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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 Scott G. Britton

Thin-seam mining presents unique challenges when management or economic conditions require significant productivity increases. These challenges can be further amplified depending on such factors as labor unions, federal and state regulations and market characteristics. This article explores the turnaround situation occurring at Tanoma Mining Co. (TMC), a medium-sized, underground coal mining company in central Pennsylvania. The company has used a systematic approach of improving management controls and direction, labor relations and communications to improve its cash flow from negative to positive within a projected five-year span. An intensive upgrade-rebuild-replacement program for mining equipment and systems has also been established to support other management activities. Discussion Thin-seam coal mining is an industry within the broader industry of coal mining. Thin seam mining faces the same cost pressures and engineering problems as its higher-seam competitors, without the advantages of moving volume per foot of extracted material. To stay at economic parity with others requires additional creativity within the management team to extract higher productivity gains from the existing workforce and mining systems. The Tanoma operation is a deep mine in Indiana County, PA, about one hour northeast of Pittsburgh. Coal is extracted from the Lower Kittanning "B" seam. It lies about 91 m (300 ft) below the surface and averages 0.9 m (I ft) in height. Continuous mining units using mobile bridge conveyors or shuttle cars

Jan 1, 1991

By D. B. Stephens

Milling operations throughout the world have created vast amounts of waste by-products, or tailings, which are often disposed on the land surface. The wastes may be disposed behind dams, on untreated ground, or on compacted clay or synthetic liners of impoundments and trenches. Often one of the principle concerns of environmental regulatory agencies is whether seepage from the waste pile could move through the vadose zone to the water table and possibly contaminate an aquifer. The seepage may be generated by the drainage of liquids initially deposited along with the tailings or by infiltrating meteoric water which leaches solutes from the tailings. The purpose of this article is to discuss some of the commonly held assumptions regarding storage of seepage wastes in the unsaturated zone. The significance of recent studies of water movement in dry climates which pertain to tailings site selection will be presented. The paper is relevant not only to seepage from impoundments at mill sites, but to many other fluid waste impoundments as well in part this article reinforces earlier work by Stephens and Siegel (1980) and an excellent review paper by McWhorter (1985). The present report addresses considerations in porous media; for a discussion of the effects of fractures and anisotropy in the unsaturated-zone, refer to the paper by McWhorter (1985).

Jan 1, 1985

By Y. Wang, G. Xu, N. A. Amoah, A. Kumar

Mining-induced coal dust causes various respiratory diseases to mine workers, such as coal workers’ pneumoconiosis (CWP). Current available underground monitors are expensive, heavy and only measure mass concentration. These disadvantages limit them for regulatory sample monitoring purposes only while personal exposure levels for most miners remain unknown, risking miners to potential overexposures. Low-cost light scattering PM sensors offer a potential solution to this problem with capability of high spatio-temporal resolution PM characterization. However, these sensors require careful calibration before they can be applied in mining environments. There is basically no comprehensive study in the literature using a standard protocol assessing these sensors for coal dust monitoring. With the aim of calibrating the PMS5003 sensors for coal dust monitoring, we design the calibration method and system to calibrate these low-cost PM sensors coal dust monitoring. Working principles of present coal dust monitor and low-cost sensors are presented in detail. The linear regression calibration model which is used for the sensor calibration is further described. Sensor calibration and evaluation protocols are comprehensively compared and discussed. This investigation reveals the feasibility of low-cost sensors for real-time personal coal dust monitoring in underground coal mines.

Mar 2, 2022

By G. Deschenes, P. J. H. Prud'homme

A laboratory study was carried out to evaluate the effect of oxygen and lead nitrate on the recovery of gold by cyanidation of a free milling gold ore, which contains 0.4 % copper as chalcopyrite. Efficient gold extraction is achieved only under specific conditions. The recovery of gold was increased from less than 90% to up to 98% by addition of lead nitrate. In the pre-leaching, the kinetics of oxidation of soluble sulphides are not an accurate indication for the length of the treatment. Even though the consumption of cyanide was reduced due to the inhibition of the dissolution of chalcopyrite by increasing additions of lead nitrate, cyanide consumption had to the held above 1.85 kg/t to maintain good recovery of gold. The continued addition of lead nitrate above 300 git had no impact on the recovery of gold. It was also found that the addition of lead nitrate at the start of cyanidation gave the same performance as when added during pre-leaching. The addition of oxygen increased the recovery of gold by 1.5%. The concentration ofNaCN had to be maintained in the range of700 mg/L because of the high concentration of copper in solution. The recovery of gold dropped significantly when the average NaCN concentration fell below 640 mg/L. Application of the findings of the laboratory study at the industrial scale led to improved plant performance.

