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By D. M. Larsen

Since start-up in 1985 the Cannon Mine has produced and shipped a 170 g Au/tonne (5 oz Au/ton) flotation concentrate to various smelters for gold and silver recovery. Several processed have been investigated to economically produce dore' at the mine site from the refractory concentrate. This paper describes recent laboratory and pilot scale test work utilized in the process design and engineering feasibility study of a 73 tonne/day (80 ton/day) pressure oxidation and CIL facility. The designed pressure oxidation circuit utilizes a series of vertical autoclave units operating at 170°C (338"F) and 1.4 MPa (200 psig). Projected operating costs are discussed.

Jan 1, 1993

By John Callahan

A stream sediment (minus 80-mesh and minus 60-mesh panned concentrates) and lithogeochdcal survey for gold did not locate any Triassic-age placer deposits in the northern Wadesboro and southern Sanford basins in North Carolina. A stream sediment geochemical program for uranium funded by the North Carolina Energy Institute did identify one and anomalous site (8.5 ppm U; 5 ppm Th) near Covenington, North Carolina and eighteen possibly anomalous sites (1-1.6 ppm U) . Five of the eighteen samples with uranium levels in the 1-1.6 ppm range have high thorium levels (112-853 ppm) and may indicate a monazite source for the uranium. Gold values as high as .83 ppm in the stream sediments and 9.3 ppm in the panned concentrates were obtained during the survey. Small (<.5mm) flattened grains of gold (1-4 grains) were observed along with coarse kyanite and/or monazite in some of the panned concentrates. A distinctive pattern of high gold values in the sediments was observed in the vicinity of Mangum, N. C. where Minard (13) reported values as high as 2.1 ppm £ram a Triassic lithology. Follow-up gold analyses on over 400 rock samples from twenty-eight exposures near Mangum failed to obtain any high values (<55 ppb). The presence of coarse kyanite, monazite and gold in panned concentrates may be from a source younger than the Triassic lithologies that the streams currently drain or adjacent Paleozoic rocks.

Jan 1, 1979

By J. A. Herbst

Ball mill grinding circuits can be subject to upsets that arise from variable characteristics of the feed ore. These upsets are transients in critical circuit variables such as ball mill mass holdup, circulating load, sump level, cyclone efficiency and product particle size. They may occur frequently so that the operation is continuously fluctuating or they may be of such magnitude that some of the equipment is overloaded, resulting in shutdown, or an undesirable product particle size. The feed ore characteristics that influence ball mill circuit behavior in this manner include the grindability of the ore, the eventual transport characteristics of the ore in the mills and the feed ore size distribution. Control strategies for grinding circuits using conventional proportional-integral (PI) control have limitations to their effectiveness in controlling against feed ore disturbances. The first of these are the interactive nature of two or more control loops on a single circuit. Under some circumstances they begin to fight each other, increasing control error and settling time. PI control loop gain constants can be tuned to give best response for some set of conditions but once these change, as they would with a change in the feed ore, they are no longer the "best" ones (Shinsky, 1967). Due to these limitations, alternatives to conventional PI control strategies have been investigated for grinding as well as other mineral processing operations. These alternatives, all computer-based, include self tuning regulators, decoupling control and optimal control (Herbst and Bascur, 1983).

Jan 1, 1984

Simulation has established itself as an accepted tool for the design and optimization of complex minerals processing plants. This paper addresses the use of simulation as a tool for the design and optimization of carbon-in-pulp and carbon-in-leach (CIP/CIL) plants. The complex, interactive nature of CIP/CIL plants makes detailed experimentation an expensive and time consuming approach to CIP/CIL plant design and/or optimization. This paper discusses a simulation-based software tool that can make the process of CIP/CIL plant design and/or optimization much more cost effective. Many of the issues and problems pertaining to the use of simulation for CIP/CIL design and operation are generic. Thus, this paper also attempts to highlight generic issues that must be solved before simulation will become a more widely used design and optimization tool. Requirements for the application of simulation for CIP/CIL plant design and optimization are highlighted. Similar problems and issues can be identified for most mineral processing plants.

Jan 1, 1994

By K. Ohga, V. J. Hucka

The presence of methane gas in mines creates hazards of explosions, fire and suffocation. Under certain conditions the occurrence of methane also poses a danger of gas and coal outbursts. Consequently, prevention of gas and coal outbursts in coal mines requires a sound knowledge of methane gas occurrence in mine workings. However, the direct method of determining methane content of coals developed by the U.S. Bureau of Mines is time and labor consuming for measurement, a new transportable methane tester was developed for Japanese coal mines. The instrument automatically measures emission gas from coal samples in the underground and also records and stores the data. Back on the surface, the tester can be connected via a RS 232 port to a PC computer for methane content estimation. Details of this technique are described here. Results on methane content determined in Japanese and U.S. western coal seams are discussed, as well.

