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By S. K. Kawatra, T. C. Eisele

Although column flotation is known to be more effective than conventional flotation for cleaning fine coal, little attention has been paid to the considerable sulfur removal potential of this process. Whereas conventional flotation can only with difficulty remove pyritic sulfur from coal, flotation columns can make this separation readily due to their greater selectivity. This project has used a modified flotation column to remove pyrite from fine coal. This column has been shown to be capable of removing 70 to 85 percent of the pyritic sulfur from coal while recovering 80 to 85 percent of the total calorific value. However, the remaining pyrite is too finely disseminated to be readily removed by physical means. Currently, experimentation is in progress using bacterially-catalyzed dissolution of pyrite in acid solution to remove ultrafine pyrite and aid in the removal of coarser pyrite inclusions.

Jan 1, 1988

By W. M. Schafer, C. F. Luckay, D. A. King

Monitoring devices have been installed at several mine sites to assess the potential for the development of acid rock drainage (ARD) in waste rock, spent ore and tailings material. In addition, instrumentation has been designed for monitoring changes in water quality in pit lakes. These devices monitor temperature, oxygen, water movement and water chemistry in the waste rock pile. This information can be used to evaluate the current and future ARD risks and the effectiveness of caps and covers. The information can also be used in the design of other reclamation strategies that limit ARD development. The instrumentation includes nested thermistors and oxygen sensing ports, neutron access tubes, heat dissipation units (HDUs) and lysimeters. Many of the monitoring devices can be linked to a data logger and telemetry systems, enabling monitoring data to be downloaded from the office.

Jan 1, 1999

By D. W. Park

The Longwall Strata-Control and Maintenance System (LoSCo-MS) is a software and data-communication system developed at the University of Alabama. This system integrates real-time shield monitoring, data presentation, analysis and the forecasting of forthcoming events. The main objective of this system is to provide stability information on longwall panels, including excessive shield load, low setting pressure, leg leakage, poor shield performance and imminent maintenance problems. Analyses of various mining and geological parameters were also performed to determine past and present roof characteristics and to forecast roof loading patterns for the following mining cycles, the next periodic weighting, etc. A local coal mine in the Warrior Coal Basin has adopted this system to provide daily evaluation of ground stability and maintenance problems in their longwall panels. Two years of experience with this system is covered in this paper.

Jan 1, 2000

By J. D. Patsey, G. T. Lineberry

Introduction A computer program was developed for analyzing drum-type hoists before modifying an existing system or designing a new one. Its use permits the preliminary evaluation of a system before seeking technical assistance from mine hoist designers and manufacturers. The user-friendly program accepts a variety of data and analyzes hoisting systems for any balance state. The program can be used to calculate skip capacity to yield a desired production rate, solve for drum face width, select a permissible wire rope, estimate total horsepower of the hoist plant, and estimate annual power cost. Whether required for a large mining complex or for a relatively small operation, a hoisting system must be carefully designed to ensure the efficient, reliable, and safe flow of material. Because shaft sinking and hoist installation can total between 2.5% and 3% of the cost of opening a deep mine, proper hoist selection is critical. Today's mining engineer has at his disposal the most powerful design and analytical aid ever, the micro- computer. There is, unfortunately, limited software for the study of hoisting systems, unlike that for other materials handling equipment (Manula and Albert, 1980; Prelaz et al., 1964; Bucklen, 1969; Thompson, 1985). HOIST reduces a time-consuming set of calculations to a concise package of interrelated subprograms. A literature review revealed no common-user pro- grams to analyze hoisting systems, although at least four major hoist designers/manufacturers/installers have their own in-house programs. To provide a tool with which the mining engineer could preliminarily analyze a materials hoisting system or could check the calculations of a hoist contractor, a computer program was developed. HOIST was written in BASIC for the IBM-PC for ease of program adaptation and to en- courage field use on compatible systems. Details of program development are omitted, since the basic principles of hoisting analyses are relatively straightforward, simple, and readily accepted (Har- mon, 1973; Nordberg, n.d.; Adler, 1957). Program features, intended usage, and benefits of the com- puterized solution are emphasized over theory development and mathematical rigor. Background The mine hoist system that is selected and installed at a mine is the "lifeline" of that mine, with installations lasting 20 years or more. Thorough study is warranted to ensure that productivity demands are met at a minimum cost per ton. The increased cost of a large, powerful, high-speed hoist must be offset by increased production to justify its selection. To optimize this tradeoff, an extensive hoisting analysis should be performed. The analyses to properly size the skip (or cage ) , the drum, and the hoist drive are conducive to computerization, permitting rapid evaluation of changeable operating and design parameters, such as velocity, acceleration, state of balance, and productivity demand. The program is particularly useful in conducting sensitivity trials, such as investigation into the effect of change of productivity on skip capacity and on horsepower of the hoist drive. HOIST is currently limited to the study of drum-type hoists with cylindrical drum(s). However, only minor changes to the program would permit analysis of friction hoists and conical drum configurations. Model development and testing The program is based on accepted equations and physical relationships. Examples of manual calculations formed the basis for decision points and program branching. Data is input in the order that it would be needed if the problems were solved manually. The choices are arranged likewise. HOIST was developed in sections, with manual solutions performed to check program logic. The testing became more rigorous as sections were completed. Output from one section becomes input for following sections, as appropriate. The simplified flow diagram of HOIST is given in Fig. 1.

