Search Documents

The dissolution kinetics of gold in iodide solutions with oxygen in an autoclave was investigated. The leaching process was described by a gas-liquid-solid heterogeneous reaction. The effect of stirring speed, temperature, partial pressure of oxygen, and concentration of lixiviants on the overall leaching rate was investigated. It was found that the dissolution of gold was limited by a heterogeneous chemical reaction. The apparent activation energy was measured to be 34.7-54.3 kJ/mol under the conditions studied. Experimental findings were in good agreement with the kinetic model proposed.

Jan 1, 1996

By S. Goodfellow, J. C. Ordóñez-Calderón, K. Esmaeili, N. Houshmand

A good understanding of the hardness of ore being handled and processed in a mining operation can significantly improve operational efficiencies by providing valuable data to support decision-making through the mining value chain (drilling, blasting, comminution). This study presents the results from the application of Machine Learning (ML) to predict rock hardness using various geophysical and geochemical features. Core samples from a mine site were logged using a multi-sensor core logging system. Measurements including ultrasonic p-wave and s-wave velocity, elemental concentration via portable XRF, and Leeb Hardness, were measured every 2 cm along the length of the core. The ML model was set up to predict the Leeb Hardness using the elemental concentrations and ultrasonic velocities as predictors. The Leeb Hardness values were grouped into three bins and used as a classification target for the ML models. Various ML models, including linear regression, support vector machines, decision tree, XGBoost, Random Forest, K-Nearest Neighbors, and Naïve Bayes were tested. The model performance demonstrated that the Random Forest and XGBoost models produced the highest accuracy of 74-91%. Random forest and XGBoost were then selected to perform regression models to estimate a Leeb hardness value rather than a hardness class. These models were able to estimate the Leeb hardness value by 4.57-4.87 % error.

Mar 2, 2022

By P. R. Taylor

A reaction is evaluated by which heated and pressurized water is used to precipitate metal oxides from loaded Kelex 100 complexes. Pure copper oxide (CuO) and pure nickel (Nio) in powder form, and ranging in average size from 12 to 25 micrometers, were found to precipitate from copper and nickel loaded Kelex 100/kerosene complexes, by water heated and pressurized to between 374 and 400 °c and 2170 psig (148 atm) and 3500 psig (238 atm). The precipitation is suggested to result from hydrolysis of the metal, following exchange for the hydrogen in the phenolic hydroxyl of the Kelex 100 structure, enhanced by the conditions provided by heated and pressurized water. The reaction is believed to have the characteristics of homogeneous nucleation and heterogeneous growth. The effects of temperature, pressure, initial metal concentration and seed addition on the kinetics of the process were studied. In addition, characterization studies were performed on the reaction products. A detailed discussion of the experimental results is presented.

Jan 1, 1992

By T. Marcher, C. Mathiesen, M. Allende, S. Bauer

"A unique pumped hydro storage facility using the ocean as a lower reservoir, combined with solar PV to create consistent, clean power will be presented: the Espejo de Tarapacá Project is comprised of a 300 MW seawater pumped storage hydroelectric plant using the Pacific Ocean as its lower reservoir and an existing natural concavity at the desert as its upper reservoir. The plant site is located in Chile’s northern coast 90 km south of Iquique. The site is characterized by a rocky shoreline and about 600 m of flat terrain moving inland, with an abundance of rock outcrops, after which there is a steep 700 m cliff. The power house and all waterways will be underground. The main focus is to present the rocks being expected in the underground works. As one of the actual most tectonically active regions of the world the seismic activity is particularly relevant and will be outlined in the presentation. INTRODUCTION Valhalla Energy is an independent Chilean-owned power development company. It focuses on the development, ownership and operation of renewable power projects. Valhalla was founded in 2011 with the goal of developing Chile’s natural renewable energy resources and strategically diversifies the country’s energy matrix away from an overdependence on imported fossil fuels. Valhalla began developing pumped storage hydro projects to provide scalable, clean, competitive, and reliable electricity by combining Chile’s superior solar resources with the country’s unique and extensive coastline suitable for storage.The capacity for renewable energy supply is driven by two distinct and unique natural characteristics found in northern Chile: (1) the abundant and reliable solar irradiation in the Atacama Desert and (2) a coastal site that benefits from a steep cliff and a natural concavity both within a relatively small land mass (see Figure 1). There are several potential sites in the northern part of the country that can be developed. The “Espejo de Tarapacá Project” is the first one to be built and subject of the present paper."

