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By Richard S. Klein

Frozen coal creates severe handling problems. Utilities require uninterrupted supplies of coal to meet their increasing coal consumption rates. Difficulties incurred due to frozen coal result in more costly downtime for the utilities. Air cannons, vibratory hammers and thaw sheds are examples of mechanical devices used to break, crack or thaw frozen coal. Recently chemical treatments have been developed as preventive measures. The freezing of coal depends upon a number of factors, of which one of the most significant is surface moisture. The more there is, the larger the frozen coal problem. Slide 1 depicts a graph of frozen coal compressive strength as a function of surface moisture. Below a certain minimum value the coal will not freeze. Above this point, compressive strength is essentially a linear function of moisture over the range practically encountered. By surface moisture is meant the free moisture on coal having a normal vapor pressure as opposed to capillary moisture or inherent moisture. In addition to the straightforward freezing of coal surface moisture binding particulates together, frost formation occurs due to temperature gradients which develop in rail-cars and stockpiles .

Jan 1, 1980

By Anthony M. Bauer

It is the nature of mining to reshape the landscape. Mining is an earth moving process with many of the same activities associated with the regrading of a site for a shopping center, drainage channel, housing project or ballfield. The difference exists only in purpose and duration of activity. The purpose of mining is to, produce a valuable product. The purpose of regrading for construction of a project is to create a predetermined landscape for a specific end use. In both situations the objective is to move earth materials as efficiently as possible. The question is then raised, if similarities exist, can mining operations be directed to shape predetermined landscapes as an integral part of its earth moving activity. This paper will explore the opportunities and issues of shaping sand, gravel and hardrock construction aggregate sites for productive end uses. It is based upon the premise that, as an earth moving operation, the process of extracting sand and gravel includes an inherent capability to shape productive lands as an integral part of the mining operation. In the course of any mining operation non-commercial materials, including overburden, fines and excess sand are handled to extract and process the commercial products. This activity exists regardless of whether or not there is a plan to reclaim the land. Moving this dirt is a basic operational cost. This cost need not be significantly increased when the material is deposited to shape land rather than be stock- piled just to clear the way for mining the deposit. Moving of dirt to create useable land can be guided by the same criteria used to remove the dirt from the deposit: for example, limiting the- hauling distance. Over a period of time earth handling costs can be reduced by minimizing the need to transport the stockpiled material a second time to the new landform location.

Jan 1, 1984

By Jr. Pitts

Elevation of surface charge density on colloidal particles in the presence of a high potential electrostatic field is demonstrated as a viable technique for preventing the accumulation of solids in solvent extraction circuits. The effect of the technique is manifest by relative turbidity measurements between pregnant leach solution and raffinate, by changes in the character of the sludge accumulations, by alteration of the zeta potential of particulates, and by a general reduction in the mass of solids.

Jan 1, 1992

By Kenneth A. Pietila

The thickening and dewatering characteristics of refuse slurries are as variable as the coal mining operations and preparation plants that create them. This paper discusses these characteristics based on field studies at a number of mine sites. The connection between bench and full scale performance is confirmed with the design, construction and operation of an integrated 18m (60 ft) diameter thickener and 2.5 meter belt filter press system in Western Kentucky. The data from this system are presented.

Jan 1, 1984

By Yun Bai, Sarah Wilson, Michael Salcher, Mark Trim

Over the last decade more than 62 miles (100 km) of civil transport tunnels were constructed in Sydney, Australia, using the sequential excavation method (SEM). The WestConnex motorway tunnels, each stage of which used over 20 roadheaders to excavate up to 40 tunnel headings, had numerous caverns up to 100 feet (30 m) wide and 82 feet (25 m) high. SEM tunnels in North America typically have far fewer active headings. This paper examines the differences in scope and risk allocation for construction phase services, including comparison of the Permit to Tunnel (PTT) process in Australia and the Required Excavation and Support process in North America.

Jun 23, 2024

By Lawrence L. Davis

This paper describes current research by the Bureau of Mines to develop technology for improving efficiency and productivity in metal/ nonmetal mines. The research program addresses a wide variety of problems associated with each of the major categories of mining: underground mining, surface mining, in situ mining, and premining investigations. An overview of the Bureau's research activities is given with emphasis on underground mining. In particular, two innovative and promising concepts currently under development are described: a unique shaft sinking system that uses an impact hammer for rock fragmentation, and a low-profile, portable crusher for underground hard-rock applications.

