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By C. A. Rowland

Comminution efficiency can be expressed in three different ways. Theoretical Efficiency: actual energy consumed, in a comminution machine compared to the theoretical energy required to make the size reduction. Operating Efficiency: compares the operating work index, calculated from production comminution machinery operating data, to the Bond Work Index from bench scale comminution tests or calculated from pilot plant operating data. Economic Efficiency: income compared to planned income. Using the Bond Work Index and operating work index, this paper explains how to determine operating efficiency.

Jan 1, 1998

By John C. Edwards, F. Friel, John J. Opferman, Robert A. Franks

A series of diesel fuel fire experiments were conducted in the Pittsburgh Research Center's Safety Research Coal Mine (SRCM) to determine products-of combustion (POC) spread rates along a single entry under zero imposed airflow conditions. Six experiments with an average fire intensity of 330 kW and three experiments with an average fire intensity of 30 kW were con- ducted in a 180 m long entry which had an average 2 m height and 4 m width. POC spread rates were measured by the response time of diffusion type CO detectors, positioned at 30 m intervals, to CO concentrations 5 ppm above ambient. For the 330 kW fires, average POC spread rates of 0.22, 0.1 3, and 0.06 m/s were determined at 30, 60, and 90 m distances from the fire. For the 30 kW fires these average spread rates were reduced to 0.08, 0.04, and 0.04 m/s. The measured maximum roof layer temperature 30 m from two of the 330 kW fire was 30 and 36"C, which is less than the 57°C alarm point of a typical mine thermal sensor. It was determined that smoke detectors can be more effective for mine fire detection than CO detectors. The experimentally determined POC spread rates can be used to provide guidance for specification of sensor spacing to improve early fire detection at zero or very low air flows.

Jan 1, 1997

By George Aul, Richard Ray

Short-hole horizontal degasification systems have been utilized in Island Creek's Virginia Division mines since 1986. These systems remove methane from the coal seam in advance of longwall mining. Without an in-seam methane drainage program, methane liberation rates from the longwall faces may exceed 0.47 cu m/s (1,000 cfrn), requiring 47 cu m/s (100,000 cfm) of air for adequate dilution capability. Optimization of the degas systems has enabled methane liberation levels and the associated ventilation requirements on the longwall faces to be reduced by 50 to 80 percent. Since the inception of the first degas system at the Virginia Pocahontas No. 6 Mine, Island Creek has developed an overall methane drainage program designed to maximize gas production and minimize ventilation requirements for methane dilution. Gas production from the degas systems is affected by four main design criteria: (1) hole location, (2) hole length and spacing, (3) collection system capacity, and (4) time available for drainage. Drilling equipment and materials for the gas collection system are selected to meet the necessary criteria while minimizing manpower requirements. Benefits gained from reducing methane liberation rates from the longwall faces are fourfold: (1) improved safety due to lower methane concentrations in the face area, (2) fewer production delays caused by excessive methane concentrations, (3) lower fan operating costs resulting from reduced air requirements, and (4) enhanced worker comfort resulting from lower air velocities and less dust generation.

Jan 1, 1991

By David N. Hedges

This paper discusses the actual recovery and installation of a longwall in a bituminous coal mine in Western Pennsylvania. The coal bed mined is in the Lower Freeport seam which averages 42 inches (1.07m) in height locally. Drainage from the mine is approximately 3.5 million gallons of water per day (13.25 million liters per day). This water deteriorates the mines predominately fire clay bottom making it extremely difficult to move equipment. Support removal is accomplished by pulling the 6 ton (5443 kg) shields out under their own hydraulic power and transporting them by track over four miles (6437m) co the next longwall panel. This paper also discusses the changes that will be made to aid in the succeeding longwall recoveries and installations.

