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Careful financial analysis of capital investments has always been a vital task in mining which is one of the most capital intensive sectors of the economy. Furthermore, mining costs have leapt ahead at an astonishing rate in recent years not just due to accelerated inflation, which affects everyone, but also due to the imposition of enormous costs of enviromental regulation and the continuing decline in ore tenor. Not only have unit costs risen, but the amount of effort expended to recover a pound of metal has increased due to the inexorable decrease in ore grades. New low-margin, high-volume mining investments place increasing importance on sound financial planning. Owing to the enormous investments involved, a greater share of individual corporate resources is committed to these projects than is normally the case in other industries. Thus, the consequences of failure are extremely grave, and a close examination of all inputs to the evaluation equation is clearly indicated.

Jan 1, 1979

By J. N. Cox

Coal preparation is based on the properties of noncombustable materials (impurities) in coal being different from the organic constituents. The most commonly used property difference is density, via its affect on settling rates; and either gravitational or centrifugal forces can be used to remove impurities. However, examination of various particles settling rate correlations shows that at smaller sizes, particle drag becomes a very important factor. Classification, based on differential settling rates, becomes impractical and some property other than density must provide the basis for fine coal cleaning. Froth flotation and agglomeration employ differences in surface properties to clean coal. These methods are very successful except that the oxidized surface of a pyrite particle is somewhat hydrophobic and will tend to be collected with the organic portion of the coal. Surface property cleaning techniques have not been very effective in rejecting sulfur, except for two-stage flotation.

Jan 1, 1984

By Subhas G. Malghan

Feldspathic deposits occur widely throughout the United States, but North Carolina, California, Connecticut and South Carolina accounted for over 80% of the total domestic feldspar output for the year 1973.1 Pegmatites and granites constitute the major feldspar reserves of the United States,2 and in addition, feldspar is produced as a by-product by firms whose major products are spodumene and mica.3 Feldspar is concentrated by hand-cobbing and flotation; the latter forms the major method of separating and concentrating feldspar. Feldspar flotation is practiced in the United States, Mexico, Finland, Norway, West Germany, Japan and the USSR. According to the U. S. Bureau of Mines estimates, the production of feldspar in the United States and rest of the world were 704,000 tons and 2,514,000 tons respectively. Feldspar is principally used as a flux in making glass, pottery, porcelain, enamel,-tile and other ceramic products. In recent years, the domestic feldspar industry is faced with a number of problems. As a result of increased cost of energy and the introduction in 1972 of new legislative programs relating to air, water, and noise pollution, land-use restrictions, and mined-land rehabilitation, the production costs have increased. Apart from the increased cost of operation, an operational problem exists with the feldspar producers in North Carolina, especially those in the Spruce Pine area. This problem is concerned with the use of hydrofluoric acid in the feldspar flotation. Feldspar producers in Spruce Pine, North Carolina have been discharging process waste water into the North Toe River. The mill waste water contains active fluoride ions. Fluoride in excessive concentrations is undesirable in waters used for drinking. It is stated that water

Jan 1, 1976

By Frank Matter

The production of ultrafine slurries and powders is possible with small media made out of Si02, A1203, Fe203, Zr03 or other raw materials due to the fact that since approximately 12 years from now, entirely new machines have been developed which allow to use this small media for the production of ultrafine pigments. Basically we distinguish between two grinding methods which are: A.) Dry Grinding with Air Classification: This method is used for more than fifty years but only since four years this technology is realized with small grinding media. Many problems like cooling, abrasion, control of the media flow, separation media from product, grinding media recycling etc. had to be resolved before it was possible to get in full production with this new system. Hereafter a flow-sheet of such a TRZK mill with an air classifier especially designed to produce end products with a top size between 2,5 and 3,0 micron and with an average particle size between 0,3 and 0,5 micron.

Jan 1, 1983

By D. T. Iseley, A. L. Atta-alla

INTRODUCTION The extension project of the East Line Subway of Atlanta's subway network includes the construction of two single track transit tunnels under Interstate Highway 285. The project will be in DeKalb County, Georgia. The length, width, and height of each tunnel are 54.25, 6.3, and 7.2 m (178, 21, and 23 ft) respectively. The ground cover above the tunnel crown ranges from 1.5 to 3.25 m (5 to 11 ft). A soil pillar about 5.5 m (18 ft) wide will remain between the tunnels. The construction of each tunnel includes (i) installation of 21 steel soil support pipes of 75 cm (30 in) diameter, (ii) jet grouting 15 soil cement shafts of 60 cm (24 in) diameter in the soil under the pipes, (iii) contact grouting behind the tunnel lining and between soil support pipes and pavement, (iv) excavation of soil inside the soil support arch, and (v) installation of steel pile foundation, steel sets, and permanent tunnel lining of cast-in-place concrete, all as shown on the cross section in Fig. 1. The soil profile can be described from top to bottom as cement/asphalt concrete pavement, a fill layer consisting mostly of stiff sandy silt/firm silty sand, a residual soil layer consisting mostly of silty sand/sandy silt, partially weathered rock, and solid rock.