Jan 1, 1979

By Richard Collins

The projected depletion and the increasing costs of petroleum and natural gas along with the public and governmental resistance to nuclear energy have caused coal to emerge as one of today's answers to both our short term and long term energy needs in power generation. In order to satisfy this need, major increases in coal production are mandatory, thus requiring more and higher capacity coal transfer terminals. The logic for selecting coal as the major fuel for power generation is based on many different reports on the existing and potential energy sources, which include petroleum, natural gas, hydropower, solar, geothermal, and nuclear. The following is a brief synopsis of these reports for each type of energy.

Jan 1, 1978

By Jürgen F. Brune, SAMUEL A. LOLON, ADITYA JUGANDA, Gregory E. Bogin Jr

Historically, there have been many occurrences ofmine fires and explosions recorded in the United States and other countries that have demonstrated the existence of explosivemethane–airmixtures, herein referred to as explosive gas zones (EGZs). The risk of mine explosions can increase if the EGZs migrate out from the gob into the surrounding mine entries. Fluctuating barometric pressure is the common cause for EGZs outflowing or outgassing from the gob. Numerical analysis using a 3D computational fluid dynamics method was developed to fully understand the outgassing phenomenon. A number of simulations using various magnitudes and periods of barometric pressure changes indicated that the EGZ outgassing potentially occurs due to lags in pressure, which are strongly influenced by mine conditions and ventilation systems. An early warning system with a real-time pressure monitoring and the application of gob ventilation boreholes are recommended to detect and mitigate explosion hazards from gob outgassing.

Aug 24, 2020

By Andrew Trusiak

Brunswick Mining, employing approximately 1600 employees, is located 40 km south of the city of Bathurst in north eastern New Brunswick. The mine has operated as two lead-zinc operations - the underground mine(No.12) and the open pit mine (No.6). The open pit orebody is presently being' mined by underground methods. It is expected that the No.12 mine will furnish the entire ore supply by the end of 1981. The flotation practice prior to 1971 has been described by Neumann and Schnarr(1) and by Erskine (2). More recently, the current flotation practice has been described by McTavish(3) and deals with some major circuit modifications between 1972 and 1978. The period 1978 to 1980 has seen the completion of. a major flotation cell replacement and expansion program for the No.6 concentrator, and the implementation of computer control in the No. 12 CuPb and Zn flotation circuits.

Jan 1, 1981

By Leping Liu, Li‑Ting Chen, Sachin Urade, Pengbo Chu

Mining industry requires constant adaptation to its practices in response to the dynamic change of the societal demand. Little information exists regarding how the US metal mining engineering education is prepared to meet with its industry needs due to the increase in critical minerals driven by the green energy transitions. This study aims to provide industrial perspectives on the current US metal mining engineering education and areas for improvement. An online survey with both closed- and open-ended questions were designed to seek opinions from the US mining industry. Findings indicated a shortage of qualified graduates from the current US metal mining engineering education system. The qualifications need to be improved include engineering sciences underlying mining methods, mining design experience, mining feasibility study, the connection between theory and practice, and understanding of the overall mining operation. The survey also identified future desired qualifications. The most desired ones in the next 5 years include an ability to acquire and apply new knowledge as needed and sufficient experience in the field. Respondents, regardless of the nature of their affiliated mining companies, unanimously recommended that collaborations between the industry and academia should be enhanced. The analysis of the results concluded four recommendations: (1) involve more multiple stakeholders in reforming mining education programs, (2) reinforce field experiences as a key part of mining engineering education programs, (3) enhance a closer collaboration between academia and industry, and (4) integrate emerging technologies (e.g., artificial intelligence/virtual reality) guided by pedagogical theories into new mining engineering curriculums.

