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By Makoto Terada

The most important consideration in planning the plugging and sealing of a mine for mine water control is to predict the water flow from the mine. For this purpose, a method of numerical analysis on the water behavior in the ground at the concerned mine area was developed and the mine water flows were simulated. A hydrological survey at the surface of the mine determined the recharge rate of ground- water and the apparent permeability of ground.

Jan 1, 1982

By G. W. Kenzy

Recently, in the United States, questions of possible deleterious synergistic health effects of the gaseous and particulate components in the diesel exhaust and mineral and coal dust have been the impetus for extensive research by several agencies. At the present time, diesel engines are tested and approved for use in gassy and non-gassy underground metal and non-metal mines under Parts 31, 32, and 36 of Title30 of the Code of Federal Regulations. Diesel-powered equipment for use in underground coal mines, though not explicitly addressed in the law, is administered under Parts 32 and 36 of Title 30, with Part 36 being applied in the case of equipment working inby the last open crosscut or in the return airways. Operation of diesel equipment in underground mines has the potential for serious health and safety hazards from the gases, vapors, and particulates in the exhaust. Therefore, various countries have rules and regulations for the safe deployment of diesel equipment. The applicable laws and regulations from several countries who have long experience with diesel-powered equipment in their mines are reviewed. Four major areas have been addressed: (1) testing and approval procedures of diesel engines, (2) ambient mine air quality specifications, (3) frequency of sampling and location of samples, and (4) air quality specifications in splits where diesel-powered equipment are operated. The review indicates that most regulations generally consider four possible hazards: (1) toxic components in the engine exhaust, (2) ignition of flammable atmospheres by the engine or electrical equipment, (3) fire hazards presented by the engine fuel oil and by combustible material that might come in contact with the equipment, and (4) mechanical hazards. There is a remarkable similarity in the laws with regard to engine design, testing and approval procedures. However, the aspects with regard to mine air quality and quantity are quite variable-- from a general statement to very specific standards for many different diesel exhaust constituents. However, the laws with regard to synergistic effects of diesel exhaust components and other mine air contaminants are an exception.

Jan 1, 1980

By J. G. Groppo

Froth flotation has been shown to be an effective method for reducing Loss-on-Ignition (LOI) of ponded or landfilled fly ash. Reduction of LOI is required for many fly ashes, particularly those produced from low-No, burners, in order to meet ASTM requirements for use as a mineral admixture in Portland cement concrete. An additional ASTM requirement, fineness, is critical in determining end use applicability, and in many cases, classification of fly ash is necessary to produce an acceptable product. Hydraulic classification has been shown to be a simple, cost-effective method for classification of a variety of minerals including silica, phosphate, mica, coal, etc. and has shown to be similarly effective on fly ash. The combination of froth flotation and hydraulic classification facilitate the production of a high quality pozzolan that meets or exceeds ASTM specifications. This combination has been rigorously evaluated and results of pilot-scale testing are presented. Pilot scale testing was conducted on fly ash from two active utility storage ponds and demonstrated that high quality, consistent pozzolan could be produced using APT's Fast Float? Technology. Along with the pozzolan, additional production of aggregate for masonry mortar and a low sulfur, medium Btu fuel were also demonstrated. The Fast Float? process incorporates several simple unit processes to ensure pozzolan consistency; classification controls particle size distribution which is critical to achieving early strength, flotation controls the grade with respect to L.O.I. (Loss on Ignition) while dewatering controls the moisture content.

