Abstract: Due to the remote locations of mining projects and the need for long transmission lines to provide electrical power, mining sites often operate with poor network power quality and low short-circuit capacity. To cope with this situation, more and more mining operators are considering the installation of appropriately designed synchronous condensers together with power factor correction and harmonic filter systems (PFC & HFS). The installation of such power quality equipment is viewed as a technological advancement in the mining application. an adequate level of short-circuit power is essential and has to be ensured for the safe and reliable operation of especially large cycloconverter-driven gearless mill drive systems (GMDs) used for grinding. This paper explores the impact, technical advantage and reasoning for the selection of this advanced hybrid technology to cope with the power system challenges of future mining projects. It also delves into the potential problems and how to address them.

Abstract: Drilling into coal mine roof strata to install roof bolts has the potential to release substantial quantities of respirable dust Due to the proximity of drill holes to the breathing zone of roof bolting personnel, dust escaping the holes and avoiding capture by the dust collection system pose a potential respiratory health risk Controls are available to complement the typical dry vacuum collection system and minimize harmful exposures during the initial phase of drilling This paper examines the use of a bit sleeve in combination with a dust-hog-type bit to improve dust extraction during the critical initial phase of drilling A twisted-body drill bit is also evaluated to determine the quantity of dust liberated in comparison with the dust-hog-type bit Based on the results of our laboratory tests, the bit sleeve may reduce dust emissions by one-half during the initial phase of drilling before the drill bit is fully enclosed by the drill hole Because collaring is responsible for the largest dust liberations, overall dust emission can also be substantially reduced The use of a twisted-body bit has minimal improvement on dust capture compared with the commonly used dust-hog-type bit

Abstract: G industrial development and economic growth led by the modernization of China and India are propelling a burgeoning demand for copper anticipated to last decades. Concurrent rapid ore depletion is driving an overall declining trend in the average grade of copper ore worldwide and compelling increasing processing costs despite new copper ore discoveries (Mudd, 2009). In response, lower-cost and low-energy heap leach processing using solvent extraction and electrowinning (SX/EW) to produce copper metal has seen expanded adoption; accounting for about 25 percent of global and nearly 50 percent of primary copper production in the United States (Komulainen, 2005 and Dutrizac, 2007). However, even this transformative process is struggling and has, except for a few exceptional cases, generally failed to be economically viable when the heap leach product stream known as the pregnant leach solution (PLS) tenors fall below 0.5 g/L of copper. Opportunity: As a result, huge amounts of valuable ore assets in the form of marginal or difficult to leach ores like low-grade chalcopyrite (Fig. 1) are lying fallow – physically accessible but economically out of reach (Davenport and Schlesinger, 2002 and Singer et al., 2008). Numerous methods to economically utilize this ore such as bioleaching, PLS strengthening via reverse osmosis (R/O) and ion exchange (IE), and direct metal removal from weak PLS or waste streams by electrowinning (EMEW — Electrometals Technologies Ltd. and Freeport-McMoRan’s flow through electrowinning cell) and selective precipitation (BioSulphide process – BioTeQ) have been explored. Despite strenuous and costly efforts, a broadly effective and dominant solution to this critical problem has not yet emerged. Blue Planet Strategies (BPS) developed DeMet approach offers new hope by cost effectively concentrating weak PLS to enable profitable and immediate copper production with existing infrastructure from the vast fallow ore resources currently considered waste.

Abstract: Focusing on raw ore with relatively high grade sulphur-bearing copper,the paper conducts phase analysis for copper ore,using different solvent extraction to continuously separate each phase.It adopts bromine water to separate the copper oxide instead of potassium cyanide which is an extremely toxic substance,and it conducts condition optimal experiment.Detect copper content of each phase after separation.If the resultant is in accordance with total copper content of the sample,the reproducibility of the test is good.Apply this method to the copper phase analysis of Kuandian iron ore sample which is copper and sulphur bearing,the satisfied result is obtained.

Abstract: The analysis and design of cross passages for twin bored tunnel projects provides unique challenges when considering the 3D geometry, geotechnical behavior, and interaction between the internal tunnel structures and the ground. Current practice involves complicated modeling to approximate the cross passage behavior and facilitate design of the necessary support structures, often consisting of a combination of geotechnical solutions (e.g. grouting, ground freeze), excavation support (shotcrete, spiling, rock bolting), and structural solutions (internal props) to maintain the mainline tunnels and the opening space. However, little work has been done to validate these solutions with field data from construction projects. The Center for Underground Construction and Tunneling at the Colorado School of Mines has been provided with strain gauge field data for the Brisbane Airport Link, courtesy of Arup, one of the design firms on the project. A thorough evaluation of this data has been conducted to establish the development of forces in the mainline tunnel structures (segments and propping) throughout the cross passage excavation sequence. Results from the gauges have been compared to basic analytical and numerical solutions for validation. The observed behavior of the cross passages during excavation was established. Key mechanisms driving behavior include the effects of prop installation and jacking on the segmental lining, the unloading effect observed with geological excavation, the development of stresses due to soil arching, and the effects of locked-in lateral stresses around the tunnels. The influence of the two-layer heterogeneous geology of the project was determined to be a key factor in driving the majority of these behaviors. The analysis is concluded with a discussion of the importance of each mechanism to potential future design of cross passages and potential future developments for cross passage instrumentation schemes.