Jan 1, 2016

By O. H. Rostad

The importance of geology in ore reserve estimation has been stated by several authors. King et, a1 (1982) reported that the geological factor was the key deficiency where serious weaknesses in ore reserve estimation appeared, especially in grade. The foundation for a successful mining operation is an ore reserve estimate that neither overstates nor understates the true situation as to tonnage and grade. Overestimation of reserves can have devastating economic results. Overestimation of tonnage may lead to wasting money on an overbuilt plant or worse yet, if grade is seriously overestimated also, to undertaking an operation that is doomed to economic failure from the outset. Understated ore reserves can result in building a plant that is smaller than optimum which may result in higher unit costs. At worst, understated tonnage of ore reserves can result in a missed opportunity for a profitable operation. Failure of the ore reserve estimator to properly take into account all geologic and allied factors pertaining to the deposit can result in an ore reserve estimate that is overstated either as to tonnage or grade or both. This paper will focus on these factors and will not discuss rules about distances above or below a drift that should be given a classification of proven or probable, etc. Each deposit has its own particular characteristics which often require modification of general rules for defining limits of proven and probable ore blocks that work satisfactorily in another deposit. A number of references are included which discuss some of these problems. Definitions of ore reserve classifications and an illustration are given in the Appendix.

Jan 1, 1985

By Hun-Joon Sohn

Chemical metathesis and electrochemical reductive conversion of chalcopyrite in the presence of cupric ions were studied in sulfuric acid solutions for temperatures up to 90°C. The process results in the displacement of iron in the chalcopyrite lattice by copper ions with rejection of ferrous ions to the aqueous phase. The rate of reaction was found to be very slow, requiring subsieve-sized particles for extensive reaction to occur. The reaction was insensitive to copper ion concentration. Stirred ball milling of chalcopyrite introduces lattice strain. The reaction rate with strained particles was markedly higher than with annealed chalcopyrite. The reaction rate was found to be diffusion-limited, showing two distinct reaction stages corresponding to the formation of CuS (covellite) followed by Cu1.8S (digenite). The experimental activation energy for the first stage was 102 J (24.4 kcal) and the second stage 123 3 (29.4 -kcal) per mole. The rate-controlling process is diffusion of lattice ions, probably iron. The enhanced rate after milling is attributed to a recrystallization process which provides new paths for diffusion along dislocations and grain boundaries.

Jan 1, 1984

By James L. Hendrix

This paper is intended to give the reader an update on the work being done at the Mackay School of Mines about the fate of cyanide on precious metals mill tailings waste. During the last two years several tailings impoundments have been sampled and analyzed for total and free cyanides. From our sampling program we are beginning to learn valuable information concerning the fate of cyanides in precious metals mill wastes. Included in this paper is a detailed description of our sampling and analytical techniques. Also, some of the data obtained from five sites are given.

Jan 1, 1986

By William R. Nash

Case histories of water problems in underground mine shafts and tunnels are outlined to illustrate varying degrees of sophistication in grouting techniques currently applied in such construction. The interception of water underground can be one of prior knowledge, i. e., the site investigation provides necessary data to plan a grouting program prior to construction start, or excavations may encounter "changed conditions" or unplanned water. The latter includes catastrophic inflows and emergency situations where the structural integrity of a building or concrete shaft lining are jeopardized. The presentation of this paper outlines some applications of grouting work in underground mine construction throughout the United States in a variety of geological provinces and for a variety of minerals.

Jan 1, 1984

By J. M. Christian

Silver has been a much maligned metal in recent years. In the last three and a half years the price has fallen from around US$7.00 -$7.80 to as low as $3.50 this spring. It has consistently under-performed most other precious metals in the past few years, and has fallen to its lowest levels since the late 1940s in inflation-adjusted terms. Perhaps this is beginning to change. Since April, silver prices have outperformed gold and platinum. While this may continue in the years ahead, key questions remain regarding the pace and timing of any future silver price advances. I want to talk about the supply and demand factors that have led silver to its recent position. Also, I will outline a possible path for silver supply, demand, and prices for the next several years. Before I dive into my discussion of the silver market, allow me to explain who I am. One of the points we always make to clients early in a relationship is that, when you are listening to someone's opinions, you always must remember who it is you are listening to, and why he might be saying whatever it is he wants you to hear. So often, people take opinions from brokers, traders, or investment advisors as gospel truth, never stopping to ask themselves two key questions: Is there any reason to believe that this person knows what he is talking about, and, second, is he trying to sell me something, in telling me this.