Jan 1, 1988

By Steve Kral

The dramatic rescue of nine Pennsylvania coal miners trapped nearly 90 m (300 ft) underground for77 hours probably would not have happened without the high technology equipment and improved mine rescue training techniques available today. By now, most everyone has heard the story of the accident that occurred at the Quecreek Mine near Somerset, PA. At about 9 pm on Wednesday, July 24, the miners were drilling coal in the room-and-pillar mine. Their drilling accidentally punched through to the adjacent, abandoned Saxman Mine. Old mine maps of the Saxman Mine led Black Wolf Coal, Quecreek’s owners, to believe they were between 60 to 90 m (200 to 300 m) away from the abandoned mine. Those maps proved to be inaccurate.

Jan 1, 2002

By Hans Ehdwall, Erling Strandon, Friedrich Steinhäusler, Victor A. Leach

INTRODUCTION The basis for any measures in radiation protection is the quantitative assessment of the radiation exposure. Due to the extensive requirement in health physics manpower and related cost it is necessary to develop certain criteria regarding the necessity of monitoring and the selection of population groups to be monitored. Depending on the overall objective of the particular programme, the specific requirements for the measurement of atmospheric levels of radon, thoron and their daughters for practical radiation protection purposes differ significantly for those in the case of research applications, such as use of data for epidemiological studies. As part of the OECD-NEA Programme on Radon Dosimetry and Monitoring Task Group 1 reviewed available models for lung dosimetry in the case of inhalation of radon 222, radon 220 and their daughters (James et al., 1981). Using defined reference atmospheres for underground- and open-pit mining conditions as well as for dwellings, normalized conversion factors were calculated for the mean bronchial dose (mGy) per Working Level Month exposure (WLM). Task Group 2 discussed the features and adequacy of the Working Level (WL)-concept as a physical correlative of the absorbed lung dose and its limits of confidence and accuracy (Johnson and Leach, 1981). The WL-concept was found acceptable for radiation protection purposes provided that modifying factors like particle size, unattached fraction and respiratory minute volume did not cause the effective dose equivalent per WLM as calculated by either the James-Birchall or Jacobi-Eisfeld lung models to be more than 50 % above that given by ICRP of 0.01 Sv/WLM. For application in epidemiological studies the WLconcept is considered acceptable if the calculated absorbed dose to the tissue does not vary by more than 50 % (at the 95 % confidence level) from that given for defined reference conditions. In the following, objectives and requirements for the measurement of radon, thoron and their daughters are discussed for operational health physics routine and special research applications according to the scheme outlined in Fig. 1.

