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By S. Angioletti

This paper addresses strategic investment decisions when they are nested in a project development format where each project is implemented in phases and each phase is approved to move on to the next phase only if certain technical and economic requirements are met. This configuration is sometimes referred to as a ?Project Portfolio?. Mining companies maintain project portfolios in their exploration investment plan. This study proposes a procedure to best manage an exploration project portfolio including technical and economic uncertainties. The procedure may support decision makers in a simple and intuitive way, while maintaining the rigor and precision required by the rather large amount of financial resources typically called for by mining projects. The procedure was tested in a real case study of a gold mining company and its exploration projects portfolio. The procedure uses the following approaches: i) investment valuation methods under technical and market uncertainties based on Option Pricing Model, Real Option Theory and Option Space; ii) portfolio management and Stage Gate®1 method; iii) Monte Carlo simulation.

Jan 1, 2010

By T. P. Meloy

Understanding the illusive nature of the catastrophic failure of brittle solids is difficult. Proposed is a hypothesis of crack cessation. If, during catastrophic failure, cracks in a brittle solid stop before terminating on a preexisting crack, this hypothesis suggests that the slope of the size distribution curve will be lower. Moreover, this hypothesis suggests that when cracks stop, negative valleys and negative comers appear. Furthermore, particle shapes also change with particle size. While the hypothesis is unverified, it suggests that crack cessation could play a role in the comminution process.

Jan 1, 1996

By K. V. Raj, VASU GANGRADE

Airflow in large-opening stone mines is largely dependent on the natural ventilation due to the large cross- section area of the opening. The openings of such stone mines are typically twice or thrice the size of typical underground coal or metal/nonmetal mines. Due to the influence of natural ventilation, air velocities as well as the static pressure drop in the mines are low. Mines rely on auxiliary fans to ventilate active faces to reduce contaminant exposure to mine workers. The National Institute for Occupational Safety and Health (NIOSH) is conducting research on ventilation of large-opening stone mines to reduce worker exposure to dust and other contaminants such as diesel particulate matter (DPM). In order to reduce worker exposure to dust and DPM, an understanding of the airflow pattern due to auxiliary fans in the mine is needed. Under this research, NIOSH researchers are exploring the computational fluid dynamics (CFD) modeling to understand the airflow behavior in large-opening mines. In this paper, the team is presenting the results from three-dimensional CFD modeling of airflow in a large-opening stone mine and investigating the effect of a fan placement with the movement of trucks.

Feb 1, 2025

By Eti Purwaningsih, Widi Astuti, Erik Prasetyo

Selective-reductive leaching of manganese from low-grade manganese ore using tannic acid as a reductant in acidic media was demonstrated by XRD, SEM-EDX characterization, and batch leaching studies at room temperature. The pH change in the liquid phase before and after leaching revealed that selectivity of manganese over iron was due to the hydrolysis of iron. The acidity in the liquid phase during leaching was dictated by two mechanisms: proton-consuming reaction (manganese oxide reduction by tannic acid) and proton-producing reaction (ferric ion reduction by tannic acid to produce ferrous ion). Based on the leaching studies, the more prevalent reaction between these two was determined by initial leaching conditions: tannic acid concentration, sulfuric acid concentration, liquid-solid ratio, temperatures, and agitation time. Kinetic studies revealed that maximum recovery was attained within 6-h agitation, which indicated a product layer diffusion process.

By E. T. Pecina

Bioleaching is a viable option for the processing of auriargentiferous refractory ores with high arsenic content. The application of mesophilic (A. ferrooxidans and ?L. ferrooxidans?) and thermophilic bacteria of the genus Sulfolobus (S. solfataricus and S. acidocaldarius) as oxidant treatment before the cyanidation of an industrial arsenical pyrite concentrate is presented. The results show that extraction of gold and silver increases due to bio-oxidation caused by mesophilic bacteria and results in a maximum gold recovery of 68%. In all strains studied, biooxidation resulted in an average silver recovery of 50%. The results showed that all evaluated strains were sensitive to solids content (5 to 20%) and average particle size (75 and 38 µm) of the concentrate.

Jan 1, 2010

By W. L. Chen

In the United States hydraulic cyclones have been used for thickening, classification and cleaning in coal preparation plants for many years. The cleaning cyclones presently in use are based on using a "heavy medium", such as a fine magnetite and water pulp. The latest addition to cleaning cyclones is the one which uses ?water only?, or simply called "Hydrocyclone". Just as was the heavy medium cyclone, the hydrocyclones were originated in the Netherlands (1, 2). Plants using hydrocyclones were built in Europe (3) and test plants were erected in Canada (4, 5, 6) and India (7). Roberts and Schaefer Company has built four plants using hydrocyclone circuits. One additional plant is in the process of construction.