Jan 1, 1984

By Thomas Oberndorfer

INTRODUCTION Since several years the author is engaged in research activities in the field of mining method modelling (Oberndorfer, 1993 and 1994). The initial goal was to improve and assist the selection of the most appropriate mining method. However during investigations it became obvious that the most beneficial application of computer support is the fast calculation of numerical assessment rather than the consideration of all, i.e. also qualitative, criterions necessary for final decision. Numerical results serve - together with qualitative considerations based on the experience of the mining engineer - as a basis for decision. The emphasis is on "fast" calculation, as only this property makes it possible to calculate and compare many distinct variations. As long as no procedure exists, which optimizes all involved parameters, calculating many variations is of great important, because it is the only way to increase the chance to pick a alternative "close to optimum", but also to learn about the sensitivity the result will react on changes of input parameters, which are rarely known exactly. Generally speaking many trials give a better basis for final decision. It is no secrete that the most important obstacle towards quick calculations of a series of alternatives is not the processing time of the computer, but the time required for setting the input data in way that the computer can start processing, which is usually inter- active man work on the screen. Furthermore usually several distinct programs are required to cover the whole range of involved problems, with corresponding problems in automatic data transfer. The research work's goal was to overcome these problems. The approach developed was to describe a mining method more in a theoretical way (i.e. to give the computer some degree of "consciousness" on mining methods), which then can be applied under any specific conditions. E.g. a cut-and-fill operation will be "generally" the same in narrow or thick deposit areas, but the resulting keyfigures, e.g. total tonnage, productivity, dilution and loss, or finally costs per ton, will differ significantly. The approach (MMM = mining method modelling) presented reflects a deduction from the general case to a specific one (rather than the other way round). The developed model is general enough to be applicable to any mining method, and also to any degree of precision the mining method should be described, contrary to programs designed for specific mining method layouts which can be adjusted in a more or less wide range. PROGRAM DEVELOPMENT The principle correctness and feasibility of the approach was proved by a prototype program. However this program was more on a research level and far away from application for "real world" problems. The reason for this was, that it was regarded wasted time to re-invent certain tools, e.g. geometry intersection, deposit modelling or visualization. Hence it was tried to attract several software producers to invest in finalizing the model. Unfortunately this endeavor was not successful. Despite this defeat - and after some months of resignation - a final start on the project was decided. he reason for this decision was not at last the research activity in respect of low-cost underground mining methods for bulk- material as a substitute of typical quarry operations due to environmental restriction. This research work - which is in particular important for Austrian mining activities in beautiful and touristically used landscape - requires a lot of calculations in the way described. Both are still in state of progress, but - regarding mining method modelling - preliminary results can be presented. A complete re-programming of the program was required. Most obvious are the changes of programming language and operating system environment. Instead of Pascal under DOS C++ under MS-WindowsNT is now used. Several problems could be solved by this, in particular memory management, device drivers for input/output, and user friendlyness by up-to-date windows technology. However also more basic structures were changed. The idea was to utilize as many existing commercially available programs as possible to minimize programming efforts. WindowsNT helps already a lot by MFC technology, but also due to its multi-task facilities. This feature allows to run simultaneously several pro-

Jan 1, 1996

By O. Ogunsola, M. Downing

This paper gives a brief overview of impacts of coal blending on coal-fired power plants performance and discuses the preliminary results of an on-going study aimed at evaluating the effect of coal properties on the effectiveness, compatibility and thermal reactivity of coal blends. Plant survey studies reported no significant impacts on an existing plant designed for a high rank coal when switched to a blend of low- and high- rank coal. However, slight modification of some aspects (handling, fuel storage/stockpile, transportation, preparation, and general housekeeping) of plant design and operation may be necessary. The preliminary results of an on-going study at the Mineral Industry Research Laboratory shows that more compatible and better blends could be made from coals where ranks are closer than from those where ranks are far apart.

Feb 24, 1997

By Michael H. Inglis

The Technology Application Center, in conjunction with the U.S. Bureau of Mines Liaison Program, is studying the use of Landsat data for the monitoring of coal surface mine reclamation activities. Landsat may provide sufficient information to reduce the number of on-site inspections now required. The focus of the project has been the Navajo Coal Mine located in north- western New Mexico and operated by Utah International, Inc. On October 15, 1977, a field team recorded spectral measurements at the mine during the time of Landsat's overpass and a corresponding aerial photographic flight. Training sets were selected from the ground and aircraft data representing vegetated, graded, ungraded and natural environments. A supervised classification of the data was performed by the Stanford University Remote Sensing Laboratory then correlated to aerial photos and mine maps. The results, to date, have been very encouraging.