Jan 1, 1991

By T. Kretschmer, F. Villwock

Conveyor systems are an essential part of many material movements in all conceivable areas of application. They are used to transport goods in raw materials extraction, agriculture, and even articles for daily use. In the process, not only distances of several kilometers but also differences in altitude of several hundred meters are bridged. The layout of the conveyor usually follows the topography at the respective installation site. Particularly in the case of large height differences, safety devices must be provided to prevent uncontrolled movement. Backstops can take over this task in predominantly ascending overland conveyors and are used either as a primary or as a secondary safety system in conjunction with a service brake. They are always used when the system comes to an unplanned standstill, whether due to a power failure, an emergency stop or a defect. When designing backstops, it must be ensured in any case that all conceivable circumstances are taken into account so that failure is ruled out without the product being unnecessarily large in size. Various safety factors are applied, some of which are even prescribed by authorities. One example is the Australian standard on machine safety for bulk material belt conveyors (AS/NZS 4024). This stipulates a redundant acceleration safety device that can absorb at least 150% of the maximum load. ALTRA Industrial Motion with its sister companies Marland and Stieber manufacture backstops for a wide range of applications. With more than 85 years of business activity in freewheeling and backstop applications, they are among the most known and experienced companies and provide a great know-how.

Mar 2, 2022

By A. R. Conroy

Microscopic observation of physical and chemical changes which take place in various materials under conditions of elevated temperature and controlled atmosphere can often yield valuable insight into the fundamental physical-chemical reactions which control processes in which these materials play an active role. The technique of high-temperature microscopy thus becomes an important tool for basic and applied research in pyrometallurgical and allied fields. Investigators have long been aware of this and through the years have applied the technique to a wide variety of problems. However, up to this time, application has been on a rather limited scale due to the high initial cost of equipment and the relatively low rate of production of data resulting from the complexity of the apparatus and attendant problems in manipulation.

Jan 1, 1964

The modelling process described in this paper was developed in order to assess the feasibility of various investments options for the exploitation of a lignite deposit located in the Prefecture of Florina, Greece. The model uses as evaluation criterion the net present value. It is based on the characteristics of the reserves and relates the decision making with numerous technical, economic and environmental factors. The examined alternatives include the construction of a new thermal power plant at the mine-mouth, the fuel supply of already existing power plants located at relatively long distances and the fuel exports in neighboring countries. Moreover, the feasibility of post-poning the exploitation of the lignite deposit and preserving its reserves for exploitation in the future is also assessed. The paper also includes a short discussion about the environmental constraints related to the supply of lignite produced from Florina mines to power plants that were designed and constructed for burning fuel mixtures with different quality characteristics.

Jan 1, 2005

By James R. Boulton

Fire detection using Carbon Monoxide sensors is based on the assumption that a rise in the level of Carbon Monoxide in the atmosphere over a fixed, predetermined ambient level is indicative of a fire. The method is simple, reliable, and effective in those mines where the only source of CO is from undesired combustion. Ambience for this purpose is defined as that level of the gas that is present on a day to day basis whose source is not a fire. In a diesel powered mine the level of CO can and does vary so widely from hour to hour and minute to minute that the selection of a predetermined, fixed level represents a compromise between sensitivity and reliability. The compromise is a best of both and worst of both situations and the computer system often resembles the little boy who cried wolf instead of a state of the art early fire monitoring and detection system. Cyprus Coal personnel have developed method of determining the ambient level of CO in the atmosphere on a real time basis and using that dynamic ambient level to determine whether or not a fire exists in the mine. The method has been given the name of Wave Trend Crossing.

