Search Documents

By R. L. Grayson, R. C. Althouse, M. J. Klishis

The health and safety of employees, efficiency of the operating system, and production are paramount goals in underground coal mining. The section foreman assumes responsibility for making his part of the total system function to meet these goals. However, section foremen often have not been prepared to assume the full range of their responsibilities upon becoming a supervisor. This paper addresses the full range of section foreman responsibilities and concomitant authority. Management principles that must be mastered by him are presented, and performance expectations as well as criteria for their evaluation are examined. The benefits realized from effective foreman training are discussed.

Jan 1, 1987

By Richard C. Mayberry

Phosphate reserves have been and still are a controversial subject. Some published estimates are particularly conservative and have caused concern in government and political circles that southeastern phosphates are a dwindling resource. "Ores and ore bodies" are a function of economics that relate to a time/demand factor. The history of phosphates and other mineral commodities is one of mineral deposits (resources) ever becoming ore (reserves) via a long term logic based on price, supply, and demand factors operating through time and improved technology. Projections indicate that southeastern phosphates are sufficient for several centuries of operations at present production rates.

Jan 1, 1981

By DING TANG, JINGHE CHEN, Shuiping Zhong, CHEN KUANG

The Zijinshan gold-copper mine, located in Shanghang County, China, is a porphyry-type, low-grade ore deposit with a geological profile of upper gold and lower copper. Despite its low-grade nature, it has become one of the largest in production scale and most profitable nonferrous metal mines in China, which can be attributed to the successful application of hydrometallurgy as well as proper engineering design. A large-scale, open-air cyanide heap leach has been successfully implemented to recover gold under the humid and rainy weather conditions of southern China. Furthermore, according to the gold ore characteristics, a combination of gravity separation, carbon-in-leach and heap leaching processes was developed to improve gold recovery. In terms of copper extraction, copper ore of a grade higher than 0.25 percent is fed to the flotation plants to produce copper concentrate (gold is also enriched here), while copper ore of a grade lower than 0.25 percent undergoes heap bioleaching followed by solvent extraction and electrowinning to produce cathode copper. Additionally, a unique bioleaching system has been established at the Zijinshan Mine: low operating pH (0.8~1.0), high concentration of total soluble iron (~50 g/L), high temperatures (45~60 °C) and low activity of microorganism (~104/mL) in the pregnant leach solution (PLS). This review paper summarizes the practical experience acquired in developing the Zijinshan gold-copper mine and could be of use in other gold and/or copper plants.

By R. E. Blair

The mining and minerals industry has been, and continues to be, at the cutting edge of high technology. Iron and steel built the Industrial Revolution/copper electrified the world/coal tars and petroleum and gas feedstocks developed the organic chemical industry. Industrial minerals now carry forward this tradition. Two, of hundreds of examples of hi-tech industrial minerals are quartz crystal and rare earths. Both demonstrate the international market aspects of mining, processing and finished product trade.

Jan 1, 1988

By J. Seifert, L. Hunter, P. W. Conrad, S. Rosenthal

"The goal of the protocol for reclaiming in-pit tailings ponds to exceed federal and state regulations was to develop a series of steps that can be followed to design, operate, and reclaim a tailings disposal pond that will develop into grazing land with a wetland for open pit sand mines in warm dry climates. By incorporating a wetland into the reclamation design, the post mining land use gives back to both the wildlife as a source of water as well as providing for a diverse range of post mining land use including but not limited to livestock grazing and ranch land use. An example design was completed using this protocol to demonstrate how the protocol can result in in a well-designed, reclaimed tailings disposal pond. BACKGROUND In an industry plagued with decaying historic mine sites, the public’s perception of mining appears to be poor. While modern mines are closely monitored and generally managed by ethical professionals, history still influences how the public perceives the mining industry. From collapsing abandoned underground workings to historic tailings dam failures, the failure to account for the environment in the past seems to affect public perspective on mining today. In a 2013 “Opinion Former Survey,” a survey conducted through interviews with a diverse range of stakeholders in various gold companies, it was noted that the most serious challenges facing the mining industry were environmental concerns and the permitting challenges associated with them (Council). In another article, this time focusing on Australian citizens and their perspectives of the mining industry, it was found that the majority of those surveyed had a big concern over the environmental impacts of mining especially when it comes to water quality and quantity (Scan). The statistics portrayed in these articles illustrate that today’s mining engineers needs to make more of an effort to change the public’s perspective of mining by being more environmentally aware. These engineers should be continuously asking themselves what they could be doing better from an environmental perspective to ensure that history is not repeated and that natural resources are used as efficiently as possible."