Jan 1, 1965

By John A. Organiscak

The Bureau of Mines evaluated a new dust control technique for longwall personnel required to work at the tailgate end of the face. This technique utilizes a water-powered scrubber to clean a portion of the face air, which is discharged behind a brattice partition at the working area. Laboratory simulation of this system in a wind tunnel resulted in average efficiencies greater than 70 pct with system efficiency directly related to scrubber quantity. Underground evaluations indicated a similar direct relationship between scrubber quantity and system efficiency. Gravimetric measurements of respirable dust made during these underground evaluations resulted in average protection efficiencies ranging from 30.7 to 42.5 pct with increasing scrubber air quantity.

Jan 1, 1983

By John Lovering

The Afton property is located 180 air miles East-Northeast of Vancouver and nine miles West of Kamloops, a city of 60,000 people, in South Central British Columbia, Canada. The mine is adjacent to the Trans-Canada Highway at an elevation of 2,200 feet above sea level. The orebody is a porphyry, copper deposit that has undergone supergene alteration. The-major economic minerals in the supergene zone are native copper and chalcocite with chalcopyrite and bornite in the hypergene areas. The grade is one percent with an overall copper distribution: 70% native, 25% chalcocite and 5% chalcopyrite with bornite and covellite. The ore also contains important, but variable amounts of gold and silver.

Jan 1, 1985

By Mohammed Laraba, Rodrigo Alvarez Garcia, Juan Maria Menendez-Aguado, Roula Abdelmalek

The aim of this research is the study of the WHIMS parameters on the improving process of a local (DD: Djebel Debbagh, East of Algeria) kaolin. The obtained results of performed XRF, SEM, and XRD characterization showed that this local material is an alumino-silicate containing kaolinite and halloysite with MnO and Fe2O3 impurities (respectively 39.30% and 34.67% alumina and 38.18% and 39.70% silica in both samples (DD2 and DD3). After homogenization, crushing, and milling, a multiparameters factorial experimentation (grain sizes, intensity, and dimension of matrix balls) showed that WHIMS is an effective process to improve the quality of this kaolin, mainly: removing their impurities. Dimensions of matrix balls (Db) = 2 cm, intensity of the applied magnetic field (I) = 1.5 T, and grain sizes (Dp) = > 100 < 250 μm) are the optimal values to reach 91.06% for manganese and 93.45% for iron as removing yield. The statistical analysis of these results sorted the investigation parameters and showed that Db has the highest and most significant influence on the recovery of iron and manganese particles. The magnetic field intensity (I) has a less important influence while the grain size has an average influence (positive on the iron recovery but a negative one on the recovery of manganese).

Jun 11, 2022

By Lawrence D. Ramspott

A test of retrievable geologic storage of spent fuel assemblies from an operating commercial nuclear reactor is underway at the Nevada Test Site (NTS) of the U.S. Department of Energy his generic test is located 420 m below the surface in the Climax granitic stock. Eleven canisters of spent fuel approximately 2.5 years out of reactor core (about 1.6 kW/canister thermal output) were emplaced in a storage drift along with 6 electrical simulator canisters. Two adjacent drifts contain electrical heaters, which are operated to simulate within the test array the thermal field of a large repository. Fuel was loaded during April-May 1980 and initial results of the test will be presented.

Jan 1, 1981

By Shuang Shuang Huang, John Fillos

Ozonation was evaluated as an alternative treatment process for leachates of municipal landfills. The study was carried out on leachate from the Fresh Kills Landfill, New York City. The leachate has strong tea color and BOD5 ranging between 90 mg/L and 130 mg/L. The average COD, TOC and NH3-N concentrations were 1800 mg/L , 550 mg/L, and 665 mg/L, respectively. The kinetics of the process were studied in a sparged batch reactor by developing concentration- time profiles for residual color and TOC. Continuous flow experiments were then carried out at two selected contact times. The process was found to be effective in the treatment of leachates for color and TOC removal.

Jan 1, 1992

By R. L. Grayson, L. L. Probert

A three-year project focusing on the depth profiling of respirable coal mine dust particles using scanning electron microscopy coupled with energy dispersive X-ray analysis resulted in the development of statistically classified particle-behavior models. The models depict the changing silicon fraction for particles at 5-, 7-, 9-, and 11-keV accelerating voltages, thereby giving a clear indication of the nature of various types of mineral particles. This paper focuses on the results for respirable quartz particles sampled from five underground coal mines across the US. Through statistical analysis of results the relationship between the fraction of surface available quartz in respirable dust samples and coal rank is established for three Pennsylvania coal seams.

Jan 1, 1995

By R. Q. Honaker, D. P. Patil, A. Sirkeci

Because of increasing production of fine coal during mining over the past century and because of inefficient fine-coal recovery technologies, a vast reserve of high-quality coal now exists in refuse ponds. A novel finecoal circuit, consisting of a hindered-bed classifier, an enhanced gravity concentrator and a flotation column, was evaluated for the recovery of fine coal from refuse ponds. The treatment of a pond derived from Pittsburgh No. 8 seam coal resulted in the production of a premium fuel containing less than 5% ash and a calorific value of about 30,170 kJ/kg with 60% mass yield. Results from the treatment of two refuse pond materials are presented in this paper.

