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By Robert M. Cox

Surface mining of coal in the South developed into a major industry during the 1960's. The economic significance of the industry is much greater than is readily apparent when one considers only the value of the coal mined. The abun-dant supply of relatively inexpensive steam coal for electric power generation that has been derived from the surface mines has provided the foundation for the industrial expansion that has occurred throughout the South. The region, in gen-eral, has enjoyed the benefits of plentiful low cost electric power. However, re-cent political decisions, at all levels of government, threaten to destroy or severely curtail the surface mining of coal and eliminate the economic advantages once enjoyed by the region. These political decisions are rapidly changing the basic rules of operation and fundamental economics of surface coal mining. Recent changes, resulting from the enactment of environmental and health and safety laws and various bureaucratic rules and regulations, have had a three-fold effect: 1) Greatly increased operating cost, 2) increased lead times for mine development, 3) limited potential reserve base for future mining. Also current legislative proposals are casting a shadow of uncertainty over the future of all coal mining operations that has created serious delays and in-creased cost for the expansion of the coal industry necessary to meet our project independence goals. Technology Surface mining is the safest and most economical way to produce raw materials from the earth's crust. It also affords a more healthier working environment for the individual miner. Surface coal mining now accounts for more than 60 percent of the annual coal production in the South. Surface mining of coal requires the removal of the overburden to expose the

Jan 1, 1977

By Dr. Ing. Hermann Boldt

The Bituminous Coal Mining Industry of the Federal Republic of Germany produces nearly 100 million t/yr of clean coal. The largest coal mining area is the Ruhr District with dimensions of 100 x 40 km (65 x 25 miles). Figure 1: Here is the general administration of Ruhrkohle Akteingesellschaft RAG with its three divisions. Other coal mining areas in Germany are the Saar District and the Aachen District. Ruhrkohle produces 70 million t/yr of clean coal. The company operates 28 mines in the Ruhr District with an average raw coal production of 18000 t/day. Their average mining depth is 831 m (2740 ft.) and the average seam thickness is 177 cm (70 in.). Figure 2: Preparation plant reject is 44.6%. All following production figures will be with reference to raw coal because the raw coal production is the technically relevant number. Mining operations are mainly in non-dipping coal deposits whereby mechanized equipment for flat seams is also applied to deposits dipping up to 45? Coal extraction is done exclusively by the longwall method. Approximately 200 longwall installations are in production at any time. The average longwall length is 221 m (730 ft) ranging between 140 and 290 m (460 ft and 960 ft). The average longwall advance of all operations is 2.8 m/day (8.4 ft per day). Average production

Jan 1, 1977

By E. Taskin

Diasporic bauxite from the Mugla-Milas region was mechanically activated in a planetary mill for different activation times and the structural changes were examined by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and specific surface area analysis (BET ? Burnauer, Emmett and Teller). Non-activated and activated bauxite samples were leached directly in alkaline (Na2O) solution at atmospheric conditions and the activation procedure led to the amorphization and structural disordering of the diasporic bauxite structure, which increased the dissolution efficiency. Effects of milling speed, liquid/bauxite ratio and leaching time on alumina extraction in direct alkaline leaching of diasporic bauxite were also studied. The alumina extraction was ~7% for non-activated bauxite and ~70% for activated (75 minute) bauxite. Key words: Diasporic bauxite, Mechanical activation, Alkaline leaching, Alumina extraction

Jan 1, 2009

By Juan J. Monsalve, AMAN SONI, Nino Ripepi, Richard Bishop

The design and strength of pillars are important parameters while implementing the room-and-pillar mining method in a limestone mine. The process becomes complex with the presence of the karst voids which are frequent phenomena in a carbonate rock formation. The karst system is a network of cavities that along with an omnipresent fracture network may lead to ground control issues in a limestone mine. The objective of this study is to provide a safe and reliable alternative design for a pillar in a case study mine for safe and efficient ore recovery. This research is a continuation of a previous study aimed at studying the effect of karst void on the strength of the same limestone pillar. It was assessed from the calculated pillar strength and the estimated redistributed stresses that the pillar is capable of countering more stress than is currently imparted on it. Numerical modeling studies combining in situ stress determination and excavation sequencing were used to estimate the existing stresses on the pillar. Different possibilities of modification to existing pillar design were simulated using Distinct-Element Modeling (DEM) to determine a better design. Discrete fracture networks (DFNs) were included to imitate the effect of the presence of discontinuities. An effort is also made to understand the variation of pillar strength with height for karst-affected pillars using two different constitutive models. This study serves as a preliminary investigation in terms of improving the future design of pillars and also while recovering old pillars prone to karst formation.