Jan 1, 2018

By John J. Sammarco, Alan G. Mayton, Elaine N. Rubinstein

Researchers from the U.S. National Institute for Occupational Safety and Health (NIOSH) developed the Saturn light that significantly improves illumination for roof-bolting machine operators while reducing glare. The existing roof-bolter lighting was the baseline and was compared to the Saturn at 100, 75 and 50 percent intensities. Discomfort glare and disability glare were measured by the De Boer rating scale and the Mars Letter Contrast sensitivity test, respectively. Thirty study participants were tested. Discomfort glare was reduced at least three levels with the Saturn luminaire. Visibility levels were four to 6.5 times better with the Saturn than with the baseline. The Saturn design is freely available for commercialization.

By Hamid Maleki

Mine seismicity is influenced by the mechanical properties of both near-seam rocks and overburden and the prudent selection of mining methods and mine layout designs. Using finite-difference modeling, experience in many U.S. mines and measurements of the pressure arch width, the author has reviewed the engineering design factors that control seismicity in room-and-pillar retreat operations for stiff stratigraphic conditions in deep western U.S. mines. By back analyzing the overburden response in now understood to have been inadequately designed historic room-and-pillar mine, the overburden collapse mechanism is addressed as well as the need for improvements in designs including panel and barrier pillar widths, and sequence of retreat.

Jan 1, 2009

By J. J. Zimmerman

Over-exposure to noise remains a widespread, serious health hazard in the U.S. mining industries. Most other categories of illnesses and injuries associated with mining have improved, with the exception of hearing loss. Mine Safety and Health Administration (MSHA) coal noise data from 2000-2004 show that the continuous mining machine is first among all equipment with 35% of the noise overexposures. Joy Mining Machinery, in collaboration with the National Institute for Occupational Safety and Health (NIOSH), is conducting research to reduce noise generated by continuous mining machines. This paper describes a ?JOY Designed for Noise Reduction? (JOY-DNR; Patent Pending) tail section as a noise control for reducing the noise overexposures of continuous mining machine operators. Underground results show a 45% and 65% noise exposure reduction for the operator when compared to a standard machine. Utilizing this newly developed noise control, along with previously proven controls, will provide continuous mining machine operators an opportunity to be within the MSHA-Permissible Exposure Limit (MSHA-PEL).

Jan 1, 2010

By J. J. Davis, C. A. J. Fletcher, M. Li, T. Jancar

This paper summarises the experimental approach to spiral modelling at the Julius Kruttschnitt Mineral Research Centre, University of Queensland, involving the use of plastic density tracers to determine partitioning performance on three models of coal spiral. This work has led to phenomenological models of the three spiral profiles most widely used in the Australian coal industry. The results from a parallel computational fluid dynamics approach to spiral modelling currently underway at the University of New South Wales are also presented. The computational simulation has been successfully applied to generic spiral geometries and is capable of predicting the fluid phase three dimensional flow fields and corresponding free surface profiles for moderate Reynolds' number and Froude numbers. Simulation predictions are compared with experimental results from a Mineral Deposits LD9 coal spiral.