Jan 1, 2002

By R. L. Frederking

Geological remote sensing is, "....the study of the Earth utilizing electro-magnetic radiation (EMR) which is either reflected or emitted from the land surface in wavelengths ranging from ultra-violet (0.3 micrometre) to microwave (3 metre)."1 Selected examples which illustrate a variety of successful geologic applications include lithologic mapping, 2 engineering soils mapping,3 tectonic interpretation,4 and mineral and petroleum exploration.5 This report examines the applicability of remote sensing for bauxite exploration in northeastern Mississippi. Specific objectives were to map lithologies of northeastern Mississippi from LANDSAT imagery, to determine the utility of LANDSAT imagery for delineating and mapping known deposits of bauxite, and to discover and map new bauxite deposits.

Jan 1, 1977

By Daniel G. Ganey

Kerr-McGee Coal Corporation has used diesel face haulage and support equipment at its dual-seam Galatia Mine in Southern Illinois since production activities commenced in 1983. The mine began production from its lower seam, the Harrisburg No. 5 coal seam, in October 1983 and from the upper Herrin No.6 coal seam in April 1985. Before production began, the company developed a program designed to make use of the flexibility offered by diesel equipment. While productivity was an important goal, the top priority of the program was to provide a safe and healthy work environment for the miners. Management believed that high productivity would naturally follow. History has proven this belief to be true.

Jan 1, 1990

By R. E. Johnson, M. Schipper-Zablotskaja, B. R. Palmer, van Sandwijk A.

A procedure has been developed for the removal of zinc from acid solutions containing aluminum, silicon, calcium, magnesium, sodium, potassium and manganese ions and high concentrations of chloride ions. The first step of the procedure involves the precipitation of aluminum and silicon at pH 4.2. The second step, the removal of the zinc as zinc oxide, was studied in detail to get in- sight into the formation of oxychlorides. A diagram was developed giving the conditions at 75O C under which the formation of oxychlorides is avoided. Under optimal conditions a zinc oxide with less than 0.5 weight percent of chloride can be produced from 11 - 16 g/l chloride solutions.

Jan 1, 1993

By W. J. Dolinar, S. P. Sandoval

The US Bureau of Mines (USBM) implemented the Fe2+/ Fe3+-SO2 anode reaction in a Cu-electrowinning cell with full-size electrodes. Electrowinning was conducted using industrial electrolyte at 258 A/ m2 (24 A/ft2) and 40°C. Manifold injection of electrolyte provided circulation between the electrodes. Five-day operation using an optimized manifold gave an average cell voltage of 0.94 V at 89% current efficiency, which amounted to an energy savings of 2.82 MJ/kg (0.355 kW-hr/lb), compared to conventional electrowinning. Acid milling 5was completely eliminated, and the SO2 concentration 23 cm (9 in.) above the cell averaged 0.06 ppm.

Jan 1, 1996

By Raphael Mourad, Colin R. Phillips

Investigation of the traps in LiF:Mg, a multi-peak phosphor, was carried out using simple phosphorescence decay analysis. Half lives at room temperature of the trapping centres (peaks -lb, -la, -1, 0, 1, 2, 3a and 3) in the phosphor after irradiation with [a] radiation were found to be 3 s, 5 s, 28 s, 4 min, 15 min, 1 h, 6 h and 2 d respectively. Justification for the method of analysis is pro- vided and the results of measurements compared with published data. The effects of pre-annealing at 400°C for 1 h and 80°C for 24 h on the trapping configuration and on the trapping efficiencies were also studied.

Jan 1, 1981

By Murray Malott

The Sheppard Subway extension is currently being constructed in Toronto, Canada for the Toronto Transit Commission (TTC). McNally International Inc., in a joint venture with PCL and the Foundation Company of Canada were awarded the Twin Tunnels contract of the Sheppard extension. The Twin Tunnels project is approximately 4.4 km in length and consists of two separate twin bore drives each 3.3 km and 650 m in length and approximately 400 m of cut and cover construction. This paper presents a case history of the construction of the soft ground tunnels through the complex Toronto glacial deposits using two 5.9 m outside diameter Lovat earth pressure balance (EPB) tunnel boring machines.

Jan 1, 1999

By John D. Elmes

The purpose of this paper is to describe the geology and the modelling work carried out to date. The Lisheen Zinc-Lead deposit was discovered in April, 1990. The deposit comprises two stratiform sulphide orebodies, hosted within the Lower Carboniferous Waulsortian limestone formation. The fully diluted geological resource is 22.5 Mt @ 13.02% Zn and 2.19% Pb, based on a total of 548 diamond drill-boles and 10,998 sampled core intersections. Due to the absence of a geological marker it was necessary to apply economic criteria to define and model the resource envelope. In common with other drill-hole geological databases, the establishment of a workable geological model presents unique challenges.

Jan 1, 1998