Jan 30, 2023

By Paul W. Johnson

Chemical mining is the in situ extraction of metals from ores located within the confines of a mine (broken or fractured ore, stope fill, caved material, ores in permeable zones) or in dumps, prepared ore heaps, slag heaps, and tailing ponds on the surface. These materials represent an enormous, untapped, potential source of all types of metals. The field of chemical mining, now in its infancy, encompasses the preparation of ore for subsequent in-place leaching, the flow of solutions and ionic species through rock masses and within rock pores, the leaching of minerals with inexpensive and regenerable lixiviants under prevailing conditions of the in-place environment, the generation and regeneration of such solutions, and the recovery of metals or metal compounds from the metal-bearing liquors. It is not inconceivable that eventually our ore reserves will consist largely of low-grade, refractory, and inaccessible new deposits and low-grade zones near previously worked deposits, caved and gob-filled stopes, waste dumps, tailing ponds, and slag-heaps. Chemical mining promises economic recovery from these types of deposits. Before it can come of age, however, a much better understanding is needed concerning its chemical and physical aspects.

Jan 1, 1967

By F. J. Susko

The Bureau of Mines applied a flotation model to the hydrodynamics of the Bureau-developed rapid flotation system. Rapid flotation is a process which separates the bubble-particle attachment and froth-pulp separation stages of the flotation sequence into two discrete unit operations allowing the operations to be individually optimized. Both an air-injected hydrocyclone and an in-line mixer were used as the bubble-particle attachment unit and a shallow-depth froth separator was used to separate the ore-laden froth from the pulp. A 10-L/min batch system was tested on a coarse coal feed sample. The system was tested using two different bubble-particle attachment units at various aeration levels in order to test the flotation model. The results of the flotation model reflect general trends observed in the experimental data.

Jan 1, 1993

By Bror Nyman

Wide settlers are a way to decrease the linear velocities of advancing liquid phases. It has, however, been found unnecessary to risk a proper settler performance by building shallow settlers in order to avoid a so-called interface turbulence due to a too big difference between the linear velocities of the organic and the aqueous phase. This conclusion has been reached from tests using a large transparent settler model, where the behaviour of a clean interface between two advancing liquids has been investigated. Also in a more realistic case, making an organic in aqueous or an aqueous in organic dispersion to move between the liquid phases, no obstacle has been found to use a somewhat more deep and correspondingly ore slowly t10wing aqueous phase. Based on above findings, support can be given to a new trend to build the settlers slightly deeper than what has been typical for the so-called low-profile design. In this way, it is much easier to avoid an excessive air introduction and other severe difficulties, like those caused by crud moving from one stage to another. It is further shown, how gravity can be used to slow down and distribute a dispersion being fed into a settler of a VSF unit. Entrainment levels have been found to be reduced by a careful design of primary dispersion distributors and picket fences of the settler. Finally, it is demonstrated, how outlets from the side of the settler can be used to simplity interstage pumping and to decrease the rotation speed of any pumping device.

Jan 1, 1996

By H. M. Park

Risk is a major factor in all mining activities, arising from many internal and external variables. The authors? research has resulted in a systematic method for the quantification of risk in mining projects (Park, 2012). This research will be presented in a series of papers, this one and two more that will be published on Mining Engineering?s web site, www.me.smenet.com. This paper identifies the variables associated with risk in mining projects, and their effects. The second paper discusses methods of assessing the overall risk associated with those variables, and presents a statistical model based on a survey of 31 experts. The third paper presents an evaluation of the statistical model, using data from previous mining investment decisions in which the authors have been involved. There are several major competing entities, including BHP Billiton, Rio Tinto, Anglo American, Xstrata, Freeport-McMoRan, Chinese government- run companies and Japanese trading companies, that have large foreign holdings, controlling deposits in most of the world?s established and productive mining districts. In general, the mining industry considers the United States, Canada, Australia and the European countries to have good mining investment environments, but because the major companies have already achieved market dominance in those countries, large investments are required there. Newcomers seeking to enter the industry, either as producing companies or as investing partners, often have difficulty breaking into these established markets. Thus newcomers are increasingly turning to new areas like South America and Africa, which are relatively less developed. The competition among businesses to secure a share of the new market is intense, but there are still good investment opportunities. However, because most of the countries in these areas are not well developed, several additional risks are associated with participation in mining projects in those areas.