Jan 1, 1979

By L. J. Prosser, A. T. Iannacchione

Unfortunately from 1991 through 1995, 44 miners were fatally injured in the stone industry. Of these 12 occurred at underground mines from a total work force of less than 2,000 miners. Nine of these 12 miners were fatally injured in falls of roof or rib. A safer environment for the miners can be achieved by evaluating the nature of the hazardous ground and by developing more efficient and effective ground control strategies. Roof and rib conditions in the underground stone industry were observed and assessed at 33 mines in Illinois, Indiana, Kentucky, Maryland, Missouri, Pennsylvania, and West Virginia [(Figure 1)]. Hazard assessment indicated that those ground failures occurring under moderate to substantial overburden (> 30 m [l00 ft]) were caused by stress concentrations and geologic structures. Ground failures near the surface are caused by solution (water) processes. Selection of the mining horizon and mine layout decisions tremendously influence ground stability.

Feb 24, 1997

When science and the human spirit come together amazing things can happen. This was perhaps never more evident than through the events that unfolded during August and October in a remote desert in northern Chile. On Aug. 5, the main shaft of the San José copper and gold mine near Copiapó in Chile?s Atacama Region collapsed, leaving 33 miners trapped more than 624 m (2,000 ft) beneath the earth?s surface.

Jan 1, 2010

By G. D. Criswell, F. Palkovits, J. M. Johnson

A paste technology investigation was completed for non-pozzolanic fly ash from Units 3 & 4 of PPL Montana’s Colstrip Steam Electric Station. The purpose was to assess the feasibility of converting from dilute slurry deposition of ash products to a system using thickened or paste ash to reduce excess water storage in the impoundment, reduce seepage losses, and increase storage efficiency. The investigation included laboratory and field testing to characterize the rheological, geotechnical and dewatering properties of the ash products, an assessment of potential seepage reductions and an evaluation of potential for increased ash storage capacity by modifying impoundment operating procedures. The studies concluded that the conversion project was feasible, cost effective, and permittable. Critical facilities for the conversion project are currently under construction.

Jan 1, 2004

By M. J. Hart

Today, aggregate producers in the Denver Metropolitan area, herein defined as Denver and surrounding communities in Adams, Arapahoe, Boulder, Douglas and Jefferson Counties, are scrambling to secure their future reserves. The Denver market is somewhat unique among the larger metropolitan markets in that the source of needed aggregate for the future is very much undecided. 2. Present Aggregate Resources Presently, the annual consumption of aggregate resources in the Denver Metropolitan area amounts to approximately 16 million tons of sand, gravel and crushed stone of which the later accounts for about 20%. Based on population growth projections for the front range, by the year 2000 the annual rate of consumption for aggregate in the Denver Metro area could be in the 25+ million ton range.

Jan 1, 1987

By David M. Lapham

In Pennsylvania, 310 sampled sites of clay and shale have been evaluated for: potential use, chiefly as structural clay products, refractories, and lightweight aggregate; lithology; physical properties tests; fired tests, both quick-fire and rotary kiln; major-element chemical analyses, and quantitative five-component X-ray mineralogy for quartz, mica, feldspar, kaolinite, and chlorite-vermiculite-montmoril-lonite. Approximately 80 percent of the samples are of some potential use. Of 220 shale samples, 84 were potential lightweight aggregate sources and 83 potential brick sources. Binary correlations of test data versus potential use indicate that certain empirically determined parameters may be critical. These are: lithology, particularly for medium to super-duty refractories and lightweight aggregate; kaol-finite content for refractories versus low-temperature fired product sources; quartz content illustrating that there is an apparently necessary minimum quantity for brick; quartz content, which is low in high grades of lightweight aggregate; mica content, which is low for refractories and possibly high for lightweight aggregate; total iron, which is low for refractories and shows a 40 percent minimum for lightweight aggregate; carbon dioxide, which is low for refractorfes, beneficial in lightweight aggregate, and probably restrictive for some tiles choroite yermicalite, which is low for refractoies and possibly beneficial in lightweight aggregate. In Pennsylvania, clay and shale materials constitute one of the state's major economic mineral resources. To date, the testing program indicates considerable development potential in brick, tile, and lightweight aggregate industries, and perhaps a future potential for aluminum from shales that exceed 20 percent A12Q3.

Jan 1, 1971

By T. Takamori

This paper reviews the present status of coal preparation in Japan concentrating on the process in coal cleaning and waste water treatment. This paper also discusses recent topics on maintenance, automatic control, raw coal management, etc.