Jan 1, 1981

By Michael J. Humenick

A laboratory experimental research project was conducted to evaluate the use of chlorine for the oxidative destruction of residual ammonia which may remain in ground water after in-situ uranium solution mining operations. The work tested the idea of the injection of high strength calcium hypochlorite solution into the mining zone to convert ammonia to nitrogen gas as a final clean-up process for ammonia removal from the ground water system. The paper details ammonia removal efficiency as a function of chlorine dose, reactant and product material balances, and how the concept may be used as a final ground water restoration process.

Jan 1, 1982

By M. Arias

"An attractive foreign investment legislation, an anti-mining framework in the jurisdiction where a head office is located, the geographical location of the mineral resources, a country that offers the technology needed by the industry for its operations -- these are some of the many factors that make mining and mineral exploration a global business. It is precisely in the complexity of this new era of globalization and market environment, that sustainability initiatives are challenged. Responsible management of mineral exploration and mining is no longer defined by the use of efficient technology and resource management. Sustainability is not only a report compliance exercise or a green revolution. Sustainability is like any business, a long term profitable proposition. This new approach encompasses four pillars: social, economic, environment, and culture. This new approach connects humans and corporations; it is the way to engage, respect and improve relations with the people with whom we work and our neighbours."

Jan 1, 2011

By John S. Timmons, Eivind B. Jensen

The Henderson mine is an underground panel-caving molybdenum mine located in the mountains of central Colorado. All development and primary production operations are performed using diesel-powered, rubber-tired mobile equipment. The growth in manpower and equipment was rapid in the five years following the July 1976 start-up, reaching about 250 machines and 2000 people to produce 9 Mt/a (10 million stpy) of ore. However, due to dramatic improvements in productivity, production is currently at a rate of 8.1 Mt/a (9 million stpy) with about 570 people and a much smaller equipment fleet. The mine's high degree of mechanization and accompanying maintenance costs have focused increased attention on the maintenance function as a cost center with potential for improvement. To realize some of that potential, several approaches to equipment maintenance have been adopted. None of these stand alone effectively, though, and their success relies on their working together in the overall program. The approaches that characterize the equipment mainte¬nance philosophy at Henderson are described here. Preventive maintenance The value of preventive maintenance as an alternative to breakdown or emergency repair is widely accepted in industry. When production began in 1976, few people at Henderson had experience maintaining diesel-powered, rubber-tired equipment. Other company operations such as its previous Urad operation and the Climax molybdenum mine near Leadville, CO used rail and Blusher technology. A maintenance consultant was hired to establish a formal preventive mainte¬nance program. The initial program contained four different preventive maintenance services, "A," "B," "C," and "D." Each was keyed to a different operating interval. • "A" service was the most frequent. It was a quick, general inspection and greasing of all fittings. •"B" service added a more detailed inspection. • "C" service included changing all filters and most fluids, such as engine oil. • "D" service was originally designed as a comprehensive inspection and testing of major component systems over a period of 24 hours during which the equipment was removed from operation. It was believed that most problems uncovered by the inspection could be reported and scheduled for repair at some later date, with only critical repairs being done during the service. In addition to these scheduled preventive maintenance services, a schedlle of minor and major rebuilds at intervals of 2500 to 5000 hours was established.

Jan 1, 1989

By R. G. McLusky

This paper analyzes the opinion in Bragg v. Robertson, 72 F.Supp. 2d 642 (S.D. W.Va. 1999), a case which threatens the future of surface mining in West Virginia and which will almost certainly result in new policies or rules that will affect surface mining everywhere. This paper addresses: (1) the jurisdictional bases of the action which relies on the federal surface mining laws to enforce a state mining program; (2) settlement agreements reached in the case that threaten to alter federal policies beyond West Virginia borders; (3) a programmatic environmental impact statement on mountaintop mining being undertaken by the federal government; and (4) an opinion by the Court outlawing excess spoil disposal in intermittent and perennial streams.