Jan 1, 1991

By T. Vandergrift, J. Sturgill, W. Gerhard, J. Carrick

As surface minable coal is depleted, many operators look to high-wall mining to extend reserve life. Recent advances in highwall mining equipment have greatly improved productivity, clean coal recovery, and attainable penetration beneath the highwall. Somewhat lagging have been systematic design approaches for ensuring web pillar and overall highwall stability. This paper presents an overview of the design, planning, and field performance of a multiple-seam highwall mining application in southwest Wyoming. The safety and efficiency obtained to date is attributable to the careful geotechnical and operational planning described herein. Field confirmation of performance and suggestions for improvement are also discussed.

Jan 1, 2004

Conventional wisdom in the mineral processing industry leads one to believe that pressure oxidation of refractory carbonaceous (preg-robbing) ores is not a practical approach to process development. Initial acid pressure oxidation testing on carbonaceous sulfide ores at the Twin Creeks Mine supported this conventional wisdom. After testing other refractory process options, including air and oxygen enriched roasting, Santa Fe Pacific Gold decided to take a second look at pressure oxidation, using conditions outside the normal range of conventional practice. A combination of very fine grinding and high operating temperature and pressure resulted in significant increases in gold extraction. This paper details the effect of operating parameters developed for Twin Creeks on gold recovery, sulfur oxidation, carbon oxidation/passivation and preg-robb through the laboratory and pilot plant investigations.

Jan 1, 1995

By Keith P. Bingham

A total transportation system providing for delivery of finished products to customers and raw materials to the plant is one of the key elements contributing to Dravo Lime Co.'s success. Dravo Lime operates one of the largest noncaptive lime and limestone plants in the US at Maysville, KY, where products produced can cost as much to deliver as they do to manufacture, depending on the product itself, its destination, and mode of transportation. With delivery costs comprising a significant portion of total costs for its products, Dravo Lime has made total transportation services an integral part of its business strategy. Prices for most products produced at Maysville are quoted f.o.b. destination. In short, Dravo Lime's Distribution Department relies on the approach that says to customers: "Leave the delivery to us." The 0.9-Mt/a (1-million stpy) Maysville facility, located about 121 km (75 miles) east of Cincinnati, OH, on the Ohio River, primarily produces sulfur-absorbing Thiosorbic lime used by coal-fired electric utilities as a scrubber reagent to remove SO2 from stack gases. The product is currently supplied to eight power plants in the Ohio River valley region which extends through portions of Kentucky, Indiana, Ohio, West Virginia, and Pennsylvania. The plant ships approximately 907 kt (1 million st) of lime and a comparable amount of limestone fines each year. In addition, it arranges for delivery of about 181 kt (200,000 st) of coal to the plant. Lime is transported by covered hopper barges, covered rail cars, covered dump trucks, and pneumatic trucks. It is transferred from barges to storage silos and trucks at a terminal on the Ohio River near Marietta, OH. At another terminal near Aliquippa, PA, lime is transferred from barges to silos, trucks, and rail cars. Future plans call for rail-truck transfer terminals. To produce lime from limestone at the Maysville plant, about 181 kt (200,000 st) of coal is burned annually in three coal-fired kilns. In transporting this coal from the mine to Maysville, Dravo takes maximum advantage of opportunities for reloading carriers with limestone for outbound backhaul movement. Coal, shipped from southeastern Kentucky mines in rail cars, is transferred to barges at a river terminal in West Virginia. After it is unloaded at Maysville, the barges are cleaned with a front-end loader and then reloaded with limestone. Limestone also is backhauled in connection with truck deliveries of coal. The economics of using backhaul shipments has permitted Dravo to enter into markets in which Maysville limestone otherwise would not be competitive. The company plans to backhaul limestone in empty open hopper cars in the future. As part of its ongoing assessment of the distribution system that supports the Maysville operation, Dravo Lime recognizes that a new environment has developed between shippers and carriers because of regulatory changes in the railroad and trucking industries. Although dry bulk shipments by barge to and from Maysville have always been unregulated, other forms of transportation have not. With railroads and motor carriers now approaching varying degrees of deregulation, contracts and agreements are replacing tariffs, and rate negotiations are becoming a daily activity. Dravo Lime plans to take advantage of these transportation changes, all of which may be beneficial to both its plant and its customers.