Jan 1, 1991

By V. O. Tenorio, P. P. V. Coronado

"INTRODUCTION Productivity in Open Pit mines depend on the observation and adjustment of critical phases of operation. As one of the most expensive activities in Open Pit production, optimization of the load-haul-dump cycle becomes a critical aspect to address. Using simulation techniques and an ad-hoc methodology for analyzing the Key Performance Indicators (KPIs) involved in the production cycle, it is possible compare actual performance and ideal operating conditions and develop an alert system when operating conditions are sub-par with the expected production standards. STUDY OBJECTIVES The purpose of this work is to implement a methodology for optimizing the haulage cycle by identifying and adjusting the factors that affect the cycle time performance. The methodology includes the implementation of an alert system emitting warning messages when one or several trucks are idle or the time of completing production tasks is falling outside a predefined value. This alert is compared with pre-defined Key Performance Indicators (KPIs) and determine corrective actions: • Demonstrate the benefits of time analysis and how this affects the productivity results in the mining process; • Demonstrate the utility of KPIs in the extraction of ore and waste, and how they help to identify equipment performance; • Develop software interfaces to visualize the Alert System in order to increase awareness in the operations supervisor; and • Make recommendations for future applications that can help improve the productive process of an Open Pit mine. PROBLEM STATEMENT Transporting material in Open Pit mines may require the utilization of high capacity equipment, which also represents an elevated cost per hour. A supervisory system that controls the adequate distribution of trucks and shovels by providing the operational status of each unit shall contribute to increase productivity and subsequently reducing operational costs. Nevertheless, there is an issue with certain dead times such as queue trucks for loading, trucks waiting to be loaded, and other delays. This creates inefficiencies in fuel consumption and energy utilization. For the identification of delays, a context-based system could be required in order to help optimizing the haulage cycle time by controlling delays in loading, haulage, and dumping. After applying this methodology, efforts were focused in correcting out-of-standard performance values."

Jan 1, 2016

By Leszek W. Lunarzewski, Adam L. Lunarzewski, Raymond C. Pilcher

The Floorgas and Roofgas simulation programs are used to identify strata relaxation zones and their boundaries, to assess active gas sources from coal seams and gas¬bearing rocks and to determine relevant gassiness prediction coefficients for any local longwall. The paper shows that by use of the print-outs from the Floorgas and Roofgas programs the following benefits are achievable: • identification of the shear and gas discharge zone positions in the floor, strata relaxation angles and various gas discharge zone positions in the roof, which are both relevant to local geological and mining conditions • optimisation of cross-measure drainage hole length, location, number and angle of inclination calculation and definition of gas make prediction coefficients such as the release ratio from adjacent coal seams, specific gas emission during longwall extraction and the relationships between gas make, longwall width and coal production levels.

Jan 1, 1995

By C. C. Bailie

This paper will be concerned with those mineable coal measures at depths necessitating deep mine operations in the range of 200 feet to 800 feet in depth. The area is generally classified as the Southern Illinois Field but more specifically includes that part of the state south of a line extending from St. Louis, Missouri on the west to Vincennes, Indiana, on the east. This embraces an area which presently includes a total of 38 shipping mines and 5 local or truck mines. Of these shipping mines, 22 are deep (shaft or slope) mines and the remaining 16 are strips. The average annual production of the shipping mines is around 29 million tons. The presently classified mineable reserves of the area are estimated at around 70 billion tons.

Jan 1, 1964

By Tetsuo Yamazaki

Natural cold seepages are characterized as rapid upward transports of methane from deeper parts of geological structures to the seafloor. Thermogenic and/or biogenic methane generated in deep sediments moves up to seafloor, and major part of methane is consumed in anaerobic oxidation of methane (AOM) and hydrogen sulfide is created in anaerobic sulfate reduction by consortium of microorganisms. Then the hydrogen sulfide is utilized by chemosynthetic communities near the seafloor, such as Acharax, Calyptogena, Bathymodiolus, and the mat-forming bacteria Beggiatoa (Fig. 1). When the supply of methane is large or rapid, remaining methane escapes from seafloor, and it is aerobically oxidized in seawater. A mass balance ecosystem model of chemosynthetic community around natural cold seepages in sediment layer and on seafloor has been created and improved by the authors (Yamazaki et al., 2005; Takeuchi et al., 2007). The model is constructed from 3 main processes as schematically shown in Fig. 2: (1) Methane supply process; (2) Ecosystem process; (3) Water column process. The part of chemosynthetic communities is in the ecosystem process. A numerical model CANDI (Carbon And Nutrient Diagenesis) was developed by Boudreau (1996) to simulate the biogeochemical processes such as organic matter, oxidant, nutrient, bi-product, and pH diagenesis in aquatic surface sediments. Then, the improved version named C. CANDI was developed (Luff and Wallmann, 2003; Luff et al., 2004). The authors created the same type carbon and nutrient diagenesis process model with calcium carbonate formation like C. CANDI (Yamazaki et al., 2005), and have added the sulfur oxidizing and immobilization processes (Takeuchi et al., 2007). The sulfur oxidizing and immobilization processes are connected with the carbon and nutrient diagenesis process model.