Jan 1, 1998

By T. A. Griffin

Gentlemen: The subject of this paper is: ADVANCED APPLICATIONS OF BUCKET WHEEL EXCAVATORS AND RECLAIMERS. Against an urgent world wide energy crisis, the role of bucket wheel excavators and reclaimers in the surface mining of fossil fuels and other ores has been raised to new prominence. This paper will review the reasons for the expanded application of bucket wheel technology, its unique contributions, and other factors relative to volume, cost, versatility, and efficiency. Today, surface mining is faced with the twin challenge of (1), accelerating the rate of removal of massive quantities of overburden and ore, and (2), replacing comparable high volumes of overburden back into the mined-out portion of the pit. Optimum quantitites for - a single electrical power plant now range from 5 to 15 million tons of coal per year. The use of bucket wheels offers the best method for meeting this challenge at lowest possible cost. For example, an advanced application that also satisfies environmental concerns involves the simultaneous functioning of two bucket wheel excavators during surface mining operations. Working at spaced intervals and different levels in conjunction with a transfer conveyor and stacker, one excavator removes the ore while the other one transfers overburden to a stacker that replaces it back into the open pit. The result of this continuously operating cycle is: (1) removal of ore and replacement of overburden back into the pit in massive quantities, (2) at accelerated volume and extreme low cost that cannot be matched by conventional loading machines of any size, and (3) fulfills a basic environmental requirement which is to

Jan 1, 1974

By R. Larry Davis

Over the past decade there has been a continual decrease in domestic oil reserves accompanied by a sharp increase in the demand for energy. Even with increased imports of foreign oil, the energy demand has not been met. This has forced many users to turn to substitute fuels. Of the many substitute fuels available most users are turning to and creating an increased demand for low sulfur coal. Because of the increased demand for low sulfur coal as well as the inherent problems in producing eastern coal, many producers have turned their attention to the large deposits of low sulfur coal in the western United States. Western coal mining is, however, not without its problems such as high moisture content, high ash content, highly variable sulfur content, multiple seams, and/or pitching seams. It is to aid in the solution of these problems that this chapter is directed.

Jan 1, 1979

By Terry D. Vandell

The purposes of this presentation are: (1) to discuss the actual as well as potential incidents that have caused and that could cause groundwater contamination at uranium in situ leach mining sites and (2) to discuss remedial actions and solutions that have been or that could be implemented in the future to stop or prevent serious groundwater contamination from in situ leach mining in Wyoming?s Powder River Basin. Open pit, underground, and existing and proposed in situ leach uranium mine sites in the Powder River Basin are shown in Figure 1. In situ leach mining or solution mining for extracting minerals in liquid form is a relatively new addition to the list of conventional mining methods currently used to extract uranium in Wyoming's Powder River Basin. Basically, the in situ leach mining method involves: (1) the injection of a leach solution lixiviant (an acidic or basic oxidizing solution) into a uranium-bearing ore body, via injection wells, to complex the contained uranium, (2) mobilization of the uranium complex from the host material via creation of a soluble complex salt, and (3) surface recovery of the solution bearing the uranium complex via production wells. Uranium is then separated from the leach solution by conventional milling unit operations (ion exchange).

Jan 1, 1981

By C. J. Bise

Continuous mining accounts for about 69% of the nation's underground coal production. This level is not expected to change much in the near future. This is because continuous mining represents the primary means of under- ground coal production. It is also the primary means of driving development entries for underground coal mines, including longwall mines. The continuous miner worksite contains many characteristics that can lead to personnel accidents. It continues to be an area of concern for mine managers, safety engineers, and training coordinators. In an effort to assist mine management in attempts to reduce the number of accidents and injuries sustained in this area, this paper presents a loss-control-based, non-intrusive strategy for conducting safety evaluations at continuous miner worksites.

Jan 1, 1991

By J. A. Organiscak

This paper examines methods for limiting occupational silica exposures for roof bolting personnel in underground coal mining. A canopy air curtain and an air tube were evaluated as means to provide filtered air over the breathing zone of these personnel. Laboratory testing showed that dust reductions beneath the air curtain and air tube approached 60 percent and 40 percent, respectively, with low interference air velocities. The data also showed that dust reductions were highest for positions closest to the device and that these levels decreased with distance. This paper also evaluates a metal rake, a flexible insert, and a rigid insert for cleaning the roof bolter dust collector box. Less dust was produced when using the rigid insert. Surprisingly, the flexible insert was sometimes no better than scraping or raking the dust onto the mine floor. However, little dust got on the coveralls when using either of the inserts.

