Search Documents

By Virginia T. McLemore, Devlon R. Shaver

Clinkers are the result of a seam of coal catching fire and burning the surrounding rocks. The fires caused the surrounding rocks to be baked at high temperatures, removing organic material and partially forming glass. These rocks become hard, orange, and brick like, forming clinker. The purpose of the study is to determine their potential to contain economic levels of critical minerals, including Rare Earth Elements. Some clinkers contain over 200 ppm total REE.

Feb 1, 2024

Grinding and energy input in stirred media mills are studied as functions of grinding time, stirring speed, media size and density, solid concentration, impeller and tank dimensions and design, and other relevant variables. Ground product size and surface area are determined with respect to the above variables. Changes in energy input and media/pulp rheological properties during grinding are described. The best conditions for grinding limestone in the laboratory stirred media mills have been identified. Equations for correlations involving power and modified Reynolds numbers have been established.

Jan 1, 1995

By V. Rajaram

The Parachute Creek Member of the Green River Formation in the Piceance Basin, Colorado, contains vast reserves of oil shale, nahcolite, dawsonite, and other accessory minerals. The dry alkali process of sulfur dioxide removal using nahcolite (naturally occurring sodium bicarbonate) has great potential. A room and pillar mining scheme has been designed to extract a nahcolite zone occurring at a depth of 472 m, from the lease application area of the Yankee Gulch Joint Venture. Geotechnical parameters affecting mine design will be discussed. A preliminary development plan for mining at the rate of 1000 t/d will be described in detail.

Jan 1, 1977

By Ronald L. Gibbs

IN THE BEGINNING Contrary to popular myth, the personal computer can trace its roots back to a time before 1981 and the IBM PC. The seeds of the personal computer revolution were probably founded in 1975 with the release of the Altair (kit) personal computer, first advertised in Popular Electronics. June of 1975 marked the beginning of the Homebrew Computer Club in San Francisco. The founding membership list of the Homebrew Club now reads like a "Who's Who" of those involved in the early development of the personal computer industry. The Apple I computer was created by Steve Wozniak in early 1976 from the newly manufactured MOS Technology 6502 chip. It had 4,000 bytes (4K) of Random Access Memory (RAM] memory, a revolutionary amount of memory in 1976. Another early pioneer, the Commodore Pet computer, was another 6502 machine, but with 8K of memory. Tandy Corporation made its name in the hobby industry with leather kits. They embarked on a new path with the production of the TRS-80 line of personal computers. Most were based on the Z-80 chip, but again, were memory limited. A number of other Z-80 based systems followed later, including the Osbourne and the KayPro Computers. These systems were based on the Digital Research CP/M operating system and had a maximum of 64,000 bytes of memory (64K). The Apple I1 Computer appeared in 1977. Newer models of the original Commodore Pet and an Atari computer followed. These machines were also limited to 64K of memory addressing, and the early models typically shipped with only 16K, 32K, or 48K of memory. The Z-80 and the 6502 were the first truly commercialized CPU chips touting boxes with key- boards, monitors (sometimes a TV), and the ability to expand (peripheral slots for serial communications, centronics parallel communications, etc.1. They all shared one technology, audio tape as a storage media. The use of a portable tape recorder provided inexpensive, if not always reliable, magnetic storage. The tape recorders were typically finicky and required patience to use. Adjustments to the volume control were often needed to find "just-the-right" setting for loading or saving information. This kept the personal computer from being accepted in many markets, and gave it a reputation as a hobbyist or experimenters' toy. In early 1979, Steve Wozniak finished the design of a floppy disk drive and controller. This was a revolutionary design which reduced the "then" standard number of controller chips from fifty-plus, to just eight. With the advent of an affordable floppy disk drive mechanism, the personal computer was about to gain respectability. From a business standpoint, it was now possible to save and reliably retrieve business information. It also provided a superior means of distribution for commercially created software. Commercial software became a commodity rather than an oddity.