Jun 26, 2023

By Johann Steynberg

The design and construction of a Concentrator based on initial pilot plant work is rarely perfect. Palabora's plant was no exception although the basic objective to produce copper in a safely conservative manner was certainly achieved in a profitable manner. identification of the metallurgical and mechanical deficiencies of the plant through operating experience and a better concept of the minerology of the orebody enabled the development of a more efficient process both in terms of the metallurgical performance and cost effectiveness. To maintain and improve this level of efficiency, continuous inspection and revision of the plant metallurgy and engineering standards is required. In this presentation a few of the investigations and changes are described: 1.0 Alternative methods to restrict and eliminate the detrimental effect of critical size material on the performance of an autogenous mill. 2.0 An analysis of the environmental condi¬tions in Palabora's grinding circuit and the introduction of high chrome balls as grinding media. 3.0 The role of magnetite in the beneficiation process at Palabora. 1.0 Alternative methods to restrict and eliminate the detrimental effect of critical size material on the performance of an autogenous mill.

Jan 1, 1985

By D. Symonds, A. J. Richins, M. G. Nelson

Mining activities at Kennecott and Park City are similar in that both districts began operation in the last half of the 18th century, and both operated on a large scale for many years. However, they are different for two important reasons. First, the mines in the Park City district were always underground. The city of Park City was above many of those mine workings. It remained in place after mining activity stopped, and as the town became an up-scale ski resort, property values increased and the tailings dumps became desirable building sites. In contrast, Kennecott eventually became an open pit mine, and the growing pit effectively consumed many of the small towns that had grown up around the underground workings. Even towns on the periphery of the open pit were razed to allow for the disposal of mine overburden. Second, almost all mining activity stopped in Park City in the early 1970s, just as the first rigorous environmental legislation in the United States was enacted. (The Ontario mine operated sporadically until 1982.) Many mine structures, waste dumps, tailings ponds and piles, and tunnels were simply abandoned as the mining companies ceased business or were bought out. Kennecott, on the other hand, has been in continuous operation for more than 120 years, so a closure plan hasn’t been finalized. Nonetheless, environmental and social problems have arisen, and the company has had to address them.

Mar 2, 2022

By Mark H. Johns

Leaching of waste material at Kennecott's Chino Mines Division at Santa Rita, New Mexico, has been accompanied by increasing difficulty in circulating leach solutions through the dumps. As a means of recognizing existing problems and considering alternative applications of the leaching concept, a leaching research program was proposed which could be applied to a specific, typical waste dump. Conclusions derived from the area could then be applied to other leaching areas at Chino. Associated with the program was an evaluation of the physical characteristics of the area using Chino's drilling and radiation logging techniques.

Jan 1, 1970

By Frank A. Jerabek

Problems of mine backfilling and fill material deposited underground, the characteristics and relationship between the deposited fill material and overlying ground, and the practical applications and limitations of hydraulic backfilling as ground support are discussed. A great variety of materials ranging from coal washery refuse to concentrator tailings is used as hydraulic fill. Some materials will solidify and cement; others will resemble quicksand, Hydraulic fill as ground support is more efficient in inclined mine openings than in horizontal mine openings, where it cannot be placed tightly to the back. This and other deficiencies of hydraulic backfilling led to the development of pneumatic stowing. Research work in hydraulic backfilling at the Pennsylvania State University is also discussed. This research work includes the investigation of segregation in the discharged fill slurry, the quantity of solids escaping in the drain liquid, the relationship of escaping solids to slurry concentration and discharge rate, and the compressibility of fine fill material.

Jan 1, 1965

By Brendan Donnelly, Lasitha Piyathilaka, Jung‑Hoon Sul, Sanghyun Jeong, Benjamin Probyn

Premature failure of armoured face conveyor (AFC) chains due to corrosion is a significant proportion of the unplanned downtime experienced on longwall equipment. The AFC chains are constantly in contact with water and wet coal. The premature failure issue of AFC chains has become more prominent since the introduction of longwall top-coal caving with its additional AFC. Reverse osmosis (RO) is a popular water treatment method for reducing salinity and dissolved solids, but its impact on the corrosion of the AFC chains is unclear. This study has been commissioned to investigate the direct effects of RO water on the corrosion of AFC chains. An immersion test was carried out using AFC chain steel submerged in two water samples: untreated dam water and treated water from an RO treatment plant. Elemental analysis was conducted for both water samples, and four corrosion indices were measured for both water samples. The RO water more vigorously dissolves calcium carbonate scales leading to increased corrosion of the AFC chains although the dam water has much higher levels of calcium, chloride, sulphate, sodium, and magnesium. Bicarbonate ions are the main alkaline factor of water that provides the buffering capacity to acids. Decreased alkalinity without balancing other ions in water causes high corrosivity and decreased scaling tendencies.