Jan 1, 1995

By B. Hines

Grinding efficiency in a vertical stirred mill is affected by a wide range of process and mill configuration variables. Of these, the media fill, size, and intrinsic density have a significant effect on power draw and grinding performance. Media-related factors that influence grinding performance include, e.g.,a higher media filling providing additional particle breakage sites, or a lower bead density decreasing the running torque at a given media filling. It has been estimated that the grinding media can cause up to a 30% change in the specific energy required to grind. FLSmidth has generally recommended that the intrinsic density (specific gravity) of the grinding media be more than triple the slurry density. This density difference helps to ensure that sufficient stress intensity is generated in the mill to provide particle breakage. It also reduces the chance of media ?float? if there is a spike in either slurry density or slurry flow rate. The VXPmills have historically operated at slurry density values between 1.2 and 1.5 kg/L, which translates to nominal bead intrinsic density range between 3.6 and 4.5 kg/L. The current trend towards regrinding bulk flotation concentrates to even finer sizes, to improve recoveries of fine grained minerals, has provided motivation to consider closed-circuit operation of stirred media mills. The slurry density in this application is typically higher than in open-circuit operation due to the higher percent solids in cyclone underflows. An additional effect is that closed-circuit operation increases the potential for media float due to higher flow rates as slurry is recycled to the mill. The normal progression in extending the operating range of existing equipment is to carry out laboratory testing before pilot-scale and plant-scale trials. The results presented in this paper examine the media density to slurry density ratio and its effect on grinding performance.

Feb 23, 2014

By Fritz Kleiner, Walter Meintrup

On Nov. 4, 1981 A/S Sydvaranger's 1-kt/h (1,100-stph) wet-process, iron ore ball mill completed its first four months of uninterrupted, full-load operation in Kirkenes, Norway. This 6.5-m-diam (21-ft-diam) mill is driven by a gearless ring or wraparound 8.1-MW (10,860-hp) motor at 13.1 rpm-a first of a kind in this segment of industry. This article examines reasons for selecting this type of drive over more conventional schemes, lists specific advantages of such large mills, and describes the installation in Norway. History For almost a decade, good operating experiences have been gained with 28 gearless ring motor drives in the cement industry, driving 2.5 to 4-m-diam (8.2 to 13-ft-diam) tube mills with drive powers ranging from about 3-4 MW (4,000 - 8,000 hp). Why then did the mineral ore processing industry hesitate until 1980 to adopt this successful concept for similar applications on ball, semiautogenous, and autogenous mills? There are a number of good reasons in the eyes of conservative mill builders and operators, the most commonly cited ones are: • No operating experience in this segment of specialized industry. • More severe environmental conditions in the wet ore grinding process. • An indifferent attitude of mill builders and electric motor manufacturers towards new drive technologies. • Limited confidence in solid-state power supply systems, such as frequency converters of the required size. There have been and still are numerous problems associated with low-speed geared mill drives of any kind, especially with individual motor/gear sizes approaching or exceeding about 4 MW (5,360 hp). Every mill builder knows about them, but operators learn to accept them as inevitable. The Decision to Change Three things combined to break this technological stalemate: the courage and progressive spirit of one major iron ore processor in Scandinavia, the cooperation of three experienced manufacturers, and an unusual application problem that could not be solved by any conventional approach. The last factor was surely the decisive one, but the first one does not come as a surprise either. The Swedes near Kiruna and the Norwegians around Kirkenes are experienced ore miners and processors, and much credit goes to them for technological breakthroughs in the industry. At A/S Sydvaranger in Kirkenes, above the Polar circle at about the latitude of Alaska's northern tip, the existing grinding facilities, with a total of 14 100 to 240-t/h (110 to 264-stph) ball mills, can not be expanded. Nevertheless, to increase mill throughput, only installing a larger mill in place of an existing smaller one was a practical alternative. For this replacement, the owners set requirements that seemed impossible to meet: • The old 100-t/h (110-stph) ball mill should be replaced with a new ball mill with 10 times the rated throughput, without significantly impairing the operation of the remaining mills, and without significantly changing the mill building. • The new mill should have a variable-speed drive to ultimately optimize the grinding process by means of a closed-loop process¬computer-controlled grinding cycle, and to minimize the specific energy consumption. • Availability, efficiency, and life expectancy of all new components must be higher than those being replaced. • Inrush-current and harmonic loads on the rather weak electric supply line must be minimized to ensure safe plant operation. All old ball mills at A/S Sydvaranger are the geared type, using single synchronous and wound-rotor, slow-speed motors with ring-and-pinion gears. Operators are familiar with the limitations and problems associated with such drives, and they are aware that the following items become major concerns when drive powers are drastically increased: • Gears are subject to wear and tear, require frequent maintenance, and eventual replacement of major parts. • Gears are sensitive to misalignment, overload, and thermal distortion, limiting their useful life. • On dual or quadruple drives, load-sharing and torque oscillations between motors can be a major reason for concern. • At these speeds, ring-and-pinion gears reach their torque transmission capabilities altogether at around 4 MW (5,360 hp) per motor/pinion. To obtain the desired variable-speed performance of the new drive, the only practical and economical conventional solution would have been a frequency-controlled, low- or medium-speed dual motor drive with about 8 MW (10,720 hp) of power. This, however, was not feasible because of limited floor space. Therefore, bids were solicited for the alternative drive method, the gearless ring motor. General Considerations Why are such large mills considered? After all, one could avoid all the problems by simply staying with smaller mill unit sizes. Under competitive pressures of free markets, however, grinding efficiencies and specific energy consumption become key factors in selecting new equipment. Specific energy consumption of ball mills decreases with increas-