Jan 1, 1993

By Ehsan Moosavi, Kamyar Tolouei, Mehran Gholinejad

The literature defines rockbursts in slightly different ways based on their generation mechanisms, field phenomena, and degree of damage, but in a way that is almost consistent. Generally, a rockburst refers to seismic events that mainly happen in underground excavations, for purposes such as underground mining, road and railway tunnels, nuclear power, etc., and that are followed by the collapse and outburst of rocks. Long-term rockburst prediction can be abstracted as a classification problem mathematically, in which we can introduce deep learning to solve it. Further, using deep learning in rockburst prediction can overcome drawbacks such as subjectivity and inconsistency brought from previous traditional approaches. A rockburst data-set, was employed to evaluate the current method for predicting rockburst grade, and the good results of overall success rate were obtained. The results indicated that the proposed algorithms can speed up parameter optimization search, the proposed method is robust model and might hold a high potential to become a useful tool in rockburst prediction research.

Apr 26, 2022

By L. L. M. Kadnuck

The U. S. Bureau of Mines studied the suitability of using flexible tendon cable supports as secondary roof supports at a western coal mine. The supports were installed in longwall tailgate entries and grouted into the mine roof. This paper quantifies how the use of cable supports can improve ventilation in underground airways. A mine ventilation simulator was used to model the changes in airway resistance and airflow and show potential for further ventilation improvements when cable supports are used. Model results indicated that cable support use translated to savings in air pressure around the longwall panel and increased airflow at the longwall face.

Jan 1, 1994

By D. R. Taylor

The use of clay granules as carriers for pesticides dates from the early 1940's and by the present day represents a business conservatively estimated at between 200 -300 thousand tons / year in the U.S. alone. Aside from economic and specific target pest efficacy advantages, the use of clay granules as pesticide carriers also delivers a number of environmental benefits which will be reviewed. Topics to be discussed will include: I) drift control (versus liquid sprays), 2) mobility (in the environment), 3) worker safety, and 4) transportation (spill) safety.

Jan 1, 1999

By J. M. Wempen

As development in underground coal mines progresses away from the critical components of the ventilation system, including the main fans and ventilation shafts, resistance within the system is markedly increased. This results in higher pressure and flow requirements from the main fan(s) to maintain adequate face ventilation. Upgrades to the primary ventilation system are often required. The use of booster fans underground is a potentially practical alternative to the addition of shafts and surface fans. This study presents simulations of the use of booster fans in two underground ventilation scenarios, one longwall and one room-and-pillar. The booster fan effects on the power requirements of the ventilation systems are evaluated.