Jan 10, 1982

By N. Magdalinovic

Generally speaking, erosion, as a process which entails degradation of surface layers of earth under the influence of the mechanical energy of surface waters, and from the point of view of biosphere sustainability, is a harmful process. This is absolutely true when agricultural and forest areas are concerned. However, if erosion is viewed selectively, this general definition about its harm raises serious questions. In other words, the erosion which takes place in the terrains where there is no vegetation because of the geological composition of the soil, does no harm. On the contrary, if the mineralogical composition of such terrains is characterized by a presence of precious and rare metals, erosion can be very useful. It contributes to the creation of new alluvial deposits of these metals in the waters in the plain land. It is here that torrents from hills come down and cause erosion. And finally, if there were no erosion, there would be no renewable deposits of gravel and sand.

Jan 1, 2007

By Romeo S. Jurani

Yucca Mountain, located in Southern Nevada approximately 160 krn northwest of Las Vegas, is currently the site of intensive surfacebased and underground investigations. The investigations are required to determine if the site is suitable for long term isolation of the Nation's high level nuclear waste inventory. A major component of the program is the Exploratory Studies Facility, or ESF. The ESF, when completed, will consist of approximately 25,600 meters of tunnels and drifts. The network of tunnels and drifts (Figure 1) will house and support a wide array of testing programs conceived to provide physical information about the site. Information on geologic, geomechanical, and hydrologic data will be used in the repository design if the site is found suitable. Besides a few special requirements, the general ESF ventilation criteria during construction are similar to that of commercial tunneling and mining operations. The minimum air velocity at the Tunnel Boring Machine (TBM) and other active mining faces is 0.51 meter per second (m/s) (100 feet per minute [fpm]). Airways, estimated leakages and ventilation controls are converted into equivalent resistances for input to mine ventilation network computer simulations. VNETPC Version 3.1 computer software is used to generate the ventilation models for optimized system design and component selection. Subsequently, actual performance of the ventilation system will be verified and validated to comply with applicable nuclear regulatory quality assurance requirements. Dust control in the ESF is dependent on effective dust collection, enclosure, and airflow dilution. Minimum use of water, as feasible, is necessary to avoid adding moisture to the potential repository horizon. The limitation of water use for test drilling and TBM operation, and the rigid compliance with applicable federal and state regulations, make the ESF a ventilation design challenge.

Jan 1, 1995

By David B. Spencer

This paper describes a process for separating non-ferrous metals such as aluminum, copper and zinc, from other residential and industrial waste by means of permanent magnets. Although the separator may be used in the recovery of non-ferrous metals from auto scrap, most of the testing to date has been aimed at recovery of non-ferrous metals from municipal solid waste, especially recovery of aluminum from the heavy fraction of a resource recovery plant. In most resource recovery plants the incoming solid waste material is first shredded and then air classified into a light and a heavy fraction. The light fraction which contains mostly paper, cardboard, etc., can be used either as a fuel for power generation or in the production of new paper products. The heavy fraction which remains consists mostly of glass, ceramics, wood, ferrous metals and non-ferrous metals. The ferrous metals may be removed from the heavy fraction by conventional magnetic separators. After primary shredding, most of the glass and ceramic is fine in size and may be screened away leaving a residue of wood, cardboard, and non-ferrous metals. This residual heavy fraction is the input material for the separator described in the present paper.

Jan 1, 1975

By Peter L. Dunn

With the advent of new high-strength magnetic materials, rare-earth magnetic separators have become more common place for processing heavy mineral sands. In many instances, rare-earth magnets have replaced conventional separators such as electromagnetic cross-belt and induced-roll type machines. This paper will present the results from a detailed test program developed to evaluate the performance of rare-earth drum and roll separators for processing heavy mineral sands. The effect of machine design parameters, such as magnetic element configuration and separator diameter, will be reviewed in light of these test results. The impact of basic operating parameters (i.e. feed rate and roll speed) on separation efficiency will also be presented.

Jan 1, 1999

By V. K. Gupta

The experimental results of some wet batch and continuous grinding experiments carried out in a 40 x 40 cm grate discharge ball mill have been analyzed for the variation of the grinding rate parameters, Si, with various operating conditions using a linearized population balance model. The wet grinding tests were carried out under conditions which were very similar to those encountered in the actual practice in plant operation. Well distributed -4 and -20 mesh feeds of two complex pyritic ores were used. The volume-percent solids in the pulp ranged from 30-40, the particle load from 5-8 kg, and the solids feed rate from 70-1 10 kg/hr.