Jan 1, 2001

By E. P. Chen

This investigation involves the development of a two-dimensional continuum model for the description of jointed media. Specific application of the model developed here is for the potential geological disposal of radioactive waste in the layered sequence of fractured volcanic tuffs under Yucca Mountain, Nevada. This is currently being considered by the Nevada Nuclear Waste Storage Investigations Project, administered by the Nevada Operations Office of the U. S. Department of Energy. The work is a direct extension of the previous constitutive model by Thomas (1982) based on the work of Morland (1974). The main feature of Thomas's model includes two parts: a continuum approximation based on average discontinuous displacements across jointing planes within a representative elementary volume, and a material constitutive description based on linear elastic matrix material behavior and nonlinear normal and shear joint behavior between jointing planes. The mathematical descriptions by Morland based on strain partitioning among matrix material and joint sets allow multiple joint sets to be included in the model. However, the initial effort by Thomas to implement Morland's mathematical model included only a single set of joints. To make the material model reflect more realistically the field characteristics, the current work extended Thomas's model to include orthogonal sets of joints. The nonlinear elastic normal joint behavior is retained in the present model. Joint shear response was treated as linear elastic in the shear stress versus shear displacement relationship prior to attaining the stress level governed by the Coulomb friction criterion. Beyond this critical stress value, a horizontal line is assumed in the work of Thomas for the shear stress versus slip displacement relationship such that the shear stress remains constant while the slip displacement increases. Motivated by experimental observation, the current work generalized the shear response to allow a line with finite slope to govern the slip behavior beyond the critical stress level. The inclusion of an orthogonal joint set led to a fourth order algebraic equation for the calculation of stress increments as compared with a second order equation obtained by Thomas. The nonlinear elastic normal joint behavior provides criteria which allow the selection of the root that yields result consistent with the loading condition of the problem. The addition of one more set of joints provides the potential to more completely study the interaction of various parameters representing the characteristics of jointed media behavior. Material responses to various loading conditions based on the present constitutive model have been obtained. These results and their comparisons to single joint set results are presented. Formulation of the Continuum Model The inclusion of an orthogonal joint set led to a fourth order algebraic equation for the calculation of stress increments as compared with a second order equation obtained by Thomas. The nonlinear elastic normal joint behavior provides criteria which allow the selection of the root that yields result consistent with the loading condition of the problem. The addition of one more set of joints provides the potential to more completely study the interaction of various parameters representing the characteristics of jointed media behavior. Material responses to various loading conditions based on the present constitutive model have been obtained. These results and their comparisons to single joint set results are presented. Let us focus our attention on the set with normal n first. Let the jump dilation displacement and jump slip dasplacement associated with the [ ]

Jan 1, 1986

By Hiroshi Himura, Shoichi Tsushima, Hiromi Goshima

This paper reports the construction of an environmentally-friendly tunnel in sedimentary soft rock near a residential area. The main tunnel, which will be used as the Onmawashi-Koen (Park) Regulating Reservoir, is a large-scale tunnel with a cross sectional area of 254.0 m2 and a lengthof 577.3 m, excavated using such support as shotcrete, rockbolts and steel H-sections. Since the large main tunnel is excavated in sedimentary soft rock, it is necessary to keep the stability of the tunnel face and the crown and to prevent surface settlement. A top heading with a length of 50 m is therefore driven as a pilot tunnel to observe the ground behavior during excavation, and to obtain information on the geological conditions based on which type of support structure is determined with consideration given to the results of field measurements and numerical analyses.