Jan 1, 1997

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 S. L. Bessinger

The need for improved safety and productivity brought about the introduction of longwall mining to the Appalachian coal fields. These same forces continue to drive developments in modern longwall equipment and mining practices. Current initiatives to improve productivity and safety are focused on automation and the effects of scale in equipment design. Longwall roof-supports, shearers and face-conveyors have changed significantly. Panel layouts have evolved to include larger total tonnages and provide for more rapid development of gate-entries. These advancements have improved longwall productivity and new production records are continually being set. Roof supports Reliability is implicit in the quest for automation. It is impossible to automate equipment if it is not reliable. To a large degree, this has been the problem with longwall shield automation efforts. The "electronic control" of shields depends on the proper functioning of electronic equipment, electrohydraulic valves and full-flow service valves onboard every support.

Jan 1, 1995

By G. Babut

The restructuring of mining operations in Valea Jiului coal basin imposed by the transation to the market economy calls for an increased coal production. Under the circumstances, the role of drainage networks grows ever more important. The paper describes an original mathematical model and software developed on its basis, with enables the ventilation engineer to assess the configurations of different systems, as well as to test their reliability and prognose their future performance before conceiving another methane drainage system or changing the existing one. The paper also includes the underlying principles of an optimization program for methane drainage networks, which will enable the detection of the optimal methane drainage system, both from a technical and an economic point of view.

Jan 1, 1996

By R. Jin

Fine coal flotation using gaseous carbon dioxide has demonstrated the potential for producing superclean coal. The success of this new flotation .procedure is attributed to the coal's high adsorption potential for CO2. To understand the nature of gas-phase CO2 adsorption at the coal surface, in-situ FTIR spectroscopy in a controlled-environment chamber with an ultravacuum sys-tem has been used and the results are discussed in view of other experimental results from differential scanning calorimetry. It has been found that specifically adsorbed CO2 molecules at the coal surface are polarized and have a characteristic doublet at 2336 and 2361 cm-1. Two adsorption states have been proposed to account for the doublet observed from in-situ FTIR spectroscopy measurements. It is believed that the band at 2336 cm-1 originates from the activated site adsorption of CO2 and that the band at 2361 cm-1 arises due to the molecular aggregation of CO2 within the coal pores.

Jan 1, 1988

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 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

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 S. Becker, M. Gruner

"Microstructure stabilized crushed rock salt is a newly developed backfill material for infrastructural openings in HAW repositories. The motivation for this research is based on the fact that the microstructure stabilized crushed rock salt is considered to be superior to the currently used crushed rock salt. The avoiding of settlements with a simultaneous 100% backfilling of openings, early stabilization of the geological barrier and low permeability (< 10-14 m²) are the main improvements. With the newly developed backfill material, the gap between the crushed rock salt and the saliniferous composite backfill materials is closed. Due to the minimized amount of a binding agent, the material will still be easy to handle like a bulk material, yet guarantees close to 100 % backfill success without any settlements. This is accomplished with a long-term stable re-mineralization that is formed by the components of the binding agent. INTRODUCTION The permanent storage of high active waste in underground geological formations (HAW-repository) is the labored method in Germany as well as internationally. Experiences have been made over the last decades, e.g. in the Waste Isolation Pilot Plant (USA) and the mines Morsleben and Asse (Germany). For this purpose salt formations are preferred as host rock due to the adequate heat conductivity, creep capability, and low permeability. In order to maintain the low permeability of the host rock and to avoid any contact of the stored waste with the biosphere, the formation of flow paths has to be prevented. The cavities which have been mined for the purpose of waste storage have to be backfilled with material that is alike to the host rock. Therefore crushed rock salt is considered as an appropriate backfill material. Crushed rock salt is a bulk material that is produced by mining saliniferous formations. This material is mainly used in underground repositories as a dry backfill that is brought into the cavities by the use of mechanical (loading machine, slinger machine or scraper) or pneumatic energy (pneumatic stowing). In Germany it is intended to use dry crushed rock salt with a maximal grain diameter < 64 mm for backfill in a future repository in saliniferous formations. With this method applied, the porosity of the backfill is up to 35 % [1]."