Oct 1, 2013

By P. J. Bethell

In the froth flotation process the detrimental effect of slimes on the froth flotability of valuable minerals has long been known.1 Work by Aplan2 on the froth flotation of coal has shown that the presence of clay slimes causes loss in flotation selectivity, and recovery of combustibles. Obviously then the presence of clay slimes to any great extent in the froth cell feed in a coal preparation plant is undesirable. This problem is exacerbated in plants treating raw 600 um (28#) by zero material due to the variation in flotation with size. The net effect of this phenomenon in a bank of cells treating raw minus 600 µm (28#) material s that by the time adequate flotation of the coarsest size fractions has occurred the finer sizes are already producing undesirable high ash material, which often leads to unacceptable overall quality. Reduction in aeration rate and/or chemical addition to combat this, further decreases the flotation rate of the coarsest fraction leading to heavy losses of coarse low ash coal to the tailings. The above mentioned characteristics formed a key aspect of the fine coal circuitry design at Elk Run Coal Company in Sylvester, WV. The plant was designed to produce compliance steam coal (less than 1.20 lbs. S02/million b.t.u.) Desliming ahead of the froth flotation was included, as the slimes in the plant feed were clay rich, had very high ash levels, and low potential recovery. Lab testwork had also shown that poor selectivity would be expected if raw minus 600 um (28#) material was froth floated.

Jan 1, 1986

By Ben W. Burdett

Since the late 19701s, the use of microcomputers in the minerals industry has grown to the point where today they can be found in virtually every plant within the industry. Their use in every aspect of instrumentation and control has increased the ease of operation and control of every phase of mineral processing. Their incorporation in sensors, transmitters, indicators, and controllers in addition to their use in distributed control and computer systems has provided operators with more timely accurate information than they have ever had before. This has led to an increase in the operator's effectiveness and an improvement in overall productivity. The ultimate aim of plant control is to maximize recovery in the mineral processing operation, and the microcomputer has spawned many tools that are now making this goal attainable. This paper discusses individual use of microcomputers in the areas previously mentioned as well as their collective use in overall control systems. The incorporation of local control systems in total plant control including the communication of information throughout all levels of plant management is also discussed. Finally the role the microcomputer is playing in today's plants is illustrated with numerous references to current examples.

Jan 1, 1985

By William H. Dresher

A recent report to President Reagan from the Business-Higher Education Forum, entitled, "America's Competitive Challenge: Need for a National Response," (1) observes that in the recent past, ". . . much of that research, which is necessary for major breakthroughs and sustained productivity improvements, was redirected to short-term objectives ... At the same time, American universities, which conduct more than half of the nation's basic research, have suffered from an accumulated under-investment in facilities and equipment amounting to an estimated $1-4 billion." Also contributing to the decline in America's productivity, the report said, are "...weak technology transfers between government and industry and between universities and industry..." This report as well as other recent reports and articles have, reopened a subject which has long been debated but rarely resolved-- the interaction between the academic community and industry in the sponsorship and conduct of research. The subject is unfortunately, too often treated as a controversial issue involving ethics and the profit motive when, in fact, the two branches of society -- industry and academia -- are necessarily part of the same system. I would like to speak to you today on the subject of university-industry interactions and to some extent discuss the role of government in such interactions. Finally, I will make some remarks as to how this subject applies to the mining industry.

Jan 1, 1984

By Yinan Zhang, Yi Luo

The widely used R70 method is modified to measure the self-heating propensity of low-rank coals. This modified R70 method enables the introduction of controlled amount of moist oxygen into the reaction vessel. Three coal lumps were collected from three different locations in a surface mine in the Powder River Basin. The coal samples were tested in oxygen flow with controlled moisture content under adiabatic condition. By measuring the relative humidity at the exhaust exit point of the testing setup, the flux and cumulative wetting heat that is consumed by coal samples can be determined. Through a better way of determining the coal’s specific heat, the total heat, including heat of wetting and coal’s oxidation heat, required to raise coal to a given temperature can be determined. Then, the contribution of heat of wetting at the different stages of the testing is quantified. The effects of evaporative heat through a group of tests have also been quantified. From this research, a better understanding of the effect of wetting heat on inducing low-rank coal’s spontaneous combustion can be acquired.

Nov 30, 2022

By Roger C. Wilmoth

The most common method of treating mine drainage to prevent water pollution consists of neutralization and aeration. This process removes the acidity, iron, aluminum, and some other heavy metals, but does not render a water suitable for domestic or industrial use because of the high dissolved solids, hardness, and sulfate in the treated water. The Environmental Protection Agency (EPA), has been sponsoring and conducting research since 1966 on the use of reverse osmosis (R.O.) for the treatment of mine drainage. This process has been found to be highly effective in the removal of nearly all the dissolved solids. In addition, since R.O. is a concentrating process, potentials for recovery of valuable heavy metals are possible. This paper is a review of the state-of-the-art on the treatment of mine drainage by reverse osmosis.