Jan 9, 1982

By William W. Shriver

When the Henderson Project is completed in 1975, it will become one of the Free World's largest primary molybdenum producers. The Henderson Mine will be located approximately 50 miles west of Denver, Colorado, on the eastern slope of the Continental Divide. Ore reserves are currently estimated to be 303,000,000 tons with a grade of 0.49% MoS2. The mill and tailing area will be located approximately 14.5 miles from the mine in the Williams Fork Valley, which is on the western slope of the Continental Divide. Ore haulage from the mine to the mill will be by ten miles of underground railroad and 4.5 miles of surface railroad. The concentrator has been designed to mill 30,000 tons per day and will yield approximately 50,000,000 pounds of contained molybdenum per year. This paper is concerned with the tailing and water supply system for the Henderson Project and in particular the environmental considerations affecting their design.

Jan 1, 1970

By Kourosh Shahriar

The occurrence of rock falls in underground coal mines entails detrimental effects as fatal or non-fatal injuries on workers, stoppages in mining operations and breakdown of equipment. In this paper, a risk assessment approach on the basis of a decision analysis trend is employed in order to assess the possibility of and manage roof falls. Risk is then assessed by determination of likelihood of occurrence and the cost of consequences (outcomes). In this regard, collected real roof fall data from Tabas and Kerman coal regions comprising of several underground coal mines are used. It is concluded that the annual accidents due to the roof falls occurrence in the all investigated mines are so high that it is economically feasible to improve the support systems and to implement a suitable educational program as well as an accurate supervision and other elements of safety management.

Jan 1, 2009

By Gerald H. Luttrell, Seyed Hassan Amini, Aaron Noble

Single-unit separations in mineral processing are typically not able to meet the strict purity requirements for consumer markets. As a result, multistage separation circuits are often employed. Because these circuits represent a large and inflexible capital investment, process engineers are careful to ensure that the circuit is optimally designed to meet the desired objectives. The set of interdependent decisions that constitute the circuit design may involve the selection of different unit operations, different equipment specifications, different operational parameters, and different unit interconnections. To assist circuit designers in assessing these options, researchers have attempted to establish standard design methodologies that involve various techniques and tools.

By Isabel F. Barton, Christian A. Rathkopf, Mark D. Barton

Rhenium (Re) is one of the rarest elements on earth and is a designated critical element in the United States and European Union for its uses in superalloys. Unusually among critical elements, Re is produced entirely as a byproduct of molybdenite (MoS2) mining, as pure Re minerals are extremely rare. However, Re concentration in natural molybdenites varies from a few parts per trillion to tens of percent. There are few known consistent patterns and no firmly established reason for this variation, making it difficult to use molybdenite Re content as a proxy for metal grades, a vector to high grades, a clue to the geological and geochemical nature of the ore deposit, a guide to overall Re resources or for any other of the applications that have been suggested for it over time. 