Abstract: The National Institute for Occupational Safety and Health has observed that many control rooms and operator compartments in the U.S. mining industry do not have filtration systems capable of maintaining low dust concentrations in these areas. In this study at a mineral processing plant, to reduce respirable dust concentrations in a control room that had no cleaning system for intake air, a filtration and pressurization system originally designed for enclosed cabs was modified and installed. This system was composed of two filtering units: one to filter outside air and one to filter and recirculate the air inside the control room. Eighty-seven percent of submicrometer particles were reduced by the system under static conditions. This means that greater than 87 percent of respirable dust particles should be reduced as the particle-size distribution of respirable dust particles is greater than that of submicrometer particles, and filtration systems usually are more efficient in capturing the larger particles. A positive pressure near 0.02 inches of water gauge was produced, which is an important component of an effective system and minimizes the entry of particles, such as dust, into the room. The intake airflow was around 118 cfm, greater than the airflow suggested by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) for acceptable indoor air quality. After one year, the loading of the filter caused the airflow to decrease to 80 cfm, which still produces acceptable indoor air quality. Due to the loading of the filters, the reduction efficiency for submicrometer particles under static conditions increased to 94 percent from 87 percent.

Abstract: Coal preparation is often necessary to produce clean and efficient thermal coal to meet the demands of the steam and coking coal markets, which have unique contract constraints. A main requirement of preparation is the removal of ashbearing minerals, such as shale and pyrite, which are separated from coal particles by a variety of processes depending on particle size. Coarse particle size fractions are processed in systems that use variance in particle density (heavy media vessels, heavy media cyclones or spirals), whereas fine size fractions are processed with flotation, which uses the material’s surface properties. The froth flotation process works by exploiting the difference between the hydrophobic nature of coal particles and the hydrophilic nature of ash-bearing minerals. Essentially, tiny air bubbles are introduced into a slurry of fine coal and ash-bearing particles and water in the flotation cell. The coal particles are naturally hydrophobic and thus attach to the bubbles, floating to the top of the reactor where they can be recovered. Conversely, the ash-bearing particles are hydrophilic and are transported to the bottom of the cell through the motion of the fluid. In practice, froth flotation also requires a variety of chemical additives, the fate and transport of which are of increasing environmental interest. At the very least, frother chemicals are needed to strengthen the production of stable, ultrafine bubbles that accumulate the floated coal particles at the top of the cell, and collector chemicals are generally needed to increase the hydrophobicity of the coal particles and thus enhance flotation performance (Laskowski, 2001). The collectors are generally oily substances that coat the coal particles and increase their contact angles with water. Conventional collectors include petroleum products like kerosene, fuel oil and, most commonly, petro-diesel (Vijaya Kumar et al., 2010). “Diesel” in this paper refers to petro-diesel. Residual diesel range organics in process waters from laboratory fine coal flotation tests

Abstract: Background In 2005, the California Office of Environmental Health Hazard Assessment (OEHHA, 2005) adopted a 70-year chronic reference exposure level (REL) for PM4 (particulate matter having aerodynamic diameter of 4 micrometers or less) crystalline silica. The REL was extrapolated from occupational hygiene epidemiological studies, essentially all of which were based on in-plant PM4 crystalline silica measurements. No well-established ambient sampling technique for PM4 crystalline silica was available at the time that OEHHA adopted its REL. The personal samplers used for the National Institute for Occupational Safety and Health (NIOSH) Method 0600 in-plant sampling of employee exposure were designed for concentrations higher than ambient levels. The limit of quantification (LOQ) of PM4 crystalline silica on NIOSH 0600 filters was too high for the effective sampling of ambient air. In 2006, in response to the need for an ambient sampling technique for PM4 crystalline silica, we developed a sampling method based on the U.S. Environmental Protection Agency’s (EPA) design and operating requirements for PM2.5 samplers (Richards and Brozell, 2006). The sample flow rates in Thermo Fisher Scientific Inc.’s Partisol 2000i low-vol PM2.5 Federal Reference Method (RFPS-04980117) samplers were adjusted from 16.7 L/ min to 11.1 L/min to change the 50 percent cut size of the sharp cut cyclone to 4 micrometers (aerodynamic) rather than 2.5 micrometers. The Teflon membrane filter used for PM2.5 sampling was replaced with a polyvinyl chloride filter to allow for NIOSH Method 7500 crystalline silica analysis. The use of a PM2.5 sampler with adjusted sample flow rate along with NIOSH Method 7500 X-ray diffraction (XRD) analyses provided a LOQ for PM4 crystalline silica of 0.31 micrograms/m. This LOQ value was based on (1) a 15.98m sample volume obtained in a 24-hr sampling period as measured by the Fenceline PM4 crystalline silica concentrations near sand mining and processing facilities in Wisconsin

Abstract: Researchers from the National Institute for Occupational Safety and Health’s Office of Mine Safety and Health Research conducted an assessment of the effects that ground control mesh might have on rock and float coal dust distribution in a coal mine. The increased use of mesh to control roof and rib spall introduces additional elevated surfaces on which rock or coal dust can collect. It is possible to increase the potential for dust explosion propagation if any float coal dust is not adequately inerted. In addition, the mesh may interfere with the collection of representative dust samples when using the pan-and-brush sampling method developed by the U.S. Bureau of Mines and used by the Mine Safety and Health Administration for band sampling. This study estimates the additional coal or rock dust that could accumulate on mesh and develops a means to collect representative dust samples from meshed entries.