Jan 1, 1992

By T. Weatherwax, A. Rai, J. Poor

"This paper provides an overview of the current use of auxiliary ventilation products and the challenges with limited air quantity in dead-end entry or working faces. The PVC’s low frictional factor, low physical constraint and minimum leakage properties were ideal to develop as ventilation duct in conjunction with the concept of ""Made in the US and Used in the US"". The PVC duct supports the operational and total cost of ownership with on-going success. This paper will discuss the continuous improvement made in ventilation ancillary products for optimum results. The paper will also cover mine site usage of second generation PVC vent duct underground and the results from the operational and technical side making a difference in health and safety and overall auxiliary ventilation. INTRODUCTION The Barrick Turquoise Ridge Inc. (TR) is located in northern central Nevada, and is situated within the Basin and Range province, near the northeast end of the Osgood Mountains (see Figure 1). The TRJV mine consists of typical Carlin type- gold mineralization characterized by low strength rock of altered limestone, siltstones, and mudstones. The weak nature of the ground facilitates the need for underhand cut and fills mining methods.Mining Method; Underhand cut and fill: The mine uses underhand cut and fill method which has 12’x12’ and or 14’x14’ top cuts with several different size undercuts. The ore body is accessed off of a secondary tertiary heading, utilizing a heading with a cross section of 14W x 14H or 15W x 15H configuration. In the wider and more massive zones, two headings in a production panel may be worked at any one time. Drift round lengths are determined by the ground conditions and drift dimension. An example of a typical topcut and associated undercut layout is shown in Figure 2."

Jan 1, 2016

By Jayson Ripke, Peter Amelunxen, Brandon Akerstrom, Fernanda Solís

It is commonly known in the industry that one of the key challenges for a greenfield project, such as Capstone Copper’s Santo Domingo project, is the obtention of samples for metallurgical testing and subsequent plant design. To face this challenge, the Santo Domingo project completed 169,692 meters of drilling. The material collected has been used for a variety of analysis including the economic recovery of iron, which contributes significant economic value to the Santo Domingo business case. Composite and variability samples, covering the main geological units considered in the life of mine (LOM) plan, were selected for bench and pilot scale testwork. Davis Tube Tests, small scale Low Intensity Magnetic Separation (LIMS) tests and a pilot utilizing a 48 in (1.2 m), diameter magnetic separation drum were completed. The testwork demonstrated that the Santo Domingo ore could achieve iron concentrate grades of 65% Fe - suitable for blast furnace, and 67% Fe - suitable for Direct Reduction, primarily by concentration of magnetite. The outcomes of this work have informed the iron concentrator plant design and scale up.

Feb 1, 2025

By Albert F. Duzy

Recently there have been some problems associated with hot coal in shipments from the USA to overseas markets. This paper will serve several functions. First, a brief review is presented, together with a selective bibliography. Second, a thorough discussion of coal oxidation is covered. Third, potential effects of storage are presented and, lastly, methods are suggested for the safe storage and bulk transfer of coal. The scope includes coal storage for power plants.

Jan 1, 1983

By M. A. Girts

Wetlands can be constructed inexpensively on mined lands to treat small flows of acid mine water. Metals are removed from the water by the wetland vegetation and indigenous bacteria. Full-scale field tests initiated at over 20 mine sites during 1984 and 1985 indicate that water quality can be upgraded to meet discharge standards with relatively minor maintenance requirements. Iron concentrations of 25-85 mg/L in the influent water fall to less than 2 mg/L during flow through a small wetland. Manganese can also be removed, though somewhat less efficiently. At the discharge, pH is easily raised to 6 by flow over limestone.

Jan 1, 1986

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 S. S. Peng

Since the introduction of shield supports in 1975, safety and production in U.S. longwall faces have improved considerably. Many faces had a daily production of up to 8,000-10,000 tons and productivity reached 600 tons per man-shift. But a longwall face requires expensive equipment which slows down the growth rate of the percentage of longwall production. Among the equipment cost the shield support accounts for 50-60%, a very large proportion. Therefore, it will have a large impact on the growth of longwall mining in the U.S. to reduce the support cost (1).

Jan 1, 1988

By C. Hanson

Two modes of potential loss of oxime extractants in liquid extraction processes for the extraction of copper have been studied. In loss "by chemical degradation, two mechanisms of acid hydrolysis are possible, some reagents degrade primarily in the organic bulk phase, Others at the interface between the organic phase-- phase protects the oxime but salts added to the aqueous acid phase can promote the rate of degradation. The reagents reported on are the LIX series (Henkel Cpn), SME529 (Shell Chem.Co.) and P5100 (Acorga) Loss by organic entrainment in the aqueous phase leaving mixer-settlers has also been studied, parameters investigated including impeller/tank geometry and the phase inlet arrangements. The consequences of extractant loss by the above mechanisms...are commented upon. They include the direct economic cost, the possible environmental problems and the implications for downstream operations such, as electrowinning.

Jan 1, 1980

The viability of physico-chemical purification methods such as selective flocculation for separation of two components having similar chemical composition and same crystal structure but different surface properties is demonstrated. Loss of selectivity was observed in a dolomite-dolomite mixture with Polyethylene Oxide (5 million molecular weight) as the flocculant. Hetero-flocculation was minimized using a low molecular weight PEO (MW -105) as the site blocking agent (SBA). Near complete separation was achieved at pH 10.5 at 100% recovery level.

