ore body (Queensland Mines Limited-1979), which was completely extracted in a period of four and a half months, consisted of a vein type deposit dipping at 30 to 45 degrees and contained a central core of pitchblende in massive and irregular pods, surrounded by lower grade fine grained disseminated pitchblende. Mineralisation extended from the surface to a depth of 72 metres over a length of 230 metres with an average but variable thickness of 1D metres. Ore near the surface had been heavily weathered and complex secondary minerals were formed which had dispersed from the main vein. Mining was carried out with large earth moving equipment. Overburden and weathered surface ore were removed initially with scrapers. At greater depths bulldozers were used to rip and assemble ore and rock at each level, and these were removed by large trucks to the ore and waste rock stockpiles. Where necessary, blasting took place during shift changes each evening. Mining was essentially continuous with two ten hour alternating shifts working for thirteen days out of fourteen. At the completion of mining a relatively small excavation (335m x 185m x 70m) remained, and this will serve as a tailings repository during the milling phase. FIELD MEASUREMENTS The inhalation of radon daughters, arising from the radioactive decay of radon gas is well established (Archer et. al. 1973) as a potential hazard in the uranium mining industry. Control over radon and its daughters to ensure that recommended exposure limits are not exceeded is achieved by providing adequate ventilation, and under normal circumstances natural ventilation from an open pit should be sufficient. However, during the dry season it is not uncommon for stable atmospheric conditions, with little horizontal air movement, to develop - particularly at night - and significant radon daughter concentrations may accumulate. Throughout the entire mining period measurements were therefore made of radon and radon daughter levels at representative locations within the pit and on the ore stockpile as it developed. Initially these measurements were carried out manually, using the Rolle method for radon daughters, (Rolle 1972) and .scintillation cells (Lucas 1964) or a two filter tube for the determination of radon (Thomas 1970). For the latter half of the period however, a continuous recording instrument, developed within the Laboratory was used to provide a detailed record of radon daughter levels within the pit. At the same time, continuous readings of wind speed and direction, and vertical temperature gradient between 10 and 3D metres were recorded on a 30 metre meteorological tower, situated 800 metres from the pit. Radon Emanation Rates It is evident that radon and radon daughter concentrations depend on the grade, or more particularly, on the surface radon emanation rate of the ore which is exposed. Accordingly, as the mine progressed, detailed measurements were made of both of these quantities. The surface emanation rate of radon was determined for each ore bench as it was exposed by placing an extended array of canisters, filled with freshly degassed activated charcoal, face down on the ore for a known time. These canisters, which had previously been calibrated in the Laboratory, adsorb radon with high efficiency, and the total radon adsorbed is measured after retrieval by detecting the gamma rays from the trapped radon daughters (Countess 1977). At the same time, as each canister was placed in position, a measurement of the local ore grade was made for each location. This was achieved with a calibrated sodium iodide scintillation detector, adjusted to detect the 609 keV gamma ray from the isotope 2148i, a decay product of radium. Finally, measurements were made of the radiation field 1 metre above the surface, with a gamma ray survey meter, which was calibrated in the Laboratory. The relationship between the scintillator count rate and ore grade was determined by comparing the scintillator output with the gamma monitor, and relating the latter measurements to ore grade (Thomson and Wilson 1980). It was observed that while emanation rates and ore grades varied widely, the ratio of emanation rate to ore grade was in general fairly stable. A plot of this ratio is presented as a function of depth below the original surface in Figure 1. For most observations the ratio is constant at a value of 80 Bq m-2 s -1 per unit ore grade, where ore grade is expressed as percentage of U308. At the surface however, where the ore was weathered, the ratio was about a factor of three higher, and at two particular depths, where high grade pitchblende was being removed, it was very much lower. This was not unexpected as earlier Laboratory studies of drill core samples from Nabarlek had indicated that the emanation coefficient (the fraction of radon produced within the ore which escapes from the mineral particles) decreases with increasing ore grade.

Jan 1, 1981

By Anthony W. Wakefield

The paper is intended merely as an introduction to methane hydrates, what they are and why they are important. It does not claim to be a cutting-edge research report, but may be useful for those to whom the subject is unfamiliar.

Jan 1, 2008