Jan 1, 1972

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

With mine activity dating back to 1792, the Lehigh Valley, about 80 km (50 miles) northeast of the historic Allentown/Bethlehem steel mills and about 160 km (100 miles) northeast of Philadelphia, PA, defined early-day coal mining. Coal mining began just nine years after the end of America?s Revolutionary War. The high-carbon, clean-burning anthracite coal that was hand-dug from the Pennsylvania hills fueled the steam engines that powered the Industrial Revolution, helping build early steam ships and even the first automobiles. Around 1910, at the peak of the U.S.?s early mining effort, there were more than 250,000 men working underground ? 10,000 of them in the Lehigh Valley.

Jan 1, 2012

By Eduardo Rojas, Pedro Landeros

El Teniente Mine expansion plans are currently under development and construction stages through an integrated project strategy that will allow the continuity of future mining. The deepest sector corresponds to Andes Norte Project that faced rockburst risks during tunneling in a completely different manner, implementing different actions for the mitigation of seismic hazard and seismic risk management, based on the following main aspects: rock mass preconditioning techniques such as destress blasting and hydraulic fracturing, improvement of rock support design with the inclusion of elements with higher energy dissipation capacities, use of mechanized equipment for the most critical activities in addition to re-entry protocols and improvements in geological, geomechanical and seismic data collection procedures to reduce the uncertainty of rock mass behavior. The current seismic risk management strategy integrates all of these elements and is the basis of construction methodologies in use, supporting the technical feasibility of tunneling in high-stress environments.

Apr 26, 2022

By A. W. Khair

This paper deals with the evaluation of the interaction between rock and the cutting tool, and with methods for determination of workability, and abrasivity of rock. A description of instrumentation is included along with research on the wearing process of bit tips and pick consumption. Analyses of bit rotation, evaluation of cutting, normal forces and energy consumption is presented. Finally influence of the basic water jet parameters and water jet assistance on the cutting process of hard and abrasive sandstone is discussed.

Jan 1, 1995

By R. J. Bridwell

Acid mine drainage (AMD) occurs in high sulfur coal and heavy metal mining environments. We show remediation methods using 3D numerical ground water flow models and chemical kinetics of pyrite oxidation for acid leaching of pyrite during air and ground water flow. A recently developed numerical model couples air and water flow with kinetics of iron-reactive bacteria, oxygen transport, specific chemical reaction rates, and pyrite oxidation to calculate migration control of pollution. A model is presented which considers diminution of acid mine drainage in pyrite rich ore bodies by raising the potentiometric surface through a vadose zone to reduce acid mine drainage. A ground water model is presented of an initially saturated mountain, containing an adit, with a sloping ground water table. Ground water recharge consists of snowfall and normal precipitation. Simulations indicate that the historically open adit creates a desaturated mountain above the adit. Significant air saturation ranging from 10-90% oxygen can occur to depths of the adit (-270 m). Remediation consists of plugging the adit, which fill s adit and mountain with water from recharge. Plugging the adit required <10 years for resaturation and rise of the water table in the mountain.

Jan 1, 1994

By William O. Rasmussen

Exploration requires processing highly varying kinds and amounts of geologic information. Successful discovery dictates that this be done quickly with maximum confidence. Most phases of exploration are more or less applicable to computer reduction on a routine basis. The use of digital computers to reduce raw data into interpretable form, lets the exploration geophysicist concentrate on interpretation and presentation, and to consistently apply more sophisticated and comprehensive analytical techniques, not practical before. In applying these concepts for the past several years, various efficient programs have evolved which provide more complete evaluation of all data including the pro- vision for more unique solutions. This has resulted in greater refinement and ability to select the most advantageous drill sites in a minimum time at a minimum cost or, in rejecting as soon as possible a project on which additional effort is no longer justified. Practical examples of computer applications in magnetics (air and ground), induced polarization and resistivity are discussed.

Jan 1, 1969

By Guangyao Si, Ismet Canbulat, Xun Luo, Yi Duan

Routine analyses of seismicity and event locations are essential for coal burst risk management, especially in the presence of unfavorable and complex geology. In an Australian longwall coal mine, a small-scale seismic monitoring network was installed to monitor a section of a major dyke intersected by the roadway, which was classified as a coal burst prone zone. The Deep Convolutional Neural Network (DCNN) technique was adopted for automatically discriminating seismic events to assess seismicity in this zone. The discriminated seismic events were located with the Shortest Path Method based on the Boundary Discretization Scheme (BDS-SPM) for temporal-spatial seismic event distribution analysis. The results demonstrate that the seismic events are discriminated with an average accuracy of 94%. Moreover, the seismic events are more accurately located using the BDS-SPM with a 3D heterogeneous velocity model compared with results obtained with a homogeneous velocity model. The temporal and spatial variances in seismic activities identify that the rock fractures in the dyke zone are closely related to the longwall mining process and a local dyke has a controlling influence on the stress concentration in its vicinity.

Apr 26, 2022