Jan 1, 2011

By N. Arbiter

Introduction The theoretical analysis of tumbling mill energetics and performance has largely neglected mill dimensionality, and, in particular, the importance of the length/diameter (L/D) ratio. This is in spite of the fact that practice varies substantially: geographically, for semi-autogenous and autogenous mills, as between North America and South Africa/Scandinavia, and historically, for overflow ball mills, for which the L/D ratio has increased significantly from the earliest small mills to the largest mills currently. The present study is concerned primarily with the influence of the L/D ratio on the design and operation of overflow ball mills, on the occurrence of the overload phenomenon, and on the limits, if any, it may impose on mill capacities because of critical pulp axial velocity limits. It will be shown that the shape factor is of major importance in this area and that its adjustment to the extent that this is practical should remove the diameter limitations previously postulated for this mill type. Dimensionality in mill design Ball mill shape factors in the period prior to 1927 (Taggart, 1927) averaged 1.1/1 for 29 center discharge mills and 1.0/1 for 30 peripheral discharge mills. With the resumption of new plant construction after the 1930s depression, the Morenci concentrator continued the 1/1 ratio with its 3.1 x 3.1 m (10 x 10 ft) mills. The ratio was increased progressively from then on, reaching 1.6 and 1.8/1 for the largest overflow mills currently. As shown recently (Arbiter, 1989), this is in sharp contrast to autogenous and SAG mill shapes, for which the ratio averages 0.4 in North America. On the other hand, South African practice, starting at the turn of the century with autogenous mills having 4/1 ratios, moved toward 1/1 until recently, when a 2.5/ 1 ratio mill was installed. The reasons given for such divergent practice for mill shape factors are in some respects contradictory and generally inconclusive. The most complete discussion from a practical viewpoint (Dor and Bassarear, 1982) is limited to primary SAG and autogenous mills. Considerations of ball mill dimensionality have had a twofold direction. On the one hand, it has been argued that ball mill efficiencies should increase with increasing diameter and that the specific energy for a particular grind should be reduced accordingly. An inadvertent test of this idea at the Bougainville operation (Burns and Erskine, 1983) resulted in drastic underpowering, which led to failure to reach design capacity until additional mills were installed. This can be taken as strong evidence against any increase in efficiency with diameter. In another direction, it has been argued (Arbiter and Harris, 1982, 1983) that there is a limit to ball mill diameters because of the demonstrable limit to axial flow velocities evident in the overload phenomenon, which as a fact is incontrovertible. But that it places a limit on mill diameters overlooks the evidence given below that appropriate variation in the L/D ratio will permit major increases in diameter, limited only by constructional or economic factors. The present study was directed toward quantifying the overload phenomenon through examination of the influence of mill dimensionality variation and mill operating variables on its occurrence. It is shown that varying the operating conditions, specifically the load fraction and the fraction critical speed, can reduce the risk of overload for existing operations; while appropriate decreases in the L/D ratio can minimize the risk in the design of new circuits. Ball mill overload Ball mill overload is a consequence of the approach to a critical velocity with increasing feed rates or circulating loads. Although the effect has been known for over 50 years, there have been no previous attempts to quantify it. The following description of the ball mill as a flow system is the preliminary to a quantitative analysis: 1) In the absence of a ball load, axial flow of pulp through a mill resembles open channel flow, except for disturbances near the shell due to shell/lifter rotation. 2) For a given ball load (Lf), the void fraction available for pulp hold-up (H) for the ascending portion of the load is approximately 0.4 Lf. In the descending portion, it is greater than this and increases with fraction critical speed (Fc) because of load expansion. 3) Increasing the feed rate increases pulp hold-up and progressively fills the available void space. At a critical flow rate, which depends on system geometry, hydraulic head and pulp rheology, void filling reaches its limit; a pool forms rapidly and fills available space outside the ball load and up to the overflow level. Prior to this, pulp discharges mainly along the ascending rim of the overflow. 4) For a small mill (Lo et al., 1990), it has been shown that with increasing feed rates the critical filling is at or near 50% of the mill volume. Power drops rapidly when this level is reached, as required by the torque formula. 5) The transition to overload is associated with the following phenomena: a) The decrease in power draw. b) Damping of mill sound. c) Reduced comminution of coarser feed sizes, probably due to reduced direct impact in the presence of a pool. d) Increased circulating loads, which further intensify the overload, and increased density of cyclone underflows, which can lead to roping. e) Conditions beyond overload are not known because feed rates are not delibelrately increased beyond this point. f) The existence of the phenomenon limits the capacity of a mill with a fixed set of operating conditions and can prevent the balancing of hard ore feed rate decreases by increases in soft ore rates.

Jan 1, 1992

By M. Ishaq, J. Rosami, J. Brune, E. Sidrow, C. Tsai, S. Slouka

Respirable rock dust poses serious long-term health effects to workers in mining and tunneling underground hard rock environments. When inhaled, respirable silica particles commonly found in quartz and other minerals will scar sensitive lung tissue and cause irreversible lung diseases. Characteristics such as concentration, type of mineral, particle size, and particle shape inhaled can harm workers to various extents. Therefore, this study characterizes rock dust particles less than 100µm in aerodynamic diameter that are released from cutting hard rock in the underground mining environment. In this study, laboratory full scale cutting tests on samples of potash rock were performed with radial picks to generate dust. Three stages of pick wear were tested: new, moderately worn, and severely worn. Comparisons between different stages of pick wear to dust concentration, size distribution, and particle shape characteristics are drawn from this study to start determining the scenarios when the released airborne dusts become potentially most hazardous for workers. Although further testing needs to be conducted to make viable conclusions, the moderately worn pick, or the pick with the most blunt tip, in these experiments are potentially the most dangerous. The blunt pick tip released the highest concentration of dust and generated particle shapes with the highest aspect ratio compared to the other two picks. The preliminary results of this study allow for the further development of optimum bit management and maintenance systems to control the exposure of respirable dust to mine workers.

Mar 2, 2022

By William I. Weisman

Natural sodium sulfate is obtained from both brines and solid deposits. The brines almost always contain other salts with sodium chloride predominating. They may be obtained from surface occurrences, such as Great Salt Lake or from shallow subterranean deposits. Althought many sodium sulfate minerals are known to exist, only three are of commercial significance. These are thenardite, the anhydrous salt; mirabilite, the decahydrate; and glauberite, the double salt of sodium and calcium sulfate. The reader is referred to Weisman (1983) for details on mineralogy and geology of sodium sulfate minerals. Sodium sulfate deposits, either in the form of brine or solid minerals, are found in many parts of the world. Natural sources, by far, provide the primary supply of commercial grades in Canada, Mexico, Spain, and probably in the U.S.S.R., Chile, Argentina, and Turkey. In the United States, production of natural material and synthetic (including by-product) are about equal in volume and have been for many years.