Jan 1, 2001

By Richard A. Brown

The direct precipitation of uranium with hydrogen peroxide has been known since 1877. Commercial use of the process began in the 1960's. During 1967 the Bureau of Mines assisted the Climax Uranium Co., Grand Junction, Colorado in the development of a uranyl peroxide precipitation process to control a molybdenum impurity problem (1). Atlas Minerals, Moab, Utah has used hydrogen peroxide to control vanadium and sodium levels in their uranium concentrates since 1969 (2). Recently, the use of hydrogen peroxide by the uranium industry has grown, particularly since the increased demand for uranium has led to the processing of low grade ores. Impurities present in low grade ores can be concentrated with the uranium during milling and will substantially complicate the refining of uranium yellowcake concentrates. Consequently, commercial nuclear fuel processors have imposed stringent specifications and penalties to control these impurities. The ability to produce a pure uranium yellowcake can eliminate penalty or reprocessing costs. Hydrogen peroxide precipitation of uranium is specific and quantitative, producing a very high purity product.

Jan 1, 1980

By J. B. Boisvert, O. Leuangthong, T. Acorn

Optimizing final pit limits for stochastic models provides access to geologic and economic uncertainty in the pit-optimization stages of a mining project. This paper presents an approach for optimizing final pit limits concurrently over all realizations in a stochastic model and using a risk-management framework to manage the geologic and economic uncertainty. A heuristic pit optimizer is used to find multiple uncertainty-rated pit shells. These uncertainty-rated pit shells follow the mean-variance criterion to approximate the efficient frontier for final pit limits. Stochastic dominance rules are then used in a risk-management framework to further eliminate suboptimal solutions along the efficient frontier. This results in a smaller set of final pit shells that can be further analyzed for production scheduling. Additionally, the original solutions are analyzed for changes in the mining limits, and two regions are targeted as potential regions for further exploration.

By Jerry R. Johanson

Introduction Many solids processes that look feasible on paper or even in pilot studies become disasters in full scale. Changes in solids flow characteristics from pilot scale to full scale be- cause of larger solids contact pressures, thermal shocks, or unforeseen temperature excursions often cause full-scale solids flow problems not encountered in the laboratory or pilot studies. Fortunately, proper applications of solids flow principals and solids flow properties measurement at full scale conditions can anticipate the problems and thus provide an accurate basis for full-scale design or existing plant modifications. Solids flow properties The basic solids flow property definitions are given in Table 1 (Johanson, 1966, 1976, 1978, 1985). In this section, the author will discuss each property and its potential for creating full-scale pilot plants. Unconfined yield strength The unconfined yield strength of a bulk solid determines the tendency for cohesive hangups of the solids in the process and is effected by the time at rest, chemical reactions, temperature, liquid content, solids size consist, and phase changes of solids or fluids involved in the process. One of the common mistakes is to consider the solids condition only at the beginning and the end of the process. For example, consider the direct reduction of iron ore. The feed solids are free-flowing, hard lump ore or pellets. The end result is a hard, free-flowing reduced sponge iron lump or pellet. One might conclude that the process involves free-flowing lumps. This conclusion may seem reasonable based on laboratory studies oreven pilot plant studies where solids contact pressures are very low. Unfortunately, during the reduction reactions at high temperatures, the rock or pellets soften and, with solids contact pressures associated with the full-scale plant, may fuse together, thus providing a possible solids hangup in the moving bed reactor not evident in the low pressure pilot scale. Fig. 1 shows some typical unconfined yield strength measurements for pellets as a function of solids contact pressure at various times at rest. Note at low consolidation pressures, generally associated with laboratory or pilot plant studies, the pellets show no strength unless held at rest for an extended time. This will produce a very free-flowing condition in pilot plants that will not exist in the full size reactor.

Jan 1, 1990

By A. B. Fly

This paper presents the equipment and techniques developed to mine subsurface mineral deposits through 16 inch bore holes entirely by hydraulic methods. Use of this equipment for excavating large cavities in oil and water well producing zones is discussed. Results of surface experiments using high pressure jet streams of water to determine the cutting rates of materials are outlined. Various basic shapes of subsurface excavations that can be mined with the equipment are illustrated and discussed. An example of the cost of mining by this method is presented. Problems encountered in the field operations led to the development of a new explosion type slurry pumping system and related slurry handling equipment.