Jan 1, 2002

By William J. Francart

In 2003, MSHA initiated a survey of the 11 Coal Mine Safety and Health Districts to develop a database for the implementation of Atmospheric Monitoring Systems (AMS) in underground coal mines. Mine operators continue to realize the benefits of improved fire detection capabilities, as the number of mines using the systems, as well as the percentage of mines, continues to increase. Fire detection data and new technology implemented in underground coal mines is discussed as well as regulatory compliance, diesel exhaust considerations and hydrogen interference in carbon monoxide detection.

Jan 1, 2005

By J. A. Herbst, S. L. Blust

Optimization of blasting, crushing, and grinding operations is filled with challenges. One of the more difficult tasks is accurately sampling and determining the size distributions of blasted and crushed materials at a reasonable cost. The task is difficult because of the large size of fragments and the tonnage involved. However, the size distribution measurements are necessary for models that predict the performance of mine-through-mill operations. This paper is concerned with the use of video sampling for this task at National Steel Pellet Company's operation in Keewatin, Minnesota Data gathering, data analysis, model building, and mine-to-mill simulation are all described.

Jan 1, 2000

By S. V. Tracy

The Outokumpu Skim-Air Flash Flotation machine was developed to separate valuable mineral from gangue as early as practical by floating it with specially designed flotation equipment installed in the grinding circuit. Machines already in service have shown the ability to produce final grade concentrate with an increase in overall recovery and flotation rate while decreasing filter cake moisture and reducing fluctuating feed grades to conventional flotation circuits. The first US production test was carried out in a southwestern copper concentrator with successful results. This report describes the results of the test along with an explanation of the process and the benefits obtainable.

Jan 1, 1986

By T. J. Kim, S. Suh

The purpose of this paper is to evaluate overall prospects of the export market in the Pacific Rim for Illinois steam coal in terms of recent changes in global socioeconomic factors. To pursue this objective, three factors affecting the prospects of Illinois coal in the Asian market were selected for detailed analysis: quality requirements of imported coal, particularly those of the Japanese market; import controls and regulatory factors; and transportation factors affecting the export of Illinois coal. Based on these analyses, alternative long-term strategies are suggested for promoting Illinois coal export in the Asian market.

Jan 1, 1988

By I. Shah, L. G. Austin

A method for quantitative investigation of the phenomena involved in fine grinding of materials that follows the changes in the breakage rates of fine particles has been presented. For relatively hard, brittle, non-coating material like quartz, the slowing down effect of breakage rates starts to be significant at relatively coarse sizes, which goes often undetected in closed circuit grinding systems, producing relatively coarse product, say P80=75µm However, for fine grinding systems, as the -10µm fractions begin to build-up, and classification becomes more difficult, the build-up of fine sizes causes a slowing down effect Compounding this problem is the difficulty of obtaining accurate cumulative weight size distributions in the fine size region.

Jan 1, 1983

By Alice Blount, F. Patrick Carr

The quantitative evaluation,of quartz and other minerals in acid-insoluble residues from carbonate rocks and other industrial mineral products derived from sedimentary and low-grade metamorphic rocks is difficult. Commonly there are a dozen or more minerals present, and the suites vary from sample to sample. Because of these factors, either the absorption coefficient must be determined on a sample to sample basis or an internal standard must be used. Internal standards in general use are unsatisfactory. For example, [A1203] is often present in product samples because of ceramic grinding elements used in their production; CaF and LiF have peaks which overlap or nearly overlap mineral peaks in the samples. A careful evaluation has shown that magnesium aluminate (synthetic spinel) works particularly well as an internal standard for these types of samples. Not only does it have few, strong diffraction peaks which do not overlap, the peaks are in the same 28 region as the minerals, usually quartz and silicates, for which quantification is desired. Spinel also consists of equidimensional particles without prominent cleavages; this promotes a random orientation of the minerals in X-ray diffraction mounts. In addition, spinel can be used to correct for loss of diffracted-beam intensity due to thin sample preparations which are often unavoidable.