Jan 1, 2008

By Nathan Painter, Kevin Andrews, Andrew Karpa

Groundwater flow in bedrock units is an important factor to be considered for most mining situations, both underground and open pit excavations. Characterization of the hydrogeologic system into which a mine will advance is an important factor for slope and entry stability, mine dewatering design, and potential environmental considerations including stream loss and water well damage. In addition, hydrogeologic characterization of bedrock is important for locating water wells and for groundwater contamination mitigation. Hydrogeologic characterization for a site begins with a desktop study and often evolves to include drilling, geologic logging, monitoring well installation, groundwater sampling, pump testing, and packer (Lugeon) testing. In addition to these methods of hydrogeologic data collection, downhole geophysical logging of exploration and monitoring well boreholes provides detailed information associated specifically with in-situ conditions of each hole. The basic suite of geophysical logging tools used for hydrogeologic characterization often includes Optical or Acoustic Televiewer (O/ATV), full wave sonic, gamma-density, fluid temperature, resistivity, specific conductance, and flowmeter. For many hydrogeologic settings, groundwater flow in the bedrock is dominated by discontinuities, or fractures, in the rock. O/ATV logging allows for determination of the frequency (clustering), orientation, and aperture width of in-situ fractures, while sonic logging allows for estimation of intact rock strength. Fluid temperature logging and flowmeter measurements provide insight with regard to potential groundwater inflow zones, and other tools provide information for geologic unit contacts. This paper outlines the process and benefits of using downhole geophysical logging for hydrogeologic characterization and provides generalized examples from industry experience.

By D. Murray

"The Mine Improvement and New Emergency Response (MINER) Act included the need for improved chemical technologies to address respiratory protective device inadequacies and refuge alternative development. The National Institute for Occupational Safety and Health’s (NIOSH) National Personal Protective Technology Laboratory (NPPTL) invests in research and development to improve the carbon dioxide (CO2) scrubbing technologies built into these mine safety systems. Testing at NIOSH NPPTL is performed using a custom-designed test system containing a chemical reactor and sensors in a constant flow of simulated expired breath to evaluate chemical performance for the scrubber materials. Current testing procedures focus on device duration or capacity, but do not report criteria needed to effectively optimize chemical performance. In this presentation, testing results which identify the chemical performance roles for CO2 scrubber components will be reported, and specific component chemical activities will be linked to both duration and CO2 absorption capacities. Chemical components being evaluated include hydroxyl, superoxides, metal, and amine active sites, distributed in salts, zeolites, metal-organic frameworks, and microporous materials. INTRODUCTION CO2 absorbents and oxygen sources are at the heart of closed circuit breathing air supply systems used in mining escape and rescue operations. CO2 absorbent technology was first developed for diving rebreathers and has been in use for over a century. Typically these devices include a soda lime formulation of pellets in the 8-12 mesh range. Larger 4-8 mesh particles are used in medical grade “low-flow” applications, since these particles present a lower flow resistance regime more amenable for use with resting individuals. Potassium superoxide and lithium hydroxide formulations are also used, where in each case the formulations involve bulk solid pellets or materials affixed to surfaces. CO2 capture technologies are now under intensive study in the energy and automotive industries, where the pursuit of optimal combustion processes has led to the development of new materials to capture, convert and store CO2, oxygen and carbon monoxide gases. Recent advances in nano-structured and high surface area catalysis have produced novel materials demonstrating chemical performance improvements in these industries, and these improvements may now also be adapted to enhance chemical efficiency and performance in escape and rescue devices. Higher surface area materials offer promise for improving the efficiency, or decreasing the burdens associated with the use of closed circuit respiratory protective devices containing CO2 absorbents. Novel chemicals that display advantages in chemical performance or decreased burden will be examined for inclusion in developing systems such as the next-generation closed-circuit mining escape respirator or refuge alternatives."

Jan 1, 2018

By Yi Luo

Longwall coal mines are frequently located in steep mountainous areas with narrow valleys. In order to protect surrounding watersheds and residential structures, support areas are left under the valleys. However, the indirect subsidence effects to the residential structures due to the potential topography effects can be a serious problem. The present study examines a longwall mine in southern West Virginia located in an area with an average slope of about 30°, or 58%, and with an overburden depth that varies from 49 to 376 m (160 to 1,235 ft). A comprehensive investigation was carried out to assess the subsidence and topography effects, as well as other ground control issues at this site. Surface and subsurface movements and deformation were predicted and their direct effects on nearby streams and structures were assessed. The potential and indirect subsidence influences of surface topography effects were assessed. The techniques and results of this investigation are presented in this paper. It shows that the direct and indirect subsidence effects on the streams and residential structures should be insignificant. The post-mining observations agreed well with this study.