Jan 1, 1982

By James Wm. White

Today a large number of open pit mines use computer-based mine management systems to automatically assign haul trucks, track equipment, and manage information. Now advances in digital communications allow the use of these systems in underground operations. Underground mine management systems help maximize production by providing impressive gains in areas such as equipment and manpower utilization, draw point equalization in block caving operations, preventive maintenance, and safety. Current systems use allocated or "locked" train and LHD dispatching. While allocated dis-patching rarely optimizes open pit production, it offers an efficient mode of operation underground where options are more limited.

Jan 1, 1996

By J. S. Roti

Calcium-based scale precipitation is a common problem in mill reclaim waters. An accumulation of these adherent deposits can result in a rapid reduction in water flow, loss of pump efficiency and eventual interruption in ore production. Heap leach applications can also experience the added problems of plugged sprinkler heads, blinded leach pads and fouled carbon columns when scale control is not maintained. The primary cause of scaling in precious metal recovery is the relative insolubility of calcium carbonate. The presence of the calcium ion and bicarbonate alkalinity is common in almost every water source. If the temperature or pH of the water is allowed to increase, the bicarbonate breaks down to carbonate and combines with calcium by the following reaction: Ca +2 +2HCO3 ? CaCO3 + H2 + CO2

Jan 1, 1986

By L. Barry Phelps

Coal mine drainage, which occurs predominantly as acid mine drainage in the East, is a serious contaminant of surface and groundwater systems (Appalachian Regional Commission, 1969). Treatment of this pollutant can be very costly and is often difficult to achieve (Appalachian Regional Commission, 1969). A major source of coal mine drainage in surface waters is polluted ground- water discharge, therefore treatment of surface water does little to combat groundwater contamination. Prevention of the formation of coal mine drainage and restricting its entrance into the groundwater protects both surface and groundwater systems. The formation of acid mine drainage may be inhibited by preventing contact between toxic spoil, air, and water (Grim and Hill, 1974). This may be accomplished by surrounding toxic spoil with a relatively impermeable barrier, thus restricting groundwater and oxygen flow through the toxic zone. Toxic spoil packages constructed in this manner would minimize the entrance of acid mine drainage into the groundwater system, allowing dilution by uncontaminated water to occur. If successful, concentrations of coal mine drainage would be reduced below toxic levels.

Jan 1, 1981

By Francisco A. Fonseca

The Carajás Hills are in Brazil's Eastern Amazon, between the Araguaia and Xingu rivers, and parallels 5° and 7° Latitude South. A location map is given in Fig. 1. It is an area of low mountains (maximum altitude 900 meters), covered by the Amazon rain forest. Annual average temperature is 25°C, ranging from 31°C (maximum) to 19°C (minimum). Annual rainfall averages 2,000mm. Although it rains throughout the whole year, heavy rains occur from December through March. At the beginning of the 20's, Brazilian explorationists made brief geological descriptions of the area. Due to the thick soil, scarce fresh rock outcrops and the tropical forest covering a completely unpopulated area, detailed geological studies were difficult and reconnaissance expeditions were limited to the river margins.

Jan 1, 1982

By Lance Kolbush, Alex Vaughn, James Fisher, Michael Barish, Tony Toney

Somerset International has worked to enhance the recovery of sub-20 micron particles in our patented Sub325 Systems by introducing chemicals in the systems prior to the centrifuge. This paper details four cases of such enhancement. Two on the fine coal recovery side at a 325 tph plant in Central PA and Warrior Met Coal 7 plant. Two on the tailings dewatering side at a 1200 tph Southern WV plant and at Warrior Met Coal 7 plant.