Jan 1, 1981

By Y. C. Kim

This paper reviews the past 18 months of geostatistical work in a coal deposit performed jointly by the University of Arizona and the Homer City Owners. The objective of the study was to better predict the in-seam sulfur values of the deposit for the purpose of future emission control. Based on initially available 112 DDH information, variogram models were developed for Sulfur, Ash and Thickness for the entire deposit. The deposit was then kriged using 333 m x 333 m (1000 ft x 1000 ft) panel size. The estimation variance information obtainable from geostatistics was next utilized to improve the development drilling activities that were underway. The results of this effort are presented in this paper. In addition, this paper describes (1) the reasons for preferring kriging over the conventional isopachs, (2) the results of empirical validation of the kriged estimates using 19 additional DDH information, and (3) up-to-date experience on the use of conditional simulation of the same deposit for the future emission control strategy development.

Jan 1, 1980

By Thomas R. Doyle

When you think of the state of Maine, you probably think of lobsters or lighthouses. The last thing you would think of is metallic mineral mining, and that is for good reason. According to the Maine Geological Survey?s website, ?no metals have been mined in Maine since 1977.? Moreover, Maine?s metallic mineral mining laws and rules, which were last rewritten in 1991, have effectively made mining in the Pine Tree State impossible. Statutory changes enacted in 2012, however, put Maine on a path to make metallic mineral mining part of the local economy in the near future. History of metallic mineral mining in Maine Currently, Maine is not a metallic mineral mining state, though that has not always been the case. The 1800s saw various mining operations in Maine, including what the Maine Geological Survey calls a ?mining boom? from 1879 to 1882, where mining of iron, silver, copper, lead and zinc expanded rapidly. Mining and mining activity in the more recent past, however, drove the debate before the state legislature when this issue was debated in 2012.

Jan 1, 2012

By C. McAllister, D. Preece, J. Berendzen

"The Multiple Blasthole Fragmentation (MBF) model models multiple explosive charge contributions and the effect on fragmentation of delay timing with its associated scatter for each blasthole. The model uses near-field blast vibration attenuation parameters and the ground p-wave velocity as inputs for part of the in situ rock property to model rock fragmentation. It models most blast design parameters explicitly and simulates the effect of wave reinforcement due to the interaction of simultaneously arriving waves or diminishing cooperative contribution from long delay intervals between charges within a blasthole or among blastholes. The fragmentation size is calculated at three-dimensional grid points within a blast, and the fines and oversized blocks are treated explicitly. The model takes a surveyed irregular geometry of the free face of a blast as the calculation boundary.This paper presents a case study on applying the MBF model at an openpit mine. Near-field vibration measurements from signature hole blasts were conducted to obtain the stress-wave magnitude and attenuation parameters as well as ground sonic velocity. A production blast was then monitored with the corresponding fragmentation measured, serving as site-specific inputs to the MBF model. Various blast design scenarios were then simulated to develop ones that provide better fragmentation to improve mill throughput for the mine. IntroductionThe semiempirical fragmentation models currently found in the literature (Cunningham, 1987; Lownds, 1995) cannot explicitly model contributions from multiple blastholes with varying delay intervals. Most of these models are not three-dimensional. Furthermore, these models predict an average fragmentation size within a volume surrounding a blasthole and use the average size to generate a size distribution over the volume. The percentage of fines and oversize blocks is included in the distribution. Typically, such models are inadequate for predicting fines and oversize blocks (Cunningham, 1987)."

Oct 1, 2016

By V. O. Tenorio, D. Tolmachoff, K. Willa Brown, K. J. Kingsbury, J. B. Nickels, G. J. Nail

A major design feature to consider from the initial pioneering works until reaching full mine production of icy regolith at the South Pole of Moon will be the ramp. This will allow the access of equipment and personnel in and out of the excavation area. Although most of the requirements considered when designing a ramp on the Earth are similar, the fact of working in low gravity, with zero atmosphere, the potential exposure to high radiation, extreme temperature levels and drastic changes of illumination, from intense light to total darkness, are new factors to be included. Transversal sections are obtained according to the progression sequence of the production levels, with changes in length, gradient, friction factor of the terrain and curvature when required by the location characteristics and the specification of the equipment utilized. A MATLAB script was developed to calculate all the variables, in order to obtain 3D generated surfaces from the range of possible profiles.