Jan 1, 1969

By M. J. McPherson, P. Mousset-Jones, J. Banik, F. Calizaya

Friction factors or coefficients of friction used to estimate the resistances of mine airways are, in the main, estimated from empirical measurements made in other airways considered to be of a similar geometry and type of lining. A somewhat more analytical approach, although still based on empiricism, is to estimate the ratio of the average height of the asperities to the hydraulic mean diameter of the airway (e/D ratio) and then to employ the Moody Chart or one of the equations that have long been established to represent the [coefficient of friction v Reynolds number curves] on that chart. Unfortunately, the Moody Chart and corresponding equations are based on pipes of uniformly distributed (sand grain) roughness whereas the asperities that exist on the surfaces of mine openings are frequently highly irregular both in their size and distribution. This is considered to be a major cause of discrepancies that have been found between coefficients of friction by the Moody Chart and those actually measured in mine airways. The work described in this paper examines an alternative method of estimating coefficients of friction for rough natural surfaces with uneven sizes and distribution of surface asperities. The technique utilizes the relatively recent developments in fractal analysis. A fractal dimension is determined from the topography of the surface. This has been correlated to coefficient of friction for a scale model of a mine airway. Further work is being carried out in actual mine airways. However, at this time, it appears promising that the fractal method may allow coefficient of friction to be predicted for given types of strata and method of roadway drivage.

Jan 1, 1993

As the surface reserves are being depleted, more and more stone operators are seeking underground mining options. Stability of underground openings is a major concern for the safety and productivity. This paper relates to a field study conducted at a large underground limestone mine in Central Pennsylvania. Identification of hazards leading to ground failures and assessment of roof fall risks are important in mitigating injuries. Field observations at this mine were integrated with Roof Fall Risk Index (RFRI) mapping software recently developed by West Virginia University. The system is designed to combine field study data related to geologic factors, mining-induced damages, roof profile, and ground water influx to generate RFRI maps. The mine has adopted a proactive ground control program consisting of comprehensive examination of drilling and bolting logs; precision surveying of roof and rib; accurate mapping of cutters, falls, and geologic structures; and installation of extensometers and microseismic monitoring systems. Investment of time and resources has eliminated fatalities and lost-time injuries due to ground fall. This paper presents the geologic settings, mining conditions, ground control issues along with risk management and control techniques adopted at the study mine.

Jan 1, 2009

By B. Cavender

Mining managers trying to rapidly reduce production costs tend to implement a traditional set of top-down managerial practices: layoffs of employees, renegotiation of supplier contracts, cancellation of employee training, restrictions on travel, reductions in office supplies, and so forth. While these practices do reduce costs, the benefit is often limited in both magnitude and duration, and the workforce is usually left demoralized. Successful cost-cutters take a different approach. They make the continuous reduction of costs a priority for all members of the organization, whether managers or workers. The culture of these firms emphasizes the commitment, voluntarily given, of individuals and work groups to this goal. Cost cutting practices often reject all of the traditional methods mentioned above, but are far more numerous, innovative, and successful. This culture of cost reduction is the result of a set of leadership competencies that establish direction for the organization, align the organization’s various constituencies with this direction, and motivate and inspire the organization. Dramatic cost reduction then becomes a routine task rather than a heroic achievement.

Jan 1, 2000

By D. R. Bomberger

An automatic microscope has been developed to .measure the size and populations of macerals and minerals in fine coal particles. Differentiations are made on the basis of reflectance. This study is concerned with the size distribution of pyrite inclusions. Most fine coal cleaning processes do not remove pyrite as completely as a straight density separation. Consideration of the pyrite size distribution is suggested as a more accurate method of predicting sulfur reduction by a cleaning process. Analyses of float-sink results and Deister Table operation in terms of pyrite particle sizes are made. Other potential applications of automatic microscopy are also discussed.

Jan 1, 1963