Jan 1, 1991

By Pierre Mousset-Jones, Felipe Calizaya

The design of an auxiliary ventilation system for long underground openings (drifts, ramps and shafts), often requires the installation of multiple fans. The fans are installed in series and separated from each other by rigid ducts of fixed or variable length. However, problems relating to excessive leakage often occur, with each project representing a unique problem requiring an efficient solution. In this study, a method to determine the design parameters of an auxiliary ventilation system is presented. The method is based on the principle of partitioning a long ductwork into segments of finite length and solving the resulting networks separately. Specifically, the method is developed to solve two types of problems: constant fan spacing, and constant fan size. In the former, the fan spacing is fixed, and the problem is solved for fan sizes. In the latter, the problem is to solve for fan spacing. An example is used to illustrate the method.

Jan 1, 1993

By R. S. Conti

The US Bureau of Mines (USBM) has developed an inflatable feed-tube seal (IFTS) for high-expansion foam generators. The IFTS is a lightweight, portable, rectangular inflatable bag that can be used by firefighters to rapidly seal large openings, such as those in underground mines, and to simultaneously provide a feed-tube for a high-expansion foam generator. Thus allows fire fighting foam to freely flow to the fire site and control or extinguish the fire. Studies indicated that a high-expansion foam plug will travel 183 m (600 ft) down an entry with a 4.5% rise in elevation, before leakage of foam from around the inflatable partition.

Jan 1, 1996

By Roshan B. Bhappu, Sukhendu L. Barua

The economics of developing and operating small precious metal mines are unique and require much more scrutiny than larger mines since a limited tonnage must carry a heavy burden of capital investment as well as operating cost per unit ton to be mined and processed. Moreover, potential operators of small mines do not have the required expertise available to critically evaluate the technical and economic aspects of their projects. In this paper, the authors have attempted to provide technical and economic guidelines for developing and operating small precious metal mines. Capital and operating cost estimates as well as return on investment are provided for various scenarios utilizing different mining and processing techniques.

Jan 1, 1987

By Kalliat T. Valsaraj, Louis J. Thibodeaux

A mathematical model is described for the transfer of hydrophobic compounds from aqueous to an immiscible organic phase using fine bubble aeration; the process otherwise known as "solvent sublation" an adsorptive bubble separation process. The limitations of the model are explored by simulating experimental results both for a batch scale process and a continuous process. The qualitative predictions of the model with respect to the influence of the organic layer (mineral oil) are tested by performing experiments using chloroform and 2,3,6-trichloroanisole as hydrophobic compounds in the aqueous phase. The continuous process is seen to be limited by the requirements of fine bubble generation and the ratio of influent feed rate to air flow rate.

Jan 1, 1989

By L. G. Austin

Equations are derived to allow for different mean velocities of axial flow for different sizes of particles in fully mixed ball mills. The equations are modified to allow for the exit classification that occurs in grate-discharge autogenous and semiautogenous tumbling mills. An approximate treatment is given that applies for other forms of residence time distribution, provided that the mill contents are close to fully mixed.

Jan 1, 2000

By Marie-Antoinette Dziurla, Barrie Johnson, Åsa Kolmert

Acidophilic bacteria are well known for their role in accelerating the oxidative dissolution of sulfide minds, such as pyrite. Other acidophiles, however, are able to catalyze dissimilatory reductive reactions. Bacteria that reduce ferric iron to ferrous, and sulfate to sulfide, were isolated from ARD-impacted environments and immobilised onto porous beads made of recycled glass. Column bioreactors containing colonized beads were constructed and peacolated with synthetic and actual ARD, and evaluated for their capacities to promote iron or sulfate reduction, and pH amelioration. Iron reduction did not require strictly anoxic conditions in bioreactors, and rates of up to 800 mg Fe3+ reduced/(l*day) were achieved, with a conversion efficiency of up to 98%. Using mixed populations of acidophilic fungi and iron-reducing bacteria, the bioreactors were capable of promoting iron reduction using paper pulp as sole carbon and energy source. Reduction of sulfate in pack bed bioreactors was observed with acidic wastewaters of pH 3 and above, though average rates of 300 mg sulfate reduced/(l*/day) were less than those recorded for circum-neutral pH systems. Bioremediation of ferric iron-rich ARD was assessed using coupled iron-reducing and sulfate reducing bioreactors.

Jan 1, 2000