Jan 1, 1984

By Irina Chernyshova, Erik Larsen, Hanumantha Rao Kota, Vladislav Slabov, Garima Jain

The mining industry faces pressure to provide metals for the green digital shift using sustainable technologies. This study evaluates biosurfactants as collectors for ultrafine and coarser particles of hematite and malachite, aiming to improve the flotation of ultrafine particles.

Jun 1, 2023

By B. Akwasi Osei

The lack of metrics to assess clamshell formation dredgeability limits the ability of engineers to predict the dredgeability of compact material and increases the risks associated with clamshell selection. Research is needed to develop metrics for predicting clamshell dredgeability. The objective of this paper is to evaluate possible metrics to predict the dredgeability of compact aggregates by hydraulically actuated clamshell dredges. Data on cylinder pressures and displacements, motor current, bucket tilt and cycle time (CT) were collected from a dredge. Work done and motor energy, potential metrics, were computed and their suitability in predicting dredgeability evaluated. Data analysis shows that; there is no correlation between tilt angle and work done or motor energy; a low correlation between CT and work done, and a strong correlation between CT and motor energy. Work done is a better measure of formation dredgeability, than motor energy, as it shows lower variability. However, in difficult digging conditions, work done alone does not accurately predict dredgeability. This work shows that, it is feasible to use cylinder pressures and motor signals data to predict dredgeability.

Jan 1, 2010

By George A. Komadina

The Pima Mining Company lies 20 miles southwest of Tucson, Arizona, and some 45 miles north of the Mexican border. The mill is situated on a hillside overlooking Tucson and the Santa Cruz Valley, the ground generally sloping northeast at a 2.5 percent grade. The hillside location allows for gravity flow generally through the plant as well as for: tailing disposal.

Jan 1, 1965

By Calvin L. Stevenson

The probability of a particle passing through a maze is predictable and consistent. This principle may be utilized to effect a particle size separation of materials by presenting a physical maze to a stream of material that will allow the fine particles to pass, while deflecting the coarse particles. A maze is effective even though all apertures encountered are many times larger than the particles being separated. By designing a machine that allows the probability parameters to be controlled and varied without changing physical dimensions, probability sizing becomes a useful tool for the separation of granular materials.

Jan 1, 1967

By Orlando Oliveros

The Los Bronces Mine and Concentrator, one of the three operating units of Compania Minera Disputada de Las Condes S.A. (an Exxon Minerals Co. affiliate), is located in the high Andes of East-Central Chile approximately 70 kilometers northeast of Santiago at an elevation of 3,650 meters above sea level. (Figure 1). Santiago, the capital city of Chile, is located at an elevation of about 500 meters above sea level and enjoys a very mild climate, similar to some areas of California. At the mine site, however, extremely heavy winter conditions prevail occasionally, with very heavy snow and the resulting snow avalanches endangering installations and people. At the same time, ideal skiing conditions are found at the nearby ski resort of Portillo and Farellones. Mount Aconcagua, the highest mountain in the western hemisphere is only about 55 kilometers further to the northeast of the Los Bronces mine.

Jan 1, 1983

By Michael E. Karmis

New and developing communication systems en-able underground miners to, not only connect to the surface from an increased communication coverage area, but also to be discovered in the event of an emergency. Communication and tracking systems are required by the U.S. Mine Safety and Health Ad-ministration (MSHA) regulations, aiming to enhance health and safety and routine production in underground operations. Modeling a mine?s potential communication coverage area will increase overall coverage and efficiency of the communication network itself. Modeling the propagation of wireless communications enables ideal broadcast locations to be found when designing a communications network. Strategic placement of broad-cast devices results in a reliable communication network that can better withstand disruption in daily operation and during a time of emergencies. Research on wireless communication in mines has been ongoing since 1922, when the U.S. Bureau of Mines performed experiments in its experimental mine in Bruceton, PA (Schiffbauer & Brune, 2006a). Ac cording to Dobroski and Stolarczyk (1982), ?as early as 1922, Bureau of Mines experiments showed that radio propagation in mines was possible but not practical.? In 2006, the underground communication technologies available to the mining industry had inherent problems that limited communication capabilities. Because harsh underground mine environments significantly reduce line of sight and propagation range and introduce power and safety concerns, the overall effectiveness of underground communication technologies were limited. After several coal mining accidents in early 2006, the U.S. Congress responded with the Mine Improvement and New Emergency Response (MINER) Act, enacted