Feb 22, 2026

By D. W. Gentry

Introduction Until recently, there were many jobs for mineral engineering graduates. Traditionally, minerals-related career paths available to university graduates stem from rather standard offerings in the disciplines of mining, metallurgy, petroleum, geology, geophysical engineering, and mineral economics. Within each discipline, there exists many career opportunities. In fact, until fairly recently, the most difficult decision for most graduates was choosing among all the available alternatives. Unfortunately, this relative state of euphoria changed quickly and dramatically within the minerals sector. Within two or three years, graduates from minerals-related engineering disciplines found it exceedingly difficult - and then almost impossible - to secure employment in the minerals sector upon graduation. At the same time, there were dramatic reductions in production requirements and, ultimately, mine closings. This resulted in massive layoffs and often termination of professional personnel possessing significant and valuable industrial experience. Obviously, this worsened an already bad employment picture for those hoping to begin a career in minerals. Certainly, there is no universal agreement on what the future offers for the US minerals industry or the career opportunities associated with it. However, there are a number of considerations that deserve study by students, faculty, administrators, and industrial personnel before minerals-related career paths are chosen. Where Will the Jobs Be and How Many? Everyone is aware that the minerals industry is very cyclic. It is not surprising then that job opportunities for new graduates also fluctuate. Typically, there is a two-to-four year lag between industry's engineering manpower needs and the academic community's ability to produce this talent. Due to the response lag, there will necessarily be years when supply and demand do not match. Employment Projections It is extremely difficult to anticipate what the key career paths might be within the next few years. Considerable speculation remains with respect to whether activity in the US minerals sector over the short-, intermediate-, and long-term will improve, remain status quo, or further deteriorate. However, some information pertaining to the prospects for career opportunities in mining engineering was offered by Tingley and Ghose (ME, Sept. 1983, p. 1274) from a study performed by Fenvessy and Schwab. Results from this industry-sponsored survey suggest that the US will experience 700 more mining engineers than needed in 1985, 1300 in 1990, and 1800 in the year 2000. These conclusions were based on the assumptions that future graduate levels remain flat and demand increases 3.6% annually. Educators quickly argued that depressed job markets, coupled with university student mobility, would negate the assumption of flat mining graduate levels in the immediate future. Student Mobility Student mobility from one engineering discipline to another is high. This is perhaps best demonstrated by the tremendous growth in programs such as computer engineering and computer science at the expense of enrollments in the more traditional engineering programs. The ability and willingness of students to quickly change engineering disciplines in response to existing and perceived job market demands have created significant student, faculty, and resource dislocations within universities nationwide. This has resulted in problems for university faculty and administrators responsible for effective use of

Jan 2, 1985

By Peter J. Huck, Bruce G. Stegman, Richard E. Thill

Introduction Backfilling of mine voids is used to prevent or control the effects of subsidence on surface structures. The pumped-slurry, blind backfilling process has been successful for stabilizing ground over abandoned and inaccessible underground coal mines. This article describes the systematic evaluation of potential monitoring systems that would improve backfill monitoring technology. It also details field proof-of-concept tests that were conducted on two systems and the difficulties encountered in implementing them. Ground subsidence over abandoned mines can have devastating effects on overlying urban areas decades after the closing of room-and-pillar mines. The result may be cracked foundations, ruptured gas and water lines, broken sewers, distortion or cracking in superstructures, and sinks and potholes in the ground surface. About 32,000 km2 (8 million acres) of land in the US has been undermined for coal. According to the US General Accounting Office, 8,100 km2 (2 million acres) have undergone subsidence and another 8,100 km2 (2 million acres) are expected to subside by the year 2000. Actual figures on land affected or threatened by subsidence are probably much higher, since these estimates were based on late 1960s studies. For more than two decades, the US Bureau of Mines has been engaged in stabilizing ground in urban areas having high risk potential for subsidence costing millions of dollars. Thousands of acres have been stabilized, protecting property worth hundreds of millions of dollars. In earlier years, backfilling was by in-mine stowing in accessible mines or by gravity-feed sluicing methods in inaccessible mines. Pumped-slurry methods have been used extensively in the past 10 years. More slurry can be injected for fill from fewer injection holes over extensive areas in abandoned mines. Since this method requires fewer boreholes, there is less disruption of surface facilities. An investigation was conducted to determine the feasibility of using advanced, remote sensing or monitoring technology for application in monitoring fill placement. Specifically, the objective was to develop conceptual systems for blind backfill monitoring that require fewer boreholes and give better definition than is now possible. Blind Backfilling Methods Blind backfilling operations are conducted from the surface and do not require personnel and equipment underground. These methods are applicable to abandoned, inaccessible workings. Two categories of blind back-filling are point support, practiced by civil engineers to protect individual structures or surface facilities, and areal backfilling methods, used to protect large areas against subsidence. Point Support Methods Point support methods are usually gravity-feed systems. In general, point support methods use small volumes of expensive fill material and require a large number of boreholes within a constructed site. Because of the processed material used for back-filling and the close spacing of the injection boreholes, control and monitoring often may be accomplished by borehole cameras. Areal Backfilling Areal backfilling is conducted mainly by the pumped-slurry injection process (Fig. 1). In eastern and interior coalfields, material used is often mine refuse or flyash, both being undesirable on the surface and costly to dispose of in an environmentally acceptable manner. Hence, the use of

Jan 12, 1983