Jan 1, 2010

By Jerry Wang, Greg Bold, Mahmood Khwaja, Rebecca Caldon, William Simcoe

Phase III and Phase IV of the Beaver Creek Clean River Project, Albany, NY, includes microtunnel construction of 2,320 feet of 48-inch/36-inch internal diameter (ID) conveyance pipe and a 525 foot long 9.5-ft horseshoe shape roadheader excavated tunnel. Notable challenges were encountered during the construction including mixed face tunnel conditions, undocumented existing fill ground conditions that resulted in settlement during shaft construction, and unstable tunnel face conditions. This paper discusses several of the key challenges encountered during construction and selected solutions to construction sequencing and methodology to successfully complete Phase III and Phase IV of the Beaver Creek Clean River Project.

Dec 1, 2022

By L. H. Pye

For large mining sites in the west, the traditional method for performing an ecological risk assessment (ERA) provides little useful information for risk managers faced with selecting and designing sound remedial options. Current U.S. Environmental Protection Agency (EPA) risk assessment guidance largely supports quantitative risk characterization of individual species as surrogates for population and ecosystem-level effects. Developing a work plan for investigating and remediating ecosystem-level changes potentially caused by large-scale historic mining/smelting contaminant release requires a decision process that incorporates a more holistic ecosystem management approach. Some of the most wasteful efforts associated with mine site ecological risk assessments arise when the risk analysis and data collection programs are not specifically linked up-front to the risk manager&apos;s decision needs. The following paper discusses the importance of employing a decision-based, ecosystem management framework when conducting ecological risk assessments at large mining sites. A case study of an ecological risk assessment currently being performed at a large New Mexico copper mine site is presented.

Jan 1, 1999

By Eleanor Kentish, Nathan Bond, Edward Batty, Simon Webber, Alan Skarda

"Crossrail is Europe’s largest construction project — a new 100km rail route running through central London. A joint venture of BAM, Ferrovial and Kier (BFK) has constructed the tunnels and escalator shafts at the new Bond Street and Farringdon Stations. The recent trend in the UK industry towards sprayed secondary linings is driven by the potential for significant savings in cost and time. BFK is unique within Crossrail by constructing both sprayed and cast secondary linings. This paper presents a direct comparison between sprayed and traditional cast in situ secondary linings at Bond Street and Farringdon Crossrail Stations. An objective comparison is drawn between procurement and mobilisation periods, production rates, flexibility, tolerances and logistics in the tunnels. The technical challenges surrounding cast and sprayed secondary linings are explored, and recommendations are made of how each method could be improved for future use. INTRODUCTION It is well established that sprayed concrete offers a fast and effective method to seal the face of an excavation. In a relatively short space of time, sprayed concrete can be applied to an open face to support the short term ground loading on the tunnels during construction. Advances in sprayed concrete lining (SCL) technology — such as the use of wet mix processes, improved accelerators, fiber reinforcement, remotely controlled spraying robots, innovative surveying equipment and nozzleman competency schemes — have greatly increased the speed and safety of tunnel excavations using this technique. As a result, design engineers have become increasingly confident to use SCL primary linings as part of the permanent structural lining (Su 2014). Historically, long term ground and water pressure loads have been considered to be carried by the main structural or secondary lining, constructed using cast in situ concrete (Pickett 2014). However, the advances described above have made sprayed secondary linings a viable option, which has already been proven on the A3 Hindhead Tunnel (Arnold 2012). Sprayed concrete secondary linings offer potentially significant savings in cost and time during the construction process. The contractor does not need to procure a bespoke formwork system for each different sized tunnel — the SCL plant required is already on site for the primary lining. Each bay is sprayed with accelerated concrete, becoming self-supporting almost immediately — compared to moving and resetting the shutter, pumping concrete and waiting for it to cure. With sprayed concrete, working sequences and cross sections can easily be changed."

Jan 1, 2016

By T. A. McAfoose

As one of the major suppliers of the chestnut Ridge energy center, Rochester and Pittsburgh Coal Company continues the search for more efficient haulage systems. This search is one that is essential in providing coal to the Keystone and Homer City power plants at the most economical cost. These two electrical generating plants located in west central Pennsylvania are part of the energy center which consists of four generating stations. Prior to the time the two stations were put on line, August, 1967 for Keystone and August, 1969 for Homer City, our company made the decision to rely on belt conveyors from the section to the surface to provide for continuous main line haulage. The proximity of these generating stations to proven reserves allow for minimal truck haulage and minemouth setups. With the addition of seven new mines, in the past ten years, revisions have been made on the original setup to interconnect the haulage of several mines to deliver the product by belt to the power plants.

Jan 1, 1979