Mar 2, 2022

By X. Zhu, Chen. L., R. Guru, M. Peiravi, M. Mohanty, L. Ackah, B. Xu

"The overall goal of this study is to develop a suitable flow sheet to extract rare earth elements (REEs) from coal ash. A total of 14 coal samples of different ranks were examined for REE concentration, and an anthracite coal sample with the highest REE concentration of more than 700 ppm in the coal ash was selected for REE extraction tests. This paper reports on the results of the experimental program completed in the first part of the study, which included hightemperature leaching with nitric acid followed by solvent extraction tests using various organic extractants, namely, tributyl phosphate, Cyanex 572, di-(2-ethylhexyl)phosphoric acid (D2EHPA) and their combinations. A 4×2×2 experimental design was used to conduct a total of 32 high-temperature leaching tests by varying acid molarity at four levels, solids content at two levels and leaching time at two levels. The highest recovery rates of 90 percent for light rare earth elements (LREEs) and 94 percent for heavy rare earth elements (HREEs) were obtained from the optimum leaching test conditions while maintaining impurity recovery to the leachate at less than 40 percent. D2EHPA was found to be the best extractant in this solvent extraction test series, providing an REE recovery rate of nearly 99 percent.IntroductionGlobal demand for rare earth elements (REEs) and other strategic metals is increasing rapidly due to their use in a variety of advanced technological applications, with more than 100 kt of rare earth oxides used worldwide on an annual basis. The United States has less than 10 percent of the world reserves of REE mineral deposits, and in 2013 imported more than 60 percent of its rare earth oxides from other countries, mainly China (United States Geological Survey, 2017). China’s institution of export quotas has significantly reduced supply to the United States, raising the urgency of finding new ways of producing REEs and/ or substitutes. Coal combustion byproducts, which are usually discarded as waste materials, are known to contain REEs in low concentrations that could be extracted with a suitable process flow sheet. This may be a worthwhile route to pursue, considering the short supply of rare earth minerals and the abundance of coal ash in thousands of ash ponds in the United States. More than 110 Mt of coal combustion byproducts are produced annually in the process of satisfying the country’s need for electricity (American Coal Ash Association, 2016), and less than 50 percent of these byproducts are being successfully used in various applications, with the remainder dumped as waste materials in landfills and ash ponds."

Jan 1, 2017

By S. J. Schatzel, J. D. Addis, V. Gangrade

In longwall mining, ventilation is considered one of the more effective means for controlling gases and dust. In order to study longwall ventilation in a controlled environment, researchers built a unique physical model called the Longwall Instrumented Aerodynamic Model (LIAM) in a laboratory at the National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) campus. LIAM is a 1:30 scale physical model geometrically designed to simulate a single longwall panel with a three-entry headgate and tailgate configuration, along with three back bleeder entries. It consists of a twopart heterogeneous gob that simulates a less compacted unconsolidated zone and more compacted consolidated zone. It has a footprint of 8.94 m (29 ft.) by 4.88 m (16 ft.), with a simulated face length of 220 m (720 ft.) in full scale. LIAM is built with critical details of the face, gob, and mining machinery. It is instrumented with pressure gauges, flow anemometers, temperature probes, a fan, and a data acquisition system. Scaling relationships are derived on the basis of Reynolds and Richardson numbers to preserve the physical and dynamic similitude. This paper discusses the findings from a study conducted in the LIAM to investigate the gob-face interaction, airflow patterns within the gob, and airflow dynamics on the face for varying roof caving characteristics. Results are discussed to show the impact of caving behind the shields on longwall ventilation.

By S. J. Schatzel, J. D. Addis, V. Gangrade

In longwall mining, ventilation is considered one of the more effective means for controlling gases and dust. In order to study longwall ventilation in a controlled environment, researchers built a unique physical model called the Longwall Instrumented Aerodynamic Model (LIAM) in a laboratory at the National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) campus. LIAM is a 1:30 scale physical model geometrically designed to simulate a single longwall panel with a three-entry headgate and tailgate configuration, along with three back bleeder entries. It consists of a twopart heterogeneous gob that simulates a less compacted unconsolidated zone and more compacted consolidated zone. It has a footprint of 8.94 m (29 ft.) by 4.88 m (16 ft.), with a simulated face length of 220 m (720 ft.) in full scale. LIAM is built with critical details of the face, gob, and mining machinery. It is instrumented with pressure gauges, flow anemometers, temperature probes, a fan, and a data acquisition system. Scaling relationships are derived on the basis of Reynolds and Richardson numbers to preserve the physical and dynamic similitude. This paper discusses the findings from a study conducted in the LIAM to investigate the gob-face interaction, airflow patterns within the gob, and airflow dynamics on the face for varying roof caving characteristics. Results are discussed to show the impact of caving behind the shields on longwall ventilation.