By W. R. Reed

This study evaluates the roof-bolter canopy air curtain (CAC) system in an exhausting face ventilation system, demonstrating its effectiveness and illustrating the CAC protection zones. Two scenarios are considered: (1) a roof-bolting machine in the center of the entry for installation of the fifth row of bolts from the face, and (2) a roof-bolting machine positioned close to the face for the installation of the last row of bolts. In both scenarios, the bolting machine is placed in an environment that contains 6.0 mg/m3 of respirable dust and is ventilated by an exhaust curtain with 9,000 cfm (4.25 m3/s) of air to simulate the roof-bolter machine operating downstream of a continuous mining machine. Two operation positions are simulated at the same bolting location: dual drill heads in the inward position for two inside bolts and in the outward position for two outside bolts. The influence of the CAC on airflows and dust dispersion is evaluated with the CAC operating at 250 cfm (0.12 m3/s) with dust reductions ranging from 39.5 to 82.8 percent. When the roof bolter is operated close to the face, increasing CAC airflow was required for adequate protection, as the dust reductions can be as low as 39.5 percent. Increasing CAC airflows to 350 cfm (0.17 m3/s) and 450 cfm (0.21 m3/s) were evaluated, demonstrating that dust reductions increased to 59.7 percent (350 cfm) and 72.0 percent (450 cfm). These results revealed improvement in respirable dust reductions compared to the CAC airflows at 250 cfm when the bolter is operated close to the face, showing the CAC can provide protection against high respirable dust concentrations for roof-bolter operators.

By K. V. Raj, C. A. Berry, A. T. Weakley, A. L. Miller, P. R. Griffiths, D. A. Parks

Diesel particulate matter (DPM) has been classified as a carcinogen to humans by the International Agency for Research on Cancer. DPM exposure is therefore regulated by the U.S. Mine Safety and Health Administration (MSHA). The current monitoring process takes days or weeks for exposure levels to be known, and a real-time monitoring device is needed. It is believed that infrared spectroscopy has potential for use in a real-time, field-portable device. This paper presents a method for measuring organic carbon (OC) and elemental carbon (EC) in DPM for a broad range of OC/EC ratios. 

By A. Yehia

Fluoride activation has been evaluated by Hallimond-tube flotation of collophanite in terms of fluoride concentration, conditioning time, pH, and temperature. The results reveal that efficient oleate flotation of collophanite can be achieved by fluoride activation. Fluoride adsorption by collophanite as a function of fluoride concentration, temperature, pH, and crystal structure suggests that, at low fluoride concentration, a fluoroapatite-type compound may form on the collophanite surface by chemisorption of fluoride ions at calcium sites; at high fluoride concentration, calcium fluoride ap¬pears to form at the collophanite surface invovling a surface-precipitation phenomenon. The formation of CaF2 on the surface of fluoride-treated collophanite is further substantiated by the FTIR spectroscopic measurements, which clearly shows a metathetic exchange with phosphate from the collophanite lattice during surface precipitation process.

Jan 1, 1986

By AKIHIRO YOSHIMURA, HIDEKAZU KATO, KOTA TAKATORI, YASUNARI MATSUNO

Chalcopyrite (CuFeS2) is the most refractory copper mineral when treated in conventional sulfate media leaching systems. This study is the first to examine the use of a dimethyl sulfoxide (CH3SOCH3), or DMSO, solution containing copper chloride (CuCl2) in the leaching of chalcopyrite. The DMSO solution containing CuCl2 could selectively dissolve the valuable metals of copper (Cu) and gold (Au) from chalcopyrite while leaving minerals with little economic value, such as pyrite (FeS2), and the penalty element arsenic (As) in the residues. Leaching chalcopyrite using a DMSO solution that contains CuCl2 offers a number of advantages, including eco-friendliness and easy operation.

ABB Industrial Systems is one of the largest electrical engineering companies in the world. ABB develops, manufactures and markets electric drives. The company has more than 100 years experience in the application of medium- and high-voltage AC machines. And ABB's continuous research and development program ensures that its machines use the latest technologies and materials. Each motor is custom designed to meet specific applications. The HXR high-efficiency motors (100 to 1,900 kW or 134 to 2,250 hp at 50 Hz) are efficient and have low noise levels. Typical applications are pumps, fans, blowers, compressors and pulverizers. The enclosed units are constructed with external cooling ribs and fans. And the motors are equipped with solid, longlife stators and rigid rotor construction. The patented rotor construction provides for low vibration levels. ABB's large synchronous motors (1 to 50 MW or 1,340 to 70,000 hp up to 900 rpm) are used in the mining industry for crushing, grinding hoisting and conveying systems. These motors are designed to customer's specifications, including existing foundations. They can be equipped with fixed or adjustable speed control.

Jan 1, 1998