Jun 1, 2010

By H. P. Cole

A team of researchers at the University of Kentucky, working under a USBM contract, developed over 65 simulation exercises for teaching and testing problem-solving and decision-making skills to miners and mining engineers. These skills involve both improving judgment and decision making in mine emergencies and enhancing the learning of real-world engineering design principles. The exercises are ideally suited for either latent image format or for computer-aided instruction. Exercise features are summarized, the structure and field testing of typical exercises described, and sample frames of individual exercises presented. Empirical data are summarized that describe the effectiveness of using these short, time-efficient performance tasks that simulate real problems and that provide immediate corrective feedback for teaching and testing critical skills. I

Jan 1, 1991

By A. Chieregati

"A heterogeneity study was conducted at Erdenet Copper Mine in Erdenet, Mongolia, to determine the fundamental sampling error associated with blasthole sampling. Using a custom designed sector sampler, six large blasthole samples were collected to perform the test that was developed by Pierre Gy, to estimate the constitutional heterogeneity factor for several types of ore. The study investigated the entire sampling protocol, from mine site to analytical laboratory, and quantified the contributions to fundamental sampling error (FSE) of the various stages of sampling and sample preparation. The total relative standard deviation (RSD) of sampling error was determined to be ±32% and ±49.4% for copper and molybdenum respectively. A classical statistics analysis conducted on the data confirmed the level of RSD. About 95% of the sampling error was produced from only one step in the sampling protocol: when the 1 kg sample was reduced to 50 g sample for chemical analysis. Therefore, it is recommended that the 1 kg sample be reduced to 50g using a slightly different protocol to minimize the FSE. The 1 kg sample should be first crushed to 0.2cm size. A 250g split should then be taken and fine ground. A 50g split should then be taken from the 250g fine ground split. These two simple steps will reduce the FSE to ±7.9% and ±17% for copper and molybdenum respectively. The modified sampling protocol effectively reduces the probability of misclassification of low grade ore to zero. INTRODUCTION The Erdenet copper-molybdenum open pit mine is located in Erdenet, in Orkhon province, Mongolia. The Erdenetiin-Ovoo copper-molybdenum deposit is between 1.5 and 3 km wide, and about 25 km in length (Erdenet Mining Corporation, 2016). Chalcopyrite, bornite covellite and chalcocite are among the major minerals found in the deposit. The mine processes approximately 26 million tons of ore annually. A study was conducted to evaluate the fundamental error associated with the blasthole cuttings and sampling protocol at the mine. The open pit mine uses 215mm diameter Russian drills to drill 17.5m holes for 15m benches. The total weight of blasthole cuttings for a 215mm diameter hole and 15m bench height is between 1.5 and 2 tonnes. This amount of sample is difficult and time consuming to collect and analyze. Therefore, a sector sampler was designed for the Russian drills to collect large samples that were representative of the blasthole cuttings (Ganguli et al., 2016). In order to eliminate the delimitation and the extraction errors, researchers consider sector samplers to be ideal for sampling blastholes (Pitard, 2008; Chieregati and Pitard, 2009). This method was intentionally more rigorous than the blasthole sampling protocol at the mine to ensure that the blasthole cuttings were properly sampled. This study was part of a broader study that also looked at the relationship between particle size and grade. The samples collected by the custom designed sector sampler were very large (195 kg on average), and therefore, sufficient for both studies. The relationship between particle size and grade has been reported in Ganguli et al. (2016)."

Jan 1, 2017

By G. T. Lineberry

Horsepower requirement is recognized as a most important equipment characteristic. Other critical equipment characteristics will be isolated and analyzed by traditional operations research techniques, using off-highway trucks as an archetype. A computer search technique has been developed, employing various production and cost analyses. With this model, the optimum combination of horsepower, capacity, and velocity can be found, minimizing handling cost per ton. An example of the program's use and interpretation of its results will conclude the paper.

Jan 1, 1984