Jan 1, 2015

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

By D. Kimball, P. Chambers

"BACKGROUND In the event of an explosion or fire in an underground mine, workers can be exposed to a deficiency of oxygen, an excess of carbon monoxide, or both. These threats can occur as separate conditions or simultaneously. A lack of oxygen in the breathing air can only be addressed via the use of a self-contained breathing apparatus (SCBA) acting as a source of oxygen. An excess of carbon monoxide can also be addressed via the use of an SCBA, but if the threat occurs in isolation (that is, the atmosphere still contains sufficient oxygen to support life) and the concentration of the threat gas is not extreme (< 2%) then the carbon monoxide threat can also be addressed by the use of a filter self-rescuer (FSR). Used together, the SCBA and FSR offer a far more efficient and universally capable life support system than when used in isolation. However, the SCBA does not take advantage of the fact that the surrounding atmosphere likely contains some level of useable oxygen; i.e., the SCBA always supplies the total required oxygen from its limited supply, resulting in a ceiling on its useful life regardless of the level of oxygen in the surrounding air. To address this technology gap, what is needed is a ""smart"" SCBA that provides filtration and catalytic protection against threat gasses and has an extended duration life-sustaining oxygen inhale stream independent of the threat content and oxygen deficiency of the surrounding atmosphere. DEVELOPMENT Developed under contract with NIOSH the Smart Escape SCBA is comprised of three major components including; 1) oxygen supply, 2) oxygen sensing & dosing electronics and, 3) a CO catalyst and carbon bed broad spectrum FSR. The SCBA is designed as a hybrid system that provides non-toxic breathing air by using an approved Chemical, Biological, Radiological and Nuclear filter self-rescuer and a catalyst to convert high levels of carbon monoxide to harmless carbon dioxide (CBRN FSR/CO). In addition, the Oxygen Sensing & Dosing Electronics (OSDE) package adds sufficient oxygen to make up for deficiencies detected in the ambient air (Figure 1). By making use of the ambient oxygen, less oxygen is required for a one-hour unit life. This means that the Smart Escape SCBA fits in a smaller and lighter package than a similar-duration conventional Self-Contained Self-Rescuers (SCSR). Alternatively, taking advantage of available ambient oxygen could offer a significant increase in working duration in a unit with the same size as current SCSRs. The research performed under this NIOSH contract involved numerous tasks including: (1) definition of performance and system requirements for the Smart Escape SCBA, including keeping environmental stressors within acceptable ranges, providing at least one hour of breathable oxygen supply, and using a mask or hood that allows high-quality voice communication; (2) designing, building, and evaluating prototype units to support extensive bench top testing at Avon Protection and third party labs to demonstrate the device’s capabilities; (3) building sufficient quantity of Smart Escape SCBAs designed to be intrinsically safe (per MSHA criteria); (4) testing and evaluation by the National Personal Protective Technology Laboratory (NPPTL)."

Jan 1, 2015

By B. Kendall

"ISSUES ASSOCIATED WITH HAND DRILLING/JACKLEGS In coal mines, hand held air, electric, and hydraulic powered drills are used along belt conveyors, in single entry development, in entries where there are obstructions, and in long wall recovering bolting. In hard rock mines pneumatically powered “jack leg” drills are typically used in narrow vein mining. Drilling and bolting in narrow confines has traditionally been performed with pneumatically or hydraulically powered hand-held drills or newer electrically powered hand held hammer due to their low cost, simplicity of operation, and extreme flexibility due to their small size. Mechanized equipment has typically been too large, too expensive, inefficient due to the confined space, and too restrictive due to lack of flexibility for use in narrow confines. Although the hand-held equipment is effective, it requires operator exposure to certain inherent hazardous conditions in use. These include falling rock from the roof, rib, and face; tripping hazards; bending twisting lifting hazards; high noise levels; and chemical fumes from the pneumatic exhaust. The operation of the hand held equipment can adversely affect the long-term health of the operator – continual jackleg operation frequently results in long term damage to hearing, shoulders, arm and wrist joints, and back injuries. This results in a reduction in life style for the operator and higher personnel turnover rates for the mining company. Hand held drills also typically have limited thrust and torque capability which limits their ability to push long resin bolts, inadequate torque to properly install resin bolts, or to properly torque mechanical or tensioned rebar bolts. Hand held drills do not offer any type of protection for the operator from roof or rib falls. They do not offer any means for handling roof or rib mesh. Since the operator stands on the ground the maximum safe drilling height without use of a ladder or “riding the drill” is limited to 8’ (2.44M)."

Jan 1, 2015

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 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 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 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