Oct 16, 2023

By Aline Tatom

This paper presents numerical and experimen¬tal results dealing with the application of ferric ion oxidation of uranium in acidic media. Conclusions are derived from matching numerical results to experimental data taken on one-dimensional laboratory leaches using ore from a South Texas Coastal plain deposit. Since the numerical results can be made quite general, we are able to extract and quantify the effects of oxidant concentration, flow velocity, mass transfer, chemical kinetics, and competitive oxidant consumers (pyrite and molybdenite) on the experimental results. Our results suggest that the leaching of uranium is a mass transfer controlled while that of pyrite is kinetically controlled.

Jan 1, 1981

By John A. L. Campbell

Surface dependent processes, such as froth flotation and flocculation, are important or potentially important techniques for combating some of the current major problems in coal preparation. In order to correctly apply or imporve a surface dependent process, it is of paramount importance to understand the interfacial phenomenon, especially the double layer properties, exhibited by the solid. The specific objective of this research was to determine the properties of the bituminous coal/liquid interface by an electrokinetic method, streaming potential, and to relate the findings, wherever possible, to the existing unit operations of froth flotation and flocculation. The electrokinetic properties of both the whole coal and its lithotypes were investigated. As part of the total investigation, the role played in the double layer by the reagents commonly employed in the surface dependent process was also established (1). These data will be presented at a latter date.

Jan 1, 1969

By W. R. Peters

An experimental hole-to-hole seismic probe system has been developed for use in coal measure geology as a means of determining the structural conditions of coal seams. The source probe produces a 500-joule electric arc discharge whose seismic wavelet has a spectrum in the 200 to 2,000 Hz frequency range. Low compliance hydrophones contained in the source probe as well as in a separate seismic detector probe are matched to the frequency range of the source. Both probes are constructed with 5-72 cm diameter housings. The transducers in the probes are equipped with fluid-inflatable boots to permit operation in either wet or dry boreholes. Preliminary tests in vertical boreholes drilled 213 m apart in sedimentary rock formations show reliable operation and useful seismic propagation measurements along horizontal and oblique paths up to 232 m in length. Because the seismic wave- let has an accurately repeatable waveshape, multiple shots and signal averaging techniques can be used to enhance the signal-to-noise ratio and extend the transmission distances.

Jan 1, 1985

By C. L. Lin

The image-based On-line Particle Size Analyzer (OPSA) system has been developed at the University of Utah to measure particle size distributions under plant conditions where overlapped and segregated particles are being transported on a moving belt conveyor. Evaluation of the OPSA system at several plant sites has been completed. The results show a consistent agreement between the particle size distributions obtained from the OPSA system and those obtained from laboratory screen analysis of belt samples. These results and the stable performance of the OPSA system during the field tests suggest that continuous quality control of crushed products is possible using the OPSA system.

Jan 1, 1999

By David A. Newman

The Geomechanics Classification (Bieniawski, 1979) was modified for entry and roof support design in underground room-and-pillar coal mines. Adjustment multipliers were introduced to incorporate the influence of strata weatherability, high horizontal stresses, and the roof support reinforcement factor into the existing classification system. Sixty-two case histories of both standing and fallen mine roof were collected from two mines in the northern Appalachian coalfield. Twenty-seven engineering and geologic parameters were recorded for each case. A partial correlation analysis was carried out on the cases to establish which parameters have a significant impact upon the supported stand-up time of coal mine roof. Survival analysis, a statistical technique used in medical research to assess the effect of a drug or treatment on a patient's life expectancy, was conducted together with stepwise multiple regression to derive values for the adjustment multipliers. A practical example is included to illustrate the application of the modified Geomechanics Classification to underground coal mine design.

Jan 1, 1985