Jan 1, 1993

Projections of coal reserves in Central Appalachia are essential for long-term planning in the region. Annual production is declining in some states, such as Virginia, and mineable reserves for the Central Appalachian Coalfield are challenged by difficult geological, mining, and market conditions. In order to project coal mining longevity in this region, interviews with mining companies were conducted to assist in the determination and assessment of technical and economic factors that impact coal seam mineability. This information was applied to seam and coal reserve data developed by state and federal governments. The results were carefully analyzed to determine the effects of various factors on the overall mineable coal reserve base.

Jan 1, 1998

By A. Mull, J. Weyer, J. Brune

"The “Reiche Zeche” mine in Freiberg, Germany, a 600-year-old lead-zinc-silver mine with extensive open mine workings, experiences severe ventilation losses due to leakage. Much air leaks into abandoned workings, decreasing the airflow available to active working areas. Usually, this leakage occurs in remote areas that lack transportation infrastructure like roadways or rail, making it difficult to haul construction materials to the sites to erect passive ventilation controls such as stoppings, regulators and seals. Transportation distances make it impractical to hand carry traditional construction materials, such as bricks and concrete. Alternative materials, such as brattice, foaming polymers, concrete canvas, and some innovative ventilation control designs have been investigated for this purpose. The suitability of the materials investigated depends on many factors including the pressure it can withstand, the ease of transportation, and workability. Impacts of mine water must be considered, as the Reiche Zeche is below drainage and experiences significant inflow of water. Researchers must consider the effects water inundation as well as how the stopping construction material reacts to being exposed to acidic mine water. INTRODUCTION Problem Statement Mining in the area around Freiberg, Germany began in the 12th century. The mine is used for research, mining engineering education, tourism and air conditioning for a local hospital. The first records of mining in the Reiche Zeche are from around 1384. Due to the strength and competency of the host rock, many of the oldest workings still stand and remain open today, although they may not be accessible. Reiche Zeche also connects to several other, closed mines in the area that are largely unmapped. This allows air to leak into neighboring mines, reducing the air available to ventilate to the working areas of Reiche Zeche. In order to improve ventilation efficiency, it is necessary to control the ventilation and reduce leakage by constructing seals, stoppings and regulators. A challenge with building traditional seals and stoppings in the Reiche Zeche is that the old workings lack transportation pathways or rails. Also, the lack of compressed air, water or electricity makes it difficult to operate power tools and drills. This means that construction materials must be hand carried – some over distances of several kilometers. Figure 1 shows a typical drift in the Reiche Zeche. Researchers investigated using lighter, more easily transportable materials including concrete canvas, expanding polyurethane and polyurea foams, and brattice. The applicability and utility of these materials depends on a variety of factors including the ventilation air pressure, chemical resistance to acidic and mineral-laden mine waters, ease of transport, and ease of construction. Stoppings and seals must be substantially constructed so that they remain tight and do not require maintenance. It is also important to consider the toxicity of the construction materials in case of a mine fire."

Jan 1, 2016

By Roger Storry, Donald Bruce, Arnaud Hochart

"INTRODUCTIONThe Port of Miami Tunnel (POMT), designed and constructed by Bouygues Civil Works Florida between 2009 and 2014, was a Public Private Partnership between the Miami Access Tunnel Concessionaire, Florida Department of Transport, Miami-Dade County and the City of Miami. The project comprises dual 11.3m internal diameter, 1.27km long, twin lane road tunnels running between Watson and Dodge islands and under the main shipping channel in Biscayne Bay (Figure 1).The POMT was a unique project which embodied many technical firsts and involved the first large diameter tunnels constructed through Florida’s challenging sedimentary carbonate strata. At the outset, a comprehensive ground investigation was performed, using both conventional and less conventional investigation techniques, to characterise the highly heterogeneous ground conditions.The findings of the investigation had a major impact on the tunnelling methods, triggering a series of mitigation works to ensure that the tunnels could be excavated safely and effectively. The mitigations included modifications to the already designed Tunnel Boring Machine (TBM), to facilitate an innovative excavation process, and a unique grouting campaign (Storry et. al. 2013a). The project was completed and opened to traffic in August, 2014 and has significantly alleviated traffic congestion in Downtown Miami.GEOLOGICAL CONTEXTThe geological conditions at the project site consist of carbonate sediments which can be divided into distinct geologic units; the Miami Limestone Formation (Layers S3, S4), the Fort Thompson Formation (Layer S5), the Anastasia Formation (Layer S6), the Key Largo Formation (Layer S7) and the Tamiami Formation (Layer S8). Multiple changes in sea level over a relatively short geologic time scale have resulted in a heterogeneous profile consisting of interbedded sedimentary rocks and sediments, which vary widely, both vertically and laterally (Figure 2)."

Jan 1, 2016